This isn't related to audio, but I'm looking for a circuit using the TL494 switchmode controller to take 12 - 24 volts, and step it down to 5volts, without the need for a transformer.
I've seen all kinds of circuits, they either use a transformer, or are a boost circuit using an inductor.
All I want, is a simply buck regulator, using an inductor, not a transformer.
I'm sure its possible, but can't find one!
thankyou for your time!
I've seen all kinds of circuits, they either use a transformer, or are a boost circuit using an inductor.
All I want, is a simply buck regulator, using an inductor, not a transformer.
I'm sure its possible, but can't find one!
thankyou for your time!
I found this... seems to be what I want, but why a transistor, not a mosfet? and whats limiting the current to only 1amp?
The inductor, for a start, but is that all?
The inductor, for a start, but is that all?
An externally hosted image should be here but it was not working when we last tested it.
They use a BJT because it's old. It's also slow (~30kHz?).
If the voltage is low (under 20V), you can use a MOSFET. Drive might be with a booster transistor, or you might use a TL598 instead (totem pole output, the rest of the circuit is identical -- but watch out for changed pins). If the supply is higher, you must limit gate voltage, perhaps with some resistors, transistors and a zener, or use an N channel FET driven with a bootstrapped driver (IR2101 style or discrete).
Tim
If the voltage is low (under 20V), you can use a MOSFET. Drive might be with a booster transistor, or you might use a TL598 instead (totem pole output, the rest of the circuit is identical -- but watch out for changed pins). If the supply is higher, you must limit gate voltage, perhaps with some resistors, transistors and a zener, or use an N channel FET driven with a bootstrapped driver (IR2101 style or discrete).
Tim
I like the look of those.
Might play around with them a bit, see what kinda current you can get with some bigger transistors..
but, it might just fail badly
I prefer self-excited oscillators with a feedback winding, which gives much better drive than an inverting transistor. I've talked with Black; he doesn't like this approach because the additional winding isn't as "simple" (i.e., it's more that could possibly be screwed up).
This is a constant current source, but the basic concept could be rewired for a current-mode buck converter.
Because of the circuit's resemblance to a blocking oscillator, BCM is probably best. CCM works for CC Buck because of the feedback resistor; you don't get DC feedback through a transformer (though you can get it through two, with diodes).
Tim
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
This is a constant current source, but the basic concept could be rewired for a current-mode buck converter.
Because of the circuit's resemblance to a blocking oscillator, BCM is probably best. CCM works for CC Buck because of the feedback resistor; you don't get DC feedback through a transformer (though you can get it through two, with diodes).
Tim
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