Adaptive-speed/CAV algorithm in a CD-ROM drive to accomplish high data transfer rate and low power consumption

This paper presents an adaptive-speed/CAV algorithm which regulates the disc velocity in a CD-ROM system to accomplish high data throughput (bit rate) during continuous playback and low power consumption during continuous data access. The adaptive-speed profile is based upon quasi-CLV control which allows drive optimisation towards both data throughput and access time. The presented algorithm can automatically distinguish between two operating modes-continuous access and continuous playback. By detecting the state of continuous access, the CD-ROM drive switches its spindle-motor loop into a constant angular velocity (CAV) mode, avoiding therefore the acceleration/braking of the motor, and thus reducing the power consumption. By detecting the state of continuous playback, the spindle motor will be set to follow an adaptive-speed profile which is highly optimized for data transfer rate. The software and hardware implementation of the CAV/quasi-CLV switching technique in a CD-ROM system is also described.