An analysis of the phase-controlled dc-ac converter is presented. This converter has a pair of switches in each side of the primary and the secondary of the isolation transformer. The voltage conversion ratio is controlled by the phase difference between the two pairs of switches. The averaged equivalent circuit for low frequency is derived. The switching surge during commutation is much reduced by dividing the reactor into two parts. As a result, the transformer is miniaturized by increasing the switching frequency and the reactive energy can be easily recovered to the dc source. This dc-ac converter is especially suitable for small uninterruptible power supply (UPS) systems.
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