JPH10172760A - Electroluminescent element driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable state EL(electro-luminescent) characteristics to be obtained even if an input voltage varies and ensure longer service life of an EL element in a driving device of the EL element using an inverter. SOLUTION: A rise and fall pressure converter 5 having its variable DC output voltage is provided, even of an input voltage from an AC power source 1 varies a constant output voltage is inputted to a pulse generator 6 of an externally energized inverter, a rectangular wave output voltage of this pulse generator 6 is imparted to a choke coil 3 and a serial circuit of the EL element 4, and a sine wave driving voltage is imparted to the EL element 4. An output voltage of the rise and fall pressure converter 5 is arbitrarily set together with degradation of the EL element 4, and brightness degradation of the EL element 4 is compensated for.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an EL (electro-lum
The present invention relates to an EL driving device for driving an element.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing a circuit configuration of a conventional EL driving device disclosed in, for example, Japanese Patent Application Laid-Open No. 4-233193. In the figure, 1 is an AC power supply, 2 is an AC power supply 1
This is a pulse generator that generates a square wave pulse by inputting the output AC, and includes a rectifier circuit on the internal input side. Reference numeral 3 denotes a choke coil connected in series with the EL element 4 on the output side of the pulse generator 2.

In the above circuit, the pulse generator 2 has a configuration of a separately-excited inverter. As shown in FIG.
The rectangular wave output is passed through the choke coil 3 to the EL element 4.
Is applied. At this time, the voltage waveform applied to the EL element 4 is a sine wave.

FIG. 6 is a diagram showing the oscillation principle of the inverter. As shown in FIG.
Of the choke coil 3 on the rectangular wave output side
And the capacitance C of the EL element 4 are connected in series and LC
A series resonance circuit is formed. Using this resonance circuit, the luminance Vel of the EL element 4 is compensated by increasing the voltage Vel applied to the EL element 4 in accordance with the deterioration due to the decrease of the C component of the EL element 4, thereby achieving a long life. It is trying to make it.

At this time, the voltage V applied to the EL element 4 is
el is Vel = Q /, where Q is the resonance value of the resonance circuit.
Represented by C.

[0006]

By the way, the above-mentioned EL driving apparatus has an advantage that luminance compensation due to deterioration of the EL element can be performed, but the power supply voltage inputted to the inverter is fixed ( For example, when the voltage is AC100V, the inductance value of the choke coil is limited to one type in order to set the initial applied voltage to a certain value.

For this reason, there has been a problem that the resonance point of the LC resonance circuit cannot be changed, and thus the distribution of rising voltage applied to the EL element cannot be arbitrarily selected.

[0008] Further, there is a problem that characteristics such as luminance and life of the EL element are impaired due to fluctuations of the voltage input to the inverter and the like.

The present invention has been made in view of the above-described problems. Even if the power supply voltage fluctuates, stable characteristics of the EL element can be obtained, and a longer life of the EL element can be achieved. It is intended to provide an EL driving device.

[0010]

An EL driving apparatus according to the present invention comprises a buck-boost converter having a variable DC output voltage, and an inverter which receives a DC voltage from the converter and generates a rectangular wave voltage having an arbitrary frequency. And a coil connected in series with the EL element on the output side of the inverter.

[0011]

FIG. 1 is a diagram showing a circuit configuration of an EL driving device according to the present invention. The same reference numerals as in FIG. 5 denote the same components.

In FIG. 1, 1 is a commercial AC power supply, 3 is a choke coil connected in series with an EL element 4 as a load, and an LC resonance circuit is constituted by these inductance L and capacitance C. Reference numeral 5 denotes a step-up / step-down converter of a step-up / step-down circuit system capable of changing a DC output voltage, and includes a rectifier circuit therein. Reference numeral 6 denotes a pulse generator which receives a DC voltage from the step-up / step-down converter 5 and generates a rectangular wave voltage having an arbitrary frequency. The pulse generator 6 is configured as a separately-excited inverter. And are connected in series.

FIG. 2 is a circuit diagram showing an example of the buck-boost converter 5.

This circuit is configured as a chopper type switching power supply combining a general step-down type circuit and a step-up type circuit. In the figure, 7 is the rectifier circuit described above, T
r1 and D1 are transistors and diodes constituting a step-down circuit, Tr2 and D2 are transistors and diodes constituting a step-up circuit, L1 is a choke coil, and C1 is a capacitor.

This embodiment has a circuit configuration in which a buck-boost converter 5 is added to the input side of a pulse generator 6 which is a separately-excited inverter. With this configuration, a constant DC voltage is always supplied to the pulse generator 6 irrespective of fluctuations in the input power supply voltage. That is, the output voltage of the step-up / step-down converter 5 can be easily varied by, for example, the circuit shown in FIG. 2, and therefore, a constant voltage can always be supplied to the pulse generator 6.

Therefore, even if the power supply voltage fluctuates, the output voltage of the buck-boost converter 5, that is, the input voltage of the pulse generator 6, which is a separately-excited inverter, can be kept constant, and the characteristics of the EL element 4 can be stabilized. can get.

Since the output voltage of the step-up / step-down converter 5 can be set arbitrarily, a voltage rise characteristic (voltage rise gradient) due to the deterioration of the EL element 4 as shown in FIG.
Can be arbitrarily set by changing the LC resonance point. FIG. 3 shows the relationship between the drive time of the EL element 4 and the applied voltage, where A is the selectable gradient of the present embodiment,
B indicates the conventional fixed gradient, respectively.

As described above, in the process of deterioration of the EL element 4, by selecting an appropriate voltage rising gradient as shown in FIG. 3, the life of the EL element 4 is extended as shown in FIG. be able to. FIG. 4 shows the relationship between the driving time and the luminance of the EL element 4, wherein C represents the luminance characteristic of the present embodiment, and D represents the luminance characteristic of the conventional example.

[0019]

As described above, according to the present invention,
Even if the power supply voltage fluctuates, stable characteristics of the EL element can be obtained, and the life of the EL element can be extended.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an EL driving device according to the present invention.

FIG. 2 is a circuit diagram showing an example of a buck-boost converter

FIG. 3 is an explanatory diagram showing a relationship between a driving time of an EL element and an applied voltage.

FIG. 4 is an explanatory diagram showing a relationship between a driving time of an EL element and luminance.

FIG. 5 is a circuit configuration diagram showing a conventional example.

FIG. 6 is a circuit diagram showing the oscillation principle of the inverter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 3 Choke coil 4 EL element 5 Buck-boost converter 6 Pulse generator (inverter)

Claims (1)

[Claims] 1. A step-up / step-down converter having a variable DC output voltage, and an inverter which receives a DC voltage from the converter and generates a rectangular wave voltage having an arbitrary frequency, and is connected in series with an EL element on an output side of the inverter. An EL driving device, characterized in that a coil is connected to the EL driving device.