CN110763910A - Digital display DC meter and current sampling circuit thereof - Google Patents
Digital display DC meter and current sampling circuit thereof Download PDFInfo
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- CN110763910A CN110763910A CN201911095661.6A CN201911095661A CN110763910A CN 110763910 A CN110763910 A CN 110763910A CN 201911095661 A CN201911095661 A CN 201911095661A CN 110763910 A CN110763910 A CN 110763910A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
- G01R19/2506—Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values ; Details concerning sampling, digitizing or waveform capturing
- G01R19/2509—Details concerning sampling, digitizing or waveform capturing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/02—General constructional details
- G01R1/18—Screening arrangements against electric or magnetic fields, e.g. against earth's field
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/36—Overload-protection arrangements or circuits for electric measuring instruments
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/04—Voltage dividers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/08—Circuits for altering the measuring range
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/12—Circuits for multi-testers, i.e. multimeters, e.g. for measuring voltage, current, or impedance at will
- G01R15/125—Circuits for multi-testers, i.e. multimeters, e.g. for measuring voltage, current, or impedance at will for digital multimeters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/142—Arrangements for simultaneous measurements of several parameters employing techniques covered by groups G01R15/14 - G01R15/26
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/16—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using capacitive devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
- G01R15/202—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices using Hall-effect devices
Abstract
The invention relates to a digital display DC meter and a current sampling circuit thereof, wherein the current sampling circuit comprises a reference signal module, a circuit protection module, a Hall current acquisition circuit, a voltage division filtering module, an emitter follower circuit and a current acquisition filtering module which are sequentially connected in series; the input end of the Hall current acquisition circuit is connected with the detected current, the input end of the reference signal module is connected with the Hall current acquisition circuit, the circuit protection module is connected with the Hall current acquisition circuit and the common end of the voltage division filtering module, and the output end of the current acquisition filtering module and the output end of the reference signal module are both connected with the processor of the digital display DC meter. The circuit is mainly used for vehicle-mounted instruments and meters, can improve the safety of the whole circuit and prevent the damage of instantaneous high voltage to a back end circuit; meanwhile, interference signals can be effectively filtered, and the EMC interference resistance of the digital display direct current meter circuit is improved; the problems that the range of the digital display direct current meter is limited, the safety is low, and the EMC anti-interference capability is poor are solved.
Description
Technical Field
The invention relates to a digital display DC meter, in particular to a digital display DC meter and a current sampling circuit thereof.
Background
The digital display DC meter is a meter which is provided with an analog-to-digital converter and displays the measured variable value in a digital form. The digital display direct current meter has the characteristics of visual intuition, convenience in setting, high intelligent control degree and the like, and along with the high-speed development of the current sensing technology, the digital display direct current meter has continuously powerful functions and continuously improved precision, is replacing a large number of traditional mechanical instruments and is widely applied to various industries and daily life.
At present, digital display direct current meters applied to the market, especially vehicle-mounted instruments and meters, have fewer corresponding digital display direct current meters on the market due to the requirements on reliability, stability and accuracy. Therefore, it is very urgent to design and develop a digital dc meter for real-time displaying current value, which is used for real-time monitoring and displaying current to meet the requirements of market and customers.
At present, a direct A/D sampling mode is basically adopted in a digital display DC meter in the market, the measuring range of the detected current is small, the detected current is difficult to reach 100A, a protection circuit is not provided, potential safety hazards exist, and the EMC anti-interference capability is poor.
Disclosure of Invention
The invention provides a current sampling circuit of a digital display DC meter, which solves the problems of measuring range, safety and poor EMC anti-interference capability of the digital display DC meter.
The invention is realized by the following technical scheme:
a current sampling circuit of a digital display DC meter comprises a Hall current acquisition circuit, wherein a detected current is connected to the input end of the Hall current acquisition circuit, the current sampling circuit also comprises a reference signal module, a circuit protection module, a voltage division filtering module, an emitter follower circuit and a current acquisition filtering module, the Hall current acquisition circuit comprises two output ends, one output end of the Hall current acquisition circuit is connected with the input end of the voltage division filtering module, the output end of the voltage division filtering module is connected with the input end of the emitter follower circuit, the output end of the emitter follower circuit is connected with the input end of the current acquisition filtering module, and the output end of the current acquisition filtering module is connected with a processor of the digital display DC meter; the input end of the circuit protection module is connected with the common end of the Hall current acquisition circuit and the voltage division filtering module, and the output end of the circuit protection module is grounded; the other output end of the Hall current acquisition circuit is connected with the input end of the reference signal module, and the output end of the reference signal module is connected with the processor of the digital display DC meter; in the technical scheme, the sampling circuit adopts the voltage division filtering module, so that the input voltage can be effectively divided, and the measuring range of the digital display meter is improved; meanwhile, the sampling circuit adopts the circuit protection module, so that the circuit can be effectively protected, and the safety of the digital display meter is improved; in addition, because the sampling circuit adopts the voltage division filtering module and the current acquisition filtering module, interference signals in the circuit can be effectively filtered, and the EMC anti-interference capability of the whole circuit is improved.
As a further improvement of the invention, the voltage division filtering module comprises a resistor R1, a resistor R13 and a capacitor C19; one end of the resistor R13 is connected with one output end of the Hall current acquisition circuit, and the other end of the resistor R13 is connected with the input end of the emitter follower circuit; one end of the resistor R1 and one end of the capacitor C19 are both connected with the other end of the resistor R13, and the other end of the resistor R1 and the other end of the capacitor C19 are both grounded; in the technical scheme, the voltage division filtering module adopts the structure, so that interference signals can be effectively filtered, useful signals are reserved, and the interference of a circuit is reduced; meanwhile, the resistor R1 and the resistor R13 form a voltage dividing circuit, when detected voltage enters the voltage dividing and filtering module, after the detected voltage is effectively divided by the resistor R1 and the resistor R13, a part of voltage is borne by the voltage dividing resistor, so that the output voltage of the voltage dividing and filtering module is reduced, the output voltage is in a reasonable range, and the measuring range of the digital display direct current meter is improved.
Further, the circuit protection module comprises a TVS tube breakdown short circuit D2, one end of the TVS tube breakdown short circuit D2 is connected with one output end of the Hall current acquisition circuit, and the other end of the TVS tube breakdown short circuit D2 is grounded; in the technical scheme, the circuit protection module adopts the structure, so that the damage to the rear-end circuit caused by external transient high-voltage input can be effectively prevented, and the safety of the circuit is improved.
Further, the emitter follower circuit comprises an emitter follower U3B, the non-inverting input terminal of the emitter follower U3B is connected with the output terminal of the voltage-dividing filter module, one power supply terminal of the emitter follower U3B is grounded, the other power supply terminal of the emitter follower U3B is connected with a power supply voltage VCC, the output terminal of the emitter follower U3B is connected with the input terminal of the current-collecting filter module, and the inverting input terminal of the emitter follower U3B is connected with the output terminal of the emitter follower U3B; in the technical scheme, the emitter follower circuit adopts the structure, so that the requirement on the output current of a superior circuit can be reduced, the driving capability of a posterior circuit is increased, and the output signal of the emitter follower circuit synchronously follows the output signal of the superior circuit.
Further, the current acquisition filtering module comprises a resistor R12 and a capacitor C18, one end of the resistor R12 is connected with the output end of the emitter circuit, the other end of the resistor R12 is connected with a processor of the digital display direct current meter, one end of the capacitor C18 is connected with the other end of the resistor R12, and the other end of the capacitor C18 is grounded; in the technical scheme, the current acquisition filtering module adopts the structure, and can perform secondary filtering on the output signal of the emitting circuit, so that the output signal is smoother, and the anti-interference performance of the circuit is improved.
Further, the reference signal module comprises a resistor R11 and a capacitor C16, one end of the resistor R11 is connected with the other output end of the Hall current acquisition circuit, the other end of the resistor R11 is connected with a processor of the digital display DC meter, one end of the capacitor C16 is connected with the other end of the resistor R11, and the other end of the capacitor C16 is grounded; in the technical scheme, the reference signal module adopts the structure to filter the reference signal, so that a smoother reference signal is provided for the processor, and the debugging of the digital display meter is facilitated.
Further, the digital display direct current meter comprises a current sampling circuit, a voltage sampling circuit, a digital power supply module, an analog power supply module, a processor and a display, wherein the input end of the current sampling circuit is connected with the detected current, and the output end of the current sampling circuit is connected with the processor; the input end of the voltage sampling circuit is connected with the detected voltage, and the output end of the voltage sampling circuit is connected with the processor; the digital power supply module, the analog power supply module and the display are all connected with the processor; the voltage sampling circuit and the current sampling circuit are both connected with a power supply voltage VCC; the current sampling circuit is the current sampling circuit in any one of the above technical schemes.
Further, the voltage sampling circuit comprises an input voltage division module, an input filtering module, an isolation amplification module, a voltage conditioning module and an output filtering module, wherein the input end of the input voltage division module is connected with the voltage to be detected, the output end of the input voltage division module is connected with the input end of the input filtering module, the output end of the input filtering module is connected with the input end of the isolation amplification module, the output end of the isolation amplification module is connected with the input end of the voltage conditioning module, the output end of the voltage conditioning module is connected with the input end of the output filtering module, and the output end of the output filtering module is connected with the processor of the; the input filtering module comprises a common-mode filtering circuit and a secondary filtering circuit; the input end of the common mode filter circuit is connected with the output end of the input voltage division module, the output end of the common mode filter circuit is connected with the input end of the secondary filter circuit, and the output end of the secondary filter circuit is connected with the input end of the isolation amplification module.
Further, the input voltage division module comprises two output ends; the secondary filter circuit comprises two input ends; the common mode filter circuit comprises a common mode inductor M1, a capacitor C5 and a capacitor C6; the common mode inductor M1 comprises a first winding 14 and a second winding 23; the input end of the first winding 14 is connected with one output end of the input voltage division module, and the output end of the first winding 14 is connected with one input end of the secondary filter circuit; the input end of the second winding 23 is connected with the other output end of the input voltage division module, and the output end of the second winding 23 is connected with the other input end of the secondary filter circuit; one end of the capacitor C5 is connected with the common end of the first winding 14 and one input end of the secondary filter circuit, and the other end of the capacitor C5 is grounded; one end of the capacitor C6 is connected to the common terminal of the second winding 23 and the other input terminal of the secondary filter circuit, and the other end of the capacitor C6 is grounded.
Further, the common mode filter circuit comprises two output ends; the isolation amplification module comprises two input ends; the secondary filter circuit comprises a resistor R17, a resistor R22, a capacitor C27, a capacitor C28, a capacitor C30, a capacitor C31 and a capacitor C41; one end of the resistor R17 is connected with one output end of the common mode filter circuit, and the other end of the resistor R17 is connected with one input end of the isolation amplification module; one end of the resistor R22 is connected with the other output end of the common mode filter circuit, and the other end of the resistor R22 is connected with the other input end of the isolation amplification module; the capacitor C41 is connected between the other end of the resistor R17 and the other end of the resistor R22; one end of the capacitor C27 connected with the capacitor C28 in parallel is connected with the other end of the resistor R17, and the other end is grounded; one end of the capacitor C30 and the capacitor C31 which are connected in parallel is connected with the other end of the resistor R22, and the other end is grounded.
In conclusion, the beneficial effects of the invention include:
1. the current sampling circuit adopts the voltage division filtering module, and after effective voltage division of the voltage division resistor, a part of voltage is borne by the voltage division resistor, so that the output voltage of the voltage division filtering module is reduced, the output voltage is in a reasonable range, and the measuring range of the digital display DC meter is improved.
2. The circuit protection module can effectively prevent the damage to the rear-end circuit caused by external transient high-voltage input, and improves the safety of the circuit.
3. The voltage division filtering module and the current collection filtering module can effectively filter interference signals in the circuit and improve the EMC anti-interference capability of the whole circuit.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a schematic diagram of a current sampling circuit of the present invention;
FIG. 2 is a schematic diagram of a voltage sampling circuit of the digital display DC meter according to the present invention;
FIG. 3 is a schematic diagram of an isolated power supply circuit of the digital display DC meter according to the present invention;
fig. 4 is a schematic diagram of a digital power supply circuit of the digital display dc meter according to the present invention;
FIG. 5 is a schematic diagram of an analog power supply circuit of the digital display DC meter according to the present invention;
fig. 6 is a block diagram of a circuit configuration of the digital dc meter according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Example 1
As shown in fig. 1, a current sampling circuit of a digital display dc meter includes a hall current collecting circuit, a detected current is connected to an input terminal of the hall current collecting circuit, the current sampling circuit further includes a reference signal module, a circuit protection module, a voltage division filter module, an emitter follower circuit and a current collection filter module, the hall current collecting circuit includes two output terminals, one output terminal of the hall current collecting circuit is connected to an input terminal of the voltage division filter module, an output terminal of the voltage division filter module is connected to an input terminal of the emitter follower circuit, an output terminal of the emitter follower circuit is connected to an input terminal of the current collection filter module, and an output terminal of the current collection filter module is connected to a processor of the digital display dc meter; the input end of the circuit protection module is connected with the common end of the Hall current acquisition circuit and the voltage division filtering module, and the output end of the circuit protection module is grounded; the other output end of the Hall current acquisition circuit is connected with the input end of the reference signal module, and the output end of the reference signal module is connected with the processor of the digital display DC meter; the Hall current acquisition circuit adopts a Hall sensor.
The voltage division filtering module comprises a resistor R1, a resistor R13 and a capacitor C19; one end of the resistor R13 is connected with one output end of the Hall current acquisition circuit, and the other end of the resistor R13 is connected with the input end of the emitter follower circuit; one end of the resistor R13 is used as the input end of the voltage division filtering module and receives the output voltage signal of the Hall current acquisition circuit; the other end of the resistor R13 is used as the output end of the voltage division filtering module; one end of the resistor R1 and one end of the capacitor C19 are both connected with the other end of the resistor R13, and the other end of the resistor R1 and the other end of the capacitor C19 are both grounded; interference signals can be effectively filtered through effective filtering of the voltage division filtering module, useful signals are reserved, and circuit interference is reduced; meanwhile, the resistor R1 and the resistor R13 form a voltage dividing circuit, when detected voltage enters the voltage dividing and filtering module, after the detected voltage is effectively divided by the resistor R1 and the resistor R13, a part of voltage is borne by the voltage dividing resistor, so that the output voltage of the voltage dividing and filtering module is reduced, the output voltage is in a reasonable range, and the measuring range of the digital display direct current meter is improved.
The circuit protection module comprises a TVS tube breakdown short circuit D2, one end of the TVS tube breakdown short circuit D2 is connected with one output end of the Hall current acquisition circuit, and the other end of the TVS tube breakdown short circuit D2 is grounded; one end of the TVS tube breakdown short circuit D2 is used as the input end of the circuit protection module; the other end of the TVS tube breakdown short circuit D2 is used as the output end of the circuit protection module; through the circuit protection module, the rear-end circuit can be effectively prevented from being damaged when external transient high-voltage input is conducted, and the safety of the circuit is improved.
The emitter follower circuit comprises an emitter follower U3B, the non-inverting input end of the emitter follower U3B is connected with the output end of the voltage-dividing filter module, namely the other end of the resistor R13, one power supply end of the emitter follower U3B is grounded, the other power supply end of the emitter follower U3B is connected with the power supply voltage VCC, the output end of the emitter follower U3B is connected with the input end of the current acquisition filter module, and the inverting input end of the emitter follower U3B is connected with the output end of the emitter follower U3B; the non-inverting input end of the emitter follower U3B is used as the input end of the emitter follower circuit and receives the output voltage signal of the voltage division filtering module; the output end of the emitter follower U3B is used as the output end of the emitter follower circuit; through the emitter follower U3B, the requirement for the output current of the upper circuit can be reduced, the driving capability of the rear circuit is increased, and the output signal of the rear circuit synchronously follows the output signal change of the upper circuit.
The current acquisition filtering module comprises a resistor R12 and a capacitor C18, one end of the resistor R12 is connected with the output end of the emitter follower circuit, namely the output end of the emitter follower U3B, the other end of the resistor R12 is connected with a processor of the digital display direct current meter, one end of the capacitor C18 is connected with the other end of the resistor R12, and the other end of the capacitor C18 is grounded; one end of the resistor R12 is used as the input end of the current acquisition filtering module and receives the output voltage signal of the emitter follower circuit; the other end of the resistor R12 is used as the output end of the current acquisition filtering module and outputs a voltage signal to the processor; through the current acquisition filtering module, the output signal of the emission following circuit is filtered again, so that the output signal is smoother, and the anti-interference performance of the circuit is improved.
The reference signal module comprises a resistor R11 and a capacitor C16, one end of the resistor R11 is connected with the other output end of the Hall current acquisition circuit, the other end of the resistor R11 is connected with a processor of the digital display DC meter, one end of the capacitor C16 is connected with the other end of the resistor R11, and the other end of the capacitor C16 is grounded; one end of the resistor R11 is used as the input end of the reference signal module and receives the output voltage signal of the Hall current acquisition circuit; the other end of the resistor R11 is used as the output end of the reference signal module and outputs a voltage signal to the processor; through the reference signal module, the reference signal can be filtered, a smoother reference signal is provided for the processor, and debugging of the digital display meter is facilitated.
Example 2:
the embodiment provides a digital display dc meter, as shown in fig. 6, the digital display dc meter includes a current sampling circuit, a voltage sampling circuit, a digital power supply module, an analog power supply module, a processor and a display, wherein an input end of the voltage sampling circuit is connected to a detected voltage, and an output end of the voltage sampling circuit is connected to the processor; the input end of the current sampling circuit is connected with the detected current, and the output end of the current sampling circuit is connected with the processor; the digital power supply module, the analog power supply module and the display are all connected with the processor; the voltage sampling circuit and the current sampling circuit are both connected with a power supply voltage VCC; the current sampling circuit is a voltage sampling circuit in embodiment 1, and the structure thereof is not described herein again.
As shown in fig. 4, the digital power supply module includes a capacitor C38, a capacitor C40, and a regulator U6, wherein the regulator U6 employs a regulator chip SPX 1117; the input end of the voltage stabilizer U6 is connected with a power supply voltage VCC, the output end of the voltage stabilizer U6 is connected with a digital power supply port of the processor, one end of the capacitor C38 is connected with the power supply voltage VCC, the other end of the capacitor C38 is grounded, one end of the capacitor C40 is connected with the output end of the voltage stabilizer, and the other end of the capacitor C40 is grounded; through stabiliser U6, filter capacitor C38 and filter capacitor C40, can effectively filter interference signal, stable output voltage keeps digital power supply to continuously output stable 3.3V voltage, provides digital power supply for the treater.
As shown in fig. 5, the analog power supply module includes a third filter circuit, a precision reference power supply circuit, and a fourth filter circuit; the third filter circuit comprises a capacitor C39 and an inductor FB1, one end of the inductor FB1 is connected with a power supply voltage VCC, the other end of the inductor FB1 is connected with the input end of the precision reference power supply circuit, one end of the capacitor C39 is connected with the power supply voltage VCC, and the other end of the capacitor C39 is grounded; the precision reference power supply circuit comprises a resistor R24, a resistor R25, a resistor R26 and a voltage stabilizing chip N1, wherein the voltage stabilizing chip N1 adopts a voltage stabilizing chip AZ431, one end of the resistor R24 is connected with the output end of a third filter circuit, namely the other end of an inductor FB1, the other end of the resistor R24 is connected with an analog power supply port of the processor, the input end of the voltage stabilizing chip N1 is connected with the other end of the resistor R24, the output end of the voltage stabilizing chip N1 is grounded, one end of the resistor R25 and the resistor R26 which are connected in series is connected with the other end of a resistor R24, the other end of the resistor R25 and the resistor R26 which are connected in series is grounded, and the reference signal end of the voltage stabilizing chip N1 is; the fourth filter circuit comprises a capacitor C37, one end of the capacitor C37 is connected with the output end of the precision reference power supply circuit, and the other end of the capacitor C37 is grounded; through third filter circuit and fourth filter circuit, can effectively filtering interference signal, reduce the output ripple, simultaneously, accurate reference power supply circuit can stabilize output voltage, keeps the simulation power supply to continuously export stable 3.3VA voltage, provides the simulation power supply for the treater.
Example 3:
on the basis of embodiment 2, this embodiment further describes the voltage sampling circuit, as shown in fig. 2, a voltage sampling circuit of a digital display dc meter includes an input voltage dividing module, an input filter module, an isolation amplifying module, a voltage conditioning module and an output filter module, wherein an input end of the input voltage dividing module is connected to a detected voltage, an output end of the input voltage dividing module is connected to an input end of the input filter module, an output end of the input filter module is connected to an input end of the isolation amplifying module, an output end of the isolation amplifying module is connected to an input end of the voltage conditioning module, an output end of the voltage conditioning module is connected to an input end of the output filter module, an output end of the output filter module is connected to a processor of the digital display dc meter, the input filter module includes a common mode filter circuit and a secondary filter circuit, an input end of the common mode, the output end of the common mode filter circuit is connected with the input end of the secondary filter circuit, and the output end of the secondary filter circuit is connected with the input end of the isolation amplification module; the input voltage division module, the input filtering module and the isolation amplifying module respectively comprise two input ends and two output ends, and the voltage conditioning module is provided with two input ends.
The input voltage division module comprises a voltage division resistor R18, a voltage division resistor R21, a voltage division resistor R51, a voltage division resistor R52, a voltage division resistor R53, a voltage division resistor R54, a voltage division resistor R55, a voltage division resistor R56 and a voltage division resistor R19 which are sequentially connected in series, wherein two free ends of the voltage division resistor R18 and the voltage division resistor R19 are used as two input ends of the input voltage division module to be respectively connected to an anode and a cathode of a detected voltage through a socket J1, two ends of the voltage division resistor R19 are used as two output ends of the input voltage division module to be respectively connected to two input ends of the common mode filter circuit, as can be seen from fig. 1, a common end of the voltage division resistor R56 and the voltage division resistor R19 is connected to one input end of the common mode filter circuit, the cathode of the detected voltage is connected to the other input end of;
when the detected voltage enters the voltage sampling circuit, after the detected voltage is effectively divided by the voltage dividing resistor R18, the voltage dividing resistor R19, the voltage dividing resistor R21, the voltage dividing resistor R51, the voltage dividing resistor R52, the voltage dividing resistor R53, the voltage dividing resistor R54, the voltage dividing resistor R55 and the voltage dividing resistor R56, a part of voltage is borne by the voltage dividing resistor, so that the output voltage of the input voltage dividing module is reduced, the output voltage is in a reasonable range, and the measuring range of the digital display direct current meter is improved.
The input filter module is a multistage filter circuit and comprises a common-mode filter circuit and a secondary filter circuit, wherein the common-mode filter circuit is a primary filter circuit, and the secondary filter circuit is a secondary filter circuit; the common mode filter circuit comprises a common mode inductor M1, a capacitor C5 and a capacitor C6; the common mode inductor M1 comprises a first winding 14 and a second winding 23; the input end of the first winding 14 is connected with one output end of the input voltage division module (the common end of the voltage division resistor R56 and the voltage division resistor R19), and the output end of the first winding 14 is connected with one input end of the secondary filter circuit; the input end of the second winding 23 is connected with the other output end of the input voltage division module (one end of the voltage division resistor R19 connected with the negative pole of the detected voltage), and the output end of the second winding 23 is connected with the other input end of the secondary filter circuit; the input end of the first winding 14 and the input end of the second winding 23 are used as 2 input ends of the input filter module and also used as 2 input ends of the common mode filter circuit; the output end of the first winding 14 and the output end of the second winding 23 are used as 2 output ends of the common mode filter circuit; one end of the capacitor C5 is connected with the output end of the first winding 14, and the other end of the capacitor C5 is grounded; one end of the capacitor C6 is connected with the output end of the second winding 23, and the other end of the capacitor C6 is grounded; because the common mode filter circuit is added, common mode electromagnetic interference can be effectively filtered, meanwhile, electromagnetic interference which is not sent to the outside can be restrained, and influence on normal work of other electronic equipment in the same electromagnetic environment is effectively avoided.
The secondary filter circuit comprises a resistor R17, a resistor R22, a capacitor C27, a capacitor C28, a capacitor C30, a capacitor C31 and a capacitor C41; one end of the resistor R17 is connected with the output end of the first winding 14, and the other end of the resistor R17 is connected with one input end of the isolation amplification module; one end of the resistor R22 is connected with the output end of the first winding 23, and the other end of the resistor R22 is connected with the other input end of the isolation amplification module; one end of the resistor R17 and one end of the resistor R22 are used as 2 input ends of the secondary filter circuit and are connected with the common mode filter circuit; the other end of the resistor R17 and the other end of the resistor R22 are used as 2 output ends of the secondary filter circuit and also used as 2 output ends of the whole input filter module, and voltage signals are output to the isolation amplification module; the capacitor C41 is connected between the other end of the resistor R17 and the other end of the resistor R22; one end of the capacitor C27 connected with the capacitor C28 in parallel is connected with the other end of the resistor R17, and the other end is grounded; one end of the capacitor C30 connected with the capacitor C31 in parallel is connected with the other end of the resistor R22, and the other end is grounded; when the output voltage of the common mode filter circuit is input into the secondary filter circuit, the secondary filter circuit carries out secondary filtering on the voltage signal, so that a high-frequency signal and a low-frequency signal can be effectively filtered, a useful signal is reserved, and the output signal is smoother; through twice effective filtering of the two-stage filter circuit, the EMC anti-interference capability of the voltage sampling circuit is improved.
Example 4:
on the basis of embodiment 3, this embodiment further improves the isolation amplification module, and the isolation amplification module includes an isolation operational amplifier chip U4 and an isolation power supply.
As shown in fig. 2 and 3, the isolation operational amplifier chip U4 adopts an AMC1300 precision isolation amplifier; the isolation operational amplifier chip U4 has two input terminals INP and INN, a power terminal VDD1, a ground terminal GND1, and two output terminals OUTP and OUTN, where the two input terminals INP and INN are used as two input terminals of the isolation amplification module, the two input terminals INP and INN are both connected to the secondary filter circuit, the input terminal INP is connected to the other end of the resistor R17, and the input terminal INN is connected to the other end of the resistor R22; the output end of the isolation power supply is connected with a power supply end VDD1 of the isolation operational amplifier chip U4; two output ends OUTP and OUTN of the isolation operational amplifier chip U4 are used as two output ends of the whole isolation amplification module and connected with the voltage conditioning module. In the embodiment, because the AMC1300 precise isolation amplifier is adopted, the isolation withstand voltage value reaches 4000VDC, and the safety performance of the circuit is improved; meanwhile, the output signal of the input filter module is amplified; in addition, in the prior art, the isolation amplification module usually adopts an optical coupling mode, and has the defect of light attenuation, and in the embodiment, by adopting the isolation operational amplifier chip U4, the light attenuation phenomenon does not exist any more, and the precision of the circuit is ensured.
The isolation power supply comprises a first filter circuit, an isolation power supply chip U5 and a second filter circuit; the isolation power supply chip U5 is an isolation power supply chip ADuM5000 which is provided with a power supply input end VDD1, an output end Viso and an output ground end GISO; the input end of the first filter circuit is connected with a power supply voltage VCC, the output end of the first filter circuit is connected with a power supply input end VDD1 and a pin RCsel of an isolation power supply chip U5, and an output end Viso and a pin Vsel of an isolation power supply chip U5 are connected with a power supply end VDD1 of an isolation operational amplifier chip U4; the second filter circuit is connected with the output end Viso of the isolation power supply chip U5. Pins GND1, RCin, GND1 of ADuM5000 are grounded when designing a circuit.
The first filter circuit comprises an inductor L3, a capacitor C32 and a capacitor C33, one end of the inductor L3 is used as the input end of the first filter circuit to be connected to a power supply voltage VCC, and the other end of the inductor L3 is used as the output end of the first filter circuit to be connected to the power supply input end VDD1 of the isolation power supply chip U5; one end of the capacitor C33 is connected with a power supply voltage VCC, and the other end of the capacitor C33 is grounded; one end of the capacitor C32 is connected to the other end of the inductor L3, and the other end of the capacitor C32 is grounded; through first filter circuit, can effectively filter the high frequency interference signal of mains voltage VCC.
The second filter circuit comprises a capacitor C34, a capacitor C35 and a capacitor C36, wherein one end of the capacitor C34, the capacitor C35 and the capacitor C36 which are connected in parallel is connected with the output end Viso of the isolation power supply chip U5, and the other end of the capacitor C34, the capacitor C35 and the capacitor C36 are connected with the output ground end GISO of the isolation power supply chip U5; through the second filter circuit, the low-frequency interference signal of the power supply voltage VCC can be effectively filtered, so that the output signal of the second filter circuit is smoother.
In the embodiment, the isolation amplification module adopts an isolation power supply chip ADuM5000, the withstand voltage value reaches 5000VDC, and the circuit safety is improved; meanwhile, in the prior art, the DC-DC is usually adopted as an isolation power supply, so that the size is large; because the isolated power supply chip ADuM5000 is adopted, the size is only one half of DC-DC, and the height is only one third of DC-DC, the size is greatly reduced, and the circuit space is saved.
Further, according to the above circuit working structure, under normal conditions, the power supply voltage provides a normal working voltage for the isolation operational amplifier chip U4 through the isolation power supply; when the power supply voltage is lower than the normal working voltage of the isolation operational amplifier chip U4, the isolation power supply chip can increase the output voltage of the isolation power supply chip, and meanwhile, due to the existence of the first filter circuit and the second filter circuit, the output voltage of the isolation power supply can be increased through discharging, so that the situation that the isolation operational amplifier chip U4 cannot work normally due to the instantaneous low voltage of the circuit can be avoided; when the power supply voltage is higher than the normal working voltage of the isolation operational amplifier chip U4, the isolation power supply chip can reduce the output voltage thereof, and meanwhile, due to the existence of the first filter circuit and the second filter circuit, the output voltage of the isolation power supply can be reduced through charging, so that the phenomenon that the isolation operational amplifier chip U4 cannot work normally due to the instantaneous high voltage of the circuit can be avoided; therefore, the circuit can be effectively protected through the isolation power supply, and the safety and the stability of the circuit are improved.
Example 5:
on the basis of embodiment 3 or 4, the voltage conditioning module and the output filter module are further described in this embodiment, where the voltage conditioning module includes a filter circuit and an amplifier circuit, where the filter circuit includes a resistor R15, a resistor R20, a resistor R23, a capacitor C26, and a capacitor C29; the amplifying circuit comprises a resistor R16, an operational amplifier U3A and a capacitor C24; one end of the resistor R20 and one end of the resistor R15 are used as two input ends of the voltage conditioning module to be connected with the isolation amplification module, and the specific steps are as follows: one end of the resistor R20 is connected with one output end OUTP of the isolation amplification module, and the other end of the resistor R20 is connected with the non-inverting input end of the operational amplifier U3A; one end of the capacitor C29 connected with the resistor R23 in parallel is connected with the other end of the resistor R20, and the other end is grounded; one end of the resistor R15 is connected with the other output end OUTN of the isolation amplification module, and the other end of the resistor R15 is connected with the inverting input end of the operational amplifier U3A; one end of the capacitor C26 is connected with the other end of the resistor R15, and the other end is grounded; one power supply end of the operational amplifier U3A is connected with a power supply voltage VCC; one end of the capacitor C24 is connected with the power supply end of the operational amplifier U3A, and the other end is grounded; one end of the resistor R16 is connected with the other end of the resistor R15, and the other end of the resistor R16 is connected with the output end of the operational amplifier U3A; the output end of the operational amplifier U3A is connected with the input end of the output filtering module. The filter circuit filters the interference signals output by the isolation amplification module through RC filtering, so that the output signals are more stable; meanwhile, the useful signal is amplified through the operational amplifier U3A, and the useful signal is further reserved.
The output filtering module comprises a resistor R57 and a capacitor C10, one end of the resistor R57 is connected with the output end of the operational amplifier U3A, and the other end of the resistor R57 is connected with the input end of the processor; one end of the capacitor C10 is connected with the other end of the resistor R57, and the other end is grounded; and the amplified useful signals are screened and filtered again through the final filtering of the output filtering module, so that the useful signals are further ensured to enter the processor.
In the prior art, a method that the detected voltage and the detected current are directly connected into a processor of the digital display direct current meter is adopted, so that the measuring range of the digital display direct current meter is small, the safety performance is low, and the anti-interference capacity is poor.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A current sampling circuit of a digital display DC meter comprises a Hall current acquisition circuit, wherein a detected current is connected to the input end of the Hall current acquisition circuit, and the current sampling circuit is characterized by further comprising a reference signal module, a circuit protection module, a voltage division filtering module, an emitter follower circuit and a current acquisition filtering module; the input end of the circuit protection module is connected with the common end of the Hall current acquisition circuit and the voltage division filtering module, and the output end of the circuit protection module is grounded; the other output end of the Hall current acquisition circuit is connected with the input end of the reference signal module, and the output end of the reference signal module is connected with the processor of the digital display DC meter.
2. The current sampling circuit of a digital display DC meter according to claim 1, wherein the voltage division filtering module comprises a resistor R1, a resistor R13 and a capacitor C19; one end of the resistor R13 is connected with one output end of the Hall current acquisition circuit, and the other end of the resistor R13 is connected with the input end of the emitter follower circuit; one end of the resistor R1 and one end of the capacitor C19 are both connected with the other end of the resistor R13, and the other end of the resistor R1 and the other end of the capacitor C19 are both grounded.
3. The current sampling circuit of a digital display DC meter according to claim 1, characterized in that said circuit protection module comprises TVS tube breakdown short circuit D2, one end of said TVS tube breakdown short circuit D2 is connected to one output terminal of the Hall current collection circuit, and the other end of TVS tube breakdown short circuit D2 is grounded.
4. The current sampling circuit of a digital display DC current meter according to claim 1, characterized in that said emitter follower circuit comprises emitter follower U3B, the non-inverting input terminal of emitter follower U3B is connected to the output terminal of the voltage-dividing filter module, one power terminal of emitter follower U3B is grounded, the other power terminal of emitter follower U3B is connected to the power voltage VCC, the output terminal of emitter follower U3B is connected to the input terminal of the current-collecting filter module, and the inverting input terminal of emitter follower U3B is connected to the output terminal of emitter follower U3B.
5. The current sampling circuit of a digital display DC meter according to claim 1, characterized in that, the current collecting and filtering module comprises a resistor R12 and a capacitor C18, one end of the resistor R12 is connected with the output end of the emitter follower circuit, the other end of the resistor R12 is connected with the processor of the digital display DC meter, one end of the capacitor C18 is connected with the other end of the resistor R12, and the other end of the capacitor C18 is grounded.
6. The current sampling circuit of the digital display DC meter according to claim 1, wherein the reference signal module comprises a resistor R11 and a capacitor C16, one end of the resistor R11 is connected with the other output end of the Hall current acquisition circuit, the other end of the resistor R11 is connected with the processor of the digital display DC meter, one end of the capacitor C16 is connected with the other end of the resistor R11, and the other end of the capacitor C16 is grounded.
7. A digital display DC meter is characterized by comprising a current sampling circuit, a voltage sampling circuit, a digital power supply module, an analog power supply module, a processor and a display, wherein the input end of the current sampling circuit is connected with a detected current, and the output end of the current sampling circuit is connected with the processor; the input end of the voltage sampling circuit is connected with the detected voltage, and the output end of the voltage sampling circuit is connected with the processor; the digital power supply module, the analog power supply module and the display are all connected with the processor; the voltage sampling circuit and the current sampling circuit are both connected with a power supply voltage VCC; the current sampling circuit is as claimed in any one of claims 1 to 6.
8. The digital DC meter according to claim 7, wherein the voltage sampling circuit comprises an input voltage dividing module, an input filtering module, an isolation amplifying module, a voltage conditioning module and an output filtering module, wherein the input end of the input voltage dividing module is connected with the detected voltage, the output end of the input voltage dividing module is connected with the input end of the input filtering module, the output end of the input filtering module is connected with the input end of the isolation amplifying module, the output end of the isolation amplifying module is connected with the input end of the voltage conditioning module, the output end of the voltage conditioning module is connected with the input end of the output filtering module, and the output end of the output filtering module is connected with the processor of the digital DC meter; the input filtering module comprises a common-mode filtering circuit and a secondary filtering circuit; the input end of the common mode filter circuit is connected with the output end of the input voltage division module, the output end of the common mode filter circuit is connected with the input end of the secondary filter circuit, and the output end of the secondary filter circuit is connected with the input end of the isolation amplification module.
9. A digital dc meter according to claim 8, wherein said input voltage divider module comprises two outputs; the secondary filter circuit comprises two input ends; the common mode filter circuit comprises a common mode inductor M1, a capacitor C5 and a capacitor C6; the common mode inductor M1 comprises a first winding (14) and a second winding (23); the input end of the first winding (14) is connected with one output end of the input voltage division module, and the output end of the first winding (14) is connected with one input end of the secondary filter circuit; the input end of the second winding (23) is connected with the other output end of the input voltage division module, and the output end of the second winding (23) is connected with the other input end of the secondary filter circuit; one end of the capacitor C5 is connected with the common end of the first winding (14) and one input end of the secondary filter circuit, and the other end of the capacitor C5 is grounded; one end of the capacitor C6 is connected to the common terminal of the second winding (23) and the other input terminal of the secondary filter circuit, and the other end of the capacitor C6 is grounded.
10. A digital dc table according to claim 8, wherein said common mode filter circuit comprises two outputs; the isolation amplification module comprises two input ends; the secondary filter circuit comprises a resistor R17, a resistor R22, a capacitor C27, a capacitor C28, a capacitor C30, a capacitor C31 and a capacitor C41; one end of the resistor R17 is connected with one output end of the common mode filter circuit, and the other end of the resistor R17 is connected with one input end of the isolation amplification module; one end of the resistor R22 is connected with the other output end of the common mode filter circuit, and the other end of the resistor R22 is connected with the other input end of the isolation amplification module; the capacitor C41 is connected between the other end of the resistor R17 and the other end of the resistor R22; one end of the capacitor C27 connected with the capacitor C28 in parallel is connected with the other end of the resistor R17, and the other end is grounded; one end of the capacitor C30 and the capacitor C31 which are connected in parallel is connected with the other end of the resistor R22, and the other end is grounded.
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