Light source controlling circuit and portable electronic apparatus

• US 20060238130A1
• Filed: 04/22/2005
• Published: 10/26/2006
• Est. Priority Date: 04/22/2004
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Hosoya, Hideyuki
• Granted Patent: US 7,427,838 B2
• Time in Patent Office: Days
• US Class Current: 315/86
• CPC Class Codes: H05B 45/56 involving measures to prevent abnormal temperature of the LEDs
• CPC Class Codes: H05B 47/20 Responsive to malfunctions or to light source life; for protection

Abstract

A light source controlling circuit controls a light source outputting continuous light. The light source controlling circuit has a power supply circuit supplying an electric power to the light source, a light source monitoring circuit monitoring a state of the light source, and a control circuit outputting a first control signal to control the light source is controlled. The light source monitoring circuit outputs a second control signal to control the light source in correspondence to a state of the light source. A portable electronic apparatus has a light source outputting continuous light, an image pickup device, and the light source controlling circuit. The light source controlling circuit, for example, controls ON/OFF of the light source in accordance with a temperature of the light source detected by the light source monitoring circuit.

Claims

1. A light source controlling circuit that controls a light source that outputs continuous light, comprising:

a power supply circuit that supplies an electric power to the light source;

a light source monitoring circuit that monitors a state of the light source; and

a control circuit that outputs a first control signal to control the light source;

wherein the light source monitoring circuit outputs a second control signal to control the light source in correspondence to the state of the light source.

2. A light source controlling circuit according to claim 1, wherein when the light source monitoring circuit detects malfunction of the light source, the light source monitoring circuit outputs the second control signal to the power supply circuit to stop an operation of the power supply circuit.

3. A light source controlling circuit according to claim 2, wherein the light source monitoring circuit comprises a temperature detecting element for detecting a temperature of the light source, and when a temperature of the light source is equal to or higher than a predetermined temperature, judges that the light source malfunctions.

4. A light source controlling circuit according to claim 1, wherein when the light source monitoring circuit detects malfunction of the light source, the light source monitoring circuit outputs the second control signal to the control circuit to stop an operation of the control circuit.

5. A light source controlling circuit according to claim 4, wherein the light source monitoring circuit comprises a temperature detecting element that detects a temperature of the light source, and when a temperature of the light source is equal to or higher than a predetermined temperature, judges that the light source malfunctions.

6. A light source controlling circuit according to claim 1, wherein the first control signal is inputted to the power supply circuit through the light source monitoring circuit.

7. A light source controlling circuit according to claim 1, wherein the light source monitoring circuit comprises:

a first resistor disposed in series between the control circuit and the power supply circuit;

a voltage division resistor portion having a thermistor and a second resistor, the voltage division resistor portion being connected to the control circuit; and

a field effect transistor having a gate terminal to which a divided voltage is inputted and a drain terminal connected to the power supply circuit.

8. A light source controlling circuit according to claim 1, wherein:

the light source monitoring circuit comprises;

a first resistor disposed in series between the control circuit and the power supply circuit;

a voltage division resistor portion having a plurality of resistors, the voltage division resistor portion being connected to the control circuit; and

a field effect transistor having a gate terminal to which a divided voltage is inputted and a drain terminal connected to the power supply circuit;

wherein the voltage division resistor portion monitors at least one of a voltage that is fed back from the light source to the power supply circuit and a current supplied to the light source.

9. A light source controlling circuit according to claim 1, wherein the light source monitoring circuit comprises:

a first resistor disposed in series between the control circuit and the power supply circuit;

a voltage division resistor portion having a thermistor and a second resistor, the voltage division resistor portion being connected to the control circuit; and

a field effect transistor having a gate terminal to which a divided voltage is inputted and a drain terminal connected to the control circuit.

10. A light source controlling circuit according to claim 1, wherein:

the light source monitoring circuit comprises;

a first resistor disposed in series between the control circuit and the power supply circuit;

a voltage division resistor portion including a plurality of resistors, the voltage division resistor portion being connected to the control circuit; and

a field effect transistor having a gate terminal to which a divided voltage is inputted and a drain terminal connected to the control circuit; and

wherein the voltage division resistor portion monitors at least one of a voltage that is fed back from the light source to the power supply circuit and a current supplied to the light source.

11. A light source controlling circuit according to claim 1, wherein the light source comprises a light emitting diode (LED).

12. A portable electronic apparatus, comprising:

an imaging device;

a light source that outputs continuous light;

a power supply circuit that supplies an electric power to the light source;

a light source monitoring circuit that monitors a state of the light source; and

a control circuit that outputs a first control signal to control the light source,

wherein the light source monitoring circuit outputs a second control signal to control the light source in correspondence to the state of the light source.

13. A portable electronic apparatus according to claim 12, wherein when the light source monitoring circuit detects malfunction of the light source, the light source monitoring circuit outputs the second control signal to the power supply circuit to stop an operation of the power supply circuit.

14. A portable electronic apparatus according to claim 13, wherein the light source monitoring circuit comprises a temperature detecting element that detects a temperature of the light source, and when a temperature of the light source is equal to or higher than a predetermined temperature, judges that the light source malfunctions.

15. A portable electronic apparatus according to claim 12, wherein when the light source monitoring circuit detects malfunction of the light source, the light source monitoring circuit outputs the second control signal to the control circuit to stop an operation of the control circuit.

16. A portable electronic apparatus according to claim 15, wherein the light source monitoring circuit comprises a temperature detecting element that detects a temperature of the light source, and when a temperature of the light source is equal to or higher than a predetermined temperature, judges that the light source malfunctions.

17. A portable electronic apparatus according to claim 12, wherein the first control signal is inputted to the power supply circuit through the light source monitoring circuit.

18. A portable electronic apparatus according to claim 12, wherein the light source monitoring circuit comprises:

a first resistor disposed in series between the control circuit and the power supply circuit;

a voltage division resistor portion having a thermistor and a second resistor, the voltage division resistor portion being connected to the control circuit; and

a field effect transistor having a gate terminal to which a divided voltage is inputted and a drain terminal connected to the power supply circuit.

19. A portable electronic apparatus according to claim 12, wherein:

the light source monitoring circuit comprises;

a first resistor disposed in series between the control circuit and the power supply circuit;

a voltage division resistor portion comprising a plurality of resistors, the voltage division resistor portion being connected to the control circuit; and

a field effect transistor having a gate terminal to which a voltage obtained through voltage division is inputted and a drain terminal connected to the power supply circuit;

wherein the voltage division resistor portion monitors at least one of a voltage that is fed back from the light source to the power supply circuit and a current supplied to the light source.

20. A portable electronic apparatus according to claim 12, wherein the light source monitoring circuit comprises:

a first resistor disposed in series between the control circuit and the power supply circuit;

a voltage division resistor portion including a thermistor and a second resistor, the voltage division resistor portion being connected to the control circuit; and

a field effect transistor having a gate terminal to which a divided voltage is inputted and a drain terminal connected to the control circuit.

21. A portable electronic apparatus according to claim 12, wherein:

the light source monitoring circuit comprises;

a first resistor disposed in series between the control circuit and the power supply circuit;

a voltage division resistor portion having a plurality of resistors, the voltage division resistor portion being connected to the control circuit; and

a field effect transistor having a gate terminal to which a divided voltage is inputted and a drain terminal connected to the control circuit;

wherein the voltage division resistor portion monitors at least one of a voltage that is fed back from the light source to the power supply circuit and a current supplied to the light source.

22. A portable electronic apparatus according to claim 12, wherein the light source comprises a light emitting diode (LED).

23. A portable electronic apparatus according to claim 12, wherein the portable electronic apparatus is a mobile telephone.

24. A portable electronic apparatus according to claim 12, wherein the control circuit controls the portable electronic apparatus.