S said:
Need Super Small Power Transformer.
Apx. 1/2" Square. , 12 - 15 MM
115V >> 10 or 12 V, .2A
Any suggestions. Please Post. Thanks.
While it's theoretically possible to get 2.5W power throughput in an
isolation transformer with a volume of 2cm^3 and a surface area of
9cm^2, it is physically impractical to maintain commercial safety
isolation or mechanical integrity of connections using conventional
methods in such a device, particularly at low frequency.
You might find signal pulse transformers that can do it above 400Hz
(functional isolation), or telecom grade isolators that can function
above 4KHz (basic isolation), but you should expect a 50 degree rise
above ambient in these devices in free air when 2.5W is handled, as
efficiency is low.
A better technique is to look at component densities and operating
frequencies that are practical before designing yourself into a
power-limited corner.
What is the size of the unit consuming the output power? Fully 20% of
the total device volume and radiating surface area should be allotted
to the power conversion circuitry. Assume that the surface temperature
of the completed device will rise 1degreeC for every milliwatt of
power dissipated from every cm^2 of surface area.
The final end-use device is not practically portable or hand-held, if
it's metal surfaces have rises exceeding 35DegreesC. Larger rises are
tolerated from thermally insulating plastic assemblies (internal temp
^). This may set a limit on miniaturization, simply based on device
power consumption and the resulting surface or device junction
temperatures.
RL
