Power converter and pulse power supply

Abstract

In a power conversion device with multiple switching elements connected in series, the aim is to improve assembly efficiency while maintaining the insulation distance between the primary wiring and the core of the pulse transformer. [Solution] The power conversion device comprises a plurality of switching elements connected in series, a plurality of gate drive circuits connected to each switching element, and a plurality of pulse transformers 3 to which secondary wiring 4 is connected and primary wiring 5 is connected in series and a trigger voltage signal is input to the primary wiring 5. The pulse transformer 3 comprises a pulse transformer substrate 7, a ring-shaped core 8 placed on the pulse transformer substrate 7, secondary wiring 4 wound around the core 8, and primary wiring 5 that passes through the center of the core 8 and through the wiring hole 9 of the pulse transformer substrate 7. The primary wiring 5 is Litz wire. The wiring hole 9 has a sloped portion in which the hole diameter decreases from one side to the other side.

Description

Technical Field

[0001] The present invention relates to a pulse transformer in a power conversion device (such as a pulse power supply device) in which a plurality of switching elements are connected in series.

Background Art

[0002] FIG. 1 shows the configuration of a series connection circuit in which a plurality of switching elements are connected in series. In the configuration of the series connection circuit of FIG. 1, switching elements 1 (SiC-MOSFETs) operable at high speed and high frequency are connected in series, and each switching element 1 is provided with a gate drive circuit 2 and a pulse transformer 3. Inputting a trigger voltage signal (an on / off command signal for the switching elements) to a primary-side wiring 5 of the pulse transformer 3 enables the plurality of switching elements 1 to perform switching simultaneously. Details of the operation of each part in the circuit of FIG. 1 are disclosed in Patent Document 1.

[0003] Patent Document 1 discloses a technique related to the pulse transformer 3 of a series connection circuit in which a plurality of switching elements are connected in series. FIG. 2 shows a mounting image of this pulse transformer 3, and FIG. 3 shows the configuration of a pulse transformer substrate.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] The primary wiring 5 of the pulse transformer 3 uses Litz wire to reduce heat generation due to high frequencies (see paragraph

[0028] of Patent Document 1). However, because Litz wire consists of multiple strands twisted together, when inserting the primary wiring 5 into the wiring hole 9 of the pulse transformer substrate 7 in Figure 3 during assembly, there was a risk that the tip of the primary wiring 5 would come into contact with the pulse transformer substrate 7 and unravel. As a result, assembling the pulse transformer 3 became time-consuming and the assembly workability was poor.

[0006] Furthermore, because pulse power supplies generate high voltages, it is necessary to maintain a long insulation distance between components within the device. However, widening the diameter of the wiring hole 9 presented a problem: it was difficult to maintain the insulation distance between the primary wiring 5 and the core 8 (secondary wiring 4).

[0007] For the reasons described above, a challenge in power conversion devices with multiple switching elements connected in series is to improve assembly efficiency while maintaining the insulation distance between the primary wiring of the pulse transformer and the core. [Means for solving the problem]

[0008] The present invention was devised in view of the above-mentioned conventional problems, and one aspect thereof is a power conversion device comprising: a plurality of switching elements connected in series; a plurality of gate drive circuits connected to each of the switching elements and outputting gate signals to each of the switching elements; and a plurality of pulse transformers to which secondary wiring is connected to each of the gate drive circuits, and primary wiring is connected in series and a trigger voltage signal is input to the primary wiring, wherein the pulse transformer comprises a pulse transformer substrate; a ring-shaped core placed on the pulse transformer substrate; the secondary wiring wound around the core; and the primary wiring that passes through the center of the core and through the wiring holes of the pulse transformer substrate, wherein the primary wiring is Litz wire, and the wiring holes of the pulse transformer substrate are characterized in that they have inclined portions in which the diameter of the holes decreases from one side to the other side. [Effects of the Invention]

[0009] According to the present invention, in a power conversion device in which multiple switching elements are connected in series, it is possible to improve assembly workability while maintaining the insulation distance between the primary side wiring of the pulse transformer and the core. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram showing the configuration of a series connection circuit in which multiple switching elements are connected in series. [Figure 2] An illustrative diagram of the implementation of a pulse transformer. [Figure 3] A diagram showing the configuration of a conventional pulse transformer board. [Figure 4] A diagram showing an example of the circuit configuration of a pulse power supply device. [Figure 5] A diagram showing the configuration of the pulse transformer substrate in the embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the power conversion device according to the present invention will be described in detail with reference to Figures 1, 2, 4, and 5.

[0012] [Examples] First, as an example of a power conversion device in this embodiment, the circuit configuration of a pulse power supply device will be described based on Figure 4. Figure 4 is the same as Figure 5 in Patent Document 1.

[0013] A capacitor C is connected in parallel to the DC power supply Vdc. A first switching element SW1 and a first resistor R1 are connected between one end of the DC power supply Vdc and the load lord. The symbol L represents the stray inductance. A series circuit of a second resistor R2 and a second switching element SW2 is connected in parallel to the load lord. As described in Patent Document 1, the first resistor R1, the second resistor R2, and the second switching element SW2 may not be required to be implemented.

[0014] When it is desired to supply energy to a load and raise the voltage of the load, the first switching element SW1 is turned ON and the second switching element SW2 is turned OFF. Thereafter, when it is desired to lower the voltage of the load, the first switching element SW1 is turned OFF and the second switching element SW2 is turned ON.

[0015] In the present embodiment, a series connection circuit obtained by connecting the plurality of switching elements 1 of Fig. 1 in series is applied to the first switching element SW1 and the second switching element SW2 of this pulse power supply device. Next, the series connection circuit in the present embodiment will be described based on Fig. 1.

[0016] As shown in Fig. 1, a plurality of switching elements 1 are connected in series. Further, a gate drive circuit 2 is connected to each switching element 1 respectively, and a gate signal is output from each gate drive circuit 2 to each switching element.

[0017] Pulse transformers 3 are also provided respectively corresponding to each switching element 1. Secondary-side wirings 4 of each pulse transformer 3 are connected to each gate drive circuit 2 respectively. Primary-side wirings 5 of each pulse transformer 3 are connected in series.

[0018] Note that reference numeral 6 in Fig. 1 denotes a snubber circuit connected to each switching element 1. The snubber circuit 6 includes a snubber capacitor CS connected in parallel to the switching element 1 and a snubber resistor RS connected in parallel to the switching element 1. The snubber circuit 6 may be omitted.

[0019] In the series connection circuit configured as described above, by inputting a trigger voltage signal to the primary-side wiring 5, a gate signal is output to each switching element 1 via the pulse transformer 3 and the gate drive circuit 2, and each switching element 1 can be caused to perform switching simultaneously.

[0020] Next, the pulse transformer 3 will be described with reference to FIG. Reference numeral 7 denotes a pulse transformer substrate. A ring-shaped core 8 is placed on the pulse transformer substrate 7. A secondary-side wiring 4 is wound around the core 8. A plurality of the pulse transformer substrates 7 are stacked and arranged in a state where the core 8 is placed thereon.

[0021] Further, in the pulse transformer substrate 7, a wiring hole, which will be described later, is formed in the central portion of the core 8. The primary-side wiring 5 is provided so as to pass through the center of the core 8 and penetrate through this wiring hole. Here, the primary-side wiring 5 is a litz wire.

[0022] The configuration of the pulse transformer 3 in the present embodiment is shown in FIG. In the wiring hole 9 of the pulse transformer substrate 7 through which the primary-side wiring 5 is inserted, an inclined portion whose hole diameter decreases as going from one surface side of the pulse transformer substrate 7 toward the other surface side is formed. That is, as shown in FIG. 5, the inlet side of the wiring hole 9 is formed to be large like a countersink.

[0023] In the present embodiment, in order to insert the primary-side wiring 5 from the upper side to the lower side in FIG. 5, the hole diameter on the upper side in FIG. 5 is formed larger than the hole diameter on the lower side in FIG. 5, and the hole diameter decreases as going from the inlet side toward the outlet side.

[0024] By forming the wiring hole 9 of the pulse transformer substrate 7 in this manner, when inserting the primary-side wiring 5 into the wiring hole 9, even if the tip end of the primary-side wiring 5 deviates outward from the center of the wiring hole 9, the tip end of the primary-side wiring 5 abuts against the inclined portion and is guided toward the center of the wiring hole 9 along the inclined portion. This makes it easy to insert the primary-side wiring 5 into the wiring hole 9, and makes it possible to improve assembly workability.

[0025] Further, since the hole diameter on the outlet side of the wiring hole 9 is narrow, the primary-side wiring 5 is fixed at the central position of the wiring hole 9, making it possible to secure an insulation distance between the primary-side wiring 5 and the core 8 (secondary-side wiring 4).

[0026] Furthermore, since the primary wiring 5 is Litz wiring, its tip is prone to unraveling. However, as in this embodiment, the inclined portion is formed in the wiring hole 9, which makes it possible to suppress the unraveling of the tip of the primary wiring 5, which is Litz wiring.

[0027] In this embodiment, a pulse power supply device was described as a power conversion device, but the application of the present invention is not limited to pulse power supplies. The invention is applicable to all power conversion devices that have a configuration in which switching elements are connected in series.

[0028] Although the present invention has been described in detail only with respect to the specific examples described above, it will be obvious to those skilled in the art that a wide variety of modifications and alterations are possible within the scope of the technical concept of the present invention, and it is natural that such modifications and alterations fall within the scope of the claims. [Explanation of Symbols]

[0029] 1…Switching element, 2…Gate drive circuit, 3…Pulse transformer, 4…Secondary wiring, 5…Primary wiring, 6…Snubber circuit, CS…Snubber capacitor, RS…Snubber resistor, 7…Pulse transformer board, 8…Core, 9…Wiring hole, Vdc…DC power supply, C…Capacitor, load…Load, SW1…First switching element, SW2…Second switching element, R1…First resistor, R2…Second resistor, L…Stray inductance

Claims

1. Multiple switching elements connected in series, A plurality of gate drive circuits, each connected to a switching element and each outputting a gate signal to a switching element, A power conversion device comprising: a plurality of pulse transformers, each of which has a secondary wiring connected to it, and whose primary wiring is connected in series and to which a trigger voltage signal is input; The pulse transformer is Pulse transformer substrate and A ring-shaped core placed on the pulse transformer substrate, The secondary wiring wound around the core, The primary wiring passes through the center of the core and through the wiring hole of the pulse transformer substrate, Equipped with, The primary wiring is Litz wire. The power conversion device is characterized in that the wiring holes of the pulse transformer substrate have inclined portions in which the diameter of the holes decreases as you move from one side to the other side.

2. Multiple switching elements connected in series, A plurality of gate drive circuits, each connected to a switching element and each outputting a gate signal to a switching element, A pulse power supply device comprising: a plurality of pulse transformers, each of which is connected to a secondary side wiring, and whose primary side wiring is connected in series and to which a trigger voltage signal is input; The pulse transformer is Pulse transformer substrate and A ring-shaped core placed on the pulse transformer substrate, The secondary wiring wound around the core, The primary wiring passes through the center of the core and through the wiring hole of the pulse transformer substrate, Equipped with, The primary wiring is Litz wire. The pulse power supply device is characterized in that the wiring holes of the pulse transformer substrate have inclined portions in which the diameter of the holes decreases as you move from one side to the other side.

Images