Power Converter Design: Wide Input


Thread Starter


Hello there,

Working on a project where I need to implement a high efficiency (>98%) and low-cost converter for SOEC/SOFC. The system specifications are only just being set.

I know that my converter will have a wide voltage input range, about 20V to 400V. I'm also looking to use a boost (or buck-boost) isolated converter. I will decide later if it will need to be bidirectional or not.

What problems do you foresee when implementing a converter with this wide input range? Also, does anyone have any topology thoughts?
As far as I can see, this will be a very challenging task. One issue is related to input side - the input stage will oprate at high current (at 20V input) but it also must work at high voltage of 400V. Therefore, if you choose a single-stage converter, you might find yourself stuck with bulky supply that nobody wants. Therefore, you might try to use more flexible approach.
Another issue is control. Generally, control transfer function gain is directly proportional to the input voltage value. With extremely wide input range, the gain will vary significantly therefore you will either slow down your regulation (maybe beyond reasonable limits) or use some adaptive control method (usually nonlinear).
It is a question with many answers, including zero. It depends on power level and isolating transformer ratio. If the power level is low (below 30-50W), maybe you could try with flyback converter. Still, the problem of 20:1 input voltage range is what certainly will give you headaches, due to very wide duty ratio and possible very short driving impulses with high input voltage. Also, there is a family of quadratic boost converters which have much higher gain than regular boost. I am not very familiar with it but it is possible for you to find an interesting solution.