CN110763909A - Digital display DC meter and voltage sampling circuit thereof - Google Patents
Digital display DC meter and voltage sampling circuit thereof Download PDFInfo
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- CN110763909A CN110763909A CN201911094951.9A CN201911094951A CN110763909A CN 110763909 A CN110763909 A CN 110763909A CN 201911094951 A CN201911094951 A CN 201911094951A CN 110763909 A CN110763909 A CN 110763909A
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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 voltage sampling circuit thereof, wherein the voltage sampling circuit comprises an input voltage division module, an input filtering module, an isolation amplifying module, a voltage conditioning module and an output filtering module which are sequentially connected in series; the input end of the input voltage division module is connected with the detected voltage, and the output end of the output filtering module is connected with a processor of the digital display DC meter; the input filter module comprises a common-mode filter circuit and a secondary filter 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. 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 voltage 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 voltage value, which is used for real-time monitoring and displaying dc voltage to meet the requirements of market and customers.
At present, a digital display DC meter in the market basically adopts a direct A/D sampling mode, the measuring range of the detected voltage is small and is difficult to reach 100V; voltage can not be isolated, potential safety hazards exist, and EMC anti-jamming capability is poor.
Disclosure of Invention
The invention provides a voltage sampling circuit of a digital display DC meter, which solves the problem of poor EMC anti-interference capability of the digital display DC meter.
The invention is realized by the following technical scheme:
a voltage sampling circuit of a digital display DC meter comprises an input voltage division 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 division module is connected with a 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 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, the output end of the output filtering module is connected with a processor of the, the input filter module comprises a common-mode filter circuit and a secondary filter 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; in the technical scheme, the sampling circuit adopts the input filter module, the voltage conditioning module and the output filter module, the input filter module is also provided with the common-mode filter circuit and the secondary filter circuit, and the signals are filtered twice, so that the attenuation and the filtering of interference signals are increased, the interference signals can be effectively filtered, useful signals are reserved, and the EMC (electro magnetic compatibility) interference resistance of the whole circuit is improved.
As a further improvement of the present invention, the input voltage dividing module includes two output terminals; 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 with the common end of the second winding 23 and the other input end of the secondary filter circuit, and the other end of the capacitor C6 is grounded; in the technical scheme, the common-mode filter circuit adopts the structure, so that common-mode electromagnetic interference can be effectively filtered, meanwhile, the common-mode filter circuit can inhibit the common-mode filter circuit from emitting electromagnetic interference to the outside, and the influence on the normal work of other electronic equipment in the same electromagnetic environment is effectively avoided.
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 connected with the capacitor C31 in parallel is connected with the other end of the resistor R22, and the other end is grounded; in the technical scheme, the secondary filtering module adopts the structure, so that high-frequency signals and low-frequency signals can be effectively filtered, useful signals are reserved, and output signals are smoother.
Further, in order to solve the problem that a digital display DC meter in the prior art cannot isolate voltage and has potential safety hazard, the isolation amplification module is further improved, and comprises an isolation operational amplifier chip U4 and an isolation power supply, wherein the isolation operational amplifier chip U4 is provided with two input ends and a power supply end VDD1, the two input ends are connected with a secondary filter circuit, and the output end of the isolation power supply is connected with the power supply end VDD1 of the isolation operational amplifier chip U4; because the isolation operational amplifier chip U4 and the isolation power supply are adopted in the scheme, the safety performance of the circuit is greatly improved.
Further, the isolation operational amplifier chip U4 adopts an AMC1300 precision isolation amplifier; because the AMC1300 precision isolation amplifier is adopted, the isolation withstand voltage value reaches 4000VDC, and the safety performance of the circuit is improved; meanwhile, the amplifier plays a role in amplifying a useful input signal.
Further, the isolation power supply comprises a first filter circuit, an isolation power supply chip U5 and a second filter circuit; 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 the power supply input end of an isolation power supply chip U5, and the output end of an isolation power supply chip U5 is connected with a power supply end VDD1 of an isolation operational amplifier chip U4; the second filter circuit is connected with the output end of the isolation power supply chip U5.
Further, the first filter circuit comprises an inductor L3, a capacitor C32 and a capacitor C33, one end of the inductor L3 is connected to a power supply voltage VCC, and the other end of the inductor L3 is connected to a power supply input end 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.
Further, the isolation power supply chip U5 has an output ground terminal, the second filter circuit includes a capacitor C34, a capacitor C35, and a capacitor C36, one end of the capacitor C34, the capacitor C35, and the capacitor C36 connected in parallel is connected to the output terminal of the isolation power supply chip U5, and the other end is connected to the output ground terminal of the isolation power supply chip U5.
Further, the isolation power supply chip U5 adopts an isolation power supply chip ADuM 5000; due to the adoption of the ADuM5000 isolating power supply chip, the withstand voltage value reaches 5000VDC, and the circuit safety is improved.
The application further provides a digital display direct current meter which comprises a voltage sampling circuit, a current sampling circuit, a digital power supply module, an analog power supply module, a processor and a display, wherein the input end of the voltage sampling circuit is connected with the detected voltage, the output end of the voltage sampling circuit is connected with 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, and the voltage sampling circuit is any one of the voltage sampling circuits in the technical scheme.
In conclusion, the beneficial effects of the invention include:
1. the voltage sampling circuit adopts the input filter module, the voltage conditioning module and the output filter module, and the input filter module is also provided with the common mode filter circuit and the secondary filter circuit to carry out twice filtering on signals, so that the attenuation and filtering of interference signals are increased, the interference signals can be effectively filtered, useful signals are reserved, and the EMC (electro magnetic compatibility) anti-jamming capability of the whole circuit is improved;
2. the common-mode filter circuit can effectively filter common-mode electromagnetic interference, and can inhibit the common-mode filter circuit from generating electromagnetic interference to the outside, thereby effectively avoiding influencing the normal work of other electronic equipment in the same electromagnetic environment;
3. the secondary filtering module can effectively filter high-frequency signals and low-frequency signals, and retain useful signals, so that output signals are smoother;
4. the input filter module, the voltage conditioning module and the output filter module can effectively filter interference signals and improve the EMC anti-interference capability of the digital display direct current meter circuit;
5. the invention adds the input voltage division module on the circuit structure of the existing digital display DC meter, thereby improving the voltage measurement range of the digital display DC meter;
6. the amplification module adopts the isolation amplification module, improves the safety of the whole circuit by applying the isolation operational amplifier chip and the isolation power supply chip, prevents the damage of instantaneous high voltage to the back end circuit, and has high safety performance.
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 voltage sampling circuit of the present invention;
FIG. 2 is a schematic diagram of an isolated power supply circuit of the present invention;
fig. 3 is a schematic diagram of a current sampling 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 voltage sampling circuit of a digital display DC meter comprises an input voltage dividing module, an input filter module, an isolation amplifying module, a voltage conditioning module and an output filter module, wherein the input end of the input voltage dividing module is connected to a detected voltage, the output end of the input voltage dividing module is connected to the input end of the input filter module, the output end of the input filter module is connected to the input end of the isolation amplifying module, the output end of the isolation amplifying module is connected to the input end of the voltage conditioning module, the output end of the voltage conditioning module is connected to the input end of the output filter module, the output end of the output filter module is connected to a processor of the digital display DC meter, the input filter module comprises a common mode filter circuit and a secondary filter circuit, the input end of the common mode filter circuit is connected to the output end of the input voltage, 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 2:
on the basis of embodiment 1, 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. 1 and fig. 2, 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 3:
on the basis of embodiment 1 or 2, in this embodiment, the voltage conditioning module and the output filter module are further described, 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.
Example 4:
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 voltage sampling circuit is any one of the voltage sampling circuits in embodiments 1 to 3, and the structure thereof is not described herein again.
As shown in fig. 3, the current sampling circuit includes a hall current collecting circuit, a reference signal module, a circuit protection module, a voltage dividing and filtering module, an emitter circuit and a current collecting and filtering module, the hall current collecting circuit includes two output ends, the detected current is connected to the input end of the hall current collecting circuit, one output end of the hall current collecting circuit is connected to the input end of the voltage dividing and filtering module, the output end of the voltage dividing and filtering module is connected to the input end of the emitter circuit, the output end of the emitter circuit is connected to the input end of the current collecting and filtering module, and the output end of the current collecting and filtering module is connected to the 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 ends of the resistor R1 and the capacitor C19 are connected with the other end of the resistor R13, and the other ends of the resistor R1 and the capacitor C19 are 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; 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; 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; 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; 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.
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.
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 is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.
Claims (10)
1. A voltage sampling circuit of a digital display DC meter comprises an input voltage division module, an input filter module, an isolation amplification module, a voltage conditioning module and an output filter module, wherein the input end of the input voltage division module is connected with a voltage to be detected, the output end of the input voltage division module is connected with the input end of the input filter module, the output end of the input filter 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 filter module, and the output end of the output filter module is connected with a processor of the digital display DC meter, and is characterized in that the input filter module comprises a common mode filter circuit and a secondary filter circuit, the input end of the common mode filter circuit is connected with the output end of the, the output end of the secondary filter circuit is connected with the input end of the isolation amplification module.
2. The voltage sampling circuit of a digital current meter according to claim 1, wherein said input voltage dividing module comprises two output terminals; 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.
3. The voltage sampling circuit of a digital current meter according to claim 1, wherein said common mode filter circuit comprises two output terminals; 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.
4. The voltage sampling circuit of digital display DC meter according to claim 1, wherein said isolation amplifying module comprises an isolation operational amplifier chip U4 and an isolation power supply, wherein the isolation operational amplifier chip U4 has two inputs and a power supply terminal VDD1, the two inputs are connected to the secondary filter circuit, and the output of said isolation power supply is connected to the power supply terminal VDD1 of the isolation operational amplifier chip U4.
5. The voltage sampling circuit of digital DC meter according to claim 4, wherein said isolation operational amplifier chip U4 employs AMC1300 precision isolation amplifier.
6. The voltage sampling circuit of a digital current meter according to claim 4, wherein said isolated power supply comprises a first filter circuit, an isolated power supply chip U5 and a second filter circuit; 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 the power supply input end of an isolation power supply chip U5, and the output end of an isolation power supply chip U5 is connected with a power supply end VDD1 of an isolation operational amplifier chip U4; the second filter circuit is connected with the output end of the isolation power supply chip U5.
7. The voltage sampling circuit of the digital display DC meter, according to claim 6, characterized in that said first filter circuit comprises an inductor L3, a capacitor C32 and a capacitor C33, one end of the inductor L3 is connected to the power supply voltage VCC, and the other end of the inductor L3 is connected to the power supply input terminal 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.
8. The voltage sampling circuit of a digital display DC meter according to claim 6, characterized in that the isolation power chip U5 has an output ground terminal, the second filter circuit comprises a capacitor C34, a capacitor C35 and a capacitor C36, one end of the parallel connection of the capacitor C34, the capacitor C35 and the capacitor C36 is connected to the output terminal of the isolation power chip U5, and the other end is connected to the output ground terminal of the isolation power chip U5.
9. The voltage sampling circuit of digital display DC meter according to any of claims 6 to 8, characterized in that said isolated power supply chip U5 is isolated power supply chip ADuM 5000.
10. A digital display DC meter is characterized by comprising a voltage sampling circuit, a current sampling circuit, a digital power supply module, an analog power supply module, a processor and a display, wherein the input end of the voltage sampling circuit is connected with a detected voltage, and the output end of the voltage sampling circuit is connected with 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 voltage sampling circuit according to any one of claims 1 to 9.
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