JP2003264092A - Lighting device for high pressure discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device for a high pressure discharge lamp, which high-frequency lights the high pressure discharge lamp in a non-resonant frequency band. <P>SOLUTION: A voltage detector 8 for detecting lamp voltage within a high pressure discharge lamp 7 having rated power of 35 W is provided, a load current detecting resistance 9 for detecting a load current passing through the high pressure discharge lamp 7 is provided, and an error amplifier 10 for amplifying the load current of the load current detecting resistance 9 to feed back into a control circuit 11 is provided. The control circuit 11 controls a drive frequency of an inverter circuit 2 so as to preset a lighting frequency within a non-resonant frequency band of 40-45 kHz in which no acoustic resonance phenomenon occurs. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for lighting a high pressure discharge lamp at a high frequency.

[0002]

2. Description of the Related Art FIG. 6 is a circuit diagram of a conventional high pressure discharge lamp lighting device. In FIG. 6, 1 is a DC power supply,
2 is a first for converting the DC voltage of the DC power supply 1 into a high frequency voltage
Switching element 2a and second switching element 2b
And an inverter circuit 3 including a control circuit for controlling the drive frequency of each switching element constituting the inverter circuit 2, 4 a load circuit including a resonance capacitor 5 and a choke coil 6, and 7 an output voltage from the load circuit 4. It is a high-pressure discharge lamp that lights at high frequency.

In the high pressure discharge lamp lighting device having such a configuration, the control circuit 3 drives and controls each switching element so that a high frequency voltage having a frequency of 10 kHz or more is supplied to the high pressure discharge lamp 7 through the load circuit 4. To do. The control circuit 3 controls the lighting frequency of the high-pressure discharge lamp 7 in order to prevent the occurrence of the acoustic resonance phenomenon of "extinction" or "fluctuation" due to the curvature of the discharge arc in the arc tube of the high-pressure discharge lamp 7, which is generally known. The non-resonant frequency is set in advance to drive and control each switching element.

As a conventional example, JP-A-7-85982.
The high pressure discharge lamp lighting device disclosed in Japanese Patent Laid-Open Publication No. 2003-242242 can be mentioned.
This is provided with an FM modulation circuit that monotonically increases the lighting frequency according to the magnitude of the DC voltage of the DC power supply. As a result, the lighting frequency is set within the non-resonant frequency band to stably light the high pressure discharge lamp, and even when there is a voltage change, the power supplied to the high pressure discharge lamp is always kept constant to maintain a predetermined brightness. Is configured as follows.

[0005]

The conventional high pressure discharge lamp lighting device is constructed so as to set the lighting frequency in advance to the non-resonant frequency and light the high pressure discharge lamp as described above. However, it is generally known that in a high-pressure discharge lamp, the speed of sound waves in the arc tube changes with cumulative lighting time, or the electrodes are consumed, so that the non-resonant frequency band itself changes. Therefore, due to these factors, the lighting frequency enters into the resonance frequency band to cause an acoustic resonance phenomenon, which causes a problem that the lighting state of the high-pressure discharge lamp cannot be kept stable. Further, there is a problem in that the predetermined brightness cannot be maintained when the load current changes due to variations in the characteristics of the high-pressure discharge lamp or circuit components, changes in the high-pressure discharge lamp over time, and the like.

The present invention has been made to solve the above-mentioned problems, and is devised so that the lighting frequency can always be set within the frequency band even when the non-resonance frequency band changes due to various factors. As a result, the high-pressure discharge lamp is stably lit at a high frequency without causing "disappearance" or "fluctuation" of the discharge arc in the arc tube. At the same time, the present invention provides a high pressure discharge lamp lighting device capable of promptly setting the load current to a predetermined value when the load current changes due to variations in the characteristics of circuit components or changes in the high pressure discharge lamp over time.

[0007]

A high pressure discharge lamp lighting device according to the present invention controls a high pressure discharge lamp, a high frequency power supply circuit for supplying high frequency power to the high pressure discharge lamp, and an output frequency of the high frequency power supply circuit. In a high pressure discharge lamp lighting device including a control circuit, when the control circuit feeds back a load current flowing in the high pressure discharge lamp to determine the output frequency of the high frequency power supply circuit, the output frequency range is defined as a non-resonant frequency band. It is a match.

Further, the high pressure discharge lamp, the high frequency power supply circuit for supplying high frequency power to the high pressure discharge lamp, the control circuit for controlling the output frequency of the high frequency power supply circuit, and the voltage detection for detecting the tube voltage of the high pressure discharge lamp. In the high-pressure discharge lamp lighting device including means and current detection means for detecting a load current flowing in the high-pressure discharge lamp, the control circuit stores the tube voltage when the high-pressure discharge lamp is lit at a predetermined frequency as a reference tube voltage. Then
A first frequency at a point where the tube voltage becomes higher than the reference tube voltage when the output frequency of the high frequency power supply circuit is lowered,
The second frequency at the point where the tube voltage becomes higher than the reference tube voltage when the output frequency is increased is stored, and the output frequency of the high frequency power supply circuit is set between these first and second frequencies. The load current is set to a predetermined value.

Further, the high-pressure discharge lamp, the high-frequency power supply circuit for supplying high-frequency power to the high-pressure discharge lamp, the control circuit for controlling the output frequency of the high-frequency power supply circuit, and the voltage detection for detecting the tube voltage of the high-pressure discharge lamp. In the high-pressure discharge lamp lighting device comprising a means and a current detection means for detecting a load current flowing in the high-pressure discharge lamp, the control circuit sets the output frequency of the high-frequency power supply circuit to a range in which the tube voltage of the high-pressure discharge lamp is a predetermined value or less. In the above, the load current is set to a predetermined value.

Further, the control circuit is configured to repeatedly change the output frequency of the high frequency power supply circuit at regular intervals.

The control circuit changes the output frequency of the high frequency power supply circuit when the tube voltage of the high pressure discharge lamp detected by the voltage detecting means or the load current detected by the current detecting means changes by a predetermined amount. It was done like this.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 is a circuit configuration diagram showing a high pressure discharge lamp lighting device according to a first embodiment. In FIG. 1, the same reference numerals as those in the conventional example indicate the same or corresponding portions. For example, 8 is a voltage detector that detects the tube voltage of the high-pressure discharge lamp 7 having a rating of 35 W, 9 is a load current detection resistor that detects the load current flowing in the high-pressure discharge lamp 7, and 10 is the detection current of the load current detection resistor 9. It is an error amplifier which is fed back to the control circuit 11. Then, the control circuit 11 controls the drive frequency of the inverter circuit 2 so as to set the lighting frequency in advance within the non-resonant frequency band of 40 KHz to 45 KHz in which the acoustic resonance phenomenon does not occur.

FIG. 2 is a characteristic diagram of the tube voltage and the load current of the high pressure discharge lamp 7 with respect to the lighting frequency. In the tube voltage characteristic, the tube voltage is high in the resonance frequency band where the acoustic resonance phenomenon occurs, and the tube voltage is low and shows a substantially constant value in the non-resonance frequency band. Regarding the load current characteristic, the load current decreases as the lighting frequency rises, and this characteristic rises or falls depending on the characteristic variations of the high-pressure discharge lamp 7 and circuit parts (for example, choke coil). Further, the non-resonant frequency band changes due to the aging of the high-pressure discharge lamp 7 and the like, and the load current characteristic also increases or decreases. As a result, in the case of one characteristic (characteristic a in the figure), the lighting frequency is fx when the load current reaches the target value ix. In the case of the other characteristic (characteristic b in the figure), it can be seen that the lighting frequency when the load current reaches the target value ix is fy, and the lighting frequency fluctuates. For this reason, it is necessary to follow the rise or fall of the load current characteristic and change the lighting frequency each time so that the load current has the target value ix. In addition,
The target value ix of the load current is a value for setting the power supplied to the high pressure discharge lamp 7 to the rated power.

Next, the lighting operation of the high pressure discharge lamp lighting device having such a structure will be described with reference to the flow charts shown in FIGS. 1, 2 and 3. When the operation of the lighting device is started (step S100), the control circuit 11 controls the drive frequency of the inverter circuit 2 so that the initial lighting frequency matches the non-resonance frequency, and lights the high-pressure discharge lamp 7 (step S100). S101). At this time, the tube voltage of the high-pressure discharge lamp 7 is detected by the voltage detector 8, and the detected tube voltage is stored as V0 (step S102). And
The driving frequency of the inverter circuit 2 is changed to gradually decrease the lighting frequency (step S103), and in this process, the voltage detector 8 detects the tube voltage Vx of the high-pressure discharge lamp 7.

Next, the control circuit 11 determines whether or not the tube voltage Vx is larger than the tube voltage V0 at the time of initial lighting (step S104), and if NO here, the lighting frequency is continued to decrease. . If YES, it is determined that the tube voltage Vx is close to the resonance frequency band because the tube voltage Vx is larger than the tube voltage V0, the falling of the lighting frequency is stopped, and the lighting frequency f1 at this time is stored ( Step S105). The reference value for determining whether the tube voltage Vx is larger than the tube voltage V0, that is, the voltage difference value is about 1
V or less.

Next, the control circuit 11 increases the lighting frequency from f1 to the opposite (step S106), and in this process determines whether the tube voltage Vx is larger than the tube voltage V0 (step S107). ). Here, in the case of NO, the increase of the lighting frequency is continued, and in the case of YES, it is judged that the resonance frequency band is approached, the increase of the lighting frequency is stopped, and the lighting frequency f2 at this time is stored. (Step 108). Then, the control circuit 11 sets the lighting frequency f1 as the lower limit value and similarly the f2 as the upper limit value, and at the lighting frequency fx at which the load current flowing through the high pressure discharge lamp 7 becomes the target value ix based on the output signal of the error amplifier 10. The discharge lamp 7 is turned on (step S109).

After that, it is judged whether or not the lighting operation is completed (step S110). If it is judged NO here, that is, the lighting operation is not completed and the extinguishing signal is not sent to the lighting device, the high pressure discharge lamp. 7 is maintained at the lighting frequency fx. After the timer stored in the control unit 11 performs a counting operation for, for example, several seconds or several minutes (step S111), the process returns to step S102 to store the tube voltage. After that, the drive frequency of the inverter circuit 2 is changed again, and the lighting frequency is lowered with fx as the base point (step S103). After this,
The above steps are repeated. If YES, that is, if it is determined that the turn-off signal has been sent to the lighting device, the operation of the lighting device is ended (step S112).

As described above, even if the non-resonance frequency band or the load current characteristic changes due to various factors such as characteristic variations of the high-pressure discharge lamp 7 and circuit components, and changes with time of the high-pressure discharge lamp 7, the lighting frequency is always kept The high-pressure discharge lamp 7 can be stably lit by setting it within the resonance frequency band and setting the load current to the target value ix. Therefore, the influence of the acoustic resonance phenomenon can be avoided and the brightness of the high pressure discharge lamp 7 can be maintained at a predetermined level.

Embodiment 2. FIG. 4 is a flowchart showing a flow of operations of the high pressure discharge lamp lighting device according to the second embodiment. The circuit configuration diagram of the high pressure discharge lamp lighting device is the same as that of the first embodiment. In the flowchart shown in FIG. 4, when the operation of the lighting device is started (step S200), the control circuit 11 controls the drive frequency of the inverter circuit 2 so that the initial lighting frequency matches the non-resonance frequency, and the high voltage The discharge lamp 7 is turned on (step S2
01). Thereafter, the lighting frequency is gradually decreased (step S202), and it is determined whether the detection voltage of the voltage detector 8, that is, the tube voltage Vx has reached the threshold value Vs (step S203).

Here, the threshold value Vs is, for example, as shown in the tube voltage characteristic diagram of FIG. 5, in the case of the high pressure discharge lamp 7 in which the tube voltage Vx has a hollow shape in the non-resonant frequency band,
This is because it corresponds to the tube voltage corresponding to the lower limit value f1 and the upper limit value f2 of the lighting frequency in the non-resonant frequency band, and is for enabling the lighting frequency to be changed in a wide range as much as possible.

Next, in the case of NO at step S203 described above, it is determined that the tube voltage Vx has not reached the threshold value Vs, and the lowering of the lighting frequency is continued. If YES, it is determined that the tube voltage Vx has approached the resonance frequency band because the tube voltage Vx has reached the threshold value Vs, the change of the lighting frequency is stopped, and the lighting frequency f1 at this time is stored (step S204). Next, the control circuit 11 sets the lighting frequency to f1.
Is gradually increased (step S205), and it is determined whether the tube voltage Vx has reached the threshold value Vs in this process (step S206).

Here, in the case of NO, the increase of the lighting frequency is continued, and in the case of YES, it is judged that the tube voltage Vx has reached the threshold value Vs, and it is judged that the resonance frequency band is approached, and the change of the lighting frequency is stopped. At the same time, the lighting frequency f2 at this time is stored (step S207). Then, the control circuit 11 lights the high-pressure discharge lamp 7 at the lighting frequency fx at which the load current becomes the target value ix based on the output signal of the error amplifier 10, with the lighting frequency f1 as the lower limit value and the lighting frequency f2 as the upper limit value. (Step S209).

As described above, even when the non-resonance frequency band or the load current characteristic changes due to the various factors described in the first embodiment, the lighting frequency is always set within the non-resonance frequency band,
In addition, the high-pressure discharge lamp 7 is stably turned on so that the load current becomes the target value ix, the influence of the acoustic resonance phenomenon can be avoided, and the brightness of the high-pressure discharge lamp 7 can be maintained at a predetermined level.

In the first and second embodiments, the initial lighting frequency of the high pressure discharge lamp 7 having a rating of 35 W is set within the range of 40 KHz to 45 KHz which is one of the non-resonant frequency bands. This may be selected from other non-resonant frequency bands.

Further, the control unit 11 controls the lighting frequency so that the lighting frequency is repeatedly decreased / increased at regular intervals, and is controlled to be decreased / increased by using the increase amount of the tube voltage of the high-pressure discharge lamp 7 as a trigger. You may control. Alternatively, the lighting frequency may be decreased / increased at regular intervals, and the lighting frequency may be changed when the tube voltage rises during that interval.

Further, the control unit 11 calculates the differential value of the tube voltage, and determines the lower limit value f1 and the upper limit value f2 of the lighting frequency in the non-resonant frequency band based on the magnitude of the differential value, The control may be performed so as to decrease / increase the lighting frequency within the range.

Further, when the control circuit 11 controls the drive frequency of the inverter circuit 2 so as to match the non-resonant frequency to light the high pressure discharge lamp 7 and then changes the lighting frequency, the direction opposite to that described above is applied. That is, it is possible to make a downward change after making an upward change.

[0028]

Since the present invention is constituted as described above, it has the following effects.

The high pressure discharge lamp lighting device according to the present invention comprises a high pressure discharge lamp, a high frequency power supply circuit for supplying high frequency power to the high pressure discharge lamp, and a control circuit for controlling the output frequency of the high frequency power supply circuit. In the high pressure discharge lamp lighting device, when the control circuit feeds back the load current flowing in the high pressure discharge lamp to determine the output frequency of the high frequency power supply circuit, the range of the output frequency is made to match the non-resonant frequency band. Even if the non-resonance frequency band or load current characteristics change due to various factors such as variations in the characteristics of the high-pressure discharge lamp or circuit components, or changes over time in the high-pressure discharge lamp, the lighting frequency should always be set within the non-resonance frequency band for high voltage. The discharge lamp can be stably lit, the influence of the acoustic resonance phenomenon can be avoided, and the brightness of the high pressure discharge lamp can be maintained at a predetermined level.

The high pressure discharge lamp, the high frequency power supply circuit for supplying high frequency power to the high pressure discharge lamp, the control circuit for controlling the output frequency of the high frequency power supply circuit, and the voltage detection for detecting the tube voltage of the high pressure discharge lamp. In the high-pressure discharge lamp lighting device including means and current detection means for detecting a load current flowing in the high-pressure discharge lamp, the control circuit stores the tube voltage when the high-pressure discharge lamp is lit at a predetermined frequency as a reference tube voltage. Then
A first frequency at a point where the tube voltage becomes higher than the reference tube voltage when the output frequency of the high frequency power supply circuit is lowered,
The second frequency at the point where the tube voltage becomes higher than the reference tube voltage when the output frequency is increased is stored, and the output frequency of the high frequency power supply circuit is set between these first and second frequencies. Since the load current is set to a predetermined value, even if the non-resonant frequency band or the load current characteristic changes due to various factors such as variations in the characteristics of the high-pressure discharge lamp or circuit components, and changes over time in the high-pressure discharge lamp, the acoustic The influence of the resonance phenomenon can be avoided and the brightness of the high pressure discharge lamp can be maintained at a predetermined level.

Further, the high pressure discharge lamp, the high frequency power supply circuit for supplying high frequency power to the high pressure discharge lamp, the control circuit for controlling the output frequency of the high frequency power supply circuit, and the voltage detection for detecting the tube voltage of the high pressure discharge lamp. In the high-pressure discharge lamp lighting device comprising a means and a current detection means for detecting a load current flowing in the high-pressure discharge lamp, the control circuit sets the output frequency of the high-frequency power supply circuit to a range in which the tube voltage of the high-pressure discharge lamp is a predetermined value or less. Since the load current is set to a predetermined value,
Without being restricted by the tube voltage characteristic of the high-pressure discharge lamp, that is, the voltage characteristic of the non-resonant frequency band, the influence of the acoustic resonance phenomenon can be always avoided and the brightness of the high-pressure discharge lamp can be maintained at a predetermined level.

Further, since the control circuit repeatedly changes the output frequency of the high frequency power supply circuit at regular intervals, the influence of the acoustic resonance phenomenon is always avoided while monitoring the tube voltage characteristic of the high pressure discharge lamp. In addition, the brightness can be maintained at a predetermined level.

Further, the control circuit changes the output frequency of the high frequency power supply circuit when the tube voltage of the high pressure discharge lamp detected by the voltage detecting means or the load current detected by the current detecting means changes by a predetermined amount. As a result, the influence of the acoustic resonance phenomenon can be promptly avoided, and the brightness of the high pressure discharge lamp can be maintained at a predetermined level. You can

[Brief description of drawings]

FIG. 1 shows a circuit configuration diagram of a high pressure discharge lamp lighting device of the present invention.

FIG. 2 is a tube voltage / load current characteristic diagram of the first embodiment.

FIG. 3 is a flowchart showing a flow of a lighting operation according to the first embodiment.

FIG. 4 is a flowchart showing a flow of a lighting operation according to the second embodiment.

FIG. 5 is a tube voltage / load current characteristic diagram of the second embodiment.

FIG. 6 is a circuit configuration diagram showing a conventional high pressure discharge lamp lighting device.

[Explanation of symbols]

1 DC power supply, 2 inverter circuit, 3 control circuit, 4
Load circuit, 5 resonance capacitor, 6 choke coil, 7 high-pressure discharge lamp, 8 voltage detector, 9 load current detection resistor, 10 error amplifier, 11 control circuit.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3K072 AA11 AC02 AC11 BA03 BC01                       BC03 CA03 CA04 CA07 DD03                       DE02 DE04 GB12 HA06

Claims (5)

[Claims] 1. A high pressure discharge lamp lighting device comprising: a high pressure discharge lamp; a high frequency power supply circuit for supplying high frequency power to the high pressure discharge lamp; and a control circuit for controlling an output frequency of the high frequency power supply circuit. The control circuit feeds back a load current flowing through the high-pressure discharge lamp to determine the output frequency of the high-frequency power supply circuit, and makes the range of the output frequency coincide with a non-resonant frequency band. Lighting device. 2. A high pressure discharge lamp, a high frequency power supply circuit for supplying high frequency power to the high pressure discharge lamp, a control circuit for controlling an output frequency of the high frequency power supply circuit, and a tube voltage of the high pressure discharge lamp. In a high pressure discharge lamp lighting device comprising a voltage detection means and a current detection means for detecting a load current flowing through the high pressure discharge lamp, the control circuit uses a tube voltage when the high pressure discharge lamp is lit at a predetermined frequency as a reference. The tube voltage is stored as a tube voltage, and the tube frequency is higher than the reference tube voltage when the output frequency of the high-frequency power supply circuit is decreased, and the tube voltage is increased when the output frequency is increased. The second frequency at a point higher than the voltage is stored, and the output frequency of the high-frequency power supply circuit is between these first and second frequencies, and the load current is set to a predetermined value. High-pressure discharge lamp lighting device characterized by. 3. A high pressure discharge lamp, a high frequency power supply circuit for supplying high frequency power to the high pressure discharge lamp, a control circuit for controlling an output frequency of the high frequency power supply circuit, and a tube voltage of the high pressure discharge lamp. In a high pressure discharge lamp lighting device comprising voltage detection means and current detection means for detecting a load current flowing through the high pressure discharge lamp, the control circuit sets the output frequency of the high frequency power supply circuit to a predetermined voltage of the high pressure discharge lamp. A high pressure discharge lamp lighting device, characterized in that the load current is set to a predetermined value within a range of a value or less. 4. The high pressure discharge lamp lighting device according to claim 2, wherein the control circuit repeatedly changes the output frequency of the high frequency power supply circuit at regular intervals. . 5. The control circuit of the high frequency power supply circuit, when the tube voltage of the high pressure discharge lamp detected by the voltage detection means or the load current detected by the current detection means changes by a predetermined amount. The high pressure discharge lamp lighting device according to claim 2 or 3, wherein the output frequency is changed.