Disclosure of Invention
The invention aims to provide a flexible multi-level bridgeless power factor correction converter combining a bridgeless structure and a multi-level technology and a modulation method thereof, aiming at the defects of the technologies, and the converter has the advantages of small inductor volume, low on-state loss at low input voltage and small direct current capacitance, has higher power density, and is more suitable for switching power supplies with low input voltage and high output voltage.
In order to achieve the above purpose, the invention designs a flexible multi-level bridgeless power factor correction converter, which comprises an alternating current inductance part, a power electronic switch network and a direct current capacitance part.
The power electronic switch network comprises an N-channel MOSFET switch tube S1N-channel MOSFET switch tube S2N-channel MOSFET switch tube S3N-channel MOSFET switch tube S4N-channel MOSFET switch tube S5And N-channel MOSFET switch tube S6And a diode D1And a diode D2(ii) a Wherein, the diode D1Anode connected to N-channel MOSFET switch tube S1Drain, N-channel MOSFET switch tube S1Source connected to N-channel MOSFET switch tube S2Drain, N-channel MOSFET switch tube S2Source connected to N-channel MOSFET switch tube S4A source electrode; diode D2Anode connected to N-channel MOSFET switch tube S3Drain, N-channel MOSFET switch tube S3Source connected to N-channel MOSFET switch tube S4A drain electrode; diode D1Cathode connected to diode D2A cathode; n-channel MOSFET switch tube S5Source connected to N-channel MOSFET switch tube S3Source, N-channel MOSFET switch tube S5The drain electrode is connected to the midpoint of the direct current capacitor part; n-channel MOSFET switch tube S6Source connected to N-channel MOSFET switch tube S1Source, N-channel MOSFET switch tube S6The drain is connected to the midpoint of the DC capacitor portion.
The DC capacitor part comprises two capacitors C connected in series1And a capacitor C2(ii) a Wherein, the capacitor C1Is connected to the diode D2Cathode of (2), capacitor C1Is connected to the capacitor C2Positive electrode, N channel MOSFET switch tube S5Drain and N-channel MOSFET switch tube S6A contact of the drain electrode; capacitor C2Is connected to the N-channel MOSFET switching tube S2Source and N-channel MOSFET switch tube S4The source contact.
The AC inductor part comprises an inductor L1And an inductance L2(ii) a Wherein, the inductance L1One end of which is connected to an N-channel MOSFET switching tube S1Drain electrode and diode D1Contact of anode, inductance L1Is connected to one end of the input, and the other end of the input is connected to the inductor L2And one terminal of the inductor L2Is connected to the N-channel MOSFET switch tube S3Drain electrode and diode D2Contact point of anode, and inductance L1Inductance of and inductance L2The inductance values of the two inductors are equal.
A modulation method of the flexible multi-level bridgeless pfc converter as described above, the modulation method comprising:
when the capacitance C
1Capacitor C
2Voltage is satisfied
Under the condition of (3), the converter is in a five-level working state;
when the capacitance C
1Capacitor C
2Voltage is satisfied
The converter is in a seven-level operating state.
Further, when
Controlling N-channel MOSFET switch tube S
1Normally-on, N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Normally off, N-channel MOSFET switch tube S
2Alternately switching on and off according to a PWM rule;
when in use
Controlling N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
6Normally off, N-channel MOSFET switch tube S
5Alternately switching on and off according to a PWM rule;
when in use
Controlling N-channel MOSFET switch tube S
3Normally-on, N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Normally off, N-channel MOSFET switch tube S
4Alternately switching on and off according to a PWM rule;
when in use
Controlling N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5Normally off, N-channel MOSFET switch tube S
6And alternately switching on and off according to a PWM rule.
Further, when
Controlling N-channel MOSFET switch tube S
1Normally-on, N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Normally-off N-channel MOSFET switch tube S
2Alternately switching on and off according to a PWM rule;
when in use
Controlling N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
6Normally-off N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
5Alternately switched on and off according to PWM rule and N-channel MOSFET switching tube S
1And N-channel MOSFETSwitch tube S
5The gate drive waveforms of (a) are complementary;
when in use
Controlling N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
6Normally-off N-channel MOSFET switch tube S
5Alternately switching on and off according to a PWM rule;
when in use
Controlling N-channel MOSFET switch tube S
3Normally-on, N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Normally-off N-channel MOSFET switch tube S
4Alternately switching on and off according to a PWM rule;
when in use
Controlling N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5Normally-off N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
6Alternately switched on and off according to PWM rule and N-channel MOSFET switching tube S
3And N-channel MOSFET switch tube S
6The gate drive waveforms of (a) are complementary;
when in use
Controlling N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5Normally-off N-channel MOSFET switch tube S
6And alternately switching on and off according to a PWM rule.
Compared with the prior art, the invention has the following advantages:
1. compared with the common two-level bridgeless Boost PFC circuit, the power factor correction converter and the modulation method can reduce the volume of the inductor by about 50 percent (five-level state) or 67 percent (seven-level state) on the premise of keeping the switching frequency consistent with the maximum allowable inductor current ripple; or on the premise of keeping the output power, the switching frequency and the inductor volume consistent, the amplitude of the high-frequency ripple current of the inductor is reduced by about 50 percent (five-level state) or 67 percent (seven-level state), the heat generated by the inductor is greatly reduced, and the efficiency of the converter is improved.
2. The power factor correction converter and the modulation method can reduce the on-state loss of the converter at low input voltage.
3. The power factor correction converter and the modulation method can realize the charge and discharge control of the two capacitors within the time of at most one quarter of a power supply voltage period, and compared with a single-inductor three-level bridgeless power factor correction converter, the direct-current capacitor is smaller.
4. The power factor correction converter and the modulation method can conveniently realize the mutual switching between two working states of five levels and seven levels without changing the circuit structure, only changing the distribution relation of two series capacitor voltages and the generation mode of six switching tube control signals.
Detailed Description
The invention is described in further detail below with reference to the figures and the specific embodiments.
As shown in fig. 1, the flexible multi-level bridgeless pfc converter includes an ac inductance portion 110, a power electronic switching network 120, and a dc capacitance portion 130.
The power electronic switching network 120 includes an N-channel MOSFET switching transistor S1N-channel MOSFET switch tube S2N-channel MOSFET switch tube S3N-channel MOSFET switch tube S4N-channel MOSFET switch tube S5And N-channel MOSFET switch tube S6And a diode D1And a diode D2(ii) a Wherein, the diode D1Anode connected to N-channel MOSFET switch tube S1Drain, N-channel MOSFET switch tube S1Source connected to N-channel MOSFET switch tube S2Drain, N-channel MOSFET switch tube S2Source connected to N-channel MOSFET switch tube S4A source electrode; diode D2Anode connected to N-channel MOSFET switch tube S3Drain, N-channel MOSFET switch tube S3Source connected to N-channel MOSFET switch tube S4A drain electrode; diode D1Cathode connected to diode D2A cathode; n-channel MOSFET switch tube S5Source connected to N-channel MOSFET switch tube S3Source, N-channel MOSFET switch tube S5The drain is connected to the midpoint of the dc capacitor portion 130; n-channel MOSFET switch tube S6Source connected to N-channel MOSFET switch tube S1Source, N-channel MOSFET switch tube S6The drain is connected to the midpoint of the dc capacitor portion 130.
The DC capacitor part 130 includes two capacitors C connected in series1And a capacitor C2(ii) a Wherein, the capacitor C1Is connected to the diode D2Cathode of (2), capacitor C1Is connected to the capacitor C2A positive electrode,N-channel MOSFET switch tube S5Drain and N-channel MOSFET switch tube S6A contact of the drain electrode; capacitor C2Is connected to the N-channel MOSFET switching tube S2Source and N-channel MOSFET switch tube S4The source contact.
The AC inductance part 110 includes an inductance L1And an inductance L2(ii) a Wherein, the inductance L1One end of which is connected to an N-channel MOSFET switching tube S1Drain electrode and diode D1Contact of anode, inductance L1Is connected to one end of the input, and the other end of the input is connected to the inductor L2And one terminal of the inductor L2Is connected to the N-channel MOSFET switch tube S3Drain electrode and diode D2Contact point of anode, and inductance L1Inductance of and inductance L2Is equal in inductance (L)1=L2=L)。
The switching operation of six N-channel MOSFET switching tubes in the power electronic switching network 120 realizes the switching operation of the inductor L in the ac inductor part 1101And an inductance L2Charging and discharging and AC input end power factor correction.
Fig. 2a to 2h show circuit diagrams of the operation modes of the converter according to the present invention during one cycle of the power supply voltage. A supply voltage vsIn the cycle, the converter has 8 working modes, wherein the positive half cycle is 4 (as shown in fig. 2 a-2 d), and the negative half cycle is 4 (as shown in fig. 2 e-2 h).
Assuming that the on-state voltage drops of the diode and the N-channel MOSFET switch tube are zero, the working process of the converter of the invention is described in detail in the following with reference to the attached drawings:
in a first operating mode shown in fig. 2a), the N-channel MOSFET switch S
1N-channel MOSFET switch tube S
2Switch-on, N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Turn-off, diode D
1Diode D
2Turning off; current i
LThrough N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2And N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4The body diode of (1) forms a loop; capacitor C
1Capacitor C
2Discharging the load. Due to L
1=L
2Voltage of each inductor
In a second mode of operation, as shown in FIG. 2b), the N-channel MOSFET switching transistor S
1Switch-on, N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Turn-off, diode D
1Diode D
2Turning off; current i
LThrough N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
6Body diode and capacitor C
2Forming a loop; capacitor C
1Discharging to the load, capacitor C
2Charging via a power electronic switching network. Due to L
1=L
2Voltage of each inductor
In a third operating mode, as shown in fig. 2c), the N-channel MOSFET switch S
5Switch-on, N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
6Turn-off, diode D
1On, diode D
2Turning off; current i
LVia a diode D
1Capacitor C
1N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
3The body diode of (1) forms a loop; capacitor C
1Charged by a power electronic switching network, capacitor C
2Discharging the load. Due to L
1=L
2Voltage of each inductor
In a fourth operating mode shown in fig. 2d), the N-channel MOSFET switch S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Turn-off, diode D
1On, diode D
2Turning off; current i
LVia a diode D
1Capacitor C
1Capacitor C
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4The body diode of (1) forms a loop; capacitor C
1Capacitor C
2Charging via a power electronic switching network. Due to L
1=L
2Voltage of each inductor
In a fifth operating mode, as shown in fig. 2e), the N-channel MOSFET switch transistor S
3N-channel MOSFET switch tube S
4Switch-on, N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Turn-off, diode D
1Diode D
2Turning off; current i
LThrough N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4And N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2The body diode of (1) forms a loop; capacitor C
1Capacitor C
2Discharging the load. Due to L
1=L
2Voltage of each inductor
In a sixth operating mode, as shown in fig. 2f), the N-channel MOSFET switch tube S
3Switch-on, N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Turn-off, diode D
1Diode D
2Turning off; current i
LThrough N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
5Body diode and capacitor C
2Forming a loop; capacitor C
1Discharging to the load, capacitor C
2Charging via a power electronic switching network. Due to L
1=L
2Voltage of each inductor
In a seventh operating mode, shown in fig. 2g), the N-channel MOSFET switch transistor S
6Switch-on, N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5Turn-off, diode D
2On, diode D
1Turning off; current i
LVia a diode D
2Capacitor C
1N-channel MOSFET switch tube S
6N-channel MOSFET switch tube S
1The body diode of (1) forms a loop; capacitor C
1Charged by a power electronic switching network, capacitor C
2Discharging the load. Due to L
1=L
2Voltage of each inductor
In the eighth operating mode shown in fig. 2h), the N-channel MOSFET switch transistor S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Turn-off, diode D
1Turn-off, diode D
2Opening; current i
LVia a diode D
2Capacitor C
1Capacitor C
2N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2The body diode of (1) forms a loop; capacitor C
1、C
2And charging through a power electronic switch network. Due to L
1=L
2Voltage of each inductor
The converter provided by the invention only changes two series capacitors C without changing the circuit structure1And a capacitor C2Voltage distribution relation of (1), and N-channel MOSFET switching tube S1N-channel MOSFET switch tube S2N-channel MOSFET switch tube S3N-channel MOSFET switch tube S4N-channel MOSFET switch tube S5N-channel MOSFET switch tube S6The generation mode of the control signal can flexibly realize the mutual switching between the five-level working state and the seven-level working state.
Fig. 3 is a schematic diagram showing the division of the operating region of the converter of the present invention in the five-level operating state. According to the supply voltage v
sDivides the converter into two operating regions: when in use
When the converter works in the area I; when in use
At this time, the converter operates in region ii.
Fig. 4 is a schematic diagram showing the division of the operating region of the converter of the present invention in the seven-level operating state. According to the supply voltage v
sThe converter is divided into three operating regions: when in use
When the converter works in the area I; when in use
When the converter is operated in the area II; when in use
The converter is operating in region iii.
Fig. 5a to 5d show the modulation method and main waveform diagram of the converter of the present invention in the five-level operation state. When the capacitance C
1Capacitor C
2Voltage is satisfied
Under the condition of (2), the converter is in a five-level working state.
As shown in FIG. 5a), when
I.e. the supply voltage is in the region i of the positive half-cycle, the N-channel MOSFET switching tube S is controlled
1Normally-on, N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Normally off, N-channel MOSFET switch tube S
2And switching on and off alternately according to a PWM rule to switch the converter between a first working mode and a second working mode. In the first working mode, each inductor voltage
Current i
LRising; in the second mode of operation, each inductor voltage
Current i
LAnd (4) descending.
As shown in FIG. 5b), when
I.e. the region II of the positive half-cycle of the supply voltage, controls the N-channel MOSFET switching tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
6Normally closedOff, N-channel MOSFET switch tube S
5And switching on and off alternately according to a PWM rule to switch the converter between a third working mode and a fourth working mode. In the third mode of operation, each inductor voltage
Current i
LRising; in the fourth working mode, each inductor voltage
Current i
LAnd (4) descending.
As shown in FIG. 5c), when
I.e. the region I of the negative half-cycle of the supply voltage, controls the N-channel MOSFET switching tube S
3Normally-on, N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Normally off, N-channel MOSFET switch tube S
4And switching on and off alternately according to a PWM rule to switch the converter between a fifth working mode and a sixth working mode. In the fifth working mode, each inductor voltage
Current i
LRising; in the sixth working mode, each inductor voltage
Current i
LAnd (4) descending.
As shown in FIG. 5d), when
I.e. the region II of the negative half-cycle of the supply voltage, controls the N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5Normally off, N-channel MOSFET switch tube S
6According to PThe WM rule is alternately switched on and off, switching the converter between the seventh and eighth operating modes. In the seventh working mode, each inductor voltage
Current i
LRising; in the eighth mode of operation, each inductor voltage
Current i
LAnd (4) descending.
Modulating six N-channel MOSFET switch tubes S according to the rule as shown in FIGS. 5 a-5 d
1、S
2、S
3、S
4、S
5、S
6The on-off state of the inductor can ensure that the variation of each inductor voltage in any switching period is always equal to
Which is only 50% of the common two-level bridgeless Boost type PFC converter. Therefore, the size of the inductor can be reduced by about 50% on the premise of keeping the switching frequency consistent with the maximum allowable inductor current ripple. The inductor voltage v is applied during one period of the power supply voltage
L1The waveform contains a total of five levels. And the charge and discharge control of the two capacitors can be realized within the time of at most one fourth of the power supply voltage period.
Fig. 6a to 6f show the modulation method and main waveforms of the converter of the present invention in the seven-level operation state. When the capacitance C
1Capacitor C
2Voltage is satisfied
The converter is in a seven-level operating state.
As shown in FIG. 6a), when
I.e. the supply voltage is in the region i of the positive half-cycle, the N-channel MOSFET switching tube S is controlled
1Normally-on, N-channel MOSFET switch tube S
3N-channel MOSFET switching tube S
4N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Normally off, N-channel MOSFET switch tube S
2And switching on and off alternately according to a PWM rule to switch the converter between a first working mode and a second working mode. In the first working mode, each inductor voltage
Current i
LRising; in the second mode of operation, each inductor voltage
Current i
LAnd (4) descending.
As shown in FIG. 6b), when
I.e. the region II of the positive half-cycle of the supply voltage, controls the N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
6Normally off, N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
5Alternately switched on and off according to PWM rule and N-channel MOSFET switching tube S
1And N-channel MOSFET switch tube S
5The gate drive waveforms of (a) are complementary to each other, so that the converter switches between the second and third modes of operation. In the second mode of operation, each inductor voltage
Current i
LRising; in the third mode of operation, each inductor voltage
Current i
LAnd (4) descending.
As shown in FIG. 6c), when
I.e. the region III of the positive half-cycle of the supply voltage, controls the N-channel MOSFET switching transistor S
1N-channel MOSFET switching tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
6Normally off, N-channel MOSFET switch tube S
5And switching on and off alternately according to a PWM rule to switch the converter between a third working mode and a fourth working mode. In the third mode of operation, each inductor voltage
Current i
LRising; in the fourth working mode, each inductor voltage
Current i
LAnd (4) descending.
As shown in FIG. 6d), when
I.e. the region I of the negative half-cycle of the supply voltage, controls the N-channel MOSFET switching tube S
3Normally-on, N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
5N-channel MOSFET switch tube S
6Normally off, N-channel MOSFET switch tube S
4And switching on and off alternately according to a PWM rule to switch the converter between a fifth working mode and a sixth working mode. In the fifth working mode, each inductor voltage
Current i
LRising; in the sixth working mode, each inductor voltage
Current i
LAnd (4) descending.
As shown in FIG. 6e), when
I.e. the region II of the negative half-cycle of the supply voltage, controls the N-channel MOSFET switch tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5Normally off, N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
6Alternately switched on and off according to PWM rule and N-channel MOSFET switching tube S
3And N-channel MOSFET switch tube S
6The gate drive waveforms of (a) are complementary to each other, switching the converter between the sixth and seventh modes of operation. In the sixth working mode, each inductor voltage
Current i
LRising; in the seventh working mode, each inductor voltage
Current i
LAnd (4) descending.
As shown in FIG. 6f), when
I.e. the region III of the negative half-cycle of the supply voltage, controls the N-channel MOSFET switching tube S
1N-channel MOSFET switch tube S
2N-channel MOSFET switch tube S
3N-channel MOSFET switch tube S
4N-channel MOSFET switch tube S
5Normally off, N-channel MOSFET switch tube S
6And switching on and off alternately according to a PWM rule to switch the converter between the seventh working mode and the eighth working mode. In the seventh working mode, each inductor voltage
Current i
LRising; in the eighth mode of operation, each inductor voltage
Current i
LAnd (4) descending.
The six switching tubes S are modulated according to the law shown in FIGS. 6a to 6f
1、S
2、S
3、S
4、S
5、S
6The on-off state of the inductor can ensure that the variation of each inductor voltage in any switching period is always equal to
Which is only 33% of the common two-level bridgeless Boost type PFC converter. Therefore, on the premise of keeping the switching frequency consistent with the maximum allowable inductor current ripple, the size of the inductor can be reduced by about 67%. In one supply voltage cycle, the inductor voltage v
L1The waveform contains seven levels in total. And the charge and discharge control of the two capacitors can be realized within the time of at most one fourth of the power supply voltage period.
It should be understood that: the above embodiments are merely illustrative, not restrictive, and any invention that does not exceed the spirit of the present invention falls within the scope of the present invention.