Application experience of power chips in intelligent car light control system

Overview of Intelligent Light Control System

This article introduces the application experience of power chips in intelligent light control systems, compares them with traditional technologies, and analyzes the technical advantages and development prospects of the intelligent diagnosis technology implemented in actual product applications in combination with examples.

The current trend of MCU and power electronics technology in intelligent light control systems is to replace traditional relays and fuses with intelligent power ICs, effectively realizing the protection and diagnosis of overheating, overvoltage, short circuit and other faults of light; MCU uses PWM modulation to control the voltage at both ends of the light to achieve the purpose of limiting the current of the light and extending the service life, and can easily realize automatic replacement when the light fails and greatly reduce standby power consumption. We use Infineon high-end switches

in intelligent light control systems. The following is a detailed introduction to its application experience in actual products.

New functions of Infineon chips

The intelligent light control system is powered by the 12V low-voltage and high-current system in the car, and all the above functions are realized by controlling the Infineon intelligent power switch through the MCU. In this light control system developed for the ROVER platform, Infineon's new generation of chips: BTS6142D and BTS5434G are used.

Among them, step-by-step current limiting is a new function with great practical significance. In the case of overload and short circuit, the chip will automatically reduce the current limit according to the increase of the tube voltage drop. This protects the chip from damage when frequent overload or short circuit occurs and the MCU fails to operate, greatly improving the service life of the chip under harsh conditions (as shown in Figure 1).

Figure 1 Relationship between step-by-step current limit control and MOS tube conduction voltage drop

In addition, Infineon's new generation of chips has extremely low standby power consumption. The standby power consumption of BTS5434G is only 5μA. In this way, the overall power consumption of the entire lighting control system is quite low.

Application design experience in actual products

In the design of actual products, the establishment delay time of the BTS6142D current sensing signal is 650μs, so the output feedback can avoid the large impact current when the high beam is started, but in the cold monitoring state, there is only a 1ms detection cycle, so the AD detection link of the MCU needs to be properly delayed and the speed is guaranteed. In addition, the BTS6142D input control needs to use the circuit shown in Figure 2 to be controlled by the I/O output signal of the MCU.

Figure 2 Control circuit diagram of BTS6142D

The impact current when the high beam is turned on is shown in Figure 3.

Figure 3 Impact current diagram when the high beam is turned on

In the design, changing the feedback signal output detection resistor value (R42) can adjust the level of the MCU input AD sampling signal to control the sampling accuracy within the full current range.

However, in actual situations, the relationship between the actual load current and the detection current is different. The actual detection is shown in the following formula:

The value varies according to different chips. In actual applications, it is recommended to connect a protective series resistor before entering the I/O:

This can improve the sampling accuracy. As shown in Figure 4, R30 Plastic Industry Network, R32.

Figure 4 BTS5434G control circuit diagram

BTS5434G can use its current sensing enable (Sense Enable) function to use the "line and" method for the current sensing output signals of multiple BTS5434Gs, and finally process them by the two AD ports of the MCU, which can effectively save MCU resources and save multiple detection resistors. As shown in Figure 4, in actual applications, a switch is also used to disconnect all the pull-up resistors used to automatically detect load open circuits in the standby state, further reducing the standby power consumption.

In the design, the current sensing enable function is started by the MCU, and the feedback signals of each channel of the chip are opened in turn, and sampled and detected respectively, which can realize time-sharing diagnosis in turn, save a lot of I/O resources, and reduce the cost of MCU.

Advantages and development prospects of intelligent diagnosis technology

Intelligent diagnosis technology can be realized after adopting the new generation of Infineon chips. By processing the AD sampling signal through the MCU, the current value and open circuit status of each light control load can be accurately obtained. In the thermal monitoring state, the MCU can easily start the switch and light up the specified light to replace the function of the fault light. By adjusting the frequency of the I/O output signal, the brightness of the specified light can be easily controlled. Hanyang Technology can extend the life of the bulb when the power supply voltage fluctuates, and low standby power consumption is about to become the standard requirement of the current automotive industry. It is difficult to obtain continuous and accurate current digital feedback signals using traditional technologies such as relays and early chips, and the peripheral circuits are also very susceptible to interference and increase standby power consumption. In addition, the traditional technology transmits much less light control information to the instrument and the driving computer through the CAN bus than the intelligent diagnosis technology.

With the increasing maturity of the automobile market, the perfect intelligent car light control system is no longer the patent of high-end cars, but has begun to become the standard of mid-range cars, becoming an important module that can reflect the technical content and configuration level of cars.