PSS, PSK Extended Data Sheet
Positive Switching Regulators (Benign)
REV. FEB 15, 2004
Page 12 of 15
Table 12: Insulation concept leading to an SELV output circuit
Conditions Front end
Switching regulator
Result
Supply
Minimum required grade
Maximum
Minimum required safety
Measures to achieve the
Safety status of
voltage
of isolation, to be provided
DC output
status of the front end
specified safety status of the
the switching
by the AC-DC front end,
voltage
output circuit
regulator output
including mains supplied
from the
circuit
battery charger
front end 1
Battery
Double or Reinforced
≤60 V
SELV circuit
None
SELV circuit
supply,
considered
as secon-
dary circuit
Mains
Basic
≤60 V
Earthed SELV circuit 2
None
Earthed SELV
≤250 V AC
ELV circuit
Input fuse 3 and earthed output
circuit
circuit 2 and earthed 2 or non
user accessible case
Double or reinforced
≤60 V
SELV circuit
None
SELV circuit
1 The front end output voltage should match the specified input voltage range of the switching regulator.
2 The earth connection has to be provided by the installer according to the relevant safety standard, e.g. IEC/EN 60950.
3 The installer shall provide an approved fuse (slow blow type with the lowest current rating suitable for the application, max. 12.5 A) in
a non-earthed input conductor directly at the input of the switching regulator. If Vo+ is earthed, insert the fuse in the Gi- line. For UL’s
purpose, the fuse needs to be UL-listed.
Safety of Operator Accessible Output Circuit
If the output circuit of a switching regulator is operator ac-
cessible, it shall be an SELV circuit according to IEC/EN
60950 related safety standards.
The following table shows some possible installation con-
figurations, compliance with which causes the output circuit
of the switching regulator to be an SELV circuit according to
IEC/EN 60950 up to a configured nominal output voltage of
30 V.
However, it is the sole responsibility of the installer or user
to assure the compliance with the relevant and applicable
safety regulations.
More information is given in:
Technical Information: Safety.