Maxic Technology Corp. recently introduced the high-PFC, high-efficiency, primary-side feedback isolated AC-DC LED lighting driver chip, the MT7920. The MT7920 is an off-line, low-power, high-precision LED driver chip. The input voltage is wide (85VAC~265VAC), working in the stream, dynamic PWM mode. The core source current sensing algorithm of the patented technology of the core technology precisely controls the current of the LED without the need for an optocoupler. The MT7920 supports a high PFC solution. The peripheral circuit is very simple. The PFC can reach 0.9 or higher in the full voltage range. MT7920 built-in overvoltage detection circuit, automatically enters hiccup mode once overvoltage (such as LED open circuit). At the same time, the MT7920 includes undervoltage lockout, current limiting and overheat protection circuits to further improve system reliability. The chip is available in a SOP8 package with an input voltage range of 85VAC-265VAC. High-precision LED current current accuracy is limited to +/-2%, up to 30W drive capability, and built-in undervoltage, overvoltage, and thermal protection. Function and built-in VDD overvoltage and LED open/short circuit protection; with primary side current and voltage sensing technology, no optocoupler required; adjustable output current and power setting, support for high PFC architecture, PFC up to over 0.99; with power-on soft-motion function . Supports power on/off 4-position dimming (optional) without the need for a dimmer. MT7920 supports the electroless capacitor solution, which solves the contradiction between the long life of LED lamp bead and the short life of electrolytic capacitor in LED lighting scheme, and improves the service life of LED lighting scheme. The chip will be widely used in AC to DC LED driver, general stream source, signal and decorative LED lighting driver and E14/E27/PAR30/PAR33/GU10 LED lamp, LED fluorescent lamp. Type of failure Xpon 1Ge Wifi Onu,Wireless Router,1Ge Wifi Onu Xpon,Wireless ONU Shenzhen GL-COM Technology CO.,LTD. , https://www.szglcom.com
1. ONU with time slot drift
This kind of failure is usually caused by the aging of the laser and the drift of the time slot for the upstream data transmission of the ONU. It is also possible that an error occurs in the data of the bandwidth map sent by the downstream OLT, which causes an error in the transmission time slot of the ONU. This kind of faulty ONU is difficult to detect. Generally, the OLT needs to monitor the upstream data of the ONU in real time. Determine whether it sends data in the time slot allocated by the OLT. For this type of abnormally luminous ONU, because it mainly affects two adjacent ONUs, in addition to isolation, the protection bandwidth between time slots can also be increased to alleviate its impact on other ONUs.
2. Long light ONU
This failure is caused by the ONU's laser for a long time. As a result, the ONUs under the entire PON port cannot communicate normally. If the ONU emits strong light, the abnormal light emission of the ONU can be determined by testing the optical power at the optical splitter during troubleshooting. However, if it is a weakly emitting ONU, the judgment will be more difficult, and the abnormal light emission of the ONU cannot be measured at the optical splitter. Only through the intervention of the OLT and the use of specific detection algorithms can the abnormal ONU be judged. Usually, the business under the entire PON port will be affected, but because of its failure phenomenon has always existed, it has brought convenience to the troubleshooting to a certain extent.
3. Intermittent glow
The judgment of this kind of failure is the most difficult and irregular. It is also the biggest fault in the current network that accounts for the abnormally luminous 0NU. It is not only impossible to measure the abnormal light emission of the ONU at the beam splitter. In addition, it is necessary to observe and monitor faulty PON ports for a long time, which brings great challenges to network maintenance.
There are many fault phenomena in the network of abnormally luminous ONUs. There is no complete mechanism and process in the industry to solve this fault. Other operators have no controllable experience. In the operation of the actual network. The author summarized a set of procedures and experience for troubleshooting abnormal light-emitting ONUs. Can effectively solve most of the existing network failures.
cause of issue
1. Long light-emitting problem: The photoelectric converter is connected to the branch fiber by mistake, and the photoelectric converter emits light for a long time; the ONU optical module has an abnormal shutdown signal. Cause the ONU to emit light for a long time.
2. Coverage interference problem: For some reasons (such as insufficient extinction ratio), individual ONUs emit light in unlicensed time slots, which affects the normal services of other ONUs.
3. Overlapping interference problem: The inconsistency of the parameters of different ONU optical modules causes partial overlap of the upstream optical signals, which affects each other's services.
December 30, 2023