> I was thinking the PWM should allow Vout to be the same as Vin
> (except for the MOSFET loss) when the PWM is at 100%

As the duty cycle changes, does the apparent (depth of) colour ?

If so, is it important ?

SMPS needn't be too complicated. The MC34063 is one I use
often, but Microchip, National, Linear etc have simpler SMSP
controllers which need fewer components

Describes step-up and step-down

http://www.onsemi.com/pub_link/Collateral/MC34063A-D.PDF

Fig18 is a buck-boost I use=20

http://www.intusoft.com/onsemipdfs/an920-d.pdf

Very handy when the input DC can be wide-ranging. For example
an SLA that could go from 11V+ to 14V and you need 12V out
or being able to grab just about any wallwart (particularly if a bridge
is added to the input to fix wrong polarity or AC)

Add a bypass element (eg FET or power transistor stage) for more
output current. Note current ratings of Q1 and Rsc. R1, R2 set Vout

Joe
--=20
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