高输入电压双管Buck-Boost变换器控制策略研究

Research on Control Strategy of Two-Switch Buck-Boost Converter for High Voltage Application

在较高输入电压应用场合,采用同步控制的双管Buck-Boost变换器存在较大的开关损耗,而单管工作的双管Buck-Boost变换器又存在复杂的升降压过渡控制问题。分析了一种含有耦合电感的双管Buck-Boost变换器,介绍了该变换器在同步控制模式下的工作模态以及耦合电感抑制反向恢复损耗及减小开关损耗的原理,给出了耦合电感的设计方法,并在此基础上提出一种非同步控制模式,可以进一步减小磁性元件损耗。在设计输入相同的条件下,对两种模式下变换器电路参数计算进行了理论推导和实验比较。研究结果表明,相比同步模式,非同步模式不仅可以实现利用耦合电感降低二极管反向恢复损耗的作用,还可以减小耦合电感等效电流脉动量从而减小磁心损耗。同时该非同步模式在变换器升、降压过渡过程中只对一个开关管进行占空比调节,可以较好地实现升降压平滑过渡。

In high voltage application, there are serious switch losses in the two-switch Buck- Boost converter when both switches are switching in high frequency; while sophisticated control logic and complex compensation technique are needed for step-up/down smooth transitions when single switch scheme is used. In this paper, based on synchronous control scheme, the two-switch Buck-Boost converter adopting coupling inductor for alleviating switch losses is discussed. An asynchronous control scheme is proposed to reduce the core loss of synchronous control method with no increase of diode reverse-recovery losses. With the same conditions, comparisons between the two control schemes including theoretical calculation and experiment are illustrated. It is proved that the asynchronous control scheme could not only alleviate the diode reverse recovery losses, reduce the equivalent current ripple of coupling inductor, but also guarantee the smooth transitions between step-up and step-down.