Advanced Analog Technology, Inc.
April 2007
AAT1164/AAT1164B/AAT1164C
IOD
VRIPPLE (COUT ) ≈
β
fSCOUT
V
(ESR) ≈ I
r
RIPPLE
L(peak) C
V
D
D (1−D)R
2
L
O
I
=
+
[
]
C(rms)
R
1−D 12
Lf
S
L
2
P
= I
(
r
)
ESR
C(rms)
C
ESR: Equivalent Series Resistance
Figure 4. Closed-Current Loop for Boost with PCM
r
= 20mΩ
C
Example 2:
C
= 38µF,
) = 4.1mV
RIPPLE OUT
OUT
V
(C
V
(ESR)
= 21.5mV
+
RIPPLE
+
−
−
V
=
25.6mV
RIPPLE
I
= 0.411A
C(rms)
P
= 0.00338W or 0.08% power loss
ESR
Boost Converter Power loss
β
−
The largest portions of power loss in the boost
converter are the internal power MOSFET, the inductor,
the Schottky diode, and the output capacitor. If the
boost converter has 90% efficiency, there is
approximately 7.89% power loss in the internal
MOSFET, 1.34% power loss in the inductor, 0.68%
power loss in the Schottky diode, and 0.08% power loss
in the output capacitor.
+
Figure 5. Block Diagram of Boost Converter with
Peak Current Mode (PCM)
Power Stage Transfer Functions
The duty to output voltage transfer function Tp is
:
Loop Compensation Design
VO
d
(s + ωesr )(s − ω
)
z2
2
n
Tp(s)
=
= Tp0
The voltage-loop gain with current loop closed sets the
stability of steady state response and dynamic
performance of transient response. The loop
compensation design is as follows:
s2
+ 2ξωns + ω
−
rC
D R + rC
L
1
Where Tp0
=
VO
,
ω
=
esr
C
r
OUT C
1
−
(
)
(
)
And
2
RL
1
(
−
D
−
r
1−D 2 RL + r
)
(
)
ω
=
, ωn =
z2
L
LCOUT R + r
(
)
L C
–
–
–
Advanced Analog Technology, Inc
Version 1.00
. –
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