LIGHT EMITTING DEVICE CURRENT REGULATOR CIRCUIT AND CONTROL METHOD THEREOF

• US 20170257920A1
• Filed: 05/21/2017
• Published: 09/07/2017
• Est. Priority Date: 05/10/2011
• Status: Active Grant

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Liu, Jing-Meng
• Granted Patent: US 10,187,941 B2
• Time in Patent Office: Days
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines

Abstract

Alight emitting device current regulator circuit is disclosed. A light emitting device circuit has a first end for receiving light emitting device operation power, and a second end. The light emitting device current regulator circuit includes: an internal voltage generation circuit coupled to the second end, for generating an internal voltage according to a second end voltage to supply electrical power to the light emitting device current regulator circuit, wherein the supply voltage generation circuit includes a charge storage device for storing charges from the second end voltage to generate the supply voltage; and a current control circuit coupled to the second end, the current control circuit regulating the light emitting device current according to a control signal, wherein the control signal at least intermittently reduces the light emitting device current to zero or low current in order to raise the second end voltage.

Claims

1. A light emitting device current regulator circuit, for regulating a light emitting device current flowing through a light emitting device circuit, wherein the light emitting device circuit has a first end and a second end, the first end being coupled to a power supply circuit, the light emitting device current regulator circuit comprising:

an internal voltage generation circuit coupled to the second end, which generates an internal voltage according to a voltage at the second end (second end voltage) to supply electrical power to the light emitting device current regulator circuit, wherein the internal voltage generation circuit includes a charge storage device for storing charges from the second end voltage to generate the internal voltage; and

a current control circuit, coupled to the second end, the current control circuit regulating the light emitting device current according to a control signal, wherein the control signal at least intermittently reduces the light emitting device current to zero or a low current in order to raise the second end voltage such that the charge storage device is intermittently charged to maintain the internal voltage not lower than a minimum level required for operation of the light emitting device current regulator circuit.

2. The light emitting device current regulator circuit of claim 1, further comprising a determination circuit for generating the control signal, wherein the determination circuit determines to generate the control signal according to a level of the internal voltage.

3. The light emitting device current regulator circuit of claim 1, further comprising a determination circuit for generating the control signal, wherein the determination circuit determines to generate the control signal according to a dimming signal and a level of the internal voltage.

4. The light emitting device current regulator circuit of claim 1, further comprising a determination circuit for generating the control signal, wherein the determination circuit determines to generate the control signal according to a timing signal.

5. The light emitting device current regulator circuit of claim 1, further comprising a determination circuit for generating the control signal, wherein the determination circuit determines to generate the control signal according to a dimming signal and a timing signal.

6. The light emitting device current regulator circuit of claim 2, wherein the determination circuit includes:

an internal voltage level obtaining circuit for generating an internal voltage level information signal according to the internal voltage; and

a setting circuit for generating the control signal according to the internal voltage level information signal.

7. The light emitting device current regulator circuit of claim 3, wherein the determination circuit includes:

an internal voltage level obtaining circuit for generating an internal voltage level information signal according to the internal voltage; and

a setting circuit for generating the control signal according to the internal voltage level information signal.

8. The light emitting device current regulator circuit of claim 6, wherein the setting circuit includes a comparison circuit for generating a determination signal to determine whether to generate the control signal according to a comparison between the internal voltage level information signal and at least one predetermined level.

9. The light emitting device current regulator circuit of claim 7, wherein the setting circuit includes a comparison circuit for generating a determination signal to determine whether to generate the control signal according to a comparison between the internal voltage level information signal and at least one predetermined level.

10. The light emitting device current regulator circuit of claim 8, wherein the setting circuit further includes a single pulse generation circuit coupled to the comparison circuit, which generates a single pulse signal according to the determination signal, wherein the single pulse signal generates the control signal.

11. The light emitting device current regulator circuit of claim 9, wherein the setting circuit further includes a single pulse generation circuit coupled to the comparison circuit, which generates a single pulse signal according to the determination signal, wherein the single pulse signal generates the control signal.

12. The light emitting device current regulator circuit of claim 3, wherein the determination circuit includes:

an internal voltage level obtaining circuit, for generating an internal voltage level information signal according to the internal voltage;

a setting circuit for generating a determination signal according to the internal voltage level information signal; and

a logic circuit for generating the control signal according to the determination signal and the dimming signal.

13. The light emitting device current regulator circuit of claim 4, wherein the determination circuit includes:

a timer circuit for generating the timing signal after counting a period of time; and

a single pulse generation circuit for generating the control signal according to the timing signal.

14. The light emitting device current regulator circuit of claim 5, wherein the determination circuit includes:

a timer circuit for generating the timing signal after counting a period of time; and

a single pulse generation circuit for generating the control signal according to the timing signal.

15. The light emitting device current regulator circuit of claim 5, wherein the determination circuit includes:

a timer circuit for generating the timing signal after counting a period of time;

a single pulse generation circuit for generating a determination signal according to the timing signal; and

a first logic circuit for generating the control signal according to the dimming signal and the determination signal.

16. The light emitting device current regulator circuit of claim 15, wherein the timer circuit is reset according to the dimming signal.

17. The light emitting device current regulator circuit of claim 15, wherein the determination circuit further includes a second logic circuit for resetting the timer circuit according to the dimming signal and the determination signal.

18. The light emitting device current regulator circuit of claim 1, wherein the internal voltage generation circuit includes a sample-and-hold circuit or a rectifier circuit.

19. The light emitting device current regulator circuit of claim 18, wherein the sample-and-hold circuit includes:

a switch circuit including a switch device coupled to the second end, the switch circuit operating the switch device according to the control signal; and

the charge storage device coupled to the switch circuit for generating the internal voltage according to the operation of the switch device.

20. The light emitting device current regulator circuit of claim 18, wherein the rectifier circuit includes:

a diode device having a forward terminal and a reverse terminal, wherein the forward terminal is coupled to the second end; and

the charge storage device coupled to the reverse terminal for generating the internal voltage.

35. The light emitting device current regulator circuit of claim 1, wherein the control signal operates by one or more duty ratios whereby the charge storage device is intermittently charged.

36. The light emitting device current regulator circuit of claim 1, wherein during a first condition in which the control signal has a first duty ratio which is not 100%, the charge storage device is charged during each cycle, and during a second condition in which the control signal has a second duty ratio, the second duty ratio is 100% in at least one cycle but is not 100% in at least another cycle such that the charge storage device is charged in at least one but not all of a plurality of cycles.

37. The light emitting device current regulator circuit of claim 1, wherein the control signal has a duty ratio which is not 100% in all duty cycles.

22-34. -34. (canceled)