Patent ID: 6397003
Filing Date: 2002-05-28
Classification: A45D,F24H

Abstract:
A hot air-blower off-state residual heat preventive control circuit installed in a hot air-blower of the type comprising a main thermal resistor, an auxiliary thermal resistor, a switching control circuit for operation by the user to turn on/off said main thermal resistor and said auxiliary thermal resistor, and a fan motor controlled to blow air toward said main thermal resistor and said auxiliary thermal resistor, the hot air-blower off-state residual heat preventive control circuit comprising:a power voltage stabilizer circuit connected to AC power supply to convert AC power supply into a rated working voltage for a microprocessor; a power frequency detection circuit, which detects the frequency of AC power supply provided to said power voltage stabilizer circuit; a microprocessor, which receives the rated working voltage from said power voltage stabilizer circuit and the power frequency data from said power frequency detection circuit, and is controlled by said switching control circuit to turn on/off said main thermal resistor, said auxiliary thermal resistor, and said fan motor subject to; a first bi-directional switch connected between said main thermal resistor and said microprocessor and controlled by said microprocessor to turn on/off said main thermal resistor: a rectifier and noise control circuit and a second bi-directional switch connected in series between said microprocessor and said fan motor and controlled by said microprocessor to turn on/off said fan motor; wherein when the user operates said switching control circuit to turn on the hot air-blower, said microprocessor drives said first bi-directional switch and said second bi-directional switch to turn on said main thermal resistor, said auxiliary thermal resistor and said fan motor; when the user operates said switching control circuit to turn off the hot air-blower, said microprocessor is driven by said switching control circuit to send a first signal to said first bi-directional switch, causing said first bi-directional switch to turn off said main thermal resistor, and to keep said fan motor and said auxiliary thermal resistor operating for a predetermined length of time, and then to send a second signal to said second bi-directional switch a predetermined length of time after the provision of said first signal to said first bi-directional switch, causing said second bi-directional switch to cut off power supply to said auxiliary thermal resistor and said fan motor.