Variable switching frequency power supply for plasma cutters and plasma arc welders

Abstract

A power supply, for a plasma cutter or a plasma arc welder, having a variable switching frequency and method of operating the power supply is generally disclosed. The power supply includes a switch for setting the switching frequency and a chopper control circuit for determining current output from the power supply, determining an operating frequency based on the determined current output and setting the switching frequency based on the determined operating frequency.

1 - 4 . (canceled) 
     
     
         5 . A power supply for forming a plasma arc in a plasma tool coupled to the power supply, the power supply comprising:
 a direct current (DC) power source;   a chopper circuit configured to modulate a switching frequency of the DC power source; and   a chopper control module configured to vary the switching frequency, the chopper control module including:
 a measurement module configured to measure an output current value of the power supply; and 
 a switch controller configured to control the switching frequency of the DC power source in response to the output current value of the power supply, wherein the switching frequency of the DC power source is controlled to be substantially equal to a fixed maximum frequency in response to the output current value from the power supply being no more than a predetermined current value, and wherein the switching frequency of the DC power source is controlled to be substantially equal to a variable frequency that varies as a function of the output current value from the power supply in response to the output current value from the power supply being greater than the predetermined current value. 
   
     
     
         6 . The power supply of  claim 5 , wherein the variable frequency decreases as the output current value from the power supply increases above the predetermined current value. 
     
     
         7 . The power supply of  claim 5 , wherein the chopper control module is further configured to:
 identify an ampere operating range of the plasma tool coupled to the power supply; and   vary the switching frequency of the chopper circuit further based on the ampere operating range of the plasma tool coupled to the power supply.   
     
     
         8 . The power supply of  claim 5 , wherein the chopper control module is further configured to monitor a ripple current of the chopper circuit and vary the switching frequency of the DC power source based on the monitored ripple current. 
     
     
         9 . The power supply of  claim 5 , wherein the chopper control module is further configured to monitor a temperature of the power supply and vary the switching frequency of the DC power source based on the monitored temperature. 
     
     
         10 . The power supply of  claim 5 , wherein the chopper control module is further configured to select the switching frequency of the DC power source from a look-up table that stores a plurality of switching frequencies. 
     
     
         11 . The power supply of  claim 5 , wherein for output current values between the predetermined current value and a maximum current value, the variable frequency decreases linearly as the output current value from the power supply increases. 
     
     
         12 . The power supply of  claim 5 , wherein the switching frequency of the DC power source is controlled by the switch controller to be substantially equal to a minimum frequency in response to the output current value from the power supply being a maximum current value. 
     
     
         13 . A method for varying a switching frequency of a power supply for forming a plasma arc in a plasma tool coupled to the power supply, the method comprising:
 receiving an output current value of the power supply;   controlling the switching frequency of the power supply to be substantially equal to a fixed maximum frequency in response to the output current value from the power supply being no more than a predetermined current value; and   controlling the switching frequency of the power supply to be substantially equal to a variable frequency that varies as a function of the output current value from the power supply in response to the output current value from the power supply being greater than the predetermined current value.   
     
     
         14 . The method of  claim 13 , wherein the variable switching frequency decreases as the output current value from the power supply increases. 
     
     
         15 . The method of  claim 13 , further comprising:
 identifying, by the processor, an ampere operating range of the plasma tool coupled to the power supply; and   controlling the switching frequency of the power supply further based on the ampere operating range of the plasma tool coupled to the power supply.   
     
     
         16 . The method of  claim 13 , further comprising:
 monitoring a ripple current of an output of the power supply; and   varying the switching frequency of the power supply based on the monitored ripple current.   
     
     
         17 . The method of  claim 13 , further comprising:
 monitoring a temperature of the power supply; and   varying the switching frequency of the power supply based on the monitored temperature.   
     
     
         18 . The method of  claim 13 , further comprising selecting the switching frequency of the power supply from a look-up table that stores a plurality of switching frequencies. 
     
     
         19 . A non-transitory computer readable medium containing instructions which, when executed by a processor, cause the processor to perform a method comprising:
 receiving an output current value of the power supply;   controlling the switching frequency of the power supply to be substantially equal to a fixed maximum frequency in response to the output current value from the power supply being no more than a predetermined current value; and   controlling the switching frequency of the power supply to be substantially equal to a variable frequency that varies as a function of the output current value from the power supply in response to the output current value from the power supply being greater than the predetermined current value.   
     
     
         20 . The non-transitory computer readable medium of  claim 19 , wherein the variable switching frequency decreases as the output current value from the power supply increases. 
     
     
         21 . The non-transitory computer readable medium of  claim 19 , wherein the instructions cause the processor to further perform:
 identifying an ampere operating range of a plasma tool coupled to the power supply; and   determining the switching frequency of the power supply further based on the ampere operating range of the plasma tool coupled to the power supply.   
     
     
         22 . The non-transitory computer readable medium of  claim 19 , wherein the instructions cause the processor to further perform:
 monitoring a ripple current of an output of the power supply; and   varying the switching frequency of the power supply based on the monitored ripple current.   
     
     
         23 . The non-transitory computer readable medium of  claim 19 , wherein the instructions cause the processor to further perform:
 monitoring a temperature of the power supply; and   varying the switching frequency of the power supply based on the monitored temperature.   
     
     
         24 . The non-transitory computer readable medium of  claim 19 , wherein the instructions cause the processor to further perform:
 selecting the switching frequency of the power supply from a look-up table that stores a plurality of switching frequencies.