CN105163431A - Drive circuit, light-emitting diode and mobile terminal - Google Patents
Drive circuit, light-emitting diode and mobile terminal Download PDFInfo
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- CN105163431A CN105163431A CN201510520232.4A CN201510520232A CN105163431A CN 105163431 A CN105163431 A CN 105163431A CN 201510520232 A CN201510520232 A CN 201510520232A CN 105163431 A CN105163431 A CN 105163431A
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Abstract
The invention discloses a drive circuit, a light-emitting diode and a mobile terminal. The drive circuit comprises a reference unit, a booster circuit, an error amplifier, a dimming control unit and a constant-flow control unit, wherein the reference unit is suitable for providing first reference voltage and second reference voltage; the booster circuit is suitable for boosting input voltage according to a feedback signal and then providing the input voltage to an input end of a light-emitting diode group; a negative phase input end of the error amplifier is connected with an output end of the light-emitting diode group; a positive phase input end of the error amplifier is suitable for inputting second reference voltage; the output end of the error amplifier is suitable for outputting the feedback signal; the diming control unit is suitable for converting the first reference voltage into reference dimming current according to a dimming control signal; a first input end of the constant-flow control unit is suitable for receiving reference diming current; a second output end of the constant-flow control unit is connected to the output end of the light-emitting diode group and is suitable for providing drive current; both the first output end and the second output end of the constant-flow control unit are grounded; and a current value of the drive current is proportional to that of the reference dimming current.
Description
Technical field
The present invention relates to electronic circuit field, particularly relate to a kind of drive circuit, illuminating circuit and mobile terminal.
Background technology
The mobile phone in intelligence epoch has been not only voice and simple short message service (SMS) data communications equipment, becomes now the individual mobile multi-media terminal that a function is superpower already.Inductance boost type backlight drive due to have light-emitting diode (LED) currents match degree good, with the advantage such as the interface links of screen is few and selected by handset designers and do large-sized smart mobile phone backlight drive.
As shown in Figure 1, existing series connection backlight drive circuit inside is integrated with power MOS pipe MN, adopt switch DC boosting framework (Boost boost framework), boost in conjunction with inductance L and Schottky diode D1, plurality of LEDs is connected and can be ensured the consistency of LED current.
BOOST many employings peak-current mode controls (Current-ModeControl).Peak-current mode control model is the control method that a kind of fixed clock is opened, peak current turns off.Feedback end FB comes in by error amplifier, then forms Boost together with the modules such as electric current and voltage detecting, slope equalizer 11 and Boost control circuit 12 and controls.Loop compensation networks 13 can guarantee that control loop is stable under various applicable cases.Series connection backlight drive circuit other relevant circuit modules all right integrated, as enable control, overheat protector, soft start, base modules etc.
Feedback end FB is generally set as it being 200mV, 300mV or other values when full brightness, goes on to say below for 200mV.The current value flowing through LED equals the resistance of feedback end FB magnitude of voltage over the ground divided by feedback resistance RSET.Such as a string LED wishes that its high-high brightness is 20mA, and so feedback resistance RSET gets 10ohm.Get 32 contrast light when supposing that PWM or a line dimming control unit 14 carry out a line light modulation, feedback end FB minimum voltage can be transferred to 5mV.When PWM or a line dimming control unit 14 carry out PWM light modulation, feedback end FB voltage equals 200mV*D, and D is the duty ratio of light modulation, and feedback end FB minimum voltage can be transferred to several mV.
But, when feedback end FB voltage low to several mV to tens mV time, it is just easily subject to the impact of grounding interference.Because the electric current of LED equals the voltage at feedback resistance RSET two ends divided by resistance value, so, if pcb board layout is improper on the one hand, the reference ground of feedback resistance RSET is away from chip, or interference during system works is larger, or the reason that both combine, this is no longer desirable equal with reference to ground and the ground of chip; And during the feedback loop control feedback end FB voltage of chip, be reference with the ground of chip.The electric current of LED so will be caused to deviate from set point.Once this current deviation be become, the intensity of such as system interference is different at different time points, and the brightness of LED so will be caused different at different time points.So terminal use, he will feel flicker intuitively.Especially be lower in brightness settings, when such as brightness settings is below 10% or 5%, disturbs the deviation caused to account for the ratio of total current larger, so more easily see flicker.
In addition, feedback control loop due to chip internal also needs feedback end FB voltage to do FEEDBACK CONTROL, so when feedback end FB Voltage Cortrol is very low (several mV), higher requirement be it is also proposed to the low-voltage disposal ability of chip internal and antijamming capability.If dealt with improperly, the electric current of LED also can be caused to change in time, same causes flicker.
Summary of the invention
The problem that the present invention solves is that existing drive circuit easily makes light-emitting diode produce flicker.
For solving the problem, the invention provides a kind of drive circuit, for connecting luminous diode group, described light-emitting diode group comprises the light-emitting diode of one or more series connection, comprising:
Reference cell, is suitable for providing the first reference voltage and the second reference voltage;
Booster circuit, is suitable for the input being provided to described light-emitting diode group after being boosted by input voltage according to feedback signal;
Error amplifier, the negative-phase input of described error amplifier connects the output of described light-emitting diode group, the normal phase input end of described error amplifier is suitable for inputting described second reference voltage, and the output of described error amplifier is suitable for exporting described feedback signal;
Dimming control unit, is suitable for, according to dimming control signal, described first reference voltage is converted to benchmark light modulation electric current;
Constant-current control unit, comprise first input end, the second input, the first output and the second output, the first input end of described constant-current control unit is suitable for receiving described benchmark light modulation electric current, second output of described constant-current control unit connects the output of described light-emitting diode group and is suitable for providing drive current, first output of described constant-current control unit and the equal ground connection of the second output, the current value of described drive current and benchmark light modulation electric current is proportional.
Optionally, described drive circuit also comprises: the first NMOS tube;
The drain electrode of described first NMOS tube connects the grid of described first NMOS tube and the output of described light-emitting diode group, the source ground of described first NMOS tube.
Optionally, described drive circuit also comprises: the first resistance;
Described first NMOS tube and described first resistant series, the drain electrode of described first NMOS tube connects the grid of described first NMOS tube by described first resistance.
Optionally, described drive circuit also comprises: the second resistance, the first electric capacity and the second electric capacity;
The first end of described second resistance connects the output of described error amplifier, and the second end of described second resistance connects the first end of described first electric capacity and the first end of the second electric capacity;
Second end of described first electric capacity and the equal ground connection of the second end of the second electric capacity.
Optionally, described dimming control unit comprises: the first operational amplifier, the second NMOS tube, the 3rd resistance, current mirroring circuit, selector switch and switch control unit, and described dimming control signal comprises the first dimming control signal;
The normal phase input end of described first operational amplifier is suitable for inputting described first reference voltage, the negative-phase input of described first operational amplifier connects the source electrode of described second NMOS tube and the first end of the 3rd resistance, and the output of described first operational amplifier connects the grid of described second NMOS tube;
Second end ground connection of described 3rd resistance;
Described current mirroring circuit comprises: input, reference current output and image current output, the quantity of described image current output is identical with described selector switch quantity, the input of described current mirroring circuit is suitable for receiving described input voltage, the reference current output of described current mirroring circuit connects the drain electrode of described second NMOS tube, and the image current output of described current mirroring circuit and the first end of described selector switch connect one to one;
Second end of described selector switch all links together and provides described benchmark light modulation electric current;
Described switch control unit is suitable for closing one or more selector switch according to described first dimming control signal.
Optionally, described dimming control unit comprises: PWM dimming unit, the first operational amplifier, the second NMOS tube, the 3rd resistance, current mirroring circuit, selector switch and switch control unit, and described dimming control signal comprises the second dimming control signal;
Described PWM dimming unit is suitable for producing PWM according to described second dimming control signal and adjusts signal, and according to described PWM adjustment signal, described first reference voltage is converted to changing voltage, magnitude of voltage=the Vreg*Duty of described changing voltage, Vreg is the magnitude of voltage of described first reference voltage, and Duty is the duty ratio that described PWM adjusts signal;
The normal phase input end of described first operational amplifier is suitable for inputting described changing voltage, the negative-phase input of described first operational amplifier connects the source electrode of described second NMOS tube and the first end of the 3rd resistance, and the output of described first operational amplifier connects the grid of described second NMOS tube;
Second end ground connection of described 3rd resistance;
Described current mirroring circuit comprises: input, reference current output and image current output, the quantity of described image current output is identical with described selector switch quantity, the input of described current mirroring circuit is suitable for receiving described input voltage, the reference current output of described current mirroring circuit connects the drain electrode of described second NMOS tube, and the image current output of described current mirroring circuit and the first end of described selector switch connect one to one;
Second end of described selector switch all links together and provides described benchmark light modulation electric current;
Described switch control unit is suitable for closed one or more selector switch.
Optionally, described dimming control signal also comprises the first dimming control signal;
Described switch control unit is suitable for closing one or more selector switch according to described first dimming control signal.
Optionally, described constant-current control unit also comprises: the 3rd NMOS tube, the 4th NMOS tube, the 5th NMOS tube and the second operational amplifier;
The drain electrode of described 3rd NMOS tube connects the described grid of the 4th NMOS tube and the first input end of described constant-current control unit, the grid of described 3rd NMOS tube connects the output of described second operational amplifier, and the source electrode of described 3rd NMOS tube connects the negative-phase input of described second operational amplifier and the drain electrode of the 4th NMOS tube;
The source electrode of described 4th NMOS tube connects described constant-current control unit first output;
The drain electrode of described 5th NMOS tube connects the normal phase input end of described second operational amplifier and the second input of described constant-current control unit, and the source electrode of described 5th NMOS tube connects described constant-current control unit second output.
Optionally, described booster circuit adopts switch DC boosting framework.
The present invention also provides a kind of illuminating circuit, comprises above-mentioned drive circuit and described light-emitting diode group.
The present invention also provides a kind of mobile terminal, comprises above-mentioned illuminating circuit and display screen, and described display screen is with the light-emitting diode group light source as a setting in illuminating circuit.
Compared with prior art, drive circuit of the present invention eliminates the feedback resistance in existing drive circuit, adopt low pressure drop current constant control, electric current on light-emitting diode is regulated by current path, during brightness regulation, feedback end voltage is constant, so just well solves the problem of LED flash.
Accompanying drawing explanation
Fig. 1 is a kind of structural representation of existing series connection backlight drive circuit;
Fig. 2 is the structural representation of drive circuit of the present invention;
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
For enabling above-mentioned purpose of the present invention, feature and advantage more become apparent, and are described in detail specific embodiments of the invention below in conjunction with accompanying drawing.
As shown in Figure 2, the embodiment of the present invention provides a kind of drive circuit, and for connecting luminous diode group 3, described light-emitting diode group 3 comprises the light-emitting diode of one or more series connection.
Described drive circuit comprises: booster circuit 1, reference cell 21, error amplifier 22, dimming control unit 23 and constant-current control unit 24.
Booster circuit 1 is suitable for be provided to the input of described light-emitting diode group 3 after input voltage VIN boosting according to feedback signal Vfb.
Reference cell 21 is suitable for providing the first reference voltage V ref1 and the second reference voltage V ref2.
The negative-phase input of error amplifier 22 connects the output of described light-emitting diode group 3, the normal phase input end of described error amplifier 22 is suitable for inputting described second reference voltage V ref2, and the output of described error amplifier 22 is suitable for exporting described feedback signal Vfb.
Dimming control unit 23 is suitable for, according to dimming control signal SL, described first reference voltage V ref1 is converted to benchmark light modulation electric current I ref.
Constant-current control unit 24 comprises first input end, the second input, the first output and the second output.The first input end of described constant-current control unit 24 is suitable for receiving described benchmark light modulation electric current I ref, and the second output of described constant-current control unit 24 connects the output of described light-emitting diode group 3 and is suitable for providing drive current Id.First output of described constant-current control unit 24 and the equal ground connection of the second output.Wherein, the current value of described drive current Id and benchmark light modulation electric current I ref is proportional.
In the present embodiment, the output of light-emitting diode group 3 is feedback end FB.Feedback end FB voltage is fed loop and controls equal with the second reference voltage V ref2 magnitude of voltage, and this voltage is used for meeting the voltage drop needed for constant-current control unit 24, and when carrying out brightness regulation to light-emitting diode group 3, feedback end FB voltage remains unchanged.Dimming control unit 23 adjusts the current value of benchmark light modulation electric current I ref according to dimming control signal SL, thus the current value of the drive current Id that constant-current control unit 24 is provided changes.
So when using the drive circuit of the present embodiment to carry out brightness regulation to light-emitting diode group 3, the electric current in light-emitting diode group 3 does not change with feedback end FB change in voltage.Because feedback end FB voltage compare is high, interference signal proportion is less, even and if feedback end FB voltage change to some extent, the curent change that it brings is also very little, so just can extraordinary solve dodge screen problem.
In addition, continue with reference to figure 1, when carrying out brightness regulation, prior art is feedback end FB Voltage Cortrol to the value needed, 5% (10mV) of such as maximum voltage.Then feedback end FB voltage participate in boost loop through error amplifier and control.There is an imbalance (offset) in error amplifier, it is certainly exist the phenomenon caused by the factor such as technique, domain, be the random imbalance of an approximate normal distribution, that is two input terminal voltages of error amplifier are not equal, but have an imbalance at random.
In existing technique, by carrying out necessary design to error amplifier, imbalance can be accomplished within several mV, but when feedback end FB voltage is more and more lower, the proportion shared by imbalance is just increasing.Which results in different chips, the discreteness of its brightness becomes large.Such as when brightness adjustment is 5%, when corresponding feedback end FB Voltage Cortrol is to 10mV, and the imbalance of error amplifier is 5mV, the output current of so different chip may have ± deviation of 50%, and when high-high brightness, feedback end FB voltage is 200mV, this imbalance only can bring ± and the deviation of 2.5%.
And in the present embodiment, on the one hand, feedback end FB voltage is constant during brightness regulation, and be fixed as the value of 200mV or some settings, the proportion shared by the imbalance of error amplifier is less; On the other hand, because the present embodiment adopts the current constant control to output current, have nothing to do with magnitude of voltage, even if so error amplifier imbalance causes more greatly feedback end FB voltage to have certain discreteness, also the discrete of electric current can not be caused.
Therefore, prior art adopts feedback end FB voltage and feedback resistance to regulate LED current, and during brightness regulation, feedback end FB voltage may be adjusted to very low, so easily brings the problem of problem and the different chip chamber electric current discreteness increase of dodging screen.And the embodiment of the present invention eliminates feedback resistance, and the electric current on light-emitting diode is regulated by current path, and during brightness regulation, feedback end FB voltage is constant, so just well solves above-mentioned technical problem.
Below each composition structure of the present embodiment drive circuit is elaborated.
The booster circuit 1 of the present embodiment adopts switch DC boosting framework.
Continue with reference to figure 2, booster circuit 1 can comprise: inductance L, diode D1, input capacitance CIN, output capacitance COUT, electric current and voltage detecting, slope equalizer 11, Boost control circuit 12 and power MOS pipe MN.
The first end of described inductance L connects the first end of input capacitance CIN and is suitable for receiving described input voltage VIN.Second end of described inductance L connects the anode of described diode D1, electric current and voltage detecting, the input of slope equalizer 11 and the drain electrode of power MOS pipe MN.The negative electrode of described diode D1 connects the first end of output capacitance COUT and the input of described light-emitting diode group 3.
The output of electric current and voltage detecting, slope equalizer 11 connects the first input end of described Boost control circuit 12.Second input of described Boost control circuit 12 connects the output of described error amplifier 22.The output of described Boost control circuit 12 connects the grid of power MOS pipe MN.The source grounding of second end of described input capacitance CIN, second end of output capacitance COUT and power MOS pipe MN.
The booster circuit 1 that the present embodiment adopts can know the specific implementation of electric current and voltage detecting, slope equalizer 11, Boost control circuit 12 with the identical those skilled in the art of prior art structure shown in Fig. 1, repeats no more herein.
In the present embodiment, during brightness regulation, feedback end FB voltage maintains static, and it is fixed on a relatively high value all the time, thus the proportion that the imbalance of error amplifier 22 accounts for is less; And be current constant control owing to exporting, even if there is certain imbalance, output current is also less with the change of voltage.So the error amplifier 22 of the present embodiment can reduce the requirement to mismatch.For CMOS technology, the mismatch wanting to reach several mV rank needs very large chip area, the current precision of constant-current source does not depend on the size of feedback voltage, feedback voltage can be allowed to have several mV even mismatch of tens mV, so reduce the mismatch requirement to error amplifier.
As everyone knows, error amplifier exists compromise in gain, bandwidth, area and mismatch etc., the requirement of the present embodiment to mismatch reduces, and just the design of error amplifier more can be partial to loop and control or reduce chip area, thus also optimize to some extent error amplifier.
The drive circuit of the present embodiment can also comprise: drop-down unit 25 automatically.
As shown in Figure 3, described automatic drop-down unit 25 can comprise: the first NMOS tube MN1.The drain electrode of described first NMOS tube MN1 connects the grid of described first NMOS tube MN1 and the output of described light-emitting diode group 3, the source ground of described first NMOS tube MN1.
As shown in Figure 4, described automatic drop-down unit 25 can also comprise: the first resistance R1.Described first NMOS tube MN1 connects with described first resistance R1, and the drain electrode of described first NMOS tube MN1 connects the grid of described first NMOS tube MN1 by described first resistance R1.Namely the drain electrode of the first NMOS tube MN1 connects the first end of the first resistance R1, and second end of described first resistance R1 connects the grid of described first NMOS tube MN1 and the output of described light-emitting diode group 3, the source ground of the first NMOS tube MN1.
When drive circuit normally works, feedback end FB is stabilized in 200mV, does not reach the threshold voltage of the first NMOS tube MN1, so the first NMOS tube MN1 closes, inoperative; And drive circuit is when quitting work, if output capacitance COUT there is electric charge make feedback end FB voltage raise, once feedback end FB voltage is higher than the threshold value (such as 0.7V) of the first NMOS tube MN1, first NMOS tube MN1 will conducting, thus is automatically released by output voltage VO UT (input of light-emitting diode group 3).First resistance R1 can regulate the ability of charge discharging resisting.The size of the first NMOS tube MN1 and the first resistance R1 can determine the size of releasability.
The drive circuit of the present embodiment can also comprise: loop compensation networks 26.
As shown in Figure 5, described loop compensation networks 26 can comprise: the second resistance R2, the first electric capacity C1 and the second electric capacity C2.
The first end of described second resistance R2 connects the output of described error amplifier 22, and second end of described second resistance R2 connects the first end of described first electric capacity C1 and the first end of the second electric capacity C2.Second end of described first electric capacity C1 and the equal ground connection of the second end of the second electric capacity C2.
BOOST is as the closed-loop system of a band feedback, and loop compensation networks 26 can carry out loop compensation to it, avoids occurring that loop instability causes vibration.
In the present embodiment, hold it is seen that the impedance of light-emitting diode group 3 and the equiva lent impedance of constant-current control unit 24 from feedback end FB.The equiva lent impedance of constant-current control unit 24 is relatively large, from intuitively, its definition just describes, when its both end voltage changes time, the variable quantity of electric current is very little, also just mean larger AC impedance, this impedance reaches a few kohm or tens kohm, much larger than the impedance of light-emitting diode group 3.
From the viewpoint exchanged, when output voltage VO UT power on be pressed with a variable quantity time, the variable quantity on feedback end FB should be the dividing potential drop of the impedance that sees down into of feedback end FB and total impedance.Impedance due to constant-current control unit 24 is far longer than the impedance of light-emitting diode group 3, so the voltage variety on output voltage VO UT almost all drops on feedback end FB, the gain from output voltage VO UT to feedback end FB is approximately 1.The loop gain variation that the change that the loop compensation networks 26 of the present embodiment can overcome this gain causes, thus guarantee loop stability.
As shown in Figure 6, the dimming control unit 23 of the present embodiment can comprise: the first operational amplifier 231, second NMOS tube MN2, the 3rd resistance R3, current mirroring circuit 232, selector switch and switch control unit 233, described dimming control signal SL comprises the first dimming control signal SL1.
Described selector switch comprises: the 1st K switch 1, the 2nd K switch 2 ... .. the n-th K switch n.
The normal phase input end of described first operational amplifier 231 is suitable for inputting described first reference voltage V ref1, the negative-phase input of described first operational amplifier 231 connects the source electrode of described second NMOS tube MN2 and the first end of the 3rd resistance R3, and the output of described first operational amplifier 231 connects the grid of described second NMOS tube MN2.The second end ground connection of described 3rd resistance R3.
Described current mirroring circuit 232 comprises: input Bit<in>, reference current output Bit<0> and image current output.The quantity of described image current output is identical with described selector switch quantity, and image current output comprises: the 1st image current output Bit<1>, the 2nd image current output Bit<2> ... n-th image current output Bit<n>.
The input Bit<in> of described current mirroring circuit 232 is suitable for receiving described input voltage VIN, the reference current output Bit<0> of described current mirroring circuit 232 connects the drain electrode MN2 of described second NMOS tube, 1st image current output Bit<1> of described current mirroring circuit 232, 2nd image current output Bit<2> ... n-th image current output Bit<n> respectively with the 1st K switch 1, 2nd K switch 2 ... .. the first end of the n-th K switch n connects one to one.Described 1st K switch 1, the 2nd K switch 2 ... .. second end of the n-th K switch n all links together and provides described benchmark light modulation electric current I ref to constant-current control unit 24.Those skilled in the art can use existing current mirroring circuit to realize, and those skilled in the art according to the particular circuit configurations of foregoing description determination current mirroring circuit 231, can repeat no more herein.
Described switch control unit 233 is suitable for closing one or more selector switch according to described first dimming control signal SL1.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 selector switch of varying number, cause the current value of benchmark light modulation electric current I ref different, thus the driving current value making constant-current control unit 24 export changes, the electric current flowing through light-emitting diode group 3 changes thereupon, reaches the object regulating brightness.Regulative mode shown in Fig. 6 can be referred to as a line light-modulating mode.The dimming control unit 23 of the present embodiment also can adopt PWM light-modulating mode.
Concrete, as shown in Figure 7, described dimming control unit comprises: PWM dimming unit 234, first operational amplifier 231, second NMOS tube MN2, the 3rd resistance R3, current mirroring circuit 232, selector switch and switch control unit 233, described dimming control signal SL comprises the second dimming control signal SL2.
Described PWM dimming unit 234 is suitable for producing PWM according to described second dimming control signal SL2 and adjusts signal, and according to described PWM adjustment signal, described first reference voltage V ref1 is converted to changing voltage Vs.The magnitude of voltage of described changing voltage Vs=Vreg*Duty, Vreg is the magnitude of voltage of described first reference voltage V ref1, and Duty is the duty ratio that described PWM adjusts signal.
The normal phase input end of described first operational amplifier 231 is suitable for inputting described changing voltage Vs, the negative-phase input of described first operational amplifier 231 connects the source electrode of described second NMOS tube MN2 and the first end of the 3rd resistance R3, and the output of described first operational amplifier 231 connects the grid of described second NMOS tube MN2.The second end ground connection of described 3rd resistance R3;
Described current mirroring circuit 232 comprises: input Bit<in>, reference current output Bit<0> and image current output.The quantity of described image current output is identical with described selector switch quantity, and image current output comprises: the 1st image current output Bit<1>, the 2nd image current output Bit<2> ... n-th image current output Bit<n>.
The input Bit<in> of described current mirroring circuit 232 is suitable for receiving described input voltage VIN, the reference current output Bit<0> of described current mirroring circuit 231 connects the drain electrode MN2 of described second NMOS tube, 1st image current output Bit<1> of described current mirroring circuit 232, 2nd image current output Bit<2> ... n-th image current output Bit<n> respectively with the 1st K switch 1, 2nd K switch 2 ... .. the first end of the n-th K switch n connects one to one.Described 1st K switch 1, the 2nd K switch 2 ... .. second end of the n-th K switch n all links together and provides described benchmark light modulation electric current I ref to constant-current control unit 24.
Described switch control unit 233 is suitable for closed one or more selector switch.
The PWM that second dimming control signal SL2 can make PWM dimming unit 234 produce different duty adjusts signal, thus have adjusted the magnitude of voltage of changing voltage Vs, thus the reference current output Bit<0> current value of current mirroring circuit 231 is changed, even if the selector switch quantity that each brightness regulation process breaker in middle control unit 233 is closed is identical, but still can change the current value of benchmark light modulation electric current I ref, the driving current value that constant-current control unit 24 exports changes, the electric current flowing through light-emitting diode group 3 becomes thereupon.
The present embodiment also can in conjunction with a line light-modulating mode and PWM light-modulating mode.Continue with reference to figure 7, dimming control signal SL comprises the first dimming control signal SL1 and the second dimming control signal SL2.Different with the above-mentioned description to Fig. 7, switch control unit 233 can close one or more selector switch according to described first dimming control signal SL1.
As shown in Figure 8, described in the present embodiment, constant-current control unit 24 also comprises: the 3rd NMOS tube MN3, the 4th NMOS tube MN4, the 5th NMOS tube MN5 and the second operational amplifier 241.
The drain electrode of described 3rd NMOS tube MN3 connects the described grid of the 4th NMOS tube MN4 and the first input end of described constant-current control unit 24, the grid of described 3rd NMOS tube MN3 connects the output of described second operational amplifier 241, and the source electrode of described 3rd NMOS tube MN3 connects the negative-phase input of described second operational amplifier 241 and the drain electrode of the 4th NMOS tube MN4.
The source electrode of described 4th NMOS tube MN4 connects described constant-current control unit 24 first output.The drain electrode of described 5th NMOS tube MN5 connects the described normal phase input end of the second operational amplifier 241 and the second input of described constant-current control unit 24, and the source electrode of described 5th NMOS tube MN5 connects described constant-current control unit 24 second output.
Described constant-current control unit 24 is that a current path mirror image controls, and receives the benchmark light modulation electric current I ref that dimming control unit 23 provides, is then exported by the mirroring ratios of 1:N.In order to raise the efficiency, can feedback end FB voltage sets must be lower, such as 100 ~ 200mV, its loss in efficiency of producing just lower (when such as output voltage VO UT is 30V, the loss in efficiency that the feedback end FB voltage of 200mV produces is 0.67%) like this.Current constant control loop has a feature, although its electric current is not with change in voltage in theory, must have a scope, that is think it is not with change in voltage in certain scope.Simple mirror image circuit is also higher to the requirement of this voltage, and does not also reach the reasonable linearity.So the present embodiment adopts the structure of low pressure drop constant-current type, do FEEDBACK CONTROL by the second operational amplifier 241, make the drain terminal voltage of two mirror image pipes equal, thus current mirror can be realized in very wide scope.
Specifically, as long as feedback end FB voltage is higher than some values (this value is called Dropout), its electric current does not just change with feedback end FB voltage.This Dropout generally can accomplish that tens mV are to mV more than 100, and the setting voltage value of feedback end FB must be greater than this Dropout value and have certain surplus.Thus when carrying out Current adjustment, adjustment be dimming control unit 23 export electric current, then through 1:N mirroring ratios to export, feedback end FB voltage sets is higher than Dropout value, just achieves foregoing target setting.
Although the present invention discloses as above, the present invention is not defined in this.Any those skilled in the art, without departing from the spirit and scope of the present invention, all can make various changes or modifications, and therefore protection scope of the present invention should be as the criterion with claim limited range.
Claims (11)
1. a drive circuit, for connecting luminous diode group, described light-emitting diode group comprises the light-emitting diode of one or more series connection, it is characterized in that, comprising:
Reference cell, is suitable for providing the first reference voltage and the second reference voltage;
Booster circuit, is suitable for the input being provided to described light-emitting diode group after being boosted by input voltage according to feedback signal;
Error amplifier, the negative-phase input of described error amplifier connects the output of described light-emitting diode group, the normal phase input end of described error amplifier is suitable for inputting described second reference voltage, and the output of described error amplifier is suitable for exporting described feedback signal;
Dimming control unit, is suitable for, according to dimming control signal, described first reference voltage is converted to benchmark light modulation electric current;
Constant-current control unit, comprise first input end, the second input, the first output and the second output, the first input end of described constant-current control unit is suitable for receiving described benchmark light modulation electric current, second output of described constant-current control unit connects the output of described light-emitting diode group and is suitable for providing drive current, first output of described constant-current control unit and the equal ground connection of the second output, the current value of described drive current and benchmark light modulation electric current is proportional.
2. drive circuit as claimed in claim 1, is characterized in that, also comprise: the first NMOS tube;
The drain electrode of described first NMOS tube connects the grid of described first NMOS tube and the output of described light-emitting diode group, the source ground of described first NMOS tube.
3. drive circuit as claimed in claim 2, is characterized in that, also comprise: the first resistance;
Described first NMOS tube and described first resistant series, the drain electrode of described first NMOS tube connects the grid of described first NMOS tube by described first resistance.
4. drive circuit as claimed in claim 1, is characterized in that, also comprise: the second resistance, the first electric capacity and the second electric capacity;
The first end of described second resistance connects the output of described error amplifier, and the second end of described second resistance connects the first end of described first electric capacity and the first end of the second electric capacity;
Second end of described first electric capacity and the equal ground connection of the second end of the second electric capacity.
5. drive circuit as claimed in claim 1, it is characterized in that, described dimming control unit comprises: the first operational amplifier, the second NMOS tube, the 3rd resistance, current mirroring circuit, selector switch and switch control unit, and described dimming control signal comprises the first dimming control signal;
The normal phase input end of described first operational amplifier is suitable for inputting described first reference voltage, the negative-phase input of described first operational amplifier connects the source electrode of described second NMOS tube and the first end of the 3rd resistance, and the output of described first operational amplifier connects the grid of described second NMOS tube;
Second end ground connection of described 3rd resistance;
Described current mirroring circuit comprises: input, reference current output and image current output, the quantity of described image current output is identical with described selector switch quantity, the input of described current mirroring circuit is suitable for receiving described input voltage, the reference current output of described current mirroring circuit connects the drain electrode of described second NMOS tube, and the image current output of described current mirroring circuit and the first end of described selector switch connect one to one;
Second end of described selector switch all links together and provides described benchmark light modulation electric current;
Described switch control unit is suitable for closing one or more selector switch according to described first dimming control signal.
6. drive circuit as claimed in claim 1, it is characterized in that, described dimming control unit comprises: PWM dimming unit, the first operational amplifier, the second NMOS tube, the 3rd resistance, current mirroring circuit, selector switch and switch control unit, and described dimming control signal comprises the second dimming control signal;
Described PWM dimming unit is suitable for producing PWM according to described second dimming control signal and adjusts signal, and according to described PWM adjustment signal, described first reference voltage is converted to changing voltage, magnitude of voltage=the Vreg*Duty of described changing voltage, Vreg is the magnitude of voltage of described first reference voltage, and Duty is the duty ratio that described PWM adjusts signal;
The normal phase input end of described first operational amplifier is suitable for inputting described changing voltage, the negative-phase input of described first operational amplifier connects the source electrode of described second NMOS tube and the first end of the 3rd resistance, and the output of described first operational amplifier connects the grid of described second NMOS tube;
Second end ground connection of described 3rd resistance;
Described current mirroring circuit comprises: input, reference current output and image current output, the quantity of described image current output is identical with described selector switch quantity, the input of described current mirroring circuit is suitable for receiving described input voltage, the reference current output of described current mirroring circuit connects the drain electrode of described second NMOS tube, and the image current output of described current mirroring circuit and the first end of described selector switch connect one to one;
Second end of described selector switch all links together and provides described benchmark light modulation electric current;
Described switch control unit is suitable for closed one or more selector switch.
7. drive circuit as claimed in claim 6, it is characterized in that, described dimming control signal also comprises the first dimming control signal;
Described switch control unit is suitable for closing one or more selector switch according to described first dimming control signal.
8. drive circuit as claimed in claim 1, it is characterized in that, described constant-current control unit also comprises: the 3rd NMOS tube, the 4th NMOS tube, the 5th NMOS tube and the second operational amplifier;
The drain electrode of described 3rd NMOS tube connects the described grid of the 4th NMOS tube and the first input end of described constant-current control unit, the grid of described 3rd NMOS tube connects the output of described second operational amplifier, and the source electrode of described 3rd NMOS tube connects the negative-phase input of described second operational amplifier and the drain electrode of the 4th NMOS tube;
The source electrode of described 4th NMOS tube connects described constant-current control unit first output;
The drain electrode of described 5th NMOS tube connects the normal phase input end of described second operational amplifier and the second input of described constant-current control unit, and the source electrode of described 5th NMOS tube connects described constant-current control unit second output.
9. drive circuit as claimed in claim 1, is characterized in that, described booster circuit adopts switch DC
Boosting framework.
10. an illuminating circuit, is characterized in that, comprises drive circuit according to claim 1 and described light-emitting diode group.
11. 1 kinds of mobile terminals, is characterized in that, comprise illuminating circuit according to claim 10 and display screen, and described display screen is with the light-emitting diode group light source as a setting 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 |
Applications Claiming Priority (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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| CN105163431A true CN105163431A (en) | 2015-12-16 |
| CN105163431B 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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| 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 |
| CN108174487A (en) * | 2018-01-17 | 2018-06-15 | 深圳市崧盛电子股份有限公司 | A kind of adjustable light power supply of displayable output parameter |
| 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 |
| CN111258366A (en) * | 2018-11-30 | 2020-06-09 | 米彩股份有限公司 | Driving circuit for LED |
| CN111369932A (en) * | 2018-12-24 | 2020-07-03 | 北京新岸线移动多媒体技术有限公司 | Driving method and driving circuit of display device |
| CN112823569A (en) * | 2018-10-10 | 2021-05-18 | 华为技术有限公司 | Dimming circuit and integrated circuit |
| 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 |
| CN114420055A (en) * | 2021-12-24 | 2022-04-29 | 北京奕斯伟计算技术有限公司 | Driving circuit and driving method, backlight module and display device |
| 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 |
| CN115185330A (en) * | 2022-08-18 | 2022-10-14 | 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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| 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 |
| CN107750076B (en) * | 2017-11-22 | 2024-04-23 | 深圳中电数码显示有限公司 | LED driving circuit |
| CN108174487A (en) * | 2018-01-17 | 2018-06-15 | 深圳市崧盛电子股份有限公司 | A kind of adjustable light power supply of displayable output parameter |
| 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 |
| CN112823569A (en) * | 2018-10-10 | 2021-05-18 | 华为技术有限公司 | Dimming circuit and integrated circuit |
| 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 |
| CN111369932A (en) * | 2018-12-24 | 2020-07-03 | 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 |
| CN114420055A (en) * | 2021-12-24 | 2022-04-29 | 北京奕斯伟计算技术有限公司 | 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 |
| CN115185330A (en) * | 2022-08-18 | 2022-10-14 | 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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