JPH06290892A - Discharge lamp lighting device image display device using it - Google Patents

Abstract

PURPOSE:To achieve the proper start in AC lighting by generating the first and the second pulse in synchronization with the sine wave voltage from an AC generating circuit, superposing these pulses on the sine wave voltage, feeding the resultant to the discharge lamp concerned, and thereby generating an arc transition. CONSTITUTION:A pulse output circuit 56 takes in a sine wave voltage (a) from an AC generating circuit 51, and the peak of the voltage is sensed by a peak sensing part 52. The sensing part 52 performs full-wave rectification, and the signal level of this full-wave rectification is compared with the threshold voltage Vth, and a trigger pulse (c) is emitted when this threshold Vth is exceeded. The trigger pulse (c) is fed to a pulse producing part 53, which produces the first pulse (d) and the second pulse (e). Among them, the pulse (d) is of a magnitude approx. 15kV generated on the counter-polarity side to the sine wave voltage when the pulse (c) is rising, while the pulse (e) is of a magnitude approx. 1kV generated on the same polarity side to the sive wave when the pulse (d) is falling. A discharge destruction is produced with impression of a high voltage on the discharge lamp concerned 1 due to the pulse (d), and transition to the arc discharge takes place with impression of the pulse (e).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for lighting a discharge lamp such as a metal halide lamp and an image display device using the discharge lamp lighting device.

[0002]

2. Description of the Related Art A discharge lamp lighting device for lighting a discharge lamp such as a metal halide lamp cannot be lit at a high frequency due to a problem of acoustic resonance (acoustic resonance). In addition, when lighting is performed with direct current, color separation occurs in the arc discharge portion in the tube of the discharge lamp, which is not preferable. Therefore, in the past, the low frequency (400
The lighting is performed at a frequency of (Hz to 500 Hz).

However, at the time of starting the discharge lamp, if only the above low frequency is supplied to the discharge lamp, glow discharge does not occur between the electrodes of the discharge lamp.
It has become indispensable to apply a high voltage pulse to the discharge lamp. On the other hand, a low frequency is supplied to the discharge lamp as described above in order to continue lighting of the discharge lamp. An AC conversion circuit including a switching element is used as a circuit for generating the low frequency. Then, the application of the high-voltage pulse is performed through this AC conversion circuit.

[0004]

In accordance with the switching operation of the switching element, for example, a low frequency as shown in FIG. 9 is generated. The pulse width of this low frequency is
10 to 20 msec, and the switching period is 5 to 1
It is 0 μsec. FIG. 10 is an enlarged view of the switching period of FIG. 9, and it can be seen that the switching period of 5 to 10 μsec includes the rest period of 4 to 5 μsec. Since a high voltage pulse is applied asynchronously with the switching operation of such a switching element,
When a high voltage pulse is applied during the switching period, particularly during the rest period, the period of the high voltage pulse is 0. Several μs
Since a period of ec to several μsec can sufficiently enter the rest period, there is a fear that the switching element in the rest state is destroyed.

The present invention has been made to solve the problems of the conventional discharge lamp lighting device as described above, and its purpose is to prevent the destruction of the AC conversion circuit despite the application of the high voltage pulse at the time of starting. It is an object of the present invention to provide a discharge lamp lighting device that can be prevented and can bring about a proper start and a long life of the device. Further, another object of the present invention is to realize a long-life image display device with few failures by using a discharge lamp lighting device capable of proper starting and long life of the discharge lamp and a discharge lamp lighted by this device. That is.

[0006]

Therefore, in the present invention, an AC generating circuit for generating a sine wave voltage for AC lighting a discharge lamp, and a sine wave voltage generated by the AC generating circuit At the time of starting the discharge lamp, a first pulse that causes dielectric breakdown in the discharge lamp and a second pulse for arc transfer are generated, and the first pulse and the second pulse are converted into the sine wave voltage. A discharge lamp lighting device was configured by including a pulse output circuit to be superimposed.

Further, according to the present invention, an AC generating circuit for generating a sine wave voltage for AC lighting the discharge lamp, and a sine wave voltage generated by the AC generating circuit are synchronized with each other at the time of starting the discharge lamp. A pulse output circuit for generating a first pulse that causes dielectric breakdown in the discharge lamp and a second pulse for arc transfer, and for superimposing the first and second pulses on the sine wave voltage; A discharge lamp lighting device comprising:
A discharge lamp lit by the discharge lamp lighting device, and an image data output device for outputting image data of an image to be displayed,
An image display device is configured by including an image forming unit that receives the irradiation light of the discharge lamp and the image data output by the image data output device and forms an image according to the image data.

Further, according to the present invention, the pulse output circuit continuously detects the peak of the sine wave voltage and the first pulse and the second pulse at the peak of the voltage detected by the peak detector. And a pulse generation section for outputting to.

Further, in the present invention, the first pulse has a polarity opposite to that of the sine wave voltage, the pulse width of the first pulse is narrower than the pulse width of the second pulse, and the first pulse is The peak value of the pulse is larger than the peak value of the second pulse.

[0010]

According to the discharge lamp lighting device having the above structure, the discharge lamp is driven by the sine wave, and at the time of starting the discharge lamp, the first pulse is synchronized with the sine wave voltage generated from the AC generating circuit. Then, a second pulse is generated, and the first and second pulses are superimposed on the sine wave voltage and reach the discharge lamp. The first pulse causes a breakdown in the discharge lamp, the second pulse causes an arc transfer, and the arc transfer occurs properly. Further, since the first and second pulses are applied at the peak of the sine wave voltage, it is possible to smoothly proceed to the lighting state after the arc transition. Also, since the first pulse for dielectric breakdown has a polarity opposite to that of the sine wave voltage, electrons do not collide with only one of the electrodes, and the life of the discharge lamp can be extended. Is.

According to the image display device using the discharge lamp lighting device having the above structure, since the discharge lamp has a long life, the life of the image display device can be extended accordingly.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In each of the drawings, the same constituents are designated by the same reference numerals, and overlapping description will be omitted. FIG. 1 shows a configuration diagram of a discharge lamp lighting device according to an embodiment of the present invention. In this embodiment, a DC voltage supplied from a DC power supply unit 2 is applied to a discharge lamp 1 such as a metal halide lamp.
A configuration is adopted in which the voltage is converted into an AC voltage via the AC conversion circuit 3 and given. A starting circuit 4 for applying a high-voltage pulse to the discharge lamp 1 at the time of starting is connected between the AC conversion circuit 3 and the discharge lamp 1.

The DC power supply unit 2 includes an AC power supply 21, a rectifier circuit 22 that rectifies the AC of the AC power supply 21, a chopper circuit 23 that controls the power of the rectified output, and a chopper circuit 2.
A smoothing circuit 24 for smoothing the output of No. 3 is included to obtain direct current. This direct current is converted into a low frequency alternating current (400 Hz to 500 Hz) by the alternating current conversion circuit 3 and applied to the discharge lamp 1. The alternating-current conversion circuit 3 includes a switching element, and the low-frequency alternating current is created by turning on / off the switching element by the conversion control circuit 5.

Here, the AC conversion circuit 3 is composed of a full-bridge inverter circuit, and the control signal of the timing shown in FIG. 2A is output from the conversion control circuit 5 for the on / off control of the switching element thereof. Then, the starting control circuit 6 takes in the control signal (a), creates a control signal (control signal in which only the switching period is at H level) (b) synchronized with this switching period, and outputs it to the starting circuit 4. The starting circuit 4 applies the high-voltage pulse to the discharge lamp 1 only during the ON period when the control signal (b) is at the H level. Here, in the case of a full-bridge inverter, the ON period refers to a period in which one of the two pairs of switching elements is in the ON state.

FIG. 3 shows an embodiment of the starting circuit 4. In this starting circuit 4, the capacitor C1 is charged by the DC voltage of the DC power supply unit 2 via the resistor r, and when the potential between both ends of the capacitor C1 rises to a predetermined level, the SCR turns on and the secondary current is supplied via the transformer TR1. A voltage is generated in a pulse shape on the side. The capacitor C2 is charged through the diode D1 by the current generated by the voltage generated on the secondary side of the transformer TR1, and the voltage across the capacitor C2 becomes GA.
When the discharge potential of P is reached, the voltage is boosted by utilizing the current flowing to the transformer TR2 side, and a high voltage (pulse) is generated on the secondary side of the transformer TR2 and applied to the discharge lamp 1. A switch SW for applying a high-voltage pulse to the discharge lamp 1 is provided on the primary side of the transformer TR2 in synchronization with the switching of the switching element of the AC conversion circuit 3 during the period from the switching period to the next switching period. Is provided. This switch SW has a control signal (b) of FIG.
It constitutes an opening / closing means that is closed only at the level and is opened at other times. The starting circuit 4 is provided with a starting switch (not shown) that is turned on so as to operate only at the time of starting.

FIG. 4 shows the configuration of a full bridge inverter circuit according to an embodiment of the AC conversion circuit 3. This circuit receives a DC voltage from the DC power supply unit 2 and applies it to a circuit in which FETs Q1, Q2, and FETs Q3, Q4, which are switching elements, are connected in series. Terminals A to F are drawn out from the connection points of the gates of the respective FETs and the respective FETs of the circuits connected in series. At the timing shown in FIG. 2, the conversion control circuit 5 gives a control signal to these terminals A to F so that the paired FETs Q1 and Q4 and the FETs Q2 and Q3 are alternately turned on and off. The circuits in which two Zener diodes ZD1 and ZD2 are connected in series are FETQ1, Q2, FETQ3, Q
Capacitors C3 to C6, which are provided in order to maintain a predetermined potential between both ends of the circuits connected in series, connect capacitors FETs C3 to C6 between the source and drain of each FET so that the FET can be rapidly turned on. It is provided to assist. Since this AC conversion circuit 3 is a full bridge type, the timing at which any pair of switching elements is turned on is as shown in FIG. 2A, and the switch SW of FIG. Is closed. Conversely speaking, during the ON period excluding the switching period, the switch S of FIG.
W is closed.

FIG. 5 shows another embodiment of the present invention. In this embodiment, an AC generation circuit 51 that generates a sine wave (for example, 200 V, 60 Hz) for the discharge lamp 1.
The sine wave voltage which is the output of is given and AC lighting is performed. On the other hand, when the discharge lamp 1 is started, a pulse is sent from the pulse output circuit 56, superposed on the sine wave voltage and applied to the discharge lamp 1.

The pulse output circuit 56 uses a sine wave voltage (a)
Is taken in, and the peak detecting section 52 detects the peak. The peak detection here will be described in detail with reference to FIG. Assuming that the sine wave voltage taken in is as shown in FIG. 6A, the peak detection unit 52 performs full-wave rectification to obtain a signal as shown in FIG. 6B. Since the zero-to-peak of the sine wave voltage is already known, if this is set to V _0P as shown in FIG. 6B, the threshold voltage value V _th slightly lower by δ is provided, and comparing the signal level of the wave rectification and the threshold voltage value V _th, the signal level of the full-wave rectification at the time exceeds the threshold voltage value V _th, and outputs a trigger pulse (c). This trigger pulse (c) is given to the pulse generator 53, where the first pulse
Pulse (d) and a second pulse (e) are generated.
First, the first pulse (d) is a pulse generated on the opposite polarity side to the sine wave voltage when the trigger pulse (c) rises, and for example, the sine wave voltage is 240 to 250 V (zero-to-peak). At that time, it is about 15 KV (same as above). On the other hand, the second pulse (e) is the trigger pulse (c).
A pulse generated on the same polarity side as the sine wave voltage at the time of the falling edge of the first pulse (d) after the rising edge of
Sine wave voltage is 240-250V (zero-to-peak)
At that time, it is about 1 KV (same as above). The pulse width of the first pulse (d) is narrower than the pulse width of the second pulse (e), and the ratio thereof is about 1: 100. Such a first pulse (d) and a second pulse (e) are continuously output from the pulse output circuit 53, and the sine wave voltage (a)
And the voltage becomes as shown in FIG. 6 (f). The first pulse (d) and the second pulse (e) are generated within this period by detecting, for example, a timer (not shown) at the start of a predetermined period after the power is turned on.

By applying the voltage shown in FIG. 6 (f) to the discharge lamp 1 at the time of starting, discharge breakdown and arc transfer in the discharge lamp 1 are performed as follows. That is, the high voltage is applied to the discharge lamp 1 by the first pulse d, so that the discharge inside the discharge lamp 1 is destroyed, but since the pulse width is narrow, the transition from the glow discharge state to the arc discharge does not occur. . On the other hand, the second pulse e following the first pulse d is made to have a pulse width that is sufficient for transition to arc discharge. Then, here, arc transfer occurs following the discharge breakdown. Since the pulse of the first pulse d is generated on the opposite polarity side to the sine wave voltage and the pulse of the second pulse e is generated on the same polarity side as the sine wave voltage, the potential added with the peak value of both pulses is generated. It is applied between both electrodes of the discharge lamp to realize accurate discharge breakdown. In addition, since the pulse of the second pulse e is generated on the same polarity side as the sine wave voltage, a quick transition from the arc transition to the lighting state by the sine wave voltage is achieved. Furthermore, since the first pulses d are alternately generated with different polarities, the electrodes with which the electrons collide are not biased, and the life of the discharge lamp is extended.

FIG. 7 shows another embodiment of the present invention. In this embodiment, a delay circuit 55 is provided between the AC generation circuit 51 and the discharge lamp 1 to delay the sine wave. On the other hand, in the pulse output circuit 56A, the peak detector 5
4 differs from the peak detector 52 of FIG. 5 in that it actually detects a peak and generates a trigger pulse (c) when the peak is detected. Other configurations are the same as those in FIG. According to this configuration,
Since the sine wave is delayed, after detecting the peak,
Even if a pulse is generated, the pulse can be superimposed near the peak of the sine wave. That is, in the embodiment of FIG. 5, the trigger pulse (c) is generated earlier than the actual peak and the pulse generation period is secured, whereas in this embodiment, the sine wave is delayed to reduce the pulse generation period. Have secured. Also in this embodiment, the same effect as that of the embodiment of FIG. 5 can be expected.

FIG. 8 shows the above-mentioned FIG. 1, FIG. 5 or FIG.
A block diagram of a liquid crystal video projector as an example of an image display device using the discharge lamp lighting device of FIG. This liquid crystal video projector is a type that projects an image on a screen 80. The liquid crystal video projector includes a discharge lamp lighting device 50, an image data output device 60, and an image forming liquid crystal system (image forming unit) 70. The discharge lamp lighting device 50 has the configuration shown in FIG. 1, and in synchronization with the switching of the switching element of the AC conversion circuit 3, a high-voltage pulse is applied during the ON period of the switching element. Alternatively, the discharge lamp lighting device 50 has the configuration shown in FIG.
It has the configuration shown in FIG. 7, and AC lighting is performed. The light emitted from the discharge lamp 1 reaches the image forming liquid crystal system 70.
The image data output device 60 gives image data (video signal) of the NTSC system to the image forming liquid crystal system 70, for example. The image forming liquid crystal system 70 includes a liquid crystal device. The image forming liquid crystal system 70 receives the irradiation light of the discharge lamp 1 and the image data output from the image data output device 60, and forms an image according to the image data on the liquid crystal device. This image is projected on the screen 80.

According to the liquid crystal video projector of this embodiment, the discharge lamp lighting device 50 shown in FIG.
Alternatively, since the device having the configuration of FIG. 7 is used, it is expected that the AC conversion circuit 3 is not destroyed and that proper starting and a longer life of the device are achieved.

The liquid crystal video projector of the embodiment is of a type that projects an image on a screen, but in another embodiment, there is a type of viewing an image displayed on the liquid crystal itself.
Further, a liquid crystal video projector is disclosed in JP-A-61-15.
Although there are various types as disclosed in Japanese Patent No. 0487, the discharge lighting device of the present invention can be applied to liquid crystal video projectors of these types and other types, as well as image display devices such as projection devices and over head projectors. Applied to.

[0024]

As described above, according to the present invention, when the discharge lamp is started, the first pulse and the second pulse are generated in synchronization with the sine wave voltage generated from the AC generating circuit. The first and second pulses are superimposed on the sine wave voltage and reach the discharge lamp, so that the first pulse causes dielectric breakdown in the discharge lamp and the second pulse causes arc transition. And cause arc transfer appropriately. Also,
Since the first and second pulses are applied at the peak of the sine wave voltage, it is possible to smoothly proceed to the lighting state after the arc transition. Also, since the first pulse for dielectric breakdown has a polarity opposite to that of the sine wave voltage, electrons do not collide with only one of the electrodes, and the life of the discharge lamp can be extended. Is.

Further, according to the present invention, there is provided an image display device provided with a discharge lamp lighting device which is capable of performing a proper operation at the time of starting the discharge lamp and extending the life of the discharge lamp. This has the effect of ensuring stability and prolonging the service life.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the discharge lamp lighting device according to the embodiment of the invention.

FIG. 3 is a configuration diagram of a main part of a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a main part of a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 5 is a configuration diagram of a discharge lamp lighting device according to another embodiment of the present invention.

6 is a waveform chart showing the operation of the main parts of the discharge lamp lighting device according to the embodiment of FIG.

FIG. 7 is a configuration diagram of a discharge lamp lighting device according to another embodiment of the present invention.

FIG. 8 is a configuration diagram of a liquid crystal video projector according to an embodiment of the present invention.

FIG. 9 is a waveform diagram for explaining the operation of the conventional discharge lamp lighting device.

FIG. 10 is a waveform diagram for explaining the operation of the conventional discharge lamp lighting device.

[Explanation of symbols]

1 Discharge Lamp 2 DC Power Supply Section 3 AC Conversion Circuit 4 Starting Circuit 5 Conversion Control Circuit 6 Starting Control Circuit 21 AC Power Supply 22 Rectifier Circuit 23 Chopper Circuit 24 Smoothing Circuit 50 Discharge Lamp Lighting Device 51 AC Generation Circuit 52, 54 Peak Detecting Section 53 Pulse generator 55 Delay circuit 56, 56A
Pulse output circuit 60 Image data output device 70 Image forming liquid crystal system (image forming section) 80 Screen

Claims (5)

[Claims] 1. An alternating current generating circuit for generating a sine wave voltage for alternating-currently lighting a discharge lamp, and a sine wave voltage generated from the alternating current generating circuit, in synchronization with the sine wave voltage, when the discharge lamp is started, the discharge lamp. A pulse output circuit for generating a first pulse that causes dielectric breakdown and a second pulse for arc transfer, and superimposing the first pulse and the second pulse on the sine wave voltage. A discharge lamp lighting device characterized by the above. 2. The pulse output circuit detects a peak of a sine wave voltage, and a peak detecting section, and continuously outputs a first pulse and a second pulse at the peak of the voltage detected by the peak detecting section. The discharge lamp lighting device according to claim 1, further comprising a pulse generator. 3. The first pulse has a polarity opposite to the polarity of the sinusoidal voltage, the pulse width of the first pulse is narrower than the pulse width of the second pulse, and the pulse width of the first pulse is The discharge lamp lighting device according to claim 1 or 2, wherein the high value is higher than the peak value of the second pulse. 4. An alternating current generating circuit for generating a sine wave voltage for alternating-currently lighting a discharge lamp, and a sine wave voltage generated by the alternating current generating circuit, in synchronization with the sine wave voltage, at the time of starting the discharge lamp.
A first pulse that causes a dielectric breakdown in the discharge lamp;
A discharge lamp lighting device comprising: a pulse output circuit for generating a second pulse for arc transfer and superposing the first and second pulses on the sine wave voltage; and lighting by the discharge lamp lighting device. A discharge lamp, an image data output device for outputting image data of an image to be displayed, an irradiation light of the discharge lamp and an image data output by the image data output device, and an image corresponding to the image data. An image display device, comprising: 5. A DC power supply unit for supplying DC power and a full bridge inverter circuit configured by switching a voltage supplied from the DC power supply unit, and AC is applied to the discharge lamp via the full bridge inverter circuit. An AC conversion circuit, a starting circuit that gives a high-voltage pulse to the discharge lamp at the time of starting, and a switching circuit of two sets of switching elements of the full-bridge inverter circuit in synchronization with switching of the two sets of switching elements during an ON period. A discharge lamp lighting device, comprising: a start control circuit that controls the high voltage pulse output from the start circuit to be applied to the discharge lamp.