Abstract: A resonant converter which may be employed as an electronic ballast for a gas discharge lamp, the converter being in the form of a full or half bridge circuit which includes at least a pair of power switches such as MOSFET's. The gates of the switches are actuated by substantially square wave cyclic gating signals having complementary duty cycle ratios and a frequency somewhat above a resonant frequency of the converter circuit. The energy supply to the lamp is variable in accordance with the duty cycle ratios of the gating signals. In order to avoid generation of high voltage and current transients in the converter when a change in operating state requiring a substantial change in duty cycle ratios of the gating signals is to be performed, as when effecting turn-on or turn-off of the lamp, the changes in the duty cycle ratio are ramped to occur incrementally over several cycles of the gating signals rather than directly to required final values of the duty cycle ratios.

Abstract: A power supply, including a resonant circuit having an output voltage and a current oscillating therethrough, and a voltage-fed half-bridge inverter producing a source voltage at an output coupled to the resonant circuit. The inverter is responsive to a driving signal. A driving circuit has a first input representing the sensed current oscillating through the resonant circuit, a second input representing the output voltage, and a reference voltage. The driving circuit includes compensation circuitry for maintaining the output voltage at the reference voltage and commanding a phase shift angle, and phase-shifting circuitry producing the driving signal based on a phase-shift of the sensed current. The amount of phase shift is commanded by the compensation circuitry.

Abstract: A power supply is disclosed which includes a resonant circuit, and a voltage-fed inverter producing an applied voltage at an output coupled to the resonant circuit, the inverter responsive to a driving signal. A driving circuit has an input representing the sensed current flowing through the resonant circuit and includes phase-shifting circuitry. The driving circuit produces the driving signal based on phase-shift of the sensed current by the phase-shifting circuitry.