基于可变关断时间断续电流模式的全桥逆变器轻载效率优化方法

Optimizing Method for Light-Load Efficiency of a H-Bridge Inverter Based on Variable Turn-Off Time Discontinuous Current Mode

工作于临界电流模式的逆变器在轻载时,开关频率显著上升,关断损耗大幅增加,效率明显降低。针对此问题,该文提出在逆变器输出功率下降至设定值时,将工作模式切换为断续电流模式(DCM),并根据输入电压、输出电压、输出功率改变关断时间以尽可能降低逆变器的开关频率,减小开关损耗,从而提升轻载时效率的优化方法。详细分析所采用的可变关断时间DCM的工作原理并推导理论计算依据。此外,还考虑了电流断续时电路寄生参数对电感电流的影响,通过比较器硬件限制电感电流峰值的方式,改善轻载电流的质量,并介绍基于此方式的变换器整机控制策略。仿真和实验结果表明,在轻载时采用可变关断时间的断续电流模式,逆变器效率得到明显提升,证明了所提优化方法的可行性和有效性。

When the inverter operates in boundary current mode under light load,the switching frequency increases significantly,the switching loss increases greatly and the efficiency decreases significantly.To solve this problem,this paper proposes that when the inverter output power drops to the set value,the working mode is switched to discontinuous condition mode(DCM);and the switching time is changed according to the input voltage,output voltage and output power to reduce the switching frequency and switching losses of the inverters,thereby improving light-load efficiency.The working principle of the DCM mode with variable turn-off time is analyzed in detail and the theoretical calculation is deduced.In addition,considering the influence of parasitic parameters on inductor current,the quality of light-load current is improved by triggering the peak value of inductor current through hardware comparator.Its control strategy is also introduced.The simulation and experimental results show that the discontinuous current mode with variable turn-off time improves the efficiency by about 2%at light load and the quality of the output current is pretty good,which verifies the proposed method.