Method and device for driving LED element, illumination apparatus, and display apparatus

• US 20050168564A1
• Filed: 01/28/2005
• Published: 08/04/2005
• Est. Priority Date: 01/30/2004
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Kawaguchi, Yoshinobu, Ito, Shigetoshi
• Granted Patent: US 7,573,446 B2
• Time in Patent Office: Days
• US Class Current: 347/237
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/32 Pulse-control circuits

Abstract

A driving method and a driving device are provided for an LED element in which light emitting layers different from each other in light emission wavelength peak, put on each other with a barrier layer being interposed, are sandwiched by a pair of p-type and n-type layers, and color of emitted light from which substantially depends only upon driving current value. The method comprises a driving current value calculation step of obtaining a value for designating a current value corresponding to a desired color of emitted light from the LED element; a driving current generation step of generating a driving current having the current value designated by the value obtained in the driving current value calculation step; and a driving current supply step of supplying the LED element with the driving current generated in the driving current generation step.

Claims

1. A driving method of an LED element in which a plurality of light emitting layers different from each other in light emission wavelength peak, put on each other with a barrier layer being interposed, are sandwiched by a pair of p-type and n-type layers, and color of emitted light from which substantially depends only upon driving current value, the method comprising:

a driving current value calculation step of obtaining a value for designating a current value corresponding to a desired color of emitted light from the LED element;

a driving current generation step of generating a driving current having the current value designated by the value obtained in the driving current value calculation step; and

a driving current supply step of supplying the LED element with the driving current generated in the driving current generation step.

2. The driving method according to claim 1, wherein the method further comprises a duty calculation step of obtaining a value for designating a duty D of a pulse current to be supplied to the LED element as the driving current, the duty D being corresponding to a desired intensity of emitted light from the LED element;

and

the pulse current having a pulse height I designated by the value obtained in the driving current value calculation step, and the duty D designated by the value obtained in the duty calculation step, is generated in the driving current generation step.

3. The driving method according to claim 2, wherein the duty D of the pulse current is obtained in the duty calculation step on the basis of the desired intensity of emitted light from the LED element and the value obtained in the driving current value calculation step.

4. The driving method according to claim 3, wherein a color signal c for designating the desired color of emitted light from the LED element is converted into a pulse height signal i in the driving current value calculation step in accordance with a color of emitted light versus driving current value characteristics of the LED element;

a duty signal d for designating the duty D is calculated in the duty calculation step on the basis of the pulse height signal i and an intensity signal p for designating the desired intensity of emitted light from the LED element, such that the product of the duty D and a function value of the pulse height I designated by the pulse height signal i corresponds to the desired intensity of emitted light from the LED element, designated by the intensity signal p; and

the pulse current having the pulse height I designated by the pulse height signal i and the duty D designated by the duty signal d is generated in the driving current generation step.

5. The driving method according to claim 1, wherein a plurality of values for designating a plurality of current values corresponding to a plurality of colors of emitted light from the LED element, are obtained in the driving current value calculation step, the plurality of colors being different from each other to be mixed to make the desired color of emitted light from the LED element;

and

a driving current including a plurality of pulses having pulse heights I different from each other, designated by the plurality of values obtained in the driving current value calculation step, is generated in the driving current generation step.

6. The driving method according to claim 5, wherein the method further comprises a duty calculation step of obtaining a plurality of duty signals d for designating duties D of the plurality of pulses, respectively, such that light in mixed colors emitted from the LED element is sensed as if the LED element emits light in the desired color at a desired intensity;

and

the driving current including the plurality of pulses having the pulse heights I different from each other, designated by the plurality of values obtained in the driving current value calculation step, and the duties D designated by the plurality of duty signals d obtained in the duty calculation step for the plurality of pulses, respectively, is generated in the driving current generation step.

7. The driving method according to claim 5, wherein the driving current in which the plurality of pulses appear in order is generated in the driving current generation step.

8. The driving method according to claim 5, wherein three or more values for designating three or more current values different from one another, corresponding to three or more colors of emitted light from the LED element, to be mixed to make the desired color of emitted light from the LED element, are obtained in the driving current value calculation step.

9. The driving method according to claim 1, wherein the value for designating the current value corresponding to the desired color of emitted light from the LED element is obtained in the driving current value calculation step with referring to a signal of color of emitted light from the LED element.

10. The driving method according to claim 1, wherein each of the plurality of light emitting layers is made of a nitride-base semiconductor.

11. A driving device for an LED element in which a plurality of light emitting layers different from each other in light emission wavelength peak, put on each other with a barrier layer being interposed, are sandwiched by a pair of p-type and n-type layers, and color of emitted light from which substantially depends only upon driving current value, the device comprising:

a driving current value calculator that obtains a value for designating a current value corresponding to a desired color of emitted light from the LED element; and

a driving current generator that generates a driving current having the current value designated by the value obtained by the driving current value calculator.

12. The driving device according to claim 11, wherein the device further comprises a duty calculator that obtains a value for designating a duty D of a pulse current to be supplied to the LED element as the driving current, the duty D being corresponding to a desired intensity of emitted light from the LED element;

and

the driving current generator generates the pulse current having a pulse height I designated by the value obtained by the driving current value calculator, and the duty D designated by the value obtained by the duty calculator.

13. The driving device according to claim 11, wherein the driving current value calculator obtains a plurality of values for designating a plurality of current values corresponding to a plurality of colors of emitted light from the LED element, the plurality of colors being different from each other to be mixed to make the desired color of emitted light from the LED element;

and

the driving current generator generates a driving current including a plurality of pulses having pulse heights I different from each other, designated by the plurality of values obtained by the driving current value calculator.

14. The driving device according to claim 13, wherein the device further comprises a duty calculator that obtains a plurality of duty signals d for designating duties D of the plurality of pulses, respectively, such that light in mixed colors emitted from the LED element is sensed as if the LED element emits light in the desired color at a desired intensity;

and

the driving current generator generates the driving current including the plurality of pulses having the pulse heights I different from each other, designated by the plurality of values obtained by the driving current value calculator, and the duties D designated by the plurality of duty signals d obtained by the duty calculator for the plurality of pulses, respectively.

15. The driving device according to claim 13, wherein the driving current value calculator obtains three or more values for designating three or more current values different from one another, corresponding to three or more colors of emitted light from the LED element, to be mixed to make the desired color of emitted light from the LED element.

16. An illumination apparatus comprising:

an LED element in which a plurality of light emitting layers different from each other in light emission wavelength peak, put on each other with a barrier layer being interposed, are sandwiched by a pair of p-type and n-type layers, and color of emitted light from which substantially depends only upon driving current value; and

a driving device for the LED element,

the device comprising;

a driving current value calculator that obtains a value for designating a current value corresponding to a desired color of emitted light from the LED element; and

a driving current generator that generates a driving current having the current value designated by the value obtained by the driving current value calculator.

17. A display apparatus comprising:

an LED element in which a plurality of light emitting layers different from each other in light emission wavelength peak, put on each other with a barrier layer being interposed, are sandwiched by a pair of p-type and n-type layers, and color of emitted light from which substantially depends only upon driving current value; and

a driving device for the LED element,

the device comprising;

a driving current value calculator that obtains a value for designating a current value corresponding to a desired color of emitted light from the LED element; and

a driving current generator that generates a driving current having the current value designated by the value obtained by the driving current value calculator.