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LED driver circuit and method, and system and method for estimating junction temperature of light emitting diode

A technology of driver circuit and light-emitting diode, which is applied in the direction of electroluminescent light source, electric light source, thermometer with electric/magnetic element directly sensitive to heat, etc., to achieve the effect of precision optimization

Active Publication Date: 2010-12-22
NXP BV
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Providing this small measurement current challenges the design of an LED driver that also needs to be able to supply the required operating current

Method used

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  • LED driver circuit and method, and system and method for estimating junction temperature of light emitting diode
  • LED driver circuit and method, and system and method for estimating junction temperature of light emitting diode
  • LED driver circuit and method, and system and method for estimating junction temperature of light emitting diode

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Embodiment Construction

[0042] The present invention provides a driver circuit for controlling LEDs.

[0043] The driver circuit of the present invention is specifically designed to implement a method of measuring the LED junction temperature, which has been proposed (but not yet published) by the applicant. First, the junction temperature measurement method will be described.

[0044] Figures 1A to 1D is a graph schematically representing the method.

[0045] Figure 1A The drive current applied to the LED is shown. Use a pulsed current source to drive the LED. The pulses drive a forward bias current through the diode in the form of a square wave that switches between high and low current values.

[0046] The low current value is the measured current, preferably less than or equal to 1 mA. More preferably, the current is less than 500 μA, more preferably less than 100 μA, even more preferably less than 50 μA. This current may even be less than 10 μA, for example in the region of 5 μA.

[004...

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PUM

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Abstract

A driver circuit (10) for a light emitting diode comprises a first driver circuit (32, 32', 32') for generating a first current output for driving the light emitting diode, wherein the first driver circuit has a control switch for interrupting the supply of the first current output. A second driver circuit (50) is for generating a second current output for driving the light emitting diode, and the second driver circuit also has a control switch for interrupting the supply of the second current output. The overall output of the driver circuit comprises a pulse width modulated output current which alternates between a high current (Ihigh) generated by the first driver circuit and a low current (I|OW) generated by the second driver circuit. By providing separate driver circuits for two different current requirements, the circuits can be optimised for each function. For example the high current value can comprise an LED operation current, and the low current value can comprise a non-zero measurement current.

Description

technical field [0001] The present invention relates to lighting devices using light emitting diodes (LEDs), and in particular to temperature-based control of such devices. Background technique [0002] The use of solid-state devices such as LEDs for lighting is developing rapidly. The use of LEDs for lighting has several advantages over the use of conventional light sources, including better light output / size ratio and improved power efficiency. The light output intensity of LEDs can be controlled by: [0003] (a) adjust the magnitude of the current through the LED, or [0004] (b) Adjust the frequency and duty cycle of the current pulses through the LED. [0005] A combination of these two techniques can also be used. [0006] During operation, the LED temperature increases, which affects the light output of the LED and the dominant wavelength of the output light. Knowledge about the temperature at the LED junction is critical to controlling the LED for maximum perfor...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H05B33/08H05B44/00
CPCH05B33/0818G01K7/01H05B45/397H05B45/28Y02B20/30
Inventor 吉安·霍赫扎德汉斯·舒密兹威廉默斯·H·M·郎厄斯莱格拉杜·苏尔代亚努
Owner NXP BV
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