Current sampling circuit capable of switching power through software

Abstract

The utility model discloses a current sampling circuit capable of switching power through software, which comprises a conversion unit used for acquiring current, converting the current into a voltage signal and uploading the voltage signal; the isolation amplifier U2 is used for amplifying the voltage signal and then outputting the amplified voltage signal; the switching power unit is used for amplifying the amplified voltage signal after adjusting the amplification factor of the post-stage amplification circuit; wherein the switching power unit comprises resistors R1, R3, R5, R8, R10 and R11 and optical relays U3, U4, U5 and U6, the resistors R1, R3 and R5 are connected in parallel and then one end is connected with the isolation amplifier U2, the resistors R8, R10 and R11 are connected in parallel and then one end is connected with the isolation amplifier U2, the optical relay U3 is connected between the resistor R1 and the resistor R3, the optical relay U4 is connected between the resistor R5 and the optical relay U3, the optical relay U5 is connected between the optical relay U6 and the R8, and the optical relay U6 is connected between the R10 and the R11. According to the utility model, the frequency converter power is set on the control panel, so that the influence caused by misoperation can be reduced.

Description

Technical Field

[0001] This utility model relates to the field of frequency converter technology, and specifically to a current sampling circuit that switches power via software. Background Technology

[0002] In most modern frequency converter designs, a single power board typically supports several power ratings. This is usually achieved by using resistors to short-circuit or DIP switches to change the amplification factor of the amplifier circuit, corresponding to different current loops in the software, thus ensuring compatibility with different frequency converter output power. However, manually changing different power ranges using resistors to short-circuit or DIP switches is prone to issues such as poor soldering or incorrect DIP switches. Mismatched current loops can even lead to IGBT failure. Summary of the Invention

[0003] The purpose of this invention is to provide a current sampling circuit that switches power via software.

[0004] To achieve the above objectives, this utility model provides the following technical solution: a current sampling circuit with software-switched power, comprising:

[0005] The conversion unit is used to acquire current and convert it into a voltage signal before uploading it.

[0006] The isolation amplifier U2 is used to amplify voltage signals before output.

[0007] The switching power unit is used to adjust the amplification factor of the subsequent amplifier circuit and then amplify the amplified voltage signal.

[0008] The switching power unit includes resistors R1, R3, R5, R8, R10, R11, and opto-relays U3, U4, U5, and U6. One end of resistors R1, R3, and R5 connected in parallel is connected to isolation amplifier U2. One end of resistors R8, R10, and R11 connected in parallel is also connected to isolation amplifier U2. Opto-relay U3 is connected between R1 and R3. Opto-relay U4 is connected between R5 and U3. Opto-relay U5 is connected between U6 and R8. Opto-relay U6 is connected between R10 and R11.

[0009] Furthermore, the conversion unit includes sampling resistors RA1, RA2, and RA3, which are connected in parallel.

[0010] Furthermore, it also includes an RC filtering unit for RC filtering of voltage signals. The RC filtering unit includes a resistor R7 and a capacitor C5. One end of the resistor R7 is connected to the conversion unit, and the other end of the resistor R7 is connected to the isolation amplifier U2 through one end of the capacitor C5. The capacitor C5 is connected in parallel with the conversion unit.

[0011] Furthermore, it also includes a voltage and current limiting unit for regulating and limiting the voltage signal. The voltage and current limiting unit includes a current limiting resistor R4, a Zener diode ZD1, and filter capacitors C1 and C2. One end of the current limiting resistor R4 is connected to the filter capacitors C1 and C2 connected in parallel through the Zener diode ZD1. One end of the filter capacitor C2 is connected to the isolation amplifier U2, and the other end of the filter capacitor C2 is connected between the capacitor C5 and the isolation amplifier U2.

[0012] Furthermore, the isolation amplifier U2 is model NSI1300D25.

[0013] Furthermore, the photorelays U3, U4, U5, and U6 are model number QX172-CuH-S.

[0014] As can be seen from the above technical solution, this utility model has the following beneficial effects:

[0015] The current sampling circuit that switches power via software sends a low-level signal to the photorelay through the DSP. After the photorelay is turned on, it changes the amplification factor of the amplifier circuit after the current sampling circuit. Corresponding to different current loops set in the software, it achieves the purpose of changing the inverter power. This allows the inverter power to be set on the control panel, reducing the impact of operational errors. Attached Figure Description

[0016] Figure 1 This is the overall circuit diagram of this utility model;

[0017] Figure 2 This is the overall circuit diagram of the optical relay of this utility model. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0019] like Figure 1-2As shown, this utility model provides a current sampling circuit with software-switched power, including a conversion unit, an isolation amplifier U2, a power switching unit, an RC filter unit, and a voltage regulation and current limiting unit. The conversion unit includes sampling resistors RA1, RA2, and RA3, which are connected in parallel. The conversion unit acquires the current and converts it into a voltage signal before uploading it. The conversion unit is connected to the isolation amplifier U2 through the RC filter unit. The RC filter unit includes a resistor R7 and a capacitor C5. One end of the resistor R7 is connected to RA3, and the other end of the resistor R7 is connected to the isolation amplifier U2 through one end of the capacitor C5. The capacitor C5 is connected in parallel with the conversion unit. The voltage signal is RC filtered by the RC filter unit.

[0020] The isolation amplifier U2 amplifies the voltage signal and outputs it. The model of the isolation amplifier U2 is NSI1300D25.

[0021] The switching power unit includes resistors R1, R3, R5, R8, R10, R11, and opto-relays U3, U4, U5, and U6. Resistors R1, R3, and R5 are connected in parallel, with one end connected to isolation amplifier U2. Resistors R8, R10, and R11 are also connected in parallel, with one end connected to isolation amplifier U2. Opto-relay U3 is connected between R1 and R3, opto-relay U4 is connected between R5 and U3, opto-relay U6 is connected between U6 and R8, and opto-relay U6 is connected between R10 and R11. Opto-relays U3, U4, U5, and U6 are model QX172-CuH-S. The switching power unit is used to adjust the amplification factor of the subsequent amplifier circuit and amplify the amplified voltage signal.

[0022] The other end of the parallel connection of resistors R1, R3, and R5 is connected to a parallel resistor R6 and capacitor C3. One end of capacitor C3 is connected to the positive input terminal of operational amplifier U1B through capacitor C4, and the other end of capacitor C4 is connected to the negative input terminal of operational amplifier U1B. The other end of the parallel connection of resistors R8, R10, and R11 is connected to capacitor C4, and the other end of the parallel connection of resistors R8, R10, and R11 is connected to the output terminal of operational amplifier U1B through a parallel resistor R9 and capacitor C6. The operational amplifier U1B is model SGM8270.

[0023] The input terminals of the photorelay U3 are equipped with resistors R15 and R13. One end of resistor R15 is connected to the photorelay U3 through one end of R13. The other end of resistor R15 receives the level signal sent by the DSP, and the other end of R13 is connected to the power supply.

[0024] The input terminals of the photorelay U4 are equipped with resistors R14 and R16. One end of resistor R16 is connected to the photorelay U4 through one end of R14, the other end of resistor R16 receives the level signal sent by the DSP, and the other end of R14 is connected to the power supply.

[0025] The input terminals of the photorelay U5 are equipped with resistors R17 and R19. One end of resistor R19 is connected to the photorelay U5 through one end of R17, the other end of resistor R19 receives the level signal sent by the DSP, and the other end of R17 is connected to the power supply.

[0026] The input terminals of the photorelay U6 are equipped with resistors R18 and R20. One end of resistor R20 is connected to the photorelay U6 through one end of R18, and the other end of resistor R20 receives the level signal sent by the DSP. The other end of R18 is connected to the power supply.

[0027] The voltage regulation and current limiting unit includes a current-limiting resistor R4, a Zener diode ZD1, and filter capacitors C1 and C2. One end of the current-limiting resistor R4 is connected to the filter capacitors C1 and C2 in parallel through the Zener diode ZD1. One end of the filter capacitor C2 is connected to the isolation amplifier U2, and the other end of the filter capacitor C2 is connected between capacitor C5 and the isolation amplifier U2. The voltage regulation and current limiting unit regulates and limits the voltage signal. The Zener diode ZD1 is model MMBZ5231BLT1G.

[0028] The nominal voltage regulation value of Zener diode ZD1 is 5.1V. The output current is converted into a voltage signal by sampling resistors RA1, RA2, and RA3 and input to the input pin of isolation amplifier U2. The gain of isolation amplifier U2 is 8.2. R1, R3, R5, R8, R10, and R11 are used to adjust the amplification factor of the subsequent amplifier circuit, where R1=R11, R3=R10, and R5=R8. Assuming the U-phase output current is I, and the equivalent parallel resistance of RA1, RA2, and RA3 is R, then Vout=8.2*I*1.414*R. Assuming the amplification factor of the subsequent amplifier circuit is A, A=R9 / R1, then IU=8.2*I*1.414*R*(R9 / R1). IU is a software-defined value corresponding to different output currents.

[0029] GPIO is a level signal sent by the DSP; the secondary signal is controlled by sending a low level via software. For example, when photorelays U3 and U6 are on, the amplification factor A1 = R9 / [(R3*R1) / (R3+R1)], and IU = 8*I*1.414*R*R9 / [(R3*R1) / (R3+R1)]. When photorelays U4 and U5 are on, the amplification factor A2 = R9 / [(R5*R1) / (R5+R1)], and IU = 8*I*1.414*R*R9 / [(R5*R1) / (R5+R1)]. The above current sampling circuit can accommodate current sampling requirements of three power levels, and the same board can be used on three different power models.

[0030] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A current sampling circuit with software-switched power, characterized in that, include: The conversion unit is used to acquire current and convert it into a voltage signal before uploading it. The isolation amplifier U2 is used to amplify voltage signals before output. The switching power unit is used to adjust the amplification factor of the subsequent amplifier circuit and then amplify the amplified voltage signal. The switching power unit includes resistors R1, R3, R5, R8, R10, R11, and opto-relays U3, U4, U5, and U6. One end of resistors R1, R3, and R5 connected in parallel is connected to isolation amplifier U2. One end of resistors R8, R10, and R11 connected in parallel is also connected to isolation amplifier U2. Opto-relay U3 is connected between R1 and R3. Opto-relay U4 is connected between R5 and U3. Opto-relay U5 is connected between U6 and R8. Opto-relay U6 is connected between R10 and R11.

2. The current sampling circuit with software-switched power according to claim 1, characterized in that: The conversion unit includes sampling resistors RA1, RA2, and RA3, which are connected in parallel.

3. The current sampling circuit with software-switched power according to claim 1, characterized in that: It also includes an RC filtering unit for RC filtering of voltage signals. The RC filtering unit includes a resistor R7 and a capacitor C5. One end of the resistor R7 is connected to the conversion unit, and the other end of the resistor R7 is connected to the isolation amplifier U2 through one end of the capacitor C5. The capacitor C5 is connected in parallel with the conversion unit.

4. The current sampling circuit with software-switched power according to claim 3, characterized in that: It also includes a voltage and current limiting unit for voltage signal regulation and current limiting. The voltage and current limiting unit includes a current limiting resistor R4, a Zener diode ZD1, and filter capacitors C1 and C2. One end of the current limiting resistor R4 is connected to the filter capacitors C1 and C2 connected in parallel through the Zener diode ZD1. One end of the filter capacitor C2 is connected to the isolation amplifier U2, and the other end of the filter capacitor C2 is connected between the capacitor C5 and the isolation amplifier U2.

5. A current sampling circuit with software-switched power according to claim 1, characterized in that: The isolation amplifier U2 is model NSI1300D25.

6. A current sampling circuit with software-switched power according to claim 1, characterized in that: The photorelays U3, U4, U5, and U6 are model number QX172-CuH-S.

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