Direct test method with two-channel oscilloscope: First remove the oscilloscope ground, one probe is connected to AC input, the other probe is connected to DC output. Measure the time difference between the input AC voltage and the normal DC output. It is normal if the time is less than 2 seconds. For non-isolated power supply, please use isolated probe test (the same test method) to avoid short circuit explosion between input and output ground.
The input end hangs a voltage probe, the output end hangs a current probe, start, and compare the time of the difference between the two signals is the start time.
Use an oscilloscope to measure the input and output voltage respectively, under normal load conditions, use a switch to power supply, see from the switch closed (that is, there is input voltage) to the output voltage to reach a stable time is the start delay time of the power supply