Crystal Oscillator Pulse Driving for Lower Peak Power

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Solution Overview

Problem

Crystal oscillator circuits require high power due to bias current losses and resistive losses, leading to increased cost and size of supporting circuitry, despite efforts to reduce power consumption through pulse injection methods.

Innovation Solution

An oscillator circuit that partially charges and discharges a resonator using alternating pulse periods, with a buffer circuit to manage voltage and reduce peak current demand, allowing for reduced power consumption and smaller, less costly power supply components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the resonator is fully charged to the input voltage during pulse periods, then the timing accuracy is improved, but the instantaneous power demand increases

Engineering Contradiction:
Improvetiming accuracyVSAvoidinstantaneous power demand
Core Design Contradiction:
Measurement precisionVSPower

Solution Approach 1:

The patent applies partial action by charging the resonator only partially towards the input voltage level during pulse periods, rather than fully charging it. This is achieved through controlled voltage application that provides sufficient charge to maintain resonance and ensure accurate timing, while deliberately limiting the charge level to reduce peak current demand and instantaneous power consumption. The partial charging approach optimizes the trade-off between timing accuracy and power requirements.

Inventive Principle:
Principle #16Partial or excessive action

Solution Approach 2:

The patent changes the voltage parameter dynamically by applying different voltage levels at different times. During pulse periods, the resonator is connected to the input voltage to charge it partially. During non-pulse periods, the resonator is disconnected or connected to a lower voltage level. This time-varying voltage parameter approach allows the system to maintain resonance with reduced instantaneous power demand while preserving timing accuracy.

Inventive Principle:
Principle #35Parameter changes

2Stability of the object's composition

If pulse width is increased to fully charge the resonator, then the resonance stability is improved, but the power consumption increases

Engineering Contradiction:
Improveresonance stabilityVSAvoidpower consumption
Core Design Contradiction:
Stability of the object's compositionVSUse of energy by moving object

Solution Approach 1:

The patent implements periodic action by alternately connecting and disconnecting the resonator from the input voltage in regular pulse periods. This periodic voltage application maintains the resonator's charge at an optimal level for stable resonance while allowing discharge during non-pulse periods, thereby reducing average power consumption. The periodic switching rhythm ensures resonance stability is maintained without requiring continuous full charging.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent applies partial action by providing just sufficient charge during pulse periods to maintain resonance stability, rather than continuously over-charging the resonator. This partial charging approach, repeated periodically, achieves the necessary resonance stability while minimizing excess energy consumption that would occur with continuous full charging.

Inventive Principle:
Principle #16Partial or excessive action

3Stability of the object's composition

If larger capacitors are used to generate the voltage rail, then the power supply stability is improved, but the device size and cost increase

Engineering Contradiction:
Improvepower supply stabilityVSAvoiddevice size
Core Design Contradiction:
Stability of the object's compositionVSVolume of moving object

Solution Approach 1:

The patent maintains continuous useful action on the resonator through periodic pulse charging, ensuring the resonator remains charged at an adequate level throughout operation. This continuous maintenance of resonance charge allows the use of smaller power supply capacitors compared to systems that require continuous full charging, thereby reducing device size while maintaining power supply stability through the sustained periodic energy input.

Inventive Principle:
Principle #20Continuity of useful action

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

The solution achieves accurate timing with reduced power consumption and lower instantaneous power demand, enabling the use of smaller and less expensive power supply components while maintaining the stability and accuracy of crystal oscillators.

Implementation Method 1

maintaining a resonance of the resonator by: connecting the resonator to an input voltage for a first pulse period to charge the resonator only partially towards the input voltage; connecting the resonator to a second, lower, voltage for a second pulse period to discharge the resonator at least partially; and repeating steps a) and b) at a rate corresponding to the resonance of the resonator

Methodology Applied
Scientific EffectResonance: Resonance

Implementation Method 2

A common form of oscillator circuit is a crystal oscillator circuit, which comprises a piezoelectric crystal resonator (usually made of quartz) and a driving amplifier

Methodology Applied
Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentEP4087123A1Oscillator circuits
Publication Date: 2022.11.09 NORDIC SEMICONDUCTOR
  • EP4087123A1 patent drawingFigure 1~2
  • EP4087123A1 patent drawingFigure 3~4
  • EP4087123A1 patent drawingFigure 5~6

AI summary

A method of operating an oscillator circuit (102) comprising a resonator (104) is provided. The method comprises maintaining a resonance of the resonator (104) by a) connecting the resonator (104) to an input voltage (Vbuf) for a first pulse period to charge the resonator (104) only partially towards the input voltage (Vbuf); b) connecting the resonator (104) to a second, lower, voltage (108) for a second pulse period to discharge the resonator (104) at least partially; and repeating steps a) and b) at a rate corresponding to the resonance of the resonator (104) and with a phase corresponding to the resonance of the resonator (104), so as to maintain the resonance of the resonator (104).