Isolated multiphase DC / DC converter

Abstract

The present disclosure provides an isolated multiphase DC / DC converter, comprising: a multiphase transformer including a primary-side circuit and a secondary-side circuit magnetically coupled to the primary-side circuit, wherein the primary-side circuit has a plurality of first terminals, and the secondary-side circuit has a plurality of second terminals; a plurality of first blocking capacitors, each of the first blocking capacitors being electrically connected to a corresponding first terminal; and a plurality of second blocking capacitors, each of the second blocking capacitors being electrically connected to a corresponding second terminal. The number of the plurality of first blocking capacitors is one less than the number of the plurality of first terminals, and the number of the plurality of second blocking capacitors is one less than the number of the plurality of second terminals.

Description

Technical Field

[0001] The present disclosure relates to a multiphase DC / DC (direct current / direct current) converter, and more particularly to an isolated multiphase DC / DC converter capable of reducing the number of blocking capacitors. Background Art

[0002] Today, the power supply industry requires converters with high efficiency, high power density, and low cost, so as to achieve lower energy loss and high cost-effectiveness, while occupying less space. In addition, in many emerging applications (such as electric vehicles and data centers, etc.), high power operation is required. By using high-power converters, the charging time of electric vehicles and the size of power cabinets in data centers can be significantly reduced.

[0003] Multiphase converter technology is widely used to provide operating electrical energy. In a multiphase converter, each phase transmits a part of the total power. Since the current stress in each phase is only a part of the total current, it is easy to limit the conduction loss and component temperature. In addition, the operation of each phase in a multiphase converter can be interleaved with each other, so that the switching ripples in each phase can cancel each other out, thereby effectively reducing the size of the filter. Furthermore, a multiphase converter with a multiphase transformer can itself achieve current sharing without applying any additional control. Due to the above reasons, multiphase DC / DC converters have great potential in high-power applications. The following are related studies on multiphase DC / DC converters: T. Jin and K. Smedley, “Multiphase LLC Series Resonant Converter for Microprocessor Voltage Regulation,” Conference Record of the 2006 Industry Applications Conference Forty-First IAS Annual Meeting, vol. 5, pp. 2136 - 2143, Oct. 2006; and J. Jacobs, A. Averberg and R. De. Doncker, “A Novel Three-Phase DC / DC Converter for High-Power Applications,” 2004 35th Annual IEEE Power Electronics Specialists Conference, vol. 3, pp. 1861 - 1867, Jun. 2004.

[0004] Even though isolated multiphase DC / DC converters have many advantages in high-power applications, there is still a need to further improve their efficiency, power density, and cost-effectiveness.

[0005] Therefore, there is an urgent need to develop an isolated multiphase DC / DC converter that can improve the above-mentioned existing technologies. Summary of the Invention

[0006] The object of the present disclosure is to provide an isolated multiphase DC / DC converter that can reduce the number of blocking capacitors, where the blocking capacitors are used to prevent transformer saturation. In an isolated multiphase DC / DC converter, the current in one phase is equal to the sum of the currents in the remaining phases, and since the DC components in the remaining phases can be eliminated by their respective blocking capacitors, there is no need to provide a blocking capacitor in this phase. Since in a multiphase transformer, one set of blocking capacitors on the primary side and one set of blocking capacitors on the secondary side can be omitted, the DC / DC converter of the present disclosure can achieve both high cost-effectiveness and high power density.

[0007] According to one aspect of the concept, the present disclosure provides an isolated multiphase DC / DC converter, comprising: a multiphase transformer including a primary-side circuit and a secondary-side circuit magnetically coupled to the primary-side circuit, wherein the primary-side circuit has a plurality of first terminals and the secondary-side circuit has a plurality of second terminals; a plurality of first blocking capacitors, each of which is electrically connected to a corresponding first terminal; and a plurality of second blocking capacitors, each of which is electrically connected to a corresponding second terminal. The number of the plurality of first blocking capacitors is one less than the number of the plurality of first terminals, and the number of the plurality of second blocking capacitors is one less than the number of the plurality of second terminals.

[0008] In some embodiments, the converter further comprises: a first inverter or a first rectifier electrically connected to the primary-side circuit of the multiphase transformer; and a second inverter or a second rectifier electrically connected to the secondary-side circuit of the multiphase transformer.

[0009] In some embodiments, the converter further comprises: a primary-side voltage source electrically coupled to the first inverter or the first rectifier; and a secondary-side voltage source electrically coupled to the second inverter or the second rectifier.

[0010] In some embodiments, the number of the plurality of first terminals is at least two, and the number of the plurality of first blocking capacitors is one less than the number of the plurality of first terminals.

[0011] In some embodiments, the number of the plurality of second terminals is at least two, and the number of the plurality of second blocking capacitors is one less than the number of the plurality of second terminals.

[0012] In some embodiments, the primary side circuit includes a plurality of first windings, the number of the plurality of first windings being equal to the number of the plurality of first terminals, and the plurality of first windings being connected to each other in a Y-type or Δ-type connection manner. The secondary side circuit includes a plurality of second windings, the number of the plurality of second windings being equal to the number of the plurality of second terminals, and the plurality of second windings being connected to each other in a Y-type or Δ-type connection manner.

[0013] In some embodiments, the primary side circuit and the secondary side circuit include one of a Y-Y type winding pair, a Y-Δ type winding pair, a Δ-Y type winding pair, and a Δ-Δ type winding pair.

[0014] In some embodiments, the plurality of first windings of the primary side circuit and the plurality of second windings of the secondary side circuit are magnetically coupled to each other through a single magnetic core or a plurality of independent magnetic cores.

[0015] According to another aspect of the concept, the present disclosure provides an electronic circuit for converting electrical energy, including: a primary side circuit; and a secondary side circuit magnetically coupled to the primary side circuit. The primary side circuit includes a plurality of first terminals, at most one first terminal being directly electrically coupled to the primary side circuit, and each of the remaining first terminals being electrically coupled to the primary side circuit via a primary side blocking capacitor.

[0016] In some embodiments, the secondary side circuit includes a plurality of second terminals, at most one second terminal being directly electrically coupled to the secondary side circuit, and each of the remaining second terminals being electrically coupled to the secondary side circuit via a secondary side blocking capacitor.

[0017] In some embodiments, the primary side circuit includes a plurality of windings, the plurality of windings being connected to each other in a Y-type or Δ-type connection manner.

[0018] In some embodiments, the secondary side circuit includes a plurality of windings, the plurality of windings being connected to each other in a Y-type or Δ-type connection manner.

[0019] In some embodiments, the primary side circuit and the secondary side circuit are magnetically coupled to each other through a single magnetic core or a plurality of independent magnetic cores.

[0020] In some embodiments, the primary side circuit includes at least two first terminals, at most one first terminal being directly electrically coupled to the primary side circuit, and each of the remaining first terminals being electrically coupled to the primary side circuit via a primary side blocking capacitor.

[0021] In some embodiments, the secondary side circuit includes at least two second terminals, at most one second terminal being directly electrically coupled to the secondary side circuit, and each of the remaining second terminals being electrically coupled to the secondary side circuit via a secondary side blocking capacitor.

[0022] According to another aspect of the concept, the present disclosure provides a polyphase transformer, comprising: at least two primary windings, interconnected in a Y-type or Δ-type connection; at least two primary terminals, electrically coupled to the at least two primary windings respectively; and at least one primary blocking capacitor, wherein each primary blocking capacitor is electrically coupled between a corresponding primary terminal and a corresponding primary winding. At most one primary terminal is directly electrically coupled to the corresponding primary winding without passing through a primary blocking capacitor.

[0023] In some embodiments, the polyphase transformer further comprises: at least two secondary windings, interconnected in a Y-type or Δ-type connection; at least two secondary terminals, electrically coupled to the at least two secondary windings respectively; and at least one secondary blocking capacitor, wherein each secondary blocking capacitor is electrically coupled between a corresponding secondary terminal and a corresponding secondary winding. At most one secondary terminal is directly electrically coupled to the corresponding secondary winding without passing through a secondary blocking capacitor.

[0024] In some embodiments, the primary terminals and the secondary terminals that are directly electrically coupled to the corresponding primary winding and the corresponding secondary winding respectively are in the same phase.

[0025] In some embodiments, the primary terminals and the secondary terminals that are directly electrically coupled to the corresponding primary winding and the corresponding secondary winding respectively are in different phases.

[0026] In some embodiments, the at least two primary windings and the at least two secondary windings are magnetically coupled to each other through a single magnetic core or at least two independent magnetic cores. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1A and Figure 1B respectively show the Y-type connected windings and the Δ-type connected windings of the polyphase transformer.

[0028] Figure 2A and Figure 2B respectively show the multi-core three-phase transformer and the single-core three-phase transformer that can be used in a three-phase converter.

[0029] Figure 3 Shows a single-phase transformer and its blocking capacitor.

[0030] Figure 4 Shows a three-phase transformer using six capacitor banks.

[0031] Figure 5 Shows a bidirectional isolated three-phase DC / DC converter including a three-phase transformer and a blocking capacitor.

[0032] Figure 6A and Figure 6BSchematic diagrams of a multi-phase transformer without and with blocking capacitors, respectively.

[0033] Figure 7 Schematic diagram of a multi-phase transformer with fewer blocking capacitors in a preferred embodiment of the present disclosure.

[0034] Figure 8 FIG. 1 is a schematic diagram of an isolated multi-phase DC / DC converter including a multi-phase transformer in a preferred embodiment of the present disclosure.

[0035] Figure 9 Schematic diagram of an N-phase three-terminal transformer according to a preferred embodiment of the present disclosure.

[0036] Figure 10A The primary side of a three-phase transformer using a YY connection is shown, wherein each end of the primary side of the three-phase transformer is connected to a blocking capacitor.

[0037] Figure 10B The primary side of a three-phase transformer using a YY connection method in a preferred embodiment of the present disclosure is shown, wherein only two of the three terminals of the primary side of the three-phase transformer are connected to blocking capacitors.

[0038] Figure 11A and Figure 11B Different variations of the multi-phase transformer including fewer blocking capacitors in the preferred embodiment of the present disclosure are shown respectively.

[0039] The description of the accompanying drawings is as follows:

[0040] 110: Y-type connection winding

[0041] 120: Δ type connection winding

[0042] 111: Node

[0043] 110_1, 110_2, 110_N: Winding

[0044] 121_1, 121_2, 121_N: nodes

[0045] 120_1, 120_2, 120_N: Winding

[0046] 210, 220: Transformer

[0047] 211, 212, 214, 215, 217, 218: Winding

[0048] P1, P2, P3, S1, S2, S3: endpoints

[0049] 213, 216, 219: Magnetic core

[0050] 221, 222, 224, 225, 227, 228: Winding

[0051] 230: Magnetic core

[0052] C P 、C S : Blocking capacitor

[0053] 300: Transformer

[0054] 310: Primary side winding

[0055] 320: Secondary winding

[0056] 305: Capacitor Bank

[0057] N P 、N S : Number of turns

[0058] L M : Excitation inductance

[0059] i LM : Excitation current

[0060] i P 、i S : Current

[0061] T S : Switching cycle

[0062] 400: Transformer

[0063] 412, 414, 416, 422, 424, 426: capacitor banks

[0064] C PA 、C PB 、C PC 、C SA 、C SB 、C SC :Capacitor Bank

[0065] 500: Converter

[0066] 510: Transformer

[0067] 520: blocking capacitor

[0068] V1, V2: voltage source

[0069] Q1, Q2, Q3, Q4, Q5, Q6, Q A , Q B , Q C , Q D , Q E , Q F :switch

[0070] L PA 、L PB 、L PC : External inductor

[0071] 600: Transformer

[0072] 610: Primary side winding

[0073] 620: Secondary side winding

[0074] P1, P2, P N-K 、P N 、S1, S2, S M-I 、S M : Terminals

[0075] 630: Magnetic core

[0076] 640, 650: Blocking capacitors

[0077] 700: Transformer

[0078] 710: Primary side winding

[0079] 720: Secondary side winding

[0080] 730: Magnetic core

[0081] 740, 750: Blocking capacitors

[0082] 800: Converter

[0083] 810: Transformer

[0084] 820, 830: Inverter or rectifier

[0085] T1, T2, T L-J 、T L : Terminals

[0086] 1010, 1020: Transformers

[0087] 1012, 1014, 1016, 1022, 1024: Blocking capacitors

[0088] 1021: Node

[0089] TR1, TR2, TR3: Windings

[0090] i PA 、i PB 、i PC : Currents

[0091] 1100: Transformer

[0092] PA, PB, PC, SA, SB, SC: Terminals Detailed implementation manners

[0093] Some typical embodiments embodying the features and advantages of the present disclosure will be described in detail in the following description. It should be understood that the present disclosure can have various variations in different aspects, all of which do not depart from the scope of the present disclosure, and the descriptions and illustrations therein are essentially for illustrative purposes rather than for limiting the present disclosure.

[0094] Figure 1A and Figure 1B respectively show the Y-connected winding 110 and the Δ-connected winding 120 of the polyphase transformer. As Figure 1A shown, in the case of adopting the Y-connected method, the right ends of all windings 110_1 to 110_N are connected to the same node 111 (i.e., the neutral point), and the left ends of all windings 110_1 to 110_N can be used as the current input or output terminals. As Figure 1B shown, in the case of adopting the Δ-connected method, one end of each winding is sequentially connected to the other end of the next winding (i.e., nodes 121_1 to 121_N). For example, the right end of the first winding 120_1 is connected to the left end of the second winding 120_2 located at node 121_2, and the left end of the first winding 120_1 located at node 121_1 is connected to the right end of the Nth winding 120_N (i.e., the last winding). In this wiring method, all windings 120_1 to 120_N are connected in series and electrically coupled to form a closed loop, and nodes 121_1 to 121_N can be used as the current input or output terminals. Nearly all primary and secondary sides of polyphase transformers adopt one of the above two winding structure connection methods.

[0095] Figure 2A and Figure 2B respectively show the multi-core three-phase transformer 210 and the single-core three-phase transformer 220 that can be used in a three-phase converter. It should be noted that the primary and secondary sides (i.e., the left and right sides) of the transformers 210 and 220 both adopt Figure 1A the Y-connected method shown.

[0096] As Figure 2A shown, windings 211, 214, and 217 are connected in a Y-connected manner and have terminals P1, P2, and P3, thus forming the primary side of the transformer 210; windings 212, 215, and 218 are connected in a Y-connected manner and have terminals S1, S2, and S3, thus forming the secondary side of the transformer 210. As Figure 2A marked by the dashed line in Figure 2AAs shown, the three-phase transformer 210 may include three phase-independent magnetic cores 213, 216, and 219. As Figure 2B shown, the three-phase transformer 220 is substantially similar to Figure 2A the three-phase transformer 210 shown, with the only difference being that the three-phase transformer 220 includes a single magnetic core 230, where the magnetic core 230 may integrate the magnetic coupling of all winding pairs. Preferably, the single magnetic core 230 and the three phase-independent magnetic cores 213, 216, and 219 may be made of any suitable magnetic material with high permeability (such as iron, cobalt, and nickel) to facilitate the formation and guidance of the magnetic field.

[0097] An isolated DC / DC converter may utilize a transformer to provide electrical isolation. To ensure the stable operation of the DC / DC converter, it is very important to avoid the saturation of the magnetic core of the transformer due to excessive magnetic flux density. To reduce the maximum magnetic flux density in the magnetic core, the DC component of the exciting current of the transformer should be zero. It should be noted that the exciting current is the current drawn from the primary side when the primary side of the transformer is excited or energized at a specific voltage, and no load is applied to the secondary side when it is drawn.

[0098] To eliminate the DC component of the exciting current, a blocking capacitor may be connected in series with the transformer. Under the steady-state condition when the charge balance of the capacitor is satisfied (i.e., when the charging current of the capacitor is equal to the discharging current during the switching period), the capacitor blocks the DC component of the exciting current. Thereby, the transformer can operate stably without excessive magnetic flux density.

[0099] Figure 3 Shows a single-phase transformer 300 with blocking capacitors C P and C S . The blocking capacitors C P and C S are respectively connected in series with the primary-side winding 310 and the secondary-side winding 320. In some embodiments, the blocking capacitors C P and C S may be a capacitor bank 305, where the capacitor bank 305 includes a plurality of capacitors connected in series and parallel. For example, as Figure 3 shown, the capacitor bank 305 includes a total of six capacitors, where the six capacitors are connected in parallel in pairs to form three capacitor pairs, and the three capacitor pairs are connected in series with each other. It should be noted that Figure 3 the transformer 300 shown includes an ideal transformer with a turns ratio of N P : N S = n:1, and an exciting inductor L M is connected in parallel with the primary-side winding 310. The steady-state condition when the charge balance of the blocking capacitor is satisfied is represented by equation (1) below, at which time the DC component of the exciting current i LM is zero.

[0100]

[0101] wherein T S 、i P 、i S and <i LM > TS respectively represent the switching period of the converter, the current flowing through capacitor C P ,the current flowing through capacitor C S ,and the DC component of the exciting current i LM [[ID=--]],wherein the DC component of the exciting current i LM is equal to the average exciting current during the switching period T S . In some embodiments, the switching period T S can be between 0.5 and 10 times the reciprocal of the resonance frequency ν of the inductor L M and the capacitor C P connected in series, where the resonance frequency ν is equal to The switching period T S can be, for example, one over several hundred kHz.

[0102] This method can be used to prevent the transformer 300 from saturating without any additional control. However, in high-power and high-voltage applications, since the capacitors used in the industry have limited voltage and current ratings, multiple capacitors need to be connected in series and in parallel to meet the required voltage and current stresses.

[0103] Figure 4 shows a three-phase transformer 400, where the windings on both the primary side and the secondary side of the three-phase transformer 400 adopt the Figure 2B Y-type connection shown. Each winding is connected in series to a capacitor or a capacitor bank to eliminate the DC component of the exciting current in the three-phase transformer 400. In this example, six capacitor banks 412, 414, 416, 422, 424, and 426 are used to prevent the transformer 400 from saturating. However, the six capacitor banks adopted will significantly increase the additional cost and reduce the power density of the DC / DC converter.

[0104] Figure 5 shows a bidirectional isolated three-phase DC / DC converter 500 including a three-phase transformer 510 and a plurality of blocking capacitors 520. The converter 500 can transfer energy in either direction between two voltage sources V1 and V2. In the converter 500, the three phases on the primary side are coupled to the primary-side voltage source V1, and the three phases on the secondary side are coupled to the secondary-side voltage source V2.

[0105] Each phase of the converter 500 includes two switches coupled to the primary side of the transformer 510 and two switches coupled to the corresponding secondary side of the transformer 510. Specifically, as Note: There seems to be a small error in the original text where "i LM " is repeated as "i LM " and then "i LM " is combined with "<i LM " in an unclear way. I translated it as best as possible while keeping the original structure. Also, the "wherein the DC component of the exciting current i LM " in the original text seems to have an extra "i" before " LM ", which I also translated as accurately as possible.Figure 5 As shown, switches Q1 and Q2 are connected to phase A of the primary side of transformer 510 via an external inductor L PA Switches Q3 and Q4 are connected to phase B of the primary side of transformer 510 via an external inductor L PB Switches Q5 and Q6 are connected to phase C of the primary side of transformer 510 via an external inductor L PC Similarly, as Figure 5 shown, switches Q A and Q B are connected to phase A of the secondary side of transformer 510, switches Q C and Q D are connected to phase B of the secondary side of transformer 510, and switches Q E and Q F are connected to phase C of the secondary side of transformer 510.

[0106] The external inductors L PA , L PB and L PC are respectively connected in series to the corresponding windings of the three-phase transformer 510 via the corresponding capacitors 520, thereby controlling the slope of the current flowing through the transformer 510. If the leakage inductance of any winding of the transformer 510 is large enough to control the slope of the current, it may be necessary to select whether to set the external inductor L PA , L PB or L PC corresponding to that winding.

[0107] If Figure 5 the operating switching frequency of the converter 500 in

[0108] Figure 6A is much greater than (at least one order of magnitude higher than) the resonant frequency of the series-connected inductor and capacitor, the converter 500 can be called an isolated three-phase dual-active bridge converter. On the other hand, if the operating switching frequency of the converter 500 is designed to be close to the resonant frequency, the converter 500 can also be called an isolated three-phase resonant converter. If the number of phases of the isolated DC / DC converter is greater than two, the converter is usually called an isolated multi-phase DC / DC converter. Furthermore, a blocking capacitor 520 needs to be set to block the DC component in the magnetizing current of the transformer 510. N-K Figure 45 is a schematic diagram of a multi-phase transformer 600 without a blocking capacitor. The primary side winding 610 and the secondary side winding 620 of the multi-phase transformer 600 can be configured in a Y-type or Δ-type wiring manner. The magnetic core 630 of the transformer 600 can include a single magnetic core or multiple magnetic cores. The primary side has N phases, and each end point of the primary side winding 610 is respectively P1, P2,..., P NMark, where 0≤K <N-1。次级侧具有M个相位,且次级侧绕组620的每一端点分别以S1、S2、…、S M-I , ... and S M Mark, where 0≤I <M-1。 Figure 6B Schematic diagram of a multi-phase transformer 600 including blocking capacitors 640 and 650. To block the DC component in the excitation current of the transformer 600, each end of the primary winding 610 is connected in series with a blocking capacitor 640, and each end of the secondary winding 620 is connected in series with a blocking capacitor 650.

[0109] Figure 7 FIG. 7 is a schematic diagram of a multi-phase transformer 700 with less blocking capacitance 740 according to a preferred embodiment of the present disclosure. Figure 7 As shown, the multi-phase transformer 700 is substantially the same as Figure 6B The multiphase transformer 600 is similar to the one in FIG. Figure 7 In the multiphase transformer 700, the Figure 6B The two terminals P of the multi-phase transformer 600 are coupled to each other. N-K and S M-I The primary winding 710 and the secondary winding 720 of the multi-phase transformer 700 can adopt a Y-type or Δ-type connection method. It should be understood that the primary winding 710 and the secondary winding 720 do not need to adopt the same connection method. For example, when the primary winding 710 adopts a Y-type connection method, the secondary winding 720 can also adopt a Δ-type connection method, and vice versa. One of the windings of the primary winding 710 and one of the windings of the secondary winding 720 can form a winding pair through the magnetic core 730. Accordingly, regardless of whether or not the magnetic core 730 is passed through, the primary winding 710 and the secondary winding 720 can form any one of a YY-type winding pair, a Y-Δ-type winding pair, a Δ-Y-type winding pair, and a Δ-Δ-type winding pair.

[0110] like Figure 7 As shown, even if the two blocking capacitors are removed, the current flowing through the terminal P N-K The average current of the corresponding winding is equal to the sum of the average currents of all other windings on the primary side of the transformer 700 and flows through the terminal S M-I The average current of the corresponding winding is equal to the sum of the average currents of all other windings flowing through the secondary side of the transformer 700, so all DC components of the excitation current of the transformer 700 can still be blocked. N-K and S M-IExcept for the corresponding windings, all other windings are serially coupled to blocking capacitors 740 or 750 to eliminate the DC component in the current. Therefore, the number of electronic components required in the DC / DC converter can be reduced, thereby making the DC / DC converter have lower manufacturing costs and dimensions. In this example, only one blocking capacitor is removed in each phase on both the primary side and the secondary side, but it should be understood that more than one blocking capacitor can also be removed from the primary side and the secondary side under specific conditions.

[0111] Figure 8 FIG. 4 is a schematic diagram of an isolated multiphase DC / DC converter 800 including a multiphase transformer 810 in a preferred embodiment of the present disclosure. As Figure 8 shown, the converter 800 can be provided with one or more inverters or rectifiers 820 on its primary side and one or more inverters or rectifiers 830 on its secondary side to operate as an isolated multiphase DC / DC converter. It should be understood that the aforementioned concept of reducing the number of blocking capacitors can also be applied to any suitable multiphase multiterminal transformer in any suitable multiphase multiterminal converter. For example, Figure 9 FIG. 5 shows an N-phase three-terminal transformer in which one blocking capacitor is removed on each of the primary side, secondary side, and tertiary side of the transformer.

[0112] Figure 10A FIG. 6 shows the primary side of a three-phase transformer 1010 with a Y-Y connection method, where the three terminals PA, PB, and PC of the primary side of the three-phase transformer 1010 are respectively connected to blocking capacitors 1012, 1014, and 1016, which is similar to Figure 4 shown. It should be noted that due to the charge balance between the blocking capacitors 1012, 1014, and 1016, the DC component in the current of each phase winding is zero. In contrast, Figure 10B FIG. 7 shows the primary side of a three-phase transformer 1020 with a Y-Y connection method in a preferred embodiment of the present disclosure. In the primary side of the three-phase transformer 1020, only two terminals PA and PB are respectively connected to blocking capacitors 1022 and 1024. It can be noted that the blocking capacitor 1016 that originally existed in Figure 10A the transformer 1010 is removed in Figure 10B the transformer 1020.

[0113] Analyzing the current on the neutral point 1021 of the Y-connected winding in Figure 10B according to Kirchhoff’s current law, equation (2) can be obtained.

[0114] i PA +i PB +i PC =0 (2)

[0115] wherein, i PA , i PB and i PC respectively represent the currents flowing through the endpoints PA, PB, and PC. Taking the average values of the currents i PA , i PB and i PC in a switching period T S yields Equations (3) and (4).

[0116] <i PA > + <i PB > + <i PC > = 0 (3)

[0117] <i PA > = -<i PB > - <i PC > (4)

[0118] wherein, <i PA >, <i PB > and <i PC > respectively represent the average values of the currents i PA , i PB and i PC in a switching period T S . Based on the charge balance between the capacitors C PA and C PB , the average values of the currents i PA and i PB are both zero, so Equations (5) and (6) can be obtained.

[0119] <i PA > = 0 (5)

[0120] <i PB > = 0 (6)

[0121] Substituting Equations (5) and (6) into Equation (4) can obtain that the average value of the current i PC is zero, as shown in Equation (7).

[0122] <i PC > = 0 (7)

[0123] Therefore, whether there is a blocking capacitor at the endpoint PC or not, it will not affect the transformer 1020, especially when the charge balance between the capacitors is satisfied. Even though only the removal of the capacitor C PC is exemplified in the transformer 1010 with a Y-type wiring method in the present disclosure, it can be understood that in fact, the capacitors C PA , C PB and C PCbe removed from any one of the autotransformers 1010, and the same technical effect can be achieved. Similarly, for a transformer with a Δ connection method, the capacitor C can also be removed PA 、C PB and C PC from any one of them.

[0124] Figure 11A and Figure 11B respectively show different variations of the polyphase transformer 1100 with fewer blocking capacitors in the preferred embodiments of the present disclosure. As Figure 11A shown, each of the terminals PA and PB on the primary side and the terminals SA and SB on the secondary side are connected in series to a blocking capacitor, while the terminals PC on the primary side and SC on the secondary side (both are phase C) are not connected to the blocking capacitor. This situation is applicable to a dual-active-bridge DC / DC converter. In a dual-active-bridge DC / DC converter, since its resonance frequency is much smaller than the switching frequency, it is necessary to remove the blocking capacitor in the same phase on the primary side and the secondary side. In some other embodiments, the blocking capacitors in phase A or B on the primary side and the secondary side can also be removed simultaneously.

[0125] If the capacitance value of the blocking capacitor is synchronized with the switching frequency (i.e., the resonance frequency corresponds to the switching frequency), the blocking capacitors removed on the primary and secondary sides must be in different phases. For example, as Figure 11B shown, it is to remove the blocking capacitor at the terminal PC (phase C) on the primary side and remove the blocking capacitor at the terminal SB (phase B, rather than phase C) on the secondary side. It can be understood that in some other embodiments, if the blocking capacitor in phase A on the primary side is removed, the blocking capacitor in phase B or C on the secondary side can be removed.

[0126] For Figure 11A and Figure 11B the three-phase transformer 1100 shown, it can save one-third of the total material cost for the blocking capacitors compared to the existing three-phase transformer. Taking a five-phase transformer as an example, it can save one-fifth of the total material cost for the blocking capacitors.

[0127] To facilitate the description and definition of the technical content of the present disclosure, terms such as "substantially", "about", "slightly", etc. are used to represent the inherent degree of uncertainty, which may be caused by factors such as quantitative comparison, numerical values, sensing, etc. These terms generally mean a deviation within 10%, 5%, 1% or 0.5% from a given value or range, and this deviation will not affect the basic function of the corresponding technical feature. Unless otherwise specifically stated, the numerical parameters stated in the present disclosure can be regarded as specific numerical values or numerical values within their error ranges.

[0128] It should be noted that the above are only preferred embodiments proposed for the purpose of illustrating the present disclosure. The present disclosure is not limited to the described embodiments, and the scope of the present disclosure is determined by the appended claims. And the present disclosure can be variously modified by those skilled in the art, but all such modifications do not depart from the scope of protection of the appended claims.

Claims

1. An isolated multi-phase DC / DC converter, comprising: A multi-phase transformer, comprising a primary-side circuit and a secondary-side circuit magnetically coupled to the primary-side circuit, wherein the primary-side circuit has a plurality of first terminals, and the secondary-side circuit has a plurality of second terminals; A plurality of first blocking capacitors, wherein each of the first blocking capacitors is electrically connected to a corresponding one of the first terminals; And A plurality of second blocking capacitors, wherein each of the second blocking capacitors is electrically connected to a corresponding one of the second terminals, Wherein, the number of the plurality of first blocking capacitors is one less than the number of the plurality of first terminals, and the number of the plurality of second blocking capacitors is one less than the number of the plurality of second terminals, Wherein, the primary-side circuit comprises a plurality of first windings respectively electrically coupled to the plurality of first terminals, the number of the plurality of first windings is equal to the number of the plurality of first terminals, and the plurality of first windings are connected to each other in a Y-type or Δ-type wiring manner.

2. The isolated multi-phase DC / DC converter according to claim 1, further comprising: A first inverter or a first rectifier electrically connected to the primary-side circuit of the multi-phase transformer; and A second inverter or a second rectifier electrically connected to the secondary-side circuit of the multi-phase transformer.

3. The isolated multi-phase DC / DC converter according to claim 2, further comprising: A primary-side voltage source electrically coupled to the first inverter or the first rectifier; and A secondary-side voltage source electrically coupled to the second inverter or the second rectifier.

4. The isolated multi-phase DC / DC converter according to claim 1, wherein, The number of the plurality of first terminals is at least two, and the number of the plurality of first blocking capacitors is one less than the number of the plurality of first terminals.

5. The isolated multi-phase DC / DC converter according to claim 1, wherein, The number of the plurality of second terminals is at least two, and the number of the plurality of second blocking capacitors is one less than the number of the plurality of second terminals.

6. The isolated multi-phase DC / DC converter according to claim 1, wherein, The secondary-side circuit comprises a plurality of second windings respectively electrically coupled to the plurality of second terminals, the number of the plurality of second windings is equal to the number of the plurality of second terminals, and the plurality of second windings are connected to each other in a Y-type or Δ-type wiring manner.

7. The isolated multiphase DC / DC converter according to claim 6, wherein, The primary-side circuit and the secondary-side circuit comprise one of a Y-Y type winding pair, a Y-Δ type winding pair, a Δ-Y type winding pair, and a Δ-Δ type winding pair.

8. The isolated multiphase DC / DC converter according to claim 6, wherein, The plurality of first windings of the primary-side circuit and the plurality of second windings of the secondary-side circuit are magnetically coupled to each other through a single magnetic core or a plurality of independent magnetic cores.

9. An electronic circuit for converting electrical energy, comprising: A primary-side circuit; and A secondary-side circuit magnetically coupled to the primary-side circuit, Among them, The primary-side circuit comprises a plurality of first terminals, at most one of the first terminals is directly electrically coupled to the primary-side circuit, and each of the remaining first terminals is electrically coupled to the primary-side circuit via a primary-side blocking capacitor, Wherein, the primary-side circuit comprises a plurality of windings, the plurality of windings are respectively electrically coupled to the plurality of first terminals, and the plurality of windings are connected to each other in a Y-type or Δ-type wiring manner.

10. The electronic circuit according to claim 9, wherein, The secondary-side circuit comprises a plurality of second terminals, at most one of the second terminals is directly electrically coupled to the secondary-side circuit, and each of the remaining second terminals is electrically coupled to the secondary-side circuit via a secondary-side blocking capacitor.

11. The electronic circuit according to claim 9, wherein, The secondary side circuit of the secondary side circuit includes a plurality of windings, and the plurality of windings are interconnected in a Y-type or Δ-type connection mode.

12. The electronic circuit according to claim 9, wherein, The primary side circuit and the secondary side circuit are magnetically coupled to each other through a single magnetic core or a plurality of independent magnetic cores.

13. The electronic circuit according to claim 9, wherein, The primary side circuit includes at least two of the first terminals, and at most one of the first terminals is directly electrically coupled to the primary side circuit, and each of the remaining first terminals is electrically coupled to the primary side circuit via the primary side blocking capacitor.

14. The electronic circuit according to claim 9, wherein, The secondary side circuit includes at least two second terminals, and at most one of the second terminals is directly electrically coupled to the secondary side circuit, and each of the remaining second terminals is electrically coupled to the secondary side circuit via a secondary side blocking capacitor.

15. A polyphase transformer, comprising: At least two primary side windings, interconnected in a Y-type or Δ-type connection mode; At least two primary side terminals, respectively electrically coupled to the at least two primary side windings; and At least one primary side blocking capacitor, wherein each primary side blocking capacitor is electrically coupled between the corresponding primary side terminal and the corresponding primary side winding; Wherein at most one of the primary side terminals is directly electrically coupled to the corresponding primary side winding without passing through the primary side blocking capacitor.

16. The polyphase transformer according to claim 15, further comprising: At least two secondary side windings, interconnected in a Y-type or Δ-type connection mode; At least two secondary side terminals, respectively electrically coupled to the at least two secondary side windings; and At least one secondary side blocking capacitor, wherein each secondary side blocking capacitor is electrically coupled between the corresponding secondary side terminal and the corresponding secondary side winding; Wherein at most one of the secondary side terminals is directly electrically coupled to the corresponding secondary side winding without passing through the secondary side blocking capacitor.

17. The polyphase transformer according to claim 16, wherein, The primary side terminal and the secondary side terminal that are directly electrically coupled to the corresponding primary side winding and the secondary side winding are in the same phase.

18. The polyphase transformer according to claim 16, wherein, The primary side terminal and the secondary side terminal that are directly electrically coupled to the corresponding primary side winding and the secondary side winding are in different phases.

19. The polyphase transformer according to claim 16, wherein, The at least two primary side windings and the at least two secondary side windings are magnetically coupled to each other through a single magnetic core or at least two independent magnetic cores.

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