Solid-state lighting apparatus including current diversion controlled by lighting device bias states and current limiting using a passive electrical component
地域：
Sai Kung
摘要
A lighting apparatus includes a string of light emitting diode (LED) sets coupled in series where each set includes at least one LED. A current diversion circuit is coupled to the string and is configured to operate responsive to a bias state transition of one of the LED sets to direct current away from another one of the LED sets. A current limiting circuit is coupled in series with the string and is configured to conduct current responsive to a forward biasing of all of the LED sets. The current limiting circuit includes only passive electrical component(s).
說明書
The present inventive subject matter relates to lighting apparatus and methods and, more particularly, to solid-state lighting apparatus and methods.
Solid-state lighting arrays are used for a number of lighting applications. For example, solid-state lighting panels including arrays of solid-state light emitting devices have been used as direct illumination sources, for example, in architectural and/or accent lighting. A solid-state light emitting device may include, for example, a packaged light emitting device including one or more light emitting diodes (LEDs), which may include inorganic LEDs, which may include semiconductor layers forming p-n junctions and/or organic LEDs (OLEDs), which may include organic light emission layers.
Solid-state lighting arrays are used for a number of lighting applications. For example, solid-state lighting panels including arrays of solid-state light emitting devices have been used as direct illumination sources, for example, in architectural and/or accent lighting. Solid-state lighting devices are also used in lighting fixtures, such as incandescent bulb replacement applications, task lighting, recessed light fixtures and the like. For example, Cree, Inc. produces a variety of recessed downlights, such as the LR-6 and CR-6, which use LEDs for illumination. Solid-state lighting panels are also commonly used as backlights for small liquid crystal display (LCD) screens, such as LCD display screens used in portable electronic devices, and for larger displays, such as LCD television displays.
權(quán)利要求
That which is claimed:1. A lighting apparatus, comprising:a string of light emitting diode (LED) sets coupled in series, each LED set comprising at least one LED; a current limiting circuit directly coupled in series with the string and being configured to conduct current responsive to a forward biasing of all of the LED sets and to otherwise be non-conducting of current; a current diversion circuit coupled to the string and configured to operate responsive to a bias state transition of a first one of the LED sets to direct current away from a second one of the LED sets and the current limiting circuit, the current diversion circuit being connected in parallel to the second one of the LEDD, sets and the current limiting circuit, which are connected in series; and wherein the current limiting circuit is comprised of a resistor without including any active electrical component. 2. The lighting apparatus of claim 1 , wherein the current diversion circuit is configured to conduct current via the first one of the LED sets and is configured to be turned off responsive to current through the second one of the LED sets. 3. The lighting apparatus of claim 2 , wherein the current diversion circuit is configured to conduct current responsive to a forward biasing of the first one of the LED sets. 4. The lighting apparatus of claim 2 , wherein the first one of the LED sets comprises more LEDs than other ones of the LED sets. 5. The lighting apparatus of claim 1 , wherein the current diversion circuit is configured to turn off responsive to a voltage at a node of the string. 6. The lighting apparatus of claim 5 , further comprising a resistor coupled in series with the string and wherein the first one of the current diversion circuits is configured to turn off responsive to a voltage at a terminal of the resistor. 7. The lighting apparatus of claim 6 , wherein the current diversion circuit comprises a bipolar transistor providing a controllable current path between a node of the string and a terminal of a power supply, and wherein current through the resistor varies an emitter bias of the bipolar transistor. 8. The lighting apparatus of claim 1 , wherein the current diversion circuit comprises:a transistor providing a controllable current path between a node of the string and a terminal of a power supply; and a turn-off circuit coupled to a node of the string and to a control terminal of the transistor and configured to control the current path responsive to a control input. 9. The lighting apparatus of claim 8 , wherein current through the first one of the LED sets provides the control input. 10. The lighting apparatus of claim 8 , wherein the transistor comprises a bipolar transistor and wherein the turn-off circuit is configured to vary a base current of the bipolar transistor responsive to the control input. 11. The lighting apparatus of claim 1 , wherein the bias states of the LED sets transition responsive to a power supply having a varying voltage such that the current diversion circuit is activated in response, to increases and decreases in the varying voltage. 12. The lighting apparatus of claim 1 , wherein the current diversion circuit comprises a plurality of current diversion circuits, respective ones of which are coupled to respective nodes of the string and configured to operate responsive to bias state transitions of respective ones of the LED sets;wherein a number of the plurality of current diversion circuits is less than a number of the LED sets. 13. A lighting apparatus comprising:a rectifier circuit configured to be coupled to an alternating current (ac) power source and to generate a rectified ac voltage; a string of serially-connected LED sets, each set comprising at least one LED; a current limiting circuit directly coupled in series with the string and being configured to conduct current responsive to a forward biasing of all of the LED sets and to otherwise be non-conducting of current; a current diversion circuit coupled to the string and configured to be selectively enabled to direct current away from the current limiting circuit and disabled responsive to bias state transitions of the LED sets as a magnitude of the rectified ac voltage varies, the current diversion circuit being connected in parallel to one of the LED sets and the current limiting circuit, which are connected in series; and wherein the current limiting circuit is comprised of a resistor without including any active electrical component. 14. The lighting apparatus of claim 13 , wherein the current diversion circuit is configured to, conduct current via a first one of the LED sets and is configured to be turned off responsive to current through a second one of the LED sets. 15. The lighting apparatus of claim 14 , wherein the first one of the LED sets comprises more LEDs than other ones of the LED sets. 16. The lighting apparatus of claim 14 , wherein the current diversion circuit is configured to conduct current responsive to a forward biasing of the first one of the LED sets. 17. The lighting apparatus of claim 13 , wherein the current diversion circuit is configured to turn off responsive to a voltage at a node of the string. 18. The lighting apparatus of claim 17 , farther comprising a resistor coupled in series with the string and wherein the current diversion circuit is configured to turn of responsive to a voltage at a terminal of the resistor. 19. The lighting apparatus of claim 13 , further comprising a resistor coupled in series with the string, wherein the current diversion circuit comprises a bipolar transistor providing a controllable current path between a node of the string and a terminal of the rectifier circuit and wherein current through the resistor varies an emitter bias of the bipolar transistor. 20. The lighting apparatus of claim 13 , wherein the current diversion circuit comprises:a transistor providing a controllable current path between a node of the string and a terminal, of the rectifier circuit; and a turn-off circuit coupled to a node of the string and to a control terminal of the transistor and configured to control the current path responsive to a control input. 21. The lighting apparatus of claim 20 , wherein a current through one of the LED sets provides the control input. 22. The lighting apparatus of claim 20 , wherein the transistor comprises a bipolar transistor and wherein the turn-off circuit is configured to vary a base current of the bipolar transistor responsive to the control input. 23. The lighting apparatus of claim 13 , wherein the current diversion circuit comprises a plurality of current diversion circuits, respective ones of which are coupled to respective nodes of the string and configured to operate responsive to bias state transitions of respective ones of the LED sets;wherein a number of the plurality of current diversion circuits is less than a number of the LET) sets. 24. An apparatus comprisinga string of serially-connected light emitting diode (LED) sets; a current limiting circuit directly coupled in series with the string and being configured to conduct current responsive to a forward biasing of all of the LED sets and to otherwise be non-conducting of current; a current diversion circuit coupled to the string of LED sets and configured to operate responsive to bias state transitions of a first one of the LED sets to direct current away from a second one of the LED sets and the current limiting circuit, the current diversion circuit being connected in parallel to the second one of the LED sets and the current limiting circuit, which are connected in series; and wherein the current limiting circuit is comprised of a resistor without including any active electrical component. 25. The apparatus of claim 24 , wherein the current diversion circuit is configured to conduct current via the first one of the LED sets and is configured to be turned off responsive to current through the second one of the LED sets. 26. The apparatus of claim 25 , wherein the first one of the LED sets comprises more LEDs than other ones of the LED sets. 27. The apparatus of claim 25 , wherein the current diversion circuit is configured to conduct current responsive to a forward biasing of the first one of the LED sets. 28. The apparatus of claim 24 , wherein the current diversion circuit is configured to turn off responsive to a voltage at a node of the string. 29. The apparatus of claim 28 , wherein the current diversion circuit is configured to turn off responsive to a voltage at a terminal of a resistor coupled in series with the string. 30. The apparatus of claim 24 , wherein the current diversion circuit comprises a bipolar transistor providing a controllable current path between a node of the string and a terminal of a power supply and wherein current through a resistor coupled in series with the string varies an emitter bias of the bipolar transistor. 31. The apparatus of claim 24 , wherein the current diversion circuit comprises:a transistor configured to provide a controllable current path between anode of the string and a terminal of a power supply; and a turn-off circuit coupled to a node of the string and to a control terminal of the transistor and configured to control the current path responsive to a control input. 32. The apparatus of claim 31 , wherein current through the first one of the LED sets provides the control input. 33. The apparatus of claim 24 , further comprising a rectifier circuit configured to be coupled to a power source and having an output configured to be coupled to the string of LED sets. 34. The apparatus of claim 24 , wherein the current diversion circuit comprises a plurality of current diversion circuits, respective ones of which are coupled to respective nodes of the string and configured to operate responsive to bias state transitions of respective ones of the LED sets;wherein a number of the plurality of current diversion circuits is less than a number of the LED sets.
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