LED drive circuit

• US 20020105373A1
• Filed: 02/07/2002
• Published: 08/08/2002
• Est. Priority Date: 02/08/2001
• Status: Active Grant

• Current Assignee: Ablic Inc. (Minebea Mitsumi, Inc.)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Sudo, Minoru
• Granted Patent: US 6,980,181 B2
• Time in Patent Office: Days
• US Class Current: 327/538
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines

Abstract

An LED drive circuit is provided, which is designed to reduce power consumption. The LED drive circuit cause at least one of a plurality of LEDs at certain time intervals.

Claims

1. An LED drive circuit formed comprising:

a driver having a constant current circuit to drive a plurality of light emitting diodes (LEDs); and

a plurality of switch connected to the each LED periodically turning on and off at least one of the LEDs at certain time intervals.

2. An LED drive circuit according to claim 1, wherein the frequency of turning on and off the LED in a cycle is 5 Hz or higher.

3. An LED drive circuit according to claim 1, wherein the value of the constant current by which the LED is driven is 5 to 30 mA.

4. An LED drive circuit according to claim 1, wherein the LED turning on/off cycle or time can be controlled by means of an external signal.

5. An LED drive circuit according to claim 1, wherein the LED to be caused to blink can be selected by means of an external signal.

6. An LED drive circuit according to claim 1, wherein the value of the constant current by which the LED is driven can be selected by means of an external signal.

7. An LED drive circuit according to claim 1, wherein the value of the constant current by which the LED is driven can be adjusted according to temperature.

8. An LED drive circuit comprising:

a driver circuit having a boosting circuit and a constant current circuit to drive an LED; and

a control circuit to increase the voltage boosted by the boosting circuit when the current for driving the LED is smaller than the value of the constant current, and for reducing the voltage boosted by the boosting circuit when the current for driving the LED has the value of the constant current.

9. An LED drive circuit formed comprising:

means for driving each of at least two LEDs by a constant current and by using a boosting circuit and a voltage boosted by the boosting circuit; and

means for increasing the voltage boosted by the boosting circuit when the current for driving the LED is smaller than the value of the constant current, for reducing the voltage boosted by the boosting circuit when the current for driving the LED has the value of the constant current, and for periodically turning on and off at least one of the LEDs at certain time intervals.