Ideas to solve the serious heat generation of MOSFETs

I do not know if you have found a problem, MOSFET act as a switching power supply equipment during operation sometimes serious heat, want to solve the heating problem of MOSFET, first we need to determine what causes, so we need to test, in order to find out where the problem is. Through the discovery of the MOS heating problem, go to choose the right key point test, is not consistent with the analysis, which is the key to solving the problem.

In the power supply test, in addition to measuring the control circuit of the other devices of the pin voltage as heavy, followed by an oscilloscope to measure the relevant voltage waveform. When we go to determine whether the switching power supply is not working properly, where to measure the power supply can reflect the working state is not normal, PWM controller output is not normal, the pulse duty cycle and amplitude is not normal, switching MOSFET is not working properly, including the transformer secondary and primary side and the output of the feedback is not reasonable.

Whether the test point is a reasonable choice is very important, the correct choice can be safe and reliable measurements, but also allows us to quickly troubleshoot to find out the cause.

Generally cause MOSFET heating is:

1: G-pole drive voltage is not enough.

2: The Id current through the drain and source is too high.

3: Driving frequency is too high.

So the focus of the test in the MOSFET, accurate test out its work, which is the root of the problem.

It should be noted that when we need to use the oscilloscope test, we should pay special attention to the gradual increase in the input voltage, if we find that the peak voltage or current beyond our design range, this time we have to pay attention to the heating of the MOSFET, if there is anomaly, you should immediately turn off the power supply, troubleshooting where the problem lies, to prevent the MOSFET from being damaged.