Power Supply Limited Power Protection via Dual Feedback

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Solution Overview

Problem

AC-DC power supplies relying solely on current-sense signals for limited power control may fail to prevent excessive output due to abnormalities in the current-sense resistor, such as short circuits, leading to potential fire hazards and non-compliance with safety standards.

Innovation Solution

Implementing a power delivery controller that utilizes both current-sense and power detection signals from the secondary side, including a SR controller, photo coupler, and bus switch, to accurately limit output power, ensuring reliable operation even if the current-sense resistor fails.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the power supply relies solely on current-sense signal for limited power control, then the device complexity is reduced, but the reliability of power limitation is compromised due to potential current-sense resistor failure

Engineering Contradiction:

Improvecontrol circuit complexityVSAvoidpower limitation reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent implements a dual-feedback mechanism by monitoring both current-sense signals and power detection signals. The power detection signal provides an independent feedback path that verifies the actual power output, ensuring that power limitation remains reliable even when the current-sense resistor fails. This redundant feedback system resolves the contradiction by maintaining reliability without requiring excessive complexity.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs preliminary verification by comparing the current-sense signal with the power detection signal before final power control decisions. This preliminary action detects potential current-sense resistor abnormalities early, allowing the system to switch to alternative control methods before failure occurs, thus maintaining reliability without permanently increasing system complexity.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If the power supply uses only current-sense signal for power control, then the measurement precision is simpler, but the accuracy of power limitation is reduced when current-sense resistor abnormalities occur

Engineering Contradiction:

Improvedetection system complexityVSAvoidoutput current measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces the power detection signal as an intermediary measurement method. Instead of relying solely on the current-sense resistor, the system uses power detection (which may involve measuring voltage and calculating power) as an intermediate step to verify actual power output. This intermediary approach maintains measurement precision even when the current-sense resistor becomes abnormal.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the measurement parameter from purely current-based sensing to a combination of power-based detection. By monitoring power consumption directly rather than inferring it solely from current-sense signals, the system achieves accurate power measurement independent of current-sense resistor status, resolving the precision-accuracy contradiction.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If the current-sense resistor fails due to short circuit, then the device complexity remains unchanged, but the safety performance deteriorates leading to potential fire hazards

Engineering Contradiction:

Improvesystem structure complexityVSAvoidfire hazard risk

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent implements beforehand cushioning by preparing alternative power detection methods that activate when current-sense resistor failure is detected. This prior preparation ensures that safety protection mechanisms are already in place before a fire hazard can occur, allowing the system to respond to current-sense failures without increasing structural complexity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent converts the potential harm of current-sense resistor failure into a beneficial safety feature by using the discrepancy between expected and actual power detection signals as an additional safety check. When the current-sense signal becomes abnormal, the power detection system provides the safety function that the failed current-sense resistor can no longer perform, turning the failure mode into a protective mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS11404863B2Power supplies with limited power protection and relevant control methods

Publication Date: 2022.08.02 LEADTREND TECH

AI summary

A power supply is configured to limit its output power, converting an input voltage on a primary side into a bus voltage on a secondary side. A current-sense resistor detects a bus current output from the power supply to provide a current-sense signal. A bus switch is electrically connected to a secondary winding on the secondary side, configured to selectively supply power to the bus voltage. A power delivery controller controls the bus switch in response to the current-sense signal and a power detection signal on the secondary side. The power delivery controller provides a power threshold in response to the bus voltage, compares the power detection signal with the power threshold, and turns off the bus switch to stop supplying power to the bus voltage if the power detection signal exceeds the power threshold, thereby limiting the output power of the power supply.