Apptech wrote:
> I'll be picky for completeness.
> In most boost converter applications, yes.
> I happen to be adapting a product at present with a boost
> converter that has (or had) no output diode!
> It's a LED driver and they feed AC pulses to the LED.

OK, that's a very different case since your final load has no energy storage
so there is nothing to flow backwards when the inductor is not dumping
current to the load.

Just to be clear to the OP, this is NOT the case in your design.

> Not good for regulation
> wit the IC used - so I'm adding Olin's diode and a smoothing
> cap and sensing the LED current.

Why not keep the diode away, but add a small current sensing resistor
between the LED and ground?  You can low pass filter that a little to get
smoother current feedback as long as you make sure the response of the
regulator is even slower, else the system will become unstable.

> LEDs must be in parallel, alas.

Why?  Does this thing use such a low voltage process that the switch can't
tolerate the voltage of two LEDs in series?  And I guess you don't want to
spend the extra $.03 for a discrete switch?


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