Greg ) writes:
Yes, I did forget the link:
http://www.innovatronix.com/cgi-bin/...alog/index.asp

These inverters are meant to power photo strobes and apparently are powered
from a car battery, though they don't specifically say so.

I guess the strobes need an especially clean electrical source.

I'm not interested necessarily in the inverters but I was curious about sine
wave vs switching power supplies. I guess a switching supply, powered from
household AC, would be sufficient to power 12VDC radios?

Greg


I think then you may be misreading things.

Traditionally power supplies were "linear", ie the AC line was fed into
a transformer which raised or lowered the voltage as needed, and then
that voltage was rectified and filtered, and sometimes regulated. They
become problematic when high current is needed, because then the transformers
are bulky. For receivers, that should never be a factor, and there
is no reason to not use a linear power supply.

Switching supplies take the AC line, and rectify it, then use that to
power a power oscillator running on frequencies above the audio range.
This means that the transformer to make this a lower voltage (and
usually it will be a lower voltage) can be smaller since it is
running at a frequency in the tens of KHz range rather than the 60 Hertz
of the AC line. Filter capacitors can also be smaller for the same current,
since again it is filtering a much higher frequency. This sort of
supply is used where high current is needed, such as tv sets or
transmitters, though since they do generate high frequency square
waves, much attention needs to be paid to keeping it inside the box,
or else you will get interference.

A DC to DC inverter is the same basic idea as the switching supply,
except it takes DC at the input to power the oscillator. A square
wave one is simple, since you can have a power oscillator with two
power transistors. These were common in the sixties, when tube
equipment was still common in cars, taking over from vibrator
power supplies. The latter used a mechanical system to switch
the incoming DC on and off at a high audio rate, to feed a power
transformer.

But when a DC to DC inverter was needed that put out a sinewave,
it was no longer a simple task. As I said, you'd need a sine
wave oscillator, and then feed that into an audio amplfier,
and often feed that into a transformer to boost the voltage up or
down.

I'm not sure why strobes would need a sinewave for charging.

Michael