| 摘要 |
PURPOSE: A head return circuit of a hard disk drive is provided to automatically change to a constant voltage mode from a constant current mode at the moment when a counter electromotive force of a voice coil motor becomes '0' or the first bouncing starts to occur, thereby magnifying the size of an initial constant current to prevent a head return failure. CONSTITUTION: An SPM(Spindle Motor)(2100) rotates a disk. A rectifier(2200) rectifies a current generated by a counter electromotive force, and outputs the current. A cathode terminal of a diode(D4) is connected to an output of the rectifier, and an anode terminal thereof is connected to a supply voltage(Vcc). A capacitor(C1) is connected between the cathode terminal and a ground. A collector terminal of a transistor(Q1) is connected to the cathode terminal. A constant current source(Icrt) is connected between the cathode terminal and an emitter terminal of the transistor. One end of a VCM(Voice Coil Motor)(2300) is connected to the emitter terminal. A VCM driver(2400) is connected between the emitter terminal and the other terminal of the VCM. A collector terminal of a transistor(Q2) is connected to the other terminal of the VCM, and is grounded with the emitter terminal. A resistor(R1) is connected between a base terminal of the transistor(Q1) and the ground. A resistor(Riret) is connected between the resistor(R1) and the cathode terminal. A switch(2600) receives a head return signal(Retract), a temperature rising signal(TSD), a power on reset signal(POR), and controls current streams. One terminal of a capacitor(C2) is grounded. A constant current source(Icret) is connected between the other terminal of the capacitor(C2) and an output terminal of the switch. A noninverting terminal of an operation amplifier(2500) is connected to the other terminal of the capacitor(C2), and an inverting terminal is connected to a reference voltage(Vref1), then an output terminal is connected to the base terminal.
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