This letter proposes a voltage balancing method for series-connected power devices in an LLC resonant converter. Series connection of power devices can allow an LLC resonant converter to operate in high-voltage applications. One key problem of series-connected power devices is the voltage imbalance due to device parameter deviations and gate drive delays. To achieve voltage balancing, an auxiliary module (AM) is connected in parallel with each power device. Each AM consists of a capacitor and an auxiliary switch with an antiparallel diode. The AM operates as a clamping circuit and voltage among the series-connected power devices can be shared evenly if the AM capacitor voltages are well-balanced. The AM capacitors are charged during the asynchronous period of the series-connected power devices. The excess energy of AM capacitors can be released by the freewheeling current during dead time in an LLC converter. By assigning a pulsing gate signal to AMs with higher voltages in every switching cycle, the AM capacitor voltages can be balanced. The proposed method will not induce additional power loss and does not affect the normal operation of power devices. Experimental results are provided to verify the effectiveness and feasibility of the proposed method.

中文翻译：

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LLC谐振转换器中串联功率器件的电压平衡方法

这封信提出了一种用于 LLC 谐振转换器中串联功率器件的电压平衡方法。功率器件的串联连接可以允许 LLC 谐振转换器在高压应用中运行。串联功率器件的一个关键问题是由于器件参数偏差和栅极驱动延迟导致的电压不平衡。为了实现电压平衡，每个功率器件并联一个辅助模块（AM）。每个 AM 由一个电容器和一个带有反并联二极管的辅助开关组成。AM 用作钳位电路，如果 AM 电容器电压平衡良好，则串联连接的功率器件之间的电压可以平均分配。AM 电容器在串联功率器件的异步期间充电。AM 电容器的多余能量可以在 LLC 转换器的死区时间内通过续流电流释放。通过在每个开关周期中将脉冲栅极信号分配给具有较高电压的 AM，可以平衡 AM 电容器电压。所提出的方法不会引起额外的功率损耗，也不会影响功率器件的正常运行。实验结果验证了所提出方法的有效性和可行性。