宽负载范围高效四开关Buck-Boost变换器的新型变频控制策略

A Novel Variable Frequency Control Strategy of High Efficiency FourSwitch Buck-Boost Converter for Wide Load Range

四开关Buck-Boost(FSBB)变换器采用四模式工作,有效降低了输入电压接近输出电压时电感电流的平均值,缓解了单模式控制、双模式控制和三模式控制效率低的问题。然而,传统的软开关或恒频硬开关控制方式难以在全负载范围内保持高效率工作。提出了一种新颖的变频控制策略,以提高宽负载范围内的效率。轻载时采用高频软开关控制,重载时采用低频硬开关控制,以提高宽负载范围下的整体效率。基于四模式FSBB的损耗模型,提出了针对负载电流的变频控制,并给出了详细的损耗分析。为验证分析的正确性,搭建了一台5 k W的实验样机。实验结果表明,在宽负载范围内,通过频率变化实现软开关和硬开关相结合的变频控制方式有效优化了整体效率,峰值效率达到98.5%。

The four switch buck-boost(FSBB)converter uses four-mode operation to effectively reduce the average value of inductor cur-rent when input voltage approaches output voltage.It alleviates the problem of low efficiency for single-mode control,two-mode control and three-mode control.However,the traditional soft switching or constant frequency hard switching control mode is difficult to maintain high efficiency during the full load range.A novel variable frequency control strategy is proposed to improve the efficiency in a wide load range.High frequency soft switching control is used under light load and low frequency hard switching control is used under heavy load to improve the overall efficiency under a wide load range.Based on the loss modelling of four-mode FSBB,the variable frequency control with respect to load current is proposed and detailed loss analysis is given.A 5 kW experimental prototype is built to validate the analy-sis.The experimental results show that during a wide load range,the variable frequency control mode combining soft switching and hard switching through frequency variation effectively optimizes the overall efficiency,and the peak efficiency reaches 98.5%.