In the ascending smart grid application, smart meters play a key role. The designer needs to choose the appropriate communication method for the communication between the smart meter and the data concentrator. The power line carrier (PLC) technology uses the power line as a data transmission medium and uses the existing power distribution network for communication. No rewiring is required, and the signal will not be attenuated or even shielded by the building wall, and the cost is relatively low. Therefore, it is favored in applications such as smart meters, street lamps and smart plugs. Many countries or regions in the world today have deployed or are about to deploy smart metering systems, and adopt PLC automatic remote meter reading. For example, the EU requires member states to replace all electricity meters with smart ones by 2022. Some industry leading companies and their early pilot projects are also of great demonstration and reference significance. For example, France has launched the Linky meter project, which has attracted much industry attention, and plans to update 35 million traditional meters from France to Linky smart meters from 2012 to 2017. This project selected PLC technology for the communication between the smart meter and the data concentrator, and then used General Packet Radio Service (GPRS) technology to transfer the data to the company's data center. 2. "NCS5650 Thermal Consideration Application Note" 3. "NCS5650 Data Manual 4. "How to choose a suitable PLC modem solution for smart meters?" 》
PufangTech`s SCADA radio modems have air data rates of 19200bps in 25KHz channel spacing and 9600bps in 12.5KHz. For master station of SCADA system, RS232 interface port is usually standard, while RS485 is often adopted by slave station.
Our SCADA Radio Modem has short Transmit-to-Receive turn around time that enables fast polling in your wireless telemetry system. It is easy to use and implement transparent data transmission.
RS232 or RS485 serial inputs and outputs are supported by PufangTech`s SCADA radio modems. The serial baud rates can be changed from 1200bps to 115200bps with a Windows based program on PC.
SCADA Radio Modem SCADA Radio Modem,SCADA Modem,Scada Radio Data Modem,SCADA Radio Systems Shenzhen PuFang Technology Co., Ltd. , https://www.hytelus.com
Figure 1: Schematic diagram of a typical PLC smart meter network.
The application of PLC smart meters involves components such as PLC meters (single-phase or three-phase), data concentrators, coupling transformers and related cables. Figure 1 shows a typical PLC smart meter network diagram. It can be seen from the figure that a large number of PLC smart meters are connected to the data concentrator through the power line, and then the data is transmitted from the concentrator to the data center of the power institution by means of GPRS, GSM or Ethernet.
The transmission of data signals in the PLC meter network includes both sending and receiving. In terms of the transmission path, the PLC modem integrated in the power meter modulates the S-FSK signal, which is amplified and filtered by the PLC line driver and then coupled to the power line via a transformer. The transformer realizes voltage conversion and impedance matching, and is also used for strong electricity (characterized by high voltage, large current, high power, low frequency, and the object of processing is electricity) and weak electricity (characterized by low voltage, small current, small power, high frequency , The object of processing is the isolation of information). In terms of the receiving path, the signal from the transformer coupled from the power line passes through the low-pass filter formed by the modem's built-in amplifier and is transmitted to the application microcontroller for FSK demodulation analysis.
As mentioned above, the line driver is used in the power transmission part of the PLC communication application and is an important part of the PLC (see Figure 2), so it is necessary to select a suitable PLC line driver for the application. Such a line driver requires high output current capability, low voltage ON Semiconductor's line driver reduction for smart meter PLC communication applications, low harmonic distortion, wide operating temperature range, and ease of heat dissipation. In addition, the aforementioned ERDF Linky project needs to comply with the strict European EN-50065 specification, so in addition to the modem, referring to the design of this project, the line driver also needs to comply with this specification.
Figure 2: The line driver is an important part of the smart meter PLC communication application.
Advantages of ON Semiconductor NCS5650 PLC line driver
ON Semiconductor has launched a high-efficiency class A / B low distortion line driver for PLC line drive applications-NCS5650. The power supply voltage (VCC) of this device is single-ended 6 to 12 V or double-balanced ± 3.0 to ± 6.0 V. The design of the NCS5650 has been optimized to receive signals from PLC modems. The output section is designed to drive up to 2 A of current and is coupled to an AC mains power supply via an isolation transformer or a simple coil.
NCS5650 meets the application requirements of PLC line drivers and provides important application advantages. If the device is optimized for the A, B, C, and D frequency bands used by the European Electrotechnical Standardization Committee (CENELEC) for smart meters, it complies with the EN-50065 specification and can be used for direct coupling or according to 1: 1, 2: 1 transformation coupling. NCS5650's unique 2 A drive capability ensures effective communication even at very low power line impedance.
In addition to power amplification of the signal, the structure of the integrated two-stage operational amplifier also constitutes a 4th-order low-pass filter with steep attenuation characteristics. In addition to helping reduce the number of devices and thereby saving costs, it has strict requirements on power line access equipment In restricted Europe, only by adding similar filters can the system ensure that the injection of high-frequency interference to the power line meets the requirements of the EN-50065 specification. In addition, this structure also allows the fault alarm to be directly interfaced with the MCU without external level translation.
NCS5650 also has advantages in electrical performance. Two-stage operational amplification can achieve a full power bandwidth of 700 kHz, and the harmonic distortion is also very low, only 0.015% @ 1 kHz. The power consumption of this device is also very low, the rail-to-rail voltage difference is as low as only 0.5 V, the quiescent current in operating mode is only 20 mA, and the current in shutdown mode is only 150 µA.
The NCS5650 supports a wide operating junction temperature range of -40 ° C to + 125 ° C, with 160 ° C over-temperature shutdown protection. The device provides two independent thermal flags with hysteresis, one of which is a thermal warning flag to let users know that the internal junction temperature has reached the thermal warning threshold set by the user, and the other is a thermal error flag to remind the internal junction The temperature has exceeded 150 ° C. The NCS5650 uses a 4 mm x 4mm QFN20 small package with a thermally conductive plate for easy heat dissipation.
It is worth mentioning that the NCS5650 can be used not only for PLC smart meters, but also for audio subwoofers, data acquisition equipment, smart appliances, valve / brake drivers, motor drivers, and test equipment.
NCS5650 typical application design
The main advantages of NCS5650 are introduced above, then we will analyze some typical application designs of this device, such as multi-point feedback (MFB) filter design, current limit setting and overcurrent alarm, over temperature shutdown alarm and setting Wait.
In fact, the European Electrotechnical Standardization Committee EN-50065-1 is a European standard for low-voltage electrical equipment signaling in the frequency range of 3 kHz to 148.5 kHz. More specifically, the first part of this standard deals with the frequency band and electromagnetic interference injected into the electrical mains. A feasible method to meet this requirement is to place a 4th order filter between the modem output and the isolation transformer connected to the AC mains. We can use the MFB filter topology to help meet the requirements of this standard. The 4th order point filter requires the use of 2 operational amplifiers. On Semiconductor's NCS5650 has an input pre-amplifier and an output power amplifier (see Figure 2), so only passive components such as resistors and capacitors are required. This is what we need to calculate. The circuit diagram of the input preamplifier is shown in Figure 3 (a), and the effect of the 4th-order low-pass filter is shown in 3 (b).
Figure 3: NCS5650 input pre-amplifier circuit diagram (a) and 4th-order low-pass filtering effect (b).
The gain function of this input preamplifier is as follows:
Combined with other formulas (see Reference 1), the values ​​of R1, R2, and R3 can be calculated.
In the NCS5650 application design, the current limit setting is also very important. In fact, the 2 A output current of NCS5650 can be set by simply adding a current limiting resistor (RLimit) between pin 15 and VEE (negative amplifier power supply, pin 10 or 11). When the current flowing out of or into the power amplifier exceeds the set point, the overcurrent alarm ILIM flag will change to a logic high level, prompting the user to take necessary measures. After the overcurrent disappears (that is, the output current recovers), the ILIM flag will return to a logic low level. The current limit setting formula is:
ILIM = (1.215 / RCL) × 8197.
In addition, under heavy load or overcurrent conditions, the amplifier temperature will rise. When the internal junction temperature exceeds 160 degrees, the device will enter shutdown mode to prevent damage. At this time, the TSD flag of pin 17 will become logic High level; when the junction temperature drops below about 145 degrees, the device returns to enabled mode. If the user wants to prevent the amplifier from entering the thermal shutdown state, the junction temperature can be monitored by the thermal alarm function. The user can select any warning junction temperature (Twarn) between 105 ° C and 145 ° C by applying the corresponding voltage on pin 14. A simple method can be used to apply this function, namely to set the ratio of the voltage divider between VCC (pins 6, 7) and VEE. The formula for calculating the voltage ratio required for setting the NCS5650 thermal alarm temperature is: VTW = 6.665 × 10-3 (TJ) +1.72. |
ON Semiconductor provides complete solutions for smart meter applications
ON Semiconductor provides a complete solution for smart meter applications. In addition to the above PLC line drivers, it also provides a new PLC modem AMIS-49587 that complies with the ERDF specification and AMIS-30585 that has been tested for industrial field applications for 8 years. Among them, AMIS-49587 supports 2.4 kb half-duplex adjustable communication rate, which has been used by French original equipment manufacturers (OEM) in advance, and has been selected by several leading meter customers in China. In addition, ON Semiconductor provides solutions for key functions such as power management, measurement, and storage. For example, in the power management module, ON Semiconductor's NCP1014, NCP1015 and other AC-DC converters, LM2596, NCP3063 and CS51411 and other DC-DC converters, MC78L05, MC7805, CAT6217 and CAT6219 low-dropout (LDO) regulator , And medium voltage and high voltage FETs such as NTMFS4823. In addition, in smart meter applications, ON Semiconductor semiconductor EEPROM, SDRM and other memory, as well as ESD / TVS, SIM card interface, logic, USB protection, monitoring, I / O expansion, clock and temperature sensor, etc. can also be used.
to sum up:
In the ascending smart grid application, smart meters play a key role. Designers need to choose a suitable line driver solution for PLC smart meter communication. ON Semiconductor's NCS5650 line driver product for PLC complies with strict European EN-50065 specifications and provides a variety of application advantages. It is very suitable for PLC line driver applications and can also be expanded to a wider range of applications. ON Semiconductor also provides complete solutions for key functions such as power / power management and protection, communication, measurement and storage for smart meter applications, facilitating customers' choice, helping them reduce procurement costs and speeding time to market.
Reference materials:
1. Online application of "On Semiconductor Semiconductor Line Driver in PLC"