PFC circuit control method, controller, chip and circuit

Abstract

The invention relates to the field of switching power supply control, in particular to a PFC circuit control method, a controller, a chip and a circuit. According to the control method of the PFC circuit, the conduction time of a current period of a PFC circuit switching device is compensated by setting the THD conduction time compensation amount changing along with an input voltage instantaneous value, and the THD conduction time compensation amount is increased along with the reduction of the input voltage instantaneous value, so that the total harmonic distortion of a system caused by negative current is improved. Furthermore, in order 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 value are adjusted in real time according to the input voltage peak value and the interruption time of the inductive current of the PFC circuit in the DCM mode, and the conduction time of the current period is compensated. Meanwhile, on the basis of the current flowing through the EMI filter capacitor, the conduction time of the current period of the PFC circuit switching device is compensated, and the influence of power factor reduction caused by the current flowing through the EMI filter capacitor is reduced.

Description

Technical Field

[0001] The present invention relates to the field of switching power supply control, and in particular 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 equipment with the characteristics of small size, light weight and high efficiency. They are an indispensable power supply mode for the rapid development of today's electronic information industry. However, these advantages are also accompanied by some negative effects, especially the harmonic pollution and reactive power increase of the power grid caused by the distortion of non-sinusoidal current waveform. At present, according to industry standards, capacitive load electrical equipment with power greater than 75W must add power factor correction (PFC) circuits to correct the power factor of the electrical equipment, so that the AC line current tracks the instantaneous change trajectory of the voltage waveform, and keeps the current and voltage in phase so that the system presents a pure resistive characteristic, thereby reducing the harmonic pollution and reactive power of the power grid caused by the distortion of non-sinusoidal current waveform, and improving the overall efficiency of the power system.

[0003] like Figure 1 As shown in the figure, BOOST PFC circuit is a commonly used topology structure, which is used to improve the power factor of the power supply and reduce harmonic distortion. It is widely used in small and medium power occasions due to its simple structure and convenient control. Figure 2d As shown in the figure, in the CRM mode of the BOOST PFC circuit, the inductor current rises from zero to the peak value in each switching cycle, and then returns to zero. This mode makes the switching frequency change with the input voltage and load. 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 efficiency. However, in the CRM mode, the negative current part will offset part of the forward 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-sinusoidal wave, and the total harmonic distortion (THD) of the system increases, resulting in a decrease in the system power factor. Summary of the invention

[0004] In view of this, in order to solve the above technical problems, an embodiment of the present invention provides a control method, a controller, a chip and a circuit of a PFC circuit.

[0005] This application adopts the following technical solutions: Obtain the basic on-time of the PFC circuit switch device; Acquire an instantaneous value of an input voltage, 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; 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.

[0006] Optionally, the control method of the PFC circuit further 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 regulating the maximum on-time compensation amount based on the input voltage peak value.

[0007] Optionally, the control method of the PFC circuit further includes establishing a second inverse functional relationship between the minimum compensation amount turning point threshold and the input voltage peak value, obtaining the input voltage peak value, and adjusting the minimum compensation amount turning point threshold value based on the input voltage peak value.

[0008] Optionally, the control method of the PFC circuit also includes: when the PFC circuit is in the DCM mode, obtaining the intermittent time of the inductor current in the DCM mode, and adjusting the maximum on-time compensation amount based on the intermittent time of the inductor current in the DCM mode, wherein when the intermittent time of the inductor current increases, the maximum on-time compensation amount decreases, and when the intermittent time of the inductor current decreases, the maximum on-time compensation amount increases.

[0009] Optionally, the control method of the PFC circuit further includes: when the PFC circuit is in the DCM mode, establishing a third inverse functional relationship between the maximum on-time compensation amount and the input voltage peak value, obtaining the input voltage peak value, and regulating the maximum on-time compensation amount based on the input voltage peak value; 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.

[0010] Optionally, the control method of the PFC circuit further includes: setting a sampling interval of an instantaneous value of the 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.

[0011] The present invention further provides a PFC circuit controller including the above-mentioned PFC circuit control method, comprising: 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.

[0012] Optionally, the PFC circuit controller further includes a first voltage peak value adjustment and compensation unit, and 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 adjustment and compensation unit is used to obtain the input voltage peak, establish a first inverse functional relationship between the maximum on-time compensation amount and the input voltage peak, and adjust the maximum on-time compensation amount based on the input voltage peak; and / or establish a second inverse functional relationship between the minimum compensation amount turning point threshold and the input voltage peak, and adjust the minimum compensation amount turning point threshold based on the input voltage peak.

[0013] Optionally, the PFC circuit controller further includes a first valley adjustment and compensation unit, and 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.

[0014] Optionally, the PFC circuit controller further includes a second voltage peak adjustment and compensation unit and a second valley adjustment and compensation unit, the second voltage peak adjustment and compensation unit is connected to the acquisition unit and the second valley adjustment and compensation unit, and the second 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, 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.

[0015] The present invention also provides a chip, comprising the above-mentioned PFC circuit controller.

[0016] The present invention also provides a circuit, including a PFC circuit and the above-mentioned PFC circuit controller.

[0017] In summary, the advantages and beneficial effects of the present invention are: The present invention provides a control method, controller, chip and circuit of a PFC circuit. The control method of the PFC circuit includes: obtaining the basic on-time of a switch device of the PFC circuit; obtaining 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; when the instantaneous value of the input voltage is greater than the minimum compensation amount turning point threshold, the 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 amount turning point threshold, the on-time compensation amount is the maximum on-time compensation amount; when the instantaneous value of the input voltage is less than the maximum compensation amount turning point threshold, the on-time compensation amount is the maximum on-time compensation amount; when the instantaneous value of the input voltage is less than the maximum compensation amount turning point threshold, the on-time compensation amount is the maximum on-time compensation amount; ac When the on-time compensation value is greater than the maximum compensation turning point threshold and less than the minimum compensation turning point threshold, the on-time compensation value is inversely proportional to the instantaneous value of the input voltage; the basic on-time and the on-time compensation value are added to obtain the current cycle on-time of the PFC circuit switch device.

[0018] By setting the THD on-time compensation amount that changes with the instantaneous value of the input voltage, the on-time of the current cycle of the PFC circuit switch device is compensated. The THD on-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. Furthermore, in order to better reduce the impact of negative current in the PFC circuit, the maximum on-time compensation amount and the minimum compensation turning point threshold are adjusted in real time according to the input voltage peak value and the discontinuous time of the inductor current of the PFC circuit in the DCM mode to compensate for the on-time of the current cycle.

[0019] At the same time, based on the current flowing through the EMI filter capacitor, the on-time of the current cycle of the PFC circuit switch device is compensated to avoid input current distortion caused by the current flowing through the EMI filter capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work, but they should fall within the scope of protection of this application.

[0021] Figure 1 This is a schematic diagram of the BOOST PFC circuit; Figure 2a It is the ideal waveform of the inductor current of the BOOST PFC circuit in the single CRM working mode; Figure 2b It is the current path of the inductor current in the ZVS process of the BOOST PFC circuit in the single CRM working mode; Figure 2c The actual waveform of the inductor current of the BOOST PFC circuit in the single CRM working mode; Figure 2d A schematic diagram of the relationship between the source-drain voltage difference of the switch device, the inductor current, and the on-time of the switch device in the BOOST PFC circuit in a single CRM operating mode; Figure 3 A schematic diagram of a process of a PFC circuit control method provided by an embodiment of the present invention; Figure 4 A waveform diagram of a PFC circuit control method provided by an embodiment of the present invention; Figure 5 A schematic diagram of a PFC circuit control method provided by an embodiment of the present invention; Figure 6 A schematic diagram of a flow chart of obtaining a basic on-time of a switching device in a control method of a PFC circuit provided by an embodiment of the present invention; Figure 7 A schematic diagram of the relationship between the maximum on-time compensation amount, the minimum compensation amount turning point threshold and the input voltage peak value of a PFC circuit control method provided by an embodiment of the present invention; Figure 8 A schematic diagram of THD compensation of a PFC circuit control method provided by another embodiment of the present invention; Fig. 9 A schematic diagram of THD compensation of a PFC circuit control method provided by another embodiment of the present invention; Fig.10 A schematic diagram of THD compensation of a PFC circuit control method provided by another embodiment of the present invention; Fig.11 A schematic diagram of an inductor current waveform of a PFC circuit control method provided by an embodiment of the present invention; Fig.12 A schematic diagram of the relationship between the maximum compensation amount and the discontinuous time of a PFC circuit control method provided by an embodiment of the present invention; Fig.13 A schematic diagram of a maximum on-time compensation amount adjusted by the intermittent time of a PFC circuit control method provided by an embodiment of the present invention; Fig.14 A schematic diagram of a maximum on-time compensation amount adjusted by discontinuous time in a control method for a PFC circuit provided by another embodiment of the present invention; Fig.15A schematic diagram of a maximum on-time compensation amount adjusted by discontinuous time in a control method for a PFC circuit provided by another embodiment of the present invention; Fig.16 It is the current diagram of BOOST PFC circuit; Fig.17 This is a simplified schematic diagram of charging and discharging the capacitor for the BOOST PFC circuit; Fig.18 A schematic diagram of PF compensation of a PFC circuit control method provided by another embodiment of the present invention; Fig.19 A schematic diagram of PF compensation of a PFC circuit control method provided by another embodiment of the present invention; Fig. 20 A schematic diagram of a PFC circuit controller provided by an embodiment of the present invention; Fig.21 A schematic diagram of a PFC circuit controller provided by another embodiment of the present invention; Fig. 22 A schematic diagram of a PFC circuit controller provided by another embodiment of the present invention; Fig.23 A schematic diagram of a PFC circuit controller provided by another embodiment of the present invention; Fig.24 A schematic diagram of a PFC circuit principle provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] like Figure 2a is the ideal waveform of the inductor current in the BOOST PFC circuit in the CRM working mode, where I L is the inductor current, I in is the input current, but in practical applications, due to the influence of parasitic parameters and resonance, such as Figure 2c As shown in FIG. 1 , the BOOST PFC circuit has negative current. Due to the existence of 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. Figure 2a , Figure 2c middle, I L is the inductor current, I in is the input current, I in_idea is the ideal current of the system, I neg It is a 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 total harmonic distortion of the power supply, it is necessary to compensate the conduction time of the PFC circuit switching device.

[0023] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0024] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] 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 "a", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. Electrical connection mainly refers to the transmission of signals, including direct electrical connection and indirect electrical connection.

[0026] It should be understood that the term "and / or" used in this article is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0027] The present invention provides a PFC control method, such as Figure 3~Figure 5 As shown, including: Step S10, obtaining a basic on-time of a switch device of a PFC circuit; Step S20, obtaining an instantaneous value of an input voltage, 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; Step S30, 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; Step S40, adding the basic on-time and the THD on-time compensation amount to obtain the current cycle on-time of the PFC circuit switch device; Step S50, controlling the on-time of the PFC circuit switch device based on the on-time of the current cycle.

[0028] Specifically, step S10 is performed to obtain the basic on-time T of the PFC circuit switch device.on_base .

[0029] In the embodiment of the present invention, based on the bus voltage value V bus , bus voltage reference value V bus_ref The basic on-time T of the switching device of the PFC circuit is obtained by calculation on_base .

[0030] In the embodiment of the present invention, Figure 6 As shown, the basic on-time T of the switching device of the PFC circuit is obtained. on_base The steps include: Step S111, obtaining the bus voltage value V bus , bus voltage reference value V bus_ref , based on the bus voltage value V bus , bus voltage reference value V bus_ref Perform voltage loop calculation to obtain compensation u t ; 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.

[0031] In an embodiment of the present invention, the voltage loop calculation method includes one of a PI (proportional integral) controller and a PID (proportional integral differential) controller.

[0032] In other embodiments, the voltage loop calculation method adopts other suitable calculation methods.

[0033] Step S112, obtaining the input voltage peak value V of the PFC circuit acpk , based on the input voltage peak V acpk , the compensation amount u t , obtain the normalized compensation amount, and eliminate the effect of the input voltage fluctuation of the PFC circuit on the compensation amount u t The impact of Use normalized compensation to ensure that the compensation u t It is not affected by the input voltage fluctuation of the PFC circuit, thereby improving the stability of the system.

[0034] In the embodiment of the present invention, based on the input voltage peak value V acpk , the compensation amount u t , get the normalized compensation u' t The expression of the compensation amount u is: t Divide by the input voltage peak V acpk The square of u' t =ut / V 2 acpk , where u' t is the normalized compensation amount, u t is the compensation amount, V acpk is the peak value of the input voltage.

[0035] Step S113, multiplying the normalized compensation amount by the coefficient K to obtain the basic on-time T of the switch device of the PFC circuit on_base , where K is a constant.

[0036] The coefficient K is used to eliminate the influence of proportional conversion such as sampling circuit ratio and digital quantization.

[0037] Execute step S20 to obtain the instantaneous value of the input voltage V ac , Maximum on-time compensation T on_thd_max , minimum on-time compensation T on_thd_min , minimum compensation turning point threshold V ac_th_min , Maximum compensation turning point threshold V ac_th_max , the minimum on-time compensation amount T on_thd_min Less than the maximum on-time compensation value T on_thd_max , the minimum compensation turning point threshold V ac_th_min Greater than the maximum compensation turning point threshold V ac_th_max .

[0038] The maximum on-time compensation value T is set according to actual needs. on_thd_max , minimum on-time compensation value T on_thd_min , minimum compensation turning point threshold, maximum compensation turning point threshold.

[0039] In an embodiment of the present invention, the maximum compensation amount turning point threshold is one third of the maximum value of the input voltage.

[0040] In other embodiments, the maximum compensation amount turning point threshold is 10V, or is set according to actual needs.

[0041] In the embodiment of the present invention, the maximum on-time compensation value T is set on_thd_max The value of and the minimum on-time compensation value T on_thd_min There is a linear relationship between the values ​​of .

[0042] Since the junction capacitance C of the PFC circuit switch device oss During the charging and discharging process, Figure 2b The current path shown is used to discharge, thereby generating a reverse inductor current (i.e., negative current) that causes input current distortion. Therefore, the junction capacitance C of the PFC circuit switch device also needs to be considered. ossSet the maximum on-time compensation value T on_thd_max Specifically, in the present invention, the maximum on-time compensation amount T on_thd_max Including the junction capacitance C of the PFC circuit switching device oss , PFC circuit inductance, input voltage instantaneous value V ac and the filter capacitor before the PFC circuit inductor; when the negative current is extremely small, the minimum on-time compensation amount T on_thd_min Set to 0 to eliminate compensation.

[0043] Step S30 is executed, when the instantaneous value of the input voltage V ac Greater than the minimum compensation turning point threshold V ac_th_min When THD on-time compensation value T on_thd is the minimum on-time compensation value T on_thd_min ; When the instantaneous value of the input voltage V ac Less than the maximum compensation turning point threshold V ac_th_max When THD on-time compensation value T on_thd is the maximum on-time compensation value T on_thd_max ; When the instantaneous value of the input voltage V ac Greater than the maximum compensation turning point threshold V ac_th_max , which is less than the minimum compensation turning point threshold V ac_th_min When THD on-time compensation value T on_thd With the instantaneous value of the input voltage V ac Inversely proportional.

[0044] In the embodiment of the present invention, the instantaneous value of the input voltage V ac When it is small, a relatively large THD on-time compensation amount is set to increase the on-time of the PFC circuit switch device, thereby reducing the proportion of negative current and correspondingly reducing the impact of negative current on the PFC circuit.

[0045] In the embodiment of the present invention, the THD on-time compensation value T on_thd and the instantaneous value of the input voltage V ac is the THD on-time compensation amount T on_thd As the input voltage instantaneous value V ac The linear compensation relationship between the decrease and increase of .

[0046] Since the input voltage peak V acpk Different, the input voltage peak V acpk The larger the value, the smaller the negative current of the PFC circuit will be; and the input voltage peak value V acpk Different, the corresponding input voltage instantaneous value V acThe voltage slope is also different. The small input voltage instantaneous value V ac The voltage slope is less than the maximum input voltage instantaneous value V ac The voltage slope, and the THD on-time compensation amount T on_thd According to the instantaneous value of input voltage V ac presents a linear compensation, so when the input voltage peak V acpk When it increases, appropriately increase the minimum compensation turning point threshold V ac_th_min , so that the THD on-time compensation value T on_thd The smaller the change, the smoother the current waveform can be achieved. Figure 7 As shown, at the input voltage peak V acpk The larger the value, the smaller the maximum on-time compensation value T. on_thd_max , while increasing the minimum compensation turning point threshold V ac_th_min , at the input voltage peak V acpk The smaller the time, the corresponding increase in the maximum on-time compensation T on_thd_max , reduce the minimum compensation turning point threshold V ac_th_min , thereby reducing the impact of negative current.

[0047] Furthermore, in order to better reduce the impact of negative current, the maximum on-time compensation value T on_thd_max , the minimum compensation turning point threshold V ac_th_min Based on the input voltage peak V acpk Make adaptive adjustments.

[0048] In another embodiment of the present invention, Figure 8 As shown, based on the input voltage peak V acpk Adjust the maximum on-time compensation value T on_thd_max ,include: Get the input voltage peak value V acpk ; Based on the input voltage peak V acpk Establish the maximum on-time compensation value T on_thd_max and the input voltage peak V acpk The first inverse relationship regulates the maximum on-time compensation amount T on_thd_max , obtain the second maximum on-time compensation amount as the maximum on-time compensation amount T on_thd_max .

[0049] In the embodiment of the present invention, the first inverse relationship is the maximum on-time compensation amount T on_thd_max As the input voltage peak V acpk The smaller it is, the larger the value is.

[0050] In another embodiment of the present invention, Fig. 9 As shown, based on the input voltage peak V acpk Adjust the minimum compensation turning point threshold V ac_th_min ,include: Get the input voltage peak value V acpk ; Based on the input voltage peak V acpk Establish the minimum compensation turning point threshold V ac_th_min and the input voltage peak V acpk The second inverse relationship between the minimum compensation amount and the turning point threshold V ac_th_min , obtain the second minimum compensation turning point threshold as the minimum compensation turning point threshold V ac_th_min .

[0051] In the embodiment of the present invention, the second inverse relationship is the minimum compensation turning point threshold V ac_th_min As the input voltage peak V acpk The smaller it is, the larger the value is.

[0052] In another embodiment of the present invention, Fig.10 As shown, based on the input voltage peak V acpk At the same time, the maximum on-time compensation value T is adjusted on_thd_max and the minimum compensation turning point threshold V ac_th_min The adjustment method is the same as that in the above embodiment and will not be described in detail.

[0053] In the embodiment of the present invention, the input voltage peak value V acpk The number of acquisitions within the power frequency cycle makes the input voltage peak value V acpk The sampling period is more flexible, providing more options and optimization space for system design.

[0054] In an embodiment of the present invention, the input voltage peak value V is obtained. acpk The frequency is 10μs.

[0055] The depth of DCM mode adopts the discontinuous time T of the PFC circuit. d Length description, such as Fig.11 As shown, the intermittent time T d The larger the value, the deeper the DCM mode, the lower the switching frequency of the PFC circuit switching device, the smaller the proportion of negative current in the entire switching cycle, and the corresponding compensation amount needs to be reduced. Therefore, further, when the PFC circuit is in the DCM mode, the maximum on-time compensation amount T is adjusted according to the depth of the DCM mode. on_thd_max Make adjustments.

[0056] In the embodiment of the present invention, Figure 12~Figure 13 As shown, it also includes a discontinuous time T based on the inductor current of the PFC circuit d Adjust the maximum on-time compensation value T on_thd_max ,include: When the PFC circuit is in DCM mode, the discontinuous time T of the inductor current in DCM mode is obtained. d , based on the DCM mode inductor current discontinuity time T d Adjust the maximum on-time compensation value T on_thd_max , obtain the third maximum on-time compensation amount as the maximum on-time compensation amount T on_thd_max , where, when the discontinuous time of the inductor current is T d When the intermittent time T of the inductor current increases, the third maximum on-time compensation amount decreases. d When it decreases, the third maximum on-time compensation amount increases.

[0057] In another embodiment of the present invention, Fig.14 As shown, based on the input voltage peak V acpk and the PFC circuit inductor current discontinuity time T d Adjust the maximum on-time compensation value T on_thd_max ,include: When the PFC circuit is in DCM mode, the input voltage peak value V acpk , based on the input voltage peak V acpk Establish the maximum on-time compensation value T on_thd_max and the input voltage peak V acpk The third inverse function relationship of the maximum on-time compensation value T on_thd_max , obtaining a fourth maximum on-time compensation amount; Get the discontinuous time T of the inductor current in DCM mode d , based on the DCM mode inductor current discontinuity time T d Adjust the fourth maximum on-time compensation amount to obtain a fifth maximum on-time compensation amount, wherein when the intermittent time T of the inductor current is d When the intermittent time T d When it decreases, the fifth maximum on-time compensation amount increases.

[0058] In the embodiment of the present invention, the third inverse relationship is the maximum on-time compensation amount T on_thd_max As the input voltage peak V acpk The smaller it is, the larger the value is.

[0059] In another embodiment of the present invention, Fig.15 As shown, it also includes a peak value based on the input voltage V acpk Adjust the minimum compensation turning point threshold V ac_th_min , and based on the input voltage peak V acpk and the PFC circuit inductor current discontinuity time T d Adjust the maximum on-time compensation value T on_thd_max The adjustment method is the same as that in the above embodiment and will not be described in detail.

[0060] By setting the THD on-time compensation amount that changes with the instantaneous value of the input voltage, the on-time of the current cycle of the PFC circuit switch device is compensated. The THD on-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. Furthermore, in order to better reduce the impact of negative current in the PFC circuit, the maximum on-time compensation amount and the minimum compensation turning point threshold are adjusted in real time according to the input voltage peak value and the discontinuous time of the inductor current of the PFC circuit in the DCM mode to compensate for the on-time of the current cycle.

[0061] Execute step S40, set the basic on-time T on_base and the THD on-time compensation amount T on_thd Add together to obtain the current cycle conduction time T of the PFC circuit switch device. on .

[0062] By setting the basic on-time T on_base and obtain the THD on-time compensation value T of the PFC circuit switch device in order to suppress the negative current on_thd Add together to form the current cycle conduction time T of the PFC circuit switch device. on .

[0063] Execute step S50, based on the current cycle on time T on The on-time of the PFC circuit switch device is controlled.

[0064] By adjusting the current cycle on time T of the PFC circuit switch device on , reducing the problem of increased THD and reduced power factor caused by negative current.

[0065] In order to suppress electromagnetic interference, EMI filtering needs to be added to the front end of the PFC circuit. The EMI filtering includes inductors and capacitors, such as Fig.16As shown in the figure, the presence of capacitors in the EMI filter will cause the input current to no longer be sinusoidal, and the power factor (PF) of the system will decrease. Therefore, it is necessary to consider the impact of capacitor current in EMI filtering on the PFC circuit.

[0066] like Fig.17 As shown in Figure 2, the effect of the EMI filter on PF can be simplified to the instantaneous value of the input voltage V ac The capacitor C in the EMI filter is charged and discharged. Since the instantaneous value of the input voltage V ac As time t changes, the instantaneous value of the input voltage V ac The expression is: , where V acpk is the input voltage peak value, f ac is the input AC voltage frequency, t is the time; The instantaneous value of the input voltage V ac As time t changes, the corresponding current i flowing through the capacitor C in the EMI filter c It will also change with time, the current i c The expression is: , where C is the capacitance of the simplified model of the input EMI filter capacitor. Therefore, in order to obtain a higher power factor, the on-time of the PFC circuit switching device needs to be further compensated.

[0067] In another embodiment of the present invention, Fig.18 As shown, the on-time of the switch device of the PFC circuit is further compensated, including: Get PF on-time compensation value T on_pf ; The PF on-time compensation value T on_pf Add the current cycle on time to obtain the second current cycle on time T on_2 As the current cycle conduction time T of the PFC circuit switch device on ; The on-time of the PFC circuit switch device is controlled based on the on-time of the current cycle.

[0068] In another embodiment of the present invention, Fig.19 As shown, the PF on-time compensation value T is obtained. on_pf The steps include: Set the sampling interval T of the instantaneous value of the input voltage; Acquire a corresponding instantaneous value of the input voltage based on the sampling interval T; In an embodiment of the present invention, the instantaneous value of the input voltage is converted into a digital signal D ac [ n ], where n is a positive integer; Obtaining a PF on-time compensation amount based on the instantaneous value of the input voltage; In an embodiment of the present invention, obtaining the PF on-time compensation amount includes: Calculate the digital signal D corresponding to two adjacent samplings ac [ n ], the deviation value is D ac [ n ]-D ac [ n -1], where D ac [ n ] The digital signal of the instantaneous value of the input voltage obtained for the nth time, D ac [ n -1] is the digital signal of the instantaneous value of the input voltage obtained for the n-1th time, where n is a positive integer; The deviation value is multiplied by the compensation coefficient k and divided by the sampling interval T, and then filtered to obtain the PF on-time compensation value T. on_pf , where the compensation coefficient k represents the size of the equivalent capacitance of the EMI filter, and k is a constant; In other embodiments, the compensation coefficient k not only represents the size of the EMI filter equivalent capacitance, but also includes the proportion 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, the value of the compensation coefficient k should be larger.

[0069] The PF on-time compensation value T on_pf Filtering is performed to smooth the signal and reduce the impact of noise.

[0070] The embodiment of the present invention further provides a PFC circuit controller including the above method, such as Fig. 20 As shown, including: An acquisition unit 100, a first adjustment and compensation unit 200, and a conduction time control unit 300; 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 on-time control unit 300; the first adjustment and compensation unit 200 is connected to the on-time control unit 300, and the on-time control unit 300 is connected to the PFC circuit switch device Q; The acquisition unit 100 is used to acquire the basic on-time of the PFC circuit switch device Q, 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 200 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 300 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.

[0071] In another embodiment of the present invention, Fig.21 As shown, the PFC circuit controller further includes a first voltage peak value adjustment and compensation unit 500, and the first voltage peak value adjustment and compensation unit 500 is connected to the acquisition unit 100 and the first adjustment and compensation unit 200; The first voltage peak adjustment and compensation unit 500 is used to obtain the input voltage peak, and establish a first inverse functional relationship between the maximum on-time compensation amount and the input voltage peak based on the input voltage peak, the first inverse functional relationship regulates the maximum on-time compensation amount, and obtains the second maximum on-time compensation amount as the maximum on-time compensation amount; and / or establish a second inverse functional relationship between the minimum compensation amount turning point threshold and the input voltage peak based on the input voltage peak, the second inverse functional relationship regulates the minimum compensation amount turning point threshold, and obtains the second minimum compensation amount turning point threshold as the minimum compensation amount turning point threshold.

[0072] In another embodiment of the present invention, Fig. 22 As 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; The first valley adjustment and compensation unit 600 is used to obtain the discontinuous time of the inductor current in the DCM mode, adjust the maximum on-time compensation amount based on the discontinuous time of the inductor current in the DCM mode, and obtain a third maximum on-time compensation amount as the maximum on-time compensation amount, wherein when the discontinuous time of the inductor current increases, the third maximum on-time compensation amount decreases, and when the discontinuous time of the inductor current decreases, the third maximum on-time compensation amount increases.

[0073] In another embodiment of the present invention, Fig.23 As shown, the PFC circuit controller further includes a second voltage peak adjustment and compensation unit 700 and a second valley adjustment and compensation unit 800, wherein the second voltage peak adjustment and compensation unit 700 is connected to the acquisition unit 100 and the second valley adjustment and compensation unit 800, and the second valley adjustment and compensation unit 800 is connected to the first adjustment and compensation unit 200; When the PFC circuit is in the DCM mode, the second voltage peak adjustment and compensation unit 700 obtains the input voltage peak, establishes a third inverse functional relationship between the maximum on-time compensation amount and the input voltage peak based on the input voltage peak, and adjusts the maximum on-time compensation amount by the third inverse functional relationship to obtain a fourth maximum on-time compensation amount; The second valley adjustment and compensation unit 800 obtains the discontinuous time of the inductor current in the DCM mode, adjusts the fourth maximum on-time compensation amount based on the discontinuous time of the inductor current in the DCM mode, and obtains the fifth maximum on-time compensation amount as the maximum on-time compensation amount, wherein when the discontinuous time of the inductor current increases, the fifth maximum on-time compensation amount decreases, and when the discontinuous time of the inductor current decreases, the fifth maximum on-time compensation amount increases.

[0074] An embodiment of the present invention further provides a chip, comprising the above-mentioned PFC circuit controller.

[0075] The embodiment of the present invention also provides a circuit, such as Fig.24 As shown, it includes a PFC circuit and the above-mentioned PFC circuit controller; One end of the first capacitor C1 is connected to the first inductor L1 and the input voltage V ac The other end of the first capacitor C1 is connected to one end of the second inductor L2, the input voltage V acThe other end of the second capacitor C2 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 switch 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 R load 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, the resistor R load and one end of a 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 switch 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 a resistor Rac1, the other end of the resistor Rac1 is connected to one end of a 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 switch device Q is connected to the Q interface of the PFC circuit controller.

[0076] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0077] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the claims attached to 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 instantaneous value of an input voltage, 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; 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 control method for 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: Also includes: When the PFC circuit is in the DCM mode, 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: 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.

6. 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.

7. A PFC circuit controller comprising the control method of the PFC circuit 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.

8. A PFC circuit controller according to claim 7, 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.

9. A PFC circuit controller according to claim 7, 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.

10. The PFC circuit controller according to claim 7, 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, 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.

11. A chip, characterized in that: Comprising a PFC circuit controller as described in any one of claims 7 to 10.

12. A circuit, characterized in that: It comprises a PFC circuit and a PFC circuit controller as claimed in any one of claims 7 to 10.

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