Coupled Inductor Soft-Switching Power Converter

Abstract

The coupled-inductor soft-switching power converter of the present invention relates to a power converter. The purpose is to overcome the problems of large output current ripple, relatively long conduction time of the resonant circuit, and relatively large volume and weight in the existing soft-switching converters. It includes N power conversion circuits, N resonant circuits, and N filtering circuits; the N power conversion circuits are all used to convert the power of the power supply and output it to the load; and the resonant inductor L rm in the m-th resonant circuit is used to resonate with the parasitic capacitance C m of the main power switch device S sm in the m-th power conversion circuit to achieve soft switching of the main power switch device S m ; the filtering inductor L m in the m-th filtering circuit is used to be coupled in the same direction with the resonant inductor L rm in the m-th resonant circuit to achieve soft switching of the auxiliary power switch device S m1 in the m-th resonant circuit.

Description

Technical Field

[0001] The present invention relates to a power converter. Background Art

[0002] As shown in the existing soft-switching converter Figure 1 By adding an auxiliary switch resonant branch, the switching devices in the converter all achieve a soft-switching state.

[0003] However, the resonant branch elements are present in the main current path, and the resonant inductor current therein changes according to the resonant law, thereby affecting the filter inductor current on the main circuit, increasing the ripple of the output current, and unable to meet the requirements in high power density and high-precision applications. Moreover, since the resonant branch elements include a resonant capacitor Cr in addition to the resonant inductor Lr, that is, there are two capacitors in the resonant circuit, the charging and discharging time of the capacitor is longer, the conduction time of the resonant circuit is longer, and the volume and weight of the converter are also relatively large. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of large output current ripple, long conduction time of the resonant circuit, and relatively large volume and weight of the existing soft-switching converter, and provide a coupled inductor soft-switching power converter.

[0005] The coupled inductor soft-switching power converter of the present invention includes N power conversion circuits, N resonant circuits, and N filter circuits; N is a positive integer greater than or equal to 1;

[0006] The power conversion circuits all include main power switching devices, the resonant circuits all include auxiliary power switching devices and resonant inductors, and the filter circuits all include filter inductors;

[0007] The N power conversion circuits are all used to convert the power of the power supply and output it to the load; and,

[0008] The resonant inductor L rm in the m-th resonant circuit is used to resonate with the parasitic capacitance C m of the main power switching device S sm in the m-th power conversion circuit to achieve soft switching of the main power switching device S m ; m = 1, 2,..., N;

[0009] The filter inductor L m in the m-th filter circuit is used to be coupled in the same direction as the resonant inductor L rm in the m-th resonant circuit to achieve soft switching of the auxiliary power switching device S m1 in the m-th resonant circuit.

[0010] The beneficial effects of the present invention are:

[0011] The coupled-inductor soft-switching power converter of the present invention adopts a coupled inductor, which has little influence on the current of the filter inductor, reduces the ripple of the output current, and can meet the requirements in high power density and high-precision applications.

[0012] The resonant circuit of the coupled-inductor soft-switching power converter of the present invention has only one capacitor, and the charging and discharging time of the capacitor is shorter, and the conduction time of the resonant circuit is shorter.

[0013] Since the components in the resonant link are reduced, the weight and volume of the converter are further reduced. Brief Description of the Drawings

[0014] Figure 1 is a circuit structure topology diagram of an existing soft-switching buck converter;

[0015] Figure 2 is a circuit structure topology diagram of the coupled-inductor soft-switching power converter of the present invention when the power conversion circuit includes 1 BUCK circuit;

[0016] Figure 3 is a circuit structure topology diagram of the coupled-inductor soft-switching power converter of the present invention when the power conversion circuit includes 2 BUCK circuits;

[0017] Figure 4 is a circuit structure topology diagram of the coupled-inductor soft-switching power converter of the present invention when the power conversion circuit includes N BUCK circuits;

[0018] Figure 5 is a circuit structure topology diagram of the coupled-inductor soft-switching power converter of the present invention when the power conversion circuit includes 1 non-isolated bidirectional power conversion circuit;

[0019] Figure 6 is a circuit structure topology diagram of the coupled-inductor soft-switching power converter of the present invention when the power conversion circuit includes N non-isolated bidirectional power conversion circuits;

[0020] Figure 7 is a schematic diagram of the principle of operating mode 1 of the coupled-inductor soft-switching power converter of the present invention;

[0021] Figure 8 is a schematic diagram of the principle of operating mode 2 of the coupled-inductor soft-switching power converter of the present invention;

[0022] Figure 9 is a schematic diagram of the principle of operating mode 3 of the coupled-inductor soft-switching power converter of the present invention;

[0023] Figure 10 is a schematic diagram of the principle of operating mode 4 of the coupled-inductor soft-switching power converter of the present invention;

[0024] Figure 11 Schematic diagram of the principle of operating mode 5 of the coupled inductor soft-switching power converter of the present invention;

[0025] Figure 12 Schematic diagram of the principle of operating mode 6 of the coupled inductor soft-switching power converter of the present invention;

[0026] Figure 13 Schematic diagram of the principle of operating mode 7 of the coupled inductor soft-switching power converter of the present invention. Detailed implementation manners

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but it is not limited to the present invention. Detailed implementation manner one

[0031] The coupled inductor soft-switching power converter of this embodiment includes N power conversion circuits, N resonance circuits, and N filtering circuits; N is a positive integer greater than or equal to 1;

[0032] Each of the power conversion circuits includes a main power switch device, each of the resonance circuits includes an auxiliary power switch device and a resonance inductor, and each of the filtering circuits includes a filtering inductor;

[0033] Each of the N power conversion circuits is used to convert the power of the power supply and output it to the load; and,

[0034] The resonance inductor L in the m-th resonance circuit rm , is used to resonate with the parasitic capacitance C of the main power switch device S in the m-th power conversion circuit m to achieve soft switching of the main power switch device S sm ; m = 1, 2..., N; m

[0035] The filtering inductor L in the m-th filtering circuit m , is used to resonate with the resonance inductor L in the m-th resonance circuit rmCoupled in the same direction to achieve the soft switching of the auxiliary power switch device S in the m-th resonant circuit m1 of. Specific Embodiment 2

[0037] This embodiment is a further description of Embodiment 1. In this embodiment, the filter circuit further includes a filter capacitor, and N filter circuits share a filter capacitor C O . Specific Embodiment 3

[0039] This embodiment is a further description of Embodiment 2. In this embodiment, in the m-th power conversion circuit, the drain of the main power switch device S m is electrically connected to the positive pole of the power supply;

[0040] Each resonant circuit further includes a resonant diode;

[0041] In the m-th resonant circuit, the drain of the auxiliary power switch device S m1 is electrically connected to the drain of the main power switch device S m , the source of the auxiliary power switch device S m1 is electrically connected to one end of the resonant inductor L rm , the other end of the resonant inductor L rm is electrically connected to the positive pole of the resonant diode D sm , and the negative pole of the resonant diode D sm is electrically connected to the source of the main power switch device S m ;

[0042] Each power conversion circuit further includes an isolation diode;

[0043] In the m-th power conversion circuit, the negative pole of the isolation diode D m is electrically connected to the source of the main power switch device S m , and the positive pole of the isolation diode D m is electrically connected to the negative pole of the power supply;

[0044] In the m-th filter circuit, one end of the filter inductor L m is electrically connected to the negative pole of the isolation diode D m , and the other end of the filter inductor L m is electrically connected to the positive pole of the isolation diode D O through the filter capacitor C m ;

[0045] One end of the resonant inductor L rm and one end of the filter inductor L m are of the same name. Specific Embodiment 4

[0047] This embodiment is a further description of Embodiment 2. In this embodiment, in the m-th power conversion circuit, the drain of the main power switch device S m is electrically connected to the positive pole of the power supply;

[0048] Each resonant circuit further includes a resonant power switch device S m2 ;

[0049] In the m-th resonant circuit, the drain of the auxiliary power switch device S m1 is electrically connected to the drain of the main power switch device S m , the source of the auxiliary power switch device S m1 is electrically connected to one end of the resonant inductor L rm , the other end of the resonant inductor L rm is electrically connected to the source of the resonant power switch device S m2 , and the drain of the resonant power switch device S m2 is electrically connected to the drain of the main power switch device S m ;

[0050] Each power conversion circuit further includes a secondary power switch device S' m ;

[0051] In the m-th power conversion circuit, the drain of the secondary power switch device S' m is electrically connected to the source of the main power switch device S m , and the source of the secondary power switch device S' m is electrically connected to the negative pole of the power supply;

[0052] In the m-th filter circuit, one end of the filter inductor L m is electrically connected to the drain of the secondary power switch device S' m , and the other end of the filter inductor L m is electrically connected to the source of the secondary power switch device S' O through a filter capacitor C m ;

[0053] One end of the resonant inductor L rm and one end of the filter inductor L m are of the same name. Specific Embodiment Five

[0055] This embodiment is a further description of Embodiments 1 to 4. In this embodiment, N is equal to 1 or 2. Specific Embodiment Six

[0057] This embodiment is a further description of Embodiments 1 to 4. In this embodiment, the turn ratio of the filter inductor L m to the resonant inductor L rm is Specific Embodiment VII

[0059] This embodiment is a further description of Embodiment VI. In this embodiment, the filter inductor L m and the filter capacitor C O respectively satisfy:

[0060]

[0061]

[0062] wherein, K m is the coupling coefficient between the filter inductor L m and the resonant inductor L rm , D is the duty cycle of the main power switch device S m , f is the switching frequency of the main power switch device S m , Z is the output reactance, U i is the input voltage, U o is the output voltage, ΔI m is the current ripple on the filter inductor L m . Specific Example

[0064] As Figure 1 shown, for the resonant operation mode of the existing soft-switching converter, the resonant loop is C1 → U i → C r → M2 → L r . That is, there are two capacitors in the resonant loop. Compared with the converter of the present invention which has only one capacitor in the resonant loop, the charging and discharging time of the capacitor is longer, and the conduction time of the resonant loop is longer. Therefore, the converter of the present invention can shorten the conduction time of the resonant loop.

[0065] The coupled-inductor soft-switching power converter of the present invention is a soft-switching BUCK and its derivative topology power converter based on the coupled inductor. By adopting the coupled inductor (magnetic integration) method, it solves the disadvantages of the existing soft-switching BUCK converter, such as large volume, large weight, and large output current ripple, reduces the ripple of the output current, further improves the power density and dynamic response of the system, shortens the conduction time of the resonant loop, and improves the system efficiency, so as to meet the requirements in high power density and high-precision occasions. In addition, a multi-path parallel output form can also be adopted to meet the application of high-power output.

[0066] The present invention provides five solutions:

[0067] The first solution uses a positive DC voltage source for power supply and consists of a BUCK circuit, a resonant loop, and an output LC loop;

[0068] The second solution is powered by a positive DC voltage source and consists of two BUCK circuits, a resonant circuit, and an output LC circuit connected in parallel;

[0069] The third solution is powered by a positive DC voltage source and consists of n BUCK circuits, a resonant circuit, and an output LC circuit connected in parallel;

[0070] The fourth solution is powered by a positive DC voltage source and consists of a non-isolated bidirectional power conversion circuit, a resonant circuit, and an output LC circuit;

[0071] The fifth solution is powered by a positive DC voltage source and consists of n non-isolated bidirectional power conversion circuits, a resonant circuit, and an output LC circuit.

[0072] Solution 1

[0073] As Figure 2 shown, Solution 1 is a soft-switching BUCK and its derivative topology power converter based on a coupled inductor, powered by a positive DC voltage source, and consists of a BUCK circuit (power conversion circuit), a resonant circuit, and an output LC circuit (filter circuit).

[0074] The BUCK circuit consists of a power switch device S1, a diode D1, and a resonant capacitor C S1 . The negative terminals of the power device S1 and D1 are connected to form the BUCK circuit. The positive terminal of the BUCK circuit is connected to the positive terminal of the DC power supply, and the negative terminal of the BUCK circuit is connected to the negative terminal of the DC voltage source. The resonant capacitor C S1 is connected in parallel with S1. The resonant capacitor can be a parasitic capacitor inside the power switch device S1 or an external capacitor.

[0075] The resonant circuit consists of a power switch device S 11 , a resonant inductor L r1 , and a diode D S1 . The positive terminal of S 11 is connected to the positive terminal of S1. The same-name terminal of L r1 is connected to the negative terminal of S 11 . The other end of L r1 is connected to the positive terminal of D S1 . The negative terminal of D S1 is connected to the negative terminal of S1.

[0076] The output LC circuit consists of a coupled inductor L1 and a capacitor C o . The same-name terminal of the coupled inductor L1 is connected to the negative terminal of D1, and the other end is connected to one end of the capacitor C o . The other end of the capacitor C o is connected to the positive terminal of D1. The load resistor R is connected in series with the inductor L and then connected in parallel with the capacitor C o .

[0077] Among them, the power switching device uses a MOSFET, GTR or IGBT with a reverse-parallel body diode.

[0078] Solution 2

[0079] As Figure 3 shown, Solution 2 is a soft-switching BUCK and its derivative topology power converter based on a coupled inductor, powered by a positive DC voltage source, and composed of two parallel BUCK circuits, a resonant circuit, and an output LC circuit.

[0080] The first BUCK circuit consists of a power switching device S1, a diode D1, and a resonant capacitor C S1 . The negative terminals of the power device S1 and D1 are connected to form a BUCK circuit. The positive terminal of the BUCK circuit is connected to the positive terminal of the DC power supply, and the negative terminal of the BUCK circuit is connected to the negative terminal of the DC voltage source. The second BUCK circuit consists of a power switching device S2, a diode D2, and a resonant capacitor C S2 . The negative terminals of the power device S2 and D2 are connected to form a BUCK circuit. The positive terminal of the BUCK circuit is connected to the positive terminal of the DC power supply, and the negative terminal of the BUCK circuit is connected to the negative terminal of the DC voltage source. The resonant capacitors C S1 , C S2 are respectively connected in parallel with S1 and S2. Among them, the resonant capacitors C S1 , C S2 can be the parasitic capacitors inside the power switching devices S1 and S2 or external capacitors.

[0081] The first resonant circuit consists of a power switching device S 11 , a resonant inductor L r1 , and a diode D S1 . The positive terminal of S 11 is connected to the positive terminal of S1. The same-name terminal of L r1 is connected to the negative terminal of S 11 . The other end of L r1 is connected to the positive terminal of D S1 . The negative terminal of D S1 is connected to the negative terminal of S1. The second resonant circuit consists of a power switching device S 21 , a resonant inductor L r2 , and a diode D S2 . The positive terminal of S 21 is connected to the positive terminal of S2. The same-name terminal of L r2 is connected to the negative terminal of S 21 . The other end of L r2 is connected to the positive terminal of D S2 . The negative terminal of D S2 is connected to the negative terminal of S2.

[0082] The first output LC circuit consists of a coupled inductor L1 and a capacitor C o The same - named terminal of the coupled inductor L1 is connected to the negative terminal of D1, and the other end is connected to one end of the capacitor C o while one end of the capacitor C o The other end is connected to the positive terminal of D1. The second output LC circuit consists of a coupled inductor L2 and a capacitor C o The same - named terminal of the coupled inductor L2 is connected to the negative terminal of D2, and the other end is connected to one end of the capacitor C o while one end of the capacitor C o The other end is connected to the positive terminal of D1. The load resistor R is connected in series with the inductor L and then in parallel with the capacitor C o

[0083] Among them, the power switching device adopts a MOSFET, GTR or IGBT with a reverse - parallel body diode.

[0084] Solution 3

[0085] As Figure 4 shown, Solution 3 is a soft - switching BUCK based on a coupled inductor and its derivative topology power converter, which is powered by a positive DC voltage source and consists of m BUCK circuits, a resonant circuit, and output LC circuits connected in parallel.

[0086] The first BUCK circuit consists of a power switching device S1, a diode D1, and a resonant capacitor C S1 The negative terminal of the power device S1 and the negative terminal of D1 are connected to form a BUCK circuit. The positive terminal of the BUCK circuit is connected to the positive terminal of the DC power supply, and the negative terminal of the BUCK circuit is connected to the negative terminal of the DC voltage source. The second BUCK circuit consists of a power switching device S2, a diode D2, and a resonant capacitor C S2 The negative terminal of the power device S2 and the negative terminal of D2 are connected to form a BUCK circuit. The positive terminal of the BUCK circuit is connected to the positive terminal of the DC power supply, and the negative terminal of the BUCK circuit is connected to the negative terminal of the DC voltage source. The m - th BUCK circuit consists of a power switching device S m , a diode D m , and a resonant capacitor C sm The negative terminal of the power device S m and the negative terminal of D m are connected to form a BUCK circuit. The positive terminal of the BUCK circuit is connected to the positive terminal of the DC power supply, and the negative terminal of the BUCK circuit is connected to the negative terminal of the DC voltage source. The resonant capacitors C S1 , C S2 , …, C sm are respectively connected in parallel with S1, S2, …, S m , where the resonant capacitor C S1 ​, C S2 , …, C sm can be the parasitic capacitance inside the power switch devices S1, S2, …, S m or can be an external capacitance.

[0087] The first resonant loop is composed of the power switch device S 11 , the resonant inductor L r1 and the diode D S1 . The positive terminal of S 11 is connected to the positive terminal of S1, the same-named terminal of L r1 is connected to the negative terminal of S 11 , the other end of L r1 is connected to the positive terminal of D S1 , and the negative terminal of D S1 is connected to the negative terminal of S1. The second resonant loop is composed of the power switch device S 21 , the resonant inductor L r2 and the diode D S2 . The positive terminal of S 21 is connected to the positive terminal of S2, the same-named terminal of L r2 is connected to the negative terminal of S 21 , the other end of L r2 is connected to the positive terminal of D S2 , and the negative terminal of D S2 is connected to the negative terminal of S2. The m-th resonant loop is composed of the power switch device S m1 , the resonant inductor L rm and the diode D sm . The positive terminal of S m1 is connected to the positive terminal of S m , the same-named terminal of L rm is connected to the negative terminal of S m1 , the other end of L rm is connected to the positive terminal of D sm , and the negative terminal of D sm is connected to the negative terminal of S m .

[0088] The first output LC loop is composed of the coupled inductor L1 and the capacitor C o . The same-named terminal of the coupled inductor L1 is connected to the negative terminal of D1, and the other end is connected to one end of the capacitor C o , while the other end of the capacitor C o is connected to the positive terminal of D1. The second output LC loop is composed of the coupled inductor L2 and the capacitor C o . The same-named terminal of the coupled inductor L2 is connected to the negative terminal of D2, and the other end is connected to one end of the capacitor C o , while the other end of the capacitor C oThe other end is connected to the positive terminal of D1. The m-th output LC circuit consists of a coupled inductor L m and a capacitor C o . The same-name terminal of the coupled inductor L m is connected to the negative terminal of D m , and the other end is connected to one end of the capacitor C o . The other end of the capacitor C o is connected to the positive terminal of D1. The load resistor R is connected in series with the inductor L and then in parallel with the capacitor C o .

[0089] The power switching device adopts a MOSFET, GTR or IGBT with a reverse-parallel body diode.

[0090] Solution 4

[0091] As Figure 5 shown, Solution 4 is a soft-switching BUCK and its derivative topology power converter based on a coupled inductor, powered by a positive DC voltage source, and consists of a non-isolated bidirectional power conversion circuit, a resonant circuit, and an output LC circuit.

[0092] The non-isolated bidirectional power conversion circuit consists of power switching devices S1, S'1 and resonant capacitors C S1 , C S'1 . The negative terminal of the power device S1 and the positive terminal of S'1 are connected to form a non-isolated bidirectional power conversion circuit. The positive terminal of the non-isolated bidirectional power conversion circuit is connected to the positive terminal of the DC power supply, and the negative terminal of the non-isolated bidirectional power conversion circuit is connected to the negative terminal of the DC voltage source. The resonant capacitors C S1 , C S'1 are respectively connected in parallel with S1 and S'1. The resonant capacitors C S1 , C S'1 can be the parasitic capacitors inside the power switching devices S1 and S'1 or external capacitors.

[0093] The resonant circuit consists of power switching devices S 11 , S 12 and a resonant inductor L r1 . The positive terminal of S 11 is connected to the positive terminal of S1. The same-name terminal of L r1 is connected to the negative terminal of S 11 . The other end of L r1 is connected to the negative terminal of S 12 . The positive terminal of S 12 is connected to the positive terminal of S1.

[0094] The output LC circuit consists of a coupled inductor L1 and a capacitor C o . The same-name terminal of the coupled inductor L1 is connected to the positive terminal of S'1, and the other end is connected to the capacitor C oOne end, while the capacitor C o The other end is connected to the negative terminal of S'1. The load resistor R is in series with the inductor L and then in parallel with the capacitor C o in parallel.

[0095] Among them, the power switch device uses a MOSFET, GTR or IGBT with a reverse-parallel body diode.

[0096] Solution 5

[0097] As Figure 6 shown, Solution 5 is a soft-switching BUCK and its derivative topology power converter based on a coupled inductor, powered by a positive DC voltage source, and consists of n non-isolated bidirectional power conversion circuits, a resonant circuit, and an output LC circuit.

[0098] The first non-isolated bidirectional power conversion circuit consists of power switch devices S1, S'1 and resonant capacitors C S1 , C S'1 . The negative terminal of the power device S1 and the positive terminal of S'1 are connected to form a non-isolated bidirectional power conversion circuit. The positive terminal of the non-isolated bidirectional power conversion circuit is connected to the positive terminal of the DC power supply, and the negative terminal of the non-isolated bidirectional power conversion circuit is connected to the negative terminal of the DC voltage source. The second non-isolated bidirectional power conversion circuit consists of power switch devices S2, S'2 and resonant capacitors C S2 , C S'2 . The negative terminal of the power device S2 and the positive terminal of S'2 are connected to form a non-isolated bidirectional power conversion circuit. The positive terminal of the non-isolated bidirectional power conversion circuit is connected to the positive terminal of the DC power supply, and the negative terminal of the non-isolated bidirectional power conversion circuit is connected to the negative terminal of the DC voltage source. The nth non-isolated bidirectional power conversion circuit consists of power switch devices S n , S' n and resonant capacitors C sn , C s'n . The negative terminal of the power device S n and the positive terminal of S' n are connected to form a non-isolated bidirectional power conversion circuit. The positive terminal of the non-isolated bidirectional power conversion circuit is connected to the positive terminal of the DC power supply, and the negative terminal of the non-isolated bidirectional power conversion circuit is connected to the negative terminal of the DC voltage source. Among them, the resonant capacitors C S1 , C S'1 , C S2 , C S'2 , …, C sn , C s'n are respectively in parallel with S1, S'1, S2, S'2, …, S n , S' n . The resonant capacitors C S1 , C S'1 , C S2 、CS'2 , …, C sn , C s'n may be power switch devices S1, S'1, S2, S'2, …, S n , S' n The parasitic capacitance inside may also be an external capacitance.

[0099] The first resonant circuit is composed of the power switch device S 11 , S 12 and the resonant inductor L r1 . The positive terminal of S 11 is connected to the positive terminal of S1, and the same-name terminal of L r1 is connected to the negative terminal of S 11 . The other end of L r1 is connected to the negative terminal of S 12 . The positive terminal of S 12 is connected to the positive terminal of S'1. The second resonant circuit is composed of the power switch device S 21 , S 22 and the resonant inductor L r2 . The positive terminal of S 21 is connected to the positive terminal of S2, and the same-name terminal of L r2 is connected to the negative terminal of S 21 . The other end of L r2 is connected to the negative terminal of S 22 . The positive terminal of S 22 is connected to the positive terminal of S'2. The nth resonant circuit is composed of the power switch device S n1 , S n2 and the resonant inductor L rn . The positive terminal of S n1 is connected to the positive terminal of S n . The same-name terminal of L rn is connected to the negative terminal of S n1 . The other end of L rn is connected to the negative terminal of S n2 . The positive terminal of S n2 is connected to the positive terminal of S' n .

[0100] The first output LC circuit is composed of the coupling inductor L1 and the capacitor C o . The same-name terminal of the coupling inductor L1 is connected to the positive terminal of S'1, and the other end is connected to one end of the capacitor C o , while the other end of the capacitor C o is connected to the negative terminal of S'1. The second output LC circuit is composed of the coupling inductor L2 and the capacitor C o . The same-name terminal of the coupling inductor L2 is connected to the positive terminal of S'2, and the other end is connected to one end of the capacitor C o , while the other end of the capacitor Co The other end is connected to the negative terminal of S'1. The nth output LC circuit consists of a coupled inductor Ln and a capacitor C o The like-named terminal of the coupled inductor Ln is connected to the positive terminal of S' n The other end is connected to one end of the capacitor C o One end of the capacitor C o The other end is connected to the negative terminal of S'1. The load resistor R is connected in series with the inductor L and then in parallel with the capacitor C o in parallel.

[0101] Among them, the power switch device uses a MOSFET, GTR or IGBT with a reverse-parallel body diode.

[0102] Such as Figures 7 to 13 shown, it is a schematic diagram of operating modes 1 to 7, where:

[0103] Operating mode 1, [t0 < t < t1]: At time t0, the diode D1 conducts, and the current i L1 flows through D1 for freewheeling. The switch S 11 is connected in series with the inductor L r1 The inductor current does not change suddenly. The switch S 11 can be turned on with zero current until S 11 is turned on with zero current at time t1, and this mode ends:

[0104] Operating mode 2, [t1 < t < t2]: At time t1, S 11 closes, i L1 = i S11 + i D1 i S11 gradually increases, then i D1 gradually decreases until at time t2, i S11 = i L1 i D1 = 0, D1 is turned off with zero current, and the resonant circuit conducts, and this mode ends:

[0105] Operating mode 3, [t2 < t < t3]: At time t2, D1 turns off, and the resonant circuit S 11 →L r1 →D S1 →C S1 resonates, U CS1 gradually decreases, i Lr1 gradually increases until at time t3, U CS1 = 0, and this mode ends. The formula for this stage is as follows:

[0106] i c (t2) = 0, U cs (t2) = U i U cs (t3) = 0

[0107]

[0108] U CS U(t)=U i cosω(t - t2

[0109]

[0110]

[0111] Operating mode 4, [t3 < t < t4]: At time t3, U CS1 = 0. At this time, due to resonance, i Lr1 is greater than i L1 , i Lr1 flows through the body diode of S1, and U CS1 is clamped at 0. In this stage, S1 can be turned on at zero voltage until time t4 when S1 is turned on and this mode ends:

[0112] Operating mode 5, [t4 < t < t5]: At time t4, switch S1 is turned on and i L1 gradually increases. Inductor L r1 is coupled in the same direction as L1, and the value of inductor L1 is much larger than that of inductor L r1 . Then i Lr1 gradually decreases. At time t5, i Lr1 = 0. The diode current cannot flow in the reverse direction, and S 11 , D s1 are turned off at zero current and this mode ends:

[0113] Operating mode 6, [t5 < t < t6]: At time t5, switch S 11 , diode D s1 are turned off at zero current. The power supply supplies power to the load until time t6 when switch S1 is turned off at zero voltage and this mode ends:

[0114] Operating mode 7, [t6 < t < t7]: At time t6, S1 is turned off at zero voltage and U CS1 = 0. C S1 is charged and U CS1 gradually increases. When t = t7, U CS1 = U i , diode D1 is turned on and this mode ends. The formula for this stage is as follows. One switching period ends and a new switching period begins.

[0115] C S1 U i = i L1 (t - t0)

[0116]

[0117] By analyzing the circuit operating mode, it can be seen that the ZCS (Zero Current Switching) soft switching of switch S 11 is determined by the coupled inductor L1 in the same direction, while the ZVS (Zero Voltage Switching) soft switching of S1 is determined by the resonance of inductor L r1 and junction capacitance C S1 . Therefore, the realization of the soft switching of S 11 and S1 is closely related to the main circuit parameters. In the calculation of the main circuit parameters, given the switching frequency, mainly the capacitance value and the inductance value are designed. The parameters need to be designed according to the requirements of the circuit output current ripple and the circuit operating mode. Reasonable circuit parameters can meet the operating requirements of the circuit and make it have excellent performance. Figure 1 Fig.

[0118] shows the operating mode of the soft-switching BUCK power converter with a coupled inductor in one cycle under the CCM (Continuous Conduction Mode). Taking the parameter design of this power converter as an example, a general method for designing the parameters of this type of power converter is derived. Lmin When the designed circuit operates in the CCM (Continuous Conduction Mode), the current in the filter inductor of the circuit always exists. Therefore, to keep the system always in the CCM mode, then i

[0119]

[0120] >0. The current ripple on the filter inductor L1 is:

[0121]

[0122] Therefore, the minimum value of the current flowing through inductor L1 is:

[0123]

[0124] That is, the range of inductor L1 is: i In the above formula, D is the duty cycle, f is the switching frequency, Z is the output reactance, U o is the input voltage, and U

[0125] According to circuit operating mode 3, inductor L r1 and capacitor C S1 start to resonate. To satisfy the ZVS turn-on of switch S1, the energy stored in capacitor C S1 needs to be completely transferred to inductor L r1 , that is, the voltage on C S1 can resonate to zero. At this time, the current on inductor L r1 reaches the maximum value i Lr1max , and ΔI Lr is the current of inductor L r1The current increment on then the capacitor C s1 satisfies the following equation:

[0126]

[0127] The resonant inductor L r1 The maximum value of the current on:

[0128]

[0129]

[0130] Larger inductance and capacitance values help reduce switching losses, but excessive parameters will cause the circuit to be unable to complete the resonance process within the corresponding time. Usually, the designed resonance time is less than Therefore, reasonably designed resonance parameters are required to make the circuit satisfy That is

[0131]

[0132] In addition, operating modes 2, 3, and 7 all operate at the moment when switch S1 is turned off. Therefore, the circuit parameters should also satisfy 0 < T 12 + T 23 + T 67 < (1 - D)T, that is

[0133]

[0134] According to operating mode 5, the filter inductor L1 and the resonant inductor L r1 are coupled in the same direction, and the coupling coefficient The turns ratio The inductor L r1 The voltage across both ends is:

[0135]

[0136] When S1 is in the conduction stage, U Lr1 = 0, then

[0137]

[0138] Therefore, when S1 is conducting, the increased current on the inductor L1 will cause r the resonant inductor L to flow through a reverse current. So, to satisfy the zero-current-switching (ZCS) turn-off of switch S 11 it is necessary to reduce the current flowing through S 11 to 0 during the turn-on period of S1. When Kn is very large, a slight increase in current ΔI on the inductor L1 will have a significant impact on the current on the inductor L r1 Therefore, the inductance value should be L1 >> Lr1 and \(K_n\Delta I > I\) Lrmax , that is

[0139]

[0140] For the filter capacitor \(C\) o , the larger its capacitance value, the smaller the voltage ripple and the smaller the output current ripple, but the worse the dynamic response. The relationship between the capacitance value \(C\) of the capacitor o and the output current ripple \(\Delta I\) of the circuit is as follows:

[0141]

[0142] The filter capacitor \(C\) o should be selected according to the specified output current ripple index, calculate the required capacitance value, and leave a certain margin, and finally obtain the actual capacitance value.

[0143] The value ranges of the circuit inductor and capacitor parameters can be obtained through the above analysis of the constraint conditions, and then the main circuit parameters can be determined, which are closely related to the working mode, switching frequency, coupling coefficient and circuit indexes of the circuit.

[0144] It can be seen from the above process that the parameter design process of this kind of converter, namely the soft-switching BUCK power converter with coupled inductors under CCM, can be summarized as follows:

[0145] 1. First, give the main circuit parameters, including the input voltage \(U\) i , the output voltage \(U\) o , the duty cycle \(D\), the output impedance \(Z\) and the switching frequency \(f\), and determine the value ranges of the unknown parameters according to the known parameters.

[0146] 2. Design the coupled inductor \(L_1 >> L\) r1 , and their inductance values are quite different. Since \(L_1 >> L\) r1 , the inductor \(L_1\) has a great influence on the inductor \(L\) r1 , while the inductor \(L\) r1 has a small influence on the inductor \(L_1\). Therefore, the influence of the inductor \(L\) r1 on the coupled inductor \(L_1\) can be ignored when analyzing. In addition, since the set inductance value \(L_1\) is very large, it can be considered that the current flowing through the inductor \(L_1\) is constant, so the circuit calculation is simplified and it is convenient to design the circuit parameters.

[0147] 3. Set the resonance period of the circuit not to exceed one-tenth of the switching period, which provides a design basis for the resonance circuit, and then the parameters can be further determined according to the soft-switching conditions of ZVS and ZCS of the circuit.

[0148] The resonance inductor \(L\) r1 and the resonance capacitor \(C\) s1The value of r1 is closely related to the conduction current of the anti-parallel diode of S1, and the resonance provides the ZVS soft-switching condition for S1. In addition, the coupled inductors L1 and L 11 provide the ZCS soft-switching condition. Therefore, the design of the resonant inductor and the resonant capacitor is crucial for the realization of such soft-switching conditions.

[0149] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed, as long as they do not depart from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features herein can be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a single embodiment can be used in other embodiments.

Claims

1. Coupled-inductor soft-switching power converter, characterized in that, It includes N power conversion circuits, N resonance circuits and N filter circuits; N is a positive integer greater than or equal to 1; The power conversion circuits each include a main power switch device, the resonance circuits each include an auxiliary power switch device and a resonance inductor, and the filter circuits each include a filter inductor; The N power conversion circuits are all used to convert the power of the power supply and then output it to the load; and, The resonant inductor L in the m-th resonant circuit rm , which is used to resonate with the parasitic capacitance C m of the main power switch device S sm in the m-th power conversion circuit, so as to achieve soft switching of the main power switch device S m ; m = 1, 2,..., N; The filtering inductor L in the m-th filtering circuit m , which is used to be coupled in the same direction with the resonant inductor L in the m-th resonant circuit rm , so as to realize the soft switching of the auxiliary power switching device S in the m-th resonant circuit m1 ; The filter circuit further includes a filter capacitor, and N filter circuits share a filter capacitor C O ; Filter inductor L m and filter capacitor C O respectively satisfy: Among them, K m is the coupling coefficient of the filter inductor L m and the resonant inductor L rm , D is the duty cycle of the main power switch device S m , f is the switching frequency of the main power switch device S m , Z is the output reactance, U i is the input voltage, U o is the output voltage, ΔI m is the current ripple on the filter inductor L m .

2. The coupled inductor soft-switching power converter according to claim 1, wherein, In the m-th power conversion circuit, the drain of the main power switch device S m is electrically connected to the positive pole of the power supply; The resonance circuits each further include a resonance diode; In the m-th resonant circuit, the auxiliary power switch device S m1 has its drain electrically connected to the drain of the main power switch device S m . The source of the auxiliary power switch device S m1 is electrically connected to one end of the resonant inductor L rm . The other end of the resonant inductor L rm is electrically connected to the anode of the resonant diode D sm . The cathode of the resonant diode D sm is electrically connected to the source of the main power switch device S m ; The power conversion circuits each further include an isolation diode; In the m-th power conversion circuit, the isolation diode D m has its negative electrode electrically connected to the source electrode of the main power switch device S m , and the positive electrode of the isolation diode D m is electrically connected to the negative electrode of the power supply; In the m-th filter circuit, filter inductor L m has one end electrically connected to the negative electrode of isolation diode D m , and the other end of filter inductor L m is electrically connected to the positive electrode of isolation diode D O through filter capacitor C m ; Resonant inductor L rm One end of which is the same-named end as one end of the filter inductor L m ​ 3. The coupled inductor soft-switching power converter according to claim 1, wherein, In the m-th power conversion circuit, the drain of the main power switch device S m is electrically connected to the positive pole of the power supply; The resonant circuit also includes a resonant power switching device S m2 ; In the m-th resonant circuit, the drain of the auxiliary power switch device S m1 is electrically connected to the drain of the main power switch device S m ; the source of the auxiliary power switch device S m1 is electrically connected to one end of the resonant inductor L rm ; the other end of the resonant inductor L rm is electrically connected to the source of the resonant power switch device S m2 ; and the drain of the resonant power switch device S m2 is electrically connected to the drain of the main power switch device S m . The power conversion circuit also includes a secondary power switching device S'. m ; In the m-th power conversion circuit, the secondary power switch device S' m has its drain electrically connected to the source of the main power switch device S m , and the source of the secondary power switch device S' m is electrically connected to the negative pole of the power supply; In the m-th filter circuit, the filter inductor L m has one end electrically connected to the drain of the secondary power switching device S' m , and the other end of the filter inductor L m is electrically connected to the source of the secondary power switching device S' O through the filter capacitor C m ; Resonant inductor L rm One end of which is the same-named end as one end of the filter inductor L m ​ 4. The coupled-inductor soft-switching power converter according to any one of claims 1 to 3, wherein N is equal to 1 or 2.

5. The coupled inductor soft-switching power converter according to any one of claims 1 to 3, characterized in that, Filter inductor L m and the resonant inductor L rm has a turn ratio of

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