KR101066355B1 - Driving Circuit and Driving Method of Passive Matrix Organic Light Emitting Diode - Google Patents

Abstract

The present invention relates to a driving circuit of a passive matrix organic EL display device capable of supplying precharge current and driving current to one constant current source, and a driving method thereof. The present invention provides a precharge / drive constant current source for supplying a precharge current to the organic EL element during the precharge period, and a drive current to the organic EL element during the driving period, and different in the precharge period and the driving period, respectively. A precharge / drive current control unit for controlling a current value output from the precharge / drive constant current source by applying a bias of magnitude, and turned on during the precharge section and the driving section; And a switching controller for outputting a control signal for controlling the on / off operation of the precharge / drive switch and the precharge / drive switch for connecting the anode electrode of the organic EL element. The precharge / drive switch is turned off so that no current flows to the organic EL element for a predetermined time between the precharge section and the driving section. According to the present invention, the area of the driving circuit is reduced, so that the area of the entire integrated circuit can be reduced, and the manufacturing process or manufacturing cost can be reduced by miniaturization of the integrated circuit including the driving circuit. do.

Description

Driving circuit and driving method of passive matrix organic electroluminescent display device {Driving Circuit and Driving Method of Passive Matrix Organic Light Emitting Diode}

1 is a block diagram illustrating a typical passive matrix organic EL display device.

2 is a circuit diagram showing a configuration of a driving circuit for driving a conventional organic EL display device.

3 is a diagram showing waveforms of signals for driving a conventional organic EL display device.

4 is a diagram showing a driving circuit of a passive matrix organic EL display device according to an embodiment of the present invention.

5 is a diagram showing waveforms of signals for driving an organic EL display device according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a passive matrix organic electroluminescent display (Organic Light Emitting Diode, hereinafter referred to as an 'organic EL') display device. Specifically, a passive matrix organic light source capable of supplying a precharge current and a driving current to one constant current source. A driving circuit of an EL display device and a driving method thereof.

In recent years, remarkable developments have been made in the field of flat panel displays. As flat panel displays, LCD (Plasma Display Panel), FED (Field Emission Display) and OLED (Organic Light Emitting Diode) are typical.

Currently, LCD is widely used as a video display device of a TV, a computer, or a mobile communication terminal. The LCD is not only heavy because it requires a backlight, but also has a disadvantage of being thick and slow in response.

Therefore, the organic EL display device (or OLED) is attracting attention as a next-generation video display device replacing the LCD.

The organic EL element (OLED) includes an extremely thin organic layer of 0.1 μm or less, and when current flows through the organic layer, electrons and holes are recombined near the interface between the electron transport layer and the hole transport layer. Light emission, which has an extremely fast response time of several hundreds of microseconds or less.

As such, the organic EL element OLED has a two-pole structure of an anode electrode (anode) and a cathode electrode (cathode), and the current is driven due to the difference in voltage-current characteristics of the individual organic EL elements OLED forming the panel. Will be

The display means using the organic EL element (OLED), that is, the driving method for the organic EL display device is classified into a passive matrix method and an active matrix method, which are orthogonal to the anode and the cathode. The active matrix method is a driving method in which a thin film transistor TFT and a capacitor Cst are integrated in each pixel to maintain a voltage by a capacitor capacity. to be.

1 is a block diagram illustrating a typical passive matrix organic EL display device.

Referring to FIG. 1, the passive matrix organic EL display device is composed of a display panel 10, a data driver 20, and a scan driver 30.

In the display panel 10, a plurality of common anode lines D1 -Dm and a plurality of common cathode lines S1 -Sn are arranged in a lattice shape, and each pixel includes an R / G / B pixel at each intersection of the lattice. Organic electroluminescent element (EL11-ELnm) is arrange | positioned. Each organic EL element is composed of an anode electrode, an organic film layer, and a cathode electrode, and a parasitic capacitor C is formed between the anode electrode and the cathode electrode. In addition, the data driver 20 is connected to the common anode lines D1 -Dm, and the scan driver 30 is connected to the common cathode lines S1 -Sn.

The data driver 20 includes a plurality of driving circuits 21 to apply a precharge current Iprec, a driving current Idrv, and a ground voltage GND for each common anode line D1 -Dm. Accordingly, under the control of a driving controller (not shown), each driving circuit 21 selectively selects each common anode line D1-Dm to the precharge current stage Iprec, the driving constant current stage, and the ground terminal GND. Connect with

The scan driver 30 includes a plurality of scan output units 31 that apply a high voltage VCC or a ground voltage GND for each common cathode line S1 -Sn. Accordingly, under the control of the driving controller (not shown), each scan output unit 31 selects the respective common cathode lines S1-Sn to the power supply voltage terminal VCC and the ground terminal GND in a predetermined pattern. Connect with

In the above configuration, when the plurality of scan output units 31 are sequentially turned on / off and select the common cathode line from the first column S1 to the nth column Sn, the driving is performed. The circuit unit 21 is synchronized with this and connects the gray scale level (Gray Scale) of the corresponding pixels, that is, the organic EL elements EL11-ELnm, to the common anode line D1-Dm to the driving constant current source Idrv. This completes the screen frame. As a method of expressing the gradation level, a pulse width modulation (PWM) method for adjusting the driving current application time or a pulse amplitude modulation (PAM) method for adjusting the magnitude of the driving current may be applied.

On the other hand, as described above, since the organic EL element ELnm is formed of an organic thin film, parasitic capacitor C is present at both ends of the anode and the cathode of the diode EL, which is low due to the parasitic capacitor C. Since there is a problem in that gray scale processing cannot be performed, the parasitic capacitor C is precharged by applying a voltage such that the diode EL can be turned on before applying current to the common anode lines D1 -Dm. Let's go. To this end, the driving circuit 21 is provided with a precharge current stage I _PRE for outputting a current of a predetermined level.

Therefore, the passive matrix organic EL display device precharges the parasitic capacitor C of the organic EL element EL11-ELnm by connecting all common anode lines D1-Dm to the precharge current stage I _PRE for a predetermined time. The pixel gray level of the organic EL element 12 in which the driving circuit 21 connects each common anode line D1-Dm to the driving circuit 21 according to a precharge period and a control of the external control signal PWM. Driving period (Driving Period) for emitting an organic EL element by connecting to the driving constant current source (Idrv) for a predetermined PWM time, and then the drive circuit 21 is again in accordance with the control of the external control signal (Reset) The anode lines D1-Dm are connected to the ground terminal GND to be divided into a discharge period for discharging the voltage charged in the parasitic capacitor C.

2 is a circuit diagram showing a configuration of a driving circuit for driving a conventional organic EL display device.

Referring to FIG. 2, a driving circuit for driving a conventional organic EL display device includes a driving constant current source 100 and an organic EL element EL11 for outputting a driving current Idrv for emitting an organic EL element EL11. A precharge constant current source 120 for outputting a precharge current Iprec for precharging, and a drive current controller 130 for applying a control signal for controlling the amount of current of the driving constant current source 100. And a precharge current controller 140 for applying a control signal for controlling the amount of current of the precharge constant current source 120 and the driving constant current source 100, the precharge constant current source 120, and a ground terminal GND. And a switching control unit 190 for sequentially applying control signals V _A, V _B , and V _C to the switches 160, 170, and 180 for connecting the organic EL elements EL11 to the switches. Therefore, in the precharge section, the driving section, and the discharge section, the current flows to the organic EL element EL11 to emit light.

3 is a diagram showing waveforms of signals for driving a conventional organic EL display device.

Referring to FIG. 3, first, when the v precharge control signal V _A is applied to the switch 160 in the switching controller 190, the switch 160 is turned on so that the precharge constant current source is turned on. A precharge current Iprec of 120 is applied to the organic EL element EL11 to precharge the capacitor C. At this time, the scan output unit 31 applies the power supply voltage VCC to the common cathode line.

Next, during the driving period, when the driving control signal V _B is applied to the switch 170 in the switching controller 190, the switch 170 is turned on to drive the driving current Idrv of the driving constant current source 100. It is applied to the organic EL element EL11 to emit light at a predetermined brightness. In this case, the scan output unit 31 applies the ground voltage GND to the common cathode line.

Lastly, during the discharge period, when a discharge control signal is applied to the switch 180 in the switching controller 190, the switch 180 is turned on so that the ground terminal GND is connected to the anode electrode of the organic EL element. Ground Thus, the charged charges are discharged. At this time, the scan output unit 31 applies the power supply voltage VCC to the common cathode line.

In each of the driving circuits of the conventional organic EL display device, the precharge constant current source 120 for applying the precharge current and the driving constant current source 100 for applying the driving current are separately designed at the output terminal of the data driver, thereby integrating the integrated circuit. There is a problem that a large portion of the area of the circuit takes up.

An object of the present invention for solving the above problems is to design the area of the data driver (integrated circuit) by designing only one precharge / drive constant current source for generating both precharge current and drive current at the output terminal of the driving circuit of the organic EL display device. To minimize.

In the driving circuit of the organic EL display device according to the present invention for achieving the above object, in the driving circuit of the passive matrix organic EL display device, one constant current source supplies a precharge current to the organic EL element during the precharge period, The driving current is supplied to the organic EL element during the driving period.

In addition, the driving circuit of the organic EL display device according to the present invention for achieving the above object provides a precharge current to the organic EL element during the precharge period, and a precharge to supply the driving current to the organic EL element during the driving period. Driving constant current source; A precharge / drive current controller configured to control a current value output from the precharge / drive constant current source by applying a bias having a different magnitude in each of the precharge section and the driving section; A precharge / drive switch which is turned on during the precharge period and the driving period to connect the precharge / drive constant current source and the anode electrode of the organic EL element; And a switching controller configured to output a control signal for controlling an on / off operation of the precharge / drive switch.

The precharge / drive switch may be turned off to prevent current from flowing into the organic EL element for a predetermined time between the precharge section and the driving section.

In addition, the object is a passive matrix including a precharge / drive constant current source for supplying a precharge current and a drive current to an organic EL element that emits light at a predetermined luminance, and a precharge / drive switch for flowing or blocking the current. A driving method of a driving circuit of an organic EL display device, comprising: a precharge step of supplying a precharge current from the precharge / drive constant current source to the organic EL element by turning on the precharge / drive switch; And a driving step in which the precharge / drive switch is turned on to supply a driving current from the precharge / drive constant current source to the organic EL element. Can be.

Wherein the precharge / drive switch is turned off between the precharge step and the driving step to block a current flowing from the precharge / drive constant current source to the organic EL element. It is done.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example

4 is a diagram showing a driving circuit of a passive matrix organic EL display device according to an embodiment of the present invention.

Referring to FIG. 4, a driving circuit of a passive matrix organic EL display device according to an exemplary embodiment of the present invention may include a precharge / drive constant current source 200, a ground terminal GND, a precharge / drive current controller 230, and a precharge. The charge / drive switch 250, the discharge switch 270, and the switching controller 290 are configured.

The precharge / drive constant current source 200 is connected to the power supply voltage VCC, applies a precharge current Iprec for charging the capacitor C of the organic EL element EL11 during the precharge period, and drives the During the period, a driving current Idrv is applied to cause the organic EL element EL11 to emit light at a predetermined luminance.

That is, the precharge / drive constant current source 200 according to the embodiment of the present invention is conventionally configured (previously, as shown in FIG. 2, the precharge constant current source 120 and the driving constant current source 100, respectively). Differently from)), the precharge current Iprec and the drive current Idrv are generated using only one precharge / drive constant current source 200 and output to the organic EL element EL11.

The control method of the present invention for generating different precharge and driving currents (Iprec / Idrv) with one constant current source 200 is described in the precharge / drive constant current source 200 in the precharge / drive current controller 230 which will be described later. ), A different bias signal is applied to each corresponding section to control the amount of current output from the constant current source 200.

Therefore, by arranging the two constant current sources 100 and 120, which are conventionally configured as one constant current source 200, the design area of the driving circuit is reduced, thereby reducing the design time and the process time, and the cost and size competitiveness due to the miniaturization of the integrated circuit. Can take the lead in

The ground terminal GND discharges the charge of the charged capacitor through the ground GND during the discharge period.

The precharge / drive current controller 230 applies different control signals V _P and V _d to the precharge / drive constant current source 100 during the precharge section and the driving section during the precharge section and the driving section. The amount of current is adjusted to output the precharge current Iprec and the driving current Idrv, respectively.

At this time, while switching from the precharge section to the driving section, the control signal is switched (Vd to Vd) in the precharge / drive current control unit 230, thereby abruptly causing an abnormal current in the precharge / drive constant current source 200. short circuit current may flow. In this case, there is a possibility that the organic EL element EL11 emits light at an incorrect luminance or impacts the organic EL element, thereby causing a defect in the element.

Therefore, when switching from the precharge section to the drive section, there is a section in which the drive current Idrv does not flow for a predetermined time so that the stable drive current flows to the organic EL element EL11. Hereinafter, this section is referred to as a 'stabilization section'. A method of preventing the driving current from flowing during the stabilization period will be described in the switching controller 290 and the precharge / drive switch 250 which will be described later.

The precharge / drive switch 250 is turned on during the precharge section and the driving section, and the precharge current Iprec and the drive current Idrv output from the precharge / drive constant current source 200. ) Is applied to the organic EL element EL11. The precharge / drive switch 250 is turned off during the stabilization period between the precharge period and the driving period so that a current flows in the precharge / drive constant current source 200. Block from flowing to (EL11).

The discharge switch 270 is turned on during the discharge period to discharge the charge charged in the organic EL element EL11 to the ground terminal GND.

The switching controller 290 controls the on / off time by applying control signals C _A and C _B to the precharge / drive switch 250 and the discharge switch 270, respectively. In particular, the control signal C _A applied by the switching controller 290 to the precharge / drive switch 250 applies a turn-on control signal during the precharge period, and applies a turn-off control signal during the stabilization period. And a turn-on control signal is applied during the driving period. Therefore, it is possible to block the inflow of the abnormal current that may occur during the stabilization period.

As described above, the driving circuit of the organic EL display device according to the embodiment of the present invention includes one precharge / drive constant current source 200, one precharge / drive current control unit 230, and one precharge / drive switch ( By providing 250, the circuit design area can be reduced, and the circuit can be simplified and the process can be simplified, and thus, the size and price of the integrated circuit can be competitive.

5 is a diagram showing waveforms of signals for driving an organic EL display device according to an embodiment of the present invention.

Referring to FIG. 5, a driving section of an organic EL display device according to an exemplary embodiment of the present invention may be divided into four sections, a precharge section, a stabilization section, a driving section, and a discharge section. The driving circuit and FIG. 5 will be described for each section. The control signal of the switching controller 290 assumes that a low level signal turns the switch on and a high level signal turns the switch off.

First, when the low level control signal C _A is applied to the precharge / drive switch 250 during the precharge period, the precharge / drive switch 250 is turned on. do. In this case, the precharge / drive current control unit 230 applies a precharge current control signal Vp to the precharge / drive constant current source 200 to generate a precharge current Iprec. Therefore, the precharge current Iprec is charged in the capacitor C of the organic EL element EL11 through the precharge / drive switch 250. At this time, the scan output unit 31 applies the power supply voltage VCC to the common cathode line.

Next, during the stabilization period, when the high level control signal C _A is applied to the precharge / drive switch 250 by the switching controller 290, the precharge / drive switch 250 is turned off. . Therefore, the current flowing to the organic EL element EL11 is cut off (NULL in FIG. 5). Therefore, the short circuit according to switching is performed by passing through the stabilization period before switching from the precharge period to the driving period. generation of current) can be prevented and the organic EL display device can be driven stably.

Next, during the driving period, when the low level control signal C _A is applied to the precharge / drive switch 250 in the switching controller 290, the precharge / drive switch 250 is turned on again. do. At this time, the precharge / drive current control unit 230 generates a drive current Idrv by applying a drive current control signal Vd to the precharge / drive constant current source 200. Therefore, the driving current Idrv is applied to the organic EL element EL11 through the precharge / drive switch 250, and the organic EL element EL11 emits light with a predetermined luminance. In this case, the scan output unit 31 applies the ground voltage GND to the common cathode line.

In the driving period, the method of determining the luminance (gray scale) of the organic EL element EL11 adjusts the time that the driving current Idrv of the same magnitude is applied to the organic EL element EL11. Pulse Width Modulation (PWM) driving method for expressing gray scale value is used, or PAM (Pulse expressing gray scale value) by adjusting the magnitude of driving current Idrv applied to the organic EL device. Amplitude Modulation) can be used.

Lastly, during the discharge period, when the low-level discharge control signal C _B is applied to the discharge switch 270 by the switching controller 290, the discharge switch 270 is turned on so that the discharge switch 270 is turned on. The ground terminal GND is grounded to the anode electrode of the organic EL element EL11. Thus, the charges charged in the capacitor C are discharged. At this time, the scan output unit 31 applies the power supply voltage VCC to the common cathode line.

By designing the driving circuit of the organic EL display device according to the embodiment of the present invention as one precharge / driving constant current source 200, the layout area of the integrated circuit can be reduced, thereby reducing the area of the entire integrated circuit. In addition, the manufacturing process and manufacturing cost can be reduced accordingly, thereby obtaining a competitive advantage.

According to the present invention having the above-described configuration, by designing a driving circuit in which the pre-charge constant current source and the driving constant current source are conventionally designed as a single constant current source, the area of the driving circuit is reduced so that the area of the entire integrated circuit is reduced. Can be reduced.

Therefore, the miniaturization of the integrated circuit including the driving circuit can reduce the manufacturing process and manufacturing cost, thereby having a competitive price and size.

While specific embodiments of the present invention have been illustrated and described, the technical spirit of the present invention is not limited to the accompanying drawings and the above description, and various modifications can be made without departing from the spirit of the present invention. It is self-evident to those who have the common knowledge of.

Claims (7)

delete A precharge / drive constant current source supplying a precharge current to the organic EL element during the precharge period, and supplying a driving current to the organic EL element during the driving period; A precharge / drive current control unit configured to control a current value output from the precharge / drive constant current source by applying biases having different magnitudes in the precharge section and the driving section; A precharge / drive switch which is turned on during the precharge period and the driving period to connect the precharge / drive constant current source and the anode electrode of the organic EL element; And It includes a switching control unit for outputting a control signal for controlling the on / off operation of the precharge / drive switch, And the precharge / drive switch is turned off to prevent current from flowing into the organic EL element for a predetermined time between the precharge period and the driving period. delete The method of claim 2, A ground terminal for discharging electric charges of the organic EL element during a discharge period following the driving period; And And a discharge switch which is turned on during the discharge period and connects the ground terminal to the anode electrode of the organic EL element. A passive matrix organic EL display device comprising a precharge / drive constant current source for supplying a precharge current and a drive current to an organic EL element emitting light at a predetermined luminance, and a precharge / drive switch for flowing or blocking the current. In the driving method of the driving circuit, A precharge step of supplying a precharge current from the precharge / drive constant current source to the organic EL element by turning on the precharge / drive switch; A driving step of turning on the precharge / drive switch to supply a driving current from the precharge / drive constant current source to the organic EL element; And A passive matrix organic EL display comprising a stabilizing step of blocking the current flowing from the precharge / drive constant current source to the organic EL element between the precharge step and the drive step by turning off the precharge / drive switch; A method of driving a drive circuit of a device. delete The method of claim 5, And a discharge step of connecting the anode electrode of the organic EL element to a ground terminal after the driving step.

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