Protective Circuit Slow-Start Inrush Current Mitigation
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Solution Overview
Problem
Conventional low drop-out (LDO) regulators experience high inrush currents when the output voltage rapidly changes, potentially damaging components and causing voltage drops, which affect connected circuits.
Innovation Solution
A protective circuit is designed with a charging unit, voltage regulating unit, and comparing unit to provide a slow start function and over-current protection, utilizing capacitors, amplifiers, and analog switches to manage input current and output voltage, ensuring safe and stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the LDO regulator starts and the output voltage rapidly changes, then the response speed is improved, but high inrush current is generated which may damage components
Solution Approach 1:
The patent applies preliminary action by implementing a slow-start function that gradually increases the output voltage from zero rather than allowing rapid voltage changes. The charging unit charges a capacitor to generate a reference voltage that ramps up over time, and the control unit adjusts the pass transistor accordingly. This preliminary controlled ramp-up prevents high inrush current while the output capacitor charges, solving the contradiction between fast response and inrush current suppression.
2Power
If the output voltage rapidly changes, then the power delivery speed is improved, but voltage drop occurs which affects other circuits
Solution Approach 1:
The control unit performs preliminary action by predicting and preventing voltage drops through proactive current limiting. When the load changes, the control unit detects the situation and limits the current through the pass transistor before a voltage drop can occur, ensuring stable voltage supply to other circuits while maintaining adequate power delivery capability.
Solution Approach 2:
The patent implements feedback through the feedback unit that continuously monitors the output voltage and feeds it back to the control unit. This feedback mechanism allows the control unit to detect voltage changes and adjust the pass transistor accordingly, maintaining voltage stability and preventing harmful voltage drops that would affect other circuits connected to the power supply.
3Reliability
If over-current protection is added to prevent component damage, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated control unit that handles both the slow-start control and over-current protection. The control unit combines the charging unit, discharge unit, feedback unit, and protection logic into one unified structure, reducing overall circuit complexity while maintaining comprehensive protection functionality. This merging approach prevents component damage through over-current protection without significantly increasing device complexity.
Data Source
AI summary
A protective circuit is provided. The protective circuit includes a charging unit, a voltage regulating unit, and a comparing unit. The charging unit receives a rise signal and an over-current signal, and outputs a first reference voltage. The voltage regulating unit receives the first reference voltage and adjusts an output voltage according, to the first reference voltage and a feedback voltage. The comparing unit receives the feedback voltage and compares the feedback voltage with a first threshold voltage to determine whether to output the rise signal to the charging unit.