CN203313488U - Backlight driving circuit and lamp bar light-adjusting unit - Google Patents
Backlight driving circuit and lamp bar light-adjusting unit Download PDFInfo
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- CN203313488U CN203313488U CN2013203147672U CN201320314767U CN203313488U CN 203313488 U CN203313488 U CN 203313488U CN 2013203147672 U CN2013203147672 U CN 2013203147672U CN 201320314767 U CN201320314767 U CN 201320314767U CN 203313488 U CN203313488 U CN 203313488U
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Abstract
The utility model discloses a backlight driving circuit and a lamp bar light-adjusting unit. The backlight driving circuit comprises at least a BOOST unit, an MCU signal processing unit and the lamp bar light-adjusting unit. The lamp bar light-adjusting unit is used for changing a work current of a lamp bar which is connected between a voltage output terminal of the BOOST unit and a current adjusting terminal of the lamp bar light-adjusting unit according to control signals, wherein the control signals are sent by the MCU signal processing unit, and are received by a control signal input terminal. The backlight driving circuit also comprises a first feedback circuit detecting an output voltage of the BOOST unit, and the first feedback circuit feeds the output voltage back to a control terminal of the BOOST unit, so that the output voltage of the voltage output terminal is controlled. By employing the backlight driving circuit and the lamp bar light-adjusting unit, switching work between 2D and 3D of a television set is well completed, and a stable current is provided for each lamp bar. Compared with the prior art that a BOOST topology circuit is constructed by special chips, circuits are simplified, universality is improved, and preparing cost is reduced.
Description
Technical field
The utility model relates to the backlight drive technical field, relates in particular to a kind of backlight drive circuit and lamp bar light modulation unit.
Background technology
LED is as the backlight of LCD TV, and application on TV is more and more extensive.Due to backlight in 3D shows, carry out presenting better display effect with synchronizeing of liquid crystal image, therefore, multi-way LED lamp is lit a kind of demand trend that becomes of just coming out as an article smoothly according to certain sequential.
At present, the Multi-path lamp strip of LCD TV, need adjust chip with special use and adjust the required electric current of control LED lamp, with the electric current of guaranteeing every street lamp bar, equates, thereby meet the television image display requirement.
Figure 1 shows that the circuit diagram of the special-purpose Boost Boost topology mode of adjusting chip and using of existing six street lamp strip adoptions.Backlight drive circuit as shown in Figure 1, it has BOOST unit, light modulation unit, MCU signal processing unit and 2D/3D switch unit, and take the special chip at middle part and be core, the needs that while meeting the 2D/3D state, back facet current is adjusted in these unit.And such a special chip price is comparatively expensive, increased widely the production cost of product.
The utility model content
For the problems referred to above, the purpose of this utility model is to provide a kind of highly versatile, simple in structure, lower-cost backlight drive circuit and lamp bar light modulation unit.
For achieving the above object, backlight drive circuit of the present utility model, comprise boost boosting unit, mcu signal processing unit, lamp bar light modulation unit at least; Wherein,
The boost boosting unit, have control end and voltage output end, the feedback signal received for the foundation control end to input voltage boost process after by voltage output end output lamp bar operating voltage;
The mcu signal processing unit, have control signal output, feedback signal output and feedback signal input, for by the control signal output, sending control signal to lamp bar light modulation unit, and after being processed, the signal received of receiving feedback signals input to the control end of boost boosting unit, exports the first feedback signal by the feedback signal output;
Lamp bar light modulation unit, have control signal input, lamp bar electric current adjustment end and feedback signal output, the control signal of sending for the MCU signal processing unit received according to the control signal input is connected to the operating current of the lamp bar between the electric current adjustment end of BOOST boosting unit voltage output end and lamp bar light modulation unit with change, and the operating voltage that detects the lamp bar exports the feedback signal input of MCU to by the feedback signal output;
Also comprise the first feedback circuit, be connected to voltage output end and the control end of BOOST boosting unit, for detection of the output voltage of BOOST boosting unit and form the second feedback signal and feed back to the control end of BOOST boosting unit to control the output voltage of voltage output end.
Preferably, described lamp bar light modulation unit is the constant current control unit with a control signal input and lamp bar electric current adjustment end, wherein, the control signal control connection that receives according to the control signal input of described constant current control unit is at the operating current of the lamp bar of lamp bar electric current adjustment end; Also comprise that one has the lamp bar voltage detecting circuit of feedback signal output, this testing circuit is connected between lamp bar incoming end and ground, for detection of the operating voltage in lamp bar work loop and by feedback signal output output feedback voltage signal.
Preferably, described constant current control unit consists of current stabilization circuit and the deep negative feedback circuit that consists of a triode, the second resistance and operational amplifier; Wherein,
Described the second resistance is connected between the base stage and operational amplifier output terminal of triode; The inverting input of the emitter concatenation operation amplifier of described triode, the collector electrode of described triode is for connecting lamp bar negative terminal; The normal phase input end connection control signal input of described operational amplifier is as control loop; One end of current stabilization circuit connects the emitter of described triode, other end ground connection.
Preferably, described current stabilization circuit consists of the first resistance at least, and an end of described the first resistance connects the emitter of described triode, other end ground connection.
Preferably, described lamp bar light modulation unit also comprises an Anti-misoperation circuit, this circuit comprises the 3rd resistance, and an end of described the 3rd resistance connects a voltage VREF, and the tie point that the other end connects the normal phase input end of current stabilization circuit and operational amplifier is used for providing a bias voltage to operational amplifier.
Preferably, described control signal input consists of the 4th resistance, the 5th resistance and the 6th resistance of series connection, and wherein, the signal connection end of described the 4th resistance is for connecting constant input voltage; Described the 5th resistance is used for being connected the 2D/3D control signal with the tie point of the 4th resistance, and the tie point of described the 6th resistance and the 5th resistance connects the normal phase input end of operational amplifier, the other end ground connection of the 6th resistance.
Preferably, described lamp bar voltage detecting circuit is connected and composed by a diode, the first divider resistance, the second divider resistance and the 3rd divider resistance, wherein, the negative pole connecting lamp bar negative terminal of described diode, an anodal end that connects described the first divider resistance, the other end of the first divider resistance connects a voltage VCC; One end of described the second divider resistance connects the positive pole of diode, and the other end connects the feedback signal output; One end of described the 3rd divider resistance connects feedback signal output, other end ground connection.
Preferably, described control signal input also comprises nine resistance in parallel with the 6th resistance; Described current stabilization circuit also includes eight resistance in parallel with the first resistance.
For achieving the above object, lamp bar light adjusting circuit of the present utility model, comprise the constant current control unit with a control signal input and a lamp bar electric current adjustment end, wherein, the control signal control connection that receives according to the control signal input of described constant current control unit is at the operating current of the lamp bar of lamp bar electric current adjustment end.
Preferably, described constant current control unit consists of current stabilization circuit and the deep negative feedback circuit that consists of a triode, the second resistance and operational amplifier; Wherein,
Described the second resistance is connected between the base stage and operational amplifier output terminal of triode; The inverting input of the emitter concatenation operation amplifier of described triode, the collector electrode of described triode is for connecting lamp bar negative terminal; The normal phase input end connection control signal input of described operational amplifier is as control loop; One end of current stabilization circuit connects the emitter of described triode, other end ground connection.
The beneficial effects of the utility model are:
The utility model can be good at the switch operating of television set 2D/3D, and can offer stable electric current of each street lamp bar, compared to prior art, use the BOOST Boost topology circuit of special chip structure, the utility model versatility is stronger, only utilize common BOOST boosting unit, MCU chip commonly used, and lamp bar light adjusting circuit can meet the needs of different electric currents under the 2D/3D signal, thereby but and increasing the electric current of lamp bar voltage detecting circuit feedback current to MCU adjustment lamp bar loop, this designs simplification circuit, improved versatility, reduced cost of manufacture.
The accompanying drawing explanation
Fig. 1 is the circuit diagram of prior art;
Fig. 2 is the circuit diagram of the described backlight drive circuit of the utility model embodiment;
Fig. 3 is the schematic diagram of the described lamp bar light modulation of the utility model embodiment 1 unit;
Fig. 4 is the schematic diagram of the described lamp bar light modulation of the utility model embodiment 4 unit.
Embodiment
Below in conjunction with Figure of description, the utility model is further described.
The described a kind of backlight drive circuit of the utility model embodiment, comprise BOOST boosting unit, mcu signal processing unit, lamp bar light modulation unit at least, wherein,
The BOOST boosting unit, have a control end and a voltage output end, by voltage output end, exports lamp bar operating voltage after for input voltage is boosted, processing;
The mcu signal processing unit, have control signal output, feedback signal output and feedback signal input, for by the control signal output, sending control signal to lamp bar light modulation unit, and after being processed, passes through the signal of receiving feedback signals input the control end output feedback signal of feedback signal output to the BOOST boosting unit;
Lamp bar light modulation unit, have a control signal input, lamp bar electric current adjustment end and feedback signal output, the control signal of sending for the mcu signal processing unit received according to the control signal input is connected to the operating current of the lamp bar between the electric current adjustment end of BOOST boosting unit voltage output end and lamp bar light modulation unit with change, and the operating voltage that detects the lamp bar exports the feedback signal input of MCU to by the feedback signal output;
Also comprise the first feedback circuit, be connected to voltage output end and the control end of BOOST boosting unit, for detection of the output voltage of BOOST boosting unit the control end that feeds back to the BOOST boosting unit to control the output voltage of voltage output end.
Operation principle of the present utility model is:
As shown in Figure 2, in the drawings, the element that the BOOST boosting unit plays the part of boosting is metal-oxide-semiconductor V31 and inductance L 1, and inductance L 1 connects input voltage (24V).When the lamp bar started to start, metal-oxide-semiconductor opened or closed, and made input voltage pass through inductance and finally produced the voltage stack, the operating voltage of finally being lighted for the lamp bar by voltage output end output.After the first unlatching of lamp bar, BOOST boosting unit self carries out a Voltage Feedback to voltage output end, feedback voltage produces a voltage through the FB point that acts on of divider resistance, the reference voltage of this voltage and BOOST boosting unit compares, according to comparative result, send a PWM duty cycle control signal to metal-oxide-semiconductor, regulate the switching frequency of metal-oxide-semiconductor, and then the voltage of regulation voltage output, make it stable supplying lamp bar.
In the lamp bar is lighted process, the mcu signal processing unit detects the voltage pressure reduction of resistance R 14 and resistance R 15, and collect the voltage pressure difference signal and to the BOOST boosting unit, send feedback voltage signal after treatment, this feedback voltage signal produces a voltage at the FB point, the reference voltage of this voltage and BOOST boosting unit compares, according to comparative result, send a PWM duty cycle control signal to metal-oxide-semiconductor, regulate the switching frequency of metal-oxide-semiconductor, and then the voltage of regulation voltage output, make it stable supplying lamp bar.
The mcu signal processing unit sends the 2D/3D control signal to lamp bar light modulation unit, so that lamp bar light modulation unit is regulated the operating current of lamp bar.
When under the 2D state, when the pwm control signal that the mcu signal processing unit sends is high level, the PWM3D pin of mcu signal processing unit is high-impedance state, the control signal input only accesses constant input voltage (as 3.3V in figure), and this voltage is given normal phase input end one voltage of operational amplifier N904B by divider resistance with being divided to.Because triode V2, the second resistance R 9 and operational amplifier N904B are connected to form the deep negative feedback circuit, under this state, the inverting input of operational amplifier, normal phase input end ' empty short ', namely the voltage of the inverting input of operational amplifier is near the voltage of normal phase input end.This circuit utilizes this characteristic just, makes the voltage response of normal phase input end in circuit at inverting input, and utilizes the variation of this voltage to change the operating current of the first resistance R 8, thereby changes the operating current of the lamp bar of connecting with the first resistance.
When pwm control signal was low level, the voltage of the normal phase input end of operational amplifier was zero, was zero thereby make the operating current of flowing through lamps bar, and the lamp bar is closed.
When under the 3D state, what the PWM3D pin of mcu signal processing unit was inputted is the PWM clock signal, when this signal is high level, this signal and constant input voltage are applied to the normal phase input end of operational amplifier at the voltage of the potential point generation of resistance R 3 and resistance R 4, and then obtain the 3D electric current of lamp bar work.When this signal was low level, voltage was zero, and the operating current of flowing through lamps bar is zero, and the lamp bar is closed.
As the utility model, further explain:
Described lamp bar light modulation unit comprises a constant current control unit with control signal input and a lamp bar electric current adjustment end, wherein, the control signal control connection that receives according to the control signal input of described constant current control unit is at the operating current of the lamp bar of lamp bar electric current adjustment end.
The utility model can detect and receive the 2D/3D control signal in real time, then lamp bar operating current is effectively controlled in real time.Than those, use professional chip and be furnished with the circuit that the 2D/3D conversion chip is carried out in special use, structure is simpler, implements convenient.
As the utility model, further improve, in described circuit, also comprise a lamp bar voltage detecting circuit, the voltage signal of this unit inspection lamp bar negative terminal feeds back to the mcu signal processing unit, and this circuit is handled it and regulated lamp bar voltage according to feedback signal.This lamp bar voltage detecting circuit obtains the voltage condition of lamp bar negative terminal, and reduce the voltage in the scope that mcu can accept, when the voltage detected surpasses preset value, reduce output voltage by feedback, when the voltage detected, during lower than preset value, improve output voltage.This unit can detect the lamp bar in real time, guarantees the normal operating conditions of lamp bar.
Figure 3 shows that specific embodiment of the utility model, now in conjunction with this embodiment, such scheme be further explained to explanation:
In this embodiment, described constant current control unit consists of current stabilization circuit and the deep negative feedback circuit that consists of a triode V2, the second resistance R 9 and operational amplifier N904B; Wherein,
Described the second resistance is connected between the base stage and operational amplifier output terminal of triode; The inverting input of the emitter concatenation operation amplifier of described triode, the collector electrode of described triode is for connecting lamp bar negative terminal; The normal phase input end of described operational amplifier connects 2D/3D control signal incoming end as control loop; One end of current stabilization circuit connects the emitter of described triode, other end ground connection.
The operation principle of foregoing circuit is as follows: triode, the second resistance and operational amplifier are connected to form the deep negative feedback circuit, under this state, the inverting input of operational amplifier, normal phase input end ' empty short ', namely the voltage of the inverting input of operational amplifier is near the voltage of normal phase input end.This circuit utilizes this characteristic just, makes the voltage response of normal phase input end in circuit at inverting input, and utilizes the variation of this voltage to change the operating current of the first resistance, thereby changes the operating current of the lamp bar of connecting with the first resistance.Specific as follows:
When normal phase input end has 2D/3D signal when input, the triode conducting, thus operational amplifier is operated in the deep negative feedback, thus make voltage on inverting input equal the voltage of normal phase input end, form ' empty short ', now, the negative terminal of lamp bar is connected to the collector electrode of triode, after the triode conducting, the negative terminal of lamp bar passes through triode, the first resistance R 8, last ground connection, formed lamp bar work loop, when the 2D/3D signal is inputted, be controlled by 2D/3D control signal incoming end generation change in voltage, and due to ' empty short ' characteristic, make the change in voltage of the voltage follow normal phase input end on inverting input, thereby make the first resistance both end voltage change, because the resistance of the first resistance is constant, according to formula U=I*R, as can be known, the electric current of the first resistance changes along with the difference of voltage, thereby make the electric current in lamp bar loop change, thereby reach the purpose of controlling lamp bar loop works electric current, take this to reach the purpose of controlling the brightness of lamp bar.The lamp bar light modulation unit of the present embodiment, also can comprise four resistance R 921 in parallel with described the first resistance at current stabilization circuit, can pass through like this to change the resistance of the 4th resistance when debugging, to adjust the size of current in lamp bar loop.
In Fig. 3, described control signal input consists of the 4th resistance R 3, the 5th resistance R 4 and the 6th resistance R 5 of series connection, and wherein, the signal connection end of described the 4th resistance is for connecting constant input voltage; Described the 5th resistance is used for being connected the 2D/3D control signal with the tie point of the 4th resistance, and the tie point of described the 6th resistance and the 5th resistance connects the normal phase input end of operational amplifier, the other end ground connection of the 6th resistance.In foregoing circuit, due to 2D PWM dim signal and/3D PWM controls dim signal and constant input voltage respectively by resistance R 3, R4 and R5 be connected on operational amplifier N904B normal phase input end (as in figure+end), thereby the different voltage differences that cause exporting to operational amplifier in the position of these two kinds of signal places in circuit, cause the electric current of first resistance of flowing through to change, and then regulate the operating current of lamp bar.
Now in conjunction with Fig. 4, this embodiment is described further:
Lamp bar light modulation unit in the present embodiment also comprises an Anti-misoperation circuit.
In this embodiment, described constant current control unit consists of current stabilization circuit and the deep negative feedback circuit that consists of a triode V2, the second resistance R 9 and operational amplifier N904B; Wherein,
Described the second resistance is connected between the base stage and operational amplifier output terminal of triode; The inverting input of the emitter concatenation operation amplifier of described triode, the collector electrode of described triode is for connecting lamp bar negative terminal; The normal phase input end of described operational amplifier connects 2D/3D control signal incoming end as control loop; One end of current stabilization circuit connects the emitter of described triode, other end ground connection.
The operation principle of foregoing circuit is as follows: triode, the second resistance and operational amplifier are connected to form the deep negative feedback circuit, under this state, the inverting input of operational amplifier, normal phase input end ' empty short ', namely the voltage of the inverting input of operational amplifier is near the voltage of normal phase input end.This circuit utilizes this characteristic just, makes the voltage response of normal phase input end in circuit at inverting input, and utilizes the variation of this voltage to change the operating current of the first resistance, thereby changes the operating current of the lamp bar of connecting with the first resistance.Specific as follows:
When normal phase input end has 2D/3D signal when input, the triode conducting, thus operational amplifier is operated in the deep negative feedback, thus make voltage on inverting input equal the voltage of normal phase input end, form ' empty short ', now, the negative terminal of lamp bar is connected to the collector electrode of triode, after the triode conducting, the negative terminal of lamp bar passes through triode, the first resistance R 8, last ground connection, formed lamp bar work loop, when the 2D/3D signal is inputted, be controlled by 2D/3D control signal incoming end generation change in voltage, and due to ' empty short ' characteristic, make the change in voltage of the voltage follow normal phase input end on inverting input, thereby make the first resistance both end voltage change, because the resistance of the first resistance is constant, according to formula U=I*R, as can be known, the electric current of the first resistance changes along with the difference of voltage, thereby make the electric current in lamp bar loop change, thereby reach the purpose of controlling lamp bar loop works electric current, take this to reach the purpose of controlling the brightness of lamp bar.The lamp bar light modulation unit of the present embodiment, also can comprise four resistance R 921 in parallel with described the first resistance at current stabilization circuit, can pass through like this to change the resistance of the 4th resistance when debugging, to adjust the size of current in lamp bar loop.
In Fig. 3, described control signal input consists of the 4th resistance R 3, the 5th resistance R 4 and the 6th resistance R 5 of series connection, and wherein, the signal connection end of described the 4th resistance is for connecting constant input voltage; Described the 5th resistance is used for being connected the 2D/3D control signal with the tie point of the 4th resistance, and the tie point of described the 6th resistance and the 5th resistance connects the normal phase input end of operational amplifier, the other end ground connection of the 6th resistance.In foregoing circuit, due to 2D PWM dim signal and/3D PWM controls dim signal and constant input voltage respectively by resistance R 3, R4 and R5 be connected on operational amplifier N904B normal phase input end (as in figure+end), thereby the different voltage differences that cause exporting to operational amplifier in the position of these two kinds of signal places in circuit, cause the electric current of first resistance of flowing through to change, and then regulate the operating current of lamp bar.In addition, also can be arranged in parallel one the 8 7th resistance R 910 with the seven or six resistance, jointly participate in the middle of whole work.
Anti-misoperation circuit comprises the 3rd resistance, and an end of described the 3rd resistance connects a voltage VREF, and the tie point that the other end connects the normal phase input end of current stabilization circuit and operational amplifier is used for providing a bias voltage to operational amplifier.Can prevent effectively that like this operational amplifier from producing misoperation when being input as zero.
Lamp bar light modulation unit in the present embodiment also comprises a lamp bar voltage detection unit, now in conjunction with Fig. 4, the present embodiment is further illustrated.
In this embodiment, described constant current control unit consists of current stabilization circuit and the deep negative feedback circuit that consists of a triode V2, the second resistance R 9 and operational amplifier N904B; Wherein,
Described the second resistance is connected between the base stage and operational amplifier output terminal of triode; The inverting input of the emitter concatenation operation amplifier of described triode, the collector electrode of described triode is for connecting lamp bar negative terminal; The normal phase input end of described operational amplifier connects 2D/3D control signal incoming end as control loop; One end of current stabilization circuit connects the emitter of described triode, other end ground connection.
The operation principle of foregoing circuit is as follows: triode, the second resistance and operational amplifier are connected to form the deep negative feedback circuit, under this state, the inverting input of operational amplifier, normal phase input end ' empty short ', namely the voltage of the inverting input of operational amplifier is near the voltage of normal phase input end.This circuit utilizes this characteristic just, makes the voltage response of normal phase input end in circuit at inverting input, and utilizes the variation of this voltage to change the operating current of the first resistance, thereby changes the operating current of the lamp bar of connecting with the first resistance.Specific as follows:
When normal phase input end has 2D/3D signal when input, the triode conducting, thus operational amplifier is operated in the deep negative feedback, thus make voltage on inverting input equal the voltage of normal phase input end, form ' empty short ', now, the negative terminal of lamp bar is connected to the collector electrode of triode, after the triode conducting, the negative terminal of lamp bar passes through triode, the first resistance R 8, last ground connection, formed lamp bar work loop, when the 2D/3D signal is inputted, be controlled by 2D/3D control signal incoming end generation change in voltage, and due to ' empty short ' characteristic, make the change in voltage of the voltage follow normal phase input end on inverting input, thereby make the first resistance both end voltage change, because the resistance of the first resistance is constant, according to formula U=I*R, as can be known, the electric current of the first resistance changes along with the difference of voltage, thereby make the electric current in lamp bar loop change, thereby reach the purpose of controlling lamp bar loop works electric current, take this to reach the purpose of controlling the brightness of lamp bar.The lamp bar light modulation unit of the present embodiment, also can comprise eight resistance R 921 in parallel with described the first resistance at current stabilization circuit, can pass through like this to change the resistance of the 4th resistance when debugging, to adjust the size of current in lamp bar loop.
In Fig. 3, described control signal input consists of the 4th resistance R 3, the 5th resistance R 4 and the 6th resistance R 5 of series connection, and wherein, the signal connection end of described the 4th resistance is for connecting constant input voltage; Described the 5th resistance is used for being connected the 2D/3D control signal with the tie point of the 4th resistance, and the tie point of described the 6th resistance and the 5th resistance connects the normal phase input end of operational amplifier, the other end ground connection of the 6th resistance.In foregoing circuit, due to 2D PWM dim signal and/3D PWM controls dim signal and constant input voltage respectively by resistance R 3, R4 and R5 be connected on operational amplifier N904B normal phase input end (as in figure+end), thereby the different voltage differences that cause exporting to operational amplifier in the position of these two kinds of signal places in circuit, cause the electric current of first resistance of flowing through to change, and then regulate the operating current of lamp bar.In foregoing circuit, due to 2D PWM dim signal and 3D PWM dim signal respectively by resistance R 909, R709 and R911 be connected on operational amplifier N904B normal phase input end (as in figure+end), thereby the different voltage differences that cause exporting to operational amplifier in the position of these two kinds of signal places in circuit, and compare as the current potential of different reference potentials and inverting input; Thereby reach the purpose of mark 2D/3D input signal.In addition, also can be arranged in parallel one the 8th resistance R 910 with the 7th resistance, jointly participate in the middle of whole work.
Described lamp bar voltage detecting circuit is connected and composed by a diode VD3, the first divider resistance R13, the second divider resistance R14 and the 3rd divider resistance R15, wherein, the negative pole connecting lamp bar negative terminal of described diode, an anodal end that connects described the first divider resistance, the other end of the first divider resistance connects a voltage VCC; One end of described the second divider resistance connects the positive pole of diode, and the other end connects the feedback signal output; One end of described the 3rd divider resistance connects feedback signal output, other end ground connection.The voltage that lamp bar negative terminal is got in this unit reduces the voltage in the scope that mcu can accept by electric resistance partial pressure (R14 and R15), when the voltage detected surpasses preset value, by feedback, reduce output voltage, during lower than preset value, improve output voltage when the voltage detected.
Lamp bar light modulation unit in the present embodiment also comprises an Anti-misoperation circuit and a lamp bar voltage detection unit, now in conjunction with Fig. 4, the present embodiment is further illustrated.
In this embodiment, described constant current control unit consists of current stabilization circuit and the deep negative feedback circuit that consists of a triode V2, the second resistance R 9 and operational amplifier N904B; Wherein,
Described the second resistance is connected between the base stage and operational amplifier output terminal of triode; The inverting input of the emitter concatenation operation amplifier of described triode, the collector electrode of described triode is for connecting lamp bar negative terminal; The normal phase input end of described operational amplifier connects 2D/3D control signal incoming end as control loop; One end of current stabilization circuit connects the emitter of described triode, other end ground connection.
The operation principle of foregoing circuit is as follows: triode, the second resistance and operational amplifier are connected to form the deep negative feedback circuit, under this state, the inverting input of operational amplifier, normal phase input end ' empty short ', namely the voltage of the inverting input of operational amplifier is near the voltage of normal phase input end.This circuit utilizes this characteristic just, makes the voltage response of normal phase input end in circuit at inverting input, and utilizes the variation of this voltage to change the operating current of the first resistance, thereby changes the operating current of the lamp bar of connecting with the first resistance.Specific as follows:
When normal phase input end has 2D/3D signal when input, the triode conducting, thus operational amplifier is operated in the deep negative feedback, thus make voltage on inverting input equal the voltage of normal phase input end, form ' empty short ', now, the negative terminal of lamp bar is connected to the collector electrode of triode, after the triode conducting, the negative terminal of lamp bar passes through triode, the first resistance R 8, last ground connection, formed lamp bar work loop, when the 2D/3D signal is inputted, be controlled by 2D/3D control signal incoming end generation change in voltage, and due to ' empty short ' characteristic, make the change in voltage of the voltage follow normal phase input end on inverting input, thereby make the first resistance both end voltage change, because the resistance of the first resistance is constant, according to formula U=I*R, as can be known, the electric current of the first resistance changes along with the difference of voltage, thereby make the electric current in lamp bar loop change, thereby reach the purpose of controlling lamp bar loop works electric current, take this to reach the purpose of controlling the brightness of lamp bar.The lamp bar light modulation unit of the present embodiment, also can comprise four resistance R 921 in parallel with described the first resistance at current stabilization circuit, can pass through like this to change the resistance of the 4th resistance when debugging, to adjust the size of current in lamp bar loop.
In Fig. 3, described control signal input consists of the 4th resistance R 3, the 5th resistance R 4 and the 6th resistance R 5 of series connection, and wherein, the signal connection end of described the 4th resistance is for connecting constant input voltage; Described the 5th resistance is used for being connected the 2D/3D control signal with the tie point of the 4th resistance, and the tie point of described the 6th resistance and the 5th resistance connects the normal phase input end of operational amplifier, the other end ground connection of the 6th resistance.In foregoing circuit, due to 2D PWM dim signal and/3D PWM controls dim signal and constant input voltage respectively by resistance R 3, R4 and R5 be connected on operational amplifier N904B normal phase input end (as in figure+end), thereby the different voltage differences that cause exporting to operational amplifier in the position of these two kinds of signal places in circuit, cause the electric current of first resistance of flowing through to change, and then regulate the operating current of lamp bar.In addition, also can be arranged in parallel one the 7th resistance R 910 with the 6th resistance, jointly participate in the middle of whole work.
Anti-misoperation circuit comprises the 3rd resistance R 6, and an end of described the 3rd resistance connects a voltage VREF, and the tie point that the other end connects the normal phase input end of current stabilization circuit and operational amplifier is used for providing a bias voltage to operational amplifier.Can prevent effectively that like this operational amplifier from producing misoperation when being input as zero.
Described lamp bar voltage detecting circuit is connected and composed by a diode VD3, the first divider resistance R13, the second divider resistance R14 and the 3rd divider resistance R15, wherein, the negative pole connecting lamp bar negative terminal of described diode, an anodal end that connects described the first divider resistance, the other end of the first divider resistance connects a voltage VCC; One end of described the second divider resistance connects the positive pole of diode, and the other end connects the feedback signal output; One end of described the 3rd divider resistance connects feedback signal output, other end ground connection.The voltage that lamp bar negative terminal is got in this unit reduces the voltage in the scope that mcu can accept by electric resistance partial pressure (R14 and R15), when the voltage detected surpasses preset value, by feedback, reduce output voltage, during lower than preset value, improve output voltage when the voltage detected.
Above; it is only preferred embodiment of the present utility model; but protection range of the present utility model is not limited to this; anyly be familiar with those skilled in the art in the technical scope that the utility model discloses; the variation that can expect easily or replacement, within all should being encompassed in 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 claim was defined.
Claims (10)
1. a backlight drive circuit, is characterized in that, comprises at least boost boosting unit, mcu signal processing unit, lamp bar light modulation unit; Wherein,
The boost boosting unit, have control end and voltage output end, the feedback signal received for the foundation control end to input voltage boost process after by voltage output end output lamp bar operating voltage;
The mcu signal processing unit, have control signal output, feedback signal output and feedback signal input, for by the control signal output, sending control signal to lamp bar light modulation unit, and after being processed, the signal received of receiving feedback signals input to the control end of boost boosting unit, exports the first feedback signal by the feedback signal output;
Lamp bar light modulation unit, have control signal input, lamp bar electric current adjustment end and feedback signal output, the control signal of sending for the MCU signal processing unit received according to the control signal input is connected to the operating current of the lamp bar between the electric current adjustment end of BOOST boosting unit voltage output end and lamp bar light modulation unit with change, and the operating voltage that detects the lamp bar exports the feedback signal input of MCU to by the feedback signal output;
Also comprise the first feedback circuit, be connected to voltage output end and the control end of BOOST boosting unit, for detection of the output voltage of BOOST boosting unit and form the second feedback signal and feed back to the control end of BOOST boosting unit to control the output voltage of voltage output end.
2. backlight drive circuit according to claim 1, it is characterized in that, described lamp bar light modulation unit comprises a constant current control unit with control signal input and lamp bar electric current adjustment end, wherein, the control signal control connection that receives according to the control signal input of described constant current control unit is at the operating current of the lamp bar of lamp bar electric current adjustment end; Also comprise that one has the lamp bar voltage detecting circuit of feedback signal output, this testing circuit is connected between lamp bar incoming end and ground, for detection of the operating voltage in lamp bar work loop and by feedback signal output output feedback voltage signal.
3. backlight drive circuit according to claim 2, is characterized in that, described constant current control unit consists of current stabilization circuit and the deep negative feedback circuit that consists of a triode, the second resistance and operational amplifier; Wherein,
Described the second resistance is connected between the base stage and operational amplifier output terminal of triode; The inverting input of the emitter concatenation operation amplifier of described triode, the collector electrode of described triode is for connecting lamp bar negative terminal; The normal phase input end connection control signal input of described operational amplifier is as control loop; One end of current stabilization circuit connects the emitter of described triode, other end ground connection.
4. backlight drive circuit according to claim 3, is characterized in that, described current stabilization circuit consists of the first resistance at least, and an end of described the first resistance connects the emitter of described triode, other end ground connection.
5. backlight drive circuit according to claim 2, it is characterized in that, described lamp bar light modulation unit also comprises an Anti-misoperation circuit, this circuit comprises the 3rd resistance, one end of described the 3rd resistance connects a voltage VREF, and the tie point that the other end connects the normal phase input end of current stabilization circuit and operational amplifier is used for providing a bias voltage to operational amplifier.
6. backlight drive circuit according to claim 2, is characterized in that, described control signal input consists of the 4th resistance, the 5th resistance and the 6th resistance of series connection, and wherein, the signal connection end of described the 4th resistance is for connecting constant input voltage; Described the 5th resistance is used for being connected the 2D/3D control signal with the tie point of the 4th resistance, and the tie point of described the 6th resistance and the 5th resistance connects the normal phase input end of operational amplifier, the other end ground connection of the 6th resistance.
7. backlight drive circuit according to claim 2, it is characterized in that, described lamp bar voltage detecting circuit is connected and composed by a diode, the first divider resistance, the second divider resistance and the 3rd divider resistance, wherein, the negative pole connecting lamp bar negative terminal of described diode, an anodal end that connects described the first divider resistance, the other end of the first divider resistance connects a voltage VCC; One end of described the second divider resistance connects the positive pole of diode, and the other end connects the feedback signal output; One end of described the 3rd divider resistance connects feedback signal output, other end ground connection.
8. backlight drive circuit according to claim 3, is characterized in that, described control signal input also comprises nine resistance in parallel with the 6th resistance; Described current stabilization circuit also includes eight resistance in parallel with the first resistance.
9. lamp bar light modulation unit, it is characterized in that, described lamp bar light modulation unit comprises the constant current control unit with a control signal input and a lamp bar electric current adjustment end, wherein, the control signal control connection that receives according to the control signal input of described constant current control unit is at the operating current of the lamp bar of lamp bar electric current adjustment end.
10. lamp bar light modulation according to claim 9 unit, is characterized in that, described constant current control unit consists of current stabilization circuit and the deep negative feedback circuit that consists of a triode, the second resistance and operational amplifier; Wherein,
Described the second resistance is connected between the base stage and operational amplifier output terminal of triode; The inverting input of the emitter concatenation operation amplifier of described triode, the collector electrode of described triode is for connecting lamp bar negative terminal; The normal phase input end connection control signal input of described operational amplifier is as control loop; One end of current stabilization circuit connects the emitter of described triode, other end ground connection.
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| CN103957644A (en) * | 2014-05-14 | 2014-07-30 | 深圳市华星光电技术有限公司 | LED backlight source for liquid crystal display device |
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