JP7779303B2 - Circuit board structure with transformer core substrate, gate drive circuit - Google Patents

Description

The present invention relates to a substrate-mounted transformer structure and a gate drive circuit equipped with the structure.

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

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

Patent No. 5221203 Patent No. 6965714 JP 2023-67333 A

The structures in Patent Documents 1 and 2 had the following problems:

(1) The structure of Patent Document 1 requires that a secondary winding 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.

In addition, the series primary windings are arranged to pass through the hollow parts of all the transformer cores, and only their ends are supported on the printed circuit board, meaning there are few fixed points and the center can bend. As a result, if vibrations are applied when the device is installed, the primary windings may swing and come into contact with the transformer cores.

As a result, depending on the position of the primary winding, the bending may prevent a uniform insulation distance from the transformer core, which can lead to partial discharges. This can lead to a deterioration in insulation and potential leakage inductance problems.

(2) The structure of Patent Document 2 requires winding the secondary wire after forming, making it unsuitable 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, separate terminals must be provided at the ends of the winding for connection, making connectivity with other circuits complicated and making assembly difficult.

The present invention was made to solve these conventional problems, and aims to improve the mass productivity and assembly efficiency of board-mounted transformer structures and reduce leakage inductance.

(1) The transformer structure of the present invention is
a conductor for fixing the transformer core on the substrate;
a hole formed in the substrate at a position corresponding to approximately the center of the transformer core;
a primary winding disposed in a hollow portion of the transformer core through the hole;
a secondary winding formed by the conductor and a pattern on the substrate;
a connecting member for connecting the secondary winding to a circuit;
It is characterized by having:

(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 also be bonded to the substrate, and the primary winding may be a Litz wire.

(3) As another aspect of the transformer structure, multiple substrates can be connected to the circuit substrate. In this case, the primary winding can be made of a copper rod. It is also possible to configure the transformer with a pair of transformer cores corresponding to the on-side circuit and the off-side circuit of a push-pull configuration.

(4) The gate drive circuit of the present invention comprises:
a modulation circuit that outputs a first modulation signal and a second modulation signal based on an on command and an off command of the gate command;
an on-side rectifier circuit and an off-side rectifier circuit each having the transformer structure;
Equipped with
The transformer core of the on-side rectifier circuit includes an on-side primary winding to which the first modulation signal is applied, and an on-side secondary winding that transforms and outputs the voltage applied to the primary winding,
The transformer core of the off-side rectifier circuit is characterized by having an off-side primary winding to which the second modulation signal is applied, and an off-side secondary winding that transforms and outputs the voltage applied to the primary winding.

This invention makes it possible to improve the mass productivity and assembly of board-mounted transformer structures and suppress leakage inductance.

FIG. 2A is a front view of the first embodiment, and FIG. 2B is a rear view of the same. FIG. 2 is a perspective view of FIG. 1; (a) is a diagram showing a configuration with a center tap, and (b) is a diagram showing a configuration in which the secondary side has a plurality of different outputs. (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. FIG. 10 is a perspective view showing an arrangement image of a second embodiment .

The following describes a transformer structure according to an embodiment of the present invention. This transformer structure is mounted on a printed circuit board and is configured as a pulse transformer board using a transformer core.

The transformer structure uses a pulse transformer board with an easy-to-assemble structure that minimizes individual variations, 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 board.

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

The modulation circuit outputs a first modulation signal and a second modulation signal based on the gate command's on command and off command. Here, the transformer core substrate is used for the on-side rectifier circuit and the off-side rectifier circuit.

In other words, 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.

The pulse transformer core of the off-side rectifier circuit also has an off-side primary winding to which the first modulation 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.

Example 1 of the transformer core substrate will be described with reference to Figures 1 to 3. Reference numeral 1 in the figures indicates the transformer core substrate.

The transformer core substrate 1 comprises a pair of pulse transformer cores 2 mounted on a substrate 6 and multiple conductors (electric wires) 3 that secure both pulse transformer cores 2 to the substrate 6. One pulse transformer core 2 is used in the ON-side rectifier circuit, and the other pulse transformer core 2 is used in the OFF-side rectifier circuit.

A hole 10 is formed in the substrate 6 at approximately the radial center position of each pulse transformer core 2. The primary winding is placed inside the hollow portion 2a of the pulse transformer core 2 through each hole 10.

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

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.
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 board 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 provide the following effects.

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

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

Furthermore, in specifications with strict vibration conditions, the pulse transformer core 2 can be more firmly fixed by using adhesive in addition to the conductors 3a-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.

(3) Furthermore, the inner diameter of the hole 10 formed in the substrate 6 is slightly larger than the diameter of the primary winding. This makes it possible to prevent the primary winding from misaligning with the pulse transformer core 2.

At this time, there is no wiring pattern between the pulse transformer core 2 and the hole 10, and the insulation distance between the primary and secondary windings is ensured uniformly around the hole 10. This ensures an insulation distance between the primary and secondary windings, which has the effect of suppressing partial discharge and leakage inductance. This point will be explained based on the comparative test in Figure 4.

<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.

Here, Figure 4(a) shows Model 1, Figure 4(b) shows Model 2, and Figure 4(c) shows Model 3. Also, in Figures 4(a) to 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).

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 ensured uniformly.

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.

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.

In this test, a standard transformer core C was used. The current values on both the low-voltage and high-voltage sides were kept within a range that did not cause magnetic saturation.

<Test Results>
The comparison results (test results) in FIG. 4 show the relative values of leakage inductance (primary side) when Model 1 is set to "100%."
in particular,
・Model 1 = 100%
・Model 2 = Approximately 150%
・Model 3 = Approximately 250%
The comparison results were obtained.

The test results confirmed that Model 1, which simulated the transformer core substrate 1, had the smallest leakage inductance value. This proves the leakage inductance suppression effect of the transformer core substrate 1.

As a result, when the transformer core substrate 1 is applied to, for example, the gate circuit of the switching element of Patent Document 3, it is expected that the leakage inductance can be suppressed, thereby speeding up the switching operation of the switching element.

In addition, the structure in which Model 1 is implemented, i.e., the structure of the transformer core board 1, has fixed primary and secondary windings, which also results in less variation in leakage inductance of each pulse transformer core 2.

Second Embodiment A second embodiment will be described with reference to Fig . 5. Here, a second embodiment using a plurality of the transformer core substrates 1 will be described, and the main board (circuit board) 30 shown in Fig. 5 will be used.

This main board 30 has a group of male connectors 31a, 31b that connect to the female connectors 5a, 5b on the board 6, allowing various electrical components 32 such as gate drive circuits to be mounted according to the number of transformer core boards 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 boards 1 can be aligned when mounted on the main board 30.

As a result, the holes 10 of each transformer core substrate 1 can be aligned to approximately the same height, improving assembly. In this case, a copper rod can be used for the primary winding instead of an electric wire, and using a copper rod improves workability when passing the primary winding through the holes 10 of each transformer core substrate 1. The copper rod also prevents misalignment or tilting of each transformer core substrate 1, improving vibration resistance.

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

The present invention is not limited to the above embodiment, and can be modified and implemented within the scope of the claims. For example, the number of pulse transformer cores 2 on the substrate 6 does not have to be two, and the effects of Examples 1 and 2 can be obtained even if the number of cores is changed.

In addition, Litz wire can be used for the primary winding of the transformer core substrate 1, making it possible to support 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.

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 (7)

A circuit board structure in which a plurality of transformer core boards each having a transformer core are mounted vertically,
The transformer core substrate is
a conductor for fixing a transformer core on the transformer core substrate;
a hole formed in the transformer core substrate at a position corresponding to approximately the center of the transformer core;
a primary winding disposed in a hollow portion of the transformer core through the hole;
a secondary winding formed by the conductor and a pattern on the transformer core substrate;
a first connector that connects the secondary winding to a circuit and is provided on a surface of the transformer core substrate on the side of the end that is to be mounted on the circuit board ;
Equipped with
The circuit board includes:
a second connector member connected to the first connector member on a mounting surface of the transformer core substrate;
A circuit board structure including a transformer core substrate, wherein electrical components can be mounted according to the number of the transformer core substrates. a plurality of the conductors;
2. The structure of a circuit board equipped with a transformer core substrate according to claim 1, wherein the conductors are provided at equal intervals in the circumferential direction of the transformer core. 2. The circuit board structure with a transformer core substrate according to claim 1, wherein the transformer core is bonded to the transformer core substrate. 2. The circuit board structure with a transformer core substrate according to claim 1, wherein the primary winding is a litz wire. 2. The circuit board structure with a transformer core substrate according to claim 1, wherein the primary winding is made of a copper rod. 2. The structure of a circuit board equipped with a transformer core substrate according to claim 1, further comprising a pair of the transformer cores corresponding to an ON-side circuit and an OFF-side circuit of a push-pull configuration. a modulation circuit that outputs a first modulation signal and a second modulation signal based on an on command and an off command of the gate command;
A circuit board structure including the transformer core substrate according to any one of claims 1 to 6;
an on-side rectifier circuit and an off-side rectifier circuit respectively provided on any one of the transformer core substrates ;
Equipped with
The transformer core of the on-side rectifier circuit includes an on-side primary winding to which the first modulation signal is applied, and an on-side secondary winding that transforms and outputs the voltage applied to the primary winding,
the transformer core of the off-side rectifier circuit includes an off-side primary winding to which the second modulation signal is applied, and an off-side secondary winding that transforms and outputs a voltage applied to the primary winding.