IC7201 is the driving control of PFC circuit IC, T7201 is the PFC circuit in the energy storage transformer, Q7201 is the PFC circuit in the switch tube.

PFC circuit, the power supply circuit IC7201 IC7301, standby power supply output voltage 20V after the foot of added to the Q7701 IC7201, the internal circuit of the integrated block began to work, oscillation pulse signal through the internal circuit processing and amplification, the output from the 7 foot driven pulse rushed added to the Q7201 g to Q7201 in the switch state. Q7201 turn-on, the outflow of city electric bridge rectifier current by a T7201 the 3 feet a foot Q7201 D pole to S pole -}R216, R217 > A, power rectifier bridge anode, in T7201 primary winding produce energy and stored in the internal. Q7201 T7201 primary winding of the induction voltage is positive, the foot is negative, the positive voltage of the foot through the D7204 to the C7214 charge, so that the voltage on the C7214 to reach the stability of 390V above.

Composed R7220, R7223, R7230, R7233, R7224, R7225 PFC circuit output voltage sampling circuit, receives the sampling voltage and 1 foot of added to the IC7201, the output voltage of the internal circuit of the integrated block the stabilizing effect of the PFC circuit. Due to the resistance of the PFC sampling circuit greatly, SMD resistor, are very small in size, body resistance surface and the circuit board between the viscose is prone to leakage, resulting in the circuit is not working properly, encounter this kind of situation to the resistance to be removed from the circuit board, adhesive removal, the resistance to the in situ can.

Switch over current protection is composed of R7216, R7217 and integrated circuits. The pressure drop in the two parallel resistance would in switch tube the two resistor Q7201 current flowing through R7216, R7217, pressure and switch on the tube current is proportional to the, the switch current increases, the voltage increased. The voltage is added to the R7213 ALCL (4 pin current detection input end of the, when the switch current is too large, ALCL (4 pin voltage increased, 4 feet inside the overcurrent protection circuit, shutdown contactors, the feet without driving pulse output, to prevent damage to the switch tube.