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

• Current Assignee: MDL Corporation
• Original Assignee: MDL Corporation
• Inventors: Kohler, Raymond
• Primary Examiner(s): Vu; David Hung
• Application Number:
  US12/246,052
• Time in Patent Office: 386 Days
• Field of Search: 315/192, 315/312, 315/291, 315/209.R, 315/185.R, 315/186, 315/191, 315/193, 315/307, 315/308, 315/224, 315/DIG.4, 345/82, 345/83, 345/84
• US Class Current: 315/307
• CPC Class Codes: H05B 45/58 involving end of life detection of LEDs
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A control circuit coupled to a power line controlled by a dimmer having a switching device includes, for example, an active power factor correction circuit receiving power from a bridge rectifier and storage capacitor and drawing an average continuous current when the switching device is “on.” An LED power driving circuit receives a controlled current from the active power factor correction circuit and generates an output current received by at least one LED outputting visible light. A positive voltage feedback circuit senses a feedback voltage across the LED, through the LED power driving circuit, and sends the feedback voltage to the active power factor correction circuit. A pump back power circuit is electrically coupled to the LED power driving circuit and applies a bias voltage to an output of the bridge rectifier to power the active power factor correction circuit when the switching device is “off.”

Claims

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.

2. The control circuit of claim 1, wherein the LED power driving circuit is a current-controlled flyback transformer.

3. The control circuit of claim 2, wherein the current controlled flyback transformer includes a load winding electrically coupled to the rectifier and filter and a sensory winding electrically coupled to the positive voltage feedback circuit, each of the load winding and the sensory winding being set to a phase, the phases of the load winding and the sensory winding being substantially equal.

4. The control circuit of claim 1, wherein the dimmer is a phase control dimmer.

5. The control circuit of claim 1, wherein the switching device is a triac.

6. The control circuit of claim 1, wherein the series regulator operates from about 5 volts to about 60 volts.

7. The control circuit of claim 1, wherein the pump back power circuit includes a capacitor having a capacitance from about 40 microfarads to about 1000 microfarads.

8. 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 current controlled flyback transformer having a primary winding, a load winding, and a sensory winding, each of the load winding and the sensory winding being set to a phase, the phases of the load winding and the sensory winding being substantially equal, the primary winding receives a controlled current from the active power factor correction circuit and the load winding generates an output current;

(g) a rectifier and filter circuit that receives the output current from the load winding and generates a rectified and filtered output voltage;

(h) at least one light emitting diode (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 current-controlled flyback transformer, and sends the feedback voltage to the active power factor correction circuit, the positive voltage feedback circuit being coupled to the sensory winding;

(j) a series regulator electrically coupled to a series regulator winding of the current-controlled flyback transformer, the series regulator providing a regulated voltage to the control circuit; and

(k) a pump back power circuit electrically coupled to the current-controlled flyback transformer 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.