Electrostatic discharge protection for luminaire

• US 8,610,358 B2
• Filed: 08/17/2011
• Issued: 12/17/2013
• Est. Priority Date: 08/17/2011
• Status: Active Grant

• Current Assignee: Express Imaging Systems, LLC
• Original Assignee: Express Imaging Systems, LLC
• Inventors: Reed, William G.
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): HAMMOND, DEDEI KHALIEAH
• Application Number:
  US13/212,074
• Publication Number:
  US 20130043792A1
• Time in Patent Office: 853 Days
• Field of Search: None
• US Class Current: 315/126
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An apparatus for protecting a solid state retrofit lighting or illumination system from electrostatic discharge damage caused by charge induced onto conductive surfaces of the lighting or illumination system.

Claims

1. A lighting system, comprising:

at least one light emitting diode;

a power supply coupled to the at least one light emitting diode and operable to convert a received power signal into a feedback-regulated power signal that is provided to the at least one light emitting diode, the power supply, including;

a rectifier;

a transformer coupled to the rectifier and having a primary winding and a secondary winding;

a switch operable to at least partially control current passing through the primary winding;

an overvoltage protection device coupled between an output of the rectifier and the primary winding; and

an overcurrent protection device coupled between the switch and a common voltage reference that is common to the rectifier and the primary winding,the overcurrent protection device being operable to conduct an induced current from a ground reference node to the primary winding of the transformer; and

a feedback circuit coupled between the at least one light emitting diode and the switch and operable to vary a magnitude of the feedback-regulated power signal.

2. The lighting system of claim 1 wherein the overvoltage protection device is a diode.

3. The lighting system of claim 1 wherein the overcurrent protection device is a resistor.

4. The lighting system of claim 3 wherein the resistor has a value of at least 631 Kiloohms and not greater than 3 Megaohms.

5. The lighting system of claim 3 wherein the resistor has a value of at least 1 Megaohm and not greater than 3 Megaohms.

6. The lighting system of claim 1 wherein the switch is at least one of a metal oxide semiconductor field effect transistor (MOSFET) and an insulated gate bipolar transistor (IGBT), and the overcurrent protection device is connected in parallel to a capacitor and is resistively coupled to a source terminal of the MOSFET or an emitter terminal of the IGBT.

7. The lighting system of claim 1 wherein the power supply is a flyback converter.

8. The lighting system of claim 1 wherein the feedback circuit senses a current through the at least one light emitting diode and in response pulse-width modulates a gate terminal of the switch to vary the magnitude of the feedback-regulated power signal.

9. A power supply to use with solid state lighting, comprising:

a galvanized isolation transformer having a primary side and a secondary side; and

a discharge path that electrically couples at least one of at least one light emitting diode, or a heat sink to which the at least one light emitting diode is thermally coupled, to a common ground of the primary side of the transformer via an overcurrent protection resistor, a capacitor electrically coupled in parallel with the overcurrent protection resistor, and a diode to handle current induced in the light emitting diode or the heat sink.

10. The power supply of claim 9 wherein the overcurrent protection resistor has a resistance that is at least 631 Kiloohms and not greater than 3 Megaohms.

11. The power supply of claim 9 wherein the overcurrent protection resistor has a resistance of at least 1 Megaohm and not greater than 3 Megaohms.

12. The power supply of claim 9, further comprising:

a bulk capacitor filter at which the diode electrically couples the induced current to the overprotection resistor, wherein the diode is a transient voltage suppressor (TVS).