MURB1620CTT4 ,16A 200V Ultrafast Rectifierhttp://onsemi.comAPPLICATION NOTEINTRODUCTION forward converter. With additional modifications, it ..
MURB1620CTT4G , SWITCHMODE Power Rectifier D2PAK Power Surface Mount Package
MURB1620CTTRL ,200V 16A HEXFRED Common Cathode Diode in a D2-Pak (UltraFast) packageApplicationsInternational Rectifier's MUR.. series are the state of the art Ultra fast recovery rec ..
MURB1660CTT4 ,16A 600V Ultrafast RectifierELECTRICAL CHARACTERISTICS (Per Leg)Characteristic Symbol Max UnitMaximum Instantaneous Forward Vol ..
MURB2020CT ,200V 20A HEXFRED Common Cathode Diode in a D2-Pak (UltraFast) packageBulletin PD-20729 rev. C 12/03MUR2020CTMURB2020CTMURB2020CT-1Ultrafast Rectifier
MURB2020CT-1 ,200V 20A HEXFRED Common Cathode Diode in a TO-262 packageFeaturest = 25nsrr • Ultrafast Recovery Time• Low Forward Voltage DropI = 20AmpF(AV)• Low Lea ..
NC7SZ126L6X ,TinyLogic UHS Buffer with 3-STATE OutputNC7SZ126 TinyLogic UHS Buffer with 3-STATE OutputOctober 1996Revised February 2005NC7SZ126TinyLogi ..
NC7SZ126M5X ,TinyLogic UHS Buffer with 3-STATE OutputNC7SZ126 TinyLogic UHS Buffer with 3-STATE OutputOctober 1996Revised February 2005NC7SZ126TinyLogi ..
NC7SZ126P5X ,TinyLogic UHS Buffer with 3-STATE OutputNC7SZ126 TinyLogic UHS Buffer with 3-STATE OutputOctober 1996Revised February 2005NC7SZ126TinyLogi ..
NC7SZ14L6X ,TinyLogic UHS Inverter with Schmitt Trigger InputElectrical Characteristics (Continued)V T = +25°CT = −40°C to +85°CCC A ASymbol Parameter Unit Con ..
NC7SZ14M5X ,TinyLogic UHS Inverter with Schmitt Trigger InputNC7SZ14 TinyLogic UHS Inverter with Schmitt Trigger InputOctober 1996Revised August 2004NC7SZ14Tin ..
NC7SZ14P5X ,TinyLogic UHS Inverter with Schmitt Trigger InputNC7SZ14 TinyLogic UHS Inverter with Schmitt Trigger InputOctober 1996Revised August 2004NC7SZ14Tin ..
MPSW42-MURB1620CT-MURB1620CTR-MURB1620CTRT4-MURB1620CTT4-UC3845BD-UC3845BD1R2-UC3845BVD
One Watt High Voltage Transistor
AND8039/D
The One-Transistor
Forward Converter
Prepared by: Marty Brown
INTRODUCTIONThe one–transistor forward converter is the most
elementary form of transformer–isolated buck converter. It
is typically used in off–line applications in the 100–300 watt
region. This application note illustrates the approach one
would take to design a high DC input voltage, one–transistor
forward converter. With additional modifications, it could
be made work as a 110 V
Description of OperationA simplified schematic of a one–transistor forward
converter can be seen in Figure 1.
+VIN
GND
Figure 1. Simplified Schematic of a One Transistor Forward ConverterOne can see a transformer has been placed between the
input voltage and a buck converter output stage. The power
switch (SW) is used to create a rectangular voltage
waveform whose amplitude is the input voltage and its duty
cycle is the controllable variable. The transformer provides
both a step–up or down function and a safety dielectric
isolation between the input line and the output load.
The major restriction of this topology is the maximum
duty cycle must be about 50 percent. Whenever a core is
driven in a unidirectional fashion, that is, current only being
driven from one direction into the primary, the core must be
reset. Magnetization energy which serves only to reorient
the magnetic domains within the core must be emptied, or
else the core will “walk–up” to saturation after a few cycles.
To do this, one needs to reset the core. Resetting is done by
rectifiers are not conducting. Any winding can provide the
reset function, but the higher the voltage on the winding, the
quicker the core will reset. Typically, this is the primary
winding or a separate reset winding of equal turns to the
primary. Current from the reset winding can then be returned
to the input capacitor and reused during the next cycle of
operation.
The typical switch voltage and current can be seen in
Figure 2. When the power switch is ON, the switch sees the
output filter inductor’s current reflected by through the
transformer. The amplitude of the primary current is the
output rectifier current times turns ratio of the transformer
(N1/N2) plus a small amount of magnetization current.
During the power switch OFF time, the switch voltage “flys”
up to about twice the input voltage. During this time, the
