A DC voltage isolation sampling circuit

Abstract

The present invention relates to the technical field of voltage sampling, and in particular to an isolated sampling circuit for direct current voltage. The circuit is constructed by using only conventional components such as optical couplers, operational amplifiers, resistors, capacitors, etc., and is provided with an input voltage-current conversion circuit (1), a first current transmission optical coupler (OP1), and an output current-voltage conversion circuit (2) for voltage conversion and output. The circuit is also provided with an output voltage-current conversion circuit (3), a second current transmission optical coupler (OP2), and a thermistor (RT) in the input voltage-current conversion circuit (1) for linear adjustment of the output voltage. The circuit as a whole solves the problems of expensive components, large temperature drift, and insignificant performance improvement in existing isolated sampling circuits, realizes high-precision voltage sampling and isolated transmission, achieves the purpose of reducing costs and improving reliability, and has a high cost-performance ratio.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage sampling, and in particular to an isolation sampling circuit for direct current voltage. Background Art

[0002] Circuit voltage sampling is often required in power electronic systems. The sampling topology of the common ground system is relatively simple, but voltage sampling is more difficult for isolated systems. Traditional voltage isolation sampling mainly includes transformer isolation, capacitor isolation, optocoupler isolation and other methods. Transformer isolation and capacitor isolation are more suitable as isolation sampling methods for AC voltage and digital signal voltage. If transformer isolation and capacitor isolation are used to sample DC voltage, it is necessary to process the voltage frequency conversion and rectification and filtering circuits to obtain a voltage signal that follows the input voltage. The circuit is complex and the cost is high. The voltage accuracy is affected by multiple factors and the accuracy is not high.

[0003] Compared with transformer isolation and capacitor isolation, optocoupler isolation is smaller in size and has strong mutual anti-interference ability between the two ends of isolation. However, ordinary optocouplers have low linearity and poor temperature stability. Although high-linearity analog optocouplers have better linearity, the discreteness of the current transfer ratio (CTR) is still relatively large, the temperature stability is also average, and the price is relatively expensive, so the cost performance is not high. Summary of the invention

[0004] The present invention provides an isolated sampling circuit for direct current voltage, which solves the technical problem that, in the existing sampling circuit using optical couplers for isolation, ordinary optical couplers have average cost but low linearity and poor temperature stability, while high-linearity analog optical couplers have high cost, poor temperature stability and large discreteness of current transfer ratio.

[0005] In order to solve the above technical problems, the present invention provides an isolated sampling circuit for direct current voltage, comprising an input voltage-current conversion circuit (1), a first current transmission optical coupler (OP1), an output current-voltage conversion circuit (2), an output voltage-current conversion circuit (3), and a second current transmission optical coupler (OP2) connected in a closed loop in sequence; and further comprising an input voltage, an input power supply (VCC1), and an input ground (GND1) connected to the input voltage-current conversion circuit (1), and an output power supply (VCC2) and an output ground (GND2) connected to the output current-voltage conversion circuit (2) and the output voltage-current conversion circuit (3); the input voltage is converted and output from the output current-voltage conversion circuit (2) as an output voltage;

[0006] The input voltage-current conversion circuit (1) is electrically connected to the transmitting end of the first current transmission optocoupler (OP1) and the receiving end of the second current transmission optocoupler (OP2); the receiving end of the first current transmission optocoupler (OP1) is electrically connected to the output current-voltage conversion circuit (2); and the transmitting end of the second current transmission optocoupler (OP2) is electrically connected to the output voltage-current conversion circuit (3).

[0007] Preferably, the input voltage-current conversion circuit (1) is provided with a resistor, a capacitor and an operational amplifier, which are used to convert the input voltage into a corresponding sampling current and transmit it to the input voltage-current conversion circuit (1) through the first current transmission optical coupler (OP1).

[0008] Preferably, the output current-voltage conversion circuit (2) is provided with a resistor and a capacitor, which are used to convert the sampled current into the output voltage output.

[0009] Preferably, the output voltage-current conversion circuit (3) is provided with a resistor and an operational amplifier, which is used to convert the output voltage into a feedback current and transmit it to the output current-voltage conversion circuit (2) through the second current transmission optical coupler (OP2) to adjust the sampling current, thereby adjusting the output voltage.

[0010] Preferably, the input voltage-current conversion circuit (1) is provided with a current regulating resistor network and a first operational amplifier (U1), and the current regulating resistor network is provided with a thermistor (RT).

[0011] Preferably, the current regulating resistor network is further provided with first to sixth resistors (R1 to R6), and the input voltage-current conversion circuit (1) is further provided with a first capacitor (C1);

[0012] One end of the first resistor (R1) is connected to the input voltage, and the other end is connected to the same-direction input end (PIN1) of the first operational amplifier (U1), one end of the first capacitor (C1) and one end of the second resistor (R2); the power supply end (PIN4) of the first operational amplifier (U1) is connected to the input power supply (VCC1), the reverse input end is connected to the E pole of the receiving end of the second current transmission optocoupler (OP2), connected to the third resistor (R3), and then connected to one end of the fourth resistor (R4) and one end of the thermistor (RT); the output end is connected to the positive pole of the transmitting end of the first current transmission optocoupler (OP1); the fifth resistor (R5) and the sixth resistor (R6) are respectively connected between the positive pole of the transmitting end of the first current transmission optocoupler (OP1) and the C pole of the receiving end of the second current transmission optocoupler (OP2) and between the negative pole of the transmitting end of the first current transmission optocoupler (OP1) and the E pole of the receiving end of the second current transmission optocoupler (OP2);

[0013] The other end of the first capacitor (C1), the other end of the second resistor (R2), the other end of the fourth resistor (R4), the other end of the thermistor (RT), and the ground end of the first operational amplifier (U1) are all connected to the input ground (GND1).

[0014] Preferably, the output current-voltage conversion circuit (2) is provided with a seventh resistor (R7), an eighth resistor (R8) and a second capacitor (C2), the output power supply (VCC2) is connected to the C pole of the receiving end of the first current transmission optocoupler (OP1), and the output voltage is output from the E pole of the receiving end of the first current transmission optocoupler (OP1);

[0015] The seventh resistor (R7) and the second capacitor (C2) are connected in series between the E pole of the receiving end of the first current transmission optocoupler (OP1) and the output ground (GND2), and the eighth resistor (R8) is connected in parallel between the two ends of the second capacitor (C2).

[0016] Preferably, the output voltage-current conversion circuit (3) is provided with a ninth resistor (R9) and a second operational amplifier (U2); the same-direction input terminal, the reverse input terminal, the output terminal, the power supply terminal and the ground terminal of the second operational amplifier (U2) are respectively connected to the E pole of the receiving terminal of the first current transmission optocoupler (OP1), the negative pole of the transmitting terminal of the second current transmission optocoupler (OP2), the positive pole of the transmitting terminal of the second current transmission optocoupler (OP2), the output power supply (VCC2) and the output ground (GND2); and the ninth resistor (R9) is connected between the reverse input terminal of the second operational amplifier (U2) and the output ground (GND2).

[0017] Specifically, the input voltage is a direct current voltage.

[0018] The invention provides an isolated sampling circuit for direct current voltage. The circuit is constructed by using only conventional components such as an optical coupler, an operational amplifier, a resistor, and a capacitor. The circuit is provided with an input voltage-current conversion circuit (1), a first current transmission optical coupler (OP1), and an output current-voltage conversion circuit (2) for voltage conversion and output. The circuit is also provided with an output voltage-current conversion circuit (3), a second current transmission optical coupler (OP2), and a thermistor (RT) in the input voltage-current conversion circuit (1) for linear adjustment of the output voltage. The circuit as a whole solves the problems of expensive components, large temperature drift, and insignificant performance improvement in existing isolated sampling circuits, realizes high-precision voltage sampling and isolated transmission, achieves the purpose of reducing costs and improving reliability, and has a high cost-performance ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a module structure diagram of a DC voltage isolation sampling circuit provided by an embodiment of the present invention;

[0020] Figure 2 The present invention provides an electrical connection diagram of an isolated sampling circuit for direct current voltage.

[0021] Graphic annotation: input voltage-current conversion circuit 1 (first operational amplifier U1, first to sixth resistors R1 to R6, first capacitor C1); first current transmission optocoupler OP1; output current-voltage conversion circuit 2 (seventh resistor R7, eighth resistor R8, second capacitor C2); output voltage-current conversion circuit 3 (ninth resistor R9, second operational amplifier U2); second current transmission optocoupler OP2; input power supply VCC1, input ground GND1, output power supply VCC2, output ground GND2. DETAILED DESCRIPTION

[0022] The following is a detailed explanation of the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided only for illustrative purposes and cannot be understood as limitations on the present invention. The selection and value sizes of components and the accompanying drawings are only preferred embodiments and are only for reference and illustration purposes. They do not constitute limitations on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0023] An isolated sampling circuit for DC voltage provided by an embodiment of the present invention is as follows: Figure 1The module structure diagram shown includes an input voltage-current conversion circuit 1, a first current transmission optocoupler OP1, an output current-voltage conversion circuit 2, an output voltage-current conversion circuit 3, and a second current transmission optocoupler OP2 connected in a closed loop sequence; it also includes an input voltage, an input power supply VCC1, and an input ground GND1 connected to the input voltage-current conversion circuit 1, and an output power supply VCC2 and an output ground GND2 connected to the output current-voltage conversion circuit 2 and the output voltage-current conversion circuit 3, and the input voltage is converted and output from the output current-voltage conversion circuit 2 as an output voltage;

[0024] The input voltage-current conversion circuit 1 is electrically connected to the transmitting end of the first current transmission optocoupler OP1 and the receiving end of the second current transmission optocoupler OP2, the receiving end of the first current transmission optocoupler OP1 is electrically connected to the output current-voltage conversion circuit 2, and the transmitting end of the second current transmission optocoupler OP2 is electrically connected to the output voltage-current conversion circuit 3.

[0025] Specifically, the input voltage is a direct current voltage.

[0026] In this embodiment, the input voltage-current conversion circuit 1 is provided with a resistor, a capacitor and an operational amplifier, which is used to convert the input voltage into a corresponding sampling current and transmit it to the input voltage-current conversion circuit 1 through the first current transmission optical coupler OP1. The output current-voltage conversion circuit 2 is provided with a resistor and a capacitor, which is used to convert the sampling current into the output voltage output. The output voltage-current conversion circuit 3 is provided with a resistor and an operational amplifier, which is used to convert the output voltage into a feedback current and transmit it to the output current-voltage conversion circuit 2 through the second current transmission optical coupler OP2 to adjust the sampling current, thereby adjusting the output voltage.

[0027] More specifically, if Figure 2As shown in the electrical connection diagram, as a preferred embodiment, the input voltage-current conversion circuit 1 is provided with a current regulating resistor network and a first operational amplifier U1, and the current regulating resistor network is provided with a thermistor RT. The current regulating resistor network is also provided with first to sixth resistors R1 to R6, and the input voltage-current conversion circuit 1 is also provided with a first capacitor C1. One end of the first resistor R1 is connected to the input voltage, and the other end is connected to the same-direction input terminal PIN1 (PIN represents the pin number, the same below) of the first operational amplifier U1, one end of the first capacitor C1 and one end of the second resistor R2; the power supply terminal PIN4 of the first operational amplifier U1 is connected to the input power supply VCC1, the reverse input terminal PIN2 is connected to the E pole PIN11 of the receiving end of the second current transmission optocoupler OP2, connected to the third resistor R3 and then connected to one end of the fourth resistor R4 and one end of the thermistor RT, and the output terminal PIN3 is connected to the positive pole PIN7 of the transmitting end of the first current transmission optocoupler OP1; the fifth resistor R5 and the sixth resistor R6 are respectively connected between the positive pole PIN7 of the transmitting end of the first current transmission optocoupler OP1 and the C pole PIN10 of the receiving end of the second current transmission optocoupler OP2 and between the negative pole PIN6 of the transmitting end of the first current transmission optocoupler OP1 and the E pole PIN11 of the receiving end of the second current transmission optocoupler OP2. The other end of the first capacitor C1 , the other end of the second resistor R2 , the other end of the fourth resistor R4 , the other end of the thermistor RT , and the ground terminal PIN5 of the first operational amplifier U1 are all connected to the input ground GND1 .

[0028] The output current-voltage conversion circuit 2 is provided with a seventh resistor R7, an eighth resistor R8 and a second capacitor C2, the output power supply VCC2 is connected to the C pole PIN8 of the receiving end of the first current transmission optocoupler OP1, and the output voltage is output from the E pole PIN9 of the receiving end of the first current transmission optocoupler OP1. The seventh resistor R7 and the second capacitor C2 are connected in series between the E pole PIN9 of the receiving end of the first current transmission optocoupler OP1 and the output ground GND2, and the eighth resistor R8 is connected in parallel to both ends of the second capacitor C2.

[0029] The output voltage-current conversion circuit 3 is provided with a ninth resistor R9 and a second operational amplifier U2. The same-direction input terminal PIN17, the reverse input terminal PIN18, the output terminal PIN14, the power supply terminal PIN15, and the ground terminal PIN16 of the second operational amplifier U2 are respectively connected to the E pole PIN9 of the receiving end of the first current transmission optical coupler OP1, the negative pole PIN13 of the transmitting end of the second current transmission optical coupler OP2, the positive pole PIN12 of the transmitting end of the second current transmission optical coupler OP2, the output power supply VCC2, and the output ground GND2, and the ninth resistor R9 is connected between the reverse input terminal PIN18 of the second operational amplifier U2 and the output ground GND2.

[0030] An isolated sampling circuit for DC voltage provided by an embodiment of the present invention has the following working process:

[0031] First, the input voltage is sampled through the first resistor R1, the second resistor R2 and the first capacitor C1, and then the output voltage of the input voltage is converted into a current signal according to the total resistance value of the temperature change through the first operational amplifier U1, the fourth resistor R4, the third resistor R3 and the thermistor RT. Then the first current transmission optocoupler OP1 transmitting end transmits the current signal to the receiving end, the seventh resistor R7, the eighth resistor R8 and the second capacitor C2 convert the received current signal into an output voltage, and at the same time, the output voltage is converted into a current through the second operational amplifier U2 and the ninth resistor R9, and transmitted to the receiving end through the second current transmission optocoupler OP2 transmitting end to form a negative feedback, and the transmission current of the path where the sixth resistor R6 and the first current transmission optocoupler OP1 transmitting end are located is adjusted, and the transmission current of the first current transmission optocoupler OP1 in turn adjusts the output voltage, and finally the voltage at the sampling point changes linearly with the input voltage.

[0032] An isolated sampling circuit for DC voltage provided in an embodiment of the present invention is constructed using only conventional components such as optocouplers, operational amplifiers, resistors, capacitors, etc., and is provided with an input voltage-current conversion circuit 1, a first current transmission optocoupler OP1, and an output current-voltage conversion circuit 2 for voltage conversion and output. An output voltage-current conversion circuit 3, a second current transmission optocoupler OP2, and a thermistor RT in the input voltage-current conversion circuit 1 are further provided to perform linear regulation of the output voltage. The circuit as a whole solves the problems of expensive components, large temperature drift, and unclear performance improvement in existing isolated sampling circuits, realizes high-precision voltage sampling and isolated transmission, achieves the purpose of reducing costs and improving reliability, and has a high cost-effectiveness.

[0033] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A DC voltage isolation sampling circuit, characterized in that: The invention comprises an input voltage-current conversion circuit (1), a first current transmission optical coupler (OP1), an output current-voltage conversion circuit (2), an output voltage-current conversion circuit (3), and a second current transmission optical coupler (OP2) connected in a closed loop in sequence; and further comprises an input voltage, an input power supply (VCC1), and an input ground (GND1) connected to the input voltage-current conversion circuit (1), and an output power supply (VCC2) and an output ground (GND2) connected to the output current-voltage conversion circuit (2) and the output voltage-current conversion circuit (3); the input voltage is converted and output from the output current-voltage conversion circuit (2) as an output voltage; The input voltage-current conversion circuit (1) is electrically connected to the transmitting end of the first current transmission optocoupler (OP1) and the receiving end of the second current transmission optocoupler (OP2); the receiving end of the first current transmission optocoupler (OP1) is electrically connected to the output current-voltage conversion circuit (2); and the transmitting end of the second current transmission optocoupler (OP2) is electrically connected to the output voltage-current conversion circuit (3); The input voltage-current conversion circuit (1) is provided with a resistor, a capacitor and an operational amplifier, and is used to convert the input voltage into a corresponding sampling current and transmit the sampling current to the output current-voltage conversion circuit (2) through the first current transmission optical coupler (OP1); The input voltage-current conversion circuit (1) is provided with a current regulating resistor network and a first operational amplifier (U1), wherein the current regulating resistor network is provided with a thermistor (RT); The current regulating resistor network is further provided with first to sixth resistors (R1 to R6), and the input voltage-current conversion circuit (1) is further provided with a first capacitor (C1); One end of the first resistor (R1) is connected to the input voltage, and the other end is connected to the same-direction input end (PIN1) of the first operational amplifier (U1), one end of the first capacitor (C1) and one end of the second resistor (R2); the power supply end (PIN4) of the first operational amplifier (U1) is connected to the input power supply (VCC1), the reverse input end is connected to the E pole of the receiving end of the second current transmission optocoupler (OP2), connected to the third resistor (R3), and then connected to one end of the fourth resistor (R4) and one end of the thermistor (RT); the output end is connected to the positive pole of the transmitting end of the first current transmission optocoupler (OP1); the fifth resistor (R5) and the sixth resistor (R6) are respectively connected between the positive pole of the transmitting end of the first current transmission optocoupler (OP1) and the C pole of the receiving end of the second current transmission optocoupler (OP2) and between the negative pole of the transmitting end of the first current transmission optocoupler (OP1) and the E pole of the receiving end of the second current transmission optocoupler (OP2); The other end of the first capacitor (C1), the other end of the second resistor (R2), the other end of the fourth resistor (R4), the other end of the thermistor (RT), and the ground end of the first operational amplifier (U1) are all connected to the input ground (GND1).

2. The isolated sampling circuit for DC voltage according to claim 1, characterized in that: The output current-voltage conversion circuit (2) is provided with a resistor and a capacitor, and is used for converting the sampled current into the output voltage output.

3. The isolated sampling circuit for DC voltage according to claim 1, characterized in that: The output voltage-current conversion circuit (3) is provided with a resistor and an operational amplifier, and is used for converting the output voltage into a feedback current and transmitting the feedback current to the output current-voltage conversion circuit (2) via the second current transmission optical coupler (OP2), thereby adjusting the sampling current and thus adjusting the output voltage.

4. The isolated sampling circuit for DC voltage according to claim 3, characterized in that: The output current-voltage conversion circuit (2) is provided with a seventh resistor (R7), an eighth resistor (R8) and a second capacitor (C2); the output power supply (VCC2) is connected to the C pole of the receiving end of the first current transmission optical coupler (OP1); and the output voltage is output from the E pole of the receiving end of the first current transmission optical coupler (OP1); The seventh resistor (R7) and the second capacitor (C2) are connected in series between the E pole of the receiving end of the first current transmission optical coupler (OP1) and the output ground (GND2), and the eighth resistor (R8) is connected in parallel between the two ends of the second capacitor (C2).

5. The isolated sampling circuit for DC voltage according to claim 4, characterized in that: The output voltage-current conversion circuit (3) is provided with a ninth resistor (R9) and a second operational amplifier (U2); the same-direction input terminal, the reverse input terminal, the output terminal, the power supply terminal and the ground terminal of the second operational amplifier (U2) are respectively connected to the E pole of the receiving terminal of the first current transmission optical coupler (OP1), the negative pole of the transmitting terminal of the second current transmission optical coupler (OP2), the positive pole of the transmitting terminal of the second current transmission optical coupler (OP2), the output power supply (VCC2) and the output ground (GND2); the ninth resistor (R9) is connected between the reverse input terminal of the second operational amplifier (U2) and the output ground (GND2).

6. A DC voltage isolation sampling circuit as claimed in any one of the preceding claims, characterized in that: The input voltage is a direct current voltage.

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