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Progress on DC/DC Converters Prototypes

Progress on DC/DC Converters Prototypes. B.Allongue 1 , G.Blanchot 1 , F.Faccio 1 , C.Fuentes 1,3 , S.Michelis 1,2 , S.Orlandi 1 , 1 CERN – PH-ESE 2 EPFL, Lausanne 3 UTFSM, Valparaiso, Chile. Outline. Summary of conductive noise properties of different converters CERN developed prototypes

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Progress on DC/DC Converters Prototypes

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  1. Progress on DC/DC Converters Prototypes B.Allongue1, G.Blanchot1, F.Faccio1, C.Fuentes1,3, S.Michelis1,2, S.Orlandi1, 1CERN – PH-ESE 2EPFL, Lausanne 3UTFSM, Valparaiso, Chile

  2. Outline • Summary of conductive noise properties of different converters • CERN developed prototypes • Other prototypes • Modeling of the common mode noise • Study of the inductor emitted noise • Different geometries • Comparison between shielded and unshielded inductors • Efficiency versus ESR • Plans for the future S. Michelis, CERN PH/ESE

  3. Conducted noise measurement • Reference test bench developed within ESE • Well defined measurement methods for reproducible and comparable results. • Independence from the system and from the bulk power source. • Arrangement of cables, input and output filter (LISN) around the converter under test, all above a ground plane. F.Faccio, PH/ESE

  4. Noise measurement on different CERN prototypes All the measurement were made in these conditions: Vin=10V, Vout=2.5V, Iout=1A and fsw=1Mhz Proto 1,2,3 were developed at CERN with the same controller. PCB layout and parasitic component choice was improved Proto 4’s PCB was designed in Aachen and the ASIC (in the red spot) was designed at CERN Proto2 ~58dBµA ~62dBµA Proto1 Proto4 Proto3 ~51dBµA ~46dBµA S. Michelis, CERN PH/ESE

  5. Noise measurement on other converters Vin=10V, Vout=2.5V, Iout=1A and fsw=1Mhz ~64dBµA ~46dBµA Proto3 CERN ST ST proto Measurement made in Aachen, Acknowledgments to R. Jussen ENPIRION PCB was developed in RWTH in Aachen Vin=6.5V, Vout=2.5V, Iout=0.542A fsw=1Mhz fsw=4Mhz Proto3 CERN ~46dBµA ~32dBµA Empirion S. Michelis, CERN PH/ESE

  6. Switched capacitor Vin=5V, Vout=1.25V, Iout=0.5A and fsw=0.5Mhz LBL switched capacitor ~55dB S. Michelis, CERN PH/ESE

  7. Modeling common mode noise • A model for a prototype (version 3) has been developed and simulated with PSPICE • All stray capacitances due to the board layout have been extracted with Q3D • Switching transistors replaced by voltage source (from measured Vds) and equivalent passives (R,C) • All discrete passive components have been fully characterized (ESR, ESL) • Good agreement between model and experiment (up to 10MHz) • Large influence of input-output capacitors – value and ESR, ESL! Input common mode current vs freq and ESL Input common mode current vs freq and Cout Input common mode current vs freq and ESR S. Michelis, CERN PH/ESE

  8. Noise influence of input output capacitor All the measurement were made in these conditions: Vin=10V, Vout=2.5V, Iout=1A and fsw=1Mhz on Proto3 Case 1 (ceramic Cin=42μF and Cout=21μF) Case 2 (ceramic Cin=100μF and Cout=100μF) Proto3 Case 4 (electrolytic Cin=5x22μF and Cout=5x22μF) Case 3 (electrolytic Cin=22μF and Cout=22μF) S. Michelis, CERN PH/ESE

  9. Outline • Summary of conductive noise properties of different converters • CERN developed prototypes • Other prototypes • Modeling of the common mode noise • Study of the inductor emitted noise • Different geometries • Comparison between shielded and unshielded inductors • Efficiency versus ESR • Plans for the future S. Michelis, CERN PH/ESE

  10. Which inductor to use? • Air-core inductors can be manufactured in different configurations (planar, solenoidal, thoroidal, ….) and a choice should be made • Value: reasonably limited in range 100-700nH • Equivalent resistance (ESR) determines converter efficiency to sensible extent Planar (on PCB) Solenoidal Toroidal ESR>100mW ESR~20-30mW ESR~20-30mW • Need to make 3D simulation to find the best suitable geometry for emitted magnetic field and ESR • Simulation of different geometry inductors with and without shield @1Mhz • Current=1A F.Faccio, PH/ESE

  11. Air core solenoid Not shielded Shielded Value @ 11mm far from the solenoid: 5µT 18nT

  12. Air core toroid Value @ 11mm far from the toroid: 6.6µT 11mm far from the centre of the toroid

  13. Example PCB Toroid This PCB toroid was developed at Bristol, Aknowledegment to David Cussans Not shielded Shielded Value @ 11mm far from the toroid: 19µT 70nT

  14. Comparison between inductors • This is a preliminary study, but it seems that air core shielded solenoid is the best option • for the emission of magnetic field. Test needs to be made to confirm these simulations! • Toroid emits much more than expected. Magnetic field is not all contained!

  15. Efficiency versus ESR The choice of the inductor must be also dictated by the ESR Calculations on Mathacd show a dramatic drop of converter’s efficiency with the increase of ESR (both considering or neglecting skin effect) S. Michelis, CERN PH/ESE

  16. Outline • Summary of conductive noise properties of different converters • CERN developed prototypes • Other prototypes • Modeling of the common mode noise • Study of the inductor emitted noise • Different geometries • Comparison between shielded and unshielded inductors • Efficiency versus ESR • Plans for the future S. Michelis, CERN PH/ESE

  17. Plans for the future • Prototype phase will continue towards the development of a 2-phase interleaved with voltage divider: • with discrete parts • fully integrated ASIC (except passive components) • Radiation tolerance studies on different technologies • Further studies on noise coupling will be carried out. • Exploring noise couplings into FE chips and shielding techniques • Modeling other noise sources: • dI/dt (switching level) • dv/dt (gate voltage-bootstrap) • Choosing the inductor technology that is most suitable for sLHC

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