Double Forward Converter Phase Control for Welding Power Stability

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Solution Overview

Problem

Existing welding-type power supplies face inefficiencies and disturbances in dynamic load conditions due to phase shifting of forward converter circuits, leading to arc outages, undershoots, and transformer saturation, as they struggle to balance average and dynamic load requirements effectively.

Innovation Solution

A welding-type power supply system that operates in three phase relationships: Phase Shifted Double Forward (PSDF), Locked-In-Phase (LIP), and Fixed Phase Stagger (FPS) modes, allowing for dynamic voltage adjustments and reduced ripple current, with a controller managing the phase relationship based on feedback and user inputs to maintain optimal operation across a range of outputs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If phase shifted double forward converter mode is used to provide dynamic voltage for short duration loads, then the power supply can meet transient voltage requirements, but it causes arc outages, undershoots, and transformer saturation due to excessive phase shifting

Engineering Contradiction:

Improveability to meet transient voltage requirementsVSAvoidarc stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system dynamically switches between PSDF mode and LIP mode based on real-time load conditions. The controller monitors the welding output and automatically adjusts the operating mode to maintain arc stability while meeting transient voltage requirements, resolving the contradiction between adaptability and reliability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the phase relationship parameter between the two forward converters from a fixed phase-shifted state to a variable state that can be locked in phase. By adjusting this parameter based on load conditions, the system achieves both transient response capability and arc stability

Inventive Principle:

Principle #35Parameter changes

2Power

If synchronized duty cycles are increased to meet increasing output voltage demand, then the power supply can provide higher voltage, but it extends the duration of phase shifted mode causing harmful disturbances

Engineering Contradiction:

Improveoutput voltageVSAvoidduration of phase shifted mode

Core Design Contradiction:

PowerVSLoss of time

Solution Approach 1:

The controller uses feedback from the welding output to monitor when high power is required and automatically transitions to LIP mode to extend the in-phase operation duration. This feedback mechanism ensures high voltage output is achieved without excessive phase shifting duration

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system prepares by locking the converters in phase before high power demand occurs, ensuring that when voltage increase is needed, the converters are already in the optimal LIP configuration to minimize phase shifted mode duration

Inventive Principle:

Principle #10Preliminary action

3Duration of action of stationary object

If leading edge or lagging edge compensation is used to allow transformer core reset time, then the power supply can maintain continuous operation, but it reduces control precision and causes momentary disturbances

Engineering Contradiction:

Improvetransformer core reset timeVSAvoidcontrol precision

Core Design Contradiction:

Duration of action of stationary objectVSMeasurement precision

Solution Approach 1:

The system uses periodic PWM cycles with controlled phase relationships to naturally provide transformer reset time while maintaining continuous power delivery. The periodic switching allows the transformer core to reset during the off-periods without requiring leading or lagging edge compensation

Inventive Principle:

Principle #19Periodic action

4Adaptability or versatility

If oversized components are chosen to handle extreme short duration requirements, then the power supply can meet dynamic loads, but it reduces efficiency during average operating conditions

Engineering Contradiction:

Improveability to handle dynamic loadsVSAvoidefficiency at average conditions

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The system dynamically adjusts the operating mode between PSDF and LIP based on load conditions. During average conditions, it operates in LIP mode for high efficiency, and only transitions to PSDF mode when dynamic loads require it, optimizing the balance between adaptability and energy efficiency

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11673201B2Method and apparatus for providing welding type power using double forward converter

Publication Date: 2023.06.13 ILLINOIS TOOL WORKS INC

AI summary

A method and apparatus for providing welding type power includes receiving input power and pulse width modulating a first forward converter and a second forward converter so that they operate as a pulse width modulated double forward converter to provide a welding type output. A phase relationship between the first forward converter and a second forward converter is selected from at least two available phase relationships using a controller. The controller includes a pwm module, and the pwm module includes a phase relationship module. The at least two available phase relationships are at least two of variable phase shifting, fixed phase staggering and locked in phase. The selected phase relationship is maintained over a predetermined range of outputs.