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DC Biased Chokes for High Frequency Power Applications M.Sc. Martin Grübl
DC Biased Chokes for High Frequency Power ApplicationsM.Sc. Martin Grübl
Overview of PIRATE-technology
2© SUMIDA. All rights reserved.
P ermanentmagneticI nlay forR everse-BiasA ctivityT echnologyE xtension
• Basic core out of soft magnetic ferrite with very high saturation flux density SUMIDA Fi339
• Together with hard magnetic inlay with outstanding inner resistance for low eddy current lossesSUMIDA Fi701
• Both materials are SUMIDA developments and unique on the world market.
• Mechanical limits of the magnet:height: min 1 mm; surface area max. 50 cm²
Applications for PIRATE-chokes
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DC Chokes use only narrow range of flux density capability
Used flux density
Flux density capability of a common ferrite core
Applications for PIRATE-chokes
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PIRATE eliminates DC Offsets• Cores can get smaller• Saturation performance rises
Unused capability of the core
Flux density capability of the core
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Applications for PIRATE-chokes
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Rule of Thumb: PIRATE Technology is possible if winding losses are three times higher than core losses𝑷𝑷𝑾𝑾𝑷𝑷𝑪𝑪
> 𝟑𝟑
0,0
1,0
2,0
3,0
4,0
0 100 200 300 400
L /µ
H
I /A
without Magnet
with Magnet Fe701
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Sample project using PIRATE-choke
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Component: PV converter DC boost choke 550µH, 30ASumida Project No: EI 140 514 11
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Sample project with PIRATE-chokes
EI 140 514 11 42Original design
EI 140 514 11 32PIRATE
Advantages of PIRATE design
Weight 2,63 kg 1,93 kg -26%
Volume 700 cm³ 525 cm³ -25%
Turns 45 28 -37%
Rdc 18 mΩ 12 mΩ -33%
Pv (@23A, 100°C) 12,4 W 8,2 W -33%
Rs (@20 kHz) 440 mΩ 370 mΩ -16%
fres 1,5 MHz 1,7 MHz +13%
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Lifetime Test Result - Industrial Application
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Magnet temperature 90°CDC-Offset: 260 mTΔB = 200 mTf = 18 kHzL= 500 µH
Degradation of the energy maximum (0,5*L*I²) of a PIRATE Choke
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Co-sintered air gap
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Distributed air gaps in ferrites decrease fringing of magnetic flux.
Original technology for distributed air gaps: Sandwich gluing of ferrites and plastics.
Disadvantage: thermal insulation due poor thermal conductivity of plastic material
New patented Sumida technology: Co-sintered air gap
Advantages:• Homogeneous structure of the ferrite column• Better heat flow conditions • Cost neutral against original technologies• Minimum air gap: 1 mm
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Co-sintered air gap
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Comparison of thermal behaviour:Original glued air gap vs. co-sintered air gap
Fi010 FR4
Characteristics Fi010 FR4
µi (air gap material) 1,1 1,0
Thermal conductivity [W/m/K] 5 0,25
Hot Spot [°C] 114 122
Thermal expansion [ppm/K] 8 70
70
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Thank you for your attention!
Further Questions ?
Backup Folien
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Datasheet of SUMIDA Fe701 Hard Magnetic Compound
Item ValueBasis NdFeB
µi 1,1
Hcb -300 kA/m
Hcj -970 kA/m
Br 420 mT
Spec. resistance 38 Ωm
Density 4,4 g/cm³
Spec. Losses (@ 100°C, 72kHz. 70mT)
<200 mW/cm³
Tmax 150 °C
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Other outstanding ferrite technologies of Sumida
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Plastoferrite (plastic bonded ferrite particles)• Overmoulded busbars for DM – filtering• Free-shaped geometries and narrow tolerances• µ = 0 – 22 possible• Cost ~1,5x costs of common production (pressed ferrite)
Injection Moulded Ferrites• Free-shaped geometries• µ = up to 4000• Similar properties to common ferrite cores• Cost ~ 1,5x costs of common production (pressed ferrite)
Thin-slide ferrites• 0,6 mm possible• Ideal for shielding
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