Power control for hair iron having ceramic heaters

Abstract

A hair iron includes two longitudinally extending arms each having a ceramic heater. Users place hair between the heaters during use. A controller coordinates heating conditions of the heaters. If a line voltage supplied to the hair iron is a high voltage, the controller is configured to alternate heating between the heaters whereby only heating of one heater occurs at one time. To reduce flicker and harmonics, the controller supplies heating current so that one heater remains off for consecutive half-cycles of alternating current while the other heater is powered on variously. The controller then switches the heating. The hair iron further includes a line voltage detector to detect whether a line voltage supplied through a cord to the hair iron is either low voltage or high voltage. During such time, the controller limits heating power to the two heaters.

1 . A hair iron, comprising:
 two longitudinally extending arms each having a heater corresponding to an opposite heater on an opposite arm of the two longitudinally extending arms, wherein during use hair becomes placed between said heater and opposite heater to heat the hair, said heater and opposite heater being a ceramic heater and each having a setpoint temperature for low and high voltage line voltage conditions;   at least one temperature sensor to sense a temperature of said heater and opposite heater;   an electrical cord to connect said heater and opposite heater to a line voltage during use;   a controller in communication with the temperature sensor and said heater and opposite heater; and   a line voltage detector between the cord and the controller, an output of the line voltage detector being supplied to the controller,   wherein the controller is configured to limit heating power to said heater and opposite heater to about fifty percent or less before the line voltage detector detects the line voltage.   
     
     
         2 . The hair iron of  claim 1 , further wherein the controller is configured to read from the at least one temperature sensor a current temperature of said heater and opposite heater and initializing a timer to time zero t0. 
     
     
         3 . The hair iron of  claim 2 , further wherein the controller is configured to calculate a warmup time for said heater and opposite heater, the warmup time corresponding to a second time t2 less a first time t1, wherein the second time t2 corresponds to a second time when a second read temperature from the at least one temperature sensor is the current temperature plus 20° C. and the first time t1 corresponds to a first time when a first read temperature from the at least one temperature sensor is the current temperature plus 10° C. 
     
     
         4 . The hair iron of  claim 3 , wherein if the warm up time is less than a first predetermined time, the controller is further configured to initiate a high voltage control routine of said heater and opposite heater. 
     
     
         5 . The hair iron of  claim 4 , wherein the first predetermined time is about 255 msec. 
     
     
         6 . The hair iron of  claim 3 , wherein if the warm up time is greater than a second predetermined time, the controller is further configured to initiate a low voltage control routine of said heater and opposite heater. 
     
     
         7 . The hair iron of  claim 6 , wherein the second predetermined time is about 344 msec. 
     
     
         8 . A hair iron, comprising:
 two longitudinally extending arms each having a heater corresponding to an opposite heater on an opposite arm of the two longitudinally extending arms, wherein during use hair becomes placed between said heater and opposite heater to heat the hair, said heater and opposite heater being a ceramic heater;   a line voltage detector to detect whether a line voltage supplied through a cord is either of a low voltage or high voltage; and   a controller to coordinate heating of said heater and opposite heater, wherein if said high voltage exists, the controller being configured to alternate heating between said heater and opposite heater and heating only one of said heater and opposite heater at any time.   
     
     
         9 . The hair iron of  claim 8 , wherein the high voltage includes an alternating current sinusoidal waveform, the waveform having consecutive half-cycles of power, wherein during a first twelve of said half-cycles of power, the controller prevents said opposite heater from receiving heating current. 
     
     
         10 . The hair iron of  claim 8 , wherein the high voltage includes an alternating current sinusoidal waveform, the waveform having consecutive half-cycles of power, wherein during a first twelve of said half-cycles of power, the controller allows said heater to receive heating current for only four of said half-cycles of power. 
     
     
         11 . The hair iron of  claim 10 , wherein said four of said half-cycles of power include two positive and two negative said half-cycles of power. 
     
     
         12 . The hair iron of  claim 8 , wherein the high voltage includes an alternating current sinusoidal waveform, the waveform having consecutive half-cycles of power, wherein during a second twelve of said half-cycles of power, the controller prevents said heater from receiving heating current. 
     
     
         13 . The hair iron of  claim 8 , wherein the high voltage includes an alternating current sinusoidal waveform, the waveform having consecutive half-cycles of power, wherein during a second twelve of said half-cycles of power, the controller allows said opposite heater to receive heating current for only four of said half-cycles of power. 
     
     
         14 . The hair iron of  claim 13 , wherein said four of said half-cycles of power include two positive and two negative said half-cycles of power. 
     
     
         15 . The hair iron of  claim 8 , wherein the high voltage includes an alternating current sinusoidal waveform, the waveform having consecutive half-cycles of power, wherein during a first twelve of said half-cycles of power, the controller allows said heater to receive heating current for only six of said half-cycles of power. 
     
     
         16 . The hair iron of  claim 15 , wherein said six of said half-cycles of power include three positive and three negative said half-cycles of power. 
     
     
         17 . The hair iron of  claim 8 , wherein the high voltage includes an alternating current sinusoidal waveform, the waveform having consecutive half-cycles of power, wherein during a second twelve of said half-cycles of power, the controller allows said opposite heater to receive heating current for only six of said half-cycles of power. 
     
     
         18 . The hair iron of  claim 17 , wherein said six of said half-cycles of power include three positive and three negative said half-cycles of power. 
     
     
         19 . The hair iron of  claim 8 , wherein the high voltage includes an alternating current sinusoidal waveform, the waveform having consecutive half-cycles of power, wherein during a second twelve of said half-cycles of power, the controller prevents said heater from receiving heating current. 
     
     
         20 . A hair iron, comprising:
 two longitudinally extending arms each having a heater corresponding to an opposite heater on an opposite arm of the two longitudinally extending arms, wherein during use hair becomes placed between said heater and opposite heater to heat the hair, said heater and opposite heater being a ceramic heater; and   a controller to coordinate heating of said heater and opposite heater, wherein if a high voltage is supplied to the hair iron, the controller is configured to alternate heating between said heater and opposite heater and heating only one of said heater and opposite heater at any time, wherein the high voltage includes an alternating current sinusoidal waveform, the waveform having consecutive half-cycles of power, the controller said heating said only one of said heater and opposite heater at 16.7% or 25% of a consecutive twelve of said half-cycles of power.