JP6417206B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that converts power.

  As a technique for downsizing a capacitor (smoothing capacitor) provided on the secondary side of a transformer of a forward type power conversion circuit, a technique that applies interleave control is known. When downsizing a capacitor by applying interleave control, a plurality of power conversion circuits are connected in parallel, and control is performed so as to shift the excitation period of each transformer included in the power conversion circuit, so that the current ripple flowing through the capacitor is high-frequency. As a result, the capacitance of the capacitor is reduced and the size is reduced.

  As a related technique, there is known a technique in which a reactor having a plurality of windings is used as a transformer of a forward converter and this reactor is also used as a flyback converter. See US Pat.

  Further, as a related technique, in a multiphase converter for a vehicle, a technique for reducing the number of reactors by forming two reactors in a core and coupling them is known. See US Pat.

JP 2002-330585 A JP 2011-205806 A

  Although the capacitor can be reduced in size by applying interleave control, the volume of the transformer increases because each power conversion circuit must be equipped with a transformer, and the effect of downsizing the capacitor when considering the entire circuit Can not get much. Therefore, in a forward type power conversion device to which interleave control is applied, it is desired to reduce the size of the core (magnetic part) constituting the transformer while maintaining the size reduction of the capacitor.

  An object according to one aspect of the present invention is to downsize a power conversion device using a transformer.

A power conversion device which is one embodiment includes a transformer, a switch element, and an output unit.
The transformer is provided with primary windings of a plurality of power conversion circuits connected in parallel to the core, and secondary windings corresponding to the primary windings.

The switch element is connected in series to each primary winding and is used for interleave control.
The output unit outputs predetermined power using energy obtained through each secondary winding.

  According to the embodiment, the core can be miniaturized using the coupling transformer, and the power converter can be miniaturized.

FIG. 1 is a diagram illustrating an embodiment of a power converter. FIG. 2 is a front view showing an embodiment of the core shape of the transformer. FIG. 3 is a diagram illustrating an equivalent circuit of the transformer. FIG. 4 is a diagram illustrating an equivalent circuit of the transformer. FIG. 5 is a front view showing another shape of the core of the transformer. FIG. 6 is a diagram illustrating an embodiment of a circuit in which a reactor of an output unit is coupled.

Hereinafter, embodiments will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating an embodiment of a power converter. The power conversion device 1 in FIG. 1 includes a first isolated power conversion circuit and a second isolated power conversion circuit. The first insulation type power conversion circuit and the second insulation type power conversion circuit have a transformer T1 (coupling transformer), switch elements S1 and S2, and an output unit. The transformer T1 includes a primary winding N11 (first primary winding) of the first isolated power conversion circuit, a secondary winding N12 (first secondary winding) corresponding to the primary winding N11, The primary winding N21 (second primary winding) of the second insulated power conversion circuit and the secondary winding N22 (second secondary winding) corresponding to the primary winding N21 are the core (magnetic). Part). One terminal of the primary winding N11 and one terminal of the primary winding N21 are connected, the other terminal of the primary winding N11 and one terminal of the switch element S1 are connected, and the other terminal of the primary winding N21 is connected. The terminal and one terminal of the switch element S2 are connected. Further, the other terminal of the switch element S1 and the other terminal of the switch element S2 are connected. That is, the primary winding N11 and the primary winding N21 are connected in parallel and provided in the transformer T1.

  The switch elements S1 and S2 are connected in series with the primary windings N11 and N21, respectively, and are used for interleave control. In the interleave control, for example, a switching unit S1, S2 is alternately turned on / off by a control unit not shown in FIG. This is an effective control for reducing the size of C1. Here, for example, MOSFETs (metal-oxide-semiconductor field-effect transistors) may be used as the switch elements S1 and S2. The control unit outputs an on / off control signal for on / off control to the switch elements S1 and S2.

The output unit will be described.
One terminal of the secondary winding N12 is connected to the anode of the rectifying element D1 (first rectifying element). The other terminal of the secondary winding N12 is connected to the anode of the rectifying element D2 (second rectifying element) and the other terminal of the capacitor C1. The cathode of the rectifying element D1 is connected to the cathode of the rectifying element D2 and one terminal of the reactor L1. The other terminal of the reactor L1 is connected to one terminal of the capacitor C1.

  One terminal of the secondary winding N22 is connected to the anode of the rectifying element D3 (first rectifying element). The other terminal of the secondary winding N22 is connected to the anode of the rectifying element D4 (second rectifying element) and the other terminal of the capacitor C1. The cathode of the rectifying element D3 is connected to the cathode of the rectifying element D4 and one terminal of the reactor L2. The other terminal of reactor L2 is connected to one terminal of capacitor C1. In FIG. 1, the reactors L <b> 1 and L <b> 2 are collectively indicated as a reactor 2 (broken line range).

  The output unit rectifies the energy obtained through the secondary winding N12 using the rectifying elements D1, D2, the reactor L1, and the capacitor C1, and outputs power at a predetermined voltage. The output unit rectifies the energy obtained through the secondary winding N22 using the rectifying elements D3 and D4, the reactor L2, and the capacitor C1, and outputs power at a predetermined voltage. The rectifying elements D1, D2, D3, and D4 may be semiconductor switches such as MOSFETs, for example.

The transformer T1 will be described.
The relationship between the magnetic flux and the inductance of each part of the transformer T1 when the switch element S1 is turned on will be described using the structure of the transformer T1 shown in FIG. 2 and the equivalent circuits shown in FIGS. FIG. 2 is a front view showing an embodiment of the core shape of the transformer. 3 and 4 are diagrams showing an equivalent circuit of the transformer.

  In the transformer T1 shown in FIG. 2, the primary winding N11 and the secondary winding N12 are wound around the outer leg 202 (first leg) of the core 201, and the primary winding is wound around the outer leg 203 (second leg). A wire N21 and a secondary winding N22 are wound, and a central leg 204 (third leg) different from the outer legs 202 and 203 is provided in the center of the core 201. It is desirable that the shape of the core of the transformer T1 is symmetric.

  2 is represented by an equivalent circuit, the magnetic flux φL (main magnetic flux) generated from the primary winding N11 of FIG. 2 is equal to the magnetic flux φm11 in the direction of the central leg 204 as shown in FIG. And the magnetic flux φm12 in the direction of the outer leg 203. That is, the magnetic flux φL can be expressed by Equation 1.

φL = φm11 + φm12 Formula 1
φL: N ₁₁ i1 (Rmo + Rmc) / (Rmo ² + 2RmcRmo)
φm11: N ₁₁ i1 (Rmo / (Rmo ² + 2RmcRmo))
φm12: N ₁₁ i1 (Rmc / (Rmo ² + 2RmcRmo))
N ₁₁ : Number of turns (number of turns) of the primary winding N ₁₁
i1: Winding current (inductor current) of the primary winding N11
Rmo: magnetoresistance of the outer leg Rmc: magnetoresistance of the central leg As shown in FIG. 3, the magnetic flux φm11 is a magnetic flux generated from the primary winding N11 and not affecting the primary winding N21. The magnetic flux φm12 is a magnetic flux generated from the primary winding N11 and affecting the primary winding N21.

Subsequently, when the inductance is obtained by converting the magnetic flux φL shown in Formula 1 according to Faraday's law, the self-inductance L of the primary winding N11 can be expressed by Formula 2.
L = Lm11 + Lm12 Formula 2
Lm11: N ₁₁ ² (Rmo / (Rmo ² + 2RmcRmo))
Lm12: N ₁₁ ² (Rmc / (Rmo ² + 2RmcRmo))
The exciting inductance Lm11 is related only to the primary winding N11, and the exciting inductance Lm12 is generated from the primary winding N11 and related to the primary winding N21.

If the coupling of the transformer T1 is expressed using the relationship between the excitation inductances Lm11 and Lm12 shown in Expression 2, the equivalent circuit of FIG. 4 is obtained.
In the equivalent circuit shown in FIG. 4, the circuit related to the primary winding N11 has a self-inductance (= excitation inductance Lm11 + excitation inductance Lm12) connected in parallel to the primary winding N11. A primary winding N11 ′ that affects the primary winding N21 of the primary winding N11 is connected in parallel to the excitation inductance Lm12.

  In addition, the circuit related to the primary winding N21 has a primary winding that affects the primary winding N11 in series with the exciting inductance Lm21 related only to the primary winding N21 as a self-inductance to the primary winding N21. N21 'is connected. In the equivalent circuit of FIG. 4, in order to simplify the explanation, the leakage inductance is not considered for each of the primary windings N11 and N21 and the secondary windings N12 and N22. That is, it is considered that the magnetic flux φL generated in the primary winding N11 is all linked to the secondary winding N12.

  Further, the primary winding N11 ′ and the primary winding N21 ′ represent coupling (broken line range 401), and each phase (operation when the switch element S1 is on (one phase) and operation when the switch element S2 is on) (Two phases)) are the parts that affect each other. In other words, it is the part sharing the magnetic flux.

When the switch element S2 is turned on, the shape of the core of the transformer T1 is symmetric with respect to the central leg 204, and thus the description thereof is omitted.
When interleave control is applied to the transformer T1 having such a configuration as in the prior art, the volume of the core can be reduced compared to the case where a plurality of transformers are used as in the prior art. For example, when the ON period of the ON / OFF control signals of the switch elements S1 and S2 is shifted by 180 degrees and interleave control (duty 50%) is performed, the center leg 204 has a higher frequency than the outer legs 202 and 203. Since it operates, the cross-sectional area of the central leg 204 can be made smaller than the cross-sectional area of each of the outer legs 202 and 203. Even when the duty is not 50%, the cross-sectional area of the central leg 204 can be reduced.

  The core shape of the transformer T1 may be other than the shape shown in FIG. 2 as long as it can be represented by the equivalent circuit shown in FIG. 5A to 5C show cores other than the shape shown in FIG. FIG. 5 is a front view showing another shape of the core of the transformer.

A core 501 shown in FIG. 5A has a shape (502, 503) in which the central leg is interrupted from the middle, unlike the central leg 204 in FIG.
The core shown in FIG. 5B includes three parts 504, 505, and 506 that form the core. The component 505 is wound with a primary winding N11, a secondary winding N12, a primary winding N21, and a secondary winding N22. The component 504 has protrusions 507, 508, and 509, and the component 506 has protrusions 510, 511, and 512. The leading end portion of the protruding portion 507 and the leading end portion of the protruding portion 510 face each other with the component 505 interposed therebetween, and each of the leading end portions is arranged outside the outer end of the secondary winding N12 so as not to contact the component 505. The leading end of the protruding portion 509 and the leading end of the protruding portion 512 face each other with the component 505 in between, and the leading end portions are arranged outside the outer end of the secondary winding N22 so as not to contact the component 505. The leading end of the protruding portion 508 and the leading end of the protruding portion 511 face each other with the component 505 interposed therebetween, and each of the leading ends is disposed between the primary winding N11 and the primary winding N21 so as not to contact the component 505.

  The core shown in FIG. 5C includes two parts 513 and 514 that form the core. The component 513 is wound with a primary winding N11, a secondary winding N12, a primary winding N21, and a secondary winding N22. The part 514 has protrusions 515, 516 and 517. The tip of the protrusion 515 is disposed outside the outer end of the secondary winding N12 of the component 513 so as not to contact the component 513. The tip of the protrusion 517 is disposed outside the outer end of the secondary winding N22 of the component 513 so as not to contact the component 513. The tip of the protrusion 516 is arranged between the primary winding N11 and the primary winding N21 of the component 513 so as not to contact the component 513.

According to the embodiment, the power converter can be downsized by downsizing the core using the transformer T1.
A modification will be described.

  A method for reducing the size of the reactor 2 shown in FIG. 1 will be described with reference to FIG. FIG. 6 is a diagram illustrating an embodiment of a circuit in which a reactor of an output unit is coupled. 6 is a circuit in which the reactors L1 and L2 shown in FIG. 1 are connected using a core (magnetic part). In this example, the reactor NL1 corresponding to the reactor L1 and the reactor NL2 corresponding to the reactor L2 are coupled to achieve higher frequency of the winding current flowing through the reactor NL1 and the reactor NL2. Further, the magnetic flux is shared by influencing part of the magnetic flux of each phase. As a result, the volume of coupling circuit 601 can be made smaller than the volume of reactors L1 and L2 shown in FIG. That is, the coupling circuit 601 can be made smaller than the reactors L1 and L2 used in the conventional output unit.

According to the modification, the power converter can be further downsized by downsizing the coupling circuit 601 and the transformer T1.
The present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the gist of the present invention.

1 power converter,
2 reactors,
201, 501 core (magnetic part),
202, 203 outer leg,
204 center leg,
504, 505, 506, 513, 514 parts,
507, 508, 509, 510, 511, 512, 515, 516, 517 protrusion,
601 coupling circuit,
C1 capacitor,
D1, D2, D3, D4 Rectifier,
L1, L2 reactor,
Lm11, Lm12, Lm21 Excitation inductance,
N11, N21 primary winding,
N12, N22 secondary winding,
NL1, NL2 reactor,
S1, S2 switch elements,
T1 transformer,

Claims (3)

A primary winding of a plurality of power conversion circuits, a secondary winding corresponding to the primary winding, provided in a magnetic part, a transformer to which each of the primary windings are connected in parallel,
Switch elements connected in series to each of the primary windings and used for interleave control,
Using energy obtained through each of the secondary windings, an output unit that outputs predetermined power;
Equipped with a,
The power conversion circuit includes a first isolated power conversion circuit and a second isolated power conversion circuit,
The first insulated power conversion circuit has a first primary winding and a first secondary winding,
The second isolated power conversion circuit has a second primary winding and a second secondary winding,
The magnetic part has a first leg around which the first primary winding and the first secondary winding are wound, and a second primary winding and the second secondary winding. A second leg and a third leg different from the first leg and the second leg;
The power converter according to claim 1, wherein a cross-sectional area of the third leg is smaller than a cross-sectional area of each of the first leg and the second leg . The power conversion device according to claim 1,
The output section includes a first rectifying element having an anode connected to one terminal of the secondary winding, a second rectifying element having an anode connected to the other terminal of the secondary winding, A circuit having one terminal connected to the cathode of the first rectifying element and the cathode of the second rectifying element, provided for each of the secondary windings, the other of the reactors of each of the circuits terminal is connected to one terminal of the capacitor, the secondary winding each of the other terminal connected to the other terminal of the capacitor, the reactor, respectively are coupled with the magnetic portion,
The power converter characterized by the above-mentioned. The power conversion device according to claim 1 or 2, wherein
The first leg and the second leg are a pair of outer legs,
The third leg is a central leg;
The center leg is provided at the center of the pair of outer legs.
The power converter characterized by the above-mentioned.

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