400DBBBA0 datasheet(20/47 Pages) ONSEMI

20 / 47 page

NCP12400

www.onsemi.com

Figure 47. Latch After the Preshort

time

VHV

time

VCC

time

DRV

VHV(start)

VHV(min)

VCC(on)

VCC(min)

HV current

source = Istart1

HV current

source = Istart2

Device starts at

VCC(on) event

VCC(inhibit)

VCC(off)

UVLO level

VCC(off )

is trigged before OCP timer elapsed

Device stops thanks

to pre−short protection

HV Sensing of Rectified AC Voltage

The NCP12400 features on its HV pin a true ac line

monitoring circuitry. It includes a minimum start−up

threshold and an autorecovery brown−out protection; both

of them independent of the ripple on the input voltage. It is

allowed only to work with an unfiltered, rectified ac input to

ensure the X2 capacitor discharge function as well, which is

described in following. The brown−out protection

thresholds are fixed, but they are designed to fit most of the

standard ac−dc conversion applications.

When the input voltage goes below VHV(stop), a

brown−out condition is detected, and the controller stops.

The HV current source maintains VCC between VCC(on) and

VCC(min) levels until the input voltage is back above

VHV(start).

400DBBBA0 Datasheet(PDF) 20 Page - ON Semiconductor