Driving apparatus of light emitting diode and driving method thereof

• US 8,427,081 B2
• Filed: 07/23/2012
• Issued: 04/23/2013
• Est. Priority Date: 09/16/2009
• Status: Expired

• Current Assignee: Novatek Microelectronics Corporation (Novatek Microelectronics Corp Limited)
• Original Assignee: Novatek Microelectronics Corporation (Novatek Microelectronics Corp Limited)
• Inventors: Hsu, Kuo-Ching, Hsu, Chin-Hsun, Chang, Tsung-Hau, Liao, Ting-Wei
• Primary Examiner(s): PHILOGENE, HAISSA
• Application Number:
  US13/556,146
• Publication Number:
  US 20120286677A1
• Time in Patent Office: 274 Days
• Field of Search: 315/291, 315/294, 315/297, 315/169.1, 315/185.R, 315/307, 315/360, 315/312, 315/287, 345/46, 345/82, 345/63, 345/204, 345/211, 345/212, 345/207, 345/690, 345/691
• US Class Current: 315/360
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines

Abstract

A driving method of a light-emitting diode (LED) adapted to a driving apparatus is provided. The driving method includes detecting whether the driving apparatus performs dimming, and if the driving apparatus performs dimming, determining whether a predetermined requirement for dimming control is met or not. When the predetermined requirement for dimming control is not met, respective current magnitudes of a plurality of driving currents are regulated, and each of the driving currents is output for a full time of a period. Conversely, when the predetermined requirement for dimming control is met, each of the driving currents is output for a partial time of a period.

Claims

1. A driving method of a light-emitting diode (LED), adapted to a driving apparatus, the driving method comprising:

detecting whether the driving apparatus performs dimming;

if the driving apparatus is detected to perform dimming, determining whether a predetermined requirement for dimming control is met or not;

when the predetermined requirement for dimming control is not met, regulating respective current magnitudes of a plurality of driving currents, and outputting each of the driving currents for a full time of a period; and

when the predetermined requirement for dimming control is met, outputting each of the driving currents for a partial time of a period.

2. The driving method of the LED as claimed in claim 1, wherein

the driving method further comprises receiving a dimming signal, and

the step of determining whether the predetermined requirement for dimming control is met or not is performed according to the dimming signal.

3. The driving method of the LED as claimed in claim 2, wherein the step of determining whether the predetermined requirement for dimming control is met or not according to the dimming signal comprises determining whether a duty cycle of the dimming signal is smaller than a predetermined value or not.

4. The driving method of the LED as claimed in claim 1, wherein in a situation where the predetermined requirement for dimming control is not met, the respective current magnitudes of the plurality of driving currents are regulated according to the dimming signal.

5. The driving method of the LED as claimed in claim 4, wherein in the situation where the predetermined requirement for dimming control is not met, the respective current magnitudes of the plurality of driving currents are determined according to the duty cycle of the dimming signal.

6. The driving method of the LED as claimed in claim 1, further comprising:

in a situation where the predetermined requirement for dimming control is met, arranging a respective current magnitude and a respective outputting time of each of the driving currents in a period according to the dimming signal.

7. The driving method of the LED as claimed in claim 6, wherein in the situation where the predetermined requirement for dimming control is met, the respective current magnitude and the respective outputting time of each of the driving currents in the period are determined according to the duty cycle of the dimming signal.

8. The driving method of the LED as claimed in claim 1, further comprising:

regardless of whether each of the driving currents is output for the full time or the partial time of the period, maintaining a sum of the driving currents calculated for a period approximately to a fixed value for a same duty cycle of the dimming signal.

9. A driving method of a light-emitting diode (LED), adapted to a driving apparatus, the driving method comprising:

receiving a dimming signal;

detecting whether the driving apparatus performs dimming;

if the driving apparatus is detected to perform dimming, regulating at least one of a respective current magnitude and a respective outputting time of each of a plurality of driving currents in a period according to a duty cycle of the dimming signal, such that a sum of the driving currents calculated for a period is substantially proportional to the duty cycle of the dimming signal.

10. The driving method of the LED as claimed in claim 9, wherein

in at least one of the regulations, only the respective current magnitude of each of the driving currents is regulated according to the duty cycle of the dimming signal, and

in at least another one of the regulations, both the respective current magnitude and the outputting time of each of the driving currents in the period are regulated according to the duty cycle of the dimming signal.

11. The driving method of the LED as claimed in claim 9, wherein

in at least one of the regulations, each of the driving currents is output for a full time of the period, and

in at least another one of the regulations, each of the driving currents is output for a partial time of the period.

12. The driving method of the LED as claimed in claim 11, wherein whether each of the driving currents is output for the partial time of the period or the full time of the period is determined according to whether the duty cycle of the dimming signal is smaller than a predetermined value or not.

13. The driving method of the LED as claimed in claim 11, wherein for the regulations for a same duty cycle of the dimming signal, regardless of whether each of the driving currents is output for the full time or the partial time of the period, a sum of the driving currents calculated for the period is substantially maintained to a fixed value.

14. A driving circuit for driving a plurality of light-emitting diodes (LEDs), the driving circuit comprising:

a plurality of switches, used to be coupled to the LEDs;

a dimming detector, for receiving a dimming signal and outputting a dimming mode signal according to the dimming signal;

a current control unit, for outputting a plurality of control signals according to the dimming mode signal and the dimming signal, wherein the control signals respectively control conducting states of the switches.

15. The driving circuit as claimed in claim 14, wherein

the driving circuit further comprises a current driving unit coupled between the switches and the current control unit, and

the current control unit further outputs a control voltage according to the dimming mode signal and the dimming signal, wherein the control voltage controls the current driving unit to regulate a plurality of driving currents for driving the LEDs.

16. The driving circuit as claimed in claim 14, wherein the dimming detector detects whether dimming is performed according to the dimming signal and outputs the dimming mode signal according to the detection result.

17. The driving circuit as claimed in claim 16, wherein the dimming detector detects whether dimming is performed by detecting a duty cycle of the dimming signal.

18. The driving circuit as claimed in claim 16, wherein the dimming detector further detects whether a duty cycle of the dimming signal is smaller than a predetermined value or not so as to output the dimming mode signal to the current control unit for arranging the status of the switches.

19. The driving circuit as claimed in claim 18, wherein the dimming detector detects whether the duty cycle of the dimming signal is smaller than the predetermined value or not so as to further output the dimming signal to the current control unit such that the current control unit controls the current driving unit to regulate driving currents for driving the LEDs.

20. The driving circuit as claimed in claim 18, wherein in a situation where the dimming detector detects that dimming is performed and the duty cycle of the dimming signal is smaller than the predetermined value, the current control unit outputs the control signals to control the switches to be conducted for a partial time of a period.

21. The driving circuit as claimed in claim 18, wherein in a situation where the dimming detector detects that dimming is performed and the duty cycle of the dimming signal is the duty cycle of the dimming signal is not smaller than the predetermined value, the current control unit outputs the control signals to control each of the switches to be conducted for a full time of a period.

22. The driving circuit as claimed in claim 19, wherein in a situation where the dimming detector detects that dimming is performed and the duty cycle of the dimming signal is the duty cycle of the dimming signal is smaller than the predetermined value, the current control unit outputs the control signals to control each of the switches to be conducted for a partial time of a period.

23. The driving circuit as claimed in claim 19, regardless of whether a duty cycle of the dimming signal is smaller than the predetermined value or not, the driving currents are regulated such that a sum of the driving currents calculated for the period is substantially proportional to the duty cycle of the dimming signal.

24. An electronic device, comprising

the driving circuit as claimed in claim 14;

and

a plurality of light-emitting diodes coupled to and driven by the driving circuit.