Elevator frequency converter circuit, elevator frequency converter and elevator frequency converter control method

Abstract

The invention provides an elevator frequency converter circuit which comprises an MCU, a rectifier bridge circuit, a bus capacitor, a protection circuit and an inverter circuit, the bus output of the rectifier bridge circuit is electrically connected with the two ends of the bus capacitor, the two ends of the bus capacitor are electrically connected with the input end of the inverter circuit, and the output of the inverter circuit is electrically connected with an elevator load. The protection circuit is connected in series between the bus capacitor and the rectifier bridge, and the protection circuit is electrically connected with the MCU; the protection circuit comprises a pre-charging circuit and a relay circuit connected with a pre-charging resistor in parallel, the relay circuit comprises a relay and a relay control circuit, and the relay control circuit controls the relay to perform short circuit on the pre-charging circuit. Impact caused by bus current fluctuation can be avoided, so that key components such as a rectifier bridge and a bus capacitor are protected, detection signals do not need to be switched by arranging multiple groups of relays, and the service life of the elevator frequency converter is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of equipment control, and in particular to an elevator inverter circuit, an elevator inverter and an elevator inverter control method. Background Art

[0002] Variable-frequency Drive (VFD) is a very common device in modern electrical equipment, and the elevator inverter is an instrument specifically used for elevator control. The elevator inverter controls the elevator in an S-type manner, that is, the acceleration at start and stop is relatively gentle, while the acceleration in the middle process is relatively fast. Such control requires the use of multiple sets of relay switching detection signals. However, the use of multiple sets of relay switching detection signals will cause large fluctuations in the bus current of the elevator inverter, which will lead to inaccurate control of the elevator inverter; in addition, due to problems such as oxidation of relay contacts, the failure rate of the elevator inverter will increase. Summary of the invention

[0003] The embodiment of the present invention provides an elevator inverter circuit, which aims to solve the problems of large bus current fluctuation and high failure rate in the existing elevator inverter. By setting the protection circuit in series between the bus capacitor and the rectifier bridge, the protection circuit includes a pre-charging circuit and a relay circuit connected in parallel with the pre-charging resistor, which can avoid the impact caused by bus current fluctuation in the initial stage of power-on of the elevator inverter, thereby protecting key components such as the rectifier bridge and the bus capacitor, and there is no need to set multiple sets of relays to switch the detection signal, thereby extending the service life of the elevator inverter.

[0004] In a first aspect, an embodiment of the present invention provides an elevator inverter circuit, the elevator inverter circuit comprising an MCU, a rectifier bridge circuit, a bus capacitor, a protection circuit and an inverter circuit, the bus output of the rectifier bridge circuit is electrically connected to the two ends of the bus capacitor, the two ends of the bus capacitor are electrically connected to the input end of the inverter circuit, the output of the inverter circuit is electrically connected to the elevator load, the protection circuit is arranged in series between the bus capacitor and the rectifier bridge, and the protection circuit is electrically connected to the MCU;

[0005] The protection circuit includes a pre-charging circuit and a relay circuit connected in parallel with the pre-charging resistor. The relay circuit includes a relay and a relay control circuit. The relay control circuit controls the relay to short-circuit the pre-charging circuit.

[0006] Optionally, the pre-charging circuit includes a first pre-charging resistor and a second pre-charging resistor which are arranged in series, and both ends of the relay are electrically connected to non-common ends of the first pre-charging resistor and the second pre-charging resistor.

[0007] Optionally, the relay includes an electric suction switch and a coil, and the coil is electrically connected to the relay control circuit.

[0008] Optionally, the relay control circuit includes a primary circuit and a secondary circuit of an optocoupler, the primary circuit is electrically connected to a flexible pin of the MCU, and the secondary circuit is electrically connected to the coil.

[0009] Optionally, the primary circuit includes a first current limiting resistor, a second current limiting resistor and a primary capacitor, and the first current limiting resistor, the second current limiting resistor and the primary capacitor are arranged in parallel.

[0010] Optionally, the secondary circuit includes a secondary resistor, a transistor, a first freewheeling diode and a second freewheeling diode, the first freewheeling diode and the second freewheeling diode are arranged in parallel, the positive electrodes of the first freewheeling diode and the second freewheeling diode are electrically connected to the collector of the transistor, the negative electrodes of the first freewheeling diode and the second freewheeling diode are electrically connected to the coil, one end of the secondary resistor is electrically connected to the emitter of the transistor, the other end of the secondary resistor is connected to the secondary coil of the optocoupler, and the base of the transistor is connected to the secondary coil of the optocoupler.

[0011] Optionally, the elevator inverter circuit further includes a fault detection circuit, and the fault detection circuit is arranged in parallel with the pre-charging circuit.

[0012] Optionally, the fault detection circuit includes a first amplifier circuit, a second amplifier circuit and a comparison circuit, the first amplifier circuit, the second amplifier circuit and the comparison circuit are arranged in series in sequence, the first amplifier circuit is arranged in parallel with the pre-charging circuit, and the output end of the comparison circuit is electrically connected to the SRF signal pin of the MCU.

[0013] In a second aspect, an embodiment of the present invention further provides an elevator inverter, wherein the elevator inverter comprises an elevator inverter circuit as described in any one of the embodiments of the present invention.

[0014] In a third aspect, an embodiment of the present invention further provides an elevator inverter control method, which is applied to the elevator inverter as described in the embodiment of the present invention, and the elevator inverter control method includes:

[0015] After power-on, when the inverter bus capacitor is fully charged, the relay is controlled by the relay control circuit to short-circuit the pre-charging circuit.

[0016] In an embodiment of the present invention, the elevator inverter circuit includes an MCU, a rectifier bridge circuit, a bus capacitor, a protection circuit and an inverter circuit, the bus output of the rectifier bridge circuit is electrically connected to both ends of the bus capacitor, the two ends of the bus capacitor are electrically connected to the input end of the inverter circuit, the output of the inverter circuit is electrically connected to the elevator load, the protection circuit is arranged in series between the bus capacitor and the rectifier bridge, and the protection circuit is electrically connected to the MCU; the protection circuit includes a pre-charging circuit and a relay circuit in parallel with the pre-charging resistor, the relay circuit includes a relay and a relay control circuit, and the relay control circuit controls the relay to short-circuit the pre-charging circuit. The present invention can avoid the impact caused by bus current fluctuations in the initial stage of power-on of the elevator inverter by arranging the protection circuit in series between the bus capacitor and the rectifier bridge, and the protection circuit includes a pre-charging circuit and a relay circuit in parallel with the pre-charging resistor, thereby protecting key components such as the rectifier bridge and the bus capacitor, and there is no need to set multiple groups of relays to switch the detection signal, thereby extending the service life of the elevator inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a structural schematic diagram of an elevator inverter circuit provided by an embodiment of the present invention;

[0019] Figure 2 is a structural schematic diagram of a protection circuit provided by an embodiment of the present invention;

[0020] Figure 3 is a structural schematic diagram of a fault detection provided by an embodiment of the present invention;

[0021] Among them, 1. rectifier bridge circuit; 2. bus capacitor; 3. inverter circuit; 4. protection circuit; 41. pre-charging circuit; 42. relay circuit; 5. MCU; 6. fault detection circuit. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] like Figure 1As shown, Figure 1 It is a structural diagram of an elevator inverter circuit provided by an embodiment of the present invention, wherein the elevator inverter circuit includes an MCU5, a rectifier bridge circuit 1, a bus capacitor 2, a protection circuit 4 and an inverter circuit 3, wherein the bus output of the rectifier bridge circuit 1 is electrically connected to both ends of the bus capacitor 2, both ends of the bus capacitor 2 are electrically connected to the input end of the inverter circuit 3, the output of the inverter circuit 3 is electrically connected to the elevator load, the protection circuit 4 is arranged in series between the bus capacitor 2 and the rectifier bridge, and the protection circuit 4 is electrically connected to the MCU5; the protection circuit 4 includes a pre-charging circuit 41 and a relay circuit connected in parallel with the pre-charging resistor, the relay circuit 42 includes a relay and a relay control circuit, and the relay control circuit controls the relay to short-circuit the pre-charging circuit 41.

[0024] In the embodiment of the present invention, the elevator inverter circuit is mainly composed of MCU5 (microcontroller), rectifier bridge circuit 1, bus capacitor 2, protection circuit 4 and inverter circuit 3. Among them, MCU5 is responsible for receiving and processing various signals and issuing control instructions as the control center; rectifier bridge circuit 1 converts input AC power into DC power; bus capacitor 2 is used to store electric energy and smooth the output of DC power; inverter circuit 3 converts DC power into AC power with adjustable frequency and voltage to drive the elevator motor to operate.

[0025] The protection circuit 4 is arranged in series between the bus capacitor 2 and the rectifier bridge, and is electrically connected to the MCU 5. The main function of the protection circuit 4 is to prevent a large impact current from directly impacting the rectifier bridge and the bus capacitor 2 at the initial stage of powering on the elevator inverter, thereby protecting these key components from damage.

[0026] The protection circuit 4 specifically includes a pre-charging circuit 41 and a relay circuit connected in parallel with the pre-charging resistor. The function of the pre-charging circuit 41 is to limit the magnitude of the impact current through the resistor at the initial stage of the elevator inverter power-on, so that the rectifier bridge and the bus capacitor 2 can smoothly withstand the impact of the current. The resistance value of the pre-charging resistor can be adjusted according to actual needs.

[0027] The relay circuit 42 includes a relay and a relay control circuit. The relay is a switching element, and its working state is controlled by the relay control circuit. At the beginning of the elevator inverter power-on, the relay is in the disconnected state, and the pre-charging circuit 41 works. After the pre-charging is completed, the relay control circuit sends a control signal to make the relay pull in, short-circuiting the pre-charging circuit 41, thereby reducing the energy consumption in the circuit.

[0028] The relay control circuit adopts the level trigger mode, and controls the relay's contact and disconnection by detecting the level signal in the circuit. It has the characteristics of fast response speed and accurate control, and can effectively protect the elevator inverter circuit.

[0029] Optionally, the pre-charging circuit 41 includes a first pre-charging resistor and a second pre-charging resistor which are arranged in series, and both ends of the relay are electrically connected to non-common ends of the first pre-charging resistor and the second pre-charging resistor.

[0030] In the embodiment of the present invention, the pre-charging circuit 41 is composed of a first pre-charging resistor and a second pre-charging resistor connected in series, and two ends of the relay are connected to the non-common ends of the two pre-charging resistors.

[0031] The first pre-charging resistor and the second pre-charging resistor are arranged in series. When the elevator inverter is powered on, the current needs to pass through these two resistors in sequence, thereby effectively limiting the size of the impact current.

[0032] As a switching element, the working state of the relay can be flexibly controlled by the relay control circuit. In the initial stage of the elevator inverter power-on, the relay is in the disconnected state, at which time the pre-charging circuit 41 works to limit the impact current. After the pre-charging is completed, the relay control circuit will send a control signal to close the relay, thereby short-circuiting the pre-charging circuit 41. In this way, the energy consumption in the circuit is reduced, and the operating efficiency of the elevator inverter is also improved.

[0033] When the electrolytic capacitor of the inverter main circuit is charged after power-on, the Soft_start signal is low level, the relay control circuit is turned on, the relay is energized, and the pre-charging resistor is short-circuited.

[0034] Please refer to Figure 2 , Figure 2 is a structural diagram of a protection circuit provided by an embodiment of the present invention. Figure 2 In the figure, a first pre-charging resistor R142 (39 ohms) and a second pre-charging resistor R143 (39 ohms) are arranged in series, the first pre-charging resistor R142 and the second pre-charging resistor R143 have a common end, the non-common end of the first pre-charging resistor R142 is connected to the bus N end, the non-common end of the second pre-charging resistor R143 is connected to the bus capacitor (1Uf), and the two ends of the relay RLY1 are respectively connected to the non-common ends of the first pre-charging resistor R142 and the second pre-charging resistor R143.

[0035] Optionally, the relay includes an electric suction switch and a coil, and the coil is electrically connected to the relay control circuit.

[0036] In the embodiment of the present invention, in the pre-charging stage, the short circuit and open circuit of the pre-charging resistor are controlled to achieve stable charging of the bus capacitor, thereby preventing damage to circuit components due to instantaneous large current impact.

[0037] The electric suction switch is the core component of the relay, usually composed of an iron core, an armature and contacts. When current flows through the coil, a magnetic field is generated, attracting the armature to move toward the iron core, thereby closing the contacts; when the coil is de-energized, the magnetic field disappears, the armature is reset under the action of the spring force, and the contacts are disconnected. The contacts of the above-mentioned electric suction switch are connected in series at both ends of the pre-charging resistor, and the closing and opening of the contacts control whether the pre-charging resistor participates in the circuit operation.

[0038] The coil is a component that generates a magnetic field. It is wound on an iron core. When current flows through the coil, a magnetic field is generated around the iron core, thereby attracting the armature. The number of turns, wire diameter, and material of the coil will affect the strength of the magnetic field it generates, which in turn affects the pull-in force and response time of the relay. In the elevator inverter circuit, the coil is connected to the relay control circuit, and the control of the pull-in and release of the relay is achieved by changing the current in the control circuit.

[0039] Optionally, the relay control circuit includes a primary circuit and a secondary circuit of an optocoupler, the primary circuit is electrically connected to a flexible pin of the MCU, and the secondary circuit is electrically connected to the coil.

[0040] In the embodiments of the present invention, please continue to refer to Figure 2 , the relay control circuit is mainly composed of optocoupler IC23 (photocoupler), primary circuit and secondary circuit. Optocoupler is a device that converts electrical signals into optical signals and then converts optical signals into electrical signals. It has the function of electrical isolation and can effectively prevent interference signals in the circuit from affecting the MCU (microcontroller). The primary circuit is connected to the flexible pin (Soft_start) of the MCU to receive the control signal from the MCU; the secondary circuit is connected to the coil of the relay to control the attraction and release of the relay. Soft_start is low level, the optocoupler is turned on, the transistor TR6 is turned on, the relay is attracted, and the pre-charge resistor is short-circuited.

[0041] Optocouplers play a key role in isolation and transmission in relay control circuits. When the MCU sends a control signal, the signal first drives the primary LED of the optocoupler to emit light through the primary circuit. The light signal is then transmitted to the secondary side through the transparent medium of the optocoupler, and is received by the secondary side's photosensitive element and converted into an electrical signal, thereby driving the secondary circuit to work.

[0042] Optionally, the primary circuit includes a first current limiting resistor, a second current limiting resistor and a primary capacitor, and the first current limiting resistor, the second current limiting resistor and the primary capacitor are arranged in parallel.

[0043] In the embodiments of the present invention, please continue to refer to Figure 2The primary circuit is a bridge connecting the MCU and the primary side of the optocoupler. The primary circuit may include a first current limiting resistor R144 (10kohms), a second current limiting resistor R145 (330ohms) and a primary capacitor C96 (100pF), which are arranged in parallel. The primary capacitor C96 is connected to a 5V power supply.

[0044] The main function of the current limiting resistors R144 and R145 is to limit the current flowing through the primary side light emitting diode of the optocoupler to prevent the light emitting diode from being damaged due to excessive current. At the same time, setting two current limiting resistors in parallel can improve the reliability of the circuit. Even if one of the resistors fails, the other resistor can continue to work to ensure the normal operation of the circuit.

[0045] The function of the primary capacitor C96 is to filter out high-frequency noise in the control signal and improve the stability of the signal. In the elevator inverter circuit, due to the existence of the rectifier bridge circuit and the inverter circuit, more high-frequency interference signals may be generated. Through the parallel capacitor, these interference signals can be effectively absorbed to ensure the accurate transmission of the control signal.

[0046] The current flows through the parallel circuit composed of the first current limiting resistor, the second current limiting resistor and the primary capacitor, and flows into the primary light-emitting diode of the optocoupler, causing it to emit light. The light signal then passes through the transparent medium inside the optocoupler to excite the photosensitive element on the secondary side (which can be a phototransistor or a photoresistor), thereby generating a corresponding electrical signal on the secondary side to drive the relay control circuit to work.

[0047] Due to the existence of the current limiting resistor, even if the voltage or current output by the MCU fluctuates, the current passing through the optocoupler can be kept within a safe range, avoiding damage to the optocoupler or affecting its transmission characteristics due to overcurrent. At the same time, the filtering effect of the primary capacitor further reduces the clutter interference in the signal and improves the accuracy and reliability of signal transmission.

[0048] Optionally, the secondary circuit includes a secondary resistor, a transistor, a first freewheeling diode and a second freewheeling diode, the first freewheeling diode and the second freewheeling diode are arranged in parallel, the positive electrodes of the first freewheeling diode and the second freewheeling diode are electrically connected to the collector of the transistor, the negative electrodes of the first freewheeling diode and the second freewheeling diode are electrically connected to the coil, one end of the secondary resistor is electrically connected to the emitter of the transistor, the other end of the secondary resistor is connected to the secondary coil of the optocoupler, and the base of the transistor is connected to the secondary coil of the optocoupler.

[0049] In the embodiments of the present invention, please continue to refer to Figure 2The secondary circuit is mainly composed of a secondary resistor R146 (1kohms), a transistor TR6, and a freewheeling diode D23. The freewheeling diode D23 includes a first freewheeling diode and a second freewheeling diode. The circuit function is realized by a specific connection method between each component. The secondary resistor R146 plays the role of current limiting and voltage dividing in the circuit. When the transistor TR6 is turned on, the secondary resistor R146 limits the current flowing through the coil to prevent damage to the relay or coil due to excessive current. At the same time, the secondary resistor R146 also forms a voltage divider circuit together with the coil, ensuring that the voltage between the base and the emitter of the transistor TR6 is within a reasonable range, thereby ensuring the normal operation of the transistor TR6.

[0050] In the relay control circuit, when the transistor changes from the on state to the off state, the current in the coil will be suddenly interrupted, generating a high back electromotive force. In order to protect other components in the circuit from the impact of the back electromotive force, this embodiment connects a freewheeling diode in parallel at both ends of the coil. In this embodiment, the first freewheeling diode and the second freewheeling diode are arranged in parallel, and when the transistor is turned off, a freewheeling path is provided for the current in the coil, and the energy of the back electromotive force is consumed on the diode, thereby protecting other components in the circuit.

[0051] Specifically, the current limiting resistors R144 and R145, when Soft_start is at a low level, allow the current that meets the design requirements to flow through the primary side of the optocoupler IC23; R146 and the secondary side of the optocoupler IC23 constitute the TR6 base drive circuit to provide a certain base drive current; the optocoupler IC23, safety isolation and signal transmission, TR6 is used to drive the relay coil; the freewheeling diode D23, prevents TR6 from being damaged by overvoltage when it is turned off.

[0052] Optionally, the elevator inverter circuit further includes a fault detection circuit 6, and the fault detection circuit 6 is arranged in parallel with the pre-charging circuit.

[0053] In the embodiment of the present invention, the main function of the fault detection circuit 6 is to monitor the working parameters in the circuit in real time during the operation of the elevator inverter. Once an abnormal situation is detected, it can respond quickly by sending a fault signal to the microcontroller (MCU) to trigger the protection mechanism, thereby effectively preventing equipment damage or accidents.

[0054] The fault detection circuit is set in parallel with the pre-charging circuit, and can independently monitor the working status of the pre-charging circuit and other circuit parts associated with it (such as the rectifier bridge circuit, bus capacitor, etc.). In the early stage of the elevator inverter startup, the pre-charging circuit is responsible for limiting the impact current and protecting the components in the circuit from damage. The fault detection circuit continuously monitors key parameters such as current and voltage during this process and subsequent operation to ensure that all links operate within a safe range.

[0055] Please refer to Figure 3 , Figure 3 is a structural diagram of a fault detection circuit provided by an embodiment of the present invention, such as Figure 3 As shown, the N and (-) of the fault detection circuit are connected to the two sides of the pre-charging resistor respectively. When current flows through the pre-charging resistor, it means that the relay is not turned on. At this time, there will be voltage at the N and (-) terminals. This voltage signal is differentially amplified, clamped by diode D37, and then amplified and sent to the comparator. The signal SRF becomes a low level. The MCU detects this low level and sends a fault alarm shutdown signal.

[0056] Optionally, the fault detection circuit includes a first amplifier circuit, a second amplifier circuit and a comparison circuit, the first amplifier circuit, the second amplifier circuit and the comparison circuit are arranged in series in sequence, the first amplifier circuit is arranged in parallel with the pre-charging circuit, and the output end of the comparison circuit is electrically connected to the SRF signal pin of the MCU.

[0057] In the embodiments of the present invention, please continue to refer to Figure 3 The main function of the fault detection circuit is to continuously monitor the working status of the pre-charging circuit during the operation of the elevator inverter. Once an abnormal signal is detected, it will immediately output a fault signal to the SRF signal pin of the MCU through the comparison circuit, thereby triggering the protection mechanism to ensure the safe and stable operation of the elevator system.

[0058] The fault detection circuit is composed of a first amplifier circuit, a second amplifier circuit and a comparison circuit connected in series in sequence. The first amplifier circuit includes a first amplifier IC21 (TL082CDR) and its bypass, the second amplifier circuit includes a first amplifier IC21 (TL082CDR) and its bypass, and the comparison circuit includes a comparator IC14 (LM393MX).

[0059] The first amplifier circuit is connected in parallel with the pre-charging circuit to directly collect the voltage or current signal in the pre-charging circuit. Since the pre-charging circuit is used to limit the impact current and protect the circuit components when the elevator inverter is started, its working state is directly related to the safety and stability of the entire inverter. The first amplifier circuit usually uses a high-precision, low-noise operational amplifier to ensure accurate amplification of weak signals. The amplification factor needs to be set according to actual needs, ensuring sufficient sensitivity while avoiding misjudgment caused by excessive amplification.

[0060] The second amplifier circuit is located after the first amplifier circuit and further processes the amplified signal. This level of amplification is usually used to adjust the amplitude of the signal to make it more suitable for subsequent processing by the comparison circuit. The second amplifier circuit is also used for filtering to remove high-frequency noise in the signal and improve the accuracy of detection. Similar to the first amplifier circuit, the design of the second amplifier circuit also needs to consider factors such as amplification factor, frequency response and noise suppression.

[0061] The comparison circuit receives the signal output by the second amplifier circuit and compares it with the preset reference level. When the signal exceeds or falls below the reference level, the comparison circuit outputs a fault signal to the MCU. The reference level setting needs to be based on the normal operating range and safety margin of the elevator inverter to ensure that the protection can be triggered in time under abnormal conditions. The output of the comparison circuit is usually a digital signal, which is convenient for the MCU to perform logic processing.

[0062] The N and (-) terminals of the first amplifier circuit are connected to the two sides of the pre-charging resistor respectively. When current flows through the pre-charging resistor, it means that the relay is not turned on. At this time, there will be voltage at the N and (-) terminals. This voltage signal is differentially amplified by the first amplifier circuit, clamped by the diode D37, amplified by the second amplifier circuit and sent to the comparison circuit. The signal SRF is compared by the comparator in the comparison circuit, and the MCU detects this low level and sends a fault alarm shutdown signal.

[0063] Optionally, an embodiment of the present invention further provides an elevator inverter, wherein the elevator inverter includes the elevator inverter circuit as described in any one of the embodiments of the present invention.

[0064] The present invention arranges a protection circuit in series between the bus capacitor and the rectifier bridge. The protection circuit includes a pre-charging circuit and a relay circuit connected in parallel with the pre-charging resistor. This can avoid the impact caused by bus current fluctuations in the initial stage of power-on of the elevator inverter, thereby protecting key components such as the rectifier bridge and the bus capacitor. There is no need to set up multiple groups of relays to switch detection signals, thereby extending the service life of the elevator inverter.

[0065] Optionally, an embodiment of the present invention further provides an elevator inverter control method, which is applied to the elevator inverter as described in the embodiment of the present invention, and the elevator inverter control method includes:

[0066] After power-on, when the inverter bus capacitor is charged, the relay control circuit controls the relay to short-circuit the pre-charging circuit. The elevator inverter circuit includes an MCU, a rectifier bridge circuit, a bus capacitor, a protection circuit and an inverter circuit. The bus output of the rectifier bridge circuit is electrically connected to the two ends of the bus capacitor, the two ends of the bus capacitor are electrically connected to the input end of the inverter circuit, the output of the inverter circuit is electrically connected to the elevator load, the protection circuit is arranged in series between the bus capacitor and the rectifier bridge, and the protection circuit is electrically connected to the MCU; the protection circuit includes a pre-charging circuit and a relay circuit connected in parallel with the pre-charging resistor, the relay circuit includes a relay and a relay control circuit, and the relay control circuit controls the relay to short-circuit the pre-charging circuit.

[0067] In the embodiment of the present invention, the elevator inverter circuit is mainly composed of an MCU (microcontroller), a rectifier bridge circuit, a bus capacitor, a protection circuit, and an inverter circuit. Among them, the MCU, as a control center, is responsible for receiving and processing various signals and issuing control instructions; the rectifier bridge circuit 1 converts the input AC power into DC power; the bus capacitor is used to store electrical energy and smooth the output of DC power; the inverter circuit converts DC power into AC power with adjustable frequency and voltage to drive the elevator motor to operate.

[0068] The protection circuit is set in series between the bus capacitor and the rectifier bridge and is electrically connected to the MCU. The main function of the protection circuit is to prevent large impact currents from directly impacting the rectifier bridge and bus capacitors at the initial stage of powering on the elevator inverter, thereby protecting these key components from damage.

[0069] The protection circuit specifically includes a pre-charging circuit and a relay circuit connected in parallel with the pre-charging resistor. The function of the pre-charging circuit is to limit the size of the impact current through the resistor at the initial stage of the elevator inverter power-on, so that the rectifier bridge and bus capacitor can smoothly withstand the impact of the current. The resistance value of the pre-charging resistor can be adjusted according to actual needs.

[0070] The relay circuit includes a relay and a relay control circuit. The relay is a switching element, and its working state is controlled by the relay control circuit. In the early stage of the elevator inverter power-on, the relay is in the disconnected state and the pre-charging circuit works. When the pre-charging is completed, the relay control circuit sends a control signal to close the relay and short-circuit the pre-charging circuit, thereby reducing the energy consumption in the circuit.

[0071] The relay control circuit adopts the level trigger mode, and controls the relay's contact and disconnection by detecting the level signal in the circuit. It has the characteristics of fast response speed and accurate control, and can effectively protect the elevator inverter circuit.

[0072] Optionally, the pre-charging circuit includes a first pre-charging resistor and a second pre-charging resistor which are arranged in series, and both ends of the relay are electrically connected to non-common ends of the first pre-charging resistor and the second pre-charging resistor.

[0073] In the embodiment of the present invention, the pre-charging circuit is composed of a first pre-charging resistor and a second pre-charging resistor connected in series, and both ends of the relay are connected to the non-common ends of the two pre-charging resistors.

[0074] The first pre-charging resistor and the second pre-charging resistor are arranged in series. When the elevator inverter is powered on, the current needs to pass through these two resistors in sequence, thereby effectively limiting the size of the impact current.

[0075] As a switching element, the working state of the relay can be flexibly controlled by the relay control circuit. In the initial stage of the elevator inverter power-on, the relay is in the disconnected state. At this time, the pre-charging circuit works to limit the inrush current. When the pre-charging is completed, the relay control circuit will send a control signal to close the relay, thereby short-circuiting the pre-charging circuit. In this way, the energy consumption in the circuit is reduced, and the operating efficiency of the elevator inverter is also improved.

[0076] When the electrolytic capacitor of the inverter main circuit is charged after power-on, the Soft_start signal is low level, the relay control circuit is turned on, the relay is energized, and the pre-charging resistor is short-circuited.

[0077] The present invention arranges a protection circuit in series between the bus capacitor and the rectifier bridge. The protection circuit includes a pre-charging circuit and a relay circuit connected in parallel with the pre-charging resistor. This can avoid the impact caused by bus current fluctuations in the initial stage of power-on of the elevator inverter, thereby protecting key components such as the rectifier bridge and the bus capacitor. There is no need to set up multiple groups of relays to switch detection signals, thereby extending the service life of the elevator inverter.

[0078] The elevator inverter control method provided in the embodiment of the present invention can realize the various control processes of the elevator inverter in the above method embodiment and can achieve the same beneficial effects. To avoid repetition, it will not be described here.

[0079] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The computer-readable storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM).

[0080] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. An elevator inverter circuit, characterized in that: The elevator inverter circuit includes an MCU, a rectifier bridge circuit, a bus capacitor, a protection circuit and an inverter circuit, wherein the bus output of the rectifier bridge circuit is electrically connected to both ends of the bus capacitor, both ends of the bus capacitor are electrically connected to the input end of the inverter circuit, the output of the inverter circuit is electrically connected to the elevator load, the protection circuit is arranged in series between the bus capacitor and the rectifier bridge, and the protection circuit is electrically connected to the MCU; The protection circuit includes a pre-charging circuit and a relay circuit connected in parallel with the pre-charging resistor. The relay circuit includes a relay and a relay control circuit. The relay control circuit controls the relay to short-circuit the pre-charging circuit.

2. The elevator inverter circuit according to claim 1, characterized in that: The pre-charging circuit includes a first pre-charging resistor and a second pre-charging resistor which are arranged in series, and both ends of the relay are electrically connected to non-common ends of the first pre-charging resistor and the second pre-charging resistor.

3. The software adaptation circuit based on voltage detection as claimed in claim 1, characterized in that: The relay comprises an electric suction switch and a coil, and the coil is electrically connected to the relay control circuit.

4. The elevator inverter circuit according to claim 3, characterized in that: The relay control circuit includes a primary circuit and a secondary circuit of an optocoupler, the primary circuit is electrically connected to the flexible pin of the MCU, and the secondary circuit is electrically connected to the coil.

5. The elevator inverter circuit according to claim 4, characterized in that: The primary circuit includes a first current limiting resistor, a second current limiting resistor and a primary capacitor, and the first current limiting resistor, the second current limiting resistor and the primary capacitor are arranged in parallel.

6. The elevator inverter circuit according to claim 4, characterized in that: The secondary circuit includes a secondary resistor, a transistor, a first freewheeling diode and a second freewheeling diode, the first freewheeling diode and the second freewheeling diode are arranged in parallel, the positive electrodes of the first freewheeling diode and the second freewheeling diode are electrically connected to the collector of the transistor, the negative electrodes of the first freewheeling diode and the second freewheeling diode are electrically connected to the coil, one end of the secondary resistor is electrically connected to the emitter of the transistor, the other end of the secondary resistor is connected to the secondary coil of the optocoupler, and the base of the transistor is connected to the secondary coil of the optocoupler.

7. The elevator inverter circuit according to any one of claims 1 to 6, characterized in that: The elevator inverter circuit also includes a fault detection circuit, and the fault detection circuit is arranged in parallel with the pre-charging circuit.

8. The elevator inverter circuit according to claim 7, characterized in that: The fault detection circuit includes a first amplifier circuit, a second amplifier circuit and a comparison circuit, the first amplifier circuit, the second amplifier circuit and the comparison circuit are arranged in series in sequence, the first amplifier circuit is arranged in parallel with the pre-charging circuit, and the output end of the comparison circuit is electrically connected to the SRF signal pin of the MCU.

9. An elevator frequency converter, characterized in that: The elevator inverter comprises the elevator inverter circuit according to any one of claims 1 to 8.

10. An elevator inverter control method, characterized in that: Applied to the elevator inverter according to claim 9, the elevator inverter control method comprises: After power-on, when the inverter bus capacitor is fully charged, the relay is controlled by the relay control circuit to short-circuit the pre-charging circuit.

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