Help to find PWM controllers and other parts for push/pull DC/DC converter

Hello Adrien
The first thing is to try to decide on the correct topology to use. Normally at this power level and for these low input voltages we would suggest a Push-Pull circuit. Diode rectification is actually a good choice for a 350Vdc output. The Vf of the diodes would be about 1.5V (if you use Sic) and if you use a full bridge rectifier you will lose about 3V across them - this is less than 1% of the output power and at 3.2A each diode would dissipate about 1.5*3.2*0.5 or 2.4W - which is manageable. If you decide to use SRs you would need to use 600V parts with an Rds on of less than 240mOhms just to break even and neglecting gate drive losses. I'm not saying that HV SR is not worthwhile but the gains are less than they would be at 12V out for example.

The controller will use the feedback network to regulate Vout at its setpoint of 350V. You will need to choose the transformer turns ratio of course to give you reasonable duty cycles.

I can't really comment on your choice of a particular MOSFET - there are a number of very good MOSFET manufacturers in the market. TI offers a range of low voltage MOSFETs with low gate charge - which will help speed up the turn-on and turn-off process,. The product range is at www.ti.com/.../products.html The best approach is to design the power stage first then start looking for a MOSFET that meets the requirements.

Many controllers have relatively weak outputs which are intended as input signals to external MOSFET drivers. This has some advantages because you can easily find 4A drivers and you can place the drivers nearer to the MOSFETs. If you are paralleling MOSFETs it's vital to use separate gate drive resistors - this will be recommended by the MOSFET manufacturer to prevent destructive high frequency gate oscillations. TI UCC27524A1 is a MOSFET driver with 5A peak current for example.

You may find our reference design at www.ti.com/.../tiduai7.pdf of interest. It is a bidirectional converter at 300W. The controller operates it as a Phase Shifted Full bridge in one direction (400V to 12V) and as a Push-Pull in the other direction (12V to 400V). Control is via a microcontroller which isn't your first choice but the power stage may be of interest.

As regards controllers - you need to decide whether to use current mode control or voltage mode control. Normally current mode control is a better choice because you get cycle-by cycle current limiting protection. Then the choice would be to use newer devices rather than older ones.

As you discovered, TI has a very large product portfolio and it's sometimes difficult to know where to start looking.
Anyhow, I did a quick search using our product selector www.ti.com/.../products.html which returned 38 devices. The lowest cost 8 pin SOIC part was UCC28085 - so that is where I would start. If you needed some added functionality the UC3525A is in a 16 pin package and appears at the top of the list and is also on your list.

Hope this helps, please let us know if you need any more information.
Regards
Colin

Hello Adrien

Current mode control usually controls the peak current in the primary side switches. In your case that would be 110A plus the output inductor current ripple (reflected through the transformer).

As regards current sensing. The best options are a Current Transformer or a Hall Effect sensor. A resistive sensor will dissipate a lot of energy.

You can find a lot of material at www.ti.com/.../login.shtml which covers all aspects of PSU design. the topic at www.ti.com/.../slup114.pdf covers current sensing in some detail, including current transformers and hall effect sensors.
Regards
Colin

Thanks a lot for your perfect helpful answers !