Active EMI filter including oscillation prevention circuit

Abstract

Disclosed is an active EMI filter for actively compensating for noise generated in a common mode and a differential mode in each of at least two high current paths, wherein the active EMI filter includes: a sensing unit for sensing the noise in the common mode and the differential mode on the high current paths; and a compensation unit that includes a negative impedance transformer, generates a compensation signal corresponding to the sensed noise, and provides the compensation signal to the sensing unit.

Description

Active EMI filter with anti-rattle circuit

[0001] One embodiment of the present invention relates to an active electromagnetic interference (EMI) filter including an anti-oscillation function and for removing common mode and differential mode noise.

[0002] Electrical devices, such as home appliances, industrial electrical appliances, and electric vehicles, typically emit noise during operation. For example, noise can be generated by switching operations within the device. This noise is not only harmful to the human body, but can also cause malfunctions or failures in other connected electronic devices.

[0003] The electromagnetic interference that electronic devices cause to other devices is called Electromagnetic Interference (EMI), and among them, noise transmitted through wires and circuit board wiring is called Conducted Emission (CE) noise.

[0004] To ensure that electronic devices operate without causing damage to surrounding components or other devices, EMI noise emissions from all electronic products are strictly regulated. Therefore, most electronic products incorporate EMI filters to reduce EMI noise to meet these regulations.

[0005] Conducted emission noise includes common mode (CM) noise and differential mode (DM) noise. Common mode noise is noise generated when a power converter converts direct current to alternating current or alternating current to direct current, and returns through ground (GND). Therefore, in the case of common mode noise, noise flows in the same direction on at least two power lines. Differential mode noise is noise generated in the power converter, just like common mode noise, but returns from the live power line to the neutral power line, not to ground. Therefore, in the case of differential mode noise, noise flows in the opposite direction on at least two power lines.

[0006] Typically, to reduce both modes of noise simultaneously, a common mode choke coil is required to remove common mode noise, and separate wiring or additional filters are required between the power supply and the load to reduce differential mode noise.

[0007] However, adding separate components or wiring to the EMI filter to control the two modes of noise can cause design constraints or increased unit cost in low-power home appliances, and it can make product miniaturization and integration difficult. In addition, in some cases, the filter and power line may require a common ground, making it impossible to use in two-hole home appliances.

[0008] Meanwhile, EMI filters can be divided into passive EMI filters and active EMI filters depending on the type of elements included. A passive EMI filter is a filter composed of at least one selected from a group of passive elements consisting of resistors, inductors, and capacitors, and an active EMI filter refers to a filter that further includes active elements.

[0009] However, active circuits or systems, such as active EMI filters, can experience oscillation, where unidentified resonant signals are detected in unwanted frequency bands. This oscillation can destabilize the active EMI filter and, in severe cases, even damage the circuit. Therefore, active EMI filters can effectively reduce noise without generating noise themselves unless oscillation occurs. Therefore, countermeasures to prevent oscillation are necessary.

[0010] The present invention is intended to improve the above-mentioned problems and to provide an active EMI filter including an anti-oscillation function and for removing common mode and differential mode noise.

[0011] However, these tasks are exemplary and the scope of the present invention is not limited thereby.

[0012] According to one aspect of the present invention, an active EMI filter is provided, which includes a sensing unit that detects common mode and differential mode noise on at least two high-current paths, and a compensation unit that generates a compensation voltage corresponding to the detected noise and provides the compensation voltage to the sensing unit, including a negative impedance converter, and wherein the compensation unit includes a stabilization unit that prevents oscillation due to the detected noise.

[0013] Here, the sensing unit includes a conductor including a through hole, at least two high-current path windings passing through the through hole and connected to each of the at least two high-current paths, and a choke coil including a sensing winding insulated from the at least two high-current paths and passing through the through hole, wherein each of the at least two high-current path windings is asymmetrically wound around the conductor.

[0014] Here, each of the at least two high-current path windings differs from each other in at least one of the number of turns, the degree of winding density, the size of the winding angle, whether the turns are overlapped, or, if overlapped, the number of overlaps.

[0015] Here, the compensation unit includes an amplifier unit that generates an amplification signal corresponding to the detected noise and a target unit that generates a compensation signal corresponding to the amplification signal, and the stabilization unit is connected to the target unit, and the magnitude of the impedance of the target unit and the stabilization unit is greater than the magnitude of the overall input impedance viewed from the compensation unit toward the sensing unit.

[0016] Here, the compensation unit includes at least one amplifier, and the at least one amplifier is implemented as a single integrated chip.

[0017] Here, a substrate having one side and the other side is further included, wherein the sensing unit is mounted on one side of the substrate and electrically connected to the sensing unit, and the compensation unit is electrically connected to the sensing unit and provided on the other side of the substrate.

[0018] Here, a substrate having one side and the other side is further included, wherein the sensing unit is mounted on one side of the substrate and electrically connected to the sensing unit, and the compensation unit is electrically connected to the sensing unit and is provided in a space on one side of the substrate where the sensing unit is not arranged.

[0019] According to various embodiments of the present invention as described above, it is possible to provide an active EMI filter that reduces both common mode noise and differential mode noise without significantly increasing price, area, volume, or weight.

[0020] In addition, the active EMI filter according to various embodiments can implement stable noise reduction operation by preventing oscillation that creates an unwanted frequency peak signal due to resonance that may occur in the noise compensation process.

[0021] Additionally, the active EMI filter according to various embodiments does not need to have a common ground with the power line, so it can be used in low-power home appliances such as monitor adapters or display chargers, or in two-prong home appliances.

[0022] Additionally, the active EMI filter according to various embodiments can be reduced in price, area, volume, and weight compared to a passive EMI filter including a bulky and heavy CM choke.

[0023] FIG. 1 is a schematic diagram illustrating the configuration of a voltage compensation system including an active EMI filter according to one embodiment of the present invention.

[0024] Fig. 2 is a drawing illustrating the active EMI filter of Fig. 1 in more detail.

[0025] Fig. 3 is a drawing specifically illustrating an example of a choke coil included in a sensing unit.

[0026] Figures 4a to 4e are drawings specifically illustrating other examples of choke coils.

[0027] Fig. 5 is a drawing for explaining the principle of noise compensation by an active EMI filter according to one embodiment.

[0028] FIG. 6 is a diagram illustrating an equivalent circuit of the voltage compensation system of FIG. 1 according to one embodiment of the present invention.

[0029] Fig. 7 illustrates an example of a specific circuit of an active EMI filter according to one embodiment of the present invention.

[0030] Figure 8 is a graph comparing the oscillation stability of the circuit illustrated in Figure 7.

[0031] Fig. 9 is a schematic diagram showing the structure of an active EMI filter according to one embodiment of the present invention.

[0032] Fig. 10 is a schematic diagram showing the structure of an active EMI filter according to another embodiment of the present invention.

[0033] According to one aspect of the present invention with reference to FIGS. 1 and 2, an active EMI filter is provided, which includes a sensing unit for detecting common mode and differential mode noise on at least two high-current paths, and a compensation unit including a negative impedance converter for generating a compensation voltage corresponding to the detected noise and providing the compensation voltage to the sensing unit, and wherein the compensation unit includes a stabilization unit for preventing oscillation due to the detected noise.

[0034] The present invention is capable of various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention, as well as the methods for achieving them, will become clearer with reference to the embodiments described in detail below, along with the drawings. However, the present invention is not limited to the embodiments disclosed below and can be implemented in various forms.

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. When describing with reference to the drawings, identical or corresponding components are given the same reference numerals and redundant descriptions thereof will be omitted.

[0036] In the following examples, terms such as first, second, etc. are not used in a limiting sense, but are used for the purpose of distinguishing one component from another. In the following examples, singular expressions include plural expressions unless the context clearly indicates otherwise. In the following examples, terms such as include or have mean that a feature or component described in the specification exists, and do not exclude in advance the possibility that one or more other features or components may be added. In the drawings, the sizes of components may be exaggerated or reduced for convenience of explanation. For example, the size and shape of each component shown in the drawings are arbitrarily shown for convenience of explanation, and therefore the present invention is not necessarily limited to what is shown.

[0037] FIG. 1 is a schematic diagram illustrating the configuration of a voltage compensation system including an active EMI filter (100) according to one embodiment of the present invention. FIG. 2 is a diagram illustrating the active EMI filter (100) of FIG. 1 in more detail.

[0038] Referring to FIGS. 1 and 2, an active EMI filter (100) according to one embodiment of the present invention can actively compensate for first noise (I11, I12) generated and input in a common mode (CM) and second noise (I21, I22) generated and input in a differential mode (DM) in each of at least two high-current paths (111, 112) connected to a first device (300). To this end, an active EMI filter (100) according to one embodiment of the present invention may include a sensing unit (120) that detects first noise (I11, I12) and second noise (I21, I22) based on a voltage difference, and a compensation unit (150) that is connected to the sensing unit (120) and generates a compensation voltage based on the detected first noise (I11, I12) and second noise (I21, I22) and provides the compensation voltage to the sensing unit (120).

[0039] The two or more high-current paths (111, 112) may be paths for transmitting power supplied by the second device (400) to the first device (300) within the active EMI filter (100), and may be, for example, power lines. According to one embodiment, each of the two or more high-current paths (111, 112) may be a live line and a neutral line, and for convenience of explanation, the following description will focus on a configuration in which the system includes two high-current paths (111, 112).

[0040] In this specification, the second device (400) may be a device of various types for supplying power in the form of current and / or voltage to the first device (300). For example, the second device (400) may be a device that generates and supplies power, or a device (e.g., a power source, etc.) that supplies power generated by another device. Of course, the second device (400) may also be a device that supplies stored energy. However, this is merely exemplary and the scope of the present invention is not limited thereto.

[0041] In this specification, the first device (300) may be a variety of devices that use the power supplied by the second device (400) described above. For example, the first device (300) may be a load driven by the power supplied by the second device (400). In addition, the first device (300) may be a load (e.g., a home appliance, a TV, a computer, a monitor, a printer, etc.) that stores energy using the power supplied by the second device (400) and is driven by the stored energy. However, this is merely an example, and the spirit of the present invention is not limited thereto.

[0042] In addition, each of the two or more high-current paths (111, 112) may be made of a conductive material and may be a path through which conductive noise generated in the process of converting the power input from the first device (300) into direct current or alternating current is transmitted. The conductive noise includes first noise (I11, I12), which is common mode noise, and second noise (I21, I22), which is differential mode noise.

[0043] The first noise (I11, I12) is generated in the second device (400), flows along two or more high current paths (111, 112), and returns through the ground. Therefore, in the case of the first noise (I11, I12), when comparing between the two high current paths (111, 112), the noise flows in the same direction. On the other hand, the second noise (I21, I22) is generated in the second device (400), passes through the first device (300) along the first high current path (111), which is a live line, and returns through the second high current path (112), which is a neutral line. Therefore, in the case of the second noise (I21, I22), when comparing between the two high current paths (111, 112), the noise flows in the opposite direction. Both the first noise (I11, I12) and the second noise (I21, I22) may be currents having a frequency of a specific band. Here, the frequency bands of the first noise (I11, I12) and the second noise (I21, I22) may be bands having a range of, for example, 150 kHz to 30 MHz.

[0044] Meanwhile, the sensing unit (120) is electrically connected to the high current paths (111, 112) to detect the first noise voltage and the second noise voltage on two or more high current paths (111, 112) together and generate a corresponding detection signal. In other words, the sensing unit (120) may mean a means for detecting common mode noise and differential mode noise on the high current paths (111, 112).

[0045] The sensing unit (120) may be a means for detecting a noise voltage on the high current path (111, 112) in a state insulated from the high current path (111, 112). In one embodiment, the sensing unit (120) may simultaneously detect a first noise voltage and a second noise voltage at a sensing winding (124) end, which will be described later in FIG. 3. In other words, the sensing unit (120) generates a detection signal at one end including the sensing winding (124). In this case, the detection signal may include information on both the first noise voltage and the second noise voltage. In an optional embodiment, the sensing unit (120) may detect the first noise voltage and the second noise voltage, respectively, and in this case, the detection signal may include a first detection signal corresponding to the first noise voltage and a second detection signal corresponding to the second noise voltage.

[0046] The compensation unit (150) is electrically connected to the sensing unit (120), receives a detection signal corresponding to the first noise voltage and the second noise voltage detected by the sensing unit (120), generates a compensation signal (e.g., a compensation voltage or a compensation current) corresponding to the first noise voltage and the second noise voltage, and transmits the compensation signal to the sensing unit (120) through the sensing coil. Hereinafter, a case where the compensation signal is a compensation voltage will be described.

[0047] The compensation unit (150) is connected only to the sensing unit (120) and is not connected to at least two high-current paths (111, 112). That is, the compensation unit (150) is not configured to transmit the compensation voltage to the high-current paths (111, 112), and accordingly, the active EMI filter (100) according to one embodiment of the present invention has the effect of filtering noise without requiring additional components to be added to the power line.

[0048] The effective impedance of the sensing unit (120) increases due to the compensation voltage transmitted by the compensation unit (150), and the flow of the first noise (I11, I12) and the second noise (I21, I22) flowing in the high current path (111, 112) is suppressed by the increased effective impedance. In conclusion, both the first noise (I11, I12) and the second noise (I21, I22) on the high current path (111, 112) are compensated.

[0049] The compensation unit (150) may be configured to provide negative impedance. The compensation unit (150) may include a negative impedance converter (NIC). In one embodiment, the compensation unit (150) may include a negative impedance converter to generate a compensation voltage through negative impedance based on detected noise and provide the voltage to the sensing unit (120). In the case of an active EMI filter including a negative impedance converter, the sensing unit (120) and the compensation unit (150) can be located at the same location, which has the advantage of eliminating the need for a separate device for compensation. In addition, since the detection and compensation paths for common mode noise and differential mode noise are aligned, there is an advantage of simultaneously reducing common mode noise and differential mode noise.

[0050] Meanwhile, the compensation unit (150) of the active EMI filter may further include a stabilization unit (153) that prevents oscillation that may occur during the feedback operation of the compensation unit (150). In detail, the compensation unit (150) may include an amplifier unit (151) that receives a detection signal corresponding to the first noise voltage and the second noise voltage detected by the sensing unit (120) and amplifies the detection signal to generate an amplified signal, a target unit (152) that generates a compensation voltage based on the amplified signal, and a stabilization unit (153) that prevents oscillation caused by the detected noise and is connected to the target unit (152).

[0051] In one embodiment, the magnitude of the impedance of the target portion (152) and the stabilizing portion (153) is characterized by being greater than the magnitude of the total input impedance viewed from the compensation portion (150) toward the sensing portion (120). Here, the total input impedance includes not only the impedance component of the sensing portion (120), but also the parasitic capacitance included in the high current path (111, 112), the capacitance of the second device (400), and the capacitance of the first device (300). Through this characteristic, the active EMI filter (100) according to one embodiment of the present invention has the effect of preventing oscillation caused by noise and stably performing voltage compensation operation.

[0052] Referring back to FIG. 2, the amplifier unit (151), the target unit (152), and the stabilization unit (153) can be implemented by various means. In one embodiment, the amplifier unit (151) may include at least one amplifier, for example, an operational amplifier (Op-amp). The target unit (152) may include at least one inductor and a capacitor. In addition, the stabilization unit (153) may include at least one capacitor and at least one inductor, or at least one amplifier and at least one capacitor. However, the above implementation methods of the amplifier unit (151), the target unit (152), and the stabilization unit (153) are exemplary, and the spirit of the present invention is not limited thereto. The specific configuration of the compensation unit (150) will be described in detail later with reference to FIG. 7.

[0053] The active EMI filter (100) configured as described above has the characteristic of detecting the voltage of common mode noise and differential mode noise on two or more high current paths (111, 112) and generating a compensation voltage in response thereto to increase the effective impedance on the high current paths (111, 112), thereby effectively compensating for common mode and differential mode noise. In addition, the EMI filter (100) configured as described above has the characteristic of minimizing oscillation due to noise, thereby achieving stable voltage compensation operation.

[0054] Fig. 3 is a drawing specifically illustrating an example of a choke coil included in a sensing unit (120). Figs. 4a to 4e are drawings specifically illustrating other examples of choke coils.

[0055] According to one embodiment with reference to FIG. 3, the sensing unit (120) may include at least one choke coil. At this time, the choke coil may include a conductor including a through hole, and conductive windings that pass through the through hole or are wound around the conductor at least once by passing through the through hole.

[0056] The conductor including the through hole may be a core (123) in the form of a closed loop, but is not limited thereto and may be implemented in a form in which a portion of the loop can be opened and closed in the form of a clamp. Any conductor may be used as long as it includes the through hole.

[0057] The conductive windings may include at least two high-current path windings (1111, 1112) and a sensing winding (124). In detail, each of the at least two high-current path windings (1111, 1112) is connected to at least two high-current paths (111, 112), respectively. For example, the high-current path windings (1111, 1112) may be a part of the high-current paths (111, 112), or may be directly or indirectly connected to the high-current paths (111, 112). The high-current path windings (1111, 1112) may be electrically connected to the high-current paths (111, 112).

[0058] At least two high-current path windings (1111, 1112) each pass through at least a through hole. For example, each of the high-current path windings (1111, 1112) may pass through the through hole at least once, or may pass through the through hole multiple times and be wound (wound) around the conductor (e.g., core (123)) at least once.

[0059] In one embodiment, each of the high-current path windings (1111, 1112) may be wound asymmetrically around a conductor (e.g., core (123)). In other words, each of the high-current path windings (1111, 1112) must have a structure such that their coupling coefficients are different from each other.

[0060] FIG. 3 illustrates an example in which the number of turns of each of the high-current path windings (1111, 1112) is different. Referring to FIG. 3, the first high-current path winding (1111) is wound once around the conductor core (123), and the second high-current path winding (1112) is wound twice around the conductor core (123), but the spirit of the present invention is not limited thereto.

[0061] FIGS. 4a to 4c further illustrate examples in which each of the high-current path windings (1111, 1112) is wound asymmetrically around a conductor (e.g., core (123)).

[0062] Fig. 4a illustrates an example in which the degree of winding density of each of the high-current path windings (1111, 1112) is different. Referring to Fig. 4a, it is illustrated that the second high-current path winding (1112) is wound more densely on the conductor core (123) than the first high-current path winding (1111). That is, the spacing g1 between the first high-current path windings (1111) wound on the core (123) is larger than the spacing g2 between the second high-current path windings (1112) wound on the core (123). (g1>g2)

[0063] Fig. 4b illustrates an example in which the sizes of the winding angles of the high-current path windings (1111, 1112) are different. Referring to Fig. 4b, it is illustrated that the size of the winding angle of the first high-current path winding (1111) is larger than the size of the winding angle of the second high-current path winding (1112). That is, with respect to one surface of the core (123), the angle (θ1) of the straight lines (rays) connecting the outermost first high-current path windings (1111) at the beginning and the end wound on the core (123) from the center of the core (123) is larger than the angle (θ2) of the straight lines (rays) connecting the outermost second high-current path windings (1112) at the beginning and the end wound on the core (123) from the center of the core (123). (θ1>θ2)

[0064] Fig. 4c illustrates different examples in which the high-current path windings (1111, 1112) are wound in an overlapping manner. Referring to Fig. 4c, the first high-current path winding (1111) is not wound in an overlapping manner and is wound on the conductive core (123) in only one layer, whereas the second high-current path winding (1112) is wound on the conductive core (123) in two layers, so that the first high-current path winding (1111) is wound in an overlapping manner of 0 turns, and the second high-current path winding (1112) is wound in an overlapping manner of 1 turn.

[0065] Since the contents illustrated in FIGS. 4a to 4c are exemplary, the idea of ​​the present invention is not limited thereto, and any configuration in which each of the high-current path windings (1111, 1112) is asymmetrically wound around a conductor can be adopted.

[0066] In this way, since each of the high-current path windings (1111, 1112) is wound asymmetrically on a conductor (e.g., core (123)), the active EMI filter can detect both common mode noise and differential mode noise, and thus the active EMI filter can compensate for both noise including common mode and differential mode.

[0067] Meanwhile, according to an optional embodiment, the active EMI filter may detect and compensate for only one of the common mode noise or the differential mode noise. For example, FIG. 4d illustrates an example in which the number of turns of each of the high current path windings (1111, 1112) is the same, but the winding direction is different. That is, both the first high current path winding (1111) and the second high current path winding (1112) are wound twice around the core (123), but the first high current path winding (1111) may be wound clockwise or counterclockwise with respect to the core (123), and the second high current path winding (1112) may be wound counterclockwise or clockwise with respect to the core (123). In this case, the choke coil can detect only the differential mode noise, and the active EMI filter compensates only the differential mode noise.

[0068] As another example, FIG. 4e illustrates an example in which the number of turns and the winding direction of each of the high-current path windings (1111, 1112) are the same, so that each of the high-current path windings (1111, 1112) is completely symmetrically wound around a conductor (e.g., core (123)). That is, both the first high-current path winding (1111) and the second high-current path winding (1112) are wound twice around the core (123), and both the first high-current path winding (1111) and the second high-current path winding (1112) can be wound in the same clockwise or counterclockwise direction with respect to the core (123). In this case, the choke coil can only detect common-mode noise, and the active EMI filter only compensates for common-mode noise.

[0069] Meanwhile, although not shown in FIGS. 3 and 4a to 4e, one end and the other end of at least two high-current path windings (1111, 1112) are directly or indirectly connected to the first device (300) and the second device (400), respectively.

[0070] Referring again to FIG. 3, in the same manner as the high-current path windings (1111, 1112), the sensing winding (124) also passes through at least a through hole. For example, the sensing winding (124) may pass through the through hole at least once, or may pass through the through hole multiple times and be wound around the conductor at least once. Meanwhile, one end and the other end of the sensing winding (124) are each connected to a compensation unit (150).

[0071] The side of the choke coil of the sensing unit (120) where the high current path windings (1111, 1112) are arranged may be referred to as the primary side (121) of the choke coil, and the side where the sensing winding (124) is arranged may be referred to as the secondary side (122) of the choke coil. The choke coil may generate an induced voltage on the secondary side (122) based on a magnetic field induced by noise (I11, I12, I21, I22) on the primary side (121) that is arranged on the high current path windings (1111, 1112). That is, the induced voltage induced on the secondary side (122) of the choke coil may be a current in which noise (I11, I12, I21, I22) is converted at a certain ratio.

[0072] In the choke coil, the turns ratio of the primary side (121) and the secondary side (122) is 1:N. sen And, the self-inductance of the primary side (121) of the choke coil (120) is L sen If so, the second side (122) is N sen 2 L sen can have self-inductance.

[0073] At this time, the voltage induced at both ends of the primary side of the choke coil due to the first noise (I11, I12) is V cm If so, the voltage V induced on the secondary side cm,sen Silver V cm N of sen Similarly, the voltage induced across the primary side of the choke coil due to the second noise (I21, I22) is V dm If so, the voltage V induced on the secondary side dm,sen Silver V dm N of sen It's a boat.

[0074] FIG. 5 is a drawing for explaining the principle of noise compensation by an active EMI filter (100) according to one embodiment.

[0075] FIG. 5(a) is a diagram explaining the principle related to the first noise (I11, I12), which is common mode noise, and FIG. 5(b) is a diagram explaining the principle related to the second noise (I21, I22), which is differential mode noise. In FIG. 5, for convenience of explanation, the conductor of the choke coil is illustrated in the form of a core (123), and two high-current path windings (1111, 1112) are illustrated, and the first high-current path winding (1111) is illustrated as being wound once through a through-hole of the core (123), and the second high-current path winding (1112) is illustrated as being wound twice through a through-hole of the core (123), thereby implementing asymmetry. In addition, the compensation unit (150) includes a negative impedance converter, but this is exemplary and the spirit of the present invention is not limited thereto.

[0076] First, referring to FIG. 5(a), when the first noise (I11) is input to the first high current path winding (1111), a first-first magnetic field (B11, not shown) is induced in the core (123), and when the first noise (I12) is input to the second high current path winding (1112), a first-second magnetic field (B12, not shown) can be induced in the core (123). Here, the first noises (I11, I12) are common mode noises and are signals or currents that flow in the same direction for each of the high current path windings (1111, 1112), so that a magnetic field is formed in the sensing unit and the core (123) in the same direction. Therefore, the first-first magnetic field (B11) and the first-second magnetic field (B12) overlap each other (or reinforce each other) to form the first magnetic field (B1), which is counterclockwise in FIG. 5. Meanwhile, the sensing winding (124) of the secondary side (122) which is insulated from the high current path winding (1111, 1112) by the first magnetic field (B1) formed, has a first induced voltage (V) corresponding to the first magnetic field (B1). cm,sen ) is induced. Meanwhile, the compensation unit (150) connected to the sensing winding (124) of the secondary side (122) generates a first induced voltage (V) by a negative impedance converter.cm,sen ) is used to generate a first compensation current (ID1) corresponding to a first compensation voltage having a first flux that can overlap (reinforce) the first magnetic field (B1). The generated first compensation current (ID1) flows into the choke coil and further strengthens the first magnetic field (B1) by reinforcing the first flux. Therefore, the effective impedance increases due to the strengthened first magnetic field (B1`), and the choke coil is activated. As a result, the flow of the first noise (I11, I12) flowing in the first current path (111) and the second current path (112) is suppressed by inductance boosting, thereby enabling noise filtering by voltage detection and voltage compensation.

[0077] Next, referring to FIG. 5(b), as the second noise (I21) is input to the first high current path winding (1111), a second-first magnetic field (B21, not shown) is induced in the core (123), and as the second noise (I22) is input to the second high current path winding (1112), a second-second magnetic field (B22, not shown) can be induced in the core (123). Here, the second noises (I21, I22) are differential mode noises and are signals or currents that flow in different directions for each of the high current path windings (1111, 1112), so that magnetic fields are formed in opposite directions in the sensing unit and the core (123). Accordingly, the 2-1 magnetic field (B21) and the 2-2 magnetic field (B22) cancel each other out, but in one embodiment, since the 1st high current path winding (1111) and the 2nd high current path winding (1112) are asymmetrically wound around the core (123), a difference exists between the 2-1 magnetic field (B21) and the 2-2 magnetic field (B22) due to different coupling coefficients, and a 2nd magnetic field (B2) is formed due to the difference. Meanwhile, a 2nd induced voltage (V) corresponding to the 2nd magnetic field (B2) is applied to the sensing winding (124) of the secondary side (122) that is insulated from the 1111, 1112 high current path windings by the formed 2nd magnetic field (B2). dm , sen) is induced. Meanwhile, the compensation unit (150) connected to the sensing winding (124) of the secondary side (122) generates a second compensation current (ID2) corresponding to the second compensation voltage having a second flux that can overlap (reinforce) the second magnetic field (B2) based on the second induced voltage by a negative impedance converter. The generated second compensation current (ID2) flows into the choke coil and makes the second magnetic field (B2) stronger by reinforcing the second flux. Therefore, the effective impedance increases by the reinforced second magnetic field (B2`), and the choke coil is activated. As a result, the flow of second noise (I21, I22) flowing in the first current path (111) and the second current path (112) is also suppressed together with the flow of first noise (I11, I12) by inductance boosting, thereby enabling common mode and differential mode noise filtering by voltage detection and voltage compensation.

[0078] Meanwhile, in FIG. 5, for the convenience of explanation, the principles related to common mode noise and differential mode noise are explained separately, but since the active EMI filter (100) according to one embodiment of the present invention can compensate for common mode noise and differential mode noise simultaneously, the operations explained in FIG. 5 can occur simultaneously.

[0079] FIG. 6 is a diagram illustrating an equivalent circuit of the voltage compensation system of FIG. 1 according to one embodiment of the present invention.

[0080] The voltage compensation system of Fig. 6 is an equivalent circuit of Fig. 1, and thus includes an active EMI filter (100) that actively compensates for common mode noise and differential mode noise of each of two or more high-current paths (111, 112). Hereinafter, with reference to Figs. 1 to 5 described above, any overlapping content with the above will be omitted, and the operating principle of the active EMI filter (100) will be mainly described.

[0081] Referring to Fig. 6, first, with respect to common mode noise, the first induced voltage induced by the first noise (I11, I12) detected in the choke coil as described in Fig. 5(a) is input to the compensation unit (150) as the first input signal of the compensation unit (150) connected to the sensing winding. The compensation unit (150) includes a negative impedance converter to generate a first compensation voltage corresponding to the first input signal.

[0082] Specifically, the first input signal is input to the amplifier (151), and the amplifier amplifies the first input signal according to the gain (A0) to generate a first amplified signal. The amplifier (151) may mean adjusting the size and / or phase of the amplification target, and in FIG. 6, the amplifier (151) is illustrated as including one Op-amp, but is not limited thereto and may include a plurality of passive elements such as resistors and capacitors in addition to the Op-amp. In addition, in an optional embodiment, the amplifier (151) may include two or more Op-amps, may include a BJT (Bipolar Junction Transistor), and a means for amplification may be used without limitation. The generated first amplified signal may be an amplified voltage, and the first amplified signal is input to the target unit (152) and the stabilization unit (153).

[0083] Meanwhile, when a first amplification signal is input to the target section (152) and the stabilizing section (153), a first compensation voltage corresponding to the negative impedance is generated based on the input first amplification signal. In one embodiment, the magnitude (Z) of the impedance of the target section (152) and the stabilizing section (153) f ) is the size (Z) of the overall input impedance when looking from the compensation unit (150) to the sensing unit (120) t) is designed to be larger than the first compensation voltage. Therefore, the first compensation current corresponding to the generated first compensation voltage flows along the sensing winding (124) toward the sensing part (120) having a small impedance, and the effective impedance of the choke coil increases as the flux increases due to the first compensation current flowing into the choke coil, and the first noise (I11, I12), which is a common mode, is suppressed.

[0084] Similarly, for differential mode noise, the second induced voltage induced by the second noise (I21, I22) detected in the choke coil as described in Fig. 5(b) is input to the compensation unit (150) as the second input signal of the compensation unit connected to the sensing winding (124). The compensation unit (150) includes a negative impedance converter to generate a second compensation voltage corresponding to the second input signal. Specifically, the second input signal is input to the amplifier unit (151), and the amplifier unit (151) amplifies the second input signal according to the gain (A0) to generate a second amplified signal. The generated second amplified signal may be an amplified voltage, and the second amplified signal is input to the target unit (152) and the stabilization unit (153). The second amplified signal is input to the target unit (152) and the stabilization unit (153), and a second compensation voltage corresponding to the negative impedance is generated based on the second amplified signal. As described above, in one embodiment, the magnitude of the impedance of the target portion (152) and the stabilizing portion (153) (Z f ) is designed to be larger than the size of the overall impedance when viewed from the compensation unit (150) toward the sensing unit (120). Therefore, the second compensation current corresponding to the second compensation voltage flows along the sensing winding toward the sensing unit (120) with a smaller impedance, and the effective impedance of the choke coil increases as the flux increases due to the second compensation current flowing into the choke coil, and the second noise (I21, I22) in the differential mode is reduced.

[0085] Here, the total impedance includes the impedance components of the sensing winding (124) and the choke coil included in the sensing unit (120), as well as Z Yand Z S Parasitic capacitance, Z, included in the high current path (111, 112) shown in LISN This is the input impedance viewed from the compensation unit (150) toward the sensing winding (124), in which the influences of the capacitance of the second device (400) shown as , the capacitance of the first device (300) which is not shown, and so on are all reflected.

[0086] Meanwhile, the target unit (152) is connected to the output unit of the amplifier unit (151) and may include at least one inductor and capacitor as essential components. Here, the inductor serves to create negative impedance together with the amplifier unit (151), and the capacitor may be provided for DC coupling to ensure circuit stability. In addition to the inductor and capacitor, the target unit (152) may also have additional resistance, and may be modified in various ways depending on the design.

[0087] Meanwhile, the stability unit (153) can be implemented in various embodiments.

[0088] In one embodiment, the stabilizing unit (153) is connected to the target unit (152) and may include at least one capacitor and at least one inductor. The stabilizing unit (153) may prevent oscillation of the active EMI filter by making the magnitude of the impedance of the target unit (152) and the stabilizing unit (153) together with the target unit (152) greater than the magnitude of the overall input impedance when viewed from the compensation unit (150) toward the sensing unit (120).

[0089] In another embodiment, the stabilizing unit (153) is connected to the output terminal or the input terminal of the amplifier unit (151) and may include at least one band filter. The stabilizing unit (153) can prevent oscillation of the active EMI filter by controlling the output of the amplifier unit (151) in a frequency band where there is a risk of oscillation. In detail, the stabilizing unit (153) can include at least one selected from the group consisting of a low-pass filter and a high-pass filter, thereby allowing the amplifier unit (151) to have a low output in the frequency band where there is a risk of oscillation. In addition, the stabilizing unit (153) can prevent oscillation of the active EMI filter by making the magnitude of the impedance of the target unit (152) and the stabilizing unit (153) in the frequency band where there is a risk of oscillation larger than the magnitude of the overall input impedance when viewed from the compensation unit (150) toward the sensing unit (120). For example, the frequency band of risk of rash may be a band ranging from more than 1 kHz to less than 1 GHz.

[0090] In another embodiment, the stabilizing unit (153) is connected to the output terminal of the amplifier unit (151) and may include at least one phase shifter. This stabilizing unit (153) can prevent oscillation of the active EMI filter by adjusting the phase of the output of the amplifier unit (151) in the oscillation risk frequency band.

[0091] Hereinafter, the effect of the present invention will be clearly explained by taking an example of a case where oscillation occurs. For the convenience of explanation, only the case of common mode noise will be taken as an example. When a first input signal is input to an amplifier (151), and the amplifier (151) amplifies the first input signal according to the gain (A0) to generate a first amplified signal, and the generated first amplified signal is input to a target unit (152) and a stabilization unit (153), if the size of the impedance of the target unit (152) and the stabilization unit (153) is smaller than the size of the overall impedance when looking from the compensation unit (150) toward the sensing unit (120), the first compensation current generated through the target unit (152) and the stabilization unit (153) is fed back to the input of the amplifier unit (151). Therefore, the amplifier unit (151) continues to amplify the fed-back input, so that the compensation unit (150) becomes like an oscillator, and an oscillation phenomenon occurs in which an unwanted peak signal is generated. This also applies similarly to differential mode noise. However, according to one embodiment of the present invention, since the stabilizing unit (153) exists, the impedance size of the target unit (152) and the stabilizing unit (153) is designed to be larger than the overall impedance size viewed from the compensation unit (150) toward the sensing unit (120), thereby preventing oscillation and performing stable current compensation operation.

[0092] Fig. 7 illustrates an example of a specific circuit of an active EMI filter (100A) according to one embodiment of the present invention.

[0093] The active EMI filter (100A) of Fig. 7 is a circuit diagram according to one embodiment, and includes content that actively compensates for common mode noise and differential mode noise of each of two or more high-current paths (111, 112) previously described, and any content that overlaps with the content described above with reference to Figs. 1 to 6 is omitted, and the configuration of the circuit diagram is mainly described.

[0094] Referring to FIG. 7, the active EMI filter (100A) may include a sensing unit (120A) and a compensation unit (150A) connected thereto, and the compensation unit (150A) may include an amplifier unit (151A), a target unit (152A), and a stabilization unit (153A).

[0095] The amplifier (151A) may include one amplifier (OPa) having a predetermined gain. The output terminal of the amplifier (OPa) is connected to the target unit (152A) and the first on-resistance (Z a1 ) can be connected to the first on-resistor (Z). In addition, the positive input terminal of the amplifier (OPa) can be connected to the stabilizing unit (153A) and the sensing winding (not shown), and the negative input terminal can be connected to the first on-resistor (Z a1 ) and second on-resistance (Z a2 ) can be connected to. In the drawing, each of the on-resistors is depicted as containing only a resistor, but each of the on-resistors may be a combination of one or more resistors, capacitors, and inductors.

[0096] The target portion (152A) includes a resistor (Rb), a capacitor (Cb), and an inductor (Lb), which are each connected in parallel, and the target portion (152A) can be connected to the stabilizing portion (152A). The stabilizing portion (152A) can further include a resistor (Rc), a capacitor (Cc), and an inductor (Lc) which are each connected in parallel, and a resistor (Rd) and a capacitor (Cd) which are connected in series with these. The target portion (152A) and the stabilizing portion (153A) can be modified in various ways, and any modification is possible as long as the magnitude of the impedance of the target portion (152A) and the stabilizing portion (152A) is configured to be greater than the magnitude of the overall impedance when viewed from the compensation portion (150A) toward the sensing portion (120A).

[0097] Looking at the operation of FIG. 7, an input signal from a sensing unit (120A) is input to a compensation unit (150A), and the input signal is amplified according to the gain of an amplifier (OPa) included in the amplification unit (151A) through an amplifier unit, and the voltage of the amplified amplified signal is applied to a target unit and a stabilization unit and converted into an amplified voltage according to the impedance of the target unit and the stabilization unit, and as shown in FIG. 6, the impedance (Zf) of the target unit and the stabilization unit is greater than the total input impedance (Zt) viewed from the compensation unit (150A) toward the sensing unit (120A), so an amplified current corresponding to the amplified voltage flows toward the sensing unit (120A) and activates the choke coil of the sensing unit (120A).

[0098] Figure 8 is a graph comparing the oscillation stability of the circuit illustrated in Figure 7.

[0099] Referring to Fig. 8, the dotted line in Fig. 8 is the loop gain by frequency of the circuit from which the stabilizing unit (153A) is excluded in Fig. 7, and the solid line in Fig. 8 is the loop gain by frequency of the circuit from which the stabilizing unit (153A) is included in Fig. 7. That is, as a result of comparing the performance of the circuit from which the stabilizing unit (153A) is excluded in Fig. 7 and the circuit illustrated in Fig. 7, it can be confirmed that the circuit from Fig. 7 including the stabilizing unit (153A) has solved the oscillation problem because the loop gain does not exceed 1 in a certain frequency band.

[0100] Figure 9 is a schematic diagram showing the structure of an active EMI filter (100C) according to one embodiment of the present invention.

[0101] FIG. 9 is a cross-sectional view showing the structure of an active EMI filter (100C), and the contents that overlap with the contents described above with reference to FIGS. 1 to 8, including the contents of actively compensating for common mode noise and differential mode noise of each of two or more high-current paths (111, 112), are omitted, and the following description focuses on the structure of the active EMI filter.

[0102] Referring to FIG. 9, the active EMI filter (100C) includes a sensing unit (120C) and a compensation unit (150C), and may include a substrate (10C) on which they are mounted.

[0103] The substrate (10C) includes one side and the other side, and may include a plurality of conductive pads on the one side and the other side, and a plurality of conductive vias (not shown) electrically connecting them. For example, the substrate (10C) may be a printed circuit board (PCB), may be a double-sided PCB, and may be applied in various ways depending on the design, without being limited to a rigid PCB or a flexible PCB.

[0104] The sensing unit (120C) may include at least one choke coil as illustrated in FIG. 3, and the choke coil may include a core (123) including a through hole and conductive windings (1111, 1112, 124) passing through the through hole or wound around the core (123) at least once through the through hole. The choke coil is mounted on one surface of the substrate (10C), and the conductive windings (1111, 1112, 123) may be electrically connected to conductive pads (P) of the substrate (10C) and may be electrically connected to a high current path (111, 112), a first device (300), and a second device (400) through the substrate (10C).

[0105] The compensation unit (150C) includes a negative impedance converter, and in one embodiment, the compensation unit (150C) may be a circuit including at least one amplifier, at least one inductor, at least one capacitor, and at least one resistor. According to an optional embodiment, the compensation unit (150C) may be implemented with the above-described components as a single integrated circuit chip (IC chip), thereby reducing the volume and facilitating management. According to an optional embodiment, at least one amplifier included in the compensation unit (150C) may be implemented as a single integrated circuit chip, and inductors, capacitors, and resistor components other than the amplifier may not be implemented as an IC chip. The compensation unit (150C) can be electrically connected to the sensing unit (120C) via the substrate (10C), and without limitation, the compensation unit (150C) can also be electrically connected to the sensing unit (120C) directly via the conductive winding of the sensing unit (120C).

[0106] Meanwhile, the compensation unit (150C) may be placed in any space of the substrate (10C) where the choke coil is not placed. Referring to Fig. 9(a), in one embodiment, the compensation unit (150C) may be placed on the other surface of the substrate (10C) where the choke coil is not placed. Referring to Fig. 9(b), in another embodiment, the compensation unit (150C) may be placed on one surface of the substrate (10C) where the choke coil is not placed. However, Fig. 9 is exemplary, and the spirit of the present invention is not limited thereto. That is, any arrangement that saves space by placing the compensation unit (150C) connected to the sensing unit (120C) on the other surface or one surface of the substrate (10C), which was previously an empty space, and has the effect of implementing the active EMI filter (100C) as a single, small device with reduced volume and weight may be utilized.

[0107] Fig. 10 is a schematic diagram showing the structure of an active EMI filter (100D) according to another embodiment of the present invention.

[0108] This is a cross-sectional view showing the structure of an active EMI filter (100D) of Fig. 10, and the contents that overlap with the contents already described with reference to Figs. 1 to 9, including the contents of actively compensating for common mode noise and differential mode noise of each of two or more high-current paths (111, 112), are omitted, and the structure is mainly described.

[0109] Referring to FIG. 10, the active EMI filter may include at least two sensing units (such as a first sensing unit (120D1), a second sensing unit (120D2)) and at least two compensation units (such as a first compensation unit (not shown), a second compensation unit (not shown)). Here, at least two compensation units may be implemented as a single integrated circuit chip (150D), thereby reducing the volume and facilitating management.

[0110] According to one embodiment, one integrated circuit chip (150D) including at least two compensation units can be placed in any space of the substrate (10D) where the sensing units (120D1, 120D2) are not placed. In FIG. 10, the integrated circuit chip (150D) is illustrated as being placed on the other surface of the substrate (10D) where the sensing units (120D1, 120D2) are not placed, but this is exemplary and the spirit of the present invention is not limited thereto.

[0111] Meanwhile, at least two sensing units may both detect common mode noise and differential mode noise. However, according to an optional embodiment, each of the at least two sensing units may detect noise of a different mode. For example, the first choke coil of the first sensing unit (120D1) may detect common mode noise and be activated by a compensation voltage from the first compensation unit to increase the effective impedance, and the second choke coil of the second sensing unit (120D2) may detect differential mode noise and be activated by a compensation voltage from the second compensation unit to increase the effective impedance. In this case, the first compensation unit and the second compensation unit may be implemented as a single integrated circuit chip (150D), thereby reducing the size and facilitating management.

[0112] Meanwhile, according to an optional embodiment, among the configurations of at least two compensation units, only the configuration of the amplifier (OP-amp) may be implemented as a single integrated circuit chip (150D). In this case, inductor, capacitor, and resistor components other than the amplifier may not be implemented as an integrated circuit chip. The integrated circuit chip (150D) may be electrically connected to the sensing units (120D1, 120D2) via the substrate (10D), and without limitation, the integrated circuit chip (150D) may be electrically connected to the sensing unit (120C) directly via the conductive windings of the sensing units (120D1, 120D2).

[0113] The specific implementations described in the present invention are exemplary embodiments and do not limit the scope of the present invention in any way. For the sake of brevity, descriptions of conventional electronic components, control systems, software, and other functional aspects of the systems may be omitted. In addition, the lines connecting or connecting members between components depicted in the drawings are merely representative of functional connections and / or physical or circuit connections, and may be replaced or represented as various additional functional connections, physical connections, or circuit connections in an actual device. In addition, unless specifically mentioned as "essential," "important," etc., a component may not be absolutely necessary for the application of the present invention.

[0114] Therefore, the idea of ​​the present invention should not be limited to the embodiments described above, and not only the scope of the patent claims described below but also all scopes equivalent to or equivalently modified from the scope of the patent claims are considered to fall within the scope of the idea of ​​the present invention.

[0115] The active EMI filter according to the present disclosure can be used in the fields of communication equipment, automobiles and electronic equipment, medical equipment, industrial equipment including power conversion devices or control systems, and home appliances, and can effectively remove common mode and differential mode noise while preventing oscillation.

Claims

1. A sensing unit that detects common mode and differential mode noise on at least two high-current paths; and A compensation unit that generates a compensation signal corresponding to the detected noise, including a negative impedance converter, and provides the compensation signal to the sensing unit; An active EMI filter, wherein the compensation section includes a stabilization section that prevents oscillation caused by detected noise.

2. In paragraph 1, The above sensing part A conductor including a through hole; At least two high-current path windings passing through at least the above through-holes and connected to each of the at least two high-current paths; and A sensing winding insulated from at least two high current paths and passing through at least the through hole; Includes a choke coil including: An active EMI filter, wherein each of the at least two high-current path windings is asymmetrically wound around the conductor.

3. In paragraph 2, Each of the above at least two high-current path windings An active EMI filter in which at least one of the following is different: the number of turns, the degree of winding tightness, the size of the winding angle, whether the turns are overlapped, or if overlapped, the number of overlaps.

4. In paragraph 1, The above compensation department an amplifier unit generating an amplified signal corresponding to the detected noise; and A target unit that generates the compensation signal corresponding to the amplified signal; Including, The above-mentioned stabilizing part is connected to the above-mentioned target part, An active EMI filter in which the magnitude of the impedance of the target portion and the stabilizing portion is greater than the magnitude of the overall input impedance viewed from the compensation portion toward the sensing portion.

5. In paragraph 1, An active EMI filter, wherein the compensation unit comprises at least one amplifier, wherein the at least one amplifier is implemented as a single integrated chip.

6. In paragraph 1, A substrate having one side and the other side; further comprising: The above sensing unit is mounted on one side of the substrate electrically connected to the above sensing unit, An active EMI filter, wherein the compensation unit is electrically connected to the sensing unit and provided on the other surface of the substrate.

7. In paragraph 1, A substrate having one side and the other side; further comprising: The above sensing unit is mounted on one side of the substrate electrically connected to the above sensing unit, An active EMI filter in which the compensation unit is electrically connected to the sensing unit and is provided in a space on one side of the substrate where the sensing unit is not disposed.

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