Switched capacitor resonant converter

Abstract

The invention provides a switched capacitor resonant converter. The switched capacitor resonant converter comprises an input end, an output end, two groups of switches, a magnetic element, a first resonant bridge arm and a second resonant bridge arm, the two groups of switches are electrically connected between the input positive electrode and the input negative electrode respectively to form a first switch bridge arm and a second switch bridge arm. The magnetic element comprises a first winding and a second winding, the first winding is electrically connected between the first switch bridge arm and the output positive electrode, and the second winding is electrically connected between the second switch bridge arm and the output positive electrode. The first resonance bridge arm or the second resonance bridge arm is electrically connected between the corresponding first switch bridge arm or the corresponding second switch bridge arm and the magnetic element. The two sets of switches are periodically controlled to form a first resonance path and a second resonance path to transmit energy to the output end, and the first resonance path and the second resonance path have substantially the same resonance parameter.

Description

Technical Field

[0001] This case relates to a resonant converter, and in particular to a switched capacitor resonant converter. Background Art

[0002] The booming field of artificial intelligence (AI) has led to a surge in demand for servers, data centers, and high-performance computing infrastructure. Power supplies, as core electronic components in these facilities, are rapidly gaining in importance. Driven by the infrastructure's demand for high computing power and throughput in short bursts, high power density, environmental friendliness, and excellent thermal management are key development priorities for power supplies. With the generational upgrades of core chips like GPUs and CPUs in these infrastructures, their power bus voltages also change, placing higher demands on power density.

[0003] Figure 1 An existing power conversion circuit is shown, in which the gain ratio of the input voltage and the output voltage is variable and has a large adjustable range, and the circuit can realize the functions of non-isolated LLC resonance and step-down. In addition, this circuit provides energy to the output by adopting two resonant paths, but its defect is that only when the resonant frequencies of the two resonant paths are consistent can the soft switching of all switching devices be realized, thereby reducing the switching loss of the switching devices to achieve high efficiency. The resonant frequency is determined by the capacitance value of the resonant capacitor and the inductance value of the resonant inductor. However, the resonant winding and the output winding of the transformer are usually designed to have different inductance values, which leads to inconsistent inductance values ​​of the resonant inductors of the two resonant paths. In this case, the soft switching of the switching devices can only be achieved by matching the parameters of the resonant capacitors in the two resonant paths. Therefore, it is necessary to set them separately. Figure 1 The capacitance values ​​of the three resonant capacitors in the circuit increase the complexity of the design.

[0004] Furthermore, in actual applications, even after multiple debugging, the two resonant paths in the power conversion circuit may still not be able to achieve resonant frequency matching, and the mismatch in resonant frequency will cause the original two switching resonant paths to be transformed into a multi-loop switching resonant state. Figure 2 and Figure 3 exemplify Figure 1 The working waveform of the power conversion circuit when the resonant frequency does not match. Figure 2 In the figure, IC1 is the resonant current flowing through the resonant capacitor C1, and IC2 is the resonant current flowing through the resonant capacitor C2; Figure 3 In the equation, IW1 is the output winding current flowing through the output winding W1, and IW2 is the output winding current flowing through the output winding W2. Figure 2As shown in Figure 1, the resonant currents IC1 and IC2 are obviously distorted, with asymmetry and high-order harmonics. Figure 3 As shown in the waveforms of the output winding currents IW1 and IW2, high-order harmonics are also clearly visible. These high-order harmonics will cause additional power loss in multiple resonant components such as the output winding, causing the circuit board where these resonant components are installed to generate a lot of heat, and also limit the efficiency of the power conversion circuit.

[0005] In addition, due to space limitations, the capacitors of existing DC / DC power converters generally use multi-layer ceramic capacitors (MLCCs), which have the characteristic that the equivalent capacitance decreases as the DC voltage across the capacitor increases. Figure 1 Taking the circuit shown in the figure as an example, this characteristic causes resonant capacitors C1 and C2 to experience different DC voltage components at different input voltages, resulting in a larger difference in capacitance value and, in turn, preventing the two resonant paths from achieving the same resonant frequency. In the case of resonant frequency mismatch, soft switching of all switching devices cannot be achieved, resulting in increased switching losses.

[0006] Therefore, it is an urgent need to invent a switched capacitor resonant converter that can improve the above-mentioned prior art. Summary of the Invention

[0007] The present invention aims to provide a switched capacitor resonant converter with a variable gain ratio between input voltage and output voltage, and simultaneously transmits energy to the output terminal through first and second resonant paths. Compared to existing power conversion circuits that utilize a single resonant cavity for energy output, this design reduces the output capacity of each resonant path and improves power density while maintaining the same total output. Furthermore, because the first and second resonant paths have substantially identical resonant parameters, soft switching of all switching devices is achieved, reducing switching losses and improving efficiency. Furthermore, because the losses in the two resonant paths are identical, heat sources are dispersed, facilitating heat dissipation.

[0008] To achieve the above-mentioned objectives, the present invention provides a switched capacitor resonant converter, comprising an input end, an output end, a first set of switches, a second set of switches, a magnetic element, a first resonant bridge arm, and a second resonant bridge arm. The input end comprises an input positive electrode (positive end) and an input negative electrode (negative end). The output end comprises an output positive electrode (positive end) and an output negative electrode (negative end), wherein the input negative electrode is coupled to the output negative electrode. The first set of switches is electrically connected between the input positive electrode and the input negative electrode to form a first switch bridge arm. The second set of switches is electrically connected between the input positive electrode and the input negative electrode to form a second switch bridge arm. The magnetic element comprises a first winding and a second winding, wherein the first winding is electrically connected between the first switch bridge arm and the output positive electrode, and the second winding is electrically connected between the second switch bridge arm and the output positive electrode. The two ends of the first resonant bridge arm are electrically connected to the first switch bridge arm and the magnetic element, respectively. The two ends of the second resonant bridge arm are electrically connected to the second switch bridge arm and the magnetic element, respectively. The first set of switches and the second set of switches are periodically controlled to form a first resonant path and a second resonant path to transmit energy to the output end, and the first resonant path and the second resonant path have substantially the same resonant parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A conventional power conversion circuit is shown.

[0010] Figure 2 and Figure 3 exemplify Figure 1 The working waveform of the power conversion circuit when the resonant frequency does not match.

[0011] Figure 4 FIG. 1 is a schematic diagram of the circuit structure of a switched capacitor resonant converter according to an embodiment of the present invention.

[0012] Figure 5 exemplify Figure 4 The operating waveforms of the first group of switches and the second group of switches of the switched capacitor resonant converter are shown.

[0013] Figure 6 exemplify Figure 4 The switching state of the switched capacitor resonant converter in the first period of the working cycle is shown.

[0014] Figure 7 exemplify Figure 4 The switching state of the switched capacitor resonant converter in the second period of the working cycle is shown.

[0015] Figure 8 and Figure 9 exemplify Figure 4 The operating waveforms of the switched capacitor resonant converter when the first and second resonant paths operate in a quasi-resonant state.

[0016] Figure 10 for Figure 4 A circuit structure diagram of a variation of a switched capacitor resonant converter.

[0017] Figure 11 for Figure 4 A circuit structure diagram of another variation of the switched capacitor resonant converter.

[0018] The description of the accompanying drawings is as follows:

[0019] C1, C2: resonant capacitors

[0020] IC1, IC2: resonant current

[0021] W1, W2: output winding

[0022] IW1, IW2: output winding current

[0023] 1: Switched capacitor resonant converter

[0024] Vin+: input positive

[0025] Vin-: input negative

[0026] Vin: input voltage

[0027] Vo+: output positive

[0028] Vo-: output negative pole

[0029] Vo: output voltage

[0030] Cin: input capacitance

[0031] Co: output capacitance

[0032] S1: First switch

[0033] S2: Second switch

[0034] S3: The third switch

[0035] S4: The fourth switch

[0036] S5: Fifth switch

[0037] S6: Sixth switch

[0038] S7: Seventh switch

[0039] S8: Eighth switch

[0040] T1: first winding

[0041] T2: Second winding

[0042] Cr1: first resonant capacitor

[0043] Lr1: first resonant inductor

[0044] Cr2: Second resonant capacitor

[0045] Lr2: Second resonant inductor

[0046] Lr3: third resonant inductor

[0047] Lr4: fourth resonant inductor

[0048] T3: The third winding

[0049] T4: fourth winding

[0050] Lm1: first excitation inductance

[0051] Lm2: Second excitation inductance

[0052] t0, t1, t2, t3, t4: time

[0053] I1, I2, I3, I4: current

[0054] Io: output current

[0055] ILm1, ILm2: Excitation current

[0056] ICr1, ICr2: resonant current DETAILED DESCRIPTION

[0057] Some typical embodiments that embody the features and advantages of this invention will be described in detail in the following sections. It should be understood that this invention is capable of various variations in different implementations without departing from the scope of this invention, and that the descriptions and illustrations herein are intended to be illustrative in nature and not to limit this invention.

[0058] See also Figure 4 , Figure 4 FIG. 1 is a schematic diagram of the circuit structure of a switched capacitor resonant converter according to an embodiment of the present invention. Figure 4 As shown, the switched capacitor resonant converter 1 includes an input terminal, an output terminal, a first set of switches, a second set of switches, a magnetic element, a first resonant bridge arm, and a second resonant bridge arm.

[0059] The input terminal includes an input positive electrode Vin+ and an input negative electrode Vin-, wherein the input positive electrode Vin+ and the input negative electrode Vin- are configured to receive an input voltage Vin from an input source. The output terminal includes an output positive electrode Vo+ and an output negative electrode Vo-, wherein the output negative electrode Vo- is coupled to the input negative electrode Vin-, and the output positive electrode Vo+ and the output negative electrode Vo- are configured to provide an output voltage Vo. In some embodiments, the switched capacitor resonant converter 1 further includes an input capacitor Cin coupled between the input positive electrode Vin+ and the input negative electrode Vin-. In some embodiments, the switched capacitor resonant converter 1 further includes an output capacitor Co coupled between the output positive electrode Vo+ and the output negative electrode Vo-.

[0060] The first set of switches is electrically connected between the positive input terminal Vin+ and the negative input terminal Vin- to form a first switch arm. In this embodiment, the first set of switches includes a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4 connected in series between the positive input terminal Vin+ and the negative input terminal Vin-. The first switch S1 and the fourth switch S4 are coupled to the positive input terminal Vin+ and the negative input terminal Vin-, respectively.

[0061] The second set of switches is electrically connected between the positive input terminal Vin+ and the negative input terminal Vin- to form a second switch bridge arm. In this embodiment, the second set of switches includes a fifth switch S5, a sixth switch S6, a seventh switch S7, and an eighth switch S8 connected in series between the positive input terminal Vin+ and the negative input terminal Vin-. The fifth switch S5 and the eighth switch S8 are coupled to the positive input terminal Vin+ and the negative input terminal Vin-, respectively.

[0062] In some embodiments, the connection point between the second switch S2 and the third switch S3 serves as the first intermediate node of the first switch bridge arm, and the connection point between the sixth switch S6 and the seventh switch S7 serves as the second intermediate node of the second switch bridge arm, wherein the first intermediate node is electrically connected to the second intermediate node to form a connection path between the first intermediate node and the second intermediate node. The resonant path in the switched capacitor resonant converter 1 includes this connection path, and the connection path does not include a resonant element.

[0063] The first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7 and the eighth switch S8 may be, for example, power electronic switching devices such as metal-oxide-semiconductor field-effect transistors (MOSFETs), SiC switches or GaN switches, but are not limited thereto. Figure 4In the illustrated embodiment, the switches are MOSFETs, wherein the drains of the first switch S1 and the fifth switch S5 are connected to the positive input terminal Vin+, the source of the first switch S1 is connected to the drain of the second switch S2, and the source of the fifth switch S5 is connected to the drain of the sixth switch S6. The source of the second switch S2, the drain of the third switch S3, the source of the sixth switch S6, and the drain of the seventh switch S7 are connected. The source of the third switch S3 is connected to the drain of the fourth switch S4, the source of the seventh switch S7 is connected to the drain of the eighth switch S8, and the sources of the fourth switch S4 and the eighth switch S8 are connected to the negative input terminal Vin-.

[0064] The magnetic element includes a first winding T1 and a second winding T2. The first winding T1 is electrically connected between the first switching arm and the positive output pole Vo+, while the second winding T2 is electrically connected between the second switching arm and the positive output pole Vo+. Specifically, the first winding T1 is electrically connected between the connection point of the third switch S3 and the fourth switch S4 in the first switching arm and the positive output pole Vo+, while the second winding T2 is electrically connected between the connection point of the seventh switch S7 and the eighth switch S8 in the second switching arm and the positive output pole Vo+.

[0065] The first resonant bridge arm has two ends electrically connected to the first switch bridge arm and the magnetic element, respectively. In this embodiment, the first resonant bridge arm is electrically connected between the connection point of the first switch S1 and the second switch S2 and the connection point of the third switch S3 and the fourth switch S4. Furthermore, in this embodiment, the first resonant bridge arm includes a first resonant capacitor Cr1 and a first resonant inductor Lr1 connected in series, wherein a first end of the first resonant capacitor Cr1 is electrically connected to the connection point of the first switch S1 and the second switch S2, a second end of the first resonant capacitor Cr1 is electrically connected to a first end of the first resonant inductor Lr1, and a second end of the first resonant inductor Lr1 is electrically connected to the connection point of the third switch S3 and the fourth switch S4.

[0066] The second resonant bridge arm has two ends electrically connected to the second switch bridge arm and the magnetic element, respectively. In this embodiment, the second resonant bridge arm is electrically connected between the connection point of the fifth switch S5 and the sixth switch S6 and the connection point of the seventh switch S7 and the eighth switch S8. Furthermore, in this embodiment, the second resonant bridge arm includes a second resonant capacitor Cr2 and a second resonant inductor Lr2 connected in series. A first end of the second resonant capacitor Cr2 is electrically connected to the connection point of the fifth switch S5 and the sixth switch S6, a second end of the second resonant capacitor Cr2 is electrically connected to the first end of the second resonant inductor Lr2, and a second end of the second resonant inductor Lr2 is electrically connected to the connection point of the seventh switch S7 and the eighth switch S8.

[0067] The first resonant capacitor Cr1 and the second resonant capacitor Cr2 can actually include multiple capacitors connected in series or in parallel, and can be formed from multilayer ceramic capacitors, but are not limited thereto. The voltage across the first resonant capacitor Cr1 is the sum of the DC voltage component generated by the input voltage Vin and the oscillating AC voltage component generated by the third winding T3. The voltage across the second resonant capacitor Cr2 is the sum of the DC voltage component generated by the input voltage Vin and the oscillating AC voltage component generated by the fourth winding T4. The DC voltage component of both voltages is the difference between the input voltage Vin and (N+2) times the output voltage Vo. Furthermore, the capacitance of the input capacitor Cin and the capacitance of the output capacitor Co are much greater than the capacitance of the first resonant capacitor Cr1 and the second resonant capacitor Cr2. Therefore, the influence of the input capacitor Cin and the output capacitor Co can be ignored in analyzing the resonance of the circuit.

[0068] In addition, in this embodiment, the magnetic element further includes a third resonant inductor Lr3 and a fourth resonant inductor Lr4, wherein the third resonant inductor Lr3 is electrically connected between the first switch bridge arm and the positive output electrode Vo+, and the fourth resonant inductor Lr4 is electrically connected between the second switch bridge arm and the positive output electrode Vo+. Specifically, the third resonant inductor Lr3 is electrically connected between the connection point of the third switch S3 and the fourth switch S4 and the first winding T1, and the fourth resonant inductor Lr4 is electrically connected between the connection point of the seventh switch S7 and the eighth switch S8 and the second winding T2. In addition, in this embodiment, the magnetic element further includes a third winding T3 and a fourth winding T4, wherein the third winding T3 is electrically connected to the first resonant bridge arm, and the fourth winding T4 is electrically connected to the second resonant bridge arm. Specifically, the third winding T3 is electrically connected between the second end of the first resonant inductor Lr1 of the first resonant bridge arm and the connection point of the third switch S3 and the fourth switch S4. The fourth winding T4 is electrically connected between the second end of the second resonant inductor Lr2 of the second resonant bridge arm and the connection point of the seventh switch S7 and the eighth switch S8. It should be noted that, in practice, the positions of the first resonant capacitor Cr1 and the first resonant inductor Lr1 in the first resonant bridge arm, as well as the third winding T3 of the magnetic element, can be interchanged without affecting the operating characteristics of the overall circuit. Similarly, the positions of the second resonant capacitor Cr2 and the second resonant inductor Lr2 in the second resonant bridge arm, as well as the fourth winding T4 of the magnetic element, can be interchanged without affecting the operating characteristics of the overall circuit.

[0069] In some embodiments, the magnetic element further includes a first excitation inductor Lm1 and a second excitation inductor Lm2, wherein the first excitation inductor Lm1 is connected in parallel to the third winding T3, and the second excitation inductor Lm2 is connected in parallel to the fourth winding T4. In some embodiments, the first winding T1, the second winding T2, the third winding T3, and the fourth winding T4 form a transformer, and the turns ratio of the first winding T1, the second winding T2, the third winding T3, and the fourth winding T4 is 1:1:N:N, where N is a natural number greater than zero. In this case, the input voltage Vin received at the input terminal and the output voltage Vo provided by the output terminal meet the equation:

[0070] Vo = Vin * [1 / 2(N+2)] (1)

[0071] Thus, by adjusting the turns ratio of the first winding T1 , the second winding T2 , the third winding T3 and the fourth winding T4 , the gain ratio between the input voltage Vin and the output voltage Vo can be changed.

[0072] In the switched capacitor resonant converter 1 of the present invention, the first set of switches and the second set of switches are periodically controlled to form a first resonant path and a second resonant path to transmit energy to the output end, and the first resonant path and the second resonant path have substantially the same resonant parameters (such as resonant frequency, capacitance of the resonant capacitor and inductance of the resonant inductor). For example, Figure 4 In the illustrated embodiment, the first resonant inductor Lr1 and the second resonant inductor Lr2 have the same inductance value, the third resonant inductor Lr3 and the fourth resonant inductor Lr4 have the same inductance value, the first resonant capacitor Cr1 and the second resonant capacitor Cr2 have the same capacitance value, and the first resonant frequency at which the first resonant path resonates is equal to the second resonant frequency at which the second resonant path resonates.

[0073] This design simultaneously transmits energy to the output terminal through the first and second resonant paths. Compared to existing power conversion circuits that utilize a single resonant cavity for energy output, this design reduces the output capacity of each resonant path and improves power density while maintaining the same total output. Furthermore, the losses in the two resonant paths are equal, distributing the heat source and facilitating heat dissipation.

[0074] by Figure 4 Taking the circuit topology of the switched capacitor resonant converter 1 shown in FIG. as an example, a first resonant path is formed by the resonance of the first resonant capacitor Cr1 and the first resonant inductor Lr1, and a second resonant path is formed by the resonance of the second resonant capacitor Cr2 and the second resonant inductor Lr2. Furthermore, during different periods of the operating cycle of the switched capacitor resonant converter 1, the first and second resonant paths share the third resonant inductor Lr3 or the fourth resonant inductor Lr4. The operation of the switched capacitor resonant converter 1 is described in detail below.

[0075] See also Figure 5 And match Figure 4 , Figure 5 exemplify Figure 4 The working waveforms of the first and second switches of the switched capacitor resonant converter 1 are shown in FIG. Figure 5 In FIG, S1, S2, S3, S4, S5, S6, S7 and S8 represent control signals of the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7 and the eighth switch S8 respectively. The period from t0 to t4 is one working cycle of the switched capacitor resonant converter 1. Figure 5 As shown, the first group of switches and the second group of switches are turned on alternately.

[0076] Figure 5 The period from time t0 to t1 shown is the first period of the working cycle of the switched capacitor resonant converter 1. In the first period, the first switch S1 and the third switch S3 in the first switch group and the sixth switch S6 and the eighth switch S8 in the second switch group are turned on, and the second switch S2 and the fourth switch S4 in the first switch group and the fifth switch S5 and the seventh switch S7 in the second switch group are turned off. The corresponding switch states are shown in FIG. Figure 6 .like Figure 6 As shown, during the first period, the first resonant capacitor Cr1, the first resonant inductor Lr1, and the third resonant inductor Lr3 resonate to form a first resonant path, which transmits power received from the input end to the output end. Furthermore, the second resonant capacitor Cr2, the second resonant inductor Lr2, and the third resonant inductor Lr3 resonate to form a second resonant path, which transmits power from the second resonant capacitor Cr2 to the output end. At this time, the fourth resonant inductor Lr4 does not participate in the resonance, while the third resonant inductor Lr3 participates in the resonance of both resonant paths (i.e., the first and second resonant paths share the third resonant inductor Lr3). It should be noted that the inductance of the third resonant inductor Lr3 during resonance is not its own inductance, but rather an inductance that is proportional to its own inductance. The specific value depends on the size of N in the turns ratio.

[0077] Figure 5 The period from time t2 to t3 shown is the second period of the working cycle of the switched capacitor resonant converter 1. In the second period, the first switch S1 and the third switch S3 in the first switch group and the sixth switch S6 and the eighth switch S8 in the second switch group are turned off, and the second switch S2 and the fourth switch S4 in the first switch group and the fifth switch S5 and the seventh switch S7 in the second switch group are turned on. The corresponding switch states are shown in FIG. Figure 7 .like Figure 7As shown, during the second period, the first resonant capacitor Cr1, the first resonant inductor Lr1, and the fourth resonant inductor Lr4 resonate to form a first resonant path, which transmits power from the first resonant capacitor Cr1 to the output terminal. Furthermore, the second resonant capacitor Cr2, the second resonant inductor Lr2, and the fourth resonant inductor Lr4 resonate to form a second resonant path, which transmits power received at the input terminal to the output terminal. At this time, the third resonant inductor Lr3 does not participate in the resonance, while the fourth resonant inductor Lr4 participates in the resonance of both resonant paths (i.e., the first and second resonant paths share the fourth resonant inductor Lr4). It should be noted that the inductance of the fourth resonant inductor Lr4 during resonance is not its own inductance, but rather an inductance that is proportional to its own inductance. The specific value depends on the value of N in the turns ratio.

[0078] See also Figure 6 and Figure 7 . Figure 6 and Figure 7 The currents I1, I2, I3 and I4 flowing through the first winding T1, the second winding T2, the third winding T3 and the fourth winding T4 are also shown. According to Kirchhoff's current theorem, ampere-turn balance and the law of conservation of power, Figure 6 In the switching state of the first period shown, it can be deduced that: I1 = Io / (N+2), I2 = Io*(N+1) / (N+2), I3 = Io / 2(N+2), I4 = Io / 2(N+2), where Io represents the output current flowing into the output terminal; Figure 7 In the switching state of the second period shown, it can be deduced that: I1 = Io*(N+1) / (N+2), I2 = Io / (N+2), I3 = Io / 2(N+2), and I4 = Io / 2(N+2). From the current expressions for the first and second periods above, it can be seen that the operating currents of the first resonant path and the second resonant path are substantially the same, and the first winding T1 and the second winding T2 together serve as output windings, alternately transferring energy to the output terminal. Furthermore, the currents in the first and second resonant paths are symmetrical, meaning that the first and second resonant paths generate the same amount of heat during energy conversion and transmission, thereby facilitating overall thermal management of the switched capacitor resonant converter 1.

[0079] Please refer to Figure 5 And match Figure 4In some embodiments, a dead time is defined between adjacent first and second time periods, i.e., from time t1 to t2 and from time t3 to t4. During the dead time, both the first and second switches are off, and the first and second resonant paths jointly provide energy to enable the switch to be turned on in the first or second time period to achieve zero voltage turn-on. Specifically, during the dead time before the first time period, i.e., from time t3 to t4, the first resonant capacitor Cr1, the first resonant inductor Lr1, the third resonant inductor Lr3, and the fourth resonant inductor Lr4 resonate together, and the magnetizing current ILm1 generated by the resonance flows through the first switch S1 and the eighth switch S8, discharging the junction capacitance of the first and eighth switches S1 and S8. Therefore, the first and eighth switches S1 and S8 can achieve zero voltage turn-on when subsequently turned on (e.g., in the first time period), thereby reducing switching losses and improving efficiency. At the same time, the second resonant capacitor Cr2, the second resonant inductor Lr2, the third resonant inductor Lr3, and the fourth resonant inductor Lr4 resonate together. The excitation current ILm2 generated by the resonance flows through the third switch S3 and the sixth switch S6, and discharges the junction capacitance of the third switch S3 and the sixth switch S6. Therefore, the third switch S3 and the sixth switch S6 can achieve zero voltage turn-on when they are subsequently turned on (for example, in the first period), thereby reducing switching losses and improving efficiency.

[0080] Similarly, during the dead time before the second period, i.e., from time t1 to t2, the first resonant capacitor Cr1, the first resonant inductor Lr1, the third resonant inductor Lr3, and the fourth resonant inductor Lr4 resonate together, and the resulting excitation current ILm1 flows through the second switch S2 and the seventh switch S7, discharging the junction capacitance of the second switch S2 and the seventh switch S7. Therefore, the second switch S2 and the seventh switch S7 can achieve zero voltage turn-on when they are subsequently turned on (e.g., during the second period), thereby reducing switching losses and improving efficiency. Simultaneously, the second resonant capacitor Cr2, the second resonant inductor Lr2, the third resonant inductor Lr3, and the fourth resonant inductor Lr4 resonate together, and the resulting excitation current ILm2 flows through the fourth switch S4 and the fifth switch S5, discharging the junction capacitance of the fourth switch S4 and the fifth switch S5. Therefore, the fourth switch S4 and the fifth switch S5 can achieve zero voltage turn-on when they are subsequently turned on (e.g., during the second period), thereby reducing switching losses and improving efficiency.

[0081] By adjusting the switching frequencies of the first and second sets of switches, the operating states of the first and second resonant paths can be adjusted. Generally speaking, the operating states of a resonant path include over-resonance, under-resonance, and quasi-resonance. Ideally, the first and second resonant paths operate in a quasi-resonance state, where the switching frequency equals the resonant frequency of switched capacitor resonant converter 1. The following analysis of the resonant frequencies during the first and second time periods uses the example of switched capacitor resonant converter 1 operating in a quasi-resonance state and a turns ratio of 1:1:N:N among the first, second, third, and fourth windings T1, T2, T3, and T4.

[0082] In the first period, assuming that only the first resonant path works alone, the resonant frequency of the first resonant path is:

[0083]

[0084] Wherein, Lr3 represents the inductance value of the third resonant inductor Lr3 , Lr1 represents the inductance value of the first resonant inductor Lr1 , and Cr1 represents the capacitance value of the first resonant capacitor Cr1 .

[0085] In the first period, assuming that only the second resonant path works alone, the resonant frequency of the second resonant path is:

[0086]

[0087] Wherein, Lr2 represents the inductance value of the second resonant inductor Lr2, and Cr2 represents the capacitance value of the second resonant capacitor Cr2.

[0088] In the first period, if fr11 = fr12, the common resonant frequency of the first resonant path and the second resonant path when connected in parallel and working simultaneously is:

[0089]

[0090] In the second period, assuming that only the first resonant path works alone, the resonant frequency of the first resonant path is:

[0091]

[0092] Wherein, Lr4 represents the inductance value of the fourth resonant inductor Lr4.

[0093] In the second period, assuming that only the second resonant path works alone, the resonant frequency of the second resonant path is:

[0094]

[0095] In the second period, if fr21 = fr22, the common resonant frequency of the first resonant path and the second resonant path when connected in parallel and working simultaneously is:

[0096]

[0097] From equations (2) to (7), it can be seen that when Cr1 = Cr2 and Lr1 = Lr2, then fr11 = fr12 and fr21 = fr22, that is, the resonant frequencies of the first resonant path and the second resonant path when operating independently are the same. Furthermore, when Cr1 = Cr2, Lr1 = Lr2, and Lr3 = Lr4, then fr11 = fr12 = fr21 = fr22 and fr13 = fr23. Under these symmetrical resonant parameters, the switched capacitor resonant converter 1 can achieve optimal efficiency. Since the switched capacitor resonant converter 1 maintains resonance at the same resonant frequency in both the first and second time periods, soft switching of all switching devices can be achieved by simply making the switching frequency equal to fr13 and fr23.

[0098] exist Figure 1 Although the power conversion circuit shown contains two resonant circuits, the resonant frequencies of the two resonant circuits are theoretically not consistent. If soft switching of all switching devices is to be achieved, it is necessary to set the resonant inductor and resonant capacitor accordingly to adapt the two resonant circuits to equal resonant frequencies. However, due to the large number of resonant elements in the topology, there are many variables in the formula, which greatly increases the difficulty of adaptation. If the power conversion circuit operates under the condition of mismatched resonant frequencies, it will result in only two switching devices among the four switching devices that are turned on at the same time to achieve soft switching, while the other two switching devices are hard switching; at the same time, if Figure 2 and Figure 3 As shown, high-order current harmonics will be generated. The hard switching and high-order current harmonics will lead to a significant increase in power loss in the power conversion circuit, thereby causing serious heating of the circuit board.

[0099] On the other hand, the switched capacitor resonant converter in the present application can solve the aforementioned problems. Specifically, only symmetrical resonant parameters are required to achieve soft switching of all switching devices, thereby improving the efficiency of the switched capacitor resonant converter. In addition, since the two resonant paths are symmetrical, the resonant devices generate heat evenly, which facilitates heat dissipation design, and the thermal management performance is better than that of a power conversion circuit using a single resonant cavity and a power conversion circuit using two resonant circuits with inconsistent resonant parameters. In addition, the present application can also avoid the problem of different DC bias voltages and inconsistent resonant frequencies caused by different capacitance values ​​of multiple resonant capacitors under different input voltages. Furthermore, the present application can also achieve that when the input voltage is different and the capacitance value of the resonant capacitor changes in the same direction, the resonant frequency remains the same, thereby improving the efficiency of the full input voltage range. What's more, compared with existing power conversion circuits (such as Figure 1) reduces the number of capacitors used, thereby freeing up space on the circuit board for other power devices, further improving efficiency. Furthermore, the present application can also incorporate a pre-charging circuit to pre-charge the first resonant capacitor Cr1 and the second resonant capacitor Cr2, providing a DC bias voltage during the startup phase, further reducing losses and improving efficiency.

[0100] See also Figure 8 and Figure 9 And match Figure 4 ,in, Figure 8 and Figure 9 exemplify Figure 4 The working waveform of the switched capacitor resonant converter 1 when it works in the quasi-resonant state. Specifically, Figure 8 Example of flow through Figure 4 The waveforms of the resonant currents of the first resonant capacitor Cr1 and the second resonant capacitor Cr2, where ICr1 represents the resonant current flowing through the first resonant capacitor Cr1, and ICr2 represents the resonant current flowing through the second resonant capacitor Cr2. Figure 8 As shown, the waveforms of the resonant currents ICr1 and ICr2 are close to sinusoidal waveforms and do not have high-frequency harmonics, so no additional power loss caused by high-frequency harmonics is generated. Figure 9 Examples show the flow through Figure 4 The waveforms of the currents I1 and I2 of the first winding T1 and the second winding T2 are shown in FIG. Figure 9 As shown, the currents I1 and I2 are also sinusoidal and do not have high-frequency harmonics, so additional power loss caused by high-frequency harmonics will not be generated.

[0101] Since DC-DC module power supplies often use higher switching frequencies (such as several megahertz) for miniaturization, if high-frequency harmonic currents are generated at this time, the operating frequency will far exceed the megahertz (because the operating frequency is a multiple of the switching frequency). This high-frequency harmonic current will cause additional core loss and winding loss (collectively referred to as high-frequency harmonic loss), and high-frequency harmonic loss accounts for a huge proportion of the overall power loss. It can be seen that the switched capacitor resonant converter 1 of this case eliminates the generation of high-frequency harmonic currents at the source, so it can greatly reduce high-frequency harmonic loss, thereby reducing the overall power loss, thereby improving practicality and facilitating engineering. The switched capacitor resonant converter 1 of this case is significantly superior to the Figure 1 The conventional power conversion circuit is shown as an example.

[0102] In addition, in the switched capacitor resonant converter 1 of the present invention, the magnetic elements include a first winding T1, a second winding T2, a third winding T3, a fourth winding T4, a first resonant inductor Lr1, a second resonant inductor Lr2, a third resonant inductor Lr3 and a fourth resonant inductor Lr4, wherein the first winding T1, the second winding T2, the third winding T3 and the fourth winding T4 are structured to form a transformer. The first resonant inductor Lr1, the second resonant inductor Lr2, the third resonant inductor Lr3 and the fourth resonant inductor Lr4 can be the leakage inductance of the transformer winding and / or the parasitic inductance of the line, or can be an external inductor independent of the transformer, but is not limited thereto. For example, in Figure 4 In the embodiment shown, the first resonant inductor Lr1, the second resonant inductor Lr2, the third resonant inductor Lr3 and the fourth resonant inductor Lr4 may be external inductors; Figure 10 In the illustrated embodiment, the first resonant inductor Lr1, the second resonant inductor Lr2, the third resonant inductor Lr3, and the fourth resonant inductor Lr4 can be parasitic inductances of the circuits and / or leakage inductances of the third winding T3, the fourth winding T4, the first winding T1, and the second winding T2, respectively. It should be noted that these resonant inductors can be implemented appropriately based on actual needs, and their specific implementation does not affect the overall circuit operation. For example, by integrating the third resonant inductor Lr3 and the fourth resonant inductor Lr4, the volume of magnetic components can be reduced, further improving power density.

[0103] In the aforementioned embodiment, the end of the first winding T1 connected to the positive output electrode Vo+, the end of the second winding T2 connected to the fourth winding T4, the end of the third winding T3 connected to the first winding T1, and the end of the fourth winding T4 connected to the second resonant capacitor Cr2 are designated as common terminals. However, in the present case, the arrangement of the common terminals of the first winding T1, the second winding T2, the third winding T3, and the fourth winding T4 is not limited to this and can be adjusted as needed. Furthermore, in the aforementioned embodiment, the first winding T1, the second winding T2, the third winding T3, and the fourth winding T4 form a single transformer. However, in another embodiment, the first winding T1, the second winding T2, the third winding T3, and the fourth winding T4 can also form two transformers, for example, one transformer formed by the first winding T1 and the third winding T3, and another transformer formed by the second winding T2 and the fourth winding T4. In this case, the windings can be matched with each other in different forms according to actual needs to form one or more transformers, and the specific implementation is not limited to the examples in this case.

[0104] In addition, in the aforementioned embodiment, the input capacitor Cin is coupled between the input positive electrode Vin+ and the input negative electrode Vin-. However, in this case, the location of the input capacitor Cin is not limited to this. In another embodiment, Figure 11As shown, the input capacitor Cin can be coupled between the input positive electrode Vin+ and the output positive electrode Vo+. In this way, the input capacitor Cin can use a capacitor with a smaller withstand voltage to reduce device cost while not affecting the operation of the entire circuit.

[0105] In the switched capacitor resonant converter 1 of the present invention, the input terminal, the output terminal, the first set of switches, the second set of switches, the magnetic element, the first resonant bridge arm, and the second resonant bridge arm can form a power conversion module. In some embodiments, the switched capacitor resonant converter includes multiple power conversion modules, wherein the multiple input positive electrodes Vin+ of the multiple power conversion modules are connected, the multiple input negative electrodes Vin- of the multiple power conversion modules are connected, the multiple output positive electrodes Vo+ of the multiple power conversion modules are connected, and the multiple output negative electrodes Vo- of the multiple power conversion modules are connected.

[0106] The above description is merely a description of preferred embodiments of the present invention. The present invention is not limited to the embodiments described. The scope of the present invention is determined by the appended claims. Furthermore, the present invention is subject to various modifications and variations as conceived by those skilled in the art, without departing from the intended scope of the appended claims.

Claims

1. A switched capacitor resonant converter, comprising: An input terminal including an input positive electrode and an input negative electrode; an output terminal comprising an output positive electrode and an output negative electrode, wherein the input negative electrode is coupled to the output negative electrode; A first set of switches is electrically connected between the input positive electrode and the input negative electrode to form a first switch bridge arm; A second set of switches is electrically connected between the input positive electrode and the input negative electrode to form a second switch bridge arm; a magnetic element comprising a first winding and a second winding, wherein the first winding is electrically connected between the first switch bridge arm and the output positive electrode, and the second winding is electrically connected between the second switch bridge arm and the output positive electrode; a first resonant bridge arm, two ends of which are electrically connected to the first switch bridge arm and the magnetic element respectively; and a second resonant bridge arm, with two ends thereof electrically connected to the second switch bridge arm and the magnetic element, respectively; in, The first set of switches and the second set of switches are periodically controlled to form a first resonant path and a second resonant path to transmit energy to the output end, and the first resonant path and the second resonant path have substantially the same resonant parameters. 2 . The switched capacitor resonant converter as claimed in claim 1 , wherein the first resonant path resonates at a first resonant frequency, the second resonant path resonates at a second resonant frequency, and the first resonant frequency is equal to the second resonant frequency.

3. The switched capacitor resonant converter of claim 1 , wherein the first resonant bridge arm comprises a first resonant capacitor and a first resonant inductor connected in series, and the second resonant bridge arm comprises a second resonant capacitor and a second resonant inductor connected in series; the first resonant capacitor and the first resonant inductor resonate to form the first resonant path, and the second resonant capacitor and the second resonant inductor resonate to form the second resonant path.

4. The switched capacitor resonant converter of claim 3 , wherein a duty cycle of the switched capacitor resonant converter comprises a first period and a second period, wherein during the first period, the first resonant path transmits power received at the input end to the output end, and the second resonant path transmits power from the second resonant capacitor to the output end; and during the second period, the first resonant path transmits power from the first resonant capacitor to the output end, and the second resonant path transmits the power received at the input end to the output end.

5. The switched capacitor resonant converter of claim 3 , wherein the magnetic element comprises a third resonant inductor and a fourth resonant inductor, the third resonant inductor being electrically connected between the first switching bridge arm and the positive output electrode, the fourth resonant inductor being electrically connected between the second switching bridge arm and the positive output electrode, and the first resonant path and the second resonant path sharing the third resonant inductor or the fourth resonant inductor.

6. The switched capacitor resonant converter of claim 5 , wherein a duty cycle of the switched capacitor resonant converter comprises a first period and a second period, wherein during the first period, the first resonant capacitor, the first resonant inductor, and the third resonant inductor resonate to form the first resonant path, and the second resonant capacitor, the second resonant inductor, and the third resonant inductor resonate to form the second resonant path; During the second period, the first resonant capacitor, the first resonant inductor, and the fourth resonant inductor resonate to form the first resonant path, and the second resonant capacitor, the second resonant inductor, and the fourth resonant inductor resonate to form the second resonant path. 7 . The switched capacitor resonant converter as claimed in claim 5 , wherein the third resonant inductor and the fourth resonant inductor have the same inductance value. 8 . The switched capacitor resonant converter as claimed in claim 3 , wherein the first resonant capacitor and the second resonant capacitor have the same capacitance value, and the first resonant inductor and the second resonant inductor have the same inductance value.

9. The switched capacitor resonant converter of claim 1 , wherein the first switching bridge arm includes a first intermediate node, the second switching bridge arm includes a second intermediate node, the first intermediate node is electrically connected to the second intermediate node to form a connection path between the first intermediate node and the second intermediate node, the first resonant path or the second resonant path includes the connection path, and the connection path does not include a resonant element.

10. The switched capacitor resonant converter of claim 1 , wherein the magnetic element further comprises a third winding and a fourth winding, the third winding being electrically connected to the first resonant bridge arm, and the fourth winding being electrically connected to the second resonant bridge arm, wherein a turns ratio of the first winding, the second winding, the third winding, and the fourth winding is 1:1:N:N, and N is a natural number greater than zero.

11. The switched capacitor resonant converter as claimed in claim 10 , wherein an input voltage received by the input terminal and an output voltage provided by the output terminal satisfy the equation: Vo=Vin*[1 / 2(N+2)] in, Vo is the output voltage, and Vin is the input voltage.

12. The switched capacitor resonant converter of claim 1 , wherein a duty cycle of the switched capacitor resonant converter comprises a first time period and a second time period, wherein some switches in the first group of switches and the second group of switches are turned on during the first time period and the second time period; and a dead time is defined between adjacent first time periods and second time periods, wherein the first resonant path and the second resonant path jointly provide energy to achieve zero voltage turn-on of some switches during the dead time. 13 . The switched capacitor resonant converter as claimed in claim 1 , further comprising an input capacitor, wherein the input capacitor is coupled between the input positive electrode and the input negative electrode. 14 . The switched capacitor resonant converter as claimed in claim 1 , further comprising an input capacitor, wherein the input capacitor is coupled between the input positive electrode and the output positive electrode.

15. The switched capacitor resonant converter according to any one of claims 1 to 14, wherein: The first switch group includes a first switch, a second switch, a third switch, and a fourth switch connected in series between the input positive electrode and the input negative electrode, wherein the first switch is connected to the second switch to form a first connection point, the second switch is connected to the third switch to form a second connection point, and the third switch is connected to the fourth switch to form a third connection point; The second set of switches includes a fifth switch, a sixth switch, a seventh switch, and an eighth switch connected in series between the input positive electrode and the input negative electrode, wherein the fifth switch and the sixth switch are connected to form a fourth connection point, the sixth switch and the seventh switch are connected to form a fifth connection point, the seventh switch and the eighth switch are connected to form a sixth connection point, and the fifth connection point is electrically connected to the second connection point; The first resonant bridge arm is electrically connected between the first connection point and the third connection point; The second resonant bridge arm is electrically connected between the fourth connection point and the sixth connection point.

16. The switched capacitor resonant converter of claim 15 , wherein a duty cycle of the switched capacitor resonant converter comprises a first period and a second period, wherein during the first period, the first switch, the third switch, the sixth switch, and the eighth switch are turned on, the second switch, the fourth switch, the fifth switch, and the seventh switch are turned off, and the first resonant path and the second resonant path are turned on; During the second period, the first switch, the third switch, the sixth switch, and the eighth switch are turned off, the second switch, the fourth switch, the fifth switch, and the seventh switch are turned on, and the first resonant path and the second resonant path are conducted.

17. The switched capacitor resonant converter as described in claim 1, wherein the input end, the output end, the first group of switches, the second group of switches, the magnetic element, the first resonant bridge arm and the second resonant bridge arm form a power conversion module; the switched capacitor resonant converter includes a plurality of the power conversion modules, and the plurality of the input positive poles of the plurality of the power conversion modules are connected, the plurality of the input negative poles of the plurality of the power conversion modules are connected, the plurality of the output positive poles of the plurality of the power conversion modules are connected, and the plurality of the output negative poles of the plurality of the power conversion modules are connected.

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