With the development of science and technology and the progress of society, people pay more and more attention to the intellectual development of infants and young children. Various educational toys are springing up one after another, including electric and non-electric, with thousands of types and quality requirements. When people buy toys, they often consider the play function of toys and ignore the safety of toys. The quality problems of many toys are only paid attention to when an accident occurs, but it is too late and has already caused harm to people, and some injuries may be accompanied by life. It can be seen how important it is to improve the safety of electric toys.
In foreign countries, especially developed countries, the most attention to the safety of electronic toys, regardless of certification testing, R & D design, customer requirements, etc., the first consideration is the safety issue, followed by the function of toys, especially electric toys, so the safety protection of toys Is the primary issue.
In clause 3.6.2 of the European and American international standard BS/ EN 50088:1996, it is clearly stipulated that the temperature of the toy or its parts can be limited by automatically opening the circuit or reducing the current during abnormal operation. The device is designed so that the user cannot change its design value. In clause 3.6.3, it is clearly stipulated that the automatic recovery of thermal cut-off: the thermal cut-off of the closed circuit can be automatically restored after the relevant components have cooled down.
It is not difficult to see that the key words in the above are "safety protection", "thermal cut-off", and "automatic recovery of thermal cut-off", which are all about the safety control of current heating of electric toys. That is, the protection control problem after over current and over temperature.
In electric toys, it is mainly composed of motor, electronic control board, power supply (dry battery, storage battery, transformer, charger), shell and parts. In the process of using electric toys, due to improper use, it often occurs: motor blocking, motor temperature is too high, battery short circuit heating, short circuit caused by damage to components on the electronic control board, battery overcharge and overdischarge heating, etc. Will make the electric toy circuit to produce large current, so that electric toys appear high temperature, burning, battery explosion and other security risks.
In terms of over-temperature and over-current protection of toys, glass fuses, temperature fuses, insurance inductors, insurance resistors, etc. have been used in the past, but they are all used once and need to be replaced frequently. They cannot complete the "automatic recovery of thermal cut-off" function specified in the standard, and poor design will have a negative effect. Some people design the application of bimetal thermostat, but the bimetal thermostat only works on the temperature, and the thermal response is too slow, forget to turn off the power supply will again turn on the fault circuit to expand the fault. To achieve the purpose of "automatic recovery of thermal cut-off", the application of "PPTC" to do temperature and overcurrent protection is the best choice at present.
PPTC, also known as "self-recovery fuse" or "ten thousand times fuse", is a high-sensitivity nonlinear thermistor. When the motor is blocked or the current in the loop is too large, PPTC jumps from a low-resistance state to a high-resistance state, thereby limiting The current of the motor or circuit plays a role of timely protection. Only a single self-healing fuse (PPTC) component can achieve the purpose of over-temperature and over-current protection. It can not only make electric toys safe and reliable, and successfully pass the European and American safety regulations certification, but also reduce component costs, reduce after-sales service costs, and vigorously improve The market competitiveness of electric toys.
The PPTC often used in electric toys is generally: R16, R30 and other plug-in series, and can also be used for patch SMD1812, SMD1210, SMD1206 and other patch series PPTC components.
