JP2005235619A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a discharge lamp lighting device capable of supplying a preheating current to each filament of the discharge lamp properly from before lighting of the discharge lamp up to a lighting start and after the lighting. <P>SOLUTION: This discharge lamp lighting device is capable of dimming, and is provided with an inverter circuit for performing high-frequency lighting of a discharge lamp, an inverter drive circuit for driving the switching devices of the inverter circuit, and a control circuit for outputting to the inverter drive circuit, inverter driving control signals when preset filament preheating of the discharge lamp is performed, when a starting voltage is applied, and when dimmed lighting according to an degree of dimming which is set is performed. To the output end of the inverter circuit, a preheating circuit composed of a capacitor, a preheating transformer, and a switching means is connected. A preheating control circuit is provided for controlling the switching means, and the preheating control circuit controls the switching means and controls the filament currents of the discharge lamp, by a preheating control signal to be output from the control circuit according to the degree of dimming when dimmed lighting of the discharge lamp is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a discharge lamp lighting device for high-frequency lighting of a discharge lamp having a filament.

  A conventional discharge lamp lighting device has a DC conversion unit that receives an AC voltage from an AC power source, converts the DC voltage into a DC voltage, and outputs it, and an inverter unit that receives the DC voltage, converts it into a high-frequency AC voltage, and supplies it to the discharge lamp. Then, the output voltage of the DC conversion unit during the lighting period is made lower than the output voltage of the preceding preheating period by the DC voltage control unit that controls the output of the DC conversion unit (for example, Patent Documents). 1).

Japanese Patent Laid-Open No. 2002-231383 (page 2-8, FIG. 1)

If the preheating current that flows through the filament of the discharge lamp is too large when the discharge lamp is lit, the thermionic emission material applied to the filament will be consumed quickly, and the inner wall of the discharge lamp tube near the filament will become black. It is known that the lamp life is shortened and the lamp life is shortened. In general, in the preceding preheating period before the discharge lamp is lit, it is necessary to heat the filament sufficiently to promote the emission of thermoelectrons, contrary to the time during lighting. Furthermore, in a discharge lamp lighting device in which the output of the discharge lamp is variable (dimming control), it is necessary to set an appropriate preheating current according to the degree of dimming.

The conventional discharge lamp lighting device proposed to avoid the above problems controls the preheating current flowing in the filament, and in addition to the preheating circuit composed of a capacitor and a preheating transformer, the AC power supply is converted into a DC voltage during the preceding preheating period. The DC power supply control unit is configured so that the output of the DC power supply unit can be varied during the preceding preheating period and the lighting period. Control is performed to increase the output of the DC power supply unit during the preceding preheating period and to reduce the output during lighting of the discharge lamp. ing. For this reason, a control circuit for controlling the DC power supply output is required, which causes a problem of increasing the size of the apparatus. Further, when applied to a dimmable discharge lamp lighting device, it is necessary to change the DC power supply output in accordance with the degree of dimming in order to allow an appropriate filament preheating current to flow. However, since the high-frequency voltage converted by the inverter changes by changing the DC power supply output, the discharge lamp current flowing to the discharge lamp also changes at the same time, and it is more complicated to obtain the desired dimming degree. Control is required, resulting in an increase in the size of the DC power supply control unit and the inverter control unit, which makes it difficult to apply to a dimmable discharge lamp lighting device.

  Also, in order to maintain a good lighting state of the discharge lamp, it is necessary to maintain the filament at an appropriate temperature, but when the discharge lamp is lit at a rated lighting or close to the rated lighting. Therefore, it is necessary to reduce the filament preheating current as much as possible so that even if the discharge lamp does not have a filament preheating current for heating the filament, a sufficient temperature can be obtained only by the discharge lamp current flowing through the discharge lamp. Because it is designed to. In the case of a conventional discharge lamp lighting device, the output of the DC power supply is made variable in order to control the filament preheating current after lighting, but there is a limit to the change of the DC power supply output, and the lighting characteristics of the discharge lamp Therefore, there is a problem that it is difficult to properly control the filament preheating current during lighting.

  The present invention has been made in view of the above problems, and provides a discharge lamp lighting device capable of appropriately supplying a filament preheating current of a discharge lamp from before the discharge lamp is lit to after starting and after lighting. It is intended.

  The discharge lamp lighting device according to the present invention drives a DC power supply, an inverter circuit that converts the DC power supply voltage into a high-frequency voltage by a switching operation of the switching element to light the discharge lamp at a high frequency, and the switching element of the inverter circuit Inverter drive circuit, and inverter drive control signal for pre-set the filament preheating of the discharge lamp, applying the starting voltage of the discharge lamp, and dimming lighting according to the set dimming degree A dimmable discharge lamp lighting device comprising a control circuit that outputs and controls a preheating circuit comprising a capacitor, a preheating transformer and a switch means at the output end of the inverter circuit, and the preheating circuit A preheating control circuit for controlling the switch means, and the control corresponding to the degree of dimming when dimming the discharge lamp. The preheating control circuit preheating control signal output from the road is for controlling said switch means and to control the filament current of the discharge lamp.

  The discharge lamp lighting device according to the present invention includes inverter control signals for inverter driving at the time of preset filament preheating of the discharge lamp, application of the starting voltage of the discharge lamp, and dimming lighting according to the set dimming degree A dimmable discharge lamp lighting device comprising a control circuit that outputs and controls to a drive circuit, wherein a preheating circuit comprising a capacitor, a preheating transformer and switch means is connected to the output end of the inverter circuit, and the preheating circuit A preheating control circuit for controlling the switch means, and the preheating control circuit controls the switch means by a preheating control signal output from the control circuit corresponding to the degree of dimming when the discharge lamp is dimmed. Since the filament current of the discharge lamp is controlled, the discharge lamp current flowing through the discharge lamp is large at the time of dimming lighting. When the dimming degree is such that the filament can be heated and the appropriate temperature of the filament is maintained, the filament preheating current is reduced, and on the contrary, the discharge lamp current flowing through the discharge lamp is small, and the discharge lamp current sufficiently heats the filament. If the dimming degree cannot be maintained at an appropriate filament temperature, the filament preheating current can be increased, and the life of the discharge lamp can be prevented from being shortened due to the filament preheating current being excessively large or small.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a discharge lamp lighting device capable of, for example, step dimming according to Embodiment 1 of the present invention.
In FIG. 1, 1 is a DC power source obtained by rectifying and smoothing or boosting a commercial AC voltage, for example, 2 is an inverter circuit that forms a half bridge with switching elements Q1 and Q2, and converts the voltage of the DC power source 1 into a high-frequency voltage. It is. Connected to the output terminal of the inverter circuit 2 is a load circuit 3 including a choke coil L1, a capacitor C1, and a discharge lamp La including a filament. In the load circuit 3, the choke coil L1 and the capacitor C1 constitute a series resonance circuit, and the discharge lamp La is connected in parallel with the capacitor C1. Further, a filament preheating circuit comprising a capacitor C2 and a preheating transformer T1 and a series circuit of switch means 4 are connected to the output terminal of the inverter circuit 2, and the preheating circuit 5 is constituted by the filament preheating circuit and the switch means 4. doing. A pair of windings on the secondary side of the preheating transformer T1 forming the filament preheating circuit is connected to a pair of filaments of the discharge lamp La via capacitors C3 and C4, respectively.

The switching elements Q1 and Q2 of the inverter circuit 2 are alternately turned on / off by a drive signal from the inverter drive circuit 7. By turning on and off Q1 and Q2, a high frequency current is output from the output terminal of the inverter circuit 2 and supplied to the discharge lamp La. The switch means 4 in the preheating circuit 5 is on / off controlled by a control signal 9 from the preheating control circuit 8. Reference numeral 6 denotes a control circuit, which is used for preset filament preheating of the discharge lamp La, for applying a starting voltage for the discharge lamp La, and for example, for dimming lighting according to a dimming signal of a dimming degree set from the outside. An inverter drive control signal 6a is output to the inverter drive circuit 7, and a preheat control signal 6b is supplied to the preheat control circuit 8 in accordance with the degree of dimming during filament preheating, starting voltage application, and dimming lighting. Output.

Operation of the discharge lamp lighting device configured as described above and capable of step dimming will be described with reference to FIGS. 1, 2, and 3.
FIG. 2 shows the relationship between the drive frequency f of the inverter circuit 2 and the voltage applied to the discharge lamp La from the resonance characteristics of the choke coil L1 in the load circuit 3 and the capacitor C1. In FIG. 2, the inverter driving frequency f1 of the pre-filament preheating of the discharge lamp La set to a value sufficiently higher than the resonance frequency f0 of the resonance circuit composed of the choke coil L1 and the capacitor C1, and the value set to a value near the resonance frequency f0. The inverter driving frequency f2 for applying a voltage (starting voltage) for starting discharge of the electric lamp La is plotted and shown. Further, FIG. 3 shows on / off of the switch means 4 in the preheating circuit 5 with respect to the dimming degree (for example, all light, that is, rated lighting, 70% of the rating, 5% of the rating) in the case of three-stage dimming. This shows the relationship.

The sequence for turning on the discharge lamp La is turned on, starts from the inverter driving frequency f1 of the filament pre-preheating set in the control circuit 6 in advance, the inverter driving frequency f2 for applying the starting voltage, and An inverter drive control signal 6 a having an inverter drive frequency fx for setting the lighting state corresponding to the dimming degree of the dimming signal set from the outside is output to the inverter drive circuit 7. The inverter drive circuit 7 drives the switching elements Q1 and Q2 of the inverter circuit 2 on and off based on the inverter drive frequencies of the series of f1, f2, and fx, and the series of processes from the filament pre-preheating to lighting. Perform the action. The control circuit 6 outputs a preheating control signal 6b to the preheating control circuit 8 in order to supply a filament preheating current to the filament of the discharge lamp La when the filament is preheated and when the starting voltage is applied. Upon receiving this preheating control signal 6b, the preheating control circuit 8 performs control so that the switch means 4 of the preheating circuit 5 is turned on.

During the filament pre-heating operation, the inverter driving circuit 7 causes the inverter driving control signal 6a from the control circuit 6 to cause the inverter driving circuit 7 to switch the switching elements Q1 and Q2 of the inverter circuit 2 at the preceding pre-heating driving frequency f1 (for example, 100 kHz). Is driven on and off. A high-frequency voltage output from the inverter circuit 2 by driving at the preceding preheating driving frequency f1 is applied to the primary winding of the capacitor C2 and the preheating transformer T1, and is applied to a pair of windings on the secondary side of the preheating transformer T1. A voltage is induced, and a filament preheating current If (for example, 400 mA) flows through a pair of filaments of the discharge lamp La through the capacitors C3 and C4. The capacitor C2 has a sufficiently large capacity so that it hardly depends on the inverter drive frequency, so that a constant voltage is applied to the primary winding of the preheating transformer T1 and is generated on the secondary side. The filament preheating current is also substantially constant without depending on the inverter driving frequency.

When the inverter drive frequency during the filament pre-heating operation is f1, the voltage applied to the discharge lamp La in the resonance circuit including the choke coil L1 and the capacitor C1 of the load circuit 3 is discharged as shown in FIG. Since it is sufficiently lower than the starting voltage applied to start, there is no discharge in this filament pre-heating period.

After the preceding preheating period, an inverter drive control signal 6a from the control circuit 6 causes the inverter drive circuit 7 to turn on the switching elements Q1 and Q2 of the inverter circuit 2 at an inverter drive frequency f2 for applying the starting voltage. Drive off. By driving at the drive frequency f2, a high voltage is generated at both ends of the capacitor C1, and by applying this high voltage to the discharge lamp La, discharge is started and the discharge lamp La is turned on. As described above, also in this starting voltage application period after the preceding preheating period, the switch means 4 is turned on and the filament preheating current is supplied to the filament of the discharge lamp La.

After the discharge lamp La is turned on, the control circuit 6 changes the inverter drive frequency according to the dimming signal of the dimming degree set from the outside (all light mentioned above, 70% of the rating, 5% of the rating), An inverter drive control signal 6 a is output to the inverter drive circuit 7. The inverter drive circuit 7 changes the drive frequency of the inverter circuit 2 by the inverter drive control signal 6a. Dimming lighting is performed by controlling the discharge lamp current IL flowing through the discharge lamp La by utilizing the fact that the impedance of the choke coil L1 changes according to the frequency due to the change of the inverter drive frequency of the inverter circuit 2.

Here, after the discharge lamp La is turned on, when the discharge lamp La shown in FIG. 3 is in full light, the discharge lamp current IL flowing through the discharge lamp La can sufficiently heat the filament and maintain an appropriate filament temperature. The preheating control circuit 8 controls the switch means 4 in the preheating circuit 5 to be turned off by the preheating control signal 6b from the control circuit 6 so that the filament preheating current is not supplied to the filament of the discharge lamp La. To.

In addition, in 70% dimming of the discharge lamp La and 5% dimming of the rated lighting in the low luminous flux lighting state, the filament is sufficiently filament only by the discharge lamp current IL flowing through the discharge lamp La during the dimming. Therefore, the preheating control circuit 8 controls the switch means 4 in the preheating circuit 5 to be turned on by the preheating control signal 6b from the control circuit 6 to prevent the discharge lamp from being heated. A filament preheating current is supplied to the filament of La.

As described above, in the present embodiment, for example, when a discharge lamp lighting device capable of three-stage dimming (all light, 70% of rating, 5% of rating) is used, the discharge lamp La is varied depending on the degree of dimming. When the filament preheating current is appropriately supplied to the light source, for example, in the case of all light, since the filament can be sufficiently heated by the discharge lamp current IL flowing through the discharge lamp La and the appropriate temperature of the filament can be maintained, In response to the preheating control signal 6b, the preheating control circuit 8 turns off the switch means 4 so that the filament preheating current is not supplied to the filament of the discharge lamp La. Overheating is eliminated, and shortening of the life of the discharge lamp due to excessive filament preheating current during lighting can be prevented. Further, since the filament preheating current is interrupted, it is possible to eliminate the power consumption of the filament that is being lit, and it is possible to reduce the power consumption of the entire discharge lamp lighting device.

Further, for example, at 70% of the rating and 5% of the rating, the filament cannot be sufficiently heated only by the discharge lamp current IL flowing through the discharge lamp La during the dimming, and the appropriate temperature of the filament cannot be maintained. Therefore, the preheating control circuit 8 receives the preheating control signal 6b from the control circuit 6 and turns on the switch means 4 so as to supply the filament preheating current to the filament of the discharge lamp La. There is no problem of shortening the life of the discharge lamp.

In the above embodiment, the switch means 4 of the preheating circuit 5 is turned off and no filament preheating current is supplied to the filament of the discharge lamp La in all light. For example, it flows to the discharge lamp La. If the filament can be sufficiently heated by the discharge lamp current IL and the proper temperature of the filament can be maintained, the switch means 4 is turned off at a dimming degree other than the total light, and the filament preheating current is supplied to the filament of the discharge lamp La. It does not matter if you do not.

Embodiment 2. FIG.
In the first embodiment, when a discharge lamp lighting device capable of step dimming is used, the filament preheating current of the discharge lamp La is appropriately supplied and cut off depending on the degree of dimming. In the present embodiment, a mode in which the filament preheating current of the discharge lamp La is appropriately supplied depending on the degree of dimming when the discharge lamp lighting device is capable of continuous dimming will be described.
In the present embodiment, when the preheating control circuit 8 controls the switch means 4 of the preheating circuit 5 in response to the preheating control signal 6b from the dimming control circuit 6, the degree of dimming by continuous dimming. Since the configuration of the discharge lamp lighting device is the same as that of FIG. 1 of the first embodiment, the illustration and description here are omitted. To do.

FIG. 4 is an enlarged view for explaining the switch means 4 in the preheating circuit 5 shown in FIG. 1 of the first embodiment and the preheating control circuit 8 for controlling the switch means 4. In FIG. 4, the same or corresponding parts as those in FIG.
The switch means 4 is ON / OFF controlled within a predetermined period T (for example, 1 msec) by a control signal 9 shown in FIG. 4 from the dimming preheating control circuit 8. Note that “ton” in the control signal 9 in FIG. 4 represents the time for turning on.
FIG. 5 shows the relationship of the ratio of the on period (ton) to the predetermined period T of the switch means 4 and the relationship of the average filament preheating current Ifave with respect to the dimming degree by the dimming signal.

The operation of the discharge lamp lighting device capable of continuous light control with the above configuration will be described with reference to FIGS. In the present embodiment, the operation from the pre-filament preheating of the discharge lamp La to the start of discharge is the same as the operation described in the first embodiment, and the description thereof is omitted. Here, the supply of the filament preheating current when the discharge lamp is dimmed with a dimming signal having a dimming degree enabling continuous dimming from the outside will be described, and the switch means in the preheating circuit 5 will be described. The operation will be described assuming that the filament preheating current Ifave (hereinafter abbreviated as “If”) is set to flow, for example, 400 mA when 4 is turned on.
After the discharge lamp La is turned on, the preheating control circuit 8 moves the switch means 4 in the preheating circuit 5 within the predetermined period T according to the dimming degree indicated by the preheating control signal 6b from the control circuit 6. The ratio is controlled by changing the ratio of the ON period.

In the present embodiment, as shown in FIG. 5, when the discharge lamp La is all light, the ratio of the ON period (ton) to the predetermined period T of the switch means 4 is set to zero%, and the discharge lamp La is In the case of 70% dimming of rated lighting, the ratio of the on period (ton) is, for example, 30%. When the discharge lamp La is dimmed in a low luminous flux state such as 5% of rated lighting, for example, the dimming degree is reduced by setting the ratio of the on period (ton) to 100%, for example. Therefore, the ratio of the on period (ton) within the predetermined period T is increased, and the ratio is continuously changed according to the dimming degree.

Since the ratio of the ON period (ton) to the predetermined period T is zero% at the time of all light, the switch means 4 keeps the OFF state with respect to the predetermined period T, so that the filament preheating to the discharge lamp La is performed. The current If is not supplied. Further, at the time of 70% dimming of the rating, the switch means 4 is controlled by the control signal 9 whose ratio of the ON period (ton) is 30%, and the filament preheating current If is supplied to the discharge lamp La. It will be. An example of the filament preheating current If at that time is shown in FIG.

When the switch means 4 is controlled by the control signal 9 in which the ratio of the ON period (ton) to the predetermined period T (1 msec) is 30% (0.3 msec), as shown in FIG. In the ON period of 30% (0.3 msec), 400 mA of filament preheating current If flows, and in the remaining 70% (0.7 msec) of OFF period, the filament preheating current is not supplied. Therefore, the average filament preheating current If in the predetermined period T is 120 mA (= 400 mA × 30%). Further, at the time of 5% dimming of the rating, since the ratio of the on period (ton) is 100%, the switch means 4 keeps the on state for a predetermined period T, so that the filament preheating is applied to the discharge lamp La. The current If = 400 mA is supplied.

As described above, in the discharge lamp lighting device that enables continuous dimming, the preheating circuit is configured such that the ratio of the on period within the predetermined period T is continuously variable according to the dimming degree from the outside. 5 is controlled, the discharge lamp current IL flowing through the discharge lamp La is large, and the filament is sufficiently heated by the discharge lamp current IL so that the appropriate temperature of the filament can be maintained. In this case, the filament preheating current If is decreased, and on the contrary, the discharge lamp current IL flowing through the discharge lamp La is small, and the filament cannot be heated sufficiently with the discharge lamp current IL, so that the appropriate temperature of the filament cannot be maintained. In this case, the filament preheating current If can be increased. As described above, since the filament preheating current can be appropriately supplied according to the dimming degree of the discharge lamp La, the discharge lamp La of the discharge lamp La is caused by excessive or small filament preheating current in the entire dimming range of the discharge lamp La. The shortening of the service life can be prevented and the power consumption in the filament can be minimized, so that the power consumption of the entire discharge lamp lighting device can be reduced.

In the above embodiment, as shown in FIG. 5, the ratio of the ON period (ton) of the switch means 4 is continuously changed with respect to the dimming degree of the discharge lamp La. On the other hand, the ratio of the on period (ton) of the switch means 4 may be changed stepwise, and the same effect can be obtained in that case.

Moreover, as what constitutes the switch means 4 described in the first and second embodiments, for example, a semiconductor such as a transistor or a MOS-FET may be used, and any of switch parts by mechanical operation such as a relay may be used. It is not limited.

1 is a configuration diagram of a discharge lamp lighting device capable of, for example, step dimming according to Embodiment 1 of the present invention. It is the figure which showed the relationship with the voltage applied to the discharge lamp with respect to the inverter drive frequency which concerns on Embodiment 1 of this invention. It is the figure which showed the on-off relationship of the switch means in the preheating circuit with respect to the light control degree of the discharge lamp which concerns on Embodiment 1 of this invention. It is an enlarged view of the switch means in the preheating circuit of the said FIG. 1 which concerns on Embodiment 2 of this invention, and the preheating control circuit part which controls a switch means. It is the figure which each showed the relationship of the ratio of the ON period with respect to the predetermined period T of a switch means with respect to the light control degree of the discharge lamp which concerns on Embodiment 2 of this invention, and the relationship of an average filament preheating current. It is the figure which showed an example of the filament preheating current when the light control degree which concerns on Embodiment 2 of this invention is 70% of ratings, for example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 DC power supply, 2 Inverter circuit, 3 Load circuit, 4 Switch means, 5 Preheating circuit, 6 Control circuit, 6a Inverter drive control signal, 6b Preheat control signal, 7 Inverter drive circuit, 8 Preheat control circuit, 9 Control signal

Claims (4)

A DC power supply, an inverter circuit that converts the DC power supply voltage into a high-frequency voltage by a switching operation of the switching element to light a discharge lamp at a high frequency, an inverter drive circuit that drives the switching element of the inverter circuit, and the preset A control circuit that outputs and controls an inverter drive control signal to the inverter drive circuit at the time of filament preheating of the discharge lamp, at the time of applying the starting voltage of the discharge lamp, and at the time of dimming lighting according to the set dimming degree A dimmable discharge lamp lighting device comprising:
A preheating circuit comprising a capacitor, a preheating transformer, and switching means is connected to the output terminal of the inverter circuit, and includes a preheating control circuit that controls the switching means of the preheating circuit, and corresponds to the degree of dimming when the discharge lamp is dimmed. Then, the preheating control circuit controls the filament current of the discharge lamp by controlling the switch means by a preheating control signal output from the control circuit. At the time of dimming lighting, the preheating control circuit supplies the filament current of the discharge lamp by controlling to turn on the switch means when the dimming degree of the discharge lamp is not more than a predetermined dimming degree. 2. The discharge lamp lighting device according to claim 1, wherein when the dimming degree is equal to or higher than a predetermined dimming degree, the switch means is controlled to be turned off so that the filament current is not supplied. The preheating control circuit at the time of dimming lighting controls the filament current of the discharge lamp by controlling the ON period of the switch means according to the dimming degree within a predetermined period. The discharge lamp lighting device according to 1. 4. The filament current of the discharge lamp is reduced by decreasing the ratio of the ON period of the switch means as the dimming degree changes from a dimming state with a low luminous flux to an all-light state. The discharge lamp lighting device described.

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