Load Independent AC/DC Power Supply for Higher Frequencies with Sine-Wave Output

For ac voltage power supplies with a dc voltage input, a series inverter can be used. The advantage of sine-wave output and low switching losses is in contrast to the poor regulation of the output voltage and the load dependence of most series inverter circuits. An improved series inverter with a divided resonance capacitor is described. This inverter can operate from no load to full load and for inductive load as well as for resistive or capacitive load. It provides excellent output voltage regulation for all kinds of loads. A steady- state analysis of the inverter for reactive load is given as well as the optimal design for the divided capacitor. A second circuit formed from two of the above inverters provides a controllable output voltage independent of the input voltage and the load and thus overcomes a disadvantage of many series inverters. Both circuits were tested in experimental setups for an output frequency of 400 Hz, and the results are discussed.