CN105304023A - Pixel recession compensation circuit of silicon-based organic light emitting micro-display - Google Patents

Abstract

The invention relates to a pixel decay compensation circuit of a silicon-based organic light-emitting microdisplay. It is composed of a pixel unit circuit, an anode voltage readout circuit and a reference current generation circuit. The pixel driving circuit includes three switching transistors, a driving transistor, a storage capacitor and an organic light emitting diode. Wherein, the gate of the first switching transistor is connected to the row driving signal, the drain is connected to the column driving signal, and the source is connected to the gate of the third switching transistor. When the first transistor is selected in the row, the column driving signal is written into the storage capacitor to control the state of the three switching transistors. The drain of the third switching transistor is connected to the anode of the organic light emitting diode, the source is connected to the drain of the driving transistor, the source of the driving transistor is connected to the positive power supply, and the gate is connected to the reference voltage of the reference current generating circuit as the driving voltage. The readout circuit is composed of a second switch transistor, the gate is connected to the readout signal, and the source is connected to the anode of the organic light emitting diode. When the readout signal is valid, the drain of the second switch transistor outputs the anode voltage.

Description

Pixel degradation compensation circuit for silicon-based organic light-emitting microdisplays

technical field

The invention relates to a pixel decay compensation circuit of a silicon-based organic light-emitting microdisplay.

Background technique

Silicon-based organic light-emitting diodes (OLED-on-Silicon, OrganicLightEmittingDiodeonSilicon) combine organic light-emitting diodes with single-crystal silicon integrated circuits. CMOS technology has the characteristics of low cost and small size, and is the cornerstone of the integrated circuit industry; OLED has the advantages of low power consumption, self-illumination, wide viewing angle, low cost, good temperature adaptability, and fast response speed. The advantages of the combination of the two make silicon-based organic light-emitting diodes a high-profile new display technology.

Generally, a display whose screen diagonal is less than 3.3cm is defined as a microdisplay. The size of the micro-display itself is small, but it can realize super large-screen display through the optical system. The micro-display system has low cost, low voltage, small size, easy to carry, flexible application, and has broad application prospects. It is widely used in medicine, military, aviation, etc. Aerospace, industrial control and consumer electronics and other fields.

Organic light-emitting diode micro-display technology has become a research hotspot at home and abroad. At present, more and more people are involved in the research of OLED fading compensation for the problem of OLED fading, and some driving compensation circuits have been proposed. When OLED displays high-contrast and high-brightness displays for a long time, the OLED pixels decay inconsistently, resulting in poor luminous consistency. When the screen is refreshed, blurred afterimages will be observed. The place where the original luminous brightness is dark decays slowly, and the luminous light will be brighter. , and the place where the original luminous brightness is high decays faster, and the luminous light will be dim.

Contents of the invention

The purpose of the present invention is to provide a silicon-based organic light-emitting diode micro-display pixel degradation compensation circuit for the defects in the prior art, which uses a current-type pulse width modulation drive circuit to effectively solve the problem of long-time After the display, the image sticking and brightness decay phenomenon are caused by the remarkable improvement of the luminous consistency of the silicon-based organic light-emitting diode micro-display.

In order to achieve the above object, the idea of the present invention is: the decline of silicon-based organic light-emitting diodes (OLED-on-Silicon, Organic Light Emitting Diode on Silicon) is due to the internal resistance of OLEDs after long-term uneven brightness display, and the internal resistance of different OLEDs If the size is different, when the internal resistance increases to a certain extent, image sticking will occur. According to the luminous characteristics of OLED, if the luminous current of OLED remains unchanged, although the internal resistance is different, the consistency of luminous brightness can be improved, and at the same time Read out the anode voltage of the OLED to monitor the decline of the OLED, and compensate the brightness of the OLED through the type scanning control algorithm, and the microdisplay can maintain a good luminous consistency after a long time display.

According to the above invention design, this paper adopts the following technical solutions:

A silicon-based organic light-emitting microdisplay pixel decay compensation circuit, composed of a pixel unit circuit (1) connected to an organic light-emitting diode OLED anode voltage readout circuit (2) and a reference current generation circuit (3), as shown in Figure 1 As shown, it is characterized by:

The pixel unit circuit (1) includes a first switching transistor T1, a third switching transistor T3, a storage capacitor Cs and a driving transistor T4;

The first switching transistor T1: the drain is connected to the array driving signal Data, the gate is connected to the row driving signal Sel, the source is connected to the gate of the third switching transistor T3, and connected to the power supply Vdd through the storage capacitor Cs; the first switching transistor T1 When the row drive signal Sel is valid, the column drive signal Data is written into the storage capacitor Cs;

The third switching transistor T3: the drain is connected to the anode of the organic light emitting diode OLED, the source is connected to the drain of the driving transistor T4, the gate is connected to the power supply VDD through the storage capacitor Cs, and the signal of the storage capacitor controls the third switching transistor T3 switch status;

The storage capacitor Cs: terminal A is connected to the source of the first switching transistor T1 and the gate of the third switching transistor T3, and the other terminal is connected to the power supply VDD;

The drive transistor T4: the gate is connected to the reference level Vref(D) of the reference current source generating circuit (3), the source is connected to the power supply VDD, and the drain is connected to the source of the third switching transistor T3;

The silicon-based organic light emitting diode (OLED): the anode is connected to the drain of the third switching transistor T3, and the cathode is connected to the negative terminal power supply Vcom; when the third switching transistor T3 is turned on, the organic light emitting diode OLED is connected in series with the driving transistor T4, so that the organic light emitting diode OLED The light-emitting diode OLED works in the lighted state;

The anode voltage readout circuit (2) of the organic light emitting diode OLED includes a second switching transistor T2;

The second switching transistor T2: the gate is connected to the readout signal Read, and the source is connected to the anode of the organic light emitting diode OLED and the drain of the third switching transistor T3; when the Read signal is valid, the second switching transistor T2 is turned on, through The drain of the second switch transistor T2 outputs the OLED anode voltage Vread;

The reference current generation circuit (3) includes a fifth drive transistor T5, a sixth drive transistor T6, a seventh drive transistor T7 and a current source Iref;

The fifth drive transistor T5: the gate is connected to the gate of the fourth drive transistor T4, the source is connected to the power supply VDD, the drain is connected to the gate and connected to the drain of the sixth drive transistor T6;

The sixth driving transistor T6: the source is grounded, the gate is connected to the drain and connected to the gate of the seventh driving transistor T7;

The seventh driving transistor T7: the source is grounded, the gate and the upper drain are connected to one end of the current source Iref;

The reference current generation circuit (3) provides a reference level Vref for the pixel unit circuit, and the reference level Vref is used to turn on the fourth drive transistor T4 to control the luminance of the organic light emitting diode; when the row drive signal Sel is at low level, The switching transistor T1 is turned on, and the column drive signal is stored in the storage capacitor Cs. When the stored value of the storage capacitor Cs is low, the switching transistor T3 is turned on, and the driving transistor T4 drives the OLED to emit light. When the stored value of the storage capacitor Cs is high Normally, the switching transistor T3 is turned off, and the OLED does not emit light; when the OLED emits light, Read is at a low level, the switching transistor T2 is turned on, and the OLED anode voltage Vread is read out; the circuit working timing diagram is shown in Figure 3.

The silicon-based organic light-emitting microdisplay pixel degradation compensation circuit is characterized in that: the first switching transistor T1, the second switching transistor T2, the third switching transistor T3 and the driving transistor T4 adopt metal-oxide layer-semiconductor-field Any one of effective transistors, polysilicon thin film transistors, zinc oxide-based thin film transistors, and organic thin film transistors.

In the silicon-based organic light-emitting microdisplay pixel decay compensation circuit, the pixel unit circuit can generate a pulse width modulation waveform, and the pixel unit circuit is controlled by a digital driving method; the operating current of the silicon-based organic light-emitting diode can be from 1nA to 1uA, depending on the The cell size of the OLED, by adjusting the value of Iref, while the voltage at the two ends of the OLED is constantly changing, to ensure that the OLED can work at a suitable brightness. Vref is the driving voltage of the pixel unit circuit, and Vref can be obtained through a self-biased low-voltage cascode current mirror, an active current mirror, and a fixed voltage source, as shown in FIG. 4 , FIG. 5 and FIG. 6 .

The pixel degradation compensation circuit for silicon-based organic light-emitting microdisplays is characterized in that, as shown in Figure 2, the pixel drive unit can pass the column drive signal through two switch transistors (T1, T1') or more than two switch transistors. The Data signal is transmitted to the gate of the third switch transistor T3, and the two or more switch transistors can be N-type or P-type transistors with the same structure and minimum process size.

The pixel degradation compensation circuit for silicon-based organic light-emitting microdisplays is characterized in that: the second switching transistor T2 adopts a P-type transistor structure, and the length W and width L of the transistor can adopt the minimum value of the transistor process size.

The silicon-based organic light-emitting microdisplay pixel degradation compensation circuit is characterized in that the third switch transistor T3 adopts a P-type transistor structure, and the length W and width L of the transistor can adopt the minimum value of the transistor process size; the minimum value of Vcom depends on the first The withstand voltage of the three-switch transistor T3, according to the process of the third switch transistor T3, the range of Vcom is -10V to 0V, and the range of VDD is 3V to 10V;

The silicon-based organic light-emitting microdisplay pixel decay compensation circuit is characterized in that: the fourth drive transistor T4 adopts a P-type transistor structure, and the difference in width to length ratio affects the output current of the OLED, and at the same time affects the OLED decay compensation effect. The value of the aspect ratio can be from 0.5 to 5; the smaller the aspect ratio, the smaller the OLED output current and the better the compensation effect.

The silicon-based organic light-emitting microdisplay pixel degradation compensation circuit is characterized in that: the capacitor Cs adopts a polycrystalline-insulator-polycrystalline PIP capacitor, a metal-insulator-metal MIM capacitor, a metal-oxide-metal MOM capacitor or Any of the deep channel capacitors; the value range of the storage capacitor Cs must be less than 120ff, and Cs can be replaced by any other equivalent capacitor, such as transistor gate capacitance.

Compared with the prior art, the present invention has the following prominent substantive characteristics and significant advantages:

First, the present invention can generate current pulse width modulated waves.

Second, the drive compensation circuit of the present invention has a significant effect on OLED fading compensation, enabling the OLED to maintain better luminous consistency after a long period of use.

Thirdly, the transistors of the pixel unit circuit of the present invention all use P-type transistors, which is beneficial to the layout design of the layout.

Fourth, the pixel circuit of the present invention can read out the anode voltage of the OLED, and the degradation degree of the OLED can be known through the degradation model.

Description of drawings

Figure 1 is a pixel degradation compensation circuit for a silicon-based organic light-emitting microdisplay.

Figure 2 is a pixel unit circuit dual-tube drive circuit.

FIG. 3 is a working timing diagram of FIG. 1 .

Figure 4 and Figure 5 are various current mirror structures of the reference current generating circuit.

Figure 6 is a reference current generating circuit composed of a fixed voltage source.

detailed description

Preferred embodiments of the present invention are described below with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Embodiment one:

Referring to Fig. 1, a silicon-based organic light-emitting microdisplay pixel degradation compensation circuit is composed of a pixel unit circuit (1) connected to an anode voltage readout circuit (2) of an organic light-emitting diode and a reference current generation circuit (3).

The pixel unit circuit (1) includes a first switching transistor T1, a third switching transistor T3, a storage capacitor Cs and a driving transistor T4;

The first switching transistor T1: the drain is connected to the array driving signal Data, the gate is connected to the row driving signal Sel, the source is connected to the gate of the third switching transistor T3, and connected to the power supply Vdd through the storage capacitor Cs; the first switching transistor T1 When the row drive signal Sel is valid, the column drive signal Data is written into the storage capacitor Cs;

The third switching transistor T3: the drain is connected to the anode of the organic light emitting diode, the source is connected to the drain of the driving transistor T4, the gate is connected to the storage capacitor Cs and connected to the power supply VDD, and the signal of the storage capacitor controls the third switching transistor T3 switch status;

The storage capacitor Cs: terminal A is connected to the source of the first switching transistor T1 and the gate of the third switching transistor T3, and the other terminal is connected to the power supply VDD;

The drive transistor T4: the gate is connected to the reference level Vref(D) of the reference current source generating circuit, the source is connected to the power supply VDD, and the drain is connected to the source of the third switching transistor T3;

The organic light emitting diode OLED: the anode is connected to the drain of the third switching transistor T3, and the cathode is connected to the negative terminal power supply Vcom; when the third switching transistor T3 is turned on, the organic light emitting diode OLED is connected in series with the driving transistor T4, so that the organic light emitting diode OLED works in the lit state;

The anode voltage readout circuit (2) of the organic light emitting diode OLED includes a second switching transistor T2;

The second switch transistor T2: the gate is connected to the read signal Read, the source is connected to the anode of the organic light emitting diode and the drain of the third switch transistor T3; when the Read signal is valid, the second switch transistor T2 is turned on, and the The drain of the second switch transistor T2 outputs the OLED anode voltage Vread;

The reference current generation circuit (3) includes a fifth drive transistor T5, a sixth drive transistor T6, a seventh drive transistor T7 and a current source Iref;

The fifth drive transistor T5: the gate is connected to the gate of the fourth drive transistor T4, the source is connected to the power supply VDD, the drain is connected to the gate and connected to the drain of the sixth drive transistor T6;

The sixth driving transistor T6: the source is grounded, the gate is connected to the drain and connected to the gate of the seventh driving transistor T7;

The seventh driving transistor T7: the source is grounded, the gate and the upper drain are connected to one end of the current source Iref;

The reference current generation circuit (3) provides a reference level Vref for the pixel unit circuit, and the reference level Vref is used to turn on the fourth drive transistor T4 to control the luminance of the organic light emitting diode; when the row drive signal Sel is at low level, The switching transistor T1 is turned on, and the column drive signal is stored in the storage capacitor Cs. When the stored value of the storage capacitor Cs is low, the switching transistor T3 is turned on, and the driving transistor T4 drives the OLED to emit light. When the stored value of the storage capacitor Cs is high Normally, the switching transistor T3 is turned off, and the OLED does not emit light; when the OLED emits light, Read is at a low level, and the switching transistor T2 is turned on, and the OLED anode voltage Vread is read;

Embodiment two:

This embodiment is basically the same as Embodiment 1, and the special features are as follows:

In the silicon-based organic light-emitting microdisplay pixel decay compensation circuit, the pixel unit circuit can generate a pulse width modulation waveform, and the pixel unit circuit is controlled by a digital driving method; the operating current of the silicon-based organic light-emitting diode can be from 1nA to 1uA, depending on the The cell size of the OLED, by adjusting the value of Iref, while the voltage at the two ends of the OLED is constantly changing, to ensure that the OLED can work at a suitable brightness. Vref can be obtained by a fixed voltage source, an active current mirror, or a self-biased low-voltage cascode current mirror.

The silicon-based organic light-emitting microdisplay pixel degradation compensation circuit is characterized in that: the pixel drive unit can transmit the column drive signal Data signal to the third through two switch transistors (T1, T1') or more than two switch transistors As for the gate of the switch transistor T3, two or more switch transistors can be N-type or P-type transistors with the same structure and minimum process size.

The pixel degradation compensation circuit for silicon-based organic light-emitting microdisplays is characterized in that: the second switching transistor T2 adopts a P-type transistor structure, and the length W and width L of the transistor can adopt the minimum value of the transistor process size.

The silicon-based organic light-emitting microdisplay pixel degradation compensation circuit is characterized in that the third switch transistor T3 adopts a P-type transistor structure, and the length W and width L of the transistor can adopt the minimum value of the transistor process size; the minimum value of Vcom depends on the first The withstand voltage of the three-switch transistor T3, according to the process of the third switch transistor T3, the range of Vcom is -10V to 0V, and the range of VDD is 3V to 10V;

The silicon-based organic light-emitting microdisplay pixel decay compensation circuit is characterized in that: the fourth drive transistor T4 adopts a P-type transistor structure, and the difference in width to length ratio affects the output current of the OLED, and at the same time affects the OLED decay compensation effect. The value of the aspect ratio can be from 0.5 to 5; the smaller the aspect ratio, the smaller the OLED output current and the better the compensation effect.

The silicon-based organic light-emitting microdisplay pixel degradation compensation circuit is characterized in that: the capacitor Cs adopts a polycrystalline-insulator-polycrystalline PIP capacitor, a metal-insulator-metal MIM capacitor, a metal-oxide-metal MOM capacitor or Any of the deep channel capacitors; the value range of the storage capacitor Cs must be less than 120ff, and Cs can be replaced by the transistor gate capacitor.

Claims (7)

1. a silicon-based organic light-emitting microdisplay pixels decline compensating circuit, connects the anode voltage sensing circuit (2) of an Organic Light Emitting Diode OLED by pixel unit circuit (1) and a reference current generating circuit (3) is formed, and it is characterized in that:

Described pixel unit circuit (1) comprises the first switching transistor T1, the 3rd switching transistor T3, memory capacitance Cs and driving transistors T4; Described first switching transistor T1: drain electrode connects array drive signals Data, grid connected row drive singal Sel, source electrode connects the grid of the 3rd switching transistor T3, and connects power supply Vdd through memory capacitance Cs; Row drive singal Data, in the effective situation of horizontal-drive signal Sel, is write into memory capacitance Cs by the first switching transistor T1; Described 3rd switching transistor T3: drain electrode is connected with the anode of OLED OLED, source electrode connects the drain electrode of driving transistors T4, grid meets memory capacitance Cs and connects power vd D, and controls the on off state of the 3rd switching transistor T3 by the signal of memory capacitance;

Described memory capacitance Cs:A holds the source electrode of connection first switch transistor T 1 and the grid of the 3rd switching transistor T3, and another pole connects power vd D; Described driving transistors T4: grid connects the reference level Vref (D) of reference current source generating circuit, source electrode connects power vd D, the source electrode of drain electrode connection the 3rd switching transistor T3; Described Organic Light Emitting Diode OLED: anode connects the drain electrode of the 3rd switching transistor T3, negative electrode connects negative terminal power supply Vcom; When the 3rd switching transistor T3 conducting, Organic Light Emitting Diode OLED connects with driving transistors T4, makes silicon-based organic light-emitting diode OLED be operated in illuminating state;

The anode voltage sensing circuit (2) of described Organic Light Emitting Diode OLED comprises second switch transistor T2; Described second switch transistor T2: grid connects read output signal Read, and source electrode is connected with the anode of OLED and the drain electrode of the 3rd switching transistor T3; When Read signal is effective, second switch transistor T2 conducting, exports OLED anode voltage Vread by the drain electrode of second switch transistor T2;

Described reference current generating circuit (3) comprises the 5th driving transistors T5, the 6th driving transistors T6, the 7th driving transistors T7 and current source Iref; Described 5th driving transistors T5: grid connects the grid of four-wheel drive transistor T4, source electrode connects power vd D, drains and to be connected with grid and to be connected to the drain electrode of the 6th driving transistors T6; Described 6th driving transistors T6: source ground, grid is connected with drain electrode and is connected to the grid of the 7th driving transistors T7; Described 7th driving transistors T7: source ground, grid also upper drain electrode connects one end of current source Iref;

Described reference current generating circuit (3) provides a reference level Vref for pixel unit circuit, and this reference level Vref is used for opening the luminosity that four-wheel drive transistor T4 controls Organic Light Emitting Diode; When horizontal-drive signal Sel is low level, switching transistor T1 conducting, by row drive singal stored in memory capacitance Cs, when the storing value of memory capacitance Cs is low level, switching transistor T3 opens, and driving transistors T4 driving OLED is luminous, when memory capacitance Cs storing value is high level, then switching transistor T3 closes, and OLED is not luminous; When OLED is luminous, Read is low level, and switching transistor T2 opens, and reads OLED anode voltage Vread.

2. silicon-based organic light-emitting microdisplay pixels according to claim 1 decline compensating circuit, is characterized in that: described first switching transistor T1, second switch transistor T2, the 3rd switching transistor T3 and driving transistors T4 adopt in metal-oxide layer-semiconductor-field-effect transistor, polycrystalline SiTFT, Zinc oxide based film transistor and OTFT any one.

3. silicon-based organic light-emitting microdisplay pixels decline compensating circuit according to claim 1, it is characterized in that: described pixel drive unit circuit (1) by the switching transistor of 2 switching transistors (T1, T1 ') or more than 2 by row drive singal Data Signal transmissions to the grid of the 3rd switching transistor T3, this switching transistor of more than 2 or 2 can adopt mutually isostructural N-type or P-type crystal pipe.

4. silicon-based organic light-emitting microdisplay pixels decline compensating circuit according to claim 1, it is characterized in that: described second switch transistor T2 adopts P-type crystal tubular construction, the long W of transistor and wide L range of size are 0.13um ~ 0.6um or are below 2um.

5. silicon-based organic light-emitting microdisplay pixels decline compensating circuit according to claim 1, it is characterized in that: described 3rd switching transistor T3 adopts P-type crystal tubular construction, the minimum of Vcom depends on that the 3rd switching transistor T3's is withstand voltage, according to the technique of the 3rd switching transistor T3, the scope of Vcom be-10V to the span of 0V, VDD be 3V to 10V.

6. silicon-based organic light-emitting microdisplay pixels decline compensating circuit according to claim 1, is characterized in that: described four-wheel drive transistor T4 adopts P-type crystal tubular construction, and the value of breadth length ratio can from 0.5 to 5; Breadth length ratio is less, and OLED output current is less, and compensating effect is better.

7. silicon-based organic light-emitting microdisplay pixels decline compensating circuit according to claim 1, is characterized in that: described memory capacitance Cs can adopt any one in polycrystalline-insulator-polycrystalline PIP capacitor, metal-insulator-metal type MIM capacitor, metal-oxide-metal MOM capacitor or deep trench electric capacity; The span of memory capacitance Cs need be less than 120ff, and Cs can replace with transistor gate electric capacity.