PLL VCO Delay Compensation for Power Supply Variation
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Solution Overview
Problem
In phase-locked loops, power supply voltage variations cause mismatched charging and discharging currents, leading to signal skew due to the lack of adjustment in the control voltage for the voltage-controlled oscillator.
Innovation Solution
A voltage-controlled oscillator with a delay time control unit that adjusts the oscillation signal's delay by varying capacitance in response to power supply voltage changes, ensuring equal magnitudes of charging and discharging currents through a voltage divider and field effect transistors, and a frequency compensation capacitor, thereby maintaining a stable VCO control signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control voltage for the VCO is kept constant when power supply voltage changes, then the VCO operates at a fixed frequency, but signal skew is generated between input and feedback signals due to mismatched charging and discharging currents
Solution Approach 1:
The patent changes the control voltage parameter dynamically in response to power supply voltage variations. When the power supply voltage changes, the control voltage for the VCO is adjusted accordingly to maintain balanced charging and discharging currents, preventing signal skew while adapting to different operating conditions
Solution Approach 2:
The patent implements a feedback mechanism where the control voltage is continuously monitored and adjusted based on power supply voltage changes. The system detects power supply variations and automatically modifies the control voltage to maintain current balance, creating a closed-loop control system that eliminates signal skew
2Reliability
If the charging and discharging currents are made equal in magnitude, then signal skew is minimized, but additional control mechanisms are required to adjust the control voltage with power supply changes
Solution Approach 1:
The patent applies preliminary action by adjusting the control voltage in advance before power supply voltage changes cause current imbalance. The delay time control unit proactively modifies the control voltage based on predicted or detected power supply variations, preventing signal skew before it occurs
Solution Approach 2:
The patent introduces a delay time control unit as an intermediary component between the power supply and the VCO. This intermediary adjusts the control voltage to compensate for power supply variations, mediating the relationship between power supply changes and VCO operation to maintain current balance
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 solution minimizes signal skew in phase-locked loops by ensuring equal charging and discharging currents, even with changes in power supply voltage, thereby maintaining accurate locking and reducing signal mismatch.
Implementation Method 1
the delay time control unit adjusts the delay of the oscillation signal by adjusting at least one capacitance between the oscillation unit and a reference node in response to the change of the power supply voltage
Implementation Method 2
A respective one of the transistors and a respective one of the capacitors are coupled in series between the oscillation unit and the reference node, and the switch control voltage is applied at gates of the transistors
Data Source
AI summary
A voltage-controlled oscillator (VCO) according to an aspect of the present invention includes an oscillation unit and a delay time control unit. The oscillation unit generates an oscillation signal with a frequency determined by a VCO control signal. The delay time control unit adjusts a delay of the oscillation signal in response to a change of a power supply voltage. Such a VCO is advantageously used for minimizing signal skew in a phase-locked loop (PLL).