KR19980083511A - Overvoltage elimination circuit of V-Cal head drum motor - Google Patents

Abstract

The present invention relates to an overvoltage elimination circuit of a BC head drum motor. The present invention relates to a drive for applying a driving current to a magnet coil at a position on a fixed printed circuit board opposite to a rotor in which a plurality of magnets of N and S poles are magnetized to a rotating cylinder inner surface. A transistor, an inverter connected to the input terminal of the driving transistor to invert the input signal of the driving transistor, and an output transistor of the inverter and a discharge transistor connected to one end of the magnet coil of the head drum motor to discharge the overvoltage, By connecting the inverter and the switching transistor to both ends of the driving transistor to apply the driving current, the switching is reversed from the driving operation of the driving transistor, thereby eliminating unnecessary overvoltage induced by the application of the driving voltage to the magnet coil. Of driving transistor Thereby preventing damage.

Description

Overvoltage elimination circuit of V-Cal head drum motor

The present invention relates to an overvoltage removing circuit of a BC head drum motor, and in particular, by connecting an inverter and a switching transistor to both ends of a driving transistor applying a driving current to the magnet coil, the magnet coil is switched as opposed to the driving operation of the driving transistor. Since the unnecessary overvoltage induced by the driving voltage is removed in the present invention, the overvoltage elimination circuit of the VR head drum motor prevents damage of the driving transistor due to the overvoltage.

In general, the VLC system has a very small recording dimension of the video signal, a track width of about 0.2-0.02 mm, a recording wavelength of about several microns, and is recorded in the tape width direction. Therefore, it is necessary to stably control the rotation of the head drum motor so as not to change the time axis of the video signal as much as possible during recording. In addition, in order to maintain tracking of the video track, it is necessary to keep the head drum rotation and tape running state (speed and positional relationship) as in recording.

In addition, referring to FIG. 1, the driving circuit of the conventional head drum motor of V-Cal as described above, the plurality of Hall sensors 71A and 71B for detecting the rotational position of the head drum motor 70 of the VC at a predetermined angle. ), Amplifiers 72A and 72B connected to the output terminals of the Hall sensors 71A and 71B to amplify the detected head position detection signal to a predetermined level, and resistors at one end of the amplifiers 72A and 72B. A plurality of driving transistors 74A and 74B are connected to each other via R1 and R2 to apply driving voltages to the magnet coils 73A and 73B of the head drum motor 70.

The drive transistors 74A and 74B are each composed of NPN transistors. In addition, a bias power supply VCC is connected to the collector terminals of the driving transistors 74A and 74B.

On the other hand, referring to the operation of the conventional head drum motor driving circuit having the above configuration, first, when the play mode or the recording mode signal is input to the V-Cal, an arbitrary detection voltage is applied to the hall sensor 71A during the first driving. Is given. Then, the Hall sensor 71A inputs a detection signal according to the head position detection voltage, for example, a high signal to the amplifier 72A, and accordingly the amplifier 72A amplifies the input high signal to a predetermined level. Then, the resistor R1 is input to the base terminal of the living transistor 74A. Then, the driving transistor 74A is driven in accordance with the high signal input to the base end to apply a bias voltage to the magnet coil 73A of the head drum motor 70. Therefore, the magnetic flux is generated in the magnet coil 73A of the head drum motor 70 to attract the magnetic pole of the rotor (not shown), so that the head drum motor 70 rotates by a predetermined rotation angle.

At this time, the Hall sensor 71B of the next phase does not perform the detection operation, and thus the driving transistor 74B of the next phase is not driven.

However, if the head drum motor 70 is rotated in the process, the Hall sensor 71B of the next phase performs the detection operation as opposed to the operation. When the hall sensor 71B executes the detection operation, the amplifier 72B amplifies the input detection voltage to a predetermined level and inputs the resistor R2 to the base terminal of the driving transistor 74B. Then, the driving transistor 74B is driven in accordance with the high signal input to the base end to apply a bias voltage to the magnet coil 73B of the head drum motor 70. Therefore, the magnetic flux is generated in the magnet coil 73A of the next phase to attract the magnetic pole of the rotor (not shown), so that the head drum motor 70 is rotated again by a predetermined rotation angle.

As the above process is repeated, the Hall sensors 71A and 71B sequentially execute the detection operation to sequentially apply driving power to the magnet coils 73A and 73B of the head drum motor 70. 70 is continuously rotated, and accordingly, the head drum (not shown) interlocked with the head drum motor 70 is also rotated. Therefore, the head mounted on the head drum plays back or records information from the video tape.

However, the conventional head drum motor 70 as described above, for example, the driving current is applied to the magnet coil (73A, 73B) by the drive transistors 74A, 74B, respectively, the head drum motor 70 by a predetermined rotation angle When rotating, the magnet coils 73A and 73B generate an overvoltage caused by magnetic energy and remain undischarged. Accordingly, the generated overvoltage generates heat in the magnet coils 73A and 73B, and accordingly, the thermal shut down function of the V-CAL system is operated to unnecessarily eject the tape. The tape is damaged, and the generated overvoltage is reversed in polarity by Faraday's law when the driving transistors 74A and 74B are turned OFF, and thus the driving transistors 74A and 74B are reversed at the next drive. As a result, the driving transistors 73B and 73D are damaged accordingly.

Accordingly, the present invention has been made to solve the above-mentioned disadvantages, by connecting the inverter and the switching transistor to both ends of the drive transistor for applying a drive current to the magnet coil to be switched in reverse to the drive operation of the drive transistor, the magnet coil The purpose of the present invention is to provide an overvoltage elimination circuit of a VAL head drum motor which prevents damage to the driving transistor caused by the overvoltage.

Another object of the present invention is to remove the heat caused by the overvoltage, so the thermal shutter (THERMAL SHUT DOWN) function is normally operated accordingly, thereby preventing the tape from being ejected during the operation of the VAL head drum motor to reduce the damage of the tape An overvoltage elimination circuit is provided.

The present invention for achieving the above object is a drive transistor for applying a drive current to the magnet coil in a position on the fixed printed circuit board facing the rotor in which a plurality of magnets of the N, S poles magnetized to the inner surface of the rotating cylinder, and this drive An inverter connected to the input terminal of the transistor to invert the input signal of the driving transistor, and a discharge transistor connected to the output terminal of the inverter and one end of the magnet coil of the head drum motor to discharge the overvoltage.

1 is an explanatory diagram illustrating a driving circuit of a conventional head drum motor.

2 is an explanatory diagram illustrating a head drum motor of the present invention;

3 is an explanatory diagram for explaining a driving circuit of the present invention head drum motor.

<Explanation of symbols for main parts of drawing>

1: Head drum motor 2A, 2B: Hall sensor

3A, 3B: Amplifier 4A-N: Magnet Coil

5A, 5B: Drive transistor 6A, 6B: Switching transistor

7A, 7B: Offset coil 8: Rotor

9: Stator 10: Head Drum

11: fixed printed circuit board 12: core

13: magnet 14: micom

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

According to the present invention, as shown in Figs. 2 and 3, the Hall sensors 2A and 2B for detecting the rotation of the head drum motor 1 of V-Cal and the detection signals detected by the Hall sensors 2A and 2B are used. Drive transistors for supplying driving current to the amplifiers 3A and 3B for amplifying at a constant level and the magnet coils 4A-N of the head drum motor 1 in accordance with the switching signals amplified by the amplifiers 3A and 3B. (5A, 5B), inverters (6A, 6B) connected to the input terminals of the drive transistors (5A, 5B) to invert the input signals of the drive transistors (5A, 5B), and output terminals of the inverters (6A, 6B). And discharge transistors 7A and 7B connected to one end of the magnet coils 4A and 4B of the head drum motor 1 to discharge the overvoltage.

Here, the head drum motor (1) is largely composed of a rotor (8) and a stator (9), wherein the stator (9) is a magnet coil (coil) on a fixed printed circuit board 11 installed below the head drum (10) 4A-N) is installed in the form of a wound core 12, and a plurality of magnets 13 of N and S poles are magnetized to the inner surface of the rotating cylinder with a predetermined gap in the opposite position of the stator 9. Rotor 8 is installed.

In addition, a bias power supply VCC is connected to the collector terminals of the transistors 5A and 5B.

Here, although the magnet coils 4A-N of the stator 9 have been described only in two phases, they are usually connected in multiple phases, for example, in three phases.

Next, the operation of the present invention having the above configuration will be described.

As shown in FIG. 3, when the play mode or the recording mode signal is input to the VAL, the motor of the present invention recognizes and drives the microcomputer 14, wherein the microcomputer 14 arbitrarily drives the driving transistor 5A. The control signal is applied. Then, when the driving transistor 5A causes a driving current to flow through the magnet coil 4A of the stator 9 of the head drum motor 1, magnetic flux is generated in the magnet coil 4A, and the magnet of the rotor 8 is generated. Since the magnetic pole of (13) is attracted, the rotor 8 rotates by a predetermined rotation angle.

At this time, the Hall sensor 2B of the next phase does not perform a detection operation, and thus the drive transistor 5B of the next phase is not driven.

Here, when a driving current flows through the magnet coil 4A, an overvoltage is generated in the magnet coil 4A by magnetic energy, and when the driving transistor 5A is turned off, the polarity thereof is maintained in a reversed state. When the driving transistor 5A is turned off, the low signal is also input to the input terminal of the inverter 6A. Therefore, the inverter 6A applies a high signal to the base end of the discharge transistor 7A. Then, this discharge transistor 7A is turned on, and accordingly all of the overvoltage currently generated on the magnet coil 4A is discharged through the discharge transistor 7A in which it is turned on.

On the other hand, when the head drum motor 1 is rotated as in the above operation, the Hall sensor 2B in the next phase performs the detection operation in contrast to the above operation. When the hall sensor 2B executes the detection operation, the amplifier 3B amplifies the input detection voltage to a predetermined level and inputs the resistor R2 to the base terminal of the driving transistor 5B. Then, the driving transistor 5B is driven in accordance with the high signal input to the base end, so that the bias voltage VCC is transferred to the magnet coil 4B of the next phase, as opposed to the driving current of the magnet coil 4A. It will flow in the direction. Therefore, magnetic flux is generated in the magnet coil 4B to push the magnet 13 magnetic pole of the rotor 8, so that the rotor 8 rotates again by a predetermined rotational angle.

Here, when a driving current flows through the magnet coil 4B, an overvoltage is generated in the magnet coil 4B by magnetic energy, and when the driving transistor 5B is turned off, the polarity is reversed. When the driving transistor 5B is turned off, the low signal is also input to the input terminal of the inverter 6B, and accordingly, the inverter 6B applies a high signal to the base terminal of the discharge transistor 7B. Then, this discharge transistor 7B is turned on, and accordingly all of the overvoltage currently generated on the magnet coil 4B is discharged through the turned-on discharge transistor 7B.

As the above process is repeated, the Hall sensors 2A and 2B sequentially apply the driving power to the magnet coils 4A and 4B of the head drum motor 1 while performing the detection operation. (1) continues to rotate, and thus the head drum 10, which is interlocked with the head drum motor 1, also rotates. Therefore, the head mounted on the head drum plays back or records information from the video tape.

As described above, the present invention connects the inverter and the switching transistor to both ends of the driving transistor for applying the driving current to the magnet coil so that the switching is reversed to the driving operation of the driving transistor, thereby being induced as the driving voltage is applied to the magnet coil. Since unnecessary overvoltage is eliminated, the damage of the driving transistor by this overvoltage is prevented, as well as the heat due to overvoltage is removed. Accordingly, the thermal shot down function is normally operated. This prevents tape damage.

Claims (1)

A driving transistor for applying a driving current to the magnet coils 4A-N at a position on the fixed printed circuit board 11 opposite to the rotor 8 in which a plurality of magnets 13 of N and S poles are magnetized on the inner surface of the rotating cylinder ( In the driving circuit of V-Cal head drum motor provided with 5A, 5B), Inverters 6A and 6B connected to the input terminals of the drive transistors 5A and 5B to invert the input signals of the drive transistors 5A and 5B, output terminals and head drum motors 1 of the inverters 6A and 6B. And a discharge transistor (7A, 7B) connected to one end of the magnet coil (4A, 4B) to discharge the overvoltage.