CN100446631C - Brightness adjusting circuit and electroluminescent display using the same - Google Patents

Abstract

A brightness adjusting circuit is used for an electroluminescent display. The brightness adjusting circuit is connected to an electroluminescent display panel. The brightness adjusting circuit is electrically connected with a voltage supply unit to provide a feedback voltage to the voltage supply unit. The voltage supply unit provides a driving voltage to the electroluminescent display panel according to the feedback voltage. The brightness adjusting circuit comprises a circuit module and a switch or a circuit module and a control voltage feed-in device. The feedback voltage of the circuit module is modulated by switching the switch according to a control signal or feeding different control voltages through the control voltage feeding device.

Description

Brightness adjustment circuit and electroluminescence display using it

technical field

The invention relates to a brightness adjustment circuit, in particular to an electroluminescence display brightness adjustment circuit.

Background technique

In recent years, in the flat panel display industry, Organic Light Emitting Diode Display (OLED Display) has the advantages of self-luminescence, high brightness, ultra-wide viewing angle, high response speed, low driving voltage and light weight. gradually gained attention. However, the current market share of electroluminescent displays is still limited. Therefore, all major display manufacturers are committed to finding the best manufacturing method to improve the production yield and product characteristics, hoping to promote electroluminescent displays as soon as possible. popularized in the market.

The organic electroluminescent display is a self-illuminating flat-panel display. Its light source is generated by itself through the conversion of the organic light-emitting diode pixel current, so by adjusting the current we can determine the maximum brightness of the panel, and then pass Coupled thin film transistors define different grayscale brightness, so that a full-color, multi-color-level effect can be presented.

The operating voltage (V _dd or V _ss ) of each pixel unit of the organic electroluminescent display is supplied by an external power supply, and the power consumption required for all the units in the organic electroluminescent display panel to emit light is all consumed by this power supply system supply. In circuit design, all working voltage input terminals (V _dd ) in all pixel units are connected in parallel, and all terminals (V _ss ) are also connected in parallel, and then individually guided to the outermost edge of the panel, and It is connected to an external power supply system through a flexible printed circuit board (Flexible Print Circuit; FPC) or wires.

The external power supply is designed as a set of stable voltage source systems, that is to say, it is designed so that the voltage at the output terminal is kept at a fixed set value, so as to ensure that the output voltage will not fluctuate due to the instability of the input voltage or noise interference The phenomenon. However, the voltage regulation method of a general stable voltage source system generally adopts a voltage feedback control method. FIG. 1 shows a schematic diagram of a known feedback-type stabilized voltage power supply device. The power supply device 100 has a power supply 102 and a feedback circuit (not shown). The power supply 102 has an output voltage terminal V _out and a feedback terminal 108 , the output voltage terminal V _out provides the working voltage (V _dd or V _ss ) of the pixel unit (not shown in the figure). The feedback circuit includes two resistors 104 and 106 connected in parallel with the pixel unit, wherein one end of the resistor 104 is electrically connected to the output voltage terminal V _out and one end of the resistor 106 is electrically connected to a reference voltage source, and the feedback terminal 108 is electrically connected to the resistor 104 and the resistor Between 106. The resistor 104 and the resistor 106 have a voltage dividing function, and the purpose is to generate a reference voltage value (generally 1.25V) set by the system and lead it into the feedback terminal 108 to monitor the stability of the output voltage. When the reference voltage value rises, the feedback terminal 108 sends a signal to reduce the output voltage of the output voltage terminal V _out so that the reference voltage returns to 1.25V; otherwise, when the reference voltage value decreases, the feedback terminal 108 sends a signal to increase the output voltage terminal V _out output to make the reference voltage back to 1.25V.

However, the known technology shown in Figure 1 is only to control the brightness of the pixel unit to be stable, but cannot adjust the brightness of the pixel unit. In order to prolong the service life of the material to solve or reduce the problem of life and image retention, some operating modes must be designed To prolong the use time of the panel, for example: do not use fixed-position images, do not use high-brightness images for a long time, etc., because high brightness and continuous conduction of organic light-emitting diodes are the two most likely to shorten the life of the panel the most important cause. If you want to deal with the two effects mentioned above, the way to avoid it can be to use intermittent lighting, such as 10 seconds or 20 seconds, and then reduce the brightness of the screen by half or to 1/3, so that it can achieve neither effect Usability can also increase the life of the panel.

Therefore, it is known to propose a circuit capable of adjusting the brightness of the pixel unit. Assuming that the pixel unit needs to be switched between 4 different brightness levels, the feedback regulated power supply device must provide switching of 4 voltage outputs. The known method is to design 4 different feedback resistor groups to match with the channel switcher. produce different output voltages. FIG. 2 shows a schematic diagram of a known feedback-type regulated power supply device that can adjust the brightness of a pixel unit. The power supply device 200 has a power supply 202 and a feedback circuit (not shown). The power supply 202 has an output voltage terminal V _out and a feedback terminal 204, the output voltage terminal V _out provides the working voltage (V _dd or V _ss ) of the pixel unit (not shown in the figure), wherein V _dd can be used for A pixel unit driven by a PMOS transistor and V _ss may be applicable to a pixel unit driven by an NMOS transistor. The feedback circuit includes four sets of series resistors connected in parallel, and four sets of two series resistors are predetermined to be connected in parallel with the pixel unit. The predetermined four groups of series resistors respectively include: 208 and 210, 214 and 216, 220 and 222, 226 and 228, wherein one end of the resistors 208, 214, 220, 226 is electrically connected to the output voltage terminal V _out and the resistors 210, 216, 222, One terminal of 228 is electrically connected to a reference voltage. Connection points 212, 218, 224 and 230 are respectively pulled out between the four series resistors 208 and 210, 214 and 216, 220 and 222, 226 and 228. The switch 206 is electrically connected to the feedback terminal 204 . Switch 206 may be electrically connected to connection points 212, 218, 224, and 230, respectively. Four sets of series resistors 208 and 210, 214 and 216, 220 and 222, 226 and 228 can be designed with different resistance values so that the switcher 206 can be fed into the feedback terminal when electrically connected to the connection points 212, 218, 224 and 230 respectively The feedback voltages of 204 are different, so as to adjust the output of V _out of the power supply 202 to change the brightness of the pixel unit. However, the known design is very unfavorable in terms of design rules for the area occupied by the circuit. How to effectively reduce the area occupied by the brightness adjustment circuit has become a very important issue.

Contents of the invention

According to the above, in order to reduce the design area occupied by the brightness adjustment circuit, the present invention provides a brightness adjustment circuit for an organic electroluminescent display, which can greatly reduce the design area occupied by the brightness adjustment circuit by at least 50%.

In a preferred embodiment of the present invention, an electroluminescence display brightness adjustment circuit is provided. The electroluminescence display includes an electroluminescence display panel and a voltage supply unit, and the voltage supply unit provides A drive voltage to the electroluminescent display panel, the brightness adjustment circuit at least includes: a circuit module and a switch, the circuit module is electrically connected to the electroluminescent display panel and the voltage supply unit, the circuit module includes: an internal circuit unit, an external A circuit unit, one end of the external circuit unit is connected to a reference voltage unit. The switcher modulates the resistance value of the circuit module according to a control signal to adjust the feedback voltage. The way of modulating the resistance value of the circuit module is to connect different parts of the external circuit and part of the internal circuit in parallel by changing the switch at different connection points, and in another embodiment of the present invention, form a series connection. Because the feedback voltage is obtained from the voltage at a specific point in the circuit module, changing the voltage division mode in the circuit module through the operation of the switch will change the voltage at the specific point, thereby changing the feedback voltage. In addition, the brightness adjustment circuit provided by the present invention can be arranged on the electroluminescence panel.

In yet another preferred embodiment of the present invention, an electroluminescent display brightness adjustment circuit is provided. The electroluminescent display includes an electroluminescent display panel and a voltage supply unit. Provide a driving voltage to the electroluminescence display panel, the brightness adjustment circuit at least includes: a circuit module, which is electrically connected with the voltage supply unit and the electroluminescence display panel; One end of the module feeds a control voltage to adjust the feedback voltage. The voltage feeding device can be a digital-to-analog conversion device.

The brightness adjustment circuit disclosed in the present invention does not need to modify or calculate the output data of the system end, but only by changing the parallel connection of some internal circuits and some external circuits, or by inputting a control voltage, to increase the brightness of the panel or diminished efficacy. In addition, the present invention can also be used to increase the brightness of organic electroluminescent displays. The circuit units in the circuit module are not limited to two groups, but can also be more than two groups, so the requirement of multi-stage brightness modulation can be achieved.

The purpose of the present invention is also to disclose an electroluminescent display using the above-mentioned brightness control circuit.

Description of drawings

In order to make the above-mentioned and other objects, features, advantages and embodiments of the present invention more comprehensible, the detailed description of the accompanying drawings is as follows:

FIG. 1 shows a schematic diagram of a known feedback-type regulated power supply device;

FIG. 2 shows a schematic diagram of a known feedback-type regulated power supply device that can adjust the brightness of a pixel unit;

Fig. 3 shows a circuit diagram for adjusting brightness of an electroluminescence display according to a first preferred embodiment of the present invention;

Fig. 4 shows a circuit diagram for adjusting brightness of an electroluminescence display according to a second preferred embodiment of the present invention; and

Fig. 5 shows a circuit diagram of a brightness adjustment circuit for an electroluminescence display according to a third preferred embodiment of the present invention.

Description of reference symbols

100, 200, 300, 400, 500: power supply unit

102, 202, 302, 402, 502: power supply

104, 106, 208, 210, 214, 216, 220, 222, 226, 228, 308, 310, 312, 316, 320, 408, 410, 412, 416, 420, 508, 510: resistance

108, 204, 304, 404, 504: feedback terminal

206, 306, 406: switcher

212, 218, 224, 230, 314, 318, 322, 414, 418, 422, 506: connection points

Detailed ways

In order to make the brightness adjustment circuit of the electroluminescence display provided by the present invention more clear, in several embodiments of the present invention, the circuit module only includes two circuit units as an example to describe in detail how to implement the present invention. Of course, the present invention does not only Only limited to the circuit module including two circuit units, the circuit module including more than two circuit units can also realize multi-stage brightness modulation as disclosed in the embodiment. In the embodiment, the PMOS transistor is used to drive the electroluminescence display or the pixel unit as an example for illustration.

Example 1

Please refer to FIG. 3 , which shows a circuit diagram of a brightness adjustment circuit for an electroluminescence display according to a first preferred embodiment of the present invention. The power supply device 300 can provide a stable driving voltage V _dd to an electroluminescence display or pixel unit (not shown in the figure). The power supply device 300 has a power supply 302, the power supply 302 includes a voltage supply unit (not shown) and a reference voltage unit (not shown), the voltage supply unit and the reference voltage unit are electrically connected to each other, and the voltage supply unit is connected to the output The voltage terminal V _out and the reference voltage unit are connected to the feedback terminal 304 , which is the structure of the general power supply 302 , and will not be repeated in the following embodiments. The power supply 302 has an output voltage terminal V _out and a feedback terminal 304 , the output voltage terminal V _out provides the driving voltage (V _dd ) of the pixel unit (not shown in the figure). The feedback circuit module (not shown) includes an internal circuit (not shown), an external circuit (not shown) and a switch 306 . The internal circuit includes resistors 308 and 310 . The resistors 308 and 310 are connected to each other and both ends are electrically connected to the output voltage terminal V _out , while the feedback terminal 304 is electrically connected to the other end of the resistor 308 , and the other end of the resistor 310 is electrically connected to the switch 306 .

The external circuit includes resistors 312 , 316 and 320 . One ends of the resistors 312 , 316 and 320 are connected to a common potential, such as ground, and the other ends are respectively connected to the connecting nodes 314 , 318 and 322 . The switch 306 can connect the junctions 314, 318, or 322 to respectively connect the resistors 312, 316, and 320 in series with the internal circuit. Since the resistors 312 , 316 and 320 have different impedances, when the switch 306 connects the resistors 312 , 316 or 320 in series with the internal circuit, the feedback voltage fed into the feedback terminal 304 by the feedback circuit module will change.

Now explain with actual data, when the reference voltage unit of the power supply 302 provides a reference voltage of 0.6V and the impedances of the resistors 308, 310, 312, 316 and 320 are 50 kohms, 10 kohms and 10 kohms respectively , 50 thousand ohms and 100 thousand ohms. When the switch 306 is connected to the connection point 314 to connect the resistors 308, 310 and 312 in series, the output voltage terminal V _out is 2.1V; when the switch 306 is connected to the connection point 318 to connect the resistors 308, 310 and 316 in series, the output voltage The output of the terminal V _out is 1.1V; when the switch 306 is connected to the connecting point 322 to connect the terminals 308 , 310 and 320 in series, the output voltage of the terminal V _out is 0.87V. Therefore, the output voltage of the output voltage terminal V _out decreases from 2.1V to 0.87V, and the driving voltage V _dd provided to the electroluminescent display or pixel unit also decreases from 2.1V to 0.87V, thereby reducing the brightness. In addition, the brightness adjustment circuit can be disposed on or outside the electroluminescence display panel.

Example 2

Please refer to FIG. 4 , which shows a circuit diagram of a brightness adjustment circuit for an electroluminescence display according to a second preferred embodiment of the present invention. The power supply device 400 can provide a stable driving voltage V _dd to an electroluminescence display or pixel unit (not shown in the figure). The power supply device 400 has a power supply 402, the power supply 402 includes a voltage supply unit (not shown) and a reference voltage unit (not shown), the voltage supply unit and the reference voltage unit are electrically connected to each other, and the voltage supply unit is connected to the output The voltage terminal V _out and the reference voltage unit are connected to the feedback terminal 404 , which is the structure of the general power supply 402 , and will not be repeated in the following embodiments. The power supply 402 has an output voltage terminal V _out and a feedback terminal 404 , the output voltage terminal V _out provides the driving voltage (V _dd ) of the pixel unit (not shown in the figure). The feedback circuit module includes an internal circuit, an external circuit and a switch 406 . The internal circuit includes resistors 408 and 410 . The resistors 408 and 410 are arranged in series and one end is electrically connected to the output voltage terminal V _out , and the feedback terminal 404 is electrically connected to one end of the resistor 408 and the other end of the resistor 410 is electrically connected to a common potential, such as ground and the switch 406 .

The external circuit includes resistors 412 , 416 and 420 . One ends of the resistors 412 , 416 and 420 are connected to a common potential, such as ground, and the other ends are respectively connected to the connecting nodes 414 , 418 and 422 . The switch 406 may connect the junctions 414, 418, or 422 to connect the resistors 412, 416, and 420 in parallel with the resistor 410 of the internal circuit, respectively. Since the resistors 412 , 416 and 420 have different impedances, when the switch 406 connects the resistors 412 , 416 and 420 in parallel with the internal circuit resistor 410 , the feedback voltage fed into the feedback terminal 404 by the feedback circuit module will change.

Let’s explain it with actual data. When the reference voltage unit of the power supply 402 provides a reference voltage of 0.6V and the impedances of the resistors 408, 410, 412, 416, and 420 are 50 k-ohms, 50 k-ohms, and 1000 k-ohms respectively , 50 thousand ohms and 40 thousand ohms. When the switcher 406 is connected to the connection point 414 to parallel the resistors 410 and 412, the output voltage terminal V _out is 1.23V; when the switcher 406 is connected to the connection point 418 to parallel the resistors 410 and 416, the output voltage terminal V _out is 1.8V V; when the switch 406 is connected to the connection point 422 to connect the resistors 410 and 420 in parallel, the output voltage terminal V _out is 1.95V. Therefore, the output voltage of the output voltage terminal V _out increases from 1.23V to 1.95V, and the driving voltage V _dd provided to the electroluminescence display or pixel unit also increases from 1.23V to 1.95V, thereby increasing the brightness. In addition, the brightness adjustment circuit can be disposed on or outside the electroluminescence display panel.

Example 3

Please refer to FIG. 5 , which shows a circuit diagram of a brightness adjustment circuit for an electroluminescence display according to a second preferred embodiment of the present invention. The power supply device 500 can provide a stable driving voltage V _dd to an electroluminescent display or pixel unit (not shown in the figure). The power supply device 500 has a power supply 502, the power supply 502 includes a voltage supply unit (not shown) and a reference voltage unit (not shown), the voltage supply unit and the reference voltage unit are electrically connected to each other, and the voltage supply unit is connected to the output The voltage terminal V _out and the reference voltage unit are connected to the feedback terminal 504 , which is the structure of the general power supply 502 , and will not be repeated in the following embodiments. The power supply 502 has an output voltage terminal V _out and a feedback terminal 504 , the output voltage terminal V _out provides the driving voltage (V _dd ) of the pixel unit (not shown in the figure). The feedback circuit module includes a circuit and a control voltage input terminal 506 . The circuit includes resistors 508 and 510 . The resistors 508 and 510 are connected to each other and one end is electrically connected to the output voltage terminal V _out , and the feedback terminal 504 is electrically connected to the other end of the resistor 508 , and the other end of the resistor 510 is electrically connected to the control voltage input terminal 506 .

A voltage feeding device (not shown) feeds a control voltage V _m from the control voltage input terminal 506. As the control voltage V _m changes, the voltage drop between the resistors 508 and 510 will also change accordingly. Therefore, the feed The feedback voltage input to the feedback terminal 504 also changes accordingly.

Now use the actual data to explain. The reference voltage unit of the power supply 402 provides a reference voltage of, for example, 0.6V and the impedances of the resistors 508 and 510 are 10 kohms and 50 kohms respectively. When input from the control voltage input terminal 506 When a control voltage V _m is 0.1V, the output voltage terminal V _out is 3.1V; when a control voltage V _m is sent from the control voltage input terminal 506 to 0.3V, the output voltage terminal V _out is 2.1V; When a control voltage V _m sent from the control voltage input terminal 506 is 0.5V, the output voltage terminal V _out is 1.1V. Therefore, the output voltage of the output voltage terminal V _out decreases from 3.1V to 1.1V, and the driving voltage V _dd provided to the electroluminescent display or pixel unit also decreases from 3.1V to 1.1V, thereby reducing the brightness. In addition, the brightness adjustment circuit can be disposed on or outside the electroluminescence display panel. In this embodiment, the voltage feeding device may be, for example, a digital-to-analog conversion device.

The brightness adjustment circuit disclosed in the present invention does not need to modify or calculate the output data of the system end, but only by changing the parallel connection of some internal circuits and some external circuits, or by inputting a control voltage, the brightness of the panel can be increased or weakened efficacy. In addition, the present invention can also be used to increase the brightness of organic electroluminescent displays. The external circuits in the circuit module are not limited to two or three groups, and may be more groups, depending on the requirements of the multi-stage brightness modulation to be realized.

Although the present invention has been disclosed above with several preferred embodiments, it is not intended to limit the present invention. Those skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the claims of the present invention.

Claims (9)

1. brightness regulating circuit, be used for an electro-exciting light-emitting display, this electro-exciting light-emitting display comprises an electric exciting light emitting display panel and a voltage feeding unit, to provide a driving voltage to this electric exciting light emitting display panel, this brightness regulating circuit comprises this voltage feeding unit at least according to a feedback voltage:

One circuit module, it is electrically connected with this voltage feeding unit and this electric exciting light emitting display panel; And

One voltage feedthrough, in order to an end feed-in one control voltage of this circuit module certainly to adjust this feedback voltage.

2. brightness regulating circuit as claimed in claim 1, wherein this voltage feedthrough is exported different voltage according to a controlling signal.

3. brightness regulating circuit as claimed in claim 1, wherein this voltage feedthrough is a digital-analogue converting device.

4. brightness regulating circuit as claimed in claim 1, wherein this circuit module comprises one first resistance and one second resistance at least, one first end of this first resistance connects this voltage feeding unit, one second end of this first resistance connects one first end of this second resistance and provides this feedback voltage to this voltage feeding unit, and one second end of this second resistance connects this voltage feedthrough.

5. electro-exciting light-emitting display comprises at least:

One electric exciting light emitting display panel;

One voltage feeding unit; And

One brightness regulating circuit is electrically connected on this voltage feeding unit and this electric exciting light emitting display panel, can provide a feedback voltage to this voltage feeding unit to provide a driving voltage to this electric exciting light emitting display panel, comprise at least:

One circuit module; And

One voltage feedthrough, an end feed-in one voltage of this circuit module is to adjust this feedback voltage certainly.

6. electro-exciting light-emitting display as claimed in claim 5, wherein this voltage feedthrough is a digital-analogue converting device.

7. electro-exciting light-emitting display as claimed in claim 5, wherein this voltage feedthrough is exported different voltage according to a controlling signal.

8. electro-exciting light-emitting display as claimed in claim 5, wherein this circuit module comprises one first resistance and one second resistance at least, one first end of this first resistance connects this voltage feeding unit, one second end of this first resistance connects one first end of this second resistance and provides this feedback voltage to this voltage feeding unit, and one second end of this second resistance connects this voltage feedthrough.

9. electro-exciting light-emitting display as claimed in claim 5, wherein this electric exciting light emitting display panel is an organic LED display panel.

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