JP2000164436A - High frequency power transformer and power converter using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency power transformer equipped with a primary coil without any center tap and a secondary coil with at least one set of center taps at a compact no-cut nano crystal soft magnetic alloy thin band coil magnetic core with a low magnetic core loss, and a power converter with high efficiency and high reliability using this high frequency power transformer. SOLUTION: This is a high frequency power transformer which is provided with a primary coil without any center tap and a secondary coil with at least one set of center taps, at a no-cut nano crystal soft magnetic alloy thin band coil magnetic core in which Fe is used as main component, and fine crystal particles whose crystal particle diameter is 50 nm or less occupy 50% or more of the whole volume of the organization. In this high frequency power transformer, the value of a leakage inductance in 50 kHz measured at the edge of the primary coil by short-circuiting the whole edge of the secondary coil is set so as to be 0.3 μH or less, relative permeability at that time is set so as to be 20,000 or more, or a square rate Br/Bs as the rate of residual magnetic flux density Br to saturated magnetic flux density Bs in the DC magnetic characteristics of the nano crystal soft magnetic alloy thin band coil magnetic core is set so as to be 0.2 or less. Then, it is possible to provide a power converter using this high frequency power transfer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uncut nanocrystalline soft magnetic alloy ribbon core comprising Fe as a main component, wherein fine crystal grains having a crystal grain size of 50 nm or less occupy 50% or more of the entire volume of the structure. The present invention relates to a high-frequency power transformer provided with a primary winding having no center tap and at least one set of secondary windings having a center tap and a power converter using the same.

[0002]

2. Description of the Related Art A full-bridge DC-DC converter shown in FIG. 3 is used as one of insulated power converters using a high-frequency power transformer. In FIG. 3, 1 is an input DC power supply, 2, 3, 4 and 5 are main switches, 6, 7, 8 and 9 are feedback diodes, 20 is a primary winding without a center tap and 2 with a center tap.
A high-frequency power transformer provided with a secondary winding, 21 is a primary winding of the high-frequency power transformer 20, 22 and 23 are secondary windings of the high-frequency power transformer 20, 31 and 3
2 is an output rectifier diode, 33 is an output smoothing choke coil, 34 is an output smoothing capacitor, 35 and 36 are output terminals, and 37 is a load.

In the full-bridge type DC-DC converter shown in FIG. 3, main switches 2 and 3 and 4 and 5 each have 1
A pair of switches, these two sets of switches are alternately switched, so that the high-frequency power transformer 2
0 is applied to the primary winding 21 of FIG. 4 and the secondary winding 22 of the high-frequency power transformer 20 is applied.
And 23, output rectifier diodes 31 and 32,
Through a smoothing choke coil 33 and a capacitor smoothing 34,
Electric power is supplied to the load 37. In FIG. 4, the period in which the main switches 2 and 3 are on is Ton23, the period in which the main switches 4 and 5 are on is Ton45, and Tp is the cycle. (Ton23
+ Ton45) / Tp is the on-duty ratio Don. In order to keep the output voltage Vo constant with respect to the fluctuation of the voltage E of the input DC power supply 1 or the fluctuation of the load 37, control is performed by changing Tp while keeping Tp constant. PWM control (pulse width modulation control) is generally used. The high-frequency power transformer 20
Is given by 1 / Tp.

FIG. 5 is a conceptual diagram of an operation BH loop of the high-frequency power transformer 20 in the present converter. The direction of the magnetic field generated in the high-frequency power transformer 20 when a current flows from the black circle side of the primary winding 21 of the high-frequency power transformer 20 shown in FIG. 3 is set to the positive side of the H axis in FIG. Therefore, while the main switches 2 and 3 are on, Ton23
The magnetic flux density of the high-frequency power transformer 20 changes by 2 Bm from point a to point b in FIG.
In the period Ton45 during which the power supply is ON, the magnetic flux density of the high-frequency power transformer 20 changes by -2Bm from the point b to the point a in FIG. That is, the high-frequency power transformer 20 in the present converter operates to draw a symmetric minor loop with respect to the origin of the BH loop.

In the high-frequency power transformer 20 of the present converter, downsizing and low loss are important issues. As a general method of reducing the size of the high-frequency power transformer 20, increasing the driving frequency is performed. But,
Extremely high frequency without considering the high frequency characteristics of elements such as the magnetic core used in the high frequency power transformer 20, the main switches 2, 3, 4, and 5, the feedback diodes 6, 7, 8, and 9, or the output rectifier diodes 31 and 32 This not only increases the loss of these elements, but also increases the loss of the high-frequency power transformer 20, which causes a decrease in converter efficiency and a decrease in reliability due to an excessive rise in temperature.

The high-frequency power transformer 20 of the present converter generally has a driving frequency selected in consideration of the high-frequency characteristics of the main switches 2, 3, 4 and 5.
It is necessary to select the most compact and low loss core.

For example, when the output power is relatively small up to about several kW, a power MOS-FET is usually selected for the main switches 4 and 5, and the driving frequency is 50 kHz.
It is selected more than degree. In this case, the magnetic core of the high-frequency power transformer 20 is conventionally mainly provided with a saturation magnetic flux density B at room temperature.
Although the s is as small as about 0.5T, a Mn-Zn ferrite core having a small core loss at several hundred kHz or more has been used.

On the other hand, in the region where the output power exceeds several kW, the main switches 2, 3, 4 and 5 are generally connected to the IGBT.
Is selected, and the driving frequency is selected from several kHz to about 20 kHz. In this case, Hagiwara, Saito, Kamo, Toyota, Yamauchi, Yoshizawa: "Inverter transformer using microcrystalline alloy for iron core", IEEJ Technical Report, MAG-90-19
4. As described on December 6, 1990 (hereinafter referred to as Document 1), the magnetic core of the high-frequency power transformer 20 has a saturation magnetic flux density at room temperature exceeding twice that of the Mn-Zn ferrite core. At 1T or more, the core loss at 20 kHz is small, and fine grains having Fe as a main component and having a grain size of 50 nm or less as described in JP-A-63-302504 account for 50% of the entire volume of the structure. Fe accounts for more than
It is known that a base nanocrystalline soft magnetic alloy ribbon wound core is excellent.

In the above-mentioned Fe-based nanocrystalline soft magnetic alloy ribbon wound core, the above-mentioned reference 1 or Fukunaga, Koga, Eguchi,
Ota, Kakehashi: "Magnetic properties of cut core with gap using iron-based magnetic ribbon, IEEJ Technical Report, MAG-89-
203, December 1, 1989 (hereinafter referred to as Reference 2)
The resin or varnish penetrates between the layers of the nanocrystalline soft magnetic alloy ribbon that composes the core by subjecting the core to resin impregnation or surface fixation, as described in It is known that when a stress is applied to a magnetic alloy ribbon, its magnetic core loss is significantly increased.

By the way, in the magnetic core for the high frequency power transformer 20, a cut magnetic core is widely used in order to facilitate the winding operation. In order to cut the nanocrystalline soft magnetic alloy ribbon wound core, the wound core is impregnated with an impregnating material such as an epoxy adhesive, and the layers of the nanocrystalline soft magnetic alloy ribbon constituting the wound core are separated. After fixing with the impregnating material, it is necessary to cut with a rotating grindstone or the like. Also, after cutting, the end surface is mirror-polished. But,
A core obtained by cutting a nanocrystalline soft magnetic alloy ribbon wound core using such a method has a remarkable increase in core loss as described in the above-mentioned Documents 1 and 2.

[0011] Therefore, in order to reduce the core loss of the core cut using a nanocrystalline soft magnetic alloy ribbon wound core, Yoshizawa,
Mori, Arakawa, Yamauchi: "High-frequency magnetic properties of Fe-Cu-Nb-Si-B nanocrystalline alloys", IEICE Technical Meeting, M
AG-94-202, November 22, 1994 (hereinafter referred to as
As described in Literature 3, a nanocrystalline soft magnetic alloy ribbon whose saturation magnetostriction constant λs is as small as 10 ⁻⁶ or less is used, and the surface of the ribbon is covered with ceramics to perform an interlayer insulation treatment. Is effective, but even in this case, the core loss of a normal nanocrystalline soft magnetic alloy ribbon wound core that is not impregnated or cut reaches about 1.4 times the core loss.

Therefore, in order to effectively utilize the low core loss characteristic of the nanocrystalline soft magnetic alloy ribbon core, stress should not be applied to the nanocrystalline soft magnetic alloy ribbon constituting the core as much as possible. Must be configured as follows. As a nanocrystalline soft magnetic alloy thin-band wound core with such a configuration, the uncut wound core is housed in an insulating case made of plastic or ceramic, etc., using silicon grease or gel-like silicon rubber as a buffer, and externally. The one in which the stress is hardly applied directly to the wound core is widely used.

[0013]

As in the full-bridge type DC-DC converter of FIG. 3, the magnetic flux density of the high-frequency power transformer 20 is symmetrical with respect to the origin of the BH loop as shown in FIG. In the high-frequency power transformer 20 of the power conversion device that performs an operation of drawing a minor loop, the BH minor loop at the time of the operation performs the asymmetric operation with respect to the origin of the BH loop as shown in FIG. The high frequency power transformer 20 suppresses the magnetic saturation and the exciting current from increasing remarkably, and the main switches 2, 3, 4 and 5
It is extremely important to ensure safe operation of the vehicle.

As is well known, the magnetic polarization of the high-frequency power transformer 20 is mainly caused by variations in the electrical characteristics of the main switches 2, 3, 4 and 5.
The exciting current is balanced at a certain value by the circuit impedance. However, when the magnetic bias of the high frequency power transformer 20 is large, the BH minor loop during operation reaches one saturation region as shown in FIG. 6, and the exciting current increases significantly. An excessive current flowed between the main electrodes of the main switches 5 and 5, and the main switches 2, 3, 4 and 5 could be broken. In particular, when the voltage of the input DC power supply 1 suddenly changes or the load 27 suddenly changes, the amount of change ΔB in the magnetic flux density during the operation of the high-frequency power transformer 20 increases transiently, so that the amount of increase in the exciting current due to the magnetization increases. , The main switches 2, 3, 4, and 5 were at high risk of breaking.

When an overcurrent protection circuit having a fast response speed for suppressing an overcurrent flowing between the main electrodes of the main switches 2, 3, 4 and 5 is provided, the main switch 2 is remarkably demagnetized. An excessive current can be prevented from flowing through 3, 4, and 5, and the main switches can be prevented from being broken. However, when the overcurrent protection circuit operates, there is a problem in that sufficient power cannot be supplied to the output side, and thus the accuracy of constant output voltage cannot be ensured.

As the most general method for preventing the high-frequency power transformer 20 from being demagnetized, a magnetic core having a small magnetic permeability is adopted for the high-frequency power transformer 20, and the operating magnetic flux density peak value Bm of the magnetic core is determined. The selection is made to have a sufficiently small value with respect to the saturation magnetic flux density Bs of the magnetic core. The simplest method for obtaining a magnetic core with a small magnetic permeability is to provide a gap in the cut magnetic core and reduce the effective relative magnetic permeability. According to this method, there is also an advantage that the effective relative permeability of the magnetic core can be arbitrarily selected by adjusting the gap width.

However, a method of reducing the effective relative permeability by providing a gap as described above in the case of a nanocrystalline soft magnetic alloy ribbon wound core is also described in the above-mentioned documents 1 to 3. As described above, since the core loss is greatly increased by providing the cut core and providing the gap, the feature of low core loss, which is the greatest advantage when used in the high-frequency power transformer 20, is impaired, and the gap portion is reduced. There is a problem that the copper loss increases due to the influence of the leakage magnetic flux generated in the above.

In the nanocrystalline soft magnetic alloy ribbon wound core,
As a method of reducing the relative magnetic permeability without providing a gap, the direction of the ribbon width direction of the same wound core (the height direction of the wound core)
And a method of applying stress to the nanocrystalline soft magnetic alloy ribbon constituting the wound core. However, in a composition system where the core loss is relatively small,
The level of relative permeability achievable using the former technique is 50
The frequency reached several tens of thousands at kHz and remained at a value one digit larger than about several thousands of Mn-Zn ferrite cores, and did not reach a level sufficient for countermeasures against magnetic bias. On the other hand, the latter method has a problem that the core loss is significantly increased as described in the above-mentioned documents 1 and 2.

For this reason, the full bridge type DC-D shown in FIG.
Like a C converter, the high-frequency power transformer 20 of a power converter in which the magnetic flux density of the high-frequency power transformer 20 operates to draw a BH minor loop symmetric with respect to the origin of the BH loop as shown in FIG. In order to use a nanocrystalline soft magnetic alloy ribbon wound core and exhibit the characteristic of low magnetic core loss, the amount of demagnetization of the high frequency transformer 20 is detected to suppress extreme demagnetization, and this is corrected. Therefore, it is necessary to take measures such as adding a demagnetization suppression circuit capable of independently controlling the on-period of each of the two sets of switches formed by the main switches 2, 3, 4, and 5. There was a problem that the score increased.

In the above description, a full-bridge DC
The problems of the high-frequency power transformer 20 using the nanocrystalline soft magnetic alloy ribbon wound core and the power converter using the same have been described by taking the -DC converter as an example. A high-frequency power transformer 20 of another power converter such as a half-bridge type converter having a primary winding having no tap and at least one pair of secondary windings having a center tap, and power conversion using the same. There was a completely similar problem with the device.

An object of the present invention is to provide a small-sized uncut nanocrystalline soft magnetic alloy thin film which can prevent the occurrence of a level of demagnetization at a level which is difficult to realize in the prior art, and which can be a practical obstacle. Provided is a high-frequency power transformer having a primary winding having no center tap and at least one set of secondary windings having a center tap in a band-wound core, and a highly efficient and highly reliable power conversion device using the same. Is to do.

[0022]

SUMMARY OF THE INVENTION The present invention provides an uncut nanocrystalline soft magnetic alloy ribbon comprising Fe as a main component and having fine crystal grains having a crystal grain size of 50 nm or less occupying 50% or more of the entire volume of the structure. In a high-frequency power transformer provided with a primary winding having no center tap on the winding core and at least one set of secondary windings with a center tap, all of the secondary winding ends are short-circuited to form a primary winding end. The value of the leakage inductance at 50 kHz measured by the method is 0.3 μH or less.

With such a configuration, the uncut nanocrystalline soft magnetic alloy ribbon wound core having a low magnetic core loss has at least one set of a primary winding having no center tap and at least one set of secondary windings having a center tap. Can be prevented without adding a complicated demagnetization suppression circuit, which is a problem when using a high-frequency power transformer provided with a power converter such as a full-bridge type converter or a half-bridge type converter. .

In the high-frequency power transformer, when the relative permeability at 50 kHz of the nanocrystalline soft magnetic alloy ribbon core is 20,000 or more, the high-frequency power transformer is prevented while preventing magnetic saturation due to magnetic polarization. Loss can be further reduced.

In the high-frequency power transformer, the squareness ratio Br / Bs, which is the ratio of the residual magnetic flux density Br to the saturation magnetic flux density Bs in the DC magnetic properties of the nanocrystalline soft magnetic alloy ribbon core, is set to 0.2 or less. In this case, the magnetic saturation due to the magnetic bias is less likely to occur, so that the change amount of the operating magnetic flux density can be set to a larger value, the number of windings can be reduced, and the high-frequency power transformer can be downsized. .

In the high-frequency power transformer, at least one set of the secondary windings with the center tap is formed by winding each winding constituting the windings approximately bifilarly on the nanocrystalline soft magnetic alloy ribbon core. And said 2
When the secondary winding is configured to be sandwich-wound with a primary winding wound substantially evenly on the nanocrystalline soft magnetic alloy ribbon core, the leakage inductance can be easily reduced. In addition, it is possible to further reduce the increase in the exciting current due to the above, and also to suppress the increase in the copper loss due to the influence of the leakage magnetic flux.

In the high-frequency power transformer, when the driving frequency is selected in the range of 5 kHz to 100 kHz, the size and efficiency can be further improved at the selected frequency as compared with the conventional high-frequency power transformer. .

The power converter using the high-frequency power transformer according to the present invention is different from the conventional power converter in that
The size and efficiency can be reduced, and an increase in the exciting current due to the demagnetization of the high-frequency power transformer can be suppressed with a simple circuit configuration.

[0029]

Embodiments of the present invention will be described below in detail. (Embodiment 1) Full-bridge type D having a switching frequency f of 50 kHz and a circuit configuration shown in FIG.
The performance of the high-frequency power transformer 20 of the C-DC converter and the performance of the full-bridge DC-DC converter were examined.

In FIG. 3, 1 is an input DC power supply,
3, 4, and 5 are main switches, 6, 7, 8, and 9 are feedback diodes, 20 is a high-frequency power transformer having a primary winding without a center tap and a secondary winding with a center tap, and 21 is the high-frequency power transformer. A primary winding of the power transformer 20, 22 and 23 are secondary windings of the high-frequency power transformer 20, 31 and 32 are output rectifier diodes, 33
Is an output smoothing choke coil, 34 is an output smoothing capacitor, 35 and 36 are output terminals, and 37 is a load.

[0031]

[Table 1]

In this embodiment, the main switches 2, 3, 4,
The main switches 2, 3, 4 and 5 of FIG.
In order to suppress the variation of the turn-off time of these MOS-FETs using T, a gate drive circuit which can take a large gate current peak value at the time of turn-off is adopted.

In the circuit of FIG. 3, the feedback diodes 6, 7, 8 and 9 regenerate the excitation energy of the high-frequency power transformer 20 to the input DC power supply 1 to increase the efficiency of the converter and to improve the efficiency of the converter. 20 has the function of suppressing the magnetization.

The magnetic core shown in Table 2 was used for the high frequency power transformer 20. In Table 2, the magnetic core A to the magnetic core H are Fe
Is a nanocrystalline soft magnetic alloy ribbon wound core whose main component is fine crystal grains having a crystal grain size of 50 nm or less occupying 50% or more of the entire volume of the structure. Of these, the magnetic core was cut and a non-magnetic insulator gap was inserted, and the rest was uncut. In addition, the core R is an uncut Fe-based amorphous soft magnetic alloy thin-wire wound core, the magnetic core N is an uncut Fe-based amorphous soft magnetic alloy thin-wire wound core containing partially crystalline, and the magnetic core L is an uncut. Mn-Zn ferrite core,
The magnetic core ヲ is a Mn—Zn ferrite core in which a gap of a nonmagnetic insulator is inserted after being cut.

[0035]

[Table 2]

Of the magnetic cores shown in Table 2, each of the magnetic cores a to 44 has an outer diameter of 44 mm, an inner diameter of 24 mm, and a height of 2 mm.
It has a toroidal shape of 0 mm and an outer diameter of 46.
It was inserted into a plastic insulating case having a size of 5 mm, an inner diameter of 21.5 mm and a height of 23 mm. Further, as shown in Table 2, the saturation flux density Bs at 120 ° C.
Since there is only 32T, if the allowance for the demagnetization is taken, the change amount ΔB of the magnetic flux density during the operation can be only about 0.35T. Therefore, each of the magnetic core お よ び and the magnetic core 重 ね is overlapped with two magnetic cores having the same size as the magnetic core イ from the magnetic core イ and inserted into a plastic insulating case having an outer diameter of 46.5 mm, an inner diameter of 21.5 mm and a height of 44 mm. did.

Table 3 shows the winding specifications of the high-frequency power transformer 20. FIG. 1 shows a winding structure described in Table 3 as a sandwich winding applied to the present invention A to the present invention G and the comparative examples m to q. FIG. 1 shows the present invention A
3 shows a 周 circumferential portion of a radial cross section of the high-frequency power transformer 20 of the present invention G and comparative examples m to q. In the figure, 50 is a magnetic core including a case,
The circle 51 and the white circle 52 that are painted black are the primary winding 21, the shaded circle 53, and the hatched circle 5 in FIG.
Numeral 4 corresponds to the secondary windings 22 and 23 in FIG.

The secondary windings 53 and 54 are each 0.23φ.
Litz wire composed of 69 pieces of the polyurethane insulated wire was wound around a magnetic core 50 covered with a case in a bifilar manner in parallel with two paras of four in total. FIG. 1 shows a cross-sectional view of the winding for one turn.

On the other hand, the primary winding is a winding 51 in which four turns of a 0.9-diameter three-layer insulated wire are wound substantially evenly around a magnetic core 50 including a case, eight turns corresponding to a half of the number of turns.
And 0.9φ φ three-layer insulated wire
Are wound around the magnetic core 50 including the case approximately eight turns corresponding to the number of turns of the secondary windings 53 and 5
4 in a sandwich shape and at the same time
And the winding 52 are connected in series to form a 16-turn primary winding 21. FIG. 1 shows a cross-sectional view of a winding of about four turns of the primary winding.

[0040]

[Table 3]

FIG. 2 shows a winding structure described in Table 3 as a uniform winding applied to Comparative Examples a to l.
FIG. 2 shows a 周 circumferential portion of a radial cross section of the high-frequency power transformer 20 of Comparative Examples a to l.
In the same figure, 50 is a magnetic core including a case, a circle 61 painted black is a primary winding 21 of FIG.
2 and the hatched circles 63 respectively represent the secondary windings 22 and 23 in FIG.
Is equivalent to

The primary winding 61 is composed of two Teflon-coated insulated wires each having a diameter of 1.4φ, and is substantially uniformly wound around the magnetic core 50 with two paras.
It consists of 6 turns. Note that in FIG.
A cross-sectional view of a winding of about four turns of the next winding 61 is shown. On the other hand, the secondary windings 62 and 63 are each 0.23φ.
2 is a bifilar winding of a litz wire composed of 69 pieces of polyurethane insulated wire, which is almost evenly wound around a magnetic core 50 covered with a case in a form in which two litz wires are alternately arranged. A cross-sectional view of a winding for a turn is shown.

Table 4 shows that 24 types of high-frequency power transformers 20 shown in Table 3 were obtained by short-circuiting all secondary winding ends.
The leakage inductance measured in the next winding, the degree of the magnetization of the high-frequency power transformer 20 when the same high-frequency power transformer 20 is mounted on the full-bridge DC-DC converter whose circuit configuration is shown in FIG. The change amount ΔB of the magnetic flux density during operation and the temperature rise ΔT are shown.

Regarding the magnetic polarization, in the range of the specifications in Table 1, the case where there is no abnormality due to the magnetic polarization even when the input voltage and the load change suddenly is 、, and the abnormality due to the magnetic polarization is only when the input voltage and the load change suddenly. Was given as Δ, and x was given when abnormalities occurred due to magnetic demagnetization even in steady operation. The change amount ΔB and the temperature rise ΔT of the magnetic flux density during operation are as follows: at an ambient temperature of 25 ° C., an input voltage of 260 V, an output voltage of 40 V, and a load current of 30 A.
These are the results measured at the time when the value was saturated by continuous energization under the input / output conditions described above.

[0045]

[Table 4]

As can be seen from Table 4, according to the high frequency power transformers A to G of the present invention using the uncut nanocrystalline soft magnetic alloy ribbon core having a low leakage inductance of a sandwich winding structure, the magnetic polarization is practically used. The temperature rise ΔT can be suppressed to a level that does not cause any problem, and the temperature rise ΔT can be suppressed to 50 ° C. or less, which is an allowable value that does not hinder practical use. Here, the allowable value of the temperature rise ΔT is shown in Table 1.
40 ℃ which is the upper limit of the ambient temperature during operation and DC during operation
-The assumed upper limit of temperature rise inside the DC converter case is 3
70 ° C, which is the sum of 0 ° C, is the allowable temperature for class E insulation, 120
It was subtracted from 50 ° C to 50 ° C or less.

On the other hand, Comparative Example a using a non-cut nanocrystalline soft magnetic alloy ribbon wound core having a large leakage inductance
To g, the high-frequency power transformer 20 of Comparative Example i using the uncut Fe-based amorphous soft magnetic alloy ribbon wound core or Comparative Example k using the uncut Mn-Zn ferrite core has a maximum value due to the influence of the magnetic polarization. The output could not be taken out stably, and measurement of the temperature rise ΔT was impossible.

Also, a nanocrystalline soft magnetic alloy ribbon wound core having a gap, and an uncut partially crystalline F
The high frequency power transformers 20 of Comparative Examples h, j and l using the e-based amorphous soft magnetic alloy thin ribbon wound core and the Mn-Zn ferrite core ギ ャ ッ プ having a gap and having a large leakage inductance suppress the influence of the magnetic polarization. However, it can be seen that the temperature rise ΔT is problematic because it exceeds 50 ° C. which is required for practical use.

Gap-attached nanocrystalline soft magnetic alloy ribbon wound core H, uncut Fe-based amorphous soft magnetic alloy ribbon wound core, uncut Fe-based amorphous soft magnetic alloy containing partially crystalline material The high frequency power transformers 20 of Comparative Examples m to q using a thin wound core, an uncut Mn-Zn ferrite core お よ び and a Mn-Zn ferrite core ギ ャ ッ プ using a gap, and having a low leakage inductance as a sandwich wound structure. Although the influence of magnetism can be suppressed, it can be seen that a problem arises because the temperature rise ΔT exceeds 50 ° C. except for Comparative Example p.

On the other hand, in the comparative example p, the temperature rise ΔT can be suppressed within 50 ° C. at the same time as the influence of the magnetic declination can be suppressed. However, since the Mn—Zn ferrite core ヲ is used, the saturation magnetic flux density is limited. ΔB must be selected to be about one-half as compared to the case where the nanocrystalline soft magnetic alloy ribbon wound cores A and H and the Fe-based amorphous soft magnetic alloy ribbon wound cores are used. As described above, since the core volume is doubled, there is a problem that the volume of the high-frequency power transformer 20 is also approximately doubled.

As a result of a detailed study based on the results obtained in the present embodiment, a primary winding without a center tap and a secondary winding with a center tap on a non-cut nanocrystalline soft magnetic alloy ribbon wound core are shown. -Frequency power transformer 2 provided with
At 0, if the value of the leakage inductance at 50 kHz measured at the primary winding end after shorting all the secondary winding ends is 0.3 μH or less, the circuit configuration of FIG. It was found that the operation of the full-bridge DC-DC converter having the specifications shown in Table 1 was not hindered.

Further, when comparing the present inventions A to G, the relative magnetic permeability μr (50 kHz) at 50 kHz is 20,000.
In the case of the present invention A to D using a nanocrystalline soft magnetic alloy ribbon wound core exceeding 45 ° C., the temperature rise ΔT is 45 ° C. having a margin of 10% or more with respect to 50 ° C. which is a practical upper limit.
It can be understood that the high-frequency power transformer and the power conversion device having high reliability and high performance can be realized.

(Embodiment 2) The switching frequency f is set to 50 k and the circuit configuration and specifications are completely the same as those of Embodiment 1.
Full-bridge DC-D changed from 20 Hz to 20 kHz
The performance of the high frequency power transformer 20 of the C converter and the performance of the full bridge type DC-DC converter were examined.

Table 5 shows the winding specifications of the high-frequency power transformer 20. Except for Comparative Examples r, s, t and u, those having the winding specifications shown in Table 3 using the magnetic cores described in Table 2 of Example 1 were used. In Table 5, in Comparative Example r
The structure of the sandwich winding and the uniform winding described in Comparative Example u are the same as those in FIGS. 1 and 2 in the first embodiment.

[0055]

[Table 5]

Comparative Examples The DC magnetic characteristics of the magnetic cores used in r, s, t and u and the relative permeability μr (50 kHz) at 50 kHz
Are shown in Table 6. The magnetic cores in Table 6 are uncut Mn-Zn.
The ferrite core and the magnetic core are Mn-Zn ferrite cores in which a nonmagnetic insulator gap is inserted after being cut. Further, as shown in Table 6, the magnetic core was
Since the saturation magnetic flux density Bs at 20 ° C. is only about one-fourth of the magnetic core from the magnetic core shown in Table 2 above, four magnetic cores each having the same size as the magnetic core from the magnetic core are superimposed on each other, and Diameter 46.5mm, inside diameter 21.5mm, height 84mm
Into a plastic insulation case.

[0057]

[Table 6]

Table 7 shows that the 24 types of high-frequency power transformers 20 shown in Table 5 were obtained by short-circuiting all secondary winding ends.
The leakage inductance measured in the next winding, the degree of magnetic declination and operation when the high-frequency power transformer 20 is mounted on the high-frequency power transformer 20 of the full-bridge DC-DC converter whose specifications are shown in FIG. And the temperature rise ΔT of the high-frequency power transformer 20.

Regarding the magnetic polarization, within the range of the specifications in Table 1, the case where there is no abnormality due to the magnetic polarization even when the input voltage and the load change suddenly is 、, and the abnormality due to the magnetic polarization is only when the input voltage and the load change suddenly. Was given as Δ, and x was given when abnormalities occurred due to magnetic demagnetization even in steady operation. The change amount ΔB and the temperature rise ΔT of the magnetic flux density during operation are as follows: at an ambient temperature of 25 ° C., an input voltage of 260 V, an output voltage of 40 V, and a load current of 30 A.
These are the results measured at the time when the value was saturated by continuous energization under the input / output conditions described above.

[0060]

[Table 7]

As can be seen from Table 7, according to the high-frequency power transformers 20 of the inventions A to G using the uncut nanocrystalline soft magnetic alloy ribbon wound core having a low leakage inductance of a sandwich winding structure, the magnetic polarization is practically used. And the temperature rise ΔT
Can be suppressed to 50 ° C. or less which does not hinder practical use.

On the other hand, Comparative Examples a to g using an uncut nanocrystalline soft magnetic alloy ribbon wound core having a large leakage inductance, and Comparative Examples using an uncut Fe-based amorphous soft magnetic alloy ribbon wound core. i and uncut Mn-Z
In the high frequency power transformer of Comparative Example r using the n ferrite core, the maximum output could not be taken out stably due to the influence of the magnetic polarization, and the measurement of the temperature rise ΔT was impossible.

Further, a nanocrystalline soft magnetic alloy thin-film wound magnetic core having a gap, and an uncut partially crystalline F
The high-frequency power transformers 20 of Comparative Examples h, j and s, which have a large leakage inductance using a Mn-Zn ferrite core using an e-based amorphous soft magnetic alloy ribbon core and a gap, suppress the influence of magnetic polarization. However, it can be seen that the temperature rise ΔT is problematic because it exceeds 50 ° C. which is required for practical use.

Further, a nanocrystalline soft magnetic alloy ribbon wound core with a gap, an uncut Fe-based amorphous soft magnetic alloy ribbon wound core, an uncut Fe-based amorphous soft Magnetic alloy ribbon wound core, uncut Mn-Z
Mn-Zn using n ferrite core wire and gap
In the high frequency power transformers of Comparative Examples m, n, o, t and u in which a ferrite core was used and the leakage winding inductance was low as a sandwich winding structure, the influence of the magnetic bias could be suppressed. Except for that, the temperature rise ΔT exceeds 50 ° C., which is a problem.

On the other hand, in Comparative Examples t and u, the influence of the magnetic bias was suppressed to a practically sufficient level, and the temperature rise Δ
T can also be suppressed within 50 ° C. However, Mn
-Zn ferrite core ヲ is used, ΔB is 0.38T due to the restriction of the saturation magnetic flux density at 120 ° C, and the nanocrystalline soft magnetic alloy ribbon wound core and the Fe based amorphous soft magnetic alloy ribbon wound Since the core volume must be selected to be 1/4 or less of that when the magnetic core and the core are used, the volume of the high-frequency power transformer 20 is also reduced to about 4 because the core volume is quadrupled as described above.
It can be seen that there is a problem of doubling or more.

As a result of a detailed study based on the results obtained in the present example, a primary winding without a center tap and a secondary winding with a center tap on the uncut nanocrystalline soft magnetic alloy ribbon wound core were obtained. -Frequency power transformer 2 provided with
At 0, if the value of the leakage inductance at 50 kHz measured at the primary winding end after shorting all the secondary winding ends is 0.3 μH or less, the circuit configuration of FIG. It has been found that the operation of the full-bridge DC-DC converter having a driving frequency of 20 kHz according to the specifications shown in Table 1 will not be affected.

Further, when the present inventions A to G are compared, the relative permeability μr (50 kHz) at 50 kHz is 20,000.
In the case of the present inventions A to D using a nanocrystalline soft magnetic alloy thin-film wound core exceeding 40 ° C., the temperature rise ΔT is 40 ° C. which has a margin of 20% or more with respect to 50 ° C. which is a practical upper limit.
It can be seen that the high-frequency power transformer 20 having high reliability and high performance and a power conversion device using the same can be realized.

Further, as in the inventions C, D and E, the residual magnetic flux density Br and the saturation magnetic flux density B
When the squareness ratio Br / Bs, which is the ratio of s, is 0.2 or less, the change amount ΔB of the magnetic flux density during operation is 1.6 in Table 7.
It has been confirmed that even if the DC-DC converter is increased to 1.86T which is about 1.1 times 9T, there is no problem in the stable operation of the DC-DC converter due to the influence of the magnetic bias.

As a result, one of the high-frequency power transformers 20
Although the number of turns of the secondary winding 21 can be reduced by one turn, in the present embodiment, the number of turns is reduced by 1 from the relation between the input voltage and the output voltage.
The turn ratio between the secondary winding and the secondary winding needs to be 4: 1,
It is not advisable to change the number of turns. Therefore, while keeping the winding specifications the same, the cross-sectional areas of
%, The ΔB was increased to 1.86T, and the operation was confirmed by reducing the volume of the magnetic core and the high-frequency power transformer. As a result, there was no problem due to the influence of the magnetic polarization, and the temperature rise ΔT was smaller than 50 ° C. A lightweight high-frequency power transformer 20 was obtained.

(Embodiment 3) A high-frequency power transformer having the same magnetic core size is connected to a full-bridge DC-
Mounted on a DC converter and measures the maximum power that can be output when the temperature rise of the high-frequency power transformer at an input voltage of DC 260V, an output voltage of 40V and an ambient temperature of 25 ° C is 50 ° C, changing the drive frequency from 2kHz to 200kHz. did.

Tables 8 to 14 show the winding specifications of the high-frequency power transformer 20 used in this embodiment. Table 8 shows a driving frequency of 2 kHz, Table 9 shows a frequency of 5 kHz, Table 10 shows a frequency of 10 kHz,
Table 11 is 20 kHz, Table 12 is 50 kHz, Table 13 is 1 kHz.
00 kHz and Table 14 were used for the study at 200 kHz. As the magnetic cores of the high-frequency power transformers 20 in Tables 8 to 14, the magnetic cores A to Y in Table 2 and the magnetic cores Y and Y having the magnetic characteristics shown in Table 15 were used. The magnetic core in Table 15 is an uncut Mn-Zn ferrite core, and the magnetic core is a Mn-Zn ferrite core in which a nonmagnetic insulator gap is inserted after cutting.

The sandwich winding and the equal winding in the winding structures shown in Tables 8 to 14 mean the same winding structures as in the first and second embodiments. Also,
As shown in Tables 8 to 14, the high-frequency power transformer 20
The number of turns of the windings differs depending on the drive frequency because the maximum output power is determined at each drive frequency.

The high-frequency power transformer 20 shown in Tables 8 to 14 was replaced with a full-bridge DC-D having the circuit configuration shown in FIG.
When the temperature rise of the high-frequency power transformer mounted on a C converter and having an input voltage of DC 260V, an output voltage of 40V and an ambient temperature of 25 ° C is 50 ° C, the maximum output power was measured by changing the drive frequency from 2kHz to 200kHz. It is shown in Table 16. In Table 16, "-" indicates that measurement could not be performed due to the influence of magnetic demagnetization or the like. The parenthesized parentheses show the winding structure of the high-frequency power transformer 20 at which the maximum output power was obtained, and correspond to Tables 8 to 14.

[0074]

[Table 8]

[0075]

[Table 9]

[0076]

[Table 10]

[0077]

[Table 11]

[0078]

[Table 12]

[0079]

[Table 13]

[0080]

[Table 14]

[0081]

[Table 15]

As can be seen from Table 16, according to the present invention, in the driving frequency range of 5 kHz or more and 100 kHz or less, without performing an unstable operation due to the influence of the magnetic bias,
A high-frequency power transformer 20 that can stably supply a larger output power than the comparative example with the same core volume can be obtained.

In the high-frequency power transformer 20 of the present invention shown in Table 16, all of the secondary winding ends were short-circuited.
The leakage inductance at 50 kHz measured at the end of the next winding showed a value of 0.3 μH or less. on the other hand,
Of the comparative examples shown in the same table, in the high-frequency power transformer 20 having the winding structure of the uniform winding from the core A, which is the uncut nanocrystalline soft magnetic alloy thin ribbon core, the leakage inductance measured in the same manner Also exceeds 0.3 μH, so that these high-frequency power transformers 2
At 0, it was found that an unstable operation was caused by the influence of the magnetic polarization, and the output could not be taken out stably.

As described above, in the high-frequency power transformer 20 in which the uncut nanocrystalline soft magnetic alloy ribbon wound core is provided with the primary winding having no center tap and the secondary winding with the center tap, the secondary winding is provided. If the value of the leakage inductance at 50 kHz measured at the primary winding end with all the wire ends short-circuited is 0.3 μH or less, the output is stable without practically exhibiting unstable operation due to the influence of magnetic bias. It has been found that electric power can be taken out and a highly reliable high-frequency power transformer 20 and a highly efficient and highly reliable full-bridge DC-DC converter using the same can be obtained.

[0085]

[Table 16]

Further, in Table 16, a center tap is provided from the core A, which is a non-cut nanocrystalline soft magnetic alloy ribbon wound core having a relative magnetic permeability μr (50 kHz) at 50 kHz of 20,000 or more, to the core D. Since the high-frequency power transformer 20 of the present invention provided with a non-primary winding and a secondary winding with a center tap has a small core loss in a high-frequency region, it can extract larger output power at a high frequency exceeding 20 kHz or more. It can be seen that it is suitable for high frequency specifications.

Further, in Table 16, in the uncut nanocrystalline soft magnetic alloy ribbon core having a squareness ratio Br / Bs, which is the ratio of the residual magnetic flux density Br to the saturation magnetic flux density Bs in the DC magnetic characteristics, is 0.2 or less. A primary winding without a center tap from a magnetic core to a magnetic core, and 2 with a center tap
The high-frequency power transformer 20 of the present invention provided with a secondary winding is:
It can be seen that since the amount of change in magnetic flux density during operation at a frequency of 10 kHz or less can be large and the number of turns can be reduced as shown in Tables 8, 9 and 10, larger output power can be obtained.

[0088]

As described above, according to the present invention,
In particular, it is possible to suppress the occurrence of demagnetization, which is a practical obstacle, without providing a complicated demagnetization suppression circuit, and to use a small, uncut nanocrystalline soft magnetic alloy ribbon wound core with low core loss and a small core to increase the temperature. Thus, a high-efficiency high-frequency power transformer having a small size and a highly efficient and highly reliable power converter using the same can be obtained. In the above embodiment, an application example to a full-bridge DC-DC converter as a typical power converter using a high-frequency power transformer has been described in detail. Applicable to all high-frequency power transformers provided with a primary winding having no tap and at least one or more sets of secondary windings having a center tap, and to all power conversion devices using the high-frequency power transformer, which are also effective. It exerts an effect, and the effect is extremely large.

[Brief description of the drawings]

FIG. 1 shows a high-frequency power transformer 1 according to the present invention.
The conceptual diagram of the winding structure cross section of an Example.

FIG. 2 is a conceptual diagram of a winding structure cross section of a high-frequency power transformer as a comparative example.

FIG. 3 is a circuit configuration block diagram of a full-bridge DC-DC converter.

FIG. 4 is a conceptual diagram of a terminal voltage of a primary winding 21 of the high-frequency power transformer 10 of the full-bridge DC-DC converter of FIG.

FIG. 5 shows a full-bridge DC- of FIG.
Operation B- of high frequency power transformer 20 of DC converter
H loop conceptual diagram.

FIG. 6 is a conceptual diagram of an operation BH loop of the high-frequency power transformer 20 of the full-bridge DC-DC converter of FIG. 3 when the magnetic core is saturated due to the magnetization.

[Explanation of symbols]

 1: input DC power supply 2, 3, 4, 5: main switch element 6, 7, 8, 9: feedback diode 20: high-frequency power transformer 21: primary winding of high-frequency power transformer 20 23: high-frequency power transformer 20-2 Next winding 31, 32: Output rectifier diode 33: Output smoothing choke coil 34: Output smoothing capacitor 35, 36: Output terminal 37: Load

Continued on the front page (72) Inventor Shigeru Hasumura 2977 Tahira, Yoshii-cho, Tano-gun, Gunma Prefecture Inside Hitachi Kinki Kiko Co., Ltd. F-term in the factory (reference) 5E058 BB19 5H730 AA15 AA19 BB27 DD04 EE03 EE08 ZZ16

Claims (6)

[Claims] 1. An uncut nanocrystalline soft magnetic alloy ribbon wound core having Fe as a main component and having fine crystal grains having a crystal grain size of 50 nm or less occupying 50% or more of the entire volume of the structure has no center tap. In a high-frequency power transformer provided with a primary winding and at least one or more sets of secondary windings with a center tap, all of the secondary winding ends are short-circuited and the leakage inductance at 50 kHz measured at the primary winding end. A high-frequency power transformer having a value of 0.3 μH or less. 2. The high-frequency power transformer according to claim 1, wherein said nanocrystalline soft magnetic alloy ribbon wound core has
A high-frequency power transformer, wherein the relative magnetic permeability at 0 kHz is 20,000 or more. 3. The high frequency power transformer according to claim 1, wherein the squareness ratio Br is a ratio of a residual magnetic flux density Br to a saturation magnetic flux density Bs in a DC magnetic characteristic of the nanocrystalline soft magnetic alloy ribbon core. A high-frequency power transformer characterized in that / Bs is 0.2 or less. 4. The high-frequency power transformer according to claim 1, wherein at least one set of said center-tapped secondary windings is formed by winding each of said windings comprising said nanocrystalline soft magnetic alloy ribbon. A bifilar coil wound substantially evenly around a magnetic core, and the secondary winding is sandwich-wound with a primary winding wound substantially evenly around the nanocrystalline soft magnetic alloy ribbon core. Power transformer. 5. The high-frequency power transformer according to claim 1, wherein the driving frequency is 5 kHz or more and 100% or more.
A high-frequency power transformer characterized by being in the range of kHz or less. 6. A power converter using the high-frequency power transformer according to claim 1.