CN104238614A - Reference voltage circuit - Google Patents
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- CN104238614A CN104238614A CN201410447165.3A CN201410447165A CN104238614A CN 104238614 A CN104238614 A CN 104238614A CN 201410447165 A CN201410447165 A CN 201410447165A CN 104238614 A CN104238614 A CN 104238614A
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Abstract
The invention discloses a reference voltage circuit. The reference voltage circuit comprises a first resistor R1, a second resistor R2, a third resistor R3, a first NPN triode Q1, a second NPN triode Q2, an operational amplifier OP, a reference voltage output end VREF and an offset cancelling module, wherein the connection relation of the components is that the second resistor R2 is connected with the first NPN triode Q1, the third resistor R3 is connected with the second NPN triode Q2, the first resistor R1, the second resistor R2 and the third resistor R3 are connected with the offset cancelling module, the offset cancelling module is connected to a positive-phase input end and a negative-phase input end of the operational amplifier OP, and an output end of the operational amplifier is connected with the reference voltage output end VREF; the offset cancelling module comprises a built-in switching circuit. The reference voltage module can effectively reduce or eliminate the influence of offset voltage on precision to achieve a high-stability and high-precision design goal, and can be widely applied to occasions with high requirements on reference voltage accuracy, for example, a drive circuit for LED (Light Emitting Diode) scan display.
Description
Technical field
The present invention relates to a kind of reference voltage circuit, refer in particular to the reference voltage circuit in the display device possessing the array that multiple light-emitting component is formed.
Background technology
LED (Light Emitting Diode, light emitting diode) as a kind of emerging light source device, in recent years, its chip structure, packing forms, type of drive and application all there occurs earth-shaking change, Ge great manufacturer, company and research institution, in the ascendant to the research of LED, its research emphasis is placed on the aspects such as luminous intensity, glow frequency (colourity), luminance purity (frequency spectrum) and the luminescence efficiency improving LED light source more.The raising of These parameters (particularly the index of optical property aspect) or improvement, except having much relations with the structure, material (or component) etc. of luminescent device self, with the luminous energy providing source of LED---driving circuit (also known as type of drive) also has extremely close relationship.Usually, the type of drive of LED mainly contains constant voltage driving, constant current driving and pulsed drive (mainly referring to that PWM drives) three kinds.Among above-mentioned driving side, first two is that stable state drives, and the voltage at LED two ends or the electric current flowing through LED do not change in time; The third is that transient state drives, and the driving voltage of LED or electric current all can change in time and change, and thus, its characteristics of luminescence also can drive with stable state to be distinguished to some extent.The colourity of the light that LED sends can change along with the curent change by its luminescent device, but, in many application scenarios or purposes (as liquid crystal panel backlight, automobile instrument panel backlight etc.), all can not allow LED that the drift of any color occurs.Wherein PWM (Pulse Width Modulation, width modulation) Driving technique can by regulating driving pulse dutycycle (total amount of turn-on time) to control LED luminance under full electric current drives, realize the particular/special requirement that light modulation is not mixed colours, therefore have extremely wide application prospect.
Application number is the Chinese invention patent application of 201110174346X, and provide a kind of constant current driving method, its circuit structure diagram as shown in Figure 1.Whole constant-current driven chip can be divided into 4 parts: bandgap voltage reference, PLC technology current circuit, 8 identical inside contain constant current output and the protection circuit of automatic zero set (AZS) circuit.The follower that PLC technology current circuit is made up of operational amplifier A 1 and M1 pipe, two pipe compositions that outer meeting resistance RSET1, RSET2 and enable signal EN1, EN2 control.Follower, M2 and the switch S 1, S2 that 8 constant current outputs containing automatic zero set (AZS) circuit are made up of A2 and power tube M3 and S3 and two resistance R1 and R2 are formed.Different electric currents is produced by arranging different RSET1 with RSET2 values.Easily find out from Fig. 1, the electric current I LED flowing through LED is:
In the equation above, VA is the voltage of A point, and VOS is the offset voltage of operational amplifier A 2.VREF is internal reference voltage.Be not difficult to find out from formula (1), the offset voltage of the ratio of drive current ILED size and M2 and M1 mirroring ratios N, reference voltage V REF, R1 and R2, RSETX and operational amplifier is relevant.Therefore, ensure the precision of output current, the offset voltage of the stability of reference voltage, the matching of resistance and operational amplifier, these factors all need to carry out thickly considering in week.
In patented claim 201110174346X, have employed the precision that automatic zero set (AZS) technology (AZT) improves voltage and current.By sampling to low-frequency noise and imbalance, input or output end then at operational amplifier, they are deducted from the instantaneous value of output signal, realize the reduction to imbalance and 1/f noise.Not only because it is a kind of lack sampling process to broadband white noise, can cause the aliasing of white noise, can increase the white noise of low frequency end while reducing 1/f noise, therefore AZT is more suitable for the discrete signal circuit such as switching capacity.AZT comprises two stages: the processing stage of imbalance sample phase and input signal.In imbalance sample phase, amplifier and input signal disconnect.Lack of proper care measured and be stored in electric capacity.Input signal processing stage, amplifier amplification input signal also deducts the offset voltage stored previous stage from output signal.AZT amplifier ultimate principle figure as shown in Figure 2.It comprises basic amplifier Gm1, compensator-amplifier unit Gm2, second level amplifier A4 and feedback amplifier A3, electric capacity Ch, and two switch S 1, S2.Ro be Gm1 and Gm2 output impedance (1) imbalance sample phase, switch S 2 is connected with b point, and make the input end short circuit of Gm1 and disconnect with input signal, therefore Gm1 only has offset voltage VOS1 at input end.The offset current I1 that offset voltage produces is:
I1＝Gm1Vos1(2)
Switch S 1 closes, and amplifier A3 fed-back output voltage is to the end of oppisite phase of Gm2.Gm2 output current I2 is:
I2＝-Gm2(A3Vo-Vos2)(3)
Vo＝Ro(I1+I2)A4(4)
Vos2 is the input offset voltage of Gm2, and Vo is output voltage.I2 is the offset current of current compensation basic amplifier Gm1, and it is contrary and proportional with output offset voltage direction.Formula (2) and formula (3) are substituted in formula (4), can bucking voltage VC be solved.Input signal processing stage, switch S 2 is connected with a point, and the input end of Gm1 is connected with input signal, and backfeed loop is disconnected (S1 shutoff), and at this moment VC store voltages is in Ch.Because cmos circuit breaker in middle metal-oxide-semiconductor realizes, input signal processing stage, channel charge injection effect when the remaining offset voltage analysis of AZT must consider switch transition.When switch S 1 turns off, channel charge part is injected into node VC, changes the voltage that Ch stores.Change in voltage is:
Vc＝qinj/Ch(6)
The voltage that output voltage and remaining offset voltage VOSres are differential input signal input signal processing stage exports when being zero is respectively:
Wherein, Vi is input signal.The voltage that remaining offset voltage VOSres is differential input signal to be exported when being zero.From formula (8), Gm1 offset voltage is reduced to 1/ (Gm1RoA3A4), and the offset voltage of Gm2 amplifier is reduced to 1/ (Gm2RoA3A4).
But in technique scheme, suppose that reference voltage V REF is constant, this is difficult to accomplish in practice.Therefore the high precision design of VREF is urgently to be resolved hurrily.
The invention provides a kind of design proposal of reference voltage of simple possible, cost is low, and precision is high, is particularly suitable for being applied in the constant-current drive circuit of LED.
Summary of the invention
A technical scheme of the present invention, provide a kind of reference voltage module, comprise operational amplifier OP, reference voltage output end VREF and imbalance cancellation module, imbalance cancellation module is connected to normal phase input end and the inverting input of operational amplifier OP, and the output terminal of operational amplifier is connected with reference voltage output end VREF; Cancellation module of wherein lacking of proper care comprises built-in on-off circuit, and the positive and negative terminal of amplifier, by built-in on-off circuit, is periodically carried out periodicity with a fixed frequency and switches by offset cancellation circuit 202.
Present invention also offers a kind of voltage reference module, it is characterized in that, by periodically switching, the offset voltage existed between positive and negative terminal is periodically added to amplifier anode or negative terminal, thus positive offset voltage and negative offset voltage are added zero, realize eliminating offset voltage to the impact of voltage accuracy.
Present invention also offers a kind of voltage reference module, it is characterized in that, also comprise clock module, clock module is connected with offset cancellation circuit.
Present invention also offers a kind of voltage reference module, it is characterized in that, under the control of pulse clock signal, periodically switch.
Present invention also offers a kind of voltage reference module, it is characterized in that, clock module is connected with operational amplifier.
Present invention also offers a kind of voltage reference module, it is characterized in that, the reference voltage of voltage reference module for providing LED constant current to drive
Present invention also offers a kind of constant-current driven module, comprise said reference voltage module.
Present invention also offers a kind of LED constant current driver module, comprise said reference voltage module.
Present invention also offers a kind of LED and show constant-current driven module, comprise said reference voltage module.
Present invention also offers the constant-current driven module that a kind of LED scans display, comprise said reference voltage module.
Present invention also offers a kind of constant-current driven chip, comprise said reference voltage module.
Present invention also offers a kind of IC chip, this chip comprises reference voltage module, comprises the first resistance R1, the second resistance R2, the 3rd resistance R3, a NPN triode Q1, the 2nd NPN triode Q2, operational amplifier OP, reference voltage output end VREF and imbalance cancellation module; The annexation of above-mentioned parts is: the second resistance R2 is connected with a NPN triode Q1,3rd resistance R3 is connected with the 2nd NPN triode Q2, first resistance R1, the second resistance R2, the 3rd resistance R3 are connected with imbalance cancellation module, and imbalance cancellation module is connected to normal phase input end and the inverting input of operational amplifier OP; Cancellation module of wherein lacking of proper care comprises built-in on-off circuit.
What it is to be noted in the present invention is so-called rectangular, and the arrangement can be such as the some the linear alignment of only 1 row or only 1 row, 1 row 1 arranges, being namely only made up of 1 driven element is also contained in this.The saying of so-called matrix not performance global shape, does not need the necessity necessarily becoming square mesh shape, and therefore, can become can in bending and flexibly carry out the configuration of change of shape.If the connection form connected is rectangular connection, no matter shape, the form of then reality.But, if also comprise true form and become rectangular, then can carry out the distribution of charge-discharge control circuit easily, therefore, become more desirable.
Advantage of the present invention, target and feature will be set forth to a certain extent in the following description, and to a certain extent, based on will be apparent to those skilled in the art to investigating hereafter, or can be instructed from the practice of the present invention.Target of the present invention and other advantages can by instructionss below, claims, and in accompanying drawing, specifically noted structure realizes and obtains.
Accompanying drawing explanation
Fig. 1 is the constant-current drive circuit figure of prior art
Fig. 2 is the automatic zero set (AZS) circuit diagram of prior art
Fig. 3 is the reference voltage circuit figure of one embodiment of the present of invention
Fig. 4 a is the reference voltage circuit figure of front semiperiod
Fig. 4 b is the reference voltage circuit figure in later half cycle
Embodiment
Describe embodiments of the present invention in detail below with reference to drawings and Examples, to the present invention, how application technology means solve technical matters whereby, and the implementation procedure reaching technique effect can fully understand and implement according to this.It should be noted that, only otherwise form conflict, each embodiment in the present invention and each feature in each embodiment can be combined with each other, and the technical scheme formed is all within protection scope of the present invention.
In the power supply system, such as, in the power supply system of LED display, power supply needs to produce the gamma electric voltage of driving required for pixel PXL, driving voltage, ground voltage and reference voltage etc.For this reason, power supply generally includes: the reference voltage generating circuit of produce the gamma voltage generation circuit of gamma electric voltage, produce the drive voltage generating circuit of driving voltage, the produce earth voltage generating circuit of ground voltage and generation reference voltage.The driving voltage produced from drive voltage generating circuit is fed into pixel via driving voltage supply lines.
When constant current integrated circuit selects LM317 chip for constant current source, output current Io=(the VREF/R)+IADJ of LM317, in formula, VREF is reference voltage, for 1.25V, IADJ is the electric current flowed out from adjustment end, and usual IADJ≤50 μ A, can ignore.The constant current effect of visible LM317 is better.As can be seen from the LED current formula of output channel, output current precision depends primarily on the precision of internal reference voltage VREF, if this reference voltage of every IC can do very accurate, so just can guarantee that the difference between IC is very little.
When design, the present invention has carried out careful design to this reference voltage, and circuit framework adopts automatic balancing technology, can effectively reduce or eliminate the impact of offset voltage on precision, reach high stability and high-precision design object.
The design philosophy of foregoing circuit is: the positive and negative terminal of amplifier is carried out periodicity with a fixed frequency and switches, so, the offset voltage existed between positive and negative terminal will be periodically added to amplifier anode or negative terminal, thus positive offset voltage and negative offset voltage are added zero, thus realize eliminating offset voltage to the impact of precision.This structure in a chip design practical application is authenticated, and test effect is very good.In this, design proposal does not increase system cost simultaneously, also enhances the reliability of system, adds the elasticity of system simultaneously.
With reference to figure 3, be the theory diagram of an embodiment designed according to reference voltage of the present invention, it is by operational amplifier 201, offset cancellation circuit 203, and clock generating circuit 203 forms.Clock generating circuit 203, in order to receive a control signal; Described control signal is the square-wave signal of a variable duty ratio, and generation one and described control signal have the clock signal of certain sequential relationship accordingly; Operational amplifier 201, its in-phase input end receives input voltage, and inverting input can receive the feedback voltage of the output load of such as Voltage-controlled Current Source; Offset cancellation circuit 202, receives described clock signal, in order to eliminate the input imbalance of described operational amplifier 201.
Offset cancellation circuit 202 is by built-in on-off circuit, periodically the positive and negative terminal of amplifier is carried out periodicity with a fixed frequency to switch, so, the offset voltage existed between positive and negative terminal will be periodically added to amplifier anode or negative terminal, thus positive offset voltage and negative offset voltage are added zero, thus realize eliminating offset voltage to the impact of precision.
Those skilled in the art should know, and the inside of offset cancellation circuit switches can by being not limited to switching tube, logic array, and the modes such as programmable logic array have been come, but the present invention is not limited to above-mentioned technological means.Such as, above-mentioned switch can be realized by transmission gate, the impact of charge injection to circuit parameter and the harmful effect of precision can be reduced further.
Course of work composition graphs 4a and 4b of above-mentioned offset cancellation circuit tells about.Fig. 4 a describes the situation of front semiperiod, and Fig. 4 b describes the situation in later half cycle.In the front semiperiod, VA+VOS=VB (a), in the later half cycle, VA '+VOS '=VB ' (b).After switching through the positive and negative terminal of an amplifier, VA=VA ', VB=VB ', VOS=-VOS '.Formula (a) and (b) are added, and the quantitative relation of each voltage after switching in conjunction with positive and negative terminal, finally can draw VA=VB.As can be seen here, the mode that this cycle switches, makes the impact of offset voltage be eliminated.
Present invention also offers a kind of IC chip, this chip comprises reference voltage module, comprises the first resistance R1, the second resistance R2, the 3rd resistance R3, a NPN triode Q1, the 2nd NPN triode Q2, operational amplifier OP, reference voltage output end VREF and imbalance cancellation module; The annexation of above-mentioned parts is: the second resistance R2 is connected with a NPN triode Q1,3rd resistance R3 is connected with the 2nd NPN triode Q2, first resistance R1, the second resistance R2, the 3rd resistance R3 are connected with imbalance cancellation module, and imbalance cancellation module is connected to normal phase input end and the inverting input of operational amplifier OP; Cancellation module of wherein lacking of proper care comprises built-in on-off circuit.
Although the embodiment disclosed by the present invention is as above, the embodiment that described content just adopts for the ease of understanding the present invention, and be not used to limit the present invention.Technician in any the technical field of the invention; under the prerequisite not departing from the spirit and scope disclosed by the present invention; any amendment and change can be done what implement in form and in details; but scope of patent protection of the present invention, the scope that still must define with appending claims is as the criterion.
Claims (10)
1. a reference voltage circuit, comprises operational amplifier, reference voltage output end and imbalance cancellation module; Wherein, cancellation module of lacking of proper care is connected to normal phase input end and the inverting input of operational amplifier; The output terminal of operational amplifier is connected with reference voltage output end; Cancellation module of wherein lacking of proper care comprises built-in on-off circuit, and the normal phase input end of operational amplifier and inverting input, by built-in on-off circuit, periodically switch with a fixed frequency by offset cancellation circuit.
2. reference voltage circuit as claimed in claim 1, it is characterized in that, by periodic switching, the offset voltage that opamp input terminal exists periodically is added to normal phase input end and the inverting input of operational amplifier, thus positive offset voltage and negative offset voltage are added zero, realize eliminating offset voltage to the impact of reference voltage precision.
3. reference voltage circuit as claimed in claim 1, is characterized in that, when on-off circuit periodically switches, in front semiperiod and later half cycle, the symbol of the offset voltage that the input end of operational amplifier receives is contrary.
4. reference voltage circuit as claimed in claim 1, is characterized in that, also comprise clock module, and clock module is connected with imbalance cancellation module, and under the control of pulse clock signal, on-off circuit periodically switches.
5. reference voltage circuit as claimed in claim 1, it is characterized in that, described on-off circuit is made up of transmission gate.
6. reference voltage circuit as claimed in claim 1, is characterized in that, the reference voltage of described reference voltage circuit for providing LED constant current to drive.
7. a constant-current drive circuit, comprises reference voltage circuit as described in one of claim 1-6.
8. a LED drive chip, comprises reference voltage circuit as described in one of claim 1-6.
9. a LED display drive chip, comprises reference voltage circuit as described in one of claim 1-6.
10. scan a driving circuit for display, comprise PLC technology current circuit and constant current output and protection circuit, and as described in one of claim 1-6 reference voltage circuit; Wherein, the reference voltage of current output channels is produced by described reference voltage circuit.
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Cited By (6)
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| CN106466177A (en) * | 2015-08-17 | 2017-03-01 | 浙江诺尔康神经电子科技股份有限公司 | A kind of artificial cochlea's nerve telemetry system comprising pulse-width adjustment |
| CN109510274A (en) * | 2018-12-11 | 2019-03-22 | 鞍钢集团工程技术有限公司 | A kind of lithium battery pre-charge circuit |
| CN109672325A (en) * | 2019-01-22 | 2019-04-23 | 西安拓尔微电子有限责任公司 | A kind of quantifiable anti-charge is counter to fill load switching circuit |
| CN109830215A (en) * | 2019-02-20 | 2019-05-31 | 京东方科技集团股份有限公司 | A kind of gamma-correction circuit, bearing calibration, source electrode drive circuit and display panel |
| CN113484788A (en) * | 2021-07-14 | 2021-10-08 | 安徽聆思智能科技有限公司 | Reference voltage source test system, reference voltage source circuit and chip |
| CN113687125A (en) * | 2020-05-18 | 2021-11-23 | 广州汽车集团股份有限公司 | Offset voltage correction method and system for operational amplifier in current detection circuit |
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