Voltage-Mode Relaxation Oscillator for Temperature-Stable Clocking

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Solution Overview

Problem

Conventional relaxation oscillators exhibit temperature-dependent oscillation periods, leading to variations in frequency, and current mode oscillators suffer from low duty ratio and poor phase noise characteristics.

Innovation Solution

A voltage mode relaxation oscillator incorporating a bandgap reference circuit to generate temperature-independent control voltage and current, using a control voltage generating circuit and reference current generating circuit to produce a temperature-independent clock signal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a conventional relaxation oscillator is used, then the circuit structure is simple, but the oscillation frequency varies with temperature

Engineering Contradiction:

Improvecircuit structureVSAvoidfrequency stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent changes the parameters of the charging and discharging currents to be temperature-dependent in a controlled manner. By setting the charging current to have positive temperature coefficient and discharging current to have negative temperature coefficient, the oscillation frequency becomes temperature-independent. This resolves the contradiction by introducing parameter changes that compensate for temperature effects without significantly increasing circuit complexity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces temperature compensation current sources as intermediary elements that mediate between the temperature variations and the oscillation frequency. These intermediary current sources generate compensating currents that offset the temperature-dependent variations in the main oscillation path, thereby stabilizing the frequency while maintaining a relatively simple circuit structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a current mode relaxation oscillator is used to compensate temperature fluctuations, then frequency stability improves, but duty ratio becomes low and phase noise characteristics deteriorate

Engineering Contradiction:

Improvefrequency stabilityVSAvoidphase noise

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent substitutes the conventional current-mode operation with a voltage-mode operation. By using voltage-mode relaxation oscillation with temperature-compensated current sources, the invention achieves frequency stability without the harmful side effects of current-mode operation such as low duty ratio and poor phase noise characteristics. This substitution resolves the contradiction by eliminating the mechanism that causes phase noise while preserving frequency stability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12592684B2Voltage mode relaxation oscillator

Publication Date: 2026.03.31 SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION

AI summary

A voltage mode relaxation oscillator includes a bandgap reference (BGR) circuit configured to generate a BGR voltage that does not depend on temperature and a BGR current that depends on temperature; a control voltage generating circuit configured to generate a control voltage that does not depend on temperature based on the BGR voltage; a reference current generating circuit configured to generate a reference current that does not depend on temperate based on the BGR current; and an oscillator circuit configured to generate a clock signal that does not depend on temperature based on the control voltage and the reference current.