Design of lightning surge protection for LED driver power supply (no grounding of power supply)
The first is the common protection method on a fuse type fuse in the AC input terminal (fuse) for overcurrent protection, then parallel varistor between two line L-N (MOV) can effectively suppress the differential abnormal overvoltage, to protect the circuit after the. According to the failure characteristics of varistor basically for short circuit, considering the varistor failure after short circuit if the front fuse failed to disconnect the circuit may cause the varistor overheat and burn, in order to prevent this from happening, we can be in series with a resistor temperature fuse (T-fuse), so that the varistor can short-circuit failure time sensitive resistance is disconnected from the power, to avoid unnecessary losses. Here we can also use ceramic gas discharge tube (GDT) to replace the temperature fuse, we use two kinds of different devices is used after the surge arrester, the residual voltage will be higher, while the surge current capacity will increase. Lightning protection design of LED driver power supply (power supply grounding)
LED lamp drive power outdoor have strict requirements of lightning surge test (such as differential mode and common mode 6KV/3KA), lightning surge protection scheme is common: respectively between L-N two and L/N-PE two line line of the varistor (MOV) to absorb abnormal surge and common mode of protection level circuit.
Due to the high demand for the power of the earth to the surge, the surge capacity of the varistor is basically proportional to its size. And if the earth is not clean, often appear abnormal surge would lead to pressure sensitive resistance grounding accelerated aging, thus affecting the service life of the product, so we will be on the varistor ceramic gas and connected on the discharge tube, to prevent leakage of varistors flow, improve the protection of the varistor voltage to prevent over fast aging, prolong the service life of the product. Lightning surge higher requirements, the corresponding varistor residual voltage is higher, if the secondary rectifier bridge or FET low voltage, rectifier or MOSFET may lead to failure, can use the differential protection that poles after the bridge rectifier and a voltage sensitive resistor or common mode inductance in parallel on the discharge tube further restrain the impact of voltage. In addition to lighting power supply lightning surge test requirements and general insulation (Hi-Pot) test requirements (such as the line to ground voltage is 1500VAC or above, the leakage current is less than 5MA, duration 60S), our solution is to choose to discharge voltage of 3000V or more, which will meet the test requirements of pressure, at the same time also meet the lightning test surge voltage above 6KV.