Ceramic PTC Thermistor: Application Motor Starter 1. Brief of product In starter circuit for single-phase a.c. motor, CPTC thermistor is in series connection with starting winding of motor. When motor starts, initial resistance of CPTC thermistor is low and provides sufficient current for auxiliary winding to start the motor normally. The devices quickly heats up its body temperature and increases its resistance as the current flows through it. The increase of resistance lowers the current and cuts off the auxiliary winding from the circuit. 2. Main parameter Zero-power resistance at 25℃ (R25) and tolerance Maximum voltage (Vmax) Operating time (to) Consumption power (P) Recovery time (tr) 3. Circuit for typical application Fig. 6 0:CSIR TYPE Capacitor motor Fig. 8 Fig. 7 Fig. 9 2:CSR TYPE Capacitor-start-drive 2:RSCR TYPE Capacitor-drive THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 1:RSIR TYPE Resistance-spilt start motor 6 www.thinking.com.tw 2014.05 Ceramic PTC Thermistor: Application Inrush Current Limiter 1. Brief of product A switching power supply has large inrush current when it turns on. If CPTC thermistor is used instead of a resistor or NTC thermistor, it works as an inrush current limiter. In addition, if relay fails, thermistor resistance rises and shuts off current when overload occurs. 2. Main parameter Maximum voltage (Vmax) Maximum link voltage (VLmax) Zero-power resistance at 25℃ (R25) Curie temperature (Tc) Heat capacity (Cth) 3. Circuit for typical application Relay. CPTC Thermistor s Bulk Load Cap. Fig. 10 Inrush current limiter THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 7 www.thinking.com.tw 2014.05 Ceramic PTC Thermistor: Application Telecom Protection 1. Brief of product PTC thermistors are widely used in telecom infrastructure equipment as an over-current protection element . Usually they operate together with overvoltage protection elements to form a resettable overload protection against all kinds of external disturbances like surge, power contact and power induction. 2. Main parameter Structure (Dip or twin SMD) Zero-power resistance at 25℃ (R25) Maximum withstanding voltage (Vw) Non-tripping current (IN) 3. Application example Subscriber Line Interface Circuit (SLIC) Fig.11 CPTC thermistors offers over-current protection to typical telephone line equipment THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 8 www.thinking.com.tw 2014.05 Ceramic PTC Thermistor: Application Overload Protection 1. Brief of product CPTC thermistor is able to replace conventional fuse installed in applications of electronic devices and transformer, etc. CPTC thermistor resistance increase when overload or abnormal heating occurs and reduces the current to a harmless residual value. Furthermore, CPTC thermistor is suitable for over-current and over-temperature protections. Conventional fuse is not able to reset after it blows; On the contrary, CPTC thermistor resumes its protection function immediately after a short cooling-down time. 2. Main parameter Structure (disc,dip) Non-tripping current (IN) Tripping current (IT) Maximum current (Imax) Maximum voltage (Vmax) Maximum operating temperature 3. Curve of characteristics The relationship of current and ambient temperature is described in Fig. 12. % Tamb (℃) Fig. 12 Temperature V.S Current Curve THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 9 www.thinking.com.tw 2014.05 Ceramic PTC Thermistor: Application 4. Application example Fig.14 Spark suppression circuit Fig.13 Circuit protection of transformer Fig.15 Current stabilization THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 10 www.thinking.com.tw 2014.05 Ceramic PTC Thermistor: Application Temperature Sensor 1. Brief of product Change of ambient temperature affects resistance of CPTC thermistor, its R-T characteristic can use for circuit control and protect the component from damage caused by over-heat. 2. Main parameter Temperature of sensor (TS) Temperature of resistor at TS+5℃ (RTS+5℃) Temperature of resistor at TS-5℃ (RTS-5℃) Zero-power resistance at 25℃ (R25) Maximum operating voltage (Vmax) 3. Principle of temperature sensor CPTC thermistor is connected to bridge arm of comparator circuit (see Fig. 16). At normal temperature, RP resistance of CPTC thermistor, is lower than Rs, and comparator's output voltage is low. The component heats up quickly and reaches its switch temperature when abnormal temperature occurs. Therefore, resistance is higher than Rs and causes increase of Vo to activates a trip (see Fig.17). Fig.16 Typical comparator circuit THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. Fig.17 Typical switch characteristic 11 www.thinking.com.tw 2014.05 Ceramic PTC Thermistor: Application 4. Circuit for typical application Fig.18 Temperature protection of electric motors Fig.19 Liquid-level indication Fig.21 Alarm installation Fig.20 Temperature compensation of transistor THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 12 www.thinking.com.tw 2014.05 Ceramic PTC Thermistor: Application Heating 1. Brief of product CPTC thermistor is widely used for heating in that it is able to maintain at a constant temperature under the specified condition. The device can be applied to heat supply source of air conditioner, preheat of diesel engine, door lock, thermal protector.and etc. 2. Main parameter Zero-power resistance at 25℃ (R25) Rated voltage (VR) Maximum voltage (Vmax) Switch temperature (TC) Surface temperature (Tsf) Maximum inrush current (Imax) Component structure 3. Circuit for typical application Fig. 22 Thermostatically Thermal protector Thermal protector PTC PTC Power Power M Supply M Supply Before protection After protection Fig. 23 Thermal protection THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 13 www.thinking.com.tw 2014.05 Ceramic PTC Thermistor: Application Electrical Ballast 1. Brief of product When rectified mains voltage is first applied, CPTC thermistor is in low resistance condition. Therefore, lamp voltage is below necessary ignition value. When current flows through cathode, resistance of CPTC thermistor rises rapidly and allows lamp voltage to reach its ignition value and light the lamp. Once the lamp is lighted, the cathode needs high-frequency power supply (20~40 KHz) and two power FET switches to avoid flickers. After the lamp is lighted, CPTC thermistor only works when the lamp is switched off. Then, delay startup is offered for next ignition. 2. Main parameter Resistance at 25℃ (R25) Switch temperature (TC) Maximum current (Imax) Maximum voltage (Vmax) Dimension 3. Circuit for typical application Fig. 24 Typical electronic ballast THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 14 www.thinking.com.tw 2014.05