Boost conversion

[tridentsx]

I am looking for information/circuit examples about boost conversion.

I want to be able to boost 5v from USB all the way up to 25v in small steps and have it s/w controlled by an MCU. What is the best/simplest way to implement this ?

-- Always boost to 25v and then regulate it down with a DAC controlled transistor ?
-- Control the boost circuit somehow by outputting different frequency from the MCU?
-- Other ways of achieving same goal ?

I would also like to know how to use the ADC to measure current to implement a shut off if a certain current level is exceeded. Would I do that by measure voltage drop over a shunt ?

I am working an an universal device programmer and this is the part I am getting stuck at generating the VPP

[Zener]

-- Always boost to 25v and then regulate it down

Yes, with a MAX629 or similar

with a DAC controlled transistor

Something like that

-- Control the boost circuit somehow by outputting different frequency from the MCU?

You could, but that is probably a lot more difficult

-- Other ways of achieving same goal ?

I am sure there are many!

Would I do that by measure voltage drop over a shunt ?

You could, high-side shunt, low-side shunt. You could also look for the voltage dropping out.

[tridentsx]

Thanks a lot for pointing me in the direction of the max629, have ordered a few for testing.

Carl

[adafruit_support_bill]

You can also look at the design page of the Ice Tube clock. That has a boost-converter circuit to drive the VFD display.