Control method and device of pfc circuit, air conditioner and medium

Abstract

The application discloses a control method and device of a PFC circuit, an air conditioner and a medium. The load power, the current input voltage and the current output voltage of the PFC circuit are acquired first, and then the target input current is obtained through the load power and the current input voltage. The target input current refers to the input current required by the PFC circuit under the current environmental state, and can represent the input current about to change of the PFC circuit. Therefore, the switching frequency of the switching device is dynamically adjusted by using the target input current and the current input voltage, so that the state about to change of the PFC circuit can be responded more quickly. When the working current of the PFC circuit reaches the target input current, the switching device can work synchronously at the adjusted switching frequency, the switching loss is effectively reduced, the heat amount of the switching device can be controlled, and the electromagnetic interference generated by the circuit is also reduced.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit control technology, and in particular to a control method, device, air conditioner, and medium for a PFC circuit. Background Technology

[0002] Currently, power factor correction (PFC) circuits are widely used in variable frequency home appliances such as variable frequency air conditioners, refrigerators, and washing machines. In related technologies, PFC circuits use a control method that drives the switching devices with a fixed switching frequency to correct the power factor of the variable frequency inverter. Although this method can achieve power factor correction, it is prone to increasing the loss of switching devices and raising the temperature. Summary of the Invention

[0003] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a control method, device, air conditioner and medium for PFC circuit, which can effectively reduce the switching loss of switching devices in PFC circuit and improve the temperature rise problem of switching devices.

[0004] In a first aspect, embodiments of the present invention provide a control method for a PFC circuit, the PFC circuit comprising a power input module, a switching device, and an output capacitor connected in sequence, the power input module having an input voltage sampling point for acquiring the current input voltage of the PFC circuit, and the output capacitor having an output voltage sampling point at both ends for acquiring the current output voltage of the PFC circuit; the control method includes: Obtain the load power, the current input voltage, and the current output voltage of the PFC circuit; The target input current is obtained based on the load power and the current input voltage; The switching frequency of the switching device is adjusted according to the target input current and the current input voltage so that when the operating current of the PFC circuit reaches the target input current, the switching device operates at the adjusted switching frequency.

[0005] The control method for the PFC circuit provided by the embodiments of the present invention has at least the following beneficial effects: the target input current is obtained by the load power of the PFC circuit and the current input voltage. The target input current refers to the input current required by the PFC circuit under the current environmental conditions, which can represent the input current that the PFC circuit is about to change. Therefore, by dynamically adjusting the switching frequency of the switching device using the target input current and the current input voltage, the PFC circuit can respond to the state that is about to change more quickly. When the operating current of the PFC circuit reaches the target input current, the switching device can operate synchronously at the adjusted switching frequency, effectively reducing switching losses and controlling the heat generation of the switching device. It also helps to reduce the electromagnetic interference generated by the circuit.

[0006] In the control method provided in this embodiment of the invention, adjusting the switching frequency of the switching device based on the target input current and the current input current includes: Based on the relationship between the target input current and the first threshold current, and the relationship between the current input voltage and the first threshold voltage, the switching frequency of the switching device is adjusted. Wherein, the first threshold voltage represents the voltage threshold at which the PFC circuit enters the intermittent on-state.

[0007] In the control method provided in this embodiment of the invention, adjusting the switching frequency of the switching device based on the relationship between the target input current and the first threshold current, and the relationship between the current input voltage and the first threshold voltage, includes: In response to the target input current being less than a first threshold current and the current input current being less than a first threshold voltage, the switching frequency of the switching device is reduced.

[0008] In the control method provided in this embodiment of the invention, the PFC circuit further includes a PFC inductor, and the power input module is simultaneously connected to the first terminal of the switching device and the output capacitor through the PFC inductor; reducing the switching frequency of the switching device includes: The target inductance value of the PFC inductor is determined based on the target input current. The switching frequency of the switching device is reduced based on the target inductance value, the current input voltage, and the current output voltage.

[0009] In the control method provided in this embodiment of the invention, reducing the switching frequency of the switching device based on the target inductance value, the current input voltage, and the current output voltage includes: The minimum switching frequency is determined based on the target inductance value, the current input voltage, and the current output voltage. The target frequency range is constructed by using the minimum switching frequency as the lower limit of the range and the initial switching frequency as the upper limit of the range. The switching frequency of the switching device is adjusted to any frequency within the target frequency range.

[0010] In the control method provided in this embodiment of the invention, adjusting the switching frequency of the switching device based on the relationship between the target input current and the first threshold current, and the relationship between the current input voltage and the first threshold voltage, includes: In response to the target input current being greater than or equal to a first threshold current, or the current input voltage being greater than or equal to a first threshold voltage, the switching frequency of the switching device is set to an initial switching frequency.

[0011] In the control method provided in this embodiment of the invention, adjusting the switching frequency of the switching device based on the relationship between the target input current and the first threshold current, and the relationship between the current input voltage and the first threshold voltage, includes: Obtain the rated input operating voltage and the maximum input operating voltage of the PFC circuit; The current coefficient is obtained based on the input rated operating voltage and the input maximum operating voltage; The reference current is obtained based on the current coefficient and the first threshold current; The switching frequency of the switching device is adjusted based on the relationship between the target input current and the reference current, and the relationship between the current input voltage and the first threshold voltage.

[0012] In the control method provided in this embodiment of the invention, the PFC circuit further includes a load current detection module for connecting and supplying power to the load, and the load power is obtained through the following steps: Obtain the load current of the load current detection module; The load power is obtained based on the current output voltage of the PFC circuit and the load current.

[0013] In the control method provided in this embodiment of the invention, obtaining the target input current based on the load power and the current input voltage includes: Obtain the circuit conversion efficiency of the PFC circuit; The target input current is obtained based on the load power, the current input voltage, and the circuit conversion rate.

[0014] In a second aspect, embodiments of the present invention provide an operation control device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. The processor executes the program to implement the control method for the PFC circuit as described in the first aspect embodiment above.

[0015] The operation control device provided according to the embodiments of the present invention has at least the following beneficial effects: the target input current is obtained by the load power of the PFC circuit and the current input voltage, and the switching frequency of the switching device is dynamically adjusted according to the target input current and the current input voltage. Therefore, when the operating current of the PFC circuit reaches the target input current, the switching device can operate at a suitable switching frequency, thereby effectively reducing switching losses and controlling the heat generation of the switching device, while also helping to reduce the electromagnetic interference generated by the circuit.

[0016] Thirdly, embodiments of the present invention provide an air conditioner including the operation control device described in the second aspect of the embodiments above.

[0017] The air conditioner provided according to the embodiments of the present invention has at least the following beneficial effects: the target input current is obtained by the load power of the PFC circuit and the current input voltage. The target input current refers to the input current required by the PFC circuit under the current environmental conditions and can represent the input current that the PFC circuit is about to change. Therefore, by dynamically adjusting the switching frequency of the switching device using the target input current and the current input voltage, the PFC circuit can respond to the state that is about to change more quickly. Furthermore, when the operating current of the PFC circuit reaches the target input current, the switching device can operate synchronously at the adjusted switching frequency, effectively reducing switching losses and controlling the heat generation of the switching device. It also helps to reduce the electromagnetic interference generated by the circuit.

[0018] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing computer-executable instructions for causing a computer to perform a control method for a PFC circuit as described in the first aspect embodiment.

[0019] The computer-readable storage medium provided according to embodiments of the present invention has at least the following beneficial effects: the target input current is obtained by the load power of the PFC circuit and the current input voltage. The target input current refers to the input current required by the PFC circuit under the current environmental conditions and can represent the input current that the PFC circuit is about to change. Therefore, by dynamically adjusting the switching frequency of the switching device using the target input current and the current input voltage, the PFC circuit can respond to the state that is about to change more quickly. Furthermore, when the operating current of the PFC circuit reaches the target input current, the switching device can operate synchronously at the adjusted switching frequency, effectively reducing switching losses and controlling the heat generation of the switching device. It also helps to reduce the electromagnetic interference generated by the circuit.

[0020] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0021] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is a schematic diagram of the PFC circuit provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the specific structure of the PFC circuit provided in the embodiment of the present invention; Figure 3 This is a flowchart of the control method for the PFC circuit provided in the embodiments of the present invention; Figure 4 This is a flowchart illustrating the specific process of adjusting the switching frequency of the switching transistor according to an embodiment of the present invention. Figure 5 This is a flowchart illustrating the adjustment of the switching frequency of a switching transistor according to another embodiment of the present invention. Figure 6 This is a schematic diagram illustrating the effect of reducing the switching frequency when the current input voltage is greater than or equal to the first threshold voltage, provided by an embodiment of the present invention. Figure 7 This is a schematic diagram of the specific process for reducing the switching frequency of the switching transistor according to an embodiment of the present invention; Figure 8 This is a graph showing the relationship between the inductance value of the PFC inductor and the input current provided in this embodiment of the invention. Figure 9This is a schematic diagram of a specific process for reducing the switching frequency of a switching transistor according to another embodiment of the present invention; Figure 10 This is a flowchart illustrating the adjustment of the switching frequency of a switching transistor according to another embodiment of the present invention. Figure 11 This is a flowchart illustrating the calculation of load power provided in an embodiment of the present invention; Figure 12 This is a flowchart illustrating the calculation of the target input current provided in an embodiment of the present invention; Figure 13 This is a schematic diagram of the overall flow of the control method for the PFC circuit provided in the embodiment of the present invention; Figure 14 This is a schematic diagram of the operation control device provided in an embodiment of the present invention. Detailed Implementation

[0023] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0024] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc. are understood to exclude the number itself, while "above," "below," "within," etc. are understood to include the number itself. "Any one" refers to one or more, and "at least one of the following" and similar expressions refer to any combination of these items, including any combination of single or multiple items. If "first" or "second" is used in the description, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of the indicated technical features.

[0025] It should be noted that the terms "setting," "installing," and "connecting" in the embodiments of this invention should be interpreted broadly. Those skilled in the art can reasonably determine the specific meaning of the above terms in the embodiments of this invention in conjunction with the specific content of the technical solution. For example, the term "connection" can be a mechanical connection, an electrical connection, or a connection that allows for mutual communication; it can be a direct connection or an indirect connection through an intermediate medium.

[0026] It should be noted that the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Currently, power factor correction (PFC) circuits are widely used in variable frequency home appliances such as variable frequency air conditioners, refrigerators, and washing machines. In related technologies, PFC circuits use a fixed switching frequency to drive the switching devices to correct the power factor of the variable frequency inverter. Although this method can achieve power factor correction, it can easily lead to increased losses and higher temperatures in the switching devices. Especially for PFC circuits with low operating current, the fixed switching frequency is relatively high, which leads to a corresponding increase in the switching losses of the switching transistors.

[0028] Based on this, embodiments of the present invention propose a control method, device, air conditioner, and medium for a PFC circuit. The target input current is obtained by using the load power and current input voltage of the PFC circuit. The target input current refers to the input current required by the PFC circuit under the current environmental conditions, which can represent the input current that the PFC circuit is about to change. Therefore, by dynamically adjusting the switching frequency of the switching device using the target input current and the current input voltage, the PFC circuit can respond to the state that is about to change more quickly. When the operating current of the PFC circuit reaches the target input current, the switching device can operate synchronously at the adjusted switching frequency, effectively reducing switching losses and controlling the heat generation of the switching device. It also helps to reduce the electromagnetic interference generated by the circuit.

[0029] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0030] Reference Figure 1 , Figure 1 This is a schematic diagram of the PFC circuit provided in an embodiment of the present invention. It can be understood that the PFC circuit includes a power input module, a switching device, and an output capacitor. One end of the power input module can be simultaneously connected to the first terminal of the switching device and the third terminal S3 of the output capacitor, and the other end of the power input module can be simultaneously connected to the second terminal of the switching device and the fourth terminal S4 of the input capacitor. The third terminal of the switching device, i.e., the control terminal, is connected to a control module used to adjust the switching frequency of the switching device. The power input module can be used to connect to an external power source. The power input module can be provided with an input voltage sampling point, for example, the input voltage sampling point can be set at the output terminal of the power input module, such as... Figure 1The first terminal S1 and the second terminal S2 shown are input voltage sampling points. These input voltage sampling points are used to connect to the input voltage sampling module. The input voltage sampling module measures the voltage supplied by the external power supply to the PFC circuit, i.e., the input voltage of the PFC circuit, through the input voltage sampling points. At the same time, the output capacitor can supply power to the downstream load. Output voltage sampling points are also set at the two ends of the output capacitor, i.e., the third terminal S3 and the fourth terminal S4. These output voltage sampling points are used to connect to the output voltage sampling module. The output voltage sampling module measures the voltage supplied by the PFC circuit to the downstream load, i.e., the output voltage of the PFC circuit, through the output voltage sampling points. Both the input voltage sampling module and the output voltage sampling module are connected to the control module, so that the control module can obtain the input voltage and output voltage of the PFC circuit.

[0031] The PFC circuit may also include a load power measurement module, which is connected to the control module. The load power measurement module measures the load power of the loads connected to the PFC circuit, allowing the control module to obtain the load power of the PFC circuit. For example, the load power measurement module can be a power meter. Alternatively, the load power measurement module can be connected to the output capacitor to measure the output power of the PFC circuit and use this output power as the load power. Or, the load measurement module can be connected to each load in the PFC circuit separately, measuring the load sub-power of each load individually, and then summing all the load sub-powers as the load power of the PFC circuit. For instance, when the PFC circuit is used in the outdoor unit of an air conditioner, it can supply power to the fan and compressor. Therefore, the load measurement module can be connected to both the fan and compressor connected to the PFC circuit separately, measuring the load sub-power of the fan and compressor respectively, and then combining the two load sub-powers to obtain the load power of the PFC circuit. It is worth noting that the control module used to control the switching frequency of the switching transistor in the PFC circuit can also obtain power from the PFC circuit. Therefore, the control module can also be used as a load of the PFC circuit. The load sub-power of the control module is measured by the load measurement module, and the load sub-power of the control module is used as part of the load power of the PFC circuit.

[0032] It should be noted that the switching device can be a metal-oxide-semiconductor field-effect transistor (MOSFT), in which case the first electrode is the drain of the MOSFT, the second electrode is the source of the MOSFT, and the third electrode is the gate of the MOSFT; the switching device can also be an insulated-gate bipolar transistor (IGBT), in which case the first electrode is the drain of the IGBT, the second electrode is the source of the IGBT, and the third electrode is the gate of the IGBT.

[0033] Reference Figure 2 , Figure 2 This is a schematic diagram of the specific structure of the PFC circuit provided in this embodiment of the invention. It is understood that the PFC circuit can be a boost circuit, such as a boost circuit. Therefore, the PFC circuit can also include a PFC inductor, a diode, and a sampling resistor. The power input module can also include a rectifier bridge. In this case, the input voltage sampling point can be located between the rectifier bridge and the input capacitor, or between the input capacitor and the PFC inductor, or at the input terminal of the rectifier bridge. For example, the input terminal of the rectifier bridge is used to connect to an external power source to provide power to the PFC circuit. The output terminal of the rectifier bridge is connected to both ends of the input capacitor. The input capacitor is simultaneously connected to the first terminal of the switching device and the anode of the diode through the PFC inductor. The cathode of the diode is connected to the third terminal S3 of the output capacitor. The input voltage sampling points can be located at both ends of the input capacitor, such as... Figure 2 The first terminal S1 and the second terminal S2 are shown in the diagram. The PFC circuit can supply power to a load, such as... Figure 2 As shown, taking a fan and a compressor as loads as an example, the output capacitor can be connected to the fan drive module corresponding to the fan and the compressor drive module corresponding to the compressor, respectively, for power supply. It should be noted that the load measurement module includes a load current detection module and sampling resistors. There can be multiple sampling resistors, which can be located between the output capacitor and the fan drive module, or between the output capacitor and the compressor drive module. Therefore, the sampling resistors can be connected to the load current detection module of the PFC circuit. Each load current detection module can measure the load current of its corresponding load, and then the load power can be calculated from the load current and the output voltage. It is worth noting that a sampling resistor is also provided between the input capacitor and the second terminal of the switching transistor. The load current detection module can use this sampling resistor to measure the load current of the control module used to control the operation of the PFC circuit. In addition, the load current detection module can also measure the total output current of the PFC circuit, and then the load power of the PFC circuit can be calculated from the total output current.

[0034] It will be understood by those skilled in the art that Figures 1 to 2The structure of the PFC circuit shown does not constitute a limitation on the embodiments of the present invention. It may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0035] Reference Figure 3 , Figure 3 This is a flowchart of a control method for a PFC circuit provided in an embodiment of the present invention. This control method for a PFC circuit can be applied to, for example... Figure 1 or Figure 2 The PFC circuit shown includes, but is not limited to, the following steps in its control method: Step S110: Obtain the load power, current input voltage, and current output voltage of the PFC circuit; Step S120: Obtain the target input current based on the load power and the current input voltage; Step S130: Adjust the switching frequency of the switching device according to the target input current and the current input voltage.

[0036] Understandably, the load power of the PFC circuit is obtained through the load power measurement module, which directly reflects the current circuit demand. Simultaneously, the current input voltage is obtained by sampling the input voltage sampling points through the input voltage sampling module, and similarly, the current output voltage is obtained by sampling the output voltage sampling points through the output voltage sampling module. The load power, current input voltage, and current output voltage comprehensively reflect the current operating state of the PFC circuit. Based on these parameters, the target input current required by the PFC circuit under the current operating conditions can be calculated. The target input current refers to the current level that the PFC circuit needs to maintain to meet the current power demand and circuit state. To achieve this goal, the PFC circuit dynamically adjusts the actual input current to ensure that the actual input current closely tracks the target input current.

[0037] Specifically, since the target input current is the current value that the PFC circuit is about to reach, the switching frequency of the switching device is dynamically adjusted according to the target input current and the current input voltage. This allows for a faster response to the impending state changes of the PFC circuit, ensuring that when the operating current of the PFC circuit reaches the target input current, the switching device can operate synchronously at the adjusted switching frequency. This improves the circuit's efficiency and enhances the dynamic response capability of the PFC circuit.

[0038] It should be noted that the current input voltage reflects the current state of the PFC circuit, such as continuous conduction, intermittent conduction, or critical conduction. The switching frequency of the switching device changes with the target input current and the current input voltage. In other words, the switching frequency of the switching device will also be dynamically adjusted in response to the current state of the PFC circuit. For example, when the operating current is small, a lower switching frequency can be used to control the switching device, thereby ensuring that the PFC circuit is in a continuous conduction state and reducing the switching frequency. This helps to reduce switching losses, reduce the heat generated by the switching device, and also helps to reduce the electromagnetic interference generated by the circuit, thereby improving the stability and reliability of the circuit.

[0039] Reference Figure 4 The control method provided in one embodiment of the present invention may include step S210 during the process of adjusting the switching frequency of the switching transistor: Step S210: Adjust the switching frequency of the switching device according to the relationship between the target input current and the first threshold current, and the relationship between the current input voltage and the first threshold voltage.

[0040] Understandably, the first threshold current is used to define the boundary between a high load state and a low load state of the PFC circuit. The first threshold current can be calculated from the maximum operating current of the PFC circuit. For example, it can be obtained by multiplying the maximum operating current by a preset threshold coefficient, which can be obtained based on the performance evaluation of the PFC circuit and is greater than 0 and less than 1.

[0041] When the target input current is equal to or greater than the first threshold current, the PFC circuit can be considered to be in a high load state, while when the target input current is less than the first threshold current, the PFC circuit can be considered to be in a low load state, thus the current load state of the PFC circuit can be determined.

[0042] The first threshold voltage is the voltage threshold used to indicate when the PFC circuit enters the intermittent on-state. It is the minimum input voltage that causes the PFC circuit to conduct intermittently during voltage peaks and troughs. When the current input voltage is equal to or greater than the first threshold voltage, the PFC circuit will be in an intermittent on-state during voltage peaks and troughs. When the current input voltage is less than the first threshold voltage, the PFC circuit will be in a continuous on-state. The first threshold voltage can be calculated using a preset maximum output voltage and the minimum duty cycle of the PFC circuit. The specific calculation process can be found in equation (1): (1); Indicates the first threshold voltage. Indicates the maximum output voltage. The minimum duty cycle represents the operating time of the PFC circuit. In a PFC circuit, the duty cycle controls the on-time of the switching devices, thus affecting the output voltage and current. The minimum duty cycle is the duty cycle value that ensures the PFC circuit maintains the corresponding output power under the conditions of lowest input voltage and maximum load power. Therefore, by comparing the target input current with the first threshold current, and comparing the current input voltage with the first threshold voltage, the current operating state of the PFC circuit can be analyzed. This allows for adjustment of the switching frequency based on the current operating state of the PFC circuit, ensuring its stability and safety.

[0043] Reference Figure 5 The control method provided in one embodiment of the present invention may further include step S310 or step S320 during the process of adjusting the switching frequency of the switching transistor: Step S310: In response to the target input current being less than the first threshold current and the current input current being less than the first threshold voltage, reduce the switching frequency of the switching device; or, Step S320: In response to the target input current being greater than or equal to the first threshold current, or the current input voltage being greater than or equal to the first threshold voltage, the switching frequency of the switching device is set to the initial switching frequency.

[0044] Understandably, when the target input current is less than the first preset current, it indicates that the PFC circuit is currently in a low-load state. At this time, the current change is relatively slow, and the demand for switching frequency is correspondingly reduced. Simultaneously, since the current input current is less than the first threshold voltage, the PFC circuit is unlikely to be in an intermittent conduction state but may be in a continuous conduction state. Therefore, the switching frequency of the switching devices can be reduced, thereby reducing switching losses and improving the overall efficiency of the circuit. Reduced switching losses mean less heat generation from the switching devices, which in turn lowers their temperature. Lower temperature rise helps extend the lifespan of the switching devices and improves circuit reliability. Furthermore, high-frequency switching operations are prone to generating electromagnetic interference, while reducing the switching frequency helps reduce electromagnetic interference, thus improving the circuit's electromagnetic compatibility.

[0045] At this time, when the PFC circuit is under low load, the current changes slowly, giving the PFC inductor sufficient time to store and release energy, thus maintaining current continuity. This allows the PFC circuit to operate stably in a continuously conducting state. Simultaneously, the inductance value of the PFC inductor increases as the input current decreases. Therefore, the inductance value corresponding to a decrease in input current is larger than the inductance value corresponding to the maximum input current, which helps the PFC circuit maintain continuous conduction over a wider load range. Because the PFC circuit is in a continuously conducting state, the inductor current is continuous throughout the entire switching cycle, making the input current waveform closer to a sine wave. This reduces harmonic content in the current, improves the smoothness of the current waveform, and significantly enhances the power factor, thus improving the performance of the PFC circuit.

[0046] Understandably, when a PFC circuit starts up, the switching frequency of the switching devices is initialized to an initial switching frequency. This initial switching frequency is a preset frequency based on the performance of each component in the PFC circuit, designed to ensure that the PFC circuit can operate normally in all operating states. Specifically, the initial switching frequency can be determined based on the rated inductance value of the PFC inductor, the maximum operating current of the PFC circuit, and a preset ripple current value.

[0047] When the target input current is greater than or equal to the first threshold current, that is, the current PFC circuit is under high load, the smoothness of the current waveform and the stability of the circuit are higher. Reducing the switching frequency of the switching device can easily lead to large fluctuations in the current waveform, affecting the power factor correction effect of the PFC circuit. Therefore, maintaining the switching frequency of the switching device can ensure that the PFC circuit can maintain stable performance and good current waveform under high load.

[0048] When the current input voltage is greater than or equal to the first threshold voltage, meaning the PFC circuit is intermittently conducting during voltage peaks and troughs, the rate of change of the current input voltage is large, leading to increased fluctuations in the input current. Maintaining the switching frequency at the initial switching frequency can also ensure the smoothness of the current waveform and avoid the impact of current fluctuations on circuit performance and power factor correction. Figure 6 As shown, Figure 6 This is a schematic diagram illustrating the effect of reducing the switching frequency when the current input voltage is greater than or equal to the first threshold voltage, as provided in an embodiment of the present invention. It can be seen that if the switching frequency of the switching device is reduced at this time, the peak current of the PFC circuit will be larger and the harmonic components will be more numerous at the voltage peak and voltage trough. Therefore, when the current input voltage is greater than or equal to the first threshold voltage, the initial switching frequency is used to drive the switching device.

[0049] Reference Figure 7The control method provided in one embodiment of the present invention, in the process of reducing the switching frequency of the switching transistor, may further include steps S410 and S420: Step S410: Determine the target inductance value of the PFC inductor based on the target input current; Step S420: Based on the target inductance value, the current input voltage, and the current output voltage, reduce the switching frequency of the switching device.

[0050] It is understandable that the inductance value of a PFC inductor increases as the input current of the PFC circuit decreases. Therefore, based on the inductance characteristics of a PFC inductor, the target inductance value of the PFC inductor can be determined by the target input current. The target inductance value corresponds to the target input current, and the target inductance value can refer to the inductance value of the PFC inductor that is about to change.

[0051] The inductance value of the PFC inductor can be determined in several ways. For example, a piecewise linear simulation method can be used to analyze the relationship between the inductance value of the PFC inductor and the input current. Figure 8 , Figure 8 This is a graph showing the relationship between the inductance value of the PFC inductor and the input current provided in this embodiment of the invention. It can be seen that the inductance value of the PFC inductor increases as the input current of the PFC circuit decreases. When the target input current is 0A, the target inductance value of the PFC inductor is at its maximum value of 400uH. When the target input current is 5A, the target inductance value decreases to 350uH, and when the target input current is 20A, the target inductance value decreases to 100uH. The curve showing the change in the inductance value of the PFC inductor is divided into... Each segment of the simulated straight line is described by establishing a linear equation, and then the target inductance value of the PFC inductor can be determined by the corresponding linear equation. The specific linear equation can be referred to in equation (2): (2); in, Indicates the target input current. This indicates the target inductance value of the PFC inductor under the target input current. Indicates the first The slope of the line segment, where the slope is... It is by dividing the change curve into After that, each line segment is obtained by approximating a straight line. This represents the intercept of the i-th line segment. This represents the number of segments, with values ​​ranging from 1 to... The specific value depends on the complexity of the curve and the required accuracy. Therefore, after obtaining the target input current, the slope and intercept of each line segment can be derived from the curve of the known inductance value of the PFC inductor, and then the target inductance value corresponding to the PFC inductor can be calculated by equation (2).

[0052] For example, the target inductance value of the PFC inductor can be calculated by the DC bias ratio corresponding to the PFC inductor at different currents. The DC bias ratio corresponding to the PFC inductor at different currents can be calculated by obtaining the correlation coefficient for calculating the DC bias ratio of the PFC inductor. The specific calculation process can be referred to formula (3): (3); in, Indicates the target input current. This indicates the target inductance value corresponding to the PFC inductor under the target input current. This represents the initial inductance value of the PFC inductor when the input current is 0A. This indicates the DC bias ratio of the PFC inductor at different currents. This is expressed as the number of turns in the inductor coil. It is expressed as the inductance coefficient. It is expressed as the length of the magnetic circuit, while , , and These are all relevant constants used to calculate the DC bias rate. It should be noted that the inductance coefficient... Magnetic circuit length and related constants , , and These parameters are the fundamental parameters of a PFC inductor, i.e., the initial parameters of the PFC inductor when it leaves the factory. Therefore, by calculating the DC bias rate of the PFC inductor at different input currents using its relevant parameters, and then determining the corresponding DC bias rate using the target input current, and multiplying it by the initial inductance value of the PFC inductor, the target inductance value of the PFC inductor at the target input current can be obtained.

[0053] Alternatively, a pre-set table showing the relationship between target input current and target inductance value can be used. Each target input current corresponds to a target inductance value, and after determining the target input circuit, the corresponding target inductance value can be directly determined by looking up the table.

[0054] After obtaining the target inductance value of the PFC inductor, the switching frequency of the switching devices is jointly controlled based on the target inductance value, the current input voltage, and the current output voltage. This reduces the switching frequency of the switching devices to decrease switching losses. Specifically, the main purpose of the PFC circuit is to improve the power factor, reduce harmonic pollution, and ensure stable operation of the circuit under various operating conditions. The target inductance value, the current input voltage, and the current output voltage are key factors for stable circuit operation. Therefore, by jointly controlling the switching frequency of the switching devices using the target inductance value, the current input voltage, and the current output voltage, it is possible to reduce the switching frequency while maintaining stable circuit output and a high power factor. In particular, it is important to prevent the PFC inductor from saturating due to excessively low adjusted switching frequency, which would lead to worsened harmonics.

[0055] Reference Figure 9 The control method provided in one embodiment of the present invention, in the process of reducing the switching frequency of the switching transistor, may further include steps S510 and S530: Step S510: Determine the minimum switching frequency based on the target inductance value, the current input voltage, and the current output voltage; Step S520: Construct the target frequency range using the minimum switching frequency as the lower limit of the range and the initial switching frequency as the upper limit of the range; Step S530: Adjust the switching frequency of the switching device to any frequency within the target frequency range.

[0056] Understandably, the minimum switching frequency can be calculated using the target inductance value, the current input voltage, the current output voltage, and the preset current ripple value. The minimum switching frequency refers to the lowest frequency at which the PFC circuit can operate stably under the current environmental conditions. If a frequency lower than the minimum switching frequency is used to control the switching device under these environmental conditions, the PFC inductor will saturate, affecting the normal operation of the circuit. Specifically, the calculation process for the minimum switching frequency can be referred to in equation (4): (4); in, Indicates the minimum switching frequency. Indicates the current input voltage. Indicates the current output voltage. Indicates the target inductance value. This indicates the preset current ripple value. It can be used with maximum operating current Calculated, such as , Weighting coefficients The value ranges from 0.2 to 0.4. First, the ratio of the difference between the peak value of the current input voltage and the current output voltage to the current output voltage is calculated. Then, the peak value of the current input voltage is combined with this ratio to obtain an expression related to the current input voltage and the current output voltage, reflecting the voltage difference that the PFC circuit needs to handle. This expression is then divided by the product of the target inductance value and the current ripple value to obtain the minimum switching frequency. Therefore, given the current input voltage, current output voltage, target inductance value, and current ripple value, the minimum switching frequency for the PFC circuit to maintain continuous conduction can be calculated. When the operating current of the PFC circuit is small, the switching frequency can be reduced to between the minimum switching frequency and the initial switching frequency, thereby ensuring that the PFC circuit operates in a continuous conduction state and reducing switching losses.

[0057] Therefore, a target frequency range is constructed by using the minimum switching frequency as the lower limit of the range and the initial switching frequency as the upper limit of the range. The target frequency range represents the adjustable range of the switching frequency of the switching device. At this time, the switching frequency of the switching device can be reduced to any frequency in the target frequency range. That is, a target switching frequency can be determined from multiple frequencies in the target frequency range, and the switching frequency of the switching device can be reduced from the initial switching frequency to the target switching frequency. Specifically, the target switching frequency can be selected from multiple frequencies in the target frequency range based on parameters such as the stability, conversion efficiency, power factor, and current ripple value of the PFC circuit.

[0058] Reference Figure 10 The control method provided in one embodiment of the present invention, in the process of adjusting the switching frequency of the switching transistor, may further include steps S610 to S640: Step S610: Obtain the rated input operating voltage and maximum input operating voltage of the PFC circuit; Step S620: Obtain the current coefficient based on the input rated operating voltage and the input maximum operating voltage; Step S630: Obtain the reference current based on the current coefficient and the first threshold current; Step S640: Adjust the switching frequency of the switching device according to the relationship between the target input current and the reference current, and the relationship between the current input voltage and the first threshold voltage.

[0059] It is understandable that the rated input operating voltage refers to the expected input voltage value of the PFC circuit when it is working normally. For example, the rated input operating voltage can be the standard voltage of the AC mains. The maximum input operating voltage can refer to the highest input voltage value that the PFC circuit can safely operate. The maximum input operating voltage is greater than the rated input operating voltage.

[0060] By comparing the ratio of the rated input voltage to the maximum input voltage, the current coefficient can be calculated. The current coefficient reflects the consideration of the input voltage range during the design of the PFC circuit, as well as the circuit's ability to operate under different voltages. Therefore, the reference current can be obtained by multiplying the current coefficient by the first threshold current. The first threshold current can be the maximum operating current of the PFC circuit, and the current coefficient is less than 1. The obtained reference current is less than the maximum operating current, and the reference current can represent the expected input current value of the PFC circuit during normal operation. Using the reference current as a benchmark value, the target input current is compared with the reference current to determine the load state of the PFC circuit. When the target input current is equal to or greater than the reference current, the PFC circuit is considered to have a high current demand and is in a high load state. When the target input current is less than the reference current, the PFC circuit is considered to have a low current demand and is in a low load state.

[0061] Reference Figure 11 The control method provided in one embodiment of the present invention may further include steps S710 to S720 during the calculation of load power: Step S710: Obtain the load current of the load current detection module; Step S720: Obtain the load power based on the current output voltage and load current of the PFC circuit.

[0062] Understandably, the load current detection module can measure the current flowing into the load in real time. There can be one or more load current detection modules. When a load current detection module is used to detect the total output current of the PFC circuit, it can directly acquire the load current and multiply it by the current output voltage to calculate the load power. When there are multiple load current detection modules, each detecting the load current flowing into its respective load, the load currents detected by all modules can be added together. The result of this summation is then multiplied by the current output voltage of the PFC circuit to obtain the load power. Because both the load current and the current output voltage are acquired in real time, it ensures that the PFC circuit can dynamically adjust the switching frequency of the switching devices based on the real-time load power.

[0063] In addition, when the PFC circuit supplies power to a load with stable power, the power of that load can be directly added to the load power. For example, the power of the control module used to control the operation of components such as power supplies and switching devices can be directly added to the load power.

[0064] Reference Figure 12 The control method provided in one embodiment of the present invention may further include steps S810 to S820 during the calculation of the target input current: Step S810: Obtain the circuit conversion efficiency of the PFC circuit; Step S820: Obtain the target input current based on the load power, current input voltage, and circuit conversion rate.

[0065] It is understandable that the circuit conversion efficiency is a measure of the ability of a PFC circuit to convert input power into output power, representing the degree of energy loss in the PFC circuit during the energy conversion process. The circuit conversion efficiency can be obtained through experimental measurement or estimated based on the components and actual design of the PFC circuit. After obtaining the circuit conversion efficiency of the PFC circuit, the target input current can be calculated using the load power, current input voltage, and circuit conversion efficiency. The specific calculation formula can be found in equation (5): (5); in, Indicates load power. Representing circuit conversion efficiency, based on the principle of power conservation, it can be used to measure load power. Divide by the current input voltage and circuit conversion rate The target input current is obtained by multiplying the products. .

[0066] The following specific embodiment illustrates the control method of the PFC circuit provided by the present invention.

[0067] Reference Figure 13 , Figure 13 This is a schematic diagram of the overall flow of the control method for the PFC circuit provided in this embodiment of the invention. Taking the application of the PFC circuit in the outdoor unit of an air conditioner as an example, the PFC circuit supplies power to the compressor, such as... Figure 13As shown, first, step S1310 is executed. After the compressor starts, the PFC circuit is activated to control the switching devices at a preset initial switching frequency. The initial switching frequency can be calculated based on the rated inductance of the PFC inductor, the maximum operating current of the PFC circuit, and the preset ripple current value. Next, step S1320 is executed to obtain the current output voltage and load current of the PFC circuit and calculate the current load power. When the PFC circuit supplies power to multiple loads (such as compressors and fans) simultaneously, the load current represents the sum of the input currents of multiple loads. If the PFC circuit also supplies power to a load with stable power, the load power of that load can be directly added to the current load power, such as the power required for the control power supply and the operation of the switching devices. Step S1330 is executed to obtain the current input voltage of the PFC circuit and calculate the target input current based on the current load power and the current input voltage. The target input current is the current value required by the PFC circuit in the current state. Then, step S1320 is executed. 1340. Determine whether the target input current is less than the first threshold current. The first threshold current can be a preset value. Specifically, the first threshold current can be obtained by multiplying the maximum operating current of the air conditioner by the current coefficient. The current coefficient can be obtained by dividing the rated operating voltage of the PFC circuit by the maximum operating voltage. If the target input current is less than the first threshold current, proceed to step S1350; otherwise, proceed to step S1360. Step S1350. Determine whether the current input voltage is less than the first threshold voltage. The first threshold voltage can be a preset limit value. Specifically, the first threshold voltage can refer to the minimum input voltage that makes the PFC circuit in an intermittent conduction state at voltage peaks and troughs. The first threshold voltage can be calculated by the preset maximum output voltage and minimum duty cycle. If the current input voltage is equal to or greater than the first threshold voltage, proceed to step S1360. Step S1360. Set the switching frequency of the switching device to the initial switching frequency. Then, return to proceed to step S1320. If the current input voltage is less than the first threshold voltage, then step S1370 is executed to calculate the target inductance value of the PFC inductor based on the target input current. The target inductance value of the PFC inductor increases as the target input current decreases. After obtaining the target inductance value, step S1380 is executed. In step S1380, the switching frequency of the switching device is adjusted based on the target inductance value, the current input voltage, and the current output voltage. Specifically, the minimum switching frequency is calculated using the target inductance value, the current input voltage, and the current output voltage. At this time, the switching frequency of the switching device can be adjusted to be within the frequency range between the minimum switching frequency and the initial switching frequency. Since the target inductance value at this time is necessarily less than the inductance value corresponding to the maximum input current, it can ensure that the PFC circuit operates in a continuous conduction state while reducing the switching frequency of the switching device, thereby helping to reduce switching losses and improve the temperature rise problem of the switching device.

[0068] Secondly, referring to Figure 14 This invention provides an operation control device 1400, including a memory 1420, a processor 1410, and a computer program stored in the memory 1420 and executable on the processor 1410. The processor 1410 executes the program to implement the control method described in the first aspect embodiment above, for example, executing... Figure 3 Method steps S110 to S130, Figure 4 Method step S210, or execution Figure 5 Method steps S310 to S320, or execution Figure 7 Method steps S410 to S420, or execution Figure 9 Method steps S510 to S530, or execution Figure 10 Method steps S610 to S640, or execution Figure 11 Method steps S710 to S720, or execution Figure 12 Method steps S810 to S820.

[0069] According to the operation control device provided in the embodiment of the present invention, the target input current is obtained by the load power of the PFC circuit and the current input voltage. The target input current refers to the input current required by the PFC circuit under the current environmental conditions, which can represent the input current of the PFC circuit that is about to change. Therefore, by dynamically adjusting the switching frequency of the switching device using the target input current and the current input voltage, the PFC circuit can respond to the state that is about to change more quickly. When the operating current of the PFC circuit reaches the target input current, the switching device can operate synchronously at the adjusted switching frequency, effectively reducing switching losses and controlling the heat generation of the switching device. It also helps to reduce the electromagnetic interference generated by the circuit.

[0070] Thirdly, embodiments of the present invention provide an air conditioner, including the operation control device as described in the second aspect embodiment above.

[0071] According to the air conditioner provided in the embodiments of the present invention, the target input current is obtained by the load power of the PFC circuit and the current input voltage. The target input current refers to the input current required by the PFC circuit under the current environmental conditions, which can represent the input current that the PFC circuit is about to change. Therefore, by dynamically adjusting the switching frequency of the switching device using the target input current and the current input voltage, the PFC circuit can respond to the state that is about to change more quickly. When the operating current of the PFC circuit reaches the target input current, the switching device can operate synchronously at the adjusted switching frequency, effectively reducing switching losses and controlling the heat generation of the switching device. It also helps to reduce the electromagnetic interference generated by the circuit.

[0072] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing computer-executable instructions for causing a computer to perform the control method described in the first aspect of the invention, for example, executing... Figure 3 Method steps S110 to S130, Figure 4 Method step S210, or execution Figure 5 Method steps S310 to S320, or execution Figure 7 Method steps S410 to S420, or execution Figure 9 Method steps S510 to S530, or execution Figure 10 Method steps S610 to S640, or execution Figure 11 Method steps S710 to S720, or execution Figure 12 Method steps S810 to S820.

[0073] According to the computer-readable storage medium provided in the embodiments of the present invention, the target input current is obtained by the load power of the PFC circuit and the current input voltage. The target input current refers to the input current required by the PFC circuit under the current environmental conditions, which can represent the input current that the PFC circuit is about to change. Therefore, by using the target input current and the current input voltage to dynamically adjust the switching frequency of the switching device, the PFC circuit can respond to the state that is about to change more quickly. When the operating current of the PFC circuit reaches the target input current, the switching device can operate synchronously at the adjusted switching frequency, effectively reducing switching losses and controlling the heat generation of the switching device. It also helps to reduce the electromagnetic interference generated by the circuit.

[0074] 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 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. Integrated physical components, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product stored in a storage medium, including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. As is known to those skilled in the art, a computer storage medium 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 include, but are 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 can be accessed by a computer. Furthermore, it is well known to those skilled in the art that 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.

[0075] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A control method for a PFC circuit, characterized in that, The PFC circuit includes a power input module, a switching device, and an output capacitor connected in sequence. The power input module is provided with an input voltage sampling point for acquiring the current input voltage of the PFC circuit, and the two ends of the output capacitor are provided with an output voltage sampling point for acquiring the current output voltage of the PFC circuit. The control method includes: Obtain the load power, the current input voltage, and the current output voltage of the PFC circuit; The target input current is obtained based on the load power and the current input voltage; The switching frequency of the switching device is adjusted according to the target input current and the current input voltage so that when the operating current of the PFC circuit reaches the target input current, the switching device operates at the adjusted switching frequency.

2. The control method according to claim 1, characterized in that, The step of adjusting the switching frequency of the switching device based on the target input current and the current input current includes: Based on the relationship between the target input current and the first threshold current, and the relationship between the current input voltage and the first threshold voltage, the switching frequency of the switching device is adjusted. Wherein, the first threshold voltage represents the voltage threshold at which the PFC circuit enters the intermittent on-state.

3. The control method according to claim 2, characterized in that, The step of adjusting the switching frequency of the switching device based on the relationship between the target input current and the first threshold current, and the relationship between the current input voltage and the first threshold voltage, includes: In response to the target input current being less than a first threshold current and the current input current being less than a first threshold voltage, the switching frequency of the switching device is reduced.

4. The control method according to claim 3, characterized in that, The PFC circuit further includes a PFC inductor, and the power input module is connected to both the first terminal of the switching device and the output capacitor through the PFC inductor; reducing the switching frequency of the switching device includes: The target inductance value of the PFC inductor is determined based on the target input current. The switching frequency of the switching device is reduced based on the target inductance value, the current input voltage, and the current output voltage.

5. The control method according to claim 4, characterized in that, The step of reducing the switching frequency of the switching device based on the target inductance value, the current input voltage, and the current output voltage includes: The minimum switching frequency is determined based on the target inductance value, the current input voltage, and the current output voltage. The target frequency range is constructed by using the minimum switching frequency as the lower limit of the range and the initial switching frequency as the upper limit of the range. The switching frequency of the switching device is adjusted to any frequency within the target frequency range.

6. The control method according to claim 2, characterized in that, The step of adjusting the switching frequency of the switching device based on the relationship between the target input current and the first threshold current, and the relationship between the current input voltage and the first threshold voltage, includes: In response to the target input current being greater than or equal to a first threshold current, or the current input voltage being greater than or equal to a first threshold voltage, the switching frequency of the switching device is set to an initial switching frequency.

7. The control method according to claim 2, characterized in that, The step of adjusting the switching frequency of the switching device based on the relationship between the target input current and the first threshold current, and the relationship between the current input voltage and the first threshold voltage, includes: Obtain the rated input operating voltage and the maximum input operating voltage of the PFC circuit; The current coefficient is obtained based on the rated input operating voltage and the maximum input operating voltage; The reference current is obtained based on the current coefficient and the first threshold current; The switching frequency of the switching device is adjusted based on the relationship between the target input current and the reference current, and the relationship between the current input voltage and the first threshold voltage.

8. The control method according to claim 1, characterized in that, The PFC circuit also includes a load current detection module for connecting to and supplying power to the load, wherein the load power is obtained through the following steps: Obtain the load current of the load current detection module; The load power is obtained based on the current output voltage of the PFC circuit and the load current.

9. The control method according to claim 1, characterized in that, The step of obtaining the target input current based on the load power and the current input voltage includes: Obtain the circuit conversion efficiency of the PFC circuit; The target input current is obtained based on the load power, the current input voltage, and the circuit conversion rate.

10. An operation control device, characterized in that, The device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the program to implement the control method for the PFC circuit as described in any one of claims 1 to 9.

11. An air conditioner, characterized in that, Includes the operation control device as described in claim 10.

12. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions for causing a computer to perform a control method for a PFC circuit as described in any one of claims 1 to 9.

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