Non-isolated hybrid resonant circuit

Abstract

The present invention provides a non-isolated hybrid resonant circuit for converting voltage and supplying power to a load. The circuit includes: a full-wave rectifier circuit connected in parallel with the load, having a first rectifier branch and a second rectifier branch connected in parallel, each rectifier branch having a rectifier switch and a winding connected in series; a first switch circuit connected between the first end of the power supply and the first end of the load, including a first switch and a second switch connected in series; a first resonant unit electrically coupled between a first connection point formed by the series connection of the first switch and the second switch and the midpoint of the first rectifier branch, wherein the windings in the first and second rectifier branches are coupled to each other. The conversion circuit provided by the present invention can achieve an odd voltage conversion ratio and can reduce the loss and volume of the transformer.

Description

Technical Field

[0001] This article relates to a conversion circuit for converting the voltage of a power supply to supply power to a load. Specifically, this article relates to a non-isolated hybrid resonant circuit. Background Art

[0002] Research data from the China Data Center Energy Conservation Technology Committee shows that the total power consumption of Chinese data centers exceeded 120 billion kWh in 2016. As more and more services are supported by data centers, the computing load and scale of data centers will still maintain high growth. To increase the computing density of data centers, the power of a single rack (RACK) will increase accordingly. In traditional racks, the AC UPS used to power the rack is located outside the rack, and the voltage of the internal DC distribution bus is 12V, with relatively stable voltage. However, when the power of a single rack exceeds 15kW, the current on the 12V DC distribution bus increases significantly, greatly reducing the efficiency, increasing the heat dissipation cost, and the cost of cables and connectors, etc. Therefore, in the new power transmission architecture, the voltage of the DC distribution bus inside the rack is increased to 48V. At the same time, the AC UPS is replaced with a DC UPS (DC-UPS), which is installed inside the rack and directly connected to the 48V DC distribution bus. This significantly reduces the current on the distribution bus, improves the power supply efficiency of the data center, reduces the power consumption cost, heat dissipation cost, and distribution bus cost, and thus reduces the total cost of ownership of the data center.

[0003] It can be seen that in the new power transmission architecture, the voltage conversion ratio between the bus and the processor chip is significantly increased, posing extremely high efficiency requirements for the power conversion module (Voltage Regulation Module, VRM) between the DC bus and the processor chip. Under such conditions, while maintaining a high power density and meeting the requirements for power conversion efficiency, the 48V VRM from the DC distribution bus to the processor chip faces huge challenges.

[0004] Generally speaking, the 48V VRM is a two-stage cascaded converter structure, which usually adopts a working mode of first stepping down the voltage and then regulating the voltage. For example, the first-stage converter can use an efficient DC transformer to step down the input 48V bus voltage (Uin) to a lower intermediate bus voltage (Uib), such as 4V. The second stage uses a multi-phase interleaved parallel BUCK converter to ensure the power supply to the load (such as a processor chip) by closed-loop controlling the BUCK output voltage Uo.

[0005] The typical topology that can usually be adopted by the first-stage converter of a 48V VRM is an LLC series resonant circuit. However, the LLC circuit has some drawbacks. All energy conversion must pass through the transformer. The switching device on the primary side of the transformer is responsible for generating the excitation of the primary winding, while the secondary side inducts the excitation of the primary side and outputs it to the final load through the rectifier. During this process, the switching device on the primary side only generates excitation, and its own excitation current does not flow to the load terminal but instead flows back to the input terminal. All load currents are provided by the secondary-side circuit. At this time, the current stress on the secondary winding and the device is relatively large. The LLC circuit can achieve a relatively high voltage ratio and can also achieve ZVS soft switching with relatively high efficiency. However, all its energy is transferred through the transformer, and in a full-wave rectifier circuit, only one winding works in each half cycle, causing the other winding to be idle.

[0006] When isolation is not required in the system, a non-isolated LLC circuit 10 as shown in Figure 1 can also be used. In Figure 1 , assume that the turns ratio of the transformer composed of windings P, S1, and S2 is N:1:1, the switching frequency fs is equal to the resonant frequency fr, and the magnetizing inductance on the transformer is Lm. As shown in Figure 1 , when the non-isolated LLC circuit is working, in the positive half cycle, switches Q1 and Q4 are turned on and switches Q2 and Q3 are turned off. At this time, inductor Lr resonates with capacitor C1, and the resonant frequency is Meanwhile, the magnetizing current I Lm rises linearly. At this time, the resonant current I Lr passes through the primary winding P, then through the secondary winding S1 and is injected into the load terminal Vo. Therefore, the primary-side current of the transformer in this circuit flows to the load instead of directly flowing back to the power supply terminal Vin. Compared with the LLC, the transformer does not need to induct all load currents. Therefore, the transformer inductive current is reduced, and at the same time, the current flowing through the switch is also reduced, and the conduction loss is reduced. At the same time, the secondary winding S2 inducts the excitation from the primary winding P and the secondary winding S1 and induces a current (N + 1) times that. During this process, the secondary winding S1 also acts as an excitation winding. Under the condition of achieving the same transformer excitation ratio, the addition of the secondary winding S1 enables the primary winding P to reduce the number of turns, thus reducing the conduction resistance and conduction loss of the primary winding P. After the positive half cycle is the process of realizing soft switching. During this process, the magnetizing current charges the parasitic capacitances of switches Q1 and Q4 and discharges the parasitic capacitances of switches Q2 and Q3 to achieve soft switching. After that is the negative half cycle. Switches Q2 and Q3 are turned on and switches Q1 and Q4 are turned off. This process is basically the same as that of the positive half cycle.

[0007] From the above switching process, the circuit achieves soft switching, a high voltage conversion ratio, the primary excitation current flows to the load, and at the same time, the idle secondary side of the transformer is reused for the excitation coil of the converter, reducing the number of turns and resistance of winding P. When the switching frequency fs is equal to the resonance frequency fr, the voltage conversion ratio is (2N + 2 + 2):1. Compared with LLC, this circuit reduces the turn ratio of the transformer and the proportion of transferred energy. Although the non-isolated LLC reduces the number of turns of the transformer, its voltage conversion ratio can only be an even number and cannot meet the requirement of an odd voltage conversion ratio.

[0008] Therefore, there is still a need for a new non-isolated resonant circuit topology that can achieve an odd voltage conversion ratio and reduce the loss of the transformer. Summary of the Invention

[0009] The object of the present invention is to solve the problem that the non-isolated LLC circuit cannot achieve an odd voltage conversion ratio, and provides a non-isolated hybrid resonant conversion circuit that can achieve an odd voltage conversion ratio and at the same time reduce the loss and volume of the transformer.

[0010] According to one aspect of the present disclosure, there is provided a conversion circuit for converting the voltage of a power supply and supplying power to a load. The power supply and the load each include a first end and a second end. The second end of the power supply is connected to the second end of the load. The conversion circuit includes: a full-wave rectifier circuit, connected in parallel with the load, and having a first rectifier branch and a second rectifier branch connected in parallel. The first rectifier branch has a first rectifier switch and a first winding connected in series, and the first rectifier switch and the first winding are connected to form a first midpoint. The second rectifier branch has a second rectifier switch and a second winding connected in series, and the second rectifier switch and the second winding are connected to form a second midpoint; a first switch circuit, connected between the first end of the power supply and the first end of the load, the first switch circuit including a first switch and a second switch, the first switch and the second switch being connected in series to form a first connection point; and a first resonant unit, coupled between the first connection point and the first midpoint, wherein the first winding and the second winding are coupled to each other.

[0011] Optionally, in the conversion circuit described herein, further included is: a third winding, electrically coupled between the first connection point and the first midpoint in series with the first resonant unit, wherein the third winding, the first winding, and the second winding are coupled to each other.

[0012] Optionally, in the conversion circuit described herein, the first resonant unit includes an inductor and a capacitor connected in series or in parallel.

[0013] Optionally, in the conversion circuit described herein, the first switching circuit further includes (2m - 2) switches connected in series with the first switch and the second switch, such that the first switching circuit includes 2m switches connected in series, wherein adjacent switches among the 2m switches are connected to form connection points. The conversion circuit further includes: (m - 1) resonant units, which together with the first resonant unit constitute m resonant units. The x-th resonant unit among the m resonant units is electrically coupled between the connection point of the (2x - 1)-th switch and the 2x-th switch among the 2m switches and the first midpoint after being connected in series with the third winding; and (m - 1) energy storage units each including an energy storage element. One end of the k-th energy storage unit among the (m - 1) energy storage units is connected to the connection point of the 2k-th switch and the (2k + 1)-th switch among the 2m switches, and the other end is connected to the second rectifying branch, and m, x, and k are integers, and m≥2, 1≤x≤m, and 1≤k≤(m - 1).

[0014] Optionally, in the conversion circuit described herein, the energy storage element is a capacitor.

[0015] Optionally, in the conversion circuit described herein, each energy storage unit further includes an inductor connected in series with the capacitor in the corresponding energy storage unit.

[0016] Optionally, in the conversion circuit described herein, the other end of each of the (m - 1) energy storage units is connected to one of the following positions: the first end of the load; the second midpoint; and the second end of the load.

[0017] Optionally, in the conversion circuit described herein, the first switching circuit further includes (m - 2) switches connected in series with the first switch and the second switch, such that the first switching circuit includes m switches connected in series, wherein adjacent switches among the m switches are connected to form connection points. The conversion circuit further includes (m - 2) resonant units to together with the first resonant unit constitute (m - 1) resonant units. The (2y - 1)-th resonant unit among the (m - 1) resonant units is electrically coupled between the connection point of the (2y - 1)-th switch and the 2y-th switch among the m switches and the first midpoint after being connected in series with the third winding. One end of the 2z-th resonant unit among the (m - 1) resonant units is connected to the connection point between the 2z-th switch and the (2z + 1)-th switch among the m switches, and the other end is connected to the second rectifying branch, and m is odd, and y and z are integers, and m≥3, 1≤y≤m / 2, and 1≤z≤(m - 1) / 2.

[0018] Optionally, in the conversion circuit described herein, the other end of the 2z-th resonant unit among the (m - 1) resonant units is connected to one of the following positions: the first end of the load; the second midpoint; and the second end of the load.

[0019] Optionally, in the conversion circuit described herein, each of the (m - 1) capacitors is further serially connected with a fourth winding, and the fourth winding, the first winding, and the second winding are coupled to each other.

[0020] Optionally, in the conversion circuit described herein, the 2z-th resonant unit among the (m - 1) resonant units is further serially connected with a fifth winding, and the fifth winding, the first winding, and the second winding are coupled to each other.

[0021] Optionally, in the conversion circuit described herein, the first switching circuit further includes a third switch and a fourth switch connected in series with the first switch and the second switch. The second switch and the third switch are connected to form a second connection point, and the third switch and the fourth switch are connected to form a third connection point. The conversion circuit further includes: a first energy storage unit, each energy storage unit including an energy storage element, one end of the first energy storage unit is connected to the second connection point, and the other end is connected to the second rectification branch; and a second resonant unit, electrically coupled between the second connection point and the first midpoint.

[0022] Optionally, in the conversion circuit described herein, a common inductor is further included, and the first resonant unit and the second resonant unit are connected to the first midpoint via the common inductor.

[0023] Optionally, in the conversion circuit described herein, the resonant inductors of the first resonant unit and the second resonant unit are shared.

[0024] Optionally, in the conversion circuit described herein, a third winding is further included, wherein after the first resonant unit and the third winding are connected in series, they are electrically coupled between the first connection point and the first midpoint, and after the second resonant unit and the third winding are connected in series, they are electrically coupled between the second connection point and the first midpoint, and the third winding, the first winding, and the second winding are coupled to each other.

[0025] Optionally, in the conversion circuit described herein, the first switching circuit further includes a third switch and a fourth switch connected in series with the first switch and the second switch. The second switch and the third switch are connected to form a second connection point, and the third switch and the fourth switch are connected to form a third connection point. The conversion circuit further includes: a first energy storage unit including an energy storage element, one end of the first energy storage unit is connected to the second connection point, and the other end is connected to the second rectification branch; and a second resonance unit electrically coupled between the third connection point and the first midpoint.

[0026] Optionally, in the conversion circuit described herein, it further includes: a third winding electrically coupled between the first connection point and the first midpoint after being connected in series with the first resonance unit; and a sixth winding electrically coupled between the third connection point and the first midpoint after being connected in series with the second resonance unit, wherein the sixth winding, the third winding, the first winding, and the second winding are coupled to each other.

[0027] Optionally, in the conversion circuit described herein, the first resonance unit and the second resonance unit have the same resonance frequency.

[0028] Optionally, in the conversion circuit described herein, it further includes a second switching circuit and a third resonance unit, wherein the second switching circuit is connected in parallel with the first switching circuit and includes a fifth switch and a sixth switch. The fifth switch and the sixth switch are connected in series to form a fourth connection point, and the third resonance unit is electrically coupled between the fourth connection point and the second midpoint.

[0029] Optionally, in the conversion circuit described herein, it further includes: a third winding electrically coupled between the first connection point and the first midpoint after being connected in series with the first resonance unit; and a seventh winding electrically coupled between the fourth connection point and the second midpoint after being connected in series with the third resonance unit. Description of the Drawings

[0030] Figure 1 Shows a schematic diagram of a non-isolated LLC circuit of the prior art.

[0031] Figure 2A Shows an example circuit of a conversion circuit according to an embodiment herein.

[0032] Figure 2B Shows Figure 2A the current flow path in the first half cycle of the circuit in

[0033] Figure 2C Shows Figure 2AThe current flow path in the latter half cycle of the circuit in

[0034] Figure 2D shows Figure 2A the current or voltage waveforms in some components of the circuit in one working cycle in

[0035] Figure 3 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0036] Figure 4 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0037] Figure 5 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0038] Figure 6 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0039] Figure 7 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0040] Figure 8 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0041] Figure 9 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0042] Figure 10 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0043] Figure 11 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0044] Figure 12 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0045] Figure 13 shows an example circuit of a conversion circuit according to another embodiment of the present application. Detailed implementation manners

[0046] Reference will now be made in detail to the various embodiments of the present application, and one or more examples of the various embodiments of the present application are shown in the drawings. In the following description of the drawings, like reference numerals indicate like or similar components. In the following text, only the differences regarding individual embodiments are described. Each example is provided for the purpose of illustrating the technical solution and does not mean a limitation on the subject matter claimed in the present application. Additionally, features described or illustrated as part of one embodiment can be used in other embodiments or combined with other embodiments to produce further embodiments. The following detailed description is intended to cover such modifications and variations.

[0047] Refer to Figure 2A , Figure 2A FIG. shows an example circuit of a conversion circuit 20 according to a first embodiment of the present application. The circuit 20 receives an input voltage Vin from a power source, converts the input voltage Vin, and outputs the converted voltage to a load. A capacitor Cin is connected in parallel with the power source, and a capacitor Co is connected in parallel with the load.

[0048] The circuit 20 includes a full-wave rectification unit 21, a switching circuit 22, a resonant unit 23, and a winding N1. The full-wave rectification unit 21 is composed of a first rectification branch and a second rectification branch connected in parallel with the capacitor Co. The first rectification branch has a winding N2 and a rectification switch QR1 connected in series, and the second rectification branch has a winding N3 and a rectification switch QR2 connected in series. The switching circuit 22 includes switches Q1 and Q2 connected in series. The resonant unit 23 includes a resonant capacitor Cr and a resonant inductor Lr connected in series. The winding N1 and the windings N2 and N3 in the full-wave rectification unit 21 are coupled to each other, thus forming a transformer.

[0049] The power source and the load each have a first end and a second end, where the second end of the power source and the second end of the load are connected (for example, grounded, that is, connected to the Figure 2A ground terminal GND in). The switching circuit 22 is connected between the first end of the power source and the first end of the load. The full-wave rectification unit 21 is connected between the first end and the second end of the load, that is, as shown in Figure 2A , the parallel first rectification branch and second rectification branch are further connected in parallel with the capacitor Co.

[0050] In the circuit 20, the resonant unit 23 is connected in series with the winding N1, so that one end of the branch formed by the series connection of the resonant unit 23 and the winding N1 is connected to the connection point formed by the series connection of the switches Q1 and Q2 (that is, the connection point n1 in Figure 2A ), and the other end is connected to the connection point formed by the series connection of the rectification switch QR1 and the winding N2 (that is, the connection point B in Figure 2A ).

[0051] The working process of the circuit 20 will be described below in conjunction with Figures 2B - 2D FIG..Figure 2B Shows the current flow path in circuit 20 during the first half cycle. Figure 2C Shows the current flow path in circuit 20 during the second half cycle. Figure 2D Shows the current or voltage waveforms of some components in circuit 20 during one working cycle. In Figure 2D , I Lr represents the current flowing through the resonant unit 23, and I Lm represents the current flowing through the exciting inductance of the transformer, and I S1 and I S2 respectively represent the currents flowing through windings N2 and N3, and V Q1 represents the voltage across switch Q1.

[0052] During one working cycle of circuit 20, in the time period t0 - t1 of the first half cycle, switch Q2 and rectifier switch QR2 are turned on, and switch Q1 and rectifier switch QR1 are turned off. In the time period t2 - t3 of the second half cycle, switch Q1 and rectifier switch QR1 are turned on, and switch Q2 and rectifier switch QR2 are turned off. That is, switch Q2 and rectifier switch QR2 are complementary to switch Q1 and rectifier switch QR1 in conduction, and the duty cycle is about 0.5.

[0053] Next, taking the case where in circuit 20, the switching frequency fs is equal to the resonant frequency fr, and the turn ratio of windings N1, N2, and N3 in the transformer is N:1:1 as an example, the operation of circuit 20 is described.

[0054] In the time period t0 - t1 of the first half cycle, the operating state of circuit 20 is as Figure 2B shown, at this time switch Q2 and rectifier switch QR2 are turned on, and switch Q1 and rectifier switch QR1 are turned off. At this time, on the one hand, the resonant inductor Lr and the resonant capacitor Cr in the resonant unit 23 resonate, and the resonant frequency is and the resonant current is i, and the resonant current flows along Figure 2B the first path shown via winding N1 and winding N2 to the load terminal to supply energy to the load terminal, rather than flowing back to the power supply. At the same time, on the other hand, winding N3 induces the excitation of winding N1 and N2, and the induced current is (N + 1)i, and the induced current flows along Figure 2B the second path shown to the load terminal to supply energy to the load terminal. Therefore, in the first half cycle, the current flowing to the output load is (N + 2)i.

[0055] In the time period t1 - t2 of the first half cycle, the exciting inductor current charges the parasitic capacitances of switch Q2 and rectifier switch QR2 and discharges the parasitic capacitances of switch Q1 and rectifier switch QR1, thereby realizing soft switching.

[0056] During the time period from t2 to t3 in the latter half of the cycle, the operating state of circuit 20 is as shown in 2C. Switch Q1 and rectifier switch QR1 are turned on, and switch Q2 and rectifier switch QR2 are turned off. At this time, on the one hand, the resonant current i in the rectifier unit 23 flows through Figure 2C the third path shown and flows through winding N1 to the load terminal to supply power to the load terminal. At the same time, on the other hand, winding N2 induces the excitation of winding N1, and the induced current is Ni. The induced current flows along Figure 2C the fourth path shown to the load terminal to provide energy to the load terminal. Therefore, in the latter half of the cycle, the current flowing to the load terminal is (N + 1)i.

[0057] It can be seen that in a whole operating cycle of circuit 20, the voltage conversion ratio is (2N + 1 + 2):1, where 2N is the voltage conversion ratio contributed by transformer winding N1, 1 is the voltage conversion ratio contributed by using the idle winding of the transformer as excitation, and 2 is the voltage conversion ratio contributed by the excitation current directly flowing to the load terminal.

[0058] Compared with Figure 1 the non-isolated LLC circuit of the prior art shown, the difference of circuit 20 is that the primary switch is connected to the load terminal. Therefore, this circuit topology of circuit 20 can achieve odd voltage ratio conversion, and at the same time, it also has the advantages that the primary current directly flows to the load and the idle winding is utilized, thereby achieving high efficiency and high voltage conversion ratio.

[0059] This circuit topology of circuit 20 has an odd voltage conversion ratio, and when the voltage conversion ratio is the same, the number of turns of the transformer can be reduced. At the same time, the current flowing through winding N1 directly flows to the load and does not need to be induced by the transformer, further reducing the loss and volume of the transformer.

[0060] Although the resonant unit 23 in circuit 20 is composed of a resonant capacitor Cr and a resonant inductor Lr connected in series, this application is not limited thereto. For example, the resonant unit 23 can also be composed of a resonant capacitor Cr and a resonant inductor Lr connected in parallel.

[0061] Although the switch circuit 22 in circuit 20 is shown as being composed of a single switch Q1 and Q2 connected in series, in some other embodiments, each of switch Q1 and Q2 is further composed of a plurality of switch elements connected in series to reduce the stress of a single switch, or further composed of a plurality of switch elements connected in parallel to increase the current-carrying capacity of the switch.

[0062] The above only describes the voltage conversion ratio of circuit 20 with the turn ratio of winding N1, winding N2 and winding N3 being N:1:1. In a more general case, the voltage conversion ratio of circuit 20 can be determined by the following formula (1):

[0063]

[0064] In the above formula (1), K1, K2, and K3 respectively represent the specific number of turns of winding N1, winding N2, and winding N3.

[0065] Although it is described in circuit 20 that windings N1, N2, and N3 are coupled to each other to form a transformer, it is not necessarily required to set winding N therein. That is, the resonant unit can be directly coupled between connection point n1 and connection point B. At this time, since there is no winding N1 (i.e., N1 = 0), the realized voltage conversion ratio can be determined according to the above formula (1). For example, when the turn ratio of winding N2 to winding N3 is 1:1 and there is no winding N1, substituting the specific turn ratio into formula (1) can determine that the voltage conversion ratio of circuit 20 in this case is 3:1.

[0066] It is possible to Figures 2A - 2D expand the circuit 20 described in Figure 3 to change the voltage conversion ratio. Figure 3 FIG. shows a circuit 30 according to another embodiment of the present application. The difference between circuit 30 and circuit 20 is that the switching circuit not only includes the original two switches Q1 and Q2, but also further expands with (2m - 2) switches, such as Figure 3 the switches Q3, Q4... Q 2m-1 and Q 2m . The expanded (2m - 2) switches (Q3, Q4... Q 2m-1 and Q 2m ) are connected in series with the original two switches Q1 and Q2, so that the switching circuit includes 2m switches connected in series, where m is an integer and m ≥ 2.

[0067] Corresponding to the switching circuit of the expanded circuit 30, circuit 30 further includes (m - 1) energy storage elements (for example, Figure 3 the DC blocking capacitors Cb shown as energy storage elements in m-1 )) and (m - 1) additional resonant units 34 (for example, Figure 3 341 to 34 shown in m-1 ). The (m - 1) resonant units 34 and the original resonant unit 33 make circuit 30 have a total of m resonant units. The resonant frequencies of these m resonant units are the same, but the resonant parameters can be the same as or different from each other. Similar to resonant unit 33, each resonant unit 34 includes a resonant capacitor Cr and a resonant inductor Lr.

[0068] Therefore, for Figure 3A conversion circuit such as circuit 30 can be described as follows: The switching circuit has 2m switches connected in series, where m is an integer and m≥2. Adjacent two of the 2m switches are connected to form a connection point, so there are (2m - 1) connection points. For example, Figure 3 shows the connection point n1 formed by the series connection of switches Q1 and Q2, the connection point n2 formed by the series connection of switches Q2 and Q3, the connection point n3 formed by the series connection of switches Q3 and Q4, and the connection point n formed by the series connection of switch Q 2m-2 and the switch before it (not shown). 2m-2 And the connection point n formed by the series connection of switch Q 2m-1 and Q 2m as well as the connection point n 2m-1 .

[0069] The subscript of the connection point n increases sequentially from the end close to the load of circuit 30 to the end far from the load. For example, as Figure 3 shown, the connection point between switches Q1 and Q2 is closest to the load end, so the connection point of switches Q1 and Q2 is the 1st connection point, that is, connection point n1. The connection point of switches Q2 and the next adjacent switch Q3 is the 2nd connection point, that is, connection point n2, and so on. The connection point between switch Q 2m-1 and Q 2m is the (2m - 1)th connection point, that is, connection point n 2m-1 .

[0070] Each of the m resonant units is connected in series with winding N1 and then connected between the corresponding odd-numbered connection points (i.e., connection points n1, n3, …, n 2m-1 ) and the midpoint B of the first rectification branch of the full-wave rectification unit. Each of the (m - 1) capacitors Cb is connected to the corresponding even-numbered connection point (i.e., connection points n2, …, n 2m-2 ), and the other end is connected to the second rectification branch of the full-wave rectification unit.

[0071] That is to say, among the above m resonant units, one end of the xth resonant unit connected in series with winding N1 is connected to the connection point between the (2x - 1)th switch and the 2xth switch among the 2m switches, where x is an integer and 1≤x≤m.

[0072] For example, when x = 1, for the first (x)th resonant unit ( Figure 3 resonant unit 33 in it) among the m resonant units, one end of its series connection with winding N1 is connected to the first (2x - 1)th switch ( Figure 3 switch Q1 in it) and the second (2x)th switch ( Figure 3The connection point n1 between the switches Q2) is connected at one end, and the other end is connected to the midpoint B of the first rectification branch of the full-wave rectification unit. For another example, when x = 2, for the second (x) resonance unit among the m resonance units ( Figure 3 The resonance unit 341) in it, one end after being connected in series with the winding N1 is connected to the third (2x - 1) switch ( Figure 3 The switch Q3) in it and the fourth (2x) switch ( Figure 3 The switch Q4) in it, and the connection point n3 between them, and the other end is connected to the midpoint B of the first rectification branch of the full-wave rectification unit. For another example, when x = m, for the m(x)th resonance unit among the m resonance units ( Figure 3 The resonance unit 34 m-1 ) in it, one end after being connected in series with the winding N1 is connected to the (2m - 1)(2x - 1)th switch ( Figure 3 The switch Q 2m-1 ) and the 2m(2x)th switch ( Figure 3 The switch Q 2m ) in it, and the connection point n 2m-1 , and the other end is connected to the midpoint B of the first rectification branch of the full-wave rectification unit.

[0073] In addition, among the above (m - 1) capacitors Cb, one end of the kth capacitor is connected to the connection point between the 2kth switch and the 2k + 1th switch among the 2m switches, and the other end is connected to the second rectification branch of the full-wave rectification unit, where k is an integer and 1 ≤ k ≤ m - 1.

[0074] For example, when k = 1, one end of the first (k) capacitor ( Figure 3 The capacitor Cb1) in it is connected to the connection point n2 between the second (2k) switch ( Figure 3 The switch Q2) in it and the third switch ( Figure 3 The switch Q3) in it, and the other end is connected to the second rectification branch of the full-wave rectification unit. For another example, when k = (m - 1), one end of the (m - 1)(k)th DC-blocking capacitor ( Figure 3 The DC-blocking capacitor Cb m-1 ) in it is connected to the (2m - 2)(2k)th switch ( Figure 3 The switch Q 2m-1 adjacent to the previous switch, not shown) and the (2m - 1)(2k + 1)th switch ( Figure 3 The switch Q 2m-1 ) in it, and the connection point n 2m-2 , and the other end is connected to the second rectification branch of the full-wave rectification unit.

[0075] As described above, the other ends of the (m - 1) capacitors Cb are connected to the second rectification branch of the full - wave rectification unit of the circuit 30. Specifically, the other ends of the capacitors Cb can be connected to various positions of the second rectification branch. For example, as Figure 3 shown, the other end of the capacitor Cb can be connected to (1) the mid - point A1 formed by the series connection of the winding N3 and the rectification switch QR2 in the second rectification branch, (2) the branch point A2 of the first and second rectification branches of the full - wave rectification unit, that is, the first end of the load, or (3) the convergence point A3 of the first and second rectification branches of the full - wave rectification unit, that is, the second end of the load (e.g., the ground terminal GND).

[0076] For Figure 3 the circuit 30, it is set that the 2m switches in the switching circuit of the circuit 30 are also M switches (i.e., M = 2m), and the turn ratios of the windings N1, N2, and N3 in the transformer are N:1:1. When the other end of the capacitor Cb is connected to the mid - point A1, its extended voltage conversion ratio is (M×(N + 2)-1):1; when the other end of the capacitor Cb is connected to the branch point A2, its extended voltage conversion ratio is (M×N+M + 1):1; when the other end of the capacitor Cb is connected to the convergence point A3, its extended voltage conversion ratio is (M×N+M + 1):1, thus realizing the expansion of the conversion ratio of the conversion circuit.

[0077] Similarly, the windings N1, N2, and N3 can be selected with other appropriate turn ratios. In a more general case, when the other end of the capacitor Cb is connected to the mid - point A1, the voltage conversion ratio of the circuit 30 can be determined by the following formula (2); when the other end of the capacitor Cb is connected to the branch point A2, the voltage conversion ratio of the circuit 30 can be determined by the following formula (3); and when the other end of the capacitor Cb is connected to the convergence point A3, the voltage conversion ratio of the circuit 30 can be determined by the following formula (4):

[0078]

[0079]

[0080]

[0081] In the above formulas (2) - (4), K1, K2, and K3 are the specific number of turns of the windings N1, N2, and N3 respectively, and M is the number of the 2m switches in the switching circuit of the circuit 30 (i.e., M = 2m). Similarly, the winding N1 can also not be set.

[0082] Figure 3 It is shown that the capacitor Cb is connected to the corresponding even - numbered connection points and the second rectification branch of the full - wave rectification unit. In some embodiments, windings can be further added to change the voltage conversion ratio. For example, Figure 4Fig. 40 shows a circuit 40 according to another embodiment of the present application.

[0083] Figure 4 The circuit 40 of Figure 3 differs from the circuit 30 of Figure 4 in that, in addition to a capacitor Cb as an energy storage element being connected between the second rectification branch of the full-wave rectification unit and the even-numbered connection point, each capacitor Cb is further connected in series with an additional winding N4 (such as m-1 the windings N41 and N4 shown in

[0084] At this time, for Figure 4 the circuit 40, it is set that the 2m switches in the switching circuit of the circuit 40 are also M switches (i.e., M = 2m), and the turn ratios of the additional winding N4 (N41 to N4 m-1 ), winding N1, winding N2, and winding N3 in the transformer are N:N:1:1. When the other end of the capacitor Cb is connected to the midpoint A1, its extended voltage conversion ratio is ((2M - 2)×N + 2M - 1):1; when the other end of the capacitor Cb is connected to the branch point A2, its extended voltage conversion ratio is ((2M - 2)×N + 2M + 1):1; when the other end of the capacitor Cb is connected to the confluence point A3, its extended voltage conversion ratio is ((2M - 2)×N + 2M + 1):1, thereby further realizing a further expansion of the conversion ratio of the conversion circuit relative to Figure 3 the circuit 30.

[0085] Similarly, the windings N1, N2, N3, and N4 can be selected with other suitable turn ratios. In a more general case, when the other end of the capacitor Cb is connected to the midpoint A1, the voltage conversion ratio of the circuit 40 can be determined by the following formula (5); when the other end of the capacitor Cb is connected to the branch point A2, the voltage conversion ratio of the circuit 40 can be determined by the following formula (6); and when the other end of the capacitor Cb is connected to the confluence point A3, the voltage conversion ratio of the circuit 40 can be determined by the following formula (7):

[0086]

[0087]

[0088]

[0089] In the above formulas (5) to (7), K1, K2, and K3 are the specific number of turns of windings N1, N2, and N3 respectively, K4 i is the specific number of turns of each winding N4, and M is the number of 2m switches in the switching circuit of the circuit 40 (i.e., M = 2m). Similarly, the winding N1 can also be not provided.

[0090] AlthoughFigure 3 and Figure 4 shows a case where a single DC-blocking capacitor Cb is used as the energy storage element. However, the present disclosure is not limited thereto, and a resonant unit can also be used as the energy storage element. In this case, the capacitor of the resonant unit used as the energy storage element not only functions as a DC-blocking capacitor but also resonates with the inductor of the resonant unit.

[0091] Figure 5 shows a circuit 50 according to another embodiment of the present application, which is another extended form of the circuit 20 in FIG. 2.

[0092] Figure 5 The difference between the circuit 50 and the circuit 20 is that the switching circuit not only includes the original two switches Q1 and Q2 but also further includes (m - 2) switches, such as Figure 5 the switches Q3,..., Q m ) shown in. The extended (m - 2) switches (Q3,..., Q m ) are connected in series with the original two switches Q1 and Q2, so that the switching circuit includes m switches connected in series, where m is an odd number and m ≥ 3.

[0093] Corresponding to the switching circuit of the extended circuit 50, the circuit 50 further includes (m - 2) resonant units 54 (for example, such as Figure 5 the resonant units 541, 542, and 54 m-2 ) shown in. Therefore, the (m - 2) resonant units 54 and the resonant unit 53 together constitute (m - 1) resonant units. The resonant unit 54 includes a resonant capacitor Cr and a resonant inductor Lr. The resonant frequencies of these (m - 1) resonant units are the same, but the resonant parameters can be the same as or different from each other.

[0094] Specifically, therefore, for Figure 5 a transformed circuit such as the circuit 50 can be described as follows: The switching circuit has m switches connected in series, where m is an odd number and m ≥ 3. Adjacent two of these m switches are connected to form connection points, so there are (m - 1) connection points. For example, Figure 5 shows a connection point n1 formed by the series connection of switches Q1 and Q2, a connection point n2 formed by the series connection of switches Q2 and Q3, a connection point n3 formed by the series connection of switches Q3 and the next switch (not shown), and a connection point n m formed by the series connection of switches Q m-1 and the previous switch (not shown).

[0095] The subscript of the connection point n increases sequentially from the end near the load of the circuit 50 to the end far from the load. For example, as Figure 5As shown, the connection point between switches Q1 and Q2 is closest to the load end. Therefore, the connection point between switches Q1 and Q2 is the 1st connection point, i.e., connection point n1. The connection point between switch Q2 and the next adjacent switch Q3 is the 2nd connection point, i.e., connection point n2, and so on. The connection point between switch Q m and the previous switch is the (m - 1)th connection point, i.e., connection point n m-1 .

[0096] Each of a part of the (m - 1) resonant units in circuit 50 is connected in series with winding N1 between the corresponding odd - numbered connection point and the mid - point B of the first rectifying branch of the full - wave rectifying unit. One end of each of the other part of the (m - 1) resonant units in circuit 50 is connected to the corresponding even - numbered connection point, and the other end is connected to the second rectifying branch of the full - wave rectifying circuit.

[0097] That is to say, among the above - mentioned (m - 1) resonant units, the (2y - 1)th resonant unit is connected in series with winding N1 between the connection point of the (2y - 1)th switch and the 2y - th switch among the m switches and the mid - point B of the first rectifying branch of the full - wave rectifying unit, where y is an integer and 1 ≤ y ≤ m / 2.

[0098] For example, when y = 1, among the (m - 1) resonant units, the first (2y - 1)th resonant unit ( Figure 5 resonant unit 53 therein) is connected in series with winding N1 between the connection point n1 of the first (2y - 1)th switch ( Figure 5 switch Q1 therein) and the second (2y)th switch ( Figure 5 switch Q2 therein) and the mid - point B of the first rectifying branch of the full - wave rectifying unit. Another example, when y = 2, among the (m - 1) resonant units, the third (2y - 1)th resonant unit ( Figure 5 resonant unit 542 therein) is connected in series with winding N1 between the connection point n3 of the third (2y - 1)th switch ( Figure 5 switch Q3 therein) and the fourth (2y)th switch (the next switch of switch Q3) and the mid - point B of the first rectifying branch of the full - wave rectifying unit.

[0099] Among the above - mentioned (m - 1) resonant units, one end of the 2z - th resonant unit is connected to the connection point of the 2z - th switch and the (2z + 1) - th switch among the m switches, and the other end is connected to the second rectifying branch of the full - wave rectifying circuit, where z is an integer and 1 ≤ z ≤ (m - 1) / 2.

[0100] For example, when z = 1, among the m - 1 resonant units, one end of the second (2z)th resonant unit ( Figure 5 resonant unit 541 therein) is connected to the second (2z)th switch (Figure 5 the connection point n2 of the switch Q2) in Figure 5 and the third (2z + 1)-th switch (

[0101] As described above, the other ends of the resonant units connected to the even-numbered connection points in the (m - 1) resonant units are connected to the second rectification branch of the full-wave rectification unit of the circuit 50. Specifically, the other ends of these resonant units can be connected to various positions of the second rectification branch. For example, as Figure 5 shown, the other ends of these resonant units can be connected to (1) the midpoint A1 formed by the series connection of the winding N3 and the rectification switch QR2 in the second rectification branch, (2) the branch point A2 of the first and second rectification branches of the full-wave rectification unit, that is, the first end of the load-side capacitor Co, and (3) the confluence point A3 of the first and second rectification branches of the full-wave rectification unit, that is, the second end of the load-side capacitor Co (e.g., the ground terminal GND).

[0102] For Figure 5 the circuit 50, assuming that the turn ratios of the windings N1, N2, and N3 in the transformer are N:1:1, when the other ends of the resonant units connected to the even-numbered connection points in the (m - 1) resonant units are connected to the midpoint A1, the expanded voltage conversion ratio is ((m - 1)×N + 2m - 1):1; when the other ends of the resonant units connected to the even-numbered connection points in the (m - 1) resonant units are connected to the branch point A2, the expanded voltage conversion ratio is ((m - 1)×N + m):1; when the other ends of the resonant units connected to the even-numbered connection points in the (m - 1) resonant units are connected to the confluence point A3, the expanded voltage conversion ratio is ((m - 1)×N + m):1, thereby realizing the expansion of the conversion ratio of the conversion circuit.

[0103] Similarly, the windings N1, N2, and N3 can be selected with other appropriate turn ratios. In a more general case, when the other ends of the resonant units connected to the even-numbered connection points in the (m - 1) resonant units are connected to the midpoint A1, the voltage conversion ratio of the circuit 50 can be determined by the following formula (8); when the other ends of the resonant units connected to the even-numbered connection points in the (m - 1) resonant units are connected to the branch point A2, the voltage conversion ratio of the circuit 50 can be determined by the following formula (9); and when the other ends of the resonant units connected to the even-numbered connection points in the (m - 1) resonant units are connected to the confluence point A3, the voltage conversion ratio of the circuit 50 can be determined by the following formula (10):

[0104]

[0105]

[0106]

[0107] In the above formulas (8)-(10), K1, K2, and K3 are the specific number of turns of windings N1, N2, and N3 respectively, and m is the number of switches in circuit 50. Similarly, winding N1 may not be provided.

[0108] Figure 5 It shows that a part of the resonant units in (m-1) resonant units are connected between the corresponding even-numbered connection points and the second rectifying branch of the full-wave rectifying unit. In some embodiments, windings can be further added to change the voltage conversion ratio. For example, Figure 6 It shows circuit 60 according to another embodiment of the present application.

[0109] Figure 6 The difference between circuit 60 of Figure 3 and circuit 30 of Figure 6 is that in addition to being connected with resonant units between the second rectifying branch of the full-wave rectifying unit and the even-numbered connection points, each of these resonant units is further connected in series with an additional winding N4 (such as (m-1) / 2 ).

[0110] At this time, for Figure 6 circuit 40, assuming that the turn ratio of the additional winding N4 (windings N41 to N4 (m-1) / 2 ) in the transformer, windings N1, N2, and N3 is N:N:1:1, when the other end of the resonant units connected to the even-numbered connection points in (m-1) resonant units is connected to the midpoint A1, the expanded voltage conversion ratio is (2×(m-1)×N + 2m - 1):1; when the other end of the resonant units connected to the even-numbered connection points in (m-1) resonant units is connected to the branch point A2, the expanded voltage conversion ratio is (2×(m-1)×N + m):1; when the other end of the resonant units connected to the even-numbered connection points in (m-1) resonant units is connected to the confluence point A3, the expanded voltage conversion ratio is (2×(m-1)×N + m):1, thereby further realizing a further expansion of the conversion ratio of the conversion circuit relative to Figure 5 circuit 50.

[0111] Similarly, for windings N1, N2, N3, and N4, other suitable turn ratios can be selected. In a more general case, when the other ends of the resonant units connected to the even-numbered connection points among the (m - 1) resonant units are connected to the midpoint A1, the voltage conversion ratio of circuit 60 can be determined by the following formula (11); when the other ends of the resonant units connected to the even-numbered connection points among the (m - 1) resonant units are connected to the branch point A2, the voltage conversion ratio of circuit 60 can be determined by the following formula (12); and when the other ends of the resonant units connected to the even-numbered connection points among the (m - 1) resonant units are connected to the convergence point A3, the voltage conversion ratio of circuit 40 can be determined by the following formula (13):

[0112]

[0113]

[0114]

[0115] In the above formulas (11) to (13), K1, K2, and K3 are the specific number of turns of windings N1, N2, and N3 respectively, K4 i is the specific number of turns of each winding N4, and m is the number of switches in circuit 60. Similarly, winding N1 can also be not provided.

[0116] Figure 7 An example circuit 70 of a conversion circuit according to another embodiment of the present application is shown.

[0117] Circuit 70 differs from Figure 3 circuit 30 in that an inductor Lrx connected in series with winding N1 is added. The resonant frequency at this time is:

[0118]

[0119] wherein, the inductor Lrx can be the leakage inductance of the transformer. The advantage of this is that the leakage inductance of the transformer can be utilized to reduce the inductance required for the resonant inductor, thereby achieving the effects of reducing the use of components and reducing the volume of the converter.

[0120] Although Figure 7 it is a further modification based on Figure 3 circuit 30, it should be noted that similar modifications can also be made on the basis of Figure 5 circuit 50, as Figure 8 shown, which will not be elaborated here.

[0121] Figure 9 An example circuit 90 of a conversion circuit according to another embodiment of the present application is shown.

[0122] Circuit 90 is the same asFigure 3 The difference between the circuit 30 is that when the resonance parameters of the m resonance units are the same, the respective resonance inductors in these resonance units can be combined into an inductor Lrx to be connected in series with the winding N1. The resonance frequency at this time is:

[0123]

[0124] At this time, the circuit operates at a fixed operating frequency, and the required value of the leakage inductance is very small. The leakage inductance of the transformer can be directly used as the resonance inductor Lrx, reducing the number and volume of components used.

[0125] Although Figure 9 is a further modification based on the circuit 30 of Figure 3 , it should be noted that similar modifications can also be made based on the technology of the circuit 50 of Figure 5 , as shown in Figure 10 , which will not be elaborated here.

[0126] Figure 11 Fig. 110 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0127] The difference between the circuit 110 and the circuit 30 of Figure 3 is that the transformer has multiple windings (such as the windings N11, N12, and N13 shown in Figure 11 ) to be connected in series with the m resonance units respectively. This circuit can also utilize the leakage inductance of the transformer to save the resonance inductor.

[0128] Although Figure 11 is a further modification based on the circuit 30 of Figure 3 , it should be noted that similar modifications can also be made based on the technology of the circuit 50 of Figure 5 , as shown in Figure 12 , which will not be elaborated here.

[0129] Figure 13 Fig. 130 shows an example circuit of a conversion circuit according to another embodiment of the present application.

[0130] Figure 13 The difference between the circuit 130 of Figure 2A and the circuit 20 is that the circuit 130 has two parallel switch circuits 132 and 132'. In the switch circuit 132, there are switches Q1 and Q2 connected in series, and in the switch circuit 132', there are switches Q3 and Q4 connected in series.

[0131] Corresponding to the parallel-connected switch circuits 132 and 132', the resonant units 133 and the winding N11 are connected in series and then connected between the connection point of the switches Q1 and Q2 and the midpoint B of the switch QR1 of the first rectification path of the full-wave rectification unit and the winding N2, and the resonant unit 133' and the winding N12 are connected in series and then connected between the connection point of the switches Q3 and Q4 and the midpoint A of the switch QR2 of the second rectification path of the full-wave rectification unit and the winding N3.

[0132] In the operation of the circuit 130, Q2, QR2, and Q3 are turned on simultaneously, and QR1, Q1, and Q4 are turned on complementarily to them. The duty cycle is about 0.5. The turns ratio of the windings N11, N2, N3, and N12 of the transformer is N:1:1:N. The circuit 130 can also achieve a voltage conversion ratio of (2N + 1 + 2):1. Compared with Figure 2A the shown circuit 20, the circuit 130 adds a path of switch circuit. The additional switch circuit consists of switches Q3 and Q4 connected in series between the first end of the power supply and the first end of the load. At the same time, a series-connected resonant unit 133' and winding N12 are connected between the midpoint of the switches Q3 and Q4 and the midpoint of the winding N3 and QR2. The added part of the circuit 130 interleaves with Figure 2A the original circuit part of the circuit 20, so that the current stress of the switches Q1 to Q4 is Figure 2A half of that of the switches Q1 and Q2 in the circuit 20, and the currents of the rectifying switches QR1 and QR2 are more balanced.

[0133] Although the above content is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure can also be designed without departing from the basic scope of the present disclosure, and the scope of the present disclosure is determined by the appended claims.

Claims

1. A conversion circuit for converting the voltage of a power supply and supplying power to a load. Both the power supply and the load include a first terminal and a second terminal. The second terminal of the power supply is connected to the second terminal of the load. The conversion circuit includes: A full-wave rectifier circuit, connected in parallel with the load, and having a first rectifier branch and a second rectifier branch connected in parallel. The first rectifier branch has a first rectifier switch and a first winding connected in series. The first rectifier switch and the first winding are connected to form a first midpoint. The second rectifier branch has a second rectifier switch and a second winding connected in series. The second rectifier switch and the second winding are connected to form a second midpoint; A first switch circuit, connected between the first terminal of the power supply and the first terminal of the load. The first switch circuit includes a first switch and a second switch. The first switch and the second switch are connected in series to form a first connection point; and A first resonant unit, coupled between the first connection point and the first midpoint, wherein the first winding and the second winding are coupled to each other Wherein the first switch circuit, the second rectifier switch (QR2) and the second winding (N3) are connected in series across the first terminal and the second terminal of the power supply.

2. The conversion circuit according to claim 1, further comprising: A third winding, electrically coupled between the first connection point and the first midpoint after being connected in series with the first resonant unit, wherein the third winding, the first winding and the second winding are coupled to each other.

3. The conversion circuit according to claim 1 or 2, wherein the first resonant unit includes an inductor and a capacitor connected in series or in parallel.

4. The conversion circuit according to claim 2, wherein The first switch circuit further includes (2m - 2) switches connected in series with the first switch and the second switch, such that the first switch circuit includes 2m switches connected in series. Adjacent switches among the 2m switches are connected to form connection points, The conversion circuit further includes: (m - 1) resonant units, together with the first resonant unit, constituting m resonant units. The x-th resonant unit among the m resonant units is electrically coupled between the connection point of the (2x - 1)-th switch and the 2x-th switch among the 2m switches and the first midpoint after being connected in series with the third winding; and (m - 1) energy storage units, each including an energy storage element. One end of the k-th energy storage unit among the (m - 1) energy storage units is connected to the connection point of the 2k-th switch and the (2k + 1)-th switch among the 2m switches, and the other end is connected to the second rectifier branch, and The m, the x and the k are integers, and m≥2, 1≤x≤m and 1≤k≤(m - 1).

5. The conversion circuit according to claim 4, wherein the energy storage element is a capacitor.

6. The conversion circuit according to claim 5, wherein each energy storage unit further includes an inductor, connected in series with the capacitor in the corresponding energy storage unit.

7. The conversion circuit according to claim 4, wherein the other end of each of the (m - 1) energy storage units is connected to one of the following positions: the first end of the load; the second midpoint; and the second end of the load.

8. The conversion circuit according to claim 2, wherein the first switch circuit further includes (m - 2) switches connected in series with the first switch and the second switch, such that the first switch circuit includes m switches connected in series, and adjacent switches among the m switches are connected to form connection points, the conversion circuit further includes (m - 2) resonant units to jointly form (m - 1) resonant units with the first resonant unit, the (2y - 1)-th resonant unit among the (m - 1) resonant units and the third winding are electrically coupled in series between the connection point between the (2y - 1)-th switch and the 2y-th switch among the m switches and the first midpoint, one end of the 2z-th resonant unit among the (m - 1) resonant units is connected to the connection point between the 2z-th switch and the (2z + 1)-th switch among the m switches, and the other end is connected to the second rectification branch, and m is an odd number, y and z are integers, and m ≥ 3, 1 ≤ y ≤ m / 2, and 1 ≤ z ≤ (m - 1) / 2.

9. The conversion circuit according to claim 8, wherein the other end of the 2z-th resonant unit among the (m - 1) resonant units is connected to one of the following positions: the first end of the load; the second midpoint; and the second end of the load.

10. The conversion circuit according to claim 4, wherein each of the (m - 1) energy storage units is further connected in series with a fourth winding, and the fourth winding, the first winding, and the second winding are coupled to each other.

11. The conversion circuit according to claim 8, wherein the 2z-th resonant unit among the (m - 1) resonant units is further connected in series with a fifth winding, and the fifth winding, the first winding, and the second winding are coupled to each other.

12. The conversion circuit according to claim 1, wherein the first switch circuit further includes a third switch and a fourth switch connected in series with the first switch and the second switch, the second switch and the third switch are connected to form a second connection point, and the third switch and the fourth switch are connected to form a third connection point, the conversion circuit further includes: a first energy storage unit, each energy storage unit includes an energy storage element, one end of the first energy storage unit is connected to the second connection point, and the other end is connected to the second rectification branch; and a second resonant unit, electrically coupled between the second connection point and the first midpoint.

13. The conversion circuit according to claim 12, further including a common inductor, and the first resonant unit and the second resonant unit are connected to the first midpoint via the common inductor.

14. The conversion circuit according to claim 12, wherein the resonant inductors of the first resonant unit and the second resonant unit are shared.

15. The conversion circuit according to any one of claims 12-14 further includes a third winding, wherein the first resonant unit and the third winding are connected in series and electrically coupled between the first connection point and the first midpoint, the second resonant unit and the third winding are connected in series and electrically coupled between the second connection point and the first midpoint, and the third winding, the first winding, and the second winding are coupled to each other.

16. According to the conversion circuit of claim 1, wherein the first switch circuit further includes a third switch and a fourth switch connected in series with the first switch and the second switch, the second switch and the third switch are connected to form a second connection point, and the third switch and the fourth switch are connected to form a third connection point. The conversion circuit further includes: a first energy storage unit, the first energy storage unit includes an energy storage element, one end of the first energy storage unit is connected to the second connection point, and the other end is connected to the second rectification branch; and a second resonant unit, electrically coupled between the third connection point and the first midpoint.

17. The conversion circuit according to claim 16 further includes: a third winding, connected in series with the first resonant unit and electrically coupled between the first connection point and the first midpoint; and a sixth winding, connected in series with the second resonant unit and electrically coupled between the third connection point and the first midpoint. wherein the sixth winding, the third winding, the first winding, and the second winding are coupled to each other.

18. According to the conversion circuit of claim 12 or 16, wherein the resonant frequencies of the first resonant unit and the second resonant unit are the same.

19. The conversion circuit according to claim 1 further includes a second switch circuit and a third resonant unit, wherein the second switch circuit is connected in parallel with the first switch circuit and includes a fifth switch and a sixth switch, the fifth switch and the sixth switch are connected in series to form a fourth connection point. the third resonant unit is electrically coupled between the fourth connection point and the second midpoint.

20. The conversion circuit according to claim 19 further includes: a third winding, connected in series with the first resonant unit and electrically coupled between the first connection point and the first midpoint; and a seventh winding, connected in series with the third resonant unit and electrically coupled between the fourth connection point and the second midpoint.

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