AAT1102 Ver la hoja de datos (PDF) - Advanced Analog Technology, Inc.

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Fabricante

AAT1102

ADVANCED PWM DC-DC CONVERTER WITH INTERNAL SWITCH AND SOFT-START

Advanced Analog Technology, Inc. 

Advanced Analog Technology, Inc.

Current Sampling Transfer

Function

Error voltage to duty transfer function Fm is:

( ) ( )( ) Fm

(s)

=

d

vei

= 2 f s 2 s 2 + 2ξwn s + wn 2

Tpi0 Rcs s s + wzi s + wsh

Where wsh

=

3ws

π

⎜⎛

⎝

1

1

−

+

α

α

⎟⎞ ,α

⎠

=

M2

M1

− Ma

+ Ma

,

ws = 2π . f s

AAT1102 (BIN2)

=

βgm Rc

s

+ wc

s

12 f s 2T p0

Rcs T pi 0

×

(s + wz1 )(s − wz2 )

(s + wzi )(s 2 + sws h + 12 f s 2 )

Where β = VFB ,

Vo

The compensator transfer function

Therefore, Fm depends on duty to inductor current

transfer functionTpi , and f s is the clock switching

Tc (s)

=

vc

v fb

=

g m Rc

s + wc

s

,

where

wc

=

1

Rc C c

frequency; Rcs is the current-sense amplifier

transresistance. For the boost converter M 1 =VIN / L

and M 2 = (VO -VIN )/ L

For AAT1102 , Rcs = 0.275 V/A, M a is slope

compensation, M a =0.8×106.

νc

νO

_ν

+

The closed-current loop transfer functionTicl is:

Comparator

( ( ) ) ( ) Ticl (s)

=

12 f s 2

Rcs T pi 0

×

s 2 + 2ξwn s + wn 2

s + wzi s 2 + wsh s + 12 f s 2

Fig.3. Voltage loop compensator

The Voltage-Loop Gain With

Current Loop Closed

The control to output voltage transfer function Td

is:

Td

(s)

=

vo (s)

vc (s)

=

Ticl

(s)Tp (s)

The voltage-loop gain with current loop closed is:

Compensator design guide:

1.

Crossover

frequency

f ci

<

1

2

fs

2. Gain margin>10dB

3. Phase margin>40∘

4. The Lvi (s) = 1 at crossover frequency, Therefore,

the compensator resistance, Rc is determined

by:

Lvi (s) = βTc (s)Td (s)

– 台灣類比科技股份有限公司 –

– Advanced Analog Technology, Inc. –

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