High frequency oscillator-inverter with improved regenerative power supply

Claim 1

A power supply for an electric discharge lamp comprising: a pair of input terminals for connection to a low frequency source of AC supply voltage, a rectifier circuit having input means coupled to the input terminals and an output at which a fluctuating unidirectional voltage is developed, a high frequency oscillator-inverter circuit including first and second switchable transistors and a resonant circuit which includes a capacitor and a first winding of a transformer, a frequency-dependent ballast coupling circuit including a second winding of said transformer for coupling high frequency oscillations generated in said high frequency oscillator-inverter circuit to an electric discharge lamp, means, including a third winding of said transformer, for applying out of phase drive signals to control electrodes of the first and second switchable transistors to alternately trigger the transistors into conduction, means, including an inductor, for coupling said oscillator-inverter circuit to said output of the rectifier circuit, an auxiliary power supply comprising a second rectifier circuit that includes a rectifier element, a second capacitor coupled to the rectifier element for deriving a DC voltage sufficient to maintain oscillation of the oscillator-inverter circuit, and means for supplying to said second capacitor, via said rectifier element, a pulsating voltage having an inverted polarity relative to the polarity of current flow in said inductor, and means coupled to said second rectifier circuit and to said oscillator-inverter circuit for switching said auxiliary power supply into and out of circuit with the oscillator-inverter circuit as a function of the voltage level of said fluctuating voltage at the output of the first rectifier circuit.