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Current transformer with phase cut rectifier?

Discussion in 'General Electronics Discussion' started by eem2am, Jan 8, 2013.

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  1. eem2am


    Aug 3, 2009

    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………

    …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:….

    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)………

    …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)

    Here is a rough version of the phase cutting circuit…..

    …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)

    ...the above discusses the phase cutting with respect to the battery charger, but mostly it will be the LED luminaires that are supplied by these phase cut rectifiers.
    The battery is just for emergency operation, ie when the mains power fails...the mains is the primary power source which the big AC 50khz current source uses to provide the 50khz sine on the power bus.

    This is an expensive system, but is waterproof!....and thats why we like it.
    Last edited: Jan 9, 2013
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