NCP1237 datasheet(23/34 Pages) ONSEMI

Part #	NCP1237

Description	Fixed Frequency Current Mode Controller for Flyback Converters

PDF	34 Pages

Scroll/Zoom	100%

Manufacturer	ONSEMI [ON Semiconductor]

Direct Link	http://www.onsemi.com

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NCP1237

http://onsemi.com

Dual−Level Overcurrent Protection

For some applications (e.g. printer adapters), it is

necessary that the controller maintains regulation while it

has detected a first level of overload. This is to authorize a

transient peak power higher than the maximum continuous

output power.

This is implemented by adding another comparator whose

threshold is VCS(tran), a CS voltage level lower than VILIM,

which starts the charging of another timer, with a duration

ttran longer than tfault (168 ms typical). If the timer reaches

its maximum duration, the controller enters protection mode

(latched or autorecovery depending on the option).

Figure 20. Dual−Level Timer−Based Overcurrent Protection

−

tLEB

blanking

−

VCS(tran)

Protection

Mode

Brown−out

release

tautorec

timer

Reset

Autorecovery

protection

mode only

PWM

Reset DRV

tfault

timer

ttran

Fault Flag

KFB

NCP1237 Datasheet(PDF) 23 Page - ON Semiconductor