CN113359920A - High-stability direct current source and control system - Google Patents
High-stability direct current source and control system Download PDFInfo
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Abstract
The invention provides a high-stability direct current source and a control system, wherein the direct current source comprises a digital outer loop control part and an analog inner loop control part, and an independent auxiliary power supply stability adjustment control loop is added to ensure the stability of the direct current source; the digital outer ring forms an intelligent control loop by a high-performance embedded controller and an AD/DA device, and the current steady-state output is quickly adjusted; the analog inner loop is a current series negative feedback circuit formed by a hardware PI regulator, interference is suppressed, and the accuracy of output current is improved. The auxiliary power supply output voltage automatic compensation system can eliminate the drift of the output current of the voltage-controlled constant current source. The output of the direct current source adopts a direct current voltage-stabilizing current-amplifying circuit and a power amplifying circuit to realize high-power output meeting the requirements. The output stability of the current source can reach 50ppm/min, the output reaches 10A, the load capacity is strong, and the current source is suitable for occasions requiring high-stability direct current sources such as a direct current check meter.
Description
Technical Field
The invention relates to the technical field of electronics, in particular to a high-stability direct current source and a control system.
Background
The direct current source is used as a branch of the direct current power supply, is used for providing stable and reliable direct current load current, is widely applied to engineering technology, scientific research departments and metering detection, and has strong practical value. The high-performance direct-current power supply is a core component for tracing the direct-current transformer calibrator and is required to meet the requirements of high precision, high stability, small ripple factor and the like; at present, various types of direct current power supplies exist at home and abroad, but increasingly high requirements are provided for the stability and reliability of the direct current power supplies in the field of tracing of direct current check meters, most of the high-stability direct current power supplies are monopolized at home and abroad at high price, various application problems still exist in commercial constant current sources at home and abroad, and the tracing requirements of the direct current check meters are difficult to be completely met in the aspects of output current range, long-term stability, ripple factor and the like. The invention mainly solves the problems of insufficient stability of domestic direct current sources and overhigh price of domestic similar products, and provides a direct current source solution which has the stability of being superior to 50ppm/min and the output current of reaching 10A and is applied to the integral calibration of a direct current calibrator.
The occupation rate of the high-precision program-controlled direct current source in the direct current power supply market is gradually improved, the direct current sources produced by domestic manufacturers are generally narrow in output range and poor in stability, the direct current source is mainly suitable for users with low requirements, and the requirements of the power supply stability and the output range of the whole calibration system of the direct current calibrator are difficult to meet. The high-stability foreign high-end direct-current power supply is expensive in price, low in cost performance and not suitable for domestic popularization and use. For example, university of Metropolis at Italy proposed a 10A constant current source for a high-field cesium frequency standard magnet system with stability only on the order of 10-4/min; korean institute of standards and science has proposed a constant current source based on the principle of nuclear magnetic resonance for a low-field proton gyromagnetic ratio measuring system, which has a stability of 10ppm/min but has an output current of only 1A at maximum and is expensive.
Disclosure of Invention
Based on the above reasons, the present invention provides a high-stability dc current source and control system. The problems of insufficient stability of domestic direct current sources and overhigh price of foreign similar products are solved. Particularly, a direct current source with stability superior to 50ppm/min, output current of 10A and proper price is designed, and the requirements of subsequent data sampling and synchronous processing of the whole device of the direct current calibrator can be greatly reduced, so that the complexity of the whole device of the direct current calibrator is simplified.
A first aspect of the present invention provides a high-stability dc current source, including: the device comprises an auxiliary power supply module, a digital external circulation module and an analog internal circulation control module; the auxiliary power supply module is electrically connected with the digital external circulation module and the analog internal circulation control module respectively; the digital external circulation module is electrically connected with the analog internal circulation control module;
the auxiliary power supply module includes: a voltage stabilizing current expanding circuit and a regulating tube voltage drop control circuit; the voltage-stabilizing current-expanding circuit is electrically connected with the adjusting tube voltage drop control circuit;
the digital outer loop module comprises: the device comprises a communication interface, an embedded processor, a digital-to-analog conversion circuit and an analog-to-digital conversion circuit; the communication interface is electrically connected with the embedded processor, the embedded processor is connected with the analog-to-digital conversion circuit, and the analog-to-digital conversion circuit is connected with the embedded processor; the adjusting tube voltage drop control circuit is electrically connected with the embedded processor;
the analog inner loop control module comprises: the device comprises a range switching circuit, a V/I conversion circuit, a power output circuit and a conditioning circuit; the digital-to-analog conversion circuit is electrically connected with the range switching circuit, the range switching circuit is electrically connected with the V/I conversion circuit, the V/I conversion circuit is electrically connected with the power output circuit and the conditioning circuit, and the power output circuit and the conditioning circuit are electrically connected with the conditioning circuit; and the adjusting tube voltage drop control circuit is electrically connected with the range switching circuit.
Further, the auxiliary power supply module includes:
and the auxiliary power supply module is used for providing stable voltage for the high-stability direct current power supply after rectifying, filtering and stabilizing the 220V alternating current voltage.
Further, the steady voltage current-expanding circuit comprises: the three-terminal voltage stabilizing circuit comprises a three-terminal voltage stabilizing chip U1, at least two triodes connected in parallel to two sides of the three-terminal voltage stabilizing chip U1 and a P-channel enhanced MOS tube; the input end of the three-end voltage-stabilizing chip U1 passes through a resistor RTThe three-terminal voltage stabilizing chip U1 has its output connected to a load circuit, and the ground terminal of the three-terminal voltage stabilizing chip U1 passes through a resistor RBGrounding; the emitter of the triode passes through a resistor RNThe base electrode of the triode is connected with the input end of the three-terminal voltage stabilizing chip U1, and the collector electrode of the triode is connected with the output end of the three-terminal voltage stabilizing chip U1; the drain electrode and the source electrode of the P-channel enhancement type MOS tube are respectively connected with the resistor RBThe grid electrode of the P-channel enhanced MOS tube is connected with a grid source voltage; when the load current increases, the resistor RTThe voltages at the two ends are increased, and the triode shunts the voltages.
Further, the voltage stabilization current expansion circuit further comprises: the diode D1 is connected in parallel with two sides of the three-terminal voltage stabilizing chip; the anode of the diode D1 is connected with the output end of the three-terminal voltage stabilizing chip, and the cathode of the diode D1 is connected with the input end of the three-terminal voltage stabilizing chip.
Further, the voltage stabilization current expansion circuit further comprises: a capacitor C10, a capacitor C11, a capacitor C12 and a capacitor C13;
one end of the capacitor C10 is connected with the resistor RTAnd the other end is connected with a resistor RB；
One end of the capacitor C11Connecting the resistor RTAnd the other end is connected with a resistor RB；
One end of the capacitor C12 is connected with the output end of the three-terminal voltage stabilizing chip U1, and the other end of the capacitor C12 is connected with the resistor RB；
One end of the capacitor C12 is connected with the output end of the three-terminal voltage stabilizing chip U1, and the other end of the capacitor C12 is connected with the resistor RB。
Further, the regulated pipe voltage drop control circuit comprises 4 identical differential amplifiers; the non-inverting input end of the differential amplifier U2 is connected with the drain electrode of the P-channel enhancement type MOS tube, the inverting input end of the differential amplifier U2 is connected with the output end of the differential amplifier U2, and the non-inverting input end of the differential amplifier U2 is connected with the drain electrode of the P-channel enhancement type MOS tube through a resistor RC1The non-inverting input end of the differential amplifier U4 is connected; the non-inverting input end of the differential amplifier U3 is connected with the source electrode of the P-channel enhancement type MOS tube, the inverting input end of the differential amplifier U3 is connected with the output end of the differential amplifier U3, and the non-inverting input end of the differential amplifier U3 is connected with the source electrode of the P-channel enhancement type MOS tube through a resistor RC2The inverting input end of the differential amplifier U4 is connected; the inverting input terminal of the differential amplifier U4 and the output terminal of the differential amplifier U4 pass through a resistor RC3Connecting; the output terminal of the differential amplifier U4 passes through a resistor RD1Connected to the inverting input terminal of the differential amplifier U5, the inverting input terminal of the differential amplifier U5 is connected through a resistor REThe output end of the differential amplifier U5 is connected, and the output end of the differential amplifier U5 is connected with a grid source voltage.
Further, the output voltage of the regulated tube voltage drop control circuit is calculated by the following formula:
wherein, VPFor regulating the output voltage of the tube-voltage-drop control circuit, Vref1For adjusting the internal reference voltage, R, of the tube-drop control circuitBIs a resistance RBResistance value of rDSIs the drain-source resistance R of a P-channel enhancement type MOS tube working in a variable resistance regionAIs a resistance RAResistance value of RDIs a resistance RDResistance value of, KpFor P-channel enhancement type MConductance constant, R, of OS tubeEIs a resistance REResistance value of VDSIs the drain-source voltage, V, of the P-channel enhancement type MOS tubeTThe turn-on voltage of the P-channel enhancement type MOS tube is shown.
A second aspect of the present invention provides a control system for controlling a high-stability direct current power supply as defined in any one of the above, comprising:
the device comprises an embedded control unit, a D/A conversion unit, an inner ring control unit and an AD sampling unit;
the embedded unit carries out fuzzy processing on an input signal to obtain a fuzzy signal and transmits the fuzzy signal to the D/A conversion unit;
the D/A conversion unit converts the fuzzy signal into a voltage signal and inputs the voltage signal to the inner ring control unit;
the inner ring control unit converts the voltage signal into a current signal and inputs the current signal to the AD sampling unit;
and after the AD sampling unit samples the current signal, the sampling result is input to the embedded control unit for feedback control.
Further, the control system further comprises: a pre-processing unit;
the preprocessing unit preprocesses the acquired signal to obtain an input signal; wherein the pre-processing comprises: and (5) differential processing.
Further, in the control system, the blurring processing is performed on the input signal by the embedded unit to obtain a blurred signal, and the blurred signal is transmitted to the D/a conversion unit, which includes:
the embedded unit fuzzifies the input signal, performs fuzzy inference through a fuzzy inference machine, and outputs fuzzy control quantity; and deblurring the fuzzy control quantity, and taking a fuzzy signal obtained after deblurring as a set value of the D/A conversion unit.
Compared with the prior art, the embodiment of the invention has the beneficial effects that:
1. according to the invention, the leakage-source voltage fluctuation of the adjusting tube is automatically compensated through the dynamic adjustment of the output of the auxiliary power supply, so that the key problem of output current drift caused by the voltage drop fluctuation of the adjusting tube is solved, and the stability of the system is greatly improved;
2. the invention further improves the system stability through an internal and external dual-cycle control mode of internal cycle analog PID regulation, external cycle digital feedback and intelligent control;
3. the invention improves the dynamic characteristic of the output current, leads the current regulation process to be faster and smoother, reduces the establishment time of the output current reaching the steady state value and increases the current output stability.
4. The invention applies the fuzzy control algorithm to the adjusting process of the output current of the direct current source, and realizes the quick adjustment of the dynamic process. The controller of the invention is closer to the idea of manually regulating the output current, but the regulation speed is faster and the output current is more stable.
5. The high-stability direct current source provided by the invention has the performance reaching the foreign product level, improves the cost performance of the product, and can be widely applied to occasions requiring high-precision direct current sources, such as tracing of a direct current calibrator and the like.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a circuit diagram of a series feedback DC constant current source provided by the prior art;
FIG. 2 is a circuit diagram of a typical constant current source provided by the prior art;
FIG. 3 is a block diagram of a control system and signal processing flow provided in accordance with an embodiment of the present invention;
FIG. 4 is a block diagram of a hardware system provided by one embodiment of the invention;
FIG. 5 is a circuit diagram of an auxiliary power circuit and a regulator drop control circuit according to an embodiment of the present invention;
fig. 6 is a circuit diagram of a dc voltage stabilizing and current spreading circuit according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a regulated tube voltage drop control circuit according to one embodiment of the present invention;
FIG. 8 is a block diagram of a software for programming a DC current source according to an embodiment of the present invention;
fig. 9 is a schematic block diagram of a dc current source multi-closed loop control system according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, 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 invention.
It should be understood that the step numbers used herein are for convenience of description only and are not intended as limitations on the order in which the steps are performed.
It is to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The terms "comprises" and "comprising" indicate the presence of the described features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The term "and/or" refers to and includes any and all possible combinations of one or more of the associated listed items.
Most of the existing high-precision direct-current power supplies adopt a series negative feedback control scheme, and have the defects of large power loss and poor stabilityThe foot problem, the typical principle of which is shown in fig. 1. The series negative feedback direct current constant current source is based on the negative feedback principle, when the voltages of the same and opposite phase input ends of the error amplifier are not equal, the difference value is amplified by the error amplifier, the voltage between the grid source and the grid source of the linear adjusting tube is changed to change the current I0 flowing between the drain source and the source of the adjusting tube, and finally the voltage between the reference voltage US of the same and opposite phase input ends of the error amplifier is equal to the voltage between two ends of the sampling resistor RS, so that the output current I0 is constant. The output current of the constant current source is as follows: i is0＝US/RS(1)
The main current scheme of domestic high-precision direct-current power supply generally uses parallel adjusting tubes, a closed-loop control mode of an analog or digital PI regulator is adopted, a typical scheme is shown in figure 2, figure 2 is a design scheme of a high-precision wide-range constant-current source which takes a single chip microcomputer as a control core, the constant-current source ensures that the adjusting tubes work in a better working state in the whole output current range by changing the input voltage of the adjusting tubes, standard resistance sampling is adopted, double closed-loop feedback control of digital PI regulation and negative feedback of the adjusting tubes is adopted, the precision of the output current is good, the efficiency of the adjusting tubes can reach more than 85%, but the output current is only 5A, the stability can only reach 0.1%/min, and the traceability requirement of a direct-current check meter can not be met. A direct current source with stability superior to 50ppm/min, output current of 10A and proper price is designed, and the requirements of subsequent data sampling and synchronous processing of the whole direct current checking device can be greatly reduced, so that the complexity of the whole direct current checking device is simplified.
A first aspect.
An embodiment of the present invention provides a high-stability dc current source, including: the device comprises an auxiliary power supply module, a digital external circulation module and an analog internal circulation control module. The auxiliary power supply module is electrically connected with the digital external circulation module and the analog internal circulation control module respectively; the digital outer circulation module is electrically connected with the analog inner circulation control module.
The auxiliary power supply module includes: a voltage stabilizing current expanding circuit and a regulating tube voltage drop control circuit; the voltage-stabilizing current-expanding circuit is electrically connected with the adjusting tube voltage drop control circuit.
It should be noted that the auxiliary power supply module is configured to provide a stable voltage for the high-stability dc current source after rectifying, filtering and stabilizing the 220V ac voltage.
In a specific embodiment, the voltage stabilizing and current spreading circuit includes: the three-terminal voltage stabilizing circuit comprises a three-terminal voltage stabilizing chip U1, at least two triodes connected in parallel to two sides of the three-terminal voltage stabilizing chip U1 and a P-channel enhanced MOS tube; the input end of the three-end voltage-stabilizing chip U1 passes through a resistor RTThe three-terminal voltage stabilizing chip U1 has its output connected to a load circuit, and the ground terminal of the three-terminal voltage stabilizing chip U1 passes through a resistor RBGrounding; the emitter of the triode passes through a resistor RNThe base electrode of the triode is connected with the input end of the three-terminal voltage stabilizing chip U1, and the collector electrode of the triode is connected with the output end of the three-terminal voltage stabilizing chip U1; the drain electrode and the source electrode of the P-channel enhancement type MOS tube are respectively connected with the resistor RBThe grid electrode of the P-channel enhanced MOS tube is connected with a grid source voltage; when the load current increases, the resistor RTThe voltages at the two ends are increased, and the triode shunts the voltages.
In another specific embodiment, the voltage stabilizing and current spreading circuit further includes: the diode D1 is connected in parallel with two sides of the three-terminal voltage stabilizing chip; the anode of the diode D1 is connected with the output end of the three-terminal voltage stabilizing chip, and the cathode of the diode D1 is connected with the input end of the three-terminal voltage stabilizing chip.
In a specific embodiment, the voltage stabilizing and current spreading circuit further includes: a capacitor C10, a capacitor C11, a capacitor C12 and a capacitor C13;
one end of the capacitor C10 is connected with the resistor RTAnd the other end is connected with a resistor RB；
One end of the capacitor C11 is connected with the resistor RTAnd the other end is connected with a resistor RB；
One end of the capacitor C12 is connected with the output end of the three-terminal voltage stabilizing chip U1, and the other end of the capacitor C12 is connected with the resistor RB；
One end of the capacitor C12 is connected with the output end of the three-terminal voltage stabilizing chip U1, and the other end of the capacitor C12 is connected with the resistor RB。
In a specific embodiment, the regulator tube voltage drop control circuit comprises 4 identical differential amplifiers; the non-inverting input end of the differential amplifier U2 is connected with the drain electrode of the P-channel enhancement type MOS tube, the inverting input end of the differential amplifier U2 is connected with the output end of the differential amplifier U2, and the non-inverting input end of the differential amplifier U2 is connected with the drain electrode of the P-channel enhancement type MOS tube through a resistor RC1The non-inverting input end of the differential amplifier U4 is connected; the non-inverting input end of the differential amplifier U3 is connected with the source electrode of the P-channel enhancement type MOS tube, the inverting input end of the differential amplifier U3 is connected with the output end of the differential amplifier U3, and the non-inverting input end of the differential amplifier U3 is connected with the source electrode of the P-channel enhancement type MOS tube through a resistor RC2The inverting input end of the differential amplifier U4 is connected; the inverting input terminal of the differential amplifier U4 and the output terminal of the differential amplifier U4 pass through a resistor RC3Connecting; the output terminal of the differential amplifier U4 passes through a resistor RD1Connected to the inverting input terminal of the differential amplifier U5, the inverting input terminal of the differential amplifier U5 is connected through a resistor REThe output end of the differential amplifier U5 is connected, and the output end of the differential amplifier U5 is connected with a grid source voltage.
The output voltage of the regulating tube voltage drop control circuit is calculated by the following formula:
wherein, VPFor regulating the output voltage of the tube-voltage-drop control circuit, Vref1For adjusting the internal reference voltage, R, of the tube-drop control circuitBIs a resistance RBResistance value of rDSIs the drain-source resistance R of a P-channel enhancement type MOS tube working in a variable resistance regionAIs a resistance RAResistance value of RDIs a resistance RDResistance value of, KpIs the conductance constant, R, of a P-channel enhancement type MOS tubeEIs a resistance REResistance value of VDSIs the drain-source voltage, V, of the P-channel enhancement type MOS tubeTThe turn-on voltage of the P-channel enhancement type MOS tube is shown.
The digital outer loop module comprises: the device comprises a communication interface, an embedded processor, a digital-to-analog conversion circuit and an analog-to-digital conversion circuit; the communication interface is electrically connected with the embedded processor, the embedded processor is connected with the analog-to-digital conversion circuit, and the analog-to-digital conversion circuit is connected with the embedded processor; the tuning tube voltage drop control circuit is electrically connected with the embedded processor.
The analog inner loop control module comprises: the device comprises a range switching circuit, a V/I conversion circuit, a power output circuit and a conditioning circuit; the digital-to-analog conversion circuit is electrically connected with the range switching circuit, the range switching circuit is electrically connected with the V/I conversion circuit, the V/I conversion circuit is electrically connected with the power output circuit and the conditioning circuit, and the power output circuit and the conditioning circuit are electrically connected with the conditioning circuit; and the adjusting tube voltage drop control circuit is electrically connected with the range switching circuit.
In a specific embodiment, in order to meet the design requirements of a direct current source with high stability and high output power, the invention realizes a high-stability digital program-controlled direct current source based on an embedded processor. The stability of the power supply is guaranteed to depend on a multi-closed-loop control system, the multi-closed-loop control system comprises a digital outer loop control part and an analog inner loop control part, an independent auxiliary power supply stability adjusting control loop is added, and a plurality of circulating control systems work coordinately and consistently, so that the stability of the direct-current power supply is guaranteed; the digital outer ring forms an intelligent control loop by a high-performance embedded controller and an AD/DA device, and can quickly adjust the steady-state output of current; the analog inner loop is a current series negative feedback circuit formed by a hardware PI regulator, so that interference can be inhibited and the accuracy of output current can be improved. The auxiliary power supply output voltage automatic compensation system can eliminate the drift of the output current of the voltage-controlled constant current source. The output of the direct current source adopts a direct current voltage-stabilizing current-amplifying circuit, a Darlington driving circuit and a power amplifying circuit to realize high-power output meeting the requirements. The output stability of the current source can reach 50ppm/min, the output reaches 10A, the load capacity is strong, and the current source is suitable for occasions requiring high-stability direct current sources such as a direct current check meter.
Referring to fig. 3, the present invention provides a control system and a signal processing method for a high-stability digital program-controlled dc current source.
The direct current source system mainly comprises two parts, namely a hardware part and a software part. The hardware part determines the stability, the anti-interference capability and the load capability of the direct current source; the software part determines the output precision of the direct current source and overall coordinates the hardware system.
The hardware system block diagram is shown in fig. 4. The hardware part of the high-precision program-controlled direct current source mainly comprises an auxiliary power supply module, a digital external circulation module and an analog internal circulation control module;
the simulation inner loop control module specifically comprises: the device comprises a V/I conversion circuit, a range switching circuit, a power output circuit and a conditioning circuit;
the digital outer loop control module comprises: the digital-to-analog conversion circuit, the embedded processor and the like;
the auxiliary power supply module includes: and the pressure stabilizing and flow expanding and adjusting pipe pressure drop control circuit.
The auxiliary power supply module provides stable working voltage for a digital chip and an analog circuit in the direct current source, the 220V alternating current voltage is divided into multiple paths of voltage output through a transformer and is used by each module after links of rectification, filtering, voltage stabilization and the like, and the auxiliary power supply and the automatic compensation circuit thereof are shown in fig. 5. Because the common voltage stabilizing chip can not provide large current output, the maximum output current of the common three-terminal voltage stabilizing chip is only 1.5A, and the current expanding design is carried out on the auxiliary power supply in order to output large current. The fluctuation of the auxiliary power supply caused by the change of the load, and further the current drift is an important factor influencing the stability of the power supply; the drift caused by the change of the auxiliary power supply is automatically compensated through the corresponding change of the tube voltage drop, and the method is an important method for improving the stability of the power supply.
The maximum output current of a direct current source of the whole check meter calibration equipment of the direct current check meter is required to be 10A, the maximum output current of a typical voltage stabilizing circuit of a three-terminal direct current voltage stabilizing chip is only 1A, and the three-terminal direct current voltage stabilizing chip cannot work in a large-current output state for a long time, so that a current expanding circuit shown in figure 6 is designed to increase the output current. Adopting an external tripolarAnd (4) tube current expansion, namely, a plurality of high-power triodes are connected in parallel at two ends of the three-end voltage stabilizing chip U1. When the load current increases, the resistance RTThe voltage at the two ends begins to increase gradually, and the triodes Q1-QNStarting to conduct and shunt, wherein the maximum current flowing through each high-power triode is I1So maximum spread I1×N＝N.I1。
As shown in FIGS. 6 and 7, the differential amplifier U5Driving a P-channel enhancement MOSFET QT，QTThe drain electrode and the source electrode of the resistor are connected with a voltage setting resistor R of an adjustable linear voltage stabilizing source in a bridging wayBBoth ends of (A), QTOperating in the variable resistance region. Output voltage V of adjustable linear voltage-stabilizing sourcePCan be expressed as:
in the above formula, Vref1An internal reference voltage which is an adjustable linear voltage-stabilizing source; r isDSThe drain-source resistance of PMOS working in the variable resistance region is expressed as 1/[2K ]P(VGS-VT)]Wherein, K isPAnd VTRespectively, the conductance constant and the turn-on voltage of the PMOS; vGSIs QTOf grid-source voltage, i.e. operational amplifier U5Can be represented as VGS＝RE(Vref-VDS)/RD。
The basic principle of improving the current stability of the regulating tube voltage drop control circuit is as follows: during normal operation, the output voltage V of the adjustable linear voltage-stabilizing source is assumedPIf the load current is reduced for some reason, the drain-source voltage V of the parallel field effect transistorDSWill increase, as can be seen from the above formula, VDSThe increase necessarily results in an increase in the output voltage of the adjustable linear regulator, thereby increasing the load current. Thus, the output voltage of the adjustable linear voltage-stabilizing source is automatically compensated and the adjusting tube V is connected in parallelDSIs finally eliminated due to VDSThe current drift caused by fluctuation improves the stability of the current source output.
The whole control circuit adopts a full-analog design, realizes the function of automatically compensating the output current drift of the constant current source by the output voltage of the auxiliary power supply, avoids high-frequency interference introduced by using digital control or a switching power supply, and increases the stability of the output current.
The main control module is a high-performance embedded system, and a communication circuit, an A/D sampling circuit, a D/A output control circuit and the like are expanded; in order to reduce interference, an optical coupler is added on a transmission channel of a digital signal and an analog signal for isolation.
The basic circuit part of the power supply mainly ensures the high-power stable output of direct current, a closed-loop series negative feedback circuit is formed by an analog PI regulator and a V/I conversion circuit, and a measuring range switching circuit is switched to different sampling resistors through a multi-way switch to select measuring ranges. The protection circuit is composed of a dual-threshold window value comparator, and a power supply can be cut off when the current source is open or the current is overlarge, so that the direct current source is protected to prevent damage.
A software framework diagram of the programmable dc current source is shown in fig. 8.
The software system part is mainly divided into an edge server and terminal power supply control software. The edge server program comprises the design of a human-computer interaction interface; the edge server is connected with the program-controlled direct current source through TCP/IP communication, so that online calibration of the direct current source is realized; the current output controls the scheduling algorithm and the display of the current output current. The power supply control program comprises a main control program and is mainly used for initializing each interface module and controlling hardware circuits of each part to work normally. The current regulation in the power supply control program needs to be written into a control algorithm to regulate the current output so as to ensure that the current output reaches the required stability.
The high precision of the high-precision program-controlled direct current source is established on the basis that the output current has higher stability, and only when the output current has high stability and fluctuates within the precision range of the output current, the direct current source can be ensured to carry out constant current output by regulating the output current. The design of a multi-closed-loop control system is just to solve the problems of stability of a direct current source and accuracy of output current. A schematic block diagram of a multi-closed-loop control system of a high-precision program-controlled dc current source is shown in fig. 9.
The inner circulation system is a series negative feedback circuit consisting of a hardware analog PID regulator, a V/I conversion circuit and a sampling circuit, wherein a controlled object of the inner loop is the V/I conversion circuit, the input quantity is the output voltage value of the D/A converter, and the output quantity is the current value. The input voltage value and the output current value of the V/I conversion circuit are in linear relation, and the input voltage U is giveniObtain corresponding output current IOObtaining a feedback voltage U through a sampling circuitfDependent on the input voltage UiComparing to form a deviation value, automatically regulating by a hardware PID to reduce the deviation and output current IOIs stable in a certain range.
The external circulation system is a digital control system consisting of an embedded controller, a D/A converter, an inner ring and an A/D sampling circuit, wherein the inner ring is used as a controlled object, the input quantity is a current set value (set remotely or locally), and the output quantity is an actual current value. The operation edge server gives an output current value to the direct current source through the communication interface, and performs A/D sampling on the direct current source after the current output is stable to calculate an actual current value (outer loop feedback current value); then comparing with the given current value to obtain the current deviation E and the variable quantity of the current deviation EC, after fuzzification processing, carrying out fuzzy reasoning by a fuzzy reasoning machine to output a control quantity U, and after the defuzzification, obtaining a digital quantity as a set value of D/A, and outputting current by a V/I conversion circuit. The embedded controller continuously adjusts the output current through a specific control algorithm, so that the current does not change along with the change of the load, the aim of constant current output is finally achieved, and the stability of the output current is ensured.
The invention provides a high-stability direct current source and a control method applied to an integral traceability system of a direct current transformer calibrator, and belongs to the field of standard source application in the traceability technology of the direct current transformer calibrator. The key points of the invention are as follows:
the current stability of the DC constant current source mainly depends on the stability of the equivalent drift of the reference voltage, the sampling resistor and the error amplifier and the noise voltage, and is influenced by the output resistance of the MOSFET.
1. The invention automatically compensates the drain-source voltage fluctuation of the adjusting tube by dynamically adjusting the output of the auxiliary power supply, solves the key problem of output current drift caused by the voltage drop fluctuation of the adjusting tube, and greatly increases the stability of the system.
2. The invention changes the single series negative feedback mode in the prior art into an internal and external dual-cycle control mode of internal cycle analog PID regulation, external cycle digital feedback and intelligent control, thereby further improving the system stability.
3. The invention improves the dynamic characteristic of the output current, leads the current regulation process to be faster and smoother, reduces the establishment time of the output current reaching the steady state value and increases the current output stability.
4. The invention applies the fuzzy control algorithm to the adjusting process of the output current of the direct current source, and realizes the quick adjustment of the dynamic process. The controller of the invention is closer to the idea of manually regulating the output current, but the regulation speed is faster and the output current is more stable.
5. The high-stability direct current source provided by the invention has the performance reaching the foreign product level, improves the cost performance of the product, and can be widely applied to occasions requiring high-precision direct current sources, such as tracing of a direct current calibrator and the like.
A second aspect.
An embodiment of the present invention provides a control system for controlling a high-stability dc current source as described above, including: the device comprises an embedded control unit, a D/A conversion unit, an inner ring control unit and an AD sampling unit.
The embedded unit carries out fuzzy processing on input signals to obtain fuzzy signals and transmits the fuzzy signals to the D/A conversion unit.
In a specific embodiment, the embedded unit performs a blurring process on the input signal to obtain a blurred signal, and transmits the blurred signal to the D/a conversion unit, including.
The embedded unit fuzzifies the input signal, performs fuzzy inference through a fuzzy inference machine, and outputs fuzzy control quantity; and deblurring the fuzzy control quantity, and taking a fuzzy signal obtained after deblurring as a set value of the D/A conversion unit.
The D/a conversion unit converts the blur signal into a voltage signal, and inputs the voltage signal to the inner loop control unit.
The inner loop control unit converts the voltage signal into a current signal and inputs the current signal to the AD sampling unit.
And after the AD sampling unit samples the current signal, the sampling result is input to the embedded control unit for feedback control.
In a specific embodiment, the method further comprises: a pre-processing unit;
the preprocessing unit preprocesses the acquired signal to obtain an input signal; wherein the pre-processing comprises: and (5) differential processing.
Claims (10)
1. A high stability dc current source, comprising: the device comprises an auxiliary power supply module, a digital external circulation module and an analog internal circulation control module; the auxiliary power supply module is electrically connected with the digital external circulation module and the analog internal circulation control module respectively; the digital external circulation module is electrically connected with the analog internal circulation control module;
the auxiliary power supply module includes: a voltage stabilizing current expanding circuit and a regulating tube voltage drop control circuit; the voltage-stabilizing current-expanding circuit is electrically connected with the adjusting tube voltage drop control circuit;
the digital outer loop module comprises: the device comprises a communication interface, an embedded processor, a digital-to-analog conversion circuit and an analog-to-digital conversion circuit; the communication interface is electrically connected with the embedded processor, the embedded processor is connected with the analog-to-digital conversion circuit, and the analog-to-digital conversion circuit is connected with the embedded processor; the adjusting tube voltage drop control circuit is electrically connected with the embedded processor;
the analog inner loop control module comprises: the device comprises a range switching circuit, a V/I conversion circuit, a power output circuit and a conditioning circuit; the digital-to-analog conversion circuit is electrically connected with the range switching circuit, the range switching circuit is electrically connected with the V/I conversion circuit, the V/I conversion circuit is electrically connected with the power output circuit and the conditioning circuit, and the power output circuit and the conditioning circuit are electrically connected with the conditioning circuit; and the adjusting tube voltage drop control circuit is electrically connected with the range switching circuit.
2. A high stability dc current source as set forth in claim 1, wherein said auxiliary power supply module comprises:
and the auxiliary power supply module is used for providing stable voltage for the high-stability direct current power supply after rectifying, filtering and stabilizing the 220V alternating current voltage.
3. A high stability DC current source according to claim 1,
the voltage-stabilizing current-expanding circuit comprises: the three-terminal voltage stabilizing circuit comprises a three-terminal voltage stabilizing chip U1, at least two triodes connected in parallel to two sides of the three-terminal voltage stabilizing chip U1 and a P-channel enhanced MOS tube; the input end of the three-end voltage-stabilizing chip U1 passes through a resistor RTThe three-terminal voltage stabilizing chip U1 has its output connected to a load circuit, and the ground terminal of the three-terminal voltage stabilizing chip U1 passes through a resistor RBGrounding; the emitter of the triode passes through a resistor RNThe base electrode of the triode is connected with the input end of the three-terminal voltage stabilizing chip U1, and the collector electrode of the triode is connected with the output end of the three-terminal voltage stabilizing chip U1; the drain electrode and the source electrode of the P-channel enhancement type MOS tube are respectively connected with the resistor RBThe grid electrode of the P-channel enhanced MOS tube is connected with a grid source voltage; when the load current increases, the resistor RTThe voltages at the two ends are increased, and the triode shunts the voltages.
4. A high stability DC current source according to claim 3,
the voltage-stabilizing current-expanding circuit further comprises: the diode D1 is connected in parallel with two sides of the three-terminal voltage stabilizing chip; the anode of the diode D1 is connected with the output end of the three-terminal voltage stabilizing chip, and the cathode of the diode D1 is connected with the input end of the three-terminal voltage stabilizing chip.
5. A high stability DC current source according to claim 4,
the voltage-stabilizing current-expanding circuit further comprises: a capacitor C10, a capacitor C11, a capacitor C12 and a capacitor C13;
one end of the capacitor C10 is connected with the resistor RTAnd the other end is connected with a resistor RB；
One end of the capacitor C11 is connected with the resistor RTAnd the other end is connected with a resistor RB；
One end of the capacitor C12 is connected with the output end of the three-terminal voltage stabilizing chip U1, and the other end of the capacitor C12 is connected with the resistor RB；
One end of the capacitor C12 is connected with the output end of the three-terminal voltage stabilizing chip U1, and the other end of the capacitor C12 is connected with the resistor RB。
6. A high stability DC current source according to claim 5,
the regulating tube voltage drop control circuit comprises 4 identical differential amplifiers; the non-inverting input end of the differential amplifier U2 is connected with the drain electrode of the P-channel enhancement type MOS tube, the inverting input end of the differential amplifier U2 is connected with the output end of the differential amplifier U2, and the non-inverting input end of the differential amplifier U2 is connected with the drain electrode of the P-channel enhancement type MOS tube through a resistor RC1The non-inverting input end of the differential amplifier U4 is connected; the non-inverting input end of the differential amplifier U3 is connected with the source electrode of the P-channel enhancement type MOS tube, the inverting input end of the differential amplifier U3 is connected with the output end of the differential amplifier U3, and the non-inverting input end of the differential amplifier U3 is connected with the source electrode of the P-channel enhancement type MOS tube through a resistor RC2The inverting input end of the differential amplifier U4 is connected; the inverting input terminal of the differential amplifier U4 and the output terminal of the differential amplifier U4 pass through a resistor RC3Connecting; the output terminal of the differential amplifier U4 passes through a resistor RD1Connected to the inverting input terminal of the differential amplifier U5, the inverting input terminal of the differential amplifier U5 is connected through a resistor REThe output end of the differential amplifier U5 is connected, and the output end of the differential amplifier U5 is connected with a grid source voltage.
7. A high stability DC current source according to claim 5,
the output voltage of the regulating tube voltage drop control circuit is calculated by the following formula:
wherein, VPFor regulating the output voltage of the tube-voltage-drop control circuit, Vref1For adjusting the internal reference voltage, R, of the tube-drop control circuitBIs a resistance RBResistance value of rDSIs the drain-source resistance R of a P-channel enhancement type MOS tube working in a variable resistance regionAIs a resistance RAResistance value of RDIs a resistance RDResistance value of, KpIs the conductance constant, R, of a P-channel enhancement type MOS tubeEIs a resistance REResistance value of VDSIs the drain-source voltage, V, of the P-channel enhancement type MOS tubeTThe turn-on voltage of the P-channel enhancement type MOS tube is shown.
8. A control system for controlling a high stability direct current power supply as claimed in any one of claims 1 to 7, comprising:
the device comprises an embedded control unit, a D/A conversion unit, an inner ring control unit and an AD sampling unit;
the embedded unit carries out fuzzy processing on an input signal to obtain a fuzzy signal and transmits the fuzzy signal to the D/A conversion unit;
the D/A conversion unit converts the fuzzy signal into a voltage signal and inputs the voltage signal to the inner ring control unit;
the inner ring control unit converts the voltage signal into a current signal and inputs the current signal to the AD sampling unit;
and after the AD sampling unit samples the current signal, the sampling result is input to the embedded control unit for feedback control.
9. The control system of claim 8, further comprising: a pre-processing unit;
the preprocessing unit preprocesses the acquired signal to obtain an input signal; wherein the pre-processing comprises: and (5) differential processing.
10. The control system of claim 8, wherein the embedded unit performs a blurring process on the input signal to obtain a blurred signal, and transmits the blurred signal to the D/a conversion unit, comprising:
the embedded unit fuzzifies the input signal, performs fuzzy inference through a fuzzy inference machine, and outputs fuzzy control quantity; and deblurring the fuzzy control quantity, and taking a fuzzy signal obtained after deblurring as a set value of the D/A conversion unit.
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Application publication date: 20210907 Assignee: Guangdong Electric Power Communication Technology Co.,Ltd. Assignor: Measurement Center of Guangdong Power Grid Co.,Ltd. Contract record no.: X2023980047769 Denomination of invention: A High Stability DC Current Source and Control System Granted publication date: 20220318 License type: Common License Record date: 20231121 |
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