LED DRIVE CIRCUIT, LED LAMP, LED LIGHTING APPLIANCE, AND LED LIGHTING SYSTEM

• US 20100225251A1
• Filed: 03/02/2010
• Published: 09/09/2010
• Est. Priority Date: 03/06/2009
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: MARUYAMA, Yasuhiro
• Granted Patent: US 8,698,420 B2
• Time in Patent Office: Days
• US Class Current: 315/307
• CPC Class Codes: H05B 45/397 Current mirror circuits
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An LED drive circuit receives an alternating-current voltage and drives an LED. The LED drive circuit has a current extractor which extracts a current from the current supply line through which an LED drive current is supplied to the LED, and a timing adjuster which adjusts the current extraction start timing and the current extraction duration in the current extractor.

Claims

1. An LED drive circuit receiving an alternating-current voltage and driving an LED, comprising:

a current extractor extracting a current from a current supply line through which an LED drive current is supplied to the LED; and

a timing adjuster adjusting a current extraction start timing and a current extraction duration in the current extractor.

2. The LED drive circuit according to claim 1,

wherein the timing adjuster comprises a voltage detection circuit monitoring an input voltage to the LED drive circuit or a voltage obtained by rectifying the input voltage, and current extraction in the current extractor is controlled according to a result of monitoring by the voltage detection circuit.

3. The LED drive circuit according to claim 2,

wherein the timing adjuster comprises a comparator comparing the result of monitoring by the voltage detection circuit with a set voltage, and the current extraction in the current extractor is controlled according to a result of comparison by the comparator.

4. The LED drive circuit according to claim 3,

wherein the comparator has hysteresis.

5. The LED drive circuit according to claim 3, wherein

the timing adjuster comprises a first transistor of which a base is connected to an output of the voltage detection circuit,

the current extractor comprises a second transistor of which a base is connected to a collector of the first transistor, and

the timing adjuster further comprises a capacitor connected between the bases of the first and second transistors.

6. The LED drive circuit according to claim 1,

wherein the timing adjuster comprises a voltage variation detection circuit detecting a variation in an input voltage to the LED drive circuit or a voltage obtained by rectifying the input voltage, and current extraction in the current extractor is controlled according to a result of monitoring by the voltage variation detection circuit.

7. The LED drive circuit according to claim 6, wherein

the timing adjuster comprises a resistor, a capacitor, and a first transistor of which a base is connected to a node between the resistor and the capacitor, and

the current extractor comprises a second transistor of which a base is connected to a collector of the first transistor.

8. The LED drive circuit according to claim 6, wherein

the timing adjuster comprises a serial circuit having a capacitor and a resistor connected in series in this order from a high-potential side to a low-potential side, and

the current extractor comprises a transistor of which a base is connected to a node between the capacitor and the resistor.

9. The LED drive circuit according to claim 6, further comprising:

an unnecessary lighting preventer preventing the LED from being lit by an unnecessary current.

10. The LED drive circuit according to claim 5, wherein

the current extractor comprises a constant-current source connected to an emitter of the second transistor provided in the current extractor, and

the second transistor provided in the current extractor is driven on a constant-current basis.

11. The LED drive circuit according to claim 7, wherein

the current extractor comprises a constant-current source connected to an emitter of the second transistor provided in the current extractor, and

the second transistor provided in the current extractor is driven on a constant-current basis.

12. The LED drive circuit according to claim 8, wherein

the current extractor comprises a constant-current source connected to an emitter of the transistor provided in the current extractor, and

the transistor provided in the current extractor is driven on a constant-current basis.

13. An LED lamp comprising:

an LED drive circuit; and

an LED connected to an output side of the LED drive circuit,

wherein the LED drive circuit receives an alternating-current voltage and drives the LED, the LED drive circuit comprising;

a current extractor extracting a current from a current supply line through which an LED drive current is supplied to the LED; and

a timing adjuster adjusting a current extraction start timing and a current extraction duration in the current extractor.

14. An LED lighting appliance comprising:

an LED lamp,

wherein the LED lamp comprises;

an LED drive circuit; and

an LED connected to an output side of the LED drive circuit, and

wherein the LED drive circuit receives an alternating-current voltage and drives the LED, the LED drive circuit comprising;

a current extractor extracting a current from a current supply line through which an LED drive current is supplied to the LED; and

a timing adjuster adjusting a current extraction start timing and a current extraction duration in the current extractor.

15. An LED lighting system comprising:

an LED lamp or an LED lighting appliance comprising an LED lamp; and

a light control unit connected to an input side of the LED lamp or the LED lighting appliance,

wherein the LED lamp comprises;

an LED drive circuit; and

an LED connected to an output side of the LED drive circuit,

wherein the LED drive circuit receives an alternating-current voltage and drives the LED, the LED drive circuit comprising;

a current extractor extracting a current from a current supply line through which an LED drive current is supplied to the LED; and

a timing adjuster adjusting a current extraction start timing and a current extraction duration in the current extractor, and

wherein the light control unit comprises a phase-control light controller.