Adaptive Switching Frequency Circuits Design Of Flyback Power Supply Chip

The flyback converter with its simple circuit topology and control,low electromagnetic interference,and economic advantages are widely used in many fields such as mobile charger,the LED driver.As the energy conservation and environmental protection is becoming more and more important,the flyback conversion efficiency has become the focus of attention,this article in view of the flyback conversion efficiency optimization in this paper,a frequency adaptive circuit,can effectively improve the conversion efficiency.This article first introduces the low power flyback switch power supply development present situation and main design method,at the same time for all parts of the flyback type switch power supply system for the power consumption analysis,and combining the flyback power switch process presents a frequency adaptive technology,according to the input voltage and load conditions dynamically controlled switching power supply,when the input voltage is higher,lower switching frequency,the primary peak current basic remains the same,which can effectively reduce the wastage of the transformer,thus improve the efficiency of the flyback converter.Then studied the design scheme of adaptive frequency,and in accordance with the proposed scheme has carried on the system level and the specific design of circuit simulation.Finally,the thesis proposed based adaptive frequency circuit,designed a flyback switch power supply prototype,and the efficiency test and the analysis of working status,verify the effectiveness of the proposed adaptive frequency circuit.Paper designed chip adopted CSMC 0.25 m BCD process,under the simulation environment of Cadence completed the function simulation and verification.The simulation results show that,this paper designs the circuit in the input voltage exceeds 170V,the frequency is 55 kHz;When the input voltage is lower than 160V,frequency is 160 kHz,and primary peak current under the conditions of different input voltage basically remain unchanged,performance index has reached the design requirements.The prototype test results show that the 12V 1.5A prototype efficiency is more than 86.4%on average,compared with the traditional single frequency technology,promote efficiency of about 0.5%of the power supply system,meet the six levels of energy efficiency standards.