Application of self recovery fuse in electric toys
Publisher: Administrator Date：2020-12-03
With the development of science and technology and the progress of society, people are paying more and more attention to the intellectual development of infants and young children. Various educational toys have sprung up, including electric and non-electric ones. There are thousands of types and quality requirements. They are very different and uneven. When people buy toys, they tend to consider the play function of the toy more than the safety of the toy. The quality problems of many toys only get people's attention when accidents occur, but it is too late and has already caused harm to people, and some injuries may last for life.
In foreign countries and especially developed countries, the safety of electronic toys is the most important. Regardless of certification, testing, R&D and customer requirements, safety is the first consideration, and the function of toys, especially electric toys, so the safety of toys Is the first issue.
In the European and American international standard "BS/EN 50088:1996", clause 3.6.2 clearly stipulates thermal interruption: a device that can limit the temperature of the toy or its parts by automatically disconnecting the circuit or reducing the current during abnormal operation. It is designed so that the user cannot change its design value; Clause 3.6.3. clearly stipulates that the automatic recovery of thermal interruption: After the relevant parts are cooled, the thermal interruption of the circuit can be automatically restored.
It is not difficult to see that the above keywords are "safety protection", "thermal interruption", and "automatic recovery thermal interruption", which are all about the safety control of electric current heating of electric toys. That is, protection and control problems after overcurrent and overtemperature.
In electric toys, they are mainly composed of motors, electronic control boards, power supplies (dry batteries, batteries, transformers, chargers), shells and parts. During the use of electric toys, due to improper use, they often appear: The motor is locked, the temperature of the motor is too high, the short circuit heating of the battery, the short circuit caused by the damage of the components on the electronic control board, the heating of the battery overcharge and overdischarge, etc. Will cause large currents to be generated in the circuits of electric toys, causing safety hazards such as high temperature, burning, and battery explosions in electric toys.
In terms of over-temperature and over-current protection of toys, glass fuses, thermal fuses, insurance inductors, insurance resistors, etc. were used in the past, but they are all used once and need to be replaced frequently, and cannot complete the "automatic recovery thermal interruption" function specified by the standard , And poor design will have a counterproductive effect. Some people design and apply bimetal thermostats, but bimetal thermostats only work on temperature, and the thermal response is too slow, and the faulty circuit will be turned on again when the power is forgotten to enlarge the fault. To achieve the purpose of "automatic recovery of thermal interruption", the application of "PPTC" for over-temperature and over-current protection is the best choice at present.
PPTC, also known as "self-recovery fuse" or "ten thousand times fuse", is a highly sensitive non-linear thermistor. When the motor is blocked or the current in the loop is too large, PPTC changes from a low resistance state to a high resistance state. Thereby, the current of the motor or circuit is limited, which plays a role of timely protection. Only a single PPTC component is needed to achieve the purpose of over-temperature and over-current protection, which not only makes electric toys safe and reliable, and smoothly passes European and American safety regulations, but also reduces component costs, reduces service costs, and greatly improves the market competitiveness of electric toys .