A method and apparatus for peak-valley current control of a Cuk PFC circuit based on average current calculation.

Abstract

A peak valley current control method and device of a Cuk PFC circuit based on average current calculation, the method comprising sampling electrical parameters in the Cuk PFC circuit; calculating a peak value of an input power frequency average current according to the sampled electrical parameters and preset electrical parameters; calculating a peak value reference current of an input filter inductor and a valley value reference current of an output filter inductor according to the peak value of the input power frequency average current, the sampled electrical parameters and the preset electrical parameters; and outputting a driving signal for controlling the Cuk PFC circuit according to the peak value reference current of the input filter inductor, the valley value reference current of the output filter inductor and the sampled electrical parameters. The method uses the relationship between the outputs of two error amplifiers, the input power frequency average current and the output average current to approximate the peak value of the input power frequency average current and the valley value reference current of the output filter inductor, thereby achieving high reliability and low output voltage ripple, and having the advantages of good voltage and current output quality, strong versatility and controllable cost.

Description

Technical Field

[0001] This invention relates to the field of PFC circuit control technology, and specifically to a peak-valley current control method and apparatus for a Cuk PFC circuit based on average current calculation. Background Technology

[0002] In recent years, with the increasing demand for high-efficiency, high-power-density, and low-ripple power supplies, such as data center server power supplies, LED driver control systems, and 5G / 6G communications, PFC converters, especially bridgeless PFC converters, have received more and more attention.

[0003] The bridgeless Cuk PFC converter has several advantages: First, the output DC voltage of the bridgeless Cuk PFC converter can be boosted or bucked. Second, thanks to the inherent intermediate energy storage coupling capacitor in the Cuk circuit, it is naturally suitable for Active Pulsating Power Buffering (PPB) technology. This technology increases control freedom, decoupling AC ripple from the DC output voltage, thereby eliminating twice the power frequency ripple and the need for filtering with a large output capacitor, effectively improving the system's power density and reliability. Third, in fields requiring negative voltage power supply, such as communication power supplies, the natural polarity reversal characteristic of the non-isolated Cuk converter perfectly matches this requirement, eliminating the expensive inverting transformer stage in traditional solutions, reducing the number of components and size, and lowering the overall cost.

[0004] The traditional Cuk PFC converter control method operates the switching transistor at a fixed switching frequency and adjusts the output voltage by changing the duty cycle (i.e., PWM). However, its output DC voltage still has a large ripple of twice the power frequency, and a large electrolytic capacitor is still required at the output for filtering. It cannot fully utilize the natural advantages of the Cuk topology. Moreover, with the use of an inductor, a capacitor and a diode more than the Boost PFC topology, it only achieves voltage reduction, so it has not become the mainstream application topology.

[0005] Regarding control methods for low-ripple Cuk PFC circuits, Yonglu Liu published a control method called "Peak-Valley Current Mode" in IEEE TPEL (Chinese Journal of Power Electronics) in January 2022. The paper, titled "Peak and Valley Current Control for Cuk PFC Converter to Reduce Capacitance," applies PPB (Active Power Buffer) technology to Cuk PFC circuits, developing a control method that requires only one switching transistor to output a high-quality DC voltage. This overcomes the drawback of using multiple transistors in general PPB technology to achieve low-ripple output, greatly simplifying the control complexity. However, its shortcomings are: First, it still uses a bridge topology, resulting in lower overall efficiency. Second, the method of generating the peak reference current does not reflect the "ripple decoupling" concept of PPB technology, preventing further reduction in output ripple. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, the present invention aims to provide a peak-valley current control method and device for a Cuk PFC circuit based on average current calculation. This method uses the relationship between the output of two error amplifiers, the input power frequency average current, and the output average current to approximate the peak value of the input power frequency average current and the valley reference current of the output filter inductor. This solves the problem of high load regulation rate in the original control method, and achieves high reliability and low output voltage ripple. It has the advantages of good voltage and current output quality, strong versatility, and controllable cost.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A peak-valley current control method for a Cuk PFC circuit based on average current calculation includes the following steps: Sample the voltage of the coupling capacitor, the voltage of the output filter capacitor, the input AC voltage, the current of the input filter inductor, and the current of the output filter inductor in the Cuk PFC circuit; The average output current is obtained based on the voltage of the output filter capacitor and the preset target voltage value of the output filter capacitor. Based on the voltage of the coupling capacitor and the preset target voltage value of the coupling capacitor, the error value of the voltage of the coupling capacitor is obtained; The peak value of the average input current at the power frequency is obtained based on the average output current and the error value of the voltage of the coupling capacitor. Based on the input AC voltage, a unit sine wave with the same phase and frequency as the input AC voltage is obtained; Based on the input AC voltage, obtain the absolute value of the input AC voltage; The peak reference current of the input filter inductor is obtained based on the peak value of the average input current at the power frequency, the unit sine wave with the same phase and frequency as the input AC voltage, the voltage of the coupling capacitor, the absolute value of the input AC voltage, and the preset target voltage value of the output filter capacitor. The valley reference current of the output filter inductor is obtained based on the average output current, the preset target voltage value of the coupling capacitor, the preset target voltage value of the output filter capacitor, the maximum value of the input AC voltage, the inductance value of the input filter inductor, the inductance value of the output filter inductor, the voltage of the coupling capacitor, the absolute value of the input AC voltage, and the peak value of the average input power frequency current. Based on the current of the input filter inductor, the current of the output filter inductor, the peak reference current of the input filter inductor, and the valley reference current of the output filter inductor, the drive signal for controlling the Cuk PFC circuit is output.

[0008] Furthermore, the input filter inductor operates in intermittent conduction mode, while the output filter inductor operates in continuous conduction mode.

[0009] Furthermore, the expression for the average value of the output current is: in, I DC This is the average value of the output current. err vDC This is the output of the first error amplification unit. f 1 represents the operator of the first error amplification unit. V C2ref The preset target voltage value for the output filter capacitor. V C2 This is the voltage across the output filter capacitor.

[0010] Furthermore, the expression for the error value of the voltage of the coupling capacitor is: in, err vC1 This represents the error value of the voltage across the coupling capacitor. f 2 represents the operator of the second error amplification unit. V C1 The voltage across the coupling capacitor. V C1ref This is the preset target voltage value for the coupling capacitor.

[0011] Furthermore, the expression for the peak value of the input power frequency average current is: in, I g The peak value of the input power frequency average current.err vDC This is the output of the first error amplification unit. err vC1 This represents the error value of the voltage across the coupling capacitor.

[0012] Furthermore, the peak reference current of the input filter inductor is: in, i pk The peak reference current of the input filter inductor. I g The peak value of the input power frequency average current. sin It is a unit sine wave with the same phase and frequency as the input AC voltage. V C1 Let | be the voltage across the coupling capacitor. V ac | represents the absolute value of the input AC voltage. V C2ref This is the preset target voltage value for the output filter capacitor.

[0013] Furthermore, the expression for the valley reference current of the output filter inductor is: in, i vy The valley reference current for the output filter inductor, I DC This is the average value of the output current. V C1ref This is the preset target voltage value for the coupling capacitor. V C2ref The preset target voltage value for the output filter capacitor. V AC_max This represents the maximum value of the input AC voltage. L L1 The inductance value of the input filter inductor. L L2 The inductance value of the output filter inductor. V C1 Let | be the voltage across the coupling capacitor. V ac | represents the absolute value of the input AC voltage. I g This represents the peak value of the average input power frequency current.

[0014] A peak-valley current control device for a Cuk PFC circuit based on average current calculation, comprising: Sampling unit: Samples the voltage of the coupling capacitor, the voltage of the output filter capacitor, the input AC voltage, the current of the input filter inductor, and the current of the output filter inductor in the Cuk PFC circuit; First error amplification unit: Obtains the average output current based on the voltage of the output filter capacitor and the preset target voltage value of the output filter capacitor; Second error amplification unit: Based on the voltage of the coupling capacitor and the preset target voltage value of the coupling capacitor, obtain the error value of the voltage of the coupling capacitor; Subtraction unit: Based on the average output current and the error value of the coupling capacitor voltage, the peak value of the average input power frequency current is obtained; Proportional calculation unit: Based on the input AC voltage, it obtains a unit sine wave with the same phase and frequency as the input AC voltage; Absolute value calculation unit: Obtains the absolute value of the input AC voltage based on the input AC voltage; The first arithmetic unit calculates the peak reference current of the input filter inductor based on the peak value of the input power frequency average current, the unit sine wave with the same phase and frequency as the input AC voltage, the voltage of the coupling capacitor, the absolute value of the input AC voltage, and the preset target voltage value of the output filter capacitor. The second calculation unit: Based on the average output current, the preset target voltage value of the coupling capacitor, the preset target voltage value of the output filter capacitor, the maximum value of the input AC voltage, the inductance value of the input filter inductor, the inductance value of the output filter inductor, the voltage of the coupling capacitor, the absolute value of the input AC voltage, and the peak value of the average input power frequency current, the valley reference current of the output filter inductor is obtained. Control logic unit: Based on the current of the input filter inductor, the current of the output filter inductor, the peak reference current of the input filter inductor, and the valley reference current of the output filter inductor, output the drive signal to control the Cuk PFC circuit.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The method for calculating the valley reference current of the output filter inductor proposed in this invention indirectly obtains the expression for the valley reference current of the output filter inductor by deriving the relationship between the average value of the output current and the valley reference current of the output filter inductor. This replaces the original control method that directly calculates the valley reference current of the output filter inductor using an error amplifier, thus solving the problem of inaccurate calculation of the median reference current in the original control method. It is simple and easy to use, reduces output ripple, and further improves the output voltage and current quality of the Cuk PFC converter.

[0016] 2. The method for calculating the peak value of the input power frequency average current proposed in this invention introduces the "ripple decoupling" concept of PPB technology, allowing the peak value of the input power frequency average current to be determined simultaneously by the first error amplification unit and the second error amplification unit. This replaces the existing control method that only uses the second error amplification unit to calculate the peak value of the input power frequency average current. This solves the problems of large load regulation and control failure under conditions of low coupling capacitor voltage and heavy load in the existing control method. It is simple to use, reduces output ripple, and reduces load regulation, further improving the output voltage and current quality of the Cuk PFC converter.

[0017] 3. The peak-valley current control method proposed in this invention can be implemented by analog circuits or by digital control chips, which reduces the dependence on high-performance digital control chips and has the characteristics of strong versatility and controllable cost.

[0018] In summary, the peak-valley current control method of the Cuk PFC circuit based on average current calculation of the present invention uses the relationship between the output of two error amplifiers, the average input power frequency current, and the average output current to approximate the peak value of the average input power frequency current and the valley reference current of the output filter inductor. This solves the problem of high load regulation rate of the original control method, and achieves high reliability and low output voltage ripple. It has the advantages of good voltage and current output quality, strong versatility, and controllable cost. Attached Figure Description

[0019] Figure 1 This is a flowchart of the peak-valley current control method of the Cuk PFC circuit based on average current calculation according to the present invention.

[0020] Figure 2 This is a schematic diagram of the peak-valley current control device of the Cuk PFC circuit based on average current calculation according to the present invention. Figure 1 .

[0021] Figure 3 This is a schematic diagram of the peak-valley current control device of the Cuk PFC circuit with bridge in this invention. Figure 2 .

[0022] Figure 4 This is a schematic diagram of the bridged Cuk PFC circuit of the present invention.

[0023] Figure 5 This is a schematic diagram of the bridgeless Cuk PFC circuit of the present invention.

[0024] Figure 6 The diagram shows the operating mode of the bridged Cuk PFC circuit based on the peak-valley current control method of the present invention.

[0025] Figure 7 The diagram shows the operating mode of the bridgeless Cuk PFC circuit under the peak-valley current control method of the present invention.

[0026] Figure 8 Waveform simulation of the bridged Cuk PFC circuit under the peak-valley current control method of this invention. Figure 1 ;in, Figure 8 In the figure, (a) represents the power supply input voltage V. ac and power input current i LF Waveform simulation diagram; Figure 8 In the diagram, (b) represents the output voltage v. dcs The waveform simulation diagram.

[0027] Figure 9 Waveform simulation of the bridged Cuk PFC circuit under the peak-valley current control method of this invention. Figure 2 ;in, Figure 9 (a) in the figure represents the input filter inductor. L1 current i L1 and input filter inductor L1 Peak reference current i p Waveform simulation comparison chart of k; Figure 9 (b) in the figure represents the output filter inductor. L2 current i L2 and the valley reference current of the output filter inductor i vy Waveform simulation comparison chart; Figure 9 (c) in the figure is a waveform simulation diagram of the switching transistor S.

[0028] Figure 10 Waveform simulation of the bridgeless Cuk PFC circuit under the peak-valley current control method of this invention. Figure 1 ;in, Figure 10 In the figure, (a) represents the power supply input voltage V. ac and power input current i LF Waveform simulation diagram; Figure 10 In the diagram, (b) represents the output voltage v. dcs The waveform simulation diagram.

[0029] Figure 11 Waveform simulation of the bridgeless Cuk PFC circuit under the peak-valley current control method of this invention. Figure 2 ;in, Figure 11 (a) in the figure represents the input filter inductor. L1 current i L1 and input filter inductor L1Peak reference current i p Waveform simulation comparison chart of k; Figure 11 (b) in the figure represents the output filter inductor. L2 current i L2 and the valley reference current of the output filter inductor i vy Waveform simulation comparison chart; Figure 11 (c) in the figure is a comparison diagram of the control signal waveforms of high-frequency transistors H1 and H2; Figure 11 (d) in the figure is the control signal waveform of the high-frequency tube H3. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments: Traditional Cuk PFC control methods (such as DCM control) have an output voltage with twice the power frequency ripple, and the output filter capacitor... C2 The electrolytic capacitor is relatively large, and it is itself the most vulnerable component in Cuk PFC due to its short lifespan, poor high-frequency performance, sensitivity to heat, and high ESR. To address these issues, this invention proposes a peak-valley current control method for Cuk PFC circuits based on average current calculation. This method requires an input filter inductor. L1 Operating in DCM mode (discontinuous conduction mode), the output filter inductor L2 Operating in CCM mode (Continuous On-Conduction Mode); see [link / reference] Figure 1 The specific methods include the following: Coupling capacitor in the sampling Cuk PFC circuit C1 voltage V C1 Output filter capacitor C2 voltage V C2 Input AC voltage V ac Input filter inductor L1 current i L1 Output filter inductor L2 current i L2 ; Based on the output filter capacitor C2 voltage V C2 Output filter capacitor C2 preset target voltage value V C2ref The average output current is obtained. I DC The average value of the output currentI DC The expression is: (1) in, err vDC The output of the first error amplification unit is used as one of the parameters in the control loop to amplify the output filter capacitor. C2 voltage V C2 With output filter capacitor C2 preset target voltage value V C2ref The error between them is also used as the average value of the output current in the control method proposed in this invention. I DC Approximate; f 1 represents the operator of the first error amplification unit, and its relevant expression is: (2) This embodiment Only f One implementation of 1 can have different expressions depending on the structure of the error amplification unit; Based on coupling capacitance C1 voltage V C1 Coupling capacitors C1 preset target voltage value V C1ref The error value of the voltage of the coupling capacitor is obtained. err vC1 The error value of the voltage of the coupling capacitor. err vC1 The expression is: (3) in, f 2 represents the operator of the second error amplification unit, and its relevant expression is: (4) This embodiment Only f In one embodiment of 2, since the first error amplification unit and the second error amplification unit of the present invention have the same structure, the operators of the first error amplification unit and the operators of the second error amplification unit also have the same expression. Based on the average output current I DC Error value of the voltage of the coupling capacitor err vC1 The average input power frequency current is obtained. i av1 peak Ig The input power frequency average current i av1 peak I g The expression is: (5) The following is about the average input power frequency current. i av1 peak I g The principle can be explained as follows: This can be derived from the law of conservation of energy; (6) in, P ac P is the instantaneous input power to the power grid. c1 For coupling capacitor C1 The instantaneous input power of the system, P DC Output filter capacitor C2 The instantaneous input power at the output terminal; from the perspective of energy decoupling, the energy flowing into the Cuk PFC circuit should be proportional to the energy consumed by the load resistor RL, and the coupling capacitance should also be subtracted. C1 This provides buffer energy for the load resistor RL. The average input power frequency current... i av1 peak I g The energy is proportional to the average energy of the input Cuk PFC circuit, therefore we can assume: (7) The output of the first error amplification unit err vDC Error value of the voltage of the coupling capacitor err vC1 It uses PI (proportional-integral control) to approximate the average input current at the power frequency. i av1 peak I g ; k p1 Operator of the first error amplification unit f A proportionality coefficient of 1 k p2 Operator for the second error amplification unit f 2 proportionality coefficient, k i1 Operator of the first error amplification unit f Integral coefficient of 1 k i2 Operator for the second error amplification unit f The integral coefficient of 2; The above approximation method has an error value compared to using only the voltage of the coupling capacitor. err vC1 To approximate the average input power frequency current i av1 peak I g A more reasonable approach, resulting in a more stable output filter capacitor. C2 voltage V C2 And better transient response.

[0031] Based on the input AC voltage V ac The input AC voltage is obtained. V ac Unit sine waves with the same phase and frequency sin ; Based on the input AC voltage V ac To obtain the absolute value of the input AC voltage | V ac |; Based on the input power frequency average current i av1 peak I g , and input AC voltage V ac Unit sine waves with the same phase and frequency sin Coupling capacitors C1 voltage V C1 The absolute value of the input AC voltage |V ac | Output filter capacitor C2 preset target voltage value V C2ref ， Obtain the peak reference current of the input filter inductor; the input filter inductor L1 Peak reference current i pk for: (8) The following discusses the input filter inductor. L1 Peak reference current i pk The principle can be explained as follows: Filter inductor L1 To achieve a good power factor when operating in DCM mode, the current filter inductor needs to be optimized. L1 Input power frequency average current i av1It can follow the input AC voltage very well. V ac To obtain the waveform, one feasible strategy is to control the input filter inductor. L1 Peak reference current i pk To indirectly control the average input power frequency current i av1 Input filter inductor L1 Peak reference current i pk The derivation process is as follows: Input power frequency average current in each switching cycle i av1 It can be expressed as (9) in, Ts For the switching cycle, d1 The duty cycle of the switch. d2 For switch off and input filter inductor L1 The duty cycle for maintaining continuous flow; Meanwhile, under steady-state conditions, with constant output power, the average input power frequency current... i av1 peak I g If it remains unchanged, then: (10) in, w g The angular frequency of the AC power supply voltage; In a switching cycle Ts It goes through three operating modes. The first operating mode is the input filter inductor. L1 Output filter inductor L2 Charging, duty cycle is d1 Then we have: (11) Second operating mode: Input filter inductor L1 Output filter inductor L2 If the duty cycle is d2, then: (12) Third operating mode: Input filter inductor L1 current i L1 The output filter inductance is 0. L2 Continue releasing energy, with a duty cycle of d3; according to the volt-second balance, we can obtain from equations (11) and (12) the following: (13) For the detailed derivation of equations (11-13), please refer to the background paper "Peak and Valley Current Control for Cuk PFC Converter to Reduce Capacitance", which can be found at: Yonglu Liu, Haojie Zhang, Hui Wang, et al. Peak and Valley Current Control for Cuk PFC Converter to Reduce Capacitance[J]. 2022,37(1):313-321. DOI:10.1109 / TPEL.2021.3099218. Assume the input filter inductor L1 The charging direction is the reference positive direction, and the input power frequency average current is at this time. i av1 Constant; combining equations (9) and (10), and substituting equation (13), we can obtain: (14) Coupling capacitor C1 voltage V C1 Using coupling capacitors C1 preset target voltage value V C1ref Replace, at the same time sin ( w g t (This is related to the input AC voltage) V ac Unit sine waves with the same phase and frequency sin; The above equation simplifies to equation (8), which is the input filter inductance. L1 Peak reference current i pk ; Based on the average output current I DC Coupling capacitors C1 preset target voltage value V C1ref Output filter capacitor C2 preset target voltage value V C2ref Maximum input AC voltage Value V AC_max Input filter inductor L1 inductance value L L1 Output filter inductor L2 inductance value L L2Voltage of coupling capacitor C1 V C1 The absolute value of the input AC voltage |V ac | Input power frequency average current i av1 peak I g The output filter inductor is obtained. L2 Valley reference current i vy The output filter inductor L2 Valley reference current i vy The expression is: (15) The following discusses the output filter inductor. L2 Valley reference current i vy The principle can be explained as follows: Output filter inductor L2 Operating in CCM mode, in order to obtain a stable output filter capacitor C2 voltage V C2 With the output power remaining constant, the average output current during each switching cycle is made... i av2 Equal to the average output current I DC ,Right now (16) At the same time, within each switching cycle, the following applies: (17) From equation (11), we can obtain: (18) Combining equations (7) and (16), and substituting equations (13), (14), and (17) into the equations, we obtain: (19) Replace the voltage VC1 of coupling capacitor C1 and the voltage VC2 of output filter capacitor C2 with the preset target voltage values ​​VC1ref of coupling capacitor C1 and VC2ref of output filter capacitor C2, and the above equation can be simplified to the valley reference current ivy of output filter inductor L2 in equation (15). Based on the input filter inductor L1 current i L1 Output filter inductor L2 current iL2 Input filter inductor L1 Peak reference current i pk Valley reference current of output filter inductor i vy The output controls the drive signal of the Cuk PFC circuit.

[0032] A peak-valley current control device for a Cuk PFC circuit based on average current calculation, comprising: Sampling unit: Samples the voltage of the coupling capacitor, the voltage of the output filter capacitor, the input AC voltage, the current of the input filter inductor, and the current of the output filter inductor in the Cuk PFC circuit; First error amplification unit: Obtains the average output current based on the voltage of the output filter capacitor and the preset target voltage value of the output filter capacitor; Second error amplification unit: Based on the voltage of the coupling capacitor and the preset target voltage value of the coupling capacitor, obtain the error value of the voltage of the coupling capacitor; Subtraction unit: Based on the average output current and the error value of the coupling capacitor voltage, the peak value of the average input power frequency current is obtained; Proportional calculation unit: Based on the input AC voltage, it obtains a unit sine wave with the same phase and frequency as the input AC voltage; Absolute value calculation unit: Obtains the absolute value of the input AC voltage based on the input AC voltage; The first arithmetic unit calculates the peak reference current of the input filter inductor based on the peak value of the input power frequency average current, the unit sine wave with the same phase and frequency as the input AC voltage, the voltage of the coupling capacitor, the absolute value of the input AC voltage, and the preset target voltage value of the output filter capacitor. The second calculation unit: Based on the average output current, the preset target voltage value of the coupling capacitor, the preset target voltage value of the output filter capacitor, the maximum value of the input AC voltage, the inductance value of the input filter inductor, the inductance value of the output filter inductor, the voltage of the coupling capacitor, the absolute value of the input AC voltage, and the peak value of the average input power frequency current, the valley reference current of the output filter inductor is obtained. Control logic unit: Based on the current of the input filter inductor, the current of the output filter inductor, the peak reference current of the input filter inductor, and the valley reference current of the output filter inductor, output the drive signal to control the Cuk PFC circuit.

[0033] See Figure 2 and Figure 3 The present invention provides an implementation of a peak-valley current control device for a Cuk PFC circuit based on average current calculation; The sampling unit includes a first isolation operational amplifier sampling subunit, a linear optocoupler sampling subunit, a second isolation operational amplifier sampling subunit, a third isolation operational amplifier sampling subunit, and a fourth isolation operational amplifier sampling subunit; the first isolation operational amplifier sampling subunit is used to acquire the input AC voltage. V ac The linear optical coupler sampling subunit is used to acquire the coupling capacitance. C1 voltage V C1 The second isolation operational amplifier sampling subunit is used to acquire the output filter capacitor data. C2 voltage V C2 The third isolation operational amplifier sampling subunit is used to acquire the input filter inductance. L1 current i L1 The fourth isolation operational amplifier sampling subunit is used to sample the input filter inductance. L2 current i L2 The first isolation operational amplifier sampling subunit, the second isolation operational amplifier sampling subunit, the third isolation operational amplifier sampling subunit, and the fourth isolation operational amplifier sampling subunit all include isolation operational amplifiers; the linear optocoupler sampling subunit includes a linear optocoupler.

[0034] The first error amplification unit includes operational amplifier I9, operational amplifier I10, resistors R20, R21, R22, R23, R24, R25, and capacitor C4; the first end of resistor R20 is connected to the output terminal of the second isolation operational amplifier sampling subunit (used to receive the output filter capacitor). C2 voltage V C2 The second terminal of resistor R20 is connected to the first terminal of resistor R21 and the inverting input (-) of operational amplifier I9. The non-inverting input (+) of operational amplifier I9 is ​​connected to the second terminal of resistor R22 and the first terminal of resistor R23. The first terminal of resistor R22 is used to receive the output filter capacitor. C2 preset target voltage value V C2ref / 16 The second terminal of resistor R23 is grounded. The second terminal of resistor R21 is connected to the output terminal of operational amplifier I9 and the first terminal of resistor R24. The second terminal of resistor R24 ​​is connected to the first terminal of resistor R25 and the inverting input terminal (-) of operational amplifier I10. The non-inverting input terminal (+) of operational amplifier I10 is grounded. The second terminal of R25 is connected to the first terminal of capacitor C4. The second terminal of capacitor C4 is connected to the output terminal of operational amplifier I10, and outputs the average value of the output current. I DC ; The second error amplification unit includes operational amplifier I7, operational amplifier I8, resistors R14, R15, R16, R17, R18, R19, and capacitor C3; the first end of resistor R14 is connected to the output terminal of the linear optocoupler sampling subunit (for receiving coupling capacitance). C1 voltage V C1 The second terminal of resistor 14 is connected to the first terminal of resistor R15 and the inverting input (-) of operational amplifier 17. The non-inverting input (+) of operational amplifier 17 is connected to the second terminal of resistor R16 and the first terminal of resistor R17. The first terminal of resistor R16 is used to receive the coupling capacitor. C1 preset target voltage value V C1ref / 80 The second terminal of resistor R17 is grounded. The second terminal of resistor R15 is connected to the output terminal of operational amplifier I7 and the first terminal of resistor R18. The second terminal of resistor R18 is connected to the first terminal of resistor R19 and the inverting input terminal (-) of operational amplifier I8. The non-inverting input terminal (+) of operational amplifier I8 is grounded. The second terminal of R19 is connected to the first terminal of capacitor C3. The second terminal of capacitor C3 is connected to the output terminal of operational amplifier I8, and outputs the error value of the voltage of the coupling capacitor. err vC1 ; The subtraction unit includes an operational amplifier I14, resistors R30, R31, R32, and R33; the first terminal of resistor R30 is connected to the connection point between the second terminal of capacitor C3 and the output terminal of operational amplifier I8 (used to receive the error value of the voltage of the coupling capacitor). err vC1 The second end of resistor R30 is connected to the first end of resistor R31, the inverting input (-) of operational amplifier I14, and the non-inverting input (+) of operational amplifier I14. These connections are then connected to the second end of resistor R32 and the first end of resistor R33. The first end of resistor R32 is connected to the junction between the second end of capacitor C4 and the output terminal of operational amplifier I10 (used to receive the average output current). I DC The first terminal of resistor R31 is connected to the output terminal of operational amplifier I14, and outputs the average current at the input power frequency. i av1 peak I g ; The proportional operation unit includes operational amplifier I2, resistor R3, and resistor R4; the first end of resistor R3 is connected to the output terminal of the first isolation operational amplifier sampling subunit (for receiving input AC voltage). V ac / 80 The absolute value operation unit is connected to the second terminal of resistor R3, the first terminal of resistor R4, the positive input terminal (+) of operational amplifier I2, and ground. The negative input terminal (-) of operational amplifier I2 is connected to the output terminal of operational amplifier I2, and the output is an AC voltage equal to the input voltage. V ac Unit sine waves with the same phase and frequency sin ; The absolute value calculation unit includes operational amplifier I3, operational amplifier I4, diode D6, diode D7, resistors R5, R6, R7, R8, and R9; the first terminal of resistor R5 is connected to the first terminal of resistor R8, the proportional calculation unit, and the output terminal of the first isolation operational amplifier sampling subunit (used to receive input AC voltage). V ac / 80 The second terminal of resistor R5 is connected to the inverting input (-) of operational amplifier I3, the cathode of diode D7, and the first terminal of resistor R6. The non-inverting input (+) of operational amplifier I3 is grounded. The anode of diode D7 is connected to the output terminal of operational amplifier I3 and the cathode of diode D6. The anode of diode D6 is connected to the second terminal of resistor R6 and the first terminal of resistor R7. The second terminal of resistor R7 is connected to the inverting input (-) of operational amplifier I4, the second terminal of R8, the first terminal of resistor R9, and the non-inverting input (+) of operational amplifier I4, which is grounded. The second terminal of resistor R9 is connected to the output terminal of operational amplifier I4, outputting the absolute value of the input AC voltage. |V ac / 80| ; The first operational unit includes operational amplifier I11, multiplier I18, resistors R26, R27, R28, and R29, and multiplier I19; the first terminal of resistor R26 is connected to the junction between the second terminal of resistor R9 and the output terminal of operational amplifier I4 (used to receive the absolute value of the input AC voltage). |V ac / 80| The second terminal of resistor R26 is connected to the first terminal of resistor R28, the inverting input (-) of operational amplifier I11, and the non-inverting input (+) of operational amplifier I11. These terminals are then connected to the second terminal of resistor R27 and the first terminal of resistor R29. The first terminal of resistor R27 is connected to the output of the linear optocoupler sampling subunit. The second terminal of resistor R29 is grounded. The output of operational amplifier I11 is connected to the second terminal of resistor R28 and the first input of multiplier I18. The second input of multiplier I18 is connected to the junction between the first terminal of resistor R31 and the output of operational amplifier I14 (used to receive the input power frequency average current). iav1 peak I g The output of multiplier I18 is connected to the first input of multiplier I19. The second input of multiplier I19 is connected to the junction between the inverting input (-) of operational amplifier I2 and the output of operational amplifier I2 (used to receive the input AC voltage). V ac Unit sine waves with the same phase and frequency sin The output of multiplier I19 is filtered by an inductor. L1 Peak reference current i pk; ; The second operational unit includes operational amplifier I11, multiplier I18, resistors R26, R27, R28, R29, R34, R35, R36, R37, and R38. The system includes resistor R39, operational amplifier I12, operational amplifier I13; multiplexed amplifier I11 for the first and second operational units; multiplier I118; resistors R26, R27, R28, and R29; the output of multiplier I118 is connected to the first terminal of resistor R34; the second terminal of resistor R34 is connected to the first terminal of resistor R35 and the positive input terminal (+) of operational amplifier I12; the second terminal of resistor R35 is grounded; the output of operational amplifier I12 is connected to the negative input terminal (-) of operational amplifier I12 and the first terminal of resistor R36; the second terminal of resistor R36 is connected to the first terminal of resistor R37 and the negative input terminal (-) of operational amplifier I13; the positive input terminal (+) of operational amplifier I13 is connected to the second terminal of resistor R38 and the first terminal of resistor R39; the first terminal of resistor R38 is connected to the connection point between the second terminal of capacitor C4 and the output terminal of operational amplifier I10 (used to receive the average output current). I DC The first terminal of resistor R39 is grounded, and the second terminal of resistor R37 is connected to the output terminal of operational amplifier I13, and also serves as the output filter inductor. L2 Valley reference current i vy ; The control logic unit includes multiple comparators and digital control modules (such as FPGA and microcontroller). When the control logic unit is as follows Figure 4 In the case of a bridged Cuk PFC circuit, the control logic unit includes comparator I20, comparator I21, and a second digital control module; the positive input terminal (+) of comparator I20 is connected to the output terminal of multiplier I19 (used to receive the input filter inductor). L1 Peak reference currenti pk The inverting input (-) of comparator I20 is connected to the output of the third isolation operational amplifier sampling subunit (used to receive the current iL1 of the input filter inductor L1). The output of comparator I20 is connected to the first input of the second digital control module. The non-inverting input (+) of comparator I21 is connected to the junction between the second end of resistor R37 and the output of operational amplifier I13 (used to receive the current iL1 of the output filter inductor). L2 Valley reference current i vy The inverting input (-) of comparator I21 is connected to the output of the fourth isolation operational amplifier sampling subunit (used to receive the output filter inductor). L2 current i L2 The output of comparator I21 is connected to the second input of the second digital control module, and the output of the second digital control module is connected to the gate of the switching transistor S, which is used to output the drive signal to control the bridged Cuk PFC circuit.

[0035] When the control logic unit is as follows Figure 5 In the bridgeless Cuk PFC circuit, the control logic unit includes comparator I15, comparator I16, comparator I17, and a first digital control module; the positive input (+) of comparator I15 is connected to the output of multiplier I19 (used to receive the input filter inductor). L1 Peak reference current i pk The inverting input (-) of comparator I15 is connected to the output of the third isolation operational amplifier sampling subunit (used to receive the current iL1 of the input filter inductor L1). The output of comparator I15 is connected to the first input of the first digital control module. The non-inverting input (+) of comparator I16 is connected to the connection point between the second end of resistor R37 and the output of operational amplifier I13 (used to receive the current iL1 of the output filter inductor L1). L2 Valley reference current i vy The inverting input (-) of comparator I16 is connected to the output of the fourth isolation operational amplifier sampling subunit (used to receive the output filter inductor). L2 current i L2 The output of comparator I16 is connected to the second input of the first digital control module, and the positive input (+) of comparator I17 is connected to the output of the first isolation operational amplifier sampling subunit (used to receive the input AC voltage). V ac / 80The inverting input terminal (-) of comparator I17 is grounded. The output terminal of comparator I17 is connected to the third input terminal of the first digital control module. The first output terminal of the first digital control module is connected to the gate of high-frequency transistor H1. The second output terminal of the first digital control module is connected to the gate of high-frequency transistor H2. The third output terminal of the first digital control module is connected to the gate of power frequency transistor M1. The fourth output terminal of the first digital control module is connected to the gate of power frequency transistor M2. The fifth output terminal of the first digital control module is connected to the gate of high-frequency transistor H3. These are used to output the drive signal for controlling the bridgeless CukPFC circuit.

[0036] Simulation test In PSIM simulation software, the method of this invention is used to respectively... Figure 4 Bridged Cuk PFC circuit and such Figure 5 Modal control testing of a bridgeless Cuk PFC circuit: Figure 6 The diagram shows the operating mode of the bridged Cuk PFC circuit based on the peak-valley current control method of this invention. It can be seen from the diagram that when the switching transistor S is on, the input filter inductor... L1 and output filter inductor L2 Charged, input filter inductor L1 current i L1 and output filter inductor L2 current i L2 Rise until the input filter inductor L1 current i L1 Greater than the input filter inductance L1 Peak reference current i pk When the switching transistor S is off, the input filter inductor... L1 and output filter inductor L2 Energy release, input filter inductor L1 current i L1 and output filter inductor L2 current i L2 The inductance decreases until the output filter inductor... L2 current i L2 Less than the output filter inductance L2 Valley reference current i vy When the switching transistor S is turned on, the next switching cycle begins. Figure 7The diagram shows the operating mode of the bridgeless Cuk PFC circuit under the peak-valley current control method of this invention. As can be seen from the diagram, during the AC positive half-cycle, the power frequency transistor M1 is always on, and the power frequency transistor M2 is always off. The logic for the high-frequency transistors is as follows: when high-frequency transistors H1 and H2 are on, and high-frequency transistor H3 is off, the input filter inductor... L1 and output filter inductor L2 Charged, input filter inductor L1 current i L1 and output filter inductor L2 current i L2 Rise until the input filter inductor L1 current i L1 Greater than the input filter inductance L1 Peak reference current i pk When high-frequency transistors H1 and H2 are turned off, high-frequency transistor H3 is turned on, and the input filter inductor... L1 and output filter inductor L2 Energy release, input filter inductor L1 current i L1 and output filter inductor L2 current i L2 The inductance decreases until the output filter inductor... L2 current i L2 Less than the output filter inductance L2 Valley reference current i vy When the high-frequency transistors H1 and H2 are turned on, the high-frequency transistor H3 is turned off, and the next switching cycle begins. During the negative half-cycle of the AC circuit, the power frequency transistor M2 is always on, and the power frequency transistor M1 is always off. The logic for the high-frequency transistors is as follows: when high-frequency transistors H1 and H2 are on, and high-frequency transistor H3 is off, the input filter inductor... L1 Reverse-charged, output filter inductor L2 Charged, input filter inductor L1 current i L1 Decrease, output filter inductor L2 current i L2 Rise until the input filter inductor L1 current i L1 Less than the input filter inductance L1 Peak reference current i pkWhen H1 and H2 are turned off, H3 is turned on, and the input filter inductor... L1 and output filter inductor L2 Energy release, input filter inductor L1 current i L1 Rise, output filter inductor L2 current i L2 The inductance decreases until the output filter inductor... L2 current i L2 Less than the output filter inductance L2 Valley reference current i vy At this time, high-frequency transistors H1 and H2 are turned on, while high-frequency transistor H3 is turned off, and the next switching cycle begins.

[0037] Figure 8 The waveform simulation diagram of the bridged Cuk PFC circuit under the peak-valley current control method of the present invention is shown. Figure 8 In Figure (a), the waveforms of the normalized input AC voltage and the input AC current after EMI filtering are shown. The test result PF is 0.995. Figure 8 (b) shows the waveform after amplifying the output -100V voltage, with ripple within 0.4V, proving the effectiveness of the peak-valley current control method for low output voltage ripple proposed in this invention. Figure 9 The waveform simulation diagram of the bridged Cuk PFC circuit under the peak-valley current control method of the present invention is shown. Figure 9 (a) in the figure represents the input filter inductor. L1 current i L1 and input filter inductor L1 Peak reference current i p The relationship between k Figure 9 (b) in the figure represents the output filter inductor. L2 current i L2 and the valley reference current of the output filter inductor i vy The relationship between them Figure 9 (c) in the figure is the control waveform of the switching transistor S. It can be seen from the three figures that the control mode switching of the bridged Cuk PFC circuit is as expected.

[0038] Figure 10 The waveform simulation diagram of the bridgeless Cuk PFC circuit under the peak-valley current control method of the present invention is shown. Figure 10In Figure (a), the waveforms of the normalized input AC voltage and the input AC current after EMI filtering are shown. The test result PF is 0.995. Figure 10 (b) shows the waveform after amplifying the -100V output voltage, with ripple within 0.4V, demonstrating the effectiveness of the peak-valley current control method for low output voltage ripple proposed in this invention.

[0039] Figure 11 The waveform simulation diagram of the bridgeless Cuk PFC circuit under the peak-valley current control method of the present invention is shown. Figure 11 (a) in the figure represents the input filter inductor. L1 current i L1 and input filter inductor L1 Peak reference current i p The relationship between k Figure 11 (b) in the figure represents the output filter inductor. L2 current i L2 and the valley reference current of the output filter inductor i vy The relationship between them Figure 11 (c) in the diagram represents the control waveforms for high-frequency transistors H1 and H2. Figure 11 (d) in the figure is the control waveform of the high-frequency tube H3. It can be seen from the four figures that the control mode switching of the bridge Cuk PFC circuit is as expected.

[0040] In summary, both bridged and bridgeless Cuk PFC circuits achieve the expected control mode and exhibit low output voltage ripple and high power factor through the peak-valley current control method based on this invention.

[0041] 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 modifications, equivalent substitutions or improvements made by those skilled in the art within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A peak-valley current control method for a Cuk PFC circuit based on average current calculation, characterized in that: Includes the following steps: Sample the voltage of the coupling capacitor, the voltage of the output filter capacitor, the input AC voltage, the current of the input filter inductor, and the current of the output filter inductor in the Cuk PFC circuit; The average output current is obtained based on the voltage of the output filter capacitor and the preset target voltage value of the output filter capacitor. Based on the voltage of the coupling capacitor and the preset target voltage value of the coupling capacitor, the error value of the voltage of the coupling capacitor is obtained; The peak value of the average input current at the power frequency is obtained based on the average output current and the error value of the voltage of the coupling capacitor. Based on the input AC voltage, a unit sine wave with the same phase and frequency as the input AC voltage is obtained; Based on the input AC voltage, obtain the absolute value of the input AC voltage; The peak reference current of the input filter inductor is obtained based on the peak value of the average input current at the power frequency, the unit sine wave with the same phase and frequency as the input AC voltage, the voltage of the coupling capacitor, the absolute value of the input AC voltage, and the preset target voltage value of the output filter capacitor. The valley reference current of the output filter inductor is obtained based on the average output current, the preset target voltage value of the coupling capacitor, the preset target voltage value of the output filter capacitor, the maximum value of the input AC voltage, the inductance value of the input filter inductor, the inductance value of the output filter inductor, the voltage of the coupling capacitor, the absolute value of the input AC voltage, and the peak value of the average input power frequency current. Based on the current of the input filter inductor, the current of the output filter inductor, the peak reference current of the input filter inductor, and the valley reference current of the output filter inductor, the drive signal for controlling the Cuk PFC circuit is output.

2. The peak-valley current control method for a Cuk PFC circuit based on average current calculation according to claim 1, characterized in that: The input filter inductor operates in intermittent conduction mode, while the output filter inductor operates in continuous conduction mode.

3. The peak-valley current control method for a Cuk PFC circuit based on average current calculation according to claim 1, characterized in that: The expression for the average value of the output current is: in, I DC This is the average value of the output current. err vDC This is the output of the first error amplification unit. f 1 represents the operator of the first error amplification unit. V C2ref The preset target voltage value for the output filter capacitor. V C2 This is the voltage across the output filter capacitor.

4. The peak-valley current control method for a Cuk PFC circuit based on average current calculation according to claim 1, characterized in that: The expression for the error value of the voltage of the coupling capacitor is: in, err vC1 This represents the error value of the voltage across the coupling capacitor. f 2 represents the operator of the second error amplification unit. V C1 The voltage across the coupling capacitor. V C1ref This is the preset target voltage value for the coupling capacitor.

5. The peak-valley current control method for a Cuk PFC circuit based on average current calculation according to claim 1, characterized in that: The expression for the peak value of the input power frequency average current is: in, I g The peak value of the input power frequency average current. err vDC This is the output of the first error amplification unit. err vC1 This represents the error value of the voltage across the coupling capacitor.

6. The peak-valley current control method for a Cuk PFC circuit based on average current calculation according to claim 1, characterized in that: The peak reference current of the input filter inductor is: in, i pk The peak reference current of the input filter inductor. I g The peak value of the input power frequency average current. sin It is a unit sine wave with the same phase and frequency as the input AC voltage. V C1 The voltage across the coupling capacitor, | V ac | represents the absolute value of the input AC voltage. V C2ref This is the preset target voltage value for the output filter capacitor.

7. The peak-valley current control method for a Cuk PFC circuit based on average current calculation according to claim 1, characterized in that: The expression for the valley reference current of the output filter inductor is: in, i vy The valley reference current for the output filter inductor, I DC This is the average value of the output current. V C1ref This is the preset target voltage value for the coupling capacitor. V C2ref The preset target voltage value for the output filter capacitor. V AC_max This represents the maximum value of the input AC voltage. L L1 The inductance value of the input filter inductor. L L2 The inductance value of the output filter inductor. V C1 The voltage across the coupling capacitor, | V ac | represents the absolute value of the input AC voltage. I g This represents the peak value of the average input power frequency current.

8. A peak-valley current control device for a Cuk PFC circuit based on average current calculation, characterized in that: include: Sampling unit: Samples the voltage of the coupling capacitor, the voltage of the output filter capacitor, the input AC voltage, the current of the input filter inductor, and the current of the output filter inductor in the Cuk PFC circuit; First error amplification unit: Obtains the average output current based on the voltage of the output filter capacitor and the preset target voltage value of the output filter capacitor; Second error amplification unit: Based on the voltage of the coupling capacitor and the preset target voltage value of the coupling capacitor, obtain the error value of the voltage of the coupling capacitor; Subtraction unit: Based on the average output current and the error value of the coupling capacitor voltage, the peak value of the average input power frequency current is obtained; Proportional calculation unit: Based on the input AC voltage, it obtains a unit sine wave with the same phase and frequency as the input AC voltage; Absolute value calculation unit: Obtains the absolute value of the input AC voltage based on the input AC voltage; First arithmetic unit: Based on the peak value of the input power frequency average current, the unit sine wave with the same phase and frequency as the input AC voltage, the voltage of the coupling capacitor, the absolute value of the input AC voltage, and the preset target voltage value of the output filter capacitor, the peak reference current of the input filter inductor is obtained. The second calculation unit: Based on the average output current, the preset target voltage value of the coupling capacitor, the preset target voltage value of the output filter capacitor, the maximum value of the input AC voltage, the inductance value of the input filter inductor, the inductance value of the output filter inductor, the voltage of the coupling capacitor, the absolute value of the input AC voltage, and the peak value of the average input power frequency current, the valley reference current of the output filter inductor is obtained. Control logic unit: Based on the current of the input filter inductor, the current of the output filter inductor, the peak reference current of the input filter inductor, and the valley reference current of the output filter inductor, output the drive signal to control the Cuk PFC circuit.

Images