On 4/3/06, Jinx <joecolquitt@clear.net.nz> wrote:
> Attached is the block diagram of a PSU I need to build. The bit
> I'm missing is "?"
>
> Input - 12V or 24V automotive/transformer tolerant, down to
> 8V-ish if possible
>
> Output - SLA charger/float, say 0.5A for charging, and 5V,
> around 0.1A. The nominal 12V is also used for 4-20mA
>
> It's necessary for it to be able to recharge a 12V SLA from a 12V
> automotive battery
>
> Any recommendations for this front end ? It doesn't have to be a
> 1-chip solution, can be reasonably complex. Lowest quiescent
> would be best, as other components are planned to be asleep to
> save power if the whole thing isn't on mains, which is when it goes
> over to the SLA as the primary supply
>
> TIA

Looks like SEPIC converter can be a good candidate here if no
transformer isolation is necessary. Just google for "SEPIC Converter"
and there will be many links.

If transformer isolation is necessary, then a Flyback converter is good.
There are many ICs for flyback converter. A 555 timer based PWM controller
and a TL431/Optocoupler based feedback circuit can also do the job
if flyback toplogy is used.

Regards,
Xiaofan

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