Quartz Oscillation Circuit With Constant-Voltage MOSFET Frequency Trim
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Solution Overview
Problem
Existing timepieces with temperature compensation functions face frequency variations due to fluctuations in power supply voltage, affecting the accuracy of quartz crystal oscillation circuits.
Innovation Solution
An oscillation device with a field-effect transistor configuration that applies constant voltage to the gate and substrate, preventing ON resistance and threshold voltage variations, ensuring a stable charge-discharge rate and oscillation frequency despite power supply fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If control signals from EEPROM or control circuits are used to adjust frequency, then frequency adjustment capability is achieved, but power supply voltage variations cause oscillation frequency variations
Solution Approach 1:
The patent changes the voltage level parameter of control signals from variable (following power supply voltage) to constant (fixed at 0.7V). This is achieved by introducing a constant voltage generation circuit that provides a stable reference voltage level, independent of power supply fluctuations. By controlling the switch with this constant voltage, the ON resistance remains stable, ensuring accurate and reliable frequency adjustment without power supply interference.
2Ease of operation
If MOSFET switches are used for frequency adjustment, then capacitance switching capability is achieved, but voltage variations cause ON resistance variations and frequency drift
Solution Approach 1:
The patent changes the gate voltage parameter of the MOSFET switch from variable to constant. By providing a fixed gate voltage (0.7V) through the constant voltage generation circuit, the ON resistance of the MOSFET becomes stable and predictable. This ensures that the capacitance switching operation is precise and does not introduce frequency errors, maintaining high oscillation frequency precision.
3Device complexity
If control signals vary with power supply voltage, then circuit simplicity is maintained, but charge-discharge rate variations occur
Solution Approach 1:
The patent introduces a constant voltage generation circuit as an intermediary between the power supply and the MOSFET control. This intermediary circuit decouples the control signal voltage from the power supply voltage variations. The constant voltage circuit acts as a buffer that provides stable voltage to the MOSFET gate, ensuring consistent charge-discharge rates of the capacitance regardless of power supply fluctuations.
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 maintains a constant oscillation frequency and accurate temperature compensation, enhancing the timepiece's accuracy and reducing the need for external radio wave reception, allowing for a metal dial and improved user satisfaction.
Implementation Method 1
the field-effect transistor having the connection relationship with the gate of the oscillation inverter of the oscillation circuit, and the field-effect transistor having the connection relationship with the drain thereof are driven with a constant voltage. Therefore, in the field-effect transistor, it is possible to prevent the ON resistance from varying due to the fluctuation in the gate voltage, and it is also possible to prevent the threshold voltage from varying due to the fluctuation in the voltage of the substrate
Implementation Method 2
a timepiece with temperature compensation function for correcting the temperature characteristic of a quartz crystal oscillation circuit for outputting a time reference signal
Data Source
AI summary
An oscillation device includes an oscillation circuit configured including an oscillation inverter, and adapted to oscillate a resonator, a frequency adjustment circuit adapted to perform frequency adjustment of the oscillation circuit, and a constant voltage circuit adapted to drive the oscillation circuit, in the oscillation circuit and the frequency adjustment circuit, a gate and a substrate of a field-effect transistor having a connection relationship with one of a gate and a drain of the oscillation inverter are driven with a constant voltage.