Wilmer Companioni - KEMET Webinar -- Capacitor Application ......Microsoft PowerPoint - Wilmer...
Transcript of Wilmer Companioni - KEMET Webinar -- Capacitor Application ......Microsoft PowerPoint - Wilmer...
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Capacitor Fundamentals
Low Voltage DC Applications
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Component
Solutions
Market
Segment
Dielectric &
Products
System Solutions
Design Discipline
Circuit
Application
Selecting the Right Component
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What is Low Voltage DC?
Consumer Industrial Computing Telecoms Automotive Medical Mil/Aero
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Trends
http://www.futuretimeline.net/subject/computers-internet.htm
http://magazine.sfpe.org/issue-73-effects-radiant-heat-flux-clean-agent-performance-class-c-fires
1.Mark Owen et al. “Datacom Equipment Power Trends and Cooling Applications”, ASHRAE Datacom Series, ASHRAE, Atlanta, GA, 2012.
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Capacitor FundamentalsParasitics
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Electrode Plates Dielectric
The value of a capacitor is measured in farads. For 1 farad of capacitance, 1 coulomb of charge is stored on the plates, when 1 volt of force is applied.
1 farad = 1 coulomb / 1 volt
1 coulomb represents ~ 6 x 1019 electrons
Common Structure
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fCXZ C 2
1
“Pure” Capacitor
Where:f is frequency (Hertz)C is capacitance (Farads)
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E-01 1.E+01 1.E+03 1.E+05 1.E+07
Imp
ed
an
ce (
Oh
ms)
Frequency (kHz)
Impedance vs. Freq. 47 µF Capacitance
C
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Capacitor with Equivalent Series Resistance
C ESR
22 ESRXZ C
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08
Imp
ed
an
ce (
Oh
ms)
Frequency (kHz)
Impedance vs. Freq. 47 µF Capacitance 0.25 Ohms ESR
0.10 Ohms ESR
0.05 Ohms ESR
0.01 Ohms ESR
0.001 Ohms ESR
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Capacitor with Equivalent Series Resistance and Inductance
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08
Imp
ed
an
ce (
Oh
ms)
Frequency (kHz)
Impedance vs. Freq. 47 µF Capacitance with 2.5 nH ESL
0.25 Ohms ESR
0.10 Ohms ESR
0.05 Ohms ESR
0.01 Ohms ESR
0.001 Ohms ESR
C ESR ESL
22ESRXXZ LC
fLX L 2Where: L is in Henries
self-resonant frequency.
LCf
2
1
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Capacitor FundamentalsParasitics and Ripple Voltage
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Capacitor Equivalent Circuit
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Switch Closed
CurrentON
ChargeCapacitor Supply
LoadRequirements
LoadCurrent
ESRVC = VL(Closed) - VESR
Capacitor ChargeESR Impact
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Switch Open
CurrentStopped
DischargeCapacitor Supply
LoadRequirements
LoadCurrent
ESR
VL(Open) = VC - VESR
VL(Open) = VL(Closed) – 2xVESR
Capacitor DischargeESR Impact
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Ripple Voltage Effects
Ideal
MLCC (X5R)
Polymer
+ ESR
+ L
+ DC Bias
+ Cap Roll-Off
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Capacitance: 200 µFESR: 33 mΩESL: 100 nH
20m
v
ESL Voltage Spikes
Capacitance InducedVoltage drop
ESR Voltage drop
Voltage recovery from Power Supply Unit (PSU)
Transient Response (C+ESR+ESL)
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Capacitor FundamentalsRipple Current and ESR
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Ripple Current Capability
• Ripple current refers to the AC portion of the current signal applied to a device.
• Heat is generated by ripple currents.
• Several factors contribute to the ripple capability of a capacitor:
– Dielectric material and associated DF
– Electrodes
– Frequency
– Package size (surface area)
– Package leads
– Allowable temperature rise
– Heat sink & cooling system
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Ripple CurrentTemperature Rise
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Ripple CurrentESR Changes with Temperature
Impedance and ESR – C1206C106K8RAC @ 25C with 0VDC Bias Impedance and ESR – C1206C106K8RAC @ 85C with 0VDC Bias
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Ripple CurrentK-SIM Example: C1206C106K8RAC
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Why ESR is ImportantPower Consumption (Heat)
Lower ESR Lower Power Losses Higher Efficiency
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Why ESR is Important
• Why ESR is important:– Power Loss = 𝐼 ∗ 𝐼 ∗ 𝐸𝑆𝑅
– Simplified to 𝐼 below (loss is a little higher with 𝐼 )
𝑃 = 1A x 1A x 0.010Ω = 10mW (using 1A average current)𝑃 = 5A x 5A x 0.010Ω = 250mW (using 5A average current)
Lower ESR Lower Power Losses Higher Efficiency
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ESR Comparisons Across Dielectrics
Dielectric Min. ESR [Ohms]
Aluminum Polymer 0.003
Ceramic 0.004
Tantalum Polymer 0.005
Aluminum Electrolytic 0.005
Tantalum MnO2 0.01
Film 0.01
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