CN201118796Y - Under voltage protection circuit - Google Patents
Under voltage protection circuit Download PDFInfo
- Publication number
- CN201118796Y CN201118796Y CNU2007203055478U CN200720305547U CN201118796Y CN 201118796 Y CN201118796 Y CN 201118796Y CN U2007203055478 U CNU2007203055478 U CN U2007203055478U CN 200720305547 U CN200720305547 U CN 200720305547U CN 201118796 Y CN201118796 Y CN 201118796Y
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Abstract
The utility model discloses an under-voltage protection circuit which is designed for solving the problem of screen flicker when shutting down a liquid crystal television. The under-voltage protection circuit comprises an amplifying circuit for supplying power to a control chip of the liquid crystal television and an amplifying power supply circuit for supplying power to the amplifying circuit, and also includes a clamp circuit connected with the amplifying circuit and an under-voltage control circuit connected with the clamp circuit. The under-voltage protection circuit is used for controlling the power supply of the control chip of the liquid crystal television, and can also be applied to the power supply control of control chips of other electrical devices.
Description
Technical field
The utility model relates to a kind of protective circuit, particularly a kind of under-voltage protecting circuit of liquid crystal television power supply.
Background technology
The liquid crystal display screen of LCD TV itself does not have lighting function, and this just need add an illuminator behind liquid crystal display screen, this backlight illuminating system by luminous component, the light uniform irradiation is constituted in the light guide plate of liquid crystal presentation surface and the power supply of driven for emitting lights parts.The main flow of luminous component is the fluorescent tube that is known as cold-cathode tube now, and it just can be lighted at the lower temperature state, but will drive the particular power source that this cold-cathode tube needs to export the 1000-1500V alternating voltage.
Because general city provides the alternating voltage of 220V/50Hz or 110V/60Hz with electrical network, and display is (no matter be early stage CRT pipe, or emerging LCD display, and even most of circuit LCD-TV) is to be operated under the condition of low pressure, so need be furnished with power circuit specially on display.Its effect is exactly the direct voltage output that the alternating voltage of civil power is converted into the most of circuit working of suitable display, thereby to monitor power supply.Given this, realize the power supply that this is special, will be transformed into the 1000-1500V alternating voltage, Here it is inverter (INVERTER) from direct voltage.
The INVERTER of present large-screen liquid crystal display television mostly is import; input voltage is 24V; a low-voltage protection circuit is all arranged; approximately about 23V; when the 24V power down is to 23V when power supply shuts down; INVERTER is protected just not to have worked; the big electrochemical capacitor in former limit continues discharge; 24V voltage causes voltage to rise owing to do not had load suddenly, and INVERTER has worked again; this is the main cause that screen dodges when causing the LCD TV shutdown; its waveform such as Fig. 1, wherein the CH1 among the figure is the waveform of 24V when the shutdown screen dodges, CH2 is the control waveform of control backlight switch.
Chinese patent CN92217306.0 discloses a kind of under-voltage protecting circuit; this under-voltage protecting circuit adopt comparator with sampled voltage and reference voltage relatively when the two difference reaches predetermined value; the state turnover of comparator; drag down the base voltage of transistor; transistor is ended, thereby realize under-voltage protection.This under-voltage protecting circuit structure relative complex, it is bigger to take up room, and cost is higher.
The utility model content
Technical problem to be solved in the utility model provides a kind of under-voltage protecting circuit, can stop the power supply to the LCD TV control chip after mains switch is closed fast, thereby solves the problem that LCD TV shutdown screen dodges.
For solving the problems of the technologies described above, the technical solution adopted in the utility model is:
This under-voltage protecting circuit comprises the amplifying circuit that is used for the power supply of LCD TV control chip, and to the amplification power supply circuits that this amplifying circuit is powered, also comprises the clamp circuit that links to each other with described amplifying circuit, the under-voltage control circuit that links to each other with described clamp circuit.
Wherein, described amplifying circuit comprises a NPN type triode, and the collector electrode of this NPN type triode is connected with the amplification power supply circuits respectively with base stage, and emitter links to each other with an output, be used for the power supply of LCD TV control chip, and emitter links to each other with another output by a resistance.
Further, described amplifying circuit also comprises pressure filter circuit.
Described pressure filter circuit comprises emitter bias resistance and collector bias resistance; Wherein, an end of emitter bias resistance is connected with the base stage of NPN type triode, and the other end links to each other with the emitter of NPN type triode; One end of collector bias resistance is connected other end ground connection with the base stage of NPN type triode; Collector bias resistance is parallel with electric capacity, and emitter bias resistance also is parallel with electric capacity.
With a described collector bias resistance voltage-stabiliser tube also in parallel.
Described amplification power supply circuits comprise the amplification power supply; This amplification power supply links to each other with the collector electrode of described NPN type triode, and should link to each other with the base stage of an optocoupler with described NPN type triode by a current-limiting resistance by the amplification power supply.
Pass through a capacity earth between described current-limiting resistance and the optocoupler.
Described amplification power supply is by a capacity earth, and a resistance in parallel with this ground capacity.
Described clamp circuit comprises a positive-negative-positive triode; The grounded collector of this positive-negative-positive triode, emitter with link to each other with the base stage of described negative-positive-negative transistor, base stage links to each other with described under-voltage control circuit with a crystal diode by a current-limiting resistance, and, between the collector electrode of this positive-negative-positive triode and base stage, be parallel with electric capacity and resistance.
Described under-voltage control circuit one end is used to insert the voltage of rectifier bridge back, other end ground connection.This under-voltage control circuit comprises crystal diode, voltage-stabiliser tube and the divider resistance that is connected in series; The base stage of described positive-negative-positive triode is connected by described current-limiting resistance and crystal diode between two divider resistances in centre of this under-voltage control circuit.
The utility model under-voltage protecting circuit; after mains switch is closed; under-voltage control circuit drags down the current potential of amplifying circuit by clamp circuit; amplifying circuit becomes by state from amplifying operating state, thereby stops the power supply of amplifying circuit to the LCD TV control chip, after control chip is not worked; just can not give big electrochemical capacitor discharge; the power down at once of the input voltage of INVERTER, and can not rise again, thereby the problem that LCD TV shutdown screen dodges solved.
Description of drawings
The oscillogram that screen dodged when Fig. 1 was the LCD TV shutdown;
Fig. 2 is an embodiment circuit diagram of the utility model under-voltage protecting circuit.
Embodiment
The purpose of this utility model is the problem that can occur shielding sudden strain of a muscle when shutting down at LCD TV, and a kind of under-voltage protecting circuit that can make the quick power down of LCD TV control chip is provided, thereby solves the problem that the shutdown screen dodges.Below in conjunction with accompanying drawing and the utility model embodiment is done detailed explanation.
Generally; the utility model under-voltage protecting circuit comprises the amplifying circuit that is used for the power supply of LCD TV control chip, reaches the amplification power supply circuits to this amplifying circuit power supply; also comprise the clamp circuit that links to each other with described amplifying circuit, the under-voltage control circuit that links to each other with described clamp circuit.Wherein this amplifying circuit is used for LCD TV control chip and the power supply of PWM controller.
As shown in Figure 2, described amplifying circuit comprises a NPN type triode, be BCP56-10T1G, the collector electrode of this NPN type triode is connected with the amplification power supply circuits respectively with base stage, emitter links to each other with an output VCC, be used for the power supply of LCD TV control chip, and emitter links to each other with another output PWMVCC by a resistance.This another output PWM VCC is used for the PWM controller power supply to LCD TV.The control chip of LCD TV can adopt the PW364 control chip of U.S. Pixelworks company.Certainly, also available here positive-negative-positive triode makes up this amplifying circuit.Present embodiment is that example provides explanation with NPN type triode.
Described amplification power supply circuits comprise 15 volts amplification power supply; This amplifies power supply and links to each other with the collector electrode of described NPN type triode, and should amplify that power supply passes through one 203 current-limiting resistance R838 and the output of an optocoupler N805 links to each other with the base stage of described NPN type triode.
Change the size of optocoupler input exciting current, can change the light intensity that shines the optocoupler light-receiving device, thereby change the size of the photoelectric current that produces because of photoelectric effect, that is can adjust the size of the base current of NPN type triode V807, thereby realize adjustment amplified current.The electric current of 15 volts of power supply supplies is supplied with LCD TV control chip and PWM controller through amplifying the back.
In order to remove interference high-frequency signal and the noise that power supply is introduced, described 15 volts are amplified capacitor C 832 ground connection that power supplies pass through a 22uF/50V, and with the resistance R 844 of this ground capacity C832 in parallel 1; Pass through capacitor C 836 ground connection of a 104/50V between described current-limiting resistance R838 and the optocoupler N805.
For the base stage that guarantees NPN type triode V807 has reliable and stable electric current, described amplifying circuit also comprises pressure filter circuit.This pressure filter circuit comprises one 104 emitter bias resistance R 839 and one 104 collector bias resistance R 913; One end of emitter bias resistance R 839 is connected with the base stage of NPN type triode V807, and the other end links to each other with the emitter of NPN type triode V807; One end of collector bias resistance R 913 is connected other end ground connection with the base stage of NPN type triode V807; In addition, be parallel with the capacitor C 838 of a 104/50V, be parallel with the capacitor C 837 of a 104/50V with emitter bias resistance R 839 with collector bias resistance R 913.
Further, with described collector bias resistance R 913 a voltage-stabiliser tube VZ804 also in parallel, promptly MMSZ15T1G can guarantee that like this base stage of NPN type triode V807 has stable voltage.
Clamp circuit among the utility model embodiment comprises positive-negative-positive triode V817, i.e. a MMBT2907ALT1G; The grounded collector of this positive-negative-positive triode, emitter links to each other with base stage with described negative-positive-negative transistor V807, base stage links to each other with described under-voltage control circuit with a crystal diode VD827 by one 333 current-limiting resistance R840, and, between the collector electrode of this positive-negative-positive triode and base stage, be parallel with the capacitor C 834 of a 104/50V and one 105 resistance R 925.
Under-voltage control circuit one termination among the utility model embodiment is gone into the 300V voltage of rectifier bridge back, other end ground connection.This under-voltage control circuit comprises from height point position divider resistance R904, R910, the R912 of the crystal diode VD811, the voltage-stabiliser tube VZ805 that are connected in series successively to electronegative potential and 684 and 105 resistance R 906.
The base stage of described positive-negative-positive triode V817, two divider resistances in centre that are connected this under-voltage control circuit by described current-limiting resistance R840 that is connected in series and crystal diode VD827 are between R910 and the R912.The divider resistance R906 of ground connection is parallel with capacitor C 829 and the C878 of two 203/50V in the under-voltage control circuit.
The operation principle of the utility model under-voltage protecting circuit is: after mains switch is closed; the 300V voltage of rectifier bridge back has not just had at once; at this moment crystal diode VD827 conducting; positive-negative-positive triode V817 conducting; base voltage with negative-positive-negative transistor V807 after the positive-negative-positive triode V817 conducting drags down into low level; negative-positive-negative transistor V807 just becomes by state by amplifying operating state; so two output VCC; PWM-VCC does not just have voltage; because output VCC is the voltage to the power supply of liquid crystal TV control chip; after the LCD TV control chip is not worked, just can not give big electrochemical capacitor discharge.The input voltage 24V of INVERTER is because the shutoff of power supply and power down at once, and can not rise again, thereby the basic shutdown screen that solves dodges, and this circuit is because the shutdown power down is very fast, so the sudden and violent mail topic of loudspeaker can also solve shutdown the time.
The utility model under-voltage protecting circuit is simple in structure, and it is less to take up room, and cost is lower.
The above; it only is embodiment of the present utility model; but protection range of the present utility model is not limited thereto; any those of ordinary skill in the art are in the disclosed technical scope of the utility model; the variation that can expect easily or replacement all should be encompassed within the protection range of the present utility model.Therefore, protection range of the present utility model should be as the criterion with the protection range that claims were limited.
Claims (10)
1, a kind of under-voltage protecting circuit; comprise the amplifying circuit that is used for the power supply of LCD TV control chip; and, it is characterized in that: also comprise the clamp circuit that links to each other with described amplifying circuit, the under-voltage control circuit that links to each other with described clamp circuit the amplification power supply circuits that this amplifying circuit is powered.
2, under-voltage protecting circuit according to claim 1 is characterized in that:
Described amplifying circuit comprises a NPN type triode, the collector electrode of this NPN type triode is connected with the amplification power supply circuits respectively with base stage, emitter links to each other with an output, be used for the power supply of LCD TV control chip, and emitter links to each other with another output by a resistance.
3, under-voltage protecting circuit according to claim 2 is characterized in that:
Described amplifying circuit also comprises pressure filter circuit.
4, under-voltage protecting circuit according to claim 3 is characterized in that: described pressure filter circuit comprises emitter bias resistance and collector bias resistance;
Wherein, an end of emitter bias resistance is connected with the base stage of NPN type triode, and the other end links to each other with the emitter of NPN type triode;
One end of collector bias resistance is connected other end ground connection with the base stage of NPN type triode;
Collector bias resistance is parallel with electric capacity, and emitter bias resistance also is parallel with electric capacity.
5, under-voltage protecting circuit according to claim 4 is characterized in that: with a described collector bias resistance voltage-stabiliser tube also in parallel.
6, under-voltage protecting circuit according to claim 2 is characterized in that: described amplification power supply circuits comprise the amplification power supply; This amplification power supply links to each other with the collector electrode of described NPN type triode, and should link to each other with the base stage of an optocoupler with described NPN type triode by a current-limiting resistance by the amplification power supply.
7, under-voltage protecting circuit according to claim 6 is characterized in that: pass through a capacity earth between described current-limiting resistance and the optocoupler.
8, under-voltage protecting circuit according to claim 6 is characterized in that: described amplification power supply is by a capacity earth, and a resistance in parallel with this ground capacity.
9, under-voltage protecting circuit according to claim 2 is characterized in that: described clamp circuit comprises a positive-negative-positive triode;
The grounded collector of this positive-negative-positive triode, emitter with link to each other with the base stage of described negative-positive-negative transistor, base stage links to each other with described under-voltage control circuit with a crystal diode by a current-limiting resistance, and, between the collector electrode of this positive-negative-positive triode and base stage, be parallel with electric capacity and resistance.
10, under-voltage protecting circuit according to claim 1 is characterized in that: described under-voltage control circuit one end is used to insert the voltage of rectifier bridge back, other end ground connection.This under-voltage control circuit comprises crystal diode, voltage-stabiliser tube and the divider resistance that is connected in series;
The base stage of described positive-negative-positive triode is connected by described current-limiting resistance and crystal diode between two divider resistances in centre of this under-voltage control circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2007203055478U CN201118796Y (en) | 2007-11-20 | 2007-11-20 | Under voltage protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2007203055478U CN201118796Y (en) | 2007-11-20 | 2007-11-20 | Under voltage protection circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN201118796Y true CN201118796Y (en) | 2008-09-17 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNU2007203055478U Expired - Fee Related CN201118796Y (en) | 2007-11-20 | 2007-11-20 | Under voltage protection circuit |
Country Status (1)
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| CN (1) | CN201118796Y (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101931317B (en) * | 2009-06-24 | 2012-08-15 | 海洋王照明科技股份有限公司 | Power supply start control circuit and power supply |
| CN102780204A (en) * | 2011-05-10 | 2012-11-14 | 海洋王照明科技股份有限公司 | Under-voltage protection circuit and lamp |
| CN109217262A (en) * | 2018-10-22 | 2019-01-15 | 国家电网公司东北分部 | Metal-oxide-semiconductor drives under-voltage protecting circuit in a kind of high power switch amplifier |
| CN113192449A (en) * | 2021-04-16 | 2021-07-30 | 惠科股份有限公司 | Display panel driving circuit and driving method |
-
2007
- 2007-11-20 CN CNU2007203055478U patent/CN201118796Y/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101931317B (en) * | 2009-06-24 | 2012-08-15 | 海洋王照明科技股份有限公司 | Power supply start control circuit and power supply |
| CN102780204A (en) * | 2011-05-10 | 2012-11-14 | 海洋王照明科技股份有限公司 | Under-voltage protection circuit and lamp |
| CN109217262A (en) * | 2018-10-22 | 2019-01-15 | 国家电网公司东北分部 | Metal-oxide-semiconductor drives under-voltage protecting circuit in a kind of high power switch amplifier |
| CN109217262B (en) * | 2018-10-22 | 2021-10-26 | 国家电网公司东北分部 | MOS tube driving undervoltage protection circuit in high-power switching amplifier |
| CN113192449A (en) * | 2021-04-16 | 2021-07-30 | 惠科股份有限公司 | Display panel driving circuit and driving method |
| CN113192449B (en) * | 2021-04-16 | 2022-05-06 | 惠科股份有限公司 | Display panel driving circuit and driving method |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20080917 Termination date: 20111120 |