Circuit for over-current protection of frequency converter bus based on isolation comparator

Abstract

The utility model discloses a circuit for overcurrent protection of a frequency converter bus based on an isolation comparator, and the circuit comprises an adjusting unit which is used for adjusting a resistor parameter to set an overcurrent protection threshold value; and the isolation comparator U12 is used for obtaining an over-current protection threshold value, comparing the over-current protection threshold value with the input voltage and then outputting a level signal for over-current protection. According to the circuit for over-current protection of the frequency converter bus based on the isolation comparator, over-current protection of the frequency converter bus is realized through a hardware circuit, and DSP resources are not occupied; the bus current is detected through the isolation comparator, so that overcurrent protection is realized, the circuit is simple, the number of used components is small, and the cost advantage is relatively outstanding.

Description

Technical Field

[0001] The utility model relates to the technical field of inverter overcurrent protection, in particular to a circuit for inverter bus overcurrent protection based on an isolation comparator. Background Art

[0002] Generally speaking, inverters use two main methods for overcurrent and short-circuit protection: software protection and hardware protection. Software overcurrent protection is implemented using algorithms and logic built into the main control chip. Software overcurrent protection typically involves the following steps: 1. Current data reading: The main control chip uses a built-in analog-to-digital converter (ADC) to read the current data sampled by the current detection circuit. This data is typically provided to the main control chip in the form of an analog voltage. 2. Conversion to digital current values: Based on the characteristics of the hardware-designed current detection circuit, the ADC converts the analog voltage into a digital current value. The converted digital current value can be processed and compared within the main control chip. 3. Overcurrent detection logic: The main control chip compares the current value against the overcurrent threshold specified in the design calibration scheme (e.g., twice the peak value of the rated output current). If the digital current value exceeds the overcurrent threshold, an overcurrent condition is detected. 4. Triggering protective measures: Once an overcurrent condition is detected, the main control chip triggers appropriate protective measures, such as suspending the output signal or disabling the emergency stop function, to protect the inverter and related equipment. Overcurrent protection implemented via software consumes DSP resources and is less responsive than hardware protection. Among the inverter hardware protection methods, locking the IGBT output is a crucial measure. The IGBT is the most critical component in the inverter's output stage, and its damage can lead to failure or damage to the entire system. Therefore, promptly locking the IGBT output is essential when overcurrent or short circuit conditions occur.

[0003] Most current inverter overcurrent protection utilizes the inverse time protection principle. This uses a Hall effect element as a detection element to convert the output current into a voltage signal, which is then amplified and detected by an op amp. The amplified three-phase voltage undergoes half-wave rectification to create a composite three-phase voltage signal. This composite voltage signal is used to detect overcurrent. This hardware-based overcurrent protection method is complex, requires numerous components, and is relatively costly. Summary of the Invention

[0004] The purpose of the utility model is to provide a circuit for overcurrent protection of a frequency converter bus based on an isolation comparator.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a circuit for overcurrent protection of a frequency converter bus based on an isolation comparator, comprising:

[0006] an adjusting unit, configured to adjust a resistance parameter to set an overcurrent protection threshold; and

[0007] The isolation comparator U12 is used to obtain the overcurrent protection threshold and compare it with the input voltage, and then output a level signal to perform overcurrent protection.

[0008] Furthermore, the model of the isolation comparator U12 is NSI22C12.

[0009] Furthermore, the adjustment unit includes resistors R127, R105, and a dip switch TP. The resistors R127, R105, and the dip switch TP are connected in parallel and then connected to the isolation comparator U12.

[0010] Furthermore, a power supply unit for supplying power to the isolation comparator U12 is included. The power supply unit includes a resistor R70 and a voltage-stabilizing diode ZD1 . The resistor R2 is connected to the anode of the voltage-stabilizing diode ZD1 and then connected to the isolation comparator U12 .

[0011] Furthermore, a sampling unit is included. The sampling unit includes resistors RA1, RA2, RA7, and RA8. The resistors RA1 and RA2 are connected in parallel and then connected to the isolation comparator U12.

[0012] Furthermore, it also includes an RC filter unit for RC filtering the input of the isolation comparator U12. The RC filter unit 2 includes a resistor R104 and a capacitor C40. One end of the resistor R104 is connected to the sampling unit, and the other end of R7 is connected to the capacitor C3 and then connected to the isolation comparator U12.

[0013] Furthermore, a pull-up resistor R68 and a pull-down resistor R69 are included. One end of the pull-up resistor R68 is connected to one end of the pull-down resistor R69 and then connected to the isolation comparator U12.

[0014] It can be seen from the above technical solution that the utility model has the following beneficial effects:

[0015] The utility model realizes the inverter bus overcurrent protection through hardware circuit, does not occupy DSP resources; detects the bus current through the isolation comparator, thereby realizing overcurrent protection, has a simple circuit, uses few components, and has a prominent cost advantage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the overall circuit diagram of the utility model. DETAILED DESCRIPTION

[0017] In the description of this utility model, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," "the other end," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this utility model and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "provided with," "connected," etc. should be understood in a broad sense. For example, "connected" can mean a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be internal communication between two components. Those skilled in the art will be able to understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0019] 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 embodiments described 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 making creative efforts are within the scope of protection of the present invention.

[0020] See also Figure 1 The utility model provides a circuit for inverter busbar overcurrent protection based on an isolated comparator. The circuit includes an adjustment unit and an isolated comparator U12. The model of the isolated comparator U12 is NSI22C12. The adjustment unit includes resistors R127, R105, and a DIP switch TP. The resistors R127, R105, and the DIP switch TP are connected in parallel to the isolated comparator U12. The overcurrent protection threshold can be set by adjusting the resistor parameters. Resistors R127 and R105 serve as reference resistors. The isolated comparator U12 has a built-in 100μA current source. The isolated comparator U12 obtains the overcurrent protection threshold, compares it with the input voltage, and outputs a level signal to perform overcurrent protection. Specifically, when the reference pin resistor value is set to 2k, the reference pin voltage is 200mV. When the input is greater than 200mV, pin 6 of the isolated comparator U12 outputs a low level, the VCE signal is pulled low, and the DSP detects the change in the VCE signal level, thereby implementing protection. Pin 7 of the isolated comparator U12 is the latch enable (active high, if not used, this pin can be left floating or connected to GND2).

[0021] The system also includes a power supply unit for supplying 5.1V voltage to the primary side of the isolation comparator U12. The power supply unit includes a current limiting resistor R70 and a voltage stabilizing diode ZD1 (5.1V). The resistor R2 is connected to the positive electrode of the voltage stabilizing diode ZD1 and then connected to the isolation comparator U12.

[0022] The system also includes a sampling unit, which includes resistors RA1, RA2, RA7, and RA8. These resistors RA1 and RA2 are connected in parallel and connected to an isolation comparator U12. The sampling unit samples the current between the negative busbars N- and N1-, connected in series with RA1, RA2, RA7, and RA8 (typically a few milliohms). The converted voltage signal is input to pins 2 and 4 of the isolation comparator U12.

[0023] It also includes an RC filter unit, which performs RC filtering on the input of the isolation comparator U12. The RC filter unit 2 includes a resistor R104 and a capacitor C40. One end of the resistor R104 is connected to the sampling unit, and the other end of R7 is connected to the capacitor C3 and then connected to the isolation comparator U12.

[0024] It also includes a pull-up resistor R68 and a pull-down resistor R69. One end of the pull-up resistor R68 is connected to one end of the pull-down resistor R69 and then connected to the isolation comparator U12.

[0025] The entire circuit implements inverter bus overcurrent protection through hardware, without occupying DSP resources; overcurrent protection is achieved by detecting bus current through an isolation comparator. The circuit is simple, uses few components, and has a prominent cost advantage.

[0026] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A circuit for overcurrent protection of a frequency converter bus based on an isolation comparator, characterized in that: include: an adjusting unit, configured to adjust a resistance parameter to set an overcurrent protection threshold; and The isolation comparator U12 is used to obtain the overcurrent protection threshold and compare it with the input voltage, and then output a level signal for overcurrent protection; The regulating unit includes resistors R127, R105, and a dip switch TP, which are connected in parallel and then connected to the isolation comparator U12; It also includes a sampling unit, which includes resistors RA1, RA2, RA7, and RA8. The resistors RA1 and RA2 are connected in parallel and then connected to the isolation comparator U12; It also includes an RC filter unit for RC filtering the input of the isolation comparator U12. The RC filter unit 2 includes a resistor R104 and a capacitor C40. One end of the resistor R104 is connected to the sampling unit, and the other end of R7 is connected to the capacitor C3 and then connected to the isolation comparator U12.

2. The circuit for overcurrent protection of a frequency converter busbar based on an isolation comparator according to claim 1, characterized in that: The model of the isolation comparator U12 is NSI22C12.

3. The circuit for overcurrent protection of a frequency converter bus based on an isolation comparator according to claim 1, characterized in that: The system further includes a power supply unit for supplying power to the isolation comparator U12 . The power supply unit includes a resistor R70 and a voltage-stabilizing diode ZD1 . The resistor R2 is connected to the anode of the voltage-stabilizing diode ZD1 and then connected to the isolation comparator U12 .

4. The circuit for overcurrent protection of a frequency converter bus based on an isolated comparator according to claim 1, characterized in that: It also includes a pull-up resistor R68 and a pull-down resistor R69. One end of the pull-up resistor R68 is connected to one end of the pull-down resistor R69 and then connected to the isolation comparator U12.

Images