US 5,404,082 A · High frequency inverter with power-line-controlled frequency modulation

Abstract

An electronic high frequency supply, such as a lamp ballast, having a full-wave rectifier, a storage capacitor charged to a voltage greater than the peak of the rectifier output, and an isolating diode between the rectifier and the storage capacitor. An inverter is connected to the storage capacitor, and has a high frequency inductive load circuit connected between the inverter output and a junction between the isolating diode and the bridge rectifier. A capacitor, connected to the junction in parallel with a series circuit formed by the isolating diode and storage capacitor, forms a high frequency resonance circuit with the inductive load circuit. Current is drawn from the rectifier only as a series of pulses at the inverter frequency. To minimize variation in the high frequency load current, the inverter frequency is varied linearly with but oppositely to the instantaneous value of the rectifier output voltage.

Claims19

Dependent claims

An electronic power supply for a high frequency load, comprising:

a high frequency section providing high frequency load current to said load,
a power input section receiving input power at a low AC frequency from a line, comprising a full-wave rectifier, an energy storage element, and an isolating element connected between the full-wave rectifier and the energy storage element, and
a resonance circuit carrying said load current, connected to the high frequency section, and to the power input section between said isolating element and said energy storage element, for causing current to be drawn from said rectifier, and to be delivered to said energy storage element, only as high frequency current pulses,
characterized by comprising means for sensing a full-wave rectified waveform of said low AC frequency to provide a sensed signal, and
control means, responsive to said sensed signal, for frequency modulating the frequency of the load current during each cycle of the low frequency power input to minimize variations in the load current over each said cycle of the low frequency power input without substantial distortion of the low frequency current drawn by said power input section.

2 more elements

An electronic ballast for a gas discharge lamp, 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,
an energy-storage capacitor connected to said supply voltage through an isolating diode,
a half-bridge inverter circuit connected to said energy-storage capacitor, having an output for providing high-frequency power at an inverter frequency,
a resonance circuit connected to the inverter circuit output, comprising at least one inductance, one high frequency capacitor, and said lamp, and
means for connecting said high frequency capacitor in parallel with a series combination of said isolating diode and said energy-storage capacitor for supplying current pulsations to said energy-storage capacitor only at a frequency related to said inverter frequency, current being drawn from said full-wave rectifier circuit, and said current pulsations being supplied to said energy storage capacitor, only at mutually different periods of time in each high frequency cycle, thereby to minimize harmonic currents from said source of low-frequency AC power,
characterized by comprising means for sensing a full-wave rectified waveform of said low AC frequency to provide a sensed signal, and
control means, responsive to said sensed signal, for frequency modulating the frequency of the lamp current over a range greater than 1.2:1 during each half cycle of the low frequency power input to minimize variation of the lamp current,
said frequency of the lamp current being varied as an approximately linear function of the full-wave rectifier voltage output during each half cycle of the low frequency power input, said frequency being reduced as said voltage output rises.

6 more elements

Dependencies are inferred from the claim text.

High frequency inverter with power-line-controlled frequency modulation

Life of this patent

High frequency inverter with power-line-controlled frequency modulation

Life of this patent

Abstract

Claims19