KR20000001694A - Circuit for driving electric-field emission display - Google Patents

Abstract

PURPOSE: A circuit for driving electric-field emission display is provided to adjust volume of electron emitted light in FED panel by controlling current flow through cathode. CONSTITUTION: The circuit comprises D/A converter connected to reference voltage terminal, switch for transmitting the reference voltage in according with whether or not data signal providing, and plurality of resistors for adjusting current flow through the cathode by adjusting base current of driving means in according with the reference voltage. Thereby excessive current is not generated even if short is generated between gate and cathode. Also, it is possible to adjust volume of electron emitted light in FED panel by controlling current flow through cathode.

Description

Field emission display drive circuit

The present invention relates to a field emission display driving circuit, and more particularly, to a field emission display driving circuit to control the amount of electrons emitted to the FED panel by controlling the amount of current supplied to the cathode.

Recently, one of the spotlights as a flat panel display is a liquid crystal display, which uses an liquid crystal to intercept a light beam from a light source to display an image. And active matrix designation.

The manual matrix designation method is a method of inputting data to pixels at intersections by applying different voltages to the upper and lower plates of the glass substrate of the liquid crystal display. According to this method, the peripheral pixels of the designated pixel are also affected. As a result, the driving circuit part is complicated by requiring a compensation circuit for implementing a clear screen.

The active matrix designation method includes one cell transistor and one capacitance per pixel such that one pixel is continuously driven by previous pixel data until the next pixel data is inputted. It can be said to seek the simplicity of the drive circuit.

However, according to the active matrix designation method, it is possible to improve the image quality and simplify the driving circuit. However, since a large number of transistors and capacitances have to be planted on the glass substrate of the liquid crystal display, the process is very complicated and the yield is also low. have.

These liquid crystal displays currently occupy the largest flat panel display market, and because only a few percent of the light source actually contributes to the screen, it requires a lot of power consumption, has a large area, and has a semi-liquid state (liquid crystal). ) Is sensitive to changes in ambient temperature. In addition, it is weak in pressure, not bright on the screen, and has a limited resolution, so many applications are limited.

A new flat panel display that can overcome this problem is a field emission display. The field emission indicator displays the screen in a similar way to the cathode ray tube (CRT), which displays the screen using the emitted electrons.The field emission indicator displays the thermal electron emission in terms of the use of cold electron emission. It is different from the cathode ray tube (CRT) used.

The field emission indicators install electron emission field emission elements on a pixel-by-pixel basis, and impinge electrons from the field emission elements on an electrode coated with a fluorescent film to display an image. Recently, the field emission indicator solves various problems such as power consumption problems of the liquid crystal display, problems of large area, sensitivity to changes in ambient temperature, weakness of pressure, lack of screen brightness, and limitation of resolution. It is getting the spotlight as the next generation flat panel indicator that can give.

The field emission indicator may integrate hundreds to thousands of field emission devices according to a process to form one pixel. The field emission device constituting the pixel of the field emission indicator may include a cathode electrode as shown in FIG. 1. A cathode 11 connected to the 10, a gate 12 provided at a predetermined interval above the cathode 11, and an anode 13 coated with a fluorescent film 14 on the back surface thereof; Equipped.

Here, the fluorescent film 14 generates light corresponding to the amount of electrons colliding to display an image.

In addition, the anode 13 plays a role of attracting electrons emitted from the cathode 11, and also has transparency to transmit light by the fluorescent film 14.

In addition, the cathode 11 has the shape of a horn forming the upper part of the tent and allows electrons to be emitted from its own tent by a driving power source from the cathode electrode 10.

In addition, the gate 12 induces the emission of electrons from the cathode 11 to the hole by a high voltage lower than the voltage applied to the anode 13, the emitted electrons are applied with a higher voltage Facing toward the anode 13.

The cell driving method in the field emission indicator having the field emission device is a passive matrix method and an active matrix method, which is similar to the LCD driving method described above.

The passive matrix method typically drives an arbitrary cell by a difference between the voltage Vg applied to the gate line and the voltage Vk applied to the cathode line, and the implementation of full color is very simple. Although there is an advantage in that the current-to-voltage ratio of the tips is very non-linear and the tips must be installed very uniformly, there are many problems that the current level control is difficult.

Accordingly, an object of the present invention is to provide a field emission display driving circuit capable of more precisely adjusting the amount of electrons emitted to a FED panel by controlling a current flowing through a cathode. .

According to a preferred embodiment of the present invention, a data circuit unit for sequentially outputting a data signal and a D / A converter for controlling the amount of current flowing to the cathode by the data signal from the data circuit unit are provided. A field emission display comprising cathode driving means for controlling an amount of electrons emitted to a field emission display panel,

The D / A converter is connected to a predetermined reference voltage terminal and is provided between a plurality of switches transferring the reference voltage according to whether a data signal is applied from the data circuit unit, and between the plurality of switches and a driving element at the bottom of the cathode. Provided is a field emission display driving circuit including a plurality of resistors for varying a base current of the driving element as a reference voltage is transmitted to variably adjust an amount of current flowing to the cathode.

1 is a view for explaining the structure of a general field emission device,

2 is a circuit diagram of a field emission display driving circuit according to an embodiment of the present invention;

3 is a circuit diagram showing an example of a switch in the D / A converter shown in FIG. 2;

4 is a circuit diagram showing another example of a switch in the D / A converter shown in FIG.

<Description of the reference numerals for the main parts of the drawings>

10 cathode electrode 11 cathode

12: gate 13: anode

14 fluorescent film 16: field emission display panel

18: gate driving means 20: cathode driving means

18a: scan circuit section 20b to 20bn: D / A converter

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a circuit diagram of a field emission display driving circuit according to an exemplary embodiment of the present invention, and reference numeral 16 denotes an n × m matrix structure of a field emission device having a cathode 11, a gate 12, and an anode (not shown). Field emission display panels (hereinafter referred to as FED panels).

Reference numeral 18 is a gate driving means for receiving a control signal input from a controller (not shown) to scan row lines Row [1] to Row [80] to which a plurality of gates 12 of the FED panel 16 are connected. The gate driving means 18 includes a scan circuit section 18a for sequentially outputting scan signals with a shift register, and a respective output terminal of the scan circuit section 18a (ie, a row line in the embodiment of the present invention). Since there are 80 transistors, the number of output stages is also 80, and transistors Q1 to Qn (NPN transistors) provided between resistors R1 to Rn are connected between the row lines Row [1] to Row [80]. Equipped.

The reason for providing the resistors R1 to Rn is to prevent the excessive current from flowing by making the amount of current flowing to the gate constant.

Reference numeral 20 is connected to the cathode 11 portion of the FED panel 16, and each cathode of the FED panel 16 is based on a predetermined bit (e.g., 4 bits) data signal (i.e. video signal). 11 shows a cathode driving means for driving the cathode driving means 20, which comprises a shift register stage (not shown) which sequentially transfers a data signal input from a controller (not shown) and a data signal from this shift register stage. A data signal of a predetermined bit (for example, 4 bits) outputted from the data circuit part 20a including a latch for temporarily storing and outputting the data, and a data signal of a predetermined bit (for example, 4 bits) output from the data circuit part 20a. It consists of a D-A converter (Digital-to-Analog Converter) 20b to 20bn which enables 16 levels of gradation processing.

Here, each of the D / A converters 20b to 20bn is connected to each other in parallel to a predetermined reference voltage terminal Vref, and the reference voltage depends on whether the data signals D1 to D4 are applied from the data circuit unit 20a. A plurality of switches S1 to S4 for transmitting (Vref) to the rear end, and a plurality of switches S1 to S4 and driving elements N1 to Nm as current sinks at the bottom of the cathode 11, NPN transistors. The amount of current flowing to the cathode 11 by varying the base current I _B of the driving elements N1 to Nm as installed in the switches S1 to S4 in a one-to-one manner, as the reference voltage Vref is transmitted. It consists of a plurality of resistors (R1 to R4) to variably control.

The resistors R1 to R4 in the D / A converters 20b to 20bn have differential values to control the current flowing to the base of the driving elements N1 to Nm to adjust the current flowing to the cathode 11. For example, the ratio of the resistance values of the resistors R1 to R4 is 1: 2: 4: 8.

Preferably, the plurality of switches S1 to S4 may be implemented as NMOS transistors in which the data signals D1 to D4 are input to the gate and the drains thereof are commonly connected to the reference voltage terminal Vref. As shown in FIG. 4, the transfer gate may be implemented as a combination of an NMOS transistor and a PMOS transistor having the data signals D1 to D4 input to the gate and having a drain connected to the reference voltage terminal Vref in common. have.

In the exemplary embodiment of the present invention, four switches and four resistors in the D / A converters 20b to 20bn are configured. However, when the 8-bit or more data signal is input instead of the 4-bit data signal, the switch is used. Of course, the number of and resistance is increased to eight or more.

Next, the operation of the field emission display driving circuit according to the embodiment of the present invention configured as described above is as follows.

The data signals D1 to D4 from the controller (not shown) are cathodes while the row lines Row [1] to Row [80] of the FED panel 16 are sequentially scanned by the gate driving means 18. It is input to the data circuit section 20a in the drive means 20, shifted, latched, and input to the D / A converters 20b to 20bn. The D / A converters 20b to 20bn input data signals of the digital component. (D1 to D4) is converted into an analog signal to drive the corresponding cathode.

For example, when only the data signal D1 is input among the data signals D1 to D4 illustrated in FIGS. 3 and 4, a switch S1 (NMOS transistor, transfer gate) connected to an input terminal of the data signal D1. Bay is turned on to adjust the base current I _B of the driving element N (reference numeral generally denoted by N1 to Nm) through the corresponding resistor R1. That is, a current of "Vref / R1" flows to the base of the driving element N, and the driving element N is turned on, so that the output current I _C ; I _C = β _F I _B , β _F is a transistor A constant value of about 95 to 99.5) is adjusted to control the amount of current flowing to the cathode connected to the driving element N, thereby controlling the amount of electrons emitted to the FED panel 16.

When only the data signal D2 is input among the data signals D1 to D4 illustrated in FIGS. 3 and 4, only the switch S2 (NMOS transistor, transfer gate) connected to the input terminal of the data signal D2 is turned on. Thus, the base current I _B of the driving element N (reference numeral shown collectively as N1 to Nm) is adjusted through the resistor R2. That is, a current of "Vref / R2" flows to the base of the driving device N, and the driving device N is turned on, so that the output current I _C is adjusted so that the cathode connected to the driving device N is controlled. Since the amount of current flowing into the FED panel 16 is controlled, the amount of electrons emitted to the FED panel 16 can be adjusted.

Further, in the case where a data signal different from the above example is input among the data signals D1 to D4 or a plurality of data signals are inputted, similar operation to that in the above example is performed.

As described above, in the D / A converters 20b to 20bn, the amount of current flowing to the cathode 11 is controlled. Depending on the input, the base current I _B of the driving device N is varied by the corresponding resistance, thereby making it easier to variably adjust the amount of current flowing to the gate of the FED panel 16.

According to the present invention as described above, it is possible to control the current flowing to the gate, so that even if a short occurs in the gate and the cathode, the excessive current does not flow, and the amount of electrons emitted to the FED panel is easy to control the current flowing to the cathode. Control can be performed more precisely.

On the other hand, the present invention is not limited only to the above-described embodiments, but may be modified and modified without departing from the scope of the present invention.

Claims (4)

A cathode driving means for controlling an amount of electrons emitted to the field emission display panel by having a data circuit section for sequentially outputting a data signal and a D / A converter for adjusting an amount of current flowing to the cathode by the data signal from the data circuit section; In the field emission display provided, The D / A converter is connected to a predetermined reference voltage terminal and is provided between a plurality of switches transferring the reference voltage according to whether a data signal is applied from the data circuit unit, and between the plurality of switches and a driving element at the bottom of the cathode. And a plurality of resistors configured to variably adjust the amount of current flowing to the cathode by varying the base current of the driving element as a reference voltage is transmitted. 2. The field emission display driving circuit of claim 1, wherein each of the plurality of switches comprises an NMOS transistor. The field emission display driving circuit of claim 1, wherein each of the plurality of switches comprises a transfer gate. 4. The field emission display driving circuit according to claim 2 or 3, wherein the plurality of resistors have mutually different resistance values.