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Registered Member #51
Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263
I have designed and tested a 12v to 19v boost converter. I'm using a uc3843 controller, and the circuit works great. My question is this: In regards to the main energy storage inductor, how can I calculate the frequency that I need to run the circuit at to prevent the inductor from saturating? I'm currently using a DR-125-4R7 (4.7uh) at about 50khz and it's working. I however have some "DR-127-1R5" which should heat a lot less, provided that they don't saturate. Can someone help me find the minimum frequency I need to clock my converter at? Average input current to my circuit is about 6-7a.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
V=L*di/dt right?
So dI/dt = V/L, and dI = (V/L) * dt.
dI is the peak ripple amplitude that will appear on the DC flowing through your inductor, dt is the worst-case time that the switch is on for, and V is 12V.
If the sum of dI calculated above, and the DC component of the inductor current, is more than the saturation current listed on the inductor datasheet, it will probably saturate at some time. The DC component is just roughly equal to the input current.
If dI works out larger than the DC component, a trip to the MOSFET store may be in your future.
I think this is roughly how to do it, it's a long time since I've messed with DC-DC converters.
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Question about the saturation of a given inductor
