KR100400743B1 - power saving circuit in display element of current driving type - Google Patents

Abstract

The present invention provides a power saving circuit of a current-driven display device that can reduce the power of the entire system by using a refresh scheme that can reduce the total power, and also recover and reuse the wasted power in the refresh scheme. A display device comprising a plurality of data driver circuits including a power supply, a data driver, and a sink element, and a plurality of scan driver circuits including a scan driver and a reverse voltage device. One end is connected between reverse voltage elements to control the refresh operation, and one end of the plurality of sink elements and the plurality of refresh elements is connected to one to convert current discharged during the refresh time into voltage. DC-DC converter that applies power to the whole system It is configured to include.

Description

Power saving circuit in display element of current driving type

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit of a display element, and more particularly to a power saving circuit of a current driven display element that obtains low power consumption by a power recovery circuit using a refresh scheme.

Recently, in the field of flat panel display, rapid progress has been made.

In particular, flat-panel displays, which began to take the lead in Liquid Crystal Display (LCD), have surpassed the Cathode Ray Tube (CRT), which has been the most used in the display field for decades. ), FED (Field Emission Display), LED (Light Emitting Diode), EL (Electroluminescence) and many other developments are being made.

Such current-driven display devices are not only good in visibility and color, but also have a simple manufacturing process, thereby expanding their applications in many areas.

However, as the size of the display panel increases, these current driven display devices consume more current in the display and the driving circuit. In addition, the higher the resolution, the less time is required to drive the display due to the physical quantity of the display, which requires more current to achieve the desired brightness.

LCD, which is widely used in portable information devices, has disadvantages such as response time, viewing angle, and color, but is widely used because it has the advantage of low power consumption.

Of course, considering the use of LCD back light, the power consumption is not small, but in recent years there is a transflective or reflective type LCD that can be used with little back light. It is used.

Recently, the organic EL display panel has been attracting attention as a flat panel display panel with less space occupancy due to the enlargement of the display device.

1 is a view showing a driving circuit of an organic EL according to the prior art.

Referring to FIG. 1, there is a power supply for applying a power supply voltage, Vdd, a PMOS controlling on / off of a constant current source at a data terminal, and controlling an amount of current flowing from the constant current source to an anode of an organic EL. An NMOS is installed as an element for data sinking. Moreover, the structure which uses NMOS as a scan driver and uses PMOS as an element for applying a reverse voltage is shown.

One side of the scan driver is usually connected directly to ground.

The control of the scan terminal and the data terminal is controlled by a controller (not shown) and input as a data signal and a scan signal.

The PMOS controlled by the scan_B signal is connected to a reverse voltage Vpp power supply and is connected to the cathode of the organic EL. This reverse voltage serves to prevent cross talk of the organic EL.

The organic EL configured as described above has a lower power consumption than the CRT, has no distortion at the edge portion, and can be made ultra thin. In addition, it is more robust than LCD and has a wide viewing angle due to self-luminous and good response characteristics, enabling large screens, wide temperature range of -40 ° to + 70 °, freely selectable emission colors, and driving at low voltage below 15V. This has a possible advantage.

However, the biggest reason that LCDs having more disadvantageous characteristics are used in portable information devices and the like than current-driven displays having the above advantages is that organic ELs have a disadvantage in that they consume more power than LCDs.

In addition, as the use of portable information terminal devices increases, the consumption of power becomes a big problem, and the use of a display for driving a display using current serves as a proposed element.

However, although the power consumption of displays driven by current is many times higher than that of LCDs, this is not significant because it is simply a comparison of LCDs and displays driven by current. That is, if the LCD includes a back light, the current driven display and the LCD do not show much difference.

In addition, if the power consumption of the display driven by the current is lowered by half from the entire level, the total power consumption can be almost reduced to the level of the LCD.

Accordingly, the present invention has been made to solve the above problems, to provide a power saving circuit of a current-driven display device that can reduce the power consumption of the display by using a refresh scheme that can reduce the total power. The purpose is.

Another object of the present invention is to provide a power saving circuit of a current driven display device which can reduce power of the entire system by recovering and reusing power wasted in the refresh scheme.

1 shows a driving circuit of an organic EL according to the prior art.

2 is a view showing a power saving circuit of a current driven display device according to the present invention;

3 and 4 show operation waveforms of respective parts of FIG. 2.

* Explanation of symbols for main parts of the drawings

10: transformer / inductor 20: control unit

30: power source portion 40: diode

Features of the power saving circuit of the current-driven display device according to the present invention for achieving the above object is a power supply, a plurality of data driver circuit having a data driver and a sink element, and a scan driver and a reverse voltage device A display device comprising a plurality of scan driving circuits, the display device comprising: a plurality of refresh elements each having one end connected between the plurality of scan driver parts and a reverse voltage element to control a refresh operation; and a plurality of sink elements and a plurality of sink elements. It comprises a DC-DC converter that connects one end of the refresh element into one, converts the current discharged during the refresh time into a voltage and applies it to the power stage of the entire system.

The DC-DC converter includes a transformer or an inductor for converting a current discharged during a refresh time into a voltage, a control unit for controlling the transformer, and a power source unit for feeding back the output of the control unit to a driving power source. have.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

A preferred embodiment of a power saving circuit of a current driven display device according to the present invention will be described with reference to the accompanying drawings.

2 is a view showing a power saving circuit of the current driven display device according to the present invention.

Referring to FIG. 2, there are Vdd as a power source for applying a power supply voltage, N data driving circuits controlling on / off of a constant current source at a data terminal and controlling an amount of current flowing from the constant current source to the anode of the organic EL. Furnace and N data sink elements, M scan drive circuits and M reverse voltage application elements used as scan drivers, M refresh elements connected to the M scan drive circuits, and N N And a transformer 10 connected to the source terminals of the data sink elements and the M refresh elements. In order to control the transformer 10, the DC-DC converter controller 20 is provided. The output of the DC-DC converter controller 20 using the transformer 10 is passed through the diode 40 to stabilize the voltage. It is delivered to the power source unit 30.

One side of the scan driver is usually connected directly to ground.

At this time, the drain terminal of the sink element in each data driver is connected to the anode of the organic EL, and the source terminals of the sink element in each data driver are connected to each other and connected to the input of the transformer 10.

The drain terminal of the refresh element in each scan driver is connected to the cathode of the organic EL, and the source terminal of the refresh element in each scan driver is connected to each other and connected to the input of the transformer 10. have.

In this case, the transformer 10 is a preferred embodiment of the present invention, and an inductor or the like may be used instead of the transformer.

The operation of the power saving circuit of the current driven display device according to the present invention configured as described above will be described in detail with reference to the accompanying drawings.

3 and 4 are diagrams showing operational waveforms of each part of FIG. 2.

In FIG. 3 and FIG. 4, T denotes a refresh time, during which all data lines and all scan lines are grounded and adjusted by a controller (not shown) to have a low signal. .

Accordingly, in the data lines, when data of each data line is changed to data 1 to data N as shown in FIG. 3, the waveforms of the data 1_B to data N_B which are sink elements operate in the opposite direction to the data waveform.

At this time, all the data lines are applied to the ground during the T time, which is the refresh time.

Subsequently, the waveforms of A_1 to A_N in the anode line also change as shown in FIG. 3 in response to the change of data 1 to data N. At this time, the anode line changes the waveform with a slight response time.

The signals of the scan lines corresponding to the data are changed while scanning as shown in FIG. 4. In this case, the signals of scans 1 to M are sequentially changed.

In addition, the scan 1 to scan M signals apply all the scan lines to the ground during the T time which is a constant refresh time.

Therefore, all but one line selected from all the scan lines fall from the reverse voltage Vpp level to the ground, and then another line selected again rises from the ground to the Vpp level. In this case, the first selected line falls to ground at the Vpp level.

Subsequently, the signals of the reverse voltage applying element scans 1_B to M_B are represented by waveforms opposite to those of the scans 1 to M.

In addition, the waveforms of B_1 to B_M in the cathode line also change as shown in FIG. 4 in response to the change of the scans 1 to M. FIG. At this time, the anode line changes the waveform with a slight response time.

Using this refresh time T, dropping signals on all data and scan lines to ground can increase the response time considerably faster and significantly reduce the amount of current required to drive the entire drive.

In this case, the refresh scheme has a significant effect on the amount of current used for driving when the amount of current required for driving is large, but the amount of power consumed by the refresh scheme is large when the amount of current required for driving is not large. Because of this, it is difficult to see the effect of reducing the amount of current used for driving.

Therefore, there are two ways to use the power wasted in the refresh schema.

One method is to reduce power consumption caused by falling from the high signal to the ground during the T time, which is the refresh time in the data lines, and then changing back to the high signal at the end of the refresh time.

The other method is to reduce the power consumption caused by falling from the high signal to the ground during the T time, which is the refresh time in the scan lines, and then switching back to the high signal at the end of the refresh time.

In this case, in the case of the signal of the scan line, most of the entire scan time has a high signal value, and only one scan time is changed to a low signal value when it is selected. Therefore, since the discharge / charging continues during the continuous high signal and continues to charge / discharge at the end of the refresh time, power consumption is further increased. Similarly, in the case of the signal of the data line, the same problem occurs when there are many consecutive high signals.

Therefore, since a large amount of current flows during the refresh time, the source terminals of the N sink elements, data 1_B to data N_B, are connected to each other and are connected to the input of the transformer 10.

A refresh element ref 1 to ref M is connected between the scan 1 to scan M, which are the M scan driving circuits, and the scan 1_B to the scan M_B, which are reverse voltage elements, respectively. The drain terminals of ref 1 to ref M are connected to the cathode of the organic EL, and the source terminals are connected to each other to the input of the transformer 10.

Therefore, a large amount of current flows through the input of the transformer 10 during the instant of the refresh time.

That is, it has the waveform of the C part which is shown in common in FIG.3 and FIG.4.

This instantaneous current creates a flow of charge in the output stage with a turns ratio of 1: m in the transformer 10. That is, it has a waveform of the portion D shown in common in Figs. 3 and 4 and generates a constant voltage to the DC-DC converter control unit 20 connected to the next stage.

The voltage generated in the DC-DC converter controller 20 is applied to the power source unit 30 of the entire system via the diode 40. That is, it has the waveform of the P part shown in FIG. 3 and FIG.

In this way, the power consumed in the use of the refresh scheme is recovered and used again, thereby lowering the power of the entire system.

As described above, the power saving circuit of the current driving display device according to the present invention has the following effects.

First, there is an effect of lowering the overall drive current by using a refresh scheme.

Second, by recovering and reusing the current used in the refresh schema, the power used in the refresh schema can be reduced.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (5)

A display element comprising a power supply, a plurality of data driver circuits having a data driver and a sink element, and a plurality of scan driver circuits having a scan driver and a reverse voltage element, A plurality of refresh elements each having one end connected between the plurality of scan drivers and a reverse voltage element to control a refresh operation; And a DC-DC converter which connects one end of the plurality of sink elements and the plurality of refresh elements into one, converts a current discharged during a refresh time into a voltage, and applies it to the power stage of the entire system. Power-saving circuit of current driven display element. The method of claim 1, wherein the DC-DC converter A transformer for converting a current discharged into a voltage during a refresh time; A control unit for controlling the transformer; And a power source unit for feeding back an output of the control unit to a driving power source. The method of claim 1, wherein the DC-DC converter An inductor that converts a discharged current into a voltage during a refresh time; A control unit for controlling the transformer; And a power source unit for feeding back an output of the control unit to a driving power source. The method according to claim 2 and 3, And a diode connected between the control unit and the power source unit to stabilize the voltage. The method of claim 1, And said sink element and refresh element are NMOS transistors.