High-pressure discharge lamp operation device and illumination appliance having the same Number:7,141,937 from the United States Patent and Trademark Office (PTO) owispatent

Title: High-pressure discharge lamp operation device and illumination appliance having the same

Abstract: A full bridge circuit including four switching elements (Q1 to Q4) is alternated with a high switching frequency and a series-connected resonance circuit (5) including an inductor (L2) and a capacitor (C2) is made to resonate at a switching frequency of the full bridge circuit multiplied by an integer (for example, frequency multiplied by three), thereby generating a high voltage pulse for start up. After a high-pressure discharge lamp (DL) is started up, the full bridge circuit is alternated with a low switching frequency so as to operate as a step-down chopper for inverting the output polarity, thereby stably supplying rectangular wave voltage of low frequency to the high-pressure discharge lamp (DL) via a filter circuit including an inductor (L1) and a capacitor (C1).

Patent Number: 7,141,937 Issued on 11/28/2006 to Kumagai,   et al.

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Inventors:	Kumagai; Jun (Kadoma, JP), Kishimoto; Akihiro (Osaka, JP), Konishi; Hirofumi (Hirakata, JP)
Assignee:	Matsushita Electric Works, Ltd. (Osaka, JP)
Appl. No.:	10/532,822
Filed:	September 26, 2003
PCT Filed:	September 26, 2003
PCT No.:	PCT/JP03/12319
371(c)(1),(2),(4) Date:	April 26, 2005
PCT Pub. No.:	WO20/04/039130
PCT Pub. Date:	May 06, 2004

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Foreign Application Priority Data

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Oct 28, 2002 [JP]			2002-312484
Oct 31, 2002 [JP]			2002-318934

Current U.S. Class:	315/224 ; 315/226; 315/291
Current International Class:	H05B 37/02 (20060101); G05F 1/00 (20060101)
Field of Search:	315/224,226,209R,291,307

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References Cited [Referenced By]

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U.S. Patent Documents

	4912374		March 1990		Nagase et al.
	5569984		October 1996		Holtslag
	5923127		July 1999		Keijser et al.
	5932976		August 1999		Maheshwari et al.
	6124682		September 2000		Lakin et al.
	6144172		November 2000		Sun
	6380694		April 2002		Uchihashi et al.
	6593703		July 2003		Sun
	6861812		March 2005		Kambara et al.
	2002/0047609		April 2002		Weng

Foreign Patent Documents

	0314077		Jan., 1994		EP
	59-18460		Feb., 1984		JP
	63-149566		Oct., 1988		JP
	5-198911		Aug., 1993		JP
	5-327161		Dec., 1993		JP
	6-5191		Jan., 1994		JP
	9-282927		Oct., 1997		JP
	10-284265		Oct., 1998		JP
	11-111040		Apr., 1999		JP
	2000-058284		Feb., 2000		JP
	2000-357617		Dec., 2000		JP
	2001-297922		Oct., 2001		JP
	2002-140926		May., 2002		JP
	2002-170425		Jun., 2002		JP
	96/20578		Jul., 1996		WO
	97/42650		Nov., 1997		WO
	00/78100		Dec., 2000		WO

Other References

English Language Abstract of JP 2000-058284. cited by other . English Language Abstract of JP 2001-297922. cited by other . English Language Abstract of JP 2002-170425. cited by other . English Language Abstract of JP 5-198911. Aug. 6, 1993. cited by other . English Language Abstract of JP 2002-140926. cited by other . English Language Abstract of JP 9-282927. Oct. 31, 1997. cited by other . English Language Abstract of JP 11-111040. Apr. 23, 1999. cited by other . English Language Abstract of JP 5-327161. Dec. 10, 1993. cited by other.

Primary Examiner: Le; Hoanganh
Assistant Examiner: Le; Tung
Attorney, Agent or Firm: Greenblum & Bernstein, P.L.C.

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Claims

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The invention claimed is:

1. A device for lighting a high-pressure discharge lamp, comprising: a DC power supply: a first switching element having one terminal connected to the high pressure side of the DC power supply; a second switching element having one terminal connected to the low-voltage side of the DC power supply; a third switching element having one terminal connected to the high pressure side of the DC power supply; a fourth switching element having one terminal connected to the low-voltage side of the DC power supply; a first inductor having one terminal connected to the other terminals of the first and second switching elements, and the other terminal connected to one terminal of the high-pressure discharge lamp; a first capacitor connected between an intermediate section of a winding of the first inductor and the low-voltage side of the DC power supply, and composing a first series resonant circuit together with the first inductor; a second capacitor having one terminal connected to the one terminal of the first inductor, and the other terminal connected to the other terminal of the high-pressure discharge lamp; a second inductor having one terminal connected to the other terminals of the third and fourth switching elements, and the other terminal connected to the other terminal of the second capacitor; and a control circuit for controlling turning on and off of the first to fourth switching elements, wherein, before the high-pressure discharge lamp is started up, the control circuit performs control in a first control mode which alternately switches between a state in which the first and fourth switching elements are on and the second and third switching elements are off and a state in which the first and fourth switching elements are off and the second and third switching elements are on, at a predetermined switching frequency, in the first control mode, the switching frequency resonates the first series resonant circuit at its harmonic frequency to generate a high voltage for starting up the high-pressure discharge lamp, and the switching frequency is lower than a resonant frequency of the first series resonant circuit and higher than a resonant frequency of a second series resonant circuit including the second inductor and the second capacitor.

2. The high-pressure discharge lamp lighting device according to claim 1, wherein, after the high-pressure discharge lamp is started up, the control circuit performs control in a second control mode which alternately switches at a low-frequency between, an operation for alert switching at a high-frequency between a state in which the first and fourth switching elements are simultaneously on, and a state in which at least one of the first and fourth switching elements is off and an operation for alternately switching at a high-frequency between a state in which the second and third switching elements are simultaneously on and a state in which at least one of the second and third switching elements is off.

3. The high-pressure discharge lamp lighting device according to claim 1, wherein, in the first control mode, a frequency of a high voltage generated by the first series resonant circuit is (2n+1) (n is a natural number) times the switching frequency.

4. The high-pressure discharge lamp lighting device according to claim 1, wherein the switching frequency is higher than two times the resonant frequency of a second series resonant circuit including the second inductor and the second capacitor.

5. The high-pressure discharge lamp lighting device according to claim 1, wherein the control circuit varies the switching frequency depending on time in the first control mode.

6. The high-pressure discharge lamp lighting device according to claim 5, wherein the control circuit has a digital arithmetic processing circuit, and the switching frequency is discretely varied by the digital arithmetic processing circuit.

7. The high-pressure discharge lamp lighting device according to claim 5, wherein the control circuit has an analog arithmetc processing circuit, and the switching frequency is continuously varied by the analog arithmetc processing circuit.

8. The high-pressure discharge lamp lighting device according to claim 5, wherein a variable range of the switching frequency is set such that the resonant frequency of the first series resonant circuit is included in a range from an integral multiple of the lower limit of the variable range to an integral multiple of the upper limit of the variable range.

9. The high-pressure discharge lamp lighting device according to claim 8, wherein the frequency corresponding to the integral multiple of the switching frequency is (2N +1) times (n is a natural number) the switching frequency.

10. The high-pressure discharge lamp lighting device according to claim 9, wherein the frequency corresponding to the integral multiple of the switching frequency is three times the switching frequency.

11. The high-pressure discharge lamp lighting device according to claim 1, wherein the first and second switching elements are PWM-controlled at a duty ratio of about 50%, and the first and second switching elements alternately repeat on and off-operations at equal time intervals.

12. The high-pressure discharge lamp lighting device according to claim 1, wherein the first inductor has a transformer structure provided with a primary winding and a secondary winding, one terminal of the primary winding is connected to one terminal of the secondary winding, and the first capacitor is connected to the connection point between the primary winding and the secondary winding.

13. The high-pressure discharge lamp lighting device according to claim 1, wherein the first inductor has a transformer structure provided with a primary winding and a secondary winding, and a ratio of the numbers of turns of the primary winding and the secondary winding is given by 1:N (N>1).

14. The high-pressure discharge lamp lighting device according to claim 1, wherein the first inductor has a transformer structure provided with a primary winding and a secondary winding, the primary winding is constituted by a litz wire, and the secondary winding is constituted by a single wire.

15. The high-pressure discharge lamp lighting device according to claim 1, further comprising a start up detector operable to detect the start up of the high-pressure discharge lamp, wherein, when the start up detector detects the start up of the high-pressure discharge lamp, the control circuit performs control in a third control mode which alternately switches at a low-frequency between, an operation for switching at a high-frequency among, a state in which the first and fourth switching elements are simultaneously on, a state in which one of the first and fourth switching elements is off, and a state in which both the first and fourth switching elements are off, sequentially in the order, and an operation for switching at a high-frequency among, a state in which the second and third switching elements are simultaneously on, a state in which one of the second and third switching elements is off, and a state in which both the second and third switching elements are off, sequentially in the order.

16. The high-pressure discharge lamp lighting device according to claim 15, herein a switching operation from the first control mode to the third control mode is conducted when a predetermined period of time passes after the start up of the high pressure discharge lamp is detected.

17. The high-pressure discharge lamp lighting device according to claim 15, wherein the switching frequency of the first control mode is higher than a high-frequency by which the switching elements are switched in the third control mode.

18. The high-pressure discharge lamp lighting device according to claim 1, further comprising a main circuit board and an auxiliary circuit board on which the electronic parts comprised in the high-pressure discharge lamp lighting device can be mounted, wherein terminal pads for soldering connection to the main circuit board are formed on both the upper and lower surfaces of the lower part of the auxiliary circuit board, a slit in which the auxiliary circuit board is inserted and which supports the auxiliary circuit board is formed in the main circuit board, and the slit has a portion which has a first width and is electrically connected to the auxiliary circuit board and a portion which has a second width which is almost equal to or smaller than the thickness of the auxiliary circuit board, and the first width is larger than the second width.

19. The high-pressure discharge lamp lighting device according to claim 18, further comprising a variable resist for output control connected to the high-pressure discharge lamp in series and mounted on the auxiliary circuit board, wherein, when the auxiliary circuit board is inserted into the main circuit board, the output control variable resistor is positioned at a position doser to the surface of the main circuit board than an intermediate point of a height of the highest part of the auxiliary circuit board with reference to the surface of the main circuit board.

20. The high-pressure discharge lamp lighting device according to claim 18, wherein an electric wiring pattern formed on the auxiliary circuit board includes a part to which a low voltage is applied and a part to which a high voltage is applied, and the part to which the high voltage is applied is formed on the peripheral portion of the auxiliary circuit board.

21. The high-pressure discharge lamp lighting device according to claim 18, wherein the auxiliary circuit board is arranged near the peripheral portion of the main circuit board.

22. The high-pressure discharge lamp lighting device according to claim 18, wherein the terminal pads are formed at symmetrical positions on the upper and lower surfaces of the auxiliary circuit board.

23. The high-pressure discharge lamp lighting device according to claim 22, wherein the terminal pads formed at the symmetrical positions of the upper and lower surfaces of the lower part of the auxiliary circuit board have electrically the same potential.

24. The high-pressure discharge lamp lighting device according to claim 18, wherein, projecting portions which can be in contact with the surface of the main circuit board when the auxiliary circuit board is inserted into the main circuit board is formed in a space between the terminal pads formed on the lower part of the auxiliary circuit board and an electronic parts mounted on the auxiliary circuit board, and on both the upper and lower surfaces of the auxiliary circuit board.

25. The high-pressure discharge lamp lighting device according to claim 24, wherein the projecting portion comprises a rod almost perpendicularly penetrates a hole running from the upper surface to the lower surface in the auxiliary circuit board.

26. The high-pressure discharge lamp lighting device according to claim 24, wherein the projecting portion comprises an electronic part arranged between the other electronic parts mounted on both the upper and lower surfaces of the auxiliary circuit board and the terminal pads.

27. The high-pressure discharge lamp lighting device according to claim 24, wherein the projecting portion comprises a U-shaped jig fixed to at least one end in the longitudinal direction of the auxiliary circuit board such that the jig straddles both the upper and lower surfaces of the auxiliary circuit board.

28. A light fixture comprising a high-pressure discharge lamp lighting device according to claim 1, and a high-pressure discharge lamp lighted by the high-pressure discharge lamp lighting device.

29. A device for lighting a high-pressure discharge lamp, comprising: a DC power supply: a first switching element having one terminal connected to the high pressure side of the DC power supply; a second switching element having one terminal connected to the low-voltage side of the DC power supply; a first inductor having one terminal connected to the other terminals of the first and second switching elements, and the other terminal connected to one terminal of a high-pressure discharge lamp; a first capacitor connected between an intermediate section of a winding of the first inductor and the low-voltage side of the DC power supply and composing a first series resonant circuit together with the first inductor; a second capacitor having one terminal connected to the one terminal of the first inductor, and the other terminal connected to the one terminal of the high-pressure discharge lamp; a second inductor having one terminal connected to the other terminal of the second capacitor; a third capacitor connected between the high-pressure side of the DC power supply and the other terminal of the second inductor, a fourth capacitor connected between the low-voltage side of the DC power supply and the other terminal of the second inductor; and a control circuit for controlling turning on and off of the first and second switching elements, wherein before the high-pressure discharge lamp is started up, the control circuit performs control in a first control mode which alternately switches between a state in which the first switching element is on and the second switching element is off and a state in which the first switching element is off and the second switching element is on, at a predetermined switching frequency, in the first control mode, the switching frequency resonates the first series resonant circuit at its harmonic frequency to generate a high voltage for starting up the high-pressure discharge lamp, and the switching frequency is lower than a resonant frequency of the first series resonant circuit and higher than a resonant frequency of a second series resonant circuit including the second inductor and the second capacitor.

30. The high-pressure discharge lamp lighting device according to claim 29, wherein after the high-pressure discharge lamp is started up, the control circuit performs control in a second control mode which alternately switches at a first low-frequency between an operation for controlling turning on and off of the first switching element at a high-frequency and an operation for controlling turning on and off the second switching element at a high-frequency.

31. The high-pressure discharge lamp lighting device according to claim 29, wherein, in the first control mode, a frequency of a high voltage generated by the first series resonant circuit is (2n+1) (n is a natural number) times the switching frequency.

32. The high-pressure discharge lamp lighting device according to claim 29, wherein the switching frequency is higher than two times the resonant frequency of a second series resonant circuit including the second inductor and the second capacitor.

33. The high-pressure discharge lamp lighting device according to claim 29, wherein the control circuit varies the switching frequency depending on time in the first control mode.

34. The high-pressure discharge lamp lighting device according to claim 33, wherein the control circuit has a digital arithmetic processing circuit, and the switching frequency is disc varied by the digital arithmetic processing circuit.

35. The high-pressure discharge lamp lighting device according to claim 33, wherein the control circuit has an analog arithmetic processing circuit, and the switching frequency is continuously varied by the analog arithmetic processing circuit.

36. The high-pressure discharge lamp lighting device according to claim 33, wherein a variable range of the switching frequency is set such that the resonant frequency of the first series resonant circuit is included in a range from an integral multiple of the lower limit of the variable range to an integral multiple of the upper limit of the variable range.

37. The high-pressure discharge lamp lighting device according to claim 36, wherein the frequency corresponding to the integral multiple of the switching frequency is (2N+1) times (n is a natural number) the switching frequency.

38. The high-pressure discharge lamp lighting device according to claim 37, wherein the frequency corresponding to the integral multiple of the switching frequency is three times the switching frequency.

39. The high-pressure discharge lamp lighting device according to claim 29, wherein the first and second switching elements are PWM-controlled at a duty ratio of about 50%, and the first and second switching elements ateratey repeat on and off-operations at equal time intervals.

40. The high-pressure discharge lamp lighting device according to claim 29, wherein the first inductor has a transformer structure provided with a primary winding and a secondary winding, one terminal of the primary winding is connected to one terminal of the secondary winding, and the first capacitor is connected to the connection point between the primary winding and the secondary winding.

41. The high-pressure discharge lamp lighting device according to claim 29, wherein the first inductor has a transformer structure provided with a primary winding and a secondary winding, and a ratio of the numbers of turns of the primary winding and the secondary winding is given by 1:N (N>1).

42. The high-pressure discharge lamp lighting device according to claim 29, wherein the first inductor has a transformer structure provided with a primary winding and a secondary winding, the primary winding is constituted by a litz wire, and the secondary winding is constituted by a single wire.

43. The high-pressure discharge lamp lighting device according to claim 29, further comprising a main circuit board and an auxiliary circuit board on which the electronic parts comprised in the high-pressure discharge lamp lighting device can be mounted, wherein terminal pads for soldering connection to the main circuit board are formed on both the upper and lower surfaces of the lower part of the auxiliary circuit board, a slit in which the auxiliary circuit board is inserted and which supports the auxiliary circuit board is formed in the main circuit board, and the slit has a portion which has a first width and is electrically connected to the auxiliary circuit board and a portion which has a second width which is almost equal to or smaller than the thickness of the auxiliary circuit board, and the first width is larger than the second width.

44. The high-pressure discharge lamp lighting device according to claim 43, further comprising a variable resistor for output control connected to the high-pressure discharge lamp in series and mounted on the auxiliary circuit board, wherein, when the auxiliary circuit board is inserted into the main circuit board, the output control variable resistor is positioned at a position doser to the surface of the main circuit board than an intermediate point of a height of the highest part of the auxiliary circuit board with reference to the surface of the main circuit board.

45. The high-pressure discharge lamp lighting device according to claim 43, wherein an electric wiring pattern formed on the auxiliary circuit board includes a part to which a low voltage is applied and a part to which a high voltage is applied, and the part to which the high voltage is applied is formed on the peripheral portion of the auxiliary circuit board.

46. The high-pressure discharge lamp lighting device according to claim 43, wherein the auxiliary circuit board is arranged near the peripheral portion of the main circuit board.

47. The high-pressure discharge lamp lighting device according to claim 43, wherein the terminal pads are formed at symmetrical positions on the upper and lower surfaces of the auxiliary circuit board.

48. The high-pressure discharge lamp lighting device according to claim 47, wherein the terminal pads formed at the symmetrical positions of the upper and lower surfaces of the lower part of the auxiliary circuit board have electrically the same potential.

49. The high-pressure discharge lamp lighting device according to claim 43, wherein, projecting portions which can be in contact with the surface of the main circuit board when the auxiliary circuit board is inserted into the main circuit board is formed in a space between the terminal pads formed on the lower part of the auxiliary circuit board and an electronic parts mounted on the auxiliary circuit board, and on both the upper and lower surfaces of the auxiliary circuit board.

50. The high-pressure discharge lamp lighting device according to claim 49, wherein the projecting portion comprises a rod almost perpendicularly penetrates a hole running from the upper surface to the lower surface in the auxiliary circuit board.

51. The high-pressure discharge lamp lighting device according to claim 49, wherein the projecting portion comprises an electronic part arranged between the other electronic parts mounted on both the upper and lower surfaces of the auxiliary circuit board and the terminal pads.

52. The high-pressure discharge lamp lighting device according to claim 49, wherein the projecting portion comprises a U-shaped jig fixed to at least one end in the longitudinal direction of the auxiliary circuit board such that the jig straddles both the upper and lower surfaces of the auxiliary circuit board.

53. A light fixture comprising a high-pressure discharge lamp lighting device according to claim 29, and a high-pressure discharge lamp lighted by the high-pressure discharge lamp lighting device.

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Description

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TECHNICAL FIELD

The present invention relates to a lighting device for a high-pressure discharge lamp and a light fixture which is equipped with the lighting device and, more particularly, to a high-pressure discharge lighting device which can be attached to a power track or the like in a small space and a light fixture which is equipped with such a high-pressure discharge lighting device.

BACKGROUND ART

There is a conventional light fixture which is used after being attached to a power track arranged on a ceiling or the like. Such a light fixture includes a lamp and a down-transformer section serving as a device for lighting the lamp. However, since the size of the down-transformer section is not so small that the down-transformer section can be stored in the power track, the down-transformer section is stored in an outer envelope arranged independently of the lamp, and the down-transformer section is arranged under the power track. Therefore, the lamp and the outer envelope disadvantageously overhang under the power track in appearance. As a method of reducing the circuit of the down-transformer section to suppress the overhang of the outer envelope, the following two methods, i.e., a method of reducing the circuit of the down-transformer section and a method of devising a structure of a printed circuit board on which the electronic parts of the down-transformer section are mounted to reduce the down-transformer section in size are known.

In the two solving methods, a light fixture including the down-transformer section which is reduced in size to have preferable appearance when attached to the power track is proposed in JP11-111040A. However, this light fixture uses, as a lamp, an incandescent lamp lighted by the down-transformer section, a halogen lamp, or the like. On the other hand, a light fixture using a high-pressure discharge lamp such as an HID (High Intensity Discharged) lamp has a problem in which the circuit cannot be reduced much in size, since the number of parts is large due to a complex circuit configuration of the device for lighting the high-pressure discharge lamp (as described later) and temperatures of the electronic parts increase.

FIG. 28 shows a basic circuit of a conventional high-pressure discharge lamp lighting device. The device includes a rectifier circuit 92 containing a step-up chopper, a power control circuit 97 containing a step-down chopper, a polarity inversion circuit 93 containing a full bridge circuit, an high-pressure pulse generation circuit Ig, a control circuit 96 for performing drive control of a switching element Q95 for the step-up chopper, and a control circuit 98 for performing drive control for a switching element Q96 for the step-down chopper. Each circuit will be described below.

The rectifier circuit 92 includes a so-called step-up chopper circuit containing an inductor L93, a diode D95, a capacitor C95, and a switching element Q95 such as a MOSFET (Metal Oxide Silicon Field Effect Transistor) and a bridge rectifier DB. The bridge rectifier DB fully rectifies an AC voltage from a commercial AC power supply AC to generate a pulsating-flow voltage. The step-up chopper circuit converts the pulsating-flow voltage generated by the bridge rectifier DB into a DC voltage to output the DC voltage.

The power control circuit 97 contains the switching element Q96 such as a MOSFET turning on/off at several 10 KHz, a diode D96, an inductor L94, and a capacitor C96, an output current of which is of chopping-wave shape. A voltage depending on an output current output from the power control circuit 97 is induced at the secondary winding of the inductor L94. The induced voltage is input to the control circuit 98 through a series-connected resistor R94. The control circuit 98 performs zero-cross switching control of the switching element Q96 on the basis of the voltage input from the secondary winding of the inductor L94. The capacitor C96 is used to remove harmonic components from the output current of a primary winding of the inductor L94.

The polarity inversion circuit 93 converts a DC voltage from the power control circuit 97 into a rectangular wave AC voltage having a low frequency of several 100 Hz through a full-bridge circuit including switching elements Q91 to Q94 such as MOSFETs and supplies the rectangular wave AC voltage to a high-pressure discharge lamp DL.

The high-pressure pulse generation circuit Ig is for generating a high-pressure pulse to cause dielectric breakdown between the electrodes of the high-pressure discharge lamp DL, and is used to start the high-pressure discharge lamp DL. After the high-pressure discharge lamp DL is started, the operation of the high-pressure pulse generation circuit Ig is halted.

The light fixture including the high-pressure discharge lamp DL lighted by the lighting device is disclosed in JP14-75045A. It is desired that the circuit of the lighting device is changed to be smaller so as to reduce the light fixture in size.

On the other hand, as another solving method, a method of devising the structure of a printed circuit board on which electronic parts are mounted to reduce an electronic circuit module in size is proposed in JP5-327161A. This has a structure in which an auxiliary circuit board is arranged perpendicularly to a main circuit board. The auxiliary circuit board has one pair of substrate support sections projecting from both the longitudinal ends to the main circuit board side, and the main circuit board has fixing holes into which the substrate support sections of the auxiliary circuit board penetrate. When the auxiliary circuit board is mounted on the main circuit board, the substrate support sections are inserted into the fixing holes, so that the auxiliary circuit board can be held perpendicularly to the main circuit board. In this manner, the electronic parts to be mounted on the printed board can be three-dimensionally mounted on the main circuit board and the auxiliary circuit board, and therefore the electronic circuit module can be reduced in size.

However, in this mounting structure, a plurality of terminal pads aligned along the long side of the auxiliary circuit board and a plurality of pads aligned on the upper surface of the main circuit board are soldered on the parts surface side of the main circuit board. For this reason, for example, in case that the soldered surface of the main circuit board is dipped into a solder tank while the auxiliary circuit board is mounted on the parts surface of the main circuit board to solder the part leads of the main circuit board, the auxiliary circuit board cannot be connected to the main circuit board simultaneously with the parts. As a matter of course, even in this mounting structure, if all the parts on the main circuit board are mounted on the upper surface of the main circuit board simultaneously with the auxiliary circuit board, soldering of the parts on the main circuit board and soldering of the auxiliary circuit board and the main circuit board can be simultaneously performed.

However, as indicated in the reference, when the surface mounting is done, reflow soldering is performed, and thus heating by the reflow soldering causes another problem such as positioning errors of the parts mounted on the auxiliary circuit board. In order to prevent the positioning errors, another member which holds the parts on the auxiliary circuit board to prevent the positioning errors of the parts is required to increase the cost disadvantageously. The substrate support sections of the auxiliary circuit board are easily broken. If the substrate support sections are broken, all the substrates cannot be used. Furthermore, since the auxiliary circuit board is mounted on the upper surface (surface on which electronic parts are mounted) of the main circuit board, the terminal pads of the auxiliary circuit board are located above the upper surface of the main circuit board. Therefore, the electronics parts to be mounted on the auxiliary circuit board are mounted at positions which are above the terminal pads and which is distant from the upper surface of the main circuit board, so that the height of the projection of the auxiliary circuit board from the upper surface of the main circuit board is made difficult to be small. For this reason, the electronic circuit module on which the electronic parts cannot be easily downsized.

The present invention has been made in consideration of the above problems, and has as its object to provide a compact high-pressure discharge lamp lighting device and a light fixture equipped with the high-pressure discharge lamp lighting device.

DISCLOSURE OF INVENTION

In order to achieve the above object, a device for lighting a high-pressure discharge lamp according to the invention includes a DC power supply, a first switching element having one terminal connected to the high-pressure side of the DC power supply, a second switching element having one terminal connected to the low-voltage side of the DC power supply, a third switching element having one terminal connected to the high-pressure side of the DC power supply, a fourth switching element having one terminal connected to the low-voltage side of the DC power supply, a first inductor having one terminal connected to the other terminals of the first and second switching elements, and the other terminal connected to one terminal of the high-pressure discharge lamp, a first capacitor connected between an intermediate section of a winding of the first inductor and the low-voltage side of the DC power supply, and composing a first series resonant circuit together with the first inductor, a second capacitor having one terminal connected to the one terminal of the first inductor, and the other terminal connected to the other terminal of the high-pressure discharge lamp, a second inductor having one terminal connected to the other terminals of the third and fourth switching elements, and the other terminal connected to the other terminal of the second capacitor, and a control circuit for controlling turning on and off of the first to fourth switching elements. In this configuration, the control circuit, before the high-pressure discharge lamp is started up, performs control in a first control mode which alternately switches between a state in which the first and fourth switching elements are on and the second and third switching elements are off and a state in which the first and fourth switching elements are off and the second and third switching elements are on, at a predetermined switching frequency. In the first control mode, the first series resonant circuit is resonated at a frequency of integral times the switching frequency to generate a high voltage for starting up the high-pressure discharge lamp.

The control circuit, after the high-pressure discharge lamp is started up, may perform control in a second control mode which alternately switches at a low-frequency between, an operation for alternately switching at a high-frequency between a state in which the first and fourth switching elements are simultaneously on, and a state in which at least one of the first and fourth switching elements is off, and an operation for alternately switching at a high-frequency between a state in which the second and third switching elements are simultaneously on and a state in which at least one of the second and third switching elements is off.

Alternatively, a device for lighting a high-pressure discharge lamp according to the invention, includes a DC power supply, a first switching element having one terminal connected to the high-pressure side of the DC power supply, a second switching element having one terminal connected to the low-voltage side of the DC power supply, a first inductor having one terminal connected to the other terminals of the first and second switching elements, and the other terminal connected to one terminal of a high-pressure discharge lamp, a first capacitor connected between an intermediate section of a winding of the first inductor and the low-voltage side of the DC power supply and composing a first series resonant circuit together with the first inductor, a second capacitor having one terminal connected to the one terminal of the first inductor, and the other terminal connected to the other terminal of the high-pressure discharge lamp, a second inductor having one terminal connected to the other terminal of the second capacitor, a third capacitor connected between the high-pressure side of the DC power supply and the other terminal of the second inductor, a fourth capacitor connected between the low-voltage side of the DC power supply and the other terminal of the second inductor, and a control circuit for controlling turning on and off of the first and second switching elements. The control circuit, before the high-pressure discharge lamp is started up, performs control in a first control mode which alternately switches between a state in which the first switching element is on and the second switching element is off and a state in which the first switching element is off and the second switching element is on, at a predetermined switching frequency. In the first control mode, the first series resonant circuit is resonated at a frequency of integral times the switching frequency to generate a high voltage for starting up the high-pressure discharge lamp.

The control circuit, after the high-pressure discharge lamp is started up, may perform control in a second control mode which alternately switches at a first low-frequency between an operation for controlling turning on and off of the first switching element at a high-frequency and an operation for controlling turning on and off the second switching element at a high-frequency.

The switching frequency may be lower than a resonant frequency of the first series resonant circuit and higher than a resonant frequency of a second series resonant circuit including the second inductor and the second capacitor.

In the first control mode, a frequency of a high voltage generated by the first series resonant circuit may be (2n+1) (n is a natural number) times the switching frequency.

The switching frequency may be higher than two times the resonant frequency of a second series resonant circuit including the second inductor and the second capacitor.

According to the high-pressure discharge lamp lighting device as described above, since resonant voltage stepping-up is performed at a frequency corresponding to an integral multiple of the switching frequency of a switching element, the resonant inductor can be considerably reduced in size, and the size and cost of the high-pressure discharge lamp lighting device can be made smaller than a conventional high-pressure discharge lamp lighting device. In addition, since the switching frequency of the switching element is not different from a conventional switching frequency, switching loss can be prevented from increasing.

The control circuit may vary the switching frequency depending on time in the first control mode. Thus, the advantage of being able to generate a stable high-pressure pulse even though the frequency characteristics of the impedance of the first series resonant circuit change due to a fluctuation of the parts can be obtained.

A variable range of the switching frequency may be set such that the resonant frequency of the first series resonant circuit is included in a range from an integral multiple of the lower limit of the variable range to an integral multiple of the upper limit of the variable range. Thus the advantage of being able to easily generate a stable high-pressure pulse having a high voltage even though the frequency characteristics of the impedance of the series resonant circuit change due to a fluctuation of the parts can be obtained.

Furthermore, the frequency corresponding to the integral multiple of the switching frequency may be (2N+1) times (n is a natural number) the switching frequency. Thus, the variable range of the frequency being (2n+1) times (n is a natural number) the switching frequency includes the resonant frequency of the first series resonant circuit, and the switching frequency is relatively easily made variable to make it possible to generate the (2n+1)-times frequency. The advantage of being able to stably generate a high-pressure pulse can be obtained.

The frequency corresponding to the integral multiple of the switching frequency may be three times the switching frequency. Thus, a high-pressure pulse having a voltage which is almost equal to that of a conventional high-pressure pulse can be generated more easily than a high-pressure pulse generated at a frequency which is an integral multiple (three or more times) the switching frequency. For this reason, activation capability at a level equal to the level of conventional activation capability can be maintained.

Furthermore, the control circuit may have a digital arithmetic processing circuit, and the switching frequency may be discretely varied by the digital arithmetic processing circuit. Thus, not only a one-way descending variation of the frequency but also the number of repetitions at a constant frequency can be easily set.

The control circuit may have an analog arithmetic processing circuit, and the switching frequency may be continuously varied by the analog arithmetic processing circuit. Thus, the frequency can be continuously changed, and the advantage of being able to reliably generate a high-pressure pulse obtained from the impedance characteristics of the first series resonant circuit can be obtained.

Furthermore, the first and second switching elements are PWM-controlled at a duty ratio of about 50%, and the first and second switching elements alternately repeat on and off-operations at equal time intervals. Thus, control signals of the switching elements can be generated by a simple control circuit, and the advantage of being able to realize reductions in size and cost of the high-pressure discharge lamp lighting device can be obtained.

The first inductor may have a transformer structure provided with a primary winding and a secondary winding, one terminal of the primary winding is connected to one terminal of the secondary winding, and the first capacitor may be connected to the connection point between the primary winding and the secondary winding. In this manner, a high-pressure pulse required to light a lamp can be generated by a small inductor, and the advantage of being able to reduce the size and cost of the high-pressure discharge lamp lighting device can be obtained.

The first inductor may have a transformer structure provided with a primary winding and a secondary winding, and a ratio of the numbers of turns of the primary winding and the secondary winding may be given by 1:N (N>1). Therefore, a first series resonant voltage for generating a high-pressure pulse can be low, and a resonant current can be reduced. For this reason, the advantage of being able to reduce the sizes of the first inductor and the first capacitor constituting the first series resonant circuit can be obtained.

Furthermore, the first inductor has a transformer structure provided with a primary winding and a secondary winding, the primary winding is constituted by a litz wire, and the secondary winding is constituted by a single wire. Thus, the resistance of the primary winding in a high-frequency region can be reduced, and the DC resistance of the secondary winding can be reduced. A high-pressure pulse required to light the discharge lamp can be generated by using a small transformer, and the advantage of being able to suppress heat from being generated by the transformer in an on-state of the high-pressure discharge lamp can be obtained.

The lighting device may further include a start up detector operable to detect the start up of the high-pressure discharge lamp. When the start up detector detects the start up of the high-pressure discharge lamp, the control circuit performs control in a third control mode. The third control mode alternately switches at a low-frequency between: an operation for switching at a high-frequency among, a state in which the first and fourth switching elements are simultaneously on, a state in which one of the first and fourth switching elements is off, and a state in which both the first and fourth switching elements are off, sequentially in the order; and an operation for switching at a high-frequency among, a state in which the second and third switching elements are simultaneously on, a state in which one of the second and third switching elements is off, and a state in which both the second and third switching elements are off, sequentially in the order. Thus, the advantage of being able to prevent an unstable state in which a lamp current generated immediately after the high-pressure discharge lamp is lighted is stopped to make a lighting state stable can be obtained.

A switching operation from the first control mode to the third control mode may be conducted when a predetermined period of time passes after the start up of the high-pressure discharge lamp is detected. Thus, when the high-pressure discharge lamp is turned off until a predetermined period of time has elapsed after the lighting state of the high-pressure discharge lamp is detected, the advantage of being able to generate a high-pressure pulse again can be obtained.

A switching operation from the first control mode to the third control mode may be conducted when a predetermined period of time passes after the start up of the high-pressure discharge lamp is detected. Thus, impedance characteristics between bridges immediately after the high-pressure discharge lamp is lighted can be reduced, and a higher current can be supplied to the high-pressure discharge lamp, and the advantage of being able to prevent an unstable state in which a current flowing in the high-pressure discharge lamp is stopped can be obtained.

The lighting device may further include a main circuit board and an auxiliary circuit board on which the electronic parts comprised in the high-pressure discharge lamp lighting device can be mounted. Terminal pads for soldering connection to the main circuit board may be formed on both the upper and lower surfaces of the lower part of the auxiliary circuit board. A slit in which the auxiliary circuit board is inserted and which supports the auxiliary circuit board may be formed in the main circuit board. The slit may have a portion which has a first width and is electrically connected to the auxiliary circuit board and a portion which has a second width which is almost equal to or smaller than the thickness of the auxiliary circuit board. The first width may be larger than the second width. In this manner, the terminal pads of the auxiliary circuit board are arranged on a surface on which soldering is performed, not a surface on which the parts of the main circuit board are mounted, a space for part leads of the main circuit board projecting to the soldering surface side of the main circuit board is effectively used to make it possible to reduce the height of the projection of the auxiliary circuit board from the upper surface of the main circuit board, and a low-profile high-pressure discharge lamp lighting device can be realized. In the step of inserting and connecting the auxiliary circuit board to the main circuit board, the auxiliary circuit board can be prevented from falling down before the auxiliary circuit board is soldered. The manufacturing cost and the parts cost can be further reduced.

Further projecting portions which can be in contact with the surface of the main circuit board when the auxiliary circuit board may be inserted into the main circuit board is formed in a space between the terminal pads formed on the lower part of the auxiliary circuit board and an electronic parts mounted on the auxiliary circuit board, and on both the upper and lower surfaces of the auxiliary circuit board. For this reason, the projecting portions support the auxiliary circuit board to make it possible to manufacture the auxiliary circuit board without any jig, and the manufacturing cost and the parts cost can be further reduced.

The projecting portion may include a rod almost perpendicularly penetrates a hole running from the upper surface to the lower surface in the auxiliary circuit board. For this reason, the projecting portions can be formed with a simple configuration, and the manufacturing cost and the parts cost can be still further reduced.

The projecting portion may include an electronic part arranged between the other electronic parts mounted on both the upper and lower surfaces of the auxiliary circuit board and the terminal pads. Thus, the electronic parts also serve as the projecting portions, and the auxiliary circuit board can be supported without using special members as the projecting portions.

The projecting portion may include a U-shaped jig fixed to at least one end in the longitudinal direction of the auxiliary circuit board such that the jig straddles both the upper and lower surfaces of the auxiliary circuit board. Thus, the auxiliary circuit board can be manufactured without a large-scale jig, and the manufacturing cost and the parts cost can be reduced. As a result, reductions in size and cost of the device can be realized.

The terminal pads may be formed at symmetrical positions on the upper and lower surfaces of the auxiliary circuit board. Thus, stress generated in the auxiliary circuit board by soldering can be suppressed from being biased, and the auxiliary circuit board can be more stably connected.

Furthermore, the terminal pads formed at the symmetrical positions of the upper and lower surfaces of the lower part of the auxiliary circuit board may have electrically the same potential. Thus, wires can be minimally drawn on the main circuit board, and a circuit which is strong to external noise can be realized.

The lighting device may further include a variable resistor for output control connected to the high-pressure discharge lamp in series and mounted on the auxiliary circuit board. When the auxiliary circuit board is inserted into the main circuit board, the output control variable resistor may be positioned at a position closer to the surface of the main circuit board than an intermediate point of a height of the highest part of the auxiliary circuit board with reference to the surface of the main circuit board. Thus, the radius of a moment of force decreases, and stress acting on the solder connection portion between the auxiliary circuit board and the main circuit board can be reduced when the resistance of the output-control variable resistor is controlled.

An electric wiring pattern formed on the auxiliary circuit board may include a part to which a low voltage is applied and a part to which a high voltage is applied, and the part to which the high voltage is applied is formed on the peripheral portion of the auxiliary circuit board. Therefore, even in a small high-pressure discharge lamp lighting device, a control circuit of which does not easily perform an erroneous operation caused by self noise can be realized.

The auxiliary circuit board may be arranged near the peripheral portion of the main circuit board. Thus, heat from the electronic circuit mounted on the auxiliary circuit board can be suppressed to low levels.

A light fixture according to the present invention includes the high-pressure discharge lamp lighting device, and a high-pressure discharge lamp lighted by the high-pressure discharge lamp lighting device. Hence, a small-size light fixture can be realized, and the advantage of being able to considerably increase the degree of freedom of installation can be obtained. Therefore, an light fixture which is preferable in appearance and which uses a high-pressure discharge lamp can be realized.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram according to the first embodiment of the present invention.

FIG. 2A is a graph showing a waveform of a drive signal supplied to a switching element Q1 in a start-up mode.

FIG. 2B is a graph showing a waveform of a drive signal supplied to a switching element Q2 in the start-up mode.

FIG. 2C is a graph showing a waveform of a voltage output from an inductor L2 in the start-up mode.

FIG. 3A is a graph showing a waveform of a drive signal supplied to the switching element Q1 in a low-voltage lighting mode.

FIG. 3B is a graph showing a waveform of a drive signal supplied to the switching element Q2 in the low-voltage lighting mode.

FIG. 3C is a graph showing a drive signal supplied to a switching element Q3 in the low-voltage lighting mode.

FIG. 3D is a graph showing a waveform of a drive signal supplied to a switching element Q4 in the low-voltage lighting mode.

FIG. 3E is a graph showing a waveform of a current flowing in a lamp DL in the low-voltage lighting mode.

FIG. 4A is a graph showing a waveform of a drive signal supplied to the switching element Q1 in a stable lighting mode.

FIG. 4B is a graph showing a waveform of a drive signal supplied to the switching element Q2 in the stable lighting mode.

FIG. 4C is a graph showing a waveform of a drive signal supplied to the switching element Q3 in the stable lighting mode.

FIG. 4D is a graph showing a waveform of a drive signal supplied to the switching element Q4 in the stable lighting mode.

FIG. 4E is a graph showing a waveform of a current flowing in the lamp DL in the stable lighting mode.

FIG. 5 is a power characteristic diagram showing basic output characteristics of a high-pressure discharge lamp.

FIG. 6 is a circuit diagram in the second embodiment of the present invention.

FIG. 7A is a graph showing a waveform of a drive signal supplied to the switching element Q1 in the start-up mode.

FIG. 7B is a graph showing a waveform of a drive signal supplied to the switching element Q2 in the start-up mode.

FIG. 7C is a graph showing a waveform of a voltage output from the inductor L2 in the start-up mode.

FIG. 8A is a graph showing a waveform of a drive signal supplied to the switching element Q1 in the stable lighting mode.

FIG. 8B is a graph showing a waveform of a drive signal supplied to the switching element Q2 in the stable lighting mode.

FIG. 8C is a graph showing a waveform of a current flowing in the lamp DL in the stable lighting mode.

FIG. 9 is a circuit diagram in the third embodiment of the present invention.

FIG. 10A is a graph showing a waveform of a drive signal supplied to the switching element Q1 in the start-up mode.

FIG. 10B is a graph showing a waveform of a drive signal supplied to the switching element Q2 in the start-up mode.

FIG. 10C is a graph showing a waveform of a drive signal supplied to the switching element Q3 in the start-up mode.

FIG. 10D is a graph showing a waveform of a drive signal supplied to the switching element Q4 in the start-up mode.

FIG. 10E is a graph showing a waveform of a voltage output from the inductor L2 in the start-up mode.

FIG. 11 is a frequency characteristic diagram showing an operation in the start-up mode.

FIG. 12A is a graph showing a waveform of a drive signal applied to the switching element Q1 in the start-up mode in the fourth embodiment of the present invention.

FIG. 12B is a graph showing a waveform of a drive signal supplied to the switching element Q2 in the start-up mode.

FIG. 12C is a graph showing a waveform of a drive signal supplied to the switching element Q3 in the start-up mode.

FIG. 12D is a graph showing a waveform of a drive signal supplied to the switching element Q4 in the start-up mode.

FIG. 12E is a graph showing a waveform of a voltage output by the inductor L2 in the start-up mode.

FIG. 13 is a frequency characteristic diagram showing an operation in the start-up mode.

FIG. 14 is a diagram for explaining a frequency varying operation using a microcomputer.
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