Energy Analysis And Circuit Design For The Flyback Switching Power Supply

In all kinds of Switching Power Supply, flyback switching power is easy toimplement isolated multiple output small power, because of its simple structure,stable and reliable working state, and easy to control. With the advent of highlyintegrated smart chip, it greatly simplifies the flyback power supply design work.Improve the efficiency of the energy transfer of the flyback transformer, reducingcircuit loss and improve the flyback converter working efficiency has been popularand difficult. Study flyback energy transfer rate, the state of the circuit and affectthe output power factor has a certain theoretical guidance for the design of theflyback circuits and transformers.The switching Power Supply designed in this thesis mainly includes as followparts: the input AC/DC rectifier circuit, DC/DC flyback converter circuit, UC2845voltage and current double closed-loop control circuit, the RCD snubber circuit,flyback isolated transformer, output rectifier regulator circuit.In the flyback circuit designed in this thesis, choose UC2845chip as theswitch drive pulse width modulation generator module. The regulator circuit mainlythrough the UC2845internal error amplifier and peripheral circuits composed oferror of the integrator voltage loop, use negative voltage feedback to adjust thePWM duty cycle of the switch and stabilize the DC output voltage of the system. Acurrent loop current is within the UC2845another error amplifier integrator, pulsewidth modulation and over-current protection system. This voltage and currentdouble closed-loop system transient performance has high steady-state accuracy,especially with internal power switch current limiting capability.