Buck Converter

437

07:38:19

A simple discrete implementable buck convertor. Uses an inductor and PWM to take a relatively high input voltage and convert it to a lower one. Upon start of simulation current is allowed to pass through inductor at the 100kHz switching speed until 10V is reached - at which point the voltage monitoring feedback comparator turns off the PWM. Output overshoots but then stabilizes do
wn to the 10V set point. In normal running the 100kHz control signal is modulated by the feedback comparator to keep an average current through the inductor to maintain the set point. PWM is provided by NANDing the 100kHz switching frequency and the control signal to drive the pMOS drive MOSFET

published 10 years ago

ETJAKEOC

10 years ago

Hmmm, I like

waynewec

10 years ago

There were obviously some software limitations that I had to work around (crazy high control voltages on the MOSFETs etc) but otherwise this is fully constructable. Just replace the PWM circuitry with a 555 in a PWM mode

Mamish

10 years ago

The control voltages are only like that because you're using n-channel mosfets when some should be p-channel. E.g. the high-side nMOS on the 20V source is always going to need at least 12V since the gate is relative to the source, which is the output voltage (~10V) in this case. A pMOS could be driven by a another nMOS with a regular 5V PWM. You can tweak that whole section with a better mix to handle regular driving logic. (I'd demonstrate but I'm not sure what the middle-left section is meant to do. Is it a sort of AND gate to limit the duty to 50% automatically?)

waynewec

10 years ago

Well - I couldnt get the pMOS to work right. I tried but quickly gave up and just cheated a little. In a real circuit I would use a pMOS with pullup and a nMOS or optocoupler to logic level. The middle left is basically an and gate - the switching frequency outputs 50% duty and then its modulated by the feedback op-amp

waynewec

10 years ago

Edited to use pMOS

Mamish

10 years ago

Looks much more sensible :)

demangqway

10 years ago

This circuit made using two dc power supply. Why you should to use two dc power supply??can you make another buck converter , make it simply?

waynewec

10 years ago

@demagqway The second dc "power supply" is only being used as a reference. It can easily be replaced by a zener reference network.

waynewec

10 years ago

@Mamish Good call on getting it switched over - this is a very buildable circuit now

waynewec

10 years ago

Edited to use zener reference

demangqway

10 years ago

Nice circuit.. I'm notsure with my circuit yesterday, but i want to build driver high power led with dc to dc converter. Thank' s wayne.

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