CN104253954B - The constant current of low-power consumption and backlight control circuit and television set - Google Patents

The constant current of low-power consumption and backlight control circuit and television set Download PDF

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Publication number
CN104253954B
CN104253954B CN201410476651.8A CN201410476651A CN104253954B CN 104253954 B CN104253954 B CN 104253954B CN 201410476651 A CN201410476651 A CN 201410476651A CN 104253954 B CN104253954 B CN 104253954B
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voltage
circuit
constant current
power supply
output end
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CN104253954A (en
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吴永芳
刘威河
廖武
杨达富
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Guangzhou Kun Electronic Technology Co. Ltd.
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Guangzhou Shiyuan Electronics Thecnology Co Ltd
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Abstract

The invention discloses a kind of constant current of low-power consumption and backlight control circuit, including front end power circuit and rear end linear constant current circuit；Front end power circuit includes power supply circuit and feedback adjustment circuit；Rear end linear constant current circuit connects reference signal input to access constant current reference voltage, and rear end linear constant current circuit and the connection of the LED string to be powered according to the size ON/OFF of constant current reference voltage provided with one；In rear end linear constant current circuit and LED string junction to be powered by voltage detecting circuit draw all the way voltage acquisition output end to gather the voltage of the junction, and the magnitude of voltage of control signal input is adjusted according to collection result, voltage detecting circuit includes diode and pull-up resistor, the negative electrode of the diode is connected to the negative electrode of the LED string, anode is connected to one end of pull-up resistor, the other end access high level of pull-up resistor；The anode of the diode connects the voltage acquisition output end.

Description

The constant current of low-power consumption and backlight control circuit and television set
Technical field
The present invention relates to power supply technical field, more particularly to a kind of constant current of low-power consumption and backlight control circuit and tool There are the constant current of the low-power consumption and the television set of backlight control circuit.
Background technology
Linear constant-current modulation circuit is widely used a kind of element circuit in Analogous Integrated Electronic Circuits, there is wide in practice General application.Wherein, in the power supply technical field of LED television, front-end circuit output constant pressure, rear end electricity are often utilized Realize boosting or decompression constant current to realize the power supply to TV SKD and LED backlight in road.
In television components are carried out with integration process, TV SKD and backlight lamp bar usually require to form a complete production network, and The different backlight LED light bars of quantity will need linear constant-current modulation circuit adaptability to export different magnitudes of voltage.In the prior art Powered the backfeed loop that output end is connected, the voltage of timely monitoring television main board power supply output end with TV SKD using one Change.
As shown in figure 1, being a kind of schematic diagram for linear constant-current modulation circuit that prior art is provided.When main board power supply output During the output voltage rise at end, voltage-stabiliser tube TL431 is linked into by the voltage signal after resistance RB135 and resistance RB134 partial pressures Reference input R0 in, and the voltage signal is made comparisons with the reference voltage (such as 2.5V) inside voltage-stabiliser tube TL431, So that voltage is reduced between voltage-stabiliser tube TL431 anode and cathodes, and then optocoupler diode PCB101A electric current becomes big, colelctor electrode and hair Dynamic electric resistor between emitter-base bandgap grading diminishes, the voltage step-down between colelctor electrode and emitter stage, therewith the inside transformation in power supply circuit Device output voltage is reduced to the voltage of setting.Therefore, with the increase of resistance RB134 resistances, power output end and mainboards of LED is supplied The output voltage at electricity output end reduces, otherwise voltage rise.
Due to the difference of application scenario, linear constant current circuit is generally required in actual production process and exports different voltages Value, and prior art is in order to meet different occasion needs, it is necessary to which the resistance to the resistance RB135 in hardware circuit is adjusted. Therefore, there is the defect that trivial operations, precision are low, power consumption is high and cost is high in prior art.In addition, in actual applications, backlight LED light bar is formed by multiple LED strips connection, and controls to adjust the electricity of LED string by the switching tube of metal-oxide-semiconductor or triode Stream keeps constant.After linear constant current circuit works, switching tube both end voltage can be because of LED string voltage error (general list LEDs Scope is 2.8~3.4, due to many of series connection, so the difference of the upper and lower bound of the voltage range of LED string can be than larger), Because the intermodulation (general range is 7%) of transformer influences, voltage more high power consumption is bigger, and this can cause the cost increase of device With the reduction of circuit efficiency.In addition, the temperature in order to reduce switching tube, general switching tube can be managed by multiple mos or triode simultaneously Connection is used, and which results in the increase of cost.
The content of the invention
The technical problems to be solved by the invention are to provide constant current and the backlight control circuit of a kind of low-power consumption, adaptively Ground adjustment LED powers the magnitude of voltage of output end, without being adjusted to hardware circuit, and can prevent when LED backlight from closing still The phenomenon of glimmer.
To solve above technical problem, the present invention provides constant current and the backlight control circuit of a kind of low-power consumption, and its feature exists In, including：Front end power circuit and rear end linear constant current circuit；
The front end power circuit includes power supply circuit and feedback adjustment circuit；It is defeated that the power supply circuit includes the first power supply Go out end, the second power supply output end and feedback control end；The feedback adjustment circuit includes feedback input end, control signal input And feedback signal output；The feedback input end with described second power supply output end be connected, the feedback signal output and The power supply circuit connection；The feedback adjustment circuit feeds back defeated according to the magnitude of voltage of the control signal input to described The signal for entering end reception is adjusted with to the power supply circuit output feedback signal, so as to control the power supply circuit to described The magnitude of voltage of first power supply output end and the second power supply output end is adjusted；
The rear end linear constant current circuit is connected with the negative electrode of LED string to be powered, the anode of the LED string to be powered It is connected with the described first power supply output end；
The rear end linear constant current circuit provided with a connection reference signal input to access constant current reference voltage, and according to Rear end linear constant current circuit described in the size ON/OFF of the constant current reference voltage and the connection of the LED string to be powered；
Linear constant-current circuit draws one with the LED string junction to be powered by voltage detecting circuit in the rear Road voltage acquisition output end adjusts according to collection result the electricity of the control signal input to gather the voltage of the junction Pressure value；
The voltage detecting circuit includes diode and pull-up resistor, and the negative electrode of the diode is connected to the LED The negative electrode of string, anode is connected to one end of pull-up resistor, the other end access high level of pull-up resistor；The anode of the diode Connect the voltage acquisition output end.
It is preferred that, the anode of the diode also connects the voltage acquisition output end by a resistance.
It is preferred that, the anode of the diode also connects the voltage acquisition output end by another diode；It is described another The anode of one diode is connected with the anode of the diode；The negative electrode of another diode is exported as the voltage acquisition End.
It is preferred that, the voltage detecting circuit also includes a filter circuit of pressure-stabilizing；The filter circuit of pressure-stabilizing is connected to institute State between voltage acquisition output end and ground；
The filter circuit of pressure-stabilizing includes voltage-regulator diode, filter capacitor and filter resistance in parallel；And the voltage stabilizing two The negative electrode of pole pipe is connected in the voltage acquisition output end, the plus earth of the voltage-regulator diode.
It is preferred that, the rear end linear constant current circuit includes comparing adjustment circuit and constant-current control circuit；The constant current control Circuit processed at least includes a switching tube and control circuit module；The adjustment circuit that compares includes operational amplifier, the computing The reverse input end of amplifier connects the reference signal input, and positive input connects through constant current detection resistance ground connection, The output end of the operational amplifier connects the control end of the switching tube by the control circuit module；The switching tube Input is connected with the negative electrode of the LED string to be powered, and the output end of the switching tube is connect by the constant current detection resistance Ground.
It is preferred that, when the switching tube is triode, the colelctor electrode of the triode and the LED string to be powered One end is connected, and emitter stage is grounded by the constant current detection resistance, and base stage is put by the control circuit module with the computing The output end connection of big device；
When the switching tube is field-effect transistor, the drain electrode of the field-effect transistor and the LED to be powered One end connection of string, source electrode is grounded by the constant current detection resistance, and grid passes through the control circuit module and the computing The output end of amplifier.
It is preferred that, the constant current detection resistance is main by resistance (RB6), resistance (RB7), resistance (RB8) and resistance (RB9) Parallel connection is constituted.
It is preferred that, the normal phase input end of the operational amplifier is connected by resistance (RB5) with the constant current detection resistance, The output end of the switching tube is connected to the junction of the resistance (RB5) and the constant current detection resistance.
It is preferred that, the normal phase input end of the operational amplifier is also grounded by electric capacity (CB5).
It is preferred that, the adjustment circuit that compares also includes a clamp diode；
The minus earth of the clamp diode；The output end of the anode of the clamp diode and the switching tube connects Connect.
It is preferred that, the voltage of the junction only collected when the voltage acquisition output end is more than or equal to default threshold During value, the magnitude of voltage of the control signal input is just adjusted, so as to further adjust the first power supply output end, the second confession The output voltage at electricity output end, so that the voltage of the junction is less than default threshold value.
It is preferred that, in addition to a control master chip；
The control master chip and the control signal input, the reference signal input and the voltage acquisition Output end is connected respectively；
The control master chip adjusts the output to the control signal according to the voltage change of the voltage acquisition output end The signal magnitude of input, the output for output end, the second power supply output end of being powered with control the front end power circuit first Magnitude of voltage；And the constant current reference voltage is inputted to the rear end linear constant current circuit by the reference signal input.
It is preferred that, when the control master chip detects the voltage acquisition output end and the reference signal input When voltage difference is more than default threshold value, the control master chip will be exported to the voltage signal of the control signal input and accounted for Sky is than reducing.
It is preferred that, the control master chip includes analog-digital converter, for the voltage of the control master chip access to be believed Number be converted to data signal.
It is preferred that, the power supply circuit includes power supply input circuit, switching power circuit, multiple-channel output transformer, LED and supplied Electricity output circuit and main board power supply output circuit；
The power supply input circuit transmits the power supply signal of access to described under the control of the switching power circuit Multiple-channel output transformer；
The multiple-channel output transformer includes main winding and auxiliary winding；The main winding will be passed after the power supply signal transformation The main board power supply output circuit is transported to, and is exported by the described second power supply output end；The auxiliary winding is by the electricity Transmit to the LED and power output circuit after source signal synchronization transformation, and exported by the described first power supply output end；Institute The coil ratio for stating main winding and the auxiliary winding is 1：N, N ＞ 0.
It is preferred that, the feedback adjustment circuit includes opto-coupled feedback unit, voltage stabilizing reference cell, voltage sampling unit and electricity Press adjustment unit；
The opto-coupled feedback unit includes optocoupler, and the optocoupler is included positioned at the light emitting diode of primary side and positioned at secondary Optical signal converter, the signal input part of the light emitting diode connects the feedback input end by first resistor (RB131)； The signal output part of the optical signal converter connects the feedback signal output；
The voltage sampling unit includes the 4th resistance of the series connection being connected between the feedback input end and ground And the 5th resistance (RB135) (RB134)；
The voltage stabilizing reference cell includes voltage stabilizing standard and is connected to the reference input and negative electrode of voltage stabilizing standard Between voltage stabilizing feedback circuit；The reference input of the voltage stabilizing standard is connected to the 4th resistance (RB134) and the 5th resistance (RB135) locate between connecting, plus earth, negative electrode connects the signal output part of the light emitting diode；
The voltage-adjusting unit includes the 6th resistance (RB150), and one end of the 6th resistance (RB150) is connected to institute State and locate between the 4th resistance (RB134) and the series connection of the 5th resistance (RB135), the other end connects the control signal input.
It is preferred that, the voltage stabilizing feedback circuit includes the first electric capacity (CB109) and 3rd resistor (RB133)；
One end of first electric capacity (CB109) is connected on the negative electrode of the voltage stabilizing standard, the other end and the 3rd electricity Hinder one end series connection of (RB133)；The other end of 3rd resistor (RB133) is connected to the reference input of the voltage stabilizing standard On.
It is preferred that, the voltage stabilizing feedback circuit includes the second electric capacity (CB110)；
One end of second electric capacity (CB110) is connected on the negative electrode of the voltage stabilizing standard, and the other end is connected to institute On the reference input for stating voltage stabilizing standard.
It is preferred that, the voltage stabilizing feedback circuit includes the first electric capacity (CB109), 3rd resistor (RB133) and the second electric capacity (CB110)；
One end of first electric capacity (CB109) is connected on the negative electrode of the voltage stabilizing standard, the other end and the 3rd electricity Hinder one end series connection of (RB133)；The other end of 3rd resistor (RB133) is connected to the reference input of the voltage stabilizing standard On；
One end of second electric capacity (CB110) is connected on the negative electrode of the voltage stabilizing standard, and the other end is connected to institute On the reference input for stating voltage stabilizing standard.
It is preferred that, the magnitude of voltage of the control signal input and the output voltage of the power supply output end of the power supply circuit Corresponding relation is：When the magnitude of voltage of the control signal input is per 1% dutycycle of stepping, the first power supply output end it is defeated Go out voltage change 0.01V, and the output voltage of the second power supply output end changes 0.1V.
It is preferred that, the scope of the magnitude of voltage of the control signal input is 0V~3.3V voltage signal or PWM ripples, institute The output voltage correspondence for stating the first power supply output end is adjustable as 11.5V~12.5V, and the output of the second power supply output end Voltage automatic adaptation.
Present invention also offers a kind of television set, including：TV SKD, backlight LED light string, and it is as described above low The constant current of power consumption and backlight control circuit；
The constant current of the low-power consumption and backlight control circuit connect respectively with the TV SKD and the backlight LED light string Connect, for when opening the power supply of the television set, according to the operating voltage of the backlight LED light string, automatic adjusument supply The voltage signal of the TV SKD, the backlight LED light string；When closing the power supply of the television set, shut-off flows through institute State the electric current of backlight LED light string.
A kind of constant current for low-power consumption that the present invention is provided and backlight control circuit and television set, are provided with front end power circuit With rear end linear constant current circuit, the supply voltage of two-way output is adjusted using front end power circuit, and in the power circuit of front end Feedback adjustment circuit is set up, and control signal input is provided with feedback adjustment circuit, to realize control front end power supply electricity Voltage of the road in the first power supply output end and the second power supply output end；And string is adapted to automatically by setting up rear end linear constant current circuit The change of the LED backlight quantity of connection, the magnitude of voltage after being connected according to LED backlight adjusts the control signal input Magnitude of voltage so that passing through front end power circuit and its feedback adjustment circuit controls the first power supply output end, the second power supply The output voltage of output end, and the first power supply output end is connected to LED backlight and is powered, and realizes and LED backlight number The adaptable voltage automation regulation of amount, reduces the power consumption of circuit switch element, also passes through the diode of voltage detecting circuit (DB2) connect with backlight LED light series winding, when LED string is opened, diode (DB2) conducting, voltage detecting circuit detects LED The operating voltage of lamp string, so as to control the feedback circuit adjustment the first power supply output end, the second power supply output end Output voltage；When the LED string is closed, diode (DB2) reversely ends, and complete switches off and flows through the LED string Electric current, therefore the present invention can be in backlight open, the operating voltage of normal acquisition LED string, and backlight LED is closed receiving Order when, LED string two ends are equivalent to open circuit, and LED is without glimmer phenomenon, it is to avoid unnecessary power consumption penalty and improve backlight LED service life.
Brief description of the drawings
Fig. 1 is a kind of schematic diagram for linear constant-current modulation circuit that prior art is provided.
Fig. 2 is the structural representation of one embodiment of the constant current of low-power consumption that the present invention is provided and backlight control circuit.
Fig. 3 is a kind of schematic diagram of the achievable mode for the front end power circuit that the present invention is provided.
Fig. 4 is a kind of physical circuit schematic diagram for the front end power circuit that the present invention is provided.
Fig. 5 is a kind of circuit theory diagrams of the achievable mode for the rear end linear constant current circuit that the present invention is provided.
Fig. 6 is the circuit theory diagrams of another achievable mode for the rear end linear constant current circuit that the present invention is provided.
Fig. 7 is a kind of physical circuit figure of the achievable mode for the voltage detecting circuit that the present invention is provided.
Fig. 8 is the physical circuit figure of another achievable mode for the voltage detecting circuit that the present invention is provided.
Fig. 9 is the structural representation of the another embodiment of the constant current of low-power consumption that the present invention is provided and backlight control circuit.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clear, complete Site preparation is described.
It is that the constant current for the low-power consumption that the present invention is provided and the structure of one embodiment of backlight control circuit are shown referring to Fig. 2 It is intended to.
In the present embodiment, the constant current of described low-power consumption and backlight control circuit include front end power circuit 101, rear end Linear constant current circuit 103 and voltage detecting circuit 104.
The front end power circuit 101 includes the power supply output end of power supply circuit 1011, first OUT1, the second power supply output end OUT2 and feedback adjustment circuit 1012；
Wherein, the feedback adjustment circuit 1012 includes feedback input end A_in, control signal input Cont and feedback Signal output part B_out；The feedback input end A_in is connected with the described second power supply output end OUT2, and the feedback signal is defeated Go out to hold B_out to be connected with the power supply circuit 1011；The feedback adjustment circuit 1012 is according to the control signal input Cont magnitude of voltage, to the output feedback signal of power supply circuit 1011, to control 1011 pairs described first of the power supply circuit Power supply output end OUT1 and the second power supply output end OUT2 magnitude of voltage are adjusted.
The rear end linear constant current circuit 103 is connected with the negative electrode LED- of LED string to be powered, the LED to be powered The anode LED+ of string is connected with the described first power supply output end OUT1.
The rear end linear constant current circuit 103 is referred to provided with a connection reference signal input PWM_REF with accessing constant current Voltage, and according to the size ON/OFF of the constant current reference voltage rear end linear constant current circuit 103 with it is described to be powered The connection of LED string.
Linear constant-current circuit 103 passes through voltage detecting circuit with the LED string junction P to be powered in the rear 104 draw voltage acquisition output terminals A DC all the way is believed with gathering the voltage of the junction, and adjusting the control according to collection result Number input Cont magnitude of voltage, so as to further adjust the first power supply output end OUT1, the second power supply output end OUT2 Output voltage；
The voltage detecting circuit 104 includes diode DB2 and pull-up resistor RB18, the diode DB2 negative electrode connect The negative electrode LED- of the LED string is connected on, diode DB2 anode is connected to pull-up resistor RB18 one end, pull-up resistor RB18 other end access high level；The anode of the diode DB2 connects the voltage acquisition output terminals A DC.Such as Fig. 2 institutes Show, in rear end, linear constant current circuit 103 and the junction P of LED string negative electrode draw output end all the way, with diode DB2 negative electrodes Connection, when the LED string is opened, diode DB2 conductings, the voltage detecting circuit 104 is detected by diode DB2 The operating voltage of the LED string, so as to control the feedback circuit 1012 to adjust the first power supply output end OUT1, second Output end of powering OUT2 output voltage；When the LED string is closed, diode DB2 reversely ends, and shut-off flows through described The electric current of LED string.
Specifically, the constant current of low-power consumption of the present embodiment offer and the main operational principle of backlight control circuit are：Beating When opening backlight of television power supply, the voltage typically smaller than 3.3V for the P points that rear end linear constant current circuit 103 connects with LED series winding, together When, high level VCC access causes the voltage V of diode DB2 and resistance RB18 tie pointAHigher than the voltage of P points, therefore, Diode DB2 is turned on, and circuit is operated by resistance RB18, diode DB2 and switching tube QB1 loops.Now, diode The voltage V of DB2 and resistance RB18 tie pointA=VDB2+VQB1, wherein, VDB2Represent electric current when flowing through diode DB2 in two poles The pressure drop that pipe DB2 input, output two ends are formed, VQB1Represent electric current when flowing through switching tube QB1 in the inputting of switching tube QB1, defeated Go out the pressure drop of two ends formation.In closing television machine backlight electric power, rear end linear constant current circuit 103 disconnects with LED string, LED Lamp string two ends are influenceed by constant voltage circuit and there is the high level much larger than 3.3V at LED- ends, therefore diode DB2 is reverse Cut-off, open circuit, i.e. LED string will be equivalent between LED string and voltage detecting circuit 104 to be passed through without weak current, thus Glimmer phenomenon will not be produced.
It is a kind of schematic diagram of the achievable mode for the front end power circuit that the present invention is provided referring to Fig. 3.
As shown in figure 3, feedback adjustment circuit 1012 provided with optocoupler PCB101, voltage-stablizer UB102 and can be connected to described the Between two power supply output end OUT and ground the and main voltage sample electricity being made up of the resistance RB134 and resistance RB135 that connect Road.
Wherein, the optocoupler PCB101 includes light emitting diode (i.e. the optocoupler PCB101 pin 1 and pin 2 positioned at primary side Component) and positioned at the optical signal converter (i.e. the component of optocoupler PCB101 pin 3 and pin 4) of secondary.
It is former that the control signal that the control signal input is inputted is accessed to being located at for optocoupler PCB101 by voltage-stablizer UB102 The light emitting diode on side；The light emitting diode is converted to control signal the position that the optocoupler PCB101 is transferred to after optical signal In the optical signal converter of secondary；The optical signal converter converts optical signals to export after electric signal to the feedback signal Output end.
Wherein, the optocoupler PCB101 includes the Light-Emitting Diode and the optical signal converter positioned at secondary positioned at primary side, It is used as the power supplies of feedback input end A_in and second by resistance R131 positioned at the input (pin 1) of the Light-Emitting Diode of primary side to export OUT connections are held, and optocoupler PCB101 primary side two ends (pin 1 and pin 2) are in parallel with resistance R132；Positioned at optocoupler PCB101 secondary Optical signal converter output end (pin 4) connection as feedback signal output B_out and power supply circuit 1011 feedback control Feedback connections in end processed, the other end (pin 3) ground connection of optical signal converter.It should be noted that resistance RB132 not this reality Apply the necessary electronic component in the feedback circuit in example.
Voltage-stablizer UB102 is preferred to use the accurate voltage-stablizer of adjustable, and built-in 2.5V (volt) reference voltage, specifically, It can be realized using model TL431 voltage-stablizer.Wherein, the anode A ground connection of the adjustable precision shunt voltage-stablizer, cloudy Pole K is connected with the light emitting diode positioned at primary side of the optocoupler PCB101；Reference input R is used to access the control signal Input Cont control signal.
As shown in figure 3, voltage-stablizer UB102 negative electrode K is connected with the pin of Light-Emitting Diode 2 of optocoupler PCB101 primary sides, voltage stabilizing Device UB102 anode A ground connection；It is anti-provided with voltage stabilizing between voltage stabilizing standard UB102 reference input (pin 1) and negative electrode (pin 3) Current feed circuit；The reference input reference input (pin 1) of the voltage stabilizing standard UB102 is connected to resistance RB134 and resistance Locate between RB135 series connection, voltage stabilizing standard UB102 anode (pin 2) ground connection, voltage stabilizing standard UB102 negative electrode (pin 3) connection The primary side other end (pin 2) of the optocoupler PCB101.
In a kind of achievable mode, the voltage stabilizing feedback circuit includes electric capacity CB109 and resistance RB133；The electricity The one end for holding CB109 is connected on the negative electrode K of the adjustable precision shunt voltage-stablizer, one end of the other end and resistance RB133 Series connection；The resistance RB133 other end is connected on the reference input R of the adjustable precision shunt voltage-stablizer.
In another achievable mode, the voltage stabilizing feedback circuit includes electric capacity CB110；The electric capacity CB110's One end is connected on the negative electrode K of the adjustable precision shunt voltage-stablizer, and it is steady that the other end is connected to the adjustable precision shunt On the reference input R of depressor.
Further, both the above implementation can be combined by the present embodiment, to realize the voltage stabilizing feedback electricity Road.I.e. described voltage stabilizing feedback circuit is simultaneously provided with electric capacity CB109, resistance RB133 and electric capacity CB110.
As shown in figure 3, voltage-stablizer UB102 negative electrode K is connected with the pin of light emitting diode 2 of optocoupler PCB101 primary sides, voltage stabilizing Device UB102 anode A ground connection；Resistance RB134 one end is connected with voltage-stablizer UB102 reference input R, other end ground connection； Electric capacity CB109 one end is connected on the negative electrode K of the adjustable precision shunt voltage-stablizer, the other end and the one of resistance RB133 End series connection；The resistance RB133 other end is connected on the reference input R of the adjustable precision shunt voltage-stablizer；The electricity The one end for holding CB110 is connected on the negative electrode K of the adjustable precision shunt voltage-stablizer, and the other end is connected to the adjustable essence On the reference input R of close shunt regulator.
Further, the reference input R of the adjustable precision shunt voltage-stablizer passes through a divider and the control Signal input part is connected.In this embodiment, it is preferred that, the divider is a resistance RB150.
Feedback input end A_in is as shown in figure 3, electric capacity CB109 one end is connected with optocoupler PCB101 2 pin, the other end and electricity It is connected after resistance RB133 series connection with resistance RB150 one end, the resistance RB150 other end is used as the control signal input Cont；Electric capacity CB110 one end is connected with voltage-stablizer UB102 negative electrode K, the reference input R of the other end and voltage-stablizer UB102 Connection；Resistance RB135 one end is connected with feedback input end A_in, and the reference input R of the other end and voltage-stablizer UB102 connects Connect.Thus, a kind of specific embodiment of feedback circuit 1012 is constituted.
The main improvement of feedback adjustment circuit 1012 and the existing feedback adjustment circuit shown in Fig. 1 shown in Fig. 3 is, Increase by a resistance RB150 on voltage-stablizer UB102 reference input R, while introducing one by control signal input Cont Control signal carries out Automated condtrol to voltage-stablizer UB102 negative electrode K output voltage values, so as to can realize to power supply circuit 1011 and its regulation of output voltage.
It is a kind of physical circuit schematic diagram for the front end power circuit that the present invention is provided referring to Fig. 4.
The power supply circuit 1011 includes power supply input circuit 11, switching power circuit 12, multiple-channel output transformer TB101, LED power output circuit 13 and main board power supply output circuit 14；
The power supply input circuit 11 under the control of the switching power circuit 12 by the power supply signal of access transmit to The multiple-channel output transformer TB101；As shown in figure 4, the multiple-channel output transformer TB101 includes main winding and auxiliary winding. Wherein, the coil of the pin of multiple-channel output transformer TB101 9 pin~11 forms primary main winding, multiple-channel output transformer TB101's The coil of the pin of 1 pin~2 forms secondary main winding；The coil of the pin of multiple-channel output transformer TB101 7 pin~8 formed it is primary it is secondary around Group, the coil of the pin of multiple-channel output transformer TB101 1 pin~6 forms secondary auxiliary winding, and (coil between wherein 1,2 pin is total to With), and be able to can not also be shared with common sparing winding between secondary major-minor winding.When it is implemented, the main winding is by institute State and transmitted after power supply signal transformation to the main board power supply output circuit 14, and carried out by the described second power supply output end OUT2 Output；The auxiliary winding will be transmitted after the synchronous transformation of the power supply signal to the LED and powered output circuit 13, and by described First power supply output end OUT1 is exported；Therefore, the multiple-channel output transformer TB101 in Fig. 4 has two output voltage, special Not, in technical field of television sets, the first power supply output end OUT1 is preferably the power supply output end for supplying LED backlight, the Two power supply output end OUT2 are preferably the power supply output end for supplying TV SKD.
In the present embodiment, output voltages of the multiple-channel output transformer TB101 per circle coil is identical, when changing wherein Output voltage all the way, then the output voltage on another road also will synchronously follow change.For example, the coil of main winding is 2 circles, Output voltage is 12V, i.e., the output voltage per circle coil is 6V；Assuming that the output voltage of auxiliary winding is 120V, then auxiliary winding Coil turn is 20 circles.And the coil turn of main winding and auxiliary winding can be adjusted according to practical application, i.e., described master The coil ratio of winding and the auxiliary winding is 1：N, N ＞ 0, i.e., when main winding output voltage be V1 when, auxiliary winding it is defeated Go out voltage for V2=N*V1.
It should be noted that the feedback input end A_in of feedback adjustment circuit 1012 can connect the power supply circuit 1011 First power supply output end OUT1 or the second power supply output end OUT2, has no effect on the implementation of the present embodiment.
The present invention can pass through the control signal input Cont of feedback adjustment circuit 1012 external control signals accessed Size, so as to control the power supply output ends of the first power supply output end OUT1 or second OUT2 magnitude of voltage.Specifically, with the feedback The feedback input end A_in of adjustment circuit 1012 is connected to exemplified by the second power supply output end OUT2 of the power supply circuit 1011, this The basic functional principle of embodiment is mainly：
When the output voltage of power supply circuit 1011 is raised, (the first power supply output end OUT1 and the second power supply output end OUT2 are same When Shi Shenggao), control signal input Cont control signal passes through resistance RB135 and resistance RB134, resistance RB150 partial pressures Voltage afterwards is transmitted to voltage-stablizer UB102 reference input R, and voltage-stablizer UB102 is by reference input R signal value and its Portion's reference voltage is compared.When reference input R signal value is more than reference voltage, between voltage-stablizer UB102 anode and cathodes Voltage reduction, and then optocoupler PCB101A electric current increase, dynamic electric resistive between optocoupler PCB101B colelctor electrodes and emitter stage Small (4 pin of optocoupler PCB101 current collection extremely optocoupler, 3 pin of transmitting extremely optocoupler), the voltage between colelctor electrode and emitter stage Step-down；PWM (Pulse Width Modulation, pulse width modulation) the control chip UB101 connected therewith feedback pin COMP level step-down, pwm chip UB101 output duty cycles reduce, so that multiple-channel output transformer TB101's is defeated Go out voltage reduction.Conversely, when reference input R signal value is less than reference voltage, may be such that multiple-channel output transformer TB101 Output voltage rise.
Therefore, for the reference input R accesses that adjust voltage-stablizer UB102 voltage signal size so as to controlling transformer TB101 output voltage, the present invention is by increasing resistance RB150 and realizing in resistance RB150 side incoming control signal This purpose.Specifically, when needing modulation second to power output end OUT2 output voltage, and voltage-stablizer UB102 inside base When quasi- voltage is 2.5V, the output voltage values calculation formula of the second power supply output end is：Vout2=reference voltage * (1+R135/ R134), wherein, reference voltage is preferably 2.5V.Preferably, a PWM_12V signal can be exported extremely by outside control chip The control signal input Cont, via resistance RB150 by PWM_12V signals transmit to resistance RB134 and resistance RB135 it Between series connection point (i.e. voltage-stablizer UB102 reference input R).
When it is implemented, control signal input Cont PWM_12V signals can use any one perseverance in 0-3.3V Determine magnitude of voltage, or, using PWM (Pulse Width Modulation, pulse width modulation) ripple of certain waveform.According to The output voltage values calculation formula of two power supply output ends：Vout2=reference voltages * (1+R135/R134), when PWM_12V signals When being output as 3.3V, the second power supply output end OUT2 output voltage is minimum, because control signal input Cont input (1 pin voltage and reference voltage are several when circuit stability works by reference voltage 2.5V of the voltage (3.3v) more than voltage-stablizer UB102 It is equal), so be the equal of now that resistance RB150 is connected on 3.3V power supply, that is, it is in parallel equivalent to by resistance RB150 On resistance RB135, it can be seen from Vout2 voltage equation, due to resistance RB135 resistance RB150 in parallel, equivalent to electricity The equivalent resistance for hindering RB135 is reduced, so that output voltage Vout2 is reduced.When PWM_12V signal outputs are 0V, second supplies Electricity output end OUT2 output voltage values are maximum, because when PWM_12V signals are 0V, equivalent to control signal input Cont is grounded, and resistance RB150 is in parallel with resistance RB134, and according to Output Voltage Formula, resistance RB134 equivalent resistance diminishes, Voltage-stablizer UB102 reference input R voltage diminishes, therefore the second power supply output end OUT2 output voltage rise.
It can be seen that, the control signal inputted by the control signal input Cont of linear regulation feedback adjustment circuit 1012 (0V~3.3V as escribed above voltage signal or PWM ripples), may be such that the second power supply output end OUT2 output voltage in reality (Vout2_max=12.5V, Vout2_min=11.5V) is adjusted between border common voltage scope 11.5V~12.5V, from And realize fine setting；Similarly, in the presence of multiple-channel output transformer TB101, the first power supply output end OUT1 output voltage Synchronous automatic adaptation regulation will be realized.
In concrete application occasion, under product ideal case (power supply circuit output reduce), can be by linear regulation outside Control signal input Cont from portion's control chip to feedback adjustment circuit 1012 input control signal for high level (such as 3.3V), the voltage of the second power supply output end OUT2 outputs so as to make power supply circuit 1011 is minimum output voltage, can be subtracted The stand-by power consumption of few TV SKD.
In addition, the LED string to be powered is in series by multiple LEDs, with the quantity of LED string to be powered Increase, the supply voltage required for after multiple LED strip connection constantly increases, it is therefore desirable to the first power supply output end OUT1 output Voltage can adaptively respond LED number change, automatically adjust its output voltage values.
It is the circuit theory of two kinds of achievable modes of the rear end linear constant current circuit that the present invention is provided referring to Fig. 5~6 Figure.
The rear end linear constant current circuit 103 includes comparing adjustment circuit 1031 and constant-current control circuit 1032；The ratio The reverse input end for including operational amplifier UB1A, the operational amplifier UB1A compared with adjustment circuit 1031 passes through a resistance RB12 It is connected with the reference signal input PWM_REF；The positive input of the operational amplifier UB1A is connected with current feedback Circuit, the control end that the output end of the operational amplifier UB1A passes through a control circuit module connecting valve pipe QB1.Specifically Ground, as shown in Figure 5,6, the current feedback circuit include what is composed in parallel by resistance RB6, resistance RB7, resistance RB8 and resistance RB9 Constant current detection resistance, in addition to resistance RB5 and electric capacity CB5.Wherein, by resistance RB6, resistance RB7, resistance RB8 and resistance RB9 groups Into one end of constant current detection resistance be connected on resistance RB5 one end, other end ground connection；The resistance RB5 other end is connected to On the normal phase input end of the operational amplifier UB1A.One end ground connection of the electric capacity CB5, the other end is connected to the computing and put On big device UB1A normal phase input end.The circuit of wherein resistance RB5 and electric capacity CB5 compositions can be to being input to operational amplifier The signal of UB1A positive input is filtered.
It is preferred that, the positive input of the operational amplifier UB1A is also associated with a clamp diode DB1, to protect State the normal work for comparing adjustment circuit 1031.
In the rear in linear constant-current circuit 103, the constant-current control circuit 1032 includes control circuit module and opened Close pipe QB1.Switching tube QB1 can (Metal-Oxid-Semiconductor, metal oxide be partly led for triode or MOS Body) field-effect transistor, abbreviation metal-oxide-semiconductor or field-effect transistor.Wherein, switching tube QB1 conducting, cut-off or conducting degree shape State is associated with the physical characteristic of its own.For example, when switching tube QB1 is triode, it is bent according to the C-V characteristic of triode Line, has saturation region, amplification region and cut-off region, and the voltage signal between the emitter stage and colelctor electrode of triode is produced respectively Different influence, such as when triode operation is in saturation region, equivalent to short circuit (conducting between the emitter stage and colelctor electrode of triode State).
The rear end linear constant current circuit 103 is by reference to signal input part PWM_REF, to access constant current reference voltage VREF, and according to the constant current reference voltage VREFSize control the conducting, cut-off or conducting degree of the switching tube QB1, from And rear end linear constant current circuit 103 described in ON/OFF and the connection of the LED string to be powered
In the present embodiment, as shown in figure 5, when the switching tube QB1 be triode when, the constant-current control circuit 1032 It is connected by the colelctor electrode of the triode with one end (LED-) of the LED string to be powered；The emitter stage of the triode It is connected with the anode of the clamp diode DB1, the base stage of the triode passes through the control circuit module and the computing Amplifier UB1A output end connection；As shown in fig. 6, when the switching tube QB1 is field-effect transistor, the current constant control Circuit 1032 is connected by the drain electrode of the field-effect transistor with one end (LED-) of the LED string to be powered；The field The source electrode of effect transistor is connected with the anode of the clamp diode DB1, and the grid of the field-effect transistor passes through described Control circuit module and the output end of the operational amplifier UB1A.
When it is implemented, clamp diode DB1 minus earth, anode is connected to operational amplifier by resistance RB5 UB1A positive input.After the startup of rear end linear constant current circuit 103, by operational amplifier UB1A adjustment, it is positive Input connects the magnitude of voltage and its constant current reference voltage V that reversely input is accessed that constant current detection resistance is gotREFIt is equal, Then as constant current reference voltage VREFDuring turn-on voltage (about 0.7V) higher than clamp diode DB1, clamp diode DB1 will Conducting ground connection, i.e., by the voltage at resistance RB6, resistance RB7, resistance RB8 and resistance RB9 the constant current detection resistance two ends composed in parallel Value is clamped diode DB1 and limited, therefore, and clamp diode DB1 serves certain protective effect.
Also, due to switching tube QB1 emitter stage (switching tube QB1 is triode) or source electrode (switching tube QB1 is metal-oxide-semiconductor) It is connected with clamp diode DB1 anode, therefore circulation switching tube QB1 constant current value can be calculated by below equation：
As constant current reference voltage VREFDuring turn-on voltage higher than clamp diode DB1, circulation switching tube QB1 constant current Signal is IConstant currentThe resistance of=DB1 turn-on voltage/constant current detection resistance；As constant current reference voltage VREFLess than clamp diode During DB1 turn-on voltage, circulation switching tube QB1 constant current signal is IConstant current=constant current reference voltage VREF/ constant current detection resistance Resistance.Generally, clamp diode DB1 turn-on voltage is 0.7V, and the resistance of constant current detection resistance is resistance RB6, resistance Equivalent resistance after RB7, resistance RB8 and resistance RB9 are in parallel.
In the present embodiment, the first power supply output end is connected to the positive pole LED+ of LED string, passes through switching tube QB1 perseverance Flow control, then constant current detection resistance (resistance RB6, resistance RB7, resistance RB8 and resistance RB9 parallel resistance) is concatenated to ground, it is permanent The size of current of LED string is converted into voltage signal and is linked into operational amplifier UB1A and constant current reference voltage by stream detection resistance VREF(it is controlled by outside master chip, or access fixed voltage, if the constant current value I that fixed voltage is then exportedConstant currentIt is then solid Definite value, it is impossible to carry out the regulation of constant current size) it is compared and amplifies, so that controlling switch pipe QB1 adjusts the electric current of LED string Keep constant.
The plurality of LEDs lamp when it is implemented, LED string can typically connect, wherein the operating voltage of single LEDs is generally 2.8V ~3.4V, the operating voltage after the series connection of plurality of LEDs lamp will accordingly increase.So that switching tube QB1 is metal-oxide-semiconductor as an example, switching tube QB1's Voltage V between drain electrode and source electrodeDS=VOUT1- LED string operating voltage-constant current reference voltage VREF.Therefore, rear end is linear Constant-current circuit 103 enters after working condition, the voltage V between switching tube QB1 drain electrode and source electrodeDSWill be by LED string The influence of operating voltage size, may also be subjected to multiple-channel output transformer TB101 crossmodulation in addition (general range is 7%) Influence.
In the prior art, with the change of LED string voltage, switching tube QB1 drain-source voltage VDSVoltage is also synchronously sent out Changing, switching tube QB1 this Partial Power (VDS* constant current value IConstant current) form that will be converted into heat comes out, VDSElectricity Pressure is bigger, and switching tube QB1 power consumption is bigger, and temperature is higher.Therefore the excessive switching tube QB1 of power consumption can reduce power-efficient and Switching tube QB1 is caused to overheat and be easily damaged.In order to reduce switching tube QB1 temperature, multiple metal-oxide-semiconductors or triode can be used Parallel connection is used as switching tube QB1, but this technical scheme result in the increase of cost.
Referring to Fig. 2, Fig. 7~Fig. 8, the present embodiment can effectively solve above-described switching tube QB1 power problemses.Tool Body, by passing through voltage detecting circuit 104 in the constant-current control circuit 1032 and the LED string junction P to be powered Voltage acquisition output terminals A DC all the way is drawn, is voltage acquisition output end to detect the voltage change of LED string to be powered in real time Pressure drop between ADC and reference signal input PWM_REF sets a threshold value, or, it is the defeated of voltage acquisition output terminals A DC Go out voltage and set a steady state value (reference signal input PWM_REF voltage VREFIt is typically small), when voltage acquisition output end Output of the pressure drop more than the threshold value, or voltage acquisition output terminals A DC between ADC and reference signal input PWM_REF When voltage is more than the steady state value, by the control signal for adjusting the control signal input Cont in front end power circuit 101 PWM_12V, controls optocoupler PCB101 by situation of change (the i.e. first power supply output end OUT1 electricity of the operating voltage of LED string Pressure situation of change) pwm chip UB101 is fed back to, pwm chip UB101 controlling switch pipes QB101 changes dutycycle, So that the magnitude of voltage that voltage acquisition output terminals A DC magnitude of voltage subtracts reference signal input PWM_REF is equal or close to The default threshold value (or voltage acquisition output terminals A DC magnitude of voltage is equal or close to the steady state value), therefore, this implementation Example can pass through control signal input Cont control signal PWM_12V, stop voltage collection output terminals A DC and reference signal Pressure drop between input PWM_REF, so as to reduce switching tube QB1 drain-source voltage VDSBy the voltage change of LED string Influence, reduces switching tube QB1 power consumption and ensure that power-efficient.
Fig. 7 is a kind of physical circuit figure of the achievable mode for the voltage detecting circuit that the present invention is provided.
The voltage detecting circuit 104 includes diode DB2 and pull-up resistor RB18, the diode DB2 negative electrode connection In the negative electrode LED- of the LED string, diode DB2 anode is connected to pull-up resistor RB18 one end, pull-up resistor RB18 Other end access high level (be preferably 3.3V)；When it is implemented, high level VCC can by with switching tube QB1 identical controls The constant-current control circuit 1032 of end control processed is provided.
The anode of the diode DB2 connects the voltage acquisition output terminals A DC.The anode of the diode DB2 also leads to Cross the resistance RB16 connections voltage acquisition output terminals A DC.Now, voltage acquisition output terminals A DC output voltage is：VADC= VA*RB17/(RB16+RB17).When the LED string is opened, diode DB2 conductings, the voltage detecting circuit 104 passes through Diode DB2 detects the operating voltage of the LED string, so as to control the feedback adjustment circuit 1012 to adjust described first Output end of powering OUT1, the second power supply output end OUT2 output voltage；When the LED string is closed, diode DB2 is reverse Cut-off, shut-off flows through the electric current of the LED string.
Output terminals A DC_12V and diode all the way are drawn in the junction P of constant-current control circuit 1032 and LED string negative electrode DB2 negative electrodes are connected, when the LED string is opened, diode DB2 conductings, and the LED string is detected by diode DB2 Operating voltage flow through resistance RB16 and transmit to external control devices or chip, so as to be adjusted by controlling the feedback circuit The first power supply output end OUT1, the second power supply output end OUT2 output voltage；When the LED string is closed, that is, open When closing pipe QB1 cut-offs, diode DB2 reversely ends, and shut-off flows through the electric current of the LED string.
Specifically, the main operational principle of the backlight control circuit for the low-power consumption that the present embodiment is provided is：
When opening backlight of television power supply, switching tube QB1 conductings enter working condition, the P points that will be connect with LED series winding Voltage be limited in colelctor electrode (when switching tube QB1 is triode) or drain (when switching tube QB1 is field-effect transistor) Magnitude of voltage (typically smaller than 3.3V) on, meanwhile, high level VCC access causes diode DB2 and resistance RB18 tie point Voltage VAHigher than the voltage of P points, therefore, diode DB2 conductings, circuit passes through resistance RB18, diode DB2 and switching tube QB1 loops are operated.Now, the voltage V of diode DB2 and resistance RB18 tie pointA=VDB2+VQB1；Now, voltage is examined The output voltage for surveying output terminals A DC is：VADC=VA*RB17/(RB16+RB17).In closing television machine backlight electric power, switch Pipe QB1 enters cut-off state, and LED string two ends keep constant pressure and there are the high level much larger than 3.3V, therefore two at LED- ends Pole pipe DB2 reversely ends, and open circuit, i.e. LED string are equivalent between LED string and voltage detecting circuit 104 will be without weak current Pass through, thus glimmer phenomenon will not be produced.
Preferably, the voltage detecting circuit 104 that the present embodiment is provided also includes a filter circuit of pressure-stabilizing 1042；It is described Filter circuit of pressure-stabilizing 1042 is connected between the voltage acquisition output terminals A DC and ground.
The filter circuit of pressure-stabilizing 1042 includes voltage-regulator diode D1, electric capacity CB7 and resistance RB17；And voltage-regulator diode D1 Negative electrode, electric capacity CB7 one end and resistance RB17 one end is commonly connected on the voltage acquisition output terminals A DC；Voltage stabilizing two The other end common ground of pole pipe D1 anode, the electric capacity CB7 other end and resistance RB17.Wherein, voltage-regulator diode D1 master Act on be prevent voltage detecting circuit 104 operation irregularity or when switching tube QB1 is turned off because high level VCC voltages are more than 3.3V and cause port ADC output voltage excessive so that burn the device that voltage acquisition output terminals A DC is connected situation hair It is raw.
Fig. 8 is the physical circuit figure of another achievable mode for the voltage detecting circuit that the present invention is provided.
The voltage detecting circuit 104 includes diode DB2 and pull-up resistor RB18, the diode DB2 negative electrode connection In the negative electrode LED- of the LED string, diode DB2 anode is connected to pull-up resistor RB18 one end, pull-up resistor RB18 Other end access high level (be preferably 3.3V)；The anode of the diode DB2 also passes through the diode DB3 connections voltage Gather output terminals A DC.The anode of the diode DB3 is connected with diode DB2 anode；The negative electrode of the diode DB3 is made For the voltage acquisition output terminals A DC, now, voltage acquisition output terminals A DC output voltage is：VADC=VA-VDB3。
Voltage acquisition output terminals A DC output voltage VADCIt will be transmitted to external control devices and carry out Treatment Analysis, with basis Analysis result controls the working condition of front end power circuit 101, so that it is defeated to control the first power supply output end OUT1 and second to power Go out to hold OUT2 output voltage.
Preferably, the voltage detecting circuit 104 that the present embodiment is provided also includes a filter circuit of pressure-stabilizing 1042；It is described Filter circuit of pressure-stabilizing 1042 is connected between the voltage acquisition output terminals A DC and ground.
The filter circuit of pressure-stabilizing 1042 includes voltage-regulator diode D1, electric capacity CB7 and resistance RB17；And voltage-regulator diode D1 Negative electrode, electric capacity CB7 one end and resistance RB17 one end is commonly connected on the voltage acquisition output terminals A DC；Voltage stabilizing two The other end common ground of pole pipe D1 anode, the electric capacity CB7 other end and resistance RB17.Wherein, voltage-regulator diode D1 master Act on be prevent voltage detecting circuit 104 operation irregularity or when switching tube QB1 is turned off because high level VCC voltages are more than 3.3V and cause port ADC output voltage excessive so that burn the device that voltage acquisition output terminals A DC is connected situation hair It is raw.
In the present embodiment, the present embodiment provide low-power consumption voltage stabilizing backlight control circuit main operational principle with The basic functional principle of Fig. 7 illustrated embodiments is identical, mainly includes：When opening backlight of television power supply, switching tube QB1 is led Logical to enter working condition, high level VCC access causes diode DB2 to turn on, circuit by resistance RB18, diode DB2 and Switching tube QB1 loops are operated, the voltage V of diode DB2 and resistance RB18 tie pointA=VDB2+VQB1；Meanwhile, two poles Pipe DB3 is turned on, by voltage VATransmit to voltage detecting output terminals A DC, now, voltage detecting output terminals A DC output voltage is： VADC=VA-VDB3.In closing television machine backlight electric power, switching tube QB1 enters cut-off state, and LED string two ends keep constant pressure Thus there is the high level much larger than 3.3V at LED- ends, therefore diode DB2 reversely ends, LED string and voltage detecting electricity Open circuit is equivalent between road 104, i.e., LED string will pass through without weak current, thus will not produce glimmer phenomenon.
A kind of constant current for low-power consumption that the present embodiment is provided and backlight control circuit, are provided with front end power circuit, rear end Linear constant current circuit and voltage detecting circuit, the supply voltage of two-way output is adjusted using front end power circuit, and in front end electricity Feedback circuit is set up in source circuit, and is provided with control signal input in a feedback circuit, to realize control front end power supply electricity Voltage of the road in the first power supply output end and the second power supply output end；And string is adapted to automatically by setting up rear end linear constant current circuit The change of the LED backlight quantity of connection, the magnitude of voltage after being connected according to LED backlight adjusts the control signal input Magnitude of voltage so that passing through front end power circuit and its feedback circuit controls the first power supply output end, the second power supply output The output voltage at end, and the first power supply output end is connected to LED backlight and is powered, and realizes and LED backlight quantity phase The voltage automation regulation of adaptation, reduces the power consumption of circuit switch element, and ensure that the stabilization of the supply voltage of motherboard circuit Property.
The present embodiment is additionally arranged voltage detecting circuit, is connect, is opened in LED string with backlight LED light series winding by diode DB2 Qi Shi, diode DB2 are turned on, and voltage detecting circuit detects the operating voltage of LED string, so as to control the feedback electricity Road adjustment the first power supply output end, the output voltage of the second power supply output end；When the LED string is closed, diode DB2 reversely ends, and complete switches off the electric current for flowing through the LED string, therefore the present invention can be in backlight open, normal acquisition The operating voltage of LED string；When on-off switching tube QB1 is to close LED backlight, LED string two ends are equivalent to open circuit, LED Without glimmer phenomenon, it is to avoid unnecessary power consumption penalty and the service life for improving backlight LED.
It is that the constant current for the low-power consumption that the present invention is provided and the structure of another embodiment of backlight control circuit are shown referring to Fig. 9 It is intended to.
The present embodiment and the distinctive points of previously described embodiment are, on the basis of previously described embodiment, enter One step, the constant current for the low-power consumption that the present embodiment is provided and backlight control circuit also include a control master chip 105.Wherein, it is preceding The essential structure of end power circuit 101 and rear end linear constant current circuit 103 and voltage detecting circuit 104 is with operation principle and above Described embodiment is identical, will not be repeated here.
Control master chip 105 and the control signal input Cont, the reference signal input PWM_REF with And the voltage acquisition output terminals A DC is connected respectively；
The control master chip 105 adjusts the output to the control according to the voltage change of the voltage acquisition output terminals A DC Signal input part Cont processed signal magnitude, powers output end OUT1, second with control the front end power circuit 101 first Output end of powering OUT2 output voltage values；And by the reference signal input PWM_REF to the rear end linear constant current Circuit 103 inputs the constant current reference voltage VREF。
Specifically, when the control master chip 105 detects the voltage acquisition output terminals A DC and the reference signal is defeated When entering to hold PWM_REF voltage difference more than default threshold value, the control master chip 105 will export defeated to the control signal Enter to hold Cont voltage signal dutycycle to reduce.When it is implemented, the control master chip 105 is built-in with analog-digital converter, use Data signal is converted in the voltage signal for accessing the control master chip 105.Obtained from voltage acquisition output terminals A DC collections Voltage signal first pass around after the conversion of analog-digital converter, obtain corresponding data signal, then by controlling in master chip 105 Other processing units processing.Because too high input voltage value can influence the normal work of analog-digital converter, and closing The magnitude of voltage of P points easily causes the resistance between former connection analog-digital converter of the prior art to produce faint electricity during LED string Signal is flowed, so that LED backlight produces glimmer phenomenon.Due to the present embodiment there is provided voltage detecting circuit 104, Ke Yi When turning off backlight electric power, by controlling diode DB2 to be moved back to so as to effectively separate the current signal of voltage detecting circuit 104 In LED string, it is to avoid the generation of " glimmer phenomenon ".
The present embodiment is defeated to control signal input Cont, the reference signal as a result of same control master chip Enter to hold the signal of tri- terminals of PWM_REF and the voltage acquisition output terminals A DC to be handled, therefore have previously described , further can be in real time according to reference signal input PWM_REF and voltage acquisition output terminals A DC on the basis of effect effect Signal intensity, and send corresponding control signal to control signal input Cont, therefore can reach rapid to LED string The beneficial effect that the change of operating voltage is responded.
Invention additionally discloses a kind of television set, including：TV SKD, backlight LED light string, and as shown in Fig. 2 or Fig. 9 Low-power consumption constant current and backlight control circuit.
The constant current of the low-power consumption and backlight control circuit connect respectively with the TV SKD and the backlight LED light string Connect, for when opening the power supply of the television set, according to the operating voltage of the backlight LED light string, automatic adjusument supply The voltage signal of the TV SKD, the backlight LED light string；When closing the power supply of the television set, shut-off flows through institute State the electric current of backlight LED light string.Wherein, the basic composition of the constant current of low-power consumption and backlight control circuit and operation principle with above It is described identical, it will not be repeated here.
Described above is the preferred embodiment of the present invention, it is noted that for those skilled in the art For, under the premise without departing from the principles of the invention, some improvements and modifications can also be made, these improvements and modifications are also considered as Protection scope of the present invention.

Claims (22)

1. constant current and the backlight control circuit of a kind of low-power consumption, it is characterised in that including：Front end power circuit and rear end are linearly permanent Current circuit；
The front end power circuit includes power supply circuit and feedback adjustment circuit；The power supply circuit includes the first power supply output End, the second power supply output end and feedback control end；The feedback adjustment circuit include feedback input end, control signal input and Feedback signal output；The feedback input end is connected with the described second power supply output end, the feedback signal output and institute State power supply circuit connection；The feedback adjustment circuit is according to the magnitude of voltage of the control signal input, to the feed back input The signal that end is received is adjusted with to the power supply circuit output feedback signal, so as to control the power supply circuit to described the The magnitude of voltage of one power supply output end and the second power supply output end is adjusted；
The rear end linear constant current circuit is connected with the negative electrode of LED string to be powered, the anode of the LED string to be powered and institute State the connection of the first power supply output end；
The rear end linear constant current circuit connects reference signal input to access constant current reference voltage provided with one, and according to described Rear end linear constant current circuit described in the size ON/OFF of constant current reference voltage and the connection of the LED string to be powered；
Linear constant-current circuit draws electric all the way with the LED string junction to be powered by voltage detecting circuit in the rear Pressure gathers output end to gather the voltage of the junction, and according to the voltage of the collection result adjustment control signal input Value；
The voltage detecting circuit includes diode and pull-up resistor, and the negative electrode of the diode is connected to the LED string Negative electrode, anode is connected to one end of pull-up resistor, the other end access high level of pull-up resistor；The anode connection of the diode The voltage acquisition output end.
2. constant current and the backlight control circuit of low-power consumption as claimed in claim 1, it is characterised in that the anode of the diode The voltage acquisition output end is also connected by a resistance.
3. constant current and the backlight control circuit of low-power consumption as claimed in claim 1, it is characterised in that the anode of the diode The voltage acquisition output end is also connected by another diode；The anode of another diode and the anode of the diode Connection；The negative electrode of another diode is used as the voltage acquisition output end.
4. constant current and the backlight control circuit of low-power consumption as claimed in claim 1, it is characterised in that the voltage detecting circuit Also include a filter circuit of pressure-stabilizing；The filter circuit of pressure-stabilizing is connected between the voltage acquisition output end and ground；
The filter circuit of pressure-stabilizing includes voltage-regulator diode, filter capacitor and filter resistance in parallel；And the voltage-regulator diode Negative electrode be connected in the voltage acquisition output end, the plus earth of the voltage-regulator diode.
5. constant current and the backlight control circuit of low-power consumption as claimed in claim 1, it is characterised in that the rear end linear constant current Circuit includes comparing adjustment circuit and constant-current control circuit；The constant-current control circuit at least includes a switching tube and control circuit Module；The adjustment circuit that compares includes operational amplifier, and the reverse input end connection of the operational amplifier is described with reference to letter Number input, positive input connects through constant current detection resistance ground connection, and the output end of the operational amplifier passes through the control Circuit module processed connects the control end of the switching tube；The negative electrode of the input of the switching tube and the LED string to be powered Connection, the output end of the switching tube is grounded by the constant current detection resistance.
6. constant current and the backlight control circuit of low-power consumption as claimed in claim 5, it is characterised in that：
When the switching tube is triode, the colelctor electrode of the triode is connected with one end of the LED string to be powered, hair Emitter-base bandgap grading is grounded by the constant current detection resistance, and base stage passes through the control circuit module and the output end of the operational amplifier Connection；
When the switching tube is field-effect transistor, drain electrode and the LED string to be powered of the field-effect transistor One end is connected, and source electrode is grounded by the constant current detection resistance, and grid passes through the control circuit module and the operation amplifier The output end connection of device.
7. constant current and the backlight control circuit of low-power consumption as claimed in claim 5, it is characterised in that：The constant current detection resistance master Will by resistance RB6, resistance RB7, resistance RB8 is in parallel with resistance RB9 constitutes.
8. constant current and the backlight control circuit of low-power consumption as claimed in claim 5, it is characterised in that：The operational amplifier is just Phase input is connected by resistance RB5 with the constant current detection resistance, and the output end of the switching tube is connected to the resistance RB5 With the junction of the constant current detection resistance.
9. constant current and the backlight control circuit of low-power consumption as claimed in claim 5, it is characterised in that：The operational amplifier is just Phase input is also grounded by electric capacity CB5.
10. constant current and the backlight control circuit of low-power consumption as claimed in claim 5, it is characterised in that：It is described to compare adjustment circuit Also include a clamp diode；
The minus earth of the clamp diode；The anode of the clamp diode is connected with the output end of the switching tube.
11. constant current and the backlight control circuit of low-power consumption as claimed in claim 1, it is characterised in that：Only when the voltage acquisition When the voltage for the junction that output end is collected is more than or equal to default threshold value, the control signal input is just adjusted Magnitude of voltage, so that the first power supply output end, the output voltage of the second power supply output end are further adjusted, so that the junction Voltage be less than default threshold value.
12. constant current and the backlight control circuit of low-power consumption as claimed in claim 1, it is characterised in that also including a control master Chip；
The control master chip is exported with the control signal input, the reference signal input and the voltage acquisition End is connected respectively；
The control master chip adjusts the output to the control signal input according to the voltage change of the voltage acquisition output end The signal magnitude at end, the output voltage for output end, the second power supply output end of being powered with control the front end power circuit first Value；And the constant current reference voltage is inputted to the rear end linear constant current circuit by the reference signal input.
13. constant current and the backlight control circuit of low-power consumption as claimed in claim 12, it is characterised in that when the control master chip When detecting the voltage difference of the voltage acquisition output end and the reference signal input more than default threshold value, the control Master chip processed reduces the voltage signal dutycycle exported to the control signal input.
14. constant current and the backlight control circuit of low-power consumption as claimed in claim 13, it is characterised in that the control master chip bag Analog-digital converter is included, for the voltage signal of the control master chip access to be converted into data signal.
15. the constant current of low-power consumption and backlight control circuit as described in any one of claim 1~14, it is characterised in that the confession Circuit includes power supply input circuit, switching power circuit, multiple-channel output transformer, LED and powered output circuit and main board power supply Output circuit；
The power supply input circuit transmits the power supply signal of access to the multichannel under the control of the switching power circuit Export transformer；
The multiple-channel output transformer includes main winding and auxiliary winding；The main winding will be transmitted after the power supply signal transformation to The main board power supply output circuit, and exported by the described second power supply output end；The auxiliary winding believes the power supply Transmit to the LED and power output circuit after number synchronous transformation, and exported by the described first power supply output end；The master The coil ratio of winding and the auxiliary winding is 1：N, N ＞ 0.
16. constant current and the backlight control circuit of low-power consumption as claimed in claim 1, it is characterised in that the feedback adjustment circuit Including opto-coupled feedback unit, voltage stabilizing reference cell, voltage sampling unit and voltage-adjusting unit；
The opto-coupled feedback unit includes optocoupler, and the optocoupler includes the light emitting diode positioned at primary side and the light positioned at secondary is believed Number converter, the signal input part of the light emitting diode passes through the first resistor RB131 connections feedback input end；The light The signal output part of signal adapter connects the feedback signal output；
The voltage sampling unit includes the 4th resistance RB134 for being connected to series connection between the feedback input end and ground and the Five resistance RB135；
The voltage stabilizing reference cell includes voltage stabilizing standard and is connected between the reference input of voltage stabilizing standard and negative electrode Voltage stabilizing feedback circuit；The reference input of the voltage stabilizing standard is connected to the 4th resistance RB134 and the 5th resistance RB135 strings Locate between connection, plus earth, negative electrode connects the signal output part of the light emitting diode；
The voltage-adjusting unit includes the 6th resistance RB150, and one end of the 6th resistance RB150 is connected to the 4th electricity Place between RB134 and the 5th resistance RB135 series connection is hindered, the other end connects the control signal input.
17. constant current and the backlight control circuit of low-power consumption as claimed in claim 16, it is characterised in that the voltage stabilizing feedback circuit Including the first electric capacity CB109 and 3rd resistor RB133；
One end of the first electric capacity CB109 is connected on the negative electrode of the voltage stabilizing standard, the other end and 3rd resistor RB133 One end series connection；The 3rd resistor RB133 other end is connected on the reference input of the voltage stabilizing standard.
18. constant current and the backlight control circuit of low-power consumption as claimed in claim 16, it is characterised in that the voltage stabilizing feedback circuit Including the second electric capacity CB110；
One end of the second electric capacity CB110 is connected on the negative electrode of the voltage stabilizing standard, and the other end is connected to the voltage stabilizing On the reference input of standard.
19. constant current and the backlight control circuit of low-power consumption as claimed in claim 16, it is characterised in that the voltage stabilizing feedback circuit Including the first electric capacity CB109,3rd resistor RB133 and the second electric capacity CB110；
One end of the first electric capacity CB109 is connected on the negative electrode of the voltage stabilizing standard, the other end and 3rd resistor RB133 One end series connection；The 3rd resistor RB133 other end is connected on the reference input of the voltage stabilizing standard；
One end of the second electric capacity CB110 is connected on the negative electrode of the voltage stabilizing standard, and the other end is connected to the voltage stabilizing On the reference input of standard.
20. constant current and the backlight control circuit of low-power consumption as claimed in claim 1, it is characterised in that the control signal input The magnitude of voltage at end and the output voltage corresponding relation of the power supply output end of the power supply circuit are：The control signal input When magnitude of voltage is per 1% dutycycle of stepping, the output voltage change 0.01V of the first power supply output end, and second power supply The output voltage change 0.1V of output end.
21. constant current and the backlight control circuit of low-power consumption as claimed in claim 13, it is characterised in that the control signal input Hold the voltage signal or PWM ripples that are 0V~3.3V for range of voltage values of input, the output voltage of the first power supply output end Correspond to and be adjustable as 11.5V~12.5V, and the output voltage automatic adaptation of the second power supply output end.
22. a kind of television set, including：TV SKD, backlight LED light string, and as described in any one of claim 1~21 The constant current of low-power consumption and backlight control circuit；
The constant current of the low-power consumption and backlight control circuit are connected respectively with the TV SKD and the backlight LED light string, For when opening the power supply of the television set, according to the operating voltage of the backlight LED light string, automatic adjusument supply to be described The voltage signal of TV SKD, the backlight LED light string；When closing the power supply of the television set, shut-off flows through the back of the body The electric current of light LED string.
CN201410476651.8A 2014-09-17 2014-09-17 The constant current of low-power consumption and backlight control circuit and television set Active CN104253954B (en)

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