bogdan2011
Member
I've been contemplating at building a two switch forward converter for some time. Since I need a power supply for some powered speakers, I thought it's a good time to build one.
As far as I've learned about this topology, the advantages are:
- single ended drive (it can use any flyback controller)
- it can do current mode easily
- single positive DC rail needed (unlike half bridge)
- can do as high power as a half bridge
- no need for a reset winding
- seems more robust
The biggest disadvantage is the high side transistor drive circuitry, which can't be the same as in a half bridge since both transistors turn on at the same time, so there's no way to charge the bootstrap capacitor. There are integrated drivers that can work with this topology, but they're rare. The easiest method is by using a gate drive transformer.
Schematic is below. Feel free to discuss and suggest anything.
I chose a typical main transformer, but any big enough core can be used, even salvaged from an ATX power supply.
The gate drive transformer can also be salvaged from ATX power supplies or EE16, EE25 or even small green toroids can be used. The smallest one I tested could fit on a fingertip, and it was bifilar winded. The windings must have the same polarity.
As far as I've learned about this topology, the advantages are:
- single ended drive (it can use any flyback controller)
- it can do current mode easily
- single positive DC rail needed (unlike half bridge)
- can do as high power as a half bridge
- no need for a reset winding
- seems more robust
The biggest disadvantage is the high side transistor drive circuitry, which can't be the same as in a half bridge since both transistors turn on at the same time, so there's no way to charge the bootstrap capacitor. There are integrated drivers that can work with this topology, but they're rare. The easiest method is by using a gate drive transformer.
Schematic is below. Feel free to discuss and suggest anything.
I chose a typical main transformer, but any big enough core can be used, even salvaged from an ATX power supply.
The gate drive transformer can also be salvaged from ATX power supplies or EE16, EE25 or even small green toroids can be used. The smallest one I tested could fit on a fingertip, and it was bifilar winded. The windings must have the same polarity.