Secondary-Side Digital Control for DC-DC Converter Current Sharing
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Solution Overview
Problem
Existing DC/DC converters using analog closed-loop control are inflexible and lack accuracy in current sharing across multiple parallel converters, leading to potential overloading and uneven distribution of load current and heat.
Innovation Solution
The implementation of secondary-side digital control allows for precise monitoring and regulation of output voltage and current, enabling more accurate droop current sharing and balanced current distribution through direct sensing and feedback control, while also supporting features like soft-start, constant current startup, and pre-bias startup to manage multi-converter systems effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog closed-loop control is used, then the control implementation is simple and mature, but the flexibility and accuracy are limited
Solution Approach 1:
The patent replaces the analog control system with a digital control system. Specifically, analog-to-digital converters (ADCs) are used to convert analog voltage and current signals into digital values that can be processed by a microcontroller or digital signal processor. This substitution enables higher measurement precision through digital sampling and processing while maintaining manageable complexity through standardized digital components and programming.
Solution Approach 2:
The patent changes the operating parameters of the control system from continuous analog signals to discrete digital values. By sampling analog voltages and currents at specific intervals and representing them as digital numbers, the system achieves higher precision through increased resolution (e.g., 12-bit or 16-bit ADCs) while the digital nature allows for flexible parameter adjustment through software configuration rather than hardware changes.
2Measurement precision
If droop current sharing is implemented, then the current distribution among parallel converters is achieved, but the accuracy of current sharing is poor
Solution Approach 1:
The patent implements a feedback mechanism where digital-to-analog converters (DACs) convert digital current reference values back into analog signals that are added to the droop voltage. This closed-loop feedback allows the system to continuously monitor and adjust the current output of each converter, ensuring accurate current sharing among parallel units while maintaining the simplicity of the droop method through automatic adjustment rather than complex manual coordination.
Solution Approach 2:
The patent creates a universal control architecture that can handle both droop current sharing and accurate current distribution through the same digital controller. The microcontroller or DSP can dynamically switch between different control algorithms and modes, providing both the simplicity of droop operation and the precision of active current balancing without requiring separate control systems for each function.
3Power
If multiple parallel-connected converters are used, then the power supply capacity is increased, but the current distribution becomes uneven leading to overloading
Solution Approach 1:
The patent implements dynamic current balancing where the digital controller continuously monitors the output current of each parallel converter and adjusts their operating parameters in real-time. This dynamic adjustment ensures that as the total power demand changes, the current distribution among converters automatically rebalances, preventing any single converter from becoming overloaded while maximizing the total power output capability of the parallel system.
Data Source
AI summary
A DC/DC converter for use in power supply applications employing multiple parallel-connected converters employs a digital controller referenced to the secondary or output side of an isolation boundary and having non-isolated direct connections to secondary side components. The controller directly monitors output voltage and output current and uses feedback control techniques to precisely control these values in a desired manner. The DC/DC converter can implement so-called “droop” current sharing with increased accuracy arising from the secondary-side digital control, so that a desired balanced sharing of current across multiple converters can be achieved. The converter uses calibration establish accurate set points, and any of a variety of additional functions/features to attain operational goals.