CN201262819Y

CN201262819Y - Liquid crystal television and sequence control circuit

Info

Publication number: CN201262819Y
Application number: CNU2008202122785U
Authority: CN
Inventors: 袁博
Original assignee: Shenzhen Skyworth RGB Electronics Co Ltd
Current assignee: Shenzhen Skyworth RGB Electronics Co Ltd
Priority date: 2008-09-28
Filing date: 2008-09-28
Publication date: 2009-06-24
Anticipated expiration: 2018-09-28

Abstract

The utility model is applicable to the technical field of the liquid crystal television and provides a liquid crystal television and a timing control circuit. The liquid crystal television comprises a back light control chip and a power-off timing control circuit which comprises a detecting module which detects the alternating current power supply signal and a control module which is connected with the detecting module and outputs control signals to the back light control chip according to the detecting result. In the utility model, the power-off timing control circuit turns off the back light control chip in real time by detecting the turn-off of the alternating current power supply signal, thus turning off the crystal screen in shortest time and avoiding the scrolling screen shutdown.

Description

A kind of LCD TV and sequential control circuit

Technical field

The utility model belongs to the technical field of LCD TV, relates in particular to a kind of LCD TV and sequential control circuit.

Background technology

In the liquid crystal television power supply product of research and development at present, cause liquid crystal display to produce the phenomenon of similar from left to right draw curtain shutdown owing to can not in time turn-off backlight control signal when AC power is cut off the power supply, liquid crystal display should be switched off the requirement that becomes blank screen rapidly when AC power is cut off the power supply and can't reach.

At present, the research staff has adopted multiple scheme that backlight control signal is turn-offed as much as possible earlier, but effect is all not fully up to expectations.

The utility model content

The purpose of this utility model is to provide a kind of LCD TV, is intended to solve existing LCD TV and produces the problem of similar from left to right draw curtain shutdown phenomenon because of can not in time turn-offing backlight control signal when AC power is cut off the power supply.

The utility model is achieved in that a kind of LCD TV, and described LCD TV comprises a backlight control chip and a power-off sequential control circuit, and described power-off sequential control circuit comprises:

Detect the detection module of ac supply signal; And

Be connected with described detection module,, output control signals to the control module of described backlight control chip according to testing result.

Another purpose of the present utility model is to provide a kind of sequential control circuit, and described sequential control circuit comprises:

Detect the detection module of ac supply signal; And

Be connected with described detection module, according to testing result, the control module of output control signal.

In the utility model, the power-off sequential control circuit goes in time to turn-off the backlight control chip by the shutoff that detects ac supply signal, thereby turns off liquid crystal display in the fastest time, avoids producing draw curtain shutdown phenomenon.

Description of drawings

Fig. 1 is the schematic block circuit diagram of the LCD TV that provides of the utility model embodiment;

Fig. 2 is the exemplary circuit figure of the power-off sequential control circuit that provides of the utility model embodiment;

Fig. 3 is the schematic block circuit diagram of the sequential control circuit that provides of the utility model embodiment;

Fig. 4 is the exemplary circuit figure of the sequential control circuit that provides of the utility model embodiment.

Embodiment

In order to make the purpose of this utility model, technical scheme and advantage clearer,, the utility model is further elaborated below in conjunction with drawings and Examples.Should be appreciated that specific embodiment described herein only in order to explanation the utility model, and be not used in qualification the utility model.

Fig. 1 shows the theory structure of the LCD TV that the utility model embodiment provides, and for convenience of explanation, only shows the part relevant with the utility model.

LCD TV comprises a backlight control chip and a power-off sequential control circuit, the power-off sequential control circuit comprises the detection module 101 that detects ac supply signal, and be connected with detection module 101, according to testing result, output control signals to the control module 102 of backlight control chip.

Fig. 2 shows the exemplary circuit structure of the power-off sequential control circuit that the utility model embodiment provides.

Detection module 101 comprises that diode D1, first resistance R 1, second resistance R 2, the 3rd resistance R 3, the 4th resistance R 4, the 5th resistance R 5, capacitor C 1, the first triode Q1 and the elementary of photoelectrical coupler U1 are light emitting diode.

The anode of diode D1 connects the output terminal of AC power, the negative electrode of diode D1 connects an end of first resistance R 1, the other end of first resistance R 1 connects the positive pole of first capacitor C 1 and an end of second resistance R 2 simultaneously, the minus earth of first capacitor C 1, one end of another termination the 3rd resistance R 3 of second resistance R 2, the other end of the 3rd resistance R 3 connects the base stage of an end and the first triode Q1 of the 4th resistance R 4 simultaneously, the emitter of the other end of the 4th resistance R 4 and the first triode Q1 is ground connection simultaneously, the collector of the first triode Q1 connects an end of the 5th resistance R 5, the negative electrode of the light emitting diode of another termination photoelectrical coupler U1 of the 5th resistance R 5, the anode of light emitting diode connects direct supply.

Control module 102 comprises that the secondary of photoelectrical coupler U1 is phototriode, the 6th resistance R 6, the 7th resistance R 7, the 8th resistance R 8, comparer U2 and the second triode Q2.

The grounded emitter of the phototriode of photoelectrical coupler U1, the collector of phototriode connects the inverting input of comparer U2, above-mentioned collector also connects an end of the 8th resistance R 8, the other end of the 8th resistance R 8 connects the power end of 5V direct supply and comparer U2 simultaneously, the earth terminal ground connection of comparer U2, the in-phase input end of comparer U2 connects the 5V direct supply by the 6th resistance R 6, and by the 7th resistance R 7 ground connection, the base stage of the output termination second triode Q2 of comparer U2, the emitter of the second triode Q2 meets the Enable Pin ENABLE of backlight control chip, its grounded collector.

The principle of work of this power-off sequential control circuit is:

1, during the circuit operate as normal, the 220V AC power is through diode D1 rectification, according to the half-wave formula:

u_{0 (av)} = \frac{\sqrt{2}}{2 π} u_{i} {&Integral;}_{0}^{t} \sin ωtd (ωt) = \frac{\sqrt{2}}{π} u_{i} \approx 0.45 u_{i}

The voltage that can get after the rectification is about 220V*0.45=99V, and through after first resistance R 1, second resistance R 2, the 3rd resistance R 3 and the 4th resistance R 4 dividing potential drops, the voltage that the base stage of the first triode Q1 is got is again:

\frac{R 4 * 99}{R 1 + R 2 + R 3 + R 4} = \frac{4.7 * 99}{100 + 100 + 7.5 + 4.7} = 2.193 V

First triode Q1 conducting this moment, the primary and secondary equal conducting of photoelectrical coupler U1, the inverting input of comparer U2 is pulled down to low level because of the conducting of U1 level of photoelectrical coupler, be lower than its in-phase input end voltage 5V*R7/ (R6+R7)=2.5V, thereby comparer U2 output terminal output high level, the second not conducting of triode Q2, its emitter meets the Enable Pin ENABLE of backlight control chip, Enable Pin ENABLE signal is the operate as normal signal, backlight control chip operate as normal, the LCD TV operate as normal.

2, when shutdown, the unexpected power down of 220V AC power, the first triode Q1 of this moment is in cut-off state because of base stage loses bias voltage, at the beginning of the photoelectrical coupler U1, secondary this moment of also not conducting, the 5V DC voltage will provide a high level greater than its in-phase input end level for the inverting input of comparer U2 by the 8th resistance R 8 like this, so the output terminal of comparer U2 jumps to low level, the second triode Q2 conducting, Enable Pin ENABLE signal is pulled down to low level, the backlight control chip quits work because of Enable Pin ENABLE power down, and liquid crystal display is switched off rapidly and becomes blank screen.

During ac dump, because the power down speed of 220V AC power has precedence over all control signals, have the fast characteristics of response speed so the power-off sequential control circuit removes to turn-off backlight control signal by the shutoff that detects ac supply signal, avoid producing draw curtain shutdown phenomenon.

But, might cause counter productive if this circuit reaction velocity is too fast, the capacity of control capacittance C1 can reach the purpose of regulating this circuit reaction velocity.

The utility model embodiment also provides a sequential control circuit, and Fig. 3 shows the theory structure of the sequential control circuit that the utility model embodiment provides, and for convenience of explanation, only shows the part relevant with the utility model.

Sequential control circuit comprises the detection module 301 that detects ac supply signal, and is connected with detection module 301, according to testing result, and the control module 302 of output control signal.

Fig. 4 shows the exemplary circuit structure of the sequential control circuit that the utility model embodiment provides.

Detection module 301 comprises that diode D1, first resistance R 1, second resistance R 2, the 3rd resistance R 3, the 4th resistance R 4, the 5th resistance R 5, capacitor C 1, the first triode Q1 and the elementary of photoelectrical coupler U1 are light emitting diode.

Control module 302 comprises that the secondary of photoelectrical coupler U1 is phototriode, the 6th resistance R 6, the 7th resistance R 7, the 8th resistance R 8, comparer U2 and the second triode Q2.

The grounded emitter of the phototriode of photoelectrical coupler U1, the collector of phototriode connects the inverting input of comparer U2, above-mentioned collector also connects an end of the 8th resistance R 8, the other end of the 8th resistance R 8 connects the power end of 5V direct supply and comparer U2 simultaneously, the earth terminal ground connection of comparer U2, the in-phase input end of comparer U2 connects the 5V direct supply by the 6th resistance R 6, and by the 7th resistance R 7 ground connection, the base stage of the output termination second triode Q2 of comparer U2, the emitter output control signal of the second triode Q2, its grounded collector.

The principle of work of sequential control circuit is identical with the principle of work of above-mentioned power-off sequential control circuit, it is the controlling object difference, its concrete principle of work here repeats no more, and this sequential control circuit can be applied to realizing the purpose of control timing in other circuit.

In the utility model embodiment, the power-off sequential control circuit goes in time to turn-off the backlight control chip by the shutoff that detects ac supply signal, thereby turns off liquid crystal display in the fastest time, avoids producing draw curtain shutdown phenomenon.

The above only is preferred embodiment of the present utility model; not in order to restriction the utility model; all any modifications of within spirit of the present utility model and principle, being done, be equal to and replace and improvement etc., all should be included within the protection domain of the present utility model.

Claims

1, a kind of LCD TV is characterized in that, described LCD TV comprises a backlight control chip and a power-off sequential control circuit, and described power-off sequential control circuit comprises:

Detect the detection module of ac supply signal; And

2, LCD TV as claimed in claim 1, it is characterized in that described detection module comprises that the elementary of diode, first resistance, second resistance, the 3rd resistance, the 4th resistance, the 5th resistance, electric capacity, first triode and photoelectrical coupler is light emitting diode;

The anode of described diode connects the output terminal of AC power, the negative electrode of described diode connects an end of first resistance, the other end of described first resistance connects the positive pole of first electric capacity and an end of second resistance simultaneously, the minus earth of described first electric capacity, one end of another termination the 3rd resistance of described second resistance, the other end of described the 3rd resistance connects the base stage of an end and first triode of the 4th resistance simultaneously, the emitter of the other end of described the 4th resistance and first triode is ground connection simultaneously, the collector of described first triode connects an end of the 5th resistance, the negative electrode of the light emitting diode of another termination photoelectrical coupler of described the 5th resistance, the anode of described light emitting diode connects direct supply.

3, LCD TV as claimed in claim 2 is characterized in that, described control module comprises that the secondary of photoelectrical coupler is phototriode, the 6th resistance, the 7th resistance, the 8th resistance, comparer and second triode;

The grounded emitter of the phototriode of described photoelectrical coupler, the collector of described phototriode connects the inverting input of comparer, described collector also connects an end of the 8th resistance, the other end of described the 8th resistance connects the power end of direct supply and described comparer simultaneously, the earth terminal ground connection of described comparer, the in-phase input end of described comparer connects direct supply by the 6th resistance, and by the 7th resistance eutral grounding, the base stage of output termination second triode of described comparer, the emitter of described second triode connects the Enable Pin of backlight control chip, the grounded collector of described second triode.

4, a kind of sequential control circuit is characterized in that, described sequential control circuit comprises:

Detect the detection module of ac supply signal; And

5, sequential control circuit as claimed in claim 4, it is characterized in that described detection module comprises that the elementary of diode, first resistance, second resistance, the 3rd resistance, the 4th resistance, the 5th resistance, electric capacity, first triode and photoelectrical coupler is light emitting diode;

6, sequential control circuit as claimed in claim 5 is characterized in that, described control module comprises that the secondary of photoelectrical coupler is phototriode, the 6th resistance, the 7th resistance, the 8th resistance, comparer and second triode;

The grounded emitter of the phototriode of described photoelectrical coupler, the collector of described phototriode connects the inverting input of comparer, described collector also connects an end of the 8th resistance, the other end of described the 8th resistance connects the power end of direct supply and described comparer simultaneously, the earth terminal ground connection of described comparer, the in-phase input end of described comparer connects direct supply by the 6th resistance, and by the 7th resistance eutral grounding, the base stage of output termination second triode of described comparer, the emitter output control signal of described second triode, the grounded collector of described second triode.