Adaptive Bias LDO Regulator Circuit for Glitch-Free Voltage Regulation

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Solution Overview

Problem

Low dropout (LDO) voltage regulators experience output voltage glitches due to abrupt switching of bias current when output current changes slowly, leading to discontinuities in the adaptive bias.

Innovation Solution

An LDO regulator circuit with a transconductance amplifier and current mirror that provides adaptive bias current with proportional control, using two transistors and a common mode current source to limit bias current, ensuring smooth transitions without switch modes by adjusting the bias current based on the output current's range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If abrupt switching of bias current is used to adjust amplifier bias, then power consumption is reduced at low output current, but output voltage glitches are introduced

Engineering Contradiction:

Improvepower consumptionVSAvoidoutput voltage stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The bias current is made dynamically adjustable based on output current conditions. The circuit automatically transitions between different bias current levels depending on whether the output current is below or above a threshold, optimizing power consumption while maintaining stability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

An intermediary circuit is introduced between the bias current source and the amplifier to smooth the transition. This intermediary prevents abrupt switching by providing a gradual transition mechanism, eliminating output voltage glitches while maintaining power savings.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If adaptive bias current is switched to control amplifier bias, then quiescent current is reduced, but discontinuities are introduced in bias current

Engineering Contradiction:

Improvequiescent currentVSAvoidbias current continuity

Core Design Contradiction:

Loss of energyVSStability of the object's composition

Solution Approach 1:

The circuit ensures continuous bias current delivery to the amplifier by designing the switching mechanism to maintain uninterrupted current flow. The transition between different bias levels is designed to be continuous rather than discontinuous, preventing glitches while maintaining low quiescent current.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The bias current system dynamically adapts to output current conditions while maintaining continuous operation. The circuit automatically adjusts bias current levels based on operating conditions without introducing discontinuities, achieving both energy efficiency and stability.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8922179B2Adaptive bias for low power low dropout voltage regulators

Publication Date: 2014.12.30 SEMICON COMPONENTS IND LLC

AI summary

A low dropout (LDO) voltage regulator includes a voltage regulation loop for providing a gate drive signal to an output device, the gate drive signal proportional to an output current. The voltage regulation loop includes a current bias input for receiving a bias current. The LDO voltage regulator further includes a current bias control circuit for providing the adaptive bias current at a first value that is proportional to current limit value lab and the width-to-length ratio of transistors of the transconductance amplifier when the output current less than or equal to a threshold and increases the bias current from a threshold to a current limit value. The output current varies substantially linearly over a range of output current values between the threshold and the current limit value.