A new single phase buck-boost converter with unity power factor

A novel cascade buck-boost power convertor topology that offers a high degree of power factor correction is proposed. Low-frequency harmonic elimination in the input current is achieved and the power factor is improved to over 99% at power levels of 500 W in typical applications using very simple control circuitry. The buck mode has the same performance as the boost mode. A broad range of output voltage and output power is obtained with unity power factor. The analysis performed and the design equations presented should enable the design to be adapted to a wide range of output power. The effect of the cascade buck-boost inductance and current ripple on the size and efficiency of the converter power stage was taken into consideration. Due to the source impedance and the EMI (electromagnetic interference) filter, the generated high-frequency harmonics do not affect communication systems.<
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