An EMI filter and a non-isolated on-board charger thereof

Abstract

The utility model discloses a kind of EMI filter and its non-isolated airborne charger, belong to electromagnetic compatibility technical field, including port 1, machine 28V DC power supply anode input interface;Port 2, DC / DC converter anode output interface;Port 3, machine 28V DC power supply cathode and storage battery group cathode common ground interface;Port 4, DC / DC converter cathode output interface;Port 5, storage battery group anode input interface;Port 6, DC / DC converter output anode access interface;Filter circuit, including first inductance L1, second inductance L2, third inductance L3 are wound on first toroidal core, winding direction is same and equal in number of turns.The utility model's six port definition is clear, respectively corresponding machine power supply, DC / DC converter and the positive and negative pole interface of storage battery group, meet the connection demand of each component in airborne charger system, using standard aviation plug connector, guarantee the reliability and compatibility of port connection, suitable for electrical connection requirement in airborne environment.

Description

Technical Field

[0001] This utility model relates to the field of electromagnetic compatibility technology, specifically to an EMI filter and its non-isolated airborne charger. Background Technology

[0002] As energy storage devices that convert chemical energy into electrical energy, batteries are widely used in the aviation field for aircraft emergency and starting power systems. To reduce the frequency of off-board maintenance of battery packs, chargers need to be installed on board for charging operations. A typical onboard charging scheme adopts a non-isolated topology, powered by the onboard 28V DC power supply. After voltage / current adjustment by a DC / DC converter, it provides constant current charging to the battery pack.

[0003] The traditional non-isolated charging circuit structure is that the positive terminal of the onboard 28V DC power supply is directly connected to the positive input terminal of the DC / DC converter, the positive output terminal of the DC / DC converter is connected to the positive terminal of the battery pack, and the negative terminal of the onboard 28V power supply is connected to both the negative terminal of the DC / DC converter and the negative terminal of the battery pack. Although this scheme is simple in structure, it generates strong common-mode and differential-mode electromagnetic interference (EMI) during operation because the DC / DC converter uses high-frequency chopping technology.

[0004] To suppress interference, a common practice is to add an EMI filter to the input side of the DC / DC converter. This filter uses a two-wire input structure, with the onboard 28V positive terminal connected to the DC / DC input positive terminal via the filter, and the onboard 28V negative terminal connected to the DC / DC input negative terminal via the filter. However, this structure has a serious drawback:

[0005] Assume the positive current at the 28V terminal of the machine is (Inflow direction is positive), the battery pack charging current is (Inflow is positive), the negative current of the DC / DC converter is (Inflow is positive), according to Kirchhoff's Current Law, we have In actual work, It is always positive, while It can be negative, positive, or zero, because An imbalance in the current flowing through the two windings of the common-mode inductor on the input side causes a net magnetic flux to be generated within the core. When the operating current is large or under transient conditions, the core is prone to saturation, causing a sharp drop in inductance and resulting in the filter losing its common-mode interference suppression capability.

[0006] Based on this, this utility model designs an EMI filter and its non-isolated airborne charger to solve the above problems. Utility Model Content

[0007] In view of the above-mentioned shortcomings of the existing technology, this utility model provides an EMI filter and its non-isolated airborne charger.

[0008] To achieve the above objectives, this utility model provides the following technical solution:

[0009] An EMI filter, characterized in that it comprises:

[0010] 6 ports;

[0011] Port 1, the positive input interface for the machine's 28V DC power supply;

[0012] Port 2, positive output interface of DC / DC converter;

[0013] Port 3 is the common ground interface between the negative terminal of the machine's 28V DC power supply and the negative terminal of the battery pack.

[0014] Port 4, negative output interface of DC / DC converter;

[0015] Port 5, positive input interface of battery pack;

[0016] Port 6, the positive output terminal of the DC / DC converter is connected to the interface;

[0017] The filter circuit includes a first inductor L1, a second inductor L2, and a third inductor L3 all wound around a first toroidal magnetic core, with the same winding direction and the same number of turns;

[0018] The fourth inductor L4, the fifth inductor L5, and the sixth inductor L6 are all wound together on the second toroidal core, with the same winding direction and the same number of turns;

[0019] Port 1 is connected in series with L1 and L4 to port 2;

[0020] Port 3 is connected in series with L2 and L5 to port 4;

[0021] Port 5 is connected in series with L3 and L6 to port 6;

[0022] When the input current at port 1 is The input current at port 3 is [value], and the input current at port 5 is [value]. When, satisfy Furthermore, the direction of the magnetic flux generated by L1 is opposite to the direction of the combined magnetic flux generated by L2 and L3.

[0023] Furthermore, the wire diameter of L2 is larger than that of L1 and L3, and the wire diameter of L5 is larger than that of L4 and L6.

[0024] Furthermore, it also includes:

[0025] The first capacitor C1 is connected across port 1 and port 3;

[0026] The second capacitor C2 is connected across port 3 and port 5;

[0027] The sixth capacitor C6 is connected across the second terminal of L1 and L2;

[0028] The seventh capacitor C7 is connected across the second terminal of L2 and L3;

[0029] The eleventh capacitor C11 is connected across the second terminal of L4 and L5;

[0030] The twelfth capacitor C12 is connected across the second terminal of L5 and L6;

[0031] C1, C2, C6, C7, C11, and C12 are X-type safety capacitors.

[0032] Furthermore, it also includes:

[0033] The first ends of the third capacitor C3, the fourth capacitor C4, and the fifth capacitor C5 are connected to port 1, port 3, and port 5 respectively, and the second ends are connected to the conductive shell.

[0034] The first terminals of the eighth capacitor C8, the ninth capacitor C9, and the tenth capacitor C10 are connected to the second terminals of L1, L2, and L3, respectively, and the second terminals are connected to the conductive outer shell.

[0035] The first ends of the thirteenth capacitor C13, the fourteenth capacitor C14, and the fifteenth capacitor C15 are connected to port 2, port 4, and port 6 respectively, and the second ends are connected to the conductive outer shell.

[0036] C3-C5, C8-C10, and C13-C15 are Y-type safety capacitors.

[0037] Furthermore, ports 1 to 6 are aviation plug-in type connectors with a rated current ≥50A.

[0038] Furthermore, the conductive outer shell is a metal shielding shell with grounding bolts on its surface.

[0039] Furthermore, the first and second annular magnetic cores are made of ferrite material with an initial permeability of 3000-4000 and a saturation magnetic flux density ≥450mT.

[0040] Furthermore, L1, L2, and L3 each have 10 turns, all in a clockwise direction; L4, L5, and L6 each have 10 turns, all in a clockwise direction.

[0041] Furthermore, the filter circuit is mounted on an FR-4 circuit board and encapsulated in an aluminum alloy housing.

[0042] A non-isolated airborne charger, using any of the EMI filters described above, characterized in that it includes a DC / DC converter, wherein port 1 of the EMI filter is connected to the positive terminal of an onboard 28V DC power supply.

[0043] Port 2 of the EMI filter is connected to the positive input of the DC / DC converter;

[0044] The EMI filter's port 3 is connected to the negative terminal of the 28V DC power supply on the machine and the negative terminal of the battery pack.

[0045] Port 4 of the EMI filter is connected to the negative terminal of the DC / DC converter;

[0046] Port 5 of the EMI filter is connected to the positive terminal of the battery pack;

[0047] Port 6 of the EMI filter is connected to the positive output of the DC / DC converter.

[0048] Compared with the prior art, the advantages of this utility model are as follows:

[0049] 1. The connection method of capacitors and inductors in the filter circuit of this utility model is arranged in a reasonable manner. The multiple X capacitors and Y capacitors can suppress electromagnetic interference in different frequency bands. The connection between the Y capacitor and the metal shell provides a low impedance path for common mode interference, which helps to reduce radiation interference. The X capacitor plays a role in suppressing differential mode interference. The two work together to improve the overall filtering effect.

[0050] 2. The six ports of this utility model are clearly defined, corresponding to the positive and negative interfaces of the onboard power supply, DC / DC converter and battery pack, respectively, which meets the connection requirements of each component in the airborne charger system. The use of standard aviation plug connectors ensures the reliability and compatibility of the port connections and is suitable for the electrical connection requirements of the airborne environment.

[0051] 3. The three inductors wound on the first toroidal magnetic core of this utility model can achieve magnetic flux cancellation by utilizing the current relationship and winding direction configuration when the circuit is working normally. This helps to avoid magnetic core saturation, ensure the stability of inductor performance, and thus maintain the normal working state of the filter circuit.

[0052] 4. The integration method of the non-isolated DC / DC converter of this utility model is simple and clear, and the connection relationship of each port is clear. It can be well adapted to the circuit structure of the airborne charger, which is convenient for assembly and debugging in practical applications and meets the electromagnetic compatibility requirements of airborne equipment for power systems. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 This is a schematic diagram of a typical non-isolated charging circuit;

[0055] Figure 2 A schematic diagram of adding an EMI filter circuit to a typical non-isolated charging circuit;

[0056] Figure 3 This is a schematic diagram of the EMI filter and non-isolated airborne charger circuit of this utility model;

[0057] Figure 4 This is a schematic diagram of the EMI filter circuit of this utility model. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0059] This application discloses an EMI filter and its non-isolated airborne charger, comprising:

[0060] The metal casing is a rectangular aluminum alloy shell, measuring 200mm × 150mm × 50mm. An M6 grounding bolt is installed on the surface of the metal casing. Connect the wire to the aircraft grounding stake;

[0061] The circuit board, made of FR-4 material, is 2.0mm thick and is fixed inside the casing.

[0062] Six aviation connectors (compliant with MIL-DTL-38999 Class III standard, rated current 60A):

[0063] Port 1, solder 6mm 2 The red wire is labeled "Machine 28V+IN";

[0064] Port 2, solder 6mm 2 The orange wire is labeled "DC / DC+OUT";

[0065] Port 3, weld 10mm 2 The black wire is labeled "GND";

[0066] Port 4, solder 6mm 2 The black wire is labeled "DC / DC-OUT";

[0067] Port 5, solder 6mm 2 The yellow wire is labeled "BAT+IN";

[0068] Port 6, solder 6mm 2 The orange wire is labeled "DC / DC+_OUT+" (DC / DC output connection);

[0069] The design of each port ensures that the filter can be safely and reliably connected to external circuits.

[0070] like Figure 3-4 As shown, the EMI filter circuit is based on capacitors and inductors to achieve electromagnetic interference (EMI) suppression. All electronic components are soldered onto the circuit board via copper foil traces, and the specific connection relationships are as follows:

[0071] C1 (X capacitor, 1μF) connects port 1 and port 3 to suppress high-frequency interference between the input power supply and ground.

[0072] C2 (X capacitor, 1μF) is connected between port 3 and port 5 to reduce interference between different input power supplies;

[0073] C3, C4, and C5 (Y capacitors, 2.2nF) are connected to port 1, port 3, and port 5 respectively at one end, and to the grounding plate on the inner wall of the casing at the other end, for bypassing single-ended interference;

[0074] C6 (X capacitor, 0.47μF) connects the second pin of L1 to the second pin of L2;

[0075] C7 (X capacitor, 0.47μF) connects to the second pin of L2 and the second pin of L3;

[0076] One end of C8, C9, and C10 (Y capacitors, 2.2nF) is connected to the second pin of L1, L2, and L3 respectively, and the other end is connected to the ground plate to further enhance the high-frequency suppression effect;

[0077] C11 (X capacitor, 0.47μF) connects to pin 2 of L4 and pin 2 of L5;

[0078] C12 (X capacitor, 0.47μF) connects to the second pin of L5 and the second pin of L6;

[0079] One end of C13, C14, and C15 (Y capacitors, 2.2nF) is connected to port (2), port 4, and port 6 respectively, and the other end is connected to the ground plate to complete the filtering on the output side.

[0080] The inductor section is designed to suppress low-frequency interference through proper winding and connection. The specific connection is as follows:

[0081] L1, L2, and L3 (with wire diameters of 1.5mm, 2.5mm, and 1.5mm respectively) are wound together on the first toroidal ferrite core (T1, outer diameter 40mm), each with 10 turns, and all are wound clockwise. Their connection relationship is as follows: L1's first pin is connected to port 1, and its second pin is connected to L4's first pin; L2's first pin is connected to port 3, and its second pin is connected to L5's first pin; L3's first pin is connected to port 5, and its second pin is connected to L6's first pin.

[0082] L4, L5, and L6 (with wire diameters of 1.5mm, 2.5mm, and 1.5mm respectively) are wound together on the second toroidal ferrite core (T2, outer diameter 40mm), each with 10 turns and a clockwise winding direction. Their connection relationship is as follows: L4's second pin is connected to port 2, L5's second pin is connected to port 4, and L6's second pin is connected to port 6.

[0083] The material parameters of the ferrite cores T1 / T2 are an initial permeability of 3000-4000 and a saturation magnetic flux density ≥450mT (100℃), ensuring the stability of the inductor under high current and high frequency environments.

[0084] After completing the filter circuit layout, it is integrated with the non-isolated DC / DC converter to achieve complete power processing functionality. The connection relationships of each port are as follows:

[0085] Port 1 is connected to the positive terminal of the 28V DC power supply on the machine via a red wire;

[0086] Port 2 is connected to the positive input terminal of the DC / DC converter via an orange wire;

[0087] Port 3 is connected to the common terminal of the 28V DC power supply negative terminal and the battery negative terminal via a black wire.

[0088] Port 4 is connected to the negative terminal of the DC / DC converter via a black wire;

[0089] Port 5 is connected to the positive terminal of the battery via a yellow wire;

[0090] Port 6 is connected to the positive output terminal of the DC / DC converter (from the output current of the DC / DC converter) via an orange wire.

[0091] The DC / DC converter has an input voltage range of 18-36V, an output voltage of 28V±5%, and an output current that is continuously adjustable from 0-30A. Through this integration, the filter and the DC / DC converter can work together to provide efficient power management and electromagnetic compatibility.

[0092] like Figure 4 As shown, when the circuit is working normally, according to Kirchhoff's Current Law (KCL), for the nodes of the magnetic core, we have: ;

[0093] Among them, the current at port 1 The power supply flows into the filter from the positive terminal of the onboard power supply (+ direction).

[0094] Current at port 3 The current flows out of the filter to the negative terminal (+ direction) of the machine power supply.

[0095] Current at port 5 The current flows out of the filter to the positive terminal (+ direction) of the battery.

[0096] like Figure 4 The winding direction shown indicates the current in L1 of the inductor winding ( The magnetic flux generated by the inflow (Direction downwards, denoted as) );

[0097] L2 current ( The outflow is an equivalent reverse current, which generates magnetic flux. (Upward direction, denoted as) );

[0098] L3 current ( The outflow is an equivalent reverse current, which generates magnetic flux. (Upward direction, denoted as) );

[0099] According to Kirchhoff's current law, due to This means that in the magnetic core, the magnetic flux generated by L1 and the combined magnetic flux from L2 and L3 exactly cancel each other out, resulting in a total magnetic flux of 0. Under this current relationship, the magnetic reluctance of the magnetic core is considered. Number of winding turns The formula for calculating magnetic flux is:

[0100]

[0101] Taking specific numerical values ​​as an example, (Number of turns) Based on the characteristics of manganese-zinc ferrite materials, the value is 8000-9000 A·T / Wb. Here, we take 8000 A·T / Wb, according to the current relationship. Substitute into the formula:

[0102]

[0103] Therefore, during circuit operation, due to the rational design of current distribution and direction, the total magnetic flux in the magnetic core is... The flux is reduced to zero, achieving zero net magnetic flux. This flux cancellation mechanism effectively avoids core saturation and ensures the normal operation of the circuit.

[0104] After verifying the flux cancellation function, the electromagnetic compatibility (EMC) suppression mechanism of the filter was further tested, including the suppression effect of conducted and radiated interference. Through the design of a three-stage LC filter network, effective suppression of high-frequency interference was achieved. The corner frequency calculation formula is as follows:

[0105]

[0106] in, Parallel equivalent inductance, The formula for calculating the attenuation rate A at the high-frequency end (e.g., 1MHz) is:

[0107]

[0108] This indicates that the filter has a 76dB suppression effect on conducted interference at 1MHz.

[0109] The aluminum casing can be considered as a shielding body, and the shielding effectiveness SE is affected by the material's electrical conductivity. and relative permeability Impact, when At that time, shielding effectiveness and frequency It is related to the electrical conductivity of the material, according to the formula:

[0110]

[0111]

[0112] In summary, the aluminum casing provides 35dB of shielding effectiveness at 30MHz and 32dB at 500MHz. Through low-pass filter design, 76dB attenuation is achieved at 1MHz. The aluminum casing provides 35dB and 32dB of shielding effectiveness at 30MHz and 500MHz, respectively.

[0113] Based on the principle of magnetic flux cancellation and the design of a three-stage LC filter network, this filter has inherent electromagnetic interference suppression capability in the 10kHz-1GHz frequency band and can be adapted to airborne equipment that meets the requirements of GJB151A.

[0114] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. An EMI filter, characterized in that, include: 6 ports; Port 1, the positive input interface for the machine's 28V DC power supply; Port 2, positive output interface of DC / DC converter; Port 3 is the common ground interface between the negative terminal of the machine's 28V DC power supply and the negative terminal of the battery pack. Port 4, negative output interface of DC / DC converter; Port 5, positive input interface of battery pack; Port 6, the positive output terminal of the DC / DC converter is connected to the interface; The filter circuit includes a first inductor L1, a second inductor L2, and a third inductor L3 all wound around a first toroidal magnetic core, with the same winding direction and the same number of turns; The fourth inductor L4, the fifth inductor L5, and the sixth inductor L6 are all wound together on the second toroidal core, with the same winding direction and the same number of turns; Port 1 is connected in series with L1 and L4 to port 2; Port 3 is connected in series with L2 and L5 to port 4; Port 5 is connected in series with L3 and L6 to port 6; When the input current at port 1 is The input current at port 3 is The input current at port 5 is When, satisfy Furthermore, the direction of the magnetic flux generated by L1 is opposite to the direction of the combined magnetic flux generated by L2 and L3.

2. The EMI filter according to claim 1, characterized in that, The wire diameter of L2 is larger than that of L1 and L3, and the wire diameter of L5 is larger than that of L4 and L6.

3. The EMI filter according to claim 2, characterized in that, Also includes: The first capacitor C1 is connected across port 1 and port 3; The second capacitor C2 is connected across port 3 and port 5; The sixth capacitor C6 is connected across the second terminal of L1 and L2; The seventh capacitor C7 is connected across the second terminal of L2 and L3; The eleventh capacitor C11 is connected across the second terminal of L4 and L5; The twelfth capacitor C12 is connected across the second terminal of L5 and L6; C1, C2, C6, C7, C11, and C12 are X-type safety capacitors.

4. The EMI filter according to claim 1, characterized in that, Also includes: The first ends of the third capacitor C3, the fourth capacitor C4, and the fifth capacitor C5 are connected to port 1, port 3, and port 5 respectively, and the second ends are connected to the conductive shell. The first terminals of the eighth capacitor C8, the ninth capacitor C9, and the tenth capacitor C10 are connected to the second terminals of L1, L2, and L3, respectively, and the second terminals are connected to the conductive outer shell. The first ends of the thirteenth capacitor C13, the fourteenth capacitor C14, and the fifteenth capacitor C15 are connected to port 2, port 4, and port 6 respectively, and the second ends are connected to the conductive outer shell. C3-C5, C8-C10, and C13-C15 are Y-type safety capacitors.

5. The EMI filter according to claim 1, characterized in that, Ports 1 to 6 use aviation plug-in type connectors with a rated current ≥50A.

6. The EMI filter according to claim 1, characterized in that, The conductive outer shell is a metal shielded shell with a grounding bolt on its surface.

7. The EMI filter according to claim 1, characterized in that, The first and second annular magnetic cores are made of ferrite material with an initial permeability of 3000-4000 and a saturation magnetic flux density ≥450mT.

8. The EMI filter according to claim 1, characterized in that, L1, L2, and L3 each have 10 turns, all in a clockwise direction; L4, L5, and L6 each have 10 turns, all in a clockwise direction.

9. The EMI filter according to claim 1, characterized in that, The filter circuit is mounted on the FR-4 circuit board and encapsulated in an aluminum alloy casing.

10. A non-isolated airborne charger, employing the EMI filter according to any one of claims 1-9, characterized in that, Includes a DC / DC converter, and port 1 of the EMI filter is connected to the positive terminal of the 28V DC power supply on the machine; Port 2 of the EMI filter is connected to the positive input of the DC / DC converter; The EMI filter's port 3 is connected to the negative terminal of the 28V DC power supply on the machine and the negative terminal of the battery pack. Port 4 of the EMI filter is connected to the negative terminal of the DC / DC converter; Port 5 of the EMI filter is connected to the positive terminal of the battery pack; Port 6 of the EMI filter is connected to the positive output of the DC / DC converter.

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