A starting circuit for a single-phase
induction motor includes a motor starting positive characteristic
thermistor and a
triac arranged in a series connection, and a
triac control positive characteristic
thermistor connected in parallel with the motor starting positive characteristic
thermistor, and including one terminal thereof connected to a gate of the
triac. The triac control positive characteristic thermistor has a volume in the range of about 4.5 mm3 to about 30 mm3. The relationship of (√2×V×sin 45°) / R≧I is maintained with the triac control positive characteristic thermistor within an
operating temperature range, where V represents a root-mean-square value of a power source
voltage, R represents a resistance of the triac control positive characteristic thermistor, and I represents a gate turn-on current of the triac. The gate turn-on current I at an
operating temperature of about 25° C. is about 20 mA or less.