Principles, design and implementation of a direct AC-to-AC power converter—Regulated electronic transformer

In the last three decades, the energy conversion market has been dominated by switching power converters due to reduction of size and cost of electronic components. This market includes four types of conversion: DC–DC, DC–AC, AC–DC, and AC–AC. While the first three types are applied directly in a single conversion, the AC–AC converter is comprised of two serial converters leading to an AC–DC–AC conversion. This article introduces, for the first time, a real direct single-stage AC–AC conversion electronic transformer. The single stage AC–AC converter is fabricated using a unique high efficiency topology, combined with the advantages of dual-stage power-quality protection. This single-stage AC–AC regulated electronic transformer is stabilized, controlled, protected, and can lock onto any line voltage (110 or 220 V) with a frequency of 45–65 Hz. Stabilization is achieved by fast pulse-width modulation technology, applied by two-way fast solid-state switches. The transformer is controlled by a 150 MHz digital signal processor and is fully protected against overcurrent and output short circuits. Our first stage transformer is a single-phase device with 5 kW power with an efficiency of better than 97% with one-tenth of the weight and volume of present conventional electromechanical transformers.