DESCRIPTIONS
SM3000
Page 3 - 8
DELTA ELEKTRONIKA B.V.
rev. February 2018
CIRCUIT DESCRIPTION
The 380 V AC line volt age is rec ti fied by a bridge
rec ti fier and smoothed by a large elec tro lytic ca pac i -
tor. The 50 Hz choke in the in put cir cuit im proves the
wave form of the in put, so that no low fre quency dis -
tor tion is pro duced on the line volt age.
Care fully de signed RFI fil ters pro tect the line and
the load from the high fre quency in ter fer ence pro -
duced in side the power sup ply.
When the unit is switched on, the elec tro lytic ca -
pac i tor is charged via the re sis tor of the IN RUSH
CUR RENT LIMITER cir cuit, so no large in rush cur -
rent will flow. As soon as the volt age is suf fi ciently
high the power sup ply starts work ing and the se ries
re sis tor is by passed by a re lay con tact.
The op er at ing switch ing fre quency of 200 kHz has many ad van tages
like small size, re duced weight, low rip ple and fast reg u la tion.
The rec ti fied 380 V (500 V DC) is chopped by the tran sis tors and
trans formed to a lower volt age. This 200 kHz power con verter is of the
feed for ward type. The reg u la tion is achieved by pulse width mod u la tion.
Care
ful de
sign, over-rating of vi
tal com
po
nents, sev
eral built-in
protections and cool op er a tion (be cause of the very high ef fi ciency)
make the SM-se ries very re li able power sup plies which can be used con -
tin u ously at max i mum rat ing.
fig. 3 - 28
Sim pli fied func tional di a gram
