PFC inductor design example

1. selection core:
We should be know below necessary information:
(a) Minimum Inductance based on DC basic, e.g. 1mH
(b) IDC current, e.g. 3A
According to formula LI*I= 1.0*3.0*3.0=9.0
We can find 60u which is in range from curve which is LI*I vs core part number, and find core
55586 is suitable .
Inductance factor of 55586 is 38uH/N*N+/-8%, so lower limit is 34.96uH/N*N
For meeting 1.0mH, it needs to wind 169Ts, according to formula IN=HL, get H is 56.6A/cm, we
continue to review curve which is DC vs initial permeability, can find initial permeability at DC
current is 68% than initial permeability at 0A, so we adjust turns from 169Ts to 249Ts.

2. wire selection
We select AWG#20 when current is 3.0A, due to big current and high temperature raise, we use
PEW or EIW wire, which temperature rate is 180 degree and reinfore insulation, ensure not short
between wire and wire.

3. Verify design result
249Ts AWG#20 is equivalent 157.9mm*mm, winding factor is about 39%, total area of window
is 401mm*mm.
Minimum inductance at 3.0DCA is 1.04mH.

4.Configuration design
Because PFC inductor is heavy and coil is big, we advise to add base, and full fix coil and base
using epoxy glue, design pin pitch according to PCB of customer.

5.Reliability testing
We run high temperature and low temperature testing, ensure the inductor can bear high and low
temperature.

6. Electrical parameter testing
L at oA
L at DC current
DCR for coil
Impulse voltage testing for winding.

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