Filter for aviation landing lamp

Abstract

The utility model provides a filter for an aviation landing lamp. The filter comprises a shell, a power characteristic circuit and a filter circuit, the power characteristic circuit is arranged in the shell; the filter circuit is arranged in the shell and connected with the power characteristic circuit, the filter circuit is composed of a multi-stage circuit structure of a power-on current suppression function circuit, a first-stage differential mode inductance filter and a first-stage common mode inductance filter, and the filter circuit comprises a first filter circuit and a second filter circuit; the first filter circuit comprises a cathode diode V1, a peak suppression diode V2, an insulated gate field effect transistor V4, resistors R1 to R4, inductors L1 to L3, capacitors C1 to C4 and capacitors C7 to C10; the second filter circuit comprises a common cathode diode V5, a diode V7, an insulated gate field effect transistor V8, resistors R5-R7, a capacitor C14, inductors L4-L6, capacitors C11-C13 and capacitors C17-C20. According to the embodiment of the invention, a circuit adopting a first-stage common-mode filter inductor and a first-stage differential-mode inductor for filtering is adopted, so that the problem of poor filtering effect of a filter for an aviation landing lamp in the prior art is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of filters, and in particular to a filter for aviation landing lights. Background Art

[0002] Aviation landing lights are important external lighting equipment for civil aircraft. They are used for landing at night or in low visibility conditions. Their main function is to provide sufficient lighting for pilots. Since aviation landing lights generate electromagnetic radiation when working, this radiation may interfere with other electronic equipment on the aircraft and affect their normal operation. In order to ensure electromagnetic compatibility, prevent mutual interference between equipment, and ensure that the signals emitted by the landing lights are clear and accurate, aviation landing lights need to be equipped with special filters. The filter can filter out electromagnetic noise and interference from the aircraft power system, protect the landing lights themselves and other electronic equipment from damage, and thus improve the safety and reliability of the entire aviation system. Utility Model Content

[0003] The main purpose of the utility model is to provide a filter for aviation landing lights, so as to at least solve the problem of poor filtering effect of the filters for aviation landing lights in the prior art.

[0004] In order to achieve the above-mentioned object, the utility model provides a filter for aviation landing lights, comprising: a housing, a power characteristic circuit and a filter circuit; the power characteristic circuit is arranged in the housing; the filter circuit is arranged in the housing and connected to the power characteristic circuit, the filter circuit is a multi-stage circuit structure composed of a power-on current suppression function circuit, a first-level differential mode inductor filter and a first-level common mode inductor filter, and the filter circuit comprises a first filter circuit and a second filter circuit;

[0005] The first filter circuit includes a common cathode diode V1, a spike suppression diode V2, an insulated gate field effect transistor V4, a current limiting resistor R1, a resistor R2, a resistor R3, a current limiting resistor R4, a capacitor C4, a differential mode inductor L1 and a differential mode inductor L3 and a differential mode capacitor C1, a differential mode capacitor C2 and a differential mode capacitor C3 together form a first differential mode filter circuit, and a common mode capacitor C7, a common mode capacitor C8, a common mode capacitor C9 and a common mode capacitor C10 and a common mode inductor L2 together form a first common mode filter circuit; the power supply signals X1-A and X1-C of the first filter circuit enter the current limiting resistor R1, the resistor R3, the insulated gate field effect transistor V4 and the capacitor C4 for power-on current suppression, and then are sent to the first differential mode filter circuit and the first common mode filter circuit; the spike suppression diode V2 suppresses the spike voltage input from the external power supply, and the resistor R2 serves to discharge after the power supply is cut off;

[0006] The second filter circuit includes a common cathode diode V5, a diode V7, an insulated gate field effect transistor V8, a current limiting resistor R5, a resistor R6, a resistor R7, a capacitor C14, a differential mode inductor L4 and a differential mode inductor L6 and a differential mode capacitor C11, a differential mode capacitor C12 and a differential mode capacitor C13 together form a second differential mode filter circuit; common mode capacitors C17, C18, C19 and C20 and a common mode inductor L5 together form a second common mode filter circuit; power supply signals X2-A and X2-C of the second filter circuit enter the current limiting resistor R5, the resistor R7, the insulated gate field effect transistor V8 and the capacitor C14 for power-on current suppression, and then are sent to the second differential mode filter circuit and the second common mode filter circuit; the spike suppression diode V6 suppresses the spike voltage input by the external power supply, and the resistor R6 serves to discharge after the power is cut off.

[0007] Furthermore, the filter for aviation landing lights also includes: a printed circuit board, which is arranged in the housing and is used to fix the welding power supply characteristic circuit and the filter circuit.

[0008] Furthermore, the inside of the shell adopts a printed circuit board assembly method; the shell thickness is greater than 0.5mm; the shell is made of 6061T6 aluminum alloy; and the surface of the shell is subjected to conductive oxidation treatment.

[0009] Furthermore, the differential mode capacitors C1 to C3 and C11 to C13 adopt CT41-2220-2C1-100V-106M and CT41-1210-2R1-100V-105K; the common mode capacitors C5 to C10 and C15 to C20 adopt CT41-1210-2R1-500V-104K and CT41-1210-2R1-500V-103K.

[0010] Furthermore, the differential mode inductors L1, L3, L4, and L6 adopt AI16 / 6 / 2.65, and the inductance value is more than 400uH; the common mode inductor L2 and the common mode inductor L5 adopt FU16 / 9 / 2.65, and the inductance value is more than 6mH.

[0011] A filter for an aviation landing light of the utility model technical solution comprises: a housing, a power characteristic circuit and a filter circuit; the power characteristic circuit is arranged in the housing; the filter circuit is arranged in the housing and connected to the power characteristic circuit, the filter circuit is a multi-stage circuit structure composed of a power-on current suppression function circuit, a first-level differential mode inductor filter and a first-level common mode inductor filter, and the filter circuit comprises a first filter circuit and a second filter circuit;

[0012] The first filter circuit includes a common cathode diode V1, a spike suppression diode V2, an insulated gate field effect transistor V4, a current limiting resistor R1, a resistor R2, a resistor R3, a current limiting resistor R4, a capacitor C4, a differential mode inductor L1 and a differential mode inductor L3 and a differential mode capacitor C1, a differential mode capacitor C2 and a differential mode capacitor C3 together form a first differential mode filter circuit, and a common mode capacitor C7, a common mode capacitor C8, a common mode capacitor C9 and a common mode capacitor C10 and a common mode inductor L2 together form a first common mode filter circuit; the power supply signals X1-A and X1-C of the first filter circuit enter the current limiting resistor R1, the resistor R3, the insulated gate field effect transistor V4 and the capacitor C4 for power-on current suppression, and then are sent to the first differential mode filter circuit and the first common mode filter circuit; the spike suppression diode V2 suppresses the spike voltage input from the external power supply, and the resistor R2 serves to discharge after the power supply is cut off;

[0013] The second filter circuit includes a common cathode diode V5, a diode V7, an insulated gate field effect transistor V8, a current limiting resistor R5, a resistor R6, a resistor R7, a capacitor C14, a differential mode inductor L4 and a differential mode inductor L6 and a differential mode capacitor C11, a differential mode capacitor C12 and a differential mode capacitor C13 together form a second differential mode filter circuit; common mode capacitors C17, C18, C19 and C20 and a common mode inductor L5 together form a second common mode filter circuit; power supply signals X2-A and X2-C of the second filter circuit enter the current limiting resistor R5, the resistor R7, the insulated gate field effect transistor V8 and the capacitor C14 for power-on current suppression, and then are sent to the second differential mode filter circuit and the second common mode filter circuit; the spike suppression diode V6 suppresses the spike voltage input by the external power supply, and the resistor R6 serves to discharge after the power is cut off. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings constituting part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0015] Figure 1 It is a circuit principle block diagram of a filter for aviation landing lights that can be selected according to an embodiment of the utility model;

[0016] Figure 2 This is a circuit diagram of a filter for aviation landing lights that can be selected according to the embodiment of the utility model.

[0017] Figure 3 This is a circuit schematic diagram before adding a filter circuit of a filter for aviation landing lights that can be selected according to an embodiment of the utility model

[0018] Figure 4This is a circuit schematic diagram after adding a filter circuit of a filter for aviation landing lights according to an embodiment of the utility model.

[0019] Figure 5 This is a circuit schematic diagram of an equivalent filtering circuit of a common mode filtering circuit of a filter for aviation landing lights that can be selected according to an embodiment of the utility model.

[0020] Figure 6 This is a circuit schematic diagram of an equivalent filter of a differential mode filter circuit of a filter for aviation landing lights that can be selected according to an embodiment of the utility model.

[0021] Figure 7 It is a circuit principle diagram of an optional filter for aviation landing lights with an energy storage capacitor installed according to an embodiment of the utility model;

[0022] Figure 8 It is a shielding principle diagram of a housing of a filter for an aviation landing light that can be selected according to an embodiment of the utility model;

[0023] Fig. 9 The present invention is a circuit schematic diagram of capacitor series equivalent of a filter for aviation landing lights that can be selected according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present utility model will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] An embodiment of the utility model provides a filter for an aviation landing light, such as Figure 1 and Figure 2 As shown, it includes: a housing, a power characteristic circuit and a filter circuit; the power characteristic circuit is arranged in the housing; the filter circuit is arranged in the housing and connected to the power characteristic circuit, the filter circuit is a multi-stage circuit structure composed of a power-on current suppression function circuit, a first-level differential mode inductor filter and a first-level common mode inductor filter, and the filter circuit includes a first filter circuit and a second filter circuit;

[0026] The first filter circuit includes a common cathode diode V1, a spike suppression diode V2, an insulated gate field effect transistor V4, a current limiting resistor R1, a resistor R2, a resistor R3, a current limiting resistor R4, a capacitor C4, a differential mode inductor L1 and a differential mode inductor L3 and a differential mode capacitor C1, a differential mode capacitor C2 and a differential mode capacitor C3 together form a first differential mode filter circuit, and a common mode capacitor C7, a common mode capacitor C8, a common mode capacitor C9 and a common mode capacitor C10 and a common mode inductor L2 together form a first common mode filter circuit; the power supply signals X1-A and X1-C of the first filter circuit enter the current limiting resistor R1, the resistor R3, the insulated gate field effect transistor V4 and the capacitor C4 for power-on current suppression, and then are sent to the first differential mode filter circuit and the first common mode filter circuit; the spike suppression diode V2 suppresses the spike voltage input from the external power supply, and the resistor R2 serves to discharge after the power supply is cut off;

[0027] The second filter circuit includes a common cathode diode V5, a diode V7, an insulated gate field effect transistor V8, a current limiting resistor R5, a resistor R6, a resistor R7, a capacitor C14, a differential mode inductor L4 and a differential mode inductor L6 and a differential mode capacitor C11, a differential mode capacitor C12 and a differential mode capacitor C13 together form a second differential mode filter circuit; common mode capacitors C17, C18, C19 and C20 and a common mode inductor L5 together form a second common mode filter circuit; power supply signals X2-A and X2-C of the second filter circuit enter the current limiting resistor R5, the resistor R7, the insulated gate field effect transistor V8 and the capacitor C14 for power-on current suppression, and then are sent to the second differential mode filter circuit and the second common mode filter circuit; the spike suppression diode V6 suppresses the spike voltage input by the external power supply, and the resistor R6 serves to discharge after the power is cut off.

[0028] In this embodiment, X1-A and X1-C are 28V+ inputs, and are isolated by a common cathode diode V1, which plays the role of anti-reverse and dual power backup power supply. R1 is connected to the positive end of the input 28V power supply, and the other end of R1 and R3 divide the voltage to supply power to the gate of MOSFET (V4). When the product is powered on, R1 charges C4. At this time, V4 is disconnected because the gate voltage has not reached the turn-on voltage. At this time, the power supply supplies power to the product through the R4 current limiting resistor, and V3 serves the purpose of protecting V4. Inductors L1 and L3 and capacitors C1, C2 and C3 together form a differential mode filter circuit to filter out the low-frequency interference of the product; C7, C8, C9 and C10 and inductor L2 together form a common mode filter circuit to filter out the high-frequency interference of the product. V2 is a spike suppression diode that suppresses the spike voltage of the external power input, and R2 serves to discharge after the power is cut off;

[0029] X2-A and X2-C are 28V+ inputs, which are isolated by the common cathode diode V5 to prevent reverse and provide dual power backup. R5 is connected to the positive end of the 28V input power supply, and the other end of R5 and R7 divide the voltage to supply power to the gate of the MOSFET (V8). When the product is powered on, R5 charges C14. At this time, V8 is disconnected because the gate voltage has not reached the turn-on voltage. At this time, the power supply supplies power to the product through the R8 current limiting resistor, and V7 serves to protect V8. Inductors L4 and L6 and capacitors C11, C12 and C13 together form a differential mode filter circuit to filter out the low-frequency interference of the product; C17, C18, C19 and C20 and inductor L5 together form a common mode filter circuit to filter out the high-frequency interference of the product. V6 is a spike suppression diode to suppress the spike voltage of the external power input, and R6 serves to discharge after the power is cut off;

[0030] The remaining signal interference is mainly common-mode interference, so common-mode filter capacitors are mainly used to filter out the interference of the remaining signals.

[0031] This embodiment is a 28V DC power supply, which is powered by the power supply after filtering. The main interference generated inside the product is generated by the motor load, and the main sources are: DC-DC power conversion module, interference generated by CPU operation, motor drive, motor pole pair number and electrical drive current. By analyzing that there are both differential mode interference and common mode interference in the power supply, both differential mode filtering and common mode filtering should be considered in the filter design. Therefore, the filter circuit is designed based on electromagnetic compatibility and power supply characteristics, and is composed of a multi-stage circuit structure, so that the filter for aviation landing lights has a higher insertion loss within a wide bandwidth. As an optimization scheme of the utility model, because there are both differential mode interference and common mode interference in the power supply, the filter circuit adopts a circuit of a combination of a first-level common mode filter inductor and a first-level differential mode inductor. Because most common mode interference frequencies are concentrated in the high frequency band, the lightning protection device is installed at the front end of the filter input, so as to avoid the problem of excessive conduction and emission of the product power line through spatial coupling after filtering out high frequency interference too early. Because the product also has other 28V signals and there is a lot of common-mode interference on the signal line, the filtering of other signals is carried out by using common-mode capacitors.

[0032] Preferably, the common cathode diodes V1 and V5 are 2DK 20200T (common cathode), with a reverse withstand voltage of 200 V and a rated current of 20 A. This type of diode not only solves the problem of redundant power supply and parallel connection of the product, but also solves the problem of reverse polarity of power supply.

[0033] As an optimization scheme of this embodiment, the insertion loss of the filter is used to describe the filter's ability to suppress interference noise, and is defined as: the ratio of the power transmitted from the noise source to the load before the filter is connected to the power transmitted from the noise source to the load after the filter is connected, expressed in dB (decibel). The circuit diagram before and after the filter is connected is shown in Figure 3 , Figure 4 As shown, the equivalent circuit of common mode filtering is shown in Figure 5 As shown, the equivalent circuit of differential mode filtering is shown in Figure 6 shown.

[0034] The insertion loss of the filter is:

[0035] IL=20lg(U1 / U2), where IL is the insertion loss, U1 is the output signal, and U2 is the input signal.

[0036] in:

[0037] U1'=a11U2+a12I2 I1=a21U2+a22I2

[0038] U1'=U0-I1Rs U2=I2RL

[0039] U2=U0 / (a11+a12RL+a21Rs+a22RsRL)

[0040] Substituting the insertion loss calculation formula yields:

[0041] IL=20lg|(a11 RL+a12+a21Rs RL+a22Rs) / (Rs+RL)|

[0042] Among them: a11, a12, a21, a22 are the parameters of the filter network.

[0043] The expression for differential mode insertion loss is:

[0044] ILCM=10log((1-ω2LC)2+((ωL+(2ω2-ω3LC2)RL Rs) / RL+Rs)2)

[0045] The expression for common mode insertion loss is:

[0046] ILGM=10log((1-ω2LC / (1+Rs / RL))2+((ωL+(ωL+ωC RL Rs) / (RL+Rs))2)

[0047] According to the formulas of common-mode insertion loss and differential-mode insertion loss, it can be seen that the insertion loss will be affected by the input impedance Rs and the load impedance RL.

[0048] The functional relationship between the input impedance Rs and the load impedance RL is established as follows:

[0049] f(Rs, RL)=((RLω2LC2)+(ωL)2) / ((Rs+RL)2)

[0050] It can be seen that: when f(Rs, RL) takes the minimum value, ILGM reaches the minimum value. When RL remains unchanged and Rs takes the maximum value, f(Rs, RL) takes the minimum value. Therefore, when calculating the insertion loss, Rs, RL and the cut-off frequency are the key to the insertion loss calculation. According to the technical requirements, the load current is 6A, according to the cut-off frequency of 100kHz, the input impedance Rs is approximately 0.2Ω, the insertion loss is calculated, and the inductance and capacitance parameters in the electromagnetic compatibility protection are approximately calculated. According to the calculation, the common mode inductance is about 6mH or more, the differential mode inductance is about 200μH or more, and the differential mode capacitance is 10uf or more; the common mode capacitance is 0.2uf or more.

[0051] As an optimization solution of the utility model, Figure 7 As shown, an energy storage module can be added to the front end of the filter circuit and the switching power supply DC-DC module to perform a power line conduction sensitivity test. In specific implementation, the energy storage module can use an energy storage capacitor, and the selection formula is the calculation formula between the energy storage capacitor capacitance required to filter out the interference signal and the frequency: f0 = 1 / (2πRSC); It can be seen from the formula that the lower the frequency to be filtered, the larger the capacitance of the energy storage capacitor needs to be; during the test, a sinusoidal interference signal is injected into the external power supply line, and a 25Hz~50kHz sensitive signal is applied to the input DC28V power line. According to the applied pulsating frequency, it can be seen that the lowest applied frequency is 25Hz, and the power line resistance is approximately calculated as 0.2Ω, and the required capacitance is: 37861uF.

[0052] Preferably, when the maximum interference is applied to the power line, the input is stabilized by the power module and the supporting capacitor, and the motor is insensitive to this type of fluctuation and will not cause abnormalities. Therefore, this embodiment does not require the addition of a special energy storage capacitor.

[0053] Furthermore, the filter for aviation landing lights also includes: a printed circuit board, which is arranged in the housing, and the printed circuit board is used to fix the welding power characteristic circuit and the filter circuit. All components are welded on the printed circuit board, and then the printed circuit board is fixed to the housing with screws to ensure the product's ability to resist vibration, impact and acceleration; after the printed circuit board is produced, the surface is sprayed with insulating paint to increase the insulation of the product; before all screws are installed, thread fastening glue is applied to the threads; in order to ensure the product's ability to resist vibration, impact and acceleration, the product is potted with thermal conductive insulating glue after installation.

[0054] Furthermore, the inside of the shell adopts a printed circuit board assembly method; the shell thickness is greater than 0.5mm; the shell is made of 6061T6 aluminum alloy; the shell surface is subjected to conductive oxidation treatment. Secondly, the mounting flange surface and the electrical connector mounting surface are polished to ensure that the surface roughness is below Ra1.6, so that the lap resistance can fully meet the requirements. The connecting fasteners are made of stainless steel 1Cr18Ni9Ti material, and the inner surface of the shell is subjected to conductive oxidation treatment.

[0055] As an optimization solution of the utility model, the filter adopts a shielding shell structure, and the shielding schematic diagram is shown in FIG. Figure 8 shown.

[0056] Definition of Shielding Effectiveness (SE):

[0057] Electric field shielding effectiveness SEE = 20lg (1 / TE) = 20lg | electric field before shielding / electric field after shielding |;

[0058] Magnetic field shielding effectiveness SEH = 20lg (1 / TH) = 20lg | magnetic field before shielding / magnetic field after shielding |;

[0059] The better the conductivity and magnetic permeability of a material, the higher the shielding effectiveness, but it is impossible for actual metal materials to take both aspects into account.

[0060] The shielding effect formula of metal plate is:

[0061] SE = A + R + B;

[0062] Among them, A is the absorption loss; R is the reflection loss; and B is the multiple reflection correction factor.

[0063] Absorption loss A = 8.98σt≈0.131sqr(fμrσr);

[0064] Among them, t is the thickness of the metal plate; f is the frequency of the electromagnetic wave; μr is the magnetic permeability of the metal material; σr is the electrical conductivity of the metal material.

[0065] The product adopts aluminum alloy structure design. The shielding effect is closely related to the conductivity of aluminum alloy. The conductivity of aluminum is 3.82×107s / m.

[0066] The calculation formula for the reflection loss of the metal plate is simplified to:

[0067] R=ZW / 4ZS

[0068] Where R is the reflection loss; ZW is the wave impedance of air; ZS is the wave impedance of the metal plate;

[0069] Therefore, the wave impedance of the aluminum plate is:

[0070] ZS=3.82×107×sqr(f)×μr×σr

[0071] Through analysis and calculation: 0.5mm thick aluminum metal plate, the absorption loss of 30MHz electromagnetic waves can reach 291dB, so the thickness of the filter shell only needs to be greater than 0.5mm. The filter shell adopts 1mm thick aluminum plate, and the printed circuit board assembly method is adopted inside. The components are welded to the printed circuit board, and finally fixed to the inside of the metal shell with fasteners. The entire product structure adopts the overall milling processing method, which greatly increases the shielding effectiveness of the whole machine, greatly blocks the internal interference signal from radiating outward, and can also effectively block the external interference signal from interfering with the product itself. Solutions for connector and product gaps: Since the top cover and the product shell are hard connections between metal and metal, they cannot completely seal the electromagnetic effect. The electrical connector uses conductive rubber for electromagnetic sealing.

[0072] Furthermore, the differential mode capacitors C1 to C3 and C11 to C13 adopt CT41-2220-2C1-100V-106M and CT41-1210-2R1-100V-105K; the common mode capacitors C5 to C10 and C15 to C20 adopt CT41-1210-2R1-500V-104K and CT41-1210-2R1-500V-103K.

[0073] As an optimization solution of the utility model, a 0.1uf filter capacitor can be selected based on previous experience. The series equivalent circuit of the filter capacitor is as follows: Fig. 9 As shown in the figure, ESR is the series equivalent resistance of the capacitor, ESL is the series equivalent inductance of the capacitor, and C is the real ideal capacitor. However, ESR and ESL are determined by the manufacturing process and materials of the capacitor and cannot be eliminated. ESR affects the signal disturbance ripple, and ESL affects the filtering frequency characteristics of the capacitor.

[0074] Capacitor reactance Zc=1 / ωC;

[0075] In the signal transmission loop, the transmission wire can be considered to have a certain inductance effect, so the inductive reactance of the wire is:

[0076] Z1=ωL;where ω=2πf;

[0077] Therefore, the complex impedance of the capacitor in actual use is:

[0078] Z=ESR+jωL-1 / jωC=ESR+j2πfL-1 / j2πfC.

[0079] It can be seen that when the frequency is very low, the capacitor plays a role, but when the frequency reaches a certain level, the role of the inductor cannot be ignored, and when the frequency is higher, the inductor plays a dominant role. After analysis and calculation, a 0.1uf capacitor can have a good filtering effect on the frequency range of 10KHz to 10MHz.

[0080] In the specific implementation, two types of capacitors are mainly used in the filter circuit, namely common mode capacitors and differential mode capacitors. Due to the technical requirements of power supply EMI filtering, its low-pass cutoff frequency is 10KHz. Considering the design margin and the transition characteristics of the cutoff curve of the passive LC low-pass network, the cutoff frequency is selected as fCN≈3~5kHz. For the π-type low-pass filter network, if the inductor L has been selected, the capacitor C is determined by the following formula:

[0081] Ccn=1 / ((2πfcm)2×Lcm)

[0082] a) When selecting differential mode capacitors, a comprehensive analysis is mainly conducted on the line withstand voltage, filter space, etc. The larger the filter capacitor added between the lines, the more beneficial it is to the differential mode interference filtering of the power supply. Therefore, a larger capacitor is selected under the premise that the filter volume, weight and temperature coefficient are satisfied. The power supply voltage of this embodiment is 28V. Considering the principle of capacitor derating, the selected capacitor withstand voltage value is 100V. The capacitor models are: CT41-2220-2C1-100V-106M and CT41-1210-2R1-100V-105K. The CT41 series capacitors are multilayer ceramic capacitors with broadband characteristics, low rate of change of capacitance with temperature, and an operating temperature of -55℃~125℃.

[0083] b) When selecting common-mode capacitors, considering common-mode interference and the principle of device derating, the rated working voltage of the selected capacitor is 500V. The common-mode capacitors selected are: CT41-1210-2R1-500V-104K and CT41-1210-2R1-500V-103K. This capacitor is a multilayer ceramic capacitor like the differential mode capacitor, with broadband characteristics, low rate of change of capacitance with temperature, and an operating temperature of -55℃~125℃.

[0084] c) 422 high-frequency communication is 100kHz, and the low-speed transmission frequency is 12.5kHz. To prevent waveform distortion, the common-mode capacitor is selected as: CT41-1206-X7R-500V-471K. This capacitor has wide-band characteristics, a low rate of change of capacity with temperature, and an operating temperature of -55℃~125℃.

[0085] Furthermore, the differential mode inductors L1, L3, L4, and L6 adopt AI16 / 6 / 2.65, and the inductance value is more than 400uH; the common mode inductor L2 and the common mode inductor L5 adopt FU16 / 9 / 2.65, and the inductance value is more than 6mH.

[0086] As an optimization scheme of the utility model, the inductor coil is wound with a magnetic ring made of a small and efficient ultra-fine crystal material as the skeleton, and its inductance can be determined by the following formula: L = ((0.4πμN2Ae) / Le)×10-8 (Henry), where μ is the magnetic permeability; N is the number of turns; Ae is the effective cross-sectional area of ​​the magnetic core; Le is the effective cross-sectional area of ​​the magnetic circuit; L value can also be calculated by the following formula when the inductance coefficient AL is known: L = AL×N2L is the inductance; AL is the inductance coefficient; N is the number of turns;

[0087] In the specific implementation, the inductor is wound with a magnetic ring made of ultra-fine crystal material as the skeleton. The ultra-fine crystal material magnetic ring has high magnetic flux density and high magnetic permeability (μi>60000), and has a high AL value. The required mH level inductance can be wound on a smaller magnetic ring, which is particularly conducive to miniaturization. The ultra-fine crystal magnetic ring also has a very high Curie temperature of 580℃, which makes it have excellent temperature characteristics and can maintain stable performance within the temperature range of (-70~350)℃. Its high magnetic saturation induction improves the ability to resist strong electric pulse interference, and its excellent comprehensive magneto-electric characteristics such as very low iron loss greatly improve its low-end insertion loss of 10kHz~150kHz, making it particularly suitable for use in occasions with extremely high requirements.

[0088] Preferably, according to the analysis, the selected inductor model is:

[0089] The power supply end 6A common mode inductor FU16 / 9 / 2.65 has a diameter of 1.04 and a single wire of 2*22 turns, and the inductance value is above 6mH.

[0090] The power supply end 6A differential mode inductor AI16 / 6 / 2.65 has a diameter of 1.04 and a single wire with 40 turns, and the inductance value is above 400uH.

[0091] A filter for aviation landing lights in one embodiment of the utility model can absorb electromagnetic interference and prevent interference from entering and exiting the product. In order to ensure that the insertion loss meets the technical requirements in the full frequency band of 10KHz-10MHz, a two-stage π-shaped low-pass combination network is adopted. The multi-stage cascade circuit can not only improve the insertion loss, but also make the input and output capacitance values ​​of the cascade circuit relatively small. The multi-stage cascade network presents a high input impedance, which meets the adaptation requirements of the power supply end. Since the conducted interference can be decomposed into common-mode interference and differential-mode interference, in order to effectively suppress the two types of common-mode and differential-mode interference, the filter circuit uses a three-phase balanced common-mode circuit and a differential-mode circuit cascade. This embodiment has the characteristics of miniaturization, high performance, and stable operation. The reliability prediction model of the filter for aviation landing lights is shown below.

[0092] a) Capacitor

[0093] The parameters and failure model of the capacitor are selected according to the formula: λp=λbπEπQπCVπch.

[0094] Among them, λb is the basic failure rate: taken as 0.00285; πE is the environmental factor: taken as 4.6; πQ is the quality factor: taken as 0.3; πCV is the capacitance factor: taken as 2.4; πch is the surface mount factor: taken as 1.5.

[0095] b)TVS diode

[0096] The parameters and failure model of the diode are selected according to the formula: λp=λbπEπQπK.

[0097] Among them, λb is the basic failure rate: taken as 0.236; πE is the environmental coefficient: taken as 6; πQ is the quality coefficient: taken as 0.2; πK is the type coefficient: taken as 1.0.

[0098] c) Inductance

[0099] The parameters and failure model of the diode are selected according to the formula: λp=λbπEπQπKπC.

[0100] Among them, λb is the working failure rate: 0.0058*10-6 / h; πE is the environmental coefficient: take 10; πQ is the quality coefficient: take 1; πK is the type coefficient: take 1; πC is the structural coefficient: take 1.

[0101] d) Connector failure rate model

[0102] Using the parameters and failure model provided by GJB / Z 299C, see the formula:

[0103] λp=λbπEπQπPπKπC.

[0104] Among them, λb is the basic failure rate: 0.0096; πE is the environmental coefficient: 3.0; πQ is the quality coefficient: 0.2; πP is the contact coefficient: 9.5; πK is the plug-in coefficient: 2.0; πC is the socket structure coefficient: 0.3.

[0105] e) Solder joint failure rate model

[0106] Using the parameters and failure model provided by GJB / Z 299C, see the formula:

[0107] λp6=λbπEπQ.

[0108] Among them, λb is the basic failure rate: λb1 is taken as 0.000092*10-6 / h; πE is the environmental factor: taken as 8; πQ is the quality factor: taken as 1.

[0109] In summary, the reliability of the filter for aviation landing lights in this embodiment is: 523321.5h.

[0110] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A filter for aviation landing lights, It is characterized in that include: shell; a power characteristic circuit, the power characteristic circuit being arranged in the housing; Filter circuit; The filter circuit is arranged in the housing and connected to the power characteristic circuit. The filter circuit is composed of a multi-stage circuit structure of a power-on current suppression function circuit, a first-stage differential mode inductor filter, and a first-stage common mode inductor filter. The filter circuit includes a first filter circuit and a second filter circuit; The first filter circuit includes a common cathode diode V1, a spike suppression diode V2, an insulated gate field effect transistor V4, a current limiting resistor R1, a resistor R2, a resistor R3, a current limiting resistor R4, a capacitor C4, a differential mode inductor L1 and a differential mode inductor L3 and a differential mode capacitor C1, a differential mode capacitor C2 and a differential mode capacitor C3 together to form a first differential mode filter circuit, and a common mode capacitor C7, a common mode capacitor C8, a common mode capacitor C9 and a common mode capacitor C10 and a common mode inductor L2 together to form a first common mode filter circuit; the power supply signals X1-A and X1-C of the first filter circuit enter the current limiting resistor R1, the resistor R3, the insulated gate field effect transistor V4 and the capacitor C4 for power-on current suppression, and then are sent to the first differential mode filter circuit and the first common mode filter circuit; The spike suppression diode V2 suppresses the spike voltage of the external power input, and the resistor R2 discharges it after the power is cut off; The second filtering circuit includes a common cathode diode V5, a diode V7, an insulated gate field effect transistor V8, a current limiting resistor R5, a resistor R6, a resistor R7, a capacitor C14, a differential mode inductor L4 and a differential mode inductor L6 and a differential mode capacitor C11, a differential mode capacitor C12 and a differential mode capacitor C13 together constitute a second differential mode filtering circuit; common mode capacitors C17, C18, C19 and C20 and a common mode inductor L5 together constitute a second common mode filtering circuit; the power supply signals X2-A and X2-C of the second filtering circuit enter the current limiting resistor R5, the resistor R7, the insulated gate field effect transistor V8 and the capacitor C14 for power-on current suppression, and are then sent to the second differential mode filtering circuit and the second common mode filtering circuit; the peak suppression diode V6 suppresses the peak voltage of the external power input, and the resistor R6 serves to discharge after the power is cut off.

2. The filter for aviation landing lights according to claim 1, It is characterized in that The filter for the aviation landing light also includes: A printed circuit board is arranged in the housing and is used for fixing and welding the power characteristic circuit and the filter circuit.

3. The filter for aviation landing lights according to claim 1, It is characterized in that The inside of the shell is assembled by a printed circuit board; the thickness of the shell is greater than 0.5 mm; the shell is made of 6061T6 aluminum alloy; and the surface of the shell is subjected to conductive oxidation treatment.

4. The filter for aviation landing lights according to claim 1, It is characterized in that Differential mode capacitors C1~C3, C11~C13 use CT41-2220-2C1-100V-106M and CT41-1210-2R1-100V-105K; Common-mode capacitors C5~C10, C15~C20 use CT41-1210-2R1-500V-104K and CT41-1210-2R1-500V-103K.

5. The filter for aviation landing lights according to claim 1, It is characterized in that Differential mode inductors L1, L3, L4, and L6 use AI16 / 6 / 2.65, with an inductance value of more than 400uH; Common-mode inductor L2 and common-mode inductor L5 use FU16 / 9 / 2.65, and the inductance value is more than 6mH.

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