CN205004016U - Organic light -emitting diode's drive circuit - Google Patents

Abstract

The utility model discloses an organic light -emitting diode's drive circuit, include: a switch transistor, the 2nd switch transistor, the 3rd switch transistor, fourth switch transistor, the 5th switch transistor, the 6th switch transistor, drive transistor, storage capacitance to and organic light -emitting diode, drive circuit still includes initialization voltage input end, reset terminal, scanning control end, luminous control end, data input end, positive and power ground end. The utility model provides an organic light -emitting diode's drive circuit can compensation transistor threshold voltage, produces the instantaneous current return circuit when preventing the OLED drive circuit initialization, enhances product performance.

Description

A kind of driving circuit of Organic Light Emitting Diode

Technical field

The utility model relates to electronic circuit technology field, particularly relates to a kind of driving circuit of Organic Light Emitting Diode.

Background technology

Existing panel display screen is made up of two essential parts usually, display pixel and driving circuit.In liquid crystal display, display pixel is the cell array of perfusion liquid crystal material.Driving circuit is the transistor circuit controlling each pixel switch (luminous, upset).In recent years, due to AMOLED (ActiveMatrixOrganicLightEmittingDiode, active matrix organic light-emitting diode) compare traditional liquid crystal display screen (LiquidCrystalDisplay, be called for short LCD) there is thinner lighter, autoluminescence, the response time is short, contrast is high, wide viewing angle, can make the advantage such as flexibility and opaque products, is considered to display technique of future generation.At present, Organic Light Emitting Diode (OrganicLightEmittingDiode is called for short OLED) technical research drops into and continues to increase, technology reaches its maturity, the yields of volume production improves constantly, and cost approaches liquid crystal display increasingly, and the market share constantly expands.

AMOLED is current driving apparatus, and when there being electric current to flow through Organic Light Emitting Diode OLED, OLED is luminous, and luminosity is determined by the electric current flowing through OLED self.Due in the driving circuit of AMOLED, drive the threshold voltage (ThresholdVoltage) of thin film transistor (TFT) can drift about along with the working time, thus cause the luminescence of OLED unstable, therefore needing to adopt can the pixel-driving circuit of compensation for drive transistor threshold voltage shift.Current low temperature polycrystalline silicon (LowTemperaturePoly-silicon, being called for short LTPS) processing procedure adopts quasi-molecule laser annealing (ExcimerLaserAnnealing mostly, be called for short ELA) technique, thin film transistor (TFT) (the Thin-FilmTransistor made, be called for short TFT) threshold voltage spatially there is unevenness, the OLED under identical data voltage driven causes gray scale to show non-uniform phenomenon because thin film transistor (TFT) threshold voltage is different; In addition, existing circuit power line IR pressure drop, OLED ghost (ImageSticking) and sweep trace or light emitting control line realize the initialized mode of drive transistor gate voltage and create momentary current loop, cause that thin film transistor (TFT) is overheated, damage problem, affect product quality.

Utility model content

Technical problem to be solved in the utility model is to provide a kind of driving circuit of Organic Light Emitting Diode, compensation transistor threshold voltage, prevents the initialization of OLED driving circuit from producing momentary current loop, enhances product performance.

For solving above technical matters, the utility model embodiment provides a kind of driving circuit of Organic Light Emitting Diode, comprise: the first switching transistor, second switch transistor, the 3rd switching transistor, the 4th switching transistor, the 5th switching transistor, the 6th switching transistor, driving transistors, memory capacitance, and Organic Light Emitting Diode;

Described driving circuit also comprises initialization voltage input end, reset terminal, scan control end, light emitting control end, data input pin, positive source and power ground end;

Described initialization voltage input end is connected respectively with the source electrode of the source electrode of described 4th switching transistor, described 5th switching transistor, the source electrode of described 6th switching transistor; Described reset terminal is connected on the grid of described 6th switching transistor; The drain electrode of described 6th switching transistor is connected jointly with the source electrode of described second switch transistor, the grid of described driving transistors; Described scan control end is connected jointly with the grid of the grid of described first switching transistor, described second switch transistor, the grid of described 5th switching transistor; Described light emitting control end is connected jointly with the grid of described 3rd switching transistor, the grid of described 4th switching transistor; Described positive source is connected on the source electrode of described driving transistors; The positive pole of described Organic Light Emitting Diode is connected jointly with the drain electrode of the drain electrode of described 3rd switching transistor, described 5th switching transistor; The negative pole of described Organic Light Emitting Diode is connected with described power ground end.

Described data input pin is connected on the source electrode of described first switching transistor; The drain electrode of described first switching transistor is connected with the drain electrode of described 4th switching transistor.

Preferably, described memory capacitance is connected between the drain electrode of the first switching transistor and the grid of described driving transistors; The drain electrode of described driving transistors is connected jointly with the source electrode of the drain electrode of described second switch transistor, described 3rd switching transistor.

The driving circuit of the Organic Light Emitting Diode that the utility model embodiment provides, by the combination of multiple switching transistor, initialization voltage input end is set simultaneously, reset terminal, scan control end, light emitting control end, data input pin, by the control of sequential, drive transistor gate voltage initialization is realized through the 6th switching transistor when reset terminal is low level, thus the momentary current loop realizing between drive transistor gate voltage initialization mode positive source and initialization voltage input end by scan control end or light emitting control end can not be formed, namely avoid high level (positive source) to be connected with low level (initialization voltage input end) formed big current.The driving circuit of the Organic Light Emitting Diode that the utility model embodiment provides, not only can compensation for drive transistor threshold voltage, eliminate power lead IR pressure drop, improve ghost, unnecessary momentary current loop can also be avoided the formation of, avoid causing that thin film transistor (TFT) is overheated, damage problem, thus improve product reliability and life-span, reduce power consumption, improve properties of product.

Accompanying drawing explanation

Fig. 1 is the structural representation of an embodiment of the driving circuit of the Organic Light Emitting Diode that the utility model provides.

Fig. 2 is a kind of sequential chart controlled the driving circuit of Organic Light Emitting Diode that the utility model embodiment provides.

Embodiment

Below in conjunction with the accompanying drawing in the utility model embodiment, the technical scheme in the utility model embodiment is clearly and completely described.

See Fig. 1, it is the structural representation of an embodiment of the driving circuit of the Organic Light Emitting Diode that the utility model provides.

Particularly, the driving circuit of described Organic Light Emitting Diode, comprise: the first switching transistor M1, second switch transistor M2, the 3rd switching transistor M3, the 4th switching transistor M4, the 5th switching transistor M5, the 6th switching transistor M6, driving transistors MDTFT, memory capacitance C1, and Organic Light Emitting Diode DOLED;

The driving circuit of Organic Light Emitting Diode also comprises initialization voltage input end VINIT, reset terminal RESET, scan control end SCAN, light emitting control end EM, data input pin VDATA, positive source ELVDD and power ground end ELVSS.

As shown in Figure 1, described initialization voltage input end VINIT is connected respectively with the source electrode of the source electrode of described 4th switching transistor M4, described 5th switching transistor M5, the source electrode of described 6th switching transistor M6; Described reset terminal RESET is connected on the grid of described 6th switching transistor M6; The drain electrode of described 6th switching transistor M6 is connected jointly with the source electrode of described second switch transistor M2, the grid of described driving transistors MDTFT; Described scan control end SCAN is connected jointly with the grid of the grid of described first switching transistor M1, described second switch transistor M2, the grid of described 5th switching transistor M5; Described light emitting control end EM is connected jointly with the grid of described 3rd switching transistor M3, the grid of described 4th switching transistor M4; Described positive source ELVDD is connected on the source electrode of described driving transistors MDTFT; The positive pole of described Organic Light Emitting Diode DOLED is connected jointly with the drain electrode of the drain electrode of described 3rd switching transistor M3, described 5th switching transistor M5; The negative pole of described Organic Light Emitting Diode DOLED is connected with described power ground end ELVSS.

During concrete enforcement, the driving circuit of Organic Light Emitting Diode also comprises data input pin VDATA.Described data input pin VDATA is connected on the source electrode of described first switching transistor M1; The grid of described first switching transistor M1 is connected with the grid of described 5th switching transistor M5; The drain electrode of described first switching transistor M1 is connected with the drain electrode of described 4th switching transistor M4.Particularly, the grid of described first switching transistor M1 is also connected jointly with the grid of scan control end SCAN, second switch transistor M2.Further, memory capacitance C1 is connected with between the drain electrode of described first switching transistor M1 and the grid of described driving transistors MDTFT; The drain electrode of described driving transistors MDTFT is connected jointly with the source electrode of the drain electrode of described second switch transistor M2, described 3rd switching transistor M3.

In the present embodiment, in order to realize the grid voltage initialization of driving transistors MDTFT, by the magnitude of voltage that the voltage initialization of B point in Fig. 1 is VINIT end, make switching transistor M1 for low level control mode by the signal of scan control end SCAN and light emitting control end EM simultaneously, switching transistor M2, switching transistor M3, switching transistor M4, switching transistor M5 opens simultaneously, although the voltage of initialization voltage input end VINIT is through switching transistor M5, M3, M2 makes B be initialized as the voltage of VINIT, but, because B point becomes low level, driving transistors MDTFT is opened, thus make driving transistors MDTFT and the 3rd switching transistor M3, 5th switching transistor M5 forms momentary current loop, high level (ELVDD) is connected can forms big current with low level (VINIT).Therefore, the initialization of driving transistors MDTFT grid voltage is realized further by the 6th switching transistor M6 in the specific implementation.There is the implementation drain electrode of the 6th switching transistor M6 be jointly connected with the drain electrode of second switch crystal M2, the drain electrode of driving transistors MDTFT in prior art, although which also can realize through the 6th switching transistor M6, second switch transistor M2 makes B be initialized as VINIT voltage, but similarly, because B point becomes low level, driving transistors MDTFT is opened, thus make driving transistors MDTFT, 6th switching transistor M6 forms momentary current loop, and the low level that positive source ELVDD and VINIT termination enter is connected to form big current.Therefore, for avoiding the generation of above problem, need to improve existing circuit structure.

Referring to Fig. 2, it is a kind of sequential chart that the driving circuit of Organic Light Emitting Diode is controlled that the utility model embodiment provides.

In conjunction with driving circuit figure (Fig. 1) and sequential chart (Fig. 2), the principle of work of the driving circuit of the Organic Light Emitting Diode that the utility model embodiment provides is analyzed.

As shown in Figure 1, the source electrode of the 6th switching transistor M6 is held with VINIT and is connected, the grid of the 6th switching transistor M6 is connected with reset terminal RESET, and the drain electrode of the 6th switching transistor M6 is connected jointly with the source electrode of the grid of driving transistors MDTFT, second switch transistor M2.As shown in Figure 2, the course of work of driving circuit mainly comprises three phases:

(1) in the T1 stage: reset terminal RESET input signal is low level, scan control end SCAN and light emitting control end EM is high level, and make the 6th switching transistor M6 conducting, B point voltage is initialized as the voltage that VINIT termination enters.Owing to can realize through the 6th switching transistor M6 when reset terminal RESET is low level when the driver' s timing T1 stage realizes drive transistor gate voltage initialization, therefore momentary current link circuit can not be formed between positive source ELVDD and initialization voltage input end VINIT.

(2) in the T2 stage: scan control end SCAN input signal is low level, reset terminal RESET and light emitting control end EM is high level, and make the first switching transistor M1 and second switch transistor M2 conducting, A point voltage is the magnitude of voltage of data input pin VDATA; Therefore, the T2 stage is compensation, data write phase.In addition, due to second switch transistor M2 conducting, make driving transistors MDTFT form diode-connected (Diode-Connected), the magnitude of voltage size that namely B point voltage is held from VINIT becomes the difference ELVDD-V of positive source ELVDD and threshold voltage _th, wherein, the magnitude of voltage of VINIT end is less than the difference ELVDD-V of positive source ELVDD and threshold voltage _th.

(3) the T3 stage: glow phase.Light emitting control end EM input signal is low level, and reset terminal RESET and scan control end SCAN is high level, and make the 3rd switching transistor M3 and the 4th switching transistor M4 conducting, OLED starts luminescence; And the first switching transistor M1, second switch transistor M2, the 6th switching transistor M6 end, A point voltage changes the magnitude of voltage of initialization voltage input end VINIT into by the magnitude of voltage of data input pin VDATA; Meanwhile, due to the capacitive coupling effect of memory capacitance C1, the voltage variety of B point equals the voltage variety of A point, and namely B point voltage is changed to: ELVDD-V _th+ (VDATA-VINIT).

In the present embodiment, because driving transistors MDTFT is operated in saturation region, its saturation current computing formula is:

$I_{sat}=\frac{1}{2}{\mathrm{\μC}}_{OX}\frac{W}{L}{(V_{sg}-V_{th})}^2---\left(1\right)$

Wherein, the μ in formula (1) is the electron mobility of raceway groove, C _oxfor the channel capacitance of driving transistors MDTFT unit area, W is channel width, and L is channel length, V _sgfor driving transistors MDTFT gate source voltage, V _thfor the threshold voltage of driving transistors MDTFT.

In order to obtain the electric current of relative constancy, require that driving transistors MDTFT is operated in saturation region, from pixel-driving circuit Fig. 1, Organic Light Emitting Diode DOLED electric current I _oLEDwith the electric current I of driving transistors MDTFT _satequal.Because the luminosity of Organic Light Emitting Diode DOLED is directly proportional to the electric current flowing through Organic Light Emitting Diode DOLED, by controlling the electric current of driving transistors MDTFT, namely the electric current of Organic Light Emitting Diode DOLED can realize the different luminosity of Organic Light Emitting Diode DOLED.Organic Light Emitting Diode DOLED electric current I _oLEDfollowing formula can be adopted to calculate:

$\begin{array}{c}{I}_{OLED}=\frac{1}{2}{\mathrm{\μC}}_{OX}\frac{W}{L}{\left(V_{sg}-V_{th}\right)}^2\\ =\frac{1}{2}{\mathrm{\μC}}_{OX}\frac{W}{L}{\left(ELVDD-\left(ELVDD-V_{th}+\left(VDATA-VINIT\right)\right)-V_{th}\right)}^2\\ =\frac{1}{2}{\mathrm{\μC}}_{OX}\frac{W}{L}{\left(VDATA-VINIT\right)}^2\end{array}---\left(2\right)$

Wherein, gate source voltage V _sg=ELVDD-(ELVDD-V _th+ (VDATA-VINIT)).

Pass through I _oLEDcomputing formula (2) can find out, I _oLEDonly relevant with the voltage of VINIT with the voltage of VDATA, and with positive source ELVDD and threshold voltage V _thirrelevant, namely the driving circuit of Fig. 1 can realize the compensation uneven to the threshold voltage of IR pressure drop and driving transistors MDTFT.Because the luminosity of OLED is directly proportional to the electric current flowing through OLED, the different luminosity of OLED can be realized by the control electric current of driving transistors and the electric current of OLED.During concrete enforcement, each switching transistor can adopt in low-temperature polysilicon film transistor, oxide semiconductor thin-film transistor or amorphous silicon film transistor one or more, those skilled in the art can choose according to the type of practical application to transistor.

The driving circuit of the Organic Light Emitting Diode that the utility model embodiment provides, by the combination of multiple switching transistor, initialization voltage input end, reset terminal, scan control end, light emitting control end, data input pin are set simultaneously, by the control of sequential, drive transistor gate voltage initialization is realized through the 6th switching transistor when reset terminal is low level, thus momentary current loop can not be formed between positive source and initialization voltage input end, namely avoid high level and to be connected with low level formed big current.The driving circuit of the Organic Light Emitting Diode that the utility model embodiment provides, not only can compensation for drive transistor threshold voltage, eliminate power lead IR pressure drop, improve ghost, circuit can also avoid the formation of unnecessary momentary current loop, avoid causing that thin film transistor (TFT) is overheated, damage problem, thus improve product reliability and life-span, reduce power consumption, improve properties of product.

The above is preferred implementation of the present utility model; it should be pointed out that for those skilled in the art, under the prerequisite not departing from the utility model principle; can also make some improvements and modifications, these improvements and modifications are also considered as protection domain of the present utility model.

Claims (3)

1. the driving circuit of an Organic Light Emitting Diode, it is characterized in that, comprise: the first switching transistor, second switch transistor, the 3rd switching transistor, the 4th switching transistor, the 5th switching transistor, the 6th switching transistor, driving transistors, memory capacitance, and Organic Light Emitting Diode;

Described driving circuit also comprises initialization voltage input end, reset terminal, scan control end, light emitting control end, data input pin, positive source and power ground end;

Described initialization voltage input end is connected respectively with the source electrode of the source electrode of described 4th switching transistor, described 5th switching transistor, the source electrode of described 6th switching transistor; Described reset terminal is connected on the grid of described 6th switching transistor; The drain electrode of described 6th switching transistor is connected jointly with the source electrode of described second switch transistor, the grid of described driving transistors; Described scan control end is connected jointly with the grid of the grid of described first switching transistor, described second switch transistor, the grid of described 5th switching transistor; Described light emitting control end is connected jointly with the grid of described 3rd switching transistor, the grid of described 4th switching transistor; Described positive source is connected on the source electrode of described driving transistors; The positive pole of described Organic Light Emitting Diode is connected jointly with the drain electrode of the drain electrode of described 3rd switching transistor, described 5th switching transistor; The negative pole of described Organic Light Emitting Diode is connected with described power ground end.

2. the driving circuit of Organic Light Emitting Diode as claimed in claim 1, it is characterized in that, described data input pin is connected on the source electrode of described first switching transistor; The drain electrode of described first switching transistor is connected with the drain electrode of described 4th switching transistor.

3. the driving circuit of Organic Light Emitting Diode as claimed in claim 2, is characterized in that, between the drain electrode that described memory capacitance is connected to described first switching transistor and the grid of described driving transistors; The drain electrode of described driving transistors is connected jointly with the source electrode of the drain electrode of described second switch transistor, described 3rd switching transistor.