Lighting circuit

• US 7,081,708 B2
• Filed: 10/14/2003
• Issued: 07/25/2006
• Est. Priority Date: 10/15/2002
• Status: Active Grant

• Current Assignee: Koito Manufacturing Company Limited
• Original Assignee: Koito Manufacturing Company Limited
• Inventors: Murakami, Kentaro, Ishibashi, Hiroki, Ito, Masayasu, Takeda, Hitoshi
• Primary Examiner(s): VU, DAVID HUNG
• Application Number:
  US10/684,738
• Publication Number:
  US 20040075393A1
• Time in Patent Office: 1,015 Days
• Field of Search: 315/307, 315/224, 315/82, 362/251, 362/543, 363/21.12, 363/23
• US Class Current: 315/82
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/385 using flyback topology

Abstract

A lighting circuit for lighting a vehicular lamp including a plurality of light-emitting diodes, includes: a selection unit for selecting the number of light-emitting diodes to be connected in series in the vehicular lamp based on an instruction from the outside; a switching regulator for applying an output voltage based on a power-supply voltage output by an external DC power supply to the selected number of light-emitting diodes to be connected in series, so as to supply a supply current to the selected number of light-emitting diodes; and an output controlling unit for controlling the output voltage of the switching regulator based on the supply current.

Claims

1. A lighting circuit for lighting a vehicular lamp comprising a plurality of light source blocks respectively comprising a plurality of light-emitting diodes connected in series, comprising:

a selection unit operable to select at least one of the plurality of light source blocks, thereby selecting a number of light-emitting diodes to be connected in said vehicular lamp based on an external instruction;

a switch operable not to flow a current through at least one of the light source blocks not selected according to the selection of said selection unit;

a switching regulator operable to apply an output voltage based on a power-supply voltage output by an external DC power supply to said selected number of light-emitting diodes, to supply a supply current to said selected number of light-emitting diodes; and

an output controlling unit operable to control said output voltage of said switching regulator based on said supply current, wherein

said vehicular lamp comprises two light source blocks connected in series,

said switch is connected in parallel to a first of said two light source blocks while being connected in series with a second of said two light source blocks,

said selection unit makes said switch conductive in a case where said first of said two light source blocks is not selected, and

said switching regulator outputs said supply current having approximately the same magnitude irrespective of whether said first of said two light source blocks is selected.

2. A lighting circuit for lighting a vehicular lamp comprising a plurality of light source blocks respectively comprising a plurality of light-emitting diodes connected in series, comprising:

a selection unit operable to select at least one of the plurality of light source blocks, thereby selecting a number of light-emitting diodes to be connected in said vehicular lamp based on an external instruction;

a switch operable not to flow a current through at least one of the light source blocks not selected according to the selection of said selection unit;

a switching regulator operable to apply an output voltage based on a power-supply voltage output by an external DC power supply to said selected number of light-emitting diodes, to supply a supply current to said selected number of light-emitting diodes; and

an output controlling unit operable to control said output voltage of said switching regulator based on said supply current, wherein

a number of said light-emitting diodes connected in series in said first of said two light source blocks is smaller than a number of said light-emitting diodes connected in series in said second of said two light source blocks,

said switch is connected in series with said first of said two light source blocks while being connected in parallel to said second of said two light source blocks, and

said selection unit makes said switch conductive in a case of selecting said first of said two light source blocks.

3. A lighting circuit for lighting a vehicular lamp, comprising:

two light source blocks connected in series, each light source block comprising one or more light emitting diodes connected in series;

a switch that is connected in parallel to a first of said two light source blocks while being connected in series with a second of said two light source blocks;

a selection unit operable to select at least one of said two light source blocks, thereby selecting a number of light-emitting diodes to be connected in series in said vehicular lamp based on an external instruction,

wherein said selection unit makes said switch conductive in a case where said first of said two light source blocks is not selected;

a switching regulator operable to apply an output voltage based on a power-supply voltage output by an external DC power supply to said selected number of light emitting diodes connected in series, to supply a supply current to said selected number of light emitting diodes connected in series,

wherein said switching regulator outputs said supply current having approximately the same magnitude when said first of said two light source blocks is selected as when said second of said two light source blocks is selected; and

an output controlling unit operable to control said output voltage of said switching regulator based on said supply current.

4. A lighting circuit for lighting a vehicular lamp, comprising:

two light source blocks connected in series, each light source block comprising one or more light emitting diodes connected in series,

wherein a number of light-emitting diodes connected in series in a first of said two light source blocks is smaller than a number of light-emitting diodes connected in series in a second of said two light source blocks;

a switch that is connected in series with the first of said two light source blocks and connected in parallel to the second of said two light source blocks;

a selection unit operable to select at least one of said two light source blocks, thereby selecting a number of light-emitting diodes to be connected in series in said vehicular lamp based on an external instruction,

wherein said selection unit makes said switch conductive when selecting said first of said two light source blocks;

a switching regulator operable to apply an output voltage based on a power-supply voltage output by an external DC power supply to said selected number of light-emitting diodes connected in series, to supply a supply current to said selected number of light-emitting diodes; and

an output controlling unit operable to control said output voltage of said switching regulator based on said supply current.