Research on Electrical Conduction Mechanism and Withstand Voltage Properties after Current Limiting of PTC (Positive Temperature Coefficient ) Device

正温度系数（PTC）器件现在被用作小型电子设备二次电池的过流限制器件，如手机、笔记型个人电脑和摄像机。目前使用的许多PTC器件在限流作用后耐压的提高、材料的优化组成、电极材料和结构等方面都存在着各种问题需要解决。本课题旨在阐明陶瓷型PTC器件在高阻区导电机理及局部放电对其限流性能的影响，陶瓷型PTC器件有望具有比聚乙烯型、钛酸钡型等传统PTC器件更高的额定电流和限流电压。此外，我们提出了一种以液体或凝胶材料为基体，以固体导电颗粒为填料的新型混合PTC装置，并通过实验验证了该装置的工作原理。即提出一种PTC装置，在短路事件中，导电微粒被蒸发耗散，进行限流操作，然后通过介电力自动有效地收集导电微粒，实现电路的再次接通。我们为新型混合PTC减振器申请了专利。测定了6种陶瓷型PTC器件在不同填料量和不同气体含量H_2、N_2比下燃烧形成陶瓷时的电阻-温度关系和电流-电压关系。然后，我们比较了陶瓷型PTC器件从导通状态到关断状态的电阻跳变比，以及返回导通状态后的电阻和过渡电压。结果表明，燃烧时H_2含量越高，电阻跳变比越大，过渡电压越大。此外，随着填料用量的增加，过渡电压增大。同时指出，隧穿电流或离子跳变电流是由陶瓷型PTC器件的传导机制引起的。还证实，在对PTC设备施加交流电压时，发生了局部放电。研究发现，瞬时放电起始电压与导通时回路电阻退化的电压相对应，表明局部放电对回路电阻退化有不良影响。少

Positive temperature coefficient(PTC) devices are now used as over-current limiting device for secondary batteries of small electronic apparatuses such as mobile phone, note type personal computer and video camera. A number of PTC devices used at present have various issues to be tackled on improvement of withstand voltage after current limiting action, optimum composition of materials, electrode materials and the configuration etc. Aim of this project is to elucidate electrical conduction mechanism in high resistance region and the influence of partial discharges on the current limiting properties of ceramic type PTC devices, which are expected to have higher current rating and limiting voltage than conventional PTC devices such as polyethylene type and barium titanate type PTC devices. Besides, we proposed a new type hybrid PTC device where liquid or gel material is used as a matrix and solid conducting particles are used as filler, and performed experiments to verify the principle o … More f operation. Namely, the PTC device is proposed where on short circuit event the conducting particles are evaporated and dissipated to perform current limiting operation, and then dielectrophoresis force allows automatic collection of the conducting particles efficiently to realize switching on the circuit again. We made an application for patent for the new hybrid PTC decive.We measured resistance-temperature relation and current-voltage relation for 6 kinds of ceramic type PTC devices with different filler amounts and different ratios of gas content H_2 and N_2 on burning to form ceramic. Then, we compared the ratio of resistance jump from on-state to off-state of the ceramic type PTC devices, and the resistance after returning to on-state and the transition voltage. As a result, it was found that the higher the H_2 gas content on burning, the larger the resistance jump ratio and the transition voltage. Besides, as the filler amount increased, the transition voltage increased. It was also indicated that tunneling current or ionic hopping current is attributed to the conduction mechanism of ceramic type PTC device. It was also confirmed that on applying ac voltage to the PTC device, partial discharges took place. It was found that the instantaneous discharge inception voltage corresponded to the voltage giving the degradation of the return resistance on backing to on-state, suggesting the bad influence of partial discharges on the return resistance degradation. Less