JP4127727B2 - Discharge lamp lighting device and image display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp lighting device and an image display device that reliably start a discharge lamp.
[0002]
[Prior art]
Conventionally, as this type of discharge lamp lighting device, for example, a configuration shown in FIG. 5 is known.
[0003]
FIG. 5 is a circuit diagram showing a conventional discharge lamp lighting device. In the discharge lamp lighting device shown in FIG. 5 , a terminal 1 is connected to a commercial AC power source (not shown) via a full-wave rectifier circuit and a smoothing circuit. A smoothing capacitor C1 for smoothing the input voltage is connected between the terminals 1. Further, the step-down chopper circuit 2 is connected to the smoothing capacitor C1 through a resistor R1 for current detection. The step-down chopper circuit 2 is connected to the smoothing capacitor C1 through the resistor R1 in series with a field effect transistor Q1 and a diode D1. Is connected. Further, a series circuit of an inductor L1, a resistor R2, and a smoothing capacitor C2 is connected in parallel to the diode D1.
[0004]
A series circuit of a resistor R3 and a timer circuit 3 is connected to the diode D1 via an inductor L1. In the timer circuit 3, a light emitting diode LED1 and a charging capacitor C3 are connected in series, a resistor R4 is connected in parallel to the charging capacitor C3, and a light emitting diode is connected in parallel to the series circuit of the light emitting diode LED1 and the resistor R4. A series circuit of LED2 and Zener diode ZD1 is connected.
[0005]
Further, the positive side of the terminal 1 is connected to the control circuit 4 via the resistor R5 to detect the output voltage, and both ends of the resistor R1 are also connected to the control circuit 4 to detect the drain current of the field effect transistor Q1, The gate of the effect transistor Q1 is also connected to the control circuit 4, the gate voltage is controlled according to the control circuit 4, the inductor L2 is magnetically connected to the inductor L1, the inductor L2 is connected to the control circuit 4, and the resistor R2 Are also connected to the control circuit 4 to detect the output current.
[0006]
An igniter 5 as a pulse generator is connected to the step-down chopper circuit 2 through a parallel circuit of a current limiting inductor L3 and a capacitor C4. The output side of the igniter 5 is a short arc type via a high voltage connector 6. A metal halide lamp MHL as a discharge lamp is connected. In the igniter 5, an inductor L4 is connected between the high-voltage connector 6 and the resistor R2, and the midpoint of the inductor L4 is connected to one end of the inductor L5 via a capacitor C5 and a diode D2, and the other end of the inductor L5 is Connected to resistor R2. In addition, a time constant circuit of a resistor R6 and a capacitor C6 is connected in parallel to the capacitor C2, and the connection point of the resistor R6 and the capacitor C6 is connected to the midpoint of the inductor L5 via the Sidac Q2. Thus, the discharge lamp lighting device 7 is formed.
[0007]
When the power is turned on, the control circuit 4 applies a gate voltage to the field effect transistor Q1 to step down and applies a voltage to the igniter 5. In addition, when the time set by the time constant circuit of the resistor R6 and the capacitor C6 has elapsed and the capacitor C6 is charged to a voltage equal to or higher than a predetermined voltage, the Sidac Q2 is turned on, and a pulse is applied to the inductor L5 and the inductor L4. Thus, a high voltage pulse is input to the metal halide lamp MHL several times according to the charge / discharge of the capacitor C6, and the metal halide lamp MHL is turned on.
[0008]
In addition, the charging capacitor C3 of the timer circuit 3 is charged in the same manner. While the charging capacitor C3 is being charged, the light emitting diode LED1 is on, and the control circuit 4 controls the field effect transistor Q1 so that it is suitable for starting. To do. In this state, when the metal halide lamp MHL does not start and the voltage of the charging capacitor C3 further rises, the Zener diode ZD1 is turned on, the charging capacitor C3 is discharged, the light emitting diode LED2 is lit, and the electric field generated by the control circuit 4 The oscillation of the effect transistor Q1 is stopped and turned off.
[0009]
When the metal halide lamp MHL is turned on, the voltage of the capacitor C6 decreases, so that the igniter 5 does not generate a pulse. Further, since the charging capacitor C3 is also charged, the light emitting diode LED1 is turned off, and the voltage of the capacitor C2 is also lowered, so that the Zener diode ZD1 is also turned off and the light emitting diode LED2 does not emit light. Thereby, the control circuit 4 detects the output voltage by the resistor R5, detects the output current by detecting the output current by the resistor R2, and also detects the drain current of the field effect transistor Q1 by the resistor R1. The field effect transistor Q1 is controlled.
[0010]
[Problems to be solved by the invention]
However, in recent years, since the discharge lamp lighting device has been downsized and the inductor L4 of the igniter 5 has also been downsized, the inductance is small, and the inrush current that flows when starting the metal halide lamp MHL cannot be sufficiently suppressed and smoothed.
[0011]
Therefore, as shown in FIGS. 5 and 6 , after the metal halide lamp MHL is started, the output voltage and the output current are zero-crossed, and the metal halide lamp MHL may be blinked at the time of start or may be extinguished.
[0012]
In addition, the no-load voltage is often extremely higher than that in a stable state in consideration of restartability, and a current exceeding the glow discharge potential increased by heating can be applied, so that the current can be transferred to arc discharge. On the other hand, the inrush current waveform at the time of arc transition becomes a smooth waveform without vibration due to the resistance of the metal halide lamp MHL which is heated and increased at the time of restart, and the occurrence of extinction due to zero crossing is small. However, when the metal halide lamp MHL is sufficiently cooled, the resistance at the time of arc transition is very small and the glow discharge is also low, so the inrush current oscillation is very large and the inductor L4 of the igniter 5 is small. There is a risk that the inrush current will be zero-crossed and the engine cannot be started.
[0013]
Furthermore, in recent years, metal halide lamps MHL, which emphasized rising characteristics such as metal halide lamps MHL for automobile headlights, are filled with xenon gas at a high pressure. When the discharge part absorbs a lot of energy due to the inrush current at the time, there is a problem that the formation of heating of the electron supply bright spot on the cathode of the discharge lamp becomes insufficient, and the extinction may occur.
[0014]
The present invention has been made in view of the above problems, and an object thereof is to provide a discharge lamp lighting device and an image display device that can reliably start a discharge lamp even when an inrush current occurs.
[0015]
[Means for Solving the Problems]
A discharge lamp lighting device according to claim 1 is a smoothing capacitor for smoothing a voltage from an input power source; and a pulse generating device connected to the output side of the smoothing capacitor to generate a pulse when starting the discharge lamp to start the discharge lamp. When; charging capacitor can be charged at a lower than stable potential is maintained immediately after the start of the discharge electric lamp voltage and; rectifying elements connected in a direction to block a voltage applied to the connected discharge lamp in series with the charging capacitor If; comprising a, when said voltage discharge lamp inrush current at the start of the is applied to the discharge lamp occurs is decreased, the voltage charged in the charging capacitor, the discharge lamp through said rectifying element intended to be applied to the voltage rush current is applied to the discharge lamp occurs when the discharge lamp is started is lowered, maintained immediately after the start of the discharge lamp A voltage to the discharge lamp through a rectifying element from charging capacitor charged at a lower voltage than a stable potential is applied to, since the voltage applied to the discharge lamp does not decrease more than necessary, and to ensure arc transition The discharge lamp starts without fail, etc.
[0016]
The image display apparatus according to claim 2, wherein the discharge lamp lighting device and as claimed in claim 1 wherein the discharge lamp; the object image the light is irradiated is formed of lit discharge lamp The discharge lamp lighting device It has an image display means for irradiating and projecting an image on an object, and exhibits its effect.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an image display device according to an embodiment of the present invention will be described with reference to the drawings. Incidentally, parts corresponding to the conventional example shown in FIG. 5, are denoted by the same reference numerals.
[0018]
FIG. 2 is a block diagram showing an image display device. As shown in FIG. 2, for example, a liquid crystal display device 11 such as a liquid crystal video projector, the liquid crystal display device 11 is connected to a discharge lamp lighting device 7 with a short arc as a discharge lamp. A 250 W metal halide lamp MHL is connected. Further, for example, the image data output device 12 of the NTSC system, the image forming liquid crystal system 13 as an image display means for forming an output image by the image data output device 12 is connected, the image forming liquid crystal system 13 metal halide lamp An image is projected on the screen 14 based on the irradiation light from the MHL.
[0019]
FIG. 1 is a block diagram showing a discharge lamp lighting device. As shown in FIG. 1, for example, a step-down chopper as a regulator circuit is connected to an input power source 31 in which a voltage doubler rectified power source or the like is connected to a commercial AC power source of AC 100V. The circuit 2 is connected, and the step-down chopper circuit 2 has a field effect transistor Q1 as a switching element and a diode D1 connected in series, and an inductor L1 and a smoothing capacitor C2 are connected in parallel to the diode D1. A control circuit 4 for control is connected to the gate of Q1.
[0020]
Further, an igniter 5 as a pulse generator for generating a high voltage pulse is connected to the smoothing capacitor C2, and a metal halide lamp MHL is connected to the igniter 5.
[0021]
Further, a diode D11 as a rectifying element and a charging capacitor C3 are connected to the output side of the smoothing capacitor C2, and an auxiliary power source 32 that also serves as a driving power source for the control circuit 4, for example, is connected to the charging capacitor C3. Yes.
[0022]
Next, the operation of the embodiment shown in FIG. 1 will be described.
[0023]
First, the output voltage of the input power supply 31 is switched by the control circuit 4 to switch the field effect transistor Q1 and stepped down by the step-down chopper circuit 2, and a voltage is applied to the igniter 5, and the igniter 5 generates a high voltage pulse to generate a metal halide lamp MHL. A high pressure pulse is applied to the metal halide lamp MHL.
[0024]
In addition, when the metal halide lamp MHL is started in this way, if the inrush current occurs and the voltage applied to the metal halide lamp MHL decreases, the charging capacitor C3 is discharged through the diode D11, and the voltage of the metal halide lamp MHL decreases. Therefore, the metal halide lamp MHL is surely started so that it does not go out. Normally, the diode D11 is formed so that no current flows directly to the charging capacitor C3 from the input power supply 31 side.
[0025]
Next, a specific embodiment will be described with reference to FIG. In the embodiment shown in FIG. 3, the auxiliary power source 32 is not used unlike the embodiment shown in FIG.
[0026]
FIG. 3 is a circuit diagram showing a discharge lamp lighting device. In the discharge lamp lighting device shown in FIG. 3, a terminal 1 is connected to a commercial AC power source (not shown) via a full-wave rectifier circuit and a smoothing circuit. A smoothing capacitor C1 that smoothes the input voltage is connected between them. Further, the step-down chopper circuit 2 is connected to the smoothing capacitor C1 through a resistor R1 for current detection. The step-down chopper circuit 2 is connected to the smoothing capacitor C1 through the resistor R1 in series with a field effect transistor Q1 and a diode D1. Is connected. Further, a series circuit of an inductor L1, a resistor R2, and a smoothing capacitor C2 of about 1 μF to 3 μF is connected in parallel to the diode D1.
[0027]
A series circuit of a resistor R3 and a timer circuit 3 is connected to the diode D1 via an inductor L1. In this timer circuit 3, a light emitting diode LED1 and a charging capacitor C3 of about 1000 μF are connected in series. From the connection point of the charging capacitor C3 and the light emitting diode LED1, a diode for preventing a reverse current having a polarity that blocks current from the terminal 1 is used. D11 is connected, a resistor R4 is connected in parallel to the charging capacitor C3, and a series circuit of the light emitting diode LED2 and the Zener diode ZD1 is connected in parallel to the series circuit of the light emitting diode LED1 and the resistor R4.
[0028]
Further, the positive side of the terminal 1 is connected to the control circuit 4 via the resistor R5 to detect the output voltage, and both ends of the resistor R1 are also connected to the control circuit 4 to detect the drain current of the field effect transistor Q1, The gate of the effect transistor Q1 is also connected to the control circuit 4, the gate voltage is controlled according to the control circuit 4, the inductor L2 is magnetically connected to the inductor L1, the inductor L2 is connected to the control circuit 4, and the resistor R2 Are also connected to the control circuit 4 to detect the output current.
[0029]
An igniter 5 is connected to the step-down chopper circuit 2, and a short arc type metal halide lamp MHL is connected to the output side of the igniter 5 via a high-pressure connector 6. In the igniter 5, an inductor L4 is connected between the high-voltage connector 6 and the resistor R2, and the midpoint of the inductor L4 is connected to one end of the inductor L5 via a capacitor C5 and a diode D2, and the other end of the inductor L5 is Connected to resistor R2. In addition, a time constant circuit of a resistor R6 and a capacitor C6 is connected in parallel to the capacitor C2, and the connection point of the resistor R6 and the capacitor C6 is connected to the midpoint of the inductor L5 via the Sidac Q2. Thus, the discharge lamp lighting device 7 is formed.
[0030]
Next, the operation of the embodiment shown in FIG. 3 will be described.
[0031]
First, when the power is turned on, the control circuit 4 applies a gate voltage to the field effect transistor Q1 to step down and applies a voltage to the igniter 5. In addition, the charging capacitor C3 of the timer circuit 3 is charged in the same manner. While the charging capacitor C3 is being charged, the light emitting diode LED1 is on, and the control circuit 4 controls the field effect transistor Q1 so that it is suitable for starting. To do.
[0032]
Furthermore, when the time set by the time constant circuit of the resistor R6 and the capacitor C6 elapses and the capacitor C6 is charged to a voltage equal to or higher than a predetermined voltage, the Sidac Q2 is turned on, and a pulse is applied to the inductor L5 and the inductor L4. Thus, a high voltage pulse is input to the metal halide lamp MHL several times according to the charge / discharge of the capacitor C6, and the metal halide lamp MHL is turned on. At this time, when an inrush current flows and the lamp voltage decreases and approaches zero crossing as shown in FIG. 4A, the smoothing capacitor C2 is passed through the diode D11 as shown in FIGS. 4B and 4D. The charge of the charging capacitor C3 connected in parallel is discharged, and a voltage is applied to the metal halide lamp MHL to prevent the voltage of the metal halide lamp MHL from decreasing. As shown in FIG. Keeps the arc transition continuous and prevents the discharge lamp from going out.
[0033]
Although the timer circuit 3 is reset when the charge of the charging capacitor C3 is discharged, there is no problem because the timer circuit 3 stops operating when the metal halide lamp MHL is originally turned on. When the lamp voltage does not decrease, the charge of the charging capacitor C3 is not discharged through the diode D11, but is consumed by the resistor R4 and reset. In addition, when the metal halide lamp MHL is unable to break down or arc, there is no problem because the timer circuit 3 operates normally because no current flows.
[0034]
On the other hand, about two seconds without a metal halide lamp MHL is started in a state in which charges the charging capacitor C3, when the voltage of the charging capacitor C3 is increased, the light emitting diode LED2 with the charge capacitor C3 Zener diode ZD1 is turned on to discharge Lights up, stops oscillation of the field effect transistor Q1 by the control circuit 4, and turns off.
[0035]
When the metal halide lamp MHL is turned on, the voltage of the capacitor C6 decreases, so that the igniter 5 does not generate a pulse. In addition, when the metal halide lamp MHL is turned on, the charging of the charging capacitor C3 is completed and discharged, so the light emitting diode LED1 is turned off, and the voltage of the capacitor C2 is also lowered, so the zener diode ZD1 is also turned off and the light emitting diode LED2 also emits light. do not do. Thereby, the control circuit 4 detects the output voltage by the resistor R5, detects the output current by detecting the output current by the resistor R2, and also detects the drain current of the field effect transistor Q1 by the resistor R1. The field effect transistor Q1 is controlled.
[0036]
Since the maximum voltage charged to the charging capacitor C3 is about 10V, it is sufficient to use a capacitor with a withstand voltage of 16V. Therefore, the metal halide lamp MHL has a stable lamp voltage of 50V and a minimum voltage at start-up. The voltage is about 15 V except when the inrush current is oscillating at the time of arc transition. In addition, while the no-load voltage is about 300V, in order to prevent the inrush current at the time of arc transition from zero-crossing, about 2V to 3V lower than the stable potential maintained for a few seconds immediately after the metal halide lamp MHL is started. It is sufficient that the charging capacitor C3 is charged with a voltage. Even in the worst case, the metal halide lamp MHL can be turned on without any problem if it is charged with about 5V. On the other hand, when the voltage of the charging capacitor C3 becomes 10V, it is determined that starting is impossible, the light emitting diode LED2 operates, the control circuit 4 stops the operation of the field effect transistor Q1, and the output of the step-down chopper circuit 2 stops. Therefore, the charging capacitor C3 is charged with a maximum voltage of 10V.
[0037]
In the above embodiment, the charging capacitor C3 is the same as that of the timer circuit 3, but a separate power source such as the auxiliary power source 32 may be used as in the case shown in FIG. A voltage of about 15V used for the control circuit 4 or the like may be directly used without using the voltage dividing of the resistor R4. In this case, since the metal halide lamp MHL can be sufficiently charged before being turned on, it is more reliable. Starting characteristics can be obtained. In this case, the charging capacitor C3 may be charged immediately before the metal halide lamp MHL is turned on or immediately after the metal halide lamp MHL is activated .
[0038]
【The invention's effect】
According to the discharge lamp lighting device of the first aspect, when an inrush current occurs when the discharge lamp starts and the voltage applied to the discharge lamp decreases, it is lower than the stable potential maintained immediately after the discharge lamp is started. Voltage is applied to the discharge lamp from the charging capacitor charged with voltage via the rectifier, and the voltage applied to the discharge lamp does not become lower than necessary, so that the arc transition is ensured and the discharge lamp disappears. It can be started reliably.
[0039]
According to the image display device of claim 2 , the discharge lamp is turned on, and the object is irradiated with the image formed by irradiating the light of the discharge lamp lit by the discharge lamp lighting device according to claim 1 . Since the image display means for projecting an image is provided, the effect can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a discharge lamp lighting device according to the present invention.
FIG. 2 is a block diagram showing the above-described image liquid crystal display device.
FIG. 3 is a circuit diagram showing a discharge lamp lighting device according to another embodiment.
FIG. 4 is a waveform diagram showing lamp voltage, current, and voltage and current of a charging capacitor C3.
FIG. 5 is a circuit diagram showing a conventional discharge lamp lighting device.
FIG. 6 is a waveform diagram showing lamp voltage and current.
[Explanation of symbols]
Igniter as a 5- pulse generator 7 Discharge lamp lighting device
13 Image forming liquid crystal system as image display means
31 input supply
C2 smoothing capacitor
C3 charging capacitor
D11 Diode as rectifier
Metal halide lamp as a MHL discharge lamp

Claims (2)

A smoothing capacitor that smoothes the voltage from the input power supply;
A pulse generator connected to the output side of the smoothing capacitor to generate a pulse when starting the discharge lamp to start the discharge lamp;
A charging capacitor which can be charged at lower than stable potential is maintained immediately after the start of the discharge electric lamp voltage;
A rectifying element connected in series with the charging capacitor and connected in a direction to block the voltage applied to the discharge lamp;
When an inrush current occurs at the start of the discharge lamp and the voltage applied to the discharge lamp decreases, the voltage charged in the charging capacitor is applied to the discharge lamp via the rectifier element. A discharge lamp lighting device. A discharge lamp lighting device according to claim 1 for lighting a discharge lamp;
Image display means for projecting an image onto an object by irradiating the object with an image formed by irradiation with light from a discharge lamp lit by the discharge lamp lighting device;
An image display device comprising:

Images