Increasing The Capacitance In A Voltage Booster

[Yrton]

Good day, everyone.
Let's picture a classic diagram of a voltage booster which is connected to a capacitor. If we double the capacitance, by replacing it using another capacitor with the same voltage rating as the previous one, will the circuit still be able to charge the new capacitor up to the same voltage as the previous one (though in a longer amount of time)?

 

[Baluncore]

Let's picture a classic diagram of a voltage booster which is connected to a capacitor.

What type of booster do you consider to be classic? Please provide a circuit or a link.

There are AC driven capacitor–diode ladders such as the Cockcroft–Walton multiplier;
https://en.wikipedia.org/wiki/Cockcroft–Walton_generator

Then there are switching DC–DC converters that employ inductive flyback; https://en.wikipedia.org/wiki/Boost_converter
Increasing the output capacitor in that application would proportionally slow the start time and reduce the ripple during operation.
But there will be a problem you must avoid. If the capacitor has a higher capacitance value it will probably have a higher “Effective Series Resistance”. It will then run hot, dry out and fail sooner. Rather than one, use several smaller capacitors in parallel, selected for low ESR. Put some ceramic and if possible some tantalum capacitance in parallel to take the edge of the current spikes.

 

[TheComet]

If the capacitor has a higher capacitance value it will probably have a higher “Effective Series Resistance”. [...] Rather than one, use several smaller capacitors in parallel, selected for low ESR

I am not sure where you are getting this from. The ESR typically decreases with increasing capacitance[1][2]. The reason for choosing different types of capacitors on the output is to better respond to rapid current transients and thus maintain a stable voltage.

With that said, you are still correct (most of the time) when you say choosing multiple smaller low ESR capacitors in place of a single low ESR capacitor can decrease ESR overall, because the differences in ESR from value to value are generally small.

[1] https://en.wikipedia.org/wiki/Equivalent_series_resistance#Capacitors
[2] http://jestineyong.com/esr-meter-table/

 

[Baluncore]

@ the Comet.
You are correct that manufacturers proportionally reduce the ESR for higher capacitance. I was referring to low-cost rolled-foil capacitors where doubling the capacitance halves the reactance, so doubles the AC ripple current. But capacitor temperature will be proportional to I²R so doubling the current requires one quarter the ESR, but the manufacturer only halves the ESR. That will be only partially countered by the increase in surface area for cooling.

For similar materials, a cylindrical capacitor will have a capacitance proportional to volume = the circular end area multiplied by the length, C = A * L. But ESR does not follow the same rule, ESR = A / L. That suggests long thin capacitors have lower ESR than short fat ones.

To double the C of an axial capacitor placed on a PCB, the fixed length will require a √2 increase in diameter. ESR will double.
To double the C of a radial capacitor placed on a PCB, the fixed diameter will require double the length. ESR will halve.

But we do not yet know the OP circuit or the reason for increasing capacitance. At least the OP is now aware of ESR.