Driver circuit for improving utilization rate of LED device and related constant current regulator

Patent metadata

Field	Value
Publication number	US-9084327-B2
Application number	US-201313789325-A
Country	US
Kind code	B2
Filing date	Mar 7, 2013
Priority date	Apr 12, 2012
Publication date	Jul 14, 2015
Grant date	Jul 14, 2015

Abstract

A driver circuit for driving an LED array is disclosed. The LED array includes a first, a second, a third, a fourth LED device and a diode device. The second LED device is connected to the first LED device. The fourth LED device is connected to the third LED device. The diode device is connected between the second LED device and the third LED device. The driver circuit includes a first constant current regulator for coupling between the first and the second LED device; a second constant current regulator for coupling between the second and the third LED device; a third constant current regulator for coupling between the third and the fourth LED device; a fourth constant current regulator for coupling between the fourth LED device and a fixed-voltage terminal; and a control circuit coupled with the first, the second, the third, and the fourth constant current regulators.

First claim

What is claimed is:

1. A driver circuit for driving a LED array, the LED array comprising: a first LED device, a second LED device, a third LED device, a fourth LED device, and a first diode device, wherein the second LED device is connected to the first LED device, the fourth LED device is connected to the third LED device, and the first diode device is connected between the second LED device and the third LED device, the driver circuit comprising:
a first constant current regulator for coupling between the first LED device and the second LED device;
a second constant current regulator for coupling between the second LED device and the third LED device;
a third constant current regulator for coupling between the third LED device and the fourth LED device;
a fourth constant current regulator for coupling between the fourth LED device and a fixed-voltage terminal; and
a control circuit coupled with the first, the second, the third, and the fourth constant current regulators;
wherein when an input voltage of a target constant current regulator of the first, the second, the third, and the fourth constant current regulators exceeds a corresponding threshold voltage, the target constant current regulator reduces a current flowing through the target constant current regulator to be lower than a predetermined threshold value under control of the control circuit.

2. The driver circuit of claim 1 , wherein the target constant current regulator comprising:
a first transistor, wherein a first terminal of the first transistor is coupled with the input terminal of the target constant current regulator;
a second transistor, wherein a first terminal of the second transistor is coupled with a second terminal and a control terminal of the first transistor;
a third transistor, wherein a first terminal of the third transistor is coupled with the first terminal of the first transistor, and a control terminal of the third transistor is coupled with the first terminal of the second transistor;
a first resistor, wherein a first terminal of the first resistor is coupled with a second terminal of the third transistor, and a second terminal of the first resistor is coupled with a control terminal of the second transistor;
a second resistor, wherein a first terminal of the second resistor is coupled with the control terminal of the second transistor, and a second terminal of the second resistor is coupled with a second terminal of the second transistor; and
a third resistor, wherein a first terminal of the third resistor is coupled with the second terminal of the third transistor, and a second terminal of the third resistor is coupled with a fixed-voltage terminal.

3. The driver circuit of claim 2 , wherein the control circuit turns off the third transistor when the input voltage of the target constant current regulator exceeds the corresponding threshold voltage.

4. The driver circuit of claim 3 , wherein the control circuit comprises a detection circuit coupled with the target constant current regulator, and the detection circuit comprising:
a fourth transistor;
a third diode device comprising one or more diodes and coupled between a first terminal of the fourth transistor and the input voltage of the target constant current regulator;
a fifth transistor, wherein a first terminal of the fifth transistor is coupled with the control terminal of the third transistor, and a control terminal of the fifth transistor is coupled with a second terminal of the fourth transistor;
a fourth resistor, wherein a first terminal of the fourth resistor is coupled with the control terminal of the fifth transistor, and a second terminal of the fourth resistor is coupled with a control terminal of the fourth transistor; and
a fifth resistor, wherein a first terminal of the fifth resistor is coupled with the control terminal of the fifth transistor, and a second terminal of the fifth resistor is coupled with a fixed-voltage terminal;
wherein the corresponding threshold voltage of the target constant current regulator is determined by a breakdown voltage of the third diode device.

5. The driver circuit of claim 4 , wherein the control circuit comprises a plurality of detection circuits respectively coupled with the first, the second, and the third constant current regulators.

6. The driver circuit of claim 5 , wherein when a temperature of the target constant current regulator exceeds a threshold temperature, the target constant current regulator reduces the current flowing through the target constant current regulator under control of the control circuit.

7. The driver circuit of claim 6 , wherein the control circuit reduces the current flowing through the target constant current regulator by reducing a voltage across the third resistor.

8. The driver circuit of claim 7 , wherein the control circuit comprises an over temperature protection circuit coupled with the target constant current regulator, and the over temperature protection circuit comprising:
a sixth transistor, wherein a first terminal of the sixth transistor is coupled with the control terminal of the third transistor, and a control terminal of the sixth transistor is coupled with the second terminal of the first transistor;
a seventh transistor, wherein a first terminal of the seventh transistor is coupled with the control terminal of the third transistor, and a control terminal of the seventh transistor is coupled with a second terminal of the sixth transistor; and
an eighth transistor, wherein a first terminal of the eighth transistor is coupled with the control terminal of the third transistor, and a control terminal of the eighth transistor is coupled with a second terminal of the seventh transistor.

9. The driver circuit of claim 8 , wherein at less one of the sixth, the seventh, and the eighth transistors is a bipolar junction transistor.

10. The driver circuit of claim 2 , wherein the LED array comprises a first switch connected between the third LED device and the first LED device, and when an input voltage of the LED array is between a second threshold voltage and a third threshold voltage, the control circuit turns off the first switch.

11. The driver circuit of claim 2 , further comprising:
a first switch for coupling between the third LED device and the first LED device;
wherein when an input voltage of the LED array is between a second threshold voltage and a third threshold voltage, the control circuit turns off the first switch.

12. The driver circuit of claim 1 , wherein the control circuit comprises a detection circuit coupled with the target constant current regulator, and the detection circuit comprising:
a fourth transistor;
a third diode device comprising one or more diodes and coupled between a first terminal of the fourth transistor and the input voltage of the target constant current regulator;
a fifth transistor, wherein a first terminal of the fifth transistor is coupled with the target constant current regulator, and a control terminal of the fifth transistor is coupled with a second terminal of the fourth transistor;
a fourth resistor, wherein a first terminal of the fourth resistor is coupled with the control terminal of the fifth transistor, and a second terminal of the fourth resistor is coupled with a control terminal of the fourth transistor; and
a fifth resistor, wherein a first terminal of the fifth resistor is coupled with the control terminal of the fifth transistor, and a second terminal of the fifth resistor is coupled with a fixed-voltage terminal;
wherein the corresponding threshold voltage of the target constant current regulator is determined by a breakdown voltage of the third diode dev

Assignees

• Richtek Technology Corp

Inventors

• Chiu Kuo-Chin
• Huang Chih-Feng

Classifications

• H05B45/48

  having LEDs organised in strings and incorporating parallel shunting devices · CPC title

• G05F1/16

  combined with discharge tubes or semiconductor devices · CPC title

• G05F3/16

  being semiconductor devices · CPC title

• H05B33/0851 Primary

  Electricity · mapped topic

• H05B33/083

  Electricity · mapped topic