Principle of surge protection for switch mode power supplies
Surge protector (SurgeProtectiveDevice, SPD), also known as surge protector, is used to limit the transient overvoltage in the charged system and guide the discharge of the inrush current of non-linear protection devices to protect the low level of voltage withstand electrical or electronic systems from lightning strikes and lightning electromagnetic pulse or operational overvoltage damage. In recent years, electronic information systems (such as television, telephone, communications, computer networks, etc.) the rapid development of electronic information equipment, a large number of emergence and popularity. Such systems and equipment are often more expensive and important, its operating voltage, voltage withstand level is very low, very susceptible to the hazards of lightning electromagnetic pulse, for which the need to use SPD to do overvoltage protection.
As countries follow different standards, product specifications are not uniform, the parameters of the logo also have their own focus, far less than other electrical product specifications, which brings great inconvenience to the design selection. In engineering design, common brands can be divided into domestic products, European products and American products according to the origin. Domestic products parameter settings are more chaotic, specifications are diverse, higher residual voltage. Specification of the product model set some imitation European products, some follow the national standard parameters, most of the products are marked In and Imax. due to the domestic products on the application of the place of lower requirements, the building level is not high, the equipment voltage value is large, so some parameter requirements can be appropriately relaxed.
European products are generally marked with the maximum discharge current, the product model is also set according to this parameter. For example, a famous European brand XXX65, XXX40, where the value of 65, 40 is Imax. but our standards clearly stipulate that the nominal discharge current In for selection, which is currently encountered in the engineering design of an embarrassing situation. After checking the product information, XX65 In value does not exceed 20kA, XX40 In value does not exceed 15kA. If in accordance with the GB50343 recommended value, these two products can only be used for the end of the three-level protection of the equipment, but in the actual design, but installed in the first and second level, which is clearly inconsistent with the national standards of the selection parameters, and the residual voltage is higher than the average model generally more than 1200V, once the wiring environment is not good, it is easy to break through. Wiring environment is not good, it is easy to break through the equipment voltage value. General European products Uc value is small, and speculative labelling line voltage, so in the selection, it is easier to mislead.
2SPD Overview
