Discussion on Pulse Waveform in ISO 7637-2_Century Wisdom (Suzhou) Testing Technology Co., Ltd

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Discussion on Pulse Waveform in ISO 7637-2

Release time:

2023-03-20 15:12

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　　Discussion on Pulse Waveform in ISO 7637-2

Foreword

With the development of automobile industry, more and more on-board electronic devices are installed in automobiles. In addition to the lighting system, anti-theft system, and automatic air conditioning system in traditional cars, car navigation, audio-visual entertainment systems, and more complex car networking systems, auxiliary driving systems, and so on have been added. These electrical equipment will generate a large amount of electromagnetic interference during operation. For example, the interference pulses of the ignition system, generator and rectifier system are transmitted to the power supply system through conduction, coupling or radiation, thereby affecting the normal operation of electronic equipment. ISO 7637-2 summarizes typical waveforms for a series of wiring harness interference problems that have occurred during the development of automotive electronics.

One, Pulse1

Pulse 1 simulates the transient phenomenon that occurs when an inductive load is disconnected from the power supply (including a blown/unplugged fuse). It is suitable for a variety of DUTs that remain directly in parallel with inductive loads.

Fig.1 Schematic diagram of the circuit generating pulse 1

Fig.2 Pulse 1 waveform

Figure 3 Century Huize UCS 200N Actual Test Waveform

　　二，Pulse 2

Pulse 2a simulates a transient phenomenon caused by a sudden interruption of current in a device in parallel with the DUT due to the inductance of the harness. Pulse 2b simulates the transient phenomenon when the DC motor is acting as a generator and the ignition switch is turned off.

4 Schematic diagram of the circuit for generating pulses 2a and 2b

When the ignition switch (1) is closed and the load switch (7) is open, Pulse 2a is generated. Pulse 2a is also produced when the fuse is blown or pulled out and the switch bounces.

Fig.5 Pulse 2a waveform

Figure 6 Century Huize UCS 200N Actual Test Waveform

When the motor is running and the ignition switch (1) is turned off, pulse 2b is generated.

Fig.7 Pulse 2b waveform

Fig. 8th Century Huize UCS 200N Actual Test Waveform

Third, Pulse3a/3b

Pulse 3 simulates transients due to the switching process.

Figure 9 Schematic circuit diagram for generating pulses 3a and 3b

The switching process, including the fuse blowing or pulling out, will cause pulse 3 to be generated. The characteristics of these transient phenomena are affected by the distributed capacitance and distributed inductance of the wiring harness.

Fig. 10 Waveform of Pulse 3a

Figure 11-Century Huize UCS 200N Actual Test Waveform

Fig. 12 Pulse 3b Waveform

Fig. 13th Century Huize UCS 200N Actual Test Waveform

Four, test equipment

Figure 14 UCS200N

UCS 200N ultra-small car transient simulator, which can simulate car transient pulses 1,2 and 3a/3b.

The UCS 200N ultra-small vehicle transient simulator integrates the electrical fast transient/burst module, the micropulse module and the required coupling network in one device. The UCS 200N series simulators meet international standards and the standard requirements of many car manufacturers around the world. Depending on the model, the maximum current of the built-in coupling network can reach 200A.

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