Power converter design – wide input range

Hi all!

I am starting a project with the main objective to implement a high efficiency (>98%) and low cost converter for SOEC/SOFC.

I am at the first stage where the system specifications are being set. I have arrived to the conclusion that my converter will have a wide voltage input range, approximately 20V to 400V. It will probably be a boost (or buck-boost) isolated converter, still need to be specified if will be bidirectional or not.

My question is, which are the problems I will have to face when implementing a converter with this wide input range and if anyone could give me any recommendation regarding topologies or any other issue.

Thanks!

Kevin

What is the required output voltage? If it is less than 20V, you only need a buck converter. There are many buck converter ICs available which have regulation capability that you can use.

Hi Rohit, thanls for your reply, but I don't think this would be solution for my case. As I said it is a SOEC/SOFC system, SOCs have high output currents, so the power capacity of my converter should be quite high, at least >3kW.

Furthermore, I would like to have an isolated topology.

3kW output with a 20V input? If I read it correctly you mentioned that the input voltage range is 20-400V. Or did you mean 200-400V? Also, what is the o/p voltage required?

You need to convert the incoming AC to DC, convert that (i.e., switch via MOSFETs) to a high frequency square wave and feed that to a high-current switching transformer (most SMPS have these) with windings so sized that it can handle the minimum input peak and give the rated peak output. The ckt that creates the HF square wave needs to be of a variable duty-cycle type with feedback so that it can adjust the square wave's pulse width in order to regulate the output.

The transformer's o/p should be rectified by high speed/high current diodes and filtered to get the required DC.

Sorry, I probably did not explain well the performance of the system.

First, there has been a recent recalculation of the specs for the system and the input range will be 20V to 180V (think as a variable dc power supply).

Then, the 3kW is the maximum power capacity. The SOC cells have an U-I characteristic which changes through a wide range and with the configuration I am desigining the dynamics of the system is not linear at all. In other words, at 20V the power load will be much lower than 3kW.

The output voltage has not been specified yet, but a boost or buck-boost topology will be required.