USB Power Supply Circuit for Cable Fault Detection

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Solution Overview

Problem

Existing USB power delivery systems lack effective means to detect and respond to faults such as internal short circuits and overvoltage conditions in cables, which can lead to damage and safety risks.

Innovation Solution

A circuit and method using a single node to sense cable impedance and voltage, comparing these values to thresholds, and asserting a flag signal to interrupt power delivery when faults are detected, allowing for periodic testing without disrupting normal operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If power delivery is continuously provided through USB cables, then the power supply function is maintained, but cable damage risks increase due to potential internal short circuits or overvoltage conditions

Engineering Contradiction:

Improvecable safetyVSAvoidshort circuit damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary impedance measurements and fault detection before power delivery issues cause damage. The controller periodically measures cable impedance and detects overvoltage conditions proactively, allowing preventive action to be taken before harmful effects occur.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors cable impedance and voltage levels, providing feedback to the controller. When abnormal conditions are detected (impedance below threshold or overvoltage), the controller responds by interrupting power delivery, creating a closed-loop safety mechanism.

Inventive Principle:

Principle #23Feedback

2Reliability

If fault detection testing is performed on USB cables, then cable integrity is verified, but normal power supply operation may be disrupted

Engineering Contradiction:

Improvefault detection accuracyVSAvoidpower delivery continuity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system performs fault detection tests periodically rather than continuously, allowing normal power delivery to proceed uninterrupted between test cycles. The controller schedules impedance measurements and fault checks at intervals, minimizing impact on continuous power supply while maintaining adequate monitoring.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system applies test signals at levels that are sufficient to detect faults but minimal enough not to disrupt normal operation. Impedance measurements are performed using small test currents that coexist with normal power delivery, and overvoltage detection uses threshold comparisons that distinguish between normal voltage variations and actual fault conditions.

Inventive Principle:

Principle #16Partial or excessive action

3Measurement precision

If multiple separate circuits are used for impedance sensing and overvoltage detection, then detection accuracy is improved, but circuit complexity increases

Engineering Contradiction:

Improvefault detection precisionVSAvoidcircuit structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system combines impedance sensing and overvoltage detection functions into a single integrated circuit block that interfaces with the existing USB power delivery controller. Both measurement functions share common components including the coupling node, sensing resistors, and control logic, reducing overall circuit complexity while maintaining detection precision for both fault types.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The detection circuit is designed to perform multiple functions using the same hardware resources. The impedance measurement circuit can also serve as a basis for overvoltage detection, and the controller uses the same interface and processing resources for both types of fault detection, maximizing component utilization and minimizing additional complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enables reliable detection and prevention of cable faults, ensuring safe and uninterrupted power delivery by integrating fault detection directly into the power interface, enhancing system reliability and safety.

Implementation Method 1

sense at least one sensing signal indicative of a value of the cable impedance and/or of a cable voltage across the cable

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Data Source

PatentUS12620998B2Methods and circuits for electrical power supply

Publication Date: 2026.05.05 STMICROELECTRONICS SRL

AI summary

A circuit includes at least one coupling node configured to be coupled, via a cable, to a load to transmit a supply voltage thereto. The circuit includes test circuitry configured to sense at least one sensing signal indicative of a value of the cable impedance and/or of the cable voltage across the cable, to perform a comparison between the at least one sensing signal and at least one threshold indicative either of a threshold resistance value for the cable impedance or indicative of a threshold voltage value for the cable voltage, produce a comparison signal as a result of the comparison.