CN104253957B - Low-power-consumption constant-current and backlight control circuit and television - Google Patents
Low-power-consumption constant-current and backlight control circuit and television Download PDFInfo
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Abstract
The invention discloses a low-power consumption constant current and backlight control circuit, which comprises a front-end power circuit and a rear-end linear constant current circuit, wherein the front-end power circuit is connected with a power supply; the front-end power supply circuit comprises a power supply circuit and a feedback adjusting circuit; the rear-end linear constant-current circuit is provided with a connection reference signal input end to access constant-current reference voltage, and the connection between the rear-end linear constant-current circuit and the LED lamp string to be powered is switched on/off according to the magnitude of the constant-current reference voltage; and a voltage acquisition output end is LED out from the connection part of the rear-end linear constant-current circuit and the LED lamp string to be powered through a voltage detection circuit so as to acquire the voltage of the connection part, and the voltage value of the input end of the control signal is adjusted according to the acquisition result.
Description
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.
In addition, prior art to linear constant current circuit when being improved, often cause the power supply in shut-off backlight LED
When, backlight LED one end is still connected with electricity consumption device and there is weak current so that the weak current is played a reversed role to backlight LED
So that backlight LED is turned on and sent faint light, this does not allow in television set manufacturing technology field.
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 a switching tube (QB3), and the input of the switching tube (QB3) connects the connection
Place, output end connects the voltage acquisition output end, and control end connects a Regulate signal input, is believed by adjusting the regulation
The magnitude of voltage of number input, is opened while turning on the connection of the rear end linear constant current circuit and the LED string to be powered
Close pipe (QB3) conducting, switching tube while the rear end linear constant current circuit and the connection of the LED string to be powered disconnect
(QB3) end.
It is preferred that, the voltage detecting circuit also includes resistance (RB19) and resistance (RB20)；
The output end of the switching tube (QB3) is connected with one end of resistance (RB19), the other end conduct of resistance (RB19)
The voltage acquisition output end voltage gathers output end；The control end of the switching tube (QB3) connects with one end of resistance (RB20)
Connect, the other end of resistance (RB20) is used as the Regulate signal input.
It is preferred that, the voltage detecting circuit also includes a switching tube (QB4), resistance (R21), resistance (RB22) and resistance
(RB23)；Wherein, resistance R21 one end is connected on the junction, and the other end is connected to switching tube QB3 and resistance RB20 company
On contact；
The output end of the switching tube (QB4) connects the other end of the resistance (RB20)；The input of switching tube (QB4)
It is connected to ground；The control end of switching tube (QB4) is on the one hand connected to ground by resistance (RB22), on the other hand connection resistance
(RB23) one end, the other end of resistance (RB23) is used as the Regulate signal input.
It is preferred that, the switching tube (QB3) is triode or FET.
It is preferred that, the switching tube (QB4) is triode or FET.
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 (QB1) and on-off circuit；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 (QB1) by the on-off circuit；The switching tube
(QB1) input is connected with the negative electrode of the LED string to be powered, and the output end of the switching tube (QB1) passes through the perseverance
Flow detection resistance ground connection.
It is preferred that, when the switching tube (QB1) is triode, the colelctor electrode of the triode and the LED to be powered
One end connection of lamp string, emitter stage is grounded by the constant current detection resistance, base stage by the control circuit module with it is described
The output end connection of operational amplifier；
When the switching tube (QB1) be field-effect transistor when, the drain electrode of the field-effect transistor with it is described to be powered
One end connection of LED string, source electrode is grounded by the constant current detection resistance, grid by the control circuit module with it is described
The output end of operational 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, the voltage acquisition are defeated
Go out end and the Regulate signal input 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；
The control master chip enters according to the on off state of the LED string to the level value of the Regulate signal input
Row synchronous adjustment, including：Join when inputting the constant current to the rear end linear constant current circuit by the reference signal input
When examining voltage so that LED string is opened, the magnitude of voltage of the Regulate signal input is adjusted so that the switching tube (QB3) is led
It is logical, when inputting the constant current reference voltage so that LED to the rear end linear constant current circuit by the reference signal input
When lamp string is turned off, the level value of the regulation input is adjusted so that the switching tube (QB3) ends.
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 voltage signal or PWM that are 0V~3.3V for range of voltage values of the control signal input input
Ripple, the output voltage of the first power supply output end, which is corresponded to, is adjustable as 11.5V~12.5V, and the second power supply output end
Output 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 pressure backlight control circuit is connected respectively with the TV SKD and the backlight LED light string, for beating
When opening the power supply of the television set, according to the operating voltage of the backlight LED light string, automatic adjusument supplies the TV owner
The voltage signal of plate, the backlight LED light string；When closing the power supply of the television set, simultaneously turn off and flow through the backlight LED
The electric current of lamp 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
(QB3) connect with backlight LED light series winding, voltage detecting circuit is by accessing the real-time controlling switch pipe (QB3) of outside Regulate signal
On off state, it is ensured that in backlight open, voltage acquisition output end can collect LED string and switching tube (QB1) junction
Magnitude of voltage；When backlight is closed, switching tube (QB3) and switching tube (QB4) synchronously end, thus LED string two ends equivalent to
Open circuit, LED is without glimmer phenomenon, it is to avoid unnecessary power consumption penalty and raising backlight LED service life.Present invention also offers
A kind of television set of adaptation power supply regulation, constant current and backlight control circuit as a result of the low-power consumption after improvement, thus
When being powered using the linear constant current and backlight control circuit to TV SKD and backlight of television LED string, equally
Above-described beneficial effect can be reached, the operating efficiency of TV SKD and backlight LED service life is improved.
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 switching tube QB3, and the input of the switching tube QB3 is connected to the LED
The negative electrode LED- (i.e. junction P) of string, the switching tube QB3 output end connect the voltage acquisition output terminals A DC, described to open
The control end for closing pipe QB3 connects a Regulate signal input Cont_S, by adjusting the Regulate signal input Cont_S's
Magnitude of voltage, leads switching tube QB3 while the connection conducting of the rear end linear constant current circuit and the LED string to be powered
Logical, switching tube QB3 ends while the rear end linear constant current circuit and the connection of the LED string to be powered disconnect.
As shown in Fig. 2 output end all the way is drawn in the junction P of constant-current control circuit 1032 and LED string negative electrode, with opening
Pipe QB3 input connection is closed, when the size that the constant current reference voltage is adjusted by the reference signal input PWM_REF
And while making the LED string unlatching, adjusted by the magnitude of voltage for adjusting the Regulate signal input so that the switch
Pipe QB3 is turned on；When inputting the constant current reference voltage to the rear end linear constant current circuit by the reference signal input
During so that LED string being turned off, the level value of the regulation input is adjusted so that the switching tube QB3 ends, so as to turn off
Flow through the electric current of the LED string.The voltage detecting circuit 104 is detected described by the voltage acquisition output terminals A DC
The operating voltage of LED string, so as to control the feedback adjustment circuit 1012 to adjust the first power supply output end OUT1, second
Output end of powering OUT2 output voltage.
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 outside control that the present invention can be accessed by the control signal input Cont of linear regulation feedback adjustment circuit 1012
The size of signal processed, 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 input end A_in of the feedback adjustment circuit 1012 is connected to the second power supply output end of the power supply circuit 1011
Exemplified by OUT2, the basic functional principle of the present 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 PCB101 electric current increase, dynamic electric resistor diminishes between optocoupler PCB101 colelctor electrodes and emitter stage
(4 pin of optocoupler PCB101 current collection extremely optocoupler, 3 pin of transmitting extremely optocoupler), the voltage between colelctor electrode and emitter stage becomes
It is low；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.
When it is implemented, in the rear in linear constant-current circuit 103, the adjustment circuit 1031 that compares is put including computing
Big device UB1A, the operational amplifier UB1A reverse input end pass through a resistance RB12 and the reference signal input PWM_
REF connections；The positive input of the operational amplifier UB1A is connected with current feedback circuit, the operational amplifier UB1A's
The control end that output end passes through an on-off circuit connecting valve pipe QB1.Specifically, as shown in Figure 5,6, the current feedback circuit bag
Include the constant current detection resistance composed in parallel by resistance RB6, resistance RB7, resistance RB8 and resistance RB9, in addition to resistance RB5 and electricity
Hold CB5.Wherein, electricity is connected to by one end of resistance RB6, resistance RB7, resistance RB8 and resistance RB9 the constant current detection resistance constituted
On the one end for hindering RB5, other end ground connection；The resistance RB5 other end is connected to the normal phase input end of the operational amplifier UB1A
On.One end ground connection of the electric capacity CB5, the other end is connected on the normal phase input end of the operational amplifier UB1A.It is wherein electric
The circuit of resistance RB5 and electric capacity CB5 compositions can be filtered to the signal for the positive input for being input to operational amplifier UB1A.
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 also includes on-off circuit and switch
Pipe QB1.Switching tube QB1 can be triode or MOS (Metal-Oxid-Semiconductor, metal-oxide semiconductor (MOS))
Field-effect transistor, abbreviation metal-oxide-semiconductor or field-effect transistor.Wherein, switching tube QB1 conducting, cut-off or conducting level state
It is associated with the physical characteristic of its own.For example, when switching tube QB1 is triode, according to the VA characteristic curve of triode,
Saturation region, amplification region and cut-off region are there is, the voltage signal between the emitter stage and colelctor electrode of triode is produced not respectively
Same influence, such as when triode operation is in saturation region, equivalent to short circuit (conducting shape 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 on-off circuit and the operation amplifier
Device UB1A output end connection；As shown in fig. 6, when the switching tube QB1 is field-effect transistor, the constant-current control circuit
1032 are connected by the drain electrode of the field-effect transistor with one end (LED-) of the LED string to be powered；The field-effect
The source electrode of transistor is connected with the anode of the clamp diode DB1, and the grid of the field-effect transistor passes through the switch
The output end of circuit and 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；When constant current reference voltage VREF is less than the pole of clamper two
During pipe DB1 turn-on voltage, circulation switching tube QB1 constant current signal is IConstant current=constant current reference voltage VREF/ constant current detection electricity
The resistance of resistance.Generally, clamp diode DB1 turn-on voltage is 0.7V, and the resistance of constant current detection resistance is resistance RB6, electricity
Hinder total resistance after RB7, resistance RB8 and resistance RB9 parallel connections.
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.
Specifically, the voltage detecting circuit 104 includes voltage acquisition input (being connected with P points), Regulate signal input
Hold Cont_S and voltage acquisition output terminals A DC；An output end is drawn in the junction of switching tube (QB1) and the LED string, with
The voltage acquisition input connection.
As shown in fig. 7, voltage detecting circuit 104 includes switching tube QB3, resistance RB19 and resistance RB20；Wherein, switching tube
QB3 can be the triode of NPN type or the metal-oxide-semiconductor of N-channel.So that switching tube QB3 is the triode of NPN type as an example, switching tube QB3
Colelctor electrode be connected on the junction P of switching tube QB1 and LED string, switching tube QB3 emitter and resistance RB19 one end
Connection, the resistance RB19 other end is connected with the voltage acquisition output terminals A DC；Resistance RB20 one end is with switching tube QB3's
Base stage is connected, and the resistance RB20 other end is used as Regulate signal input Cont_S.By controlling the Regulate signal input
Cont_S level value, when the LED string is turned on, controlling switch pipe QB3 be conducting state, by switching tube QB1 with it is described
The junction P of LED string magnitude of voltage VACollection is exported to the voltage acquisition output terminals A DC；In LED string shut-off
When, controlling switch pipe QB3 is cut-off state, is connected so as to disconnect the voltage detecting circuit 104 with the electric of the junction P
Connect.
Preferably, switching tube QB1 switch controlling signal is synchronous with Regulate signal input Cont_S Regulate signal, and
Preferably it is controlled using same control terminal.
Specifically, in backlight open, controlling switch pipe QB1 is in the conduction state, while being Regulate signal input
Cont_S accesses high level, then switching tube QB3 is synchronously turned on, then flows through setting electric current of the electric current of LED string for circuit, and electricity
Pressure collection output terminals A DC magnitude of voltage is：VADC=VA* RB17/ (RB19+RB17), VADCSignal sends external control terminal to.
When closing backlight, when controlling switch pipe QB1 is turned off, and low level is set for Regulate signal input Cont_S,
Then switching tube QB3 synchronously ends, and equivalent to open circuit between LED string and voltage detecting circuit 104, therefore LED string is complete
Close, no glimmer phenomenon, also, because switching tube QB3 is in cut-off state, therefore voltage acquisition output terminals A DC does not have in theory
There is voltage signal, therefore, its external control terminal connected is carried out at correlation without the signal to voltage acquisition output terminals A DC
Reason.For example, when external control terminal includes analog-digital converter, then will not be to voltage acquisition output terminals A DC when backlight is closed
Signal carry out analog-to-digital conversion (because voltage acquisition output terminals A DC no signals output).Fig. 8 is the voltage detecting that the present invention is provided
The physical circuit figure of another achievable mode of circuit.
In second of embodiment of voltage detecting circuit 104, it enters on the basis of the embodiment that Fig. 7 is provided
One step, it is additionally provided with switching tube QB4, resistance RB22 and resistance RB23.Wherein, switching tube QB4 can be triode or metal-oxide-semiconductor.
Specifically, so that switching tube QB4 is triode as an example, on the basis of first embodiment, resistance RB20 one end
It is connected with switching tube QB3 base stage, the resistance RB20 other end is connected with switching tube QB4 colelctor electrode, switching tube QB4 transmitting
Pole is grounded；Switching tube QB4 base stage after series resistor RB22 by being grounded, and by being used as Regulate signal after series resistor RB23
Input Cont_S, i.e. resistance RB23 one end are used as Regulate signal input Cont_S, the base stage of the other end and switching tube QB4
Connection, the Regulate signal that Regulate signal input Cont_S is accessed accesses switching tube QB4.
Preferably, switching tube QB1 switch controlling signal is synchronous with Regulate signal input Cont_S Regulate signal, and
Preferably it is controlled using same control terminal.
Therefore, the basic functional principle of the voltage regulator circuit 104 of present embodiment is：
In backlight open, controlling switch pipe QB1 is in the conduction state, while being Regulate signal input Cont_S accesses
High level, then switching tube QB4 synchronously conductings, the then electric current for flowing through LED string is the setting electric current of circuit, switching tube QB4 conductings
Resistance RB21 and resistance RB20 carries out causing switching tube QB3 conductings after partial pressure afterwards, and voltage acquisition output terminals A DC magnitude of voltage is：
VADC=VA* RB17/ (RB19+RB17), VADCSignal sends external control terminal to.
When closing backlight, when controlling switch pipe QB1 is turned off, and low level is set for Regulate signal input Cont_S,
Then switching tube QB4, switching tube QB3 synchronously end, equivalent to open circuit between LED string and voltage detecting circuit 104, therefore LED
Lamp string is fully closed, no glimmer phenomenon, also, because switching tube QB3 is in cut-off state, therefore voltage acquisition output end
ADC is in theory without voltage signal, and therefore, its external control terminal connected is without the letter to voltage acquisition output terminals A DC
Number carry out relevant treatment.For example, when external control terminal includes analog-digital converter, then will not be adopted when backlight is closed to voltage
The signal for collecting output terminals A DC carries out analog-to-digital conversion (because the output of voltage acquisition output terminals A DC no signals).
It is preferred that, a filter circuit of pressure-stabilizing 1041 is equipped with the voltage detecting circuit 104 shown in Fig. 6 or Fig. 7；It is described
Filter circuit of pressure-stabilizing 1041 is connected between the voltage acquisition output terminals A DC and ground.
The filter circuit of pressure-stabilizing 1041 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.
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 switching tube QB3
Qi Shi, switching tube QB3 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, switching tube
QB3 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 LED
The operating voltage of lamp string；When on-off switching tube QB1 is to close LED backlight, LED string two ends are equivalent to open circuit, and LED is without micro-
Bright 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
Voltage acquisition output terminals A DC and Regulate signal the input Cont_S 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。
The control master chip 105 is additionally operable to the on off state according to the LED string to the Regulate signal input
Cont_S level value synchronizes adjustment, including：When linear to the rear end by the reference signal input PWM_REF
Constant-current circuit 103 inputs the constant current reference voltage VREFDuring so that LED string being opened, by the Regulate signal input Cont_
S magnitude of voltage is adjusted so that the switching tube QB3 is turned on, when by the reference signal input PWM_REF to the rear end
Linear constant current circuit 103 inputs the constant current reference voltage VREFDuring so that LED string being turned off, by the electricity of the regulation input
Level values are adjusted so that the switching tube QB3 ends.
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 when closing LED string P points
Magnitude of voltage easily causes the resistance between former connection analog-digital converter of the prior art to produce low current signal, so that
LED backlight produces glimmer phenomenon.Due to the present embodiment there is provided voltage detecting circuit 104, can when turning off backlight electric power,
By controlling triode QB3 cut-offs to be moved back to so as to effectively separate the current signal of voltage detecting circuit 104 in LED string,
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
At the signal for entering to hold PWM_REF, the voltage acquisition output terminals A DC and Regulate signal input tetra- terminals of Cont_S
Reason, therefore on the basis of previously described effective effect, further can be in real time according to reference signal input PWM_REF
And voltage acquisition output terminals A DC signal intensity, and to control signal input Cont and Regulate signal input Cont_S
Corresponding control signal is sent, therefore the beneficial effect that the rapid change to LED string operating voltage is responded can be reached.
Further, the embodiment of the present invention additionally provides a kind of television set, including：TV SKD, backlight LED light string,
And constant current and the backlight control circuit of previously described low-power consumption.
The linear constant current and backlight control circuit are connected respectively with the TV SKD and the backlight LED light string,
For the operating voltage according to the backlight LED light string by incoming control signal, the power supply of the television set can opened
When, according to the operating voltage of the backlight LED light string, automatic adjusument supplies the TV SKD, the backlight LED light string
Voltage signal；When closing the power supply of the television set, shut-off flows through the electric current of the backlight LED light string.Wherein, it is linear permanent
Basic composition and the operation principle of stream and backlight control circuit with it is described previously identical, will not be repeated here.The television set is being carried
While the flexibility of high voltage regulation, LED power consumptions are reduced, LED service life and the overall performance of mainboard is improved.
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 (24)
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 a switching tube QB3, and the input of the switching tube QB3 connects the junction, output end
The voltage acquisition output end is connected, control end connects a Regulate signal input, by adjusting the Regulate signal input
Magnitude of voltage, switching tube QB3 is led while turning on the connection of the rear end linear constant current circuit and the LED string to be powered
Logical, switching tube QB3 ends while the rear end linear constant current circuit and the connection of the LED string to be powered disconnect.
2. 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 includes resistance RB19 and resistance RB20；
The output end of the switching tube QB3 is connected with resistance RB19 one end, and the resistance RB19 other end is adopted as the voltage
Collect output end voltage collection output end；The control end of the switching tube QB3 is connected with resistance RB20 one end, and resistance RB20's is another
One end is used as the Regulate signal input.
3. constant current and the backlight control circuit of low-power consumption as claimed in claim 2, it is characterised in that
The voltage detecting circuit also includes switching tube QB4, resistance R21, resistance RB22 and resistance RB23；Wherein, resistance R21
One end is connected on the junction, and the other end is connected on switching tube QB3 and resistance RB20 tie point；
The output end of the switching tube QB4 connects the other end of the resistance RB20；Switching tube QB4 input is connected to ground；
On the one hand switching tube QB4 control end is connected to ground by resistance RB22, on the other hand connection resistance RB23 one end, resistance
The RB23 other end is used as the Regulate signal input.
4. constant current and the backlight control circuit of low-power consumption as claimed in claim 2, it is characterised in that the switching tube QB3 is
Triode or FET.
5. constant current and the backlight control circuit of low-power consumption as claimed in claim 3, it is characterised in that the switching tube QB4 is
Triode or FET.
6. 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.
7. 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 QB1 and switch
Circuit；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 is opened by described
Powered-down road connects the control end of the switching tube QB1；The moon of the input of the switching tube QB1 and the LED string to be powered
Pole is connected, and the output end of the switching tube QB1 is grounded by the constant current detection resistance.
8. constant current and the backlight control circuit of low-power consumption as claimed in claim 7, it is characterised in that：
When the switching tube QB1 is triode, one end of the colelctor electrode of the triode and the LED string to be powered connects
Connect, emitter stage is grounded by the constant current detection resistance, base stage passes through the control circuit module and the operational amplifier
Output end is connected；
When the switching tube QB1 is field-effect transistor, the drain electrode of the field-effect transistor and the LED string to be powered
One end connection, source electrode is grounded by the constant current detection resistance, and grid is put by the control circuit module with the computing
The output end connection of big device.
9. constant current and the backlight control circuit of low-power consumption as claimed in claim 7, 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.
10. constant current and the backlight control circuit of low-power consumption as claimed in claim 7, it is characterised in that：The operational amplifier
Normal phase input end 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 and the junction of the constant current detection resistance.
11. constant current and the backlight control circuit of low-power consumption as claimed in claim 7, it is characterised in that：The operational amplifier
Normal phase input end is also grounded by electric capacity CB5.
12. constant current and the backlight control circuit of low-power consumption as claimed in claim 7, 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.
13. 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.
14. 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 and the control signal input, the reference signal input, the voltage acquisition output end
And the Regulate signal input 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；
The control master chip carries out same according to the on off state of the LED string to the level value of the Regulate signal input
Successive step, including：It is electric when inputting the constant current reference to the rear end linear constant current circuit by the reference signal input
When pressing so that LED string is opened, by the magnitude of voltage adjustment of the Regulate signal input so that the switching tube QB3 is turned on, when
The constant current reference voltage is inputted so that LED string is closed to the rear end linear constant current circuit by the reference signal input
When disconnected, the level value of the regulation input is adjusted so that the switching tube QB3 ends.
15. constant current and the backlight control circuit of low-power consumption as claimed in claim 14, 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.
16. constant current and the backlight control circuit of low-power consumption as claimed in claim 15, 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.
17. the constant current of low-power consumption and backlight control circuit as described in any one of claim 1~16, 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.
18. 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 includes 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.
19. constant current and the backlight control circuit of low-power consumption as claimed in claim 18, it is characterised in that the voltage stabilizing feedback circuit
Including the first electric capacity CB109 and 3rd resistor RB133；
First electric capacity CB109 one end is connected on the negative electrode of the voltage stabilizing standard, the other end and the one of 3rd resistor RB133
End series connection；The 3rd resistor RB133 other end is connected on the reference input of the voltage stabilizing standard.
20. constant current and the backlight control circuit of low-power consumption as claimed in claim 18, it is characterised in that the voltage stabilizing feedback circuit
Including the second electric capacity CB110；
Second electric capacity CB110 one end is connected on the negative electrode of the voltage stabilizing standard, and the other end is connected to the voltage stabilizing benchmark
On the reference input of device.
21. constant current and the backlight control circuit of low-power consumption as claimed in claim 18, 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；
First electric capacity CB109 one end is connected on the negative electrode of the voltage stabilizing standard, the other end and the one of 3rd resistor RB133
End series connection；The 3rd resistor RB133 other end is connected on the reference input of the voltage stabilizing standard；
Second electric capacity CB110 one end is connected on the negative electrode of the voltage stabilizing standard, and the other end is connected to the voltage stabilizing benchmark
On the reference input of device.
22. 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.
23. constant current and the backlight control circuit of low-power consumption as claimed in claim 22, 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.
24. a kind of television set, including TV SKD, backlight LED light string, and as described in any one of claim 1~23
The constant current of low-power consumption and backlight control circuit；
The backlight control circuit is connected respectively with the TV SKD and the backlight LED light string, for opening described
During the power supply of television set, according to the operating voltage of the backlight LED light string, automatic adjusument supplies the TV SKD, institute
State the voltage signal of backlight LED light string；When closing the power supply of the television set, simultaneously turn off and flow through the backlight LED light string
Electric current.
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| CN201410476624.0A CN104253957B (en) | 2014-09-17 | 2014-09-17 | Low-power-consumption constant-current and backlight control circuit and television |
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|---|---|---|---|
| CN201410476624.0A CN104253957B (en) | 2014-09-17 | 2014-09-17 | Low-power-consumption constant-current and backlight control circuit and television |
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| CN104253957B true CN104253957B (en) | 2017-09-29 |
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Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105099170A (en) * | 2015-09-14 | 2015-11-25 | 东莞市亚通光电有限公司 | Power supply circuit for detecting backlight module |
| CN105471038B (en) * | 2015-12-28 | 2020-01-31 | 联想(北京)有限公司 | control method and electronic equipment |
| CN107660013B (en) * | 2016-07-26 | 2024-04-05 | 上海莱托思电子科技有限公司 | LED two-end constant-current driving chip and constant-current driving method |
| CN106531087B (en) * | 2016-11-29 | 2019-02-12 | 深圳市华星光电技术有限公司 | A kind of backlight drive circuit and liquid crystal display |
| JP2020052157A (en) * | 2018-09-26 | 2020-04-02 | セイコーエプソン株式会社 | Display driver, electronic apparatus, and movable body |
| CN109637461B (en) | 2018-12-20 | 2020-07-07 | 深圳创维－Rgb电子有限公司 | Mini LED television control system and method |
| CN109640446A (en) * | 2018-12-24 | 2019-04-16 | 欧普照明股份有限公司 | A kind of IC chip, driving circuit and lamp control system |
| CN115083358B (en) * | 2022-07-05 | 2024-06-28 | 珠海格力电器股份有限公司 | Display panel backlight control circuit and control method |
| CN115395943B (en) * | 2022-10-26 | 2023-01-13 | 深圳芯能半导体技术有限公司 | Level shift circuit and switching tube drive circuit |
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| CN203313488U (en) * | 2013-06-03 | 2013-11-27 | 青岛海信电器股份有限公司 | Backlight driving circuit and lamp bar light-adjusting unit |
| CN103560673A (en) * | 2013-11-15 | 2014-02-05 | 青岛海信电器股份有限公司 | Power supply circuit and liquid crystal display television |
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| US20070138971A1 (en) * | 2005-08-15 | 2007-06-21 | Liang Chen | AC-to-DC voltage converter as power supply for lamp |
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| CN203313488U (en) * | 2013-06-03 | 2013-11-27 | 青岛海信电器股份有限公司 | Backlight driving circuit and lamp bar light-adjusting unit |
| CN103560673A (en) * | 2013-11-15 | 2014-02-05 | 青岛海信电器股份有限公司 | Power supply circuit and liquid crystal display television |
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Effective date of registration: 20181031 Address after: 510663 5, No. 192, Ke Zhu Road, Guangzhou economic and Technological Development Zone, Guangdong Patentee after: GUANGZHOU SHIZHEN INFORMATION TECHNOLOGY Co.,Ltd. Address before: 510663, 4, No. 192, Ke Zhu Road, science and Technology City, Guangzhou high tech Industrial Development Zone, Guangdong Patentee before: Guangzhou Shiyuan Electronic Technology Company Limited |
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