1. Now make a three-way output power supply. The three ways are flyback topology power supply, and the output voltage of these three ways is 12v/0.6a respectively; 30V/0.6A; 150V/0.2A ,
2. Among the three circuits, the 12V output circuit is equivalent to an auxiliary power supply to provide voltage for the MCU control board, as well as a 12V voltage for the fan. In addition, it provides voltage for a control IC (st9s313c) chip behind the output, as well as a 12V voltage for the first pin of the control optocoupler;
3. The whole machine outputs 12V at first, and then controls the PS behind the power board through MCU_ On two pins, make st9s313c work, and the output low level of the third pin of this chip makes the optocoupler U7 work, so that the output voltage from pin 4 to pin 3 of U7 is 12V. The feedback output voltage of 24V on the output transformer of U7 is then sent to the Q1A triode to adjust the voltage. The base of the triode Q1A has a 15V zener diode, so that the output voltage of Q1A is about 12.9v, and the 13.7v voltage is sent to the seventh pin of the two tl3845p to make them work, However, the power consumption of power input is too large, which is about 18W. The power consumption drops to about 3W in 2-3 seconds. If you repeatedly let PS_ The 30V and 150V output caused by on conduction will cause the MOS tubes of these two circuits to burn out. The burned MOS tubes appear to be undamaged in appearance, but have actually been short circuited, and the sampling resistance of the 30V circuit is burned out,
I grabbed two output waveforms with light load with the frequency of 55KHz, 100kHz and 100kHz with the oscilloscope. Now I don't know why such a large starting static power consumption and the explosion of 30V and 150V MOS tubes?
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