Adaptive Power Switch Current Limiting for Substrate Current Protection
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Solution Overview
Problem
Conventional current limiting circuits in power switches set a constant current limit, leading to damage when loads demand high power, causing substrate current increase and potential damage to the power switch due to reduced output voltage.
Innovation Solution
A power switch circuit with an adaptive current limiting mechanism using a current sensing resistor, charge pump, and an adaptive current limiting circuit that dynamically adjusts current limits based on input and output voltages, preventing damage by limiting substrate current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant current limit value is set in the conventional current limiting circuit, then the circuit structure is simple, but the power switch may be damaged when the load demands high power causing substrate current increase
Solution Approach 1:
The patent implements dynamic current limiting by replacing the fixed constant current limit with an adaptive current limiting circuit that continuously monitors output voltage and adjusts the current limit accordingly. The circuit uses operational amplifiers and transistors to create a feedback mechanism where the current limit value changes dynamically based on real-time voltage conditions, preventing power switch damage while maintaining circuit protection functionality.
Solution Approach 2:
The patent employs feedback control by monitoring the output voltage of the power switch and using this information to adjust the current limiting value. The adaptive current limiting circuit receives voltage feedback signals and modifies its current limiting behavior accordingly, creating a closed-loop control system that enhances power switch protection without requiring overly complex circuit architecture.
2Power
If the output voltage is reduced to be lower than a voltage threshold such as 0V, then the load can obtain large amount of power, but the substrate current generated by impact ionization of hot carriers inside the power switch is gradually increased to a maximum value causing damage
Solution Approach 1:
The patent applies preliminary anti-action by implementing current limiting before the substrate current can reach damaging levels. The adaptive current limiting circuit proactively monitors output voltage and preemptively adjusts the current limit to prevent the conditions that would lead to hot carrier generation and substrate current damage, rather than reacting after damage occurs.
Solution Approach 2:
The patent changes the current limit parameter dynamically based on output voltage conditions. Instead of using a fixed current limit, the circuit adjusts the current limiting parameter in real-time according to voltage measurements, allowing the system to deliver high power when safe while preventing substrate current damage when voltage thresholds are approached.
3Reliability
If an adaptive current limiting circuit is implemented to dynamically adjust current limits based on input and output voltages, then power switch protection is improved, but the circuit complexity increases
Solution Approach 1:
The patent achieves multi-functionality by designing the adaptive current limiting circuit to perform multiple protective functions simultaneously. The circuit not only limits current but also monitors voltage conditions, provides feedback control, and prevents multiple failure modes (overcurrent, overheating, substrate current damage) using a single integrated circuit structure, thereby improving protection without proportionally increasing complexity.
Data Source
AI summary
A power switch circuit of adaptively limiting a current is provided. The power switch circuit includes a current sensing resistor, a power switch, a charge pump and an adaptive current limiting circuit. A first terminal of the current sensing resistor is coupled to an input voltage. A first terminal of the power switch is connected to a second terminal of the current sensing resistor. A second terminal of the power switch is connected to a first terminal of a capacitor. A second terminal of the capacitor is grounded. An output terminal of the charge pump is connected to a control terminal of the power switch. According to the input voltage, a voltage of the current sensing resistor and a voltage of the capacitor, the adaptive current limiting circuit determines whether to control an operation of the power switch for limiting the current flowing through the power switch.