# US 10,766,400 B2 · Vehicle lamp and lighting circuit of light source

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- Number: US 10,766,400 B2
- Document ID: US10766400B2
- Status: Granted
- Kind: B2
- Application number: 15/991,636
- Filed: 2018-05-29
- Published: 2018-11-29
- Granted: 2020-09-08
- Earliest claimed: 2017-05-26
- Assignees: Koito Manufacturing Co., Ltd.
- Applicants: Koito Manufacturing Co., Ltd.
- Inventors: Satoshi Kikuchi; Tomoyuki Ichikawa
- Web page: https://patentgrep.com/patent/US10766400B2

## CPC

- H05B 47/10: Controlling the light source
- B60Q 1/04: the devices being headlights
- B60Q 1/143: {combined with another condition, e.g. using vehicle recognition from camera images or activation of wipers}
- F21S 41/141: Light emitting diodes [LED]
- F21S 41/148: the main emission direction of the LED being perpendicular to the optical axis
- F21S 41/153: arranged in a matrix
- F21S 41/19: Attachment of light sources or lamp holders (achieving variable light distribution by movable light sources F21S41/657)
- F21S 41/255: Lenses with a front view of circular or truncated circular outline
- F21S 41/32: Optical layout thereof
- F21S 41/39: Attachment thereof (achieving variable light distribution by movable reflectors F21S41/675)
- F21S 41/663: by switching light sources (by switching incandescent light sources F21S41/162)
- F21S 41/675: by moving reflectors
- H05B 45/14: using electrical feedback from LEDs or from LED modules
- H05B 45/345: Current stabilisation; Maintaining constant current
- H05B 45/3725: Switched mode power supply [SMPS]
- H05B 45/48: having LEDs organised in strings and incorporating parallel shunting devices
- F21W 2102/14: having vertical cut-off lines; specially adapted for adaptive high beams, i.e. wherein the beam is broader but avoids glaring other road users
- H05B 45/375: using buck topology
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- B60Q: ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
- F21S: NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
- F21W: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO USES OR APPLICATIONS OF LIGHTING DEVICES OR SYSTEMS

## Abstract

A lighting circuit is configured to drive a light source including a plurality of light emitting elements connected in series. The lighting circuit includes a plurality of bypass switches respectively connected in parallel to the light emitting elements, a switching converter, and a converter controller configured to (i) stabilize a lamp current generated by the switching converter to a first target amount in a lighting-on state where at least one of the plurality of light emitting elements is turned on, and to (ii) stabilize the lamp current to a second target amount smaller than the first target amount in a complete lighting-off state where all of the plurality of light emitting elements are turned off.

## Claims

### Claim 1

A lighting circuit configured to drive a light source including a plurality of light emitting elements connected in series, the lighting circuit comprising:
a plurality of bypass switches respectively connected in parallel to the light emitting elements;
a switching converter; and
a converter controller configured to (i) stabilize a lamp current generated by the switching converter to a first target amount in a lighting-on state where at least one of the plurality of light emitting elements is turned on, and to (ii) stabilize the lamp current to a second target amount smaller than the first target amount in a complete lighting-off state where all of the plurality of light emitting elements are turned off,
wherein the converter controller includes:
a first controller configured to generate a first control pulse by a control method with a relatively high precision in the lighting-on state;
a second controller configured to generate a second control pulse by a control method with a relatively low precision in the complete lighting-off state; and
a driver circuit configured to drive the switching converter according to the first control pulse and the second control pulse.

### Claim 2 (depends on 1)

The lighting circuit according to claim 1, further comprising:
a determination circuit configured to compare a voltage across the light source with a threshold voltage and determine that the light source is at the complete lighting-off state if the voltage across the light source is lower than the threshold voltage.

### Claim 3 (depends on 1)

The lighting circuit according to claim 1, further comprising:
a bypass controller configured to control the plurality of bypass switches; and
a determination circuit configured to detect the complete lighting-off state according to a control signal from the bypass controller.

### Claim 4 (depends on 1)

A vehicle lamp comprising:
a light source including a plurality of light emitting elements connect in series; and
the lighting circuit according to claim 1 which is configured to turn on the light source.

### Claim 5 (depends on 4)

The vehicle lamp according to claim 4, further comprising:
a scanning optical system configured to receive light emitted from the light source and scan a front area of a vehicle.

### Claim 6

A lighting circuit configured to drive a light source including a plurality of light emitting elements connected in series, the lighting circuit comprising:
a plurality of bypass switches respectively connected in parallel to the light emitting elements;
a switching converter;
a converter controller configured to (i) stabilize a lamp current generated by the switching converter to a first target amount in a lighting-on state where at least one of the plurality of light emitting elements is turned on, and to (ii) stabilize the lamp current to a second target amount smaller than the first target amount in a complete lighting-off state where all of the plurality of light emitting elements are turned off; and
a determination circuit configured to compare a voltage across the light source with a threshold voltage and determine that the light source is at the complete lighting-off state if the voltage across the light source is lower than the threshold voltage,
wherein the converter controller is configured to stabilize the lamp current to the second target amount smaller than the first target amount when the determination circuit determines that the light source is at the complete lighting-off state.

### Claim 7 (depends on 6)

A vehicle lamp comprising:
a light source including a plurality of light emitting elements connect in series; and
the lighting circuit according to claim 6 which is configured to turn on the light source.

### Claim 8 (depends on 7)

The vehicle lamp according to claim 7, further comprising:
a scanning optical system configured to receive light emitted from the light source and scan a front area of a vehicle.

### Claim 9 (depends on 6)

The lighting circuit according to claim 6, further comprising:
a bypass controller configured to control the plurality of bypass switches; and
a determination circuit configured to detect the complete lighting-off state according to a control signal from the bypass controller.