I'm looking to make a DC/DC conversion with:
an input range of 8V to 20V
output of 12V
and output current of 60A
Am I able to use a SEPIC to do this? If not, why not?
What would be the most economical way to do this?
I have some flexibility in my output current requirement ... I'm trying to find a direction for the best approach to get high current though.
That power level is 720 watts out of the converter.
The RMS current in the capacitors would require too much capacitance to be practical.
I don't know if you have an isolation requirement, I am going to suggest that you use a phase shifted full bridge converter. Look at the UCC28950 converter for the controller but you will need an internal house keeping supply. A small flyback should work there. Choose a converter with a minimum start-up voltage below the 8V to generate the required internal house keeping voltage. The UCC3800 family has parts that operate to below 5 volts.
Isolation is a soft requirement. Cost constraints are dominant.
I don't see any handy application references for the UCC28950 with a DC V input that varies above and below the V ouput. I also don't see much that provides a high output current.
It also looks like it will be much more expensive than the SEPIC solutions (per Watt). I'm hesitant to invest too much time into design variations with something that seems expensive. Can you point to some kind of circuit that is similar to what I'm looking to achieve so that I can put together a preliminary BOM cost?
Thanks for your suggestion regardless of availability of more information.
This is nonisolated solution. Works grate in wide input voltage rang. LTC3789 and LTC3780.
Sorry it took so long to get back to you. I was trying to see what other options would be available. The problem is that you need a converter that can convert a voltage both up and down and when the input is equal to the output short the input to the output. Without switching the charge on the "shorted switches" will dissipate and the shorted switches will become open. With switching you will be both bucking and boosting the voltage at the same time. This could create some interesting control problems.
In my opinion best choise at the power levels that you are talking about would be to use a UC2827-2. This provides a buck regulator followed by what is effectively a buss converter.
I've drawn the power section that I would start with using the buck portion to drop the input voltage to about 6 volts and then boosting it either in a push-pull configuration to 12 volts on the output or an auto-transformer configuration to achieve the same results.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.