JPH0339917Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a light emission drive circuit for an electroluminescent element (hereinafter referred to as an EL element) that emits light by applying a pulse voltage.

Conventional technology Conventionally, a light emitting drive circuit for an EL element that applies a pulse voltage to the EL element to emit light has been developed, for example, by
Various methods are known, such as Japanese Patent No. 52-45466.

The light emitting drive circuit disclosed in the above publication has two switch elements, transistors Tr1, Tr2, and
The first and second switch circuits 1 and 2 in which Tr3 and Tr4 are connected in series are connected in parallel to the power supply E, and the EL element 3 is connected to the first and second switch circuits 1 and 2 in series.
2 two transistors Tr1, Tr2 and Tr
3. Connected between connection points A and B of Tr4.

Furthermore, the pulse voltage is
It is equipped with control means 4 and 5 for applying voltage to Tr1, Tr2 and Tr3 and Tr4 at appropriate timing, and the control means 4 and 5 control the above-mentioned four transistors Tr.
Controls the conduction timing of Tr 1 to Tr 4, supplies the voltage of the power source E to the EL element 3 in a pulsed manner in the opposite direction,
It emits light.

Problems to be Solved by the Invention The above-described light emitting drive circuit can apply the output voltage of the power source E to both ends of the EL element 3 in the forward and reverse directions, but the transistors Tr1, Tr2 and
Depending on the supply timing of the pulse voltages applied to Tr3 and Tr4 from the control means 4 and 5, the transistors Tr1 to Tr4 may become conductive at the same time and be destroyed.

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a light emission driving circuit for an EL element in which the switch elements of two switch circuits do not become conductive at the same time.

Means for Solving the Problems The light emitting drive circuit for an EL element according to the present invention includes first and second switch circuits in which a thyristor, a diode, and a switch element are connected in series, which are connected in parallel to both ends of a power supply, and the power supply and the above. The gate means of the thyristor is connected between the gate and cathode of the thyristor, and the gate means of the thyristor is connected between the gate of the thyristor and the cathode of the diode that constitutes the same switch circuit as the thyristor. The thyristor comprises a reverse bias means for reverse biasing the gate, and a control circuit connected to the control pole of the switch element of each of the first and second switch circuits to alternately make both the switch elements conductive. It is characterized in that an EL element is connected between the connection points with the diode.

Function Since the light emitting drive circuit of the EL element according to the present invention is constructed as described above, when the switch elements of the first and second switch circuits are made conductive alternately, the same switch circuit as the conductive switch element is activated. Current flows through the formed diode, and the resulting voltage drop causes the thyristor of the same switch circuit to be reverse biased.

Therefore, the thyristors of the same switch circuit as the conductive switch element are necessarily rendered non-conductive, and only the thyristors of different switch circuits are rendered conductive.

In other words, when a switch element is conductive and current flows, the thyristors in the same switch circuit are always controlled to be non-conductive by the reverse bias caused by the voltage drop of the diode, so all switch elements including the thyristor are simultaneously turned off. There is no conduction,
This means that two switch circuits are never conductive at the same time.

Embodiment FIG. 1 is an electric circuit diagram showing an embodiment of the light emitting driving circuit for an EL element according to the present invention. In the figure, the same numbers and symbols as those in FIG. 2 indicate the same functional members. .

As is clear from FIG. 1, the first and second switch circuits 6,
7 are thyristor SCR1, diode 8,
Series connection of transistor Tr2 which is a switch element, thyristor SCR2, diode 9,
It consists of a series connection of transistors Tr4, which are switch elements.

Resistors R1, R2 and R
3 and R4 are connected as gate means 10 and 11.

Further, the gates of the thyristors SCR1 and SCR2 are connected to the cathodes of diodes 8 and 9 forming the same switch circuits 6 and 7, respectively, by power supply lines L1 and L2. Therefore, when current flows through diode 8 or 9,
The dropped voltage reverse biases the gate of the thyristor SCR1 or SCR2 via the power supply path L1 or L2.

That is, the power supply path L1 or L2 forms the reverse bias means 12 and 13.

The bases, which are the control poles of transistors Tr2 and Tr4, which are switch elements of the first and second switch circuits 6 and 7, are connected to an oscillator 15 that outputs a pulse signal, resistors R5, R6, R7, R8, and an inverter 16. The control circuit 14 is connected to the control circuit 14 shown in FIG.

The EL element 3 includes first and second switch circuits 6,
7, i.e. each thyristor SCR1,
It is connected between connection points C and D between SCR2 and diodes 8 and 9.

Hereinafter, the method according to the present invention consisting of the above-mentioned configuration will be explained.
The operation of one embodiment of the light emission driving circuit for the EL element will be described.

Now, when a predetermined voltage is output from the power supply E and a high level signal is output from the oscillator 15 of the control circuit 14, this high level signal is transmitted to the resistors R5 and R6.
After being inverted, that is, made low level by the inverter 16,
It is supplied to transistor Tr4 via resistors R7 and R8.

Therefore, the transistor Tr4 is made non-conductive, while the transistor Tr2 is made conductive because current flows through the resistor R1 or the resistors R3 and R4, the EL element 3, and the diode 8.

As a result, the thyristors SCR1 and SCR2 try to conduct together, but the gate of the thyristor SCR1 is reverse biased by the voltage drop generated in the diode 8, so the thyristor SCR1 does not become conductive. thyristor
Only SCR2 becomes conductive.

Therefore, a current flows through the loop of the thyristor SCR2, the EL element 3, the diode 8, and the transistor Tr2, and the EL element 3 emits light. When charging of the EL element 3 is completed, the current flowing through the thyristor SCR2 becomes less than the holding current, and the thyristor SCR2 returns to a non-conducting state, with the cathode side of the thyristor SCR2 at a + potential and the cathode side of the thyristor SCR1 at a - potential.
becomes electric potential.

On the other hand, after an appropriate period of time taking into consideration the charging characteristics of the EL element 3, when the signal level output from the oscillator 15 is reversed and made low, the transistor Tr2
is made non-conducting, and the thyristor described above
The reverse bias state of the gate of SCR1 is released,
Further, the low level signal is inverted to high level by the inverter 16 and is supplied to the transistor TR4 via the resistors R7 and R8.

Therefore, contrary to the above case, the transistor
When TR4 becomes conductive, the gate of thyristor SCR2 is reverse biased by the voltage drop generated across diode 9, and this thyristor SCR2 becomes non-conductive.

In other words, transistor Tr4 and thyristor
SCR1 becomes conductive, and a current flows through the EL element 3 in the opposite direction to that in the previous case via the thyristor SCR1, diode 9, and transistor Tr4, and the EL element 3 naturally emits light.

Thereafter, the above-described operation is repeated by inverting the signal level output from the oscillator 15 of the control circuit 14 at appropriate intervals.

Therefore, the output voltage of the power source E is applied to both ends of the EL element 3 in the opposite direction, that is, an AC pulse voltage with a voltage width twice that of the output voltage is supplied, and the desired light emitting operation is performed. It turns out.

As is clear from the above operation, in the light emission driving circuit for the EL element according to the present invention, when the transistor Tr2 is made conductive by the control circuit 14,
The thyristor SCR1, which forms the first switch circuit 6 together with the transistor Tr2, is always rendered non-conductive due to the voltage drop generated across the diode 8 of the same switch circuit 6, and conversely, when the transistor Tr4 is rendered conductive, the transistor Tr4 becomes conductive.
The thyristor SCR2, which together with the switch circuit 4 forms the second switch circuit 7, is necessarily rendered non-conductive by the voltage drop generated across the diode 9 of the same switch circuit 7.

Therefore, the thyristors SCR1 and SCR2 are not conductive at the same time, that is, the first and second thyristors
The switch circuits 6 and 7 are never conductive at the same time.

In addition, since the present invention uses a thyristor, the amount of energy required for its conducting operation is reduced, that is, the power consumption used for purposes other than the light emitting operation of the EL element is reduced. In addition, EL
The supply characteristics of the energy supplied to the element can also be made steep, which is advantageous in terms of luminance of the EL element compared to the conventional configuration using transistors.

Effects of the invention The light emitting drive circuit for an EL element according to the invention is comprised of a series connection body of a thyristor, a diode, and a switch element that are connected in parallel to a power supply. Since an EL element is connected between the points and gate means and reverse bias means are provided at the gate of each thyristor, even if the drive timing of the switch element is different from the desired timing, the 2
Two thyristors do not become conductive at the same time, that is, the first and second switch circuits do not become conductive at the same time, and this has the effect of reliably preventing destruction of the element that may occur due to such simultaneous conduction.

In addition, since a thyristor is used,
In addition to reducing the power consumption of EL elements other than light emission, it is also possible to improve the supply characteristics of the energy supplied to the EL elements, which means that steeper energy supply characteristics can be achieved with less power consumption, which is advantageous in terms of brightness. We can also expect the following effect.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram showing an example of the light emitting drive circuit for an EL element according to the present invention, and Fig.
FIG. 2 is a schematic electrical circuit diagram of an example of a light emission drive circuit for an EL element. 6...First switch circuit, 7...Second switch circuit, 8, 9...Diode, 10, 11...
...gate means, 12, 13...reverse bias means,
14...control circuit, 15...oscillator, 16...inverter.

Claims (1)

[Scope of utility model registration request] The first and second thyristors, diodes, and switch elements connected in parallel to both ends of the power supply are connected in series.
a switch circuit, a gate means of the thyristor connected between the power supply and the gate and cathode of the thyristor, and a connection between the gate of the thyristor and the cathode of the diode constituting the same switch circuit as the thyristor. and a reverse bias means for reverse biasing the gate with a voltage drop generated in the diode, which is connected to a control pole of each of the switch elements of the first and second switch circuits, and alternately conducts both of the switch elements. and an EL control circuit that connects an EL element between the connection point of the thyristor and the diode.
Light emitting drive circuit for the device.