一种具有恒电压增益和自动功率限制能力的双向LLC-DCX变换器及其调制策略

Bidirectional LLC-DCX Converter with Constant Voltage Gain and Automatic Power Limitation and Its Modulation Strategy

对于汽车低压辅助电源系统,双电源(48 V/12 V)系统架构已经成为12 V供电系统到48 V供电系统的过渡方案。为提高效率及实现电池组自动均压,研究了低压大电流的双向隔离DC-DC变换器拓扑及其控制方法。首先,提出了一种混合供电系统的架构,可以减小DC-DC变换器的功率容量以及电池组的数量;其次,结合所研究的架构,提出了LLC-DCX(DC-transformer)变换器的同开同关调制策略;再次,在传统LLC变换器中添加钳位二极管限制启动电流,并在过载情况下实现恒功率限制。最后,通过纯模拟控制,采用一台720 W(12 V/60 A)的LLC变换器样机,对变换器的调制策略、功率分配以及电池均压等特性进行验证,其结果表明了所提出方案的有效性。

The dual-power supply(48 V/12 V)system architecture has become a solution for the transition from a 12 V to a 48 V power supply system used in an automotive low-voltage auxiliary power supply system.To improve the efficiency and realize automatic voltage equalization of battery packs,the topology of a bidirectional isolated DC-DC converter with low output voltage and large output current and its control method are studied.Firstly,to reduce the power capacity of the DC-DC converter and the number of battery packs,a hybrid power supply architecture is proposed.Secondly,with the combination of the novel architecture,a synchronized turn-on and turn-off modulation strategy is proposed,which can achieve constant voltage gain of LLC-DCX converters.Thirdly,clamping diodes are added to the conventional LLC converters to limit the inrush current during start-up.In addition,constant power limitation is achieved under the over-load condition.Finally,experiments based on a 720 W(output of 12 V/60 A)LLC converter prototype were conducted th-rough pure analog control to verify the modulation strategy,power distribution and characteristics such as battery voltage equalization,which demonstrates the effectiveness of the proposed solution.