Boost Converter Tutorial?

Input?

RL

Like you, right?

Cheers

Phil Hobbs

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Snicker...

I also came across a voltage vs. current move paper by TI (maybe unitrode) not sure. That may have something in it too.

It should be some where in those links above.

Cheers

Display driver.

Best regards, Spehro Pefhany

Oh joy -- so, do you have the frequency headroom to use a lower inductance coil with the same core, to get the saturation current up?

Has the value of inductor been selected properly? The rule of thumb for a boost converter in continuous conduction mode is L = (V * D)/(R*I_l*f), where the parameters are evaluated at the _lowest_ specified (worst case for a boost) input voltage. V is the input voltage, I_l is the DC inductor current (I_o/(1-D)), D is the duty cycle, f is the switching frequency. R is the "ripple current ratio" and has an optimum value of 0.4 for continuous conduction mode in most cases.

At low voltages the inductor can be sized solely based on the DC load current requirements - if the current limiting is fast enough it doesn't matter if the inductor saturates under abnormal conditions.

If the inductor is still too big maybe use discontinuous mode instead? It'll be harder to stabilize, unfortunately.

Car ignition key?

Of course ;-) ...Jim Thompson

That's where my thoughts are progressing... ...Jim Thompson

Just how big does this inductor have to be? Looking here:

A 100 uH 150 mA inductor looks like it could be a chip inductor a few mm high.

A stupid look on their face as they ignore you? ;-)

Zits?

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

nnnnkkkkkk-splutter.. :D

est

and

ake it

But 4 ohms d.c.r. means it'll drop 600mV @ 150mA. Increasing f by a factor of 3 reduces i^2*r loss by that same factor. Or, keep the loss and trade for a smaller L and C.

Switching inductors without magnetic shields make RFI, magnetic nasties, etc. Shielded are better.

-- Cheers, James Arthur

Do try to pay attention sometimes!

All I asked for was load curves for bicycle dynamos.

I didn't ask anyone to design it for me - I already have that well in hand.

I didn't reject the few (unsolicited) solutions from the minority of smart-asses pretending to know more than they did - I just ignored them.

Well I certainly saved myself some aggro by ignoring the unsuitable topology suggested by your chum.

Can't help wondering whether he'd have got it right if he had known how to do the correct way.

Ian _and_ a notable other poster on this topic are severely ignorant about the real world.

PWM BUCK is trivial. I chose BURST for the hub dynamo because it would be a freebie around the 555, and I was intent on rubbing the 555 up some snobbish noses ;-)

PWM BOOST is NOT trivial, though I'm well on my way to an off-the-wall STABLE solution... found by running the math instead of my mouth. ...Jim Thompson