Light Emitting Device Power Supply Circuit, and Light Emitting Device Driver Circuit and Control Method Thereof

• US 20120242238A1
• Filed: 03/15/2012
• Published: 09/27/2012
• Est. Priority Date: 03/22/2011
• Status: Active Grant

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Liu, Jing-Meng, Hsiu, Leng-Nien, Chen, Pei-Yuan, Liao, Chia-Wei
• Granted Patent: US 8,710,755 B2
• Time in Patent Office: Days
• US Class Current: 315/200.R
• CPC Class Codes: H05B 45/3575 by means of dummy loads or bleeder circuits, e.g. for dimmers
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology

Abstract

The present invention discloses a light emitting device power supply circuit, a light emitting device driver circuit and a control method thereof. The light emitting device driver circuit is coupled to a tri-electrode AC switch (TRIAC) dimmer circuit, and it controls the brightness of a light emitting device circuit according a rectified dimming signal. The light emitting device driver circuit includes a power stage circuit and a light emitting device control circuit. The light emitting device control circuit generates a switch control signal. The power stage circuit operates at least one power switch thereof according to the switch control signal to generate a latching current for firing the TRIAC dimmer circuit, and the latching current is inputted to the light emitting device circuit.

Claims

1. A light emitting device driver circuit for driving a light emitting device circuit according to a rectified dimming signal, wherein the rectified dimming signal is generated from an AC input signal which passes through a tri-electrode AC switch (TRIAC) dimming circuit and a rectifier circuit, the light emitting device driver circuit comprising:

a power stage circuit coupled between the rectifier circuit and the light emitting device circuit, the power stage circuit operating at least one power switch therein according to a switch control signal to generate a latching current for firing the TRIAC dimming circuit, wherein the latching current flows through the light emitting device circuit; and

a light emitting device control circuit coupled to the power stage circuit, the light emitting device control circuit generating the switch control signal according to a detection signal.

2. The driver circuit of claim 1, wherein the detection signal is generated according to the rectified dimming signal or a signal related to the rectified dimming signal, and the detection signal is generated when the rectified dimming signal changes from a neutral level to a predetermined level, and wherein the switch control signal turns ON the power switch continuously for a predetermined period.

3. The driver circuit of claim 1, wherein the detection signal is generated according to at least one method below:

(1) by detecting the rectified dimming signal or a signal related to the rectified dimming signal, and the detection signal is generated when the rectified dimming signal is at a neutral level or below a predetermined level;

(2) by detecting an input or an output current flowing through the power stage circuit or a signal related to the input or the output current, and the detection signal is generated when the input or the output current is zero; and

(3) by generating the detection signal with a frequency corresponding to a frequency of the AC input signal or the rectified dimming signal.

4. The driver circuit of claim 3, further comprising a voltage detection circuit coupled to the rectifier circuit to detect the rectified dimming signal or the signal related to the rectified dimming signal.

5. The driver circuit of claim 3, wherein the power stage circuit further includes:

a current detection circuit coupled to the power switch to detect the input or the output current; and

an inductor device coupled to the power switch to generate the latching current.

6. The driver circuit of claim 1, wherein in one operation period of the power switch, the light emitting device control circuit first controls the power switch to generate the latching current according to the detection signal, and then, after the latching current is generated, the light emitting device control circuit controls the power switch to regulate an output voltage or an output current of the power stage circuit to a predetermined target according to a feedback signal.

7. The driver circuit of claim 1, wherein the light emitting device control circuit includes:

a comparator circuit, which compares the detection signal and the rectified dimming signal or a signal related to the rectified dimming signal, for generating a trigger signal according to the comparison result; and

a latch circuit, which determines an ON time of the switch control signal according to the trigger signal.

8. A light emitting device control method, comprising:

receiving a rectified dimming signal, which is generated from an AC input signal which passes through a tri-electrode AC switch (TRIAC) dimming circuit and a rectifier circuit;

generating a switch control signal according to a detection signal;

controlling at least one power switch of a power stage circuit according to the switch control signal to generate a latching current for firing the TRIAC dimming circuit; and

inputting the latching current to the light emitting device.

9. The control method of claim 8, wherein the detection signal is generated according to the rectified dimming signal or a signal related to the rectified dimming signal, and the detection signal is generated when the rectified dimming signal changes from a neutral level to a predetermined level;

and the step of generating the latching current includes;

turning ON the power switch continuously for a predetermined period by the switch control signal according to the detection signal.

10. The control method of claim 8, wherein the detection signal is generated according to at least one method below:

(1) by detecting the rectified dimming signal or a signal related to the rectified dimming signal, and the detection signal is generated when the rectified dimming signal is at a neutral level or below a predetermined level;

(2) by detecting an input or an output current flowing through the power stage circuit or a signal related to the input or the output current, and the detection signal is generated when the input or the output current is zero; and

(3) by generating the detection signal with a frequency corresponding to a frequency of the AC input signal or the rectified dimming signal.

11. The control method of claim 8, wherein in one operation period of the power switch, the power switch is first controlled to generate the latching current according to the detection signal, and the control method further comprising:

after the latching current is generated, the power switch is then controlled to regulate an output voltage or an output current of the power stage circuit to a predetermined target according to a feedback signal.

12. The control method of claim 8, wherein the step of generating the switch control signal includes:

comparing the detection signal with the rectified dimming signal or a signal related to the rectified dimming signal, and generating a trigger signal according to the comparison result; and

determining an ON time of the switch control signal according to the trigger signal.

13. Alight emitting device power supply circuit, comprising:

a tri-electrode AC switch (TRIAC) dimming circuit for generating an AC dimming signal according to an AC input signal;

a rectifier circuit for generating a rectified dimming signal according to the AC dimming signal; and

alight emitting device driver circuit for driving alight emitting device circuit according to the rectified dimming signal, the light emitting device driver circuit including;

a power stage circuit coupled between the rectifier circuit and the light emitting device circuit, the power stage circuit operating at least one power switch therein according to a switch control signal to generate a latching current for firing the TRIAC dimming circuit, wherein the latching current flows through the light emitting device circuit; and

a light emitting device control circuit coupled to the power stage circuit, the light emitting device control circuit generating the switch control signal according to a detection signal.

14. The power supply circuit of claim 13, wherein the detection signal is generated according to the rectified dimming signal or a signal related to the rectified dimming signal, and the detection signal is generated when the rectified dimming signal changes from a neutral level to a predetermined level, and wherein the switch control signal turns ON the power switch continuously for a predetermined period.

15. The power supply circuit of claim 13, wherein the detection signal is generated according to at least one method listed below:

(1) by detecting the rectified dimming signal or a signal related to the rectified dimming signal, and the detection signal is generated when the rectified dimming signal is at a neutral level or below a predetermined level;

(2) by detecting an input or an output current flowing through the power stage circuit or a signal related to the input or the output current, and the detection signal is generated when the input or the output current is zero; and

(3) by generating the detection signal with a frequency corresponding to a frequency of the AC input signal or the rectified dimming signal.

16. The power supply circuit of claim 15, further comprising a voltage detection circuit coupled to the rectifier circuit to detect the rectified dimming signal or the signal related to the rectified dimming signal.

17. The power supply circuit of claim 15, wherein the power stage circuit further includes:

a current detection circuit coupled to the power switch to detect the input or the output current; and

an inductor device coupled to the power switch to generate the latching current.

18. The power supply circuit of claim 13, wherein in one operation period of the power switch, the light emitting device control circuit first controls the power switch to generate the latching current according to the detection signal, and then, after the latching current is generated, the light emitting device control circuit controls the power switch to regulate an output voltage or an output current of the power stage circuit to a predetermined target according to a feedback signal.

19. The power supply circuit of claim 13, wherein the light emitting device control circuit includes:

a comparator circuit, which compares the detection signal and the rectified dimming signal or a signal related to the rectified dimming signal, for generating a trigger signal according to the comparison result; and

a latch circuit, which determines an ON time of the switch control signal according to the trigger signal.