Frequency converter output overcurrent protection circuit

Abstract

The utility model discloses a frequency converter output overcurrent protection circuit comprising a reference power supply circuit used for stably outputting a 5V voltage; the current sampling circuit is used for collecting the IGBT output current and converting the IGBT output current into a voltage signal to be output; the comparison circuit is used for comparing the acquired voltage signal with a set value and then outputting a level signal; and the buffer circuit is used for acquiring the level signal and outputting a VCE signal. According to the frequency converter output overcurrent protection circuit, output current is detected through the current detection circuit, the comparator is used for comparing real-time current values and controlling output overcurrent signals, and the phase inverter is used for carrying out waveform shaping on the output signals, so that the integrity of the signals is ensured.

Description

TECHNICAL FIELD

[0001] The utility model relates to frequency converter protection technical field, concretely relates to a frequency converter output overcurrent protection circuit. BACKGROUND

[0002] General frequency converter usually has hardware overcurrent protection and software overcurrent protection. The hardware overcurrent protection commonly used at present has the following several kinds, fast fuse: install fast fuse at the DC side or AC input end of frequency converter, when the current exceeds its rated value, fast fuse can cut off the circuit in very short time, protects frequency converter from being damaged, overcurrent relay: overcurrent relay can monitor the output current of frequency converter in real time, once exceeds the preset value, immediately act, cut off the control circuit, makes frequency converter stop working, current sensor and controller: add current sensor in the output circuit of frequency converter, monitors the current change in real time, and transmits the signal to the controller. The controller sends control signal according to the preset protection threshold, and cuts off or adjusts the working state of frequency converter, inverter module protection: for the damage situation of inverter module, can increase independent protection circuit on each inverter bridge arm, such as installing fast recovery diode, to prevent the occurrence of straight-through phenomenon. The fuse, relay, sensor etc. in the hardware overcurrent protection scheme mentioned above are relatively high in price, and the cost is not easy to control.

[0003] Software overcurrent protection is realized through the algorithm and logic built-in main control chip, the main control chip reads current data, converts analog voltage into digital current value through ADC, and the main control chip compares the set overcurrent value, judges whether overcurrent, and triggers protection measures. Software overcurrent protection occupies DSP resource, and the response speed is not as fast as hardware protection. SUMMARY

[0004] The utility model aims at providing a kind of frequency converter output overcurrent protection circuit.

[0005] To achieve the above object, the utility model provides the following technical scheme: a kind of frequency converter output overcurrent protection circuit, comprising:

[0006] Current sampling circuit is used to convert into voltage signal output after gathering IGBT output current;

[0007] Comparison circuit is used to output level signal after comparing voltage signal with set value;And

[0008] Buffer circuit is used to output VCE signal after waveform shaping of level signal;And

[0009] Reference power supply circuit is used to stabilize the output 5V voltage and power supply current sampling circuit, comparison circuit and buffer circuit.

[0010] Further, the reference power supply circuit comprises TL431, resistors R1, R2, R3, R6, C1, C2, C4, one end of the capacitor C1 is connected to the cathode of TL431 through R1, the resistors R2 and R1 are connected in parallel and then connected to the anode of TL431 through R3 and R6 in turn, the reference electrode of TL431 is connected between the resistors R6 and R3, the capacitor C4 is connected in parallel with R6, one end of the capacitor C2 is connected between R2 and R3, and the other end is connected to C4.

[0011] Further, the current sampling circuit comprises operational amplifiers U2A, U2B, resistors R4, R5, R7, RA1, RA2, RA3, R13, R17, R18, R14, R12, capacitors C6, C3, C11, one end of the resistor R4 is connected to the non-inverting input terminal of operational amplifier U2B through resistor R5 and capacitor C3 in turn, the resistor R5 and capacitor C3 are connected in parallel, the resistors RA1, RA2, and RA3 are connected in parallel and then connected to the non-inverting input terminal of operational amplifier U2A through resistor R13 at one end and connected to the inverting input terminal of operational amplifier U2A through resistor R17 at the other end, the output terminal of operational amplifier U2B is connected between R13 and operational amplifier U2A through capacitor C6, one end of the resistor R7 is connected to the inverting input terminal of operational amplifier U2B, and the other end is connected between capacitor C6 and operational amplifier U2B, one end of the resistor R12 is connected between C6 and R7, and the other end is connected between C6 and R13, the resistor R18 is connected in parallel with C11 and then connected between R17 and operational amplifier U2A at one end and connected to the output terminal of operational amplifier U2A at the other end, one end of the resistor R14 is connected to the output terminal of operational amplifier U2A.

[0012] Further, the models of the operational amplifiers U2A and U2B are TL082IDR.

[0013] Further, the comparison circuit comprises a photocoupler U3, resistors R8, R9, R16, R20, R22, R11, R10, R15, R21, capacitors C5, C12, C10, C13, operational amplifiers U4A, U4B, one end of the capacitor C5 is connected to the 1 port of the photocoupler U3 through the parallel connection of the resistors R8 and R9, one end of the resistor R11 is connected to the resistor R8, and the other end of the resistor R11 is connected to the output terminal of the operational amplifier U4A, the 2 port of the photocoupler U3 is connected between the resistor R11 and the operational amplifier U4A, one end of the resistor R10 is connected to the 4 port of the photocoupler U3, one end of the resistor R16 is connected to the non-inverting input terminal of the operational amplifier U4A through one end of the capacitor C10, one end of the resistor R15 is connected between the capacitor C10 and the operational amplifier U4A, and the other end of the resistor R15 is connected between the resistor R11 and the operational amplifier U4A, one end of the capacitor C12 is connected to the non-inverting input terminal of the operational amplifier U4B, the parallel connection of the resistor R22 and the capacitor C13 is connected between the resistor R16 and the capacitor C10 through the resistor R20, and the other end of the parallel connection of the resistor R22 and the capacitor C13 is connected to the inverting input terminal of the operational amplifier U4B, the negative input terminal of the operational amplifier U4A is connected to the non-inverting input terminal of the operational amplifier U4B through one end of the resistor R21, and the output terminal of the operational amplifier U4B is connected to the output terminal of the operational amplifier U4A through the other end of the resistor R21.

[0014] Further, the model of the photocoupler U3 is PS2501L.

[0015] Further, the model of the operational amplifiers U4A and U4B is LM393DR2G.

[0016] Further, the buffer circuit comprises a resistor R23, a capacitor C15 and an inverter U5, and the resistor R23 is connected to the inverter U5 through one end of the capacitor C15.

[0017] Further, the model of the inverter U5 is 74HC14D.

[0018] According to the technical scheme, the utility model has the following beneficial effects:

[0019] The frequency converter output overcurrent protection circuit detects the output current through the current detection circuit, compares the real-time current value by using the comparator, controls the output overcurrent signal, and uses the inverter to perform waveform shaping on the output signal, so that the integrity of the signal is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a reference power supply circuit diagram of the utility model;

[0021] Figure 2 It is a current sampling circuit diagram of the utility model;

[0022] Figure 3 The comparison circuit diagram of the utility model;

[0023] Figure 4 The buffer circuit diagram of the utility model. DETAILED DESCRIPTION

[0024] In the description of the utility model, it needs to explain, the direction or position relation that the terms "upper", "lower", "internal", "external", "front end", "rear end", "two ends", "one end", "another end" and the like indicate is based on the direction or position relation shown in the drawing, is only for the convenience of describing the utility model and simplifying the description, and is not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the utility model. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0025] In the description of the utility model, it needs to explain, unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "connection" and the like should be broadly understood, for example, "connection", can be fixed connection, or can be detachable connection, or integrally connected, can be mechanical connection, or can be electrical connection, can be directly connected, or indirectly connected through an intermediate medium, can be the communication inside two elements. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0026] The technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary skilled in the art without creative labor belong to the scope of protection of the utility model.

[0027] Please refer to Figures 1-4 The utility model provides a kind of frequency converter output overcurrent protection circuit, including reference power supply circuit, current sampling circuit, comparison circuit and buffer circuit, wherein reference power supply circuit includes TL431, resistance R1, R2, R3, R6, C1, C2, C4, one end of the capacitor C1 is connected to the cathode of TL431 by R1, resistance R2 is connected in parallel with R1, then in turn is connected to the anode of TL431 by R3, R6, the reference pole of TL431 is connected between resistance R6 and R3, the capacitor C4 is connected in parallel with R6, one end of the capacitor C2 is connected between R2, R3, and the other end is connected C4.

[0028] When the +5ref reference power supply circuit starts to work, first +VWP charges the back-end capacitor C2, at this time the voltage at the output end of the reference power supply circuit is less than 5V, the voltage at the TL431 reference voltage pin divided by R3, R6 (in this circuit R1=R2=R3=R6) is also less than 2.5V, so the cathode and anode of TL431 is in an open circuit state; when the voltage across the capacitor (i.e. the output voltage of the entire 5V reference power supply circuit) is charged to a state greater than 5V, the voltage at the TL431 reference voltage pin divided by R3, R6 will be greater than 2.5V, at this time the anode and cathode of TL431 is in a conducting state, the back-end load circuit is powered by C2, when the back-end load consumes the voltage across the capacitor to 5V or less, the voltage divided at the TL431 reference voltage pin will be less than 2.5V, at this time the anode and cathode of TL431 returns to an open circuit state, +VWP will charge the back-end capacitor C2 again, thereby realizing dynamic regulation of the output voltage of the +5ref reference power supply circuit, stabilizing the output voltage at 5V, and realizing stable output of 5V voltage.

[0029] The current sampling circuit comprises operational amplifiers U2A and U2B, resistors R4, R5, R7, RA1, RA2, RA3, R13, R17, R18, R14, R12, and capacitors C6, C3 and C11. One end of the resistor R4 is connected to the non-inverting input terminal of the operational amplifier U2B in sequence through the resistor R5 and the capacitor C3, and the resistor R5 and the capacitor C3 are connected in parallel. The resistors RA1, RA2 and RA3 are connected in parallel, and one end of the resistors is connected to the non-inverting input terminal of the operational amplifier U2A through the resistor R13, and the other end is connected to the inverting input terminal of the operational amplifier U2A through the resistor R17. The output terminal of the operational amplifier U2B is connected to R13 and the operational amplifier U2A through the capacitor C6. One end of the resistor R7 is connected to the inverting input terminal of the operational amplifier U2B, and the other end is connected to the capacitor C6 and the operational amplifier U2B. One end of the resistor R12 is connected to C6 and R7, and the other end of the resistor R12 is connected to C6 and R13. The resistor R18 and the capacitor C11 are connected in parallel, and one end of the resistor is connected to R17 and the operational amplifier U2A, and the other end is connected to the output terminal of the operational amplifier U2A. One end of the resistor R14 is connected to the output terminal of the operational amplifier U2A. The models of the operational amplifiers U2A and U2B are TL082IDR.

[0030] The U2B part circuit is used as voltage follower, wherein R4=R5=R7, +5ref gets +2.5ref reference voltage after voltage division and operation amplifier U2B; the U2A part is differential amplification circuit, RA1, RA2, RA3 are sampling resistors, assuming that the voltage across RA3 is Vin, Vin=I*1.414*2.5*R, wherein I is the rated current of W phase output, 2.5 times is the overcurrent point, and R is the parallel equivalent resistance of RA1, RA2 and RA3; according to the principle of the same phase amplification circuit, V_out=[(2.5-Vin)*R13 / (R13+R12)+Vin]*(R18 / R17+1) can be obtained, and the current sampling circuit obtains 5V voltage and outputs after voltage division.

[0031] The comparison circuit comprises optocoupler U3, resistors R8, R9, R16, R20, R22, R11, R10, R15, R21, capacitors C5, C12, C10, C13, operation amplifiers U4A and U4B, one end of the capacitor C5 is connected to the 1 port of the optocoupler U3 through the parallel connection of the resistors R8 and R9, one end of the resistor R11 is connected between the resistors R8 and R9, the other end of the resistor R11 is connected to the output end of the operation amplifier U4A, the 2 port of the optocoupler U3 is connected between the resistor R11 and the operation amplifier U4A, one end of the resistor R10 is connected to the 4 port of the optocoupler U3, one end of the resistor R16 is connected to the non-inverting input end of the operation amplifier U4A through one end of the capacitor C10, one end of the resistor R15 is connected between the capacitor C10 and the operation amplifier U4A, and the other end of the resistor R15 is connected between the resistor R11 and the operation amplifier U4A, one end of the capacitor C12 is connected to the non-inverting input end of the operation amplifier U4B, the parallel connection of the resistor R22 and the capacitor C13 is connected between the resistor R16 and the capacitor C10 through the resistor R20, and the other end of the parallel connection of the resistor R22 and the capacitor C13 is connected to the inverting input end of the operation amplifier U4B, the negative input end of the operation amplifier U4A is connected to the non-inverting input end of the operation amplifier U4B through one end of the resistor R21, and the output end of the operation amplifier U4B is connected to the output end of the operation amplifier U4A through the other end of the resistor R21. The model of the optocoupler U3 is PS2501L, and the models of the operation amplifiers U4A and U4B are LM393DR2G.

[0032] The comparison circuit obtains the voltage after voltage division and outputs a level signal after comparison, and specifically, R8, R9, R16, R20 and R22 are voltage division resistors, R11 is a current limiting resistor, and R10 is a pull-up resistor; the voltage at pin 3 of U4A is V3=5*(R20+R22) / (R16+R20+R22), and the voltage at pin 6 of U4B is V6=5*R22 / (R16+R20+R22); when V_outV6, U4 outputs a low level; when V_out>V3, U4 outputs a low level; when V6V_outV3, U4 outputs a high level; when U4 outputs a low level, U3 optocoupler is turned on, and the FAULT signal is pulled low.

[0033] The buffer circuit comprises a resistor R23, a capacitor C15 and an inverter U5, the resistor R23 is connected to the inverter U5 through one end of the capacitor C15, the inverter U5 is of the type 74HC14D, R23 and C15 constitute an RC filter, 74HC14D is an inverter, and pins 2 and 3 of the inverter are connected; when the input FAULT signal is a low level, the output VCE signal is also a low level; when the input FAULT signal is a high level, the output VCE signal is also a high level; the inverter is added here to shape the waveform, so that the VCE signal becomes a standard level signal output.

[0034] The overcurrent protection circuit of the frequency converter outputs an overcurrent protection signal through a logic circuit composed of TL431, TL082IDR, LM393DR2G and 74HC14D for current sampling, comparison and output, the overcurrent protection is realized by hardware, so that the response speed is fast and no DSP resource is occupied; and the 74HC14D inverter is used for waveform shaping, so that the VCE signal becomes a standard level signal output.

[0035] Although the embodiments of the utility model have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the utility model, the scope of the utility model is defined by the appended claims and their equivalents.

Claims

1. A frequency converter output overcurrent protection circuit, characterized by include: The current sampling circuit is used to collect the output current of the IGBT and convert it into a voltage signal output. The comparator circuit is used to compare the acquired voltage signal with the set value and then output a level signal. as well as A buffer circuit is used to acquire a level signal, shape the waveform, and then output the VCE signal; and The reference power supply circuit is used to stably output a 5V voltage to power the current sampling circuit, the comparison circuit, and the buffer circuit.

2. The over-current protection circuit for a frequency converter output according to claim 1, characterized in that: The reference power supply circuit includes a TL431, resistors R1, R2, R3, R6, C1, C2, and C4. One end of capacitor C1 is connected to the cathode of TL431 through R1. Resistor R2 is connected in parallel with R1 and then connected to the anode of TL431 through R3 and R6. The reference terminal of TL431 is connected between resistors R6 and R3. Capacitor C4 is connected in parallel with R6. One end of capacitor C2 is connected between R2 and R3, and the other end is connected to C4.

3. The over-current protection circuit for a frequency converter output according to claim 1, characterized in that: The current sampling circuit includes operational amplifiers U2A and U2B, resistors R4, R5, R7, RA1, RA2, RA3, R13, R17, R18, R14, R12, and capacitors C6, C3, and C11. One end of resistor R4 is connected to the non-inverting input of operational amplifier U2B via resistor R5 and capacitor C3. Resistor R5 and capacitor C3 are connected in parallel. One end of the parallel connection of resistors RA1, RA2, and RA3 is connected to the non-inverting input of operational amplifier U2A via resistor R13, and the other end is connected to the inverting input of operational amplifier U2A via resistor R17. The output terminal of operational amplifier U2B is connected between operational amplifier U2A and R13 via capacitor C6. One end of resistor R7 is connected to the inverting input terminal of operational amplifier U2B, and the other end is connected between capacitor C6 and operational amplifier U2B. One end of resistor R12 is connected between C6 and R7, and the other end of resistor R12 is connected between C6 and R13. Resistor R18 is connected in parallel with C11, and one end is connected between R17 and operational amplifier U2A, and the other end is connected to the output terminal of operational amplifier U2A. One end of resistor R14 is connected to the output terminal of operational amplifier U2A.

4. The over-current protection circuit for a frequency converter output according to claim 3, characterized in that: The operational amplifiers U2A and U2B are model TL082IDR.

5. The over-current protection circuit for a frequency converter output according to claim 1, characterized in that: The comparator circuit includes an optocoupler U3, resistors R8, R9, R16, R20, R22, R11, R10, R15, R21, capacitors C5, C12, C10, and C13, and operational amplifiers U4A and U4B. One end of capacitor C5 is connected to port 1 of optocoupler U3 through parallel resistors R8 and R9. One end of resistor R11 is connected between resistors R8 and R9, and the other end of resistor R11 is connected to the output terminal of operational amplifier U4A. Port 2 of optocoupler U3 is connected between R11 and operational amplifier U4A. One end of resistor R10 is connected to port 4 of optocoupler U3, and one end of resistor R16 is connected to operational amplifier U4A through one end of capacitor C10. The non-inverting input terminal of operational amplifier U4A is connected to the non-inverting input terminal of operational amplifier U4B. One end of resistor R15 is connected between C10 and operational amplifier U4A, and the other end is connected between resistor R11 and operational amplifier U4A. One end of capacitor C12 is connected to the non-inverting input terminal of operational amplifier U4B. One end of resistors R22 and C13 connected in parallel is connected between R16 and C10 through R20, and the other end is connected to the inverting input terminal of operational amplifier U4B. The negative input terminal of operational amplifier U4A is connected to the non-inverting input terminal of operational amplifier U4B through one end of resistor R21. The output terminal of operational amplifier U4B is connected to the output terminal of operational amplifier U4A through the other end of resistor R21.

6. The over-current protection circuit for a frequency converter output according to claim 5, characterized in that: The optocoupler U3 is model PS2501L.

7. The over-current protection circuit for a frequency converter output according to claim 5, characterized in that: The operational amplifiers U4A and U4B are model LM393DR2G.

8. The inverter output overcurrent protection circuit according to claim 1, characterized in that: The buffer circuit includes a resistor R23, a capacitor C15, and an inverter U5. The resistor R23 is connected to the inverter U5 through one end of the capacitor C15.

9. The inverter output overcurrent protection circuit according to claim 8, characterized in that: The inverter U5 is model 74HC14D.

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