改进型准有源栅极控制电路研究与设计

Research and Design of Improved Quasi-active Gate Control Circuit

高压大功率变换器中如何降低半导体开关器件的电压应力是关键技术问题,而开关器件直接串联是重要的解决方案之一。在开关器件直接串联的高压电路中,开关器件的动、静态均压特性是关键指标。准有源栅极控制QAGC(quasi-active gate control)电路是具有代表性的串联均压拓扑,其特点是通过一个外部驱动源实现串联器件的动态、静态电压应力均衡,与此同时,可用于多个开关器件直接串联控制。研究表明,当QAGC驱动串联器件多于2个时,均压网络为上层器件提供的驱动电荷不足,降低串联器件的均压效果,严重时可能导致上层器件无法开通。针对这一问题研究了一种改进型QAGC电路,该电路将QAGC与一个辅助直流源相结合,辅助直流源在上层器件开通时刻提供额外驱动电荷,可保证器件的动、静态均压特性。分析了改进型QAGC的工作原理及设计方法,采用LTspice进行仿真并搭建实验平台进行验证,仿真和实验结果验证了电路拓扑的正确性。

How to reduce the voltage stress of semiconductor switching devices in high-voltage and high-power converters is a core technical problem,and the direct series connection of switching devices is one of the attractive solutions.In the high-voltage circuits with series-connected switching devices,the dynamic and static voltage-sharing characteristic is a key index.The quasi-active gate control(QAGC)circuit is a representative series voltage-sharing topology,which features balanced dynamic and static voltage stress on series-connected devices through an external drive source.Meanwhile,it can be applied to control multiple series-connected switching devices.However,when QAGC drives more than two series-connected devices,the voltage-sharing network cannot provide sufficient driving charge for the upperlayer devices.Hence,the voltage-sharing effect among the series-connected devices would be reduced,which may even lead to the failure of upper-layer devices.To solve this problem,an improved QAGC circuit is studied,which combines QAGC with an auxiliary DC source.The auxiliary DC source provides extra driving charge when the upper-layer devices are switched on,thereby ensuring the dynamic and static voltage-sharing characteristics of devices.The working principle and design method for the improved QAGC are analyzed.Simulations were carried out using LTspice,and an experimental platform was built.Simulation and experimental results verified the correctness of the circuit topology.