A single-stage resonant buck-boost ac voltage regulator

Abstract

This paper proposed a single-stage resonant buck-boost ac voltage regulator. The proposed regulator can output a voltage which is larger or lower than the input ac one and is dependence on depending on the instantaneous duty-ratio. This property is not found in the conventional single-stage ac voltage regulator that the ac output instantaneous voltage is always lower than the input ac voltage. The proposed ac voltage regulator uses a series-resonant circuit to configure adaptively the resonant voltage pulse trains. The proposed ac voltage synthesized the resonant voltage pulse trains following the input voltage amplitude to the synthesized sinusoidal waveform (SSW) before output filter. Because the SSW very closes sinusoidal waveform, the proposed ac voltage regulator can use a simple LC filter to filter the undesired harmonics and to get the sinusoidal voltage waveform with low total harmonic distortion (THD). The proposed ac voltage regulator is controlled by constant frequency pulse width modulation technique. Its control circuit is simple. A design example of a 600W proposed ac voltage regulator is examined to assess the system performance. Under rated output power, the power efficiency is over 91% and the total harmonic distortion (THD) is within 6%.