Glitch-Free Start-Up Tracking Pin Error Amplifier

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Solution Overview

Problem

Switching regulators often experience transient glitches during start-up due to manufacturing variations causing initial output voltage initialization issues, leading to potential overshooting and instability in the regulated output.

Innovation Solution

An error amplifier with a voltage offset circuit that provides a pre-selected offset during soft-start to ensure the output is not initialized high, using a combination of current sources and transistors to manage the offset, which can be gradually or abruptly removed during normal operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the output voltage is initialized high during start-up, then the regulator can quickly reach operational state, but transient glitches and overshooting occur

Engineering Contradiction:

Improvestart-up speedVSAvoidoutput stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent applies preliminary action by pre-initializing the error amplifier output to a specific voltage level (e.g., 0V or a predetermined voltage) before the regulator starts operating. This preliminary initialization prevents transient glitches and overshooting during start-up by ensuring the amplifier begins in a known stable state, thus resolving the contradiction between quick start-up and output stability.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If manufacturing variations are present, then component tolerance is acceptable for mass production, but initial output voltage initialization becomes unpredictable

Engineering Contradiction:

Improvemass production feasibilityVSAvoidinitial voltage initialization accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent implements self-service by designing the error amplifier to automatically initialize its own output to a predetermined voltage level without requiring external calibration or adjustment. This self-initialization mechanism compensates for manufacturing variations in components, ensuring consistent and predictable start-up behavior across mass-produced units, thus resolving the contradiction between ease of manufacture and initialization precision.

Inventive Principle:

Principle #25Self-service

3Reliability

If a voltage offset is added to prevent glitches, then start-up stability improves, but circuit complexity increases

Engineering Contradiction:

Improvestart-up stabilityVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the voltage offset function with the existing error amplifier circuit by integrating the initialization mechanism directly into the amplifier's input or output stage. This combination approach adds the necessary voltage offset for stable start-up while minimizing additional external components, thus resolving the contradiction between start-up stability and circuit complexity.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS7498874B1Glitch-free start-up with a tracking pin

Publication Date: 2009.03.03 NAT SEMICON CORP

AI summary

An error amplifier for closed loop operation is provided. The error amplifier has a track input and a feedback input. During soft-start, a voltage offset is added to the error amplifier input. In one embodiment, the voltage offset is gradually removed during the soft-start.