LDO In-Rush Control Circuit for Power-Up Voltage Slope Matching

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Solution Overview

Problem

During the power-up period in semiconductor devices, the rising slope of the internal voltage generated by the internal voltage generator is smaller than the external voltage, leading to undesirably large in-rush current that can affect peripheral circuits and the reliability of the internal voltage generator.

Innovation Solution

A semiconductor device with a low-dropout (LDO) regulator and an in-rush control circuit that short-circuits the external and internal voltages during the power-up period using a first and second power-up signal to equalize the rising slopes, preventing in-rush current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the internal voltage generator charges the capacitor with large current during power-up, then the rising slope of internal voltage can match the external voltage, but in-rush current is generated that adversely affects peripheral circuits and reliability

Engineering Contradiction:

Improverising slope of internal voltageVSAvoidin-rush current

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The in-rush control circuit activates before the main voltage regulation begins, pre-charging the capacitor through a controlled path. This preliminary action ensures the capacitor is partially charged before the full-power voltage generator engages, preventing the sudden large current surge that would otherwise occur during initial power-up.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The in-rush control circuit acts as an intermediary between the voltage generator and the capacitor during the power-up transition. It provides a controlled intermediate charging path that limits current magnitude while still achieving the necessary voltage rise, mediating between the high-current requirement and the in-rush current constraint.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the rising slope of internal voltage is smaller than external voltage during power-up, then in-rush current is prevented, but the internal voltage generator cannot quickly establish stable voltage for peripheral circuits

Engineering Contradiction:

Improvein-rush currentVSAvoidvoltage establishment speed

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The voltage generation process is divided into distinct periodic phases: an initial slow-charging phase where the in-rush control circuit gradually charges the capacitor, followed by a second phase where the main voltage generator rapidly establishes stable voltage. This periodic action allows the system to balance current limitation with quick voltage establishment.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The in-rush control circuit performs preliminary charging of the capacitor before the main voltage generator takes over. This preliminary action reduces the initial voltage difference between internal and external voltages, allowing the subsequent voltage establishment to occur more quickly without generating harmful in-rush current.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250285659A1In-rush control circuit and voltage generator including the same

Publication Date: 2025.09.11 SAMSUNG ELECTRONICS CO LTD

AI summary

A semiconductor device includes a low-dropout (LDO) regulator, configured to generate an internal voltage using an external voltage, and an in-rush control circuit connected to the LDO regulator and configured to short-circuit the external voltage and the internal voltage to each other during a power-up period. The power generator may short-circuit the external voltage and the internal voltage to each other to prevent in-rush current.