that relying solely on simulation is also a recipe for trouble
.....agree entirely, simulation is just a part of the prep......a prototype would alwyas be made and tested.
What application needs 12V to 100V input voltage?
Many LED specs are this wide, because its cheaper to have one lamp that can be used by many different applications with different supply voltages.
However, in this case, the 12-100V input voltage is either a car battery (12V) , or a fork lift truck battery (~80-90V).
....ie the same lamp can be used on the car or the forklift
I have several horror stories of PSUs related to optocouplers
Please share you SMPS optocoupler feedback horror stories...heres one.....
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As an aside, I once worked at a huge company where 400 out of 1000 field prototype SMPS’s went unstable. The equipment that they were running was inoperable as a result of the SMPS’s instability.
The 400 unstable units were exactly the same as the stable ones except for the optocoupler……..their optocoupler was the exact same part number as the ones in the stable units, but was branded differently, being manufactured by Fairchild instead of Vishay. (so it was the same opto, but just manufactured by a different company)
Though it was the (slight) change in optocoupler that precipitated the instability, the fact was that the SMPS did not have enough margin designed in to its feedback loop in order to handle the “normal” optocoupler parameter variations between the differently branded opto’s, ….in conjunction with the extra capacitance of the load…..
All 1000 SMPS units had actually been stable when operated into electronic loads in the lab.
-It was the field connection of these 400 SMPS’s that precipitated the instability….that is, the load equipment included a fairly large input capacitor bank, and this precipitated the instability, in conjunction with the different optocoupler parameters.
(The 600 SMPS’s with the Vishay optocoupler were stable when connected to the load and its capacitor bank)
The SMPS had an output LC filter. As you know, the cut-off frequency of this filter should be well above the crossover frequency of the SMPS (2 to 3 times).
With the added capacitance of the load capacitor bank, the LC cut off frequency was then brought down too low when compared to the SMPS crossover frequency……that is, the crossover frequency of those SMPS’s that featured the Vishay optocoupler, with its slightly variant parameters.
Using the cascode connection of the optocoupler, one can make it easier to achieve stability with these situations. You will be able to more easily avoid being caught out.