|
Forward Converter
| Forward
Dc to Dc converter, works
exactly like buck converter, but in this case it is isolated by the
Power transformer |
| Opposite
than Bust converter, the energy is transferred the moment the MOSFET
is turned ON, just like the Buck converter |
| Fig
1 show the basic circuit, Fig 2 represent the closed loop regulator
Diodes rectifiers after the transformer conduce in forward mode
every time MOSFET is switched ON, the Duty Cycle, the Vi and the
transformer turn ratio determines the voltage output level, LC like
in buck converter filter the switching energy and converts to RMS
voltage output |
| R3
sense the voltage output and it is compared with voltage reference
Vref. photo isolated transistor then feedback the PWM signal
required to regulate the voltage according to the value of Diode
Zener Vref.+ Photo diode Vf (Vf = voltage forward of photo diode) |
| The
inductor and capacitor size determinate the switching frequency and
the power output |
Advantages/Applications:
And
it is used for:
Low
output noise and ripple voltage
Avoiding
flux symmetry problems
Disadvantages
Higher
cost than flyback
Inefficient
use of power Transformer
Regulation
problem at high load
Power
circuit has 2 pole
MOSFET
selection
•
Vds
> 1.2 Vin(max)
Ids(max)
> 1.2 Po/(n * Vin(min) * Dmax)
Diode
Selection
Ifmax
>= Io(max)
|
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