A conversion circuit topology

Abstract

The present invention provides a conversion circuit for converting an input voltage into an output voltage, comprising: a first full-wave rectifier circuit, a first switch branch and a first resonant unit. The first full-wave rectifier circuit comprises a first and a second branch connected in parallel, each comprising a winding and a rectifier switch connected in series to form a midpoint. The first switch branch comprises a first switch and a second switch connected in series to form a first connection point. The first resonant unit is connected between the first connection point and the midpoint of the second branch, wherein the first resonant unit is not connected in series to a transformer winding. The conversion circuit provided in the present invention improves the conversion efficiency while reducing the voltage stress of the switch tube.

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. Background Art

[0002] According to the survey data of China Data Center Energy Conservation Technology Committee, the total power consumption of China's data centers exceeded 120 billion kWh in 2016. Despite the alarming power consumption of data centers, as more and more services are supported by data centers, the computing load and scale of data centers will continue to grow rapidly. In order to improve the computing density of data centers, the power of a single rack (RACK) will increase accordingly. The number of processor chips in traditional racks is small, so the power of a single rack is generally less than 15kW. For traditional racks, the AC UPS used to power the rack is located outside the rack, and the internal DC distribution bus voltage is 12V, which is relatively stable. However, as the number of processor chips in a single rack increases, the power of a single rack increases. When the power of a single rack exceeds 15kW, the current on the 12V DC distribution bus increases significantly, which greatly reduces efficiency and increases the cost of heat dissipation, cables and connectors. Therefore, a new power transmission architecture is proposed, in which the DC distribution bus voltage inside the rack is increased to 48V. At the same time, a DC UPS (DC-UPS) is used to replace the AC UPS and is installed inside the rack and directly connected to the 48V DC distribution bus. The new 48V distribution bus structure significantly reduces the distribution bus current, improves the power supply efficiency of the data center, reduces the electricity cost, heat dissipation cost and distribution bus cost, and thus reduces the total cost of ownership of the data center. In addition, the DC-UPS is directly connected to the 48V distribution bus, which further improves the power supply reliability of the rack and makes the bus voltage range between 40V and 59.5V. The bus voltage is always within the safety extra-low voltage SELV range, ensuring the safety of maintenance operations.

[0003] The power conversion module (Voltage Regulation Module, VRM) between the DC bus and the processor chip has extremely high efficiency requirements. For example, when the core voltage of the processor chip is lower than 1V and the load of the 48V-VRM varies between 30% and 90%, its power conversion efficiency needs to be always higher than 92%. However, in the new power transmission architecture, the challenges faced by the 48V-VRM are significantly higher than those of the 12V distribution bus. On the DC distribution bus side, the 12V distribution bus voltage is stable and has a small range of variation. The 48V distribution bus is directly connected to the DC-UPS, and the voltage range is directly affected by the DC-UPS, with a wide voltage range from 40V to 59.5V. On the processor chip side, in order to reduce the energy consumption of the processor chip, the core voltage of the processor chip is further reduced. In addition, in order to provide short-term chip acceleration performance, the processor chip requires the 48V-VRM to provide significantly increased voltage and current. Take a certain GPU as an example, its core voltage range is 0.6V to 1.1V, in energy saving mode, the core voltage is 0.6V, the rated current is 400A, in rated working condition, the core voltage is 0.8V, the rated current is 600A. However, in GPU acceleration mode, 48V-VRM is required to provide 1.1V core voltage and 1200A output current to GPU within 200 microseconds.

[0004] It can be seen that in the new power transmission architecture, the voltage conversion ratio between the bus and the processor chip is significantly improved. Under such conditions, the 48V-VRM from the DC distribution bus to the processor chip faces huge challenges in meeting the requirements for power conversion efficiency while maintaining high power density.

[0005] Generally speaking, 48V-VRM is a two-stage cascade converter structure, which usually adopts a working mode of first stepping down and then regulating the voltage. For example, the first-stage converter can use an efficient DC transformer to reduce the input 48V bus voltage (Uin) to a lower intermediate bus voltage (Uib), such as 4V. The second stage uses a multi-phase staggered parallel BUCK converter to control the BUCK output voltage Uo through a closed loop to ensure the power supply of the load (such as a processor chip).

[0006] The typical topology that can be used for the first-stage converter of 48V-VRM is LLC series resonant circuit. This circuit can adjust the excitation current of the transformer to charge and discharge the parasitic capacitance of the primary switch tube during the dead time of the primary switch tube to achieve ZVS operation of the primary switch tube, achieving extremely small switch tube turn-on loss. At the same time, the resonance mode allows the primary switch tube to achieve a smaller turn-off current, thereby reducing the turn-off loss. For the switch tube on the secondary side (such as a diode), because there is no output inductor, the voltage stress on the switch tube on the secondary side is low. When the switch tube on the secondary side uses a synchronous rectifier tube, a switch tube with lower withstand voltage and better performance can be selected to achieve lower conduction loss. In addition, due to the soft switching characteristics, it is easier to achieve high power density applications at high frequencies. Since a transformer is used, a high conversion ratio can be achieved very conveniently. Assuming that the transformer turns ratio is N:1:1, when the switching frequency fs is equal to the resonant frequency fr, its conversion ratio is N (full-bridge LLC) or 2N (half-bridge LLC).

[0007] However, the LLC circuit also has some defects. Because of the use of transformers, all energy conversion must pass through the transformer. The switch tube on the primary side of the transformer is responsible for generating the excitation of the primary winding, while the secondary side senses the excitation of the primary side and outputs it to the final load through the rectifier. In this process, the primary switch tube only generates excitation, and its own excitation current does not flow to the load end, but flows back to the input end. All load currents are provided by the secondary circuit. At this time, the current stress of the secondary winding and the device is relatively large.

[0008] The above LLC circuit can achieve a higher voltage transformation ratio and ZVS soft switching, but all energy is transferred through the transformer. When isolation is not required in the actual system, a non-isolated LLC circuit can also be used. The non-isolated LLC circuit realizes soft switching, a large transformation ratio, and the primary excitation current flows to the load. 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 the primary winding. Although the non-isolated LLC reduces the number of transformer turns, only an additional 2 primary currents flow into the load end in this type of transformer. This feature determines that when the non-isolated LLC needs a relatively large conversion ratio, the additional conversion ratio of the non-isolated LLC is reduced in the overall conversion ratio, and the benefits brought by it are reduced. Therefore, under high conversion ratio conditions, the efficiency approaches the efficiency of LLC.

[0009] Another converter implementation is called a switching tank converter (Switching Tank Converter, STC). Compared with LLC, this converter does not use a transformer, but realizes power conversion by directly transmitting current to the load end. Figure 1An example circuit of STC 100 is shown, in which a DC voltage exists on capacitor C1, and when the duty cycle of switch S1~S4 is 0.5, the DC voltage is 0.5Vin. Switches S1, S3, SR1, and SR4 are turned on simultaneously in the first half cycle, and switches S2, S4, SR2, and SR3 are turned on simultaneously in the second half cycle, so that a conversion ratio of Vin / Vo=4:1 can be achieved. The circuit can change the voltage conversion ratio of the circuit by adjusting the number of series switches and resonant cavities. The advantage of this circuit is that there is no transformer, and all energy flows directly to the load through the modulation circuit, which reduces the conversion process of the transformer and reduces the voltage stress of the switch tubes S1~S4. The disadvantage is that the conversion achieved is relatively low, and more levels need to be superimposed when a higher conversion ratio needs to be achieved, which increases the complexity of the circuit. At the same time, ZVS cannot be achieved, only ZCS can be achieved, and the control accuracy requirements in the ZCS process are high. Therefore, the STC has a higher efficiency at low conversion ratios, but as the voltage conversion ratio increases, its efficiency gradually becomes lower than that of the LLC topology due to the increased complexity of the circuit and the influence of the devices. Summary of the invention

[0010] The purpose of the present invention is to solve the problem of complex circuit and low efficiency of the above-mentioned switching resonant cavity converter in conversion ratio, and to provide a conversion circuit that can achieve different voltage conversion ratio requirements while reducing switching losses.

[0011] According to one aspect of the present invention, a conversion circuit is provided, which is used to convert an input voltage to provide an output voltage, wherein both the input voltage and the output voltage include a first end and a second end, and the second end of the input voltage is connected to the second end of the output voltage, and the conversion circuit includes:

[0012] A full-bridge circuit, comprising a first bridge arm and a second bridge arm connected in parallel and electrically connected between the first end and the second end of the output voltage;

[0013] A first switch branch, electrically connected between the first end of the input voltage and the first end of the output voltage, and comprising a first switch and a second switch connected in series to form a first connection point;

[0014] a first resonance unit, electrically connected between the first connection point and a midpoint of the first bridge arm, and

[0015] The first transformer comprises: a first primary winding connected in series with the first resonant unit; and a first secondary winding connected between a midpoint of the first bridge arm and a midpoint of the second bridge arm.

[0016] According to another aspect of the present invention, a conversion circuit is provided, which is used to convert an input voltage to provide an output voltage, wherein the input voltage and the output voltage both include a first end and a second end, and the second end of the input voltage is connected to the second end of the output voltage, and the conversion circuit includes:

[0017] A full-wave rectifier circuit, comprising a first branch and a second branch connected in parallel between the first end and the second end of the output voltage, the first branch comprising a first secondary winding of a transformer and a first rectifier switch connected in series to form a first midpoint, and the second branch comprising a second secondary winding of the transformer and a second rectifier switch connected in series to form a second midpoint;

[0018] a first switch branch, connected between the first end of the input voltage and the first midpoint, and comprising a first switch, a second switch, a third switch and a fourth switch connected in series, wherein the first switch and the second switch are connected to form a first connection point, 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;

[0019] A first resonance unit, electrically connected between the first connection point and the second midpoint;

[0020] a second resonance unit, electrically connected between the third connection point and the second midpoint;

[0021] The first primary winding of the transformer is connected in series with the first resonant unit; and

[0022] A first capacitor is connected between the second connection point and the first midpoint.

[0023] According to another aspect of the present invention, a conversion circuit is provided, which is used to convert an input voltage to provide an output voltage, wherein the input voltage and the output voltage both include a first end and a second end, and the second end of the input voltage is connected to the second end of the output voltage, and the conversion circuit includes:

[0024] A full-wave rectifier circuit, comprising a first branch, a second branch, a third branch and a fourth branch connected in parallel between the first end and the second end of the output voltage, wherein the first branch comprises a first secondary winding of a first transformer and a first rectifier switch connected in series to form a first midpoint, the second branch comprises a second secondary winding and a second rectifier switch of the first transformer connected in series to form a second midpoint, the third branch comprises a first secondary winding of a second transformer and a third rectifier switch connected in series to form a third midpoint, and the fourth branch comprises a second secondary winding of the second transformer and a fourth rectifier switch connected in series to form a fourth midpoint;

[0025] a first switch branch, connected between the first end of the input voltage and the first midpoint, and comprising a first switch, a second switch, a third switch and a fourth switch connected in series, wherein the first switch and the second switch are connected to form a first connection point, 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;

[0026] A first resonance unit, connected between the first connection point and the second midpoint;

[0027] A second resonance unit, connected between the third connection point and the fourth midpoint;

[0028] The primary winding of the first transformer is connected in series with the first resonant unit;

[0029] The primary winding of the second transformer is connected in series with the second resonant unit; and

[0030] A capacitor is connected between the second connection point and the third midpoint.

[0031] According to another aspect of the present invention, a conversion circuit is provided, which is used to convert an input voltage to provide an output voltage, wherein the input voltage and the output voltage both include a first end and a second end, and the second end of the input voltage is connected to the second end of the output voltage, and the conversion circuit includes:

[0032] A full-wave rectifier circuit, comprising a first branch and a second branch connected in parallel between the first end and the second end of the output voltage, the first branch comprising a first secondary winding of a transformer and a first rectifier switch connected in series to form a first midpoint, and the second branch comprising a second secondary winding of the transformer and a second rectifier switch connected in series to form a second midpoint;

[0033] a first switch branch, connected between the first end of the input voltage and the first midpoint, and comprising a first switch, a second switch, a third switch and a fourth switch connected in series, wherein the first switch and the second switch are connected to form a first connection point, 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;

[0034] A first resonance unit;

[0035] The multiple primary windings of the transformer include a first primary winding and a second primary winding, the first primary winding and the first resonant unit are connected in series and electrically connected between the first connection point and the second midpoint, and the second primary winding is electrically connected between the third connection point and the second midpoint; and

[0036] A first capacitor is connected between the second connection point and the first midpoint.

[0037] According to another aspect of the present invention, a conversion circuit is provided, which is used to convert an input voltage to provide an output voltage, wherein the input voltage and the output voltage both include a first end and a second end, and the second end of the input voltage is connected to the second end of the output voltage, and the conversion circuit includes:

[0038] A full-wave rectifier circuit, comprising n branches connected in parallel between the first end and the second end of the output voltage, each of the n branches comprising a secondary winding of a transformer and a rectifier switch connected in series to form a midpoint, the n branches comprising at least one first-type branch and at least one second-type branch, the like-named ends of the secondary windings of the first-type branches being connected, and the opposite-named ends of the secondary windings of the first-type branches and the secondary windings of the second-type branches being connected;

[0039] A first switch branch comprises m switches connected in series, wherein adjacent switches among the m switches are connected to form a connection point;

[0040] (m-1) conversion branches, each conversion branch comprising a capacitor, a (2y-1)th conversion branch among the (m-1) conversion branches connected between a connection point between a (2y-1)th switch and a 2yth switch among the m switches and a midpoint of one of the at least one second-type branches, and a 2zth conversion branch among the (m-1) conversion branches connected between a connection point between a 2zth switch and a (2z+1)th switch among the m switches and a midpoint of one of the at least one first-type branches; and

[0041] The first primary winding of the transformer is connected in series with one of the (m-1) conversion branches.

[0042] Wherein, m, n, y and z are integers, m≥n≥2, m≥3, 1≤y≤m / 2 and 1≤z≤(m-1) / 2.

[0043] According to another aspect of the present invention, a conversion circuit is provided, which is used to convert an input voltage to provide an output voltage, wherein the input voltage and the output voltage both include a first end and a second end, and the second end of the input voltage is connected to the second end of the output voltage, and the conversion circuit includes:

[0044] A first full-wave rectifier circuit, comprising a first branch and a second branch connected in parallel between the first end and the second end of the output voltage, the first branch comprising a first winding of a transformer and a first rectifier switch connected in series to form a first midpoint, and the second branch comprising a second winding of the transformer and a second rectifier switch connected in series to form a second midpoint;

[0045] A first switch branch connected between the first end of the input voltage and the first midpoint, and comprising a first switch and a second switch connected in series to form a first connection point; and

[0046] The first resonance unit is connected between the first connection point and the second midpoint, wherein the first resonance unit is not connected in series with the winding of the transformer.

[0047] According to another aspect of the present invention, a conversion circuit is provided, which is used to convert an input voltage to provide an output voltage, wherein the input voltage and the output voltage both include a first end and a second end, and the second end of the input voltage is connected to the second end of the output voltage, and the conversion circuit includes:

[0048] A full-wave rectifier circuit, comprising n branches connected in parallel between the first end and the second end of the output voltage, each of the n branches comprising a winding of a transformer forming a midpoint and a rectifier switch connected in series, the n branches comprising at least one first-type branch and at least one second-type branch, the windings of the transformers of the first-type branches having like-name ends connected, and the windings of the transformers of the first-type branches and the windings of the transformers of the second-type branches having different-name ends connected;

[0049] A first switch branch comprises m switches connected in series, wherein adjacent switches among the m switches are connected to form a connection point; and

[0050] (m-1) conversion branches, each conversion branch comprising a capacitor, a (2y-1)th conversion branch among the (m-1) conversion branches connected between a connection point between a (2y-1)th switch and a 2yth switch among the m switches and a midpoint of one of the at least one second-type branches, a 2zth conversion branch among the (m-1) conversion branches connected between a connection point between a 2zth switch and a (2z+1)th switch among the m switches and a midpoint of one of the at least one first-type branches,

[0051] Wherein, when the i-th conversion branch among the (m-1) conversion branches is a non-resonant unit, the (i-1)-th conversion branch and the (i+1)-th conversion branch among the (m-1) conversion branches are both resonant units, m, n, y, i and z are integers, m≥n≥2, 1≤y≤m / 2, m≥4, i≤m-2 and 1≤z≤(m-1) / 2. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to enable the above features described herein to be understood in detail, a more specific description briefly summarized above may be referred to the embodiments. The accompanying drawings relate to embodiments of the present disclosure and are described below:

[0053] Figure 1 A circuit example of a conventional STC is shown.

[0054] Figure 2 An example circuit of a conversion circuit according to the first embodiment of this document is shown.

[0055] Figure 3A Shows Figure 1 Deformation of the circuit.

[0056] Figure 3B Shows Figure 3A Waveform diagram of electrical signals in a circuit.

[0057] Figure 3C Shows Figure 3A Schematic diagram of current flow in a circuit during half a working cycle.

[0058] Figure 4 Shows Figure 1 Deformation of the circuit.

[0059] Figure 5 Shows Figure 1 Deformation of the circuit.

[0060] Fig. 6A and Figure 6B Shows Figure 1 Deformation of the circuit.

[0061] Figure 7 Shows Figure 1 Deformation of the circuit.

[0062] Figure 8 Shows Figure 1 Deformation of the circuit.

[0063] Fig. 9 Shows Figure 1 Deformation of the circuit.

[0064] Fig. 10A and Fig. 10B Shows Figure 1 Deformation of the circuit.

[0065] Figures 11A to 11C Shows Figure 1 Deformation of the circuit.

[0066] Fig.12 Shows Figure 1 Deformation of the circuit.

[0067] Fig.13A An example circuit of a conversion circuit according to the second embodiment of this document is shown. Fig. 13B Shows Fig.13A Waveform diagram of electrical signals in a circuit.

[0068] Fig. 13C Shows Fig.13A Schematic diagram of current flow in a circuit during half a working cycle.

[0069] Fig.14 Shows Fig.13A Deformation of the circuit.

[0070] Fig.15 Shows Fig.13A Deformation of the circuit.

[0071] Fig.16A and Fig. 16B Shows Fig.13A Deformation of the circuit.

[0072] Fig.17 Shows Fig.13A Deformation of the circuit.

[0073] Fig.18 Shows Fig.13A Deformation of the circuit.

[0074] Fig.19 Shows Fig.13A Deformation of the circuit.

[0075] Fig. 20A and Fig. 20B Shows Fig.13A Deformation of the circuit.

[0076] FIG. 21A to FIG. 21D Shows Fig.13A Deformation of the circuit.

[0077] Fig. 22 Shows Fig.13A Deformation of the circuit.

[0078] Fig.23 An example circuit of a conversion circuit according to the third embodiment of this document is shown.

[0079] Fig.24 Shows Fig.23 Deformation of the circuit.

[0080] Fig.25 Shows Fig.23 Deformation of the circuit.

[0081] Fig.26 Shows Fig.23 Deformation of the circuit.

[0082] Fig. 27 Shows Fig.23 Deformation of the circuit.

[0083] Fig.28 Shows Fig.23 Deformation of the circuit.

[0084] Fig.29 Shows Fig.23 Deformation of the circuit.

[0085] Fig.30 Shows Fig.23 Deformation of the circuit.

[0086] Fig.31 Shows Fig.23 Deformation of the circuit.

[0087] Fig.32 Shows Fig.23 Deformation of the circuit.

[0088] Fig.33 Shows Fig.23 Deformation of the circuit.

[0089] Fig.34A and Fig.34B Shows Fig.23 Deformation of the circuit.

[0090] Fig.35 Shows Fig.23 Deformation of the circuit.

[0091] FIG. 36A to FIG. 36C Shows Fig.23 Deformation of the circuit.

[0092] Fig.37 A comparison of winding losses between a conversion circuit according to an embodiment of the present invention and a conventional conversion circuit is shown. DETAILED DESCRIPTION

[0093] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, and will be described in the following order.

[0094] [First embodiment]

[0095] [Modification of the first embodiment]

[0096] [Second Embodiment]

[0097] [Variation of the Second Embodiment]

[0098] [Third Embodiment]

[0099] [Variation of the Third Embodiment]

[0100] One or more examples of each embodiment of this invention are shown in the accompanying drawings. In the following description of the drawings, the same reference numerals indicate the same or similar parts. In the following, only the differences related to individual embodiments are described. Each example is provided to illustrate the technical solution of this invention and is not intended to limit the subject matter claimed for protection herein. In addition, the features illustrated or described 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 include such modifications and changes.

[0101] [First embodiment]

[0102] See also Figure 2 , Figure 2 FIG. 1 is a diagram showing an example circuit of a conversion circuit 10 according to a first embodiment of the present invention. The circuit 10 receives an input voltage Vin, converts the input voltage Vin, and outputs the converted voltage.

[0103] The circuit 10 includes a full-bridge rectifier circuit 11 composed of rectifier tubes SR1, SR2, SR3 and SR4, a switch branch 12 composed of switches S1 and S2, a resonant unit 13 composed of a resonant capacitor Cr and a resonant inductor Lr, and a transformer Tr composed of a primary winding Tr1 and a secondary winding Tr2.

[0104] The input voltage and the output voltage each have a first terminal and a second terminal. The second terminal of the input voltage is connected to the second terminal of the output voltage, such as Figure 2 The switch branch 12 is connected between the first end of the input voltage and the first end of the output voltage, and the switch branch 12 includes switches S1 and S2, which are connected in series to form a connection point p1. The full-bridge rectifier circuit 11 is connected between the first end and the second end of the output voltage. The rectifier tubes SR1 and SR2 in the full-bridge rectifier circuit 11 are connected in series to form a first bridge arm, and the rectifier tubes SR3 and SR4 are connected in series to form a second bridge arm.

[0105] In an example of the circuit 10, the circuit 10 may include an output capacitor Co for output filtering, the output capacitor Co is connected between the first end and the second end of the output voltage, and is connected in parallel with the first bridge arm and the second bridge arm of the full-bridge rectifier circuit 11. Additionally, the circuit 10 may also include an input capacitor Cin for input filtering, the input capacitor Cin may be connected between the first end and the second end of the input voltage, or the input capacitor Cin may also be connected between the first end of the input voltage and the first end of the output voltage, such as Figure 2 The input capacitor Cin is shown by the dotted line.

[0106] In the circuit 10, the resonance unit 13 includes a resonance capacitor Cr and a resonance inductor Lr connected in series, and one end of the resonance unit 13 is connected to the connection point p1, and the other end of the resonance unit 13 is connected to one end of the primary winding Tr1. The other end of the primary winding Tr1 is connected to the midpoint m1 of the first bridge arm of the full-bridge rectifier circuit 11. The secondary winding Tr2 is connected between the midpoint m1 of the first bridge arm and the midpoint m2 of the second bridge arm. In some embodiments, the positions of the resonance unit 13 and the primary winding Tr1 can be interchanged. It is sufficient to ensure that the resonance unit 13 and the primary winding Tr1 are connected in series.

[0107] The working state of the circuit 10 is described below. In a working cycle of the circuit 10, in the first half of a working cycle, the switch S2 and the rectifiers SR1 and SR4 are turned on, and the switch S1 and the rectifiers SR2 and SR3 are turned off. In the second half of a working cycle, the switch S1 and the rectifiers SR2 and SR3 are turned on, and the switch S2 and the rectifiers SR1 and SR4 are turned off. Therefore, the duty cycle of the switches S1 and S2 and the rectifiers SR1, SR2, SR3 and SR4 is 0.5.

[0108] In the first half of a working cycle, the current flows from the input end to the output end through the first path formed by the switch S2, the resonant capacitor Cr, the resonant inductor Lr, the primary winding Tr1 and the rectifier SR1. At this time, the resonant frequency is Therefore, the input end directly provides energy to the output end through the first path. At the same time, the secondary winding Tr2 senses the resonant current in the primary winding Tr1, and provides energy to the output end through the second path formed by SR1 and SR4. In the half cycle after the conversion from the first half cycle, the parasitic capacitance of S2, SR1, and SR4 is charged by the excitation inductor current and the parasitic capacitance of S1, SR2, and SR3 is discharged, thereby realizing the soft switching of the device. In the second half of a working cycle, similar to the first half cycle, the current provides energy to the output end through the third path formed by the rectifier tube SR2, the primary winding Tr1, the resonant capacitor Cr, the resonant inductor Lr, and the switch S1. At the same time, the secondary winding Tr2 senses the resonant current in the primary winding Tr1, and provides energy to the output end through the fourth path formed by SR2 and SR3.

[0109] Assuming that the current at the input end is i, in one working cycle, the equivalent current in the resonant unit 13 is 2i, so the transformer Tr 1 The primary current is also 2i, and this current flows directly to the output terminal. At the same time, when the transformer Tr 1 When the turns ratio is N:1, the secondary induced current of the transformer Tr is 2Ni. Therefore, the total current flowing to the output end is (2N+2)i. As for the input end, since only half of the resonant cycle of the current flows through S1, the current on the input side is half of the equivalent current of the resonant unit 13, that is, i. Therefore Figure 2 The voltage conversion ratio of the circuit shown (i.e., the ratio of the input voltage to the output voltage of the circuit) is (2N+2):1, where 2N is the conversion ratio brought about by the transformer turns ratio, and 2 is caused by the fact that the current flowing through the primary winding of the transformer flows directly to the output terminal.

[0110] In a conventional STC with only two switches, the voltage conversion ratio is only 2. For circuit 10, the voltage conversion ratio is (2N+2):1, so the voltage conversion ratio of the circuit is improved, and the number of primary turns of the transformer can be reduced at the same voltage conversion ratio, thereby improving the utilization efficiency of the transformer. At the same time, the current flowing through the primary winding of the transformer in the circuit directly flows to the output end, which is 2. This part of the current does not need to be generated by transformer induction, further reducing the loss and volume of the transformer.

[0111] Although the resonance unit 13 in the circuit 10 is composed of a resonance capacitor Cr and a resonance inductor Lr connected in series, the invention is not limited thereto. For example, the resonance unit 13 may also be composed of a resonance capacitor Cr and a resonance inductor Lr connected in parallel.

[0112] [Modification of the first embodiment]

[0113] The above describes an example of the conversion circuit of the first embodiment of the present invention, however, the conversion circuit according to the first embodiment of the present invention may have various variations. The following describes various variations of the full-bridge rectifier conversion circuit 10, and only describes the differences between the various variations and the conversion circuit 10, and the same parts are not repeated.

[0114] Figure 3A A schematic diagram of a conversion circuit 20 according to a modification of the first embodiment of the present invention is shown.

[0115] like Figure 3A As shown, the circuit 20 includes a full-bridge rectifier circuit 21 composed of rectifier tubes SR1, SR2, SR3 and SR4, a switch branch 22 composed of switches S1, S2, S3 and S4, a resonance unit 23 composed of a resonant capacitor Cr1 and a resonant inductor Lr1, a resonance unit 24 composed of a resonant capacitor Cr2 and a resonant inductor Lr2, a transformer composed of a primary winding Tr1 and a secondary winding Tr2, and a capacitor C1.

[0116] The input voltage and the output voltage each have a first end and a second end, wherein the second ends of the input voltage and the output voltage are connected. The switch branch 22 is connected between the first ends of the input voltage and the output voltage, and the switch branch 22 includes switches S1, S2, S3 and S4 connected in series. The full-bridge rectifier circuit 21 is connected between the first end and the second end of the output voltage. The rectifier tubes SR1 and SR2 in the full-bridge rectifier circuit 21 constitute a first bridge arm, and the rectifier tubes SR3 and SR4 constitute a second bridge arm.

[0117] The resonance unit 23 includes a resonance capacitor Cr1 and a resonance inductor Lr1 connected in series, and the resonance unit 23 is connected in series with the primary winding Tr1. The resonance unit 24 includes a resonance capacitor Cr2 and a resonance inductor Lr2 connected in series, and the resonance unit 24 is also connected in series with the primary winding Tr1. Here, it should be noted that the "series connection" used in this article not only indicates the situation in which the current flowing through the series electronic components is equal after the series connection between two electronic components in a general sense, but also generally refers to the situation where two electronic components are connected to form a common connection point. For example, for Figure 3A In the case where one end of the resonant unit 23 is connected to the connection point p1 between the switches S1 and S2 and the other end of the resonant unit 23 is connected to one end of the primary winding Tr1, it is considered that the resonant unit 23 and the primary winding Tr1 are connected in series; similarly, for Figure 3AIn the case where one end of the resonant unit 24 is connected to the connection point p3 between the switches S3 and S4, and the other end of the resonant unit 24 is connected to one end of the primary winding Tr1, the resonant unit 24 and the primary winding Tr1 are also considered to be connected in series. Although the currents flowing through the resonant units 23, 24 and the primary winding Tr1 in the resonant units 23, 24 and the primary winding Tr1 connected in this way are not equal, this article still describes that the resonant unit 23 and the primary winding Tr1 are connected in series, and the resonant unit 24 and the primary winding Tr1 are connected in series. The other end of the primary winding Tr1 is connected to the midpoint m1 of the first bridge arm of the full-bridge rectifier circuit 21. The secondary winding Tr2 is connected between the midpoint m1 of the first bridge arm and the midpoint m2 of the second bridge arm. One end of the capacitor C1 is connected to the connection point p2 between the switches S2 and S3, and the other end is connected to the midpoint m2 of the second bridge arm.

[0118] See also Figure 3B and Figure 3C The operation of the circuit 20 is described. Figure 3B 1 shows the change of current or voltage in each element in one working cycle of the circuit 20. Among them, iLr represents the current of each of the resonance unit 23 and the resonance unit 24, iLm represents the current of the excitation inductance on the transformer, Vs1 and Vs3 represent the voltage across the switches S1 and S3, and isr1, isr2, isr3 and isr4 represent the current in the rectifier tubes SR1, SR2, SR3 and SR4. Figure 3C An example of current flow in the first half of a circuit's operating cycle is shown.

[0119] t0-t4 represents a working cycle of the circuit 20. In the circuit 20, the switches S4, S2 and the rectifiers SR1, SR4 are turned on at the same time, and the switches S3, S1 and the rectifiers SR2, SR3 are turned on in a complementary and symmetrical manner, with a duty cycle close to 0.5. The complementary and symmetrical conduction here means that the conduction time of the positive half-cycle switch tube in the circuit is basically the same as the conduction time of the negative half-cycle switch tube. Figure 3A Taking the circuit in the figure as an example, the time period t0~t2 is the first half of the working cycle, and the time period t2~t4 is the second half of the working cycle, where t0~t1 and t2~t3 are the time periods when the switch tube is turned on in the positive and negative half cycles respectively. These two time periods are basically the same, that is, symmetrical conduction, that is, (t1-t0)=(t3-t2). In the time period t0~t1, switches S4, S2 and rectifier tubes SR1 and SR4 are turned on, while switches S3, S1 and rectifier tubes SR2 and SR3 are turned off. At this time, the current flows through switch S4, resonant capacitor Cr2, resonant inductor Lr2, transformer primary winding Tr1 and rectifier tube SR1 to form the first resonant path, and the resonant frequency is The input end provides energy to the output end through the first path. The voltage on the DC blocking capacitor C1 is 0.5Vin, and the rectifier SR4, switch S2, resonant capacitor Cr1, resonant inductor Lr1, transformer primary winding Tr1 and rectifier SR1 form a resonant second path with a resonant frequency of Energy is provided to the output end by capacitor C1. At the same time, the secondary winding Tr2 of the transformer further senses the resonant current of the primary winding Tr1, and provides energy to the output end through the third path formed by the rectifier tubes SR4 and SR1. Among them, the resonant capacitors Cr1 and Cr2 act as resonant elements and also play the role of DC isolation capacitors. The DC voltage on the resonant capacitor Cr1 is 0.75Vin, and the voltage on the resonant capacitor Cr2 is 0.25Vin. The excitation voltages at both ends of the resonant units 23 and 24 are the same, and the resonant frequencies are consistent (i.e., fr1=fr2). At this time, the currents of the two resonant units are consistent and flow to the primary side of the transformer together. During the time t1~t2, the parasitic capacitances of switches S4, S2 and rectifier tubes SR1, SR4 are charged by the excitation inductor current, and the parasitic capacitances of switches S3, S1 and rectifier tubes SR2, SR3 are discharged, thereby realizing soft switching. The time period from t2 to t4 is the second half of the working cycle. In the time period from t2 to t3, switches S3, S1 and rectifiers SR2 and SR3 are turned on, and switches S4, S2 and rectifiers SR1 and SR4 are turned off. At this time, the first path formed by rectifier SR2, transformer primary winding Tr1, resonant inductor Lr2, resonant capacitor Cr2, switch S3, capacitor C1 and rectifier SR3 provides energy to the output end. The second path formed by rectifier SR2, transformer primary winding Tr1, resonant inductor Lr1, resonant capacitor Cr1 and switch S1 provides energy to the output end. Finally, the transformer secondary winding Tr2 senses the current on the primary side, and the third path formed by rectifiers SR2 and SR3 provides energy to the output end. During the time period from t3 to t4, the parasitic capacitance of switches S3, S1 and rectifiers SR2, SR3 is charged by the magnetizing inductor current and the parasitic capacitance of switches S4, S2 and rectifiers SR1, SR4 is discharged, thereby realizing soft switching.

[0120] Assuming that the current at the input end is i, then in one working cycle of circuit 20, the equivalent currents of resonant units 23 and 24 are 2i respectively, and the equivalent current of the primary side of the transformer is 4i, and this current flows directly to the output end. At the same time, when the turns ratio of the transformer is N:1, the current induced on the secondary side of the transformer is 4Ni, so the total current flowing to the output is (4N+4)i. As for the input end, since only the current of half a resonant cycle flows through switch S4, the current on the input side is half of the current of the resonant unit, that is, i. Therefore, the voltage conversion ratio of circuit 20 is (4N+4):1, where 4N is the conversion ratio brought by the turns ratio of the transformer, and 4 is caused by the current flowing through the primary winding of the transformer flowing directly to the output end. Therefore, the conversion ratio of this circuit is very high. At the same voltage conversion ratio, the number of primary turns of the transformer can be reduced, thereby improving the utilization efficiency of the transformer. At the same time, the current flowing through the primary winding of the transformer in this circuit flows directly to the output end as 4. This part of the current does not need to be generated by transformer induction, further reducing the loss and volume of the transformer.

[0121] The resonant capacitor Cr1 and the resonant inductor Lr1 in the resonant unit 23 and the resonant capacitor Cr2 and the resonant inductor Lr2 in the resonant unit 24 are two sets of resonant parameters with the same resonant frequency, and the two sets of parameters may be the same or different. The switches S1 to S4 connected in series may be formed by connecting a plurality of switch elements in series to reduce the voltage stress of a single switch, or may be formed by connecting a plurality of switch elements in parallel to increase the current carrying capacity of the switch unit.

[0122] Figure 4 The circuit 30 is for Figure 3A In the circuit 30, a part of each of the resonant inductors Lr1 and Lr2 is combined into a common inductor Lrc ​​shared by the two resonant units, and the common inductor Lrc ​​is connected in series with the primary side of the transformer. The resonant frequency at this time is:

[0123]

[0124] The advantage of doing this is that the leakage inductance of the transformer can be utilized to reduce the inductance required for the resonant inductor, thereby reducing the use of components and reducing the size of the converter.

[0125] Figure 5 The circuit 40 is for Figure 3A In the circuit 40, when the parameters of the two resonant units are the same, the resonant inductors of the two resonant units can be combined into a common inductor Lrc ​​shared by the two resonant units, and the common inductor Lrc ​​is connected in series with the primary side of the transformer, and the capacitance of the resonant capacitors Cr1 and Cr2 is the same. The resonant frequency at this time is The circuit 40 works in the DC transformer mode. The circuit operates at a fixed operating frequency. The leakage inductance requirement is very small. The leakage inductance of the transformer can be directly used as the common resonant inductor Lrc, which reduces the number and volume of components used.

[0126] Fig. 6A The circuit 50 is for Figure 3A A further variation of the circuit 20 in FIG. Figure 3A In the case where the resonant units 23 and 24 in the circuit 20 share a primary winding Tr1, in the circuit 50, the transformer has two primary windings Tr11 and Tr12 for the resonant units, respectively, and a secondary winding Tr2. The turns ratio of Tr11, Tr12 and Tr2 may be, for example, N:N:1. Fig. 6A As shown, one end of the primary winding Tr11 is connected to a resonant unit composed of a resonant capacitor Cr1 and a resonant inductor Lr1, and the other end is connected to the midpoint m1 of the first bridge arm. One end of the primary winding Tr12 is connected to another resonant unit composed of a resonant capacitor Cr2 and a resonant inductor Lr2, and the other end is connected to the midpoint m1 of the first bridge arm. The secondary winding Tr2 of the transformer Tr is connected between the midpoint m1 of the first bridge arm and the midpoint m2 of the second bridge arm. In some embodiments, the positions of the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1 and the primary winding Tr11 can be interchanged. It is sufficient to ensure that the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1 and the primary winding Tr11 are connected in series. Similarly, the positions of the resonant unit composed of the resonant capacitor Cr2 and the resonant inductor Lr2 and the primary winding Tr12 can be interchanged. It is sufficient to ensure that the resonant unit composed of the resonant capacitor Cr2 and the resonant inductor Lr2 and the primary winding Tr12 are connected in series.

[0127] Figure 6B The circuit 50' is for Figure 3A A further variation of the circuit 20 in FIG. Figure 3A The case where the resonant units 23 and 24 share a primary winding Tr1 in the circuit 20 may also be Figure 6B The two primary windings Tr11 and Tr12 shown in the figure share a resonance unit. In the circuit 50', the transformer has two primary windings Tr11 and Tr12, and a secondary winding Tr2. The turns ratio of Tr11, Tr12 and Tr2 can be, for example, N:N:1. One end of the primary winding Tr11 is connected to the connection point p3, one end of the primary winding Tr12 is connected to the connection point p1, and the other ends of the primary windings Tr11 and Tr12 are commonly connected to one end of a resonance unit composed of a resonance inductor Lr and a resonance capacitor Cr, and the other end of the resonance unit is connected to the midpoint m1 of the first bridge arm.

[0128] exist Fig. 6A and 6B In the circuit, the leakage inductance of the transformer can also be used as part or all of the resonant inductance of the resonant unit to reduce circuit elements.

[0129] Figure 7 The circuit 60 is a Figure 3A A further variation of the circuit 20 in FIG. 60. In the circuit 60, when the parameters of the resonant capacitor Cr1 and the resonant inductor Lr1 in the resonant unit 63 are the same as those of the resonant capacitor Cr2 and the resonant inductor Lr2 in the resonant unit 64, the resonant capacitor Cr3 and the resonant inductor Lr3 having the same parameters as those of the resonant units 63 and 64 can be used to replace the single DC blocking capacitor connected to the connection point p2 between the switches S2 and S3 to form the resonant unit 65. The resonant capacitor Cr3 not only plays the role of a DC blocking capacitor, but also participates in the circuit resonance together with the resonant inductor Lr3.

[0130] Figure 8 The circuit 70 is for Figure 3A A further variation of the circuit 20 in FIG. 70. In the circuit 70, the output capacitor Co connected in parallel with the first bridge arm and the second bridge arm of the full-bridge rectifier circuit of the circuit 70 can be used as the resonant capacitor Cr shared by the two resonant units. In this case, the resonant unit connected between the connection point of the switch branch and the midpoint m1 of the first bridge arm can only include the resonant inductor.

[0131] Therefore, in the circuit 70, the resonant capacitor Cr is shared by the resonant inductors Lr1 and Lr2, the resonant capacitor Cr resonates with the resonant inductor Lr1 as one resonant unit, and the resonant capacitor Cr resonates with the resonant inductor Lr2 as another resonant unit. The circuit 70 can achieve the same circuit effect and simplifies the circuit configuration. Although the resonant inductor Lr2 is connected in series with the capacitor C2 and the resonant inductor Lr1 is connected in series with the capacitor C3, as shown in FIG. Figure 8 As shown, however, the capacitors C2 and C3 are mainly used as DC blocking capacitors, and the capacitors C2 and C3 can be omitted.

[0132] The transformer in the circuit can also be further split into two independent transformers. Fig. 9 The circuit 80 is a Figure 3AA further variation of the circuit 20 in the circuit 80. In the circuit 80, the full-bridge rectifier circuit may further include a third bridge arm composed of rectifier tubes SR5 and SR6. The third bridge arm is connected in parallel with the first bridge arm composed of rectifier tubes SR1 and SR2 and the second bridge arm composed of rectifier tubes SR3 and SR4. The circuit 80 includes a first transformer Tr and a second transformer Tr', and the turns ratio of the primary winding and the secondary winding is N:1. One end of the primary winding Tr11 of the first transformer Tr is connected to one end of the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1, and the other end is connected to the midpoint m1 of the first bridge arm, and the secondary winding Tr21 of the first transformer Tr is connected between the midpoint m1 of the first bridge arm and the midpoint m2 of the second bridge arm. One end of the primary winding Tr12 of the second transformer Tr' is connected to one end of another resonant unit composed of a resonant capacitor Cr2 and a resonant inductor Lr2, and the other end is connected to the midpoint m3 of the third bridge arm, and the secondary winding Tr22 of the second transformer Tr' is connected between the midpoint m2 of the second bridge arm and the midpoint m3 of the third bridge arm. In some embodiments, the positions of the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1 and the primary winding Tr11 can be interchanged. It is sufficient to ensure that the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1 and the primary winding Tr11 are connected in series.

[0133] The advantage of circuit 80 is that it can reduce the current stress of a single transformer and a single rectifier tube, or in other words, increase the current carrying capacity of the transformer and SR when using the same components, thereby increasing the output power of the converter.

[0134] The conversion circuit in this paper can be further extended to change the voltage conversion ratio. Fig. 10A An extended form of the conversion circuit in this article is shown. Fig. 10A The circuit 90 shown is for Figure 2 In the circuit 90, the switch branch 92 not only includes the original two switches S1-S2, but also further expands to (2m-2) switches (S3, S4...S 2m-1 , S 2m ). Expanded (2m-2) switches (S3, S4…S 2m-1 , S 2m ) are connected in series with the original two switches S1 and S2, so that the switch branch 92 includes 2m switches connected in series, that is, an even number of switches, where m is an integer and m≥2.

[0135] The circuit 90 further includes (m-1) DC blocking capacitors Cx and (m-1) resonant units 94. The (m-1) resonant units 94 and the original resonant unit 93 make the circuit 90 have m resonant units. The m resonant units are all connected in series with the primary winding Tr1. The resonant units 94 each include a resonant capacitor Crx and a resonant inductor Lrx.

[0136] Therefore, for Fig. 10A The conversion circuit of the circuit 90 can be described as follows: the switch branch 92 has 2m switches connected in series, where m is an integer and m≥2. Two adjacent switches among the 2m switches are connected to form a connection point, so there are (2m-1) connection points.

[0137] Considering the connection point close to the output terminal of the circuit 90 as the first connection point, the switch branch 92 has connection points No. 1, 2, 3, ..., (2m-2), (2m-1) from the output terminal to the input terminal. Fig. 10A As shown, the connection point between switches S1 and S2 is closest to the output terminal, so the connection point between switches S1 and S2 is connection point 1 ( Fig. 10A The connection point between switch S2 and the next switch S3 adjacent to switch S2 is connection point No. 2, and so on. 2m-1 and S 2m The connection point between them is the (2m-1)th connection point.

[0138] Each of the m resonant units is connected between an odd-numbered connection point and the primary winding Tr1 of the transformer, and each of the (m-1) DC blocking capacitors Cx is connected between an even-numbered connection point and the midpoint m2 of the second bridge arm.

[0139] Among the above m resonance units, one end of the xth resonance unit is connected to a connection point of the (2x-1)th switch and the 2xth switch among the 2m switches, where x is an integer and 1≤x≤m.

[0140] For example, when x=1, for the first (x) resonance unit of m resonance units ( Fig. 10A The resonant unit 93 in the embodiment has one end connected to the first (2x-1) switch ( Fig. 10A The switch S1 in the Fig. 10A The other end is connected to the primary winding Tr1 of the transformer. For another example, when x=m, for the m(x)th resonant unit ( Fig. 10A The resonant unit 94 in the embodiment has one end connected to the 2m-1(2x-1)th switch ( Fig. 10A Switch S in 2m-1 ) and the 2m(2x)th switch ( Fig. 10A Switch S in 2m ), and the other end is connected to the primary winding Tr1 of the transformer.

[0141] Among the above-mentioned (m-1) DC blocking capacitors Cx, one end of the kth DC blocking capacitor is connected to the connection point of the 2kth switch and the 2k+1th switch among the 2m switches, and the other end is connected to the midpoint m2 of the second bridge arm, where k is an integer and 1≤k≤m-1.

[0142] For example, when k = 1, the first (k) DC blocking capacitor ( Fig. 10A One end of the DC blocking capacitor Cx in the circuit is connected to the second (2k) switch ( Fig. 10A The switch S2 in the Fig. 10A The other end is connected to the middle point m2 of the second bridge arm. For another example, when k=(m-1), the (m-1)(k)th DC blocking capacitor ( Fig. 10A One end of the switch (not shown) is connected to the (2m-2)(2k)th switch ( Fig. 10A The AND switch S 2m-1 The adjacent previous switch, not shown) and the (2m-1)(2k+1)th switch ( Fig. 10A Switch S in 2m-1 ) and the other end is connected to the midpoint m2 of the second bridge arm. Fig. 10A The conversion ratio of the circuit 90 is (2mN+2m):1, where N is the turns ratio of the primary winding and the secondary winding of the transformer Tr. Thus, the conversion ratio of the conversion circuit is expanded.

[0143] Although Fig. 10A The circuit 90 shows the situation where m resonant units are connected in series with a single primary winding Tr1, as shown in FIG. Fig. 6A As described above, the primary winding Tr1 may also be composed of a plurality of sub-windings, and each sub-winding is respectively connected in series with a corresponding resonant unit among the m resonant units.

[0144] It can be seen that for Figure 3A The circuit 20 in FIG. 1 can be regarded as Figure 2 The circuit 10 in FIG. 1 is expanded by a pair of switches, a DC blocking capacitor and a resonant unit.

[0145] Similar to Figure 6B The content described, compared to Fig. 10A The m resonance units shown in FIG. 1 are connected in series to a common primary winding Tr1, or a plurality of primary windings may share one resonance unit, such as Fig. 10B The circuit 90' is shown.

[0146] In the circuit 90', the switch branch 92 not only includes the original two switches S1 and S2, but also further expands to include (2m-2) switches (S3, S4...S 2m-1 , S 2m ). Expanded (2m-2) switches (S3, S4…S 2m-1 , S 2m ) are connected in series with the original two switches S1 and S2, so that the switch branch 92 includes 2m switches connected in series, that is, an even number of switches, where m is an integer and m≥2. The circuit 90' further includes (m-1) DC blocking capacitors Cx and m primary windings Tr1. The m primary windings Tr1 are all connected in series with the resonant unit composed of the resonant inductor Lr and the resonant capacitor Cr.

[0147] In the circuit 90', two adjacent switches among the 2m switches of the switch branch 92 are connected to form a connection point, so there are (2m-1) connection points. The connection point close to the output end of the circuit 90' is regarded as the first connection point, and the switch branch 92 has connection points No. 1, 2, 3, ..., (2m-2), (2m-1) from the output voltage end to the input end. For example, Fig. 10B As shown, the connection point between switches S1 and S2 is closest to the output terminal, so the connection point between switches S1 and S2 is connection point 1 ( Fig. 10B The connection point between switch S2 and the next switch S3 adjacent to switch S2 is connection point No. 2, and so on. 2m-1 and S 2m The connection point between them is the (2m-1)th connection point.

[0148] Each of the m primary windings Tr1 is connected between an odd-numbered connection point and the resonant unit, and each of the (m-1) DC blocking capacitors Cx is connected between an even-numbered connection point and the midpoint m2 of the second bridge arm.

[0149] In the above-mentioned m primary windings Tr1, one end of the xth primary winding is connected to the connection point of the (2x-1)th switch and the 2xth switch among the 2m switches, where x is an integer and 1≤x≤m.

[0150] Among the above-mentioned (m-1) DC blocking capacitors Cx, one end of the kth DC blocking capacitor is connected to the connection point of the 2kth switch and the 2k+1th switch among the 2m switches, and the other end is connected to the midpoint m2 of the second bridge arm, where k is an integer and 1≤k≤m-1.

[0151] Fig.11A Another extended form of the conversion circuit of the present application is shown. Fig.11A The circuit 100 is for Figure 2Another expansion of the circuit 10 in the circuit 100. The switch branch 102 of the circuit 100 not only includes the original two switches S1-S2, but also further expanded with (m-2) switches (S3, ..., Sm). The expanded (m-2) switches (S3, ..., Sm) are connected in series with the original two switches S1-S2, so that the switch branch 102 includes m switches connected in series, where m is an integer and m≥3. The circuit 100 further includes (m-2) resonant units. Therefore, the (m-2) resonant units 104 and the resonant unit 103 together constitute (m-1) resonant units. The resonant unit 104 includes a resonant capacitor Crx and a resonant inductor Lrx. Each resonant unit (resonant unit 103 and resonant unit 104) in the circuit 100 has the same resonant parameters.

[0152] Specifically, therefore, for Fig.11A The conversion circuit of the circuit 100 can be described as follows: the switch branch 102 has m switches connected in series, where m is an integer and m≥3. Two adjacent switches among the m switches are connected to form a connection point, so there are (m-1) connection points. The connection point close to the output end of the circuit 100 is regarded as the first connection point, and the switch branch 102 has the first, second, third, ..., m-1 connection points from the output end to the input end. For example, Fig.11A As shown, the connection point of switches S1 and S2 is closest to the output terminal, so the connection point of switches S1 and S2 is connection point 1 ( Fig.11A The connection point of switches S2 and S3 is connection point 2 ( Fig.11A Marked as "②"), switch S3 and switch S4 ( Fig.11A The connection point marked as "③" in the figure is the connection point No. 3, and by analogy, the connection point between switch Sm and the switch before switch Sm is the connection point No. (m-1).

[0153] One end of each of the (m-1) resonant units (103, 104) in the circuit 100 is connected to the corresponding connection point, and the other end is connected to the primary winding Tr1 of the transformer or the midpoint m2 of the second bridge arm of the full-bridge rectifier circuit. Among them, for the resonant unit with one end connected to the odd-numbered connection point, its other end is connected to the primary winding Tr1 of the transformer. For the resonant unit with one end connected to the even-numbered connection point, its other end is connected to the midpoint m2 of the second bridge arm of the full-bridge rectifier circuit.

[0154] In the above-mentioned (m-1) resonant units, one end of the (2y-1)th resonant unit is connected to the connection point of the (2y-1)th switch and the 2yth switch among the m switches, and the other end is connected to the primary winding Tr1 of the transformer, where y is an integer and 1≤y≤m / 2.

[0155] For example, when y=1, among the (m-1) resonance units, the first (2y-1) resonance unit ( Fig.11A One end of the resonant unit 103 in the circuit is connected to the first (2y-1) switch ( Fig.11A The switch S1 in the Fig.11A The other end is connected to the connection point of the switch S2 in the transformer, and the other end is connected to the primary winding Tr1 of the transformer.

[0156] In the above-mentioned (m-1) resonant units, one end of the 2zth resonant unit is connected to the connection point of the 2zth switch and the (2z+1)th switch among the m switches, and the other end is connected to the midpoint m2 of the second bridge arm of the full-bridge rectifier circuit, where z is an integer and 1≤z≤(m-1) / 2.

[0157] For example, when z=1, among the m-1 resonance units, the second (2z) resonance unit ( Fig.11A The resonant unit 104 in 1 ) is connected to the second (2z) switch ( Fig.11A The other end is connected to the midpoint m2 of the second bridge arm of the full-bridge rectifier circuit.

[0158] The following describes the conversion ratio of the expansion circuit 100. When m is an even number, the conversion ratio of the circuit 100 is (mN+m):1, where N is the turns ratio of the primary winding and the secondary winding of the transformer Tr. It can be seen that Figure 7 The circuit 60 shown is actually Figure 2 The circuit 10 is expanded by two switches to provide a circuit example of a switch branch having an even number of switches. Figure 7 The conversion ratio of the circuit 60 is (4N+4):1 (i.e., (mN+m):1, m=4) discussed above. Thus, the conversion ratio of the conversion circuit is expanded. When m is an odd number, the conversion ratio of the circuit 100 is ((m-1)N+m):1, where N is the turns ratio of the primary winding and the secondary winding of the transformer Tr. Thus, the conversion ratio of the conversion circuit is expanded. Fig. 11B Shown in Figure 2 Based on the circuit 10, a switch branch 102' with three switches after a switch S3 is expanded to form a circuit 100'. One end of the resonance unit 103' is connected to the connection point of the switches S1 and S2, and the other end is connected to the primary winding Tr1 of the transformer. One end of the resonance unit 104' is connected to the connection point between the switches S2 and S3, and the other end is connected to the midpoint m2 of the second bridge arm of the full-bridge rectifier circuit. The conversion ratio of the circuit 100' is (2N+3):1 (that is, ((m-1)N+m):1, m=3).

[0159] Although Fig.11A and 11B The diagram shows the situation where the resonant units connected to the odd-numbered connection points among the (m-1) resonant units are all connected in series with a single primary winding Tr1. Fig. 6A As described above, the primary winding Tr1 may also be composed of a plurality of sub-windings, and each sub-winding is respectively connected in series with a corresponding resonant unit among the (m-1) resonant units connected to an odd-numbered connection point.

[0160] Similar to Figure 6B The content described, compared to Fig.11A and 11B The case where the multiple resonant units are connected in series to the common primary winding Tr1 may also be the case where multiple primary windings share one resonant unit, such as Fig. 11C The circuit 100 is shown in FIG.

[0161] The switch branch 102 of the circuit 100" not only includes the original two switches S1-S2, but also is further expanded with (m-2) switches (S3, ..., Sm). The expanded (m-2) switches (S3, ..., Sm) are connected in series with the original two switches S1-S2, so that the switch branch 102 includes m switches connected in series, where m is an integer and m≥3. The circuit 100 further includes a plurality of resonant units 104 and a plurality of primary windings Tr1. Each of the plurality of resonant units 104 includes a resonant capacitor Crx and a resonant inductor Lrx. Each of the plurality of resonant units 104 has the same resonant parameters.

[0162] In the circuit 100", the switch branch 102 has m switches connected in series, where m is an integer and m≥3. Two adjacent switches among the m switches are connected to form a connection point, so there are (m-1) connection points. The connection point close to the output end of the circuit 100 is regarded as the first connection point, and the switch branch 102 has the first, second, third, ..., m-1 connection points from the output end to the input end. For example, Fig. 11C As shown, the connection point of switches S1 and S2 is closest to the output terminal, so the connection point of switches S1 and S2 is connection point 1 ( Fig. 11C The connection point of switches S2 and S3 is connection point 2 ( Fig. 11C The connection point between switch S3 and switch S4 is connection point 3 ( Fig. 11C In the figure, it is marked as "③"). Similarly, the connection point between switch Sm and the switch before switch Sm is the (m-1)th connection point.

[0163] One end of each of the multiple primary windings Tr1 in circuit 100" is connected to an odd-numbered connection point, and the other end thereof is connected to a resonant unit composed of a resonant capacitor Cr and a resonant inductor Lr. One end of each of the multiple resonant units 104 in circuit 100" is connected to an even-numbered connection point, and the other end thereof is connected to the midpoint m2 of the second bridge arm of the full-bridge rectifier circuit.

[0164] One end of one of the above-mentioned multiple primary windings Tr1 is connected to the connection point of the (2y-1)th switch and the 2yth switch among the m switches, and the other end is connected to the resonant unit composed of the resonant capacitor Cr and the resonant inductor Lr, where y is an integer and 1≤y≤m / 2.

[0165] One end of one of the above-mentioned multiple resonant units 104 is connected to the connection point of the 2zth switch and the (2z+1)th switch among the m switches, and the other end is connected to the midpoint m2 of the second bridge arm of the full-bridge rectifier circuit, where z is an integer and 1≤z≤(m-1) / 2.

[0166] Fig.12 Shows Figure 3A A variation of circuit 20. Fig.12 In the circuit 110 shown, the circuit 110 has two switch branches 112 and 115 connected in parallel, and the switch branches 112 and 115 are respectively connected between the first end of the input voltage and the first end of the output voltage. The switch branch 112 has four switches S1-S4 connected in series, and the switch branch 115 has four switches S5-S8 connected in series. The full-bridge rectifier circuit of the circuit 110 is connected between the first end and the second end of the output voltage, and has a first bridge arm composed of rectifier tubes SR1 and SR2 connected in series, and a second bridge arm composed of rectifier tubes SR3 and SR4 connected in series. The circuit 110 has four resonant units 113, 114, 116 and 117, two DC blocking capacitors C1 and C2, and a transformer Tr. The transformer Tr has two primary windings Tr11 and Tr12, and a secondary winding Tr2. The turns ratio of Tr11, Tr12 and Tr2 is N:N:1.

[0167] The resonance unit 113 is connected between the connection point p1 of the switches S1 and S2 and the primary winding Tr11. The resonance unit 114 is connected between the connection point p3 of the switches S3 and S4 and the primary winding Tr11. The resonance unit 116 is connected between the connection point p4 of the switches S5 and S6 and the primary winding Tr12. The resonance unit 117 is connected between the connection point p6 of the switches S7 and S8 and the primary winding Tr12. The DC blocking capacitor C1 is connected between the connection point p2 of the switches S2 and S3 and the midpoint m2 of the second bridge arm. The DC blocking capacitor C2 is connected between the connection point p6 of the switches S6 and S7 and the midpoint m1 of the first bridge arm.

[0168] In a working cycle of the circuit 110, in the first half of the cycle, switches S4, S2, S7, S5 and rectifiers SR1 and SR4 are turned on, while switches S3, S1, S8, S6 and rectifiers SR2 and SR3 are turned off. In the second half of the cycle, switches S4, S2, S7, S5 and rectifiers SR1 and SR4 are turned off, while switches S3, S1, S8, S6 and rectifiers SR2 and SR3 are turned on. The circuit 110 also achieves a conversion ratio of (4N+4):1. Figure 3A Compared with the circuit 20, the current stress of the switches S1-S8 of the switch branch in the circuit 110 can be reduced by half, and the current of the rectifier tubes SR1-SR4 is more balanced.

[0169] [Second Embodiment]

[0170] Combination of the above Figure 2-12 The case where the rectifier circuit in the conversion circuit is a full-bridge rectifier circuit is described. However, this document is not limited to this. For example, the rectifier circuit in the conversion circuit may also be a full-wave rectifier circuit.

[0171] Fig.13A FIG. 1 is a schematic diagram of a conversion circuit 120 according to a second embodiment of the present invention. The circuit 120 receives an input voltage Vin, converts the input voltage Vin, and outputs the converted voltage.

[0172] The circuit 120 includes a full-wave rectifier circuit 121, a switch branch 122, resonant units 123 and 124, and a transformer primary winding Tr1.

[0173] The input voltage and the output voltage each have a first end and a second end, wherein the second ends of the input voltage and the output voltage are connected. The full-wave rectifier circuit 121 has a first branch consisting of a switch SR1 and a transformer secondary winding Tr22, and a second branch consisting of a switch SR2 and a transformer secondary winding Tr21. The switch SR1 and the transformer secondary winding Tr22 are connected in series to form a connection point, referred to as a first midpoint m1. The switch SR2 and the transformer secondary winding Tr21 are connected in series to form a connection point, referred to as a second midpoint m2.

[0174] In an example of the circuit 120, the circuit 120 may include an output capacitor Co for output filtering, the output capacitor Co is connected between the first end and the second end of the output voltage, and is connected in parallel with the first branch and the second branch of the full-wave rectifier circuit 121. Additionally, the circuit 120 may also include an input capacitor Cin for input filtering, the input capacitor Cin may be connected between the first end and the second end of the input voltage, or the input capacitor Cin may also be connected between the first end of the input voltage and the first end of the output voltage, as shown in FIG. Fig.13A The input capacitor Cin is shown by the dotted line.

[0175] The switch branch 122 is connected between the first end of the input voltage and the first midpoint m1 of the full-wave rectifier circuit 121, and the switch branch 122 includes four switches S1-S4 connected in series. Switches S1 and S2 are connected to form a connection point p1, switches S2 and S3 are connected to form a connection point p2, and switches S3 and S4 are connected to form a connection point p3.

[0176] The resonant units 123 and 124 have resonant capacitors Cr1 and Cr2 and resonant inductors Lr1 and Lr2, respectively. Fig.13A The resonant unit shown is composed of a resonant capacitor and a resonant inductor connected in series, but the present invention is not limited thereto, and the resonant unit may also be composed of a resonant capacitor and a resonant inductor connected in parallel.

[0177] One end of the resonance unit 123 is connected to the connection point p1, and one end of the resonance unit 124 is connected to the connection point p3. In addition, the other ends of the resonance units 123 and 124 are both connected to the second midpoint m2 via the transformer primary winding Tr1.

[0178] The transformer primary winding Tr1, the secondary winding Tr21 and the secondary winding Tr22 form a transformer Tr with a turns ratio of N:1:1.

[0179] The DC blocking capacitor C1 is connected between the connection point p2 and the first midpoint m1.

[0180] See also Fig. 13B and 13C The operation of the circuit 120 in one duty cycle is described. Fig. 13B 1 shows the change of current or voltage in each element in one working cycle (t0-t4) of the circuit 120 when the switching frequency is equal to the resonant frequency. In which, iLr represents the current of each of the resonant unit 123 and the resonant unit 124, Vs3 and Vs1 represent the voltage across the switches S3 and S1, and isr1, isr2, is4 and is3 represent the current in the switches SR1, SR2, S4 and S3. Fig. 13C An example of current flow in the first half of a working cycle of the circuit 120 is shown.

[0181] In one working cycle of the circuit 120, switches S4, S2, SR1 and switches S3, S1, SR2 are turned on in a complementary and symmetrical manner, and the duty cycle is close to 0.5. t0-t2 is the first half of the working cycle of the circuit, in which during the time period t0-t1, switches S4, S2, SR1 are turned on, while switches S3, S1, SR2 are turned off. At this time, the current from the input end provides energy to the output end through the first resonant path formed by switch S4, resonant capacitor Cr2, resonant inductor Lr2, primary winding Tr1 and secondary winding Tr21, and the resonant frequency is At the same time, the voltage on the DC blocking capacitor C1 is 0.5Vin, and the energy on the DC blocking capacitor C1 provides energy to the output end through the second resonant path formed by the switch SR1, the switch S2, the resonant capacitor Cr1, the resonant inductor Lr1, the primary winding Tr1 and the secondary winding Tr21. The resonant frequency is At this time, since the primary winding Tr1 and the secondary winding Tr21 of the transformer actually form a series relationship, the secondary winding Tr22 of the transformer Tr senses the resonant current of both the primary winding Tr1 and the secondary winding Tr21, and provides energy to the output end through the third path formed by the switch SR1 and the secondary winding Tr22. In the time period t1 to t2, switches S4, S2, and SR1 are turned off. At this time, the current on the magnetizing inductor charges the parasitic capacitance of switches S4, S2, and SR1, and discharges the parasitic capacitance of switches S3, S1, and SR2, thereby realizing soft switching. t2 to t4 is the second half of the working cycle of the circuit. In the time period t2 to t3, switches S3, S1, and SR2 are turned on and switches S4, S2, and SR1 are turned off. Similar to the first half cycle, the current flows to the output end through a resonant path formed by switch SR2, primary winding Tr1, resonant inductor Lr2, resonant capacitor Cr2, switch S3, DC blocking capacitor C1 and secondary winding Tr22, and the current flows to the output end through another resonant path formed by switch SR2, primary winding Tr1, resonant inductor Lr1, resonant capacitor Cr1, switch S1 and secondary winding Tr22. Finally, secondary winding Tr21 senses the current of primary winding Tr1 and secondary winding Tr22, and flows to the output end through the resonant path formed by switch SR2 and secondary winding Tr21. In the time period of t3 to t4, switches S3, S1 and SR2 are turned off. At this time, the parasitic capacitance of switches S3, S1 and SR2 is charged by the current on the excitation inductor, and the parasitic capacitance of switches S4, S2 and SR1 is discharged, thereby realizing soft switching.

[0182] Assuming that the current at the input end is i, in one working cycle of the circuit 120, the currents of the two resonant units are 2i respectively, and the primary current of the transformer Tr is 4i, and this current flows directly to the output end through a secondary winding. The current induced by the other secondary side of the transformer Tr is 4(N+1)i, so the total current flowing to the output end is 4(N+2)i. For the input end, since only the current of half a resonant cycle flows through the switch S4, the current on the input side is half of the current of the resonant unit 124, that is, i. Therefore, the voltage conversion ratio of the circuit is (4N+8):1.

[0183] and Figure 3A Compared with the conversion circuit using a full-bridge rectifier circuit shown in the figure, Fig.13A The voltage conversion ratio of the circuit 120 is further increased by 4 under the same transformer turns ratio, mainly because the full-wave rectifier circuit has two secondary windings Tr21 and Tr22. When working, the secondary windings Tr21 and Tr22 are connected in series with the primary winding Tr1 of the transformer in turn, and the actual equivalent turns ratio becomes (N+1). The advantage of the conversion circuit using the full-wave rectifier circuit is that the switches SR1 and SR2 are both source-grounded, so the driving of the switches SR1 and SR2 is simpler than the full-bridge rectifier. When the drive of the switches S1 to S4 connected in series is driven and powered using the bootstrap method, since each bridge arm of the full-bridge rectifier circuit has two switches, and each branch of the full-wave rectifier circuit only contains one switch, the number of power supply levels can be reduced by one level relative to the full-bridge rectifier circuit. Therefore, the full-wave rectifier type conversion circuit has a relatively greater advantage in the number of components, occupied area and cost of the drive circuit. The voltage stress of switches SR1 and SR2 in the full-wave rectifier conversion circuit is 2Vo, where Vo is the output voltage. However, only one switch is turned on in one switching state. Here, it is assumed that the on-resistance of the MOSFET is Ron_2Vo. The voltage stress of switch SR in the full-bridge rectifier conversion circuit is Vo, but the rectified current will flow through two switch tubes. Here, it is assumed that the on-resistance of the MOSFET is Ron_Vo. When Ron_2Vo<2×Ron_Vo, using a full-wave rectifier conversion circuit has an efficiency advantage.

[0184] Similarly, the resonance units 123 and 124 are two sets of resonance parameters with the same resonance frequency, and the two sets of parameters may be the same or different. The switches S1 to S4 connected in series may be formed by connecting a plurality of switch elements in series to reduce the voltage stress of a single switch, or may be formed by connecting a plurality of switch elements in parallel to increase the current carrying capacity of the switch unit.

[0185] [Variation of the Second Embodiment]

[0186] Similar to the full-bridge rectifier type conversion circuit, the full-wave rectifier type conversion circuit also has various variations. The following describes various variations of the full-wave rectifier type conversion circuit 120, and only describes the differences between the various variations and the conversion circuit 120, and the same parts are not repeated.

[0187] Fig.14 The circuit 130 is for Fig.13A In the circuit 130, a part of each of the resonant inductors Lr1 and Lr2 is combined into a common inductor Lrc ​​shared by the two resonant units, and the common inductor Lrc ​​is connected in series with the primary side of the transformer. The resonant frequency at this time is:

[0188]

[0189] The advantage of doing this is that the leakage inductance of the transformer can be utilized to reduce the inductance required for the resonant inductor, thereby reducing the use of components and reducing the size of the converter.

[0190] Fig.15 The circuit 140 is for Fig.13A In the circuit 140, when the parameters of the two resonant units are the same, the resonant inductances of the two resonant units can be combined into a common inductance Lrc shared by the two resonant units, and the common inductance Lrc is then connected in series with the primary side of the transformer. The capacitance of the resonant capacitors Cr1 and Cr2 is the same. The circuit 140 operates in the DC transformer mode, the circuit operates at a fixed operating frequency, the leakage inductance requirement is very small, and the leakage inductance of the transformer can be directly used as the common resonant inductor Lrc, which reduces the number and volume of components used.

[0191] Fig.16A The circuit 150 is for Fig.13A A further variation of the circuit 120 in FIG. Fig.13A In the case where multiple resonant units share a primary winding, Fig.16AIn the circuit 150, the transformer has two primary windings Tr11 and Tr12 respectively connected in series with two resonant units (i.e., a resonant unit composed of a resonant inductor Lr1 and a resonant capacitor Cr1, and a resonant unit composed of a resonant inductor Lr2 and a resonant capacitor Cr2), and two secondary windings Tr21 and Tr22. The turns ratio of the primary winding Tr11, the primary winding Tr12, the secondary winding Tr21, and the secondary winding Tr22 is N:N:1:1. One end of the primary winding Tr11 is connected to the second midpoint m2, and the other end is connected to the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1. One end of the primary winding Tr12 is connected to the second midpoint m2, and the other end is connected to the resonant unit composed of the resonant capacitor Cr2 and the resonant inductor Lr2. In some embodiments, the positions of the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1 and the primary winding Tr11 can be interchanged. It is sufficient to ensure that the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1 is connected in series with the primary winding Tr11. Similarly, the positions of the resonant unit composed of the resonant capacitor Cr2 and the resonant inductor Lr2 and the primary winding Tr12 can be interchanged. It is sufficient to ensure that the resonant unit composed of the resonant capacitor Cr2 and the resonant inductor Lr2 and the primary winding Tr12 are connected in series.

[0192] Fig. 16B The circuit 150' is for Fig.13A A further variation of the circuit 120 in FIG. Fig.13A The case where the resonant units 123 and 124 share a primary winding Tr1 in the circuit 120 may also be Fig. 16B The two primary windings Tr11 and Tr12 shown in the figure share a resonance unit. In the circuit 150', the transformer has two primary windings Tr11 and Tr12. One end of the primary winding Tr11 is connected to the connection point p1, one end of the primary winding Tr12 is connected to the connection point p3, and the other ends of the primary windings Tr11 and Tr12 are commonly connected to one end of a resonance unit composed of a resonance inductor Lr and a resonance capacitor Cr, and the other end of the resonance unit is connected to the midpoint m2 of the second branch.

[0193] exist Fig.16A and 16B In the circuit, the leakage inductance of the transformer can also be used as part or all of the resonant inductance of the resonant unit to reduce circuit elements.

[0194] Fig.17 The circuit 160 is for Fig.13AIn the circuit 160, when the parameters of the resonant capacitor Cr1 and the resonant inductor Lr1 in the resonant unit 163 are the same as those of the resonant capacitor Cr2 and the resonant inductor Lr2 in the resonant unit 164, the resonant capacitor Cr3 and the resonant inductor Lr3 with the same parameters as those of the resonant units 163 and 164 can be used to replace the original single DC blocking capacitor connected to the connection point p2 of the switches S2 and S3 to form the resonant unit 165. The resonant capacitor Cr3 not only plays the role of a DC blocking capacitor, but also participates in the circuit resonance together with the resonant inductor Lr3.

[0195] Fig.18 The circuit 170 is for Fig.13A A further variation of the circuit 120 in the circuit 170. In the circuit 170, the output capacitor Co connected in parallel with the first branch and the second branch of the full-wave rectifier circuit of the circuit 170 can be used as a resonant capacitor Cr shared by two resonant units. At this time, the resonant unit connected between the connection point of the switch branch and the midpoint m2 of the first branch can only include a resonant inductor. In the circuit 170, the resonant capacitor Cr is shared by the resonant inductors Lr1 and Lr2, the resonant capacitor Cr resonates with the resonant inductor Lr1 as a resonant unit, and the resonant capacitor Cr resonates with the resonant inductor Lr2 as another resonant unit. The circuit 170 simplifies the circuit configuration. Although the resonant inductor Lr2 in the circuit 170 is connected in series with the capacitor C2, and the resonant inductor Lr1 is connected in series with the capacitor C3, the capacitors C2 and C3 are mainly used as DC blocking capacitors, and the capacitors C2 and C3 can be omitted.

[0196] The transformer in the circuit can also be further split into two independent transformers. Fig.19 The circuit 180 is Fig.13A A further variation of the circuit 120 in FIG. In the circuit 180, the full-wave rectifier circuit may further include a third branch and a fourth branch connected in parallel with the first branch and the second branch. The third branch includes a switch SR3 and a secondary winding Tr'21 of a transformer Tr' connected in series, and the switch SR3 and the secondary winding Tr'21 of the transformer Tr' are connected to form a connection point, which is called a third midpoint m3. The fourth branch includes a switch SR4 and a secondary winding Tr'22 of a transformer Tr' connected in series, and the switch SR4 and the secondary winding Tr'22 of the transformer Tr' are connected to form a connection point, which is called a fourth midpoint m4.

[0197] One end of the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1 is connected to the connection point p1 of the switches S1 and S2. One end of another resonant unit composed of the resonant capacitor Cr2 and the resonant inductor Lr2 is connected to the connection point p3 of the switches S3 and S4. One end of the primary winding Tr1 of the transformer Tr is connected to the second midpoint m2, and the other end is connected to the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1. The turns ratio of the primary winding Tr1, the secondary winding Tr21 and the secondary winding Tr22 of the transformer Tr is N:1:1. One end of the primary winding Tr'1 of the transformer Tr' is connected to the fourth midpoint m4, and the other end is connected to the resonant unit composed of the resonant capacitor Cr2 and the resonant inductor Lr2. The turns ratio of the primary winding Tr'1, the secondary winding Tr'21 and the secondary winding Tr'22 of the transformer Tr' is N:1:1. In some embodiments, the positions of the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1 and the primary winding Tr1 can be interchanged. It is sufficient to ensure that the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1 and the primary winding Tr1 are connected in series. Similarly, the positions of the resonant unit composed of the resonant capacitor Cr2 and the resonant inductor Lr2 and the primary winding Tr'1 can be interchanged. It is sufficient to ensure that the resonant unit composed of the resonant capacitor Cr2 and the resonant inductor Lr2 and the primary winding Tr'1 are connected in series.

[0198] One end of the DC blocking capacitor C1 is connected to a connection point p2 between the switches S2 and S3 , and the other end is connected to a third midpoint m3 .

[0199] The advantage of circuit 180 is that it can reduce the current stress of a single transformer and a single rectifier tube, or in other words, increase the current carrying capacity of the transformer and switch SR when using the same components, thereby increasing the output power of the converter.

[0200] The conversion circuit in this paper can be further extended to change the voltage conversion ratio. Fig. 20A Shows Fig.13A An extended form of the conversion circuit 120. Fig. 20A The circuit 190 shown is compared to Fig.13A The circuit 120 in FIG. 1 has a switch branch 192 which includes not only the original four switches S1-S4, but also further expands to include (2m-4) switches (S5, S6...S 2m-1 , S 2m ). Expanded (2m-4) switches (S5, S6…S 2m-1 , S 2m ) are connected in series with the original four switches S1-S4, so that the switch branch 192 includes 2m switches connected in series, where m is an integer and m≥3.

[0201] The circuit 190 further includes (m-2) DC blocking capacitors Cx and (m-2) resonant units 195. Therefore, in the circuit 190, the (m-2) Cx and the DC blocking capacitor C1 together constitute (m-1) DC blocking capacitors, and the (m-2) resonant units 195 and the resonant units 193 and 194 together constitute m resonant units. The resonant units 195 each include a resonant capacitor Crx and a resonant inductor Lrx.

[0202] Therefore, for Fig. 20A The conversion circuit of the circuit 190 can be described as follows: the switch branch 192 has 2m switches connected in series, where m is an integer and m≥3. Two adjacent switches among the 2m switches are connected to form a connection point, so there are (2m-1) connection points.

[0203] Considering the connection point close to the output terminal of the circuit 190 as the first connection point, the switch branch 192 has connection points No. 1, 2, 3, ..., (2m-2), (2m-1) from the output terminal to the input terminal. Fig. 20A As shown, the connection point between switches S1 and S2 is closest to the output terminal, so the connection point between switches S1 and S2 is connection point 1 ( Fig. 20A The connection point of switches S2 and S3 is connection point 2 ( Fig. 20A The connection point of switches S3 and S4 is connection point 3 ( Fig. 20A In the figure, it is marked as "③"), and so on. 2m-1 and S 2m The connection point is the (2m-1) connection point.

[0204] Each of the m resonant units (i.e., resonant units 193, 194 and (m-2) resonant units 195) is connected between an odd-numbered connection point and the primary winding Tr1, and each of the (m-1) DC blocking capacitors (i.e., DC blocking capacitor C1 and (m-2) DC blocking capacitors Cx) is connected between an even-numbered connection point and the first midpoint m1.

[0205] Among the m resonance units, one end of the xth resonance unit is connected to the connection point of the (2x-1)th switch and the 2xth switch among the 2m switches, where m and x are integers, and m≥3, 1≤x≤m. For example, when x=1, for the first (x)th resonance unit ( Fig. 20A The resonant unit 193 in the embodiment has one end connected to the first (2x-1) switch ( Fig. 20A The switch S1 in the Fig. 20AThe other end is connected to the primary winding Tr1 of the transformer. For another example, when x=2, for the second (x) resonant unit ( Fig. 20A The resonant unit 194 in the embodiment has one end connected to the third (2x-1) switch ( Fig. 20A The switch S3 in the Fig. 20A The other end is connected to the connection point between the switch S4 in the transformer and the primary winding Tr1 of the transformer.

[0206] Among the (m-1) DC blocking capacitors Cx, one end of the kth DC blocking capacitor is connected to the connection point of the 2kth switch and the 2k+1th switch among the 2m switches, and the other end is connected to the first midpoint m1, where m and k are integers, and m≥3, 1≤k≤m-1. For example, when k=1, the first (k) DC blocking capacitor ( Fig. 20A One end of the DC blocking capacitor C1 in the circuit is connected to the second (2k) switch ( Fig. 20A The switch S2 in the Fig. 20A The other end is connected to the first midpoint m1. For another example, when k=(m-1), one end of the (m-1)(k)th DC blocking capacitor is connected to the 2m-2(2k)th switch ( Fig. 20A The AND switch S 2m-1 The adjacent previous switch, not shown) and the 2m-1(2k+1)th switch ( Fig. 20A Switch S in 2m-1 ) and the other end is connected to the first midpoint m1.

[0207] Therefore, for Fig. 20A In the circuit 190, when the turns ratio of the primary winding Tr1, the secondary winding Tr21 and the secondary winding Tr22 of the transformer is N:1:1, the conversion ratio of the circuit 190 is (mN+2m):1. Thus, the conversion ratio of the conversion circuit is expanded.

[0208] Reference Fig.17 When the resonance parameters of the resonance units in the conversion circuit are the same, the DC blocking capacitors can be replaced by resonance units with the same resonance parameters.

[0209] Although Fig. 20A The circuit 190 shows the situation where m resonant units are connected in series with a single primary winding Tr1, as shown in FIG. Fig.16A As described above, the primary winding Tr1 may also be composed of a plurality of sub-windings, and each sub-winding is respectively connected in series with a corresponding resonant unit among the m resonant units.

[0210] Similar to Fig. 16B The content described, compared to Fig. 20A The m resonance units shown in FIG. 1 are connected in series to a common primary winding Tr1, or a plurality of primary windings may share one resonance unit, such as Fig. 20B As shown in circuit 190'.

[0211] In the circuit 190', the switch branch 192 not only includes the original two switches S1-S2, but also further expands to include (2m-2) switches (S3, S4...S 2m-1 , S 2m ). Expanded (2m-2) switches (S3, S4…S 2m-1 , S 2m ) are connected in series with the original two switches S1 and S2, so that the switch branch 92 includes 2m switches connected in series, that is, an even number of switches, where m is an integer and m≥2. The circuit 190' further includes (m-1) DC blocking capacitors Cx and m primary windings Tr1. The m primary windings Tr1 are all connected in series with the resonant unit composed of the resonant inductor Lr and the resonant capacitor Cr.

[0212] In the circuit 190', two adjacent switches among the 2m switches of the switch branch 192 are connected to form a connection point, so there are (2m-1) connection points. The connection point close to the output end of the circuit 190' is regarded as the first connection point, and the switch branch 192 has connection points No. 1, 2, 3, ..., (2m-2), (2m-1) from the output voltage end to the input end. For example, if Fig. 20B As shown, the connection point between switches S1 and S2 is closest to the output terminal, so the connection point between switches S1 and S2 is connection point 1 ( Fig. 20B The connection point between switch S2 and the next switch S3 adjacent to switch S2 is connection point No. 2 ( Fig. 20B In the figure, the switch S 2m-1 and S 2m The connection point between them is the (2m-1)th connection point.

[0213] Each of the m primary windings Tr1 is connected between an odd-numbered connection point and a resonant unit composed of a resonant inductor Lr and a resonant capacitor Cr, and each of the (m-1) DC-isolating capacitors Cx is connected between an even-numbered connection point and the midpoint m1 of the first branch.

[0214] In the above-mentioned m primary windings Tr1, one end of the xth primary winding is connected to the connection point of the (2x-1)th switch and the 2xth switch among the 2m switches, where x is an integer and 1≤x≤m.

[0215] Among the above-mentioned (m-1) DC blocking capacitors Cx, one end of the kth DC blocking capacitor is connected to the connection point of the 2kth switch and the 2k+1th switch among the 2m switches, and the other end is connected to the midpoint m1 of the first branch, where k is an integer and 1≤k≤m-1.

[0216] Fig.21A Another extended form of the conversion circuit in this article is shown. Fig.21A The circuit 200 is Fig.17 An expansion of the circuit 160, Fig.21A The switch branch 202 of the circuit 200 shown not only includes the original four switches S1-S4, but also further expands (m-4) switches (S5, ..., Sm). The expanded (m-4) switches (S5, ..., Sm) are connected in series with the original four switches S1-S4, so that the switch branch 202 includes m switches, where m is an integer and m≥5. The circuit 200 further includes (m-4) additional resonant units 206. The (m-4) additional resonant units 206 and the resonant units 203-205 together constitute (m-1) resonant units. The (m-4) additional resonant units 206 include a resonant capacitor Crx and an additional resonant inductor Lrx. Each resonant unit in the circuit 200 has the same resonant parameters.

[0217] Specifically, therefore, for Fig.21A The conversion circuit of the circuit 200 can be described as follows: the switch branch 202 has m switches connected in series, where m is an integer and m≥5. Two adjacent switches among the m switches are connected to form a connection point, so there are (m-1) connection points. The connection point close to the output end of the circuit 200 is regarded as the first connection point, and the switch branch 202 has the first, second, third, ..., (m-1) connection points from the output end to the input end. For example, Fig.21A As shown, the connection point between switches S1 and S2 is closest to the output terminal, so the connection point between switches S1 and S2 is connection point 1 ( Fig.21A The connection point of switches S2 and S3 is connection point 2 ( Fig.21A The connection point of switches S3 and S4 is connection point 3 ( Fig.21A The connection point of switches S4 and S5 is connection point 4 ( Fig.21A In the figure, it is marked as "④"). Similarly, the connection point between the switch Sm and a switch (not shown) before the switch Sm is the connection point No. (m-1).

[0218] One end of the (m-1) resonant units (203-206) in the circuit 200 is connected to the corresponding connection point, and the other end is connected to the primary winding Tr1 or the first midpoint m1. Among them, for the resonant unit with one end connected to the odd-numbered connection point, the other end is connected to the primary winding Tr1 of the transformer. For the resonant unit with one end connected to the even-numbered connection point, the other end is connected to the first midpoint m1.

[0219] In the (m-1) resonant units, one end of the (2y-1)th resonant unit is connected to the connection point of the (2y-1)th switch and the 2yth switch among the m switches, and the other end is connected to the primary winding Tr1 of the transformer, where y is an integer and 1≤y≤m / 2. For example, when y=1, in the m-1 resonant units, the first (2y-1)th resonant unit ( Fig.21A One end of the resonant unit 203 in the circuit is connected to the first (2y-1) switch ( Fig.21A The switch S1 in the Fig.21A The other end is connected to the primary winding Tr1 of the transformer. For another example, when y=2, among the m-1 resonant units, the third (2y-1) resonant unit ( Fig.21A One end of the resonant unit 204 in the embodiment is connected to the third (2y-1) switch ( Fig.21A The switch S3 in the Fig.21A The other end is connected to the connection point of the switch S4 in the transformer, and the other end is connected to the primary winding Tr1 of the transformer.

[0220] Further, in the (m-1) resonance unit, one end of the 2yth resonance unit is connected to the connection point of the 2yth switch and the (2y+1)th switch among the m switches, and the other end is connected to the first midpoint m1. For example, when y=1, in the (m-1) resonance unit, the second (2y)th resonance unit ( Fig.21A One end of the resonant unit 205 in the circuit is connected to the second (2y) switch ( Fig.21A The switch S2 in the Fig.21A The other end is connected to the first midpoint m1. For another example, when y=2, among the (m-1) resonant units, the fourth (2y) resonant unit ( Fig.21A Middle resonance unit 206 1 ) is connected to the fourth (2y) switch ( Fig.21A The switch S4 in the Fig.21A The other end is connected to the connection point of the switch S5 in the circuit, and the other end is connected to the first midpoint m1.

[0221] for Fig.21AIn the circuit 200, the turns ratio of the primary winding Tr1, the secondary winding Tr21 and the secondary winding Tr22 of the transformer is N:1:1. When m is an odd number, the conversion ratio of the circuit 100 is ((m-1)N+2m):1. When m is an even number, the conversion ratio of the circuit 100 is (mN+2m):1, where N is the turns ratio of the transformer Tr. Thus, the conversion ratio of the conversion circuit is expanded.

[0222] Although Fig.21A The diagram shows the situation where the resonant units connected to the odd-numbered connection points among the (m-1) resonant units are all connected in series with a single primary winding Tr1. Fig.16A As described above, the primary winding Tr1 may also be composed of a plurality of sub-windings, and each sub-winding is respectively connected in series with a corresponding resonant unit among the (m-1) resonant units connected to an odd-numbered connection point.

[0223] Similar to Fig. 16B The content described, compared to Fig.21A The case where the multiple resonant units are connected in series to the common primary winding Tr1 may also be the case where multiple primary windings share one resonant unit, such as Fig. 21B The circuit 200' is shown.

[0224] The switch branch 202 of the circuit 200' not only includes the original two switches S1-S2, but also further expands (m-2) switches (S3, ..., Sm). The expanded (m-2) switches (S3, ..., Sm) are connected in series with the original two switches S1-S2, so that the switch branch 102 includes m switches connected in series, where m is an integer and m≥5. The circuit 200' further includes a plurality of resonant units 207 and a plurality of primary windings Tr1. Each of the plurality of resonant units 207 includes a resonant capacitor Crx and a resonant inductor Lrx. Each of the plurality of resonant units 207 has the same resonant parameters.

[0225] In the circuit 200', the switch branch 202 has m switches connected in series, where m is an integer and m≥5. Two adjacent switches among the m switches are connected to form a connection point, so there are (m-1) connection points. The connection point close to the output end of the circuit 100 is regarded as the first connection point, and the switch branch 102 has the first, second, third, ..., m-1 connection points from the output end to the input end. For example, Fig. 21B As shown, the connection point of switches S1 and S2 is closest to the output terminal, so the connection point of switches S1 and S2 is connection point 1 ( Fig. 21B The connection point of switches S2 and S3 is connection point 2 ( Fig. 21B The connection point between switch S3 and switch S4 is connection point 3 ( Fig. 21B In the figure, it is marked as "③"). Similarly, the connection point between switch Sm and the switch before switch Sm is the (m-1)th connection point.

[0226] One end of each of the multiple primary windings Tr1 in the circuit 200' is connected to an odd-numbered connection point, and the other end thereof is connected to a resonant unit composed of a resonant capacitor Cr and a resonant inductor Lr. One end of each of the multiple resonant units 207 in the circuit 200' is connected to an even-numbered connection point, and the other end thereof is connected to the midpoint m1 of the first branch of the full-bridge rectifier circuit.

[0227] One end of one of the above-mentioned multiple primary windings Tr1 is connected to the connection point of the (2y-1)th switch and the 2yth switch among the m switches, and the other end is connected to the resonant unit composed of the resonant capacitor Cr and the resonant inductor Lr, where y is an integer and 1≤y≤m / 2.

[0228] One end of one of the above-mentioned multiple resonant units 207 is connected to the connection point of the 2zth switch and the (2z+1)th switch among the m switches, and the other end is connected to the midpoint m1 of the first branch of the full-bridge rectifier circuit, where z is an integer and 1≤z≤(m-1) / 2.

[0229] Fig. 21C The circuit 200" shows another extended form of the conversion circuit in this article. Fig. 21C The switch branch 202 of the circuit 200" shown includes m switches, where m is an integer and m ≥ 3. The circuit 200" further includes (m-1) conversion branches 208 (208 1 , 208 2 , …, 208 m-1 ), for example, each conversion branch 208 can be a resonant unit composed of a resonant capacitor Cr and a resonant inductor Lr. In addition, the full-wave rectifier circuit of the circuit 200" includes n branches, for example, Fig. 21C The full-wave rectifier circuit shown includes a switch SR1 and a secondary winding Ns of a transformer Tr. 1 The first branch is composed of switch SR2 and a secondary winding Ns of transformer Tr. 2 The second branch is composed of switch SR3 and a secondary winding Ns of transformer Tr. 3 The third branch is composed of the switch SRn and a secondary winding Ns of the transformer Tr. n The switch and the secondary winding of each of the n branches are connected in series to form the midpoint of the corresponding branch. In this embodiment, the number of branches n in the full-wave rectifier circuit is not greater than the number of switches m in the switch branch 202, and the number of branches n is at least 2, that is, in addition to satisfying m≥3, m≥n≥2 must also be satisfied.

[0230] The n branches of the full-wave rectifier circuit include at least one first-type branch and at least one second-type branch, wherein the like-named ends of the secondary windings of the first-type branches are connected, and the opposite-named ends of the secondary windings of the first-type branches and the secondary windings of the second-type branches are connected. Fig. 21C As shown in FIG. , the switch SR1 and a secondary winding Ns of the transformer Tr are connected. 1 The first branch is composed of switch SR3 and a secondary winding Ns of transformer Tr. 3 The third branch is the first type branch, and is composed of switch SR2 and a secondary winding Ns of transformer Tr. 2 The second branch is composed of switch SRn and a secondary winding Ns of transformer Tr. n The nth branch is a second type branch. Additionally, in the n branches of the full-wave rectifier circuit, the switches of the first type branch are turned on and off at the same time, and the switches of the first type branch and the switches of the second type branch are turned on in a complementary and symmetrical manner.

[0231] Fig. 21C The switch branch 202 of the circuit 200" has m switches connected in series, where m is an integer and m≥3. Two adjacent switches among the m switches are connected to form a connection point, so there are (m-1) connection points. The connection point close to the output end of the circuit 200" is regarded as the first connection point, and the switch branch 202 has connection points No. 1, 2, 3, ..., (m-1) from the output end to the input end. For example, Fig. 21C As shown, the connection point between switches S1 and S2 is closest to the output terminal, so the connection point between switches S1 and S2 is connection point 1 ( Fig. 21C The connection point between the switch S2 and the next switch (not shown) adjacent to the switch S2 is the connection point No. 2 ( Fig. 21C In the figure, it is marked as "②"). Similarly, the connection point between the switch Sm and a switch (not shown) before the switch Sm is the connection point No. (m-1).

[0232] In the (m-1) conversion branches 208 in the circuit 200", for the conversion branch having one end connected to the odd-numbered connection point of the switch branch 202, the conversion branch is connected between the odd-numbered connection point of the switch branch 202 and the midpoint of one of the second-type branches among the n branches; and for the conversion branch having one end connected to the even-numbered connection point of the switch branch 202, the conversion branch is connected between the even-numbered connection point of the switch branch 202 and the midpoint of one of the first-type branches among the n branches.

[0233] In the (m-1) conversion branches 208, one end of the (2y-1)th conversion branch is connected to the connection point of the (2y-1)th switch and the 2yth switch among the m switches, and the other end is connected to the midpoint of one of the second-type branches among the n branches, where y is an integer and 1≤y≤m / 2. For example, when y=1, in the (m-1) conversion branches 208, the first (2y-1)th conversion branch ( Fig. 21C The conversion branch 208 1 ) is connected to the first (2y-1) switch ( Fig. 21C The switch S1 in the Fig. 21C The other end is connected to the midpoint of one of the second type branches in the n branches, for example, the midpoint of the second branch.

[0234] Further, in the (m-1) conversion branches, one end of the 2zth conversion branch is connected to the connection point of the 2zth switch and the (2z+1)th switch in the m switches, and the other end is connected to the midpoint of one of the first-type branches in the n branches, where z is an integer and 1≤z≤(m-1) / 2. For example, when z=1, in the (m-1) conversion branches, the second (2z)th conversion branch ( Fig. 21C The conversion branch 208 2 ) is connected to the second (2z) switch ( Fig. 21C The switch S2 in the Fig. 21C The other end is connected to a connection point of the switch S3 in the n-th branch, and the other end is connected to a midpoint of one of the first-type branches in the n-th branch, for example, the midpoint of the third branch.

[0235] In addition, the circuit 200" further includes a primary winding Np of the transformer Tr, which is connected in series with one of the (m-1) conversion branches. For example, Fig. 21C The primary winding Np and the conversion branch 208 are shown. 1 The primary winding Np can also be connected in series with the conversion branch 208. 2 , …, 208 m-1 Any one of them is connected in series. Fig. 21C The circuit can achieve a voltage conversion ratio of Vin / Vo=2(Np+m).

[0236] Although Fig. 21C A primary winding Np connected in series with any one of the (m-1) conversion branches is shown, but the present invention is not limited thereto and may also include multiple primary windings Np connected in series with multiple of the (m-1) conversion branches. Fig.21DAs shown, the circuit 200" may include (m-1) primary windings Np (Np 1 、Np 2 ,…,Np m-1 ), and each of the (m-1) primary windings Np is connected in series with a corresponding conversion branch in the (m-1) conversion branches. Fig.21D When the turns ratio of the primary winding Np is 1:1:…:1, Vin / Vo=2(N 1 +N 2 +…+N m-1 +m) voltage conversion ratio, where N1, N 2 ,…,N m-1 They are the primary winding Np 1 、Np 2 ,…,Np m-1 The number of turns.

[0237] Although Fig. 21C and Fig.21D The multiple conversion branches 208 in are all shown as resonant units, but some of the multiple conversion branches 208 can also be composed of non-resonant units. For example, the non-resonant unit can be a unit composed of only one capacitor, or a capacitor and an inductor whose resonant frequency is much smaller than or much larger than the switching frequency of the circuit (less than 1 / 3 of the switching frequency or greater than 3 times the switching frequency). When the multiple conversion branches 208 include a conversion branch composed of a non-resonant unit, the adjacent conversion branches on both sides of the conversion branch composed of the non-resonant unit need to be resonant units. In other words, the i-th conversion branch among the (m-1) conversion branches 208 is a non-resonant unit, and the (i-1)th conversion branch and the (i+1)th conversion branch among the (m-1) conversion branches 208 are both resonant units, where m≥4, i≤m-2, and i is an integer.

[0238] Fig. 22 Shows Fig.13A A variation of the circuit 120. Fig. 22 In the circuit 210 shown, the full-wave rectifier circuit has a first branch consisting of a switch SR1 and a transformer secondary winding Tr22, and a second branch consisting of a switch SR2 and a transformer secondary winding Tr21. The switch SR1 and the transformer secondary winding are connected in series to form a first midpoint m1, and the switch SR2 and the transformer secondary winding Tr21 are connected in series to form a midpoint m2.

[0239] The circuit 210 has two switch branches 212 and 215, the switch branch 212 is connected between the first end of the input voltage and the first midpoint m1, and the switch branch 215 is connected between the first end of the input voltage and the second midpoint m2. The switch branch 212 has four switches S1-S4 connected in series, and the switch branch 215 has four switches S5-S8 connected in series. The circuit 210 also has four resonant units 213, 214, 216 and 217, two DC blocking capacitors C1 and C2, and transformer primary windings Tr11 and Tr12. The turns ratio of the transformer primary winding Tr11, the primary winding Tr12, the secondary winding Tr12 and the secondary winding Tr22 is N:N:1:1.

[0240] The resonance unit 213 is connected between the connection point p1 of the switches S1 and S2 and the primary winding Tr11. The resonance unit 214 is connected between the connection point p3 of the switches S3 and S4 and the primary winding Tr11. The resonance unit 216 is connected between the connection point p4 of the switches S5 and S6 and the primary winding Tr12. The resonance unit 217 is connected between the connection point p6 of the switches S7 and S8 and the primary winding Tr12. The DC blocking capacitor C1 is connected between the connection point p2 of the switches S2 and S3 and the first midpoint m1. The DC blocking capacitor C2 is connected between the connection point p5 of the switches S6 and S7 and the second midpoint m2.

[0241] In a working cycle of the circuit 210, in the first half of the cycle, switches S4, S2, S7, S5, and SR1 are turned on, while switches S3, S1, S8, S6, and SR2 are turned off. In the second half of the cycle, switches S4, S2, S7, S5, and SR1 are turned off, while switches S3, S1, S8, S6, and SR2 are turned on. The circuit 210 also achieves a conversion ratio of (4N+8). Fig.13A Compared with the circuit 120, the current stress of the switches S1-S8 of the switch branch in the circuit 210 can be reduced by half, and the currents of the switches SR1 and SR2 are more balanced.

[0242] [Third Embodiment]

[0243] Fig.23 A circuit example of the conversion circuit 220 according to the third embodiment of this document is shown.

[0244] like Fig.23 As shown, the circuit 220 receives an input voltage Vin, converts the input voltage Vin, and outputs the converted voltage.

[0245] The circuit 220 includes a full-wave rectification circuit 221 , a switch branch 222 and a resonant unit 223 .

[0246] The input voltage and the output voltage each have a first end and a second end, wherein the second end of the input voltage is connected to the second end of the output voltage. The full-wave rectifier circuit 221 has a first branch consisting of a switch SR1 and a first winding Tr22 of a transformer Tr, and a second branch consisting of a switch SR2 and a second winding Tr21 of a transformer Tr. The switch SR1 and the first winding Tr22 of the transformer Tr are connected in series to form a first midpoint m1, and the switch SR2 and the second winding Tr21 of the transformer Tr are connected in series to form a second midpoint m2.

[0247] In an example of the circuit 220, the circuit 220 may include an output capacitor Co for output filtering, the output capacitor Co is connected between the first end and the second end of the output voltage, and is connected in parallel with the first branch and the second branch of the full-wave rectifier circuit 221. Additionally, the circuit 220 may also include an input capacitor Cin for input filtering, the input capacitor Cin may be connected between the first end and the second end of the input voltage, or the input capacitor Cin may also be connected between the first end of the input voltage and the first end of the output voltage, as shown in FIG. Fig.23 The input capacitor Cin is shown by the dotted line.

[0248] The switch branch 222 is connected between the first end of the input voltage and the first midpoint m1, and includes two switches S1 and S2 connected in series. The switches S1 and S2 are connected to form a connection point p1.

[0249] The resonance unit 223 has a resonance capacitor Cr and a resonance inductor Lr. Fig.23 The resonant unit shown is composed of a resonant capacitor and a resonant inductor connected in series, but the present invention is not limited thereto, and the resonant unit may also be composed of a resonant capacitor and a resonant inductor connected in parallel.

[0250] One end of the resonance unit 223 is connected to the connection point p1, and the other end is connected to the second midpoint m2. The resonance unit 223 is not connected in series with any winding of the transformer Tr.

[0251] The turns ratio of the first winding Tr22 and the second winding Tr21 of the transformer Tr is 1:1. In one working cycle of the circuit 220, the switches S2 and SR1 are turned on in a complementary and symmetrical manner to the switches S1 and SR2, and the duty cycle is close to 0.5. In the first half of the working cycle, the switches S2 and SR1 are turned on, while the switches S1 and SR2 are turned off. At this time, the current from the input end provides energy to the output end through the first resonant path formed by the switch S2, the resonant capacitor Cr, the resonant inductor Lr, and the second winding Tr21, and the resonant frequency is At the same time, the first winding Tr22 of the transformer senses the resonant current of the second winding Tr21, and provides energy to the output end through the second path formed by the switch SR1 and the first winding Tr22. In the time period from the first half cycle to the second half cycle, the parasitic capacitance of the switches S2 and SR1 is charged by the current on the excitation inductor, and the parasitic capacitance of the switches S1 and SR2 is discharged, thereby realizing soft switching. In the time period of the second half of the working cycle, the switches S1 and SR2 are turned on and the switches S2 and SR1 are turned off. Similar to the first half cycle, at this time, the current flows to the output end through a resonant path formed by the switch SR2, the resonant inductor Lr, the resonant capacitor Cr, the switch S1 and the first winding Tr22, and at the same time, the second winding Tr21 senses the current of the first winding Tr22, and flows to the output end through another resonant path formed by the switch SR2 and the winding Tr21.

[0252] Assuming that the current at the input end is i, in one working cycle of the circuit 220, the current of the resonant unit is 2i, and this current flows directly to the output end through one winding of the transformer Tr. Since the actual turns ratio of the transformer Tr is 1:1, the current induced by the other winding of the transformer Tr is also 2i, so the total current flowing to the output is 4i. For the input end, since only the current of half a resonant cycle flows through the switch S2, the current on the input side is half of the current of the resonant unit 213, that is, i. Therefore, the voltage conversion ratio of the circuit is 4:1.

[0253] [Variation of the Third Embodiment]

[0254] Similar to the second mode and its variations described herein, the third embodiment described herein may also have various variations. Various variations of the full-wave rectifier type conversion circuit 220 are described below, and only the differences between the various variations and the conversion circuit 220 are described, and the same parts are not repeated.

[0255] Fig.24 A schematic diagram of a conversion circuit 230 according to a variation of the third embodiment of the present invention is shown.

[0256] Compared to Fig.23 The circuit 220, Fig.24 The circuit 230 shown expands two switches S3 and S4 connected in series in the switch branch, so that the switch branch includes four switches S1-S4 connected in series, wherein switches S1 and S2 are connected in series to form a connection point p1, switches S2 and S3 are connected in series to form a connection point p2, and switches S3 and S4 are connected in series to form a connection point p3.

[0257] The circuit 230 is further extended with a DC blocking capacitor C1 and another resonant unit 234 composed of a resonant capacitor Cr2 and a resonant inductor Lr2. One end of the DC blocking capacitor C1 is connected to the connection point p2, and the other end is connected to the first midpoint m1. One end of the resonant unit 234 is connected to the connection point p3, and the other end is connected to the second midpoint m2.

[0258] Since in one working cycle of the circuit 230 , the first winding Tr21 and the second winding Tr22 of the series-connected transformer Tr are mutually inductive in the first half cycle and the second half cycle of one working cycle, the voltage conversion ratio achieved by the circuit 230 is 8:1.

[0259] exist Fig.25 The circuit 240 shows Fig.23 Another variation of the circuit 220 is shown in FIG. Fig.23 The resonance unit shown includes a resonance capacitor Cr and a resonance inductor Lr, but the leakage inductance of the transformer Tr having the second winding Tr21 and the first winding Tr22 may be used as the resonance inductor of the resonance unit. Fig.25 In the circuit 240, the leakage inductance Lk of the transformer Tr is used as a resonant inductor to resonate with the resonant capacitor Cr. The circuit 240 can also achieve Fig.23 The effect of the circuit 220 is improved, and the circuit configuration is simplified.

[0260] Fig.26 The circuit 250 is for Fig.24 In the circuit 250, a part of each of the resonant inductors Lr1 and Lr2 is combined into a common inductor Lrc ​​shared by the two resonant units, and the resonant frequency is:

[0261]

[0262] The advantage of doing this is that the leakage inductance of the transformer can be utilized to reduce the inductance required for the resonant inductor, thereby reducing the use of components and reducing the size of the converter.

[0263] Fig. 27 The circuit 260 is a Fig.24 In the circuit 260, when the parameters of the two resonant units are the same, the resonant inductors of the two resonant units can be combined into a common inductor Lrc ​​shared by the two resonant units. The capacitance of the resonant capacitors Cr1 and Cr2 is the same. The circuit 140 operates in the DC transformer mode, the circuit operates at a fixed operating frequency, the leakage inductance requirement is very small, and the leakage inductance of the transformer can be directly used as the common resonant inductor Lrc, which reduces the number and volume of components used.

[0264] Fig.28 The circuit 270 is for Fig.24 In the circuit 270, when the parameters of the resonant capacitor Cr1 and the resonant inductor Lr1 in the resonant unit 273 are the same as those of the resonant capacitor Cr2 and the resonant inductor Lr2 in the resonant unit 274, the resonant capacitor Cr3 and the resonant inductor Lr3 with the same parameters as those of the resonant units 273 and 274 can be used to replace the original single DC blocking capacitor connected to the connection point p2 of the switches S2 and S3 to form the resonant unit 275. The resonant capacitor Cr3 not only plays the role of a DC blocking capacitor, but also participates in the circuit resonance together with the resonant inductor Lr3.

[0265] Fig.29 The circuit 280 is a Fig.24 A further variation of the circuit 230 in FIG. 280. In the circuit 280, the output capacitor Co connected in parallel with the first branch and the second branch of the full-wave rectifier circuit of the circuit 280 can be used as a resonant capacitor Cr shared by two resonant units. Therefore, in the circuit 280, the resonant capacitor Cr is shared by the resonant inductors Lr1 and Lr2, the resonant capacitor Cr resonates with the resonant inductor Lr1 as one resonant unit, the resonant capacitor Cr resonates with the resonant inductor Lr2 as another resonant unit, and at this time, the resonant unit connected to the connection point of the switching circuit may have only a resonant inductor. The circuit 280 simplifies the circuit configuration. Although the resonant inductor Lr2 in the circuit 280 is connected in series with the capacitor C2, and the resonant inductor Lr1 is connected in series with the capacitor C3, the capacitors C2 and C3 are mainly used as DC blocking capacitors, and the capacitors C2 and C3 can be omitted.

[0266] Fig.30 The circuit 290 is a Fig.24 A further variation of the circuit 230 in FIG. In the circuit 290, the full-wave rectifier circuit may further include a third branch and a fourth branch connected in parallel with the first branch and the second branch. The third branch includes a switch SR3 and a first winding Tr'21 of a transformer Tr' connected in series, and the switch SR3 and the first winding Tr'21 of the transformer Tr' are connected to form a connection point, which is called a third midpoint m3. The fourth branch includes a switch SR4 and a second winding Tr'22 of a transformer Tr' connected in series, and the switch SR4 and the second winding Tr'22 of the transformer Tr' are connected to form a connection point, which is called a fourth midpoint m4.

[0267] One end of the resonant unit composed of the resonant capacitor Cr1 and the resonant inductor Lr1 is connected to the connection point p1 of the switches S1 and S2, and the other end is connected to the second midpoint m2. One end of another resonant unit composed of the resonant capacitor Cr2 and the resonant inductor Lr2 is connected to the connection point p3 of the switches S3 and S4, and the other end is connected to the fourth midpoint m4. The turns ratio of the first winding Tr21 and the second winding Tr22 of the transformer Tr is 1:1. The turns ratio of the first winding Tr'21 and the second winding Tr'22 of the transformer Tr' is 1:1.

[0268] One end of the DC blocking capacitor C1 is connected to a connection point p2 between the switches S2 and S3 , and the other end is connected to a third midpoint m3 .

[0269] The advantage of circuit 290 is that it can reduce the current stress of a single transformer and a single rectifier tube, or in other words, increase the current carrying capacity of the transformer and switch SR when using the same components, thereby increasing the output power of the converter.

[0270] same, Fig.23 The circuit 220 can also be further expanded to change the voltage conversion ratio. Fig.31 An extended form is shown. Fig.31 In the circuit 300 shown, the switch branch 302 includes not only the original two switches S1-S2, but also further expanded to include (2m-2) switches (S3, S4...S 2m-1 , S 2m ). Expanded (2m-2) switches (S3, S4…S 2m-1 , S 2m ) are connected in series with the original two switches S1 and S2, so that the switch branch 92 includes 2m switches connected in series, where m is an integer and m≥2.

[0271] The circuit 300 further includes (m-1) DC blocking capacitors Cx (C x1 , C x2 ) and (m-1) resonant units 304. The (m-1) resonant units 304 and the original resonant unit 303 make the circuit 300 have m resonant units. The resonant units 304 each include a resonant capacitor Crx and a resonant inductor Lrx.

[0272] Therefore, for Fig.31 The conversion circuit 300 can be described as follows: the switch branch 302 has 2m switches connected in series, where m is an integer and m≥2. Two adjacent switches among the 2m switches are connected to form a connection point, so there are (2m-1) connection points.

[0273] Considering the connection point close to the output terminal of the circuit 300 as the first connection point, the switch branch 92 has connection points No. 1, 2, 3, ..., (2m-2), (2m-1) from the output terminal to the input terminal. Fig.31 As shown, the connection point between switches S1 and S2 is closest to the output terminal, so the connection point between switches S1 and S2 is connection point 1 ( Fig.31 , and the connection point between switch S2 and the next switch adjacent to switch S2 is connection point No. 2 ( Fig.31 In the figure, the switch S 2m-1 and S 2m The connection point between them is the (2m-1)th connection point.

[0274] Each of the m resonance units is connected between an odd-numbered connection point and the second midpoint m2, and each of the (m-1) DC blocking capacitors Cx is connected between an even-numbered connection point and the first midpoint m1.

[0275] In the above m resonance units, one end of the xth resonance unit is connected to the connection point of the (2x-1)th switch and the 2xth switch in the 2m switches, where x is an integer and 1≤x≤m. For example, when x=1, for the first (x)th resonance unit ( Fig.31 The resonant unit 303 in the embodiment has one end connected to the first (2x-1) switch ( Fig.31 The switch S1 in the Fig.31 The other end is connected to the second midpoint m2. For another example, when x=m, for the m(x)th resonance unit ( Fig.31 The resonant unit 304 in the embodiment has one end connected to the (2m-1)(2x-1)th switch ( Fig.31 Switch S in 2m-1 ) and the 2m(2x)th switch ( Fig.31 Switch S in 2m ), and the other end is connected to the second midpoint m2.

[0276] In the above (m-1) DC blocking capacitors Cx, one end of the kth DC blocking capacitor is connected to the connection point between the 2kth switch and the (2k+1)th switch among the 2m switches, and the other end is connected to the middle point m2 of the second bridge arm, where k is an integer and 1≤k≤(m-1). For example, when k=1, the first (k) DC blocking capacitor ( Fig.31 The capacitor C x1 ) is connected to the second (2k) switch ( Fig.31 switch S2) and the third switch ( Fig.31The other end is connected to the first midpoint m1. For another example, when k=(m-1), the (m-1)(k)th DC blocking capacitor ( Fig.31 The DC blocking capacitor C x2 ) is connected to the (2m-2)(2k)th switch ( Fig.31 The AND switch S 2m-1 The adjacent previous switch, not shown) and the (2m-1)(2k+1)th switch (switch S in FIG. 10 2m-1 ) and the other end is connected to the first point m1.

[0277] Therefore, for Fig.31 The conversion ratio of the circuit 300 is 4m:1. This achieves the expansion of the conversion ratio of the conversion circuit. Fig.24 The circuit 230 in FIG. Fig.23 The circuit 220 in FIG. 1 is expanded by a pair of switches, a DC blocking capacitor and a resonant unit.

[0278] Fig.32 Another expansion is shown. Fig.32 The circuit 331 is for Fig.23 Another expansion of the circuit 220 in FIG. The switch branch 312 of the circuit 310 not only includes the original two switches S1-S2, but also further includes (m-2) switches (S3, ..., Sm). The expanded (m-2) switches (S3, ..., Sm) are connected in series with the original two switches S1-S2, so that the switch branch 312 includes m switches connected in series, where m is an integer and m≥3. The circuit 310 further includes (m-2) resonant units 314 (314 1 ,314 2 ). Therefore, the (m-2) resonance units 314 and the resonance unit 313 together constitute (m-1) resonance units. The resonance unit 314 includes a resonance capacitor Crx and a resonance inductor Lrx. Each resonance unit in the circuit 310 (the resonance unit 313 and the resonance unit 314) has the same resonance parameters.

[0279] Specifically, for Fig.32 The conversion circuit of the circuit 310 can be described as follows: the switch branch 312 has m switches connected in series, where m is an integer and m≥3. Two adjacent switches among the m switches are connected to form a connection point, so there are (m-1) connection points. The connection point close to the output end of the circuit 310 is regarded as the first connection point, and the switch branch 312 has connection points No. 1, 2, 3, ..., (m-1) from the output end to the input end. For example, Fig.32As shown, the connection point of switches S1 and S2 is closest to the output terminal, so the connection point of switches S1 and S2 is connection point 1 ( Fig.32 The connection point of switches S2 and S3 is connection point 2 ( Fig.32 In the figure, it is marked as "②"). Similarly, the connection point between the switch Sm and a switch (not shown) before the switch Sm is the connection point No. (m-1).

[0280] Each of the (m-1) resonance units (313, 314) in the circuit 310 has one end connected to the corresponding connection point, and the other end connected to the first midpoint m1 or the second midpoint m2. Among them, for the resonance unit with one end connected to the odd-numbered connection point, its other end is connected to the second midpoint m2. For the resonance unit with one end connected to the even-numbered connection point, its other end is connected to the first midpoint m1.

[0281] In the above (m-1) resonant units, one end of the (2y-1)th resonant unit is connected to the connection point of the (2y-1)th switch and the 2yth switch among the m switches, and the other end is connected to the primary winding Tr1 of the transformer, where y is an integer and 1≤y≤m / 2. For example, when y=1, in the (m-1)th resonant unit, the first (2y-1)th resonant unit ( Fig.32 One end of the resonant unit 313 in the circuit is connected to the first (2y-1) switch ( Fig.32 The switch S1 in the Fig.32 The other end is connected to the connection point of the switch S2 in the circuit, and the other end is connected to the second midpoint m2.

[0282] In the (m-1) resonance unit, one end of the 2zth resonance unit is connected to the connection point of the 2zth switch and the (2z+1)th switch among the m switches, and the other end is connected to the first midpoint m1, where z is an integer and 1≤z≤(m-1) / 2. For example, when z=1, in the (m-1) resonance unit, the second (2z)th resonance unit ( Fig.32 One end of the resonant unit 3141 in is connected to the second (2z) switch ( Fig.32 The switch S2 in the Fig.32 The other end is connected to the first midpoint m1. The conversion ratio of the expansion circuit 310 is still m:1.

[0283] Fig.33 Shows Fig.24 A variation of circuit 230. Fig.33In the circuit 320 shown, the full-wave rectifier circuit has a first branch consisting of a switch SR1 and a first winding Tr22, and a second branch consisting of a switch SR2 and a second winding Tr21. The switch SR1 and the first winding Tr22 are connected in series to form a first midpoint m1, and the switch SR2 and the transformer second winding Tr21 are connected in series to form a midpoint m2.

[0284] The circuit 320 has two switch branches 322 and 325, the switch branch 322 is connected between the first end of the input and the first midpoint m1, and the switch branch 325 is connected between the first end of the input and the second midpoint m2. The switch branch 322 has four switches S1-S4 connected in series, and the switch branch 325 has four switches S5-S8 connected in series. The circuit 320 also has four resonant units 323, 324, 326 and 327, and two DC blocking capacitors C1 and C2. The turns ratio of the second winding Tr12 and the first winding Tr22 is 1:1.

[0285] The resonance unit 323 is connected between the connection point p1 of the switches S1 and S2 and the second midpoint m2. The resonance unit 324 is connected between the connection point p3 of the switches S3 and S4 and the second midpoint m2. The resonance unit 326 is connected between the connection point p4 of the switches S5 and S6 and the first midpoint m1. The resonance unit 327 is connected between the connection point p6 of the switches S7 and S8 and the first midpoint m1. The DC blocking capacitor C1 is connected between the connection point p2 of the switches S2 and S3 and the first midpoint m1. The DC blocking capacitor C2 is connected between the connection point p5 of the switches S6 and S7 and the second midpoint m2.

[0286] In a working cycle of the circuit 320, in the first half of the cycle, switches S4, S2, S7, S5, and SR1 are turned on, while switches S3, S1, S8, S6, and SR2 are turned off. In the second half of the cycle, switches S4, S2, S7, S5, and SR1 are turned off, while switches S3, S1, S8, S6, and SR2 are turned on. The circuit 320 also achieves a conversion ratio of 8:1. Fig.24 Compared with the circuit 230, the current stress of the switches S1-S8 of the switch branch in the circuit 320 can be reduced by half, and the currents of the switches SR1 and SR2 are more balanced.

[0287] Fig.34A Shows Fig.23 A variation of the circuit 220. Fig.34A In the circuit 330 shown, the full-wave rectifier circuit has a first branch consisting of a switch SR1 and a first winding Tr22, and a second branch consisting of a switch SR2 and a second winding Tr21. The switch SR1 and the first winding Tr22 are connected in series to form a first midpoint m1, and the switch SR2 and the transformer second winding Tr21 are connected in series to form a midpoint m2.

[0288] The circuit 330 has two switch branches 332 and 335. The switch branch 332 is connected between the first end of the input voltage and the first midpoint m1, and the switch branch 325 is connected between the first end of the input voltage and the second midpoint m2. The switch branch 332 has switches S1 and S2 connected in series, and the switch branch 325 has switches S3 and S4 connected in series. The circuit 330 also has resonant units 334 and 336. The turns ratio of the second winding Tr12 to the first winding Tr22 is 1:1.

[0289] The resonance unit 334 is connected between the connection point p1 of the switches S1 and S2 and the second midpoint m2. The resonance unit 336 is connected between the connection point p2 of the switches S3 and S4 and the first midpoint m1.

[0290] For example, when the circuit 330 is working, switches S2, S3 and SR1 are turned on or off at the same time, switches S1, S4 and SR2 are turned on or off at the same time, and the switches S2, S3 and SR1 are turned on in a complementary and symmetrical manner to the switches S1, S4 and SR2. The circuit 330 also achieves a conversion ratio of 4:1. Fig.23 Compared with the circuit 220, the current stress of the switches S1-S4 of the switch branch in the circuit 330 can be reduced by half, and the currents of the switches SR1 and SR2 are more balanced.

[0291] Similar to Fig.25 As described above, the leakage inductance of the transformer Tr having the second winding Tr21 and the first winding Tr22 can be used as at least a part of the resonant inductance of the resonant unit. Fig.34B In the circuit 330', the leakage inductance Lk of the transformer Tr is used as a resonant inductor to resonate with the resonant capacitors Cr1 and Cr2 respectively. The circuit 330' can also achieve Fig.34A The effect of the circuit 330 is improved, and the circuit configuration is simplified.

[0292] Combination of the above Fig.33 , 34A 34B describe the situation where two groups of switch branches and two groups of resonant units share a full-wave rectifier circuit. In other embodiments, two groups of switch branches and full-wave rectifier circuits can share the same resonant unit. Fig.35 Shows Fig.23 A variation of circuit 220 .

[0293] Circuit 340 shows two sets of circuits working in parallel, where Fig.35 The dotted box contains one of the circuits, and the ones outside the dotted box contain another group of circuits.

[0294] One circuit in the dotted box has a full-wave rectifier circuit 341 and a switch branch 342. The full-wave rectifier circuit 341 has a first branch consisting of a switch SR1 and a transformer winding N1, and a second branch consisting of a switch SR2 and a transformer winding N2. The switch branch 342 is connected between the first end of the input voltage and the midpoint m1 of the first branch, and the switch branch 342 has switches S1 and S2 connected in series. Another circuit outside the dotted box has a full-wave rectifier circuit 343 and a switch branch 345. The full-wave rectifier circuit 343 has a third branch consisting of a switch SR3 and a transformer winding N3, and a fourth branch consisting of a switch SR4 and a transformer winding N4. The switch branch 345 is connected between the first end of the input voltage and the midpoint m3 of the third branch, and the switch branch 342 has switches S3 and S4 connected in series. A connection point formed by the series connection of switches S1 and S2 and a connection point formed by the series connection of switches S3 and S4 are a common connection point pc, and a midpoint of the second branch and a midpoint of the fourth branch are a common midpoint mc.

[0295] Circuit 340 further includes a resonant unit 344, one end of which is connected to the common connection point pc, and the other end of which is connected to the common midpoint mc. Therefore, resonant unit 344 is shared by two groups of circuits shown in circuit 340. Circuit 340 also achieves a conversion ratio of 4:1. The current stress of switches S1-S4 of the switch branch in circuit 330 can be reduced by half, and the current of switches SR1-SR4 is also reduced by half.

[0296] Fig.36A Shows Fig.23 Another variation of circuit 220 is shown. Fig.36A The switch branch 352 of the circuit 350 shown includes m switches, where m is an integer and m ≥ 3. The circuit 350 further includes (m-1) conversion branches 353 (353 1 ,353 2 , …, 353 m-1 ), for example, each conversion branch 353 can be a resonant unit composed of a resonant capacitor Cr and a resonant inductor Lr. In addition, the full-wave rectifier circuit of the circuit 350 includes n branches, for example, Fig.36A The full-wave rectifier circuit shown includes a switch SR1 and a secondary winding Ns of a transformer Tr. 1 The first branch is composed of switch SR2 and a secondary winding Ns of transformer Tr. 2 The second branch is composed of switch SR3 and a secondary winding Ns of transformer Tr. 3 The third branch is composed of the switch SRn and a secondary winding Ns of the transformer Tr. nThe switch and the secondary winding of each of the n branches are connected in series to form the midpoint of the corresponding branch. In this embodiment, the number of branches n in the full-wave rectifier circuit is not greater than the number of switches m in the switch branch 352, and the number of branches n is at least 2, that is, in addition to satisfying m≥3, m≥n≥2 must also be satisfied.

[0297] The n branches of the full-wave rectifier circuit include at least one first-type branch and at least one second-type branch, wherein the like-named ends of the secondary windings of the first-type branches are connected, and the opposite-named ends of the secondary windings of the first-type branches and the secondary windings of the second-type branches are connected. Fig.36A As shown in FIG. , the switch SR1 and a secondary winding Ns of the transformer Tr are connected. 1 The first branch is composed of switch SR3 and a secondary winding Ns of transformer Tr. 3 The third branch is the first type branch, and is composed of switch SR2 and a secondary winding Ns of transformer Tr. 2 The second branch is composed of switch SRn and a secondary winding Ns of transformer Tr. n The nth branch is a second type branch. Additionally, in the n branches of the full-wave rectifier circuit, the switches of the first type branch are turned on and off at the same time, and the switches of the first type branch and the switches of the second type branch are turned on in a complementary and symmetrical manner.

[0298] Fig.36A The switch branch 352 of the circuit 350 has m switches connected in series, where m is an integer and m≥3. Two adjacent switches among the m switches are connected to form a connection point, so there are (m-1) connection points. The connection point close to the output end of the circuit 350 is regarded as the first connection point, and the switch branch 352 has connection points No. 1, 2, 3, ..., (m-1) from the output end to the input end. For example, Fig.36A As shown, the connection point between switches S1 and S2 is closest to the output terminal, so the connection point between switches S1 and S2 is connection point 1 ( Fig.36A The connection point between the switch S2 and the next switch (not shown) adjacent to the switch S2 is the connection point No. 2 ( Fig.36A In the figure, it is marked as "②"). Similarly, the connection point between the switch Sm and a switch (not shown) before the switch Sm is the connection point No. (m-1).

[0299] Among the (m-1) conversion branches 353 in the circuit 350, for the conversion branch having one end connected to the odd-numbered connection point of the switch branch 352, the conversion branch is connected between the odd-numbered connection point of the switch branch 352 and the midpoint of one of the second-type branches among the n branches; and for the conversion branch having one end connected to the even-numbered connection point of the switch branch 352, the conversion branch is connected between the even-numbered connection point of the switch branch 352 and the midpoint of one of the first-type branches among the n branches.

[0300] In the (m-1) conversion branches 353, one end of the (2y-1)th conversion branch is connected to the connection point of the (2y-1)th switch and the 2yth switch among the m switches, and the other end is connected to the midpoint of one of the second-type branches among the n branches, and the (2y-1)th switch and the switches in the second-type branch are turned on or off at the same time, where y is an integer and 1≤y≤m / 2. For example, when y=1, in the m-1 conversion branches 353, the first (2y-1)th conversion branch ( Fig.36A The conversion branch 353 1 ) is connected to the first (2y-1) switch ( Fig.36A The switch S1 in the Fig.36A The other end is connected to the midpoint of one of the second type branches in the n branches, for example, the midpoint of the second branch.

[0301] Further, in the (m-1) conversion branches, one end of the 2zth conversion branch is connected to the connection point of the 2zth switch and the (2z+1)th switch in the m switches, and the other end is connected to the midpoint of one of the first-type branches in the n branches, and the 2zth switch and the switches in the first-type branch are turned on or off at the same time, where z is an integer and 1≤z≤(m-1) / 2. For example, when z=1, in the (m-1) conversion branches, the second (2z)th conversion branch ( Fig.36A The conversion branch 353 in 2 ) is connected to the second (2z) switch ( Fig.36A The switch S2 in the Fig.36A The other end is connected to a connection point of the switch S3 in the n-th branch, and the other end is connected to a midpoint of one of the first-type branches in the n-th branch, for example, the midpoint of the third branch.

[0302] When the number of switches in the switch branch 352 of the circuit 350 is m, it can achieve a voltage conversion ratio of Vin / Vo=2m.

[0303] Although Fig.36AThe multiple conversion branches 353 in are all shown as resonant units, but some of the multiple conversion branches 353 can also be composed of non-resonant units. For example, the non-resonant unit can be a unit composed of only one capacitor, or a capacitor and an inductor whose resonant frequency is much smaller than or much larger than the switching frequency of the circuit (less than 1 / 3 of the switching frequency or greater than 3 times the switching frequency). When the multiple conversion branches 353 include a conversion branch composed of a non-resonant unit, the adjacent conversion branches on both sides of the conversion branch composed of the non-resonant unit need to be resonant units. In other words, the i-th conversion branch among the (m-1) conversion branches 353 includes a non-resonant unit, and the (i-1)th conversion branch and the (i+1)th conversion branch among the (m-1) conversion branches 353 are both resonant units, where m≥4, i≤m-2, and i is an integer.

[0304] For example, in one embodiment, the conversion branch connected between the odd-numbered node and the midpoint of the second type of branch (i.e., the (2y-1)th conversion branch in 353 of the above (m-1) conversion branches) can all be composed of resonance units, and the conversion branch connected between the even-numbered node and the midpoint of the first type of branch (i.e., the 2zth conversion branch in 353 of the above (m-1) conversion branches) can all be composed of capacitors. In this case, the number m of switches of the switch branch needs to be an even number, because the last connection point of the switch branch needs to be an odd-numbered node connected to the resonance unit, so that the condition that the adjacent conversion branches of the conversion branch composed of only one capacitor are all resonance units is satisfied.

[0305] For example, when the number of switches in the switch branch and the number of branches in the full-wave rectifier circuit are both 3 (ie, m=n=3), the specific conversion circuit can be as follows: Fig.36B shown.

[0306] exist Fig.36B In the circuit 350', the switch branch 352 includes three switches S1-S3, and the full-wave rectifier circuit includes three branches. 1 The first branch is composed of switch SR3 and secondary winding Ns 3 The third branch is the first type branch, and the switch SR2 and the secondary winding Ns 2 The second branch formed is a second type branch.

[0307] The conversion branch 353 in the circuit 350' 1 Connected between the connection point of switches S1 and S2 (odd-numbered connection point ①) and the midpoint m2 of the second branch as the second type branch, and the conversion branch 353 2Connected between the connection point of switches S2 and S3 (even-numbered connection point ②) and the midpoint m3 of the third branch as the first type branch. Note that the conversion branch 353 2 It can also be connected between the connection point of switches S2 and S3 and the midpoint m1 of the first branch which is also a first-type branch. In this case, switches S1, S3, and SR2 are turned on or off at the same time, switches S2, SR1, and SR3 are turned on or off at the same time, and the group of switches S1, S3, and SR2 and the group of switches S2, SR1, and SR3 are turned on in a complementary and symmetrical manner.

[0308] For example, when the number of switches in the switch branch is 4 and the number of branches in the full-wave rectifier circuit is 3 (ie, m=4, n=3), the specific conversion circuit can be as follows: Fig.36C shown.

[0309] exist Fig.36C In the circuit 350", the switch branch 352 includes four switches S1-S4, and the full-wave rectifier circuit includes three branches. The switch SR1 and the secondary winding Ns 1 The first branch is the first type branch, which consists of switch SR2 and secondary winding Ns. 2 The second branch is composed of switch SR3 and secondary winding Ns 3 The third branch formed is the second type branch.

[0310] Conversion branch 353 in circuit 350″ 1 Connected between the connection point of switches S1 and S2 (odd-numbered connection point ①) and the midpoint m2 of the second branch as the second type branch, the conversion branch 353 2 Connected between the connection point of switches S2 and S3 (even-numbered connection point ②) and the midpoint m3 of the third branch as the first type branch, and the conversion branch 353 3 Connected between the connection point of switches S3 and S4 (even-numbered connection point ③) and the midpoint m3 of the third branch as the second type branch. It should be noted that the conversion branch 353 2 and conversion branch 353 3 They can also be connected to the midpoint m2 of the second branch or the midpoint m3 of the third branch as the second type of branch. In this case, switches S1, S3, SR2, and SR3 are turned on or off at the same time, switches S2, S4, and SR1 are turned on or off at the same time, and the group of switches S1, S3, SR2, and SR3 and the group of switches S2, S4, and SR1 are turned on in a complementary and symmetrical manner.

[0311] The switches mentioned in the above embodiments, such as the first switch and the second switch, can be formed by connecting a plurality of switches in parallel. Similarly, the winding can also be formed by connecting a plurality of windings in parallel.

[0312] Fig.37 The loss comparison between the conversion circuit discussed in this article and the traditional LLC transformer and the non-isolated LLC transformer is shown.

[0313] exist Fig.37 In the present invention, the inventors calculated the voltage conversion ratio of 8:1. Fig.24 The respective losses of the conversion circuit 230 and the LLC transformer and the non-isolated LLC transformer with the same voltage conversion ratio of 8:1 are shown.

[0314] exist Fig.37 In the figure, the circuit working conditions are: input voltage Vin = 48V, output voltage Vout = 4.8V, operating frequency f = 1.2MHz, output current Io = 50A. The current of the primary winding and the secondary winding are disassembled. Fig.24 The circuit 230 in the circuit has only two windings in the full-wave rectifier circuit, and does not need the primary winding in the LLC (or non-isolated LLC), so the circuit 230 does not have this part of the winding loss. The winding current in the full-wave rectifier is subjected to Fourier decomposition (FFT). Since the output current is the same, the DC component of the secondary current of the three circuits is the same. Since the utilization rate of the winding is high, the current in the first and second half cycles of the circuit 230 is basically the same, so the first harmonic current value (marked as 1st in the figure) is only 1.6A. In the traditional LLC full-wave rectifier, the winding only works for half a cycle, so the first harmonic current is the largest, reaching 40.8A. The other harmonics of the three circuits (such as the second harmonic 2nd, the third harmonic 3rd, and the fourth harmonic 4th in the figure) are relatively close. Reflecting on the effective value of the winding, it can be seen that the effective value (RMS) of the secondary current of LLC is 40.89A, the non-isolated LLC is 33.2A, and the effective value of the winding current in circuit 220 is the smallest, only 29.28A. In addition, since both LLC and non-isolated LLC require primary windings, the common secondary-primary-secondary (SPS) winding structure is used in the calculation, while circuit 230 only requires two windings.

[0315] Assuming that the transformer winding is made of 12-layer PCB, LLC and non-isolated LLC have only 4 winding units, while circuit 230 has 6 winding units. Therefore, with the same copper usage, the winding impedance of circuit 230 is the smallest. Combining the above current effective value and winding impedance, the total winding loss under this condition can be calculated. It can be seen that for Fig.24The conversion circuit 230 in the embodiment has a winding loss of about 0.26W, while the winding loss of the LLC transformer with the same conversion ratio is about 1.506W, and the winding loss of the non-isolated LLC transformer with the same conversion ratio is about 0.801W. It can be seen that the transformer loss in the conversion circuit discussed in this article has been greatly reduced, only about 20% of the original LLC circuit.

[0316] Therefore, the conversion circuit discussed in this article has an improved conversion ratio compared to the STC conversion circuit with the same number of switches, and at the same conversion ratio, the winding loss of the conversion circuit discussed in this article is significantly reduced compared to the traditional LLC transformer and the non-isolated LLC transformer.

[0317] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the disclosure is determined by the claims that follow.

Claims

1. A conversion circuit, for converting an input voltage to provide an output voltage, wherein both the input voltage and the output voltage comprise a first end and a second end, the second end of the input voltage is connected to the second end of the output voltage, and the conversion circuit comprises: A first full-wave rectifier circuit, comprising a first branch and a second branch connected in parallel between the first end and the second end of the output voltage, the first branch comprising a first winding of a transformer and a first rectifier switch connected in series to form a first midpoint, and the second branch comprising a second winding of the transformer and a second rectifier switch connected in series to form a second midpoint; A first switch branch connected between the first end of the input voltage and the first midpoint, and comprising a first switch and a second switch connected in series to form a first connection point; and The first resonance unit is connected between the first connection point and the second midpoint, wherein the first resonance unit is not connected in series with the winding of the transformer. 2 . The conversion circuit according to claim 1 , wherein a leakage inductance of the transformer is used as at least a part of a resonant inductance of the first resonant unit.

3. The conversion circuit according to claim 1 further comprises: a second switch branch connected between the first end and the second midpoint of the input voltage and comprising a third switch and a fourth switch connected in series to form a second connection point, and The second resonance unit is connected between the second connection point and the first midpoint. 4 . The conversion circuit according to claim 3 , wherein a leakage inductance of the transformer is used as at least a part of a resonant inductance of the first resonant unit and / or the second resonant unit.

5. The conversion circuit according to claim 1 further comprises: a second full-wave rectifier circuit, comprising a third branch and a fourth branch connected in parallel between the first end and the second end of the output voltage, the third branch comprising a third winding and a third rectifier switch of the transformer connected in series to form a third midpoint, the fourth branch comprising a fourth winding and a fourth rectifier switch of the transformer connected in series, a common connection point of the fourth winding and the fourth rectifier switch being connected to the second midpoint; and The second switch branch is connected between the first end of the input voltage and the third midpoint and comprises a third switch and a fourth switch connected in series, wherein a common connection point of the third switch and the fourth switch is connected to the first connection point.

6. The conversion circuit according to claim 1, wherein The first switch branch further includes (m-2) switches connected in series with the first switch and the second switch, so that the first switch branch includes m switches connected in series, wherein adjacent switches among the m switches are connected to form a connection point, The conversion circuit further comprises (m-2) resonance units, which together with the first resonance unit constitute (m-1) resonance units. The first full-wave rectifier circuit further comprises (n-2) branches connected in parallel with the first branch and the second branch, so that the full-wave rectifier circuit comprises n branches connected in parallel, each of the n branches comprises a winding of the transformer and a rectifier switch connected in series to form a midpoint, the n branches comprise at least one first-type branch and at least one second-type branch, the transformer windings of the first-type branches have like-name ends connected, and the transformer windings of the first-type branches and the transformer windings of the second-type branches have different-name ends connected, One end of the (2y-1)th resonance unit among the (m-1)th resonance units is connected to a connection point between the (2y-1)th switch and the 2yth switch among the m switches, and the other end is connected to a midpoint of one of the at least one second-type branch. One end of the 2zth resonance unit among the (m-1)th resonance units is connected to a connection point between the 2zth switch and the (2z+1)th switch among the m switches, and the other end is connected to a midpoint of one of the at least one first-type branch, and m, n, y and z are integers, m≥n≥2, 1≤y≤m / 2 and 1≤z≤(m-1) / 2.

7. The conversion circuit according to claim 6, wherein: The rectifier switches of the first type of branches are turned on and off at the same time, and the rectifier switches of the first type of branches and the rectifier switches of the second type of branches are turned on complementarily.

8. The conversion circuit according to claim 1, wherein The first switch branch further includes (2m-2) switches connected in series with the first switch and the second switch, so that the first switch branch includes 2m switches connected in series, wherein adjacent switches among the 2m switches are connected to form a connection point, The first full-wave rectifier circuit further includes (n-2) branches connected in parallel with the first branch and the second branch, so that the full-wave rectifier circuit includes n branches connected in parallel, each of the n branches includes a transformer winding and a rectifier switch connected in series to form a midpoint, the n branches include at least one first-type branch and at least one second-type branch, the rectifier switch of the first-type branch is turned on and off at the same time, the rectifier switch of the first-type branch and the rectifier switch of the second-type branch are turned on complementarily, the same-name ends of the windings of the transformers of the first-type branches are connected, and the opposite-name ends of the windings of the transformers of the first-type branches and the second-type branches are connected, The conversion circuit further comprises: (m-1) resonance units, so as to constitute m resonance units together with the first resonance unit, one end of the xth resonance unit among the m resonance units is connected to the connection point of the (2x-1)th switch and the 2xth switch among the 2m switches, and the other end is connected to the midpoint of one of the at least one second-type branch; and (m-1) capacitors, one end of the kth capacitor among the (m-1) capacitors is connected to a connection point between the 2kth switch and the (2k+1)th switch among the 2m switches, and the other end is connected to a midpoint of one of the at least one first-type branch, and m, n, x and k are integers, m≥2, n≤2m, 1≤x≤m and 1≤k≤m-1.

9. The conversion circuit according to any one of claims 1 to 8 further comprises an output capacitor, wherein the output capacitor is connected in parallel with the first branch.

10. The conversion circuit according to claim 9 further comprises an input capacitor, wherein The input capacitor is electrically connected between the first end of the input voltage and the second end of the input voltage, or The input capacitor is electrically connected between the first end of the input voltage and the first end of the output voltage.

11. A conversion circuit, for converting an input voltage to provide an output voltage, wherein the input voltage and the output voltage both comprise a first end and a second end, the second end of the input voltage is connected to the second end of the output voltage, and the conversion circuit comprises: A full-wave rectifier circuit, comprising n branches connected in parallel between the first end and the second end of the output voltage, each of the n branches comprising a winding of a transformer forming a midpoint and a rectifier switch connected in series, the n branches comprising at least one first-type branch and at least one second-type branch, the windings of the transformers of the first-type branches having like-name ends connected, and the windings of the transformers of the first-type branches and the windings of the transformers of the second-type branches having different-name ends connected; A first switch branch comprises m switches connected in series, wherein adjacent switches among the m switches are connected to form a connection point; and (m-1) conversion branches, each conversion branch comprising a capacitor, a (2y-1)th conversion branch among the (m-1) conversion branches connected between a connection point between a (2y-1)th switch and a 2yth switch among the m switches and a midpoint of one of the at least one second-type branches, a 2zth conversion branch among the (m-1) conversion branches connected between a connection point between a 2zth switch and a (2z+1)th switch among the m switches and a midpoint of one of the at least one first-type branches, in, When the i-th conversion branch among the (m-1) conversion branches is a non-resonant unit, the (i-1)-th conversion branch and the (i+1)-th conversion branch among the (m-1) conversion branches are both resonant units, m, n, y, i and z are integers, m≥n≥2, 1≤y≤m / 2, m≥4, i≤m-2 and 1≤z≤(m-1) / 2.

12. The conversion circuit according to claim 11, wherein: The rectifier switches of the first type of branches are turned on and off at the same time, and the rectifier switches of the first type of branches and the rectifier switches of the second type of branches are turned on complementarily.

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