D8, C27, R40 for the peak absorption circuit , switch to suppress spikes damage within the U3 switch off when incurred.

 

2,5 V standby voltage regulator

 

+5 V voltage through R115, R116 partial pressure to U7 (TL431) (1) Reference voltage input pin through the internal circuit control voltage output. U7 work is characterized by ( 1 ) pin voltage increases , ( 3 ) pin voltage decreases. By Ul0 control U3 (4) pin voltage , the duty cycle adjust -chip PWM generator , forcing the secondary output voltage stability.

 

3 . Main power supply circuit during startup

 

Upon receipt of the signal power on the motherboard , the motherboard output on / standby control voltage (+5 V) via CON3 connector ( 7 ) feet added Vll (9014) b -pole, so that c extremely low potential , U9 (PC817) was optocoupler electrical conduction , 15V through R30, U9 secondary added V9 (C1008) b pole, so V9 conduction. V9 e pole +12 V output voltage through V4, R13 added Ul (6) feet. U8 (TL431), D4, Dll (ER106), R21, R22, R31, R52, R51 and so on mains voltage detection circuit , under normal circumstances , V4 ON state . AC 220V voltage is too low , U8 trigger pin ( 1 ) pin voltage drops , U8 deadline to make V4 stopped working for no vCC Ul work , the machine was in standby. After Ul (NCP1377B) main power chip ( 6 ) feet to get 12V working voltage , the internal oscillator to work from ( 5 ) pin output PWM signal is applied to the control electrode V2 , the V2 to work in high-frequency switching state. Changes in pulse voltage generated in Tl , Tl T1 primary voltage pulse induced voltage generated in the secondary by D12, D14, D19 (ST20N150) fast recovery diode rectifier , as E7, E8, E9, C8, El0 +24 V obtained after filtering / 6A voltage. The circuit U2 (LM34167) of DC-DC converters , which convert the voltage of +24 V to +12 V/3A voltage, the Ell, E14 filter output .

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