Cuk type power factor correction circuit based on switched inductor

Abstract

The application discloses a Cuk type power factor correction circuit based on a switching inductor, which comprises switching tubes S1-S3, diodes D1-D5, inductors L1-L5, capacitors C1 and C o Among them, diodes D3-D5 and inductors L3 and L4 form a switching inductor structure.The converter voltage gain is D / (2-D), compared with a traditional Cuk PFC converter, the power factor correction circuit realizes positive voltage output, improves the step-down gain, ensures that the whole duty cycle range is in a step-down state, and the duty cycle is larger than that of the traditional Cuk PFC converter in the case of high step-down ratio, and the emergence of the limit duty cycle condition is effectively avoided.The application of the bridgeless structure can realize lower on-state loss.The power factor correction circuit has the advantages of continuous input and output current, high power factor and high efficiency, and has great practical value.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter technology, specifically a Cuk-type power factor correction circuit based on a switched inductor. Background Technology

[0002] With the depletion of traditional energy resources and increasingly severe air pollution, smart grids, primarily based on distributed generation and clean energy, are gradually replacing traditional power grids that rely mainly on fossil fuel power generation. There are many applications in smart grids that require low-voltage DC power, such as lithium battery charging and auxiliary power supplies in distribution cabinets. Therefore, developing AC-DC converters with high step-down ratios and high efficiency is particularly necessary.

[0003] Traditional single-phase active power factor correction (APFC) converters consist of a front-end bridge rectifier circuit and a rear-end DC-DC circuit. Commonly used DC-DC circuits include Buck, Boost, Buck-Boost, Cuk, Sepic, and Zeta circuits. Because Buck converters have an inherent input current dead zone (zero input current), this leads to significant total harmonic distortion (THD) and a low power factor (PF). Boost converters are the most widely used due to their continuous input current, but they are only suitable for boost mode; adding another stage is necessary to achieve low output voltage, which undoubtedly increases overall cost and size. Buck-Boost converters have a negative output voltage polarity and discontinuous input current, resulting in a low power factor. Sepic converters have continuous input current but discontinuous output current, leading to high output voltage ripple. Cuk converters have continuous input current, low ripple, and a wide output voltage range, making them widely used in low-voltage power supply applications. Summary of the Invention

[0004] To address the issues of low efficiency, limited duty cycle range in buck mode, and negative output voltage polarity in traditional Cuk PFC converters, which necessitate the addition of an inverting amplifier circuit, thus increasing the converter's size and cost, this invention proposes a Cuk-type power factor correction circuit based on a switched inductor. This circuit achieves positive voltage output, improves buck gain, ensures buck operation across the entire duty cycle range, and provides a higher duty cycle than traditional Cuk PFC converters at high buck ratios, effectively avoiding extreme duty cycle conditions.

[0005] The technical solution adopted in this invention is as follows:

[0006] A Cuk-type power factor correction circuit based on a switched inductor, including an AC power supply u s Switches S1~S3, diodes D1~D5, inductors L1~L5, capacitors C1, C o ,

[0007] AC power supply u s One side is connected to the source of the switching transistor S3 and one end of the inductor L1, and the other end of the inductor L1 is connected to the cathode of the diode D1.

[0008] AC power supply u s On the other side, the source of the switching transistor S2 and one end of the inductor L2 are connected respectively, and the other end of the inductor L2 is connected to the cathode of the diode D2.

[0009] The negative terminal of capacitor C1 is connected to the anode of diode D1, the anode of diode D2, and the source of switching transistor S1, respectively.

[0010] One end of inductor L5 is connected to the positive terminal of capacitor C1, the cathode of diode D3, and one end of inductor L3. The other end of inductor L5 is connected to the output capacitor C. o Positive terminals connected;

[0011] The other end of inductor L3 is connected to the cathodes of diodes D4 and D5, respectively;

[0012] One end of inductor L4 is connected to the anodes of diodes D3 and D5, respectively; the other end of inductor L4 is connected to the anode of diode D4, the drain of switching transistors S1, S2, and S3, and the output capacitor C, respectively. o negative electrode;

[0013] Output capacitor C o With load R L in parallel.

[0014] In this power factor correction circuit, inductor L3, inductor L4, diode D3, diode D4, and diode D5 constitute a switching inductor unit.

[0015] In this power factor correction circuit, the power switching transistors S1~S3 are insulated gate bipolar transistors (IGBTs), integrated gate commutated thyristors (IGCTs), or power field-effect transistors (MOSFETs).

[0016] The power factor correction circuit outputs a positive voltage with a voltage gain of D / (2-D).

[0017] This power factor correction circuit has the following four operating modes in CCM mode:

[0018] Operating mode 1: The circuit operates under AC power supply u sDuring the positive half-cycle, switches S1 and S3 are turned on, while switch S2 is turned off. Diodes D2 and D5 are forward-biased and conduct, while the remaining diodes are reverse-biased and cut off. During this process, the AC power supply u... s Inductor L2 is charged, and capacitor C1 discharges to charge inductor L5, causing the current in inductors L2 and L5 to increase linearly. Inductors L3 and L4, through diode D5, supply current to inductor L5 and output capacitor C. o and load R L During discharge, the currents in inductors L3 and L4 decrease linearly.

[0019] Operating mode 2: The circuit operates under AC power supply u s During the positive half-cycle, switch S3 is turned on, while switches S1 and S2 are turned off. Diodes D2, D3, and D4 are forward-biased and conduct, while the remaining diodes are reverse-biased and cut off. During this process, inductor L2 discharges, while capacitor C1 and inductors L3 and L4 are charged. The currents in inductors L3 and L4 increase linearly, while the current in inductor L2 decreases linearly. Inductor L5 supplies power to the load R. L and output capacitor C o Discharge occurs, and the current in inductor L5 decreases linearly.

[0020] Operating mode 3: At this time, the circuit operates under AC power supply u s During the negative half-cycle, switches S1 and S2 are turned on, while switch S3 is turned off. Diodes D1 and D5 are forward-biased and conduct, while the remaining diodes are reverse-biased and cut off. During this process, the AC power supply u... s Inductor L1 is charged, and capacitor C1 discharges to charge inductor L5, causing the current in inductors L1 and L5 to increase linearly. Inductors L3 and L4, through diode D5, supply power to inductor L5 and output capacitor C... o and load R L During discharge, the currents in inductors L3 and L4 decrease linearly.

[0021] Operating mode four: The circuit operates under AC power supply u s During the negative half-cycle, switch S2 is turned on, while switches S1 and S3 are turned off. Diodes D1, D3, and D4 are forward-biased and conduct, while the remaining diodes are reverse-biased and cut off. During this process, inductor L1 discharges, while capacitor C1 and inductors L3 and L4 are charged. The currents in inductors L3 and L4 increase linearly, while the current in inductor L1 decreases linearly. Inductor L5 supplies power to the load R. L and output capacitor C o Discharge occurs, and the current in inductor L5 decreases linearly.

[0022] This invention provides a Cuk-type power factor correction circuit based on a switched inductor, with the following technical advantages:

[0023] 1) The voltage gain of the power factor correction circuit of this invention is changed from M=D / (1-D) in the traditional Cuk PFC converter to M=D / (2-D), and the converter is in buck mode throughout the full duty cycle. A high buck ratio helps solve the reverse recovery problem of the switching transistor, which is beneficial for stabilizing the output voltage and improving efficiency.

[0024] 2) The power factor correction circuit of this invention introduces a switching inductor unit, which makes the input power supply current and the output load current continuous and with small ripple, which is beneficial for filtering the input and output and improving the power factor.

[0025] 3) The power factor correction circuit of this invention realizes positive polarity voltage output, which makes the application scenarios more extensive; the output voltage sampling circuit does not require an inverter, which helps to reduce the size of the converter and reduce costs.

[0026] 4) The power factor correction circuit of this invention adopts a bridgeless structure, which reduces conduction losses and helps to improve the overall efficiency of the converter. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Figure 1 This is a main topology diagram of a Cuk-type power factor correction circuit based on a switching inductor according to the present invention.

[0029] Figure 2 This is a schematic diagram of the first operating mode of a Cuk-type power factor correction circuit based on a switching inductor according to the present invention.

[0030] Figure 3 This is a schematic diagram of the second operating mode of a Cuk-type power factor correction circuit based on a switching inductor according to the present invention.

[0031] Figure 4 This is a schematic diagram of the third operating mode of a Cuk-type power factor correction circuit based on a switching inductor according to the present invention.

[0032] Figure 5 This is a schematic diagram of the fourth operating mode of a Cuk-type power factor correction circuit based on a switching inductor according to the present invention.

[0033] Figure 6 This is a steady-state key waveform diagram of a Cuk-type power factor correction circuit based on a switched inductor according to the present invention.

[0034] Figure 7 This is a schematic diagram comparing the voltage gain of a Cuk-type power factor correction circuit based on a switched inductor according to the present invention with that of a conventional Cuk PFC converter.

[0035] Figure 8The image shows the input voltage and current waveforms of a Cuk-type power factor correction circuit based on a switched inductor under steady-state conditions, according to the present invention.

[0036] Figure 9 The output voltage and current waveforms of a Cuk-type power factor correction circuit based on a switched inductor according to the present invention are shown in steady state. Detailed Implementation

[0037] like Figure 1 As shown, this invention discloses a Cuk-type power factor correction circuit based on a switched inductor, comprising switching transistors S1~S3, diodes D1~D5, inductors L1~L5, and capacitors C1 and C2. o ;

[0038] The converter inductors L3 and L4, and diodes D3, D4 and D5 form a switching inductor unit;

[0039] AC power supply u s One side is connected to the source of switching transistor S3 and one end of inductor L1, and the other end of inductor L1 is connected to the cathode of diode D1; AC power supply u s On the other side, the source of the switching transistor S2 and one end of the inductor L2 are connected respectively, and the other end of the inductor L2 is connected to the cathode of the diode D2.

[0040] The negative terminal of capacitor C1 is connected to the anodes of diodes D1 and D2 and the source of switching transistor S1, respectively.

[0041] One end of inductor L5 is connected to the positive terminal of capacitor C1, the cathode of diode D3, and one end of inductor L3. The other end of inductor L5 is connected to the output capacitor C. o Positive terminals connected;

[0042] The other end of inductor L3 is connected to the cathodes of diodes D4 and D5, respectively;

[0043] One end of inductor L4 is connected to the anodes of diodes D3 and D5 respectively;

[0044] The other end of inductor L4 is connected to the anode of diode D4, the drain of switching transistors S1, S2, and S3, and the output capacitor C. o Negative terminals connected;

[0045] Output capacitor C o With load R L in parallel.

[0046] The specific parameters of the circuit are as follows: the effective value of the AC input voltage of the converter is 220V, the frequency is 50Hz, the switching frequency is 50kHz, the rated output power is 200W, and the DC side output voltage is V. o =48V, inductors L1=L2=2mH, L3=L4=22uH, L5=100uH, DC output capacitor Co =1600μF, capacitor C1=1μF, load resistance R L =11.5Ω.

[0047] The Cuk-type power factor correction circuit based on a switched inductor, under steady-state operation in CCM mode, includes the following operating modes:

[0048] Working Mode 1: such as Figure 2 As shown, the circuit is currently operating with AC power supply u. s During the positive half-cycle, switches S1 and S3 are turned on, diodes D2 and D5 are forward-biased and conducting, and all other semiconductor devices are turned off. In this process, the power supply charges inductor L2, capacitor C1 charges inductor L5, and inductors L3 and L4 charge inductor L5 and output capacitor C through diode D5. o and load discharge. This process corresponds to Figure 6 During the time interval (t0~t1), the voltage relationship across the inductor in this process is as follows:

[0049] (1);

[0050] Among them, V C1 It is the voltage stress of capacitor C1, V S1 It is the voltage stress of the switching transistor S1, V g This is the drive signal for switch S1. It is assumed that all components are in ideal condition, the diode forward voltage drop is zero, the capacitor has a sufficiently large capacitance and no equivalent series resistance, and the inductor has no resistance.

[0051] Working Mode 2: such as Figure 3 As shown, the circuit operates under AC power supply u s During the positive half-cycle, switch S3 is turned on, diodes D2, D3, and D4 are forward-biased and conducting, and all other semiconductor devices are turned off. During this process, inductor L2 discharges, capacitor C1, inductors L3 and L4 are charged, and inductor L5 charges the load and output capacitor C. o Discharge. This process corresponds to... Figure 6 During the time interval (t1~t2), the voltage relationship across the inductor in this process is as follows:

[0052] (2);

[0053] Working Mode 3: such as Figure 4 As shown, the circuit is currently operating with AC power supply u. s During the negative half-cycle, switches S1 and S2 are turned on, diodes D1 and D5 are forward-biased and conducting, and all other semiconductor devices are turned off. In this process, the power supply charges inductor L1, capacitor C1 charges inductor L5, and inductors L3 and L4 charge inductor L5 and output capacitor C1 via diode D5. o and load discharge. This process corresponds to Figure 6During the time interval (t0~t1), the voltage relationship across the inductor in this process is as follows:

[0054] (3);

[0055] Working Mode 4: such as Figure 5 As shown, the circuit operates under AC power supply u s During the negative half-cycle, switch S3 is turned on, diodes D1, D3, and D4 are forward-biased and conducting, and all other semiconductor devices are turned off. During this process, inductor L1 discharges, capacitor C1, inductors L3 and L4 are charged, and inductor L5 charges the load and output capacitor C. o Discharge. This process corresponds to... Figure 6 During the time interval (t1~t2), the voltage relationship across the inductor in this process is as follows:

[0056] (4);

[0057] Voltage gain analysis when the converter is operating stably:

[0058] Let the switching period of the switching transistor S1 be T. S The duty cycle is D, which means the duration of the working mode is DT. S The duration of the second working mode is (1-D)T S Based on the volt-second balance characteristic of inductors, we can obtain:

[0059] (5);

[0060] By combining equations (1) and (2), we can obtain:

[0061] (6);

[0062] The voltage gain of the power factor correction circuit described in this invention is:

[0063] (7).

[0064] The step-down gain curve of the Cuk-type power factor correction circuit based on a switched inductor in this invention is shown below. Figure 7 As shown. (Through) Figure 7 As can be seen, the converter described in this invention operates in buck mode throughout the entire duty cycle range. In buck mode, the duty cycle range of the converter described in this invention is wider than that of the traditional Cuk PFC converter, effectively avoiding the occurrence of extreme duty cycle conditions of the switching transistors.

[0065] Figure 8This diagram shows the input voltage and current waveforms of the Cuk-type power factor correction circuit based on a switched inductor described in this invention under steady-state conditions. For a more intuitive comparison with the voltage waveform, the current waveform is the actual value multiplied by a gain of 30. It can be seen that the input voltage and input current are in phase and both are sinusoidal, verifying the feasibility of power factor correction.

[0066] Figure 9 This is a steady-state output voltage and current waveform diagram of the Cuk-type power factor correction circuit based on a switched inductor described in this invention. The output voltage is stable at around 48V, and the output current waveform is smooth.

[0067] Compared to traditional Cuk PFC converters, the Cuk-type power factor correction circuit based on a switched inductor described in this invention achieves positive voltage output, improves buck gain, and ensures buck operation across the entire duty cycle range. It also offers a larger duty cycle than traditional Cuk PFC converters at high buck ratios, effectively avoiding extreme duty cycle conditions. The bridgeless structure enables lower conduction losses. This Cuk-type power factor correction circuit based on a switched inductor features continuous input and output current, high power factor, and high efficiency, making it highly practical.

Claims

1. A Cuk-type power factor correction circuit based on a switched inductor, including an AC power supply u s Switches S1~S3, diodes D1~D5, inductors L1~L5, capacitors C1, C o Its features are: AC power supply u s One side is connected to the source of the switching transistor S3 and one end of the inductor L1, and the other end of the inductor L1 is connected to the cathode of the diode D1. AC power supply u s On the other side, the source of the switching transistor S2 and one end of the inductor L2 are connected respectively, and the other end of the inductor L2 is connected to the cathode of the diode D2. The negative terminal of capacitor C1 is connected to the anode of diode D1, the anode of diode D2, and the source of switching transistor S1, respectively. One end of inductor L5 is connected to the positive terminal of capacitor C1, the cathode of diode D3, and one end of inductor L3. The other end of inductor L5 is connected to the output capacitor C. o Positive terminals connected; The other end of inductor L3 is connected to the cathodes of diodes D4 and D5, respectively; One end of inductor L4 is connected to the anodes of diodes D3 and D5; the other end of inductor L4 is connected to the anode of diode D4, the drain of switching transistors S1, S2, and S3, and the output capacitor C. o negative electrode; Output capacitor C o With load R L in parallel; This power factor correction circuit has the following four operating modes: Operating mode 1: The circuit operates under AC power supply u s During the positive half-cycle, switches S1 and S3 are turned on, and switch S2 is turned off; diodes D2 and D5 are forward-biased and conduct, while the remaining diodes are reverse-biased and cut off; during this process, the AC power supply u... s Inductor L2 is charged, and capacitor C1 discharges to charge inductor L5, causing the current in inductors L2 and L5 to increase linearly. Inductors L3 and L4, through diode D5, supply current to inductor L5 and output capacitor C... o and load R L During discharge, the currents in inductors L3 and L4 decrease linearly. Operating mode 2: The circuit operates under AC power supply u s During the positive half-cycle, switch S3 is turned on, while switches S1 and S2 are turned off; diodes D2, D3, and D4 are forward-biased and conduct, while the remaining diodes are reverse-biased and cut off; during this process, inductor L2 discharges, while capacitor C1 and inductors L3 and L4 are charged. The currents in inductors L3 and L4 increase linearly, while the current in inductor L2 decreases linearly; inductor L5 supplies power to the load R. L and output capacitor C o Discharge occurs, and the current in inductor L5 decreases linearly. Operating mode 3: At this time, the circuit operates under AC power supply u s During the negative half-cycle, switches S1 and S2 are turned on, and switch S3 is turned off; diodes D1 and D5 are forward-biased and conduct, while the remaining diodes are reverse-biased and cut off; during this process, the AC power supply u... s Inductor L1 is charged, and capacitor C1 discharges to charge inductor L5, causing the current in inductors L1 and L5 to increase linearly. Inductors L3 and L4 discharge through diode D5 to inductor L5 and output capacitor C. o and load R L During discharge, the currents in inductors L3 and L4 decrease linearly. Operating mode four: The circuit operates under AC power supply u s During the negative half-cycle, switch S2 is turned on, while switches S1 and S3 are turned off; diodes D1, D3, and D4 are forward-biased and conduct, while the remaining diodes are reverse-biased and cut off; during this process, inductor L1 discharges, while capacitor C1 and inductors L3 and L4 are charged. The currents in inductors L3 and L4 increase linearly, while the current in inductor L1 decreases linearly; inductor L5 supplies power to the load R. L and output capacitor C o Discharge occurs, and the current in inductor L5 decreases linearly.

2. The Cuk-type power factor correction circuit based on a switched inductor according to claim 1, characterized in that: In this power factor correction circuit, inductor L3, inductor L4, diode D3, diode D4, and diode D5 constitute a switching inductor unit.

3. The Cuk-type power factor correction circuit based on a switched inductor according to claim 1, characterized in that: In this power factor correction circuit, the power switching transistors S1~S3 are insulated gate bipolar transistors (IGBTs), integrated gate commutated thyristors (IGCTs), or power field-effect transistors (MOSFETs).

4. The Cuk-type power factor correction circuit based on a switched inductor according to claim 1, characterized in that: The power factor correction circuit outputs a positive voltage with a voltage gain of D / (2-D).

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