Frequency converter output over-ground overcurrent protection circuit

Abstract

The utility model discloses a frequency converter output over-ground overcurrent protection circuit comprising a sampling unit which is used for collecting current of a W item and outputting a current sampling value after limiting the size of the current; the isolation amplifier U2 is used for isolating and amplifying a power supply input and output to the isolation amplifier U2; and the dual-operational amplifier unit comprises an amplification chip U1A and a comparison chip U1B, the negative input end of the comparison chip U1B is connected with the output end of the amplification chip U1A, the input end of the chip U1A is connected with the isolation amplifier U2, and the chip U1A is used for amplifying a current sampling value and then outputting the amplified current sampling value. The over-current threshold value can be adjusted by modifying the resistance value of the resistor, whether the circuit is over-current or not can be judged through the comparator, output is adjusted through the isolation amplifier U2 and the double operational amplifier unit, and therefore the output over-ground over-current protection circuit is achieved, the circuit is simple, the number of used components is small, and cost is low.

Description

Technical Field

[0001] The utility model relates to the technical field of overcurrent protection of frequency converters, and particularly relates to an overcurrent protection circuit for the output of a frequency converter to the ground. Background Art

[0002] At present, various brands of frequency converters have very perfect protection measures. Among all protections, overcurrent to the ground is a very important protection, which affects the safety and reliability of the frequency converter. Overcurrent protection mainly refers to the situation where the peak value of the current exceeds the allowable value of the frequency converter with a sudden change. Overcurrent protection has an inverse time limit characteristic. Therefore, how to suppress overcurrent in the application process of the frequency converter is a very crucial issue.

[0003] For a frequency converter, overcurrent protection is an essential link in the existing frequency converter testing and operation process. In practical applications, it is necessary to monitor the alternating current in real time so as to turn off the circuit in time when an excessive current appears to avoid damage.

[0004] At present, the overcurrent protection circuits of frequency converters on the market use many components, have a complex structure, and are costly. Summary of the Invention

[0005] The purpose of the utility model is to provide an overcurrent protection circuit for the output of a frequency converter to the ground.

[0006] To achieve the above purpose, the utility model provides the following technical solution: An overcurrent protection circuit for the output of a frequency converter to the ground, comprising:

[0007] A sampling unit, which is used to collect the current of W items, limit the magnitude of the current, and then output a current sampling value;

[0008] An isolation amplifier U2, which is used to isolate and amplify the power supply input to and output from the isolation amplifier U2;

[0009] A dual operational amplifier unit, the dual operational amplifier circuit includes an amplification chip U1A and a comparison chip U1B. The negative input terminal of the comparison chip U1B is connected to the output terminal of the amplification chip U1A. The input terminal of the chip U1A is connected to the isolation amplifier U2. The chip U1A is used to amplify the current sampling value and then output it. The chip U1B is used to compare the amplified current sampling value with the voltage after voltage division and determine whether there is overcurrent.

[0010] Further, the sampling unit includes resistors RA1 and RA2. The resistors RA1 and RA2 are connected in parallel and then connected to the isolation amplifier U2. RA1 and RA2 limit the magnitude of the current.

[0011] Further, the model of the isolation amplifier U2 is NSI1300D25.

[0012] Further, the models of the amplification chip U1A and the comparison chip U1B are TL082IDR chips.

[0013] Further, it further includes an adjustment resistor unit for adjusting the overcurrent threshold after modifying the resistor value. The adjustment resistor unit includes R5, R6, R9, and R10. One end of the series connection of the resistors R5 and R6 is connected to the isolation amplifier U2, and the other end is connected to the positive input terminal of the amplification chip U1A. One end of the series connection of the resistors R9 and R10 is connected to the isolation amplifier U2, and the other end is connected to the output terminal of the amplification chip U1A. The adjustment resistor unit adjusts the amplified current sampling value and controls the current sampling value of item W; R11 is the amplification factor resistor, and the amplification factor of U1A is adjusted by changing the resistance value.

[0014] Further, it further includes a power supply energy storage unit for supplying power to the isolation amplifier U2. The power supply energy storage unit includes a resistor R2, a zener diode ZD1, and an energy storage capacitor C1. One end of the resistor R2 is connected to the positive electrode of the zener diode ZD1 and then connected to one end of the energy storage capacitor C1, and the other end of the energy storage capacitor C1 is connected to the isolation amplifier U2.

[0015] Further, it further includes a voltage division unit for dividing the 5V power supply voltage. The voltage division unit includes voltage division resistors R1 and R3. One end of the voltage division resistor R1 is connected to one end of R3 and then connected to the positive input terminal of the comparison chip U1B.

[0016] Further, it further includes an RC filtering unit one for performing RC filtering on the input of the isolation amplifier U2. The RC filtering unit one includes a resistor R8 and a capacitor C5. One end of the resistor R8 is connected to the sampling unit, and the other end of R8 is connected to the capacitor C5 and then connected to the isolation amplifier U2.

[0017] Further, it further includes an RC filtering unit two for performing RC filtering on the input of the dual operational amplifier unit. The RC filtering unit two includes a resistor R7 and a capacitor C3. One end of the resistor R7 is connected to the isolation amplifier U2, and the other end of R7 is connected to the capacitor C3 and then connected to the input terminal of the amplification chip U1A.

[0018] Further, it further includes a filtering unit. The filtering unit includes filtering capacitors C2, C4, and C6. The filtering capacitor C2 is connected in parallel with the energy storage capacitor C1 and then connected to the isolation amplifier U2. One end of the filtering capacitor C4 is connected to the capacitor C3 and then connected to the input terminal of the amplification chip U1A. One end of the filtering capacitor C6 is connected to C4, and the other end is connected to the output terminal of the amplification chip U1A.

[0019] As can be seen from the above technical solutions, the present utility model has the following beneficial effects:

[0020] The overcurrent threshold can be adjusted by modifying the resistance value. Whether the circuit is overcurrent can be judged by a comparator. The output is adjusted by an isolation amplifier U2 and a dual operational amplifier unit, so as to realize an output overcurrent protection circuit for the ground. The circuit is simple, uses fewer components, has a lower cost, and the selected devices of the circuit have lower power consumption, which can extend the service life of the frequency converter and improve the safety and reliability of the frequency converter. Description of the Drawings

[0021] Figure 1 This is the overall circuit diagram of the present invention. Detailed Implementation Modes

[0022] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front end", "rear end", "both ends", "one end", "the other end", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0023] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] Please refer to Figure 1, the present utility model provides an inverter output overcurrent protection circuit to ground, which includes a sampling unit, an isolation amplifier U2, a dual operational amplifier unit, an adjustable resistor unit, a power supply energy storage unit, a voltage dividing unit, an RC filtering unit I, an RC filtering unit II, and a filtering unit. The sampling unit includes resistors RA1 and RA2. The resistors RA1 and RA2 are connected in parallel and then connected to the isolation amplifier U2. RA1 and RA2 limit the magnitude of the current to avoid overload or damage of the components in the circuit. The sampling unit is used to collect the current of item W and output a current sampling value after limiting the magnitude of the current;

[0026] The model of the isolation amplifier U2 is NSI1300D25, which isolates and amplifies the current by 8.2 times for the power supplies input to and output from the isolation amplifier U2;

[0027] The dual operational amplifier unit. The dual operational amplifier circuit includes an amplification chip U1A and a comparison chip U1B. The negative input terminal of the comparison chip U1B is connected to the output terminal of the amplification chip U1A. The input terminal of the chip U1A is connected to the isolation amplifier U2. The chip U1A is used to amplify the current sampling value and then output it. The chip U1B is used to compare the amplified current sampling value with the voltage after voltage division and determine whether there is overcurrent. Specifically, when the voltage of IW is greater than the voltage after 5V voltage division, the signal Vearth to ground is at a low level. When the voltage of IW is less than the voltage after 5V voltage division, the signal Vearth to ground is at a high level, so as to determine whether there is overcurrent. IW is the amplified current sampling value of item W output. R4 is a pull-up resistor. The models of the amplification chip U1A and the comparison chip U1B are TL082IDR chips.

[0028] The adjustable resistor unit includes R5, R6, R9, and R10. The resistors R5 and R6 are connected in series and then one end is connected to the isolation amplifier U2, and the other end is connected to the positive input terminal of the amplification chip U1A. The resistors R9 and R10 are connected in series and then one end is connected to the isolation amplifier U2, and the other end is connected to the output terminal of the amplification chip U1A. The adjustable resistor unit is used to modify the resistance value to change the amplification factor and adjust the overcurrent threshold. The adjustable resistor unit can adjust the amplified current sampling value and control the current sampling value of item W. R11 is an amplification factor resistor. By changing the resistance value, the amplification factor of U1A can be adjusted, and the magnitude of the current sampling value of item W output from the isolation amplifier U2 can be adjusted.

[0029] The power supply energy storage unit includes a resistor R2, a zener diode ZD1, and an energy storage capacitor C1. R2 is a current limiting resistor. The resistor R2 is connected to the positive electrode of the zener diode ZD1 (5.1V) and then connected to one end of the energy storage capacitor C1. The other end of the energy storage capacitor C1 is connected to the isolation amplifier U2. The power supply energy storage unit supplies 5.1V voltage to the primary side of the isolation amplifier U2.

[0030] The voltage dividing unit includes voltage dividing resistors R1 and R3. One end of the voltage dividing resistor R1 is connected to one end of R3 and then connected to the positive input terminal of the comparison chip U1B; the voltage dividing unit divides the 5V power supply voltage.

[0031] The first RC filtering unit includes a resistor R8 and a capacitor C5. One end of the resistor R8 is connected to the sampling unit, and the other end of R8 is connected to the capacitor C5 and then connected to the isolation amplifier U2; the first RC filtering unit performs RC filtering on the input of the isolation amplifier U2.

[0032] The second RC filtering unit includes a resistor R7 and a capacitor C3. One end of the resistor R7 is connected to the isolation amplifier U2, and the other end of R7 is connected to the capacitor C3 and then connected to the input terminal of the amplifier chip U1A; the second RC filtering unit performs RC filtering on the input of the dual operational amplifier unit.

[0033] The filtering unit includes filtering capacitors C2, C4, and C6. The filtering capacitor C2 is connected in parallel with the energy storage capacitor C1 and then connected to the isolation amplifier U2. One end of the filtering capacitor C4 is connected to the capacitor C3 and then connected to the input terminal of the amplifier chip U1A. One end of the filtering capacitor C6 is connected to C4, and the other end is connected to the output terminal of the amplifier chip U1A.

[0034] The overcurrent threshold can be adjusted by modifying the resistance value of the resistor. Whether the circuit is overcurrent can be judged by the comparator. The output is adjusted through the isolation amplifier U2 and the dual operational amplifier unit, so as to realize the output overcurrent protection circuit for the ground. The circuit is simple, uses fewer components, has a lower cost, the selected devices of the circuit have lower power consumption, can extend the service life of the frequency converter, and improve the safety and reliability of the frequency converter.

[0035] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An output-to-ground overcurrent protection circuit for an inverter, characterized in that, Including: A sampling unit, which is used to collect the current of W items, limit the magnitude of the current, and then output a current sampling value; An isolation amplifier U2, which is used to isolate and amplify the power supply input to and output from the isolation amplifier U2; A dual operational amplifier unit, which includes an amplification chip U1A and a comparison chip U1B. The negative input terminal of the comparison chip U1B is connected to the output terminal of the amplification chip U1A. The input terminal of the chip U1A is connected to the isolation amplifier U2. The chip U1A is used to amplify the current sampling value and then output it. The chip U1B is used to compare the amplified current sampling value with the voltage after voltage division and determine whether there is overcurrent.

2. The overcurrent protection circuit for the output of the frequency converter to the ground according to claim 1, characterized in that: The sampling unit includes resistors RA1 and RA2. The resistors RA1 and RA2 are connected in parallel and then connected to the isolation amplifier U2. The resistors RA1 and RA2 limit the magnitude of the current.

3. The output-to-ground overcurrent protection circuit for a frequency converter according to claim 1, characterized in that: The model of the isolation amplifier U2 is NSI1300D25.

4. The output-to-ground overcurrent protection circuit for an inverter according to claim 1, wherein: The models of the amplification chip U1A and the comparison chip U1B are TL082IDR chips.

5. The output-to-earth overcurrent protection circuit for a frequency converter according to claim 1, characterized in that: It further includes an adjustment resistor unit for adjusting the overcurrent threshold after modifying the resistor value. The adjustment resistor unit includes resistors R5, R6, R9, and R10. The resistors R5 and R6 are connected in series, and one end is connected to the isolation amplifier U2, and the other end is connected to the positive input terminal of the amplification chip U1A. The resistors R9 and R10 are connected in series, and one end is connected to the isolation amplifier U2, and the other end is connected to the output terminal of the amplification chip U1A. The adjustment resistor unit adjusts the amplified current sampling value and controls the current sampling value of W items. The resistor R11 is an amplification factor resistor, and the amplification factor of U1A is adjusted by changing its resistance value.

6. The output-to-earth overcurrent protection circuit of an inverter according to claim 1, wherein: It further includes a power supply energy storage unit for supplying power to the isolation amplifier U2. The power supply energy storage unit includes a resistor R2, a zener diode ZD1, and an energy storage capacitor C1. The resistor R2 is connected to the positive electrode of the zener diode ZD1 and then connected to one end of the energy storage capacitor C1. The other end of the energy storage capacitor C1 is connected to the isolation amplifier U2.

7. A ground overcurrent protection circuit for the output of an inverter according to claim 1, characterized in that: It further includes a voltage division unit for dividing the 5V power supply voltage. The voltage division unit includes voltage division resistors R1 and R3. One end of the voltage division resistor R1 is connected to one end of the resistor R3 and then connected to the positive input terminal of the comparison chip U1B.

8. The overcurrent protection circuit for the output of the frequency converter to the ground according to claim 1, wherein: It further includes an RC filtering unit one for inputting RC filtering to the isolation amplifier U2. The RC filtering unit one includes a resistor R8 and a capacitor C5. One end of the resistor R8 is connected to the sampling unit, and the other end of the resistor R8 is connected to the capacitor C5 and then connected to the isolation amplifier U2.

9. The overcurrent protection circuit for the output of the frequency converter to the ground according to claim 1, characterized in that: It further includes an RC filtering unit two for inputting RC filtering to the dual operational amplifier unit. The RC filtering unit two includes a resistor R7 and a capacitor C3. One end of the resistor R7 is connected to the isolation amplifier U2, and the other end of the resistor R7 is connected to the capacitor C3 and then connected to the input terminal of the amplification chip U1A.

10. The output-to-ground overcurrent protection circuit for an inverter according to claim 9, wherein: It further includes a filtering unit, and the filtering unit includes filtering capacitors C2, C4, and C6. The filtering capacitor C2 is connected in parallel with the energy storage capacitor C1 and then connected to the isolation amplifier U2. One end of the filtering capacitor C4 is connected to the capacitor C3 and then connected to the input end of the amplification chip U1A. One end of the filtering capacitor C6 is connected to the filtering capacitor C4, and the other end is connected to the output end of the amplification chip U1A.

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