LED controller with phase-shift dimming function and LED phase-shift dimming circuit and method thereof

• US 8,258,714 B2
• Filed: 04/27/2010
• Issued: 09/04/2012
• Est. Priority Date: 05/26/2009
• Status: Active Grant

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Liu, Jing-Meng
• Primary Examiner(s): Tan, Vibol
• Application Number:
  US12/768,046
• Publication Number:
  US 20100301764A1
• Time in Patent Office: 861 Days
• Field of Search: 315/250, 315/210, 315/192, 315/307, 315/209.R, 315/291, 315/224, 315/308, 315/185.R, 315/247, 345/102, 345/690, 327/276, 327/135
• US Class Current: 315/250
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

The present invention discloses an LED controller with phase-shift dimming function and an LED Phase-Shift dimming circuit and method thereof. The LED controller includes: a power circuit for supplying DC power to multiple LED channels; and an LED phase-shift dimming circuit for receiving a pulse width modulation (PWM) input signal and generating multiple phase-shifted PWM signals with a shifted phase between one another, wherein a turn-ON timing of each of the multiple phase-shifted PWM signals follows a turn-OFF timing of a previous PWM signal which is the input PWM signal or a previous one of the multiple phase-shifted PWM signals.

Claims

1. An LED controller with phase-shift dimming function, comprising:

a power circuit for supplying DC power to multiple LED channels; and

an LED phase-shift dimming circuit for receiving an input pulse width modulation (PWM) signal and generating multiple phase-shifted PWM signals with a shifted phase between one another, wherein a turn-ON timing of each of the multiple phase-shifted PWM signals follows a turn-OFF timing of a previous PWM signal which is the input PWM signal or a previous one of the multiple phase-shifted PWM signals,

wherein the LED phase-shift dimming circuit includes multiple delay locked loops (DLLs) coupled in series, and each DLL duplicates a PWM signal which it receives to generate the phase-shifted PWM signal with a shifted phase to the received PWM signal.

2. The LED controller of claim 1, wherein each DLL calculates a pulse width of the received PWM signal by a high frequency clock signal and generates the phase-shifted PWM signal with the same pulse width.

3. The LED controller of claim 1, wherein the LED phase-shift dimming circuit includes multiple pulse width mirrors coupled in series, and each pulse width mirror comprises:

an edge detector for detecting a rising and/or a falling edge of a PWM signal received by the pulse width mirror;

a pulse width memory circuit for memorizing a pulse width of the received PWM signal; and

a pulse width generator for generating the phase-shifted PWM signal with the same pulse width as the received PWM signal.

4. The LED controller of claim 1, wherein the LED phase-shift dimming circuit includes multiple pulse width mirrors coupled in series, and each pulse width mirror comprises:

an edge detector for detecting a rising and/or a falling edge of a PWM signal received by the pulse width mirror;

a duty-to-ramp circuit for generating a ramp signal according to a duty of the received PWM signal; and

a pulse width generator for generating the phase-shifted PWM signal with the same pulse width as the received PWM signal.

5. An LED phase-shift dimming circuit for receiving an input pulse width modulation (PWM) signal and outputting multiple phase-shifted PWM signals with a shifted phase between one another, the LED phase-shift dimming circuit comprising multiple delay locked loops (DLLs) coupled in series, wherein each DLL calculates a pulse width of a received PWM signal by a high frequency clock signal and generates the phase-shifted PWM signal with the same pulse width as the received PWM signal, wherein a turn-ON timing of each of the multiple phase-shifted PWM signals follows a turn-OFF timing of a previous PWM signal which is the input PWM signal or a previous one of the multiple phase-shifted PWM signals.

6. An LED phase-shift dimming circuit for receiving an input pulse width modulation (PWM) signal and outputting multiple phase-shifted PWM signals with a shifted phase between one another, the LED phase-shift dimming circuit comprising multiple pulse width mirrors coupled in series, wherein each pulse width mirror includes:

an edge detector for detecting a rising and/or a falling edge of a PWM signal received by the pulse width mirror;

a pulse width memory circuit for memorizing a pulse width of the received PWM signal; and

a pulse width generator for generating the phase-shifted PWM signal with the same pulse width as the received PWM signal.

7. The LED phase-shift dimming circuit of claim 6, wherein the pulse width memory circuit includes a current source and a capacitor, and wherein the capacitor starts charging at the rising edge of the received PWM signal and stops charging at the falling edge of the received PWM signal to memorize the pulse width.

8. The LED phase-shift dimming circuit of claim 7, wherein the pulse width generator determines a pulse width of the phase-shifted.PWM signal according to the discharge time of the capacitor.

9. The LED phase-shift dimming circuit of claim 6, wherein the pulse width memory circuit includes a counter which starts counting at the rising edge of the received PWM signal and stops counting at the falling edge of the received PWM signal for memorizing the pulse width.

10. The LED phase-shift dimming circuit of claim 9, wherein the pulse width generator determines a pulse width of the phase-shifted PWM signal according to a time to reverse-count the count in the counter.

11. An LED phase-shift dimming circuit for receiving an input pulse width modulation (PWM) signal and outputting multiple phase-shifted PWM signals with a shifted phase between one another, the LED phase-shift dimming circuit comprising multiple pulse width mirrors coupled in series, wherein each pulse width mirror includes:

an edge detector for detecting a rising and/or a falling edge of a PWM signal received by the pulse width mirror;

a duty-to-ramp circuit for generating a ramp signal according to a duty of the received PWM signal; and

a pulse width generator for generating the phase-shifted PWM signal with the same pulse width as the received PWM signal.

12. The LED phase-shift dimming circuit of claim 11, wherein the edge detector includes:

a short delay circuit for short-delaying the received PWM signal; and

a logic gate for generating a short pulse related to the received PWM signal according to the received PWM signal and an output of the short delay circuit.

13. The LED phase-shift dimming circuit of claim 11, wherein the duty-to-ramp circuit includes a current source and a capacitor, and wherein the capacitor is charged and discharged to generating the ramp signal according to an output of the edge detector.

14. The LED phase-shift dimming circuit of claim 13, wherein the duty-to-ramp circuit further includes a feedback comparator circuit for comparing the phase-shifted PWM signal with the received PWM signal and controlling the current of the current source thereby.

15. An LED phase-shift dimming control method for controlling multiple LED channels, comprising:

receiving an input pulse width modulation (PWM) signal; and

duplicating and converting the input PWM signal to multiple phase-shifted PWM signals with a shifted phase between one another for corresponding LED channels respectively, wherein a turn-ON timing of each of the multiple phase-shifted PWM signals follows a turn-OFF timing of a previous PWM signal which is the input PWM signal or a previous one of the multiple phase-shifted PWM signals,

wherein the step of duplicating and converting the input PWM signal to multiple phase-shifted PWM signals includes;

detecting a turn-ON timing of the input PWM signal;

memorizing the pulse width of the input PWM signal;

duplicating the input PWM signal to generate a first phase-shifted PWM signal with the same pulse width as the input PWM signal; and

outputting the first phase-shifted PWM signal at or after the turn-OFF timing of the input PWM signal.

16. The method of claim 15, wherein the step of duplicating and converting the input PWM signal to multiple phase-shifted PWM signals further includes:

duplicating the first phase-shifted PWM signal to generate a second phase-shifted PWM signal, and outputting the second phase-shifted PWM signal at or after the turn-OFF timing of the first PWM signal.

17. The method of claim 15, wherein the step of duplicating and converting the input PWM signal to multiple phase-shifted PWM signals includes:

generating a ramp signal according to the duty of the input PWM signal;

duplicating the input PWM signal to generate a first PWM signal with the same pulse width as the input PWM signal; and

outputting the first PWM signal at or after the turn-OFF timing of the input PWM signal.

18. The method of claim 17, wherein the step of duplicating and converting the input PWM signal to multiple phase-shifted PWM signals further includes:

duplicating the first PWM signal to generate a second PWM signal, and outputting the second PWM signal at or after the turn-OFF timing of the first PWM signal.

19. The method of claim 17, wherein the step of duplicating and converting the input PWM signal to multiple phase-shifted PWM signals further includes:

feedback comparing the first PWM signal with the input PWM signal to control a slope of the ramp signal.

20. The method of claim 18, wherein the step of duplicating and converting the input PWM signal to multiple phase-shifted PWM signals further includes:

feedback comparing the first PWM signal with the input PWM signal to generate a current for controlling a slope of the ramp signal; and

in the step of duplicating the first PWM signal to generate the second PWM signal, mirror duplicating the current for controlling a slope of the ramp signal corresponding to the second PWM signal.

21. The method of claim 18, wherein the step of duplicating and converting the input PWM signal to multiple phase-shifted PWM signals includes:

feedback comparing the first PWM signal with the input PWM signal to generate a clock signal for controlling a slope of the ramp signal; and

in the step of duplicating the first PWM signal to generate the second PWM signal, controlling a slope of the ramp signal corresponding to the second PWM signal by the clock signal.