Research And Design Of Non-electrolytic Capacitor LED Driver Based On Buck-Boost Bidirectional Converter

Leds have slowly replaced other Light sources as the dominant Light source in the market because of their small size,low power consumption,low cost and long life.In order to make LED work perfectly,a simple,reliable and efficient power supply is particularly important.LED load for the constant power load and the ac input power input power of two times the power frequency of pulse energy,cause the input power and output power imbalance,need a large capacitance value of electrolytic capacitors to balance the power input and the output power of pulse is poor,but the life of the electrolytic capacitor is very short,restricting the power of the whole life.Therefore,power coupling technology is studied to remove electrolytic capacitors or replace electrolytic capacitors with ceramic capacitors and film capacitors,so as to make the life of power supply match the life of LED.Research and design of LED power supply without electrolytic capacitor mainly includes Boost PFC converter and power coupling circuit.In this paper,Boost PFC converter is selected as the main circuit to complete voltage conversion and power factor correction,and buck-boost bidirectional converter is selected as the power coupling circuit to make it parallel in the output end of PFC converter to complete the absorption of pulsating power of double power frequency,so that the load can get constant power.For the control of power coupled circuit,the traditional open-loop control has the problem of poor anti-disturbance ability and inaccurate control.The double-loop control method has the problem of current loop tracking ability,so that the pulsating energy of double power frequency cannot flow into the power coupling circuit completely,and the pulsating energy of double power frequency still exists in the energy obtained from the load,which affects the lighting quality.For this reason,this paper proposes a Pulse Energy Modulation(PEM)method,and gives a detailed theoretical calculation process.Considering the cost and control precision,this paper adopts STM32 single chip microcomputer to make digital chip control,and calculates the duty cycle of switching tube by calculating the pulse energy that needs to be processed in each switching cycle of power decoupling circuit,so as to realize the accurate control of power coupling circuit.When the electrolytic capacitor is removed,the life of the power supply matches that of the LED load.Based on the above theoretical analysis,this paper firstly builds a simulation model through Matlab/Simulink software for verification.Finally,the experimental prototype was built for verification.