P
Premier
M
Magnetics Inc.
"INNOVATORS IN MAGNETICS TECHNOLOGY"
PM-CIXX
CURRENT SENSE
INDUCTORS
CALCULATE THE SCALE FACTOR
From the Table the Secondary Turns are:
N
S
= 100
THEN:
K
V
= R
T
/ N
S
= 100 / 100
= 1 volt/amp
APPLICATION EXAMPLE
APPLICATION EXAMPLE
GIVEN:
Part# = PM-CI02
Peak Current (I
PK
) = 30.0 Amps
Terminating Resistor (R
T
) = 100 Ohms
Operating Frequency (f) = 100KHz
Duty Cycle (Dmax) = .40 (40% on time)
CALCULATE OPERATING FLUX DENSISTY
From the Table the FLUX FACTOR is:
K
B
= 68.49 x 10
3
Flux Utilization Constant (K
F
) is:
1.0 For Unipolar Operation
2.0 For Bipolar Operation
THEN:
B
OP
= K
B
x I
PK
x R
T
x (Dmax / K
F
x f)
= 68.49x10
3
x 30 x 100 x (.4 / 1 x 100x10
3
)
= 822 gauss (OK less than 2000 gauss)
ESTIMATE ERROR DUE TO LOSSES
From the Table the Secondary DCR is:
R
S
= 1.40 Ohms Maximum
From the Table the approximate Loss Factor is:
K
L
= 3.33 x 10
-9
Note: The loss factor (K
L
) is valid approximation
from10KHz to 200KHz
Secondary Copper Losses are:
P_loss
S
= (I
PK
/ N
S
)
2
x R
S
= (30/100)
2
x 1.40
CALCULATE PULSE DROOP
From the Table the Secondary Inductance is:
L
S
= 20mHy Minimum
Note: The actual droop is dependent on the actual L
S
in the circuits enviorment.
Droop Exponent (D) = R
T
x Dmax / (L
S
x f)
= 0.126 Watt
Core losses are:
P_loss
C
= K
L2
x f
1.621
x B
OP2.569
= (3.33x10
-9
)
2
x (100x10
3
)
1.621
x 822
2.569
= 0.0435 Watt
Output Power is:
= 100 x .4 / (20x10 x 100x10 )
P_out
S
= 0.020
= (30/100)
2
x 100
THEN:
%_Droop = (1-e
-D
) x 100
= 1.98 %
OK less than 10%
(Depending on the application
Droop to 20% may be acceptable)
Specifications subject to change without notice.
-3
3
= (I
PK
/ N
S
)
2
x R
T
= 9.00 Watt
THEN:
%_Error
= [(P_loss
S
+ P_loss
C
) / P_out] x 100
= [(.126 + .0435) / 9] x 100
= 1.88 %
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. ]
