JP3128815B2 - Rotation erasure circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation erasure circuit for performing rotation erasure in a helical recording VTR having an editing function.

2. Description of the Related Art Conventionally, in an analog VTR having an editing function, an oscillation and drive circuit for erasing rotation is provided outside a rotary cylinder.

Problems to be Solved by the Invention In the conventional configuration described above, a floating capacitance or a floating reactance of a rotary transformer or a wiring is generated, and in a high-definition VTR or a digital VTR having a wide recording / reproducing signal band, the frequency of the rotation erase current is set outside the recording / reproducing band. Cannot be set. Alternatively, there has been a problem that even if the frequency band can be out of the band, very large power is required for driving.

Therefore, an object of the present invention is to enable rotation erasure with a high-frequency signal outside a reproduction band at low power even in a VTR that records a wideband signal such as a high-vision VTR or a digital VTR.

Means for Solving the Problems To achieve this object, the rotation erasing circuit of the present invention comprises:
An electromagnetic converter disposed on a circuit cylinder for erasing a helical track; an oscillating unit disposed on the rotary cylinder and supplying an erasing current to the electromagnetic converter; Power supply means for supplying power via a ring, and control means for supplying an operation control signal of the oscillating means from outside the rotary cylinder via a slip ring, wherein the output stage of the oscillating means is By constituting a self-excited oscillation circuit that resonates with the reactance component of the electromagnetic conversion means, and by controlling the bias voltage of the oscillation means by the voltage of the control means,
The erasing current is configured to be analog-controlled.

According to the present invention having the above-described configuration, the power supply unit and the control unit supply the power and the control signal to the inside of the rotary cylinder, so that the oscillation unit that supplies the erasing current to the electromagnetic conversion unit is similar to the electromagnetic conversion unit. It can be mounted on a rotating cylinder, and unnecessary floating capacitance and floating reactance generated from the output of the oscillating means to the electromagnetic converting means is extremely reduced, so that the erasing current is efficiently supplied to the rotating erasing means even at a high frequency.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a rotation erasing circuit according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an electromagnetic conversion means block, which is an erasing head with an intermediate tap.
2 is an oscillation means block, comprising transistors Tr1 and Tr2, resistors R1 to R6, and capacitors C1 to C3,
Reference numeral 3 denotes a power supply means block, which includes slip rings S1, S
4 is a control means block, which comprises an operational amplifier OP1 and a slip ring S3.

The operation of the rotation erasing circuit of the present embodiment configured as described above will be described below.

The power applied to the terminal T1 is transmitted by the power supply means 3 through the slip rings S1 and S2 into the rotary cylinder, and is supplied to the oscillation means 2 via the electromagnetic conversion means 1. Here, the capacitor C4 is for noise reduction of the slip ring. During the period in which the rotation erasure is performed, a high level of TTL is added to the terminal T2 as a rotation erasure control signal, and the impedance is converted by the operational amplifier OP1 of the control means 4, and then transmitted to the oscillation means 2 on the rotation cylinder via the slip ring S3. Is done. As a result, in the oscillation means 2, the transistors Tr1, Tr2
The control voltage divided by the bias resistors R3, R4, R5, and R6 is applied to the base of the transistor Tr1, and the transistors Tr1 and Tr2 enter an operating state. When the transistors Tr1 and Tr2 are activated, the capacitors C2 and C3 are connected so as to provide a positive feedback, and the oscillating means 2 enters a resonance state at a resonance frequency of the capacitor C1 and the reactance component of the head H1 of the electromagnetic conversion means. An erase current flows through the head H1. This oscillation circuit operates as a self-excited oscillation circuit including the head H1. Transistor Tr1,
Since the bias of Tr2 is determined by the voltage value of the output of the control means 4, the erase current flowing through the head H1 is controlled in an analog manner by the voltage value of the control means 4. During the period during which rotation erasure is stopped, a TTL low level is applied to terminal T2,
The transistors Tr1 and Tr2 of the oscillating means 2 are turned off and the oscillation stops.

As described above, according to the rotation erasing circuit of the present embodiment, the power supply means 3 and the control means 4 supply the power and the control signal to the inside of the rotary cylinder, so that the electromagnetic conversion means 1
An oscillating means 2 for supplying an erasing current to the rotating cylinder is mounted on the rotary cylinder in the same manner as the electromagnetic converting means 1, and unnecessary floating capacitance and floating reactance generated from the output of the oscillating means 2 to the electromagnetic converting means 1 are extremely small. Thus, the erasing current is efficiently supplied to the rotation erasing means even at a high frequency, so that there is an effect that the rotation erasure can be performed with a high frequency signal outside the reproduction band with low power consumption.

Hereinafter, a second embodiment of the present invention will be described with reference to a circuit diagram of a control unit block of the present embodiment. The purpose of this embodiment is to improve the first embodiment so that the erasing current flowing through the electromagnetic conversion means 1 for erasing the rotation can be controlled from outside the rotary cylinder.

In this embodiment, in order to achieve this object, the output current of the oscillating means 2 of the first embodiment is controlled by an analog quantity by the control means 4, and only the control means block 4 shown in FIG. As shown in FIG. 2, the TTL level control signal applied to the terminal T2 is converted into an analog amount by the volume VR1,
The configuration is such that the impedance is converted by the operational amplifier OP1 and transmitted to the cylinder via the slip ring S3.

The operation of the present embodiment configured as described above will be described below.

In this embodiment, as described above, the control signal of the TTL level applied to the terminal T2 is converted into an analog amount by the volume VR1, then impedance-converted by the operational amplifier OP1, and transmitted into the cylinder via the slip ring S3. On the other hand, the control signal transmitted in this manner is supplied to the bases of the transistors Tr1 and Tr2 by the oscillating means 2 with the bias resistors R3, R4, R5 and R6.
The current supplied to the electromagnetic converter 1 for rotation erasure is controlled by an analog amount by controlling the bias voltage of the oscillating unit 2 in an analog manner with the volume VR1 of the control unit 4. I have.

According to the rotation erasing circuit of the present embodiment configured as described above, the erasing current supplied to the electromagnetic erasing means 1 for erasing the rotation can be controlled in an analog amount by a volume outside the rotary cylinder. In addition to the effect similar to that of the first embodiment in that rotation consumption can be performed by a high-frequency signal outside the reproduction band with power consumption, there is an effect that the rotation removal current can be easily set from outside the rotation cylinder.

Hereinafter, a third embodiment of the present invention will be described. An object of the present embodiment is to provide a rotation erasure circuit capable of controlling a rotation erasure current from outside the rotation cylinder by an analog amount while reducing transmission channels between the inside and outside of the rotation cylinder.

In order to achieve the above object, a rotation erasing circuit according to the present embodiment is provided with an electromagnetic conversion means for erasing a helical track on a rotary cylinder and an oscillation for supplying an erasing current to the electromagnetic conversion means. Means 2 and a power supply means 3 for supplying electric power to the oscillating means 2 from outside the rotary cylinder via a slip ring, and the oscillating means 2 resonates with a reactance component of the electromagnetic conversion means 1. The excitation oscillation circuit has a configuration in which the power is supplied through a resistor, and the output current of the oscillation unit 2 is controlled by a voltage supplied through the power supply unit 3.

Hereinafter, the operation of the configuration of the present embodiment will be described with reference to FIG. 3 which is a circuit diagram thereof.

At the time of the rotation erasing operation, the control signal of the TTL high-level rotation erasing current applied to the power supply means 3 from the terminal T3 is converted into an analog amount by the volume VR1, and impedance-converted by the operational amplifier OP1, and the slip rings S1 and S2 are converted. The electric power is supplied to the oscillating means 2 in the cylinder through the electric power. In the oscillating means 2, the output voltage of the power supply means 3 divided by the bias resistors R3, R4, R5, R6 is applied to the bases of the transistors Tr1 and Tr2, and the collector current corresponding to the base voltage flows through the transistors Tr1 and Tr2. It becomes an operation state. Transistor Tr
1, when Tr2 is in the operating state, the capacitors C2 and C3 are connected so as to provide a positive feedback, and the oscillating means 2 is connected to the capacitor C1.
The head H1 of the electromagnetic conversion means 1 is oscillated at a resonance frequency by the reactance component of the head H1, and an erasing current corresponding to the output voltage of the power supply means 3 flows through the head H1 of the electromagnetic conversion means 1. During the period during which the rotation erasure is stopped, the TTL low level is applied to the terminal T3, and the transistors Tr1 and Tr2 of the oscillating means are turned off to stop the oscillation.

Note that the capacitor C5 is for noise suppression, and the resistors R1 and R2 are emitter resistors for stabilizing the emitter current.

As described above, according to the present embodiment, the output voltage of the power supply unit is controlled in addition to the effect similar to that of the first embodiment in that rotation erasure can be performed by a high-frequency signal outside the reproduction band with low power consumption. Thus, there is an effect that the rotation erasing current can be easily set from outside the rotation cylinder without increasing the number of transmission channels between the inside and outside of the rotation cylinder.

Hereinafter, a fourth embodiment of the present invention will be described. An object of the present embodiment is to provide a rotation erasing circuit capable of supplying an erasing current of a stable value to a rotating erasing head even with respect to variations in head and stray capacitance.

In order to achieve the above object, the rotation elimination circuit according to the present embodiment provides a resistance component to the output impedance of the oscillating means 2 according to the third embodiment, and performs damping of a resonance circuit formed by the reactance component of the electromagnetic conversion means 1. The oscillation means 2 and the electromagnetic conversion means 1 are as shown in FIG.

Hereinafter, the operation will be described with reference to FIG. The resistances R7 and R8 of the oscillating means 2 are each a transistor TR
A collector resistor that supplies current to 1 and TR2, and a resistor R3
R6 is for base bias, resistors R1 and R2 are emitter resistors for current feedback, capacitors C2 and C3 are for positive feedback, and capacitor C1 is the reactance component of head H2 of electromagnetic conversion means 1. For resonating, terminal
When a voltage is applied from T4, the oscillating means 2 starts oscillating. Here, the output impedance of the oscillating means 2 is the capacitor C1
In addition, the resistors R7 and R8 are included, and the resonance circuit between the capacitor C1 and the erase head H2 is damped by the resistors R7 and R8, and the variation and fluctuation of the rotation erase current due to the variation of the erase head H2 and the stray capacitance are reduced. You. At the same time, the change of the erasing current with respect to the voltage supplied from the power supply unit 3 to the oscillation unit 2 becomes stable.

In the present embodiment, the third embodiment of the present invention is also implemented. However, the same can be applied to the first and second embodiments, and the output impedance is simply given a resistance component.
The circuit can be stabilized by damping the resonance.

As described above, according to the present embodiment, the first and second output impedances of the oscillating means 2 are simply given a resistance component.
Further, there is an effect that the rotation erasing circuit of the third embodiment can be further stabilized.

As described above, according to the present invention, the oscillating means for supplying an erasing current to the electromagnetic conversion means by supplying power and a control signal into the rotating cylinder by the power supply means and the control means, In the same way as above, it can be mounted on a rotating cylinder, the unnecessary floating amount and floating reactance generated from the output of the oscillating means to the electromagnetic converting means is extremely reduced, and the erasing current is efficiently supplied to the rotating erasing means even at high frequency,
Even in a VTR that records a wideband signal such as a high-definition VTR or a digital VTR, there is an effect that a rotation erasure circuit using a high-frequency signal outside the reproduction band can be easily configured with low power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a configuration of a rotation erasing circuit according to a first embodiment of the present invention, and FIG. 2 is an internal configuration of a control means block of the rotation erasing circuit according to the second embodiment. Showing a circuit diagram,
FIG. 3 is a circuit diagram showing a configuration of a rotation erasing circuit in a third embodiment of the present invention, and FIG. 4 is a circuit diagram showing a configuration of a rotation erasing circuit in a fourth embodiment of the present invention. 1 ... Electromagnetic conversion means, 2 ... Oscillation means, 3 ... Power supply means, 4 ... Control means, S1 to S3 ... Slip ring, Tr
1, Tr2: Transistor, R1 to R8: Resistor, C1 to C5:
Capacitors, H1, H2 ... Erase head, T1 to T4 ... Terminals.

Claims (3)

(57) [Claims] An electromagnetic converter disposed on a rotary cylinder for erasing a helical track; an oscillator disposed on the rotary cylinder for supplying an erasing current to the electromagnetic converter; Power supply means for supplying power from outside the cylinder via a slip ring, and control means for supplying an operation control signal for the oscillation means from outside the rotary cylinder via a slip ring, The output stage of the means constitutes a self-excited oscillation circuit which resonates with a reactance component of the electromagnetic conversion means, and the bias voltage of the oscillation means is controlled by the voltage of the control means, so that the erase current is analog-controlled. And the rotation elimination circuit. 2. An electromagnetic conversion means disposed on a rotary cylinder for erasing a helical track; an oscillating means disposed on the rotary cylinder for supplying an erasing current to the electromagnetic conversion means; Power supply means for supplying electric power from outside the cylinder via a slip ring, and control means for supplying an operation control signal for the oscillation means from outside the rotary cylinder, wherein the oscillation means performs the electromagnetic conversion. A self-excited oscillation circuit that resonates with the reactance component of the means is configured to be supplied with power through a resistor, and the output current of the oscillation means is controlled by a voltage supplied through the power supply means. Rotation erasure circuit. 3. The rotation erasure circuit according to claim 1, wherein the output impedance of the oscillating means has a resistance component, and the resonance circuit constituted by the reactance component of the electromagnetic conversion means is damped.