JP4639636B2 - High pressure discharge lamp lighting device - Google Patents

Description

The present invention relates to a high pressure discharge lamp lighting device. In particular, the present invention relates to a high pressure discharge lamp lighting device having an enclosed mercury amount of 0.15 mg / mm ³ or more used as a light source of a projector device.

FIG. 4 shows a high pressure discharge lamp lighting device.
The circuit configuration includes a DC power source VDC, a chopper circuit 1 having a switching element Qx, a smoothing circuit 2 including capacitors CX and C1, and a lighting starter circuit 3.
The operation of the circuit is supplied to the discharge lamp 10 as a direct current output in the smoothing circuit 2 while performing switching control in order to supply a predetermined current in the chopper circuit 1.

When a high voltage pulse is applied to the discharge lamp 10 by the starter circuit 3, dielectric breakdown is generated between the electrodes, and glow discharge is started. The duration of the glow discharge varies depending on various conditions, and may end in several microseconds or may last several tens of milliseconds or longer.
The discharge lamp 10 enters an arc discharge state when the glow discharge ends. The arc discharge voltage is lower than the glow discharge voltage.

The capacitor C1 included in the smoothing circuit 2 is a smoothing capacitor for reducing high-frequency ripple after the discharge lamp 10 shifts to arc discharge, and a capacitor having a relatively large capacity is connected thereto.
Further, the capacitor Cx is connected with a small capacity so as to quickly shift to arc discharge at the start of lighting. Therefore, at the start of lighting and until the transition to arc discharge, emphasis is placed on the transition to arc discharge rather than reduction of high-frequency ripple, the switch SW is opened, the capacitor Cx is used, and the discharge lamp is arc-discharged. After the transition to, the switch SW is closed and the capacity is increased by the parallel circuit of the capacitor Cx and the capacitor C1.
Such a technique is disclosed in, for example, Japanese Patent No. 3188873.

On the other hand, a discharge lamp, which is a light source of a projector device, generally has a very large amount of mercury enclosed. For this reason, when the discharge lamp is turned off, liquid or solid mercury often adheres to the electrode. This is because the electrode made of metal is the part that is most easily cooled by turning off the discharge lamp, and mercury is easily condensed.
When the discharge lamp is dielectrically broken in this state, arc discharge tends to occur starting from mercury adhering to the electrode. This arc discharge is different from the above-described arc discharge by heat, and can be said to be a special arc discharge. The mercury adhering to the electrode evaporates and disappears when it is exhausted.
In other words, in the case of a normal discharge lamp, after the start of lighting (dielectric breakdown), it shifts to glow discharge via glow discharge. However, in the case of a discharge lamp with a large amount of enclosed mercury, the special discharge is temporarily performed in the glow discharge state. You may experience an arc condition.
The present inventor has found that when this special arc discharge occurs, the discharge lamp is likely to turn off (turn off).

Provided is a lighting device for a high-pressure discharge lamp having an enclosed mercury amount of 0.15 mg / mm ³ or more, and even if a special arc discharge is experienced at the start of lighting, the discharge lamp can be stably maintained without turning off. It is in.

In order to solve the above problems, a high pressure discharge lamp lighting device according to the present invention includes a high pressure discharge lamp in which mercury of 0.15 mg / mm ³ or more is sealed, and a power supply device for the discharge lamp. The power supply device includes a chopper circuit, a smoothing circuit connected to the output end of the chopper circuit, and an initiator connected to the rear end of the smoothing circuit. And the startability improving circuit is connected in parallel to the output terminal of the chopper circuit, and the startability improving circuit includes a large-capacitance capacitor in parallel with a resistor, a switch, and a diode in a reverse direction with respect to charging of the large-capacity capacitor. Connected in series with the circuit, the switch is open until the discharge lamp transitions to arc discharge and is closed after transition to arc discharge .

  Furthermore, a full bridge circuit for generating an alternating current is connected to the output side of the smoothing circuit.

  With the above configuration, even if a special arc is generated due to the adhesion of mercury to the electrode, the transition from glow discharge to arc discharge can be achieved satisfactorily.

FIG. 1 shows a high pressure discharge lamp lighting device according to the present invention. The power supply apparatus includes a chopper circuit 1, a smoothing circuit 2, and a starter circuit 3 that is a starter. A lighting device is constituted by the power feeding device and the discharge lamp.
The chopper circuit 1 includes a switching element Qx, a drive circuit Gx that controls the switching element Qx, and a diode Dx. A direct current from the direct current power source Vdc is converted into a current value corresponding to a predetermined switching cycle.
The smoothing circuit 2 smoothes the output of the chopper circuit 2 and includes a coil Lx, a capacitor Cx, and a startability improving circuit 21. The startability improving circuit 21 is configured by connecting a parallel circuit of a diode D1, a resistor R1, and a switch SW and a capacitor C1 in series. The capacitor Cx and the startability improving circuit 21 are connected in parallel. Here, the capacitor Cx has a small capacity, and the capacitor C1 has a large capacity. The diode D1 is connected in the opposite direction to the charging direction of the capacitor C1.
The starter circuit 3 includes an igniter transformer Tr, and generates a high voltage pulse when the discharge lamp 10 is started.
As will be described later, the discharge lamp 10 has an enclosed mercury amount of 0.15 mg / mm ³ or more.

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 Tr1 by the starter circuit 3, a break occurs between the electrodes of the discharge lamp 10 and discharge starts. In addition, the high voltage pulse is about several KV to several tens KV in numerical examples.

  Next, when dielectric breakdown occurs in the discharge lamp, a relatively large current must be supplied to the discharge lamp in order to keep the subsequent lighting stable. Since the capacitor C1 has a large capacity and is in a charged state in advance, a large current from the capacitor C1 is supplied to the discharge lamp 10. Note that the switch SW remains open from the time of dielectric breakdown.

When the discharge of the capacitor C1 is completed, current is subsequently supplied from the output terminal of the chopper circuit 1. At this time, it is quickly supplied to the discharge lamp 10 via the small-capacitance capacitor Cx. This is because the capacitor Cx has a small capacity, so that the current supply to the discharge lamp 10 is performed quickly.
In addition, although the capacitor C1 has a large capacity, charging of the capacitor C1 is suppressed due to the opening of the switch SW and the presence of the resistor R1 and the diode D1 having a high resistance value.
That is, immediately after the dielectric breakdown, the discharge is stably maintained by utilizing the discharge current of the capacitor C1 having a large capacity, and when the discharge current of the capacitor C1 is depleted, the current flowing from the chopper circuit 1 is the capacitor C1. It is supplied to the discharge lamp without being charged.
Here, taking a numerical example of the capacitance of the capacitor, the capacitor Cx is in the range of 100 pF to 0.1 μF, for example, 0.09 μF, and the capacitor C1 is in the range of 0.2 to 10 μF, for example, 0.47 μF. . The resistor R1 is in the range of 50K ohms to 200K ohms, for example, 100K ohms.

  Thereafter, after the discharge lamp 10 shifts to arc discharge, the capacitor C1 can be used for ripple removal of DC current by closing the switch SW.

As described above, in a discharge lamp having an enclosed mercury amount of 0.15 mg / mm ³ or more, mercury is often attached to the electrode when starting to light. When a discharge is generated with this mercury as a starting point, the moment is closer to an arc discharge (referred to as “special arc” or “special arc state” for convenience) rather than glow discharge.
Moreover, when the mercury adhering to the electrode becomes the starting point of the special arc, it 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 is successfully generated from the cathode. If it does not occur well, the discharge lamp goes out.

Depending on the type of discharge lamp, the voltage between electrodes is 100 to 200 V in glow discharge, whereas the voltage between electrodes is 10 to 20 V in arc discharge in the initial stage of starting.
Therefore, when the glow discharge changes to the special arc or from the special arc to the glow discharge, the voltage between the electrodes changes with a difference.

Returning to FIG. 1, consider the case where the discharge lamp has changed from a special arc state to a glow discharge state. In this case, the interelectrode voltage changes from a state of 10 to 20V to a state of 100 to 200V. For this reason, the current flowing from the chopper circuit 1 becomes difficult to flow into the discharge lamp 10 and tends to flow into the capacitor C1.
The diode D1 serves to prevent this current from flowing into the capacitor C1. By connecting the diode D1 in the reverse flow direction, it is possible to prevent the flow into the capacitor C1 even in this case, and to continue the current supply to the discharge lamp.

Such a function is theoretically possible even if it is not a parallel circuit of the diode D1, the resistor R1, and the switch SW. For example, the diode D1 and the resistor R1 can be eliminated, and the switch SW and the capacitor C1 can be connected as a series circuit by controlling the opening and closing of the switch SW. However, the occurrence of a special arc is not predictable, and it is extremely short, and the switch SW cannot be turned on when it is repeatedly turned off and turned on again.
The startability improving circuit of the present invention can cope with the problem of special arc generation with a very simple configuration.

FIG. 2 shows a lighting device for an AC lighting type discharge lamp. In the figure, the circuit has basically the same configuration as the circuit shown in FIG. 1 except that the full bridge circuit 4 is provided between the smoothing circuit 2 and the discharge lamp 10.
The full bridge circuit 2 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, the pair of switching elements Q1 and Q4 and the pair of switching elements Q2 and Q3 are alternately turned on, the current flowing through the path of the switching element Q1, the inductance L1, the discharge lamp 10, the switching element Q4, and the switching The current flowing through the path of the element Q3 → the discharge lamp 10 → the inductance L1 → the switching element Q2 is alternately generated.

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 consists of molybdenum normally in these sealing parts 12 is embed | buried airtightly by the shrink seal | sticker, 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. In addition, 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. The higher the mercury vapor pressure, the more suitable the light source suitable for the projector device. Can be realized.
For example, the rare gas is filled with about 13 kPa of argon gas to improve the lighting startability.
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 the discharge lamp for direct current lighting shown in FIG. 1, 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, it is possible to provide emitted light with good color rendering properties.

In FIG. 2, the means for generating an alternating current is not limited to a full bridge circuit, and other circuit configurations can be employed. In particular, even if the number of switching elements is not four, it is sufficient if at least two switching elements can be alternately turned on and off with a dead time interposed.
The starter circuit 3 is not limited to a system in which a high-voltage transformer is connected to the current path, and may be a system in which a trigger wire is disposed on the outer surface of the discharge lamp 10 (so-called external trigger system).

  As described above, the high pressure discharge lamp lighting device of the present invention has a parallel circuit of a small-capacitance capacitor and a startability improvement circuit, and the startability improvement circuit includes a parallel circuit of a resistor, a switch and a diode, and a large-capacity capacitor. By configuring in series, it is possible to achieve a good transition from glow discharge to arc discharge even if a special arc is generated due to the adhesion of mercury to the electrode.

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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chopper circuit 2 Smoothing circuit 3 Starter circuit 4 Full bridge circuit 10 Discharge lamp 20 Electrode 21 Startability improvement circuit

Claims (2)

In a high pressure discharge lamp lighting device comprising a high pressure discharge lamp in which mercury of 0.15 mg / mm ³ or more is enclosed, and a power supply device for the discharge lamp,
The power supply device includes a chopper circuit, a smoothing circuit connected to the output end of the chopper circuit, and an initiator connected to the rear end of the smoothing circuit,
In the smoothing circuit, a small-capacitance capacitor and a startability improving circuit are connected in parallel to the output terminal of the chopper circuit,
In the startability improving circuit, a large-capacity capacitor is connected in series with a parallel circuit of a resistor, a switch, and a diode in a reverse direction with respect to charging of the large-capacity capacitor,
The switch is open until the discharge lamp shifts to arc discharge, and closes after the switch shifts to arc discharge .   2. The high pressure discharge lamp lighting device according to claim 1, wherein a full bridge circuit for generating an alternating current is connected to an output side of the smoothing circuit.

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