I need to test a tantalum capacitor(check if it gets shorted for a spike higher than the rated voltage) and I'm planning for providing voltage spikes to the input connector from a bench top power supply. Is there any technique apart from switching the supply ON and OFF quickly to provide a voltage spike?
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\$\begingroup\$ That test doesn't test short circuit capability. \$\endgroup\$– Andy akaCommented Jul 1, 2016 at 9:22
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\$\begingroup\$ Sorry, I should have been more clear. I'm trying to check if the tantalum cap gets shorted for a spike higher than the rated voltage. \$\endgroup\$– Saranraj AnnamalaiCommented Jul 1, 2016 at 9:32
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\$\begingroup\$ You need to be able to control spike height (voltage) and spike width (duration) and shape. Also consider that in normal use the capacitor will have a standing DC voltage (say 2/3rds working voltage) with the spike voltage superimposed. Just switching the supply on and off won't be a repeatable test \$\endgroup\$– JIm DeardenCommented Jul 1, 2016 at 9:53
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\$\begingroup\$ You can easily build an impulse generator circuit from a few passive components (in conjunction with your PSU) - do a Google search, particularly for 8/20us, as this is a common waveform for surge testing. You can tweak the values to get the response you want. \$\endgroup\$– user57709Commented Jul 1, 2016 at 10:07
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\$\begingroup\$ Be careful with it: Tantalums can become spectacularly pyrotechnic. Far better to actually heal the device by using a higher voltage than it will see via a 1k or so resistor. \$\endgroup\$– Peter SmithCommented Jul 1, 2016 at 10:54
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2 Answers
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simulate this circuit – Schematic created using CircuitLab
Values to get the results you want, by experimentation and observation, or by calculation if so inclined. It's foolish to knowingly exceed the ratings of a type of capacitor known for spectacular failures - you should concentrate on clamping/dumping any such pulse so that the capacitor does not see it - using any part beyond its ratings is a poor design choice and subject to any manufacturing change which meets the rated behavior but changes the beyond-rated behavior.
Depending on what you actually want/need you can add additional resistance in series with C1 or in parallel with Q1
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\$\begingroup\$ Thanks for the circuit. I wanted to confirm if the voltage spike in the power supply would have damaged the cap. Hence testing it \$\endgroup\$ Commented Jul 3, 2016 at 1:36
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It is typical that when you devise a particular testing scheme you have to design and configure the test setup as well. That could be the use and integration of ready made lab equipment or you could be building you your own test sets. (Note that it is not uncommon to use a combination of these approaches, for example, using a pulse generator to trigger a high voltage driver circuit that you build. Another example may be a ready made MCU board like an Arduino to activate a driver/monitor circuit).
answered Jul 1, 2016 at 10:48