JP7033835B2 - Switching power supply and power converter - Google Patents

Description

Embodiments of the present invention relate to a switching power supply device and a power conversion device.

A power conversion device used in a backbone power system or the like may have a circuit part charged to a high voltage, and when arranging circuit parts or circuit elements in close proximity to such a circuit part, sufficient insulation measures are taken. Need to be applied.

There is a switching power supply device provided inside such a power conversion device and supplying power to various control circuits, drive circuits, and the like of the power conversion device. A transformer used in such a switching power supply device is connected to a high-voltage charging unit, and a switching element generates a higher-voltage switching pulse or the like. Therefore, a measure for electrically insulating from other circuit parts or the like is required. Be given.

As a measure for insulating, there is a method of filling the periphery of the transformer with an insulating resin. When the transformer is filled with a thermosetting resin, stress is applied to the core of the transformer when the resin is cured, and the magnetic properties of the core may change due to the stress.

Some switching power supply circuits are sensitive to changes in the magnetic characteristics of the transformer core, and it is desirable to reduce the stress applied to the transformer core. For example, in a flyback type switching power supply, the energy stored in proportion to the excitation inductance of the core is transmitted to the secondary side, so a decrease in the excitation inductance may lead to a decrease in the performance of the switching power supply. ..

Japanese Unexamined Patent Publication No. 2002-198234

Embodiments provide a switching power supply and a power conversion device in which the magnetic characteristics of the transformer core are less likely to fluctuate due to stress.

The switching power supply device according to the embodiment extends along the winding, the first leg portion and the second leg portion arranged in parallel, and the direction in which the first leg portion and the second leg portion extend, and the above-mentioned The magnetic flux generated in the third leg portion provided between the first leg portion and the second leg portion and in which the winding is wound and the third leg portion by the winding is the first leg portion. A magnetic core including a magnetic circuit passing through the second leg portion, an insulating case for accommodating the winding and the magnetic core, an exterior resin for sealing the entire case, and the case. It comprises a transformer comprising an insulating spacer provided between the magnetic core and the magnetic core. The third leg portion is a joint surface of one end of the third leg portion, and has a direction orthogonal to the extending direction of the first leg portion, the second leg portion, and the third leg portion. The spacer is provided on the side of the other end of the third leg, including the joining surface.

In the present embodiment, a switching power supply device and a power conversion device that are less likely to cause fluctuations in the magnetic characteristics of the transformer core due to stress are realized.

It is a block diagram which illustrates the switching power supply device which concerns on embodiment. It is a block diagram which illustrates the power conversion apparatus using the switching power supply apparatus of FIG. It is a block diagram which illustrates a part of the power conversion apparatus of FIG. 4 (a) and 4 (b) are schematic cross-sectional views illustrating the transformer of the switching power supply device of FIG. It is a schematic diagram which illustrates the magnetic core of the transformer of FIG. 4A and FIG. 4B. FIG. 6A is a schematic diagram for explaining the operating principle of the transformer of the switching power supply device of the embodiment. FIG. 6B is a graph illustrating the magnetic characteristics of the transformer of FIG. 6A. FIG. 7A is a schematic diagram for explaining the operating principle of the transformer of the switching power supply device of the embodiment. FIG. 7B is a graph illustrating the magnetic characteristics of the transformer of FIG. 7A. 8 (a) and 8 (b) are schematic cross-sectional views illustrating a transformer of a switching power supply device of a comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
It should be noted that the drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the sizes between the parts, and the like are not necessarily the same as the actual ones. Further, even when the same part is represented, the dimensions and ratios may be different from each other depending on the drawing.
In addition, in the present specification and each figure, the same elements as those described above with respect to the above-mentioned figures are designated by the same reference numerals, and detailed description thereof will be omitted as appropriate.

FIG. 1 is a block diagram illustrating a switching power supply device according to an embodiment.
As shown in FIG. 1, the switching power supply device 10 of the embodiment includes input terminals 11a and 11b and output terminals 12a to 14b. An unstable or fluctuating DC voltage is input to the input terminals 11a and 11b. In this example, three pairs of output terminals are provided. The switching power supply device 10 can be connected to three loads operating by direct current via three pairs of output terminals 12a to 14b.

The switching power supply device 10 includes a transformer 30. In addition, the switching power supply device 10 includes an input capacitor 21, a switching element 22, rectifier circuits 24 to 26, and a control circuit 28.

The transformer 30 includes terminals 35a and 35b on the primary side and terminals 35c to 35h on the secondary side. The terminals on the secondary side are provided for three pairs in this example. The transformer 30 converts the high-frequency AC voltage input from the terminals 35a and 35b on the primary side into an AC voltage corresponding to the respective turns ratio, and outputs the AC voltage to the terminals 35c to 35h on the secondary side. In the transformer 30, the terminals 35a and 35b on the primary side and the terminals 35c to 35h on the secondary side are electrically insulated from each other. Further, in this example, each of the three pairs of DC terminals 35c to 35h on the secondary side is electrically insulated.

In this example, the transformer 30 is a transformer for a flyback type switching power supply circuit. Therefore, the winding on the secondary side is wound so as to be in the direction opposite to the winding direction of the winding on the primary side. In such a transformer 30, energy is stored in the primary winding based on the peak of the current flowing in the primary winding and the excitation inductance, and when the current flowing in the primary side is cut off, the stored energy is two. It is transmitted to the next side. Since the energy transmitted from the primary side to the secondary side depends on the exciting inductance generated by the primary winding, it is desirable that the value of the exciting inductors does not fall below the design value.

The input capacitor 21 is connected between the input terminals 11a and 11b. The input capacitor 21 is provided to absorb a steep fluctuation of the input DC voltage. The terminal on the high potential side of the input capacitor 21 is connected to the terminal 35a of the transformer 30 together with the input terminal 11a.

The switching element 22 is connected by a main terminal between one terminal 35b of the winding on the primary side of the transformer 30 and the input terminal 11b. The control terminal of the switching element 22 is connected to the output of the control circuit 28. The switching element 22 is a self-extinguishing semiconductor element such as an IGBT or MOSFET, and operates on and off according to a drive signal generated by the control circuit 28.

When the switching element 22 is turned on, an exciting current flows through the winding on the primary side of the transformer 30. Energy is stored in the excitation inductance of the primary winding. When the switching element 22 is turned off, the energy stored in the exciting inductance is transmitted to the secondary side.

The rectifier circuits 24 to 26 are connected between the terminals 35c to 35h of the secondary winding of the transformer 30 and the output terminals 12a to 14b, respectively. Rectifier circuits 24-26 include a rectifier diode and a smoothing capacitor, as in this example. The commutator circuits 24 to 26 rectify and smooth the high-frequency AC voltage output to the secondary side of the transformer 30 and output it as a DC voltage.

In this example, the control circuit 28 is connected between the output of the rectifier circuit 26 and the switching element 22. The control circuit 28 detects and inputs the output voltage of the rectifier circuit 26, generates a duty cycle control signal corresponding to the detected output voltage, and drives the switching element 22.

FIG. 2 is a block diagram illustrating a power conversion device using the switching power supply device of FIG.
As shown in FIG. 2, the power conversion device 40 includes AC terminals 41a to 41c that can be connected to an AC circuit, and DC terminals 42a and 42b that can be connected to a DC circuit. The AC circuit that can be connected to the power conversion device 40 can include, for example, an AC power supply, an AC transmission line, an AC load, and the like. The AC circuit is, for example, a power system. The DC circuit that can be connected to the power conversion device 40 can include, for example, a DC power supply, a DC transmission line, a DC load, and the like. The DC circuit is, for example, a DC transmission line.

The power converter 40 has an arm corresponding to each phase of the AC circuit, the arm including a unit converter 50 connected in cascade. The unit converter 50 is connected to M units per arm. M may be 1, but preferably M is an integer of 2 or more.

A transformer 45 is connected in series to an arm connected in series between the DC terminals 42a and 42b. A buffer reactor may be connected in place of the transformer 45.

In this example, the power converter 40 is a Modular Multilevel Converter (MMC). In the MMC, the charging / discharging of the capacitor is controlled by the switching element provided in each unit converter 50, and the voltage across the capacitor is controlled for each unit converter 50.

FIG. 3 is a block diagram illustrating a part of the power conversion device of FIG.
FIG. 3 shows a simplified circuit configuration of the unit converter 50. As shown in FIG. 3, the unit converter 50 includes a gate control circuit 52, gate drive circuits 53 and 54, switching elements 55 and 56, a capacitor 57, and a main circuit feeding unit 58.

The gate control circuit 52 is connected to a control device (not shown). The gate control circuit 52 receives the control signal transmitted from the control device and generates a gate signal based on the control signal.

The gate drive circuit 53 is connected between the gate control circuit 52 and the switching element 55. The gate drive circuit 54 is connected between the gate control circuit 52 and the switching element 56. The gate drive circuits 53 and 54 generate a gate drive signal for driving the switching elements 55 and 56 based on the gate signal supplied from the gate control circuit 52.

The switching elements 55 and 56 are connected in series. The switching elements 55 and 56 are self-extinguishing semiconductor elements such as IGBTs and MOSFETs. The switching elements 55 and 56 are driven by the gate drive circuits 53 and 54.

The capacitor 57 is connected in parallel to the series circuit of the switching elements 55 and 56. The capacitor 57 is charged and discharged by turning the switching elements 55 and 56 on and off.

The main circuit feeding unit 58 is connected in parallel to the capacitor 57. The main circuit feeding unit 58 has a switching power supply device 10. The switching power supply device 10 is the flyback type multi-output power supply device described above. In this example, the switching power supply device 10 is connected to the capacitor 57 via the input terminals 11a and 11b. The switching power supply device 10 is connected to the gate drive circuit 53 via the output terminals 12a and 12b, and is connected to the gate drive circuit 54 via the output terminals 13a and 13b. The switching power supply device 10 is connected to the gate control circuit 52 via the output terminals 14a and 14b.

The switching power supply device 10 converts the voltage of the capacitor 57 into an appropriate voltage and supplies it to the gate control circuit 52 and the gate drive circuits 53 and 54. The gate control circuit 52 and the gate drive circuits 53, 54 are operated by a power supply electrically isolated from each other in order to appropriately drive the switching elements 55, 56.

In the MMC used for the backbone system of electric power, the voltage across the capacitor 57 reaches several thousand V, and the transformer 30 supplies a power source isolated from each other to each circuit, so that the transformer 30 has a sufficient space from the charging unit. It is necessary to secure the distance and creepage distance. Therefore, the transformer is externally filled with an insulating resin and arranged in the switching power supply device 10.

The switching power supply device of the embodiment is not limited to the MMC, and can be used for a power conversion device having a high voltage exceeding 1000 V on the primary side or the secondary side.

4 (a) and 4 (b) are schematic cross-sectional views illustrating the transformer of the switching power supply device of FIG.
FIG. 4 (b) shows a cross section seen by an arrow on the AA line of FIG. 4 (a).
As shown in FIGS. 4A and 4B, the transformer 30 includes an exterior resin 31, a case 32, a magnetic core 33, a winding 34, and a spacer 36.

FIG. 5 is a schematic diagram illustrating the magnetic core of the transformer of FIGS. 4 (a) and 4 (b).
As shown in FIG. 5, the magnetic core 33 is, in this example, a so-called EE core connecting two cores having the shape of the letter “E”.

The magnetic core 33 includes two E-shaped cores 33a and 33b. The E-shaped cores 33a and 33b have three legs 331 to 333. The three legs 331 to 333 are prismatic members extending substantially in parallel. A central leg (third leg) 331 is provided between the left and right legs (first leg, second leg) 331 and 332. One end of the legs 331 to 333 is open, and the other end is connected to a prismatic member (magnetic circuit) extending substantially perpendicular to the legs 331 to 333. The E-shaped cores 33a and 33b are, for example, ferrite cores.

The two E-shaped cores 33a and 33b connect one end of each of the three legs 331 to 333 to form an EE core. The joint surface at this end includes a direction substantially perpendicular to the direction in which the legs 331 to 333 extend.

If there is a gap or the like on the joint surface at this end, magnetic flux leakage will occur, which will cause a decrease in the value of the exciting inductance. Therefore, the ends of the E-shaped cores 33a and 33b are sufficiently closely connected and connected. To. Further, as will be described later, since the joint surface is a plane including a direction substantially perpendicular to the direction in which the leg portion 331 is stretched, a stress of an appropriate magnitude parallel to the leg portion 331 is applied from the side of the other end portion. Allows for closer contact.

In this embodiment, the core may have a central leg around which the windings are wound, and left and right legs through which the magnetic flux generated by the central leg passes to form a magnetic circuit. .. For example, the magnetic core is not limited to the EE core, but may be an EI core, a PQ core, or the like.

The explanation will be continued by returning to FIG.
The magnetic core 33 is provided with a winding 34. The winding 34 is wound around the central leg of the E-shaped core. The winding 34 includes a primary winding and a plurality of secondary windings, as described above. Although not shown, these windings are wound in a state of being electrically insulated from each other by an insulating sheet or the like.

The magnetic core 33 is housed in the case 32 together with the winding 34. The internal dimensions of the case 32 are set slightly larger than the external dimensions of the magnetic core 33. That is, when the magnetic core 33 is housed in the case 32, a space 35 exists between the inner surface of the case 32 and the outer peripheral surface of the magnetic core 33. The case 32 is made of an insulating material such as polycarbonate.

The spacer 36 is provided between the inner surface of the case 32 and the outer peripheral surface of the magnetic core 33. The spacer 36 is provided on the side of the other end of the central leg of the magnetic core 33 and at a position corresponding to the joint surface provided at one end. The spacer 36 functions as a support member for the magnetic core 33 with respect to the case 32. The thickness of the spacer 36 is set to match the width of the space 35 between the inner surface of the case 32 and the outer peripheral surface of the magnetic core 33. The spacer 36 is formed of an insulating material like the case 32, and may be formed of a member different from the case 32 or may be integrally formed with the case 32.

The magnetic core 33 and the winding 34 are sealed by a case 32. The space 35 between the inner surface of the case 32 and the magnetic core 33 and the winding 34 is secured by the spacer 36. If it is difficult to seal the magnetic core 33 and the winding 34 with the case 32, the magnetic core 33 and the winding 34 are housed in a partially opened case, and then a fluid resin, for example, is used. The case may be filled with a silicone resin or the like.

The exterior resin 31 is provided in close contact with the outer surface of the case 32 in which the magnetic core 33 and the winding 34 are housed. The outer shape of the exterior resin is set according to the shape of the case 32, and is, for example, a cube or a rectangular parallelepiped. The exterior resin 31 is formed of an insulating material, and a thermosetting resin is preferably used. The exterior resin 31 is, for example, an epoxy resin. The thermosetting resin for the exterior resin 31 is fluidized at a high temperature, molded using a molding die or the like, and cured by returning to room temperature.

The transformer 30 is formed as follows. That is, the winding 34 is wound around the magnetic core 33. The magnetic core 33 around which the winding 34 is wound is housed in the case 32 after the space 35 is secured by the spacer 36. The case 32 containing the magnetic core 33 and the winding 34 is placed on a molding die, and the resin for the exterior resin 31 is fluidized at a high temperature and injected into the molding die. After that, it is cooled to cure the resin, and the transformer 30 covered with the exterior resin 31 is formed.

6 (a) and 7 (a) are schematic views for explaining the operating principle of the transformer of the switching power supply device of the embodiment. 6 (b) and 7 (b) are graphs illustrating the magnetic properties of the transformers of FIGS. 6 (a) and 7 (a), respectively.
6 (a) and 6 (b) show the characteristics of the transformer at the position corresponding to the leg portion 331 of the magnetic core 33 and when the pressure is applied in the direction parallel to the extending direction of the leg portion 331. Changes are shown.
In FIGS. 7 (a) and 7 (b), pressure is applied in a direction corresponding to the joint surface of the central leg portion 331 of the magnetic core 33 and parallel to the direction in which the joint surface is formed. Changes in the characteristics of the transformer in the case are shown.

As shown in FIGS. 6 (a) and 6 (b), when pressure is applied along the direction in which the leg portion 331 extends, that is, in the direction perpendicular to the joint surface of the leg portion 331, the magnetic core increases with the increase in pressure. The amount of displacement of is increased. Then, as the pressure increases, the value of the exciting inductance initially increases, and when the pressure is further increased, the exciting inductance decreases. Since the pressure is applied so as to press the joint surfaces of the central legs against each other, it is considered that the minute gap becomes smaller and the exciting inductance increases within an appropriate pressure range. In this example, when a pressure of about 500 N is applied, a value of excitation inductance of 700 μH or more is secured.

On the other hand, as shown in FIGS. 7 (a) and 7 (b), when the pressure is applied in the direction perpendicular to the direction in which the leg portion 331 is stretched, that is, in the direction parallel to the joint surface of the leg portion 331, the pressure is applied. The exciting inductance decreases without increasing with increasing. The amount of displacement is the same as in FIG. In this example, the value of the exciting inductance of 700 μH or more does not exist except at the beginning of pressure application.

Consider a case where the resin is sealed by setting the temperature to a high temperature for forming the exterior resin 31, and the resin is cured by returning the resin to room temperature. Since the coefficients of thermal expansion of the exterior resin 31, the case 32, and the magnetic core 33 are different, stress is applied to the case 32 when the exterior resin 31 is cured.

By applying pressure along the direction in which the legs of the magnetic core extend, that is, perpendicular to the joint surface at the ends of the legs of the magnetic core, it is possible to prevent a decrease in the value of the excitation inductance due to stress. .. In the present embodiment, by providing the spacer 36 at a position corresponding to the joint surface of the central leg portion 331 of the magnetic core 33, the stress when the exterior resin 31 is cured is the stress of the central leg portion 331 of the magnetic core 33. It can be applied almost perpendicularly to the joint surface of. Therefore, by appropriately selecting the thickness, material, and the like of the spacer 36, the value of the excitation inductance can be set to an appropriate value by the stress applied through the spacer 36.

The effect of the switching power supply device 10 of the embodiment will be described while comparing with the case of the comparative example.
8 (a) and 8 (b) are schematic cross-sectional views illustrating a transformer of a switching power supply device of a comparative example.
FIG. 8 (b) shows a cross section seen by an arrow on the BB line of FIG. 8 (a).
As shown in FIGS. 8 (a) and 8 (b), the transformer 130 is provided with the spacer 136 at a position different from that of the above-described embodiment. The spacer 136 is provided at a position different from the position corresponding to the central leg. In this comparative example, the spacer 136 is provided at a position corresponding to the left and right legs.

In the case of this comparative example, after the exterior resin 31 is sealed, the stress at the time of resin curing is applied substantially perpendicularly to the joint surfaces of the left and right legs via the spacer 136. In this comparative example, the spacer 136 is arranged at a position corresponding to the left and right legs so that the magnetic core 33 and the winding 34 can be positioned more stably and easily when the magnetic core 33 and the winding 34 are arranged in the case 32. However, as described above, when stress is applied to the joint surface of the central leg where the winding 34 is wound and magnetic flux is generated, the exciting inductance tends to increase, and from the viewpoint of securing the exciting inductance value, It is more preferable to place the spacer at the position corresponding to the central leg.

For example, when the spacer is provided along the leg portion, the stress at the time of resin curing can be applied almost parallel to the joint surface of the leg portion, so that the excitation inductance is considered to decrease before and after the exterior resin 31 is filled. ..

In the switching power supply device 10 of the embodiment, the spacer 36 provided between the magnetic core 33 of the transformer 30 and the case 32 is provided at a position corresponding to the leg portion of the magnetic core in which the magnetic flux is generated. Therefore, the stress generated when the exterior resin 31 of the transformer 30 is cured is applied in a substantially vertical direction to the joint surface of the leg portion of the magnetic core in which the magnetic flux is generated, and the value of the exciting inductance is set to an appropriate value. Can be done.

According to the embodiment described above, it is possible to realize a switching power supply device and a power conversion device in which the magnetic characteristics of the magnetic core of the transformer are less likely to fluctuate due to stress.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention and its equivalents described in the claims. In addition, each of the above-described embodiments can be implemented in combination with each other.

10 switching power supply, 21 input capacitor, 22 switching element, 24-26 rectifier circuit, 28 control circuit, 30 transformer, 31 exterior resin, 32 case, 33, 33a, 33b magnetic core, 34 winding, 35 space, 36 spacer , 40 power converter, 50 unit converter, 52 gate control circuit, 53, 54 gate drive circuit, 55, 56 switching element, 57 capacitor, 58 main circuit power supply unit, 331 to 333 legs

Claims (7)

Winding and
The first and second legs arranged in parallel,
A third leg portion that is stretched along the direction in which the first leg portion and the second leg portion are stretched, is provided between the first leg portion and the second leg portion, and the winding is wound around the first leg portion. When,
A magnetic circuit in which the magnetic flux generated in the third leg by the winding passes through the first leg and the second leg, and the magnetic circuit.
With magnetic core, including
An insulating case for accommodating the winding and the magnetic core,
The exterior resin that seals the entire case and
An insulating spacer provided between the case and the magnetic core ,
Equipped with a transformer, including
The third leg is a joint surface of one end of the third leg, and has a direction orthogonal to the extending direction of the first leg, the second leg, and the third leg. Including the joint surface including
The spacer is a switching power supply device provided on the side of the other end of the third leg. The switching power supply device according to claim 1, wherein the magnetic core includes an E-shaped core having the first leg portion, the second leg portion, and the third leg portion. The switching power supply device according to claim 2, wherein the magnetic core is an EE core in which one end of each of the first leg portion, the second leg portion, and the third leg portion of the E-shaped core is joined to each other. .. The switching power supply device according to any one of claims 1 to 3, wherein the exterior resin contains a thermosetting resin. The switching power supply device according to any one of claims 1 to 4, wherein the transformer is a primary winding and a secondary winding having different winding directions. The switching power supply device according to any one of claims 1 to 5.
A control circuit that operates by being supplied with power by the switching power supply device,
Power conversion device equipped with. The switching power supply device according to any one of claims 1 to 5.
A drive circuit supplied with power by the switching power supply device to operate, a main circuit including a switching element driven by the drive circuit, and a main circuit.
Equipped with multiple unit converters, including
The plurality of unit converters are power converters connected in cascade.

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