提高不对称半桥反激变换器轻载效率的数字化控制方法  

Digital control method for improving light-load efficiency of asymmetrical half-bridge flyback converter

作　　者：龙柏光 王俊峰[1] 王凯[1] 马聪[1] LONG Baiguang;WANG Junfeng;WANG Kai;MA Cong(Xi’an Microelectronics Technology Institute,Xi’an 710054,China)

机构地区：[1]西安微电子技术研究所,陕西西安710054

出　　处：《微电子学与计算机》2023年第9期106-113,共8页Microelectronics & Computer

摘　　要：传统的不对称半桥反激变换器(Asymmetrical half-bridge flyback converter,AHBFC)控制方法是采用互补PWM控制.在轻载时,由于其箝位管导通时间过长,初级侧具有很大的导通损耗和循环损耗,变换器效率较低.为了解决轻载效率低问题,提出了一种基于TMS320F28335的数字化控制方法.采用非互补PWM控制,结合电感伏秒平衡关系设计控制算法预估励磁电流的过零点,变换器工作于断续模式,从而大幅降低了变压器初级侧的导通损耗和循环损耗;在主开关管开启前,引入辅助脉冲,使功率开关零电压开通(zero-voltage switching,ZVS),实现了开关损耗的降低.分析了互补控制下轻载运行时的主要损耗,给出了所提控制方法的工作原理和设计流程,并将该方法应用于一台输入电压48 V,输出12 V/100 W的数字电源原理样机.实验结果表明,在轻载下,采用提出的控制方法,变换器能够实现两个开关管的零电压开通,相较于传统互补的控制方法,转换效率提高了3%~11%,空载电流降低了37.5%.The traditional control method of asymmetric half-bridge flyback converter(AHBFC)is to use complementary PWM control.Under light load,due to the long turn-on time of its clamping tube,the primary side has large turn-on loss and cycle loss,and the converter efficiency is low.In order to solve the problem of low light-load efficiency,a digital control method based on TMS320F28335 is proposed.Non-complementary PWM control is adopted.The zero-crossing point of excitation current is estimated by control algorithm combined with the inductance voltage-second balance relationship.The converter works in intermittent mode,thus greatly reducing the conduction loss and circulating loss at the primary side of the transformer.Before the main switch is turned on,the auxiliary pulse is introduced to make the power switch zero-voltage switching(ZVS),which reduces the switching loss.The main loss of light load under the complementary control is analyzed,the working principle and design flow of the proposed control method are given,and the method is applied to a digital power supply prototype with input voltage of 48 V and output of 12 V/100 W.The experimental results show that under light load,the converter can realize zero voltage turn-on of two switches with this control method.Compared with the traditional complementary control method,the conversion efficiency is improved by 3%~11%,and the no-load current is reduced by 37.5%.

关 键 词：不对称半桥反激 轻载效率 数字控制 软开关 

分 类 号：TN45[电子电信—微电子学与固体电子学]