JPS62165898A - Fluorescent lamp burning controller - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to a lighting device using a fluorescent lamp, and more particularly to a lighting control device suitable for an automobile instrument panel using a liquid crystal display device.

[Conventional technology]

In recent years, digital displays have come into widespread use as instrument panels for automobiles, and as a result, liquid crystal display devices have come into widespread use.

Incidentally, since such liquid crystal display devices for automobiles generally employ a color display method, they often require a light source for illumination. At this time, fluorescent lamps have conventionally been mainly used as the light source.

However, using a common hot cathode type fluorescent lamp has a relatively short lifespan and is not practical.
As disclosed in Publication No. 0660, etc., cold cathode type fluorescent lamps were mainly used.

On the other hand, even when hot cathode type fluorescent lamps are used, as disclosed in JP-A No. 60-72198, when the emission 'vttm of the fluorescent lamp becomes 50% or less of the rated value, Preheating the hot cathode 1: A method has been proposed to reduce the iL flow and extend the life of the hot cathode.

[Problem that the invention seeks to solve]

Among the conventional examples described above, the method using a cold cathode fluorescent lamp has the following problems. In other words, cold cathode fluorescent lamps do have a long lifespan because they do not have a filament, but their luminous efficiency is lower than that of 'kW' lamps, and they cannot be heated with a heater at low temperatures. Without it, it is difficult to turn on the light.

In addition, although the latter method of reducing the preheating current can extend the lifespan when the lights are turned on continuously, there is a problem in that there is no particular consideration given to extending the lifespan when the lights are frequently turned on and off. There are some points.

It is an object of the present invention to address the problems of the prior art described above; 2.
To provide a lighting control device which can sufficiently extend the life of a hot cathode type fluorescent lamp even when a hot cathode type fluorescent lamp is used for illuminating an automobile instrument panel.

Measures to solve problem C] The above problem is that when a fluorescent lamp is turned on from an off state,
Initially, the solution is to suppress the discharge current and release the suppression of the discharge current after the time required for the hot cathode to reach a predetermined temperature of 8 degrees Celsius.

[For production]

By suppressing the discharge current when the temperature of the cathode is low, the occurrence of sputtering at the cathode can be suppressed, thereby extending the service life of the cathode.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluorescent lamp lighting control device according to the present invention will be described in detail below with reference to illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which the present invention is applied to the lighting control of fluorescent lamps used for illuminating an automobile instrument panel using a liquid crystal display element.
2 is a battery, 2 is an ignition switch, 3 is an inverter circuit for dimming 400 fluorescent lamps, and 5 is a control circuit for controlling the light of the inverter Li path 3.

Is this control circuit 5 a microcomputer? ; say l, 6
It functions to output a duty signal a to the inverter circuit 3 based on the input from the light switch and the input from the 70Lm resistor.

The inverter circuit 3 also includes a transformer 'P', capacitors C1 to C4, transistors Q1 to Q3 . diode 0
1-D2. It is composed of resistance ratios 1 to R4, among which transistors Q1. Q2. ianti-Kl)t2R
3. A push-pull blocking oscillator is configured by the capacitor C1 and the transformer TR. Then, when the ignition switch 2 is turned on, the t source is supplied,
Oscillation is started, thereby supplying the fluorescent lamp 4 with an AC voltage boosted by the transformer T ratio. At this time, current is also supplied to the filament of the fluorescent lamp 4 via the capacitors C2 and C3.

The discharge current of the fluorescent lamp 4 is controlled via a ballast capacitor C4, a diode Di, and a transistor Q3. When the discharge current flows in the opposite direction, it follows the diode D2.

The transistor Q3 is controlled 0N-OFF?blJ by the control circuit 5 via the resistor 1 (4). Then, a discharge current flows only when the transistor Q3 is ON, and the ON duty of the signal a at this time causes a discharge current to flow. 1illj H
The brightness can be adjusted by making the discharge proportional to the current.

This dimming control is used for dimming control at night.

That is, since the instrument panel illumination using a liquid crystal display element needs to be dimmed at night, the light switch 6 is turned off.
When N is selected, the brightness of the illumination is reduced to 50%.

Further, a system is adopted in which the light can be freely adjusted between 50% and 10% using a variable resistor 7. For this reason, the control circuit 5 determines the human input signals from the switch 6 and the variable resistor 7, and sets the duty signal a to the output voltage corresponding to the control input.
Outputs N tuney.

Figure 2 shows the characteristics of the inverter circuit 3,
As the brightness of the fluorescent lamp 4 decreases, the preheating flow '1 flowing through the filament of the fluorescent lamp 4 automatically increases.

Therefore, according to this embodiment, even when the discharge current is decreasing due to dimming control to a low brightness of 10%, it is possible to maintain lighting and discharge by lighting the torch. be.

As described above, the control circuit 5 includes a microcombicoater, receives the ON/OFF state of the ignition switch 2, and performs control operations according to the time chart shown in FIG.

First, if two ignition switches are turned on at time to, then this time [. Until the predetermined time T has elapsed and the time [1] is reached, the ON duty signal a is outputted such that the output current corresponds to a luminance of 10% of the rated luminance. Then, at time t1 when time T has elapsed, the ON duty of No. 41a is set to the value given by variable resistor 7, or 100%.

As a result, according to the above embodiment, immediately after the ignition switch 2 is turned on, the discharge current of the fluorescent lamp 4 is suppressed to 10% of the rated value, regardless of the states of the light switch 6 and the variable resistor 7. , then after a predetermined period of time T passes, the shade a
When preheating of the light tray has been obtained, control is performed to shift the current to 100% of the rated value or to the discharge value given by the light switch 6 and the variable resistor t. Become. At this time, during this time T, the filament preheating current is increased, but this is automatically given by the characteristics of the inverter circuit 3 explained in FIG.

Figure 4 shows how to start the fluorescent light (turn it on from off)
The relationship between the value of the initial discharge current ('14 degrees) and the number of flashing lifespans is ignored.

From this characteristic, it can be seen that as the brightness immediately after startup is increased, the number of blinks until the end of its life decreases. This is because when a high voltage is applied at startup, many electrons collide with the filament of the fluorescent lamp at high speed, causing a sputtering phenomenon and evaporating the activating material coated on the filament.

In other words, it can be seen that the lifespan is shorter when there are many electronic children that repeatedly blink at high brightness. and,
From this, even if the brightness is set to 100% and blinks repeatedly, if you lower the brightness to, say, 10% just after the BIJJ occurs, then increase the brightness to 100%. In other words, it can be seen that if the above embodiment is used, the number of blinking lifetimes can be made almost the same as when blinking at 10% brightness, and a remarkable improvement can be obtained.

FIG. 5 is a flowchart showing the contents of processing by the control circuit 5, including night dimming processing by the light switch 6, which starts when the ignition switch 2 is turned on.

When the process shown in FIG. 5 starts, first, the O of the signal a is
The N duty is set to 10%, and it is checked in <82 whether the predetermined time T has elapsed or not, and when the result is No, the process returns to Sl. Therefore, the control explained in FIG. 3 can be obtained by the processing of these Sl and 82.

Next, the result in S2 is ψES, that is, the time [,
After that, the process moves to steps 83 to S5, and the ON-OF l+'' state of the light switch 6 is checked to control the dimming during the day and at night. That is, processing S3 allows one of S4 and S5 to be repeated.

In the above embodiment, the inverter circuit 3 is used, and due to the characteristics shown in FIG. 2, the filament preheating current increases automatically at time T in FIG. However, the present invention
Of course, in this embodiment, the increase in preheating current may be obtained by another control means, or the increase in preheating current may not be performed.

In addition, in the above embodiment, since the control circuit 5 includes a microcomputer, the necessary control can be obtained just by adding a software configuration, which can greatly contribute to cost reduction. However, it goes without saying that the present invention is not limited to this, and may be implemented as a hardware embodiment.

[Embodiments of the invention]

As explained above, according to the present invention, a thermal box type fluorescent lamp is used and can maintain a sufficiently long life even if it is repeatedly blinked at a high frequency, thereby eliminating the problems of the conventional technology and It is possible to easily provide a fluorescent lamp lighting control device that can be applied to an automobile instrument panel using a display element to provide practicality.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a fluorescent lamp lighting device according to the present invention, FIG. 2 is a characteristic curve diagram showing characteristics of an inverter circuit, and FIG. 3 is an operation of an embodiment of the present invention. FIG. 4 is a characteristic curve diagram showing an example of the characteristics of a fluorescent lamp, and FIG. 5 is a flowchart showing the operation of an embodiment of the present invention. ]...Battery, 2...Ignition switch, 3...Inverter circuit, 4...
...Fluorescent lamp, 5...Control circuit, 6...
...Light switch, 7...Variable resistor. Agent Patent attorney Junji Takeshi Department (1 other person) 1 Figure I---Battery 6- ・-
Light switch 2・-11i 7th switch +
7. --- One variable 46 stakes 3 --- Invar 70 paths 4 --- One fluorescent light 112 figures too 90 110 70 60 50 40 3
0 20 10 Fluorescent fork-shaped cliff [%J 1!3 Figure tQ i. Fig. 4 OIO50lOO Discharge Tortoise Current (Brightness) [%1 Fig. 5

Claims (1)

[Claims] 1. In a fluorescent lamp lighting circuit that performs dimming control in a cathode preheating state, a control means for reducing the discharge current of the fluorescent lamp to a predetermined value is provided, and the fluorescent lamp is turned on from an off state. 1. A fluorescent lamp lighting control device, characterized in that the control means is configured to operate for a predetermined period of time when the control device is turned on. 2. In claim 1, the control means comprises:
A fluorescent lamp lighting control device comprising a function of increasing a cathode preheating current of the fluorescent lamp, and configured to operate this function during the predetermined period of time.