No output, normal fuse

This phenomenon indicates that the switching power supply is not working or has entered the protection state. Firstly, it is necessary to measure whether the starting pin of the power control chip has a starting voltage. If there is no starting voltage or the starting voltage is too low, it is necessary to check whether the starting resistor and the external component of the starting pin are leaking. At this time, if the power control chip is normal, the above check is performed. You can quickly find the fault. If there is a starting voltage, then whether the output of the control chip has a high or low transition at the instant of power-on, if there is no jump, it means that the control chip is bad, the peripheral oscillator circuit component or the protection circuit has a problem, and the control can be replaced first. Chip, then check the external components; if there is a jump, the switch is generally bad or damaged.