Practical circuit of push-pull converter switching power supply

The picture shows a practical circuit of a push-pull converter switching regulated power supply. CW494 is a modulator integrated circuit for a double-ended converter, including error amplifier, reference voltage source, clock oscillator, pulse width modulator and other circuits. Transformer T1 is a high-frequency transformer that transmits energy to the load. T2 is an excitation push transformer, which can amplify the two series of excitation pulses output by the CW494 pulse modulator and transmit them to the base of the drive and switch tubes in the push-pull conversion circuit after being amplified by the excitation push transistor. Transformer T3 transforms and rectifies the pulsating AC voltage on the sampling winding, and then transmits it to pin 16 of the pulse modulation circuit CW494 through the sampling resistor as the inverting input of the error amplifier. The switching power tube of this power supply uses fast series F461. Where voltage feedback occurs, the input and output are directly connected. If input and output need to be isolated, a photocoupler can be used.