Switching Regulator

Sure, but this is supposed to be an educational project. Soldering and stuff maybe.

I really like the TI LMR14020/030/050 (2.5/3.0/5.0A). The 14030 is pretty much my go-to buck from (car) battery down. I generally use it at 2.2 MHz.

Not likely. There isn't much in DIPs, anymore.

It might be interesting to model the transformer. Since it's being used at it's maximum rating, it might be useful to know how that was specified. Diode conduction angle may be small, peak currents high, resistive losses high, saturation potential...heat >> smoke...

Rectified voltage may be 40% higher than 12V...much more unloaded depending on the transformer design. The devil is in the details.

DIP is not usuallly a power package.

Just buy a 2A phone charger.

You're not going to get 10W DC out of that transformer without doing power factor correction.

I'm constantly amazed at how Chinese eBay sellers can sell things including shipping for less than I'd have to pay just to have it shipped!

Clocked (non-hysterertic) buck converters are pretty easy to understand - the DC gets chopped into PWM and is then LC filtered to the average value.

Boost converters use inductor physics black magic.

There's a paper out there somewhere from a few years back outlining a design for a uh, hysterical boost converter. Seemed like one of those academic things that would be more trouble than it's worth though

I free air, namely with some cooling, most properly designed transformers can be overloaded quite a lot.

I think they pay little or nothing for shipping. China scams the international postal union to get the USPS to pay for it.

That uses the MonolithicPower MP1584 buck converter chip, which is $1.53 qty 1k from Avnet Express, a major industrial supplier. So how can the eBay seller chivazhu sell the complete board for $0.99, with free shipping from Hong Kong?

The MP1584 is a pretty cool part, it can work to 1.5 MHz and its bucking switch can handle 3 amps.

Here's the chip that they _say_ they are using:

It will probably be dissipating around 1W at 5V/2A out, plus the heating in the inductor- enough to make it quite warm but it will

--sp

I only commented on the apparent misconception that the input current of a chopper equals the output current.

Dimensioning the transformer is indeed another thing.

joe

No they don't. :) The just act to realise a zero average voltage.

As a student I made some current controlled boost converters. The sub-harmonic behaviour was subdued by adding slope compensation. Very funny.

joe

}snip{

hysteretic?

joe

Octoparts says Avnet Asia will sell you 10k for ~$0.26 ea.

George H.