"N_Cook" wrote in message
...
Burnt and burst SMPS supervisor on this otherwise no-name and little
chance Chinese thing. As laser and motor/s in the DVD deck and heatsink
bonded to a video chip a reasonable power draw.
But the SMPS IC , in a conventional 8 pin DIP package also contains the Tx
driver transistor. So air gap under the IC and reverse side of pcb
enlarged pad of pcb-copper as some sort of vain attempt at heatsink.
Thermal connection to this is via just pins 4 and 5 combined in normal
soldering , connected to the Tx. There is a hole through the pcb as though
for some sort of clip to go perhaps top and bottom of the IC and bolted
through to this under pad but no sign of anything having been fitted
there, no deformation of the tinning over the pad around the hole. Turning
over the unit and shaking over paper meant the blasted away top part ,
mainly, of the IC emerged but no clip at all.
Is it possible to have combined supervisor and driver transistor in an
8pin DIP package with no heatsink tab provision? or are there combined
SMPS TX with internal driver transistor buried in the base?
Also ps supply provision marked on pcb ac 85V - 250V
IC logi i in a reversed D
marked in 3 lines ICE 2?26 maybe more numbers, ? maybe a 4
logo then 0 and more
XK4.. probably more numbers
probable pinning
p1 0.1uF to 0V
p2 to optocoupler
p3 over current sense
p4-p5 to Tx low side
p6 n/c
p7 supply 25V
p8 0V


SMPS controller ICs with the letters "ICE" as the first part of their type
number are quite common. Such ICs are often coupled directly to a power FET
switching element, but are just as commonly connected directly to a small
SMPS Tx, particularly when it is a standby supply. I have always been amazed
that these chips can stand the better part of 400 volts across their
internal FET, and that it can supply enough current to drive the Tx
directly. I guess the thermal issues are dictated by how good the RDSon of
the internal device is. The closer it is to zero ohms, the lower the
dissipation, and some these days are pretty damn close to zero for all
practical purposes.

Arfa