Active choking coil

Abstract

The utility model discloses an active choking coil, which comprises at least three groups of coils, two groups of coils are used for power current of a power line to flow through, and the other group of coils are used for active suppression current to flow through; the active suppression current generating circuit is coupled with the coils and generates the suppression current; the capacitor is connected in parallel with the two groups of coils through which power current flows, so as to serve as a filter of the power line; according to the utility model, the common-mode and differential-mode noise suppression effect or the EMI suppression effect is enhanced mainly through the active current generator circuit, so that the cost and the size of the isolator or the EMI suppression circuit are reduced. Because the length of the copper wire is reduced, the energy consumption of the isolator or the EMI suppression circuit is lower than that of the traditional method, and the energy loss is reduced.

Description

Technical Field

[0001] The utility model relates to an active choke coil and a power line filter thereof, wherein the choke coil can be at least one of a common mode choke coil and a differential mode choke coil. Background Art

[0002] To improve power line communications, isolators are used to filter out noise. These are typically composed of passive inductors and capacitors, and to filter both common-mode and differential-mode noise, they often include a common-mode choke. If the isolator is located in the path of high power currents, the inductor is typically bulky and expensive, and the copper wire wrapped around the core is long, consuming more power. Common-mode chokes are also commonly used for electromagnetic interference (EMI) suppression and have a wide range of applications. This technology uses active circuitry to enhance the effectiveness of the isolator and EMI suppression circuitry, reducing cost and size, and minimizing energy loss caused by copper wire heating.

[0003] In addition, isolators are usually composed of passive inductors and capacitors. Generally speaking, an isolator is actually a high-frequency filter. In addition to differential-mode noise, the noise it filters often also contains common-mode noise. Therefore, a practical isolator must be able to filter out both differential-mode noise and common-mode noise at the same time. Figure 1A and Figure 1B As shown in the figure, this is the isolator circuit commonly used in the prior art. Common-mode chokes occupy an important position in the isolator, and are mainly used to suppress high-frequency common-mode noise or common-mode current. Common-mode chokes often require a pair of inductors with relatively large inductance values. If the isolator is located on a path where a large alternating current passes (such as the entrance of an electric meter), the common-mode chokes made with prior art require a large magnetic core plus a sufficient number of windings to achieve the effect of suppressing common-mode noise. In addition, in order to keep the temperature rise of the isolator within a safe range when a large power current flows through the copper wire, the cross-sectional area of the copper wire must also be large enough, so the common-mode choke is expensive and large in size. Common-mode chokes are also often used to suppress electromagnetic interference of high-current equipment to comply with safety regulations. In addition to isolators, common-mode chokes are also often used to suppress EMI of high-current equipment to comply with safety regulations, such as Figure 2A 、 Figure 2B 、 Figure 2C As shown. The circuit that purely suppresses EMI does not need to consider the higher input impedance on the transmission side, so there are usually parallel capacitors on both sides. Figure 2B As shown in the figure, due to the problem of magnetic leakage, the common-mode choke also has some differential-mode filtering effect, so there are also some EMI suppression circuits composed entirely of common-mode chokes and capacitors.

[0004] Common-mode chokes typically require a larger core and thicker copper windings to achieve a higher common-mode inductance. Furthermore, they must maintain a safe temperature rise when operating at rated current. Because these two requirements must be met simultaneously, common-mode chokes capable of handling high currents often suffer from bulk and high cost. Utility Model Content

[0005] The utility model discloses an active choke comprising: at least three sets of coils, two of which are used to pass power current (the magnetic fields generated by low-frequency power currents can cancel each other out, while the magnetic fields generated by high-frequency common-mode noise currents are mutually reinforcing), and another set of coils for passing a high-frequency suppression current; an active suppression current generating circuit that couples these coils and generates an active suppression current; and a capacitor coupled to the two sets of coils for passing power currents to function as a power line filter. The active suppression current generating circuit is used to generate a suppression current proportional to the common-mode noise current, thereby generating a magnetic field generated by the original common-mode noise current in the magnetic cores of the coils, thereby suppressing the common-mode noise current from flowing through the two sets of power current coils.

[0006] Isolator circuits or EMI suppression circuits often incorporate differential-mode coils in addition to common-mode chokes, with various combinations and winding methods. These differential-mode coils can also be enhanced with similar active current suppression circuits to simultaneously reduce cost, size, and power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1A 、 Figure 1B 、 Figure 2A 、 Figure 2B 、 Figure 2C Schematic diagram showing the prior art.

[0008] Figure 3 A schematic diagram showing an embodiment of the present invention.

[0009] Figure 4A Schematic diagram showing the prior art.

[0010] Figure 4B 、 Figure 5 、 Figure 6A 、 Figure 6B 、 Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 、 Figure 11 A schematic diagram showing an embodiment of the present invention.

[0011] Figure Numbers

[0012] 40A, 50: Active common-mode choke circuit

[0013] I in1 , I in2 , I CN :Noise current

[0014] CMC1~CMC3: Common mode coil

[0015] DMC1~DMC3: Differential mode coil

[0016] B1, B2, N1, N2: Isolator or EMI suppression circuit ports

[0017] I + , I - : Suppression current

[0018] 201: Coupler

[0019] 202_C, 202_D: Current generator

[0020] L P :Main inductor

[0021] L S , L S1 :Secondary side inductance

[0022] L0:L S1 Inductance value

[0023] L S2 :Reference inductance

[0024] L1: Inductance value of the current generator reference inductor

[0025] I L1 : Flowing through inductor L S2 Current

[0026] C R :capacitance

[0027] Z, KZ: matching resistor

[0028] R1~R3: Impedance

[0029] V1, V2, V: voltage

[0030] ω: angular frequency

[0031] 1, 2: Input terminal

[0032] Q1~Q4: output terminal

[0033] Nc, Nc1, Nc2, Mc, Mc1, Mc2, Nd, Nd1, Nd2, Md: Number of coil turns DETAILED DESCRIPTION

[0034] Like the previously disclosed high current inductor circuit, the common mode choke of the present invention can also improve its equivalent inductance by actively suppressing the current. Figure 3 As shown, Figure 3 A schematic diagram of the present invention illustrates common-mode noise current flowing into common-mode coils CMC1-CMC2. In this embodiment, when common-mode noise current flows into common-mode coils CMC1-CMC2, a magnetic field is generated within the magnetic core. If a similar magnetic field can be generated by another active common-mode suppression current, the common-mode noise current can be suppressed from flowing through the common-mode choke coils CMC1-CMC2. Ideally, the common-mode noise current can be completely suppressed by the magnetic field generated by the active suppression current. In one embodiment, if the magnitude and phase of the noise current flowing through two ports of the common-mode choke coils CMC1-CMC2, such as ports B1 and B2, and ports N1 and N2, differ, the suppressed noise is the average of the two noises. The remaining noise will be in differential mode, and its impact can be further reduced by other differential-mode filtering circuits. Figure 3 The voltage difference generated by medium- and low-frequency power currents across the inductor is small, and the low-frequency currents flow in opposite directions in the two lines, so the resulting magnetic fields largely cancel each other out, minimizing magnetic saturation. High-frequency common-mode noise, however, generates a voltage difference and current across the coils. If the common-mode noise currents on both power lines are equal, the active common-mode suppression current can significantly reduce the common-mode noise current flowing through the common-mode coils CMC1 and CMC2 of the common-mode choke, as the magnetic field generated by the active common-mode suppression current completely replaces the magnetic field when the active common-mode suppression current is equal to zero.

[0035] Figure 4A A high current inductor circuit of the prior art is shown, wherein Figure 4A Display main inductance L P , secondary side inductance L S , current I in The current value I0 flows through the main inductor L P It is used to provide voltage V. Figure 4B A schematic diagram showing an active common mode choke and power line filter circuit 40 according to an embodiment of the present invention is provided. Figure 4B and Figure 4A The difference is that Figure 4A This is a general method to enhance the equivalent inductance of a certain inductor. Figure 4B This is for enhancing the common mode inductance of common mode choke coils, but has no effect on differential mode noise suppression. Figure 4B The noise current I flowing through the two paths in1 / I in2 The copper wire is thick (because it has to carry a large power current), and the active suppression current I + / I - The coil only needs to use thin wire.

[0036] In the present invention, the active common mode choke and power line filter circuit 40 includes three sets of common mode coils CMC1 to CMC3, two of which are used to pass the power current, and the other common mode coil CMC3 is used to pass the active suppression current I + Active common mode choke circuit 40A coupled common mode coil CMC1 ~ CMC3, the active common mode choke circuit 40A includes a coupler 201 and a common mode current generator 202_C, for common mode noise current I in1 , I in2 Generates a corresponding proportional suppression current I + , replacing the magnetic field generated by the common-mode noise current in the cores of the common-mode coils CMC1-CMC3. In a complete isolator or EMI suppression circuit, a parallel capacitor (not shown) is connected between the terminals of the two common-mode choke coils CMC1-CMC2, through which the power current flows, to filter out differential-mode noise.

[0037] In this embodiment, the turns ratio of the common mode choke coils CMC1:CMC2:CMC3 is N:N:M, and N and M are constants; if there is a noise current I in1 , I in2 The noise current (composed of common-mode and differential-mode noise) flows through the common-mode coils CMC1-CMC2. The voltages generated by the common-mode coils CMC1-CMC2 are V1 and V2, respectively. The common-mode coil CMC3 then generates a coupling voltage M(V1+V2) / 2N. The common-mode current generator 202_C receives the coupling voltage (aM(V1+V2)) / N) from the coupler 201 or another coupler to generate a suppression current I + , a is generally equal to 1 in the communication frequency band. The common mode current generator 202_C uses the same coupler 201 or another coupler to couple and output a corresponding proportion of the suppression current I + , to replace the magnetic field generated by the common mode noise current in the common mode choke core. If the non-ideal mutual inductance between coils such as leakage magnetic flux is not considered, the magnetic field replaced at this time is only the common mode part, and the magnetic field generated by the differential mode noise cannot be suppressed. Other capacitors or differential mode inductors are needed to filter out the differential mode noise. Figure 5 As shown in the schematic diagram, in the active common-mode choke circuit 50, the common-mode current generator 202_C can be implemented by an amplifier, which drives another reference inductor L at its load end. S2, whose inductance is L1. In this embodiment, the amplifier has a first input terminal 1 and a second input terminal 2, which are respectively coupled to the input terminal and the output terminal of the common mode coil CMC3, and the amplifier has a first output terminal Q1, a second output terminal Q2, a third output terminal Q3, and a fourth output terminal Q4, wherein the first output terminal Q1 and the fourth output terminal Q4 are connected in series with the reference inductor L as the load terminal. S2 The first input terminal 1 and the third output terminal Q3 are coupled in parallel to a coupler 201 (capacitor C in this embodiment), the second output terminal Q2 is coupled in parallel to the second input terminal 2, and a matching resistor Z is provided between the first input terminal 1 and the coupler 201; a matching resistor Z is provided between the second input terminal 2 and the second output terminal Q2; a matching resistor KZ is provided in parallel to the first input terminal 1 and the first output terminal Q1; and a matching resistor KZ is provided in parallel to the second input terminal 2 and the fourth output terminal Q4. In this embodiment, the reference inductor L S2 Connect a large capacitor C in series R .

[0038] If the noise current I in1 =I in2 =I CN , that is to say, the noise is pure common mode noise, suppressing the current I + Equal to 0, the common mode noise current I in1 , I in2 The voltage across the common mode coils CMC1 and CMC2, each with N turns, is V. The voltage induced by the common mode coil CMC3 as a suppression coil (with M turns) is (M / N)×V. Under ideal conditions, the suppression current I + =(2N / M)I CN , at this time most of the common mode noise current can be suppressed. Figure 5 As shown, this suppression current I + A reference inductor L can be driven by an amplifier S2 (The amplifier is in reference to the inductor L S2 The voltage V given at both ends L1 ), and the current generated by it is H times the current to generate the suppression current I + When the number of turns of the common mode coil CMC1 and the common mode coil CMC2 is N, the inductance is L0, and the amplifier ratio is K, then the reference inductance L S2 The inductance value L1 is equal to (M 2 ×K×H / (2N 2 ))L0. The resulting suppression current I + Approximately equal to (2N / M)I CN That is, if the suppression current I + Equal to (2N / M)I CN , most of the common-mode noise current can be suppressed, making Iin1 or I in2 Close to 0. In this embodiment, the impedance value of the matching resistor Z is much larger than ωL0 or ωL1 in the communication frequency band.

[0039] If the source of the common-mode noise current comes from the power transmission side (such as radiation noise in the air), this noise cannot be filtered by the isolator (because it has been mixed with the communication signal on the power transmission side). In this case, to reduce its impact, we can only hope that this common-mode noise does not convert into differential-mode noise during the transmission process (general communication signal transceivers have good common-mode noise resistance). Figure 6A and Figure 6B As shown, Figure 6A and Figure 6B The schematic diagrams of symmetrical differential mode choke circuits are shown respectively. If the differential mode choke of the isolator can be symmetrical, the common mode noise on the power consumption side or the common mode noise from the power transmission side will be closer to the common mode when it reaches B1 / N1 (transceiver port), which can reduce the impact on communication. Figure 1A The single-sided differential mode coil shown is mainly due to its low production cost and is used in short indoor distances, without considering the impact of radiation or coupled common mode noise. Symmetrical isolators are more suitable for long outdoor power lines, as they can prevent radiation or coupling (for example, underground noise coupling to buried wires) from interfering with communication signal transmission. Figure 6A and Figure 6B The difference is that Figure 6B If the coils with two independent magnetic cores are both equipped with active suppression circuits, the suppression of differential mode and common mode noise can be enhanced. Figure 6A and Figure 6B The displayed Nc, Mc, Nd, and Md represent the number of coil turns.

[0040] like Figure 7 As shown, the utility model can also be used as a differential mode choke. Figure 7 The schematic diagram of the active differential mode choke circuit 70 is shown. Differential mode coils DMC1-DMC3 can also use the same principle as above to enhance the suppression effect of differential mode noise. The symmetrical differential mode chokes DMC1-DMC2 help balance the common mode noise current in the two circuits, so a smaller proportion of it is converted into differential mode noise and appears on the transmission side. Finally, the differential mode suppression current generator 202_D outputs a differential mode suppression current to suppress the differential mode noise, replacing the magnetic field generated by the differential mode noise current in the magnetic cores of the differential mode coils DMC1-DMC2. The corresponding circuit schematic is shown in FIG. Figure 8 As shown in Figure 1, the principle is the same as above. Under ideal conditions, this circuit can only suppress differential mode noise but not common mode noise. The entire active isolator circuit is shown in Figure 1. Figure 6AThe above mentioned concepts can also be used in EMI suppression circuits. Since there is no requirement for high impedance on the transmission side, capacitors can be added on both sides, such as Figure 9 Some EMI suppression circuits focus on suppressing common-mode noise current, while differential-mode noise current can be filtered out only by the leakage magnetic effect of the common-mode choke and the capacitor. This circuit can abandon the differential-mode inductor and only use the common-mode choke and capacitor to complete it, as shown in the following figure. Figure 10 shown.

[0041] In actual active inductance enhancement circuits, in order to suppress oscillation, it is often necessary to reduce the Q value (Quality Factor) of the LC. Therefore, some small resistors are often added in the capacitor path. These resistors will reduce the differential mode noise filtering effect, but can make the entire circuit stable and prevent the circuit from generating unwanted oscillations. For example, Figure 11 The resistors R1 to R3 are shown. Figure 9 、 Figure 10 、 Figure 11 The displayed Nc, Nc1, Nc2, Mc, Mc1, Mc2, Nd, Nd1, Nd2, and Md represent the number of coil turns.

Claims

1. An active choke coil, characterized in that: Include: At least three sets of coils, two sets of coils are used for power current flowing through a power line, and the other set of coils is used for active suppression current flowing through; an active suppression current generating circuit, which is coupled to the coils and generates the suppression current; as well as a capacitor connected in parallel to the two sets of coils for passing power current to serve as a filter for the power line; The suppression current generating circuit is configured to generate a suppression current in a corresponding proportion according to a noise current, so as to offset a portion of the magnetic field generated by the noise current in the magnetic cores of the coils, thereby suppressing the noise current from flowing through the two sets of coils of the power current; And the noise current includes a common mode noise current and a differential mode noise current.

2. The active choke coil according to claim 1, wherein: The active suppression current generating circuit comprises: a coupler; and a current generator; The coupler and the current generator are used to output the suppression current in a corresponding proportion according to the noise current, so as to replace a part of the magnetic field generated by the noise current in the magnetic cores of the coils.

3. The active choke coil according to claim 2, characterized in that The current generator is implemented by an amplifier, which drives another reference inductor at its load end; the amplifier has a first input end and a second input end, the first input end and the second input end are respectively coupled to the coil input end and the output end for flowing the suppression current, and the amplifier has a first output end, a second output end, a third output end, and a fourth output end: wherein the first output end and the fourth output end are connected in series with the reference inductor as load ends; a coupler is coupled in parallel to the first input end and the third output end, the second output end is coupled in parallel to the second input end, and a first matching resistor is provided between the first input end and the coupler; a second matching resistor is provided between the second input end and the second output end; a third matching resistor is connected in parallel to the first input end and the first output end; a fourth matching resistor is connected in parallel to the second input end and the fourth output end, and the reference inductor is connected in series with another capacitor.

4. The active choke coil according to claim 1, wherein: The two capacitors are respectively coupled to two sides of the two coils for passing power current.

5. The active choke coil according to claim 1, wherein: At least one resistor is disposed on the path of the capacitor.

6. The active choke coil according to claim 1, wherein: High-frequency common-mode noise will generate a voltage difference and current across the two coils through which the power current flows. When the common-mode noise currents on the two power lines are equal in magnitude, the magnetic field generated by the active common-mode rejection current completely replaces the magnetic field when the active common-mode rejection current is equal to 0.

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