# High Voltage Power Supply Design

I need to charge a 1000uF 400V capacitor bank off of a 7V LiPo battery within roughly 5 seconds, and have the circuit be as small and light weight as possible. With a constant voltage supply and a resistor to limit the current, the peak current when the capacitors are discharged is around 200mA, and with a constant current power supply the peak current is around 100mA. The constant current supply would also make other parts of my circuit easier, so I would like to have the power supply current limited if possible.

The flyback converter seems like the best topology so far, but how does the flyback compare to other topologies like cascaded boost and boost with autotransformer converters for this kind of voltage?

Would constant current flyback controllers like the UCC28700 and LT3798 work for this? All the ones I can find seem to be designed for stepping down voltages from rectified AC power to a low voltage DC, and I'm not sure if it is possible to run the the opposite way.

There are a few other questions on here about high voltage supplies, but they're all limited to current levels in the uA, so I'd appreciate some direction.

• Are those current numbers at 400V or 7V? Because 400V*0.2A = 80W charge supply! That's a big flashgun. Commented Nov 5, 2015 at 12:42
• Your requirements are unclear. This site is not geared up to write lengthy generalized comparisons between several techniques of the kind you mention so maybe you can make this easier by being clearer in your requirements. Commented Nov 5, 2015 at 12:44
• Yep, in order to charge 1000uF within 5s, it would have to supply 80W peak if it didn't support current limiting, or 40W peak if it did. I'm not sure what's unclear in my requirements, I want to make the lightest possible constant current/constant voltage power supply to those specs. Commented Nov 5, 2015 at 12:59
• After doing some more reading it doesn't seem like push-pull or forward converters are suitable at these voltage levels, so I removed them from the post. Feel free to correct me if that's not the case. Commented Nov 5, 2015 at 13:02
• What part of my requirements were you unclear on? Commented Nov 5, 2015 at 13:05