# US 10,766,088 B2 · Metal working power supply converter system and method

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- Number: US 10,766,088 B2
- Document ID: US10766088B2
- Status: Granted
- Kind: B2
- Application number: 16/298,510
- Filed: 2019-03-11
- Published: 2019-07-04
- Granted: 2020-09-08
- Earliest claimed: 2013-06-24
- Assignees: Illinois Tool Works Inc.
- Applicants: Illinois Tool Works Inc.
- Inventors: Alan A. Manthe; Jason Alan Dunahoo; Craig Steven Knoener; Mary Divya Poulose
- Web page: https://patentgrep.com/patent/US10766088B2

## CPC

- B23K 9/093: {the frequency of the pulses produced being modulable}
- B23K 9/1043: {characterised by the electric circuit (B23K9/1012 takes precedence)}
- H02M 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M 3/285: {Single converters with a plurality of output stages connected in parallel (parallel operation of a plurality of converters in DC distribution networks H02J1/10)}
- H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop}
- H02M 3/1584: {with a plurality of power processing stages connected in parallel}
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)

## 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.

## Claims

### Claim 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, the first and second solid state switching circuits being electrically coupled to provide a combined output; and
control circuitry coupled to the first and second solid state switching circuits, the control circuitry operable to:
provide a first Pulse Width Modulation (PWM) control signal to the first solid state switching circuit based upon a desired duty cycle;
monitor output power of the first solid state switching circuit in response to the first PWM control signal for a first duration of time;
determine a period of the first solid state switching circuit output power during the monitored first duration;
determine a second PWM control signal for the second solid state switching circuit at a second duration of time following the first duration of time based upon the determined period of the output power based on the first PWM control signal; and
apply the second PWM control signal to the second solid state switching circuit based upon the determined period of the first solid state switching circuit.

### Claim 2 (depends on 1)

The welding or cutting power supply system of claim 1, wherein the period is determined by counting a number of clock cycles while the first solid state switching circuit is producing the output power.

### Claim 3 (depends on 2)

The welding or cutting power supply system of claim 2, wherein the number of clock cycles is counted by augmenting a counter implemented by the control circuitry.

### Claim 4 (depends on 1)

The welding or cutting power supply system of claim 1, wherein a duty cycle of each solid state switching circuit is limited to 50% or less.

### Claim 5 (depends on 1)

The welding or cutting power supply system of claim 1, wherein a duty cycle of each solid state switching circuit is generally equal.

### Claim 6 (depends on 1)

The welding or cutting power supply system of claim 1, wherein at least two solid state switches of each solid state switching circuit are coupled across a common DC bus.

### Claim 7 (depends on 6)

The welding or cutting power supply system of claim 6, wherein each solid state switching circuit comprises an output transformer and a freewheeling diode across the common DC bus.

### Claim 8 (depends on 1)

The welding or cutting power supply system of claim 1, wherein the first solid state switching circuit comprises a first transformer between a first solid state switch and an output rectifying circuit, and the second solid state switching circuit comprises a second transformer between a second solid state switch and the output rectifying circuit.

### Claim 9 (depends on 8)

The welding or cutting power supply system of claim 8, wherein the output rectifying circuit comprises a first and a second rectifier, wherein the first rectifier is between the first solid state switching circuit and a respective transformer and an output inductance.

### Claim 10 (depends on 1)

The welding or cutting power supply system of claim 1, wherein the welding or cutting power supply system produces output power suitable for a GMAW welding process.

### Claim 11

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 for a welding or cutting operation, the first and second solid state switching circuits being electrically coupled in parallel; and
control circuitry coupled to the first and second solid state switching circuits, the control circuitry operable to:
determine a first Pulse Width Modulation (PWM) control signal for the first solid state switching circuit based upon a desired duty cycle;
provide the first PWM control signal to the first solid state switching circuit;
monitor a first duration of the first PWM control signal;
determine a period of the first solid state switching circuit output power during the monitored first duration;
determine a second PWM control signal for the second solid state switching circuit at a second duration of time following the first duration of time based upon the determined period of the output power based on the first PWM control signal; and
apply the second PWM control signal to the second solid state switching circuit based upon the determined period of the first solid state switching circuit.

### Claim 12 (depends on 11)

The welding or cutting system of claim 11, wherein the control circuitry is further operable to apply the second PWM control signal to the second switching circuit in response to the first duration of time reaching a predetermined activation duration.

### Claim 13 (depends on 12)

The welding or cutting system of claim 12, wherein the control circuitry is further operable to:
monitor the second duration of time; and
end application of the second PWM control signal to the second switching circuit in response to the second duration of time reaching the predetermined activation duration.

### Claim 14 (depends on 11)

The welding or cutting system of claim 11, wherein the period is determined by counting a number of clock cycles while the first solid state switching circuit is producing the output power.

### Claim 15 (depends on 14)

The welding or cutting system of claim 14, wherein the number of clock cycles is counted by augmenting a counter implemented by the control circuitry.

### Claim 16 (depends on 11)

The welding or cutting system of claim 11, wherein the first solid state switching circuit comprises a first transformer between a first solid state switch and an output rectifying circuit, and the second solid state switching circuit comprises a second transformer between a second solid state switch and the output rectifying circuit.

### Claim 17 (depends on 16)

The welding or cutting system of claim 16, wherein the output rectifying circuit comprises a first and a second rectifier, wherein the first rectifier is between the first solid state switching circuit and the respective transformer and an output inductance.

### Claim 18 (depends on 16)

The welding or cutting system of claim 16, wherein the first and second switching circuits are controlled to operate in an interleaved switching pattern.

### Claim 19 (depends on 16)

The welding or cutting system of claim 16, wherein the outputs of the first and second switching circuits are independently transformed and rectified.