Two-wire dimmer circuit for a screw-in compact fluorescent lamp

  • US 8,704,459 B2
  • Filed: 07/19/2012
  • Issued: 04/22/2014
  • Est. Priority Date: 10/31/2007
  • Status: Active Grant
First Claim
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1. A dimmer switch adapted to be coupled between an AC power source generating an AC line voltage and a lighting load, the dimmer switch controlling the intensity of the lighting load within a dynamic range bounded by a high-end intensity setting and a low-end intensity setting, the dimmer switch comprising:

  • a controllably conductive switching device adapted to be coupled in series electrical connection between the AC power source and the lighting load, the controllably conductive switching device controlling the amount of power delivered to the lighting load, the controllably conductive switching device operable to be rendered conductive in an AC line voltage half cycle;

    a detect circuit coupled in parallel electrical connection with the controllably conductive switching device, the detect circuit operable to provide a control signal representative of whether the controllably conductive switching device is conducting a load current to the lighting load after the controllably conductive switching device has been rendered conductive in the AC line voltage half cycle; and

    a controller operatively coupled to the controllably conductive switching device and the detect circuit, the controller operable to render the controllably conductive switching device conductive at a predetermined time within the AC line voltage half cycle following a zero-crossing of the AC line voltage, and to subsequently determine in response to the control signal from the detect circuit whether the controllably conductive switching device is conducting the load current to the lighting load after the controller has rendered the controllably conductive switching device conductive;

    wherein the controller is operable to automatically adjust the low-end intensity setting of the dimmer switch in response to the control signal from a first low-end intensity setting value to a second low-end intensity setting value thereby setting a dimming range of the dimmer switch depending on whether the controller determines that the controllably conductive switching device is conducting load current to the lighting load.

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