TOPswitch HX feedback loop?

[cupoftea]

Hi,
The expression for "Transfer function of a Voltage Mode Flyback power stage" is in the form of "vout(s)/vErr(s) = "

("vErr" refers to the Error voltage of the Feedback loop Error amplifier)
This is then multiplied by the "Error Amplifier and Modulator transfer function" which is in the form of "vErr(s)/vout(s) = "

However, the attached (page 467) gives the Transfer function for the TOPswitch Error Amp and Modulator in the form of "D(s)/vout(s)".

......So how can we use it to produce the overall open loop transfer function, ?...since it would need to be in the form of "vout(s)/vErr(s) = "

 

[FvM]

So how can we use it to produce the overall open loop transfer function, ?

By multiplying with flyback transfer function, probably discussed at a different place in the book. You didn't give a citation, thus we can't check.

 

[cupoftea]

Thanks, the attached is the voltage mode Flyback Power stage transfer function (it says buckboost but ayk, you derive flyabck from buckboost)
The attached is from the other book by the same author, of the stuff in the top post.

I think you will agree that the open loop feedback loop transfer function for voltage mode flyback in dcm or ccm cannot be calculated from this little lot?

 

[cupoftea]

https://www.onsemi.com/pdf/datasheet/fsgm0565rb-d.pdf

....as you see above, it has Rthj-c of 3 degc/w , which isnt far off metal tab to220, so it surely cant be just plastic?

--- Updated Jul 9, 2023 ---

Woops my apologies, the reply in post #4 should not be there.

 

[cupoftea]

So, Apologies...Back to the original thread..

The following (below) links show that there is no way for anyone to do a TOPswitch-HX flyback design in CCM, and assure its stability.....
An offline Flyback is often in CCM at the low level of the universal mains input (eg at 90VAC input).
TOPswitch-HX is also not covered any more by the PI Expert or PI Designer software.

https://www.edaboard.com/threads/expression-for-small-signal-controller-transfer-function-for-type-3-compensator.351360/

Problems with the AN57 document of Power Integrations | Power Integrations, Inc.

Hello,

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topswitch flybacks are voltage mode? | Power Integrations, Inc.

Hello, I note that topswitch flybacks are voltage mode. I note that most of the powerint.com design notes show feedback using TL431/opto. However, page 641 of the book, "switch mode power supplies" by Christophe basso, states that "A voltage mode CCM flyback can be stabilized using a type 3...

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