Design Of High Precision Constant Current And Constant Voltage AC-DC Converter

In recent years,with the development of science and technology,more and more electronic products comes into people's lives,in order to make these electronic products work efficiently and reliably,high performance power management system is particularly important,high precision constant current and constant voltage power management system can not only provide stable power for the electrical equipment,but also be of great significance to the extension of life of batteries of electrical equipment.There is an urgent demand for high performance switching model power supply.Based on the CSMC0.5 ? m process,this paper designs a chip with high precision constant current and constant voltage performance.Firstly,this paper introduces the peripheral circuit structure,the internal logic diagram of the circuit,and the fundamental support module of this chip:Power supply starting circuit,bandgap reference,division of clock signal and initialization of this chip.In this paper,two aspects of performance,high precision constant current and high precision constant voltage are designed respectively.In order to achieve high precision constant current and constant voltage performance,the constant current feedback loop and constant voltage feedback loop are designed respectively.In the constant current feedback loop,The primary side current signal is obtained by the primary side sampling resistor and the primary side current signal is processed by the combination of the sigma-delta ADC and the digital multiplier,The average output current is calculated by them.The constant voltage feedback loop is sampled by the auxiliary winding.The output voltage is calculated by the combination of signal sampling control circuit and signal amplification control circuit,in order to improve the accuracy of the output voltage,the cable compensation module and the asymmetric signal generation module are also designed,together with constant voltage feedback loop circuit achieving high precision constant voltage performance.The output signals of constant current and constant voltage feedback loop are connected with constant current constant voltage switching module and generates the final control voltage.According to the value of the control voltage,The on and off signal of switching model power supply are generated by using variable slope delta wave technique and current peak control respectively.Finally,based on the cadence specter simulator,the simulation results show that the value of constant current is 1A,accuracy of the constant current is±4.2%,the value of constant voltage is 5 V,the accuracy of constant voltage is±3.8%.after packaging,the chip testing results show that value of constant current is lA,the accuracy constant current is ±4.7%,the value of constant voltage is 5 V,the accuracy constant voltage is ± 4.3%,which indicates that the testing results and simulation data is basically consistent.