JPS6236966A - Light source device - Google Patents

Abstract

PURPOSE:To keep the tube wall temperature constant even under a high temperature environment at idling by detecting the tube wall temperature of a fluorescent tube and controlling the pre-heat voltage of a filament accordingly. CONSTITUTION:A photosensor 2 sensing the light quantity is provided in the vicinity of a fluorescent tube 1 and a thermister 3 sensing the tube wall temperature is provided in the vicinity of a filament 1a. The output of the sensor 2 is converted into a DC level by an amplifier 4, led to the input terminal 5a of a control section 5 and the output of the thermister 3 is led to an input terminal 5b. A control section 5 is switched by using a control signal S1 to switch lighting/pre-heat, and outputs a control voltage V1 controlling the light quantity constant in response to the output of the sensor 2 at lighting and a control voltage V2 controlling the tube wall temperature constant at pre- heating. The control voltages V1, V2 and the control signal S1 are inputted to a balast 6, from which the voltage V1 is converted into a high frequency AC voltage to prevent flicker at lighting to be supplied to a filament 1a and the voltage V2 is converted into an AC voltage at pre-heating to be supplied to the filament 1a.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention can be used as a light source for exposing documents in copying machines, reading devices, etc., or as a light source for electrophotographic optical writing printers, liquid crystal shutters, etc. The present invention relates to a light source device including a fluorescent tube as a light emitting means.

[Conventional technology]

In the above-mentioned device, since it is necessary to immediately light up the fluorescent tube, a means is provided to apply a voltage to the filament in order to preheat the filament in the fluorescent tube when the eye is in the unlit state. ing. Conventionally, this preheating voltage has been applied at a predetermined rated voltage regardless of the temperature of the fluorescent tube during idling.

[Problems with conventional technology]

Generally, the luminous efficiency of a fluorescent tube is determined by mercury vapor pressure and tube current. In particular, since mercury vapor pressure depends on temperature, the luminous efficiency is greatly affected by temperature. For example, the luminous efficiency is highest when the tube wall temperature of a fluorescent tube is approximately 40°C.
), and even if it is higher or lower than this, the luminous efficiency will decrease.

generally known. It is also known that the mercury vapor pressure is determined by the temperature at the lowest point of the tube wall temperature (hereinafter referred to as the coldest point). Therefore, when lighting the fluorescent tube, it is desirable to maintain the temperature of this coldest point at about 40C'C.

However, in the above-mentioned conventional device, if the structure is focused on stabilizing the amount of light at low temperatures, the amount of light at high temperatures tends to become unstable. Especially when idling, as mentioned above, the filament 1-
Since the rated voltage is applied to the filament, the temperature of the tube wall near the filament will rise too much in a high-temperature environment. As a result, variations in salinity occur throughout the wall of one tube, making the coldest point 40 [
Because it could no longer be maintained at "C", a large unevenness in light amount of about 20% or more occurred immediately after idling.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to provide a light source device that stabilizes the amount of light immediately after idling in a high-temperature environment.

(Key points of the invention) In order to achieve the above object, the present invention provides a fluorescent tube.

In an optical a device having one stage of voltage application for applying a pre-first voltage to the filament of this fluorescent tube.

Temperature detection means for detecting a tube wall temperature of the fluorescent tube.

The apparatus is characterized by comprising a control means for controlling the voltage applied by the voltage application means based on the output signal from the temperature detection means.

“Embodiments of the Invention” An embodiment of the present invention will be described below with reference to two drawings.

FIG. 1 is a circuit diagram schematically showing an embodiment of the present invention. In the same figure, the proximal part of fluorescent tube] is.

A photosensor 2 is provided to detect the amount of light from the fluorescent tube 1, and a round thermistor 3 is mounted on the wall of the fluorescent tube 1 to detect the temperature of the tube wall near the filament 1a. The light amount signal output from the photo sensor 2 is converted into a DC voltage level by the amplifier 4, and then sent to the control unit 5.
The output signal of the thermistor 3 is led to the input terminal 5) of the control section 5. moreover,
The other input terminal 5c receives two lights 'tA according to the present invention.
It is output from the main control unit of, for example, a copying machine, in which the device is used. A control signal S1 is inputted to instruct switching between lighting of the fluorescent lamp 1 and switching of the filament 11a to the preset state 15. The operation mode J of the control section 5 is switched by this control signal S1 when one fluorescent tube 1 is lit.

The output signal of the photosensor 2 is the control voltage 1 for controlling the light intensity of the fluorescent tube 1 at a constant level, while the filament 1-
When preheating 1a, a control voltage (7) for controlling the tube wall temperature at a constant level is output between the output terminals 5d and 5e in response to the output signal of the thermistor 3, respectively. These control voltages Vl and V2 are led between input terminals 6a and 6b of the paralast 6, and the above-mentioned control signal S+ is input to another input terminal 6C. balas) 64;l:,
Based on this control signal S1, the lighting and preheating are switched 1
During lighting, the -1- control voltage V+ is converted into a high frequency alternating current voltage to prevent flicker and is supplied to the fluorescent tube 1, and when heating is overheating, the control voltage (2) is converted into an alternating voltage and supplied to the filament 1a. Therefore, when the fluorescent tube 1 is turned on, the amount of light is controlled to be constant based on the output signal of the photosensor 2, and when it is preheated, the tube wall temperature is controlled to be constant based on the output signal of the thermistor 3.

Hereinafter, regarding the control signal 5 and Halastro described above,
This will be explained in more detail.

FIG. 2 specifically shows the control section 5, which is the most characteristic feature of the present invention.

In the same figure, the output signal of the photosensor 2 is inputted to the end terminal of the amplifier 11 for error detection via the amplifier 4.
The output signal of the thermistor 3 is input to one terminal of the other error detection amplifier 12. The transistors 13 and 14 receive the control signal s input from the 2-input terminal 5c.
This is a switch circuit that turns on and off depending on the voltage of the amplifier 11 and 12. Based on this switch operation, a voltage E of the level I is input to one terminal of the amplifier 11 and the terminal of the amplifier 12.The outputs of the amplifiers 11 and 12 are , an analog OR (OR) is taken by two diodes 115 and 16, and is applied as a control signal S2 to the inverting input terminal of the comparator 17.The other input terminal of the comparator 17 is A sawtooth-shaped PWM (pulse width modulation) signal S is input, and the control unit 82 receives the pulse width modulation and outputs it. , 18b.

The voltage is input to the DC-DC converter 18, which includes a coil 18C, a diode I' 18d, a capacitor 188, and the like, and the output voltage is taken out between the output terminals 5d and 5a.

Next, the operation of the control section 5 having the configuration described in "2" will be explained.

The control signal S1 is set to 1 to preheat the filament la, and is set to I to light the fluorescent tube 1. First, when the control signal S1 is at the II level, the transistor 13 is turned on and the 1-transistor 14 is turned off. Therefore, the amplifier 12 becomes active, and its amplified output signal is sent to the comparator 17 as a control signal S2 via the diode 1'16.The level of this control section S2 is detected by the thermistor 3. The lower the temperature is, the smaller the value becomes.The thermistor 17 compares the PWM signal S3 and the control signal S2.

The lower the level of the control signal S2, the longer the pulse width is output. D(, -DC converter 18.

It operates according to this pulse width, and the longer the pulse width, the greater the voltage it outputs. Therefore, when the filament 1a is preheated, the output voltage of the DC-DC converter 18 is applied to the output terminal 5d as the control voltage (2).

This control voltage (2) changes depending on the temperature detected by the thermistor 3, and is set high when the temperature is low and low when the temperature is high.

On the other hand, when the fluorescent tube 1 is turned on, that is, when the control signal S1 is switched to L level, unlike the above, the transistor 13 is turned off and the transistor 14 is turned on. The I signal is input to the child terminal. Therefore, the amplifier 11 becomes active this time.

The output signal is sent to the control signal S2 via the diode 1°15.
The signal is sent to the comparator 17 as a signal. After that, the comparator 17 and the DC-DC converter 18 perform the same operation as described above, and the output voltage of the D(, -DC converter 18 is set to the control voltage V+) and the output voltage is applied to the output terminal 5.
It is taken out from between d and 5a. Therefore, this control voltage ■1
also changes depending on the amount of light detected by the photosensor 2,
When the amount of light is small, the setting is large, and when the amount of light is large, the setting is small.

Next, FIG. 3 shows a more specific configuration of the Harastro described above. In the figure, input terminal 6a.

Control voltages Vl and V2 outputted between the output terminals 5d and 5a of the control section 5 are inputted between the terminals 6b and 6b.

A DC-AC inverter 21. is connected between the input terminals 6a and 6b.
22 is connected, and the control voltages Vl and V2 are applied. The DC-AC impark 21 is used for lighting the fluorescent tube 1.

The voltage between the input terminals 6a and 6b is converted into a high frequency AC voltage and applied to both ends of the fluorescent tube 1. The other DC-AC inverter 22 is used for residual heat of the filament 1a, and has an input terminal 6a.

Convert the voltage between filament 1a to AC voltage and
are applied to each of them. The transistors 23 and 24 are turned on and off in response to the control signal 81 input from the input terminal 6C.
It is a switch circuit that turns off.

The signal appearing on each collector side is the oscillation control signal S4
．． It is input to the DC-AC inverters 21 and 22 as S5. The DC-AC inverters 21 and 22 each receive an oscillation control signal S4. The above operation is performed only when S5 is at H level.

The overall operation of Harastro with the above configuration will be explained next. First, when the filament 1a is preheated, that is, when the control signal S1 is at H level, the transistor 2
3.24 are both off. Therefore, the 3rd oscillation control unit signal S4 is at L level.

The oscillation control signal S5 becomes H level, and only the DC-AC inverter 22 operates. At this time, the control signal S1 is H
level, the control voltage ■1 is output from the control unit 5, and this control voltage ■1 is converted into an alternating current voltage by the DC-AC inverter 22.
is applied as a preheating voltage v4 to perform preheating. In this case, the I)C-AC inverter 21 stops the Djfl, and the two fluorescent lamps 1 are in an unlit state.

・If you want to turn on the fluorescent tube j, that is, control (*
``U' When the switch is made to ``U'' S 1 month, LE, LE, transistors 23 and 24 are both turned on.Therefore, the 2 oscillation control signal JS4 is 1 [l, HA, LE 2 oscillation control signal +; 3S5 is I, level, now the mind; i i)
Only the C-A C inverter 21 operates. At this time, since the control signal feather-81 is at level 1, the control signal l;
A control voltage V2 is output from month 1 [; I get attacked.

Next, Fig. 4 (-1) shows the timing of the change in the L reading tube electrician 3 and the change in the residual heat voltage V4 as the control general S1 changes. As is not clear in the diagram, when the control signal S1 or 11 is selected, the residual heat voltage is 4.
is applied to the filament 11a to perform preheating, and when the control signal S1 becomes I, rail, the tube voltage 3 is applied to the fluorescent tube j to start lighting. ) (1' Voltage V3. Voltage ray of residual heat voltage V4, ray core'', which changes depending on the control voltages Vl and V2 obtained from the control unit 5, respectively, and this control voltage V
Photosensor 2. It is determined by the detection signal level of the thermistor 3. Therefore,
Tube voltage V3. The voltage level of residual heat voltage (4) becomes small when the amount of light from the fluorescent tube 1 is large or when the temperature of the tube wall is high.

In the opposite case, the amount of light and the tube wall temperature are controlled to be constant by increasing the amount of light.

Alternatively, as shown in FIG. 4 (bl), the sequence may be such that the preheat voltage 4 is applied at a high level for a time T when the control signal S1 falls, and then the tube voltage 3 is applied. .In this way, just before the tube voltage ■3 is applied,
That is, by sufficiently applying the preheat voltage (4) immediately before lighting, it is possible to prevent the fluorescent tube 1 from becoming black due to the insufficient preheat voltage (V1).

The position of the thermistor 3 is f from the fluorescent tube 1.
The filament I shown in FIG. It is more preferable to be near a or near the cold point I[k.

2.If the temperature of the fluorescent tube 1 can be detected.

In addition to the Mister 3, it may also be a temperature sensor such as a thermocouple.

[Effects of the Invention] As explained below, according to the present invention, the preheating voltage of the filament 1 is controlled according to the temperature condition of the fluorescent tube, thereby reducing the high temperature environment during idling. 1・
Also in this case, the temperature of the tube wall can be maintained constant, and abnormal heating of the tube wall can be prevented. Therefore, the present invention is able to suppress the unevenness in the amount of light immediately after idling to within 5%, and at the same time, there is almost no decrease in luminous efficiency, and it also has the very excellent effect of making it possible to save power consumption, etc. It is something.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention (not shown). Fig. 2 is a circuit diagram specifically showing a control section according to the embodiment. Fig. 3 is a circuit diagram of an embodiment of the invention. A circuit diagram specifically showing the Haras I. Fig. 4 is a time chart 1 showing the relationship between the control signal S+, the tube voltage ■3, and the preheating voltage V4 according to the same embodiment.]... Fluorescent tube. 1a゛... Filament L-. 2... Photo sensor. 3... Thermistor. 5... Control section. 6... Ballast. 11.12... Amplifier for error detection I7... Comparator. 18... I) C-1] C converter. 21.22...DC-ΔC inverter.

Claims (3)

[Claims] (1) In a light source device having a fluorescent tube and a voltage applying means for applying a preheating voltage to a filament of the fluorescent tube, the temperature detecting means detects a tube wall temperature of the fluorescent tube; A light source device comprising: control means for controlling the voltage applied by the voltage application means based on the output signal of the light source device. (2) The light source device according to claim 1, wherein the temperature detection means is provided near the coldest point of the fluorescent tube. (3) The light source device according to claim 1, wherein the temperature detection means is provided near the filament of the fluorescent tube.