Specifications
3. Switching power supplies are also recipients of
radio interference. The normal operation of the
power supply can be disturbed due to RF noise
getting coupled into the power supply. Thus, the
power supply may generate excessive RF noise
and lose output voltage regulation due to excessive
transmitter energy being coupled through the AC /
DC lines to the power supply’s regulator feedback
path. This may be due to antenna being too close
or due to the antenna or feed system not radiating
properly. First check the antenna system SWR.
Then, if necessary, relocate either the antenna or
the power supply farther apart.
4. The receiver may “hear” the power supply. A slowly
moving, slightly buzzing carrier heard in the re-
ceiver may be caused by the antenna being too
close. As with the transmitter related noise pick up,
a loose coaxial connector or a broken or a missing
ground may aggravate this problem. Normally these
noises will be below the background or “band”
noise. Increase the separation between the power
supply and the receiving antenna. Use an outdoor
antenna. This will reduce the amount of signal
picked up from the power supply and also increase
the amount of the desired signal.
5. The conducted RF noise from these power supplies
is limited to the maximum allowable levels by inter-
nal filtration. The filtered RF noise currents are
bypassed to the chassis of the power supply. The
chassis is, in turn connected to the earth ground pin
of the AC input power cord (for Class 1 units).
Thus, the filtered noise currents are intentionally
leaked to the earth ground. This is termed as the
“Earth Leakage Current”. For safety against electric
shock, this earth leakage current is also required to
be limited. It will be seen that these two require-
ments are conflicting.
11.
LAYOUT:
Layout of the module is shown
below
Figure 1—Layout of Power Supply Module
F1 Fuse
S1 to S4 Holes for 4 screws to fasten the module (Pads under holes
S1, S3 & S4 should be connected to earth ground)
S5 & S6 Pads under these holes provide + and - output connections.
L & N L (line) and N (neutral) terminals for 120V, 60 Hz input power supply wires
LED1, LED2 Terminal for connecting green L.E.D.(s) for monitoring
JUMP 1 Jumper terminal for connecting share BUS wire
VR1 Potentiometer for output voltage control
4.