EPR-21 – 5 V, 30 W DC-DC Converter
19-Nov-02
9 PIXls Design Spreadsheet
DCDC_DPAFwd_rev1.02_061802
DPA_061802_R102xls: DPA-Switch
Forward Transformer Design
Spreadsheet
Copyright Power Integrations
Inc. 2002
INPUT
INFO
OUTPUT
UNIT
OUTPUT VOLTAGE AND CURRENT
EP21 DC-DC Converter
VMAIN
IMAIN
VOUT2
IOUT2
POUT
5
6
Volts
Amps
Volts
Main output voltage
Main output current
Output2 voltage
Output2 current
Total output power
Amps
30 Watts
DC bias voltage from output inductor
VBIAS
12.0
Volts
winding
INPUT VOLTAGE AND UV/OV
VMIN
VMAX
36
72
DC volts
DC volts
Minimum DC input voltage
Maximum DC input voltage
min
max
Minimum undervoltage On-Off
threshold
VUV OFF
30
30.0
33.1 DC volts
Maximum undervoltage Off-On
VUV ON
VOV ON
VOV OFF
32.2
74.8
-
34.6 DC volts
- DC volts
threshold (turn-on)
Minimum overvoltage Off-On threshold
Maximum overvoltage On-Off threshold
94.6 DC Volts
(turn-off)
Line Sense resistor value (L-pin) - goal
seek (VUV OFF) for std 1% resistor
series
RL
618.0 kOhm
ENTER DPA-Switch VARIABLES
DPA-Switch
Chosen Device
ILIMIT
dpa424
DPA424
16VDC
Power 15.5 W
Amps
36VDC
35W
From DPA-Switch datasheet
2.32
2.68
Frequency - (F)=400kHz,
f
Full (F) frequency option - 400 kHz
(L)=300kHz
fS
375000
425000
400000
Hertz
From DPA-Switch datasheet
External limit reduction factor (KI=1.0
for default ILIMIT, KI <1.0 for lower
ILIMIT)
KI
1
ILIMITEXT
RX
2.32 Amps
- kOhm
External current limit
Current Limit resistor value (X-pin) -
assumes minimum datasheet curve (fig
32)
Maximum allowed duty cycle at VUV
ON MIN undervoltage threshold
DUVON GOAL
0.71
KDI
0.15
Maximum current ripple factor
DPA-Switch average on-state Drain to
VDS
2 Volts
Source Voltage
Required drain voltage for guaranteed
transformer reset
VDSOP
178.7 Volts
DIODE Vf SELECTION
Main output diodes forward voltage
drop
Secondary output diodes forward
VDMAIN
VDOUT2
0.5 Volts
0.5 Volts
Power Integrations, Inc.
Tel: +1 408 414 9660 Fax: +1 408 414 9760
www.powerint.com
Page 14 of 32
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