High frequency board signal problem

HIGH FREQUENCY PCB board signal problem

High-frequency driver and driver board with protection function, if users want to test the normal static (without mains) output waveform, you need to pay attention to the following points:

1. If the power tube IGBT or MOSFET is already connected in the circuit, plus the drive power and PWM input signal, you can see the corresponding output signal at the output with an oscilloscope.

2. If the power tube is not connected, just do an output test, then the two points of the collector and emitter (or drain and source) of the power tube must be short-circuited. Because if the collector or drain is left floating, the driver or driver board will consider the power tube to be short-circuited and activate the internal protection mechanism. At this time, the protection signal waveform of the driver output will be seen, regardless of waveform shape or period. The input PWM signal is completely different. The main problem to be solved in IGBT application is how to implement perfect protection for IGBT under overcurrent, short circuit and overvoltage conditions. An overcurrent fault typically takes a little longer to overheat the power supply, so its protection is addressed by the main control board. Overvoltage typically occurs when the IGBT is turned off, and the larger di/dt produces a higher voltage on the parasitic inductance, which requires clamping with a snubber circuit or a suitable reduction in the rate of turn-off. After a short-circuit fault occurs, an extremely large current is generated instantaneously, and the IGBT is quickly damaged. The overcurrent protection of the main control board is too late, and must be immediately protected by the drive circuit or the driver.

Therefore, the design of the short-circuit protection function of the driver is perfect, which is essential for the safe operation of the power supply. It is necessary to get a driver circuit and test whether its short circuit protection function is perfect before use.