AN4164 datasheet(23/38 Pages) STMICROELECTRONICS

Part #	AN4164

Description	This document describes a 12 V-350 mA power supply set in non-isolated flyback topology

PDF	38 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

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23 / 38 page

AN4164

Feedback loop calculation guidelines

Doc ID 023660 Rev 1

23/38

Feedback loop calculation guidelines

7.1

Transfer function

The set PWM modulator + power stage is indicated with G1(f), while C(f) is the “controller”,

i.e. the network which is in charge to ensure the stability of the system.

The mathematical expression of the power plant G1(f) is the following:

Equation 2

where VOUT is the output voltage, Ipkp is the primary peak current, fp is the frequency of the

pole due to the output load and fz the frequency of the zero due to the ESR of the output

capacitor:

Equation 3

Equation 4

Figure 38.

Control loop block diagram

AM11582v1

)

(

)

(

)

(f)

OUT

Vdc

fsw

Ipkp

Vdc

fsw

Ipkp

⋅

2ESR)

·(R

OUT

⋅

·ESR

OUT

⋅

AN4164 Datasheet(PDF) 23 Page - STMicroelectronics