Current transformer battery charger...variable current output

[Flyback]

Hello,

How can I implement a variable phase-cutting rectifier on a 50KHz current transformer secondary?

I have a current transformer with a split secondary which is charging a battery from its secondary. The primary current is a fixed sine wave.

Schematic: Full wave rectifier on current transformer output………
https://i46.tinypic.com/28jxsgg.jpg

…As you see, there is a full wave rectifier which puts DC into the battery from the secondary as follows…..

Full Wave Current waveform into battery:….
https://i46.tinypic.com/ipb989.jpg


The primary current is fixed and is a sinusoidal 50KHz.



I now wish to reduce this current by phase cutting the rectified sinusoidal output. I can do this by periodically shorting out the rectifier diodes.

Here is the waveform that I now require into the battery……(0.3 duty cycle)………
https://i48.tinypic.com/qq4ksi.jpg

…as you can see its phase cut version of the initial waveform and has a 0.3 duty cycle.

I also want to be able to do any duty cycle from 0.1 to 0.9…….so for example, I may sometimes want the following waveform to charge the battery………

Current waveform into battery (0.7=duty cycle)
https://i49.tinypic.com/2wo9e7d.jpg


Here is a rough version of the phase cutting circuit…..
https://i48.tinypic.com/2vhyq04.jpg

…as you can see, the controlled voltage source switchs the FETs on and off periodically via the FET drivers, shorting out the rectifier diodes as it does so.



Though my question is, how can I most simply provide this “phase cut” waveform?
What circuitry can most simply do this job?

…on any particular product I only need one duty cycle…and it might be anywhere between 0.1 to 0.9…..(so that makes things easier)

 

[MikeMl]

Why do it at 50KHz? Why not just use an SCR at line frequency (50 or 60Hz)? The battery doesn't care if it gets ripple.

 

[Flyback]

It has to be done at 50KHz, the boss has decreed it....its to do with the inductove couplers.
We already have an extra "card" which we can insert to do the low frequency PWM dimming that you describe.....but we can't do it like that in the coupler circuitry......we need to do it by shorting the rectifers discussed at the high frequency (100KHz)....since its a full wave rectified 50KHz sine........we may well implement low frequency PWM dimming of the phase cut waveform.....but under discussion now is the need for the high frequency phase cutting as discussed.

 

[tcmtech]

To me it sounds like your boss doesn't know what he is talking about or dealing with and just wants an overly complicated way of doing something simple just for the sake of doing it that way.

What is the 50 Khz power source coming from and what are its voltage current and power parameters available to you plus what type of battery and its chemistry, voltage, Ah's, and charge rates does it need?

 

[Flyback]

The 50KHz sinusoidal current source is a switch mode current source, producing a sinusoidal output. It is 200W rated. The voltage at the luminaire depends on the load....if the load is opened, the voltage rises and the control card shuts down that luminaire.
Battery is NiCd, five D cells in series. we are doing charging at about 0.1C.

The high frequency phase cutting is needed. one needs an extra "card" to get the low frequnecy PWM dimming functionality. We have couplers for each luminaire current level, and the range isnt good enough, so we need this way of phase cutting.