Expandable phase modular transformer, method and DC-DC converter

Abstract

The invention belongs to the technical field of transformers, and discloses an expandable phase modular transformer, a method and a DC-DC converter, and the transformer is characterized in that one end of a low-voltage bridge module is connected with a primary-side high-voltage bridge, and the other side of the low-voltage bridge module is connected with a secondary-side high-voltage bridge; the low-voltage bridge module comprises n parallel modules which are connected in parallel; each parallel module comprises two input ends and two output ends; one end of one input end of each parallel module is connected with the first end of the primary side high-voltage bridge, and the other input end of each parallel module is connected with the low-voltage bridge; a plurality of parallel switch tubes are arranged in the low-voltage bridge; the other end of the low-voltage bridge is connected with the first end of the first inductor Lk; a low-voltage bridge capacitor C9 is connected in parallel in each low-voltage bridge; the second end of the first inductor Lk is connected with the first end of the second inductor Lm and the first end of the primary side of the transformer. The embedded full bridge is adopted, so that the transformer effectively counteracts leakage inductance reactance, and optimal operation at any frequency is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of transformers, and in particular relates to an expandable phase modular transformer, a method and a DC-DC converter. Background Art

[0002] Traditional power systems require new transformer technologies to support the efficient integration and transmission of renewable energy. However, the intermittent nature of renewable energy can cause voltage deviations in microgrids, impacting system stability and operation. With the development of smart grid technology, transformers must possess a higher level of intelligence, enabling self-monitoring, remote control, and fault diagnosis to improve grid stability and reliability. Furthermore, the bulky size of transformers has limited their development. The application of new materials and advancements in power electronics have enabled the integration of transformers with power electronics (such as inverters and rectifiers), creating new energy conversion and control solutions. Furthermore, with the rapid development of high-frequency technology, new transformer designs can operate at higher frequencies, providing higher power density and efficiency. With the increasing global focus on energy efficiency and the rapid development of energy storage systems, data center power supplies, and transportation electrification, the demand for high-power, high-density isolated DC-DC converters is increasing. However, the design of high-power, high-frequency transformers presents significant challenges due to the trade-offs between thermal management, leakage inductance minimization, and insulation requirements.

[0003] The Chinese patent application, CN101399498A, entitled "DC Converter Power Supply Device and Method for Improving a DC Converter Power Supply Device," comprises: a transformer; a transformer primary-side circuit; and a transformer secondary-side circuit, wherein the secondary-side circuit includes a rectifier circuit with a shaping and conversion function for converting a square-wave voltage output by the transformer into a DC output voltage; and a control unit for controlling the transformer secondary-side circuit based on the DC output voltage to adjust the DC output voltage to a stable target value. The invention also discloses a method for improving a DC converter power supply, comprising: coupling a rectifier circuit with a shaping and conversion function to a secondary winding to convert the square-wave voltage output by the transformer into a DC output voltage; monitoring the DC output voltage and, based on the DC output voltage, adjusting the DC output voltage to a stable target value. Application of this invention can improve the dynamic performance of a DC converter power supply. However, the transformer described in this patent application cannot offset leakage inductance to ensure optimal operation at any frequency. Summary of the Invention

[0004] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide an expandable phase modular transformer, method and DC-DC converter, which solves this problem through its simple open-loop control and natural current sharing, so that it can be connected in parallel and expanded to different power ratings. The transformer overcomes the problems of transformer parallel connection and resonance point displacement in the traditional bidirectional DC converter design. By adopting an embedded full bridge, the transformer of the present invention effectively offsets the leakage inductance reactance, ensuring optimal operation at any frequency. In addition, the present invention also retains the inherent advantages of the transformer in the traditional bidirectional DC converter design, including load-independent voltage gain, simple open-loop control, full-load range zero voltage switching and low circulating current.

[0005] To achieve the above object, the technical solution adopted by the present invention is: In the first aspect, the present invention provides an expandable phase modular transformer, comprising a low-voltage bridge module; one end of the low-voltage bridge module is connected to the primary side high-voltage bridge, and the other side is connected to the secondary side high-voltage bridge; the low-voltage bridge module comprises n parallel modules connected in parallel; the parallel module comprises a low-voltage bridge, a first inductor L k , the second inductor L m and transformer; each parallel module includes two input terminals and two output terminals; one end of an input terminal of each parallel module is connected to the first end of the primary side high voltage bridge, and the other input terminal is connected to the low voltage bridge; the low voltage bridge has a plurality of parallel switching tubes; the other end of the low voltage bridge is connected to the first inductor L k The first end of each low-voltage bridge is connected in parallel with a low-voltage bridge capacitor C9; the first inductor L k The second end of the second inductor L m and the first end of the primary side of the transformer; the second inductor L m The second end of the primary side of the transformer and the second end of the primary side are both connected to the second end of the primary side high-voltage bridge; the two ends of the secondary side of the transformer are respectively connected to the two input ends of the secondary side high-voltage bridge.

[0006] Optionally, the number of parallel modules connected in parallel in the low-voltage bridge module is not less than two.

[0007] Optionally, the transformer is a high-frequency transformer.

[0008] Optionally, the low-voltage bridge includes a first field-effect transistor Q1, a second field-effect transistor Q2, a third field-effect transistor Q3, and a fourth field-effect transistor Q4; the source of the first field-effect transistor Q1 is connected to the low-voltage bridge capacitor C9 and the source of the third field-effect transistor Q3; the drain of the first field-effect transistor Q1 is connected to the source of the second field-effect transistor Q2; the drain of the second field-effect transistor Q2 is connected to the second end of the ninth capacitor C9 and the drain of the fourth field-effect transistor Q4; the drain of the third field-effect transistor Q3 is connected to the first inductor L k and a source of the fourth field effect transistor Q4.

[0009] In a second aspect, the present invention provides a DC-DC converter, comprising the aforementioned expandable phase modular transformer, and a primary-side high-voltage bridge and a secondary-side high-voltage bridge; the primary-side high-voltage bridge and the secondary-side high-voltage bridge both have a first input terminal, a second input terminal, a first output terminal, and a second output terminal; the first input terminal and the second input terminal of the primary-side high-voltage bridge are connected to a power supply; the transformer comprises a primary-side induction coil and a secondary-side induction coil; the first input terminal and the second input terminal of the secondary-side high-voltage bridge are respectively connected to the first end and the second end of the secondary-side induction coil.

[0010] Optionally, the drain of the first field effect transistor Q1 is connected to the first output terminal of the primary side high voltage bridge; the second inductor L of each parallel module m The second ends of the primary side high voltage bridge are connected to the second output end.

[0011] Optionally, the primary-side high-voltage bridge includes: a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first field-effect transistor S1, a second field-effect transistor S2, a third field-effect transistor S3 and a fourth field-effect transistor S4; the first field-effect transistor S1, the second field-effect transistor S2, the third field-effect transistor S3 and the fourth field-effect transistor S4 are all connected in parallel with a capacitor; the drain of the first field-effect transistor S1 is connected to the negative electrode of the power supply, and the negative electrode of the power supply is connected to the first end of the first capacitor C1; the first field-effect transistor S1 The source of the second field effect transistor S2 is connected to the first end of the fourth capacitor C4 and the drain of the second field effect transistor S2; the source of the second field effect transistor S2 is connected to the second end of the first capacitor C1; the second end of the fourth capacitor C4 is the first output end of the primary side high voltage bridge; the drain of the third field effect transistor S3 is connected to the positive electrode of the power supply, and the positive electrode of the power supply is connected to the first end of the second capacitor C2; the source of the second field effect transistor S2 is connected to the first end of the third capacitor C3 and the drain of the fourth field effect transistor S4; the second end of the third capacitor C3 is the second output end of the primary side high voltage bridge.

[0012] Optionally, the secondary side includes: a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a fifth field-effect transistor S5, a sixth field-effect transistor S6, a seventh field-effect transistor S7 and an eighth field-effect transistor S8; the fifth capacitor C5, the sixth capacitor C6, the seventh capacitor C7 and the eighth capacitor C8 are all connected in parallel with a capacitor; the source of the fifth field-effect transistor S5 is connected to the second end of the sixth capacitor C6 and the drain of the sixth field-effect transistor S6; the drain of the fifth field-effect transistor S5 is connected to the negative electrode of the power supply and the first end of the seventh capacitor C7; the source of the sixth field-effect transistor S6 is connected to the second end of the seventh capacitor C7; the drain of the seventh field-effect transistor S7 is connected to the first end of the eighth inductor C8; the source of the seventh field-effect transistor S7 is connected to the drain of the eighth field-effect transistor S8; and the source of the eighth field-effect transistor S8 is connected to the second end of the eighth inductor C8.

[0013] Optionally, the low voltage bridge capacitor C9 is a ceramic capacitor; the first inductor L k and the second inductor L m All are air-core inductors.

[0014] In a third aspect, the present invention provides a method for using the expandable phase modular transformer, comprising the following steps: In one half cycle, the second field effect transistor Q2 and the third field effect transistor Q3 are turned off, and then the first field effect transistor Q1 and the fourth field effect transistor Q4 are turned on to achieve natural zero voltage switching; In another half cycle, the same zero voltage switching analysis is performed on the second field effect transistor Q2 and the third field effect transistor Q3, so that all switches of the low voltage bridge achieve zero voltage switching.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a scalable phase modular transformer that enables parallel connection of transformer stages, improving current sharing capabilities. In the design of a single transformer, high frequency and high power are essentially a trade-off. By paralleling high-frequency, low-power transformers, the system can be expanded to different power ratings, and through the coordination of switching transistors, zero voltage switching (ZVS) can be achieved. The transformer of the present invention can be used in power grids, substations, and power transmission and distribution, improving operational efficiency and reducing standby capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the components in the drawings are only schematic and are used to help understand the present invention, and are not intended to specifically limit the shapes and proportional dimensions of the components of the present invention. In the drawings: Figure 1 This is a topology diagram of the expandable phase modular transformer used in the DC-DC converter of the present invention.

[0017] Figure 2 The diagram is a multi-stage parallel diagram of an expandable phase modular transformer used in a DC-DC converter according to the present invention. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0020] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the invention is usually placed when in use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0021] When an element is referred to as being "disposed on" another element, it may be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may also be an intermediate element. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only embodiments. If the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and it does not mean that the structure must be completely horizontal, but it can be slightly tilted.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined or explained in subsequent figures. In the description of the present invention, it should be understood that the terms "comprise" and "include" indicate the presence of the described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their combinations.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0024] The present invention will be described in detail below with reference to the accompanying drawings.

[0025] like Figure 1 As shown, a DC-DC converter of the present invention includes an expandable phase modular transformer, a primary-side high-voltage bridge, and a secondary-side high-voltage bridge.

[0026] The expandable phase modular transformer includes a low-voltage bridge module. One end of the primary-side high-voltage bridge is connected to a power supply, and the other end is connected to the secondary-side high-voltage bridge through the low-voltage bridge module.

[0027] The low-voltage bridge module includes n parallel modules connected in parallel with each other.

[0028] The parallel module includes a low voltage bridge, a first inductor L k , the second inductor L mand a transformer; each parallel module includes two input terminals and two output terminals. One input terminal of each parallel module is connected to the first terminal of the primary-side high-voltage bridge, and the other input terminal is connected to the low-voltage bridge; the low-voltage bridge has multiple parallel-connected switching tubes.

[0029] The other end of the low voltage bridge is connected to the first inductor L k The first end of each low-voltage bridge is connected in parallel with a low-voltage bridge capacitor C9; the first inductor L k The second end of the second inductor L m The first end of the first inductor L m The second end of the primary side of the transformer and the second end of the primary side are both connected to the second end of the primary side high-voltage bridge; the two ends of the secondary side of the transformer are respectively connected to the input end of the secondary side high-voltage bridge.

[0030] The primary-side high-voltage bridge and the secondary-side high-voltage bridge both have a first input terminal, a second input terminal, a first output terminal, and a second output terminal; the first input terminal and the second input terminal of the primary-side high-voltage bridge are connected to a power supply; the transformer includes a primary-side induction coil and a secondary-side induction coil; the first input terminal and the second input terminal of the secondary-side high-voltage bridge are respectively connected to the first end and the second end of the secondary-side induction coil.

[0031] The secondary side includes: a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a fourteenth capacitor C 14 , the fifteenth capacitor C 15 , the sixteenth capacitor C 16 , the seventeenth capacitor C 17 , a fifth field-effect transistor S5, a sixth field-effect transistor S6, a seventh field-effect transistor S7, and an eighth field-effect transistor S8; the source of the fifth field-effect transistor S5 is connected to the second end of the sixth capacitor C5 and the drain of the sixth field-effect transistor; the drain of the fifth field-effect transistor S5 is connected to the negative electrode of the power supply and the first end of the seventh capacitor C7; the source of the sixth field-effect transistor S6 is connected to the second end of the seventh capacitor C7; the drain of the seventh field-effect transistor S7 is connected to the first end of the eighth inductor C8, the source of the seventh field-effect transistor S7 is connected to the positive electrode of the power supply and the drain of the eighth field-effect transistor; the source of the eighth field-effect transistor is connected to the second end of the eighth inductor C8.

[0032] The low-voltage bridge includes a first field-effect transistor Q1, a second field-effect transistor Q2, a third field-effect transistor Q3, and a fourth field-effect transistor Q4; the source of the first field-effect transistor Q1 is connected to the low-voltage bridge capacitor C9 and the source of the third field-effect transistor Q3; the drain of the first field-effect transistor Q1 is connected to the source of the second field-effect transistor Q2 and the first output end of the primary-side high-voltage bridge; the drain of the second field-effect transistor Q2 is connected to the second end of the ninth capacitor C9 and the drain of the fourth field-effect transistor Q4; the drain of the third field-effect transistor Q3 is connected to the first inductor L k and a source of the fourth field effect transistor Q4.

[0033] The second inductor L of each parallel module m The second ends of the primary side high voltage bridge are connected to the second output end.

[0034] The primary side high voltage bridge comprises: a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first field effect transistor S1, a second field effect transistor S2, a third field effect transistor S3 and a fourth field effect transistor S 4、 The first field effect transistor S1, the second field effect transistor S2, the third field effect transistor S3 and the fourth field effect transistor S4 are respectively connected in parallel with a tenth capacitor C 10 , the eleventh capacitor C 11 , the twelfth capacitor C 12 , the thirteenth capacitor C 13 The drain of the first field effect transistor S1 is connected to the negative electrode of the power supply, which is connected to the first end of the first capacitor C1. The source of the first field effect transistor S1 is connected to the first end of the fourth capacitor C4 and the drain of the second field effect transistor S2.

[0035] The source of the second field-effect transistor S2 is connected to the second end of the first capacitor C1; the second end of the fourth capacitor C4 is the first output end of the primary-side high-voltage bridge; the drain of the third field-effect transistor S3 is connected to the positive electrode of the power supply, and the positive electrode of the power supply is connected to the first end of the second capacitor C2; the source of the second field-effect transistor S2 is connected to the first end of the third capacitor C3 and the drain of the fourth field-effect transistor S4; the second end of the third capacitor C3 is the second output end of the primary-side high-voltage bridge.

[0036] The secondary side includes: a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a fifth field effect transistor S5, a sixth field effect transistor S6, a seventh field effect transistor S7, and an eighth field effect transistor S8.

[0037] The fifth capacitor C5, the sixth capacitor C6, the seventh capacitor C7 and the eighth capacitor C8 are respectively connected in parallel with the fourteenth capacitor C 14 , the fifteenth capacitor C 15 , the sixteenth capacitor C 16 , the seventeenth capacitor C 17 The source of the fifth field-effect transistor S5 is connected to the second end of the sixth capacitor C6 and the drain of the sixth field-effect transistor S6; the drain of the fifth field-effect transistor S5 is connected to the negative electrode of the power supply and the first end of the seventh capacitor C7; the source of the sixth field-effect transistor S6 is connected to the second end of the seventh capacitor C7; the drain of the seventh field-effect transistor S7 is connected to the first end of the eighth inductor C8; the source of the seventh field-effect transistor S7 is connected to the drain of the eighth field-effect transistor S8; and the source of the eighth field-effect transistor S8 is connected to the second end of the eighth inductor C8.

[0038] The first field effect transistor Q1, the second field effect transistor Q2, the third field effect transistor Q3, and the fourth field effect transistor Q4 are connected to each other through a capacitor half bridge. 10 , the eleventh capacitor C 11 , the twelfth capacitor C 12 , the thirteenth capacitor C 13 They are connected in parallel on both sides of the field effect transistor to prevent the transistors on the same side from being turned on in series and short-circuited.

[0039] The first inductor L k is the leakage inductance, the second inductor L m is the magnetizing inductance.

[0040] Among them, the field effect transistor on the primary side requires the input voltage to be strictly positive, which is achieved by introducing a common-mode bias voltage u in the high-voltage bridge. gn This is achieved. The field-effect transistors of the transformer high-voltage bridge are arranged in a half-bridge configuration, using transistors with unipolar voltage blocking capability, which gives it a clear commutation path, enabling high switching frequency and moderate switch node overvoltage. In half-bridge operation, assuming a duty cycle of 50%, the phase with the instantaneous lowest grid phase voltage simultaneously turns on the primary and secondary side transistors during one-third of the grid cycle. In this way, the input stage reference point potential n is always clamped to the most negative phase voltage, thereby u gn Strictly restricted position.

[0041] In the case of an integrated low-voltage bridge, the low-voltage bridge with floating DC capacitor C9 replaces the resonant capacitor of the transformer in the traditional DC-DC converter, V b is the voltage across C9. V c is the output voltage of the low voltage bridge, with an amplitude equal to V b For current, i priand i scc The current flowing through the primary and secondary coils of the transformer. Since the primary and secondary sides have identical FETs, the first FET Q1, second FET Q2, third FET Q4, and fourth FET Q5 of the low-voltage bridge are all 90° phase-delayed compared to the fifth FET S5, sixth FET S6, seventh FET S7, and eighth FET S8, and are driven by two high-voltage bridges.

[0042] Since the low voltage driving signal and the high voltage driving signal have a 90° delay, when the first field effect transistor Q1, the second field effect transistor Q2, the third field effect transistor Q3 and the fourth field effect transistor Q4 of the low voltage bridge are turned on or off, the current i pri Therefore, during the switching transition of the low voltage bridge, i pri The poles will not change.

[0043] During the no-load period of the low-voltage bridge, the current i pri Keep the peak value, and the voltage V on the low voltage bridge b The output capacitance of the low voltage bridge switch is small, so the output capacitance of the low voltage bridge switch can be ignored. In addition, by optimizing and shortening the dead time of the low voltage bridge, the loss caused by the dead time can be reduced. pri , the capacitor C9 is charged and discharged alternately, and the ripple on C9 can be deduced as: Formula 1 Where: V b is the voltage of capacitor C9, ΔV b is the change in the voltage of capacitor C9, L k is the inductance L k The inductance value, C9 is the capacitance value of capacitor C9, f n is the rated frequency.

[0044] In order to meet the ripple voltage requirement, the capacitance value of the low-voltage bridge capacitor C9 is selected.

[0045] Based on the superposition principle, the original equivalent circuit diagram can be decomposed into two parts: the high-voltage bridge part and the low-voltage bridge part. In the high-voltage bridge subcircuit, the circuit will always charge the low-voltage bridge capacitor C9 of the low-voltage bridge. In the low-voltage bridge subcircuit, there is only one excitation power supply.

[0046] In steady state, assuming the transformer ratio is 1:1, the input voltage V in should be consistent with the output voltage V out equal.

[0047] Formula 2 Where: Vin is the input voltage on the primary side of the transformer, and Vout is the output voltage on the secondary side of the transformer Since the driving signals of the primary and secondary high voltage bridges are the same, V pri and V sec Should have the same magnitude and phase angle.

[0048] Formula 3 Where: Vpri is the voltage across the primary coil, and Vsec is the voltage across the secondary coil.

[0049] For the current i T and component i T1 In steady state, it should be equal to 0, otherwise the current will continue to charge and discharge the floating low-voltage bridge capacitor C9. T Should be equal to i T2 ,This steady state is a stable equilibrium point, whereby no control is required.

[0050] Formula 4 Where: i T1 is the current of the parallel module flowing through the first low-voltage bridge, i T2 is the current flowing through the second low-voltage bridge module.

[0051] Because I T In steady state, V pri or V Sec phase, so this current is dedicated to transmitting actual power. For different output frequencies P, i T The amplitude will be through V b Adjustment. Due to I out Equal to 0.5I T , so the voltage V b The steady-state value of can be derived as Formula 5 Where: Vb is the voltage applied to the low-voltage bridge capacitor C9; P is the output power; Lk is the inductance value of the first inductor Lk; Vin(out) is the input and output voltage.

[0052] The floating voltage V applied to the low voltage bridge b With f s , P, L k and 1 / V in(out) Directly proportional.

[0053] Formula 6 Where: V b is the voltage applied to the low voltage bridge capacitor C9; f sis the rated frequency; P is the output power; Lk is the inductance value of the first inductor Lk, V in(out) is the input and output voltage.

[0054] By using lower voltage level devices, the low voltage bridge can be embedded in the high frequency transformer. pri When stable, it is equal to V sec , so the low voltage bridge output voltage V c Directly applied to L k This means that L k The voltage drop on the output of the embedded low-voltage bridge is completely offset, so the transformer of the present invention does not need resonant tuning and can always operate at any switching frequency f s Best job next time.

[0055] In order to expand the rated current, parallel connection of transformer stages is more ideal than parallel connection of converter stages due to the high power density. After transferring all electronic embedded parameters from the secondary side to the primary side, the corresponding equivalent circuit can be simplified. All low-voltage bridges and two high-voltage bridges are replaced by square voltage Vc, and V pri and V sec According to Kirchhoff's voltage law, the terminal voltage V AB It can be written as Formula 7 Where: V AB is the terminal voltage when the transformer stages are connected in parallel; L kN is the Nth inductor L k Inductance value; i TN is the current value flowing through the Nth low-voltage bridge; V cN is the voltage across N low-voltage bridges at a given time; r wn is the equivalent resistance of the low voltage bridge.

[0056] According to the previous analysis, the first inductor L k The voltage drop across the c are completely cancelled, so the total voltage drop across each electronic transformer can be written as Formula 8 Due to the unique structure of the transformer designed in the present invention, it can be conveniently connected in parallel to increase the rated power. According to Kirchhoff's voltage law, when the transformer stages are connected in parallel, the terminal voltage V AB for Formula 9 In steady state, the first to Nth first inductors L k The voltage drop across the c1-N The voltages are completely offset, so the total voltage drop across each multi-stage parallel transformer can be expressed as Formula 10 The current distribution of each embedded electronic module in parallel is Formula 11 Definition i r1-N is the resonant current through each transformer, considering each embedded module resistance R ω1-N In the case of each transformer, the resonant impedance Z N It can be expressed as Formula 12 From this formula, it can be deduced that the current distribution between each resonant branch is Formula 13 When all the resonant tanks have the same resonant frequency, the first inductors L k The voltage drop will be completely offset by the low voltage bridge capacitor C9 of the 1st to nth resonance, so the current shunting should be the same as in Equation 12.

[0057] Since the current sharing performance of the transformer is decoupled from the first inductor Lk, the transformer will have a naturally stable current sharing performance, and due to the positive temperature coefficient of the resistor, current sharing can always be achieved.

[0058] The method for using the expandable phase modular transformer comprises the following steps: Since the low voltage bridge drive signal (first field effect transistor Q1, second field effect transistor Q2, third field effect transistor Q3 and fourth field effect transistor Q4) and the high voltage bridge drive signal (first field effect transistor S1, second field effect transistor S2, third field effect transistor S3, fourth field effect transistor S4, fifth field effect transistor S5, sixth field effect transistor S6, seventh field effect transistor S7 and eighth field effect transistor S8) have a 90° delay, when the low voltage bridge switch is turned on or off, the current i pri will reach its peak.

[0059] Therefore, during the switching transition of the low voltage bridge, i pri For example, for the rectification from the second FET Q2 and the third FET Q3 to the first FET Q1 and the fourth FET Q4, i pri Will hold up well with very short downtime.

[0060] Before the second FET Q2 and the third FET Q3 are turned off, the current i priWhen the second FET Q2 and the third FET Q3 are turned off, the positive current i pri The current will flow through the diodes of the first field effect transistor Q1 and the fourth field effect transistor Q4. pri After passing through the diodes of the second MOSFET Q2 and the third MOSFET Q3, natural soft switching is achieved through the first MOSFET Q1 and the fourth MOSFET Q4. In the other half cycle, the second MOSFET Q2 and the third MOSFET Q3 can be soft-switched in the same way, which means that all switches of the low-voltage bridge can achieve similar natural soft switching.

[0061] During the low-voltage bridge no-load period, the current ipri remains at its peak value, and the voltage Vb across the low-voltage bridge is very small, so the output capacitance of the low-voltage bridge switch can be ignored. Furthermore, the dead time of the low-voltage bridge can be optimized and shortened to reduce the losses caused by this dead time. For the triangular wave ipri, the low-voltage bridge capacitor C9 is alternately charged and discharged, and the ripple on the low-voltage bridge capacitor C9 can be derived as: Formula 14 In order to meet the ripple voltage requirement, the capacitance value of the low-voltage bridge capacitor C9 is selected.

[0062] Considering the capacitance C of the high voltage bridge on both sides pri and C sec , under a 1:1 ratio, the total capacitance Ctotal is derived as Formula 15 Where: C pri is the input capacitance, C sec is the output capacitor.

[0063] Assuming the input voltage V in and the output voltage V out All are 400V, with a rated power of 12kM. Transformer leakage inductance L k is 1460nH, the excitation inductance L m is 25μH. By determining the excitation inductance L m , the stopping time Td can be derived, considering i m After, i pri 、i sec and i m The relationship between them can be written as: Formula 16 Where: ipri is the input current and isec is the output current.

[0064] Before the second FET S2 and the third FET S3 are turned on, V pri and V sec All drop to 0, which means that the high voltage bridge obtains soft switching function.

[0065] In order to achieve parallelization of transformer stages and scale up the total power, two separate external inductors L are used on the primary and secondary sides respectively. pri and L sec If N embedded electronic modules are connected in parallel, each electronic unit should provide an average magnetizing current. If the total power demand increases, more electronic modules can be stacked. Therefore, the electromagnetic inductance in each electronic unit should be updated based on the latest total parallel number. However, this is not desirable for modular and scalable designs, as the transformer air gap design is related to the number of parallel electronic modules.

[0066] In L pri and L sec With the help of , both the primary and secondary side high voltage bridges can achieve soft switching without air gap and corresponding L m The current flowing through each electronic module can be dedicated to delivering actual power.

[0067] Unless otherwise specified, the device components involved in the above embodiments are all conventional device components, and the structural settings, working modes or control modes involved are all conventional settings, working modes or control modes in the art unless otherwise specified.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A scalable phase modular transformer, characterized in that: It includes a low-voltage bridge module; one end of the low-voltage bridge module is connected to the primary side high-voltage bridge, and the other end is connected to the secondary side high-voltage bridge; the low-voltage bridge module includes n parallel modules connected in parallel; the parallel module includes a low-voltage bridge, a first inductor L k , the second inductor L m and transformer; each parallel module includes two input terminals and two output terminals; one end of an input terminal of each parallel module is connected to the first end of the primary side high voltage bridge, and the other input terminal is connected to the low voltage bridge; the low voltage bridge has a plurality of parallel switching tubes; the other end of the low voltage bridge is connected to the first inductor L k The first end of each low-voltage bridge is connected in parallel with a low-voltage bridge capacitor C9; the first inductor L k The second end of the second inductor L m and the first end of the primary side of the transformer; the second inductor L m The second end of the primary side of the transformer and the second end of the primary side are both connected to the second end of the primary side high-voltage bridge; the two ends of the secondary side of the transformer are respectively connected to the two input ends of the secondary side high-voltage bridge.

2. The expandable phase modular transformer according to claim 1, characterized in that: The number of parallel modules connected in parallel in the low-voltage bridge module is no less than two.

3. The expandable phase modular transformer according to claim 1, characterized in that: The transformer is a high-frequency transformer.

4. The expandable phase modular transformer according to claim 1, characterized in that: The low-voltage bridge includes a first field-effect transistor Q1, a second field-effect transistor Q2, a third field-effect transistor Q3, and a fourth field-effect transistor Q4; the source of the first field-effect transistor Q1 is connected to the low-voltage bridge capacitor C9 and the source of the third field-effect transistor Q3; the drain of the first field-effect transistor Q1 is connected to the source of the second field-effect transistor Q2; the drain of the second field-effect transistor Q2 is connected to the second end of the ninth capacitor C9 and the drain of the fourth field-effect transistor Q4; the drain of the third field-effect transistor Q3 is connected to the first inductor L k and a source of the fourth field effect transistor Q4.

5. A DC-DC converter, characterized in that: It comprises an expandable phase modular transformer as described in any one of claims 1 to 4, and a primary-side high-voltage bridge and a secondary-side high-voltage bridge; the primary-side high-voltage bridge and the secondary-side high-voltage bridge both have a first input terminal, a second input terminal, a first output terminal and a second output terminal; the first input terminal and the second input terminal of the primary-side high-voltage bridge are connected to a power supply; the transformer comprises a primary-side induction coil and a secondary-side induction coil; the first input terminal and the second input terminal of the secondary-side high-voltage bridge are respectively connected to the first end and the second end of the secondary-side induction coil.

6. A DC-DC converter according to claim 5, characterized in that: The drain of the first field effect transistor Q1 is connected to the first output terminal of the primary side high voltage bridge; the second inductor L of each parallel module m The second ends of the primary side high voltage bridge are connected to the second output end.

7. The DC-DC converter according to claim 5, characterized in that: The primary side high voltage bridge comprises: a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first field effect transistor S1, a second field effect transistor S2, a third field effect transistor S3 and a fourth field effect transistor S4; the first field effect transistor S1, the second field effect transistor S2, the third field effect transistor S3 and the fourth field effect transistor S4 are all connected in parallel with a capacitor; the drain of the first field effect transistor S1 is connected to the negative electrode of the power supply, and the negative electrode of the power supply is connected to the first end of the first capacitor C1; the source ... The first terminal of the fourth capacitor C4 is connected to the drain of the second field effect transistor S2; the source of the second field effect transistor S2 is connected to the second end of the first capacitor C1; the second end of the fourth capacitor C4 is the first output end of the primary side high voltage bridge; the drain of the third field effect transistor S3 is connected to the positive electrode of the power supply, and the positive electrode of the power supply is connected to the first end of the second capacitor C2; the source of the second field effect transistor S2 is connected to the first end of the third capacitor C3 and the drain of the fourth field effect transistor S4; the second end of the third capacitor C3 is the second output end of the primary side high voltage bridge.

8. The DC-DC converter according to claim 5, characterized in that: The secondary side includes: a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a fifth field-effect transistor S5, a sixth field-effect transistor S6, a seventh field-effect transistor S7 and an eighth field-effect transistor S8; the fifth capacitor C5, the sixth capacitor C6, the seventh capacitor C7 and the eighth capacitor C8 are all connected in parallel with a capacitor; the source of the fifth field-effect transistor S5 is connected to the second end of the sixth capacitor C6 and the drain of the sixth field-effect transistor S6; the drain of the fifth field-effect transistor S5 is connected to the negative electrode of the power supply and the first end of the seventh capacitor C7; the source of the sixth field-effect transistor S6 is connected to the second end of the seventh capacitor C7; the drain of the seventh field-effect transistor S7 is connected to the first end of the eighth inductor C8; the source of the seventh field-effect transistor S7 is connected to the drain of the eighth field-effect transistor S8; and the source of the eighth field-effect transistor S8 is connected to the second end of the eighth inductor C8.

9. The DC-DC converter according to claim 5, characterized in that: The low voltage bridge capacitor C9 is a ceramic capacitor; the first inductor L k and the second inductor L m All are air-core inductors.

10. The method for using the expandable phase modular transformer according to any one of claims 1 to 4, characterized in that: The following steps are involved: In one half cycle, the second field effect transistor Q2 and the third field effect transistor Q3 are turned off, and then the first field effect transistor Q1 and the fourth field effect transistor Q4 are turned on to achieve natural zero voltage switching; In another half cycle, the same zero voltage switching analysis is performed on the second field effect transistor Q2 and the third field effect transistor Q3, so that all switches of the low voltage bridge achieve zero voltage switching.

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