基于PWM+PFM控制的两级DC-DC变换器效率优化

Efficiency optimization of two-stage DC-DC converter based on PWM+PFMcontrol

为了提高LLC谐振变换器宽输入电压范围和解决轻载时损耗大导致整体效率不高的问题,基于Boost-LLC两级式拓扑,提出一种全负载范围数字控制效率优化方法。根据不同的负载对前后两级建立双环控制,前级升压Boost电路通过脉宽调制(PWM)方式实现不同负载对应调整输出电压大小,并将其值作为后级LLC电路的母线电压;后级LLC谐振变换器在脉冲频率调制(PFM)下,通过对谐振频率进行调整,提高轻载时的效率,使其在全负载范围内的效率能够进一步提高。实验表明:数字控制效率优化方法使两级DC-DC变换器在整个负载范围能够实现高效率,并且整机转换效率不小于94%。

In order to promote the wide input voltage range of LLC resonant converter and solve the problem of low overall efficiency caused by large loss at light load,a digital control efficiency optimization method for full load range was proposed based on Boost-LLC two-stage topology.The dual-loop control was established for the front and rear two stages according to different loads,the corresponding adjustment of the output voltage for different loads was realized through pulse width modulation(PWM)for the front stage Boost circuit,and its value was used as the bus voltage of the rear stage LLC circuit.The resonant frequency was adjusted by the LLC circuit under pulse frequency modulation(PFM)to improve the efficiency at light load,so that its efficiency in the full load range can be further improved.The experiments indicate that the digital control efficiency optimization method enables the two-stage DCDC converter to achieve high efficiency in the full load range,and the overall conversion efficiency is not less than 94%.