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High-frequency Filtering of DC Power Lines

High-frequency Filtering of DC Power Lines. Technical, constructional and practical issues with filtering on dc power lines Wolfgang L. Klampfer Manager Training Center. Contents. EMC issues for base stations Filtering at high frequencies Contacting under high load Conventional solutions

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High-frequency Filtering of DC Power Lines

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  1. High-frequency Filtering of DC Power Lines Technical, constructional and practical issues with filtering on dc power lines Wolfgang L. KlampferManager Training Center

  2. Contents EMC issues for base stations Filtering at high frequencies Contacting under high load Conventional solutions A new approach

  3. Basestations and EMC Standard requirements in Europe Noise sources and distribution

  4. Requirements for Base Stations Radio Interface Enclosure Antenna DC Supply AC Mains Other lines

  5. Requirements for Base Stations Radio Interface • Emission • EN 55022CISPR 16-1 • Immunity • EN 61000-4-4 • EN 61000-4-6 Enclosure Antenna DC Supply AC Mains Other lines

  6. Conducted Emission according to EN 55022, CISPR 16-1 Supply EUT DC LISN PE EMI Receiver

  7. Differential mode noise L N PE L R

  8. ESL ESR Parasitic components as cause for differential mode noise

  9. Current through ESL and ESR “Lower” frequencies Switching frequency and harmonics Loop structures ESL ESR Characteristics for differential mode noise

  10. Common mode noise L N PE L R

  11. ICM ~ = Insulation as cause for common mode noise

  12. Usually high frequency problems, e.g. switching/oscillating at higher frequencies Affected by circuit layout, e.g. heat sinks Cables Characteristics of common mode noise

  13. Perfectly balanced only differential mode no radiation Slight unbalance differential to common mode conversion conducted and radiated noise at high frequencies Differential to common mode conversion

  14. Filtering at high frequencies Problems with resonances and solutions Special filter requirements for base stations

  15. Two metal plates, separated by insulation Often realised by 2 metallized plastic foils Wire wound to a coil Usually winding is placed on magnetic material (core) Capacitors and chokes for noise suppression

  16. Frequency response of capacitors and chokes

  17. L ~ Load ~ Load AC mains path RF path Use of capacitors and chokes in circuits C

  18. Resonances of capacitors and chokes Inductors can have significant capacitance between windings Connection leads of capacitors work like small series inductances

  19. Frequency response of feedthrough capacitors

  20. Special Requirements: Customized power requirements Mixed AC and DC configurations Environmental stress High attenuation Special enclosure forms Filters for Base Stations AC Mains

  21. 20A L1 L2 GND Filter Circuit 20A 60A L1 L2 GND 20A L1 L2 GND 60A Load Line 20A 20A L1 L2 GND 20A Power Layout

  22. Environmental Requirements Corrosion resistance Thermal shock Vibration Impact resistance Transportation shock and vibration Earthquakes

  23. Attenuation Requirements • Insertion Loss, Line to GND, 50W 1.0 MHz – 5.0 MHz ³ 20 dB 5.0 MHz – 10.0 MHz ³ 30 dB 10.0 MHz – 30.0 MHz ³ 40 dB 30.0 MHz – 4.0 GHz ³ 40 dB

  24. Contacting at high loads Special issues and requirements for contacts

  25. Requirements for dc power connections • Reliable contact • Easy connect/disconnect • Low contact resistance • High number of connect-disconnect cycles • Hot-pluggable

  26. Potential threats and problems • Reliable contact • Force of contacts over time • Easy connect/disconnect • Installation/maintenance time • Low contact resistance • Risk of overheating • High number of connect-disconnect cycles • Wear-out of contact surface • Hot-pluggable • Arcing between male and female connector; destruction of contacts

  27. Specialties about a proper contact Fixed beams Surround spring (Activates only cantilevered beams) Cantilevered beams Crimp barrel

  28. Function of the surround spring Male pin engaging fixed beams – hot plug surface Male pin engaging cantilevered beams • assists cantilevered beams at operating temperatures > 80 °C • provides high mechanical shock/vibration stability with no contact bounce

  29. Function of the beams • Fixed beams • provide mechanical guidance • thermal conductivity • sacrificial hot plug / hot swap location • Cantilevered beams • low contact resistance • low current density • optimum insertion force

  30. Contact material selection for power connectors • High conductivity copper = low temperature rise • Good manufacturing process • Copper with good spring properties at contact interface = normal force • Copper with good formability for crimping to finely stranded copper conductors

  31. Conventional solution Standard approach for dc filtering and connecting

  32. Traditional installation until today DC Power to Filter Filter to Bus Bar

  33. Some considerations for the conventional solution • 8 parts with 10 (!) connection points • Necessary extra provisions for capacitor grounding • Overall attenuation relies on quality of connection • Work- and cost-intensive installation • Many connections means many potential failure sources

  34. Relation between attenuation and earth resistance

  35. A new approach Advanced filtering and contacting solution

  36. Requirements for a contacting-filtering solution • Easy connect and disconnect under full-load • Easy and quick installation • Reduced number of connection points • Reliable filtering up to several GHz • Protection against reverse polarity • Protection against wrong connections in case of several power lines

  37. The solution: ACARA • 2 parts with 2 connection points • High-quality contacts for connection and disconnection under full-load • Time/cost/space saving solution

  38. Frequency response of ACARA

  39. Reverse polarity protection and code keying Pins for keying of connector pairs 6 positions for keying pins Protection against reverse polarity

  40. Thank you very much for your attention Any questions?

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