Poles and zeros for two transistor forward?

treez · 26th September 2012, 05:23 AM

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 · 26th September 2012, 06:37 AM

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 · 08:32 AM

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 · 26th September 2012, 02:40 PM

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

26th September 2012, 05:23 AM	#1
treez Banned Join Date: Sep 2012	Poles and zeros for two transistor forward? 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?

26th September 2012, 06:37 AM	#2
jan.didden diyAudio Member Join Date: May 2002 Location: Great City of Turnhout, Belgium Blog Entries: 6	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 __________________ /Yes! Its out: Linear Audio Vol 5! I'm not an "accademic", just a plodder who loves a challenge - Ian Hegglun

26th September 2012, 08:22 AM	#3
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	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/(2piESRC) no tricks here. Last edited by darkfenriz; 26th September 2012 at 08:32 AM. Reason: mistake*

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26th September 2012, 02:40 PM	#4
Terry Given diyAudio Member Join Date: Mar 2008	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

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