Specifications

Chapter 5 – Power Supplies for PL Smart Transceivers
168 PL 3120/PL 3150/PL 3170 Power Line Smart Transceiver Data Boo
k
5W and 10W Echelon Power Supply Plus Couplers
One very convenient power supply implementation combines an isolated universal-input power supply and a C-band
line-to-neutral coupling circuit into a single package. The power supply inside the combined unit provides power for
a PL Smart Transceiver-based product while a communication transformer couples the communication signal to the
product over a common pair of low-voltage wires. A simple interface circuit is then used inside the PL Smart
Transceiver-based product to separate the DC power and communication signals. Details of this interface circuit are
provided in coupling circuit Example 8 in Chapter 4. Detailed specifications for these units are given in the data
sheet for Echelon model 78101R and 78113R power supplies (5watt and 10 watt versions respectively).
Figure 5.9 Echelon Power Supply Plus Coupler
Off-the-Shelf and Custom Switching Power Supplies
As mentioned earlier, switching power supplies can be a significant source of noise and signal attenuation unless
specifically designed to avoid these effects. As a result, the input impedance of a switching power supply that has not
been pre-verified must be evaluated and an inductor will most likely need to be added to its input as described later
in the section titled Power Supply-Induced Attenuation. In addition, a switching power supply that has not been pre-
verified to meet the input and output noise requirements presented later in this chapter may need additional filtering
components.
Selection of an appropriate operating frequency for a switching power supply will minimize the effect of switching
noise on communication performance. By choosing an operating frequency such that the fundamental and harmonics
of that switching supply avoid the transceiver's communication frequencies, the amount and cost of additional filter
components will be minimized. Table 5.8 lists the recommended switching frequency ranges. The switching supply
should be designed such that the fundamental switching frequency falls within the stated ranges under all line, load,
environmental, and production conditions. Supplies with other fundamental operating frequencies may be able to meet
the required noise masks with greater effort and/or cost; however, meeting the noise requirements with a power supply
fundamental frequency (or second or third harmonic) in the 70kHz to 90kHz or 110kHz to 138kHz range is very
challenging and not recommended.
Table 5.8 Recommended Switching Power Supply Fundamental Operating Frequencies
Recommended Frequency Ranges
46kHz - 55kHz
90kHz - 110kHz
>155kHz