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Light-emitting element drive device, flat illumination device, and liquid crystal display device

A technology for light-emitting components and driving devices, which is applied in lighting devices, electrical components, electroluminescent light sources, etc., to achieve the effect of suppressing forward voltage deviation

Inactive Publication Date: 2013-04-03
PANASONIC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The light-emitting element driving device of this prior art example has a plurality of LED string loads composed of one or more LEDs connected in series.

Method used

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  • Light-emitting element drive device, flat illumination device, and liquid crystal display device
  • Light-emitting element drive device, flat illumination device, and liquid crystal display device
  • Light-emitting element drive device, flat illumination device, and liquid crystal display device

Examples

Experimental program
Comparison scheme
Effect test

Embodiment approach 1

[0076] use Figure 3 ~ Figure 6 The light emitting element driving device according to Embodiment 1 of the present invention will be described. image 3 It is a block diagram showing an example of the overall configuration of the light emitting element drive device according to the first embodiment. Such as image 3 As shown, the light-emitting element driving device includes: voltage conversion circuits 1-2; switching circuits 30-31; constant current sources 21-24; minimum value detection units 32, 34; PWM control units 33, 35; VF determination unit 40; switch control unit 41; and current control unit 42, and drive LED string loads 11-14.

[0077] In addition, a configuration in which the voltage conversion circuit 1, the minimum value detection unit 32, and the PWM control unit 33 are combined is a specific example of one voltage application unit. In addition, the structure which combined the switching circuits 30 and 31 is a specific example of a switching means. In add...

Embodiment approach 2

[0113] use Figure 8 ~ Figure 9 A light emitting element driving device according to Embodiment 2 of the present invention will be described. In the second embodiment, the main difference from the light-emitting element driving device in the first embodiment is that a voltage conversion circuit 3, LED string loads 15, 16, constant current sources 25, 26, and selectors 30e to 30f are added. ; selectors 31 e to 31 f ; minimum value detection unit 36 ​​; and PMW control unit 37 . Figure 8 It is a block diagram showing an example of the overall configuration of the light emitting element drive device according to the second embodiment.

[0114] The voltage conversion circuit 3 is a step-up switching power supply, and is composed of a coil L3, a diode D3, a transistor M3 and a capacitor C3. Based on the control signal Vpwm3 from the PWM control unit 37, the voltage conversion circuit 3 boosts a predetermined input voltage Vcc to a voltage Vout3 required to drive each LED string ...

Embodiment approach 3

[0136] use Figure 10 A light emitting element driving device according to Embodiment 3 of the present invention will be described. Embodiment 3 differs from the light emitting element driving device of Embodiment 2 mainly in that it has a VF determination unit 40 b different from VF determination unit 40 and a switching control unit 41 b different from switching control unit 41 . Figure 10 It is a block diagram showing an example of the overall configuration of the light emitting element driving device according to the third embodiment. In the light emitting element driving device of this embodiment, after the control unit controls the switching unit so that all the light emitting element strings are connected to the same voltage applying unit, the control unit controls the switching unit so that the light emitting element strings connected to the voltage applying unit The light-emitting element string having the largest forward voltage drop among the light-emitting element...

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PUM

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Abstract

A light emitting element drive apparatus that drives light emitting elements reduces power loss caused by variability between forward voltage drops of the light emitting elements. A plurality of voltage applying sections (1, 32 and 33; and 2, 34 and 35) generate application voltages based on a detection voltage determined based on a maximum forward voltage drop among the forward voltage drops of the light emitting element arrays (11 to 14), and apply the generated application voltages to the light emitting elements (11 to 14). Switching sections (30 and 31) switch between a plurality of voltage applying sections (1, 32 and 33; and 2, 34 and 35) to which the light emitting element arrays (11 to 14) individually connect. Controlling sections (40 to 42) control the switching sections (30 and 31) to switch connection to minimize the difference between forward voltage drops of light emitting element arrays (11 to 14).

Description

technical field [0001] The present invention relates to a light-emitting element driving device that drives a light-emitting element such as an LED (Light Emitting Diode) connected to a power supply circuit with a constant current, a planar lighting device having the light-emitting element driving device, and the planar lighting device. A liquid crystal display device used as a back light. Background technique [0002] In recent years, LCD (Liquid Crystal Display: Liquid Crystal Display) backlight applications have become popular as one of the applications of LEDs. In general, when LEDs are used as LCD backlights, light emission can be obtained by passing a predetermined constant current to a plurality of LEDs connected in series. At this time, the number of LEDs and the amount of current are determined according to the amount of light required. In addition, a drive voltage for driving the LED is generated by a voltage conversion circuit that converts the power supply volt...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01L33/00
CPCY02B20/346H05B33/0827H05B33/0815H05B45/38H05B45/46Y02B20/30
Inventor 高田刚中西英行大西敏辉山村晓宏小林隆宏
Owner PANASONIC CORP