Efficient transformerless 30V-3A supply

356

06:05:21

Traces: pre-regulated voltage (blue), output voltage (green), buck PWM (orange). ~80% efficient.

A transformerless design that doesn't waste 150+ volts straight across a regulator, using a buck converter as the key component. As always, a 100Hz converter and its component values are extremely unrealistic, but higher than that it takes far too long to stabilise in simulation.

Mains rectifier (top left), buck converter (top centre), linear regulator (top right), basic PWM (bottom).

published 10 years ago

hurz

10 years ago

Quite high input cap 680uF which might cause extrem startup/plugin current. And related to this, the mosfet is in dangerous by to high Ugs. You avoid this by a low 200Ohm in parallel but it higly depends on Hfe of BJT driver how low it turns the gate. I would place a zener to limit max Ugs. The first amp for your PWM might be critical. It can flip over and get to a pseudo stable point you don't want it to be.

faceblast

10 years ago

where does vcc/vss supply come from

Voltransistor

10 years ago

Cool! @faceblast-you mean for the op-amps? I'm pretty sure you can get the power supply from the diode bridge, branches out to a resistor(>22k-ohm), to a 5v zener diode in parallel(for regulation down to 5v), then another smoothing capacitor in parallel.

Mamish

10 years ago

@hurz Ideally I'd make it a 100kHz converter and drop both caps by a few orders of magnitude, but it's bad for simulation. Ugs was a concern so I aimed for 10V (+-20 being a limit on most pmos) though the zener is a good idea. As for op amps I'm just sort of bad at PWM lol. Regardless, PID isn't viable with this much ripple on the blue, or I might have tried.

Mamish

10 years ago

@faceblast Vss on op amps? Considering the total driver current is <20uA it'd be reasonable to get it straight from a mains regulation. EC won't let me try obviously.

hurz

10 years ago

Forget the AC source and rectifier use a DC so you can work with realistic PWM frequencies. Keep it up!

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