METHODS AND APPARATUS FOR SEGMENTING AND DRIVING LED-BASED LIGHTING UNITS

• US 20130313987A1
• Filed: 05/26/2012
• Published: 11/28/2013
• Est. Priority Date: 05/26/2012
• Status: Active Grant

• Current Assignee: VastView Technology Inc.
• Original Assignee: VastView Technology Inc.
• Inventors: Chu, Hung-Chi, Shen, Yuh-Ren
• Granted Patent: US 8,816,591 B2
• Time in Patent Office: Days
• US Class Current: 315/193
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix

Abstract

A plurality of LED-based lighting units is segmented into a plurality of LED-based lighting segments connected in series. Each lighting segment has a plurality of LED-based lighting units connected in series with at least a series-connection switch, and a bypass-connection switch is connected in parallel with the series of LED-based lighting units. The total number of LED-based lighting units can be determined by a maximum voltage level of an input voltage supply and the forward voltage of the LED-based lighting unit for achieving optimal efficiency. The number of lighting segments and the number of lighting units in each lighting segment are properly chosen based on the total number of the LED-based lighting units in such away that any number up to the total number of all the LED-based lighting units can be connected in series by respectively controlling the series-connection switch and the bypass-connection switch of each LED-based lighting segment.

Claims

1. An apparatus for segmenting and driving LED-based lighting units, comprising:

a plurality of LED-based lighting segments connected in series, each of said LED-based lighting segments having a positive end, a negative end, a bypass-connection switch connecting said positive end to said negative end, and one or more LED-based lighting units connected in series with at least a series-connection switch between said positive end and said negative end;

an input voltage supply coupled to said plurality of LED-based lighting segments; and

a controller for controlling said plurality of LED-based lighting segments;

wherein each of said plurality of LED-based lighting segments is separately controlled by said controller and comprises a series-connection mode for being connected in series with other LED-based lighting segments, and a bypassed mode for being short-circuited.

2. The apparatus as claimed in claim 1, wherein said controller has a respective pair of control signals connected to each of said plurality of LED-based lighting segments for turning on said bypass-connection switch of the LED-based lighting segment in said bypassed mode, and turning off said bypass-connection switch and turning on said series-connection switch of the LED-based lighting segment in said series-connection mode.

3. The apparatus as claimed in claim 1, further comprising a current control device connected in series with said plurality of LED-based lighting segments.

4. The apparatus as claimed in claim 3, wherein said current control device sends a voltage level to said controller and said controller controls each of said plurality of LED-based lighting segments to respectively operate in said series-connection mode or said bypassed mode according to said voltage level.

5. The apparatus as claimed in claim 4, wherein said controller controls each of said plurality of LED-based lighting segments to respectively operate in said series-connection mode or said bypassed mode according to a voltage level of said input voltage supply and said voltage level sent by said current control device.

6. The apparatus as claimed in claim 3, wherein said controller comprises a state machine, a first A/D converter for converting a voltage level of said input voltage supply to a first digital signal sent to said state machine, a second A/D converter for converting a voltage level of said current control device to a second digital signal sent to said state machine, and a memory device connected to said state machine for sending a respective pair of control signals to each of said plurality of LED-based lighting segments for turning on said bypass-connection switch of the LED-based lighting segment in said bypassed mode, and turning off said bypass-connection switch and turning on said series-connection switch of the LED-based lighting segment in said series-connection mode.

7. The apparatus as claimed in claim 3, wherein said current control device is a current sensing resistor.

8. The apparatus as claimed in claim 3, wherein said current control device is a variable current source controlled by said controller.

9. The apparatus as claimed in claim 3, wherein said apparatus comprises a total of N LED-based lighting units with

10. The apparatus as claimed in claim 1, wherein said apparatus comprises a total of N LED-based lighting units with

11. The apparatus as claimed in claim 10, wherein V_IN is an input voltage of said input voltage supply and said controller controls said plurality of LED-based lighting segments so that only one of said LED-based lighting units is connected in series when 0≦

V_IN≦

V_F, at least two of said LED-based lighting units are connected in series when V_F<

V_IN≦

2V_F, at least three of said LED-based lighting units are connected in series when 2V_F<

V_IN≦

3V_F, . . . , at least (N-1) of said LED-based lighting units are connected in series when (N-2)V_F<

V_IN≦

(N-1)V_F, and N of said LED-based lighting units are connected in series when (N-1)V_F<

V_IN≦

V_IN(max)≦

NV_F.

12. The apparatus as claimed in claim 1, wherein said apparatus comprises a total of N LED-based lighting units segmented into k LED-based lighting segments respectively having S₁, S₂, . . . , and S_k LED-based lighting units with k being an integer number greater than 3, └

log₂ N┘

+1≦

k≦

N, └

log₂ N┘

being an integer part of log₂ N, and S₁, S₂, . . . , and S_k are integer numbers with

13. The apparatus as claimed in claim 1, wherein said apparatus comprises a total of N LED-based lighting units segmented into k LED-based lighting segments respectively having S₁, S₂, . . . , and S_k LED-based lighting units with k being an integer number, 3<

k≦

└

log₂ N┘

, └

log₂ N┘

being an integer part of log₂ N, and S₁, S₂, . . . , and S_k are integer numbers with

14. The apparatus as claimed in claim 1, wherein said controller comprises a dimming control unit for sending a respective pair of control signals to each of said plurality of LED-based lighting segments for turning on said bypass-connection switch of the LED-based lighting segment in said bypassed mode, and turning off said bypass-connection switch and turning on said series-connection switch of the LED-based lighting segment in said series-connection mode.

15. The apparatus as claimed in claim 1, wherein said controller comprises a state machine for sending a respective pair of control signals to each of said plurality of LED-based lighting segments for turning on said bypass-connection switch of the LED-based lighting segment in said bypassed mode, and turning off said bypass-connection switch and turning on said series-connection switch of the LED-based lighting segment in said series-connection mode, an A/D converter for converting a voltage level of said input voltage supply to a digital signal sent to said state machine.

16. The apparatus as claimed in claim 1, wherein said apparatus further comprises an uncontrolled LED-based lighting unit connected in series with said plurality of LED-based lighting segments.

17. The apparatus as claimed in claim 1, wherein each of said plurality of LED-based lighting units comprises one or more LEDs connected in series.

18. The apparatus as claimed in claim 1, wherein each of said plurality of LED-based lighting units comprises a plurality of LEDs connected in parallel.

19. The apparatus as claimed in claim 1, wherein each of said plurality of LED-based lighting units comprises a plurality of LEDs connected in a combination of parallel and series connections.

20. The apparatus as claimed in claim 1, wherein said controller controls each of said plurality of LED-based lighting segments to respectively operate in said series-connection mode or said bypassed mode according to a voltage level of said input voltage supply.

21. A method for segmenting and driving LED-based lighting units, comprising the steps of:

segmenting a total of N LED-based lighting units into k LED-based lighting segments respectively having S₁, S₂, . . . , and S_k LED-based lighting units connected in series between a positive end and a negative end of the respective LED-based lighting segment, each of said LED-based lighting units having a forward voltage V_F at a maximum current I_max;

coupling an input voltage supply to said plurality of LED-based lighting segments, said input voltage supply having a maximum voltage level V_IN(max); and

sending a respective pair of control signals to each of said plurality of LED-based lighting segments to respectively connect the corresponding LED-based lighting segment in series or respectively bypass the corresponding LED-based lighting segment;

wherein k is an integer number greater than 3, └

log₂ N┘

+1≦

k≦

N, └

log₂ N┘

being an integer part of log₂ N, and S₁, S₂, . . . , and S_k are integer numbers with

22. The method as claimed in claim 21, further connecting a current control device in series with said plurality of LED-based lighting segments.

23. The method as claimed in claim 22,

24. The method as claimed in claim 21,

25. The method as claimed in claim 24, wherein V_IN is an input voltage of said input voltage supply and said controller controls said plurality of LED-based lighting segments so that only one of said LED-based lighting units is connected in series when 0≦

V_IN≦

V_F, at least two of said LED-based lighting units are connected in series when V_F<

V_IN≦

2V_F, at least three of said LED-based lighting units are connected in series when 2V_F<

V_IN≦

3V_F, . . . , at least (N-1) of said LED-based lighting units are connected in series when (N-2)V_F<

V_IN≦

(N-1)V_F, and N of said LED-based lighting units are connected in series when (N-1)V_F<

V_IN≦

V_IN(max)≦

NV_F.

26. A method for segmenting and driving LED-based lighting units, comprising the steps of:

segmenting a total of N LED-based lighting units into k LED-based lighting segments respectively having S₁, S₂, . . . , and S_k LED-based lighting units connected in series between a positive end and a negative end of the respective LED-based lighting segment, each of said LED-based lighting units having a forward voltage V_F at a maximum current I_max;

coupling an input voltage supply to said plurality of LED-based lighting segments, said input voltage supply having a maximum voltage level V_IN(max); and

sending a respective pair of control signals to each of said plurality of LED-based lighting segments to respectively connect the corresponding LED-based lighting segment in series or respectively bypass the corresponding LED-based lighting segment;

wherein k is an integer number with 3<

k≦

└

log₂ N┘

, └

log₂ N┘

being an integer part of log₂ N, and S₁, S₂, . . . , and S_k are integer numbers with

27. The method as claimed in claim 26, further connecting a current control device in series with said plurality of LED-based lighting segments.

28. The method as claimed in claim 27,

29. The method as claimed in claim 26,

30. The method as claimed in claim 29, wherein V_IN is an input voltage of said input voltage supply and said controller controls said plurality of LED-based lighting segments so that only one of said LED-based lighting units is connected in series when 0≦

V_IN≦

V_F, at least two of said LED-based lighting units are connected in series when V_F<

V_IN≦

2V_F, at least three of said LED-based lighting units are connected in series when 2V_F<

V_IN≦

3V_F, . . . , at least (N-1) of said LED-based lighting units are connected in series when (N-2)V_F<

V_IN≦

(N-1)V_F, and N of said LED-based lighting units are connected in series when (N-1)V_F<

V_IN≦

V_IN(max)≦

NV_F.