Non-linear inductance and resonant conversion circuit
By setting the nonlinear inductance of the magnetic sheet in the air gap of the core column, and combining it with the adjustment of the excitation inductance in the resonant converter circuit, the problem of low efficiency of traditional resonant converters under wide gain operation is solved, and the circuit gain range is widened and the peak efficiency is improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- FSP POWERLAND TECHNOLOGY INC
- Filing Date
- 2026-03-20
- Publication Date
- 2026-06-12
AI Technical Summary
Traditional resonant converters suffer from increased losses and decreased efficiency due to reduced magnetizing inductance under wide gain operating requirements. Furthermore, improper transformer turns design leads to increased copper and iron losses, further reducing overall efficiency.
By using a nonlinear inductor and placing a magnetic sheet in the air gap of the central column of the magnetic core, the magnetic sheet reaches saturation magnetic induction intensity in advance, thereby achieving adaptive adjustment of the inductance value. Combined with the adjustment of the inductance value of the excitation inductor in the resonant converter circuit, the gain range can be widened or the peak efficiency can be improved.
It effectively broadens the circuit gain range, improves peak efficiency, reduces the saturation probability of the magnetizing inductor, and enhances the stability and efficiency of the circuit.
Smart Images
Figure CN122202008A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power electronics, and more particularly to a nonlinear inductor and resonant converter circuit. Background Technology
[0002] For applications such as charging pile power modules, traditional resonant converters have the problem of requiring a wide gain adjustment range. To meet the wide gain operation requirements, the magnetizing inductance usually needs to be reduced. However, reducing the magnetizing inductance will increase the magnetizing current, leading to increased losses and decreased efficiency of the converter at the rated operating point. At the same time, traditional resonant converters need to operate within a wide switching frequency range, and the number of transformer turns needs to be designed according to the minimum switching frequency condition, resulting in an excessive number of turns. This, in turn, increases the copper and iron losses of the resonant converter under rated operating conditions, reducing the overall efficiency. Summary of the Invention
[0003] This application aims to provide a nonlinear inductor and resonant converter circuit that can adaptively change the inductance to broaden the gain range or improve the peak efficiency in a circuit.
[0004] To achieve the above objectives, the technical solution of this application is as follows: A nonlinear inductor includes a magnetic core, a winding, and a magnetic sheet. The winding is wound on the magnetic core. The magnetic core includes a first magnetic core and a second magnetic core, which are disposed opposite to each other. The magnetic sheet is disposed in the air gap between the first magnetic core and the second magnetic core.
[0005] Optionally, the first magnetic core and the second magnetic core each include: a first side post, a first middle post, a second side post and a first horizontal post, wherein the first side post, the first middle post and the second side post are arranged in parallel in sequence, and the first horizontal post connects the first side post, the first middle post and the second side post.
[0006] Optionally, a core air gap is formed between the first central column of the first magnetic core and the first central column of the second magnetic core.
[0007] Optionally, the magnetic sheet is disposed on one side of the first central column of the first magnetic core relative to the first central column of the second magnetic core, or on one side of the first central column of the second magnetic core relative to the first central column of the first magnetic core, and an air gap between the magnetic sheet and the magnetic core relative to the magnetic sheet is formed.
[0008] Optionally, the magnetic sheet may include a non-annular magnetic sheet or a hollow annular magnetic sheet.
[0009] Optionally, the shape of the magnetic sheet may include a circle, an ellipse, or a square.
[0010] Optionally, the winding is wound on the first central column of the first magnetic core and the first central column of the second magnetic core.
[0011] Optionally, when neither the magnetic core nor the magnetic sheet is saturated, the inductance value of the nonlinear inductor is expressed as follows: in, This represents the inductance value of the nonlinear inductor when neither the magnetic core nor the magnetic sheet is saturated. This represents the effective cross-sectional area of the magnetic core; This represents the effective cross-sectional area of the magnetic sheet; This indicates the length of the air gap in the magnetic core; This indicates the length of the air gap between the magnetic sheet and the magnetic core; Indicates the number of turns in the winding; It represents the vacuum permeability.
[0012] Optionally, when the magnetic sheet is saturated, the inductance value of the nonlinear inductor is expressed as follows: in, This represents the inductance value of the nonlinear inductor only when the magnetic sheet is saturated.
[0013] Optionally, when the magnetic sheet is saturated, the current of the nonlinear inductor is expressed as follows: in, This represents the current at the inductance switching point of the nonlinear inductor. This indicates the saturation magnetic induction intensity of the magnetic sheet.
[0014] A resonant converter circuit includes: a primary-side converter module, a resonant converter module, and a secondary-side converter module, which are connected in sequence. The primary-side converter module converts the input voltage into AC power by changing the switching frequency. The resonant converter module controls the gain of the AC power and then rectifies it into an output voltage through the secondary-side converter module. The resonant conversion module includes a first capacitor, a first inductor, a second inductor, and a first transformer. The primary windings of the first capacitor, the first inductor, the second inductor, and the first transformer are connected in series, and the two ends of the series connection are the first terminals of the resonant conversion module. The two ends of the secondary winding of the first transformer are the second terminals of the resonant conversion module. The second inductor is connected in parallel across the primary winding, and the second inductor is a nonlinear inductor as described above.
[0015] Optionally, in wide input or output application scenarios, the primary-side conversion module is controlled to reduce the switching frequency. When the absolute value of the current of the second inductor reaches the current at the switching point of the inductance value of the nonlinear inductor, the inductance value of the second inductor decreases and the gain range is widened. When the peak efficiency needs to be improved, the primary-side conversion module is controlled to adjust the switching frequency to be close to the resonant point, and the resonant conversion module is controlled to increase the inductance values of the resonant inductor and the magnetizing inductor before the magnetic sheet saturates, thereby improving the peak efficiency.
[0016] This application proposes a nonlinear inductor and a resonant converter circuit. By placing a magnetic sheet in the air gap of the central column of the magnetic core, the adaptive inductance value adjustment of the nonlinear inductor is achieved by utilizing the magnetic sheet to reach saturation magnetic induction intensity in advance. The excitation inductor of the resonant converter circuit adopts the aforementioned nonlinear inductor. In the same circuit, the circuit gain or peak efficiency can be increased by adjusting the inductance value of the excitation inductor.
[0017] To make the above-mentioned features and advantages of the application more apparent and understandable, specific embodiments are provided below, and detailed descriptions are given in conjunction with the accompanying drawings. Attached Figure Description
[0018] Figure 1 The structural diagram of the nonlinear inductor provided in this application.
[0019] Figure 2 The structural diagram of the magnetic core provided in this application.
[0020] Figure 3 A cross-sectional view of the magnetic core and magnetic sheet provided in this application.
[0021] Figure 4 The diagram illustrates four embodiments of the magnetic sheet, wherein... Figure 4 Figure a in the diagram is a schematic diagram of a circular ring-shaped magnetic sheet. Figure 4 Figure b in the diagram is a schematic diagram of an elliptical ring-shaped magnetic sheet. Figure 4 Figure c in the diagram is a schematic diagram of a square ring-shaped magnetic sheet. Figure 4 The diagram in Figure d is a schematic diagram of a circular, non-ring-shaped magnetic sheet.
[0022] Figure 5 This is a circuit diagram for a resonant converter.
[0023] Figure 6 This is a schematic diagram of the circuit waveform under the condition where the non-gain requirement of the resonant converter circuit proposed in this application is the highest.
[0024] Figure 7 This is a schematic diagram of the circuit waveform under the condition that the gain requirement of the resonant converter circuit proposed in this application is increased.
[0025] Figure 8The circuit waveform diagram of the resonant converter circuit proposed in this application under the condition of highest non-gain requirement after adjusting the nonlinear inductance.
[0026] Figure 9 This is a schematic diagram of the circuit waveform under the condition that the peak efficiency requirement of the resonant converter circuit proposed in this application needs to be improved. Detailed Implementation
[0027] To make the objectives and technical solutions of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the described embodiments of this application without creative effort are within the scope of protection of this application.
[0028] This application provides a nonlinear inductor; please refer to [link / reference]. Figure 1 , Figure 1 The diagram shows the structure of the nonlinear inductor provided in this application. The nonlinear inductor 1 includes a magnetic core 11 and a winding 12, with the winding 12 wound on the magnetic core 11. Please refer to [link to relevant documentation]. Figure 2 , Figure 2 The structural diagram of the magnetic core provided in this application.
[0029] As an example, the nonlinear inductor 1 further includes a magnetic sheet 13, which is disposed in the air gap of the magnetic core 11. See also... Figure 3 , Figure 3 A cross-sectional view of the magnetic core and magnetic sheet provided in this application.
[0030] As an example, the magnetic core 11 includes a first magnetic core 111 and a second magnetic core 112, with the first magnetic core 111 and the second magnetic core 112 arranged opposite to each other to form a receiving space.
[0031] As an example, the first magnetic core 111 includes a first side post 1111, a first middle post 1112, a second side post 1113 and a first transverse post 1114. The first side post 1111, the first middle post 1112 and the second side post 1113 are arranged in parallel in sequence, and the first transverse post 5115 connects the first side post 1111, the first middle post 1112 and the second side post 1113.
[0032] As an example, the second magnetic core 112 has the same structure as the first magnetic core 111. The second magnetic core 112 includes a first side post 1121, a first middle post 1122, a second side post 1123 and a first transverse post 1124. The first side post 1121, the first middle post 1122 and the second side post 1123 are arranged in parallel in sequence. The first transverse post 1124 connects the first side post 1121, the first middle post 1122 and the second side post 1123.
[0033] Specifically, a length of [missing information] is formed between the first central post 1112 of the first magnetic core 111 and the first central post 1122 of the second magnetic core 112. The magnetic core has an air gap of 11.
[0034] As an example, winding 12 is wound on the first central post 1112 of the first magnetic core 111 and the first central post 1122 of the second magnetic core 112. Winding 12, the first magnetic core 111, and the second magnetic core 112 together constitute a nonlinear inductor, generating a magnetic flux of... φ .
[0035] As an example, the magnetic sheet 13 is disposed on one side of the first central post 1112 of the first magnetic core 111 opposite to the first central post 1122 of the second magnetic core 112, or on one side of the first central post 1122 of the second magnetic core 112 opposite to the first central post 1112 of the first magnetic core 111, and a length of [missing information] is formed between the magnetic sheet 13 and the magnetic core opposite to the magnetic sheet 13. The air gap between the magnetic sheet 13 and the magnetic core 11.
[0036] As an example, the magnetic sheet 13 includes a non-ring-shaped magnetic sheet or a hollow ring-shaped magnetic sheet. The shape of the magnetic sheet 13 is not limited to the shape of the first central post 1112 of the first magnetic core 111 and the first central post 1122 of the second magnetic core 112; different shapes can be used, such as circular, elliptical, or square. Please refer to [link to relevant documentation]. Figure 4 , Figure 4 The diagram illustrates four embodiments of the magnetic sheet, wherein... Figure 4 Figure a in the diagram is a schematic diagram of a circular ring-shaped magnetic sheet. Figure 4 Figure b in the diagram is a schematic diagram of an elliptical ring-shaped magnetic sheet. Figure 4 Figure c in the diagram is a schematic diagram of a square ring-shaped magnetic sheet. Figure 4 The diagram in Figure d is a schematic diagram of a circular, non-annular magnetic sheet; schematic diagrams of embodiments of magnetic sheets of other shapes are not shown here.
[0037] In a specific embodiment of this application, the first central column 1112 of the first magnetic core 111 and the first central column 1122 of the second magnetic core 112 are circular. The magnetic sheet 13 can be a circular non-ringed magnetic sheet, an elliptical non-ringed magnetic sheet, or a square non-ringed magnetic sheet, or it can be a circular ringed magnetic sheet, an elliptical ringed magnetic sheet, or a square ringed magnetic sheet, etc.
[0038] In another specific embodiment of this application, the first central column 1112 of the first magnetic core 111 and the first central column 1122 of the second magnetic core 112 are elliptical. The magnetic sheet 13 can be a circular non-ring magnetic sheet, an elliptical non-ring magnetic sheet, or a square non-ring magnetic sheet, or it can be a circular ring magnetic sheet, an elliptical ring magnetic sheet, or a square ring magnetic sheet, etc.
[0039] In another specific embodiment of this application, the first central pillar 1112 of the first magnetic core 111 and the first central pillar 1122 of the second magnetic core 112 are square. The magnetic sheet 13 can be a circular non-ring magnetic sheet, an elliptical non-ring magnetic sheet, or a square non-ring magnetic sheet, etc., or it can be a circular ring magnetic sheet, an elliptical ring magnetic sheet, or a square ring magnetic sheet, etc.
[0040] As an example, Indicates the air gap length of magnetic core 11; This indicates the length of the air gap from magnetic sheet 13 to magnetic core 11.
[0041] As an example, the magnetic sheet 13 is made of the same material as the magnetic core 11.
[0042] Specifically, the effective cross-sectional area of magnetic sheet 13 is Figure 3 Cross-section of the middle magnetic sheet 13.
[0043] Specifically, the maximum length of the effective cross section of the magnetic sheet 13 is less than or equal to the diameter of the first central column 1112 of the first magnetic core 111 and the first central column 1122 of the second magnetic core 112.
[0044] Specifically, the first magnetic core 111, the second magnetic core 112, and the winding 12 are equivalent to a set of inductors. The magnetic sheet 13 is equivalent to another set of inductors. The nonlinear inductor 1 can be considered as two sets of inductors connected in series.
[0045] The following will continue to combine Figure 3 The working principle of the nonlinear inductor 1 proposed in this application is introduced.
[0046] When neither the magnetic core 11 nor the magnetic sheet 13 is saturated, the inductance value of the nonlinear inductor 1 is expressed as follows: in, This represents the inductance value of the nonlinear inductor 1 when neither the magnetic core 11 nor the magnetic sheet 13 is saturated; This indicates the effective cross-sectional area of magnetic core 11; This indicates the effective cross-sectional area of magnetic sheet 13; Indicates the air gap length of magnetic core 11; This indicates the length of the air gap from magnetic sheet 13 to magnetic core 11; Indicates the number of turns in the winding; It represents the vacuum permeability.
[0047] Furthermore, due to the effective cross-sectional area of magnetic sheet 13 Smaller than the effective cross-sectional area of the magnetic core 11 The magnetic flux density of magnetic sheet 13 If the magnetic field strength is too large, magnetic sheet 13 will reach saturation magnetic induction intensity earlier. At this point, magnetic sheet 13 is saturated while magnetic core 11 is unsaturated, which is equivalent to a short circuit in the inductor formed by magnetic sheet 13. The inductance value of nonlinear inductor 1 then decreases, as shown below: in, This represents the inductance value of nonlinear inductor 1 when only magnetic plate 13 is saturated. At this time, the current in nonlinear inductor 1 is expressed as follows: in, This represents the current at the switching point of the inductance value of nonlinear inductor 1. This indicates the saturation magnetic induction intensity of magnetic sheet 13.
[0048] As an example, the maximum magnetic flux density of nonlinear inductor 1 is expressed as follows: in, This represents the maximum magnetic flux density of the nonlinear inductor 1; This represents the equivalent inductance of the first magnetic core 111, the second magnetic core 112, and the winding 12; This represents the equivalent inductance of magnetic sheet 13; This represents the maximum current of nonlinear inductor 1.
[0049] The nonlinear inductor 1 proposed in this application achieves inductance adjustment by setting a magnetic sheet in the air gap of the middle column of the magnetic core 11 and utilizing the magnetic sheet 13 to reach saturation magnetic induction intensity in advance.
[0050] This application also provides a resonant converter circuit; please refer to [link / reference]. Figure 5 , Figure 5 The diagram shows a resonant converter circuit, which includes a primary-side converter module, a resonant converter module, and a secondary-side converter module. The primary-side converter module, the resonant converter module, and the secondary-side converter module are connected in sequence. The primary-side converter module converts the input voltage into AC power by changing the switching frequency. The resonant converter module controls the gain of the AC power, and the secondary-side converter module rectifies it into an output voltage VOUT.
[0051] As an example, the resonant converter module adopts an LLC resonant converter structure, which includes: a resonant capacitor C. r Resonant inductor L r Magnetizing inductance L m And transformer T1, resonant capacitor C r Resonant inductor L r The primary winding N1 of transformer T1 is connected in series, and the two ends of the series connection form the first terminal of the resonant converter module; the two ends of the secondary winding N2 of transformer T1 form the second terminal of the resonant converter module, and the magnetizing inductance L... mThe excitation inductor L is connected in parallel across the primary winding N1. m The aforementioned nonlinear inductor is used.
[0052] Specifically, inductor L m It can be equivalent to the first magnetizing inductance L m1 With the second magnetizing inductor L m2 Series connection, first magnetizing inductor L m1 The inductance L is equivalent to the inductance formed by the first magnetic core 111, the second magnetic core 112, and the winding 12 in the aforementioned nonlinear inductor. s1 Second excitation inductor L m2 This is equivalent to the inductance L formed by the magnetic sheet in the aforementioned type of nonlinear inductor. s2 .
[0053] Furthermore, the resonant converter circuit employs the aforementioned nonlinear inductor, which can broaden the circuit gain or improve the peak efficiency by changing the inductance value of the magnetizing inductor. Let's continue with the following... Figure 1 and Figure 3 The working principle of the resonant converter circuit is introduced.
[0054] When the required gain range is small under rated operating conditions, a larger magnetizing inductance Lm can be designed to improve peak efficiency. In wide input or output applications, a large gain is required. A large gain necessitates a small magnetizing inductance Lm. A small magnetizing inductance Lm results in a large magnetizing current Im. This large magnetizing current Im leads to high conduction losses and high turn-off losses for the power transistors, thus affecting peak efficiency. Therefore, under varying operating conditions, maintaining a fixed inductance value (either large or small) for the magnetizing inductance Lm will result in insufficient gain or reduced peak efficiency. The problem of reduction.
[0055] In a specific embodiment of this application, please refer to Figure 6 and Figure 7 , Figure 6 This is a schematic diagram of the circuit waveform under the condition where the non-gain requirement of the resonant converter circuit proposed in this application is the highest. Figure 7 This is a schematic diagram of the circuit waveform under the condition that the gain requirement of the resonant converter circuit proposed in this application is increased. In the diagram, the red curve represents the resonant current. The green curve represents the first magnetizing inductance L. m1 Current, the gray curve represents the second magnetizing inductance L m2 The current is represented by the blue curve, which indicates the output voltage VOUT. Using the resonant converter circuit proposed in this application, the magnetizing inductor L... m Using the aforementioned nonlinear inductor, the primary-side converter module reduces the switching frequency in wide input or output application scenarios. Resonant current With excitation current Increase, when the excitation current When the absolute value of the excitation current reaches the switching point of the inductance value of the nonlinear inductor, that is, when the excitation current reaches the switching point of the inductance value... The current is equal to the inductance value of the nonlinear inductor and the current at the switching point. At this time, due to the effective cross-sectional area of the magnetic sheet of the nonlinear inductor Smaller than the effective cross-sectional area of the magnetic core The magnetic flux density of the magnetic sheet It will reach saturation magnetic induction intensity ahead of time. The magnetic saturation of the nonlinear inductor is equivalent to the second magnetizing inductance L. m2 Short-circuited, only the first magnetizing inductor L remains. m1 The magnetizing inductance L is connected in parallel across the primary winding N1. m The inductance value drops to 2 / 3 of its original value. For example... Figure 6 and Figure 7 As shown, the output voltage VOUT is increased from approximately 558V to approximately 697V, ensuring that the switching frequency is maintained. The topology gain range is satisfied before the magnetic core saturates.
[0056] As an example, the maximum magnetic flux density of an inductor L with a fixed inductance value is expressed as follows: in, This represents the maximum magnetic flux density of an inductor with a fixed inductance value. This represents the maximum current of an inductor with a fixed inductance value.
[0057] In a specific embodiment of this application, the inductance value of inductor L is the same as the inductance value of the nonlinear inductor 1 before magnetic saturation, both being 37 microhenries (μH). The maximum current of an inductor with a fixed inductance value is... The maximum current of the nonlinear inductor is 40A. The current at the inductance switching point of the nonlinear inductor is 44A. The inductance of the nonlinear inductor is 26A. After the magnetic plate of the nonlinear inductor becomes saturated, what is the inductance value of the nonlinear inductor when the magnetic plate is saturated? Reduce the inductance value of the nonlinear inductor when neither the magnetic core nor the magnetic sheet is saturated. 2 / 3, i.e., magnetizing inductance L m The maximum magnetic flux density of the nonlinear inductor decreases to 2 / 3 of its original value. Compared to the maximum magnetic flux density of an inductor with a fixed inductance value It decreased by 5%, reducing the excitation inductance L. m The probability of saturation is reduced, thus improving the stability of circuit operation.
[0058] Further, please refer to Figure 8 , Figure 8 This diagram illustrates the circuit waveform under the highest non-gain requirement of the resonant converter circuit proposed in this application after adjusting the nonlinear inductor. The diagram shows the inductance value of the nonlinear inductor when the parameters are adjusted to saturate the magnetic sheet. Reduce the inductance value of the nonlinear inductor when neither the magnetic core nor the magnetic sheet is saturated. When it is 1 / 2, that is, the magnetizing inductance L m The maximum magnetic flux density of the nonlinear inductor decreases to half of its original value. Compared to the maximum magnetic flux density of an inductor with a fixed inductance value It decreased by 11%.
[0059] In another specific embodiment of this application, please refer to Figure 9 , Figure 9 This is a schematic diagram of the circuit waveform under conditions requiring improved peak efficiency of the resonant converter circuit proposed in this application. Using the resonant converter circuit proposed in this application, when improved peak efficiency is required... Under operating conditions, the primary-side conversion module adjusts the switching frequency. As the resonant point approaches, the resonant converter module increases the resonant inductance L. r and magnetizing inductance L before magnetic saturation m The inductance value of the magnetizing inductance L at the peak efficiency point is determined. m The inductance value increases, thereby reducing the excitation current. Peak efficiency was achieved at this point. The improvement is further enhanced when applying the magnetizing inductance L in wide input or output scenarios. m Using the aforementioned nonlinear inductor, the circuit can still meet the requirement of widening the circuit gain range. For example... Figure 9 As shown, adjust the switching frequency. Near the resonant point, the inductance of the nonlinear inductor 1 before magnetic saturation is increased to 40 microhenries, and the resonant inductance increases from 4.8 microhenries to 7.7 microhenries, with peak efficiency... Even with the increase, the output voltage VOUT can still meet the gain requirement of around 558V.
[0060] It should be noted that the nonlinear inductor proposed in this application is not limited to the application of resonant converter circuits, and the present invention is not limited thereto.
[0061] This application proposes a nonlinear inductor and a resonant converter circuit. By placing a magnetic sheet in the air gap of the central column of the magnetic core, the adaptive inductance value adjustment of the nonlinear inductor is achieved by utilizing the magnetic sheet to reach saturation magnetic induction intensity in advance. The excitation inductor of the resonant converter circuit adopts the aforementioned nonlinear inductor. In the same circuit, the circuit gain or peak efficiency is broadened by adaptively adjusting the inductance value of the excitation inductor.
[0062] Although this application has been disclosed above with reference to embodiments, it is not intended to limit this application. Anyone skilled in the art may make some modifications and refinements without departing from the spirit and scope of this application. Therefore, the scope of protection of this application shall be determined by the appended claims.
Claims
1. A nonlinear inductor, characterized in that, It includes a magnetic core, a winding, and a magnetic sheet. The winding is wound on the magnetic core. The magnetic core includes a first magnetic core and a second magnetic core, which are disposed opposite to each other. The magnetic sheet is disposed in the air gap between the first magnetic core and the second magnetic core.
2. The nonlinear inductor as described in claim 1, characterized in that, The first magnetic core and the second magnetic core each include: a first side post, a first middle post, a second side post and a first horizontal post. The first side post, the first middle post and the second side post are arranged in parallel in sequence, and the first horizontal post connects the first side post, the first middle post and the second side post.
3. The nonlinear inductor as described in claim 2, characterized in that, A magnetic core air gap is formed between the first central column of the first magnetic core and the first central column of the second magnetic core.
4. The nonlinear inductor as described in claim 3, characterized in that, The magnetic sheet is disposed on one side of the first central column of the first magnetic core relative to the first central column of the second magnetic core, or on one side of the first central column of the second magnetic core relative to the first central column of the first magnetic core, and an air gap is formed between the magnetic sheet and the magnetic core relative to the magnetic sheet.
5. The nonlinear inductor as described in claim 4, characterized in that, The magnetic sheet includes a non-annular magnetic sheet or a hollow annular magnetic sheet.
6. The nonlinear inductor as described in claim 4, characterized in that, The shape of the magnetic sheet may be circular, elliptical, or square.
7. The nonlinear inductor as described in claim 2, characterized in that, The winding is wound on the first central column of the first magnetic core and the first central column of the second magnetic core.
8. The nonlinear inductor as described in claim 4, characterized in that, When neither the magnetic core nor the magnetic sheet is saturated, the inductance value of the nonlinear inductor is expressed as follows: ， in, This represents the inductance value of the nonlinear inductor when neither the magnetic core nor the magnetic sheet is saturated. This represents the effective cross-sectional area of the magnetic core; This represents the effective cross-sectional area of the magnetic sheet; This indicates the length of the air gap in the magnetic core; This indicates the length of the air gap between the magnetic sheet and the magnetic core; Indicates the number of turns in the winding; It represents the vacuum permeability.
9. The nonlinear inductor as described in claim 8, characterized in that, When the magnetic sheet is saturated, the inductance value of the nonlinear inductor is expressed as follows: ， in, This represents the inductance value of the nonlinear inductor only when the magnetic sheet is saturated.
10. The nonlinear inductor as described in claim 9, characterized in that, When the magnetic sheet is saturated, the current of the nonlinear inductor is expressed as follows: ， in, This represents the current at the inductance switching point of the nonlinear inductor. This indicates the saturation magnetic induction intensity of the magnetic sheet.
11. A resonant converter circuit, characterized in that, include: The system comprises a primary-side conversion module, a resonant conversion module, and a secondary-side conversion module, which are connected sequentially. The primary-side conversion module converts the input voltage into AC power by changing the switching frequency. The resonant conversion module controls the gain of the AC power, which is then rectified into an output voltage by the secondary-side conversion module. The resonant conversion module includes a first capacitor, a first inductor, a second inductor, and a first transformer. The primary windings of the first capacitor, the first inductor, the second inductor, and the first transformer are connected in series, and the two ends of the series connection are the first ends of the resonant conversion module. The two ends of the secondary winding of the first transformer are the second ends of the resonant conversion module. The second inductor is connected in parallel across the primary winding. The second inductor is a nonlinear inductor as described in any one of claims 1-10.
12. The resonant converter circuit as described in claim 11, characterized in that, When in a wide input or output application scenario, the primary-side conversion module is controlled to reduce the switching frequency. When the absolute value of the current of the second inductor reaches the current at the switching point of the inductance value of the nonlinear inductor, the inductance value of the second inductor decreases and the gain range is widened. When the peak efficiency needs to be improved, the primary-side conversion module is controlled to adjust the switching frequency to be close to the resonant point, and the resonant conversion module is controlled to increase the inductance values of the resonant inductor and the magnetizing inductor before the magnetic sheet saturates, thereby improving the peak efficiency.