JPH0633545Y2 - Power supply circuit for reel break in video tape recorder - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention is intended to prevent the slack of a tape generated when a magnetic tape is stopped in a video tape recorder (VTR) using an AC power input series regulator. The present invention relates to a reel brake power supply circuit used in.

(Prior Art) A slack of the tape occurs when the running of the magnetic tape is stopped. Conventionally, the reel is braked to eliminate this slack. The driving method of this brake has different circuit configurations for AC power input and DC power input. Fig. 2 shows the stationary type, that is, AC power input type.
FIG. 3 is a circuit diagram showing a driving method of a brake used in a VTR, and FIG. 3 is a circuit diagram showing a driving method of a brake in a portable type, that is, a DC power input type VTR.

In FIG. 2, the AC power supply is stepped down by the transformer 20, then full-wave rectified, and further smoothed by the capacitor 21 to form the transistor Q ₂₀ and the integrated circuit 22 for the regulator.
It is converted into a constant level DC voltage through a series regulator composed of. This DC voltage is supplied to the control system circuit (not shown) and the solenoid L
₂₀ and switching transistor Q ₂₁ . This is the base of the Torasujisuta Q ₂₁ signals to turn ON / OFF the brake of the reels is input to release the brake, type "H" level signal to the base of the Torasujisuta Q _21, the Torasujisuta Q ₂₁ ON to solenoid L
Apply current to ₂₀ . This current produces an electromagnetic force in the solenoid L ₂₀ , pulling the brake to release it. On the other hand, when stopping the running of the tape, since the "L" level signal to the base of the Torasujisuta Q ₂₁ is the input transistor Q ₂₀ is turned OFF. For this reason, no current flows through the solenoid L _20, and the brake is returned by the force of a spring (not shown) or the like to brake the reel.

On the other hand, the portable power supply shown in FIG. 3 is provided with a power failure detection circuit constituted by the comparator 30. The output of the comparator 30 and the signal for returning the brake are the diodes D ₃₀ , D _31.
ON by turning on the transistors Q ₃₁ and Q ₃₂ for supplying the drive current to the brake recovery solenoid L _30.
It is controlled OFF. Also, in this type of power circuit,
The solenoid L ₃₁ for brake suction is driven by a circuit system that balances with the drive system of the solenoid L _30. This solenoid L ₃₁ operates when a brake suction command signal is input to the transistors Q ₃₂ , Q _33. It is designed to generate electromagnetic force.

On the other hand, at the time of power failure, the stationary type shown in FIG. 2 is not supplied with the current of the solenoid L ₂₀ , so the brake is applied, and the portable type shown in FIG. 3 turns on the transistor Q ₃₀ by the output of the comparator 30, A current flows through the solenoid L ₃₀ via the capacitor _4, and the brake is restored for this purpose.

(Problems to be solved by the invention) However, in a stationary power supply circuit, there is a problem that power consumption increases because it is necessary to keep current flowing to the solenoid when the brake is removed. Also,
In the portable type power supply circuit, in order to drive the comparator 30 and the solenoid L ₃₀ , the first charging circuit including the diode D ₄ and the capacitor C ₄ and the diode D ₅
It is necessary to provide a backup circuit for the second charging circuit consisting of the capacitor C ₅ and the capacitor C ₅ .

On the other hand, in the case of the stationary type, the power consumption may be reduced even in the VTR, and the mechanical part may be shared between the stationary type and the portable type.In these cases, even in the stationary type, the brake is controlled by the portable pulse type. It is necessary to use the one that requires the power failure detection circuit and the backup circuit.

(Means for Solving Problems) In the reel brake power supply circuit of the video tape recorder of the present invention, the voltage of the AC power supply stepped down by the transformer is rectified and smoothed by the rectifier circuit and the smoothing capacitor, and the transistor for the regulator is used. Is converted into a DC voltage of a certain level through a series regulator consisting of a regulator and an integrated circuit for a regulator, and is supplied to a brake recovery solenoid for applying a brake and a brake suction solenoid for removing the brake. Applied to a video tape recorder, the cathode side of two diodes, the anode side of which is connected to both ends of the secondary coil of the transformer, is connected to the input side of the series regulator via two transistors connected in cascade. While connected to the smoothing capacitor The output side of the capacitor is connected to the base of a transistor connected to the input side of the series regulator via a resistor, and the connection point is connected to the brake recovery solenoid via a diode and two switching transistors, and an AC When the power supply is constantly input, the output of the series regulator is supplied to the brake recovery solenoid and the brake suction solenoid as an operating power supply,
When the AC power is not input, the two switching transistors are turned on by the charge accumulated in the smoothing capacitor via the resistor and the diode, and the charge accumulated in the smoothing capacitor is turned on. However, via the transistor for the regulator turned on by the transistor connected to the input side of the series regulator is turned on,
It is supplied to the brake returning solenoid as an operating power source.

(Operation) When AC power is constantly input, the front side of the two transistors connected in cascade is turned on and the second stage is turned on via the two diodes respectively connected to both ends of the secondary coil of the transformer. The side turns off. Therefore, the input side of the regulator integrated circuit is not grounded, and the series regulator operates normally. That is, the output of the series regulator is supplied to the brake recovery solenoid and the brake suction solenoid as operating power.

On the other hand, when the AC power is not input, the charge accumulated in the smoothing capacitor is given to the two switching transistors via the resistor and the diode, so that the two switching transistors are turned on. Also, at this time, the charge accumulated in the smoothing capacitor is supplied to the base of the rear stage of the two transistors connected in cascade via the resistor, so that the transistor of the rear stage is turned on, which allows the regulator transistor to be turned on. The transistor is turned on. Therefore, the electric charge accumulated in the smoothing capacitor is supplied to the brake recovery solenoid as an operating power source through the on-state regulator transistor.

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

FIG. 1 shows a power supply circuit for a reel brake in a video tape recorder according to the present invention.

In Fig. 1, when AC power is supplied, 4
After stabilizing the rectified voltage rectified by the full-wave rectifying element 1 consisting of two rectifying diodes and the smoothing capacitor C ₁ with a series regulator composed of the combination of the transistor Q ₁ and the integrated circuit 2 for regulator, the solenoid for brake recovery L _1, supplies power to the brake suction solenoid L _2, and supplies power to the other circuitry.
These solenoids L ₁ and L ₂ are driven by two pairs of balanced transistors Q ₄ , Q ₅ and Q ₆ , Q ₇ , respectively.
The pair of transistors Q ₄ and Q ₅ that contribute to one operation send a current to the brake recovery solenoid L ₁ in response to a brake recovery command from a system controller (not shown), and the pair of transistors that contribute to the other operation. Transistors Q ₆ and Q ₇ of the same also receive a brake suction command from the system controller and flow a brake suction current.

On the other hand, the anode side of the diodes D ₅ and D ₆ is connected to both ends of the secondary coil of the transformer, and the cathode side is
It is connected to the base of the switching transistor Q ₂ via the resistor R ₁ . The collector of the switching transistor Q ₂ is, has its emitter connected to the base of the switching transistor Q ₃ which are commonly connected, the collector of the switching transistor Q ₃ is connected to the input side of the regulator for integrated circuits 2 There is. The output side of the smoothing capacitor C ₁ is connected to the collector of the switching transistor Q ₂ via the resistor R ₁ , and its connection point a is connected to the base of the switching transistor Q ₄ and the switching transistor Q ₅ via the diode D ₇ . It is connected to the emitter.

In the above configuration, when the AC power is input, the base current is supplied to the switching transistor Q ₂ from the diodes D ₅ and D ₆ , so this transistor
Since Q ₂ and the transistor Q ₃ which are connected in cascade is OFF, the input side grounded without series regulator regulator integrated circuit 2 is operated stationary. When an instruction to release the brake from the system controller when such steady state, "H" level signal is input to the base of Torasujisuta Q _7, Torasujisuta Q ₇ and Q ₆
Is turned on, and current flows through the brake suction solenoid L ₂ to release the brake. On the other hand, when the brake is applied, a signal of “H” level is input from the system controller to the base of the transistor Q ₄ and the transistor Q ₅
Also, Q ₄ turns on, current flows to the brake recovery solenoid L _1, and the brake is applied.

On the other hand, when AC power is not input due to power failure,
Since the base current of the transistor Q ₂ flowing from the diodes D ₅ and D ₆ disappears, the transistor Q ₂ turns off. Therefore, the charge accumulated in the smoothing capacitor C ₁ is
It is discharged in the closed loop circuit through R ₁ , diode D ₇ , and transistors Q ₄ and Q ₅ . At this time, the transistor Q ₃ turns on.
Since it is, and the series regulator for Torasujisuta Q ₁ is completely turned ON, the charges accumulated in the smoothing capacitor C ₁ is Torasujisuta Q _1, brake condensate appointed solenoid L _1, flows through the Torasujisuta Q ₅ , Brake is applied because current is passed to the brake recovery solenoid L ₁ . At this time, since the transistor Q ₁ is completely turned on, there is little loss, and the accumulated charge can be efficiently supplied to the brake recovery solenoid L ₁ . Also trussista
Q ₃ is an element necessary to prevent the loss of the transistor Q ₁ due to the operation of the regulator integrated circuit 2 and to sufficiently drive the brake recovery solenoid L ₁ only by the charge accumulated in the smoothing capacitor C _1. Is.

(Effect of the Invention) As described above, according to the present invention, the smoothing capacitor of the rectifier circuit is used as the backup capacitor of the solenoid in the power supply circuit for the reel brake when the AC power is input, so that the brake can be reliably operated. You can call. In addition, the power consumption is low because the series regulator transistor is turned on and the brake is applied during a power failure.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a reel brake power supply circuit in a video tape recorder according to the present invention, and FIGS. 2 and 3 are circuit diagrams showing a conventional power supply circuit.
The figure is a circuit diagram used for a stationary type VTR, and Fig. 3 is a circuit diagram used for a portable type VTR. 2 …… Integrated circuit for regulator L ₁ …… Solenoid for brake recovery L ₂ …… Solenoid for brake suction C ₁ …… Smoothing capacitor Q ₁ …… Transistor

Claims (1)

[Scope of utility model registration request] 1. A voltage of an AC power source stepped down by a transformer is rectified and smoothed by a rectifier circuit and a smoothing capacitor, and converted into a constant level DC voltage through a series regulator composed of a transistor for regulator and an integrated circuit for regulator. A video tape recorder configured to be converted and supplied to a brake return solenoid for applying a brake and a brake suction solenoid for removing a brake, wherein an anode is provided at each end of a secondary coil of the transformer. The cathode side of the two diodes whose sides are connected is connected to the input side of the series regulator via two transistors connected in cascade, while the output side of the smoothing capacitor is input to the series regulator via a resistor. Transistor connected to the side It is connected to the base, the connection point is connected to the brake recovery solenoid via a diode and two switching transistors, and when the AC power is constantly input, the output of the switching regulator is the power supply for operation. Is supplied to the brake recovery solenoid and the brake suction solenoid, and when the AC power is not input, the two switchings are performed via the resistor and the diode by the charge accumulated in the smoothing capacitor. While the transistor is turned on, the charge accumulated in the smoothing capacitor is passed through the regulator transistor, which is turned on by turning on the transistor connected to the input side of the series regulator,
A reel brake power supply circuit in a video tape recorder, which is supplied to the brake returning solenoid as an operating power supply.