1. Field of the Invention
The present invention relates to a portable dryer, and more particularly, to a multi-setting portable dryer and related circuit design.
2. Description of the Prior Art
The conventional dryer is operable only after establishing connection with an AC power plug through a power cord. The use of the dryer is then limited by the length of the cord to the area that can be reached by the cord from the AC power receptacle. Therefore, it is very inconvenient for traveling purposes, in particular, when traveling in countries where the AC power specifications, such as voltages, cycles, and receptacles vary from one to another. Different converters and transformers are needed if the user wants to use a conventional dryer. Furthermore, since the conventional AC-powered dryers are powered by AC currents with sinusoidal amplitudes, most use a diode to control the generation of heat. When the switch is shifted to a low heat setting, the one-way conduction property of the diode filters out a half cycle of the AC current that passes through the heating filament. When the switch is shifted to a high heat setting, the current to the heating filament does not go through the diode so that heat can be generated at full output. At the same time, in order to provide a DC current to the motor, an additional bridge rectifier has to be employed to supply the needed DC power.