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|  | m8online
on 03/16 at 04:14 AM
| Category(s): | Technical Questions, power.national.com |
| Subject: | LM3478: Isolated DCDC converter |
| Message: (Notified via email on every direct response) |
Hello,
We are looking for an alternative solution to the 1W isolated DCDC modules like Traco TMA series.
We use them a lot for powering isolated digital outputs.
The main problem with these modules is there rather high idle losses. They are about 150mW per module. We use 8 - 12 of these for each one of our products, leading to a rather high heat development.
I have attached a set-up with an LM3478 with one of Würths WE-flex transformer products.
I like LM3478 for this because it has a small package with a relatively low pin/component count, and a very nice price.
A sketch setup of how I would use it is attached.
LM3478 however, is not specified to be a flyback controller. Why is this? Are there any reasons not to use it for this purpose?
Would there be any parts better suited for this purpose? For example with an integrated driver, or fewer external parts. I have also been thinking about using LM22672 for this because if its small BOM and good properties, but I guess the 100% duty cycle will make this not suitable.
Next question is the feedback. I chose to use indirect feedback as the extra components around an optocoupler are undesirable from both power consumption and cost view. The accuracy needed is not very high. The TME modules specify a load regulation of about 10%.
I do expect that it will be harder to get the loop stable. Are there any easy ways to approach this?
Attached File - ISO_DCDC.pdf
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