JPH04355789A - Device for driving plane type display panel - Google Patents

Abstract

PURPOSE:To offer the driving device which reduces the power consumption regarding the driving of scanning electrodes by utilizing some of electric charges, used to drive a (k)th scanning electrode, to drive a (K+1)th scanning electrode. CONSTITUTION:A two-way switch 11 is provided between an odd-numbered electrode scanning side driver 14 and an even-numbered electrode scanning side driver 15 and after the writing of the (k)th scanning electrode ends, some of the electric charges accumulated in the (k)th scanning electrode are transferred to the (k+1)th scanning electrode through the two-way switch 11 to reduce electric charges which are newly applied.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a flat panel display device used for displaying characters and graphics, and in particular to an electroluminescent (hereinafter abbreviated as EL) device. The present invention relates to a drive device for a flat panel display panel.

0002

2. Description of the Related Art A matrix display device using a thin film EL panel will be explained as an example of a conventional matrix display panel driving device. Figure 3 shows this conventional thin film EL.
10 shows a block diagram of a drive circuit of a display device.
1 is an EL display panel composed of EL display elements, 1 is a data electrode, and 2 is a scan electrode, which are orthogonal to each other. 3 is a data side driver that applies a modulation voltage [Vm] to the EL display element via the data electrode 1 and whose output stage is composed of a push-pull transistor QD; 4 is a write voltage to the EL display element via the scan electrode 2; [-Vw] or refresh voltage [Vr] is applied, and the output stage is composed of a pull-down transistor QS; 5 is a modulation voltage [Vm
], 6 is a write voltage [-
7 is a refresh voltage generation circuit that supplies a refresh voltage [Vr], 8 is a first discharge circuit for discharging the write voltage [-Vw] charged in the EL element to the ground. , 9 is a second discharge circuit for discharging the refresh voltage (Vr) charged in the EL element to the ground.

The data side driver 3 receives a display data signal Di.
, data clock signal CKD, data enable signal DEN, and data latch signal DLS. Similarly, the scanning side driver 4 receives the scanning signals SD,
Scan/shift signal CKS, scan/enable signal SEN
, scanning strobe signal SST. It is assumed that the driver operates in response to each control signal as shown in Table 1.

0004

[Table 1]

In this driving method, it is necessary to apply a write voltage [-Vw] and a refresh voltage [Vr] to the ground line of the scanning side driver 4, so the scanning side driver 4 must perform a floating operation. The control signal for controlling the side driver 4 needs to be insulated by photocoupler coupling or the like. Note that the number of data electrodes here is m, D1 to Dm, and the number of scan electrodes is n, S1 to Sn.

The operation of the drive circuit configuration in the conventional thin film EL display device configured as described above will be explained with reference to a timing chart of drive voltages applied to each electrode in FIG. However, in FIG. 4, 1H is 1 scanning period, 1
V indicates one frame period. In line sequential scanning, the data side driver 4 causes the EL to emit light in response to the display data signal Di for one line of the selected scan electrode (FIG. 4(a)).
On/off control of the push-pull transistor QD is performed so that the modulation voltage generation circuit 5 outputs the modulation voltage [Vm] only to the display element.

On the other hand, on the scanning side, as shown in FIG. 4(b), in synchronization with the data side driver 3, the scanning side driver 4 sequentially drives the pull-down transistors for one scan in the order of S1 to Sn of the scanning electrodes 2. It is turned on only during the period, and the write voltage generation circuit 6 continuously generates the write voltage [-
Since the writing voltage [-Vw] is applied only to the scan electrode selected by the scan side driver 4, all the EL elements on the selected scan electrode line are charged. As a result, the modulation voltage [Vm] and the write voltage [-V
w] are superimposed, and a voltage of Vm+Vw is applied to the light-emitting display element and a voltage of Vw is applied to the non-light-emitting display element. Light emission starting voltage [Vt
h], by setting Vth≧Vw and [Vm+Vw]≧Vth, information data can be displayed in the form of light emission.

After completion of line sequential scanning from S1 to Sn, a refresh voltage [Vr
: generally Vm+Vw] is reversely charged again to all the EL display elements of the EL display panel 10, and the EL display elements are refreshed.
The display element emits light again to complete one frame. Such a driving method in which light is emitted twice in one frame is called a simultaneous inversion refresh driving method.

FIG. 5 shows a timing chart of control signals corresponding to a series of operations. Here, MD is a control signal for the modulation voltage generation circuit 5, W is a control signal for the write voltage generation circuit 6, REF is a control signal for the refresh voltage generation circuit 7, PD is a control signal for the first discharge circuit 8, and GD is a control signal for the first discharge circuit 8.
is a control signal for the second discharge circuit 9.

The operating time in one scanning period [Th] of 1H is roughly divided into a writing period [Tw] and a charge discharging period [Td]. Usually, the modulation period [Tm] is Tm=T
It is set to w. This charge discharge period [Td] is the high voltage write voltage [-
Vw] is maintained for a long period of time, the insulation properties of the EL element will deteriorate, resulting in fatal defects such as dielectric breakdown and electrode disconnection of the EL element.
It is necessary to immediately discharge the high voltage accumulated charge, and this is the purpose of the discharge period.

In the discharge operation, when DEN is L, the output of the data side driver 3 is grounded, and when PD is H, the first discharge circuit 8 is grounded, so that the accumulated charge of the EL element is transferred from the ground to the data side driver 3 to the data electrode. Discharge is performed in a loop of 1→EL element→scanning electrode 2→scanning side driver 4→first discharge circuit 8→ground.

Note that T1 and T2 are pause periods for preventing the write operation and the discharge operation from overlapping and the output of the write voltage generation circuit 6 being short-circuited to the ground via the first discharge circuit 8.

[0013]

However, in the above configuration, the write voltage once charged to the kth scan electrode is completely discharged to the ground during the charge discharge period [Td]. When driving the th scan electrode, it was necessary to add all the charges necessary for driving from the write voltage generation circuit. In other words, there was a problem in that the charges for driving the scanning electrodes were disposable.

In view of this point, the present invention does not discharge all the charges once used to drive the k-th scan electrode, but reuses some of the charges when driving the k+1-th scan electrode. Another object of the present invention is to provide a driving device for a flat panel display panel that reduces the power required to drive scan electrodes.

[0015]

[Means for Solving the Problems] The present invention provides a display panel in which a display element is interposed between data electrodes and scanning electrodes that are orthogonal to each other, a data-side driver connected to the data electrodes, and an odd-numbered side driver. An odd electrode scan driver connected to the scan electrode, an even electrode scan driver connected to the even scan electrode, a modulation voltage generation circuit that applies a modulation voltage to the display element via the data side driver, and an odd electrode scan driver connected to the scan electrode. an odd electrode write voltage generation circuit that applies a write voltage to the display element via the side driver, an even electrode write voltage generation circuit that applies the write voltage to the display element via the even electrode scan side driver, and an odd electrode scan side driver. and an odd electrode discharge circuit connected between the driver and the ground, an even electrode discharge circuit connected between the even electrode scanning side driver and the ground, and a bidirectional characteristic between the odd electrode scanning side driver and the even electrode scanning side driver. After writing to the k-th scan electrode is completed, a part of the electric charge charged in the k-th scan electrode is transferred to k via the bidirectional switch element.
This is a driving device for a flat panel display panel characterized in that the scanning electrode is moved to the +1st scanning electrode.

[0016]

[Operation] With the above-described configuration, the present invention uses a switch element having bidirectional characteristics provided between an odd-numbered electrode scanning side driver and an even-numbered electrode scanning side driver to By transferring part of the charge charged in the th scan electrode to the k+1th scan electrode, the charge newly applied to drive the k+1th scan electrode from the write voltage generation circuit can be reduced. As a result, power consumption for driving the scan electrodes is reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of a driving device for a flat panel display panel according to a first embodiment of the present invention. In FIG. 1, 10 is an EL display panel, 11 is a bidirectional switch, 12 is an odd number side scan electrode of S1 to Sn-1, and 13 is a bidirectional switch.
Even number side scan electrodes S2 to Sn, 14 are odd number side scan electrodes 1
15 is an even number electrode scanning side driver connected to the even numbered scanning electrode 13;
6 is an odd electrode write voltage generation circuit that supplies a write voltage [-Vw] to the odd electrode scan electrode 12 via the odd electrode scan driver 14; 17 is an even electrode scan driver 1;
A write voltage [-Vw
18 is an odd-numbered electrode first discharge circuit for forcibly discharging the writing voltage [-Vw] charged in the EL element of the odd-numbered scanning electrode 12; 19 is an even-numbered scanning electrode This is an even-numbered electrode first discharge circuit for forcibly discharging the write voltage [-Vw] charged in the 13 EL elements. Note that the scanning side drivers 14 and 15
is composed of a pull-down transistor QS as in the conventional example.

The diode Dr is used to prevent mutual interference between the odd and even electrode write voltages and to supply the refresh voltage [Vr] from the refresh voltage generation circuit 7 to each scanning side driver 14, 15. Similarly, the diode Dg prevents mutual interference between the odd and even electrode write voltages and leads the refresh voltage [Vr] charged in the EL element to the second discharge circuit 9 for discharging it to the ground.

The operation of the flat display panel drive device of this embodiment constructed as described above will be described below with reference to FIG.
This will be explained along with a timing chart.

In the line sequential scanning period, writing and discharge operations by the first discharge circuit are independently driven for the odd-numbered scanning electrode blocks and the even-numbered scanning electrode blocks. The selection of scanning electrodes is performed using a 2H cycle scanning/shift signal C.
If it is set to KS, the selection valid period is 2H, so the selection of odd numbered electrodes or even numbered electrodes is performed using the scan enable signal SEN1.
, can be controlled by SEN2. Scanning/enable signal SEN
1 and SEN2 are alternately set to H every 1H to select an odd numbered electrode or an even numbered electrode.

First, the write operation is performed by the data side driver 3.
data enable signal DEN, modulation voltage generation circuit 5
control signal MD, and control signals W1 and W2 of write voltage generation circuits 16 and 17. Its operating period is SEN
1 is TW1, SEN2 is TW2, and TW1=
It has a relationship of TW2 and is equal to one scanning period (1H:Th).

When the selected electrode is the k-th even-numbered electrode, first, after writing to the k-1th odd-numbered electrode is completed, the scan enable signal SEN2 and the switch control signal SW of the even-numbered electrode scanning side driver 15 are set to H. As a result, the bidirectional switch 11 is turned on, and the electric charge charged in the k-1th odd numbered electrode is transferred to the kth even numbered electrode via the odd numbered electrode scanning side driver 14, the bidirectional switch 11, and the even numbered electrode scanning side driver 15. Move. After the charge has been transferred, when W2 is set to H and a write voltage is applied from the even electrode write voltage generation circuit 17, all ELs connected to the k-th even electrode are
The element is charged to the write voltage [-Vw].

However, even if the bidirectional switch 11 is turned on, not all of the charge on the k-1th odd numbered electrode will move to the kth even numbered electrode, and as a matter of course, the potentials of the k and k-1 electrodes will become equal. At this point, the charge movement ends. As explained in the conventional example, if the voltage is kept on the selective scanning electrode, the insulation properties of the EL element will deteriorate, so the charge remaining on the k-1st odd numbered electrode will be removed after the bidirectional switch 11 is turned off. PD1 is set to H and discharged to the ground via the odd-numbered electrode discharge circuit 18.

Further, the data side driver 3 outputs the modulation voltage [Vm] from the modulation voltage generation circuit 5 to the data electrode 1 only for the EL display element that emits light in response to the display data signal Di, and outputs the modulation voltage [Vm] to the data electrode 1, and writes the write voltage [- Vw], a light emitting display is performed, and one scanning period is completed.

In the next scanning period, the selected electrode is on the odd-numbered electrode side, so after the writing of the k-th even-numbered electrode is completed, the scan enable signal SEN1 and the switch control signal SW of the odd-numbered electrode scanning side driver 14 are set to H. As a result, the bidirectional switch 11 is turned on, and the charge charged in the kth even electrode is transferred to the k+1st odd electrode via the even electrode scanning driver 15, the bidirectional switch 11, and the odd electrode scanning driver 14.

After the charge is transferred, W1 is changed to H.
When a write voltage is applied from the odd-numbered electrode write voltage generation circuit 16, all E connected to the k+1th odd-numbered electrode
The L element is charged to the write voltage [-Vw]. After turning off the bidirectional switch 11, the charge remaining in the k-th even electrode is discharged to the ground via the even electrode discharge circuit 19 by setting PD2 to H.

The operation of the data-side driver 3 at this time is the same as when the selection electrode is on the even-numbered electrode side. As a result, a light emitting display is performed and one scanning period ends.

It should be noted that during the pause period [T0], the discharge operations overlap as in the conventional example, and the write voltage generation circuit 16
, 17 is provided to prevent the outputs of the first discharge circuits 18 and 19 from being short-circuited to ground.

After the line sequential scanning is completed by repeating the above operations, a refresh voltage [Vr] is applied to all the EL elements at once to refresh them, and the selected EL elements are caused to emit light again. Finally, the refresh voltage [Vr] charged in all the EL elements is discharged to the ground via the data side driver 3 by turning on the scan strobe signal SST of the second discharge circuit 9 and the scan side drivers 14 and 15.
Finish one frame.

As explained above, according to this embodiment,
A part of the charge used to drive the k-th scanning electrode is set to k+1
The write voltage generating circuit 1 is used to drive the k+1th scan electrode.
Since the amount of newly given charge is reduced from 6 and 17,
The power consumption required for driving the scanning electrodes can be reduced, which has a great practical effect.

Although this embodiment has been described using the EL simultaneous inversion refresh drive method as an example, it goes without saying that a frame inversion drive method in which the polarity of the write voltage is inverted every frame is also effective. stomach. Furthermore, as a display panel, not only an EL display element but also a display element having a capacitive load such as an AC-driven PDP is equally effective.

[0032]

As described above, according to the present invention, by using part of the charge used to drive the k-th scan electrode to drive the k+1-th scan electrode, the electric power required to drive the scan electrode can be reduced. consumption can be reduced, and its practical effects are great.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a driving device for a flat panel display panel according to an embodiment of the present invention.

[Figure 2] Operating voltage waveform diagram of the same example

[Figure 3] Block diagram of a drive device for a conventional flat panel display panel

[Figure 4] Timing chart of drive voltages applied to each electrode in the conventional example

[Figure 5] Operating voltage waveform diagram of conventional example

[Explanation of symbols]

1 Data electrode 3 Data side driver 5 Modulation voltage generation circuit 7 Refresh voltage generation circuit 9 Second discharge circuit 10 EL display panel 11 Bidirectional switch 12 Odd number side scanning electrode 13 Even number side scanning electrode 14 Odd number electrode scanning side driver 15 Even number electrode scanning Side driver 16 Odd number electrode write voltage generation circuit 17 Even number electrode write voltage generation circuit 18 Odd number electrode first discharge circuit 19 Even number electrode second discharge circuit

Claims (2)

[Claims] 1. A display panel comprising a display element interposed between data electrodes and scan electrodes that are orthogonal to each other, a data side driver connected to the data electrodes, and an odd number side driver connected to the odd side scan electrodes. an electrode scan driver, an even-numbered electrode scan-side driver connected to the even-numbered scan electrode, a modulation voltage generation circuit that applies a modulation voltage to the display element via the data-side driver, and an even-numbered electrode scan-side driver connected to the odd-numbered electrode scan side driver. an odd electrode write voltage generation circuit that applies a write voltage to the display element, an even electrode write voltage generation circuit that applies a write voltage to the display element via the even electrode scan side driver, and between the odd electrode scan side driver and ground. an odd-numbered electrode discharge circuit connected between the even-numbered electrode scanning-side driver and the ground, and a bidirectional characteristic between the odd-numbered electrode scanning-side driver and the even-numbered electrode scanning-side driver. Equipped with a switch element,
Driving a flat panel display panel, characterized in that after completion of writing to the k-th scan electrode, the charge charged in the k-th scan electrode is transferred to the k+1-th scan electrode via the bidirectional switch element. Device. 2. The drive device for a flat panel display panel according to claim 1, wherein the display element is electroluminescent.