Transformer structure, gate drive circuit

Abstract

The present invention improves the mass-producibility and ease of assembly of a substrate-mounted transformer structure and suppresses leakage inductance. A transformer core substrate 1 has holes 10 that correspond to the approximate center positions of respective pulse transformer cores 2 in the radial direction. Respective primary windings are provided inside the pulse transformer cores 2 via the holes 10. Respective secondary windings that are wound onto the pulse transformer cores 2 are formed from a wiring pattern that is inside a substrate 6 and six conductors (electrical wires) 3 that are soldered to the substrate 6. The transformer core substrate 1 can be connected to a main board 30 by connectors 5a, 5b.

Description

Transformer structure, gate drive circuit

[0001] The present invention relates to a substrate-mounted transformer structure and a gate drive circuit incorporating the structure.

[0002] Transformers for driving gates of semiconductor elements for pulse power supplies are known, for example, from Patent Documents 1 and 2. Patent Document 1 describes a structure in which multiple transformer cores are attached to a printed circuit board so that the hollow portions of the cores are aligned in a row.

[0003] In Patent Document 2, a secondary wire is mounted on a substrate and wound around a core after being formed into multiple turns. Also, multiple gate drive circuit substrates are connected in series, and the primary wire of the pulse transformer is inserted through a hole in the substrate and placed at the center of the core on the substrate.

[0004] Japanese Patent No. 5221203 Japanese Patent No. 6965714 Japanese Patent Laid-Open No. 2023-67333

[0005] The structures of Patent Documents 1 and 2 have the following problems.

[0006] (1) The structure of Patent Document 1 requires a secondary winding to be wound around each transformer core, which requires a base for mounting on a board. In other words, a base for fixing to the board must be prepared, and a secondary winding must be wound around each individual core, which is not suitable for mass production.

[0007] In addition, the series primary windings are arranged to penetrate the hollow parts of all the transformer cores, and only their ends are supported on the printed circuit board, so there are few fixing points and the center can bend. Therefore, if vibrations are applied when the transformer is installed in a device, the primary windings may swing and come into contact with the transformer cores.

[0008] As a result, depending on the position of the primary winding, the bending may prevent a uniform insulation distance from being secured between the primary winding and the transformer core, which may result in partial discharge, deteriorating insulation and potentially causing leakage inductance problems.

[0009] (2) The structure of Patent Document 2 requires winding the secondary wire after forming, which is not suitable for mass production. In particular, the substrate of Patent Document 2 requires a separate fixing mechanism when connecting to the gate drive circuit, and because the secondary wire is also a wire, a separate terminal must be provided at the end of the winding for connection, making connection to other circuits complicated and making assembly difficult.

[0010] The present invention has been made to solve these conventional problems, and aims to improve the mass productivity and assembly efficiency of a board-mounted transformer structure and to suppress leakage inductance.

[0011] (1) The transformer structure of the present invention is characterized by comprising: a conductor for fixing a transformer core on a substrate; a hole formed in the substrate at a position corresponding to approximately the center of the transformer core; a primary winding that passes through the hole and is placed in the hollow portion of the transformer core; a secondary winding formed by the conductor and a pattern on the substrate; and a connecting member that connects the secondary winding to a circuit.

[0012] (2) One aspect of the transformer structure includes a plurality of the conductors, each of which is arranged at equal intervals around the circumference of the transformer core. The transformer core may be bonded to the substrate, and the primary winding may be a litz wire. (3) Another aspect of the transformer structure includes a plurality of the substrates connected to the circuit substrate. In this case, the primary winding may be made of a copper rod. A configuration may also be provided in which a pair of the transformer cores are provided corresponding to the on-side circuit and the off-side circuit of a push-pull configuration.

[0013] (4) A gate drive circuit of the present invention comprises: a modulation circuit that outputs a first modulated signal and a second modulated signal based on an ON command and an OFF command of a gate command; and an ON-side rectifier circuit and an OFF-side rectifier circuit that have the transformer structure; wherein the transformer core of the ON-side rectifier circuit comprises an ON-side primary winding to which the first modulated signal is applied and an ON-side secondary winding that transforms and outputs the voltage applied to the primary winding, while the transformer core of the OFF-side rectifier circuit comprises an OFF-side primary winding to which the second modulated signal is applied and an OFF-side secondary winding that transforms and outputs the voltage applied to the primary winding.

[0014] According to the present invention, it is possible to improve the mass productivity and assembly efficiency of a substrate-mounted transformer structure and to suppress leakage inductance.

[0015] [Correction based on Rule 91 19.09.2024] (a) is a front view of Example 1, (b) is a rear view of the same. Perspective view of Figure 1. (a) is a configuration diagram with a center tap, (b) is a configuration diagram with multiple different outputs on the secondary side. (a) is the test result of Model 1, (b) is the test result of Model 2, and (c) is the test result of Model 3. Perspective view showing the layout image of Example 2.

[0016] A transformer structure according to an embodiment of the present invention will now be described. This transformer structure is mounted on a printed circuit board and is configured as a pulse transformer board using a transformer core.

[0017] The transformer structure employs a pulse transformer substrate that is easy to assemble with little individual variation, thereby improving productivity and reducing the leakage inductance of the transformer core. In this embodiment, the transformer structure is referred to as a transformer core substrate.

[0018] This transformer core substrate is used, for example, in a gate drive circuit with a push-pull configuration as described in Patent Document 3. This gate drive circuit includes a modulation circuit, an ON-side rectification circuit, an OFF-side rectification circuit, a demodulation circuit, and a gate circuit, and controls a semiconductor element to be driven.

[0019] The modulation circuit outputs a first modulation signal and a second modulation signal based on an ON command and an OFF command of the gate command. Here, the transformer core substrate is used for the ON-side rectifier circuit and the OFF-side rectifier circuit.

[0020] That is, the pulse transformer core of the on-side rectifier circuit has an on-side primary winding to which the first modulation signal is applied, and an on-side secondary winding that transforms the voltage applied to the primary winding and outputs it to the demodulation circuit.

[0021] In addition, the pulse transformer core of the off-side rectifier circuit has an off-side primary winding to which the first modulated signal is applied, and an off-side secondary winding that transforms the voltage applied to the primary winding and outputs it to the demodulation circuit.

[0022] A first embodiment of the transformer core substrate will be described with reference to Figures 1 to 3. In the figures, reference numeral 1 denotes the transformer core substrate.

[0023] The transformer core substrate 1 includes a pair of pulse transformer cores 2 mounted on a substrate 6 and a plurality of conductors (electric wires) 3 that secure both pulse transformer cores 2 to the substrate 6, with one pulse transformer core 2 being used in the ON-side rectifier circuit and the other pulse transformer core 2 being used in the OFF-side rectifier circuit.

[0024] The substrate 6 is formed with holes 10 at approximately the radial center positions of the pulse transformer cores 2. The primary winding is arranged in the hollow portion 2a of the pulse transformer core 2 through each hole 10.

[0025] On the other hand, the secondary winding wound around each pulse transformer core 2 is composed of a wiring pattern inside the substrate 6 and six conductors (electric wires) 3a to 3f soldered to the substrate 6. As shown in Fig. 2, each of these conductors 3a to 3f has an inverted U shape and is provided at equal intervals at 60-degree positions around each pulse transformer core 2. Each of the conductors 3a to 3f is connected with the pulse transformer core 2 sandwiched inside, simultaneously fixing the pulse transformer core 2 and providing electrical continuity.

[0026] Furthermore, conductors 3a to 3f and the pins of female connectors 5a and 5b are connected by wiring patterns provided on the front and back surfaces of substrate 6. That is, part of the secondary winding is formed by the wiring pattern on substrate 6, and conductors 3a to 3f and the corresponding pins of female connectors 5a and 5b are wired and connected within substrate 6. For example, conductors 3a and 3b and the corresponding pins of female connector 5a can be connected by the wiring pattern on the front surface of substrate 6, and conductors 3c to 3f and the corresponding pins of female connector 5b can be connected by the wiring pattern on the back side of the substrate.

[0027] Furthermore, the secondary winding using a wiring pattern can be configured with a center tap T as shown in FIG. 3(a), or with the secondary side Q having multiple different outputs O1 and O2 as shown in FIG. 3(b) (P in FIG. 3 indicates the primary side). Additionally, the female connector 5 to be connected and the ratio of the number of turns can be set arbitrarily by wiring the substrate 6. However, no wiring pattern is provided between the pulse transformer core 2 and the hole 10. The transformer core substrate 1 configured in this manner can achieve the following effects.

[0028] (1) Compared to Patent Documents 1 and 2, the process of winding the secondary winding is eliminated, and mounting by solder flow like TMD components is possible. This facilitates mass production, improves productivity, and enables cost reduction.

[0029] (2) Each pulse transformer core 2 is fixed to the circuit board 6 by conductors 3a to 3f, improving vibration resistance and product quality. This also simplifies positioning and prevents core misalignment, improving manufacturing efficiency and making it suitable for mass production.

[0030] In specifications with severe vibration conditions, the pulse transformer core 2 can be more firmly fixed by using adhesive in addition to the conductors 3a to 3f. This can also be said to be an effect of mounting the pulse transformer core 2 on the substrate 6, and quality can also be improved by suppressing individual differences.

[0031] (3) Furthermore, the inner diameter of the hole 10 formed in the substrate 6 is slightly larger than the diameter of the primary winding, which makes it possible to suppress misalignment of the primary winding with respect to the pulse transformer core 2.

[0032] In this case, there is no wiring pattern between the pulse transformer core 2 and the hole 10, and the insulation distance between the primary winding and the secondary winding is ensured uniformly around the hole 10. This ensures an insulation distance between the primary winding and the secondary winding, and has the effect of suppressing partial discharge and leakage inductance. This point will be explained based on the comparative test in FIG. 4.

[0033] <Contents of the comparison test> Using frequency response analysis of 2D magnetic field analysis in JMAG (electromagnetic field analysis software), the magnitude of leakage inductance on the primary side was compared for models 1 to 3, which had different winding shapes and arrangements.

[0034] Here, Fig. 4(a) shows Model 1, Fig. 4(b) shows Model 2, and Fig. 4(c) shows Model 3. In Fig. 4(a) to Fig. 4(c), C indicates the transformer core, P indicates the low-voltage side (primary side), and Q indicates the high-voltage side (secondary to seventh sides).

[0035] Model 1 In Model 1, the low-voltage side P passes through the center of the transformer core C, and the high-voltage side Q is wound around the transformer core C at 60-degree intervals. This Model 1 simulates the transformer core substrate 1, and the insulation distance between the low-voltage side P and the high-voltage side Q is uniformly secured.

[0036] Model 2 In Model 2, the low-voltage side P passes through the center of the transformer core C, but the high-voltage side Q is moved to the end of the transformer core C. This Model 2 simulates Figure 10 of Patent Document 1.

[0037] Model 3: In Model 3, the low-voltage side P is wound close to one end of the transformer core C, and the high-voltage side Q is wound close to the opposite side. Model 2 simulates Figure 9 of Patent Document 1, and resembles the state in which the primary winding is bent.

[0038] In this test, a standard transformer core C was used. The current values ​​on both the low-voltage side and the high-voltage side were set within a range where there was no magnetic saturation.

[0039] <Test Results> The comparison results (test results) in Figure 4 show the relative values ​​of leakage inductance (primary side) when Model 1 is set to "100%." ​​Specifically, the following comparison results were obtained: Model 1 = 100% Model 2 = approximately 150% Model 3 = approximately 250%

[0040] According to the test results, it was confirmed that the leakage inductance value was the smallest in model 1 simulating the transformer core substrate 1. This proves the leakage inductance suppression effect of the transformer core substrate 1.

[0041] As a result, when the transformer core substrate 1 is applied to the gate circuit of the switching element of Patent Document 3, for example, the effect of speeding up the switching operation of the switching element can be expected by suppressing leakage inductance.

[0042] In addition, in the structure for mounting the model 1, i.e., the structure of the transformer core substrate 1, the primary winding and secondary winding are fixed, so an effect of reducing the variation in leakage inductance of each pulse transformer core 2 was obtained.

[0043] [Correction based on Rule 91 19.09.2024] A second embodiment will be described with reference to Fig. 5. Here, an embodiment using a plurality of the transformer core substrates 1 is shown, and the main board (circuit board) 30 shown in Fig. 5 is used.

[0044] The main board 30 includes a group of male connectors 31a, 31b that are connected to the female connectors 5a, 5b of the substrate 6, and various electrical components 32 such as gate drive circuits can be mounted according to the number of the transformer core substrates 1. According to this embodiment, by connecting the female connectors 5a, 5b to the male connectors 31a, 31b, the height of the group of transformer core substrates 1 can be made uniform when mounted on the main board 30.

[0045] As a result, the holes 10 of the transformer core substrates 1 can be aligned to approximately the same height, improving assembly efficiency. In this case, a copper rod may be used for the primary winding instead of an electric wire, and using the copper rod improves the workability when passing the primary winding through the hole 10 of the transformer core substrates 1. Furthermore, the copper rod prevents the transformer core substrates 1 from shifting or tilting, improving vibration resistance.

[0046] Furthermore, since it can be connected to the main board 30 using the female connectors 5a and 5b, there is no need to prepare a base specifically for fixing the core and connect the secondary winding separately, as in Patent Document 1, which is also expected to improve productivity and assembly.

[0047] The present invention is not limited to the above-described embodiment, and can be modified within the scope of the claims. For example, the number of pulse transformer cores 2 on the substrate 6 does not need to be two, and the effects of Examples 1 and 2 can be obtained even when the number of cores is changed.

[0048] Furthermore, a litz wire can be used as the primary winding of the transformer core substrate 1, which enables high-speed driving. Furthermore, a gate drive circuit with a push-pull configuration using the transformer core substrate 1 also naturally constitutes the present invention.

[0049] REFERENCE SIGNS LIST 1... transformer core substrate 2... pulse transformer core 2... hollow portion 3a to 3f... conductors 5a, 5b, 31a, 31b... connectors 6, 30... substrate 10... hole portion

Claims

1. A transformer structure comprising: a conductor for fixing a transformer core onto a substrate; a hole formed in the substrate at a position approximately corresponding to the center of the transformer core; a primary winding that passes through the hole and is placed in a hollow portion of the transformer core; a secondary winding formed by the conductor and a pattern on the substrate; and a connecting member that connects the secondary winding to a circuit.

2. The transformer structure according to claim 1, characterized in that it comprises a plurality of said conductors, each of which is provided at equal intervals in the circumferential direction of said transformer core.

3. The transformer structure according to claim 1, wherein said transformer core is bonded to said substrate.

4. A transformer structure as claimed in claim 1, characterized in that said primary winding is made of Litz wire.

5. A transformer structure according to claim 1, characterized in that a plurality of said substrates are connected to a substrate of said circuit.

6. A transformer structure as claimed in claim 5, characterized in that said primary winding is constructed from a copper rod.

7. The transformer structure according to claim 1, characterized in that it comprises a pair of said transformer cores corresponding to an ON side circuit and an OFF side circuit of a push-pull configuration.

8. A gate drive circuit comprising: a modulation circuit which outputs a first modulated signal and a second modulated signal based on an on command and an off command of a gate command; and an on-side rectifier circuit and an off-side rectifier circuit which have the transformer structure described in any one of claims 1 to 7, wherein the transformer core of the on-side rectifier circuit comprises an on-side primary winding to which the first modulated signal is applied, and an on-side secondary winding which transforms and outputs the voltage applied to the primary winding, while the transformer core of the off-side rectifier circuit comprises an off-side primary winding to which the second modulated signal is applied, and an off-side secondary winding which transforms and outputs the voltage applied to the primary winding.

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