8 kJ/s high frequency capacitor charging power supply using parallel inverters

An 8 kJ/s, high frequency, capacitor charging high voltage power supply (HVPS) combining series resonant technology and pulsewidth modulation has been developed at Maxwell Laboratories, Inc. The power supply charges a capacitor at a rate of 8 kJ/s, and has a regulation of <0.1% with an efficiency of >90%. The HVPS is comprised of the following modules; EMI filter, inrush current limit circuit, input power rectification and filtering, parallel series resonant inverters, high voltage transformer and rectification, control and inverter drive. The key element in achieving the 8 kJ/s output in a simple and efficient manner is the use of parallel H-bridge minverters. Current sharing in the inverters is achieved via a balancing reactor. The use of IGBTs, a patent pending pulsewidth modulation control scheme for the series resonant inverters and a nominal 50 kHz resonant frequency make it possible to achieve regulation better than 0.1% for load rep-rates up to 2000 pps. In addition to superior regulation for high load frequencies, this control approach prevents the supply from being damaged if it is accidentally operated into an open circuit. The series resonantinverter topology is also inherently protected against short circuitssince it reflects a high impedence to the output.