IR2166
P FC D esign E quations
ꢀ
S tep1: C alculate P FC inductor value:
ꢀ
2
MIN
(VBUS
−
2 VAC
) VAC
η
ꢀꢀ
MIN
ꢀꢀꢀꢀꢀꢀꢀ
ꢀ
[H enries] (1)
ꢀ
LPFC
=
2
f MIN POUT VBUS
ꢀ
w here,
ꢀ
VBUS
ꢀ
ꢁꢀꢀ
D C bus voltage
ꢀꢀꢀꢁꢀꢀ
M inim um rm s A C input voltage
P FC efficiency (typically 0.95)
VAC
ꢀ
MIN
ꢀ
ꢁꢀꢀ
ꢁꢀꢀ
ꢁꢀꢀ
η
ꢀ ꢀ
ꢀꢀ
M inim um P FC switching frequency at m inim um A C input voltage
B allast output power
f MIN
POUT
ꢀ
S tep 2: C alculate peak P FC inductor current:
2
2
POUT
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ꢀ ꢀ
ꢀ
ꢀ
ꢀ
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
[A m ps P eak] (2)
iPK
=
VAC
η
MIN
iPK
N ote: The PFC inductor m ust not saturate at
over the specified ballast operating tem perature range.
P roper core sizing and air-gapping should be considered in the inductor design.
S tep 3: C alculate m axim um on-tim e:
2
POUT L PFC
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ꢀ ꢀ
ꢀ
ꢀ
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
[Seconds] (3)
tON
=
2
MAX
VAC
η
MIN
S tep 4: C alculate m axim um C O M P voltage:
tON
MAX
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ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
V COMP
=
[V olts] (4)
MAX
0.9 E − 6
S tep 5: S elect zener diode D C O M P value:
≈
ꢀ
ꢀ
ꢀ
zener voltage
V COMP
[V olts] (5)
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
ꢀ
D COMP
MAX
S tep 6: C alculate resistor R S U P P LY value:
VAC
+ 10
MIN
PK
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[O hm s] (6)
R SUPPLY
=
IQCCUV
ꢀ
28
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