定频变占空比控制的倍压型宽增益LLC谐振变换器

Voltage Doubling Wide Gain LLC Resonant Converter Controlled by Constant Frequency and Variable Duty Cycle

传统LLC谐振变换器在宽电压范围应用时开关频率工作范围过宽,且电压调节性能较差。针对上述问题设计了一种定频变占空比的脉宽调制策略,该策略基于倍压结构的全桥LLC谐振变换器,通过改变原边侧开关网络工作在全桥和半桥的占空比,调节谐振槽输入电压;同时,控制副边侧双向开关,可改变整流网络工作在全桥和倍压两种整流模式的占比,最终实现4倍电压增益的调节范围。与变频控制相比,该策略下变换器负载和励磁电感对增益的影响较小,可选用较大的励磁电感来减小循环电流。变换器原边侧开关管实现ZVS导通,整流二极管实现ZCS关断。最后,仿真与实验验证了该调制策略下变换器的可行性。

The traditional LLC resonant converter has an excessively wide switching frequency operating range when applied in a wide voltage range,and the performance of voltage regulation is poor.To solve the above problems,a pulse width modulation strategy with constant frequency and variable duty cycle is proposed,which is based on a full bridge LLC resonant converter with voltage doubling structure.The input voltage of the resonant tank is changed by changing the duty ratio of the primary side switch network in full bridge and the half bridge;At the same time,under the control of secondary side bidirectional switch,the proportion of the rectifier network working in the full bridge and voltage doubler rectification modes can be changed,and finally achieve a quadruple voltage gain range.Compared with pulse frequency modulation,the influence of converter load and magnetizing inductance on the gain is weaker,and a larger magnetizing inductance can be selected to reduce the circulating current.The primary side switch of the converter realizes the ZVS turn-on,and the rectifier diode realizes the ZCS turn-off.Finally,simulation and experiment verify the feasibility of the converter under this modulation strategy.