# US 8,570,696 B2 · Protection circuit for hard disk > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,570,696 B2 - Document ID: US8570696B2 - Status: Granted - Kind: B2 - Application number: 13/314,286 - Filed: 2011-12-08 - Published: 2013-04-25 - Granted: 2013-10-29 - Earliest claimed: 2011-10-25 - Assignees: HON FU JIN PRECISION INDUSTRY (ShenZhen) CO., LTD.; Hon Hai Precision Industry Co., Ltd. - Applicants: Wei-Dong Cong; Guo-Yi Chen - Inventors: Wei-Dong Cong; Guo-Yi Chen - Web page: https://patentgrep.com/patent/US8570696B2 ## CPC - G06F 21/80: in storage media based on magnetic or optical technology, e.g. disks with sectors (preventing unauthorised reproduction or copying of disc-type recordable media G11B20/00) - G06F 21/81: by operating on the power supply, e.g. enabling or disabling power-on, sleep or resume operations - G11B 19/02: Control of operating function, e.g. switching from recording to reproducing - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A protection circuit includes a switch circuit, a sample circuit, a comparison circuit, and a relay circuit. The switch circuit is connected between a hard disk power supply and a hard disk to control whether to output power from the hard disk power supply to the hard disk. The sample circuit samples the voltage being supplied to the hard disk, the comparison circuit receives the sampled voltage, compares the sampled voltage to a reference voltage, and controls the switch circuit to be turned on or off accordingly. The relay circuit is connected between a system power supply and an enable terminal of the comparison circuit. The relay circuit outputs a high level signal to turn on the switch circuit when the system power supply is being supplied and the hard disk power supply is not being supplied to the hard disk. ## Claims ### Claim 1 A protection circuit for hard disks, the protection circuit comprising: a switch circuit connected between a hard disk power supply and a hard disk to control whether to output power from the hard disk power supply to the hard disk; a sample circuit to sample a voltage being supplied to the hard disk; a comparison circuit to receive the sampled voltage, compare the sampled voltage to a reference voltage, and control the switch circuit to be turned on or off accordingly; and a relay circuit connected between a system power supply and an enable terminal of the comparison circuit, wherein the relay circuit outputs a high level signal to turn on the switch circuit when the system power supply is supplying power and the hard disk power supply is not supplying power. ### Claim 2 (depends on 1) The protection circuit of claim 1, wherein the switch circuit comprises a first electronic switch and a second electronic switch, the hard disk power supply comprises a first power supply connected to a first terminal of the first electronic switch and a second power supply connected to a first terminal of the second electronic switch, second terminals of the first and second electronic switches are connected to the hard disk, control terminals of the first and second electronic switches are connected to the comparison circuit. ### Claim 3 (depends on 2) The protection circuit of claim 2, wherein the sample circuit comprises first to fourth resistors, a first terminal of the first resistor is connected to the second terminal of the first electronic switch, a second terminal of the first resistor is grounded through the second resistor, a node between the first and second resistors is connected to the comparison circuit, a first terminal of the third resistor is connected to the second terminal of the second electronic switch, a second terminal of the third resistor is grounded through the fourth resistor, a node between the third and fourth resistors is connected to the comparison circuit. ### Claim 4 (depends on 3) The protection circuit of claim 3, wherein the comparison circuit comprises first and second comparators, a three-state buffer, a positive input of the first comparator is connected to the node between the first and second resistors, a positive input of the second comparator is connected to the node between the third and fourth resistors, negative inputs of the first and second comparators are connected to receive the reference voltage, outputs of the first and second comparators are connected to an input of the three-state buffer, an output of the three-state buffer is connected to the control terminals of the first and second electronic switches, the output of the three-state buffer is further connected to the system power supply, an enable terminal of the three-state buffer is connected to the relay circuit. ### Claim 5 (depends on 4) The protection circuit of claim 4, wherein the reference voltage is provided by the system power supply divided by fifth and sixth resistors, the system power supply is grounded through the fifth and sixth resistors, the negative inputs of the first and second comparators are connected to a node between the fifth and sixth resistors. ### Claim 6 (depends on 4) The protection circuit of claim 4, wherein the relay circuit comprises a seventh resistor and a capacitor, the system power supply is connected to the enable terminal of the three-state buffer through the seventh resistor, the enable terminal of the three-state buffer is further grounded through the capacitor. ### Claim 7 (depends on 1) The protection circuit of claim 1, wherein the first electronic switch is a field effect transistor, a drain of the field effect transistor is the first terminal of the first electronic switch, a source of the field effect transistor is the second terminal of the first electronic switch, a gate of the field effect transistor is the control terminal of the first electronic switch. ### Claim 8 (depends on 1) The protection circuit of claim 1, wherein the second electronic switch is a field effect transistor, a drain of the field effect transistor is the first terminal of the second electronic switch, a source of the field effect transistor is the second terminal of the second electronic switch, a gate of the field effect transistor is the control terminal of the second electronic switch.