Push Pull DC to DC Converter

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Push Pull Converter

Push Pull Converter, are two forward topologies where the summing energy is the transformer with a center tap winding
Fig 1 show the basic circuit, note that transformer are connected between the two MOSFETS drain terminals to utilize both polarities of magnetic flux of the transformer, and the center tap is connected to Vi
Diodes  D1 rectifier the forwarded energy from the two MOSFETS.
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 size of the inductor and capacitor determinate the switching frequency and the power output
 It is used for:
 Small size and weight (widely used in Car audio amplifiers)
 Provide high output power and efficient designs
 Easier base drive (both switching devices are referenced to GND)
 Inherent flux symmetry problems
 MOSFETS rating twice the input supply voltage
 Power circuit has 2 pole
 MOSFET selection
 Vds > 1.1 Vin(max)
 Ic(max) >  Po/(n*Vin(min))
 Diode Selection
 Ifmax >= Io(max), If(avg)=0.5Io(max)
 D01 should be fast reverse recovery rectifiers

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