Dave Plowman (News) wrote:
In article ,
Andy Wade wrote:

A very sensible solution I must say, using a transformer rather than a
long-wave transmitter to power your lighting :~)

A further thought is that at such a high frequency (125 kHz) the
inductance of the bulb filaments could also be significant, meaning that
(a) the inductive voltage drop in the wiring is not necessarily in phase
quadrature with the load voltage, thus making its effect worse, and (b)
the voltage across the lamp terminals might need to be significantly
higher than 12V to get the lamp running at the correct power.

It certainly seems strange. Most SMPS are just outside the audio range but
well below RF. About 30 kHz being typical.

cost cutting exercise, higher frequency equals less inductor. Would
work if short leads used. If they marked the transformers clearly as
only for use with say 2' leads they could avoid a lot of returns and
complaints.


NT