LED drive circuit and LED illumination unit

• US 8,878,449 B2
• Filed: 11/29/2012
• Issued: 11/04/2014
• Est. Priority Date: 11/30/2011
• 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: Kanamori, Atsushi, Warita, Hirohisa, Shimizu, Takayuki
• Primary Examiner(s): Tran, Thienvu
• Assistant Examiner(s): LO, CHRISTOPHER KWOK YEUNG
• Application Number:
  US13/689,155
• Publication Number:
  US 20130134895A1
• Time in Patent Office: 705 Days
• Field of Search: 315/291, 315/224, 315/307, 315/200.R, 315/294, 315/201, 315/297, 315/210, 315/246, 315/185.R, 315/209.R, 315/219, 315/308
• US Class Current: 315/226
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/3575 by means of dummy loads or bleeder circuits, e.g. for dimmers
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

There is provided an LED drive circuit that can be connected to an alternating-current power supply through a phase control dimmer and that drives an LED load, the LED drive circuit including: an LED current control circuit; a capacitance component and a resistance component that are connected in series between an input of the LED current control circuit and a reference potential; a switch element that is connected to both ends of the resistance component; and a switch control portion that turns off the switch element for a given period of time after a timing when the phase control dimmer is turned on and that turns on the switch element after the given period of time elapses.

Claims

1. An LED drive circuit that can be connected to an alternating-current power supply through a phase control dimmer and that drives an LED load, the LED drive circuit comprising:

an LED current control circuit;

a capacitance component and a resistance component that are connected in series between a power input line for inputting electric power to the LED current control circuit and a reference potential;

a switch element that is connected to both ends of the resistance component and that operates such that, when the switch element is off, the resistance component is set active and, when the switch element is on, the resistance component is bypassed; and

a switch control portion

that turns off the switch element at a same time that the phase control dimmer is turned on, then keeps the switch element off for a given period of time, and turns on the switch element after the given period of time elapses, or

that keeps the switch element off for a given period for time from a time point that the phase control dimmer is turned on and turns on the switch element after the given period of time elapses.

2. The LED drive circuit of claim 1, further comprising:

a detection portion which detects that an output voltage of the phase control dimmer reaches a threshold voltage or less,

wherein, when the detection is performed, the switch control portion turns off the switch element.

3. The LED drive circuit of claim 1,

wherein the given period of time can be changed according to the phase control dimmer that is connected.

4. The LED drive circuit of claim 1, further comprising:

a detection portion which detects a gradient of an output voltage of the phase control dimmer,

wherein the given period of time can be changed according to a detection signal of the detection portion.

5. An LED illumination unit comprising:

an LED drive circuit that can be connected to an alternating-current power supply through a phase control dimmer and that drives an LED load, the LED drive circuit including;

an LED current control circuit;

a capacitance component and a resistance component that are connected in series between a power input line for inputting electric power to the LED current control circuit and a reference potential;

a switch element that is connected to both ends of the resistance component and that operates such that, when the switch element is off, the resistance component is set active and, when the switch element is on, the resistance component is bypassed; and

a switch control portion

that turns off the switch element at a same time that the phase control dimmer is turned on, then keeps the switch element off for a given period of time, and turns on the switch element after the given period of time elapses, or

that keeps the switch element off for a given period of time from a time point that the phase control dimmer is turned on and turns on the switch element after the given period of time elapses; and

the LED load that is connected to an output side of the LED drive circuit.

6. The LED illumination unit of claim 5,

wherein the LED drive circuit includes a detection portion which detects that an output voltage of the phase control dimmer reaches a threshold voltage or less, and, when the detection is performed, the switch control portion turns off the switch element.

7. The LED illumination unit of claim 5,

wherein the given period of time can be changed according to the phase control dimmer that is connected.

8. The LED illumination unit of claim 5,

wherein the LED drive circuit includes a detection portion which detects a gradient of an output voltage of the phase control dimmer, and the given period of time can be changed according to a detection signal of the detection portion.