An inductor and its manufacturing method, a voltage conversion circuit, and an electronic device.

Abstract

This application provides an inductor and its manufacturing method, a voltage conversion circuit, and an electronic device, relating to the field of electronic technology, for reducing the board area of ​​a Buck switching circuit. The inductor includes a first thin-film magnetic core, a second thin-film magnetic core, and a coil. The second thin-film magnetic core is embedded within the first thin-film magnetic core. The second thin-film magnetic core has a top surface and a bottom surface, and a through-hole penetrating both the top and bottom surfaces. The wall of the through-hole is covered with a conductive layer. The coil is embedded within the first thin-film magnetic core. The coil includes a first coil portion and a second coil portion. The first coil portion is spirally wound around the top surface of the second thin-film magnetic core. The second coil portion is spirally wound around the bottom surface of the second thin-film magnetic core, and a first end of the second coil portion is coupled to a first end of the first coil portion through the through-hole. The relative permeability of the first thin-film magnetic core is less than the relative permeability of the second thin-film magnetic core.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to an inductor and its manufacturing method, a voltage conversion circuit, and an electronic device. Background Technology

[0002] In electronic products such as wearable devices like wristbands, smartwatches, and Bluetooth headsets, mobile display terminals like mobile phones and tablets, and even devices like servers, AI processors, and network processors, inductors are commonly used electronic components. Taking a mobile phone as an example, to power the chip inside the phone, it includes a buck switching circuit. By charging and discharging the inductor in the buck switching circuit, the voltage provided by the battery can be converted into the operating voltage of the chip.

[0003] When the phone is in standby mode, the aforementioned chip requires a relatively small supply current. In this case, to improve the switching efficiency of the Buck switch circuit, an inductor with a large inductance can be used for filtering. Alternatively, when the phone is running demanding applications, the chip needs to receive a large current in a short period. In this case, to improve the dynamic response of the Buck switch circuit, an inductor with a smaller inductance can be used for filtering, reducing the AC impedance to current jumps and improving the phone's response speed. However, when the Buck switch circuit includes two inductors with significantly different inductance values, it occupies a large board area, which is detrimental to the miniaturization design of electronic products. Summary of the Invention

[0004] This application provides an inductor and its manufacturing method, a voltage conversion circuit, and an electronic device for reducing the board area of ​​a Buck switch circuit.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] One aspect of this application provides an inductor. The inductor includes a first thin-film magnetic core, a second thin-film magnetic core, and a coil. The second thin-film magnetic core is embedded within the first thin-film magnetic core. The second thin-film magnetic core has a top surface and a bottom surface, and a through-hole penetrating both the top and bottom surfaces. A conductive layer covers the wall of the through-hole. The coil is embedded within the first thin-film magnetic core. The coil includes a first coil portion and a second coil portion. The first coil portion is spirally wound around the top surface of the second thin-film magnetic core. The second coil portion is spirally wound around the bottom surface of the second thin-film magnetic core, and a first end of the second coil portion is coupled to a first end of the first coil portion through the through-hole. The relative permeability of the first thin-film magnetic core is less than the relative permeability of the second thin-film magnetic core.

[0007] Therefore, when the current flowing through the coil is small and does not reach the saturation current of the first and second thin-film magnetic cores, neither the first nor the second thin-film magnetic core has reached magnetic saturation. In this case, the coil and the first thin-film magnetic core surrounding the coil can form a closed first magnetic field path. The coil and the second thin-film magnetic core located between the first and second coil sections can form a closed second magnetic field path. At this time, because the relative permeability of the second thin-film magnetic core is large, the inductance of the inductor is determined by both the first and second thin-film magnetic cores, so the inductor has a large inductance. When the current flowing through the coil gradually increases and is greater than or equal to the saturation current of the second thin-film magnetic core, the second thin-film magnetic core gradually enters a magnetic saturation state and eventually reaches complete magnetic saturation, with its relative permeability decreasing to about 1. In this case, the coil cannot form a closed second magnetic field path with the second thin-film magnetic core. The coil only forms a closed first magnetic field path with the first thin-film magnetic core. At this point, since the relative permeability of the second thin-film magnetic core drops to a very low level, the inductance of the inductor is mainly maintained by the first thin-film magnetic core, which has a lower relative permeability, thus causing the inductance to decrease.

[0008] In this way, the inductance of the aforementioned inductor can decrease as the current in the coil increases, thus the inductance can vary according to the change in the current flowing through the coil. When this inductor is placed in the voltage conversion circuit of an electronic device, when the electronic device, such as a mobile phone, is in standby mode, the voltage conversion circuit is under light load, its load current is small, and the current in the coil of the inductor is also small. At this time, the relative permeability of the second thin-film magnetic core is large, and the inductance of the inductor is determined by both the first and second thin-film magnetic cores, so the inductor has a large inductance. In this case, the inductor can reduce the ripple of the output current of the voltage conversion circuit during filtering, thereby reducing the AC loss of the ripple current and improving the conversion efficiency of the voltage conversion circuit under light load conditions. Furthermore, when the electronic device switches applications or runs large programs, the voltage conversion circuit is under heavy load, its load current is large, and the current in the coil of the inductor is also large. As mentioned above, the second thin-film magnetic core is in a magnetic saturation state, reducing its relative permeability to approximately 1. Therefore, the inductance is mainly maintained by the first thin-film magnetic core, which has a lower relative permeability, further reducing the inductance. During filtering, this inductor reduces the AC impedance of current jumps, thereby improving the dynamic response of the voltage conversion circuit under heavy load conditions. As shown above, the voltage conversion circuit only needs to use an inductor with variable inductance to meet the different inductance requirements under light and heavy loads, eliminating the need for two inductors with significantly different inductance values, thus reducing the board area in electronic devices. Furthermore, since the inductor provided in this embodiment has variable inductance, the number of inductors in the voltage conversion circuit is reduced, thereby decreasing the sum of the DC resistance values ​​of all inductors in the voltage conversion circuit and improving voltage conversion efficiency.

[0009] Optionally, the second thin-film magnetic core also has a perforated structure penetrating its top and bottom surfaces. The perforated structure is located within the area of ​​the inner coil of the first coil portion or the area of ​​the inner coil of the second coil portion, within the range of its vertical projection onto the second thin-film magnetic core. Part of the material in the first thin-film magnetic core fills the perforated structure. In this way, the portion of the first thin-film magnetic core with relatively low permeability located within the perforated structure connects its upper and lower portions, allowing the magnetic induction lines generated by the coil and the entire first thin-film magnetic core to be continuous at the perforated structure location, without being affected by the air gap formed by the magnetically saturated second thin-film magnetic core. This avoids the inductance decreasing too much as the current increases, thus preventing it from failing to meet design requirements.

[0010] Optionally, the inductor further includes a first end electrode and a second end electrode disposed on the outer surface of the first thin-film magnetic core. A second end of the first coil portion passes through the first thin-film magnetic core and is coupled to the first end electrode. A second end of the second coil portion passes through the first thin-film magnetic core and is coupled to the second end electrode. The inductor can be coupled to other components in the voltage conversion circuit via the aforementioned first and second end electrodes.

[0011] Optionally, the relative permeability of the second thin-film magnetic core can be 25 to 1000 times that of the first thin-film magnetic core. For example, the material of the second thin-film magnetic core includes at least one alloy material such as nickel-zinc ferrite, manganese-zinc ferrite, silicon steel, ferromolybdenum, or ferronickel, and the relative permeability of the second thin-film magnetic core can be 500 to 50000. The material of the first thin-film magnetic core includes at least one iron-silicon-chromium alloy or carbonyl iron, and the relative permeability of the first thin-film magnetic core can be 20 to 50.

[0012] Optionally, the first thin-film magnetic core can be a cube or a cuboid. This allows the cavity within the mold to be shaped into a regular form, such as a cube or cuboid, when the material constituting the first thin-film magnetic core, along with the second thin-film magnetic core and the coil, is pressed together using a molding process. This simplifies the mold manufacturing process. Furthermore, the second thin-film magnetic core has a circular sheet structure, resulting in a smaller thickness and thus helping to reduce the size of the inductor.

[0013] A second aspect of this application provides a method for manufacturing an inductor. The method includes: first, forming a second thin-film magnetic core using a second magnetic material, and forming through holes penetrating the top and bottom surfaces of the second thin-film magnetic core. Next, forming a spiral-shaped metal trace on the top surface of the second thin-film magnetic core to form a first coil portion of a coil. Forming a spiral-shaped metal trace on the bottom surface of the second thin-film magnetic core to form a second coil portion of the coil. A first end of the second coil portion is coupled to a first end of the first coil portion through the through hole. The order in which the first and second coil portions are manufactured is not limited in this application. Next, the second thin-film magnetic core with the coil is placed in a mold. A first magnetic material is injected into the mold and pressed together with the second thin-film magnetic core and the coil to form a first thin-film magnetic core including the second thin-film magnetic core and the coil. The relative permeability of the first magnetic material is less than the relative permeability of the second magnetic material. The above-described inductor manufacturing method has the same technical effects as the inductor provided in the foregoing embodiments, and will not be repeated here.

[0014] Optionally, after forming the second thin-film magnetic core and before forming the coil, the method further includes: forming a perforated structure penetrating the top and bottom surfaces of the second thin-film magnetic core. Based on this, the method for forming the first coil portion includes: fabricating a spiral metal trace around the perforated structure on the top surface of the second thin-film magnetic core to form the first coil portion. Alternatively, the method for forming the second coil portion includes: fabricating a spiral metal trace around the perforated structure on the bottom surface of the second thin-film magnetic core to form the second coil portion. The technical effects of the above-described perforated structure are the same as described above and will not be repeated here.

[0015] Optionally, forming the first coil portion includes: first, forming a metal thin film layer on the top surface of the second thin-film magnetic core. Next, using photolithography, a spiral-shaped metal trace is fabricated on the metal thin film layer to form the first coil portion of the coil. In this way, the photolithography process allows for the patterning of a very thin metal thin film layer, forming a spiral-shaped metal trace pattern on the top surface of the second thin-film magnetic core. Furthermore, the process of forming the second coil portion on the bottom surface of the second thin-film magnetic core is similar and will not be elaborated here.

[0016] Optionally, the relative permeability of the second magnetic material is 25 to 1000 times that of the first magnetic material. For example, the second magnetic material includes at least one alloy material such as nickel-zinc ferrite, manganese-zinc ferrite, silicon steel, ferromolybdenum, or ferronickel, and its relative permeability can be 500 to 50000. The first magnetic material includes at least one iron-silicon-chromium alloy or carbonyl iron material, and its relative permeability can be 20 to 50.

[0017] A third aspect of this application provides an inductor. The inductor includes a coil, a first magnetic core, and a second magnetic core. The coil is embedded within the first magnetic core, and the first magnetic core covers at least a portion of the outer surface of the coil. The second magnetic core covers at least a portion of the coil. The relative permeability of the second magnetic core is greater than that of the first magnetic core. Therefore, since the relative permeability of the second magnetic core can be greater than that of the first magnetic core, the saturation current of the second magnetic core is less than that of the first magnetic core.

[0018] Based on this, when the current flowing through the coil is small and does not reach the saturation current of the first and second magnetic cores, neither the first nor the second magnetic core has reached magnetic saturation. In this case, the coil and the first magnetic core surrounding the coil can form a closed first magnetic field path. The coil and the second magnetic core covering the coil can form a closed second magnetic field path. At this time, because the relative permeability of the second magnetic core is very large, the inductor has a large inductance. As the current flowing through the coil gradually increases and becomes greater than or equal to the saturation current of the second magnetic core, the second magnetic core gradually enters a magnetic saturation state and eventually reaches complete magnetic saturation, with its relative permeability decreasing to about 1. In this case, the coil cannot form a closed second magnetic field path with the second magnetic core. The coil only forms a closed first magnetic field path with the first magnetic core. At this time, because the relative permeability of the second magnetic core decreases to a very low level, the inductance of the inductor is mainly maintained by the first magnetic core with its lower relative permeability, thus causing the inductance to decrease. In this way, the inductance of the aforementioned inductor can decrease as the current in the coil increases, thus the inductance can change according to the current. For example, when the aforementioned inductor is placed in the voltage conversion circuit of an electronic device, on the one hand, when the electronic device, such as a mobile phone, is in standby mode, the voltage conversion circuit is in a light-load state, its load current is small, and the current in the coil of the inductor is also small. At this time, as mentioned above, the relative permeability of the second magnetic core is very large, so the inductor has a large inductance. This inductor can reduce the ripple of the output current during the filtering process, thereby reducing the AC loss of the ripple current and improving the conversion efficiency of the voltage conversion circuit under light-load conditions. On the other hand, when the mobile phone switches applications or runs large programs, the voltage conversion circuit is in a heavy-load state, its load current is large, and the current in the coil of the inductor is also large. At this time, as mentioned above, the second magnetic core is in a magnetic saturation state, causing its relative permeability to decrease to about 1, so the inductance is mainly maintained by the first magnetic core with a lower relative permeability, thereby causing the inductance to decrease. During the filtering process, this inductor can reduce the AC impedance during current jumps, thereby improving the dynamic response of the voltage conversion circuit under heavy load conditions. As can be seen from the above, only the variable inductance of the aforementioned inductor is needed in the voltage conversion circuit to meet the different inductance requirements under light and heavy loads. This eliminates the need for two inductors with significantly different inductance values ​​in the voltage conversion circuit, thus reducing the board area in electronic devices.

[0019] Optionally, the first magnetic core wraps around and contacts the outer surface of the coil. The second magnetic core wraps around and contacts the outer surface of the first magnetic core. In this way, since the first magnetic core is located inside the second magnetic core, when the current flowing through the coil is small and neither the first nor the second magnetic core has reached magnetic saturation, the magnetic field lines generated by the coil and the second magnetic core can pass through the relatively less permeable first magnetic core along a closed magnetic field line path, enter the relatively more permeable second magnetic core, and then return to the coil. This allows the second magnetic core, with its high permeability, to determine the inductance of the inductor. When the current flowing through the coil is small, as mentioned above, the relative permeability of the second magnetic core drops to a very low level, and the inductance is mainly maintained by the relatively less permeable first magnetic core, resulting in a decrease in inductance.

[0020] Optionally, the inductor includes a first end electrode and a second end electrode disposed on the outer surface of the first magnetic core. A first end of the coil passes through the first and second magnetic cores and is coupled to the first end electrode. A second end of the coil passes through the first and second magnetic cores and is coupled to the second end electrode. The inductor can be coupled to other components in the voltage conversion circuit via the aforementioned first and second end electrodes.

[0021] Optionally, the coil includes a first conductor segment and a second conductor segment connected together. A second magnetic core is embedded within the first magnetic core. The second magnetic core wraps around the outer surface of the first conductor segment and is in contact with the outer surface of the first conductor segment. The second magnetic core is embedded within the first magnetic core, and the first magnetic core wraps around the outer surfaces of the second conductor segment and the second magnetic core, and is in contact with the outer surfaces of both. In this way, when a small current flows through the coil, neither the first nor the second magnetic core reaches magnetic saturation. In this case, the second conductor segment and the first magnetic core wrapping its outer surface can generate magnetic induction lines distributed along a closed first magnetic induction path. The first conductor segment and the second magnetic core including its outer surface can generate a closed second magnetic induction line path. At this time, because the relative permeability of the second magnetic core is very large, the inductor has a large inductance, which can improve the conversion efficiency of the voltage conversion circuit under light load conditions. As the current flowing through the coil gradually increases and becomes greater than or equal to the saturation current of the second magnetic core, the second magnetic core gradually enters a magnetic saturation state and eventually reaches complete magnetic saturation, with its relative permeability decreasing to approximately 1. In this situation, the first conductor segment cannot form a closed second magnetic induction path with the second magnetic core. Only the second conductor segment forms a closed first magnetic induction path with the first magnetic core in the inductor. At this time, since the relative permeability of the second magnetic core drops to a very low level, the inductance of the inductor is mainly maintained by the first magnetic core with its lower relative permeability, thereby reducing the inductance and improving the dynamic response of the voltage conversion circuit under heavy load conditions.

[0022] Optionally, the inductor also includes a first end electrode and a second end electrode disposed on the outer surface of the first magnetic core. The first end of the second conductive segment passes through the first magnetic core and is coupled to the first end electrode, and the second end of the second conductive segment is coupled to the first end of the first conductive segment. The second end of the first conductive segment passes through at least the first magnetic core and is coupled to the second end electrode. The technical effects of the first and second end electrodes are the same as described above and will not be repeated here. Furthermore, since the first conductive segment is the portion of the coil closer to the second end electrode, the second magnetic core surrounding the first conductive segment can be positioned close to the second end electrode, making it easier to wrap the second magnetic core around the coil.

[0023] Optionally, the relative permeability of the second magnetic core can be 25 to 1000 times that of the first magnetic core. For example, the material of the first magnetic core includes at least one of iron-silicon-chromium alloy and carbonyl iron material, and the relative permeability of the first magnetic core can be 20 to 50. The material of the second magnetic core includes at least one of alloy materials such as nickel-zinc ferrite, manganese-zinc ferrite, silicon steel, ferromolybdenum, or ferronickel, and the relative permeability of the second magnetic core can be 500 to 50000.

[0024] A fourth aspect of this application provides a method for manufacturing an inductor, comprising: first, forming a coil by winding metal wires; next, placing the coil into a mold, injecting a first magnetic material into the mold, and pressing it with the coil to form a first magnetic core enclosing the coil; then, forming a second magnetic core enclosing the first magnetic core and the coil using a second magnetic material. The relative permeability of the first magnetic material is less than the relative permeability of the second magnetic material. The above-described inductor manufacturing method has the same technical effects as the inductor provided in the foregoing embodiments, and will not be repeated here.

[0025] Optionally, the relative permeability of the second magnetic material is 25 to 1000 times that of the first magnetic material. For example, the second magnetic material includes at least one alloy material such as nickel-zinc ferrite, manganese-zinc ferrite, silicon steel, ferromolybdenum, or ferronickel, and its relative permeability can be 500 to 50000. The first magnetic material includes at least one iron-silicon-chromium alloy or carbonyl iron material, and its relative permeability can be 20 to 50.

[0026] A fifth aspect of this application provides a method for manufacturing an inductor, comprising: first, forming a coil by winding metal wires; next, forming a tubular second magnetic core using a second magnetic material, and embedding a first conductor segment of the coil into the inner hole of the second magnetic core, such that the second magnetic core wraps around and contacts the outer surface of the first conductor segment; then, placing the coil and the second magnetic core into a mold, injecting a first magnetic material into the mold, and pressing it against the coil and the second magnetic core to form a first magnetic core that wraps around the outer surface of the second conductor segment of the coil and the outer surface of the second magnetic core. This first magnetic core is in contact with the outer surface of the second conductor segment and the outer surface of the second magnetic core. The above-described inductor manufacturing method has the same technical effects as the inductor provided in the foregoing embodiments, and will not be repeated here.

[0027] Optionally, the relative permeability of the second magnetic material is 25 to 1000 times that of the first magnetic material. For example, the second magnetic material includes at least one alloy material such as nickel-zinc ferrite, manganese-zinc ferrite, silicon steel, ferromolybdenum, or ferronickel, and its relative permeability can be 500 to 50000. The first magnetic material includes at least one iron-silicon-chromium alloy or carbonyl iron material, and its relative permeability can be 20 to 50.

[0028] A sixth aspect of this application provides an inductor. The inductor includes a coil, a first magnetic core, and a second magnetic core. The coil is embedded within the first magnetic core. The second magnetic core includes an upper cover, a lower base, and a first core post. The upper cover covers and contacts the upper surface of the first magnetic core. The lower base covers and contacts the lower surface of the first magnetic core. The first core post is embedded within the first magnetic core, and the coil is wound around the first core post. A first end of the first core post passes through the first magnetic core and connects to the upper cover, and a second end of the first core post passes through the first magnetic core and connects to the lower base. The relative permeability of the first magnetic core is less than the relative permeability of the second magnetic core. Thus, when a small current flows through the coil, the upper cover, lower base, and first core post in the first and second magnetic cores do not reach magnetic saturation. At this time, the magnetic induction lines generated by the coil and the second magnetic core can sequentially enter the upper cover, the first magnetic core, the lower base of the second magnetic core, and then return to the first core post along a closed second magnetic induction line path. Furthermore, the coil is wound around the first core post, which makes the distribution of magnetic induction lines in the second magnetic induction line path more concentrated. When the current in the coil gradually increases, the second magnetic core can reach the magnetic saturation state more quickly, so that the inductance of the inductor decreases faster as the current increases.

[0029] Optionally, the second magnetic core also includes a second core post, which is embedded within the first magnetic core, with a gap between them. Part of the material from the first magnetic core fills the gap. The coil is wound around the first and second core posts. A first end of the second core post passes through the first magnetic core and is coupled to the upper cover, and a second end of the second core post passes through the first magnetic core and is coupled to the lower base. The material constituting the second core post is the same as the material constituting the second magnetic core. As mentioned above, the second core post also has a higher relative permeability, so the magnetic induction lines generated by the coil, the second magnetic core, and the second core post can sequentially enter the upper cover, the first magnetic core, the lower base of the second magnetic core, and then return to the first and second core posts along a closed second magnetic induction line path. Furthermore, the coil is wound around the first and second core posts, making the distribution of magnetic induction lines in the second magnetic induction line path more concentrated. When the current in the coil gradually increases, the second magnetic core can reach magnetic saturation more quickly, thus causing the inductance of the inductor to decrease more rapidly as the current increases. Based on this, since there is a gap between the first and second core pillars, and this gap is filled with a portion of the first magnetic core material with relatively low permeability, when the current flowing through the coil gradually increases, causing the second magnetic core to reach magnetic saturation, the portion with relatively low permeability inside the gap connects its upper and lower portions with relatively low permeability. This allows the magnetic field lines generated by the coil and the entire first magnetic core to be continuous at the gap. This avoids the inductance decreasing too much as the current increases, which would prevent it from failing to meet design requirements.

[0030] Optionally, the first magnetic core further includes a side surface located between the upper and lower surfaces of the first magnetic core. The second magnetic core does not cover the side surface. The inductor also includes a first end electrode and a second end electrode disposed on the side surface of the first magnetic core. A first end of the coil passes through the first magnetic core and is coupled to the first end electrode. A second end of the coil passes through the first magnetic core and is coupled to the second end electrode. The second end of the coil passes through both the first and second magnetic cores and is coupled to the second end electrode. The inductor can be coupled to other components in the voltage conversion circuit via the aforementioned first and second end electrodes.

[0031] Optionally, the relative permeability of the second magnetic core can be 25 to 1000 times that of the first magnetic core. For example, the material of the first magnetic core includes at least one of iron-silicon-chromium alloy and carbonyl iron material, and the relative permeability of the first magnetic core can be 20 to 50. The material of the second magnetic core includes at least one of alloy materials such as nickel-zinc ferrite, manganese-zinc ferrite, silicon steel, ferromolybdenum, or ferronickel, and the relative permeability of the second magnetic core can be 500 to 50000.

[0032] A seventh aspect of this application provides a method for manufacturing an inductor. The method includes: first, forming a second magnetic core using a second magnetic material. The second magnetic core includes an upper cover, a lower base, and a first core post located between the upper cover and the lower base. A first end of the first core post is connected to the upper cover, and a second end of the first core post is connected to the lower base. Next, a coil is formed by winding metal wires around the first core post. Then, the coil and the second magnetic core are placed in a mold, the first magnetic material is injected into the mold, and the material is pressed together with the coil and the second magnetic core to form a first magnetic core enclosing the coil and the first core post. The upper surface of the first magnetic core is in contact with the upper cover, and the lower surface is in contact with the lower base. The above-described inductor manufacturing method has the same technical effects as the inductor provided in the foregoing embodiments, and will not be repeated here.

[0033] Optionally, the method for forming the second magnetic core further includes: simultaneously fabricating the upper cover, lower base, and first core post using a second magnetic material, and fabricating a second core post located between the upper cover and lower base. The first end of the second core post is connected to the upper cover, and the second end of the second core post is connected to the lower base. A gap exists between the second core post and the first core post. The method for winding the coil includes: winding a coil using metal wires on the first and second core posts. The method for forming the first core post includes: placing the coil and the second magnetic core into a mold, injecting a first magnetic material into the mold, and pressing it against the coil and the second magnetic core to form a first magnetic core that encloses the coil, the first core post, and the second core post, with a portion of the material from the first magnetic core filling the gap.

[0034] Optionally, the relative permeability of the second magnetic material is 25 to 1000 times that of the first magnetic material. For example, the second magnetic material includes at least one alloy material such as nickel-zinc ferrite, manganese-zinc ferrite, silicon steel, ferromolybdenum, or ferronickel, and its relative permeability can be 500 to 50000. The first magnetic material includes at least one iron-silicon-chromium alloy or carbonyl iron material, and its relative permeability can be 20 to 50.

[0035] An eighth aspect of this application provides a voltage conversion circuit. The voltage conversion circuit includes a control switch and any of the inductors described above. The control switch is coupled between the input terminal of the voltage conversion circuit and a first electrode of the inductor. The second electrode of the inductor is coupled to the output terminal of the voltage conversion circuit. This voltage conversion circuit has the same technical effects as the inductor provided in the foregoing embodiments, and will not be repeated here.

[0036] A ninth aspect of this application provides an electronic device. The electronic device includes a printed circuit board and at least one voltage conversion circuit as described above. The voltage conversion circuit is disposed on the printed circuit board. Attached Figure Description

[0037] Figure 1This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application;

[0038] Figure 2 This is a schematic diagram of a voltage conversion circuit provided in an embodiment of this application;

[0039] Figure 3 This is a schematic diagram of a voltage conversion circuit provided in an embodiment of this application;

[0040] Figure 4 This is a schematic diagram of the structure of an inductor provided in an embodiment of this application;

[0041] Figure 5a for Figure 4 A schematic diagram of the structure of the second thin-film magnetic core;

[0042] Figure 5b For along Figure 5a The sectional view obtained by cutting the dotted line EE in the middle;

[0043] Figure 6 This is a partial structural schematic diagram of an inductor provided in an embodiment of this application;

[0044] Figure 7 for Figure 4 A graph showing the change in inductance of a medium-sized inductor with respect to current.

[0045] Figure 8a For along Figure 4 A sectional view obtained by cutting through the dotted line OO in the image;

[0046] Figure 8b For along Figure 4 A sectional view obtained by cutting through the dotted line OO in the image;

[0047] Figure 9a This is a schematic diagram of another inductor structure provided in an embodiment of this application;

[0048] Figure 9b This is a partial structural schematic diagram of an inductor provided in an embodiment of this application;

[0049] Figure 10 For along Figure 4 A sectional view obtained by cutting through the dotted line OO in the image;

[0050] Figure 11a This is a schematic diagram of another inductor structure provided in an embodiment of this application;

[0051] Figure 11b For along Figure 11a A sectional view obtained by cutting through the dotted line FF in the image;

[0052] Figure 12for Figure 11a A graph showing the change in inductance of a medium-sized inductor with respect to current.

[0053] Figure 13a for Figure 11a A schematic diagram of the magnetic field line distribution of the inductor structure shown;

[0054] Figure 13b for Figure 11a Another schematic diagram of magnetic field line distribution for the inductor structure shown;

[0055] Figure 14 for Figure 11a The diagram shows a structure with terminal electrodes on the inductor.

[0056] Figure 15a This is a schematic diagram of another inductor structure provided in an embodiment of this application;

[0057] Figure 15b For along Figure 15a A sectional view obtained by cutting through the dotted line GG in the image;

[0058] Figure 16 for Figure 15a A graph showing the change in inductance of a medium-sized inductor with respect to current.

[0059] Figure 17a for Figure 15a A schematic diagram of the magnetic field line distribution of the inductor structure shown;

[0060] Figure 17b for Figure 15a Another schematic diagram of magnetic field line distribution for the inductor structure shown;

[0061] Figure 18 for Figure 15a The diagram shows a structure with terminal electrodes on the inductor.

[0062] Figure 19a This is a schematic diagram of another inductor structure provided in an embodiment of this application;

[0063] Figure 19b for Figure 19a The diagram shows a top view of the inductor.

[0064] Figure 20a This is a schematic diagram of another inductor structure provided in an embodiment of this application;

[0065] Figure 20b for Figure 20a The diagram shows a top view of the inductor.

[0066] Figure 21 for Figure 20a A graph showing the change in inductance of a medium-sized inductor with respect to current.

[0067] Figure 22a for Figure 20a A schematic diagram of the magnetic field line distribution of the inductor structure shown;

[0068] Figure 22b for Figure 20a Another schematic diagram of magnetic field line distribution for the inductor structure shown;

[0069] Figure 23 for Figure 20a The diagram shows a structure with terminal electrodes on the inductor.

[0070] Figure label:

[0071] 01-Electronic device; 10-Display module; 11-Middle frame; 12-Back cover; 20-Inductor; 100-Voltage conversion circuit; 101-DC-DC control chip; 201-First thin-film magnetic core; 202-Second thin-film magnetic core; 203-Coil; 30-Through hole; 31-Conductive layer; 213-First coil section; 223-Second coil section; 32-Hollow structure; 41-First end electrode; 42-Second end electrode; 301-First magnetic core; 302-Second magnetic core; 233-First conductor segment; 243-Second conductor segment; 312-Top cover; 322-Bottom; 332-First core post; 342-Second core post. Detailed Implementation

[0072] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0073] Hereinafter, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0074] Furthermore, in this application, directional terms such as "upper" and "lower" are defined relative to the orientation of the components shown in the accompanying drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation of the components in the accompanying drawings.

[0075] In this application, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled" can refer to a method of electrical connection for signal transmission; "coupled" can be a direct electrical connection or an indirect electrical connection through an intermediate medium.

[0076] This application provides an electronic device, including, for example, a mobile phone, tablet computer, in-vehicle computer, and smart wearable product. This application does not impose any special limitations on the specific form of the aforementioned electronic device. For ease of explanation, the following description uses a mobile phone as an example. Figure 1 As shown, the electronic device 01 includes a display module 10, a middle frame 11, and a back cover 12.

[0077] Display module 10 is used to display images. In some embodiments of this application, display module 10 includes a liquid crystal display (LCD) module and a backlight unit (BLU). Alternatively, in other embodiments of this application, display module 10 may be an organic light-emitting diode (OLED) display screen.

[0078] The middle frame 11 is located between the display module 10 and the rear shell 12, and the side of the middle frame 11 facing the display module 10 is used to support the display module 10. Furthermore, the aforementioned electronic device 01 also includes a printed circuit board (PCB). The surface of the middle frame 11 facing the rear shell 12 is used to support electronic components such as the PCB, camera, and battery. The camera and battery are not shown in the diagram. The rear shell 12 is connected to the middle frame 11 to form a cavity for accommodating the aforementioned electronic components such as the PCB, camera, and battery. This prevents external moisture and dust from entering the cavity and affecting the performance of the electronic components.

[0079] In addition, the aforementioned electronic device 01 also includes, for example Figure 2The voltage conversion circuit 100 is shown. The voltage conversion circuit 100 is mounted on the PCB. Its input terminal Ui is coupled to a battery in the electronic device, and its output terminal Uo is coupled to chips on the PCB, such as a system-on-chip (SoC), a central processing unit (CPU), or a graphics processing unit (GPU). The voltage conversion circuit 100 is used to convert the battery voltage, for example, by stepping it down and providing it as the operating voltage to the aforementioned chips.

[0080] Among them, such as Figure 2 As shown, the voltage conversion circuit 100 includes an inductor 20, a switching transistor Q, a diode D, and a capacitor Co. The switching transistor Q can be a transistor. The first terminal of the switching transistor Q, for example, its source (s), is coupled to the input terminal Ui of the voltage conversion circuit 100, which can be coupled to a power source, such as the positive terminal of a battery. The second terminal of the switching transistor Q, for example, its drain (d), is coupled to the first terminal of the inductor 20. The second terminal of the inductor 20 is coupled to the output terminal Uo of the voltage conversion circuit 100. The gate (g) of the switching transistor Q is used to receive a control signal that controls the switching transistor Q to turn on and off. Furthermore, the cathode (c) of the diode D is coupled to the first terminal of the inductor 20, and the anode (a) is coupled to a power source, such as the negative terminal of the aforementioned battery. The first terminal of the capacitor Co is coupled to the output terminal Uo of the voltage conversion circuit 100, and the second terminal is coupled to a power source, such as the negative terminal of the aforementioned battery. Inductor 20 serves as an energy storage and filter. When the switching transistor Q is turned on, inductor 20 charges. When the switching transistor Q is turned off, inductor 20 discharges and continuously provides a stable operating voltage to each chip through capacitor Co.

[0081] It should be noted that, Figure 2 The description uses a voltage conversion circuit 100 including an inductor 20 as an example. In other embodiments of this application, such as... Figure 3 As shown, the voltage conversion circuit 100 may include at least two inductors 20. Furthermore, the switching transistor Q and diode D in the voltage conversion circuit 100 may be integrated into the control chip 101 of the direct current (DC) to DC circuit, i.e., the DC-DC circuit.

[0082] The structure of the inductor 20 described above will be illustrated in detail below.

[0083] Example 1

[0084] The inductor 20 provided in this example includes, for example: Figure 4 The diagram shows a first thin-film magnetic core 201, a second thin-film magnetic core 202, and a coil 203. The second thin-film magnetic core 202 and the coil 203 are embedded within the first thin-film magnetic core 201. The second thin-film magnetic core 202 can be a circular sheet structure. The first thin-film magnetic core 201 can be a cube or cuboid block structure.

[0085] Furthermore, the structure of the second thin-film magnetic core 202 is as follows: Figure 5a As shown, the second thin-film magnetic core 202 has a top surface A and a bottom surface B. Figure 6 As shown, coil 203 includes a first coil portion 213 and a second coil portion 223. The first coil portion 213 is spirally wound around the top surface A of the second thin-film magnetic core 202. Similarly, the second coil portion 223 is spirally wound around the bottom surface B of the second thin-film magnetic core 202.

[0086] In order to couple the first coil portion 213 and the second coil portion 223, as follows Figure 5a As shown, the second thin-film magnetic core 202 has a through-hole 30 penetrating the top surface A and the bottom surface B. The wall of the through-hole 30 is covered with a material such as... Figure 5b (along Figure 5a The conductive layer 31 is shown in the cross-sectional view obtained by cutting the dotted line EE in the image. In this way, the first end of the first coil portion 213 located on the top surface A of the second thin film magnetic core 202 can contact the first end of the second coil portion 223 located on the bottom surface B of the second thin film magnetic core 202 through the aforementioned through hole 30, thereby coupling the first coil portion 213 and the second coil portion 223.

[0087] Based on this, the relative permeability of the first thin-film magnetic core 201 is lower than that of the second thin-film magnetic core 202. In some embodiments of this application, the first thin-film magnetic core 201 can be constructed using a first magnetic material with a relatively low permeability (e.g., a relative permeability of 20 to 50). For example, the material constituting the first thin-film magnetic core 201 may include at least one of iron-silicon-chromium (FeSiCr) alloy or carbonyl iron. In this case, the first thin-film magnetic core 201 can have a higher magnetic saturation strength.

[0088] Furthermore, the second thin-film magnetic core 202 can be constructed using a second magnetic material with relatively high permeability (e.g., a relative permeability of 500 to 50,000). For example, the material constituting the second thin-film magnetic core 202 may include at least one of alloy materials such as nickel-zinc ferrite (NiZnFeO), manganese-zinc ferrite (MnZnFeO), silicon steel, ferromolybdenum, or ferronickel, or amorphous (or nanocrystalline) magnetic materials. In this case, the second thin-film magnetic core 202 can have a lower magnetic saturation intensity.

[0089] In some embodiments of this application, the following methods can be used to manufacture such a product. Figure 4 The inductor 20 is shown. For example, the second thin-film magnetic core 202 is first formed using the aforementioned second magnetic material that constitutes the second thin-film magnetic core 202. Next, as shown in the example, a... Figure 5a The through-hole 30 is shown. Then, a metal thin film layer (e.g., a copper layer) can be formed on the top surface A and bottom surface B of the second thin-film magnetic core 202, respectively. Using a patterning process (e.g., photolithography, including masking, exposure, etching, etc.), a first coil portion 213 wound with metal traces, such as copper traces, is formed on the top surface A of the second thin-film magnetic core 202, and a second coil portion 223 wound with copper traces is formed on the top surface B of the second thin-film magnetic core 202. The first coil portion 213 and the second coil portion 223 are coupled through the aforementioned through-hole 30 to form the aforementioned coil 203.

[0090] Next, the coil 203 and the second thin-film magnetic core 202, fabricated through the above steps, are placed into a mold. Then, the first magnetic material constituting the first thin-film magnetic core 201 is mixed with a colloid composed of organic materials and poured into the mold. Next, the material in the mold is solidified by applying pressure, thereby forming a first thin-film magnetic core 201 with the coil 203 and the second thin-film magnetic core 202 embedded inside, achieving the fabrication of... Figure 4 The purpose of the inductor shown.

[0091] In some embodiments of this application, the relative permeability of the second thin-film magnetic core 202 can be much greater than the relative permeability of the first thin-film magnetic core 201. For example, the relative permeability of the second thin-film magnetic core 202 can be 25 to 1000 times that of the relative permeability of the first thin-film magnetic core 201.

[0092] Based on this, when the current flowing through coil 203 is small, the curve of the inductance of inductor 20 changing with the current in coil 203 is shown. Figure 7 It can be seen that when the current value corresponding to node m1 is 0.01A, the magnitude of this current does not reach the saturation current of the first thin-film magnetic core 201 and the second thin-film magnetic core 202. At this time, neither the first thin-film magnetic core 201 nor the second thin-film magnetic core 202 has reached magnetic saturation. Under these circumstances, based on a magnetic induction line path distribution diagram of the inductor 20... Figure 8a (along Figure 4As shown in the cross-sectional view obtained by cutting along the dotted line OO, the coil 203 and the first thin-film magnetic core 201 surrounding the coil 203 can form a closed first magnetic induction line path ①. The coil 203 and the second thin-film magnetic core 202 located between the first coil portion 213 and the second coil portion 223 can form a closed second magnetic induction line path ②. At this time, since the second thin-film magnetic core 202 has not reached magnetic saturation, its relative permeability is relatively large. Therefore, the inductance of the inductor 20 is jointly determined by the first thin-film magnetic core 201 and the second thin-film magnetic core 202, resulting in a large inductance for the inductor 20. For example, Figure 7 The inductance value corresponding to the middle node m1 is 531.4707nH.

[0093] also, Figure 7 As shown, as the current flowing through coil 203 gradually increases, the inductance of inductor 20 gradually decreases. For example, when the current value on coil 203 corresponding to node m2 is 0.05A, the inductance of inductor 20 decreases to 530.1696nH. When the current value on coil 203 corresponding to node m3 is 0.2A, the inductance of inductor 20 decreases to 416.6498nH. When the current value on coil 203 corresponding to node m4 is 1A, the inductance of inductor 20 decreases to 143.095nH. When the current value on coil 203 corresponding to node m5 is 2A, the inductance of inductor 20 decreases to 92.3445nH.

[0094] When the current flowing through coil 203 is greater than or equal to the saturation current of the second thin-film magnetic core 202, for example Figure 7 When the current value corresponding to node m6 is 3A, the second thin-film magnetic core 202 gradually enters a magnetic saturation state and eventually reaches complete magnetic saturation, with its relative permeability decreasing to about 1. At this time, the relative permeability of the second thin-film magnetic core 202 is equivalent to that of a non-magnetic material, such as polyimide (PI). Under these circumstances, the coil 203 cannot form a closed second magnetic induction line path ② with the second thin-film magnetic core 202. Therefore, according to another magnetic induction line path distribution diagram of the inductor 20, Figure 8b As shown, the coil 203 forms a closed first magnetic induction path ① only with the first thin-film magnetic core 201. At this time, because the relative permeability of the second thin-film magnetic core 202 drops to a very low level, the inductance of the inductor 20 is mainly maintained by the first thin-film magnetic core 201, which has a lower relative permeability, thus causing the inductance to decrease, for example, to a certain value. Figure 7 The inductance value corresponding to the middle node m6 is 79.0537nH.

[0095] In this way, the inductance of the aforementioned inductor 20 can decrease as the current in the coil 203 increases, thus the inductance of inductor 20 can vary according to the change in the current flowing through the coil 203. For example, when the aforementioned inductor 20 is placed in the voltage conversion circuit 100 of the electronic device 01, on the one hand, when the electronic device 01, such as a mobile phone, is in standby mode, the voltage conversion circuit 100 is in a light-load state, and its load current is small. The current in the coil 203 of the inductor 20 is also small, for example, it can be 0.01A-0.05A. At this time, as can be seen from the above, the relative permeability of the second thin-film magnetic core 202 is relatively large. The inductance of inductor 20 is determined by both the first thin-film magnetic core 201 and the second thin-film magnetic core 202, so the inductor 20 has a large inductance, for example, its inductance can reach about 500nH. In this case, the inductor 20 can reduce the ripple of the output current of the voltage conversion circuit 100 during the filtering process, thereby reducing the AC loss of the ripple current and improving the conversion efficiency of the voltage conversion circuit 100 under light load conditions. When the load current of the voltage conversion circuit 100 is slightly larger, for example, 0.1A-2A, the relative permeability of the second thin-film magnetic core 202 gradually cancels out the current, and the inductance of the inductor 20 decreases accordingly. Figure 7 As shown, its inductance can be reduced from 530nH to 90nH.

[0096] On the other hand, when electronic device 01 switches applications or runs large programs, voltage conversion circuit 100 is under heavy load, with a large load current. The current in coil 203 of inductor 20 is also large, for example, 2A-5A. At this time, as mentioned above, the second thin-film magnetic core 202 is in a magnetic saturation state, reducing its relative permeability to about 1. Therefore, the inductance is mainly maintained by the first thin-film magnetic core 201, which has a lower relative permeability, further reducing the inductance to about 80nH and enabling voltage conversion circuit 100 to maintain a load current of 5A. During filtering, inductor 20 can reduce the AC impedance of current jumps, thereby improving the dynamic response of voltage conversion circuit 100 under heavy load conditions.

[0097] As can be seen from the above, the voltage conversion circuit 100 only needs to set the inductor 20 with variable inductance to meet the different inductance requirements of the voltage conversion circuit 100 under light load and heavy load. Therefore, it is not necessary to set two inductors with large inductance in the voltage conversion circuit 100, thereby reducing the board area in the electronic device 01 and reducing the resistance value (Rdc) of the inductor 20 under DC.

[0098] Based on this, such as Figure 9aAs shown, the second thin-film magnetic core 202 is further provided with a perforated structure 32 penetrating its top surface A and bottom surface B. For example, a portion of the material in the second thin-film magnetic core 202 can be removed to form the perforated structure 32 penetrating its top surface A and bottom surface B. This perforated structure 32 is not conductive.

[0099] like Figure 9b As shown, the hollow structure 32 is located within the area where the inner ring of the first coil portion 213 or the area where the inner ring of the second coil portion 223 is located is within the range of its vertical projection onto the second thin-film magnetic core 202. Thus, as... Figure 9a As shown, after the coil 203 and the second thin-film magnetic core 202 are embedded in the first thin-film magnetic core 201, some of the material in the first thin-film magnetic core 201 will fill the hollow structure 32.

[0100] In this case, since the relative permeability of the first thin-film magnetic core 201 is lower than that of the second thin-film magnetic core 202, the portion of the first thin-film magnetic core 201 with lower relative permeability located within the hollow structure 32 will connect to the rest of the first thin-film magnetic core 201. In this situation, when the current flowing through the coil 302 is too large, causing the second thin-film magnetic core 202 to be in a magnetically saturated state, the magnetic induction lines generated by the coil 203 and the entire first thin-film magnetic core 201 can remain continuous at the location of the hollow structure 32, without being affected by the air gap formed by the magnetically saturated second thin-film magnetic core 202. This avoids the inductance of the inductor 20 decreasing too much as the current increases, preventing the voltage conversion circuit 100 from being under heavy load and the inductance of the inductor 20 from failing to meet design requirements.

[0101] It should be noted that the first coil part 213 is as follows: Figure 9b As shown, the coils spiral around the top surface A of the second thin-film magnetic core 202, either from the inside out or from the outside in. Therefore, the inner ring of the first coil portion 213 refers to the innermost metal loop of the first coil portion 213.

[0102] Based on this, in order to enable the aforementioned inductor 20 to interact with other components in the voltage conversion circuit 100 (e.g., Figure 2 The diode D shown, or Figure 3 The DC-DC control chip 101 shown is coupled to the output terminal Uo of the voltage conversion circuit 100, and the inductor 20 is as follows: Figure 10As shown, it also includes a first end electrode 41 and a second end electrode 42 disposed on the outer surface of the first thin-film magnetic core 201. The second end of the first coil portion 213 (i.e., the end not coupled to the second coil portion 223) can pass through the first thin-film magnetic core 201 and be coupled to the first end electrode 41. The second end of the second coil portion 223 (i.e., the end not coupled to the first coil portion 213) can pass through the first thin-film magnetic core 201 and be coupled to the second end electrode 42.

[0103] In this case, the second end of the first coil portion 213 (i.e., the end not coupled to the second coil portion 223) can be coupled to other components in the voltage conversion circuit 100 (or the output terminal Uo of the voltage conversion circuit 100) through the first terminal electrode 41. The second end of the second coil portion 223 (i.e., the end not coupled to the first coil portion 213) can be coupled to the output terminal Uo of the voltage conversion circuit 100 (or other components in the voltage conversion circuit 100) through the second terminal electrode 42.

[0104] Example 2

[0105] The inductor 20 provided in this example, such as Figure 11a or Figure 15a As shown, the device includes a coil 203, a first magnetic core 301, and a second magnetic core 302. The coil 203 is embedded within the first magnetic core 301. The second magnetic core 302 may enclose at least a portion of the coil 203.

[0106] In order to achieve the goal of the second magnetic core 302 wrapping at least a portion of the coil 203, the following example illustrates the arrangement of the second magnetic core 302, the coil 203, and the first magnetic core 301 in the inductor 20.

[0107] In some embodiments of the present application, Figure 11a As shown, the first magnetic core 301 wraps around the outer surface of the coil 203 and is in contact with the outer surface of the coil 203. Figure 11b (along Figure 11a As shown in the cross-sectional view obtained by cutting the dotted line FF in the figure, the second magnetic core 302 wraps around the outer surface of the first magnetic core 301 and is in contact with the outer surface of the first magnetic core 301.

[0108] Based on this, the relative permeability of the first magnetic core 301 is lower than that of the second magnetic core 302. In some embodiments of this application, the first magnetic core 301 can be constructed using a first magnetic material with a relatively low permeability (e.g., a relative permeability of 20 to 50). For example, the material constituting the first magnetic core 301 may include at least one of an iron-silicon-chromium (FeSiCr) alloy or a carbonyl iron material. In this case, the first magnetic core 301 can have a higher magnetic saturation strength.

[0109] Furthermore, the second magnetic core 302 can be constructed using a second magnetic material with a relatively high permeability (e.g., a relative permeability of 500 to 50,000). For example, the material constituting the second magnetic core 302 may include at least one of alloy materials such as nickel-zinc ferrite (NiZnFeO), manganese-zinc ferrite (MnZnFeO), silicon steel, ferromolybdenum, or ferronickel, or amorphous (or nanocrystalline) magnetic materials. In this case, the second magnetic core 302 may have a lower magnetic saturation strength.

[0110] In some embodiments of this application, the following methods can be used to manufacture such a product. Figure 11a The inductor 20 is shown. For example, a coil 203 is first wound to form a coil, and then the coil 203 is placed in a mold. In this embodiment, the coil 203 can be made of enameled wire with an insulating layer coated on the surface of copper wire. Next, the magnetic powder material constituting the first magnetic core 301 is mixed with a colloid made of organic material and poured into a mold. Then, the material in the mold is solidified by applying pressure, thereby forming the first magnetic core 301 encasing the coil 203. Next, the second magnetic material constituting the second magnetic core 302 is used to form the second magnetic core 302 encasing the first magnetic core 301 and the coil 203, achieving the fabrication of... Figure 11a The purpose of the inductor shown is as follows. As can be seen from the above, the relative permeability of the second magnetic core 302 is greater than that of the first magnetic core 301. For example, the relative permeability of the second magnetic core 302 can be 25 to 1000 times that of the first magnetic core 301.

[0111] Based on this, when the current flowing through coil 203 is small, the curve of the inductance of inductor 20 changing with the current in coil 203 is shown. Figure 12 It can be seen that when the current value corresponding to node m1 is 0.01A, the magnitude of this current has not reached the saturation current of the first magnetic core 301 and the second magnetic core 302. At this time, neither the first magnetic core 301 nor the second magnetic core 302 has reached magnetic saturation. Under these circumstances, based on a magnetic induction line path distribution diagram of inductor 20... Figure 13a As shown, coil 203 and the first magnetic core 301 surrounding coil 203 can form a closed first magnetic induction path ①. Coil 203 and the second magnetic core 302 surrounding the first magnetic core 301 and coil 203 can form a closed second magnetic induction path ②. At this time, since the second magnetic core 302 has not reached magnetic saturation, its relative permeability is relatively large. Therefore, the inductance of the inductor is jointly determined by the first magnetic core 301 and the second magnetic core 302, resulting in a large inductance for the inductor 20. For example, Figure 12 The inductance value corresponding to the middle node m1 is 531.4628nH.

[0112] also, Figure 12As shown, the inductance of inductor 20 gradually decreases as the current flowing through coil 203 gradually increases. For example, when the current value on coil 203 corresponding to node m2 is 0.05A, the inductance of inductor 20 decreases to 523.7285nH. When the current value on coil 203 corresponding to node m3 is 0.2A, the inductance of inductor 20 decreases to 374.7749nH. When the current value on coil 203 corresponding to node m4 is 1A, the inductance of inductor 20 decreases to 399.5029nH. When the current value on coil 203 corresponding to node m5 is 2A, the inductance of inductor 20 decreases to 199.2926nH.

[0113] Furthermore, when the current flowing through coil 203 is greater than or equal to the saturation current of the second magnetic core 302, for example... Figure 12 When the current value corresponding to node m6 is 3A, the second magnetic core 302 gradually enters a magnetic saturation state and eventually reaches complete magnetic saturation, with its relative permeability decreasing to about 1, comparable to the permeability of air. Under these conditions, coil 203 cannot form a closed second magnetic induction path ② with the second magnetic core 302. Therefore, based on another magnetic induction path distribution diagram of inductor 20, Figure 13b As shown, the coil 203 forms a closed first magnetic induction line path ① only with the first magnetic core 301. At this time, because the relative permeability of the second magnetic core 302 drops to a very low level, the inductance of the inductor 20 is mainly maintained by the first magnetic core 301, which has a lower relative permeability, thus causing the inductance to decrease, for example, to a certain value. Figure 12 The inductance value corresponding to the middle node m6 is 146.0379nH. Compared with the inductor 20 provided in Example 1, the inductance of the inductor 20 provided in Example 2 decreases more slowly when the current flowing through the coil 203 causes the second magnetic core 302 to be in a magnetic saturation state.

[0114] In this way, the inductance of the aforementioned inductor 20 can decrease as the current in the coil 203 increases, thus the inductance of inductor 20 can vary according to the change in the current flowing through the coil 203. For example, when the aforementioned inductor 20 is placed in the voltage conversion circuit 100 of the electronic device 01, on the one hand, when the electronic device 01, such as a mobile phone, is in standby mode, the voltage conversion circuit 100 is in a light-load state, and its load current is small. The current in the coil 203 of the inductor 20 is also small, for example, it can be 0.01A-0.05A. At this time, as can be seen from the above, the relative permeability of the second magnetic core 202 is relatively large, and the inductance of inductor 20 is determined by both the first magnetic core 301 and the second magnetic core 302. Therefore, inductor 20 has a large inductance, for example, its inductance can reach about 520nH. In this case, the inductor 20 can reduce the ripple of the output current of the voltage conversion circuit 100 during the filtering process, thereby reducing the AC loss of the ripple current and improving the conversion efficiency of the voltage conversion circuit 100 under light load conditions. When the load current of the voltage conversion circuit 100 is slightly larger, for example, 0.1A-2A, the relative permeability of the second magnetic core 202 gradually cancels out the current, and the inductance of the inductor 20 decreases accordingly. Figure 12 As shown, its inductance can be reduced from 400nH to 200nH.

[0115] On the other hand, when electronic device 01 switches applications or runs large programs, voltage conversion circuit 100 is under heavy load, with a large load current. The current in coil 203 of inductor 20 is also large, for example, 2A-5A. At this time, as mentioned above, the second magnetic core 302 is in a magnetic saturation state, reducing its relative permeability to about 1. Therefore, the inductance is mainly maintained by the first magnetic core 301, which has a lower relative permeability, further reducing the inductance to about 140nH, allowing voltage conversion circuit 100 to maintain a load current of 5A. During filtering, inductor 20 can reduce the AC impedance of current jumps, thereby improving the dynamic response of voltage conversion circuit 100 under heavy load conditions.

[0116] As can be seen from the above, the voltage conversion circuit 100 only needs to set the inductor 20 with variable inductance to meet the different inductance requirements of the voltage conversion circuit 100 under light load and heavy load. Therefore, it is not necessary to set two inductors with large inductance in the voltage conversion circuit 100, thereby reducing the board area in the electronic device 01 and reducing the resistance value (Rdc) of the inductor 20 under DC.

[0117] Based on this, in order to enable the aforementioned inductor 20 to interact with other components in the voltage conversion circuit 100 (e.g., Figure 2 The diode D shown, or Figure 3The DC-DC control chip 101 shown is coupled to the output terminal Uo of the voltage conversion circuit 100, and the inductor 20 is as follows: Figure 14 As shown, it also includes a first end electrode 41 and a second end electrode 42 disposed on the outer surface of the second magnetic core 302. The first end of the coil 203 passes through the first magnetic core 301 and the second magnetic core 302 and is coupled to the first end electrode 41. The second end of the coil 203 passes through the first magnetic core 301 and the second magnetic core 302 and is coupled to the second end electrode 42.

[0118] In this case, the first end of the coil 203 can be coupled to other components in the voltage conversion circuit 100 (or the output terminal Uo of the voltage conversion circuit 100) via the first terminal electrode 41. The second end of the coil 203 can be coupled to the output terminal Uo of the voltage conversion circuit 100 (or other components in the voltage conversion circuit 100) via the second terminal electrode 42.

[0119] In order to achieve the goal of the second magnetic core 302 wrapping at least a portion of the coil 203, in some other embodiments of this application, such as Figure 15a As shown, coil 203 includes a first conductor segment 233 and a second conductor segment 243 connected to each other. A second magnetic core 302 surrounds and contacts the outer surface of the first conductor segment 233. Figure 15b (along Figure 15a As shown in the cross-sectional view obtained by cutting along the dotted line GG in the image, both the coil 203 and the second magnetic core 302 are embedded within the first magnetic core 301. The first magnetic core 301 encloses the second conductor segment 243 of the coil 203 (as shown in the image). Figure 15a The outer surface of the first magnetic core 301 (as shown) and the outer surface of the second magnetic core 302 are in contact with the outer surface of the second conductor segment 243 and the outer surface of the second magnetic core 302. Based on this, the relative permeability of the first magnetic core 301 is less than the relative permeability of the second magnetic core 302. The materials of the first magnetic core 301 and the second magnetic core 302 are the same as described above and will not be repeated here.

[0120] In some embodiments of this application, the following methods can be used to manufacture such a product. Figure 15a The inductor 20 is shown. For example, a coil 203 is first wound to form a coil. Then, a tubular second magnetic core 302 is formed using the aforementioned second magnetic material constituting the second magnetic core 302. The second magnetic core 302 is then fitted onto the coil 203 such that it wraps around and contacts the outer surface of the first conductor segment 233 within the coil 203.

[0121] Next, the coil 203, fitted with the second magnetic core 302, is placed into another mold. Then, the magnetic powder material constituting the first magnetic core 301 is mixed with a colloid made of organic material and poured into the mold. Next, the material in the mold is cured by applying pressure to form the first magnetic core 301, which includes the second magnetic core 302 and the coil 203, thus achieving the fabrication of... Figure 15a The purpose of the inductor 20 shown.

[0122] As mentioned above, the relative permeability of the second magnetic core 302 is greater than that of the first magnetic core 301. Therefore, as also stated above, when the current flowing through the coil 203 is small, the curve showing the change in inductance of the inductor 20 with the current in the coil 203 indicates that... Figure 16 It can be seen that when the current value corresponding to node m1 is 0.01A, the magnitude of this current has not reached the saturation current of the first magnetic core 301 and the second magnetic core 302. At this time, neither the first magnetic core 301 nor the second magnetic core 302 has reached magnetic saturation. Under these circumstances, based on a magnetic induction line path distribution diagram of inductor 20... Figure 17a As shown, the first magnetic core 301 and the second conductor segment 243 (as shown) in the coil 203 Figure 15a As shown, a closed first magnetic induction line path ① can be generated. The second magnetic core 302 and the first conductor coil 233 in the coil 203 (as shown) Figure 15a As shown, a closed second magnetic induction line path ② can be generated on the cross-section of the tubular second magnetic core 302. At this time, since the second magnetic core 302 has not reached magnetic saturation, its relative permeability is relatively large. Therefore, the inductance of the inductor 20 is jointly determined by the first magnetic core 301 and the second magnetic core 302, resulting in a large inductance for the inductor 20. For example, Figure 16 The inductance value corresponding to the middle node m1 is 486.9236nH.

[0123] also, Figure 16 As shown, as the current flowing through coil 203 gradually increases, the inductance of inductor 20 gradually decreases. For example, when the current value on coil 203 corresponding to node m2 is 0.05A, the inductance of inductor 20 decreases to 240.1096nH. When the current value on coil 203 corresponding to node m3 is 0.2A, the inductance of inductor 20 decreases to 183.2572nH. When the current value on coil 203 corresponding to node m4 is 1A, the inductance of inductor 20 decreases to 129.1716nH. When the current value on coil 203 corresponding to node m5 is 2A, the inductance of inductor 20 decreases to 124.6575nH.

[0124] Furthermore, when the current flowing through coil 203 is greater than or equal to the saturation current of the second magnetic core 302, for example... Figure 16When the current value corresponding to node m6 is 3A, the second magnetic core 302 gradually enters a magnetic saturation state and eventually reaches complete magnetic saturation, with its relative permeability decreasing to about 1. Under these conditions, coil 203 cannot form a closed second magnetic induction path ② with the second magnetic core 302. Therefore, another magnetic induction path distribution diagram of inductor 20 is shown. Figure 17b As shown, the coil 203 forms a closed first magnetic induction line path ① only with the first magnetic core 301. At this time, because the relative permeability of the second magnetic core 302 drops to a very low level, the inductance of the inductor 20 is mainly maintained by the first magnetic core 301, which has a lower relative permeability, thus causing the inductance to decrease, for example, to a certain value. Figure 16 The inductance value corresponding to the middle node m6 is 121.1340nH.

[0125] As in this example, Figure 11a Compared to the inductor shown, since the second magnetic induction line path ② is concentrated in the tubular second magnetic core 203, when the current flowing through the coil 203 causes the second magnetic core 302 to be in a magnetic saturation state, Figure 15a The inductance of the inductor 20 shown decreases rapidly.

[0126] Thus, as mentioned above, the inductance of the inductor 20 can decrease as the current in the coil 203 increases. Therefore, the inductance of the inductor 20 can vary according to the change in the current flowing through the coil 203. For example, when the inductor 20 is placed in the voltage conversion circuit 100 of the electronic device 01, the current in the coil 203 of the inductor 20 can be 0.01A-0.05A when the voltage conversion circuit 100 is under light load. At this time, the inductor 20 has a large inductance, for example, its inductance can reach about 480nH-240nH. This improves the conversion efficiency of the voltage conversion circuit 100 under light load. When the load current of the voltage conversion circuit 100 is slightly larger, for example, it can be 0.1A-1A, the relative permeability of the second magnetic core 202 gradually cancels out, and the inductance of the inductor 20 decreases accordingly. Figure 16 As shown, its inductance can decrease from 210nH to 130nH. Furthermore, when the voltage conversion circuit 100 is under heavy load, the current in the coil 203 of the inductor 20 is also relatively large, for example, 1A-5A. The inductance of the inductor 20 is further reduced to approximately 120nH to improve the dynamic response of the voltage conversion circuit 100 under heavy load conditions.

[0127] Based on this, in order to enable the aforementioned inductor 20 to interact with other components in the voltage conversion circuit 100 (e.g., Figure 2 The diode D shown, or Figure 3 The DC-DC control chip 101 shown is coupled to the output terminal Uo of the voltage conversion circuit 100. Similarly, the inductor 20 is as described above. Figure 18 As shown, it also includes a first end electrode 41 and a second end electrode 42 disposed on the outer surface of the first magnetic core 301. The first end of the second conductor segment 243 passes through the first magnetic core 301 and is coupled to the first end electrode 41, and the second end of the second conductor segment 243 is coupled to the first end of the first conductor segment 233. Furthermore, the second end of the first conductor segment 233 passes through at least the first magnetic core 301 and is coupled to the second end electrode 42.

[0128] It should be noted that "the second end of the first conductor segment 233 at least passes through the first magnetic core 301 to couple with the second terminal electrode 42" means that when the second magnetic core 302 is far from the second terminal electrode 42, the second end of the first conductor segment 233 can couple with the second terminal electrode 42 only by passing through the first magnetic core 301. Alternatively, when the second magnetic core 302 is close to the second terminal electrode 42, the second end of the first conductor segment 233 can couple with the second terminal electrode 42 by passing through both the second magnetic core 302 and the first magnetic core 301.

[0129] In this case, the first end of the second conductor segment 243 in the coil 203 can be coupled to other components in the voltage conversion circuit 100 (or the output terminal Uo of the voltage conversion circuit 100) through the first terminal electrode 41. The second end of the first conductor segment 233 in the coil 203 can be coupled to the output terminal Uo of the voltage conversion circuit 100 (or other components in the voltage conversion circuit 100) through the second terminal electrode 42.

[0130] As can be seen from the above, in the production of such Figure 15a When the inductor 20 is shown, the pre-fabricated tubular second magnetic core 302 can be inserted into the coil 203. The portion of the coil 203 enclosed by the second magnetic core 302 serves as the aforementioned first conductor segment 233. Since the coil 203 is mostly spiral-shaped, but can be straight near the first end electrode 41 or the second end electrode 42, it can be designed to more easily insert the tubular second magnetic core 302 into the coil 203 as follows: Figure 18 As shown, the second magnetic core 302 is positioned close to the first end electrode 41. In this case, the first conductor segment 233 of the coil 203, which is wrapped by the second magnetic core 302, is the portion of the coil 203 that is close to the second end electrode 42.

[0131] Example 3

[0132] The inductor 20 provided in this example includes, for example: Figure 19a The diagram shows a coil 203, a first magnetic core 301, and a second magnetic core 302, with the coil 302 embedded within the first magnetic core 301. The relative permeability of the first magnetic core 301 is less than that of the second magnetic core 302. The materials constituting the coil 203, the first magnetic core 301, and the second magnetic core 302 are as described above and will not be repeated here.

[0133] The difference between this and the inductor 20 provided in the previous example is that, as Figure 19a As shown, the second magnetic core 302 includes an upper cover 312, a lower base 322, and a first core post 332. During the fabrication of the inductor 20, the second magnetic core 302, including the upper cover 312, lower base 322, and first core post 332, can be formed using the aforementioned second magnetic material constituting the second magnetic core 302. Then, as... Figure 19b As shown, a coil 203 is formed by winding metal wires around the first core post 332, so that the coil 203 is wrapped around the first core post 332. Next, the second magnetic core 302 with the coil 203 wound around it is placed in another mold, and the first magnetic material constituting the first magnetic core 201 is mixed with a colloid made of organic material and poured into the mold. Next, the material in the mold is solidified by applying pressure to form the first magnetic core 201 located between the upper cover 312 and the lower bottom 322, and enclosing the coil 203 and the first core post 332, thereby completing the process. Figure 19a The fabrication of inductor 20 shown.

[0134] In this configuration, the upper cover 312 covers the upper surface of the first magnetic core 301 (the surface near the upper cover 312) and is in contact with the upper surface of the first magnetic core 301. The lower base 322 covers the lower surface of the first magnetic core 301 (the surface near the lower base 322) and is in contact with the lower surface of the first magnetic core 301. Furthermore, the first core post 332 is embedded within the first magnetic core 301, with its first end passing through the first magnetic core 301 and connecting to the upper cover 312, and its second end passing through the first magnetic core 301 and connecting to the lower base 322.

[0135] As mentioned above, when a small current flows through coil 203, neither the first magnetic core 301 nor the second magnetic core 302 reaches magnetic saturation. At this time, inductor 20 has a large capacitance. As the current in coil 203 gradually increases, due to the first core post 332 in the second magnetic core 302... Figure 19b As shown, it is located in the middle of the coil. Therefore, under the action of the first core column 332 connecting the upper cover 312 and the lower bottom 322, the second magnetic core 302 can reach the magnetic saturation state more quickly, so that the inductance of the inductor 20 decreases faster as the current increases.

[0136] In other embodiments of this example, to prevent the inductance of inductor 20 from decreasing too rapidly and falling below the design inductance value as the current in coil 203 increases, the second magnetic core 302 also includes, for example... Figure 20a The second core post 342 is shown. The second core post 342 is embedded within the first magnetic core 301.

[0137] Furthermore, the second core post 342 and the first core post 332 have a gap such as Figure 20b The gap H shown is filled with a portion of the material from the first magnetic core 301. In this case, when manufacturing as shown... Figure 20a When the inductor 20 is shown, the coil can be wound around the first core post 332 and the second core post 342. The first end of the second core post 342 passes through the first magnetic core 301 and is connected to the upper cover 312, and the second end of the second core post 342 passes through the first magnetic core 301 and is connected to the lower base 322.

[0138] As mentioned above, the relative permeability of the second magnetic core 302 is greater than that of the first magnetic core 301. Therefore, as also stated above, when the current flowing through the coil 203 is small, the curve showing the change in inductance of the inductor 20 with the current in the coil 203 indicates that... Figure 21 It can be seen that when the current value corresponding to node m1 is 0.01A, the magnitude of this current has not reached the saturation current of the first magnetic core 301 and the second magnetic core 302. At this time, neither the first magnetic core 301 nor the second magnetic core 302 has reached magnetic saturation. Under these circumstances, based on a magnetic induction line path distribution diagram of inductor 20... Figure 22a As shown, coil 203 and the first magnetic core 301 can generate a closed first magnetic induction line path ①. The magnetic induction lines generated by coil 203 and the second magnetic core 302 can sequentially enter the upper cover 312, the first magnetic core 301, and the lower base 322 along the closed second magnetic induction line path ②, and then return to the first core post 332 and the second core post 342. Since coil 203 is wrapped around the first core post 332 and the second core post 342, the distribution of magnetic induction lines in the second magnetic induction line path ② is more concentrated. At this time, since the second magnetic core 302 has not reached magnetic saturation, its relative permeability is relatively large. At this time, the inductance of inductor 20 is jointly determined by the first magnetic core 301 and the second magnetic core 302, so the inductor 20 has a large inductance, for example, Figure 21 The inductance value corresponding to the middle node m1 is 807.4817nH.

[0139] also, Figure 21 As shown, as the current flowing through coil 203 gradually increases, the inductance of inductor 20 gradually decreases. For example, when the current value on coil 203 corresponding to node m2 is 0.05A, the inductance of inductor 20 decreases to 788.9193nH. When the current value on coil 203 corresponding to node m3 is 0.2A, the inductance of inductor 20 decreases to 558.6405nH. When the current value on coil 203 corresponding to node m4 is 1A, the inductance of inductor 20 decreases to 182.6046nH. When the current value on coil 203 corresponding to node m5 is 2A, the inductance of inductor 20 decreases to 147.4592nH.

[0140] Furthermore, when the current flowing through coil 203 is greater than or equal to the saturation current of the second magnetic core 302, for example... Figure 21 When the current value corresponding to node m6 is 3A, the second magnetic core 302 gradually enters a magnetic saturation state and eventually reaches complete magnetic saturation, with its relative permeability decreasing to about 1. Under these conditions, coil 203 cannot form a closed second magnetic induction path ② with the second magnetic core 302. Therefore, based on a magnetic induction path distribution diagram of inductor 20, Figure 22b As shown, the coil 203 forms a closed first magnetic induction line path ① only with the first magnetic core 301. At this time, because the relative permeability of the second magnetic core 302 drops to a very low level, the inductance of the inductor 20 is mainly maintained by the first magnetic core 301, which has a lower relative permeability, thus causing the inductance to decrease, for example, to a certain value. Figure 21 The inductance value corresponding to the middle node m6 is 119.7743nH.

[0141] As described above, because coil 203 is wound around the first core post 332 and the second core post 342, the distribution of magnetic induction lines in the second magnetic induction line path ② is more concentrated. Therefore, when the current in coil 203 gradually increases, the second magnetic core 302 can reach magnetic saturation more quickly, causing the inductance of inductor 20 to decrease faster with increasing current. Furthermore, after the second magnetic core 302 reaches magnetic saturation, the first magnetic core 301 inside the gap H between the first core post 332 and the second core post 342 connects the remaining parts of the first magnetic core 301, ensuring that the magnetic induction lines generated by coil 203 and the entire first magnetic core 301 are continuous at the gap H. This prevents the inductance of inductor 20 from decreasing too much with increasing current, thus avoiding a drop in inductance that fails to meet design requirements.

[0142] Thus, as mentioned above, the inductance of the inductor 20 can decrease as the current in the coil 203 increases. Therefore, the inductance of the inductor 20 can vary according to the change in the current flowing through the coil 203. For example, when the inductor 20 is placed in the voltage conversion circuit 100 of the electronic device 01, the current in the coil 203 of the inductor 20 can be 0.01A-0.05A when the voltage conversion circuit 100 is under light load. At this time, the inductor 20 has a large inductance, for example, its inductance can reach about 800nH. This improves the conversion efficiency of the voltage conversion circuit 100 under light load. When the load current of the voltage conversion circuit 100 is slightly larger, for example, it can be 0.1A-2A, the relative permeability of the second magnetic core 202 gradually cancels out, and the inductance of the inductor 20 decreases accordingly. Figure 21As shown, its inductance can decrease from 670nH to 140nH, and the inductance value decreases very quickly. Furthermore, when the voltage conversion circuit 100 is under heavy load, the current in the coil 203 of the inductor 20 is also relatively large, for example, 2A-5A. The inductance of the inductor 20 further decreases to about 120nH while maintaining a current of 5A to improve the dynamic response of the voltage conversion circuit 100 under heavy load conditions.

[0143] Based on this, in order to enable the aforementioned inductor 20 to interact with other components in the voltage conversion circuit 100 (e.g., Figure 2 The diode D shown, or Figure 3 The DC-DC control chip 101 shown is coupled to the output terminal Uo of the voltage conversion circuit 100. Similarly, the inductor 20 is as described above. Figure 23 As shown, it also includes a first end electrode 41 and a second end electrode 42 disposed on the side of the first magnetic core 301.

[0144] In this configuration, the side surface of the first magnetic core 301 is located between its upper surface (the surface in contact with the upper cover 312) and its lower surface (the surface in contact with the lower base 322), and the second magnetic core 302 does not cover the side surface of the first magnetic core 301. In this configuration, the first end of the coil 203 passes through the first magnetic core 301 and is coupled to the first end electrode 41. The second end of the coil 203 passes through the first magnetic core 301 and is coupled to the second end electrode 42.

[0145] In this case, the first end of the coil 203 can be coupled to other components in the voltage conversion circuit 100 (or the output terminal Uo of the voltage conversion circuit 100) via the first terminal electrode 41. The second end of the coil 203 can be coupled to the output terminal Uo of the voltage conversion circuit 100 (or other components in the voltage conversion circuit 100) via the second terminal electrode 42.

[0146] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. An inductor, characterized in that, The inductor includes coil; A first magnetic core, the coil being embedded within the first magnetic core; The second magnetic core includes an upper cover, a lower base, and a first core post; the upper cover covers the upper surface of the first magnetic core and is in contact with the upper surface of the first magnetic core. The bottom cover covers the lower surface of the first magnetic core and is in contact with the lower surface of the first magnetic core; The first core post is embedded in the first magnetic core, the coil is wound around the first core post, the first end of the first core post passes through the first magnetic core and is connected to the upper cover, and the second end of the first core post passes through the first magnetic core and is connected to the lower bottom. The relative permeability of the first magnetic core is less than that of the second magnetic core.

2. The inductor according to claim 1, characterized in that, The second magnetic core further includes a second core post, which is embedded in the first magnetic core and has a gap between it and the first core post; a portion of the material of the first magnetic core fills the gap; the coil is wound around the first core post and the second core post; a first end of the second core post passes through the first magnetic core and is coupled to the upper cover, and a second end of the second core post passes through the first magnetic core and is coupled to the lower bottom; wherein the material constituting the second core post is the same as the material constituting the second magnetic core.

3. The inductor according to claim 1, characterized in that, The first magnetic core also includes a side surface located between the upper and lower surfaces of the first magnetic core; the second magnetic core does not cover the side surface; The inductor further includes a first end electrode and a second end electrode disposed on the side of the first magnetic core; the first end of the coil passes through the first magnetic core and is coupled to the first end electrode; the second end of the coil passes through the first magnetic core and is coupled to the second end electrode; the second end of the coil passes through the first magnetic core and the second magnetic core and is coupled to the second end electrode.

4. The inductor according to claim 1, characterized in that, The relative permeability of the second magnetic core is 25 to 1000 times that of the first magnetic core.

5. A method for manufacturing an inductor, characterized in that, The method includes: A second magnetic core is formed using a second magnetic material. The second magnetic core includes an upper cover, a lower base, and a first core post located between the upper cover and the lower base. A first end of the first core post is connected to the upper cover, and a second end of the first core post is connected to the lower base. A coil is formed by winding metal wires on the first core post. The coil and the second magnetic core are placed in a mold. A first magnetic material is injected into the mold and pressed with the coil and the second magnetic core to form a first magnetic core that encloses the coil and the first core post. The upper surface of the first magnetic core is in contact with the upper cover, and the lower surface is in contact with the lower bottom.

6. The inductor manufacturing method according to claim 5, characterized in that, The method for forming the second magnetic core further includes: simultaneously fabricating the upper cover, lower base, and first core post using a second magnetic material, fabricating a second core post located between the upper cover and lower base, wherein the first end of the second core post is connected to the upper cover, the second end of the second core post is connected to the lower base, and there is a gap between the second core post and the first core post; forming the coil by winding metal wires on the first core post and the second core post; placing the coil and the second magnetic core into a mold, injecting the first magnetic material into the mold, and pressing it with the coil and the second magnetic core to form a first magnetic core that encloses the coil, the first core post, and the second core post, wherein part of the material of the first magnetic core fills the gap.

7. A voltage conversion circuit, characterized in that, Includes a control switch and an inductor as described in any one of claims 1-4; The control switch is coupled between the input terminal of the voltage conversion circuit and the first electrode of the inductor; The second electrode of the inductor is coupled to the output terminal of the voltage conversion circuit.

8. An electronic device, characterized in that, It includes a printed circuit board and at least one voltage conversion circuit as described in claim 7; the voltage conversion circuit is disposed on the printed circuit board.

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