Charge pumps as power supplies

[rtarbell]

Just curious,

Has anyone thought of using a "large scale" charge pump as a supply for an audio amplifier?

As an example, one could use a regular bipolar supply with "low voltage" rails for a regular class AB amplifier, and then they could use two charge pumps to create high voltage rails, thus making a rail switching amp. In this case, the high voltage supply secondaries on the transformer (and the components that go with it) could be done away with, saving cost. From the schematic I have of a higher power charge pump, it takes the incoming rail voltage and simply doubles it. There would be some added cost in terms of two switching FETs, two diodes (probably soft recovery), two capacitors (large, filter type, must be rated at least twice the low voltage rail), and a switch controlling IC (could use a high/low side switch controller).

I've seen many charge pumps in small IC packages (they are at most a couple of watts); how about discrete ones with more power?

[anatech]

Hi rtarbell,
It is far less expensive to do things the other way around. Use a high voltage power supply and reduce that for your low voltage stuff.

If you attempt to use a charge pump, the currents required would be extremely high. High current = higher losses.

If this was a good idea you would see more companies doing things this way. It is not very workable, all things considered.

-Chris

[djk]

http://www.ortodoxism.ro/datasheets/philips/TDA1562.pdf

[anatech]

Hi djk,
In 1998 no less.

More would do this and to a greater degree if it was a good idea. This is a good idea for possibly an automotive or boom box application.

-Chris

[jamesrnz]

well what about a bridge style flying capacitor in series with the supply and then transfered to the storage cap?