CN113938017A

CN113938017A - Conversion circuit topology

Info

Publication number: CN113938017A
Application number: CN202110747546.3A
Authority: CN
Inventors: 叶益青; 周嫄; 叶浩屹; 辛晓妮; 付志恒; 鲍华尧
Original assignee: Delta Electronics Shanghai Co Ltd
Current assignee: Delta Electronics Shanghai Co Ltd
Priority date: 2020-07-13
Filing date: 2021-07-02
Publication date: 2022-01-14

Abstract

A variation circuit for converting an input voltage into an output voltage includes a full bridge circuit, a first switch branch, a first resonance unit, and a first transformer. The full-bridge circuit comprises a first bridge arm and a second bridge arm which are electrically connected between a first end and a second end of an output voltage in parallel. The first switch branch circuit is electrically connected between a first end of an input voltage and a first end of an output voltage, and comprises a first switch and a second switch which are connected in series to form a first connecting point. The first resonance unit is electrically connected between the first connecting point and the midpoint of the first bridge arm. The first transformer comprises a first primary winding connected in series with the first resonance unit and a first secondary winding connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm. The conversion circuit provided by the invention improves the conversion efficiency while reducing the voltage stress of the switching tube.

Description

Conversion circuit topology

Technical Field

The present disclosure relates to a converter circuit for converting a voltage of a power supply to supply power to a load.

Background

Research data of the energy-saving technical committee of the Chinese data center shows that the total electricity consumption of the Chinese data center exceeds 1200 hundred million kilowatt hours in 2016. Despite such staggering power consumption of data centers, however, as more and more services are supported by data centers, the computational load and size of data centers still remain high. To increase the operating density of a data center, the power of a single RACK (RACK) is increased. The number of processor chips in a conventional rack is small, so the power of a single rack is generally less than 15 kW. For a traditional rack, an alternating current UPS for supplying power to the rack is located outside the rack, the voltage of an internal direct current distribution bus is 12V, and the voltage is stable. However, as the number of processor chips in a single rack increases, the power of a single rack increases, and when the power of a single rack exceeds 15kW, the current on the 12V dc distribution bus increases significantly, greatly reducing efficiency, increasing the cost of heat dissipation, cables and connectors, etc. Therefore, a new power transmission architecture is proposed, in which the DC distribution bus inside the rack is raised to 48V, and at the same time, the ac UPS is replaced by a DC UPS (DC-UPS), and installed inside the rack, directly connected to the 48V DC distribution bus. Neotype 48V distribution bus structure has significantly reduced distribution bus current, has improved data center's power supply efficiency, has reduced power consumption cost, heat dissipation cost and distribution bus cost, and then, has reduced data center's total cost of ownership. In addition, the DC-UPS is directly connected with the 48V distribution bus, the power supply reliability of the rack is further improved, the range of the bus voltage is between 40V and 59.5V, the bus voltage is always in the safe ultralow voltage SELV range, and the safety of maintenance operation is guaranteed.

The power conversion Module (VRM) between the dc bus and the processor chip has a very high efficiency requirement, 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%, the power conversion efficiency is always higher than 92%. However, in the new power transmission architecture, the challenge faced by 48V-VRM is significantly higher than in the case of 12V distribution bus. On one side of the direct current distribution bus, the voltage of the 12V distribution bus is stable, and the variation range is small. And the 48V distribution bus is directly connected with the DC-UPS, the voltage range is directly influenced by the DC-UPS, and the voltage range is wide and ranges from 40V to 59.5V. On the processor chip side, in order to reduce the power consumption of the processor chip, the core voltage of the processor chip is further reduced. In addition, to provide short-term chip acceleration performance, processor chips require 48V-VRMs to provide significantly increased voltage and current. Taking a certain GPU as an example, the core voltage range of the GPU is 0.6V to 1.1V, the core voltage is 0.6V and the rated current is 400A in the energy-saving mode, and the rated current is 600A in the rated working condition and the core voltage is 0.8V. However, in GPU acceleration mode, the 48V-VRM is required to provide 1.1V of core voltage and 1200A of output current to the GPU in 200 microseconds.

It can be seen that in the new power transmission architecture, the voltage conversion ratio between the bus bar and the processor chip is significantly improved. Under such conditions, satisfying the requirements for power conversion efficiency while maintaining high power density, 48V-VRM from dc distribution bus to processor chip faces a significant challenge.

Generally, a 48V-VRM is a two-stage cascaded converter structure, which generally adopts a buck-first and then voltage-regulating operation mode. For example, the first stage converter may employ an efficient dc transformer to step down the incoming 48V bus voltage (Uin) to a lower intermediate bus voltage (Uib), such as 4V. And the second stage adopts a multiphase interleaving BUCK converter in parallel connection, and ensures the power supply of a load (such as a processor chip) by controlling the BUCK output voltage UO in a closed loop.

The typical topology that the first-stage converter of the 48V-VRM can usually adopt is an LLC series resonant circuit, the circuit can charge and discharge a parasitic capacitor of a primary side switching tube within the dead time of the primary side switching tube by adjusting the exciting current of a transformer, so that ZVS operation of the primary side switching tube is realized, the minimum switching-on loss of the switching tube is realized, and meanwhile, the primary side switching tube can realize smaller turn-off current by a resonant mode, so that the turn-off loss is reduced. For the secondary side switching tube (such as diode), the voltage stress on the secondary side switching tube is low because there is no output inductance. When the switch tube on the secondary side adopts the synchronous rectifier tube, the switch tube with lower voltage resistance and better performance can be selected to realize lower on-state loss. Furthermore, high power density applications at high frequencies are easier to achieve due to soft switching characteristics. Due to the use of the transformer, a high conversion ratio can be realized very conveniently. Assuming that the transformer turns ratio is N:1:1, when the switching frequency fs is equal to the resonance frequency fr, the conversion ratio is N (full bridge LLC) or 2N (half bridge LLC).

However, LLC circuits also have some drawbacks. Because of the transformer, all energy conversion must be carried out by the transformer, the switching tube on the primary side of the transformer is responsible for generating the excitation of the primary winding, and the secondary side is the excitation of the inductive primary side and is output to the final load through the rectifier. In the process, the primary side switching tube only generates excitation, the self excitation current does not flow to the load end but flows back to the input end again, all the load current is provided by the secondary side circuit, and the current stress of the secondary side winding and the device is larger at the moment.

The LLC circuit described above can achieve high voltage ratio and ZVS soft switching, but all the energy is transferred through the transformer. Non-isolated LLC circuits may also be used when isolation is not required in an actual system. The non-isolated LLC circuit realizes soft switching, large transformation ratio and flow of primary side excitation current to a load, and meanwhile, the idle secondary side of the transformer is repeatedly used for an excitation coil of the converter, so that the number of turns of the primary side winding and the resistance are reduced. Although the number of turns of the transformer is reduced by the non-isolated LLC, only 2 extra primary current flows into the load end in the transformer, and the characteristic determines that when the conversion ratio is required to be larger, the additionally increased conversion ratio of the non-isolated LLC is reduced in the whole conversion ratio, so that the benefit is reduced, and the efficiency approaches the efficiency of the LLC under the condition of high conversion ratio.

Another implementation of a Converter is referred to as a Switching Tank Converter (STC). Compared with LLC, this converter does not use a transformer, but performs power conversion by directly supplying current to the load side. Fig. 1 shows an example of a circuit of STC 100, where a dc voltage is present across capacitor C1, which is 0.5Vin for a duty cycle of 0.5 for on-off S1-S4. The switching tubes S1, S3, SR1 and SR4 are turned on simultaneously in the first half period, and the switching tubes S2, S4, SR2 and SR3 are turned on simultaneously in the second half period, so that the conversion ratio of Vin/Vo to 4:1 can be realized. The circuit can change the voltage conversion ratio of the circuit by adjusting the number of the series switches and the resonant cavities. The circuit has the advantages that no transformer is arranged, all energy flows to the load directly through the modulation circuit, the conversion process of the transformer is reduced, and the voltage stress of the switching tubes S1-S4 is reduced. The method has the disadvantages that the realized conversion ratio is lower, more stages are needed to be superposed when the higher conversion ratio is needed to be realized, the complexity of a circuit is increased, ZVS cannot be realized, only ZCS can be realized, and the control precision requirement in the ZCS process is higher. Therefore, STC is more efficient at low conversion ratios, but as the voltage conversion ratio becomes larger, its efficiency gradually becomes lower than LLC topology due to higher complexity of the line and influence of the device.

Disclosure of Invention

The invention aims to solve the problems of complex circuit and low efficiency of the switch resonant cavity converter in conversion ratio, and provides a conversion circuit which can realize different voltage conversion ratio requirements in reducing switching loss.

According to an aspect of the present disclosure, there is provided a conversion circuit for converting an input voltage to provide an output voltage, the input voltage and the output voltage each including a first terminal and a second terminal, the second terminal of the input voltage and the second terminal of the output voltage being connected, the conversion circuit including:

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;

a first switch branch electrically connected between the first end of the input voltage and the first end of the output voltage and including a first switch and a second switch connected in series to form a first connection point;

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

A first transformer, comprising: the first primary winding is connected with the first resonance unit in series; and a first secondary winding connected between the midpoint of the first leg and the midpoint of the second leg.

According to another aspect of the present disclosure, there is provided a conversion circuit for converting an input voltage to provide an output voltage, the input voltage and the output voltage each including a first terminal and a second terminal, the second terminal of the input voltage and the second terminal of the output voltage being connected, the conversion circuit including:

a full-wave rectification 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 forming a first midpoint and a first rectification switch connected in series, the second branch comprising a second secondary winding of the transformer forming a second midpoint and a second rectification switch connected in series;

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

the first resonance unit is electrically connected between the first connecting point and the second midpoint;

the second resonance unit is electrically connected between the third connecting point and the second midpoint;

the first primary winding of the transformer is connected with the first resonance unit in series; and

a first capacitor connected between the second connection point and the first midpoint.

a full-wave rectification circuit including 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, the first branch including a first secondary winding and a first rectification switch of a first transformer forming a first midpoint in series, the second branch including a second secondary winding and a second rectification switch of the first transformer forming a second midpoint in series, the third branch including a first secondary winding and a third rectification switch of a second transformer forming a third midpoint in series, the fourth branch including a second secondary winding and a fourth rectification switch of the second transformer forming a fourth midpoint in series;

a first switch branch connected between the first end and the first midpoint of the input voltage and including a first switch, a second switch, a third switch, and a fourth switch connected in series, the first switch and the second switch being connected to form a first connection point, the second switch and the third switch being connected to form a second connection point, and the third switch and the fourth switch being connected to form a third connection point;

a first resonance unit connected between the first connection point and the second midpoint;

a second resonance unit connected between the third connection point and the fourth midpoint;

the primary winding of the first transformer is connected with the first resonance unit in series;

the primary winding of the second transformer is connected in series with the second resonance unit; and

a capacitor connected between the second connection point and the third midpoint.

a first resonance unit;

the plurality of primary windings of the transformer comprise a first primary winding and a second primary winding, the first primary winding and the first resonance unit are connected in series and then are 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

a full-wave rectification circuit comprising n parallel branches connected between the first end and the second end of the output voltage, each of the n branches comprising a secondary winding of a transformer forming a midpoint and a rectification switch connected in series, the n branches comprising at least one first type branch and at least one second type branch, the homonymous ends of the secondary windings of the first type branch being connected, the secondary windings of the first type branch being connected to the heteronymous ends of the secondary windings of the second type branch;

a first switching leg comprising m switches in series, wherein adjacent ones of the m switches are connected to form a connection point;

(m-1) switching legs, each switching leg comprising a capacitance, a (2y-1) th one of the (m-1) switching legs being connected between connection points of a (2y-1) th one of the m switches and a 2y switch and a midpoint of one of the at least one second class of legs, a 2 z-th one of the (m-1) switching legs being connected between connection points of a 2 z-th one of the m switches and a (2z +1) th one of the m switches and a midpoint of one of the at least one first class of legs; and

a first primary winding of the transformer is connected in series with one of the (m-1) conversion branches,

wherein m, n, y and z are integers, m is more than or equal to n and more than or equal to 2, m is more than or equal to 3, 1 is more than or equal to y and less than or equal to m/2, and 1 is more than or equal to z and less than or equal to (m-1)/2.

a first full-wave rectification 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 rectification switch connected in series forming a first midpoint, the second branch comprising a second winding of the transformer and a second rectification switch connected in series forming a second midpoint;

a first switch branch connected between the first end of the input voltage and the first midpoint and including a first switch and a second switch connected in series to form a first connection point; and

and the first resonance unit is connected between the first connecting point and the second midpoint, wherein the first resonance unit is not connected with a winding of the transformer in series.

a full-wave rectification circuit comprising n branches connected in parallel between the first and second ends of the output voltage, each of the n branches comprising a winding of a transformer and a rectification switch connected in series forming a midpoint, 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 branch being connected at their homonymous ends, the windings of the transformers of the first-type branch being connected at their synonym ends with the windings of the transformers of the second-type branch;

a first switching leg comprising m switches in series, wherein adjacent ones of the m switches are connected to form a connection point; and

(m-1) switching legs, each switching leg comprising a capacitance, a (2y-1) th one of the (m-1) switching legs being connected between connection points of a (2y-1) th one of the m switches and a 2y switch and a midpoint of one of the at least one second class of legs, a 2 z-th one of the (m-1) switching legs being connected between connection points of a 2 z-th one of the m switches and a (2z +1) th one of the m switches and a midpoint of one of the at least one first class of legs,

when the ith conversion branch in the (m-1) conversion branches is a non-resonant unit, the (i-1) conversion branch and the (i +1) conversion branch in the (m-1) conversion branches are resonant units, m, n, y, i and z are integers, m is more than or equal to n and more than or equal to 2, y is more than or equal to 1 and less than or equal to m/2, m is more than or equal to 4, i is more than or equal to m-2, and z is more than or equal to 1 and less than or equal to (m-1)/2.

Drawings

In order that the above-described features described herein can be understood in detail, a more particular description briefly summarized above may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described below:

fig. 1 shows a circuit example of a conventional STC.

Fig. 2 shows an example circuit of a transformation circuit according to a first embodiment herein.

Fig. 3A shows a variation of the circuit of fig. 1.

Fig. 3B shows a waveform diagram of an electrical signal in the circuit of fig. 3A.

Fig. 3C shows a current flow diagram of the circuit of fig. 3A during a half duty cycle.

Fig. 4 shows a variant of the circuit of fig. 1.

Fig. 5 shows a variant of the circuit of fig. 1.

Fig. 6A and 6B show a variation of the circuit of fig. 1.

Fig. 7 shows a variant of the circuit of fig. 1.

Fig. 8 shows a variant of the circuit of fig. 1.

Fig. 9 shows a variant of the circuit of fig. 1.

Fig. 10A and 10B show a variation of the circuit of fig. 1.

Fig. 11A to 11C show a modification of the circuit of fig. 1.

Fig. 12 shows a variant of the circuit of fig. 1.

Fig. 13A illustrates an example circuit of a transform circuit according to a second embodiment herein. Fig. 13B shows a waveform diagram of an electric signal in the circuit of fig. 13A.

Fig. 13C shows a current flow diagram for the circuit of fig. 13A during a half duty cycle.

Fig. 14 shows a variation of the circuit of fig. 13A.

Fig. 15 shows a variation of the circuit of fig. 13A.

Fig. 16A and 16B show a modification of the circuit of fig. 13A.

Fig. 17 shows a variation of the circuit of fig. 13A.

Fig. 18 shows a variation of the circuit of fig. 13A.

Fig. 19 shows a variation of the circuit of fig. 13A.

Fig. 20A and 20B show a modification of the circuit of fig. 13A.

Fig. 21A to 21D show a modification of the circuit of fig. 13A.

Fig. 22 shows a variation of the circuit of fig. 13A.

Fig. 23 shows an example circuit of a transform circuit according to a third embodiment herein.

Fig. 24 shows a variation of the circuit of fig. 23.

Fig. 25 shows a variation of the circuit of fig. 23.

Fig. 26 shows a variation of the circuit of fig. 23.

Fig. 27 shows a variation of the circuit of fig. 23.

Fig. 28 shows a variation of the circuit of fig. 23.

Fig. 29 shows a variation of the circuit of fig. 23.

Fig. 30 shows a variation of the circuit of fig. 23.

Fig. 31 shows a variation of the circuit of fig. 23.

Fig. 32 shows a variation of the circuit of fig. 23.

Fig. 33 shows a variation of the circuit of fig. 23.

Fig. 34A and 34B show a modification of the circuit of fig. 23.

Fig. 35 shows a variation of the circuit of fig. 23.

Fig. 36A to 36C show a modification of the circuit of fig. 23.

Fig. 37 shows a winding loss comparison of a conversion circuit according to embodiments herein and a conventional conversion circuit.

Detailed Description

Embodiments herein will now be described in detail with reference to the accompanying drawings, which will be described in the following order.

[ first embodiment ]

[ variation of the first embodiment ]

[ second embodiment ]

[ variation of the second embodiment ]

[ third embodiment ]

[ variation of the third embodiment ]

One or more examples of the various embodiments herein are illustrated in the accompanying drawings. In the following description of the drawings, the same reference numerals indicate the same or similar components. In the following, only the differences with respect to individual embodiments are described. Each example is provided for the purpose of illustrating the present technology and is not meant to be a limitation of the subject matter claimed herein. In addition, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. The following detailed description is intended to embrace such modifications and variations.

[ first embodiment ]

Referring to fig. 2, fig. 2 shows an example circuit of the transform circuit 10 according to the first embodiment herein. The circuit 10 receives an input voltage Vin, converts the input voltage Vin, and outputs the converted voltage.

The circuit 10 includes a full-bridge rectifier circuit 11 composed of rectifiers SR1, SR2, SR3 and SR4, a switching 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 Tr 2.

The input voltage and the output voltage each have a first terminal and a second terminal. Wherein the second terminal of the input voltage and the second terminal of the output voltage are connected, such as ground GND in fig. 2. The switching leg 12 is connected between a first terminal of the input voltage and a first terminal of the output voltage, and the switching leg 12 comprises switches S1 and S2, S1 and S2 connected in series forming a connection point p 1. The full-bridge rectifier circuit 11 is connected between a first terminal and a second terminal of the output voltage. In the full-bridge rectifier circuit 11, the rectifier tubes SR1 and SR2 are connected in series to form a first arm, and the rectifier tubes SR3 and SR4 are connected in series to form a second arm.

In one example of the circuit 10, the circuit 10 may include an output capacitor Co for output filtering, the output capacitor Co being connected between a first terminal and a second terminal of the output voltage, in parallel with the first leg and the second leg of the full bridge rectifier circuit 11. Additionally, the circuit 10 may also include an input capacitance Cin for input filtering, which may be connected between the first and second terminals of the input voltage, or the input capacitance Cin may also be connected between the first terminal of the input voltage and the first terminal of the output voltage, as illustrated by the dashed line connected input capacitance Cin in fig. 2.

In the circuit 10, the resonance unit 13 includes a resonance capacitor Cr and a resonance inductor Lr which are 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 Tr 1. The other end of the primary winding Tr1 is connected to the midpoint m1 of the first leg of the full-bridge rectifier circuit 11. Secondary winding Tr2 is connected between midpoint m1 of the first leg and midpoint m2 of the second leg. In some embodiments, the positions of the resonant unit 13 and the primary winding Tr1 may be interchanged. As long as the resonance unit 13 and the primary winding Tr1 are ensured to be connected in series.

The operation of the circuit 10 is described below. In one duty cycle of the circuit 10, in the first half of the one duty cycle, the switch S2 and the rectifiers SR1, SR4 are turned on, and the switch S1 and the rectifiers SR2, SR3 are turned off. In the second half of one duty 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 ratio of the switches S1 and S2 and the rectifiers SR1, SR2, SR3 and SR4 is 0.5.

In the first half of a duty cycle, current flows from the input terminal throughA first path formed by the switch S2, the resonant capacitor Cr, the resonant inductor Lr, the primary winding Tr1 and the rectifier tube SR1 is connected to the output end, and the resonant frequency is

The input terminal supplies energy to the output terminal directly through the first path. At the same time, the secondary winding Tr2 induces a resonant current in the primary winding Tr1 and provides energy to the output through the second path formed by SR1, SR 4. When the first half cycle is converted and then the second half cycle is converted, parasitic capacitances of S2, SR1 and SR4 are charged by exciting inductor current, parasitic capacitances of S1, SR2 and SR3 are discharged, and therefore soft switching of the device is achieved. In the second half of a duty cycle, similar to the first half, current is supplied to the output terminal through a third path consisting of the rectifier 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 induces a resonant current in the primary winding Tr1 and provides energy to the output through the fourth path formed by SR2, SR 3.

Assuming that the current at the input terminal is i, the equivalent current in the resonant unit 13 is 2i during one duty cycle, so the transformer Tr₁Also 2i and the current flows directly to the output. At the same time, when the transformer Tr₁The turns ratio of (a) is N:1, the secondary side induction current of the transformer Tr is 2 Ni. The total current flowing to the output is therefore (2N +2) i. Since only a half of the resonant period of the current flows through S1, the input-side current is half of the equivalent current of the resonant unit 13, i.e., i. The conversion ratio of the circuit voltage shown in fig. 2 (i.e. the ratio of the input voltage and the output voltage of the circuit) is therefore (2N + 2): 1, where 2N is the transformation ratio of the transformer turn ratio, and 2 is caused by the current flowing through the primary winding of the transformer from the circuit flowing directly to the output terminal.

In a conventional STC with only 2 switches, the voltage conversion ratio is only 2. For circuit 10, the voltage conversion ratio is (2N + 2): 1, therefore the voltage conversion ratio of the circuit is improved, the number of primary windings of the transformer can be reduced under the same voltage conversion ratio, the utilization efficiency of the transformer is improved, meanwhile, the current flowing through the primary winding of the transformer in the circuit directly flows to the output end of the transformer to be 2, the current does not need to be induced by the transformer, and the loss and the volume of the transformer are further reduced.

Although the resonant unit 13 in the circuit 10 is composed of the resonant capacitor Cr and the resonant inductor Lr which are connected in series, the present disclosure is not limited thereto, and for example, the resonant unit 13 may be composed of the resonant capacitor Cr and the resonant inductor Lr which are connected in parallel.

[ variation of the first embodiment ]

The example of the conversion circuit according to the first embodiment herein is described above, however, the conversion circuit according to the first embodiment herein may be variously modified. Various modifications of the full-bridge rectification type converter circuit 10 are described below, and only differences of the various modifications with respect to the converter circuit 10 are described, and the same parts are not described again.

Fig. 3A shows a schematic diagram of a transformation circuit 20 according to a variation of the first embodiment herein.

As shown in fig. 3A, the circuit 20 includes a full-bridge rectifier circuit 21 including rectifiers SR1, SR2, SR3, and SR4, a switching branch 22 including switches S1, S2, S3, and S4, a resonant unit 23 including a resonant capacitor Cr1 and a resonant inductor Lr1, a resonant unit 24 including a resonant capacitor Cr2 and a resonant inductor Lr2, a transformer including a primary winding Tr1 and a secondary winding Tr2, and a capacitor C1.

The input voltage and the output voltage each have a first terminal and a second terminal, wherein the second terminals of the input voltage and the output voltage are connected. The switching leg 22 is connected between the first ends of the input voltage and the output voltage, and the switching leg 22 includes switches S1, S2, S3, and S4 connected in series. The full-bridge rectifier circuit 21 is connected between the first and second ends of the output voltage. The rectifier tubes SR1 and SR2 in the full-bridge rectifier circuit 21 form the first arm, and the rectifier tubes SR3 and SR4 form the second arm.

The resonant unit 23 comprises a resonant capacitor Cr1 and a resonant inductor Lr1 which are connected in series, the resonant unit 23 is connected in series with the primary winding Tr1, the resonant unit 24 comprises a resonant capacitor Cr2 and a resonant inductor Lr2 which are connected in series, and the resonant unit 24 is also connected in series with the primary winding Tr 1. Here, it should be noted that "in series" as used herein refers not only to a case where a series connection between two electronic elements in a general sense is made such that currents flowing through the electronic elements in series are equal, but also to a case where two electronic elements are connected to form a common connection point. For example, for the case where one end of the resonance unit 23 is connected to the connection point p1 at the switches S1 and S2 and the other end of the resonance unit 23 is connected to one end of the primary winding Tr1 as shown in fig. 3A, the resonance unit 23 and the primary winding Tr1 are considered to be connected in series; similarly, for the case where one end of the resonance unit 24 is connected to the connection point p3 at the switches S3 and S4 and the other end of the resonance unit 24 is connected to one end of the primary winding Tr1 shown in fig. 3A, the resonance unit 24 and the primary winding Tr1 are also considered to be connected in series. Although the currents flowing through the

resonance units

23 and 24 and the primary winding Tr1 in the

resonance units

23 and 24 and the primary winding Tr1 thus connected are not equal, it is described herein that the resonance unit 23 and the primary winding Tr1 are connected in series, and the resonance 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 leg of the full-bridge rectifier circuit 21. Secondary winding Tr2 is connected between midpoint m1 of the first leg and midpoint m2 of the second leg. Capacitor C1 has one end connected to the connection point p2 of switches S2 and S3 and the other end connected to the midpoint m2 of the second leg.

The operation state of the circuit 20 is described with reference to fig. 3B and 3C. Fig. 3B shows the change in current or voltage in each element during one duty cycle of circuit 20. Where iLr denotes a current of each of the resonance unit 23 and the resonance unit 24, iLm denotes a current of an excitation inductance on the transformer, Vs1 and Vs3 denote voltages across the switches S1 and S3, and isr1, isr2, isr3, and isr4 denote currents in the rectifiers SR1, SR2, SR3, and SR 4. Fig. 3C shows an example of the current flow in the first half of a duty cycle of the circuit.

t0-t4 represents one duty cycle of the circuit 20. In the circuit 20, the switches S4 and S2 and the rectifiers SR1 and SR4 are turned on simultaneously, the switches S3 and S1 and the rectifiers SR2 and SR3 are turned on symmetrically in a complementary manner, and the duty ratio is close to 0.5. Complementary symmetrical conduction here meansThe conducting time of the positive half-cycle switching tube in the circuit is basically the same as the conducting time of the negative half-cycle switching tube. Taking the circuit in fig. 3A as an example, the time period t0-t 2 is the first half of the duty cycle, the time period t 2-t 4 is the second half of the duty cycle, where t0-t 1 and t 2-t 3 are the time periods when the switching tubes are turned on in the positive and negative half cycles, respectively, and these two time periods are substantially the same, i.e., (t1-t0) ═ t3-t 2. In the time period from t0 to t1, the switches S4 and S2 and the rectifiers SR1 and SR4 are turned on, the switches S3 and S1 and the rectifiers SR2 and SR3 are turned off, the current flows through the switch S4, the resonant capacitor Cr2, the resonant inductor Lr2, the primary winding Tr1 of the transformer and the rectifier SR1 to form a resonant first path, and the resonant frequency is

The input provides energy to the output through a first path. The voltage on the blocking capacitor C1 is 0.5Vin, a resonant second path is formed by the rectifier SR4, the switch S2, the resonant capacitor Cr1, the resonant inductor Lr1, the primary winding Tr1 of the transformer and the rectifier SR1, and the resonant frequency is

The output is supplied with energy by a capacitor C1. Meanwhile, the secondary winding Tr2 of the transformer further induces the resonant current of the primary winding Tr1, and supplies power to the output terminal through the third path formed by the rectifiers SR4 and SR 1. The resonant capacitors Cr1 and Cr2 are used as resonant elements and also as blocking capacitors. The dc voltage of the resonant capacitor Cr1 is 0.75Vin, the voltage of the resonant capacitor Cr2 is 0.25Vin, the excitation voltages at the two ends of the

resonant units

23 and 24 are the same, and the resonant frequencies are the same (that is, fr1 is fr2), and at this time, the currents of the two resonant units are the same and flow to the primary side of the transformer together. In the time from t1 to t2, the parasitic capacitances of the switches S4 and S2 and the rectifying tubes SR1 and SR4 are charged by exciting inductance current, and the parasitic capacitances of the switches S3 and S1 and the rectifying tubes SR2 and SR3 are discharged, so that soft switching is realized. the time period from t2 to t4 is the second half of the working period, in the time period from t2 to t3, the switches S3 and S1 and the rectifier tubes SR2 and SR3 are turned on, and the switches S4 and S2 and the rectifier tubes SR1 and SR4 are turned off,at the moment, a first path is formed by the rectifier SR2, the primary winding Tr1 of the transformer, the resonant inductor Lr2, the resonant capacitor Cr2, the switch S3, the capacitor C1 and the rectifier SR3 to supply energy to the output end. A second path is formed by a rectifier SR2, a primary winding Tr1 of the transformer, a resonant inductor Lr1, a resonant capacitor Cr1 and a switch S1 to supply energy to the output end. Finally, the secondary winding Tr2 of the transformer induces the current of the primary side, and a third path is formed by rectifier tubes SR2 and SR3 to provide energy for the output end. In the time period from t3 to t4, the parasitic capacitances of the switches S3 and S1 and the rectifiers SR2 and SR3 are charged by the exciting inductor current, and the parasitic capacitances of the switches S4 and S2 and the rectifiers SR1 and SR4 are discharged, so that soft switching is realized.

Assuming that the current at the input terminal is i, the equivalent currents of the

resonant units

23 and 24 are 2i, respectively, the equivalent current at the primary side of the transformer is 4i, and the current flows directly to the output terminal in one working period of the circuit 20. Meanwhile, when the turns ratio of the transformer is N: at 1, the current induced in the secondary side of the transformer is 4Ni, so the total current flowing to the output is (4N +4) i. Since only half the resonant period of current flows through the switch S4, the input side current is half the resonant cell current, i.e., i. The circuit 20 voltage conversion ratio is therefore (4N +4):1, where 4N is the transformation ratio of the transformer, and 4 is caused by the current flowing through the primary winding of the transformer from the circuit flowing directly to the output terminal. Therefore, the conversion ratio of the circuit is very high, the number of primary windings of the transformer can be reduced under the same voltage conversion ratio, the utilization efficiency of the transformer is improved, meanwhile, the current flowing through the primary winding of the transformer in the circuit directly flows to the output end of the transformer to be 4, the partial current does not need to be generated by the induction of the transformer, and the loss and the volume of the transformer are further reduced.

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 resonant parameters may be the same or different. The switches S1 to S4 connected in series may be formed by connecting a plurality of switching elements in series to reduce the voltage stress of a single switch, or may be formed by connecting a plurality of switching elements in parallel to increase the current capacity of the switching unit.

Circuit 30 in fig. 4 is a further variation of circuit 20 in fig. 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 two resonant cells, and the common inductor Lrc is connected in series with the primary side of the transformer, where the resonant frequency is:

the transformer has the advantages that the leakage inductance of the transformer can be utilized, and the inductance required by the resonant inductor is reduced, so that the effects of reducing the use of components and reducing the size of a converter are achieved.

Circuit 40 in fig. 5 is a further variation of circuit 20 in fig. 3A. In the circuit 40, when the parameters of the two resonant units are the same, the respective resonant inductances of the two resonant units can be combined into a common inductance Lrc shared by the two resonant units, the common inductance Lrc is connected in series with the primary side of the transformer, and the capacitance values of the resonant capacitances Cr1 and Cr2 are the same. Resonant frequency at this time

The circuit 40 works in a DC transformer mode, the circuit runs at a fixed working frequency, the leakage inductance requirement value is small, the leakage inductance of the transformer can be directly used as the common resonant inductance Lrc, and the using quantity and the volume of components are reduced.

Circuit 50 in fig. 6A is a further variation of circuit 20 in fig. 3A. In contrast to the case where the

resonance units

23 and 24 share one primary winding Tr1 as shown in the circuit 20 in fig. 3A, in the circuit 50, the transformer has two primary windings Tr11 and Tr12 for the resonance units, respectively, and one secondary winding Tr 2. The turn ratio of Tr11, Tr12, and Tr2 may be, for example, N: N: 1. As shown in fig. 6A, one end of the primary winding Tr11 is connected to the resonant unit formed by the resonant capacitor Cr1 and the resonant inductor Lr1, the other end is connected to the midpoint m1 of the first arm leg, one end of the primary winding Tr12 is connected to the other resonant unit formed by the resonant capacitor Cr2 and the resonant inductor Lr2, and the other end is connected to the midpoint m1 of the first arm leg. Secondary winding Tr2 of transformer Tr is connected between midpoint m1 of the first leg and midpoint m2 of the second leg. 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 may be interchanged. It is sufficient to ensure that the resonance unit composed of the resonance capacitor Cr1 and the resonance inductor Lr1 is connected in series with the primary winding Tr 11. Also, the positions of the resonance unit constituted by the resonance capacitor Cr2 and the resonance inductor Lr2 and the primary winding Tr12 may be interchanged. It is sufficient to ensure that the resonance unit composed of the resonance capacitor Cr2 and the resonance inductor Lr2 is connected in series with the primary winding Tr 12.

Circuit 50' in fig. 6B is a further variation of circuit 20 in fig. 3A. In comparison with the case where the

resonance units

23 and 24 share one primary winding Tr1 as shown in the circuit 20 in fig. 3A, it is also possible to share one resonance unit for two primary windings Tr11 and Tr12 as shown in fig. 6B. In the circuit 50', the transformer has two primary windings Tr11 and Tr12, and one secondary winding Tr 2. The turn ratio of Tr11, Tr12, and Tr2 may 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 formed by a resonance inductance Lr and a resonance capacitance Cr, and the other end of the resonance unit is connected to the midpoint m1 of the first bridge arm.

In the circuits of fig. 6A and 6B, the leakage inductance of the transformer can also be utilized as the resonant inductance of a part or all of the resonant unit to reduce circuit elements.

Circuit 60 in fig. 7 is a further variation of circuit 20 in fig. 3A. In the circuit 60, when the resonant capacitor Cr1 and the resonant inductor Lr1 in the resonant unit 63 have the same parameters as 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 the

resonant units

63 and 64 may be used instead of the original single blocking capacitor connected to the connection point p2 between the switches S2 and S3 to constitute the resonant unit 65. The resonant capacitor Cr3 plays a role of a blocking capacitor and participates in circuit resonance together with the resonant inductor Lr 3.

Circuit 70 in fig. 8 is a further variation of circuit 20 in fig. 3A. In the circuit 70, the output capacitance Co connected in parallel with the first arm and the second arm of the full-bridge rectifier circuit of the circuit 70 may be used as the resonance capacitance Cr shared by the two resonance cells. At this time, only a resonant inductor may be included in the resonant cell connected between the connection point of the switching leg and the midpoint m1 of the first leg.

Therefore, in the circuit 70, the resonance capacitance Cr is shared by the resonance inductances Lr1 and Lr2, the resonance capacitance Cr resonates with the resonance inductance Lr1 as one resonance unit, and the resonance capacitance Cr resonates with the resonance inductance Lr2 as the other resonance unit. The circuit 70 achieves 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 in the circuit 70 as shown in fig. 8, the capacitors C2 and C3 are mainly used as dc blocking capacitors and the capacitors C2 and C3 may be omitted.

The transformer in the circuit can be further divided into two independent transformers. Circuit 80 in fig. 9 is a further variation of circuit 20 in fig. 3A. In the circuit 80, the full-bridge rectifier circuit may further include a third arm formed by rectifiers SR5 and SR 6. The third arm is connected in parallel to a first arm formed of rectifier tubes SR1 and SR2 and a second arm formed of rectifier tubes SR3 and SR 4. The circuit 80 comprises a first transformer Tr and a second transformer Tr' having a primary winding and a secondary winding turns ratio of N: 1. one end of a primary winding Tr11 of the first transformer Tr is connected to one end of a resonance unit consisting of a resonance capacitor Cr1 and a resonance inductor Lr1, the other end of the primary winding Tr11 is connected to a midpoint m1 of the first bridge arm, and a secondary winding Tr21 of the first transformer Tr is connected between a midpoint m1 of the first bridge arm and a midpoint m2 of the second bridge arm. One end of a primary winding Tr12 of a second transformer Tr ' is connected to one end of another resonance unit consisting of a resonance capacitor Cr2 and a resonance inductor Lr2, the other end of the primary winding Tr12 of the second transformer Tr ' is connected to a midpoint m3 of the third bridge arm, and a secondary winding Tr22 of the second transformer Tr ' is connected between a midpoint m2 of the second bridge arm and a 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 may be interchanged. It is sufficient to ensure that the resonance unit composed of the resonance capacitor Cr1 and the resonance inductor Lr1 is connected in series with the primary winding Tr 11.

The circuit 80 advantageously reduces the current stress on the single transformer and single rectifier, or increases the current capacity of the transformer and SR when the same components are used, thereby increasing the output power of the converter.

The conversion circuit herein can be further extended to change the voltage conversion ratio. Fig. 10A shows an expanded form of the conversion circuit herein. The circuit 90 shown in fig. 10A is an extension of the circuit 10 in fig. 2. In the circuit 90, the switch branch 92 includes not only the original two switches S1-S2, but also (2m-2) switches (S3, S4 … S)_2m-1、S_2m). Extended (2m-2) switches (S3, S4 … S)_2m-1、S_2m) Connected in series with the original two switches S1 and S2 such that the switching leg 92 contains 2m switches, i.e., an even number of switches, connected in series, where m is an integer and m ≧ 2.

The circuit 90 further comprises (m-1) blocking capacitances Cx and (m-1) resonant cells 94. Of which (m-1) resonant cells 94 and the original resonant cell 93 are such that the circuit 90 has m resonant cells. The m resonant cells are each connected in series with the primary winding Tr 1. The resonant cells 94 each include a resonant capacitor Crx and a resonant inductor Lrx.

Therefore, a conversion circuit such as the circuit 90 of fig. 10A can be described as follows: the switching leg 92 has 2m switches connected in series, where m is an integer and m ≧ 2. Two adjacent switches of the 2m switches are connected to form a connection point, and thus have (2m-1) connection points.

Considering the connection point near the output of circuit 90 as connection point No. 1, switching branch 92 has connection points No. 1, 2, 3, …, (2m-2), (2m-1) from the output to the input. For example, as shown in fig. 10A, the connection point between the switches S1 and S2 is closest to the output terminal, so the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 10A), and the connection point of the switch S2 and the next switch S3 adjacent to the switch S2 is the connection point No. 2, and so on, the switch S_2m-1And S_2mThe connection point between is(2m-1) point of attachment.

Wherein each of the m resonant cells is connected between the odd-numbered connection point and the primary winding Tr1 of the transformer, and each of the (m-1) blocking capacitances Cx is connected between the even-numbered connection point and the midpoint m2 of the second leg.

In the m resonance units, one end of the x-th resonance unit is connected to a connection point of the (2x-1) -th switch and the 2 x-th switch among the 2m switches, where x is an integer, and 1 ≦ x ≦ m.

For example, when x is 1, for the first (x) resonant unit (the resonant unit 93 in fig. 10A) of the m resonant units, one end thereof is connected to the connection point between the first (2x-1) switch (the switch S1 in fig. 10A) and the second (2x) switch (the switch S2 in fig. 10A), and the other end thereof is connected to the transformer primary winding Tr 1. For another example, when x is m, for the m- (x) th resonant unit (the resonant unit 94 in fig. 10A) of the m resonant units, one end thereof is connected to the 2m-1(2x-1) th switch (the switch S in fig. 10A)_2m-1) And 2m (2x) th switch (switch S in FIG. 10A)_2m) And the other end is connected to the primary winding Tr1 of the transformer.

In the (m-1) blocking capacitances Cx, one end of the kth blocking capacitance is connected to the connection point of the 2 kth switch and the 2k +1 th switch of the 2m switches, and the other end is connected to the midpoint m2 of the second leg, where k is an integer, and 1 ≦ k ≦ m-1.

For example, when k is 1, one end of the first (k) blocking capacitance (blocking capacitance Cx in fig. 10A) is connected to a connection point of the second (2k) switch (switch S2 in fig. 10A) and the third switch (switch S3 in fig. 10A), and the other end is connected to the midpoint m2 of the second arm. For another example, when k is (m-1), one end of the (m-1) (k) th blocking capacitor (not shown in fig. 10A) is connected to the (2m-2) (2k) th switch (and switch S in fig. 10A)_2m-1Adjacent previous switch, not shown) and (2m-1) (2k +1) th switch (switch S in FIG. 10A)_2m-1) And the other end is connected to the midpoint m2 of the second leg. Thus, for the circuit 90 of FIG. 10A, the conversion ratio is (2mN +2m):1, where N is the turns of the primary and secondary windings of the transformer TrRatio of ratios. Thereby realizing the expansion of the conversion ratio of the conversion circuit.

Although the circuit 90 of fig. 10A shows the case where m resonant cells are each connected in series with a single primary winding Tr1, as described with respect to fig. 6A, the primary winding Tr1 may be formed of a plurality of sub-windings, each of which is connected in series with a corresponding one of the m resonant cells.

It can be seen that the circuit 20 in fig. 3A can be regarded as a circuit in which a pair of switches, a dc blocking capacitor and a resonant unit are added to the circuit 10 in fig. 2.

Similarly to what has been described with respect to fig. 6B, it is also possible to have a resonant unit common to a plurality of primary windings, as shown in the circuit 90' of fig. 10B, compared to the case where m resonant units are connected in series in common to the common primary winding Tr1 shown in fig. 10A.

In the circuit 90', the switch branch 92 not only contains the original two switches S1 and S2, but also is further extended by (2m-2) switches (S3, S4 … S)_2m-1、S_2m). Extended (2m-2) switches (S3, S4 … S)_2m-1、S_2m) Connected in series with the original two switches S1 and S2 such that the switching leg 92 contains 2m switches, i.e., an even number of switches, connected in series, where m is an integer and m ≧ 2. The circuit 90' further comprises (m-1) blocking capacitances Cx and m primary windings Tr 1. The m primary windings Tr1 are connected in series to a resonant unit constituted by a resonant inductor Lr and a resonant capacitor Cr.

In circuit 90', two adjacent switches of the 2m switches of switch leg 92 are connected to form a connection point, and thus have (2m-1) connection points. Considering the connection point near the output of the circuit 90' as connection point No. 1, the switching branch 92 has connection points No. 1, 2, 3, …, (2m-2), (2m-1) from the output voltage terminal to the input terminal. For example, as shown in fig. 10B, the connection point between the switches S1 and S2 is closest to the output terminal, so the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 10B), and the connection point of the switch S2 and the next switch S3 adjacent to the switch S2 is the connection point No. 2, and so on, the switch S_2m-1And S_2mThe connection point between is the connection point No. (2 m-1).

Wherein each of the m primary windings Tr1 is connected between the odd-numbered connection point and the resonant cell, and each of the (m-1) blocking capacitances Cx is connected between the even-numbered connection point and the midpoint m2 of the second leg.

In the above-described 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 2 xth switch among the 2m switches, where x is an integer, and 1. ltoreq. x.ltoreq.m.

Fig. 11A shows another extension of the conversion circuit of the present application. The circuit 100 of fig. 11A is another extension of the circuit 10 of fig. 2. The switching branch 102 of the circuit 100 contains not only the original two switches S1-S2, but is further extended by (m-2) switches (S3, …, Sm). The expanded (m-2) switches (S3, …, Sm) are connected in series with the original two switches S1-S2 such that the switching leg 102 contains m switches connected in series, where m is an integer and m ≧ 3. The circuit 100 further comprises (m-2) resonant cells. Therefore, (m-2) resonance units 104 and resonance unit 103 constitute (m-1) resonance units together. The resonant cell 104 includes a resonant capacitor Crx and a resonant inductor Lrx. The respective resonance units (the resonance unit 103 and the resonance unit 104) in the circuit 100 have the same resonance parameters.

Specifically, the conversion circuit shown in fig. 11A as the circuit 100 can be described as follows: the switching leg 102 has m switches connected in series, where m is an integer and m ≧ 3. Two adjacent ones of the m switches are connected to form a connection point, and thus have (m-1) connection points. Considering the connection point near the output of the circuit 100 as connection point No. 1, the switching leg 102 has connection points No. 1, 2, 3, …, m-1 from the output to the input. For example, as shown in fig. 11A, the connection point of the switches S1 and S2 is closest to the output terminal, so the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 11A), and the connection point of the switches S2 and S3 is the connection point No. 2 (identified as "c" in fig. 11A), the connection point of the switch S3 and the switch S4 (identified as "c" in fig. 11A) is the connection point No. 3, and so on, the connection point of the switch Sm and the switch Sm one before the switch Sm is the connection point No. (m-1).

Each of the (m-1) resonant cells (103, 104) in the circuit 100 has one end connected to a corresponding connection point and the other end connected to the primary winding Tr1 of the transformer or the midpoint m2 of the second leg of the full-bridge rectifier circuit. Among them, as for the resonance units whose one ends are connected to the odd-numbered connection points, the other ends are connected to the primary winding Tr1 of the transformer. As for the resonance unit having one end connected to the even-numbered connection point, the other end thereof is connected to the midpoint m2 of the second leg of the full-bridge rectifier circuit.

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 2 y-th switch in the m switches, and the other end is connected to the primary winding Tr1 of the transformer, wherein y is an integer and is more than or equal to 1 and less than or equal to m/2.

For example, when y is 1, among the (m-1) resonant units, one end of the first (2y-1) resonant unit (the resonant unit 103 in fig. 11A) is connected to a connection point of the first (2y-1) switch (the switch S1 in fig. 11A) and the second (2y) switch (the switch S2 in fig. 11A), and the other end is connected to the primary winding Tr1 of the transformer.

In the (m-1) resonant units, one end of the 2z resonant unit is connected to the connection point of the 2z switch and the (2z +1) switch in the m switches, and the other end is connected to the midpoint m2 of the second bridge arm of the full-bridge rectification circuit, wherein z is an integer, and z is more than or equal to 1 and less than or equal to (m-1)/2.

For example, when z is 1, of m-1 resonance units, the second (2z) resonance unit (resonance unit 104 in fig. 11A)₁) One end of which is connected to the connection point of the second (2z) switch (switch S2 in fig. 11A) and the third (2z +1) switch (switch S3 in fig. 11), and the other end of which is connected to the midpoint m2 of the second leg of the full-bridge rectifier circuit.

The conversion ratio of the expansion circuit 100 is described below. 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 the circuit 60 shown in fig. 7 is in fact an example of a circuit with an even number of switching branches, expanded by two switches on the basis of the circuit 10 of fig. 2. The conversion ratio of the circuit 60 of fig. 7 is thus (4N +4):1 (i.e., (mN + m):1, m ═ 4) as discussed above. Thereby realizing the expansion of the conversion ratio of the conversion circuit. 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. Thereby realizing the expansion of the conversion ratio of the conversion circuit. Fig. 11B shows a circuit 100 'with a switching branch 102' having 3 switches after an extension of one switch S3 from the circuit 10 of fig. 2. One end of the resonant 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 resonant cell 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 leg of the full-bridge rectifier circuit. The conversion ratio of circuit 100' is (2N +3):1 (i.e., ((m-1) N + m):1, m ═ 3).

Although fig. 11A and 11B show the case where the resonance units connected to the odd-numbered connection points among the (m-1) resonance units are all connected in series with the single primary winding Tr1, as described with respect to fig. 6A, the primary winding Tr1 may be formed of a plurality of sub-windings, and each sub-winding is connected in series with the corresponding resonance unit connected to the odd-numbered connection point among the (m-1) resonance units, respectively.

Similar to what has been described with respect to fig. 6B, it is also possible to have a plurality of primary windings share one resonance unit, as shown in the circuit 100 ″ of fig. 11C, compared to the case where the multiple resonance units are connected in series in common to the common primary winding Tr1 shown in fig. 11A and 11B.

The switching branch 102 of the circuit 100 "contains not only the original two switches S1-S2, but is further extended by (m-2) switches (S3, …, Sm). The expanded (m-2) switches (S3, …, Sm) are connected in series with the original two switches S1-S2 such that the switching leg 102 contains m switches connected in series, where m is an integer and m ≧ 3. The circuit 100 further comprises a plurality of resonant cells 104 and a plurality of primary windings Tr 1. Each of the plurality of resonant cells 104 includes a resonant capacitor Crx and a resonant inductor Lrx. Each of the plurality of resonant cells 104 has the same resonance parameters.

In circuit 100 ", switching leg 102 has m switches connected in series, where m is an integer and m ≧ 3. Two adjacent ones of the m switches are connected to form a connection point, and thus have (m-1) connection points. Considering the connection point near the output of the circuit 100 as connection point No. 1, the switching leg 102 has connection points No. 1, 2, 3, …, m-1 from the output to the input. For example, as shown in fig. 11C, the connection point of the switches S1 and S2 is closest to the output terminal, so the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 11C), and the connection point of the switches S2 and S3 is the connection point No. 2 (identified as "C" in fig. 11C), the connection point of the switch S3 and the switch S4 is the connection point No. 3 (identified as "C" in fig. 11C), and so on, the connection point of the switch Sm and the switch Sm one before the switch Sm is the connection point No. (m-1).

One end of each of the plurality of primary windings Tr1 in the circuit 100 ″ is connected to the odd-numbered connection point, and the other end thereof is connected to the resonance unit constituted by the resonance capacitor Cr and the resonance inductor Lr. Each of the plurality of resonant cells 104 in the circuit 100 ″ has one end connected to the even-numbered connection point and the other end connected to the midpoint m2 of the second leg of the full-bridge rectifier circuit.

One end of one of the plurality of primary windings Tr1 is connected to a connection point of a (2y-1) th switch and a 2 y-th switch among the m switches, and the other end is connected to a resonance unit constituted by a resonance capacitance Cr and a resonance inductance Lr, where y is an integer, and 1 ≦ y ≦ m/2.

One end of one of the plurality of resonant cells 104 is connected to a connection point of the 2 z-th switch and the (2z +1) -th switch among the m switches, and the other end is connected to a midpoint m2 of the second leg of the full-bridge rectifier circuit, where z is an integer, and 1 ≦ z ≦ m-1)/2.

Fig. 12 shows a variation of the circuit 20 of fig. 3A. In the circuit 110 shown in fig. 12, the circuit 110 has two switching

legs

112 and 115 connected in parallel, the switching

legs

112 and 115 each being connected between a first terminal of an input voltage and a first terminal of an output voltage. The switching leg 112 has four switches S1-S4 connected in series and the switching leg 115 has four switches S5-S8 connected in series. The full-bridge rectifier circuit of circuit 110 is connected between the first and second terminals of the output voltage, and has a first leg formed by series connection of rectifiers SR1 and SR2, and a second leg formed by series connection of rectifiers SR3 and SR 4. The circuit 110 has four

resonant cells

113, 114, 116 and 117, two dc blocking capacitances C1 and C2, and a transformer Tr. The transformer Tr has two primary windings Tr11 and Tr12, and one secondary winding Tr 2. The turn ratio of Tr11, Tr12 and Tr2 is N: N: 1.

The resonance unit 113 is connected between the connection point p1 of the switches S1 and S2 and the primary winding Tr 11. The resonance unit 114 is connected between the connection point p3 of the switches S3 and S4 and the primary winding Tr 11. The resonance unit 116 is connected between the connection point p4 of the switches S5 and S6 and the primary winding Tr 12. The resonance unit 117 is connected between the connection point p6 of the switches S7 and S8 and the primary winding Tr 12. A dc blocking capacitor C1 is connected between the connection point p2 of switches S2 and S3 and the midpoint m2 of the second leg. A dc blocking capacitor C2 is connected between the connection point p6 of switches S6 and S7 and the midpoint m1 of the first leg.

In one operation cycle of the circuit 110, in the first half cycle, the switches S4, S2, S7, S5 and the rectifiers SR1 and SR4 are turned on, while the switches S3, S1, S8, S6 and the rectifiers SR2 and SR3 are turned off, and in the second half cycle, the switches S4, S2, S7, S5 and the rectifiers SR1 and SR4 are turned off, while the switches S3, S1, S8, S6 and the rectifiers SR2 and SR3 are turned on. Circuit 110 also implements (4N +4):1 conversion ratio. Compared with the circuit 20 of fig. 3A, the current stress of the switches S1 to S8 of the switching branch in the circuit 110 can be reduced by half, and the currents of the rectifiers SR1 to SR4 are more balanced.

[ second embodiment ]

The case where the rectifying circuit in the inverter circuit is a full bridge rectifying circuit is described above in conjunction with fig. 2 to 12. However, this document is not limited thereto, and for example, the rectifying circuit in the inverter circuit may be a full-wave rectifying circuit.

Fig. 13A shows a schematic diagram of a transform circuit 120 of the second embodiment herein. The circuit 120 receives an input voltage Vin, converts the input voltage Vin, and outputs the converted voltage.

The circuit 120 includes a full-wave rectification circuit 121, a switching branch 122,

resonant units

123 and 124, and a primary winding Tr1 of the transformer.

The input voltage and the output voltage each have a first terminal and a second terminal, wherein the second terminals of the input voltage and the output voltage are connected. The full-wave rectification circuit 121 has a first branch composed of the switch SR1 and the transformer secondary winding Tr22, and a second branch composed of the switch SR2 and the transformer secondary winding Tr 21. The switch SR1 and the transformer secondary Tr22 are connected in series to form a connection point, referred to as a first midpoint m 1. The switch SR2 and the transformer secondary Tr21 are connected in series to form a connection point, referred to as the second midpoint m 2.

In one example of the circuit 120, the circuit 120 may include an output capacitor Co for output filtering, connected between a first terminal and a second terminal of the output voltage in parallel with a first branch and a second branch of the full-wave rectification circuit 121. Additionally, the circuit 120 may also include an input capacitance Cin for input filtering, which may be connected between the first and second ends of the input voltage, or the input capacitance Cin may also be connected between the first end of the input voltage and the first end of the output voltage, as illustrated by the dashed line connected input capacitance Cin in fig. 13A.

The switching leg 122 is connected between a first end of the input voltage and a first midpoint m1 of the full-wave rectification circuit 121, and the switching leg 122 includes four switches S1-S4 connected in series. The connection point p1 is formed by connecting the switches S1 and S2, the connection point p2 is formed by connecting the switches S2 and S3, and the connection point p3 is formed by connecting the switches S3 and S4.

The

resonant cells

123 and 124 have resonant capacitances Cr1 and Cr2 and resonant inductances Lr1 and Lr2, respectively. Although fig. 13A shows a resonant unit formed by a resonant capacitor and a resonant inductor connected in series, the present disclosure is not limited thereto, and the resonant unit may also be formed by a resonant capacitor and a resonant inductor connected in parallel.

One end of the resonant unit 123 is connected to the connection point p1, and one end of the resonant unit 124 is connected to the connection point p3, and further, the other ends of the

resonant units

123 and 124 are connected to the second midpoint m2 via the primary winding Tr1 of the transformer.

The primary winding Tr1, the secondary winding Tr21 and the secondary winding Tr21 of the transformer form a winding with the turn ratio of N:1:1, transformer Tr.

The dc blocking capacitor C1 is connected between the connection point p2 and the first midpoint m 1.

The operation of the circuit 120 in one operation cycle is described with reference to fig. 13B and 13C. Fig. 13B shows changes in current or voltage in each element in one duty cycle (t0 to t4) of the circuit 120 in the case where the switching frequency is equal to the resonance frequency. Where iLr denotes a current of each of the resonance unit 123 and the resonance unit 124, Vs3 and Vs1 denote voltages across the switches S3 and S1, and isr1, isr2, is4, and is3 denote currents in the switches SR1, SR2, S4, and S3. Fig. 13C shows an example of the current flow in the first half of one duty cycle of the circuit 120.

In one duty cycle of the circuit 120, the switches S4, S2, SR1 are symmetrically turned on complementary to the switches S3, S1, SR2, and the duty cycle is close to 0.5. t0-t 2 are the first half of the working cycle of the circuit, and in the time period of t0-t 1, the switches S4, S2 and SR1 are turned on, and the switches S3, S1 and SR2 are turned off. At this time, a current is supplied from the input terminal to the output terminal through a first resonance path formed by the switch S4, the resonance capacitor Cr2, the resonance inductor Lr2, the primary winding Tr1, and the secondary winding Tr21 at a resonance frequency of

Meanwhile, the voltage on the blocking capacitor C1 is 0.5Vin, the energy on the blocking capacitor C1 provides energy to the output end through a second resonant path formed by a switch SR1, a switch S2, a resonant capacitor Cr1, a resonant inductor Lr1, a primary winding Tr1 and a secondary winding Tr21, and the resonant frequency is

At this time, since the primary winding Tr1 and the secondary winding Tr21 of the transformer are actually connected in series, the transformer TThe secondary winding Tr22 of r then induces a resonant current of both the primary winding Tr1 and the secondary winding Tr21 and provides power to the output terminal through a third path formed by the switch SR1 and the secondary winding Tr 22. In a time period from t1 to t2, the switches S4, S2 and SR1 are turned off, and at this time, the parasitic capacitances of the switches S4, S2 and SR1 are charged by the current on the exciting inductor, and the parasitic capacitances of the switches S3, S1 and SR2 are discharged, so that soft switching is realized. t 2-t 4 are the second half of the working cycle of the circuit, and in the time period from t 2-t 3, the switches S3, S1 and SR2 are turned on, and the switches S4, S2 and SR1 are turned off. Similar to the first half cycle, at this time, current flows to the output terminal through a resonant path formed by the switch SR2, the primary winding Tr1, the resonant inductor Lr2, the resonant capacitor Cr2, the switch S3, the blocking capacitor C1, and the secondary winding Tr22, and current flows to the output terminal through another resonant path formed by the switch SR2, the primary winding Tr1, the resonant inductor Lr1, the resonant capacitor Cr1, the switch S1, and the secondary winding Tr22, and finally the secondary winding 21 senses current of the primary winding Tr1 and the secondary winding Tr22 and flows to the output terminal through a resonant path formed by the switch SR2 and the secondary winding Tr 21. In a time period from t3 to t4, the switches S3, S1 and SR2 are turned off, and at this time, the parasitic capacitances of the switches S3, S1 and SR2 are charged by the current on the exciting inductor, and the parasitic capacitances of the switches S4, S2 and SR1 are discharged, so that soft switching is realized.

Assuming that the current at the input terminal is i, in a working period of the circuit 120, the currents of the two resonant units are 2i, the current at the primary side of the transformer Tr is 4i, and the current flows directly to the output terminal through one secondary winding, and the current induced by the other secondary side of the transformer Tr is 4(N +1) i, so that the total current flowing to the output terminal is 4(N +2) i. Since only a half of the resonant period of current flows through the switch S4, the input side current is half of the current of the resonant unit 124, i.e., i. Thus, the voltage conversion ratio of the circuit is (4N + 8): 1.

compared to the converter circuit using the full-bridge rectifier circuit shown in fig. 3A, the voltage conversion ratio of the circuit 120 of fig. 13A is further increased by 4 at the same transformer turn ratio, mainly because the full-wave rectifier circuit has two secondary windings Tr21 and Tr 22. In operation, the secondary windings Tr21 and Tr22 alternately form a series connection with the primary winding Tr1 of the transformer, and the actual equivalent turn ratio becomes (N + 1). The conversion circuit using the full-wave rectification circuit has an advantage in that the switches SR1 and SR2 are both grounded, so that the switches SR1 and SR2 are simpler to drive than full-bridge rectification. When the switches S1 to S4 connected in series are driven to supply power by using a bootstrap method (bootstrap-strap), since each arm of the full-bridge rectifier circuit has two switches and each branch of the full-wave rectifier circuit includes only one switch, the number of stages of power supply can be reduced by one stage compared with the case of the full-bridge rectifier circuit. Therefore, the full-wave rectification type conversion circuit is relatively advantageous in terms of the number of components of the driving circuit, the occupied area and the cost. The full-wave rectification type conversion circuit has the advantage that the voltage stress of the switches SR1 and SR2 is 2Vo, where Vo is the output voltage, but only one switch is turned on in one switching state, where the on-resistance of the MOSFET is assumed to be Ron _2Vo, while the voltage stress of the switch SR of the full-bridge rectification type conversion circuit is Vo, but the rectification current flows through the two switching tubes, where the on-resistance of the MOSFET is assumed to be Ron _ Vo, and when Ron _2Vo <2 × Ron _ Vo, the full-wave rectification type conversion circuit is used with efficiency.

Similarly, the

resonant units

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

[ variation of the second embodiment ]

Similar to the full-bridge rectification type conversion circuit, there are various modifications of the full-wave rectification type conversion circuit. Various modifications of the full-wave rectification type conversion circuit 120 are described below, and only differences of the various modifications with respect to the conversion circuit 120 are described, and the same parts will not be described again.

The circuit 130 in fig. 14 is a further variation of the circuit 120 in 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 two resonant units, and the common inductor Lrc is connected in series with the primary side of the transformer, where the resonant frequency is:

Circuit 140 in fig. 15 is a further variation of circuit 120 in fig. 13A. In circuit 140, when the parameters of the two resonant cells are the same, the respective resonant inductances of the two resonant cells can be combined into a common inductance Lrc that is shared by the two resonant cells, which common inductance Lrc is then connected in series with the primary side of the transformer. Resonant frequency at this time

The capacitance values of the resonant capacitors Cr1 and Cr2 are the same. The circuit 140 works in a DC transformer mode, the circuit runs at a fixed working frequency, the leakage inductance requirement value is small, the leakage inductance of the transformer can be directly used as the common resonant inductance Lrc, and the using quantity and the volume of components are reduced.

The circuit 150 in fig. 16A is a further variation of the circuit 120 in fig. 13A. In comparison with the case where one primary winding is shared by a plurality of resonance units of fig. 13A, in the circuit 150 of fig. 16A, the transformer has two primary windings Tr11 and Tr12 and two secondary windings Tr21 and Tr22, which are respectively connected in series with two resonance units (i.e., a resonance unit composed of the resonance inductance Lr1 and the resonance capacitance Cr1 and a resonance unit composed of the resonance inductance Lr2 and the resonance capacitance Cr 2). The turn 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 a resonant unit formed by the resonant capacitor Cr1 and the resonant inductor Lr 1. One end of the primary winding Tr12 is connected to the second midpoint m2, and the other end is connected to a resonant unit formed by the resonant capacitor Cr2 and the resonant inductor Lr 2. 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 may be interchanged. It is sufficient to ensure that the resonance unit composed of the resonance capacitor Cr1 and the resonance inductor Lr1 is connected in series with the primary winding Tr 11. Also, the positions of the resonance unit constituted by the resonance capacitor Cr2 and the resonance inductor Lr2 and the primary winding Tr12 may be interchanged. It is sufficient to ensure that the resonance unit composed of the resonance capacitor Cr2 and the resonance inductor Lr2 is connected in series with the primary winding Tr 12.

The circuit 150' in fig. 16B is a further variation of the circuit 120 in fig. 13A. In comparison with the case where the

resonance units

123 and 124 share one primary winding Tr1 as shown in the circuit 120 in fig. 13A, it is also possible to share one resonance unit for two primary windings Tr11 and Tr12 as shown in fig. 16B. In the circuit 150', the transformer has two primary windings Tr11 and Tr 12. 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 formed by the resonance inductance Lr and the resonance capacitance Cr, and the other end of the resonance unit is connected to the midpoint m2 of the second branch.

In the circuits of fig. 16A and 16B, the leakage inductance of the transformer can also be utilized as the resonance inductance of a part or all of the resonance unit to reduce the circuit elements.

The circuit 160 in fig. 17 is a further variation of the circuit 120 in fig. 13A. In the circuit 160, when the resonant capacitor Cr1 and the resonant inductor Lr1 in the resonant unit 163 have the same parameters as the resonant capacitor Cr2 and the resonant inductor Lr2 in the resonant unit 164, the resonant capacitor Cr3 and the resonant inductor Lr3 having the same parameters as the

resonant units

163 and 164 may be used to replace the original single dc blocking capacitor connected to the connection point p2 of the switches S2 and S3, so as to form the resonant unit 165. The resonant capacitor Cr3 plays a role of a blocking capacitor and participates in circuit resonance together with the resonant inductor Lr 3.

Circuit 170 in fig. 18 is a further variation of circuit 120 in fig. 13A. In the circuit 170, an output capacitor Co connected in parallel with a first branch and a second branch of a full-wave rectification circuit of the circuit 170 may be used as a resonance capacitor Cr shared by two resonance units. At this time, only a resonant inductor may be included in the resonant unit connected between the connection point of the switching leg and the midpoint m2 of the first leg. 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 one resonant cell, and the resonant capacitor Cr resonates with the resonant inductor Lr2 as another resonant cell. The circuit 170 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 in the circuit 170, the capacitors C2 and C3 are mainly used as dc blocking capacitors and the capacitors C2 and C3 may be omitted.

The transformer in the circuit can be further divided into two independent transformers. The circuit 180 in fig. 19 is a further variation of the circuit 120 in fig. 13A. In the circuit 180, the full-wave rectification 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 comprises a switch SR3 and a secondary winding Tr '21 of the transformer Tr' which are 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 m 3. The fourth branch comprises a switch SR4 and a secondary winding Tr '22 of the 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 m 4.

One end of a resonance unit constituted by the resonance capacitor Cr1 and the resonance inductor Lr1 is connected to the connection point p1 of the switches S1 and S2. One end of another resonant cell constituted by 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 a primary winding Tr1 of the transformer Tr is connected to the second midpoint m2, and the other end of the primary winding Tr1 is connected to a resonance unit formed by a resonance capacitor Cr1 and a resonance inductor Lr 1. The turn 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 a primary winding Tr '1 of the transformer Tr' is connected to the fourth midpoint m4, and the other end is connected to a resonance unit formed by a resonance capacitor Cr2 and a resonance inductor Lr 2. The turn 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 may be interchanged. It is sufficient to ensure that the resonance unit composed of the resonance capacitor Cr1 and the resonance inductor Lr1 is connected in series with the primary winding Tr 1. Also, the positions of the resonance unit constituted by the resonance capacitor Cr2 and the resonance inductor Lr2 and the primary winding Tr' 1 may be interchanged. It is only necessary to ensure that the resonance unit composed of the resonance capacitor Cr2 and the resonance inductor Lr2 is connected in series with the primary winding Tr' 1.

One end of the dc blocking capacitor C1 is connected to the connection point p2 of the switches S2 and S3, and the other end is connected to the third midpoint m 3.

Circuit 180 advantageously reduces current stress on the single transformer and single rectifier, or increases the current capacity of the transformer and switch SR, using the same components, thereby increasing the output power of the converter.

The conversion circuit herein can be further extended to change the voltage conversion ratio. Fig. 20A shows an expanded form of the conversion circuit 120 of fig. 13A. FIG. 20A shows a circuit 190 that compares to the circuit 120 of FIG. 13A, in which the switch branch 192 not only contains the original four switches S1-S4, but also is further extended by (2m-4) switches (S5, S6 … S)_2m-1、S_2m). Extended (2m-4) switches (S5, S6 … S)_2m-1、S_2m) Connected in series with the original four switches S1-S4 such that the switching leg 192 contains 2m switches connected in series, where m is an integer and m ≧ 3.

The circuit 190 further includes (m-2) blocking capacitances Cx and (m-2) resonant cells 195. Thus, in circuit 190, (m-2) Cx and dc blocking capacitance C1 together constitute (m-1) dc blocking capacitances, and (m-2) resonating unit 195 and resonating

units

193 and 194 together constitute m resonating units. The resonant cells 195 each include a resonant capacitor Crx and a resonant inductor Lrx.

Therefore, a conversion circuit such as the circuit 190 of fig. 20A can be described as follows: the switching leg 192 has 2m switches connected in series, where m is an integer and m ≧ 3. Two adjacent switches of the 2m switches are connected to form a connection point, and thus have (2m-1) connection points.

Considering the connection point near the output of the circuit 190 as connection point No. 1, the switching branch 192 has connection points No. 1, 2, 3, …, (2m-2), (2m-1) from the output to the input. For exampleAs shown in fig. 20A, the connection point between the switches S1 and S2 is closest to the output terminal, so that the connection point between the switches S1 and S2 is the connection point No. 1 (indicated as "r" in fig. 20A), and the connection point between the switches S2 and S3 is the connection point No. 2 (indicated as "c" in fig. 20A), and the connection point between the switches S3 and S4 is the connection point No. 3 (indicated as "c" in fig. 20A), and so on, and the switch S is connected to the output terminal_2m-1And S_2mThe connection point of (2m-1) is the connection point of (C).

Wherein each of the m resonant cells (i.e., the

resonant cells

193, 194 and the (m-2) resonant cell 195) is connected between the odd-numbered connection point and the primary winding Tr1, and each of the (m-1) dc blocking capacitances (i.e., the dc blocking capacitances C1 and the (m-2) dc blocking capacitances Cx) is connected between the even-numbered connection point and the first midpoint m 1.

In the m resonant units, one end of the x resonant unit is connected to the connection point of the (2x-1) th switch and the 2x switch in the 2m switches, wherein m and x are integers, m is more than or equal to 3, and 1 is more than or equal to x and less than or equal to m. For example, when x is 1, for the first (x) resonant unit (the resonant unit 193 in fig. 20A) of the m resonant units, one end thereof is connected to a connection point between the first (2x-1) switch (the switch S1 in fig. 20A) and the second (2x) switch (the switch S2 in fig. 20A), and the other end thereof is connected to the transformer primary winding Tr 1. For another example, when x is 2, for the second (x) resonant unit (the resonant unit 194 in fig. 20A) of the m resonant units, one end thereof is connected to the connection point between the third (2x-1) switch (the switch S3 in fig. 20A) and the fourth (2x) switch (the switch S4 in fig. 20A), and the other end thereof is connected to the transformer primary winding Tr 1.

In the (m-1) blocking capacitors Cx, one end of the kth blocking capacitor is connected to the connection point of the 2 kth switch and the 2k +1 th switch in the 2m switches, and the other end is connected to the first midpoint m1, wherein m and k are integers, m is greater than or equal to 3, and k is greater than or equal to 1 and less than or equal to m-1. For example, when k is 1, one end of the first (k) blocking capacitor (blocking capacitor C1 in fig. 20A) is connected to a connection point of the second (2k) switch (switch S2 in fig. 20A) and the third (2k +1) switch (switch S3 in fig. 20A), and the other end is connected to the first midpoint m 1. For another example, when k is (m-1), one end of the (m-1) (k) -th dc blocking capacitor is connected to the first end2m-2(2k) switches (AND switch S in FIG. 20A)_2m-1Adjacent previous switch, not shown) and 2m-1(2k +1) th switch (switch S in FIG. 20A)_2m-1) And the other end is connected to the first midpoint m 1.

Thus, for the circuit 190 of fig. 20A, when the turns ratio of the primary winding Tr1, the secondary winding Tr21, and the secondary winding Tr22 of the transformer is N:1: at 1, the circuit 190 conversion ratio is (mN +2m): 1. thereby realizing the expansion of the conversion ratio of the conversion circuit.

Referring to fig. 17, when the resonant parameters of the resonant units in the conversion circuit are the same, the dc blocking capacitor may be replaced by the resonant unit with the same resonant parameter.

Although the circuit 190 of fig. 20A shows the case where m resonant cells are each connected in series with a single primary winding Tr1, as described with respect to fig. 16A, the primary winding Tr1 may be formed of a plurality of sub-windings, each of which is connected in series with a corresponding one of the m resonant cells.

Similarly to what has been described with respect to fig. 16B, it is also possible to have a resonance unit common to a plurality of primary windings, as shown in the circuit 190' of fig. 20B, compared to the case where m resonance units are connected in series in common to the common primary winding Tr1 shown in fig. 20A.

In the circuit 190', the switch branch 192 not only includes the original two switches S1-S2, but also is further extended by (2m-2) switches (S3, S4 … S)_2m-1、S_2m). Extended (2m-2) switches (S3, S4 … S)_2m-1、S_2m) Connected in series with the original two switches S1 and S2 such that the switching leg 92 contains 2m switches, i.e., an even number of switches, connected in series, where m is an integer and m ≧ 2. The circuit 190' further comprises (m-1) blocking capacitances Cx and m primary windings Tr 1. The m primary windings Tr1 are connected in series to a resonant unit constituted by a resonant inductor Lr and a resonant capacitor Cr.

In circuit 190', two adjacent switches of the 2m switches of switch leg 192 are connected to form a connection point, and thus have (2m-1) connection points. The connection point near the output of the circuit 190' is considered as connection number 1The switching branch 192 has the connection points No. 1, 2, 3, …, (2m-2), (2m-1) from the output voltage terminal to the input terminal. For example, as shown in fig. 20B, the connection point between the switches S1 and S2 is closest to the output terminal, so the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 20B), and the connection point of the switch S2 and the next switch S3 adjacent to the switch S2 is the connection point No. 2 (identified as "②" in fig. 20B), and so on, the switch S_2m-1And S_2mThe connection point between is the connection point No. (2 m-1).

Wherein each of the m primary windings Tr1 is connected between the odd-numbered connection point and the resonant cell formed by the resonant inductance Lr and the resonant capacitance Cr, and each of the (m-1) blocking capacitances Cx is connected between the even-numbered connection point and the midpoint m1 of the first branch.

In the above (m-1) blocking capacitances Cx, one end of the kth blocking capacitance is connected to the connection point of the 2 kth switch and the 2k +1 th switch of the 2m switches, and the other end is connected to the midpoint m1 of the first branch, where k is an integer, and 1. ltoreq. k. ltoreq.m-1.

Fig. 21A shows another expanded form of the conversion circuit herein. The circuit 200 of fig. 21A is an extension of the circuit 160 of fig. 17, and the switching branch 202 of the circuit 200 shown in fig. 21A contains not only the original four switches S1-S4, but is further extended with (m-4) switches (S5, …, Sm). The expanded (m-4) switches (S5, …, Sm) are connected in series with the original four switches S1-S4 such that the switching leg 202 contains m switches, where m is an integer and m ≧ 5. The circuit 200 further comprises (m-4) additional resonant cells 206. (m-4) additional resonance units 206 and

resonance units

203 and 205 together constitute (m-1) resonance units. (m-4) additional resonant cells 206 contain resonant capacitors Crx and additional resonant inductors Lrx. Each resonant cell in circuit 200 has the same resonant parameters.

Specifically, the following description is provided for a conversion circuit such as the circuit 200 of fig. 21A: the switching leg 202 has m switches connected in series, where m is an integer and m ≧ 5. Two adjacent ones of the m switches are connected to form a connection point, and thus have (m-1) connection points. Considering the connection point near the output of the circuit 200 as connection point No. 1, the switching leg 202 has connection points No. 1, 2, 3, …, (m-1) from the output to the input. For example, as shown in fig. 21A, the connection point between the switches S1 and S2 is closest to the output terminal, so the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 21A), and the connection point of the switches S2 and S3 is the connection point No. 2 (identified as "c" in fig. 21A), the connection point of the switches S3 and S4 is the connection point No. 3 (identified as "c" in fig. 21A), the connection point of the switches S4 and S5 is the connection point No. 4 (identified as "r" in fig. 21A), and so on, the connection point of the switch Sm and a switch (not shown) preceding the switch Sm is the connection point No. (m-1).

The (m-1) resonant cells (203-206) in the circuit 200 have one end connected to the corresponding connection point and the other end connected to the primary winding Tr1 or the first midpoint m 1. Among them, as for the resonance units whose one ends are connected to the odd-numbered connection points, the other ends are connected to the primary winding Tr1 of the transformer. For the resonant cells whose one end is connected to the even-numbered connection points, the other end thereof is connected to the first midpoint m 1.

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 2 y-th switch in the m switches, and the other end is connected to the primary winding Tr1 of the transformer, wherein y is an integer, and y is more than or equal to 1 and less than or equal to m/2. For example, when y is 1, among the m-1 resonant units, one end of the first (2y-1) resonant unit (the resonant unit 203 in fig. 21A) is connected to a connection point of the first (2y-1) switch (the switch S1 in fig. 21A) and the second (2y) switch (the switch S2 in fig. 21A), and the other end is connected to the primary winding Tr1 of the transformer. For another example, when y is 2, among the m-1 resonant units, one end of the third (2y-1) resonant unit (the resonant unit 204 in fig. 21A) is connected to a connection point of the third (2y-1) switch (the switch S3 in fig. 21A) and the fourth (2y) switch (the switch S4 in fig. 21A), and the other end is connected to the primary winding Tr1 of the transformer.

Further, in the (m-1) resonant cells, one end of the 2 y-th resonant cell is connected to a connection point of the 2 y-th switch and the (2y +1) -th switch among the m switches, and the other end is connected to the first midpoint m 1. For example, when y is 1, among the (m-1) resonant cells, one end of the second (2y) resonant cell (the resonant cell 205 in fig. 21A) is connected to a connection point of the second (2y) switch (the switch S2 in fig. 21A) and the third (2y +1) switch (the switch S3 in fig. 21A), and the other end is connected to the first midpoint m 1. For another example, when y is 2, of the (m-1) resonance units, the fourth (2y) resonance unit (the resonance unit 206 in fig. 21A)₁) Is connected to the connection point of the fourth (2y) switch (switch S4 in fig. 21A) and the fifth (2y +1) switch (switch S5 in fig. 21A), and is connected to the first midpoint m 1.

For the circuit 200 of fig. 21A, the turns ratio of the primary Tr1, secondary Tr21, and secondary 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 its (mN +2m):1, where N is the turns ratio of the transformer Tr. Thereby realizing the expansion of the conversion ratio of the conversion circuit.

Although fig. 21A shows the case where the resonance units connected to the odd-numbered connection points of the (m-1) resonance units are all connected in series with the single primary winding Tr1, as described with respect to fig. 16A, the primary winding Tr1 may be formed of a plurality of sub-windings, and each sub-winding is connected in series with the corresponding resonance unit connected to the odd-numbered connection point of the (m-1) resonance units, respectively.

Similarly to what has been described with respect to fig. 16B, it is also possible to have a resonant unit common to a plurality of primary windings, as shown in the circuit 200' of fig. 21B, compared to the case where the multiple resonant units are connected in series in common to the common primary winding Tr1 shown in fig. 21A.

The switching branch 202 of the circuit 200' contains not only the original two switches S1-S2, but is further extended by (m-2) switches (S3, …, Sm). The expanded (m-2) switches (S3, …, Sm) are connected in series with the original two switches S1-S2 such that the switching leg 102 contains m switches connected in series, where m is an integer and m ≧ 5. The circuit 200' further comprises a plurality of resonant cells 207 and a plurality of primary windings Tr 1. Each of the plurality of resonant cells 207 includes a resonant capacitor Crx and a resonant inductor Lrx. Each of the plurality of resonance units 207 has the same resonance parameter.

In circuit 200', switching leg 202 has m switches connected in series, where m is an integer and m ≧ 5. Two adjacent ones of the m switches are connected to form a connection point, and thus have (m-1) connection points. Considering the connection point near the output of the circuit 100 as connection point No. 1, the switching leg 102 has connection points No. 1, 2, 3, …, m-1 from the output to the input. For example, as shown in fig. 21B, the connection point of the switches S1 and S2 is closest to the output terminal, so the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 21B), and the connection point of the switches S2 and S3 is the connection point No. 2 (identified as "c" in fig. 21B), the connection point of the switch S3 and the switch S4 is the connection point No. 3 (identified as "c" in fig. 21B), and so on, the connection point of the switch Sm and the switch Sm one before the switch Sm is the connection point No. (m-1).

One end of each of the plurality of primary windings Tr1 in the circuit 200' is connected to the odd-numbered connection point, and the other end thereof is connected to the resonance unit constituted by the resonance capacitor Cr and the resonance inductor Lr. Each of the plurality of resonant cells 207 in the circuit 200' has one end connected to the even-numbered connection point and the other end connected to the midpoint m1 of the first branch of the full-bridge rectifier circuit.

One of the plurality of resonance units 207 has one end connected to a connection point of the 2 z-th switch and the (2z +1) -th switch among the m switches and the other end connected to a midpoint m1 of the first branch of the full-bridge rectifier circuit, where z is an integer and 1. ltoreq. z.ltoreq (m-1)/2.

Circuit 200' of FIG. 21C illustrates a conversion circuit hereinAnother extension of (4). The switching leg 202 of the circuit 200' shown in FIG. 21C contains m switches, where m is an integer and m ≧ 3. The circuit 200' further comprises (m-1) conversion branches 208 (208)₁、208₂、…、208_m-1) For example, each conversion branch 208 may be a resonant unit composed of a resonant capacitor Cr and a resonant inductor Lr. In addition, the full-wave rectification circuit of the circuit 200 ″ includes n branches, for example, the full-wave rectification circuit shown in fig. 21C includes a switch SR1 and a secondary winding Ns of the transformer Tr₁A first branch formed by a switch SR2 and a secondary winding Ns of a transformer Tr₂A second branch formed by a switch SR3 and a secondary winding Ns of a transformer Tr₃A third branch and a secondary winding Ns composed of a switch SRn and a transformer Tr_nAnd forming the nth branch. The switch and the secondary winding of each of the n legs are connected in series to form a midpoint of the respective leg. In this embodiment, the number n of legs in the full-wave rectification circuit is not greater than the number m of switches in the switching leg 202, and the number n of legs is at least 2, i.e., m ≧ n ≧ 2 is satisfied in addition to m ≧ 3.

The n branches of the full-wave rectification circuit comprise at least one first branch and at least one second branch, wherein the homonymous ends of the secondary windings of the first branch are connected, and the heteronymous ends of the secondary windings of the first branch and the secondary windings of the second branch are connected. For example, as shown in FIG. 21C, the signal is generated by a switch SR1 and a secondary winding Ns of a transformer Tr₁A first branch formed by a switch SR3 and a secondary winding Ns of a transformer Tr₃The third branch is the first branch and is composed of a switch SR2 and a secondary winding Ns of the transformer Tr₂A second branch and a secondary winding Ns composed of a switch SRn and a transformer Tr_nThe nth branch is formed as a second kind of branch. Additionally, in the n branches of the full-wave rectification 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 symmetry manner.

The switching leg 202 of the circuit 200' of FIG. 21C has m switches connected in series, where m is an integer and m ≧ 3. Two adjacent ones of the m switches are connected to form a connection point, and thus have (m-1) connection points. Considering the connection point near the output of the circuit 200 "as connection point No. 1, the switching leg 202 has connection points No. 1, 2, 3, …, (m-1) from the output to the input. For example, as shown in fig. 21C, the connection point between the switches S1 and S2 is closest to the output terminal, so the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 21C), and the connection point of the switch S2 and the next switch (not shown) adjacent to the switch S2 is the connection point No. 2 (identified as "C" in fig. 21C), and so on, the connection point of the switch Sm and the switch (not shown) preceding the switch Sm is the connection point No. (m-1).

Of the (m-1) switching legs 208 in circuit 200 ", for a switching leg connected at one end to the odd-numbered connection point of switching leg 202, the switching leg is connected between the odd-numbered connection point of switching leg 202 and the midpoint of one of the second class of legs of the n legs; whereas for a switching leg having one end connected to the even-numbered connection point of the switching leg 202, the switching leg is connected between the even-numbered connection point of the switching leg 202 and the midpoint of one of the first class of n legs.

Among the (m-1) switching legs 208, the (2y-1) th switching leg has one end connected to the connection points of the (2y-1) th switch and the 2 y-th switch among the m switches and the other end connected to the midpoint of one of the second class legs among the n legs, where y is an integer, and 1. ltoreq. y.ltoreq.m/2. For example, when y is 1, of the (m-1) conversion branches 208, the first (2y-1) conversion branch (the conversion branch 208 in fig. 21C)₁) Is connected to the connection point of the first (2y-1) switch (switch S1 in fig. 21C) and the second (2y) switch (switch S2 in fig. 21C), and is connected to the midpoint of one of the second class of legs of the n legs, e.g., the midpoint of the second leg.

Further, among the (m-1) switching legs, one end of the 2 z-th switching leg is connected to the connection point of the 2 z-th switch and the (2z +1) -th switch among the m switches, and the other end is connected to the first-type leg among the n legsWherein z is an integer, and 1. ltoreq. z.ltoreq (m-1)/2. For example, when z is 1, of the (m-1) conversion legs, the second (2z) conversion leg (conversion leg 208 in fig. 21C)₂) Is connected to the connection point of the second (2z) switch (switch S2 in fig. 21C) and the third (2z +1) switch (switch S3 in fig. 21C), and is connected to the midpoint of one of the first class of legs in the nth leg, for example, the midpoint of the third leg.

In addition, the circuit 200 "further includes a primary winding Np of the transformer Tr connected in series with one of the (m-1) switching legs. For example, fig. 21C shows the primary winding Np and the switching branch 208₁In series, but not limited thereto, the primary winding Np may also be connected to the switching branch 208₂、…、208_m-1Any of which are connected in series. The circuit of fig. 21C can achieve a voltage conversion ratio of Vin/Vo ═ 2(Np + m).

Although fig. 21C shows one primary winding Np connected in series with any one of the (m-1) converting branches, this document is not limited thereto, and a plurality of primary windings Np connected in series with a plurality of the (m-1) converting branches may be included. For example, as shown in FIG. 21D, the circuit 200 ″ may include (m-1) primary windings Np (Np) having the same number of (m-1) switching branches₁、Np₂、…、Np_m-1) And each of the (m-1) primary windings Np is connected in series with a corresponding one of the (m-1) switching legs. When the turn ratio of the primary winding Np in fig. 21D is 1:1: …:1, Vin/Vo-2 (N) can be achieved₁+N₂+…+N_m-1+ m) voltage conversion ratio, where N₁、N₂、…、N_m-1Are primary windings Np respectively₁、Np₂、…、Np_m-1The number of turns of (c).

Although the plurality of conversion branches 208 in fig. 21C and 21D are each illustrated as a resonant cell, some of the plurality of conversion branches 208 may also be formed of non-resonant cells, for example, the non-resonant cells may be cells formed of only one capacitor, or formed of capacitors and inductors having resonant frequencies much smaller or larger than the switching frequency of the circuit (the switching frequency is smaller than 1/3 or larger than 3 times the switching frequency). When the plurality of conversion branches 208 include a conversion branch formed by non-resonant cells, it is necessary that the adjacent conversion branches on both sides of the conversion branch formed by non-resonant cells are all resonant cells. In other words, the ith conversion branch in 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 in the (m-1) conversion branches 208 are resonant units, where m is greater than or equal to 4, i is less than or equal to m-2, and i is an integer.

Fig. 22 shows a variation of the circuit 120 of fig. 13A. In the circuit 210 shown in fig. 22, the full-wave rectification circuit has a first branch constituted by the switch SR1 and the transformer secondary winding Tr22, and a second branch constituted by the switch SR2 and the transformer secondary winding Tr 21. The switch SR1 and the secondary transformer winding are connected in series to form a first midpoint m1, and the switch SR2 and the secondary transformer winding Tr21 are connected in series to form a midpoint m 2.

Circuit 210 has two switching

legs

212 and 215, switching leg 212 being connected between a first end of the input voltage and a first midpoint m1, and switching leg 215 being connected between the first end of the input voltage and a second midpoint m 2. The switching leg 212 has four switches S1-S4 connected in series and the switching leg 215 has four switches S5-S8 connected in series. The circuit 210 also has four

resonant cells

213, 214, 216 and 217, two dc blocking capacitors C1 and C2, and transformer primary windings Tr11 and Tr 12. The turn ratio of the primary winding Tr11, the primary winding Tr12, the secondary winding Tr12 and the secondary winding Tr22 of the transformer is N: N:1: 1.

The resonance unit 213 is connected between the connection point p1 of the switches S1 and S2 and the primary winding Tr 11. The resonance unit 214 is connected between the connection point p3 of the switches S3 and S4 and the primary winding Tr 11. The resonant unit 216 is connected between the connection point p4 of the switches S5 and S6 and the primary winding Tr 12. The resonant cell 217 is connected between the connection point p6 of the switches S7 and S8 and the primary winding Tr 12. The dc blocking capacitor C1 is connected between the connection point p2 of the switches S2 and S3 and the first midpoint m 1. The dc blocking capacitor C2 is connected between the connection point p5 of the switches S6 and S7 and the second midpoint m 2.

In one duty cycle of the circuit 210, in the first half cycle, the switches S4, S2, S7, S5, SR1 are turned on, while the switches S3, S1, S8, S6, SR2 are turned off, and in the second half cycle, the switches S4, S2, S7, S5, SR1 are turned off, while the switches S3, S1, S8, S6, SR2 are turned on. The circuit 210 also achieves a conversion ratio of (4N + 8). Compared with the circuit 120 of fig. 13A, 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.

[ third embodiment ]

Fig. 23 shows a circuit example of the conversion circuit 220 according to the third embodiment herein.

As shown in fig. 23, the circuit 220 receives an input voltage Vin, converts the input voltage Vin, and outputs the converted voltage.

The circuit 220 includes a full-wave rectifying circuit 221, a switching branch 222 and a resonant unit 223.

The input voltage and the output voltage each have a first terminal and a second terminal, wherein the second terminal of the input voltage and the second terminal of the output voltage are connected. The full-wave rectification circuit 221 has a first branch consisting of the switch SR1 and the first winding Tr22 of the transformer Tr, and a second branch consisting of the switch SR2 and the second winding Tr21 of the 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 m 2.

In one example of the circuit 220, the circuit 220 may include an output capacitor Co for output filtering, connected between a first terminal and a second terminal of the output voltage in parallel with a first branch and a second branch of the full-wave rectification circuit 221. Additionally, the circuit 220 may also include an input capacitance Cin for input filtering, which may be connected between the first and second terminals of the input voltage, or the input capacitance Cin may also be connected between the first terminal of the input voltage and the first terminal of the output voltage, as illustrated by the dashed line connected input capacitance Cin in fig. 23.

The switching leg 222 is connected between the first end of the input voltage and the first midpoint m1, and the switching leg 222 comprises two switches S1 and S2 connected in series. The switches S1 and S2 are connected to form a connection point p 1.

The resonance unit 223 has a resonance capacitance Cr and a resonance inductance Lr. Although fig. 23 shows the resonant unit formed by the resonant capacitor and the resonant inductor connected in series, the present disclosure is not limited thereto, and the resonant unit may be formed by the resonant capacitor and the resonant inductor connected in parallel.

One end of the resonant cell 223 is connected to the connection point p1, and the other end is connected to the second midpoint m 2. The resonance unit 223 is not connected in series with any winding of the transformer Tr.

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, SR1 are symmetrically turned on complementary to the switches S1, SR2, and the duty cycle is close to 0.5. During the first half of the duty cycle, switches S2, SR1 are on, while switches S1, SR2 are off. At this time, a current is supplied from the input terminal to the output terminal through a first resonance path formed by the switch S2, the resonance capacitor Cr, the resonance inductor Lr, and the second winding Tr21, and the resonance frequency is set to be

Meanwhile, the first winding Tr22 winding of the transformer induces a resonance current of the second winding Tr21 and supplies power to the output terminal through the second path formed by the switch SR1 and the first winding Tr 22. In the time period of switching from the former half period to the latter half period, the parasitic capacitances of the switches S2 and SR1 are charged by the current on the exciting inductor, and the parasitic capacitances of the switches S1 and SR2 are discharged, so that soft switching is realized. During the second half of the duty cycle, switches S1, SR2 are turned on and switches S2, SR1 are turned off. Similar to the first half cycle, at this time, the current flows to the output terminal through one resonant path formed by the switch SR2, the resonant inductor Lr, the resonant capacitor Cr, the switch S1, and the first winding Tr22, while the second winding Tr21 induces the current of the first winding Tr22 and flows to the output terminal through the other resonant path formed by the switch SR2 and the winding Tr 21.

Assuming that the current at the input terminal is i, the current of the resonant unit is 2i during one duty cycle of the circuit 220, and the current flows directly to the output terminal through one winding of the transformer Tr. Since the actual turns ratio of the transformer Tr is 1:1, the current induced in the other winding of the transformer Tr is also 2i, so the total current flowing to the output is4 i. Since only a half of the resonant period of current flows through the switch S2, the input side current is half of the current of the resonant unit 213, i.e., i. Therefore, the voltage conversion ratio of the circuit is 4: 1.

[ variation of the third embodiment ]

The third embodiment described herein may also have a variety of variations, similar to the second embodiment described herein and its variations. Various modifications of the full-wave rectification type conversion circuit 220 are described below, and only differences of the various modifications with respect to the conversion circuit 220 are described, and the same parts are not described again.

Fig. 24 shows a schematic diagram of a transformation circuit 230 according to a variation of the third embodiment herein.

Compared to the circuit 220 of fig. 23, the circuit 230 shown in fig. 24 extends two switches S3 and S4 connected in series in a switching leg such that the switching leg comprises four switches S1-S4 connected in series, wherein the switches S1 and S2 are connected in series to form the connection point p1, the switches S2 and S3 are connected in series to form the connection point p2, and the switches S3 and S4 are connected in series to form the connection point p 3.

The circuit 230 is further extended with a blocking capacitor C1 and another resonant unit 234 composed of a resonant capacitor Cr2 and a resonant inductor Lr 2. 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 m 1. One end of the resonant cell 234 is connected to the connection point p3, and the other end is connected to the second midpoint m 2.

Since the first winding Tr21 and the second winding Tr22 of the transformer Tr connected in series are induced to each other in the first half period and the second half period of one duty cycle in one duty cycle of the circuit 230, the circuit 230 achieves a voltage conversion ratio of 8: 1.

another variation of the circuit 220 of fig. 23 is shown in the circuit 240 of fig. 25. Although the resonance unit shown in fig. 23 includes the resonance capacitance Cr and the resonance inductance Lr, the leakage inductance of the transformer Tr having the second winding Tr21 and the first winding Tr22 may be used as the resonance inductance of the resonance unit. Therefore, in the circuit 240 of fig. 25, the leakage inductance Lk of the transformer Tr is used as a resonance inductance to resonate with the resonance capacitance Cr. The circuit 240 also achieves the effect of the circuit 220 of fig. 23 and simplifies the circuit configuration.

The circuit 250 in fig. 26 is a further variation of the circuit 230 in fig. 24. In circuit 250, a portion of each of the resonant inductors Lr1 and Lr2 is combined into a common inductor Lrc shared by two resonant cells at a resonant frequency of:

Circuit 260 in fig. 27 is a further variation of circuit 230 in fig. 24. In circuit 260, when the parameters of the two resonant cells are the same, the respective resonant inductances of the two resonant cells may be combined into a common inductance Lrc that is shared by the two resonant cells. Resonant frequency at this time

The circuit 270 of fig. 28 is a further variation of the circuit 230 of fig. 24. In the circuit 270, when the resonant capacitor Cr1 and the resonant inductor Lr1 in the resonant unit 273 have the same parameters as the resonant capacitor Cr2 and the resonant inductor Lr2 in the resonant unit 274, the resonant capacitor Cr3 and the resonant inductor Lr3 having the same parameters as 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 constitute the resonant unit 275. The resonant capacitor Cr3 plays a role of a blocking capacitor and participates in circuit resonance together with the resonant inductor Lr 3.

Circuit 280 in fig. 29 is a further variation of circuit 230 in fig. 24. In the circuit 280, an output capacitor Co connected in parallel with a first branch and a second branch of a full-wave rectification circuit of the circuit 280 may be used as a resonance capacitor Cr shared by two resonance units. Therefore, in the circuit 280, the resonance capacitance Cr is shared by the resonance inductances Lr1 and Lr2, the resonance capacitance Cr resonates with the resonance inductance Lr1 as one resonance unit, the resonance capacitance Cr resonates with the resonance inductance Lr2 as the other resonance unit, and at this time, the resonance unit connected at the connection point of the switch circuit may have only the resonance inductance. 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 may be omitted.

Circuit 290 in fig. 30 is a further variation of circuit 230 in fig. 24. In the circuit 290, the full-wave rectification 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 comprises a switch SR3, a first winding Tr '21 of a transformer Tr' connected in series, and a connection point, called a third midpoint m3, formed by connecting a switch SR3 and the first winding Tr '21 of the transformer Tr'. The fourth branch comprises a switch SR4 and a second winding Tr '22 of the 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 m 4.

One end of a 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 m 2. Another resonant unit constituted by the resonant capacitor Cr2 and the resonant inductor Lr2 has one end connected to the connection point p3 of the switches S3 and S4 and the other end connected to the fourth midpoint m 4. The turn 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.

The circuit 290 advantageously reduces the current stress on the transformer and rectifier, or increases the current capability of the transformer and switch SR, using the same components, thereby increasing the output power of the converter.

Likewise, the circuit 220 of fig. 23 may be further extended to change the voltage conversion ratio. Fig. 31 shows an expanded form. In the circuit 300 shown in fig. 31, the switch branch 302 thereof not only includes the original two switches S1-S2, but also is further extended by (2m-2) switches (S3, S4 … S)_2m-1、S_2m). Extended (2m-2) switches (S3, S4 … S)_2m-1、S_2m) Connected in series with the original two switches S1 and S2 such that the switching leg 92 contains 2m switches connected in series, where m is an integer and m ≧ 2.

The circuit 300 further includes (m-1) blocking capacitances Cx (C)_x1、C_x2) And (m-1) resonant cells 304. Where (m-1) resonant cells 304 and the original resonant cell 303 result in a circuit 300 with m resonant cells. The resonant cells 304 each include a resonant capacitor Crx and a resonant inductor Lrx.

Therefore, a conversion circuit such as the circuit 300 of fig. 31 can be described as follows: the switching leg 302 has 2m switches connected in series, where m is an integer and m ≧ 2. Two adjacent switches of the 2m switches are connected to form a connection point, and thus have (2m-1) connection points.

Considering the connection point near the output of the circuit 300 as connection point No. 1, the switching branch 92 has connection points No. 1, 2, 3, …, (2m-2), (2m-1) from the output to the input. For example, as shown in fig. 31, the connection point between the switches S1 and S2 is closest to the output terminal, so the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 31), and the connection point of the switch S2 and the next switch adjacent to the switch S2 is the connection point No. 2 (identified as "c" in fig. 31), and so on, the switch S_2m-1And S_2mThe connection point between is the connection point No. (2 m-1).

Wherein each of the m resonant cells is connected between the odd-numbered connection point and the second midpoint m2, and each of the (m-1) blocking capacitances Cx is connected between the even-numbered connection point and the first midpoint m 1.

In the above m resonant cellsAnd one end of the x-th resonance unit is connected to a connection point of a (2x-1) -th switch and a 2 x-th switch among the 2m switches, wherein x is an integer, and 1 ≦ x ≦ m. For example, when x is 1, for a first (x) resonant cell (the resonant cell 303 in fig. 31) of the m resonant cells, one end thereof is connected to a connection point of a first (2x-1) switch (the switch S1 in fig. 31) and a second (2x) switch (the switch S2 in fig. 31), and the other end thereof is connected to the second midpoint m 2. For another example, when x is equal to m, for the m- (x) th resonance unit (resonance unit 304 in fig. 31) of the m resonance units, one end thereof is connected to the (2m-1) (2x-1) th switch (switch S in fig. 31)_2m-1) And 2m (2x) th switch (switch S in FIG. 31)_2m) And the other end to a second midpoint m 2.

In the above (m-1) blocking capacitances Cx, one end of the kth blocking capacitance is connected to the connection point of the 2 kth switch and the (2k +1) th switch among the 2m switches, and the other end is connected to the midpoint m2 of the second leg, where k is an integer, and 1. ltoreq. k.ltoreq.m-1. For example, when k is 1, the first (k) dc blocking capacitors (capacitor C in fig. 31)_x1) Is connected to the connection point of the second (2k) switch (switch S2 in fig. 31) and the next switch (not shown in fig. 31 adjacent to switch S2) and is connected to the first midpoint m 1. For another example, when k is (m-1), the (m-1) (k) th dc blocking capacitor (dc blocking capacitor C in fig. 31)_x2) Is connected to the (2m-2) (2k) th switch (AND switch S in FIG. 31)_2m-1Adjacent previous switch, not shown) and (2m-1) (2k +1) th switch (switch S in FIG. 10)_2m-1) And the other end is connected to the first point m 1.

Thus, for the circuit 300 of FIG. 31, the conversion ratio is 4m: 1. Thereby realizing the expansion of the conversion ratio of the conversion circuit. It can be seen that the circuit 230 in fig. 24 can be regarded as a circuit obtained by extending a pair of switches, a dc blocking capacitor and a resonant unit to the circuit 220 in fig. 23.

Fig. 32 shows another expanded form. The circuit 331 of fig. 32 is another extension of the circuit 220 of fig. 23. The switch branch 312 of the circuit 310 not only includes the originalAnd (m-2) switches (S3, …, Sm) are further extended. The expanded (m-2) switches (S3, …, Sm) are connected in series with the original two switches S1-S2 such that the switching leg 312 contains m switches connected in series, where m is an integer and m ≧ 3. Circuit 310 further includes (m-2) resonant cells 314 (314)₁、314₂). Therefore, (m-2) resonance units 314 and resonance unit 313 constitute (m-1) resonance units together. The resonant unit 314 includes a resonant capacitor Crx and a resonant inductor Lrx. The respective resonance units (resonance unit 313 and resonance unit 314) in the circuit 310 have the same resonance parameters.

Specifically, a conversion circuit such as the circuit 310 of fig. 32 can be described as follows: switching leg 312 has m switches connected in series, where m is an integer and m ≧ 3. Two adjacent ones of the m switches are connected to form a connection point, and thus have (m-1) connection points. Considering the connection point near the output of circuit 310 as connection point No. 1, switching branch 312 has connection points No. 1, 2, 3, …, (m-1) from the output to the input. For example, as shown in fig. 32, the connection point of the switches S1 and S2 is closest to the output terminal, so that the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 32), and the connection point of the switches S2 and S3 is the connection point No. 2 (identified as "c" in fig. 32), and so on, the connection point of the switch Sm and one switch (not shown) before the switch Sm is the connection point No. (m-1).

Each of the (m-1) resonant cells (313, 314) in the circuit 310 has one end connected to a respective connection point and another end connected to the first midpoint m1 or the second midpoint m 2. Wherein, for a resonant cell having one end connected to the odd-numbered connection point, the other end thereof is connected to the second midpoint m 2. For the resonant cells whose one end is connected to the even-numbered connection points, the other end thereof is connected to the first midpoint m 1.

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 2 y-th switch in the m switches, and the other end is connected to the primary winding Tr1 of the transformer, wherein y is an integer and is more than or equal to 1 and less than or equal to m/2. For example, when y is 1, among the (m-1) resonant cells, one end of the first (2y-1) resonant cell (the resonant cell 313 in fig. 32) is connected to a connection point of the first (2y-1) switch (the switch S1 in fig. 32) and the second (2y) switch (the switch S2 in fig. 32), and the other end is connected to the second midpoint m 2.

In the (m-1) resonant cells, one end of the 2 z-th resonant cell is connected to a connection point of the 2 z-th switch and the (2z +1) -th switch among the m switches, and the other end is connected to a first midpoint m1, where z is an integer, and 1. ltoreq. z.ltoreq (m-1)/2. For example, when z is 1, among the (m-1) resonant cells, one end of the second (2z) resonant cell (the resonant cell 3141 in fig. 32) is connected to a connection point of the second (2z) switch (the switch S2 in fig. 32) and the third (2z +1) switch (the switch S3 in fig. 32), and the other end is connected to the first midpoint m 1. For the conversion ratio of the spreading circuit 310, it is still m: 1.

fig. 33 shows a variation of the circuit 230 of fig. 24. In the circuit 320 shown in fig. 33, the full-wave rectification circuit has a first branch constituted by the switch SR1 and the first winding Tr22, and a second branch constituted by the switch SR2 and the second winding Tr 21. 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 m 2.

The circuit 320 has two switching

legs

322 and 325, the switching leg 322 being connected between the first end of the input and the first midpoint m1, and the switching leg 325 being connected between the first end of the input and the second midpoint m 2. The switching leg 322 has four switches S1-S4 connected in series and the switching leg 325 has four switches S5-S8 connected in series. The circuit 320 also has four

resonant cells

323, 324, 326 and 327 and two dc blocking capacitances C1 and C2. The turn ratio of the second winding Tr12 to the first winding Tr22 is 1: 1.

The resonance unit 323 is connected between the connection point p1 of the switches S1 and S2 and the second midpoint m 2. The resonant unit 324 is connected between the connection point p3 of the switches S3 and S4 and the second midpoint m 2. The resonant cell 326 is connected between the connection point p4 of the switches S5 and S6 and the first midpoint m 1. The resonant unit 327 is connected between the connection point p6 of the switches S7 and S8 and the first midpoint m 1. The dc blocking capacitor C1 is connected between the connection point p2 of the switches S2 and S3 and the first midpoint m 1. The dc blocking capacitor C2 is connected between the connection point p5 of the switches S6 and S7 and the second midpoint m 2.

In one duty cycle of the circuit 320, in the first half cycle, the switches S4, S2, S7, S5, SR1 are turned on, while the switches S3, S1, S8, S6, SR2 are turned off, and in the second half cycle, the switches S4, S2, S7, S5, SR1 are turned off, while the switches S3, S1, S8, S6, SR2 are turned on. Circuit 320 also achieves an 8:1 conversion ratio. Compared with the circuit 230 of fig. 24, 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.

Fig. 34A shows a variation of the circuit 220 of fig. 23. In the circuit 330 shown in fig. 34A, the full-wave rectification circuit has a first branch constituted by the switch SR1 and the first winding Tr22, and a second branch constituted by the switch SR2 and the second winding Tr 21. 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 m 2.

The circuit 330 has two switching

legs

332 and 335, the switching leg 332 being connected between the first end of the input voltage and a first midpoint m1, and the switching leg 325 being connected between the first end of the input voltage and a second midpoint m 2. The switching leg 332 has switches S1 and S2 connected in series and the switching leg 325 has switches S3 and S4 connected in series. The circuit 330 also has

resonant cells

334 and 336. The turn ratio of the second winding Tr12 to the first winding Tr22 is 1: 1.

The resonant cell 334 is connected between the connection point p1 of the switches S1 and S2 and the second midpoint m 2. The resonant cell 336 is connected between the connection point p2 of the switches S3 and S4 and the first midpoint m 1.

For example, when the circuit 330 is in operation, the switches S2, S3 and SR1 are simultaneously on or off, the switches S1, S4 and SR2 are simultaneously on or off, and the set of S2, S3 and SR1 and the set of S1, S4 and SR2 are complementarily symmetrically on. Circuit 330 also achieves a 4:1 conversion ratio. Compared with the circuit 220 in fig. 23, 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.

Similarly to what has been described with respect to fig. 25, the leakage inductance of the transformer Tr having the second winding Tr21 and the first winding Tr22 may be used as at least a part of the resonant inductance of the resonant unit. For example, in the circuit 330' of fig. 34B, the leakage inductance Lk of the transformer Tr is used as a resonance inductance to resonate with the resonance capacitances Cr1 and Cr2, respectively. The circuit 330' can also achieve the effect of the circuit 330 of fig. 34A and simplify the circuit configuration.

While the above description has been made with reference to fig. 33, 34A and 34B for the case where two sets of switching legs and two sets of resonant units share a single full-wave rectification circuit, in other embodiments, two sets of switching legs and full-wave rectification circuits may share the same resonant unit. Fig. 35 shows a variation of the circuit 220 of fig. 23.

Two sets of circuits are shown in parallel operation in circuit 340, one of which is shown in the dashed box of fig. 35, and the other of which is shown outside the dashed box.

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

The circuit 340 further comprises a resonant unit 344, one end of the resonant unit 344 being connected to the common connection point pc and the other end being connected to the common midpoint mc. Thus, the resonance unit 344 is shared by the two sets of circuits shown in the circuit 340. Circuit 340 also achieves a 4:1 conversion ratio. The current stress of the switches S1-S4 of the switch branch in the circuit 330 can be reduced by half, and the current of the switches SR 1-SR 4 can also be reduced by half.

Fig. 36A shows another variation of the circuit 220 of fig. 23. FIG. 36A shows a circuit 350 in which the switching leg 352 includes m switches, where m is an integer and m ≧ 3. Circuit 350 further includes (m-1) conversion branches 353 (353)₁、353₂、…、353_m-1) For example, each conversion branch 353 may be a resonant unit composed of a resonant capacitor Cr and a resonant inductor Lr. In addition, the full-wave rectification circuit of the circuit 350 includes n branches, for example, the full-wave rectification circuit shown in fig. 36A includes a switch SR1 and a secondary winding Ns of the transformer Tr₁A first branch formed by a switch SR2 and a secondary winding Ns of a transformer Tr₂A second branch formed by a switch SR3 and a secondary winding Ns of a transformer Tr₃A third branch and a secondary winding Ns composed of a switch SRn and a transformer Tr_nAnd forming the nth branch. The switch and the secondary winding of each of the n legs are connected in series to form a midpoint of the respective leg. In this embodiment, the number n of legs in the full-wave rectification circuit is not greater than the number m of switches in the switching leg 352, and the number n of legs is at least 2, i.e., m ≧ n ≧ 2 is satisfied in addition to m ≧ 3.

The n branches of the full-wave rectification circuit comprise at least one first branch and at least one second branch, wherein the homonymous ends of the secondary windings of the first branch are connected, and the heteronymous ends of the secondary windings of the first branch and the secondary windings of the second branch are connected. For example, as shown in FIG. 36A, the signal is generated by a switch SR1 and a secondary winding Ns of a transformer Tr₁A first branch formed by a switch SR3 and a secondary winding Ns of a transformer Tr₃The third branch is the first branch and is composed of a switch SR2 and a secondary winding Ns of the transformer Tr₂A second branch and a secondary winding Ns composed of a switch SRn and a transformer Tr_nThe nth branch is formed as a second kind of branch. Additionally, in the n branches of the full-wave rectification circuit, the switches of the first-type branch are simultaneously turned on and off, and the switches of the first-type branch and the second-type branch are connected to the same terminalThe switches of the branches are complementarily symmetrically conducted.

The switching leg 352 of the circuit 350 of FIG. 36A has m switches connected in series, where m is an integer and m ≧ 3. Two adjacent ones of the m switches are connected to form a connection point, and thus have (m-1) connection points. Considering the connection point near the output of the circuit 350 as connection point No. 1, the switching branch 352 has connection points No. 1, 2, 3, …, (m-1) from the output to the input. For example, as shown in fig. 36A, the connection point between the switches S1 and S2 is closest to the output terminal, so the connection point of the switches S1 and S2 is the connection point No. 1 (identified as "r" in fig. 36A), and the connection point of the switch S2 and the next switch (not shown) adjacent to the switch S2 is the connection point No. 2 (identified as "c" in fig. 36A), and so on, the connection point of the switch Sm and the switch (not shown) preceding the switch Sm is the connection point No. (m-1).

Among the (m-1) conversion legs 353 in the circuit 350, for a conversion leg whose one end is connected to the odd-numbered connection point of the switching leg 352, the conversion leg is connected between the odd-numbered connection point of the switching leg 352 and the midpoint of one of the second-type legs among the n legs; whereas for a switching branch having one end connected to the even-numbered connection point of the switching branch 352, the switching branch is connected between the even-numbered connection point of the switching branch 352 and the midpoint of one of the first class of n branches.

In the (m-1) switching branch 353, one end of the (2y-1) th switching branch is connected to the connection point of the (2y-1) th switch and the 2 y-th switch in the m switches, the other end is connected to the midpoint of one of the second type branches in the n branches, and the (2y-1) th switch and the switch in the second type branch are simultaneously turned on or off, wherein y is an integer, and 1 ≦ y ≦ m/2. For example, when y is equal to 1, of the m-1 conversion legs 353, the first (2y-1) conversion legs (the conversion legs 353 in fig. 36A)₁) Is connected to the connection point of the first (2y-1) switch (switch S1 in fig. 36A) and the second (2y) switch (switch S2 in fig. 36A), and is connected to the midpoint of one of the second class of legs of the n legs, for example, the midpoint of the second leg.

Further, in the (m-1) conversion branches, one end of the 2 z-th conversion branch is connected to the connection point of the 2 z-th switch and the (2z +1) -th switch among the m switches, the other end is connected to the midpoint of one of the first kind of branches among the n branches, and the 2 z-th switch and the switch in the first kind of branch are simultaneously turned on or off, wherein z is an integer, and 1 ≦ z ≦ m-1)/2. For example, when z is 1, of the (m-1) conversion legs, the second (2z) conversion leg (conversion leg 353 in fig. 36A)₂) Is connected to the connection point of the second (2z) switch (switch S2 in fig. 36A) and the third (2z +1) switch (switch S3 in fig. 36A), and is connected to the midpoint of one of the first class of legs in the nth leg, for example, the midpoint of the third leg.

When the switching number of the switching branch 352 of the circuit 350 is m, it can realize a voltage conversion ratio of Vin/Vo being 2 m.

Although the plurality of conversion arms 353 in fig. 36A are each illustrated as a resonant unit, some of the plurality of conversion arms 353 may be configured of a non-resonant unit. For example, a non-resonant cell may be a cell consisting of only one capacitor, or a capacitor and an inductor having a resonant frequency much less than or much greater than the switching frequency of the circuit (less than 1/3 or more than 3 times the switching frequency). When the plurality of conversion arms 353 include a conversion arm formed of a non-resonant unit, it is necessary that the adjacent conversion arms on both sides of the conversion arm formed of the non-resonant unit are both resonant units. In other words, the ith conversion branch in 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 in the (m-1) conversion branches 353 are both resonant units, wherein m is greater than or equal to 4, i is less than or equal to m-2, and i is an integer.

For example, in one embodiment, the switching legs connected between the odd-numbered nodes and the midpoints of the second-type legs (i.e., the (2y-1) th switching legs of 353 in the above-described (m-1) switching legs) may each be constituted by a resonance unit, and the switching legs connected between the even-numbered nodes and the midpoints of the first-type legs (i.e., the 2 z-th switching legs of 353 in the above-described (m-1) switching legs) may each be constituted by a capacitor. At this time, the number m of switches of the switching branch needs to be an even number, because the last connection point of the switching branch needs to be an odd-numbered node connected to the resonant unit, so that the condition that the adjacent switching branches of the switching branch composed of only one capacitor are all resonant units is satisfied.

For example, when the number of switches in the switching legs and the number of legs in the full-wave rectification circuit are both 3 (i.e., m-n-3), a specific conversion circuit may be as shown in fig. 36B.

In the circuit 350' in fig. 36B, the switching branch 352 includes 3 switches S1 to S3, and the full-wave rectification circuit includes 3 branches. Composed of a switch SR1 and a secondary winding Ns₁A first branch formed by a switch SR3 and a secondary winding Ns₃The third branch is the first branch and is composed of a switch SR2 and a secondary winding Ns₂The second branch formed is a second type of branch.

Conversion branch 353 in circuit 350₁Is connected between the connection point (odd-numbered connection point (r)) of the switches S1 and S2 and the midpoint m2 of the second branch as the second-type branch, and the branch 353 is switched₂Connected between the connection point of the switches S2 and S3 (even connection point @) and the midpoint m3 of the third branch as the first branch, it should be noted that the switching branch 353₂It may also be connected between the connection point of the switches S2 and S3 and the midpoint m1 of the first branch, which is also the first branch of the first type. At this time, the switches S1, S3, SR2 are simultaneously turned on or off, the switches S2, SR1, SR3 are simultaneously turned on or off, and the set of switches S1, S3, SR2 and the set of switches S2, SR1, SR3 are complementarily and symmetrically turned on.

For example, when the number of switches in a switch leg is4 and the number of legs in a full-wave rectification circuit is3 (i.e., m is4 and n is 3), a specific conversion circuit may be as shown in fig. 36C.

In the circuit 350 ″ in fig. 36C, the switching leg 352 includes 4 switches S1 to S4, and the full-wave rectification circuit includes 3 legs. Composed of a switch SR1 and a secondary winding Ns₁The first branch is the first branch composed of switch SR2 and secondary winding Ns₂A second branch formed by a switch SR3 and a secondary winding Ns₃The third branch of the structureThe way is a second type of branch.

Conversion branch 353 in circuit 350 ″₁The switching branch 353 is connected between the connection point (odd connection point (r)) of the switches S1 and S2 and the midpoint m2 of the second branch as the second branch type₂Is connected between a connection point (even-numbered connection point) of the switches S2 and S3 and a midpoint m3 of a third branch as a first-type branch, and the branch 353 is switched₃Is connected between the connection point (even connection point (c)) of the switches S3 and S4 and the midpoint m3 of the third branch as the second-type branch. It should be noted that branch 353 is switched over₂And a conversion branch 353₃Or both may be connected to the midpoint m2 of the second branch or the midpoint m3 of the third branch as the second type of branch. At this time, the switches S1, S3, SR2, SR3 are simultaneously turned on or off, the switches S2, S4, SR1 are simultaneously turned on or off, and the set of switches S1, S3, SR2, SR3 and the set of switches S2, S4, SR1 are complementarily and symmetrically turned on.

The switches mentioned in the above embodiments, such as the first switch and the second switch, may be formed by connecting a plurality of switches in parallel. Likewise, the winding may be formed by connecting a plurality of windings in parallel.

Fig. 37 shows a comparison of the respective losses of the conversion circuit discussed herein and a conventional LLC transformer and a non-isolated LLC transformer.

In fig. 37, the inventors calculated that the voltage conversion ratio was 8: the conversion circuit 230 and the voltage conversion ratio in fig. 24 of 1 are also 8:1 LLC transformer and non-isolated LLC transformer, respectively.

In fig. 37, the circuit operating conditions are all: the input voltage Vin is 48V, the output voltage Vout is 4.8V, the operating frequency f is 1.2MHz, and the output current Io is 50A. The current in the primary winding and the secondary winding are broken down, and the circuit 230 in fig. 24 has no loss in the windings because the circuit 230 has only two windings in the full-wave rectification circuit and does not need the primary winding in the LLC (or non-isolated LLC). The winding current in full-wave rectification is subjected to Fourier decomposition (FFT), and the Direct Current (DC) components of the secondary side currents of the three circuits are the same because the output currents are the same. The circuit 230 has a high winding utilization rate, and the current is substantially the same in the front half period and the back half period, so that the first harmonic current value (marked as 1st in the figure) is only 1.6A. And in the traditional LLC full-wave rectification, a winding only works for a half cycle, so that the first harmonic current is maximum and reaches 40.8A. While the other harmonics of the three circuits (e.g., second harmonic 2nd, third harmonic 3rd, fourth harmonic 4th in the figure) are relatively close. Reflecting the effective values in the winding store, it can be seen that the effective value of the secondary current (RMS) of the 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, because both LLC and non-isolated LLC require primary windings, a common secondary-primary-secondary (SPS) winding structure is used in the calculation, and circuit 230 requires only two windings.

Assuming that a 12-layer PCB is also used for the transformer winding, the LLC and the non-isolated LLC have only 4 winding units, while the circuit 230 has 6 winding units, so that the circuit 230 has the least impedance of the winding with the same amount of copper. The total winding loss under this condition can be calculated by combining the above effective value of current and winding impedance. It can be seen that for the converter circuit 230 in fig. 24, the winding loss is 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 herein is greatly reduced, only about 20% of the original LLC circuit.

Thus, the converter circuit discussed herein has an improved conversion ratio compared to an STC converter circuit having the same number of switches, and at the same conversion ratio, the winding loss of the converter circuit discussed herein is significantly reduced compared to conventional LLC transformers and non-isolated LLC transformers.

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 thereof is determined by the claims that follow.

Claims

1. A conversion circuit for converting an input voltage to provide an output voltage, the input voltage and the output voltage each including a first terminal and a second terminal, the second terminal of the input voltage and the second terminal of the output voltage being connected, the conversion circuit comprising:

A first transformer, comprising:

the first primary winding is connected with the first resonance unit in series; and

and the first secondary winding is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm.

2. The conversion circuit of claim 1, wherein one end of the first primary winding is connected to a midpoint of the first leg, the other end is connected to one end of the first resonant cell, and the other end of the first resonant cell is connected to the first connection point.

3. The conversion circuit of claim 1, wherein

The first switching leg further comprises a third switch and a fourth switch connected in series with the first switch and the second switch, the second switch is connected with the third switch to form a second junction, the third switch and the fourth switch are connected to form a third junction, and

the conversion circuit further includes:

the first capacitor is electrically connected between the second connection point and the midpoint of the second bridge arm; and

and the second resonance unit is electrically connected between the third connecting point and the midpoint of the first bridge arm.

4. The converter circuit of claim 3, wherein the first transformer further comprises a second primary winding, and the second resonant unit is connected in series with the second primary winding.

5. The conversion circuit of claim 4 wherein the first primary winding and the second primary winding are common.

6. The conversion circuit of claim 3, further comprising a second switching branch, a third resonant cell, a fourth resonant cell, and a second capacitor, wherein:

the second switch branch is connected with the first switch branch in parallel, the second switch branch comprises a fifth switch, a sixth switch, a seventh switch and an eighth switch, and the fifth switch, the sixth switch, the seventh switch and the eighth switch are connected in series to form a fourth connection point, a fifth connection point and a sixth connection point in sequence;

the third resonance unit is electrically connected between the fourth connection point and the midpoint of the second bridge arm;

the second capacitor is electrically connected between the fifth connection point and the midpoint of the first bridge arm,

the fourth resonance unit is electrically connected between the sixth connection point and the midpoint of the second bridge arm.

7. The converter circuit of claim 6, wherein the first transformer further comprises a third primary winding in series with the third resonant cell and a fourth primary winding in series with the fourth resonant cell.

8. The conversion circuit of claim 1, wherein

the conversion circuit further includes:

a third bridge arm connected in parallel with the first bridge arm and the second bridge arm;

the fifth resonance unit is electrically connected between the third connecting point and the midpoint of the third bridge arm;

a second transformer, comprising:

a fifth primary winding connected in series with the fifth resonance unit;

the second secondary winding is connected between the midpoint of the second bridge arm and the midpoint of the third bridge arm; and

a third capacitor connected between the second connection point and the midpoint of the second leg.

9. The conversion circuit of claim 1, wherein

The first switching leg further comprises (2m-2) switches connected in series with the first switch and the second switch, such that the first switching leg comprises 2m switches connected in series, adjacent ones of the 2m switches being connected to form a connection point,

the conversion circuit further includes:

(m-1) resonance units which form m resonance units together with the first resonance unit, wherein the x-th resonance unit in the m resonance units is electrically connected between the connection point of the (2x-1) th switch and the 2 x-th switch in the 2m switches and the midpoint of the first bridge arm; and

(m-1) capacitors, wherein the kth capacitor of the (m-1) capacitors is electrically connected between the connection point of the 2 kth switch and the (2k +1) th switch of the 2m switches and the midpoint of the second bridge arm,

wherein m, x and k are integers, and m is not less than 2, 1. ltoreq. x.ltoreq.m and 1. ltoreq. k.ltoreq (m-1).

10. The conversion circuit of claim 9, wherein resonant inductors in the m resonant cells are common.

11. The conversion circuit according to claim 9, wherein capacitance values of the resonance capacitances in the m resonance units are the same.

12. The conversion circuit of claim 9, wherein the first primary winding comprises m sub-windings, and an x-th one of the m resonant cells is connected to a midpoint of the first leg via the x-th one of the m sub-windings.

13. The conversion circuit of claim 12, wherein the m sub-windings are common.

14. The conversion circuit of claim 1, wherein

the first primary winding comprises m sub-windings, wherein the xth sub-winding of the m sub-windings is electrically connected between the connection point of the (2x-1) th switch and the 2x th switch of the 2m switches and the midpoint of the first bridge arm after being connected in series with the first resonance unit, and

the conversion circuit further comprises (m-1) capacitors, wherein the kth capacitor in the (m-1) capacitors is electrically connected between the connection point of the 2 kth switch and the (2k +1) th switch in the 2m switches and the midpoint of the second bridge arm,

m, x and k are integers, and m is not less than 2, x is not less than 1 and not more than m, and k is not less than 1 and not more than (m-1).

15. The conversion circuit of claim 1, wherein

The first switching leg further comprising (m-2) switches connected in series with the first switch and the second switch, such that the first switching leg comprises m switches connected in series, wherein adjacent ones of the m switches are connected to form a connection point,

the conversion circuit further comprises (m-2) resonant cells to form (m-1) resonant cells together with the first resonant cell,

the (2y-1) th resonance unit in the (m-1) resonance units is electrically connected between the connection point of the (2y-1) th switch and the 2y th switch in the m switches and the midpoint of the first bridge arm after being connected in series with the first primary winding,

a 2 z-th resonant unit of the (m-1) resonant units is electrically connected between a connection point between the 2 z-th switch and the (2z +1) -th switch of the m switches and a midpoint of the second leg, and

m, y and z are integers, and m is not less than 3, 1 is not less than y and not more than m/2, and 1 is not less than z and not more than (m-1)/2.

16. The conversion circuit of claim 15, wherein the first primary winding comprises a plurality of sub-windings, and a (2y-1) th one of the (m-1) resonant cells is connected to the midpoint of the first leg via a respective one of the plurality of sub-windings.

17. The conversion circuit of claim 16, wherein the plurality of sub-windings are common.

18. The conversion circuit of claim 1, wherein

the first primary winding comprises a plurality of sub-windings, the connection point of the (2y-1) th switch and the 2y switch of the m switches is connected to one end of the first resonance unit through one of the sub-windings, the other end of the first resonance unit is connected to the midpoint of the first bridge arm,

the conversion circuit further includes a plurality of resonance units, a connection point between a 2 z-th switch and a (2z +1) -th switch of the m switches is connected to a midpoint of the second leg via one of the plurality of resonance units, and

19. The conversion circuit of any of claims 1-18, further comprising an output capacitor, the output capacitor being connected in parallel with the first leg.

20. The conversion circuit defined in claim 19, further comprising 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 and the first end of the output voltage.

21. A conversion circuit as claimed in any one of claims 1 to 18, wherein all the resonant cells comprise an inductance and a capacitance connected in series or in parallel.

22. The conversion circuit of claim 1, wherein the first resonant cell contains only a resonant inductance, and the conversion circuit further comprises a resonant capacitance in parallel with the first leg, the resonant capacitance cooperating with the resonant inductance.