Power Supplies Topologies,Full Bridge converter

Full Bridge Converter

To Power Supplies Topologies, table of contents, Quick links

Full Bridge Converter

Full Bridge Converter are two Half bridge Converters, but the output of each powered stage are inverted in polarity, driving the transformer harder like in H mode load

Fig 1 show the basic circuit, note that transformer are connected between the two half bridge outputs in order to utilize both polarities of magnetic flux of the transformer, with no capacitors dividers like in Half bridge

Diodes D2 rectifier the forwarded energy from the four 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

Advantages/Applications:

It is used for:

Provide high output power and efficient designs

Optimize transformer utilization

Advantages

Provides same advantages as HB

Only one 60cps bulk cap.

Provides 2 times the output power of the HB with the same Switch MOSFETS

Disadvantages

It requires 4 MOSFETS and 4 drivers

Power circuit has 2 pole

It can be used in current mode PWM control

MOSFET selection

Vds > 1.1 Vin(max)

Ids(max) > Po/(n*Vin(min))

Diodes Selection

Ifmax >= Io(max), If(avg)=0.5Io(max)

D01 should be fast (20-100nS)

Go to top

To Power Supplies Topologies, table of contents, Quick links