Specifications

Chapter 4 – Coupling Circuits
146 PL 3120/PL 3150/PL 3170 Power Line Smart Transceiver Data Boo
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Low-Voltage Coupling Circuits
While the same coupling circuits that are used to couple to the AC mains can also be used to couple to lower voltage AC
or DC lines, simplified and lower cost options are possible for these lower voltage applications. This section discusses
the simplifications that are possible when coupling to AC and DC lines with peak voltages below 48V.
For applications where power line communication on power lines with ≤48Vpk voltage is desired, coupling capacitor
C101 does not need to have as high a voltage rating as required when coupling to the AC mains. Lower voltages also
eliminate the need for a resistor to bleed stored charge from the coupling capacitor. While the user needs to determine
the appropriate surge requirements for their particular low-voltage environment (and then perform surge testing
applicable to that environment) varistor type protection is not needed in most instances. Fuses are generally not required
for these lower voltage coupling circuits.
Low-Voltage AC Coupling Circuits
The simplifications described above are applied to both non-isolated and isolated low-voltage AC coupling circuits given
in Examples 9 and 10 in this chapter, respectively.