CN111130341B - Digital closed-loop control charge pump based on MEMS (micro-electromechanical system) capacitor - Google Patents

Digital closed-loop control charge pump based on MEMS (micro-electromechanical system) capacitor Download PDF

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CN111130341B
CN111130341B CN202010041491.XA CN202010041491A CN111130341B CN 111130341 B CN111130341 B CN 111130341B CN 202010041491 A CN202010041491 A CN 202010041491A CN 111130341 B CN111130341 B CN 111130341B
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digital
charge pump
signal
mems
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CN111130341A (en
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周斌
魏琦
李司棋
王月
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Tsinghua University
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Tsinghua University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
    • H02M3/07—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider using capacitors charged and discharged alternately by semiconductor devices with control electrode, e.g. charge pumps

Abstract

The invention relates to a digital closed-loop control charge pump based on an MEMS (micro electro mechanical system) capacitor, which comprises a charge pump, an MEMS capacitor module, a C/D (digital/digital) conversion module, a digital controller and a D/A (digital/analog) control module, wherein the charge pump is connected with the MEMS capacitor module through a communication network; the output end of the charge pump is connected with the driving electrode of the MEMS capacitance module, and the driving detection electrode of the MEMS capacitance module outputs a capacitance variation signal to the C/D conversion module; the C/D conversion model converts the capacitance variation signal into a digital signal capable of reflecting capacitance variation and sends the digital signal to the digital controller; the digital controller generates a digital control signal according to the input digital signal and a set value and sends the digital control signal to the D/A control module; and the D/A control module generates an analog control signal according to the digital control signal and sends the analog control signal to the input end of the charge pump to form a closed loop. The invention can be widely applied to the field of driving and detecting of capacitive MEMS devices.

Description

Digital closed-loop control charge pump based on MEMS (micro-electromechanical system) capacitor
Technical Field
The invention relates to the technical field of integrated circuits, in particular to a digital closed-loop control charge pump based on a micro-electromechanical system (MEMS) capacitor.
Background
The MEMS sensor has the advantages of small volume, light weight, low power consumption, low price, mass production and the like. With the increasing development of MEMS sensors, the performance of the MEMS sensors in the aspects of measurement accuracy, reliability and the like is continuously improved, and the MEMS sensors are widely applied to the military field and the civil field. In the development process of miniaturization of the capacitive MEMS device, along with the reduction of capacitance, some capacitive MEMS devices cannot realize functions such as driving and closed-loop detection by the supply voltage alone. Therefore, some capacitive MEMS devices have high voltage and high precision driving requirements, such as MEMS inertial sensors, MEMS electrostatic actuators, and the like.
In a monolithic integrated system, converting the supply voltage to a high voltage for driving is typically applied to the charge pump circuit. As shown in FIG. 1, in the conventional analog closed-loop charge pump scheme, the output voltage V is obtained by boosting the charge pumpOUTThen, by the resistance R1、R2Dividing the voltage to obtain a feedback voltage VFBAnd with a reference voltage VREFComparing and amplifying to obtain a control voltage VCTRLControlled by voltage-controlled oscillatorsAnd (5) making the amplitude of the clock to form a closed loop. The above scheme has the following problems: because the driving capability of the high-voltage charge pump circuit is weak, a large-resistance voltage division network is required, and resistance noise is introduced as a feedback element for voltage detection; the temperature compensation with high precision is not facilitated; the large resistance, the large capacitance and the amplifier bring larger power consumption and area loss; amplifier-induced 1/f noise can degrade MEMS device accuracy, especially for MEMS inertial devices, which are mostly applied in narrow bands. Each of these factors reduces the overall performance of the charge pump and MEMS device.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a digital closed-loop control charge pump based on an MEMS capacitor, which can overcome the problems of resistance noise and efficiency loss introduced by a feedback element due to analog closed-loop control, reduce circuit narrow-band noise, further improve the performance of the MEMS device in different environments through temperature compensation, and improve the overall accuracy of the MEMS device.
In order to achieve the purpose, the invention adopts the following technical scheme: a digital closed-loop control charge pump based on MEMS capacitance comprises a charge pump, an MEMS capacitance module, a C/D conversion module, a digital controller and a D/A control module; the output end of the charge pump is connected with the driving electrode of the MEMS capacitance module, a high-voltage signal is sent to the MEMS capacitance module, and the driving detection electrode of the MEMS capacitance module outputs a capacitance variation signal to the C/D conversion module; the C/D conversion module converts the capacitance variation signal into a digital signal capable of reflecting capacitance variation and sends the digital signal to the digital controller; the digital controller generates a digital control signal according to the input digital signal and a set value and sends the digital control signal to the D/A control module; and the D/A control module generates an analog control signal according to the digital control signal and sends the analog control signal to the input end of the charge pump to form a closed loop.
Furthermore, the MEMS capacitor-based digital closed-loop control charge pump further comprises a temperature detection module, wherein the input end of the temperature detection module is connected with the MEMS capacitor module, the output end of the temperature detection module is connected with the digital controller, and the acquired temperature signal of the MEMS capacitor module is sent to the digital controller to realize temperature compensation.
Further, the charge pump comprises a plurality of stages of charge and discharge structures; except the last stage of the charge-discharge structure, each stage of the charge-discharge structure comprises a PMOS (P-channel metal oxide semiconductor) tube and a capacitor, the grid electrode and the drain electrode of the PMOS tube in each stage of the charge-discharge structure are in short circuit, and the drain electrode of the PMOS tube is respectively connected with the positive electrode of the capacitor in the charge-discharge structure and the source electrode of the PMOS tube in the next stage of the charge-discharge structure to form a series structure; the source electrode of the PMOS tube in the first-stage charge-discharge structure is used as the voltage input end V of the charge pumpINThe last stage of charge-discharge structure comprises another PMOS tube, and the drain electrode of the other PMOS tube is used as a high-voltage output end HV of the charge pump; the negative electrodes of the capacitors in the odd-number charge-discharge structures are connected in parallel and then connected with the input end of the inverted clock; and the cathodes of the capacitors in the even-numbered charge-discharge structures are connected in parallel and then connected with the input end of the positive phase clock.
Furthermore, the MEMS capacitive module converts a high voltage signal input by the charge pump to a capacitance change signal through a mechanical structure, where the mechanical structure includes two fixed comb teeth and a movable comb tooth disposed between the two fixed comb teeth, one of the fixed comb teeth and the movable comb tooth form the driving electrode connected to the charge pump, and the other fixed comb tooth and the movable comb tooth form the driving detection electrode connected to the C/D conversion module; the movable comb teeth are connected with a high-frequency carrier signal; when the movable comb teeth move between the two fixed comb teeth under the action of a high-voltage signal input by the charge pump, the generated pressure difference is converted into a capacitance change signal by the driving detection electrode and is sent to the C/D conversion module.
Further, the C/D conversion module comprises a C/V module and an A/D module; the C/V module is used for generating an analog voltage signal capable of reflecting the capacitance variation of the MEMS capacitance module; the A/D module is used for converting the analog voltage signal into a digital signal capable of reflecting the capacitance variation of the MEMS capacitance module.
Further, the C/V module comprises an OTA operational amplifier, a feedback capacitor, a feedback resistor and an analog switch demodulation module; the positive end of the OTA operational amplifier is connected with the drive detection electrode of the MEMS capacitance module, and the reverse end of the OTA operational amplifier is connected with the input end of the demodulation module; the feedback capacitor and the feedback resistor are connected in parallel between the positive end and the output end of the OTA operational amplifier; and the analog switch demodulation module demodulates an analog voltage signal which is output by the OTA operational amplifier and can reflect the capacitance variation of the MEMS capacitance module under the input of a high-frequency carrier, and a demodulation result is sent to the A/D module.
Further, when the high frequency carrier input to the analog switch demodulation module is consistent with the high frequency carrier signal input to the MEMS capacitor module, the proportional relationship between the voltage detected by the capacitor and the change in capacitance depends only on the inherent mechanical structure of the MEMS capacitor.
Further, the A/D module comprises a loop filter module, a quantizer and a DAC feedback module; the input end of the loop filter module is connected with the output end of the C/V module, the output end of the DAC feedback module and an external control voltage; the output end of the loop filter module is connected with the input end of the quantizer; and the output end of the quantizer is respectively connected with the input end of the DAC feedback module and the digital controller.
Furthermore, the digital controller comprises a temperature compensation unit, a digital demodulation unit, a logic operation unit, a low-pass filtering unit and a proportional-integral control unit; the input end of the temperature compensation unit is respectively connected with the output end of the C/D conversion module and the output end of the temperature detection module, and the output end of the temperature compensation unit is connected with the input end of the digital demodulation unit; the input end of the digital demodulation unit is also connected with a high-frequency carrier signal, and the output end of the digital demodulation unit is connected with the logic operation unit; the logic operation unit is also connected with the set value input end and used for calculating the difference value between the output of the digital demodulation unit and the set value and sending the difference value to the low-pass filtering unit; the output end of the low-pass filtering unit is connected with the input end of the proportional-integral control unit, and the output end of the proportional-integral control unit is connected with the D/A control module.
Further, the D/a control module includes three D/a control schemes: scheme I realizes closed-loop control by adjusting the input voltage of the charge pump, and comprises a first D/A conversion module and a first amplifier; the first D/A conversion module converts a digital control signal output by the digital controller to obtain a first analog signal and sends the first analog signal to the first amplifier, the first amplifier controls the amplitude of a power supply voltage input into the charge pump according to the first analog signal, and positive phase and reverse phase clock input ends of the charge pump are directly connected with an input clock; the scheme II realizes closed-loop control by adjusting the clock amplitude of the charge pump, and comprises a second D/A conversion module and a second amplifier; the second D/A conversion module converts a digital control signal output by the digital controller to obtain a second analog signal and then sends the second analog signal to the second amplifier, the second amplifier controls the amplitude of the clock input of the charge pump according to the second analog signal, and the power supply voltage input end of the charge pump is directly connected with power supply voltage; according to the scheme III, closed-loop control is realized by adjusting the clock frequency of the charge pump, and the closed-loop control comprises a digital delay phase-locked loop module and a third D/A conversion module; at the time of t-1, the digital delay phase-locked loop module generates an output clock at the time of t according to the digital control signal output by the digital controller, and each time of 1 represents 1 complete cycle of the digital delay phase-locked loop module; the third D/A conversion module controls the clock input of the charge pump according to the output clock; and the power supply voltage input end of the charge pump is directly connected with the power supply voltage.
Due to the adoption of the technical scheme, the invention has the following advantages: 1. the invention is based on the MEMS capacitor and the digital control closed-loop structure, and can reduce the noise, the power consumption, the area and the temperature drift of the closed-loop charge pump which is more suitable for the capacitive MEMS device by utilizing the inherent mechanical characteristics of the capacitive MEMS device. 2. The proportional relation of the voltage and the capacitance change obtained by capacitance detection only depends on the inherent mechanical structure of the MEMS capacitor, and further can be used as a reference source of a capacitive MEMS device. 3. The digital controller adopted by the invention can obtain the digital information of the driving high-voltage signal, can be used for driving compensation of part of MEMS device interface circuits, and improves the overall performance of the MEMS device. Therefore, the invention can be widely applied to the field of capacitive MEMS device driving.
Drawings
FIG. 1 is a block diagram of an analog closed-loop control charge pump of the prior art;
FIG. 2 is a schematic block diagram of the MEMS capacitance based digital closed loop control charge pump of the present invention;
FIG. 3 is a schematic diagram of a D/A control module and a charge pump according to an embodiment of the invention;
FIG. 4a is a schematic diagram of a mechanical structure of a single-end synovial damping comb of a MEMS capacitor module according to an embodiment of the invention;
FIG. 4b is a schematic diagram of a MEMS capacitive module according to an embodiment of the present invention;
FIG. 5 is a single-ended schematic diagram of a capacitance-to-digital voltage conversion module (C/D) according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a digital controller according to an embodiment of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and examples.
As shown in fig. 2, based on the inherent mechanical characteristics of the capacitive MEMS device, the present invention provides a digital closed-loop control charge pump (hereinafter referred to as charge pump) based on MEMS capacitance, wherein the charge pump is used for generating a high-voltage driving signal, and performing MEMS capacitance detection and digital closed-loop control on the high-voltage driving signal. Specifically, the device comprises a charge pump 1, an MEMS capacitance module 2, a C/D conversion module 3, a digital controller 4, a D/A control module 5 and a temperature detection module 6; a high-voltage signal HV output by the charge pump 1 is connected with an input end driving electrode of the MEMS capacitance module 2, and a driving detection electrode of the MEMS capacitance module 2 outputs a capacitance variation signal and sends the capacitance variation signal to the C/D conversion module 3; the C/D conversion module 3 generates a digital signal D < n-1:0> capable of reflecting the capacitance variation and sends the digital signal D < n-1:0> to the digital controller 4 to realize high-voltage detection based on the MEMS capacitance; the digital controller 4 realizes digital demodulation and filtering and control of high-frequency noise according to the digital signal D < n-1:0> reflecting the capacitance variation and a set value (corresponding to the ideal output voltage of the charge pump 1), and obtains a digital control signal D < n-1:0> _ fb which is sent to the D/A control module 5; the D/A control module 5 obtains an analog control signal (comprising the input voltage and the clock signal of the charge pump 1) according to a digital control signal D < n-1:0> _ fb output by the digital controller 4 and feeds the analog control signal back to the charge pump 1, so that the digital closed-loop control of the charge pump circuit based on the MEMS capacitor is realized; meanwhile, the temperature detection module 6 collects the temperature signal of the MEMS capacitance module 2 and transmits the digital information of the temperature signal to the digital controller 4, so that temperature compensation is realized.
In the foregoing embodiments, as shown in fig. 3, the charge pump 1 adopts a multi-stage Dickson module series structure, and the input end of the charge pump 1 is an analog control signal, i.e., an input voltage and a clock signal, provided by the D/a control module 5; the output end of the charge pump 1 is a high-voltage signal HV, and is connected to the driving electrode of the MEMS capacitor module 2. Specifically, the charge pump 1 includes a plurality of stages of charge and discharge structures (the present invention is described by taking a three-stage series structure as an example, but not limited thereto), except for the last stage of charge and discharge structure, each stage of charge and discharge structure includes a PMOS transistor and a capacitor, in each stage of charge and discharge structure, a gate of the PMOS transistor is short-circuited with a drain, and a drain of the PMOS transistor is connected to an anode of the capacitor in the current stage of charge and discharge structure and a source of the PMOS transistor in the next stage of charge and discharge structure, respectively, to form a series structure; the last stage of charge-discharge structure comprises a PMOS tube, and the source electrode of the PMOS tube in the first stage of charge-discharge structure is used as the voltage input end V of the charge pump 1INThe drain electrode of the PMOS tube in the last stage of charge-discharge structure is used as a high-voltage output end HV of the charge pump 1; the negative electrodes of the capacitors in the odd-number charge-discharge structures are connected in parallel and then connected with the input end of the inverted clock; and the cathodes of the capacitors in the even-numbered charge-discharge structures are connected in parallel and then connected with the input end of the positive phase clock. The alternating switching state of the PMOS tube is realized through the high-low level switching of the clock, the alternating charging and discharging of the capacitor in each level of charging and discharging structure are realized, the charge is continuously transmitted to the rear level and is continuously accumulated in the capacitor of each node, the voltage of the node is continuously pumped up, and the electricity is further realizedDirect current-to-direct current (DC-DC) conversion of a source low voltage signal to a high voltage drive voltage signal.
In the above embodiments, the base (Bulk) of the PMOS transistor can be externally connected to remove VDDBesides, the base electrodes of the PMOS transistors in the last stage of the charge and discharge structure are connected to the high voltage output terminal HV of the charge pump 1, and similarly, the base electrodes of the PMOS transistors in the other stages of the charge and discharge structure are respectively connected to the drain terminals of the PMOS transistors in the current stage of the charge and discharge structure, so that the conversion efficiency of the charge pump can be improved.
In the above embodiments, the high voltage output terminal HV of the charge pump 1 may be externally connected to other loads.
In the above embodiments, the MEMS capacitive module 2 converts the input high voltage signal into the capacitance change signal (± Δ C) through its mechanical structure, thereby implementing the high voltage detection function. The invention is introduced by taking a variable-area comb-tooth capacitor structure as an example, and is shown in fig. 4a as a schematic diagram of a mechanical structure of a single-end sliding film damping comb-tooth of an MEMS capacitor module, and is shown in fig. 4b as a schematic diagram of a principle of the MEMS capacitor module. In the electrode distribution, the MEMS capacitive module 2 is divided into a driving electrode and a driving detection electrode. In the mechanical structure, the MEMS capacitor module 2 is composed of fixed comb teeth connected with the base and movable comb teeth connected with the mass block, the comb teeth are arranged in a parallel overlapping and interval distribution manner, when the vibration direction is longitudinal, the comb teeth on the upper side and the lower side are both fixed structures, and the middle comb tooth is a movable structure; the fixed comb teeth at the driving electrode end are input into a driving high-voltage signal HV of the MEMS capacitor module, and the middle movable comb teeth are input into a high-frequency carrier signal ref1(ii) a When pressure difference exists between the fixed comb teeth and the movable comb teeth, electrostatic force is generated between the fixed comb teeth and the movable comb teeth according to a virtual displacement principle, the electrostatic force drives the movable comb teeth to vibrate along the longitudinal direction, so that the change of the overlapping area between the comb teeth is caused, and the change of capacitance is caused; therefore, the fixed comb teeth at the end of the drive detection electrode can convert the vibration signal into a capacitance change signal, and at the moment, the drive detection electrode of the MEMS capacitance module 2 is used as an output end and is connected to the C/D conversion module 3, so that the high-voltage detection of the MEMS capacitance can be realized.
In the above embodiments, as shown in fig. 5, the C/D conversion module 3 includes a C/V module and an a/D module for implementingThe conversion from the capacitance change signal to the digital signal is realized, namely, the capacitance detection function is realized. The input end of the C/D conversion module 3 is the capacitance variation C output by the MEMS capacitance module 20+ -. DELTA.C where C0Is the capacitance at vibration amplitude of 0; the output end of the C/D conversion module 3 is a digital signal D reflecting the capacitance change (+/-delta C) of the MEMS capacitor module<n-1:0>And is connected to the digital controller 4, wherein n is the number of quantizer bits in the a/D module in the C/D conversion module 3. The C/D conversion module 3 realizes high-voltage detection by utilizing the inherent mechanical characteristics of the MEMS capacitor, and effectively solves the problems of noise, high power consumption, area efficiency loss and the like caused by devices such as a large resistor, a large capacitor, an operational amplifier and the like required in a feedback loop of the analog closed-loop charge pump in the prior art.
In the above embodiments, as shown in the C/V conversion module part of FIG. 5, the C/V module of the C/D conversion module 3 includes an OTA operational amplifier and a feedback capacitor CfA feedback resistor RfAnd an analog switch demodulation module; wherein, the capacitance variation signal C0The +/-Delta C is input to the positive end of the OTA operational amplifier, and a feedback capacitor C is connected in parallel between the positive end and the output end of the OTA operational amplifierfAnd a feedback resistor RfThe output end of the OTA operational amplifier is an analog voltage signal V reflecting capacitance change (+/-delta C) of the MEMS capacitor modulep/n_carrThe analog voltage signal Vp/n_carrThe analog voltage signal V is obtained after the demodulation of the analog switch demodulation modulep/nAnd the input is input to an A/D conversion module.
Meanwhile, when the input high frequency carrier signal ref of the C/V module in the C/D conversion module 32Input high-frequency carrier signal ref with the MEMS capacitive module 21When they are in agreement, i.e. when ref1＝ref2In this case, even if they become larger or smaller in common due to the influence of environmental factors, the result of the capacitance detection circuit is not affected. Thus, the analog voltage signal Vp/nThe proportional relation with the capacitance change (± Δ C) of the MEMS capacitor module 2 depends only on the inherent mechanical structure of the MEMS capacitor, and is not affected by environmental factors such as temperature, and thus, the MEMS capacitor module can be used as a reference source of a capacitive MEMS device.
In addition, the above-mentioned analog switch demodulation module is only one implementation manner, and a digital demodulation manner may also be adopted to directly obtain a digital signal reflecting capacitance change, which is described in detail in the digital controller 4.
In a preferred embodiment, the a/D module in the C/D conversion module 3 (i.e., Sigma-Delta ADC) includes a loop filter module, a quantizer and a DAC feedback module, as shown in the a/D module portion of fig. 5. The input of the A/D module is an analog voltage signal Vp/nAfter passing through the loop filter module and the quantizer, the digital signal D reflecting the capacitance change of the MEMS capacitor module 2 is obtained<n-1:0>As output of the overall C/D conversion module 3. At the same time, the digital signal D<n-1:0>Forming a feedback analog signal through the DAC feedback module, wherein the feedback analog signal is in contact with an analog voltage signal V output by the C/V modulep/nAfter logical operation, the loop filter module is connected with the input end of the loop filter module to realize Sigma-Delta modulation, namely realizing noise shaping and quantization output. The external control voltage acts on the loop filter module to realize tuning so as to adapt to different working environments.
In the above embodiments, as shown in fig. 6, the digital controller 4 includes a temperature compensation unit, a digital demodulation unit, a logic operation unit, a low-pass filter unit, a PI (proportional integral) control unit, and the like. Wherein, the input end of the digital controller 4 is the digital signal D output by the C/D conversion module 3<n-1:0>And a set value (corresponding to the desired output voltage of the charge pump 1); meanwhile, the temperature signal acquired by the temperature detection module 6 at the MEMS capacitance module 2 is used as the input of the temperature compensation unit, namely a high-frequency carrier signal ref2_dAs an input to a digital demodulation unit; the output of the digital controller 4 is a digital signal D<n-1:0>Fb, to the D/a control module 5. Digital signal D output by C/D conversion module 3<n-1:0>After passing through the temperature compensation unit and the digital demodulation unit, a restored digital voltage signal is obtained, the digital voltage signal has good temperature stability, and low-frequency noise introduced by the analog switch demodulation module is effectively avoided in a digital demodulation mode; then, the logic operation unit compares the restored voltage numbersAfter the difference between the word signal and the set value passes through the low-pass filtering unit and the PI control unit, the filtering and digital control of high-frequency noise are realized, and the high-frequency noise is sent to the D/A control module 5 as the output of the digital controller 4.
The clock input of the charge pump 1 is multiplexed by the clock of the digital controller 4, so that the efficiency of the MEMS device interface circuit can be improved. Meanwhile, the digital information of the driving high-voltage signal obtained by the digital controller 4 is used for driving compensation of the MEMS device interface circuit, so that the precision of the interface circuit can be further improved. Taking the capacitive MEMS gyroscope as an example, the driving compensation can cause the driving shaft to work more stably at the resonant frequency point of the second-order system, thereby improving the overall performance of the capacitive MEMS gyroscope.
In the above embodiments, as shown in FIG. 3, the input of the D/A control module 5 is the power voltage VDDDigital signal D<n-1:0>Fb and an input clock; the output of the D/A control module 5 is the input voltage V of the charge pump 1INOr clock signals CLKP, CLKN, which are sent to the voltage or clock input of the charge pump 1 to form a closed loop. The D/a control module 5 includes three D/a control schemes:
scheme I of the D/A control module 5 by regulating the input voltage V of the charge pump 1INRealizing closed-loop control, comprising a first D/A conversion module and an amplifier K1(ii) a Digital signal D output by digital controller 4<n-1:0>Fb outputs an analog signal through the first D/A conversion block, the analog signal passes through the amplifier K1Controlling the input voltage V of the charge pump 1 after amplificationINThe positive phase clock and the negative phase clock input terminals of the charge pump 1 are directly connected to the constant input clocks CLKP, CLKN, respectively.
Scheme II of the D/A control module 5, which realizes closed-loop control by adjusting the amplitude of the clocks CLKP, CLKN of the charge pump 1, comprises a second D/A conversion module and an amplifier K2(ii) a Digital signal D output by digital controller 4<n-1:0>Fb outputs an analog signal through the second D/A conversion block, the analog signal passes through an amplifier K2Amplifying the voltage to control the amplitude of positive and negative clock inputs CLKP and CLKN of the charge pump 1, and the input voltage V of the charge pump 1INWith mains electricityPressure VDDAre directly connected.
Scheme III of the D/A control module 5 realizes closed-Loop control by adjusting the frequency of clocks CLKP and CLKN of the charge pump 1, and comprises a digital Delay-Locked Loop (DLL) module and a third D/A conversion module; digital signal D output by digital controller 4<n-1:0>If fb is [ t-1 ]]The input clock end of the time digital DLL module controls [ t-1 ] through the control logic in the digital DLL module]Input clock of time and t-1]The feedback clock at the time is sampled and compared to adjust the variable delay line to generate [ t [ [ t ]]The DLL of the time outputs the clock, and each 1 time represents 1 complete cycle of the digital DLL module; the DLL output clock signal outputs an analog clock signal through a third D/A conversion module, and is connected to a positive phase clock and a reverse phase clock input end CLKP and CLKN of the charge pump 1; input voltage terminal V of charge pump 1INAnd a supply voltage VDDAre directly connected.
In the above embodiments, some of the power supplies and clock signals are not shown for simplicity. Wherein, each module is supplied with power by a single power supply with a voltage VDDBy means of a reference voltage VrefAnd realizing differential C/V module detection.
In each of the above embodiments, Vref＝VDD/2。
In summary, the present invention is based on the MEMS capacitive detection and digital control closed loop structure, and utilizes the inherent mechanical characteristics of the capacitive MEMS device, and has the advantages of low noise, low power consumption, small area, good temperature stability, etc., which are more suitable for the capacitive MEMS device. Meanwhile, the proportional relation of the voltage and the capacitance change obtained by capacitance detection only depends on the inherent mechanical structure of the MEMS capacitor, and further can be used as a reference source of a capacitive MEMS device; the adopted digital controller 4 can obtain the digital information D < n-1:0> of the driving high-voltage signal, and can be used for driving compensation of part of MEMS device interface circuits, thereby improving the overall performance of the MEMS device; the charge pump and digital controller may multiplex the clocks.
The above embodiments are only for illustrating the present invention, and the structure, size, arrangement position and shape of each component can be changed, and on the basis of the technical scheme of the present invention, the improvement and equivalent transformation of the individual components according to the principle of the present invention should not be excluded from the protection scope of the present invention.

Claims (10)

1. A digital closed-loop control charge pump based on MEMS capacitance is characterized in that: the MEMS capacitive touch screen comprises a charge pump, an MEMS capacitive module, a C/D conversion module, a digital controller and a D/A control module;
the output end of the charge pump is connected with the driving electrode of the MEMS capacitance module, a high-voltage signal is sent to the MEMS capacitance module, and the driving detection electrode of the MEMS capacitance module outputs a capacitance variation signal to the C/D conversion module;
the C/D conversion module converts the capacitance variation signal into a digital signal capable of reflecting capacitance variation and sends the digital signal to the digital controller;
the digital controller generates a digital control signal according to the input digital signal and a set value and sends the digital control signal to the D/A control module;
and the D/A control module generates an analog control signal according to the digital control signal and sends the analog control signal to the input end of the charge pump to form a closed loop.
2. The MEMS capacitance-based digital closed-loop-controlled charge pump of claim 1, wherein: the temperature compensation system further comprises a temperature detection module, wherein the input end of the temperature detection module is connected with the MEMS capacitor module, the output end of the temperature detection module is connected with the digital controller, and the acquired temperature signal of the MEMS capacitor module is sent to the digital controller to realize temperature compensation.
3. The MEMS capacitance-based digital closed-loop-controlled charge pump of claim 1, wherein: the charge pump comprises a plurality of stages of charge and discharge structures;
except the last stage of the charge-discharge structure, each stage of the charge-discharge structure comprises a PMOS (P-channel metal oxide semiconductor) tube and a capacitor, the grid electrode and the drain electrode of the PMOS tube in each stage of the charge-discharge structure are in short circuit, and the drain electrode of the PMOS tube is respectively connected with the positive electrode of the capacitor in the charge-discharge structure and the source electrode of the PMOS tube in the next stage of the charge-discharge structure to form a series structure;
the source electrode of the PMOS tube in the first-stage charge-discharge structure is used as the voltage input end V of the charge pumpINThe last stage of charge-discharge structure comprises another PMOS tube, and the drain electrode of the other PMOS tube is used as a high-voltage output end HV of the charge pump;
the negative electrodes of the capacitors in the odd-number charge-discharge structures are connected in parallel and then connected with the input end of the inverted clock;
and the cathodes of the capacitors in the even-numbered charge-discharge structures are connected in parallel and then connected with the input end of the positive phase clock.
4. The MEMS capacitance-based digital closed-loop-controlled charge pump of claim 1, wherein: the MEMS capacitance module converts a high-voltage signal input by the charge pump into a capacitance change signal through a mechanical structure, the mechanical structure comprises two fixed comb teeth and movable comb teeth arranged between the two fixed comb teeth, one of the fixed comb teeth and the movable comb teeth form a driving electrode which is connected with the charge pump, and the other of the fixed comb teeth and the movable comb teeth form a driving detection electrode which is connected with the C/D conversion module; the movable comb teeth are connected with a high-frequency carrier signal; when the movable comb teeth move between the two fixed comb teeth under the action of a high-voltage signal input by the charge pump, the generated pressure difference is converted into a capacitance change signal by the driving detection electrode and is sent to the C/D conversion module.
5. The MEMS capacitance-based digital closed-loop-controlled charge pump of claim 1, wherein: the C/D conversion module comprises a C/V module and an A/D module;
the C/V module is used for generating an analog voltage signal capable of reflecting the capacitance variation of the MEMS capacitance module;
the A/D module is used for converting the analog voltage signal into a digital signal capable of reflecting the capacitance variation of the MEMS capacitance module.
6. The MEMS capacitance-based digital closed-loop-controlled charge pump of claim 5, wherein: the C/V module comprises an OTA operational amplifier, a feedback capacitor, a feedback resistor and an analog switch demodulation module;
the positive end of the OTA operational amplifier is connected with the drive detection electrode of the MEMS capacitor module, and the output end of the OTA operational amplifier is connected with the input end of the analog switch demodulation module;
the feedback capacitor and the feedback resistor are connected in parallel between the positive end and the output end of the OTA operational amplifier;
and the analog switch demodulation module demodulates an analog voltage signal which is output by the OTA operational amplifier and can reflect the capacitance variation of the MEMS capacitance module under the input of a high-frequency carrier, and a demodulation result is sent to the A/D module.
7. The MEMS capacitance-based digital closed-loop-controlled charge pump of claim 6, wherein: when the high-frequency carrier wave input into the analog switch demodulation module is consistent with the high-frequency carrier wave signal input into the MEMS capacitor module, the proportional relation between the voltage and the capacitance change obtained by capacitor detection only depends on the inherent mechanical structure of the MEMS capacitor.
8. The MEMS capacitance-based digital closed-loop-controlled charge pump of claim 5, wherein: the A/D module comprises a loop filtering module, a quantizer and a DAC feedback module;
the input end of the loop filter module is connected with the output end of the C/V module, the output end of the DAC feedback module and an external control voltage; the output end of the loop filter module is connected with the input end of the quantizer;
and the output end of the quantizer is respectively connected with the input end of the DAC feedback module and the digital controller.
9. The MEMS capacitance-based digital closed-loop-controlled charge pump of claim 2, wherein: the digital controller comprises a temperature compensation unit, a digital demodulation unit, a logic operation unit, a low-pass filtering unit and a proportional-integral control unit;
the input end of the temperature compensation unit is respectively connected with the output end of the C/D conversion module and the output end of the temperature detection module, and the output end of the temperature compensation unit is connected with the input end of the digital demodulation unit;
the input end of the digital demodulation unit is also connected with a high-frequency carrier signal, and the output end of the digital demodulation unit is connected with the logic operation unit;
the logic operation unit is also connected with the set value input end and used for calculating the difference value between the output of the digital demodulation unit and the set value and sending the difference value to the low-pass filtering unit;
the output end of the low-pass filtering unit is connected with the input end of the proportional-integral control unit, and the output end of the proportional-integral control unit is connected with the D/A control module.
10. The MEMS capacitance-based digital closed-loop-controlled charge pump of claim 1, wherein: the D/A control module comprises three D/A control schemes:
scheme I realizes closed-loop control by adjusting the input voltage of the charge pump, and comprises a first D/A conversion module and a first amplifier; the first D/A conversion module converts a digital control signal output by the digital controller to obtain a first analog signal and sends the first analog signal to the first amplifier, the first amplifier controls the amplitude of a power supply voltage input into the charge pump according to the first analog signal, and positive phase and reverse phase clock input ends of the charge pump are directly connected with an input clock;
the scheme II realizes closed-loop control by adjusting the clock amplitude of the charge pump, and comprises a second D/A conversion module and a second amplifier; the second D/A conversion module converts a digital control signal output by the digital controller to obtain a second analog signal and then sends the second analog signal to the second amplifier, the second amplifier controls the amplitude of the clock input of the charge pump according to the second analog signal, and the power supply voltage input end of the charge pump is directly connected with power supply voltage;
according to the scheme III, closed-loop control is realized by adjusting the clock frequency of the charge pump, and the closed-loop control comprises a digital delay phase-locked loop module and a third D/A conversion module; at the time of t-1, the digital delay phase-locked loop module generates an output clock at the time of t according to the digital control signal output by the digital controller, and each time of 1 represents 1 complete cycle of the digital delay phase-locked loop module; the third D/A conversion module controls the clock input of the charge pump according to the output clock; and the power supply voltage input end of the charge pump is directly connected with the power supply voltage.
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