Ring VCO Delay Cells With Sub-Threshold Control Boosting
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Solution Overview
Problem
Conventional voltage controlled oscillators (VCOs) require a significant voltage input to initiate oscillation, resulting in a silent region where the oscillation frequency is zero, limiting their functionality, especially in low power supply operations.
Innovation Solution
A voltage controlled oscillator design incorporating a control signal adjuster and ring-connected delay cells, where the control signal adjuster boosts a low first control signal to generate a second control signal, enabling oscillation even when the input voltage is below the transistor threshold, using two sets of current generation transistors to maintain oscillation signal frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional VCO circuits use a voltage input to control oscillation frequency, then the oscillation frequency can be adjusted, but a silent region occurs when the voltage input is below the transistor threshold voltage, resulting in zero oscillation frequency
Solution Approach 1:
The patent introduces a control signal adjuster as an intermediary component between the voltage input and the delay cells. This adjuster includes a first transistor that amplifies the control voltage when it is below the threshold voltage, and a second transistor that passes through the control voltage when it is above the threshold voltage. This intermediary structure ensures reliable oscillation initiation across the full voltage range without silent regions.
Solution Approach 2:
The patent changes the operating parameters of the control signal adjuster transistors based on the input voltage level. When the control voltage is below the threshold, the first transistor amplifies it to reach the required level. When the control voltage is above the threshold, the second transistor passes it through unchanged. This dynamic parameter adjustment eliminates the silent region and extends the adaptable voltage range.
2Use of energy by moving object
If the voltage input is kept low to reduce power consumption, then energy efficiency improves, but the VCO cannot initiate oscillation due to being below the transistor threshold voltage
Solution Approach 1:
The control signal adjuster acts as an intermediary that conditionally amplifies the control voltage. When the input voltage is low (below threshold), the first transistor amplifies it to enable oscillation initiation. When the input voltage is already sufficient (above threshold), the second transistor passes it through unchanged. This allows the VCO to operate at low voltages for power efficiency while maintaining the capability to initiate oscillation through selective amplification.
3Adaptability or versatility
If the control signal adjuster amplifies low control voltages to enable oscillation, then the operating voltage range is extended, but the circuit complexity increases due to additional transistors and control logic
Solution Approach 1:
The control signal adjuster is segmented into two distinct transistor paths: a first transistor for amplifying low control voltages and a second transistor for passing through high control voltages. This segmentation allows each transistor to be optimized for its specific function, simplifying the overall design while achieving extended voltage control range. The segmented approach avoids the need for complex amplification circuits that would operate across the entire voltage range.
Solution Approach 2:
The control signal adjuster dynamically switches between two operating modes based on the input voltage level. When the control voltage is below the threshold, the first transistor is activated for amplification. When the control voltage is above the threshold, the second transistor is activated for direct transmission. This dynamic switching simplifies the circuit structure compared to a static complex amplification circuit, as each transistor operates in a well-defined mode.
Data Source
AI summary
A voltage controlled oscillator including a control signal adjuster and ring-connected delay cells is disclosed. The control signal adjuster receives a first control signal to generate a second control signal boosted from the first control signal when the first control signal is lower than a transistor threshold voltage. The ring-connected delay cells are controlled by the first and second control signals both to generate an oscillation signal. Each of the delay cells has a first set of current generation transistors and a second set of current generation transistors. Each transistor of the first set of current generation transistors has a control terminal receiving the first control signal while each transistor of the second set of current generation transistors has a control terminal receiving the second control signal. The first and second sets of current generation transistors collectively output an oscillation signal with unchanged frequency of associated input signal.