Reliability indexes mainly include reliability, average life, failure rate and failure density.
1. reliability: the reliability of the product, i.e. the normal working probability, refers to the probability that the product will complete the specified function under the specified conditions and within the specified time. When calculating the reliability, the greater 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 commonly expressed by failure probability or damage probability. The failure probability is the probability of the event corresponding to the reliability. Reliability and failure probability are very simple and intuitive for evaluating 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 service life: the average service life of a product refers to the average normal working time of the product. It has different meanings for irreparable products and repairable products.
For non repairable products, the average life refers to the average working time before the product fails, which is usually called MTTF, that is, the average time before reaching the failure.
For Repairable Products, the mean life refers to the average working time between two adjacent failures, i.e. the mean time between failures, which is usually called MTBF, i.e. the mean time between failures.
The meanings of MTTF and MTBF are similar, and their mathematical expressions are the same.
3. failure rate: the failure rate (failure rate and failure intensity) of the product at any time t is defined as the probability of failure in unit time after the product works to time t. It can also be said that the failure efficiency is equal to the ratio of the number of failures of the product in a unit time after time t to the number of products still working at time t.
Failure rate is often used to indicate 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 represents the percentage of failure rate of the tested product within 1 hour (or 1000 hours). Fit is commonly used as the unit of failure rate in foreign countries, that is, one failed element occurs after one million elements work for 1000 hours, 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 shall not be replaced.
The unit of failure density is 1/h, that is, the ratio of the number of products failed in each hour to the total number of products tested.
Shenzhen power adapter
Shenzhen juyuanhai Electronics Co., Ltd. is a high-tech enterprise that independently develops, produces and sells Shenzhen power adapter, vehicle charger, charging back clip and mobile power supply.
When evaluating the reliability of different products, one or two indicators can be selected from the above four indicators to represent the reliability. Which indicator is used depends on the convenience of use. For general switching power adapter, electronic equipment or system, reliability (failure probability) can be adopted; For complex electronic equipment or systems, the average service life can be used, because it is impossible to test such products with a large number; For the components, the reliability is characterized by the failure rate obtained through a large number of test statistics; For the equipment that is used once or will not be repaired after failure, the failure density is used to characterize its reliability.
The reliability of switching power supply products can be quantitatively evaluated by 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 standards to evaluate and measure product quality. The mean time between failures (MTBF) of a civil electronic complete machine usually refers to the mean time between the product leaving the factory and the first failure; The mean time between failures (MTBF) of complete industrial electronic products usually refers to the mean time between two failures.
In order to improve the reliability and MTBF of switching power adapter, the most basic factors affecting MTBF should be determined first, and then solved according to their causes. The failure of switching power supply products is mostly caused by the damage of components. The mean time between failures (MTBF) of electronic components is their life cycle. Once an electronic component fails, it marks the end of the life of the power adapter. The more 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 shall be selected as far as possible, and components meeting national quality standards shall be selected. In the development stage of switching power adapter, self-made or non-standard components should be avoided as far as possible.
In addition to components, the failure of welding points is another important factor that causes the failure of switching power supply products. Because mistakes are inevitable in the process of PCB production, assembly and welding, if the number of solder joints is large and the quality of welding technology or flux is poor, the average trouble free working time of the switching power supply will inevitably become shorter.
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