PFC circuit and control method thereof, computer readable storage medium and refrigeration equipment

Abstract

The invention discloses a PFC circuit and a control method thereof, a computer readable storage medium and refrigeration equipment, and the control method comprises the steps: controlling the PFC circuit based on an interval period control mode, so as to determine the duty ratio information of the PFC circuit in each control period; and when it is determined that the PFC circuit works in the discontinuous current mode according to the duty ratio information, the carrier control frequency of a switching tube in the PFC circuit is improved, so that the PFC circuit works in the continuous current mode. According to the method, when it is determined that the PFC circuit works in a discontinuous current mode according to duty ratio information of a control period, the PFC circuit works in a continuous current mode by improving the carrier control frequency of a switching tube in the PFC circuit, so that inductive current distortion is reduced, power factors and harmonic waves during light-load operation are improved, and the efficiency of the PFC circuit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigeration equipment, and in particular to a control method of a PFC (Power Factor Correction) circuit, a computer-readable storage medium, a PFC circuit and a refrigeration equipment. Background Art

[0002] In the air-conditioning system, the PFC circuit is designed according to the full load power or maximum output power of the air-conditioning system, that is, the inductance, capacitance, inductor ripple current, PFC control frequency and other parameters of the PFC circuit are designed while meeting the maximum power requirement of the air-conditioning system.

[0003] This design method can ensure that the inductor current of the PFC circuit is in continuous mode in high-power situations. However, in actual operation, the air-conditioning system is not completely in full-load power operation state, and it will inevitably operate under light load conditions. When the load of the PFC circuit is light, the PFC circuit will enter the current discontinuous mode, resulting in serious inductor current distortion, large harmonics, and poor power factor. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, the first object of the present invention is to provide a control method for a PFC circuit, when it is determined that the PFC circuit operates in a discontinuous current mode according to the duty cycle information of the control period, by increasing the carrier control frequency of the switch tube in the PFC circuit, so that the PFC circuit operates in a continuous current mode, so as to reduce the inductor current distortion, improve the power factor and harmonics during light load operation, and improve the efficiency of the PFC circuit.

[0005] A second object of the present invention is to provide a computer-readable storage medium.

[0006] The third objective of the present invention is to provide a PFC circuit.

[0007] A fourth objective of the present invention is to provide a refrigeration device.

[0008] To achieve the above-mentioned purpose, a first aspect of the present invention provides a control method for a PFC circuit, the method comprising: controlling the PFC circuit based on an inter-cycle control method to determine the duty cycle information of the PFC circuit in each control cycle; when it is determined according to the duty cycle information that the PFC circuit operates in a current discontinuous mode, increasing the carrier control frequency of a switch tube in the PFC circuit to make the PFC circuit operate in a current continuous mode.

[0009] According to the control method of the PFC circuit of the embodiment of the present invention, the PFC circuit is controlled based on the inter-cycle control mode to determine the duty cycle information of the PFC circuit in each control cycle, and when it is determined that the PFC circuit works in the discontinuous current mode according to the duty cycle information, the carrier control frequency of the switch tube in the PFC circuit is increased to make the PFC circuit work in the continuous current mode. Therefore, when the method determines that the PFC circuit works in the discontinuous current mode according to the duty cycle information of the control cycle, the carrier control frequency of the switch tube in the PFC circuit is increased, so that the PFC circuit works in the continuous current mode, so as to reduce current distortion, improve the power factor and harmonics during light load operation, and improve the efficiency of the PFC circuit.

[0010] In addition, the control method of the PFC circuit according to the above embodiment of the present invention may also have the following additional technical features:

[0011] According to an embodiment of the present invention, determining duty cycle information of a PFC circuit in each control cycle includes: sampling an inductor current of the PFC circuit in adjacent first and second control cycles, respectively, wherein a sampling time point of the inductor current in the first control cycle is different from a sampling time point of the inductor current in the second control cycle; and determining the duty cycle information according to a current sampling value in the first control cycle and a current sampling value in the second control cycle.

[0012] According to one embodiment of the present invention, the duty cycle information is determined based on the current sampling value of the first control period and the current sampling value of the second control period, including: calculating the first duty cycle corresponding to the switching on of the switch tube based on the current sampling value of the first control period, and calculating the second duty cycle corresponding to the switching off of the switch tube based on the first duty cycle and the current sampling value of the second control period; determining the current intermittent duty cycle of the PFC circuit based on the first duty cycle and the second duty cycle.

[0013] According to an embodiment of the present invention, determining that the PFC circuit operates in the current discontinuous mode according to the duty cycle information includes: determining that the PFC circuit operates in the current discontinuous mode when the current discontinuous duty cycle is greater than or equal to a first preset value.

[0014] According to one embodiment of the present invention, a second duty cycle corresponding to the switch tube being turned off is calculated based on the first duty cycle and the current sampling value of the second control period, including: calculating the inductor peak current of the PFC circuit based on the first duty cycle; calculating the second duty cycle based on the first duty cycle, the inductor peak current and the current sampling value of the second control period.

[0015] According to one embodiment of the present invention, the inductor peak current is calculated by the following formula:

[0016]

[0017] Among them, I peak Indicates the inductor peak current, V m Sinθ represents the input voltage of the PFC circuit, D1 represents the first duty cycle, T s It represents the time of one control cycle, and L represents the inductance of the inductor in the PFC circuit.

[0018] According to one embodiment of the present invention, the second duty cycle is calculated by the following formula:

[0019]

[0020] Where D2 represents the second duty cycle, I peak represents the inductor peak current, D1 represents the first duty cycle, and I1 represents the current sampling value of the second control period.

[0021] According to one embodiment of the present invention, when the PFC circuit operates in a current continuous mode, the control method of the PFC circuit further includes: obtaining an average load current of the PFC circuit; and when the average load current exceeds a preset current threshold, reducing a carrier control frequency of a switch tube in the PFC circuit.

[0022] According to an embodiment of the present invention, when the average load current exceeds a preset current threshold, it is determined that the PFC circuit is in heavy load operation.

[0023] According to one embodiment of the present invention, obtaining the load average current of the PFC circuit includes: sampling the load current twice in each load control cycle to obtain a first load current sampling value and a second load current sampling value; determining the load average current according to the first load current sampling value and a pulse width when the load current is sampled for the first time, the second load current sampling value and a pulse width when the load current is sampled for the second time.

[0024] To achieve the above object, a second aspect of the present invention provides a computer-readable storage medium on which a control program of a PFC circuit is stored. When the control program of the PFC circuit is executed by a processor, the control method of the PFC circuit is implemented.

[0025] According to the computer-readable storage medium of the embodiment of the present invention, the control method of the PFC circuit is implemented when the control program of the PFC circuit is executed by the processor. Based on the control method of the PFC circuit, the carrier control frequency of the switch tube in the PFC circuit is increased to make the PFC circuit operate in a current continuous mode, so as to reduce current distortion, improve the power factor and harmonics during light load operation, and improve the efficiency of the PFC circuit.

[0026] To achieve the above-mentioned purpose, a third aspect of the present invention proposes a PFC circuit, including a memory, a processor, and a control program of the PFC circuit stored in the memory and executable on the processor. When the processor executes the control program of the PFC circuit, the control method of the PFC circuit is implemented.

[0027] According to the PFC circuit of the embodiment of the present invention, when the processor executes the control program of the PFC circuit, the control method of the PFC circuit is implemented. Based on the control method of the PFC circuit, by increasing the carrier control frequency of the switch tube in the PFC circuit, the PFC circuit is operated in a current continuous mode to reduce current distortion, improve the power factor and harmonics during light load operation, and improve the efficiency of the PFC circuit.

[0028] To achieve the above-mentioned purpose, a fourth aspect of the present invention proposes a refrigeration device, comprising: a PFC circuit; and a control unit, configured to control the PFC circuit based on a periodic control method to determine the duty cycle information of the PFC circuit in each control cycle, and when it is determined according to the duty cycle information that the PFC circuit operates in a current discontinuous mode, increase the carrier control frequency of the switch tube in the PFC circuit to make the PFC circuit operate in a current continuous mode.

[0029] According to the refrigeration equipment of the embodiment of the present invention, the control unit controls the PFC circuit based on the inter-cycle control mode to determine the duty cycle information of the PFC circuit in each control cycle, and when it is determined that the PFC circuit works in the discontinuous current mode according to the duty cycle information, the carrier control frequency of the switch tube in the PFC circuit is increased to make the PFC circuit work in the continuous current mode. Therefore, when the refrigeration equipment determines that the PFC circuit works in the discontinuous current mode according to the duty cycle information of the control cycle, the carrier control frequency of the switch tube in the PFC circuit is increased, so that the PFC circuit works in the continuous current mode, so as to reduce the input current distortion of the PFC circuit, improve the power factor and harmonics during light load operation, and improve the working efficiency of the refrigeration equipment.

[0030] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of a control method of a PFC circuit according to an embodiment of the present invention;

[0032] Figure 2 is an electric control topology diagram of an outdoor unit of an air conditioner according to an embodiment of the present invention;

[0033] Figure 3is a waveform diagram of an inductor current and a control signal according to an embodiment of the present invention;

[0034] Figure 4 is a block diagram of a control module according to an embodiment of the present invention;

[0035] Figure 5 is a circuit diagram of an inverter circuit according to an embodiment of the present invention;

[0036] Figure 6 A waveform diagram of a PWM (Pulse width modulation) signal and a load current in a load control cycle according to an embodiment of the present invention;

[0037] Figure 7 is a flow chart of a control method of a PFC circuit according to an embodiment of the present invention;

[0038] Figure 8 is a block diagram of a PFC circuit according to an embodiment of the present invention;

[0039] Fig. 9 FIG. 4 is a block diagram of a refrigeration device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0041] The following describes a control method for a PFC circuit, a computer-readable storage medium, a PFC circuit, and a refrigeration device provided in embodiments of the present invention with reference to the accompanying drawings.

[0042] Figure 1 FIG. 4 is a flow chart of a control method of a PFC circuit according to an embodiment of the present invention.

[0043] See also Figure 2 As shown, the electric control topology of the outdoor unit of the air conditioner includes a rectifier unit 10, a PFC circuit 20, a DC bus capacitor C and an inverter circuit 30. The rectifier unit 10 converts the AC voltage provided by the AC source AC into a DC voltage, the PFC circuit 20 sinusoids the input current, and the inverter circuit 30 converts the DC voltage filtered and output by the DC bus capacitor C into a three-phase AC power to supply the motor 40 of the compressor. Among them, the PFC circuit 20 can complete the power factor correction function on the one hand, and on the other hand, it can increase the output voltage to provide a stable voltage for the operation of the rear-end motor 40.

[0044] In the related art, the PFC circuit is designed according to the full load power or maximum output power of the system. For example, the inductance of the inductor L, the control frequency for controlling the switch tube S1, the capacity of the bus electrolytic capacitor C, the inductor ripple current, etc. are designed under the condition of meeting the maximum power demand. The inductor current of the PFC circuit designed according to the full load power or maximum output power of the system is in a continuous mode under a larger power situation. When the air conditioner is running under a light load, the load of the PFC circuit 20 is relatively light, and the inductor current will be in a discontinuous mode. In this mode, the input current is severely distorted, the harmonics are relatively large, and the power factor is relatively poor.

[0045] In order to solve the above technical problems, the present application proposes a control method for a PFC circuit. Figure 1 The control method of the present application is described in detail.

[0046] like Figure 1 As shown, the control method of the PFC circuit in the embodiment of the present invention may include the following steps:

[0047] S1, controlling the PFC circuit based on an inter-cycle control method to determine the duty cycle information of the PFC circuit in each control cycle;

[0048] S2, when it is determined according to the duty cycle information that the PFC circuit operates in the discontinuous current mode, increasing the carrier control frequency of the switch tube in the PFC circuit to make the PFC circuit operate in the continuous current mode.

[0049] The inter-cycle control method refers to controlling the PFC circuit with the working parameters obtained in non-adjacent control cycles. For example, taking the control cycles as the first control cycle, the second control cycle, the third control cycle, and the fourth control cycle, assuming that the control parameters are adjusted every three control cycles, the working parameters of the PFC circuit in the first control cycle are first obtained, and then the corresponding duty cycle d1 is determined according to the obtained working parameters, and then the duty cycle d1 is used as the duty cycle of the first control cycle, the second control cycle, and the third control cycle to control the on and off of the switch tube of the PFC circuit. The working parameters of the PFC circuit are obtained again in the fourth control cycle, and then the duty cycle d2 of the fourth control cycle is determined according to the re-acquired working parameters, and three control cycles are operated with the duty cycle d2, that is, the fourth control cycle, the fifth control cycle, and the sixth control cycle are operated with the duty cycle d2, and so on.

[0050] The duty cycle information may be a time parameter or a ratio, and is not specifically limited. For example, the duty cycle information may include the on-time length of the switch tube of the PFC circuit in each control cycle, the off-time length of the switch tube of the PFC circuit in each control cycle, the time length during which the inductor current of the PFC circuit is zero in each control cycle, or the ratio of the corresponding time length to the control cycle, i.e., the corresponding duty cycle.

[0051] In the process of controlling the PFC circuit by the inter-cycle control mode, the embodiment obtains the duty cycle information of the PFC circuit in each control cycle based on the acquired operating parameters of the PFC circuit, and further determines that the PFC circuit is operating in the discontinuous current mode according to the duty cycle information, and increases the carrier control frequency of the switch tube in the PFC circuit so that the PFC circuit operates in the continuous current mode, thereby improving the inductor current distortion that occurs when the PFC circuit load is light, improving harmonics, and improving the power factor. For example, when the operating parameter of the PFC circuit is the inductor current, the time length of the inductor current being 0 in each control cycle can be determined according to the inductor current of the PFC circuit acquired in real time, and then the duty cycle corresponding to the inductor current being 0 is determined according to the comparison between the time length of the inductor current being 0 and the control cycle, and when the duty cycle corresponding to the inductor current being 0 is greater than 0, it is determined that the PFC circuit is in the discontinuous current mode, otherwise, it is considered that the circuit is in the continuous current mode.

[0052] In one embodiment of the present invention, determining the duty cycle information of the PFC circuit in each control cycle includes: sampling the inductor current of the PFC circuit in adjacent first and second control cycles, respectively, wherein the sampling time point of the inductor current in the first control cycle is different from the sampling time point of the inductor current in the second control cycle; and determining the duty cycle information according to the current sampling value of the first control cycle and the current sampling value of the second control cycle.

[0053] Among them, the duty cycle information may include the switch tube on time length, switch tube off time length, inductor current zero time length, switch tube on corresponding duty cycle, switch tube on corresponding duty cycle, and inductor current zero corresponding duty cycle within a control cycle.

[0054] The sampling time point of the inductor current in the first control cycle is different from the sampling time point of the second control cycle, which means that if the switch tube is turned on during the sampling time point of the first control cycle, the switch tube is turned off during the sampling time point of the second control cycle; if the switch tube is turned off during the sampling time point of the first control cycle, the switch tube is turned on during the sampling time point of the second control cycle.

[0055] by Figure 3For example, the control signal is input to the control end of the switch tube, which is used to control the on and off of the switch tube, wherein the switch tube is on when the control signal is at a high level, and the switch tube is off when the control signal is at a low level. In the first control cycle, during the on-time period (t1-t3) of the switch tube, the sampling time point t2 is selected to sample the inductor current and obtain the current sampling value I1. In the second control cycle, during the off-time period (t5-t7) of the switch tube, the sampling time point t6 is selected to sample the inductor current and obtain the current sampling value I2. Then, the duty cycle information of I2 is determined according to the current sampling value I1 and the current sampling value.

[0056] In one embodiment of the present invention, the duty cycle information is determined according to the current sampling value I1 of the first control period and the current sampling value I2 of the second control period, including: calculating the first duty cycle D1 corresponding to the switching on of the switch tube according to the current sampling value I1 of the first control period, and calculating the second duty cycle D2 corresponding to the switching off of the switch tube according to the first duty cycle D1 and the current sampling value I2 of the second control period; determining the current intermittent duty cycle D3 of the PFC circuit according to the first duty cycle D1 and the second duty cycle D2.

[0057] exist Figure 2 The circuit topology shown in the figure also has Figure 4 The control module 50 shown in the figure is used to obtain the bus voltage sampling value, the bus current sampling value, and the input current (inductor current) sampling value and the input voltage sampling value of the PFC circuit, and output the control signal for driving the switch tube S1 in the PFC circuit 20 and the driving signal of the switch tube in the inverter circuit 30. The generation of the specific signal can be determined based on the received sampling value and the user set value.

[0058] For example, after the current sampling value I1 (the input current sampling value of the PFC circuit) of the first control period is obtained, it is input to the control module 50, and the control module 50 determines the first duty cycle D1 according to the current sampling value I1, the input voltage sampling value of the PFC circuit, and the bus voltage sampling value, and the control signal in the first control period and the second control period is output according to the first duty cycle D1, so as to control the switch tube of the PFC circuit to be turned on and off. Then, the time length corresponding to the inductor current being reduced to zero is calculated according to the first duty cycle D1 and the current sampling value I2 of the second control period, so as to calculate the ratio of the time length corresponding to the inductor current being reduced to zero to the control period, so as to obtain the second duty cycle D2 corresponding to the switch tube being turned off, and according to the formula 1=D1+D2+D3, the current intermittent duty cycle D3 of the PFC circuit is determined.

[0059] In one embodiment of the present invention, a second duty cycle D2 corresponding to the switch tube being turned off is calculated according to the first duty cycle D1 and the current sampling value I2 of the second control period, including: calculating the inductor peak current Ipeak of the PFC circuit according to the first duty cycle D1; calculating the second duty cycle D2 according to the first duty cycle D1, the inductor peak current Ipeak and the current sampling value I2 of the second control period.

[0060] In one embodiment of the present invention, the inductor peak current is calculated by the following formula:

[0061]

[0062] Among them, I peak Indicates the inductor peak current, V m Sinθ represents the input voltage of the PFC circuit, D1 represents the first duty cycle, T s It represents the time of one control cycle, and L represents the inductance of the inductor in the PFC circuit.

[0063] In one embodiment of the present invention, the second duty cycle is calculated by the following formula:

[0064]

[0065] Where D2 represents the second duty cycle, I peak represents the inductor peak current, D1 represents the first duty cycle, and I1 represents the current sampling value of the second control period.

[0066] Specifically, refer to Figure 3 As shown, the adjacent periods are the first control period (t1-t4), the second control period (t4-t8) and the third control period (t8-t11). In the PFC circuit control process, the PFC circuit is controlled by an alternate period control method, that is, the current sampling value I1 is read in the first control period, and the first duty cycle D1 required for controlling the switch tube is calculated, and the control signal is output according to the first duty cycle D1. In the second control period, the control signal maintains the first duty cycle D1 output. In the third control period, the sampling time point t9 is selected again during the switch tube opening period (t8-t10) to obtain the current sampling value I3, and the duty cycle D1' is determined according to the current sampling value I3. The control signal is output according to the duty cycle D1'. In the fourth control period, the control signal maintains the duty cycle D1' output, and the subsequent control periods are analogous, thereby realizing the control of the PFC circuit in an alternate period control method.

[0067] The following describes in detail the method for determining the second duty cycle D2 and the third duty cycle D3 by taking the first control period and the second control period as examples.

[0068] In the first control cycle, the first duty ratio D1, the input voltage of the PFC circuit, the time of the control cycle, and the inductance of the inductor in the PFC circuit are substituted into formula (1) to calculate the inductor peak current Ipeak. In addition, according to the first duty ratio D1, the time point corresponding to the inductor peak current Ipeak can be determined to be t3. At t3, the switch tube is controlled to be turned off, and the inductor current gradually decreases.

[0069] At the same time, the sampling time point of the inductor current is changed in the first control cycle, and the sampling time point is set at the midpoint of the switch tube of the PFC circuit being turned off, that is, the middle moment when the control signal is at a low level. Based on the known control cycle time and the first duty cycle D1, the time (t5-t8) when the control signal is at a low level in the second control cycle can be determined, and the middle moment t6 between t5-t8 is taken as the sampling time point of the second control cycle. In the second control cycle, the current sampling value I2 corresponding to the middle moment of the switch tube being turned off is obtained, and the sampling time point of the next control cycle (the third control cycle) is switched to the middle moment (t9) when the switch tube is turned on, so as to prepare for the sampling of the inductor current in the third control cycle. That is, in the third control cycle, the inductor current is sampled at time t9, and the first duty cycle D' is calculated based on the current sampling value I3 obtained at time t9, so as to determine the duration of the high level in the third control cycle, and control the switch to level at t10.

[0070] After obtaining the current sampling value I2 in the second control period, the first duty cycle D1, the inductor peak current Ipeak and the current sampling value I2 are substituted into formula (2) to calculate the second duty cycle D2 corresponding to the switch tube being turned off, and then the current discontinuous duty cycle D3 of the PFC circuit is determined by the formula D3=1-D1-D2. In addition, when the current sampling value I2=0 obtained in the second control period, the second duty cycle D2=(1-D1) / 2 is set.

[0071] It should be noted that, taking the control cycle time as T as an example, then D1 = (t3-t1) / T = (t5-t4) / T, D2 = (t8-t5) / T, D3 = (t8-t7) / T.

[0072] In one embodiment of the present invention, determining that the PFC circuit operates in the discontinuous current mode according to the duty cycle information includes: determining that the PFC circuit operates in the discontinuous current mode when the discontinuous current duty cycle D3 is greater than or equal to a first preset value. The first preset value can be set according to actual conditions.

[0073] That is to say, when the current discontinuous duty cycle D3 is greater than or equal to the first preset value, it is considered that the PFC circuit operates in the current discontinuous mode, the carrier control frequency of the switch tube in the PFC circuit is increased according to the preset step size, and the operating mode of the PFC circuit is judged in real time according to the current discontinuous duty cycle D3 determined in real time, until the current discontinuous duty cycle D3 is less than the first preset value, and it is determined that the PFC circuit operates in the current continuous mode, the current carrier control frequency is maintained to control the switch tube.

[0074] In one embodiment of the present invention, when the PFC circuit operates in a current continuous mode, the control method of the PFC circuit further includes: obtaining an average load current of the PFC circuit; and when the average load current exceeds a preset current threshold, reducing a carrier control frequency of a switch tube in the PFC circuit.

[0075] In one embodiment of the present invention, when the load average current exceeds a preset current threshold, it is determined that the PFC circuit is in heavy load operation. That is, the load size of the PFC circuit is judged by the load average current, and when the load average current exceeds the preset current threshold, it is considered that the PFC circuit is in heavy load mode.

[0076] Specifically, when the PFC circuit operates in the current continuous mode, it is determined whether the PFC circuit is in the heavy load mode based on the average load current of the PFC circuit. When the average load current exceeds the preset current threshold, it is determined that the PFC circuit load is large and is in the heavy load mode. Because the high carrier control frequency will increase the circuit loss in the heavy load mode, the carrier control frequency of the switch tube in the PFC circuit is reduced and adjusted to make the carrier control frequency of the switch tube in the PFC circuit return to the preset value to reduce the switch tube loss of the PFC circuit.

[0077] In addition, when it is determined that the average load current exceeds the preset current threshold, the carrier control frequency of the switch tube in the PFC circuit can be directly reduced to a preset value, or the carrier control frequency can be reduced step by step according to the preset frequency, and the load average current is monitored and judged in real time during the reduction process. When it is determined that the load average current is less than or equal to the preset current threshold, the carrier control frequency is stopped from being reduced, and the switch tube is controlled according to the current carrier control frequency. It can be understood that the preset value is the minimum carrier control frequency. If the average load current still exceeds the preset current threshold when the carrier control frequency is reduced to the preset value, the PFC circuit is controlled to stop working and an alarm signal is issued.

[0078] It should be noted that the above-mentioned PFC circuit operates in the current continuous mode, including: when the PFC circuit is running, the PFC circuit is determined to operate in the current continuous mode according to the duty cycle information, and when the PFC circuit operates in the light load mode, the carrier control frequency of the switch tube in the PFC circuit is increased to make the PFC circuit operate in the current continuous mode. The load average current is the average value of the load input current based on the power supply of the PFC circuit, and of course, the effective value of the load input current can also be used.

[0079] In one embodiment of the present invention, obtaining the load average current of the PFC circuit includes: sampling the load current twice in each load control cycle to obtain a first load current sampling value and a second load current sampling value; determining the load average current according to the first load current sampling value and a pulse width when the load current is sampled for the first time, the second load current sampling value and a pulse width when the load current is sampled for the second time.

[0080] Specifically, Figure 2 For example, the topology diagram of PFC circuit 20 is taken as an example. At this time, the load of PFC circuit 20 is motor 40, and the average load current is the average current output by inverter circuit 30, and the severity of the load is judged by this. For example, the bus current can be sampled in phase-shifted double sampling mode. The phase-shifted double sampling mode is to complete two current samplings in each motor load control cycle, thereby determining the two output currents of inverter circuit 30, and then determining the average load current. Figure 5 A method for determining the average load current is described in detail.

[0081] like Figure 5 As shown, the inverter circuit 30 is composed of 6 switch tubes (VT1, VT2, VT3, VT4, VT5, VT6). The control module realizes the output of three-phase electricity (iu, iv, iw) to drive the motor 40 by controlling the conduction and shutdown of the 6 switch tubes. A sampling resistor R2 is connected in series to the input end of the inverter circuit 30 to sample the bus current. When the control module uses a seven-segment PWM signal to control the inverter circuit 30, the waveform of the drive signal in a load control cycle (t21-t25) is as follows: Figure 6As shown, PWM-U represents the PWM signal, i.e., the driving signal, used to control the U-phase bridge arm, PWM-V represents the PWM signal, i.e., the driving signal, used to control the V-phase bridge arm, and PWM-W represents the PWM signal, i.e., the driving signal, used to control the W-phase bridge arm, wherein a high level indicates that the upper bridge arm switch tube of the corresponding bridge arm is turned on, and the lower bridge arm switch tube is turned off; a low level indicates that the upper bridge arm switch tube of the corresponding bridge arm is turned off, and the lower bridge arm switch tube is turned on. For example, taking PWM-U as an example, when PWM-U is at a high level, the switch tube VT1 is turned on, and the switch tube VT4 is turned off; when PWM-U is at a low level, the switch tube VT1 is turned off, and the switch tube VT4 is turned on.

[0082] When the phase-shifted double sampling mode is adopted, the bus current is sampled once between time t21-t22, i.e., the first load current sampling value idc1, and the bus current is sampled once between time t22-t23, i.e., the second load current sampling value idc2. The PWM pulse width at the first sampling is ts1=t22-t21, and the PWM pulse width at the second sampling is ts2=t23-t22, wherein the time of one load control cycle is Ts=t25-t21. Specifically, the load average current can be calculated by the following formula.

[0083]

[0084] Among them, I dc Indicates the average load current, T s Indicates the time of the load control cycle, i dc1 represents the first load current sampling value, t s1 Indicates the pulse width when the load current is sampled for the second time, i dc2 represents the second load current sampling value, t s2 Indicates the pulse width when the load current is sampled for the second time.

[0085] The control method of this embodiment adjusts the carrier control frequency when it is detected that the PFC circuit is in the discontinuous current mode, so that the PFC circuit operates in the continuous current mode. When the PFC circuit is in the continuous current mode, the load size is judged according to the average load current. When it is determined that the load connected to the PFC circuit is heavy, the carrier control frequency is adjusted to a preset value to reduce the switch tube loss.

[0086] As a specific embodiment of the present application, Figure 7 As shown, the control method of the PFC circuit may include the following steps:

[0087] S701, controlling the switch tube according to the carrier control frequency fc.

[0088] S702, sampling the inductor current of the PFC circuit in the first control period to determine a current sampling value I1 of the first control period.

[0089] S703, calculating a first duty cycle D1 corresponding to the switching on of the switch tube according to the current sampling value I1 of the first control period, and determining a current sampling time point of the second control period.

[0090] S704 , the first control period and the second control period are controlled by using the first duty cycle D1 , and a current sampling value I2 of the second control period is obtained.

[0091] S705 , calculating the inductor peak current Ipeak of the PFC circuit according to the first duty cycle D1 .

[0092] S706, calculating a second duty cycle D2 according to the first duty cycle D1, the inductor peak current Ipeak and the current sampling value I2 of the second control period.

[0093] S707 , determining a current discontinuous duty cycle D3 of the PFC circuit according to the first duty cycle D1 and the second duty cycle D2 .

[0094] S708, determining whether the current intermittent duty cycle D3 is greater than or equal to a first preset value Dmin. If so, executing step S709; if not, executing step S710.

[0095] S709, fc=fc+Δfc. Execute step S701.

[0096] S710, obtaining an average load current Idc of the PFC circuit.

[0097] S711, determine whether the load average current Idc is greater than a preset current threshold Idcmin. If so, execute step S701; if not, execute step S712.

[0098] S712, control fc=fc-Δfc. Execute step S710.

[0099] In summary, according to the control method of the PFC circuit of the embodiment of the present invention, the PFC circuit is controlled based on the inter-cycle control mode to determine the duty cycle information of the PFC circuit in each control cycle, and when it is determined that the PFC circuit works in the discontinuous current mode according to the duty cycle information, the carrier control frequency of the switch tube in the PFC circuit is increased to make the PFC circuit work in the continuous current mode. Therefore, when the method determines that the PFC circuit works in the discontinuous current mode according to the duty cycle information of the control cycle, the carrier control frequency of the switch tube in the PFC circuit is increased, so that the PFC circuit works in the continuous current mode, so as to reduce current distortion, improve the power factor and harmonics during light load operation, and improve the efficiency of the PFC circuit.

[0100] Corresponding to the above embodiment, the present invention also proposes a computer-readable storage medium.

[0101] The computer-readable storage medium of the embodiment of the present invention stores a control program of a PFC circuit, and the control program of the PFC circuit implements the above-mentioned control method of the PFC circuit when executed by a processor.

[0102] According to the computer-readable storage medium of the embodiment of the present invention, the control method of the PFC circuit is implemented when the control program of the PFC circuit is executed by the processor. Based on the control method of the PFC circuit, the carrier control frequency of the switch tube in the PFC circuit is increased to make the PFC circuit operate in the current continuous mode, so as to reduce the input current distortion, improve the power factor and harmonics during light load operation, and improve the efficiency of the PFC circuit.

[0103] Corresponding to the above embodiment, the present invention further proposes a PFC circuit.

[0104] like Figure 8 As shown, the PFC circuit 20 of the embodiment of the present invention includes a memory 21, a processor 22, and a control program of the PFC circuit stored in the memory 21 and executable on the processor 22. When the processor 22 executes the control program of the PFC circuit, the control method of the PFC circuit described above is implemented.

[0105] According to the PFC circuit of the embodiment of the present invention, when the processor executes the control program of the PFC circuit, the control method of the PFC circuit is implemented. Based on the control method of the PFC circuit, by increasing the carrier control frequency of the switch tube in the PFC circuit, the PFC circuit is operated in a current continuous mode to reduce current distortion, improve the power factor and harmonics during light load operation, and improve the efficiency of the PFC circuit.

[0106] Corresponding to the above embodiment, the present invention also proposes a refrigeration device.

[0107] like Fig. 9 As shown, the refrigeration device 100 according to the embodiment of the present invention includes: a PFC circuit 20 and a control unit 110 .

[0108] The control unit 110 is configured to control the PFC circuit 20 based on an inter-cycle control method to determine the duty cycle information of the PFC circuit 20 in each control cycle, and when it is determined according to the duty cycle information that the PFC circuit 20 operates in the current discontinuous mode, increase the carrier control frequency of the switch tube in the PFC circuit 20 to make the PFC circuit 20 operate in the current continuous mode.

[0109] According to the refrigeration equipment of the embodiment of the present invention, the control unit controls the PFC circuit based on the inter-cycle control mode to determine the duty cycle information of the PFC circuit in each control cycle, and when it is determined that the PFC circuit works in the discontinuous current mode according to the duty cycle information, the carrier control frequency of the switch tube in the PFC circuit is increased to make the PFC circuit work in the continuous current mode. Therefore, when the refrigeration equipment determines that the PFC circuit works in the discontinuous current mode according to the duty cycle information of the control cycle, the carrier control frequency of the switch tube in the PFC circuit is increased, so that the PFC circuit works in the continuous current mode, so as to reduce input current distortion, improve the power factor and harmonics during light load operation, and improve the working efficiency of the refrigeration equipment.

[0110] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0111] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0112] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0113] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0114] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0115] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A control method for a PFC circuit, characterized in that: The method comprises: Controlling the PFC circuit based on an alternate cycle control method to determine duty cycle information of the PFC circuit in each control cycle; When it is determined according to the duty cycle information that the PFC circuit operates in the discontinuous current mode, the carrier control frequency of the switch tube in the PFC circuit is increased so that the PFC circuit operates in the continuous current mode.

2. The method according to claim 1, characterized in that Determining duty cycle information of the PFC circuit in each control cycle, including: In a first control cycle and a second control cycle that are adjacent to each other, the inductor current of the PFC circuit is sampled respectively, wherein a sampling time point of the inductor current in the first control cycle is different from a sampling time point of the inductor current in the second control cycle; The duty cycle information is determined according to the current sampling value of the first control period and the current sampling value of the second control period.

3. The method according to claim 2, characterized in that Determining the duty cycle information according to the current sampling value of the first control period and the current sampling value of the second control period includes: Calculating a first duty cycle corresponding to turning on the switch tube according to the current sampling value of the first control period, and calculating a second duty cycle corresponding to turning off the switch tube according to the first duty cycle and the current sampling value of the second control period; A current discontinuous duty cycle of the PFC circuit is determined according to the first duty cycle and the second duty cycle.

4. The method according to claim 3, characterized in that Determining, according to the duty cycle information, that the PFC circuit operates in a current discontinuous mode includes: When the current discontinuous duty cycle is greater than or equal to a first preset value, it is determined that the PFC circuit operates in a current discontinuous mode.

5. The method according to claim 3, characterized in that: Calculating a second duty cycle corresponding to the switching-off of the switch tube according to the first duty cycle and the current sampling value of the second control period includes: Calculating the inductor peak current of the PFC circuit according to the first duty cycle; The second duty cycle is calculated according to the first duty cycle, the inductor peak current and the current sampling value of the second control period.

6. The method according to claim 5, characterized in that The inductor peak current is calculated by the following formula: Among them, I peak represents the inductor peak current, V m Sinθ represents the input voltage of the PFC circuit, D1 represents the first duty cycle, T s represents the time of one control cycle, and L represents the inductance of the inductor in the PFC circuit.

7. The method according to claim 5, characterized in that The second duty cycle is calculated by the following formula: Wherein, D2 represents the second duty cycle, I peak represents the inductor peak current, D1 represents the first duty cycle, and I1 represents the current sampling value of the second control period.

8. The method according to any one of claims 1 to 7, characterized in that In the case where the PFC circuit operates in a current continuous mode, the method further includes: Obtaining an average load current of the PFC circuit; When the load average current exceeds a preset current threshold, the carrier control frequency of the switch tube in the PFC circuit is reduced.

9. The method according to claim 8, characterized in that When the load average current exceeds a preset current threshold, it is determined that the PFC circuit is in heavy load operation.

10. The method according to claim 8, characterized in that Obtaining an average load current of the PFC circuit, including: Sampling the load current twice in each load control cycle to obtain a first load current sampling value and a second load current sampling value; The load average current is determined according to the first load current sampling value and the pulse width when the load current is sampled for the first time, and the second load current sampling value and the pulse width when the load current is sampled for the second time.

11. A computer-readable storage medium, characterized in that: A control program of a PFC circuit is stored thereon, and when the control program of the PFC circuit is executed by a processor, a control method of a PFC circuit according to any one of claims 1 to 10 is implemented.

12. A PFC circuit, characterized in that: The invention comprises a memory, a processor and a control program of a PFC circuit which is stored in the memory and can be run on the processor. When the processor executes the control program of the PFC circuit, the control method of the PFC circuit according to any one of claims 1 to 10 is implemented.

13. A refrigeration device, characterized in that: include: PFC circuit; The control unit is configured to control the PFC circuit based on an inter-cycle control method to determine the duty cycle information of the PFC circuit in each control cycle, and when it is determined according to the duty cycle information that the PFC circuit operates in a current discontinuous mode, increase the carrier control frequency of the switch tube in the PFC circuit to make the PFC circuit operate in a current continuous mode.

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