JP3356907B2 - Electroluminescence drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescence (hereinafter, referred to as EL) drive circuit having a booster circuit and a discharge circuit.

[0002]

2. Description of the Related Art A conventional EL driving circuit will be described.
FIG. 4 is a configuration diagram of a conventional EL drive circuit. The EL drive circuit is roughly divided into a battery 1, a booster circuit 2b, a rectifier circuit 3, a discharge circuit 4b, and an EL plate 5. The booster circuit 2b is composed of a coil 8 and a transistor 11, and the discharge circuit 4b is composed of a resistor 12 and a transistor 13. As shown in FIG.
And two different control signals A 'and B' which operate exclusively
Controls the transistors 11 and 13 to operate alternately.

More specifically, the battery 1 supplies power to the booster circuit 2b. The operation of the booster circuit 2b is controlled by the control signal A '. The control signal A ′ is a group of DC pulses as shown in FIG. 5, and controls on / off of the transistor 11 at a high frequency as a base drive signal of the transistor 11. At this time, when the current of the coil 8 decreases, a high back electromotive voltage is generated at the collector of the transistor 11. The generated high back electromotive voltage is applied to the EL plate 5 via the rectifier circuit 3 to charge the electric charge. Rectifier circuit 3 is E
This prevents the charge charged in the L plate 5 from flowing back to the booster circuit 2b. For this reason, the electric charge charged in the EL plate 5 is discharged to the discharge circuit 4.
Released only by b.

The operation of the discharge circuit 4b is controlled by a control signal B '. When the transistor 13 of the discharge circuit 4b is turned on by the control signal B ', the transistor 11 of the booster circuit 2b is turned off. That is, the control signal A ′
And B 'operate alternately and exclusively.

[0005]

In the above EL driving circuit, the voltage of the EL plate 5 when the transistor 13 of the discharging circuit 4b is on (that is, in the discharging process) is:
The voltage instantaneously becomes 0 V as indicated by C 'in FIG. Therefore, the effective value of the voltage applied to the EL plate 5 decreases, and the luminance of the EL plate 5 decreases.

An object of the present invention is to provide an EL driving circuit which raises the luminance of an EL plate while paying attention to the above conventional problems.

[0007]

In order to achieve the above object, the present invention provides an EL drive having means for supplying different control signals to a booster circuit and a discharge circuit, respectively, and operating the booster circuit even during operation of the discharge circuit. Circuit configuration.
An electroluminescence driving circuit according to claim 1 of the present invention is a power supply, a booster circuit including a coil and a first transistor connected in series between terminals of the power supply, and a booster circuit connected to an output of the booster circuit. a discharge circuit configured by two transistors, includes connected the electroluminescent plate between said power supply and said discharge circuit, the gate size of said first transistor said
Make the gate size larger than the gate size of the second transistor,
The first transistor and the second transistor are controlled by different control signals, respectively, so that the booster circuit operates even during the operation of the discharge circuit. The electroluminescence driving circuit according to claim 2 of the present invention includes a power supply, an electroluminescence plate, a booster circuit having a first transistor, and a discharge circuit having a second transistor.
The gate size of the first transistor is larger than the gate size of the second transistor, and the first transistor and the second transistor are controlled by different control signals.

[0008]

In the configuration of the EL drive circuit, since the booster circuit operates even during the operation of the discharge circuit, a high voltage pulse is generated from the booster circuit. Thereby, the voltage of the EL plate increases in the discharging process. Therefore, the effective voltage value of the EL plate increases, and the luminance of the EL plate increases.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an EL drive circuit according to an embodiment of the present invention will be described. The AC drive type EL emits light when an AC voltage is applied to the electrodes. In order to increase the emission luminance of EL using a DC rectangular wave voltage, it is necessary that the peak value is sufficiently high and the effective voltage value is large.

FIG. 1 is a circuit diagram showing a specific embodiment of an EL drive circuit according to the present invention. As shown in the figure, the EL drive circuit includes a battery 1 as a power supply, a booster circuit 2a including a coil 8 and a MOS or bipolar transistor 9, a rectifier circuit 3, a discharge circuit 4a including a MOS or bipolar transistor 10, and a discharge circuit 4a. It is formed by an EL plate 5 connected between the drains of the transistors 10 of the circuit 4a, an oscillation circuit 6, and a frequency dividing circuit 7 for dividing the oscillation frequency of the oscillation circuit 6.

The equivalent capacitance value of the EL plate 5 is 1000
pF. The inductance value of the coil 8 is 1 m
H. The output capacitance value of the transistor 9 is 10 p
F, the gate size of the transistor 9 is 12
mm and the gate length is 5 μm . The output capacitance value of the transistor 10 is 1 pF, and the gate size of the transistor 10 is 1.2 mm in gate width and 5 μm in gate length.

The boosting circuit 2a and the discharging circuit 4a are controlled by two control signals A and B having different frequencies obtained by dividing the signal of the oscillation circuit 6 by the frequency dividing circuit 7, respectively. FIG. 3 shows the control signals A and B. The control signal A has a frequency of about 650 k
Hz, which controls the on / off of the transistor 9 as a gate drive signal of the transistor 9 and operates even during the operation of the control signal B. The control signal B has a frequency of about 500H
At z, it is supplied to the transistor 10. Control signals A and B
When the voltage is 2 V or more, the supplied transistor is turned on. The on time of the transistor 10 is about 30
μs. When the transistor 9 changes from the on-state to the off-state, the current of the coil 8 changes rapidly, so that a high-voltage pulse voltage is generated at the drain of the transistor 9.
The high-voltage output voltage of the booster circuit 2a is applied to the EL through the rectifier circuit 3.
The plate 5 is charged, and the voltage of the EL plate 5 is increased to about 140V. When the transistor 10 of the discharging circuit 4a is in the ON state, the charge charged in the EL plate 5 is discharged. However, since the gate size of the transistor 10 is small, the discharge current is controlled.
As a result, the transistor 9 is turned on / off 20 times. For this reason, the high voltage output voltage generated from the booster circuit 2a charges the EL plate 5 via the rectifier circuit 3, and the voltage of the EL plate 5 increases. The number of times of charging in the discharging process depends on transistor 1
0 is proportional to the number of times the transistor 9 of the booster circuit 2a in the on state changes from the on state to the off state. EL plate 5
The voltage waveform of FIG. 3 is controlled by the control signal A of the booster circuit 2a.
A voltage waveform as shown in FIG. For this reason, the effective voltage value of the EL plate 5 increases, and the EL emission luminance increases.

FIG. 2 shows an EL drive circuit according to a second embodiment of the present invention. The EL drive circuit of this embodiment is different from the circuit of FIG. 1 in that one electrode of the EL plate 5 is grounded, but the structure and operation of the other parts are the same.

[0014]

As is clear from the description of the above embodiment,
According to the present invention, the booster circuit is operated even during the operation of the discharge circuit in the EL drive circuit, and the discharge circuit impedance is made larger than the impedance of the booster circuit, thereby increasing the EL voltage effective value and increasing the EL emission luminance. Is what you can do.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an EL drive circuit according to one embodiment of the present invention.

FIG. 2 is a circuit diagram of an EL drive circuit according to another embodiment of the present invention.

FIG. 3 is an operation waveform diagram at each point of the EL drive circuit of FIG. 1;

FIG. 4 is a circuit diagram of a conventional EL drive circuit.

FIG. 5 is an operation waveform diagram at each point of the EL drive circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 2a Booster circuit 3 Rectifier circuit 4a Discharge circuit 5 EL plate 6 Oscillation circuit 7 Divider circuit 8 Coil 9 Transistor 10 Transistor

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yuji Ueno 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-8-45663 (JP, A) JP-A-8- 55679 (JP, A) JP-A-57-174888 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 33/08 G09G 3/12

Claims (2)

(57) [Claims] 1. A booster circuit comprising a power supply, a coil and a first transistor connected in series between terminals of the power supply, and a discharge circuit connected to an output of the booster circuit and comprising a second transistor. And an electroluminescence plate connected between the power supply and the discharge circuit, wherein a gate size of the first transistor is provided.
Is larger than the gate size of the second transistor.
And the first transistor and the second transistor
There are controlled by different control signals, respectively, electroluminescent drive circuit being characterized in that to work the booster circuit even during operation of the discharge circuit. 2. A power supply, an electroluminescence plate,
A booster circuit having a first transistor, and a discharge circuit having a second transistor, wherein a gate size of the first transistor is larger than a gate size of the second transistor; The second
An electroluminescence driving circuit characterized in that the transistors are controlled by different control signals.