CN219609052U - Direct current sampling circuit - Google Patents
Direct current sampling circuit Download PDFInfo
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- CN219609052U CN219609052U CN202320346279.3U CN202320346279U CN219609052U CN 219609052 U CN219609052 U CN 219609052U CN 202320346279 U CN202320346279 U CN 202320346279U CN 219609052 U CN219609052 U CN 219609052U
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Abstract
The utility model discloses a direct current sampling circuit. The direct current sampling circuit comprises a shunt connected in series in a tested circuit, and further comprises: the differential amplifying unit is used for carrying out differential amplification on the voltage signals output by the two ends of the current divider; the isolation direct-current-to-alternating-current unit is used for converting the amplified direct-current voltage signal into a pulse signal under the electrical isolation condition; the detection and control unit is used for controlling the frequency of the pulse signal output by the isolated direct current-to-current converting unit and converting the amplitude of the direct current circuit in the tested circuit according to the pulse signal output by the isolated direct current-to-current converting unit; and the power supply generating unit is used for providing power supply for all power utilization components of the direct current sampling circuit. Compared with the prior art, the utility model has the advantages of simpler sampling circuit and lower cost, and effectively overcomes the defects of expensive cost of the common analog isolation amplifier and more complex digital isolator circuit in the existing direct current sampling circuit.
Description
Technical Field
The utility model relates to a direct current sampling circuit.
Background
The current common DC current sampling mode adopts a Hall sensor and a shunt, wherein the Hall sensor has the advantages of simple structure, high precision, easy influence of magnetic field, shielding system requirement and high cost, and the shunt is adopted to sample DC current signals to become the preferred scheme of each manufacturer according to the advantages and disadvantages, and has the advantages of simple structure, large measuring range, no influence of external magnetic field, but has the disadvantages of direct connection and electric non-isolation of the shunt and the main loop. The current DC sampling adopts an isolation mode generally comprising an analog isolation amplifier and a digital isolator, but the analog isolation amplifier has high cost and few options, and the digital isolator can be isolated and output through the digital isolator after being converted into a digital signal through an AD converter, so that the circuit is complex and the overall cost is high.
Disclosure of Invention
The utility model aims to overcome the defects of the existing direct current sampling technology based on a current divider, and provides a direct current sampling circuit which can realize electrically isolated direct current sampling with lower cost and higher accuracy.
The technical scheme adopted by the utility model specifically solves the technical problems as follows:
the direct current sampling circuit comprises a shunt connected in series in a tested circuit, and further comprises:
the differential amplifying unit is used for carrying out differential amplification on the voltage signals output by the two ends of the current divider;
the isolation direct-current-to-alternating-current unit is used for converting the amplified direct-current voltage signal into a pulse signal under the electrical isolation condition;
the detection and control unit is used for controlling the frequency of the pulse signal output by the isolated direct current-to-current converting unit and converting the amplitude of the direct current circuit in the tested circuit according to the pulse signal output by the isolated direct current-to-current converting unit;
and the power supply generating unit is used for providing power supply for all power utilization components of the direct current sampling circuit.
Further, the direct current sampling circuit further comprises a range conditioning unit arranged between the differential amplifying unit and the isolated direct current-to-direct current converting unit, and the range conditioning unit comprises at least two parallel range amplifying circuits with different amplification factors and is used for amplifying the voltage signals after differential amplification by different amplification factors respectively; the isolation direct current-to-alternating current unit comprises a plurality of paths of isolation direct current-to-alternating current circuits which are the same as the measuring range amplifying circuits in number and in one-to-one correspondence, and the isolation direct current-to-alternating current units are used for respectively converting direct current voltage signals output by the corresponding measuring range amplifying circuits into pulse signals under the condition of electrical isolation.
Preferably, the differential amplifying unit comprises a limiting circuit, a common mode and differential mode filter circuit and a differential operational amplifying circuit which are connected in sequence.
Further preferably, the differential operational amplifier circuit is a differential operational amplifier circuit having a decoupling circuit.
Still further preferably, the differential amplifying unit includes: diodes D1 and D2, resistors R1 to R3, capacitors C1 to C5 and a differential operational amplifier N1; one end of the resistor R1 is simultaneously connected with one output end of the shunt, the cathode of the diode D1 and the anode of the diode D2, one end of the resistor R2 is simultaneously connected with the other output end of the shunt, the anode of the diode D1 and the cathode of the diode D2, the other end of the resistor R1 is simultaneously connected with one end of the capacitor C1, one end of the capacitor C2 and one input end of the differential operational amplifier N1, the other end of the resistor R2 is simultaneously connected with the other end of the capacitor C2, one end of the capacitor C3 and the other input end of the differential operational amplifier N1, the other end of the capacitor C1 and the other end of the capacitor C3 are grounded, one end of the capacitor C5 is connected with the power negative input end of the differential operational amplifier N1, the other end of the capacitor C4 and the other end of the capacitor C5 are grounded, and the resistor R3 serves as an amplification gain adjusting resistor and is connected between gain setting pins of the differential operational amplifier N1.
Preferably, the range amplifying circuit comprises an inverting amplifying circuit, a buffer circuit and an output filter circuit which are connected in sequence.
Further preferably, the inverting amplifying circuit and the buffer circuit each include an operational amplifier, and all the operational amplifiers in the range conditioning unit are integrated in the same integrated circuit.
Preferably, the isolated dc-ac circuit includes: the device comprises an optocoupler, a pulse transformer, a first resistor and a second resistor; one input end of the optical coupler is connected with a working power supply through a second resistor, the other input end of the optical coupler is connected with an I/O port of the detection and control unit, one output end of the optical coupler is connected with one end of a primary coil of the pulse transformer, the other output end of the optical coupler is grounded, the other end of the primary coil of the pulse transformer is connected with the output end of the range amplifying circuit, one end of a secondary coil of the pulse transformer is connected with one end of the first resistor and then is commonly grounded, and the other end of the secondary coil of the pulse transformer is connected with the other end of the first resistor and then is commonly connected with an AD port of the detection and control unit.
Preferably, the power supply generating unit is an isolated power supply generating unit that is electrically isolated.
Preferably, the range conditioning unit comprises a range amplifying circuit with two paths of amplifying factors, one large and one small.
Compared with the prior art, the utility model has the following beneficial effects:
the DC current signal sampled by the current divider is amplified and conditioned, is converted into an AC signal by controlling the trigger-on optocoupler, is isolated and output to the AD port of the controller by the pulse transformer for detection and identification, and obtains the signal amplitude proportional to the primary DC current.
Drawings
FIG. 1 is a schematic diagram of a circuit frame structure of a DC current sampling circuit according to an embodiment of the present utility model;
FIG. 2 is a circuit diagram of a differential amplifying unit in an embodiment;
FIG. 3 is a circuit diagram of a span conditioning unit in an embodiment;
FIG. 4 is a circuit diagram of a DC to AC isolation unit and a detection and control unit in an embodiment;
FIG. 5 is a circuit diagram of a isolated power generation unit in an embodiment;
FIG. 6 is a schematic diagram of the workflow of the detection and control unit in an embodiment;
FIG. 7 is a schematic diagram of waveforms of AD port AN1 and I/O port I/O1 in AN embodiment.
Description of the embodiments
Aiming at the defects of the prior art, the utility model solves the problems that the direct current signal sampled by the current divider is amplified and conditioned, is converted into an alternating current signal by controlling the triggering and conducting optocoupler, is isolated and output to the AD port of the controller by the pulse transformer for detection and identification, and obtains the signal amplitude proportional to the direct current at the primary side, thereby realizing the electrically isolated direct current sampling with lower cost and higher accuracy.
Specifically, the direct current sampling circuit of the utility model comprises a shunt connected in series in a tested line, and:
the differential amplifying unit is used for carrying out differential amplification on the voltage signals output by the two ends of the current divider;
the isolation direct-current-to-alternating-current unit is used for converting the amplified direct-current voltage signal into a pulse signal under the electrical isolation condition;
the detection and control unit is used for controlling the frequency of the pulse signal output by the isolated direct current-to-current converting unit and converting the amplitude of the direct current circuit in the tested circuit according to the pulse signal output by the isolated direct current-to-current converting unit;
and the power supply generating unit is used for providing power supply for all power utilization components of the direct current sampling circuit.
In order to ensure that the sampling circuit has higher sampling precision while the sampling range is wider, the following improvement scheme is further provided:
the direct current sampling circuit further comprises a range conditioning unit arranged between the differential amplifying unit and the isolated direct current-to-current converting unit, and the range conditioning unit comprises at least two parallel range amplifying circuits with different amplification factors and is used for amplifying the voltage signals subjected to differential amplification by different times respectively; the isolation direct current-to-alternating current unit comprises a plurality of paths of isolation direct current-to-alternating current circuits which are the same as the measuring range amplifying circuits in number and in one-to-one correspondence, and the isolation direct current-to-alternating current units are used for respectively converting direct current voltage signals output by the corresponding measuring range amplifying circuits into pulse signals under the condition of electrical isolation.
For the convenience of public understanding, the following detailed description of the utility model will be made with reference to a preferred embodiment in conjunction with the accompanying drawings:
the direct current sampling circuit of the embodiment comprises a shunt connected in series in a tested line, and a differential amplifying unit, a range conditioning unit, an isolated direct current-to-current converting unit, a detection and control unit and an isolated power supply generating unit which are shown in figure 1; the differential amplifying unit is used for carrying out differential amplification on the voltage signals output by the two ends of the current divider, and comprises a limiting circuit, a common mode and differential mode filter circuit and a differential operational amplifying circuit which are connected in sequence; the range conditioning unit comprises at least two parallel range amplifying circuits with different amplification factors and is used for amplifying the voltage signals subjected to differential amplification by different amplification factors respectively; the isolation direct current-to-alternating current unit is used for converting the amplified direct current voltage signals into pulse signals under the electrical isolation condition, and the isolation direct current-to-alternating current unit in the embodiment comprises a plurality of paths of isolation direct current-to-alternating current circuits which are the same as the measuring range amplifying circuits in number and in one-to-one correspondence, and is used for respectively converting the direct current voltage signals output by the corresponding measuring range amplifying circuits into pulse signals under the electrical isolation condition; the detection and control unit is used for controlling the frequency of the pulse signal output by the isolated direct current-to-current converting unit and converting the amplitude of the direct current circuit in the tested circuit according to the pulse signal output by the isolated direct current-to-current converting unit; the isolated power supply generating unit converts the system power supply VCC into VCC-ISO+, VCC-ISO-, vref-ISO in an electrical isolation manner to be provided for the differential amplifying unit, the range conditioning unit, the isolated direct current-to-current converting unit and the detecting and controlling unit.
The specific circuit of the differential amplifying unit of this embodiment is shown in fig. 2, and includes: diodes D1 and D2, resistors R1 to R3, capacitors C1 to C5 and a differential operational amplifier N1; one end of the resistor R1 is simultaneously connected with one output end of the shunt, the cathode of the diode D1 and the anode of the diode D2, one end of the resistor R2 is simultaneously connected with the other output end of the shunt, the anode of the diode D1 and the cathode of the diode D2, the other end of the resistor R1 is simultaneously connected with one end of the capacitor C1, one end of the capacitor C2 and one input end of the differential operational amplifier N1, the other end of the resistor R2 is simultaneously connected with the other end of the capacitor C2, one end of the capacitor C3 and the other input end of the differential operational amplifier N1, the other end of the capacitor C1 and the other end of the capacitor C3 are grounded, one end of the capacitor C5 is connected with the power negative input end of the differential operational amplifier N1, the other end of the capacitor C4 and the other end of the capacitor C5 are grounded, and the resistor R3 serves as an amplification gain adjusting resistor and is connected between gain setting pins of the differential operational amplifier N1. In the circuit, diodes D1 and D2 form a limiting circuit for limiting the amplitude of an input signal, resistors R1 and R2 and capacitors C1, C2 and C3 form a common mode and differential mode filter circuit, capacitors C4 and C5 form a decoupling circuit for avoiding coupling interference, R3 is a resistor for adjusting the gain of an amplifying circuit, vref-ISO is a reference voltage and is used for lifting the output signal level of a differential operational amplifier.
In order to expand the measurement range and improve the measurement accuracy, the range conditioning unit in the embodiment comprises a range amplifying circuit with two paths of amplification factors, one large and one small, and the range amplifying circuit comprises an inverting amplifying circuit, a buffer circuit and an output filter circuit which are sequentially connected. The specific circuit of the range conditioning unit is shown in fig. 3, wherein the range conditioning unit comprises four operational amplifiers N2A-N2D integrated in the same integrated circuit, the operational amplifier N2A, N B forms a small-range amplifying circuit, and the operational amplifier N2C, N D forms a large-range amplifying circuit; as shown in FIG. 3, resistors R4-R6, a capacitor C6 and an operational amplifier N2B form an inverting amplifying circuit of the small-range amplifying circuit, an operational amplifier N2A forms a buffer circuit of the small-range amplifying circuit, resistors R7 and C8 are output filter circuits of the small-range amplifying circuit, and meanwhile, the resistor R7 plays a role in driving output current limiting of the operational amplifier N2A; the resistors R8-R10, the capacitor C9 and the operational amplifier N2C form an inverting amplifying circuit of the wide-range amplifying circuit, the operational amplifier N2D forms a buffer circuit of the wide-range amplifying circuit, the resistors R11 and C10 are output filter circuits of the wide-range amplifying circuit, and meanwhile the resistor R11 plays a role in driving output current limiting of the operational amplifier N2D.
The isolation direct current-to-alternating current unit of the embodiment comprises two paths of isolation direct current-to-alternating current circuits, which are used for respectively converting direct current voltage signals output by the large-range amplifying circuit and the small-range amplifying circuit into pulse signals under the condition of electrical isolation; the isolated dc-to-ac circuit includes: the device comprises an optocoupler, a pulse transformer, a first resistor and a second resistor; one input end of the optical coupler is connected with a working power supply through a second resistor, the other input end of the optical coupler is connected with an I/O port of the detection and control unit, one output end of the optical coupler is connected with one end of a primary coil of the pulse transformer, the other output end of the optical coupler is grounded, the other end of the primary coil of the pulse transformer is connected with the output end of the range amplifying circuit, one end of a secondary coil of the pulse transformer is connected with one end of the first resistor and then is commonly grounded, and the other end of the secondary coil of the pulse transformer is connected with the other end of the first resistor and then is commonly connected with an AD port of the detection and control unit. As shown in fig. 4, the optocouplers N3 and N4 are controlled by the microprocessor N5 through the I/O ports I/O1 and I/O2 to trigger and turn on at a certain frequency, respectively, rectangular pulse signals with corresponding frequencies are generated at the input ends of the pulse transformers T1 and T2, and then the pulse transformers T1 and T2 inductively output pulse signals with the same frequency at the secondary side, and are respectively input into the AD ports AN1 and AN2 of the microprocessor N5; the microprocessor N5 controls and triggers the optical couplers N3 and N4 to be conducted through the PWM signals output by the I/O ports I/O1 and I/O2, and detects pulse signal peaks of secondary induction output of the pulse transformers T1 and T2 through the AD ports AN1 and AN2 to obtain signal amplitude values proportional to primary side direct current.
As shown in fig. 5, the power VCC in this embodiment is used as a power supply for the MCU in the circuit of the detection and control unit and an input driving power supply for the optocouplers N3 and N4 in the isolated dc-ac converting unit, and on the other hand, VCC generates an isolated VCC-iso+ via the isolated power module P1, where VCC-iso+ is used as a positive power supply for the operational amplifier N1 of the differential amplifying unit and the operational amplifier N2 of the range conditioning unit. VCC-ISO+ generates VCC-ISO-, VCC-ISO-again through DC/DC chip N6, and VCC-ISO-is used as the negative power of differential amplification unit operational amplifier N1. VCC-ISO+ generates reference voltage Vref-ISO through a resistor R16 and a voltage stabilizing tube D3, and the reference voltage Vref-ISO is respectively provided for an N1 operational amplifier circuit in the differential amplifying unit and N2B and N2C operational amplifier circuits in the range conditioning unit, and is used for level lifting of input signals.
The detection and control unit outputs PWM signals through an I/O port of the microprocessor, converts direct current signals into alternating current signals, isolates and senses output pulse signals to the microprocessor through the pulse transformer, the microprocessor detects pulse signal peaks through an AD port to obtain AD values which are proportional to primary side direct current, and the AD values are multiplied by the proportionality coefficient to obtain primary side current amplitude values. In this embodiment, as shown in fig. 6, the working flow of the detection and control unit is that the microprocessor detects the peak value of the pulse signal through the AD port AN1 and the AD port AN2 to obtain AD values A1 and A2, and a reference AD value A0 is preset in the microprocessor (the preferred range of the reference AD value A0 is 90% -100% of the maximum AD value), and when A1 is less than or equal to A0, A1 is used when calculating the signal amplitude proportional to the primary dc current, otherwise A2 is used. That is, when the AD value output by the small-range amplifying circuit is within the reference AD value A0, the detection result obtained by the small-range amplifying circuit is directly adopted; when the AD value output by the small-range amplifying circuit exceeds the reference AD value A0, the detection result obtained by the large-range amplifying circuit is adopted, so that the measurement range is enlarged, and the detection precision is improved within a certain range.
Fig. 7 is a schematic waveform diagram of AD port AN1 and I/O port I/O1 in the present embodiment. The frequency of the I/O1 output waveform is preferably between tens of hertz and hundreds of hertz, or the duty ratio is fixedly adjusted, and the frequency is matched with the sampling rate of the microprocessor, so that the peak voltage of the VAN1 can be accurately acquired, and the microprocessor converts the actual direct current amplitude of the primary side according to the peak voltage. The waveforms of the AD port AN2 and the I/O port I/O2 are similar to those of fig. 7, and will not be repeated.
Claims (10)
1. The direct current sampling circuit comprises a shunt connected in series in a tested circuit, and is characterized by further comprising:
the differential amplifying unit is used for carrying out differential amplification on the voltage signals output by the two ends of the current divider;
the isolation direct-current-to-alternating-current unit is used for converting the amplified direct-current voltage signal into a pulse signal under the electrical isolation condition;
the detection and control unit is used for controlling the frequency of the pulse signal output by the isolated direct current-to-current converting unit and converting the amplitude of the direct current circuit in the tested circuit according to the pulse signal output by the isolated direct current-to-current converting unit;
and the power supply generating unit is used for providing power supply for all power utilization components of the direct current sampling circuit.
2. The DC sampling circuit according to claim 1, further comprising a differential amplifying unit and a differential amplifying circuit
The measuring range conditioning unit comprises at least two parallel measuring range amplifying circuits with different amplification factors and is used for amplifying the voltage signals subjected to differential amplification by different times; the isolation direct current-to-alternating current unit comprises a plurality of paths of isolation direct current-to-alternating current circuits which are the same as the measuring range amplifying circuits in number and in one-to-one correspondence, and the isolation direct current-to-alternating current units are used for respectively converting direct current voltage signals output by the corresponding measuring range amplifying circuits into pulse signals under the condition of electrical isolation.
3. The direct current sampling circuit according to claim 1 or 2, wherein the differential amplifying unit includes a limiter circuit, a common-mode and differential-mode filter circuit, and a differential operational amplifying circuit, which are connected in order.
4. The direct current sampling circuit according to claim 3, wherein the differential operational amplification circuit is a differential operational amplification circuit having a decoupling circuit.
5. The direct current sampling circuit according to claim 4, wherein the differential amplifying unit includes: diodes D1 and D2, resistors R1 to R3, capacitors C1 to C5 and a differential operational amplifier N1; one end of the resistor R1 is simultaneously connected with one output end of the shunt, the cathode of the diode D1 and the anode of the diode D2, one end of the resistor R2 is simultaneously connected with the other output end of the shunt, the anode of the diode D1 and the cathode of the diode D2, the other end of the resistor R1 is simultaneously connected with one end of the capacitor C1, one end of the capacitor C2 and one input end of the differential operational amplifier N1, the other end of the resistor R2 is simultaneously connected with the other end of the capacitor C2, one end of the capacitor C3 and the other input end of the differential operational amplifier N1, the other end of the capacitor C1 and the other end of the capacitor C3 are grounded, one end of the capacitor C5 is connected with the power negative input end of the differential operational amplifier N1, the other end of the capacitor C4 and the other end of the capacitor C5 are grounded, and the resistor R3 serves as an amplification gain adjusting resistor and is connected between gain setting pins of the differential operational amplifier N1.
6. The direct current sampling circuit according to claim 2, wherein the range amplifying circuit comprises an inverting amplifying circuit, a buffer circuit and an output filter circuit which are connected in sequence.
7. The direct current sampling circuit according to claim 6, wherein the inverting amplifier circuit and the buffer circuit each include an operational amplifier, and all the operational amplifiers in the range conditioning unit are integrated in the same integrated circuit.
8. The dc current sampling circuit of claim 2 wherein said isolated dc-to-ac circuit comprises: the device comprises an optocoupler, a pulse transformer, a first resistor and a second resistor; one input end of the optical coupler is connected with a working power supply through a second resistor, the other input end of the optical coupler is connected with an I/O port of the detection and control unit, one output end of the optical coupler is connected with one end of a primary coil of the pulse transformer, the other output end of the optical coupler is grounded, the other end of the primary coil of the pulse transformer is connected with the output end of the range amplifying circuit, one end of a secondary coil of the pulse transformer is connected with one end of the first resistor and then is commonly grounded, and the other end of the secondary coil of the pulse transformer is connected with the other end of the first resistor and then is commonly connected with an AD port of the detection and control unit.
9. The direct current sampling circuit according to claim 1 or 2, wherein the power supply generating unit is an isolated power supply generating unit that is electrically isolated.
10. The direct current sampling circuit according to claim 2, wherein the range conditioning unit comprises a two-way amplification one-large-small range amplification circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320346279.3U CN219609052U (en) | 2023-03-01 | 2023-03-01 | Direct current sampling circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320346279.3U CN219609052U (en) | 2023-03-01 | 2023-03-01 | Direct current sampling circuit |
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| Publication Number | Publication Date |
|---|---|
| CN219609052U true CN219609052U (en) | 2023-08-29 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202320346279.3U Active CN219609052U (en) | 2023-03-01 | 2023-03-01 | Direct current sampling circuit |
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| CN (1) | CN219609052U (en) |
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- 2023-03-01 CN CN202320346279.3U patent/CN219609052U/en active Active
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