A brake unit circuit for frequency converter

Abstract

The present invention provides a braking unit circuit of a frequency converter, comprising a frequency converter, a brake pipe driving circuit, a brake resistor box, a forward voltage absorption circuit and a reverse voltage absorption circuit, wherein a bus P of the frequency converter is electrically connected to a positive pole of the frequency converter, a bus N of the frequency converter is electrically connected to a negative pole of the frequency converter, and a brake pipe driving circuit is connected in parallel between the bus P and the bus N of the frequency converter; current of the frequency converter flows out from the bus P and reaches the forward voltage absorption circuit, the brake pipe driving circuit drives the forward voltage absorption circuit to be turned on, the current passes through the forward voltage absorption circuit to reach a first end of the brake resistor box, and passes through a second end of the brake resistor box to reach the reverse voltage absorption circuit, the brake pipe driving circuit drives the reverse voltage absorption circuit to be turned on, and the current flows back to the bus N of the frequency converter to form a braking circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency converter application, and in particular to a braking unit circuit of a frequency converter. Background Art

[0002] In a construction elevator, the freight elevator will convert mechanical energy into electrical energy during the uniform descent process. In order to consume the generated electrical energy, a braking resistor needs to be installed in the elevator. The braking resistor will consume the energy generated during braking. Therefore, it is necessary to detect the DC bus voltage in the inverter and discharge the bus capacitor in a timely manner. At present, the braking unit of the construction elevator is also based on this principle for braking. However, the construction site environment is complex. When construction workers are carrying goods, it is easy for the goods to touch the braking resistor in the resistor box, causing the braking resistor to short-circuit with the resistor box (that is, the earth). This situation will cause the braking unit or the inverter to short-circuit, and even endanger personal safety. Therefore, it is necessary to trigger the protection in time when the braking resistor is short-circuited and cut off the power supply to the braking resistor to prevent equipment damage or casualties.

[0003] Figure 1 This is a relatively common braking unit circuit. When the braking unit triggers the protection, the existing braking unit cannot provide a freewheeling path for the IGBT device. Directly shutting down the IGBT will generate a very large spike voltage, causing the IGBT to be broken down or even damaged, and the short-circuit protection function cannot be achieved. Summary of the invention

[0004] In view of this, the present invention proposes a brake unit circuit of a frequency converter with voltage anomaly protection and short circuit protection functions.

[0005] The technical solution of the present invention is implemented as follows: The present invention provides a brake unit circuit of a frequency converter, comprising a frequency converter (1), a brake pipe drive circuit (2) and a brake resistor box (3), wherein a bus P of the frequency converter (1) is electrically connected to a positive pole of the frequency converter (1), a bus N of the frequency converter (1) is electrically connected to a negative pole of the frequency converter (1), and the brake pipe drive circuit (2) is connected in parallel between the bus P and the bus N of the frequency converter (1); and further comprising a forward voltage absorption circuit (4) and a reverse voltage absorption circuit (5) The current of the frequency converter (1) flows out from the bus P and reaches the forward voltage absorption circuit (4). The brake pipe drive circuit (2) drives the forward voltage absorption circuit (4) to be turned on. The current passes through the forward voltage absorption circuit (4) to reach the first end of the brake resistor box (3), and passes through the second end of the brake resistor box (3) to reach the reverse voltage absorption circuit (5). The brake pipe drive circuit (2) drives the reverse voltage absorption circuit (5) to be turned on. The current then flows back to the bus N of the frequency converter (1), forming a brake circuit.

[0006] On the basis of the above technical solution, preferably, the forward voltage absorption circuit (4) includes a first IGBT, a first fast recovery diode D1, a second fast recovery diode D2, a first resistor R2 and a first capacitor C2, the gate of the first IGBT is electrically connected to the brake pipe drive circuit (2), the collector of the first IGBT is electrically connected to the bus P of the inverter (1), the emitter of the first IGBT is electrically connected to the positive electrode of the first fast recovery diode D1, the negative electrode of the first fast recovery diode D1 is electrically connected to the first end of the brake resistor box (3), the first resistor R2 and the first capacitor C2 are connected in series and then in parallel at both ends of the first fast recovery diode D1; the second fast recovery diode D2 is connected in reverse parallel between the emitter of the first IGBT and the bus N of the inverter (1); and the emitter of the first IGBT is also electrically connected to the brake pipe drive circuit (2).

[0007] Further preferably, the reverse voltage absorption circuit (5) comprises a second IGBT, a third fast recovery diode D3, a fourth fast recovery diode D4, a second resistor R3 and a second capacitor C3; the gate of the second IGBT is electrically connected to the brake pipe drive circuit (2); the collector of the second IGBT is electrically connected to the negative electrode of the third fast recovery diode D3; the positive electrode of the third fast recovery diode D3 is electrically connected to the second end of the brake resistor box (3); the second resistor R3 and the second capacitor C3 are connected in series and then in parallel at both ends of the third fast recovery diode D3; the emitter of the second IGBT is electrically connected to the bus N of the inverter (1); the fourth fast recovery diode D4 is reversely connected in parallel between the bus P of the inverter (1) and the collector of the second IGBT; and the emitter of the second IGBT is also electrically connected to the brake pipe drive circuit (2).

[0008] More preferably, when the voltage between the bus P and the bus N of the inverter (1) exceeds a preset value of the brake tube drive circuit (2), the brake tube drive circuit (2) provides a high level to the gate of the first IGBT and the gate of the second IGBT respectively, so that the first IGBT and the second IGBT are turned on respectively, and the current on the bus P of the inverter (1) flows from the collector of the first IGBT to its emitter, and then flows through the first fast recovery diode D1 and enters the first end of the brake resistor box (3), and then flows out from the second end of the brake resistor box (3), passes through the third fast recovery diode D3, the collector and emitter of the second IGBT, and finally returns to the bus N of the inverter (1), forming a complete brake circuit.

[0009] Further preferably, when the voltage between the bus P and the bus N of the inverter (1) is lower than a preset value of the brake pipe drive circuit (2) and when the brake resistor box (3) is internally short-circuited or the first end or the second end of the brake resistor box (3) is short-circuited to the ground, the brake pipe drive circuit (2) turns off the first IGBT and the second IGBT, and the current on the bus N of the inverter (1) flows through the second fast recovery diode D2, the first fast recovery diode D1, the third fast recovery diode D3 and the fourth fast recovery diode D4 in turn, and returns to the bus P of the inverter (1), forming a complete freewheeling loop.

[0010] More preferably, the brake pipe drive circuit (2) comprises a voltage detection module (21), a trigger latch module (22) and an IGBT drive module (23); the voltage detection module (21) is electrically connected to a bus P and a bus N of the frequency converter (1); the voltage detection module (21) is also electrically connected to the trigger latch module (22); the trigger latch module (22) is electrically connected to the IGBT drive module (23) and the frequency converter (1), respectively; the IGBT drive module (23) is electrically connected to the first IGBT and the second IGBT, respectively;

[0011] When the voltage detection module (21) detects that the voltage between the bus P and the bus N of the frequency converter (1) exceeds a preset value, the voltage detection module (21) sends a trigger signal to the trigger latch module (22), and the trigger latch module (22) sends the trigger signal to the IGBT drive module (23) to provide a gate drive voltage for the first IGBT and the second IGBT, so that the first IGBT and the second IGBT are turned on;

[0012] When the voltage detection module (21) detects that the voltage between the bus P and the bus N of the frequency converter (1) is lower than a preset value, the voltage detection module (21) sends a stop trigger signal to the trigger latch module (22), and the trigger latch module (22) sends the stop trigger signal to the IGBT drive module (23), and the IGBT drive module (23) turns off the first IGBT and the second IGBT.

[0013] Further preferably, it further comprises a fault detection module (24), the fault detection module (24) being electrically connected to the emitter of the first IGBT, the emitter of the second IGBT and the trigger latch module (22) respectively, and the fault detection module (24) detecting the conduction voltage drop on the first IGBT or the second IGBT;

[0014] When the on-state voltage drop on the first IGBT or the second IGBT exceeds a preset value of the fault detection module (24), the fault detection module (24) sends a fault signal to the trigger latch module (22), the trigger latch module (22) latches the fault signal, and then sends the fault signal to the inverter (1) and the IGBT drive module (23), and the IGBT drive module (23) maintains the off state of the first IGBT or the second IGBT.

[0015] Further preferably, the brake pipe drive circuit (2) is an ACPL-332J or ACPL-316J model IGBT drive circuit.

[0016] The brake unit circuit of a frequency converter provided by the present invention has the following beneficial effects compared with the prior art:

[0017] (1) The present invention forms a complete braking circuit between the busbars through the forward voltage absorption circuit, the reverse voltage absorption circuit and the braking resistor box, so that the inverter can brake reliably when switching between different working conditions;

[0018] (2) The forward voltage absorption circuit and the reverse voltage absorption circuit form a braking circuit during normal braking;

[0019] (3) The forward voltage absorption circuit and the reverse voltage absorption circuit can isolate the IGBT when the bus voltage is too low or the brake resistor box is short-circuited, and form a complete freewheeling circuit to suppress the peak voltage on the IGBT and make it work within the safe working area;

[0020] (4) The brake tube drive circuit monitors the bus voltage on the one hand and the on-state voltage drop of the IGBT on the other hand. When the on-state voltage drop is abnormal or the brake resistor box is short-circuited, the IGBT is kept in the off state to prevent the IGBT from being damaged by excessive peak voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 The present invention is a wiring diagram of a brake circuit of an existing frequency converter;

[0023] Figure 2 A wiring diagram of a brake unit circuit of a frequency converter of the present invention;

[0024] Figure 3A schematic diagram of a current of a brake circuit of a brake unit circuit of a frequency converter according to the present invention;

[0025] Figure 4 A schematic diagram of a current of a freewheeling circuit of a braking unit circuit of a frequency converter according to the present invention;

[0026] Figure 5 The present invention is a block diagram of a brake pipe driving circuit structure of a brake unit circuit of a frequency converter. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0028] like Figure 2 As shown, the present invention provides a braking unit circuit of a frequency converter, including a frequency converter 1, a brake pipe drive circuit 2, a brake resistor box 3, a forward voltage absorption circuit 4 and a reverse voltage absorption circuit 5, wherein the bus P of the frequency converter 1 is electrically connected to the positive pole of the frequency converter 1, the bus N of the frequency converter 1 is electrically connected to the negative pole of the frequency converter 1, and the brake pipe drive circuit 2 is connected in parallel between the bus P and the bus N of the frequency converter 1; wherein the current of the frequency converter 1 flows out from the bus P and reaches the forward voltage absorption circuit 4, the brake pipe drive circuit 2 drives the forward voltage absorption circuit 4 to be turned on, the current passes through the forward voltage absorption circuit 4 to reach the first end of the brake resistor box 3, and passes through the second end of the brake resistor box 3 to reach the reverse voltage absorption circuit 5, the brake pipe drive circuit 2 drives the reverse voltage absorption circuit 5 to be turned on, and the current flows back to the bus N of the frequency converter 1 to form a braking circuit. Figure 2 It can be seen that when the present invention works normally, the brake pipe driving circuit 2 will compare whether the bus voltage exceeds its preset range. When the bus voltage exceeds the set value of the brake pipe driving circuit 2, the brake pipe driving circuit 2 will make the forward voltage absorption circuit 4 and the reverse voltage absorption circuit 5 conductive, and the brake resistor box 3, i.e. R1, is connected to the circuit to perform a normal braking function.

[0029] like Figure 2 Combination Figure 3As shown, the forward voltage absorption circuit 4 includes a first IGBT, a first fast recovery diode D1, a second fast recovery diode D2, a first resistor R2 and a first capacitor C2. The gate of the first IGBT is electrically connected to the brake pipe drive circuit 2, the collector of the first IGBT is electrically connected to the bus P of the inverter 1, the emitter of the first IGBT is electrically connected to the positive electrode of the first fast recovery diode D1, the negative electrode of the first fast recovery diode D1 is electrically connected to the first end of the brake resistor box 3, the first resistor R2 and the first capacitor C2 are connected in series and then connected in parallel to the two ends of the first fast recovery diode D1; the second fast recovery diode D2 is reversely connected in parallel between the emitter of the first IGBT and the bus N of the inverter 1; the emitter of the first IGBT is also electrically connected to the brake pipe drive circuit 2. The first resistor R2 and the first capacitor C2 constitute a first resistance-capacitance absorption circuit. In the normal braking state, the first IGBT, that is, Z1 in the figure is turned on, and the current flows from the collector of the first IGBT to the emitter, and then enters the brake resistor box 3 through the first fast recovery diode D1.

[0030] like Figure 2 Combination Figure 4 As shown, the reverse voltage absorption circuit 5 includes a second IGBT, a third fast recovery diode D3, a fourth fast recovery diode D4, a second resistor R3 and a second capacitor C3. The gate of the second IGBT is electrically connected to the brake pipe drive circuit 2, the collector of the second IGBT is electrically connected to the negative electrode of the third fast recovery diode D3, the positive electrode of the third fast recovery diode D3 is electrically connected to the second end of the brake resistor box 3, the second resistor R3 and the second capacitor C3 are connected in series and then connected in parallel to the two ends of the third fast recovery diode D3; the emitter of the second IGBT is electrically connected to the bus N of the inverter 1; the fourth fast recovery diode D4 is reversely connected in parallel between the bus P of the inverter 1 and the collector of the second IGBT; the emitter of the second IGBT is also electrically connected to the brake pipe drive circuit 2. The second resistor R3 and the second capacitor C3 also constitute a second RC absorption circuit. In the normal braking state, the second IGBT, namely Z2 in the figure, is turned on, and the current flowing through the braking resistor box 3 passes through the third fast recovery diode D3, the collector and emitter of the second IGBT in turn, and returns to the bus N of the inverter 1, that is, the forward voltage absorption circuit 4, the braking resistor box 3 and the reverse voltage absorption circuit 5 form a complete loop, namely the braking loop.

[0031] Combination Figure 3 and Figure 4It can be seen that when the present invention is actually used, the first IGBT and the second IGBT are also controlled by the brake tube drive circuit 2. When the voltage between the bus P and the bus N of the inverter 1 exceeds the preset value of the brake tube drive circuit 2, the brake tube drive circuit 2 will provide a high level to the gates of the first IGBT and the second IGBT, so that the first IGBT and the second IGBT are continuously turned on. The current on the bus P of the inverter 1 flows from the collector of the first IGBT to its emitter, and then flows through the first fast recovery diode D1 and enters the first end of the brake resistor box 3, and then flows out from the second end of the brake resistor box 3, and passes through the third fast recovery diode D3, the collector and emitter of the second IGBT, and finally returns to the bus N of the inverter 1, forming a complete brake circuit.

[0032] When the voltage between the busbar P and the busbar N of the inverter 1 is lower than the preset value of the brake tube drive circuit 2, the brake tube drive circuit 2 will provide a low level to the gates of the first IGBT and the second IGBT, so that the first IGBT and the second IGBT remain turned off. At this time, the current on the busbar N of the inverter 1 flows through the second fast recovery diode D2, the first fast recovery diode D1, the third fast recovery diode D3 and the fourth fast recovery diode D4 in turn, and returns to the busbar P of the inverter 1, forming a complete freewheeling loop. In this freewheeling loop, no matter whether the voltage between the busbar P and the busbar N of the inverter 1 exceeds the preset value or is lower than the preset value, the direction of the current flowing through the brake resistor box 3 remains unchanged. The lead of the brake resistor box 3 is long and its parasitic inductance is large. Since the current direction of the brake resistor box 3 remains unchanged, the parasitic inductance will not generate a large induced voltage, thereby suppressing the peak value of the voltage spike on the first IGBT and the second IGBT, so that the first IGBT and the second IGBT are located in the safe working area. The capacitor C1 disposed between the bus P and the bus N of the inverter 1 can also absorb the peak voltage signal.

[0033] During braking of the present invention, if the first end and the second end of the brake resistor box 3 are short-circuited, the current in the busbar flows through the first IGBT, the first fast recovery diode D1, the third fast recovery diode D3 and the second IGBT in sequence, and the overcurrent easily causes permanent damage to each device. At this time, the brake tube drive circuit 2 keeps turning off the first IGBT and the second IGBT, and the reversely connected second fast recovery diode D2 and the fourth fast recovery diode D4 form a complete freewheeling loop with the first fast recovery diode D1, the third fast recovery diode D3 and the brake resistor box 3, which can reduce the induced voltage generated by the parasitic inductance, effectively suppress the peak voltage signal on each IGBT, and make the first IGBT and the second IGBT located in the safe working area.

[0034] In addition, if the first or second end of the brake resistor box 3 is short-circuited with the ground during braking of the present invention, since the bus power supply of the inverter 1 is usually rectified by the AC power grid, when short-circuited, the current will pass through the first IGBT and the first fast recovery diode D1, and then form a loop with the ground through the first or second end of the brake resistor box 3, and the current in the above-mentioned devices will increase rapidly, causing some devices to be overcurrent and permanently damaged. Similarly, in this case, the brake tube drive circuit 2 keeps turning off the first IGBT and the second IGBT. As mentioned above, the reversely connected second fast recovery diode D2 and the fourth fast recovery diode D4, together with the first fast recovery diode D1, the third fast recovery diode D3 and the brake resistor box 3, form a complete freewheeling loop, which can reduce the induced voltage generated by the parasitic inductance, effectively suppress the peak voltage signal on each IGBT, and make the first IGBT and the second IGBT located in the safe working area.

[0035] In addition, when the present invention is not braking, if the first end or the second end of the braking resistor box 3 is short-circuited with the ground, although the first IGBT and the second IGBT are not turned on, the first IGBT and the second IGBT both contain body diodes, which can automatically turn on when subjected to reverse voltage, thereby forming a current loop. The first fast recovery diode D1 and the third fast recovery diode D3 of the present invention are opposite to the body diodes contained in the first IGBT and the second IGBT, preventing the body diodes of the IGBT from automatically turning on when short-circuited and generating excessive current flowing through the first IGBT and the second IGBT, preventing the first IGBT and the second IGBT from forming an overcurrent loop inside, thereby protecting each IGBT.

[0036] like Figure 5 As shown, the figure provides a structural block diagram of a brake pipe driving circuit 2. The brake pipe driving circuit 2 includes a voltage detection module 21, a trigger latch module 22 and an IGBT driving module 23. The voltage detection module 21 is electrically connected to the bus P and the bus N of the inverter 1, and the voltage detection module 21 is also electrically connected to the trigger latch module 22; the trigger latch module 22 is electrically connected to the IGBT driving module 23 and the inverter 1 respectively, and the IGBT driving module 23 is electrically connected to the first IGBT and the second IGBT respectively;

[0037] When the voltage detection module 21 detects that the voltage between the bus P and the bus N of the inverter 1 exceeds its preset value, after voltage comparison, the voltage detection module 21 sends a trigger signal to the trigger latch module 22, and the trigger latch module 22 sends the trigger signal to the IGBT drive module 23 to provide a gate drive voltage for the first IGBT and the second IGBT, so that the first IGBT and the second IGBT are turned on;

[0038] When the voltage detection module 21 detects that the voltage between the bus P and the bus N of the inverter 1 is lower than its preset value, after voltage comparison, the voltage detection module 21 sends a stop trigger signal to the trigger latch module 22, and the trigger latch module 22 sends the stop trigger signal to the IGBT drive module 23, and the IGBT drive module 23 turns off the first IGBT and the second IGBT.

[0039] The above scheme is based on whether the bus voltage exceeds the preset value to judge, so as to maintain each IGBT on or off. The brake pipe drive circuit 2 of the present invention also includes a fault detection module 24, which is electrically connected to the emitter of the first IGBT, the emitter of the second IGBT and the trigger latch module 22 respectively. The fault detection module 24 detects the conduction voltage drop on the first IGBT or the second IGBT, and can obtain the conduction voltage drop by measuring and comparing the bus voltage and the emitter voltage of each IGBT. The fault detection module 24 can be equipped with a voltage comparison circuit. .

[0040] When the on-state voltage drop on the first IGBT or the second IGBT exceeds the preset value of the fault detection module 24, the fault detection module 24 sends a fault signal to the trigger latch module 22, the trigger latch module 22 latches the fault signal, and then sends the fault signal to the inverter 1 and the IGBT drive module 23, and the IGBT drive module 23 keeps the first IGBT or the second IGBT in the off state.

[0041] The brake tube drive circuit 2 in the present invention can be an ACPL-332J or ACPL-316J IGBT drive circuit of Avago Technologies, USA, which integrates voltage monitoring and short-circuit soft shutdown functions, and can provide a guarantee for the reliable operation of the IGBT. The trigger latch module 22 in the present invention can use an RS trigger to latch the fault state, and let the brake tube drive circuit 2 always output the drive signal to turn off the IGBT until the inverter 1 sends a fault reset signal to release the fault state.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A brake unit circuit of a frequency converter, comprising a frequency converter (1), a brake pipe drive circuit (2) and a brake resistor box (3), wherein a bus P of the frequency converter (1) is electrically connected to a positive pole of the frequency converter (1), a bus N of the frequency converter (1) is electrically connected to a negative pole of the frequency converter (1), and the brake pipe drive circuit (2) is connected in parallel between the bus P and the bus N of the frequency converter (1); characterized in that: It also includes a forward voltage absorption circuit (4) and a reverse voltage absorption circuit (5), wherein the current of the frequency converter (1) flows out from the bus P and reaches the forward voltage absorption circuit (4), the brake pipe drive circuit (2) drives the forward voltage absorption circuit (4) to be turned on, the current passes through the forward voltage absorption circuit (4) to reach the first end of the brake resistor box (3), and passes through the second end of the brake resistor box (3) to reach the reverse voltage absorption circuit (5), the brake pipe drive circuit (2) drives the reverse voltage absorption circuit (5) to be turned on, and the current flows back to the bus N of the frequency converter (1), thereby forming a brake circuit; The forward voltage absorption circuit (4) comprises a first IGBT, a first fast recovery diode D1, a second fast recovery diode D2, a first resistor R2 and a first capacitor C2, the gate of the first IGBT is electrically connected to the brake pipe drive circuit (2), the collector of the first IGBT is electrically connected to the bus P of the inverter (1), the emitter of the first IGBT is electrically connected to the positive electrode of the first fast recovery diode D1, the negative electrode of the first fast recovery diode D1 is electrically connected to the first end of the brake resistor box (3), the first resistor R2 and the first capacitor C2 are connected in series and then in parallel at both ends of the first fast recovery diode D1; the second fast recovery diode D2 is connected in reverse parallel between the emitter of the first IGBT and the bus N of the inverter (1); the emitter of the first IGBT is also electrically connected to the brake pipe drive circuit (2); The reverse voltage absorption circuit (5) comprises a second IGBT, a third fast recovery diode D3, a fourth fast recovery diode D4, a second resistor R3 and a second capacitor C3; the gate of the second IGBT is electrically connected to the brake pipe drive circuit (2); the collector of the second IGBT is electrically connected to the negative electrode of the third fast recovery diode D3; the positive electrode of the third fast recovery diode D3 is electrically connected to the second end of the brake resistor box (3); the second resistor R3 and the second capacitor C3 are connected in series and then in parallel to the two ends of the third fast recovery diode D3; the emitter of the second IGBT is electrically connected to the bus N of the inverter (1); the fourth fast recovery diode D4 is connected in reverse parallel between the bus P of the inverter (1) and the collector of the second IGBT; the emitter of the second IGBT is also electrically connected to the brake pipe drive circuit (2); The brake pipe drive circuit (2) comprises a voltage detection module (21), a trigger latch module (22) and an IGBT drive module (23); the voltage detection module (21) is electrically connected to a bus P and a bus N of the frequency converter (1); the voltage detection module (21) is also electrically connected to the trigger latch module (22); the trigger latch module (22) is electrically connected to the IGBT drive module (23) and the frequency converter (1), respectively; the IGBT drive module (23) is electrically connected to the first IGBT and the second IGBT, respectively; When the voltage detection module (21) detects that the voltage between the bus P and the bus N of the frequency converter (1) exceeds a preset value, the voltage detection module (21) sends a trigger signal to the trigger latch module (22), and the trigger latch module (22) sends the trigger signal to the IGBT drive module (23) to provide a gate drive voltage for the first IGBT and the second IGBT, so that the first IGBT and the second IGBT are turned on; When the voltage detection module (21) detects that the voltage between the bus P and the bus N of the frequency converter (1) is lower than a preset value, the voltage detection module (21) sends a stop trigger signal to the trigger latch module (22), and the trigger latch module (22) sends the stop trigger signal to the IGBT drive module (23), and the IGBT drive module (23) turns off the first IGBT and the second IGBT.

2. The brake unit circuit of a frequency converter according to claim 1, characterized in that: When the voltage between the busbar P and the busbar N of the frequency converter (1) exceeds a preset value of the brake tube drive circuit (2), the brake tube drive circuit (2) provides a high level to the gate of the first IGBT and the gate of the second IGBT respectively, so that the first IGBT and the second IGBT are respectively turned on, and the current on the busbar P of the frequency converter (1) flows from the collector of the first IGBT to its emitter, and then flows through the first fast recovery diode D1 and enters the first end of the brake resistor box (3), then flows out from the second end of the brake resistor box (3), passes through the third fast recovery diode D3, the collector and emitter of the second IGBT, and finally returns to the busbar N of the frequency converter (1), forming a complete brake circuit.

3. The brake unit circuit of a frequency converter as claimed in claim 2, characterized in that: When the voltage between the busbar P and the busbar N of the frequency converter (1) is lower than a preset value of the brake pipe drive circuit (2) and when the brake resistor box (3) is short-circuited internally or the first end or the second end of the brake resistor box (3) is short-circuited to the ground, the brake pipe drive circuit (2) turns off the first IGBT and the second IGBT, and the current on the busbar N of the frequency converter (1) flows through the second fast recovery diode D2, the first fast recovery diode D1, the third fast recovery diode D3 and the fourth fast recovery diode D4 in sequence, and returns to the busbar P of the frequency converter (1), forming a complete freewheeling loop.

4. The brake unit circuit of a frequency converter according to claim 1, characterized in that: It also includes a fault detection module (24), the fault detection module (24) is electrically connected to the emitter of the first IGBT, the emitter of the second IGBT and the trigger latch module (22), and the fault detection module (24) detects the conduction voltage drop on the first IGBT or the second IGBT; When the on-state voltage drop on the first IGBT or the second IGBT exceeds a preset value of the fault detection module (24), the fault detection module (24) sends a fault signal to the trigger latch module (22), the trigger latch module (22) latches the fault signal, and then sends the fault signal to the inverter (1) and the IGBT drive module (23), and the IGBT drive module (23) maintains the off state of the first IGBT or the second IGBT.

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