Lamp ballast with frequency modulated lamp frequency

An electronic ballast for a discharge lamp, comprising:

• a high frequency section providing alternating lamp current to said lamp at said high frequency,
• a power input section receiving input power at a low frequency, and having a pulsating DC output,
• a circuit coupling between the high frequency section and the pulsating DC output for drawing current pulses from the power input section,
• characterized in that said power input section provides power only as a series of said current pulses at a repetition rate synchronized to said high frequency, arranged to minimize current distortion in the low frequency input power, and
• said ballast further comprises means for sensing a parameter which varies during each cycle of said low frequency to provide a sensed signal, and
• control means, responsive to said sensed signal, for frequency modulating said high frequency of the lamp current during each cycle of the low frequency power input to minimize low frequency modulation of the lamp current without significant increase in distortion of the current drawn by said power input section.

An electronic lamp ballast, comprising

• input means for connecting to a source of low-frequency AC power,
• a full-wave rectifier circuit connected to said input means for providing a pulsating full-wave rectified supply voltage at a supply voltage output,
• an energy-storage capacitor connected to said supply voltage output through an isolating diode,
• an inverter circuit connected to said energy-storage capacitor for providing high-frequency power at an inverter frequency,
• a resonance circuit comprising at least one inductance and one capacitor, and
• means for connecting at least one electrical discharge lamp to said resonance circuit and to said inverter circuit to operate said lamp with alternating current at said inverter frequency,
• characterized in that said means for connecting comprises a component connected to said isolating diode for supplying current pulsations to said energy-storage capacitor only at a pulse repetition rate synchronized to said inverter frequency, and
• the ballast further comprises:
• means for sensing a parameter which varies during each half cycle of said low frequency to provide a sensed signal, and
• control means, responsive to said sensed signal, for frequency modulating the inverter frequency during each half cycle of the low frequency power input to minimize variation in the lamp current without significantly increasing distortion of the low frequency current drawn by said power input section.

A method of providing high power factor current from a first-frequency alternating voltage source, comprising:

• providing a power input rectifier section receiving input power at said first frequency from said source, having an output whose waveform is substantially the full-wave rectified equivalent of the waveform of said alternating voltage source,
• providing a high frequency section operating at a second frequency which is substantially higher than said first frequency, for delivering alternating current to a load at said second frequency, and
• providing a circuit coupling between the high frequency section and said output for drawing current pulses from said power input section,
• characterized by selecting values for said circuit such that said circuit and high frequency section present an equivalent resistive impedance to said output, and
• drawing current from said output only as a first series of said current pulses at a repetition rate synchronized to said second frequency.

An electronic power supply for a load, comprising:

• a power input section receiving input power at a low frequency, and having a pulsating DC output,
• a high frequency section providing alternating current to said load at said high frequency, said high frequency being substantially higher than said low frequency, and
• a circuit coupling between the high frequency section and the pulsating DC output for drawing current pulses from the power input section,
• characterized in that said power input section provides power only as a first series of said current pulses at a repetition rate synchronized to said high frequency, arranged to minimize current distortion in the low frequency input power, and
• said high frequency section comprises an energy storage element for storing energy over a period at least equal to one half cycle of said low frequency, and means for providing charging current to said storage element as a second series of second current pulses at a second repetition rate synchronized to said high frequency.