JP4399650B2 - High pressure discharge lamp lighting device - Google Patents

Description

  The present invention relates to an improvement of a high pressure discharge lamp lighting device that starts a high pressure discharge lamp with a high frequency current and lights it with a low frequency rectangular wave after a predetermined time.

In recent years, high-pressure discharge lamp lighting devices have become smaller and lighter due to computerization, and high-pressure discharge lamp lighting devices that steadily light high-pressure discharge lamps with a low-frequency rectangular wave current are used for lighting in indoor commercial facilities and for liquid crystal projectors. It has been widely used in light sources for automobiles, headlights for vehicles such as automobiles, and light source devices for industrial equipment.
As such a high pressure discharge lamp lighting device, one having a circuit configuration shown in FIG. 5 is generally known.
The high pressure discharge lamp lighting device shown in FIG. 5 receives the voltages of the transistor 1, the diode 2, the choke coil 3, the capacitor 4, the resistors 6 and 7, and the resistor 8 to control the duty ratio of the transistor 1. A step-down chopper circuit I composed of the control circuit 3, a transistor 9-12 connected to the output of the step-down chopper circuit I, a bridge circuit II composed of a second control circuit 13 for controlling these transistors, and the bridge circuit The circuit includes a series circuit of a choke coil 14 and a capacitor 16 connected to the middle point of the transistor to be configured, and a starting circuit III including a pulse transformer 15 for starting the high-pressure discharge lamp 17.

Here, in the operation of the high pressure discharge lamp lighting device shown in FIG. 5, when the DC power is supplied, the first control circuit 3 of the step-down chopper circuit I operates, and the transistor 1 performs the PWM operation so that the step-down chopper circuit I operates. A DC voltage is generated in the capacitor 4 which is the output end.
Here, assuming that the DC voltage supplied to the step-down chopper circuit I is 400 V, the direct current generated in the capacitor 4 when the duty ratio of the transistor 1 is kept constant in a state where the high pressure discharge lamp 17 is not lit. The voltage is about 400 V, which is almost the same as the input DC voltage, and when the voltage of the resistors 6 and 7 is detected and the duty ratio of the transistor 1 is limited by the first control circuit 13, the voltage generated in the capacitor 4 is set. It becomes the arbitrary voltage (for example, 200V) made.

Further, in the bridge circuit II, the transistors 9, 12 and 10, 11 are alternately turned on / off by the second control circuit 13, so that a rectangular wave AC voltage is applied to the middle point of the transistors constituting the bridge circuit II. Is output.
Here, the high-pressure discharge lamp lighting device shown in FIG. 5 performs an operation of switching from a high frequency to a low frequency, for example, operating at 30 kHz for 3 seconds immediately after starting the device and then operating at 200 Hz.

When the starter circuit III that receives the rectangular wave output of the bridge circuit II performs a high-frequency operation as described above immediately after the start-up of the device, a high-frequency rectangular wave voltage is applied to the series circuit of the choke coil 14 and the capacitor 16, and the choke coil 14, The capacitor 16 resonates, and a sinusoidal resonance voltage is generated at the end of the capacitor 16, which is applied to the high-pressure discharge lamp 17.
This resonance voltage is determined by the inductance value of the choke coil 14, the capacitance of the capacitor 16, and the operating frequency of the bridge circuit II, and is adjusted to a voltage of about 700 V peak, for example.
While applying the resonance voltage to the end of the high-pressure discharge lamp 17, a pulse voltage of about several kV to several tens of kV is superimposed on the resonance voltage by the pulse transformer 15 and applied to the high-pressure discharge lamp 17. Is subjected to dielectric breakdown, high-frequency lighting with the current limited by the choke coil 14 at the operating frequency (for example, 30 kHz) of the bridge circuit II, and after both electrodes of the high-pressure discharge lamp 17 are sufficiently heated by the high-frequency current. For example, after 3 seconds, the operating frequency of the bridge circuit II is reduced to 200 Hz, for example, and stable low-frequency rectangular wave lighting is achieved.
Further, Patent Document 1 describes a similar lighting method that includes an inductance element and a capacitor resonance circuit and performs high-frequency lighting at the start of a high-pressure discharge lamp and then low-frequency rectangular wave lighting. The direct current component of is not described.

JP-A-8-124687

However, in the process in which a high-frequency lamp current flows after the high-pressure discharge lamp 17 is broken down by the pulse voltage of the pulse transformer 15, the electrodes of the high-pressure discharge lamp 17 are cooled immediately after the breakdown, so that the constant voltage as shown in FIG. During this period, current flows only from the electrode on the side that is easy to discharge, and becomes a high-frequency current on which a rectifying DC component is superimposed.
After that, the temperature of the high-pressure discharge lamp 17 rises, and the direct current component is reduced as the discharge gradually proceeds from the opposite electrode, and finally a symmetric high-frequency current is transferred. Although the time is high, when the high-frequency current superimposed with the direct current component is asymmetrical, the electrode on the anode side is extremely heated, causing damage to the electrode and reducing the lamp life.

  Therefore, in order to solve the above problem, the present invention improves the operation at high frequency lighting of the bridge circuit II that performs rectangular wave lighting, reduces the direct current component of the high frequency current that flows when the high pressure discharge lamp 17 is started, and the period thereof. The technical issue is to shorten

A first aspect of the present invention includes a first transistor series circuit and a second transistor series circuit, a bridge circuit that switches a DC voltage and supplies power to a lamp, and a first transistor series circuit and a first transistor series circuit A high-pressure discharge lamp lighting device comprising a starting circuit for starting a lamp, comprising a choke coil and a first capacitor connected in series to the middle point of two transistor series circuits, wherein the first transistor series circuit or the second transistor A high-pressure discharge lamp lighting device including a DC voltage circuit connected in parallel to one of transistors constituting a transistor series circuit and capable of holding at least a voltage lower than the DC voltage. here,
The DC voltage circuit is a second capacitor. In this configuration, one of the first and second transistor series circuits is alternately turned on and the other is turned off for a predetermined period before the start of lamp lighting and after the start of lighting. Furthermore, a voltage detection circuit for detecting the voltage of the second capacitor is provided, and the predetermined period is a period until the voltage of the second capacitor detected by the voltage detection circuit falls within a predetermined range. . Here, the center value of the predetermined range is set to ½ of the DC voltage applied to the bridge circuit. In addition, a switch connected in series to the second capacitor is provided, and the switch is kept in a conductive state before a predetermined period of time, and then turned off. In addition, a DC power supply circuit that supplies a DC voltage to the bridge circuit is provided.

  A second aspect of the present invention is a high-pressure discharge lamp device including the high-pressure discharge lamp and the high-pressure discharge lamp lighting device according to the first aspect.

  In the high-pressure discharge lamp lighting device according to the present invention, it is possible to extend the lamp life by reducing the current stress applied to the electrode on one side of the high-pressure discharge lamp during high-frequency lighting immediately after starting the lamp.

[Embodiment of the Invention]
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a circuit configuration diagram showing a high pressure discharge lamp lighting device according to the present invention, and FIG. 2 is a circuit operation diagram for showing the operation of FIG.
1 is the same as FIG. 5 except that a capacitor 18 is connected between the drain and source of the transistor 12 of the bridge circuit of FIG. 5 showing the circuit configuration of the conventional example.

The operation of the circuit shown in FIG. 1 is the same as that of the step-down chopper circuit I shown in FIG.
As for the bridge circuit II, as shown in FIG. 2, initially, the transistors 11 and 12 are in a non-conductive state, and the transistors 9 and 10 are alternately turned on and off at a high frequency.
First, when the transistor 9 is turned on and the transistor 10 is turned off, a current flows from the step-down chopper circuit I through the path of the transistor 9, the choke coil 14, the capacitor 16, and the capacitor 18, and the capacitor 18 is charged.
When the transistor 9 becomes non-conductive and the transistor 10 becomes conductive in the next cycle, the capacitor 18 is used as a power source, and a current flows through the path of the capacitor 16, the choke coil 14, and the transistor 10.

  By repeating the above operation, a high-frequency rectangular wave voltage is generated at the midpoint of the bridge circuit as in the conventional example, the series circuit of the choke coil 14 and the capacitor 16 resonates, and a sinusoidal resonance occurs at the end of the capacitor 16. A voltage is generated and applied to the high-pressure discharge lamp 17.

  Next, while the resonance voltage is applied to the end of the high-pressure discharge lamp 17, a pulse voltage of about several kV to several tens of kV is superimposed on the resonance voltage by the pulse transformer 15 and applied to the high-pressure discharge lamp, thereby causing high-pressure discharge. The lamp 17 causes dielectric breakdown. This time, the transistor 9, the choke coil 14, the pulse transformer 15, the high-pressure discharge lamp 17, the capacitor 18, and the high-pressure discharge lamp 17, the pulse transformer 15, and the choke are similarly supplied from the capacitor 18 in the next cycle. A current flows through the path of the coil 14 and the transistor 10, and the high-pressure discharge lamp performs high-frequency lighting as in the conventional example.

Here, as in the conventional example, the electrodes of the high-pressure discharge lamp 17 are cooled. First, current flows in the direction of the transistor 9, the choke coil 14, the pulse transformer 15, the high-pressure discharge lamp 17, and the capacitor 18, and in the opposite direction. When current is difficult to flow in the direction of the high-pressure discharge lamp 17, the pulse transformer 15, the choke coil 14 and the transistor 10 using a certain capacitor 18 as a power source, the capacitor 18 is charged and the voltage is increased accordingly.
Therefore, the potential of the capacitor 18 increases as the transistors 9 and 10 repeat conduction and non-conduction in a rectifying state, and the value of the high-frequency current flowing through the path of the transistor 9, the choke coil 14, the capacitor 16, and the capacitor 18 decreases. .
While this state is repeated, the temperature of the high-pressure discharge lamp 17 rises, and discharge starts from the opposite electrode, and finally shifts to a symmetric high-frequency current. Damage to the electrode on the anode side can be reduced because the period during which the high-frequency current with superimposed components flows is short.

  The transistor of the bridge circuit II to which the capacitor 18 is connected may be other than the transistor 12, and the series circuit of the transistor on the side where the capacitor is attached is stopped during high-frequency operation, and the transistor in the series circuit of the other transistor is alternately turned on. If it is, the same effect will be acquired. Further, the capacitor 18 has a capability of holding a voltage (ideally a half voltage value) lower than the output voltage of the step-down chopper circuit I during the operation of only one transistor series circuit (half-bridge operation). A circuit other than a capacitor may be used.

Further, in this embodiment, a period of several seconds is determined in advance for the period from the operation of only one transistor series circuit (half-bridge operation) to the operation of both transistor series circuits (full-bridge operation). However, the voltage applied to the capacitor 18 may be detected to determine whether or not the rectified lighting state is set, and the above operation may be shifted when the rectified state ends.
Specifically, when the discharge is normal during high-frequency lighting (when rectified lighting is not performed), the capacitor 18 is applied with a voltage that is approximately half the output voltage of the step-down chopper circuit I. In the rectified lighting state, for example, in the rectified state from the choke coil 14 to the capacitor 18, a voltage higher than half of the output voltage of the step-down chopper circuit I is applied to the capacitor 18, and in the reverse direction in the rectified state. Therefore, a voltage smaller than half of the output voltage of the step-down chopper circuit I is applied to the capacitor 18. Therefore, if the voltage of the capacitor 18 is within a predetermined range, that is, within a certain range centered on a half value of the output voltage of the step-down chopper circuit I, the lamp is lit normally and out of range. If so, the rectified lighting state is established, and therefore the operation state of the bridge circuit may be shifted based on the detected voltage.
The voltage detection circuit applied to the capacitor 18 can be constituted by, for example, a resistance dividing circuit 19 as shown in FIG.

  In the above embodiment, the capacitor 18 is always connected. However, as shown in FIG. 4, a switch 20 composed of a switching element or the like is connected in series to the capacitor 18 to shift to a full bridge operation state. Thereafter, the capacitor 18 may be separated for stable operation thereafter.

Circuit diagram of high pressure discharge lamp lighting device in the present invention The figure explaining operation | movement of the circuit of FIG. It is a figure explaining the example of a development of the present invention. It is a figure explaining the example of a development of the present invention. Circuit diagram of conventional high-pressure discharge lamp lighting device The figure explaining operation | movement of the circuit of FIG.

Explanation of symbols

I Step-down chopper circuit
II Bridge circuit
III Start circuit 9, 10, 11, 12 Transistor 13 Control circuit 14 Choke coil 15 Pulse transformer 16, 18 Capacitor 17 High pressure discharge lamp 19 Resistance dividing circuit 20 Switch

Claims (7)

A bridge circuit comprising a first transistor series circuit and a second transistor series circuit, for switching a DC voltage to supply power to the lamp; and
A high pressure discharge lamp lighting device comprising: a choke coil connected in series to a midpoint of the first transistor series circuit and the second transistor series circuit and a first capacitor, and a starting circuit for starting the lamp. And
A DC voltage circuit connected in parallel to one of the transistors constituting the first transistor series circuit or the second transistor series circuit and capable of holding at least a voltage lower than the DC voltage ;
A high pressure discharge lamp lighting device characterized in that one of the first or second transistor series circuit is alternately turned on and the other is turned off for a predetermined period before the start of lamp lighting and after the start of lighting.
The high pressure discharge lamp lighting device according to claim 1,
The high-voltage discharge lamp lighting device, wherein the DC voltage circuit is a second capacitor.
The high pressure discharge lamp lighting device according to claim 2 ,
Furthermore, a voltage detection circuit for detecting the voltage of the second capacitor is provided,
The high-pressure discharge lamp lighting device, wherein the predetermined period is a period until the voltage of the second capacitor detected by the voltage detection circuit falls within a predetermined range.
The high pressure discharge lamp lighting device according to claim 3 ,
A high-pressure discharge lamp lighting device, wherein a center value of the predetermined range is ½ of the DC voltage.
A bridge circuit comprising a first transistor series circuit and a second transistor series circuit, for switching a DC voltage to supply power to the lamp; and
A high pressure discharge lamp lighting device comprising: a choke coil connected in series to a midpoint of the first transistor series circuit and the second transistor series circuit and a first capacitor, and a starting circuit for starting the lamp. And
A second capacitor connected in parallel to one of the transistors constituting the first transistor series circuit or the second transistor series circuit and capable of holding at least a voltage lower than the DC voltage; and the second capacitor A high-pressure discharge lamp lighting device comprising switches connected in series, wherein the switch is kept in a conductive state before the predetermined period has elapsed and then turned off.
The high pressure discharge lamp lighting device according to any one of claims 1 to 5 , further comprising a DC power supply circuit for supplying a DC voltage to the bridge circuit. .
A high-pressure discharge lamp comprising the high-pressure discharge lamp and the high-pressure discharge lamp lighting device according to any one of claims 1 to 6 .

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