JP2013131540A - Core, transformer, choke coil, and switching power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core having a low calorific value and excellent temperature characteristics.SOLUTION: A core, around which a coil is wound, comprises a plurality of core members. At least one of the core members contacts with a heat radiation member. A temperature at which a magnetic loss of the core member contacting with the heat radiation member becomes the minimum is lower than a temperature at which a magnetic loss of the core member other than the core member contacting with the heat radiation member becomes the minimum. Thereby, a core having a low calorific value and excellent temperature characteristics can be provided.

Description

The present invention relates to a core used for a transformer and a choke coil, and more particularly to a core having reduced heat generation and improved temperature characteristics. The present invention also relates to a transformer or choke coil using such a core. The present invention also relates to a switching power supply device using such a transformer or choke coil.

  Since transformers and choke coils used in switching power supply devices generate heat during operation, it is desirable to employ a core that generates a small amount of heat and has excellent heat dissipation characteristics. There are two possible ways to keep the core from getting hot. As a first method, there is a method of using a low-loss magnetic material for the core so as not to generate heat. Further, as another method of the first method that does not cause the core itself to generate heat, there is a method of making the core shape difficult to generate heat. For example, the E-type core described in Patent Document 1 is said to be able to suppress the temperature rise of the central leg portion that is likely to store heat by making the cross-sectional area of the central leg portion larger than the cross-sectional area of the outer leg portion. Yes.

  Further, as a second method for preventing the core from becoming high temperature, there is a method of efficiently radiating heat from the core that has generated heat. For example, there is a method in which a heat radiating member or refrigerant is brought into contact with the core and heat is radiated by heat transfer. For example, the core described in Patent Document 2 has a quasi-closed magnetic circuit structure including a magnetic gap portion, and a polymer member is interposed in the magnetic gap portion. By interposing the polymer member having a thermal conductivity higher than that of air, the heat dissipation efficiency of the core is increased, and the temperature rise of the core can be suppressed.

  Further, as another method of the second method for efficiently radiating heat, there is a method for making the core easy to radiate heat. For example, the core described in Patent Document 1 is provided with a heat radiating hole in the center leg portion, and can radiate heat through outside air in the heat radiating hole. Further, if necessary, a heat radiating member having high thermal conductivity can be inserted into the heat radiating hole to improve heat radiating characteristics. In addition, the core described in Patent Document 3 is said to be able to improve the heat dissipation characteristics of the core by expanding the heat dissipation route of heat generated in the upper beam portion.

JP 2002-203726 A JP 2011-077304 A JP 2009-088250 A

  However, even if the techniques described in Patent Document 1 to Patent Document 3 described above are used, there is a problem that the temperature rise is not sufficiently suppressed particularly in a transformer or choke coil having a large heat generation amount. Improvement for reducing heat generation is desired. The present invention has been made in view of the above, and an object thereof is to provide a core having a small calorific value and excellent temperature characteristics. Another object of the present invention is to provide a transformer and a choke coil using such a core. Another object of the present invention is to provide a switching power supply device using such a transformer and a choke coil.

  In order to solve the above-described problems and achieve the object, the core according to claim 1 is a core around which a coil is wound, and includes a plurality of core members, and at least one of the core members is a heat dissipation member. The temperature at which the magnetic loss of the core member that is in contact with the heat radiating member is minimum is the magnetic loss of the core member other than the core member that is in contact with the heat radiating member. It is characterized by being lower than the temperature.

  According to the core of claim 1, the temperature at which the magnetic loss of the core member in contact with the heat radiating member among the plurality of core members is minimized is other than the core member in contact with the heat radiating member. It is possible to apply a core member having a more appropriate temperature characteristic to the temperature distribution of the core generated by using the heat radiating member by lowering the temperature than the temperature at which the magnetic loss of the core member is minimized. it can. In particular, by appropriately selecting the temperature characteristics of the core member in contact with the heat radiating member, it is possible to reduce the magnetic loss of the entire core in which a plurality of core members are combined. As a result, the temperature rise can be suppressed.

  Moreover, in this invention, it is preferable that the temperature difference from which each magnetic loss of the said several core member becomes the minimum is 5 to 50 degreeC. If the temperature difference that minimizes the magnetic loss of multiple core members is too large, the magnetic loss in the temperature range between the temperature at which the loss of any core member is minimized and the temperature at which the loss of other core members is minimized Will increase. For this reason, the temperature difference at which the magnetic loss is minimized is preferably 50 ° C. or less, and if the temperature difference at which the magnetic loss of the plurality of core members is minimized is too small, the effect of reducing the magnetic loss is reduced. For this reason, the temperature difference at which the magnetic loss is minimized is preferably 5 ° C. or more.

  In the present invention, it is preferable that the plurality of core members are made of ferrite. Since the core member is made of ferrite, the core member suitable for the operating temperature is selected for the ferrite core member that has a low thermal conductivity and generates a relatively large temperature distribution. Loss can be further reduced. As a result, the heat generation amount of the entire core obtained by combining a plurality of core members is reduced, and the temperature rise is suppressed.

  The present invention is a transformer characterized by using the above-described core. By using the core, a transformer with a small calorific value is provided, so that the power transmitted by the transformer can be increased or the transformer can be downsized.

  The present invention is a choke coil using the above-described core. Since the choke coil with a small calorific value is provided by using the core, it is possible to increase the electric power stored in the choke coil and to reduce the size of the choke coil.

  The present invention is a switching power supply device including the transformer. According to this switching power supply device, since the amount of heat generated by the transformer is reduced, a highly reliable switching power supply device can be provided.

  The present invention is a switching power supply device comprising the choke coil. According to this switching power supply device, since the amount of heat generated by the choke coil is reduced, a highly reliable switching power supply device can be provided.

  The present invention can provide a core having a small calorific value and excellent temperature characteristics. In addition, the present invention can provide a transformer and a choke coil using such a core. In addition, the present invention can provide a switching power supply device using such a transformer and a choke coil.

FIG. 1 is a perspective view showing a core 10 according to the first embodiment. FIG. 2 is a diagram showing temperature characteristics of magnetic loss of the core member 10A and the core member 10B. FIG. 3 is a perspective view showing a core according to a modification of the first embodiment. FIG. 4 is a perspective view showing a core according to the second embodiment. FIG. 5 is a diagram showing temperature characteristics of magnetic loss of the core member 20A and the core member 20B. FIG. 6 is a perspective view showing a core according to a modification of the second embodiment. FIG. 7 is a perspective view showing a core according to the third embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that are equivalent. Furthermore, the constituent elements described below can be appropriately combined. In addition, various omissions, substitutions, or changes of components can be made without departing from the scope of the present invention.

(Embodiment 1)
FIG. 1 is a perspective view showing a core according to the first embodiment. The core 10 is assembled by facing the openings of the core member 10A and the core member 10B each having an E shape. The heat radiating member 10C is in contact with the lower surface of the core member 10B. In addition, in order to improve the adhesiveness of a contact surface and to improve heat dissipation, a heat dissipation sheet, grease, or adhesive may be used between the core member 10B and the heat dissipation member 10C. FIG. 2 shows the temperature characteristics of the magnetic loss of the core member 10A and the core member 10B. The temperature T1 at which the magnetic loss of the core member 10A is minimized is higher than the temperature T2 at which the loss of the core member 10B is minimized. When the assembled core 10 is used for a transformer or a choke coil, the coil 12 is wound around the main leg portion 11 of the core 10. In the present embodiment, the core 10 is a ferrite sintered body, but the material of the core 10 is not limited to this.

  Conventionally, the core member 10A and the core member 10B are assembled by a combination of core members having the same temperature at which the magnetic loss is minimized. When the temperature rise of the core is small, the heat radiating member 10C is not used. However, when the temperature rise of the core is large, it is necessary to lower the temperature of the core in order to prevent thermal runaway of the core, and the temperature is reduced using the heat radiating member 10C. That is, when using a heat radiating member with a core having a large temperature rise, the temperature of the core member 10B that is in contact with the heat radiating member 10C is low, and the core member 10A that is not in contact with the heat radiating member and easily stores heat is a temperature. There was a temperature distribution in which the temperature increased. As a result, the conventional core cannot use a core member suitable for the temperature, and generates a large amount of heat. On the other hand, in the core 10 according to the first embodiment, the temperature at which the magnetic loss of the core member 10B that is cooled in contact with the heat radiating member 10C is minimum is higher than the temperature at which the magnetic loss of the core member 10A that is not radiated is minimum. Is also low. As a result, the core member suitable for each is used, and the magnetic loss of the entire core, that is, the core 10 is reduced, and the temperature rise is reduced.

  The temperature difference at which the magnetic loss between the core member 10A and the core member 10B is minimized is preferably 5 ° C. or more and 50 ° C. or less, and more preferably the temperature difference at which the core member has a minimum magnetic loss is 5 ° C. It shall be above 30 ° C. More preferably, the temperature difference at which the magnetic loss of the plurality of core members is minimized is 5 ° C. or more and 15 ° C. or less. If the temperature difference that minimizes the magnetic loss of multiple core members is too large, the magnetic loss in the temperature range between the temperature at which the loss of any core member is minimized and the temperature at which the loss of other core members is minimized This is because of the increase.

  The transformer using the core 10 generates less heat. For this reason, the transformer using the core 10 can increase the power that can be transmitted and can be downsized. The choke coil using the core 10 generates a small amount of heat. For this reason, the choke coil using the core 10 can increase the stored electric power and can be downsized. In the switching power supply device in which the transformer using the core 10 or the choke coil using the core 10 is mounted, the amount of heat generated by the transformer or the choke coil is reduced, so that the reliability is improved. Needless to say, the effect of the present invention can be obtained even when the core member 10B in the present embodiment is formed of an I core as shown in FIG.

  In addition, the fixing of the core member 10A constituting the core 10 in the present embodiment is not particularly mentioned, but generally, the core member 10A is bonded using an adhesive on the contact surface with the core member 10B, or the core member 10A. The top surface of is held with metal fittings. In this case, the metal fitting can also be regarded as a heat radiating member, but the essence in the present invention is to apply a core member suitable for the operating temperature to a core having a temperature distribution. That is, even if a plurality of core members are in contact with the heat radiating member, a core member that mainly serves as a heat radiating path and has a relatively low temperature at which the magnetic loss is minimized relative to the core member that has a relatively low temperature. Even if it is in contact with the heat radiating member, it cannot be the main heat radiating path, and for core members that have a relatively high temperature, a core member that has a relatively high temperature that minimizes magnetic loss is used. There is to apply.

  The configurations of the present embodiment and its modifications can be applied as appropriate in the following. Moreover, what has the structure similar to this embodiment and its modification has an effect | action and effect similar to this embodiment and its modification.

(Embodiment 2)
FIG. 4 is a perspective view showing a core according to the second embodiment. The core 20 is assembled by facing the openings of the core member 20A and the core member 20B, both of which are E-shaped. A heat radiating member 20C is in contact with the lower surface of the core member 20B. In addition, in order to improve the adhesiveness of a contact surface and to improve heat dissipation, a heat dissipation sheet, grease or adhesive may be used between the core member 20B and the heat dissipation member 20C. FIG. 5 shows the temperature characteristics of the magnetic loss of the core member 20A and the core member 20B. The temperature T3 at which the magnetic loss of the core member 20A is minimized is higher than the temperature T4 at which the loss of the core member 20B is minimized. When the assembled core 20 is used for a transformer or a choke coil, the coil 22 is wound around the main leg portion 21 of the core 20.

  The core 20 according to the present embodiment is configured such that the thickness of the core member 20B constituting the core 20 is 10 mm and the thickness h from the heat radiating member surface is 10 mm. Like the core 20 of the present embodiment, the temperature distribution of the core member 20B in contact with the heat radiating member 20C is reduced by setting the thickness h of the core member 20B from the contact surface with the heat radiating member 20C to 10 mm or less. It can be further reduced. Therefore, a core member having a more optimal temperature characteristic is applied to the core member 20B. As a result, the amount of heat generated by the entire core is reduced, and a temperature rise is suppressed. Needless to say, the effect of the present invention can be obtained even when the core member 20B according to the present embodiment is formed of an I core as shown in FIG.

  The temperature difference at which the magnetic loss between the core member 20A and the core member 20B is minimized is preferably 5 ° C. or more and 50 ° C. or less, and more preferably, the temperature difference at which the core member has a minimum magnetic loss is 5 ° C. It shall be above 30 ° C. More preferably, the difference in temperature at which the magnetic loss of the plurality of core members is minimized is 5 ° C. or more and 15 ° C. or less, as in the first embodiment.

  The configuration of the present embodiment can also be applied as appropriate in the following. Moreover, what has the structure similar to this embodiment has an effect | action and effect similar to this embodiment.

(Embodiment 3)
FIG. 7 is a perspective view showing a core according to the third embodiment. The core 30 is assembled by facing the openings of the core member 30A and the core member 30B, both of which are E-shaped, with the I-shaped core member 30C interposed therebetween. A heat radiating member 30D is in contact with the upper surface of the core member 30A. A heat radiating member 30E is in contact with the lower surface of the core member 30B. In order to improve the adhesion of the contact surface with the heat radiating member and enhance the heat radiating property, a heat radiating sheet, grease, An adhesive may be used. The temperature at which the magnetic loss of the core member 30A and the core member 30B is minimized is lower than the temperature at which the magnetic loss of the core member 30C is minimized. The temperature characteristics of the magnetic loss between the core member 30A and the core member 30B may be different. When the assembled core 30 is used for a transformer or a choke coil, for example, the coils 32A and 32B are wound around the main legs 31A and 31B of the core 30.

  In the core 30 according to the third embodiment, the temperature at which the magnetic loss of the core member 30A or the core member 30B that is cooled in contact with the heat radiating member 30D or the heat radiating member 30E is minimized is the magnetic force of the core member 30C that is not radiated. Below the temperature at which loss is minimized. As a result, the core member suitable for the operating temperature of each core member is used, and the magnetic loss of the entire core, that is, the core 30 is reduced, and the temperature rise is reduced.

  The configuration of the present embodiment can also be applied as appropriate in the following. Moreover, what has the structure similar to this embodiment has an effect | action and effect similar to this embodiment.

  Hereinafter, although the Example of this invention is described, this invention is not limited to this Example at all.

Example 1
Evaluation was performed using the core 10 in the first embodiment described above. The core member was Mn-Zn ferrite with varying magnetic loss temperature characteristics. The temperature rise of the core was measured by the following method. A maximum magnetic flux density of 230 mT was generated in the main leg portion 11 of the core 10, and the core 10 was excited continuously at a frequency of 100 kHz. On the other hand, the temperature of the heat radiating member 10C was cooled so as to be always constant at 100 ° C. When the temperature of the core 10 was stabilized, the temperature of the upper surface of the core member 10A was measured with a thermocouple. Table 1 shows the measurement results of the temperature rise. As can be seen from Table 1, a core having an appropriate temperature characteristic according to the temperature distribution of the core as in the embodiment, as compared with the conventional example in which the upper and lower cores are composed of the same core with the minimum magnetic loss. The temperature can be reduced.

(Example 2)
Using the core 20 in Embodiment 2 described above, the relationship between the thickness h of the core member in contact with the heat radiating member surface from the heat radiating member surface and the core temperature increase was evaluated. The core member was Mn-Zn ferrite with varying magnetic loss temperature characteristics. As the core member 20A, a core having a temperature of 115 ° C. at which the magnetic loss is minimized was used. As the core member 20B, a core having a temperature of 100 ° C. at which the magnetic loss is minimized is used. The temperature rise of the core was measured by the same method as in Example 1. Table 2 shows the measurement results of the temperature rise. As can be seen from Table 2, the temperature can be further reduced with sample No. 10 with a thickness of 10 mm than sample No. 9 with a thickness from the contact surface of the core member 20B with the heat dissipation member 20C of 13 mm. It was.

10, 20, 30 Core 10A, 10B, 20A, 20B, 30A, 30B, 30C Core member 10C, 20C, 30D, 30E Heat dissipation member 11, 21, 31A, 31B Main leg portion 12, 22, 32A, 32B Coil

Claims (7)

  A core around which a coil is wound, comprising a plurality of core members, wherein at least one of the core members is in contact with a heat dissipation member, and magnetic loss of the core member in contact with the heat dissipation member is minimized The core is characterized in that the core temperature is lower than the temperature at which the magnetic loss of the core member other than the core member in contact with the heat radiating member is minimized.   2. The core according to claim 1, wherein the temperature difference at which the magnetic loss of the plurality of core members is minimized is 5 ° C. or more and 50 ° C. or less.   The core according to claim 1, wherein the core is made of ferrite.   A transformer using the core according to any one of claims 1 to 3.   A choke coil using the core according to any one of claims 1 to 3.   A switching power supply comprising the transformer according to claim 4.   A switching power supply comprising the choke coil according to claim 5.

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