A miniature transformer applicable to a low-power charger and its rapid assembly method

Abstract

The present application relates to a micro-transformer applicable to a low-power charger and a rapid assembly method thereof, which includes a fixed iron core and a movable iron core arranged on a base, and an air gap is reserved between the fixed iron core and the movable iron core; a limit seat located at one end of the skeleton is detachably installed on the base, and the movable iron core is located between the limit seat and the skeleton; a plurality of bimetallic sheets are installed on one side of the skeleton close to the limit seat, and the bimetallic sheets are configured to control the increase of the air gap when the temperature rises; a plurality of shape memory alloy springs are arranged between the limit seat and the movable iron core, and the shape memory alloy springs are configured to transform into austenite phase and soften when the temperature rise exceeds its phase transition temperature; when the temperature is lower than its phase transition temperature, the shape memory alloy springs transform into martensite phase and recover elasticity to drive the movable iron core away from the limit seat, so as to reduce the air gap. The present application has the effect of automatically adjusting the air gap with the temperature rise and controlling the temperature rise to ensure the electromagnetic efficiency in different load states.

Description

Technical Field

[0001] This application relates to the technical field of transformers, and particularly relates to a micro-transformer applicable to a low-power charger and a rapid assembly method thereof. Background Art

[0002] The micro-transformer in a low-power charger is an electronic component used for voltage conversion and isolation. Different from the large transformers in traditional linear power supplies, the micro-transformer has the characteristics of small size, light weight, and high efficiency. It mainly includes a bobbin, a primary coil, a secondary coil, and an insulating material for isolating the primary coil and the secondary coil. The primary coil serves as the input end, and the secondary coil serves as the output end. The number of turns of the primary coil is much larger than that of the secondary coil, which can convert high voltage into low voltage. When winding on the bobbin, the "sandwich" winding method is generally adopted, that is, winding a group of primary coils in the inner circle and then winding several groups of secondary coils, and finally winding a group of primary coils in series with the primary coil in the inner circle on the periphery, which can improve the magnetoelectric conversion efficiency.

[0003] In the related technology, Chinese Patent with application number CN202311349390.9 proposed a micro-transformer applicable to a low-power charger and a rapid assembly method thereof. The micro-transformer includes a bobbin disposed on a base; an iron core including two semi-iron core parts symmetrically disposed outside the bobbin; a coil winding including two primary coil windings and several secondary coil windings wound around the bobbin; pins disposed on the bobbin. A potting space is formed between the base and the iron core, and epoxy resin is potted in the potting space. The epoxy resin is cured and formed to make the bobbin, the iron core, the coil winding, and the pins form an integral structure. On the one hand, it increases the connection strength of the transformer, thereby improving the overall strength of the transformer and avoiding problems such as structural scattering and contact point breakage of the transformer when it is dropped or collided in the charger. On the other hand, it plays an insulating protection role. The transformer formed by potting with epoxy resin has the function of waterproofing and moisture-proofing, and improves the insulation performance of the transformer in the charger.

[0004] The above-mentioned related technology has the following defects: For the semi-iron core, it is generally integrally formed by an outer frame part and an iron column part. During assembly, the two iron column parts of the two semi-iron cores penetrate into the hollow part of the bobbin. The two iron column parts serve as the magnetic path of the transformer, and an air gap provided between the two iron column parts can be used to control the magnetic flux density and adjust the performance of the transformer, avoiding the influence on the magnetoelectric conversion efficiency and increasing heat dissipation after magnetic saturation of the two iron column parts. Currently, the air gap is generally an optimal air gap determined under all working conditions. For the transformer under different loads, this optimal air gap is not the optimal air gap; moreover, when the transformer is in a high-load state, the constant air gap will cause an increase in iron loss of the iron core and a significant increase in heat generation, which is not conducive to the control of the overall efficiency of the transformer. Summary of the invention

[0005] In order to improve the problem that the constant air gap of the existing transformer is not conducive to improving the overall efficiency of the transformer, the present application provides a miniature transformer suitable for a low-power charger and a quick assembly method thereof.

[0006] The first aspect of the present application provides a micro transformer suitable for a low-power charger, which adopts the following technical solution:

[0007] A micro transformer suitable for a low-power charger, comprising a base, a frame, a primary coil and a secondary coil, wherein the base is provided with an input pin connected to the primary coil and an output pin connected to the secondary coil, an insulating layer is provided between the primary coil and the secondary coil, the base is provided with a fixed iron core fixed to the base and a movable iron core slidably provided on the base, the fixed iron core and the movable iron core both comprising an outer frame portion and an iron column portion, and an air gap is reserved between the two iron column portions;

[0008] A limit seat located at one end of the frame is detachably mounted on the base, and the movable iron core is located between the limit seat and the frame;

[0009] A plurality of bimetallic strips are installed on one side of the frame close to the limit seat, and the bimetallic strips are configured to deform and warp toward a side away from the frame when the temperature they sense increases, and push the movable iron core close to the limit seat, so as to increase the air gap;

[0010] A plurality of shape memory alloy springs are arranged between the limit seat and the movable iron core. The shape memory alloy springs are configured such that when the temperature sensed by them exceeds their phase transition temperature, the shape memory alloy springs transform into an austenite phase and soften; and when the temperature sensed by them is lower than their phase transition temperature, the shape memory alloy springs transform into a martensite phase and restore elasticity to drive the movable iron core away from the limit seat so that the air gap is reduced.

[0011] Furthermore, the bimetallic strips are provided in plurality and are distributed in an equally spaced circular array along the central axis of the cylindrical portion of the skeleton, a plurality of insert seats are fixedly connected to the skeleton, the insert seats have an insert opening for inserting the head end of the bimetallic strip, the insert seats with two insert openings facing each other form a group, and the two ends of the bimetallic strip are respectively inserted into the two insert seats of the same group.

[0012] Furthermore, the limiting seat has a plurality of accommodating grooves for embedding and fixing one end of a plurality of the shape memory alloy springs.

[0013] Further, a plurality of limiting protrusions corresponding to the movable iron core are fixedly connected to one side of the limiting seat close to the skeleton. When the movable iron core slides to abut against the limiting protrusions, the air gap between the two iron column parts of the movable iron core and the fixed iron core is 1 mm.

[0014] Further, when the movable iron core slides to abut against the socket, the air gap between the two iron column parts of the movable iron core and the fixed iron core is not less than 0.1 mm.

[0015] Further, polytetrafluoroethylene patches are provided on the inner peripheral walls of the base and the cylindrical part of the skeleton, and the polytetrafluoroethylene patches are arranged corresponding to the movement track of the movable iron core.

[0016] Further, a buckle cover is fixed on the base and wraps around the outer frame parts of the fixed iron core and the movable iron core. The buckle cover is open at both axial ends of the cylindrical part of the skeleton. The inner wall of the buckle cover abuts against the fixed iron core and a sliding gap is reserved between the buckle cover and the movable iron core.

[0017] Further, a plurality of tenons are fixedly connected to two opposite side walls of the base corresponding to the butt joint of the two outer frame parts, and a tenon seat for clamping connection with the tenons is fixedly connected to one end of the buckle cover close to the base.

[0018] A rapid assembly method for a micro-transformer applicable to a low-power charger provided in the second aspect of the present application adopts the following technical solutions:

[0019] A rapid assembly method for a micro-transformer applicable to a low-power charger, based on the above-mentioned micro-transformer applicable to a low-power charger, includes the following steps:

[0020] S1. Coil winding, winding the primary coil and the secondary coil on the cylindrical part of the skeleton by the sandwich method, and installing the skeleton on the base;

[0021] S2. Iron core installation, placing the fixed iron core and the movable iron core at both ends of the skeleton, and inserting the two iron column parts into the hollow part of the cylindrical part of the skeleton;

[0022] S3. Fitting installation, installing a plurality of the bimetallic sheets at one end of the skeleton close to the movable iron core, then completely attaching the movable iron core to the skeleton, installing a plurality of the shape memory alloy springs on the limiting seat, and then installing the limiting seat on the base, and adjusting the shape memory alloy springs to align them with the movable iron core;

[0023] S4. Momentum verification: place the base horizontally, slide the movable iron core left and right in the gap between the limit seat and the frame and detect the size of the air gap to verify that the size of the air gap is not less than 0.1 mm and not more than 1 mm under the limit momentum of the movable iron core in two directions.

[0024] Furthermore, in step S2, before installing the movable iron core, a polytetrafluoroethylene patch is provided at a position of the base and the frame corresponding to the motion track of the movable iron core;

[0025] In step S3, a buckle cover mounted on the base is also assembled at the joint of the two outer frame parts, and the buckle cover is used to assist in fixing the fixed iron core and limit the shaking amount of the movable iron core.

[0026] In summary, the beneficial technical effects of this application are:

[0027] 1. When the temperature rise of the micro-transformer during operation is sensed by the multiple shape memory alloy springs on the limit seat, once the temperature rise exceeds the phase change temperature of the shape memory alloy spring, the shape memory alloy spring transforms into austenite and softens, and its own elastic force decreases or even disappears, and it can no longer push the movable iron core, so that the iron column of the movable iron core can slide freely in the cylindrical part of the skeleton at this time; and the bimetallic strip expands and deforms due to heat, so that its middle part is strongly bent in the direction away from the skeleton. Under the push of the bending deformation force of multiple bimetallic strips, the movable iron core can move toward the limit seat. At this time, the distance between the two iron columns is enlarged, so that the air gap is increased, which can control the temperature rise of the transformer to a certain extent, avoid overheating, and ensure the electromagnetic efficiency of the micro-transformer;

[0028] 2. When the temperature of the micro-transformer decreases, based on the principle of thermal expansion and contraction, the bending tendency of the middle part of the bimetallic strip weakens, the pushing effect on the movable iron core is lost, and it shrinks to the corresponding bending degree according to the corresponding temperature; and for the shape memory alloy spring, once the temperature of the micro-transformer drops to the temperature sensed by the shape memory alloy spring is lower than the phase transition temperature, the shape memory alloy spring transforms into the martensite phase and restores its elasticity to drive the movable iron core away from the limit seat, so that the movable iron core moves to be close to the bent parts of the multiple bimetallic strips, and at this time the distance between the two iron column parts is reduced to reduce the air gap;

[0029] 3. Through the arrangement of multiple bimetallic strips and multiple shape memory alloy springs, the air gap between the movable iron core and the fixed iron core increases with the temperature rise of the micro-transformer, and decreases and recovers with the temperature drop of the micro-transformer, thereby realizing the dynamic adjustment of the air gap of the micro-transformer, and autonomously controlling its temperature rise to ensure its electromagnetic efficiency under different load conditions as much as possible;

[0030] 4. Since both ends of the bimetal are embedded in the sockets at both ends, while increasing the bending deformation thrust of the bimetal, the actuation stroke is reduced, which is particularly suitable for high-precision adjustment with an air gap in the range of 0.1 mm to 1 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of the overall structure of an embodiment of the present application;

[0032] Figure 2 is a side view of the overall structure of an embodiment of the present application;

[0033] Figure 3 is a top view of the overall structure of an embodiment of the present application;

[0034] Figure 4 is along Figure 3 the sectional structure schematic diagram taken along line A-A in

[0035] Figure 5 is an exploded structure schematic diagram of an embodiment of the present application;

[0036] Figure 6 is an exploded structure schematic diagram from another perspective of an embodiment of the present application;

[0037] Figure 7 is along Figure 3 the sectional structure schematic diagram taken along line B-B in

[0038] Description of the reference numerals:

[0039] 1, base; 11, input pin; 12, output pin; 13, tenon; 14, fixing hole; 15, positioning hole;

[0040] 2, skeleton; 21, socket; 211, socket opening;

[0041] 31, primary coil; 32, secondary coil;

[0042] 41, fixed iron core; 42, movable iron core; 401, outer frame part; 402, iron column part; 43, air gap;

[0043] 5, limit seat; 51, receiving groove; 52, limit protrusion; 53, fixing column; 54, fixing screw;

[0044] 61, bimetal; 62, shape memory alloy spring;

[0045] 7, buckle cover; 71, sliding gap; 72, tenon seat; 73, positioning column. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The technical solution of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0047] An embodiment of the present application discloses a micro-transformer applicable to a low-power charger. Referring to Figures 1-4 , it includes a base 1, a bobbin 2, a primary coil 31 and a secondary coil 32. An input pin 11 connected to the primary coil 31 and an output pin 12 connected to the secondary coil 32 are provided on the base 1. An insulating layer is provided between the primary coil 31 and the secondary coil 32.

[0048] A fixed iron core 41 fixed on the base 1 and a movable iron core 42 slidably arranged on the base 1 are provided on the base 1. The sliding direction of the movable iron core 42 is arranged along the axial direction of the cylindrical part of the bobbin 2. Both the fixed iron core 41 and the movable iron core 42 include an outer frame part 401 and an iron column part 402, and the outer frame part 401 and the iron column part 402 are integrally in an "E" shape. A gap 43 is reserved between the two iron column parts 402. Based on the conventional setting of the micro-transformer, the size range of the gap 43 is 0.1 mm to 1 mm. A limit seat 5 located at one end of the bobbin 2 is detachably installed on the base 1. The iron column part 402 of the movable iron core 42 is located between the limit seat 5 and the bobbin 2. Specifically, the limit seat 5 is in an L shape. A plurality of fixing screws 54 threadedly connected to the base 1 penetrate through the horizontal section thereof, and a plurality of fixing columns 53 penetrating through the base 1 are fixedly connected to the bottom end of the vertical section thereof. Fixing holes 14 for the fixing columns 53 to pass through are formed through the base 1. Thus, through the misaligned fixation of the fixing columns 53 and the fixing screws 54, the stability of the limit seat 5 on the base 1 can be greatly improved.

[0049] Moreover, referring to Figure 4 , Figure 5 and Figure 6 , a plurality of bimetallic strips 61 are installed on one side of the bobbin 2 close to the limit seat 5. The bimetallic strips 61 are configured to warp and deform towards the side away from the bobbin 2 and push the movable iron core 42 close to the limit seat 5 when the temperature they sense rises, so as to increase the gap 43; specifically, the bimetallic strip 61 is a copper-iron nickel bimetallic strip 61. The iron nickel metal strip is arranged on the side close to the bobbin 2, and the copper metal strip is arranged on the side close to the limit seat 5. The copper metal strip can undergo a large expansion deformation at 40 °C to 60 °C.

[0050] Meanwhile, a plurality of shape memory alloy springs 62 are provided between the limit seat 5 and the movable iron core 42. The shape memory alloy springs 62 are configured such that when the temperature they sense exceeds their phase transition temperature, the shape memory alloy springs 62 transform into the austenite phase and soften; and when the temperature they sense is lower than their phase transition temperature, the shape memory alloy springs 62 transform into the martensite phase and recover elasticity to drive the movable iron core 42 away from the limit seat 5, so as to reduce the air gap 43. Specifically, the phase transition temperature range of the shape memory alloy spring 62 can be any value between 40°C and 60°C, and can be specifically selected according to the working conditions of the micro-transformer. And in the initial normal temperature condition, the elastic deformation force of the shape memory alloy spring 62 pushes the movable iron core 42 to abut against the skeleton 2, and at this time the air gap 43 reaches the set minimum value.

[0051] Among them, referring to Figure 5 , a plurality of bimetallic strips 61 are provided and are arranged in an equidistant circular array along the central axis of the cylindrical portion of the skeleton 2. A plurality of sockets 21 are fixedly connected to the skeleton 2. The sockets 21 have sockets 211 for the head ends of the bimetallic strips 61 to be inserted. Two sockets 211 facing each other of the sockets 21 form a group, and both ends of the bimetallic strip 61 are respectively inserted into the two sockets 21 of the same group; and during actual installation, when both ends of the bimetallic strip 61 are completely inserted into the two sockets 21 of the same group, the middle portion of the bimetallic strip 61 has a certain tendency to bend away from the skeleton 2, and the distance from its convex portion to the skeleton 2 is not more than the thickness of the socket 21.

[0052] Thus, when the micro-transformer of the present application is working, a large amount of heat is usually generated due to copper loss and iron loss. These heats are accumulated in the charger for assembling the micro-transformer, and usually such a low-power charger does not configure an active heat dissipation system, resulting in the heat being stored in the charger housing for a long time. And both copper loss (winding loss) and iron loss (core loss) will increase with the increase of temperature, which will further lead to the reduction of the electromagnetic efficiency of the micro-transformer.

[0053] When these temperature rises are sensed by the plurality of shape memory alloy springs 62 on the limit seat 5, once the temperature rise exceeds the phase transition temperature of the shape memory alloy springs 62, the shape memory alloy springs 62 transform into austenite and soften, and their own elastic force decreases or even disappears, and they can no longer push against the movable iron core 42, so that the iron column portion 402 of the movable iron core 42 at this time can slide freely in the cylindrical portion of the skeleton 2.

[0054] Meanwhile, these temperature rises are also detected by multiple bimetal sheets 61 on the skeleton 2. The thermal expansion deformation of the copper metal sheet on the bimetal sheet 61 is much greater than that of the iron-nickel metal sheet when heated. On the one hand, both ends of the bimetal sheet 61 are inserted into the sockets 21 at both ends. On the other hand, the bimetal sheet 61 has a tendency to bend with its middle part deviating from the skeleton 2. Therefore, the deformation difference between the copper metal sheet and the iron-nickel metal sheet in the bimetal sheet 61 is reflected in the middle part of the bimetal sheet 61, that is, the middle part of the bimetal sheet 61 bends strongly in the direction away from the skeleton 2. Under the pushing force of the bending deformation of multiple bimetal sheets 61, the movable iron core 42 can be moved towards the direction close to the limit seat 5. At this time, the distance between the two iron column parts 402 is enlarged, so that the air gap 43 increases. After the air gap 43 increases, the magnetic resistance will increase, thereby reducing the magnetic flux density, which helps to prevent the magnetic core from saturating and reduce the hysteresis loss and eddy current loss (iron loss). Therefore, the temperature rise of the transformer can be controlled to a certain extent, overheating can be avoided, and the electromagnetic efficiency of the micro-transformer can be ensured. And because both ends of the bimetal sheet 61 are embedded in the sockets 21 at both ends at this time, the bending offset of the middle part of the bimetal sheet 61 is much smaller than that when one end of the bimetal sheet 61 is fixed and the other end is movably arranged. Thus, while increasing the bending deformation thrust of the bimetal sheet 61, the actuation stroke is reduced, which is especially suitable for high-precision adjustment within the range of 0.1 mm to 1 mm of the air gap 43.

[0055] When the temperature of the micro-transformer decreases, based on the principle of thermal expansion and contraction, the tendency of the middle part of the bimetal sheet 61 to bend weakens, and the pushing effect on the movable iron core 42 is lost, and it retracts to the corresponding bending degree according to the corresponding temperature; for the shape memory alloy spring 62, once the temperature of the micro-transformer drops to a temperature lower than the phase transition temperature sensed by the shape memory alloy spring 62, the shape memory alloy spring 62 transforms into the martensite phase and recovers its elasticity to drive the movable iron core 42 away from the limit seat 5, so that the movable iron core 42 moves to closely adhere to the bending parts of multiple bimetal sheets 61. At this time, the distance between the two iron column parts 402 decreases, so that the air gap 43 decreases. Thus, through the arrangement of multiple bimetal sheets 61 and multiple shape memory alloy springs 62, the air gap 43 between the movable iron core 42 and the fixed iron core 41 increases with the temperature rise of the micro-transformer, and decreases and recovers with the temperature drop of the micro-transformer, realizing the dynamic adjustment of the air gap 43 of the micro-transformer, and its temperature rise can be autonomously controlled to ensure its electromagnetic efficiency as much as possible under different load conditions.

[0056] Specifically, to ensure the effectiveness of this dynamic adjustment of the air gap 43, refer to Figure 4 and Figure 6, on the limit seat 5, there are a number of receiving grooves 51 for one end of a number of shape memory alloy springs 62 to be embedded and fixed. In addition, on one side of the limit seat 5 close to the skeleton 2, a number of limit protrusions 52 corresponding to the movable iron core 42 are fixedly connected. When the movable iron core 42 slides to abut against the limit protrusions 52, the air gap 43 between the two iron column parts 402 of the movable iron core 42 and the fixed iron core 41 is 1 mm. And when the movable iron core 42 slides to abut against the socket 21, the air gap 43 between the two iron column parts 402 of the movable iron core 42 and the fixed iron core 41 is not less than 0.1 mm.

[0057] In this way, by means of the arrangement of the receiving grooves 51, the shape memory alloy springs 62 entering the austenite phase can be effectively stored to avoid affecting the normal movement of the movable iron core 42. And by controlling the sizes of the limit protrusions 52 and the socket 21, during the adjustment of the movable iron core 42, the air gap 43 of the micro-transformer is always maintained within the required range of 0.1 mm to 1 mm, so as to ensure that the electromagnetic efficiency of the micro-transformer is as good as possible.

[0058] On the other hand, polytetrafluoroethylene patches (not shown in the figure) are provided on the inner peripheral walls of the cylindrical parts of the base 1 and the skeleton 2. The polytetrafluoroethylene patches are arranged corresponding to the movement track of the movable iron core 42. Thus, the sliding resistance of the outer frame part 401 of the movable iron core 42 on the base 1 and the iron column part 402 in the cylindrical part of the skeleton 2 can be greatly reduced, so as to ensure the driving effect of the bimetallic strip 61 on the movable iron core 42 when deforming and the shape memory alloy spring 62 when restoring elasticity.

[0059] At the same time, referring to Figure 6 and Figure 7 , a buckle cover 7 is fixed on the base 1 and wraps around the axial part of the outer frame part 401 of the fixed iron core 41 and the movable iron core 42 along the cylindrical part of the skeleton 2. The buckle cover 7 is open at both axial ends along the cylindrical part of the skeleton 2. The inner wall of the buckle cover 7 abuts against the fixed iron core 41 and a sliding gap 71 is reserved between it and the movable iron core 42. Specifically, there are two buckle covers 7 which are respectively sleeved on the butt joint seams of the two outer frame parts 401 and their adjacent parts. A number of tenons 13 are fixedly connected to two opposite side walls of the base 1 corresponding to the butt joint of the two outer frame parts 401. One end of the buckle cover 7 close to the base 1 is fixedly connected with a tenon seat 72 which is snap-connected with the tenons 13. And a number of positioning columns 73 are fixedly connected to the bottom end of one side of the buckle cover 7 extending into the space between the iron column part 402 and the outer frame part 401. Positioning holes 15 for the positioning columns 73 to be embedded are formed on the base 1. In this way, through the fitting action of the positioning columns 73 in the positioning holes 15 and the snap connection between the tenons 13 and the tenon seat 72, the buckle cover 7 can be stably fixed on the base 1, and can play a good role in fixing and limiting the fixed iron core 41 and the movable iron core 42.

[0060] In this way, when the fixed iron core 41 and the movable iron core 42 are installed at both ends of the bobbin 2, they are basically limited in position. The addition of the buckle cover 7 can assist in fixing the fixed iron core 41, enabling the fixed iron core 41 to be firmly fixed on the base 1 and improving the assembly efficiency of the micro-transformer. At the same time, the buckle cover 7 can limit the outer frame portion 401 of the movable iron core 42 to restrict the sway amount of the movable iron core 42, so that while the movable iron core 42 has the ability to slide, it will not affect the effective adjustment effect of the bimetallic strip 61 and the shape memory alloy spring 62 on the movable iron core 42 due to excessive self-sway, thereby ensuring the dynamic control effect of the air gap 43.

[0061] Therefore, after installing the micro-transformer of the present application into the low-power charger, it is also necessary to ensure that when the low-power charger is working, the movable iron core 42 of the micro-transformer should be in a horizontal state on the horizontal base 1 to avoid the influence of the gravity of the movable iron core 42 itself on the adjustment effect of the bimetallic strip 61 and the shape memory alloy spring 62.

[0062] The embodiment of the present application discloses a rapid assembly method for a micro-transformer applicable to a low-power charger. Based on the above-mentioned micro-transformer applicable to a low-power charger, refer to Figure 1 , which includes the following steps:

[0063] S1. Coil winding: Wind the primary coil 31 and the secondary coil 32 on the cylindrical portion of the bobbin 2 by the sandwich method, and install the bobbin 2 on the base 1. Specifically, first wind the inner primary coil 31 on the cylindrical portion of the bobbin 2. After wrapping the insulating layer, then wind several secondary coils 32. An insulating layer is also wrapped between each layer of the secondary coils 32. After the outermost secondary coil 32 is wound, wind another insulating layer, and connect several secondary coils 32 in series. Then, wind the outer primary coil 31 and connect the inner and outer primary coils 31 in series. Subsequently, connect the primary coil 31 to the input pin 11 and connect the secondary coil 32 to the output pin 12.

[0064] S2. Iron core installation: Place the fixed iron core 41 and the movable iron core 42 at both ends of the bobbin 2, and insert the two iron pillar portions 402 into the hollow portion of the cylindrical portion of the bobbin 2. If necessary, glue can also be applied to the fixed iron core 41 to stably fix the fixed iron core 41 on the base 1.

[0065] S3. Fitting installation: Install several bimetal sheets 61 at one end of the skeleton 2 close to the movable iron core 42, and arrange multiple bimetal sheets 61 symmetrically on the skeleton 2 in the form of an equidistant circular array. Specifically, after inserting the two ends of the bimetal sheet 61 into two sockets 21 of the same group, keep the middle of the bimetal sheet 61 having a certain tendency to bend outward; then press the movable iron core 42 completely against the skeleton 2. After installing several shape memory alloy springs 62 on the limit seat 5, install the limit seat 5 on the base 1, and adjust the shape memory alloy springs 62 to align them with the movable iron core 42.

[0066] S4. Momentum verification: Place the base 1 horizontally, and slide the movable iron core 42 left and right in the gap between the limit seat 5 and the skeleton 2 and detect the size of the air gap 43 to verify that the size of the air gap 43 is not less than 0.1 mm and not greater than 1 mm under the limit momentum of the movable iron core 42 in two directions.

[0067] In addition, in step S2, before installing the movable iron core 42, polytetrafluoroethylene patches are also provided at the parts of the base 1 and the skeleton 2 corresponding to the movement track of the movable iron core 42 to reduce the sliding resistance of the movable iron core 42.

[0068] Moreover, in step S3, a buckle cover 7 installed on the base 1 is also assembled at the butting place of the two outer frame parts 401. The buckle cover 7 is used to assist in fixing the fixed iron core 41 and restricting the swaying amount of the movable iron core 42. Thus, while ensuring the moving ability of the movable iron core 42, the rapid assembly efficiency of the micro-transformer of the present application can be ensured.

[0069] The implementation principle of the micro-transformer applicable to a low-power charger in the embodiment of the present application is as follows:

[0070] When the micro-transformer of the present application works, heat will be generated, resulting in temperature rise. When these temperature rises are sensed by multiple shape memory alloy springs 62 on the limit seat 5, once the temperature rise exceeds the phase change temperature of the shape memory alloy springs 62, the shape memory alloy springs 62 turn into austenite and soften, and their own elastic force decreases or even disappears, and they can no longer push against the movable iron core 42, so that the iron column part 402 of the movable iron core 42 at this time can slide freely in the cylindrical part of the skeleton 2.

[0071] Meanwhile, these temperature rises are also detected by multiple bimetal pieces 61 on the framework 2. When heated, the bimetal pieces 61 expand and deform, causing their middle parts to bend strongly away from the framework 2. Pushed by the bending deformation forces of the multiple bimetal pieces 61, the movable iron core 42 can move towards the direction close to the limit seat 5. At this time, the distance between the two iron column parts 402 is enlarged, increasing the air gap 43. To a certain extent, this can control the temperature rise of the transformer, avoid overheating, and ensure the electromagnetic efficiency of the micro-transformer. Moreover, since both ends of the bimetal pieces 61 at this time are embedded in the socket 21 at both ends, while increasing the bending deformation thrust of the bimetal pieces 61, the actuation stroke is reduced, which is especially suitable for high-precision adjustment within the range of 0.1mm to 1mm for the air gap 43.

[0072] When the temperature of the micro-transformer decreases, based on the principle of thermal expansion and contraction, the tendency of the middle part of the bimetal piece 61 to bend weakens, losing the pushing effect on the movable iron core 42, and it retracts to the corresponding bending degree according to the corresponding temperature. For the shape memory alloy spring 62, once the temperature of the micro-transformer drops to a temperature where the shape memory alloy spring 62 senses that the temperature is lower than the phase transition temperature, the shape memory alloy spring 62 transforms into the martensite phase and restores its elasticity to drive the movable iron core 42 away from the limit seat 5, causing the movable iron core 42 to move to closely adhere to the bending parts of the multiple bimetal pieces 61. At this time, the distance between the two iron column parts 402 decreases, so that the air gap 43 decreases.

[0073] Thus, through the arrangement of the multiple bimetal pieces 61 and the multiple shape memory alloy springs 62, the air gap 43 between the movable iron core 42 and the fixed iron core 41 increases with the temperature rise of the micro-transformer, and decreases and recovers with the temperature drop of the micro-transformer, realizing the dynamic adjustment of the air gap 43 of the micro-transformer, and enabling autonomous control of its temperature rise to ensure its electromagnetic efficiency as much as possible under different load conditions.

[0074] Unless otherwise defined, the technical terms or scientific terms used in this application shall have the ordinary meanings understood by those of ordinary skill in the art to which this application pertains. The words "first", "second", "third" and similar terms used in the specification and claims of this application do not denote any order, quantity or importance, but are only used to distinguish different components. The words "a" or "an" and similar terms do not denote a quantity limitation, but mean that there is at least one. The words "comprising" or "including" and similar terms mean that the elements or objects appearing before "comprising" or "including" cover the elements or objects listed after "comprising" or "including" and their equivalents, and do not exclude other elements or objects. The terms "upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationships may also change accordingly.

[0075] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereby. Therefore, all equivalent changes made according to the structure, shape, and principle of the present application shall be covered within the protection scope of the present application.

Claims

1. A micro-transformer applicable to a low-power charger, comprising a base (1), a bobbin (2), a primary coil (31) and a secondary coil (32). An input pin (11) connected to the primary coil (31) and an output pin (12) connected to the secondary coil (32) are provided on the base (1). An insulating layer is provided between the primary coil (31) and the secondary coil (32), characterized in that, A fixed iron core (41) fixed on the base (1) and a movable iron core (42) slidably arranged on the base (1) are provided on the base (1). Both the fixed iron core (41) and the movable iron core (42) include an outer frame portion (401) and an iron column portion (402). An air gap (43) is reserved between the two iron column portions (402). A limit seat (5) located at one end of the skeleton (2) is detachably installed on the base (1). The movable iron core (42) is located between the limit seat (5) and the skeleton (2). A plurality of bimetallic sheets (61) are installed on one side of the skeleton (2) close to the limit seat (5). The bimetallic sheets (61) are configured to warp and deform towards the side away from the skeleton (2) and push the movable iron core (42) close to the limit seat (5) when the temperature they sense rises, so as to increase the air gap (43). A plurality of shape memory alloy springs (62) are arranged between the limit seat (5) and the movable iron core (42). The shape memory alloy springs (62) are configured to transform into the austenite phase and soften when the temperature they sense exceeds their phase change temperature; and transform into the martensite phase and recover elasticity to drive the movable iron core (42) away from the limit seat (5) when the temperature they sense is lower than their phase change temperature, so as to reduce the air gap (43).

2. The micro-transformer applicable to a low-power charger according to claim 1, wherein A plurality of bimetallic sheets (61) are provided and are circumferentially and equally spaced in an array around the central axis of the cylindrical portion of the skeleton (2). A plurality of socket seats (21) are fixedly connected to the skeleton (2). The socket seats (21) have socket openings (211) for the head ends of the bimetallic sheets (61) to be inserted. The two socket seats (21) with opposite socket openings (211) form a group, and the two ends of the bimetallic sheet (61) are respectively inserted into the two socket seats (21) of the same group.

3. The micro-transformer applicable to a low-power charger according to claim 1, characterized in that, The limit seat (5) has a plurality of receiving grooves (51) for one ends of the plurality of shape memory alloy springs (62) to be inserted and fixed.

4. A micro-transformer applicable to a low-power charger according to claim 3, characterized in that, A plurality of limit protrusions (52) corresponding to the movable iron core (42) are fixedly connected to one side of the limit seat (5) close to the skeleton (2). When the movable iron core (42) slides to abut against the limit protrusions (52), the air gap (43) between the two iron column portions (402) of the movable iron core (42) and the fixed iron core (41) is 1 mm.

5. A micro-transformer applicable to a low-power charger according to claim 2, characterized in that, When the movable iron core (42) slides to abut against the socket seat (21), the air gap (43) between the two iron column portions (402) of the movable iron core (42) and the fixed iron core (41) is not less than 0.1 mm.

6. A micro-transformer applicable to a low-power charger according to claim 1, characterized in that, Polytetrafluoroethylene patches are provided on the inner peripheral walls of the cylindrical portions of the base (1) and the skeleton (2), and the polytetrafluoroethylene patches are arranged corresponding to the movement track of the movable iron core (42).

7. A miniature transformer applicable to a low-power charger according to claim 1, characterized in that, A buckle cover (7) is fixed on the base (1) and wraps around the outer frame part (401) of the fixed iron core (41) and the movable iron core (42). The buckle cover (7) is open at both axial ends of the cylindrical part of the skeleton (2). The inner wall of the buckle cover (7) abuts against the fixed iron core (41), and a sliding gap (71) is reserved between the inner wall of the buckle cover (7) and the movable iron core (42).

8. A micro-transformer applicable to a low-power charger according to claim 7, characterized in that, A plurality of tenons (13) are fixedly connected to two opposite side walls of the base (1) corresponding to the butt joint of the two outer frame parts (401). A tenon seat (72) that is snap-connected to the tenons (13) is fixedly connected to one end of the buckle cover (7) close to the base (1).

9. A rapid assembly method for a micro-transformer applicable to a low-power charger, based on a micro-transformer applicable to a low-power charger as described in any one of claims 1-8, characterized in that, It includes the following steps: S1. Coil winding: Wind the primary coil (31) and the secondary coil (32) on the cylindrical part of the skeleton (2) by the sandwich method, and install the skeleton (2) on the base (1). S2. Iron core installation: Place the fixed iron core (41) and the movable iron core (42) at both ends of the skeleton (2), and insert the two iron column parts (402) into the hollow part of the cylindrical part of the skeleton (2). S3. Fitting installation: Install a plurality of the bimetallic sheets (61) at one end of the skeleton (2) close to the movable iron core (42), then press the movable iron core (42) completely against the skeleton (2). After installing a plurality of the shape memory alloy springs (62) on the limit seat (5), install the limit seat (5) on the base (1), and adjust the shape memory alloy springs (62) to align them with the movable iron core (42). S4. Momentum verification: Place the base (1) horizontally, and slide the movable iron core (42) left and right in the gap between the limit seat (5) and the skeleton (2) and detect the size of the air gap (43) to verify that the size of the air gap (43) is not less than 0.1 mm and not more than 1 mm under the ultimate momentum of the movable iron core (42) in two directions.

10. A rapid assembly method for a micro-transformer applicable to a low-power charger according to claim 9, characterized in that, In step S2, a polytetrafluoroethylene patch is also arranged at the positions of the base (1) and the skeleton (2) corresponding to the movement track of the movable iron core (42) before installing the movable iron core (42). In step S3, a buckle cover (7) installed on the base (1) is also assembled at the butt joint of the two outer frame parts (401), and the buckle cover (7) is used to assist in fixing the fixed iron core (41) and limit the sway amount of the movable iron core (42).

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