Design And Research Of Small Forward Digital Power Supply

Switching power supply is widely used in various electronic equipments due to the small space occupation,high working frequency and high efficiency.The traditional analog switching power supply has been developed for much time and have many different products.The analog technologis in switching power supply have been matured now.However,there are always defects that can not be conquered,with the increase of the use,the component become ageing,the accuracy will reduce and the anti-interference of power supply will be weak.These years,because of the growth of digital circuit,the research of repacing analog control with digital control has been widely concerned.In this paper,we study and design a small digital forward conveter power that controlled by C8051F340.This paper describes the operating principle of some basic topologies of switching power supply and some control methods.In hardware,we select the magnetic core by AP method.Based on the parameters of the magnetic core,the turns and the diameters of the primary and secondary windings are designed.Measure the parameter of transformer,we choose the best one.Choose the ring magnetic core to make inductance.Use Linear optocoupler PC817 to design sampling circuit.Convert the output voltage to the voltage which the chip can identified.Use IR2110 to design driving circuit,it can convert the PWM wave to the wave which can make the switch work.Measure the wave of input and output in the oscillograph.Choose the right components to build the forward topology.Design RCD circuit to reduce peak voltage between both ends of switch.In the aspect of software,choose PI algorithm as algorithm that control the PWM wave,it contains proportional operation and integral operation.Proportional control adjusts the output voltage according to the error,and integral control adjusts by previous output voltage,they control at the same time so that the output voltage can be more stable.Optimize the software,join integral separation,anti integral windup and dead time in the software.Integral separation procedure can make the proportional control alone at start-up,the power supply can be adjusted quickly.The anti windup procedure can prevent the system from getting out of control due to the one-way deviation.Dead time can be set in a certain range to reduceredundant operations.Design the PCB,weld the component on the PCB,measure the parameters of the power supply when it works.Through measurements,we conclude that the transformer,inductor,sampling circuit and driving circuit are all suitable for the power supply system.All the component can work normally.The algorithm can work rapidly.The output voltage that we need has small error and small ripple wave.When the load is change,the PWM wave can change automatically to maintain the output voltage.