Stability of phase shifted converters

Hello.

I have built a phase shifted converter based in the UCC28951 from TI, but I have problems with stability. The load has built-in capacitors and the converter oscillates wildly. I have changed the Type-II compensator to a Type-III one, but oscillations do not stop. Calculation of the Type-III compensator is based in application note SLVA662 from TI.

The input voltage is 48 V, output is 311 V, nominal output power is 600 W and the output capacitance is about 2000 uF. Fsw = 100 kHz.

Is this kind of converter valid at all for this output capacitance?

Reply to
Miguel Gimenez
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Usual method of tackling this is to overcompensate massively first, in order to troubleshoot the power train over load and line conditions. You can even run it without feedback by manually controlling the transferred phase width by overiding pin4.

When all your ducks are in a row, for basic DC transfer and crude control, you can address finer points of transient reponse and compensation.

RL

Reply to
legg

If you put a buffer on the DC to prevent kickout, you can sneak a cap multiplier inside that loop too. Good Medicine for many things.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

We're lately doing power supplies and dummy loads for aircraft systems testing, which is high power but rude and crude stuff. Our world is plenty noisy.

One of my units is a 3-phase AC source that the customer regulates by PWM shorting it. Envision some really ugly waveforms.

Reply to
john larkin

I don't understand your question. My problem is that the customer could load my supply with a giant solenoid, or a motor, or a huge capacitor, or a battery, or a negative-impedance switcher, all of which change loop dynamics if I sense (or worse, remote sense) from my output.

Reply to
john larkin

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