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According to this link putting a high voltage capacitor on a low voltage system is usually safe: High-voltage capacitor in a low-voltage system

So, if a system requires 16V 2200µF capacitor, I can safely put 25 volts and even 50 / 63 volts if the capacitance is 2200µF. I can't put less than 16 volts because it will damage or blow up the capacitor.

But what happens if you go way too high?

This is mostly a theoretical "what if" question. Let's say one has no space and economical limit:

  1. What happens if I put a capacitor that has 100,000x the actual voltage rating that the circuit requires? Does the circuit function properly?

  2. What happens if the circuit is a high frequency circuit (say few megahertz) and the capacitor is replaced with 100,000x the original voltage rating? Does the circuit function properly?

  3. Is there a limit to how high you can go on the voltage on any capacitor (tantalum to tantalum, ceramic to ceramic, etc.) (again, considering you have no economical or space limit)?

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What happens if I put a capacitor that has 100,000x the actual voltage rating that the circuit requires? Does the circuit function properly?

Other things being equal, yes.

What happens if the circuit is a high frequency circuit (say few megahertz) and the capacitor is replaced with 100,000x the original voltage rating? Does the circuit function properly?

This is where the 'other things' might not be equal. A higher voltage rating capacitor must be physically larger. Once in an RF circuit, the length of a component contributes delay and inductance, the area contributes stray capacitance to other components and ground. The RF circuit might still function with these increases, or it might not.

Is there a limit to how high you can go on the voltage on any capacitor (tantalum to tantalum, ceramic to ceramic, etc.) (again, considering you have no economical or space limit)?

It's a practical consideration. Above a certain voltage, uniformity of the electric field in the dielectric becomes difficult to assure, so you have to build a high voltage component as several low voltage components in series, or to operate at a lower design field (uneconomic). For instance, a 2 kV plastic capacitor is often built internally as two 1 kV caps in series, by adding an extra floating electrode to the dielectric film. High and uncertain leakage constructions like tantalum would probably need external balancing components to make sure the voltage divides equally between them.

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I'd say there is no definitive answer to this question. If the only difference between the capacitors would be voltage rating, you could go as high as you want and it would not affect the circuit at all.

But usually there is more to it. A high voltage capacitor is usually larger and thus has more inductance, possibly higher ESR etc. which of course may affect the circuit.

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