Can a D class give DC output?

[nigelwright7557]

The only problem with a class d and DC is the residual carrier you get on the output.
My 2092 design has a few volts of residual carrier at the output.

[phase_accurate]

Just as a sidenote: If an application requires better suppression of the carrier fundamental than the ordinary 2nd order lowpass offers then there are of course some options available.

Nosey question: Will the amp be used for some kind of positioning system ?

Regards

Charles

[effebi]

Thanks all for the intersting suggestions. I believe I wouls stay half-bridged since to float the load or the PS needs a lot of work that I am not sure it is worth to do.
I am even thinking that I do not need an amplifier. It would probably make sense to just synthethize the (shifted) sinusoid just accordind to a digital clock in in input. The DC level would be the other input. AC amplitude is constant once choosen. Feasible?

Originally Posted by phase_accurate

Nosey question: Will the amp be used for some kind of positioning system ?

Regards

Charles

You are correct, Charles. The amplifier is meant to move an electromagnectic actuator, that is *very* linear with the amount of current supplied to it. The residuals at hf are not a problem since the actuator itself has a quite narrow band. Outside the current loop there will be a position loop, in a very similar way of how you control a DC motor.

[Pafi]

Originally Posted by effebi

Thanks all for the intersting suggestions. I believe I wouls stay half-bridged since to float the load or the PS needs a lot of work that I am not sure it is worth to do.

I don't think that a proper synchro-rectifier would be simpler to design. It can be quite tricky! (Especially if this is the first time you heard about it.)

[phase_accurate]

If an exact DC balance doesn't have to be maintained some charge-pump could be used for instance for the DC balancing act.

Regards

Charles

[effebi]

Originally Posted by Pafi

I don't think that a proper synchro-rectifier would be simpler to design. It can be quite tricky! (Especially if this is the first time you heard about it.)

Then the questions then are:
Cannot the actual massive linear (transf-bridge-Capacitors) PS, about 2kW with 50 mF x rail, suffice, no way?
Would not some normal improvement (i.e. a PI filter) help, no way?

Must the eventual SMPS be specially bult in order to be synchronous with the amplifier?

[Pafi]

some charge-pump could be used for instance for the DC balancing act.

What is a switch mode converter. IMHO 2 identical half bridge is simpler than 1 half bridge (twice as powerful as in the first case) + an other different switching regulator (charge pump or whatever).

[Pafi]

Originally Posted by effebi

Then the questions then are:
Cannot the actual massive linear (transf-bridge-Capacitors) PS, about 2kW with 50 mF x rail, suffice, no way?
Would not some normal improvement (i.e. a PI filter) help, no way?

Must the eventual SMPS be specially bult in order to be synchronous with the amplifier?

If you want to use the original PSU, then Charles has a point, an additional charge pump or similar thing can help. Filter is not enough.

But the transformer may be configured to parallel secunders instead of the present series connection, and full bridge may be used. The PSU current capability gets higher this way!

[effebi]

Ok understood that full bridged has many advantages, that may overcome the cost of lifting the load.
But is it a bridged configuration really able to go down to 1 Ohm? Now rails are +-50V, even paralleling the transformer secondary coils an going for only 0-50, would it be feasible?

BTW I never saw yet a D class with parallel OPs , I belive because current sharing here can be a issue (the usual .22 Ohm source resistor will be way to big here I guess).