TW569173B - Driver for controlling display cycle of OLED and its method - Google Patents

Abstract

The present invention provides a driver for controlling display cycle of OLED and its method. The driver includes: a current buffer, a switch unit and PWM gray-level control unit. The current buffer is connected to a current source providing a constant current. The switch unit is connected to a precharge voltage source, the current buffer and an analog ground, and has an output terminal connected to the OLED. The PWM gray-level control unit is connected to a memory and the switch unit for receiving a start signal and then performing gray-level display control based on an image data transmitted from the memory. The gray-level control method performs rational partition on gray-level display time based on the display level in the display cycle, and respectively corresponds to a ratio based on the gray-level value corresponding to the image data. After receiving the image data, the driver performs conducting time control for the current buffer and OLED based on the corresponding gray-level display time, thereby achieving the purpose of gray-level display control.

Description

569173 _Case No. 91118049_year month_ || i_ V. Description of the Invention (1) [Application Field of the Invention] The present invention relates to a driver for an organic electroluminescent diode, in particular to a driver for controlling an organic electroluminescent diode Driver and method of display period of the body (OLED). [Background of the Invention] OLED displays are a new generation of flat-panel display technology using the principle of Organic Light-Emitting Diodes. Structurally, it is an Ermeiji structure. The current applied by the yin and yang electrodes, the organic compound material in between is excited by visible light, which is a self-luminous phenomenon. That is, the organic thin film in the 0LED will emit light by itself after reaching a certain amount of electricity, so there is no need for a backlight and a color filter. Therefore, the 0LED display is a current-controlled element. In other words, the light emission of each pixel (p i X e 1) can be achieved by controlling the amount of current. However, most of the 0LED displays on the market are monochrome products. In the monochrome 0LED display products, in order for the 0LED display to display different light and shade functions, we must start with the current control characteristics of the 0LED. For example, the lightness and darkness can be determined by the magnitude of the current flowing through the organic thin film of the 0LED display. Different gray levels can use different current sources to drive their lightness and darkness. This approach is quite complicated in terms of hardware design. Moreover, if the gray level is higher, more hardware is needed, and the design lacks a lot of flexibility. In addition, the entire 0LED display cycle includes a precharge phase, a display phase, and a discharge phase. The pre-charge phase is to allow the next display

569173 Case No. 91118049 Λ__η Name Amendment V. Description of the invention (2) Shows that the stage can proceed smoothly. After performing the current control (0 L E D display light-emitting display stage), after the discharge (DischarSe) stage, a complete display cycle is completed. Therefore, how to design a simple control circuit that allows the OLED display to control the display period and at the same time allows the monochromatic light to have the function of grayscale, has become the goal of the research and development personnel. [Objective and summary of the invention] In order to make OLED display, there are not only two options: bright and non-bright, and increase the difference between light and dark, so that the display can be richer. In addition, we also set presets for different panels. Charging time and discharging time to maintain the display quality of the panel. To achieve the above object, the present invention provides a driver for controlling a display period of an organic electro-luminescent diode (0 L E D), which includes: a current buffer, a switching unit, and a pulse width modulation gray-scale control unit. Among them, the current buffer is connected to a current source which provides a rated current. The switching unit is connected to a precharge voltage source, a current buffer, and an analog ground, and has an output terminal connected to the OLED. The PWM gray level control unit is connected to a memory and a switching unit, and is used to perform gray level display control after receiving a starting tfl number according to an image data transmitted by the memory. The method of gray level control is based on the proportion of the gray level display time according to the display stage in the display cycle, and each of them corresponds to a proportion according to the gray level value corresponding to the image data. The gray-scale display time is used to protect the on-time of the current buffer and the OLED to achieve the purpose of gray-scale display control. The invention provides a method for controlling the display of organic electro-luminescent diode (OLED).

Page 6 569173 _Case No. 91118049 _ year month day __ V. Description of the invention (3) The method of displaying cycle includes the following steps: First, receive an image data. Then, a grayscale display time is calculated based on the given image data. Next, pre-charge the OLED in the pre-charge phase. Then, a rated current is continuously supplied to the OLED to perform gray scale display until the gray scale display time is up. The OLED is discharged until the end of the display phase. Finally, the OLED is discharged to the end of the discharge phase. In order to make the above and other objects, features, and advantages of the present invention more comprehensible, several preferred embodiments are exemplified below, in conjunction with the accompanying drawings, as follows: [Detailed description of the invention] Please refer to "Figure 1" is a schematic diagram of an OLED driving system composed of a driver using the present invention. Random access memory (RAM) 1 0 stores the image data to be displayed each time, including the gray scale value to drive each 0 LED (respectively connected to SEG 1 ~ η); and the current source 30 is responsible for supplying a fixed current For each driver, a precharge voltage source 40 is responsible for supplying a precharge voltage to each driver. From the "Figure 1", it can be clearly found that each of the first driver 201, the second driver 202, and the n-th driver 20 0n is individually connected to the random access memory 10, the current source 30, and the Charging voltage source 40 is connected. Each driver finally outputs to the 0LED connected to each display cycle to control the 0LED display. For how to achieve the gray scale display of each pixel (p i X e 1) of the OLED display through the driver in the present invention, and control the operation process of the entire display cycle at the same time, please refer to the description in "Fig. 2". For the convenience of explanation, "Figure 2" is explained with a driver. Because the way to control the gray scale display is pulse width modulation (Pulse Width

569173 Case No. 91118049 Amendment V. Description of Invention (4)

Modulation (hereinafter referred to as PWM), therefore, the present invention uses a PWM gray-scale control unit. Each driver 20 includes a current buffer 22, a PWM gray-scale control unit 24, and a switching unit 26. Among them, the P medical gray-level control unit 24 is connected to the random access memory 10 to receive image data. The current buffer 22 is connected to the current source 30, and is used to output a constant current source control to 0 L E D. The switching unit 26 is connected to the precharge voltage source 40, the current buffer 22, the PWM gray-scale control unit 24, the analog ground (GNDA), and the 0LED (connected through s EG), which is used to receive the P WM gray-scale control The control of the unit 24 is to switch the current buffer 2 2. One of the precharge voltage source 40 and the analog ground (GNDA) is connected to the 0LED. The PWM gray-level control unit 24 controls the entire switching unit 26 to switch to one of the above three connections, and also controls the switching time. Including the time of the precharge phase when the pre-charging voltage source 40 and 〇LED are turned on, the gray-scale display time and time of the display stage when the current buffer 22 is turned on with 〇LED, and 'analog ground (GNDA) Discharge time when connected to 0LED. In other words, the PWM gray level control unit 2 4 controls the time of the entire display cycle, and the time length of each phase of the three 1 Pf segments is the rated value. However, the overall time of the display phase is fixed, but the grayscale display time is converted into the day when the current buffer 22 and 0LED are turned on with the grayscale value given by the random access memory 10: That is, provided by the random access memory 10. Attached to an f is the signal for enabling the start of the entire display phase (enable), which is provided by an external circuit, which is provided by another control line (out of day). The gray scale display of the present invention is achieved by controlling the on-time of the current buffer 22 and the 0LED. For specific methods, please refer to "Figure 3".

569173 ___Case No. 91118049_Year Month Revision __ V. Description of the invention (5) The operation principle of the PWM gray-scale control unit 24 can be specifically explained. It uses two bits and four types of gray levels to describe the gray level display. First, the pre-charge time and discharge time are fixed values, and can be set according to the panel specifications given by the panel supplier. In the display phase, the on-time of the OLED and the current buffer (that is, the time when the OLED emits light) can be divided into four types to obtain a four-monochrome grayscale display (such as Γ FIG. 3). Shown. The time of the display phase is fixed, and the display phase has two states: one is the conduction state of the current buffer, and the other is the ground state. Taking the gray level value 1 as an example, the OLED is grounded (GNDA) all the time during the display phase, and the on-time of the OLED and the current buffer 22 is zero, and its brightness is the lowest, that is, it is not bright. In the case of the grayscale value 2, the OLED is turned on for one third of the time with the current buffer 22, and two-thirds of the time is grounded, and its brightness is the next lowest. Taking the gray level value 3 as another example, 〇 L E D is turned on for two-thirds of the time with the current buffer 22, and one-third of the time is grounded, and its brightness is the next highest. Finally, with the gray level value 4, the time during which the OLED and the current buffer 22 are turned on is the entire display stage, and its brightness is the highest. Therefore, the present invention is quite simple in control, and only needs to control the switching action once in the display stage. Therefore, no matter how many bits of the grayscale value, the present invention can use the same method to achieve the purpose of grayscale control. For example, for three-bit grayscale values, the grayscale display time is 0, 1/7, 2/7, 3/7, ... 1 times the display stage. The time allocation method for other bits is the same. This control method is simple and practical, and the circuit design is relatively simple and not complicated. In addition, for different panels, some panels have a larger load and require a longer precharge time, and some panels have a smaller load and do not require a precharge time. also

Page 9569173 ---- Case No. 91118049 _ Year, Month, and Revision _ V. Description of the invention (6) That is, for different specifications of different panels, different pre-charge time and discharge time can be set to maintain the display of the panel Quality, as shown in "Figure 4". From the above point of view, the present invention actually provides a method for driving the OLED display cycle. For the specific process, please refer to "Fig. 5". The steps involved are explained as follows. First, the pre-charge phase, display phase, and discharge phase must be set during the entire display cycle. After receiving the enable (e n a b 1 e) signal, the entire control action is started. Initially, the above-mentioned random access memory 10 receives image data (step 5 10), and then calculates a gray scale value and converts it to a gray scale display time (step 5 2 0). With the time value of the gray scale display, you can control the gray scale display time during the display phase. Next, pre-charging for the rated time is performed (step 530), that is, the entire display cycle is started. Next, the PWM gray-scale control unit 24 starts counting and calculates whether or not the pre-charging time (T 1) is reached (step 5 4 0). Once the pre-charging time is up, the pw M grayscale control unit 24 controls the switching unit 26 to switch to the current buffer 22 and performs grayscale display according to the grayscale display time (step 5 50). The grayscale display method ^ 3 picture ". That is, the PWM gray-scale control unit 24 first controls the “1 changing unit 2 6 to connect the current buffer 2 2 to the output (connected via sE G and OLE D), and then controls the switching unit 26 to output (through SEG Phase 1) connected to GNDA, which can be discharged after being bloated, and its on-time needs to be controlled by the number of bits of gray scale value for display control. In the display stage, step 57〇! Λstep 56β0), if the display time of the eight-fruit gray scale is reached, the discharge is performed (step (T3) is reached, that is, regardless of the display situation in the display stage, the discharge is performed after time. The discharge time (T4) is based on the panel:

569173 Case No. 91118049 Month, Amendment 5. Design of the invention (7) (corresponding to the pre-charging time), this point is the same as the one described in "Figure 4". The above steps explain the entire control flow of the PWM gray-level control unit 24. This control flow can be made by means of a circuit, that is, the PWM gray-level control unit 24 of the present invention. [Effects of the invention] By using the driver and the driving method of the present invention, not only the hardware part is relatively simple in design, but also the complexity is low. In addition, according to the load of different panels, the present invention can also set different pre-charge time and discharge time to maintain the display quality of the panel.

Although the preferred embodiment of the present invention is disclosed as described above, it is not intended to limit the present invention. Any person skilled in the related art can make some changes and retouching without departing from the spirit and scope of the present invention. The patent protection scope of the invention shall be determined by the scope of the patent application scope attached to this specification.

Page 11 569173 _Case No. 91118049 _ Year Month Day __ Brief description of the diagram [Simplified illustration of the diagram] Figure 1 is the system architecture of the display system for controlling the display cycle of the organic electroluminescent diode (OLED) Fig. 2 is a functional block diagram of a specific embodiment of a driver for controlling a display period of an organic electroluminescent diode (OLED) according to the present invention; Fig. 3 is a first schematic view of a display period of the present invention; The second schematic diagram of the display cycle of the invention; and FIG. 5 is a control flowchart of the display cycle of the organic electroluminescent diode (OLED) of the invention. [Symbol description] 10 RAM 20 driver 201 first driver 202 second driver 20n driver N 22 current buffer 24 PWM gray level control unit 26 switching unit 30 current source 40 pre-charge voltage source GND ground GNDA Analog grounded OLED organic electroluminescent diode SEGU ~ η) Scan line

Page 12 2002.09.09.012

Claims (1)

569173 _Case No. 91118049_Amended in January / August 6, Application scope 1. A driver for controlling the display period of an organic electro-luminescent diode (OLED), which can control one of the organic circuits connected to the driver in each scanning cycle. The light-emitting gray-scale value of the excitation light diode includes: a current buffer connected to a current source providing a rated current, a switching unit connected to a precharge voltage source, the current buffer, and analog ground, and An output terminal connected to the organic motor light-emitting diode; and a pulse width modulation (PWM) gray-scale control unit connected to a memory and the switching unit for receiving each scan cycle together After the initial signal, gray-scale display control is performed according to an image data transmitted from the memory, and the switching unit is controlled at a first time to make the pre-charge voltage source and the organic electric light-emitting diode conductive, and then according to the image data The gray scale value is converted into a gray scale display time to control the switching unit so that the current buffer and the organic motor light emitting diode are turned on to make the organic The excitation light-emitting diode performs gray-scale light emission, and when the gray-scale display time is up, the switching unit is controlled so that the organic electrical excitation light-emitting diode is connected to the analog ground to a second time, and at the second time, When the time is up, the switching unit is controlled so that the organic electroluminescence photodiode is connected to the analog ground until a third time ends; wherein the sum of the first time, the second time, and the third time is The display period. 2. The driver according to item 1 of the scope of patent application, wherein the grayscale value is a grayscale value of more than two bits. 3. The driver according to item 1 of the scope of patent application, wherein the gray scale display Page 13 569173 _Case No. 9118049 , The grayscale display time is 0, 1/3, 2/3, 1 times the second time; for example, when the grayscale value is three bits, the grayscale display time is 0, 1/7 , 2/7,… 1 times the second time, and so on. 4. The driver according to item 1 of the scope of patent application, wherein the first time is set according to the display panel of different organic electro-luminescent diodes. 5. A method for controlling the display of organic electroluminescent diode (OLED) with a gray scale value, which sets a display period in advance, including a pre-charge phase, a display phase and a discharge phase. The method includes the following steps: receiving An image data; calculating a gray-scale display time based on the image data; pre-charging the organic electric excitation photodiode in the pre-charging stage; continuously supplying a rated current to the organic electric excitation photodiode for gray-scale display Until the gray-scale display time is reached; discharging the organic electro-luminescent diode to the end of the display phase; and discharging the organic electro-luminescent diode to the end of the discharging phase. 6. The method as described in item 5 of the scope of patent application, wherein the grayscale value is a grayscale value of more than two bits. 7. The method as described in item 5 of the scope of patent application, wherein the conversion of the gray scale display time is based on the scale value of the gray scale value for the second time ratio. Page 14 569173 _Case No. 9118049_year month__ VI. Patent application scope, for example, when the grayscale value is two bits, the grayscale display time is 0, 1/3, 2/3 , 1 times the second time; for example, when the grayscale value is three bits, the grayscale display time is 0, 1/7, 2/7, ... 1 times the second time, and so on. 8. The method as described in item 5 of the scope of patent application, wherein the first time is set according to a display panel of different organic electroluminescent diodes. 9. A driving structure for controlling the display period of an organic electroluminescent diode (0LED), which can control the organic electroluminescent diodes in a display matrix formed by a plurality of organic electroluminescent diodes each time a row or column is scanned The light emitting gray scale value of the body, the driving structure is composed of a plurality of drivers with the same number of organic electro-excitation light-emitting diodes as scanning rows or columns, each of which includes: a current buffer, and a current providing a fixed current Source phase connection; a switching unit connected to a precharge voltage source, the current buffer, and analog ground, and having an output terminal connected to a plurality of organic motor light emitting diodes; and a pulse width modulation (PWM ) A gray-scale control unit is connected to a memory and the switching unit, and is used for performing gray-scale display control according to an image data transmitted by the memory after receiving an initial signal for each scan, and a Controlling the switching unit to turn on the pre-charge voltage source and the organic electro-optic light-emitting diode, and then convert it to a gray-scale display according to the gray-scale value of the image data Time to control the switching unit so that the current buffer and the motor organic light emitting diode is turned on so that the organic electroluminescent Page 15 569173 _ Case No. 91118049 _ year month day__ VI. Patent application scope Diode emits light in grayscale, and when the grayscale display time is up, the switching unit is controlled to make the organic electroluminescent diode and The analog ground phase is connected until a second time is up, and the switching unit is controlled when the second time is up, so that the organic electrical excitation photodiode is connected with the analog ground phase until a third time is up to; The sum of the first time, the second time, and the third time is the display period. 10. The driving structure according to item 9 of the scope of patent application, wherein the grayscale value is a grayscale value of more than two bits. 1 1. The driving architecture as described in item 9 of the scope of patent application, wherein the conversion of the grayscale display time is based on the grayscale value and the second time is proportionally allocated. For example, when the grayscale value is two Bit, the grayscale display time is 0, 1/3, 2/3, 1 times the second time; for example, when the grayscale value is three bits, the grayscale display time is 0, 1 / 7, 2/7,… 1 times the second time, and so on. 1 2. The driving architecture as described in item 9 of the scope of patent application, wherein the first time is set according to the display panel of different organic electroluminescent diodes. Page 16