Saturday, October 27, 2007

Feedforward Shunt Regulator again

I redid the Shunt Regulator again. One channel seem to "runaway" when switched on for a while. This caused some speaker cone movements even when no source is playing.

Measuring the incoming supply, the voltage between the two 10M45S, and the output voltage, it seems that only one of the chip is giving this problem. Looks like the small heatsinks are not enough to dissipate the heat, resulting in thermal runaway... i think this what it is called.

So, i did it using plain old point to point wiring on a spare heatsink that i have. This new version will be muncho mancho enough to take the heat, else nothing would. ;)

During testing, the voltage did not fluctuate much. No runaway this time. Cathode resistors measured spot on at around 2.98v. The 10M45S are sourcing around 10mA per chip as per specification. It's just that the 10% coffin resistors are not accurate enough to produce equi-voltage between L and R. I may have to measure for a pair that fits the bill.

Maybe I should start digging for my 2k2 vishay power resistor somewhere in my box...

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