Low-Dropout Regulator Power-On Control for Inrush Current
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Solution Overview
Problem
Existing low-dropout regulator circuits experience a large inrush current when initially powered on, which can damage components or wires.
Innovation Solution
A low-dropout regulator circuit with a control circuit that manages the power switch circuit to control the flow of current, avoiding a large inrush current by gradually increasing the current flow as the input voltage stabilizes, without the need for additional low-pass filter circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the power switch circuit is directly connected to the input voltage without control, then the circuit can immediately provide output voltage, but a large inrush current flows through the power switch circuit when initially powered on
Solution Approach 1:
The control circuit performs preliminary action by detecting the input voltage before enabling the power switch circuit. When the input voltage exceeds a threshold, the control circuit activates the power switch circuit in a controlled manner, preventing inrush current before it can occur. This preliminary detection and controlled activation resolves the contradiction by ensuring safe power-on without sacrificing speed.
Solution Approach 2:
The control circuit acts as an intermediary between the input voltage and the power switch circuit. It mediates the power-on process by monitoring input voltage conditions and selectively enabling the power switch circuit only when appropriate, thereby preventing inrush current while maintaining fast response when conditions are met.
2Object-affected harmful factors
If a low-pass filter circuit is added to reduce inrush current, then the inrush current is reduced, but the circuit area increases
Solution Approach 1:
The invention extracts the inrush current suppression function from the traditional low-pass filter circuit approach and implements it through a control circuit that manages power switch activation. This removes the need for additional filter components, achieving inrush current reduction without increasing circuit area.
Solution Approach 2:
The control circuit uses feedback by detecting the input voltage and using this information to control the power switch circuit activation. This feedback mechanism enables intelligent control of current flow, suppressing inrush current through active management rather than passive filtering, thereby avoiding additional circuit area.
3Object-affected harmful factors
If the power switch circuit is controlled to limit current, then inrush current is reduced, but the response time for voltage stabilization increases
Solution Approach 1:
The control circuit implements dynamic control by continuously monitoring input voltage and adjusting power switch circuit activation accordingly. This dynamic approach allows the system to provide rapid response when input voltage is stable and above threshold, while preventing inrush current during voltage transitions, thus resolving the time versus current protection contradiction.
Data Source
AI summary
A low-dropout regulator circuit includes a reference circuit, an amplifying circuit, a power switch circuit, a feedback circuit, and a control circuit. The reference circuit is configured to generate a reference voltage. The amplifying circuit is configured to generate an amplifying voltage according to the reference voltage and a feedback voltage. The power switch circuit is configured to receive the amplifying voltage and generate an output voltage at an output terminal according to an input voltage. The feedback circuit is configured to generate the feedback voltage according to the output voltage. The control circuit is configured to control the power switch circuit according to the input voltage and a signal from the reference circuit.