Electrostatic discharge protection for luminaire
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.
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).