Poles and zeros for two transistor forward?

[treez]

Hello,

Can any reader list the poles and zeros for a two transistor forward converter?

i.e. for the power stage and modulator?

The control chip is UCC38C44
http://www.ti.com/lit/ds/symlink/ucc38c44.pdf

Vin = 385VDC
Vout = 80V
Load = 20 Ohms (maximum, heavyest load)
Switching frequency = 85KHz
C(out) = 940uF
ESR of Cout = 0.1 Ohm
L(out) = 186uH
Turns ratio (Ns/Np) = 46/50
Current sense resistor = 0.15 Ohms
Continuous conduction Mode.
Duty cycle at max load (20R) = 0.24



...its for Class B amp supply. (output is actually +/-40V, but lets call it 80V...i hope thats OK?

 

[jan.didden]

It's over my head but TI has a free downloadable spice simulator for it's own products that will do this for you, called Tina.

jan didden

 

[darkfenriz]

Current loop: pole at Rsense and (Lout/turns ratio) i.e. R/2piL
Voltage loop: pole at Cout Rload i.e. 1/2piRC, zero at Cout ESR i.e. 1/(2*pi*ESR*C)
no tricks here.

 

[Terry Given]

yes. and given that Treez cant play with the current loop at all, might as well pretend its perfect, and treat the entire power stage as a transconductance. gm = delta_Iout/delta_Vcomp. thats pretty easy to work out - but dont forget the x1/3 from Vcomp to Vcurrentsense