Unity power factor boost converter with phase shifted parallel IGBT operation for medium power applications

Phase-shifted parallel (PSP) operation of IGBTs is proposed for unity PF boost converters, to increase both the converter power rating and operating frequency. This technique allows unity PF operation of medium power AC and DC motor drives, and switch mode power supplies from a single-phase, unregulated AC Supply, with minimum line current harmonic distortion. Since operating frequency is increased by integer multiples of IGBT switching frequency, the same core size for the boost inductor can be used to transfer larger amounts of power at the expense of additional power switching elements and a simple pulse separation circuit. Equal average current sharing is inherent in PSP operation strategy without any external circuits for equalisation. The design and implementation of a 28 kW, 40 kHz unity PF boost converter with two phase-shifted parallel IGBTs are presented. Advantages and disadvantages of PSP IGBT operation in increasing the power rating of boost converters are also given in comparison with other converter and power semiconductor parallel operation techniques.