Power factor correction circuit, control method, motor drive circuit, and electrical device

Abstract

This application discloses a power factor correction circuit, control method, motor drive circuit, and electrical equipment. A filter circuit is set on the output side of the rectifier bridge. The voltage ripple of the DC bus is filtered out by the filter capacitor in the filter circuit. When the DC bus voltage is lower than a preset voltage threshold, the control switch module is in the conducting state. In this state, the filter capacitor is connected to the circuit for charging. When the DC bus voltage is higher than the preset voltage threshold, the control switch module is in the off state. In this state, the voltage output by the rectifier bridge supplies power to the load. The above process increases the charging time of the filter capacitor. Under the sinusoidal AC input voltage, the charging current of the filter capacitor is a periodic symmetrical waveform, which makes the phase of the AC input current synchronize with the phase of the AC input voltage, improves the power factor on the circuit input side, and significantly reduces the harmonic distortion of the AC input current.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a power factor correction circuit, control method, motor drive circuit and electrical equipment. Background Technology

[0002] An uncontrolled rectifier circuit rectifies the AC input through a rectifier bridge and outputs the rectified positive and negative voltages to the motor's inverter circuit to drive the motor. In related technologies, an electrolytic capacitor is connected in parallel between the positive and negative voltages as a filter device. The electrolytic capacitor charges only near the peak value of the sinusoidal AC input voltage, resulting in a narrow spike pulse current in the sinusoidal AC input current only near the voltage peak value. As a result, the rectifier bridge bears a large inrush current. In addition, the AC input current and AC input voltage are separated by a large phase angle, resulting in a low power factor on the circuit input side and severe harmonic distortion of the AC input current. Summary of the Invention

[0003] This application provides a power factor correction circuit, control method, motor drive circuit, and electrical equipment, which can improve the power factor on the input side and significantly reduce AC input current harmonic distortion.

[0004] In a first aspect, embodiments of this application provide a power factor correction circuit, comprising:

[0005] A rectifier bridge, wherein the input side of the rectifier bridge is connected to an AC input, and the output side of the rectifier bridge is connected to a DC load via a DC bus;

[0006] A filtering circuit, comprising a filtering capacitor and a switching module, wherein one end of the filtering capacitor is connected to the positive terminal of the DC bus, and the other end of the filtering capacitor is connected to the negative terminal of the DC bus through the switching module;

[0007] The controller is used to acquire the DC bus voltage on the output side of the rectifier bridge, and is also used to control the switching module to be in the on state when the DC bus voltage is lower than a preset voltage threshold, or to control the switching module to be in the off state when the DC bus voltage is higher than the preset voltage threshold.

[0008] In some embodiments, the power factor correction circuit further includes a voltage detection circuit and a comparison circuit. The voltage detection circuit is coupled to the DC bus to output the collected DC bus voltage to the comparison circuit. The comparison circuit is used to output a comparison result signal between the DC bus voltage and the preset voltage threshold to the controller. The controller is used to control the switching module to switch between an on state and an off state according to the comparison result signal.

[0009] In some embodiments, the comparison circuit includes a first input terminal, a second input terminal, and a comparison result output terminal. The first input terminal is connected to the output terminal of the voltage detection circuit, the second input terminal is connected to a reference voltage source, the voltage value of the reference voltage source is equal to the preset voltage threshold, and the comparison result output terminal is connected to the first signal pin of the controller.

[0010] In some embodiments, the switching module includes a switching transistor and a switching drive circuit. The second signal pin of the controller is connected to the input terminal of the switching drive circuit, and the output terminal of the switching drive circuit is connected to the control pin of the switching transistor. The controller is used to obtain a control signal based on the comparison result signal received by the first signal pin, and output the control signal to the switching drive circuit through the second signal pin. The switching drive circuit is used to output a drive signal to drive the switching transistor to turn on or off based on the control signal.

[0011] In some embodiments, when the DC bus voltage is lower than a preset voltage threshold, the comparison result signal is a high-level signal, the controller is used to obtain a high-level control signal based on the high-level comparison result signal, and the switch drive circuit is used to output a high-level drive signal based on the high-level control signal to put the switch in the on state;

[0012] Alternatively, if the DC bus voltage is higher than a preset voltage threshold, the comparison result signal is a low-level signal. The controller is used to obtain a low-level control signal based on the low-level comparison result signal, and the switch drive circuit is used to output a low-level drive signal based on the low-level control signal, so that the switch is in the off state.

[0013] In some embodiments, the switch driving circuit further includes a first resistor, a second resistor, and a fast-switching diode. The switch driving circuit is connected to the control pin of the switching transistor through the first resistor. One end of the second resistor is connected to the control pin of the switching transistor, and the other end is connected to the negative terminal of the DC bus. The fast-switching diode is connected in parallel with the first resistor.

[0014] Secondly, embodiments of this application provide a control method for a power factor correction circuit, applied to the power factor correction circuit described in the first aspect, the control method comprising:

[0015] Obtain the DC bus voltage on the output side of the rectifier bridge;

[0016] When the DC bus voltage is lower than a preset voltage threshold, the switch module is controlled to be in the ON state; or when the DC bus voltage is higher than the preset voltage threshold, the switch module is controlled to be in the OFF state.

[0017] In some embodiments, controlling the switch module to be in a conducting state includes:

[0018] When a high-level comparison result signal is received, a high-level control signal is output to trigger the switch module to be in the conducting state; the high-level comparison result signal indicates that the DC bus voltage is lower than the preset voltage threshold.

[0019] The control of the switch module to be in the off state includes:

[0020] When a low-level comparison result signal is received, a low-level control signal is output to trigger the switch module to be in the off state; the low-level comparison result signal indicates that the DC bus voltage is higher than the preset voltage threshold.

[0021] Thirdly, embodiments of this application provide a motor drive circuit, including:

[0022] The power factor correction circuit as described in the first aspect;

[0023] or,

[0024] At least one controller and a memory for communicatively connecting to the at least one controller; the memory stores instructions executable by the at least one controller to enable the at least one controller to perform the control method as described in the second aspect.

[0025] Fourthly, embodiments of this application provide an electrical device, including a motor and a motor drive circuit as described in the third aspect.

[0026] The power factor correction circuit, control method, motor drive circuit, and electrical equipment of this application embodiment have at least the following beneficial effects: A filter circuit is set on the output side of the rectifier bridge, and the voltage ripple of the DC bus is filtered out by the filter capacitor in the filter circuit. When the DC bus voltage is lower than the preset voltage threshold, the control switch module is in the conducting state. In this state, the filter capacitor is connected to the circuit for charging. When the DC bus voltage is higher than the preset voltage threshold, the control switch module is in the off state. In this state, the voltage output by the rectifier bridge supplies power to the load. The above process increases the charging time of the filter capacitor. Under the sinusoidal AC input voltage, the charging current of the filter capacitor is a periodic symmetrical waveform, which makes the phase of the AC input current synchronize with the phase of the AC input voltage, improves the power factor on the circuit input side, and significantly reduces the harmonic distortion of the AC input current.

[0027] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the description and the accompanying drawings. Attached Figure Description

[0028] Figure 1 A block diagram of a power factor correction circuit provided in one embodiment of this application;

[0029] Figure 2 A circuit diagram of a power factor correction circuit provided in one embodiment of this application;

[0030] Figure 3 This is an overall flowchart of a control method for a power factor correction circuit provided in one embodiment of this application;

[0031] Figure 4 This is a connection diagram of a power factor correction circuit provided in one embodiment of this application. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various implementations. Simultaneously, the steps or actions described in the method description can be rearranged or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0033] In the description of this application, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0034] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0035] Uncontrolled rectifier circuits can rectify sinusoidal AC input voltages. To reduce voltage ripple after rectification, electrolytic capacitors are connected between the DC bus and the capacitors. The charging and discharging characteristics of the electrolytic capacitors filter out the voltage ripple, resulting in a smoother DC bus voltage. In related technologies, the rectifier bridge of a capacitor-filtered single-phase uncontrolled rectifier circuit consists of four unidirectional diodes. When the AC input voltage of the rectifier bridge is less than the DC bus voltage, none of the diodes in the rectifier bridge conduct, and the electrolytic capacitors discharge to the load, supporting the DC bus voltage. When the AC input voltage of the rectifier bridge is greater than the DC bus voltage, the diodes in the rectifier bridge conduct, and the rectified AC input voltage charges the electrolytic capacitors while simultaneously providing the DC bus voltage to the load. Therefore, when the AC input voltage is close to its peak value, the circuit will generate a large spike pulse current (charging the electrolytic capacitor and supplying power to the load). The diodes of the rectifier bridge need to withstand a large inrush current, which is not conducive to the long-term stable operation of the circuit components. Furthermore, because the AC input current and AC input voltage are separated by a large phase angle, the power factor on the circuit input side is low and the harmonic distortion of the AC input current is very serious.

[0036] Based on this, embodiments of this application provide a power factor correction circuit, a control method, a motor drive circuit, and an electrical device. A filter circuit is set on the output side of the rectifier bridge. The voltage ripple of the DC bus is filtered out by the filter capacitor in the filter circuit. When the DC bus voltage is lower than a preset voltage threshold, the control switch module is in the conducting state. In this state, the filter capacitor is connected to the circuit for charging. When the DC bus voltage is higher than the preset voltage threshold, the control switch module is in the off state. In this state, the voltage output by the rectifier bridge supplies power to the load. The above process increases the charging time of the filter capacitor. Under a sinusoidal AC input voltage, the charging current of the filter capacitor is a periodic symmetrical waveform, which makes the phase of the AC input current synchronized with the phase of the AC input voltage, thereby improving the power factor on the circuit input side and significantly reducing the harmonic distortion of the AC input current.

[0037] The power factor correction circuit, control method, motor drive circuit, and electrical equipment are described below with reference to the accompanying drawings.

[0038] This application provides a power factor correction circuit, specifically, referring to... Figure 1 or Figure 2 The power factor correction circuit shown includes:

[0039] The rectifier bridge has an AC input connected to its input side and a DC load connected to its output side via a DC bus.

[0040] The filter circuit includes a filter capacitor and a switching module. One end of the filter capacitor is connected to the positive terminal of the DC bus, and the other end of the filter capacitor is connected to the negative terminal of the DC bus through the switching module.

[0041] The controller is used to acquire the DC bus voltage Vdc on the output side of the rectifier bridge, and also to control the switch module to be in the on state when the DC bus voltage Vdc is lower than the preset voltage threshold Vth, or to control the switch module to be in the off state when the DC bus voltage Vdc is higher than the preset voltage threshold Vth.

[0042] The AC input connected to the input side of the rectifier bridge can be an external AC power supply or an AC output converted by an internal transformer on the secondary side. Taking a sinusoidal voltage as an example, the voltage waveform after rectification is a periodic positive half-cycle sine wave, ensuring that the DC bus voltage Vdc on the output side of the rectifier bridge maintains a constant positive and negative direction. A filter capacitor and a switching module are connected between the positive and negative terminals of the DC bus, connected in series. The positive terminal of the DC bus is connected to the negative terminal through the filter capacitor and the switching module. The DC bus is also connected to the downstream load through its positive and negative terminals. When the switching module is in the ON state, the filter capacitor filters out voltage ripple. When the switching module is in the OFF state, one end of the filter capacitor is connected to the positive terminal of the DC bus, and the other end is left floating. The controller controls whether the switching module is in the ON or OFF state, thereby controlling the charging and discharging time of the filter capacitor, adjusting the phase and waveform of the AC input current, thus improving the power factor on the input side and reducing AC input current harmonic distortion.

[0043] Specifically, the controller monitors the DC bus voltage Vdc in real time and compares it with a preset voltage threshold Vth. When the DC bus voltage Vdc is lower than the preset voltage threshold Vth, it indicates that the DC bus voltage Vdc is not high enough, and the controller keeps the switching module in the on state. At this time, the rectifier bridge charges the filter capacitor. When the DC bus voltage Vdc is higher than the preset voltage threshold Vth, it indicates that the DC bus voltage Vdc is high enough, and the controller keeps the switching module in the off state, and the rectifier bridge output voltage directly supplies power to the load. Therefore, by controlling the on and off state of the switching module, the controller enables the filter capacitor to be connected to the circuit for charging or disconnected from the circuit, synchronizing the phase of the AC input current and AC input voltage, improving the power factor on the input side, reducing AC input current harmonic distortion, and simultaneously reducing the peak value of the inrush current when the filter capacitor is charging (Vdc is lower than the preset voltage threshold Vth), thus avoiding the impact of peak current pulses on the rectifier bridge and other circuit components, and improving circuit stability.

[0044] Understandably, the preset voltage threshold Vth can be adjusted according to the circuit's output power and load characteristics. Generally speaking, the lower the preset voltage threshold Vth, the higher the circuit's power factor and the lower the harmonic distortion of the AC input current. However, the charging time of the filter capacitor becomes shorter, resulting in poorer support for the DC bus voltage Vdc. Conversely, the lower the preset voltage threshold Vth, the lower the circuit's power factor and the higher the harmonic distortion of the AC input current. However, the charging time of the filter capacitor becomes longer, resulting in stronger support for the DC bus voltage Vdc.

[0045] The selection of circuit components for the switching module is determined based on the actual situation. Typically, switching devices that meet certain switching speed requirements need to be selected, such as semiconductor switching transistors capable of rapid switching states, to meet the frequency of the AC input. It is understandable that when using switching transistors such as MOSFETs or bipolar transistors as the main body of the switching module, the controller can rely on only one output signal to control the switching state of the switching transistor. For example, the controller outputs a high-level signal to keep the switching transistor in the on state, and no high-level signal to keep the switching transistor in the off state.

[0046] In some embodiments, the power factor correction circuit further includes a voltage detection circuit and a comparison circuit. The voltage detection circuit is coupled to the DC bus to output the acquired DC bus voltage Vdc to the comparison circuit. The comparison circuit is used to output a comparison result signal between the DC bus voltage Vdc and a preset voltage threshold Vth to the controller. The controller is used to control the switching module to switch between the on state and the off state according to the comparison result signal.

[0047] The voltage detection circuit is used to detect the output voltage after the rectifier bridge. Therefore, the acquisition terminal of the voltage detection circuit is coupled to the output side of the rectifier bridge to output the acquisition result. This acquisition result is input to the comparator circuit, which compares the acquisition result with a preset voltage threshold Vth and outputs a comparison result signal. A relatively simple implementation of the voltage detection circuit is to set a sampling resistor between the positive and negative terminals of the DC bus, and determine the DC bus voltage Vdc by measuring the voltage across the sampling resistor. The voltage detection circuit can also use other more complex implementations, which will not be listed here. The comparator circuit can use a comparator to perform voltage comparison and then output the comparison result signal as a high or low level signal. The comparator circuit can also use an integrated chip, which compares the acquisition result with an internal preset voltage threshold Vth and then outputs a voltage value or level comparison result signal. The controller controls the working state of the switching module according to the magnitude of the comparison result signal. For example, it controls the switching module to turn on after receiving a high-level comparison result signal and controls the switching module to turn off after receiving a low-level comparison result signal.

[0048] In some embodiments, the comparison circuit includes a first input terminal, a second input terminal, and a comparison result output terminal. The first input terminal is connected to the output terminal of the voltage detection circuit, the second input terminal is connected to a reference voltage source, the voltage value of the reference voltage source is equal to a preset voltage threshold Vth, and the comparison result output terminal is connected to the first signal pin of the controller.

[0049] In this embodiment, a comparator circuit is constructed around a comparator. Therefore, the first and second input terminals are coupled to the two input terminals of the comparator, respectively. Based on the required level of the comparison result signal, it is determined whether the first input terminal corresponds to the non-inverting or inverting input terminal of the comparator. For example, if the DC bus voltage Vdc is set to be less than a preset voltage threshold Vth, the comparison result signal needs to be a high-level signal. In this case, the reference voltage source is coupled to the non-inverting input terminal of the comparator, and the output terminal of the voltage detection circuit is coupled to the inverting input terminal of the comparator. Conversely, if the DC bus voltage Vdc is set to be less than the preset voltage threshold Vth, the comparison result signal needs to be a low-level signal. In this case, the reference voltage source is coupled to the inverting input terminal of the comparator, and the output terminal of the voltage detection circuit is coupled to the non-inverting input terminal of the comparator.

[0050] Additionally, the controller includes a first signal pin for receiving the comparison result signal output from the comparison result output terminal. Based on the received level signal, the controller outputs a control signal corresponding to the level value of the level signal, thereby controlling the switching module to turn on and off. For example, when a high-level signal is received, a control signal is issued to turn the switching module on; when no high-level signal is received, no control signal is issued, and the switching module remains in the off state.

[0051] In some embodiments, the switching module includes a switching transistor and a switching drive circuit. The second signal pin of the controller is connected to the input terminal of the switching drive circuit, and the output terminal of the switching drive circuit is connected to the control pin of the switching transistor. The controller is used to obtain a control signal based on the comparison result signal received by the first signal pin, and output the control signal to the switching drive circuit through the second signal pin. The switching drive circuit is used to output a drive signal to drive the switching transistor to turn on or off based on the control signal.

[0052] The main component of the switching module is a switching transistor. The control terminal of the switching transistor controls the switching module to switch between on and off states based on the received voltage level signal. The controller outputs a control signal corresponding to the comparison result signal on its second signal pin, based on the voltage level of the comparison result signal. Considering the voltage withstand characteristics of the switching transistor, the voltage level of the control signal output by the controller may not be high enough to turn on the transistor. Therefore, the controller can indirectly control the switching transistor's on / off state through a switch driver circuit. For example, if the controller outputs a high-level control signal of 3.3V, the switch driver circuit can convert it into a 15V drive signal to turn on the transistor. When the controller does not output a control signal, the switch driver circuit also does not output a drive signal, thus achieving on / off control of the switching transistor.

[0053] Taking an NPN channel MOSFET as an example, when the MOSFET receives a high-level drive signal, the MOSFET turns on. This corresponds to the moment when the DC bus voltage Vdc is less than the preset voltage threshold Vth. When the MOSFET receives a low-level drive signal, the MOSFET turns off. This corresponds to the moment when the DC bus voltage Vdc is greater than the preset voltage threshold Vth.

[0054] In other words, in some embodiments, when the DC bus voltage Vdc is lower than a preset voltage threshold Vth, the comparison result signal is a high-level signal. The controller obtains a high-level control signal based on the high-level comparison result signal, and the switch drive circuit outputs a high-level drive signal based on the high-level control signal to put the switch in the on state. Alternatively, when the DC bus voltage Vdc is higher than the preset voltage threshold Vth, the comparison result signal is a low-level signal. The controller obtains a low-level control signal based on the low-level comparison result signal, and the switch drive circuit outputs a low-level drive signal based on the low-level control signal to put the switch in the off state.

[0055] In some embodiments, the switch driving circuit further includes a first resistor R1, a second resistor R2, and a fast-switching diode D5. The switch driving circuit is connected to the control pin of the switching transistor through the first resistor R1. One end of the second resistor R2 is connected to the control pin of the switching transistor, and the other end is connected to the negative terminal of the DC bus. The fast-switching diode D5 is connected in parallel with the first resistor R1. The fast-switching diode D5 is used to improve the switching speed and response time, enabling the switching transistor to switch quickly between the on and off states. The resistance value of the first resistor R1 is much lower than the resistance value of the second resistor R2.

[0056] In summary, by setting a filter circuit on the output side of the rectifier bridge, the voltage ripple of the DC bus is filtered out by the filter capacitor in the filter circuit. When the DC bus voltage Vdc is lower than the preset voltage threshold Vth, the control switch module is in the on state, and the filter capacitor is connected to the circuit for charging in this state. When the DC bus voltage Vdc is higher than the preset voltage threshold Vth, the control switch module is in the off state, and the voltage output by the rectifier bridge supplies power to the load in this state. The above process increases the charging time of the filter capacitor. Under the sinusoidal AC input voltage, the charging current of the filter capacitor is a periodic symmetrical waveform, which makes the phase of the AC input current synchronized with the phase of the AC input voltage, improves the power factor on the input side of the circuit, and significantly reduces the harmonic distortion of the AC input current.

[0057] Reference Figure 3 As shown, this application embodiment also provides a control method for a power factor correction circuit, applied to the power factor correction circuit of any of the above embodiments. The control method includes, but is not limited to, the following steps:

[0058] Step S110: Obtain the DC bus voltage Vdc on the output side of the rectifier bridge;

[0059] In step S120, when the DC bus voltage Vdc is lower than the preset voltage threshold Vth, the control switch module is in the on state, or when the DC bus voltage Vdc is higher than the preset voltage threshold Vth, the control switch module is in the off state.

[0060] The controller monitors the DC bus voltage Vdc in real time and compares it with a preset voltage threshold Vth. When Vdc is lower than the threshold, indicating insufficient voltage, the controller turns the switching module on, allowing the rectifier bridge to charge the filter capacitor. Conversely, when Vdc is higher, indicating sufficient voltage, the controller turns the switching module off, allowing the rectifier bridge output voltage to directly supply power to the load. Therefore, by controlling the switching module's on / off state, the controller synchronizes the phase of the AC input current and voltage, improving the power factor on the input side and reducing AC input current harmonic distortion. Furthermore, the lower DC bus voltage Vdc during capacitor charging reduces the peak inrush current, preventing spike current pulses from impacting the rectifier bridge and other circuit components, thus improving circuit stability.

[0061] In some embodiments, the control switch module being in the ON state in step S120 includes:

[0062] When a high-level comparison result signal is received, a high-level control signal is output to trigger the switch module to be in the on state; the high-level comparison result signal indicates that the DC bus voltage Vdc is lower than the preset voltage threshold Vth.

[0063] In step S120 above, the control switch module is in the off state, including:

[0064] When a low-level comparison result signal is received, a low-level control signal is output to trigger the switch module to be in the off state; the low-level comparison result signal indicates that the DC bus voltage Vdc is higher than the preset voltage threshold Vth.

[0065] When the DC bus voltage Vdc is lower than the preset voltage threshold Vth, the comparison result signal is a high-level signal. The controller uses this high-level comparison result signal to obtain a high-level control signal, and the switch drive circuit uses this high-level control signal to output a high-level drive signal to turn the switch on. When the DC bus voltage Vdc is higher than the preset voltage threshold Vth, the comparison result signal is a low-level signal. The controller uses this low-level comparison result signal to obtain a low-level control signal, and the switch drive circuit uses this low-level control signal to output a low-level drive signal to turn the switch off.

[0066] The power factor correction circuit and its control method of this application will be described in detail below through a specific example.

[0067] Reference Figure 2 As shown, the power factor correction circuit includes a rectifier bridge, a filter capacitor C, an NPN channel MOSFET Q1, a voltage detection circuit, a comparator, a reference voltage source, a switch drive circuit, and a controller MCU.

[0068] The input side of the rectifier bridge is connected to the AC input, and the output side of the rectifier bridge is connected to the DC bus;

[0069] The positive terminal of the filter capacitor C is connected to the positive terminal of the DC bus, the negative terminal of the filter capacitor C is connected to the drain of the MOSFET Q1, and the source of the MOSFET Q1 is connected to the negative terminal of the DC bus.

[0070] The voltage detection circuit is located on the output side of the rectifier bridge and monitors the DC bus voltage Vdc in real time. The output of the voltage detection circuit is connected to the inverting input of the comparator, and the reference voltage source is connected to the non-inverting input of the comparator. The reference voltage source is used to output the preset voltage threshold Vth. The output of the comparator is connected to the first signal pin of the controller MCU.

[0071] The second signal pin of the controller MCU is connected to the input terminal of the switch drive circuit, and the output terminal of the switch drive circuit is connected to the gate of MOSFET Q1. When the voltage between the gate and source of MOSFET Q1 is higher than the turn-on threshold voltage, MOSFET Q1 enters the turn-on state; when the voltage between the gate and source of MOSFET Q1 is lower than the turn-on threshold voltage, MOSFET Q1 enters the turn-off state. By controlling the turn-on and turn-off of MOSFET Q1, the filter capacitor C is either connected to the circuit for charging or disconnected from the circuit. This synchronizes the phase of the AC input current and AC input voltage, improving the power factor on the input side and reducing AC input current harmonic distortion. Simultaneously, the DC bus voltage Vdc of the filter capacitor C during charging is less than the preset voltage threshold Vth, reducing the peak value of the inrush current and preventing the impact of current spikes on rectifier bridges and other circuit components, thus improving circuit stability.

[0072] The DC bus voltage Vdc is monitored in real time. When the DC bus voltage Vdc is lower than the preset voltage threshold Vth, the comparator compares the DC bus voltage Vdc with the preset voltage threshold Vth and obtains a high-level comparison result signal, which is transmitted to the controller MCU. The controller MCU outputs a 3.3V high-level control signal. After receiving the 3.3V high-level control signal, the switch drive circuit generates a 15V drive signal and applies the drive signal to the gate of MOSFET Q1. MOSFET Q1 is turned on, and the filter capacitor C is connected to the circuit for charging. When the DC bus voltage Vdc is higher than the preset voltage threshold Vth, the comparator compares the DC bus voltage Vdc with the preset voltage threshold Vth and obtains a low-level comparison result signal, which is transmitted to the controller MCU. The controller MCU does not output a control signal, and the switch drive circuit does not apply a high-level drive signal to MOSFET Q1. MOSFET Q1 is in the cutoff state, which is equivalent to being disconnected from the circuit.

[0073] Through the above steps, this simple active PFC circuit with filter capacitor C connected in series with MOSFET Q1 can actively adjust the input AC current waveform to synchronize the current and voltage waveforms, effectively increasing the charging time of filter capacitor C, reducing the spike pulses in the input AC current caused by the charging of filter capacitor C, and reducing the charging current of filter capacitor C. In practical applications, the preset voltage threshold Vth can be adjusted according to the output power and load characteristics to achieve the best effect. Compared with existing technologies, this example can achieve active power factor correction at low cost, reduce AC input current harmonic distortion, and ensure that the DC bus voltage Vdc during filter capacitor C charging is less than the preset voltage threshold Vth, reducing the peak value of the inrush current, avoiding the impact of spike current pulses on rectifier bridge and other circuit components, and improving circuit stability. It is suitable for household appliance circuits and low-power power supplies with a power range of up to 2000W, balancing cost and performance.

[0074] This application also provides a motor drive circuit, including the power factor correction circuit of any of the above embodiments, or including at least one controller and a memory for communicative connection with the at least one controller; the memory stores instructions that can be executed by the at least one controller, and the instructions are executed by the at least one controller to enable the at least one controller to perform the control method as described in any of the above embodiments.

[0075] like Figure 4 As shown, Figure 4 This is a schematic diagram of a motor drive circuit 1000 provided in one embodiment of this application.

[0076] The motor drive circuit 1000 in this embodiment includes one or more processors 1001 and a memory 1002. Figure 4 The example uses a processor 1001 and a memory 1002.

[0077] Processor 1001 and memory 1002 can be connected via a bus or other means. Figure 4 Taking the example of a connection between China and Israel via a bus.

[0078] Memory 1002, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory 1002 may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory 1002 may optionally include memory 1002 remotely located relative to processor 1001, and these remote memories can be connected to the motor drive circuit 1000 via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0079] Those skilled in the art will understand that Figure 4 The device structure shown does not constitute a limitation on the motor drive circuit 1000, and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0080] This application also provides an electrical device, including a motor and the motor drive circuit of the foregoing embodiments.

[0081] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network nodes. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0082] It will be understood by those skilled in the art that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which can include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0083] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0084] In the several embodiments provided in this application, it should be understood that the disclosed systems, instruments, and methods can be implemented in other ways. For example, the instrument embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the shown or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between instruments or units may be electrical, mechanical, or other forms. Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, i.e., they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0085] It should also be understood that the various implementation methods provided in this application can be combined arbitrarily to achieve different technical effects.

[0086] The above is a detailed description of the preferred embodiments of this application. However, this application is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A power factor correction circuit, characterized in that, include: A rectifier bridge, wherein the input side of the rectifier bridge is connected to an AC input, and the output side of the rectifier bridge is connected to a DC load via a DC bus; A filtering circuit, comprising a filtering capacitor and a switching module, wherein one end of the filtering capacitor is connected to the positive terminal of the DC bus, and the other end of the filtering capacitor is connected to the negative terminal of the DC bus through the switching module; The controller is used to acquire the DC bus voltage on the output side of the rectifier bridge, and is also used to control the switching module to be in the conducting state when the DC bus voltage is lower than a preset voltage threshold, or to control the switching module to be in the disconnected state when the DC bus voltage is higher than the preset voltage threshold.

2. The power factor correction circuit according to claim 1, characterized in that, The power factor correction circuit further includes a voltage detection circuit and a comparison circuit. The voltage detection circuit is coupled to the DC bus to output the collected DC bus voltage to the comparison circuit. The comparison circuit is used to output a comparison result signal between the DC bus voltage and the preset voltage threshold to the controller. The controller is used to control the switching module to switch between the on state and the off state according to the comparison result signal.

3. The power factor correction circuit according to claim 2, characterized in that, The comparison circuit includes a first input terminal, a second input terminal, and a comparison result output terminal. The first input terminal is connected to the output terminal of the voltage detection circuit, the second input terminal is connected to a reference voltage source, the voltage value of the reference voltage source is equal to the preset voltage threshold, and the comparison result output terminal is connected to the first signal pin of the controller.

4. The power factor correction circuit according to claim 3, characterized in that, The switching module includes a switching transistor and a switching drive circuit. The second signal pin of the controller is connected to the input terminal of the switching drive circuit, and the output terminal of the switching drive circuit is connected to the control pin of the switching transistor. The controller is used to obtain a control signal based on the comparison result signal received by the first signal pin, and output the control signal to the switching drive circuit through the second signal pin. The switching drive circuit is used to output a drive signal to drive the switching transistor to turn on or off based on the control signal.

5. The power factor correction circuit according to claim 4, characterized in that, When the DC bus voltage is lower than a preset voltage threshold, the comparison result signal is a high-level signal. The controller is used to obtain a high-level control signal based on the high-level comparison result signal. The switch drive circuit is used to output a high-level drive signal based on the high-level control signal to put the switch in the on state. Alternatively, if the DC bus voltage is higher than a preset voltage threshold, the comparison result signal is a low-level signal. The controller is used to obtain a low-level control signal based on the low-level comparison result signal, and the switch drive circuit is used to output a low-level drive signal based on the low-level control signal, so that the switch is in the off state.

6. The power factor correction circuit according to claim 4, characterized in that, The switch driving circuit further includes a first resistor, a second resistor, and a fast-switching diode. The switch driving circuit is connected to the control pin of the switching transistor through the first resistor. One end of the second resistor is connected to the control pin of the switching transistor, and the other end is connected to the negative terminal of the DC bus. The fast-switching diode is connected in parallel with the first resistor.

7. A control method for a power factor correction circuit, characterized in that, Applied to the power factor correction circuit as described in any one of claims 1 to 6; the control method includes: Obtain the DC bus voltage on the output side of the rectifier bridge; When the DC bus voltage is lower than a preset voltage threshold, the switch module is controlled to be in the ON state; or when the DC bus voltage is higher than the preset voltage threshold, the switch module is controlled to be in the OFF state.

8. The control method according to claim 7, characterized in that, The control of the switch module to be in the ON state includes: When a high-level comparison result signal is received, a high-level control signal is output to trigger the switch module to be in the conducting state; the high-level comparison result signal indicates that the DC bus voltage is lower than the preset voltage threshold. The control of the switch module to be in the off state includes: When a low-level comparison result signal is received, a low-level control signal is output to trigger the switch module to be in the off state; the low-level comparison result signal indicates that the DC bus voltage is higher than the preset voltage threshold.

9. A motor drive circuit, characterized in that, include: The power factor correction circuit as described in any one of claims 1 to 6; or, At least one controller and a memory for communicatively connecting with said at least one controller; The memory stores instructions that can be executed by the at least one controller to enable the at least one controller to perform the control method as described in claim 7 or 8.

10. Electrical equipment, including a motor and the motor drive circuit as described in claim 9.

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