CN114123886A - Drive circuit, OIS chip and electronic equipment - Google Patents
Drive circuit, OIS chip and electronic equipment Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P7/00—Arrangements for regulating or controlling the speed or torque of electric DC motors
- H02P7/02—Arrangements for regulating or controlling the speed or torque of electric DC motors the DC motors being of the linear type
- H02P7/025—Arrangements for regulating or controlling the speed or torque of electric DC motors the DC motors being of the linear type the DC motors being of the moving coil type, e.g. voice coil motors
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/02—Mountings, adjusting means, or light-tight connections, for optical elements for lenses
- G02B7/04—Mountings, adjusting means, or light-tight connections, for optical elements for lenses with mechanism for focusing or varying magnification
- G02B7/09—Mountings, adjusting means, or light-tight connections, for optical elements for lenses with mechanism for focusing or varying magnification adapted for automatic focusing or varying magnification
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B13/00—Viewfinders; Focusing aids for cameras; Means for focusing for cameras; Autofocus systems for cameras
- G03B13/32—Means for focusing
- G03B13/34—Power focusing
- G03B13/36—Autofocus systems
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Abstract
A drive circuit, OIS chip and electronic equipment, the circuit includes: the current source module is used for providing constant current; the driving output module comprises a first operational amplifier and at least one first transistor, wherein a first input end of the first operational amplifier is connected to a fixed voltage end, a second input end of the first operational amplifier is connected to a third end of the first transistor, an output end of the first operational amplifier is connected to a second end of the first transistor, and a first end of the first transistor is used for outputting driving current according to the constant current. The constant current is generated through the current source module, the mirror image current of the constant current is obtained through the driving output module and is used as the driving current, and the driving current is the mirror image of the constant current and is irrelevant to the resistance, so that the accuracy of outputting the driving current is improved.
Description
Technical Field
The present application relates to the field of electronic technologies, and in particular, to a driving circuit, an OIS (optical anti-shake) chip, and an electronic device.
Background
Camera modules are used in a variety of consumer electronic devices, including smart phones, mobile audio players, laptops and desktop computers. The camera module generally has an Auto Focus (AF) function that automatically adjusts a focus by a controller acquiring information of a photographed picture and then instructing a specific driving current output from a driving circuit to be supplied to a coil of a motor to control a lens movement.
The principle of the existing driving circuit is that through the virtual short and virtual break characteristics of an operational amplifier, a reference voltage output to the operational amplifier by a digital-to-analog conversion unit is transmitted to a detection resistor, so that a driving current is output.
Disclosure of Invention
In view of this, the present application provides a driving circuit, an OIS chip and an electronic device to solve the problem of low driving current precision caused by the correlation between the driving current and the resistance of the detection resistor in the conventional driving circuit.
The application provides a drive circuit, including: the current source module is used for providing constant current;
the driving output module comprises a first operational amplifier and at least one first transistor, wherein a first input end of the first operational amplifier is connected to a fixed voltage end, a second input end of the first operational amplifier is connected to a third end of the first transistor, an output end of the first operational amplifier is connected to a second end of the first transistor, and a first end of the first transistor is used for outputting driving current according to the mirror image current of the constant current.
Optionally, the current source module includes a constant current generating unit and a control unit; the constant current generating unit is used for generating the constant current; the control unit is connected with the input end of the constant current generation unit and the first input end of the first operational amplifier, and is used for controlling the voltage of the first input end and the voltage of the second input end of the first operational amplifier to be equal to the voltage of the input end of the constant current generation unit so as to eliminate the influence of offset voltage of the first operational amplifier.
Optionally, the current source module further includes a proportional amplification unit; the proportional amplification unit is connected between the third end of the first transistor and the output end of the constant current generation unit and is used for amplifying the driving current in a preset proportion.
Optionally, the constant current generating unit includes at least one of: a constant current source, a mirror current subunit, and a cascode subunit.
Optionally, when the constant current generating unit is a mirror current subunit, the mirror current subunit includes at least a second transistor, a third transistor, and a current source, a first end of the second transistor is connected to the output end of the current source, a second end of the second transistor is connected to the second end of the third transistor, a third end of the second transistor, and a third end of the third transistor are all grounded, the second transistor and the third transistor form a current mirror, and a first end of the third transistor is used for outputting a constant current.
Optionally, the control unit includes a second operational amplifier; the first input end of the second operational amplifier is connected with the first end of the second transistor, the second input end of the second operational amplifier is connected with the fixed voltage end, and the output end of the second operational amplifier is connected with the second end of the second transistor.
Optionally, the current source module further includes a fixed voltage generating unit; the output end of the fixed voltage generating unit is connected to the fixed voltage end for outputting a fixed voltage.
Optionally, the fixed voltage generating unit is a digital-to-analog converting unit based on a resistor.
Optionally, the driving circuit is a constant current driving circuit including the digital-to-analog conversion unit; the digital-to-analog conversion unit comprises a voltage source and a resistor, wherein the voltage source is connected with one end of the resistor to form the fixed voltage, the other end of the resistor is grounded, and the resistor is used for controlling the voltage value of the fixed voltage; and the proportion amplification unit is used for carrying out proportion amplification on the driving current according to the output result of the digital-to-analog conversion unit and a preset proportion value.
The application also provides an OIS chip which comprises the driving circuit.
The application also provides an electronic device comprising the driving circuit or the OIS chip.
The application of the drive circuit, the OIS chip and the electronic equipment generates the constant current through the current source module, the mirror current of the constant current is obtained through the drive output module and is used as the drive current, and the precision of the output drive current is improved because the drive current is the mirror image of the constant current and is irrelevant to the resistance.
Furthermore, a fixed voltage is generated by the fixed voltage generating unit, the first operational amplifier and the second operational amplifier are connected with the fixed voltage, so that the change range of input signals of the two operational amplifiers is small, the operational amplifier can be always in a normal working state, and the linearity of the driving current is improved.
Further, when the driving circuit is a constant current driving circuit including the digital-to-analog conversion unit, a voltage is generated by the digital-to-analog conversion unit based on the resistance and is supplied to the first operational amplifier and the second operational amplifier, and the magnitude of the driving current does not depend on the resistance proportion any more at this time, so that the resistance type and the resistance proportion of the digital-to-analog conversion unit are not limited, and even if the required driving current is small, the input and the output of the second operational amplifier are not adjusted in a large range, thereby stabilizing the working state of the first operational amplifier.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a driving circuit;
FIG. 2 is a schematic structural diagram of a driving circuit according to an embodiment of the present disclosure;
FIG. 3 is a schematic structural diagram of a driving circuit according to an embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of a driving circuit according to an embodiment of the present application.
With the above figures, there are shown specific embodiments of the present application, which will be described in more detail below. These drawings and written description are not intended to limit the scope of the inventive concepts in any manner, but rather to illustrate the inventive concepts to those skilled in the art by reference to specific embodiments.
Detailed Description
The technical solutions in the embodiments of the present application are clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. The following embodiments and their technical features may be combined with each other without conflict.
The operational amplifier has the characteristics of an imaginary short and an imaginary break. The virtual shortness means: because the voltage amplification factor of the operational amplifier is large and the output voltage of the operational amplifier is usually limited, the input differential voltage of the operational amplifier is small, which can reach below 1mV (millivolt), so that the two input end potentials can be regarded as approximately equal, namely, equivalent to a short circuit. The larger the open-loop voltage amplification factor of the operational amplifier is, the more nearly equal the potentials of the two input ends are. Therefore, when the operational amplifier is analyzed, two input ends of the operational amplifier can be regarded as equipotential, and the circuit is not really a short circuit, which is called false short circuit, or virtual short for short.
The virtual interruption means: meanwhile, because the differential mode input resistance of the operational amplifier is very large, the current flowing into the input end of the operational amplifier is very small and is far smaller than the current of a circuit outside the input end, so that the two input ends of the operational amplifier can be regarded as open circuits, and the larger the input resistance is, the closer the two input ends are to the open circuit. Therefore, when the operational amplifier is analyzed, the two input ends can be regarded as an equivalent open circuit, and the characteristic is called a false open circuit, which is called a virtual break for short. However, the two inputs of the actual circuit are not really open.
Hereinafter, the circuit of the specific embodiment is analyzed based on the above analysis of the virtual short and the virtual break of the operational amplifier.
Fig. 1 is a schematic structural diagram of a driving circuit.
In the drive circuit, a DAC circuit for digital-to-analog conversion passes through a bias current IBIASAnd a resistor R _ DAC for generating a reference voltage VrefThe reference voltage VrefConnected to the non-inverting input terminal of an operational amplifier OP, the inverting input terminal of the operational amplifier OP being connected to one terminal of a detection resistor R, the other terminal of the detection resistor R being grounded to generate a feedback voltage Vfb. The output end of the operational amplifier OP is connected with the gate of the driving transistor for outputting a gate driving voltage Vout, the source of the driving transistor is connected with the inverting input end of the operational amplifier OP, and the drain of the driving transistor is used for outputting a driving current Iout。
Reference voltage VrefThe following formula is satisfied:
Vref＝IBIAS*R_DAC (1)
by using the pseudo-short characteristic of the operational amplifier, it is possible to obtain: vref＝Vfb。
Gate drive voltage V due to output of operational amplifieroutIs finite, when the operational amplifier open loop gain is sufficiently large, the reference voltage VrefAnd a feedback voltage VfbAre almost equal, and therefore the final drive current IoutCan be calculated by the following formula:
Iout＝Vfb/R＝Vref/R＝(IBIAS*R_DAC)/R (2)
as can be seen from the formula (2), the driving current IoutAnd a bias current IBIASIs linearly dependent and its value depends on the ratio of the resistor R _ DAC and the resistor R. When designing a circuit, the resistor R _ DAC and the detection resistor R are usually selected to have the same resistor type to eliminate the influence of the resistor on the output driving current, and the resistance of the resistor R is fixed, so that the appropriate bias current I is selectedBIASProportional to the resistance, the required drive current I can be obtainedout。
From the above analysisThe drive circuit realizes the required drive current IoutThe key point is that the virtual short characteristic of the operational amplifier is utilized to enable the reference voltage VrefAnd a feedback voltage VfbBut in practice the operational amplifier will have an offset voltage VoffsetThe above equation (2) is actually:
Iout＝Vfb/R＝(Vref+Voffset)/R＝(IBIAS*R_DAC)/R+Voffset/R (3)
also, since there is a deviation between the resistor R _ DAC and the resistor R, if K represents a ratio of the resistor R _ DAC and the resistor R and Δ K represents a ratio deviation of the resistor R _ DAC and the resistor R, the above equation (3) can be written as:
Iout＝IBIAS*(K+ΔK)+Voffset/R (4)
it can be seen that there is an offset voltage V due to the operational amplifieroffsetAnd the deviation exists between the resistor R _ DAC and the resistor R, namely, the resistor is mismatched, so that the driving current precision is greatly influenced. In addition, when the required drive current is small, the reference voltage VrefThe value is also slightly smaller to reach the level of μ V (microvolt), and when the input voltage is too small, the working state of the operational amplifier is affected, so that the gain of the operational amplifier is reduced, and the reference voltage V is reducedfbAnd a feedback voltage VrefThe difference is larger, further reducing the accuracy of the drive current.
Aiming at the problems, the invention provides a novel driving circuit which can solve the problem of resistor mismatch and improve the precision of driving current.
Referring to fig. 2, a schematic diagram of a driving circuit according to an embodiment of the present disclosure is shown.
The driving circuit of the embodiment includes a current source module 1 and a driving output module 2.
The current source module 1 is used to provide a constant current.
The driving output module 2 comprises a first operational amplifier and at least one first transistor, wherein a first input end of the first operational amplifier is connected to the fixed voltage end, a second input end of the first operational amplifier is connected to the third end of the first transistor, an output end of the first operational amplifier is connected to the second end of the first transistor, and a first end of the first transistor is used for outputting driving current according to the mirror image current of the constant current.
The first input terminal of the first operational amplifier may be connected to a current source, a voltage source through a resistor, or directly to a fixed voltage generating unit for generating a fixed voltage. The first transistor comprises one or more of a diode, a triode, a field effect transistor, a thyristor, etc.
Specifically, the driving current output by the first transistor is related to the mirror current of the constant current, for example, the driving current is multiple times of the mirror current, and the mirror current is an accurate mirror image of the constant current value, so the output driving current is also accurate, the size of the driving current does not depend on the resistance proportion any more, the influence caused by resistance mismatch is eliminated, and the precision of the driving current is improved.
The drive circuit of this embodiment produces the constant current through current source module, obtains the mirror image current of constant current as drive current through driving output module, because drive current is the mirror image current of constant current, and is irrelevant with resistance, has improved output drive current's precision.
In an alternative embodiment, the first operational amplifier may be omitted, and the second input terminal of the first transistor may be directly connected to other voltage modules, so as to simplify the circuit design.
In an alternative embodiment, the current source module includes a constant current generating unit and a control unit; the constant current generating unit is used for generating the constant current; the control unit is connected with the input end of the constant current generation unit and the first input end of the first operational amplifier, and is used for controlling the voltage of the first input end and the voltage of the second input end of the first operational amplifier to be equal to the voltage of the input end of the constant current generation unit so as to eliminate the influence of offset voltage of the first operational amplifier.
In this embodiment, the control module controls the voltage of the first input end and the voltage of the second input end of the first operational amplifier to be equal to the voltage of the input end of the constant current generation unit, and since the voltage of the second input end of the first operational amplifier is the voltage of the feedback loop, the influence of the offset voltage of the first operational amplifier can be eliminated, the driving current output by the driving circuit is no longer influenced by the offset voltage of the first operational amplifier, and the precision of the driving current is improved.
In an alternative embodiment, the constant current generating unit includes at least one of: a constant current source, a mirror current subunit, and a cascode subunit.
In an alternative embodiment, when the constant current generating unit is a mirror current sub-unit, the mirror current sub-unit includes at least a second transistor, a third transistor and a current source, a first terminal of the second transistor is connected to an output terminal of the current source, a second terminal of the second transistor is connected to a second terminal of the third transistor, a third terminal of the second transistor and a third terminal of the third transistor are all grounded, the second transistor and the third transistor form a current mirror, and a first terminal of the third transistor is used for outputting a constant current.
In this embodiment, the constant current generating unit includes a second transistor and a third transistor, a first end of the second transistor is connected to a current source, a second end of the second transistor is connected to a second end of the third transistor, a third end of the second transistor and a third end of the third transistor are both grounded, the second transistor and the third transistor form a current mirror, and a first end of the third transistor is used for outputting a constant current. Specifically, the second transistor includes one or more of a diode, a triode, a field effect transistor and a thyristor, the third transistor includes one or more of a diode, a triode, a field effect transistor and a thyristor, the second transistor and the third transistor can be the same or different, a current mirror is formed by the second transistor, the third transistor and a current source to generate a constant current, and the circuit is simple in structure and easy to implement.
In an alternative embodiment, the control unit comprises a second operational amplifier; the first input end of the second operational amplifier is connected with the first end of the second transistor, the second input end of the second operational amplifier is connected with the fixed voltage end, and the output end of the second operational amplifier is connected with the second end of the second transistor. In other alternative embodiments, the control unit may include a plurality of operational amplifiers, or circuits including other amplification functions.
In the driving circuit of this embodiment, the first input terminal of the second operational amplifier is connected to the first terminal of the second transistor, the second input terminal of the second operational amplifier is connected to the fixed voltage terminal, and the output terminal of the second operational amplifier is connected to the second terminal of the second transistor.
In an alternative embodiment, the driving circuit further includes a fixed voltage generating unit; the output end of the fixed voltage generating unit is connected to the fixed voltage end for outputting a fixed voltage.
At this time, the first input terminal of the second operational amplifier and the second input terminal of the first operational amplifier are connected to the same fixed voltage terminal. Because the fixed voltage value of the fixed voltage end is a fixed value and cannot change greatly, the situations that the input voltage of the operational amplifier is too small, the operational amplifier cannot work normally and the like cannot occur, the gain of the operational amplifier cannot be reduced, and the virtual short requirement can be met. Because the first input end of the second operational amplifier and the second input end of the first operational amplifier are connected with the same fixed voltage end, the voltages of the first input end and the second input end of the first operational amplifier are equal to those of the first input end and the second input end of the second operational amplifier according to the virtual short characteristic of the operational amplifier. The reference voltage V is smaller than that in FIG. 1 when the required drive current is smallerrefThe value is also small and reaches the level of μ V, so that the input voltage of the operational amplifier is too small, the working state of the operational amplifier is affected, and the gain is reducedSo that the feedback voltage VfbAnd a reference voltage VrefThe difference is larger, deteriorating the accuracy of the driving current. Therefore, the driving circuit of the embodiment can ensure that the input signal variation range of the two operational amplifiers is very small by connecting the first operational amplifier and the second operational amplifier with the same fixed voltage end, the operational amplifier can be always in a normal working state, and the precision of the driving current is improved.
Optionally, the first input terminal is a non-inverting input terminal of the operational amplifier, and the second input terminal is an inverting input terminal of the operational amplifier. In other alternative embodiments, the first input terminal may also be an inverting input terminal of the operational amplifier, and the second input terminal may also be a non-inverting input terminal of the operational amplifier. The first transistor, the second transistor and the third transistor are all NMOS transistors; the first end is a drain electrode of the transistor, the second end is a grid electrode of the transistor, and the third end is a source electrode of the transistor; in other alternative embodiments, the first transistor, the second transistor, and the third transistor may also be PMOS transistors.
In an alternative embodiment, the fixed voltage generating unit is a digital-to-analog converting unit based on a resistor.
Compared with the driving circuit in fig. 1, the resistor R _ DAC and the resistor R are usually selected to have the same resistor type to eliminate the influence of the resistor on the output driving current, as can be seen from equation (2), the driving current IoutAnd a bias current IBIASThe value of the linear correlation depends on the ratio of the resistor R _ DAC and the resistor R, the resistance value of the resistor R is usually fixed, and the required driving current can be obtained by selecting a proper bias current value and a proper resistor ratio. When the required driving current is small, the reference voltage VrefThe value is also slightly smaller to reach the level of μ V, and the input voltage is too small, which affects the operating state of the operational amplifier and further deteriorates the precision of the driving current. In this embodiment, when the fixed voltage generating unit is a resistance-based digital-to-analog converting unit, the magnitude of the output driving current does not depend on the resistance ratio any more, and therefore, the selection of the resistance type of the digital-to-analog converting unit may not be limitedThe proportion of the resistors is selected, so that the working state of the operational amplifier is in a stable state even if the required driving current is small, and the precision of the driving current is improved.
In other alternative embodiments, the fixed voltage generating unit may also be directly provided by a voltage source, or may be connected to a resistor through the voltage source and formed by dividing the voltage through the resistor.
Referring to fig. 3, a schematic diagram of a driving circuit according to an embodiment of the present disclosure is shown.
In addition to the above embodiments, in the driving circuit of this embodiment, the first transistor, the second transistor, and the third transistor are transistors NM1, NM2, and NM3, respectively, and the first transistor, the second transistor, and the third transistor may be N-channel transistors or P-channel transistors.
The current source module 1 includes a constant current generating unit 11 and a control unit 12.
The constant current generation unit 11 includes a second transistor NM2, a third transistor NM3, and a current source.
The control unit 12 includes a second operational amplifier OP 2.
In the current source module 1, the non-inverting input terminal of the second operational amplifier OP2 is connected to the current source and the drain of the second transistor NM2 to form the voltage VC, the inverting input terminal of the second operational amplifier OP2 is connected to the fixed voltage VA, the output terminal of the second operational amplifier OP2 is connected to the gates of the second transistor NM2 and the third transistor NM3, the sources of the second transistor NM2 and the third transistor NM3 are grounded, and the drain of the third transistor NM3 is used for outputting the mirror current of the constant current to the driving output module 2.
In the driving output module 2, a non-inverting input terminal of the first operational amplifier OP1 is connected to the fixed voltage VA, an inverting input terminal of the first operational amplifier OP1 is connected to a source of the first transistor NM1 and a drain of the third transistor NM3 to form the feedback voltage VB, an output terminal of the first operational amplifier OP1 is connected to a gate of the first transistor NM1 to form the gate driving voltage VD, and a drain of the first transistor NM1 is used for outputting the driving current Iout according to the mirror current.
The operating principle of the driving circuit in fig. 3 is as follows:
the constant voltage VA, which is used as the input signal of the first operational amplifier OP1 and the second operational amplifier OP2, is at a volt level, which ensures that the first operational amplifier OP1 and the second operational amplifier OP2 operate normally. Since the voltages at the non-inverting input terminal of the first operational amplifier OP1 and the inverting input terminal of the second operational amplifier OP2 are the same and are all fixed voltage VA, the voltages at the non-inverting input terminal and the inverting input terminal of the first operational amplifier OP1 and the second operational amplifier OP2 are all equal by using the virtual short characteristic of the operational amplifiers, that is, VC is VA, and VB is VA to obtain VC is VB, and at this time, the voltage V between the gate and the source of the second transistor NM2 is the same as VGS1And a voltage V between the gate and the source of the third transistor NM3GS2Equal, voltage V between drain and source of the second transistor NM2DS1And a voltage V between drain and source of the third transistor NM3DS2Equally, the current flowing through the second transistor NM2 is mirrored to the third transistor NM3, the current is mirrored accurately, and the mirrored current is output through the drain of the third transistor NM 3.
In practical circuits, the first operational amplifier OP1 and the second operational amplifier OP2 have offset voltages, which results in a voltage VCAnd VBThere is a difference, it is assumed that the offset voltages of the non-inverting input terminal and the inverting input terminal of the first operational amplifier OP1 and the second operational amplifier OP2 are both Voffset(offset voltage V)offsetEither positive or negative).
The current flowing through the second transistor NM2 is:
wherein, the ID1Is the current flowing through the second transistor, the μnIs the mobility of carriers in the channel, said CoxGate capacitance per unit area, gate length W1, gate width L1, and gate voltage VGS1Is the voltage between the gate and the source of the second transistor, the VTHIs the threshold voltage of the second transistor, the VDS1Is the firstAnd the voltage between the drain electrode and the source electrode of the two transistors and the lambda are channel modulation coefficients.
The current flowing through the third transistor NM3 is:
wherein, the ID2The μ is a current flowing through the third transistornIs the mobility of carriers in the channel, said CoxGate capacitance per unit area, gate length W2, gate width L2, and gate voltage VGS2Is the voltage between the gate and source of the third transistor, the VTHIs the threshold voltage of the third transistor, the VDS2The λ is a channel modulation coefficient which is a voltage between a drain and a source of the third transistor.
Therefore, there are:
for the second operational amplifier OP2, there is
VDS1＝VC＝VA+Voffset (8)
For the first operational amplifier OP1, there is
VDS2＝VB＝VA-Voffset (9)
Wherein λ is a channel modulation coefficient, satisfying the following formula:
wherein, for NMOS transistor, VEn4V/L (volt/L), L is the NMOS transistor channel length. In a typical design of a circuit, the channel length L of an NMOS transistor is greater than 4 μm (micrometers), and the channel modulation factor λ is smaller than 1-16 (unit is 1/V), channel modulation coefficients λ and V are set according to formula (7) and formulas (8) and (9)DS1And VDS2The multiplication results in that the offset voltage value of the operational amplifier is one sixteenth of the original value, so that the influence of the offset voltage of the operational amplifier is greatly reduced, and the influence of the offset voltage on the output driving current is further reduced.
When V isDS1And VDS2Very small difference, VDS1＝VDS2The above equation (7) is simplified as:
wherein W1/L1 is the channel width-length ratio of the second transistor, and W2/L2 is the channel width-length ratio of the third transistor.
The drive current I can be derivedoutComprises the following steps:
since the image current is more accurate, and the driving current I is finally outputoutThe value of (b) depends only on the channel width to length ratios of the second transistor NM2 and the third transistor NM3, eliminating the influence of the offset voltage of the operational amplifier. Due to the drive current IoutThe input end of the operational amplifier is connected with fixed voltage, the variation range of the input signal is very small, the operational amplifier can be always in a normal working state, and the linearity and the precision of the driving current are improved.
At the same time, the voltage V is fixed by trimmingAA voltage value that can change a voltage V between drain and source of the third transistor NM3DSSo that the on-resistance R of the third transistor NM3 may be adjusteddson. When the voltage V between the drain and the source of the third transistor NM3 is reducedDSWhile, the on-resistance RdsonThe power consumption of the driving circuit can be reduced and the driving capability can be improved.
The driving circuit can be applied to the technical field of constant current, namely, the constant current driving circuit, and can also be applied to other technical fields, such as radio frequency transceivers.
Based on the formula:
it is known that the parameters affecting the precision of the driving current include the channel modulation factor of the transistor, and when the channel modulation factor of the transistor is less than 1/16, the offset voltage effect of the operational amplifier can be reduced.
The driving circuit of the embodiment connects the current source and the drain of the second transistor through the non-inverting input terminal of the second operational amplifier, connects the fixed voltage terminal through the inverting input terminal, and connects the gate of the second transistor through the inverting input terminal, and since the virtual short characteristics of the first operational amplifier and the second operational amplifier make the input voltages of the first operational amplifier and the second operational amplifier equal, the voltages Vgs1 and Vgs2 between the gate and the source of the second transistor and the third transistor are equal, and the voltages Vds1 and Vds2 between the drain and the source are also equal, and the value of the final output driving current only depends on the width-to-length ratio of the second transistor and the third transistor, thereby eliminating the offset voltage influence of the first operational amplifier, improving the accuracy of current mirroring, and improving the accuracy of the driving current.
Referring to fig. 4, a schematic diagram of a driving circuit according to an embodiment of the present disclosure is shown.
On the basis of the above embodiments, in the driving circuit of the present embodiment, the current source module 1 further includes a proportional amplifying unit 13 and a fixed voltage generating unit 14.
The proportional amplifying unit 13, i.e., I _ DAC, is connected between the third terminal of the first transistor NM1 and the output terminal of the constant current generating unit 11, and is configured to perform a preset proportional amplification on the driving current. The driving current can be adjusted through the proportional amplification unit I _ DAC, and the application range is widened.
The fixed voltage generating unit 14 is a resistance-based digital-to-analog converting unit.
When the driving circuit is a constant current driving circuit including the digital-to-analog conversion unit, the digital-to-analog conversion unit includes a voltage source and a resistor R _ DAC, the voltage source is connected with one end of the resistor R _ DAC to form the fixed voltage, the other end of the resistor R _ DAC is grounded, and the proportional amplification unit 13 is configured to perform proportional amplification on the driving current according to a preset proportional value according to an output result of the digital-to-analog conversion unit.
The resistor R _ DAC is used for controlling the voltage value of the fixed voltage, namely the voltage value of the input end of the first operational amplifier OP1 and the second operational amplifier OP2 is controlled by the resistor R _ DAC, so that the first operational amplifier OP1 and the second operational amplifier OP2 are controlled to work in a reasonable interval.
The constant current drive circuit is connected to an output of a controller, such as an output of a DSP (digital signal processor). Taking AF (auto focus) as an example, the AF operation mode refers to: after entering an automatic focusing mode, the driving current output by the constant current driving circuit is from 0 to the maximum value, so that the lens moves from the original position to the maximum displacement position, at the moment, the imaging surface of the sensor automatically shoots pictures and stores the pictures in the DSP, the DSP calculates the Modulation Transfer Function (MTF) value of each picture through the pictures, thereby finding the maximum value in the MTF curve, obtaining the current corresponding to the point through an algorithm, and indicating the constant current driving circuit to provide the current for the voice coil of the driving motor again, so that the lens is stabilized on the imaging surface, and the automatic focusing effect is achieved. A digital-to-analog converter (DAC) is also typically provided between the constant current driver circuit and the controller, and is configured to convert a digital current output by the controller into an analog current and to instruct the constant current driver circuit to output a corresponding drive current.
In this embodiment, when the scaling unit 13, i.e. the I _ DAC, scales the driving current according to a preset scaling value, for example, the preset scaling value is K, I in the constant current driving circuitD2Is the current flowing through the third transistor NM3, IAF_outFor the driving current of the constant current driving circuit, the driving current needs to satisfy the following formula:
IAF_out＝K.ID2
wherein, the preset proportion value K is the driving current I output by the actual constant current driving circuitAF_outAnd the current ratio required by the digital-to-analog conversion unit.
The constant current driving circuit of the embodiment can output the driving current with a specific value according to the requirement of the controller through the proportional amplifying unit I _ DAC, and the application range of the circuit is widened.
The embodiment of the application further provides an OIS chip including the above-mentioned drive circuit, and through the above-mentioned drive circuit, the OIS chip can realize accurate lens movement control and realize the effect of reducing the blur of the picture.
The embodiment of the invention also provides an electronic device, such as a mobile phone, a tablet computer and the like, comprising the driving circuit or the OIS chip. The electronic equipment adopts the driving circuit or the OIS chip, improves the accuracy of lens movement, compensates the light path with hand shake, and accordingly achieves the effect of reducing the blur of the photos.
The above-mentioned embodiments are only examples of the present application, and not intended to limit the scope of the present application, and all equivalent structures or equivalent flow transformations made by the contents of the specification and the drawings, such as the combination of technical features between the embodiments and the direct or indirect application to other related technical fields, are also included in the scope of the present application.
Claims (11)
1. A driver circuit, comprising:
the current source module is used for providing constant current;
the driving output module comprises a first operational amplifier and at least one first transistor, wherein a first input end of the first operational amplifier is connected to a fixed voltage end, a second input end of the first operational amplifier is connected to a third end of the first transistor, an output end of the first operational amplifier is connected to a second end of the first transistor, and a first end of the first transistor is used for outputting driving current according to the mirror image current of the constant current.
2. The drive circuit according to claim 1, wherein the current source module includes a constant current generating unit and a control unit;
the constant current generating unit is used for generating the constant current;
the control unit is connected with the input end of the constant current generation unit and the first input end of the first operational amplifier, and is used for controlling the voltage of the first input end and the voltage of the second input end of the first operational amplifier to be equal to the voltage of the input end of the constant current generation unit so as to eliminate the influence of offset voltage of the first operational amplifier.
3. The driving circuit of claim 2, wherein the current source module further comprises a scale amplification unit;
the proportional amplification unit is connected between the third end of the first transistor and the output end of the constant current generation unit and is used for amplifying the driving current in a preset proportion.
4. The drive circuit according to claim 2 or 3, wherein the constant current generating unit includes at least one of:
a constant current source, a mirror current subunit, and a cascode subunit.
5. The driving circuit as claimed in claim 4, wherein when the constant current generating unit is a mirror current sub-unit, the mirror current sub-unit comprises at least a second transistor, a third transistor and a current source, a first terminal of the second transistor is connected to an output terminal of the current source, a second terminal of the second transistor is connected to a second terminal of the third transistor, a third terminal of the second transistor and a third terminal of the third transistor are all grounded, the second transistor and the third transistor form a current mirror, and a first terminal of the third transistor is used for outputting a constant current.
6. The drive circuit according to claim 5, wherein the control unit includes a second operational amplifier;
the first input end of the second operational amplifier is connected with the first end of the second transistor, the second input end of the second operational amplifier is connected with the fixed voltage end, and the output end of the second operational amplifier is connected with the second end of the second transistor.
7. The driving circuit according to claim 3, wherein the current source module further includes a fixed voltage generating unit;
the output end of the fixed voltage generating unit is connected to the fixed voltage end for outputting a fixed voltage.
8. The driving circuit according to claim 7, wherein the fixed voltage generating unit is a resistance-based digital-to-analog converting unit.
9. The driving circuit according to claim 8, wherein the driving circuit is a constant current driving circuit including the digital-to-analog conversion unit;
the digital-to-analog conversion unit comprises a voltage source and a resistor, wherein the voltage source is connected with one end of the resistor to form the fixed voltage, the other end of the resistor is grounded, and the resistor is used for controlling the voltage value of the fixed voltage;
and the proportion amplification unit is used for carrying out proportion amplification on the driving current according to the output result of the digital-to-analog conversion unit and a preset proportion value.
10. An OIS chip comprising a driver circuit as claimed in any of claims 1 to 9.
11. An electronic device comprising the driver circuit of any one of claims 1-9, or comprising the OIS chip of claim 10.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111310813.7A CN114123886A (en) | 2021-11-04 | 2021-11-04 | Drive circuit, OIS chip and electronic equipment |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111310813.7A CN114123886A (en) | 2021-11-04 | 2021-11-04 | Drive circuit, OIS chip and electronic equipment |
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| Publication Number | Publication Date |
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| CN114123886A true CN114123886A (en) | 2022-03-01 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202111310813.7A Pending CN114123886A (en) | 2021-11-04 | 2021-11-04 | Drive circuit, OIS chip and electronic equipment |
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| 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 |
| CN115864907A (en) * | 2023-02-14 | 2023-03-28 | 基合半导体（宁波）有限公司 | Control circuit, method, chip, electronic device, and storage medium |
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