The Design Of Flyback Type Switching Power Supply

Along with the development of the power electronic technology, the application ofswitch power supply is more and more extensive.Flyback type switch power with itsdesign simple, small volume, light weight and the characteristics of highefficiency,which is widely used in all kinds of small power situation the electricalequipment and systems, the performance of the quality directly related to the wholesystem, the realization of the function with switching power supply has many types,including flyback type switch power. Because of the simple lines, need less, that canprovide many components road isolation advantages of output and widely used in smallpower field.Flyback type switch power supply by PWM control chip (general UC3842) andpower switch device (MOSFET) composition, with input rectifier filter circuit,ground-clamp protection circuit, high frequency transformers, output rectifier filtercircuit, feedback circuit, drive circuit and simplifying protection circuit, which iscomposed of transformer leakage of feeling and power device parasitic capacitance ofzero voltage switch to make the switch, and greatly reduce loss, thus reduce the volumeof the switch, and improve the efficiency.In this thesis, the UC3842chip as the core, and design a new flyback type220Vcurrent input, output voltage of the multiple fixed switching power supply, analyses theworking principle， according to the characteristics of the UC3842gives detailed circuitparameters and high frequency transformer design method. Through the analysis that isbased flyback small signal model, put forward a new type of flyback compensationcontrol method, based on the analysis of the UC3842flyback type switch power supplyused to output the feasibility of direct feedback. Compared to the traditional law controlmethod, which has the characteristic of fast response, the closed-loop gain, high stability,voltage ripple small, load rate and low voltage adjustment, adjust the advantages of lowrate, and the experiment has proved that the method of the good effect. Finally, throughthe use of SABER software, that build the circuit level simulation research, make amodel of flyback type switch power supply.