JPS622745Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a drive circuit for a plunger used for switching operations in a tape recorder.

High-grade tape recorders called cassette decks generally use the suction action of a plunger to switch between playback, recording, fast forward, rewind, and pause operations. The plunger is
Although a large current is required at the start of suction, the holding current after suction ends is extremely small compared to when suction is started. Utilizing the characteristics of such a plunger, a general plunger drive circuit is constructed of a driving transistor that is conductive only when suction starts, and a holding transistor that supplies a holding current after suction ends. Further, the plunger control circuit in a tape recorder outputs a control signal to drive each plunger in response to various operations such as playback, fast forwarding, rewinding, etc., and this control circuit is implemented as an IC (integrated circuit). When switching each operation, it is necessary to consider the timing of the start of suction between each plunger and the return operation to the non-suction state, and generally a time constant circuit or the like is installed between the output terminal of the control circuit and the drive circuit of the plunger. has been established.

The present invention seeks to provide a simple circuit for delaying the return of the plunger to the non-suction state for a predetermined period of time, and will be described in detail below with reference to the drawings. The illustrated circuit is one embodiment of the plunger drive circuit of the present invention. In the figure, 1 is a control circuit that outputs control signals in response to various operations such as recording, playback, fast forwarding, rewinding, and pausing.
A first output terminal 2 that outputs an H (height) level signal during a playback operation and also outputs an L (low) level signal for each pause operation, and a second output terminal that outputs an H level signal during a pause operation. It includes at least an output terminal 3. 4 is a playback plunger that slides and displaces the slide board on which the magnetic head is attached to the playback operation position by suction action, and presses the pinch roller against the capstan;
Reference numeral 5 denotes a first driving transistor which is turned on when the regeneration plunger 4 starts suction to supply a driving current to the plunger 4, and has a collector connected to the plunger 4 and an emitter grounded. A first differential circuit 6 is connected to the base circuit of the first driving transistor 5, and is composed of a capacitor 7 and a resistor 8. Reference numeral 9 denotes a first transistor which is turned on at the same time as the first driving transistor 5 and which causes a holding current to flow through the regeneration plunger 4 after the suction operation is completed.
A holding transistor whose collector connects to the regeneration plunger 4 via a current limiting resistor 10.
and the emitter is grounded. The input terminal of the first differentiating circuit 6 and the first
The base of the holding transistor 9 is connected to the cathode of a backflow prevention diode 11, and the anode of the diode 11 is connected to the first output terminal 2 of the control circuit 1. Reference numeral 12 denotes a temporary stop plunger which applies a brake to the reel shaft by suction operation and holds the slide board at a temporary stop position slightly retreated from the regeneration operation position when the regeneration plunger 4 returns to the non-suction operation state.
Reference numeral 13 denotes a second driving transistor which is turned on when the temporary stopping plunger 12 starts to attract and causes a driving current to flow through the plunger 12, and has a collector connected to the plunger 12 and an emitter grounded. A second differential circuit 14 is connected to the base circuit of the second driving transistor 13, and is composed of a capacitor 15 and a resistor 16. Reference numeral 17 denotes a second holding transistor which is turned on at the same time as the second driving transistor 13 and causes a holding current to flow through the temporary stop plunger 12 after the suction operation is completed, and whose collector is connected to the current limiting resistor 18. It is connected to the temporary stop plunger 12 and its emitter is grounded. The input terminal of the second differentiating circuit 14 and the base of the second holding transistor 17 are connected to the second output terminal 3 of the control circuit 1.

The present invention is constructed as described above, and the operation of this circuit will now be explained. In the stopped state, L level signals are output to both the first output terminal 2 and the second output terminal 3 of the control circuit 1, and the regeneration plunger 4 and the pause plunger 12
is in a non-aspiration state. In such a stopped state,
When the user performs a playback operation, an H level signal is output from the first output terminal 2 of the control circuit 1. The first
The H level signal outputted to the output terminal 2 is applied to the base of the first driving transistor 5 and the first holding transistor 9 via the backflow prevention diode 11 and the first differentiating circuit 6. As a result, the first driving transistor 5
The differentiated output of the differentiating circuit 6 brings it into a conductive state for a short time, causing the regeneration plunger 4 to perform a suction operation together with the first holding transistor 9. The reproducing plunger 4 displaces the slide substrate to the reproducing operation position by the suction operation of the reproducing plunger 4, thereby configuring the reproducing operation of the tape recorder. held in state.

The reproducing operation is configured as described above. Next, a case will be described in which a pause operation is performed during the reproducing operation state. If the user performs a pause operation during the playback operation state, control circuit 1
The H level signal outputted to the first output terminal 2 of is inverted to L level, and at the same time, the H level signal is outputted to the second output terminal 3. When an H level signal is output to the second output terminal 3, the H level signal is applied to the base of the second driving transistor 13 and the second holding transistor 17 through the second differentiating circuit 14. Ru. As a result, the second driving transistor 13 becomes a second differential circuit.
14 becomes conductive for a short time, causing the temporary stop plunger 12 to perform a suction operation together with the second holding transistor 17. The suction operation of the temporary stop plunger 12 applies a brake to the reel shaft, and the slide board is held at the temporary stop position, which is slightly retreated from the reproducing operation position. As described above, the second
When an H level signal is output to the output terminal 3, the temporary stop plunger 12 is immediately attracted.
The operation accompanying the inversion of the output signal output to the first output terminal 2 of the control circuit 1 from the H level to the L level will be described. When the output of the first output terminal 2 is reversed from the H level to the L level, the regeneration plunger 4, which had been held in the suction operation state by the first holding transistor 9, is returned to the non-suction state; The operation is delayed for a predetermined period of time. That is, even if the output of the first output terminal 2 is inverted to L level, the backflow prevention diode 11 is connected between the first output terminal 2 and the first differentiating circuit 6 , so that the first differentiating circuit 6 is not discharged through the control circuit 1, but is discharged through the resistor 19 connected to the base circuit of the first holding transistor 9. During this period, a bias current is supplied to the base of the first holding transistor 9, and the first holding transistor 9 is maintained in a conductive state. Then, when the charge stored in the capacitor 7 is discharged, the first holding transistor 9 is reversed to a non-conducting state, and the regeneration plunger 4 is brought into a non-suction state. When the user performs a pause operation while in the regeneration operation state as described above, the pause plunger 12 performs a suction operation, and after applying a brake to the reed shaft, the regeneration plunger 4 returns to the non-suction operation state with a delay. A suspended state is configured. When the pause state is released, an H level signal is output to the first output terminal 2, and the output from the second output terminal 3 becomes L level. As a result, the charge stored in the capacitor 15 constituting the second differentiating circuit 14 is immediately discharged through the control circuit 1, so that the temporary stop plunger 12 is immediately returned to the non-suction state, and at the same time, the regeneration plunger 4 is activated. The tape recorder enters the suction state and returns to the playback state.

In this embodiment, the case where the present invention is applied to a drive circuit of a plunger that switches between playback operation and pause operation in a tape recorder has been described.
Not only can it be used as a drive circuit for a plunger used for switching between fast forwarding and rewinding, but it can also be used as a drive circuit for a plunger used in devices other than tape recorders.

As explained above, the present invention effectively utilizes the charge stored in the capacitor that constitutes the differential circuit by providing a diode to prevent backflow, thereby delaying the return of the plunger to the non-suction operating state. This has the advantage that there is no need to provide a special time constant circuit, and the circuit configuration can be simplified.

[Brief explanation of the drawing]

The illustrated circuit is one embodiment of the plunger circuit of the present invention. Explanation of main figure numbers, 1... Control circuit, 4... Regeneration plunger, 5... First driving transistor, 6 ... First differential circuit, 9... First holding transistor, 11... Backflow Prevention diode, 1
2... Temporary stop plunger, 13... Second drive transistor, 14 ... Second differential circuit, 1
7...Second holding transistor.

Claims (1)

[Scope of utility model registration request] a driving transistor that is conductive only when the plunger starts suction and supplies a driving current to the plunger; a holding transistor that is conductive at the same time as the driving transistor and supplies a holding current to the plunger after a suction operation; a differentiating circuit connected to the base circuit of the driving transistor and comprising a capacitor and a resistor so as to make the transistor conductive only when suction starts; and a control circuit supplying a control signal to the bases of the driving transistor and the holding transistor. , comprising a backflow prevention diode connected between the control circuit and the bases of the differentiation circuit and the holding transistor, and when the control signal from the control circuit disappears, the discharge current of the capacitor constituting the differentiation circuit causes the A plunger drive circuit characterized in that a holding transistor is made conductive for a predetermined period of time.