Light-emitting diode driving circuits and driving methods thereof

• US 9,072,128 B2
• Filed: 09/27/2013
• Issued: 06/30/2015
• Est. Priority Date: 12/27/2012
• Status: Active Grant

• Current Assignee: Princeton Technology Corporation
• Original Assignee: Princeton Technology Corporation
• Inventors: Su, Ching-Piao, Chen, Chiung-Hung, Hsu, Chien-Te
• Primary Examiner(s): Tran, Thuy Vinh
• Assistant Examiner(s): Kaiser, Syed M
• Application Number:
  US14/039,306
• Publication Number:
  US 20140184090A1
• Time in Patent Office: 641 Days
• Field of Search: 315/307, 315/250, 315/312, 315/194, 315/360, 315/291, 315/293, 332/109, 345/204, 345/102, 327/172, 327/175, 327/114, 327/3, 327/31, 327/35, 327/36
• US Class Current: 1/1
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

A driving circuit includes a first PWM driving module and a second PWM driving module. The first PWM driving module generates a first square-wave signal to drive a first illumination unit according to a first data signal of a data stream, wherein the first square-wave represents an illumination period of the first illumination unit in a display cycle. The second PWM driving module generates a second square-wave signal to drive the second illumination unit according to a second data signal of the data stream, wherein the second square-wave signal, which has a different phase with the first square-wave signal, represents an illumination period of the second illumination unit in the display cycle.

Claims

1. A driving circuit, comprising:

a first PWM driving module, generating a first square-wave signal to drive a first illumination unit according to a first data signal of a data stream, wherein the first square-wave signal represents an illumination period of the first illumination unit in a display cycle, wherein a first register unit receives the first data signal and outputs the first data signal to the first PWM driving module; and

a second PWM driving module, generating a second square-wave signal to drive a second illumination unit according to a second data signal of the data stream, wherein the second square-wave signal represents an illumination period of the second illumination unit in the display cycle, wherein a second register unit receives the second data signal and outputs the second data signal to the second PWM driving module, and the first square-wave signal has a different phase with the second square-wave signal,

wherein a width of the first square-wave signal is different from a width of the second square-wave signal.

2. The driving circuit of claim 1, wherein a rising edge of the first square-wave signal is located at the beginning of the display cycle, and a rising edge of the second square-wave signal is behind the rising edge of the first square-wave signal.

3. The driving circuit of claim 1, wherein a rising edge of the first square-wave signal is located at the beginning of the display cycle, and a rising edge of the second square-wave is behind the falling edge of the first square-wave.

4. The driving circuit of claim 1, wherein the first PWM driving module comprises:

a first PWM generating unit, outputting the first square-wave signal according to the first data signal, and

a first driving circuit, coupled to the first PWM generating unit, for driving the first illumination unit according to the first square-wave signal, and

wherein the second PWM driving module comprises;

a second PWM generating unit, outputting a second square-wave signal according to the second data signal, and

a second driving circuit, coupled to the second PWM generating unit, for driving the second illumination unit according to the second square-wave signal.

5. The driving circuit of claim 4, wherein the first PWM generating unit comprises:

a first counter, counting a clock signal to output a first counting signal; and

a first comparator, generating the first square-wave signal according to the first counting signal and the first data signal, and

wherein the second PWM generating unit comprises;

a second counter, counting the clock signal to output a second counting signal, and

a second comparator, generating the second square-wave signal according to the second counting signal and the second data signal, wherein a starting value of the first counter is different from a starting value of the second counter.

6. The driving circuit of claim 4, wherein the first illumination unit is coupled to the second illumination unit in parallel, and a first terminal of the first illumination unit and a first terminal of the second illumination unit are coupled to a power line, a second terminal of the first illumination unit is coupled to the first PWM driving module, and a second terminal of the second illumination unit is coupled to the second PWM driving module.

7. The driving circuit of claim 1, wherein the first PWM generating unit further comprises:

a first PWM register, coupled between the first register unit and the first comparator, for storing the first data signal, and

wherein the second PWM generating unit further comprises;

a second PWM register, coupled between the second register unit and the second comparator, for storing the second data signal.

8. The driving circuit of claim 7, wherein the first comparator comprises a positive terminal coupled to the first counter and a negative terminal coupled to the first PWM register, such that the first square-wave signal is at a high voltage level when the first counting signal is higher than the first data signal, and the second comparator comprises a first terminal coupled to the second counter and a negative terminal coupled to the second PWM register, such that the second square-wave signal is at a high voltage level when the second counting signal is higher than the second data signal.

9. The driving circuit of claim 7, wherein the first comparator comprises a positive terminal coupled to the first PWM register and a negative terminal coupled to the first counter, such that the first square-wave signal is at a high voltage level when the first data signal is higher than the first counting signal, and the second comparator comprises a positive terminal coupled to the second PWM register and a negative terminal coupled to the second counter, such that the second square-wave signal is at a high voltage level when the second data signal is higher than the second counting signal.

10. The driving circuit of claim 1, wherein the first illumination unit and the second illumination unit are light-emitting diodes (LEDs).

11. A driving method, driving a first illumination unit and a second illumination unit, comprising:

generating a first square-wave signal according to a first data signal of a data stream, wherein the first data signal is buffered by a first register unit, wherein the first square-wave signal represents an illumination period of the first illumination unit in a display cycle, and a rising edge of the first square-wave signal is located at a beginning of the display cycle;

driving the first illumination unit according to the first square-wave signal;

generating a second square-wave signal according to the second data signal of the data stream, wherein the second data signal is buffered by a second register unit, wherein the second square-wave signal represents an illumination period of the second illumination unit in the display cycle, and a falling edge of the second square-wave signal is located at the end of the display cycle, and wherein the first square-wave signal has a different phase with the second square-wave signal, wherein a width of the first square-wave signal is different from a width of the second square-wave signal; and

driving the second illumination unit according to the second square-wave signal.

12. The driving method of claim 11, wherein the rising edge of the first square-wave signal is located at the beginning of the display cycle, and the rising edge of the second square-wave signal is behind the rising edge of the first square-wave signal.

13. The driving method of claim 11, wherein the rising edge of the first square-wave signal is located at the beginning of the display cycle, and the rising edge of the second square-wave signal is behind a falling edge of the first square-wave signal.

14. The driving method of claim 13, wherein the step of generating the first square-wave signal and the step of generating the second square-wave signal comprise:

outputting a first counting signal by counting a clock signal with a first counter;

outputting a second counting signal by counting the clock signal with a second counter;

comparing the first counting signal and the first data signal and in response thereto generating the first square-wave signal; and

comparing the second counting signal and the second data signal and in response thereto generating the second square-wave signal,

wherein a starting value of the first counter is different from a starting value of the second counter.

15. The driving method of claim 14, wherein the first square-wave signal is at a high voltage level when the first data signal is higher than the first counting signal, and the second square-wave signal is at a high voltage level when the second counting signal is higher than the second data signal.

16. The driving method of claim 14, wherein the first square-wave signal is at a high voltage level when the first data signal is higher than the first counting signal, and the second square-wave signal is at a high voltage level when the second data signal is higher than the second counting signal.

17. The driving method of claim 11, wherein the first illumination unit and the second illumination unit are light-emitting diodes (LEDs).