JPH03119688A - El driving device - Google Patents

Abstract

PURPOSE:To extend the luminous life of an EL by intermittently applying an alternating current to the EL. CONSTITUTION:When an AC power source 1 is excited and a timer 4 and a pulse 3 are turned on, an output signal synthesized by an AND circuit 5 turns a switch 6 on into the conducting state, a DC current I (shown by a broken line in the figure) based on the synthetic resistance of loads 7 and 8 flows, and the branch current I-p flowing toward a rectifier via an EL 8 and the switch 6 moves the electric field of an EL light emitting layer in the positive direction. When the pulse 3 is turned off while the timer 4 is kept on, the switch 6 is turned off into the insulating state, and no current I-p flows. A reverse electromotive force is generated by the energy stored in a coil 7 by a branch current I-a, and a current I-n in the opposite direction to the branch current I-p flows via the EL. The electric field of the EL light emitting layer is applied by the current I-a even when the switch 6 is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a drive device that emits EL as a flat light source, which is used for display purposes, signal decoration purposes, and the like.

<Prior art> In recent years, there has been increasing interest in the practical application of EL as a flat light source with uniform brightness. The above-mentioned all-solid-state surface emitting device, EL (electroluminescence), consists of a flat light-emitting layer made of a material such as zinc sulfide that emits light when an electric field is applied, sandwiched between two different insulating layers on both sides. A transparent electrode is provided on one of the insulating layers, and a similar electrode is provided on the other insulating layer, and an alternating current is applied between the two electrodes, thereby moving the electric field of the EL light emitting layer and emitting light. In order to cause EL to emit light, it is necessary to apply an alternating current, such as an alternating current, with a different potential between the two electrodes of the insulating layer. Most of the devices currently in practical use either (1) directly apply a commercial 100V sine wave alternating current to the EL picture electrode, or (Z) use an AC-AC inverter, or generate L< with a DC-AC inverter. It is a square wave alternating current.

FIG. 4 shows a configuration diagram of the drive according to (1) above.

A: Direct method B: Capacitor input method C1: Choke input method.

A configuration diagram of the drive according to (2) above is shown in FIG.

DC-AC when replacing the AC-DC converter with a DC power supply
Configure the inverter.

This inverter type has a high application period of alternating current (1
) to compensate for the low brightness, which is a drawback of direct application.

There are other methods that apply amplifier circuits found in wireless communication devices, but this type of method lacks versatility because the electrical load on the device varies greatly when the load specifications of the EL change.

<Problems to be Solved by the Invention> (1) The luminance of EL is directly proportional in the range of several Hz to several KHz if the voltage applied to the electrode is constant.

According to the direct application method using a commercial AC power supply described in (1) of the above <Prior art>, the EL emission period is 50 Hz or 60 Hz and the brightness is as low as a few radlux, so it lacks general practicality. Seem.

In order to compensate for this drawback, it is known to increase the brightness by using one type of AC-AC inverter as described in <Prior Art> (2).

According to this drive system) ζ, the basic configuration shown in Figure 5 is known, but the use of a smoothing capacitor and a transformer is essential for this configuration to function efficiently, but they are not used here. Capacitors are generally large in shape because they are electrolytic capacitors with high withstand voltage and large capacity, but they are difficult to reduce in size and weight due to the magnetic saturation of the transformer and load fluctuations. Even if this smoothing capacitor is replaced with a Sennichi-Ku coil, there will probably be no major difference in shape.

Used in the inverter described below (Conventional technology)
2) In the transformer shown in Fig. 5, it is essential to wind the power conversion coil around the iron core or magnetic core on the primary side and the secondary side based on the magnetic characteristics, so the EL of the present invention
It is larger in shape compared to the coil used in the drive device. Note that, as a matter of course, the coil used in the EL drive device according to the present invention does not require a secondary winding coil.

Furthermore, since the secondary voltage of the transformer used for driving the EL is high, the transformer is generally large in size due to the characteristics caused by mutual magnetic induction. In addition, if this type of transformer is incorrectly designed, it may become a source of heat or cause problems in terms of efficiency.

[2] Next, there is the issue of deterioration due to the lifespan of EL.The life of the luminance of the light emitting layer, which is one of the causes of deterioration, is generally such that if the voltage applied to the EL electrode is constant, the brightness decreases in inverse proportion to the alternating cycle. do.

This is especially noticeable in high brightness areas. According to the data, 1
When an alternating current of 00V/IKHz is applied, the brightness gradually decreases as the emission time elapses, and after several thousand hours, the brightness decreases to 5096
It also reduces to a certain degree.

It is practically essential to compensate for the above-mentioned drawbacks and extend the service life.

As stated above, an object of the present invention is to provide a highly practical and appropriate device that overcomes the disadvantages of increasing the size of the drive device and the deterioration of the EL light emitting layer due to high-intensity light emission.

Means for Solving the Problems> As a means for solving the above problems, the present invention adopts an appropriate processing configuration according to the present invention for high brightness, and
Aiming at high voltage application and high frequency of the alternating current applied to the electrodes.

In addition, in order to realize a practical and appropriate EL drive device, the smoothing capacitor and transformer, which impede miniaturization and weight reduction, are removed to create a more efficient configuration.

In addition, as a means to solve the time constraints on the luminescence life of EL, the alternating current applied to the EL electrodes can be adjusted appropriately by adjusting the luminescence time of the 0N-OFFL luminescent layer so that it emits light only when it is ON, as shown in Figure 3. According to the configuration of the present invention described above, the alternating current applied to the EL electrode is made into a direct alternating current. It becomes possible to make component parts smaller and lighter. In addition, in practice, it is possible to utilize the high luminance of EL over a longer period of time.

<Example> Hereinafter, an example of the EL drive device according to the present invention will be described with reference to FIGS. 1, 2, and 3.

Embodiment 1 Reference numeral 1 in FIG. 1 is an AC power supply, and 2 is a full-wave rectifier. This configuration converts the power into direct current. 3 is a pulse generation circuit that determines the application period of the alternating current, and 4 is a timer for making the light emission brightness uniform due to the afterimage phenomenon by turning the above-mentioned pulses ON and OFF over time. Also, 5 is 3 above
This is an AND circuit for synthesizing the pulse generated at 4° and the timer signal. 6 is a switch driven by the control signal from 5 above. 7 is a coil containing a magnetic core. 8 is an EL light emitter.

To explain the present invention in detail using the configuration shown in FIG. 1, the AC power supply 1 is energized, the timer 4 is ON, and the pulse 3 is also ON.
Then, the output signal synthesized by the AND circuit of 5 is 6
When the switch is turned on, it becomes conductive, and the DC current I shown by the broken line in Figure 1 based on the combined resistance of loads 7 and 8 flows through EL of 8 and the switch of 6, and then the branch to (→) of the rectifier. The current 1-p is a current responsible for moving the electric field of the EL light-emitting layer in the positive direction. (Figure 2) On the other hand, the branch current I-b shown by the broken line in Figure 1 is a current that moves the electric field of the EL light-emitting layer in the positive direction. Energy stored in 7 coils connected in parallel as follows: Induced electromotive force = (1/2) L12
is the inductance of the coil 7, ■ is the branch current 1-b)
This is the current for generating .

Next, when the timer 4 is ON and the pulse 3 is OFF, the switch 6 is turned OFF and is in an insulated state. Naturally E
The current 1-p that moves the electric field of the L light-emitting layer in the positive direction does not flow. However, a back electromotive force is generated due to the energy stored in the coil due to the branch current 1-b, and a current 1-n flows in the opposite direction to the branch current 1-p as shown by a solid line via the EL. This current I-n acts on the electric field of the EL light emitting layer in a direction opposite to the direction in which the electric field moves in the branch current I-p.

With the above configuration, at 08 o'clock of switch 6, branch current I-
The electric field of the EL light-emitting layer moves in the positive direction due to p, and when the switch 6 is turned off, the electric field moves in the opposite direction due to the current ■-, which is equivalent in terms of action to an alternating current alternating current (Figure 6). This is an effective method. In other words, the electric field of the EL light emitting layer is configured to move in response to changes in the potential of the applied alternating current.

If the above-described DC/AC current according to the present invention is applied to the EL and is practically effective, there is no need for a smoothing capacitor or transformer that increases the size and reliability of the drive device.

Note that the full-wave rectifier 2 shown in FIG. 1 may be a half-wave rectifier. Further, the switch 6 may be a switch using a semiconductor.

Example 2 Next, a means for extending the luminescence life of EL according to the present invention will be explained.

As mentioned in the above section of <Problems to be Solved by the Invention>, TV is generated from the pulse generation circuit 3 in FIG. The square wave pulse is a control signal for applying a DC alternating current generated by the action of the switch 6 and the coil 7 via the AND circuit 5 to cause the EL to emit light if the timer signal 4 is ON. . 4 in this state
When the timer signal is turned OFF, the pulse from the pulse generation circuit 3 continues to be output, but the switch 6 remains OFF until the timer signal is turned ON again via AND of 5.
The EL of the load, which is an FF, does not emit light because no alternating current is applied to it.

By turning this timer signal ON-OFF, EL
The light emission repeats intermittently and stops in response to a timer signal. This phenomenon is shown in the time chart of FIG.

According to the above configuration, the EL light emission time is 0 of the timer signal.
Only at 8 o'clock. Naturally, the lifespan of EL is determined by the timer.
It is the cumulative total of time.

Note that by temporally changing the ON-OFF output of the timer signal, the light emission time and brightness can be changed arbitrarily.

<Effects of the Invention> According to the above explanation, the light emitting life of the EL is extended by the amount of time that is the sum of the intermittent light emitting stop time than the total light emitting use time of the EL.

Moreover, the reduction in the number of parts achieved by the configuration of the present invention,
Small size and weight reduction are effective in improving product reliability and reducing product cost.

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 are a block diagram constituting the present invention, an EL application waveform diagram of a DC alternating current, and a time chart. (Main reference numbers in Figure 1) 1... AC power supply 2... Rectifier 3... Pulse generation circuit 4... Timer 5... AND circuit
6...FET switch 7...Coil 8
. . . EL light emitter FIG. 4 is a general configuration diagram of an AC power direct application method. 5 and 6 are a basic configuration diagram of an AC-AC inverter type and an EL application waveform diagram of an AC alternating current. (Main reference numbers in Figure 5) 1... AC power supply 2... Rectifier 3... Electrolytic capacitor 4... Transformer 5... Switching circuit 6... Semiconductor switch 7... EL light emission Engraving of the body drawings (no changes in content) Figure 3 Procedural amendment (method) February 20, 1990 Sent February 21, 1990

Claims (2)

[Claims] (1) By intermittently applying an alternating current to EL, E
Means for extending the luminescent life of L. (2) In response to the means described in claim (1) above, a coil containing an iron core or a magnetic core is electrically connected in parallel to the EL to reduce the electromotive force caused by the magnetic action of the coil. An EL drive device characterized by its application.