Sigma-Delta Current Balancing in Multi-Phase Switching Converters
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Solution Overview
Problem
Prior digital controlled multi-phase switching converters suffer from poor current balance performance due to limited current resolution, which is constrained by system clock frequency and sampling rate, resulting in high frequency ripples in the average output current.
Innovation Solution
A digital controller for multi-phase switching converters that includes an analog digital converting circuit, subtracters, proportional integrators, sigma-delta modulators, and a control circuit, which generates control signals by subtracting digital phase current signals from a reference signal, integrating errors, conducting sigma-delta modulation, and adjusting control signals based on the resulting bias signals to improve current balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If prior digital controlled multi-phase switching converters use conventional current control methods with limited resolution, then the device complexity is reduced, but the current balance performance deteriorates due to high frequency ripples
Solution Approach 1:
The patent segments the current control process into multiple independent phases, with each phase having its own current sensing, error detection, and control signal generation path. This segmentation allows precise independent control of each phase current while maintaining overall system simplicity through modular architecture.
Solution Approach 2:
The patent implements feedback mechanisms by comparing each phase's current sensing signal with a reference current signal, detecting current errors, and adjusting control signals based on these errors. This feedback loop ensures high current balance performance by continuously correcting deviations from the reference current.
2Measurement precision
If the sampling rate of the analog digital converter is increased to improve current resolution, then the current balance performance is improved, but the loss of time increases due to longer conversion periods
Solution Approach 1:
The patent performs preliminary actions by pre-calculating and storing current reference signals, and preparing control signals in advance based on predicted current trends. This allows the system to maintain high current resolution without requiring excessively long sampling periods, as the controller is already prepared with reference values and control strategies.
Solution Approach 2:
The patent changes parameters by dynamically adjusting the sampling rate and resolution based on operating conditions. During transient states, higher resolution and sampling rates are used for precise control, while during steady states, lower rates suffice, thus reducing overall time loss while maintaining measurement precision when needed.
3Manufacturing precision
If the system uses higher current resolution control, then the current balance performance is improved, but the device complexity increases due to higher bit-depth signal processing
Solution Approach 1:
The patent applies partial action by using high-resolution control only for the critical current balance function, while other functions use standard resolution. This selective approach achieves high current resolution where needed without requiring the entire system to operate at high complexity levels.
Solution Approach 2:
The patent introduces intermediary elements such as digital filters and signal conditioners that process high-resolution current sensing signals before they reach the main control logic. These intermediaries simplify the overall signal processing complexity by preprocessing signals and removing noise, allowing high current resolution to be achieved without proportionally increasing system complexity.
Data Source
AI summary
A method for controlling a multi-phase switching converter with a plurality of switching circuits, including: sensing the output current of the switching circuit and generating a current sensing signal; generating a digital phase current signal based on the current sensing signal; subtracting the digital phase current signal from a current reference signal and generating a current error signal; proportionally integrating the current error signal and generating a first bias signal; conducting a sigma-delta modulation of the first bias signal and generating a second bias signal, wherein the first bias signal is a P-bit digital signal, the second bias signal is a Q-bit digital signal, and P is larger than Q; and adjusting a control signal controlling the switching circuit based on the second bias signal.