CN114421429B - Converter protection device, converter and air conditioner - Google Patents

Abstract

The invention discloses a frequency converter protection device, a frequency converter and an air conditioner, wherein the frequency converter protection device comprises: the first output port of the processing unit outputs a first control level for sucking the relay of the precharge circuit; the first switch unit is connected in the control loop of the relay, and the control end of the first switch unit is connected with the first output port; a detection circuit for detecting whether the relay is in a suction state or not and outputting a detection signal; the first comparison unit receives a first preset voltage and a detection signal and outputs a high level to the overcurrent detection port when the relay is disconnected; when the overcurrent detection port receives the high level, the processing unit controls the load motor to stop running. According to the invention, by setting the relay engaging condition, the relay is ensured to be engaged in time; and the load motor is timely disconnected through detecting the on/off state of the relay.

Description

Converter protection device, converter and air conditioner

Technical Field

The invention relates to the technical field of frequency converters, in particular to a frequency converter protection device, a frequency converter and an air conditioner.

Background

A pre-charging circuit is arranged on a main circuit of the existing frequency converter, so that larger current impact is prevented from being generated during power-on, and power devices in the rectifier bridge are protected.

Referring to fig. 1, there is shown a control circuit of a relay of the existing precharge circuit 20, wherein the precharge circuit 20 includes a charging resistor R1 and a relay RY1 connected in parallel with the charging resistor R1, at the time of power-up, RY1 is turned off, a charging current charges a charging capacitor C1 through the charging resistor R1, after the charging capacitor C1 is full, a bus voltage Vdc is stabilized, at this time, the relay RY1 is electrically attracted, the charging resistor R1 is short-circuited, and then a processing unit 50 (for example, MCU (Microcontroller Unit, micro control unit)) controls IPM (Intelligent Power Module ) 40 to start a load motor.

In the conventional process of using the precharge circuit 20 to relay RY1, there are the following two problems.

On the one hand, if the suction time of the relay RY1 is too long, a larger current is also generated, which affects the service life of the power devices in the rectifying circuit 10, and if the suction time of the relay RY1 is too slow, the starting time of the whole machine is too long.

On the other hand, if the relay RY1 is turned off during the operation of the load motor, in the prior art, the current flows through the charging resistor R1, resulting in a decrease of the bus voltage Vdc, resulting in under-voltage protection, and the processing unit 50 turns off the IPM 40 again, in this way, a large current may flow through the charging resistor R1 due to untimely turn off of the IPM 40 by the processing unit 50, which may affect the service life of the frequency converter.

Disclosure of Invention

The invention aims to provide a frequency converter protection device, which ensures the timely attraction of a relay by setting the attraction condition of the relay; and the load motor is timely disconnected through detecting the on/off state of the relay, so that the damage to the charging resistor caused by the current flowing through the charging resistor is avoided.

In order to achieve the aim of the invention, the invention is realized by adopting the following technical scheme:

the application relates to a converter protection device, its characterized in that includes:

the voltage acquisition unit is used for acquiring bus voltage Vdc and is connected with the processing unit, when Vdc is greater than an undervoltage protection set value and the change rate of the bus voltage is smaller than or equal to a preset value, a first output port of the processing unit outputs a first control level for enabling a relay of the precharge circuit to be attracted, and otherwise, a second control level is output;

the first switch unit is connected in the control loop of the relay, and the control end of the first switch unit is connected with the first output port;

a detection circuit for detecting whether the relay is in a suction state or not, and outputting a detection signal to a first detection port of the processing unit;

the first comparison unit receives a first preset voltage and the detection signal and outputs a high level to the overcurrent detection port when the relay is disconnected;

And when the overcurrent detection port receives the high level, the processing unit controls the load motor to stop running.

In some embodiments of the present application, when the overcurrent detection port receives a high level, the IPM outputs a trigger signal to the processing unit and enters an external interrupt service;

in the external interrupt service, the processing unit controls to turn off the output of the PWM wave to the IPM.

In some embodiments of the present application, the frequency converter protection device further includes a first voltage dividing circuit;

one end of a coil of the relay is connected with a power supply;

the detection circuit is an optical coupler;

the anode A of the optical coupler is connected with a pull-up resistor, the cathode K is connected with the other end of the coil and a connection point between the first switch units, the emitter E is grounded, the collector C is connected with one end of a part of the first voltage dividing circuit outputting voltage division, and the other end of the part of the first voltage dividing circuit outputting voltage division is connected with the emitter E.

In some embodiments of the present application, one end of the coil of the relay is connected to a power source; the detection circuit is a level transmission circuit;

the level transfer circuit is used for transferring the level at the connection point between the other end of the coil and the first switch unit into the detection signal, when the coil is powered off, the level at the connection point is high level, and the transferred detection signal is also high level.

In some embodiments of the present application, the level delivery circuit includes a high-level conductive switching element and a pull-down resistor;

the connecting point is connected with the control end of the high-level on-state switching element, the first end is connected with a power supply, the second end is connected with the pull-down resistor, and the output end of the detection circuit is connected with the connecting point between the second end and the pull-down resistor.

In some embodiments of the present application, the inverter protection circuit is used for protecting an inverter for an air conditioner, the air conditioner includes:

and the pressure switch is connected in series in the control loop.

In some embodiments of the present application, the frequency converter protection device further includes:

the second comparison unit receives K1vdc and K1vlow, the output end of the second comparison unit is connected with one end of a diode, and the other end of the diode is respectively connected with the first output port and the second detection port of the processing unit;

the processing unit judges the fault of the frequency converter according to the level at the first output port, the level at the first detection port and the level at the second detection port;

wherein K1 is a scaling factor of less than 1.

In some embodiments of the present application, the second comparing unit is a comparator, where an anode terminal thereof receives K1 Vdc and a cathode terminal thereof receives K1 Vlow;

The first switch unit is an NPN transistor, the base electrode of the NPN transistor is connected with the first output port, the collector electrode of the NPN transistor is connected with the coil, and the emitter electrode of the NPN transistor is grounded;

the cathode of the diode is connected with the output end of the second comparison unit, and the anode of the diode is respectively connected with the base electrode of the first switch unit, the first output port and the second detection port.

Compared with the prior art, the frequency converter protection device provided by the application has the following advantages and beneficial effects:

(1) By collecting the bus voltage, setting the bus voltage value and limiting the change rate of the bus voltage threshold, the relay actuation condition is set, so that larger charging current impact is avoided, and the relay actuation can be realized in time;

(2) The processing unit can judge the on/off state of the relay according to the signal detected by the first detection port, and when the relay is detected to be off, the load is rapidly and timely disconnected, so that the charging resistor is prevented from being damaged due to the fact that current flows through the charging resistor, and the service life of the frequency converter is prolonged.

The second object of the present invention is to provide a frequency converter, which can be protected by a frequency converter protection device.

The third object of the present invention is to provide an air conditioner capable of realizing reliable control of the air conditioner by protecting a frequency converter in the air conditioner.

Other features and advantages of the present invention will become apparent upon review of the detailed description of the invention in conjunction with the drawings.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a control schematic diagram of a pre-charge circuit relay in a prior art frequency converter;

FIG. 2 is a schematic diagram of a first embodiment of a frequency converter protection device according to the present invention;

FIG. 3 is a graph showing the voltage change of the bus bars before and after the relay RY1 is pulled in the embodiment of the frequency converter protection device according to the present invention;

FIG. 4 is a circuit diagram of an embodiment of a detection circuit in an embodiment of a frequency converter protection device according to the present invention;

FIG. 5 is a circuit diagram of a detection circuit in an embodiment of a frequency converter protection device according to the present invention;

FIG. 6 is a schematic diagram of a second embodiment of a frequency converter protection device according to the present invention;

FIG. 7 is a schematic diagram of a third embodiment of a frequency converter protection device according to the present invention;

FIG. 8 is a schematic diagram of a fourth embodiment of a frequency converter protection device according to the present invention;

FIG. 9 is a signal diagram I of various components of an embodiment of a frequency converter protection device according to the present invention;

fig. 10 is a second signal diagram of each component in the embodiment of the protection device for a frequency converter according to the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.

All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. In the description of the present invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the present invention and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.

In the description of the present invention, it should be noted that the terms "mounted," "connected," and "coupled" are to be construed broadly, as well as, for example, fixedly coupled, detachably coupled, or integrally coupled, unless otherwise specifically indicated and defined. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art. In the description of the above embodiments, particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.

Basic operation principle of air conditioner

The present embodiment provides an air conditioner that performs a cooling and heating cycle of the air conditioner by using a compressor, a condenser, an expansion valve, and an evaporator. The refrigerating and heating cycle includes a series of processes involving compression, condensation, expansion and evaporation, and refrigerating or heating an indoor space.

The low-temperature low-pressure refrigerant enters the compressor, the compressor compresses the refrigerant gas into a high-temperature high-pressure state, and the compressed refrigerant gas is discharged. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and heat is released to the surrounding environment through the condensation process.

The expansion valve expands the liquid-phase refrigerant in a high-temperature and high-pressure state formed by condensation in the condenser into a low-pressure liquid-phase refrigerant. The evaporator evaporates the refrigerant expanded in the expansion valve and returns the refrigerant gas in a low-temperature and low-pressure state to the compressor. The evaporator may achieve a cooling effect by exchanging heat with a material to be cooled using latent heat of evaporation of a refrigerant. The air conditioner may adjust the temperature of the indoor space throughout the cycle.

The outdoor unit of the air conditioner refers to a portion of a refrigeration cycle including a compressor, an outdoor heat exchanger, and an outdoor fan, the indoor unit of the air conditioner includes a portion of an indoor heat exchanger and an indoor fan, and a throttling device (e.g., a capillary tube or an electronic expansion valve) may be provided in the indoor unit or the outdoor unit.

The indoor heat exchanger and the outdoor heat exchanger function as a condenser or an evaporator. The air conditioner performs a heating mode when the indoor heat exchanger is used as a condenser, and performs a cooling mode when the indoor heat exchanger is used as an evaporator.

The mode of converting the indoor heat exchanger and the outdoor heat exchanger into a condenser or an evaporator generally adopts a four-way valve, and the arrangement of a conventional air conditioner is specifically referred to and will not be described herein.

The refrigeration working principle of the air conditioner is as follows: the compressor works to enable the interior of an indoor heat exchanger (in an indoor unit, an evaporator at the moment) to be in an ultralow pressure state, liquid refrigerant in the indoor heat exchanger is rapidly evaporated to absorb heat, air blown out by an indoor fan is cooled by an indoor heat exchanger coil and then changed into cold air to be blown into the indoor, the evaporated refrigerant is pressurized by the compressor and then condensed into liquid state in a high-pressure environment in an outdoor heat exchanger (in an outdoor unit, a condenser at the moment), heat is released, the heat is emitted to the atmosphere by the outdoor fan, and the refrigerating effect is achieved through circulation.

The heating working principle of the air conditioner is as follows: the gaseous refrigerant is pressurized by the compressor to become high-temperature high-pressure gas, and enters the indoor heat exchanger (a condenser at the moment), so that the gaseous refrigerant is condensed, liquefied and released heat to become liquid, and meanwhile, the indoor air is heated, so that the aim of improving the indoor temperature is fulfilled. The liquid refrigerant is decompressed by the throttling device, enters the outdoor heat exchanger (an evaporator at the moment), evaporates, gasifies and absorbs heat to become gas, and simultaneously absorbs heat of outdoor air (the outdoor air becomes colder) to become gaseous refrigerant, and enters the compressor again to start the next cycle.

[ frequency converter ]

The frequency converter is widely used in air conditioners and is used for adjusting the frequency of a motor for a compressor in the air conditioner in a frequency conversion manner.

In this application, it relates generally to a frequency converter protection device for a frequency converter in an air conditioner.

Referring to fig. 1, 2, 6 and 7, the inverter includes a rectifying circuit 10, a precharge circuit 20, a PFC circuit 30, an IPM 40, a load motor, which herein refers to a motor for a compressor, an inverter protection device, and a processing unit 50.

The processing unit 50 performs frequency conversion control of the compressor.

The input end of the rectifying circuit 10 is connected to a single-phase alternating current power AC, and the rectifying circuit 10 is configured to rectify the single-phase alternating current provided by the single-phase alternating current power AC to obtain a rectified direct current.

The rectifying circuit 10 may be a single-phase bridge rectifier bridge composed of four diodes

The precharge circuit 20 includes a charging resistor R1 and a relay RY1 connected in parallel with the charging resistor R1.

When the power is on, the relay RY1 is disconnected, the charging capacitor C1 is charged by the charging current through the charging resistor R1, after the charging capacitor C1 is full, the bus voltage Vdc is stable, the relay RY1 is electrified and is in attraction, the charging resistor R1 is short-circuited, and then the processing unit 50 controls the IPM 40 to start the load motor.

The electrolytic capacitor C1 is connected in parallel with a load, wherein the load can be a compressor, and the compressor is subjected to variable frequency control by adopting the IPM 40.

The bus voltage V can be sampled by the voltage sampling unit _dc 。

The voltage sampling unit may include resistors R2, R3, R4, and R5 connected in series between the positive and negative poles of the bus dc power supply.

The frequency conversion protection device is used for frequency conversion protection of the motor for the compressor in the air conditioner, so that the reliable control of the air conditioner is realized.

[ frequency converter protection device 1]

Referring to fig. 2, a frequency converter protection device is shown.

The frequency converter protection device includes a voltage acquisition unit that acquires the bus voltage Vdc, a first switch unit 80, a detection circuit 60, and a first comparison unit 70 as described above.

The voltage acquisition unit, the first switching unit 80 and the detection circuit 60 are respectively connected with the processing unit 50.

The dc voltage Vdc collected by the voltage collecting unit is input to the voltage sampling port AD of the processing unit 50.

The first switching unit 80 is connected in the control loop of the relay RY1, i.e., the control terminal of the first switching unit 80 is connected to the first output port OUT1 of the processing unit 50.

The detection circuit 60 is configured to detect the actuation condition of the relay RY1, and output a detection signal to the first detection port DET1 of the processing unit 50.

One end of the coil is connected with a power supply, and the other end is connected with a control loop, in this application, the power supply, the coil and the first switch unit 80 are sequentially connected in series to form a control loop, wherein the power supply is an external direct current power supply +15V.

The first switching unit 80 controls on or off of the first switching unit 80 according to a signal output from the first output port OUT1 of the processing unit 50 to implement the actuation or the off of the relay RY 1.

For example, when the signal output from the first output port OUT1 is at the first control level, the first switching unit 80 is turned on, and at this time, the power supply +15v supplies power to the coil, and the relay RY1 is turned on.

When the signal output from the first output port OUT1 is at the second control level, the first switching unit 80 is turned off, and at this time, the control circuit is turned off, the coil is deenergized, and the relay RY1 is turned off.

The first comparing unit 70 receives and compares the detection signal with a first preset voltage, and when the relay RY1 is turned on or off, the detecting circuit 60 detects the corresponding signal and outputs a different detection signal to the first detection port DET1 of the processing unit 50 after processing.

The processing unit 50 determines the on/off condition of the relay RY1 based on the detection signal received by the first detection port DET1.

In the present application, the processing unit 50 determines that the relay RY1 is engaged based on the detection signal of the high level received by the first detection port DET1, and determines that the relay RY1 is turned off based on the detection signal of the second level received by the first detection port DET 1.

The relay RY1 is attracted, which means that the coil of the relay RY1 is powered on and the corresponding normally open switch is closed; relay RY1 is open, indicating that the coil of relay RY1 is de-energized, and the corresponding normally open switch is open.

In order to timely engage the relay, the engagement condition of the relay is set in the present application.

The suction conditions have two following: (1) bus voltage Vdc is greater than undervoltage protection set point Vlow; (2) The change rate DeltaVdc/Deltatof the bus voltage Vdc is smaller than or equal to a preset value.

The undervoltage protection set value Vlow is a voltage protection set value set when the frequency converter performs undervoltage protection in the prior art.

When the processing unit 50 knows that the above two pull-in conditions are satisfied, the first control level is output at the first output port OUT1, and otherwise the second control level is output.

As described above, the dc voltage Vdc is collected by the voltage collection unit and input to the processing unit 50 through the voltage sampling port AD port.

The processing unit 50 obtains a change curve of the bus voltage Vdc before and after the actuation of the relay RY1, as shown in fig. 3.

The level at the detection end (i.e., the one end C of the coil) of the detection circuit 60 is used to detect the state of the actuation/disconnection of the relay RY1, and to output a detection signal (i.e., the signal at the a point) indicating the actuation/disconnection of the relay RY1 to the first detection port DET1.

For example, when the relay RY1 is suctioned, the detection end receives a low level, and after detection by the detection circuit 60, the output detection signal is also at a low level, and at this time, the detection signal is collected by the first detection port DET1 of the processing unit 50, so that it is determined that the current relay RY1 is in the suctioned state.

When the relay RY1 is turned off, the detection end receives a high level, and after detection by the detection circuit 60, the output detection signal is also a high level, and at this time, the detection signal is collected by the first detection port DET1 of the processing unit 50, so that it is determined that the current relay RY1 is in an off state.

Alternatively, when the relay RY1 is suctioned, the detection end may receive a low level, detect the signal by the detection circuit 60, output a detection signal to a high level, and collect the signal at this time by the first detection port DET1 of the processing unit 50, thereby determining that the current relay RY1 is in the suctioned state, and so on.

The first control level output from the first output port OUT1 of the processing unit 50 to the control terminal of the first switching unit 80 may be a high level (or a low level), and the second control signal may be a low level (or a high level), so long as the processing unit 50 can control the actuation of the relay RY1 when the actuation condition of the relay RY1 is satisfied.

In this application, referring to fig. 2, the first switching unit 80 is selected as an NPN triode Q1, a base thereof is connected to the first output port OUT1 through a current limiting resistor R8, a power source (+15v DC) is connected to a collector of the triode Q1 through a coil, and an emitter thereof is grounded.

The base pull-down resistor R9 is disposed at the base of the triode Q1, and is used for ensuring normal operation of the NPN triode Q1, preventing malfunction of the triode Q1 due to influence of noise signals, so that the transistor is turned off more reliably, the base of the triode Q1 cannot be suspended, when an input signal is uncertain (if the input signal is in a high-resistance state), the base pull-down resistor R9 is added, so that the base can be effectively grounded, and discharge can be performed through the base pull-down resistor R9 when the triode Q1 is turned off.

When the relay RY1 satisfies the actuation condition, the first output port OUT1 outputs a first control signal of a high level, and at this time, the transistor Q1 is turned on, and at this time, the relay RY1 is actuated.

When the relay RY1 does not satisfy the pull-in condition, the first output port OUT1 outputs the second control signal of the low level, and at this time, the transistor Q1 is turned off, and at this time, the relay RY1 is turned off.

The state of whether or not relay RY1 is actually energized (i.e., whether or not the coil is energized) is detected by detection circuit 60.

The detection terminal of the detection circuit 60 receives the level at the connection point C and outputs a detection signal to the first detection port DET1 of the processing unit 50.

In this application, the detection circuit 60 is selected as the optocoupler PC1.

The anode A of the optical coupler PC1 is connected with the pull-up resistor R7, the cathode K is connected with the connection point C, the emitter E is grounded, the collector C is connected with one end of a part of the first voltage dividing circuit which outputs voltage division, and the other end of the part of the first voltage dividing circuit which outputs voltage division is connected with the emitter E.

For example, the first voltage dividing circuit includes resistors R11 and R12 connected in series, and the resistor R13 and the capacitor C2 form a filter circuit that filters the divided voltage of the output of the first voltage dividing circuit.

The output divided portion of the first voltage dividing circuit is a resistor R12.

One end of the resistor R12 is connected to the collector C, and the other end is connected to the emitter E.

One end of the resistor R12 outputs a divided voltage, i.e., a detection signal, at the point a through the resistor R13.

The first comparing unit 70 has two input terminals, the first input terminal receives the divided voltage output at the point a and the second input terminal receives the first preset voltage, and outputs a signal to the over-current detecting port CIN of the IPM 40 by comparing with the received divided voltage.

In this way, when the relay RY1 is turned off, the detection circuit 60 outputs a detection signal to the first comparing unit 70, and the overcurrent detection port CIN of the IPM 40 receives the high-level signal output from the first comparing unit 70, thereby causing overcurrent protection of the IPM 40 and immediately stopping the load operation.

Compared with the prior art, the control scheme in the application directly acts on the IPM 40 without operating the IPM 40 through the processing unit 50, so that the reaction is quicker, and the damage to the charging resistor R1 caused by the large current flowing through the charging resistor R1 is avoided.

In this application, the first comparing unit 70 is selected as the comparator U1.

At the time of the cathode K of the optocoupler PC1 receiving a low level (representing the pull-in of the relay RY 1), the optocoupler PC1 is turned on, the power +5V of the first voltage dividing circuit is grounded through the resistor R11, the collector C and the emitter E (i.e., the shorting resistor R12), and thus a low level detection signal is output at the A point

At this time, a detection signal of low level is detected at the first detection port DET1 of the processing unit 50, indicating that the current relay RY1 is engaged; and at the same time the detection signal is fed to the positive input of the comparator U1.

According to the voltage value of the power supply of the first voltage dividing circuit, the first preset voltage received by the negative input end of the comparator U1 may be set, so that when the relay RY1 is attracted, the output detection signal is compared with the first preset voltage, and then the output signal is output to the overcurrent detection port CIN of the IPM 40.

The first preset voltage may be set to any voltage value between 0V and 5V, and is sent to the negative input terminal of the comparator U1, where the comparator U1 outputs a low level to the overcurrent detection port CIN of the IPM 40, and at this time, the overcurrent protection of the IPM 40 is not triggered.

In this application, a second voltage dividing circuit formed by connecting resistors R14 and R15 in series is disposed at the negative input end of the comparator U1, and the divided voltage on the resistor R14 is the first preset voltage.

By setting the resistance values of the resistors R14 and R15, the first preset voltage is set to any voltage value between more than 0V and less than 5V, for example, 2.5V.

With continued reference to fig. 2, when the cathode K of the optocoupler PC1 receives (characterizing the relay is open) a high level, the optocoupler PC1 is not conductive, and a +5v high level detection signal is output at point a

At this time, a detection signal of a high level is detected at the first detection port DET1 of the processing unit 50, indicating that the current relay RY1 is turned off; and at the same time the detection signal is fed to the positive input of the comparator U1.

The first preset voltage may be set to any voltage value between 0V and 5V, and is sent to the negative input terminal of the comparator U1, where the comparator U1 outputs a high level to the overcurrent detection port of the IPM 40, and at this time, the overcurrent protection of the IPM 40 is triggered to immediately disconnect the load.

In some embodiments of the present application, the first switching unit 80 may be selected to be a PNP transistor, so long as the detection and control as described above can be satisfied.

Referring to fig. 4, a circuit diagram of another embodiment of a detection circuit is shown.

The level transfer circuit is used for transferring the level at the connection point C between the coil and the collector of the NPN triode Q1 as a detection signal.

When relay RY1 is in the on state, the level at connection point C is low, and the transmitted detection signal is also low, and when relay RY1 is off, the level at connection point C is high, and the transmitted detection signal is also high.

The level transfer circuit may include a high-level conductive switching element, for example, NPN transistor Q3', and pull-down resistor R1'.

The connection point C (i.e., the detection end) is connected to the control end of the high-level conductive switching element, the first end of the high-level conductive switching element is grounded through the pull-down resistor R1', the second end of the high-level conductive switching element is connected to the VCC power supply voltage, and the output end of the detection circuit 60 is connected to the connection point between the first end and the pull-down resistor R1'.

Referring to fig. 4, the switching element with high-level conduction is an NPN triode Q3', the base of the triode Q3' can be connected to the point C through the base current limiting resistor R2', the emitter is connected to the pull-down resistor R1', the collector is connected to the VCC power supply voltage, and the output end of the detection circuit 60 is connected to the point C between the emitter and the pull-down resistor R1 '.

The base current limiting resistor R2 'is used for limiting the current flowing into the base electrode of the NPN triode Q3', avoiding burning Q3 'when the level output by the connecting point C is unstable or high, and protecting the NPN triode Q3'.

The base pull-down resistor R3 'can also be added at the base of NPN transistor Q3'.

The base pull-down resistor R3 'is used for ensuring the normal operation of the NPN triode Q3', preventing the triode Q3 'from generating misoperation due to the influence of noise signals, enabling the triode Q3' to be cut off more reliably, enabling the base of the triode Q3 'not to be suspended, enabling the base pull-down resistor R3' to be effectively grounded when an input signal is uncertain (when the input signal is in a high resistance state), and discharging through the base pull-down resistor R3 'when the triode Q3' is cut off.

When relay RY1 is on, transistor Q3' is off and detection circuit 60 outputs a low level at point a when low level is output at connection point C.

At this time, the detection signal of the low level is detected by the first detection port DET1 of the processing unit 50, indicating that the relay RY1 is engaged; and at the same time the detection signal is fed to the positive input of the comparator U1.

The first preset voltage may be set to any voltage value between 0V and 5V, and is sent to the negative input terminal of the comparator U1, where the comparator U1 outputs a low level to the overcurrent detection port CIN of the IPM 40, and at this time, the overcurrent protection of the IPM 40 is not triggered. When relay RY1 is turned off, high level is output at connection point C, transistor Q3' is turned on, and detection circuit 60 outputs high level.

At this time, a detection signal of a high level is detected by the first detection port DET1 of the processing unit 50, indicating that the relay RY1 is turned off; and at the same time the detection signal is fed to the positive input of the comparator U1.

The first preset voltage may be set to any voltage value between 0V and 5V, and is sent to the negative input terminal of the comparator U1, where the comparator U1 outputs a high level to the overcurrent detection port CIN of the IPM 40, and at this time, the overcurrent protection of the IPM 40 is triggered, and the load operation is immediately stopped.

Thus, the on state of the relay RY1 can be detected, and when the relay RY1 is turned off, the comparator U1 outputs a high-level detection signal to the overcurrent detection port CIN of the IPM 40, thereby immediately stopping the load operation.

In some embodiments of the present application, the detection signal (i.e., the signal at the point a) may also be input to the negative input of the comparator U1, which may be adjusted according to the specific circuit configuration. For example, referring to fig. 5, the detection circuit may also be a level shift circuit.

The level conversion circuit is used for converting the level at the connection point C between the coil and the collector of the NPN triode Q1 into a detection signal.

When the relay RY1 is attracted, the level at the connection point C is low and the converted detection signal is high, and when the relay RY1 is turned off, the level at the connection point C is high and the converted detection signal is low.

The level shift circuit includes a switching element turned on at a low level and a pull-down resistor R4'.

The connection point C (i.e., a detection end) is connected to the control end of the low-level conductive switching element, the first end is connected to the pull-down resistor R4', the second end is connected to the VCC power supply voltage, and the output end of the detection circuit 60 is connected to the connection point between the first end and the pull-down resistor R4'.

The low-level on switching element is a PNP triode Q2', the base electrode of the triode Q2' is connected with a connection point C through a base electrode current limiting resistor R5', the collector electrode is connected with a pull-down resistor R4', the emitter electrode is connected with VCC power supply voltage, and the output end of the detection circuit 60 is connected with the connection point between the pull-down resistor R4' and the collector electrode.

The base current limiting resistor R5 'is used for limiting the current flowing into the base electrode of the PNP triode Q2', avoiding burning Q2 'when the level output by the connecting point C is unstable or high, and protecting the PNP triode Q2'.

A base pull-up resistor R6 'may also be added at the base of PNP transistor Q2'.

The output level may be unstable at the connection point C, and the base pull-up resistor R6' pulls up the base to a certain high level, preventing malfunction.

When relay RY1 is engaged, low level is output at connection point C, transistor Q2' is turned on, and detection circuit 60 outputs high level at point a.

At this time, the detection signal of the high level is detected by the first detection port DET1 of the processing unit 50, indicating that the relay RY1 is engaged; and at the same time the detection signal is fed to the negative input of the comparator U1.

The first preset voltage may be set to any voltage value between 0V and 5V, and is sent to the positive input terminal of the comparator U1, where the comparator U1 outputs a low level to the overcurrent detection port CIN of the IPM 40, and at this time, the overcurrent protection of the IPM 40 is not triggered. When relay RY1 is turned off, transistor Q2' is turned off when a high level is output at connection point C, and detection circuit 60 outputs a low level at point a.

At this time, a detection signal of a low level is detected by the first detection port DET1 of the processing unit 50, indicating that the relay RY1 is turned off; and at the same time the detection signal is fed to the negative input of the comparator U1.

The first preset voltage may be set to any voltage value between 0V and 5V, and is sent to the positive input end of the comparator U1, where the comparator U1 outputs a high level to the overcurrent detection port CIN of the IPM 40, and at this time, the overcurrent protection of the IPM 40 is triggered, and the load operation is immediately stopped.

Thus, the on state of the relay RY1 can be detected, and when the relay RY1 is turned off, the detection signal of the high level is outputted through the comparator U1 and inputted to the overcurrent detection port CIN of the IPM 40, and the load operation is immediately stopped.

With continued reference to fig. 2, in this application, when IPM 40 detects an overcurrent signal, it is described that relay RY1 is turned off, at which time IPM immediately stops the load, and also issues a trigger signal to processing unit 50 via FO port to port INT, and enters external interrupt service.

In the external interrupt service, the processing unit 50 controls to turn off the output of the PWM wave to the IPM 40.

The trigger signal output from the FO port to the port INT may be selected to be at a high level, so that whether the frequency converter has an overcurrent fault may also be determined by the level signal output from the FO port.

The opening of the relay RY1 as described above indicates that the coil of the relay RY1 is deenergized and the normally open switch thereof is opened.

As above, the off/on state of the relay RY1 can be judged by the high/low level detected by the first detection port DET 1.

[ frequency converter protection device 2]

When the frequency converter is used on the air conditioner, a plurality of protection switches for the air conditioner can be connected in series to the control loop of the relay RY1, so that the reliable use of the frequency converter in the air conditioner is ensured.

Thus, referring to fig. 6, a pressure switch S may also be provided.

The pressure switch S is a protection switch commonly used in air conditioners, and the working principle is as follows: when the system pressure of the air conditioner is normal, two elastic diaphragms in the pressure switch S are conducted; and when abnormal pressure protection occurs, the pressure switch S presents a normal open state but can be restored.

Referring to fig. 6, a pressure switch S is connected in series in the control loop of the relay RY1, specifically between the other end of the coil and the first switching element 80.

When the first switching element 80 is selected as the NPN transistor Q1, the pressure switch S is connected in series between the other end of the coil and the collector of the NPN transistor Q1.

When the system pressure is normal, the pressure switch S is closed, and the working principle of the frequency converter protection circuit is as described above.

When the system pressure is abnormal, the pressure switch S is turned off, and at this time, no matter whether the suction condition of the relay RY1 is satisfied or the first output port OUT1 of the processing unit 50 outputs a high level or a low level, the control circuit in which the relay RY1 is located is not connected, and at this time, the relay RY1 cannot be sucked.

When the pressure switch S is turned off, the relay RY1 is also turned off, and the load is still running, at this time, the load running can be stopped immediately according to the signal output by the first comparing unit 70, and then the PWM wave output to the IPM 40 is turned off by the software processing unit 50, so as to avoid the charging resistor R1 from being burned out due to the large current flowing through the charging resistor R1.

Specifically, when the pressure switch S is turned off, the high level is output at the connection point C, the optocoupler PC1 is turned off, the high level +5v is output at the point a to the positive input terminal of the comparator U1, the negative input terminal of the comparator U1 receives the first preset voltage between greater than 0V and less than 5V, and the comparator U1 outputs the high level to the overcurrent detection port CIN of the IPM 40, so that the load operation is immediately stopped by the overcurrent protection function of the IPM 40.

[ frequency converter protection device 3]

In order to detect various faults of the frequency converter, see fig. 7, the frequency converter protection device further comprises a second comparison unit 30.

In some embodiments of the present application, the second comparison unit 30 is selected as the comparator U2.

Comparator U2 has two inputs: the first input terminal is a positive input terminal, and the second input terminal is a negative input terminal.

The first input terminal receives k1×vdc, the second input terminal receives k1×vlow, and the output terminal is connected to a cathode of a diode, and an anode of the diode is connected to the first output port OUT1 and the second detection port DET2 of the processing unit 50 through a current limiting resistor R8, respectively.

Wherein K1 is a scaling factor of less than 1.

As described above, the voltage sampling units that collect the bus voltage Vdc are R2, R3, R4, and R5 connected in series.

Design k1=r5/(r2+r3+r4+r5).

The second voltage dividing circuit may be set such that the voltage division of the second voltage dividing circuit is K1×vlow.

The second voltage dividing resistor is a series resistor R9 and R10, and the voltage dividing of the resistor R10 is set to K1×vlow by setting the resistance values of the resistors R9 and R10.

When K1 Vdc is greater than K1 Vlow, the second comparison unit 30 outputs a high level; when K1 Vdc is smaller than K1 Vlow, the second comparing unit 30 outputs a low level.

The type of failure of the inverter is determined by the level output from the first output port OUT1, the level detected by the first detection port DET1, and the level detected by the second detection port DET2.

Referring to table 1, the faults of the frequency converter corresponding to the different levels output from the first output port OUT1, the level detected by the first detection port DET1, and the level detected by the second detection port DET2 are described.

Referring to fig. 7, a fault determination of the frequency converter is performed.

(1) When relay RY1 satisfies the pull-in condition (including Vdc > Vlow), first output port OUT1 outputs a high level.

Since K1 Vdc > K1 Vlow, the comparator U2 outputs a high level, and if the detected B point is also a high point level, it indicates that the converter is not under-voltage.

Since the first output port OUT1 outputs a high level, the first switch unit 80 is turned on, and when the point C is at a low level, the point a also outputs a low level, and when the relay is normally closed, the relay is not under-voltage, and the IPM is not abnormally operated.

At this time, the frequency converter is judged to be in a normal state.

This is the case, see the first row in table 1.

(2) When the relay RY1 satisfies the pull-in condition, the first output port OUT1 outputs a high level.

Since K1 Vdc > K1 Vlow, the comparator U2 outputs a high level.

Thus, under normal conditions, the B point should be detected as high, if the B point is detected as low, it means that K1 Vdc < K1 Vlow in the comparator U2 causes the comparator U2 to output low, so that the diode D2 is turned on, and the B point is pulled down to low.

At this time, the frequency converter is judged to be in an undervoltage state.

Since Vdc < Vlow does not satisfy the suction condition of the relay RY1 any more, the relay RY1 is turned off, and the high level is output at the point a as well when the connection point C is at the high level.

This is the case, see the second row in table 1.

As described above, the under-voltage causes the relay to open, the detection signal at the first detection port DET1 of the processing unit 50 can be detected, and the load operation is immediately stopped by the IPM 40 overcurrent protection.

Thereafter, the PWM wave is not outputted to the IPM 40 by the processing unit 50 through software.

(3) When the relay RY1 does not satisfy the pull-in condition, the first output port OUT1 outputs a low level.

Since K1 Vdc < K1 Vlow, the comparator U2 outputs a low level, and the point B is also a low level.

Since the first output port OUT1 outputs a low level, the first switching unit 80 is turned off, and when the connection point C is at a high level, the point a also outputs a high level.

At this time, it is determined that the inverter is in a charging state.

See the third row in table 1 for this case.

TABLE 1

Thus, the current state of the frequency converter and the existing faults can be obtained by the conditions in table 1.

[ frequency converter protection device 4]

Referring to fig. 8, a second comparing unit 30, which is the same as that in fig. 7, is also provided.

Referring to table 2, the faults of the frequency converter corresponding to the level outputted from the different first output port OUT1, the level detected by the first detection port DET1, and the level detected by the second detection port DET2 are described.

Referring to fig. 8, a fault determination of the frequency converter is performed.

(1') when the relay RY1 satisfies the pull-in condition (including Vdc > Vlow), the first output port OUT1 outputs a high level.

Since K1 Vdc > K1 Vlow, the comparator U2 outputs a high level, and if the detected B point is also a high point level, it indicates that the converter is not under-voltage.

If the pressure switch S is normal, the connection point C is at a low level, and the point a also outputs a low level, and at this time, the relay RY1 is normally engaged, is not under-voltage, and the IPM 40 is not abnormally operated.

At this time, the frequency converter is judged to be in a normal state.

This is the case, see the first row in table 2.

Wherein waveforms after operation of the components are seen in fig. 9 and 10, where IU represents the phase current of the motor.

(2') when the relay RY1 satisfies the pull-in condition, the first output port OUT1 outputs a high level.

Since K1 Vdc > K1 Vlow, the comparator U2 outputs a high level.

Thus, under normal conditions, the B point should be detected as high, if the B point is detected as low, it means that K1 Vdc < K1 Vlow in the comparator U2 causes the comparator U2 to output low, so that the diode D2 is turned on, and the B point is pulled down to low.

At this time, the frequency converter is judged to be in an undervoltage state.

If the pressure switch S is normal, the engaging condition of the relay RY1 is no longer satisfied because Vdc < Vlow, and therefore the relay RY1 is turned off, and the connection point C is at the high level, and the point a also outputs the high level.

This is the case, see second row in table 2.

As described above, the under-voltage causes the relay RY1 to open, the detection signal at the first detection port DET1 of the processing unit 50 can be detected, and the load operation is stopped immediately by the IPM 40 overcurrent protection.

Thereafter, the PWM wave is not outputted to the IPM 40 by the processing unit 50 through software.

(3') when the relay RY1 satisfies the pull-in condition, the first output port OUT1 outputs a high level.

Since K1 Vdc > K1 Vlow, the comparator U2 outputs a high level, and the point B is also a high level.

If the output high level at the point a is detected, this indicates that the relay RY1 is turned off.

However, since the first output port OUT1 outputs a high level and the relay RY1 should be actuated, it is determined that the pressure switch S is abnormally opened at this time.

See the third row in table 2 for this case.

As described above, the pressure switch S is abnormally opened, the detection signal at the first detection port DET1 of the processing unit 50 can be detected, and the load operation is immediately stopped by the IPM 40 overcurrent protection.

Thereafter, the PWM wave is not outputted to the IPM 40 by the processing unit 50 through software.

(4') when the relay RY1 does not satisfy the pull-in condition, the first output port OUT1 outputs a low level.

Since K1 Vdc < K1 Vlow, the comparator U2 outputs a low level, and the point B is also a low level.

If the pressure switch S is normal, the connection point C is at a high level, and the point a also outputs a high level.

At this time, it is determined that the inverter is in a charging state.

This is the case, see fourth row in table 2.

TABLE 2

Therefore, whether the fault is that the pressure switch S is tripped to cause the relay RY1 to be opened or that the relay RY1 is tripped due to the under-voltage can be obtained by the conditions in table 2, whether the overcurrent fault exists can be detected by the level of the FO port, whether the relay RY1 is tripped can be judged by the level detected by the first detection port DET1, and various faults of the frequency converter can be distinguished, so that the maintenance personnel can detect the cause of the shutdown.

The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be apparent to one skilled in the art that modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some of the technical features thereof; such modifications and substitutions do not depart from the spirit and scope of the corresponding technical solutions.

Claims (9)

1. A frequency converter protection device, comprising:

the voltage acquisition unit is used for acquiring bus voltage Vdc and is connected with the processing unit, when Vdc is greater than an undervoltage protection set value Vlow and the change rate of the bus voltage is smaller than or equal to a preset value, a first output port of the processing unit outputs a first control level for sucking a relay of the precharge circuit, and otherwise, a second control level is output;

the first switch unit is connected in the control loop of the relay, the control end of the first switch unit is connected with the first output port, and one end of the coil of the relay is connected with a power supply;

the detection circuit is used for detecting whether the relay is in a suction state or not, the detection circuit is an optical coupler, an anode A of the optical coupler is connected with a pull-up resistor, a cathode K is connected with a connection point between the other end of the coil and the first switch unit, and an emitter E is grounded;

the collector C of the optical coupler is connected with one end of a part of the first voltage dividing circuit outputting voltage division, the other end of the part of the first voltage dividing circuit outputting voltage division is connected with the emitter E, and the collector C of the optical coupler outputs a detection signal to a first detection port of the processing unit;

A first comparing unit which receives a first preset voltage and the detection signal and outputs a high level to an overcurrent detection port of the IPM when the relay is disconnected; when the overcurrent detection port receives the high level, triggering the overcurrent protection of the IPM, and controlling the load motor to stop running.

2. The inverter protection device of claim 1, wherein when the overcurrent detection port receives a high level, the IPM outputs a trigger signal to the processing unit and enters an external interrupt service;

in the external interrupt service, the processing unit controls to turn off the output of the PWM wave to the IPM.

3. The frequency converter protection device according to claim 1, wherein one end of a coil of the relay is connected to a power source;

the detection circuit is a level transmission circuit;

the level transfer circuit is used for transferring the level at the connection point between the other end of the coil and the first switch unit into the detection signal, when the coil is powered off, the level at the connection point is high level, and the transferred detection signal is also high level.

4. A transducer protection device according to claim 3, wherein,

The level transfer circuit comprises a high-level conductive switching element and a pull-down resistor;

the connecting point is connected with the control end of the high-level on-state switching element, the first end is connected with a power supply, the second end is connected with the pull-down resistor, and the output end of the detection circuit is connected with the connecting point between the second end and the pull-down resistor.

5. The inverter protection device according to claim 1, wherein the inverter protection circuit is configured to protect an inverter for an air conditioner, the air conditioner comprising:

and the pressure switch is connected in series in the control loop.

6. The frequency converter protection device according to any one of claims 1 to 5, further comprising:

the second comparison unit receives K1vdc and K1vlow, the output end of the second comparison unit is connected with one end of a diode, and the other end of the diode is respectively connected with the first output port and the second detection port of the processing unit;

the processing unit judges the fault of the frequency converter according to the level at the first output port, the level at the first detection port and the level at the second detection port;

wherein K1 is a scaling factor of less than 1.

7. The apparatus of claim 6, wherein the frequency converter protection device comprises,

the second comparison unit is a comparator, wherein the positive electrode end of the second comparison unit receives K1 times Vdc, and the negative electrode end of the second comparison unit receives K1 times Vlow;

the first switch unit is an NPN transistor, the base electrode of the NPN transistor is connected with the first output port, the collector electrode of the NPN transistor is connected with the coil of the relay, and the emitter electrode of the NPN transistor is grounded;

the cathode of the diode is connected with the output end of the second comparison unit, and the anode of the diode is respectively connected with the base electrode of the first switch unit, the first output port and the second detection port.

8. A frequency converter, characterized in that it comprises a frequency converter protection device according to any one of claims 1 to 7.

9. An air conditioner, characterized in that the air conditioner comprises the inverter according to claim 8.