[SOLVED] Oscillator as Inverter?

[Jay_]

I read this thread: https://www.edaboard.com/threads/43456/

Can we convert a DC voltage to sinusoidal AC by using an oscillator circuit like Wein-bridge or Clapp? Can this be done for voltages as high as mains (230V rms)? If not why, not?

 

[kabeer02]

wein bridge give out pure sine wave signal and its not advisable to swich anolog signal through a transitor with high power it might End up damaging many things.

 

[FvM]

The answer would distinguish between the principle option and technical considerations.

In principle it's possible. Technically, you'll want a conversion with high efficiency. It can't be achieved by a linear oscillator that's dissispating a considerable share of the supplied power by nature. A simple electromechanical chopper would give a higher efficiency than the said oscillators. Modern inverter designs are combining almost lossless electronical switches with sine modulation or extract a sine waveform by passive filters.

 

[Jay_]

Thanks FvM. Say (I am not going to do the following!), I connect a high voltage DC to the supply of a Colpitt oscillator. I also take care of the values of the resistors, capacitors and the inductors, how inefficient would my the circuit be as compared to the modern inverter designs? Thanks.

 

[Borber]

To generate 100W AC power using sine wave oscillator and linear power amplifier you need 125W from DC supply. Efficiency of such converter is worse than 80% usually it is about 75%. Square wave inverter teheoretic efficiency is 100%.
Inverters with sine wave output are using PWM and filtering at the output. That's what FvM meant talking about switches and sine modulation.

 

[LvW]

I read this thread: https://www.edaboard.com/threads/43456/
Can we convert a DC voltage to sinusoidal AC by using an oscillator circuit like Wein-bridge or Clapp? Can this be done for voltages as high as mains (230V rms)? If not why, not?

It depends on how you DEFINE converter operation.
Normally, a converter transfers one input variable (variable!!) to an output variable with a more or less proportional transfer ratio.
This is NOT possible using any kind of linear oscillator since - in this case - the dc voltage is necessary to allow operation of the active circuit (ensuring a suitable operation point), but you cannot control the oscillator output by varying the dc voltage.

 

[FvM]

To generate 100W AC power using sine wave oscillator and linear power amplifier you need 125W from DC supply. Efficiency of such converter is worse than 80% usually it is about 75%.

I connect a high voltage DC to the supply of a Colpitt oscillator. I also take care of the values of the resistors, capacitors and the inductors, how inefficient would my the circuit be as compared to the modern inverter designs?

The efficiency calculation applies to an ideal class-B push-pull output stage, not a class-A Colpitts oscillator. Borber is already assuming separated oscillator and output stages, which sounds resonable if you wan to implement an inverter with linear output stage.

It depends on how you DEFINE converter operation.
Normally, a converter transfers one input variable (variable!!) to an output variable with a more or less proportional transfer ratio.

Yes, but it's quite obivious that converter refers to a so-called "DC/AC converter" or "inverter" in this post. (The latter term is also ambiguous, by the way).

 

[Jay_]

I understand