The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> High-Power Design >> Double input dc-dc converter output voltage for one input and input current for
https://designers-guide.org/forum/YaBB.pl?num=1217483154

Message started by jay kumar on Jul 30^th, 2008, 10:45pm

Title: Double input dc-dc converter output voltage for one input and input current for
Post by jay kumar on Jul 30^th, 2008, 10:45pm

Hi, I am new to this forum.Actually i have doubt regarding to the control loop design in DC-DC converter.
I want to design voltage loop and current loop for multi-input dc-dc converter.For that i want to use method like sequential loop closing method or any other method. How to design control loop for this case .... will it be dependent on voltage loop? I want to design current loop to keep input power always same and voltage loop to keep output voltage always same and it is double input dc-dc converter. How to design such control loops? i know design of single voltage loop. but how voltage and input current loop can be designed for double input dc-dc converter?

Title: Re: Double input dc-dc converter output voltage for one input and input current for
Post by Eugene on Jul 31^st, 2008, 8:11am

Jay,

Before you dive into the control aspects of your converter, make sure you have thought through the physics of your proposal. You are asking for a constant power at the input and constant voltage at the output. I assume you want to regulate the output voltage because the load will vary. As the load varies with output voltage held constant, the output power will vary. The only way you can vary output power without varying input power is to vary the efficiency. Is that really what you want to do?

If you want to control input power only at a very high frequency while you control output voltage at a very low frequency, you might be able to come up with an appropriate control scheme but why not just use an input filter if that's what you have in mind?

Title: Re: Double input dc-dc converter output voltage for one input and input current for
Post by jay kumar on Jul 31^st, 2008, 10:48am

This converter is combination of two converters with two switches(MOSFET) so i want to converter input power of one using duty ratio of corresponding converter and output voltage of converter using another converter switch.So it is kind of MIMO system and it is a converter made up of two converters e.g. one buck and other buck-boost converter integrated with each other sharing one common output inductor.So it is kind of integrated converter made up of two converters.So two switches which u can control .So i just want to have control strategy for it....I think it is MIMO system

Title: Re: Double input dc-dc converter output voltage for one input and input current for
Post by Eugene on Jul 31^st, 2008, 10:42pm

Look at it from an input power in versus output power out standpoint. It really doesn't matter how many converters, switches or control loops you include between the input and output, you still have the problem of varying the efficiency of the overall system if you want to control both input power and output voltage. Do you care about efficiency?

Title: Re: Double input dc-dc converter output voltage for one input and input current for
Post by jay kumar on Aug 1^st, 2008, 4:45am

I want to design for voltage controller and current controller for such system. It is MIMO system and i am not getting how to design controller for MIMO system

Title: Re: Double input dc-dc converter output voltage for one input and input current for
Post by Eugene on Aug 2^nd, 2008, 10:31am

Jay,

You're not answering my question about efficiency, but if I were to deduce one from your entries, I'd say you don't care about the efficiency of your proposed system. OK.

Do you want to control input power independent of output voltage? If not, then why do you need these two control loops? If you do want independent controls, then given that the output power can only be less than or equal to the input power, what do you plan to do with the excess power? I must be missing something.

I'll back out of this discussion at this point and give someone else a chance to help. Good luck.