Charge Pump Output Current Limiting Circuit

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Solution Overview

Problem

Charge pumps face challenges in accurately limiting output current due to factors like switch non-overlap time, current source drift, and changes in current pulse waveform, especially as switching frequency increases, leading to inefficiencies and inaccuracies in current regulation.

Innovation Solution

A charge pump with an output current limiting circuit that integrates an observation current and compares it to a reference signal to control the charging current, ensuring accurate current limiting by constraining the charge provided during both charging and discharging phases, using a switched capacitor and switches operable in multiple phases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If switching frequency is increased to minimize capacitor size and improve efficiency, then productivity and energy efficiency are improved, but output current limiting accuracy deteriorates due to switch non-overlap time, current source drift, and waveform changes

Engineering Contradiction:

Improveswitching frequencyVSAvoidoutput current limiting accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the output current is monitored and compared against a reference, and the charging current is adjusted accordingly to maintain accurate current limiting even at high switching frequencies where traditional methods fail

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the control parameter from fixed charge quantity per cycle to dynamically adjusted charge quantity based on integrated observation of output current, allowing accurate current limiting to be maintained across varying switching frequencies

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If fixed charge quantity is used per switching cycle, then device complexity is reduced, but output current limiting accuracy deteriorates under varying operating conditions

Engineering Contradiction:

Improvecontrol circuit complexityVSAvoidcurrent limiting accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The control circuit automatically adjusts the charging current based on integrated observation of the output current, eliminating the need for complex external control mechanisms while maintaining accurate current limiting under varying operating conditions

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS11411490B2Charge pumps with accurate output current limiting

Publication Date: 2022.08.09 ANALOG DEVICES INT UNLTD CO

AI summary

Charge pumps with accurate output current limiting are provided herein. In certain embodiments, a charge pump includes an output terminal for providing a regulated output voltage, a switched capacitor, and switches that control connectivity of the switched capacitor to selectively charge or discharge the switched capacitor. The switches are operable in two or more phases including a charging phase in which the switched capacitor is charged with a charging current and a discharging phase in which the switched capacitor is coupled to the output terminal. The charge pump further includes an output current limiting circuit that controls the charging current to limit an amount of output current delivered by the charge pump to the output terminal. The output current limiting circuit limits the output current based on comparing a reference signal to an integral of an observation current that changes in relation to the charging current.