Overcurrent Protection Circuit with Dynamic Thresholds
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Solution Overview
Problem
Existing power supply circuits face challenges in accurately detecting overcurrent conditions and managing heat removal, leading to potential operational issues and erroneous shutdowns due to the limitations of traditional overcurrent detection methods.
Innovation Solution
An overcurrent protection circuit that operates in multiple modes, utilizing a capacitor for soft-start, accurate overcurrent detection, and adjustable shutdown timing, without increasing external components, by charging and discharging the capacitor based on terminal voltage thresholds and PWM signal periods to prevent erroneous detection and ensure sufficient heat removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional overcurrent detection methods are used, then overcurrent protection is provided, but detection accuracy is low leading to erroneous shutdowns
Solution Approach 1:
The patent applies dynamics by making the detection threshold variable rather than fixed. The threshold voltage is dynamically adjusted based on the terminal voltage level: when terminal voltage is below a first threshold, the detection threshold is set to a second voltage level; when terminal voltage exceeds the first threshold, the detection threshold switches to a third voltage level. This dynamic adaptation allows accurate detection across different operating conditions while preventing erroneous shutdowns during voltage transitions.
Solution Approach 2:
The patent changes the detection parameter (threshold voltage) based on operating conditions. By monitoring terminal voltage and switching between different threshold levels (second voltage vs. third voltage), the system adapts its detection sensitivity to match the current operating state, thereby improving detection accuracy and reducing false positives during transient conditions.
2Reliability
If soft-start function is implemented using a capacitor, then overcurrent at start-up is prevented, but the capacitor cannot be used for overcurrent protection simultaneously
Solution Approach 1:
The patent makes the capacitor serve multiple functions: it acts as a soft-start capacitor to prevent overcurrent during power-up, and simultaneously functions as part of the overcurrent protection detection circuit. The capacitor's voltage (terminal voltage) is used as the basis for dynamic threshold adjustment in the overcurrent detection mechanism. This multi-functionality eliminates the need for separate components while providing both soft-start and accurate overcurrent protection capabilities.
Solution Approach 2:
The patent merges the soft-start function and overcurrent protection function into a unified system. The same capacitor that performs soft-start is also integrated into the overcurrent detection circuitry, where its voltage level determines the appropriate detection threshold. This combination reduces component count and creates a more efficient system where one component supports multiple critical functions.
3Reliability
If overcurrent detection is performed continuously, then protection is provided, but heat removal time is insufficient causing repeated shutdowns
Solution Approach 1:
The patent implements periodic action by using PWM (pulse-width modulation) signals to control the switching of power devices. The overcurrent detection is synchronized with these periodic PWM cycles, allowing the system to detect overcurrent conditions at appropriate intervals rather than continuously. This periodic detection approach provides adequate protection while allowing sufficient time between cycles for heat dissipation, preventing repeated rapid shutdowns.
Solution Approach 2:
The patent applies preliminary action by detecting overcurrent conditions before they cause excessive heat accumulation. The dynamic threshold detection system identifies overcurrent states early in the PWM cycle, allowing protective action to be taken before thermal damage occurs. This proactive detection approach ensures protection is provided while maintaining adequate heat removal time between operational cycles.
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
The solution provides high accuracy in overcurrent detection and effective heat removal, preventing erroneous shutdowns and ensuring reliable operation of power supply circuits by using the same capacitor for soft-start, overcurrent protection, and shutdown management.
Implementation Method 1
a capacitor 21 connected to a terminal SS
Data Source
AI summary
In some embodiments, an overcurrent protection circuit is configured to operate in accordance with operation modes including a first operation mode in which when the power supply circuit is activated, the capacitor is charged until the terminal voltage reaches a first voltage, a second operation mode in which depending on a time period in which a current flowing through an output transistor of the power supply circuit exceeds a predetermined value, the capacitor is charged so that the terminal voltage increases from the first voltage toward a second voltage, and the power supply circuit is shut down when the terminal voltage reaches the second voltage, and a third operation mode in which when the power supply circuit is shut down, the capacitor is discharged until the terminal voltage reaches a third voltage, and the shutdown of the power supply circuit is released when the terminal voltage reaches the third voltage.