In Figure 1, F1 refers to the input fuse. Proper fuse selection should be a safety agency
approved, slow blow fuse. Selection of the proper fuse rating is necessary to ensure power
converter and system protection (potential failure if the rating is too high) and prevent false
fuse blowing (which could happen if the rating is too low). Below is the formula to calculate
the proper rating:
I
=
3
x
V
o
1
x
I
o
1
/
η
/
Vin(min.)
V
o
1
= output voltage
I
o
1
= output current;
η
= the converter’s efficiency;
Vin(min)
= the minimum input voltage
Futher circuit notations:
♦
NTC
is a thermistor.
♦
CY
and CX are safety capacitors.
♦
C1
is a high frequency ceramic capacitor or polyester capacitor, 0.1μF/50V.
♦
C2
is output filtering high frequency aluminum electrolytic capacitor. Select a 220μF
rating if the output current is greater than 5A, or a 100μF rating if the output current is less
than 5A. The insulation voltage should be derated to less than 80% of rated value.
For dual or triple output converters, the circuit of input side remains the same and the outputs
should be considered independently in component selection (see Figure 3).
The application circuit shown in Figure 1 is typical application circuit, whereby all MORNSUN
products will meet EMI Class B, and Class 3 lightening strike and surge testing (see component
datasheets for more details). To comply with more stringent EMC testing, additional filtering
should be incorporated. See Figure 2 for a suggested filtering circuit.
MORNSUN [ MORNSUN SCIENCE& TECHNOLOGY LTD. ]
