Getting started with evaluation modules and software tools for dynamic ground projection

[Guide]In recent years, with the addition of sign projectors, ground projections around vehicles have made considerable progress. Automakers have used logo projection to help car owners customize their cars, while also providing other functions by illuminating the ground around the doors. However, these systems currently can only Display a single pattern and do not support any functions other than the basic pattern.

In recent years, with the addition of sign projectors, ground projections around vehicles have made considerable progress. Automakers have used logo projection to help car owners customize their cars, while also providing other functions by illuminating the ground around the doors. However, these systems currently can only display a single pattern and do not support any functions other than the basic pattern. As cars become more advanced, OEMS is looking for other ways to allow cars to interact with drivers and passengers while still providing features such as customization and style, as shown in Figure 1.

Figure 1: Dynamic ground projection used to interact with the driver and passengers

With the introduction of the DLP3021-Q1 digital micromirror device (DMD), TI has further promoted the development of logo projection, which can completely project red-green-blue (RGB) format video through a thumb-sized module. The internal FLASH can send the locally stored image and video content directly to the DMD, simplifying the requirements for the integrated DMD module of the vehicle, and no additional graphics processing unit (GPU) is required. But without a GPU, how to display video or continuous images on the device? This article will discuss how to use TI's dynamic ground projection tool to display images and videos stored in flash memory.

The DLP3021LEQ1EVM dynamic ground projector evaluation module (EVM) (shown in Figure 2) is a projection-ready EVM that can simulate a product system, so it provides a quick way to evaluate dynamic ground projection. The EVM integrates all the key systems required to make a dynamic floor projector, and can be evaluated immediately upon receiving the EVM (including the lighting driver, compact light engine, and formatting unit with DMD controller). The DMD controller allows you to modify the projection content via a personal computer (using an FTDI cable) or a serial peripheral interface adapter board (both of which are included in the EVM). The board is connected to the computer via USB, but you can start projecting content without connecting to the computer. After power on, the unit will start to display the contents stored in the flash memory, making the EVM a plug-and-play system that supports the rapid evaluation of the DLP3021-Q1 DMD.

Figure 2: DLP3021-Q1 dynamic ground projector EVM

DLP Composer is a graphical user interface (GUI) tool that allows you to customize the content loaded into the flash memory, not even limited to images. After finding the video or still image you wish to load into the device, the program will get the content, automatically zoom and convert it to the DMD intrinsic format. For further customization, you can adjust the sequence set to adjust the frame rate and specific RGB duty cycle. This interface allows you to easily change the value and adapt the content to different environments through individual duty cycle adjustments.

For example, if your projection requires high brightness but low color accuracy, you can set the green duty cycle to more than twice that of other channels. The EVM comes pre-installed with sample videos and sequences for reference. You can also edit the default register configuration in the GUI. Some of these registers have read and write permissions. You can change the settings without reprogramming the flash memory, which helps to quickly select the content to be loaded and configure the DMD power-on.

After programming the content and setting the default configuration, you can start using the DLP3021-Q1 EVM to project the content. After programming the flash memory using DLP Control Program or controlling the playback of loaded content through DLP Composer, you can also perform other system configurations. First, connect the adapter board to your computer and make sure the program recognizes your device. After the connection is established, you can navigate to the “Scripting” page where you can send commands to the DMD controller. The terminal uses the Python programming language and also contains a program-specific function library. You can run and pause your script by specifying pause conditions in the code or using the buttons at the top of the window. In the other “Registers” pages of the software, you can individually read and write the modifiable registers. You can also modify multiple registers at once by going to the “Commands” page and getting or setting the values ​​in the group.

According to the level of customization, you first need to know what specifications are necessary. The application report “Requirements for Dynamic Ground Projection Applications” introduces formulas and estimates that can help you determine the necessary light output based on environmental quality (such as environmental illuminance and projection surface reflectivity). For more information about projection content, please refer to “DLP3021-Q1 Dynamic Ground Projection System Design”. This application report focuses on the storage requirements of flash memory and the necessary compression factors.

In the included hardware, online resources and software tools (such as DLP Composer and DLP Control Program), there are multiple ways to test and demonstrate the functions of the DLP3021-Q1 DMD. DLP3021-Q1 EVM can accelerate your design cycle and development process through its plug-and-play function. Since you can test different applications and brightness levels without developing a circuit board and optical engine, EVM is an ideal tool for prototyping and development.

(Source: Texas Instruments)

The Links:   CM100DY-24H   N089L6-L03

How to use SiC to build a better electric vehicle traction inverter

“In this article, we will investigate the advantages of using SiC technology in electric vehicle traction inverters. We will show how the energy efficiency of the inverter is improved under various load conditions, from light load to full load. Using a higher operating voltage and high-efficiency 1200V SiC FET can help reduce copper loss. The switching frequency of the inverter can also be increased to output a more ideal sinusoidal waveform to the motor windings and reduce the iron loss in the motor. It is expected that under the influence of all these factors, the mileage of a pure electric vehicle on a single charge will increase by 5-10%. At the same time, the reduced loss can also simplify the cooling problem.

“

In this article, we will investigate the advantages of using SiC technology in electric vehicle traction inverters. We will show how the energy efficiency of the inverter is improved under various load conditions, from light load to full load. Using a higher operating voltage and high-efficiency 1200V SiC FET can help reduce copper loss. The switching frequency of the inverter can also be increased to output a more ideal sinusoidal waveform to the motor windings and reduce the iron loss in the motor. It is expected that under the influence of all these factors, the mileage of a pure electric vehicle on a single charge will increase by 5-10%. At the same time, the reduced loss can also simplify the cooling problem.

Introduction

Recent news indicates that the number of pure electric vehicles (BEV) is increasing faster than previously expected. This has prompted automakers (including existing manufacturers and newly joined manufacturers) to reinvest in the development of electric vehicles, trying to find the most effective technology to maximize energy efficiency, reduce volume and weight, and replace as much as possible from expensive battery packs. Benefit from this, thereby extending the mileage on a single charge. This allows SiC transistors to quickly enter the on-board chargers and DC converters of electric vehicles. Given that traction inverters handle 10 times the power level, if SiC transistors can have similar advantages in this environment, it will rewrite the power semiconductor landscape. To this end, SiC technology needs to provide clear cost performance advantages and remove all inevitable obstacles in order to achieve a reliable inverter system design that can be put into manufacturing. The boost stage used in front of the inverter will undoubtedly use SiC, for the same reason we gave when discussing car chargers and DC converters. In this article, we will examine the main advantages of using SiC technology in electric vehicle inverters and discuss several implementation options based on UnitedSiC technology.

Main advantages of SiC technology

The driving conditions of typical electric vehicles, especially those used in cities, will cause the inverter to operate under light or medium load for most of its operating life, but with frequent stops and starts. However, all worst-case stresses must be considered when designing the inverter, such as rapid acceleration, steep slopes, and operation at various ambient temperatures. Figure 1 shows a typical two-level voltage source inverter that can be used to drive an internal permanent magnet motor. This is a common configuration for pure electric vehicles, and its inverter is placed near the motor. Normally, the inverter switch will be under control to apply a 3-phase AC voltage to the motor windings. This goal is achieved by switching the power switch according to the command of the controller, the frequency is 4-10kHz, and the basic AC frequency of up to 1kHz can be generated. The total power level can range up to 50-250kW, which is suitable for electric buses. The DC voltage used depends on the battery system, and due to the use of a boost converter to convert various battery voltages to the fixed DC voltage used by the inverter, this voltage may increase from the current 300-500V to 600- in the near future. 800V, a higher voltage can reduce current and copper loss while providing the same power.

Figure 1: Electric vehicle traction inverter using two-level voltage source converter architecture

The loss of the power switch comes from the conduction loss when the current flows through the switch and the switching loss when the switch is opened and closed. The conduction loss has nothing to do with the switching frequency, but the switching loss is proportional to the switching frequency.

Figure 2 shows the characteristics of SiC FETs and silicon IGBTs. At any given current, I_D*V_DS The product of can all represent a given conduction loss. Therefore, it is easy to see that when unipolar SiC FETs are used, there is no inflection point voltage that occurs when IGBTs are not used. This is beneficial for all current levels up to 200A, and correspondingly lower in light load and medium load operation. It is especially beneficial under current.

Figure 2: Conduction loss characteristics of 200A SiC FET and IGBT

Figure 3 is a comparison of the conduction and switching losses of inverters based on low conduction loss IGBTs and SiC FETs suitable for 750 V devices when operating at a 400 V bus at 8 kHz. IGBT solutions have considerable switching losses even at 8kHz, so they cannot be used effectively at 25kHz. SiC-based solutions not only have low conduction losses at all output levels (at 8kHz, the losses will be greatly reduced), but also can be used at higher inverter frequencies (high energy efficiency).

Figure 3: Comparison of power loss in conduction and switching of inverters based on 1200V IGBT and SiC FET.In all cases there is a loss difference, the difference is very large at 25kHz

Another aspect of an electric vehicle inverter that is different from traditional industrial motor drives is that it requires two-way power transmission. During regenerative braking, the system controls the switch to allow the inverter to act as a rectifier and the motor to act as a generator, allowing electrical energy to flow back into the battery. The SiC FET allows the third quadrant to conduct electricity with the same low conduction loss, which means that synchronous rectification can be used to maintain very low losses in this operating mode. When using IGBTs, this is impossible, and the loss of reverse power flow with reverse parallel freewheeling diodes is relatively high.

Rated voltage

At present, many electric vehicle inverters are based on 750V IGBT, and the inverter bus voltage is 300-500V. In order to handle high power more efficiently, the 1200V switch allows the use of batteries with a voltage of 600-800V.

Table 1 shows some calculation data of the 450A, 750V half-bridge module used in the traction drive of a 200KW pure electric vehicle. The drive is based on the low conduction loss IGBT and UnitedSiC FET with the same rating of 750V. Each switch position uses 3 IGBTs and 3 diodes. They were replaced with 6 stacked SiC FETs, each with a resistance of 5.4mohm and no more than half of the original volume. Cases 1 and 2 show the difference in total conduction loss, switching loss, and total loss at 8kHz. At 200kW, the total loss will be halved, and at 50kW, the total loss will be close to a quarter of the original. Given that the inverter runs under light load most of the time, this feature is very beneficial. Please note that when SiC FET is used, the conduction loss and switching loss are relatively low, but at 200KW, the difference in switching loss is nearly 8 times. The table also shows that the same module can also be used up to 300KW, keeping all FETs below Tj=150C, thus allowing the same inverter hardware to be used in a 300KW system. Case 3 shows a better way to handle 300KW, which is to use 8 SiC FETs for each switch to reduce the peak loss from 3425W to 2666W.

Table 1: Comparison of operating power loss between 750V IGBT and 750V SiC FET-based 450A, 750V 3-phase inverter modules used in 200kW electric vehicle inverters. The lower part of the table compares the 400A, 1200V IGBT module used in a 200kW inverter with the corresponding 1200V SiC FET module. In all cases, we consider the use of nail-fin heat sink type 3-phase modules at a cooling temperature of 90°C. In all cases, the maximum junction temperature is kept below 150°C, even if the SiC FET is rated at 175°C and can withstand a short time of 200°C. The lower switching loss can be used to run the inverter at 25kHz, thereby improving the waveform quality and reducing the iron loss. Even in this case, it can be seen that the SiC FET solution (Table 1 Case 4) has lower losses than the IGBT solution under all load conditions. When the output power is 200KW, the IGBT solution will dissipate 3580W at 8kHz, while the SiC FET solution will dissipate 2061W at 25kHz.The module can achieve 250KW output in 6 parallel SiC FETs

If only 4 SiC FETs are used per switch, lower costs can be achieved at the expense of higher losses. This situation is shown in Case 5 of Table 1. At this time, the loss is still much lower than the IGBT-based solution.

The lower part of the table compares the losses when using 1200V transistors and operating bus voltage of 800V. It compares the case of 4 IGBTs and 4 diodes per switch (Case 6) with 4 SiC FETs per switch (Case 7, 9). If SiC FETs are used, the loss at 8kHz is less than half of the full power, and at 50kW it is a quarter of the full power. Case 8 shows how this module can be easily expanded to 300KW operating power with 6 SiC FETs per switch. Although these IGBTs cannot be switched at 25kHz due to high switching losses, Case 9 shows how to use SiC FETs to achieve this frequency while maintaining high energy efficiency. The loss is still much lower than the loss when the IGBT operates at 8kHz, and likewise, a smoother waveform can also help reduce the iron loss of the motor, and the inverter switching frequency greatly exceeds the audible frequency range. Please note that in all cases, the power output of this module is higher under the same board area.

Extreme conditions

For all motor drives, including electric vehicle inverters, an important safety requirement is to be able to withstand short circuits during maintenance or operation. This type of short circuit may occur everywhere in the DC bus, from the motor winding to the ground on the entire circuit or between the windings. For semiconductor switches, this means that the switch must be able to withstand when it opens and a short circuit occurs, until the gate drive detects the short circuit within 3-5 µs and closes the switch. In addition, when the switch is already conducting, a short circuit may also occur. In any case, the switch must be able to withstand such a short circuit, no matter how high the initial temperature of the chip is when such a short circuit occurs, and the device characteristics cannot be changed, so that the service life is degraded.

Figure 4 compares the short circuit withstand time (SCWT) difference of IGBT, SiC MOSFET and SiC FET. During a short circuit, the SiC MOSFET experiences extremely high peak currents, which may damage the MOSFET gate diode. This can be managed by using a lower gate voltage drive, which can reduce short-circuit current at the expense of very high conduction losses. SiC FETs (including Si MOSFETs stacked on SiC JFETs) perform much better in this regard. The peak saturation current can be adjusted to provide the required short-circuit withstand time, and the change in conduction loss caused by this adjustment is very small. The saturation current is set by the JFET, so it is different from the V applied to the MOSFET_GS Irrelevant. Experiments have shown that SiC FETs can safely handle such stresses caused by more than 100 repetitive events. In addition, even if the starting chip temperature reaches 200°C, the device can handle this type of short circuit.

Figure 4: Comparison of short-circuit withstand capability of IGBT, SiC MOSFET and SiC FET, and ranking of ability to handle repetitive shocks

The semiconductor in Figure 4 is drawn to scale, where the SiC FET is the smallest 100A device with the chip volume. An important advantage of SiC JFET is that it can withstand the large amount of heat generated during a short circuit, which forms the basis of SiC FET stacked cascode. The different chip sizes also explain why the use of SiC FETs can reduce on-resistance for a given module footprint.

The technical method of SiC-based inverters

The most commonly used inverter topology is the well-known two-level voltage source converter in Figure 1. The type of switch used with this type of inverter is called hard switching, which causes the high voltage across the switch to overlap with the current passing through the switch during the conversion period. Based on the results in Figure 3, one method designers can use is to use fast switching SiC devices to reduce switching losses and conduction losses, even at frequencies up to 25kHz. In this case, the switching occurs at high dV/dts. In pure electric vehicles, as in standard industrial drives, the length of the wire between the inverter and the motor is not a problem. However, directly applying high dV/dt waveforms to the motor windings may cause large displacement currents in the isolation range. You can use a filter at the output of the inverter to rectify this, and only make the high dV/dt part smoother, like the so-called dV/dt filter, or use a set of sinus filters to smooth the waveform, providing almost Perfect sine curve output. Obviously, if the switching frequency is higher, filtering will be easier. It is expected that reducing the ripple in the current waveform will increase the overall energy efficiency of the motor by 1-3% and extend the life of the motor. This energy efficiency benefit can be translated into longer mileage on a single charge or reduced battery size.

Another method is to keep the switch at a low frequency of 5-8kHz and run a device with a very low dV/dt rating, such as below 8V/ns. In this case, the switching overlap loss per cycle may be very high, but the low frequency can make the total power loss controllable. Figure 5 shows the preferred technology for using SiC FETs in this situation. The stacked low-voltage MOSFET is only used as an enable switch to ensure long-off operation under startup and short-circuit fault conditions, but the SiC JFET gate switches directly. This enables very low dV/dts and lowest loss. This solution can achieve excellent short-circuit handling capability. If the JFET gate reaches +2.5V instead of 0V, it can further reduce the conduction loss by 15-20%. In order to manage the third quadrant conduction, JFET can be used with low dead time, or only a small JBS diode can be added during the dead time to carry the freewheeling current. The graph on the right of Figure 5 shows the third quadrant behavior of a SiC JFET.

Figure 5: Directly drive the gate of the JFET and use a stacked N-channel MOSFET as a switching scheme to start the switch.It makes it easier to implement low dV/dt switches

There is also a more complex method that can achieve the highest energy efficiency is to use a fully resonant switch, like the auxiliary resonant converter method. For this purpose, Pre-Switch Inc. has developed a new controller. Figure 6 shows the circuit topology and typical switching waveforms, which can completely eliminate turn-on and turn-off switching losses while maintaining low dV/dts. Although this circuit helps to reduce IGBT switching losses and improve energy efficiency, the IGBT still has to withstand losses due to the need to remove the stored charge in each cycle. In addition, the influence of the conduction loss of the inflection point voltage in the IV curve still exists. Therefore, SiC FET can obtain the best peak energy efficiency under all load conditions. It is a unipolar device without tail current and knee voltage. The converter can also operate at a very high frequency such as 50-100kHz, resulting in a smoother sinusoidal output waveform. This can further improve the efficiency of the motor by reducing the iron loss, and combined with the minimum power loss of the inverter, it can increase the maximum single-charge driving range of pure electric vehicles. Figure 6 is an example of a compact 200kW inverter using this model and SiC FET.

Figure 6: ARCP topology that can eliminate all switching losses in the inverter. The combination of this structure and SiC FET can achieve very high power density without high dV/dt switching problems.This will bring very high motor operating efficiency and very high inverter energy efficiency

in conclusion

Many industrial and academic groups have conducted in-depth investigations and concluded that SiC MOSFETs have significant advantages in improving the energy efficiency of traction inverters and extending the mileage of pure electric vehicles on a single charge. In this article, we discussed the reasons for this evaluation result and considered the robustness requirements of the power transistors used in SiC inverters. We introduced three implementation topologies suitable for pure electric vehicle inverters, allowing users to choose the method that best suits their overall system constraints. In order to obtain the highest energy efficiency, the ARCP solution eliminates all switching losses and can maximize the use of the ultra-low conduction loss characteristics of SiC FETs.

The Links:   SKD115-16   LLG-VLGE1486-01A   IGBTS

World Peace Group launched a USB headset solution based on Artery products

“In recent years, with the continuous iteration of Bluetooth technology, wireless earphones have become a trend-setter in the new era. But not all headphones are suitable for “wireless”. In some timely confrontation game scenarios that have strict requirements on audio-visual delay, users said that using Bluetooth headphones is prone to long sound delay, resulting in the phenomenon of audio and video out of sync , so that it can not meet the ever-changing situation in the game situation.

“

On March 9, 2022, Dalian General Holdings, a leading semiconductor component distributor dedicated to the Asia-Pacific market, announced that its subsidiary World Peace has launched a USB headset solution based on Artery AT32F403A MCU.

Figure 1 – The Display board of the Artery-based USB headset solution of the United Nations General Assembly

In recent years, with the continuous iteration of Bluetooth technology, wireless earphones have become a trend-setter in the new era. But not all headphones are suitable for “wireless”. In some timely confrontation game scenarios that have strict requirements on audio-visual delay, users said that using Bluetooth headphones is prone to long sound delay, resulting in the phenomenon of audio and video out of sync , so that it can not meet the ever-changing situation in the game situation. Therefore, compared to Bluetooth transmission, game enthusiasts are more willing to choose the “wired” method to suit practical application scenarios. Based on Artery AT32F403A MCU, the USB headphone solution launched by Dalianda Shiping can reduce the distortion caused by computer boards, provide better and clearer sound effects, and also have better compatibility.

Figure 2-Scenario application diagram of the Artery-based USB headset solution of Dalian and World Peace

Founded in 2016, Artery is a chip (MCU) design company dedicated to promoting innovation in 32-bit microcontrollers. It was recognized as a high-tech enterprise in 2019. Arteli focuses on ARM^®Cortex^®-M4/M0+ 32-bit microcontroller R&D and innovation, with R&D branches in Taiwan and Jiangsu, and sales and technical support branches in Shenzhen. The AT32F403A used in this solution is a high-performance MCU under Artery, which is equipped with a 32-bit ARM^®Cortex^®-M4 core, with 55nm advanced process, effectively improve the overall performance, can achieve up to 240MHz operation speed.

In addition to integrating high-performance computing performance, AT32F403A also has built-in single-precision floating-point unit (FPU) and digital signal processor (DSP), and it has rich peripherals and flexible clock control mechanism, which can meet the application in various fields . Not only that, the product also has a complete USB sample program, which not only has a highly flexible and flexible customized product, but also meets the needs of current customers.

Figure 3 – The block diagram of the Artery-based USB headset solution of Dalian and Worldping

In this solution, the AT32F403A is connected to the computer through USB Audio Class, and the²S controls the WM8988 Audio codec to realize the complete USB headset function, which can eventually reach 16K/48K/96K audio sampling rate, and supports sampling rate switching, mute, volume adjustment, Feedback and other functions.

Core technical advantages:

• Support 16K/48K/96K audio sampling rate;
• Support 16bit sampling;
• Support sampling rate switching;
• Support mute;
• Support volume adjustment;
• Support Feedback.

Program Specifications:

• Core: ARM 32-bit Cortex-M4F CPU and FPU;
• Working voltage: 2.7V~5.5V;
• 240MHz maximum frequency, with memory protection unit;
• 256~1024KB Flash, 96 + 128KB SRAM;
• Built-in 48MHz factory calibrated RC (1% accuracy at TA = 25˚C, 2% accuracy at TA = -40˚C to +105˚C) with automatic clock calibration (ACC) function;
• Built-in 40kHz RC oscillator;
• 3 x 12-bit, 0.5µs A/D converters (up to 16 channels);
• 2 12-bit D/A converters;
• 14-channel DMA controller;
• Up to 80 fast I/Os;
• Up to 17 timers;
• Support Compact Flash, SRAM, PSRAM, NOR and NAND memory;
• Support LCD parallel interface, 8080/6800 mode;
• 3 x I²C, 8 x USART, 4 x SPI, 2 x CAN, 2 x SDIO, USB 2.0 FS;
• Temperature: -40˚C ~ 105˚C;
• Packages: QFN48, LQFP48, LQFP64, LQFP100.

The Links:   LM150X08-TL05   EPM7512AEQC208-10N

CMMB Car Digital TV System Application Solution

1 Introduction

China Mobile Multimedia Broadcasting (CMMB) is a mobile multimedia broadcasting and television technology with independent innovation and independent intellectual property rights in my country. Since the official broadcast before the 2008 Beijing Olympic Games, it has completed the network coverage of 320 cities above the prefecture level in the country, and built The world’s largest mobile multimedia broadcast and television network. As an open technology and industrial platform, the CMMB technology standard has formed a complete industrial ecological industry chain from chip manufacturing to transmitting equipment and receiving terminals. In terms of CMMB receiving terminals, many mature and stable personal terminal products supporting CMMB have been launched in the current market. Meanwhile, CMMB is expanding and promoting applications in some professional fields. In the field of automobiles, CMMB vehicle-mounted receiving terminals that provide different models and solutions are emerging and applied, and the combination of automobiles and CMMB has become a new business growth point for the entire CMMB industry. Some terminal manufacturers have launched various forms of CMMB terminal products and modules suitable for automobile installation.

In this paper, through the analysis of CMMB on-board digital TV solution, it focuses on in-depth research and summary of CMMB on-board after-installation system solutions, and analyzes the characteristics, advantages and disadvantages of each scheme in detail. The installation scheme is illustrated by an example, and finally the development direction of the CMMB vehicle digital TV scheme is discussed and prospected.

2 CMMB car digital TV solution

CMMB car digital TV is mainly divided into pre-installation, quasi-pre-installation and post-installation solutions.

The CMMB on-board pre-installation solution refers to the pre-installation and adjustment of the CMMB on-board receiving equipment and its services before the whole vehicle is rolled off the production line. For the entire car audio and video system, product development and production need to be carried out in accordance with the requirements of the car regulations, and there are very high requirements for the function, performance, and reliability of the product. Therefore, product development, testing, road testing, and production require considerable investment in all aspects. more time for validation and optimization. At present, major domestic brand car manufacturers have carried out product project approval, and integrated the design and implantation of the CMMB function as an important function of the entire vehicle audio and video system.

The CMMB vehicle-mounted pre-installation solution is mainly aimed at the models of various brands that are already in production. According to the market sales needs, the CMMB vehicle-mounted receiving equipment is implanted into the vehicle after the vehicle is offline and distributed to various sales channels, and then enters the channel for sales.

The CMMB on-board after-installation solution is mainly aimed at the cars that have already been sold. Since the CMMB function is not standard, car owners can choose to purchase and install the CMMB on-board after-installation system in 4S stores and other regular auto parts sales channels according to their own needs to realize the complete vehicle. CMMB system service.

3 CMMB vehicle after-installation system solution

The CMMB products currently installed on the market are generally post-installed products. The vehicle central control screen or headrest LCD screen is used as the Display carrier, and the CMMB function is integrated. In this way, services such as navigation can be provided during normal driving. You can watch TV programs when you are resting, improve the practicability and serviceability of the multimedia audio and video navigation system, and realize various applications of navigation, watching TV, and listening to radio.

For CMMB vehicle after-installation system solutions, its product types and types are diverse, this article will introduce in detail. For different car brands, different model configurations, and different installation schemes, the required accessories and procedures are different, so the installation cost and time are also different, but all require the equipment and lines to be hidden. Design, do not damage the original car interior decoration.

The following will focus on introducing several typical solutions of the current CMMB vehicle after-installation system.

3.1 Option 1.Multimedia all-in-one solution for special cars

The special-purpose multimedia all-in-one machine developed for a specific model usually replaces the original car audio and video system, and installs a multimedia all-in-one machine with CMMB function in the central control of the car. At present, the design of all-in-one machine products in many domestic aftermarket markets is to mold the structure of the center console according to the different styles of the car to make an integrated car machine, and it is a special machine for special vehicles, which requires professional installation. The specific terminal form is shown in the following figure:

Figure 1. Example of an all-in-one multimedia machine for special cars

3.2 Option two. CMMB Car TV Box Solution

This solution is mainly aimed at the fact that the original car central control system already has an LCD screen and audio and video input interfaces. By adding a CMMB car TV box terminal, the video signal is introduced into the central control screen. The operation mode is generally divided into remote control or touch screen. Professional installation is required, and there are restrictions on car configuration. For example, some low-profile models without a central control display cannot be installed. At present, many domestic brands offer this product. The specific terminal form is shown in the following figure:

Figure 2. CMMB car TV box product example.

3.3 Option three. CMMB car TV box + headrest LCD display solution

This solution embeds the LCD screen into the front headrest of the car, and displays the CMMB signal on the headrest screen by installing the CMMB on-board TV box for rear passengers to watch. This solution has good versatility and is convenient for rear passengers to watch, but the headrests of the front seats need to be modified, the process and installation are more complicated, and there are restrictions on car headrests, and some vehicle headrests cannot be embedded in the LCD screen. The shape of the CMMB car TV box and headrest LCD screen is shown in the following figure:

Figure 3. CMMB car TV box and headrest LCD display product example.

3.4 Option Four.Portable Vehicle PND/GPS Terminal

At present, the portable vehicle-mounted PND/GPS terminal is mainly installed on the front windshield of the vehicle through a suction cup. It has strong functions and is easy to install, but the receiving sensitivity is slightly worse than that of the vehicle-mounted TV box. Rear passengers are inconvenient to see. The specific vehicle PND/GPS terminal form is shown in the following figure:

Figure 4. Portable Vehicle PND/GPS Product Example

3.5 Comparison of CMMB vehicle after-installation solutions

Table 1 Comparison of CMMB vehicle after-installation system solutions

4 Examples of CMMB in-vehicle after-installation system installation solutions

Due to the different configurations and after-installation facilities of various models, and involving circuit modification and operation training, a professional installation team is required; the following will combine the actual installation process and the installation scheme and installation process of scheme two and scheme three. Give an example.

This installation example requires three video outputs for the CMMB digital TV box, which not only introduces the video signal into the car audio and video system of the original car central control, but also installs two sets of headrest screens to provide CMMB video programs for rear passengers to enjoy. The program is mainly divided into two parts: “CMMB car TV box”, “headrest display”. The overall structure of the system is shown in the figure below.

Figure 5. Example of CMMB in-vehicle after-installation system installation scheme

“CMMB Car TV Box” is mainly responsible for receiving CMMB signals, processing CMMB TV data, receiving user’s remote control commands, and connecting to the original car’s 12V car power supply. It has three video outputs and can support simultaneous display on multiple monitors. The video signal is sent to the headrest display and the original car central control display through the CVBS video interface, and the audio stereo signal is output to the original car audio through wired or wireless, and output through the original car audio.

The “headrest display” is to display the image part to the user, and it is necessary to embed the LCD screen into the headrest of the car through a modification process.

An example of the specific installation configuration list of the entire system is as follows:

Table 2 Configuration list of vehicle digital TV receiving terminal

In the actual installation, the installation process of the CMMB car TV box is roughly as follows:

Figure 6. Example of CMMB car TV box installation process flow

5 Summary and Outlook

The development route and direction of CMMB terminal technology are mainly reflected in the support and terminal realization of various data value-added services and interactive services. The technical standards, specifications and test verification work are the preparatory stage of the business, and the final realization of the technology should be completed through the application of the actual business, including the realization in different application scenarios and application fields.

In the field of automobiles, traditional car audio and video systems can only provide VCD, DVD audio-visual functions, and map navigation functions. CMMB is the first system independently developed in China to provide high-quality radio and television programs and information services for mobile receiving terminals. , not only can provide car owners with clear and smooth radio and TV program services, but also with the development of CMMB terminal technology and data services, data services based on CMMB broadcast network can be provided during normal driving, including real-time road condition query, financial information, car owners Care, information push and other value-added information services. The CMMB in-vehicle receiving equipment can improve the practicability and serviceability of the multimedia audio-visual navigation system, which can effectively fill the gap of radio and television coverage and services for the passengers, and meet the urgent needs of car owners to watch TV and listen to the radio anytime, anywhere.

For the CMMB vehicle after-installation system, it will inevitably develop from a non-standard to a standardized direction that meets the requirements of the vehicle level, and more solutions and products suitable for vehicle applications and easy to install will be introduced. At the same time, for the CMMB car digital TV system, it will not only be popularized and popularized in the after-installation market in the automotive field, but also will develop from the after-installation market that has been widely used to the pre-installation market that is standard in the original car.

The Links:   QM200E2Y-HB   GD50P1L120C6S   ALLIGBT.COM

The Causes of Howling of Power Inductors and the Introduction of Effective Countermeasures

“When running laptops, tablets, smartphones, televisions, and in-vehicle Electronic devices, you may sometimes hear a “squeaky” noise. This phenomenon is called “howling” and may be caused by passive components such as capacitors and inductors. The principle of howling of capacitors and inductors is different, especially the howling of inductors, the reasons are various and very complicated. In this article, we will introduce the causes of howling of power inductors, the main components of power circuits such as DC-DC converters, and effective countermeasures.

“

When running laptops, tablets, smartphones, televisions, and in-vehicle electronic devices, you may sometimes hear a “squeaky” noise. This phenomenon is called “howling” and may be caused by passive components such as capacitors and inductors. The principle of howling of capacitors and inductors is different, especially the howling of inductors, the reasons are various and very complicated. In this article, we will introduce the causes of howling of power inductors, the main components of power circuits such as DC-DC converters, and effective countermeasures.

Power Inductor Howling Causes

Intermittent work, variable frequency mode, load changes, etc. may cause human audible frequency vibration and sound waves are elastic waves propagating in the air, and human hearing can hear “sounds” in the frequency range of about 20 to 20 kHz. In power inductors of DC-DC converters, when alternating current and pulse waves of frequencies in the audible range of the human ear flow, the main body of the inductor vibrates. This phenomenon is called “coil noise” and is sometimes heard into the whistling phenomenon (Figure 1).

Figure 1: Power Inductor Howling Mechanism

As the functions of electronic equipment continue to increase, the power inductors of DC-DC converters have also become one of the sources of noise. The DC-DC converter is turned ON/OFF by switching devices, thereby generating a pulse-like current. By controlling the ON time length (pulse width), a stable DC current with a constant voltage can be obtained. This method is called PWM (Pulse Amplitude Modulation), and it is widely used as a mainstream method of DC-DC converters.

However, the switching frequency of the DC-DC converter is high, reaching several 100 kHz to several MHz. Since the vibration of this frequency is beyond the audible range of the human ear, no noise is felt. So, why does the power inductor of the DC-DC converter make a “creepy” whistle?

There are several possible reasons. The first possibility is to allow the DC-DC converter to work intermittently for the purpose of saving battery power, or to switch the DC-DC converter from the PWM method to the PFM (pulse frequency modulation) method. In case of operation in variable frequency mode. Figure 2 shows the basic principles of PWM and PFM.

Figure 2: PWM (pulse amplitude modulation) method and PFM (pulse frequency modulation) method

Howling caused by intermittent operation of DC-DC converters such as PWM dimming

For the purpose of energy saving, etc., the automatic dimming function of the backlight of the liquid crystal Display of mobile devices has introduced the DC-DC converter to work intermittently. This is a system that automatically adjusts the brightness of the backlight according to the ambient illuminance, thereby extending battery life.

There are various methods of dimming, among which, the method of controlling the on-time and off-time of the LED is called PWM dimming. The advantage of the PWM dimming system is that the chromaticity changes caused by dimming are less, and it is mainly used in the backlight of notebook computers and tablet computers.

PWM dimming makes the DC-DC converter work intermittently at a lower frequency of around 200Hz, and adjusts the brightness by repeatedly turning on/off. In a constant cycle of on/off, when the on time is adjusted longer, it will become brighter, and if it is shortened, it will become darker. In the intermittent operation of about 200Hz, the eyes basically do not perceive the backlight stroboscopic situation. However, since it is at the audible frequency of the human ear, when the intermittently operating current flows through the power inductor mounted on the substrate, the main body of the inductor will vibrate due to the influence of frequency, resulting in whistling.

Note: Duty Cycle

In a DC-DC converter, the ratio of the ON time to the switching cycle (ON time + OFF time of the switching device) is called the duty ratio. When PWM dimming LEDs, the ON time/(ON time + OFF time) is called the duty cycle and represents the brightness.

Howling Caused by Frequency Variable Mode DC-DC Converters

The characteristic of the PWM mode DC-DC converter is that its efficiency can be as high as about 80~90% in normal operation. However, under light load conditions such as standby time, the efficiency will be severely reduced. The losses due to switching are proportional to frequency. For this reason, constant switching losses occur at light loads, thus reducing efficiency.

Therefore, in order to improve this problem, a DC-DC converter that automatically replaces the PWM method with the PFM (pulse frequency modulation) method is used under light load conditions. The PFM method is a method of controlling the switching frequency with a fixed ON time in accordance with load reduction. Since the ON time is constant, by increasing the OFF time, the switching frequency will gradually decrease. Since switching losses are proportional to frequency, lower frequency can achieve higher efficiency at light loads. But the reduced frequency will enter the audible range of about 20~20kHz, and the power inductor will whistle.

howling caused by load

In order to conserve battery power, various power-saving technologies are used in mobile devices such as notebook computers, which may cause the inductor to whistle. For example, in order to balance low power consumption and processing power, the CPU of a notebook computer has a mode that periodically changes the current consumption. When the cycle is in the audible frequency range of the human ear, the power inductor may be affected by this effect. Howling is generated.

Note: The role of power inductors in DC-DC converters

Inductors allow direct current to flow smoothly, and for currents that change, such as alternating currents, through self-induction, electromotive force is generated in the direction of preventing the change, and it acts as a resistance. At this point, the inductor converts electrical energy into magnetic energy, accumulates it, and releases it after converting it into electrical energy. The magnitude of this energy is proportional to the inductor inductance value.

Power inductors, also known as power coils and power choke coils, are the main components used in switching power supply circuits such as DC-DC converters. Pulses are smoother.

Since a large current flows in the power inductor of the power supply circuit, the winding type is the mainstream product. This is because by using a magnetic material with high magnetic permeability (ferrite or soft magnetic metal) in the magnetic core, a high inductance value can be realized with a small number, and the product can be made more compact. Figure 3 shows the basic circuit of a DC-DC converter (non-isolated type and chopper type) using a power inductor.

Figure 3: Basic circuit of DC-DC converter (non-isolated type and chopper type)

Mechanism of Vibration and Noise Amplification of Power Inductor Body

Vibration that occurs in the body of the power inductor can cause howling when a current of frequencies in the audible range flows through the human ear. There are several possible reasons for the vibration and noise.

cause of vibration

1. Magnetostriction (magnetic strain) effect of magnetic core

2. ? Magnetic core magnetization leads to mutual attraction

3. Leakage flux causes winding vibration

The cause of noise amplification

1. Contact with other components

2. Leakage magnetic flux acts on surrounding magnetic bodies

3. Consistent with the natural vibration of the entire assembly including the base plate

Figure 4 summarizes the causes of vibration and noise amplification that lead to whistling in power inductors. The main contents of these reasons are explained below.

Figure 4: Vibration causes and expansion causes of whistling in power inductors

Various causes and effects of vibration

Cause of vibration?: Magnetic core magnetostriction (magnetic strain)

When a magnetic body is magnetized by applying a magnetic field, its shape changes slightly. This phenomenon is called “magnetostriction” or “magnetic strain”. In inductors with magnetic cores such as ferrites, the alternating magnetic field generated by the windings causes the magnetic core to expand and contract, and its vibration sound may be detected.

Figure 5: Magnetostriction (magnetic strain) effect of a magnetic body

Magnetic bodies are small-scale aggregates called domains (Figure 5). The magnetic moments of the atoms inside the magnetic domain are oriented in the same direction, so the magnetic domain is a tiny magnet with a constant spontaneous magnetization orientation, but the magnetic body as a whole does not exhibit the characteristics of a magnet. This is because the plurality of magnetic domains constituting the magnetic body are arranged so that the spontaneous magnetizations cancel each other, and thus appear in a demagnetized state when viewed from the surface.

When a magnetic field is applied to the magnetic material in this demagnetized state from the outside, the spontaneous magnetization directions of the respective magnetic domains are unified to the direction of the external magnetic field, so that the magnetic domain range gradually changes. This phenomenon is caused by the movement of the boundary between the magnetic domains, the magnetic wall. As a result, as the magnetization progresses, the dominant magnetic domain gradually expands its range, and finally becomes a single magnetic domain, oriented toward the direction of the external magnetic field (saturated magnetization state). In this magnetization process, tiny positional changes occur at the atomic level, while at the macroscopic level, it is manifested as magnetostriction, that is, changes in the shape of the magnetic body.

The shape change due to magnetostriction is extremely small, about 1/10,000 to 1/1,000,000 of the original size, but as shown in When an alternating magnetic field is applied, the magnetic body will repeatedly expand and contract and vibrate. Therefore, in the power inductor, the vibration of the magnetic core due to magnetostriction cannot be completely eliminated. Although the vibration level of the power inductor itself is small, when it is mounted on the substrate, if its vibration is consistent with the natural vibration number of the substrate, the vibration will be amplified, and a whistling will be heard.

Cause of vibration: The magnetization of the magnetic core of the magnetic body causes mutual attraction

Figure 6: The drum core and the shielded core attract each other causing howling

When a magnetic body is magnetized by an external magnetic field, it will exhibit the properties of a magnet and attract each other with surrounding magnetic bodies. Figure 6 shows an example of a fully shielded power inductor. This is a power inductor with a closed magnetic circuit structure, but there is a gap between the drum core and the shielded magnetic core (toroidal core), and noise is sometimes emitted from there. When an alternating current flows through the winding, the drum core and the shield core, which are magnetized by the generated magnetic field, will be attracted to each other by the magnetic force. If the vibration is within the audible frequency range of the human ear, noise will be heard.

The gap between the drum core and the shield core is closed with an adhesive, but in order to prevent cracking due to stress, a hard material is not used, and the vibration caused by mutual attraction cannot be completely suppressed.

Vibration reason: leakage magnetic flux causes winding vibration

In an unshielded power inductor without a shielded core, whistling does not occur due to the mutual attraction caused by the magnetization of the drum core and the shielded core. But other problems occur in unshielded products. Since the unshielded product has an open magnetic circuit structure, the leakage magnetic flux will have an effect on the winding thickness. Since current flows in the windings, according to Fleming’s left-hand rule, a force acts on the windings. For this reason, when an AC current flows through the windings, the windings themselves vibrate, which produces howling (Figure 7).

Figure 7: Magnetic Flux Causes Winding Vibration

Various causes of noise amplification

The cause of noise amplification?contact with other components

In a power supply circuit board where many electronic components and devices are mounted at a high density, if the inductor comes into contact with other components, the micro vibration of the inductor will be amplified, and a whistling will be heard.

Cause of noise amplification? Leakage magnetic flux acts on surrounding magnetic bodies

When there is a magnetic body such as a shielding case near the inductor, the magnetic body vibrates due to the influence of the leakage magnetic flux of the inductor, and howling occurs.

The cause of noise amplification?Consistent with the natural vibration of the entire assembly including the base plate

Under normal circumstances, the air vibration caused by the magnetostriction of a small magnetic core used in products such as inductors is basically not recognized as howling. However, when an inductor is composed of multiple components and is mounted on a substrate, it will generate a number of natural vibrations at frequencies that are audible to the human ear, and the vibration will be amplified to form a whistle. At the same time, if the number of natural vibrations of the entire module matches, there is a possibility that howling may occur after installation in the module.

Fig. 8 shows an example of analyzing the vibration of a board mounted with a power inductor using a computer simulator using the FEM (Finite Element Method). In the analytical model used, the power inductor is placed in the center of the substrate (FR4), and the long sides of the substrate are fixed on two sides.

Generally, there are multiple natural values ​​(natural vibration numbers) at which a structure resonates, and accordingly, there are various vibration modes. In this “power inductor + substrate” analysis model, as the frequency increases, various vibration modes appear for each natural vibration number. In the 1st, 2nd, 5th, and 18th vibration modes shown in Figure 8, the power inductor may be the vibration source. Among them, the vibration frequency of the first-order mode is basically the same as the vibration frequency of the power inductor itself. However, it is worth noting that the second-order mode, where the vibration in the Z direction (height direction) is more pronounced, has a high frequency in the case of a single power inductor, but has an extremely low frequency when it is fixed on the substrate.

The following summarizes the key points of how to counteract the noise of power inductors in DC-DC converters.

Point 1: Avoid the flow of audible frequency currents to the human ear

Avoiding the flow of currents at frequencies audible to the human ear is the most basic countermeasure.

However, when intermittent operation for the purpose of energy saving, or DC-DC converters in variable frequency mode cannot avoid energization at frequencies audible to human ears, please try the following measures to reduce noise.

Point 2: Do not place magnetic objects around

Do not place magnetic objects (shields, etc.) that may be affected by leakage flux near the inductor. When approaching is unavoidable, a shielded (closed magnetic circuit structure) inductor with less leakage flux should be used, and attention should be paid to the placement direction.

Key point 3: Stagger the number of natural vibrations

Howling can sometimes be reduced by staggering the number of natural vibrations or increasing the number of vibrations. For example, by changing conditions such as the shape, type, layout, and substrate fastening of the inductor, the natural vibration frequency of the entire assembly including the substrate changes. In addition, howling is common in large power inductors over 7mm in size. By using a small power inductor of 5mm or less, the natural vibration frequency will be increased, which can reduce the howling.

Key point 4: Replacement with metal integral molding type

As described above, in a fully shielded power inductor, the drum core and the shielded magnetic core are magnetically attracted to each other, and whistling occurs at the gap. Meanwhile, in unshielded power inductors, the wire vibration caused by the leakage magnetic flux can cause howling.

For this kind of power inductor whistling problem, it is an effective solution to replace it with a metal integral molding type. This is a power inductor that is integrally molded by embedding an air-core coil in soft magnetic metal powder. Since there is no gap, the magnetic cores are not attracted to each other. At the same time, since the coil is integrated with the magnetic body when the coil is fixed, the problem of winding vibration caused by magnetic flux can also be avoided. Not only that, TDK’s products also use metal magnetic materials with small magnetostriction, so vibration caused by magnetostriction can be suppressed, and it is expected to reduce howling by replacing unshielded or fully shielded products.

Figure 8: Example of noise evaluation for various types of power inductors

TDK’s metal-integrated power inductors can effectively deal with howling, and at the same time, have very little leakage flux, so they are also suitable for placement near signal lines, etc.

At the same time, TDK’s power inductors using ferrite cores feature a wider variety of inductances and can cope with higher inductance values. It has excellent mass productivity and is mostly used in various types of equipment.

The Links:   EPCS64SI16N   G150XG03V5   LCD-DISPLAY

Growing market demand for DDoS protection software by enterprises in 2020-2028

A Distributed Denial of Service (DDoS) attack is a malicious attack that disrupts normal traffic to a website by overloading it with more traffic than the server can handle. The main purpose of this cyber attack is to make the website inoperable.

These types of attacks have increased in recent years, driving the need for the best DDoS protection software solutions. Many unplanned data centers have been disrupted due to the impact of DDoS attacks, which are driven primarily by easy-to-use tools and potential profit from extortion.

These attacks typically target organizations directly, causing huge financial and reputational damage, so having a solid DDoS protection software solution is critical.

According to a report by Market Research Inc., the DDoS protection software market is expected to grow at a CAGR of +14% between 2020-2028.

　　Important statistics illustrate growing demand for DDoS software solutions

Due to the exponential growth of multi-vector DDoS attacks, coupled with the ease of DDoS rental services today, the demand for the DDoS software market will continue to grow.

These statistics below show that deadly DDoS attacks are on the rise and there is an urgent need to have a strong pool of DDoS protection.

DDoS attacks increased fivefold between 2014 and 2017;

In 2020, the total number of DDoS attacks reached 17 million, and the cost of one such attack was between $20,000 and $40,000 per hour; in the second quarter of 2018, the average size of such attacks reached a staggering 37 GBps, while By the first quarter of 2019, this number had soared to 100 Gbps, an increase of 967%; the largest attack to date was the attack against GitHub in February 2018 with an attack speed of 3TBps; in the third quarter of 2020, China was the Attacks on the hardest-hit countries, accounting for 83% of all attack incidents; DDoS activity increased by 542% between Q4 2019 and Q1 2020; Global DDoS Protection and Mitigation market size is expected to compound at 14% Annual growth rate growth – from $2.4 billion in 2019 to $6 billion in 2028.

　Factors Driving DDoS Protection and Mitigation Market Growth

There has been an increase in cyber-attack incidents in recent years, mainly due to a combination of factors such as the shift to digitalization, the increase in the number of connected devices, and the increased computing power of processors. Therefore, there is an urgent need to develop software solutions to mitigate these threats.

Major factors driving DDoS protection and mitigation market growth between 2020 and 2028 include rising market penetration of Internet of Things (IoT) and connected devices and demand from small and medium enterprises.

Organizations are aware of the impact of these attacks and want to have disaster recovery plans in place.

　How DDoS Protection Works

Many businesses are faced with the question – how can I protect my website from DDoS attacks? Today, many vendors on the market offer software solutions that protect websites from these attacks.

It uses algorithms and advanced software to manage incoming traffic to a website. Additionally, it denies access to illegal traffic and lets only legitimate people pass through.

　　DDoS Prevention Solutions

DDoS protection programs include purchasing and managing devices that can screen incoming traffic and defend against attacks. These are cloud-based security services and network appliances that mitigate incoming threats.

Between 2020 and 2028, hardware solutions and services are expected to grow to determine network connectivity and reduce downtime in the event of equipment or power failures.

　DDoS deployment model

In terms of deployment, the DDoS protection and mitigation market is segmented into cloud, on-premises, and hybrid. Among them, the hybrid model is expected to experience the largest growth between 2020 and 2028. It allows organizations to keep their critical data on-premises and move non-critical data to the cloud.

Recently, many DDoS attacks have gone undetected by on-premises or cloud-based solutions. Organizations cannot detect and block them; as a result, they are moving to a hybrid deployment model.

　Key Players Providing DDoS Detection and Mitigation Solutions

As DDoS attacks continue to grow, so do the players offering software solutions to detect and mitigate such attacks. Currently, the best players in the market include:

NETSCOUT

Indusface Managed DDoS Mitigation

Akamai Technologies

Cloudflare

Link11

Huawei Technologies

Verisign

Nexusguard

　Largest Market Share in DDoS Protection and Mitigation Market

According to a Market Research Inc data report, North America will hold the largest and most significant market share in the DDoS protection and mitigation market during 2020-2028. The main driver for this is that North America is one of the early adopters of DDoS protection and mitigation solutions and there are no solution providers in this space. Currently, many businesses in North America are implementing DDoS protection and mitigation solutions to overcome these threats.

Market growth in Asia Pacific (APAC) is also set to increase in view of rapid economic growth and stability in developing countries, and better regulatory reforms.

In recent years, DDoS attacks have become increasingly sophisticated as the threat and impact of network DDoS attacks have continued to evolve. While volumetric attack levels were largely flat, there was an increase in the number of application-specific attacks and targeted high-intensity attacks.

DDoS protection software solutions are designed to eliminate downtime from these attacks and enhance website availability to keep businesses productive and efficient. On-premises, cloud and hybrid software solutions for small, medium and large enterprises are all the way forward.

　

The Links:   6MBP50RA060-01   LM10V331

I’m in quarantine hotel, “made” an AI vision accelerator

“The previous article said that I had returned to China, but when I was still in quarantine in the hotel, I received a small toy from Xilinx. The unboxing video has been sent to Station B. Those who have seen it should know that this is actually Xilinx’s Kria KV260 Vision AI Starter Kit. As can be seen from the name, this thing is specially designed for vision applications. kit. Today’s article is to briefly introduce this product, and more importantly, to talk about some of my thoughts on this little toy. In one sentence, I have never played with such an FPGA board that can be developed without writing RTL.

“

The previous article said that I had returned to China, but when I was still in quarantine in the hotel, I received a small toy from Xilinx. The unboxing video has been sent to Station B. Those who have seen it should know that this is actually Xilinx’s Kria KV260 Vision AI Starter Kit. As can be seen from the name, this thing is specially designed for vision applications. kit. Today’s article is to briefly introduce this product, and more importantly, to talk about some of my thoughts on this little toy. In one sentence, I have never played with such an FPGA board that can be developed without writing RTL.

Let’s talk about the development board first. There are actually two boxes I received, one is the KV260 board, and the other is some necessary accessories, such as HDMI cable, SD card, power adapter, network cable, and a camera module. However, in order to make this board run, it is best to need a monitor (with HDMI or DP interface), or you can get a USB keyboard, USB camera, etc.

But neither of these two things is necessary. I have also seen someone send the video directly to the laptop monitor through the RTSP protocol using a network cable, and then open it with a player that supports RTSP. I don’t have a USB keyboard either, so I use the serial port UART for simple command transmission. There are some pits in it, and I will summarize it later. If you have a keyboard, just plug it into the board and type commands.

Modular System SoM:

New Ideas for Board Design

As for the Kria KV260 board, it actually has two parts, one is the FPGA card itself, which is the part covered by the red fan. Another part is the motherboard base board or also called the carrier board. This is a bit different from the development boards we usually use. Of course, many professional FPGA development boards also have expansion cards based on the FMC interface, but the FMC card is mainly used for relatively simple functions such as IO expansion, and the KV260 board and the above part are actually the main body of the FPGA, all other The interface parts are all on the big board below.

This design method is called SoM, which is System on Module. Its essence is actually a modular approach. We can design these core boards and motherboards separately to meet the needs of different application scenarios.

For example, for the development board, it definitely needs more interfaces and more debugging functions, so we can do more IO of the motherboard to facilitate our development.

On the other hand, for actual application and deployment, so many interfaces and debugging functions are not needed. Then you can use a minimal motherboard, keeping only the necessary functions. The FPGA board above remains unchanged.

In the same way, we can use the same motherboard to develop different FPGA devices, just replace the above board. Especially when you are familiar with the underlying resources, and new FPGA devices will come out in the future, you don’t need to buy a new board to re-familiarize yourself with, just change the FPGA board, which is very convenient.

Specific to this Kria KV260, the FPGA board above is called K26 SoM, and its main body is a Zynq UltraScale+ MPSoC. This is a 16-nanometer device containing a quad-core ARM Cortex-A53 processor and a series of SoC subsystems built around it, including an embedded GPU, memory controller, and various IO and bus control units, etc. . The programmable logic part, also known as PL, contains 256,000 programmable logic units, more than 1,000 DSP units, and a hard-core video Codec, which can support 4K60 frame video codec.

In addition, this K26 SoM has 245 IO pins, can support 15 cameras, 4 USB ports, and 40G Ethernet, and can provide 1.4Tflops of AI processing power.

It can be seen from these performance indicators that this is a SoM board specially designed for vision applications. I will send all the specific technical documents about this board to Knowledge Planet, and friends who are interested can take a look.

There are many interfaces on the motherboard: Ethernet, 4 USB3.0, HDMI, DP, JTAG, UART, etc., it should also be very convenient for us to carry out actual development and learning.

However, I think the biggest feature of this development kit is not just this modular hardware design method, but also its development method.

FPGA development without writing RTL

Friends who have played with FPGA should know that FPGA development is very troublesome, especially compared with these software development based on CPU or GPU. For example, if we want to play Raspberry Pi, connect the power directly to the peripherals, and then start writing python to develop.

In contrast, FPGA is completely two concepts. The traditional development method uses a special hardware design language Verilog, VHDL or SystemVerilog, which is very troublesome to learn; it also requires special development software, such as Xilinx’s Vivado or Vitis, this also requires a lot of learning costs.

Not only that, the compilation and debugging time of FPGA is very long. For a normal-sized industrial-grade FPGA design, the compilation time usually takes several hours, which discourages many developers and application manufacturers. In addition, developers have to learn to master the corresponding simulation test methods. In the previous article, I specifically summarized the FPGA learning route, divided into introductory articles and advanced articles. Interested friends can take a look.

All in all, on the one hand, FPGAs have various benefits. For example, Microsoft’s brainwave project uses FPGAs to effectively accelerate their real-time AI inference; but on the other hand. The learning and development method of FPGA is very complicated and cumbersome, which is also the most important factor restricting the large-scale development of FPGA.

However, the development method of this KV260 is very different. We don’t need Vitis or RTL language to quickly run a visual application. In fact, according to Xilinx, the first full configuration can be done within an hour. According to my experience, plus my experience of stepping on pits, the complete configuration of the system can be completed with a high probability of one hour.

KV260 Instance C Stepping on the pit summary

Xilinx has a dedicated page that walks through configuring the KV260 all the way up to running a smart camera application. Happily, this configuration process supports macOS, which is relatively rare in FPGA development. For the specific start-up process, you can watch the video. It’s just that there are many small pits in this operation and configuration process, here is a brief summary.

1. Step 4: Typo

There is a typo here, it should be

$ ls /dev/tty.*

2. Step 4: Set the number of COM ports and baud rate

In Xilinx’s web page, it is said that there will be 4 ports. But at least in my practice, I saw 4 COM ports. The second lowest numbered port is the UART port.

In addition, you need to pay attention to the setting of the baud rate, otherwise there will be garbled characters. The correct command is as follows:

$ screen /dev/tty.usbserial 115200

where 115200 is the correct baud rate.

3. Step 5: Crash when using Mac Terminal

When running this command, using the Mac’s default Terminal app crashes and fails to complete a normal installation. I later used an app called serial, which is similar to putty. You can go on normally. In addition, as long as you install it once, you can use the Mac terminal to run the next commands normally.

summary

As can be seen from this small experiment, using this Kria KV260 development kit, the realization of a vision acceleration application can be quickly completed. We can then add our own applications on top of this, or use this as a reference to develop our own acceleration designs.

In this process, it is not necessary to touch the underlying hardware content of the FPGA. If you are a software developer, you can use this platform to directly develop and accelerate upper-layer software and algorithms, which greatly reduces the threshold for using FPGA. This process is also very interesting, and at the same time, you can gradually come into contact with the knowledge details of the collaborative development of software and hardware, and exercise your skills in this area.

I have uploaded all the learning materials about Kria KV260 to Knowledge Planet, and friends who want to learn can start here. Xilinx also has many official training courses online and offline, you can pay attention to them. Also welcome to take a look at the FPGA learning route I wrote before, it should also be helpful to you.

The Links:   MG200H1AL2   M50100TB200   LCD-INVERTER