CN113272663B - Constant current source sampling circuit and method - Google Patents

Constant current source sampling circuit and method Download PDF

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Publication number
CN113272663B
CN113272663B CN202080008209.6A CN202080008209A CN113272663B CN 113272663 B CN113272663 B CN 113272663B CN 202080008209 A CN202080008209 A CN 202080008209A CN 113272663 B CN113272663 B CN 113272663B
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constant current
current source
resistor
module
triode
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CN113272663A (en
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赵龙武
赵德琦
吴壬华
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Shenzhen Shinry Technologies Co Ltd
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Shenzhen Shinry Technologies Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/14—Measuring resistance by measuring current or voltage obtained from a reference source
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
    • G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
    • G05F1/561—Voltage to current converters

Abstract

A constant current source sampling circuit and method, the constant current source sampling circuit includes: the constant current source circuit comprises a constant current source circuit (210), a resistor to be sampled (230), a Micro Control Unit (MCU), a power supply (220) and a sampling voltage output end (Vout), wherein a first end (211) of the constant current source circuit (210) is connected with the positive electrode of the power supply (220), a first end (231) of the resistor to be sampled (230) is connected with a second end (212) of the constant current source circuit (210) and the sampling voltage output end (Vout), the negative electrode of the power supply (220) is connected with a second end (232) of the resistor to be sampled (230) and a third end (213) of the constant current source circuit (210), and a fourth end (214) of the constant current source circuit (210) is connected with the Micro Control Unit (MCU); the sampling voltage output terminal (Vout) is connected to the Micro Control Unit (MCU). The Micro Control Unit (MCU) determines the constant current value output by the constant current source circuit (210) by detecting the initial resistance value of the resistor (230) to be sampled, so that the resistors (230) to be sampled in different resistance value intervals correspond to different constant current values, the sampling voltage meets the requirements of the Micro Control Unit (MCU) on the sampling range and the sampling precision, and the sampling efficiency of the constant current source sampling circuit is improved.

Description

Constant current source sampling circuit and method
Technical Field
The application relates to the technical field of electronics, in particular to a constant current source sampling circuit and a constant current source sampling method.
Background
The constant current source circuit is a current source circuit in which an output current is kept constant. The constant current source sampling circuit converts the resistance value of the resistor to be tested into a voltage value through a fixed constant current source, and then acquires a voltage signal through a singlechip and converts the voltage signal into a digital signal.
In the practical application scene of the constant current source sampling circuit, the reference voltage of the sampling range of the singlechip analog-digital converter is generally 2.5V, and the resistance value change range of the resistor to be detected is large. When the resistance value of a resistor to be detected is small, an output voltage signal is weak and easy to interfere, and the sampling precision requirement of a single chip microcomputer cannot be met by the conventional constant current source sampling circuit; when the resistance value of the resistor to be tested is large, the output voltage signal exceeds the range limit of the single chip microcomputer, the sampling precision and the sampling range cannot be guaranteed by the conventional constant current source sampling circuit, and the sampling efficiency is low.
Disclosure of Invention
In order to solve the problems in the constant current source sampling circuit, the application provides the constant current source sampling circuit and the method, the constant current source sampling circuit can switch the current value of the constant current source through the control module, the requirements of the measuring range and the precision of a single chip microcomputer are met, and the sampling efficiency is improved.
In a first aspect of the embodiments of the present application, a constant current source sampling circuit is provided, which is applied to resistance sampling, and is characterized in that the constant current source sampling circuit includes: the sampling circuit comprises a constant current source circuit, a resistor to be sampled, a micro control unit, a power supply and a sampling voltage output end;
the first end of the constant current source circuit is connected with the anode of the power supply; the second end of the constant current source circuit is connected with the first end of the resistor to be sampled and the sampling voltage output end; the second end of the resistor to be sampled is connected with the negative electrode of the power supply and the third end of the constant current source circuit; one end of the micro control unit is connected with the sampling voltage output end, and the other end of the micro control unit is connected with the fourth end of the constant current source circuit.
In one embodiment, the constant current source circuit includes: the device comprises a first constant current source module, a second constant current source module and a control module;
the positive electrode of the power supply is connected with the first end of the first constant current source module and the first end of the control module; the second end of the control module is connected with the first end of the second constant current source module; the third end of the control module is connected with the negative electrode of the power supply and the second end of the resistor to be sampled; the fourth end of the control module is connected with the micro control unit; the second end of the second constant current source module, the third end of the second constant current source module and the fourth end of the second constant current source module are respectively connected with the corresponding second end of the first constant current source module, the third end of the first constant current source module and the fourth end of the first constant current source module; the fifth end of the first constant current source module is connected with the fifth end of the second constant current source module and the sampling voltage output end;
in one embodiment, the first constant current source module comprises a load sub-module, a constant current source sub-module, and a bias voltage sub-module;
the positive electrode of the power supply is connected with the first end of the load sub-module and the first end of the bias voltage sub-module; the second end of the load sub-module and the second end of the second constant current source module are connected with the first end of the constant current source sub-module; the second end of the bias voltage sub-module is connected with the second end of the constant current source sub-module and the third end of the second constant current source module; the third end of the constant current source sub-module is connected with the fourth end of the second constant current source module; and the fourth end of the constant current source submodule is connected with the fifth end of the second constant current source module and the sampling voltage output end.
In one embodiment, the constant current source sub-module includes: the first triode and the first resistor are connected with the first resistor;
the second end of the load sub-module and the second end of the second constant current source module are connected with the collector terminal of the first triode; the second end of the bias voltage submodule and the third end of the second constant current source module are connected with the base electrode end of the first triode; an emitter terminal of the first triode is connected with a first end of the first resistor and a fourth end of the second constant current source module; the second end of the first resistor is connected with the fifth end of the second constant current source module and the sampling voltage output end;
the bias voltage submodule provides bias voltage for the base electrode of the first triode; the load submodule is a load resistor of the first triode;
the first constant current source module is used for controlling the first triode to be in an amplification state, so that the current output by the emitter terminal of the first triode is the current output by the fifth terminal of the first constant current source module.
In one embodiment, the load submodule includes a second resistor and a second transistor;
the positive electrode of the power supply is connected with the first end of the second resistor; the second end of the second resistor is connected with the emitter end of the second triode; a collector terminal of the second triode is suspended; the base electrode end of the second triode and the second end of the second constant current source module are connected with the collector electrode end of the first triode;
the second constant current source module comprises a third resistor, a third triode and a controllable precise voltage-stabilizing source;
the second end of the control module is connected with the first end of the third resistor; the second end of the third resistor is connected with the emitter end of the third triode; the base electrode terminal of the third triode is connected with the base electrode terminal of the second triode and the collector electrode terminal of the first triode; a collector terminal of the third triode is connected with a base terminal of the first triode and a cathode terminal of the controllable precise voltage-stabilizing source; the reference pole terminal of the controllable precise voltage-stabilizing source is connected with the emitter terminal of a first triode and the first end of the first resistor; and the anode end of the controllable precise voltage-stabilizing source is connected with the second end of the first resistor and the sampling voltage output end.
In one embodiment, when the resistance values of the second resistor and the third resistor are equal, and the models of the second transistor and the third transistor are the same, the current output by the fifth terminal of the first constant current source module is the same as the current output by the fifth terminal of the second constant current source module.
In one embodiment, the bias voltage submodule comprises a fourth resistor and a first capacitor connected in parallel;
the positive electrode of the power supply is connected with the first end of the fourth resistor and the first end of the first capacitor; a second end of the fourth resistor and a second end of the first capacitor are connected with a base electrode end of the first triode, a collector electrode end of the third triode and a cathode end of the controllable precise voltage-stabilizing source;
the fourth resistor provides bias voltage for the base electrode of the first triode; and the first capacitor provides positive bias voltage for the base electrode of the first triode when the circuit is conducted.
In one embodiment, the control module comprises: the first switch tube, the second switch tube, the fifth resistor, the sixth resistor and the second capacitor;
the positive electrode of the power supply is connected with the first end of the first switching tube, the first end of the fifth resistor and the first end of the second capacitor; the second end of the first switching tube is connected with the first end of the second constant current source module; the third end of the first switch tube is connected with the second end of the fifth resistor, the second end of the second capacitor and the first end of the sixth resistor; the second end of the sixth resistor is connected with the first end of the second switching tube; the second end of the second switching tube is connected with the negative electrode of the power supply and the second end of the resistor to be sampled; the third end of the second switch tube is connected with the micro control unit;
when the micro control unit outputs a first voltage to the third end of the second switch tube, the first switch tube is conducted with the second switch tube, and the control module is in a communication state; when the micro control unit outputs a second voltage or does not output the voltage to the third end of the second switch tube, the first switch tube and the second switch tube are cut off, and the control module is in a disconnected state.
In one embodiment, the first switch tube includes any one of a relay, a transistor, and a metal oxide semiconductor field effect transistor MOS, and the second switch tube includes any one of a relay, a transistor, and a MOS.
In a second aspect of the embodiments of the present application, there is provided a constant current source sampling method, which is applied to the constant current source sampling circuit, and the method may include:
when the second end of the constant current source circuit outputs an initial constant current value, the micro control unit measures an initial resistance value of the resistor to be sampled and determines a target resistance value interval in which the initial resistance value falls;
the micro control unit determines a target constant current value corresponding to the target resistance value interval according to the corresponding relation between the resistance value interval set and the constant current value set;
and the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to the target constant current value so as to measure the final resistance value of the resistor to be sampled.
In one embodiment, the set of resistance value intervals comprises a first resistance value interval and a second resistance value interval, and the set of constant current values comprises a first constant current value and a second constant current value; the first resistance value interval corresponds to the first constant current value, and the second resistance value interval corresponds to the second constant current value.
In one embodiment, the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to the target constant current value, so as to measure the final resistance value of the resistor to be sampled, and the method includes: when the target resistance value interval is the first resistance value interval, the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to the first constant current value so as to measure the final resistance value of the resistor to be sampled; and when the target resistance value interval is the second resistance value interval, the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to the second constant current value so as to measure the final resistance value of the resistor to be sampled.
According to the embodiment of the application, aiming at the resistance to be sampled with a large variation range, the micro control unit determines the constant current value output by the constant current source circuit by detecting the initial resistance value of the resistance to be sampled, the voltage of the sampling voltage output end is the product of the constant current value and the sampling resistance value, so that the resistance to be sampled in different resistance value intervals corresponds to different constant current values, the sampling voltage meets the requirements of the sampling range and the sampling precision of the micro control unit, and the sampling efficiency of the constant current source sampling circuit is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a constant current source sampling circuit in an embodiment of the present application;
fig. 2 is a schematic structural diagram of a constant current source sampling circuit in an embodiment of the present application;
fig. 3 is a schematic diagram of a specific structure of another constant current source sampling circuit in the embodiment of the present application;
fig. 4 is a schematic structural diagram of another constant current source sampling circuit in an embodiment of the present application;
fig. 5 is a schematic flowchart of a constant current source sampling method in the embodiment of the present application.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.
The terms "first," "second," and the like in the description and claims of the present application and in the foregoing drawings are used for distinguishing between different objects and not for describing a particular sequential order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements but may alternatively include other steps or elements not expressly listed or inherent to such process, system, article, or apparatus.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein may be combined with other embodiments.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a constant current source sampling circuit according to an embodiment of the present disclosure.
The application provides a constant current source sampling circuit, including constant current source circuit 210, power 220, wait to sample resistance 230, sample voltage output end (fig. 1 shows with Vout), little control unit (MCU).
The first end 211 of the constant current source circuit 210 is connected to the positive electrode of the power supply 220, the second end 212 of the constant current source circuit 210 is connected to the first end 231 of the resistor 230 to be sampled and the sampling voltage output end Vout, the second end 232 of the resistor 230 to be sampled is connected to the negative electrode of the power supply 220 and the third end 213 of the constant current source circuit 210, one end of the micro control unit MCU is connected to the sampling voltage output end Vout, and the other end of the micro control unit MCU is connected to the fourth end 214 of the constant current source circuit 210.
In one embodiment, the to-be-sampled resistor 230 is a connection confirmation function (CC) resistor Rcc, the constant current source circuit 210 is applied to an electric vehicle conduction charging system, and the connection confirmation function of the electric vehicle conduction charging system is to connect resistors Rcc with different resistance values through a charging gun to determine a vehicle interface connection state and a charging cable capacity of a charging pile.
The micro control unit MCU is configured to, when the second end 212 of the constant current source circuit 210 outputs an initial constant current value, measure an initial resistance value of the resistor 230 to be sampled, determine a target resistance value interval in which the initial resistance value falls, determine a target constant current value corresponding to the target resistance value interval according to a correspondence between a resistance value interval set and a constant current value set, and control the second end 212 of the constant current source circuit 210 to re-output a constant current corresponding to the target constant current value, so as to measure a final resistance value of the resistor 230 to be sampled.
Optionally, the constant current source circuit 210 includes a plurality of constant current source modules connected in parallel, each constant current source module is controlled by a control module corresponding to the constant current source module to operate, the control module of each constant current source module is controlled by the micro control unit MCU, when any of the constant current source modules operates, the constant current source module in an operating state outputs a constant current, and the current output by the constant current source circuit 210 is the sum of the currents output by the constant current source modules in the operating state.
Through the above connection manner, the micro control unit MCU determines the constant current value of the constant current source circuit by detecting the initial resistance value of the resistance to be sampled 230, the voltage of the sampling voltage output terminal Vout is the product of the constant current value and the resistance value of the resistance to be sampled 230, so that the resistance to be sampled 230 in different resistance value intervals corresponds to different constant current values, the sampling voltage meets the requirements of the micro control unit MCU on sampling range and sampling precision, and the sampling efficiency of the constant current source sampling circuit is improved.
In one embodiment, the set of resistance value intervals includes a first resistance value interval and a second resistance value interval, the set of constant current values includes a first constant current value and a second constant current value, the first resistance value interval corresponds to the first constant current value, and the second resistance value interval corresponds to the second constant current value.
When the target resistance interval is the first resistance interval, the MCU controls the second end 212 of the constant current source circuit 210 to output a constant current corresponding to the first constant current value, so as to measure the final resistance of the resistor 230 to be sampled.
When the target resistance interval is the second resistance interval, the MCU controls the second end 212 of the constant current source circuit 210 to output a constant current corresponding to the second constant current value, so as to measure the final resistance of the resistor 230 to be sampled.
In one embodiment, as shown in fig. 2, the constant current source circuit 210 shown in fig. 2 includes a first constant current source module 310, a second constant current source module 330, and a control module 320.
The positive electrode of the power source 220 is connected to the first end 311 of the first constant current source module 310 and the first end 321 of the control module 320, the second end 322 of the control module 320 is connected to the first end 331 of the second constant current source module 330, the third end 323 of the control module 320 is connected to the negative electrode of the power source 220 and the second end 232 of the to-be-sampled resistor 230, the fourth end 324 of the control module 320 is connected to the MCU, the second end 332, the third end 333 and the fourth end 334 of the second constant current source module 330 are correspondingly connected to the second end 312, the third end 313 and the fourth end 314 of the first constant current source module 310, respectively, and the fifth end 315 of the first constant current source module 310 is connected to the fifth end 335 of the second constant current source module 330 and the sampling voltage output end Vout.
The control module 320 is configured to control whether the second constant current source module 330 operates.
Specifically, in one embodiment, the MCU controls the control module 320 to be in a connected state, such that the fifth terminal 315 of the first constant current source module 310 outputs a constant current corresponding to the second constant current value, the fifth terminal 335 of the second constant current source module 330 outputs a constant current corresponding to a third constant current value, and the first constant current value is equal to the sum of the second constant current value and the third constant current value.
In another embodiment, the MCU controls the control module 320 to be in an off state, so that the fifth terminal 315 of the first constant current source module 310 outputs a constant current corresponding to the second constant current value, and when the control module 320 is in the off state, the second constant current source module 330 is in an open state, and no current is output from the second constant current source module 330.
Optionally, as shown in fig. 2, the constant current source circuit 210 may further include a first control module, where the first control module is located between the first constant current source module 310 and the power source 220, and the first control module is configured to control an on/off state of the first constant current source module 310. When the micro control unit MCU controls the first control module to be in the on state and the control module 320 to be in the off state, the second end 212 of the constant current source circuit 210 outputs a constant current corresponding to the second constant current value; when the MCU controls the first control module to be in a connected state and the control module 320 to be in a connected state, the second end 212 of the constant current source circuit 210 outputs a constant current corresponding to the first constant current value.
In one embodiment, as shown in fig. 3, the first constant current source module 310 includes a load sub-module 410, a constant current source sub-module 430, and a bias voltage sub-module 420.
The positive terminal of the power supply 220 is connected to the first terminal 411 of the load submodule 410 and the first terminal 421 of the bias voltage submodule 420. The second terminal 332 of the second constant current source module 330 is connected to the first terminal 431 of the constant current source module 430. The second terminal 422 of the bias voltage sub-module 420 is connected to the second terminal 432 of the constant current source sub-module 430 and the third terminal 333 of the second constant current source module 330, the third terminal 433 of the constant current source sub-module 430 is connected to the fourth terminal 334 of the second constant current source module 330, and the fourth terminal 434 of the constant current source sub-module 430 is connected to the fifth terminal 335 of the second constant current source module 330 and the sampling voltage output terminal Vout.
In one embodiment, as shown in fig. 4, the present application provides a constant current source sampling circuit, wherein the constant current source submodule 430 includes: a first triode Q1 and a first resistor R1.
The second terminal of the load submodule 410 and the second terminal of the second constant current source module 330 are connected to the collector terminal of the first transistor Q1, the second terminal of the bias voltage submodule 420 and the third terminal of the second constant current source module 330 are connected to the base terminal of the first transistor Q1, the emitter terminal of the first transistor Q1 is connected to the first terminal of the first resistor R1 and the fourth terminal of the second constant current source module 330, and the second terminal of the first resistor R1 is connected to the fifth terminal of the second constant current source module 330 and the sampling voltage output terminal Vout.
The bias voltage submodule 420 provides a bias voltage to the base of the first transistor Q1, and the load submodule 410 is a load resistor of the first transistor Q1.
The first constant current source module 310 is configured to control the first transistor Q1 to be in an amplifying state, so that the current output from the emitter terminal of the first transistor Q1 is the current output from the fifth terminal of the first constant current source module 310.
In one embodiment, as shown in fig. 4, the load submodule 410 includes a second resistor R2 and a second transistor Q2.
The positive electrode of the power supply 220 is connected to the first terminal of the second resistor R2, the second terminal of the second resistor R2 is connected to the emitter terminal of the second transistor Q2, the collector terminal of the second transistor Q2 is floating, and the base terminal of the second transistor Q2 is connected to the second terminal of the second constant current source module 330 and the collector terminal of the first transistor Q1.
The second constant current source module 330 includes a third resistor R3, a third transistor Q3, and a controllable precision regulator U1.
A second end of the control module 320 is connected to a first end of the third resistor R3, a second end of the third resistor R3 is connected to an emitter terminal of the third transistor Q3, a base terminal of the third transistor Q3 is connected to a base terminal of the second transistor Q2 and a collector terminal of the first transistor Q1, a collector terminal of the third transistor Q3 is connected to a base terminal of the first transistor Q1 and a cathode terminal of the controllable precision regulator U1, a reference terminal of the controllable precision regulator U1 is connected to an emitter terminal of the first transistor Q1 and a first end of the first resistor R1, and an anode terminal of the controllable precision regulator U1 is connected to a second end of the first resistor R1 and the sampling voltage output terminal.
Optionally, when the resistance values of the second resistor R2 and the third resistor R3 are equal, and the types of the second transistor Q2 and the third transistor Q3 are the same, the current output by the fifth terminal 315 of the first constant current source module 310 is the same as the current output by the fifth terminal 335 of the second constant current source module 330.
Optionally, as shown in fig. 4, the bias voltage submodule 420 includes a fourth resistor R4 and a first capacitor C1 connected in parallel. A positive electrode of the power supply 220 is connected to a first end of the fourth resistor R4 and a first end of the first capacitor C1; a second end of the fourth resistor R4 and a second end of the first capacitor C1 are connected to a base terminal of the first transistor Q1, a collector terminal of the third transistor Q3 and a cathode terminal of the controllable precision regulator U1. The fourth resistor R4 provides a bias voltage to the base of the first transistor Q1, and the first capacitor C1 provides a positive bias voltage to the base of the first transistor Q1 when the first constant current source module 310 is turned on.
In one embodiment, as shown in fig. 4, the control module 320 includes: the circuit comprises a first switch tube Q4, a second switch tube Q5, a fifth resistor R5, a sixth resistor R6 and a second capacitor C2.
A positive electrode of the power source 220 is connected to the first terminal of the first switching tube Q4, the first terminal of the fifth resistor R5 and the first terminal of the second capacitor C2, the second terminal of the first switching tube Q4 is connected to the first terminal of the third resistor R3, the third terminal of the first switching tube Q4 is connected to the second terminal of the fifth resistor R5, the second terminal of the second capacitor C2 and the first terminal of the sixth resistor R6, the second terminal of the sixth resistor R6 is connected to the first terminal of the second switching tube Q5, the second terminal of the second switching tube Q5 is connected to the negative electrode of the power source 220 and the second terminal of the resistor Rcc to be sampled, and the third terminal of the second switching tube Q5 is connected to the micro control unit MCU (not shown in fig. 4).
When the MCU outputs a first voltage to the third terminal of the second switching tube Q5, the first switching tube Q4 and the second switching tube Q5 are turned on, and the control module 320 is turned on. When the MCU outputs a second voltage or does not output a voltage to the third terminal of the second switching transistor Q5, the first switching transistor Q4 and the second switching transistor Q5 are turned off, and the control module 320 is turned off. The first voltage is greater than or equal to the turn-on voltage of the second switch tube Q5, and the second voltage is less than the turn-on voltage of the second switch tube Q5.
Optionally, the first switching tube Q4 includes any one of a relay, a transistor, and a mosfet, and the second switching tube Q5 includes any one of a relay, a transistor, and a MOS. In one embodiment, as shown in fig. 4, the first switch Q4 is a PMOS transistor, and the second switch Q5 is an NMOS transistor.
In one embodiment, as shown in fig. 4, the power source is connected in parallel with a third capacitor C3, and the third capacitor C3 is used for filtering the power source.
The operation principle of the constant current source sampling circuit provided in the present application is described below with reference to fig. 2 to 4.
The first constant current source module 310 is a constant current source module that takes emitter current of the first transistor Q1 as output current, and when the first transistor Q1 is in an amplification state, current at the emitter terminal of the first transistor Q1 is the output current of the first constant current source module. The second resistor R2 and the second triode Q2 form a load submodule 410 of a collector of the first triode Q1, and provide collector voltage for a collector of the first triode Q1; the fourth resistor R4 and the first capacitor C1 form a bias voltage submodule of the base of the first triode Q1, and the bias voltage of the base is provided for the base of the first triode Q1. A reference electrode of a controllable precise voltage-stabilizing source U1 in the second constant current source module 330 is connected to an emitter electrode of the first triode Q1, and provides a stabilizing voltage U1 for the emitter electrode of the first triode Q1; the cathode end of the controllable precise voltage-stabilizing source U1 is connected to the base electrode of the first triode Q1, so that the voltage of the reference electrode terminal in the controllable precise voltage-stabilizing source U1 controls the voltage of the base electrode terminal of the first triode Q1 through negative feedback, the first triode Q1 works in an amplification state, and under the condition that the base electrode current of the first triode Q1 is far smaller than the collector electrode current of the first triode Q1, the current of the first triode Q1 is equal to the current of the emitter electrode terminal of the first triode Q1.
The BE junctions of the third resistor R3 and the third transistor Q3 in the second constant current source module 330 are connected in parallel with the BE junctions of the second resistor R2 and the second transistor Q2 in the load submodule 410, and the BE junctions represent the parts from the base B to the emitter E of the transistors. Under the condition that the models of the second triode Q2 and the second triode Q3 are the same, the BE junction voltage drops of the Q2 and the Q3 are the same, the voltages at two ends of the second resistor R2 and the third resistor R3 are the same, and if the resistance values of the R2 and the R3 are the same, the current at the emitter end of the Q2 is the same as the current at the emitter end of the Q3. In the case of the floating collector terminal of Q2, Q2 acts as a diode, and the current at the base terminal of Q2 is equal to the current at the emitter terminal of Q2 and equal to the current at the collector terminal of the first transistor Q1. When the base current of the third transistor Q3 is much smaller than the collector current of the third transistor Q3, the collector current of the third transistor Q3 is the same as the emitter current of the third transistor Q3, and at this time, the collector current of the third transistor Q3 is equal to the collector current of the first transistor Q1, because the collector current of the first transistor Q1 is equal to the emitter current of the first transistor Q1, the current output from the fifth terminal 315 of the first constant current source module 310 is the same as the current output from the fifth terminal 335 of the second constant current source module 330 under the condition that the resistances of R2 and R3 are the same and the models of Q2 and Q3 are the same.
As shown in fig. 4, the control module 320 is composed of a PMOS transistor Q4, a fifth resistor R5, a second capacitor C2, a sixth resistor R6, and an NMOS transistor Q5, and in the constant current source sampling circuit provided by the present application, since there is a voltage at both ends of a circuit to be controlled, the PMOS transistor is used to control the circuit to be turned on or off. The maximum voltage value that little the control unit MCU can output is 3.3V, when the voltage of Q4 source S end is greater than 3.3V, can't be directly through the voltage control Q4 grid G end' S that little the control unit MCU output voltage be greater than the S end so that Q4 disconnection, consequently in the constant current source sampling circuit that this application provided, through little the control unit MCU control NMOS pipe Q5 'S the disconnection to control Q4' S disconnection.
Compare present constant current source sampling circuit, the constant current source sampling circuit that this application embodiment provided, including the constant current source circuit, treat the sampling resistor, little the control unit MCU, power and sampling voltage output, wherein little the control unit MCU treats the initial resistance value of sampling resistor and confirms the constant current value of constant current source circuit output through detecting, the voltage of sampling voltage output is the product of constant current value and sampling resistance value, so that the resistance of treating the sampling resistor of different resistance value intervals corresponds different constant current values, sampling voltage satisfies the requirement of little the control unit MCU sampling range and sampling precision, the sampling efficiency of constant current source sampling circuit has been improved.
As shown in fig. 5, the present application further provides a constant current source sampling method, which is applied to the constant current source sampling circuit shown in fig. 1, fig. 2, fig. 3, or fig. 4, and the method may include:
501. when the second end of the constant current source circuit outputs an initial constant current value, the micro control unit measures an initial resistance value of the resistor to be sampled and determines a target resistance value interval in which the initial resistance value falls.
502. And the micro control unit determines a target constant current value corresponding to the target resistance value interval according to the corresponding relation between the resistance value interval set and the constant current value set.
Optionally, the resistance value interval set includes a first resistance value interval and a second resistance value interval, the constant current value set includes a first constant current value and a second constant current value, the first resistance value interval corresponds to the first constant current value, and the second resistance value interval corresponds to the second constant current value.
503. And the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to the target constant current value so as to measure the final resistance value of the resistor to be sampled.
In one embodiment, the set of resistance intervals includes a first resistance interval and a second resistance interval, the set of constant current values includes a first constant current value and a second constant current value, the first resistance interval corresponds to the first constant current value, and the second resistance interval corresponds to the second constant current value.
In one embodiment, the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to a target constant current value, so as to measure a final resistance value of the resistor to be sampled, and the method specifically includes: when the target resistance value interval is a first resistance value interval, the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to the first constant current value so as to measure the final resistance value of the resistor to be sampled. When the target resistance value interval is a second resistance value interval, the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to the second constant current value so as to measure the final resistance value of the resistor to be sampled.
The foregoing embodiments have been described in detail, and specific examples are used herein to explain the principles and implementations of the present application, where the above description is only for the purpose of assisting in understanding the core concepts of the present application; meanwhile, for a person skilled in the art, according to the idea of the present application, the specific implementation manner and the application scope may be changed, and in summary, the content of the present specification should not be construed as a limitation to the present application.

Claims (8)

1. A constant current source sampling circuit is applied to resistance sampling, and is characterized by comprising: the sampling circuit comprises a constant current source circuit, a resistor to be sampled, a micro control unit, a power supply and a sampling voltage output end;
the first end of the constant current source circuit is connected with the anode of the power supply; the second end of the constant current source circuit is connected with the first end of the resistor to be sampled and the sampling voltage output end; the second end of the resistor to be sampled is connected with the negative electrode of the power supply and the third end of the constant current source circuit; one end of the micro control unit is connected with the sampling voltage output end, and the other end of the micro control unit is connected with the fourth end of the constant current source circuit;
the constant current source circuit includes: the device comprises a first constant current source module, a second constant current source module and a control module;
the positive electrode of the power supply is connected with the first end of the first constant current source module and the first end of the control module; the second end of the control module is connected with the first end of the second constant current source module; the third end of the control module is connected with the negative electrode of the power supply and the second end of the resistor to be sampled; the fourth end of the control module is connected with the micro control unit; the second end and the third end of the second constant current source module are respectively connected with the corresponding second end, the corresponding third end and the corresponding fourth end of the first constant current source module through the fourth end; the fifth end of the first constant current source module is connected with the fifth end of the second constant current source module and the sampling voltage output end;
the first constant current source module comprises a load submodule, a constant current source submodule and a bias voltage submodule;
the positive electrode of the power supply is connected with the first end of the load sub-module and the first end of the bias voltage sub-module; the second end of the load sub-module and the second end of the second constant current source module are connected with the first end of the constant current source sub-module; the second end of the bias voltage sub-module is connected with the second end of the constant current source sub-module and the third end of the second constant current source module; the third end of the constant current source sub-module is connected with the fourth end of the second constant current source module; and the fourth end of the constant current source submodule is connected with the fifth end of the second constant current source module and the sampling voltage output end.
2. The constant current source sampling circuit of claim 1, wherein the constant current source submodule comprises: the first triode and the first resistor are connected with the first resistor;
the second end of the load sub module and the second end of the second constant current source module are connected with a collector terminal of the first triode; the second end of the bias voltage submodule and the third end of the second constant current source module are connected with the base electrode end of the first triode; an emitter terminal of the first triode is connected with a first end of the first resistor and a fourth end of the second constant current source module; the second end of the first resistor is connected with the fifth end of the second constant current source module and the sampling voltage output end;
the bias voltage submodule provides bias voltage for the base electrode of the first triode; the load submodule is a load resistor of the first triode;
the first constant current source module controls the first triode to be in an amplification state, so that the current output by the emitter terminal of the first triode is the current output by the fifth terminal of the first constant current source module.
3. The constant current source sampling circuit of claim 2, wherein the load submodule comprises a second resistor and a second transistor;
the positive electrode of the power supply is connected with the first end of the second resistor; the second end of the second resistor is connected with the emitter end of the second triode; a collector terminal of the second triode is suspended; the base electrode end of the second triode and the second end of the second constant current source module are connected with the collector electrode end of the first triode;
the second constant current source module comprises a third resistor, a third triode and a controllable precise voltage-stabilizing source;
the second end of the control module is connected with the first end of the third resistor; the second end of the third resistor is connected with the emitter end of the third triode; the base electrode end of the third triode is connected with the base electrode end of the second triode and the collector electrode end of the first triode; a collector terminal of the third triode is connected with a base terminal of the first triode, a second terminal of the bias voltage submodule and a cathode terminal of the controllable precise voltage-stabilizing source; the reference pole terminal of the controllable precise voltage-stabilizing source is connected with the emitter terminal of a first triode and the first end of the first resistor; and the anode end of the controllable precise voltage-stabilizing source is connected with the second end of the first resistor and the sampling voltage output end.
4. The sampling circuit of claim 3, wherein the bias voltage submodule comprises a fourth resistor and a first capacitor connected in parallel;
the positive electrode of the power supply is connected with the first end of the fourth resistor and the first end of the first capacitor; a second end of the fourth resistor and a second end of the first capacitor are connected with a base electrode end of the first triode, a collector electrode end of the third triode and a cathode end of the controllable precise voltage stabilizing source;
the fourth resistor provides bias voltage for the base electrode of the first triode; and the first capacitor provides positive bias voltage for the base electrode of the first triode when the constant current source circuit is conducted.
5. The constant current source sampling circuit according to any one of claims 1 to 4, wherein the control module comprises: the first switch tube, the second switch tube, the fifth resistor, the sixth resistor and the second capacitor;
the positive electrode of the power supply is connected with the first end of the first switching tube, the first end of the fifth resistor and the first end of the second capacitor; the second end of the first switch tube is connected with the first end of the second constant current source module; the third end of the first switch tube is connected with the second end of the fifth resistor, the second end of the second capacitor and the first end of the sixth resistor; the second end of the sixth resistor is connected with the first end of the second switching tube; the second end of the second switch tube is connected with the negative electrode of the power supply and the second end of the resistor to be sampled; the third end of the second switch tube is connected with the micro-control unit;
when the micro control unit outputs a first voltage to the third end of the second switch tube, the first switch tube is conducted with the second switch tube, and the control module is in a communication state; when the micro control unit outputs a second voltage or does not output the voltage to the third end of the second switch tube, the first switch tube and the second switch tube are cut off, and the control module is in an off state.
6. A constant current source sampling method applied to the constant current source sampling circuit according to claim 1, the method comprising:
when the second end of the constant current source circuit outputs an initial constant current value, the micro control unit measures an initial resistance value of the resistor to be sampled and determines a target resistance value interval in which the initial resistance value falls;
the micro control unit determines a target constant current value corresponding to the target resistance value interval according to the corresponding relation between the resistance value interval set and the constant current value set;
and the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to the target constant current value so as to measure the final resistance value of the resistor to be sampled.
7. The constant current source sampling method according to claim 6, wherein the set of resistance value intervals includes a first resistance value interval and a second resistance value interval, and the set of constant current values includes a first constant current value and a second constant current value; the first resistance value interval corresponds to the first constant current value, and the second resistance value interval corresponds to the second constant current value.
8. The constant current source sampling method according to claim 7, wherein the micro control unit controls the second terminal of the constant current source circuit to output a constant current corresponding to the target constant current value to measure the final resistance value of the resistance to be sampled, and comprises:
when the target resistance value interval is the first resistance value interval, the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to the first constant current value so as to measure the final resistance value of the resistor to be sampled;
and when the target resistance value interval is the second resistance value interval, the micro control unit controls the second end of the constant current source circuit to output a constant current corresponding to the second constant current value so as to measure the final resistance value of the resistor to be sampled.
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