Isolated current detection and protection circuit

Abstract

The invention discloses an isolated current detection and protection circuit. According to the isolated current detection and protection circuit, a sampling circuit collects a current signal of a motor B1; the isolation operational amplifier U1 receives a signal of the sampling circuit, the differential signal-to-unipolar signal circuit converts a differential signal into a unipolar signal and divides the unipolar signal into two paths, one path is output and transmitted to the single chip microcomputer for operation processing, and the other path is output to the hardware over-current protection circuit; the comparator U2 compares the input single-pole signal with a reference signal and outputs a control signal to the fault processing unit through an output end. The sampling circuit is arranged to collect current signals of the motor, the signals are isolated and amplified through the isolation amplifier, differential signals are converted into single-pole signals, the single-pole signals are output to the single-chip microcomputer for current calculation, and the single-pole signals are output to the hardware overcurrent protection circuit for overcurrent protection; a single-chip microcomputer is not needed, processing is directly carried out through hardware, the reaction speed is high, and reliability is high.

Description

Technical Field

[0001] The invention belongs to the technical field of motor protection, and in particular relates to an isolated current detection and protection circuit. Background Art

[0002] A motor is a device that converts electrical energy into mechanical energy through a drive shaft. The drive shaft drives the external mechanical device to operate to achieve the required functions. When the motor lubrication fails or the external mechanical device is stuck, causing the drive shaft speed to drop or stop, the motor's electrical energy cannot be effectively converted into mechanical energy, which will cause the current inside the motor to increase rapidly, causing the internal temperature of the motor to increase, causing the motor to burn out or even cause a fire.

[0003] In servo drives and frequency converters, there needs to be a current measurement circuit for the motor and an overcurrent protection function. Currently, products on the market usually use software to calculate the overcurrent value to determine the overcurrent function, so the judgment time is relatively long. This design uses hardware circuits to achieve overcurrent protection, so as to respond to overcurrent faster and ensure safety. Summary of the invention

[0004] The purpose of the present invention is to provide an isolated current detection and protection circuit, which collects the current signal of the motor by setting a sampling circuit, isolates and amplifies the signal through an isolation amplifier, then converts the differential signal into a unipolar signal and outputs it to a single-chip microcomputer for current calculation, and outputs it to a hardware overcurrent protection circuit, performs overcurrent detection through a comparator, and performs overcurrent protection through a fault processing unit; it does not need to go through a single-chip microcomputer, but is directly processed by hardware, with fast response speed and high reliability.

[0005] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0006] The present invention is an isolated current detection and protection circuit, comprising a sampling circuit, wherein the sampling circuit collects the current signal of the motor B1 and converts it into a voltage signal, and performs filtering processing through a primary filtering circuit; an isolation amplifier circuit, wherein the isolation amplifier circuit comprises an isolation operational amplifier U1, wherein the isolation operational amplifier U1 receives the signal output by the primary filtering circuit for isolation and amplification processing, and then performs filtering processing through a secondary filtering circuit; a differential signal conversion unipolar signal circuit, wherein the differential signal conversion unipolar signal circuit converts the differential signal output by the secondary filtering circuit into a unipolar signal and then divides it into two paths, one path is output after being converted by an ADC analog-to-digital converter and then transmitted to a single-chip microcomputer for calculation processing, and the other path is output to a hardware overcurrent protection circuit; wherein the hardware overcurrent protection circuit comprises a comparator U2, wherein the non-inverting input terminal of the comparator U2 receives the unipolar signal output by the differential signal conversion unipolar signal circuit; the inverting input terminal of the comparator U2 receives a reference signal; the comparator U2 compares the input unipolar signal with the reference signal, and outputs a control signal to a fault processing unit through an output terminal.

[0007] As a preferred technical solution of the present invention, the sampling circuit adopts a sampling resistor R1; the sampling resistor R1 is connected in series between the stator windings of the motor B1, converts the current signal of the motor B1 into a voltage signal and transmits it to the primary filtering circuit.

[0008] As a preferred technical solution of the present invention, the sampling circuit adopts a current transformer; the current transformer collects the current signal of the motor B1 and transmits it to the primary filtering circuit.

[0009] As a preferred technical solution of the present invention, the first-stage filtering circuit includes resistors R3, R4 and a capacitor C1; the first ends of the resistors R3 and R4 are respectively connected to the two ends of the sampling circuit; the second end of the resistor R3 is connected to the input terminal 2 of the isolation operational amplifier U1; the second end of the resistor R4 is connected to the input terminal 3 of the isolation operational amplifier U1; and the two ends of the capacitor C1 are respectively connected to the second ends of the resistors R3 and R4.

[0010] As a preferred technical solution of the present invention, pin 1 of the isolation operational amplifier U1 is connected in series with capacitor C2 to ground, and pin 8 of the isolation operational amplifier U1 is connected in series with capacitor C4 to ground; pins 4 and 5 of the isolation operational amplifier U1 are grounded; and the output end pins 6-7 of the isolation operational amplifier U1 outputs the amplified signal to the secondary filtering circuit.

[0011] As a preferred technical solution of the present invention, the secondary filtering circuit includes resistors R5, R6 and capacitor C5; the first ends of the resistors R5 and R6 are respectively connected to the output terminals 6-7 of the isolation operational amplifier U1; the second ends of the resistors R5 and R6 are connected to the input terminal of the differential signal conversion unipolar signal circuit; the two ends of the capacitor C5 are respectively connected to the second ends of the resistors R5 and R6.

[0012] As a preferred technical solution of the present invention, the differential signal conversion unipolar signal circuit includes an operational amplifier U3, resistors R7, R8, R12 and R13; the first end of the resistor R7 is connected to the second end of the resistor R5, and the second end of the resistor R7 is connected to the non-inverting input terminal of the operational amplifier U3; the first end of the resistor R8 is connected to the second end of the resistor R6, and the second end of the resistor R6 is connected to the inverting input terminal of the operational amplifier U3; the non-inverting input terminal of the operational amplifier U3 is also connected in series with the resistor R12 to the reference voltage source VREF; the two ends of the resistor R12 are connected in parallel with the two ends of the capacitor C6; the inverting input terminal and the output terminal of the operational amplifier U3 are also connected in series with the resistor R13; the two ends of the resistor R13 are connected in parallel with the two ends of the capacitor C7.

[0013] As a preferred technical solution of the present invention, the signal output from the output end of the operational amplifier U3 is filtered and outputted by a three-stage filtering circuit; the three-stage filtering circuit includes a resistor R15 and a capacitor C8; the first end of the resistor R15 is connected to the output end of the operational amplifier U3, the first end of the capacitor C8 is connected to the second end of the resistor R15, and the second end of the capacitor C8 is grounded; the second end of the resistor R15 is connected to the anode of the diode D1 and the cathode of the diode D2, the cathode of the diode D1 is connected to the voltage source VDD2, and the anode of the diode D2 is grounded.

[0014] As a preferred technical solution of the present invention, the inverting input end of the comparator U2 is connected to the first end of the resistor R10, and the second end of the resistor R10 is connected to the reference voltage source VREF1; the first end of the resistor R10 is also connected in series with resistors R9, R11, R14 and R16 to ground; the middle connection point of the resistors R9 and R11 is connected to the collector of the transistor Q1, the base of the transistor Q1 is connected to the single-chip control port, and the emitter of the transistor Q1 is grounded; the middle connection point of the resistors R11 and R14 is connected to the collector of the transistor Q2, the base of the transistor Q2 is connected to the single-chip control port, and the emitter of the transistor Q2 is grounded; the middle connection point of the resistors R14 and R16 is connected to the collector of the transistor Q3, the base of the transistor Q3 is connected to the single-chip control port, and the emitter of the transistor Q3 is grounded.

[0015] As a preferred technical solution of the present invention, the control signal outputted from the output end of the comparator U2 is transmitted to the fault processing unit after passing through the RC charging circuit; the RC charging circuit comprises a resistor R4 and a capacitor C3; a first end of the resistor R4 is connected to the output end of the comparator U2, and a second end of the resistor R4 is connected to the fault processing unit; a first end of the capacitor C3 is connected to the second end of the resistor R4, and a second end of the capacitor C3 is grounded;

[0016] The fault processing unit receives the control signal of the comparator U2 to control the motor B1 to cut off the power supply.

[0017] The present invention has the following beneficial effects:

[0018] The present invention collects the current signal of the motor by setting a sampling circuit, isolates and amplifies the signal through an isolation amplifier, then converts the differential signal into a unipolar signal and outputs it to a single-chip microcomputer for current calculation, and outputs it to a hardware overcurrent protection circuit, performs overcurrent detection through a comparator, and performs overcurrent protection through a fault processing unit; it does not need to pass through a single-chip microcomputer, but is directly processed through hardware, so the response speed is fast and the reliability is high;

[0019] By setting a threshold-settable circuit to adjust the threshold value of the hardware overcurrent circuit, accurate overcurrent protection and fast response can be achieved.

[0020] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0022] Figure 1 The invention is a circuit diagram of an isolated current detection and protection circuit. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See also Figure 1As shown, the present invention is an isolated current detection and protection circuit, including a sampling circuit, an isolation amplifier circuit, a differential signal conversion unipolar signal circuit and a hardware overcurrent protection circuit;

[0025] The sampling circuit collects the current signal of the motor B1 and converts it into a voltage signal, and performs filtering processing through the primary filtering circuit; the sampling circuit adopts a sampling resistor R1; the sampling resistor R1 is connected in series between the stator windings of the motor B1, converts the current signal of the motor B1 into a voltage signal and transmits it to the primary filtering circuit; the primary filtering circuit includes resistors R3, R4 and capacitor C1; the first ends of the resistors R3 and R4 are respectively connected to the two ends of the sampling circuit; the second end of the resistor R3 is connected to the input terminal 2 pin of the isolation operational amplifier U1; the second end of the resistor R4 is connected to the input terminal 3 pin of the isolation operational amplifier U1; the two ends of the capacitor C1 are respectively connected to the second ends of the resistors R3 and R4;

[0026] The isolation amplifier circuit includes an isolation operational amplifier U1, which receives the signal output by the primary filter circuit for isolation and amplification, and then performs filtering through the secondary filter circuit;

[0027] Specifically, the 1st pin of the isolation operational amplifier U1 is connected in series with the capacitor C2 to the ground, and the 8th pin of the isolation operational amplifier U1 is connected in series with the capacitor C4 to the ground; the 4th and 5th pins of the isolation operational amplifier U1 are grounded; the output terminal 6-7 pins of the isolation operational amplifier U1 outputs the amplified signal to the secondary filtering circuit; the secondary filtering circuit includes resistors R5, R6 and capacitor C5; the first ends of the resistors R5 and R6 are respectively connected to the output terminals 6-7 pins of the isolation operational amplifier U1; the second ends of the resistors R5 and R6 are connected to the input end of the differential signal conversion unipolar signal circuit; the two ends of the capacitor C5 are respectively connected to the second ends of the resistors R5 and R6;

[0028] The differential signal conversion unipolar signal circuit converts the differential signal output by the secondary filtering circuit into a unipolar signal and then divides it into two paths. One path is output after being converted by the ADC analog-to-digital converter and then transmitted to the single-chip microcomputer for calculation processing, and the other path is output to the hardware overcurrent protection circuit; the differential signal conversion unipolar signal circuit includes an operational amplifier U3, resistors R7, R8, R12 and R13; the first end of the resistor R7 is connected to the second end of the resistor R5, and the second end of the resistor R7 is connected to the non-inverting input end of the operational amplifier U3; the first end of the resistor R8 is connected to the second end of the resistor R6, and the second end of the resistor R6 is connected to the inverting input end of the operational amplifier U3; the non-inverting input end of the operational amplifier U3 is also connected in series with the resistor R12 to the reference voltage source VREF; the two ends of the resistor R12 are connected in parallel with the two ends of the capacitor C6; the inverting input end and the output end of the operational amplifier U3 are also connected in series with the resistor R13; the two ends of the resistor R13 are connected in parallel with the two ends of the capacitor C7.

[0029] The hardware overcurrent protection circuit includes a comparator U2, wherein the non-inverting input terminal of the comparator U2 receives a unipolar signal output by a differential signal conversion unipolar signal circuit; the inverting input terminal of the comparator U2 receives a reference signal; the comparator U2 compares the input unipolar signal with the reference signal, and outputs a control signal to the fault processing unit through the output terminal.

[0030] The signal output from the output end of the operational amplifier U3 is filtered and then outputted by a three-stage filtering circuit; the three-stage filtering circuit includes a resistor R15 and a capacitor C8; the first end of the resistor R15 is connected to the output end of the operational amplifier U3, the first end of the capacitor C8 is connected to the second end of the resistor R15, and the second end of the capacitor C8 is grounded; the second end of the resistor R15 is connected to the anode of the diode D1 and the cathode of the diode D2, the cathode of the diode D1 is connected to the voltage source VDD2, and the anode of the diode D2 is grounded; the diodes D1 and D2 are used as limiters to ensure that the sampled analog signal is within a certain range.

[0031] In one embodiment, the inverting input terminal of the comparator U2 is connected to the first terminal of the resistor R10, and the second terminal of the resistor R10 is connected to the reference voltage source VREF1; the first terminal of the resistor R10 is also connected in series with resistors R9, R11, R14 and R16 to ground; the middle connection point of the resistors R9 and R11 is connected to the collector of the transistor Q1, the base of the transistor Q1 is connected to the single-chip control port, and the emitter of the transistor Q1 is grounded; the middle connection point of the resistors R11 and R14 is connected to the collector of the transistor Q2, the base of the transistor Q2 is connected to the single-chip control port, and the emitter of the transistor Q2 is grounded; the middle connection point of the resistors R14 and R16 is connected to the collector of the transistor Q3, the base of the transistor Q3 is connected to the single-chip control port, and the emitter of the transistor Q3 is grounded;

[0032] The working principle and beneficial effects of the above technical solution are:

[0033] R9 / R10 / R11 / R14 / R16 / Q1 / Q2 / Q3 form a circuit with four-level threshold settings. By changing the different resistance ratios, the reference voltage at the reverse input end of U2 is changed. The threshold setting can be done through a dial code or a single-chip microcomputer.

[0034] Preferably, the control signal output from the output end of the comparator U2 is transmitted to the fault processing unit after passing through the RC charging circuit; the resistor R4 and the capacitor C3 form an RC charging circuit, which forms a delay waiting to prevent malfunction; the first end of the resistor R4 is connected to the output end of the comparator U2, and the second end of the resistor R4 is connected to the fault processing unit; the first end of the capacitor C3 is connected to the second end of the resistor R4, and the second end of the capacitor C3 is grounded; the fault processing unit receives the control signal of the comparator U2 to control the motor B1 to disconnect the power supply. By setting the fault processing unit, a corresponding response can be made to the fault that occurs. For the fault caused by overcurrent, it does not need to pass through the single-chip microcomputer, and is directly processed by hardware, with fast response speed and high reliability;

[0035] In one embodiment, the fault handling can be provided by providing a dry contact to the outside, and the power supply can be disconnected when overcurrent is detected. Through this hardware, the controller can directly shut down the output, thereby protecting the product and reducing losses.

[0036] In one embodiment, as a supplementary solution of the present application, the sampling circuit uses a current transformer; the current transformer collects the current signal of the motor B1 and transmits it to the primary filtering circuit.

[0037] To summarize, a sampling circuit is set to collect the current signal of the motor, and the signal is isolated and amplified through an isolation amplifier, and the differential signal is converted into a unipolar signal through a differential signal conversion unipolar signal circuit and output to the single-chip microcomputer for current calculation, and output to the hardware overcurrent protection circuit, and overcurrent detection is performed through a comparator, and overcurrent protection is performed through a fault processing unit; it does not need to go through a single-chip microcomputer, but is directly processed by hardware, with fast response speed and high reliability; by setting a circuit with a settable threshold to adjust the threshold value of the hardware overcurrent circuit, accurate overcurrent protection and fast response can be achieved.

[0038] It is worth noting that in the above system embodiment, the various units included are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; in addition, the specific names of the functional units are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention.

[0039] In addition, a person skilled in the art can understand that all or part of the steps in the above-mentioned embodiments can be completed by instructing related hardware through a program, and the corresponding program can be stored in a computer-readable storage medium, such as a ROM / RAM, a disk or an optical disk.

[0040] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can better understand and use the present invention. The present invention is limited only by the claims and their full scope and equivalents. .

Claims

1. An isolated current detection and protection circuit, characterized in that: include A sampling circuit, wherein the sampling circuit collects the current signal of the motor B1, converts it into a voltage signal, and performs filtering processing through a primary filtering circuit; An isolation amplifier circuit, the isolation amplifier circuit comprising an isolation operational amplifier U1, the isolation operational amplifier U1 receives the signal output by the primary filter circuit for isolation and amplification, and then performs filtering processing through the secondary filter circuit; A differential signal conversion unipolar signal circuit, wherein the differential signal conversion unipolar signal circuit converts the differential signal output by the secondary filtering circuit into a unipolar signal and then divides it into two paths, one of which is output through an ADC analog-to-digital converter and then transmitted to a single-chip microcomputer for calculation processing, and the other is output to a hardware overcurrent protection circuit; Among them, the hardware overcurrent protection circuit includes a comparator U2, the non-inverting input terminal of the comparator U2 receives the unipolar signal output by the differential signal conversion unipolar signal circuit; the inverting input terminal of the comparator U2 receives the reference signal; the comparator U2 compares the input unipolar signal with the reference signal, and outputs a control signal to the fault processing unit through the output terminal.

2. The isolated current detection and protection circuit according to claim 1, characterized in that: The sampling circuit uses a sampling resistor R1; the sampling resistor R1 is connected in series between the stator windings of the motor B1, converts the current signal of the motor B1 into a voltage signal and transmits it to the primary filtering circuit.

3. The isolated current detection and protection circuit according to claim 1, characterized in that: The sampling circuit uses a current transformer; the current transformer collects the current signal of the motor B1 and transmits it to the primary filtering circuit.

4. The isolated current detection and protection circuit according to claim 1, characterized in that: The primary filtering circuit includes resistors R3, R4 and capacitor C1; The first ends of the resistors R3 and R4 are connected to the two ends of the sampling circuit respectively; the second end of the resistor R3 is connected to the input terminal 2 pin of the isolation operational amplifier U1; the second end of the resistor R4 is connected to the input terminal 3 pin of the isolation operational amplifier U1; Two ends of the capacitor C1 are connected to second ends of the resistors R3 and R4 respectively.

5. The isolated current detection and protection circuit according to claim 4, characterized in that: Pin 1 of the isolation operational amplifier U1 is connected in series with capacitor C2 to ground, and pin 8 of the isolation operational amplifier U1 is connected in series with capacitor C4 to ground; pins 4 and 5 of the isolation operational amplifier U1 are grounded; The output terminal 6-7 of the isolation operational amplifier U1 outputs the amplified signal to the secondary filtering circuit.

6. The isolated current detection and protection circuit according to claim 5, characterized in that: The secondary filtering circuit includes resistors R5, R6 and capacitor C5; The first ends of the resistors R5 and R6 are respectively connected to the output terminals 6-7 of the isolation operational amplifier U1; the second ends of the resistors R5 and R6 are connected to the input terminal of the differential signal conversion unipolar signal circuit; Two ends of the capacitor C5 are connected to the second ends of the resistors R5 and R6 respectively.

7. The isolated current detection and protection circuit according to claim 6, characterized in that: The differential signal conversion unipolar signal circuit includes an operational amplifier U3, resistors R7, R8, R12 and R13; The first end of the resistor R7 is connected to the second end of the resistor R5, and the second end of the resistor R7 is connected to the non-inverting input terminal of the operational amplifier U3; the first end of the resistor R8 is connected to the second end of the resistor R6, and the second end of the resistor R6 is connected to the inverting input terminal of the operational amplifier U3; The non-inverting input terminal of the operational amplifier U3 is also connected in series with a resistor R12 to a reference voltage source VREF; both ends of the resistor R12 are connected in parallel with both ends of the capacitor C6; A resistor R13 is connected in series between the inverting input terminal and the output terminal of the operational amplifier U3; both ends of the resistor R13 are connected in parallel with both ends of the capacitor C7.

8. The isolated current detection and protection circuit according to claim 7, characterized in that: The signal output from the output end of the operational amplifier U3 is filtered by a three-stage filtering circuit and then output; The three-stage filter circuit includes a resistor R15 and a capacitor C8; the first end of the resistor R15 is connected to the output end of the operational amplifier U3, the first end of the capacitor C8 is connected to the second end of the resistor R15, and the second end of the capacitor C8 is grounded; The second end of the resistor R15 is connected to the anode of the diode D1 and the cathode of the diode D2. The cathode of the diode D1 is connected to the voltage source VDD2, and the anode of the diode D2 is grounded.

9. The isolated current detection and protection circuit according to claim 1, characterized in that: The inverting input terminal of the comparator U2 is connected to the first terminal of the resistor R10, and the second terminal of the resistor R10 is connected to the reference voltage source VREF1; The first end of the resistor R10 is connected in series with resistors R9, R11, R14 and R16 to ground; The middle connection point of the resistors R9 and R11 is connected to the collector of the transistor Q1, the base of the transistor Q1 is connected to the control port of the single chip computer, and the emitter of the transistor Q1 is grounded; The middle connection point of the resistors R11 and R14 is connected to the collector of the transistor Q2, the base of the transistor Q2 is connected to the control port of the single chip computer, and the emitter of the transistor Q2 is grounded; The middle connection point of the resistors R14 and R16 is connected to the collector of the transistor Q3 , the base of the transistor Q3 is connected to the control port of the single chip microcomputer, and the emitter of the transistor Q3 is grounded.

10. The isolated current detection and protection circuit according to claim 1, characterized in that: The control signal outputted from the output terminal of the comparator U2 is transmitted to the fault processing unit after passing through the RC charging circuit; The RC charging circuit includes a resistor R4 and a capacitor C3; a first end of the resistor R4 is connected to the output end of the comparator U2, and a second end of the resistor R4 is connected to the fault processing unit; The first end of the capacitor C3 is connected to the second end of the resistor R4, and the second end of the capacitor C3 is grounded; The fault processing unit receives the control signal of the comparator U2 to control the motor B1 to cut off the power supply.

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