Patent ID: 6147459
Filing Date: 2000-11-14
Classification: H05B,Y02B

Abstract:
A ballast for a gas-discharge lamp comprising:a frequency-determining oscillator circuit comprising a capacitor whose charge increases and decreases in an alternating fashion between a maximum value and a minimum value in time with the oscillation frequency of the oscillator circuit;an invertor circuit which converts a provided DC voltage at the frequency prescribed by the oscillator circuit into an AC voltage which is present at its output and to which a series resonant circuit for feeding the gas-discharge lamp is connected; anda charge injector circuit which has an injector current path from the gas-discharge lamp to the capacitor over which charge packets are conducted onto the capacitor at a frequency synchronized with the capacitor AC voltage, the size and/or phase angle of which packets are/is a function of the voltage present at the gas-discharge lamp and/or the current flowing through it;wherein the capacitor is connected to a recharging path over which the capacitor is charged or discharged while the oscillator circuit is in its respective astable state and wherein said recharging path is a resistive current path with a positive feedback characteristic.