Development of UPS using new type of circuits

Using a half-bridge converter and a half-bridge inverter respectively in the AC/DC conversion section and the DC/AC conversion section of an uninterruptible power supply (UPS) makes it possible to omit the isolating transformer and render the UPS both more efficient and smaller. But as using such a circuit necessitates storage batteries of very high voltage, it is in particular not suitable as a type of circuit for small-capacity UPSs of the 1 to 3 kVA class. We therefore conceived two techniques in order to lower necessary storage battery voltage: one that uses a bidirectional chopper, and one that uses an auxiliary, inverter. We incorporated these techniques into a 3 kVA UPS and a 1 kVA UPS respectively, allowing us to develop small, high-performance UPSs.<>