1. The status quo of LED North American standards
LED energy-saving lamp as a new type of product, the current North American product safety standards do not specifically for this type of product technical requirements, LED product testing has become a topic in the industry. The United States UL laboratory for the current situation of this industry, is organizing the preparation of LED energy-saving lamp safety certification standard UL8750, this standard is still a draft, has not been formally adopted as a certification standard. Therefore, the certification test problem of LED energy-saving lamps has not been completely solved for the time being.
The basic principle of LED energy-saving lamps is to convert AC power into direct current through a switching power supply module to power the light-emitting diode. According to the basic principle and structural characteristics of LED energy-saving lamps, the United States MET laboratory proposed a transitional detection scheme at this stage: The United States certification standard for traditional energy-saving lamps UL1993(corresponding to the Canadian standard CAN/CSA-C22.2No.0, CAN/CSA-C22.2No.74), LED energy-saving lamps are tested and certified with the power module standard UL1310 or UL1012(corresponding to the Canadian standard CAN/CSA-C22.2No.107).
Technical points in testing
The following is based on UL1993, UL1310 and UL1012 standards, the key issues in the certification test of LED energy-saving lamps, do some elaboration.
1. Material
LED energy-saving lamps can be made into a variety of shapes, to daylight tube LED energy-saving lamps, for example, its shape is the same as ordinary daylight tubes, by daylight tube transparent polymer shell will be the power module and light emitting diode inside. The transparent polymer shell acts as a fire and electric shock protection in the product. According to the standard requirements, the energy-saving lamp shell material must reach V-1 grade or above, so the transparent polymer shell must use V-1 grade or above. It should be noted that in order to achieve the required V-1 grade of the product shell, its thickness must be greater than or equal to the thickness required by the V-1 grade of the raw material, and the fire rating and thickness requirements can be found on the UL yellow card of the raw material.
In the actual test, it was found that in order to ensure the brightness of the LED lamp, the manufacturer often makes the transparent polymer shell very thin, which requires the detection engineer to pay attention to ensure that the material reaches the required thickness of the fire grade. Because different raw materials have different thickness requirements for the same fire rating, some raw materials can meet the higher fire rating requirements under a smaller thickness, it is recommended that manufacturers can choose the appropriate raw materials to make product shells.
2. Drop test
According to the requirements of the product standard, the product should simulate the drop situation that may occur in the actual use of the drop test, the product should fall from a height of 0.91 meters to the hardboard, the product shell should not break to reveal the dangerous live parts inside. Manufacturers must consider this strength requirement when selecting materials for product housings
3. Electrical strength
The transparent shell encloses the power module inside, and the transparent shell material must meet the requirements of electrical resistance. According to the standard requirements, based on the North American voltage of 120 volts, the internal high-voltage live parts and the housing (covered with metal foil for test) should be able to withstand the AC 1240 volts of electrical strength test. Under normal circumstances, the thickness of the product shell is about 0.8mm, which can meet the requirements of this electrical strength test.
4. Power module
The power module is an important part of LED energy-saving lamps, and the power module mainly uses switching power supply technology. According to the type of power module, you can consider using different standards for testing and certification. If the power module is a classII power supply, this can be tested with the UL1310 for authentication. classII power supply refers to the isolated transformer, the output voltage is less than 60 volts DC, the current is less than 150/Vmax ampere power supply.
For non-CLASSIi power supplies, UL1012 is used for testing and authentication. The technical requirements of the two standards are very similar and can be referred to each other. The internal power module of most LED lights is a non-isolated power supply, and the DC power output voltage is also greater than 60 volts, so it is not suitable for UL1310 standard, but for UL1012
.
5. Insulation requirements
Due to the limited internal space of LED energy-saving lamps, in the structural design, attention should be paid to the insulation requirements between dangerous live parts and accessible metal parts. The insulation can be spatial distance and creepage distance, or it can be an insulation sheet. According to the standard requirements, the space distance between the dangerous live parts and the accessible metal parts should reach 3.2 mm, and the creepage distance should reach 6.4 mm. If the distance is not enough, you can add insulation sheet as additional insulation, the thickness of the insulation sheet should be greater than 0.71 mm, if the thickness is less than 0.71 mm, the product should be able to withstand 5000V high voltage test.
6. Temperature rise test
Temperature rise test is a must-do item of product safety test, the standard has a certain temperature rise limit for different components. In the product design stage, the manufacturer should attach great importance to the heat dissipation of the product, especially for some parts (such as insulation sheets, etc.) should pay special attention.
If the parts work under high temperature conditions for a long time, it is easy to damage, resulting in fire or electric shock risk. The power module inside the lamp is in a closed and narrow space, and the heat dissipation is limited. Therefore, when the manufacturer selects the components, it is necessary to pay attention to the selection of the appropriate component specifications to ensure that the components work under a certain margin, so as to avoid overheating when the components work under conditions close to full load for a long time.
Seven. Structure
The power module of the LED energy-saving lamp is installed inside the housing, space is limited, and some manufacturers in order to save space, the pin-type component surface is welded on the PCB, this practice is not acceptable. These surface-welded pin components are likely to fall off due to welding and other reasons, posing a hazard. Therefore, these components should be welded as far as possible. If the surface welding method is forced to be adopted, additional protection should be provided for this component by adding glue to fix it.
8. Fault test
Product fault test is a very important test item in product certification test. This test project is to short-circuit or open some components on the line to simulate the faults that may occur during actual use, thus evaluating the safety of the product under a single fault condition. In order to meet this safety requirement, in the product design, it is necessary to consider adding a suitable fuse at the input end of the product to prevent the output short circuit or the internal component failure when the overcurrent occurs, resulting in the risk of fire.
Three, factory inspection
North American product certification requires a factory inspection, which includes the first factory inspection and follow-up inspection. If the factory is applying for North American product certification for the first time, the first factory inspection should be conducted. The first factory inspection is mainly aimed at the quality assurance system of the factory, requiring the factory to have a perfect quality assurance system to ensure that the quality of the product is effectively supervised and guaranteed. If the factory has established a quality management system according to the ISO9000 standard and passed the ISO9000 certification, it can basically meet the management system requirements of the first factory inspection.
If the factory has not passed ISO9000 certification, it must have clear procedures and documents in raw material procurement, incoming material inspection, inventory management, product design, engineering changes, production line testing, instrument calibration and complaint follow-up, and effectively implement them. Follow-up inspection is mainly for product structure inspection and production line product testing, to ensure that the product structure of the production line is consistent with the certified sample, and through the relevant production line testing. After the product has passed the test certification, the manufacturer must strictly follow the structure and component list of the certified sample for product production, and any changes that may involve product safety must be notified to the certification body for evaluation. If necessary, retesting and reporting changes may be required. The product test report has clear requirements for the product production line test, and the manufacturer must carry out relevant tests in accordance with the requirements, such as high voltage test, ground continuity test, etc.
