P
Premier
M
Magnetics Inc.
"INNOVATORS IN MAGNETICS TECHNOLOGY"
!
Designed for use with Leading Controller Chips
#
Provides DC/DC Conversion & Isolation
GENERAL APPLICATION INFORMATION
SWITCH MODE DC/DC
POWER CONVERSION
TRANSFORMERS
"
Design Engineenring Support Available.
$
Multiple Configurations.
Premier Magnetics' Switch Mode Output transformers have been designed for use with the most popular current-
mode switching regulators such as Linear Technologies LT1X7X & National Semiconductors LM25XX series of High
Efficiency Switching Regulators. These output transformers have been optimized to provide maximum power
throughput in the smallest packages currently available. This combination of components finds wide use in
Distributed Power Systems where a main dc voltage bus is converted for use on or near the circuits being served.
These types of switching regulators provide a very simple solution to power conversion designs. The inductor or
transformer used are critical to the overall performance of the converter and typically define the overall efficiency,
output power and physical size.
The following tables of transformers were designed for use in the Flyback Buck-Boost circuit configuration. This
conversion topology allows the output voltage to be regulated higher or lower than the input voltage. It can also
provide isolated or non-isolated multiple outputs. Typical efficiency of this topology is 75%.
Below is a typical application circuit utilizing Linear Technologies LT1X7X switching regulator in the flyback buck-
boost configuration. The use of Premiers VTP-01XXX or VTK-01XXX optional output filter choke will drastically reduce
output ripple and noise. The component values listed are intended for reference purposes only. The Output Filter(s),
Damper Network & Foldback Current Limiting Network are optional depending on the specific application.
General Component Values:
R3 = 1.0K 1/8W
D1 = MBRXXX, Schottky Rectifier
C3 = 2.2uF Film
D2 = MBRXXX, Schottky Rectifier
R4 = 1.5K 1W Snubber
D3 = MBRXXX, Schottky Rectifier
C4 = .47uF Film
C1 = Electrolytic
R5 = 2.0K 1W
C7 = Electrolytic
C5 = 0.1uF Ceramic
R6 = 1% Metal Film as needed.
L1 = 10uHy @ Rated DC amps (VTP-XXXX)
C6 = 1000uF Electrolytic
L2 = 10uHy @ Rated DC amps (VTP-XXXX)
C8 = 1000uF Electrolytic
Np:Ns2
R1 = 1% Metal Film, For 5Vdc = 3.0K, For 9Vdc = 9.09K
R1 = [Vout-Vref/Vref] * R2, where Vref = 1.244 for LT1X7X series
R2 = 1% Metal Film, For 5Vdc = 1.0K, For 9Vdc = 1.5K
C2 = Input Bypass Capacitor 100uF Electrolytic
SCHEMATIC
D3
OUTPUT FILTER
L2
C7
+
C8
+
+Vout2
Isolated Output
FLYBACK Buck-Boost CONVERTER USING LT1X7X
RC Snubber
Damper
D1
OUTPUT FILTER
-Vout2
+Vin
R4
C4
R5
C5
T1
C1
+
L1
C6
+
+Vout1
D2
Vin
Linear Technology
LT-1X70 = 5A
LT-1X71 = 2.5A
LT-1X72 = 1.25A
LT-107X = 40KHz
LT-117X = 100KHz
R1
Vsw
Np:Ns1
R6
Foldback
Current Limiting
pmsm 6/97
C2
* *
E1 E2 GND
FB
Vc
Frequency
Compensation
R3
C3
1N914
+
R2
Specifications subject to change without notice.
20381 BARENTS SEA CIRCLE, LAKE FOREST, CA 92630
•
TEL: (949) 452-0511
•
FAX: (949) 452-0512
•
http://www.premiermag.com
1
PMI [ PREMIER MAGNETICS, INC. ]
