Temperature-Compensated Oscillation Circuit for Stable Frequency
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Solution Overview
Problem
Existing oscillation circuits experience significant frequency variations due to power supply voltage and ambient temperature fluctuations, as the oscillation frequency of ring oscillators depends on both factors, making it difficult to stabilize frequency completely by maintaining constant current supply.
Innovation Solution
An oscillation circuit design incorporating a temperature-dependent current source, conjunction circuits with delay functions, and logic gates that generate control voltages based on ambient temperature, allowing for the stabilization of oscillation frequency by adjusting delay times and pulse widths, thereby minimizing frequency variations caused by power supply voltage and temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant current is supplied to the ring oscillator, then the oscillation frequency is stabilized against current variations, but the frequency still varies due to power supply voltage and ambient temperature changes
Solution Approach 1:
The patent implements feedback control by detecting the oscillation frequency and adjusting the control voltage applied to the varactor diodes accordingly. The frequency detection circuit monitors the actual oscillation frequency, and the control voltage adjustment compensates for deviations caused by power supply voltage and temperature variations, thereby maintaining stable oscillation frequency
Solution Approach 2:
The patent changes the capacitance parameter of the resonant circuit by applying control voltage to varactor diodes. This allows dynamic adjustment of the oscillation frequency to compensate for environmental variations. The control voltage modifies the capacitance values in real-time, enabling frequency stabilization despite changes in power supply voltage and temperature
2Measurement precision
If the oscillation frequency is made dependent on ambient temperature for detection purposes, then temperature detection is enabled, but the frequency stability for other applications is compromised
Solution Approach 1:
The patent divides the oscillation circuit into separate functional segments: one oscillation circuit dedicated to frequency-stable signal generation and another oscillation circuit used for temperature detection. This segmentation allows each circuit to optimize its specific function without interfering with the other, enabling both stable frequency operation and accurate temperature measurement
Data Source
AI summary
An output signal ZA of NAND 48a is given to a first input of NAND 48b and is given to a second input of the above NAND 48b, simultaneously through a delay circuit. Furthermore, an output signal ZB of the NAND 48b is given to the first input of NAND 48a and is given to the second input of NAND 48a, simultaneously through a delay circuit. The delay circuit includes a charging and discharging circuit consisting of a NMOS 42 having the conductivity controlled by a voltage VN depending on a temperature signal from a temperature-dependent current source 30 and a capacitor 44, and a NMOS 45 being turned on/off by the voltage of the above capacitor 44. By setting temperature characteristics of the voltage VN and temperature characteristics of the threshold voltage of the NMOS 45 so as to cancel each other, the oscillation frequency variation of the oscillation circuit consisting of astable multi-vibrators can be restrained.