Bridgeless cuk pfc converter based on switched-inductor-capacitor

Abstract

The application discloses a bridgeless Cuk PFC converter based on a switched-inductor-capacitor structure, which comprises switching tubes S1-S3, diodes D1-D4, inductors L1-L5, capacitors C1, C2 and C o The diodes D3 and D4, the capacitor C2 and the inductors L3 and L4 form a switched-inductor-capacitor structure. The original freewheeling diode is replaced by the switched-inductor-capacitor structure, so that the voltage gain of the converter is D / 2(1-D), compared with a traditional Cuk PFC converter, the converter realizes positive voltage output and improves the voltage reduction gain, and the duty cycle range in the voltage reduction mode is wider. Meanwhile, the bridgeless structure is adopted, so that lower on-state loss can be realized. The converter has continuous input and output currents, high power factor and high efficiency, and has rich application.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter technology, specifically a bridgeless CukPFC converter based on switched inductors and capacitors. Background Technology

[0002] With the increasing demand for low-voltage power supplies in applications such as LED lighting, power battery charging, and consumer electronics, research on buck converters has become a hot topic. Meanwhile, to meet national power quality standards, chargers connected to mains power require power factor correction (PFC) functionality. For example, traditional power battery chargers often employ flyback topologies or a two-stage structure with a boost PFC followed by a DC-DC converter. While these topologies are relatively mature, they result in some efficiency loss and increased cost.

[0003] The Cuk converter's output circuit has an inductor, and its structure is similar to the Buck converter. It features ripple-free output current and low ripple, offering significant advantages for power battery charging. Because the Cuk PFC converter, as a single-stage structure, can simultaneously achieve a high input power factor and low output voltage and current ripple in an AC-DC converter, it has attracted widespread attention. Traditional Cuk PFC converters use a rectifier bridge structure, which is inefficient, has a limited duty cycle range in buck mode, and produces a negative output voltage polarity, requiring an additional inverting amplifier circuit, thus increasing the converter's size and cost. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a bridgeless Cuk PFC converter based on switched inductors and capacitors. The original freewheeling diode is replaced with a switched inductor and capacitor structure containing five components, resulting in a converter voltage gain of D / 2(1-D). Compared to traditional Cuk PFC converters, this converter achieves positive voltage output, improves buck gain, and has a wider duty cycle range in buck mode.

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

[0006] A bridgeless Cuk PFC converter based on switched inductors and capacitors, including AC power supply u s Switches S1, S2, S3; diodes D1, D2, D3, D4; inductors L1, L2, L3, L4, L5; capacitors C1, C2, C3, C4, C5. 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 sOn 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 positive terminal of capacitor C2 and the cathode of diode D4, respectively;

[0012] The negative terminal of capacitor C2 is connected to the anode of diode D3 and one end of inductor L4, respectively.

[0013] The other end of inductor L4 is connected to the anode of diode D4, the drain of switching transistor S1, the drain of switching transistor S3, and the output capacitor C, respectively. o negative electrode;

[0014] Output capacitor C o With load R L in parallel.

[0015] In this bridgeless Cuk PFC converter, capacitor C2, inductors L3 and L4, and diodes D3 and D4 constitute a switching inductor-capacitor unit.

[0016] In this bridgeless Cuk PFC converter, the power switching transistors S1, S2, and S3 are insulated gate bipolar transistors (IGBTs), integrated gate commutated thyristors (IGCTs), or power field-effect transistors (MOSFETs).

[0017] The bridgeless Cuk PFC converter has a positive output voltage polarity and a voltage gain of D / 2(1-D).

[0018] The bridgeless Cuk PFC converter has the following four operating modes in CCM mode:

[0019] Operating mode 1: The circuit operates under AC power supply u s During the positive half-cycle, switches S1 and S3 are turned on, while switch S2 is turned off. Diode D2 is forward-biased and conducts, while the other diodes are reverse-biased and cut off. During this process, the AC power supply u... s Inductor L2 is charged, capacitor C1 discharges and charges inductor L5, causing the current in inductors L2 and L5 to increase linearly. Inductors L3 and L4, and capacitor C2 discharge to inductor L5 and output capacitor C... o As the load discharges, the currents in inductors L3 and L4 decrease linearly.

[0020] Operating mode 2: The circuit operates under AC power supply us 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 capacitors C1 and C2, 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 and output capacitor C. o During discharge, the current in inductor L5 decreases linearly.

[0021] 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. Diode D1 is forward-biased and conducts, while the other diodes are reverse-biased and cut off. During this process, the AC power supply u... s Inductor L1 is charged, capacitor C1 discharges and charges inductor L5, causing the current in inductors L1 and L5 to increase linearly. Inductors L3 and L4, and capacitor C2, charge inductor L5 and output capacitor C. o As the load discharges, the currents in inductors L3 and L4 decrease linearly.

[0022] 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 capacitors C1 and C2, 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 and output capacitor C. o During discharge, the current in inductor L5 decreases linearly.

[0023] This invention discloses a bridgeless Cuk PFC converter based on switched inductors and capacitors, with the following technical advantages:

[0024] 1) Compared to the voltage gain of the traditional Cuk PFC converter, which is M = D / (1-D), the buck gain of the converter described in this invention is twice as high, at M = D / 2(1-D). In buck mode, the duty cycle range of the original Cuk PFC converter is extended from 0 to 0.5 to 0 to 0.67. With a higher buck ratio, the converter described in this invention has a larger duty cycle, which is beneficial for solving the reverse recovery problem of the switching transistor, reducing current stress, and improving efficiency.

[0025] 2) The converter described in 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.

[0026] 3) The converter described in this invention achieves positive voltage output, making it applicable to a wider range of scenarios. The output voltage sampling circuit eliminates the need for an inverter, which helps reduce the converter's size and cost.

[0027] 4) The converter described in this invention adopts a bridgeless structure, which reduces conduction losses and helps to improve converter efficiency. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Figure 1 This is a diagram of the main topology of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention.

[0030] Figure 2 This is a schematic diagram of the first operating mode of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention.

[0031] Figure 3 This is a schematic diagram of the second operating mode of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention.

[0032] Figure 4 This is a schematic diagram of the third operating mode of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention.

[0033] Figure 5 This is a schematic diagram of the fourth operating mode of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention.

[0034] Figure 6 This is a steady-state key waveform diagram of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention.

[0035] Figure 7 This is a schematic diagram comparing the voltage gain of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention with that of a conventional Cuk PFC converter.

[0036] Figure 8 This is a steady-state waveform diagram of the input-side voltage and current of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention.

[0037] Figure 9 This is a steady-state output voltage and current waveform diagram of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention. Detailed Implementation

[0038] like Figure 1 As shown, the bridgeless Cuk PFC converter based on switched inductors and capacitors includes switching transistors S1-S3, diodes D1-D4, inductors L1-L5, and capacitors C1, C2, and C3. o ;

[0039] The converter inductors L3 and L4, capacitor C2, and diodes D3 and D4 form a switching inductor-capacitor unit.

[0040] 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.

[0041] The negative terminal of capacitor C1 is connected to the anodes of diodes D1 and D2 and the source of switching transistor S1, respectively.

[0042] 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;

[0043] The other end of inductor L3 is connected to the positive terminal of capacitor C2 and the cathode of diode D4, respectively;

[0044] The negative terminal of capacitor C2 is connected to the anode of diode D3 and one end of inductor L4;

[0045] 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;

[0046] Output capacitor C o With load R L in parallel.

[0047] The specific parameters of the converter are as follows: the effective value of the input AC voltage is 220V, the frequency is 50Hz, the switching frequency is 100kHz, the rated output power is 180W, and the DC side output voltage is V. o =48V, inductors L1=L2=2mH, L3=L4=22uH, L5=47uH, DC output capacitor C o =1600μF, capacitors C1=1μF, C2=63μF, load resistance R L =12.8Ω.

[0048] The bridgeless Cuk PFC converter, under steady-state operation in CCM mode, includes the following operating modes:

[0049] Working Mode 1: such as Figure 2 As shown, the circuit is currently operating with AC power supply u. sDuring the positive half-cycle, switches S1 and S3 are turned on, diode D2 is forward-biased and conducts, 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 capacitor C2. o and load discharge. This process corresponds to Figure 6 During the time interval (t0 to t1), the voltage relationship across the inductor in this process is as follows:

[0050]

[0051] Among them, V C1 and V C2 These are the voltage stresses of capacitors C1 and C2, respectively, and 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's forward voltage drop is zero, the capacitor has a sufficiently large capacitance and no equivalent series resistance, and the inductor has no DC resistance.

[0052] 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, capacitors C1 and C2, 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:

[0053]

[0054] 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, diode D1 is forward-biased and conducts, 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 C through capacitor C2. o and load discharge. This process corresponds to Figure 6 During the time interval (t0 to t1), the voltage relationship across the inductor in this process is as follows:

[0055]

[0056] Working Mode 4: such as Figure 5 As shown, the circuit operates under AC power supply u sDuring the negative half-cycle, switch S2 is turned on, diodes D1, D3, and D4 are forward-biased and conducting, and all other semiconductor devices are turned off. In this process, inductor L1 discharges, and capacitors C1 and C2, as well as inductors L3 and L4, are charged. 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:

[0057]

[0058] Voltage gain analysis when the converter is operating stably:

[0059] 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:

[0060]

[0061] By combining equations (1) and (2), we can obtain:

[0062]

[0063] The voltage gain of the converter described in this invention is:

[0064]

[0065] The buck gain curve of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention is shown below. Figure 7 As shown. (Through) Figure 7 It can be seen that, under the same gain range, the duty cycle range of the converter described in this invention is wider than that of the conventional Cuk PFC converter.

[0066] Figure 8 This diagram shows the steady-state input voltage and current waveforms of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention. For ease of comparison with the voltage waveform, the amplitude of the actual current waveform is only magnified by a factor of 30, without changing its phase or other parameters. It can be seen that the input voltage and input current are in phase, verifying the power factor correction function.

[0067] Figure 9 This diagram shows the steady-state output voltage and current waveforms of a bridgeless Cuk PFC converter based on switched inductors and capacitors according to the present invention. The output voltage is stable at around 48V, and the output current waveform is smooth.

[0068] This invention discloses a bridgeless Cuk PFC converter based on switched inductors and capacitors. It replaces the original freewheeling diode with a switched inductor-capacitor structure, resulting in a converter voltage gain of D / 2(1-D). Compared to traditional Cuk PFC converters, this invention achieves positive voltage output, improves buck gain, and offers a wider duty cycle range in buck mode. Furthermore, the bridgeless structure enables lower conduction losses. The converter described in this invention features continuous input and output current, high power factor, and high efficiency, making it highly versatile.

Claims

1. A bridgeless Cuk PFC converter based on switched-inductor-capacitor, comprising an alternating current power supply u s , switching tubes S1, S2, S3, diodes D1, D2, D3, D4, inductors L1, L2, L3, L4, L5, capacitors C1, C2, C o , characterized in that: AC power supply u s One side is connected with switch tube S3 source, inductance L1 one end, inductance L1 other end is connected with diode D1 cathode; AC power supply u s The other side is connected with the source electrode of the switch tube S2 and one end of the inductor L2, respectively, and the other end of the inductor L2 is connected with 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 the inductor L5 is connected to the positive pole of the capacitor C1, the negative pole of the diode D3, and one end of the inductor L3, respectively, and the other end of the inductor L5 is connected to the output capacitor C o positive pole; The other end of inductor L3 is connected to the positive terminal of capacitor C2 and the cathode of diode D4, respectively; The negative terminal of capacitor C2 is connected to the anode of diode D3 and one end of inductor L4, respectively. The other end of the inductor L4 is connected to the anode of the diode D4, the drain of the switch S1, the drain of the switch S2, the drain of the switch S3, and the output capacitor C, respectively. o negative electrode Output capacitor C o With load R L In parallel; This bridgeless Cuk PFC converter includes 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, while switch S2 is turned off; diode D2 is forward-biased and conducts, while the other diodes are reverse-biased and cut off; during this process, the AC power supply u... s Inductor L2 is charged, capacitor C1 discharges and charges inductor L5, and the current in inductors L2 and L5 increases linearly; inductors L3 and L4, and capacitor C2 discharge to inductor L5 and output capacitor C o As the load discharges, 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, capacitors C1 and C2, and inductors L3 and L4 are charged, with the currents in inductors L3 and L4 increasing linearly and the current in inductor L2 decreasing linearly; inductor L5 supplies power to the load and output capacitor C... o Discharge occurs, and the current in inductor L5 decreases linearly. Working mode three: the circuit works in AC power u s The negative half cycle, switch S1 and S2 open, switch S3 off; diode D1 positive bias conduction, the rest of the diode are reverse cut-off; this process AC power u s Charging inductance L1, C1 discharge to inductance L5 charging, inductance L1, L5 current linear rise; inductance L3 and L4, C2 to inductance L5, output capacitor C o And load discharge, inductance L3 and L4 current linear decline; 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, capacitors C1 and C2, and inductors L3 and L4 are charged, with the currents in inductors L3 and L4 increasing linearly and the current in inductor L1 decreasing linearly; inductor L5 supplies power to the load and output capacitor C... o During discharge, the current in inductor L5 decreases linearly.

2. The bridgeless Cuk PFC converter based on switched-inductor-capacitor of claim 1, wherein: In this bridgeless Cuk PFC converter, capacitor C2, inductors L3 and L4, and diodes D3 and D4 constitute a switching inductor-capacitor unit.

3. The bridgeless Cuk PFC converter based on switched-inductor-capacitor of claim 1, wherein: In this bridgeless Cuk PFC converter, the power switching transistors S1, S2, and S3 are insulated gate bipolar transistors (IGBTs), integrated gate commutated thyristors (IGCTs), or power field-effect transistors (MOSFETs).

4. The bridgeless Cuk PFC converter based on switched-inductor-capacitor of claim 1, wherein: The bridgeless Cuk PFC converter has a positive output voltage polarity and a voltage gain of D / 2(1-D).

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