Frequency converter drive circuit with backup emergency brake protection and frequency converter

Abstract

The invention discloses a frequency converter driving circuit with backup emergency braking protection, which comprises a frequency converter MCU (Microprogrammed Control Unit), and a rectifying circuit, a filter circuit, an energy consumption braking circuit and an inverter circuit which are connected in sequence, the energy consumption braking circuit comprises a voltage detection comparison circuit, a service braking circuit and a standby braking circuit, and by introducing the standby braking circuit, when the service braking circuit fails due to overheat of a resistor or other reasons, the frequency converter MCU can be rapidly switched to the standby braking circuit, so that the continuous effectiveness of the braking function is ensured; the redundancy design obviously enhances the reliability and safety of the system, so that the frequency converter can still realize quick braking of the motor after a service braking circuit fails, the frequency converter is prevented from being damaged by bus direct-current voltage, the motor is ensured to stop quickly and stably in a scene required by working of the motor, and the service life of the motor is prolonged. Backup emergency braking protection of the frequency converter is achieved, and the accuracy and reliability of the braking process are improved.

Description

Technical Field

[0001] The invention relates to the technical field of frequency converters, and in particular to a frequency converter drive circuit and a frequency converter with backup emergency braking protection. Background Art

[0002] The inverter braking circuit is an important component of the inverter, which allows the motor to stop quickly and smoothly when needed. The working principle of the inverter braking circuit is based on the regenerative power generation state of the motor. When the motor speed exceeds the set value during deceleration or parking due to a large inertia load, the motor enters the power generation state, and the braking circuit starts to work. Specifically, the power generation energy of the motor is fed back to the DC circuit of the inverter through the rectifier circuit, which may cause the DC voltage to increase abnormally. In order to prevent the DC voltage from being too high, the braking circuit is connected to the DC circuit to convert the voltage increment into the effective power consumption of the braking resistor, thereby achieving rapid braking.

[0003] Currently, for frequency conversion systems, rapid motor braking is achieved by connecting a high-power resistor in series on the bus. However, since the resistor will be powered on after the motor enters the energy-consuming braking state, the resistor is easily burned out after multiple continuous braking. At this time, the braking circuit of the frequency converter will fail, resulting in the frequency converter being unable to achieve rapid motor braking before overhaul and maintenance.

[0004] The Chinese patent with publication number CN219843424U discloses a brake protection circuit applied to a frequency converter, which performs overcurrent detection through a second circuit and outputs an overcurrent detection signal to a control chip, and the control chip disconnects the output load, or performs through-detection through a third circuit and outputs a through-detection signal to a control chip, and the control chip disconnects the output load, thereby protecting the brake circuit from burning to prevent accidents such as fire. Although the brake protection circuit applied to the frequency converter controls the circuit on and off of the brake circuit by detecting the electrical signal of the brake circuit to achieve the purpose of protecting the brake circuit, if the brake circuit is cut off during the motor parking process, not only the motor cannot brake quickly as expected, resulting in loss of position control accuracy (when the frequency converter is applied to a servo system) or extended emergency stop time (when the frequency converter is applied to high-speed rotating equipment), increasing safety hazards, but also the sharply increased DC voltage on the frequency converter drive circuit may trigger the frequency converter overvoltage protection, and even directly damage the bus capacitor or power module.

[0005] In view of this, it is urgent to design a frequency converter drive circuit with backup emergency braking protection. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a frequency converter drive circuit and a frequency converter with backup emergency brake protection.

[0007] In a first aspect of the present invention, there is provided a frequency converter drive circuit with backup emergency brake protection, comprising a frequency converter MCU and a rectifier circuit, a filter circuit, an energy-consuming brake circuit and an inverter circuit connected in sequence, wherein both ends of the filter circuit are the bus DC voltage of the frequency converter; The energy consumption braking circuit comprises a voltage detection and comparison circuit, a normal braking circuit and a standby braking circuit, wherein the normal braking circuit and the standby braking circuit are respectively connected between the bus DC voltages; The input end of the voltage detection comparison circuit is connected to the bus DC voltage, and controls the conduction of the common braking circuit according to the bus DC voltage and the reference voltage; The voltage detection comparison circuit and the common braking circuit are respectively connected to the voltage detection input terminal of the inverter MCU, and the signal output terminal of the inverter MCU is connected to the backup braking circuit. The inverter MCU controls the conduction of the backup braking circuit according to the bus DC voltage and the braking circuit voltage of the common braking circuit.

[0008] Based on the first aspect, in a possible implementation manner, the voltage detection comparison circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a voltage comparator, a first transistor and a second transistor; the first resistor and the second resistor are connected in series, the first end of the first resistor and the first end of the second resistor are respectively connected to the bus DC voltage, the second end of the second resistor is connected to the non-inverting input end of the voltage comparator, the inverting input end of the voltage comparator is connected to the reference voltage, the output end of the voltage comparator is respectively connected to the first end of the third resistor and the first end of the fourth resistor, the second end of the fourth resistor is respectively connected to the base of the first transistor and the base of the second transistor, the collector of the first transistor and the second end of the third resistor are both connected to a high level, the collector of the second transistor is connected to a low level, the emitter of the first transistor and the emitter of the second transistor are both connected to the first end of the fifth resistor, and the second end of the fifth resistor is connected to the control end of the common braking circuit.

[0009] Based on the first aspect, in a possible implementation, the common braking circuit includes a first braking resistor, a second braking resistor and a first power device, the first end of the first braking resistor and the first end of the second braking resistor are respectively connected to the bus DC voltage, the second end of the first braking resistor and the second end of the second braking resistor are respectively connected to the first end and the second end of the first power device, and the control end of the first power device is connected to the second end of the fifth resistor.

[0010] Based on the first aspect, in a possible implementation manner, the second end of the second resistor and the second end of the second braking resistor are respectively connected to a voltage detection input end of the inverter MCU.

[0011] Based on the first aspect, in a possible implementation manner, a resistance ratio of the first braking resistor to the second braking resistor ranges from 10:1 to 40:1.

[0012] Based on the first aspect, in a possible implementation, the backup braking circuit includes a third braking resistor and a second power device, the first end of the third braking resistor and the first end of the second power device are respectively connected to the bus DC voltage, the second end of the third braking resistor is connected to the second end of the second power device, and the control end of the second power device is connected to the signal output end of the inverter MCU.

[0013] Based on the first aspect, in a possible implementation manner, the first power device and the second power device are IGBTs or MOS tubes.

[0014] Based on the first aspect, in a possible implementation, a current limiting starting circuit is further provided between the rectifier circuit and the filter circuit, and the current limiting starting circuit includes a starting resistor and a relay. The starting resistor is connected in series to the output loop of the rectifier circuit, and the normally open contacts of the relay are connected in parallel at both ends of the starting resistor.

[0015] Based on the first aspect, in a possible implementation, the filtering circuit includes a first diode, a first inductor and a first capacitor, the positive electrode of the first diode and the first end of the first capacitor are respectively connected to the output end of the rectifier circuit, the negative electrode of the first diode is respectively connected to one end of the current limiting starting circuit and the first end of the first inductor, and the second end of the first capacitor is connected to the second end of the first inductor.

[0016] In a second aspect of the present invention, a frequency converter is provided, comprising the above-mentioned frequency converter drive circuit with backup emergency brake protection.

[0017] The working principle of the inverter drive circuit with backup emergency brake protection in this technical solution is: When the common braking circuit is normal, when the motor makes the DC circuit voltage of the inverter rise during the stopping process, when the voltage detection and comparison circuit detects that the bus DC voltage exceeds the set value, the voltage detection and comparison circuit outputs a common braking conduction signal to the common braking circuit, and the common braking circuit is turned on to perform energy-consuming braking, so that the motor stops quickly; When the common braking circuit fails, when the motor causes the DC circuit voltage of the inverter to rise during the parking process, the voltage detection and comparison circuit detects and feeds back the information that the bus DC voltage exceeds the set value to the inverter MCU. At the same time, the common braking circuit feeds back the information that it is not turned on normally to the inverter MCU. At this time, the inverter MCU sends a backup braking conduction signal to the backup braking circuit, and the backup braking circuit is turned on to perform energy-consuming braking, so that the motor stops quickly.

[0018] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: In the traditional braking method, high-power resistors are easily burned out after continuous braking, causing the braking circuit to fail. The present invention introduces a backup braking circuit. When the common braking circuit fails due to resistor overheating or other reasons, the inverter MCU can quickly switch to the backup braking circuit to ensure the continued effectiveness of the braking function. This redundant design significantly enhances the reliability and safety of the system, so that the inverter can still achieve rapid braking of the motor after the common braking circuit fails, avoiding damage to the inverter by the bus DC voltage, and ensuring that the motor stops quickly and smoothly in the scenario required for its operation, thereby realizing the backup emergency braking protection of the inverter.

[0019] The present invention monitors the bus DC voltage in real time through a voltage detection and comparison circuit and compares it with a reference voltage, thereby controlling the conduction of a common braking circuit; at the same time, the inverter MCU controls the conduction of a standby braking circuit according to the bus DC voltage and the braking circuit voltage of the common braking circuit. This intelligent redundant control method not only improves the accuracy and reliability of the braking process, but also can judge the current potential fault by monitoring the circuit information, providing a basis for preventive maintenance of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a block diagram of a frequency converter drive circuit with backup emergency brake protection according to an embodiment of the present invention.

[0021] Figure 2 This is a topological diagram of a frequency converter drive circuit with backup emergency brake protection according to an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the energy-consuming braking circuit according to an embodiment of the present invention.

[0023] Figure 4 This is another schematic diagram of an energy-consuming braking circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0025] Example 1

[0026] Combined with Figure 1 To Attachment Figure 2 The technical solution of the present invention is a frequency converter drive circuit with backup emergency brake protection, including a frequency converter MCU10 and a rectifier circuit 20, a filter circuit 30, an energy consumption brake circuit 40 and an inverter circuit 50 connected in sequence, wherein the two ends of the filter circuit 30 are the bus DC voltage Ud of the frequency converter 10, The energy consumption braking circuit 40 includes a voltage detection and comparison circuit 41, a normal braking circuit 42 and a backup braking circuit 43, and the normal braking circuit 42 and the backup braking circuit 43 are respectively connected between the bus DC voltage Ud; The input end of the voltage detection comparison circuit 41 is connected to the bus DC voltage Ud, and controls the conduction of the common braking circuit 42 according to the bus DC voltage Ud and the reference voltage Vref; The voltage detection comparison circuit 41 and the common braking circuit 42 are respectively connected to the voltage detection input end of the inverter MCU10, and the signal output end of the inverter MCU10 is connected to the backup braking circuit 43. The inverter MCU10 controls the conduction of the backup braking circuit 43 according to the bus DC voltage Ud and the braking circuit voltage of the common braking circuit 42.

[0027] In this embodiment, the voltage detection comparison circuit 41 sends a common braking conduction signal to the common braking circuit 42 by comparing the bus DC voltage Ud with the reference voltage Vref; wherein the reference voltage Vref is obtained through the inverter power supply circuit, which is not further explained in this embodiment and does not affect the implementation of this technical solution.

[0028] In this embodiment, the backup brake circuit 43 is turned on by the backup brake conduction signal sent by the inverter MCU10, and the conditions for triggering its action are: the voltage detection comparison circuit 41 feeds back to the inverter MCU10 the information that the bus DC voltage Ud exceeds the set value (at this time, the common brake circuit 42 should be turned on), and detects that the common brake circuit 42 is not turned on. At the same time, when the backup brake circuit 43 is put into the backup emergency brake to quickly stop the motor for protection, the inverter displays a warning of energy consumption brake maintenance, reminding the inverter that the brake resistor in the common brake circuit 42 needs to be replaced.

[0029] In this embodiment, the working principle of the inverter drive circuit with backup emergency brake protection of this technical solution is: When the common braking circuit 42 is normal, when the motor causes the DC circuit voltage of the inverter to rise during the stopping process, and the voltage detection and comparison circuit 41 detects that the bus DC voltage Ud exceeds the set value, the voltage detection and comparison circuit 41 outputs a common braking conduction signal to the common braking circuit 42, and the common braking circuit 42 is turned on to perform energy-consuming braking, so that the motor stops quickly; When the common braking circuit 42 fails, when the motor causes the DC circuit voltage of the inverter to rise during the parking process, the voltage detection comparison circuit 41 detects and feeds back the information that the bus DC voltage Ud exceeds the set value to the inverter MCU10. At the same time, the common braking circuit 42 feeds back the information that it is not turned on normally to the inverter MCU10. At this time, the inverter MCU10 sends a backup braking turn-on signal to the backup braking circuit 43. The backup braking circuit 43 is turned on to perform energy-consuming braking, so that the motor stops quickly.

[0030] In this embodiment, as shown in the attached Figure 3 and attached Figure 4As shown, the voltage detection comparison circuit 41 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a voltage comparator U1, a first transistor Q1 and a second transistor Q2; the first resistor R1 and the second resistor R2 are connected in series, the first end of the first resistor R1 and the first end of the second resistor R2 are respectively connected to the bus DC voltage, the second end of the second resistor R2 is connected to the non-inverting input end of the voltage comparator U1, the inverting input end of the voltage comparator U1 is connected to the reference voltage, and the output end of the voltage comparator U1 is connected to the reference voltage. The first end of the third resistor R3 and the first end of the fourth resistor R4 are respectively connected, the second end of the fourth resistor R4 is respectively connected to the base of the first transistor Q1 and the base of the second transistor Q2, the collector of the first transistor Q1 and the second end of the third resistor R3 are both connected to a high level +VCC, the collector of the second transistor Q2 is connected to a low level -VCC, the emitter of the first transistor Q1 and the emitter of the second transistor Q2 are both connected to the first end of the fifth resistor R5, and the second end of the fifth resistor R5 is connected to the control end of the common braking circuit.

[0031] In this embodiment, as shown in the attached Figure 3 and attached Figure 4 As shown, the common braking circuit 42 includes a first braking resistor Rd1, a second braking resistor Rd2 and a first power device Q1, the first end of the first braking resistor Rd1 and the first end of the second braking resistor Rd2 are respectively connected to the bus DC voltage, the second end of the first braking resistor Rd1 and the second end of the second braking resistor Rd2 are respectively connected to the first end and the second end of the first power device Q1, and the control end of the first power device Q1 is connected to the second end of the fifth resistor R5.

[0032] In this embodiment, when the bus DC voltage Ud exceeds the set value, the voltage across the second resistor R2 is greater than the reference voltage Vref, and the output end of the voltage comparator U1 outputs a high level, driving the first transistor Q1 to turn on, thereby controlling the first power device Q1 to turn on, so that the common braking circuit 42 works to perform energy-consuming braking; when the bus DC voltage Ud does not exceed the set value, the voltage across the second resistor R2 is less than the reference voltage Vref, the output end of the voltage comparator U1 outputs a low level, the first transistor Q1 is turned off, and the first power device Q1 is turned off.

[0033] In this embodiment, two braking resistors are provided on the common braking circuit 42 to detect whether the common braking circuit 42 performs energy-consuming braking and to provide feedback on the working status of the common braking circuit 42 .

[0034] In this embodiment, when the first power device Q1 is turned on, both the first braking resistor Rd1 and the second braking resistor Rd2 are turned on and generate heat.

[0035] In this embodiment, the second end of the second resistor R2 and the second end of the second braking resistor Rd2 are respectively connected to the voltage detection input end of the inverter MCU10, so that the inverter MCU10 obtains the bus DC voltage Ud signal and the braking circuit voltage signal of the common braking circuit 42.

[0036] In this embodiment, the resistance ratio of the first braking resistor Rd1 to the second braking resistor Rd2 is in the range of 10:1 to 40:1. When the common braking circuit 42 is working, the first braking resistor Rd1 bears most of the bus DC voltage Ud, so that the voltage applied to the second braking resistor Rd2 is at a lower level, thereby avoiding affecting the inverter MCU10.

[0037] In this embodiment, as shown in the attached Figure 3 and attached Figure 4 As shown, the backup braking circuit 43 includes a third braking resistor Rd3 and a second power device Q2, the first end of the third braking resistor Rd3 and the first end of the second power device Q2 are respectively connected to the bus DC voltage, the second end of the third braking resistor Rd3 is connected to the second end of the second power device Q2, and the control end of the second power device Q2 is connected to the signal output end of the inverter MCU10.

[0038] In this embodiment, as shown in the attached Figure 3 , the first power device Q1 and the second power device Q2 are MOS tubes; the drain of the first power device Q1 is connected to the second end of the first braking resistor Rd1, the source of the first power device Q1 is connected to the second end of the second braking resistor Rd2, and the gate of the first power device Q1 is connected to the second end of the resistor R5; the drain of the second power device Q2 is connected to the second end of the third braking resistor Rd3, the source of the second power device Q2 and the first end of the third braking resistor Rd3 are connected to the bus DC voltage Ud, and the gate of the second power device Q2 is connected to the signal output end of the inverter MCU10.

[0039] In this embodiment, as shown in the attached Figure 4, the first power device Q1 and the second power device Q2 are IGBTs; the collector of the first power device Q1 is connected to the second end of the first braking resistor Rd1, the emitter of the first power device Q1 is connected to the second end of the second braking resistor Rd2, and the gate of the first power device Q1 is connected to the second end of the resistor R5; the collector of the second power device Q2 is connected to the second end of the third braking resistor Rd3, the emitter of the second power device Q2 and the first end of the braking resistor Rd3 are connected to the bus DC voltage Ud, and the gate of the second power device Q2 is connected to the signal output end of the inverter MCU10.

[0040] In this embodiment, a current limiting starting circuit 60 is further provided between the rectifier circuit 20 and the filter circuit 30. The current limiting starting circuit 60 includes a starting resistor Rc and a relay KM. The starting resistor Rc is connected in series to the output circuit of the rectifier circuit 20, and the normally open contacts of the relay KM are connected in parallel to both ends of the starting resistor Rc.

[0041] In this embodiment, the filter circuit 30 includes a first diode D1, a first inductor L1 and a first capacitor C1, the positive electrode of the first diode D1 and the first end of the first capacitor C1 are respectively connected to the output end of the rectifier circuit 20, the negative electrode of the first diode D1 is respectively connected to one end of the current limiting starting circuit 60 and the first end of the first inductor L1, and the second end of the first capacitor C1 is connected to the second end of the first inductor L1; the filter circuit 30 of this embodiment adopts DLC type filtering to output a stable DC voltage.

[0042] In this embodiment, as shown in the attached Figure 2 As shown, the rectifier circuit 20 is a three-phase full-bridge rectifier, and the inverter circuit 50 is a three-phase full-bridge inverter.

[0043] The present invention introduces a backup braking circuit 43. When the normal braking circuit 42 fails due to resistor overheating or other reasons, the inverter MCU10 can quickly switch to the backup braking circuit 43 to ensure the continued effectiveness of the inverter's braking function. This redundant design significantly enhances the reliability and safety of the system, so that the inverter can still achieve backup emergency rapid braking of the motor after the normal braking circuit 42 fails, avoiding damage to the inverter by the bus DC voltage, and ensuring that the motor stops quickly and smoothly when needed, thereby realizing backup emergency braking protection of the inverter. Compared with the existing practice of abandoning motor rapid braking for the purpose of protecting the braking circuit, the present invention overcomes the current industry technical bias in the inverter field that a single braking circuit is the primary protection object.

[0044] In this embodiment, the bus DC voltage is monitored in real time by the voltage detection comparison circuit 41, and compared with the reference voltage, so as to control the conduction of the common braking circuit 42; at the same time, the inverter MCU10 controls the conduction of the standby braking circuit 43 according to the bus DC voltage Ud and the braking circuit voltage of the common braking circuit 42. This intelligent redundant control method not only improves the accuracy and reliability of the braking process, but also can judge the current potential fault by monitoring the circuit information, providing a basis for preventive maintenance of the equipment.

[0045] Example 2

[0046] Combined with Figure 1 To Attachment Figure 4 The technical solution of the present invention is a frequency converter, including the frequency converter drive circuit with backup emergency braking protection described in Example 1.

[0047] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0048] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A frequency converter drive circuit with backup emergency brake protection, comprising a frequency converter MCU and a rectifier circuit, a filter circuit, an energy-consuming brake circuit and an inverter circuit connected in sequence, wherein the two ends of the filter circuit are the bus DC voltage of the frequency converter, characterized in that: The energy consumption braking circuit comprises a voltage detection and comparison circuit, a normal braking circuit and a standby braking circuit, wherein the normal braking circuit and the standby braking circuit are respectively connected between the bus DC voltages; The input end of the voltage detection comparison circuit is connected to the bus DC voltage, and controls the conduction of the common braking circuit according to the bus DC voltage and the reference voltage; The voltage detection comparison circuit and the common braking circuit are respectively connected to the voltage detection input terminal of the inverter MCU, and the signal output terminal of the inverter MCU is connected to the backup braking circuit. The inverter MCU controls the conduction of the backup braking circuit according to the bus DC voltage and the braking circuit voltage of the common braking circuit.

2. A frequency converter drive circuit with backup emergency brake protection according to claim 1, characterized in that: The voltage detection comparison circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a voltage comparator, a first transistor and a second transistor; the first resistor and the second resistor are connected in series, the first end of the first resistor and the first end of the second resistor are respectively connected to the bus DC voltage, the second end of the second resistor is connected to the non-inverting input end of the voltage comparator, the inverting input end of the voltage comparator is connected to the reference voltage, the output end of the voltage comparator is respectively connected to the first end of the third resistor and the first end of the fourth resistor, the second end of the fourth resistor is respectively connected to the base of the first transistor and the base of the second transistor, the collector of the first transistor and the second end of the third resistor are both connected to a high level, the collector of the second transistor is connected to a low level, the emitter of the first transistor and the emitter of the second transistor are both connected to the first end of the fifth resistor, and the second end of the fifth resistor is connected to the control end of the common braking circuit.

3. A frequency converter drive circuit with backup emergency brake protection according to claim 2, characterized in that: The common braking circuit includes a first braking resistor, a second braking resistor and a first power device, wherein the first end of the first braking resistor and the first end of the second braking resistor are respectively connected to the bus DC voltage, the second end of the first braking resistor and the second end of the second braking resistor are respectively connected to the first end and the second end of the first power device, and the control end of the first power device is connected to the second end of the fifth resistor.

4. A frequency converter drive circuit with backup emergency brake protection according to claim 3, characterized in that: The second end of the second resistor and the second end of the second braking resistor are respectively connected to the voltage detection input end of the inverter MCU.

5. The inverter drive circuit with backup emergency brake protection according to claim 3, characterized in that: The resistance ratio of the first braking resistor to the second braking resistor is in the range of 10:1 to 40:

1.

6. The inverter drive circuit with backup emergency brake protection according to claim 3, characterized in that: The backup braking circuit includes a third braking resistor and a second power device, wherein the first end of the third braking resistor and the first end of the second power device are respectively connected to the bus DC voltage, the second end of the third braking resistor is connected to the second end of the second power device, and the control end of the second power device is connected to the signal output end of the inverter MCU.

7. A frequency converter drive circuit with backup emergency brake protection according to claim 6, characterized in that: The first power device and the second power device are IGBTs or MOS tubes.

8. A frequency converter drive circuit with backup emergency brake protection according to any one of claims 1 to 7, characterized in that: A current limiting starting circuit is also provided between the rectifier circuit and the filter circuit. The current limiting starting circuit includes a starting resistor and a relay. The starting resistor is connected in series to the output loop of the rectifier circuit, and the normally open contacts of the relay are connected in parallel to both ends of the starting resistor.

9. A frequency converter drive circuit with backup emergency brake protection according to claim 8, characterized in that: The filtering circuit includes a first diode, a first inductor and a first capacitor, the positive electrode of the first diode and the first end of the first capacitor are respectively connected to the output end of the rectifier circuit, the negative electrode of the first diode is respectively connected to one end of the current limiting starting circuit and the first end of the first inductor, and the second end of the first capacitor is connected to the second end of the first inductor.

10. A frequency converter, characterized in that: A frequency converter drive circuit with backup emergency braking protection comprising any one of claims 1 to 9.

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