Voltage-Independent Load Sharing Control for Power Supplies
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Solution Overview
Problem
Existing load sharing methods in power supply systems face challenges such as complex designs requiring custom loop stability compensation, potential noise injection, and single points of failure due to the need to route share bus signals, along with inefficiencies from diodes used to prevent back-feeding.
Innovation Solution
A voltage-independent load sharing control scheme that uses adjustable voltage drops and current sense resistors, with an error amplifier to equalize intermediate voltages and prevent reverse currents, allowing for simpler and more flexible power supply system design without the need for trim/adjust pins or close proximity to power supplies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional active load sharing controllers are used to achieve accurate current sharing, then load sharing precision is improved, but device complexity increases due to custom loop stability compensation requirements
Solution Approach 1:
The patent introduces an intermediary error amplifier that compares the intermediate voltages from different power supply paths and generates correction signals. This mediator simplifies the control architecture by handling the complexity of loop stability compensation centrally, rather than requiring each supply to have custom compensation circuits, thus maintaining current sharing accuracy while reducing overall device complexity.
Solution Approach 2:
The patent implements a feedback mechanism where the error amplifier continuously monitors intermediate voltages and adjusts the controllable voltage drops accordingly. This feedback loop ensures accurate current sharing by dynamically correcting voltage imbalances, achieving precision without requiring complex custom compensation for each supply channel.
2Ease of operation
If share bus signals are routed to all power supplies to enable load sharing, then current distribution control is improved, but reliability decreases due to single point of failure
Solution Approach 1:
The patent segments the load sharing control by providing each power supply path with its own independent controllable voltage drop element and current sense resistor. This segmentation allows each path to operate independently while still achieving coordinated current sharing through the error amplifier, eliminating the need for a common share bus and thus removing the single point of failure.
Solution Approach 2:
The patent applies local quality by implementing local current sensing and local voltage adjustment for each power supply path. Each path has its own controllable voltage drop that can be independently adjusted based on local conditions, enabling distributed control that improves reliability while maintaining load sharing functionality.
3Reliability
If diodes are added in series with each supply output to prevent back-feeding, then reverse current protection is improved, but power loss increases due to diode voltage drop
Solution Approach 1:
The patent replaces the mechanical diode-based reverse current protection with an electronic solution using controllable voltage drops (such as MOSFETs or other active elements) that can be dynamically controlled. This substitution eliminates the fixed voltage drop of diodes, reducing power loss while maintaining reverse current protection capability through active control.
Solution Approach 2:
The patent introduces dynamic control of the voltage drops in each power supply path, allowing the system to adaptively adjust the voltage characteristics based on operating conditions. This dynamic approach enables efficient current sharing and reverse current protection without the constant power loss associated with static diode voltage drops.
4Measurement precision
If trim/adjust pins or feedback networks are used for load sharing control, then current sharing accuracy is improved, but ease of manufacture decreases due to noise injection concerns and routing requirements
Solution Approach 1:
The patent enables each power supply path to be self-sufficient with its own current sense resistor and controllable voltage drop element. The local sensing and control eliminate the need for external trim pins or feedback network routing, reducing noise injection concerns and simplifying manufacturing while maintaining current sharing accuracy through the centralized error amplifier control.
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
This solution enables accurate and efficient load sharing between multiple power supplies, preventing back-feeding and reducing thermal stress, while simplifying the design and increasing system reliability by eliminating the need for custom loop compensation and minimizing noise injection.
Implementation Method 1
an error amplifier to equalize intermediate voltages and prevent reverse currents
Implementation Method 2
provides a controllable voltage drop for each power supply path
Data Source
AI summary
An apparatus and method for load sharing among N current supplies, where N > 1. N current supply paths are coupled to corresponding N independent power sources, respectively. A system load is coupled to the outputs of the N current supply paths to receive N current supplies. There is a common current share bus configured to connect to the N current supply paths to provide a common current share signal, used to indicate the current contribution needed from each of the N current supply paths. In this configuration, each of the N current supply paths adjusts an adjustable voltage drop between its power source and the current supply it provides to the system load in accordance with the common current share signal so that the current supplied from each current supply path is consistent with the common current share signal.