Driving device, light-emitting device, projection device and control method

• US 9,270,175 B2
• Filed: 08/28/2014
• Issued: 02/23/2016
• Est. Priority Date: 08/30/2013
• Status: Active Grant

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Hamanaka, Hideo
• Primary Examiner(s): VO, TUYET THI
• Application Number:
  US14/472,231
• Publication Number:
  US 20150061527A1
• Time in Patent Office: 544 Days
• Field of Search: 315/247, 315/185.S, 315/224, 315/225, 315/291, 315307-326
• US Class Current: 1/1
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology

Abstract

A driving device is provided with: a power circuit in which it is possible to modify an output current value of an output terminal configured to have a load connected thereto; an output capacitor connected between the output terminal of the power circuit and a reference potential node; a switching element connected between the output terminal of the power circuit and the reference potential node; and a control unit that controls the output current value of the power circuit.

The control unit turns the switching element ON and OFF and controls the output current value of the power circuit during a period in which the switching element is ON such that the voltage of the output terminal of the power circuit during this period is equal to or lower than the voltage applied to the load during a period when this load is OFF.

Claims

1. A driving device, comprising:

a power circuit that can modify an output current or an output voltage of an output terminal configured to have a load connected thereto;

an output capacitor connected between the output terminal of the power circuit and a reference potential node;

a switching device connected between the output terminal of the power circuit and the reference potential node; and

a control unit that controls the output current or the output voltage of the power circuit,

wherein the control unit turns the switching device ON and OFF, and

wherein the control unit controls the output current or the output voltage of the power circuit while the switching device is ON such that a voltage of the output terminal of said power circuit while the switching device is ON becomes less than or equal to a voltage applied to the load while said switching device is OFF thereafter.

2. The driving device according to claim 1,

wherein the control unit sets the output current or the output voltage of the power circuit to zero while the switching device is ON.

3. The driving device according to claim 1,

wherein the control unit sets the output voltage of the power circuit while the switching device is ON to less than or equal to the output voltage while the switching device is OFF thereafter.

4. The driving device according to claim 1,

wherein the control unit maintains the same output voltage or output current of the power circuit while the switching device is OFF.

5. The driving device according to claim 1,

wherein the control unit stepwisely increases the output voltage or the output current of the power circuit while the switching device is OFF.

6. The driving device according to claim 1,

wherein the control unit lowers the output voltage or the output current of the power circuit immediately after the switching device switches from ON to OFF to less than or equal to the output voltage or the output current immediately before the switching device switches from OFF to ON.

7. The driving device according to claim 1,

wherein a length of the switching device being ON is such that the voltage of the output terminal of the power circuit becomes less than or equal to a voltage applied to the load while the switching device is OFF thereafter.

8. The driving device according to claim 1,

wherein a length of the switching device being ON is set based on a difference between the output voltage or the output current of the power circuit immediately before said switching device is switched from OFF to ON and the output voltage or the output current immediately after the switching device is switched from ON to OFF.

9. The driving device according to claim 1, further comprising:

a second switching device that is between the output terminal of the power circuit and the reference potential node, the second switching device configured to be connected in series with the load,

wherein the control unit turns the second switching device ON and OFF in a phase opposite to the switching device being turned ON and OFF.

10. The driving device according to claim 1, further comprising:

a plurality of second switching devices, each configured to be connected to a respective load, one end connected to the reference potential node and another end connected to said respective load,

wherein the control unit turns the plurality of the second switching devices ON and OFF such that the plurality of second switching devices are sequentially ON with time intervals therebetween,

wherein the control unit turns OFF the switching device when any one of the plurality of the second switching devices are ON, and

wherein the control unit turns ON the switching device when all of the plurality of the second switching devices are OFF.

11. The driving device according to claim 1, further comprising:

a plurality of second switching devices, each configured to be connected to a respective load, one end connected to the reference potential node and another end connected to said respective load,

wherein the control unit turns the plurality of the second switching devices ON and OFF such that the plurality of the second switching devices are sequentially ON when the switching device is OFF.

12. The driving device according to claim 1, further comprising:

a plurality of second switching devices, each configured to be connected to a respective load, one end connected to the reference potential node and another end connected to said respective load,

wherein the control unit turns the plurality of the second switching devices ON and OFF such that the plurality of second switching devices are sequentially ON when the switching device is OFF, and

wherein the control unit switches any of the plurality of the second switching devices from OFF to ON when the output voltage or the output current of the power circuit rises.

13. The driving device according to claim 1,

wherein the plurality of the loads are diodes, and

wherein the plurality of the second switching devices are turned ON in order of ascendancy of forward voltage drops of the plurality of the loads connected to the respective plurality of the second switching devices.

14. A light-emitting device, comprising:

the driving device according to claim 1, and

a light-emitting element as the load.

15. A projection device, comprising:

the light-emitting device according to claim 14.

16. A method of controlling a driving device having a power circuit that can modify an output current or an output voltage of an output terminal configured to have a load connected thereto, an output capacitor connected between the output terminal of the power circuit and a reference potential node, a switching device connected between the output terminal of the power circuit and the reference potential node, and a control unit that controls the output current or the output voltage of the power circuit, the method comprising:

controlling the switching device to be ON and OFF and controlling the output current or the output voltage of the power circuit while the switching device is ON such that a voltage of the output terminal of said power circuit while the switching device is ON becomes less than or equal to a voltage applied to the load while said switching device is OFF thereafter.

17. A driving device, comprising:

a power circuit that can modify an output current or an output voltage of an output terminal configured to have a load connected thereto;

an output capacitor connected between the output terminal of the power circuit and a reference potential node;

a switching device connected between the output terminal of the power circuit and the reference potential node; and

a control unit that controls the output current or the output voltage of the power circuit,

wherein the control unit sets the output current or the output voltage of the power circuit to a high level, a low level that is lower than this high level, and a middle level that is higher than the low level but lower than the high level, in this order in cycle repeatedly,

wherein the control unit turns the switching device OFF when the output current or the output voltage of the power circuit is set to the high level and the middle level, and

wherein the control unit turns the switching device ON when the output current or the output voltage of the power circuit is set at the low level.

18. The driving device according to claim 17,

wherein the control unit turns the switching device ON and OFF after the output current or the output voltage of the power circuit becomes the medium level,

wherein the control unit sets the output current or the output voltage of the power circuit to the low level when the switching device is ON,

wherein the control unit maintains the same output current or output voltage of the power circuit when the switching device is OFF, and

wherein the control unit stepwisely raises the output current or the output voltage of the power circuit from the middle level to the high level while the switching device is OFF.

19. The driving device according to claim 17,

wherein the control unit, after the output current or the output voltage of the power circuit has been set to the middle level, stepwisely raises the output current or the output voltage of the power circuit from the middle level to the high level while the switching device remains OFF thereafter.