Power Management IPS20 and IPS21

© Copyright 2006-2009 - ASIC Advantage, Inc.

AADS00001/AA743

- Revision 5– Dec 2008

3 / 12

TYPICAL FEEDBACK CIRCUITRY WITH CONTROL OF PRIMARY FLYBACK CONVERTER

1) Current limiting:

The current limiting is adjustable through RISENSE

2) Regulated Voltage:

The regulated voltage is adjustable through RV1 and RV2

3) Compensation

The voltage-control trans-conductance operational amplifier can be fully compensated. Both of its compensation

pins are directly accessible for external compensation components.

The suitable compensation network is shown in Fig.1. It consists of a capacitor C1 and a resistor R1in series,

connected in parallel with another capacitor C2.

The current-control trans-conductance operational amplifier can be fully compensated. Both of its compensation

pins are directly accessible for external compensation components.

The suitable compensation network is shown in Fig.1. It consists of a resistor R2 and a capacitor

C2 in series, in parallel with a capacitor C3. Resistor R4 provides the input impedance that the compensation

network works with. Capacitor C4, with R4, implements a small amount of filtering.

(Nominal VSENSE = 1.19V)

Nominal IS threshold :

IPS20= 54mV

IPS21= 100mV

Fig. 1

U2

OPTOCOUPLER

OUT+

OUT-

SecondaryGND

TX1

C5

RV1

RV2

OUTPUT

+

C6

VCC

1

VSENSE

2

VCOMP

3

OPTO

4

GND

8

OUT(-)

7

IS

6

ICOMP

5

U1

IPS20/21

C1

R1

R3

R2

C2

RISENSE

C3

C4

L1

D1

SCHOTTKY

IN+

IN+

DC or Rectified AC

FLYBACK

CONVERTER

R4