Phase Redundant Power Supply Current Sensing
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Solution Overview
Problem
Multi-phase power supplies in server systems face challenges in accurately measuring phase current without temperature compensation, which affects load balancing and reliability, especially in redundant power supply systems where precise current sensing is crucial for uninterrupted operation.
Innovation Solution
Implementing a current sense transistor coupled in series with the output inductor in each power stage, mirroring the ORing FET, allows for accurate phase current sensing without temperature compensation, ensuring reliable operation even in redundant power supply configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sensing methods are used in multi-phase power supplies, then temperature compensation circuits and techniques are required, but this increases device complexity and reduces measurement precision
Solution Approach 1:
The patent uses a current sense transistor that mirrors the ORing FET to create a simplified copy of the power switch. This copy transistor provides a direct electrical connection for current sensing without requiring temperature compensation circuits, as the sense transistor inherently tracks the temperature characteristics of the main power switch. The copying approach eliminates complex compensation while maintaining accurate current measurement.
Solution Approach 2:
The current sense transistor acts as an intermediary element between the power switch and the measurement circuitry. By placing the sense transistor in series with the ORing FET, it provides a controlled interface for current sensing that isolates the measurement system from temperature variations, eliminating the need for additional compensation circuits while preserving measurement accuracy.
2Reliability
If redundant power supply phases are implemented, then system reliability improves, but current sensing accuracy becomes more critical for proper load balancing
Solution Approach 1:
Each power phase uses a current sense transistor that mirrors its corresponding ORing FET, creating an accurate representation of the phase current. This copying mechanism ensures that each redundant phase can be independently and accurately monitored, enabling proper load balancing across all phases while maintaining the reliability benefits of redundancy.
Solution Approach 2:
The patent implements separate current sensing circuits for each power phase using individual sense transistors. This segmentation allows independent measurement and control of each phase's current, which is essential for load balancing in redundant power supply configurations. Each phase can be monitored and adjusted independently while maintaining overall system reliability.
3Measurement precision
If temperature compensation techniques are used for current sensing, then measurement accuracy under varying temperature conditions improves, but the system requires additional components and calibration complexity
Solution Approach 1:
The current sense transistor is designed to mirror the ORing FET's electrical characteristics, including temperature-dependent parameters. This copying approach inherently compensates for temperature variations without requiring additional compensation circuits or calibration procedures. The sense transistor automatically tracks the main switch's characteristics across the temperature range, providing accurate current measurement with minimal complexity.
Solution Approach 2:
The current sensing system uses the ORing FET's own characteristics to perform self-compensation. The sense transistor, being electrically identical to the ORing FET, automatically adapts to temperature changes affecting the power switch. This self-service mechanism eliminates the need for external temperature compensation circuits or complex calibration procedures, as the system compensates for itself through the inherent matching of the sense transistor to the power switch.
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 method provides accurate and temperature-independent phase current sensing, enhancing load balancing and system reliability by enabling uninterrupted power delivery in case of power stage failures, reducing the need for complex temperature compensation techniques.
Implementation Method 1
a current sense transistor coupled in series with the output inductor in each power stage. The current sense transistor mirrors the output voltage disconnect transistor, referred to as the ORing field effect transistor, or "ORing FET"
Data Source
AI summary
A power stage in a multi-phase switching power supply incorporates a current sense circuit coupled to the output voltage disconnect transistor to conduct a portion of an inductor current flowing in the output inductor of the power stage. The current sense circuit is controlled by the same control signal controlling the output voltage disconnect transistor. The portion of the inductor current being conducted by the current sense circuit includes an upslope current and a downslope current of the inductor current. A phase redundant controller generates a sense current signal indicative of the portion of the inductor current conducted by the current sense circuit. Accurate current sensing is implemented for the power stage where the current sense value dose not require temperature compensation.