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Method and circuit for controlling an LED

  • US 7,609,008 B1
  • Filed: 10/06/2008
  • Issued: 10/27/2009
  • Est. Priority Date: 06/06/2008
  • Status: Expired due to Fees
First Claim
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1. A control circuit coupled to a power line controlled by a dimmer having a switching device, the control circuit comprising:

  • (a) a hold network that receives a variable input voltage from the dimmer-controlled power line and maintains a minimum hold current for the dimmer when the switching device is in an “

    on”

    state;

    (b) a filter that receives the variable input voltage and is configured to damp inductive-capacitive (LC) resonances;

    (c) a bridge rectifier that receives and converts the damped variable input voltage to a fixed polarity variable input voltage;

    (d) a storage capacitor that maintains fixed polarity variable input voltage for the control circuit;

    (e) an active power factor correction circuit that receives power from the bridge rectifier and the storage capacitor and draws an average continuous current when the switching device is in the “

    on”

    state;

    (f) a light emitting diode (LED) power driving circuit that receives a controlled current from the active power factor correction circuit and generates an output current;

    (g) a rectifier and filter circuit that receives the output current from the LED power driving circuit and generates a rectified and filtered output voltage;

    (h) at least one LED that receives the output voltage from the rectifier and filter circuit, the at least one LED outputting visible light;

    (i) a positive voltage feedback circuit that senses a feedback voltage across the at least one LED, through the LED power driving circuit, and sends the feedback voltage to the active power factor correction circuit;

    (j) a series regulator electrically coupled to the LED power driving circuit, the series regulator providing a regulated voltage to the control circuit;

    (k) a pump back power circuit electrically coupled to the LED power driving circuit that applies a bias voltage to an output of the bridge rectifier to power the active power factor correction circuit when the switching device is in an “

    off”

    state; and

    (l) an open loop protection circuit that is configured to regulate output of the active power correction circuit when the at least one LED is not electrically coupled to the LED power driving circuit.

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