Power supply

• US 5,528,484 A
• Filed: 09/13/1994
• Issued: 06/18/1996
• Est. Priority Date: 01/14/1993
• Status: Expired due to Fees

• Current Assignee: HPM Industries Pty Ltd. (Legrand SA)
• Original Assignee: HPM Industries Pty Ltd. (Legrand SA)
• Inventors: Hayashi, Koichi
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): HAN, YOUNGHUIE JESSICA
• Application Number:
  US08/302,822
• Time in Patent Office: 644 Days
• Field of Search: 363/47, 363/48, 363/19, 363/89, 315/247
• US Class Current: 363/47
• CPC Class Codes: H02M 1/425 using a single converter stage both for correction of AC input power factor and generation of a high frequency AC output voltage
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• CPC Class Codes: H05B 41/28 using static converters
• CPC Class Codes: H05B 41/285 Arrangements for protecting lamps or circuits against abnormal operating conditions
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A power supply which incorporates a high frequency inverter and which is suitable for use in conjunction with a florescent lamp. The power supply comprises a full wave rectifier (10) and a reservoir capacitor (12) connected across the rectifier for the purpose of providing successive half-cycles of the voltage waveform V2 across the capacitor with a minimum instantaneous voltage level greater than zero. A solid state switching device (14) and an oscillator (15) are connected in circuit with the reservoir capacitor. The oscillator generates a gating signal to the switching device. The switching device is arranged to provide an output voltage V4 which has a frequency determined by the applied gating signal V3 and which has a peak amplitude value which varies over successive cycles with the waveform of the voltage V2 across the reservoir capacitor.

Claims

1. A power supply comprising a full wave ac-to-dc rectifier, a reservoir capacitor connected permanently in current conductive relationship across the dc side of the rectifier, an inverter stage comprising a solid state switching device and an oscillator connected in circuit with the reservoir capacitor, the oscillator being connected in circuit with the switching device, being arranged to generate a gating signal at a frequency significantly greater than that of the voltage waveform across the rectifier and being arranged to apply the gating signal to the switching device, the reservoir capacitor having a capacitance value which causes the successive half-cycles of the voltage waveform across the dc side of the rectifier to have a minimum instantaneous value which is greater than zero but small relative to the maximum instantaneous value of the voltage waveform, and the switching device being arranged to provide an output voltage which has a frequency determined by the applied gating signal and which has a peak amplitude value which varies over successive cycles with the waveform of the voltage across the reservoir capacitor.

2. The power supply as claimed in claim 1 wherein a voltage supply for the oscillator is derived as a proportion of the voltage across the reservoir capacitor and wherein the reservoir capacitor is selected to provide a voltage which has an instantaneous minimum level sufficient to sustain operation of the oscillator.

3. A power supply for a fluorescent lamp and which comprises a full wave ac-to-dc rectifier, a reservoir capacitor connected permanently in current conductive relationship across the rectifier, an inverter stage comprising a solid state switching device and an oscillator connected in circuit with the reservoir capacitor, the oscillator being connected in circuit with the switching device, being arranged to generate a gating signal at a frequency significantly greater than that of the voltage waveform across the reservoir capacitor and being arranged to apply the gating signal to the switching device, the reservoir capacitor having a capacitance value which causes successive half-cycles of the voltage waveform across the dc side of the rectifier to have a minimum instantaneous value which is small relative to the maximum instantaneous value of the voltage waveform but sufficiently large to sustain excitation of the florescent lamp, and the switching device being arranged to provide an output voltage which has a frequency determined by the applied gating signal and which has a peak amplitude value which varies over successive cycles with the waveform of the voltage across the reservoir capacitor.

4. The power supply as claimed in claim 3 wherein a voltage supply for the oscillator is derived as a proportion of the voltage across the reservoir capacitor and wherein the reservoir capacitor is selected to provide a voltage which has an instantaneous minimum level sufficient to sustain operation of the oscillator.

5. The power supply as claimed in claim 4 wherein the reservoir capacitor is selected to provide a voltage which has an instantaneous minimum level of not less than 30 volts when the power supply is connected to a mains voltage power supply.

6. The power supply as claimed in any one of claims 3 to 5 wherein the oscillator is controlled to provide the gating signal at a rate of 20 to 50 kHz and with an ON time of 2 to 10 μ

S during each oscillation period.

7. The power supply as claimed in claim 6 wherein the oscillator is controlled to provide an ON time which increases with decreasing amplitude of the voltage waveform across the reservoir capacitor.

8. The power supply as claimed in claim 3 wherein the switching device comprises a FET in series with a high frequency inductor.

9. The power supply as claimed in claim 3 wherein the reservoir capacitor has a capacitance value which causes successive half-cycles of the voltage waveform across the dc side of the rectifier to have a minimum instantaneous value which is not greater than 50% of the maximum instantaneous value of the voltage waveform.