Switching transformer, switching power supply equipped therewith, electric on-board compressor equipped therewith and method for manufacturing a switching transformer

Abstract

Task: To provide a switching transformer that reduces only the parasitic capacitance while maintaining the magnetic coupling between the windings of the switching transformer and can achieve a reduction in interference. Means of solving: The switching transformer 15 comprises: a primary winding 13 on the low-voltage side and a secondary winding 14 on the high-voltage side, a coil 43 having a central winding shaft section 61 around which the primary and secondary windings are wound, and flange sections 62, and a core 46 having a central leg section 67 that is inserted into a through-hole of the winding shaft section 61 and insulates the low-voltage side and the high-voltage side. An air gap layer G is formed between the winding shaft section 61 and the central leg section 67.

Description

TECHNICAL AREA

[0001] The present invention relates to a switching transformer that isolates a low-voltage side and a high-voltage side, a switching power supply provided therewith, an electric on-board compressor provided therewith, and a method for manufacturing a switching transformer. STATE OF THE ART

[0002] Due to the global environmental problems that have become apparent in recent years, hybrid and electric vehicles are being developed in which electric compressors with motors are used in the air conditioning system to cool the vehicle interior, instead of engine-driven compressors. In this case, the vehicles are equipped, for example, with a high-voltage power source consisting of a high-voltage battery with approximately 300 V DC (300 V) and a low-voltage power source consisting of a standard 12 V DC battery. The electric compressor motor is supplied with alternating current, which is converted from the DC voltage of the high-voltage power source by an inverter circuit.

[0003] In contrast, a control circuit that controls the inverter circuit is supplied with a DC voltage from the low-voltage power source, which is converted to a predetermined voltage (e.g., 15 V DC) by a switched-mode power supply. For this purpose, a switching transformer is provided in this switched-mode power supply, consisting of an isolation transformer in which the primary side of the switching transformer, i.e., the low-voltage side connected to the low-voltage power source, and the secondary side, i.e., the high-voltage side connected to the high-voltage power source, are isolated.

[0004] Regarding interference reduction, the primary side (low voltage side) and the secondary side (high voltage side) of the switching transformer were each grounded to the chassis of the electric compressor (chassis-GND: ground) via Y-capacitors (line bypass capacitors), and in addition, an EMI filter circuit was provided between the low voltage power source and the switching power supply.

[0005] Regarding the suppression of EMI interference originating from the switched-mode power supply, a design was also proposed in which a primary-side ground, isolated by the switching transformer, and a secondary-side ground are connected via a return-to-ground capacitor. With this design, it can be expected that the interference transmitted to each other via the parasitic capacitance (coupling capacitance) between the windings of the switching transformer is fed back, and the common-mode interference current flowing to ground (chassis of the electric compressor) is suppressed, thereby reducing the noise voltage (see, for example, patent document 1).

[0006] Furthermore, a sandwich winding structure is frequently used in the design of switching transformers, where the secondary winding is sandwiched between the primary winding to improve the coupling between the primary and secondary windings. However, improving magnetic coupling through such a design increases the area on which the primary and secondary windings face each other, leading to an increase in parasitic capacitance between the primary and secondary windings and thus to an increase in common-mode interference.

[0007] Therefore, in some designs, the primary and secondary windings of the switching transformer were separated to reduce the area between them, thereby reducing the magnetic coupling and parasitic capacitance. This design had the effect of reducing the amount of common-mode interference (see, for example, patent document 2). LIST OF REFERENCE DOCUMENTS PATENT DOCUMENTS Patent Document 1: JP 7009325 B Patent Document 2:JP 2021-2913 A BRIEF SUMMARY OF THE INVENTIONAL TASKS OF THE INVENTION

[0008] In a switching transformer, the magnetic coupling between the primary and secondary windings, and the parasitic capacitance between them, are generally in a trade-off relationship, making it difficult to increase the magnetic coupling while simultaneously reducing the parasitic capacitance. However, the parasitic capacitance between the primary and secondary windings must be reduced because it is a cause of common-mode current (common-mode interference).

[0009] In patent document 2, the coupling between the primary and secondary windings was reduced to reduce common-mode interference, thereby reducing the parasitic capacitance between the respective windings and thus reducing the common-mode current. However, a disadvantage of this design was that the magnetic coupling between the respective windings was weak, which made it difficult to ensure the voltage regulation required for a power supply, making it unsuitable for feedbackless power supplies (power supplies in which the circuit on the primary side is not controlled by the voltage on the secondary side).

[0010] Regarding the reduction of EMI interference caused by interference from switched-mode power supplies, it has been found that not only the parasitic capacitance between the primary and secondary windings, but also the parasitic capacitance between the windings across the core of the switching transformer in the high-frequency band has an influence and can cause a deterioration of the interference.

[0011] The present invention was developed to solve the previously described conventional technical problem and aims to provide a switching transformer that reduces only the parasitic capacitance while maintaining the magnetic coupling between the windings of the switching transformer and can reduce interference, a switching power supply equipped therewith, an on-board compressor equipped therewith and a method for manufacturing a switching transformer. SOLUTION OF THE TASKS

[0012] The switching transformer of the present invention has a primary winding and a secondary winding and insulates the low-voltage side and the high-voltage side, comprising: a coil having a central winding shaft section around which the primary winding and the secondary winding are wound, and flange sections formed on both sides in the axial direction of the winding shaft section, and a core having a central leg section inserted into a through-bore of the winding shaft section, characterized in that an air gap layer or a shielding layer is formed between the winding shaft section and the central leg section.

[0013] The switching transformer of the invention according to claim 2 is characterized in that, in the invention described above, a recess is formed on the inner surface of the winding shaft section or on the outer surface of the middle leg section and the air gap layer is formed.

[0014] The switching transformer of the invention according to claim 3 is characterized in that the core in the invention according to claim 1 has an outer leg section that covers the outside of the coil, and the outer leg section has an overhang that extends away from the middle leg section.

[0015] The switching transformer of the invention according to claim 4 is characterized in that, in the invention described above, the dimension between the inner surface of the overhang and the outermost primary or secondary winding is equal to or substantially equal to the dimension of the air gap layer or the shielding layer in the direction orthogonal to the middle leg section.

[0016] The switching power supply of the invention according to claim 5 is characterized in that the low-voltage side is connected to a low-voltage power source and the high-voltage side is connected to a high-voltage power source, wherein the primary winding of the switching transformer of the previously described individual inventions is located on the low-voltage side and the secondary winding is located on the high-voltage side in order to switch the low-voltage power source and to supply current to a control circuit positioned on the high-voltage side.

[0017] The electric on-board compressor of the invention according to claim 6 is characterized by: a switching power supply of the previously described invention for switching a low-voltage power source installed in a vehicle, a control circuit, an inverter circuit which is supplied with the mains voltage by a high-voltage power source installed in the vehicle and is controlled by the control circuit, and a motor which is driven by this inverter circuit.

[0018] The method for manufacturing a switching transformer of the invention according to claim 7 is characterized in that, if insulated wires are used as the primary winding and secondary winding in the inventions according to claims 1 to 4, no barrier tape is used that is provided between the primary winding and the secondary winding and a flange section of a coil, and the width dimension of the flange section is increased within the width dimension of the barrier tape.

[0019] The method for manufacturing the switching transformer of the invention according to claim 8 is characterized in that, in the invention described above, the width by which the width dimension of the flange section is increased is equal to or substantially equal to the dimension of the air gap layer or the shielding layer in the direction orthogonal to the middle leg section. EFFECTS OF THE INVENTION

[0020] The parasitic capacitance between the primary and secondary windings of the switching transformer includes a parasitic capacitance caused by the physical distance between the respective windings, and a parasitic capacitance across the core (ferrite material: Mn-Zn, etc.).

[0021] The present invention relates to a switching transformer comprising a primary winding and a secondary winding, and isolating the low-voltage side and the high-voltage side, comprising: a coil having a central winding shaft section around which the primary and secondary windings are wound, and flange sections formed on both sides in the axial direction of the winding shaft section, and a core with a central leg section inserted into the through-bore of the winding shaft section, wherein an air gap layer or shielding layer is formed between the winding shaft section and the central leg section, such that the distance between the innermost primary or secondary winding, with which the primary or secondary winding is closest to the core,and the middle leg section of the core is ensured by the air gap layer or the shielding layer, and the coupling between the primary winding and the secondary winding via the core can be improved.

[0022] This means that the parasitic capacitance between the primary winding and the secondary winding across the core can be reduced, and as a result, the amount of disturbance converted into common-mode noise can be reduced while maintaining the magnetic coupling between the respective windings.

[0023] By including the air gap layer, there is a risk of increasing the leakage flux, however, the influence of the increased leakage flux is limited due to the sufficiently large relative magnetic permeability of the core and the structure of the switching transformer.

[0024] In practice, as in the invention according to claim 2, the recess is formed on the inner surface of the winding shaft section or on the outer surface of the middle leg section to create the air gap layer. The air gap layer formed by the recess can also be used to form the shielding layer.

[0025] If, as in the invention according to claim 3, an overhang is provided on the outer leg section of the core that covers the outside of the coil, projecting away from the middle leg section, the disadvantage of a reduced distance between the primary or secondary winding (as the outermost layer) and the outer leg section of the core can be avoided by providing an air gap layer between the winding shaft section and the middle leg section. This also eliminates any increase in parasitic capacitance between the primary and secondary windings across the outer leg section of the core.

[0026] In this case, as in the invention according to claim 4, an unnecessary increase in the external dimensions of the switching transformer can be prevented by making the dimension between the inner surface of the overhang and the outermost primary or secondary winding equal to or substantially equal to the dimension of the air gap layer or the shielding layer in the direction orthogonal to the middle leg section.

[0027] In the switching transformer of the previously described individual inventions, as in the invention according to claim 5, the low-voltage side is connected to the low-voltage power source and the high-voltage side is connected to the high-voltage power source, wherein the primary winding is located on the low-voltage side and the secondary winding is located on the high-voltage side, so that the switching transformer is suitable for the switching power supply that switches the low-voltage power source and supplies power to the control circuit positioned on the high-voltage side.

[0028] Furthermore, the switching power supply of the previously described invention, as in the invention according to claim 6, is particularly suitable in the electric on-board compressor, provided with the control circuit, the inverter circuit, which is supplied with mains voltage by the high-voltage power source installed in the vehicle and controlled by the control circuit, and the motor, which is driven by this inverter circuit, when switching the low-voltage power source installed in the vehicle.

[0029] If insulated wires are used as the primary and secondary windings, the parasitic capacitance between the primary and secondary windings across the core can be further reduced by not using a barrier tape between the primary and secondary windings and the flange section of the coil, as in claim 7 of the invention, and by increasing the width dimension of the flange section within the width dimension of the barrier tape.

[0030] In this case too, a sufficient reduction effect of the parasitic capacity can be achieved by making the width by which the width dimension of the flange section is increased equal to or substantially equal to the dimension of the air gap layer or the shielding layer in the direction orthogonal to the middle leg section, as in the invention according to claim 8. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] It shows: Fig. 1 a block diagram of an electrical circuit of an electric on-board compressor of an embodiment for the application of a switching power supply of the present invention. Fig. 2 a view to illustrate the structure of a switching transformer of the present invention. Fig. 3 a sectional view of the core of the switching transformer of Fig. 2. Fig. 4 A view illustrating the impedance between a primary winding and a secondary winding of the switching transformer of Fig. 2. Fig. 5. A view illustrating the structure of the switching transformer of the switching power supply. Fig. 1 in the case where insulated wires are used as the primary and secondary windings. Fig. 6 A view illustrating the grounding structure of the switching transformer of the switched-mode power supply from Fig. 1. Fig. 7 a sectional view of the core of the switching transformer of Fig. 6. Fig. 8 A view illustrating the reduction effect of a common-mode disturbance by the grounding structure of Fig. 6. Fig. 9. A view illustrating the reduction effect of common-mode interference by the grounding structure of Fig. 6. Fig. 10. A view illustrating common-mode interference when the grounding point in the switching transformer is changed. Fig. 6. Fig. 11 also a view to illustrate the common-mode interference when the grounding point in the switching transformer is changed. Fig. 6. Fig. 12 A view illustrating the grounding structure of the switching transformer of Fig. 6 with different winding specifications. DESCRIPTION OF THE EXECUTION FORMS

[0032] The embodiments of the present invention are explained in detail below with reference to drawings. (1) Electric on-board compressor 1

[0033] In Fig. Figure 1 shows an electric on-board compressor, which is installed in vehicles such as an electric vehicle or hybrid vehicle, etc., and forms the refrigerant circuit of a vehicle air conditioning system for climate control of the vehicle interior, and Figure 2 shows its chassis (housing). This chassis 2 incorporates a compression mechanism (not shown), a motor 3 for driving this compression mechanism, an inverter circuit 4 for operating this motor 3, a control circuit 6 for controlling this inverter circuit 4, EMI filter circuits 7, 8, and a switched-mode power supply 9 of the present invention.

[0034] The vehicle is equipped with: a high-voltage power source (HV power source) 11, which consists, for example, of a high-voltage battery with approximately 300 V direct current (DC 300 V) for supplying current to and driving the motor 3 of the electric on-board compressor 1 and a drive motor (not shown), and a low-voltage power source (LV power source) 12, which consists of a standard battery (12 V DC battery) with approximately 12 V direct current (DC 12 V), wherein the high-voltage side of the electric on-board compressor 1 is connected to the high-voltage power source 11 and the low-voltage side is connected to the low-voltage power source 12. Furthermore, the chassis 2 of the electric on-board compressor 1 is connected to the vehicle body and thus grounded.

[0035] The inverter circuit 4 consists of six switching elements (not shown) made up of three-phase bridge-connected IGBTs, each switching element being controlled by a gate drive signal generated by a gate driver of the control circuit 6. The control circuit 6 consists of a microprocessor and switches each switching element of the inverter circuit 4 by means of a gate driver to perform PWM modulation, thereby converting the DC voltage of the high-voltage current source 11 to a predetermined AC voltage and supplying it to the motor 3.

[0036] The EMI filter circuit 7 is connected between the high-voltage power source 11 and the inverter circuit 4 and reduces the EMI interference generated by the switching of the inverter circuit 4. Furthermore, the EMI filter circuit 8 is connected between the low-voltage power source 12 and the switched-mode power supply 9 and reduces the EMI interference generated by the switching in the switched-mode power supply 9, as described later. (2) Switching power supply 9

[0037] This switching power supply 9 is a DC-DC converter that switches the low-voltage power source 12 (12 V DC) to generate a predetermined DC voltage (HV 15 V, HV 5 V) and supply power to the control circuit 6. It is constructed from electrical components, described later, mounted on a carrier 10. HV 15 V is the voltage supplied to the gate driver (included in the control circuit 6), which generates the gate drive signal for the inverter circuit 4. HV 5 V is the voltage that serves as the power source for the control circuit 6.

[0038] In this embodiment, the switching power supply 9 comprises a switching transformer 15, which consists of an isolation transformer comprising a primary winding 13 located on the low-voltage side (connected to the low-voltage power source 12) and a secondary winding 14 that is insulated from the primary winding 13 and located on the high-voltage side (connected to the high-voltage power source 11). In this embodiment, a magnet wire is used for the primary winding 13, and the primary winding has a first winding section 51 (Np-1) with a winding start 51A and a winding end 51B, and a second winding section 52 (Np-2) with a winding start 52A and a winding end 52B.

[0039] The winding end 52B of the second winding section 52 is connected to the EMI filter circuit 8 via a primary-side power supply line (LV+) 16 and further connected to the low-voltage power source 12. Additionally, the winding start 52A of the second winding section 52 is connected to the winding end 51B of the first winding section 51, and the winding start 51A of the first winding section 51 is, in the exemplary embodiment, connected to the drain terminal of a switching element 17 consisting of a MOSFET.

[0040] The source terminal of this switching element 17 is connected to an LVGND 18, which represents the ground (primary ground) on the low voltage side (connected to the low voltage power source 12), and the winding start 51A of the first winding section 51 of the switching transformer 15 is not directly connected to the LVGND 18.

[0041] In the drawings, figure 19 shows a switched-mode power supply controller (controller), wherein the switched-mode power supply controller 19 is powered by the low-voltage power source 12 via a primary-side power supply line 16. The output of the switched-mode power supply controller 19 is connected to the gate of the switching element 17, and the switching of the switching element 17 is controlled by the switched-mode power supply controller 19.

[0042] This positions the primary winding 13 of the switching transformer 15 on the low-voltage side (connected to the low-voltage power source 12). Figure 21 shows a smoothing capacitor connected between the primary-side power supply line 16 and the primary-side ground 18. In this embodiment, the LVGND 18, which is isolated from the secondary side (a later described HVGND 26) by the switching transformer 15, is connected to the chassis 2 (ground) via a Y-capacitor (line bypass capacitor) 22, which attenuates common-mode interference. One end of the low-voltage power source 12 is also connected to the chassis 2.

[0043] In contrast, in this embodiment, a magnet wire is also used for the secondary winding 14 of the switching transformer 15, and the secondary winding has a first winding section 23 (Ns-1) with a winding start 23A and a winding end 23B, as well as a second winding section 24 (Ns-2) with a winding start 24A and a winding end 24B. The winding end 24B of this second winding section 24 is connected to an HVGND 26, which represents the ground (secondary-side ground) on the high-voltage side (connected to the high-voltage power source 11).

[0044] The winding start 23A of the first winding section 23 is connected via a diode 31 to an HV15V line (a first high-voltage power supply line) 32, and the gate driver of the control circuit 6 described above is connected to this HV15V line 32. The winding start 24A of the second winding section 24 is connected via a diode 33 and a regulator (LDO: low-dropout regulator) 34 to an HV5V line (a second high-voltage power supply line) 36, and the HV5V line 36 serves as the current source for the control circuit 6.

[0045] Furthermore, the winding start 24A of the second winding section 24 is connected to the winding end 23B of the first winding section 23, and the winding end 24B of the second winding section 24 is connected to the HVGND 26 as previously described.

[0046] Figures 37 to 39 show smoothing capacitors, each connected between the HV15V line 32 and the HVGND 26, and between the HV5V line 36 and the HVGND 26 downstream of the regulator 34. In the exemplary embodiment, the HVGND 26 (secondary-side ground), which is isolated from the primary side (LVGND 18) by the switching transformer 15, is connected to the chassis 2 (ground) via a Y-capacitor (line bypass capacitor) 41, which dampens common-mode interference.

[0047] The switching power supply controller 19 controls the switching element 17 according to the winding ratio of the switching transformer 15 so that DC 15 V (HV 15 V) is output to the HV15V line 32. This supplies the gate driver of the control circuit 6 with DC 15 V (HV 15 V), and the control circuit 6 itself is supplied via the regulator 34 with DC 5 V (HV 5 V) from an intermediate output corresponding to the winding ratio of the first winding section 23 and the second winding section 24.

[0048] The switching power supply 9 switches the low-voltage power source 12, supplies the control circuit 6 with the mains voltage, and isolates the low-voltage side, on which the primary winding 13 is located (connected to the low-voltage power source 12 as described above), and the high-voltage side, on which the secondary winding 14 is located (connected to the high-voltage power source 11 as described above) (represented in the drawings by the dashed line “Isolation”), by means of the switching transformer 15. As a measure against EMI interference resulting from the switching of the switching element 17 of the switching power supply 9, the winding end 52B of the second winding section 52 and the winding end 24B of the second winding section 24 of the switching transformer 15 are connected to each other via a coupling capacitor 42.

[0049] By connecting the winding end 52B of the second winding section 52 of the switching transformer 15 to the winding end 24B of the second winding section 24 via the coupling capacitor 42, disturbances that are transmitted between the windings of the switching transformer 15 (between the primary winding 13 and the secondary winding 14) during the switching of the switching element 17 via the parasitic capacitance (coupling capacitance) are fed back, and the common-mode interference current flowing on the chassis 2 side of the electric compressor 1 (ground: ultimately on the vehicle side) is suppressed. This reduces the noise voltage. (3) Structure of the switching transformer 15

[0050] Next, with reference to Fig. 2 and Fig. 3 The structure of the switching transformer 15 in this embodiment is explained. In the drawings, 43 shows a coil around which the first winding section 51 (Np-1) and the second winding section 52 (Np-2) of the primary winding 13 and the first winding section 23 (Ns-1) and the second winding section 24 (Ns-2) of the secondary winding 14 are wound, 46 a core and 47 a barrier band.

[0051] The coil 43 consists of a hard synthetic resin and has a central winding shaft section 61 and flange sections 62, each formed on both sides in the axial direction of the winding shaft section 61, with a through bore 60 formed on the winding shaft section 61. The first winding section 51 (Np-1) and the second winding section 52 (Np-2) of the primary winding 13, as well as the first winding section 23 (Ns-1) and the second winding section 24 (Ns-2) of the secondary winding 14, are wound around the outer surface of the winding shaft section 61 of this coil 43. In this embodiment, the first winding section 51 (Np-1) is wound on the innermost layer, the second winding section 24 (Ns-2) is wound on the outside of it, the first winding section 23 (Ns-1) is wound on the outside of it, and the second winding section 52 (Np-2) is wound on the outermost layer.

[0052] This means that the first winding section 51 (Np-1) of the primary winding 13 and the second winding section 52 (Np-2) clamp the first winding section 23 (Ns-1) and the second winding section 24 (Ns-2) of the secondary winding 14, thereby maintaining the magnetic coupling between the primary winding 13 and the secondary winding 14. In this embodiment, a recess 63 is formed on the inner surface of the through-hole 60 of the winding shaft section 61 of the coil 43.

[0053] The barrier tape 47 is wound around the winding shaft section 61 between the first and second windings 13, 14 and the flange section 62 of the coil 43. In this case, the barrier tape 47 is necessary because the first and second windings 13, 14, as previously described, consist of magnet wire, and it is wound around the winding shaft section 61 with a width that meets the safety standards.

[0054] In contrast, core 46 consists of a pair of core materials 46A, 46B made of ferrite (Mn-Zn). The core materials 46A, 46B are each symmetrically shaped and, as in Fig. The core materials 46A and 46B are shown in Figure 3, arranged opposite each other, forming the core 46. Each core material has a base section 66, a middle leg section 67 extending from the center of the base section 66, and an outer leg section 68 extending from the outer end of the base section 66.

[0055] The middle leg sections 67 of the respective core materials 46A, 46B are then inserted from both sides into the through-hole 60 of the winding shaft section 61 of the coil 43, around which the primary winding and the secondary windings 13, 14 and the barrier band 47 are wound. In this state, the base sections 66 of the respective core materials 46A, 46B correspond to the outside of the flange section 62 of the coil 43. In the exemplary embodiment, the outer leg section 68 also covers the outside of the second winding section 52, which serves as the outermost layer. Furthermore, an overhang 68A is formed on the outer leg section 68, projecting outwards from the middle leg section 67.

[0056] Fig. Figure 3 shows a section through the core 46 in a horizontal direction in Fig. 2. The black circles in Fig. Figure 2 shows the previously described winding starts of the respective windings, while the white circles show the winding ends. The hatched circles show the hot ends oscillating at high frequency. Since the underside (on the side of the support 10) is separated from the middle leg section 67 in Fig. If 2 is symmetrical to the top, it is not marked with a reference symbol.

[0057] In this embodiment, as previously described, the recess 63 is formed on the inner surface of the through-bore 60 of the winding shaft section 61 of the coil 43, so that in the state in which the middle leg section 67 of the core 46 is inserted, an air gap layer (in Fig. 2 (designated by G). Furthermore, as previously described, the overhang 68A is formed on the outer leg section 68. This overhang 68A is formed as the outermost layer corresponding to the second winding section 52, and a gap of a predetermined dimension is formed between the second winding section 52 and the inner surface of the overhang 68A.

[0058] In this embodiment, the dimension between the second winding section 52 and the inner surface of the overhang 68A is equal to or substantially equal to the dimension of the air gap layer G in the direction orthogonal to the middle leg section 67.

[0059] Since the air gap layer G is formed between the winding shaft section 61 of the coil 43 of the switching transformer 15 and the middle leg section 67 of the core 46, the distance between the first winding section 51 as the innermost layer, which is closest to the core 46, and the middle leg section 67 of the core 46 can be ensured by the air gap layer G, and the coupling between the primary winding 13 and the secondary winding 14 via the core 46 can be improved.

[0060] This means that it is possible to reduce the parasitic capacitance between the primary winding 13 and the secondary winding 14 via the core 46 and to reduce the amount of common-mode interference while maintaining the magnetic coupling between the respective windings 13 and 14. While the air gap layer G may increase the leakage flux, its impact is limited due to the sufficiently high relative magnetic permeability of the core 46 and the structure of the switching transformer 15.

[0061] Furthermore, in the exemplary embodiment, the outer leg section 68 of the core 46, which covers the outside of the coil 43, is provided with an overhang 68A that extends away from the middle leg section 67. This prevents the problem of the distance between the second winding section 52 (the outermost layer) and the outer leg section 68 of the core 46 becoming smaller by providing the air gap layer G between the winding shaft section 61 and the middle leg section 67. This also eliminates any increase in parasitic capacitance between the primary winding 13 and the secondary winding 14 across the outer leg section 68 of the core 46.

[0062] Fig. Figure 4 shows the frequency characteristic of the impedance between the primary and secondary windings of the switching transformer. In this drawing, L1 shows the switching transformer 15 in the exemplary embodiment of Fig. 2, L2 the case in which the dimension of the air gap layer G in the direction orthogonal to the middle leg 67 is twice as large as in Fig. 2, L3 the case in which no air gap layer G is provided, and L4 the case in which the primary winding and the secondary winding are separated from each other, as described in patent document 2 above.

[0063] In the case of L4, the magnetic coupling between the primary and secondary windings is lower, resulting in a high impedance across the entire frequency band. In the case of L3, the impedance drops sharply in the FM band. For L2, the distance between the winding (the outermost layer) and the outer leg of the core is smaller, resulting in a low impedance in the FM band.

[0064] In contrast, L1 of the switching transformer is 15. Fig. 2 and Fig. 3. The impedance in frequency bands below the FM band is low, as with L3, and in the FM band is higher than with L2 and L3, which shows that the amount of interference converted into common-mode noise can be reduced.

[0065] In the exemplary embodiment, the air gap layer G is formed by a recess 63 on the inside of the winding shaft section 61 of the coil 43, and the air gap layer G can be easily formed. In this case, the recess 63 can also be formed on the side of the middle leg 67 of the core 46. Furthermore, a shielding layer can be formed there using the air gap layer G formed by the recess 63. This shielding layer consists of a material with a low dielectric constant.

[0066] Furthermore, in the exemplary embodiment, the dimension between the inner surface of the overhang 68A and the second winding section 52 as the outermost layer is equal to or substantially equal to the dimension of the air gap layer G in the direction orthogonal to the middle leg section 67, so that an unnecessary increase in the outer dimension of the switching transformer 15 can be prevented.

[0067] The switching power supply 15, as in the exemplary embodiment, is provided in the electric on-board compressor 1 with the control circuit 6, the inverter circuit 4, which is supplied with the mains voltage by the high-voltage power source 11 and controlled by the control circuit 6, and the motor 3, which is driven by this inverter circuit 4, and is particularly suitable for switching the low-voltage power source 12 installed in the vehicle. (4) Other structures of the switching transformer 15

[0068] Next, we will show Fig. 5 The structure of the switching transformer 15 in the case where insulated wires are used as the primary winding 13 and secondary winding 14. In this drawing, components with the same reference numerals as in Fig. 2 the same or similar functions.

[0069] The primary winding 13 and the secondary winding 14 in this embodiment consist of reinforced insulated wires with multiple insulating films. These reinforced insulated wires differ from ordinary magnet wires (enamel wires) in their high insulating capacity, meaning they do not require barrier tape according to safety standards.

[0070] Therefore, in this embodiment, the barrier band 47 used in the previously mentioned embodiment is not used. Instead, the width dimension of the flange section 62 of the coil 43 is increased within the width dimension of the barrier band 47. This further reduces the parasitic capacitance between the primary winding 13 and the secondary winding 14 across the core 62.

[0071] The width by which the width dimension 62 of the coil 43 is increased should be equal to or substantially equal to the dimension of the air gap layer G in the direction orthogonal to the central leg section 67. This ensures a sufficient reduction effect of the parasitic capacitance. (5) Grounding of the switching transformer 15

[0072] Next, the grounding structure and grounding method of the switching transformer 15 will be described. Fig. 1 with reference to Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11 to Fig. 12 explained. In the individual drawing, components with the same reference symbols as in Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5 the same or similar effects, and since the switching transformer 15 in this case as in Fig. 1. If it is connected to a line, the explanation will be... Fig. 1 omitted.

[0073] Also in Fig. In the exemplary embodiment, the switching transformer 15 is an isolation transformer, consisting of the primary winding 13, which is connected to the low-voltage power source 12, and the secondary winding 14, which is insulated from the primary winding 13 (connected to the high-voltage power source 11 as previously described). In this exemplary embodiment, a magnet wire is used for the primary winding 13, and the primary winding has a first winding section 51 (Np-1) with a winding start 51A and a winding end 51B, and a second winding section 52 (Np-2) with a winding start 52A and a winding end 52B.

[0074] In Fig. Figure 6 shows the coil around which the first winding section 51 (Np-1) and the second winding section 52 (Np-2) of the primary winding 13 and the first winding section 23 (Ns-1) and the second winding section 24 (Ns-2) of the secondary winding 14 are wound, the core 46 and the barrier tape 47.

[0075] The coil 43 consists of a hard synthetic resin and has the central hollow winding shaft section 61 and flange sections 62, each formed on both sides in the axial direction of the winding shaft section 61. The first winding section 51 (Np-1) and the second winding section 52 (Np-2) of the primary winding 13, as well as the first winding section 23 (Ns-1) and the second winding section 24 (Ns-2) of the secondary winding 14, are wound around the outer surface of the winding shaft section 61 of this coil 43, in the case of Fig. 6 the first winding section 51 (Np-1) is wound on the innermost layer, outside of it is the second winding section 24 (Ns-2), outside of it is the first winding section 23 (Ns-1) and on the outermost layer is the second winding section 52 (Np-2).

[0076] That is, the winding specification in Fig. 6 is designed such that the first winding section 51 (Np-1) of the primary winding 13 and the second winding section 52 (Np-2) clamp the first winding section 23 (Ns-1) and the second winding section 24 (Ns-2) of the secondary winding 14, thereby maintaining the magnetic coupling between the primary winding 13 and the secondary winding 14.

[0077] The barrier tape 47 is wound around the winding shaft section 61 between the first and second windings 13, 14 and the flange section 62 of the coil 43. In this case, the barrier tape 47 is necessary because the first and second windings 13, 14, as previously described, consist of magnet wire, and it is wound around the winding shaft section 61 with a width that meets the safety standards.

[0078] In contrast, the core 46 consists of a pair of core materials 46A, 46B made of ferrite (Mn-Zn). The core materials 46A, 46B are each symmetrically shaped and arranged opposite each other, thus forming the core 46. The core materials 46A, 46B each have a base section 66, a middle leg section 67 projecting from the center of the base section 66, and an outer leg section 68 projecting from the outer end of the base section 66.

[0079] The middle leg sections 67 of the respective core materials 46A, 46B are then inserted from both sides into the winding shaft section 61 of the coil 43, around which the primary winding and the secondary windings 13, 14 and the barrier band 47 are wound. In this state, the base sections 66 of the respective core materials 46A, 46B correspond to the outer surface of the flange section 62 of the coil 43. Furthermore, the previously described outer leg section 68 covers the outer surface of the second winding section 52, which serves as the outermost layer. In addition, the first winding section 51 (Np-1) is adjacent to the middle leg section 67 of the core 46, and the second winding section 52 (Np-2) is adjacent to the outer leg section 68.

[0080] The black circles in Fig. Figure 6 shows the previously described winding starts of the respective windings, while the white circles show the winding ends. The hatched circles show the hot ends oscillating at high frequency. Since the underside (on the side of the support 10) is separated from the middle leg section 67 in Fig. If 6 is symmetrical to the top, it is not marked with a reference symbol.

[0081] On the support 10, on which the switching transformer 15 is provided, a connection section (Land) 71 for LVGND, a connection section (Land) 72 for HVGND and a connection section (Land) 73 for earth are each formed separately, wherein the connection section 71 for LVGND is connected to the previously in Fig. 1 described LVGND 18 is switched through, the connection section 72 for HVGND to HVGND 26 is switched through and the connection section 73 for earth to earth (chassis 2) is switched through.

[0082] In contrast, the switching transformer 15 has a grounding terminal 74, one end of which is connected to and attached to the core 46. The other end of this grounding terminal 74 of the switching transformer 15 is designed so that it can be selectively connected to the previously described connection section 71 for LVGND, the connection section 72 for HVGND, or the connection section 73 for earth. (5-1) Earthing structure 1 of the switching transformer 15

[0083] It is known that EMI interference can be improved by grounding core 46, but in the case of switching transformer 15 with the in Fig. 6 shown winding specification, i.e., in the case where the first winding section 51 of the primary winding 13, which is on the low-voltage side, is positioned on the innermost layer and the second winding section 52 on the outermost layer, the other end of the earthing terminal 74 is, as in Fig. 6 is shown, connected to the connecting section 71 for LVGND. This grounds the core 46 of the switching transformer 15 to LVGND 18.

[0084] Fig. Figure 8 shows the measurement results for the common-mode interference, where L6 represents the case in which the core 46 of the switching transformer 15 is connected to the Fig. 6 shown in the winding specification is not grounded, and L5 represents the case in which the grounding terminal 74 is as shown in Fig. 6 is connected to the connection section 71 for LVGND and the core 46 is grounded to LVGND 18. Fig. 9 shows the difference between L5 and L6 in Fig. 8, where L7 corresponds to L5 and L8 indicates the difference relative to L7.

[0085] As with L6 in Fig. As shown in Figure 8, the switching power supply 9 in the exemplary embodiment contains many common-mode interference voltages in the high-frequency band on the low-voltage side (which is connected to the low-voltage power source 12), and through the grounding of the core 46 of the switching transformer 15 to LVGND 18, as shown in Figure 8. Fig. As shown in Figure 6, the low-voltage side (which is connected to the low-voltage power source 12) and the core 46 are brought to the same potential, so that unnecessary reverse currents are suppressed and the high-frequency interference (VHF band) on the low-voltage side is eliminated, as with L5 in Figure 6. Fig. As shown in Figure 8, the results can be significantly improved by suppressing unnecessary couplings. This is also demonstrated by comparing L7 and L8 in Figure 8. Fig. 9 clearly. In addition, the low-frequency interference on the high-voltage side is improved by suppressing unnecessary coupling.

[0086] The measurement results of the common-mode interference in the case where the earthing terminal 74 of the switching transformer 15 does not meet the winding specification in Fig. 6 is connected to the connection section 72 for HVGND and the core 46 is grounded to HVGND 26, are in Fig. 10 and Fig. 11 shown. L10 in Fig. Figure 10 shows the case in which the core 46 of the switching transformer 15 is not grounded, and Figure 9 shows the case in which the grounding terminal 74 is connected to the connecting section 72 for HVGND and the core 46 is grounded to HVGND 26. Fig. 11 is the difference between L10 and L9 in Fig. 10 is shown, where L12 corresponds to L10 and L11 indicates the difference relative to L12.

[0087] If the core 46 of the switching transformer 15 matches the winding specification in Fig. When terminal 6 is grounded to HVGND 26, the unnecessary coupling between the low-voltage and high-voltage sides increases, causing high-frequency interference to leak from the low-voltage side to the high-voltage side and intensify. It is also evident that low-frequency interference from the high-voltage side to the low-voltage side also leaks and intensifies.

[0088] That is, if, as in Fig. 6 where the first winding section 51 (Np-1) is wound on the innermost layer, the second winding section 24 (Ns-2) is wound on the outside of it, the first winding section 23 (Ns-1) is wound on the outside of it and the second winding section 52 (Np-2) is wound on the outermost layer, it is evident that the core 46 should be grounded primarily to LVGND 18. (5-2) Earthing structure 2 of the switching transformer 15

[0089] In contrast, as in Fig. Figure 12 shows the winding specification in which the first winding section 23 (Ns-1) of the secondary winding 14 is wound on the high-voltage side on the innermost layer, followed by the second winding section 52 (Np-2), then the first winding section 51 (Np-1), and on the outermost layer the second winding section 24 (Ns-2). The first winding section 23 (Ns-1) is positioned near the middle leg section 67 of the core 46, and the second winding section 24 (Ns-2) is positioned near the outer leg section 68. In this case, the grounding terminal 74 should be connected to the connection section 72 for HVGND, and the core 46 should be grounded to HVGND 26.

[0090] If the core 46 of the switching transformer 15 matches the winding specification in Fig. When terminal 12 is grounded to HVGND 26, the high-voltage side (connected to the high-voltage power source 11) and the core 46 are brought to the same potential, thus suppressing unnecessary reverse currents and significantly improving high-frequency interference on the high-voltage side by suppressing unnecessary coupling. Furthermore, low-frequency interference on the low-voltage side is also improved by suppressing unnecessary coupling.

[0091] Depending on the winding specification of the switching transformer 15 and the frequency band in which noise reduction is required, it is also conceivable to connect the grounding terminal 74 to the earth connection section 73 and to ground the core 46 to earth (chassis 2). That is, depending on the winding specification of the primary winding 13 and the secondary winding 14 of the switching transformer 15 and the noise components, a preferred grounding destination should be determined in advance, and during assembly, the grounding terminal 74 should be connected either to the connection section 71 for LVGND, the connection section 72 for HVGND, or the connection section 73 for earth.

[0092] In this way, the connection section 71 for LVGND, the connection section 72 for HVGND and the connection section 73 for earth, which are connected to LVGND 18 on the low-voltage side, HVGND 26 on the high-voltage side and earth (chassis 2) respectively, are formed on the carrier 10 and the earthing terminal 74 of the core 46 can be selectively connected to the connection section 71 for LVGND, the connection section 72 for HVGND and the connection section 73 for earth, so that it is possible, according to the winding specification of the primary winding 13 and the secondary winding 14 and the frequency bands in which interference reduction is required, to connect the core 46 either to LVGND 18 or to HVGND 26 or to earth (chassis 2).

[0093] This allows common-mode interference to be reduced more effectively and easily.

[0094] In the winding specification, where the primary winding 13 and the secondary winding 14 are wound around the coil 43, the primary winding 13, as in Fig. As shown in Figure 6, which is positioned on the innermost layer, unnecessary back currents can be suppressed by connecting the earthing terminal 74 to the connection section 71 for LVGND, and a significant effect of interference improvement on the low voltage side can be achieved.

[0095] In the winding specification, where the primary winding 13 and the secondary winding 14 are wound around the coil 43, the secondary winding 14, as in Fig. As shown in Figure 12, which is positioned on the innermost layer, unnecessary back currents can be suppressed by connecting the earthing terminal 74 to the connection section 72 for HVGND, and a significant effect of interference improvement on the high voltage side can be achieved.

[0096] Furthermore, in the winding specification, where the first winding section 51, as in Fig. 6 shown, on the innermost layer and the second winding section 52 is positioned on the outer layer and the primary winding 13 is located close to the middle leg section 67 and outer leg section 68 of the core 46, by connecting the earthing terminal 74 to the connection section 71 for LVGND unnecessary return currents are suppressed and a significant effect of interference improvement on the low voltage side can be achieved.

[0097] In contrast, in the winding specification, where the first winding section 23, as in Fig.As shown in Figure 12, the second winding section 24 is positioned on the innermost layer and the secondary winding section 24 on the outermost layer, and the secondary winding 14 is located close to the middle leg section 67 and outer leg section 68 of the core 46, unnecessary reverse currents can be suppressed by connecting the grounding terminal 74 to the connection section 72 for HVGND, and a significant effect of interference improvement on the high voltage side can be achieved.

[0098] The winding specification of the switching transformer 15 is not limited to that described above, and the present invention is also effective for other winding specifications. In the exemplary embodiment, the high-voltage power source 11 and the low-voltage power source 12 are installed in the vehicle, with the primary winding 13 (the first winding section 51, the second winding section 52) of the switching transformer 15 being located on the low-voltage side, and the secondary winding 14 (the first winding section 23, the second winding section 24) being located on the high-voltage side. However, the present invention is not limited to this and is also effective if only the high-voltage power source 11 is installed and the switching transformer 15 generates the low voltage that is supplied to the control circuit 6 by the high-voltage power source 11.

[0099] In this case, contrary to the preceding embodiment, the primary winding 13 with the first winding section 51 and the second winding section 52 is located on the high-voltage side and the secondary winding 14 with the first winding section 23 and the second winding section 24 is located on the low-voltage side, so that, for example, in a winding specification where the first winding section 51 forms the innermost layer and the second winding section 52 forms the outermost layer, the grounding terminal 74 is connected to the connection section 72 for HVGND, and if the first winding section 23 forms the innermost layer and the second winding section 24 forms the outermost layer, the grounding terminal 74 is connected to the connection section 71 for LVGND.

[0100] Furthermore, the embodiment was explained using the switched-mode power supply 9 for the electric on-board compressor 1 as an example; however, the present invention is effective for all types of switched-mode power supplies with a switching transformer. LIST OF REFERENCE MARKS 1 electric on-board compressor 2 Chassis (Earth) 3 Engine 4 Inverter circuit 6 Control circuit 7, 8 EMI filter circuits 9 Switching power supply 10 carriers 11 High-voltage power source 12 Low-voltage power source 13 Primary winding 14 Secondary winding 15 Switching transformer 17 Switching element 18 LVGND 19 Switching power supply controllers (controllers) 23 First winding section (secondary winding) 24 second winding section (secondary winding) 26 HVGND 43 coil 46 core 51 First winding section (primary winding) 52 Second winding section (primary winding) 60 through hole 61 Winding shaft section 62 Flange section 63 In-depth study 67 middle thigh section 68 outer thigh section 68A Overhang 71 Connection section for LVGND 72 Connection section for HVGND 73 Connecting section for Earth G Air gap layer QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 7009325 B

[0007] JP 2021-2913 A

[0007]

Claims

[1] Switching transformer comprising a primary winding and a secondary winding and isolating the low-voltage side and the high-voltage side, comprising: a coil which has a central winding shaft section around which the primary winding and the secondary winding are wound, and has flange sections, each formed on both sides in the axial direction of the winding shaft section, and a core having a middle leg section that is inserted into a through-bore of the winding shaft section, characterized by that an air gap layer or a shielding layer is formed between the winding shaft section and the middle leg section. [2] Switching transformer according to claim 1, characterized by , that a depression is formed on the inner surface of the winding shaft section or on the outer surface of the middle leg section and the air gap layer is formed. [3] Switching transformer according to claim 1, characterized by , that the core has an outer leg section that covers the outside of the coil, and the outer leg section has an overhang that extends away from the middle leg section. [4] Switching transformer according to claim 3, characterized by , that the dimension between the inner surface of the overhang and the outermost primary or secondary winding is equal to or substantially equal to the dimension of the air gap layer or the shielding layer in the direction orthogonal to the middle leg section. [5] Switching power supply with a switching transformer according to one of claims 1 to 4, characterized by, that the low-voltage side is connected to a low-voltage power source and the high-voltage side is connected to a high-voltage power source, and the primary winding of the switching transformer is on the low-voltage side and the secondary winding is on the high-voltage side to switch the low-voltage power source and to supply power to a control circuit positioned on the high-voltage side. [6] Electric onboard compressor, characterized by : a switching power supply according to claim 5 for switching the low-voltage power source installed in a vehicle, a control circuit, an inverter circuit which is supplied with mains voltage by the high-voltage power source installed in the vehicle and controlled by the control circuit, and a motor which is driven by the inverter circuit. [7] Method for manufacturing a switching transformer according to any one of claims 1 to 4, characterized by, that if insulated wires are used as the primary winding and the secondary winding, no barrier tape is used that is provided between the primary winding and the secondary winding and a flange section of the coil, and the width dimension of the flange section is increased within the width dimension of the barrier tape. [8] Method for manufacturing a switching transformer according to claim 7, characterized by , that the width by which the width dimension of the flange section is increased is equal to or substantially equal to the dimension of the air gap layer or the shielding layer in the direction orthogonal to the middle leg section.

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