Conversion circuit, power supply circuit, fan and air conditioner

Abstract

According to the conversion circuit, the power supply circuit, the fan and the air conditioner, the voltage of the high-voltage direct-current bus can be reduced to the target voltage, and a stable low-voltage power supply is provided for the first frequency converter, so that the first frequency converter can select an I PM module and other electronic elements of a low voltage grade, and the hardware cost is remarkably reduced. Besides, the control module can detect the bus voltage and the actual output voltage of the step-down module in real time, and closed-loop adjustment is carried out through the voltage detection circuit, so that the target load is ensured to obtain stable target voltage, and the power supply quality is ensured. Meanwhile, by reasonably distinguishing the voltage levels of the target load and the non-target load and only adopting the voltage reduction design for the target load (such as a fan), the high cost caused by the fact that the whole machine uses a high-voltage voltage level device is avoided, and the reduction of the overall hardware cost of the system is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and in particular to a conversion circuit, a power supply circuit, a fan and an air conditioner. Background Art

[0002] The three-phase inverter air conditioner is an air conditioning system that uses three-phase power and inverter technology to adjust the operating speed of the compressor according to actual needs to achieve temperature control and energy efficiency. This air conditioning system has been widely used in commercial and industrial fields and can provide stable and reliable environmental control.

[0003] In the prior art, a three-phase variable frequency air conditioner usually uses a high voltage DC bus (e.g., 540V) to directly power multiple inverter modules, including different loads such as compressors and fans. Due to the high voltage of the DC bus, the multiple inverter modules all need to use high voltage IPM modules (intelligent power modules) and corresponding high voltage electronic components, which significantly increases the hardware cost. Therefore, there is a technical problem of excessively high hardware cost in the three-phase variable frequency air conditioner. Summary of the invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies and provide a conversion circuit, a power supply circuit, a fan and an air conditioner to solve the technical problem of excessively high hardware cost in three-phase variable frequency air conditioning units in the related art.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a conversion circuit, the conversion circuit at least comprising:

[0007] A step-down module, wherein the positive input terminal of the step-down module is connected to the DC bus, the positive output terminal and the negative output terminal are connected to the first inverter, and the target voltage is provided for the first inverter, and the negative input terminal and the negative output terminal of the step-down module are connected; wherein the DC bus is used to provide a DC bus voltage for the second inverter, the first inverter is an inverter connected to a target load, and the second inverter is an inverter connected to a non-target load; wherein the target voltage is the voltage of the DC bus voltage after being stepped down by the step-down module;

[0008] A voltage detection circuit, the voltage detection circuit is used to detect the DC bus voltage and the actual output voltage of the negative output terminal;

[0009] A control module is used to control the step-down module to step down the DC bus voltage based on the DC bus voltage and the actual output voltage of the negative output terminal, so that the actual output voltage of the negative output terminal approaches the target voltage.

[0010] In a second aspect, the present invention provides a power supply circuit, which includes the conversion circuit and the rectification circuit as described above.

[0011] In a third aspect, the present invention provides a wind fan, comprising the above-mentioned conversion circuit, and the wind fan is a target load connected to the first inverter.

[0012] In a fourth aspect, the present invention provides an air conditioner, comprising the above-mentioned conversion circuit, wherein the conversion circuit is connected to at least one fan and at least one compressor, and the compressor is a non-target load connected to the second inverter.

[0013] Beneficial effects:

[0014] The present invention provides a step-down module, and the conversion circuit can reduce the high-voltage DC bus voltage to the target voltage, and provide a stable low-voltage power supply for the first inverter, thereby allowing the first inverter to select low-voltage IPM modules and other electronic components, which significantly reduces the hardware cost. In addition, since the control module can detect the bus voltage and the actual output voltage of the step-down module in real time, and perform closed-loop regulation through the voltage detection circuit, it ensures that the target load obtains a stable target voltage and the power supply quality. At the same time, by reasonably distinguishing the voltage level of the target load and the non-target load, only the target load (for example, it can be a fan) is designed with a step-down design, which avoids the high cost caused by the use of high-voltage voltage level devices for the whole machine, and achieves a reduction in the overall hardware cost of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a structural schematic diagram of a conversion circuit provided by an embodiment of the present invention;

[0016] Figure 2 is a schematic structural diagram of a voltage reduction module used in an embodiment of the present invention;

[0017] Figure 3 is a schematic structural diagram of a voltage reduction module used in an embodiment of the present invention;

[0018] Figure 4 It is a circuit diagram of a conversion circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0020] In related technologies, with the development of frequency conversion technology, three-phase frequency conversion air conditioner units have gradually become mainstream products in the home and commercial air conditioning markets. Compared with traditional fixed-frequency air conditioners, frequency conversion air conditioners have higher energy efficiency and more sophisticated temperature control capabilities. They can adjust the motor speed through the frequency converter and accurately control the operating status of the compressor and fan.

[0021] A typical three-phase inverter air conditioning unit consists of the following main components:

[0022] Rectifier circuit: used to rectify the input three-phase AC power into high-voltage DC power (such as 540VDC) and provide a stable DC bus voltage for the entire three-phase variable frequency air conditioning unit.

[0023] The inverter of the compressor is usually directly connected to the 540V DC bus and controls the speed and torque output of the compressor motor through the inverter. Since the compressor requires a large amount of power, its drive circuit uses a high-voltage IPM (Intelligent Power Module) module to implement it.

[0024] Fan inverter: used to drive the fan motor, which mainly plays the role of heat dissipation and ventilation. Although the power demand of the fan is relatively small, it shares the same high-voltage DC bus with the compressor, so it has to use the same high-voltage level IPM module and other high-voltage components.

[0025] Since the DC bus voltage is 540V, this places high demands on the withstand voltage level of the power devices in the fan inverter. Therefore, the fan inverter must use IPM modules and other high-voltage components (such as high-voltage MOSFET, IGBT modules, drive circuits and protection circuits, etc.) with the same voltage level as the compressor, which leads to a significant increase in hardware costs.

[0026] It is understandable that when the motor power is small (for example, the fan can be used only for heat dissipation), a high-voltage IPM module is not necessary, but due to the limitation of the DC bus voltage, high-voltage IPM modules and other high-voltage components are often used in related technologies.

[0027] In addition, IPM modules with high voltage levels often require longer dead time to prevent the switching devices of the upper and lower bridge arms from being turned on at the same time and causing a short circuit. This will cause a large deviation between the inverter output voltage and the actual given voltage, causing distortion of the motor output current waveform. Due to the increase in motor waveform distortion and harmonic components, the fan may generate greater noise and vibration when working, affecting the overall stability of the air conditioner and the user experience.

[0028] Therefore, in three-phase variable frequency air-conditioning units, the fan inverter must use a high-voltage IPM module due to the limitation of the shared DC bus 540V high voltage, which leads to excessively high hardware costs for the fan driver and causes problems such as large dead time, current waveform distortion, and high fan noise.

[0029] In summary, in the related art, there is at least a technical problem of excessively high hardware cost in the three-phase variable frequency air conditioner. In view of this technical problem, this embodiment provides a conversion circuit, which may include: a buck module, the positive input end of the buck module is connected to the DC bus, the positive output end and the negative output end are connected to the first inverter, and the target voltage is provided to the first inverter, and the negative input end and the negative output end of the buck module are connected; wherein the DC bus is used to provide a DC bus voltage to the second inverter, the first inverter is a inverter connected to the target load, and the second inverter is a inverter connected to the non-target load; wherein the target voltage is the voltage of the DC bus voltage after the buck module steps down the voltage. A voltage detection circuit, the voltage detection circuit is used to detect the DC bus voltage and the actual output voltage of the negative output end. A control module, the control module is used to control the buck module to perform a step-down process on the DC bus voltage based on the DC bus voltage and the actual output voltage of the negative output end, so that the actual output voltage of the negative output end approaches the target voltage.

[0030] In this embodiment, by setting a step-down module, the conversion circuit can reduce the high-voltage DC bus voltage to the target voltage and provide a stable low-voltage power supply for the first inverter, thereby allowing the first inverter to select low-voltage IPM modules and other electronic components, which significantly reduces the hardware cost. In addition, since the control module can detect the bus voltage and the output voltage of the step-down module in real time, and perform closed-loop regulation through the voltage detection circuit, it ensures that the target load obtains a stable target voltage and guarantees the power supply quality. At the same time, by reasonably distinguishing the voltage levels of the target load and the non-target load, only the target load (for example, it can be a fan) is designed with a step-down design, which avoids the high cost of using high-voltage voltage level devices for the whole machine, and achieves a reduction in the overall hardware cost of the system.

[0031] Example

[0032] like Figure 1 As shown, this embodiment provides a conversion circuit, which can be applied in the three-phase variable frequency air conditioner. The conversion circuit may include:

[0033] A step-down module, wherein the positive input terminal of the step-down module is connected to the DC bus, the positive output terminal and the negative output terminal are connected to the first inverter, and the target voltage is provided for the first inverter, and the negative input terminal and the negative output terminal of the step-down module are connected; wherein the DC bus is used to provide a DC bus voltage for the second inverter, the first inverter is an inverter connected to a target load, and the second inverter is an inverter connected to a non-target load; wherein the target voltage is the voltage of the DC bus voltage after being stepped down by the step-down module.

[0034] In this embodiment, the step-down module may be a step-down module composed of at least one step-down circuit. The at least one step-down circuit may be in parallel and connected in parallel between the front-stage circuit and the rear-stage circuit. The front-stage circuit may be a rectifier circuit. The rear-stage circuit may be a first frequency converter, and a corresponding target load (for example, a fan). It is understandable that the front-stage circuit may further include an input end of three-phase alternating current. The rear-stage circuit may further include a second frequency converter, and a corresponding non-target load (for example, a compressor). The step-down circuit may be a buck-based step-down circuit, or a step-down circuit in other circuit structure forms.

[0035] In this embodiment, the step-down module can also be a step-down module formed by connecting multiple step-down circuits in series, so as to achieve multi-stage step-down. Through the series connection of multiple step-down circuits, each step-down circuit undertakes a part of the voltage drop task, which can reduce the voltage stress of the switch tube and other components in each stage of the circuit, thereby effectively improving the overall reliability and work efficiency. It is understandable that under high voltage, the duty cycle of a single-stage step-down circuit may be very low, causing the switch device to operate in a low efficiency range. Through multi-stage step-down, the duty cycle of a single-stage step-down circuit can be maintained within a more ideal range, thereby improving the overall conversion efficiency.

[0036] Furthermore, the distribution ratio of the voltage reduction of each level of the step-down circuit can be flexibly adjusted according to actual needs. For example, different step-down levels can be set by changing the reference voltage of each level of the step-down circuit, thereby meeting the load's requirements for different voltages and achieving flexible power supply.

[0037] In this embodiment, the buck module may also be a multi-channel synchronous BUCK shunt buck circuit. For example, it may be a dual-channel synchronous BUCK shunt buck circuit, a three-channel or even a four-channel synchronous BUCK shunt buck circuit, etc. In the multi-channel synchronous BUCK shunt buck circuit, multiple switch devices and corresponding freewheeling diodes may be provided, and these multiple switch devices and corresponding freewheeling diodes may reuse an energy storage inductor and a filter capacitor.

[0038] In some embodiments, the buck module may also be a Sepic buck-boost circuit, which can buck or boost the voltage when the input voltage is higher or lower than the target voltage.

[0039] In some embodiments, the buck module may also be a buck-boost converter (Buck-Boost circuit), which can adjust the output voltage when the input voltage is higher than, equal to or lower than the output voltage, and can both buck and boost the voltage.

[0040] In some implementations, the buck module may also be a buck LDO regulator or a Cuk converter, etc.

[0041] In this embodiment, the DC bus is the main power path in the three-phase variable frequency air-conditioning unit. The DC bus is connected to the output end of the rectifier circuit. On the one hand, it transmits the DC power after the three-phase AC rectification to the subsequent conversion module, and on the other hand, it supplies power to the second inverter and the corresponding non-target load. The DC bus directly supplies power to the second inverter connected to the non-target load, providing a high-voltage DC power supply that has not been reduced in voltage.

[0042] In this embodiment, the positive output terminal and the negative output terminal are two voltage output ports of the buck module, which are used to provide a stable target voltage for the first inverter. Specifically, the positive output terminal is the positive electrode port of the buck module output voltage, which is used to provide the positive voltage signal of the target voltage to the first inverter. For example, when the buck module is a buck-based buck circuit, the positive output terminal can be a connection node between an energy storage inductor and a filter capacitor. The negative output terminal is the negative electrode port of the buck module, which can be connected to the negative electrode node of the DC bus. The negative output terminal is used to provide a negative voltage reference of the target voltage for the first inverter. In the buck module, the negative output terminal is connected to the negative input terminal to form a common contact, thereby ensuring that the voltage output of the entire buck module is consistent with the target voltage. It can be understood that the voltage relationship between the negative output terminal and the positive output terminal determines the actual output voltage of the buck module. The voltage detection circuit and the control module detect and adjust the voltage between the positive output terminal and the negative output terminal to ensure that the output voltage value is consistent with the required target voltage, thereby achieving stable power supply to the target load.

[0043] In this embodiment, the first frequency converter may be a power electronic device that provides AC power to the target load. The device is used to drive the connected target load, and the voltage and frequency of its output can be adjusted according to the control requirements to meet the needs of the target load under different working conditions. For example, when the target load is a fan in an air conditioner, the first frequency converter can control the speed of the fan by adjusting the frequency, thereby adjusting the air volume or heat dissipation effect of the air conditioner. The input end of the first frequency converter is connected to the positive output end and the negative output end of the step-down module, and receives the target voltage obtained by stepping down the DC bus voltage. This design allows the power module of the first frequency converter (for example, it can be an IPM module) to select components with lower voltage levels, thereby reducing the overall hardware cost. It is understandable that the first frequency converter may include an inverter bridge (for example, it may be composed of a plurality of switching devices such as IGBTs), which is responsible for converting DC power into AC voltage and providing it to the target load. The first frequency converter may also include a PWM control unit for controlling the on and off of the inverter bridge switch to adjust the output AC voltage and frequency to achieve speed control of the target load.

[0044] In this embodiment, the target load may be represented as a load that needs to be powered by a voltage after voltage reduction processing, for example, it may be a fan in an air conditioner. The air conditioner may be a three-phase variable frequency air conditioner unit, or of course, it may be an air conditioner in other forms. Compared with the compressor, the fan has a lower voltage requirement and a relatively small power requirement, so the DC bus voltage may be stepped down by the step-down module for power supply.

[0045] In this embodiment, the target load may be a fan in an air conditioner or an electric valve. It is understood that the electric valve is used to control the flow and pressure of the refrigerant to achieve efficient cooling or heating of the air conditioner. By controlling the amount of refrigerant entering the evaporator, the temperature and pressure of the air conditioner can be accurately adjusted. Therefore, the electric valve can be driven by a low-power DC motor, and its switching degree is adjusted by the corresponding first inverter (equipped with an IPM module of a low-power level), so as to accurately control the refrigerant flow.

[0046] In this embodiment, the target load may also be a drain pump. It is understandable that the drain pump is used to discharge condensed water during the operation of the air conditioner. In particular, in a wall-mounted or ceiling-mounted air conditioner, condensed water needs to be discharged in time through the drain pump to ensure normal operation. The drain pump usually has a small power and can be powered by a stepped-down voltage, and its operating speed can be adjusted by the first inverter to adapt to different working conditions.

[0047] In some embodiments, the target load may also be an air conditioner shutter adjustment motor, a heat exchanger auxiliary fan, or an electronic air purification device, etc.

[0048] In this embodiment, the target voltage can be expressed as a voltage value obtained after the DC bus voltage is stepped down by the step-down module. This voltage value can provide a stable DC power supply for the target load (for example, a fan, an electric valve or a drainage pump in an air conditioner, etc.). Specifically, the target voltage can be a voltage value lower than the DC bus voltage and match the voltage tolerance range of the target load. When the target load is a fan, the target voltage can be a voltage value between 200V and 400V, for example, 370V. When the target load is an electric valve or an air conditioner shutter adjustment motor, the target voltage can be a voltage value between 12V and 48V.

[0049] In this embodiment, the second frequency converter can be represented as a frequency converter directly connected to the DC bus, which can be used to convert the high-voltage DC bus voltage (for example, 540VDC) into AC power, and provide an AC power supply with adjustable frequency and voltage for non-target loads. It can be understood that the second frequency converter is relative to the first frequency converter, and the input end of the second frequency converter directly receives the DC bus voltage that has not been stepped down, while the first frequency converter receives the lower target voltage after stepping down. It can also be understood that the second frequency converter can include an inverter bridge (for example, it can be composed of a plurality of switching devices such as IGBTs) and a PWM control unit. Accordingly, other protection circuits and filter circuits can be further included. The devices inside the second frequency converter (for example, switching devices such as IGBTs) can be devices with a higher withstand voltage level relative to the first frequency converter, so as to cope with larger voltage stress. The second frequency converter can be used to drive non-target loads that require high voltage and high power (for example, it can be a compressor of an air conditioner).

[0050] In this embodiment, the non-target load can be represented as a high-power load powered by AC power converted by directly receiving the DC bus voltage through the second inverter. The non-target load can be a compressor. It is understood that the compressor is a core component in the air conditioner and is used to compress the refrigerant to achieve a refrigeration cycle. The compressor usually requires a high-power input and is therefore powered directly by the DC bus through the second inverter. The non-target load can also be a high-power motor. It is understood that in some air conditioners, these air conditioners may include a high-power motor for driving other high-load devices (e.g., condenser fans, large centrifugal pumps, etc.), and therefore, the high-power motor can also belong to the non-target load.

[0051] A voltage detection circuit is used to detect the DC bus voltage and the actual output voltage of the negative output terminal.

[0052] In this embodiment, the voltage detection circuit can be represented as a signal acquisition circuit that can measure the DC bus voltage and the actual output voltage of the buck module in real time, and transmit the output signal (which can be a digital signal or an analog signal) to the control module. The voltage detection circuit can provide the control module with accurate voltage detection signals, so that the control module can dynamically adjust the buck module based on these signals to ensure that the actual output voltage (VOUT) is consistent with the target voltage.

[0053] In this embodiment, the voltage detection circuit may include an input terminal, a voltage detection unit and an output terminal. Specifically, the input terminal may further include a first input terminal and a second input terminal. The first input terminal is connected to the positive input terminal of the DC bus (that is, the positive input terminal of the buck module) for detecting the DC bus voltage. The second input terminal is connected to the negative output terminal of the buck module (that is, the reference point of the output terminal) as a reference for voltage detection. The voltage detection unit (for example, it can be a voltage divider unit that can divide the high voltage signal in proportion to adapt to the signal input range of the control module) is used to collect and process the input voltage signal and convert it into a signal form suitable for output and processing. The output terminal is used to transmit the processed voltage signal to the control module. The output signal can be an analog signal (for example, it can be a proportional voltage signal) or a digital signal (for example, it can be an SPI interface output). More specifically, when the output signal is an analog signal, the output signal can be an analog voltage signal (for example, it can be an analog voltage signal of 0-5V), and the analog voltage signal can be used for sampling by the ADC (analog-to-digital converter) inside the control module. When the output signal is a digital signal, the voltage detection circuit can convert the voltage signal into a digital signal through a built-in ADC, and output it to the control module through a digital interface (SPI).

[0054] In some embodiments, the voltage detection circuit may be a resistor divider circuit. The resistor divider circuit may be composed of two or more resistors connected in series, and may be capable of proportionally dividing a high voltage to a low voltage (e.g., 540 VDC to 0-5 V).

[0055] In some implementations, the voltage detection circuit may also be an isolated voltage detection circuit, which can isolate the high voltage signal from the low voltage control circuit through an isolation amplifier and output a low voltage signal proportional to the high voltage signal.

[0056] A control module is used to control the step-down module to step down the DC bus voltage based on the DC bus voltage and the actual output voltage of the negative output terminal, so that the actual output voltage of the negative output terminal approaches the target voltage.

[0057] In this embodiment, the control module can receive the output signal transmitted by the voltage detection circuit. It is understandable that the output signal is a signal representing the DC bus voltage and the actual output voltage (VOUT) of the negative output terminal. Specifically, the control module can receive the output signal from the voltage detection circuit through the input interface, and the output signal can be an analog voltage signal or a digital signal processed by analog-to-digital conversion (ADC). The control module processes the received output signal and compares it with the internally set target voltage to calculate the difference (error value) between the actual output voltage and the target voltage. Based on the error value, the control module can generate a control instruction (e.g., PWM duty cycle), adjust the working state of the switching device (e.g., IGBT) in the buck module (e.g., BUCK buck circuit), and ensure that the output voltage of the buck module can respond quickly and stabilize within the target voltage range.

[0058] In this embodiment, a voltage loop closed-loop control algorithm may be preset in the control module, and the voltage loop closed-loop control algorithm is used to implement execution control of the output voltage of the buck module, so that the actual output voltage (VOUT) can stably approach the target voltage.

[0059] Specifically, the control module first receives an output signal representing a DC bus voltage (VP) and an actual output voltage (VOUT). Then the control module compares the actual output voltage (VOUT) with the set target voltage (Vref) and calculates a voltage error signal. The error signal can be expressed as the difference between the target voltage (Vref) and the actual output voltage (VOUT). Then, the control module can generate a control signal for adjusting the working state of the buck module based on the error signal and the DC bus voltage (VP). More specifically, when generating the control signal, the DC bus voltage (VP) can be used as a feedforward signal to participate in the regulation. Its function is to predict the change trend of the output voltage in advance according to the fluctuation of the input voltage, and perform pre-compensation, thereby improving the dynamic response performance of the control. For example, the ratio of the target voltage (Vref) to the DC bus voltage (VP) can be used as a feedforward signal to generate a more accurate control signal. Finally, the control module converts the generated control signal into a PWM signal for controlling the buck module, and adjusts the actual output voltage (VOUT) of the buck module by adjusting the duty cycle or frequency of the PWM. It can be understood that the control module can continuously monitor the error between the actual output voltage (VOUT) and the target voltage (Vref), and dynamically adjust the control parameters according to the change of the error to ensure that the actual output voltage (VOUT) can quickly recover to the set value (that is, the target voltage) when the DC bus voltage (VP) fluctuates or the load changes.

[0060] In this embodiment, the voltage loop closed-loop control algorithm may be a PI or PID control algorithm. Specifically, the error signal is adjusted by using a proportional-integral (PI) or proportional-integral-differential (PID) control algorithm.

[0061] In this embodiment, the voltage loop closed-loop control algorithm may also be a feedforward compensation control algorithm. Specifically, the DC bus voltage is introduced as a feedforward signal on the basis of the PI or PID control algorithm. Through the DC bus voltage compensation, it is possible to respond quickly when the DC bus voltage fluctuates and reduce the transient fluctuation of the output voltage.

[0062] In some embodiments, the control module may also be preset with an adaptive control algorithm, through which the execution control of the output voltage of the buck module is implemented so that the actual output voltage (VOUT) can stably approach the target voltage. Specifically, according to the dynamic changes of the DC bus voltage and the actual output voltage, the control parameters (for example, proportional gain and integral gain) are automatically adjusted to improve the control accuracy and stability of the control module under different working conditions.

[0063] In some embodiments, the control module may also be preset with a fuzzy control algorithm, through which the execution control of the output voltage of the buck module is realized, so that the actual output voltage (VOUT) can stably approach the target voltage. Specifically, a fuzzy rule base may be preset to set the fuzzy relationship between the input variable (for example, an error signal) and the output variable (for example, a PWM signal); a control output is generated through a fuzzy reasoning mechanism, and the output is defuzzified to obtain an actual control signal.

[0064] In this embodiment, the control module may be a control module based on a microcontroller. Specifically, the microcontroller may be an MCU. The MCU may be preset with the above-mentioned voltage loop closed-loop control algorithm, adaptive control algorithm or fuzzy control algorithm, etc.

[0065] In this embodiment, the control module may be a control module based on a digital signal processor. Specifically, the digital signal processor may be a DSP. The DSP may be preset with the above-mentioned voltage loop closed-loop control algorithm, adaptive control algorithm or fuzzy control algorithm, etc.

[0066] In some implementations, the control module may also be a control module based on an FPGA (field programmable gate array).

[0067] In some embodiments, the control module may also be a control module based on an analog controller.

[0068] In some implementations, the control module may also be a control module based on an application specific control chip (ASIC).

[0069] This embodiment provides a step-down module, and the conversion circuit can reduce the high-voltage DC bus voltage to the target voltage and provide a stable low-voltage power supply for the first inverter, thereby allowing the first inverter to use low-voltage IPM modules and other electronic components, which significantly reduces the hardware cost. In addition, since the control module can detect the bus voltage and the output voltage of the step-down module in real time, and perform closed-loop regulation through the voltage detection circuit, it ensures that the target load obtains a stable target voltage and guarantees the power supply quality. At the same time, by reasonably distinguishing the voltage levels of the target load and the non-target load, only the target load (for example, it can be a fan) is designed with a step-down design, which avoids the high cost of using high-voltage voltage level devices for the entire machine, and achieves a reduction in the overall hardware cost of the system.

[0070] like Figure 2 As shown, in some embodiments, the step-down module includes at least one step-down circuit. When the step-down module includes at least two step-down circuits, the at least two step-down circuits are connected in parallel.

[0071] In this implementation, the voltage-reducing circuit may be a voltage-reducing circuit based on BUCK.

[0072] In this embodiment, the voltage-reducing circuit may also be a Sepic buck-boost circuit. The Sepic buck-boost circuit may be capable of performing voltage reduction or voltage increase when the input voltage is higher or lower than the target voltage.

[0073] In this embodiment, the buck circuit may also be a buck-boost converter (Buck-Boost circuit), which can adjust the output voltage when the input voltage is higher than, equal to or lower than the output voltage, and can both buck and boost the voltage.

[0074] In this implementation, the buck circuit may also be a buck LDO regulator or a Cuk converter, etc.

[0075] In this implementation, when the voltage-reducing module includes multiple voltage-reducing circuits, the voltage-reducing module may be a combination of the multiple voltage-reducing circuits mentioned above.

[0076] In this embodiment, when the buck module includes at least two buck circuits, a parallel connection is adopted so that each buck circuit can share the total load current of the DC bus at the same time. By connecting multiple buck circuits in parallel, the current stress of the electronic devices (for example, switching devices, energy storage inductors and freewheeling diodes) in each buck circuit can be effectively reduced, and power loss and heat accumulation can be reduced, thereby improving the reliability and efficiency of the overall circuit. In addition, the parallel structure can enable other parallel buck circuits to continue to work normally when a single buck circuit fails, thereby enhancing the redundancy and fault tolerance of the circuit and effectively improving the stability and operational safety of the circuit. Therefore, this embodiment can significantly improve the overall load capacity and efficiency while maintaining a stable output voltage, and is suitable for high-reliability power supply systems in high-power scenarios.

[0077] like Figure 3 As shown, in some embodiments, the step-down module includes at least two step-down circuits, and the at least two step-down circuits are connected in series.

[0078] In this implementation, the voltage-reducing circuit may be a voltage-reducing circuit based on BUCK.

[0079] In this embodiment, the voltage-reducing circuit may also be a Sepic buck-boost circuit. The Sepic buck-boost circuit may be capable of performing voltage reduction or voltage increase when the input voltage is higher or lower than the target voltage.

[0080] In this embodiment, the buck circuit may also be a buck-boost converter (Buck-Boost circuit), which can adjust the output voltage when the input voltage is higher than, equal to or lower than the output voltage, and can both buck and boost the voltage.

[0081] In this implementation, the buck circuit may also be a buck LDO regulator or a Cuk converter, etc.

[0082] In this implementation, the voltage reduction module may be a combination of the above-mentioned multiple voltage reduction circuits.

[0083] In this embodiment, a multi-channel buck circuit structure connected in series can achieve step-by-step voltage reduction, thereby optimizing the voltage conversion ratio of each stage, improving the efficiency of the buck module and reducing energy loss and heat accumulation. The series buck circuit can disperse the voltage drop of each stage, so that the voltage stress borne by the voltage conversion device at each stage is lower, and then use power devices with lower withstand voltage level and lower loss, thereby improving the operating efficiency of the entire circuit.

[0084] In this embodiment, the step-down module includes at least two step-down circuits, and they are configured in a serial connection so that each step-down circuit can gradually reduce the DC bus voltage, thereby realizing multi-level voltage conversion and hierarchical step-down regulation. The use of multiple step-down circuits connected in series can gradually reduce the voltage value at multiple voltage nodes, significantly reducing the voltage stress borne by the electronic devices (for example, switching devices, energy storage inductors, and freewheeling diodes) in each step-down circuit, reducing the voltage resistance level requirements of the devices, so that lower voltage resistance and lower cost power devices can be selected, further reducing the overall hardware cost.

[0085] In some implementations, each of the step-down circuits includes at least:

[0086] A switch device, wherein a voltage input terminal of the switch device is connected to a DC bus, and a signal input terminal of the switch device is connected to the control module.

[0087] In this implementation, the voltage input terminal of the switch device is also the positive input terminal of the buck module.

[0088] In this embodiment, the switching device can be a MOSFET (metal oxide semiconductor field effect transistor), an IGBT (insulated gate bipolar transistor), a triode, a silicon carbide field effect transistor, a bipolar transistor, and the like.

[0089] An energy storage inductor, one end of which is connected to the output end of the switching device.

[0090] When the switching device is an IGBT, one end of the energy storage inductor is connected to the emitter of the IGBT. The collector of the IGBT is connected to the DC bus. When the IGBT is turned on, the DC voltage flows to the emitter through the collector of the IGBT, and is applied to one end of the energy storage inductor, and the energy storage inductor starts to store energy. When the IGBT is turned off, since the current in the energy storage inductor cannot change instantly, the current will continue to flow through the freewheeling diode (connected between the energy storage inductor and the load) to maintain the continuity of the load current.

[0091] When the switch device is a MOSFET, and when the MOSFET is an N-channel MOSFET, one end of the energy storage inductor is connected to the source of the MOSFET, and the drain of the MOSFET is connected to the DC bus.

[0092] When the switch device is a triode, one end of the energy storage inductor is connected to the emitter of the triode, and the collector of the triode is connected to the DC bus.

[0093] A freewheeling diode, wherein the cathode of the freewheeling diode is connected to the output end of the switching device, and the anode of the freewheeling diode is connected to the first inverter.

[0094] A filter capacitor, one end of which is connected to the other end of the energy storage inductor and is connected to the first inverter as the positive output end of the step-down module, and the other end of which is connected to the first inverter and the positive electrode of the freewheeling diode as the negative output end.

[0095] It can be understood that the positive electrode of the freewheeling diode is connected to the first inverter on one hand, and is connected to the other end of the filter capacitor on the other hand. The positive electrode of the freewheeling diode and the other end of the filter capacitor are the negative output end of the step-down module. The intersection of the energy storage inductor and the filter capacitor is the positive output end of the step-down module.

[0096] In this embodiment, each buck circuit may also include a drive circuit. The drive circuit is used to provide amplification and isolation of the gate drive signal between the control module and the switch device. It is understandable that since the control signal (for example, it can be a PWM signal) of the control module has a low voltage and cannot directly drive the high-power switch device, it is necessary to use a drive circuit for signal amplification. In this embodiment, each buck circuit adopts a buck topology composed of a switch device, an energy storage inductor, a freewheeling diode and a filter capacitor, and realizes efficient buck regulation of the DC bus voltage based on the reasonable configuration of each component. This topology can control the charging and discharging process of the inductor by turning on and off the switch device in each switching cycle, and effectively realize the smooth conversion of the input DC bus voltage to the target voltage; through the energy storage of the energy storage inductor and the conduction and freewheeling of the freewheeling diode, the continuity of the current can be maintained, and the voltage ripple caused by the discontinuous current can be avoided, thereby reducing the ripple level of the output voltage; at the same time, the addition of the filter capacitor can further smooth the output voltage, reduce the voltage fluctuation caused by the current change, and effectively improve the stability and regulation accuracy of the output voltage. The buck circuit using this structure can maintain a high conversion efficiency under different input voltage conditions, and can easily achieve precise control of different output voltages by adjusting the duty cycle of the switching device. Therefore, this embodiment can achieve efficient and stable conversion of multiple target voltages, and can be applied to complex application scenarios with different input voltages and load changes, effectively improving the voltage regulation performance and operating efficiency of the circuit.

[0097] In some embodiments, the voltage reduction module may include at least:

[0098] A first switch device and a second switch device, wherein voltage input terminals of the first switch device and the second switch device are both connected to the DC bus, and signal input terminals of the first switch device and the second switch device are both connected to the control module.

[0099] In this embodiment, the first switching device and the second switching device can be MOSFET (metal oxide semiconductor field effect transistor), IGBT (insulated gate bipolar transistor), triode, silicon carbide field effect transistor or bipolar transistor, etc.

[0100] An energy storage inductor, one end of which is connected to the output end of the first switching device and the output end of the second switching device respectively.

[0101] A first freewheeling diode and a second freewheeling diode, wherein cathodes of the first freewheeling diode and the second freewheeling diode are respectively connected to output ends of the first switching device and the second switching device, and anodes of the first freewheeling diode and the second freewheeling diode are connected to the first frequency converter;

[0102] A filter capacitor, one end of which is connected to the other end of the energy storage inductor and is connected to the first inverter as the positive output end of the step-down module, and the other end of which is connected to the first inverter and the positive electrodes of the first and second freewheeling diodes as the negative output end.

[0103] In this embodiment, the step-down module may further include a drive circuit. The drive circuit is used to provide amplification and isolation of the gate drive signal between the control module and the first switch device and the second switch device. It is understandable that since the control signal (for example, a PWM signal) of the control module has a low voltage and cannot directly drive the high-power switch device, a drive circuit is required to amplify the signal. Figure 4 In a specific embodiment, the first switch device may be UND1, and the second switch device may be UND2. The first freewheeling diode may be a diode D1, and the second freewheeling diode may be a diode D2. The energy storage inductor may be an energy storage inductor L2. The filter capacitor may be a filter capacitor C3. The control module may be an MCU.

[0104] Specifically, UND1 and UND2 are two parallel IGBT switching devices, which are used to realize the periodic current regulation of the high-voltage DC bus voltage to the lower energy storage inductor. The collectors of UND1 and UND2 are connected to the DC bus voltage node (VP) as voltage input terminals. The emitter is used as a current output terminal to connect one end of the energy storage inductor. The signal input terminals (that is, the gate) of UND1 and UND2 are connected to the MCU to receive the PWM control signal, thereby realizing the opening and closing of the IGBT. The opening and closing of UND1 and UND2 are precisely controlled by the PWM signal of the MCU. By adjusting the PWM duty cycle, the output voltage (VOUT) can be precisely controlled. The energy storage inductor L2 is an energy storage element. When UND1 and UND2 are turned on and off, the current stores and releases energy through the energy storage inductor L2, thereby maintaining the continuity of the load current.

[0105] One end of the energy storage inductor L2 is connected to the emitters of UND1 and UND2, and the other end is connected to one end of the filter capacitor C3, and further serves as the positive output end of the buck circuit to supply power to the first inverter (target load). When UND1 and UND2 are turned on, the energy storage inductor L2 gradually stores energy and the current increases linearly. When UND1 and UND2 are turned off, the energy storage inductor L2 releases energy and continues to provide current to the target load.

[0106] The freewheeling diodes D1 and D2 are used to provide a reverse freewheeling path for the inductor current when UND1 and UND2 are turned off to ensure that the current is not suddenly interrupted. The cathodes of the freewheeling diodes D1 and D2 are connected to the emitters of UND1 and UND2, and are also connected to one end of the energy storage inductor L2. The anodes of the freewheeling diodes D1 and D2 are connected to the other end of the filter capacitor C3.

[0107] The function of the filter capacitor C3 is to release the current in the energy storage inductor L2, reduce the influence of current fluctuation on the actual output voltage, and thus provide a stable target voltage. One end of the filter capacitor C3 is connected to the other end of the energy storage inductor L2, and the intersection serves as the positive output end of the buck module. The other end of the filter capacitor C3 is connected to the positive poles of the freewheeling diodes D1 and D2, and further serves as the negative output end of the entire buck module, connected to the common reference end of the load (the first inverter).

[0108] MCU is the control module of the circuit, which receives the input of the voltage detection circuit (DC bus voltage VP and actual output voltage VOUT), and outputs PWM signals to control the conduction moment and conduction time of UND1 and UND2 based on the voltage loop closed-loop control algorithm. The PWM signals generated by MCU are connected to the gates of UND1 and UND2 to control the switch states of the two IGBTs, thereby achieving precise control of the output voltage.

[0109] In this embodiment, by introducing a dual-channel synchronous BUCK shunt buck circuit, each channel includes an independent switch device (first and second switch devices), a freewheeling diode (first and second freewheeling diodes) and a shared energy storage inductor and filter capacitor, it is possible to achieve shunt control of multiple current channels, so that under the same DC bus voltage, each current is effectively distributed through a parallel structure, reducing the current stress of each switch device and current path. This dual-channel buck topology can significantly improve the current carrying capacity and power density of the buck module, and because of the use of a two-channel synchronous control strategy, each switch device can be synchronized and adjusted through precise PWM, while ensuring the stability of the output voltage, reducing the voltage ripple and power loss caused by inconsistent current transient response, thereby greatly improving the dynamic response performance of voltage regulation. Moreover, the design of shared energy storage inductors and filter capacitors can effectively simplify the circuit structure, reduce the volume of the inductor and the number of filter elements, thereby reducing costs and circuit complexity.

[0110] In some implementations, the conversion circuit may further include:

[0111] A bus filter inductor, one end of which is connected to the positive electrode of the front-stage rectifier circuit, and the other end of which is connected to the voltage input end of the first switching device and the second switching device, for suppressing the current ripple on the DC bus.

[0112] like Figure 4 In a specific embodiment, the bus filter inductor may be a bus filter inductor L1. One end of the bus filter inductor L1 is connected to the pre-stage rectifier circuit shown in the figure. The other end of the bus filter inductor L1 is connected to UND1 and UND2 shown in the figure.

[0113] In this embodiment, by introducing a bus filter inductor into the conversion circuit, the current ripple on the DC bus can be effectively suppressed, and the stability and power quality of the DC bus voltage can be improved. One end of the bus filter inductor is connected to the positive electrode of the front-stage rectifier circuit, and the other end is connected to the voltage input end of the first switching device and the second switching device, which is used to form a low-frequency current filter path in the high-voltage DC bus, reduce the high-frequency ripple component in the rectified DC bus current, and prevent the DC bus voltage fluctuation caused by current fluctuation.

[0114] In some implementations, the conversion circuit may further include:

[0115] A first bus filter capacitor, one end of which is connected to the other end of the bus filter inductor and the voltage input ends of the first switch device and the second switch device respectively.

[0116] A second bus filter capacitor, one end of the second bus filter capacitor is connected to the other end of the first bus filter capacitor, and the other end of the second bus filter capacitor is connected to the negative electrode of the front-stage rectifier circuit.

[0117] like Figure 4 In a specific embodiment, the first bus filter capacitor may be a bus filter capacitor C1, and the second bus filter capacitor may be a bus filter capacitor C2.

[0118] In this embodiment, by adding the first bus filter capacitor and the second bus filter capacitor, the filtering effect and power stability of the DC bus voltage can be further enhanced. Specifically, one end of the first bus filter capacitor is connected to the other end of the bus filter inductor, and is directly connected to the voltage input end of the first switch device and the second switch device, and an effective LC filter network can be formed on the basis of the bus filter inductor, further absorbing the high-frequency voltage ripple in the DC bus, suppressing the peaks and oscillations generated by the DC bus voltage during the switching process, thereby providing a more stable input voltage for the lower circuit. The second bus filter capacitor is connected in series with the first bus filter capacitor, and the other end thereof is connected to the negative terminal of the rectifier circuit to form a dual-capacitor filter structure across the bus voltage. The dual-capacitor structure can not only enhance the high-frequency filtering effect on the input voltage, but also provide additional charge buffering when the load current changes, effectively suppressing the transient fluctuation of the DC bus voltage. Through this multi-stage filtering design, the present implementation can significantly improve the stability of the DC bus voltage, reduce the impact of current and voltage ripples on switching devices, thereby improving the stability and conversion efficiency of the entire circuit, while significantly reducing switching noise and electromagnetic interference, and ensuring the reliable operation of the buck circuit under complex working conditions.

[0119] like Figure 4 As shown, in a specific implementation scheme, the implementation scheme may include: a rectifier circuit, a dual-way synchronous BUCK shunt buck circuit, and a compressor inverter circuit and a fan inverter circuit. The rectifier circuit and the compressor inverter circuit are used to control and drive the compressor to operate normally and reliably. The dual-way synchronous BUCK shunt buck circuit and the fan inverter circuit reduce the bus voltage of 540V of the three-phase electrical level to the bus voltage of 310V of the single-phase electrical level, and adopt a voltage sampling circuit and a voltage loop closed-loop control algorithm to collect the voltage values ​​of the front and rear ends of the energy storage inductor L2, and transmit them to the MCU to calculate and control the duty cycle of the PWM wave, and at the same time control the opening and closing of the IGBT to supply power to the fan alone. Since the voltage is stepped down from 540VDC DC power supply to 310VDC low voltage, a low-voltage IPM power module can be used first, and the dead time can be effectively reduced, thereby improving the voltage utilization rate of the first inverter output and reducing the motor current distortion rate, effectively improving the motor noise.

[0120] When UND1 and UND2 are turned on, the energy storage inductor L2 is magnetized and stores energy, and the current flowing through the energy storage inductor L2 increases linearly, while charging the filter capacitor C3 and providing energy to the load. When turned on, it is rectified to 540VDC by the rectifier bridge, and the current flows through the bus filter inductor L1, bus filter capacitor C1 / C2, switch tube UND1 / UND2, energy storage inductor L2, and load. The diode has a single-phase conduction characteristic and no current flows, and the filter capacitor C3 is charged. Since the inductor current cannot change suddenly, the inductor current changes from small to large. At this time, the inductor energy storage is charged, that is, the left is positive and the right is negative, and the inductor voltage VL = VOUT-VP.

[0121] When UND1 and UND2 are turned off, since the inductor current cannot change suddenly, the energy storage inductor L2 is equivalent to the power supply discharging, that is, the right is positive and the left is negative. The current flows out through the right side of the energy storage inductor L2, flows back to the left side of the inductor through the load and the D1 / D2 diodes, and the inductor voltage VL = VOUT.

[0122] After stable operation, the inductor volt-second conservation law is observed. When the inductor is turned on, the inductor voltage is equal to the input voltage VP; when the inductor is turned off, the inductor voltage is equal to the output voltage VOUT. Let T be the period, TON be the on-time, TOFF be the off-time, and D be the duty cycle (D = TON / T). According to the inductor volt-second conservation law, we have:

[0123] Von*TON=Voff*TOFF

[0124] When on, Von=VL=VOUT-VP

[0125] When turned off, Voff=VL=VOUT

[0126] VOUT*TON=(VOUT-VP)*TOFF

[0127] The final conclusion is: the output voltage is lower than the input voltage = TON = DT, and D is less than 1, so voltage reduction is achieved.

[0128] TON=(VP-VOUT) / VOUT

[0129] Among them, the three-phase high-power variable frequency air conditioning unit has a high cooling capacity, so the compressor output power is required to be large, far exceeding the fan power, and a certain cooling capacity must be achieved. Therefore, the bus voltage VP rectified by the three-phase rectifier bridge directly supplies power to the compressor inverter bridge to control the reliable operation of the compressor. The fan in the variable frequency unit only plays a role in heat dissipation, and only needs its speed to meet the requirements. Therefore, the stepped-down voltage VOUT supplies power to the fan inverter bridge, and its inverter device IPM module can select single-phase low-power materials, and the motor can also select a lower-cost single-phase DC motor. Since the low-voltage level IPM module allows the dead time to be set to a smaller time, it can improve the voltage utilization rate of the inverter output, improve the motor current distortion rate, and thus reduce motor noise.

[0130] This embodiment provides a power supply circuit, which includes the above-mentioned conversion circuit and rectification circuit.

[0131] This embodiment provides a wind turbine, which includes the above-mentioned conversion circuit, and the wind turbine is a target load connected to the first frequency converter.

[0132] This embodiment provides an air conditioner, the air conditioner comprising the conversion circuit, the conversion circuit connecting at least one fan and at least one compressor, the compressor being a non-target load connected to the second inverter.

[0133] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0134] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, and this embodiment will not be described in detail here.

[0135] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0136] In the above embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0137] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A conversion circuit, characterized in that: The conversion circuit at least comprises: A step-down module, wherein the positive input terminal of the step-down module is connected to the DC bus, the positive output terminal and the negative output terminal are connected to the first inverter, and the target voltage is provided for the first inverter, and the negative input terminal and the negative output terminal of the step-down module are connected; wherein the DC bus is used to provide a DC bus voltage for the second inverter, the first inverter is an inverter connected to a target load, and the second inverter is an inverter connected to a non-target load; wherein the target voltage is the voltage of the DC bus voltage after being stepped down by the step-down module; A voltage detection circuit, the voltage detection circuit is used to detect the DC bus voltage and the actual output voltage of the negative output terminal; A control module is used to control the step-down module to step down the DC bus voltage based on the DC bus voltage and the actual output voltage of the negative output terminal, so that the actual output voltage of the negative output terminal approaches the target voltage.

2. The circuit according to claim 1, characterized in that The step-down module includes at least one step-down circuit. When the step-down module includes at least two step-down circuits, the at least two step-down circuits are connected in parallel.

3. The circuit according to claim 1, characterized in that The step-down module includes at least two step-down circuits, and the at least two step-down circuits are connected in series.

4. The circuit according to claim 2 or 3, characterized in that: Each of the step-down circuits at least comprises: A switch device, wherein a voltage input terminal of the switch device is connected to a DC bus, and a signal input terminal of the switch device is connected to the control module; An energy storage inductor, one end of which is connected to the output end of the switching device; a freewheeling diode, wherein a cathode of the freewheeling diode is connected to an output end of the switching device, and an anode of the freewheeling diode is connected to the first frequency converter; A filter capacitor, one end of which is connected to the other end of the energy storage inductor and is connected to the first inverter as the positive output end of the step-down module, and the other end of which is connected to the first inverter and the positive electrode of the freewheeling diode as the negative output end.

5. The circuit according to claim 1, characterized in that The step-down module at least comprises: A first switch device and a second switch device, wherein voltage input terminals of the first switch device and the second switch device are both connected to the DC bus, and signal input terminals of the first switch device and the second switch device are both connected to the control module; An energy storage inductor, one end of which is connected to the output end of the first switching device and the output end of the second switching device respectively; A first freewheeling diode and a second freewheeling diode, wherein cathodes of the first freewheeling diode and the second freewheeling diode are respectively connected to output ends of the first switching device and the second switching device, and anodes of the first freewheeling diode and the second freewheeling diode are connected to the first frequency converter; A filter capacitor, one end of which is connected to the other end of the energy storage inductor and is connected to the first inverter as the positive output end of the step-down module, and the other end of which is connected to the first inverter and the positive electrodes of the first and second freewheeling diodes as the negative output end.

6. The circuit according to claim 5, characterized in that The conversion circuit also includes: A bus filter inductor, one end of which is connected to the positive electrode of the front-stage rectifier circuit, and the other end of which is connected to the voltage input end of the first switching device and the second switching device, for suppressing the current ripple on the DC bus.

7. The circuit according to claim 6, characterized in that The conversion circuit also includes: A first bus filter capacitor, one end of which is connected to the other end of the bus filter inductor and voltage input ends of the first switch device and the second switch device respectively; A second bus filter capacitor, one end of the second bus filter capacitor is connected to the other end of the first bus filter capacitor, and the other end of the second bus filter capacitor is connected to the negative electrode of the front-stage rectifier circuit.

8. A power supply circuit, characterized in that: The power supply circuit includes a conversion circuit and a rectification circuit as described in any one of claims 1 to 7.

9. A fan, characterized in that: The wind turbine comprises the conversion circuit as claimed in any one of claims 1 to 7, and the wind turbine is a target load connected to the first inverter.

10. An air conditioner, characterized in that: The air conditioner comprises the conversion circuit as claimed in any one of claims 1 to 7, wherein the conversion circuit is connected to at least one fan and at least one compressor, and the compressor is a non-target load connected to the second inverter.

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