Transcript KEMET Logistics

Capacitors Application
Edward Chen
18th Dec 2004
All capacitors utilize the same basic mechanism in their
structure
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
18th Dec 2004
2
ESL - Inductive Reactance (X )
L
opposes Capacitive Reactance
ESR
X
L
0
Z
X
XC
X
Impedance is now a
factor of resultant
Z=
2
(X -X ) + ESR
C
2
L
18th Dec 2004
3
L
o
s
s
F
a
c
t
o
r
s
i
n
C
a
p
a
c
i
t
o
r
s
E
S
R
B
a
s
e
d
o
n
V
e
c
t
o
r
r
e
l
a
t
i
o
n
s
h
i
p
T
h
e
t
a
X
D
F
=
c
o
t
(
T
h
e
t
a
) =
E
S
R
/
X
C
Z
P
F
=
c
o
s
(
T
h
e
t
a
)=
E
S
R
/
Z
Q
=
t
a
n
(
T
h
e
t
a
) =
X
/
E
S
R
=
1
/
D
F
C
C
w
h
e
r
e
D
F
=
D
i
s
s
i
p
a
t
i
o
n
F
a
c
t
o
r
P
F
=
P
o
w
e
r
F
a
c
t
o
r
Q
=
"
Q
"
o
r
f
i
g
u
r
e
o
f
m
e
r
i
t
18th Dec 2004
4
Reactance
Self-Resonance
Frequency
The frequency at which XC = XL is the self-resonant
self-resonantfrequency.
frequency.
At this frequency, XC=-XL, or zero, and the impedance is equal to the
ESR.
Prior to this frequency, component behaves as capacitor; after this
frequency, component behaves as inductor.
1
F
2 LC
18th Dec 2004
5
Capacitor Application
• Decoupling
• Coupling
• Filtering
• Timing/Wave-shaping
18th Dec 2004
Decoupling
Power
Supply
Vin
Vin
Vout
Load
(ex.IC)
Vout
Function: Absorb the voltage change (noise).
Suitable Cap: Tan Cap, KO Cap, MLCC, Al E Cap
18th Dec 2004
Coupling
Function: Remove the DC voltage of A circuit
and Transmit the exchange voltage
to B circuit. (Allow an AC signal pass,
but stop DC.)
Suitable Capacitors: Tan Cap, MLCC
Ex. Horn.
18th Dec 2004
Filtering
Function:
• Rectified AC smoothing
• Frequency selective filtering
Suitable Cap: KO, Tan Cap, Hi C/V MLCC, Al E Cap
18th Dec 2004
Timing / Wave-shaping
Function: Timer Circuit (RC Timer).
Suitable Cap: MLCC, KO Cap.
18th Dec 2004