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 timing and voltage conditions to heat the heaters to avoid light flicker and power harmonics. Thermistors provide current heater temperatures of the heaters and a controller calculates a desired heating power. The heating power includes application to the heaters of various half-cycles of AC power from an external AC line voltage.

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 having a corresponding thermistor; and   a controller to coordinate heating of said heater and opposite heater by connecting or not said heater and opposite heater to an AC line voltage at times of zero crossings of a waveform of the AC line voltage and to receive from the corresponding thermistor a current temperature of said heater and opposite heater to calculate a desired heating power.   
     
     
         2 . The hair iron of  claim 1 , further including a TRIAC to said connect or not said heater and opposite heater to the AC line voltage. 
     
     
         3 . The hair iron of  claim 1 , further wherein the controller includes a PID controller corresponding to said heater and opposite heater and connected to the corresponding thermistor. 
     
     
         4 . The hair iron of  claim 3 , wherein the controller is further configured to alternate heating between said heater and opposite heater and heating only one of said heater and opposite heater at any time. 
     
     
         5 . The hair iron of  claim 3 , wherein the desired heating power corresponds to a waveform of the AC line voltage and having or not a DC offset depending upon a number of even or odd on-and-off half-cycles of the waveform of the AC line voltage, the even on-and-off half-cycles having no DC offset but the odd on-and-off half-cycles having said DC offset. 
     
     
         6 . The hair iron of  claim 5 , wherein if each said desired heating power of said heater and opposite heater has no said DC offset, the controller applying said each said desired heating power. 
     
     
         7 . The hair iron of  claim 5 , wherein if each said desired heating power of said heater and opposite heater have said DC offset, the controller applying said desired heating power for said heater in an opposite pattern of applying said desired heating power for said opposite heater. 
     
     
         8 . The hair iron of  claim 7 , wherein the controller applies said desired heating power for said heater and opposite heater over eight (8) AC half-cycles of the AC line voltage. 
     
     
         9 . The hair iron of  claim 5 , wherein if one but not both of said desired heating power of said heater and opposite heater has said DC offset, the controller applying said desired heating power for said heater in an opposite pattern of applying said desired heating power for said opposite heater. 
     
     
         10 . The hair iron  9 , wherein the controller applies said desired heating power for said heater and opposite heater over sixteen (16) AC half-cycles of the AC line voltage. 
     
     
         11 . 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 having a corresponding thermistor; and   a controller to coordinate heating of said heater and opposite heater by connecting or not said heater and opposite heater to an AC line voltage at times of zero crossings of a waveform of the AC line voltage, wherein the controller coordinates timing so that the heater and opposite heater have no DC offset over a range of AC half-cycles of the waveform.   
     
     
         12 . The hair iron of  claim 11 , further including a TRIAC to said connect or not said heater and opposite heater to the AC line voltage. 
     
     
         13 . The hair iron of  claim 11 , further wherein the controller includes a PID controller corresponding to said heater and opposite heater and connected to the corresponding thermistor. 
     
     
         14 . The hair iron of  claim 13 , wherein the controller is further configured to alternate heating between said heater and opposite heater and heating only one of said heater and opposite heater at any time. 
     
     
         15 . The hair iron of  claim 11 , wherein the range of AC half-cycles of the waveform is eight (8) AC half-cycles. 
     
     
         16 . The hair iron of  claim 11 , wherein the range of AC half-cycles of the waveform is sixteen (16) AC half-cycles. 
     
     
         17 . The hair iron of  claim 11 , wherein the controller is further configured to receive from the corresponding thermistor a current temperature of said heater and opposite heater to calculate a desired heating power. 
     
     
         18 . The hair iron of  claim 17 , wherein the desired heating power includes desired AC half-cycles of power being on for 0, 25, 50, 75 and 100 percent (%) of the desired AC half-cycles. 
     
     
         19 . The hair iron of  claim 18 , further including said desired AC half-cycles of power being on for 12.5, 37.5, 62.5 and 87.5 percent (%). 
     
     
         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 having a corresponding thermistor; and   a controller to coordinate heating of said heater and opposite heater by connecting or not said heater and opposite heater to an AC line voltage at times of zero crossings of a waveform of the AC line voltage, wherein the controller coordinates timing so that the heater and opposite heater have no DC offset over a range of AC half-cycles of the waveform and alternates heating between said heater and opposite heater such that only one of said heater and opposite heater are powered at any one time.