THS6222: Please recommended PLC for use with 230VAC/32A power line, frequency <1MHz.

Hello Felix,

Our THS6222 can be used for PLC on AC powerlines.  I do know the THS6222RHFEVM is not built to directly connect to AC mains power, but you could evaluate the THS6222 via the EVM for the signaling & PLC transmission standard that you choose.  Depending on the market you are in (USA, Europe, China, etc), the PLC standard may differ across customer applications.

The THS6222 datasheet has information about interfacing with powerlines; normally an Rseries resistor is placed after the THS6222 outputs, followed by an output network matching the THS6222 to a transformer.  After the transformer you may connect to AC lines; please refer to datasheet diagrams for additional details.

I do not have a standard or exact circuit method I can recommend at this time, but I can answer questions as you come across them.  

Best,

Alec

Hello Felix,

I better understand your question now, thank you for your patience.  I can check amongst my team, but as we do not make any PLC products I am not sure we have a specific recommendation.

The selection of the turns ratio can depend on whether you need to step up or step down a voltage across the transformer.  As your powerline impedance is low (7 Ohms), you would require a large transformer to interface with a 230V 32A line.  An SMT transformer on a PCB would likely have a current rating in singular amps or even in milliamps. 

If you are certain your customer needs to operate at 32A consistently, you will need a large separate transformer from the PCB.  Could you share what your customer circuit & application is? 

You could start by looking into this article; here is a Digikey link to PLC pulse transformers, including one from Wurth Electronic: https://www.digikey.com/en/products/filter/pulse-transformers/

Best,

Alec 

Hello Felix,

I have some ideas to share which may help your customer's use-case.  However, to start I will remind you and the customer that working on interface circuitry to powerlines is dangerous and requires appropriate caution and focus.  High voltages, high currents and unpredictable signal noise are some of the factors to be considered.

There are existing PLC standards for various applications and regions of the world.  There are certain transmission frequencies available which will depend on what regulatory body oversees PLC and wireline communication.

1. For the output network of the THS6222 line driver, you are matching the amplifier output to the selected transformer, not the powerline itself.  The chosen transformer, as we discussed previously, would not need to match the powerline impedance, but the output matching network of the THS6222.  Since the matching circuitry is between the line-driver and the chosen transformer, there is no need to regard the 32A circuit-breaker limit of the powerline.  There will not be 32A going through the line driver, and the load on the THS6222 will not be 7 Ohms.

2. Selecting the Rseries (or Rs) resistors determines the drive strength/current of the transmitter circuit.  A common choice to interface with powerlines is also showcased in the THS6222RHFEVM, as 25 Ohms in series with each line-driver output.  Choices range from a few Ohms (such as 2.5 Ohms, commonly used in e-meters to 25 or even 50 Ohms.  For lower Rseries values you will need matching circuitry between Rseries and the transformer. 

3. Various resources exist for PLC interface or 'coupling' circuitry.  I am sharing a dedicated paper on the topic here.  The general idea is to interface between the transmitter and powerline with a transformer followed by AC coupling capacitors.  These capacitors should be chosen with appropriate voltage rating and to filter out the 50-60Hz powerline signal.  Various transformers and capacitor circuits exist for the purpose of PLC interfacing.  You may wish to research hum transformers, as well as proper protection circuitry for interfacing with AC mains powerlines.  Specific capacitors, noted as Y-safety capacitors, exist to bridge the isolation barrier between high voltage/current and low-voltage circuitry.

4. Another paper on the topic for CENELEC regulation can be found here.

5. In addition to transformer usage and capacitively coupling to the AC powerline, it should be considered to add diodes and other protection circuitry between the transmitter circuit (THS6222) and the powerline.  There are a lot of options for choosing components here, the important idea is to consider how the AC powerline could potentially damage the communications circuit.  The coupling capacitors used between the transformer and the AC powerline could inject high current into the system as well.  An isolation transformer should be considered.

I know this is a lot of information; designing a fully-capable PLC communications system is complex and requires good understanding of power circuitry, AC mains powerline risks & interfacing, and an understanding of PLC signaling, filtering, and device selection.  The THS6222 is the right device for the customer application, but it is up to the discussion between yourself and the customer to determine their preference on interfacing to AC powerlines.

I cannot provide exact component recommendations for interfacing to AC powerlines; I also cannot design a working circuit for you, as my expertise is with the line-driver component, not the overall PLC system.

Please be safe and good luck with your design.

Best,

Alec