----- Original Message ----- From: Jones Beene To: vortex Sent: Wednesday, October 20, 2004 6:41 PM Subject: All Over Reactance
The short answer to Jone's comments about shrinking power supplies and why did it take so long, etc. is that transformers are needed to isolate the circuits from the mains and to get different voltages at high currents efficiently. The reactance come in in making efficient transformers and that's a matter of configuration and frequency. The ferrites are insulators and so have negligible eddy current loss at high frequencies. The other limit is the speed of the switching transistors. They dissipated very little power when hard on or hard off, but get hot on the way to and fro, so the quicker the better, like CMOS chips. The higher the frequency, the higher the percentage of the time in hot transit. Keep improving transistor and materials and you can keep pushing the switching frequency up and the size down. Carver has been noted for audio amplifier designs that provide gobs of power with few components and little iron. In some of these, the speaker is basically connected to the mains through a pulse width modulator with a bit of inductive smoothing. Mike Carrell
