Directly driven high efficiency LED circuit
AssigneeOsram Sylvania Inc.
InventorsWarren Moskowitz, Philip Moskowitz
Life of this patent
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Abstract
A system for directly driving light emitting diodes (LEDs). A string of LEDs is coupled across an input voltage and includes a plurality of separate groups of LEDs. Each of a plurality of switches is coupled in parallel with an associated one of the groups of LEDs for controlling current flow through the associated group of LEDs in response to a control signal from a controller circuit. A switch protection circuit is associated with at least one of the switches. The switch protection circuit is configured to place the switch into a conducting state in the event of failure of an LED in the associated group of LEDs.
Claims19
A system to drive light emitting diodes (LEDs) comprising:
- a string of LEDs coupled across a voltage source configured to provide an input voltage, the string of LEDs comprising a plurality of separate groups of LEDs;
- a plurality of switch circuits, each of the switch circuits comprising a switch coupled in parallel with an associated one of the groups of LEDs to control current flow through the associated group of LEDs in response to a control signal from a controller circuit;
- a switch protection circuit associated with at least one of the switches, the switch protection circuit configured to place the at least one of the switches into a conducting state in the event of failure of an LED in the associated group of LEDs, wherein the failure places the LED into an open state;
- and
- a controller protection circuit associated with the at least one of the switches, the controller protection circuit configured to isolate the controller circuit from a voltage applied across the at least one of the switches and comprises a diode.
A method of driving LEDs, comprising:
- coupling a string of LEDs across a voltage supply configured to provide an input voltage, the string of LEDs comprising a plurality of separate groups of LEDs;
- configuring a plurality of switches, each of the switches being coupled in parallel with an associated one of the groups of LEDs for controlling current flow through the associated group of LEDs in response to a control signal from a controller circuit;
- associating a switch protection circuit with at least one of the switches, the switch protection circuit configured to place the at least one of the switches into a conducting state in the event of failure of an LED in the associated group of LEDs, wherein the failure places the LED into an open state;
- and
- associating a controller protection circuit with the at least one of the switches, the controller protection circuit configured to isolate the controller circuit from a voltage applied across the at least one of the switches, wherein the controller protection circuit comprises a diode.
A system to drive light emitting diodes (LEDs) comprising:
- a string of LEDs coupled across a voltage source configured to provide an input voltage, the string of LEDs comprising a plurality of separate groups of LEDs;
- a plurality of switch circuits, each of the switch circuits comprising a switch coupled in parallel with an associated one of the groups of LEDs to control current flow through the associated group of LEDs in response to a control signal from a controller circuit;
- and
- a switch protection circuit associated with at least one of the switches, the switch protection circuit configured to place the at least one of the switches into a conducting state in the event of failure of an LED in the associated group of LEDs, wherein the failure places the LED into an open state wherein the at least one of the switches comprises a metal-oxide-semiconductor field-effect transistor (MOSFET) and the switch protection circuit comprises a resistor electrically coupled between the drain and the gate of the MOSFET.
Dependencies are inferred from the claim text.