LM5022-Q1: Sepic converter

Hello Abdelrhaffar,

Thanks for reaching out to us via e2e.

Can you please re-phrase the following question:
> Q2;  Who finds the small signal of the circuit (the SEPIC)? 

Thanks a lot

Harry

Hello, 

With respect to the compensation, you might take a look at this application note: AN-1990 Compensation for Current Mode Control SEPIC Converters (Rev. A). 

Setting the cross over frequency at ~1/10 to 1/5 of the switching frequency is a general rule of power supply design, as this is the frequency range where it is possible to close the loop (where the maximum theoretical frequency is Fsw/2). 

For the small signal model of a SEPIC converter, we recommend checking in the literature. Please let us know if further support is needed. 

Kind regards,

EM 

 to design a compensation network ( type 2 ),  of a Sepic converter, I need to Know the parameters of the small-signal control-to-output transfer function of Sepic. 

thank you.

Hello Abdelrhaffar,

Chapter 3 - Compensator Design   of the document that was recommended in the previous post explains how to design the compensation network.

Best regards
Harry

hi Harry,

but the LM5020 control use the error amplifier, which is an op-amp configured as an inverting amplifier, and the document that was recommended use a Transconductance Amplifier Circuit.

-another question, why the RFB1 resistance is not included in the calculation. (Datasheet LM5022-Q, section :18.2.2.10 Control Loop Compensation).

thank you.

Hello, 

Please refer to this document explaining the compensation network with both an OTA and an OPAMP: https://www.ti.com/lit/an/slva662/slva662.pdf 

As reported at page 2, the bottom feedback resistor when using an OPAMP is just considered a biasing resistor. 

Kind regards,

EM