APPARATUS AND METHOD FOR SWITCHING A LIGHT SOURCE

• US 20060170369A1
• Filed: 08/26/2005
• Published: 08/03/2006
• Est. Priority Date: 02/01/2005
• Status: Active Grant

• Current Assignee: MiTAC International Corporation (MiTAC Holdings Corp.)
• Original Assignee: MiTAC International Corporation (MiTAC Holdings Corp.)
• Inventors: Lien, Te-Li
• Granted Patent: US 7,446,480 B2
• Time in Patent Office: Days
• US Class Current: 315/158
• CPC Class Codes: H05B 45/30 Driver circuits
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

An apparatus and its corresponding method for switching a light source are provided. The apparatus includes a light sensor, a decision device and a light source. The light sensor senses the ambient luminance and outputs a sensing signal to indicate whether the luminance is greater than a predetermined quantity. The decision device is connected to the light sensor. It receives a switching signal and outputs a lighting signal according to the sensing signal and the switching signal. The light source is coupled to the decision device and is activated whenever the lighting signal demands light.

Claims

1. An apparatus for switching a light source, comprising:

a light sensor for sensing an ambient luminance and outputting a sensing signal to indicate whether the luminance is greater than a predetermined value;

a decision device, coupled to the light sensor, receiving a switching signal and outputting a lighting signal according to the switching signal and the sensing signal; and

a light source, coupled to the decision device, deciding whether or not to emit light according to the lighting signal.

2. The apparatus for switching a light source of claim 1, wherein the predetermined value is about 51 lux.

3. The apparatus for switching a light source of claim 1, wherein, when the sensing signal is at a logic high voltage, it means that the luminance is greater than the predetermined value.

4. The apparatus for switching a light source of claim 3, wherein the light sensor further comprises:

a direct current voltage source providing a logic high voltage;

a ground providing a logic low voltage; and

an ambient light sensor, coupled among the direct current voltage source, the ground and an output end of the light sensor, sensing the luminance, connecting the direct current voltage source and the output end when the luminance is greater than the predetermined value so that the light sensor outputs the logic high voltage; and

disconnecting the direct current voltage source and the output end when the luminance is less than or equal to the predetermined value so that the light sensor outputs the logic low voltage.

5. The apparatus for switching a light source of claim 1, wherein when the luminance is greater than the predetermined value, the decision device outputs a lighting signal indicating that the light source should not emit light;

and when the luminance is less than or equal to the predetermined value, the decision device directly outputs the switching signal as the lighting signal.

6. The apparatus for switching a light source of claim 5, wherein when the lighting signal is at a logic high voltage, the lighting signal indicates that the light source should not emit light.

7. The apparatus for switching a light source of claim 6, wherein the decision device further comprises:

a direct current voltage source providing the logic high voltage; and

an analog switch, coupled between the direct current voltage source and an output end of the decision device, receiving the lighting signal and the switching signal;

connecting the direct current voltage source and the output end when the luminance is greater than the predetermined value so that the decision device outputs the lighting signal with the logic high voltage; and

connecting the switching signal and the output end when the luminance is less than or equal to the predetermined value so that the decision device directly outputs the switching signal as the lighting signal.

8. The apparatus for switching a light source of claim 1, wherein the light source emits light when the lighting signal is at a logic low voltage.

9. The apparatus for switching a light source of claim 8, wherein the light source further comprises:

a direct current voltage source providing a logic high voltage;

a switching device, coupled to the direct current voltage source, receiving the lighting signal, turned on when the lighting signal is at the logic low voltage and outputs the voltage of the direct current voltage source; and

a light emitting diode (LED), coupled to the switching device, emitting light when the output of the switching device is at the logic high voltage.

10. The apparatus for switching a light source of claim 9, wherein the switching device is a PMOS transistor.

11. A method for switching a light source, comprising steps as follows:

sensing an ambient luminance; and

deciding whether or not a light source should emit light according to a switching signal and according to whether or not the luminance is greater than a predetermined value.

12. The method for switching a light source of claim 11, wherein the predetermined value is about 51 lux.

13. The method for switching a light source of claim 11, wherein the step deciding whether or not the light source should emit light further comprises:

disabling the light source from emitting light when the luminance is greater than the predetermined value; and

deciding whether or not the light source should emit light according to the switching signal when the luminance is less than or equal to the predetermined value.