A direct current filter circuit resistant to conducted interference

Abstract

The utility model belongs to filter field discloses a kind of DC filter circuit of anti-conduction interference, including several capacitors and inductance;Capacitor C4 and capacitor C2 are connected in parallel to ground, and are connected with input voltage Vin;Capacitor C4 and capacitor C2 are connected in parallel, and capacitor C1 is connected in series, capacitor C1 and capacitor C10 are connected in parallel, and capacitor C1 and inductance L1 are connected in series.The utility model can reduce equipment power line conduction emission, simple structure, easy to realize.

Description

Technical Field

[0001] This utility model belongs to the field of filters, and in particular relates to a DC filter circuit that resists conducted interference. Background Technology

[0002] Intelligent detection equipment is a crucial subsystem of intelligent control systems, significantly impacting the system's target locking performance and penetration capabilities. It is a complex device integrating high-power microwave amplifiers, mid-to-high frequency linear electronic circuits, high-speed digital circuits, electronic and electrical control, and precision mechanics. Due to these characteristics, intelligent detection equipment exhibits the widest internal frequency spectrum, typically ranging from hundreds of kHz to tens of GHz. The power supply system design of the intelligent control system must consider operating environment and conditions, primarily employing thermal battery power to convert secondary power and provide power to the subsystems. Therefore, the secondary power supply configured on intelligent detection equipment is highly efficient, requires minimal space, and is relatively lightweight, providing favorable operating conditions. However, it utilizes a DC-DC switching power supply, which is prone to causing severe electromagnetic interference to the external environment. Utility Model Content

[0003] The technical problem this invention aims to solve is that the secondary power supply configured on intelligent detection equipment is prone to causing serious electromagnetic interference to the external environment.

[0004] To solve the above-mentioned technical problems, the specific technical solution of this utility model is as follows:

[0005] A DC filter circuit for resisting conducted interference includes several capacitors and inductors; capacitors C4 and C2 are connected in parallel to ground and connected to the input voltage Vin; capacitors C4 and C2 are connected in parallel and then in series with capacitor C1; capacitor C1 is connected in parallel with capacitor C10; capacitor C1 is connected in series with inductor L1; capacitors C5 and C175 are connected in parallel after inductor L1 and in parallel with inductor L2; capacitors C5 and C175 are connected in parallel and then in series with capacitor C174; capacitor C176 is connected in parallel with capacitor C174; capacitors C6, C7, and C8 are connected in parallel after L2.

[0006] This invention has the following advantages: it can reduce conducted emissions from the power line of the device, and its structure is simple and easy to implement. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of a DC filter circuit for resisting conducted interference.

[0008] Figure 2 Comparison chart of power line conducted emission test results for GJB151B-2013 / CE102 with added DC filter circuit. Detailed Implementation

[0009] To better understand the purpose, structure, and function of this utility model, a more detailed description of this utility model is provided below with reference to the accompanying drawings.

[0010] This design incorporates a filter circuit at the power port to suppress both differential-mode and common-mode interference. Differential-mode interference is typically suppressed using differential-mode inductors and capacitors. The principle is to use differential-mode devices to form a new low-impedance loop that returns the interference signal to the source. Common-mode interference is suppressed using common-mode inductors and capacitors. The principle is to use common-mode devices to form a low-impedance loop that ensures that interference signals inside the device are bypassed and discharged to the ground or chassis when passing through the power line.

[0011] First, the input voltage Vin undergoes initial filtering through two parallel 106 capacitors C4 and C2, which are grounded in parallel to reduce high-frequency noise in the input voltage. A 682 capacitor C1 is connected in series with inductor L1 to form a first-stage LC filter, further suppressing high-frequency interference. Two 682 capacitors C10 are connected in parallel with C1, enhancing the filtering effect of the first-stage LC filter. The second-stage filter consists of inductor L2 and a 682 capacitor C174, connected in series after the first-stage filter. To improve the filtering effect, two 682 capacitors C176 are connected in parallel with C174, sharing the filtering task. Two 106 capacitors C5 and C175 are connected in parallel after L1, providing additional filtering capability to the circuit. Finally, two 106 capacitors C6 and C7 are connected in parallel after L2, forming a third-stage filter. A 106 capacitor C8 is then connected in parallel with two capacitors C6 and C7, further enhancing the filtering effect. The entire filtering circuit has been optimized for electromagnetic compatibility. Through this series-parallel structure, the circuit can effectively filter out noise of different frequencies, ensure the stability of the output voltage, reduce electromagnetic interference, and improve the overall performance and reliability of the circuit.

[0012] For 26V DC power supply systems, the power supply switching frequency is mostly in the hundreds of kHz. For a filter to have good filtering characteristics, its cutoff frequency should be lower than the power supply's switching frequency. For LC filter circuits, the cutoff frequency is calculated using the formula: [formula omitted for brevity]. Where L is the inductance and C is the capacitance. Theoretically, the larger L and C are, the lower the cutoff frequency and the better the filter's filtering effect.

[0013] To address the issue of excessive conducted and radiated emissions in DC-DC converter circuits, a first-order filter circuit is used. A 2mH common-mode inductor is wound with a ferrite core (ferrite cores have high permeability and a wide frequency response range, providing excellent suppression of mid-to-high frequencies; non-ferrite cores have even higher permeability than ferrite cores, but their frequency response is mainly concentrated in the low-frequency range, offering excellent suppression of low-frequency interference). This inductor, along with a 6800pF common-mode capacitor, forms an LC common-mode filter circuit to absorb common-mode interference in the 0.1MHz–10MHz frequency range. The common-mode inductor generates a leakage current of tens of microhenries during operation. The common-mode inductor, which is equivalent to a differential-mode inductor, is combined with a 106 differential-mode capacitor to form an LC differential-mode filter circuit, absorbing differential-mode interference in the frequency range of 10kHz to 1MHz. The characteristic of this filter circuit is that it uses multiple common-mode capacitors and common-mode inductors to form a common-mode LC filter circuit, suppressing common-mode interference in different frequency bands; it also uses multiple differential-mode capacitors and common-mode inductors of different capacitance values ​​to generate leakage inductance, forming a differential-mode LC filter circuit to suppress differential-mode interference in different frequency bands. This ensures that the intelligent detection equipment meets the power line conducted emission CE102 test requirements specified in GJB151B. See the input EMI filter circuit for details. Figure 1 A comparison of the equipment before and after adding a DC filter can be found in [link to image]. Figure 2 The required components are shown in Table 1.

[0014] Table 1. MEI Filter Component Selection List

[0015] capacitor JCT41-1210-2R1-50V-106K 3 C6, C7, C8 +26V Inductor R10KH13×7×5J 2 L1, L2 DC-DC partial input filtering capacitor JCT41-1210-2R1-50V-106K 4 C2, C4, C5, C175 DC-DC partial input filtering capacitor JCT41-0805-2R1-500V-682M 4 C1, C10, C174, C176 Y capacitor

[0016] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and improvements without departing from the principles of the present invention, and these modifications and improvements should also be considered to fall within the protection scope of the present invention.

Claims

1. A DC filter circuit for resisting conducted interference, characterized in that, This includes several capacitors and inductors; capacitors C4 and C2 are connected in parallel to ground and connected to the input voltage Vin; capacitors C4 and C2 are connected in parallel and then in series with capacitor C1; capacitor C1 is connected in parallel with capacitor C10; capacitor C1 is connected in series with inductor L1; capacitors C5 and C175 are connected in parallel after inductor L1 and in parallel with inductor L2. Capacitors C5 and C175 are connected in parallel and then in series with capacitor C174. Capacitor C176 is connected in parallel with capacitor C174. Capacitors C6, C7, and C8 are connected in parallel after L2.

Images