JPH07281149A - Lighting device - Google Patents

Abstract

PURPOSE:To provide a lighting device capable of providing a safe display device by interrupting the operation of a lighting driving circuit with a signal detected by a temp. detection member arranged on an end part of a tubular light source. CONSTITUTION:A temp. information signal is detected by the temp. detection member 50 when a fluorescent tube 30 is driven. Although the temp. information signal is inputted to a waveform shaping circuit 60, only fixed potential is outputted from the waveform shaping circuit 60, and an output signal of a lighting control circuit 70 holds fixed level potential also. In such a state, when the life of the fluorescent tube 30 is ended, and the temp. of the discharge electrode part of the fluorescent tube end part rises, the output of the temp. detection member 50 rises or falls gradually also. Temp. information is converted into a voltage level by the output of the detection member 50 or the detection member 50 and the internal circuit of the waveform shaping circuit 60, and the converted temp. information is compared with prescribed potential in the waveform shaping circuit 60, and an abnormal temp. information signal is outputted to a lighting control circuit 70. When the abnormal temp. information signal is inputted to the lighting control circuit 70, a signal interrupting the operation of the lighting driving circuit 20 is generated, and the lighting driving circuit 20 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an illumination source on the back, back side or top side of a passive display panel found in personal computer devices, liquid crystal television devices, liquid crystal monitor devices, etc. The present invention relates to an illuminating device for displaying a display image with a good appearance.

[0002]

2. Description of the Related Art A liquid crystal display device utilizes optical anisotropy of liquid crystal to transmit or reflect light to control and modulate the transmittance of the light for display. Therefore, since the liquid crystal display device is positioned as a so-called passive device (non-light emitting body), there is a problem that the display becomes difficult to see unless the back lighting means is provided when the surroundings are dark. Further, as described above, almost all liquid crystal display devices use optical anisotropy, so that it is indispensable to stack polarizing plates, and because of this polarizing plate, about 50% of illumination light is used. Will be cut. Especially color
In a liquid crystal display device using a filter, the amount of light is further reduced due to colorization. Therefore, it is an essential requirement to attach a lighting means to the device for general indoor use. Recently, a liquid crystal display device having an illuminating device, which is such an illuminating means, has been widely used as a portable information source such as a liquid crystal television mainly in portable electronic devices due to its usefulness.

A fluorescent tube is mainly used as an illumination source in these illumination devices, and other illumination sources include a light emitting diode (LED), electroluminescence (EL), and a light bulb. Since the present invention is more effective when used for a fluorescent tube or a light bulb having a high heat generation temperature, a conventional example using a fluorescent tube will be mainly described.

The construction of the fluorescent tube incorporated in the lighting device is described in detail in Japanese Utility Model Laid-Open No. 2-35582, and the fluorescent tube driving circuit is described in detail in Japanese Utility Model Laid-Open No. 1-54026.

As described in Japanese Utility Model Laid-Open No. 2-35582, a reflecting member for reflecting the light going to the rear part of the fluorescent tube to the liquid crystal panel side which is the front surface of the fluorescent tube is arranged at the rear part of the fluorescent tube.
The reflective member is mainly made of a resin material because it can be easily processed to form a large number of reflective plates and can be formed into a free shape. On the other hand, the reflector may be plated on steel, which is a metallic material, to be commercialized. The exterior of the display device is made of a resin material which has good workability and can easily be formed into a free shape, as described above. As the resin material,
ABS material, PS (eg vinyl chloride) material, carbon fiber reinforced resin (CFRP, eg trading card) material, liquid crystal polymer (LC)
P) material or the like is used.

The fluorescent tube driving circuit is described in detail in Japanese Utility Model Laid-Open Publication No. 1-54026, and a basic fluorescent tube driving circuit is shown in FIG. 4 to explain the prior art. Power to the lighting circuit,
A primary power source of the transformer 37, which is connected to the base and collector of the transistor (hereinafter, referred to as Q) 34 and the base and collector of the transistor Q35 on the capacitor (hereinafter, C) 36 side of the transformer 37 when power is applied to the power source 18. A voltage is applied to the winding side and the primary side of the transformer 37 performs self-excited transmission, and the transmitted signal is transmitted to the secondary side of the transformer 37, which is the side of the fluorescent tube 30 of the transformer, to turn on the fluorescent tube 30.
Resistors (hereinafter, R) 31 and R32 are bias resistors of Q3 and Q4. The coil 33 is for smoothing the power supply. C38 is for current limiting.

At this time, the thermal fuse 100 is in contact with the outer surface of the fluorescent tube 30, and the thermal fuse 100 is arranged at two places between the secondary side terminal of the transformer 37 and the fluorescent tube as shown in FIG. ing. This thermal fuse 100 is adopted for the following reasons.

Regarding the operation of the fluorescent tube, which is a material for fluorescent tube manufacturers, "ELEVAM CO., LTD., Cold cathode tube / hot cathode tube, small color light manual, basic edition Vol. 1, 1989".
Year ”. As shown in this document, the hot cathode fluorescent tube is turned on, and the emitter coated on the filament is used for a long time, it is gradually consumed and the emitter disappears at the end of the life of the fluorescent tube, causing tungsten arc discharge. Become. This tungsten discharge raises the temperature of the fluorescent tube. When the discharge is further continued, glow discharge occurs due to the support material of the tungsten filament, and the temperature of the fluorescent tube rises significantly.

Although the hot cathode tube has the above-mentioned drawbacks, it has many advantages over the cathode tube, such as low discharge, low current consumption, and high brightness, and is therefore widely used in portable liquid crystal televisions, liquid crystal monitors, and the like. . A thermal fuse or a glow detection protection circuit is used as a protection circuit against a temperature rise of the fluorescent tube 30 which is a countermeasure against the drawback of the hot cathode tube.

In FIG. 4, the temperature fuse is used to protect against an excessive temperature rise, but another protection method is the fluorescent tube 30 as disclosed in Japanese Utility Model Laid-Open No. 1-54026.
There is a method of stopping the driving of the fluorescent tube when the driving voltage is detected and a predetermined voltage state is reached. This detection circuit will be referred to as a glow detection circuit, and the outline of the glow detection circuit will be described with reference to FIG.

In FIG. 4, the glow detection circuit has a structure in which both terminals of the secondary winding of the transformer 37 are connected in parallel with the fluorescent tube 30, and C101, R102, R105, and R1.
07 and parts D104 and D103. C
The substantially sine wave waveform shown in FIG. 5 appears between the cathodes of 101, R102, and D104, and when there is a voltage difference E between the voltage V1 and the voltage V2 of the sine wave waveform, the reference potential is C101 and only 1 / 2E. Adjusted. This adjusted voltage is D1
The glow detection signal 108 is smoothed by 03, C106, and R105. The fuse 100 is attached to improve safety.

Using the glow detection signal 108 of FIG. 5, the power supply of the primary winding of the transformer 37 of FIG.
4 and Q35 are forcibly cut off to stop the glow discharge at the above voltage.

[0013]

As described above, in the prior art, since a capacitor is used as a component of the glow detection circuit, there is a large variation in the capacitance value of the capacitor, which makes it impossible to perform accurate glow detection. there were. For example, a capacitance value of ± 20% is a general capacitance accuracy, and if a capacitor with a small variation in capacitance value is used, the price becomes very high. Furthermore, there is a problem that the glow voltage cannot be accurately detected because the temperature change of the capacitor is large.

On the other hand, the thermal fuse has a problem that the variation of the fusing temperature is large and the contact surface with the fluorescent tube is a point contact and the temperature detection power is poor.

It is an object of the present invention to solve the above problems and to obtain a lighting device which can provide a safe display device.

[0016]

In order to solve the above-mentioned problems, the present invention provides a lighting device having a fluorescent tube which is a tubular light source, wherein a temperature detecting member is provided at an end of the tubular light source, and It is characterized in that the operation of the illumination drive circuit is stopped by a signal detected by the temperature detection member.

Further, in a lighting device having a fluorescent tube which is a tubular light source, a temperature detecting member is arranged at an end of the tubular light source, and a signal detected by the temperature detecting member is waveform-shaped by a waveform shaping circuit. However, the above-mentioned is characterized in that it is provided with a stop means for operating the illumination control circuit provided in the illumination circuit by the waveform shaping output signal to stop the operation of the illumination drive circuit.

A lighting device characterized in that a temperature sensitive IC is used as the temperature detecting member.

A thermistor element, a thermocouple element or a temperature sensitive IC is used as the temperature detecting member.

The output signal of the waveform shaping circuit is an output signal of a flip-flop circuit or a latch circuit.

[0021]

The function is to detect the temperature of the fluorescent tube by using a thermistor, a thermocouple or a temperature sensitive IC, and to stop the fluorescent tube drive circuit.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described with reference to FIG. 1, which is a system block diagram showing an embodiment of the present invention. In Figure 1,
An external power source including the AC adapter 15 and the car adapter 16 or a power source from a built-in power source such as a battery 17 is used as a power source for a lighting circuit by the power source circuit 10 and the lighting drive circuit 2
Supplied to zero. The fluorescent tube 30, which is an illumination source, is turned on and driven by the illumination drive circuit 20. At the end of the fluorescent tube where the discharge electrode of the fluorescent tube 30 is arranged, a thermistor or a Seiko-Electronic CMOS temperature sensor S-810 is provided.
A temperature sensitive IC, a CMOS temperature sensor, and a detection member 50, which is a thermocouple, which are found in 0BF, are provided. The output of the detection member 50 is connected to the waveform shaping circuit 60, the output of the waveform shaping circuit 60 is connected to the illumination control circuit 70, and the output of the illumination control circuit 70 is connected to the illumination drive circuit 20.

The operation of the system shown in FIG. 1 will be described. Normally, the fluorescent tube 30 is driven by the illumination drive circuit, and in this state, the temperature information signal is detected from the temperature detecting member 50. The temperature information signal enters the waveform shaping circuit 60, but only a constant potential is output from the waveform shaping circuit, and the output signal of the illumination control circuit also holds a constant level potential. In this state, when the life of the fluorescent tube 30 is reached and the temperature of the discharge electrode section at the end of the fluorescent tube rises, the output of the temperature detecting member also gradually rises or falls. The output of the temperature detecting member 50 or the temperature detecting member 50 and the internal circuit of the waveform shaping circuit 60 convert the temperature information into a voltage level, and the converted temperature information is compared with a specified potential in the waveform shaping circuit 60 to detect abnormal temperature information. The signal is output to the lighting control circuit 70. When the abnormal temperature information signal enters the illumination control circuit 70, a signal for interrupting the operation of the illumination drive circuit is generated and the illumination drive circuit 20 is stopped.

The system of FIG. 1 is more specifically shown in FIG. 2, which is an embodiment of the present application. In FIG. 2, a thermistor is used as the temperature detecting member 50. 18 is a power supply and 19 is earth. R61 and R62 connected in series with the thermistor are arranged in the waveform shaping circuit 60. When the temperature rises, the resistance value of the thermistor decreases, and when the + input terminal potential of the comparator 65 becomes lower than the −input terminal potential set by R63 and R64, the output of the comparator 65 is inverted. A waveform shaping circuit 66 including a flip-flop and a latch circuit receives the output inversion signal of the comparator and performs a waveform shaping process.
Shut off. By shutting off Q71, R31, R32, Q3
The illumination drive circuit composed of 4, Q35, C36, C38 and the transformer 37 is stopped and the fluorescent tube is turned off.

In FIGS. 1 and 2, since the temperature detecting member such as a thermistor is mainly used, the waveform shaping circuit 60 and the control circuit 70 are required.
If a MOS temperature sensor is provided and the output of the CMOS temperature sensor is directly connected to the bases of Q34 and Q35, a waveform shaping circuit and an illumination control circuit are not required as separate members.

[0026]

The illumination device of the present invention can accurately detect the glow because the glow detecting circuit does not use a capacitor having a large variation in capacitance value. Further, since the temperature fuse is not used, which has a problem that the variation of the fusing temperature is large and the contact surface with the fluorescent tube is point contact, and the temperature detection power is poor, accurate glow detection can be performed. In this way, since the glow detection can be accurately grasped as a change in temperature rise, abnormal temperature rise occurs due to glow discharge, and the reflector of the lighting device is burnt, or the interior member of the display device using the lighting device or Therefore, there is an effect that a safe lighting device can be obtained which is protected from burning the exterior member.

[Brief description of drawings]

FIG. 1 is a system block diagram showing an embodiment and an embodiment of the present invention.

FIG. 2 is a partial circuit diagram in FIG. 1, which is an embodiment of the present invention.

FIG. 3 is a circuit diagram of a fluorescent tube driving circuit of the related art.

FIG. 4 is a circuit diagram of a fluorescent tube glow discharge detection circuit as a conventional technique.

5 is a waveform diagram for explaining the operation of FIG. 4 which is a conventional technique.

[Explanation of symbols]

 10 power supply circuit 20 lighting drive circuit 30 fluorescent tube 40 liquid crystal panel 50 detection element 60 waveform shaping circuit 65 comparator 66 waveform shaping circuit 70 lighting control circuit 100 temperature fuse

Claims (5)

[Claims] 1. In a lighting device having a fluorescent tube as a tubular light source, a temperature detecting member is provided at an end of the tubular light source, and an operation of an illumination driving circuit is performed by a signal detected by the temperature detecting member. A lighting device characterized by being stopped. 2. In a lighting device having a fluorescent tube as a tubular light source, a temperature detecting member is disposed at an end of the tubular light source, and a signal detected by the temperature detecting member is waveform-shaped by a waveform shaping circuit. An illumination device characterized by comprising stop means for causing an illumination control circuit provided in the illumination circuit to operate by a waveform shaping output signal to stop the operation of the illumination drive circuit. 3. The lighting device according to claim 1, wherein a temperature-sensitive IC is used as the temperature detecting member. 4. The lighting device according to claim 2, wherein a thermistor element, a thermocouple element or a temperature sensitive IC is used as the temperature detecting member. 5. The lighting device according to claim 2, wherein the output signal of the waveform shaping circuit is an output signal of a flip-flop circuit or a latch circuit.