EPR-9 Datasheet, PDF (24/32 Pages) Power Integrations, Inc. – Engineering Prototype Report 5 W, Universal Input, Dual Output, Isolated, TNY266 (EP9)

5 W Universal Input Dual Output Isolated TNY266
03-April-2001
8.8 Acoustic Emissions
The power supply was subjected to acoustic emissions measurement. The worst-case noise was
measured for variations of both AC line and output loading conditions and is presented in Figure. 8.8.1.
The test unit was placed in an anechoic acoustic chamber, with a microphone located approximately 1”
(25 mm) above the transformer (T1). The power supply was oriented in a horizontal position with the
power supply output loaded via an external Kikusui electronic load. The microphone output was fed to an
Audio Precision audio analyzer to provide the measurements shown. The curves shown indicate the
spectral content of the noise generated by the supply once the ANSI-A weighting factor has been applied.
The audio limit line (Figure 8.8.1) visible at +35 dB represents the generally accepted threshold for power
supply audio noise. A discrete audio frequency amplitude was used rather than a dBA value (dBA
represents the whole audio spectrum). Large peaks may not raise the dBA value yet can result in
unacceptable perceived noise.
As a reference, the approximate dBA background noise floor level is 30 dBA. The microphone sensitivity is
such that 20 µP = 0 dB SPL.
Up to a further 20 dB reduction can be expected from the measurement shown, once the power supply is
sealed inside an enclosure.
Audio Precision
FFT SPECTRUM ANALYSIS
04/18/01 10:47:42
+80
+70
+60
+50
+40
d
B
+30
r
+20
A
+10
+35 dB=Audio Noise
+0
-10
-20
Ambient Noise
-30
0
2k
4k
6k
8k
10k
12k
14k
16k
18k
20k 22k
Hz
Figure 8.8.1 - Worst Case Audio Level, 120 V_AC Input, Full Load.
Power Integrations, Inc.
Tel: [phone] Fax: [phone]
www.powerint.com
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