Research On 3KW Low Voltage And High Current Switching Power Supply

At present,the main way of heating in winter in northern provinces and cities in our country is to burn coal directly or indirectly,and various pollutants discharged into the atmosphere cause large-scale haze,which damages the health of the people.In order to replace the high-pollution coal,it is urgent to study a clean energy conversion method for heating.This topic is to study a low-voltage and high-current.The switching power supply device takes electricity from the public power grid,lowers the voltage through AC-DC,and then supplies power to the electrothermal film made of special materials,which converts electric energy into heat energy to achieve the purpose of heating.The circuit topology of the low voltage and high current switching power supply described in this paper consists of two stages: the first stage is BOOST active power factor correction circuit(APFC),and the second stage is full bridge step-down converter with input and output separated by transformer.In order to improve the power density and reduce the weight,the full bridge step-down converter in the latter stage adopts the high efficiency series resonant soft switching(LLC)technology.Because of the large output current,the post-stage circuit is designed to be composed of two full-bridge series resonant soft-switching bridges with 90 degrees staggered phase.The input and output are used in parallel to reduce the difficulty of power device selection.The control method is based on digital processing chip(DSP).The former APFC circuit adopts the control strategy of voltage outer loop and current inner loop,and the second APFC circuit adopts the control strategy of single cycle width modulation.The second APFC circuit adopts the control strategy of competition between voltage loop and current loop,and the second APFC circuit uses the combination of finite bipolarity frequency modulation(PFM)and width modulation(PWM).Through this project,the design method and control method of switching circuit with high power factor(PF value)are studied,and the design method and control method of series resonant soft switching circuit with parallel interleaving of 90 degrees are studied.Finally,based on the DSP chip 28035,a converter with output power of 3KW,maximum output voltage of 35 V and maximum output current of 90 A is designed and tested.