Importance

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Abstract

An overvoltage and surge protection circuit for a hard disk drive is provided. The overvoltage and surge protection circuit is intended for protecting an interior circuit part from a surge voltage caused by an overvoltage generated due to wrong insertion of first and second power supply voltages, and an external condition, in a hard disk drive which receive the first power supply voltage as an operational voltage of an interior circuit device and the second power supply voltage as a device driving voltage. The overvoltage and surge protection circuit includes an overvoltage protection circuit having a first and second power supply input terminals for receiving the first and second power supply voltages, respectively, and a surge protection circuit. The overvoltage protection circuit lowers the level of the second power supply voltage below the level of the first power supply voltage, using the first power supply voltage applied through the second power supply input termninal, and applies the lowered second power supply voltage to a load of the interior circuit device, when the second power supply voltage is applied through the first power supply input terminal. The surge protection circuit lowered the surge voltage to a constant voltage below the first power supply voltage, and applied the constant voltage to the load of the interior circuit device, when the surge voltage is applied through the first power supply input terminal and the overvoltage protection circuit.

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First Claim