CN201262819Y - A LCD TV and its timing control circuit - Google Patents

Abstract

The utility model is applicable to the technical field of liquid crystal televisions, and provides a liquid crystal television and a sequence control circuit. The liquid crystal television includes a backlight control chip and a power-down sequence control circuit. The power-down sequence control circuit includes: a detection module for detecting AC power signals and a control module that is connected to the detection module and outputs a control signal to the backlight control chip according to the detection result. In the utility model, the power-down sequence control circuit detects the cut-off of the AC power signal to turn off the backlight control chip in time, so as to turn off the LCD screen in the fastest time and avoid the phenomenon of pulling the screen off.

Description

A LCD TV and its timing control circuit

technical field

The utility model belongs to the technical field of liquid crystal televisions, in particular to a liquid crystal television and a sequence control circuit.

Background technique

In the currently developed LCD TV power supply products, because the backlight control signal cannot be turned off in time when the AC power supply is cut off, the LCD screen will turn off from left to right, and the LCD screen cannot be turned off when the AC power supply is cut off. The screen should be turned off quickly to a black screen.

At present, R&D personnel have adopted various schemes to turn off the backlight control signal as early as possible, but the effects are not satisfactory.

Utility model content

The purpose of the utility model is to provide a liquid crystal television, aiming at solving the problem that the existing liquid crystal television cannot turn off the backlight control signal in time when the AC power supply is cut off, which causes the phenomenon of turning off the screen from left to right.

The utility model is realized in this way, a kind of liquid crystal television, described liquid crystal television comprises a backlight control chip and a power-down sequence control circuit, and described power-down sequence control circuit comprises:

a detection module for detecting an AC power signal; and

It is connected with the detection module, and outputs a control signal to the control module of the backlight control chip according to the detection result.

Another object of the present utility model is to provide a timing control circuit, which includes:

a detection module for detecting an AC power signal; and

A control module that is connected with the detection module and outputs a control signal according to the detection result.

In the utility model, the power-down sequence control circuit detects the cut-off of the AC power signal to turn off the backlight control chip in time, so as to turn off the LCD screen in the fastest time and avoid the phenomenon of pulling the screen off.

Description of drawings

Fig. 1 is the schematic block diagram of the circuit of the liquid crystal television that the utility model embodiment provides;

Fig. 2 is the example circuit diagram of the power-down sequence control circuit that the utility model embodiment provides;

Fig. 3 is the circuit schematic block diagram of the timing control circuit provided by the embodiment of the utility model;

Fig. 4 is an example circuit diagram of the timing control circuit provided by the embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

Fig. 1 shows the principle structure of the liquid crystal television provided by the embodiment of the present invention, and for the convenience of description, only the parts related to the present invention are shown.

The LCD TV includes a backlight control chip and a power-down sequence control circuit. The power-down sequence control circuit includes a detection module 101 that detects an AC power signal, and a control module that is connected to the detection module 101 and outputs a control signal to the backlight control chip according to the detection result. 102.

FIG. 2 shows an example circuit structure of the power-down sequence control circuit provided by the embodiment of the present invention.

The detection module 101 includes a diode D1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a capacitor C1, a first triode Q1 and a photocoupler U1. diode.

The anode of the diode D1 is connected to the output terminal of the AC power supply, the cathode of the diode D1 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to the positive pole of the first capacitor C1 and one end of the second resistor R2 at the same time, and the first capacitor C1 The negative pole of the second resistor R2 is connected to one end of the third resistor R3, the other end of the third resistor R3 is connected to one end of the fourth resistor R4 and the base of the first triode Q1 at the same time, and the fourth resistor R4 The other end and the emitter of the first triode Q1 are grounded at the same time, the collector of the first triode Q1 is connected to one end of the fifth resistor R5, and the other end of the fifth resistor R5 is connected to the cathode of the light-emitting diode of the photocoupler U1, The anode of the light-emitting diode is connected to a DC power supply.

The control module 102 includes the secondary side of the optocoupler U1 ie a phototransistor, a sixth resistor R6 , a seventh resistor R7 , an eighth resistor R8 , a comparator U2 and a second transistor Q2 .

The emitter of the phototransistor of the photocoupler U1 is grounded, the collector of the phototransistor is connected to the inverting input terminal of the comparator U2, the collector is also connected to one end of the eighth resistor R8, and the other end of the eighth resistor R8 is connected to 5V DC at the same time The power supply and the power supply terminal of the comparator U2, the ground terminal of the comparator U2 are grounded, the non-inverting input terminal of the comparator U2 is connected to the 5V DC power supply through the sixth resistor R6, and grounded through the seventh resistor R7, and the output terminal of the comparator U2 is connected to the first The base of the second triode Q2, the emitter of the second triode Q2 are connected to the enabling terminal ENABLE of the backlight control chip, and the collector thereof is grounded.

The working principle of the power-down sequence control circuit is:

1. When the circuit is working normally, the 220V AC power supply is rectified by diode D1, according to the half-wave formula:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; av</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; t</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&omega;td</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 0.45</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

It can be obtained that the rectified voltage is about 220V*0.45=99V, and after being divided by the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4, the base of the first triode Q1 is divided into The resulting voltage is:

$\frac{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 99</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 4.7</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 99</span>}}{\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 7.5</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4.7</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2.193</span>}\mathrm{<span\; class="notranslate">\; V</span>}$

At this time, the first triode Q1 is turned on, the primary and secondary sides of the photocoupler U1 are both turned on, and the inverting input terminal of the comparator U2 is pulled down to a low level because the photocoupler U1 is turned on. Since the voltage at its non-inverting input terminal is 5V*R7/(R6+R7)=2.5V, the output terminal of the comparator U2 outputs a high level, the second transistor Q2 is not turned on, and its emitter is connected to the enabling of the backlight control chip Terminal ENABLE, enabling terminal ENABLE signal is a normal working signal, the backlight control chip works normally, and the LCD TV works normally.

2. When the power is turned off, the 220V AC power supply suddenly loses power. At this time, the first triode Q1 is in the cut-off state because the base loses the bias voltage, and the primary and secondary sides of the photocoupler U1 are not turned on at this time, so The 5V DC voltage will provide a high level greater than the level of its non-inverting input terminal to the inverting input terminal of the comparator U2 through the eighth resistor R8, so the output terminal of the comparator U2 jumps to a low level, and the second three-pole The tube Q2 is turned on, the ENABLE signal of the enable terminal is pulled down to low level, the backlight control chip stops working due to the power failure of the enable terminal ENABLE, and the LCD screen is quickly turned off and becomes a black screen.

When the AC power is turned off, because the power-down speed of the 220V AC power supply takes precedence over all control signals, the power-down sequence control circuit detects the power-off of the AC power supply signal to turn off the backlight. The control signal has the characteristics of fast response and avoids the curtain shutdown Phenomenon.

However, if the response speed of the circuit is too fast, it may cause negative effects, and the purpose of adjusting the response speed of the circuit can be achieved by adjusting the capacity of the capacitor C1.

The embodiment of the utility model also provides a sequence control circuit. FIG. 3 shows the principle structure of the sequence control circuit provided by the embodiment of the utility model. For the convenience of description, only the parts related to the utility model are shown.

The timing control circuit includes a detection module 301 that detects an AC power signal, and a control module 302 that is connected to the detection module 301 and outputs a control signal according to the detection result.

Fig. 4 shows an example circuit structure of the timing control circuit provided by the embodiment of the present invention.

The detection module 301 includes a diode D1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a capacitor C1, a first triode Q1 and a photocoupler U1. diode.

The anode of the diode D1 is connected to the output terminal of the AC power supply, the cathode of the diode D1 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to the positive pole of the first capacitor C1 and one end of the second resistor R2 at the same time, and the first capacitor C1 The negative pole of the second resistor R2 is connected to one end of the third resistor R3, the other end of the third resistor R3 is connected to one end of the fourth resistor R4 and the base of the first triode Q1 at the same time, and the fourth resistor R4 The other end and the emitter of the first triode Q1 are grounded at the same time, the collector of the first triode Q1 is connected to one end of the fifth resistor R5, and the other end of the fifth resistor R5 is connected to the cathode of the light-emitting diode of the photocoupler U1, The anode of the light-emitting diode is connected to a DC power supply.

The control module 302 includes the secondary side of the photocoupler U1 ie a phototransistor, a sixth resistor R6 , a seventh resistor R7 , an eighth resistor R8 , a comparator U2 and a second transistor Q2 .

The emitter of the phototransistor of the photocoupler U1 is grounded, the collector of the phototransistor is connected to the inverting input terminal of the comparator U2, the collector is also connected to one end of the eighth resistor R8, and the other end of the eighth resistor R8 is connected to 5V DC at the same time The power supply and the power supply terminal of the comparator U2, the ground terminal of the comparator U2 are grounded, the non-inverting input terminal of the comparator U2 is connected to the 5V DC power supply through the sixth resistor R6, and grounded through the seventh resistor R7, and the output terminal of the comparator U2 is connected to the first The base of the second transistor Q2, the emitter of the second transistor Q2 output the control signal, and the collector thereof is grounded.

The working principle of the timing control circuit is the same as that of the above-mentioned power-down timing control circuit, but the control objects are different. The specific working principle will not be repeated here. The timing control circuit can be applied to other circuits to realize the control timing the goal of.

In the embodiment of the utility model, the power-down sequence control circuit detects the cut-off of the AC power signal to turn off the backlight control chip in time, so as to turn off the LCD screen in the fastest time and avoid the phenomenon of pulling the screen off.

The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present utility model shall be included in this utility model. within the scope of protection of utility models.

Claims (6)

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

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

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

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

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;

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.

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.

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