Rev. A 10/18
4
Application Note
AN-72
www.power.com
Step-by-Step Design Procedure
This design procedure uses the PI Expert design software (available
from Power Integrations), which automatically performs the key
calculations required for an InnoSwitch3 flyback power supply design.
PI Expert allows designers to avoid the typical highly iterative design
process. Look-up tables and empirical design guidelines are provided
in this procedure where appropriate to simplify the design task.
Iterate the design to eliminate warnings. Any parameters outside the
recommended range of values can be corrected by following the
guidance given in the right hand column. Once all warnings have
been cleared, the output transformer design parameters can be used
to create a prototype transformer.
Step 1 ‒ Application Variables
Enter: VIN_MIN, VIN_MAX, LINEFREQ, CAP_INPUT, VOUT,
PERCENT_CDC, IOUT, EFFICIENCY, FACTOR_Z, and
ENCLOSURE
Minimum and Maximum Input Voltage, V_MIN, V_MAX (VAC)
Determine the input voltage range from Table 2 for a particular
regional requirement.
Line Frequency, LINEFREQ (Hz)
50 Hz for universal or single 100 VAC, 60 Hz for single 115 VAC input.
50 Hz for single 230 VAC input. These values represent typical line
frequencies rather than minimum. For most applications this gives
adequate overall design margin. For absolute worst-case or based on
the product specification reduce these numbers by 6% (47 Hz or 56 Hz).
Total Input Capacitance, CAP_INPUT (
µ
F)
Enter total input capacitance using Table 3 for guidance.
Region
Nominal Input
Voltage (VAC)
Minimum Input
Voltage (VAC)
Maximum Input
Voltage (VAC)
Nominal Line
Frequency (Hz)
Japan
100
85
132
50 / 60
United States, Canada
120
90
132
60
Australia, China, European Union Countries,
India, Korea, Malaysia, Russia
230
185
265
50
Indonesia, Thailand, Vietnam
220
185
265
50
Rest of Europe, Asia, Africa, Americas
and rest of the world
115, 120, 127
90
155
50 / 60
220, 230
185
265
50 / 60
240
185
265
50
Visit: https://en.wikipedia.org/wiki/Mains_electricity_by_country
Table 2.
Standard Worldwide Input Line Voltage Ranges and Line Frequencies.
2
APPLICATION VARIABLES
Design Title
3
VIN_MIN
85
85
V
Minimum AC input voltage
4
VIN_MAX
265
265
V
Maximum AC input voltage
5
VIN_RANGE
UNIVERSAL
Range of AC input voltage
6
LINEFREQ
60
Hz
AC Input voltage frequency
7
CAP_INPUT
40.0
uF
Input capacitor
8
VOUT
5.00
5.00
V
Output voltage at the board
9
PERCENT_CDC
0%
0%
Percentage (of output voltage) cable drop
compensation desired at full load
10
IOUT
4.00
4.00
A
Output current
11
POUT
20.00
W
Output power
12
EFFICIENCY
0.89
0.89
AC-DC efficiency estimate at full load given that
the converter is switching at the valley of the
rectified minimum input AC voltage
13
FACTOR_Z
0.50
Z-factor estimate
14
ENCLOSURE
ADAPTER
ADAPTER
Power supply enclosure
Figure 2. Application Variable Section of InnoSwitch3-CE Design Spreadsheet with Gray Override Cells.