Digital PWM Controller for Welding Power Supply Inductance Compensation
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Solution Overview
Problem
Traditional analog controllers in switched-mode welding power supplies struggle to respond quickly to dynamic changes in welding arcs, often failing to handle rapid events effectively due to their inherent limitations in processing time and accuracy.
Innovation Solution
A digital pulse width modulation (PWM) controller is introduced, which includes gate drive circuitry to switch power semiconductor switches and employs advanced methods to calculate and set the duty cycle, accounting for factors like bus voltage variations, delays, and arc impedance, enabling precise control of output current and voltage through a closed current control loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional analog controllers are used in switched-mode welding power supplies, then the system structure is simple, but the response speed to dynamic welding arc changes is insufficient
Solution Approach 1:
The patent replaces traditional analog control systems with a digital control system that uses a microprocessor or digital signal processor. This substitution enables much faster processing and response to dynamic welding arc changes, as digital systems can process signals at microsecond or nanosecond intervals compared to the slower response of analog circuits. The digital controller implements PWM control algorithms that can dynamically adjust switching frequencies and duty cycles to respond rapidly to arc impedance variations.
Solution Approach 2:
The patent employs digital signal processing techniques that allow dynamic adjustment of control parameters such as switching frequency, duty cycle, and current thresholds. The system can change these parameters in real-time based on detected arc conditions, enabling adaptive response to varying welding loads. The digital controller can implement complex control algorithms that modify multiple parameters simultaneously to optimize performance under different operating conditions.
2Measurement precision
If analog controllers are used to control welding power output, then the control circuitry is simple, but the accuracy in handling rapid current changes is insufficient
Solution Approach 1:
The patent replaces analog measurement and control circuits with digital equivalents that provide superior measurement precision. Digital analog-to-digital converters sample current signals at high rates and convert them to precise digital values for processing. The digital controller can detect and respond to rapid current changes with much higher precision than analog systems, as digital sampling can capture transient events with microsecond timing accuracy and resolve current levels with high bit-depth precision.
Solution Approach 2:
The patent implements a closed-loop digital feedback control system that continuously monitors welding current, voltage, and arc impedance and adjusts control parameters accordingly. The digital controller samples feedback signals at high rates, processes them through control algorithms, and adjusts PWM duty cycles to maintain precise control over the welding output. This feedback mechanism enables the system to compensate for variations in cable inductance, contact resistance, and arc characteristics with high accuracy.
3Adaptability or versatility
If traditional control methods are used, then the system is easier to manufacture, but the ability to handle dynamic welding requirements is limited
Solution Approach 1:
The patent implements a dynamic control system that can adapt its behavior based on real-time welding conditions. The digital controller adjusts switching frequencies, duty cycles, and control loop parameters dynamically in response to detected arc impedance changes, current levels, and welding process requirements. This dynamic adaptability allows the same controller to optimize performance across a wide range of welding processes and conditions, from low-current TIG welding to high-current stick welding.
Solution Approach 2:
The patent designs a universal digital control platform that can support multiple welding processes and control modes through software configuration rather than hardware changes. The same microprocessor-based controller can be programmed to implement different welding processes (TIG, stick, MIG/MAG), different control strategies (constant current, constant voltage, pulse welding), and different waveforms. This multi-functionality is achieved through programmable control algorithms that can be adjusted via user interface or automatic process recognition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The digital PWM controller improves the responsiveness and accuracy of welding power supplies, allowing for better control of welding arcs by dynamically adjusting the duty cycle, reducing peak to peak ripple, and effectively managing the effects of weld cable inductance, thereby enhancing the overall performance compared to traditional analog systems.
Implementation Method 1
utilizes power semiconductor switches to chop a DC source of power and convert the chopped power to a voltage and/or current suitable for welding
Implementation Method 2
configured to measure a peak to peak switching ripple in a voltage present on welding output terminal, and determine a weld cable inductance
Data Source
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AI summary
Systems, devices (138), and methods for measuring a peak to peak switching ripple in a voltage present on welding output terminals are provided. The systems, devices, and methods are utilized to determine, during a welding operation, a weld cable inductance based on the measured peak to peak voltage ripple.