JPH06231896A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To enable illuminance to be controlled over a wide range, and stable lighting state to be provided by generating a pulse having such width as corresponding to the preset illuminance and power on the basis of an electrical signal from an illuminance detecting device and a power detecting device, and then feeding back the pulse to a DC/AC converter. CONSTITUTION:An illuminance detecting device 7 converts the light of a discharge lamp into an illuminance signal S6 through a photoelectric conversion circuit 7b via an optical fiber 7a. A power detecting device 8 inputs signal from a power supply device 5 to a current and voltage detecting circuit 8b, and outputs AC/voltage signals S7 and S8. Feedback signal polarity selector circuits 8c and 8d reverse the negative polarity of the signals S7 and S8, and feed DC/voltage signals S3 and S4 to a multiplier 9a2. In this case, when a signal S5 is larger than reference voltage V01 to set illuminance, the output V1 of an operational amplifier 9a1 becomes positive and forward in line with the output V2 of the multiplier 9a2. Thus, an operation signal A outputted from an operational amplifier 9a3 drops. As a result, the width of the output pulse of a pulse width modulation section 9b is reduced and the illuminance is thereby lowered.

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 having an illuminance control function, and more particularly to a discharge lamp lighting device having a wide control range and capable of performing stable lighting.

[0002]

2. Description of the Related Art A discharge lamp originally has a property that the brightness changes when the input power is changed. Therefore, it is necessary to control the input power to the discharge lamp so that the illuminance on the object to be irradiated is always kept constant. Various discharge lamp lighting devices have been proposed.

FIG. 6 shows an example of a conventional discharge lamp lighting device. This discharge lamp lighting device includes a power supply device 3 for boosting AC power supplied from a commercial AC power supply 1 and supplying it to a discharge lamp 2. The illuminance control device 4 is configured to detect the intensity of the light emitted by the discharge lamp 2 and control the output power of the power supply device 3.

The power supply device 3 is composed of a switch circuit 3a in which a thyristor is combined and a leakage transformer 3b connected to the output side of the switch circuit 3a. The switch circuit 3a outputs the AC power shown in FIG. Is configured to.

As shown in FIGS. 6 and 7, the illuminance control device 4 detects an intensity of light emitted from the discharge lamp 2 and converts it into a voltage signal, and an illuminance detection circuit 4a. 4a to the reference voltage V ₁
Power control circuit 4b that outputs an operation signal S ₂ in comparison with
And the operation signal S ₂ sent from the power control circuit 4b.
On the basis of the trigger pulse S ₃
And a trigger pulse S transmitted to the switch circuit 3a.
_When the timing of ₃ is changed as shown by arrows a and b in FIG. 8, the output power P of the power supply device 3 changes, so that the illuminance on the irradiation target (not shown) can be kept constant. it can. Reference numeral 4a ₁ in FIG. 7 is a diffusion plate for diffusing the received light L, 4a ₂ is a photoelectric conversion element, 4a
Reference numeral ₃ is an operational amplifier, and V is a reference voltage corresponding to the set illuminance applied to one input end of the operational amplifier 4b ₁ .

[0006]

However, the conventional discharge lamp lighting device has the following problems. (1) As described above, in order to control the intensity of the light emitted by the discharge lamp, it is necessary to control the input power to the discharge lamp, but the input power is 50 to 60% of the rated power of the discharge lamp. If it is reduced to, the off time T ₁ of the switch circuit 3a (see FIG. 8) becomes longer, causing a so-called flicker phenomenon,
It adversely affects the exposure. Note that T ₂ is the ON time of the switch circuit 3a.

(2) Conductor wire 4d near the discharge lamp (see FIG. 6)
Then, since the conducting wire 4e led from the power control circuit 4b is close to the discharge lamp 2, an electromagnetic sensitive phenomenon occurs, and as a result, noise occurs in the illuminance control device 4 and the operation of the illuminance control device 4 fails. Be certain.

In view of the above-mentioned problems, it is a first object of the present invention to provide a discharge lamp lighting device which has a wide illuminance control range and enables stable lighting, and further an illuminance control device. A second object is to provide a discharge lamp lighting device that does not generate noise therein.

[0009]

In order to solve the above problems, the present invention has the following two means. (1) A power supply that rectifies commercial AC power, converts it to high-frequency power via a pulse width control type DC-AC converter, rectifies the high-frequency power, and then converts it to rectangular-wave AC power via a polarity switching circuit. A device, an illuminance detection device that detects the brightness of a discharge lamp connected to this power supply device and outputs an electric signal, and a power detection device that detects the electrical state of the output side of the power supply device and outputs an electric signal. Generating a pulse having a pulse width corresponding to the set illuminance and the set power based on an electric signal sent from the illuminance detection device and the power detection device,
A discharge lamp lighting device, comprising: a power control device that feeds back the pulse to the DC-AC converter as a control signal. (2) The illuminance detection device includes an optical fiber whose tip is arranged in the vicinity of a discharge lamp, and a photoelectric conversion circuit which photoelectrically converts the light received through the optical fiber and outputs an electric signal. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is arranged apart from the discharge lamp.

[0010]

The waveform of the output power of the DC-AC converter changes remarkably in the time axis direction depending on the output pulse width sent from the power control device, but the waveform of the output power of the polarity switching circuit changes in the time axis direction. Does not occur. Therefore, there is no possibility of causing a so-called flicker phenomenon while the discharge lamp is lit,
Stable lighting is possible.

As a result of the above, the illuminance control range can be significantly expanded. That is, conventionally, the flicker phenomenon occurs when the input power is reduced to 50 to 60% of the rated power, but according to the present invention, the flicker phenomenon does not occur even when the input power is reduced to about 15%.

Since the light emitted from the discharge lamp is received by the tip of the optical fiber and transmitted through this optical fiber, there is no risk of noise in the illuminance control device.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show an embodiment of the present invention. The main parts of this embodiment are a power supply device 5 for converting commercial AC power into rectangular wave AC power, and light emitted from a discharge lamp 6. An illuminance detection device 7 which detects the intensity and further converts it into a voltage signal for output, and detects an AC current and an AC voltage on the output side of the power supply device 5 and outputs a DC current signal S ₃ and a DC voltage signal S ₄ . And a pulse width required to achieve the set illuminance and the set power by receiving the electric signals S ₅ , S ₃ , S ₄ sent from the illuminance detecting device 7 and the power detecting device 8 described above. It is configured by a power control device 9 and the like that outputs the pulse of.

The power supply device 5 is an AC power supply (not shown).
1, a DC-AC converter 5b, a transformer 5c, a rectifier 5d, a polarity switching circuit 5e, and the like connected to the output side of the rectifier 5a in the order shown in FIG.

As shown in FIG. 2, the DC / AC converter 5b includes four FETs (field effect transistors) Q ₁ ,
Q _1, the Q _2, Q ₂ disposed on each side of the bridge obtained by a switching circuit, each FETs Q _1, Q _1,
Q _2, Q ₂ of the control voltage signal e at appropriate time difference between the gate terminal G and source terminal S, e, e, is applied to e, 2 sets of FETQ arranged in diagonal direction in FIG. _1, Q
₁ and Q ₂ and Q ₂ are alternately turned on and off periodically to generate high frequency AC power of a magnitude corresponding to the ON operation time.

The polarity switching circuit 5e has the same structure as the DC-AC converter 5b, but operates so that the time during which the FET is off is extremely short in order to prevent flickering of the discharge lamp 6. The difference is that it is driven so that the cycle of on / off operation matches the specified frequency of the discharge lamp (normally 50 to 60 hertz). The on / off operation of this FET is, for example, a multivibrator. Is controlled by the switching signal generator 8a which constitutes a part of the power detection device 8 using

Therefore, when the power control is performed, the DC-
Although the waveform of the output power of the AC converter 5b changes greatly in the time axis direction, the waveform of the output power of the polarity switching circuit 5e does not change in the time axis direction.

The illuminance detecting device 7 includes an optical fiber 7a having a tip portion 7a 'disposed near the discharge lamp 6 via a support 6a, and a photoelectric conversion circuit 7b connected to a terminal portion 7a "of the optical fiber 7a. 4, a rod-shaped quartz glass 10 is attached to the tip end portion 7a 'of the optical fiber 7a in order to prevent the optical fiber from being burned by the discharge lamp 6. As shown in FIG. Reference numeral 11 is a coupler for connecting the optical fiber 7a and the quartz glass 10.

The photoelectric conversion circuit 7b, as shown in FIG.
A diffusing lens 7b ₁ for receiving and diffusing light emitted from the end portion 7a ″ of the optical fiber 7a, and a diffusing plate 7b.
₂ and a filter 7b that transmits only light of a predetermined wavelength
_3, a photoelectric conversion element 7b ₄ for converting the received light into a current signal S _6, is constituted by an amplifier 7b ₅ for converting the current signal S ₆ to the luminance signal S _5. Although not shown here, if the filter 7b ₃ is configured to be replaceable, it can be applied to discharge lamps of various wavelengths without replacing the entire photoelectric conversion circuit,
It is convenient.

The power detection device 8 includes a current / voltage detection circuit 8b, a feedback signal polarity switching circuit 8c for converting the alternating current signal S ₇ sent from the current / voltage detection circuit 8b into a direct current signal S ₃ , and a current. A feedback signal polarity switching circuit 8d for converting the AC voltage signal S ₈ sent from the voltage detection circuit 8b into a DC voltage signal S ₄ , and the feedback signal switching circuit 8c,
It is composed of a switching signal generator 8a for synchronizing the polarity switching operation of 8d and the polarity switching operation of the polarity switching circuit 5e, and the switching signal generator 8a operates at a predetermined frequency as already described. It is configured by using a multi-vibrator.

The feedback signal polarity switching circuit 8c, as shown in FIG. 3, an amplifier 8c ₁ for amplifying the alternating current signal S ₇ that the current voltage detection circuit 8b detects, this amplifier 8c ₁
Inverter 8c for receiving the output signal of and reversing its polarity
₂ and a switching element a which receives the switching signal sent from the switching signal generator 8a and alternately performs the opening / closing operation.
It is constituted by a switch circuit 8c ₃ having b, etc., one switching element a is connected to the output side of the amplifier 8c ₁ , and the other switching element b is connected to the output side of the inverter 8c ₂ . The feedback signal polarity switching circuit 8d has the same structure as the feedback signal polarity switching circuit 8c.

The feedback signal polarity switching circuit 8c operates as follows. That is, when the waveform of the input signal S ₇ to the feedback signal polarity switching circuit 8c has a positive polarity, the signal amplified by the amplifier 8c ₁ is the switching circuit 8c.
_It passes through one switching element a in the closed state of ₃ . When the waveform of the input signal S ₇ has a negative polarity, the signal amplified by the amplifier 8c ₁ passes through the inverter 8c ₂ and is converted into a positive polarity, and then the other switching element b becomes conductive. (Not shown),
The output terminal of the feedback signal polarity switching circuit 8c is reached. The feedback signal polarity switching circuit 8d operates similarly. In this manner, the DC current signal S ₃ and the DC voltage signal S ₄ sent from the feedback signal polarity switching circuits 8c and 8d are input to the power control device 9.

At this time, the switching signal generator 8a controls the polarity switching circuit 5e and the feedback signal polarity switching circuits 8c and 8d.
Since both of them are simultaneously switched in polarity, an AC signal can be smoothly converted into a DC signal regardless of whether the waveform is positive or negative.

The power control device 9 controls the signals S ₅ , S sent from the illuminance detection device 7 and the power detection device 8.
_3, the accept S _4, a calculation section 9a outputs the required operation signal A, and the pulse width modulation portion 9b a pulse P of the pulse width periodically output corresponding to the operation signal A, the pulse width modulation the DC to change the pulse P having a pulse width from the vessel 9b is output is modulated periodically to the control signal e - the FETs Q ₁ constituting the AC converter _{5b, Q 1, Q 2,} Q 2
It is configured by a driver 9c for distributing and applying to the.

As shown in FIG. 1, the arithmetic unit 9a includes a first operational amplifier 9a ₁ whose output voltage changes in response to a change in the illuminance signal S ₅ , a DC current signal S ₃ and a DC voltage signal S. A multiplier 9a ₂ for multiplying by ₄ , an output voltage V _{1 of the first} operational amplifier 9a _{1 and} an output voltage V ₂ of the multiplier 9a ₂ are both applied, and the output voltage V ₃ changes in response to the change. A second operational amplifier 9a _{3 and the} like, and a reference voltage V ₀₁ for illuminance setting is applied to the inverting input terminal of the _first operational amplifier 9a _{1 and} a second operational amplifier 9a ₃ A reference voltage V ₀₂ for power setting is applied to each inverting input terminal.

The reference voltage V ₀₁ is the illuminance signal S ₅
So that the output voltage of the _first operational amplifier 9a ₁ becomes zero,
The output voltage V ₀₂ of the first operational amplifier 9a ₁ is zero and the output voltage V ₂ of the multiplier 9a ₂ is V _{02.
When 2} is a magnitude corresponding to the output voltage of the power supply device 5 corresponding to the set illuminance, the output voltage of the second operational amplifier 9a ₃ is set to zero.

Therefore, when an abnormality occurs in the operation of the power supply device 5, for example, when the characteristics of the FET constituting the polarity switching circuit 5e is changed and the output waveform of the power supply device 5 is distorted, this abnormality is generated. Current-voltage detection circuit 8b and the second
It is repaired by the operational amplifier 9a ₃ (see Japanese Patent Application No. 4-364828 for details).

Next, the operation of the discharge lamp lighting device of this embodiment will be described. Now, since a discharge lamp having a relatively large output with respect to the set illuminance is used, the case where the illuminance signal S ₅ is larger than the reference voltage V ₀₁ for the illuminance setting will be described. The output of the first operational amplifier 9a ₁ will be described. voltages V ₁ becomes a positive voltage, since the multiplier 9a _second output voltage V ₂ and the forward voltage, the second operational amplifier 9a ₃ of the output voltage V _3, i.e. the operation signal a is decreased. Therefore,
The pulse width of the output pulse P of the pulse width modulator 9b becomes narrow.

By this operation, the output power of the DC / AC converter 5b and the DC voltage on the input side of the polarity switching circuit 5e are reduced, and the output power of the power supply device 5 is also reduced. Therefore, the illuminance is lowered and the illuminance signal S ₅ is balanced in the state of approaching the reference voltage V ₀₁ , and at the same time, the input signal of the second operational amplifier 9a ₃ is balanced with the reference voltage V ₀₂ .

When the equilibrium state is reached, if the power corresponding to the set illuminance is not obtained due to the abnormality in the power supply device 5, the output voltage of the multiplier 9a ₂ and the reference voltage V ₀₂ Output pulse P until the equilibrium state is reached
Pulse width increases, the power supply device 5 increases the output power so as to cover the insufficient power, and realizes a predetermined illuminance.

As will be described later, when the illuminance is insufficient due to deterioration of the discharge lamp, the input power of the discharge lamp is increased, but when this input power becomes larger than the reference voltage V _{02 of} the second operational amplifier 9a _3. Since the value of the operation signal A decreases, the input power does not exceed the allowable input of the discharge lamp, and damage to the discharge lamp is prevented.

As described above, when the electric power to the discharge lamp is controlled, the output waveform of the DC-AC converter 5b changes in the time axis direction, but the output waveform of the polarity switching circuit 5e changes with time. Since it does not change in the axial direction, it becomes possible to significantly limit the input power of the discharge lamp 6, and according to an experiment conducted by the inventor, even if the power supply is limited to 15% of the maximum power supply, the flicker phenomenon occurs. It turned out that no.

Considering another operation of this embodiment, that is, a case where the brightness of the discharge lamp is lowered due to long-term use, the output voltage of the _first operational amplifier 9a ₁ becomes negative and the multiplier 9a. since the _second output voltage and a reverse voltage, the output voltage of the second operational amplifier 9a ₃ rises, wide pulse P having a pulse width of the DC - sent to AC converter 5b. Therefore, the output power of the power supply device 5 is increased and a predetermined illuminance can be realized.

By applying the above-mentioned two operations, it becomes possible to extend the life of the discharge lamp. That is, using a discharge lamp with a sufficient output, limiting the power supplied to the discharge lamp at the beginning, and increasing the power supplied as the brightness of the discharge lamp decreases, exposure with constant illuminance can be performed for a long time. It can be carried out.

Conventionally, since the electric power supplied to the discharge lamp cannot be significantly limited, the above-described usage cannot be adopted, and when the brightness of the discharge lamp decreases to some extent, it is necessary to replace it with a new discharge lamp. However, the discharge lamp lighting device of this embodiment is economically advantageous because the discharge lamp can be used for a long time.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and for example, the support of the optical fiber may have a water jacket structure so as to liquid-cool the discharge lamp (details are actually applied). (See flat 4-54645)
It goes without saying that various changes can be made without departing from the scope of the present invention.

[0037]

As described above, the present invention exhibits the following excellent effects. (1) Since the switching frequency of the polarity switching circuit is constant and the discharge pause time can be set to be short, even if the input power to the discharge lamp is controlled, there is no risk of flickering during lighting. Therefore, the illuminance control range can be significantly expanded. In other words, conventionally, the input power is 5
The flicker phenomenon occurred at 0 to 60%, but according to the present invention, the flicker phenomenon does not occur even if the input power is reduced to 15% of the rated power.

(2) As a result of the above item (1), the life of the discharge lamp can be remarkably extended, and discharge lamps of various outputs can be lit by using the same discharge lamp lighting device.

(3) Since the photoelectric conversion circuit of the illuminance detecting device is arranged apart from the discharge lamp, noise does not occur in the illuminance detecting device and the operation of the power control device is reliable.

[Brief description of drawings]

FIG. 1 is a horizontally long block diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram of the DC-AC converter in FIG.

3 is a diagram showing a feedback signal polarity switching circuit in FIG.

FIG. 4 is an enlarged cross-sectional view of section IV in FIG.

5 is a diagram showing a photoelectric conversion circuit in FIG.

FIG. 6 is a block diagram of a conventional discharge lamp lighting device.

7 is a circuit diagram showing a configuration of an illuminance detection circuit and a power control circuit in FIG.

FIG. 8 is a diagram illustrating an operation of the switch circuit shown in FIG.

[Explanation of symbols]

5 Power Supply Device 5a Rectifier 5b DC-AC Converter 5c Transformer 5d Rectifier 5e Polarity Switching Circuit 6 Discharge Lamp 6a Supporting Device 7 Illuminance Detection Device 7a Optical Fiber 7b Photoelectric Conversion Circuit 7b ₁ Diffusing Lens 7b ₂ Diffuser 7b ₃ Filter 7b ₄ Photoelectric Conversion Element 7b ₅ Amplifier 8 Power detection device 8a Switching signal generator 8b Current voltage detection circuit 8c Feedback signal polarity switching circuit 8c ₁ Amplifier 8c ₂ Inverter 8c ₃ Switch circuit 8d Feedback signal polarity switching circuit 9 Power control device 9a Arithmetic unit 9a ₁ First operational amplifier 9a ₂ Multiplier 9a ₃ Second operational amplifier 9b Pulse width modulation unit 9c Driver 10 Rod-shaped quartz glass 11 Coupler

Claims (2)

[Claims] 1. A commercial AC power is rectified and then converted to high frequency power via a pulse width control type DC-AC converter,
A power supply device that further rectifies the high-frequency power and then converts it into rectangular-wave AC power via a polarity switching circuit, an illuminance detection device that detects the brightness of a discharge lamp connected to this power supply device, and outputs an electric signal, and the power supply. A power detection device that detects an electrical state on the output side of the device and outputs an electrical signal, and a pulse width corresponding to the set illuminance and the set power based on the electrical signal sent from the illuminance detection device and the power detection device. And a power control device for feeding back the pulse to the DC-AC converter, the discharge lamp lighting device. 2. The illuminance detection device includes an optical fiber whose tip is disposed in the vicinity of a discharge lamp, and a photoelectric conversion circuit that photoelectrically converts the light received through the optical fiber and outputs an electric signal. The discharge lamp lighting device according to claim 1, wherein the circuit is arranged apart from the discharge lamp.