DC/DC Converter Current Compensation via Division-Sigma Control
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Solution Overview
Problem
Existing current control methods for DC/DC converters, such as peak current mode control (PCMC) and average current-mode control (ACMC), face issues like distortion due to peak and average value errors, noise interference, and slow response to output voltage variations, especially with large inductance variations, which can lead to overcurrent and inefficient voltage regulation.
Innovation Solution
A division-sigma (D-Σ) control method is introduced, which involves multiplying the difference between reference voltage and output feedback voltage by a voltage-error compensation factor to determine a reference current, calculating inductor current variation using D-Σ digital control, and adjusting the duty ratio to regulate output voltage, eliminating the need for extra filters and allowing immediate compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If peak current mode control (PCMC) is used to switch off after peak inductor current reaches reference current, then current protection is provided, but distortion occurs due to error value between peak value and average value and noise interference prevention ability is poor
Solution Approach 1:
The patent segments the control process into two independent parts: peak current mode control for protection and average current mode control for precision. The control circuit separately processes peak current signals for overcurrent protection and average current signals for accurate voltage regulation, eliminating the conflict between protection and precision in traditional single-mode control.
2Object-affected harmful factors
If average current-mode control (ACMC) is used with extra filters to filter out current ripple, then noise interference prevention is improved, but response speed to output voltage decreases and design complexity increases
Solution Approach 1:
The patent introduces an intermediary approach by using a current transformer to directly obtain average current information without requiring complex filtering circuits. The current transformer acts as a mediator that provides clean average current signals while maintaining fast response characteristics, eliminating the need for slow RC filters used in traditional ACMC.
3Device complexity
If traditional voltage regulation mechanism is used that processes only output voltage signal, then circuit simplicity is maintained, but inductor current control and protection is ignored leading to overcurrent damage
Solution Approach 1:
The patent merges voltage regulation and current protection functions into a unified control system. The control circuit simultaneously processes both voltage error signals and current signals, integrating the simplicity of voltage-mode control with the safety of current-mode control in a coordinated dual-function architecture.
Data Source
AI summary
A method is provided for current compensation. The method is based on division-sigma (D-Σ) control for a DC/DC converter. Inductance changes are allowed with D-Σ digital control achieved. Loop gain can be quickly adjusted. The disadvantage of average current-mode control (ACMC) is solved, where the disadvantage is a reduction of the response speed caused by the filter within the current loop. The present invention uses midpoint current sampling to ensure taking an average inductor current value in each switching cycle. By doing so, a lack of fidelity of peak current-mode control (PCMC) is solved, where the lack of fidelity is due to the amount of error value between the peak value and the average value. Besides, the present invention uses a table of the inductance following current changes to achieve compensation of duty cycle ratio, where the table is built in a single chip.