Digital control method and device for improving PF value under high input voltage

Abstract

The invention discloses a digital control method and device for improving a PF value under high input voltage, and relates to the technical field of power converters. The method comprises the following steps: sampling an input voltage, and calculating a reactive current of an input capacitor; calculating an inductive current as a reference current of a current loop to compensate an advance quantity of an input capacitor; carrying out optimization calculation, simulating a capacitance current envelope by using a linear decline function, and adjusting the amplitude of a compensation function to reduce the effective value deviation with the actual current; and discretizing the continuous compensation function, forcing the current reference to be zero, and compensating total harmonic distortion in combination with DCM duty ratio feedforward control. Through optimization calculation and discretization processing, real-time cosine resolving operation is avoided, the operation pressure of a DSP is relieved, meanwhile, the problems of current distortion and rapid current rising are effectively avoided, the power factor of the BOOST PFC circuit is improved, and total harmonic distortion is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power converter, in particular to a digital control method and device for improving PF value under high input voltage. BACKGROUND

[0002] With the rapid development of power electronics technology, power factor correction (PFC) technology has become an indispensable part of modern power supply design, aiming to solve the problems of current waveform distortion, electromagnetic interference (EMI) and electromagnetic compatibility caused by capacitive load. Among them, BOOST PFC technology has become the most widely used scheme due to its simple structure and high efficiency.

[0003] Among various control strategies of BOOST PFC, average current control under current mode continuity is widely adopted due to its simple control and good stability. However, this technology still has significant defects in practical application: due to the influence of current loop bandwidth limitation, inductance volume constraint and input capacitance, input current is prone to zero-crossing distortion and phase advance problems, especially in the case of high input voltage or large input filter capacitance, the problem is more prominent.

[0004] Currently, to solve the problems of phase advance and current distortion caused by high input voltage and input filter capacitance, the following three compensation schemes are mainly used:

[0005] (1) Sine calculation compensation method: by real-time calculation of the reactive current generated by the input capacitance, the corresponding compensation reference signal is generated to offset the advance effect, which can effectively improve the power factor (PF), but its implementation depends on high-performance digital signal processor (DSP), which requires pre-stored cosine table and a large number of trigonometric function operations, with huge memory and operation resource consumption and high cost. In addition, in high switching frequency applications, the computing power of the DSP may become a bottleneck, limiting the scope of application of this method.

[0006] (2) Adding a low-pass filter method: a first-order low-pass filter is added in series before the current loop, which uses its lagging phase characteristic to offset the advance effect of the input current. However, this method requires the introduction of additional capacitors, resistors and other components, which not only increases the system cost but also poses a challenge to high power density design. More importantly, its compensation effect is only effective for fixed frequency, and when the input frequency changes, the compensation effect will be significantly weakened or even invalid, with poor adaptability.

[0007] (3) Input voltage phase delay method: by applying a fixed delay Δt to the input voltage signal involved in the current loop control, the inductor current is forced to follow the lagging voltage signal to compensate for the phase advance. The delay parameter of this method needs to be dynamically adjusted according to the load and input voltage, which may lead to input current zero-crossing distortion under light load conditions, increasing the total harmonic distortion (THD) and affecting system performance.

[0008] In summary, while existing technologies can partially improve the performance of PFC circuits, they suffer from problems such as high cost, large resource consumption, poor adaptability, or the introduction of additional harmonics. Therefore, there is an urgent need for a digital control method that can effectively improve the power factor (PF) and reduce the total harmonic distortion (THD) at high input voltages, while also reducing computational resource consumption and avoiding hardware complexity. Summary of the Invention

[0009] The problem to be solved by this invention is to provide a digital control method and device for improving the power factor (PF) value under high input voltage. While optimizing the PF value under high input voltage and large input capacitance conditions, it avoids the introduction of additional components and optimizes the zero-crossing distortion problem of input current. It can dynamically adapt to load changes and provide an efficient and low-cost solution for PFC design in high input voltage scenarios.

[0010] This invention adopts the following technical solution: a digital control method for improving the power factor (PF) value under high input voltage, comprising the following steps:

[0011] Step 1: Based on the average current mode BOOST PFC circuit, sample the input voltage and perform zero-crossing detection to calculate the reactive current of the input capacitor;

[0012] Step 2: Calculate the inductor current and use it as the reference current in the current loop to compensate for the lead of the input capacitor.

[0013] Step 3: Perform optimization calculations, use a linear decreasing function to simulate the capacitor current envelope, obtain the compensation current, and adjust the amplitude of the compensation function to reduce the deviation from the effective value of the actual current.

[0014] Step 4: Discretize the continuous compensation function and update the reference current by interrupt counting;

[0015] Step 5: When the reference current is less than 0, force the reference current to be 0;

[0016] Step 6: Combine DCM duty cycle feedforward control to control the problem of rapid current rise caused by the large feedforward and integral of inductor current at low input voltage, and compensate for total harmonic distortion.

[0017] Preferably, the average current mode BOOST PFC circuit includes: an AC power supply, a front-end filter, a rectifier circuit, a back-end filter, and a BOOST circuit.

[0018] The front-end filter forms a multi-stage LC filter through three capacitors C1, C2, and C3 and the inductance between the capacitors. The AC power supply passes through the front-end filter to filter out high-frequency noise and interference before being input into the rectifier circuit.

[0019] The rectifier circuit consists of a rectifier bridge composed of diodes D1-D4, which is used to convert the filtered AC signal into a DC signal, providing DC input for the BOOST circuit to boost voltage and correct power factor.

[0020] The back-end filter filters the rectified DC signal again through capacitor C4 before inputting it to the BOOST circuit;

[0021] The BOOST circuit adjusts the switching state to boost the input DC voltage to the required output voltage level, and outputs a stable DC voltage Vout.

[0022] Preferably, in step 1, the reactive current of the input capacitor is calculated, assuming the current output by the AC power supply is I. AC With the output voltage V AC In phase, the capacitance C of the filter capacitor is composed of capacitors C1, C2, C3, and C4.

[0023] Input voltage sampling is performed, and the input voltage at time t is expressed as v. AC (t):

[0024] v AC (t)=V AC sin(ωt);

[0025] Where ω represents the angular frequency of the input voltage;

[0026] The reactive current of the input capacitor is denoted as i. C (t):

[0027]

[0028] Preferably, in step 2, the inductor current is calculated and expressed as i L :

[0029] i L (t)=I AC sin(ωt)-ω×C×V AC cos(ωt)

[0030] The obtained inductor current i L (t) serves as the reference current Iref for the current loop, compensating for the lead of the input capacitor.

[0031] Preferably, in step 3, the capacitor current envelope is simulated by a linearly decreasing function, as shown in the following formula:

[0032]

[0033] Where T is the period of the input AC voltage, and Iref_comp is the compensation current.

[0034] Preferably, in step 4, the continuous compensation function is discretized, as shown in the following formula:

[0035] Iref comp(n) =ωCV AC -k·n

[0036] Among them, parameters n is the interrupt count within half a cycle, and N is the total number of interrupts within half a cycle.

[0037] Furthermore, in step 4, the reference current is updated by interrupting the count, and the reference current compensation is updated each time the input voltage is detected to be zero-crossing, as shown in the following formula:

[0038] Iref′=Iref-Iref_comp

[0039] Where Iref′ is the updated reference current.

[0040] Preferably, in step 5, the reference current Iref′ that appears during continuous compensation is compared with the input voltage V. AC Different problems arise due to the single-phase conduction of the rectifier bridge diodes. When Iref′<0, the forced reference current Iref′ is 0, and the output current loop reference current Iref′ is used to avoid current distortion at the zero-crossing point of the input voltage.

[0041] The present invention also provides a digital control device for improving the power factor (PF) value under high input voltage, comprising: a current detection module, a voltage detection module, a calculation module, and a control module.

[0042] The current detection module is used to detect the input current i AC (t), providing current data;

[0043] The voltage detection module is used to detect the input voltage v. AC (t), detect the zero-crossing point of the input voltage, and calculate the reference values ​​of reactive current and inductor current based on the input voltage;

[0044] The calculation module calculates the reactive current i based on the detected input voltage and the preset input capacitor value. C (t) The inductor current reference value Iref is calculated, discretized, and the reference current Iref′ is updated.

[0045] The control module: when Iref′<0, forces Iref′ to 0, and combines it with DCM duty cycle feedforward control to output a control signal to adjust the state of the switching transistors in the BOOST PFC circuit and improve the power factor.

[0046] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0047] 1. This invention is based on the existing BOOST PFC circuit. By optimizing the digital control scheme to compensate for the current lead caused by the input filter capacitor, the power factor (PF) value under high input voltage is improved. While effectively reducing THD, the computational pressure and resource consumption of the DSP are also reduced.

[0048] 2. This invention provides a method that optimizes the power factor (PF) value under high input voltage and large input capacitance without requiring additional control circuit components or real-time trigonometric function calculations, and with low computing power requirements.

[0049] 3. By forcing the current reference to zero and combining it with DCM duty cycle feedforward control, this invention effectively suppresses the current distortion and rapid current rise when the input voltage crosses zero, improves the power factor of the BOOST PFC circuit, reduces total harmonic distortion, and can adapt to load changes. Attached Figure Description

[0050] Figure 1 This is a structural diagram of the external filter circuit of the average current mode BOOST PFC circuit in an embodiment of the present invention.

[0051] Figure 2 This is a simplified diagram of the BOOST PFC circuit structure according to an embodiment of the present invention;

[0052] Figure 3 This is a current-voltage relationship diagram of the BOOST PFC circuit in an embodiment of the present invention;

[0053] Figure 4 This is a flowchart of the digital control method for improving the power factor (PF) value under high input voltage according to the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments involved in this invention. All non-innovative embodiments based on these embodiments by other researchers in the art are within the protection scope of this invention. Furthermore, the step numbers in the embodiments of this invention are only set for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0055] Example 1

[0056] A digital control method is provided to improve the power factor (PF) value under high input voltage by compensating for the reactive current of the PFC input filter. This method compensates for the phase lead of the input current caused by the input capacitor, thereby improving the PF value under low computing power requirements.

[0057] In this embodiment, the average current mode BOOST PFC circuit has an external filter such as... Figure 1 As shown, it mainly includes: AC power supply, front-end filter, rectifier circuit, back-end filter and BOOST circuit;

[0058] First, the front-end filter forms a multi-stage LC filter through three capacitors C1, C2, and C3 and the inductance between them. The AC power supply is connected to the front-end filter to filter out high-frequency noise and interference in the input AC power supply, reduce electromagnetic interference (EMI), and then input to the rectifier circuit.

[0059] The rectifier circuit consists of a rectifier bridge composed of four diodes D1-D4. The filtered signal enters the rectifier circuit, converting the AC signal into a DC signal. This is the front-end processing step of the PFC circuit, providing DC input for subsequent BOOST boost and power factor correction.

[0060] Then, after passing through the back-end filter, the rectified DC signal is filtered again by capacitor C4 to reduce voltage fluctuations. The filtered DC signal is input to the BOOST circuit. The BOOST circuit adjusts the switching state to boost the input DC voltage to the required output voltage level, and finally outputs a stable DC voltage Vout.

[0061] Therefore, the inductance on the filter side will not affect the phase of the PFC inductor current. Figure 1 The circuit is simplified to obtain the simplified BOOST PFC circuit structure, as follows: Figure 2 As shown, the capacitance of the filter capacitor C is composed of C1, C2, C3, and C4.

[0062] An AC power supply (AC) is connected in parallel with a filter capacitor (C). The other end of the filter capacitor (C) is connected to one input terminal of a rectifier bridge, and the other input terminal of the rectifier bridge is connected to the other end of the AC power supply, forming an AC input circuit. The current flowing through the filter capacitor (C) is I. C The current output by the AC power supply is I. AC The output terminal of the rectifier bridge is connected to one end of an inductor, and the other end of the inductor serves as the output terminal, with an output current I. L .

[0063] Figure 2The simplified model highlights the key components and basic functions related to power factor correction and boost in the BOOST PFC circuit. Through capacitor filtering and reactive power compensation, AC-DC conversion of the rectifier bridge, and energy storage and current smoothing of the inductor, the AC input is converted into a stable DC output.

[0064] Furthermore, to make Figure 2 I in AC Current leads input voltage V AC , to obtain Figure 3 The current-voltage relationship shown is specifically the capacitor current I. C Inductor current I L (This can be understood as the average value related to the PFC inductor current), AC input current I AC and AC input voltage V AC The relationship between them.

[0065] Specifically, the capacitor current I C With AC input voltage V AC It exhibits a linear relationship, and I C The phase leads V AC And with V AC The increase of I C It also increases linearly.

[0066] AC input current I AC It is the capacitor current I C and inductor current I L The synthesis of I C Advanced V AC Considering the PFC current loop response speed is fast enough, the inductor current I L The circuit is controlled to follow changes in the input voltage, but the input capacitor C causes a voltage V that leads the input voltage in phase. AC Current I at 90° C The leading current on the capacitor is what causes the total input current I. AC Leading the input voltage V AC The reason is that the PF value depends on I. AC With V AC The phase relationship between them, therefore the leading I AC The current caused the overall power factor (PF) value to be low.

[0067] Therefore, the decrease in PF value is mainly due to the reactive current I of capacitor C. C This causes the reactive current I to be generated given the input capacitor value and input voltage. CIt can be calculated accurately. Therefore, by subtracting this reactive current from the total input current to form a new PFC current loop reference, the ideal total input current can be obtained, thereby improving the PF value.

[0068] The digital control method for improving the power factor (PF) under high input voltage provided in this embodiment has the following process: Figure 4 As shown.

[0069] First, calculate the reactive current of the input capacitor:

[0070] For an ideal PFC circuit with a power factor of 1, the input current I AC With input voltage V AC For capacitors in phase, the reactive current calculation is as follows:

[0071] Input voltage sampling is performed, and the input voltage at time t is expressed as v. AC (t):

[0072] v AC (t)=V AC sin(ωt);

[0073] Where ω represents the angular frequency of the input voltage;

[0074] Then the input current at time t is expressed as i AC (t):

[0075] i AC (t)=I AC sin(ωt);

[0076] The reactive current on the input capacitor is represented by i. C (t):

[0077]

[0078] from Figure 2 From this, we can know:

[0079] i AC (t)=i L (t)+i C (t)

[0080] i L (t)=i AC (t)-i C (t)

[0081] Therefore, i can be calculated. L for:

[0082] i L (t)=I AC sin(ωt)-ω×C×V ACcos(ωt)

[0083] The obtained inductor current i L (t) serves as the reference current Iref for the current loop, which can theoretically fully compensate for the lead of the input capacitor, thereby increasing the PF value.

[0084] Specifically, the reference current required for the current loop is obtained through the above calculations. Traditional methods require trigonometric function calculations. To accurately set the reference current, it is necessary to obtain the required phase angle information and make corresponding compensations by pre-storing the input voltage sampling values ​​within half a cycle (the higher the sampling frequency, the more information is stored, and the more accurate the final input voltage phase angle is).

[0085] Then, optimization calculations are performed.

[0086] Since the current compensation method in the traditional way consumes a lot of computing power and memory resources of the DSP, this embodiment further optimizes the calculation based on the inductor current compensation to reduce the computing pressure on the DSP.

[0087] Using the cosine function to evaluate the reactive current i C When performing compensation, the corresponding cosine phase angle ω needs to be obtained, as shown in the following formula:

[0088] i C (t)=ωCV AC cos(ωt)

[0089] However, in practice, it is quite difficult to implement due to limitations in DSP performance and interrupt time.

[0090] Therefore, in this embodiment, the cosine function compensation is replaced with a linearly decreasing function to simulate the capacitor current envelope, and i is obtained. COMP To avoid real-time cosine calculation, the formula is as follows:

[0091]

[0092] Where T is the period of the input AC voltage, and Iref_comp is the compensation current.

[0093] Since the reactive current of the capacitor simulated by the linearly decreasing function has a large effective value deviation from the actual current (when the amplitude is set the same), the amplitude of the compensation function can be adjusted appropriately.

[0094] Next, discretization is performed.

[0095] Discretizing the continuous compensation function yields:

[0096] Iref comp(n) =ωCV AC -k·n

[0097] Among them, parameters n is the interrupt count within half a cycle, and N is the total number of interrupts within half a cycle.

[0098] The reference current is updated by interrupt counting, as shown in the following formula:

[0099] Iref′=Iref-Iref_comp

[0100] Where Iref′ is the updated reference current.

[0101] Then, the current reference is forced to zero.

[0102] Due to continuous compensation, Iref′ will differ from the input voltage V. AC The issue stems from the different phases of the rectifier bridge diodes, which are affected by the single-phase conduction of the diodes. When Iref′ is different from the input voltage V... AC When in different phases, due to i L Being clamped by a diode causes the current loop integral error to accumulate continuously, and there is even a risk of saturation.

[0103] Therefore, when Iref′<0, the reference current Iref′ is forced to be 0 to avoid current distortion at the zero-crossing point of the input voltage.

[0104] Finally, feedforward control is performed by combining the DCM duty cycle.

[0105] In this embodiment, by combining DCM duty cycle feedforward control, the problem of rapid current rise caused by the large feedforward and integral amount of inductor current at low input voltage can be controlled more effectively, so that the total harmonic distortion (THD) can be compensated in addition.

[0106] Specifically, due to the limitations of the PFC inductor selection, at high input voltages and when the input voltage is at a low phase angle, the PFC operation changes from continuous current mode to discontinuous current mode due to the small input current. In this situation, the traditional duty cycle feedforward control scheme in CCM mode cannot effectively control the input current; therefore, a DCM duty cycle feedforward control scheme is required.

[0107] CCM duty cycle feedforward is:

[0108]

[0109] DCM duty cycle feedforward is:

[0110]

[0111] Where T is the switching period, I ref The reference current after compensation, L is the inductance value, V in Vout These are the input and output voltages.

[0112] During work, by comparing formulas and The magnitude of the value is used as the basis for determining whether to enter DCM feedforward control. When the input voltage is at a low phase angle, the DCM duty cycle feedforward control is activated. At this point, the input voltage is at a low phase angle. When the input voltage just crosses zero, the current compensation is forced to zero, and the feedforward output is also zero, as shown in the DCM duty cycle feedforward calculation formula. This avoids current distortion caused by abnormal duty cycle control after the input voltage crosses zero, effectively reducing THD.

[0113] Example 2

[0114] This embodiment provides a digital control device for improving the power factor (PF) value under high input voltage. By compensating for the reactive current of the PFC input filter, the PF value under high input voltage is improved. Specifically, it includes a current detection module, a voltage detection module, a calculation module, and a control module.

[0115] Current detection module: used to detect input current i AC (t), provides current data.

[0116] Voltage detection module: used to detect input voltage V AC (t) is used to calculate reference values ​​for reactive current and inductor current based on the input voltage.

[0117] Calculation module: Calculates the reactive current i based on the detected input voltage and the preset input capacitor value. C (t) The inductor current reference value Iref is calculated, and then optimized, discretized, and updated.

[0118] The control module: when Iref′<0, forces Iref′ to 0, and in conjunction with DCM duty cycle feedforward control, outputs a control signal to adjust the state of the switching transistors in the BOOST PFC circuit, thereby achieving the purpose of improving the power factor.

[0119] In summary, the method of this invention avoids real-time cosine descaling by optimizing calculations and discretizing the process, thus reducing the computational burden on the DSP. Simultaneously, by forcing the current reference to zero and combining it with DCM duty cycle feedforward control, it effectively avoids current distortion and rapid current rise, improving the power factor of the BOOST PFC circuit and reducing total harmonic distortion.

[0120] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A digital control method for improving the power factor (PF) value under high input voltage, characterized in that, Includes the following steps: Step 1: Based on the average current mode BOOST PFC circuit, sample the input voltage and perform zero-crossing detection to calculate the reactive current of the input capacitor; Step 2: Calculate the inductor current and use it as the reference current in the current loop to compensate for the lead of the input capacitor. Step 3: Perform optimization calculations, use a linear decreasing function to simulate the capacitor current envelope, obtain the compensation current, and adjust the amplitude of the compensation function to reduce the deviation from the effective value of the actual current. Step 4: Discretize the continuous compensation function and update the reference current by interrupt counting; Step 5: When the reference current is less than 0, force the reference current to be 0; Step 6: Combine DCM duty cycle feedforward control to control the problem of rapid current rise caused by the large feedforward and integral of inductor current at low input voltage, and compensate for total harmonic distortion.

2. The digital control method for improving the PF value under high input voltage according to claim 1, characterized in that, The average current mode BOOST PFC circuit includes: AC power supply, front-end filter, rectifier circuit, back-end filter and BOOST circuit. The front-end filter forms a multi-stage LC filter through three capacitors C1, C2, and C3 and the inductance between the capacitors. The AC power supply passes through the front-end filter to filter out high-frequency noise and interference before being input into the rectifier circuit. The rectifier circuit consists of a rectifier bridge composed of diodes D1-D4, which is used to convert the filtered AC signal into a DC signal, providing DC input for the BOOST circuit to boost voltage and correct power factor. The back-end filter filters the rectified DC signal again through capacitor C4 before inputting it to the BOOST circuit; The BOOST circuit adjusts the switching state to boost the input DC voltage to the required output voltage level, and outputs a stable DC voltage Vout.

3. The digital control method for improving the PF value under high input voltage according to claim 2, characterized in that, In step 1, the reactive current of the input capacitor is calculated as follows: Assume the output current I of the AC power supply AC With the output voltage V AC In phase, the capacitance C of the filter capacitor is composed of capacitors C1, C2, C3, and C4. Input voltage sampling is performed, and the input voltage at time t is expressed as v. AC (t): v AC (t)=V AC sin(ωt); Where ω represents the angular frequency of the input voltage; The input current at time t is expressed as i AC (t): i AC (t)=I AC sin(ωt); The reactive current of the input capacitor is represented by i. C (t):

4. The digital control method for improving the PF value under high input voltage according to claim 3, characterized in that, In step 2, the inductor current is calculated as follows: AC input current i AC It is the capacitor current i C and inductor current i L The synthesis is represented as: i AC (t)=i L (t)+i C (t) i L (t)=i AC (t)-i C (t) Calculate the inductor current, expressed as i L : i L (t)=I AC sin(ωt)-ω×C×V AC cos(ωt) The obtained inductor current i L (t) serves as the reference current Iref for the current loop, compensating for the lead of the input capacitor.

5. The digital control method for improving the PF value under high input voltage according to claim 4, characterized in that, In step 3, the capacitor current i is simulated using a linearly decreasing function. C Envelope, the formula is as follows: Where T is the period of the input AC voltage, and Iref_comp is the compensation current.

6. The digital control method for improving the PF value under high input voltage according to claim 5, characterized in that, In step 4, the continuous compensation function is discretized, as shown in the following formula: Iref_comp(t)=ωCV AC -k·n Among them, parameters n is the interrupt count within half a cycle, and N is the total number of interrupts within half a cycle.

7. The digital control method for improving the PF value under high input voltage according to claim 6, characterized in that, In step 4, the reference current is updated by interrupting the count, and the reference current compensation is updated every time the input voltage is detected to be zero, as shown in the following formula: Iref′=Iref-Iref_comp Where Iref′ is the updated reference current.

8. The digital control method for improving the PF value under high input voltage according to claim 7, characterized in that, In step 5, the reference current Iref′ and the input voltage V appear during continuous compensation are used as the basis. AC The inversion problem is caused by the single-phase conduction of the rectifier bridge diodes, which prevents the actual input current from following the change of Iref′, resulting in abnormal accumulation of the current loop integral during loop operation. When Iref′<0, the reference current Iref′ is forced to be 0 to avoid current distortion at the zero-crossing point of the input voltage.

9. The digital control method for improving the PF value under high input voltage according to claim 1, characterized in that, In step 5, due to limitations in the selection of the PFC inductor, under high input voltage, when the input current is at a low phase angle and the PFC operating state changes from continuous current mode to discontinuous current mode, DCM duty cycle feedforward control is used to control the input current, as follows: CCM duty cycle feedforward is: DCM duty cycle feedforward is: Where T is the switching period, I ref The reference current after compensation, L is the inductance value, V in V out Input and output voltages; when When the input voltage is at a low phase angle, the DCM duty cycle feedforward control is activated. When the input voltage just crosses zero, the current compensation is forced to zero, and the feedforward output is also zero.

10. A digital control device for improving the power factor (PF) value under high input voltage, characterized in that, include: Current detection module, voltage detection module, calculation module, control module; The current detection module is used to detect the input current i AC (t), providing current data; The voltage detection module is used to detect the input voltage v. AC (t), calculate the reference values ​​of reactive current and inductor current based on the input voltage; The calculation module calculates the reactive current i based on the detected input voltage and the preset input capacitor value. C (t) The inductor current reference value Iref is calculated, discretized, and the reference current Iref′ is updated. The control module: when Iref′<0, forces Iref′ to 0, and combines it with DCM duty cycle feedforward control to output a control signal to adjust the state of the switching transistors in the BOOST PFC circuit and improve the power factor.

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