Introduction With the development of modern automotive electronics and the automotive industry, the level of intelligence of automobiles is getting higher and higher, and the requirements for the intelligence of various control systems such as vehicle lighting control are also getting higher and higher. New control functions are constantly increasing with market needs, such as central door lock, window lifting, rearview mirror adjustment, sunroof control, seat adjustment, ignition delay control, etc. Traditional relay control wiring is complicated, causing serious electromagnetic interference, which reduces the reliability of the system and also brings many problems to assembly and maintenance. Undoubtedly, the use of intelligent power devices to replace traditional relays and fuses will be the general trend. This experiment uses the intelligent power device BTS6143D from Infineon Technologies. BTS6143D is an intelligent high-side power switch developed by Infineon Technologies, designed to meet the harsh working environment and operating requirements of automotive electronic components. This paper will combine the intelligent power device BTS6143D to study and analyze its starting characteristics and short-circuit protection characteristics in the intelligent lighting control system [1]. This article first briefly introduces the basic structure of the intelligent power device BTS6143D, including its internal functional block diagram and circuit diagram in a lighting control system. It then describes the steps of a short-circuit test. Finally, through analysis of the test results, it demonstrates that when a short-circuit fault occurs in an automotive lighting control system, the BTS6143D provides faster and more effective protection than traditional relays and fuses. 1. Introduction to BTS6143D The BTS6143D is an N-channel FET power transistor designed by Infineon Technologies. It integrates a charge pump, current drive, and fault feedback function with load current detection (including overload, overtemperature, and short-circuit detection). It is a high-side intelligent power switch chip integrating SIPMOS® on-chip technology. The BTS6143D is suitable for the harsh operating environments of automotive electronics, with an operating temperature range from -40°C to +150°C. It uses 12V or 24V load control and is suitable for various resistive, inductive, or capacitive loads, especially loads with high inrush current, such as lamps. It can be used as an alternative to relays, fuses, and discrete circuit control methods. In addition, the BTS6143D has multiple protection functions: short circuit protection, overload protection, overvoltage protection, over-temperature shutdown, grounding and power failure protection, electrostatic discharge protection, and reverse power connection protection. The internal functional block diagram of the BTS6143D is shown in Figure 1: [align=center] Figure 1 Internal Functional Block Diagram of BTS6143D[/align] Pin Configuration and Function Description: Pins 1 and 5 are output pins, which need to be externally shorted; Pin 2 is an input pin, serving as the chip's control signal line; Pin 3 is the power supply voltage input pin, supplying power to the entire chip; Pin 4 is a fault diagnosis pin; under normal operating conditions, the output current of pin 4 is proportional to the load current. 2. Application of BTS6143D in Intelligent Lighting Control Systems Current vehicle lighting control mostly uses relay-driven methods. However, relay-driven systems have the following disadvantages: * Power relays require a large driving current from their excitation coils, consuming significant power and involving complex interface circuits; * The use of relays increases the size and weight of the controller; * Relays have relatively low switching frequencies, leading to contact bounce, which makes it difficult to meet the mechanical vibration requirements of vehicles operating under energized conditions. Furthermore, contact bounce affects relay lifespan and causes significant EMI; * It is difficult to effectively diagnose and protect against overheating, overvoltage, and short-circuit faults in vehicle lights; * They require the use of fuses to prevent overcurrent. However, once a fuse trips (blows), the circuit is completely cut off, requiring manual fuse replacement. With the development of the automotive industry, more and more intelligent chips are replacing relays and fuses in vehicle lighting control systems. Because the power devices used have comprehensive protection functions (overvoltage protection, overcurrent protection, overload protection, short-circuit protection, over-temperature shutdown, open-circuit detection, etc.), fuses and some discrete components are eliminated, reducing the size of the controller; simultaneously, fault diagnosis functions are enabled, identifying not only which device is faulty but also the cause of the error, thus facilitating repair. The application circuit of BTS6143D in the lighting control system is shown in Figure 2: [align=center] Figure 2 Application circuit of BTS6143D in the lighting control system[/align] 3. Test steps 3.1 Test conditions The open circuit voltage of the battery is 12.41V; the length of the load connection wire is about 1.5m (resistance R=0.12ohm, inductance L=3μH). The cross-sectional area of ​​the wire is 0.75 mm². A 55W vehicle lamp is connected. The measuring device is a Lecroy oscilloscope. The test ambient temperature is about 20℃. 3.2 Test circuit diagram For easy comparison, two sets of short circuit tests were arranged, as shown in Figure 3. (a) Figure is a schematic diagram of the test circuit of BTS6143D driving vehicle lamp, and (b) Figure is a schematic diagram of the connection of relay driving vehicle lamp. [align=center]Figure 3 Schematic diagram of the test circuit[/align] The specific meanings are shown in Table 1 below: [align=center]Table 1 Measurement point colors and meanings[/align] Note: - IIS is the short-circuit current; - VIS is the fault diagnosis pin voltage, i.e., the voltage of pin 4; - VOUT is the output voltage; - VIN is the input voltage. 3.3 Starting characteristic test The starting characteristic test is divided into cold start test and hot start test. The so-called cold start test is the situation where the headlights are turned on after being turned off for a long time; the hot start test is the situation where the headlights are turned on again shortly after being turned off, before the filament has cooled down. Since the resistance of the headlight filament has a positive temperature coefficient, the cold start and hot start characteristics of the headlights show a large difference. 3.3.1 BTS6143D Driven Headlight Starting Characteristics As shown in Figure 4(a) of the test results, during a cold start, the filament temperature is low, resulting in low resistance and a large instantaneous surge current, reaching up to 30A. After the headlight has been on for a period of time, the filament resistance gradually increases with the rise in filament temperature. When the headlight is turned off and restarted before the filament has cooled down, as shown in Figure 4(b), the instantaneous surge current is significantly reduced to less than 10A. The significant difference in instantaneous surge current between cold and hot starts of the headlight may accelerate bulb damage. Based on the test results, it is recommended to use pulse width modulation (PWM) to achieve a soft start process for the headlight, allowing the filament to heat up gradually and reducing the instantaneous surge current. The test results also help explain why the probability of headlight damage is higher immediately after being turned on. [align=center]Figure 4. Test results of BTS6143D-driven vehicle headlight starting characteristics[/align] 3.3.2 Relay-driven vehicle headlight starting characteristics The instantaneous surge current of the relay-driven vehicle headlight during cold start is 36A, and the instantaneous surge current during hot start is 10A, as shown in Figure 6, test results of starting characteristics (a) and (b). Due to the easy vibration of the relay contacts, it can be found that its starting process has obvious voltage and current vibration. This vibration not only affects the service life of the relay, but also poses a great hidden danger to the safe starting of the headlight. The starting process of the headlight driven by BTS6143D is relatively smooth, thus highlighting the superiority of using BTS6143D to drive the headlight. [align=center]Figure 5. Schematic diagram of relay-driven vehicle headlight starting characteristics test[/align] 3.4 Short circuit characteristic test During the operation of the vehicle system, the surrounding environment is complex and there are many metal wires. Although all wires are insulated, after a long period of operation, without necessary maintenance, various problems will inevitably occur. This experiment divides the short-circuit characteristic test into two common scenarios: 1) A short circuit occurs before the system is powered on, which is called short-circuit type I, or inherent short-circuit test. This is used to simulate the situation where the system is short-circuited before the car is running; 2) A short circuit occurs during vehicle operation, which is called short-circuit type II, or acquired short-circuit test. This is used to simulate an output short circuit caused by unexpected reasons under normal vehicle operation conditions. The following will describe these two short-circuit test scenarios. 3.4.1 BTS6143D Driven Headlight Inherent Short Circuit Test The BTS6143D has short-circuit detection and automatic shutdown functions. Its default short-circuit detection conditions are: the voltage difference between the drain and source of the power transistor VON > VON(SC) (typical value 3.5V), and t > td(sc) (typical value 650μs). As shown in Figure 7, VON = Vpowder - Vredon varies from 6V to 12V. The short-circuit fault detection and shutdown time is approximately 650μs. After short-circuit shutdown, the BTS6143D no longer outputs. In the short-circuit test in this paper, the maximum short-circuit current was 110A. This value is related to the resistance of the wire; the higher the resistance of the wire, the lower the corresponding short-circuit current, and the safer the BTS6143D is. In this sense, the longer the wire, the less likely the BTS6143D is to be damaged. However, if the wire is too long, most of the battery voltage drops across the wire, easily causing VON. [align=center]Figure 6 BTS6143D Inherent Short Circuit Test Results[/align] 3.4.2 BTS6143D Driven Vehicle Light Post-Short Circuit Test As shown in Figure 8, after a short circuit fault occurs, as the current rises, VON = Vpowder - Vred gradually increases. When VON > VON(SC) (approximately 140μs after the short circuit), the BTS6143D recognizes the short circuit fault and begins to shut down. After 30μs, the current drops to zero. During the entire short circuit process, the maximum short circuit current can reach 180A, and its peak current is related to the wire resistance. The smaller the wire resistance, the larger the peak current, and the instantaneous large current can easily damage the BTS6143D chip. When the wire resistance is too large, VON needs a long time to reach (or may never reach) VON(SC), thus the short circuit protection function is less effective, essentially becoming overheat protection. Additionally, because the inductance of the conductors can cause the drain voltage (pink line) of the FET to exceed the battery voltage and the source voltage (red line) to fall below 0V, the voltage between the drain and source may exceed the maximum allowable operating voltage of the BTS6143D. Therefore, low-inductance conductors should be selected. [align=center]Figure 7 Schematic diagram of the short-circuit test results of BTS6143D[/align] 3.4.3 Relay-driven vehicle light short-circuit test To compare with the short-circuit protection function of the BTS6143D, a short-circuit test was conducted using a relay to drive the vehicle light. The results are shown in Figure 9. During this short-circuit process, the maximum short-circuit current reached 100A, and the battery voltage was pulled down to nearly 4V. The fuse blowing protection time was 60ms, which is much longer than the short-circuit turn-off time of 650μs of the BTS6143D. It can be seen that in the event of a short-circuit fault, the use of intelligent power switches provides faster and more effective protection for the system than traditional relays. [align=center]Figure 9 Relay Short Circuit Test Results[/align] 4. Conclusion Through the above comparative tests, the following conclusions can be drawn: using the BTS6143D to drive high-power automotive headlights is a better choice. Using the BTS6143D, pulse width modulation (PWM) can be employed to control the start-up and operation of the headlights, thereby more effectively suppressing the instantaneous surge current during headlight startup and effectively extending the headlight's lifespan. Most importantly, it can shorten the protection time for short-circuit faults, providing faster and more effective protection for the headlight control system. Unlike fuses, the BTS6143D's short-circuit protection does not damage the chip. After the short-circuit fault is cleared, the system can return to normal without replacing the chip, which facilitates maintenance and repair.