Control method and control device of power factor correction circuit and air conditioner

Abstract

The application discloses a control method and device of a power factor correction circuit and an air conditioner. The control method sets different frequency values for input voltages in different phase intervals, realizes periodic variable load frequency control, fixes a first frequency value which is relatively low in a first phase interval, i.e. near a zero-crossing point, fixes a second frequency value which is slightly higher than the first frequency value in a second phase interval, i.e. near a wave peak, controls the nonlinear change of the carrier frequency in a third phase interval according to the voltage, current and other parameters of the PFC circuit, or controls the linear change of the carrier frequency according to the input voltage, thereby reducing the switching times of the switching tube in the phase period of the input voltage, reducing the interference of high-order harmonics, controlling the heat generation of the switching tube in the working process and reducing electromagnetic interference.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air conditioners, and in particular to a control method and control device of a power factor correction circuit and an air conditioner. BACKGROUND

[0002] The existing PFC (Power Factor Correction) control technology through digital software often adopts a modulation method with a fixed carrier frequency to correct the power factor. In order to improve the current ripple quality of the PFC circuit, the carrier frequency can be increased to shorten the regulation period of the PFC and reduce the harmonic distortion rate of the current. However, increasing the carrier frequency will cause the switching tube to work more frequently, the switching tube to generate more heat, and greater switching loss and electromagnetic interference. SUMMARY

[0003] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0004] The embodiments of the present application provide a control method and control device of a power factor correction circuit and an air conditioner, which reduce the heat generation and electromagnetic interference of a switching device by controlling the frequency value of a carrier frequency at different input voltages.

[0005] Embodiments of the first aspect of the present application provide a control method of a power factor correction circuit, the power factor correction PFC circuit comprising a boost module, the boost module comprising a switching device and an inductive device, the control method comprising:

[0006] obtaining an input voltage, an output voltage, an input current, a ripple current and an inductance value of the inductive device of the PFC circuit, wherein the ripple current is a fixed value or is determined according to the operating parameters of the PFC circuit, and the inductance value is a fixed value or is determined according to the operating parameters of the PFC circuit;

[0007] determining a voltage phase according to the input voltage;

[0008] in a first phase interval of the voltage phase period, setting the carrier frequency to a first frequency value, in a second phase interval of the voltage phase period, setting the carrier frequency to a second frequency value, and in a third phase interval of the voltage phase period, determining the carrier frequency according to the input voltage, the output voltage, the input current, the ripple current and the inductance value, wherein the first phase interval, the second phase interval and the third phase interval do not overlap with each other, the zero-crossing point phase of the voltage phase is in the first phase interval, the peak value phase of the voltage phase is in the second phase interval, and the second frequency value is greater than the first frequency value;

[0009] The on-time of the switching device is determined according to the input voltage, the output voltage, the input current and the carrier frequency.

[0010] The control method of the power factor correction circuit according to the first aspect of the present application has at least the following beneficial effects: according to the relationship between the carrier frequency and the input voltage, the output voltage, the input current, the ripple current and the inductance value, different frequency values are set for the input voltage in different phase intervals, periodic variable carrier frequency control is realized, in the first phase interval, i.e. near the zero-crossing phase, a fixed first frequency value is set, in the second phase interval, i.e. near the peak phase, a second frequency value slightly higher than the first frequency value is fixed, and in the third phase interval, the carrier frequency is controlled to change nonlinearly according to the voltage, current and other parameters of the PFC circuit, thereby reducing the switching frequency of the switching tube in the phase period of the input voltage, reducing the interference of high-order harmonics, controlling the heat of the switching tube during operation, and reducing electromagnetic interference.

[0011] In some embodiments, the second phase interval is a degenerate interval. That is, the two endpoints of the second phase interval are the same and equal to the peak phase of the voltage phase, and the carrier frequency converges to a point in the second phase interval.

[0012] In some embodiments, the first phase interval, the second phase interval and the third phase interval constitute a complete phase interval period. The first phase interval, the second phase interval and the third phase interval together constitute a complete voltage phase period, and according to the change law of the carrier frequency, the carrier frequency can reach a maximum frequency value in the third phase interval, which is suitable for optimizing the current harmonics during a high input voltage period.

[0013] In some embodiments, at the two endpoints of the third phase interval, the frequency value of the carrier frequency is the first frequency value and the second frequency value, respectively. Since the third phase interval has the first frequency value and the second frequency value at the left and right ends, respectively, and based on the fact that the three phase intervals together constitute a complete voltage phase period, it can be known that the carrier frequency changes continuously when switching between the three intervals, achieving relatively smooth ripple control.

[0014] In some embodiments, the ripple current is fixed at a preset ripple value or determined according to the input current. In order to facilitate the calculation of the carrier frequency, the preset ripple value can be used as the ripple current value in the calculation of the carrier frequency, or the value of the ripple current can be set according to the change law of the input current, for example, by dividing multiple intervals according to the input current from small to large, and the intervals correspond to different ripple current values.

[0015] In some embodiments, the inductance value is determined according to a nominal inductance value of the inductor device or according to the input current. The actual inductance value of the inductor device varies with the input current during operation of the PFC circuit. In order to facilitate calculation of the carrier frequency, the inductance value can be directly fixed as the nominal inductance value of the inductor device during calculation, thereby reducing calculation consumption.

[0016] The second aspect of the present application provides a control method of a power factor correction circuit. The power factor correction (PFC) circuit includes a boost module, and the boost module includes a switching device. The control method includes:

[0017] obtaining an input voltage, an output voltage and an input current of the PFC circuit;

[0018] determining a voltage phase according to the input voltage;

[0019] setting the carrier frequency as a first frequency value in a first phase interval of the voltage phase period, setting the carrier frequency as a second frequency value in a second phase interval of the voltage phase period, and controlling the carrier frequency to linearly vary according to the input voltage in a third phase interval of the voltage phase period, wherein the first phase interval, the second phase interval and the third phase interval do not overlap with each other, a zero-crossing point phase of the voltage phase is in the first phase interval, a peak value phase of the voltage phase is in the second phase interval, and the second frequency value is greater than the first frequency value;

[0020] determining a conduction time of the switching device according to the input voltage, the output voltage, the input current and the carrier frequency.

[0021] The control method of the power factor correction circuit according to the second aspect of the present application has at least the following beneficial effects: different frequency values are set in different phase intervals according to the input voltage to realize periodic variable carrier frequency control. In the first phase interval, i.e. near the zero-crossing point phase, a lower first frequency value is fixed. In the second phase interval, i.e. near the peak value phase, a second frequency value slightly higher than the first frequency value is fixed. In the third phase interval, the carrier frequency is controlled to linearly vary according to the input voltage, thereby reducing the switching times of the switching tube in the phase period of the input voltage, reducing the interference of high-order harmonics, controlling the heat of the switching tube during operation, and reducing electromagnetic interference.

[0022] In some embodiments, the second phase interval is a degenerate interval. That is, the two endpoints of the second phase interval are the same and equal to the peak value phase of the voltage phase, and the carrier frequency converges to a point in the second phase interval.

[0023] In some embodiments, the first phase interval, the second phase interval and the third phase interval constitute a complete phase interval period. The first phase interval, the second phase interval and the third phase interval jointly constitute a complete voltage phase period, and the carrier frequency can reach a maximum frequency value in the third phase interval according to the variation law of the carrier frequency, which is suitable for optimizing the current harmonics during a high input voltage period.

[0024] In some embodiments, the frequency value of the carrier frequency at the two endpoints of the third phase interval is the first frequency value and the second frequency value, respectively. Since the first frequency value and the second frequency value are at the left and right ends of the third phase interval, respectively, and the three phase intervals jointly constitute a complete voltage phase period, it can be known that the carrier frequency continuously changes when switching among the three intervals, and a relatively smooth ripple control is achieved.

[0025] In some embodiments, the third phase interval includes a carrier frequency rising interval and a carrier frequency falling interval, and at least one continuous interval in the third phase interval includes at least one carrier frequency rising interval and at least one carrier frequency falling interval. The carrier frequency rising interval and the carrier frequency falling interval in the third phase interval are combined, and the variation law of the obtained carrier frequency is consistent with the variation law of the input voltage, thereby reducing the influence of the ripple current on the operation of the PFC circuit.

[0026] The third aspect embodiment of the present application provides a control device, including at least one processor and a memory connected to the at least one processor in communication; the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the control method of the power factor correction circuit of the first aspect or the control method of the power factor correction circuit of the second aspect.

[0027] The control device according to the third aspect embodiment of the present application has at least the following beneficial effects: by executing the above control method through the control device, different frequency values are set in different phase intervals for the input voltage, and periodic variable carrier frequency control is achieved, wherein a fixed lower first frequency value is set in the first phase interval, i.e. near the zero-crossing phase, a second frequency value slightly higher than the first frequency value is fixed in the second phase interval, i.e. near the peak phase, and in the third phase interval, the carrier frequency is controlled to change nonlinearly according to the voltage, current and other parameters of the PFC circuit, or the carrier frequency is controlled to change linearly according to the input voltage, thereby reducing the switching frequency of the switching tube in the phase period of the input voltage, reducing the interference of high-order harmonics, controlling the heat of the switching tube in the working process, and reducing electromagnetic interference.

[0028] The fourth aspect embodiment of the present application provides a circuit board including the control device of the third aspect.

[0029] According to the line card of the fourth aspect of the present application, at least the following beneficial effects are achieved: the control device is integrated on the line card, so that the line card has the functions of the control device, different frequency values are set in different phase intervals for the input voltage, and periodic variable carrier frequency control is achieved, wherein a first frequency value is fixed in a first phase interval, i.e. near the zero-crossing phase, a second frequency value slightly higher than the first frequency value is fixed in a second phase interval, i.e. near the peak phase, and in a third phase interval, the carrier frequency is controlled to change nonlinearly according to the voltage, current and other parameters of the PFC circuit, or the carrier frequency is controlled to change linearly according to the input voltage, so that the switching times of the switching tube are reduced in the phase period of the input voltage, the interference of high-order harmonics is reduced, the heat of the switching tube in the working process is controlled, and electromagnetic interference is reduced.

[0030] The fifth aspect of the present application provides an air conditioner comprising the line card of the fourth aspect.

[0031] According to the air conditioner of the fourth aspect of the present application, at least the following beneficial effects are achieved: the line card is provided in the air conditioner to control the air conditioner, the heat of the switching tube in the circuit is reduced on the premise that the ripple current of the air conditioner is controlled within a small range, and specifically, different frequency values are set in different phase intervals for the input voltage, and periodic variable carrier frequency control is achieved, wherein a first frequency value is fixed in a first phase interval, i.e. near the zero-crossing phase, a second frequency value slightly higher than the first frequency value is fixed in a second phase interval, i.e. near the peak phase, and in a third phase interval, the carrier frequency is controlled to change nonlinearly according to the voltage, current and other parameters of the PFC circuit, or the carrier frequency is controlled to change linearly according to the input voltage, so that the switching times of the switching tube are reduced in the phase period of the input voltage, the interference of high-order harmonics is reduced, the heat of the switching tube in the working process is controlled, and electromagnetic interference is reduced.

[0032] The sixth aspect of the present application provides a computer readable storage medium, which stores computer executable instructions, and the computer executable instructions are used to make a computer execute the control method of the power factor correction circuit of the first aspect or the control method of the power factor correction circuit of the second aspect.

[0033] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be achieved and obtained by the structure particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a circuit diagram of a power factor correction circuit provided by an embodiment of the present application;

[0035] Figure 2 is a flow chart of a control method of a nonlinear carrier frequency provided by an embodiment of the present application;

[0036] Figure 3 is a schematic diagram of module connection in a power factor correction circuit provided by an embodiment of the present application;

[0037] Figure 4 is a waveform diagram of nonlinear variation of a carrier frequency in a third phase interval provided by an embodiment of the present application;

[0038] Figure 5 is a waveform diagram of nonlinear variation of a carrier frequency in a third phase interval provided by an embodiment of the present application;

[0039] Figure 6 is a waveform diagram of linear variation of a carrier frequency in a third phase interval provided by an embodiment of the present application;

[0040] Figure 7 is a waveform diagram of linear variation of a carrier frequency in a third phase interval provided by an embodiment of the present application;

[0041] Figure 8 is a flow chart of a control method of a linear carrier frequency provided by an embodiment of the present application;

[0042] Figure 9 is a schematic diagram of module connection in a power factor correction circuit provided by an embodiment of the present application;

[0043] Figure 10 is a schematic diagram of module connection of a control device of the present application. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0045] The embodiments of the present application provide a control method, a control device and an air conditioner of a power factor correction circuit. When the PFC circuit performs PFC control, the carrier frequency near the zero-crossing phase and the peak phase is adjusted according to the relationship between the carrier frequency and the input voltage, the output voltage, the input current, the ripple current and the inductance value of the inductor, so that the heat generation of the switching device in the PFC circuit is reduced under the premise of ensuring that the current harmonic does not exceed the standard, thereby further optimizing the circuit components and reducing the electromagnetic protection requirement.

[0046] The embodiments of the present application will be further described below with reference to the drawings.

[0047] The embodiment of the present application provides a control method of a power factor correction circuit, which is applied to a PFC circuit, the PFC circuit referring to Figure 1 , comprising a rectifier module, a boost module, a filter module and a controller connected in sequence, wherein the rectifier module is used for converting alternating current (AC) mains into direct current (DC) voltage, the DC voltage being input voltage Uin of the current PFC circuit, and DC current corresponding to the input voltage Uin being input current Iin of the current PFC circuit, an output end of the rectifier module being connected to the boost module, wherein the boost module is used for boost voltage, comprising an inductive device and a switching device, the inductive device being connected in series to a positive output end of the rectifier module, one end of the switching device being connected to the inductive device, the other end of the switching device being connected to a negative output end of the rectifier module, a controlled end of the switching device being connected to an enable pin of the controller, the filter module being connected in parallel to the switching device, a load (represented by a resistor R in Figure 1 ) being connected in parallel to two ends of the filter module, and voltage input to the load being output voltage Uo of the current PFC circuit. It can be known that the controller can realize boost output and PFC control process by controlling conduction and turn-off of the switching device.

[0048] It can be understood that the above PFC circuit can further comprise a diode, a positive electrode of the diode being connected to a connection position of the inductive device and the switching device, and a negative electrode of the diode being connected to one end of the filter module. The filter module can be realized by a capacitor device or other filter circuit. In order to facilitate representation, only a single capacitor is used to represent the filter circuit in Figure 1 .

[0049] It can be known from the above PFC circuit that, in the case of PFC control of the controller, voltage phase variation of the input voltage Uin follows a waveform of the input voltage Uin, and the input current Iin also varies according to the same phase rule, that is, the voltage phase of the PFC circuit is synchronized with the input voltage Uin, referring to Figure 4 and Figure 5 , Figure 4 and Figure 5The carrier frequency-phase curve (represented by a solid line) of this invention is formed by the overlap of two coordinate systems with the same horizontal axis. One coordinate system uses phase as the horizontal axis and carrier frequency as the vertical axis to represent the carrier frequency-phase curve (represented by a dashed line) of this invention. The other coordinate system uses phase as the horizontal axis and input voltage Uin as the vertical axis to represent the voltage-phase curve (represented by a dashed line) of the PFC circuit. It can be understood that the carrier frequency and phase are not directly related and need to be transformed by the input voltage Uin. Under the premise of PFC control, the input voltage Uin changes periodically according to the phase. The carrier frequency of this invention follows the variable carrier frequency formula (explained below), and the carrier frequency is positively correlated with the input voltage Uin. Therefore, the carrier frequency-phase curve can actually be transformed from the carrier frequency-input voltage curve. For the convenience of explaining the phase interval later, this invention will only refer to the carrier frequency-phase curve for explanation.

[0050] It is understood that the above-described PFC circuit is only one circuit form for implementing the control method of the embodiments of the present invention. Various modifications, optimizations, and extensions made based on the above-described PFC circuit can also implement the control method of the embodiments of the present invention. To avoid listing too many examples, they will not be elaborated here.

[0051] Based on the above PFC circuit, referring to Figure 2 The control methods include, but are not limited to, the following steps:

[0052] Step S100: Obtain the input voltage, output voltage, input current, ripple current, and inductance value of the inductor of the PFC circuit, wherein the ripple current is a fixed value or determined according to the operating parameters of the PFC circuit, and the inductance value is a fixed value or determined according to the operating parameters of the PFC circuit.

[0053] Step S200: Determine the voltage phase based on the input voltage;

[0054] Step S300: Within the first phase interval of the voltage phase cycle, the carrier frequency is set to a first frequency value; within the second phase interval of the voltage phase cycle, the carrier frequency is set to a second frequency value; within the third phase interval of the voltage phase cycle, the carrier frequency is determined based on the input voltage, output voltage, input current, ripple current, and inductance value. The first, second, and third phase intervals do not overlap. The zero-crossing phase of the voltage phase is located in the first phase interval, the peak phase of the voltage phase is located in the second phase interval, and the second frequency value is greater than the first frequency value.

[0055] Step S400: Determine the conduction time of the switching device based on the input voltage, output voltage, input current, and carrier frequency;

[0056] The steps in the above control method can be performed by the controller in the PFC circuit, which collects several electrical parameters such as voltage and current in the PFC circuit through step S100, performs nonlinear change control on the carrier frequency, and the ripple current and inductance value can be determined by other means, such as the controller obtaining a preset value of the ripple current, or determining the value of the ripple current according to the input current, etc.; in some embodiments, the collection of the above electrical parameters requires the use of corresponding collection devices and calculation devices, for example, referring to Figure 3 In the PFC circuit, an input voltage sampling module, an input voltage phase calculation module, an input current sampling module, an output voltage sampling module, and a ripple current and inductance value determination module are also provided, wherein the input voltage sampling module and the input current sampling module are connected at the output end of the rectifier module to obtain the DC voltage and DC current output by the rectifier module, the output voltage sampling module is connected before the load to obtain the DC bus voltage, the input voltage phase calculation module is used to reconstruct the corresponding voltage phase according to the collected input voltage, and the voltage phase is tracked in real time, and the ripple current and inductance value determination module is used to obtain the inductance value of the inductor. It can be understood that there are many implementation methods for the above collection devices, such as voltage sensors, etc., which will not be listed one by one here, and designers can select different devices according to their needs.

[0057] Among them, the inductance value of the ripple current and the inductor is real-time changed according to the running state of the PFC current, therefore, in order to reduce the calculation burden of the controller when calculating the carrier frequency, in actual operation, the value of the ripple current and the inductance value can be determined in different ways, for example, the value of the ripple current can be determined in two ways, one is to directly set a fixed value for the PFC circuit, and directly use the fixed value to calculate in the process of calculating the carrier frequency, the other is to determine the value of the ripple current according to the input current of the PFC circuit, and different ripple current values are set according to the size of the input current; the inductance value can also be determined in different ways, one is to directly set a fixed value, and the fixed value is related to the inductance calibration value of the inductor, the other is to determine according to the input current of the PFC circuit. It can be understood that the input current is related to the input voltage, load frequency and other parameters, therefore, in the process of setting the ripple current value or inductance value according to the size of the input current, the input voltage and other parameters can also be referred to, which is not limited here.

[0058] In order to realize PFC control, the carrier frequency needs to be changed according to the voltage phase to adapt to the change rule of the input voltage; through the collected value of the input voltage in step S100 (the PFC circuit receives sinusoidal alternating input mains), the voltage phase of the current input voltage can be deduced, that is, the controller performs step S200 to calculate the change rule of the voltage phase.

[0059] In order to reduce the inductance in the current PFC circuit, the prior art often realizes through the way of increasing the carrier frequency, but increasing the carrier frequency will cause the switching times of the switching tube of the PFC circuit to increase, the heat of the switching tube to increase, and the electromagnetic protection requirement of the inductor device to increase accordingly, resulting in unstable operation of the PFC circuit, in order to solve the above problems, the carrier frequency generated by the PFC variable load frequency generation module of the embodiment is set to different frequency values according to different input voltages, thereby reducing the heat of the switching tube in the working cycle as a whole, specifically, according to step S300, the carrier frequency of the embodiment has the following characteristics:

[0060] The frequency value of the nonlinear change of the carrier frequency can be calculated according to the following formula:

[0061]

[0062] Where, ΔI is the ripple current of the PFC circuit, L is the inductance value of the inductor device. From the above formula, the carrier frequency changes with ΔI, L, Uin and Uo, where As a variable coefficient, then the carrier frequency can be considered to be positively correlated with the input voltage Uin to some extent.

[0063] Based on the above carrier frequency calculation formula, at the zero-crossing point of the input voltage Uin (corresponding to the zero-crossing phase) the voltage value is very small, the input current Iin is also very small, and the current harmonic is too large, therefore in order to ensure the current harmonic, the first frequency value is used at the zero-crossing phase of the voltage phase and near the zero-crossing phase, and at the peak point of the input voltage Uin (corresponding to the peak phase) the voltage value is very high, at this time the input voltage Uin may be greater than the output voltage Uo, resulting in the carrier frequency becoming negative, therefore in order to ensure that the carrier frequency near the peak phase is greater than 0, the second frequency value is used at the peak phase of the voltage phase and near the peak phase, for example: Figure 5

[0064] ​In the first half of the phase period (for example, 0 to π / 2), the range between the zero-crossing phase and θ1 is set as the first phase interval, the range between θ5 and π / 2 is set as the second phase interval, and the phase range between the first phase interval and the second phase interval is set as the third phase interval, wherein the frequency value of the fixed carrier frequency in the first phase interval is fc, the frequency value of the fixed carrier frequency in the second phase interval is fb, and fb is greater than fc; in this way, at the zero-crossing phase, a fixed value fc is set, which can avoid the carrier frequency from becoming too low following a lower voltage value, thereby improving the problem of poor current harmonics at the zero-crossing phase and near the zero-crossing phase, and at the peak phase, a fixed value fb is set, which can avoid the carrier frequency from becoming too high following a higher voltage value, thereby reducing the switching frequency of the switch tube at the peak phase and near the peak phase, reducing the heat dissipation of the switch tube, and thus controlling the heat of the PFC circuit in the overall working process; the two fixed frequency values can be set according to the characteristics of actual circuit components, and the actual current harmonic condition during circuit operation should be considered, and the corresponding first frequency value fc and second frequency value fb are set under the condition that the current harmonics near the zero-crossing phase and near the peak phase are small. It can be understood that the width of the first phase interval is determined by when the carrier frequency reaches the first frequency value fc, and only the phase interval corresponding to the range below the first frequency value fc near the zero-crossing phase is the first phase interval, and similarly, the width of the second phase interval is determined by when the carrier frequency reaches the second frequency value fb, and only the phase interval corresponding to the range below the second frequency value fb near the peak phase is the second phase interval. It is worth noting that if the frequency value corresponding to the peak phase is greater than or equal to the second frequency value fb, then the second phase interval converges to a degenerate interval, that is, the two endpoint values of the interval are the same, and the carrier frequency converges to the second frequency value fb, as shown in Figure 4

[0065] In the second half of the phase period (for example, π / 2 to π), it is axisymmetric to the first half of the period, and thus is also applicable to the carrier frequency set in the embodiment of the present application, that is, the range between θ4 and the zero-crossing phase is set as the first phase interval, the range between π / 2 and θ6 is set as the second phase interval, and the phase range between the first phase interval and the second phase interval is set as the third phase interval, wherein the frequency value of the fixed carrier frequency in the first phase interval is fc, and the frequency value of the fixed carrier frequency in the second phase interval is fb, and fb is greater than fc. The widths of the first phase interval and the second phase interval in the second half of the phase period are also determined in the same way as the first half of the phase period, and thus will not be repeated here.

[0066] Therefore, from the entire phase period (for example, 0 to π), the zero-crossing phase (0 or π) is located in the first phase interval, and the peak phase (π / 2) is located in the second phase interval. ​

[0067] It can be understood that the control method of the embodiment of the present application can be applied only to the first half of the phase period or only to the second half of the phase period, and the other half of the phase period without applying the control method of the embodiment of the present application can be set according to actual conditions.

[0068] When the periodically changing carrier frequency is obtained according to step S300, the controller determines the on-time of the switching device according to the input voltage, the output voltage, the input current and the carrier frequency according to step S400 to realize the PFC control of the PFC circuit, and the calculation is performed according to the boost ratio determined by the output voltage Uo and the input current Iin, which is not described in detail here. It can be understood that the PFC control of step S400 is directly controlled by the controller or instructed by the controller to control the PFC control module. In some embodiments, referring to Figure 3 , the PFC control module controls the output end of the PFC variable carrier frequency generation module, the output end of the input current sampling module and the output end of the output voltage sampling module, and the duty cycle of the switching device, i.e. the on-time of the switching device in a carrier frequency period, can be obtained by calculating according to the above parameters.

[0069] According to the above calculation formula of the nonlinearly changing carrier frequency, the maximum frequency value fa of the carrier frequency is in the third phase interval, and the maximum frequency value fa is the highest point of the frequency in the third phase interval, which limits the change rule of the carrier frequency in the third phase interval to some extent. In combination with the frequency value of the carrier frequency in the whole phase period, it can be known that the minimum frequency point of the carrier frequency in the whole period is the first frequency value fc, and the maximum frequency point is the maximum frequency value fa. Specifically, when the nonlinearly changing carrier frequency is used, the curve of the carrier frequency in the third phase interval changes according to the above calculation formula of the carrier frequency:

[0070]

[0071] The curve of the carrier frequency in the third phase interval is shown in Figure 4 or Figure 5 Taking the first half of the phase period (0 to π / 2) as an example, the carrier frequency first rises from the first frequency value fc in the third phase interval, rises to the maximum frequency value fa and then falls to the second frequency value fb. In the second half of the phase period (π / 2 to π), the same is true, and the first half of the phase period is axisymmetric, which is not repeated here.

[0072] When the frequency values at the two endpoints of the third phase interval are the first frequency value fc and the second frequency value fb respectively, it indicates that the carrier frequency is continuously changed when it is transitioned from the first phase interval to the third phase interval and from the third phase interval to the second phase interval, which realizes the smooth change of the carrier frequency and improves the fluency of the control.

[0073] In the above formula for calculating the carrier frequency with nonlinear variation, the ripple current is fixed at a preset ripple value or determined according to the input current. Specifically, the magnitude of the ripple current is related to the input current Iin. Obviously, during the operation of the PFC circuit, the input current Iin varies with time, and the controller will consume certain computing resources for continuously calculating the ripple current according to the input current Iin. In order to reduce the computing burden of the controller, the ripple current value can be set as needed. In this embodiment, two ways of setting the ripple current are provided. One is to directly set the preset ripple value as the value of the ripple current, which is equivalent to considering that the ripple current is constant during the entire PFC control process. The other is to set a plurality of ripple current values from small to large, corresponding to a plurality of current value ranges of the input current Iin, that is, the input current Iin is segmented according to the number of ripple current values, and each segment corresponds to a ripple current value.

[0074] In the above formula for calculating the carrier frequency with nonlinear variation, the inductance value is determined according to the inductance calibration value of the inductor or according to the input current. Specifically, similar to the ripple current, the magnitude of the inductance value is also related to the input current Iin. Obviously, during the operation of the PFC circuit, the input current Iin varies with time, and the inductance value also varies in real time with the input current Iin. In order to reduce the computing burden of the controller, the inductance value can be set as needed. In this embodiment, two ways of setting the inductance value are provided. One is to determine the inductance value according to the inductance calibration value of the inductor, so that the inductance value in the formula is equal to the inductance calibration value or the inductance calibration value multiplied by a proportional constant. At this time, the inductance value in the formula is equivalent to a fixed value. The other is to set a plurality of inductance values from small to large, corresponding to a plurality of current value ranges of the input current Iin, that is, the input current Iin is segmented according to the number of inductance values, and each segment corresponds to an inductance value.

[0075] It can be understood that, in addition to determining the ripple current or the inductance value according to the input current Iin, the ripple current or the inductance value can also be determined according to the input voltage Uin, the load power and other factors. Only the change amount related to the change of the input current Iin during the operation of the PFC circuit can be used as a reference factor for determining the ripple current or the inductance value.

[0076] In another embodiment, based on the above PFC circuit, referring to Figure 8 , the control method includes but is not limited to the following steps:

[0077] Step S500, acquiring the input voltage, output voltage and input current of the PFC circuit;

[0078] Step S600, determining the voltage phase according to the input voltage;

[0079] In step S700, the carrier frequency is set to a first frequency value in a first phase interval of the voltage phase period, the carrier frequency is set to a second frequency value in a second phase interval of the voltage phase period, and the carrier frequency is controlled to linearly change according to the input voltage in a third phase interval of the voltage phase period, wherein the first phase interval, the second phase interval and the third phase interval do not overlap with each other, a zero-crossing point phase of the voltage phase is in the first phase interval, a peak value phase of the voltage phase is in the second phase interval, and the second frequency value is greater than the first frequency value.

[0080] In step S800, the on-time of the switching device is determined according to the input voltage, the output voltage, the input current and the carrier frequency.

[0081] The difference between the present embodiment and the previous embodiment is that the carrier frequency is linearly changed in the third phase interval. The determination of the carrier frequency in the first phase interval and the second phase interval is the same as that in the previous embodiment, which will not be repeated here. Therefore, the case of the third phase interval will be described in detail below.

[0082] When the carrier frequency is linearly changed, the frequency value of the carrier frequency in the third phase interval has a linear relationship with the voltage phase. As shown in Figure 6 or Figure 7 Taking the first half phase period (0 to π / 2) as an example, since the maximum frequency value fa is the maximum frequency point, in the third phase interval, the carrier frequency increases linearly from the first frequency value fc following the voltage phase from the phase point θ1 to the phase point θ2, reaches the maximum frequency value fa, and the first frequency value fc to the maximum frequency value fa is a straight line. Similarly, the carrier frequency decreases linearly from the maximum frequency value fa following the voltage phase from the phase point θ2 to the phase point θ5, reaches the second frequency value fb, and the maximum frequency value fa to the second frequency value fb is a straight line. It can be understood that the phase point θ2 can be set as needed. In order to better fit the voltage change curve, the slope of the linear change of the carrier frequency is changed by adjusting the phase point θ2, thereby controlling the current harmonics. Similarly, in the second half phase period (π / 2 to π), θ3 is also set in the same way, and the slope of the linear change of the carrier frequency is set according to the distance between θ3 to θ6 and θ3 to θ4.

[0083] According to the above change rule of the carrier frequency, it can be known that the third phase interval includes a carrier frequency rising interval and a carrier frequency falling interval. In at least one continuous interval in the third phase interval, at least one carrier frequency rising interval and at least one carrier frequency falling interval are included. The joint of the carrier frequency rising interval and the carrier frequency falling interval is the frequency point corresponding to the maximum frequency value fa, for example, referring to Figure 6 or Figure 7It can be seen that, in a continuous interval of linearly changing carrier frequency, the carrier frequency is always first increased to the maximum frequency point and then decreased, which can better fit the change rule of the input voltage Uin, and the current ripple can be controlled in a smaller range.

[0084] It can be understood that, when the linearly changing carrier frequency is used, the carrier frequency does not need to be calculated in real time, because the first frequency value fc, the second frequency value fb and the maximum frequency value fa are fixed, and the phases corresponding to the frequency value points of the carrier frequency are also fixed, so the module of the PFC circuit can be simplified, compared with Figure 3 The ripple current and inductance value determination module can be removed, and the output end of the output voltage sampling module does not need to be connected to the PFC frequency generation module, as shown in Figure 9 .

[0085] It is worth noting that, according to the different characteristics of the components in the PFC circuit, the slope change range of the carrier frequency in the third phase interval is different, and in some phase range, after passing the maximum frequency point fa, the situation that Uin is greater than Uo may occur, at this time, the carrier frequency is negative, obviously, the negative number does not conform to the control rule of the actual product, at this time, the carrier frequency needs to be maintained in a positive value, that is, in those phase ranges, the carrier frequency is directly fixed as the second frequency value fb, therefore, in the nonlinearly changing carrier frequency, θ5 and θ6 can be artificially set to a certain extent.

[0086] The carrier frequency control method of the above two embodiments of the application is applied to the PFC circuit for PFC control, controls the carrier frequency to follow the periodic change of the voltage phase in the PFC circuit, and sets different frequency values for different voltage phases, fixes the lowest first frequency value fc near the zero-crossing phase of the voltage phase, fixes the slightly higher second frequency value fb near the peak phase of the voltage phase, and sets the highest maximum frequency value fa in the remaining phase interval, by using the reasonable distribution of the frequency values, the switching times of the switching tube are reduced, the interference of high-order harmonics is reduced, the heat of the switching tube in the working process is controlled, so that smaller inductor devices can be selected in the circuit design process, and the cost of anti-electromagnetic interference can also be reduced.

[0087] The embodiment of the application also provides a control device of a power factor correction circuit, which comprises at least one processor and a memory connected in communication with the at least one processor; the memory stores instructions capable of being executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the control method of the power factor correction circuit.

[0088] Reference Figure 10For example, the control processor 1001 and the memory 1002 in the control device 1000 can be connected by a bus. The memory 1002, as a kind of non-transitory computer readable storage medium, can be used to store non-transitory software programs and non-transitory computer executable programs. In addition, the memory 1002 can include a high-speed random access memory, and can also include a non-transitory memory, such as at least one disk memory, a flash memory device, or other non-transitory solid state memory device. In some embodiments, the memory 1002 can optionally include a memory remotely arranged relative to the control processor 1001, and these remote memories can be connected to the control device 1000 through a network. Examples of the above-mentioned network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0089] Those skilled in the art can understand that, Figure 10 The device structure shown in the above-mentioned figure does not constitute a limitation on the control device 1000, and can include more or fewer components than those shown in the figure, or combine certain components, or different component arrangements.

[0090] The embodiment of the present application performs the above-mentioned control method through the control device, sets different frequency values for the input voltage in different phase intervals, realizes periodic variable carrier frequency control, wherein a fixed lower first frequency value is set in the first phase interval, i.e. near the zero-crossing phase, and a slightly higher second frequency value than the first frequency value is set in the second phase interval, i.e. near the wave peak phase, and in the third phase interval, the carrier frequency is controlled to change nonlinearly according to the voltage, current and other parameters of the PFC circuit, or the carrier frequency is controlled to change linearly according to the input voltage, thereby reducing the switching times of the switching tube within the phase period of the input voltage, reducing the interference of high-order harmonics, and controlling the heat generation of the switching tube during the working process, reducing electromagnetic interference.

[0091] The embodiment of the present application also provides a circuit board comprising the above-mentioned control device. The above-mentioned control device is integrated on the circuit board, so that the circuit board has the functions of the above-mentioned control device, sets different frequency values for the input voltage in different phase intervals, realizes periodic variable carrier frequency control, wherein a fixed lower first frequency value is set in the first phase interval, i.e. near the zero-crossing phase, and a slightly higher second frequency value than the first frequency value is set in the second phase interval, i.e. near the wave peak phase, and in the third phase interval, the carrier frequency is controlled to change nonlinearly according to the voltage, current and other parameters of the PFC circuit, or the carrier frequency is controlled to change linearly according to the input voltage, thereby reducing the switching times of the switching tube within the phase period of the input voltage, reducing the interference of high-order harmonics, and controlling the heat generation of the switching tube during the working process, reducing electromagnetic interference.

[0092] This invention also provides an air conditioner, including the aforementioned circuit board. By incorporating this circuit board into the air conditioner to control it, the ripple current of the air conditioner can be kept within a small range, while reducing the heating of the switching transistors in the circuit. Specifically, different frequency values ​​are set for different phase intervals of the input voltage to achieve periodic variable carrier frequency control. In the first phase interval, near the zero-crossing phase, a lower first frequency value is fixed. In the second phase interval, near the peak phase, a slightly higher second frequency value is fixed. In the third phase interval, the carrier frequency is controlled to change nonlinearly based on parameters such as voltage and current of the PFC circuit, or linearly based on the input voltage. This reduces the number of switching operations of the switching transistors within the phase period of the input voltage, reduces interference from higher harmonics, controls the heating of the switching transistors during operation, and reduces electromagnetic interference.

[0093] A fifth aspect of the present invention provides a computer-readable storage medium storing computer-executable instructions that are executed by one or more control processors, for example, by... Figure 10 One of the control processors 1001 executes the method, which enables the one or more control processors to perform the overcurrent protection method in the above method embodiments, for example, to perform the method described above. Figure 2 Method steps S100 to S400 and Figure 8 The method steps S500 to S800.

[0094] 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 units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0095] As will be appreciated by one of ordinary skill in the art, all or some of the steps, systems, and techniques disclosed herein can be embodied in software, firmware, hardware, and / or suitable combination thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a micro-processing unit, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on computer readable media, which can comprise computer storage media (or non-transitory media), and communication media (or transitory media). As is well known to those of ordinary skill in the art, the term computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of 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 technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. Further, as is well known to those of ordinary skill in the art, communication media typically embodies computer readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave or other transport mechanism, and includes any information delivery media.

[0096] The above description is that of the preferred embodiments of the present application. Various equivalents substitutions and modifications can be conceived by those skilled in the art without departing from the spirit of the present application, and these equivalents substitutions and modifications are included in the scope of the claims.

Claims

1. A control method for a power factor correction (PFC) circuit, wherein the PFC circuit includes a boost module, the boost module including switching devices and inductors, and the control method includes: The input voltage, output voltage, input current, ripple current, and inductance value of the inductor of the PFC circuit are obtained, wherein the ripple current is a fixed value or determined according to the operating parameters of the PFC circuit, and the inductance value is a fixed value or determined according to the operating parameters of the PFC circuit. Determine the voltage phase based on the input voltage; Within the first phase interval of the voltage phase cycle, the carrier frequency is set to a first frequency value. Within the second phase interval of the voltage phase cycle, the carrier frequency is set to a second frequency value. Within the third phase interval of the voltage phase cycle, the carrier frequency is determined based on the input voltage, the output voltage, the input current, the ripple current, and the inductance value. The first phase interval, the second phase interval, and the third phase interval do not overlap. The zero-crossing phase of the voltage phase is located in the first phase interval, and the peak phase of the voltage phase is located in the second phase interval. The first phase interval, the second phase, and the third phase interval constitute a complete phase interval cycle. The second frequency value is greater than the first frequency value. The on-time of the switching device is determined based on the input voltage, the output voltage, the input current, and the carrier frequency.

2. The control method according to claim 1, characterized in that, The second phase interval is the degradation interval.

3. The control method according to claim 1, characterized in that, At the two endpoints of the third phase interval, the frequency values ​​of the carrier frequency are the first frequency value and the second frequency value, respectively.

4. The control method according to claim 1, characterized in that, The ripple current is fixed to a preset ripple value, or determined based on the input current.

5. The control method according to claim 1 or 4, characterized in that, The inductance value is determined based on the inductance rating of the inductor device, or based on the input current.

6. A control method for a power factor correction (PFC) circuit, wherein the PFC circuit includes a boost module, the boost module includes switching devices, and the control method includes: Obtain the input voltage, output voltage, and input current of the PFC circuit; Determine the voltage phase based on the input voltage; Within the first phase interval of the voltage phase cycle, the carrier frequency is set to a first frequency value. Within the second phase interval of the voltage phase cycle, the carrier frequency is set to a second frequency value. Within the third phase interval of the voltage phase cycle, the carrier frequency is controlled to change linearly according to the input voltage. The first phase interval, the second phase interval, and the third phase interval do not overlap. The zero-crossing phase of the voltage phase is located in the first phase interval, and the peak phase of the voltage phase is located in the second phase interval. The first phase interval, the second phase, and the third phase interval constitute a complete phase interval cycle. The second frequency value is greater than the first frequency value. The on-time of the switching device is determined based on the input voltage, the output voltage, the input current, and the carrier frequency.

7. The control method according to claim 6, characterized in that, The second phase interval is the degradation interval.

8. The control method according to claim 6, characterized in that, At the two endpoints of the third phase interval, the frequency values ​​of the carrier frequency are the first frequency value and the second frequency value, respectively.

9. The control method according to claim 6, characterized in that, The third phase interval includes a carrier frequency rising interval and a carrier frequency falling interval, and at least one continuous interval in the third phase interval contains at least one carrier frequency rising interval and at least one carrier frequency falling interval.

10. A control device for a power factor correction circuit, characterized in that, It includes at least one processor and a memory for communicatively connecting to the at least one processor; the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the control method as described in any one of claims 1 to 5 or to perform the control method as described in any one of claims 6 to 9.

11. A circuit board, characterized in that, Includes the control device as described in claim 10.

12. An air conditioner, characterized in that, Includes the circuit board as described in claim 11.

13. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions for causing a computer to perform the control method as described in any one of claims 1 to 5 or to perform the control method as described in any one of claims 6 to 9.

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