Parallel resonant capacitor charging power supply operating above the

Abstract

A power supply for supplying a load capacitor and comprising a parallel resonant circuit having an inductor and a capacitor, a switching network operating at a frequency at or above the resonant frequency and applying alternating current to the resonant circuit and the primary side of a power transformer, a rectifier for rectifying the induced currents on the secondary winding of the transformer, and applying the rectified output to the load capacitor, and a controller for controlling the output of the power supply based on a comparison of the output voltage V.sub.out with a desired (setpoint) voltage V.sub.prog. The resonant capacitance may consist of the power transformer winding self-capacitance. The resonant inductance may consist of the primary winding of the power transformer. The controller provides switching signals to operate the power supply at the resonant frequency of the resonant tank circuit during a 'rapid rate charging mode' at which a maximum output current I.sub.out is applied to the load. When the controller senses that the output voltage V.sub.out is closely approaching the desired voltage V.sub.prog, it gradually increases the switching frequency from the resonant frequency toward a maximum frequency during a 'decreasing rate charging mode'. When the controller senses that V.sub.out equals V.sub.prog, it maintains the maximum switching frequency to provide a minimum output current I.sub.out.