CN105163431B - Drive circuit, illuminating circuit and mobile terminal - Google Patents
Drive circuit, illuminating circuit and mobile terminal Download PDFInfo
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- CN105163431B CN105163431B CN201510520232.4A CN201510520232A CN105163431B CN 105163431 B CN105163431 B CN 105163431B CN 201510520232 A CN201510520232 A CN 201510520232A CN 105163431 B CN105163431 B CN 105163431B
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Abstract
A kind of drive circuit, illuminating circuit and mobile terminal, drive circuit include：Reference cell, is adapted to provide for the first reference voltage and the second reference voltage；Booster circuit, suitable for being provided after input voltage is boosted according to feedback signal to the input of light emitting diode group；Error amplifier, the output end of the negative-phase input connecting luminous diode group of error amplifier, the normal phase input end of error amplifier is suitable to the second reference voltage of input, and the output end of error amplifier is suitable to output feedback signal；Dimming control unit, suitable for dimming electric current on the basis of the first reference voltage is changed according to dimming control signal；The first input end of constant-current control unit is suitable to receive benchmark light modulation electric current, the output end of second output end connecting luminous diode group of constant-current control unit is simultaneously adapted to provide for driving current, the first output end and the second output end of constant-current control unit are grounded, and the current value of driving current and benchmark light modulation electric current is proportional.
Description
Technical field
The present invention relates to electronic circuit field, more particularly to a kind of drive circuit, illuminating circuit and mobile terminal.
Background technology
The mobile phone in intelligent epoch be not only voice and simple short message service (SMS) data communications equipment, now
So as the superpower personal mobile multi-media terminal of One function.Inductance boost type backlight drive is due to light emitting diode
(LED) currents match degree it is good, with the interface links of screen it is few the advantages of and large-sized smart mobile phone is done by handset designers' choosing
Backlight drive.
As shown in figure 1, existing series connection backlight drive circuit has been internally integrated power MOS pipe MN, boosted using switch DC
Framework (Boost boostings framework), is boosted, plurality of LEDs series connection can ensure LED with reference to inductance L and Schottky diode D1
The uniformity of electric current.
Using peak-current mode control (Current-Mode Control) more than BOOST.Peak-current mode controls mould
Formula is the control method that a kind of fixed clock is opened, peak point current is turned off.Feedback end FB comes in by error amplifier, Ran Houyu
The module such as electric current and voltage detecting, slope equalizer 11 and Boost control circuits 12 constitutes Boost controls together.Loop is mended
Repay network 13 and may insure that control loop is stable under various applicable cases.Connect backlight drive circuit can with it is integrated its
The circuit module of his correlation, such as enables control, overheat protector, soft start, base modules.
Feedback end FB is usually set in full brightness be 200mV, 300mV or other values, continues below by taking 200mV as an example
Explanation.The current value for flowing through LED is equal to feedback end FB magnitudes of voltage over the ground divided by feedback resistance RSET resistance.Such as a string
LED wishes that its high-high brightness is 20mA, then feedback resistance RSET takes 10ohm.Assuming that PWM or a line dimming control unit 14 are entered
The line of row one takes 32 contrast light when dimming, and feedback end FB minimum voltages can be transferred to 5mV.PWM or a line dimming control unit 14 are entered
When row PWM is dimmed, feedback end FB voltages are equal to 200mV*D, and D is the dutycycle of light modulation, and feedback end FB minimum voltages can be transferred to
Several mV.
However, when feedback end FB voltages it is low arrive several mV to tens mV when, it is easy for being influenceed by grounding interference.
Because LED electric current is equal to the voltage divided by resistance value at feedback resistance RSET two ends, then, if on the one hand pcb board layout is not
Properly, feedback resistance RSET reference ground off-chip piece farther out, or during system work disturbs larger, or both the original combined
Cause, this reference ground is no longer preferably equal with the ground of chip；And during the feedback loop control feedback end FB voltages of chip, be
Using the ground of chip as reference.The electric current that so may result in LED deviate from setting value.Once this current deviation is time-varying
, the intensity of such as system interference is different at different time points, then may result in LED brightness at different time points
It is different.So from the point of view of terminal user, he will intuitively feel flicker.Especially brightness settings be than relatively low, than
When such as brightness settings are 10% or less than 5%, the ratio that the caused deviation of interference accounts for total current is bigger, then sudden strain of a muscle is more easily seen
It is bright.
Further, since the feedback control loop of chip internal is also required to feedback end FB voltages to do feedback control, then work as feedback
When end FB voltages are adjusted to very low (several mV), low-voltage disposal ability and antijamming capability to chip internal it is also proposed
Higher requirement.If dealt with improperly, the electric current for also resulting in LED changes with the time, and same causes flicker.
The content of the invention
The problem of present invention is solved is that existing drive circuit easily makes light emitting diode produce flicker.
To solve the above problems, the present invention provides a kind of drive circuit, for connecting luminous diode group, described luminous two
Pole pipe group includes the light emitting diode of one or more series connection, including：
Reference cell, is adapted to provide for the first reference voltage and the second reference voltage；
Booster circuit, suitable for being provided after input voltage is boosted according to feedback signal to the input of the light emitting diode group
End；
Error amplifier, the negative-phase input of the error amplifier connects the output end of the light emitting diode group, institute
The normal phase input end for stating error amplifier is suitable to input second reference voltage, and the output end of the error amplifier is suitable for defeated
Go out the feedback signal；
Dimming control unit, suitable for dimming electricity on the basis of first reference voltage is changed according to dimming control signal
Stream；
Constant-current control unit, including first input end, the second input, the first output end and the second output end, the perseverance
The first input end of flow control unit is suitable to receive the benchmark light modulation electric current, and the second output end of the constant-current control unit connects
Connect the output end of the light emitting diode group and be adapted to provide for driving current, the first output end of the constant-current control unit and
Two output ends are grounded, and the current value of the driving current and benchmark light modulation electric current is proportional.
Optionally, the drive circuit also includes：First NMOS tube；
The grid of drain electrode connection first NMOS tube of first NMOS tube and the output of the light emitting diode group
End, the source ground of first NMOS tube.
Optionally, the drive circuit also includes：First resistor；
First NMOS tube is connected with the first resistor, and the drain electrode of first NMOS tube passes through the first resistor
Connect the grid of first NMOS tube.
Optionally, the drive circuit also includes：Second resistance, the first electric capacity and the second electric capacity；
The first end of the second resistance connects the output end of the error amplifier, and the second end of the second resistance connects
Connect the first end of first electric capacity and the first end of the second electric capacity；
Second end of first electric capacity and the second end of the second electric capacity are grounded.
Optionally, the dimming control unit includes：First operational amplifier, the second NMOS tube, 3rd resistor, current mirror
Circuit, selecting switch and switch control unit, the dimming control signal include the first dimming control signal；
The normal phase input end of first operational amplifier is suitable to input first reference voltage, and first computing is put
The negative-phase input of big device connects the source electrode of second NMOS tube and the first end of 3rd resistor, first operational amplifier
Output end connect the grid of second NMOS tube；
The second end ground connection of the 3rd resistor；
The current mirroring circuit includes：Input, reference current output end and image current output end, the image current
The quantity of output end is identical with the selecting switch quantity, and the input of the current mirroring circuit is suitable to receive the input electricity
Pressure, the reference current output end of the current mirroring circuit connects the drain electrode of second NMOS tube, the mirror of the current mirroring circuit
The first end of image current output end and the selecting switch connects one to one；
Second end of the selecting switch is both connected to together and provides the benchmark light modulation electric current；
The switch control unit is suitable to close one or more selecting switch according to first dimming control signal.
Optionally, the dimming control unit includes：PWM dimming units, the first operational amplifier, the second NMOS tube,
Three resistance, current mirroring circuit, selecting switch and switch control unit, the dimming control signal are believed including the second brightness adjustment control
Number；
The PWM dimming units are suitable to produce PWM adjustment signals according to second dimming control signal, and according to described
PWM adjusts signal and first reference voltage is converted into conversion voltage, magnitude of voltage=Vreg*Duty of the conversion voltage,
Vreg is the magnitude of voltage of first reference voltage, and Duty is the dutycycle that the PWM adjusts signal；
The normal phase input end of first operational amplifier is suitable to input the conversion voltage, first operational amplifier
Negative-phase input connect the source electrode of second NMOS tube and the first end of 3rd resistor, first operational amplifier it is defeated
Go out the grid of end connection second NMOS tube；
The second end ground connection of the 3rd resistor；
The current mirroring circuit includes：Input, reference current output end and image current output end, the image current
The quantity of output end is identical with the selecting switch quantity, and the input of the current mirroring circuit is suitable to receive the input electricity
Pressure, the reference current output end of the current mirroring circuit connects the drain electrode of second NMOS tube, the mirror of the current mirroring circuit
The first end of image current output end and the selecting switch connects one to one；
Second end of the selecting switch is both connected to together and provides the benchmark light modulation electric current；
The switch control unit is suitable to close one or more selecting switch.
Optionally, the dimming control signal also includes the first dimming control signal；
The switch control unit is suitable to close one or more selecting switch according to first dimming control signal.
Optionally, the constant-current control unit also includes：3rd NMOS tube, the 4th NMOS tube, the 5th NMOS tube and second
Operational amplifier；
The grid of drain electrode connection the 4th NMOS tube of 3rd NMOS tube and the first of the constant-current control unit
Input, the grid of the 3rd NMOS tube connects the output end of second operational amplifier, the source of the 3rd NMOS tube
Pole connects the negative-phase input of second operational amplifier and the drain electrode of the 4th NMOS tube；
The source electrode of 4th NMOS tube connects the output end of constant-current control unit first；
The normal phase input end and the current constant control of drain electrode connection second operational amplifier of 5th NMOS tube
Second input of unit, the source electrode of the 5th NMOS tube connects the output end of constant-current control unit second.
Optionally, the booster circuit is using switch DC boosting framework.
The present invention also provides a kind of illuminating circuit, including above-mentioned drive circuit and the light emitting diode group.
The present invention also provides a kind of mobile terminal, including above-mentioned illuminating circuit and display screen, and the display screen is with luminous electricity
Light emitting diode group in road is used as background light source.
Compared with prior art, drive circuit of the invention eliminates the feedback resistance in existing drive circuit, using low
Electric current on pressure drop current constant control, light emitting diode is adjusted by current path, and feedback terminal voltage is constant during brightness regulation, so
The problem of just solving LED flash well.
Brief description of the drawings
Fig. 1 is a kind of structural representation of existing series connection backlight drive circuit；
Fig. 2 is the structural representation of present invention driver circuit；
Fig. 3 is a structural representation of the automatic drop-down unit of the present invention；
Fig. 4 is another structural representation of the automatic drop-down unit of the present invention
Fig. 5 is the structural representation of loop compensation networks of the present invention；
Fig. 6 is a structural representation of dimming control unit of the present invention；
Fig. 7 is another structural representation of dimming control unit of the present invention
Fig. 8 is the structural representation of constant-current control unit of the present invention.
Embodiment
It is understandable to enable the above objects, features and advantages of the present invention to become apparent, below in conjunction with the accompanying drawings to the present invention
Specific embodiment be described in detail.
As shown in Fig. 2 the embodiment of the present invention provides a kind of drive circuit, it is described luminous for connecting luminous diode group 3
Diode group 3 includes the light emitting diode of one or more series connection.
The drive circuit includes：Booster circuit 1, reference cell 21, error amplifier 22, dimming control unit 23 and perseverance
Flow control unit 24.
Booster circuit 1 is suitable to provide to the light emitting diode group after according to feedback signal Vfb, input voltage VIN is boosted
3 input.
Reference cell 21 is adapted to provide for the first reference voltage V ref1 and the second reference voltage V ref2.
The negative-phase input of error amplifier 22 connects the output end of the light emitting diode group 3, the error amplifier
22 normal phase input end is suitable to input the second reference voltage V ref2, and the output end of the error amplifier 22 is suitable to output
The feedback signal Vfb.
Dimming control unit 23 is suitable on the basis of according to dimming control signal SL, the first reference voltage V ref1 is changed
Dim electric current Iref.
Constant-current control unit 24 includes first input end, the second input, the first output end and the second output end.The perseverance
The first input end of flow control unit 24 is suitable to receive the benchmark light modulation electric current Iref, the second of the constant-current control unit 24
Output end connects the output end of the light emitting diode group 3 and is adapted to provide for driving current Id.The constant-current control unit 24
First output end and the second output end are grounded.Wherein, the driving current Id and benchmark light modulation electric current Iref current value into
Ratio.
In the present embodiment, the output end of light emitting diode group 3 is feedback end FB.Feedback end FB voltages are by feedback control loop
Control is equal with the second reference voltage V ref2 magnitudes of voltage, and this voltage is used for meeting the voltage needed for constant-current control unit 24
Drop, when carrying out brightness regulation to light emitting diode group 3, feedback end FB voltages keep constant.Dimming control unit 23 is according to light modulation
Control signal SL adjustment benchmark light modulation electric currents Iref current value, so that the driving current Id that constant-current control unit 24 is provided
Current value changes.
So, when carrying out brightness regulation to light emitting diode group 3 using the drive circuit of the present embodiment, light emitting diode group
Electric current on 3 does not change with feedback end FB voltage changes.Because feedback end FB voltage ratios are higher, interference signal proportion
It is smaller, even and if feedback end FB voltages be varied from, the curent change that it brings is also very small, thus can be with extraordinary
The problem of solving splashette.
In addition, with continued reference to Fig. 1, when carrying out brightness regulation, prior art is that feedback end FB voltages are adjusted to needs
Value, 5% (10mV) of such as maximum voltage.Feedback end FB voltages are by error amplifier and then participate in the control of boost loops.By mistake
There is an imbalance (offset) in poor amplifier, it is the phenomenon certainly existed as caused by the factors such as technique, domain, is
The random imbalance of one approximate normal distribution, that is to say, that two input terminal voltages of error amplifier are not equal, but are had
One random imbalance.
In existing process, by carrying out necessary design to error amplifier, imbalance can be accomplished within several mV,
But when feedback end FB voltages are more and more lower, the shared proportion of imbalance is just increasing.Which results in different chips, its
The discreteness of brightness becomes big.For example when brightness adjustment is 5%, when correspondence feedback end FB voltages are adjusted to 10mV, and error is amplified
The imbalance of device is 5mV, then the output current of different chips may have ± 50% deviation, and in high-high brightness, feedback end
FB voltages are 200mV, and this imbalance only can bring ± 2.5% deviation.
And in the present embodiment, on the one hand, feedback end FB voltages are constant during brightness regulation, and are fixed as 200mV
Or the value of some setting, the proportion shared by the imbalance of error amplifier is smaller；On the other hand, due to the present embodiment use pair
The current constant control of output current, it is unrelated with magnitude of voltage, even if so error amplifier imbalance causes feedback end FB voltages than larger
There is certain discreteness, will not also cause the discrete of electric current.
Therefore, prior art adjusts LED current using feedback end FB voltages and feedback resistance, during brightness regulation, feedback
End FB voltages may be adjusted to very low, then what the problem of easily bringing splashette and different chip chamber electric current discretenesses increased
Problem.And the electric current that the embodiment of the present invention is eliminated on feedback resistance, and light emitting diode is adjusted by current path, brightness
Feedback end FB voltages are constant during regulation, and above-mentioned technical problem is thus solved well.
Each composition structure to the present embodiment drive circuit elaborates below.
The booster circuit 1 of the present embodiment is using switch DC boosting framework.
With continued reference to Fig. 2, booster circuit 1 can include：Inductance L, diode D1, input capacitance CIN, output capacitance
COUT, electric current and voltage detecting, slope equalizer 11, Boost control circuits 12 and power MOS pipe MN.
The first end connection input capacitance CIN of inductance L first end simultaneously is suitable to receive the input voltage VIN.Institute
State inductance L the second end connect anode, electric current and the voltage detecting of the diode D1, the input of slope equalizer 11 and
Power MOS pipe MN drain electrode.The negative electrode connection output capacitance COUT of diode D1 first end and the light emitting diode
The input of group 3.
It is first defeated that electric current and voltage detecting, the output end of slope equalizer 11 connect the Boost controls circuit 12
Enter end.Second input of the Boost controls circuit 12 connects the output end of the error amplifier 22.The Boost controls
The output end connection power MOS pipe MN of circuit 12 processed grid.The second end of the input capacitance CIN, output capacitance COUT
Second end and power MOS pipe MN source grounding.
The booster circuit 1 that the present embodiment is used can those skilled in the art identical with the prior art construction shown in Fig. 1
It could be aware that electric current and voltage detecting, slope equalizer 11, Boost control the specific implementation of circuit 12, herein no longer
Repeat.
Feedback end FB voltages are fixed during brightness regulation in the present embodiment, it be fixed on all the time one it is of a relatively high
Value, so that the proportion that the imbalance of error amplifier 22 is accounted for is smaller；And because output is current constant control, even if there is certain mistake
Adjust, output current is also smaller with the change of voltage.So the error amplifier 22 of the present embodiment can reduce the requirement to mismatch.
For CMOS technology, want to reach that the mismatch of several mV ranks needs very big chip area, the current precision of constant-current source does not take
Certainly in the size of feedback voltage, feedback voltage can be allowed to have several mV even tens mV mismatch, so reducing to by mistake
The mismatch requirement of poor amplifier.
Traded off it is well known that error amplifier exists in terms of gain, bandwidth, area and mismatch, the present embodiment is to losing
The requirement matched somebody with somebody is reduced, it is possible to loop control is more inclined in the design of error amplifier or reduces chip area, from
And error amplifier has also been optimized.
The drive circuit of the present embodiment can also include：Automatic drop-down unit 25.
As shown in figure 3, the automatic drop-down unit 25 can include：First NMOS tube MN1.The first NMOS tube MN1
Drain electrode connection the first NMOS tube MN1 grid and the output end of the light emitting diode group 3, first NMOS tube
MN1 source ground.
As shown in figure 4, the automatic drop-down unit 25 can also include：First resistor R1.The first NMOS tube MN1 with
The first resistor R1 series connection, the drain electrode of the first NMOS tube MN1 passes through first resistor R1 connections the first NMOS
Pipe MN1 grid.That is the drain electrode connection first resistor R1 of the first NMOS tube MN1 first end, the second of the first resistor R1
End connection the first NMOS tube MN1 grid and the output end of the light emitting diode group 3, the first NMOS tube MN1 source electrode
Ground connection.
During drive circuit normal work, feedback end FB is stable in 200mV, is not reaching to the first NMOS tube MN1 threshold value electricity
Pressure, so the first NMOS tube MN1 is closed, does not work；And drive circuit is when being stopped, if having electricity on output capacitance COUT
Lotus causes feedback end FB voltages to raise, once feedback end FB voltages are higher than the first NMOS tube MN1 threshold value (such as 0.7V), first
NMOS tube MN1 will be turned on, so as to automatically output voltage VO UT (input of light emitting diode group 3) release.First
Resistance R1 can adjust the ability of charge discharging resisting.First NMOS tube MN1 and first resistor R1 size may decide that releasability
Size.
The drive circuit of the present embodiment can also include：Loop compensation networks 26.
As shown in figure 5, the loop compensation networks 26 can include：Second resistance R2, the first electric capacity C1 and the second electric capacity
C2。
The first end of the second resistance R2 connects the output end of the error amplifier 22, and the of the second resistance R2
Two ends connect the first end of the first electric capacity C1 and the second electric capacity C2 first end.The second end of the first electric capacity C1 and
Two electric capacity C2 the second end is grounded.
BOOST can carry out loop compensation as a closed-loop system with feedback, loop compensation networks 26 to it, it is to avoid
Appearance loop is unstable to cause vibration.
In the present embodiment, from feedback end FB ends it is seen that impedance and the constant-current control unit 24 of light emitting diode group 3
Equiva lent impedance.The equiva lent impedance of constant-current control unit 24 is relatively large, for directly perceived, and it defines and just illustrated, when it
When both end voltage changes, the variable quantity very little of electric current also implies that larger AC impedance, this impedance reaches several k
Ohm or more than ten k ohm, much larger than the impedance of light emitting diode group 3.
From the viewpoint of exchange, when voltage has a variable quantity on output voltage VO UT, the change on feedback end FB
Amount should be the partial pressure of impedance and total impedance that feedback end FB is seen down into.Because the impedance of constant-current control unit 24 is much big
In the impedance of light emitting diode group 3, so the voltage variety almost all on output voltage VO UT falls on feedback end FB, from
Output voltage VO UT to feedback end FB gain are about 1.The loop compensation networks 26 of the present embodiment can overcome this gain
Change caused by loop gain variation, so that it is guaranteed that loop stability.
As shown in fig. 6, the dimming control unit 23 of the present embodiment can include：First operational amplifier 231, the 2nd NMOS
Pipe MN2,3rd resistor R3, current mirroring circuit 232, selecting switch and switch control unit 233, the dimming control signal SL bags
Include the first dimming control signal SL1.
The selecting switch includes：1st switch K1, n-th of switch Kn of the 2nd switch K2 ... ...
The normal phase input end of first operational amplifier 231 is suitable to input the first reference voltage V ref1, and described the
The negative-phase input of one operational amplifier 231 connects the source electrode of the second NMOS tube MN2 and 3rd resistor R3 first end, institute
The output end for stating the first operational amplifier 231 connects the grid of the second NMOS tube MN2.The second end of the 3rd resistor R3
Ground connection.
The current mirroring circuit 232 includes：Input Bit<in>, reference current output end Bit<0>It is defeated with image current
Go out end.The quantity of the image current output end is identical with the selecting switch quantity, and image current output end includes：1st
Image current output end Bit<1>, the 2nd image current output end Bit<2>... n-th of image current output end Bit<n>.
The input Bit of the current mirroring circuit 232<in>Suitable for receiving the input voltage VIN, the current mirror electricity
The reference current output end Bit on road 232<0>Connect the drain electrode MN2 of second NMOS tube, the 1st of the current mirroring circuit 232 the
Individual image current output end Bit<1>, the 2nd image current output end Bit<2>... n-th of image current output end Bit<n>
The first end with the 1st switch K1, n-th of switch Kn of the 2nd switch K2 ... .. connects one to one respectively.Described 1st is opened
K1, n-th of switch Kn of the 2nd switch K2 ... .. the second end is closed to be both connected to together and the benchmark light modulation electric current Iref is provided
To constant-current control unit 24.Those skilled in the art can use existing current mirroring circuit to realize, those skilled in the art
The particular circuit configurations of current mirroring circuit 231 can be determined according to foregoing description, here is omitted.
The switch control unit 233 is suitable to close one or more selections according to the first dimming control signal SL1
Switch.First dimming control signal SL1 can be stored in a line digital dimming register.
First dimming control signal SL1 can make switch control unit 233 close the selecting switch of varying number, cause base
Quasi- light modulation electric current Iref current value is different, so that the driving current value that constant-current control unit 24 is exported changes, flows
The electric current for crossing light emitting diode group 3 changes therewith, reaches the purpose of regulation brightness.Regulative mode shown in Fig. 6 can be referred to as
One line light-modulating mode.The dimming control unit 23 of the present embodiment can also use PWM light-modulating modes.
Specifically, as shown in fig. 7, the dimming control unit includes：PWM dimming units 234, the first operational amplifier
231st, the second NMOS tube MN2,3rd resistor R3, current mirroring circuit 232, selecting switch and switch control unit 233, the light modulation
Control signal SL includes the second dimming control signal SL2.
The PWM dimming units 234 are suitable to produce PWM adjustment signals, and root according to the second dimming control signal SL2
The first reference voltage V ref1 is converted into conversion voltage Vs according to PWM adjustment signals.The voltage of the conversion voltage Vs
Value=Vreg*Duty, Vreg is the magnitude of voltage of the first reference voltage V ref1, and Duty is the duty that the PWM adjusts signal
Than.
The normal phase input end of first operational amplifier 231 is suitable to input conversion the voltage Vs, first computing
The negative-phase input of amplifier 231 connects the source electrode of the second NMOS tube MN2 and 3rd resistor R3 first end, described first
The output end of operational amplifier 231 connects the grid of the second NMOS tube MN2.The second end ground connection of the 3rd resistor R3；
The current mirroring circuit 232 includes：Input Bit<in>, reference current output end Bit<0>It is defeated with image current
Go out end.The quantity of the image current output end is identical with the selecting switch quantity, and image current output end includes：1st
Image current output end Bit<1>, the 2nd image current output end Bit<2>... n-th of image current output end Bit<n>.
The input Bit of the current mirroring circuit 232<in>Suitable for receiving the input voltage VIN, the current mirror electricity
The reference current output end Bit on road 231<0>Connect the drain electrode MN2 of second NMOS tube, the 1st of the current mirroring circuit 232 the
Individual image current output end Bit<1>, the 2nd image current output end Bit<2>... n-th of image current output end Bit<n>
The first end with the 1st switch K1, n-th of switch Kn of the 2nd switch K2 ... .. connects one to one respectively.Described 1st is opened
K1, n-th of switch Kn of the 2nd switch K2 ... .. the second end is closed to be both connected to together and the benchmark light modulation electric current Iref is provided
To constant-current control unit 24.
The switch control unit 233 is suitable to close one or more selecting switch.
The PWM that second dimming control signal SL2 can make PWM dimming units 234 produce different duty adjusts signal, from
And conversion voltage Vs magnitude of voltage is have adjusted, so that the reference current output end Bit of current mirroring circuit 231<0>Current value is sent out
Changing, even if the selecting switch quantity that switch control unit 233 is closed during brightness regulation every time is identical, but still can be with
Change benchmark light modulation electric current Iref current value, the driving current value that constant-current control unit 24 is exported changes, flowed through luminous
The electric current of diode group 3 becomes therewith.
The present embodiment can also combine a line light-modulating mode and PWM light-modulating modes.With continued reference to Fig. 7, dimming control signal
SL includes the first dimming control signal SL1 and the second dimming control signal SL2.It is different with the above-mentioned description to Fig. 7,
Switch control unit 233 can close one or more selecting switch according to the first dimming control signal SL1.
As shown in figure 8, constant-current control unit 24 also includes described in the present embodiment：3rd NMOS tube MN3, the 4th NMOS tube
MN4, the 5th NMOS tube MN5 and the second operational amplifier 241.
Drain electrode connection the 4th NMOS tube MN4 of 3rd NMOS tube MN3 grid and the constant-current control unit
24 first input end, the grid of the 3rd NMOS tube MN3 connects the output end of second operational amplifier 241, described
3rd NMOS tube MN3 source electrode connects the leakage of the negative-phase input and the 4th NMOS tube MN4 of second operational amplifier 241
Pole.
The source electrode of the 4th NMOS tube MN4 connects the output end of constant-current control unit 24 first.5th NMOS
The normal phase input end of pipe MN5 drain electrode connection second operational amplifier 241 and the second of the constant-current control unit 24 defeated
Enter end, the source electrode of the 5th NMOS tube MN5 connects the output end of constant-current control unit 24 second.
The constant-current control unit 24 is a current path mirror image control, receives the benchmark that dimming control unit 23 is provided
Electric current Iref is dimmed, then passes through 1：N mirroring ratios are exported.In order to improve efficiency, it can be set to feedback end FB voltages
Than relatively low, such as 100~200mV, so the loss in efficiency produced by it just than it is relatively low (such as when output voltage VO UT is 30V,
0.67%) loss in efficiency that 200mV feedback end FB voltages are produced is.Current constant control loop has a feature, although in theory
Its electric current is that, not with voltage change, but must have a scope, that is to say, that is thought as in some scope and does not become with voltage
Change.Simple requirement of the mirror image circuit to this voltage is also higher, and does not also reach the relatively good linearity.So this
Embodiment uses the structure of low pressure drop constant-current type, does feedback control by the second operational amplifier 241 so that two mirror image pipes
Drain terminal voltage it is equal, so as to realize current mirror in a wide range.
Specifically, if feedback end FB voltages be higher than some value (this value is referred to as Dropout), its electric current just not with
Feedback end FB voltages and change.This Dropout can typically accomplish tens mV to mV more than 100, and feedback end FB setting voltage
Value have to be larger than this Dropout value and have certain surplus.So as to which when electric current regulation is carried out, adjustment is brightness adjustment control
The electric current that unit 23 is exported, then by 1：N mirroring ratios are to exporting, and feedback end FB voltages are set higher than Dropout values,
It is achieved that foregoing sets target.
Although present disclosure is as above, the present invention is not limited to this.Any those skilled in the art, are not departing from this
In the spirit and scope of invention, it can make various changes or modifications, therefore protection scope of the present invention should be with claim institute
The scope of restriction is defined.
Claims (10)
1. a kind of drive circuit, for connecting luminous diode group, the light emitting diode group includes one or more series connection
Light emitting diode, it is characterised in that including：
Reference cell, is adapted to provide for the first reference voltage and the second reference voltage；
Booster circuit, suitable for being provided after input voltage is boosted according to feedback signal to the input of the light emitting diode group；
Error amplifier, the negative-phase input of the error amplifier connects the output end of the light emitting diode group, the mistake
The normal phase input end of poor amplifier is suitable to input second reference voltage, and the output end of the error amplifier is suitable to output institute
State feedback signal；
Dimming control unit, suitable for dimming electric current on the basis of first reference voltage is changed according to dimming control signal；
Constant-current control unit, including first input end, the second input, the first output end and the second output end, the constant current control
The first input end of unit processed is suitable to receive the benchmark light modulation electric current, the second output end connection institute of the constant-current control unit
State the output end of light emitting diode group and be adapted to provide for driving current, the first output end of the constant-current control unit and second defeated
Go out end to be grounded, the current value of the driving current and benchmark light modulation electric current is proportional；
First NMOS tube, the grid and the light emitting diode group of drain electrode connection first NMOS tube of first NMOS tube
Output end, the source ground of first NMOS tube.
2. drive circuit as claimed in claim 1, it is characterised in that also include：First resistor；
First NMOS tube is connected with the first resistor, and the drain electrode of first NMOS tube is connected by the first resistor
The grid of first NMOS tube.
3. drive circuit as claimed in claim 1, it is characterised in that also include：Second resistance, the first electric capacity and the second electricity
Hold；
The first end of the second resistance connects the output end of the error amplifier, the second end connection institute of the second resistance
State the first end of the first electric capacity and the first end of the second electric capacity；
Second end of first electric capacity and the second end of the second electric capacity are grounded.
4. drive circuit as claimed in claim 1, it is characterised in that the dimming control unit includes：First operation amplifier
Device, the second NMOS tube, 3rd resistor, current mirroring circuit, selecting switch and switch control unit, the dimming control signal include
First dimming control signal；
The normal phase input end of first operational amplifier is suitable to input first reference voltage, first operational amplifier
Negative-phase input connect the source electrode of second NMOS tube and the first end of 3rd resistor, first operational amplifier it is defeated
Go out the grid of end connection second NMOS tube；
The second end ground connection of the 3rd resistor；
The current mirroring circuit includes：Input, reference current output end and image current output end, the image current output
The quantity at end is identical with the selecting switch quantity, and the input of the current mirroring circuit is suitable to receive the input voltage, institute
The reference current output end for stating current mirroring circuit connects the drain electrode of second NMOS tube, the image current of the current mirroring circuit
The first end of output end and the selecting switch connects one to one；
Second end of the selecting switch is both connected to together and provides the benchmark light modulation electric current；
The switch control unit is suitable to close one or more selecting switch according to first dimming control signal.
5. drive circuit as claimed in claim 1, it is characterised in that the dimming control unit includes：PWM dimming units,
First operational amplifier, the second NMOS tube, 3rd resistor, current mirroring circuit, selecting switch and switch control unit, the light modulation
Control signal includes the second dimming control signal；
The PWM dimming units are suitable to produce PWM adjustment signals according to second dimming control signal, and according to the PWM
First reference voltage is converted to conversion voltage, magnitude of voltage=Vreg*Duty of the conversion voltage, Vreg by adjustment signal
For the magnitude of voltage of first reference voltage, Duty is the dutycycle that the PWM adjusts signal；
The normal phase input end of first operational amplifier is suitable to input the conversion voltage, first operational amplifier it is negative
Phase input connects the source electrode of second NMOS tube and the first end of 3rd resistor, the output end of first operational amplifier
Connect the grid of second NMOS tube；
The second end ground connection of the 3rd resistor；
The current mirroring circuit includes：Input, reference current output end and image current output end, the image current output
The quantity at end is identical with the selecting switch quantity, and the input of the current mirroring circuit is suitable to receive the input voltage, institute
The reference current output end for stating current mirroring circuit connects the drain electrode of second NMOS tube, the image current of the current mirroring circuit
The first end of output end and the selecting switch connects one to one；
Second end of the selecting switch is both connected to together and provides the benchmark light modulation electric current；
The switch control unit is suitable to close one or more selecting switch.
6. drive circuit as claimed in claim 5, it is characterised in that the dimming control signal also includes the first brightness adjustment control
Signal；
The switch control unit is suitable to close one or more selecting switch according to first dimming control signal.
7. drive circuit as claimed in claim 1, it is characterised in that the constant-current control unit also includes：3rd NMOS tube,
4th NMOS tube, the 5th NMOS tube and the second operational amplifier；
The grid of drain electrode connection the 4th NMOS tube of 3rd NMOS tube and the first input of the constant-current control unit
End, the grid of the 3rd NMOS tube connects the output end of second operational amplifier, and the source electrode of the 3rd NMOS tube connects
Connect the negative-phase input of second operational amplifier and the drain electrode of the 4th NMOS tube；
The source electrode of 4th NMOS tube connects the output end of constant-current control unit first；
The normal phase input end and the constant-current control unit of drain electrode connection second operational amplifier of 5th NMOS tube
The second input, the source electrode of the 5th NMOS tube connects the output end of constant-current control unit second.
8. drive circuit as claimed in claim 1, it is characterised in that the booster circuit is using switch DC boosting framework.
9. a kind of illuminating circuit, it is characterised in that including the drive circuit described in claim 1 and the light emitting diode group.
10. a kind of mobile terminal, it is characterised in that including the illuminating circuit and display screen described in claim 9, the display screen
Background light source is used as using the light emitting diode group in illuminating circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510520232.4A CN105163431B (en) | 2015-08-21 | 2015-08-21 | Drive circuit, illuminating circuit and mobile terminal |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510520232.4A CN105163431B (en) | 2015-08-21 | 2015-08-21 | Drive circuit, illuminating circuit and mobile terminal |
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| Publication Number | Publication Date |
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| CN105163431A CN105163431A (en) | 2015-12-16 |
| CN105163431B true CN105163431B (en) | 2017-10-31 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201510520232.4A Active CN105163431B (en) | 2015-08-21 | 2015-08-21 | Drive circuit, illuminating circuit and mobile terminal |
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Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107750076A (en) * | 2017-11-22 | 2018-03-02 | 深圳中电数码显示有限公司 | A kind of LED drive circuit |
| CN108174487B (en) * | 2018-01-17 | 2024-02-13 | 深圳市崧盛电子股份有限公司 | Dimmable power supply capable of displaying output parameters |
| CN112823569B (en) * | 2018-10-10 | 2022-11-18 | 华为技术有限公司 | Dimming circuit and integrated circuit |
| CN111258366A (en) * | 2018-11-30 | 2020-06-09 | 米彩股份有限公司 | Driving circuit for LED |
| CN111369932B (en) * | 2018-12-24 | 2023-03-17 | 北京新岸线移动多媒体技术有限公司 | Driving method and driving circuit of display device |
| CN110096089A (en) * | 2019-04-26 | 2019-08-06 | 北京集创北方科技股份有限公司 | Driving circuit and display device |
| CN111200892B (en) * | 2020-02-28 | 2023-08-29 | 深圳市晟碟半导体有限公司 | LED control device, circuit and control method thereof |
| TWI764444B (en) * | 2020-12-17 | 2022-05-11 | 大陸商北京集創北方科技股份有限公司 | Constant current source generating circuit, LED display driver chip, LED display device, and information processing device |
| CN113359943A (en) * | 2021-07-22 | 2021-09-07 | 成都利普芯微电子有限公司 | Reference current regulating circuit and reference current generating circuit |
| CN114420055B (en) * | 2021-12-24 | 2023-03-24 | 北京奕斯伟计算技术股份有限公司 | Driving circuit and driving method, backlight module and display device |
| CN115185330B (en) * | 2022-08-18 | 2024-02-02 | 上海艾为电子技术股份有限公司 | LDO drive circuit, drive chip and electronic equipment |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN203387492U (en) * | 2013-07-30 | 2014-01-08 | 南京化工职业技术学院 | LED brightness control device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| TW200504662A (en) * | 2003-07-17 | 2005-02-01 | Analog Integrations Corp | Method of using current mirror to drive LED |
| JP2009044081A (en) * | 2007-08-10 | 2009-02-26 | Rohm Co Ltd | Driver |
| US8710753B2 (en) * | 2011-12-07 | 2014-04-29 | Dialog Semiconductor Inc. | High performance adaptive switched LED driver |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN203387492U (en) * | 2013-07-30 | 2014-01-08 | 南京化工职业技术学院 | LED brightness control device |
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