# US 2014/0197741 A1 · Led lighting apparatus

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- Number: US 2014/0197741 A1
- Document ID: US20140197741A1
- Status: Published application
- Kind: A1
- Application number: 14/232,778
- Filed: 2012-07-12
- Published: 2014-07-17
- Earliest claimed: 2011-07-15
- Assignees: Citizen Electronics Co., Ltd.; Citizen Holdings Co., Ltd.
- Inventors: Keisuke Sakai; Rintaro Takahashi; Takashi Akiyama
- Web page: https://patentgrep.com/patent/US20140197741A1

## CPC

- H05B 45/3575: by means of dummy loads or bleeder circuits, e.g. for dimmers
- H05B 45/44: with an active control inside an LED matrix
- H05B 45/48: having LEDs organised in strings and incorporating parallel shunting devices
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL

## Abstract

When an LED lighting apparatus which is a lighter load than an incandescent lamp or halogen lamp is connected to a dimmer, a malfunction may occur. The invention prevents the occurrence of such malfunction without defeating the purpose of low power consumption of the LED lighting apparatus. More specifically, the LED lighting apparatus includes a rectifier circuit, a light-emitting circuit connected to the rectifier circuit and containing a single or a plurality of LEDs in which current begins to flow when an output voltage of the rectifier circuit exceeds a threshold voltage, and a bypass circuit having a bypass path for making the current flow to the rectifier circuit without passing through the light-emitting circuit, and a detecting unit for detecting the current flowing through the light-emitting circuit, and wherein when the current detected by the detecting unit exceeds a predetermined value, the bypass circuit shuts off the current flowing through the bypass path.

## Claims

### Claim 1

An LED lighting apparatus comprising:
a rectifier circuit;
a first light-emitting circuit connected to said rectifier circuit and containing a single or a plurality of LEDs in which current begins to flow when an output voltage of said rectifier circuit exceeds a threshold voltage;
a first bypass circuit having a bypass path for making the current flow to said rectifier circuit without passing through said first light-emitting circuit, and a detecting unit for detecting the current flowing through said first light-emitting circuit,
a second bypass circuit connected to said first light-emitting circuit;
a second light-emitting circuit connected to said second bypass circuit and containing a single or a plurality of LEDs in which current begins to flow when the output voltage of said rectifier circuit exceeds a threshold voltage; and
a current limiting circuit for limiting the current flowing into said second light-emitting circuit,
wherein when the current detected by said detecting unit exceeds a predetermined value, said first bypass circuit shuts off the current flowing through said bypass path.

### Claim 2 (depends on 1)

The LED lighting apparatus according to claim 1, wherein said first bypass circuit maintains the sum of the current flowing through said first bypass circuit and the current flowing through said first light-emitting circuit constant.

### Claim 3 (depends on 1)

The LED lighting apparatus according to claim 1, wherein said first bypass circuit includes a current detecting resistor and a depletion-type FET placed in said bypass path, and wherein said depletion-type FET controls opening and closing of said first bypass path by detecting the current flowing through said first light-emitting circuit by said current detecting resistor.

### Claim 4 (depends on 1)

The LED lighting apparatus according to claim 1, wherein said first bypass circuit includes a current detecting resistor and a depletion-type FET placed in said bypass path, and wherein said depletion-type FET controls opening and closing of said first bypass path by detecting the current flowing through said first light-emitting circuit by said current detecting resistor.

### Claim 5 (depends on 1)

The LED lighting apparatus according to claim 1,
wherein said first bypass circuit includes a current detecting resistor and an enhancement-type FET placed in said bypass path, a bipolar transistor for controlling said enhancement-type FET, and a pull-up resistor, and wherein said bipolar transistor detects the current flowing through said first light-emitting circuit by said current detecting resistor, and controls opening and closing of said bypass path by using said enhancement-type FET.

### Claim 6 (depends on 2)

The LED lighting apparatus according to claim 2, wherein said first bypass circuit includes a current detecting resistor and an enhancement-type FET placed in said bypass path, a bipolar transistor for controlling said enhancement-type FET, and a pull-up resistor, and wherein said bipolar transistor detects the current flowing through said first light-emitting circuit by said current detecting resistor, and controls opening and closing of said bypass path by using said enhancement-type FET.

### Claim 7 (depends on 1)

The LED lighting apparatus according to claim 1, further comprising a filter circuit connected in parallel with said first bypass circuit and constructed from a series connection of a resistor and a capacitor.

### Claim 8 (depends on 7)

The LED lighting apparatus according to claim 7, wherein said filter circuit is placed after said first bypass circuit but before said first light-emitting circuit.