A Design Of Low Power Dissipation Power Chip Of PFM Based On The Primary Side Feedback

With the continuous progress of science and technology,the switching power supply is developing in the direction of high efficiency,small volume and more portable.In order to achieve output voltage,traditional secondary feedback control mode need to sample output voltage and compare with the precision reference voltage,feedback to the primary side circuit by the optocoupler signal.The primary side feedback control is sampling output winding voltage in the direct to achieve the purpose of isolation and precise control of the output voltage,while eliminating the surrounding auxiliary circuit,making the system simple,lightweight.At the same time,the PFM control mode is adopted to achieve very low standby power consumption.So,the research of AC-DC switching power supply on the low power consumption of the primary side feedback is of great significance.On the basis of the research on the power supply of the primary side feedback switch,this paper presents a low power primary feedback loop control system.According to the analysis and design of the system control loop,the chip module is determined and the performance index of the primary side feedback converter and the parameters of the important modules are set.To achieve high precision constant pressure control and line loss compensationof output voltage,the chip is using new constant pressure control loop,comparing with a log voltage and voltage sampling to control the switch frequency.Precise constant current control loop is used to realize high precision constant current control and primary inductance compensation.By using the cycle by cycle peak current detection control mode,the compensation of line network and the suppression of audio noise are realized.At the same time,it is using real-time detection of output voltage to aviod output voltage short and overvoltage.Based on the 0.8?m 40V high voltage BCD process,the circuit of the chip was designing and simulatingand through tapeout verification.Finally,testing the DC parameters and system of the chip,the results show that the functions and parameters reach the design target.