It is all based on the definition of inductance: V=L*(di/dt) or the applied voltage equals the inductance in henries times the rate of change of current in amperes per second.
If you have chosen your cycle time, then you have to decide what current ripple you are satisfied with during the cycle. You already know the voltages involved.
Take a look at this basic switching regulator tutorial:
I want to charge a bank of four 12V, 100Ah lead-acid batteries using a
Ken Muldrew snipped-for-privacy@ucalgazry.ca (remove all letters after y in the alphabet)
Hello Ken,
To add to John's explanation: You also need to figure out what the highest expected peak current in the inductor will be and size it accordingly. Else you'd be treated to an impressive pyrotechnic scenario.
In a prototype you can watch the inductor current on a scope. If you see a marked rise in slope steepness (like a shark fin) near the current peaks that would indicate that the inductor's core might be too close to saturation.
Often you only see typical saturation data published such as "inductance drops to 75% at x amps". Then you have to contact the mfg to find out what the worst case would be.
Regards, Joerg
try this penguin site, It's a calculator page
martin
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