混合模式PFC芯片设计

Mixed Mode PFC Chip Design

随着科技的进步,电子产品的功能越来越完备,与此同时其自身的耗电量也在不断增加,开关电源通过对电源的细化管理达到了节能的目的。本论基于BCD工艺,设计了一款混合模式控制的AC/DC开关电源芯片。芯片重载时采用平均电流模式控制,通过核心控制模块乘除法器,采样前端电压电流信号,同时参考后端电压信号,经过误差放大器,得到平均电流控制环,与振荡器信号比较,经放大电路增大驱动能力,最终输出开关电源控制信号。轻载时采用临界模式控制,通过ZCD模块完成两种模式的相互切换,当检测到电感电流变为零时,通过改变数字逻辑控制电路的输出信号,使充电电感提前进入充电周期,从而实现了在不同负载条件下,该混合模式控制芯片都可以具有较高的转换效率。

With the progress of technology,the functions of electric products becomes more and more completely,at the same time the power consumption becomes increasing too.Through the fine management of the power,the switching power supply achieves the purpose of saving energy.This paper designed one AC /DC switching power supply chip by mixed model control,basing on BCD process,with the EDA tool Cadence. The mixed mode PFC chip uses average circuit mode control with heavy load.The core control module is multiplying unit,it can sampling voltage and current signals of front circuit,and at the same time referent the voltage signals of back circuit.With the help of error amplifier,it can get the average current control loop,and then the current loop signal compares with the oscillator signal,the signal output from the comparator through amplifying circuit to increase driver ability,finally getting the gate driver signal.The mixed mode PFC chip uses critical mode control with light load.The chip achieves mutual switching between average current mode and critical mode by ZCD circuit module.When the ZCD mode detects zero current signal of inductance,it will output signal to logic control circuit,and the output signal of logic mode will change,then inductance will enter into charging cycle ahead of schedule.So that the chip can get higher conversion efficiency under different load conditions.