5. lightning damage

Lightning strikes are a common natural phenomenon, especially in the rainy season.  The damage and losses are estimated at hundreds of billions of dollars a year worldwide.  Lightning is classified into direct lightning and indirect lightning. Indirect lightning mainly includes conduction lightning and induction lightning.  Because the energy impact brought by direct lightning is very large, extremely destructive, the general power supply is unable to withstand, so the main discussion here is indirect lightning.  

The surge shock caused by lightning is a transient wave and belongs to transient interference. It can be surge voltage or surge current.  Along a power line or other path (conducting lightning) or through an electromagnetic field (inductive lightning) to a power line.  The waveform is characterized by a rapid rise and then a slow fall.  This phenomenon can have a fatal impact on the power supply, the instantaneous surge impact far beyond the electrical stress of ordinary electronic devices, resulting in the direct result of electronic components damage.  

6. Power grid voltage exceeds power supply load

When the distribution of the same transformer power grid branch is too long and there is large power equipment in the branch, the power grid voltage will fluctuate violently when the large equipment starts and stops, and even lead to the instability of the power grid.  It is possible to damage the driver when the grid transient voltage exceeds 310 VAC (not even with lightning protection, since lightning protection deals with pulse spikes of tens of microseconds, while grid fluctuations can be tens or even hundreds of milliseconds).  Therefore, special attention should be paid to the large power machinery on the street lighting branch power grid. It is best to monitor the fluctuation of the power grid, or power supply by a separate power grid transformer.  

7. solder joint failure

Power supply packaging mainly involves the connection process between PCB board and components, among which solder joint plays an important role.  The main function of solder joints is to realize the mechanical connection and electrical connection of electronic components and substrates (FOR PCB board in LED power supply), and the quality of solder joints seriously affects the reliability of devices.  On the one hand, solder joint failure comes from welding failure in production and assembly, such as solder bridge, virtual welding, void, Manhattan phenomenon.  On the other hand, in the service process, when the ambient temperature changes, due to the thermal expansion coefficient difference between the components and PCB board, thermal stress will be generated in the solder joint, and the periodic change of stress will cause fatigue damage to the solder joint, and eventually lead to fatigue failure.