smps with a fixed duty cycle?

... or would it just be a miniature space heater? :)

Michael

I don't know what duty cycle means in that context. Most such supplies have rectifier conduction spikes that are fairly narrow.

Yes. Airplane power systems are 400 Hz to save weight.

You are trying to compair two totally different things. The linear supply could care less about the AC frequency in one sense. As long as the transformer is rated for the frequency and the capacitors are sized for the frequency , the pulsating DC has nothing to do with the regulation.

For the linears the higher the frequency within limits the less iron can be used and the smaller the filter capacitors.

The point I was trying to make is, no feedback was used to make an attempt to modify the primary waveform shape in any way for the 50/60Hz transformers.

If someone were to design an SMPS with no feedback loop whatsoever (which normally changes the duty cycle), running at a constant 50% duty cycle, what would be the ramifications?

Thanks,

Michael

Generally known as a "square wave inverter" they can be found in many high powered audio amplifiers. The output DC still contains ripple at twice the supply frequency but requires little filtering as a rectified square wave is pure DC.

The switching is mostly done with IGBTs these days and can have outputs up to 10kW.

.... Phil

There's no 50% duty cycle. The positive half-wave and negative half-wave both contribute. There's a 'conduction angle' that can be calculated, and there are series-choke options that will change the conduction angle, if that matters to you. But that doesn't just depend on power supply design, it also depends on load.

Depends on the type. if it's a forward converter it will behave senibly.

Cheap potted SIP DC/DC converters are usually unregulated forward converters running about 50%. With a fixed DC input, the output is usually stable enough to run opamps and logic and stuff.

One of my products makes isolated 24 volts into +-10, with more regulators downstream.