Design Of Single-terminal Flyback Multi-channel Switching Power Supply

The power supply provides the necessary energy for all electrical and electronic products,and it requires continuous and stable output.Which is the most widely used in low-power products is switching power supply.Switching power supply is an important part of power electronics technology research,it will be different forms of power through the power converter,transformed into a variety of energy to meet the demand.Its remarkable feature is the high efficiency and energy saving,which conforms to the environmental protection and energy saving environment of all walks of life in today's society.Therefore,the researchers have paid great attention to the research,and the laboratories have been pushing forward the research on switching power supply.In this paper,single-ended flyback multi-channel switching power supply in-depth study.Flyback switching power supply has the advantages of simple circuit and can provide multi-channel DC output efficiently.The conversion efficiency is high and the loss is small.The transformer turns ratio is small.When the input voltage fluctuates in a large range,it can still be stable Output.Flyback switching power supply also has some problems,such as harmful output noise and large output ripple and so on.This paper analyzes the two main causes of the ripple output of the flyback switching power supply:(1)The difference in the core size of the transformer leads to the difference of the inductance value of the transformer,which leads to the large change of the output voltage ripple.(2)flyback transformer parameter design is not accurate,feedback adjustment signal response delay and power supply circuit design problems lead to instability of the output voltage.In order to solve the problem of transformer core size selection,three kinds of calculation methods of transformer design are studied.A suitable AP method is selected to find the closest core according to the calculated AP value table,which makes the output ripple smaller.For the design of the parameters of the flyback transformer is not accurate,first find the transformer core size table to get some parameters,after the relevant calculation of the other parameters of the transformer,and then adjust the parameters according to the actual test results,and ultimately make the switching power supply to produce a stable output.In order to solve the problem of feedback response signal lag,this paper designs a double closed-loop structure,which adds the current feedback inner loop to the traditional voltage loop control(that is,the sampling output signal is input to the main power supply chip to adjust the output PWM wave)The current signal is then converted to a voltage signal to the power supply chip to control the PWM wave.For the main circuit design problem,this paper uses the power chip FA13844,it has the characteristics of low power consumption,high efficiency,designed the main control circuit structure is clear and stable.After solving the above problems,we completed the flyback switching power supply schematic design and PCB production,welding the actual circuit,and hand-wound high-frequency transformers.By repeatedly correcting the transformer and circuit parameters,test the input Out of the voltage ripple,voltage regulation and load regulation,and ultimately completed a single-ended flyback multi-channel switching power supply.The main technical specifications of the multi-channel switching power supply are as follows: the output power is about 30W;the output voltage is + 5V / 1A,± 15 V / 100 mA,+ 15 V / 100 mA,+24V / 250 m A;the corresponding ripple is 19mV(+5V)?44mV(+15V)?34mV(-15V)?80mV(+24V).According to the test results concluded that the design of the switch power supply indicators meet the requirements of the output stability.