JPS61184704A - Power supply circuit of magnetic recorder - Google Patents

Abstract

PURPOSE:To fuse the fuse and to cut off immediately a current supply path even in case an electronic parts forming the current supply path has a short trouble, an earth trouble, etc. to flow a current larger than the allowable limit to a magnetic head, by putting a fuse into the current supply path of the magnetic head. CONSTITUTION:Electrolytic capacitors 13 and 14 for stabilization of voltage are provided between input terminals 11a and 11b as well as between input terminals 12a and 12b respectively. The plus (+) side terminal 12a of 12V is connected to the emitter of a pnp transistor TR 18 which give the ON/OFF control to the head drive current I supplied to a magnetic head 17 via and in series to a fuse 15 and a choke coil 16. In case a current limiting resistor 21 has a short-circuit or a short-circuit occurs among collectors and emitters of TRs 18, 22 and 23 by soem reason in a power supply circuit, a head drive current I higher than an allowable limit level IM flows to a W/R coil 26 of the head 17. In such a case, the fuse 15 is immediately fused.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a Winchester-type magnetic recording device that is supplied with power to drive each component in addition to data and various commands from a host device. In particular, the present invention relates to a power supply circuit for a magnetic recording device in which a fuse is inserted in a current supply path of a magnetic head in order to prevent damage to the magnetic head.

[Prior Art] Among information processing systems that use computers and the like to perform various information processing, there are systems in which power for driving each component of each terminal device is supplied from a host device. As shown in FIG. 2, such an information processing system includes a host device 1 composed of a computer or the like, and a magnetic recording device 2. Keyboard device 3. CR7 display device 4. Each terminal such as the printing device 5 has a data line 6. They are connected via a power supply line 7. In addition, the host device 1 is supplied with an AC power of, for example, 5V, from an external AC power supply 8.
A power supply circuit 9 for converting to a stable DC power supply such as 12V is built-in.

Each terminal does not have a power supply circuit, and when the power of the host device 1 is turned on, the power supply circuit 9 of the host device 1
A DC power of 5V, 12V, etc. is supplied from the power supply line 7 through each power supply line 7. Each terminal uses the supplied DC power to drive each component. For example, in the case of the magnetic recording device 2, each motor such as a spindle motor that rotates a magnetic disk as a magnetic recording medium and a carriage motor that moves a carriage on which a magnetic head is mounted uses the supplied 5V and 12V DC power. At the same time, the R/W (I-containing continuous) coil of the magnetic head is energized. As soon as the prescribed power is supplied to each component,
Data is written to and read from the magnetic disk in response to a write/read command sent from the host device 1 via the data line 6.

[Problems to be Solved by the Invention] However, the magnetic recording device 2 in which power is supplied from the host device to drive each component as described above has the following problems. That is, the magnetic recording device 2
Since the is not equipped with a power circuit, it is not equipped with safety devices such as fuses and breakers that are normally built into the power circuit to detect abnormal voltage occurrence, short circuit accidents, grounding accidents, etc. and interrupt the circuit. . Therefore, in the event that each component electronic component in the magnetic recording device 2 is short-circuited, or the (+) and (-) side wires of the supplied 12V or 5V are short-circuited, the power supply circuit 9 of the host device 1 In addition, there is a risk that each electronic component on the magnetic recording device 2 side may be damaged.

In particular, in the magnetic recording device [2], the magnetic head drive current flowing through the W/R coil of the magnetic head is limited to about 100 to 150 mA by using the 12V DC power supply supplied from the host device 1 using a choke coil, current limiting resistor, etc. It is being reduced. Then, it is supplied to the magnetic head via a transistor or the like that is controlled to be turned on or off by a write command from the host device 1. Therefore, if the current limiting resistor is short-circuited or the transistor is short-circuited, there is a risk that a current exceeding the allowable limit will flow through the W/R coil and cause the W/R coil to burn out. When the magnetic head burns out, a head crash phenomenon occurs in which the magnetic head comes into close contact with the recording surface of the magnetic disk.
There is a risk of damaging not only the magnetic head but also the magnetic disk on which important information is recorded.

The present invention has been made based on the above circumstances, and its object is to insert a fuse into the current supply path of a magnetic head so that even if each electronic component constituting the current supply path is Even if a short circuit accident, grounding accident, etc. occurs and a current exceeding the permissible limit attempts to flow through the magnetic head,
It is an object of the present invention to provide a power supply circuit for a magnetic recording device that can immediately cut off a current supply path when a fuse blows, protect electronic components such as a magnetic head, and improve the reliability of the entire device.

[Means for Solving the Problems] A power supply circuit of a magnetic recording device of the present invention is configured to drive each component including a magnetic head using power supplied from a host device via a power supply line. In this magnetic recording device, a fuse is inserted in a current supply path that supplies a head drive current from a power supply line to a magnetic head.

In another invention, in addition to the above invention, an indicator light is provided to indicate that the fuse has blown.

[Function] In the power supply circuit of the magnetic recording device configured in this way, a short circuit accident, a grounding accident, etc. may occur in each electronic component that constitutes the power supply path, and the head drive current to the magnetic head may exceed the allowable limit. As soon as this occurs, the fuse blows and the current supply path is cut off.

In another invention, in addition to the above effects, when a fuse is blown, an indicator light indicates that the fuse has been blown.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing the power supply circuit of the magnetic recording device of the embodiment, and 11a and 11b in the figure are (+) sub-input terminals of the 5V DC power supply to which the power supply line 7 from the host device 1 is connected. and (-) sub-input terminal. Also, 12a,
12b is also 1 from host device 1! The (+) sub-input terminal of the 12V DC power supply to which the power supply line 7 is connected and (
−) This is a sub-input terminal. Electrolytic capacitors 13 and 14 for voltage stabilization are inserted between the input terminals 118 and 111) and between the input terminals 12a and 12b, respectively.

A 12V (+) sub-input terminal 12a is connected to the emitter of a pnp transistor 18 that controls on/off the head drive current I flowing to the magnetic head 17 via a fuse 15 and a choke coil 16 in series. In addition, between the choke coil 16 side end of the fuse 15 and the ground, there is a current limiting resistor 19 and a light emitting diode (L) as an indicator light.
A series circuit with ED) 20 is inserted.

Note that the current value at which the fuse 15 blows is set to the permissible limit value IM of the head drive current I flowing through the magnetic head.

The collector of the transistor 18 is connected via a current limiting resistor 21 to the emitter of each pnp type transistor 22, 23 which is controlled to turn on or off by write data, and the collector of each transistor 22, 23 is connected to a diode 24, respectively. W/R of the magnetic head 17 through .25
It is connected to both ends of the coil 26. The intermediate terminal of this W/R coil 26 is grounded.

On the other hand, the WE input terminal 27 to which the data line 6 to which the write enable signal WE from the host device 1 is transmitted is connected is connected to the base of the transistor 28.
The collector of is connected to the base of the transistor 18 via a resistor 29. The emitter of the transistor 28 is grounded via a diode 30, and the base is connected via a resistor 31 to the (+) sub-input terminal 11a of the transistor 28. Further, a resistor 32 is inserted between the base and ground. Furthermore, a resistor 33 is also connected between the emitter and base of the transistor 18.

The WG input terminal 34 to which the data line 6 to which the write gate signal WG from the host device 1 is transmitted is connected is connected to a set of D-type flip-flops 35 (
A pair of data input terminals 36a and 36b connected to the data line 6 to which the write data WD from the host device 1 is transmitted are connected to each input terminal of the line receiver 37. has been done. and,
The output terminal of this line receiver 37 is connected to the T input terminal of the flip-flop 35.
The output terminal of 5 is connected to the D input terminal. Also,
The Q output terminal and output terminal of this flip-flop 35 are connected to a buffer 38.39 and a resistor 40.41, respectively.
are connected to the respective bases of the aforementioned transistors 22 and 23 via the transistors 22 and 23.

Note that the collector of the transistor 18 and each transistor 2
A series circuit of resistors 42 and 43 and a series circuit of resistors 42 and 44 are inserted between the base of the resistor 2.23 and the base of the resistor 2.23.

Although not shown, there is also a 5V input terminal 11a.

11b and 12V input terminals 12a and 12b are a spindle motor that rotates a magnetic disk, and a magnetic head 17.
It is also connected to a carriage motor that controls the movement of the carriage carrying the .

In the power supply circuit of the magnetic recording device configured as described above, when the power supply circuit 9 on the host device 1 side is turned on, the input terminal 11 of the magnetic recording device is connected via the power supply line 7.
5V and 12V DC power are supplied to input terminals 12a and 12b, respectively. When 12V DC power is supplied to input terminal 12a, fuse 1
5. Since the driving current flows through the light emitting diode 20 via the resistor 19, the light emitting diode 20 lights up. Therefore, the operator of this magnetic recording device can confirm that power is being supplied normally.

Next, when the host device 1 starts normal operation and loads data into this magnetic recording device, it first sends H to the WE input terminal 27 of the magnetic recording device via the data line 6.
A level write enable signal WE is sent. WE input terminal 2
When the H-level write enable signal WE is input to the transistor 7, the transistor 28 becomes conductive. When the transistor 28 conducts, the 12V (+) input terminal 12a is connected to the fuse 15° choke coil 16. Resistance 33, 29. Current flows between the collector and emitter of transistor 28 and through diode 30. As a result, the base potential of the transistor 18, which controls energization to the magnetic head 17, decreases and the transistor 18 becomes conductive.

Next, an H-level write gate signal WG is sent to the WG input terminal 34 via the data line 6, and write data WD is sent to the data input terminals 36a and 36b. Then, the set (S) terminal and reset (1'7) terminal of the flip 70 knob 35 become H level, and the write data W
D is amplified by the line receiver 37 and transferred to the flip-flop 3.
It is input to the king input terminal of No.5. As a result, write data signals having mutually opposite signal levels are output from the Q and C output terminals of the flip-flop 35, and each transistor 22 and 23 responds to the input write data WD with this write data signal. It is controlled to turn on and off. It should be noted that since the prospective data signals applied to the bases of the transistors 22, 23 have opposite signal levels, the transistors 22, 23 are not turned on or off at the same time.

Therefore, the head drive current I supplied from the (+)fill input terminal 12a through the transistor 18 and the current limiting resistor 21 is supplied to the magnetic head 17 through one of the transistors 22 and 23. /R flows to the coil 26 and is discharged to ground via the intermediate terminal.

Thus, data corresponding to the input write data WD is written onto the recording surface of the magnetic disk.

In the power supply circuit of such a magnetic recording device, if the current limiting resistor 21 is short-circuited due to a factor such as a river, or if the collectors and emitters of the transistors 18, 22, and 23 are short-circuited, the magnetic W/R coil 2 of head 17
6, a head drive current I exceeding the allowable limit of 1M flows. W
/R Coil 26 has a head drive current I exceeding the permissible limit of 1M.
As soon as the current flows, the fuse 15 inserted in the current supply path of the magnetic head 17 melts. Therefore, the head drive current I flowing through the W/R coil 26 of the magnetic head 17
is cut off, so burning out of the W/R coil 26 due to excessive current can be prevented.

Furthermore, head crash phenomena due to burnout of the magnetic head 17 can be prevented, and spread of failures to other components such as the magnetic disk can be minimized.

Furthermore, by blowing the fuse 15, the power supply circuit 9 of the host device 1 can also be protected.

Furthermore, when the fuse 15 blows, the light emitting diode 20
Since the N flow supply is also cut off, the light emitting diode 20 goes out, and the operator of this magnetic recording device can confirm that some abnormal phenomenon has occurred in the power supply circuit. Therefore, it is possible to prevent the continued operation of writing and reading data to and from a magnetic disk using a magnetic recording device that is still out of order. In addition, inspection and repair can be performed by immediately shutting off the power to the information processing system and disconnecting the magnetic recording device from the system.

[Effects of the Invention] As described above, according to the present invention, a fuse that blows when the head drive current exceeds the allowable limit is inserted in the current supply path of the magnetic head. Therefore, even if a short circuit or grounding accident occurs in each of the electronic components that make up the current supply path, and a current that exceeds the allowable limit attempts to flow to the magnetic head, the current supply path is immediately cut off by the fuse blowing, and the magnetic head The reliability of the entire magnetic recording device can be improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a power supply circuit of a magnetic recording device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the entire information processing system. 1... host device, 2... magnetic recording device, 6...
Data line, 7...Power supply line, 11a, 11b,
12a, 12b... Input terminal, 13.14... Electrolytic capacitor, 15... Fuse, 16... Choke coil, 17... Magnetic head, 18.22, 23.2
8... Transistor, 20... Light emitting diode (indicator light), 21... Current limiting resistor, 26... W/R
Coil, 35...Flip-flop, 36a, 36b
...Data input terminal.

Claims (2)

[Claims] (1) It is connected to a host device via a data line and a power supply line, and drives each component including the magnetic head using power supplied from the host device via the power line, and the host device In a magnetic recording device, the magnetic head writes and reads data to and from a magnetic recording medium based on a command sent from the magnetic head via the data line, in which a head drive current is supplied from the power supply line to the magnetic head. A power supply circuit for a magnetic recording device, characterized in that a fuse is inserted in a current supply path. (2) It is connected to a host device via a data line and a power supply line, and drives each component including the magnetic head using power supplied from the host device via the power line, and the host device In a magnetic recording device, the magnetic head writes and reads data to and from a magnetic recording medium based on a command sent from the magnetic head via the data line, in which a head drive current is supplied from the power supply line to the magnetic head. A power supply circuit for a magnetic recording device, characterized in that a fuse is inserted in a current supply path, and an indicator light is provided to indicate that the fuse has blown.