Over-current detection device, frequency converter regenerative braking circuit and frequency converter

Abstract

The utility model discloses an overcurrent detection device, a frequency converter regenerative braking circuit and a frequency converter, and the overcurrent detection device comprises a sampling unit which is used for sampling a current of a to-be-detected circuit and outputting a sampling signal, and the sampling signal corresponds to a voltage proportional to the current of the to-be-detected circuit; the input end of the amplification unit is connected with the output end of the sampling unit, and the amplification unit is used for receiving the sampling signal, amplifying the sampling signal and then outputting an amplified signal; the input end of the RC charging and discharging unit is connected with the output end of the amplifying unit, the charging and discharging unit is charged when receiving the amplifying signal and outputs a first output signal, and the first output signal corresponds to the voltage at the two ends of a capacitor of the RC charging and discharging unit; the input end of the comparison unit is connected with the output end of the charging and discharging unit, and the comparison unit compares the received first output signal with a preset value and outputs a second output signal when the first output signal is larger than or equal to the preset value.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of overcurrent detection, and in particular to an overcurrent detection device, a frequency converter regenerative braking circuit, and a frequency converter. Background Art

[0002] Overcurrent refers to the situation where the current in a circuit exceeds its normal or rated value. When overcurrent occurs in a circuit, the heat, electromagnetic force, etc. generated by it will increase sharply, causing serious damage to the equipment, lines and insulating materials in the circuit, and even causing safety accidents such as fire. The larger the overcurrent, the greater the destructive power it produces. Therefore, in order to reduce this destructive power as quickly as possible and prevent potential safety accidents, the time to cut off the circuit should be inversely proportional to the size of the overcurrent. However, in the protection measures against overcurrent, the traditional analog circuit solution has the same response time when dealing with overcurrents of different sizes. Utility Model Content

[0003] In order to solve the above technical problems, the utility model provides an overcurrent detection device, a frequency converter regenerative braking circuit and a frequency converter.

[0004] In a first aspect, an embodiment of the present application provides an overcurrent detection device, comprising:

[0005] A sampling unit, which is used to sample the current of the circuit to be measured and output a sampling signal, wherein the sampling signal corresponds to a voltage proportional to the current of the circuit to be measured;

[0006] an amplifying unit, whose input end is connected to the output end of the sampling unit, and is used to receive the sampling signal and output an amplified signal after amplifying the sampling signal;

[0007] An RC charge-discharge unit, whose input end is connected to the output end of the amplifying unit, and the charge-discharge unit is charged upon receiving the amplified signal and outputs a first output signal, wherein the first output signal corresponds to the voltage across the capacitor of the RC charge-discharge unit;

[0008] A comparison unit, whose input end is connected to the output end of the charge-discharge unit, compares the received first output signal with a preset value, and outputs a second output signal when the first output signal is greater than or equal to the preset value.

[0009] Optionally, the sampling unit includes a shunt resistor, the shunt resistor is used to be connected in series with the circuit to be measured, and the sampling signal corresponds to the voltage across the shunt resistor.

[0010] Optionally, the overcurrent detection device also includes a high-voltage isolation unit, the input end of the high-voltage isolation unit is connected to the output end of the sampling unit, the output end of the high-voltage isolation unit is connected to the amplification unit, and the high-voltage isolation unit is used to output an isolation signal after isolating the sampling signal.

[0011] Optionally, the amplification unit includes an amplification circuit and a multiplier circuit, the input end of the amplification circuit is connected to the output end of the high-voltage isolation unit, the output end of the amplification circuit is connected to the input end of the multiplier circuit, the amplification circuit is used to receive the isolated signal, and amplify the isolated signal to output a first amplified signal; the multiplier circuit is used to receive the first amplified signal, and multiply the first amplified signal to output a second amplified signal.

[0012] Optionally, the multiplier circuit has a first input terminal and a second input terminal, wherein each input terminal is respectively connected to an output terminal of the amplifier circuit.

[0013] Optionally, the high-voltage isolation unit is an isolation amplification unit, and when the received sampling signal is smaller than a preset threshold, the high-voltage isolation unit outputs an isolation amplification signal.

[0014] Optionally, the second output signal is used to trigger an action of a switch actuator in the circuit to be tested to disconnect the circuit to be tested.

[0015] Optionally, the overcurrent detection device has a first input terminal, a second input terminal and an output terminal, the sampling unit is connected to the circuit to be tested via the first input terminal and the second input terminal, and the second output signal is output via the output terminal.

[0016] In the second aspect, an embodiment of the present application provides a frequency converter regenerative braking circuit, comprising a braking resistor and a switch actuator, characterized in that the frequency converter regenerative braking circuit comprises the overcurrent detection device described in any one of the above items, the sampling unit of the overcurrent detection device is connected in series between the braking resistor and the switch actuator, the frequency converter regenerative braking circuit comprises the above-mentioned current detection device, and the second output signal output by the current detection device is used to trigger the action of the switch actuator to disconnect the frequency converter regenerative braking circuit.

[0017] In a third aspect, an embodiment of the present application provides a frequency converter, which includes the above-mentioned frequency converter regenerative braking circuit.

[0018] The positive and progressive effects of the utility model are:

[0019] The overcurrent detection device, inverter regenerative braking circuit and inverter provided by the present application collect the current in the circuit to be tested through the acquisition unit, and realize different response times under different overload currents after being processed by the analog circuit, that is, the greater the overcurrent after exceeding the preset overcurrent value, the shorter the response time of the overcurrent detection device. The response time of the overcurrent detection device is inversely proportional to the size of the overcurrent, so these serious faults can be identified and responded to more quickly. This quick response helps to reduce equipment damage and prevent accidents from expanding. The present application realizes that the response time is inversely proportional to the size of the overcurrent through an analog circuit, and the circuit is simple, which greatly reduces the design cost and material cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following drawings are only intended to illustrate and explain the present application, and do not limit the scope of the present application.

[0021] Figure 1 A schematic diagram of an overcurrent detection device according to an implementation of an embodiment of the present application is shown;

[0022] Figure 2 A schematic diagram of an amplification unit according to another implementation of an embodiment of the present application is shown;

[0023] Figure 3 A schematic diagram of a frequency converter regenerative braking circuit according to an implementation of an embodiment of the present application is shown;

[0024] Description of reference numerals:

[0025] 10: Overcurrent detection device;

[0026] 101: sampling unit;

[0027] 1011: Shunt resistor;

[0028] 102: high voltage isolation unit;

[0029] 103: amplification unit;

[0030] 1031: amplifier circuit;

[0031] 1032: multiplier circuit;

[0032] 105: RC charging and discharging unit;

[0033] 107: comparison unit;

[0034] 20: Braking resistor;

[0035] 30: Switch actuator. DETAILED DESCRIPTION

[0036] In order to have a clearer understanding of the technical features, purposes and effects of the embodiments of the present application, the specific implementation methods of the embodiments of the present application are now described with reference to the accompanying drawings.

[0037] Overcurrent refers to the situation where the current in a circuit exceeds its normal or rated value. When overcurrent occurs in a circuit, the heat, electromagnetic force, etc. generated by it will increase sharply, causing serious damage to the equipment, lines and insulating materials in the circuit, and even causing safety accidents such as fire. The larger the overcurrent, the greater the destructive power it produces. Therefore, in order to reduce this destructive power as quickly as possible and prevent potential safety accidents, the time to cut off the circuit should be inversely proportional to the size of the overcurrent. However, in the protection measures against overcurrent, the traditional analog circuit solution has the same action time when dealing with overcurrents of different sizes.

[0038] Based on the above problems, the embodiments of the present application provide an overcurrent detection device 10, an inverter regenerative braking circuit and an inverter, which can realize that the circuit cut-off time is inversely proportional to the size of the overcurrent through an analog circuit.

[0039] The specific implementation of the embodiments of the present application is described in detail below with reference to the accompanying drawings.

[0040] Example 1

[0041] Embodiment 1 provides an overcurrent detection device 10, such as Figure 1 As shown, the device includes a sampling unit 101, an amplifying unit 103, an RC charge and discharge unit 105 and a comparing unit 107, wherein the sampling unit 101 is used to sample the current of the circuit to be tested and output a sampling signal, and the sampling signal corresponds to a voltage proportional to the current of the circuit to be tested; the input end of the amplifying unit 103 is connected to the output end of the sampling unit 101, the amplifying unit 103 receives the sampling signal, and outputs the amplified signal after amplifying the received sampling signal; the input end of the RC charge and discharge unit 105 is connected to the output end of the amplifying unit 103, and the charge and discharge unit charges and outputs a first output signal when receiving the amplified signal, and the first output signal corresponds to the voltage across the capacitor of the RC charge and discharge unit 105; the input end of the comparing unit 107 is connected to the output end of the charge and discharge unit, and the comparing unit 107 compares the received first output signal with a preset value, and outputs a second output signal when the first output signal is greater than or equal to the preset value.

[0042] The voltage across the capacitor of the RC charge and discharge unit 105 is related to the time constant and the charging current of the RC charge and discharge unit 105. When the time constant is the same, the greater the charging current, the faster the voltage across the capacitor rises, and the shorter the time it takes for the voltage across the capacitor to reach the preset value. When the voltage across the capacitor reaches the preset value, the comparison unit 107 outputs the second output signal, thereby achieving that the greater the overcurrent after exceeding the preset overcurrent value, the shorter the response time of the overcurrent detection device 10, that is, the response time of the overcurrent detection device 10 is inversely proportional to the magnitude of the overcurrent.

[0043] When a major fault such as a short circuit or overload occurs in the power system, the current will increase rapidly. The overcurrent detection device 10 of the present application collects the current in the circuit to be tested through a collection unit, and realizes different response times under different overload currents after being processed by an analog circuit, that is, the greater the overcurrent after exceeding the preset overcurrent value, the shorter the response time of the overcurrent detection device 10. The response time of the overcurrent detection device 10 is inversely proportional to the size of the overcurrent, so these serious faults can be identified and responded to more quickly. This quick response helps to reduce equipment damage and prevent accidents from expanding. The present application realizes that the response time is inversely proportional to the size of the overcurrent through an analog circuit. The circuit is simple, which greatly reduces the design cost and material cost.

[0044] In some embodiments, the sampling unit 101 includes a shunt resistor 1011, which is connected in series with the circuit to be measured. The currents passing through each load in the series circuit are equal, so the current of the circuit to be measured is sampled through the shunt resistor 1011, and the sampling signal corresponds to the voltage across the shunt resistor 1011. The solution of using the shunt resistor 1011 for sampling has high sampling accuracy, simple circuit and good stability.

[0045] In some embodiments, the overcurrent detection device 10 further includes a high-voltage isolation unit 102, the input end of the high-voltage isolation unit 102 is connected to the output end of the sampling unit 101, the output end of the high-voltage isolation unit 102 is connected to the amplification unit 103, and the high-voltage isolation unit 102 is used to output an isolation signal after isolating the sampling signal. The high-voltage isolation unit can isolate the high voltage to prevent the high voltage from damaging the overcurrent detection device.

[0046] Specifically, when the overcurrent detection device 10 is used in the inverter regenerative braking circuit, the sampling unit is connected in series between the DC bus and the braking resistor. In order to avoid the high voltage on the DC bus, a high-voltage isolation unit is used to isolate the high voltage, thereby protecting the control circuit and reducing losses.

[0047] In some embodiments, the amplifying unit 103 includes an amplifying circuit 1031 and a multiplier circuit 1032, the input end of the amplifying circuit 1031 is connected to the output end of the high-voltage isolation unit 102, the output end of the amplifying circuit 1031 is connected to the input end of the multiplier circuit 1032, the amplifying circuit 1031 is used to receive the isolated signal, and amplify the isolated signal to output a first amplified signal; the multiplier circuit 1032 is used to receive the first amplified signal, and multiply the first amplified signal to output a second amplified signal.

[0048] Optionally, the amplifier circuit 1031 is a differential amplifier circuit.

[0049] In some implementations, the multiplier circuit 1032 has a first input terminal and a second input terminal, wherein each input terminal is respectively connected to an output terminal of the amplifier circuit 1031 .

[0050] The two input terminals of the multiplier are respectively connected to the output terminals of the amplifier circuit 1031 , so as to multiply the first amplified signal by itself, and the first amplified signal can be greatly amplified without performing additional complex calculations, thereby increasing the discrimination between different current values.

[0051] The resistance of the shunt resistor 1011 is relatively small, usually in the micro-Ω level, and the sampling signal corresponds to the voltage across the shunt resistor 1011. In order to increase the discrimination between different currents, the sampling signal needs to be significantly amplified. The overcurrent monitoring device of this embodiment, based on the use of the amplifier circuit 1031 to amplify the sampling signal once, performs a square operation through the multiplier circuit, thereby significantly amplifying the sampling signal.

[0052] In some implementations, the high-voltage isolation unit 102 is an isolation amplifier circuit, which performs isolation and amplification processing on the sampling signal and then outputs an isolation amplified signal.

[0053] In some implementations, the isolation amplifier circuit includes an optocoupler.

[0054] In an exemplary implementation based on this embodiment, the current detection device includes a sampling unit 101, an isolation amplifier circuit, an amplifier unit 103, an RC charge and discharge unit 105, and a comparison unit 107, wherein the amplifier unit 103 includes a differential amplifier circuit 1031 and a multiplier circuit 1032. The sampling unit 101 includes a shunt resistor 1011, two input terminals and two output terminals, the isolation amplifier circuit has two input terminals and two output terminals, the differential amplifier circuit 1031 has two input terminals and one output terminal, and the multiplier circuit 1032 has two input terminals and one output terminal. The shunt resistor 1011 is connected in series with the circuit under test through the two input terminals of the sampling unit 101, the two input terminals of the isolation amplifier circuit are respectively connected to the two input terminals of the differential amplifier circuit 1031, the two input terminals of the multiplier circuit 1032 are respectively connected to the output terminal of the differential amplifier circuit 1031, the input terminal of the RC charge and discharge circuit is connected to the output terminal of the multiplier circuit 1032, and the output terminal of the RC charge and discharge circuit is connected to the input terminal of the comparison unit 107. The sampling unit 101 samples the current of the circuit to be tested and outputs a sampling signal of a voltage proportional to the current of the circuit to be tested to the isolation amplifier circuit. The isolation amplifier circuit performs isolation amplification processing on the sampling signal to obtain an isolation amplification signal and outputs it to the differential amplifier circuit 1031. The differential amplifier circuit 1031 performs amplification processing on the received isolation amplification signal to obtain a first amplification signal and outputs it to the multiplier circuit 1032. The multiplier circuit 1032 multiplies the two first amplification signals to obtain a second amplification signal and outputs it to the RC charge and discharge unit 105. The RC charge and discharge unit 105 charges the capacitor when receiving the second amplification signal, and outputs a first output signal to the comparison unit 107. The first output signal corresponds to the voltage across the capacitor of the RC charge and discharge unit 105. The comparison unit 107 compares the first output signal with a preset value, and outputs a second output signal when the first output signal reaches the preset value.

[0055] In some embodiments, the second output signal is used to trigger the action of the switch actuator 30 in the circuit under test to disconnect the circuit under test.

[0056] In some embodiments, the overcurrent detection device 10 has a first input terminal, a second input terminal and an output terminal, the sampling unit 101 is connected to the circuit to be tested via the first input terminal and the second input terminal, and the second output signal is output via the output terminal.

[0057] Through the two input terminals and one output terminal of the current detection device 10 , it is convenient to connect the current protection device to a circuit that needs to perform overcurrent detection. The current protection device is simple to use and has a wide range of applications.

[0058] Example 2

[0059] Embodiment 2 provides a frequency converter regenerative braking circuit. Figure 3 As shown, the inverter regenerative braking circuit includes a braking resistor 20, an overcurrent monitoring device in Embodiment 1, and a switch actuator 30. Figure 3 As shown, the sampling unit 101 of the overcurrent detection device 10 is connected between the braking resistor 20 and the switch actuator 30 to sample the current of the inverter regenerative braking circuit, and the output end of the overcurrent detection device 10 outputs a second output signal, which is used to trigger the action of the inverter regenerative braking circuit switch actuator 30 to disconnect the circuit to be tested.

[0060] During the process of motor deceleration, braking or lowering of heavy objects with potential loads, the motor may enter a regenerative power generation state and generate a large amount of regenerative electric energy. If this part of the regenerative electric energy is not consumed in time, it will directly act on the DC circuit part of the inverter, which may damage the inverter. The braking resistor 20 in the inverter regenerative braking circuit is used to consume this part of the electric energy. In order to avoid damage to the equipment caused by excessive regenerative electric energy and the inability to fully consume the braking resistor 20, the inverter regenerative braking circuit of the present application uses an overcurrent detection device 10 to make the action time of the switch actuator 30 inversely proportional to the size of the overcurrent exceeding the preset value, that is, the larger the overcurrent after exceeding the preset overcurrent value, the shorter the response time of the current detection device.

[0061] Example 3

[0062] Embodiment 3 provides a frequency converter, which includes the frequency converter regenerative braking circuit as in Embodiment 2.

[0063] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0064] Nouns and pronouns relating to persons in this patent application are not limited to a specific gender.

[0065] The above description is only an illustrative specific implementation of the embodiment of the present application, and is not intended to limit the scope of the embodiment of the present application. Any equivalent changes, modifications and combinations made by any technician in this field without departing from the concept and principle of the embodiment of the present application should fall within the scope of protection of the embodiment of the present application.

Claims

1. An overcurrent detection device (10), characterized in that: include: A sampling unit (101), which is used to sample the current of the circuit to be tested and output a sampling signal, wherein the sampling signal corresponds to a voltage proportional to the current of the circuit to be tested; an amplifying unit (103), whose input end is connected to the output end of the sampling unit (101), and is used to receive the sampling signal and output an amplified signal after amplifying the sampling signal; an RC charging and discharging unit (105), whose input end is connected to the output end of the amplifying unit (103); the RC charging and discharging unit (105) is charged upon receiving the amplified signal, and outputs a first output signal, wherein the first output signal corresponds to the voltage across the capacitor of the RC charging and discharging unit (105); A comparison unit (107) has an input end connected to the output end of the RC charge and discharge unit (105), and the comparison unit (107) compares the received first output signal with a preset value, and outputs a second output signal when the first output signal is greater than or equal to the preset value.

2. The overcurrent detection device (10) according to claim 1, characterized in that: The sampling unit (101) comprises a shunt resistor (1011), the shunt resistor (1011) is used to be connected in series with the circuit to be tested, and the sampling signal corresponds to the voltage across the two ends of the shunt resistor (1011).

3. The overcurrent detection device (10) according to claim 2, characterized in that: The overcurrent detection device (10) further comprises a high-voltage isolation unit (102), the input end of the high-voltage isolation unit (102) being connected to the output end of the sampling unit (101), the output end of the high-voltage isolation unit (102) being connected to the amplification unit (103), and the high-voltage isolation unit (102) being used to output an isolation signal after isolating the sampling signal.

4. The overcurrent detection device (10) according to claim 3, characterized in that: The amplifying unit (103) comprises an amplifying circuit (1031) and a multiplier circuit (1032); the input end of the amplifying circuit (1031) is connected to the output end of the high-voltage isolation unit (102); the output end of the amplifying circuit (1031) is connected to the input end of the multiplier circuit (1032); the amplifying circuit (1031) is used to receive the isolation signal, and amplify the isolation signal to output a first amplified signal; the multiplier circuit (1032) is used to receive the first amplified signal, and multiply the first amplified signal to output a second amplified signal.

5. The overcurrent detection device (10) according to claim 4, characterized in that: The multiplier circuit (1032) has a first input terminal and a second input terminal, wherein each input terminal is respectively connected to the output terminal of the amplifier circuit (1031).

6. The overcurrent detection device (10) according to claim 5, characterized in that: The high-voltage isolation unit (102) is an isolation amplifier circuit, which performs isolation amplification processing on the sampling signal and then outputs an isolation amplified signal.

7. The overcurrent detection device (10) according to any one of claims 1 to 6, characterized in that: The second output signal is used to trigger the action of a switch actuator (30) in the circuit to be tested to disconnect the circuit to be tested.

8. The overcurrent detection device (10) according to claim 7, characterized in that: The overcurrent detection device (10) has a first input end, a second input end and an output end, the sampling unit (101) is connected to the circuit to be tested via the first input end and the second input end, and the second output signal is output via the output end.

9. A frequency converter regenerative braking circuit, comprising a braking resistor (20) and a switch actuator (30), characterized in that: The inverter regenerative braking circuit also includes an overcurrent detection device (10) as described in any one of claims 1 to 8, a sampling unit (101) of the overcurrent detection device (10) is connected in series between the braking resistor (20) and the switch actuator (30), and a second output signal output by the current detection device (10) is used to trigger the action of the switch actuator (30) to disconnect the inverter regenerative braking circuit.

10. A frequency converter, characterized in that: It comprises the inverter regenerative braking circuit as claimed in claim 9.

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