CN208208301U - Voltage-type pixel unit circuit with threshold compensation - Google Patents

Abstract

The utility model discloses a voltage type pixel unit circuit with threshold value compensation, which is characterized in that it comprises: a first transistor M1, a second transistor M2, a third transistor M3, a fourth transistor M4, a fifth transistor M5, a sampling and holding Capacitor C1, data signal line VDATA, sampling control signal line SMP, hold signal line HLD, power line VDD, common cathode power line VCOM of the light emitting device, and the light emitting device. The novel voltage-type pixel unit drive circuit with threshold compensation proposed in this patent can effectively solve the fluctuation of the drive current of the pixel array caused by the change of the threshold of the drive tube, thereby improving the display consistency of the entire display.

Description

Voltage type pixel unit circuit with threshold compensation

technical field

The utility model relates to a pixel unit circuit for self-luminous display, in particular to a pixel unit circuit driven by an OLED/LED micro display.

Background technique

In recent years, with the development of AR (Augmented Reality, augmented reality)/VR ((Virtual Reality, virtual reality) technology, the closely related micro-display technology has also received extensive attention. Micro-display (Microdisplay) technology is a display A branch of the technical field generally refers to displays whose diagonal size is less than 1 inch (2.54cm) or those that are small enough to require optical amplification as microdisplays. Currently common microdisplay technologies include OLEDoS (Organic Light-Emitting Diode on Silicon , Silicon-based organic light emitting), LEDoS (Light Emitting Diode on Silicon, silicon-based diode light emitting), LCoS (Liquid Crystal on Silicon, liquid crystal on silicon) and DMD (Digital Micro mirror Device, digital micromirror device) four, of which OLEDoS and LEDoS Both belong to active light emission, while LCoS and DMD belong to passive light emission; at the same time, OLEDoS and LEDoS also have the advantages of low power consumption, high contrast and fast response, so they are more suitable for application in AR and VR technologies.

OLEDoS and LEDoS micro-displays are different from conventional processes using amorphous silicon, microcrystalline silicon or low-temperature polycrystalline silicon. Semiconductor (complementary metal oxide semiconductor) technology, so it can not only realize the active addressing matrix of display screen pixels, but also realize the drive control circuit of various functions such as scan chain circuit, digital-to-analog conversion circuit, and bandgap reference, thus greatly The external wiring of the device is reduced, the reliability is increased, and the weight is realized.

The pixel unit circuit of OLEDoS and LEDoS is a circuit that realizes the current control of each pixel in the display array of the microdisplay. The accuracy of each pixel current control directly affects the display consistency of the entire microdisplay; while the current traditional voltage-type pixel unit Due to the deviation of the manufacturing process of the circuit, the parameters of the driving tube between the pixels will be inconsistent, which will lead to a certain difference in the current between the pixel units. In addition, pixel unit circuits with different structures will affect the design of the overall driving scheme, so the rationality of pixel unit circuit design is very important.

The existing pixel unit capacitor is shown in FIG. 1 , which belongs to the voltage type pixel unit circuit and is composed of the most basic 2T1C (two transistors and one capacitor). Its basic working principle is:

(1) Data writing stage: when WR is at a high level, the M2 tube is turned on, and the input voltage signal VDATA is written to the gate of the M1 tube and the capacitor C1;

(2) Light-emitting stage: WR becomes low level, M2 tube is turned off, the data voltage stored on C1 drives M1 tube to generate corresponding drive current, the drive current flows through the OLED or LED device and emits light, and the brightness of the light is the same as write data corresponding to the voltage.

Problems existing in the prior art solutions:

Since the resolution of a microdisplay is generally 800×600 or above (1280×1024 or even higher), the number of pixel unit circuits reaches hundreds of thousands or even millions. However, due to the deviation in the manufacturing process of the existing CMOS process, there will be certain differences in the threshold voltage (Vth) of the M1 transistor in different pixel unit circuits, and then each driving transistor (M1) in the pixel array converts the input voltage to There will also be certain differences in the current, which will eventually affect the consistency of the display.

Utility model content

Aiming at the problem of display consistency caused by the threshold deviation of the voltage-type pixel unit circuit driving tube used in the existing self-luminous display, a novel voltage-type pixel unit circuit structure with threshold compensation is provided.

The utility model firstly discloses a voltage-type pixel unit circuit with threshold value compensation, which includes: a first transistor M1, a second transistor M2, a third transistor M3, a fourth transistor M4, a fifth transistor M5, and a sampling and holding capacitor C1 , data signal line VDATA, sampling control signal line SMP, hold signal line HLD, power line VDD, common cathode power line VCOM of the light emitting device, light emitting device,

The power line VDD is connected to the upper plate of the sampling and holding capacitor C1 on the one hand, and connected to the source of the fourth transistor M4 on the other hand; the lower plate of the sampling and holding capacitor C1 is respectively connected to the gate of the first transistor M1, the second transistor M1 the drain of the second transistor M2;

The sampling control signal line SMP is respectively connected to the gate of the second transistor M2 and the gate of the third transistor M3;

The holding signal line HLD is connected to the gate of the third transistor M4 and the gate of the fifth transistor M5;

The data signal line VDATA is connected to the drain of the third transistor M3;

The drain of the first transistor M1, the source of the second transistor M2, and the drain of the fourth transistor M4 are interconnected;

The source of the first transistor M1, the source of the third transistor M3, and the source of the fifth transistor M5 are interconnected;

The drain of the fifth transistor M5 is connected to the anode of the light emitting device;

The cathode of the light emitting device is connected to the power line VCOM.

Preferably, the light emitting device is OLED or LED.

Preferably, the first transistor M1 is an NMOS transistor, and the second transistor M2, the third transistor M3, the fourth transistor M4 and the fifth transistor M5 are all PMOS transistors.

The utility model also discloses a threshold voltage compensation driving method, based on the voltage-type pixel unit circuit with threshold compensation, including two stages:

(1) Data sampling and threshold compensation stage: In this stage, the sampling control signal line SMP is at low level, the signal line HLD is kept at high level, the first transistor M1, the second transistor M2 and the third transistor M3 are turned on, and the fourth The transistor and the fifth transistor M5 are turned off, and the light-emitting device is in a non-luminous state; at this time, the gate and drain of the first transistor M1 are short-circuited together through the second transistor M2, so that the first transistor M1 forms a diode connection form; with this At the same time, the data signal line VDATA is connected to the source of the first transistor M1 through the third transistor M3. At this stage, since the fourth transistor M4 is cut off, the gate of the fourth transistor M4 is the lower pole of the sample and hold capacitor C1. The board holding voltage is VDATA+Vth, wherein Vth is the threshold voltage of the first transistor M1;

(2) Light-emitting stage: In this stage, the sampling control signal line SMP is at high level, HLD is at low level, the second transistor M2 and the third transistor M3 are cut off, the fourth transistor M4 and the fifth transistor M5 are turned on, and the sampling control signal line is kept at the sampling level. The voltage VDATA+Vth on the storage capacitor C1 drives the first transistor M1 to generate a driving current I _M1 and flows through the fifth transistor M5 and the light emitting device, and the light emitting device emits light of corresponding intensity according to the magnitude of the driving current I _M1 ; the driving current I _M1 The size is specifically:

(2-1) If the first transistor M1 works in the subthreshold region:

In the formula, I ₀ represents the normalized drain current when the first transistor M1 works at the subthreshold, V _th represents the threshold voltage of the first transistor M1, n is an empirical value related to the process, V _T is the thermal voltage, W and L respectively represent the width and length of the channel of the first transistor M1, V _DATA represents the input data voltage, and V _x represents the source terminal voltage of the first transistor M1;

(2-2) If the first transistor M1 works in the linear region:

In the formula, μ represents the mobility of the first transistor M1, C _ox represents the gate-oxygen capacitance per unit area of the first transistor M1, V _DS,M1 represents the source-drain voltage of the first transistor M1, and V _th represents the threshold voltage of the first transistor M1 , V _DATA represents the input data voltage, V _x represents the source terminal voltage of the first transistor M1, W and L represent the width and length of the channel of the first transistor M1 respectively;

(2-3) If the first transistor M1 works in the saturation region:

In the formula, μ represents the mobility of the first transistor M1, C _ox represents the gate oxygen capacitance per unit area of the first transistor M1, V _th represents the threshold voltage of the first transistor M1, V _DATA represents the input data voltage, and V _x represents the first The source terminal voltage of the transistor M1, W and L respectively represent the width and length of the channel of the first transistor M1.

The utility model also discloses an image or video display method. Based on the threshold voltage compensation driving method, the alternate operation of the two working stages completes the update of the display data of one frame, and then completes the display of the image or video. .

Beneficial effects of the utility model

The novel voltage-type pixel unit drive circuit with threshold compensation proposed in this patent can effectively solve the fluctuation of the drive current of the pixel array caused by the change of the threshold of the drive tube, thereby improving the display consistency of the entire display.

Description of drawings

Figure 1 is a traditional voltage-type pixel unit circuit

Fig. 2 is the voltage type pixel unit circuit of the present utility model

Fig. 3 is the sampling compensation stage of the voltage type pixel unit circuit of the present invention

Fig. 4 is the light-emitting stage of the voltage-type pixel unit circuit of the present invention

Fig. 5 is the working timing diagram of the voltage-type pixel unit circuit of the present invention

Detailed ways

The utility model will be further described below in conjunction with embodiment, but protection scope of the utility model is not limited to this:

In conjunction with FIG. 2, a voltage-type pixel unit circuit with threshold compensation includes: a first transistor M1, a second transistor M2, a third transistor M3, a fourth transistor M4, a fifth transistor M5, a sampling and holding capacitor C1, and a data signal line VDATA, sampling control signal line SMP, hold signal line HLD, power line VDD, common cathode power line VCOM of the light emitting device, light emitting device,

The power line VDD is connected to the upper plate of the sampling and holding capacitor C1 on the one hand, and connected to the source of the fourth transistor M4 on the other hand; the lower plate of the sampling and holding capacitor C1 is respectively connected to the gate of the first transistor M1, the second transistor M1 the drain of the second transistor M2;

The sampling control signal line SMP is respectively connected to the gate of the second transistor M2 and the gate of the third transistor M3;

The holding signal line HLD is connected to the gate of the third transistor M4 and the gate of the fifth transistor M5;

The data signal line VDATA is connected to the drain of the third transistor M3;

The drain of the first transistor M1, the source of the second transistor M2, and the drain of the fourth transistor M4 are interconnected;

The source of the first transistor M1, the source of the third transistor M3, and the source of the fifth transistor M5 are interconnected;

The drain of the fifth transistor M5 is connected to the anode of the light emitting device;

The cathode of the light emitting device is connected to the power line VCOM.

Wherein: the light emitting device may be OLED or LED. The first transistor M1 is an NMOS transistor, and the second transistor M2 , the third transistor M3 , the fourth transistor M4 and the fifth transistor M5 are all PMOS transistors.

A driving method for threshold voltage compensation, based on the voltage-type pixel unit circuit with threshold compensation, including two stages:

(1) Data sampling and threshold compensation stage: in combination with FIG. 3 , at this stage, the sampling control signal line SMP is at a low level, and the holding signal line HLD is at a high level, and the first transistor M1, the second transistor M2 and the third transistor M3 conduct turn on, the fourth transistor and the fifth transistor M5 are cut off, and the light-emitting device is in a non-luminous state; at this time, the gate and drain of the first transistor M1 are short-circuited together through the second transistor M2, so that the first transistor M1 forms a diode connection At the same time, the data signal line VDATA is connected to the source of the first transistor M1 through the third transistor M3. At this stage, since the fourth transistor M4 is cut off, the gate of the fourth transistor M4 is the sample and hold capacitor The lower plate of C1 maintains a voltage of VDATA+Vth, wherein Vth is the threshold voltage of the first transistor M1;

(2) Light-emitting stage: in combination with FIG. 4 , at this stage, the sampling control signal line SMP is at high level, HLD is at low level, the second transistor M2 and the third transistor M3 are turned off, and the fourth transistor M4 and the fifth transistor M5 are turned on , the voltage VDATA+Vth kept on the sampling and holding capacitor C1 drives the first transistor M1 to generate a driving current I _M1 and flows through the fifth transistor M5 and the light-emitting device, and the light-emitting device emits light of corresponding intensity according to the magnitude of the driving current I _M1 ; The magnitude of the current I _M1 is specifically:

(2-1) If the first transistor M1 works in the subthreshold region:

In the formula, I ₀ represents the normalized drain current when the first transistor M1 works at the subthreshold, V _th represents the threshold voltage of the first transistor M1, n is an empirical value related to the process, V _T is the thermal voltage, W and L respectively represent the width and length of the channel of the first transistor M1, V _DATA represents the input data voltage, and V _x represents the source terminal voltage of the first transistor M1;

(2-2) If the first transistor M1 works in the linear region:

In the formula, μ represents the mobility of the first transistor M1, C _ox represents the gate-oxygen capacitance per unit area of the first transistor M1, V _DS,M1 represents the source-drain voltage of the first transistor M1, and V _th represents the threshold voltage of the first transistor M1 , V _DATA represents the input data voltage, V _x represents the source terminal voltage of the first transistor M1, W and L represent the width and length of the channel of the first transistor M1 respectively;

(2-3) If the first transistor M1 works in the saturation region:

In the formula, μ represents the mobility of the first transistor M1, C _ox represents the gate oxygen capacitance per unit area of the first transistor M1, V _th represents the threshold voltage of the first transistor M1, V _DATA represents the input data voltage, and V _x represents the first The source terminal voltage of the transistor M1, W and L respectively represent the width and length of the channel of the first transistor M1.

It can be seen that since a Vth is compensated in the sampling stage, the final current formula has nothing to do with Vth. The novel voltage-type pixel unit drive circuit with threshold compensation proposed in this patent can effectively solve the fluctuation of the drive current of the pixel array caused by the change of the threshold of the drive tube, thereby improving the display consistency of the entire display.

An image or video display method, based on the threshold voltage compensation driving method, with reference to Figure 5, the alternate operation of the two working stages completes a frame of display data update, and then completes the image or video display.

The specific embodiments described herein are only examples to illustrate the spirit of the present invention. Those skilled in the technical field to which the utility model belongs can make various modifications or supplements to the described specific embodiments or adopt similar methods to replace them, but they will not deviate from the spirit of the utility model or go beyond the appended claims defined range.

Claims (3)

1. a kind of voltage-type pixel unit circuit with threshold compensation, it is characterised in that it includes: the first transistor M1, the second crystalline substance Body pipe M2, third transistor M3, the 4th transistor M4, the 5th transistor M5, sampling holding capacitor C1, data signal line VDATA, Sampling control signal line SMP, common cathode power supply line VCOM, the photophore for keeping signal wire HLD, power supply line VDD, luminescent device Part,

On the one hand the power supply line VDD connects the top crown of sampling holding capacitor C1, on the other hand connect the 4th transistor M4's Source electrode；The bottom crown of the sampling holding capacitor C1 is separately connected the drain electrode of the grid of the first transistor M1, second transistor M2；

The sampling control signal line SMP is separately connected the grid of the grid of second transistor M2, third transistor M3；

The grid of the grid for keeping signal wire HLD connection third transistor M4, the 5th transistor M5；

The drain electrode of the data signal line VDATA connection third transistor M3；

The drain electrode of the first transistor M1, the source electrode of second transistor M2, the 4th transistor M4 drain electrode mutual connection；

The source electrode of the first transistor M1, the source electrode of third transistor M3, the 5th transistor M5 source electrode mutual connection；

The drain electrode of the 5th transistor M5 is connected with the anode of luminescent device；

The cathode of the luminescent device is connected with power supply line VCOM.

2. circuit according to claim 1, it is characterised in that the luminescent device is OLED or LED.

3. circuit according to claim 1, it is characterised in that the first transistor M1 is NMOS tube, second transistor M2, the Three transistor M3, the 4th transistor M4 and the 5th transistor M5 are PMOS tube.