NCP431A, SC431A, NCP431B, SC431B, NCP432B, SC432B Series

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Figure 36. Knee of Reference

Regulator with TL431 or other references in secondary

side of a SMPS needs bias resistor to increase cathode

current to reach high and stable gain (refer to Figure 37).

This bias resistor does not have to be used in regulator with

NCP431/NCP432 thanks to its low minimum cathode

current.

Figure 37. SMPS Secondary Side and Feedback

Connection on Primary Side

The NCP431/NCP432 operates with very low leakage

and reference input current. Sum of these currents is lower

than 100 nA. Regulator with the NCP431/NCP432

minimizes parasitic power consumption.

The best way to achieve extremely low no−load

consumption

in

SMPS

applications

is

to

use

NCP431/NCP432 as regulator on the secondary side. The

consumption is reduced by minimum parasitic consumption

and very low bias current of NCP431/NCP432.