A control method, a controller, a chip and a circuit for a PFC circuit

Abstract

The present invention relates to the field of switching power supply control, and particularly to a control method, a controller, a chip and a circuit for a PFC circuit. The control method of the PFC circuit compensates the conduction time of the current cycle of the switching device of the PFC circuit by setting a THD conduction time compensation amount that varies with the instantaneous value of the input voltage. The THD conduction time compensation amount increases as the instantaneous value of the input voltage decreases, thereby improving the total harmonic distortion of the system caused by negative current. Further, to better reduce the influence of the negative current of the PFC circuit, the maximum conduction time compensation amount and the minimum compensation amount turning point threshold are adjusted in real time according to the peak value of the input voltage and the discontinuous time of the inductor current in the DCM mode of the PFC circuit to compensate the conduction time of the current cycle. At the same time, based on the current flowing through the EMI filter capacitor, the conduction time of the current cycle of the switching device of the PFC circuit is compensated to reduce the influence of the power factor reduction caused by the current flowing through the EMI filter capacitor.

Description

Technical Field

[0001] The present invention relates to the field of switching power supply control, and particularly to a control method, a controller, a chip and a circuit for a PFC circuit. Background Art

[0002] With the rapid development of power electronics technology, switching power supplies are widely used in electronic devices due to their small size, light weight and high efficiency. They are an indispensable power supply method for the rapid development of the current electronic information industry. However, these advantages are also accompanied by some negative effects, especially the grid harmonic pollution and increased reactive power caused by the distortion of non-sinusoidal current waveforms. Currently, according to industry standards, capacitive load electrical equipment with a power greater than 75W must be equipped with a power factor correction (PFC) circuit to correct the power factor of the electrical equipment, so that the alternating current line current follows the instantaneous change trajectory of the voltage waveform, and the current and voltage are in the same phase, making the system exhibit a pure resistive characteristic, thereby reducing the harmonic pollution and reactive power of the grid caused by the distortion of non-sinusoidal current waveforms and improving the overall efficiency of the power system.

[0003] As Figure 1 shown, the BOOST PFC circuit is a commonly used topology for improving the power factor of the power supply and reducing harmonic distortion. Due to its simple structure and convenient control, it has been widely used in medium and small power applications. As Figure 2d shown, in the CRM mode of the BOOST PFC circuit, the inductor current rises from zero to the peak value and then returns to zero in each switching cycle. This mode causes the switching frequency to change with the input voltage and load, and at the same time, the inductor current has a reverse part in each cycle, which helps to achieve soft switching ZVS (zero voltage switching), thereby reducing the switching loss of the switching device and improving the efficiency. However, in the CRM mode, the negative current part will cancel out a part of the positive current, resulting in the actual input current being less than the expected value, and the total input current waveform no longer presents a perfect sine wave, that is, a non-sine wave, and the total harmonic distortion (Total Harmonic Distortion, THD) of the system increases, resulting in a reduction in the power factor of the system. Summary of the Invention

[0004] In view of this, to solve the above technical problems, embodiments of the present invention provide a control method, a controller, a chip and a circuit for a PFC circuit.

[0005] The present application adopts the following technical solutions:

[0006] Obtain the basic conduction time of the switching device of the PFC circuit;

[0007] Obtain the instantaneous value of the input voltage, the maximum conduction time compensation amount, the minimum conduction time compensation amount, the minimum compensation amount turning point threshold, and the maximum compensation amount turning point threshold, where the minimum conduction time compensation amount is less than the maximum conduction time compensation amount, and the minimum compensation amount turning point threshold is greater than the maximum compensation amount turning point threshold;

[0008] When the instantaneous value of the input voltage is greater than the minimum compensation amount turning point threshold, the THD conduction time compensation amount is the minimum conduction time compensation amount; when the instantaneous value of the input voltage is less than the maximum compensation amount turning point threshold, the THD conduction time compensation amount is the maximum conduction time compensation amount; when the instantaneous value of the input voltage is greater than the maximum compensation amount turning point threshold and less than the minimum compensation amount turning point threshold, the THD conduction time compensation amount is inversely proportional to the instantaneous value of the input voltage;

[0009] Add the basic conduction time and the THD conduction time compensation amount to obtain the current cycle conduction time of the PFC circuit switching device;

[0010] Perform conduction time control on the PFC circuit switching device based on the current cycle conduction time.

[0011] Optionally, the control method of the PFC circuit further includes establishing a first inverse function relationship between the maximum conduction time compensation amount and the peak value of the input voltage, obtaining the peak value of the input voltage, and regulating the maximum conduction time compensation amount based on the peak value of the input voltage.

[0012] Optionally, the control method of the PFC circuit further includes establishing a second inverse function relationship between the minimum compensation amount turning point threshold and the peak value of the input voltage, obtaining the peak value of the input voltage, and regulating the minimum compensation amount turning point threshold based on the peak value of the input voltage.

[0013] Optionally, the control method of the PFC circuit further includes: when the PFC circuit is in the DCM mode, obtaining the discontinuous time of the inductor current in the DCM mode, and adjusting the maximum conduction time compensation amount based on the discontinuous time of the inductor current in the DCM mode, where when the discontinuous time of the inductor current increases, the maximum conduction time compensation amount decreases, and when the discontinuous time of the inductor current decreases, the maximum conduction time compensation amount increases.

[0014] Optionally, the control method of the PFC circuit further includes: when the PFC circuit is in the DCM mode, establishing a third inverse function relationship between the maximum conduction time compensation amount and the peak value of the input voltage, obtaining the peak value of the input voltage, and regulating the maximum conduction time compensation amount based on the peak value of the input voltage;

[0015] Obtain the discontinuous time of the inductor current in the DCM mode, and adjust the maximum conduction time compensation amount based on the discontinuous time of the inductor current in the DCM mode, where when the discontinuous time of the inductor current increases, the maximum conduction time compensation amount decreases, and when the discontinuous time of the inductor current decreases, the maximum conduction time compensation amount increases.

[0016] Optionally, the control method of the PFC circuit further includes: setting a sampling interval of the instantaneous value of the input voltage, and obtaining the corresponding instantaneous value of the input voltage based on the sampling interval;

[0017] Obtain the PF conduction time compensation amount based on the instantaneous value of the input voltage;

[0018] Add the PF conduction time compensation amount, the THD conduction time compensation amount, and the basic conduction time to obtain the current cycle conduction time of the switching device of the PFC circuit;

[0019] Perform conduction time control on the switching device of the PFC circuit based on the current cycle conduction time.

[0020] The present invention also provides a PFC circuit controller including the above control method of the PFC circuit, including:

[0021] An acquisition unit, a first adjustment compensation unit, and a conduction time control unit;

[0022] The acquisition unit is connected to the output end, the input end, the adjustment compensation unit, and the conduction time control unit of the PFC circuit; the adjustment compensation unit is connected to the conduction time control unit, and the conduction time control unit is connected to the switching device of the PFC circuit;

[0023] The acquisition unit is used to obtain the basic conduction time, the instantaneous value of the input voltage, the maximum conduction time compensation amount, the minimum conduction time compensation amount, the minimum compensation amount turning point threshold, and the maximum compensation amount turning point threshold of the switching device of the PFC circuit, the minimum conduction time compensation amount is less than the maximum conduction time compensation amount, and the minimum compensation amount turning point threshold is greater than the maximum compensation amount turning point threshold;

[0024] When the instantaneous value of the input voltage is greater than the minimum compensation amount turning point threshold, the THD conduction time compensation amount is the minimum conduction time compensation amount; when the instantaneous value of the input voltage is less than the maximum compensation amount turning point threshold, the THD conduction time compensation amount is the maximum conduction time compensation amount; when the instantaneous value of the input voltage is greater than the maximum compensation amount turning point threshold and less than the minimum compensation amount turning point threshold, the THD conduction time compensation amount is inversely proportional to the instantaneous value of the input voltage;

[0025] The conduction time control unit is configured to add the basic conduction time and the conduction time compensation amount to obtain the current cycle conduction time of the PFC circuit switching device, and perform conduction time control on the PFC circuit switching device based on the current cycle conduction time.

[0026] Optionally, the PFC circuit controller further includes a first voltage peak adjustment compensation unit, and the first voltage peak adjustment compensation unit is connected to the acquisition unit and the first adjustment compensation unit;

[0027] The first voltage peak adjustment compensation unit is configured to obtain the input voltage peak, establish a first inverse function relationship between the maximum conduction time compensation amount and the input voltage peak, and regulate the maximum conduction time compensation amount based on the input voltage peak; and / or establish a second inverse function relationship between the minimum compensation amount turning point threshold and the input voltage peak, and regulate the minimum compensation amount turning point threshold based on the input voltage peak.

[0028] Optionally, the PFC circuit controller further includes a first valley adjustment compensation unit, and the first valley adjustment compensation unit is connected to the acquisition unit and the first adjustment compensation unit;

[0029] The first valley adjustment compensation unit is configured to obtain the discontinuous time of the inductor current in the DCM mode, and adjust the maximum conduction time compensation amount based on the discontinuous time of the inductor current in the DCM mode. Wherein, when the discontinuous time of the inductor current increases, the maximum conduction time compensation amount decreases; when the discontinuous time of the inductor current decreases, the maximum conduction time compensation amount increases.

[0030] Optionally, the PFC circuit controller further includes a second voltage peak adjustment compensation unit and a second valley adjustment compensation unit. The second voltage peak adjustment compensation unit is connected to the acquisition unit and the second valley adjustment compensation unit, and the second valley adjustment compensation unit is connected to the first adjustment compensation unit;

[0031] When the PFC circuit is in the DCM mode, a first inverse function relationship between the maximum conduction time compensation amount and the input voltage peak is established. The second voltage peak adjustment compensation unit obtains the input voltage peak and regulates the maximum conduction time compensation amount based on the input voltage peak;

[0032] The second valley adjustment compensation unit obtains the discontinuous time of the inductor current in the DCM mode, and adjusts the maximum conduction time compensation amount based on the discontinuous time of the inductor current in the DCM mode. Wherein, when the discontinuous time of the inductor current increases, the maximum conduction time compensation amount decreases; when the discontinuous time of the inductor current decreases, the maximum conduction time compensation amount increases.

[0033] The present invention also provides a chip, including the above-mentioned PFC circuit controller.

[0034] The present invention also provides a circuit, including a PFC circuit and the above-mentioned PFC circuit controller.

[0035] In summary, the advantages and beneficial effects of the present invention are as follows:

[0036] The present invention provides a control method, a controller, a chip and a circuit for a PFC circuit. The control method of the PFC circuit includes: obtaining the basic conduction time of the switching device of the PFC circuit; obtaining the instantaneous value of the input voltage, the maximum conduction time compensation amount, the minimum conduction time compensation amount, the minimum compensation amount turning point threshold, and the maximum compensation amount turning point threshold, where the minimum conduction time compensation amount is less than the maximum conduction time compensation amount, and the minimum compensation amount turning point threshold is greater than the maximum compensation amount turning point threshold; when the instantaneous value of the input voltage is greater than the minimum compensation amount turning point threshold, the conduction time compensation amount is the minimum conduction time compensation amount; when the instantaneous value of the input voltage is less than the maximum compensation amount turning point threshold, the conduction time compensation amount is the maximum conduction time compensation amount; when the instantaneous value V ac of the input voltage is greater than the maximum compensation amount turning point threshold and less than the minimum compensation amount turning point threshold, the conduction time compensation amount is inversely proportional to the instantaneous value of the input voltage; adding the basic conduction time and the conduction time compensation amount to obtain the current cycle conduction time of the switching device of the PFC circuit.

[0037] By setting the THD conduction time compensation amount that changes with the instantaneous value of the input voltage to compensate the conduction time of the current cycle of the switching device of the PFC circuit, the THD conduction time compensation amount increases as the instantaneous value of the input voltage decreases, thereby improving the total harmonic distortion (THD) of the system caused by negative current. Further, to better reduce the influence of the negative current of the PFC circuit, the maximum conduction time compensation amount and the minimum compensation amount turning point threshold are adjusted in real time according to the peak value of the input voltage and the discontinuous time of the inductor current in the DCM mode of the PFC circuit to compensate the conduction time of the current cycle.

[0038] Meanwhile, based on the current flowing through the EMI filter capacitor, the conduction time of the current cycle of the switching device of the PFC circuit is compensated to avoid the input current distortion caused by the current flowing through the EMI filter capacitor. Description of the Drawings

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings, but they should fall within the protection scope of this application.

[0040] Figure 1 Schematic diagram of a BOOST PFC circuit;

[0041] Figure 2a Ideal waveform of inductor current in a BOOST PFC circuit under a single CRM operating mode;

[0042] Figure 2b Current path of inductor current during ZVS in a BOOST PFC circuit under a single CRM operating mode;

[0043] Figure 2c Actual waveform of inductor current in a BOOST PFC circuit under a single CRM operating mode;

[0044] Figure 2d Schematic diagram of the relationship between the source-drain voltage difference of the switching device, inductor current, and conduction time of the switching device in a BOOST PFC circuit under a single CRM operating mode;

[0045] Figure 3 Schematic diagram of the flow of a control method for a PFC circuit provided by an embodiment of the present invention;

[0046] Figure 4 Waveform schematic diagram of a control method for a PFC circuit provided by an embodiment of the present invention;

[0047] Figure 5 Schematic diagram of a control method for a PFC circuit provided by an embodiment of the present invention;

[0048] Figure 6 Schematic diagram of the flow for obtaining the basic conduction time of the switching device in a control method for a PFC circuit provided by an embodiment of the present invention;

[0049] Figure 7 Schematic diagram of the relationship between the maximum conduction time compensation amount, minimum compensation amount turning point threshold, and input voltage peak value in a control method for a PFC circuit provided by an embodiment of the present invention;

[0050] Figure 8 Schematic diagram of THD compensation in a control method for a PFC circuit provided by another embodiment of the present invention;

[0051] Figure 9Schematic diagram of THD compensation for a control method of a PFC circuit provided by another embodiment of the present invention;

[0052] Figure 10 Schematic diagram of THD compensation for a control method of a PFC circuit provided by another embodiment of the present invention;

[0053] Figure 11 Schematic diagram of the inductor current waveform for a control method of a PFC circuit provided by an embodiment of the present invention;

[0054] Figure 12 Schematic diagram of the relationship between the maximum compensation amount and the discontinuous time for a control method of a PFC circuit provided by an embodiment of the present invention;

[0055] Figure 13 Schematic diagram of adjusting the maximum conduction time compensation amount by the discontinuous time for a control method of a PFC circuit provided by an embodiment of the present invention;

[0056] Figure 14 Schematic diagram of adjusting the maximum conduction time compensation amount by the discontinuous time for a control method of a PFC circuit provided by another embodiment of the present invention;

[0057] Figure 15 Schematic diagram of adjusting the maximum conduction time compensation amount by the discontinuous time for a control method of a PFC circuit provided by another embodiment of the present invention;

[0058] Figure 16 Current schematic diagram of the BOOST PFC circuit;

[0059] Figure 17 Simplified schematic diagram of charging and discharging the capacitor in the BOOST PFC circuit;

[0060] Figure 18 Schematic diagram of PF compensation for a control method of a PFC circuit provided by another embodiment of the present invention;

[0061] Figure 19 Schematic diagram of PF compensation for a control method of a PFC circuit provided by another embodiment of the present invention;

[0062] Figure 20 Schematic diagram of a PFC circuit controller provided by an embodiment of the present invention;

[0063] Figure 21 Schematic diagram of a PFC circuit controller provided by another embodiment of the present invention;

[0064] Figure 22 Schematic diagram of a PFC circuit controller provided by another embodiment of the present invention;

[0065] Figure 23 Schematic diagram of a PFC circuit controller provided by another embodiment of the present invention;

[0066] Figure 24 Schematic diagram of the principle of a PFC circuit provided by an embodiment of the present invention. Detailed implementation manners

[0067] As Figure 2a is the ideal waveform of the inductor current in the BOOST PFC circuit in the CRM operating mode, where I L is the inductor current, I in is the input current. However, in actual applications, due to the influence of parasitic parameters and resonance, as Figure 2c shows, there is a negative current in the BOOST PFC circuit. Due to the existence of the negative current, the total input current waveform of the PFC circuit no longer presents a perfect sine wave, and the total harmonic distortion (THD) of the PFC circuit increases, resulting in a decrease in the system power factor. In Figure 2a 、 Figure 2c ,I L is the inductor current, I in is the input current, I in_idea is the ideal current of the system, I neg is the negative current. When the instantaneous value of the input voltage is smaller, the corresponding negative current is larger. Therefore, in order to suppress the negative current and improve the problem of the total harmonic distortion of the power supply, it is necessary to compensate the conduction time of the switching device of the PFC circuit.

[0068] For a better understanding of the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0069] It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0070] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms of "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. Electrical connection mainly represents the transmission of signals, including direct electrical connection and indirect electrical connection.

[0071] It should be understood that the term "and / or" used herein is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone.

[0072] The present invention provides a control method for a PFC, as Figures 3 to 5 shown, including:

[0073] Step S10, obtaining the basic conduction time of the switching device of the PFC circuit;

[0074] Step S20, obtaining the instantaneous value of the input voltage, the maximum conduction time compensation amount, the minimum conduction time compensation amount, the minimum compensation turning point threshold, and the maximum compensation turning point threshold, where the minimum conduction time compensation amount is less than the maximum conduction time compensation amount, and the minimum compensation turning point threshold is greater than the maximum compensation turning point threshold;

[0075] Step S30, when the instantaneous value of the input voltage is greater than the minimum compensation turning point threshold, the THD conduction time compensation amount is the minimum conduction time compensation amount; when the instantaneous value of the input voltage is less than the maximum compensation turning point threshold, the THD conduction time compensation amount is the maximum conduction time compensation amount; when the instantaneous value of the input voltage is greater than the maximum compensation turning point threshold and less than the minimum compensation turning point threshold, the THD conduction time compensation amount is inversely proportional to the instantaneous value of the input voltage;

[0076] Step S40, adding the basic conduction time and the THD conduction time compensation amount to obtain the current cycle conduction time of the switching device of the PFC circuit;

[0077] Step S50, controlling the conduction time of the switching device of the PFC circuit based on the current cycle conduction time.

[0078] Specifically, execute step S10 to obtain the basic conduction time T of the switching device of the PFC circuit on_base .

[0079] In an embodiment of the present invention, based on the bus voltage value V bus , the bus voltage reference value V bus_ref , the basic conduction time T of the switching device of the PFC circuit is obtained through calculation on_base .

[0080] In an embodiment of the present invention, as Figure 6 shown, the steps of obtaining the basic conduction time T of the switching device of the PFC circuit on_base include:

[0081] Step S111, obtaining the bus voltage value V bus , the bus voltage reference value V bus_ref , and performing voltage loop calculation based on the bus voltage value V bus , the bus voltage reference value V bus_ref to obtain the compensation amount ut ;

[0082] In the embodiment of the present invention, the bus voltage value V bus is the output voltage of the PFC circuit; the bus voltage reference value V bus_ref is the output target voltage of the PFC circuit.

[0083] In the embodiment of the present invention, the method for calculating the voltage loop includes one of a PI (Proportional Integral) controller and a PID (Proportional Integral Derivative) controller.

[0084] In other embodiments, the method for calculating the voltage loop adopts other suitable calculation methods.

[0085] Step S112: Obtain the peak value V of the input voltage of the PFC circuit acpk , and based on the peak value V of the input voltage acpk and the compensation amount u t , obtain the normalized compensation amount, and eliminate the influence of the input voltage fluctuation of the PFC circuit on the compensation amount u t ;

[0086] Adopt the normalized compensation amount to ensure that the compensation amount u t is not affected by the input voltage fluctuation of the PFC circuit, thereby improving the stability of the system.

[0087] In the embodiment of the present invention, based on the peak value V of the input voltage acpk and the compensation amount u t , the expression for obtaining the normalized compensation amount u' t is: the compensation amount u t divided by the square of the peak value V of the input voltage acpk , that is: u' t =u t / V 2 acpk , where u' t is the normalized compensation amount, u t is the compensation amount, and V acpk is the peak value of the input voltage.

[0088] Step S113: Multiply the normalized compensation amount by the coefficient K to obtain the basic conduction time T of the switching device of the PFC circuit on_base , where K is a constant.

[0089] Adopt the coefficient K to eliminate the influence of proportional conversion such as the sampling circuit ratio and digital quantization.

[0090] Execute step S20 to obtain the instantaneous value V of the input voltage ac, maximum conduction time compensation amount T on_thd_max , minimum conduction time compensation amount T on_thd_min , minimum compensation amount turning point threshold V ac_th_min , maximum compensation amount turning point threshold V ac_th_max , the minimum conduction time compensation amount T on_thd_min is less than the maximum conduction time compensation amount T on_thd_max , the minimum compensation amount turning point threshold V ac_th_min is greater than the maximum compensation amount turning point threshold V ac_th_max .

[0091] Set the maximum conduction time compensation amount T on_thd_max , minimum conduction time compensation amount T on_thd_min , minimum compensation amount turning point threshold, maximum compensation amount turning point threshold.

[0092] In the embodiment of the present invention, the maximum compensation amount turning point threshold is one-third of the maximum input voltage.

[0093] In other embodiments, the maximum compensation amount turning point threshold is 10V, or set according to actual requirements.

[0094] In the embodiment of the present invention, set the value of the maximum conduction time compensation amount T on_thd_max and the value of the minimum conduction time compensation amount T on_thd_min to be in a linear relationship.

[0095] Due to the junction capacitance C of the PFC circuit switching device oss During the charging and discharging process, it will discharge through the current path as shown in Figure 2b , thus generating a reverse inductor current (i.e., negative current) resulting in input current distortion. Therefore, it is also necessary to consider the junction capacitance C of the PFC circuit switching device oss to set the maximum conduction time compensation amount T on_thd_max . Specifically, in the present invention, the maximum conduction time compensation amount T on_thd_max includes being determined based on the junction capacitance C of the PFC circuit switching device oss , the PFC circuit inductor, the instantaneous input voltage V ac and the filter capacitor in front of the PFC circuit inductor; when the negative current is extremely small, the minimum conduction time compensation amount T on_thd_min is set to 0, that is, no compensation is required.

[0096] Execute step S30. When the instantaneous input voltage V ac is greater than the minimum compensation amount turning point threshold V ac_th_min , the THD conduction time compensation amount T on_thd is the minimum conduction time compensation amount Ton_thd_min ; when the instantaneous value V of the input voltage ac is less than the turning point threshold V of the maximum compensation amount ac_th_max , the conduction time compensation amount T of THD on_thd is the maximum conduction time compensation amount T on_thd_max ; when the instantaneous value V of the input voltage ac is greater than the turning point threshold V of the maximum compensation amount ac_th_max and less than the turning point threshold V of the minimum compensation amount ac_th_min , the conduction time compensation amount T of THD on_thd is inversely proportional to the instantaneous value V of the input voltage ac .

[0097] In the embodiment of the present invention, when the instantaneous value V of the input voltage ac is relatively small, a relatively large conduction time compensation amount of THD is set to increase the conduction time of the switching device of the PFC circuit, thereby reducing the proportion of negative current, and correspondingly reducing the influence of negative current on the PFC circuit.

[0098] In the embodiment of the present invention, the conduction time compensation amount T of THD on_thd and the instantaneous value V of the input voltage ac are a linear compensation relationship in which the conduction time compensation amount T of THD on_thd increases as the instantaneous value V of the input voltage ac decreases.

[0099] Since the peak value V of the input voltage acpk is different, the larger the peak value V of the input voltage acpk , the smaller the negative current of the PFC circuit; and, since the peak value V of the input voltage acpk is different, the corresponding voltage slope of the instantaneous value V of the input voltage ac is also different. The voltage slope of a small instantaneous value V of the input voltage ac is less than the voltage slope of a large instantaneous value V of the input voltage ac , and the conduction time compensation amount T of THD on_thd is a linear compensation presented according to the instantaneous value V of the input voltage ac . Therefore, when the peak value V of the input voltage acpk increases, the turning point threshold V of the minimum compensation amount is appropriately increased ac_th_min , so that the change in the conduction time compensation amount T of THD obtained on_thd is smaller, thereby realizing a smooth current waveform. Therefore, as Figure 7 shown, when the peak value V of the input voltage acpk is larger, the maximum conduction time compensation amount T is correspondingly reduced on_thd_max , and at the same time, the turning point threshold V of the minimum compensation amount is increasedac_th_min , when the peak value V of the input voltage acpk is smaller, the corresponding maximum conduction time compensation amount T is increased on_thd_max , and the minimum compensation amount turning point threshold V is reduced ac_th_min , thereby reducing the influence of negative current.

[0100] Furthermore, in order to better reduce the influence of negative current, the maximum conduction time compensation amount T on_thd_max and the minimum compensation amount turning point threshold V ac_th_min are adaptively adjusted based on the peak value V of the input voltage acpk .

[0101] In another embodiment of the present invention, as Figure 8 shown, adjusting the maximum conduction time compensation amount T based on the peak value V of the input voltage acpk includes: on_thd_max

[0102] Obtain the peak value V of the input voltage acpk ;

[0103] Based on the peak value V of the input voltage acpk establish a first inverse relationship between the maximum conduction time compensation amount T on_thd_max and the peak value V of the input voltage acpk , and the first inverse relationship regulates the maximum conduction time compensation amount T on_thd_max to obtain a second maximum conduction time compensation amount as the maximum conduction time compensation amount T on_thd_max .

[0104] In an embodiment of the present invention, the first inverse relationship is that the maximum conduction time compensation amount T on_thd_max becomes smaller as the peak value V of the input voltage acpk increases.

[0105] In another embodiment of the present invention, as Figure 9 shown, adjusting the minimum compensation amount turning point threshold V based on the peak value V of the input voltage acpk includes: ac_th_min

[0106] Obtain the peak value V of the input voltage acpk ;

[0107] Based on the peak value V of the input voltage acpk establish a second inverse relationship between the minimum compensation amount turning point threshold V ac_th_min and the peak value V of the input voltage acpk , and the second inverse relationship regulates the minimum compensation amount turning point threshold V ac_th_min ​​, obtain the second minimum compensation amount turning point threshold as the minimum compensation amount turning point threshold V ac_th_min .

[0108] In the embodiment of the present invention, the second inverse relationship is that the minimum compensation amount turning point threshold V ac_th_min decreases as the peak value V of the input voltage acpk increases.

[0109] In another embodiment of the present invention, as Figure 10 shown, based on the peak value V of the input voltage acpk simultaneously adjust the maximum conduction time compensation amount T on_thd_max and the minimum compensation amount turning point threshold V ac_th_min , the adjustment method is the same as that in the above embodiment and will not be elaborated.

[0110] In the embodiment of the present invention, set the acquisition times of the peak value V of the input voltage acpk within the power frequency period, so that the sampling period of the peak value V of the input voltage acpk is more flexible, providing more choices and optimization space for system design.

[0111] In the embodiment of the present invention, the frequency of obtaining the peak value V of the input voltage acpk is 10 μs.

[0112] The depth of the DCM mode is described by the discontinuous time T d length of the PFC circuit. As Figure 11 shown, the larger the discontinuous time T d , the deeper the DCM mode. The switching frequency of the switching device of the PFC circuit is usually lower, and the proportion of the negative current in the entire switching cycle becomes smaller. Therefore, it is necessary to reduce the corresponding compensation amount. Further, when the PFC circuit is in the DCM mode, adjust the maximum conduction time compensation amount T on_thd_max according to the depth of the DCM mode.

[0113] In the embodiment of the present invention, as Figures 12 to 13 shown, it further includes adjusting the maximum conduction time compensation amount T d based on the discontinuous time T on_thd_max of the inductor current of the PFC circuit, including:[[]]

[0114] When the PFC circuit is in the DCM mode, obtain the discontinuous time T d of the inductor current in the DCM mode, and adjust the maximum conduction time compensation amount T d based on the discontinuous time T on_thd_max of the inductor current in the DCM mode, and obtain the third maximum conduction time compensation amount as the maximum conduction time compensation amount Ton_thd_max wherein, when the discontinuous time T of the inductor current d increases, the third maximum conduction time compensation amount decreases, and when the discontinuous time T of the inductor current d decreases, the third maximum conduction time compensation amount increases.

[0115] In another embodiment of the present invention, as Figure 14 shown, based on the peak value V of the input voltage acpk and the discontinuous time T of the inductor current of the PFC circuit d adjust the maximum conduction time compensation amount T on_thd_max , including:

[0116] When the PFC circuit is in the DCM mode, obtain the peak value V of the input voltage acpk , and based on the peak value V of the input voltage acpk establish a third inverse function relationship between the maximum conduction time compensation amount T on_thd_max and the peak value V of the input voltage acpk , and the third inverse function relationship regulates the maximum conduction time compensation amount T on_thd_max to obtain a fourth maximum conduction time compensation amount;

[0117] Obtain the discontinuous time T of the inductor current in the DCM mode d , and based on the discontinuous time T of the inductor current in the DCM mode d adjust the fourth maximum conduction time compensation amount to obtain a fifth maximum conduction time compensation amount, wherein, when the discontinuous time T of the inductor current d increases, the fifth maximum conduction time compensation amount decreases, and when the discontinuous time T d decreases, the fifth maximum conduction time compensation amount increases.

[0118] In the embodiment of the present invention, the third inverse relationship is that the maximum conduction time compensation amount T on_thd_max becomes smaller as the peak value V of the input voltage acpk increases.

[0119] In another embodiment of the present invention, as Figure 15 shown, it further includes adjusting the minimum compensation amount turning point threshold V acpk based on the peak value V of the input voltage, and adjusting the maximum conduction time compensation amount T ac_th_min based on the peak value V of the input voltage and the discontinuous time T of the inductor current of the PFC circuit acpk d , and the adjustment method is the same as that of the above embodiment and will not be elaborated herein. on_thd_max

[0120] ​By setting the THD conduction time compensation amount that varies with the instantaneous value of the input voltage, the conduction time of the current cycle of the switching device in the PFC circuit is compensated. The THD conduction time compensation amount increases as the instantaneous value of the input voltage decreases, thereby improving the total harmonic distortion (THD) of the system caused by negative current. Further, to better reduce the influence of the negative current in the PFC circuit, the maximum conduction time compensation amount and the minimum compensation amount turning point threshold are adjusted in real time according to the peak value of the input voltage and the discontinuous time of the inductor current in the DCM mode of the PFC circuit to compensate the conduction time of the current cycle.

[0121] Execute step S40, and add the basic conduction time T on_base and the THD conduction time compensation amount T on_thd to obtain the conduction time T on of the current cycle of the switching device in the PFC circuit.

[0122] By adding the basic conduction time T on_base and the THD conduction time compensation amount T on_thd obtained to suppress negative current as the conduction time T on of the current cycle of the switching device in the PFC circuit.

[0123] Execute step S50, and perform conduction time control on the switching device in the PFC circuit based on the conduction time T on of the current cycle.

[0124] By adjusting the conduction time T on of the current cycle of the switching device in the PFC circuit, the problems of increased THD and reduced power factor caused by negative current are reduced.

[0125] To suppress electromagnetic interference, EMI filtering needs to be added at the front end of the PFC circuit. The EMI filtering includes an inductor and a capacitor. As Figure 16 shown, the presence of the capacitor in the EMI filter will cause the input current not to be sinusoidal and the power factor (PF) of the system to decrease. Therefore, the influence of the capacitor current in the EMI filtering on the PFC circuit needs to be considered.

[0126] As Figure 17 shown, the influence of the EMI filter on the PF can be simplified to the charging and discharging of the capacitor C in the EMI filter by the instantaneous value V ac of the input voltage. Since the instantaneous value V ac of the input voltage changes with time t, the expression of the instantaneous value V ac of the input voltage is:

[0127] , where Vacpk is the peak value of the input voltage, f ac is the frequency of the input AC voltage, and t is the time;

[0128] The instantaneous value V of the input voltage ac while changing with time t, the corresponding current i flowing through the capacitor C in the EMI filter c will also change with time. The current i c has the following expression:

[0129] , where C is the capacitance value of the simplified model of the input EMI filter capacitor. Therefore, in order to obtain a higher power factor, it is necessary to further compensate the conduction time of the switching device of the PFC circuit.

[0130] In another embodiment of the present invention, as Figure 18 shown, it further includes further compensating the conduction time of the switching device of the PFC circuit, including:

[0131] Obtain the PF conduction time compensation amount T on_pf ;

[0132] Add the PF conduction time compensation amount T on_pf to the current cycle conduction time to obtain the second current cycle conduction time T on_2 as the current cycle conduction time T of the switching device of the PFC circuit on ;

[0133] Control the conduction time of the switching device of the PFC circuit based on the current cycle conduction time.

[0134] In another embodiment of the present invention, as Figure 19 shown, the steps of obtaining the PF conduction time compensation amount T on_pf include:

[0135] Set the sampling interval T of the instantaneous value of the input voltage;

[0136] Obtain the corresponding instantaneous value of the input voltage based on the sampling interval T;

[0137] In the embodiment of the present invention, convert the obtained instantaneous value of the input voltage into a digital signal D ac n , where n is a positive integer;

[0138] Obtain the PF conduction time compensation amount based on the instantaneous value of the input voltage;

[0139] In the embodiment of the present invention, obtaining the PF conduction time compensation amount includes: ​

[0140] Calculate the deviation value of the digital signals D obtained corresponding to two adjacent samplings ac n , where the deviation value is D ac n -D ac n -1], where D ac n is the digital signal of the instantaneous value of the input voltage obtained at the nth time, and D ac n -1] is the digital signal of the instantaneous value of the input voltage obtained at the (n - 1)th time, and n is a positive integer;

[0141] Multiply the deviation value by the compensation coefficient k and divide it by the sampling interval T, and then perform filtering processing to obtain the PF conduction time compensation amount T on_pf , where the compensation coefficient k characterizes the size of the equivalent capacitance of the EMI filter, and k is a constant;

[0142] In other embodiments, the compensation coefficient k not only characterizes the size of the equivalent capacitance of the EMI filter, but also includes the ratio in the digital signal quantization process. Although the quantization ratio is relatively fixed, the value of the compensation coefficient k is mainly related to the input equivalent capacitance. When the input capacitance is larger, a larger value of the compensation coefficient k should be selected.

[0143] Perform filtering processing on the PF conduction time compensation amount T on_pf to smooth the signal and reduce the influence of noise.

[0144] The embodiment of the present invention also provides a PFC circuit controller including the above method, as Figure 20 shown, including:

[0145] An acquisition unit 100, a first adjustment and compensation unit 200, and a conduction time control unit 300;

[0146] The acquisition unit 100 is connected to the output end of the PFC circuit 400, the input end of the PFC circuit 400, the first adjustment and compensation unit 200, and the conduction time control unit 300; the first adjustment and compensation unit 200 is connected to the conduction time control unit 300, and the conduction time control unit 300 is connected to the PFC circuit switch device Q;

[0147] The acquisition unit 100 is used to acquire the basic conduction time, the instantaneous value of the input voltage, the maximum conduction time compensation amount, the minimum conduction time compensation amount, the minimum compensation amount turning point threshold, and the maximum compensation amount turning point threshold of the PFC circuit switch device Q, the minimum conduction time compensation amount is less than the maximum conduction time compensation amount, and the minimum compensation amount turning point threshold is greater than the maximum compensation amount turning point threshold; ​​​​​

[0148] The first adjustment and compensation unit 200 is configured such that when the instantaneous value of the input voltage is greater than the minimum compensation amount turning point threshold, the THD conduction time compensation amount is the minimum conduction time compensation amount; when the instantaneous value of the input voltage is less than the maximum compensation amount turning point threshold, the THD conduction time compensation amount is the maximum conduction time compensation amount; when the instantaneous value of the input voltage is greater than the maximum compensation amount turning point threshold and less than the minimum compensation amount turning point threshold, the THD conduction time compensation amount is inversely proportional to the instantaneous value of the input voltage.

[0149] The conduction time control unit 300 is configured to add the basic conduction time and the conduction time compensation amount to obtain the current cycle conduction time of the PFC circuit switching device, and perform conduction time control on the PFC circuit switching device based on the current cycle conduction time.

[0150] In another embodiment of the present invention, as Figure 21 shown, the PFC circuit controller further includes a first voltage peak adjustment and compensation unit 500, and the first voltage peak adjustment and compensation unit 500 is connected to the acquisition unit 100 and the first adjustment and compensation unit 200;

[0151] The first voltage peak adjustment and compensation unit 500 is configured to obtain the input voltage peak, establish a first inverse function relationship between the maximum conduction time compensation amount and the input voltage peak based on the input voltage peak, and regulate the maximum conduction time compensation amount with the first inverse function relationship to obtain a second maximum conduction time compensation amount as the maximum conduction time compensation amount; and / or establish a second inverse function relationship between the minimum compensation amount turning point threshold and the input voltage peak based on the input voltage peak, and regulate the minimum compensation amount turning point threshold with the second inverse function relationship to obtain a second minimum compensation amount turning point threshold as the minimum compensation amount turning point threshold.

[0152] In another embodiment of the present invention, as Figure 22 shown, the PFC circuit controller further includes a first valley adjustment and compensation unit 600, and the first valley adjustment and compensation unit 600 is connected to the acquisition unit 100 and the first adjustment and compensation unit 200;

[0153] The first valley adjustment and compensation unit 600 is configured to obtain the discontinuous time of the DCM mode inductor current, and adjust the maximum conduction time compensation amount based on the discontinuous time of the DCM mode inductor current to obtain a third maximum conduction time compensation amount as the maximum conduction time compensation amount, wherein when the discontinuous time of the inductor current increases, the third maximum conduction time compensation amount decreases, and when the discontinuous time of the inductor current decreases, the third maximum conduction time compensation amount increases.

[0154] In another embodiment of the present invention, as Figure 23 shown, the PFC circuit controller further includes a second voltage peak adjustment compensation unit 700 and a second valley adjustment compensation unit 800. The second voltage peak adjustment compensation unit 700 is connected to the acquisition unit 100 and the second valley adjustment compensation unit 800, and the second valley adjustment compensation unit 800 is connected to the first adjustment compensation unit 200;

[0155] When the PFC circuit is in the DCM mode, the second voltage peak adjustment compensation unit 700 acquires the input voltage peak value, establishes a third inverse function relationship between the maximum conduction time compensation amount and the input voltage peak value based on the input voltage peak value, and the third inverse function relationship regulates the maximum conduction time compensation amount to obtain a fourth maximum conduction time compensation amount;

[0156] The second valley adjustment compensation unit 800 acquires the discontinuous time of the inductor current in the DCM mode, adjusts the fourth maximum conduction time compensation amount based on the discontinuous time of the inductor current in the DCM mode, and obtains a fifth maximum conduction time compensation amount as the maximum conduction time compensation amount. Wherein, when the discontinuous time of the inductor current increases, the fifth maximum conduction time compensation amount decreases, and when the discontinuous time of the inductor current decreases, the fifth maximum conduction time compensation amount increases.

[0157] An embodiment of the present invention further provides a chip, including the above-mentioned PFC circuit controller.

[0158] An embodiment of the present invention further provides a circuit, as Figure 24 shown, including a PFC circuit and the above-mentioned PFC circuit controller;

[0159] One end of the first capacitor C1 is connected to one end of the first inductor L1 and the input voltage V ac One end of the first capacitor C1 is connected to one end of the second inductor L2 and the other end of the input voltage V ac The other end of the first capacitor C1 is connected to the anode of the first diode D1, the cathode of the fourth diode D4, the anode of the sixth diode D6, and the other end of the first inductor L1. The other end of the second capacitor C2 is connected to the anode of the third diode D3, the cathode of the second diode D2, the anode of the seventh diode D7, and the other end of the second inductor L2. The cathode of the first diode D1 is connected to the cathode of the third diode D3, one end of the third inductor L3, and one end of the third capacitor C3. The other end of the third inductor L3 is connected to the drain of the PFC circuit switching device Q and the anode of the fifth diode D5. The cathode of the fifth diode D5 is connected to one end of the fourth capacitor C4 and the resistor Rload One end is connected to one end of the first resistor R1. The anode of the fourth diode D4 is connected to the anode of the second diode D2, the other end of the third capacitor C3, one end of the resistor Rcs, the other end of the fourth capacitor, and the other end of the resistor R load The other end is connected to one end of the second resistor R2. The other end of the first resistor R1 is connected to the other end of the second resistor R2 and the VBU interface of the PFC circuit controller. The other end of the resistor Rcs is connected to the source of the PFC circuit switching device Q and the VCS interface of the PFC circuit controller. The cathode of the seventh diode D7 is connected to the cathode of the sixth diode D6 and one end of the resistor Rac1. The other end of the resistor Rac1 is connected to one end of the resistor Rac2 and the VAC interface of the PFC circuit controller; the other end of the resistor Rac2 is grounded, and the gate of the PFC circuit switching device Q is connected to the Q interface of the PFC circuit controller.

[0160] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0161] It should be understood that for those of ordinary skill in the art, improvements or changes can be made according to the above description, and all such improvements and changes should fall within the protection scope of the appended claims of this application.

Claims

1. A control method for a PFC circuit, characterized in that: include: Obtain the basic on-time of the PFC circuit switch device; Acquire an input voltage instantaneous value, a maximum on-time compensation amount, a minimum on-time compensation amount, a minimum compensation amount turning point threshold, and a maximum compensation amount turning point threshold, wherein the minimum on-time compensation amount is less than the maximum on-time compensation amount, and the minimum compensation amount turning point threshold is greater than the maximum compensation amount turning point threshold, wherein when the PFC circuit is in a DCM mode, acquire a discontinuous time of the inductor current in the DCM mode, and adjust the maximum on-time compensation amount based on the discontinuous time of the inductor current in the DCM mode, and when the discontinuous time of the inductor current increases, the maximum on-time compensation amount decreases, and when the discontinuous time of the inductor current decreases, the maximum on-time compensation amount increases; When the instantaneous value of the input voltage is greater than the minimum compensation turning point threshold, the THD on-time compensation amount is the minimum on-time compensation amount; when the instantaneous value of the input voltage is less than the maximum compensation turning point threshold, the THD on-time compensation amount is the maximum on-time compensation amount; when the instantaneous value of the input voltage is greater than the maximum compensation turning point threshold and less than the minimum compensation turning point threshold, the THD on-time compensation amount is inversely proportional to the instantaneous value of the input voltage; Adding the basic on-time and the THD on-time compensation amount to obtain the on-time of the current cycle of the PFC circuit switch device; The on-time of the PFC circuit switch device is controlled based on the on-time of the current cycle.

2. A method for controlling a PFC circuit according to claim 1, characterized in that: The method also includes establishing a first inverse functional relationship between the maximum on-time compensation amount and the input voltage peak value, obtaining the input voltage peak value, and adjusting the maximum on-time compensation amount based on the input voltage peak value.

3. The control method of a PFC circuit according to claim 1, characterized in that: The method also includes establishing a second inverse functional relationship between the minimum compensation turning point threshold and the input voltage peak value, obtaining the input voltage peak value, and adjusting the minimum compensation turning point threshold value based on the input voltage peak value.

4. The control method of a PFC circuit according to claim 1, characterized in that: It also includes establishing a third inverse functional relationship between the maximum on-time compensation amount and the input voltage peak when the PFC circuit is in the DCM mode, obtaining the input voltage peak, and adjusting the maximum on-time compensation amount based on the input voltage peak; The discontinuous time of the inductor current in the DCM mode is obtained, and the maximum on-time compensation amount is adjusted based on the discontinuous time of the inductor current in the DCM mode, wherein when the discontinuous time of the inductor current increases, the maximum on-time compensation amount decreases, and when the discontinuous time of the inductor current decreases, the maximum on-time compensation amount increases.

5. The control method of a PFC circuit according to claim 1, characterized in that: Also includes: Setting a sampling interval of an instantaneous value of an input voltage, and acquiring a corresponding instantaneous value of the input voltage based on the sampling interval; Obtaining a PF on-time compensation amount based on the instantaneous value of the input voltage; Add the PF on-time compensation amount, the THD on-time compensation amount, and the basic on-time to obtain the current cycle on-time of the PFC circuit switch device; The on-time of the PFC circuit switch device is controlled based on the on-time of the current cycle.

6. A PFC circuit controller for implementing the PFC circuit control method according to claim 1, characterized in that: include: An acquisition unit, a first adjustment and compensation unit, and a conduction time control unit; The acquisition unit is connected to the output end of the PFC circuit, the input end of the PFC circuit, the adjustment and compensation unit, and the on-time control unit; the adjustment and compensation unit is connected to the on-time control unit, and the on-time control unit is connected to the PFC circuit switch device; The acquisition unit is used to acquire the basic on-time of the PFC circuit switch device, the instantaneous value of the input voltage, the maximum on-time compensation amount, the minimum on-time compensation amount, the minimum compensation amount turning point threshold, and the maximum compensation amount turning point threshold, wherein the minimum on-time compensation amount is less than the maximum on-time compensation amount, and the minimum compensation amount turning point threshold is greater than the maximum compensation amount turning point threshold; The first adjustment and compensation unit is used for, when the instantaneous value of the input voltage is greater than the minimum compensation turning point threshold, the THD on-time compensation amount is the minimum on-time compensation amount; when the instantaneous value of the input voltage is less than the maximum compensation turning point threshold, the THD on-time compensation amount is the maximum on-time compensation amount; when the instantaneous value of the input voltage is greater than the maximum compensation turning point threshold and less than the minimum compensation turning point threshold, the THD on-time compensation amount is inversely proportional to the instantaneous value of the input voltage; The on-time control unit is used to add the basic on-time and the on-time compensation amount to obtain the current cycle on-time of the PFC circuit switch device, and control the on-time of the PFC circuit switch device based on the current cycle on-time.

7. A PFC circuit controller according to claim 6, characterized in that: The PFC circuit controller further includes a first voltage peak value adjustment and compensation unit, wherein the first voltage peak value adjustment and compensation unit is connected to the acquisition unit and the first adjustment and compensation unit; The first voltage peak value adjustment and compensation unit is used to obtain the input voltage peak value, establish a first inverse functional relationship between the maximum on-time compensation amount and the input voltage peak value, and adjust the maximum on-time compensation amount based on the input voltage peak value; And / or establish a second inverse functional relationship between the minimum compensation amount turning point threshold and the input voltage peak value, and adjust the minimum compensation amount turning point threshold based on the input voltage peak value.

8. A PFC circuit controller according to claim 6, characterized in that: The PFC circuit controller further includes a first valley adjustment and compensation unit, wherein the first valley adjustment and compensation unit is connected to the acquisition unit and the first adjustment and compensation unit; The first valley adjustment and compensation unit is used to obtain the discontinuous time of the inductor current in the DCM mode, and adjust the maximum on-time compensation amount based on the discontinuous time of the inductor current in the DCM mode, wherein when the discontinuous time of the inductor current increases, the maximum on-time compensation amount decreases, and when the discontinuous time of the inductor current decreases, the maximum on-time compensation amount increases.

9. A PFC circuit controller according to claim 6, characterized in that: The PFC circuit controller further includes a second voltage peak value adjustment and compensation unit and a second wave valley adjustment and compensation unit, wherein the second voltage peak value adjustment and compensation unit is connected to the acquisition unit and the second wave valley adjustment and compensation unit, and the second wave valley adjustment and compensation unit is connected to the first adjustment and compensation unit; When the PFC circuit is in the DCM mode, a first inverse functional relationship between the maximum on-time compensation amount and the input voltage peak is established, and the second voltage peak adjustment compensation unit obtains the input voltage peak, and adjusts the maximum on-time compensation amount based on the input voltage peak; The second valley adjustment and compensation unit obtains the discontinuous time of the inductor current in the DCM mode, and adjusts the maximum on-time compensation amount based on the discontinuous time of the inductor current in the DCM mode, wherein when the discontinuous time of the inductor current increases, the maximum on-time compensation amount decreases, and when the discontinuous time of the inductor current decreases, the maximum on-time compensation amount increases.

10. A chip, characterized in that: Comprising a PFC circuit controller as described in any one of claims 6 to 9.

11. A circuit, characterized in that: It comprises a PFC circuit and a PFC circuit controller as claimed in any one of claims 6 to 9.

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