KR101665317B1 - Coupled Inductor for Current Balance - Google Patents

Abstract

Disclosed is a coupled inductor for current balance. According to an embodiment of the present invention, the coupled inductor includes a first conductor having a predetermined length, a second conductor disposed to be insulated from the first conductor in parallel to the first conductor, and a core unit which covers the first conductor and the second conductor and has a first core and a second core to face each other. The present invention can increase the lifespan of a device and reduce the size of a power system stack due to a design with a compact structure.

Description

Coupled Inductor for Current Balance [

An embodiment of the present invention relates to a couple inductor for current balancing.

The contents described in this section merely provide background information on the present embodiment and do not constitute the prior art.

Magnetic devices typically include a magnetic core made of ferrite, iron powder or similar magnetic material. The magnetic device also includes a winding of conductive leads. The current flowing in the winding creates a magnetic field. In a typical design, the magnetic core generally has a relatively high magnetic permeability compared to the surrounding medium, e.g., air. Thus, in the presence of a magnetic core, the magnetic flux is confined to the magnetic core that forms the flux closure path.

The two windings of the couple inductor are magnetically coupled together. The two couple windings may be wound on at least one or more magnetic cores, e.g., a toroidal core. The first winding generates a first magnetic field for driving a first magnetic field or a magnetic flux. The magnetic flux generated by the primary winding is confined to the magnetic core forming the flux closure path. Similarly, the second winding generates a second magnetic field or a second magnetic field that drives the magnetic flux

In general, the magnetic permeability of the magnetic material of the magnetic core of the couple inductor is larger than the surrounding medium. However, the coupling between the two windings of the couple inductor is not perfect. In other words, there may be a leakage path with a low permeability between the winding and the surrounding medium. Coupling between the media around the windings can create a leakage magnetic flux. Leakage magnetic flux in the equivalent circuit of a coupled inductor is replaced by a leakage inductance.

When a plurality of IGBTs (Insulated Gate Bipolar Transistors) are used in parallel, it is very important to share the current evenly. Impedance matching from the current output point to the convergence point of each device is considered for precise even distribution. However, it is technically difficult to select the device considering the imbalance of about 20% ~ 30%. On the other hand, when a large current flows, it is structurally difficult to design the output of each inductor to pass across the cores. It takes a lot of space when designing the output of each inductor to pass across the cores.

An embodiment of the present invention is to provide a coupled inductor that reduces the current imbalance of each element connected in parallel using the principle of a coupled inductor. In order to achieve this, it is an object of the present invention to provide a coupled inductor that is designed with a flat bus bar structure and reduces a current imbalance between each device to a minimum space.

This embodiment comprises: a first conductor having a predetermined length; A second conductor disposed in parallel with the first conductor and positioned to be insulated from the first conductor; And a core portion surrounding the first conductor and the second conductor and having a first core and a second core which are opposed to each other, and a core portion coupled to the first and second conductors, .

Also, the present invention provides a coupled inductor for current balancing, wherein the first core and the second core each have a horseshoe shape.

Also, an air gap is provided between the first core and the second core.

In addition, the first conductor and the second conductor each have a shape of a flat bus bar and are stacked in an insulated manner.

A first terminal located at one end of the first conductor; A second terminal located at the other end of the first conductor; A third terminal located at one end of the second conductor; And a fourth terminal located at the other end of the second conductor, wherein the other end of the first conductor is adjacent to one end of the second conductor, and one end of the second conductor is adjacent to the other end of the second conductor And a pair of inductors for current balancing.

According to another aspect of the present embodiment, there is provided an inverter for converting a DC input voltage into an AC voltage; And a coupled inductor coupled between output terminals of the inverter, wherein the coupled inductor includes a first inductor and a second inductor, wherein the first inductor and the second inductor are magnetically coupled And a power system is provided.

The first inductor may have a bus bar shape, and the second inductor may have a shape of a flat bus bar insulated in parallel with the first inductor. do.

The coupled inductor may include: a first conductor having a predetermined length; A second conductor disposed in parallel with the first conductor and positioned to be insulated from the first conductor; And a core portion surrounding the first conductor and the second conductor, the core portion including a first core and a second core which are opposed to each other.

In addition, the directions of currents flowing through the first conductor and the second conductor are opposite to each other.

The coupled inductor according to the embodiment of the present invention ideally shares the current when the IGBTs are connected in parallel, and it is possible to select a device for driving the coupled inductor without considering a margin of 20% to 30%.

In addition, since the coupled inductors have the same current stress, the lifetime of the device can be increased, while the compact inductance structure reduces the size of the power system stack.

1 shows a circuit diagram of a coupled inductor for current sharing of a load in a DC / AC power system in accordance with an embodiment of the present invention.
FIG. 2 shows a simplified equivalent circuit of each of the non-coupled inductor and coupled inductor of FIG.
FIG. 3 shows a simulation waveform showing the current flowing in each inductor of the uncoupled inductor and the coupled inductor and the difference of the current.
4 shows a conceptual diagram of a coupled inductor according to an embodiment.
5 illustrates a coupled inductor in the form of a flat bus bar of a coupled inductor according to an embodiment.
6 illustrates a magnetic core of a coupled inductor according to one embodiment.
7 shows a front view, a side view, and a plan view of a coupled inductor according to one embodiment.
8 illustrates an assembly of a coupled inductor according to one embodiment.
9 illustrates a front view, a side view, and a top view of an assembly of a coupled inductor according to one embodiment.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 shows a circuit diagram of a coupled inductor for current sharing of a load in a DC / AC power system in accordance with an embodiment of the present invention. The present embodiment can be applied to power systems of DC / DC, AC / DC, etc. of various structures. In addition, the present embodiment can be applied to various current sharing applications.

The DC / AC power system 100 includes an input DC power source (V _in ), a first leg (Leg) 110, a second leg 120, a coupled inductor 130, and a load. Coupled inductor 130 may be represented by equivalent circuit 130a as shown in FIG. 1 (b). The first leg 110 and the second leg 120, which are composed of the switching elements S ₁ , S ₂ , S ₃ , and S ₄ , are connected in parallel. The output of each of the first leg 110 and the second leg 120 is coupled to two inputs of the coupled inductor 130 and the output of the coupled inductor 130 is coupled to the load.

In an embodiment of the present invention, the switching elements S ₁ , S ₂ , S ₃ , and S ₄ are insulated gate bipolar transistor (IGBT) elements. Alternatively, however, it may be various types of devices that can be controlled, such as metal oxide semiconductor field effect transistors (MOSFETs), bipolar junction transistors (BJTs), GaN transistors, SiC transistors,

The first leg 110 includes switches S ₁ and S ₃ connected in series and the second leg 120 includes switches S ₂ and S ₄ connected in series. In this embodiment, the switching elements S ₁ , S ₂ , S _{3 , and} S ₄ may be combinations of various IGBTs, such as an IGBT, a parallel IGBT, or a series of IGBTs. The switching elements S ₁ , S ₂ , S _{3 , and} S ₄ are controlled to generate the three-level waveforms of the first leg and the second leg outputs. Here, the three level waveform means that the output voltage is positive, negative and floating voltage or zero.

When S ₁ and S ₄ are on, the first leg 110 and the second leg 120 output a positive voltage of the same magnitude as the input power supply V _in . Similarly, when S ₂ and S ₃ are on, the first leg 110 and the second leg 120 output a negative voltage of the same magnitude as the input power source V _in . When the switching elements S ₁ , S ₂ , S _{3 and} S ₄ are all turned off, the output 110 and the second leg 120 of the first leg are in a high floating state, . As such, the first leg 110 and the second leg 120 output three levels of voltage waveforms: a positive voltage, a negative voltage, and a float voltage.

The first leg 110 and the second leg 120 of FIG. 1 are three level legs, but may include a two level leg, a resonant leg, or any combination of the above.

Coupled inductor 130 is shown equivalently as an ideal 1: 1 transformer, two leakage inductances L _lk1 and L _lk2 and Magnetizing inductance (L _m ) as shown in Figure 1 (b) . Although not shown in the equivalent circuit 130a, the first resistor R ₁ of the first inductor L ₁ and the second resistor R ₂ of the second inductor L ₂ may be included. It should be noted that the ideal transforma- tive polarity dot phases are inversely connected to each other. Therefore, the magnetizing current is expressed by Equation (1).

In the ideal transformer of FIG. 1 (b), the output of the first leg 110 is connected to the first input terminal and the output of the second leg 120 is connected to the second input terminal. The coupled inductor 130 provides the load current of the DC / AC power system 100 to be evenly distributed between the first leg 110 and the second leg 120. Coupled inductor 130 is used to simultaneously achieve static current sharing and dynamic current sharing. Static current sharing refers to the fact that each input current varies when the input currents of the couple inductors fluctuate slowly. Dynamic current sharing means that each input current of the coupled inductors fluctuates sharply, Are shared with each other.

The first leg 110, the second leg 120 and the coupled inductor 130 shown in FIG. 1 are merely exemplary, and those skilled in the art will recognize that the legs and coupled inductors can be implemented in a variety of different ways have. For example, a DC / AC power system can accommodate three or more legs connected in parallel. Thus, the coupled inductor may be coupled to one output of the corresponding leg to include a plurality of windings, respectively.

The load is represented by a parallel connection of a capacitor and resistor connected to the output terminal of the coupled inductor, but can be represented by a combination of inductor, capacitor and resistor depending on the application. The capacitor C _O provides a low impedance path for the high frequency noise generated in the first leg 110 and the second leg 120 by shunting the resistor. As a result, there is an effect of eliminating the high frequency noise of the DC / AC power system 100.

FIG. 2 shows a simplified equivalent circuit of each of the non-coupled inductor and coupled inductor of FIG.

2 (a) shows an uncoupled inductor, where R ₁ and R ₂ are impedances of a first conductor and a second conductor, respectively, and values thereof are unbalanced to 50 mΩ and 20 mΩ, respectively. 2 (a) shows an inductor L1 and L2 and an ammeter I (I) for measuring a current flowing in each of the inductors L ₁ and L ₂ when an input voltage V _s1 is applied to the uncoupled inductor. is composed of _1, I _2), a voltmeter for measuring the voltage of the load (R _o) (V ₃₎ and a voltmeter (V _ripple) for measuring a ripple (ripple) of the load voltage and the like. 2 (a) is a simulation circuit for predicting a current flowing in each conductor and a difference thereof when the impedance values of the first conductor and the second conductor in the uncoupled inductor are unbalanced to 50 mΩ and 20 mΩ, to be.

Fig. 2 (b) shows a coupled inductor, where R ₄ and R ₅ are the impedances of the fourth conductor and the fifth conductor, respectively, and their values are equivalent to the cases of imbalance of 50 mΩ and 20 mΩ, respectively. 2B shows an ammeter I ₃ and I ₄ for measuring a current flowing in each of the inductors L ₁ -M and L ₂ -M when an input voltage V _s2 is applied to the coupled inductor, , it consists of a load (R _{o _c)} a voltmeter (V _{ripple _c)} for measuring the voltmeter (V ₈₎ and the ripples (ripple) of the load voltage to determine the voltage of the like. FIG. 2 (b) is a simulation circuit for predicting the current flowing in each conductor and the difference when the impedance values of the first conductor and the second conductor in the coupled inductor are unbalanced to 50 mΩ and 20 mΩ, respectively.

FIG. 3 shows a simulation waveform showing the difference between the currents flowing in the inductors (L ₁ , L ₂ , L ₁ -M and L ₂ -M) and their currents in FIGS. 2 (a) and 2 (b). As shown in Fig. 1, when using IGBTs in parallel, it is very important to divide the currents evenly. In this embodiment, if the coupled inductor has two paths, the coupled inductor can reduce the current imbalance of the two devices connected in parallel using the static current sharing and dynamic current sharing principle.

3 (a) shows the currents flowing through the uncoupled inductors L ₁ and L ₂ of FIG. 2 (a), respectively. Figure 3 (c) shows that the difference in the currents flowing through L ₁ and L ₂ is (+/-) 18 A due to the imbalance of the impedance of R ₁ and R ₂ of the uncoupled inductor. On the other hand, FIG. 3 (b) shows the currents flowing through the coupled inductors L ₃ and L ₄ of FIG. 2 (b), respectively. 3 (c) shows that the difference in currents flowing through L ₃ and L ₄ is (+/-) 9 A due to the imbalance of the impedance of R ₄ and R ₅ of the coupled inductor. The reason for this difference is that the directions of the currents flowing through the inductors in the couple inductors are opposite to each other in the direction in which they pass through the magnetic core, so that when the currents flowing in the inductors fluctuate, the magnetic fields act in a direction canceling each other, This is because the imbalance is reduced. As shown in FIG. 3, by using the principle of the coupled inductor, the current imbalance of each element connected in parallel can be reduced by about 50% from 18 A to 9 A.

4 shows a conceptual diagram of a coupled inductor according to an embodiment. It is structurally difficult to design such that the output of each of the couple inductors crosses between the cores because of the large cross-sectional area of the conductor in the case of a large current. In order to improve this, a couple inductor is designed to occupy a minimum space by designing each inductor of the coupled inductor as a flat bus bar structure as in the embodiment of FIG. The coupled inductor includes a first magnetic core 410a, a second magnetic core 410b, a first conductor 420, a second conductor 430, and air gaps 440a and 440b.

The coupled inductor includes a first magnetic core 410a and a second magnetic core 410b coupled to have air gaps 440a and 440b having a predetermined gap; A first conductor 420 positioned in an inner space formed by the first magnetic core 410a and the second magnetic core 410b; And a second conductor (430). As the magnetic cores 410a and 410b, a material having high permeability of at least one of Permalloy, Sendite, and Ferrite may be used.

Since the directions of the currents flowing through the first and second conductors 420 and 430 are opposite to each other in the directions in which the magnetic cores 410a and 410b pass through each other, Thereby reducing the unbalance of the currents of the conductor 420 and the second conductor 430.

5 illustrates a coupled inductor in the form of a flat bus bar of a coupled inductor according to an embodiment.

The reason why the coupled inductor is realized by the flat bus bar structure is that it is structurally difficult to design the output of each of the coupled inductors to cross between the cores because the sectional area of the conductor must be large when a large current flows, It is because it occupies. The bus bar type couple inductor includes a first leg output terminal 510, a second leg output terminal 520, a final output terminal 530, a first magnetic core 540a, a second magnetic core 540b, A band 550, air gaps 560a and 560b, and an insulating film 570. [

The first leg output terminal 510 is an output terminal of the switches S ₁ and S _{3 in} FIG. In Figure 5, the output terminal 510 of the first leg is located on the left side of the first conductor 420.

The second leg output terminal 520 is an output terminal of the switches S ₂ and S _{4 in} FIG. In FIG. 5, the output terminal 520 of the second leg is located on the right side of the second conductor 430.

The final output terminal 530 has two output terminals of the coupled inductor, which are located at the lower right end of the first conductor and the lower left end of the second conductor, respectively.

In Figure 5, the first magnetic core 540a is located at the top of the middle of the coupled inductor. The first magnetic core 540a is a U-type core having a thickness of 6 mm to 12 mm and a cross-sectional area of 20 mm to 60 mm in width, which is obtained by laminating silicon steel sheets 0.2 mm to 0.5 mm in thickness.

In Fig. 5, the second magnetic core 540b is located at the lower end of the center portion of the coupled inductor. Similarly, the second magnetic core 540b is a U-shaped core having a cross-sectional area ranging from 6 mm to 12 mm and a width of 20 mm to 60 mm, in which silicon steel plates of 0.2 mm to 0.5 mm are laminated. The specifications such as the sizes of the first magnetic core 540a and the second magnetic core 540b need not be limited to those exemplified above.

The magnetic core band 550 keeps the air gaps 560a and 560b constant and wraps the center portion of the first magnetic core 540a and the second magnetic core 540b up and down to fix the couple inductor.

The air gaps 560a and 560b prevent saturation of the magnetic cores 540a and 540b, so that the intensity of the magnetic force can be set to a larger value while the magnetic flux density is kept constant. The magnetic force is proportional to the intensity of the current, which in turn increases the energy stored in the inductor.

The current of the second conductor 430 including the first conductor 420 including the first leg output terminal 510 and the final output terminal 530 and the second leg output terminal 520 and the final output terminal 530 Since the directions of the magnetic cores 540a and 540b passing through the magnetic cores 540a and 540b are opposite to each other, the coupling effect causes the magnetic fields to cancel each other to reduce the unbalance of the currents of the first and second conductors 420 and 430 do.

6 illustrates a magnetic core of a coupled inductor according to one embodiment.

The magnetic core 610 of FIG. 6 is in the form of a U, and at least one of materials having high permeability such as permalloy, Sendite, and ferrite may be used. In one preferred embodiment, the magnetic core 610 of FIG. 6 will be readily understood by one of ordinary skill in the art, having a cross-sectional area of 8 mm in thickness and 40 mm in width, laminated with a 0.27 mm silicon steel sheet, but not limited to this standard .

7 shows a front view, a side view, and a plan view of a coupled inductor according to one embodiment. The front two-dot chain line of the front view of the magnetic core 610 shows the boundary of the inner circumferential surface of the magnetic core 610. The top view of the magnetic core 610 has a rectangular shape. The top view of the magnetic core 610 is in the form of a rectangle, and the two two-dot chain lines in the middle portion show the respective boundaries of the inner circumferential surface of the magnetic core 610. In the side view, the magnetic core 610 is U-shaped.

8 illustrates an assembly of a coupled inductor according to one embodiment. The coupled inductor includes a first conductor 810, a second conductor 220, first and second magnetic cores 830a and 830b, and a magnetic core band 840. The first inductor 810 and the second inductor 820 have a shape of a flat bus bar and are connected to the first terminal 812 and the first conductor 810 at one end on the extension line of the first conductor 810, (810) has a first extension extending at a right angle to the longitudinal direction of the first conductor (810) and a second terminal (814) at the end of the first extension; And the second conductor 820 includes a third terminal 822 having one end of the second conductor 820 adjacent to the other end of the second conductor 820 extended in the longitudinal direction of the second conductor 820; And the other end of the second conductor 820 has a second extension at a right angle to the longitudinal direction and further includes a fourth terminal 824 at an end of the second extension.

The first conductor 810 is in the form of a bus bar having a left upper end and a right lower end respectively extended. A first leg output terminal 812 is located on the left upper end of the first conductor 810 and a final output terminal 814 is located on the lower right end of the first conductor 810.

The second conductor 820 is in the form of a bus bar having a right upper end and a left lower end respectively extended. The second leg output terminal 822 is located on the right upper end of the second conductor 620 and the final output terminal 824 is located on the lower left end of the second conductor 820.

In a preferred embodiment, the first magnetic core 830a and the second magnetic core 830b are U-shaped cores having a cross-sectional area of 8 mm in thickness and 40 mm in width by laminating 0.27 mm silicon steel plates. It is to be understood by those of ordinary skill in the art that the specifications provided herein are not limited thereto.

The magnetic core band 840 serves to fix the first magnetic core 830a and the second magnetic core 830b while keeping the air gaps 850a and 850b constant. The magnetic core band 840 surrounds the center of the first magnetic core 830a and the second magnetic core 830b up and down to fix the couple inductor. A first conductor 810 and a second conductor 820 are positioned between the first magnetic core 830a and the second magnetic core 830b.

9 illustrates a front view, a side view, and a top view of an assembly of a coupled inductor according to one embodiment.

The front view of the coupled inductor includes a first conductor 810, a second conductor 820, a first magnetic core 830a, a second magnetic core 830b, a magnetic core band 840 and air gaps 850a and 850b Respectively. The first terminal 812 and the other end of the first conductor 810 at one end on the extension of the first conductor 810 have a first extension extending at a right angle to the longitudinal direction of the first conductor 810, And a second terminal 814 at the end of the portion. The second conductor 820 is formed such that one end of the second conductor 820 adjacent to the other end of the second conductor 820 is connected to the third terminal 822 and the second conductor 820 extending in the longitudinal direction of the second conductor 820. [ Has a second extension at a right angle to the longitudinal direction and a fourth terminal 824 at the end of the second extension.

The first and second conductors 810 and 820 are connected in parallel to each other so that the first and second conductors 810 and 820 are connected to each other via the first and second conductors 810 and 820, 830b and a magnetic core band 840, respectively.

The side view of the coupled inductor shows the first conductor 810, the second conductor 820 and the magnetic cores 830a and 830b.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as defined by the appended claims. will be. Therefore, the embodiments of the present invention are not intended to limit the scope of the present invention but to limit the scope of the technical idea of the embodiment of the present invention.

Claims (9)

A first conductor having a predetermined length;
A second conductor disposed in parallel with the first conductor and positioned to be insulated from the first conductor; And
And a core portion surrounding the first conductor and the second conductor and including a first core and a second core which are opposed to each other,
Wherein each of the first conductor and the second conductor has a shape of a flat bus bar and has a shape in which the first and second conductors are insulated from each other and overlap each other. The method according to claim 1,
Wherein the first core and the second core are each in the shape of a horseshoe. The method according to claim 1,
And an air gap is provided between the first core and the second core. delete The method according to claim 1,
A first terminal located at one end of the first conductor;
A second terminal located at the other end of the first conductor;
A third terminal located at one end of the second conductor; And
And a fourth terminal located at the other end of the second conductor,
Wherein the other end of the first conductor is adjacent to one end of the second conductor and the other end of the second conductor is adjacent to the other end of the second conductor. An inverter for converting a DC input voltage into an AC voltage; And
And a coupled induuctor coupled between output terminals of the inverter,
Wherein the coupled inductor comprises a first inductor having a plate bus bar shape and a second inductor isolated in parallel with the first inductor and having the shape of a bus bar of the flat plate, Are magnetically coupled to each other. delete The method according to claim 6,
The coupled inductor includes:
A first conductor having a predetermined length;
A second conductor disposed in parallel with the first conductor and positioned to be insulated from the first conductor; And
A core portion surrounding the first conductor and the second conductor and having a first core and a second core facing each other,
≪ / RTI > 9. The method of claim 8,
Wherein directions of currents of the first conductor and the second conductor are opposite to each other in a direction of passing through the core portion.

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