charge pump for high current

[haroo]

hello

i want to know can i made charge pump to step up 10v to about 18v with 5A? if iam using capacitor 10000u and 20khz freq?

or it is impossible? if so.. why it is impossible?

 

[tcmtech]

Yes its possible but you will need a capacitor with a very low ESR (Equivalent Series Resistance) value opposed to a common electrolytic type.

On top of that ideally using multiple sets running in a two three or four phase charge pump configuration is even better that way you have multiple capacitors either charging up while others are dumping at the same time.

 

[simonbramble]

why not use a normal boost converter? With a charge pump, the inrush currents at that sort of power would be huge, so you would have to rate your FETs accordingly. A boost converter is a neater way of doing this.. Also, charge pumps are good at doubling and halving voltages, but you have a 'non integer' boost ratio (20V would be better), so this would make the regulation tricky.

I think you will have much less grief understanding how a boost converter works than starting with something simple that has many pitfalls along the way.

The LTC3786 is a suitable part

 

[AnalogKid]

You will need a bipolar driver capable or sourcing and sinking 10 A, and some high speed power diodes, but with the diode drops it should work out. As above, you will need some exceptional capacitors, probably 2 or 3 of different constructions in parallel. Or, an Linear Tech LT1270 will do it smaller, cheaper, cooler.

ak

 

[simonbramble]

The LT1270 won't do 18V/5A on the output. The current in LT boost converters is a specification of the peak inductor current. Obviously with a boost you need to put more current in per Amp of output current, so to get 5A out at nearly double the input voltage, you will need a peak current of about 14A