RC Relaxation Oscillator Frequency Control With Periodic Voltage Sampling
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Solution Overview
Problem
Traditional relaxation oscillators are power-hungry due to the use of continuous comparators and current sources with high quiescent current, making them unsuitable for low-power applications.
Innovation Solution
A relaxation oscillator design that employs a resistor-capacitor (RC) circuit for charging and discharging operations, a sampling circuit to transfer voltage differences to an integration capacitor, and a controllable oscillator to generate an output clock, eliminating the need for a power-hungry continuous comparator and high quiescent current source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a continuous comparator and current source are used in the relaxation oscillator, then the output clock frequency can be controlled, but the power consumption increases significantly
Solution Approach 1:
The patent replaces the continuous comparator with a periodic sampling mechanism that operates at discrete intervals. The sampling circuit captures voltage differences at specific moments during RC charging/discharging cycles, converting continuous monitoring into periodic measurements. This dramatically reduces power consumption while maintaining frequency control through accumulated sampling results that guide oscillator adjustments.
Solution Approach 2:
The patent substitutes the traditional electronic continuous comparator system with a hybrid approach combining RC circuitry, sampling switches, and digital accumulation logic. Instead of continuous analog comparison, the system uses periodic voltage sampling followed by digital processing to determine frequency adjustments, reducing continuous power-hungry analog operations.
2Measurement precision
If the RC circuit operates at high frequency to maintain precise timing, then the output clock accuracy improves, but the power consumption increases
Solution Approach 1:
The RC circuit operates in periodic charging and discharging phases rather than continuous high-frequency switching. The sampling circuit captures voltage information at strategic moments during these phases, allowing accurate timing measurement without requiring the RC circuit to operate continuously at maximum frequency, thus reducing average power consumption.
Solution Approach 2:
The system performs preliminary voltage sampling and accumulation during RC charging/discharging phases before generating the final frequency control decision. This preliminary action allows the RC circuit to operate at lower frequencies while still gathering sufficient timing information for accurate clock generation.
3Use of energy by stationary object
If a sampling circuit is introduced to reduce power consumption, then the quiescent current decreases, but the circuit complexity increases
Solution Approach 1:
The sampling circuit is integrated with the existing RC charging/discharging structure, combining voltage sampling, holding, and accumulation functions into a unified circuit architecture. The sampling switches share nodes with the RC circuit, and the accumulation logic reuses control signals, merging multiple functions into a compact design that minimizes additional complexity.
Solution Approach 2:
The sampling circuit components serve multiple functions: the sampling switches simultaneously perform voltage capture and circuit phase transitions, the holding capacitor stores both voltage sampling results and timing information, and the accumulation logic processes both amplitude and timing data for comprehensive frequency control.
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 design achieves an ultra-low power consumption by reducing the operational frequency of the RC circuit and sampling circuit, allowing for efficient power management and precise control of the output clock frequency without deviating from the target frequency.
Implementation Method 1
a resistor-capacitor (RC) circuit, arranged to perform an RC charging operation to set a first voltage, perform an RC discharging operation to set a second voltage
Data Source
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AI summary
A relaxation oscillator includes a resistor-capacitor (RC) circuit, an integration capacitor, a sampling circuit, and a controllable oscillator. The RC circuit performs an RC charging operation to set a first voltage, performs an RC discharging operation to set a second voltage, and performs a reset operation to reset the first voltage to a first reference voltage and reset the second voltage to a second reference voltage. The sampling circuit performs a charge delivery operation to sample a voltage difference between the first voltage and the second voltage, and transfers the voltage difference to the integration capacitor. The controllable oscillator generates an output clock in response to a control input provided by the integration capacitor.