ST ST7540, Примечание к применению

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Board description AN2451
40/55 Doc ID 12791 Rev 3
Figure 38 shows the efficiency vs. output current curve. Minimum efficiency occurs at low -
load condition, as expected from any SMPS. This is not an issue for our application, since
low efficiency corresponds also to low power consumption and thus to low dissipation.
On the other hand, at output current values over 500 mA (full-load condition), both the
transformer and the VIPer are forced to operate close to their current limitations and thus the
efficiency is reduced.
In general, efficiency is affected by the losses which are due to R1 (series input resistor
limiting in-rush current) and to the filtering on both the primary and secondary side. Filtering
is more important than efficiency because a powerline communication appliance has very
restrictive EM disturbance limits and it is also highly sensitive to noise coming from the
power supply.
Figure 38. SMPS efficiency curve
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50 100 150 200 250 300 350 400 450 500
Iout [mA]
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