Jukebox Focus Drive Circuit

This thesis which is a project collaborated with a company focuses on the design of driver circuits for voice coil motor (VCM) in CD-ROMs according to the requirement of market. With the rapid development of light memory technology, the capacity of information stored in CD rockets conspicuously, which lead to the compaction of the space between channels. To ensure the laser bean focus on the information channels precisely, the higher requirement on servo system is desirable. The technology lies in the hands of a few famous multinational companies, such as TI, Maxim, ROHM etc. In China, Huayue and Aimtron developed similar products only in recent years. Therefore, it is both academically and economically important to perform research on the circuit. The principle and operation of the focus servo circuit are analyzed in the thesis. The circuit works well with a wide frequency range (more than 30 KHz) and independent phase shift. With a 5-V supply, this circuit achieves a maximum output swing of 4.2V; output offset current of ±6mA and quiescent supply current of 18.15mA. The over-temperature protection, over-current protection, under-voltage protection and Standby function are incorporated. With some discrete device and a sensing resistor in series with the motor, the circuit is capable of driving brushless motor or other inductive load. The principle of motor and VCM in CD-ROMs is first given in the thesis. In addition, a current-mode control driver circuit with little independent phase shift is designed. The thesis is emphasized on second-generation current conveyor (CCII), PI controller and power driving circuit. Considering the inductive load of VCM, compensated circuit is designed for output stage to solve the problem that the current of inductance can't convert simultaneously. Finally, simulations of the whole system...