JP2003302925A - Display element driving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display element driving circuit which does not generate dark spots causing to decrease the lives of display elements, decreases power consumption as much as possible, and is also inexpensive and convenient to use. <P>SOLUTION: The display element driving circuit is comprised of a display element 13, and a 1st switching means 11 and a 2nd switching means 12 for changing over power supply to the display element 13 by external operation, and is configured so that one of the two output terminals of the 1st switching means 11 is connected in series with one of those of the 2nd switching means; one of the two terminals of the display element 13 is connected with the node; the other output terminal of the 1st switching means 11 is connected to high potential voltage source V<SB>a</SB>; the other output terminal of the 2nd switching means 12 is connected to a low potential voltage source V<SB>b</SB>; the other output terminal of the display element 13 is connected a voltage source V<SB>c</SB>and when either the 1st switching means 11 or the 2nd switching means 12 is brought into the ON state, the other is brought into the OFF state. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a display device such as a light emitting diode or an organic EL display device.

[0002]

2. Description of the Related Art Conventionally, a drive circuit for an organic EL display element is
As shown in FIG. 11, a driving circuit having a structure in which one transistor 102, which is a switching element for driving, is connected in series is used (Japanese Patent Laid-Open No. 8-23468).
3 gazette). The organic EL display element has a structure in which an insulating thin film of an organic material is sandwiched between electrodes and has high resistance and capacitance components. In the above conventional drive circuit, the switching element 10
When 2 is off, that is, when no voltage or current is applied, the organic EL display element 101 becomes the switching element 102.
Due to the electric charge charged at the time of ON, the same state as that in which a potential equal to or lower than the light emission threshold voltage is applied during a long discharge time is generated. Therefore, an electrochemical action is exerted on the thin film portion to increase black spots and the like, which shortens the life of the device. If a resistor is connected in parallel with the organic EL display element in order to prevent this, the waveform of the drive output is blunted, the efficiency is reduced, and an additional current flows through the resistor during driving, resulting in power loss. Occur.

[0003]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, the present invention does not generate black spots which cause shortening of the element life in a display element, reduces power consumption as much as possible, and is inexpensive and easy to use. The purpose is to provide.

[0004]

The display element drive circuit of the present invention is made to solve the above-mentioned problems.
The first switching means includes a display element, a first switching means for switching power supply to the display element by an external operation, and a second switching means for switching power supply to the display element by an external operation. , And one output terminal of the two output terminals of the second switching means are connected in series, and one terminal of the two terminals of the display element is connected to this connection point, and the output terminal of the first switching means is connected. The other output terminal is connected to a high potential voltage source whose voltage value is set, the other output terminal of the second switching means is connected to a low potential voltage source whose voltage value is set, and the other of the display elements is connected. Is a display element drive circuit in which a terminal of is connected to a voltage source whose voltage value is set, and when either one of the first switching means and the second switching means is in an ON state, Write are those configured such that the off-state. As a result, the electrode of the display element does not become in an open state and is always set to a predetermined potential, so that the capacitive component of the element can be charged and discharged, and by setting the predetermined potential appropriately, A reverse bias can also be applied during non-lighting, and since one of the switching means is always in an off state, no extra current is consumed, the device life is lengthened, and the power consumption can be reduced as much as possible.

Further, the display element drive circuit of the present invention is characterized in that the first and second switching means are field effect transistors. As a result, since it is a field effect transistor, the power consumption of the drive circuit can be reduced as much as possible.

Further, the display element drive circuit of the present invention is characterized in that the first and second switching means are bipolar transistors. This allows
It is possible to provide a low-priced and easy-to-use drive circuit.

Further, the display element drive circuit of the present invention is characterized in that the first and second switching means are optical switching elements. As a result, the external input voltage does not depend on the display element drive voltage, and thus a drive circuit with good usability can be provided.

Further, the display element drive circuit of the present invention is characterized in that the first and second switching means are analog switch elements. This makes it possible to reduce the power consumption of the drive circuit as much as possible and provide a drive circuit that is easy to use.

Further, the display element drive circuit of the present invention comprises a display element and a single-pole double-throw switching means for switching the power supply to the display element by an external operation. It has a common terminal, a normally open terminal, and a normally closed terminal, and connects either one of the normally open terminal and the normally closed terminal to a high potential voltage source whose voltage value is set, and the other terminal The display element is connected to the set low potential voltage source, and the display element is driven by connecting one of the two terminals to the common terminal and the other terminal to the set voltage source. Circuit so that when one of the normally open terminal and the normally closed terminal is in the ON state with the common terminal, the other is in the OFF state with the common terminal Are those that form. As a result, the electrode of the display element does not become in an open state and is always set to a predetermined potential, so that the capacitive component of the element can be charged and discharged, and a predetermined high potential voltage source, low potential voltage source, By properly setting the voltage source and the voltage source, a reverse bias can be applied when the display element is not lit, and since one switching element means is always in the off state, no extra current is consumed and the element life is extended. The power consumption can be reduced as much as possible.

Further, the display element drive circuit of the present invention is characterized in that a high potential current source, a low potential current source, and a current source are used instead of the high potential voltage source, the low potential voltage source, and the voltage source. To do. Thus, when the display element is a light emitting element, stable light emission intensity is obtained, and since it is not necessary to connect a resistor in series with the display element, power consumption is reduced as much as possible, and a user-friendly drive circuit is provided. be able to.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a display element drive circuit used in the present embodiment. In FIG. 1, 11 is a first switching means, 1
2 is a second switching means, 13 is a display element,
Further, Va is a high potential voltage source, Vb is a low potential voltage source, and Vc
Is a voltage source and M is a connection point.

The first switching means 11 and the second switching means 12 are switches for switching the voltage input to the drive circuit, and the switching of the switches is freely turned on / off by an input from the outside of the operator. Can be switched. One terminal 11b of the two terminals of the first switching means 11 is connected to one terminal 12a of the two terminals of the second switching means 12, and its connection point is M.
And On the other hand, the other terminal 11a of the two terminals of the first switching means 11 is connected to the high potential voltage source Va whose voltage value is set to Va, and the second switching means 11 is connected.
The other terminal 12b of the two terminals is connected to the low potential voltage source Vb whose voltage value is set to Vb. The first switching means 11 and the second switching means 12 connected in this way are controlled so that their on / off states are always opposite to each other. That is, when the switching means 11 is on, the switching means 12 is off,
Further, the switching means 12 is set to be on when the switching means 11 is off. The display element 13 is a display element that lights up when either one of the switching means 11 and the switching means 12 is turned on, and a light emitting diode, an organic EL, or the like is used. One terminal 13b of the two terminals of the display element 13 is connected to the connection point M, and the other terminal 13a is connected to the voltage source Vc whose voltage value is set to Vc.

The operation of driving the display element drive circuit used in this embodiment will be described below. Display element 13
Is set to Vt as a threshold voltage required to turn on or display, and the first switching means 11 is turned on,
When the second switching means is off, the display element 13 lights up, and when the first switching means 11 is off and the second switching means is on, the display element 1
When 3 is set to non-lighting or non-display state,
The connection point M is on the anode (anode) terminal side of the display element 13, and the connection point with the voltage source Vc is on the cathode (cathode) terminal side. The voltage value Vc has a relationship of Va-Vc> Vt. Here, if the voltage value Vc is Vc = Vb, it is possible to discharge all the charges charged during lighting, and if the voltage value Vc is Vc> Vb, during non-lighting,
A reverse bias will be applied to the display element 13. When the display element 13 is an organic EL, the reverse bias has an electrochemical action that is opposite to that at the time of lighting. Therefore, the reverse bias is an effective means for extending the life of the display element 13 within a range not exceeding the maximum rating of the reverse bias. Becomes

Contrary to the above setting, when the first switching means 11 is off and the second switching means is on, the display element 13 is lit and the first switching means 11 is on, When the display element 13 is set to non-light when the second switching means is off, the connection point M is on the cathode (anode) terminal side of the display element 13 and the connection point with the voltage source Vc is It is the anode (cathode) terminal side. The voltage value Vc has a relationship of Vc-Vb> Vt. Here, if the voltage value Vc is Vc = Va, all the charges charged during lighting can be discharged during non-lighting, and if the voltage value Vc is Vc <Va, reverse bias is displayed during non-lighting. It will be applied to the element 13. In the case of an organic EL, the reverse bias is an effective means for extending the life of the display element 13 within the range where the maximum rating of the reverse bias is not exceeded, since the electrochemical action acts in the opposite direction to that at the time of lighting.

As described above, in the present embodiment, when either the first switching means 11 or the second switching means 12 is in the on state, the other is set in the off state. Does not become an open state, and the high-potential voltage source Va and the low-potential voltage source Vb always set the predetermined potential, so that the capacitance component of the element can be charged and discharged, and the predetermined voltage source Vc By setting properly, a reverse bias can be applied when the display element is not lit, and since one switching means is always in the off state, no extra current is consumed, the element life is extended, and power consumption is reduced. It can be reduced as much as possible.

Embodiments 2 to 5 of the present invention will be described below with reference to the drawings. Aspects different from Embodiment 1 are as follows.
Since only the switching means is provided, only the aspect of the switching means will be described in each embodiment. (Embodiment 2) FIG. 2 is a block diagram of a display element drive circuit used in this embodiment. In FIG. 2, 21 is a P-type FET, 22 is an N-type FET, 23 is a display element, S is a source terminal, D is a drain terminal, and G is a gate terminal. The display element 23 has the same configuration as the display element 13 used in the first embodiment, and thus a duplicate description will be omitted.

The P-type FET 21 and the N-type FET 22 are P-type and N-type field effect transistors (FET: Fi, respectively).
This is an Eld Effect Transistor, and is a configuration that replaces the first switching means and the second switching means used in the first embodiment. The source terminal S21a of the P-type FET 21 is connected to the high potential voltage source Va side, and the source terminal S22b of the N-type FET 22 is connected to the low potential voltage source Vb side. In addition, P-type FET 21, N-type FE
The drain terminals D21b and 22a of T22 are connected to each other to form a connection point M, which is used as a drive output terminal of the display element 23. A characteristic feature of the display element drive circuit configured as described above is that P-type and N-type field effect transistors are used as the first switching means and the second switching means.

The operation of the switching means used in this embodiment will be described below. Each FET21,
When the gate terminals G21c and 22c of the FET 22 are connected to form an input terminal, if a logic signal 1 (high level) is input to the input terminal, the P-type FET 21 is turned off and the N-type FET 22 is turned on, and the input terminal To logic signal 0
When (low level) is input, it is set so that the P-type FET 21 is turned on and the N-type FET 22 is turned off. In the display element 23, one electrode terminal 23b has a connection point M
Since the other electrode terminal 23a is connected to the voltage source Vc, when the display element 23 is turned on when the logic signal 1 (high level) is input to the input terminal, the connection point M side is the anode ( When the display element 23 is turned on when a logic signal 0 (low level) is input to the input terminal, the voltage source Vc side is set to be the anode (cathode) terminal.

As described above, in the present embodiment, the structure of the drive circuit can be simplified by using the P-type and N-type FETs as the first and second switching means. Also,
Since the FET is a voltage drive type element, it is possible to reduce the power consumption of the display element drive circuit. Furthermore, since the FET is suitable for use as an IC, it is easy to miniaturize. It is suitable for realizing a drive circuit of a display element.

(Third Embodiment) FIG. 3 is a block diagram of a display element drive circuit used in the present embodiment. In FIG. 3, 31 is a PNP type transistor, 32 is an NPN type transistor, 33 is a display element, B is a base terminal, C is a collector terminal, and E is an emitter terminal. The display element 33 is the display element 1 used in the first embodiment.
Since the configuration is the same as that of 3, the duplicate description will be avoided.

The PNP-type transistor 31 and the NPN-type transistor 32 are bipolar transistors, and have a configuration that replaces the first switching means and the second switching means used in the first embodiment. The emitter terminal E of the PNP type transistor 31 is connected to the high potential voltage source Va side, and the emitter terminal E of the NPN type transistor 32 is connected to the low potential voltage source Vb side.
The two collector terminals C are connected to each other and the connection point M is used as a drive output terminal of the display element 33. A characteristic of the display element drive circuit configured as described above is that the PNP type transistor 31 and the NPN type transistor 32 which are bipolar transistors are used as the first switching means and the second switching means. is there.

The operation of the switching means of this embodiment will be described below. Each transistor 31,
When the logic 1 signal (high level) is input to the input terminal when the input terminal is connected to the base terminal B of 32 through a resistor, the PNP transistor 31 is turned off and the NPN transistor 32 is turned on. Logic 0 at input terminal
When a signal (low level) is input, the PNP transistor 31 is turned on and the NPN transistor 32 is turned off.

As described above, in the present embodiment, the PNP type transistor 31 and the NPN type transistor 32 are used as the first switching means and the second switching means, thereby simplifying the structure of the display element drive circuit. Since the bipolar transistors such as the PNP type transistor and the NPN type transistor are suitable for an IC (integrated circuit), the circuit can be downsized.

(Embodiment 4) FIG. 4 is a block diagram of a display element drive circuit used in this embodiment. In FIG. 4, 41 is a first optical switching element, 42 is a second optical switching element, 43 is a display element, and V
a is a high potential voltage source, Vb is a low potential voltage source, Vc is a voltage source, C is a collector terminal, and E is an emitter terminal. The display element 43 has the same configuration as the display element 13 used in the first embodiment, and thus a duplicate description will be omitted.

The first optical switching element 41 and the second optical switching element 42 are optical switching elements composed of a light emitting diode and a phototransistor, and are the first switching means and the second switching used in the first embodiment. This is an alternative to the means. The collector terminal C of the optical switching element 41 is on the high potential voltage source Va side, and the emitter terminal E of the optical switching element 42 is on the low potential voltage source Va.
It connects to the b side, the emitter terminal E of the optical switching element 41 and the collector terminal C of the optical switching element 42 are connected, and the connection point M is made into the drive output terminal of the display element 43. The characteristic feature of the display element drive circuit configured as above is that the first optical switching element and the second optical switching element are used as the first switching means and the second switching means. is there.

The operation of the switching means of this embodiment will be described below. The input circuit is configured by using the invert circuit 45 so that one of the light emitting diodes on the input side of each of the optical switching elements 41 and 42 is in a light emitting state and the other light emitting diode is in a non-light emitting state. At this time, when a signal that causes the light emitting diode on the input side of the optical switching element 41 to be in a light emitting state is input, the optical switching element 41 is turned on and the optical switching element 42 is turned off. The optical switching element 41 is set to the off state and the optical switching element 42 is set to the on state when a signal that causes the side light emitting diode to be in the non-light emitting state is input.

As described above, in the present embodiment, the first optical switching element and the second optical switching element are used as the first switching means and the second switching means. It is simple, and the input signal can be a low voltage signal independent of the driving voltage. In this embodiment, an optical switching element including a light emitting diode and a phototransistor as a light receiving element has been described. However, a photodetecting element such as a photodiode or selenium as a light receiving element and a MOS-FET as an output drive unit may be used. Good.

(Fifth Embodiment) A fifth embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a block diagram of a display element driver circuit used in this embodiment. In FIG. 5, 51 is a first analog switch, 52 is a second analog switch, 53 is a display element, and Va
Is a high potential voltage source, Vb is a low potential voltage source, Vc is a voltage source,
M is a connection point, and C is a control input terminal. Display element 53
2 has the same configuration as that of the display element 13 used in the first embodiment, and a duplicate description will be omitted.

The first analog switch 51 and the second analog switch 52 are substitutes for the first switching means and the second switching means used in the first embodiment. One output terminal of the analog switch 51 is connected to the high potential voltage source Va side, and the analog switch 52
One of the output terminals is connected to the low-potential voltage source Vb side, and the other terminals of the analog switches 51 and 52 are connected to each other, and the connection point M is used as a drive output terminal of the display element 53. The characteristic features of the display element drive circuit configured as above are
There is an analog switch used as a switching means.

The operation of the switching means of this embodiment will be described below. One of the control input terminals C of the analog switches 51 and 52 directly inputs the drive input signal, and the other control input terminal C constitutes an input circuit which inputs the drive input signal by inverting the logic of the inverter circuit 55. At this time, when a logic 1 signal (high level) is input to the input terminal C of the analog switch 51, the analog switch 51 is turned on and the analog switch 52 is turned off, and a logic 0 signal is input to the input terminal C of the analog switch 51. When (low level) is input, the analog switch 51 is turned off and the analog switch 52 is turned on.

As described above, in the present embodiment, by using the analog switch as the switching means, the circuit is simple, and since the FET (field effect transistor) is used, it can be easily integrated into an IC, and the input signal is further improved. Can use a low voltage signal independent of the drive voltage.

(Sixth Embodiment) The sixth embodiment will be described below with reference to FIG. 6 shows a block diagram of a display element drive circuit used in this embodiment. In FIG. 6, 61 is a single-pole / double-throw switching means, 62 is a display element, and Va is a high potential voltage source. Vb is a low potential voltage source, Vc is a voltage source, NO is a normally open terminal, C
O is a common terminal and NC is a normally closed terminal.

The single-pole double-throw switching means 61 has a common terminal CO and a normally open terminal N as output terminals.
It has three terminals, O and a normally closed terminal NC, and can freely control the ON / OFF conduction state with reference to the common terminal from the outside. 2 of the normally open terminal NO and the normally closed terminal NC of the switching means 61
One of these terminals is connected to the high potential voltage source Va and the other is connected to the low potential voltage source Vb. In FIG. 6, the voltage value of the normally open terminal NO of the switching means 61 is Va.
The case where the normally closed terminal NC is connected to the low potential voltage source Vb whose voltage value is set to Vb is shown in FIG. The display element 62 has one electrode terminal connected to the common terminal CO of the single-pole double-throw switching means 61 and the other electrode terminal connected to the voltage source Vc. The display element 62 is a display element that lights up when either the normally open terminal NO or the normally closed terminal NC is in the ON state with the common terminal CO, and a light emitting diode, an organic EL, or the like is used. One terminal 62a of the two terminals of the display element 62 is connected to the common terminal CO, and the other terminal 62b is a voltage source Vc whose voltage value is set to Vc.
Connect with. The characteristic feature of the display element drive circuit configured as described above is that either the normally open terminal NO or the normally closed terminal NC is the common terminal C.
It is set such that when it is in the ON state with O, the other is in the OFF state with the common terminal CO.

The operation of the display element drive circuit of this embodiment will be described below. The threshold voltage required to turn on the display element 62 is set to Vt, the common terminal CO and the normally open terminal NO of the single-pole double-throw switching means 61 are turned on, and the common terminal CO and the normally closed terminal NC are turned on. When the display is off, the display element 62 lights up,
OFF between common terminal CO and normally open terminal NO,
When the display element 62 is set not to light when the common terminal CO and the normally closed terminal NC are on, the common terminal CO is on the anode (anode) terminal side of the display element 62 and is connected to the voltage source Vc. The connection point is on the cathode (cathode) terminal side. The voltage value Vc has a relationship of Va-Vc> Vt. Here, if the voltage value Vc is Vc = Vb, all the charges charged during lighting can be discharged during non-lighting, and if the voltage value Vc is Vc> Vb, reverse bias can be applied during non-lighting. become. When the display element 62 is an organic EL, the application of the reverse bias is effective in extending the element life of the display element 62 within the range where the maximum rating of the reverse bias is not exceeded because the electrochemical action acts in the opposite direction to the time of lighting. It becomes a means.

On the contrary to the above setting, the common terminal CO
Between normally open terminal NO and OFF, common terminal CO
And the normally closed terminal NC are in the ON state, the display element 62 lights up, the common terminal CO and the normally open terminal NO are in the ON state, and the common terminal CO and the normally closed terminal NC are in the OFF state, the display element 62 is in the ON state. , The common terminal CO is on the cathode (cathode) terminal side of the display element 62, and the connection point with the voltage source Vc is on the anode (anode) terminal side. Then, the voltage value Vc is
There is a relationship of Va-Vc> Vt. Here, if the voltage value Vc is Vc = Vb, all the charges charged during lighting can be discharged during non-lighting, and if the voltage value Vc is Vc> Vb, reverse bias can be applied during non-lighting. become.
When the display element 62 is an organic EL, the application of the reverse bias is effective in extending the element life of the display element 62 within the range where the maximum rating of the reverse bias is not exceeded because the electrochemical action acts in the opposite direction to the time of lighting. It becomes a means.

As described above, in this embodiment, when either the normally open terminal NO or the normally closed terminal NC is in the ON state with the common terminal CO, the other is in the OFF state with the common terminal CO. Since the electrode of the display element 62 is not set to the open state and is always set to the predetermined potential, the capacitance component of the element can be charged / discharged, and the predetermined high potential voltage source Va and the low potential voltage source V can be charged and discharged.
By setting b and the voltage source Vc to appropriate voltage values, a reverse bias can be applied when the display element 62 is not lit,
Further, since one of the switching element means is always in the off state, no extra current is consumed, the element life is lengthened, and the power consumption can be reduced as much as possible.

In the first to sixth embodiments, the display element drive circuit driven by voltage has been described above. However, the display element drive circuit such as a light emitting diode or an organic EL element which controls the brightness by flowing a current has a voltage source. Often supplied as a current source. 8 to 10 are diagrams showing an example of the invention derived from the first embodiment,
A resistor is inserted in the drive circuit. As a simple circuit for handling the current value for controlling the drive of the display element, there is a circuit in which a resistor is inserted in the drive circuit as shown in FIG. 8 and FIG. Aspects have the disadvantage of causing power consumption. On the other hand, FIG.
The voltage source can also be treated as a current source, as shown at 0. In FIG. 8, the current values supplied to the terminals supplying the voltages of the voltage values Va, Vb, Vc are Ia,
Ib, Ic, and Vaa, Vbb, Vcc voltage sources and R for supplying currents Ia, Ib, Ic, respectively.
If the resistors a, Rb, and Rc are used, Vaa
-Va = Ia * Ra, Vbb-Vb = Ib * Rb, Vc
There is a relation of c-Vc = Ic * Rc, and the current supply and the voltage supply can be handled in the same way. Next, a display element drive circuit driven by current will be described.

(Seventh Embodiment) The seventh embodiment of the present invention will be described below with reference to FIG. FIG. 7 is a block diagram of a display element driver circuit used in this embodiment. In FIG. 7, 71 is a first switching means, 72 is a second switching means, 73 is a display element, and Ia is a current value I.
a is a high-potential current source, Ib is a low-potential current source whose current value is Ib, and Ic is a current source whose current value is Ic. The characteristic feature of the display element drive circuit configured as described above is that the high-potential voltage source Va, the low-potential voltage source Vb, and the voltage source Vc used in the first to sixth embodiments are respectively the high-potential current source Ia. , The low-potential current source Ib and the current source Ic.

The operation of driving the display element drive circuit used in this embodiment will be described below. Display element 73
Is the minimum current required to turn on or display the
And the first switching means 71 is turned on,
When the second switching means 72 is in the off state, the display element 73 lights up, when the first switching means 71 is in the off state and the second switching means 72 is in the on state,
When the display element 73 is set to the non-lighting state or the non-display state, the connection point M is the anode (anode) of the display element 73.
It is on the terminal side, and the connection point with Ic is on the cathode (cathode) terminal side. The current value Ic has a relationship of Ia-Ic> It. Here, if the current value Ic is Ic = Ib, it is possible to discharge all the charges charged during lighting, and if the current value Ic is Ic> Ib, the reverse bias is displayed during non-lighting. It will be applied to the element 73. In the case of an organic EL, the reverse bias is an effective means for extending the element life of the display element 73 within the range where the maximum rating of the reverse bias is not exceeded because the electrochemical action acts in reverse to the time of lighting.

Contrary to the above setting, when the first switching means 71 is off and the second switching means 72 is on, the display element 73 is turned on and the first switching means 71 is turned on. ON, second switching means 72
When the display element 73 is set to non-light when the display element 73 is off, the connection point M becomes the cathode (anode) terminal side of the display element 73, and the connection point with the voltage source Vc is the anode (cathode) terminal. Be on the side. The current value Ic is Ia-
There is a relation of Ic> It. When the current value Ic is set to Ic = Ia, all the charges charged at the time of lighting can be discharged at the time of non-lighting. When the current value Ic is set to Ic> Ia, a reverse bias is applied to the display element 73 at the time of non-lighting. Will be applied. In the case of an organic EL, the reverse bias is an effective means for extending the element life of the display element 73 within the range where the maximum rating of the reverse bias is not exceeded because the electrochemical action acts in reverse to the time of lighting.

As described above, in this embodiment, when either the first switching means 71 or the second switching means 72 is in the ON state, the other is set in the OFF state. Does not become an open state, and the high-potential current source Ia and the low-potential voltage source Ib are always set to a predetermined potential, so that the capacitive component of the element can be charged and discharged, and the determined potential is appropriate. By setting to, a reverse bias can be applied when the display element is not lit, and since one switching means is always in the off state, extra current is not consumed, the element life is extended, and power consumption is reduced as much as possible. Can be made.

In this embodiment, the voltage sources Va, V
It is needless to say that this mode can be applied to the second to sixth embodiments because only b and Vc are replaced with the current sources Ia, Ib and Ic. Further, in the above-described embodiments of claims 1 to 7, the voltage values Va, Vb, Vc of the voltage supply source and the current values Ia, Ib, Ic of the current supply source are set independently. One or more of the determined values may be zero, that is, the ground level. Further, although the organic EL display element has been described as an example in the present embodiment, the present invention is not limited to the organic EL display element, and any display element can be applied.

[0043]

As is apparent from the above description, according to the present invention, the terminal of the display element is always supplied with a predetermined potential even when the display element is not lit, so that the display element is charged when lit. Since the electric charge is discharged when it is not lit and a reverse bias can be applied, the electric charge when lit is not accumulated in the display element, resulting in black dots caused by the electrochemical action which is a factor of the short life of the display element. Can be suppressed, the life of the display element can be extended, and power consumption for driving the display element drive circuit can be extremely reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a display element drive circuit used in a first embodiment of the present invention.

FIG. 2 is a block diagram showing a display element drive circuit used in a second embodiment of the present invention.

FIG. 3 is a block diagram showing a display element drive circuit used in a third embodiment of the present invention.

FIG. 4 is a block diagram showing a display element drive circuit used in a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a display element drive circuit used in a fifth embodiment of the present invention.

FIG. 6 is a block diagram showing a display element drive circuit used in a sixth embodiment of the present invention.

FIG. 7 is a block diagram showing a display element drive circuit used in a seventh embodiment of the present invention.

FIG. 8 is a block diagram showing a state in which a resistor is inserted in the display element drive circuit according to the first embodiment of the present invention.

FIG. 9 is a block diagram showing a state in which a resistor is inserted in the display element drive circuit according to the first embodiment of the present invention.

FIG. 10 is a block diagram showing a state in which a resistor is inserted in the display element drive circuit according to the first embodiment of the present invention.

FIG. 11 is a block diagram showing a conventional display element drive circuit.

[Explanation of symbols]

11, 71 First switching means 12, 72 Second switching means 13, 23, 33, 43, 53, 62, 73 Display element 21 P-type FET (field effect transistor) 22 N-type FET (field effect transistor) 31 PNP type transistor (bipolar transistor) 32 NPN type transistor (bipolar transistor) 41, 42 Optical switching element 51, 52 Analog switch 61 Single pole double throw type switching means Va High potential voltage source Vb Low potential voltage source Vc Voltage source M Connection point CO common terminal NO normally open terminal NC normally closed terminal

Claims (7)

[Claims] 1. A display element, first switching means for switching power supply to the display element by an external operation, and second switching means for switching power supply to the display element by an external operation. Becomes the first
Switching means and second switching means 2
One of the two output terminals is connected in series, one of the two terminals of the display element is connected to this connection point, and the other output terminal of the first switching means is connected to the voltage value. Is connected to a high potential voltage source, the other output terminal of the second switching means is connected to a low potential voltage source whose voltage value is set, and the other terminal of the display element is connected to the voltage value. Is a display element drive circuit connected to a voltage source set to, and is configured such that when one of the first switching means and the second switching means is in an on state, the other is in an off state. Display element drive circuit. 2. The display element drive circuit according to claim 1, wherein the first and second switching means are field effect transistors. 3. The display element drive circuit according to claim 1, wherein the first and second switching means are bipolar transistors. 4. The first and second switching means are optical switching elements.
The display element drive circuit described in 1. 5. The display element drive circuit according to claim 1, wherein the first and second switching means are analog switch elements. 6. A display element and a single-pole double-throw switching means for switching the power supply to the display element by an external operation. The single-pole double-throw switching means comprises:
A common terminal, a normally open terminal, and a normally closed terminal are provided, and one of the normally open terminal and the normally closed terminal is connected to a high-potential voltage source whose voltage value is set, and the other terminal is connected to the voltage value. Connected to a low potential voltage source that is set, the display element,
Connect one of the two terminals to the common terminal,
A display element drive circuit in which the other terminal is connected to a voltage source having a voltage value set, and when one of the normally open terminal and the normally closed terminal is in the ON state with the common terminal, the other is A display element drive circuit configured to be in an off state with the common terminal. 7. A high potential current source, a low potential current source, and a current source are used in place of the high potential voltage source, the low potential voltage source, and the voltage source. Display element drive circuit.