Modified phase shifted gate drive
A modified phase shift scheme that provides the minimum on-time and regulation benefits of the conventional phase shift method with the reduced circulating current benefits of the traditional PWM control. A welding machine comprises an inverter operatively connected to a controller, wherein the controller controls a welding process of the welding machine using modified phase shifted switching of the inverter.
1. A power source for an electric arc welder comprising:
inverter means having a primary circuit and a secondary circuit, where said primary circuit has four switches and is capable of alternately creating primary voltage pulses to induce secondary voltage pulses in said secondary circuit, and where said secondary circuit includes an output circuit capable of being connected to an output welding circuit;
means for turning on a first switch and a second switch of said primary circuit to establish a fixed phase shift between a first resultant output pulse of said first switch and a second resultant output pulse of said second switch;
means for turning off said first switch and said second switch subsequent to a minimum on-time of each of said first and second switches being achieved;
means for turning on a third switch and a fourth switch of said primary circuit to establish said fixed phase shift between a third resultant output pulse of said third switch and a fourth resultant output pulse of said fourth switch; and
means for turning off said third switch and said fourth switch subsequent to a minimum on-time of each of said third and fourth switches being achieved.
2. The power source of claim 1 further comprising means for establishing a dead time between said first output pulse and said third output pulse.
3. The power source of claim 1 further comprising means for establishing a dead time between said second output pulse and said fourth output pulse.
4. The power source of claim 1 wherein said established fixed phase shift is capable of producing no overlap between said first output pulse and said second output pulse to produce a zero output voltage level in said output circuit.
5. The power source of claim 1 wherein said subsequent turning off of said first switch and said second switch is capable of producing a minimum overlap between said first output pulse and said second output pulse to produce a minimum, non-zero output voltage level in said output circuit.
6. The power source of claim 1 wherein said established fixed phase shift is capable of producing no overlap between said third output pulse and said fourth output pulse to produce a zero output voltage level in said output circuit.
7. The power source of claim 1 wherein said subsequent turning off of said third witch and said fourth switch is capable of producing a minimum overlap between said third output pulse and said fourth output pulse to produce a minimum, non-zero output voltage level in said output circuit.
8. The power source of claim 1 wherein said subsequent turning off of said first switch and said second switch occurs simultaneously and is capable of producing a maximum overlap between said first output pulse and said second output pulse to produce a maximum output voltage level in said output circuit.
9. The power source of claim 1 wherein said subsequent turning off of said third switch and said fourth switch occurs simultaneously and is capable of producing a maximum overlap between said third output pulse and said fourth output pulse to produce a maximum output voltage level in said output circuit.
10. The power source of claim 1 wherein said subsequent turning off of said first switch and said second switch occurs simultaneously and is capable of producing an intermediate overlap between said first output pulse and said second output pulse to produce an intermediate output voltage level in said output circuit.
11. The power source of claim 1 wherein said subsequent turning off of said third switch and said fourth switch occurs simultaneously and is capable of producing an intermediate overlap between said third output pulse and said fourth output pulse to produce an intermediate output voltage level in said output circuit.
12. A power source for an electric arc welder comprising:
an inverter having a primary circuit and a secondary circuit, where said primary circuit has four switches and is capable of alternately creating primary voltage pulses to induce secondary voltage pulses in said secondary circuit, and where said secondary circuit includes an output circuit capable of being connected to an output welding circuit;
a first switch and a second switch of said primary circuit;
a third switch and a fourth switch of said primary circuit; and
a controller for independently controlling the timing associated with turning on and turning off each of said first switch, said second switch, said third switch, and said fourth switch.
13. The power source of claim 12 wherein each of said switches includes an isolated gate bipolar transistor (IGBT).
14. The power source of claim 12 wherein each of said switches includes a field effect transistor (FET).
15. The power source of claim 12 further comprising a gate drive circuit operatively connected to each of said switches to drive said switches.
16. The power source of claim 15 further comprising an opto-coupler device operatively connected between each of said gate drive circuits and said controller to electrically isolate said controller from said gate drive circuits.
17. A method, employing a power source for an electric arc welder including an inverter having a primary circuit and a secondary circuit, where said primary circuit has four switches and is capable of alternately creating primary voltage pulses to induce secondary voltage pulses in said secondary circuit, and where said secondary circuit includes an output circuit capable of being connected to an output welding circuit, said method comprising:
turning on a first switch and a second switch of said primary circuit to establish a fixed phase shift between a leading edge of a first resultant output pulse of said first switch and a leading edge of a second resultant output pulse of said second switch;
turning off said first switch and said second switch subsequent to a minimum on-time of each of said first and second switches being achieved to establish a trailing edge of said first resultant output pulse and a trailing edge of said second resultant output pulse;
turning on a third switch and a fourth switch of said primary circuit to establish said fixed phase shift between a leading edge of a third resultant output pulse of said third switch and a leading edge of a fourth resultant output pulse of said fourth switch; and
turning off said third switch and said fourth switch subsequent to a minimum on-time of each of said third and fourth switches being achieved to establish a trailing edge of said third resultant output pulse and a trailing edge of said fourth resultant output pulse.
18. The method of claim 17 wherein said turning off of said first switch and said second switch occurs simultaneously, and wherein said turning off of said third switch and said fourth switch occurs simultaneously.
19. The method of claim 17 further comprising establishing a dead time between said first output pulse and said third output pulse and between said second output pulse and said fourth output pulse.
20. The method of claim 19 further comprising performing processing with respect to a measured feedback current and a measured feedback voltage during said dead time.