19-Nov-02
EPR-21 – 5 V, 30 W DC-DC Converter
voltage drop
VDB
0.7 Volts
Bias diode forward voltage drop
TRANSFORMER CORE SELECTION
Core Type
Core
Bobbin
AE
LE
AL
pr14x8
PR14x8
PR14x8_Bo
P/N:
P/N:
0.253 cm^2
2.53 cm
2000 nH/T^2
4.4 mm
B65755-J-R87
B65542-B-T1
Core Effective Cross Sectional Area
Core Effective Path Length
Ungapped Core Effective Inductance
Bobbin Physical Winding Width
BW
Maximum actual gap when zero gap
LG MAX
D FACTOR
L
0.005
1.10
0.005 mm
1.00
specified
Duty cycle factor
Transformer primary layers (split
primary recommended)
NMAIN
NS2
4
0
Main rounded turns
Vout2 rounded secondary turns (AC
stacked winding)
Approximate Output2 voltage of with
NS2 = 0 turns (AC stacked secondary)
VOUT2 ACTUAL
0.0 Volts
TRANSFORMER DESIGN PARAMETERS
NP
15
Primary rounded turns
Max operating flux density at minimum
BM
1449 Gauss
switching frequency
Max transient flux density at minimum
switching frequency
BP
2794 Gauss
Minimum primary magnetizing
inductance (assumes LG MAX-5um)
Peak magnetizing current at minimum
input voltage
LP MIN
0.342 mHenries
IMAG
0.151 Amps
0.38 mm
OD_P
AWG_P
Primary wire outer diameter
Primary Wire Gauge (rounded to
27 AWG
maximum AWG value)
DUTY CYCLE VALUES
Duty cycle at minimum undervoltage
threshold
DUVON MIN
0.68
0.61
0.29
0.22
Duty cycle at minimum DC input
voltage
DVMIN
Duty cycle at maximum DC input
voltage
DVMAX
Duty cycle at maximum DC overvoltage
threshold
DOVOFF MAX
CURRENT WAVESHAPE PARAMETERS
Maximum peak primary current at
maximum DC input voltage
IP
1.835 Amps
Maximum primary RMS current at
minimum DC input voltage
IPRMS
1.246 Amps
COUPLED INDUCTOR OUTPUT PARAMETERS
Main / Output2 coupled output
inductance (referred to Main winding)
Main / Output2 coupled inductor full-
load stored energy
LMAIN
8
8.0 uHenries
144 uJoules
WLMAIN
Power Integrations, Inc.
Tel: +1 408 414 9660 Fax: +1 408 414 9760
www.powerint.com
Page 15 of 32
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