Demagnetization protection circuit and demagnetization protection device of frequency conversion equipment and frequency conversion equipment

Abstract

The utility model discloses a demagnetization protection circuit of frequency conversion equipment, the frequency conversion equipment comprises a frequency conversion motor and an IPM module used for driving the frequency conversion motor, and the IPM module comprises three phase current sampling ends; the demagnetization protection circuit comprises a voltage sampling module which comprises a one-way conduction module and three current sampling branches, one ends of the three current sampling branches are respectively connected with three phase current sampling ends and the one-way conduction module, and the other ends of the three current sampling branches are all grounded; the voltage comparator is connected with the one-way conduction module, and the one-way conduction module is used for conducting the current sampling branch and the input end of the voltage comparator under the condition that at least one of the three current sampling branches has reverse current flowing to the phase current sampling end. According to the utility model, the reverse current demagnetization protection can be realized only through the single voltage comparator, so that the product cost can be effectively reduced, and the miniaturization of the product can be better realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to variable frequency equipment technical field especially, relates to a variable frequency equipment's demagnetization protection circuit, demagnetization protection device and variable frequency equipment. BACKGROUND

[0002] In the process of actual application of variable frequency equipment such as air conditioner compressor, when variable frequency motor in variable frequency equipment reversely rotates or stops, reverse electromotive force will be generated in the winding of variable frequency motor, leading to the generation of reverse current on the phase current circuit of IPM module in variable frequency equipment, and the reverse current will gradually weaken the magnetic field of variable frequency motor, when the reverse current is too large, it will lead to the demagnetization of variable frequency motor, damage its variable frequency function, and affect its performance and service life.

[0003] At present, there is a demagnetization protection scheme that multiple comparators are used to independently detect and compare three phase current sampling ends of IPM module, which needs to use at least three comparators and other components, affecting product cost and being not conducive to product miniaturization. UTILITY MODEL CONTENTS

[0004] The utility model discloses a variable frequency equipment's demagnetization protection circuit, demagnetization protection device and variable frequency equipment can only realize reverse current detection to three phase current sampling ends of IPM module through single voltage comparator, realize demagnetization protection to variable frequency equipment, effectively reduce product cost, and better realize product miniaturization.

[0005] In the first aspect, the utility model discloses a variable frequency equipment's demagnetization protection circuit, and the variable frequency equipment includes variable frequency motor and IPM module for driving the variable frequency motor, and the IPM module includes three phase current sampling ends, and the demagnetization protection circuit includes: voltage sampling module, including unidirectional conduction module and three current sampling branches, one end of three current sampling branches is connected to three phase current sampling ends respectively, one end of three current sampling branches is also connected to unidirectional conduction module, and the other end of three current sampling branches is all grounded, voltage comparator is connected with unidirectional conduction module, and unidirectional conduction module is used to conduct current sampling branch and the input end of voltage comparator in the condition that at least one of three current sampling branches exists reverse current to phase current sampling end, and control unit is connected with the output end of voltage comparator and three phase current sampling ends respectively, and is used to control the working state of IPM module according to the output level of voltage comparator.

[0006] The degaussing protection circuit of the frequency conversion equipment can be applied to the frequency conversion equipment, the frequency conversion equipment comprises a frequency conversion motor and an IPM module used for driving the frequency conversion motor, three current sampling branches are formed by connecting three-phase current ends of the IPM module with ground ends, when the frequency conversion motor reversely rotates, the voltage of the three-phase current ends of the IPM module is lower than the voltage of the ground ends, and in the case that at least one of the three current sampling branches has reverse current flowing to the phase current sampling end, the utility model embodiment can connect the ground ends of the three current sampling branches through the unidirectional conduction module, the voltage comparator is connected with the unidirectional conduction module, the current sampling branch and the input end of the voltage comparator are conducted, and the control unit is connected with the output end of the voltage comparator and the three phase current sampling ends respectively, the working state of the IPM module is controlled according to the output level of the voltage comparator; wherein, it can be understood that, based on the above-mentioned circuit structure, the utility model embodiment can only make the unique voltage comparator communicate with the phase having reverse current through the unidirectional conduction module when reverse current is generated in a certain phase, collect the sampling voltage corresponding to at least one phase reverse current, and output the level signal according to the sampling voltage through the voltage comparator, and the control unit sends the control signal to the IPM module according to the level signal, so that the IPM module drives the frequency conversion motor to operate or stop, realizes the overcurrent detection of each phase reverse current, and further, while realizing the degaussing protection of the frequency conversion equipment, the number of comparators and other components can be effectively reduced, the product cost is reduced, and the product miniaturization can be better realized.

[0007] In some embodiments, sampling resistors are arranged on the three current sampling branches, the unidirectional conduction module comprises three diodes, positive ends of the three diodes are communicated, and negative ends of the three diodes are respectively connected to one end of the three sampling resistors close to the phase current sampling end.

[0008] In some embodiments, the voltage sampling module further comprises a voltage dividing module, one end of the voltage dividing module is connected to the unidirectional conduction module, and the other end of the voltage dividing module is connected to a direct current power supply end, the voltage dividing module comprises a first voltage dividing resistor and a second voltage dividing resistor, and the voltage comparator is connected between the first voltage dividing resistor and the second voltage dividing resistor.

[0009] In some embodiments, the voltage comparator comprises a sampling voltage end connected to the unidirectional conduction module, and a reference voltage end used for acquiring a reference voltage, wherein the voltage comparator is configured to output a first level signal when a sampling voltage acquired at the sampling voltage end is greater than the reference voltage, and output a second level signal when the sampling voltage is less than or equal to the reference voltage.

[0010] In some embodiments, the control unit is configured to: send a first control signal to the IPM module to drive the variable frequency motor to operate when the first level signal is received; and send a second control signal to the IPM module to drive the variable frequency motor to stop when the second level signal is received.

[0011] In some embodiments, the demagnetization protection circuit further comprises: a current sampling module, one end of which is connected to the three phase current sampling ends respectively, and the other end of which is connected to the current detection end of the IPM module, for transmitting the current signals of the three current sampling branches to the IPM module.

[0012] In some embodiments, the current sampling module comprises: an input resistor and a filter circuit, one end of the input resistor being connected to the three phase current sampling ends respectively, and the other end of the input resistor being connected to the current detection end and the filter circuit respectively.

[0013] In some embodiments, the control unit comprises three control signal ends connected to the three phase current sampling ends respectively, and the demagnetization protection circuit further comprises: a level pull-up module connected to the three control signal ends respectively.

[0014] In the second aspect, the utility model embodiment provides a kind of demagnetization protection device, including the demagnetization protection circuit of the variable frequency equipment of any one of first aspect.

[0015] The degaussing protection device in the degaussing protection device can be applied to the variable frequency equipment, the variable frequency equipment comprises a variable frequency motor and an IPM module used for driving the variable frequency motor, three current sampling branches are formed by connecting three-phase current ends of the IPM module with ground ends, when the variable frequency motor reversely rotates, the voltage of the three-phase current ends of the IPM module is lower than the voltage of the ground ends, and at least one of the three current sampling branches has reverse current flowing to the phase current sampling end, the utility model embodiment can connect the ground ends of the three current sampling branches through the unidirectional conduction module, the voltage comparator is connected with the unidirectional conduction module, the current sampling branch and the input end of the voltage comparator are conducted, and the control unit is connected with the output end of the voltage comparator and the three phase current sampling ends respectively, the working state of the IPM module is controlled according to the output level of the voltage comparator, wherein, it can be understood that, based on the above circuit structure, the utility model embodiment can only make the unique voltage comparator communicate with the phase having reverse current through the unidirectional conduction module when reverse current is generated in a certain phase, the sampling voltage corresponding to at least one phase reverse current is collected, the voltage comparator outputs a level signal according to the sampling voltage, the control unit sends a control signal to the IPM module according to the level signal, so that the IPM module drives the variable frequency motor to run or stop, overcurrent detection of each phase reverse current is realized, and then while realizing degaussing protection of the variable frequency equipment, the number of comparators and other components can be effectively reduced, product cost is reduced, and product miniaturization can be better realized.

[0016] In a third aspect, the utility model provides a variable frequency equipment, including the degaussing protection circuit of variable frequency equipment of any one of first aspect or the degaussing protection device of any one of second aspect.

[0017] The utility model discloses a kind of variable frequency equipment, at least have following beneficial effect: the demagnetization protection circuit of variable frequency equipment can be applied to variable frequency equipment, variable frequency equipment includes variable frequency motor and IPM module for driving variable frequency motor, three current sampling branches formed by the connection of three-phase current end and ground end of IPM module, when variable frequency motor reversely rotates, the voltage of three-phase current end of IPM module is lower than the voltage of ground end, at least one of three current sampling branches exists reverse current flowing to phase current sampling end, the utility model embodiment can be connected the ground end of three current sampling branches by unidirectional conduction module, voltage comparator is connected with unidirectional conduction module, current sampling branch and the input end of voltage comparator are conducted, and are connected with the output end of voltage comparator and three phase current sampling ends respectively by control unit, according to the output level of voltage comparator Control the working state of IPM module;Wherein, it can be understood that, based on the above circuit structure, the utility model embodiment can only make the only voltage comparator be communicated with the phase existing reverse current by unidirectional conduction module when reverse current is generated in certain phase, gather the sampling voltage corresponding to at least one phase reverse current, and output level signal according to sampling voltage by voltage comparator, control unit sends control signal to IPM module according to level signal, so that IPM module drives variable frequency motor to run or stop, realize the overcurrent detection of every phase reverse current, and then, while realizing demagnetization protection to variable frequency equipment, the number of comparator and other components can be effectively reduced, product cost is reduced, product miniaturization can be better realized.

[0018] Other features and advantages of the present application will be set forth in the descriptions below, and in part will be apparent from the description, or can be learned by practice of the present application. The purposes and other advantages of the present application can be realized and obtained by the structure particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of this specification, illustrate embodiments of the present application and serve to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0020] The present application will be further described below in conjunction with the drawings and embodiments;

[0021] Figure 1 is an optional structure schematic view of the demagnetization protection circuit of the variable frequency equipment provided by the utility model embodiment;

[0022] Figure 2 is an optional structure schematic view of the demagnetization protection circuit of the variable frequency equipment provided by the utility model embodiment, and sampling resistance is arranged;

[0023] Figure 3 is an optional structure schematic diagram of the demagnetization protection circuit of the variable frequency equipment provided by the embodiment of the utility model, set up a kind of optional structure schematic diagram of voltage divider module in the demagnetization protection circuit of the variable frequency equipment provided by the embodiment of the utility model;

[0024] Figure 4 is an optional structure schematic diagram of the demagnetization protection circuit of the variable frequency equipment provided by the embodiment of the utility model, set up a kind of optional structure schematic diagram of voltage comparator in the demagnetization protection circuit of the variable frequency equipment provided by the embodiment of the utility model;

[0025] Figure 5 is an optional structure schematic diagram of the demagnetization protection circuit of the variable frequency equipment provided by the embodiment of the utility model, set up a kind of optional structure schematic diagram of current sampling module in the demagnetization protection circuit of the variable frequency equipment provided by the embodiment of the utility model;

[0026] Figure 6 is an optional structure schematic diagram of the demagnetization protection circuit of the variable frequency equipment provided by the embodiment of the utility model, set up a kind of optional structure schematic diagram of level pull-up module in the demagnetization protection circuit of the variable frequency equipment provided by the embodiment of the utility model.

[0027] Reference signs:

[0028] 100, demagnetization protection circuit;110, voltage sampling module;111, unidirectional conduction module;120, voltage comparator;130, control unit;140, IPM module;150, variable frequency motor. DETAILED DESCRIPTION

[0029] This part will describe the specific embodiments of the utility model in detail, and the preferred embodiments of the utility model are shown in the drawings, and the drawings are used to supplement the description of the text part with graphics, so that people can intuitively and visually understand each technical feature and the overall technical scheme of the utility model, but it cannot be understood as the limitation of the protection scope of the utility model.

[0030] In the description of the utility model, the meaning of several is one or more, the meaning of multiple is two or more, greater than, less than, more than, etc. are understood as not including the number, above, below, within, etc. are understood as including the number, "any one" means one or more, "at least one of the following" and similar expressions mean any combination of these items, including single or multiple items. If it is described to the first, second, only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the sequence of indicated technical features.

[0031] It should be noted that the terms such as setting, installing and connecting in the embodiments of the present utility model should be understood in a broad sense, and the skilled in the art can determine the specific meaning of the above terms in the embodiments of the present utility model in combination with the specific content of the technical solutions.

[0032] It should be noted that the technical features involved in each embodiment of the present utility model described below can be combined with each other as long as there is no conflict.

[0033] In the process of actual application of the frequency conversion device such as the compressor of the air conditioner, when the frequency conversion motor in the frequency conversion device reverses rotation or stops, a reverse electromotive force will be generated in the winding of the frequency conversion motor, which causes a reverse current to be generated on the phase current circuit of the IPM module in the frequency conversion device, the reverse current will gradually weaken the magnetic field of the frequency conversion motor, when the reverse current is too large, it will cause the frequency conversion motor to demagnetize, damage its frequency conversion function, and affect its performance and service life; at present, there is a demagnetization protection scheme for independently detecting and comparing the three phase current sampling ends of the IPM module through multiple comparators, which at least needs to use three comparators and other components, affects the product cost, and is not conducive to product miniaturization.

[0034] Therefore, the purpose of the present utility model is to at least solve one of the technical problems in the prior art, provide a demagnetization protection circuit, a demagnetization protection device and a frequency conversion device, which can realize reverse current detection on the three phase current sampling ends of the IPM module through a single voltage comparator, effectively reduce the product cost while realizing demagnetization protection of the frequency conversion device, and better realize product miniaturization.

[0035] The embodiments of the present utility model will be described below in combination with the drawings.

[0036] Reference Figure 1 , Figure 1Is an optional structure schematic view of the demagnetization protection circuit 100 of the frequency conversion equipment provided by the embodiment of the utility model; the first aspect, the utility model discloses a kind of demagnetization protection circuit 100 of frequency conversion equipment provided by the embodiment of the utility model, and frequency conversion equipment includes variable frequency motor 150 and the IPM module 140 for driving variable frequency motor 150, and IPM module 140 includes three phase current sampling end;Demagnetization protection circuit 100 includes: voltage sampling module 110, including unidirectional conduction module 111 and three current sampling branches, one end of three current sampling branches is connected to three phase current sampling end respectively, one end of three current sampling branches is also connected to unidirectional conduction module 111, and the other end of three current sampling branches is all grounded;Voltage comparator 120 is connected with unidirectional conduction module 111, and unidirectional conduction module 111 is used to in the case where at least one of three current sampling branches exists reverse current flowing to phase current sampling end, current sampling branch and the input end of voltage comparator 120 are conducted;Control unit 130 is connected with the output end of voltage comparator 120 and three phase current sampling end respectively, and is used to control the working state of IPM module 140 according to the output level of voltage comparator 120.

[0037] Corresponding Figure 1 , variable frequency motor 150 IPM module 140 drive, for frequency conversion operation;IPM module 140 is used to drive variable frequency motor 150, and includes three phase current sampling end: U, V, W phase;Voltage sampling module 110 includes unidirectional conduction module 111 and three current sampling branches a1, a2, a3, and unidirectional conduction module 111 is used to conduct current sampling branch and the input end of voltage comparator 120 when detecting reverse current, and one end of a1, a2, a3 each branch is connected to three phase current sampling end IU, IV, IW of IPM module 140, and the other end is grounded;Voltage comparator 120 is connected with unidirectional conduction module 111, and is used to compare the voltage at the both ends of sampling resistance and reference voltage, input end is connected to unidirectional conduction module 111, and output end is connected to control unit 130;Control unit 130 is connected with the output end of voltage comparator 120 and three phase current sampling end respectively, and when voltage comparator 120 outputs high level, control unit 130 sends control signal to IPM module 140, so that IPM module 140 drives variable frequency motor 150 to operate, and when voltage comparator 120 outputs low level, control unit 130 sends control signal to IPM module 140, so that IPM module 140 drives variable frequency motor 150 to stop.

[0038] In some embodiments, it can be understood that, in the normal working state, the current flows from the IPM module 140 to the variable frequency motor 150, does not pass through the unidirectional conduction module 111, the voltage drop on the sampling resistor is monitored, but does not trigger the voltage comparator 120, and the control unit 130 keeps the IPM module 140 normal working; when the variable frequency motor 150 generates a reverse current, the current will flow from the variable frequency motor 150 to the IPM module 140, the reverse current passes through the unidirectional conduction module 111 and flows through the sampling resistor, the voltage drop on the sampling resistor exceeds the reference voltage, the voltage comparator 120 outputs a high level signal, the control unit 130 receives the high level signal, sends a control signal to the IPM module 140, and makes the IPM module 140 drive the variable frequency motor 150 to stop, through the above process, the demagnetization protection circuit 100 can effectively monitor and protect the variable frequency equipment, and prevent the demagnetization phenomenon of the variable frequency motor 150 caused by the reverse current.

[0039] In some embodiments, the variable frequency equipment includes an electrical equipment capable of changing the output frequency to adjust the rotating speed of the variable frequency motor 150, in the embodiment, the variable frequency equipment includes the variable frequency motor 150 and the IPM module 140, the IPM module 140 is an intelligent power module, which is responsible for driving the variable frequency motor 150; the variable frequency motor 150 can change its rotating speed by adjusting the power supply frequency, and is applied to application occasions requiring accurate speed control, such as air conditioner compressors; the IPM module 140 can integrate a plurality of power semiconductor devices such as IGBT or MOSFE and protection circuits, and is used for efficiently converting direct current into three-phase alternating current, so as to drive the variable frequency motor 150. The IPM module 140 contains three phase current sampling ends for monitoring the current passing through the variable frequency motor 150.

[0040] In some embodiments, the voltage sampling module 110 is used to monitor the current output from the IPM module 140 to the variable frequency motor 150. It is composed of a unidirectional conduction module 111 and three current sampling branches, each current sampling branch is connected to a phase current sampling end and finally grounded, when the variable frequency motor 150 normally operates, the current flows from the IPM to the variable frequency motor 150; when the variable frequency motor 150 reversely rotates and generates a reverse current, the current will flow back to the IPM from the ground wire, forming a reverse current.

[0041] In some embodiments, the unidirectional conduction module 111 can be composed of a diode, which ensures that the current can only flow in one direction. In the embodiment, the unidirectional conduction module 111 can be used to prevent the forward current from affecting the voltage comparator 120, while allowing the reverse current to trigger the voltage comparator 120, when the reverse current is detected, the unidirectional conduction module 111 connects the corresponding current sampling branch to the input end of the voltage comparator 120.

[0042] In some embodiments, each of the three current sampling branches corresponds to a phase current sampling terminal of the IPM module 140, and is used to measure the current flowing through each phase. The three current sampling branches can be provided with sampling resistors to convert the current into a voltage signal for subsequent processing by the voltage comparator 120. The voltage comparator 120 is used to compare the sampling voltage from the unidirectional conduction module 111 with a pre-set reference voltage. If the sampling voltage exceeds the reference voltage, it indicates that an abnormal reverse current has occurred. At this time, the voltage comparator 120 generates a high-level output to inform the control unit 130 to take action.

[0043] In some embodiments, the control unit 130 can receive signals from the voltage comparator 120 and decide whether to stop the operation of the IPM module 140 to avoid demagnetization of the variable frequency motor 150 caused by excessive reverse current. The control unit 130 can also communicate with multiple sensors or controllers to implement control logic for specific application scenarios.

[0044] In some embodiments, the control unit 130 can receive signals from the voltage comparator 120 and decide whether to stop the operation of the IPM module 140 to avoid demagnetization of the variable frequency motor 150 caused by excessive reverse current. The control unit 130 can also communicate with multiple sensors or controllers to implement control logic for specific application scenarios.

[0045] In some embodiments, the IPM module 140 can include an inverter bridge composed of six IGBT tubes, divided into three bridge arms, each bridge arm containing an upper bridge IGBT and a lower bridge IGBT, the DC bus voltage being connected to the collector of the upper bridge IGBT tube of the three bridge arms in the inverter bridge, and the emitter of the lower bridge IGBT tube of the three bridge arms in the inverter bridge forming three phase current sampling ends.

[0046] In some embodiments, the comparator and the control unit 130 can be integrated into the same MCU chip at the same time, which can further save space and cost, and the reference voltage of the voltage comparator 120 can be set by programming the VREF threshold value, so that the demagnetization protection circuit 100 in the embodiment can meet the overcurrent protection requirements of different variable frequency motors 150 without changing the hardware structure.

[0047] Reference Figure 2 , Figure 2 In the demagnetization protection circuit 100 of the variable frequency device provided in the embodiment of the utility model, a kind of optional structure schematic diagram of sampling resistance is provided; in some embodiments, sampling resistance is arranged on three current sampling branches, one-way conduction module 111 includes three diodes, the anode of three diodes is communicated, and the cathode of three diodes is respectively connected to one end of three sampling resistances close to phase current sampling end;Wherein, each branch of three current sampling branches corresponds to a phase current sampling end of IPM module 140, and one sampling resistance is arranged on each branch, sampling resistance R1 is arranged on current sampling branch a1 connected to U-phase current sampling end IU, sampling resistance R2 is arranged on current sampling branch a2 connected to V-phase current sampling end IV, and sampling resistance R3 is arranged on current sampling branch a3 connected to W-phase current sampling end IW, which are respectively used to convert the current flowing through the phase current sampling end into a voltage signal, and the selection of resistance value determines the conversion ratio between current and voltage, when current flows through these resistances, voltage drop is generated, and the voltage drop is used to monitor the size of current.

[0048] In some embodiments, one-way conduction module 111 can be composed of three diodes (D1, D2, D3), the anode of each diode is communicated to form a common node, and the cathode is respectively connected to one end of three current sampling branches close to phase current sampling end (IU, IV, IW). It can be understood that the diode (D1, D2, D3) has a one-way conduction characteristic, that is, current can only flow from the anode to the cathode, in the case of forward rotation of the variable frequency motor 150, current flows from the IPM module 140 to the variable frequency motor 150, and does not pass through the diode, when reverse current occurs, current flows from the variable frequency motor 150 to the IPM module 140, at this time, the diode is turned on to allow current to pass through.

[0049] Reference Figure 3 ,Figure 3 In the demagnetization protection circuit 100 of the frequency conversion equipment provided in the embodiment of the utility model, a kind of optional structure schematic diagram of voltage dividing module is set;In some embodiments, voltage sampling module 110 further includes: voltage dividing module, one end is connected with unidirectional conduction module 111, the other end is connected with direct current power supply end, voltage dividing module includes first voltage dividing resistor and second voltage dividing resistor, voltage comparator 120 is connected between first voltage dividing resistor and second voltage dividing resistor, wherein, voltage dividing module is made of first voltage dividing resistor R4 and second voltage dividing resistor R5, for voltage division from direct current power supply end VCC, one end of voltage dividing module is connected to unidirectional conduction module 111, the other end is connected to direct current power supply end VCC.

[0050] In some embodiments, first voltage dividing resistor R4 is connected between direct current power supply end VCC and second voltage dividing resistor R5, second voltage dividing resistor R5 is connected between first voltage dividing resistor R4 and voltage comparator 120, voltage comparator 120 is connected between first voltage dividing resistor R4 and second voltage dividing resistor R5, for sampling negative voltage at both ends of resistance R1-R3.

[0051] It can be understood that when current flows from IPM module 140 to frequency conversion motor 150, it does not pass through diode D1-D3, when frequency conversion motor 150 generates reverse current, current flows from frequency conversion motor 150 to IPM module 140, reverse current passes through diode D1-D3 and flows through sampling resistor, voltage dividing module divides voltage of direct current power supply end VCC by R4 and R5 to obtain sampling voltage.

[0052] Reference Figure 4 , Figure 4 In the demagnetization protection circuit 100 of the frequency conversion equipment provided in the embodiment of the utility model, a kind of optional structure schematic diagram of voltage dividing module is set;In some embodiments, voltage sampling module 110 further includes: voltage dividing module, one end is connected with unidirectional conduction module 111, the other end is connected with direct current power supply end, voltage dividing module includes first voltage dividing resistor and second voltage dividing resistor, voltage comparator 120 is connected between first voltage dividing resistor and second voltage dividing resistor, wherein, voltage dividing module is made of first voltage dividing resistor R4 and second voltage dividing resistor R5, for voltage division from direct current power supply end VCC, one end of voltage dividing module is connected to unidirectional conduction module 111, the other end is connected to direct current power supply end VCC.

[0053] In some embodiments, the control unit 130 is configured to: send a first control signal to the IPM module 140 to drive the variable frequency motor 150 to run when a first level signal is received; and send a second control signal to the IPM module 140 to drive the variable frequency motor 150 to stop when a second level signal is received; wherein the first control signal is sent to the IPM module 140 to drive the variable frequency motor 150 to run when a high level first level signal is received, and the second control signal is sent to the IPM module 140 to drive the variable frequency motor 150 to stop when a low level second level signal is received.

[0054] It can be understood that the control unit 130 receives the output signal of the voltage comparator 120, and if the voltage comparator 120 outputs a high level signal, it indicates that a reverse current is detected, and the control unit 130 sends a control signal to the IPM module 140 to drive the variable frequency motor 150 to stop, so as to prevent the variable frequency motor 150 from demagnetizing.

[0055] Reference Figure 5 , Figure 5 In the demagnetization protection circuit 100 of the variable frequency device provided in the embodiments of the present application, an optional structure diagram of a current sampling module is provided; in some embodiments, the demagnetization protection circuit 100 further comprises: a current sampling module, one end of which is connected to three phase current sampling ends respectively, and the other end is connected to a current detection end of the IPM module 140, for transmitting current signals of three current sampling branches to the IPM module 140; wherein the current sampling module comprises: an input resistor and a filter circuit, one end of the input resistor is connected to the three phase current sampling ends respectively, and the other end of the input resistor is connected to the current detection end and the filter circuit respectively.

[0056] In some embodiments, the current sampling module is configured to, in a case where at least one of the three current sampling branches has a forward current flowing to the ground end, turn on the current sampling branch and the current detection end Vrs, transmit the current signals of the three current sampling branches to the IPM module 140, so that the IPM module 140 performs forward current protection, and controls the IPM module 140 to drive the variable frequency motor 150 to run or stop.

[0057] In some embodiments, the current sampling module is configured to, in a case where at least one of the three current sampling branches has a forward current flowing to the ground end, turn on the current sampling branch and the current detection end Vrs, transmit the current signals of the three current sampling branches to the IPM module 140, so that the IPM module 140 performs forward current protection, and controls the IPM module 140 to drive the variable frequency motor 150 to run or stop.

[0058] In some embodiments, the current sampling module further comprises a filtering loop composed of a filtering resistor R7 and a filtering capacitor C1, the filtering resistor R7 and the filtering capacitor C1 are connected in parallel, one end of which is connected to the current detection end Vrs, and the other end is grounded, for filtering high-frequency noise in the current signal and improving the stability of the signal.

[0059] In some embodiments, the current sampling module further comprises a forward conduction module, the forward conduction module comprises three forward conduction diodes D4, D5 and D6, the anode ends of the three forward conduction diodes D4, D5 and D6 are respectively connected to the three current sampling branches, and the cathode ends are all connected to the input end of the input resistor R6, in the case that there is a forward current flowing to the ground end in at least one of the three current sampling branches, the current flows through the corresponding forward conduction diode from the IPM module 140, and a voltage drop is generated when the current passes through the input resistor (R6), and the voltage drop signal is transmitted to the current detection end of the IPM module 140; in the case that the cathode ends of the three diodes are respectively connected to one end of the three sampling resistors close to the phase current sampling end, the forward conduction diodes D4, D5 and D6 are disconnected.

[0060] It is worth noting that when the variable frequency motor 150 rotates reversely, a large reverse current will be generated in the winding of the variable frequency motor 150, which will cause the magnetic field of the variable frequency motor 150 to weaken or even disappear, which is called demagnetization phenomenon, and the resistance of the present application detects the reverse current to control the variable frequency motor 150 to stop, and although the present application does not perform voltage detection based on the reverse current when the variable frequency motor 150 rotates forward, it performs overcurrent detection based on the forward current, and the Vrs port and the control unit 130 can both perform power-off protection on the IPM when detecting a large current, compared with the traditional scheme in which the comparator performs overcurrent detection when rotating forward and reversing, the present application only performs voltage protection detection when reversing, and uses overcurrent protection when rotating forward.

[0061] Reference Figure 6 , Figure 6 In the demagnetization protection circuit 100 provided by the embodiment of the present application, a kind of optional structure schematic diagram of level pull-up module is arranged.In some embodiments, the control unit 130 comprises three control signal ends connected with three phase current sampling ends respectively, and the demagnetization protection circuit 100 further comprises: a level pull-up module connected with the three control signal ends respectively, wherein the level pull-up module is used to pull the level of control signal end to high level state, to ensure the stable transmission of signal, comprising pull-up resistor R8, R9, R10, which are connected to the three control signal ends and the DC power supply end VCC of the control unit 130 respectively, when there is no external signal input to the control signal end, the resistance pulls the level of control signal end to the high level state corresponding to VCC.

[0062] In some embodiments, the current sampling resistors R11, R12 and R13 are respectively arranged on the current branches connecting the three control signal terminals of the control unit 130 and the three phase current sampling terminals, R11 is connected with the phase current sampling terminal IU, R12 is connected with the phase current sampling terminal IV, and R13 is connected with the phase current sampling terminal IW, for monitoring the current flowing through the variable frequency motor 150. It can be understood that, in the case that the variable frequency motor 150 rotates forward and at least one of the three current sampling branches has a forward current flowing to the ground terminal, when the forward current flows through the current sampling resistors R11, R12 and R13, a voltage drop will be generated across the resistors, which is proportional to the current flowing through the resistors. The control unit 130 can indirectly measure the current by monitoring the voltage across the resistors, and then realize the forward current detection of the IPM module 140 and the corresponding overcurrent protection.

[0063] In some embodiments, when the variable frequency motor 150 rotates forward: the current flows through the resistors R1, R2 and R3 to the ground terminal, the diodes D1, D2 and D3 are cut off, and the diodes D4, D5 and D6 are turned on, for forward current overcurrent protection; when the variable frequency motor 150 rotates reversely: the current flows through the resistors R1, R2 and R3 to the IPM module 140, the diodes D1, D2 and D3 are turned on, and the diodes D4, D5 and D6 are cut off, for reverse current overcurrent protection, triggering the MCU to send the variable frequency motor 150 control signal, so as to make the variable frequency motor 150 stop maintaining operation or stop rotating.

[0064] In the second aspect, the utility model embodiment provides a kind of demagnetization protection device, including the demagnetization protection circuit of the frequency conversion equipment of any one of first aspect;Wherein, according to the utility model embodiment provides a kind of demagnetization protection device of frequency conversion equipment, the demagnetization protection circuit in demagnetization protection device can be applied to frequency conversion equipment, frequency conversion equipment includes variable frequency motor and the IPM module for driving variable frequency motor, the three current sampling branches formed by the connection of the three-phase current end of IPM module and ground terminal, when variable frequency motor reverse rotation, the voltage of the three-phase current end of IPM module is lower than the voltage of ground terminal, at least one of three current sampling branches exists the case where reverse current flows to phase current sampling end, the utility model embodiment can be connected by unidirectional conduction module ground terminal of three current sampling branches, voltage comparator is connected with unidirectional conduction module, current sampling branch and the input end of voltage comparator are conducted, and by control unit respectively with the output end of voltage comparator and three phase current sampling end connection, according to the output level of voltage comparator control IPM module's working condition;Wherein, it can be understood, based on the above circuit structure, the utility model embodiment can only when reverse current is generated in a phase, make only voltage comparator be communicated with the phase that exists reverse current by unidirectional conduction module, gather the sampling voltage corresponding to at least one phase reverse current, and by voltage comparator according to sampling voltage output level signal, control unit according to level signal sends control signal to IPM module, to make IPM module drive variable frequency motor operation or shutdown, realize to each phase reverse current's overcurrent detection, further, while realizing demagnetization protection to frequency conversion equipment, the number of comparator and other components can be effectively reduced, product cost is reduced, product miniaturization can be better realized.

[0065] In a third aspect, the utility model provides a kind of variable frequency equipment, including the demagnetization protection circuit of the variable frequency equipment of any one of first aspect, or the demagnetization protection device of any one of second aspect;Wherein, according to the utility model embodiment provides a kind of variable frequency equipment, the demagnetization protection circuit of variable frequency equipment can be applied to variable frequency equipment, variable frequency equipment includes variable frequency motor and the IPM module for driving variable frequency motor, the three current sampling branches formed by the connection of the three-phase current end of IPM module and ground terminal, when variable frequency motor reversely rotates, the voltage of the three-phase current end of IPM module is lower than the voltage of ground terminal, at least one of three current sampling branches exists the case where reverse current flows to phase current sampling end, the utility model embodiment can connect the ground terminal of three current sampling branches by unidirectional conduction module, voltage comparator is connected with unidirectional conduction module, current sampling branch and the input end of voltage comparator are conducted, and by control unit, voltage comparator output end and three phase current sampling end are connected respectively, according to the output level of voltage comparator, the working state of IPM module is controlled;Wherein, it can be understood that, based on the above circuit structure, the utility model embodiment can only when reverse current is generated in a phase, make the only voltage comparator be connected with the phase existing reverse current by unidirectional conduction module, collect the sampling voltage corresponding to at least one phase reverse current, and by voltage comparator, according to the sampling voltage output level signal, control unit sends control signal to IPM module according to level signal, to make IPM module drive variable frequency motor to run or stop, realize the overcurrent detection of each phase reverse current, further, while realizing demagnetization protection to variable frequency equipment, the number of comparator and other components can be effectively reduced, product cost is reduced, product miniaturization can be better realized.

[0066] The utility model has been described in detail above in connection with the drawings, but the utility model is not limited to the above embodiment, within the knowledge range of ordinary skill in the art, various changes can be made without departing from the purpose of the utility model.

Claims

1. A demagnetization protection circuit of a variable frequency device, characterized by comprising: The variable frequency device comprises a variable frequency motor and an IPM module for driving the variable frequency motor, the IPM module comprising three phase current sampling terminals; the demagnetization protection circuit comprises: a voltage sampling module comprising a unidirectional conduction module and three current sampling branches, one end of each of the three current sampling branches being connected to the three phase current sampling terminals respectively, one end of each of the three current sampling branches also being connected to the unidirectional conduction module, and the other end of each of the three current sampling branches being grounded; a voltage comparator connected to the unidirectional conduction module, the unidirectional conduction module being configured to conduct the current sampling branch and the input terminal of the voltage comparator in the case that at least one of the three current sampling branches has a reverse current flowing to the phase current sampling terminal; a control unit connected to the output terminal of the voltage comparator and the three phase current sampling terminals respectively, and configured to control the working state of the IPM module according to the output level of the voltage comparator.

2. The demagnetization protection circuit of a variable frequency device according to claim 1, wherein A sampling resistor is arranged on each of the three current sampling branches, and the unidirectional conduction module comprises three diodes, the anode terminals of the three diodes being connected in communication, and the cathode terminals of the three diodes being connected to one end of the three sampling resistors close to the phase current sampling terminals respectively.

3. The demagnetization protection circuit of a variable frequency apparatus according to claim 1 or 2, characterized by, The voltage sampling module further comprises: a voltage dividing module connected to the unidirectional conduction module at one end and to a direct current power supply terminal at the other end, the voltage dividing module comprising a first voltage dividing resistor and a second voltage dividing resistor, and the voltage comparator being connected between the first voltage dividing resistor and the second voltage dividing resistor.

4. The demagnetization protection circuit of a variable frequency device according to claim 1, wherein The voltage comparator comprises: a sampling voltage terminal connected to the unidirectional conduction module; a reference voltage terminal configured to obtain a reference voltage; wherein the voltage comparator is configured to output a first level signal when the sampling voltage obtained at the sampling voltage terminal is greater than the reference voltage, and output a second level signal when the sampling voltage is less than or equal to the reference voltage.

5. The demagnetization protection circuit of a variable frequency device according to claim 4, wherein The control unit is configured to send a first control signal to the IPM module to make the IPM module drive the variable frequency motor to run when the first level signal is received, and send a second control signal to the IPM module to make the IPM module drive the variable frequency motor to stop when the second level signal is received.

6. The demagnetization protection circuit of a variable frequency device according to claim 1, wherein The demagnetization protection circuit further comprises: a current sampling module connected to the three phase current sampling terminals at one end and connected to the current detection terminals of the IPM module at the other end, and configured to transmit the current signals of the three current sampling branches to the IPM module.

7. The demagnetization protection circuit of a variable frequency device according to claim 6, wherein The current sampling module comprises: an input resistor and a filter circuit, one end of the input resistor being connected to the three phase current sampling terminals respectively, and the other end of the input resistor being connected to the current detection terminals and the filter circuit respectively.

8. The demagnetization protection circuit of a variable frequency device according to claim 1, wherein The control unit comprises three control signal terminals connected to the three phase current sampling terminals respectively, and the demagnetization protection circuit further comprises: a level pull-up module connected to the three control signal terminals respectively.

9. A demagnetization protection device characterized by comprising: A demagnetization protection circuit of a variable frequency device according to any one of claims 1 to 8.

10. A frequency conversion device, comprising: A demagnetization protection circuit including the variable frequency device of any one of claims 1 to 8, or the demagnetization protection device of claim 9.

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