Closing the loop

AN1723

14/24

Doc ID 9553 Rev 4

Equation 17

where K is equal to 0.152. Therefore the PWM gain is also equal to:

Equation 18

This means that even if the input voltage changes, the error amplifier does not change its

value to keep the loop in regulation, therefore ensuring better line regulation and line

transient response. In summary, the open loop gain can be written as:

Equation 19

Example 1:

●

●

●

●

●

The gain and phase bode diagrams are plotted respectively in Figure 14 and Figure 15.

Figure 14.

Module plot

V

OSCMAX

V

OSCMIN

KV

CC

⋅

()

=

–

G

PWM

s

()

1

K

----

const

==

Gs

()

G

PWM

s

R

2

R

1

R

2

+

----------------------

A

0

⋅⋅

s

()

A

LC

s

()

⋅

()

=

AM11322v1