Oscillation Circuit Resistor Ratio for Zero Temperature Drift

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Solution Overview

Problem

Existing oscillation circuits face challenges in maintaining frequency accuracy due to temperature drift, especially when passive components have the same temperature direction, making it difficult to achieve zero temperature drift.

Innovation Solution

The proposed oscillation circuit architecture includes a current mirror circuit, a charging and discharging circuit, an output stage circuit, and specifically uses two resistors with the same directional temperature drifts, where the first resistor has a greater resistance than the second resistor, and their resistance drifts are designed to compensate for temperature variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If resistors with different temperature drift directions are used in series, then zero temperature drift can be achieved, but this approach is not available in advanced processes where all resistors have positive temperature drifts

Engineering Contradiction:

Improvefrequency accuracyVSAvoidavailability of passive components with different temperature drifts

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the parameter of resistance ratio between two resistors with the same temperature drift direction. By setting R1/R2 = (1+α)/(1-α) where α is the temperature drift coefficient, the temperature variations are compensated mathematically, achieving zero temperature drift without requiring resistors with opposite drift directions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Instead of using resistors with opposite temperature drift directions (conventional approach), the patent inverts the approach by using two resistors with the same temperature drift direction but different resistance values in a specific ratio, achieving the opposite effect of temperature compensation

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If passive components are used in oscillation circuits, then the circuit can generate oscillation signals, but the frequency accuracy is limited by temperature drift of these passive components

Engineering Contradiction:

Improvefrequency stabilityVSAvoidtemperature drift effect

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a feedback mechanism where the voltage across the capacitor is fed back to control the charging/discharging current. This feedback loop automatically adjusts the charging/discharging rates to compensate for temperature-induced frequency drift, maintaining stable oscillation frequency

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent converts the harmful effect of temperature drift into a beneficial self-regulation mechanism. The temperature-induced changes in resistor values are transformed into corresponding changes in charging/discharging currents that automatically compensate for frequency drift, turning the harmful thermal effect into a frequency-stabilizing mechanism

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution effectively reduces the impact of temperature variations on frequency accuracy, potentially achieving zero temperature drift, thereby enhancing the stability and accuracy of the oscillation circuit and the overall circuit system.

Implementation Method 1

The first resistor and the second resistor have same directional temperature drifts, a first resistance of the first resistor is greater than a second resistance of the second resistor, and a first resistance drift of the first resistor with a temperature variation is smaller than a second resistance drift of the second resistor with the temperature variation

Methodology Applied

Scientific EffectTemperature drift compensation:

Data Source

PatentUS12308795B2Oscillation circuit and circuit system using the same

Publication Date: 2025.05.20 NUVOTON

AI summary

An oscillation circuit includes: a current mirror circuit outputting a reference current; a charging and discharging circuit charging a first charge storage element by using one of the reference currents or discharging the first charge storage element, to generate a first control voltage; an output stage circuit including a first switch transistor controlled by the first control voltage to output a first oscillation signal; a first resistor; a second resistor; and a diode circuit. The first resistor and the second resistor have same directional temperature drifts, a first resistance of the first resistor is greater than a second resistance of the second resistor, and a first resistance drift of the first resistor with a temperature variation is smaller than a second resistance drift of the second resistor with the temperature variation, such that the effect of the temperature variation on a frequency accuracy is reduced.