How to quickly analyze the failure of switching power supply and repair it in time
To overhaul the switching power supply, start with the +5VSB, PS-ON and PW-OK signals to locate the fault area, which is an effective method for quick overhaul.
5VSB, PS-ON, PW-OK control signal
The switching power supply relies on the combination of +5VSB and PS-ON control signals to realize the power on and off. +5VSB is the power supply for the host system in the ATX standby state, as well as the working power supply for the circuit related to on-off automatic management and remote wake-up communication. In the standby and controlled start-up state, its output voltage is 5V high level. Use The purple line is led out from the 9-pin ATX plug. PS-ON is the control signal for turning on and off the power supply of the host computer or remotely waking up the power supply of the network computer. Different types of switching power supplies have different voltage values of 3V, 3.6V, and 4.6V when they are in standby. When the POWER switch on the panel of the host is pressed or the network wake-up is realized for remote booting, the PS-ON is grounded by the electronic switch of the main board after the controlled startup, and the green line is used to input from pin 14 of the plug. PW-OK is the output signal for the main board to detect whether the power supply is good or bad. The gray line is used to lead out from pin 8 of the plug. The standby state is zero level, and the controlled start-up voltage output is stable at 5V high level.
Off-line live detection power supply, first measure the PS-ON and PW-OK signals in the standby state, the former is high level, the latter is low level, and the pin 9 of the plug does not output other voltages except +5VSB. The second is to artificially wake up the switching power supply, and use a wire to short-circuit the 14-pin PS-ON signal of the ATX plug with any one of the ground terminals (3, 5, 7, 13, 15, 16, 17). The first step is the key to detection, wake up the ATX power supply from the standby state to the start-up controlled state, at this time the PS-ON signal is low level, the PW-OK, +5VSB signal is high level, the plug +3.3V, ±5V, There is an output of ±12V, and the fan of the switching power supply rotates. The above operations can also be used as a method for offline power-on verification of the purchased ATX switching power supply.
