全桥LLC谐振变换器的混合式控制策略

Hybrid Control Strategy of Full Bridge LLC Converters

基于全桥LLC谐振变换器提出了一种新颖的混合式控制策略。该控制策略结合了变频控制和定频控制的优点,电路简单,只需要一个控制芯片。在混合式控制策略下,全桥LLC谐振变换器能够工作在变频模式和移相模式,在全负载范围内实现开关管的ZVS而不需要辅助电路,整流二极管工作在ZCS状态因而其电压应力仅为输出电压,开关频率变化范围窄,因此适用于宽范围输入电压应用场合。本文对全桥LLC谐振变换器的工作原理以及工作特性进行详细分析,给出混合式控制策略的具体实现方案,并通过一台250～500V输入、3kW的原理样机验证了该混合式控制策略的可行性。

This paper proposes a novel hybrid control strategy of full bridge LLC resonant converter. The control strategy integrates the advantages of both variable frequency control and fixed frequency control. It can be easily implemented by using only one IC. Under this control strategy, full bridge LLC resonant converter can operate under both variable frequency mode and phase shift mode. All the switches can realize zero-voltage switching from nearly zero to full load without any auxiliary circuit, and the rectified diodes can achieve zero-current switching, so the voltage stress across them is only the output voltage. Moreover, the switching frequency range is relatively narrow, so the converter is very suitable for wide-input-voltage-range applications. The detail operation principles and characteristics of the converter are analyzed, and the implementation of the proposed hybrid control strategy is given and discussed. A prototype of 250-500V input, 3kW output is built to verify the effectiveness of the strategy.