基于有源钳位的高效单级开关功率放大器

High Efficiency Single Stage Switching Audio Amplifier Based on Active Clamp

在传统双极性移相调制(bipolar phase shift modulation,BPSM)半桥高频链逆变电路基础上,引入二极管–钳位电容电路和有源钳位桥(active clamping bridge,ACB)电路实现辅助换流,提出了一种双极性移相调制半桥单级开关功率放大器(single-stage switching amplifier,SSA)电路,称之为BPSM ACB-SSA电路。在周波变换器换流期间,滤波电感电流通过续流二极管续流,钳位电容吸收滤波电感能量,并通过ACB电路送回电源端。通过钳位电路实现了周波变换器开关管的零电压开关(zero voltage switching,ZVS),并实现了变压器副边电压钳位。通过优化参数设计,可以实现原边逆变桥与ACB电路的ZVS。与传统两级D类功率放大器相比,BPSM ACB-SSA电路具有更高的效率和更小的体积。详细分析了BPSM ACB-SSA电路工作原理及换流特性,给出了软开关的条件,并设计了一台峰值功率120W的实验样机,验证了理论分析的正确性。

A single-stage switching amplifier （SSA） based on bipolar phase shift modulation （BPSM） is proposed in this paper. Freewheeling diodes, clamping capacitor and active clamping bridge （ACB） are inserted to the traditional half bridge high frequency link inverter as auxiliary commutating circuits, the proposed circuit is called as BPSM ACB-SSA. Flow path for the filter inductor current is provided by the freewheeling diodes during the commutation dead time of cycloconverter and the energy of filter inductor is absorbed by clamping capacitor. The energy stored in clamping capacitor is returned to the power supply through ACB circuit and the clamping capacitor voltage is balanced automatically. Zero voltage switching （ZVS） condition of cycloconverter switches are created by auxiliary commutating circuits and the secondary voltages of the transformer are clamped. By optimizing the parameters design, ZVS of the primary switches and ACB switches can be realized. BPSM ACB-SSA has much higher efficiency and smaller size compared with two stage class-D amplifier. The detail operation principle and commutation characteristics of BPSM ACB-SSA are analyzed and the soft switching condition of power switches is given in this paper. Finally, experimental results from a 120W prototype are presented to verify the analysis of the proposed circuit.