JP2006278095A - Power supply device for high pressure discharge lamp and light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device for a high pressure discharge lamp capable of stably maintaining the discharge lamp without lights-out even if specific arc-discharge is passed through at the start of lighting. <P>SOLUTION: The power supply device has a chopper circuit including a switching element, a smoothing circuit 2 including at least one smoothing capacitor connected to output terminals of the chopper circuit 1, and a feedback type control circuit 4 driving the switching element of the chopper circuit 1. A second switch element is connected to output side of the smoothing circuit. The second switch element is a semiconductor element controlled so as to perform an analogue operation at the start of lighting and to conduct at stationary lighting by the control circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power supply device for a high-pressure discharge lamp and a light source device. In particular, the present invention relates to a power supply device for a high-pressure discharge lamp used as a light source of a projector device and the light source device.

FIG. 4 shows a power supply device for a high-pressure discharge lamp.
The power feeding device includes a chopper circuit 1 having a switching element Qx, a smoothing circuit 2 including a coil and a capacitor, a lighting starter circuit 3, and a control circuit 4 for driving the switching element Qx.
The control circuit 4 obtains the lighting voltage and lighting current of the discharge lamp 10 by converting them into lighting power based on the detection values of the resistors R1, R2, and R3, and compares them with the reference power value to compare with the switching element Qx. Feedback control.
The output of the chopper circuit 1 becomes a direct current output in the smoothing circuit 2 and is supplied to the discharge lamp 10.

The lighting operation will be described. First, when a high voltage pulse is generated by the starter circuit 3, dielectric breakdown occurs between the electrodes of the discharge lamp 10, and glow discharge occurs. When the electrode warms up, the glow discharge eventually becomes an arc discharge, and the discharge lamp is stably lit.
The glow discharge varies depending on the lighting conditions, and may end in several microseconds or may last several tens of milliseconds or more.

On the other hand, the discharge lamp used for the light source of the projector device has a very large amount of enclosed mercury. For this reason, the mercury vaporized at the time of lighting is in a liquid state (granular) at the time of extinguishing and adheres a lot on the electrode. This is because the electrode made of metal becomes the most easily cooled portion by turning off the discharge lamp, and mercury is easily condensed.
When the discharge lamp is turned on from this state, mercury attached to the electrode becomes easier to discharge than mercury present in other parts, and arc discharge is generated by the mercury on the electrode. This arc discharge is a special arc discharge that occurs temporarily, unlike the arc discharge that occurs when the electrode is warmed, and it disappears when the mercury adhering to the electrode evaporates and becomes exhausted. It is a thing. Of course, a special arc may not be generated depending on the adhesion state of mercury. In this case, glow discharge occurs as described above. That is, it can be said that the special arc occurs irregularly depending on the state of mercury at the time of extinction.

Here, in the case of a normal discharge lamp, after the start of lighting (dielectric breakdown), it goes through a glow discharge state to an arc discharge state. However, in a discharge lamp with a large amount of enclosed mercury, the glow discharge state In this case, the special arc may be temporarily experienced irregularly.
When this special arc occurs, the discharge lamp cannot be stably lit, and is extinguished (disappears) at the initial stage of lighting.
Japanese Patent No. 3188873

  Even if the so-called special arc discharge is experienced at the start of lighting, it is possible to maintain the discharge lamp stably without extinguishing.

A power supply device for a high pressure discharge lamp according to the present invention drives a chopper circuit including a switching element, a smoothing circuit including at least one smoothing capacitor connected to an output end of the chopper circuit, and a switching element of the chopper circuit. It has a feedback system control circuit.
In the first invention (invention 1), a second switch element is connected to the output side of the smoothing circuit, and the second switch element performs analog operation at the start of lighting by the control circuit. In addition, the semiconductor element is controlled to be conductive during steady lighting.

According to a second aspect of the present invention (invention 2), the switching element is a semiconductor element controlled by the control circuit so as to perform an analog operation at the time of lighting start and a switching operation at the time of steady lighting. It is characterized by.
That is, the first invention has a switch element separately connected to the output side of the smoothing circuit, and this switch element has an analog operation at the start of lighting, whereas the second invention has a switching element for a chopper circuit. To have the same function.

  According to a third aspect of the present invention (invention 4), a polarity switching circuit for generating an alternating current is connected to the output terminal of the smoothing circuit, and an analog operation at the start of lighting is connected to the switching element of the polarity switching circuit. Let

In the first and second inventions, a polarity switching circuit may be connected to the output side of the smoothing circuit.
In the first to third aspects of the invention, in the light source device comprising a high pressure discharge lamp enclosing 0.15 mg / mm ³ or more of mercury and a power supply device for the high pressure discharge lamp, the power supply device has the above-described configuration. It is characterized by that.

  With the above configuration, even when a so-called special arc occurs at the start of lighting of the discharge lamp, the transition from glow discharge to arc discharge can be achieved satisfactorily.

FIG. 1 shows an embodiment of the first invention of a power supply device for a high-pressure discharge lamp according to the present invention.
The power feeding apparatus includes a chopper circuit 1, a smoothing circuit 2, a starter circuit 3 that is a starter, and a control circuit 4. The power supply device and the discharge lamp 10 constitute a light source device.
The chopper circuit 1 includes a switching element Qx, a drive circuit Gx that controls the switching element Qx, and a diode Dx, and converts a DC current from the DC power supply Vdc into a current value corresponding to a predetermined switching period.
The smoothing circuit 2 smoothes the output of the chopper circuit 1 and has a coil Lx and a capacitor Cx.
The starter circuit 3 includes an igniter transformer Tr, and generates a high voltage pulse when the discharge lamp 10 is started.

The control circuit 4 receives the voltage signals from the resistors R1 and R2 and the current signal from the resistor R3, generates lighting power for the discharge lamp, and transmits it to the drive circuit Gx in comparison with a predetermined reference value. Thereby, feedback control is performed in which the discharge lamp 10 is maintained at a constant power.
The control circuit 4 includes a current / power calculation circuit, a pulse width modulation circuit, and the like.
As will be described later, the discharge lamp 10 has an enclosed mercury amount of 0.15 mg / mm ³ or more.
Compared with FIG. 4, the switching element Qx is connected to the minus line, but it is not different in terms of circuit function.

Next, the operation at the start of lighting of the discharge lamp 10 will be described.
First, when a high voltage pulse is generated in the transformer Tr by the starter circuit 3, a break occurs between the electrodes of the discharge lamp 10 and discharge starts. When dielectric breakdown occurs in the discharge lamp, current is supplied from the chopper circuit 1. The high voltage pulse is about several KV to several tens of KV in numerical examples.

  A switching element SW made of a semiconductor element is connected to the output terminal of the smoothing circuit 2. The switch element SW is a semiconductor element made of, for example, an FET, and performs an analog operation when lighting is started.

The reason why the switch element SW is operated in an analog manner at the start is as follows.
That is, the discharge lamp after dielectric breakdown is in a glow discharge state, but as described above, a special arc may be temporarily generated.
The lamp voltage is high during glow discharge, but the lamp voltage is low during arc discharge. When a special arc occurs temporarily and the glow discharge is resumed, the lamp voltage changes from a low state to a high state. It becomes.
Since this change occurs in a very short time, it is difficult to follow the feedback system control via the control circuit 4. In the conventional discharge lamp, the discharge lamp has been extinguished due to the following delay.
To give an example of this phenomenon quantitatively, the time during which the feedback system control can react at the time of steady lighting is at most about 200 μsec. On the other hand, in order to prevent the extinction due to the special arc, at least within 100 μsec. Follow-up reaction is required.

  Here, in order to achieve a quick follow-up reaction by analog operation of the switch element SW, the smoothing capacitor Cx must be charged at a predetermined voltage or higher. This is because the discharge of the capacitor Cx can quickly cope with a sudden change in the lamp voltage. As an example of the capacitance of the capacitor, when the output power is about 120 W and the switching frequency is around 100 KHz, it is about 0.5 μF.

The present invention is characterized in that the switch SW is analog-controlled at the start of lighting in order to prevent the extinction due to such a special arc.
When the switch SW is an FET, when the voltage applied to the gate is gradually increased, the drain current gradually increases based on the device-specific gate voltage-drain current characteristics. In the case of a bipolar transistor, the same operation is performed between the base current and the collector current.
Here, the analog operation means that a predetermined voltage is applied to the gate (between the gate and the source) to perform an equivalent resistance operation, and the switch element is equivalently in a resistance state. When the voltage applied to the gate is gradually increased, the device uses the operation that the drain current gradually increases based on the gate voltage-drain current characteristics specific to the device, and a predetermined voltage is applied to the gate to obtain a predetermined drain current. Behave in the same way. Prepare a gate voltage higher than the drain current desired for the switching operation as the gate application voltage, and alternately switch the time to apply and not apply the gate voltage to allow the drain current to flow intermittently. That is, it is different from functioning as a switch element equivalently.

FIG. 6 is a diagram for explaining the analog operation of the switch element SW, and shows the characteristics of the drain current and the gate-source voltage when a MOSFET is used as the switch element.
The figure shows that the drain current does not flow when the gate-source voltage V _GS is below a certain level, and that the drain current can be controlled by taking the value of the gate-source voltage V _GS. Yes.
In addition, when the gate-source voltage V _GS is gradually increased, the drain current also gradually increases. In the example in the figure, if the gate-source voltage V _{GS is set} to 4.2 V, the drain current is about 1 A. It shows flowing.
Incidentally, in this MOSFET, when, for example, 0 V and 6 V, for example, are alternately applied to the gate-source voltage V _GS , the drain current is switched intermittently.

The timing at which the switch SW is operated in analog may be before the starter circuit 3 is activated or immediately after the starter circuit 3 is activated. It is sufficient that the analog operation can be performed at a timing at which a special arc will occur.
In addition to the FET, the switch SW can be a bipole transistor or the like.

  After the discharge lamp 10 shifts to arc discharge, that is, after steady lighting, the switch element SW is always on (conductive). It is conceivable that this timing is set by a method of detecting the lamp voltage by the resistors R1 and R2, or by a timer from the start of the starter circuit 3.

Here, the special arc will be described.
As described above, in a discharge lamp having an enclosed mercury amount of 0.15 mg / mm ³ or more, mercury often adheres to the electrode when starting to light. If a discharge is generated with this mercury as a starting point, the moment is closer to an arc discharge (referred to as a “special arc” for convenience) rather than a glow discharge.
Moreover, when the mercury adhering to the electrode becomes the starting point of the special arc, the mercury evaporates in a relatively short time. At this time, the discharge can be maintained if the next discharge arc is generated from another mercury (mercury adhering to other parts of the electrode) or makes a transition to the discharge from the cathode. If neither can continue well, the discharge lamp goes off.

Depending on the type of the discharge lamp, the voltage between the electrodes is 100 to 200 V in the glow discharge, whereas the voltage between the electrodes is approximately 10 V in the arc discharge in the initial stage of starting.
Therefore, when changing from glow discharge to special arc, or from special arc to glow discharge, the voltage between the electrodes changes with a difference.

FIG. 2 shows a lighting device for an AC lighting type discharge lamp, and shows a modification of FIG. FIG. 2 is basically the same as the circuit shown in FIG. 1 except that a full bridge circuit 5 is provided between the smoothing circuit 2 and the discharge lamp 10.
The full bridge circuit 5 includes switching elements Q1 to Q4 including transistors and FETs connected in a bridge shape, and driving circuits G1 to G4 for the switching elements Q1 to Q4. An AC rectangular wave current can be supplied to the discharge lamp 10 by switching the switching elements Q1 to Q4.
Specifically, at the start of lighting, the pair of switching elements Q1 and Q4 and the pair of switching elements Q2 and Q3 are alternately turned on to switch the switching element Q1, the transformer Tr1, the discharge lamp 10, the switching element Q4, and the switching element SW. And a current flowing through the path of the switching element Q3 → the discharge lamp 10 → the transformer Tr1 → the switching element Q2 → the switching element SW are alternately generated. When the discharge lamp is stable, the pair of switching elements Q1 and Q4 and the pair of switching elements Q2 and Q3 are alternately turned on, and the current flows through the path of the switching element Q1, the transformer Tr1, the discharge lamp 10, the switching element Q4, and the switching element SW. And the electric current which flows through the path | route of switching element Q3-> discharge lamp 10-> transformer Tr1-> switching element Q2-> switch element SW is produced | generated alternately.
A switch element SW is connected between the smoothing circuit 2 and the full bridge circuit 5. This switch element SW is the same as the switch element shown in FIG. 1, and is controlled so as to perform an analog operation at the start of lighting and to be conductive during steady lighting.

FIG. 3 shows the overall configuration of the discharge lamp.
The discharge lamp 10 has a substantially spherical light emitting portion 11 formed by a discharge vessel made of quartz glass, and a pair of electrodes 20 are disposed on the light emitting portion 11 so as to face each other. Moreover, the sealing part 12 is formed so that it may extend from the both ends of the light emission part 11, and the conductive metal foil 13 which usually consists of molybdenum is embed | buried airtight by these shrink seals in these sealing parts 12, for example. . The pair of electrodes 20 have their shaft portions welded to and electrically connected to the metal foil 13, and the other end of the metal foil 13 is welded with an external lead 14 protruding outward.

The light emitting unit 11 is filled with mercury, rare gas, and halogen gas.
Mercury is used to obtain a necessary visible light wavelength, for example, radiated light having a wavelength of 400 to 700 nm, and 0.15 mg / mm ³ or more is enclosed. Although the amount of sealing varies depending on the temperature condition, the vapor pressure becomes extremely high at 150 atm or higher when the lamp is turned on. Also, by enclosing more mercury, it is possible to make a discharge lamp with a high mercury vapor pressure of 200 atm or higher and 300 atm or higher when the lamp is turned on. Can be realized.
As the rare gas, for example, argon gas is sealed at about 13 kPa, and the lighting startability is improved.
As the halogen, iodine, bromine, chlorine and the like are enclosed in the form of a compound with mercury or other metal, and the amount of halogen enclosed is selected from the range of 10 ⁻⁶ to 10 ⁻² μmol / mm ³ . Its function also has a longer life using halogen cycles. However, it is very small and has a high internal pressure such as the discharge lamp of the present invention. The main purpose.
In the case of a discharge lamp for direct current lighting, the electrode 20 has different shapes and volumes for the cathode and the anode.

For example, the discharge lamp has a maximum outer diameter of 9.4 mm, a distance between electrodes of 1.0 mm, an arc tube inner volume of 85 mm ³ , a rated voltage of 75 V, and a rated power of 120 W.
In addition, this type of discharge lamp is built in a miniaturized projector device, and the overall size of the device is extremely small, while a high light quantity is required. Is extremely severe, and the lamp wall load value of the lamp is 0.8 to 2.0 W / mm ² , specifically 1.3 W / mm ² .
When such a high mercury vapor pressure or tube wall load value is mounted on a presentation device such as a projector device or an overhead projector, emitted light with good color rendering can be provided.

FIG. 5 shows the internal structure of the control circuit 4 in FIGS.
In addition to the current / power calculation circuit to which the current signal and the voltage signal are input and the feedback system including the pulse width control circuit for driving the switching element Qx, the circuit includes a circuit unit for driving the switch element SW, and a bias 1 generation circuit And a bias 2 generation circuit. The bias 1 generation circuit generates a signal for analog operation of the switch element SW at the start of lighting, and the bias 2 generation circuit is for complete conduction during steady lighting. A signal selected by the signal switching circuit is input to the switch element SW.
In FIG. 2, it goes without saying that a circuit for driving the full bridge circuit 5 is added in addition to the control circuit 4 shown in FIG.

FIG. 7 shows the operation of the switching element SW in FIGS. 1 and 2 and the time variation of the lamp current. The vertical axis of (a) indicates the equivalent resistance value between the source and drain of the switching element SW, and the horizontal axis indicates time, and represents the operation of the switching element SW. The vertical axis of (b) indicates the lamp current, the horizontal axis indicates time, and the lamp current changes with time.
With respect to the switching element SW, the period T1 is a lighting start time and indicates a period during which the switching element SW operates in an analog manner, and the period T2 indicates a period during which steady switching is performed and the switching element SW performs a closing operation. The change in lamp current during the period in which the switching element SW is closed represents a change from constant current control to constant power control.

Here, the switch element SW may be configured to be connected independently as shown in FIGS. 1 and 2, but in the circuit shown in FIG. 4, the switch element SW can also be used as the switching element Qx of the chopper circuit 1.
In this case, the switching element Qx performs an analog operation at the start of lighting and a switching operation (chopper) during steady lighting by the control circuit 4. The analog operation and timing are all the same as described in FIG.

Further, even in the configuration having the polarity switching circuit shown in FIG. 2, the switching element Qx of the chopper circuit can be operated in an analog manner without providing the switching element SW.
Advantages in this case are advantageous in terms of cost, efficiency, and mounting space because there is no need to add an expensive switch element.

FIG. 8 shows the operation of the switching element Qx and the time variation of the lamp current in claim 2 (corresponding to FIG. 4). The vertical axis of (a) indicates the source / drain current of the switching element Qx, the horizontal axis indicates time, and represents the operation of the switching element Qx. The vertical axis of (b) indicates the lamp current, the horizontal axis indicates time, and the lamp current changes with time.
Regarding the switching element Qx, a period T1 is a lighting start time and indicates a period in which the switching element Qx operates in an analog manner, and a period T2 indicates a steady lighting and a period in which the switching element Qx performs a switching operation. The change in lamp current during the switching operation of the switching element Qx represents a change from constant current control to constant power control.

The switch element can also be used as any one of the switching elements Q1 to Q4 of the polarity switching circuit.
In this case, the switching element performs an analog operation at the start of lighting and a switching operation during steady lighting by the control circuit 4. The analog operation and timing are all the same as described in FIG.
The analog operation of the analog operation switching element Qx is due to the fact that the switch element SW is not connected separately, so that the circuit configuration is simplified and the switch element SW is always turned on during steady lighting. Thermal problems and element wear problems are eliminated.

  As described above, the power supply device for a high-pressure discharge lamp according to the present invention performs an equivalent resistance operation by performing an analog operation of any switch element at the start of lighting, so that even if a so-called special arc occurs, the power supply device is excellent. Transition from glow discharge to arc discharge can be achieved.

1 shows a high pressure discharge lamp lighting device of the present invention. 1 shows a high pressure discharge lamp lighting device of the present invention. The discharge lamp used for the high-pressure discharge lamp lighting device of the present invention is shown. A high pressure discharge lamp lighting device is shown. The control circuit of the high pressure discharge lamp lighting device of the present invention is shown. An example of the characteristic of MOSFET is shown. The timing chart for explanation of the present invention is shown. The timing chart for explanation of the present invention is shown.

Explanation of symbols

1 Chopper circuit 2 Smoothing circuit 3 Starter circuit 4 Full bridge circuit 10 Discharge lamp 20 Electrode

Claims (5)

Power supply device for high-pressure discharge lamp having a chopper circuit including a switching element, a smoothing circuit including at least one smoothing capacitor connected to an output terminal of the chopper circuit, and a feedback control circuit for driving the switching element of the chopper circuit In
A second switch element is connected to the output side of the smoothing circuit,
The power supply device for a high pressure discharge lamp, wherein the second switch element is a semiconductor element that is controlled by the control circuit to perform an analog operation at the time of starting lighting and to be turned on at the time of steady lighting. High-voltage discharge lamp power supply apparatus having a chopper circuit including a switching element, a smoothing circuit including at least one smoothing capacitor connected to an output terminal of the chopper circuit, and a feedback control circuit for driving the switching element of the chopper circuit In
The power supply device for a high-pressure discharge lamp, wherein the switching element is a semiconductor element controlled by the control circuit to perform an analog operation when starting lighting and perform a switching operation during steady lighting.   The high-voltage discharge lamp power supply device according to claim 1, wherein a polarity switching circuit that generates an alternating current is connected to an output side of the smoothing circuit. A chopper circuit including a switching element, a smoothing circuit including at least one smoothing capacitor connected to the output terminal of the chopper circuit, a polarity switching circuit connected to the output terminal of the smoothing circuit and generating an alternating current, In a power supply device for a high-pressure discharge lamp having a feedback control circuit that drives a switching element of a chopper circuit,
The power supply device for a high-pressure discharge lamp, wherein the polarity switching circuit includes a semiconductor element controlled by the control circuit to perform an analog operation when starting lighting and perform a switching operation during steady lighting. In a light source device comprising a high pressure discharge lamp enclosing 0.15 mg / mm ³ or more of mercury and a power supply device for the high pressure discharge lamp,
The power supply device according to any one of claims 1 to 4, wherein the power supply device is a light source device.

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