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AAT1168 Datasheet, PDF (16/22 Pages) Advanced Analog Technology, Inc. – TRIPLE-CHANNEL TFT LCD POWER SOLUTION WITH OPERATIONAL AMPLIFIERS
◁
Advanced Analog Technology, Inc.
May 2008
AAT1168/1168A/1168B
( )2
PESR = ILpeak .rC
ESR: Equivalent Series Resistance
+
−
Example 2: COUT = 38µF, rC = 20m Ω
VRIPPLE (COUT ) = 4mV
VRIPPLE (ESR) = 22mV
VRIPPLE = 26mV
PESR = 0.023W or 0.6% power loss
+
−
−β
+
Boost Converter Power loss
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 3.3% power loss in the internal MOSFET,
1% power loss in the inductor, 5.1% power loss in the
Schottky diode, and 0.6% power loss in the output
capacitor.
Loop Compensation Design
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:
β
Figure 4. Closed-current Loop for Boost with PCM
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:
Tp(s) =
VO
d
=
Tp0
(s + wesr )(s − wz2)
s2 + 2ξwns + wn2
Where Tp0
=
VO
−rC
(1− D)(RL
+ rC )
,
w esr
=
1
CrC
And
w z2
=
RL (1− D)2
L
−r
, wn
=
(1− D)2 RL + r
LC (RL + rC )
ξ = C[r (RL + rC ) + RLrc (1− D)2] + L ,
2 LC (RL + rC )[r + (1− D)2 RL ]
r = rL + DrDS + (1− D)RF
rL is the inductor equivalent series resistance, rC is
capacitor ESR, RL is the converter load resistance, C
is output filter capacitor, rDS is the transistor turn on
resistance, and RF is the diode forward resistance.
The duty to inductor current transfer function Tpi is:
Tpi (s)
=
il
d
=
Tpi0
s2
+
s + w zi
2ξwns +
w
2
n
Where
Tpi0
=
VO (RL
L (RL
+ 2rC
+ rC )
)
,
w zi
=
C (RL
1
/ 2 + rC )
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– Advanced Analog Technology, Inc. –
Version 1.00
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