Secondary-side controlled series resonant AC VRM using bi-directional switches

A new secondary-side controlled (SSC) series resonant (SR) AC voltage regulator module (VRM) is proposed to convert a high frequency AC distribution bus voltage to a tightly regulated low voltage DC output, e.g. 1 V, at a high efficiency to power next generation IC chips and microprocessors. The proposed simple topology combines the rectification and the regulation functions of an AC VRM into a single power conversion stage, which leads to a low conduction loss. The low-loss high-speed complementary heterostructure field effect transistors (CHFET) from Honeywell are used as the bi-directional switches in this topology. In order to achieve soft switching conditions for all the power switches and to eliminate the stringent gate drive timing requirement, the 'Combo-Switch' configuration using CHFET is proposed. Special design issues when using CHFETs as the bi-directional switches are discussed. A design example for converting a 30 V/ 500 kHz trapezoidal waveform AC bus to 1 V DC with 50 W output is presented. The estimated efficiency is 81.4%. The experimental results using the prototype CHFETs are also presented along with practical design considerations.