Differential mode inductor and noise filter for DC large current

Abstract

Provided is a noise filter that does not cause magnetic saturation by using a magnetic core in a circuit through which a large current flows. A large current is shunted to a plurality of conductors, and a noise filter using a magnetic core is provided in each of the plurality of conductors. The magnetic core may be configured such that one electrical conductor passes through a plurality of different magnetic cores, and the frequency band can be broadened by varying the characteristics of the plurality of magnetic cores. It is also possible to provide a core-type noise filter capable of coping with common-mode noise in addition to blocking differential-mode noise.

Description

Technical Field

[0001] This invention relates to a differential mode inductor and noise filter for high current circuits that can effectively block noise in circuits with high current flow.

[0002] More specifically, the present invention relates to an inductor device and a noise filtering method for noise filtering, which serves as a noise filter in a circuit with high current flow in a switching mode, avoiding the influence of magnetic saturation of differential mode inductors, thereby achieving effective noise filtering. Background Technology

[0003] Inverters and high-voltage DC / DC converters used in electric vehicles, hybrid vehicles, electric aircraft, and other power motors typically switch at 10kHz to 200kHz, but their harmonics can sometimes cause noise interference problems.

[0004] For example, the wiring harness between the inverter and battery of an electric vehicle can radiate harmonic noise from switching operations, which can affect AM broadcasting, wireless communication, and in-vehicle communication.

[0005] In addition, test platforms used for the development of electric vehicles and DC / DC converters used for solar power generation can also leak harmonics of switching noise, thus causing EMC problems.

[0006] Typically, in power electrical circuits, differential-mode noise and common-mode noise are mixed together. In high-current circuits, magnetic saturation occurs due to the large current, making it impossible to filter out differential-mode noise using a noise filter made of an inductor with a toroidal core.

[0007] Therefore, in the prior art, inductors with differential-mode magnetic cores cannot be used to block noise in circuits with high current flow. Filters using magnetic cores are usually common-mode filters with common-mode magnetic cores.

[0008] Typically, most noise suppression measures are developed at the voltage and current level in the so-called low-voltage field. However, in the technical field of this invention, noise suppression measures in circuits with extremely high current flow are relatively weak. That is, in electric vehicles and hybrid vehicles with high current flow, noise radiation is mostly contained by shielding wires. However, the wiring harness structure using shielded wires is complex and costly. Therefore, there is a need for a noise reduction device for high-current applications that reduces the noise itself.

[0009] In addition, magnetic saturation here refers to the phenomenon that even for materials with high permeability, if a very large magnetic field is applied, the permeability will decrease, resulting in a relative permeability close to 1, that is, close to the permeability μ0 of vacuum.

[0010] Therefore, for example, when using a ferrite core as a noise eliminator, in the case of using a ferrite core as a noise eliminator for a wire with a strong magnetic field, i.e. a large current flowing through it, the inductance will decrease due to the strong magnetic field generated by the large current, thus making it unusable as a noise eliminator.

[0011] Even for magnetic materials with very high permeability, i.e., strong magnetic materials, the slope of the rising and falling branches of the hysteresis curve in the B-H curve can become zero, i.e., magnetic saturation occurs when the relative permeability becomes 1.

[0012] Due to this magnetic saturation, when a magnetic field H is applied, the spins of a magnetic body will align neatly. However, once the state is reached where all the spins can no longer align neatly, no matter how much the magnetic field is increased, the magnetic flux density caused by the spin alignment will not increase further.

[0013] Therefore, magnetic saturation occurs, meaning that even if the magnetic field is further increased, the magnetic flux density will not increase further. Once magnetic saturation is reached, as will be described later, the noise blocking effect caused by the energy consumption due to the reversal of the magnetic moment in the magnetic core will also disappear, the relative permeability will become 1, and the effect of using inductance to block noise current will also decrease.

[0014] Therefore, in the prior art, magnetic cores are not used as a means to suppress differential-mode noise propagating in wires with large current flow.

[0015] Patent Document 1 discloses the following: "A noise filter is configured to have a segmented magnetic core, which surrounds a busbar to attenuate noise propagating in the busbar. For wiring with large current flow, such as busbars, especially in differential mode noise filters, suppressing magnetic saturation of the magnetic core is crucial. In the noise filter described in Patent Document 1 below, an air gap spacer is provided, which is sandwiched between one magnetic core component and another magnetic core component, thereby forming an air gap between the two magnetic core components and suppressing magnetic saturation" (paragraph 0002), and Japanese Patent Application Publication No. 2005-93536 is introduced as Patent Document 1.

[0016] However, for circuits with large current flows, such as those in electric vehicles, simply adding an air gap is insufficient to effectively block differential-mode noise.

[0017] Patent Document 2 discloses the following: "The ferrite core of the filter unit mounted on the inverter device as an EMC filter needs to be selected with appropriate impedance characteristics and high-frequency characteristics according to the magnitude and frequency of the noise current and the carrier frequency of the inverter. In fact, according to the model of various inverter devices with different ratings, the selected EMC filter is installed and verified, and a decision is made after evaluating and confirming its noise reduction effect. For example, in the case of a large amount of noise current generated, in order to avoid magnetic saturation of the ferrite core, the following selection change is required, namely, increasing the number of toroidal ferrite cores 1 shown in FIG8 and arranging multiple of them coaxially, and winding the cable 2 together on the ferrite core to form a filter unit 3" (paragraph 0007).

[0018] However, even with a structure in which multiple ferrite cores are arranged coaxially, if the current flowing through the circuit causes magnetic saturation of these multiple cores, the structure cannot be used in such circuits.

[0019] Patent document 3 discloses the following: "When a signal line is inserted, especially a power line, the problem is that the magnetic saturation of the aforementioned core material limits the effective current value" (paragraph 0039). "Therefore, in the line noise attenuator according to the embodiments of the present invention, the number of winding turns in a single magnetic core material is limited to a limit number of turns that will not cause magnetic saturation due to the required signal current value, and the element formed by the parallel combination of the inductor 1 and the resistor 2 is used as a unit element, thereby realizing the practical application of a noise attenuator that can withstand the required current of the power line, etc."

[0020] Furthermore, the limit number of turns at which magnetic saturation occurs depends on the current flowing through the conductor and is not uniquely determined, but rather adjusted according to the current value (paragraph 0040).

[0021] That is, although this is an invention that controls the number of turns of the wire wound on the filter core to a level that will not cause magnetic saturation, this prior art is only suitable for the current level of power lines such as communication equipment, and cannot be used for noise filters in circuits through which larger currents flow.

[0022] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2018-125426 Patent Document 2: Japanese Patent Application Publication No. 2011-192825 Patent Document 3: Japanese Patent Application Publication No. 2010-130368 Summary of the Invention

[0023] Technical issues Therefore, the purpose of this invention is to provide an inductor that employs a magnetic core and is easy to operate, and a noise filter that uses the inductor, which will not cause magnetic saturation even when used to suppress noise in circuits with unprecedentedly large currents, i.e., hundreds of amperes to more than one thousand amperes, and can effectively filter out differential mode noise.

[0024] Problem-solving methods The present invention includes the following methods.

[0025] [1] An inductor for use in a noise filter has an input terminal and an output terminal, wherein a conductor is divided into multiple wires between the two terminals, and the multiple wires are respectively passed through a magnetic core.

[0026] [2] According to the inductor described in [1], the wire passing through the magnetic core is wound one or more turns on the core.

[0027] [3] According to the inductor described in [1], the magnetic core and the plurality of wires are configured such that magnetic saturation will occur when the sum of the currents flowing between the input terminal and the output terminal through the plurality of wires passes through one magnetic core, but magnetic saturation will not occur even if the individual shunt currents of the plurality of wires pass through each magnetic core separately.

[0028] [4] According to the inductor described in [1], the wire wound on a magnetic core is further divided into multiple wires.

[0029] [5] A noise filter wherein differential-mode noise and / or common-mode noise is removed by connecting an inter-line capacitor and a capacitor to ground to a plurality of inductors described in any one of [1] to [4].

[0030] [6] According to the noise filter described in [5], there is an even number of inductors, in addition to which there is a common mode winding core formed by a group of multiple wires with opposite current directions passing through the core, thereby serving as a common mode noise core.

[0031] The inventors of this application recognized that in order to effectively block differential-mode noise, it is necessary to maintain the required inductance without magnetic saturation, thus achieving the following structure.

[0032] High-current differential-mode inductors prevent magnetic saturation by dividing and shunting magnetic cores in parallel with an air gap, but connecting the cores in parallel or adding an air gap can reduce the inductance. However, when wire is wound around the core, the inductance is proportional to the square of the number of turns, thus maintaining the required inductance in differential mode even under high current.

[0033] That is, the inductor of the present invention has the following configuration: even if the sum of the currents flowing through the inductor of the present invention is sufficient to cause magnetic saturation of a magnetic core, by shunting the current to multiple conductors and providing a toroidal magnetic core of the inductor for each conductor, the current passing through the holes of each toroidal magnetic core can be suppressed to a level that will not cause magnetic saturation of each toroidal magnetic core. By winding multiple turns of conductor on the toroidal magnetic core to compensate for the reduced combined inductance, since magnetic saturation will not occur, the noise filtering effect of the magnetic core will not be affected. Furthermore, since the sum of the currents flowing through multiple conductors is the desired large current, differential mode noise can be effectively filtered out even in wires with large currents flowing through them by the noise blocking effect of the toroidal magnetic core, thereby effectively playing the role of a noise filter.

[0034] Furthermore, the characteristics of a magnetic core as a noise filter can change depending on the material, shape, size, whether an air gap is provided in the magnetic core, the total reluctance of the magnetic core when an air gap is provided, and the overall permeability of the magnetic core. Therefore, according to the performance requirements of the inductor as a whole according to the present invention, the optimal magnetic core is selected, thereby enabling the construction of an inductor for a noise filter with the desired characteristics.

[0035] The noise blocking effect of the wire flowing through the hole in the toroidal magnetic core is that the magnetic core and the wire form an inductor. By utilizing the reactance and resistance components of the impedance in the inductor, for high-frequency noise, on the one hand, the noise current is limited by the reactance, and on the other hand, the energy dissipation effect is generated by the reversal of the magnetic moment of the magnetic body constituting the magnetic core, thereby limiting the noise current. Moreover, the frequency characteristics of the two are different.

[0036] Furthermore, when an air gap is present in the magnetic core, as the magnetic reluctance of the magnetic circuit increases, the magnetic flux density generated by the magnetomotive force produced by the current flowing through the wire in the core hole decreases, thus increasing the saturation current value at which magnetic saturation occurs. However, correspondingly, due to the reduction in magnetic losses, the effect of limiting noise current through energy consumption is also weakened.

[0037] Furthermore, when magnetic saturation is avoided by creating an air gap in the magnetic core, wires and busbars used for high currents require a large cross-sectional area, making them difficult to wind easily onto the magnetic core. Therefore, the required cross-sectional area can be obtained by dividing the wires and busbars into smaller specifications.

[0038] In addition, regarding the structure of winding conductors on the magnetic core, besides directly passing the conductor through the magnetic core without winding, the following structures can also be used: winding only one turn on the magnetic core and then passing it through, winding two turns, three turns, etc., that is, winding multiple turns on the magnetic core and then connecting it to the two terminals of the inductor.

[0039] When wound in this way, the range of inductance adjustment is expanded, making it easy to manufacture products with the desired characteristics.

[0040] Besides differential-mode magnetic cores, circuits can be constructed by adding capacitors and common-mode magnetic cores to generate filters corresponding to noise conditions. By adding these components, the characteristics of the noise filter can be altered. For example, capacitors can be connected between lines and to ground, or between magnetic cores, thus achieving a variety of structures.

[0041] The effects of the invention According to the present invention, a noise filter with a novel structure can be provided, enabling the use of a noise filter utilizing a differential-mode magnetic core even in DC high-current circuits such as electric vehicles and high-current power supplies, i.e., in circuits through which high current flows but cannot be used due to magnetic saturation in noise filters using conventional magnetic cores.

[0042] The inductor for noise filtering of the present invention has two connection terminals. When a large current flows between the two terminals, the inductor of the present invention operates as a noise filter that performs the desired noise blocking action, thereby effectively suppressing electromagnetic radiation caused by noise generated in the downstream circuit after noise blocking. This avoids the need to use various complex and bulky shielded cables, shielded connectors, and shielding of lithium-ion batteries as in the present invention.

[0043] Furthermore, in the inductor of the present invention, by optimizing the structure, material, wire configuration and winding, and number of turns of the magnetic core used for noise blocking, as well as the structure of the entire inductor, the filter characteristics can be adjusted to the desired features.

[0044] Furthermore, although the term "inductor" is used in this invention, this does not mean that only the inductive component of impedance is used. Rather, this term is used simply because it has low-pass filter characteristics that block high-frequency noise. Given the concern about magnetic saturation, it goes without saying that this invention also emphasizes the resistive component of impedance. In practical circuit applications, resistance, inductance, capacitance, and other factors are all considered. Attached Figure Description

[0045] Figure 1 1-A is a schematic diagram illustrating the structure of the prior art where magnetic saturation occurs, and 1-B is a schematic diagram illustrating the structure of the present invention where magnetic saturation does not occur.

[0046] Figure 2 This is a schematic diagram of an inductor in which a conductor is wound multiple turns on a magnetic core, as an embodiment of the present invention.

[0047] Figure 3This is a schematic diagram of an inductor for differential mode noise, as an embodiment of the present invention.

[0048] Figure 4 This is a schematic diagram of a differential-mode noise filter as an embodiment of the present invention.

[0049] Figure 5 This is a schematic diagram of a noise filter as an embodiment of the present invention, the noise filter having a common-mode magnetic core. Detailed Implementation

[0050] Figure 1 This illustrates the basic principles of the invention. In Figure 1 In the prior art structure shown in 1-A, a conductor 1 carrying a large current passes through a hole in the magnetic core 2, allowing the large current to flow from the input electrode 3 to the output electrode 4.

[0051] exist Figure 1 In the present invention shown in Figure 1-B, the conductor is divided into multiple wires, specifically three wires 1a, 1b, and 1c in the example, and each wire passes through a hole in the magnetic core 2a, 2b, and 2c respectively. The three conductors are configured such that the values ​​of the current flowing through them are approximately equal. To improve the noise blocking effect, it is crucial to keep the states of the multiple wires as consistent as possible, which is essential for improving the characteristics of the noise filter.

[0052] exist Figure 1 In the case of 1-A, the material of the magnetic core is set such that when a current of 30A passes through the hole of the magnetic core, the current will cause magnetic saturation. Figure 1 In the invention shown in 1-B, a current of 10A is passed through three conductors, namely conductors 1a, b, and 1c, which are respectively passed through holes in three magnetic cores of the same material, namely magnetic cores 2a, 2b, and 2c. Figure 1 Similarly, 1-A in the diagram shows a conductor. Figure 1 In section 1-B, one input electrode 3 and one output electrode 4 are respectively provided. In the case of this invention, in... Figure 1 The three magnetic cores 2a, 2b, and 2c in 1-B saturate under a current of 30A. Figure 1 If the magnetic core 2 of 1-A has the same size, it is obvious that it will not saturate under a current of 10A. Even if a smaller size is used, since the current has been reduced to 10A, it is sufficient to set the size of the magnetic core so that it will not saturate under a current of 10A.

[0053] It goes without saying that the inductor of the present invention, as a noise filter with a capacitor, can improve the noise blocking effect by performing necessary shielding and grounding.

[0054] like Figure 2As shown, conductors 16a, 16b, and 16c passing through the magnetic core can also be wound multiple turns on the magnetic cores 2a1, 2b1, and 2c1. Figure 2 The example shows only one turn of the winding.

[0055] As the number of turns increases, the inductance increases, but magnetic saturation is more likely to occur. By selecting an appropriate number of turns, the desired overall characteristics of the inductor can be obtained more diversely and easily.

[0056] like Figure 3 As shown, by configuring the differential-mode magnetic core into multiple conductors that are wound multiple turns and then passed through the magnetic core, as described above, the inductor of the present invention can simultaneously adjust the inductance by the number of turns and avoid saturation by dividing it into multiple conductors. Furthermore, using multiple magnetic cores can increase the degree of freedom in the overall shape.

[0057] For example, the driving current of the motor, that is, the large current Ia flowing from the power source to the motor, flows from the input electrode 3a to the output electrode 4a, and the current Ib returning from the motor flows from the input electrode 3b to the output electrode 4b.

[0058] Since the differential-mode noise current is a differential-mode noise current, it is an alternating high-frequency current flowing from 3a to 4a, from 3b to 4b, or in the opposite direction.

[0059] like Figure 4 As shown, by placing capacitors Ca, Cag, and Cbg between the inductor lines and between the inductor and ground, it can be used as a noise filter.

[0060] like Figure 5 As shown, except Figure 4 In addition to the differential-mode magnetic core, by setting the common-mode magnetic core 7, it can also be used as a filter to reduce both common-mode noise and differential-mode noise.

[0061] Explanation of reference numerals in the attached figures 1: Conductor 1a, 1b, 1c: Multiple conductors 2a, 2b, 2c: Differential mode magnetic cores 2a2, 2b2, 2c2: Magnetic cores without conductors wound around them 2a1, 2b1, 2c1: Magnetic cores wound with conductive materials 3, 3a, 3b: Input electrodes 4, 4a, 4b: Output electrodes 7: Common mode magnetic core Ca, Cag, Cbg: Capacitors

Claims

1. An inductor for use in a noise filter, having an input terminal and an output terminal, characterized in that, The conductor is divided into multiple wires between two terminals, and the multiple wires are respectively passed through the magnetic core of the magnetic body.

2. The inductor according to claim 1, characterized in that, A wire passing through the core of a magnetic body is wound one or more turns around the core.

3. The inductor according to claim 1, characterized in that, The magnetic core and the multiple wires are configured such that magnetic saturation will occur when the sum of the currents flowing between the input and output terminals through the multiple wires passes through one magnetic core, but magnetic saturation will not occur even if the individual shunt currents of the multiple wires pass through each magnetic core separately.

4. The inductor according to claim 1, characterized in that, The wire wound around a magnetic core is further divided into multiple wires.

5. A noise filter, characterized in that, Differential-mode noise and / or common-mode noise are removed by connecting line-to-line capacitors and ground capacitors to the plurality of inductors described in any one of claims 1 to 4.

6. The noise filter according to claim 5, characterized in that, It has an even number of inductors, and in addition, it has a common-mode winding core, which is formed by a group of multiple wires with opposite current directions passing through the core, thereby serving as a core for common-mode noise.

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