CN1633220A - Active electroluminescence display and its power supply circuit - Google Patents

Abstract

An active electroluminescent display, such as an active organic light emitting display, includes an active electroluminescent display panel and a power supply circuit. The active electroluminescent display panel comprises a pixel array and an electrode for driving the pixel array. The electrode is electrically connected with the pixel array. The electrode has a first electrical connection point and a second electrical connection point. The power supply circuit comprises a feedback circuit, a power system, a power input line and a voltage-stabilizing reference line. The power supply system is provided with an output end and a feedback end. The power supply system outputs a bias voltage at the output terminal according to the feedback voltage. One end of the power input line is electrically connected with the first electrical connection point. The other end of the power input line is used for receiving bias voltage. One end of the voltage-stabilizing reference line is electrically connected with the second electrical connection point. The other end of the voltage-stabilizing reference line is used for outputting feedback voltage.

Description

Active electroluminescence display and its power supply circuit

technical field

The present invention relates to an active electroluminescence display, and in particular to a power supply circuit for driving an active electroluminescence display.

Background technique

Please refer to FIG. 1 , which is a schematic structural diagram of an LED pixel. It can be seen from FIG. 1 that the source S of the TFT Q1 in the LED pixel 106 receives the bias voltage Vdd through the electrode PL, its drain D is coupled to the anode of the LED OLED, and its gate G receives the voltage Vdata. The cathode of the light emitting diode OLED is coupled to a fixed voltage, such as the bias voltage Vss. The driving circuit (not shown in FIG. 1 ) makes the voltage Vdata generate a corresponding voltage according to different gray scale values, so as to control the voltage difference Vsg between the gate G and the source S of the thin film transistor Q1. The magnitude of the current I flowing through the organic light emitting diode OLED is controlled by the voltage difference Vsg, so that the organic light emitting diode OLED generates corresponding brightness according to the current I. Therefore, the variation of the bias voltage Vdd will affect the magnitude of the voltage difference Vgs, and the variation of the bias voltage Vss will also affect the voltage difference between the two ends of the light-emitting diode OLED, so the unstable bias voltage Vdd and Vss will further affect the light-emitting diode. of luminous brightness.

Please refer to FIG. 2 , which is a schematic structural diagram of a conventional organic light emitting display. Figure 2 shows the connection between the active electroluminescence panel and the external power supply circuit seen in the data specification of the common DC-DC converter.

The organic light emitting display 100 includes a display panel 102 and an external power source 104 . The display panel 102 has a pixel array 108 composed of active thin film transistors. The pixel array 108 includes a plurality of electroluminescent elements, such as organic light emitting diodes, forming pixels 106 . The bias voltage Vdd is provided by the external power source 104 and transmitted to each pixel 106 via the electrode PL. Therefore, the electrodes PL are all connected in parallel, and then guided to the outer edge of the display panel 102 via the power input line K. The power input line K is then coupled to the external power source 104 via the metal wire I to receive the bias voltage Vdd. In order to provide a stable bias voltage Vdd to the pixel array 108, the external power supply 104 is designed as a stable power supply system 110, that is, the output terminal N is used as a voltage feedback point, so that the bias voltage Vdd is divided into feedback through the series resistors R1 and R2. Voltage. The stabilized power supply system 110 uses the feedback voltage as the size of the monitored output voltage (bias voltage Vdd), so that the bias voltage Vdd output by the stabilized power supply system 110 will remain at a fixed value to ensure that the bias voltage Vdd will not be unstable due to the input voltage Or the phenomenon that the bias voltage Vdd is unstable due to noise interference.

However, when the bias voltage Vdd is applied to the electrode PL through the power input line K, a non-negligible voltage drop ΔVdd will be generated. The voltage drop ΔVdd will cause the bias voltage Vdd on the electrode PL to be lower than a set value, so that the LED pixel 106 cannot achieve a predetermined luminance.

For example, when the impedance of the power input line K is 3 ohms, the output bias voltage of the external power supply 104 is +3V. When the current required by the pixel array 108 is 200mA, for example, the brightness to be displayed is relatively bright, the power input line K will generate a voltage drop of 0.2A×3Ω=0.6V, so the stable output bias voltage provided by the external power supply 104 is +3V When it reaches the electrode PL via the power input line K, it drops to 2.4V. Therefore, the originally set value of the bias voltage Vdd is reduced from +3V to +2.4V, and the fluctuation range reaches 20%.

And when the current required by the pixel array 108 is 30mA, for example, the brightness of the display is relatively dark, and the power input line produces a voltage drop of 0.03A×3Ω=0.09V, so the output bias voltage +3V provided by the external power supply passes through the power input line to When the electrode is on, it drops to 2.91V. The bias voltage originally required by the pixel driving circuit is reduced from the original set value of +3V to +2.91V, with a variation range of 3%. It can be known that the power consumption of the pixel array 108 will cause different voltage drops on the power input line K, so that the bias voltage Vdd received by the pixel array 108 will have a corresponding change. As a result, the luminance of the organic light emitting diode OLED will vary with the variation of the bias voltage Vdd, resulting in unstable luminance of the display screen.

Contents of the invention

In view of this, the purpose of the present invention is to provide an active electroluminescent display and its power supply circuit, by using the voltage on the electrode as the feedback voltage, to solve the problem of the voltage drop on the power input line and the power consumption of the display panel. The problem of changing and changing makes the bias voltage input to the pixel more stable.

According to the purpose of the present invention, the active electroluminescent display panel of the present invention has an electrode. The electrode has a first electrical connection point and a second electrical connection point. The power supply circuit includes a feedback circuit, a DC-DC converter, a power input line and a voltage regulation reference line. The DC-DC converter has an output terminal and a feedback terminal. The feedback circuit provides a feedback voltage to the DC-DC converter. The DC-DC converter outputs a bias voltage to the first electrical connection point through the power input line according to the feedback voltage. One end of the voltage stabilizing reference line is electrically connected to the second electrical connection point, and the other end is coupled to the feedback circuit to output a feedback reference voltage corresponding to the feedback voltage.

In order to make the above-mentioned purposes, features and advantages of the present invention more comprehensible, a preferred embodiment is specifically cited below, and is described in detail in conjunction with the accompanying drawings as follows:

Description of drawings

FIG. 1 is a schematic structural diagram of a light emitting diode pixel.

FIG. 2 is a schematic structural diagram of a conventional organic light emitting display.

FIG. 3 is a schematic diagram of an active electroluminescent display circuit architecture according to a preferred embodiment of the present invention.

Detailed ways

The traditional approach can only ensure that the bias voltage output by the DC-DC converter remains stable. However, since the active electroluminescent components, such as organic light emitting diodes, the part of the power input line of the display on the substrate is formed of polysilicon semiconductor material, it has a larger resistance value than ordinary metal lines. Therefore, when the bias voltage is from the DC-DC converter, through the metal wire and then through the power input line to the electrode, a non-negligible voltage drop will occur. This voltage drop will cause the bias voltage on the electrode to be lower than the set value, so that the LED pixel cannot achieve the predetermined luminous brightness. Moreover, the fluctuation range of the bias voltage will increase with the increase of the power consumption of the pixel array, so that the luminance of the light-emitting diode becomes very unsatisfactory, resulting in the phenomenon that the brightness of the picture is not stable.

Please refer to FIG. 3 , which is a schematic diagram of an active electroluminescent display circuit architecture according to a preferred embodiment of the present invention. The active electroluminescent display 200 includes an active electroluminescent display panel 204 and a power supply circuit 210 . The active electroluminescent display panel 204 includes electrodes PL, and a pixel array 208 composed of a plurality of pixels 206 . The pixel 206 includes a TFT and an electroluminescence component (the TFT and the electroluminescence component are not shown in the figure), and the TFT is used to drive the electroluminescence component. The active electroluminescence display 200 is, for example, an organic light emitting diode display, and the electroluminescence component is, for example, an organic light emitting diode. The electrode PL is electrically connected to the pixel array 208 , and the electrode PL has a first electrical connection point X1 and a second electrical connection point X2 .

The power supply circuit 210 includes a feedback circuit 212 , a DC-DC converter 202 , a power input line K1 and a voltage regulation reference line K2 . The DC-DC converter 202 has an output terminal Vout and a feedback terminal FB. The DC-DC converter 202 outputs a bias voltage Vdd1 at the output terminal Vout according to a feedback voltage V1. The part of the power input line K1 on the substrate is formed by semiconductor process, and it is coupled to the first electrical connection point X1 and the output terminal Vout to provide the bias voltage Vdd1 to the electrode PL.

The feedback circuit 212 includes a first resistor R1' and a second resistor R2' connected in series. One end of the first resistor R1' is coupled to the reference line K2, and one end of the second resistor R2' is grounded. The feedback circuit 212 divides the voltage from the regulated reference line K2 (ie, the bias voltage Vdd2 ) into the feedback voltage V1 , and then provides it to the DC-DC converter 202 .

In order to solve the problem caused by the voltage drop ΔVdd′ of the power input line K1 on the substrate varying with the power consumption of the pixel array 208 , another reference line K2 for stabilizing voltage is provided. The part of the voltage stabilizing reference line K2 on the substrate is also formed by a semiconductor process, one end of which is electrically connected to the second electrical connection point X2 of the electrode PL, and the other end is coupled to the feedback circuit 212 to provide a corresponding The feedback reference voltage VF of the feedback voltage V1, that is, the bias voltage Vdd2 (Vdd2=Vdd1-ΔVdd') on the electrode PL can be used as the feedback reference voltage VF through the voltage stabilization reference line K2, and the feedback voltage is generated by the feedback circuit 212 V1 is then transmitted to the feedback terminal FB of the DC-DC converter 202 .

The DC-DC converter 202 outputs the bias voltage Vdd1 according to the feedback voltage V1 on the feedback terminal FB, that is, the DC-DC converter 202 outputs the bias voltage Vdd1 at the output terminal Vout according to the feedback voltage V1 corresponding to the feedback reference voltage VF. The voltage Vdd1 is transmitted to the electrode PL through the power input line K1. The DC-DC converter 202 compares the feedback voltage V1 with an internal reference voltage to control the magnitude of the bias voltage Vdd1. When the feedback reference voltage VF (ie, the bias voltage Vdd2 ) changes, the DC-DC converter 202 adjusts the bias voltage Vdd1 to keep the feedback reference voltage VF (ie, the bias voltage Vdd2 ) on the electrode PL at a certain value.

Therefore, when the power consumption of the pixel array 208 increases, the bias voltage Vdd2 on the electrode PL decreases, and the bias voltage Vdd2 is the feedback reference voltage VF, which is divided by the feedback circuit 212 via the voltage stabilization reference line K2 and then transmitted to the DC-DC Converter 202. When the DC-DC converter 202 detects that the feedback voltage V1 corresponding to the feedback reference voltage VF is lower than the internal reference voltage, it increases the output bias voltage Vdd1 to keep the bias voltage Vdd2 on the electrode PL at a certain value.

Although the voltage stabilizing reference line K2 itself has impedance, the impedance of the voltage stabilizing reference line K2 and the resistor R1 ′ can be regarded as an impedance, and the feedback voltage V1 can be obtained through proper calculation with the resistor R2 ′. Moreover, since the value of the current flowing through the reference line K2 for feeding back the voltage is quite small, it can be ignored, and there will be no problem of voltage drop.

The difference between this embodiment and the conventional one is that a voltage stabilizing reference line K2 is provided on the active electroluminescence display panel 204 to connect to the external power supply line, one end of the voltage stabilizing reference line K2 is electrically connected to the electrode PL, and its The other terminal outputs the feedback reference voltage VF as the magnitude of the bias voltage Vdd2 on the monitoring electrode PL. In this way, the brightness of the pixel array 208 will not be uneven due to the variation of the bias voltage Vdd2 on the electrode PL, resulting in uneven brightness of the screen. Therefore, the variation of the power consumption of the pixel array 208 does not affect the luminance of the light-emitting diodes. In addition, the resistors R1 ′, R2 ′ can also be fabricated in the display panel 204 , or designed in the DC-DC converter 202 .

In the organic light emitting diode display and its driving method disclosed in the above embodiments of the present invention, the voltage on the electrodes is used as the feedback voltage, so that regardless of the voltage drop of the power input line due to the power consumption of the display panel, Both will keep the bias voltage on the electrode at a certain value.

In summary, although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make various modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the appended claims of the application.

Claims (6)

1. power supply circuit, in order to provide an active electric exciting light emitting display panel required power supply, this active electric exciting light emitting display panel has an electrode and an array of pixels, and this electrode has one first and electrically connects point and one second electric connection point, and this power supply circuit comprises at least:

One DC-to-DC converter, it has an output and a feedback end, in order to according to a feedback voltage in this output, to export a bias voltage;

One power input line couples the output of this DC-to-DC converter and this first and electrically connects point, so that this bias voltage to be provided;

One feedback circuit is coupled to the feedback end of this DC-to-DC converter, in order to this feedback voltage to be provided; And

One voltage stabilizing reference line couples this second electric connection point and this feedback circuit, so that the feedback reference voltage corresponding to this feedback voltage to be provided.

2. power supply circuit as claimed in claim 1 is characterized in that this feedback circuit comprises:

One first resistance, one end are coupled to this voltage stabilizing reference line; And

One second resistance, itself and this first resistance polyphone is minute to extrude this feedback voltage.

3. power supply circuit as claimed in claim 1 is characterized in that this voltage stabilizing reference line and this power input line are partly to be formed on this active electric exciting light emitting display panel.

4. active electric exciting light emitting display panel comprises at least:

One substrate;

One array of pixels, it is made of a plurality of active thin-film transistors and EL component, is formed on this substrate;

One electrode is formed on this substrate, and in order to drive this array of pixels, this electrode comprises one first and electrically connects point and one second electric connection point; And

One power supply circuit comprises at least:

One DC-to-DC converter, it has an output and a feedback end, in order to according to a feedback voltage in this output, to export a bias voltage;

One power input line, it partly is formed on this substrate, and couples output and this first electric connection point of this DC-to-DC converter, so that this bias voltage to be provided;

One feedback circuit is coupled to the feedback end of this DC-to-DC converter, in order to this feedback voltage to be provided; And

One voltage stabilizing reference line, it partly is formed on this substrate, and couples this second electric connection point and this feedback circuit, so that the feedback reference voltage corresponding to this feedback voltage to be provided.

5. active electric exciting light emitting display panel as claimed in claim 4 is characterized in that described feedback circuit comprises:

One first resistance, one end are coupled to this voltage stabilizing reference line; And

One second resistance, itself and this first resistance polyphone is minute to extrude this feedback voltage.

6. an active self-luminescence LCD is characterized in that comprising power supply circuit as claimed in claim 1.

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