Power Adapters Manufacturers

Insulation protection requirements for power adapters
1、Types of insulation
To ensure the normal operation of the circuit and the circuit appears higher than the dangerous voltage, must use insulation materials and insulation protection. UL60950 will be divided into five categories of insulation: functional insulation, basic insulation, additional insulation, double insulation and enhanced insulation.
① Functional insulation: is the equipment must work correctly insulation, does not provide safety protection against electric shock, but can reduce the fire and combustion. For example, the enameled wire coating.
② Basic insulation: the most basic insulation to avoid electric shock. Relying on basic insulation alone is not safe, but also through additional insulation and protective grounding secondary protection to achieve safety requirements, such as coil insulation.
③ additional insulation: independently added to the basic insulation on the insulation, to ensure that the basic insulation in the event of failure, to provide protection against electric shock of the second level. Additional insulation single-layer material thickness must be greater than or equal to the minimum 0.4mm.
④Double insulation: a combination of basic insulation and additional insulation, a secondary insulation system.
⑤ Enhanced insulation: A single insulation system to prevent electric shock, equivalent to double insulation. The minimum thickness of the single layer used inside is greater than or equal to 0.4mm. there may be several layers, but each layer cannot be tested separately.
2, equipment level and insulation requirements
Different types of circuits require different types of insulation:
① Class I equipment. This type of equipment is protected by protective grounding, i.e., the metal chassis is connected to the protective ground as Class 1 protection. Only basic insulation is required between any hazardous voltage parts and the chassis, such as station communication power supply.
② Class II equipment. Double insulation and reinforced insulation are used without metal chassis and grounding screws, e.g., portable chargers.
③ Class III equipment. Powered by an SELV source and an internal power supply with no potentially hazardous voltage generation, so only basic insulation is required, e.g., circuit board power supplies. Figure 8.2.3 shows a simple functional block diagram inside the power supply. From the block diagram, first distinguish whether the internal circuit functional blocks are LCC, SELV, TNV, ELV or hazardous voltages, and then determine the level and amount of insulation between the functional blocks and between the internal components and the use. From the diagram it can be seen that at least two poles of insulation are required between hazardous voltages and user accessible parts.
For example, an ELV path to floating ground must have two poles of insulation and at least 1 level between the ELV and the user, otherwise the ELV circuit will be unsafe if a single level fails. However, if the ELV circuit is ground-protected (providing 1 level of protection), the addition of only 1 level is sufficient. Similar situations such as heat sinks and metal enclosures must use Class 2 insulation to isolate the user from hazardous voltages. Level 1 may not be used unless the metal is made grounded.

3、Insulation material
According to the working voltage, electrical strength, temperature requirements, mechanical strength and working environment to choose solid insulation materials, and these materials should be moisture and flame retardant materials; if the wire insulation, but also requires material flexibility.
Semiconductor devices and other components are molded in solid insulating materials, and their insulation is individually quality assessed and tested in the factory manufacturing process. There are thickness requirements for films, tapes and sheets of solid insulating materials: in the case of single-layer insulations, the minimum thickness is greater than or equal to 0.4 mm; in the case of two-layer insulations, there are no thickness requirements, but each layer must meet the electrical strength requirements; in the case of three or more layers, there are also no minimum thickness requirements, but each two-layer combination must meet the corresponding electrical strength requirements. There is also no thickness requirement for basic or functional insulation.

If you want to know more about switching power supply information, you can consult Xiamen Eahunt Electronics.

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