Voltage Mode Half Bridge made easier.

[cupoftea]

We are doing a 3kW Half bridge converter. Vin 600V, vout = 24v.
Done in voltage mode for obvious reasons. (Split cap balancing etc)

Cant we just find the output LC resonant frequency....(which is also the frequency of the
troublesome output double poles).
So then all we do is find the Output capacitance.
Then add ESR in series with it such that 1/(2.pi.ESR.Cout) = the aforementioned
resonant frequency.

..then we have an ESR zero which cancels one of the dreaded output LC filter poles.
And then our power stage dynamics have just one output pole instead of the troublesome pole pair.

This makes our feedback compensation much easier, and indeed we only need type 2 feedback compensation.
Is this right?
Why dont people do this?

 

[dick_freebird]

Putting resistor in series with the filter cap? I don't think so.

 

[cupoftea]

Thanks, ...Its to enhance the ESR.
The rail is just a general service rail.
Ayk, there isnt much ripple (relatively) in the output cap of a half bridge, due to the output inductor.
A major telco used to do it some 14 years ago when i was there.

 

[Easy peasy]

Average current mode - CT on the quiet side of the transformer - is a great way to remove the output LC pole

and gives really good dynamic performance when coupled with Vin feed forward.