JP2785512B2 - Crosstalk prevention device for rotary transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for preventing crosstalk between channels of a rotary transformer of a helical scan type cylinder used for a video tape recorder or the like.

[0002]

2. Description of the Related Art In recent years, helical scan type cylinders used in video tape recorders and the like are equipped with an increasing number of heads, and crosstalk between channels in the rotary transformer becomes a problem. A crosstalk prevention device is attached to each channel. It became so.

[0003] A conventional crosstalk prevention device will be described below. FIG. 3 is a configuration diagram of a conventional crosstalk prevention device. 1 is a head, 2 is a winding of a rotary transformer,
Reference numeral 3 denotes a transistor, 5 denotes a head amplifier, 6 denotes a capacitor, 7 denotes a control pulse, 8 denotes a reproduction output terminal, and 9 denotes a low-pass filter (hereinafter, LPF). As shown in FIG. 3, one of the windings of the rotary transformer is grounded, the other end is connected to the collector of the transistor, and the head amplifier 5 is connected via the capacitor 6. The crosstalk prevention device includes a control pulse 7, an LPF 9, and a transistor 3 to which the control pulse 7 is applied to the base through the LPF 9 and the emitter is grounded.

[0004] The operation of the crosstalk prevention device having the above components will be described below. When the control pulse 7 shown in FIG. 4A is input, the waveform is smoothed as shown in FIG. 3B through the LPF 9 and applied to the base of the transistor 3. As a result, the transistor 3 is turned on, both ends of the rotary transformer are grounded, and crosstalk is prevented.

[0005]

However, in the above conventional configuration, the transistor is turned on as shown in FIG.
A spike noise is likely to occur at the timing of turning on / off (t1, t2 in FIG. 4).
If the cut-off frequency of F is lowered, there is a disadvantage that the responsiveness of the system deteriorates.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a crosstalk preventing device which prevents generation of spike noise and is suitable for a semiconductor integrated circuit having a quick response.

[0007]

In order to achieve the above object, the present invention provides a transistor having a collector and an emitter connected between both ends of a rotary transformer winding, and a transistor connected to a base of the transistor to form a control pulse signal. It has the structure provided with the means.

Further , the shaping means has a structure for changing the transient characteristics of the control pulse signal.

[0009]

According to the present invention, the control pulse waveform is changed at a relatively slow speed only when the transistor is turned off (or turned on) by the above-described configuration, and the control pulse waveform is changed so as to change quickly after the transition of the operation state of the transistor. Prevents the occurrence of mustache.

[0010]

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

FIG. 1 is a block diagram showing a crosstalk preventing apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a head, 2 is a winding of a rotary transformer, 3 is a transistor, 4 is an interface circuit (shaping means) for blunting pulses with a plurality of time constants, 5 is a head amplifier,
6 is a capacitor, 7 is a control pulse, and 8 is a reproduction output terminal. One end of the winding 2 of the rotary transformer is grounded, the other end is connected to the collector of the transistor 3, and the input end of the head amplifier 5 is connected via the capacitor 6 . Crosstalk prevention device is an interface circuit
An emitter to which a control pulse 7 is applied to the base through 4
The transistor 3 of the ground, and is configured or <br/> et an interface circuit 4.

FIG. 2 is a configuration diagram of an interface circuit of the crosstalk prevention device according to one embodiment of the present invention. In FIG. 2, 10 is a control pulse input terminal, 11 is a control pulse output terminal, 12 is an inverter, 13 and 14 are switches, and 15, 16, and 17 are current sources (currents J17≪J15,
J16), 18 are comparators, 19 is a capacitor, 2
0 is a reference voltage source, 21 is a voltage-current converter, and 22 is impedance. When the control pulse 7 is t as shown in FIG.
When it rises at 1, the switch 13 is turned on and the switch 14 is turned off in FIG.
This potential is applied to the transistor 3 by the voltage / current converter 21.
Becomes the base current for turning on. Next, at timing t in FIG.
When the control pulse 7 falls at 2, the switch 13 turns off, and the switch 14 remains off when the potential of the capacitor 19 is higher than the reference voltage source 20 by the comparator 18. Therefore, electric charges are discharged from the capacitor 19 by the current source 17 with a long time constant.

When the potential of the capacitor 19 becomes smaller than the reference voltage source 20 at time t3 in FIG. 4, the switch 14 is turned on, and the capacitor 19 is discharged with a short time constant by the current source 16 (t3 → t4). As a result, a current waveform as shown in FIG. 4D is output from the voltage-current converter 21.
The transistor 3 is turned off.

As described above, according to the present embodiment, the base current of the transistor 3 gradually decreases at the time of the transition of the operation state of the transistor, the generation of the whiskers is suppressed, and the others are switched to short time constants. Responsivity (t4-t2) <
(T5−t2) can be secured.

In this embodiment, both ends of the rotary transformer are grounded to prevent crosstalk. However, both ends may be short-circuited by a transistor. The same applies to an npn transistor, a pnp transistor, and other switch elements.

In this embodiment, the time constant is switched between two types when the transistor is turned on → off. However, if necessary, the same can be applied when the transistor is turned off → on, and the rise and fall of the transistor base current can be freely set. Can be done.

[0017]

As is apparent from the above embodiment, according to the present invention, the rotary transformer is connected between both ends of the winding.
With a transistor and its base connected to multiple time constants
By providing the shaping means for deforming the control pulse, it is possible to provide a crosstalk prevention device which prevents spike noise and has a quick response and is suitable for a semiconductor integrated circuit.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a crosstalk prevention device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an interface circuit of the crosstalk prevention device according to one embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional crosstalk prevention device.

FIG. 4 is a transistor control waveform diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 Rotary transformer winding 3 Transistor 4 Interface circuit 7 Control pulse 10 Control pulse input terminal 11 Control pulse output terminal 12 Inverter 13, 14 Switch 15, 16, 17 Current source 18 Comparator 19 Capacitor 20 Reference voltage source 21 Voltage-current converter

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 5/02 H04N 5/782

Claims (1)

(57) [Claims] 1. A transistor having a collector and an emitter connected between both ends of a rotary transformer winding , and a control pulse which is connected to a base of said transistor and has a plurality of time constants.
An apparatus for preventing crosstalk of a rotary transformer, comprising: means for shaping .