When the working status of the components does not exceed the reference indicators provided by the supplier in the specification book, the long-life operation of the switch power adapter can be achieved. The reduced use of components can provide product reliability. The important reason why the actual lifespan cannot reach the rated lifespan is that the working condition of the components is in the worst condition. The worst-case scenario is when the product operates under various normal or abnormal working conditions (including changes in dynamic load size, short circuits, working in high and low temperature environments, with the lowest and highest input working voltage, and in cold machine startup and shutdown situations).

During the use of switch mode power adapters, they can be divided into three stages: initial failure, occasional failure, and wear failure, with different causes of corresponding failures.

Initial failures of power supply products: Switching power adapters typically experience failures within 30 days during their initial use. Over time, the product stabilizes and the failure rate gradually decreases. The main factor is due to potential defects, which require measures such as comprehensive design and component screening to prevent faults from occurring. There is an aging test during the production process of the switch power adapter, but the time is only 2-4 hours, and the potential defects of a very small number of components cannot be screened out.

Occasional faults in power products: After initial troubleshooting, it will enter the stage of occasional faults. Mainly caused by sudden situations such as product drops and lightning, unrelated to working hours, and can maintain a certain failure rate. Our goal is to prevent occasional defects in the production process and control excessive fluctuations in the usage environment, so that occasional faults are close to zero.

Wear fault of power supply products: After the occasional fault stage, as the working time goes on, the fault will occur again. The fault at this time is mainly caused by product wear and tear, which can also be understood as the lifespan of some components having reached their limit.

Based on the reliability requirements of the product, the cost requirements of design, maturity, safety, after-sales maintenance costs, and the difficulty of assembly, the rating level is comprehensively determined. The military standard GBJ/Z35-93 recommends the following three downgrade levels:

1. Level I, it is the maximum reduction in rating and has the greatest improvement effect on the reliability of component usage. Applicable to the following situations: the implementation of the product will cause serious damage to the application system or pose a safety hazard to users; Design solutions that require high reliability of the product and adopt new processes and technologies; Due to technical or cost reasons, products that fail cannot be repaired; The application system has strict restrictions on the weight and size of the product.

Level II is a moderate reduction in rating, which significantly improves the reliability of component usage. The failure of the product may cause damage to the application system; Has high reliability requirements and adopts certain biased gate designs; High after-sales service fees.

3. Level III is the minimum derating and has the greatest relative benefit in improving the reliability of component usage, but the effect of reliability improvement is not as good as the previous levels II and I. Applicable to: After the product malfunctions, it will not cause damage to the application system or pose a safety hazard to operators; The product adopts mature design standards; hair

• Analysis of the Serv…