PFC (Power Factor Correction) control method and device based on current mode and control circuit

Abstract

The invention discloses a PFC control method, device and control circuit based on a current mode, and the method comprises the steps: obtaining a first inductive current sampling value of an inductor at a carrier zero point and a second inductive current sampling value of the inductor at a carrier period point, comparing the difference between the two values with a preset current threshold value, and determining a current sampling current mode; if it is determined that the previous sampling current mode is an intermittent inductive current mode and the current sampling current mode is a continuous inductive current mode, obtaining a current feed-forward coefficient group and determining a current correction coefficient to be updated corresponding to the current feed-forward coefficient group; and obtaining a minimum value in the current discontinuous mode feed-forward coefficient and the current continuous mode feed-forward coefficient as a current target feed-forward coefficient. According to the embodiment of the invention, when it is determined that the PFC control circuit is in the critical conduction mode in the current carrier period, the actual current target feed-forward coefficient is rapidly determined by the current feed-forward coefficient group, the determined current target feed-forward coefficient is more accurate as a feed-forward value, and a better feed-forward compensation effect is realized.

Description

[0001] This application claims priority to Chinese Patent Application No. CN202411575940.3, filed on November 6, 2024, entitled "PFC Control Method, Device and Control Circuit Based on Current Mode", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of PFC control technology, and in particular to a current-mode-based PFC control method, device, and control circuit. Background Technology

[0003] To improve the dynamic performance of PFC (Power Factor Correction) and reduce the impact of grid fluctuations and background harmonics, grid voltage feedforward control is often added to PFC control. The amount of grid voltage feedforward is closely related to the continuous mode (CCM) and discontinuous mode (DCM) of the inductor current. Using the wrong mode feedforward will lead to overcompensation or undercompensation, affecting dynamic and steady-state performance.

[0004] Conventional solutions use the minimum value of the theoretical calculation results of DCM and CCM, which include inductance and current sampling values. For inductors, there may be significant differences in inductance between different batches, temperatures, and switching frequencies, and the current sampling values ​​may also have some deviations. Therefore, directly using the theoretical calculation results may result in inaccurate DCM and CCM feedforward values, failing to achieve the feedforward compensation effect, and even adversely affecting dynamic and steady-state performance. Summary of the Invention

[0005] The present invention provides a current-mode-based PFC control method, device, and control circuit, which aims to solve the problem that in the prior art, the feedforward measurement takes the minimum value of the theoretical calculation results of DCM and CCM. Using the theoretical calculation results may cause inaccurate feedforward values ​​of DCM and CCM, fail to achieve the feedforward compensation effect, and even have an adverse effect on dynamic and steady-state performance.

[0006] In a first aspect, embodiments of the present invention provide a current-mode-based PFC control method applied to a PFC control circuit, wherein the PFC control circuit includes an inductor, a switching transistor, a diode, a capacitor, and a load resistor arranged in a preset connection configuration; the current-mode-based PFC control method includes:

[0007] In each interrupt cycle of PFC control, the first inductor current sample value at the carrier zero point and the second inductor current sample value at the carrier period point are acquired.

[0008] Based on the relationship between the difference between the current sampling values ​​of the first inductor current sampling value and the second inductor current sampling value and the preset current threshold, the current sampling current mode is determined and the current feedforward coefficient group is obtained.

[0009] If it is determined that the previously stored sampling current mode is an intermittent inductor current mode and the current sampling current mode is a continuous inductor current mode, then the PFC control circuit is determined to be in critical conduction mode within the current carrier cycle.

[0010] If the current time interval calculation result of the difference between the current system time and the previously stored correction coefficient update time is greater than or equal to the preset correction coefficient update cycle, then the current correction coefficient is determined based on the current feedforward coefficient group.

[0011] The current discontinuous mode feedforward coefficients in the current feedforward coefficient group are updated based on the current correction coefficients, and the current feedforward coefficient group is updated accordingly.

[0012] Obtain the minimum value among the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient in the current feedforward coefficient group, and use it as the current target feedforward coefficient corresponding to the PFC control circuit.

[0013] Secondly, embodiments of the present invention also provide a current-mode-based PFC control device, configured in a PFC control circuit, wherein the PFC control circuit includes an inductor, a switching transistor, a diode, a capacitor, and a load resistor arranged in a preset connection manner; the current-mode-based PFC control device includes:

[0014] The current sampling value acquisition unit is used to acquire the first inductor current sampling value at the carrier zero point and the second inductor current sampling value at the carrier period point in each interruption cycle of PFC control.

[0015] The current feedforward coefficient group acquisition unit is used to determine the current sampling current mode and acquire the current feedforward coefficient group based on the relationship between the difference between the current sampling values ​​of the first inductor current sampling value and the second inductor current sampling value and a preset current threshold.

[0016] The previous feedforward coefficient group acquisition unit is used to determine that the PFC control circuit is in critical conduction mode in the current carrier period if it is determined that the stored previous sampling current mode is discontinuous inductor current mode and the current sampling current mode is continuous inductor current mode.

[0017] The current correction coefficient acquisition unit is used to determine the current correction coefficient based on the current feedforward coefficient group if the current time interval calculation result of the difference between the current system time and the previously stored correction coefficient update time is greater than or equal to the preset correction coefficient update cycle.

[0018] The current feedforward coefficient group update unit is used to update the current discontinuous mode feedforward coefficients in the current feedforward coefficient group based on the current correction coefficients, and to update the current feedforward coefficient group.

[0019] The current target feedforward coefficient acquisition unit is used to acquire the minimum value of the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient in the current feedforward coefficient group, and use it as the current target feedforward coefficient corresponding to the PFC control circuit.

[0020] Thirdly, embodiments of the present invention also provide a control circuit, which includes an inductor, a switching transistor, a diode, a capacitor, and a load resistor arranged in a preset connection manner; the control circuit is used to execute the current-mode-based PFC control method as described in the first aspect.

[0021] This invention provides a current-mode-based PFC control method, apparatus, and control circuit. The method includes: acquiring a first inductor current sample value at a carrier zero point and a second inductor current sample value at a carrier period point; determining the current sampling current mode based on the relationship between the difference between the first and second inductor current sample values ​​and a preset current threshold, and acquiring a current feedforward coefficient group; if the previously stored sampling current mode is determined to be an intermittent inductor current mode and the current sampling current mode is a continuous inductor current mode, acquiring a previous feedforward coefficient group corresponding to the previous sampling current mode; determining a current correction coefficient based on the previous feedforward coefficient group and the current feedforward coefficient group; updating the current intermittent mode feedforward coefficient in the current feedforward coefficient group based on the current correction coefficient, and updating the current feedforward coefficient group; acquiring the minimum value between the current intermittent mode feedforward coefficient and the current continuous mode feedforward coefficient in the current feedforward coefficient group, and using it as the current target feedforward coefficient corresponding to the PFC control circuit. The embodiments of the present invention can quickly determine the actual current target feedforward coefficient using the current feedforward coefficient group when the PFC control circuit is determined to be in critical conduction mode within the current carrier cycle. The determined current target feedforward coefficient is more accurate as the feedforward value, thus achieving a better feedforward compensation effect. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A circuit diagram of the PFC control circuit used in the current-mode-based PFC control method provided in this embodiment of the invention.

[0024] Figure 2 A schematic flowchart of the current-mode-based PFC control method provided in an embodiment of the present invention;

[0025] Figure 3 A schematic diagram of the first waveform of the carrier signal, comparison signal, sampling signal and inductor current ADC sampled value used by the PFC control circuit in one carrier cycle in the current-mode-based PFC control method provided in the embodiments of the present invention.

[0026] Figure 4 This is a schematic diagram of the second waveform of the carrier signal, comparison signal, sampling signal, and inductor current ADC sampled value used by the PFC control circuit in one carrier cycle in the current-mode-based PFC control method provided in this embodiment of the invention.

[0027] Figure 5 This is a schematic diagram of the third waveform of the carrier signal, comparison signal, sampling signal, and inductor current ADC sampled value used by the PFC control circuit in one carrier cycle in the current-mode-based PFC control method provided in the embodiments of the present invention.

[0028] Figure 6 A schematic diagram of a sub-process of the current-mode-based PFC control method provided in an embodiment of the present invention;

[0029] Figure 7 A schematic block diagram of a current-mode-based PFC control device provided in an embodiment of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0032] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0033] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0034] Please also refer to Figure 1 and Figure 2 , Figure 1 This is a circuit diagram of the PFC control circuit used in the current-mode-based PFC control method provided in an embodiment of the present invention. Figure 2 This is a flowchart illustrating the current-mode-based PFC control method provided in an embodiment of the present invention. Figure 1 As shown, the PFC control circuit specifically applied by the current-mode-based PFC control method includes an inductor L1, a switching transistor Q1, diodes (specifically five diodes, designated as diode D1, diode D2, diode D3, diode D4, and diode D5), a capacitor C1, and a load resistor RL, arranged in a preset connection configuration. More specifically, the cathode of diode D2 is connected to the anode of diode D1, and also to a power supply (e.g., the mains grid, with an input voltage of u). g The positive terminal of the first diode D1 is connected to the positive terminal of the third diode D3, and also to the negative terminal of the power supply; the negative terminal of the third diode D3 is connected to the first terminal of the inductor L1; the second terminal of the inductor L1 is connected to the drain of the switching transistor Q1 (specifically a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor), and also to the positive terminal of the fifth diode D5; the source of the switching transistor Q1 is connected to the positive terminals of both the second diode D2 and the fourth diode D4; the negative terminal of the fifth diode D5 is connected to the first terminal of the capacitor C1, and also to the first terminal of the load resistor RL; the second terminal of the capacitor C1 is connected to the source of the switching transistor Q1; the second terminal of the load resistor RL is connected to the source of the switching transistor Q1.

[0035] like Figure 2 As shown, the current-mode-based PFC control method includes steps S110 to S160.

[0036] S110. During each interrupt cycle of PFC control, the first inductor current sample value at the carrier zero point and the second inductor current sample value at the carrier period point are acquired.

[0037] In this embodiment, in order to accurately determine the inductor current mode in the PFC control circuit, it is necessary to first obtain the following data within each interruption cycle of the PFC control: Figure 1 The PFC control circuit shown has the following first inductor current sampling value i at the carrier zero point: L_up (For reference) Figures 3-5 The trigger sampling point marked on the left corresponds to the first inductor current sampling value i. L_up The sampled value of the second inductor current i at the carrier period point (the carrier period point can be understood as the carrier peak point) and the inductor L1. L_dn (For reference) Figures 3-5 The trigger sampling point marked on the right corresponds to the second inductor current sampling value i. L_dn The obtained first inductor current sample value i L_up Second inductor current sampling value i L_dn After comparing the magnitudes, it can be used to quickly determine whether the inductor current mode of inductor L1 is continuous or discontinuous. Each interruption cycle of PFC control can be equivalent to one carrier cycle. This application uses a one-carrier-cycle time interval as an example to illustrate the execution process of the PFC control method within the current interruption cycle. That is, if it is determined that the start time of the current carrier cycle is reached, the steps in step S110 are executed. The same process is used to determine the PFC control method in other carrier cycles. Furthermore, the acquired first inductor current sample value i... L_up Second inductor current sampling value i L_dn It cannot be directly applied to determine the current sampling current mode; further processing is required. Figures 3-5 In the sampled signal s, during one carrier period T s The on-time T includes one carrier cycle. on (i.e. Figures 3-5 The trigger sampling marked on the left corresponds to the corresponding time period of the sampled signal and the off-time T of one carrier cycle. off (i.e. Figures 3-5 The trigger sampling marked on the right corresponds to the corresponding time period of the sampling signal, and satisfies T. on +T off =T s ,and Figures 3-5In the diagram, Carry corresponds to the waveform of the carrier signal, and CMP corresponds to the waveform of the comparison signal. Within the current carrier cycle, the sampled grid voltage connected to the PFC control circuit is the input voltage u. g Furthermore, the output voltage of the PFC control circuit is the same as the output voltage u across the load resistor RL. o .

[0038] S120. Based on the relationship between the difference between the current sampling values ​​of the first inductor current sampling value and the second inductor current sampling value and the preset current threshold, determine the current sampling current mode and obtain the current feedforward coefficient group.

[0039] In this embodiment, a preset current threshold Δi can also be set in advance as a comparison value for determining the sampling current mode. After determining the current sampling current mode based on the relationship between the difference in current sampling values ​​and the preset current threshold, the current feedforward coefficient group corresponding to the PFC control circuit is then accurately obtained.

[0040] In one embodiment, such as Figure 6 As shown, step S120 includes:

[0041] S121. If it is determined that the difference between the absolute values ​​of the first inductor current sample value and the second inductor current sample value is greater than the preset current threshold, then the current sampling current mode is determined to be the discontinuous inductor current mode.

[0042] S122. If the difference between the absolute values ​​of the first inductor current sample value and the second inductor current sample value is less than the preset current threshold, then the current sampling current mode is determined to be the continuous inductor current mode.

[0043] In this embodiment, if the first inductor current sampling value i is determined... L_up absolute value | i L_up | and the second inductor current sampling value i L_dn absolute value | i L_dn If the difference between the current sampled values ​​is greater than the preset current threshold Δi, then the current sampling current mode can be determined to be discontinuous inductor current mode (i.e., discontinuous mode DCM); if the first inductor current sampled value i is determined to be... L_up absolute value | i L_up | and the second inductor current sampling value i L_dn absolute value | i L_dn If the difference between the current sampled values ​​is less than the preset current threshold Δi, then the current sampling current mode can be determined to be continuous inductor current mode (i.e., continuous mode CCM). After determining the current sampling current mode, the corresponding current feedforward coefficient group in the PFC control circuit can also be determined.

[0044] Furthermore, within the current interrupt cycle of the PFC control circuit, the previous feedforward coefficient set from the previous interrupt cycle can also be obtained, specifically including the feedforward coefficients of the previous discontinuous mode, denoted as d. DCM1 The feedforward coefficients of the previous continuous mode, denoted as d. CCM1 The average value of the inductor current sampled in the previous interrupt cycle is denoted as i. L1 :

[0045] i L1 =(i L1_up +i L1_dn ) / 2;

[0046]

[0047] Among them, i L1_up This refers to the first inductor current sample value of inductor L1 at the carrier zero point in the previous carrier period relative to the current carrier period (or the current interrupt period), i L1_dn This refers to the second inductor current sample value of inductor L1 at a carrier cycle point in the previous carrier cycle relative to the current carrier cycle (or the current interrupt cycle); L refers to the inductance value of inductor L1 in the PFC control circuit, f s It is the carrier frequency of the PFC control circuit (refer to...). Figures 3-5 During one carrier period T of the sampled signal s s Once determined, its reciprocal is used as the carrier frequency f. s ), i L1 This refers to the inductor current of inductor L1 in the PFC control circuit (i.e., the average value of the inductor current sampled in the previous interrupt cycle). The grid sampling voltage obtained by the PFC control circuit in the previous carrier cycle relative to the current carrier cycle is the input voltage u. g1 Furthermore, the output voltage of the PFC control circuit is the same as the output voltage u across the load resistor RL. o1 .

[0048] In one embodiment, such as Figure 6 As shown, step S120 further includes:

[0049] S123. Obtain the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient, and form the current feedforward coefficient group.

[0050] Wherein, the current discontinuous mode feedforward coefficient is And the current continuous mode feedforward coefficient is d DCM2 The current discontinuous mode feedforward coefficient in the current carrier cycle, d CCM2is the current continuous mode feedforward coefficient in the current carrier cycle, L is the inductance value of inductor L1 in the PFC control circuit in the current carrier cycle, and f s The carrier frequency of the PFC control circuit in the current carrier cycle (see reference). Figures 3-5 During one carrier period T of the carrier signal s s Once determined, its reciprocal is used as the carrier frequency f. s ), i L It is the inductor current of the PFC control circuit in the current carrier cycle, and i L =(i L_up +i L_dn ) / 2, u g The input voltage of the PFC control circuit during the current carrier cycle, u o It is the output voltage corresponding to the load resistor RL in the PFC control circuit during the current carrier cycle.

[0051] In this embodiment, when specifically obtaining the current feedforward coefficient group corresponding to the current sampling current mode, it is necessary to obtain the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient. Moreover, the obtained current discontinuous mode feedforward coefficient and current continuous mode feedforward coefficient are not directly used as the final feedforward coefficients at this time, but need to be adjusted and corrected later.

[0052] S130. If it is determined that the previously stored sampling current mode is an intermittent inductor current mode and the current sampling current mode is a continuous inductor current mode, then the PFC control circuit is determined to be in critical conduction mode within the current carrier cycle.

[0053] In this embodiment, the current sample value of inductor L1 at the carrier zero point of the previous carrier cycle (that is, the first inductor current sample value i of inductor L1 at the carrier zero point of the previous carrier cycle relative to the current carrier cycle) is... L1_up ), and the current sample value of the inductor at the carrier cycle point of the previous carrier cycle (that is, the second inductor current sample value i of inductor L1 at the carrier cycle point of the previous carrier cycle relative to the current carrier cycle). L1_dn It can also be used to determine the previous sampling current mode by referring to the determination method of the current sampling current mode, and to calculate the previous feedforward coefficient group corresponding to the previous sampling current mode (i.e., to determine the previous discontinuous mode feedforward coefficient d by referring to the calculation formula in the previous example). DCM1 The feedforward coefficients d of the previous continuous mode CCM1 and the average value of the inductor current sampling in the previous interrupt cycle i L1The obtained previous sampling current mode corresponding to the PFC control circuit has been stored and can be used to combine with the current sampling current mode and the current feedforward coefficient group to jointly determine the correction coefficient for the feedforward coefficient.

[0054] In one embodiment, step S130 is followed by:

[0055] If it is determined that the PFC control circuit is in critical conduction mode within the current carrier cycle, then the current time interval calculation result is determined as the difference between the current system time and the previously stored correction coefficient update time.

[0056] In this embodiment, if the PFC control circuit is determined to be in critical conduction mode (i.e., BCM mode, where BCM stands for Boundary Conduction Mode) within the current carrier cycle, the waveform diagram it satisfies can be found by referring to... Figure 4 This means that the previously stored sampled current mode is a discontinuous inductor current mode (its sampled waveform can be found in the reference diagram). Figure 3 Furthermore, the current sampling current mode is the continuous inductor current mode (its sampling waveform can be found in the reference diagram). Figure 5 At this point, it is also necessary to calculate the time difference between the current system time and the previously stored correction coefficient update time, as the result of the current time interval calculation. The calculation of the current correction coefficient only begins when the current time interval calculation result is greater than or equal to the preset correction coefficient update period. If the current time interval calculation result is not yet equal to the preset correction coefficient update period, the calculation of the current correction coefficient will only begin after a waiting period until the current time interval calculation result is greater than or equal to the preset correction coefficient update period.

[0057] S140. If the current time interval calculation result of the difference between the current system time and the previously stored correction coefficient update time is greater than or equal to the preset correction coefficient update cycle, then the current correction coefficient is determined based on the current feedforward coefficient group.

[0058] In this embodiment, after obtaining the current feedforward coefficient set, more specifically, the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient can be obtained. At this time, the current correction coefficient can be determined by combining the current discontinuous mode feedforward coefficient, the current continuous mode feedforward coefficient, and a preset correction coefficient determination strategy.

[0059] In one embodiment, step S140 includes:

[0060] The current correction coefficient is determined based on the ratio between the current continuous mode feedforward coefficient and the current discontinuous mode feedforward coefficient in the current feedforward coefficient group.

[0061] In this embodiment, if the formula corresponding to the correction coefficient determination strategy is k = d CCM2 / d DCM2 k represents the current correction coefficient, d CCM2 Denotes the current continuous mode feedforward coefficients and d DCM2 The current discontinuous mode feedforward coefficient is represented by [reference to a formula]. According to the correction coefficient determination strategy, the current correction coefficient is determined based on the ratio between the current continuous mode feedforward coefficient and the current discontinuous mode feedforward coefficient in the current feedforward coefficient group. This method allows for rapid determination of the current correction coefficient based on the current continuous mode feedforward coefficient and the current discontinuous mode feedforward coefficient. However, in practice, the correction coefficient determination strategy is not limited to the above formula and can be flexibly configured according to user needs.

[0062] S150, The current discontinuous mode feedforward coefficients in the current feedforward coefficient group are updated based on the current correction coefficients, and the current feedforward coefficient group is updated.

[0063] In this embodiment, after the current correction coefficient is determined, the current discontinuous mode feedforward coefficient in the current feedforward coefficient group can be updated based on the current correction coefficient, thereby realizing timely updates to the current feedforward coefficient group.

[0064] In one embodiment, step S150 includes:

[0065] The current discontinuous mode feedforward coefficient in the current feedforward coefficient group is updated by multiplying the current correction coefficient, and the current feedforward coefficient group is updated accordingly.

[0066] In this embodiment, specifically, the current discontinuous mode feedforward coefficient in the current feedforward coefficient group is multiplied by the current correction coefficient, that is... Where d′ DCM represents the updated current discontinuous mode feedforward coefficient, and k represents the current correction coefficient. It can be seen that, based on the obtained current correction coefficient, the current discontinuous mode feedforward coefficients in the current feedforward coefficient group can be quickly updated, thereby achieving a complete update of the current feedforward coefficient group.

[0067] S160. Obtain the minimum value among the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient in the current feedforward coefficient group, and use it as the current target feedforward coefficient corresponding to the PFC control circuit.

[0068] In this embodiment, since the aforementioned process specifically involves adjusting the current discontinuous mode feedforward coefficient based on the current correction coefficient, after completing the above adjustment, the minimum value among the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient in the current feedforward coefficient group can be obtained and used as the current target feedforward coefficient corresponding to the PFC control circuit. At this time, the current target feedforward coefficient can be used as the feedforward coefficient ultimately used by the controller in the PFC control circuit, that is, as the feedforward of the duty cycle output by the corresponding control loop in the entire PFC control circuit.

[0069] Of course, the above process is the process of determining the current target feedforward coefficient using the current feedforward coefficient set of the carrier in one carrier cycle. The process of determining the current target feedforward coefficient in any subsequent carrier cycle is the same as the above process.

[0070] It is evident that the implementation of this method can quickly determine the actual current target feedforward coefficient using the current feedforward coefficient set when the PFC control circuit is determined to be in critical conduction mode within the current carrier cycle. The determined current target feedforward coefficient is more accurate as the feedforward value, achieving a better feedforward compensation effect.

[0071] Figure 7 This is a schematic block diagram of a current-mode-based PFC control device provided in an embodiment of the present invention. Figure 7 As shown, corresponding to the above-described current-mode-based PFC control method, the present invention also provides a current-mode-based PFC control device 100. This current-mode-based PFC control device 100 includes: a current sampling value acquisition unit 110, a current feedforward coefficient group acquisition unit 120, a previous feedforward coefficient group acquisition unit 130, a current correction coefficient acquisition unit 140, a current feedforward coefficient group update unit 150, and a current target feedforward coefficient acquisition unit 160.

[0072] The current sampling value acquisition unit 110 is used to acquire the first inductor current sampling value at the carrier zero point and the second inductor current sampling value at the carrier period point in each interruption cycle of PFC control.

[0073] In this embodiment, in order to accurately determine the inductor current mode in the PFC control circuit, it is necessary to first obtain the following data within each interruption cycle of the PFC control: Figure 1 The PFC control circuit shown has the following first inductor current sampling value i at the carrier zero point: L_up (For reference) Figures 3-5 The trigger sampling point marked on the left corresponds to the first inductor current sampling value i. L_up The sampled values ​​of the second inductor current i at the carrier period point of inductor L1. L_dn (For reference) Figures 3-5The trigger sampling point marked on the right corresponds to the second inductor current sampling value i. L_dn The obtained first inductor current sample value i L_up Second inductor current sampling value i L_dn After comparing the magnitudes, it can be used to quickly determine whether the inductor current mode of inductor L1 is continuous or discontinuous. Each interrupt cycle of the PFC control circuit can be equivalent to one carrier cycle, and this application uses a one-carrier-cycle time interval as an example to illustrate the execution process of the PFC control method within the current interrupt cycle.

[0074] The current feedforward coefficient group acquisition unit 120 is used to determine the current sampling current mode and acquire the current feedforward coefficient group based on the relationship between the difference between the current sampling values ​​of the first inductor current sampling value and the second inductor current sampling value and a preset current threshold.

[0075] In this embodiment, a preset current threshold Δi can also be set in advance as a comparison value for determining the sampling current mode. After determining the current sampling current mode based on the relationship between the difference in current sampling values ​​and the preset current threshold, the current feedforward coefficient group corresponding to the PFC control circuit is then accurately obtained.

[0076] In one embodiment, the current feedforward coefficient group acquisition unit 120 is specifically used for:

[0077] If the difference between the absolute values ​​of the first inductor current sample value and the second inductor current sample value is greater than the preset current threshold, then the current sampling current mode is determined to be the discontinuous inductor current mode.

[0078] If the difference between the absolute values ​​of the first and second inductor current samples is less than the preset current threshold, then the current sampling current mode is determined to be the continuous inductor current mode.

[0079] In this embodiment, if the first inductor current sampling value i is determined... L_up absolute value | i L_up | and the second inductor current sampling value i L_dn absolute value | i L_dn If the difference between the current sampled values ​​is greater than the preset current threshold Δi, then the current sampling current mode can be determined to be discontinuous inductor current mode (i.e., discontinuous mode DCM); if the first inductor current sampled value i is determined to be... L_up absolute value | i L_up | and the second inductor current sampling value i L_dn absolute value | i L_dnIf the difference between the current sampled values ​​is less than the preset current threshold Δi, then the current sampling current mode can be determined to be continuous inductor current mode (i.e., continuous mode CCM). After determining the current sampling current mode, the corresponding current feedforward coefficient group in the PFC control circuit can also be determined.

[0080] Furthermore, within the current interrupt cycle of the PFC control circuit, the previous feedforward coefficient set from the previous interrupt cycle can also be obtained, specifically including the feedforward coefficients of the previous discontinuous mode, denoted as d. DCM1 The feedforward coefficients of the previous continuous mode, denoted as d. CCM1 The average value of the inductor current sampled in the previous interrupt cycle is denoted as i. L1 :

[0081] i L1 =(i L1_up +i L1_dn ) / 2;

[0082]

[0083] Among them, i L1_up This refers to the first inductor current sample value of inductor L1 at the carrier zero point in the previous carrier period relative to the current carrier period (or the current interrupt period), i L1_dn This refers to the second inductor current sample value of inductor L1 at a carrier cycle point in the previous carrier cycle relative to the current carrier cycle (or the current interrupt cycle); L refers to the inductance value of inductor L1 in the PFC control circuit, f s It is the carrier frequency of the PFC control circuit (refer to...). Figures 3-5 During one carrier period T of the sampled signal s s Once determined, its reciprocal is used as the carrier frequency f. s ), i L1 This refers to the inductor current of inductor L1 in the PFC control circuit (i.e., the average value of the inductor current sampled in the previous interrupt cycle). The grid sampling voltage obtained by the PFC control circuit in the previous carrier cycle relative to the current carrier cycle is the input voltage u. g1 Furthermore, the output voltage of the PFC control circuit is the same as the output voltage u across the load resistor RL. o1 .

[0084] In one embodiment, the current feedforward coefficient group acquisition unit 120 is further specifically used for:

[0085] Obtain the current discontinuous mode feedforward coefficients and the current continuous mode feedforward coefficients, and form the current feedforward coefficient group.

[0086] Wherein, the current discontinuous mode feedforward coefficient is And the current continuous mode feedforward coefficient is d DCM2 The current discontinuous mode feedforward coefficient in the current carrier cycle, d CCM2 is the current continuous mode feedforward coefficient in the current carrier cycle, L is the inductance value of inductor L1 in the PFC control circuit in the current carrier cycle, and f s The carrier frequency of the PFC control circuit during the current carrier cycle (see reference). Figures 3-5 During one carrier period T of the sampled signal s s Once determined, its reciprocal is used as the carrier frequency f. s ), i L It is the inductor current of the PFC control circuit in the current carrier cycle, and i L =(i L_up +i L_dn ) / 2, u g The input voltage of the PFC control circuit during the current carrier cycle, u o It is the output voltage corresponding to the load resistor RL in the PFC control circuit during the current carrier cycle.

[0087] In this embodiment, when specifically obtaining the current feedforward coefficient group corresponding to the current sampling current mode, it is necessary to obtain the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient. Moreover, the obtained current discontinuous mode feedforward coefficient and current continuous mode feedforward coefficient are not directly used as the final feedforward coefficients at this time, but need to be adjusted and corrected later.

[0088] The previous feedforward coefficient group acquisition unit 130 is used to determine that the PFC control circuit is in critical conduction mode in the current carrier period if it is determined that the stored previous sampling current mode is discontinuous inductor current mode and the current sampling current mode is continuous inductor current mode.

[0089] In this embodiment, the current sample value of inductor L1 at the carrier zero point of the previous carrier cycle (that is, the first inductor current sample value i of inductor L1 at the carrier zero point of the previous carrier cycle relative to the current carrier cycle) is... L1_up ), and the current sample value of the inductor at the carrier cycle point of the previous carrier cycle (that is, the second inductor current sample value i of inductor L1 at the carrier cycle point of the previous carrier cycle relative to the current carrier cycle). L1_dn It can also be used to determine the previous sampling current mode by referring to the determination method of the current sampling current mode, and to calculate the previous feedforward coefficient group corresponding to the previous sampling current mode (i.e., to determine the previous discontinuous mode feedforward coefficient d by referring to the calculation formula in the previous example). DCM1 The feedforward coefficients d of the previous continuous mode CCM1and the average value of the inductor current sampling in the previous interrupt cycle i L1 The obtained previous sampling current mode corresponding to the PFC control circuit has been stored and can be used to combine with the current sampling current mode and the current feedforward coefficient group to jointly determine the correction coefficient for the feedforward coefficient.

[0090] In one embodiment, the previous feedforward coefficient group acquisition unit 130 is further specifically used for:

[0091] If it is determined that the PFC control circuit is in critical conduction mode within the current carrier cycle, then the current time interval calculation result is determined as the difference between the current system time and the previously stored correction coefficient update time.

[0092] In this embodiment, if the PFC control circuit is determined to be in critical conduction mode (i.e., BCM mode, where BCM stands for Boundary Conduction Mode) within the current carrier cycle, the waveform diagram it satisfies can be found by referring to... Figure 4 This means that the previously stored sampled current mode is a discontinuous inductor current mode (its sampled waveform can be found in the reference diagram). Figure 3 Furthermore, the current sampling current mode is the continuous inductor current mode (its sampling waveform can be found in the reference diagram). Figure 5 At this point, it is also necessary to calculate the time difference between the current system time and the previously stored correction coefficient update time, as the result of the current time interval calculation. The calculation of the current correction coefficient only begins when the current time interval calculation result is greater than or equal to the preset correction coefficient update period. If the current time interval calculation result is not yet equal to the preset correction coefficient update period, the calculation of the current correction coefficient will only begin after a waiting period until the current time interval calculation result is greater than or equal to the preset correction coefficient update period.

[0093] The current correction coefficient acquisition unit 140 is used to determine the current correction coefficient based on the current feedforward coefficient group if the current time interval calculation result of the difference between the current system time and the previously stored correction coefficient update time is greater than or equal to the preset correction coefficient update cycle.

[0094] In this embodiment, after obtaining the previous feedforward coefficient set and the current feedforward coefficient set, more specifically, the previous discontinuous mode feedforward coefficient, the previous continuous mode feedforward coefficient, the current discontinuous mode feedforward coefficient, and the current continuous mode feedforward coefficient can be obtained. At this point, the current correction coefficient can be determined by combining the previous discontinuous mode feedforward coefficient, the previous continuous mode feedforward coefficient, the current discontinuous mode feedforward coefficient, and the current continuous mode feedforward coefficient with a preset correction coefficient determination strategy.

[0095] In one embodiment, the current correction coefficient acquisition unit 140 is specifically used for:

[0096] The current correction coefficient is determined based on the ratio between the current continuous mode feedforward coefficient and the current discontinuous mode feedforward coefficient in the current feedforward coefficient group.

[0097] In this embodiment, if the formula corresponding to the correction coefficient determination strategy is k = d CCM2 / d DCM2 k represents the current correction coefficient, d CCM2 Denotes the current continuous mode feedforward coefficients and d DCM2 The current discontinuous mode feedforward coefficient is represented by [reference to a formula]. According to the correction coefficient determination strategy, the current correction coefficient is determined based on the ratio between the current continuous mode feedforward coefficient and the current discontinuous mode feedforward coefficient in the current feedforward coefficient group. This method allows for rapid determination of the current correction coefficient based on the current continuous mode feedforward coefficient and the current discontinuous mode feedforward coefficient. However, in practice, the correction coefficient determination strategy is not limited to the above formula and can be flexibly configured according to user needs.

[0098] The current feedforward coefficient group update unit 150 is used to update the current discontinuous mode feedforward coefficients in the current feedforward coefficient group based on the current correction coefficients, and update the current feedforward coefficient group.

[0099] In this embodiment, after the current correction coefficient is determined, the current discontinuous mode feedforward coefficient in the current feedforward coefficient group can be updated based on the current correction coefficient, thereby realizing timely updates to the current feedforward coefficient group.

[0100] In one embodiment, the current feedforward coefficient group update unit 150 is specifically used for:

[0101] The current discontinuous mode feedforward coefficient in the current feedforward coefficient group is updated by multiplying the current correction coefficient, and the current feedforward coefficient group is updated accordingly.

[0102] In this embodiment, specifically, the current discontinuous mode feedforward coefficient in the current feedforward coefficient group is multiplied by the current correction coefficient, that is... Where d′ DCM represents the updated current discontinuous mode feedforward coefficient, and k represents the current correction coefficient. It can be seen that, based on the obtained current correction coefficient, the current discontinuous mode feedforward coefficients in the current feedforward coefficient group can be quickly updated, thereby achieving a complete update of the current feedforward coefficient group.

[0103] The current target feedforward coefficient acquisition unit 160 is used to acquire the minimum value of the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient in the current feedforward coefficient group, and use it as the current target feedforward coefficient corresponding to the PFC control circuit.

[0104] In this embodiment, since the aforementioned process specifically involves adjusting the current discontinuous mode feedforward coefficient based on the current correction coefficient, after completing the above adjustment, the minimum value among the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient in the current feedforward coefficient group can be obtained and used as the current target feedforward coefficient corresponding to the PFC control circuit. At this time, the current target feedforward coefficient can be used as the feedforward coefficient ultimately used by the controller in the PFC control circuit, that is, as the feedforward of the duty cycle output by the corresponding control loop in the entire PFC control circuit.

[0105] Of course, the above process is the process of determining the current target feedforward coefficient using the current feedforward coefficient set of the carrier within one carrier cycle. The process of determining the current target feedforward coefficient in any subsequent carrier cycle is the same as the above process.

[0106] It is evident that the embodiment of this device can quickly determine the actual current target feedforward coefficient using the current feedforward coefficient set when the PFC control circuit is determined to be in critical conduction mode within the current carrier cycle. The determined current target feedforward coefficient is more accurate as the feedforward value, thus achieving a better feedforward compensation effect.

[0107] This invention also provides a control circuit, which includes an inductor, a switching transistor, a diode, a capacitor, and a load resistor arranged in a preset connection manner; the control circuit is used to execute the aforementioned current-mode-based PFC control method.

[0108] The control circuit can be specifically applied to Boost circuits, single-phase PFC, three-phase PFC, Vienna topology PFC, and other circuits. Moreover, the control circuit can be specifically applied to charging pile modules, on-board chargers, and other devices.

[0109] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0110] In the several embodiments provided by this invention, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For example, the division of each unit is merely a logical functional division, and there may be other division methods in actual implementation. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0111] The steps in the method of this invention can be adjusted, merged, or reduced in order according to actual needs. The units in the device of this invention can be merged, divided, or reduced according to actual needs. Furthermore, the functional units in the various embodiments of this invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0112] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, a terminal, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention.

[0113] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A current-mode-based PFC control method, applied to a PFC control circuit, characterized in that, The PFC control circuit includes an inductor, a switching transistor, a diode, a capacitor, and a load resistor arranged in a preset connection configuration; the current-mode-based PFC control method includes: In each interrupt cycle of PFC control, the first inductor current sample value at the carrier zero point and the second inductor current sample value at the carrier period point are acquired. Based on the relationship between the difference between the current sampling values ​​of the first inductor current sampling value and the second inductor current sampling value and the preset current threshold, the current sampling current mode is determined and the current feedforward coefficient group is obtained. If it is determined that the previously stored sampling current mode is an intermittent inductor current mode and the current sampling current mode is a continuous inductor current mode, then the PFC control circuit is determined to be in critical conduction mode within the current carrier cycle. If the current time interval calculation result of the difference between the current system time and the previously stored correction coefficient update time is greater than or equal to the preset correction coefficient update cycle, then the current correction coefficient is determined based on the current feedforward coefficient group. The current discontinuous mode feedforward coefficients in the current feedforward coefficient group are updated based on the current correction coefficients, and the current feedforward coefficient group is updated accordingly. Obtain the minimum value among the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient in the current feedforward coefficient group, and use it as the current target feedforward coefficient corresponding to the PFC control circuit.

2. The method according to claim 1, characterized in that, The determination of the current sampling mode based on the relationship between the difference between the first inductor current sample value and the second inductor current sample value and a preset current threshold includes: If the difference between the absolute values ​​of the first inductor current sample value and the second inductor current sample value is greater than the preset current threshold, then the current sampling current mode is determined to be the discontinuous inductor current mode. If the difference between the absolute values ​​of the first and second inductor current samples is less than the preset current threshold, then the current sampling current mode is determined to be the continuous inductor current mode.

3. The method according to claim 2, characterized in that, The step of obtaining the current feedforward coefficient set includes: Obtain the current discontinuous mode feedforward coefficients and the current continuous mode feedforward coefficients, and form the current feedforward coefficient group; wherein, the current discontinuous mode feedforward coefficients are... And the current continuous mode feedforward coefficient is d DCM2 The current discontinuous mode feedforward coefficient in the current carrier cycle, d CCM2 It is the current continuous mode feedforward coefficient in the current carrier cycle, L is the inductance value of the inductor in the PFC control circuit, and f s i is the carrier frequency of the PFC control circuit. L The inductor current, u, in the PFC control circuit during the current carrier cycle. g The input voltage of the PFC control circuit during the current carrier cycle, u o It is the output voltage corresponding to the load resistor in the PFC control circuit during the current carrier cycle.

4. The method according to claim 1, characterized in that, After the step of determining that the PFC control circuit is in a critical conduction mode within the current carrier cycle, the method further includes: If it is determined that the PFC control circuit is in critical conduction mode within the current carrier cycle, then the current time interval calculation result is determined as the difference between the current system time and the previously stored correction coefficient update time.

5. The method according to claim 3, characterized in that, Determining the current correction coefficient based on the current feedforward coefficient set includes: The current correction coefficient is determined based on the ratio between the current continuous mode feedforward coefficient and the current discontinuous mode feedforward coefficient in the current feedforward coefficient group.

6. The method according to claim 5, characterized in that, The current discontinuous mode feedforward coefficients in the current feedforward coefficient group are updated based on the current correction coefficients, and the current feedforward coefficient group is updated, including: The current discontinuous mode feedforward coefficient in the current feedforward coefficient group is updated by multiplying the current correction coefficient, and the current feedforward coefficient group is updated accordingly.

7. A current-mode-based PFC control device, configured in a PFC control circuit, characterized in that, The PFC control circuit includes an inductor, a switching transistor, a diode, a capacitor, and a load resistor arranged in a preset connection configuration; the current-mode-based PFC control device includes: The current sampling value acquisition unit is used to acquire the first inductor current sampling value at the carrier zero point and the second inductor current sampling value at the carrier period point in each interruption cycle of PFC control. The current feedforward coefficient group acquisition unit is used to determine the current sampling current mode and acquire the current feedforward coefficient group based on the relationship between the difference between the current sampling values ​​of the first inductor current sampling value and the second inductor current sampling value and a preset current threshold. The previous feedforward coefficient group acquisition unit is used to determine that the PFC control circuit is in critical conduction mode in the current carrier period if it is determined that the stored previous sampling current mode is discontinuous inductor current mode and the current sampling current mode is continuous inductor current mode. The current correction coefficient acquisition unit is used to determine the current correction coefficient based on the current feedforward coefficient group if the current time interval calculation result of the difference between the current system time and the previously stored correction coefficient update time is greater than or equal to the preset correction coefficient update cycle. The current feedforward coefficient group update unit is used to update the current discontinuous mode feedforward coefficients in the current feedforward coefficient group based on the current correction coefficients, and to update the current feedforward coefficient group. The current target feedforward coefficient acquisition unit is used to acquire the minimum value of the current discontinuous mode feedforward coefficient and the current continuous mode feedforward coefficient in the current feedforward coefficient group, and use it as the current target feedforward coefficient corresponding to the PFC control circuit.

8. The current-mode-based PFC control device according to claim 7, characterized in that, The current feedforward coefficient group acquisition unit is specifically used for: If the difference between the absolute values ​​of the first inductor current sample value and the second inductor current sample value is greater than the preset current threshold, then the current sampling current mode is determined to be the discontinuous inductor current mode. If the difference between the absolute values ​​of the first and second inductor current samples is less than the preset current threshold, then the current sampling current mode is determined to be the continuous inductor current mode.

9. The current-mode-based PFC control device according to claim 8, characterized in that, The current feedforward coefficient set acquisition unit is also used for: Obtain the current discontinuous mode feedforward coefficients and the current continuous mode feedforward coefficients, and form the current feedforward coefficient group; wherein, the current discontinuous mode feedforward coefficients are... And the current continuous mode feedforward coefficient is d DCM2 The current discontinuous mode feedforward coefficient in the current carrier cycle, d CCM2 It is the current continuous mode feedforward coefficient in the current carrier cycle, L is the inductance value of the inductor in the PFC control circuit, and f s i is the carrier frequency of the PFC control circuit. L The inductor current, u, in the PFC control circuit during the current carrier cycle. g The input voltage of the PFC control circuit during the current carrier cycle, u o It is the output voltage corresponding to the load resistor in the PFC control circuit during the current carrier cycle.

10. A control circuit, characterized in that, The control circuit includes an inductor, a switching transistor, a diode, a capacitor, and a load resistor arranged in a preset connection manner; the control circuit is used to execute the current-mode-based PFC control method as described in any one of claims 1-6.

Images