JP7142527B2 - Coupled inductors and switching circuits - Google Patents

Description

The present invention relates to coupled inductors and switching circuits comprising such coupled inductors.

In recent years, the power conversion circuits of transportation equipment (e.g. hybrid cars, electric vehicles, fuel cell vehicles, etc.) and electronic equipment (e.g. smartphones, personal computers, etc.) with built-in storage batteries have been made smaller and lighter while maintaining high output. There is a demand for power density.

The interleave method is drawing attention as a circuit method for achieving high power density. The interleave method is a control method in which a power supply is divided into multiple systems and each phase has a phase difference to cancel out ripples and the like. For example, in the two-phase interleave method, the current phases are given a phase difference of 180° to cancel the ripples. By adopting the interleave method, it is possible to reduce the size and weight of the output smoothing capacitor and to reduce the ripple.

On the other hand, the interleaved method increases the number of parts of the inductor, so there is a limit to how high power density can be achieved. Therefore, in addition to the interleave method, the use of a coupled inductor that magnetically couples inductors of each phase is being considered. The following effects are expected by using coupled inductors.

(1) In the conventional interleaving method, the number of inductors equal to the number of paralleled phases increases. can reduce the number of parts.

(2) In general, the core size is greatly related to the maximum magnetic flux in the core. Since the alternating magnetic flux generated between the integrated circuits can be shared, the magnetic flux in the core can be reduced, and the size of the inductor can be reduced.

As an example of the coupled inductor described above, as described in Patent Document 1 below, two E-shaped cores, an I-shaped core sandwiched between the two E-shaped cores and wound with two coils, 2 with a first gap provided between the central leg of one E-shaped core and the I-shaped core and a second gap provided between the central leg of the other E-shaped core and the I-shaped core; Phase coupled inductors are known.

In recent years, it has been studied to apply the two-phase interleaved coupled inductor described in Patent Document 1 to a three-phase interleaved circuit. By expanding to three phases, the input current can be shunted as compared to the case of two phases, so that a further increase in capacity can be realized. Also, it is possible to further reduce the capacity of the smoothing capacitor on the output side.

As a three-phase coupled inductor, there is known one that uses a three-axis core in which three shaft bodies are arranged along three mutually orthogonal axes and integrated as described in Patent Document 2 below. ing.

Japanese Patent No. 5934001 JP 2011-204946 A

However, verification of coupled inductors compatible with three-phase interleaved circuits has not progressed sufficiently. For example, even if another leg is added to the core of the two-phase coupled inductor described in Patent Document 1, the magnetic path length and mutual inductance of each phase cannot be made the same, and the magnetic flux bias and each phase loss imbalance occurs and symmetry cannot be maintained. Therefore, the performance as a coupled reactor is degraded.

When using the triaxial core of Patent Document 2, since the triaxial core has protrusions protruding in six directions from a common central portion, the shape of the core is complicated, and the manufacturing of the core requires a great deal of effort. required man-hours. Therefore, the manufacturing cost of the coupled inductor rises.

Although Patent Document 2 discloses a three-phase coupled inductor, there is no document disclosing a multi-phase coupled inductor of four or more phases.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a small, inexpensive multiphase coupled inductor having three or more phases, which has stable performance.

In order to solve the above problems, the present invention provides a coupled inductor for use in an interleaved multiphase switching circuit having three or more phases . A unit is formed comprising a plurality of said inductor units (e.g. three when used in a three-phase switching circuit), said plurality of windings wound on a common core of each inductor unit providing different windings of said switching circuit. The windings of different inductor units are connected in parallel to the same phase of the switching circuit .

By winding a plurality of windings around a plurality of locations of the core in this way, each inductor unit magnetically couples a plurality of inductors, and thus becomes equivalently composed of one inductor. A plurality of windings wound around a common core of each inductor unit are connected to different phases of the switching circuit. In such a configuration, by driving the multiphase switching circuit with a phase shift, the inductor currents of each phase interfere with each other, and alternately excited magnetic fluxes interlink with other windings. As a result, the inductor current waveform is driven at a multiple of the switching frequency that matches the number of phases (three times in the case of a three-phase switching circuit). During operation, the DC magnetic flux cancels each other out in each inductor unit, while the AC magnetic flux circulates in the magnetic flux path formed in each core while sharing and strengthening or canceling each other in the core of each inductor unit. . Therefore, the inductance of each inductor unit can be increased to reduce the magnetic flux generated in each core, and the cores can be miniaturized.

Further, with the above configuration, it is easy to make the magnetic path length and mutual inductance of each inductor unit the same length and value. Therefore, performance as a coupled inductor can be stabilized.

In particular, with the above configuration, the inductor units are electrically connected to each other, but not mechanically connected, and are separable from each other. Therefore, the arrangement position of each inductor unit can be freely selected. Therefore, it is possible to increase the degree of freedom in arranging the polyphase coupled inductors and reduce restrictions on the installation space.

In such a configuration, the plurality of windings wound around a common core are preferably connected so that the DC components of the magnetic fluxes generated by the plurality of windings cancel each other out at the core.

Moreover, the core of each inductor unit is preferably formed in an endless loop shape without an air gap. As a result, leakage magnetic flux can be reduced, so that heat generation in the windings due to leakage magnetic flux reaching the windings and generating eddy currents in the windings can be suppressed.

Since the coupled inductor needs to utilize the leakage inductance, it is necessary not to make the coupling coefficient too high. Of course, if the coupling coefficient is too low, the effect of magnetic coupling cannot be obtained. Therefore, the coupling coefficient of each inductor unit is preferably 0.3 or more and 0.85 or less.

The core is preferably made of soft magnetic powder with an insulating coating. As a result, leakage magnetic flux is more likely to occur than when ferrite is used as the core material. Therefore, even without providing an air gap, a moderate leakage magnetic flux can be generated in the entire core, making it easy to obtain a moderate coupling coefficient. In addition, there is no need to separately provide a path through which leakage magnetic flux flows. Therefore, it is possible to reduce the size of the multiphase coupled inductor while preventing heat generation in the windings due to leakage flux around the air gap. The initial magnetic permeability of the core using soft magnetic powder with insulating coating is preferably 30 or more and 200 or less.

By forming an interleaved multiphase switching circuit using the coupled inductors described above, a high power density of the circuit can be achieved.

According to the present invention, it is possible to provide a small and inexpensive multiphase coupled inductor of three or more phases with stable performance.

1 is a perspective view showing a three-phase coupled inductor according to this embodiment; FIG. FIG. 3 is a perspective view showing one inductor unit that constitutes a coupled inductor; 1 is a circuit diagram showing an interleaved three-phase boost chopper circuit using three-phase coupled inductors; FIG. FIG. 4 is a plan view showing the arrangement of inductor units in a three-phase coupled inductor; It is a table|surface which shows the test result of a confirmation test. FIG. 4 is a diagram showing current waveforms of a three-phase coupled inductor; 1 is a circuit diagram showing an interleaved four-phase boost chopper circuit using four-phase coupled inductors; FIG. 1 is a perspective view showing a four-phase coupled inductor; FIG. FIG. 4 is a diagram showing current waveforms of a four-phase coupled inductor; 4 is a table summarizing the relationship between the number of phases and various characteristics when a coupled inductor is multiphased. FIG. 4 is a plan view showing another embodiment of a four-phase coupled inductor;

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a multiphase coupled inductor, particularly a three-phase coupled inductor 10, according to this embodiment.
As shown in FIG. 1, this three-phase coupled inductor 10 includes three inductor units (first inductor unit 1, second inductor unit 2, and third inductor unit 3). Each of the inductor units 1 to 3 has a common configuration, each having a core 7 and a plurality of windings 8 wound around each core 7 at two locations.

In the following description, the number of the inductor unit to which each core belongs is attached with a subscript after the reference numeral 7 representing the core. That is, reference numeral 7 ₁ represents the core of the first inductor unit 1, reference numeral 7 ₂ represents the core of the second inductor unit 2, and reference numeral 7 ₃ represents the core of the third inductor unit.

FIG. 2 shows a perspective view of the first inductor unit 1, which is one of the three inductor units 1-3.
As shown in FIG. 2, the core 7 ₁ of the first inductor unit 1 has a pair of leg portions 71 and a pair of connecting portions 72 bridged between one end and the other end of the pair of leg portions 71. . In this embodiment, a pair of legs 71 are arranged in parallel, and a connecting part 72 is arranged in a direction perpendicular to the legs 71 to form the core 71 as _a whole into a rectangular frame shape. As the core 71, any shape can be adopted as long as it has _a closed loop shape, and besides a rectangular frame shape, for example, an annular core (toroidal core) can also be used. No air gap is provided in the core 7 ₁ .

As shown in FIG. 1, the remaining inductor units (the second inductor unit 2 and the third inductor unit 3) also have cores 7 ₂ and 7 ₃ of the same shape as the core 7 ₁ of the first inductor unit 1, respectively. No air gap is provided in these cores 7 ₂ and 7 ₃ . In FIG. 1, only the leg portion 71 of the core 7 ₁ of the first inductor unit 1 is shown by a broken line, and the cores 7 ₂ and 7 ₃ of the other inductor units 2 and 3 are shown by broken lines for the sake of simplification of the drawing. Illustration of the portion 71 is omitted.

Each of the cores 7 ₁ to 7 ₃ is manufactured by compressing soft magnetic powder using a mold and then annealing the green compact. As the soft magnetic powder, soft magnetic powder with an insulating coating, which is obtained by coating soft magnetic metal powder composed of pure iron, amorphous, soft magnetic alloy (sendust, permalloy, etc.), nanocrystalline, etc. with an insulating coating, should be used. can be done. As the insulating coating, metal oxides such as Al ₂ O ₃ , Y ₂ O ₃ , MgO and ZrO ₂ , oxides of semi-metals, glass materials, or mixtures thereof, and resin materials as binders are blended. used. The binder component decomposes with the annealing and vaporizes as a gas. The initial magnetic permeability (meaning the relative magnetic permeability at a magnetic field of 0 A/m) of the core using this insulating-coated soft magnetic powder is preferably 30 or more and 200 or less. Moreover, the leg portion 71 and the connecting portion 72 may be formed of the same material or may be formed of different materials.

One winding 8 is attached to each leg 71 of each of the cores 7 ₁ to 7 ₃ . Therefore, the windings 8 wound on the common cores 7 ₁ -7 ₃ are magnetically coupled. Each winding 8 has the same number of turns, is made of the same conductive material, and has the same cross-sectional dimensions. Each winding 8 therefore has an equal inductance. Two windings 8 wound on the same core are connected so as to have opposite polarities. Specifically, when two windings 8 wound around the same core are connected in parallel and a direct current is applied to _each of them _, the magnetic fluxes φ ( Each winding 8 is connected in such a way that a .function.

Two windings 8 wound around a common core 7 in each inductor unit 1 to 3, which will be described later in detail, are two different phases of a three-phase (u-phase, v-phase, and w-phase) switching circuit. connected to That is, one of the two windings 8 of the first inductor unit 1 is connected to the u phase and the other is connected to the w phase, and one of the two windings 8 of the second inductor unit 2 is connected to the u phase and the other is connected to the v phase. Also, one of the two windings 8 of the third inductor unit 3 is connected to the v phase, and the other is connected to the w phase. In FIG. 1, the above-described connection mode is indicated by parenthesizing the connection destination phase after the reference numeral 8 representing each winding.

In the coupled inductor 10 described above, for example, in each of the inductor units 1 to 3, one end of the two legs 71 is fixed to one connecting portion 72, and the pre-wound winding 8 is attached to each leg. 71 and then fixing the other connecting part 72 to the other end of each leg 71 . The fixing of the leg portion 71 and the connecting portion 72 can be performed, for example, by adhesion. Of course, the windings 8 may be wound around the leg portions 71 after the cores 7 ₁ to 7 ₃ are integrally formed.

Since the coupled inductor 10 manufactured in this manner needs to utilize leakage inductance, it is necessary not to make the coupling coefficient too high. Of course, if the coupling coefficient is too low, the effect of magnetic coupling cannot be obtained. From the above point of view, it is preferable to set the coupling coefficients of the individual inductor units 1 to 3 within the range of 0.3 to 0.85 (preferably 0.3 to 0.75). By using the soft magnetic powder with an insulating coating as the material of the core 7 as described above, it is possible to easily adjust the coupling coefficient and easily obtain the coupling coefficient within this range. Coupling coefficients of the inductor units 1 to 3 are set to the same value. The coupling coefficient here is obtained from the following formula according to the open-circuit method specified in JIS C 5321.
Coupling coefficient k = (1-Lsc/Lop) ^1/2
where Lsc is the short L value (2 wires shorted) and Lop is the open L value.

The above-described coupled inductor 10 is arranged in a three-phase (u-phase, v-phase, and w-phase) switching circuit that employs an interleaved system, as shown in FIG. The switching circuit here means a circuit in which a high-frequency current flows with switching. FIG. 3 shows a schematic configuration of a power supply circuit, particularly a DC-DC boost chopper circuit, as an example of a switching circuit.

As shown in FIG. 3, the power source E is connected in parallel with one end of each winding 8 of the coupled inductor 10 . At this time, as already described, each phase (u, v, w) of the switching circuit is connected to the windings 8 of the same number (two) provided in different inductor units 1 to 3. . Specifically, one winding 8 (u1) of the two windings 8 of the first inductor unit 1 is connected to the u phase, and the other winding 8 (w2) is connected to the w phase. One of the two windings 8 of the second inductor unit 2 (u2) is connected to the u phase, and the other 8 (v1) is connected to the v phase. Furthermore, one winding 8 (v2) of the two windings 8 of the third inductor unit 3 is connected to the v phase, and the other winding 8 (w1) is connected to the w phase. Thus, each winding 8 of coupled inductor 1 is cyclically connected to each phase of the circuit. Two windings (for example, winding 8(u1) and winding 8(u2)) connected to the same phase of the switching circuit are connected in parallel in each phase.

The other ends of the two windings 8 (u1) and 8 (u2) connected to the u phase are connected to the anode of the first diode D1 and one end of the first switching element Q1, and the two windings connected to the v phase. The other ends of the windings 8(v1) and 8(v2) are connected to the anode of the second diode D2 and one end of the second switching element Q2. The other ends of the two windings 8(w1) and 8(w2) connected to the w-phase are connected to the anode of the third diode D3 and one end of the third switching element Q3. The other end of each switching element Q1-Q3 is connected to the ground side. Each of the switching elements Q1 to Q3 repeats opening and closing operations at regular intervals according to a control signal from a control device (not shown). At this time, each of the switching elements Q1 to Q3 repeats opening and closing operations while shifting the phase by 120°.

The voltage and current output from the cathode of each diode D1-D3 are smoothed by a smoothing capacitor C and consumed by a load R.

In the case of a single-phase system in which the boost chopper circuit is composed of a single unit (one phase), the current sent to the smoothing capacitor on the output side is intermittent, so the smoothing capacitor repeats vigorous charging and discharging. Therefore, a large capacity is required for the smoothing capacitor, and the size of the smoothing capacitor is increased. On the other hand, in the interleave method (multiphase method) shown in FIG. 3, in which circuits are operated in parallel, each phase is controlled to alternately switch. The miniaturization of the capacitor C can be achieved.

In addition, since the interleaved circuit is extended to three phases, the input current can be split compared to a two-phase interleaved circuit, so that a further increase in capacity can be achieved. Also, it is possible to further reduce the capacity of the smoothing capacitor on the output side.

In the three-phase coupled inductor 1 of this embodiment, each of the inductor units 1 to 3 magnetically couples two inductors to form one inductor equivalently. Two windings (eg, 8(u1) and 8(w2)) wound around a common core of each inductor unit 1 to 3 are connected to two different phases (eg, u-phase and w-phase) of the switching circuit. are connected to each. That is, two windings connected to different phases are magnetically coupled. In such a configuration, by shifting the current phase and driving the three-phase _interleaved boost chopper circuit, the inductor currents _Iu , Iv, and _Iw of the respective phases interfere with each other, and the alternately excited magnetic flux is induced in the other. It becomes a form that interlinks with the winding of This results in a state where the inductor current waveform is driven at three times the switching frequency.

As shown in FIG. 1, during the operation of the coupled inductor 10, the DC magnetic fluxes φ generated from the inductor average current in each inductor unit 1-3 cancel each other out. On the other hand, the AC magnetic flux circulates through the endless loop magnetic flux paths formed in the cores 7 ₁ to 7 ₃ while being shared in the cores of the inductor units 1 to 3 and reinforcing or canceling each other. In this way, by mutually canceling the DC magnetic flux, the magnetic flux in the core can be reduced, while the magnetic flux path in which the AC component magnetic flux circulates is formed, so that the inductance of each of the inductor units 1 to 3 increases. Therefore, the magnetic flux generated in the cores 7 ₁ to 7 ₃ can be reduced, the cores 7 ₁ to 7 ₃ can be miniaturized, and a small coupled inductor 10 with a small ripple width and improved superimposition characteristics can be provided. It becomes possible.

Further, in the coupled inductor 10 of the present embodiment, the inductor units 1 to 3 are formed with the same structure, so the magnetic path length and mutual inductance of the inductor units 1 to 3 can be the same value. Therefore, the performance of the coupled inductor 10 can be stabilized.

Furthermore, no air gap is formed in the magnetic flux paths of the cores 7 ₁ to 7 ₃ , and the cores 7 ₁ to 7 ₃ form a closed magnetic circuit, thereby reducing leakage magnetic flux. Therefore, it is possible to prevent heat generation in the windings 8 due to leakage magnetic flux reaching the windings 8 and eddy currents being generated in the windings. It is also possible to prevent a decrease in inductance. As a result, it is possible to provide the three-phase coupled inductor 10 that is small in size and generates little heat in the windings 8 .

When the cores 7 ₁ to 7 ₃ are made of general ferrite, the initial magnetic permeability of ferrite is high (approximately 2300), so the leakage magnetic flux is reduced. Therefore, the ripple width cannot be suppressed unless the size of the inductor is increased, and the demand for miniaturization cannot be met. It is effective to provide an air gap in the magnetic flux path in order to increase the leakage magnetic flux, but this causes the problem of heat generation in the winding 8 as already described. On the other hand, as in the present embodiment, by forming the cores 7 ₁ to 7 ₃ with an initial magnetic permeability of 30 to 200 using soft magnetic powder with an insulating coating, moderate coupling can be achieved even when no air gap is provided. Factors (0.30-0.85) can be obtained. Therefore, it is possible to provide a small-sized coupled inductor 10 having a stable ripple suppression effect and DC current superimposition characteristics while preventing heat generation in the windings 8, which is a problem when an air gap is provided.

In the coupled inductor 1 of this embodiment, the inductor units 1 to 3 are electrically connected through wiring, but not mechanically connected. That is, the individual inductor units 1-3 are in a separable state. Therefore, each inductor unit 1 to 3 can be arranged at any position. For example, as shown in FIG. 1, each inductor unit 1 to 3 can be arranged at each vertex position of a triangle in plan view seen from the winding axis direction, or as shown in FIG. It is also possible to employ a configuration in which the inductor units 1 to 3 are developed in a line and arranged in a plane such that the respective winding axes are positioned on the same plane. Furthermore, it is also possible to dispose one inductor unit at a position distant from the other two inductor units. Therefore, it is possible to increase the degree of freedom in the layout of the three-phase coupled inductor 10 and reduce the restrictions on the installation space.

In particular, in the arrangement shown in FIG. 4, each winding axis of the coupled inductor 10 is positioned on the same plane parallel to the inductor installation surface (100: see FIG. 7) provided on the circuit board or the like. It is possible to arrange it so that In this case, since the distance from each winding 8 to the inductor mounting surface is made uniform, the heat dissipation of each winding 8 can be made uniform. Therefore, the width of the temperature rise of each winding 8 can be made uniform, and variations in the magnetic properties of each winding 8 can be suppressed. In addition, since it is not necessary to install a separate component for heat dissipation, the overall size of the coupled inductor 10 can be reduced.

As the cores 7 ₁ to 7 ₃ , it is possible to employ existing cores of simple endless loop shape, such as UU cores and toroidal cores. Therefore, there is no need to prepare a core having a complicated three-dimensional structure as described in Patent Document 2, and the manufacturing cost of the cores 7 ₁ to 7 ₃ can be reduced.

Next, confirmation tests were conducted to confirm the effect of the coupled inductor 10 according to the present embodiment, and the details and results thereof will be described.

In this confirmation test, the coupled inductor 10 shown in FIG. 1 was used in the three-phase interleaved boost chopper circuit shown in FIG. 3, and the output voltage was measured when the duty ratio was varied. The inductance of each winding 8 is 200 μH, the coupling coefficient of each inductor unit 1-3 is 0.7, and the input voltage is DC 400V. Moreover, the phase shift between each phase is 120°, and switching is performed at 50 kHz.

As is clear from the test results shown in FIG. 5, according to this embodiment, the output voltage increases as the duty ratio increases. Therefore, it was confirmed that even when the coupled inductor 1 of the present embodiment was used, the booster circuit operated without problems.

FIG. 6 shows, in the _{switching circuit} shown in FIG. The results of measuring _Iu2 are shown (coupling coefficient is 0.5, frequency is 55 kHz, and duty ratio is 0.65).

As is clear from FIG. 6, the average current of each winding and the ripple width of each winding current are halved with respect to _Iu . In each winding current, gentle slope regions X and Y are generated, and the influence of the magnetic coupling of the windings 8(u1) and 8(u2) can be seen.

In the above description, the three-phase coupled inductor 10 was exemplified, but by adopting the same configuration, it is also possible to provide a multi-phase coupled inductor of four or more phases.

In this multiphase coupled inductor, “number of phases×(number of phases−1)/2” cores and inductor units are used. For example, 3 cores and inductor units are used for 3 phases, 6 for 4 phases, 10 for 5 phases, 15 for 6 phases, and 21 for 7 phases. Also, since two windings 8 are attached to each core, the total number of turns of the coupled inductor is twice the number of cores.

FIG. 7 shows a four-phase coupled inductor 11 as an example of a multiphase coupled inductor. This coupled inductor 11 comprises first to sixth inductor units 1-6. Each inductor unit 1 to 6 has the same configuration as the inductor units 1 to 3 described in the three-phase coupled inductor 10 already described, and each has a core 7 (7 ₁ to 7 ₆ ) and a position opposite to the core 7 at 180°. It has two windings 8 arranged in the . Note that FIG. 7 illustrates a case where a toroidal core is used as each core 7 .

FIG. 8 shows an interleaved four-phase switching circuit using the four-phase coupled inductor 11 described above. As shown in FIG. 8, three windings 8 are connected in parallel to each of four phases (phases a, b, c, and d). That is, windings 8(a1), 8(a2), 8(a3) are connected to phase a, and windings 8(b1), 8(b2), 8(b3) are connected to phase b. . Windings 8(c1), 8(c2) and 8(c3) are connected to the c-phase, and windings 8(d1), 8(d2) and 8(d3) are connected to the d-phase.

The switching elements Q1 to Q4 of the polyphase switching circuit perform switching operations so that the current phases are shifted by an angle obtained by dividing 360° by the number of phases. Therefore, in the four-phase switching circuit, the switching elements Q1 to Q4 repeat opening and closing operations while shifting the phase by 90°.

As with the three-phase coupled inductor, also in the four-phase coupled inductor, two windings 8 (e.g., 8(a1) and 8(b1)) wound on a common core 7 are used in the four-phase switching circuit. It is connected to two different phases (a phase, b phase). Conversely, two windings connected to different phases among the twelve windings 8 shown in FIG. For example, two windings of the combinations listed below are magnetically coupled by being mounted on a common core 7 (see FIG. 7).
・Winding 8 (a1) and winding 8 (b1)
・Winding 8 (a2) and winding 8 (c1)
・Winding 8 (a3) and winding 8 (d1)
・Winding 8 (b2) and winding 8 (c2)
・Winding 8 (b3) and winding 8 (d2)
・Winding 8 (c3) and winding 8 (d3)

FIG. 9 shows, in the _{switching circuit} shown in FIG. It shows the result of measuring I _a2 and the current I _a3 of the winding 8 (a3) connected to the a-phase (coupling coefficient is 0.5, frequency is 55 kHz, and duty ratio is 0.65). .

As is clear from FIG. 9, the average current of each winding and the ripple width of each winding current are each 1/3 of _Ia . In addition, each winding current has a region with a gentle slope as in the case of three phases, and the effect of magnetic coupling of the windings 8 (a1), 8 (a2), and 8 (a3) can be seen. be able to.

In the coupled inductor 11 having four phases in this way, the same effects as those of the already described three-phase coupled inductor 10 can be obtained. Even when the number of phases is increased to five or more, the same effect can be obtained by connecting the two windings 8 wound around the common core 7 to two different phases.

FIG. 10 is a table summarizing changes in various characteristics when the number of phases is changed in a multiphase coupled inductor.

Among the items in FIG. 10, "parallel number" is the number of windings to be connected in parallel to each phase. "I (phase)" represents the current value of each phase, and "I (winding)" represents the current value of each winding. "R" represents the sum of the resistance values of the windings, and "P (copper)" represents the heat radiation amount (copper loss) of the windings per core. L represents the inductance value required for each phase number, and "copper wire diameter" represents the diameter dimension of the copper wire forming the winding required from the value of "P (copper)". “H” is represented by H=N×I/l (l is the magnetic path length, N is the number of turns, and I is the current value), and the smaller this value, the better the DC superimposition characteristics. “ΔI” represents the ripple width in each core, and ΔB represents the amount of change in magnetic flux density (ΔB=μ×H). "P (iron)" represents the heat radiation amount (iron loss) of the core of the entire coupled inductor. In FIG. 10, the value of each item is 1 for a one-phase switching circuit.

From the value of "copper S" in FIG. 10, it can be understood that the copper wire diameter can be made smaller as the number of phases increases in the multiphase coupled inductor. Therefore, as the number of phases increases, it becomes easier to manufacture windings, and it becomes possible to achieve cost reduction. It can also be understood from the value of "H" that the superimposed magnetizing force decreases as the number of phases increases, and the DC superimposition characteristics improve. Furthermore, from the value of "L", it can be understood that the required L value increases as the number of phases increases, and from the values of "ΔB" and "P-iron", it can be understood that the iron loss can be reduced as the number of phases increases. Moreover, from the result of "P (copper)", the copper loss (the amount of heat radiation of the winding) in each core 7 decreases as the number of phases increases. Therefore, heat management can be facilitated by distributing the heat dissipation amount of the entire coupled inductor.

In FIG. 7, each inductor unit (1 to 6) is planarly arranged so that each winding axis is positioned on the same plane. Therefore, when the inductor units (1 to 6) are arranged on the inductor installation surface 100, the distances from the windings 8 to the inductor installation surface 100 are made uniform. Therefore, the heat dissipation of each winding 8 can be made uniform, the temperature rise width of each winding 8 can be made uniform, and variations in the magnetic characteristics of each winding 8 can be suppressed. Moreover, since the coupled inductor 11 has a planar shape, the height dimension can be reduced.

As shown in FIG. 11, each inductor unit (1-6) can also be arranged in a line on the inductor mounting surface 100. FIG. As described above, the multiphase coupled inductor of this embodiment has the advantage that the degree of freedom in shape is high because each inductor unit (1 to 6) is in a separable state.

In the above description, the case where the coupled inductors 10 and 11 are arranged in the boost chopper circuit is exemplified. Can be used for circuits. For example, it can be used in PFC (power factor correction) circuits, converter circuits, transformer applications (whether step-down or step-up) in inverter circuits, inverter applications, converter applications, and the like.

1 first inductor unit 2 second inductor unit 3 third inductor unit 4 fourth inductor unit 5 fifth inductor unit 6 sixth inductor unit 7 core 8 winding 10 coupled inductor (three-phase)
11 Coupled inductor (4-phase)
71 leg portion 72 connecting portion

Claims (8)

In a coupled inductor used in an interleaved three or more phase multiphase switching circuit,
an inductor unit is formed by a core and a plurality of windings wound around a plurality of locations of the core;
comprising a plurality of the inductor units,
the plurality of windings wound around a common core of each inductor unit are respectively connected to different phases of the switching circuit;
A coupled inductor characterized in that windings of different inductor units are connected in parallel to the same phase of the switching circuit . 2. The coupled inductor according to claim 1, wherein said plurality of windings wound on a common core are connected such that the DC components of the magnetic flux generated in said plurality of windings cancel each other out at said core. 3. A coupled inductor according to claim 1 or 2 , wherein the core of each inductor unit is formed in an endless loop shape with no air gap. The coupled inductor according to any one of claims 1 to 3 , wherein each inductor unit is arranged such that each winding axis is positioned on the same plane parallel to the inductor mounting surface. The coupled inductor according to any one of claims 1 to 4 , wherein each inductor unit has a coupling coefficient of 0.3 or more and 0.85 or less. The coupled inductor according to any one of claims 1 to 5 , wherein the core is made of soft magnetic powder with an insulating coating. 7. The coupled inductor according to claim 6 , wherein the core has an initial magnetic permeability of 30 or more and 200 or less. An interleaved multiphase switching circuit comprising a coupled inductor according to any one of claims 1-7 .

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