Metal working power supply converter system and method

Patent metadata

Field	Value
Publication number	US-9584024-B2
Application number	US-201313925579-A
Country	US
Kind code	B2
Filing date	Jun 24, 2013
Priority date	Jun 24, 2013
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

A power supply for welding, cutting and similar operations includes a dual two-switch forward converter. The converter has two inverter circuits coupled in parallel but controlled to provide output power in an interleaved fashion. To avoid “walking” of the circuits (which could result in different duty cycles and imbalance of the load sharing), control signals are determined and applied to a first of the inverter circuits, and “on” times of the first circuit is monitored, such as by augmenting a counter to determine the number of clock cycles the first circuit is “on”. The same duration is then used for commanding output from the second inverter circuit. The duty cycles of both circuits is thus ensured to be the same regardless of changes in the total output power.

First claim

The invention claimed is:

1. A welding or cutting power supply system, comprising:
a converter circuit comprising first and second solid state switching circuits each having two power electronic switches for producing output power at a controllable level suitable for a welding or cutting operation, the first and second solid state switching circuits being electrically coupled to provide combined output;
an output inductance coupled to outputs of both the first and second solid state switching circuits; and
control circuitry coupled to the first and second solid state switching circuits and configured to:
provide first and second pulse width modulation (PWM) control signals for controlling states of the power electronic switches of the first and second solid state switching circuits, respectively, in switching cycles;
maintain desired loading of the first and second solid state switching circuits independent of a level of the output power, wherein for each switching cycle of the first and second solid state switching circuits the control circuitry is configured to apply the first PWM control signals to the first solid state switching circuit based upon a duty cycle that is desired;
determine a duration of the first PWM control signals applied only to the first solid state switching circuit independent of the output power by monitoring on times of the first solid state switching circuit and counting a number of clock cycles the first PWM control signals are applied to the first solid state switching circuit; and
apply the second PWM control signals to the second solid state switching circuit based upon the determined duration without re-determining the duty cycle for the second solid state switching circuit;

wherein the first PWM control signals are applied to the first solid state switching circuit for the determined duration only during a first portion of each switching cycle, and the second PWM control signals are applied to the second solid state switching circuit only during a second portion of a respective switching cycle after the first portion of the respective switching cycle, and both the first and second solid state switching circuits produce output that is the same polarity.

2. The system of claim 1 , wherein the number of the clock cycles is counted by augmenting a counter implemented by the control circuitry.

3. The system of claim 1 , wherein the duty cycle of each of the first and second solid state switching circuits is limited to 50% or less.

4. The system of claim 1 , wherein the duty cycle of each of the first and second solid state switching circuits is generally equal.

5. The system of claim 1 , wherein the two power electronic switches of each of the first and second solid state switching circuits are coupled across a common DC bus.

6. The system of claim 5 , wherein each of the first and second solid state switching circuits comprises an output transformer and a freewheeling diode across the common DC bus.

7. The system of claim 1 , wherein each of the first and second solid state switching circuits comprises a transformer between each of the two power electronic switches of the first and second solid state switching circuits and an output rectifying circuit.

8. The system of claim 7 , wherein each of the first and second solid state switching circuits comprises a rectifier between the transformer and an output inductance.

9. The system of claim 1 , wherein the power supply system produces output power suitable for a Gas Metal Arc Welding (GMAW) welding process.

10. A welding or cutting system, comprising:
a power supply comprising first and second solid state switching circuits each having two power electronic switches for producing output power at a controllable level suitable for a welding or cutting operation, the first and second solid state switching circuits being electrically coupled in parallel;
an output inductance coupled to outputs of both the first and second solid state switching circuits; and
a control circuitry coupled to the first and second solid state switching circuits and configured to:
provide first and second pulse width modulation (PWM) control signals for controlling states of the power electronic switches of the first and second solid state switching circuits, respectively, in switching cycles;
maintain desired loading of the first and second solid state switching circuits independent of a level of the output power;
determine the first PWM control signals for the first solid state switching circuit based upon a desired duty cycle;
determine a duration of the first PWM control signals applied only to the first solid state switching circuit independent of the output power by monitoring on times of the first solid state switching circuit and counting a number of clock cycles the first PWM control signals are applied to the first solid state switching circuit; and
apply second PWM control signals to the second solid state switching circuit based upon the determined duration without re-determining the duty cycle for the second solid state switching circuit;

wherein the first PWM control signals are applied to the first solid state switching circuit for the determined duration only during a first portion of each switching cycle, and the second PWM control signals are applied to the second solid state switching circuit only during a second portion of a respective switching cycle after the first portion of the respective switching cycle, and both the first and second solid state switching circuits produce output that is the same polarity.

11. The system of claim 10 , wherein the number of the clock cycles is counted by augmenting a counter implemented by the control circuitry.

12. The system of claim 10 , wherein the duty cycle of each of the first and second solid state switching circuits is limited to 50%.

13. The system of claim 10 , wherein the duty cycle of each of the first and second solid state switching circuit is generally equal.

14. A welding or cutting method in each of a plurality of successive switching cycles, comprising:
applying first pulse width modulation (PWM) control signals to a first switching circuit of a power converter comprising at least two switching circuits operated in a desired switching pattern, the first PWM control signals being based upon a desired duty cycle to produce a welding or cutting output;
determining a PWM duration of the first PWM control signals applied only to the first switching circuit independent of output power by monitoring on times of the first solid state switching circuit and counting a number of clock cycles the first PWM control signals are applied to the first solid state switching circuit; and
applying second PWM control signals to a second switching circuit of the power converter for a duration based upon the determined PWM duration;
wherein the first PWM control signals are applied to the first solid state switching circuit for the determined duration only during a first portion of each switching cycle, and the second PWM control signals are applied to the second solid state switching circuit only during a second portion of a respective switching cycle after the first portion of the respective switching cycle, and both the first and second solid state switching circuits produce output that is the same polarity.

15. The method of claim 14 , wherein the second PWM signals applied to the second switching circuit are not determined separately other than by determining the duration based upon the PWM duration of the first PWM signals applied to the first switching circuit.

16. The method

Assignees

• Illinois Tool Works

Inventors

• Manthe Alan A
• Dunahoo Jason Alan
• Knoener Craig Steven
• Poulose Mary Divya

Classifications

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title

• B23K9/1043

  characterised by the electric circuit (B23K9/1012 takes precedence) · CPC title

• B23K9/093 Primary

  the frequency of the pulses produced being modulable · CPC title

• H02M3/33523

  with galvanic isolation between input and output of both the power stage and the feedback loop · CPC title

• H02M3/1584

  with a plurality of power processing stages connected in parallel · CPC title