CN2516996Y - Liquid crystal flat panel display discharge circuit - Google Patents

Abstract

The utility model discloses a liquid crystal flat panel display discharge circuit. The circuit comprises three active elements and a plurality of resistance elements, wherein the three active elements comprise three transistors and a plurality of resistors. It forms a discharge path to effectively discharge the residual power of the LCD, so as to increase the discharge speed of the LCD without increasing the power loss.

Description

Liquid crystal flat panel display discharge circuit

technical field

The utility model relates to a liquid crystal display (LCD) discharge circuit, in particular to a circuit for effectively releasing the residual power of the liquid crystal display.

technical background

Liquid crystal display is a very common electronic device nowadays, widely used in many circuit supplies and communication equipment or information devices, such as LCD TV, notebook computer, personal digital assistant (PDA) and mobile phone, LCD projectors, etc. are widely used, and it can be said that as long as the electronic information equipment that needs display settings can see its application.

Compared with the traditional cathode ray tube (CRT), liquid crystal display has many advantages, including less space, less power consumption, and no radiation, etc., and due to the rapid development of semiconductor technology, the production process of liquid crystal display is also changing. It is being improved and various crafting techniques are in use at the same time.

The forming principle of liquid crystal display is to use the deflection angle of liquid crystal to display. Its types can be roughly divided into monochrome and color, but monochrome has almost withdrawn from the market, and color LCD can be divided into STN super rotation array and TFT active The super-rotational array can be divided into single-scanning type and double-scanning type. Since the super-rotational array scans from the top to the bottom of the display at one time, water ripples and afterimages are likely to occur due to the long distance, so double-scanning improves single-scan flaws. The way of double scanning is to divide the scanning distance of the display into the upper half and the lower half, and only scan to half at a time to shorten the scanning distance.

And because the liquid crystal display will have the problem of residual voltage, so a discharge circuit will be designed to release the residual voltage of the liquid crystal display.

As shown in Fig. 1, it is a discharge circuit of an existing liquid crystal display. As shown in Figure 1, an input voltage terminal (EN_LCD) is connected to the base (B) of a bipolar transistor 12 through a resistor 13, and the base (B) of the transistor 12 is connected to the emitter (E) A resistor 14, and the collector (C) of the transistor is connected to another voltage input terminal (VDD_12) via a resistor 15. And the gate (G) of a metal oxide semiconductor field effect transistor (MOSFET) 11 is connected to the collector (C) terminal of this transistor 12, and the drain (D) of transistor (MOSFET) 11 is connected to a voltage of 5V The input terminal, and the source (S) of the transistor 11 is connected to a voltage input terminal (VCC_LCD) of a liquid crystal display (shown in the figure) in addition to connecting a resistor 16 to ground.

Wherein, when the voltage input terminal (EN_LCD) input is a high potential (H), for example, 5V, the transistor 12 is turned on, and the output voltage of the collector terminal of the transistor 12 is not enough to make the transistor 11 turn on, so the transistor 11 is inactive. In the conduction state, the VCC_LCD terminal is connected to a liquid crystal display (not shown in the figure) and there is a residual voltage, so at this time, the residual power at the VCC_LCD terminal will be discharged through the resistor 16. For the selection of the resistor 16, usually the resistance value is selected The smaller the one, the faster the release of the residual power will be. However, the resistor 16 is usually connected in parallel with the power supply of VCC_LCD, so it consumes power at the same time when supplying power. Therefore, the selection of the resistor 16 should not be too small to avoid excessive consumption. However, it cannot be selected too large to avoid affecting the discharge time, so it is impossible to have the best of both worlds and one of the conditions must be sacrificed.

Contents of the invention

The utility model is a further improvement to solve the above-mentioned shortcoming of the prior art. The main purpose of the present invention is to provide a discharge circuit, which increases the discharge speed of the discharge circuit by adding a transistor and a resistor, so as to effectively improve the circuit characteristics.

Another object of the present invention is to provide a discharge circuit that does not consume excess power when there is no input voltage signal, so as to effectively maintain the characteristics of the circuit and save power consumption.

To achieve the above purpose, the utility model provides a discharge circuit, which is composed of three active elements and several resistance elements. It includes a first transistor, a second transistor and a third transistor. Wherein the base of the first transistor is connected to an input voltage terminal (EN_LCD) via a first resistor, the emitter of the first transistor is connected to the ground terminal, and the base and the emitter are connected to a second resistor, the transistor The collector of is connected to a first power supply end via a third resistance element. Moreover, the gate of the second transistor is connected to the collector of the first transistor, the drain of the second transistor is connected to a second power supply terminal, and the source of the second transistor is connected to a liquid crystal flat panel display. And the base of the third transistor is connected to the input voltage end through a fourth resistance element, and the emitter of the third transistor is connected to the ground end, and the collector of the third transistor is connected to the input voltage end through a fifth resistance element. Source of the second transistor.

Brief description of the drawings

Through the following detailed description of specific embodiments in conjunction with the accompanying drawings, the above and other purposes and features of the present utility model will become apparent, in the accompanying drawings:

Fig. 1 is a schematic diagram of the discharge circuit structure of an existing liquid crystal display;

Fig. 2 is a schematic diagram of the discharge circuit structure of a preferred embodiment of the present invention;

Detailed ways:

The utility model discloses a discharge circuit of a liquid crystal flat panel display. The residual power of the liquid crystal display can be effectively released through the arrangement of the discharge circuit of the utility model, so as to increase the discharge speed of the liquid crystal display without increasing power loss.

Please refer to FIG. 2 , which shows a discharge circuit of a preferred embodiment of the present invention. The base (B) of a bipolar NPN transistor 22 is connected to an input voltage terminal (EN_LCD) via a resistor 23, the emitter (E) of the transistor 22 is connected to the ground terminal, and the base (B) and emitter A resistor 24 is connected between the electrodes (E), and the collector (C) of the transistor 22 is connected to a power supply terminal (VDD_12 ) through a resistor 25 .

Furthermore, the gate (G) of a metal oxide semiconductor field effect transistor (MOSFET) 21 is connected to the collector (C) of the transistor 22, and the drain (S) of the transistor 21 is connected to a 5V power supply terminal, the The source (S) of the transistor 21 is connected to a power supply terminal (VCC_LCD) of a liquid crystal flat panel display (not shown). Furthermore, the base (B) of another bipolar NPN transistor 20 is connected to the input voltage terminal (EN_LCD) via a resistor 29, and the emitter (E) of the transistor 20 is connected to the ground, and the third transistor The collector (C) is connected to the source (S) of the transistor 21 via a resistor 28 .

Wherein, when the input voltage terminal (EN_LCD) is logic low potential (L), the transistor 22 is not turned on, and the transistor 21 is turned on by receiving the voltage provided by the resistor 25 connected to the power supply terminal (VDD_12), The transistor 20 is also not turned on, so that the resistor 28 forms a floating state, and the resistor 28 does not consume power at this time.

Furthermore, when the input voltage terminal (EN_LCD) is a logic high potential (H), the transistor 22 is turned on, and the transistor 21 cannot get enough voltage at the collector (C) of the transistor 22 because of the turn-on of the transistor 22 , thus making transistor 21 non-conductive. Furthermore, at this time, the transistor 20 is also in a conduction state due to receiving the logic high potential voltage of the input voltage terminal (EN_LCD). At this time, the transistor 20 and the resistor 28 will form a discharge path to receive the liquid crystal from the (VCC_LCD) terminal. Display residual voltage. In this case, the resistance value of the resistor 28 can be designed to be relatively small (for example, 100 ohms) to speed up the discharge speed.

Alternatively, the transistor 20 can also be a metal oxide semiconductor field effect transistor (MOSFET), wherein the gate (G) of the MOSFET is connected to the input voltage terminal (EN_LCD) via the resistor 29, and the source of the MOSFET The drain (D) of the MOSFET is connected to the source (S) of the transistor 21 via the resistor 28.

The discharge circuit of the utility model improves the discharge speed and does not consume electric power in normal times, so the defects in the prior art are overcome. Through the above, the discharge circuit, structural features and various embodiments of the utility model have been disclosed in detail.

Apparently, the above descriptions are only preferred embodiments of the present utility model, and cannot be used to limit the implementation scope of the present utility model. Changes and modifications made without departing from the spirit and scope of the utility model defined by the claims shall still belong to the scope covered by the utility model patent application.

Claims (7)

1, a kind of liquid crystal flat panel display discharge circuit is characterized in that, comprising:

One the first transistor, the base stage of this first transistor is connected to an Input voltage terminal (EN_LCD) via one first resistance, the emitter of this first transistor is held with being connected to, and the base stage of this first transistor and emitter are connected with one second resistance, and the collector of this first transistor is connected to one first power source supply end via one the 3rd resistive element;

One transistor seconds, the grid of this transistor seconds is connected to the collector of this first transistor, and the drain electrode of this transistor seconds connects a second source feed end, and the source electrode of this transistor seconds is connected to this liquid crystal flat panel display;

One the 3rd transistor, the 3rd transistorized base stage is connected to this Input voltage terminal via one the 4th resistive element, the 3rd transistorized emitter is connected to ground, and the 3rd transistorized collector is connected to the source electrode of this transistor seconds via one the 5th resistive element.

2, liquid crystal flat panel display discharge circuit according to claim 1 is characterized in that the 5th resistance value can be 100 ohm.

3, liquid crystal flat panel display discharge circuit according to claim 1 is characterized in that the 3rd transistor is the NPN bipolar transistor.

4, liquid crystal flat panel display discharge circuit according to claim 1 is characterized in that this first transistor is the NPN bipolar transistor.

5, liquid crystal flat panel display discharge circuit according to claim 1 is characterized in that this transistor seconds is mos field effect transistor (MOS FET).

6, liquid crystal flat panel display discharge circuit according to claim 1, it is characterized in that the 3rd transistor is a MOS FET, wherein the grid of this MOS FET is connected to this Input voltage terminal via the 4th resistance, this MOS FET source electrode is connected to ground, and the drain electrode of this MOSFET is connected to the source electrode of this transistor seconds via the 5th resistance.

8, liquid crystal flat panel display discharge circuit according to claim 1, wherein the 3rd transistor is a MOS FET, wherein the grid of this MOS FET is connected to this Input voltage terminal via the 4th resistance, this MOS FET source electrode is connected to ground, and the drain electrode of this MOS FET is connected to the source electrode of this transistor seconds via the 5th resistance.

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