CN104467424B - Switching Power Supply for display panel - Google Patents
Switching Power Supply for display panel Download PDFInfo
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- CN104467424B CN104467424B CN201410852246.1A CN201410852246A CN104467424B CN 104467424 B CN104467424 B CN 104467424B CN 201410852246 A CN201410852246 A CN 201410852246A CN 104467424 B CN104467424 B CN 104467424B
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Abstract
A kind of Switching Power Supply for display panel is disclosed, including：First converter, for producing the first output voltage and the second output voltage from the first input voltage；Second converter, for using the first output voltage as input voltage, and produce the 3rd output voltage；Voltage feedback loop, the first voltage feedback signal of the first output voltage is characterized for obtaining, and first voltage feedback signal is compared with the first reference signal, to obtain the first thermal compensation signal；Current feedback loop, the current feedback signal for the electric current for flowing through backlight is characterized for obtaining, and current feedback signal is compared with the second reference signal, to obtain the second thermal compensation signal；And selection circuit, for selecting the thermal compensation signal of conduct the 3rd that numerical value is larger in the first thermal compensation signal and the second thermal compensation signal, wherein, the first converter according to the action of the 3rd compensation signal control first switch pipe with produce obtain constant output voltage and/or output current.The Switching Power Supply can improve conversion efficiency and reduce size and cost.
Description
Technical field
The present invention relates to display technology field, in particular it relates to the Switching Power Supply for display panel.
Background technology
In liquid crystal display panel, layer of liquid crystal molecule is located at before backlight, and liquid crystal molecule does not light in itself.Liquid crystal molecule
Layer changes the transmission or refraction of light under electric field action, so as to the display image under the irradiation of backlight.Light emitting diode
(LED) because it is free of heavy metal Hg, the advantages that color rendition is good, fast response time, energy-saving safety long lifespan, small volume,
Through the mainstream technology as backlight.
Liquid crystal display panel can include two independent power supplys, respectively mainboard and backlight power supply.For example, for leading
First power supply of plate power supply produces 12V DC voltage, the second source for backlight power supply from such as 220V alternating current
24V DC voltage is produced from such as 220V alternating current.However, two independent power supplys use relatively more electronic devices,
Such as respective transformer, as a result cause volume greatly and cost is high.
Size and manufacturing cost that two-way output needed for display panel is advantageous to reduce power supply are provided using single power supply.
In order to provide two-way output using single power supply, existing display panel voltage source typically comprises the first to the 3rd change
Parallel operation, wherein the two-way output of the first converter respectively as the second converter the first input voltage and the 3rd converter the
Two input voltages.First input voltage decompression transformation is mainboard supply voltage by the second converter, and the 3rd converter is defeated by second
Enter boost in voltage and be transformed to backlight supply voltage.
In further improved display panel voltage source, the first and second converters can be used, wherein the first converter
One of two output voltage one of main board power supply voltage and backlight supply voltage is provided, another way output voltage is then used as the
The input voltage of two converters.Second converter produces another in main board power supply voltage and backlight supply voltage.
Above-mentioned existing display panel voltage source, multiple inductance elements are employed in the case of using three converters, from
And it is still unfavorable in terms of the volume and cost of power supply.Using two converters in the case of, the first converter by
When load changes, it is unfavorable that the working condition of the second converter of rear class and the conversion efficiency of whole power supply may be produced
Influence.For example, when the first converter is used for backlight power supply, the first converter may make for the adjustment process that light modulation is carried out
The second converter input voltage it is too low, so as to which supply voltage needed for mainboard can not be produced.
The content of the invention
In view of this, the invention provides a kind of Switching Power Supply for display panel, improved while size is reduced
The conversion efficiency of display panel voltage source, and dimming function can be realized.
According to the present invention, there is provided a kind of Switching Power Supply for display panel, including：First converter, for from first
Input voltage produces the first output voltage and the second output voltage, and the second output voltage is used for the power supply of backlight；Second conversion
Device, for using the first output voltage as input voltage, and produce the 3rd output voltage；Voltage feedback loop, for obtaining
The first voltage feedback signal of the first output voltage is characterized, and by first voltage feedback signal compared with the first reference signal
Compared with to obtain the first thermal compensation signal；Current feedback loop, the current feedback letter for the electric current for flowing through backlight is characterized for obtaining
Number, and current feedback signal is compared with the second reference signal, to obtain the second thermal compensation signal；And selection circuit, use
A larger thermal compensation signal of conduct the 3rd of numerical value in the first thermal compensation signal of selection and the second thermal compensation signal, wherein, first becomes
Parallel operation according to the action of the 3rd compensation signal control first switch pipe with produce obtain constant output voltage and/or output
Electric current.
Preferably, the first converter is inverse excitation type converter, and the second converter is BUCK converters.
Preferably, the selection circuit includes the first diode and the second diode, wherein the first diode and the two or two
The respective anode of pole pipe is respectively connecting to voltage feedback loop and the respective output end of current feedback loop, the first diode and
The negative electrode of two diodes is commonly connected to common node, and the common node is connected to the compensating end of the first converter.
Preferably, the Switching Power Supply also includes light-adjusting module, and the light-adjusting module includes analog light-adjusting circuit and PWM is adjusted
At least one in optical circuit, the analog light-adjusting circuit and the PWM light adjusting circuits are respectively according to simulation dim signal and PWM
Dim signal adjusts the brightness of backlight.
Preferably, the analog light-adjusting circuit provides second reference signal, by changing second reference signal
Numerical value make it that the output current of the first converter is corresponding with the second reference signal, so as to realize the light modulation of backlight.
Preferably, the Switching Power Supply also includes the second switch pipe source-series with backlight, wherein the PWM light adjusting circuits
The light modulation of backlight is realized by periodically turning on and disconnecting second switch pipe.
Preferably, the Switching Power Supply also includes light-modulating mode detection circuit, for judging that external dimmer signal is simulation
Dim signal or PWM dim signals, if external dimmer signal be simulation dim signal, by external dimmer signal provide to
The analog light-adjusting circuit, if external dimmer signal is PWM dim signals, external dimmer signal is provided to the PWM
Light adjusting circuit.
Preferably, the PWM light adjusting circuits produce dimming control signal, the PWM dim signals according to PWM dim signals
It is synchronous with the dimming control signal.
Preferably, enable signal is produced according to the dimming control signal, so as in the high period of dimming control signal
Between enable and current feedback loop and disable voltage feedback loop, disable current feedback between the low period of dimming control signal
Loop and enabled current feedback loop.
Preferably, the voltage feedback loop includes voltage control module, and the voltage control module is anti-by first voltage
Feedback signal is compared with the first reference signal, to obtain the first thermal compensation signal.
Preferably, the voltage control module includes：First reference signal generation circuit, for producing the first benchmark letter
Number；Comparator, for first voltage feedback signal to be compared with the first reference signal；Sampling hold circuit, for receiving ratio
Compared with the comparison signal of device output, and comparison signal is obtained between the low period of PWM dim signals, and dim and believe in PWM
Number high period between keep comparison signal；And compensation circuit, for compensating comparison signal to produce the first thermal compensation signal, its
In, the first reference signal generation circuit is according to the numerical value of first voltage feedback signal the first reference signal of dynamic regulation.
Preferably, the reference signal holding circuit includes：First electric capacity；The partial pressure of first resistor and second resistance composition
Network；And first switch, wherein first switch between the high period of the PWM dim signals by first voltage feedback signal
The first electric capacity is supplied to, the voltage on the first electric capacity is supplied to potential-divider network between the low period of the PWM dim signals,
The first reference signal is obtained in the intermediate node of first resistor and second resistance.
Preferably, second converter includes：3rd switching tube, it is connected to the input for receiving the first output voltage
Between end and the output end for connecting external inductors；Continued flow tube, it is connected between output end and ground；Comparator, for by table
The second voltage feedback signal of the 3rd output voltage is levied compared with the 3rd reference signal, to produce error signal；And switch
Signal generating circuit, it is defeated with maintenance the 3rd for controlling the conducting and disconnection of the 3rd switching tube and continued flow tube according to error signal
Go out voltage constant.
Preferably, the Switching Power Supply also includes the second reference signal generation circuit, the second reference signal generation circuit bag
The first reference signal source and the second reference signal source are included, the reference signal that the first reference signal source provides is more than reference signal source
The reference signal of offer, the second reference signal generation circuit select the first reference signal source to provide the 3rd benchmark letter in heavy duty
Number, select the second reference signal source to provide the 3rd reference signal in underloading.
Preferably, the second converter, voltage feedback loop, current feedback loop, selection circuit and light-adjusting module are integrated
In a chip.
Only need to use two converters according to the Switching Power Supply of the present invention.Such as BOOST topology knots can not only be removed
3rd converter of structure, and the peripheral electron device such as corresponding inductance can be removed.Due to removing the 3rd converter, directly drive
Dynamic backlight, therefore the conversion efficiency of power supply can be improved.Due to removing some electronic devices, therefore can reduce shared by power supply
PCB surface product and cost.
In a preferred embodiment, above-mentioned Switching Power Supply includes the light-adjusting module of compatible analog light modulation and PWM light modulations.
In PWM light modulations, using the enabled and disabling of PWM dim signal control voltage feedback control loops and current feedback loop so that first
Converter can take into account the demand of the input voltage of the second converter and the driving of backlight and light modulation demand, and further carry
The conversion efficiency of high power supply.
Brief description of the drawings
By the description to the embodiment of the present invention referring to the drawings, above-mentioned and other purposes of the invention, feature and
Advantage will be apparent from, in the accompanying drawings：
Fig. 1 is the schematic circuit according to the display panel voltage source of prior art；
Fig. 2 is the schematic block diagram according to the Switching Power Supply for display panel of embodiments of the invention；
Fig. 3 is the schematic block diagram according to the power source drive device for display panel of embodiments of the invention；
Fig. 4 be the present invention the power source drive device for display panel in use voltage control module it is schematic
Circuit diagram；
Fig. 5 is the working waveform figure of the voltage control module shown in Fig. 4；
Fig. 6 is that the reference signal generation module used in the power source drive device for display panel of the present invention shows
Meaning property circuit diagram.
Embodiment
Several preferred embodiments of the present invention are described in detail below in conjunction with accompanying drawing, but the present invention is not restricted to
These embodiments.The present invention covers any replacement made in the spirit and scope of the present invention, modification, equivalent method and side
Case.
Thoroughly understand in order that the public has to the present invention, be described in detail in present invention below preferred embodiment specific
Details, and description without these details can also understand the present invention completely for a person skilled in the art.
Fig. 1 is the schematic circuit according to the Switching Power Supply for display panel of prior art.This is used for display surface
The Switching Power Supply of plate includes three converters.First converter is anti exciting converter, and provides two-way output, respectively as the
The input voltage vin 2 of the converter of input voltage vin 1 and the 3rd of two converters.Second converter is BUCK converters, is used for
Produce main board power supply voltage Vout.3rd converter is BOOSST converters, for producing backlight supply voltage Vled.
After external communication voltage Vac (generally electric main) filters by rectifier bridge U1 rectifications, input capacitance Cin,
Input voltage vin 0 as the first converter.Alternatively, outside alternating voltage Vac and rectifier bridge U1 an input it
Between connect resistance R10, to limit electric current, so as to provide additional protection when short circuit internally and overload.
First converter 100 includes transformer T.Transformer has a primary side winding L1 and three vice-side winding L2 extremely
L4, for transmitting energy and signal feedback.The primary side winding L1 of transformer first end and vice-side winding L2 to L4 is respective
Second end is Same Name of Ends, and the primary side winding L1 of transformer the second end and the respective first ends of vice-side winding L2 to L4 are of the same name
End.
In primary side side, the primary side winding L1 of transformer T first end receives input voltage vin 0.Switching tube M0 leakage
Pole is connected to the primary side winding L1 of the transformer T the second end, and source electrode is grounded via resistance R12.Primary-side-control circuit 110
Drive end DRV provides driving voltage to switching tube M0 grid so that switching tube M0 is periodically turned on and disconnected.
Alternatively, can be connected between the primary side winding L1 of transformer T both ends by resistance R11, electric capacity C11 and
The peak absorbing circuit of diode D11 compositions.Diode D11 anode is connected to primary side winding L1 the second end.Resistance R11 and
Electric capacity C11 is connected in parallel between diode D11 negative electrode and primary side winding L1 first end.In the switching tube M0 disconnection phase
Between, diode D11 and resistance R11 play a part of clamp circuit, so as to prevent switching tube M0 from being damaged due to overvoltage.
In secondary side, the vice-side winding L2 and L3 of the transformer T are used for energy transmission, vice-side winding L4 be used to power and
Signal feeds back.
The vice-side winding L2 of transformer T first end connection diode D1 anode, the second end ground connection.In diode
Electric capacity C1 is connected between D1 negative electrode and ground, so as to produce output voltage at electric capacity C1 both ends, as the second converter 200
Input voltage vin 1.
The vice-side winding L3 of transformer T first end connection diode D2 anode, the second end ground connection.In diode
Electric capacity C2 is connected between D2 negative electrode and ground, so as to produce output voltage at electric capacity C2 both ends, as the 3rd converter 300
Input voltage vin 2.
The vice-side winding L4 of transformer T first end is connected to diode D12 anode.In diode D12 the moon
Electric capacity C12 is connected between pole and ground, so as to produce the supply voltage Vcc1 of primary-side-control circuit at electric capacity C12 both ends.In addition,
The potential-divider network being made up of resistance R13 and R14 is connected between vice-side winding L4 first end and the second end, and in resistance
R13 and R14 intermediate node produces zero passage detection (ZCD) signal.
When switching tube M0 is turned on, transformer T primary side winding L1 bears positive voltage Vin0, and inductive current is started from scratch line
Property rise.When the electric current reaches control voltage, switching tube M0 shut-offs.
When switching tube M0 is turned off, secondary side diode D1 afterflows are equivalent to bear negative voltage to vice-side winding.Now primary side electricity
Inducing current linear decline.In the case where being continuously turned on (CCM) pattern, inductive current does not reduce also when reaching 0, and switching tube M0 is led again
It is logical.Under discontinuous conduction mode (DCM) pattern, until inductive current, to 0, switching tube M0 is just turned on again.In quasi-resonance mould
Formula, switching tube M0 are just turned on again in the lowest point of its source-drain voltage waveform.
At work, primary-side-control circuit 110 produces expected frequency and the drive signal of dutycycle, controlling switch pipe M0 weeks
Turn on and disconnect to phase property, to maintain output voltage and/or output current substantially constant.
In addition, in secondary side, resistance R1 and R2 are connected in series between input voltage vin 2 and ground.In resistance R1 and R2
Intermediate node, obtain the voltage feedback signal FB for characterizing input voltage vin 2.Further, resistance R1, R2, a reference source U2
Feedback control loop is formed with optocoupler U3.
A reference source U2 is, for example, can be with commercially-available model TL431 a reference source.Produced according to voltage feedback signal FB
Raw corresponding output voltage, signal is precisely compensated for so as to drive optocoupler U3 to produce.The thermal compensation signal is provided to primary-side-control electricity
The compensating end COMPV on road 110.
Primary-side-control circuit 110 is according to the feedback signal of the voltage Vin2 from vice-side winding L3 and from vice-side winding L4
Zero passage detection Signal-controlled switch pipe M0 conducting and disconnection so that voltage Vin2 meets power reguirements.First conversion
The proportional relation of two output voltage Vin1 and Vin2 of device 100.Select vice-side winding L2 and the L3 number of turn so that in voltage
While Vin2 meets power reguirements, voltage Vin can also meet power reguirements.
Second converter 200 receives input voltage vin 1, and in the low pass of output end connection inductance L1 and Cout1 composition
Filter network.Electric capacity Cout1 is also used as output capacitance, output voltage Vout is provided at its both ends, for main board power supply.
The inside of second converter 200 includes switching tube and continued flow tube, the group together with the inductance L1 and electric capacity Cout1 of outside
Into BUCK topological structures.Switching tube is periodically turned on and disconnected in the control of pwm signal, to maintain output voltage Vout bases
This is constant.
3rd converter 300 receives input voltage vin 2, and in input series inductance L2, connects and export in output end
Electric capacity Cout2.Output voltage Vled is provided at electric capacity Cout2 both ends, is powered for backlight.
The inside of 3rd converter 300 includes switching tube and continued flow tube, the group together with the inductance L2 and electric capacity Cout2 of outside
Into BOOST topological structures.Switching tube is periodically turned on and disconnected in the control of pwm signal, to maintain output voltage Vout
Substantially constant.
In Fig. 1, backlight is shown as LED string.Series-connected switches pipe M1 and sampling between LED string and ground
Resistance Rs.Sampling resistor Rs provides current feedback signal to the 3rd converter, to maintain constant output current so that LED
The brightness constancy gone here and there when lighting.Switching tube is periodically turned on and disconnected in the control of pwm signal, by changing LED
Lighting for string flows through the average current of LED string with the fall time to change, with the backlight illumination needed for obtaining.
The above-mentioned display panel according to prior art is on the basis of the first converter provides two output voltage, using the
Two converters are depressured to provide main board power supply voltage, and use the 3rd converter boost to provide backlight supply voltage.So
And the converter of cascade reduces the conversion efficiency of power supply.
In addition, the second converter and the 3rd converter use respective inductance and diode, and make in the feedback loop
With additional a reference source, the increase with manufacturing cost is accumulated so as to the PCB surface for causing circuit occupancy more.
Fig. 2 is the schematic block diagram according to the Switching Power Supply for display panel of embodiments of the invention.This is used to show
Showing the Switching Power Supply of panel includes two converters, wherein the first converter be used for the second converter provide input voltage and
Directly powered for backlight, input voltage is further transformed to main board power supply voltage by the second converter.
First converter 100 includes the first output end OUT1, for providing voltage Vin1, the second output end OUT2, is used for
Voltage Vin2, and compensating end COMPV are provided, for receiving thermal compensation signal from feedback control loop.The first of first converter 100 is defeated
Go out to hold OUT1 to provide input voltage for the second converter 200, the second output end OUT2 directly powers for backlight.Adopt in fig. 2
Other aspects of circuit structure in first converter 100 are identical with the first converter 100 shown in Fig. 1, therefore do not go to live in the household of one's in-laws on getting married
State the details of the first converter 100.
Second converter 200 receives input voltage vin 1, and in the low pass of output end connection inductance L1 and Cout1 composition
Filter network.Electric capacity Cout1 is also used as output capacitance, output voltage Vout is provided at its both ends, for main board power supply.
The inside of second converter 200 includes switching tube and continued flow tube, the group together with the inductance L1 and electric capacity Cout1 of outside
Into BUCK topological structures.Switching tube is periodically turned on and disconnected in the control of pwm signal, to maintain output voltage Vout bases
This is constant.
Resistance R1 and R2 are connected in series between input voltage vin 1 and ground.In resistance R1 and R2 intermediate node, obtain
For characterizing the voltage feedback signal FB1 of input voltage vin 1.Voltage control module 500 is used for voltage feedback signal
FB1 and the first reference signal REF1 carries out error calculation, and generates the first error compensating signal COMP1.
Sampling resistor Rs is connected between LED string and ground.Sampling resistor Rs provides the electricity that LED string is flowed through for characterizing
Flow ILEDCurrent feedback signal ISEN.Current control module 600 is used to believe current feedback signal ISEN and the second benchmark
Number REF2 carries out error calculation, and generates the first error compensating signal COMP2.
As shown in Fig. 2 diode D3 anode is connected to voltage control module 500, diode D4 anode is connected to electricity
Flow control module 600, and diode D3 and D4 negative electrode are connected to common node.Diode D3 and D4 form selection circuit,
A selection larger in first error compensating signal COMP1 and the second error compensating signal COMP2 is supplied to buffer B2
Input.Buffer B2 produces the 3rd error compensating signal COMP3, and its output end is connected to the compensation of the first converter 100
Hold COMPV.
3rd error compensating signal COMP3 can pass through the primary-side-control electricity that an optocoupler is transferred to the first converter 100
In road 110.
Voltage Vin1 is characterized in the 3rd error compensating signal COMP3 that the compensating end COMPV of the first converter 100 is received
When, primary-side-control circuit 110 is controlled by original according to voltage feedback signal FB1 and the first reference signal REF1 controlling switch pipe M0
While the energy of secondary is transferred to, so as to maintain Vin1 to stabilize to the value of setting.Connect in the compensating end COMPV of the first converter 100
The 3rd error compensating signal COMP3 received characterizes the electric current I for flowing through LED stringLEDWhen, primary-side-control circuit 110 is anti-according to electric current
The constant I of electric current of LED string is flowed through in feedback signal ISEN and the second reference signal REF2, controlLEDFor the value of setting, wherein, second
Reference signal REF2 is set according to the setting value and Rs value.
Include being connected between LED string and sampling resistor Rs according to the Switching Power Supply for display panel of the embodiment
Switching tube M1, and for providing drive signal IDRV light-adjusting module 800 to switching tube M1.In simulation dims, light modulation
Module 800 for example provides the second reference signal REF2 in current control module 600, and by changing the second reference signal REF2
Size, so as to change the first converter output terminal OUT2 output voltage Vin2, so as to change the electric current for flowing through LED string
ILED, to obtain required backlight illumination.In PWM light modulations, light-adjusting module 800 for example provides PWM driving letters to switching tube M1
Number, by changing the lighting with the fall time to change the brightness of LED string of LED string.
Switching tube M1 is the transistor for being used as power switch in this area, e.g. selected from field-effect transistor and bipolar crystalline substance
One kind in body pipe.Switching tube M1 is not limited to known power switch, can also include the power transistor of exploitation in the future.
Only needed to use two converters according to the Switching Power Supply for display panel of the embodiment.It can not only remove
Such as the 3rd converter of BOOST topological structures, and the peripheral electron device such as corresponding inductance can be removed.Due to removing the
Three converters, LED string is directly driven, therefore the conversion efficiency of power supply can be improved.Due to removing some electronic devices, therefore
PCB surface product and the cost shared by power supply can be reduced.
Fig. 3 is the schematic block diagram according to the power source drive device for display panel of embodiments of the invention.The electricity
Source drive device includes the second converter, voltage feedback loop and the current feedback loop and light-adjusting module shown in Fig. 2.Voltage
Feedback control loop includes voltage control module 500, and current feedback loop includes current control module 600.
Second converter 200 receives input voltage vin 1, and in the low of output end vo connection inductance L1 and Cout1 composition
Pass filter network.Electric capacity Cout1 is also used as output capacitance, output voltage Vout is provided at its both ends, for main board power supply.
Second converter 200 includes switching signal generation circuit 210.It is electric from main board power supply for example with resistance pressure-dividing network
Pressure obtains voltage feedback signal FB2.In the second converter 200, comparator cp1 is by voltage feedback signal FB2 and the 3rd benchmark
Signal REF3 compares, and obtains error signal.Switching signal generation circuit 210 is according to error signal output pwm signal, via slow
Rush device B5 and drive signal for switching tube M21 is provided, the drive signal for continued flow tube M22 is provided via buffer B6.Open
Pipe M21 periodically conducting and disconnection is closed, to maintain output voltage Vout1 as desired main board power supply voltage.
As described above, resistance R1 and R2 are connected in series between input voltage vin 1 and ground.In resistance R1 and R2 centre
Node, obtain the voltage feedback signal FB1 of the input voltage vin 1 for characterizing the second converter 200.Voltage control module 500
For for voltage feedback signal FB1 and the first reference signal REF1 to be carried out into error calculation, and generation the first error compensation letter
Number COMP1.
Sampling resistor Rs is connected between LED string and ground.Sampling resistor Rs provides the electricity that LED string is flowed through for characterizing
Flow ILEDCurrent feedback signal ISEN.Current control module 600 is used to believe current feedback signal ISEN and the second benchmark
Number REF2 carries out error calculation, and generates the second error compensating signal COMP2.
In the embodiment shown in fig. 3, diode D3 and D4 compositions selection circuit.Selection circuit believes the first error compensation
Larger one input for selecting to be supplied to buffer B2 in number COMP1 and the second error compensating signal COMP2.Buffer B2
Produce the 3rd error compensating signal COMP3.In embodiment alternatively, selection circuit can be formed by comparator and switch.
Comparator compares the first error compensating signal COMP1 and the second error compensating signal COMP2, and according to comparative result control
The action of switch is made, so as to select larger one in the first error compensating signal COMP1 and the second error compensating signal COMP2
It is individual.
Preferably, the power source drive device also includes light-adjusting module 800.Light-adjusting module 800 further comprises light-modulating mode
Detect circuit 810, analog light-adjusting circuit 820, PWM light adjusting circuits 830, phase inverter B3, buffer B1 and B4.
Light-modulating mode detection circuit 810 receives the dim signal Vdim of outside, and judges that external dimmer signal Vdim is
Simulate dim signal or PWM dim signals.It can be pwm signal to simulate dim signal or PWM dim signals.According to judgement
As a result, light-modulating mode detection circuit 810 starts one in analog light-adjusting circuit 820 and PWM light adjusting circuits 830.Alternatively, may be used
To provide simulation dim signal to analog light-adjusting circuit 820 simultaneously, PWM dim signals are provided to PWM light adjusting circuits 830, so as to
Start analog light-adjusting circuit 820 and PWM light adjusting circuits 830 simultaneously.In this case, light-modulating mode detection circuit 810 can save
Slightly.Therefore, the application provide power source drive device can carry out simulate light modulation or PWM light modulation or the two at the same carry out mixing tune
Light.
When external dimmer signal Vdim is simulates dim signal, analog light-adjusting circuit starts, and is believed according to external dimmer
Number Vdim exports a reference signal Qa and the second reference signal REF2, reference signal Qa is used as into current control module 600
Size with external dimmer signal Vdim change in duty cycle, both cause the second reference signal REF2 with simulation dim signal become
Change, the electric current ILED of LED string is flowed through so as to change the first converter output terminal OUT2 output voltage Vin2 and change, from
And the backlight illumination needed for obtaining.
When external dimmer signal Vdim is PWM dim signals, PWM light adjusting circuits 830 start, and are believed according to external dimmer
Number Vdim exports the dimming control signal PWMC synchronous with PWM dim signals to switching tube M1, and the signal can be via buffer B1
Output switch pipe M1 drive signal IDRV, to control M1 turn-on and turn-off.Between the high period of PWMC signals, switching tube
M1 is turned on.Between the low period of PWMC signals, switching tube M1 disconnects.So as to by changing when lighting and extinguishing of LED string
Between ratio come the brightness that changes.
In addition, in PWM dimming process, in PWM dimming control signals PWMC between low period, the power supply of LED string
Loop is disconnected, and is zero equivalent to the electric current of LED strip is flowed through, but LED electric current is now flowed through without regulation, only need to pass through voltage control
Molding block 500 stablizes the first output voltage of the first converter 100, therefore needs to make current control module 600 during this period
Do not work, only voltage control module 500 works.In PWM dimming control signals PWMC, it is necessary to adjust stream between high period
Based on the electric current for crossing LED, therefore need to make current control module 600 work during this period, and the not work of voltage control module 500
Make.To realize this function, voltage control module 500 and current control module can be generated according to PWM dimming control signals PWMC
600 enable signal, such as PWM dimming control signal PWMC can be received respectively by phase inverter B3 and buffer B4, with respectively
Generate the enable signal S/H1 of the voltage control module 500 and signal S/H2 of current control module 600.In PWM brightness adjustment controls
Between signal PWMC high period, the enable signal S/H1 of phase inverter B3 outputs is invalid, the enable signal S/ of buffer B4 outputs
H2 is effective, and only current control module 600 works and exports the second thermal compensation signal COMP2.Correspondingly, the 3rd thermal compensation signal
COMP3 is corresponding with current feedback signal ISEN, and provides to the compensating end COMPV of the first converter 100.As a result,
Between the high period of two pwm signals, the first converter 100 mainly maintains suitable output voltage Vin2, to meet for backlight
Power supply and the demand of light modulation.
Between PWM dimming control signals PWMC low period, the enable signal S/H1 of phase inverter B3 outputs is effective, buffering
The enable signal S/H2 of device B4 outputs is invalid, and only voltage control module 500 works and exports the first thermal compensation signal COMP1.Phase
Ying Di, the 3rd thermal compensation signal COMP3 is corresponding with voltage feedback signal FB1, and provides to the compensating end of the first converter 100
COMPV.As a result, between the low period of the second pwm signal, the first converter 100 mainly maintains suitable output voltage Vin1,
With meet be for main board power supply the needs of.
Preferably, the power source drive device also includes I2C bus interface circuits 710.I2C bus interface circuits 710 are from outside
Clock signal SCL and data-signal SDA is received, and produces a reference signal, when electric without simulation light modulation in power source drive device
When road or not actuated analog light-adjusting circuit, the second reference signal REF2 is used as using the reference signal.I2C bus interface circuits
710 provide the second reference signal REF2 to current control circuit 600, are carried on the back so as to easily be changed according to external control signal
Light source power supply voltage.
According to the light modulation of power source drive device compatible analog and PWM light modulations for display panel of the embodiment.Adjusted in PWM
Light time, the enable signal of voltage control module 500 and current control module 600 is produced using PWM dim signals so that first becomes
Parallel operation 100 can take into account the demand of the input voltage of the second converter 200 and the driving of LED string and light modulation demand, and enter
One step improves the conversion efficiency of power supply.I is included due to using2C bus interface circuits 710, therefore can setting with peripheral circuits
Meter.Second converter, voltage and current feedback control loop and light-adjusting module can be integrated in a chip, so as to enter
One step reduces PCB surface product and the cost shared by power supply.
Fig. 4 is that the voltage control module 500 used in the power source drive device for display panel of the present invention is shown
Meaning property circuit diagram.Fig. 5 is the working waveform figure of the voltage control module shown in Fig. 4.It is adaptive that voltage control module 500 includes dynamic
Answer reference signal generation circuit 510, operational amplifier EA1, sampling hold circuit 520 and compensation circuit 530.
Dynamic self-adapting reference signal generation circuit 510 includes electric capacity C51, single-pole double-throw switch (SPDT) S51 and by resistance
The potential-divider network of R51 and R52 compositions.When dim signal Vdim is PWM dim signals, single-pole double-throw switch (SPDT) S51 dims in PWM
Switch under the control of signal.Between the high period of PWM dim signals, switch S51 switches to B so that becomes for characterizing second
The voltage feedback signal FB1 of the input voltage vin 1 of parallel operation 200 charges to electric capacity C51.In the low period of PWM dim signals
Between, switch S51 switches to A so that the voltage on electric capacity C51 is supplied to operation amplifier after partial pressure shape as reference signal REF1
Device EA1 in-phase input end.Operational amplifier EA1 inverting input receiving voltage feedback signal FB1.Due to reference signal
REF1 depends on voltage feedback signal FB1, thus reference signal REF1 is adjusted according to voltage feedback signal FB1 automatic dynamics.
Oscillogram as shown in Figure 5, C51 voltage more and more higher, then REF1 more and more highers so that input voltage vin can be stablized quickly.
Thus, the voltage control module 500 can be with the job stability of the first converter 100.
Sampling hold circuit 520 includes switch S52.Switch S52 first end is connected to operational amplifier EA1 output
End, the second end is connected to compensation circuit 530.Compensation circuit includes the electricity being connected in series between switch S52 the second end and ground
Hinder R53 and electric capacity C52.The first offset voltage COMP1 is produced at switch S52 the second end.When dim signal Vdim dims for PWM
During signal, switch S52 switches under the control of PWM dim signals.When PWM dim signals are high level, switch S52 disconnects,
So as to keep voltage at switch S52 the second end.When PWM dim signals are low level, switch S52 closures, the of S52 is switched
Voltage on two ends need not start from scratch change, but change since previous retention value.Thus, the voltage control module
500 can improve dynamic responding speed.
Further, since the voltage feedback signal FB1 of the input voltage vin 1 for characterizing the second converter 200 is as voltage
A reference source, therefore such as TL431 etc outside reference source need not be used, further reduce peripheral electron device.
Fig. 6 is that the reference signal generation module used in the power source drive device for display panel of the present invention shows
Meaning property circuit diagram.A part of the reference signal generation module 220 as the second converter 200, for producing the 3rd reference signal
REF3.Reference signal generation module 220 includes the first reference signal source REFa and the second reference signal source REFb, respectively via opening
Close S21 and S22 and be connected to common node.The 3rd reference signal REF3 is produced at common node.First reference signal source REFa
Reference signal be more than the second reference signal source REFb reference signal.
The load condition of the second converter 200 is detected using additional pattern detection circuit, to obtain load condition letter
Number.Pattern detection circuit can be located at the outside of power source drive device as shown in Figure 3, and via I2C bus interface circuits
710 are provided to the second converter 200 inside power source drive device.Alternatively, pattern detection circuit can be located at as shown in Figure 3
Power source drive device inside.
S21 and S22 is switched to be controlled by load status signal and its non-signal respectively.When load status signal indicates non-underloading
When, switch S21 conductings, S22 disconnects so that the first reference signal source REFa provides the 3rd reference signal REF3.Work as load condition
During signal designation underloading, switch S21 disconnects, S22 conductings so that the second reference signal source REFb provides the 3rd reference signal
REF3。
When the second converter 200 enters light condition, because the second reference signal source REFb provides numerical value less the
Three reference signal REF3, so as to improve the conversion efficiency of the second converter 200.
According to embodiments of the invention as described above, these embodiments do not have all details of detailed descriptionthe, not yet
It is only described specific embodiment to limit the invention.Obviously, as described above, can make many modifications and variations.This explanation
Book is chosen and specifically describes these embodiments, is in order to preferably explain the principle and practical application of the present invention, so that affiliated
Technical field technical staff can be used using modification of the invention and on the basis of the present invention well.The present invention is only by right
The limitation of claim and its four corner and equivalent.
Claims (13)
1. a kind of Switching Power Supply for display panel, including：
First converter, for producing the first output voltage and the second output voltage, the second output voltage from the first input voltage
The output current of backlight, the power supply for backlight are flowed through for producing；
Second converter, for using the first output voltage as input voltage, and produce the 3rd output voltage；
Voltage feedback loop, the first voltage feedback signal of the first output voltage is characterized for obtaining, and first voltage is anti-
Feedback signal is compared with the first reference signal, to obtain the first thermal compensation signal；
Current feedback loop, characterizes the current feedback signal of the output current for obtaining, and by current feedback signal with
Second reference signal compares, to obtain the second thermal compensation signal；
Selection circuit, for selecting the conduct the 3rd that numerical value is larger in the first thermal compensation signal and the second thermal compensation signal to compensate letter
Number；
Light-adjusting module, the light-adjusting module include at least one in analog light-adjusting circuit and PWM light adjusting circuits, the simulation tune
Optical circuit and the PWM light adjusting circuits adjust the brightness of backlight according to simulation dim signal and PWM dim signals respectively；And
Light-modulating mode detects circuit, for judging that external dimmer signal is simulation dim signal or PWM dim signals, if outside
Portion's dim signal is simulation dim signal, then provides external dimmer signal to the analog light-adjusting circuit, if external dimmer
Signal is PWM dim signals, then provides external dimmer signal to the PWM light adjusting circuits,
Wherein, the action of first switch pipe of first converter in the 3rd the first converter of compensation signal control is obtained with producing
Obtain first output voltage of constant and/or the output current.
2. Switching Power Supply according to claim 1, wherein, the first converter is inverse excitation type converter, and the second converter is
BUCK converters.
3. Switching Power Supply according to claim 1, wherein, the selection circuit includes the first diode and the two or two pole
Pipe, wherein the first diode and respective anode of the second diode is respectively connecting to voltage feedback loop and current feedback loop is each
From output end, the negative electrode of the first diode and the second diode is commonly connected to common node, and the common node is connected to
The compensating end of first converter.
4. Switching Power Supply according to claim 1, wherein, the analog light-adjusting circuit provides second reference signal,
The output current of the converter of numerical value first by changing second reference signal is relative with the second reference signal
Should, so as to realize the light modulation of backlight.
5. Switching Power Supply according to claim 1, in addition to the second switch pipe source-series with backlight, wherein the PWM
Light adjusting circuit realizes the light modulation of backlight by periodically turning on and disconnecting second switch pipe.
6. Switching Power Supply according to claim 1, wherein, the PWM light adjusting circuits produce light modulation according to PWM dim signals
Control signal, the PWM dim signals are synchronous with the dimming control signal.
7. Switching Power Supply according to claim 6, wherein, enable signal is produced according to the dimming control signal, so as to
Current feedback loop is enabled between the high period of dimming control signal and disables voltage feedback loop, in dimming control signal
Low period between disable current feedback loop and enabled voltage feedback loop.
8. Switching Power Supply according to claim 1, wherein, the voltage feedback loop includes voltage control module, described
Voltage control module compares first voltage feedback signal with the first reference signal, to obtain the first thermal compensation signal.
9. Switching Power Supply according to claim 8, wherein, the voltage control module includes：
First reference signal generation circuit, for producing the first reference signal；
Comparator, for first voltage feedback signal to be compared with the first reference signal；
Sampling hold circuit, for receiving the comparison signal of comparator output, and obtained between the low period of PWM dim signals
Comparison signal is taken, and comparison signal is kept between the high period of PWM dim signals；And
Compensation circuit, for compensating comparison signal to produce the first thermal compensation signal,
Wherein, the first reference signal generation circuit is according to the number of first voltage feedback signal the first reference signal of dynamic regulation
Value.
10. Switching Power Supply according to claim 9, wherein, the reference signal holding circuit includes：
First electric capacity；
The potential-divider network of first resistor and second resistance composition；And
First switch,
Wherein first voltage feedback signal is supplied to the first electricity by first switch between the high period of the PWM dim signals
Hold, the voltage on the first electric capacity be supplied to potential-divider network between the low period of the PWM dim signals,
The first reference signal is obtained in the intermediate node of first resistor and second resistance.
11. Switching Power Supply according to claim 2, wherein, second converter includes：
3rd switching tube, be connected to for receive the first output voltage input and for connect external inductors output end it
Between；
Continued flow tube, it is connected between output end and ground；
Comparator, for the second voltage feedback signal for characterizing the 3rd output voltage to be compared with the 3rd reference signal, with production
Raw error signal；And
Switching signal generation circuit, for controlling the conducting and disconnection of the 3rd switching tube and continued flow tube according to error signal, with dimension
Hold the 3rd output voltage constant.
12. Switching Power Supply according to claim 11, in addition to the second reference signal generation circuit, the production of the second reference signal
Raw circuit includes the first reference signal source and the second reference signal source, and the reference signal that the first reference signal source provides is more than second
The reference signal that reference signal source provides, the second reference signal generation circuit select the first reference signal source to provide the in heavy duty
Three reference signals, the second reference signal source is selected to provide the 3rd reference signal in underloading.
13. Switching Power Supply according to claim 1, wherein by the second converter, voltage feedback loop, current feedback ring
Road, selection circuit and light-adjusting module are integrated in a chip.
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| CN201410852246.1A CN104467424B (en) | 2014-12-31 | 2014-12-31 | Switching Power Supply for display panel |
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| CN201410852246.1A CN104467424B (en) | 2014-12-31 | 2014-12-31 | Switching Power Supply for display panel |
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| CN104467424B true CN104467424B (en) | 2018-04-10 |
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| CN106849672A (en) * | 2017-03-14 | 2017-06-13 | 深圳市华星光电技术有限公司 | Dual output flyback voltage converting circuit and display device |
| CN108259706B (en) * | 2018-04-12 | 2020-10-30 | 京东方科技集团股份有限公司 | Video signal adjusting device and adjusting method |
| WO2020181422A1 (en) * | 2019-03-08 | 2020-09-17 | 深圳市柔宇科技有限公司 | Panel assembly and electronic device |
| CN114038395B (en) * | 2021-07-26 | 2022-12-27 | 重庆康佳光电技术研究院有限公司 | Power supply driving circuit, driving method and display device |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101960922A (en) * | 2008-03-24 | 2011-01-26 | 东芝照明技术株式会社 | Power supply units and lighting fixtures |
| CN103281823A (en) * | 2013-05-08 | 2013-09-04 | 矽力杰半导体技术(杭州)有限公司 | Constant current and constant voltage output multi-channel power supply system |
| CN103476184A (en) * | 2013-09-26 | 2013-12-25 | 矽力杰半导体技术(杭州)有限公司 | Power system with multiplexed output |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101960922A (en) * | 2008-03-24 | 2011-01-26 | 东芝照明技术株式会社 | Power supply units and lighting fixtures |
| CN103281823A (en) * | 2013-05-08 | 2013-09-04 | 矽力杰半导体技术(杭州)有限公司 | Constant current and constant voltage output multi-channel power supply system |
| CN103476184A (en) * | 2013-09-26 | 2013-12-25 | 矽力杰半导体技术(杭州)有限公司 | Power system with multiplexed output |
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