PLL Charge Injection Circuit for Faster Phase Locking
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Solution Overview
Problem
Phase-locked loops face challenges in achieving fast locking due to constraints such as stability, dynamic response, precision, and noise, leading to longer phase lock times and increased delay in the feedback loop.
Innovation Solution
A control signal pulse width extraction-based phase-locked acceleration circuit is introduced, incorporating a pulse width extraction control circuit and a current injection switch module, which injects charges into the low pass filter step-by-step based on the phase relationship between the reference and feedback clock signals, synchronizing phases and reducing phase-locked time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional phase-locked loop structure is used, then stability and noise filtering are maintained, but phase lock time is long and feedback loop delay is increased
Solution Approach 1:
The patent applies preliminary action by injecting compensation charges into the low pass filter before the phase locking process completes. The charge pump circuit proactively adds charges to counteract the anticipated voltage drop caused by feedback loop delay, allowing the phase lock to occur faster without compromising stability. This is achieved by monitoring the phase difference and pre-adjusting the control voltage to compensate for expected delays.
Solution Approach 2:
The patent implements preliminary anti-action by introducing a compensation mechanism that counteracts the harmful effect of feedback loop delay. The charge pump circuit generates compensation charges that oppose the voltage drop that would normally occur due to loop delay, effectively neutralizing its impact before it can degrade performance. This allows the system to maintain stability while reducing phase lock time.
2Loss of time
If feedback loop delay is reduced for faster locking, then phase lock time decreases, but stability and precision are compromised
Solution Approach 1:
The patent introduces compensation charges as an intermediary element between the phase frequency detector and the voltage-controlled oscillator. These compensation charges mediate the relationship by adjusting the control voltage to account for feedback loop delays, allowing the system to maintain precise phase detection despite reduced loop delay. The intermediary compensation mechanism enables faster locking without sacrificing precision.
3Speed
If voltage control is increased to accelerate phase locking, then phase lock speed improves, but voltage overshoot occurs affecting stability
Solution Approach 1:
The patent applies partial action by injecting compensation charges only during the phase locking transient period, rather than continuously. The charge pump circuit adds charges proportionally to the phase difference and time remaining, providing just enough acceleration without excessive voltage increase. This partial action approach enables faster locking while preventing voltage overshoot that would compromise stability.
Data Source
AI summary
Disclosed are a control signal pulse width extraction-based phase-locked acceleration circuit and a phase-locked loop system, the phase-lock acceleration circuit includes a pulse width extraction control circuit and a current injection switch module; the control output terminal of the pulse width extraction control circuit is connected to the current injection control terminal of the current injection switch module, and the stepping current control terminal of the current injection switch module and the driving input terminal of the pulse width extraction control circuit are both connected to the preset control signal output end of a phase frequency detector for use in controlling, according to pulse width changes of signals outputted by the preset control signal output end, the current injection switch module to inject charges until the phases of a reference clock signal and feedback clock signal inputted by the phase frequency detector are synchronized.