A topology-converted multi-resonant dc-dc converter

Abstract

The application discloses a kind of topological transformation type multi-resonant DC converters, including inverter unit, resonant cavity unit and rectifier unit;Inverter unit is used to convert input DC into square wave signal;The output node on inverter unit is A node and B node respectively;Resonant cavity unit includes inductance, capacitor, high-frequency transformer and auxiliary switch tube;High-frequency transformer primary side winding is divided into A section winding and B section winding;One end of A section winding is connected with one end of inductance, and the other end of inductance is connected with A node through capacitor, and the other end of A section winding is connected with the segmented node of high-frequency transformer;One end of B section winding is connected with B node, and the other end is connected with the segmented node of high-frequency transformer;Auxiliary switch tube is connected in parallel in the two ends of B section winding, for controlling the working mode switching of B section winding, realize topological transformation;Rectifier unit includes four switch tubes, for converting AC power output by resonant cavity unit into DC power for use by subsequent load.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of direct current converters, in particular to a topology switching type high-efficiency wide-gain multi-resonant direct current converter. BACKGROUND

[0002] In recent years, with the progress of science and technology and the continuous breakthroughs in power electronics technology, isolated resonant current conversion devices have been widely used in direct current building fields and power distribution system construction processes, especially in distributed energy storage and new energy scenarios. The application technology of topology conversion technology and new wide-bandgap devices is continuously advancing and breaking through. In particular, in the field of energy storage, due to the continuous development of electrochemical energy storage, the continuous exploration of sodium sulfide batteries and lithium batteries, and the continuous updating of energy storage battery materials, higher requirements are put forward for energy storage converters. In order to meet the demand for voltage fluctuation regulation of new materials with wider voltage range and ensure safety, more stringent requirements are put forward for isolated wide-gain high-efficiency converters.

[0003] Compared with PWM type converters, resonant type converters have the advantages of high frequency, high efficiency, high power density and low electromagnetic interference. Under traditional control, resonant converters use frequency regulation control (PFM) and have good soft switching performance. However, when using frequency regulation control methods, resonant topologies represented by LLC and CLLC are usually adjusted within 1-1.2 times the standardized voltage gain range, and the adjustment range is relatively narrow. When the working condition is greater than 1.2, the inductance ratio needs to be further reduced, which often leads to the reduction of the quality factor of the converter, resulting in the decrease of efficiency. It is urgent to propose a new topology structure or control method to make the converter have the characteristics of wide gain regulation capability and high efficiency operation. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art and provide a topology switching type high-efficiency wide-gain multi-resonant direct current converter with wide voltage gain range and high conversion efficiency, which compensates for the wide-gain efficiency decay problem of traditional LLC resonant topology through switching of MOSFET switches, and provides a new solution for wide-gain high-efficiency implementation method of resonant converters.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] A topology conversion type multi-resonant direct current converter, comprising an inverter unit, a resonant cavity unit and a rectifier unit; the inverter unit is composed of a full-bridge structure composed of four MOSFET switches, and is used to convert input direct current into a square wave signal; the output nodes on the inverter unit are A node and B node respectively;

[0007] The resonant cavity unit comprises an inductor, a capacitor, a high-frequency transformer and an auxiliary switch tube; the primary side winding of the high-frequency transformer is divided into an A section winding and a B section winding, the A section winding has a turn ratio M:1 with the secondary side and a corresponding excitation inductance L m1 , and the B section winding has a turn ratio N:1 with the secondary side and a corresponding excitation inductance L m2 ;

[0008] One end of the A section winding is connected with one end of the inductor, the other end of the inductor is connected with the A node through the capacitor, and the other end of the A section winding is connected with the section node of the high-frequency transformer;

[0009] One end of the B section winding is connected with the B node, and the other end is connected with the section node of the high-frequency transformer; the auxiliary switch tube is arranged in parallel across the B section winding and is used for controlling the working mode switching of the B section winding to realize the topology conversion; the auxiliary switch tube is composed of two reverse series MOSFET switch tubes;

[0010] The rectifying unit comprises four switch tubes and is used for converting the alternating current output by the resonant cavity unit into direct current for use by the subsequent load;

[0011] By controlling the turn-on and turn-off of the auxiliary switch tube, the multi-resonant DC converter can obtain two different working circuits, which are an LLC circuit and an LLCLC circuit.

[0012] Further, the four MOSFET switch tubes in the inverter unit are respectively a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; the first switch tube and the third switch tube are connected in series, the second switch tube and the fourth switch tube are connected in series, and the two series circuits are connected in parallel to form a full-bridge topology; the A node is arranged between the first switch tube and the third switch tube, and the B node is arranged between the second switch tube and the fourth switch tube.

[0013] Further, the equivalent output capacitance of the auxiliary switch tube is C a , and the value of the equivalent output capacitance C a is C oss / 2, where C oss is the output capacitance of a single MOSFET switch tube constituting the auxiliary switch tube.

[0014] Further, when the auxiliary switch tube is turned on, the converter operates in an LLC mode; at this time, the B section winding is short-circuited and does not participate in the work; only the inductor, the capacitor and the A section winding constitute an effective circuit in the circuit to perform power conversion; in this mode, the equivalent excitation inductance L M_LLC of the converter is L m1 , and the transformer turn ratio is M:1;

[0015] L M_LLC = L m1 (1)

[0016] LLC converter can improve operating efficiency at the main resonance frequency point; the LLC converter is modeled using the equivalent fundamental harmonic analysis FHA, and KCL / KVL equations are solved, and the DC voltage gain V gain_LLC is expressed as

[0017]

[0018] where ω = 2πf s , ω is the angular frequency, L1 and C1 are the inductance and capacitance values of the inductance and capacitance respectively, j is the imaginary unit, f s is the switching frequency, R eq is the AC equivalent resistance, which is related to R o as follows:

[0019]

[0020] Let the imaginary part V gain_LLC of the gain V gainIm_LLC = 0, and the expression for the main resonance frequency point f r is obtained as

[0021]

[0022] When the auxiliary switch is turned off, the converter operates in the LLCLC mode; due to the auxiliary switch being turned off, the equivalent output capacitance C a of the auxiliary switch is connected in parallel with L m2 and participates in the operation;

[0023] In this mode, C a is connected in parallel with L m2 to form an equivalent excitation inductance L M2 , which is expressed as:

[0024]

[0025] Further, the equivalent excitation inductance L M_LLCLC of the converter is expressed as follows, where the transformer turns ratio is (M+N):1;

[0026]

[0027] Similar to the LLC converter, the LLCCLC converter is modeled using the equivalent fundamental harmonic analysis FHA, and the DC voltage gain V gain_LLCLC is solved as

[0028]

[0029] Similarly, let the imaginary part V gainIm_LLCLC of the gain of this mode = 0, and the main resonance frequency point f rThe expression is the same as the LLC mode, as shown in formula (5).

[0030] The application also provides an application of the topology conversion type multi-resonant DC converter.

[0031] Compared with the prior art, the technical scheme of the application has the beneficial effects that:

[0032] 1. Simple topology structure and low manufacturing cost: The topology conversion type multi-resonant DC converter proposed by the application has a similar structure to the traditional LLC converter, and the overall topology design is relatively simple, easy to implement, and has a low manufacturing cost. a The equivalent output capacitor C of the auxiliary switch tube acts as part of the resonant circuit, which avoids the additional introduction of an auxiliary capacitor while realizing the topology switching function, thereby simplifying the circuit design.

[0033] 2. Wide voltage gain range, suitable for various application requirements: By introducing the topology switching mechanism, the converter can freely switch between LLC mode and LLCLC mode, realizing a wider voltage gain range. Compared with the traditional LLC converter which can usually only adjust within 1-1.2 times the gain range, the voltage adjustment range of the application is larger, and the M, (N+M) segment two resonance points can be efficiently operated through the winding turn ratio, and the inductance ratio between M and (N+M) can be realized through the LLCLC excitation structure, ensuring high efficiency in the whole range, which can better meet the wide voltage fluctuation requirements in multiple scenarios such as energy storage batteries, DC microgrids, and photovoltaic systems.

[0034] 3. Excellent soft switching performance, improving efficiency: The converter of the application can realize soft switching characteristics in the full load range:

[0035] The switch tube of the inverter unit can realize zero voltage switching (ZVS), effectively reducing the turn-on and turn-off losses of the switch tube;

[0036] The rectifier unit can realize zero current switching (ZCS), further reducing the reverse recovery loss of the diode. Through the optimized soft switching mechanism, the overall efficiency of the converter is significantly improved, and the heat and loss during system operation are reduced.

[0037] 4. High power density and low electromagnetic interference:

[0038] The application can keep high power density of the converter under high frequency operation, and effectively reduce electromagnetic interference (EMI) during operation, meet the modern design requirements of power electronic devices. This feature is particularly suitable for electric vehicle charging systems, direct current building power supply systems, and direct current microgrids, and other scenes with high requirements for high efficiency and low interference.

[0039] 5. Modular design, easy to apply and promote: due to the generality of the topology design and the modularization of the circuit structure, the application can be widely used in direct current power supply systems, photovoltaic systems, energy storage converters, direct current adaptation technology and electric vehicles. Modular design makes it easier to integrate the application with existing power electronic systems, realize rapid promotion and engineering landing of technology.

[0040] In summary, the application not only effectively solves the problems of narrow gain range and efficiency decay of traditional LLC resonant converters, but also provides a new solution for realizing wide gain, high efficiency and multi-scene adaptive direct current converters, and has significant engineering application value and market prospect. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The structure diagram of the topology conversion type multi-resonant direct current converter is shown.

[0042] Figure 2 The structure diagram of the LLC converter is shown.

[0043] Figure 3 The voltage gain curve of the LLC converter is shown.

[0044] Figure 4 The structure diagram of the LLCLC converter is shown.

[0045] Figure 5 The voltage gain curve of the LLCLC is shown.

[0046] Figure 6 The voltage gain curve of the converter of the application is shown. DETAILED DESCRIPTION

[0047] The application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0048] Figure 1 The structure diagram of the topology conversion type multi-resonant direct current converter is shown, which includes three parts of inverter unit, resonant cavity unit and rectifier unit.

[0049] The inverter unit is used for converting input direct current into square wave signals, and is composed of a full-bridge structure composed of four MOSFET switch tubes, and the four MOSFET switch tubes are respectively a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4; the first switch tube S1 and the third switch tube S3 are connected in series, the second switch tube S2 and the fourth switch tube S4 are connected in series, and the two groups of series circuits are connected in parallel to form a full-bridge topology; an A node is arranged between the first switch tube S1 and the third switch tube S3, and a B node is arranged between the second switch tube S2 and the fourth switch tube S4.

[0050] The resonant cavity unit includes an inductor L1, a capacitor C1, a high-frequency transformer T and an auxiliary switch tube S a ; the primary side winding of the high-frequency transformer T is divided into an A section winding and a B section winding, the A section winding has a turn ratio relationship M:1 with the secondary side and corresponds to an excitation inductance L m1 , and the B section winding has a turn ratio relationship N:1 with the secondary side and corresponds to an excitation inductance L m2 ; one end of the A section winding is connected with one end of the inductor L1, the other end of the inductor L1 is connected with the A node through the capacitor C1, and the other end of the A section winding is connected with a segmented node of the high-frequency transformer T; one end of the B section winding is connected with the B node, and the other end is connected with the segmented node of the high-frequency transformer T;

[0051] The auxiliary switch tube S a is arranged in parallel at both ends of the B section winding and is used for controlling the working mode switching of the B section winding, so as to realize the adjustment of the multi-resonance characteristic; the auxiliary switch tube S a is composed of two MOSFET switch tubes connected in reverse series; Figure 1 The C a is an equivalent output capacitor of the auxiliary switch tube S a , and the value is C oss / 2, and the C oss is an output capacitor of a single MOSFET switch tube constituting the auxiliary switch tube S a .

[0052] The rectifier unit adopts a full-bridge structure and includes four switch tubes SR1-SR4, which are used for converting alternating current output by the resonant cavity unit into direct current for use by a subsequent load;

[0053] The resonant cavity unit is a key element of the multi-resonance DC converter in the embodiment, and plays a crucial role in the operation performance of the entire converter. The multi-resonance DC converter of the present application combines multi-resonance technology and topology conversion technology, forming a new type of resonant network. The auxiliary switch tube S a is introduced in the multi-resonance cavity unit, and the S aBy switching the converter on and off, it can obtain two different operating circuits: an LLC circuit and an LLCLC circuit. This allows the converter to achieve a wide voltage gain range within a narrow frequency range, contributing to high-efficiency operation.

[0054] When S a When activated, the converter operates in LLC mode, and its topology is as follows: Figure 2 As shown. At this time, the B segment winding (L) m2 ) and C a When short-circuited, it does not participate in the operation; the total equivalent magnetizing inductance L of the transformer... M Equal to the magnetizing inductance value L of section A winding m1 The circuit only contains L1, C1, and L... m1 To form an effective circuit for power conversion.

[0055] The circuit only contains L1, C1, and segment A winding (L m1 This constitutes an effective circuit for power conversion. In this mode, the equivalent magnetizing inductance L of the converter... M_LLC =L m1 The transformer turns ratio is M:1.

[0056] L M_LLC =L m1 (1)

[0057] Thanks to its simple structure and excellent soft-switching characteristics, the LLC converter can achieve high operating efficiency near the main resonant frequency. The LLC circuit is modeled using the Fundamental Harmonic Approximation (FHA) method, and the KCL / KVL formulas are solved to obtain its DC voltage gain V. gain_LLC It can be represented as

[0058]

[0059] Where ω=2πf s ω is the angular frequency, L1 and C1 are the inductance and capacitance values ​​of inductor L1 and capacitor C1, respectively, j is the imaginary unit, and f is the frequency. s It is the switching frequency. R eq It is the AC equivalent resistance, which is related to R. o The relationship is as follows.

[0060]

[0061] Let the gain V gain_LLC The imaginary part V gainIm_LLC =0, which gives the principal resonant frequency point f. r The expression is

[0062]

[0063] Figure 3 The voltage gain curve of the LLC converter is given. At f r , the converter voltage gain is normalized to the standard gain, Figure 3 The voltage gain in the LLC mode is normalized to the standard gain. According to Figure 3 , it can be known that the converter voltage gain is constant at f r , and is independent of the load. At this point, the converter has a high operating efficiency. At other points, the voltage gain decreases with the increase of the load.

[0064] When S a is off, the converter operates in the LLCLC mode, and its topology is shown in Figure 4 . Since S a is off, the equivalent output capacitance C a of S a is in parallel with the magnetizing inductance L m2 of the B section winding, and participates in the operation.

[0065] In this mode, C a is in parallel with L m2 to form the equivalent magnetizing inductance L M2 of the B section winding, which can be expressed as

[0066]

[0067] Further, the total equivalent magnetizing inductance L M of the converter can be written as L M_LLCLC , and the specific expression is as follows, and the transformer turns ratio is (M+N):1.

[0068]

[0069] Similar to the LLC converter, the FHA is used to model the LLCLC converter, and the DC voltage gain V gain_LLCLC is solved as

[0070]

[0071] Similarly, by setting the imaginary part of the gain in this mode V gainIm_LLCLC =0, the expression of the main resonance frequency point f r is obtained, which is the same as that of the LLC mode, as shown in equation (5).

[0072] Figure 5 The voltage gain curve of the LLCLC converter is given. Similarly, at f r , the converter voltage gain is constant, and is independent of the load. At other points, the voltage gain decreases with the increase of the load.

[0073] Figure 6The voltage gain curve of the converter of the present application is shown. LLC and LLCLC each has its own characteristics. There are similarities and differences in the same points. Such as the resonant frequency point, voltage gain range, excitation inductance size, topology complexity, etc. In the same point, the two topologies have the same main resonant frequency point; high efficiency can be achieved at the resonant frequency point; similar voltage gain curve change trend. In the different point, the LLC converter has the following characteristics: ① simple structure; ② the inductance ratio k1 is fixed, and is independent of frequency regulation. By using the similarities of the two topologies (such as the same resonant frequency point, and the resonant circuit structure is partially shared), and combining the different advantages of the two topologies, they can be integrated into a new converter. The switching of the topology is realized by turning on or turning off the auxiliary switch tube. The key goal of the design of the new topology converter proposed in the present application is to achieve a wide voltage gain in a narrow frequency range, and then to improve the operating efficiency in the full gain and full load range.

[0074] In LLC mode, by taking advantage of simple structure and good soft switching characteristics, the converter operates near the resonant frequency, achieving high efficiency operation at the rated operating point.

[0075] In the LLCLC mode, by taking advantage of the increase in inductance ratio and the change of C a during the voltage regulation process, it is helpful to further achieve high efficiency operation in the full gain range.

[0076] The present application is not limited to the embodiments described above. The above description of specific embodiments is intended to describe and illustrate the technical solutions of the present application, and the specific embodiments described above are merely illustrative and not restrictive. Without departing from the purpose of the present application and the scope protected by the claims, those skilled in the art can make many forms of specific changes under the inspiration of the present application, and these all belong to the protection scope of the present application.

Claims

1. A topology-conversion type multi-resonant DC-DC converter, characterized in that, It includes an inverter unit, a resonant cavity unit, and a rectifier unit; the inverter unit is composed of a full-bridge structure consisting of four MOSFET switches, used to convert the input DC power into a square wave signal; the output nodes on the inverter unit are node A and node B; The resonant cavity unit includes an inductor (L1), a capacitor (C1), a high-frequency transformer (T), and an auxiliary switching transistor (S). a The primary winding of the high-frequency transformer (T) is divided into winding A and winding B. Winding A has a turns ratio of M:1 with the secondary winding, and the corresponding magnetizing inductance is... L m1 The B-section winding has a turns ratio of N:1 with the secondary winding, and the corresponding magnetizing inductance is... L m2 ; One end of the A-section winding is connected to one end of the inductor (L1), and the other end of the inductor (L1) is connected to node A through capacitor (C1). The other end of the A-section winding is connected to the segment node of the high-frequency transformer (T). One end of the B-segment winding is connected to node B, and the other end is connected to the segment node of the high-frequency transformer (T); the auxiliary switching transistor (S) a The auxiliary switching transistor (S) is connected in parallel across the B-segment winding to control the switching of the B-segment winding's operating mode and achieve topology transformation. a It consists of two MOSFET switches connected in reverse series; The rectifier unit includes four switching transistors, which are used to convert the AC power output from the resonant cavity unit into DC power for use by the subsequent load. By controlling the auxiliary switching transistor (S) a By switching the DC-DC converter on and off, the multi-resonant DC-DC converter can obtain two different operating circuits: LLC circuit and LLCLC circuit.

2. The topology-conversion type multi-resonant DC-DC converter according to claim 1, characterized in that, The four MOSFET switches in the inverter unit are the first switch (S1), the second switch (S2), the third switch (S3), and the fourth switch (S4). The first switch (S1) and the third switch (S3) are connected in series, and the second switch (S2) and the fourth switch (S4) are connected in series. The two sets of series circuits are connected in parallel to form a full-bridge topology. Node A is set between the first switch (S1) and the third switch (S3), and node B is set between the second switch (S2) and the fourth switch (S4).

3. A topology-conversion type multiresonant DC-DC converter according to claim 1, characterized in that, Auxiliary switching transistor (S) a The equivalent output capacitance is C a Equivalent output capacitance C a The value is C oss / 2, C oss To construct an auxiliary switching transistor (S) a The output capacitance of a single MOSFET switch.

4. A topology-conversion type multiresonant DC-DC converter according to claim 1, characterized in that, When the auxiliary switch (S) a When the converter is turned on, it operates in LLC mode; at this time, the B-segment winding is short-circuited and does not participate in the operation; only the inductor (L1), capacitor (C1), and A-segment winding constitute the effective circuit for power conversion; in this mode, the converter's equivalent magnetizing inductance is... L M_LLC = L m1 The transformer turns ratio is M :1; (1)； LLC converters can improve operating efficiency at the main resonant frequency. The LLC converter is modeled using the equivalent fundamental frequency analysis method (FHA), and the KCL / KVL formulas are solved to determine its DC voltage gain. V gain_LLC Represented as (2)； (3)； in, ω= 2 πf s , ω It is angular frequency. L 1 , C 1 These are the inductance and capacitance values ​​of the inductor (L1) and capacitor (C1), respectively. j The imaginary unit, f s It is the switching frequency. R eq It is the AC equivalent resistance, which is related to the load. R o The relationship is as follows: (4)； Let gain V gain_LLC imaginary part V gainIm_LLC =0, thus obtaining the principal resonant frequency point. f r The expression is (5)； When the auxiliary switch (S) a When the auxiliary switch (S) is turned off, the converter operates in LLCLC mode; due to the auxiliary switch (S) a ) Turn off, auxiliary switch (S) a The equivalent output capacitance of ) C a and L m2 They work in parallel and participate in the operation. In this mode, C a and L m2 The parallel connection forms an equivalent magnetizing inductance. L M2 , is represented as: (6)； Therefore, the equivalent magnetizing inductance of the converter L M_LLCLC The following is a representation, where the transformer turns ratio is ( M+N ):1; (7)； Similar to LLC converters, the equivalent fundamental frequency analysis (FHA) method is used to model the LLCLC converter and solve for its DC voltage gain. V gain_LLCLC for (8)； (9)； Similarly, the imaginary part of the gain for this mode. V gainIm_LLCLC =0, thus obtaining the principal resonant frequency point. f r The expression is the same as that of the LLC mode, as shown in (5).

5. An application based on the topology-conversion type multiresonant DC-DC converter according to any one of claims 1-4, characterized in that, It is applied in DC power systems, DC adapter technology, photovoltaic systems, DC microgrid systems, and electric vehicles.

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