PM-CIXX
CURRENT SENSE
INDUCTORS
Premier
P
M
Magnetics Inc.
"INNOVATORS IN MAGNETICS TECHNOLOGY"
APPLICATION EXAMPLE
APPLICATION EXAMPLE
CALCULATE THE SCALE FACTOR
From the Table the Secondary Turns are:
NS = 100
GIVEN:
Part# = PM-CI02
THEN:
Peak Current (IPK) = 30.0 Amps
Terminating Resistor (RT) = 100 Ohms
Operating Frequency (f) = 100KHz
Duty Cycle (Dmax) = .40 (40% on time)
KV = RT / NS
= 100 / 100
= 1 volt/amp
CALCULATE OPERATING FLUX DENSISTY
From the Table the FLUX FACTOR is:
KB = 68.49 x 103
ESTIMATE ERROR DUE TO LOSSES
From the Table the Secondary DCR is:
RS = 1.40 Ohms Maximum
Flux Utilization Constant (KF) is:
1.0 For Unipolar Operation
2.0 For Bipolar Operation
From the Table the approximate Loss Factor is:
KL = 3.33 x 10-9
THEN:
Note: The loss factor (KL) is valid approximation
from10KHz to 200KHz
BOP = KB x IPK x RT x (Dmax / KF x f)
= 68.49x103 x 30 x 100 x (.4 / 1 x 100x103)
= 822 gauss (OK less than 2000 gauss)
Secondary Copper Losses are:
P_lossS = (IPK / NS )2 x RS
= (30/100)2 x 1.40
= 0.126 Watt
CALCULATE PULSE DROOP
From the Table the Secondary Inductance is:
LS = 20mHy Minimum
Core losses are:
P_lossC = KL x f1.621 x BOP
2
2.569
Note: The actual droop is dependent on the actual LS
in the circuits enviorment.
= (3.33x10-9)2 x (100x103)1.621 x 8222.569
= 0.0435 Watt
Droop Exponent (D) = RT x Dmax / (LS x f)
= 100 x .4 / (20x10-3 x 100x103)
= 0.020
Output Power is:
P_outS
= (IPK / NS )2 x RT
= (30/100)2 x 100
= 9.00 Watt
THEN:
%_Droop = (1-e-D) x 100
= 1.98 %
THEN:
OK less than 10%
(Depending on the application
Droop to 20% may be acceptable)
%_Error = [(P_lossS + P_lossC ) / P_out] x 100
= [(.126 + .0435) / 9] x 100
= 1.88 %
Specifications subject to change without notice.
pmci 4/97
20381 BARENTS SEA CIRCLE, LAKE FOREST, CA 92630 • TEL: (949) 452-0511 • FAX: (949) 452-0512 • http://www.premiermag.com
2
PMI [ PREMIER MAGNETICS, INC. ]
