A frequency converter isolation circuit

Abstract

The present application discloses a frequency converter isolation circuit, including: a switching power supply circuit, a control circuit, a drive circuit, a power circuit and a current sampling circuit; the switching power supply circuit is respectively connected to the power supply ends of the control circuit, the drive circuit and the current sampling circuit, the current sampling detection input end of the control circuit is connected to the current sampling detection output end of the current sampling circuit, the drive circuit is respectively connected to the control circuit and the power circuit, the current sampling circuit is connected in parallel with the sampling resistor in the power circuit; the current sampling circuit and the control circuit share a common ground; the control circuit is isolated from the upper bridge drive circuit and the lower bridge drive circuit of the drive circuit. The present application has upper bridge drive isolation, lower bridge drive isolation, and current sampling is resistor sampling. While ensuring the quality of the current sampling signal and the stability of the frequency converter, the cost of the entire isolation circuit is not increased.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to a frequency converter isolation circuit. Background Art

[0002] The frequency converter is a type of adjustable speed drive system. It uses variable frequency drive technology to change the frequency and amplitude of the working voltage of the AC motor to smoothly control the speed and torque of the AC motor. The most common one is the AC / AC converter whose input and output are both AC.

[0003] In the existing inverter three-phase full-bridge inverter isolation drive solution, it is necessary to sample the inverter current in order to better control the inverter to work stably. However, the sampling methods adopted in the existing technology are either expensive or easily interfered with, with large interference and insufficient sampling accuracy.

[0004] Therefore, a low-cost inverter isolation circuit with improved current sampling accuracy is needed. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a frequency converter isolation circuit, which improves the current sampling accuracy without increasing the price. The specific scheme is as follows:

[0006] A frequency converter isolation circuit, comprising: a switching power supply circuit, an MCU control circuit, a drive circuit, a power circuit and a current sampling circuit;

[0007] The switching power supply circuit is respectively connected to the power supply ends of the MCU control circuit, the drive circuit and the current sampling circuit, the current sampling detection input end of the MCU control circuit is connected to the current sampling detection output end of the current sampling circuit, the drive circuit is respectively connected to the MCU control circuit and the power circuit, the current sampling circuit is connected in parallel with the sampling resistor in the power circuit; the current sampling circuit and the MCU control circuit share a common ground; the MCU control circuit is isolated from the upper bridge drive circuit and the lower bridge drive circuit of the drive circuit.

[0008] Optionally, the current sampling circuit includes a filter circuit for filtering out current sampling interference signals and a first-stage current sampling signal differential amplifier for amplifying the AC current sampling signal, which are connected in sequence, and a third diode connected inside the filter circuit for clamping the current sampling signal.

[0009] Optionally, the filtering circuit includes a seventh resistor, an eighth resistor and a third capacitor; one end of the seventh resistor is connected to one end of the sampling resistor in the power circuit as the first sampling end of the current sampling circuit, the other end of the seventh resistor is connected to one end of the third capacitor, one end of the eighth resistor is connected to the other end of the sampling resistor in the power circuit as the second sampling end of the current sampling circuit, and the other end of the eighth resistor is connected to the other end of the third capacitor.

[0010] Optionally, the first-stage current sampling signal differential amplifier includes a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor and a fourth operational amplifier; one end of the ninth resistor is connected to the other end of the seventh resistor, the other end of the ninth resistor is respectively connected to one end of the twelfth resistor and the negative input terminal of the fourth operational amplifier, one end of the tenth resistor is connected to the other end of the eighth resistor, the other end of the tenth resistor is respectively connected to one end of the eleventh resistor and the positive input terminal of the fourth operational amplifier, the other end of the twelfth resistor is connected to the output terminal of the fourth operational amplifier, and the other end of the eleventh resistor is grounded.

[0011] Optionally, the current sampling circuit also includes a second-stage adding current sampling signal amplifier connected to the first-stage current sampling signal differential amplifier as the current sampling detection output terminal of the current sampling circuit, and used to raise the voltage of the AC current sampling signal to above the reference ground voltage.

[0012] Optionally, the second-stage addition current sampling signal amplifier includes a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a fourth capacitor and a fifth operational amplifier; one end of the thirteenth resistor is connected to the output end of the fourth operational amplifier, the other end of the thirteenth resistor, one end of the fourteenth resistor, one end of the fourth capacitor and the positive input end of the fifth operational amplifier are interconnected, one end of the fifteenth resistor is grounded, the other end of the fifteenth resistor, the other end of the fourth capacitor, the negative input end of the fifth operational amplifier and one end of the sixteenth resistor are interconnected, the other end of the fourteenth resistor serves as the power supply end of the current sampling circuit, and the other end of the sixteenth resistor and the output end of the fifth operational amplifier are connected as the current sampling detection output end of the current sampling circuit.

[0013] Optionally, the driving circuit includes an upper bridge driving circuit and a lower bridge driving circuit;

[0014] The upper bridge driving circuit includes an upper bridge isolation driving optocoupler, a first diode, a first resistor, a second resistor, a third resistor, a first capacitor, a first voltage zener diode, and a second voltage zener diode;

[0015] The VO end of the upper bridge isolation driving optocoupler is respectively connected to the cathode of the first diode and one end of the first resistor, the anode of the first diode is connected to one end of the second resistor, the other end of the second resistor, one end of the first capacitor, the other end of the first resistor, one end of the third resistor and the cathode of the second Zener diode are connected to each other, and is connected to the power circuit as the first driving end of the driving circuit, the other end of the third resistor, the other end of the first capacitor and the cathode of the second Zener diode are connected to each other, and is connected to the power circuit as the second driving end of the driving circuit, and the anode of the first Zener diode is connected to the anode of the second Zener diode;

[0016] The lower bridge driving circuit includes a lower bridge isolation driving optocoupler, a second diode, a fourth resistor, a fifth resistor, a sixth resistor, a second capacitor, a third voltage stabilizing diode and a fourth voltage stabilizing diode;

[0017] The VO end of the lower bridge driving circuit is respectively connected to the cathode of the second diode and one end of the fourth resistor, the anode of the second diode is connected to one end of the fifth resistor, the other end of the fifth resistor, the other end of the fourth resistor, one end of the sixth resistor, one end of the second capacitor and the cathode of the fourth voltage-stabilizing diode are connected to each other, and the third driving end of the driving circuit is connected to the power circuit, the other end of the sixth resistor, the other end of the second capacitor and the cathode of the third voltage-stabilizing diode are connected to each other, and the fourth driving end of the driving circuit is connected to the power circuit, the anode of the third voltage-stabilizing diode is connected to the anode of the fourth voltage-stabilizing diode, and the NC end of the lower bridge isolation driving optocoupler is connected to the MCU control circuit.

[0018] Optionally, the upper bridge driving circuit includes an upper bridge isolation driving chip, a fifth diode, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, a thirteenth capacitor, a fifth voltage zener diode and a sixth voltage zener diode;

[0019] The CLAMP end of the upper bridge isolation driver chip is connected to one end of the twentieth resistor, the Gout end of the upper bridge isolation driver chip is respectively connected to the cathode of the fifth diode and one end of the seventeenth resistor, the anode of the fifth diode is connected to one end of the eighteenth resistor, the other end of the eighteenth resistor, one end of the thirteenth capacitor, the other end of the seventeenth resistor, one end of the nineteenth resistor and the cathode of the sixth voltage zener diode, and the other end of the twentieth resistor are connected to each other, and are connected to the power circuit as the first driving end of the drive circuit, the other end of the nineteenth resistor, the other end of the thirteenth capacitor and the cathode of the sixth voltage zener diode are connected to each other, and are connected to the power circuit as the second driving end of the drive circuit, and the anode of the fifth voltage zener diode is connected to the anode of the sixth voltage zener diode;

[0020] The lower bridge driving circuit includes a lower bridge isolation driving chip, a fourth diode, a twenty-first resistor, a twenty-second resistor, a twenty-third resistor, a twenty-fourth resistor, a fourteenth capacitor, a seventh voltage zener diode and an eighth voltage zener diode;

[0021] The CLAMP end of the lower bridge isolation driver chip is connected to one end of the twenty-fourth resistor, the Gout end of the lower bridge driver circuit is respectively connected to the cathode of the fourth diode and one end of the twenty-first resistor, the anode of the fourth diode is connected to one end of the twenty-second resistor, the other end of the twenty-second resistor, the other end of the twenty-first resistor, one end of the twenty-third resistor, one end of the fourteenth capacitor, the cathode of the eighth voltage-regulating diode, and the other end of the twenty-fourth resistor are connected to each other, and the third driver end of the driver circuit is connected to the power circuit, the other end of the twenty-third resistor, the other end of the fourteenth capacitor, and the cathode of the seventh voltage-regulating diode are connected to each other, and the fourth driver end of the driver circuit is connected to the power circuit, and the anode of the seventh voltage-regulating diode is connected to the anode of the eighth voltage-regulating diode.

[0022] Optionally, the control end of the upper bridge power circuit is connected to the first driving end as the first control end of the power circuit, the output end of the upper bridge power circuit is connected to the input end of the lower bridge power circuit, and is connected to the second driving end as the U-phase output end of the power circuit, the control end of the lower bridge power circuit is connected to the third driving end as the second control end of the power circuit, the output end of the lower bridge power circuit is connected to one end of the sampling resistor, and is connected to the fourth driving end as the ULE phase output end of the power circuit, and the other end of the sampling resistor is grounded.

[0023] Optionally, the upper bridge power circuit and the lower bridge power circuit are both full-bridge three-phase rectifier circuits.

[0024] In the present invention, the frequency converter isolation circuit includes: a switching power supply circuit, an MCU control circuit, a drive circuit, a power circuit and a current sampling circuit; the switching power supply circuit is respectively connected to the power supply ends of the MCU control circuit, the drive circuit and the current sampling circuit, the current sampling detection input end of the MCU control circuit is connected to the current sampling detection output end of the current sampling circuit, the drive circuit is respectively connected to the MCU control circuit and the power circuit, and the current sampling circuit is connected in parallel with the sampling resistor in the power circuit; the current sampling circuit and the MCU control circuit share a ground; the MCU control circuit is isolated from the upper bridge drive circuit and the lower bridge drive circuit of the drive circuit.

[0025] The upper bridge drive of the present invention is isolated, the lower bridge drive is isolated, and the current sampling is resistance sampling. Under the condition of ensuring the quality of the current sampling signal and the stability of the inverter, the cost of the entire isolation circuit is not increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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 embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0027] Figure 1 A schematic diagram of a converter isolation circuit structure disclosed in an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of a switching power supply circuit structure disclosed in an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of a current sampling circuit topology disclosed in an embodiment of the present invention;

[0030] Figure 4 A topological schematic diagram of a driving circuit disclosed in an embodiment of the present invention;

[0031] Figure 5 A schematic diagram of a power circuit topology disclosed in an embodiment of the present invention;

[0032] Figure 6 A schematic diagram of the structure of an MCU control circuit disclosed in an embodiment of the present invention;

[0033] Figure 7 A schematic diagram of the structure of an upper bridge driving circuit disclosed in an embodiment of the present invention;

[0034] Figure 8 The present invention is a schematic diagram of a lower bridge driving circuit structure disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] 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 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.

[0036] The embodiment of the present invention discloses a frequency converter isolation circuit, see Figure 1 As shown, the circuit includes: a switching power supply circuit 1, an MCU control circuit 2, a drive circuit 3, a power circuit 4 and a current sampling circuit 5;

[0037] The switching power supply circuit 1 is respectively connected to the power supply ends of the MCU control circuit 2, the drive circuit 3 and the current sampling circuit 5, the current sampling detection input end of the MCU control circuit 2 is connected to the current sampling detection output end of the current sampling circuit 5, the drive circuit 3 is respectively connected to the MCU control circuit 2 and the power circuit 4, the current sampling circuit 5 is connected in parallel with the sampling resistor in the power circuit 4; the current sampling circuit 5 and the MCU control circuit 2 share a common ground; the MCU control circuit 2 and the upper bridge drive circuit 3 and the lower bridge drive circuit 3 of the drive circuit 3 are isolated.

[0038] Specifically, the switching power supply circuit 1 supplies power to the MCU control circuit 2, the drive circuit 3 and the current sampling circuit 5 respectively; the current sampling circuit 5 samples from the power circuit 4 to obtain a current sampling signal, and outputs the current sampling signal from the current sampling detection output end to the MCU control circuit 2; the MCU control circuit 2 outputs a control signal to the drive circuit 3 according to the current sampling signal; the drive circuit 3 sends a drive signal to drive the power circuit 4 according to the control signal.

[0039] Specifically, the switching power supply circuit 1 generates multiple power supplies to respectively supply power to the MCU control circuit 2, the drive circuit 3, and the current sampling circuit 5. The MCU control circuit 2 sends 6 PWM waves as input switch signals to the drive circuit 3, and the drive circuit 3 sends 6 drive signals to drive the IGBT switches in the upper bridge power circuit and the lower bridge power circuit in the power circuit 4. The current sampling circuit 5 collects the current sampling signal from the power circuit 4 and outputs it to the MCU control circuit 2 for detection.

[0040] For details, see Figure 2As shown, the switching power supply circuit 1 includes a high voltage input, an upper bridge drive power supply output, a lower bridge drive power supply output, and a control part power supply output. Among them, DC+ is the positive electrode of the high voltage input, and DC- is the high voltage input ground; +VCC-U is the positive electrode of the upper bridge drive power supply, -VEE-U is the negative electrode of the upper bridge drive power supply, and the reference ground is the U phase output; +VCC-DOWN is the positive electrode of the lower bridge drive power supply, -VEE-DOWN is the negative electrode of the lower bridge drive power supply, and the reference ground is the high voltage input ground DC-; +VCC-MCU is the positive electrode of the control part power supply, -VCC-MCU is the negative electrode of the control part power supply, and GND is the reference ground of the control part power supply.

[0041] Specifically, the switching power supply circuit 1 is divided into three outputs, wherein the high-voltage inputs DC+ and DC- are located on the primary side, the lower bridge drive power supply is located on the primary side, and the reference ground is the high-voltage input ground DC-; the upper bridge drive power supply is a floating power supply, and the reference ground is the U-phase output; the control part power supply is located on the secondary side and is isolated from the high-voltage input.

[0042] For details, see Figure 3 As shown, the current sampling circuit 5 may include a filter circuit 51 for filtering out current sampling interference signals, a first-stage current sampling signal differential amplifier 52 for amplifying the AC current sampling signal, and a third diode D3 connected inside the filter circuit 51 for clamping the current sampling signal.

[0043] Specifically, the filter circuit 51 of the above-mentioned current sampling circuit 5 includes a seventh resistor R7, an eighth resistor R8 and a third capacitor C3; one end of the seventh resistor R7 serves as the first sampling end DC- of the current sampling circuit 5, the other end of the seventh resistor R7 is connected to one end of the third capacitor C3, one end of the eighth resistor R8 serves as the second sampling end ULE of the current sampling circuit 5, and the other end of the eighth resistor R8 is connected to the other end of the third capacitor C3.

[0044] Specifically, the above-mentioned first-stage current sampling signal differential amplifier 52 includes a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12 and a fourth operational amplifier U4; one end of the ninth resistor R9 is connected to the other end of the seventh resistor R7, the other end of the ninth resistor R9 is respectively connected to one end of the twelfth resistor R12 and the negative input end of the fourth operational amplifier U4, one end of the tenth resistor R10 is connected to the other end of the eighth resistor R8, the other end of the tenth resistor R10 is respectively connected to one end of the eleventh resistor R11 and the positive input end of the fourth operational amplifier U4, the other end of the twelfth resistor R12 is connected to the output end of the fourth operational amplifier U4 as the current sampling detection output end of the current sampling circuit 5, and the other end of the eleventh resistor R11 is grounded.

[0045] For further information, see Figure 3 As shown, the output end of the fourth operational amplifier U4 of the first-stage current sampling signal differential amplifier 52 can also be connected to the second-stage addition current sampling signal amplifier 53, and the second-stage addition current sampling signal amplifier 53 is used to raise the voltage of the AC current sampling signal to above the reference ground voltage, thereby improving the sampling accuracy.

[0046] Specifically, the second-stage addition current sampling signal amplifier 53 includes a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a fourth capacitor C4 and a fifth operational amplifier U5; one end of the thirteenth resistor R13 is connected to the output end of the fourth operational amplifier U4, the other end of the thirteenth resistor R13, one end of the fourteenth resistor R14, one end of the fourth capacitor C4 and the positive input end of the fifth operational amplifier U5 are connected to each other, one end of the fifteenth resistor R15 is grounded, the other end of the fifteenth resistor R15, the other end of the fourth capacitor C4, the negative input end of the fifth operational amplifier U5 and one end of the sixteenth resistor R16 are connected to each other, the other end of the fourteenth resistor R14 serves as the power supply end of the current sampling circuit 5, and the other end of the sixteenth resistor R16 is connected to the output end of the fifth operational amplifier U5 as the current sampling detection output end of the current sampling circuit 5.

[0047] Specifically, after the output end of the fourth operational amplifier U4 is connected to the second-stage addition current sampling signal amplifier 53, it no longer serves as the current sampling detection output end of the current sampling circuit 5. Instead, the output end of the fifth operational amplifier U5 in the second-stage addition current sampling signal amplifier 53 serves as the current sampling detection output end of the current sampling circuit 5 again.

[0048] The fourth operational amplifier U4 and the fifth operational amplifier U5 are powered by dual power supplies of +VCC-MCU and -VCC-MCU.

[0049] Specifically, the input ULE and DC- of the current sampling circuit 5 are connected to the sampling resistors of the power circuit 4 for sampling, the current sampling detection output terminal I_U of the current sampling circuit 5 is connected to the current sampling detection input terminal I_U of the MCU control circuit 2, and the PWM wave outputs PWM-UH and PWM-UL of the MCU control circuit 2 are connected to the PWM wave input terminals of the upper and lower bridge isolation drive optocouplers U1 and U2 of the drive circuit 3, forming complementary inputs. The three power outputs of the switching power supply circuit 1, namely +VCC-U and -VEE-U, +VCC-DOWN and -VEE-DOWN, +VCC-MCU and -VCC-MCU, sequentially supply power to the upper bridge drive optocoupler U1, the lower bridge drive optocoupler U2, the MCU control circuit 2, the fourth operational amplifier U4 and the fifth operational amplifier U5.

[0050] For details, see Figure 4 As shown, the driving circuit 3 includes an upper bridge driving circuit 31 and a lower bridge driving circuit 32;

[0051] The upper bridge driving circuit 31 includes an upper bridge isolation driving optocoupler U1, a first diode D1, a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1, a first voltage zener diode DZ1, and a second voltage zener diode DZ2;

[0052] The VO end of the upper bridge isolation driving optocoupler U1 is respectively connected to the cathode of the first diode D1 and one end of the first resistor R1, the anode of the first diode D1 is connected to one end of the second resistor R2, the other end of the second resistor R2, one end of the first capacitor C1, the other end of the first resistor R1, one end of the third resistor R3, and the cathode of the second Zener diode DZ2 are connected to each other, the first driving end UHG of the driving circuit 3 is connected to the power circuit 4, the other end of the third resistor R3, the other end of the first capacitor C1, and the cathode of the second Zener diode DZ2 are connected to each other, the second driving end U of the driving circuit 3 is connected to the power circuit 4, and the anode of the first Zener diode DZ1 is connected to the anode of the second Zener diode DZ2;

[0053] The lower bridge driving circuit 32 includes a lower bridge isolation driving optocoupler U2, a second diode D2, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a second capacitor C2, a third voltage zener diode DZ3 and a fourth voltage zener diode DZ4;

[0054] The VO end of the lower bridge driving circuit 32 is respectively connected to the cathode of the second diode D2 and one end of the fourth resistor R4, the anode of the second diode D2 is connected to one end of the fifth resistor R5, the other end of the fifth resistor R5, the other end of the fourth resistor R4, one end of the sixth resistor R6, one end of the second capacitor C2 and the cathode of the fourth Zener diode DZ4 are interconnected, the third driving end ULG of the driving circuit 3 is connected to the power circuit 4, the other end of the sixth resistor R6, the other end of the second capacitor C2 and the cathode of the third Zener diode DZ3 are interconnected, the fourth driving end ULE of the driving circuit 3 is connected to the power circuit 4, and the anode of the third Zener diode DZ3 is connected to the anode of the fourth Zener diode DZ4.

[0055] Among them, the first diode D1 and the second resistor R2 constitute an upper bridge discharge circuit, the first resistor R1 constitutes an upper bridge charging circuit, the second diode D2 and the fifth resistor R5 constitute a lower bridge discharge circuit, the fourth resistor R4 constitutes a lower bridge charging circuit, the third resistor R3 prevents the upper bridge power device in the power circuit 4 from being mis-conducted, the sixth resistor R6 prevents the lower bridge power device in the power circuit 4 from being mis-conducted, the first capacitor C1 filters out interference between the control end and the output end of the power device in the upper bridge power circuit of the power circuit 4, the second capacitor C2 filters out interference between the control end and the output end of the power device in the lower bridge power circuit, the second voltage zener diode DZ2 clamps the positive voltage of the upper bridge power circuit, the first voltage zener diode DZ1 clamps the negative voltage of the upper bridge power circuit to prevent the power device in the upper bridge power circuit from overvoltage breakdown, the fourth voltage zener diode DZ4 clamps the positive voltage of the upper bridge power circuit, and the third voltage zener diode DZ3 clamps the negative voltage of the upper bridge power circuit to prevent the power device in the lower bridge power circuit from overvoltage breakdown.

[0056] Specifically, the driving circuit 3 shares a common ground with the high-voltage input DC+ and DC-, and the MCU control circuit 2 shares a common ground with the current sampling circuit 5. However, through differential sampling, only a low-end sampling resistor is needed to sample the current, without the need for traditional phase-to-phase current sampling. At the same time, because the MCU control circuit 2 and the lower bridge drive of the driving circuit 3 are isolated by an optical coupler, it can be ensured that the driving interference will not affect the MCU control circuit 2. In fact, the reference ground of the lower bridge drive of the MCU control circuit 2 and the driving circuit 3 is connected through the sampling resistor, the eighth resistor R8, the tenth resistor R10, and the eleventh resistor R11, which is electrically non-isolated but signal isolated.

[0057] For details, see Figure 5 As shown, the power circuit 4 includes an upper bridge power circuit Q1, a lower bridge power circuit Q2 and a sampling resistor RS1;

[0058] The control end of the upper bridge power circuit Q1 is connected to the first driving end UHG as the first control end of the power circuit 4, the output end of the upper bridge power circuit Q1 is connected to the input end of the lower bridge power circuit Q2, and is connected to the second driving end U as the U-phase output end of the power circuit 4, the control end of the lower bridge power circuit Q2 is connected to the third driving end ULG as the second control end of the power circuit 4, the output end of the lower bridge power circuit Q2 is connected to one end of the sampling resistor RS1, and is connected to the fourth driving end ULE as the ULE-phase output end of the power circuit 4, and the other end of the sampling resistor RS1 is grounded.

[0059] Among them, all the power devices in the power circuit 4 can be IGBTs, the control end of the upper bridge power circuit Q1 is the gate of each IGBT in the upper bridge power circuit Q1, the input end of the upper bridge power circuit Q1 is the collector of each IGBT in the upper bridge power circuit Q1, and the output end of the upper bridge power circuit Q1 is the emitter of each IGBT in the upper bridge power circuit Q1.

[0060] It should be noted that Figure 5 is an equivalent diagram of the power circuit 4 , wherein the upper bridge power circuit Q1 and the lower bridge power circuit Q2 of the power circuit 4 are actually a full-bridge three-phase rectifier circuit including 6 power devices.

[0061] For details, see Figure 6 As shown, the MCU control circuit 2 includes an MCU control chip U3, and its external ports include +VCC-MCU, GND, I_U, PWM-UH, and PWM-UL. Among them, +VCC-MCU is the positive input of the control part power supply, GND is the reference ground of the control part power supply, I_U is the U-phase current detection input port, PWM-UH is the U-phase upper bridge control PWM wave output, and PWM-UL is the U-phase lower bridge control PWM wave output.

[0062] Among them, the ANODE end of the upper bridge isolation driver optocoupler U1 is connected to the PWM-UH end of the MCU control chip U3, the CATHODE end of the upper bridge isolation driver chip U1 is connected to the PWM-UL end of the MCU control chip U3, the ANODE end of the lower bridge isolation driver optocoupler U2 is connected to the PWM-UL end of the MCU control chip U3, and the CATHODE end of the lower bridge isolation driver chip U2 is connected to the PWM-UH end of the MCU control chip U3.

[0063] It can be seen that in the embodiment of the present invention, the upper bridge driver is isolated, the lower bridge driver is isolated, and the current sampling is resistor sampling. Under the condition of ensuring the quality of the current sampling signal and the stability of the inverter, the cost of the entire isolation circuit is not increased.

[0064] Furthermore, the lower bridge drive power supply is isolated from the MCU control circuit 2 power supply, and the reference ground of the lower bridge drive power supply and the MCU control circuit 2 power supply is connected through the sampling resistor RS1 to achieve electrical isolation, and the expensive phase-to-phase current sampling sensor can be used for direct resistance sampling. However, the control side PWM wave input and the drive signal output are isolated by the drive optical coupler, which can achieve signal isolation, and ensure that the interference of the drive end will not flow to the MCU control end, making the inverter more anti-interference and more reliable.

[0065] Further, in another embodiment of the present invention, see Figure 7 and Figure 8 As shown, the driving circuit 3 includes an upper bridge driving circuit 31 and a lower bridge driving circuit 32;

[0066] The upper bridge driving circuit 31 includes an upper bridge isolation driving chip U1, a fifth diode D5, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a thirteenth capacitor C13, a fifth voltage zener diode DZ5 and a sixth voltage zener diode DZ6;

[0067] The CLAMP end of the upper bridge isolation driver chip U1 is connected to one end of the twentieth resistor R20, the Gout end of the upper bridge isolation driver chip U1 is respectively connected to the cathode of the fifth diode D5 and one end of the seventeenth resistor R17, the anode of the fifth diode D5 is connected to one end of the eighteenth resistor R18, the other end of the eighteenth resistor R18, one end of the thirteenth capacitor C13, the other end of the seventeenth resistor R17, one end of the nineteenth resistor R19 and the cathode of the sixth voltage stabilizing diode DZ6, and the other end of the twentieth resistor R20 are connected to each other as a driving circuit The first driving end UHG of 3 is connected to the power circuit, the other end of the nineteenth resistor R19, the other end of the thirteenth capacitor C13 and the cathode of the sixth voltage zener diode DZ6 are connected to each other, the second driving end U of the driving circuit 3 is connected to the power circuit, the anode of the fifth voltage zener diode DZ5 and the anode of the sixth voltage zener diode DZ6 are connected to each other, the IN+ end of the upper bridge isolation driving chip U1 is connected to the PWM-UH end of the MCU control chip U3, and the IN- end of the upper bridge isolation driving chip U1 is connected to the PWM-UL end of the MCU control chip U3;

[0068] The lower bridge driving circuit 32 includes a lower bridge isolation driving chip U2, a fourth diode D4, a twenty-first resistor R21, a twenty-second resistor R22, a twenty-third resistor R23, a twenty-fourth resistor R24, a fourteenth capacitor C14, a seventh voltage zener diode DZ7 and an eighth voltage zener diode DZ8;

[0069] The CLAMP end of the lower bridge isolation driver chip U2 is connected to one end of the twenty-fourth resistor R24, the Gout end of the lower bridge driver circuit 32 is respectively connected to the cathode of the fourth diode D4 and one end of the twenty-first resistor R21, the anode of the fourth diode D4 is connected to one end of the twenty-second resistor R22, the other end of the twenty-second resistor R22, the other end of the twenty-first resistor R21, one end of the twenty-third resistor R23, one end of the fourteenth capacitor C14 and the cathode of the eighth voltage zener diode DZ8, and the other end of the twenty-fourth resistor R24 ​​are connected to each other as the driving circuit. The third driving terminal ULG of the circuit 3 is connected to the power circuit, the other end of the twenty-third resistor R23, the other end of the fourteenth capacitor C14 and the cathode of the seventh voltage-stabilizing diode DZ7 are connected to each other, the fourth driving terminal ULE of the driving circuit 3 is connected to the power circuit, the anode of the seventh voltage-stabilizing diode DZ7 and the anode of the eighth voltage-stabilizing diode DZ8 are connected to each other, the IN+ terminal of the lower bridge isolation driving chip U2 is connected to the PWM-UL terminal of the MCU control chip U3, and the IN- terminal of the lower bridge isolation driving chip U2 is connected to the PWM-UH terminal of the MCU control chip U3.

[0070] Finally, it should be noted that, in this article, 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 "include", "comprise" 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, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0071] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0072] The technical content provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for general technical personnel in the field, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A frequency converter isolation circuit, characterized in that: include: A switching power supply circuit, an MCU control circuit, a drive circuit, a power circuit and a current sampling circuit; wherein the power circuit includes an upper bridge power circuit, a lower bridge power circuit and a sampling resistor; The switching power supply circuit is respectively connected to the power supply ends of the MCU control circuit, the drive circuit and the current sampling circuit, the current sampling detection input end of the MCU control circuit is connected to the current sampling detection output end of the current sampling circuit, the drive circuit is respectively connected to the MCU control circuit and the power circuit, and the current sampling circuit is connected to the two ends of the sampling resistor in the power circuit; the current sampling circuit and the MCU control circuit share a common ground; the MCU control circuit is isolated from the upper bridge drive circuit and the lower bridge drive circuit of the drive circuit; The current sampling circuit includes a filter circuit for filtering out current sampling interference signals and a first-stage current sampling signal differential amplifier for amplifying an AC current sampling signal, which are connected in sequence, and a third diode connected inside the filter circuit for clamping the current sampling signal; The filter circuit comprises a seventh resistor, an eighth resistor and a third capacitor; one end of the seventh resistor is connected to one end of the sampling resistor in the power circuit as a first sampling end of the current sampling circuit, the other end of the seventh resistor is connected to one end of the third capacitor, one end of the eighth resistor is connected to the other end of the sampling resistor in the power circuit as a second sampling end of the current sampling circuit, and the other end of the eighth resistor is connected to the other end of the third capacitor; The first-stage current sampling signal differential amplifier comprises a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor and a fourth operational amplifier; one end of the ninth resistor is connected to the other end of the seventh resistor, the other end of the ninth resistor is respectively connected to one end of the twelfth resistor and the negative input end of the fourth operational amplifier, one end of the tenth resistor is connected to the other end of the eighth resistor, the other end of the tenth resistor is respectively connected to one end of the eleventh resistor and the positive input end of the fourth operational amplifier, the other end of the twelfth resistor is connected to the output end of the fourth operational amplifier as the current sampling detection output end of the current sampling circuit, and the other end of the eleventh resistor is grounded; The current sampling circuit also includes a second-stage addition current sampling signal amplifier connected to the first-stage current sampling signal differential amplifier as a current sampling detection output terminal of the current sampling circuit and used to raise the voltage of the AC current sampling signal to above the reference ground voltage; The second-stage addition current sampling signal amplifier includes a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a fourth capacitor and a fifth operational amplifier; one end of the thirteenth resistor is connected to the output end of the fourth operational amplifier, the other end of the thirteenth resistor, one end of the fourteenth resistor, one end of the fourth capacitor and the positive input end of the fifth operational amplifier are connected to each other, one end of the fifteenth resistor is grounded, the other end of the fifteenth resistor, the other end of the fourth capacitor, the negative input end of the fifth operational amplifier and one end of the sixteenth resistor are connected to each other, the other end of the fourteenth resistor serves as the power supply end of the current sampling circuit, and the other end of the sixteenth resistor and the output end of the fifth operational amplifier are connected as the current sampling detection output end of the current sampling circuit.

2. The frequency converter isolation circuit according to claim 1, characterized in that: The driving circuit includes an upper bridge driving circuit and a lower bridge driving circuit; The upper bridge driving circuit includes an upper bridge isolation driving optocoupler, a first diode, a first resistor, a second resistor, a third resistor, a first capacitor, a first voltage zener diode, and a second voltage zener diode; The VO end of the upper bridge isolation drive optocoupler is respectively connected to the cathode of the first diode and one end of the first resistor, the anode of the first diode is connected to one end of the second resistor, the other end of the second resistor, one end of the first capacitor, the other end of the first resistor, one end of the third resistor and the cathode of the second voltage regulator diode are connected to each other, and the first drive end of the drive circuit is connected to the power circuit, the other end of the third resistor, the other end of the first capacitor and the cathode of the second voltage regulator diode are connected to each other, and the second drive end of the drive circuit is connected to the power circuit, the anode of the first voltage regulator diode is connected to the anode of the second voltage regulator diode, and the NC end of the upper bridge isolation drive optocoupler is connected to the MCU control circuit; The lower bridge driving circuit includes a lower bridge isolation driving optocoupler, a second diode, a fourth resistor, a fifth resistor, a sixth resistor, a second capacitor, a third voltage stabilizing diode and a fourth voltage stabilizing diode; The VO end of the lower bridge driving circuit is respectively connected to the cathode of the second diode and one end of the fourth resistor, the anode of the second diode is connected to one end of the fifth resistor, the other end of the fifth resistor, the other end of the fourth resistor, one end of the sixth resistor, one end of the second capacitor and the cathode of the fourth voltage-stabilizing diode are connected to each other, and the third driving end of the driving circuit is connected to the power circuit, the other end of the sixth resistor, the other end of the second capacitor and the cathode of the third voltage-stabilizing diode are connected to each other, and the fourth driving end of the driving circuit is connected to the power circuit, the anode of the third voltage-stabilizing diode is connected to the anode of the fourth voltage-stabilizing diode, and the NC end of the lower bridge isolation driving optocoupler is connected to the MCU control circuit.

3. The frequency converter isolation circuit according to claim 1, characterized in that: The driving circuit includes an upper bridge driving circuit and a lower bridge driving circuit; The upper bridge driving circuit includes an upper bridge isolation driving chip, a fifth diode, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, a thirteenth capacitor, a fifth voltage stabilizing diode and a sixth voltage stabilizing diode; The CLAMP end of the upper bridge isolation driver chip is connected to one end of the twentieth resistor, the Gout end of the upper bridge isolation driver chip is respectively connected to the cathode of the fifth diode and one end of the seventeenth resistor, the anode of the fifth diode is connected to one end of the eighteenth resistor, the other end of the eighteenth resistor, one end of the thirteenth capacitor, the other end of the seventeenth resistor, one end of the nineteenth resistor and the cathode of the sixth voltage zener diode, and the other end of the twentieth resistor are connected to each other, and are connected to the power circuit as the first driving end of the drive circuit, the other end of the nineteenth resistor, the other end of the thirteenth capacitor and the cathode of the sixth voltage zener diode are connected to each other, and are connected to the power circuit as the second driving end of the drive circuit, and the anode of the fifth voltage zener diode is connected to the anode of the sixth voltage zener diode; The lower bridge driving circuit includes a lower bridge isolation driving chip, a fourth diode, a twenty-first resistor, a twenty-second resistor, a twenty-third resistor, a twenty-fourth resistor, a fourteenth capacitor, a seventh voltage zener diode and an eighth voltage zener diode; The CLAMP end of the lower bridge isolation driver chip is connected to one end of the twenty-fourth resistor, the Gout end of the lower bridge driver circuit is respectively connected to the cathode of the fourth diode and one end of the twenty-first resistor, the anode of the fourth diode is connected to one end of the twenty-second resistor, the other end of the twenty-second resistor, the other end of the twenty-first resistor, one end of the twenty-third resistor, one end of the fourteenth capacitor, the cathode of the eighth voltage-regulating diode, and the other end of the twenty-fourth resistor are connected to each other, and the third driver end of the driver circuit is connected to the power circuit, the other end of the twenty-third resistor, the other end of the fourteenth capacitor, and the cathode of the seventh voltage-regulating diode are connected to each other, and the fourth driver end of the driver circuit is connected to the power circuit, and the anode of the seventh voltage-regulating diode is connected to the anode of the eighth voltage-regulating diode.

4. The frequency converter isolation circuit according to claim 2 or 3, characterized in that: The control end of the upper bridge power circuit is connected to the first driving end as the first control end of the power circuit, the output end of the upper bridge power circuit is connected to the input end of the lower bridge power circuit, and is connected to the second driving end as the U-phase output end of the power circuit, the control end of the lower bridge power circuit is connected to the third driving end as the second control end of the power circuit, the output end of the lower bridge power circuit is connected to one end of the sampling resistor, and is connected to the fourth driving end as the ULE phase output end of the power circuit, and the other end of the sampling resistor is grounded.

5. The frequency converter isolation circuit according to claim 4, characterized in that: The upper bridge power circuit and the lower bridge power circuit are both full-bridge three-phase rectifier circuits.

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