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Precautions for high-frequency board
08 Jan,2025
For high-frequency drivers and driver boards with protection functions, if users want to test normal static (without main power) output waveforms, they need to pay attention to the following points:
1. If the power transistor IGBT or MOSFET is already connected in the circuit, adding the driving power supply and PWM input signal, the corresponding output signal can be seen at the output terminal with an oscilloscope.
2. If the power transistor is not connected and is only conducting an output test, then the two points that should be connected to the collector and emitter (or drain and source) of the power transistor must be short circuited. Because if the collector or drain is suspended, the driver or driver board will consider the power transistor to be in a short circuit state and activate the internal protection mechanism. At this time, what will be seen is the waveform of the protection signal output by the driver, which is completely different from the input PWM signal in terms of waveform shape and period. The main problem that IGBT needs to solve in application is how to implement relatively complete protection for IGBT in overcurrent, short circuit, and overvoltage situations. Overcurrent faults generally take a slightly longer time to overheat the power supply, so their protection is solved by the main control board. Overvoltage generally occurs when IGBT is turned off, and a larger di/dt generates a higher voltage on the parasitic inductance, which requires the use of buffer circuits to clamp or appropriately reduce the turn off rate. After a short circuit fault occurs, a huge current will be generated instantly, which will quickly damage the IGBT. The overcurrent protection of the main control board is simply too late and must be immediately protected by the driving circuit or driver.
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