Reliability indicators mainly include reliability, average life, failure rate and failure density.
1. Reliability: The reliability of the product is the probability of normal operation, which refers to the probability that the product can complete the specified function under the specified conditions and within the specified time. When calculating the reliability, the larger the number of products at the beginning of the test and the smaller the test interval, the higher the accuracy of the reliability.
When evaluating product reliability, it is also often expressed as failure probability or damage probability. Failure probability is the probability of a corresponding event for reliability. Reliability and failure probability are very simple and intuitive to assess the reliability of components, switching power supplies, transformers, chargers or complex systems. The greater the reliability, the smaller the failure probability and the higher the reliability.
2. Average lifespan: The average lifespan of a product refers to the average normal working time of the product, and has different meanings for non-repairable products and repairable products.
For non-repairable products, average life refers to the average working time before the product fails, usually called MTTF, which is the average time before failure.
For repairable products, the average lifespan refers to the average working time between two adjacent failures, that is, the mean time between failures, commonly referred to as MTBF, which is the mean time between failures.
The meanings of MTTF and MTBF are similar, and their mathematical expressions are also consistent.
3. Failure rate: The failure rate (failure rate, failure intensity) of a product at any time t is defined as: the probability of failure within a unit time after the product works to time t. It can also be said that the failure rate is equal to the ratio of the number of product failures in a unit time after time t to the number of products still working at time t.
The failure rate is often used to represent the reliability index of electronic products and components. The lower the failure rate, the higher the reliability. The unit of failure rate is the percentage of time, such as %/h, %/kh, which means the percentage of failure of the tested product within 1 hour (or 1000 hours). In foreign countries, Fit is commonly used as the unit of failure rate, that is, 1 failed component occurs after 1,000,000 working hours of 1 million components, which is called 1 Fit.
4. Failure density: The failure density (failure frequency) of a product refers to the ratio of the number of failed products per unit time to the initial number (total number) of tested products. Products that fail during the test will not be replaced.
The unit of failure density is 1/h, that is, the ratio of the number of failed products per hour to the total number of tested products.
Shenzhen power adapter
When evaluating the reliability of different products, one or two indicators can be selected from the above four indicators of reliability, and which indicator is used depends on the convenience of use. For general switching power adapters, electronic equipment or systems, reliability (probability of failure) can be used; for complex electronic equipment or systems, average life can be used, because such products cannot be tested in large quantities; for components The failure rate obtained through a large number of test statistics is used to characterize the reliability; for equipment that is one-time use or fails to be repaired, the failure density is used to characterize its reliability.
The reliability of switching power supply products can be quantitatively evaluated by means of mean time between failures (MTBF). At present, the electronic industry at home and abroad has taken the mean time between failures as one of the main criteria for evaluating and measuring product quality. The average trouble-free working time of a complete civil electronic machine usually refers to the average working time from the time the product leaves the factory to the first failure; operating hours.
To improve the reliability and mean time between failures of switching power adapters, the most basic factors that affect the mean time between failures should be determined first, and then solved according to their causes. The failure of switching power supply products is mostly caused by damage to components. The average trouble-free working time of electronic components is their life cycle, and once the electronic components fail, it marks the end of the life of the power adapter. The more the number of components used in the switching power supply, the higher the failure rate, the lower the reliability, and the shorter the mean time between failures. Therefore, when designing the switching power supply, try to use integrated components to reduce the number of components in the whole machine and simplify the circuit structure. At the same time, components with low failure rate should be selected as far as possible, and components that meet national quality standards should be selected. In the stage of developing switching power adapters, the use of self-made or non-standard components should be avoided as much as possible.
In addition to the components, the failure of the welding point is another important factor that causes the failure of the switching power supply product. Because mistakes are inevitable in the production of printed circuit boards, as well as in the process of assembly and welding, if the number of product solder joints is large, and the quality of soldering technology or flux is poor, the average trouble-free working time of the switching power supply will inevitably change. short.
