Laser Power Control System for Fast Optical Disc Transitions
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Solution Overview
Problem
In optical disc drives, the low bandwidth of feedback control circuits, such as automatic power control (APC) systems, results in slow laser power transitions when switching between read/write states, leading to prolonged settling times.
Innovation Solution
A laser power control system comprising a target circuit, state decision circuit, buffers, and a multiplexer or bandwidth adjuster to quickly adjust the control signal and bandwidth, allowing for faster transitions between operational states by pre-storing control data and dynamically adjusting the bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a feedback control circuit with low bandwidth is used to control laser power, then the system stability is improved, but the transition time between laser power levels increases
Solution Approach 1:
The patent pre-calculates and stores optimal control parameters for different operational states in lookup tables. When a state transition is detected, the system retrieves pre-computed parameters instead of calculating them in real-time, enabling fast transitions while maintaining stability. This preliminary action eliminates the delay inherent in real-time feedback adjustment.
Solution Approach 2:
The patent dynamically switches between different control strategies based on the operational state. During transitions, the system uses a first control strategy with higher bandwidth for fast response, while during steady states, it uses a second control strategy with lower bandwidth for stability. This dynamic adaptation resolves the contradiction between transition speed and stability.
2Speed
If the control effort is increased to reduce transition time, then the transition speed is improved, but the system complexity increases
Solution Approach 1:
The patent segments the operational space into multiple discrete states (e.g., read state, write state, peak power state) and pre-computes optimal control parameters for each state. This segmentation allows the system to handle transitions between states using simple table lookups rather than complex real-time calculations, reducing system complexity while maintaining fast transition speeds.
Solution Approach 2:
The patent introduces an intermediary control mechanism that includes lookup tables and state transition logic. This intermediary layer sits between the operational state detection and the actual laser power control, enabling fast transitions through pre-computed parameters without requiring complex real-time control algorithms, thus reducing overall system complexity.
Data Source
AI summary
A laser power control system and related method for reducing a settling time in a target laser power transition are disclosed. The laser power control system includes a state decision circuit, for generating a state decision signal according to a selected operational state of a target circuit; a plurality of buffers, for storing a plurality of control data corresponding to a plurality of candidate operational states of the target circuit respectively; and a multiplexer, coupled between the state decision circuit and the buffers, for coupling a selected buffer of the buffers and the target circuit according to the state decision signal for outputting a control datum stored in the selected buffer to the target circuit.