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Topic: Constant current power supplies (Read 6 times) previous topic - next topic


find a tiny, cheap, constant voltage power supply that isn't already stuck inside a wall wart to experiment with.

The simplest would be your cell phone / usb chargers. Buy one and break it apart.



That is one of those gated oscillator smps types: it turns itself on/off between 1.69v - 0.8v (on the feedback pin), making it suitable for low-power applications but largely not usable for a device needing a constant voltage.

The grandfather of those designs are the Linear LT1107.


@ *dhenry* I think you have some details incorrect... Again. The first switchers I remember were made WELL before integrated designs for chips were out of the development stages., Remember PWM? it was in discrete form (3 or 4 IC's) and the real cheap ones used a flyback oscillator... and a linear regulator.
I remember the first one I saw, very clearly... It was plugged in and promptly went up in smoke, along with a $300.00 basic 4 function calculator.

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Bob, I think he was talking about the designs to turn off the device.  In 'the good ol days', they used and on-off switch and a human to turn them off.  Later, inactivity timers took the job on and did a pretty well.  These days, they actually sample the current and shut down when the battery or other device their hooked to stops pulling current; actually, they don't shut down completely, just drop really, really low.  It's a green thing.
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It's a green thing.

A gated oscillator is actually quite different from what you were talking about.

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