How to quickly analyze the switching power supply failure and timely repair
Off-line test ATX power supply, first measured in the standby state of the PS-ON and PW-OK signal, the former is high, the latter is low, plug 9 feet in addition to output + 5VSB, the output of other voltage. Followed by the ATX switch power to wake up, with a wire to ATX plug 14 feet PS-ON signal, and any ground (3,5,7,13,15,16,17) in the short of a foot, This step is the key to the detection, the ATX power from the standby state wake-up to start the controlled state, this time PS-ON signal is low, PW-OK, + 5VSB signal is high, ATX plug + 3.3V, 5V, ± 12V with output, switching power supply fan rotation. The above operation can also be used as an optional ATX switching power supply off-line verification method.
1 simple by PFC type to points: active PFC-type power supply and passive PFC-type power supply.
2 active PFC power supply maintenance focus is to seize: the power of the main control IC, such as the CM6800 and its series of types of IC pin function, almost all of the faults are around the master IC pin function to carry out the analysis of.
3 passive PFC is relatively simple, only need to understand such as AZ7500, LM494, and other IC pulse width modulation signal process and the pin function, and understand the working principle of the comparator, such as the common AS339, LM339
4 Moreover, maintenance analysis depends on the individual's understanding of the knowledge of electronic circuits, power principles of understanding,
Specific analysis you can cite an example.
Maintenance of ATX switching power supply, starting from + 5VSB, PS-ON and PW-OK signals to locate the fault area, is an effective way to quickly check the line.
5VSB, PS-ON, PW-OK control signal
ATX switching power supply, rely on + 5VSB, PS-ON control signal combination to achieve the power on and off. + 5VSB is the power supply for the host system in the ATX standby state, as well as open and close the automatic management and remote wake-up communication related to the working power of the relevant circuit, in the standby and controlled start state, the output voltage is 5V high, The purple line leads from the ATX plug 9 feet. PS-ON for the host to open or close the power or network computer remote wake-up power control signal, different models of ATX switching power supply, standby voltage value of 3V, 3.6V, 4.6V different. When you press the POWER switch of the main unit panel or enable the network to wake up the remote power on, the PS-ON is controlled by the electronic switch of the motherboard after the start, and the green line is input from the ATX plug. PW-OK is for the motherboard to detect the power output signal is good or bad, the use of gray line from the ATX plug 8 feet lead, standby state is zero level, controlled start voltage output stable after the 5V high.
