DELTA ELEKTRONIKA BV
SM3000
Page 3 - 8
DESCRIPTIONS
1991, rev. May 2008
CIRCUIT DESCRIPTION
The 380 V AC line volt age is rec tified by a bridge
rectifier and smoothed by a large electrolytic ca paci-
tor. The 50 Hz choke in the in put cir cuit improves the
waveform of the in put, so that no low frequency dis -
tortion is produced on the line voltage.
Carefully de signed RFI fil ters protect the line and
the load from the high frequency in terference pro -
duced in side the power sup ply.
When the unit is switched on, the elec trolytic ca -
pacitor is charged via the resistor of the IN RUSH
CURRENT LIMITER cir cuit, so no large in rush cur-
rent will flow. As soon as the voltage is suf ficiently
high the power supply starts working and the se ries
resistor is bypassed by a re lay con tact.
The op erating switching fre quency of 200 kHz
has many ad
vantages like small size, re
duced
weight, low rip ple and fast reg ulation.
The rec tified 380 V (500 V DC) is chopped by the
transistors and transformed to a lower voltage. This
200 kHz power converter is of the feed forward type.
The reg ulation is achieved by pulse width mod ula-
tion.
Careful de sign, over-rating of vi tal com ponents,
several built-in protections and cool op eration (be -
cause of the very high efficiency) make the SM-se-
ries very re liable 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
