Theoretic analysis and experimental study of a novel bridgeless partial active PFC

For the sake of energy saving, harmonic current suppression and drive performance improvement, inverter-fed air-conditioner drive systems are used more and more extensively, and the selected motors include ASM,BLDCM and PMSM. Generally, the front stage AC/DC converter of inverter aircon is complete active power factor corrector (PFC), which can bring about better correction effects. Whereas the traditional boost complete active PFC is designed to provide higher output DC voltage, consequentially causing high switching stresses to power switches and the resultant lower conversion efficiency, which makes it disadvantageous to high power applications. Herein, a novel synthesized active PFC scheme is presented here, by integrating active PFC and passive PFC technologies. Its features are briefly described below: bridged PFC topology is replaced by bridgeless PFC topology, a high value inductor is used at the AC mains side, and the power switches are kept in off-state for pi/3 or pi/6 by the side of input voltage peak value, making a condition for natural rectifying and inductor freewheeling. In other time zones, the power switches are switched on- and off according to control strategy. It is found that the partial PFC is evidently characteristic of series compensation, which is a method of increasing power factor. Principle of the partial PFC is analyzed theoretically and proved by simulation and implementation. The ST7MC1K2 is selected as the only MCU, and the power circuit mainly consists of bridgeless PFC (BLPFC) power module FPAB50PH60 with overload and over-current protection functions. As a result, the harmonic current components of resulting input current are consistent with IEC61000-3-2 at different power outputs, and the input power factor is high up to 0.99 at medium and higher power outputs. The efficiency is higher than that of traditional complete PFC by 2-3%, up to 98%. Under light loads, the averaged DC voltage approaches the peak value of input voltage. Under heavy loads, the averaged DC voltage will not be lower than the peak value by 40 V. The ripple voltage peak to peak value is much lower than that of passive PFC. And the partial PFC has promising application prospects, specially suitable for applications with step-down conversion and high power factor, such as high power inverter-fed household appliances and communication switching mode power supply.