Three stage power source for electric arc welding

• US 8,785,816 B2
• Filed: 10/23/2006
• Issued: 07/22/2014
• Est. Priority Date: 07/13/2004
• Status: Active Grant

• Current Assignee: Lincoln Global Incorporated (Lincoln Electric Holdings Incorporated)
• Original Assignee: Lincoln Global Incorporated (Lincoln Electric Holdings Incorporated)
• Inventors: Luo, Li-Feng, Kooken, Todd E.
• Primary Examiner(s): Yuen, Henry
• Assistant Examiner(s): MAYE, AYUB A
• Application Number:
  US11/551,957
• Publication Number:
  US 20070051712A1
• Time in Patent Office: 2,829 Days
• Field of Search: 219/130.1, 219/137.PS, 219/137.7, 219/130.21, 219/130.33, 219/130.51, 219/130.5
• US Class Current: 219/130.1
• CPC Class Codes: B23K 9/095 Monitoring or automatic control of welding parameters
• CPC Class Codes: B23K 9/1043 characterised by the electric circuit B23K9/1012 takes precedence
• CPC Class Codes: B23K 9/1056 by using digital means B23K9/1068 takes precedence
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/0085 Partially controlled bridges
• CPC Class Codes: H02M 1/342 Active non-dissipative snubbers
• CPC Class Codes: H02M 1/4216 operating from a three-phase input voltage H02M1/4233 takes precedence
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H02M 5/458 using semiconductor devices only
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02P 70/10 Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

Abstract

A three stage power source for an electric arc welding process comprising an input stage having an AC input and a first DC output signal; a second stage in the form of an unregulated DC to DC converter having an input connected to the first DC output signal, a network of switches switched at a high frequency with a given duty cycle to convert the input into a first internal AC signal, an isolation transformer with a primary winding driven by the first internal high frequency AC signal and a secondary winding for creating a second internal high frequency AC signal and a rectifier to convert the second internal AC signal into a second DC output signal of the second stage, with a magnitude related to the duty cycle of the switches; and, a third stage to convert the second DC output signal to a welding output for welding wherein the input stage has a regulated DC to DC converter with a boost power switch having an active soft switching circuit.

Claims

1. A power source for welding;

comprising;

a first stage to receive a first signal and output a second signal having a first fixed DC voltage;

a second stage to receive said second signal and output an isolated third signal having a second fixed DC voltage, said second stage includes an input connected to said first stage;

a network of switches coupled to the input and switched at a high frequency with a given duty cycle to convert said input into a first internal AC signal;

an isolation transformer with a primary winding driven by said first internal AC signal and a secondary winding for creating a second internal AC signal, and a rectifier coupled to said secondary winding to convert said second internal AC signal into said second fixed DC voltage with a magnitude related to said duty cycle of said switches so as to define said third signal; and

a third stage to receive said third signal and output a welding signal, said third stage being separate and distinct of said first stage and said second stage;

wherein at least one of said first stage and said third stage is regulated and said second stage is an unregulated inverter stage having a duty cycle of at least 80% and a soft switching circuit without a phase shift modulation, wherein further an energy of said duty cycle being stored in a leakage inductance of said isolation transformer forces a voltage across said network of switches to zero so as to provide an inherent soft switch.

2. The power source of claim 1, wherein said duty cycle is at least 90%.

3. The power source of claim 1, wherein said second stage contains an isolated transformer which outputs said third signal, and wherein said second DC voltage is related to said first DC voltage.

4. The power source of claim 1, wherein said first stage comprises at least one of a boost circuit, a buck circuit and a buck+boost circuit.

5. The power source of claim 1, wherein said third stage is a chopper.

6. The power source of claim 1, further comprising a capacitor between said second stage and said third stage to de-couple said second stage and said third stage such that only said third stage will experience a peak power of the power source.

7. The power source of claim 1, wherein said network of switches witched at a frequency of at least 18 kHz.

8. The power source of claim 1, wherein said first stage and said second stage have a combined operational efficiency of at least 90%.

9. The power source of claim 1, wherein said power source comprises only a single transformer, and said single transformer is an isolation transformer within said second stage.

10. The power source of claim 1, wherein said first signal is an AC signal.

11. The power source of claim 1, wherein said first stage is regulated having an active soft switching circuit.

12. The power source of claim 1, wherein said network of switches includes a plurality of isolated gate bipolar transistors (IGBTs) and said given duty cycle is fixed, being at least 90% up to about 100% such that a leakage inductance of said isolation transformer forces a voltage across said IGBTs to zero so that said network of switches define an inherent soft switching transition.

13. The power source of claim 2, wherein said duty cycle is about 100%.

14. The power source of claim 6, wherein said power source has a peak to average power ratio of at least 4.

15. The power source of claim 7, wherein said network of switches are switched at a frequency of at least 100 kHz.

16. The power source of claim 14, wherein said peak to average power ratio is at least 5.

17. A power source for welding;

comprising;

a first stage to receive a first signal and output a second signal having a first fixed DC voltage;

a second stage to receive said second signal and output an isolated third signal having a second fixed DC voltage, said second stage having a single transformer and an input connected to said first stage, a network of switches coupled to the input and switched at a high frequency with a given duty cycle to convert said input into a first internal AC signal, said single transformer being an isolation transformer with a primary winding driven by said first internal AC signal and a secondary winding for creating a second internal AC signal, and a rectifier coupled to said secondary winding to convert said second internal AC signal into said second fixed DC voltage of said second stage with a magnitude related to said duty cycle of said switches so as to define said third signal; and

a third stage to receive said third signal and output a welding signal, said third stage being separate and distinct of said first stage and said second stage;

wherein at least one of said first stage and said third stage is regulated, said single transformer is the only transformer within said power source, and said second stage is unregulated having a soft switching circuit without a phase shift modulation, wherein further an energy of said duty cycle is stored in said single transformer forces a voltage across said network of switches to zero so as to provide an inherent soft switch.

18. The power source of claim 17, wherein said single transformer is an isolated transformer.

19. The power source of claim 17, wherein said second stage is an unregulated inverter stage and has a duty cycle of at least 80%.

20. The power source of claim 17, wherein said first stage comprises at least one of a boost circuit, a buck circuit and a buck+boost circuit.

21. The power source of claim 17, wherein said third stage is a chopper.

22. The power source of claim 17, further comprising a capacitor between said second stage and said third stage to de-couple said second stage and said third stage such that only said third stage will experience a peak power of the power source.

23. The power source of claim 17, wherein said network of switches is switched at a frequency of at least 18 kHz.

24. The power source of claim 17, wherein said first stage and said second stage have a combined operational efficiency of at least 90%.

25. The power source of claim 17, wherein said first signal is an AC signal.

26. The power source of claim 17, wherein said first stage is regulated having an active soft switching circuit.

27. The power source of claim 17, wherein said network of switches includes a plurality of isolated gate bipolar transistors (IGBTs) and said given duty cycle is fixed, being at least 90% up to about 100% such that a leakage inductance of said isolation transformer forces a voltage across said IGBTs to zero so that said network of switches define said inherent soft switch.

28. The power source of claim 19, wherein said duty cycle is at least 90%.

29. The power source of claim 22, wherein said power source has a peak to average power ratio of at least 4.

30. The power source of claim 23, wherein said network of switches are switched at a frequency of at least 100 kHz.

31. The power source of claim 28, wherein said duty cycle is about 100%.

32. The power source of claim 29, wherein said peak to average power ratio is at least 5.

33. A power source for welding comprising:

a first stage to receive a first signal and output a second signal having a first fixed DC voltage;

a second stage to receive said second signal and output an isolated third signal having a second fixed DC voltage, said second stage includes an input connected to said first stage, a network of switches coupled to the input and switched at a high frequency with a given duty cycle to convert said input into a first internal AC signal, an isolation transformer with a primary winding driven by said first internal AC signal and a secondary winding for creating a second internal AC signal, and a rectifier coupled to said secondary winding to convert said second internal AC signal into said second fixed DC voltage of said second stage with a magnitude related to said duty cycle of said switches; and

a third stage to receive said third signal and output a welding signal, at least one of said first stage and said third stage being regulated, said third stage being separate and distinct of said first stage and said second stage;

wherein said power source produces a peak power and an average power and has a peak to average power ratio of at least 4, and said second stage is unregulated having a soft switching circuit without a phase shift modulation, wherein further an energy of said duty cycle is stored in said single transformer forces a voltage across said network of switches to zero so as to provide an inherent soft switch.

34. The power source of claim 33, wherein the peak to average power ratio is at least 5.

35. The power source of claim 33, wherein said second stage is an unregulated inverter stage having a duty cycle of at least 80%.

36. The power source of claim 33, wherein said second stage contains an isolated transformer which outputs said third signal, and wherein said second DC voltage is related to said first DC voltage.

37. The power source of claim 33, wherein said first stage comprises at least one of a boost circuit, a buck circuit and a buck+boost circuit.

38. The power source of claim 33, wherein said third stage is a chopper.

39. The power source of claim 33, further comprising a capacitor between said second stage and said third stage to de-couple said second stage and said third stage such that only said third stage will experience a peak power of the power source.

40. The power source of claim 33, wherein said network of switches switched at a frequency of at least 18 kHz.

41. The power source of claim 33, wherein said first stage and said second stage have a combined operational efficiency of at least 90%.

42. The power source of claim 33, wherein said power source comprises only a single transformer, and said single transformer is an isolation transformer within said second stage.

43. The power source of claim 33, wherein said first signal is an AC signal.

44. The power source of claim 33, wherein said first stage is regulated having an active soft switching circuit.

45. The power source of claim 33, wherein said network of switches includes a plurality of isolated gate bipolar transistors (IGBTs) and said given duty cycle is fixed, being at least 90% up to about 100% such that a leakage inductance of said isolation transformer forces a voltage across said IGBTs to zero so that said network of switches define said inherent soft switch.

46. The power source of claim 35, wherein said duty cycle is at least 90%.

47. The power source of claim 40, wherein said network of switches are switched at a frequency of at least 100 kHz.

48. The power source of claim 46, wherein said duty cycle is about 100%.

49. A power source for welding;

comprising;

a first stage to receive a first signal and output a second signal having a first fixed DC voltage;

a second stage to receive said second signal and output an isolated third signal having a second fixed DC voltage, said second stage being unregulated and having a soft switching circuit, said second stage includes an input connected to said first stage, a network of switches coupled to the input and switched at a high frequency with a given duty cycle to convert said input into a first internal AC signal, an isolation transformer with a primary winding driven by said first internal AC signal and a secondary winding for creating a second internal AC signal, and a rectifier coupled to said secondary winding to convert said second internal AC signal into said second fixed DC voltage of said second stage with a magnitude related to said duty cycle of said switches; and

a third stage to receive said third signal and output a welding signal, at least one of said first stage and said third stage being regulated, said third stage being separate and distinct of said first stage and said second stage;

wherein said soft switching circuit is without a phase shift modulation, wherein further an energy of said duty cycle is stored in said single transformer forces a voltage across said network of switches to zero so as to provide an inherent soft switch.

50. The power source of claim 49, wherein said second stage is an unregulated inverter stage having a duty cycle of at least 80%.

51. The power source of claim 49, wherein said second stage contains an isolated transformer which outputs said third signal, and wherein said second DC voltage is related to said first DC voltage.

52. The power source of claim 49, wherein said first stage comprises at least one of a boost circuit, a buck circuit and a buck+boost circuit.

53. The power source of claim 49, wherein said third stage is a chopper.

54. The power source of claim 49, further comprising a capacitor between said second stage and said third stage to de-couple said second stage and said third stage such that only the third stage will experience a peak power of the power source.

55. The power source of claim 49, wherein said network of switches are switched at a frequency of at least 18 kHz.

56. The power source of claim 49, wherein said first stage and said second stage have a combined operational efficiency of at least 90%.

57. The power source of claim 49, wherein said first signal is an AC signal.

58. The power source of claim 49, wherein said first stage is regulated having an active soft switching circuit.

59. The power source of claim 49, wherein said network of switches includes a plurality of isolated gate bipolar transistors (IGBTs) and said given duty cycle is fixed, being at least 90% up to about 100% such that a leakage inductance of said isolation transformer forces a voltage across said IGBTs to zero so that said network of switches define said inherent soft switch.

60. The power source of claim 50, wherein said duty cycle is at least 90%.

61. The power source of claim 51, wherein said isolated transformer is the only transformer within said power source.

62. The power source of claim 54, wherein said power source has a peak to average power ratio of at least 4.

63. The power source of claim 55, wherein said network of switches are switched at a frequency of at least 100 kHz.

64. The power source of claim 60, wherein said duty cycle is about 100%.

65. The power source of claim 62, wherein said peak to average power ratio is at least 5.