advertisement

High Frequency Magnetics; Black Magic, Art or Science? Magnetics Core Loss Dr. Ray Ridley APEC Industry Session on Magnetics Wednesday March 23 2016 www.ridleyengineering.com 1 Introduction Core loss calculations and measurements New core material needs Need for extensive data Approximations to data Different excitation waveforms Temperature variations Standardized data base proposals © 2016 Ridley Engineering Inc 2 Immediate Goals for Core Materials 0.6 T MPP SATURATION LOSS 0.3 T FERRITE Improvements SATURATION LIMITED CORE LOSS LIMITED 10K 100K 1 M Frequency (Hz) 10 M 100 M Would be nice to at least extend saturation range further © 2016 Ridley Engineering Inc 3 B-H Loop and Core Losses B 𝛥𝐵 H Core loss calculations and measurements © 2016 Ridley Engineering Inc 4 Core Loss MPP 200u 5000 mW/cm3 300 kHz 0.1 T 5 W/cm3 © 2016 Ridley Engineering Inc 5 Core Loss PC95 350 mW/cm3 300 kHz 0.1 T 0.350 W/cm3 > 10 times better than MPP © 2016 Ridley Engineering Inc 6 Core Loss Steinmetz Equation Pc kf B x y Steinmetz equation can be used to approximate the actual loss measurements Three coefficients define the loss for a given material © 2016 Ridley Engineering Inc 7 Steinmetz Equation Limitations Pc kf x B y Equation assumes curves are 1) Equally spaced with frequency 2) Equal slopes at different frequencies © 2016 Ridley Engineering Inc 8 Modifying the Steinmetz Equation Pc kf x B y Discrete step changes in coefficients from Mag Inc. <100 kHz 100-500 kHz >500 kHz © 2016 Ridley Engineering Inc a c d 0.074 0.036 0.014 1.43 1.64 1.84 2.85 2.62 2.28 9 Steinmetz Equation Changing Coefficients Pc kf x B y <100 kHz 100-500 kHz >500 kHz © 2016 Ridley Engineering Inc k x y 0.074 0.036 0.014 1.43 1.64 1.84 2.85 2.62 2.28 10 Ridley-Nace Variable Steinmetz Equation Continuously-variable coefficients with Ridley-Nace formula Pc (a ln f b) f B c ( df e ) Five coefficients needed to describe materials Example for Magnetics R material: Pc (3.626 ln f 28.32) f © 2016 Ridley Engineering Inc 1.729 B ( 0.00076 f 2.8332) 11 Continuously Variable k Term Magnetics R Material Measured Core Loss 20 10000 Loss mW / cm3 k 3.626 ln f 28.32 16 1000 12 100 8 10 Measurements 4 0 1 0 200 400 600 800 1000 Frequency Pc (a ln f b) f B c 0.1 0.01 0.005 ( df e ) a 3.626 b 28.32 0.01 Flux Density T 0.1 0.2 12 Continuously Variable y Term Magnetics R Material Measured Core Loss 10000 3 Loss mW / cm3 1000 y 0.00076 f 2.8332 2 100 1 10 0 1 0 200 400 600 800 1000 Frequency 0.1 Pc (a ln f b) f B c 0.01 0.005 0.01 © 2016 Ridley Engineering Inc Flux DensityT 0.1 0.2 d 0.00076 ( df e ) e 2.8332 13 Oliver Variable Steinmetz Equation (Powdered Iron Core Material) Pcore f df 2 B 2 a b c 2.3 1.65 3 B B B Continuously-variable coefficients with Oliver formula Four coefficients needed to describe materials, plus 2.3 and 1.65 exponents subject to change with different materials www.micrometals.com/appnotes/appnotedownloads/coreloss update.pdf © 2016 Ridley Engineering Inc 14 Core Loss Temperature Variation Loss Multiplier 5 g (T ) a 5T 5 a 4T 4 a 3T 3 a 2T 2 a1T a 0 4 Manufacturer’s Data 3 2 1 -60 0 60 120 Temperature Six coefficients needed to describe temperature variation Every material has a different curve Does the curve also change with frequency and flux level? © 2016 Ridley Engineering Inc 15 Different Core Excitations B B t t B B t t Need to modify equations to suit each of these waveforms © 2016 Ridley Engineering Inc 16 General Triangular Flux Waveform B 2B D2Ts D1Ts Pc ( D) D1 Pc © 2016 Ridley Engineering Inc f 2 D1 D2 Pc f 2 D2 Ts t Pc (a ln f b) f c B ( df e ) 17 Duty Cycle Core Loss Multiplier B = 0.15 T 6 5 DCM : D ' D 4 3 2 1 0 CCM : D ' 1 D 0 0.1 0.2 Pc ( D) D1 Pc © 2016 Ridley Engineering Inc 0.3 f 2 D1 0.4 D2 Pc 0.5 0.6 f 2 D2 18 Putting it All Together © 2016 Ridley Engineering Inc 19 What We Need from the Manufacturers 1) Raw core loss sinewave test data over wide range of frequency, B, temperature 2) Who is going to fund the modeling into a standard format database? 20 Magnetics Forecast High-ripple current inductor designs will dominate the practical high-performance market Practical “high performance” means converters up to 5 MHz Core material improvements will be just incremental (unless some breakthrough material emerges) Insufficient funding is going into fundamental magnetic material research to give a good chance of any breakthroughs. Data Standardization is badly needed from the core manufacturers to ease confusion Core loss raw data is needed, not just curves. Creative core geometries need to be applied to POL inductors and other high-ripple parts Magnetic core will not go away (however much it is wished for) Isolation transformers will creep back into PoL applications to boost efficiency – More magnetics! Multi-converter processing will continue to proliferate. © 2016 Ridley Engineering Inc 21 Some References Cliff Jamerson: Targeting Switcher Magnetics Core Loss Calculations, Power Electronics Technology, Jan 2001. Ed Herbert: http://www.psma.com/technical-forums/magnetics/core-loss-studies Christopher Oliver: www.micrometals.com/appnotes/appnotedownloads/coreloss update.pdf Power Supply Design Center Articles http://www.ridleyengineering.com/design-center.html [89] Core Loss Modeling [90] Core Loss Modeling with Non-Sinusoidal Waveforms - Part II [91] Core Loss Modelling - Sinewave Versus Triangle Wave - Part III Ray Ridley and Art Nace [A03] Modeling Ferrite Core Losses Christopher Oliver [A06] Core Loss Modeling & Measurement Power Supply Design Software http://www.ridleyengineering.com/software.html © 2016 Ridley Engineering Inc 22