Solid-state lighting apparatus including current diversion controlled by lighting device bias states and current limiting using a passive electrical component

Patent metadata

Field	Value
Publication number	US-11178740-B2
Application number	US-201113338076-A
Country	US
Kind code	B2
Filing date	Dec 27, 2011
Priority date	Dec 27, 2011
Publication date	Nov 16, 2021
Grant date	Nov 16, 2021

Abstract

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).

First claim

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 comprising
a 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

Assignees

• Van De Ven Antony P
• Ni Liqin
• Ideal Ind Lighting Llc

Inventors

• Van De Ven Antony P
• Ni Liqin

Classifications

• H05B45/59

  for reducing or suppressing flicker or glow effects · CPC title

• H05B45/48 Primary

  having LEDs organised in strings and incorporating parallel shunting devices · CPC title

• H05B47/25

  Circuit arrangements for protecting against overcurrent · CPC title

• H05B45/50

  responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits · CPC title