JPH0240593Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a small electric device that uses a battery as a driving power source, especially a transistor switch that regulates the on/off of current to the load. Regarding display of battery consumption status.

Conventionally, this type of small electrical equipment has a light-emitting diode 29 interposed at the base end of a transistor switch 25 that regulates on/off when electricity is applied to the load 12, as shown in FIG. When the load 12 is energized, the light emitting diode 29 is caused to emit light by using the base current I ₂ that flows into the base end of the switching transistor 23 through the light emitting diode 29 by applying the on voltage formed by the switch. is displayed.

Normally, when the switching section 20 is on the steady state, the saturated emitter-collector voltage V ₂ of the control section 22 and the saturated base-emitter voltages V ₄ and V ₅ of the transistor switch 25 maintain approximately constant values regardless of the amount of current. Maintain and therefore supply voltage
The change in V ₁ appears as a change in the drive voltage V ₃ of the display section 26. As a result, when a battery is used as a power source, when the battery is exhausted and the output voltage is reduced, the current flowing into the light emitting diode 29 is reduced, and the battery consumption state is displayed as a change in the amount of light. .

However, the voltage-current characteristics of the light-emitting diode 29 generally rise at around 1.5V as shown in Figure 4a, and as the battery wears out, the voltage across the light-emitting diode 29 approaches the rising point a. Then, the base current suddenly decreased, and even a slight voltage fluctuation caused the switching unit 20 to turn off unnecessarily, resulting in unstable operation and malfunction.

The present invention was developed by focusing on the above problem, and by connecting a resistor in parallel with the light emitting diode, it compensates for the decrease in base current caused by the current characteristics of the light emitting diode, impairing the conventional display function. The purpose of the present invention is to provide a small battery-powered electric device that can increase the stability of the circuit when the power supply voltage drops and prevent malfunctions without causing any problems.

The present invention will be specifically described below based on embodiments shown in the drawings.

Although the drawings show an example in which the present invention is implemented in a tape winder for a video tape cassette, the present invention is not limited to this, and it goes without saying that the present invention can be similarly implemented in various small electric devices using batteries as a driving source.

FIG. 1 is an external perspective view of a tape winder 1 embodying the present invention.
A mounting table 4 is recessed into which a tape cassette 3 to be rewound is removably fitted.

Drive shafts 9 and 10 are rotatably protruded from the mounting table 4 in correspondence with the rotation centers of the reels 5 and 6 on the take-up side and the feed-out side of the tape cassette 3.
The base end 11 of the drive shaft 10 that fits into the reel 6 on the feeding side is connected with a belt to the rotation shaft 13 of a motor 12 provided in the main body case 2, and the drive shaft 10 for rewinding is connected to the rotation shaft movement of the motor 12. By rotating at high speed, the tape cassette 3 set on the mounting table 4
The inner tape 14 is wound onto the reel 6 on the feeding side at high speed.

As shown in FIG.
When the main switch 17 is turned on, a voltage is applied using the power source, and the flip-flop circuit 19 is set to a predetermined initial state.

The flip-flop circuit 19 is “1” during standby.
Applying a signal to a switching section 20 (to be described later) to maintain the switching 20 in an off state, and inverting it by turning on the start switch 21 to apply a "0" signal to the switching section 20,
The switching unit 20 is turned on and the motor 12 is energized.

Further, when the motor rotation detecting section 32 detects that the motor rotating shaft 13 has stopped when the winding end of the tape 14 has been reached, a signal is sent from the stop signal generating section 33 to the flip-flop circuit 19 after a predetermined period of time has elapsed since the detection of the rotation stop. Output and flip-flop circuit 1
9 is returned to its initial state and the switching section 20 is turned off.

The present invention is characterized by the configuration of the switching section 20.

The switching 20 is PNP as shown in Figure 3.
A control section 22 consisting of type transistors, and two sets of
A transistor switch 25 configured by connecting NPN type transistors 23 and 24 in Darlington,
The display section 26 is interposed between the control section 2 and the transistor switch 25 and displays the ON period of the transistor switch 25.

The control section 22 connects its base end to the output end of the flip-flop circuit 19, its emitter end to the positive side of the battery 16, and its collector end to the base end of the first transistor 23 of the transistor switch 25 via the display section 26. By connecting
It is turned on in conjunction with the output of the "0" signal from the flip-flop circuit 19, and the power supply voltage _V1 is applied to the transistor switch 25 as an on signal.

The display section 26 has an overcurrent prevention resistor 30 connected in series with a light emitting diode 29, and a malfunction prevention resistor 31 connected in parallel.
By interposing the transistor switch 25 between the collector terminal of the transistor switch 2 and the base terminal of the transistor switch 25, the ON signal output from the control section 22 is transmitted to the transistor switch 2.
5 and causes a predetermined base current to flow through the switch 25 to turn it on. Then, a drive current flows through the motor 12 connected to the collector circuit of the transistor switch 25, the motor rotation shaft 13 starts rotating, the drive shaft 10 connected to the motor rotation shaft 13 rotates at high speed, and the tape cassette 3 inner tape 14
is wound onto the feeding reel 6.

In the steady rotation state, the base current _I1 supplied to the transistor switch 25 is the current flowing through the light emitting diode 29, as shown by the solid line in FIG. 4b.
This is the sum of I ₂ and the current I ₃ flowing through the malfunction prevention resistor 31. Here, while the power supply voltage V ₁ is high, V ₃ is also sufficiently high, so that the base current I ₁ is secured in an amount sufficient to keep the transistor switch 25 in the on state.

By the way, the collector-emitter voltage V ₂ of the control unit 22 and the base-emitter voltages V ₄ and V ₅ of the transistor switch 25 in the saturated state where the switching unit 20 is turned on maintain substantially constant values despite fluctuations in the collector current. Therefore the power supply voltage
Fluctuations in V ₁ appear exclusively as fluctuations in the voltage applied to the display section 26. Hence the drop in supply voltage V ₁ ,
That is, as the voltage V ₃ applied to the display section 26 decreases, the base current I ₁ also decreases, but the current passes through the light emitting diode 29 up to the rising point a in the case of the light emitting diode 29 alone as shown in FIG. current
_I2 mainly carries the base current _I1 , and the rising point a
After passing 2 in Figure 4b, the current _I3 flowing through the malfunction prevention resistor 31 covers the base current _I1 .
Compared to the case where the display unit 26 is composed of only the light emitting diode 29 and the overcurrent prevention resistor 30, which is shown by the dotted solid line, the change in the base current I ₁ near the rising point a is smoother and the slope is gentler. Therefore, the base current I ₁ changes gently even before and after the rising point a, and the power supply voltage V ₁ observed when the battery 16 is exhausted
Even with sudden fluctuations in the base current, the change in the base current is small and a sufficient amount of base current is maintained to keep the switching section 20 in a stable on state.

The value of the malfunction prevention resistor 31 is the same as that of the motor 12.
It is appropriately set based on the minimum power supply voltage V ₀ necessary to drive the transistor switch 25, the minimum base current I ₀ necessary to maintain the on state of the transistor switch 25, etc., so that no current flows to the light emitting diode 29 side. It is preferable that the base current I 0 be able to supply enough base current I ₀ to maintain the on state during the minute voltage change period even after the voltage change.

Further, the transistor switch 25 is connected to the motor 12.
It is possible to increase or decrease the number of stages by one stage or three stages or more depending on the capacity of the controller 22, and the control section 22 is not limited to a transistor switch, but can be implemented by a normal on/off switch or the like.

As described above, the present invention includes a light emitting diode 29 and a malfunction prevention resistor 31 connected in parallel to the base end of the transistor switch 20 that regulates on/off of a load such as the motor 12, so that light is emitted when the battery 16 is depleted. When the voltage applied to the diode 29 decreases, the amount of current flowing through the diode 29 decreases rapidly, which can be effectively alleviated by the malfunction prevention resistor 31. This has the advantage of ensuring current, increasing the stability of the switching section 20, and preventing malfunctions.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view showing an embodiment of the present invention;
Figure 2 is a block diagram showing the outline of the drive circuit;
The figure is an electric circuit diagram showing an example of the switching section, and FIGS. 4a and 4b are graphs showing the current-voltage characteristics of the display section. FIG. 4a is a graph showing the characteristics of a light emitting diode, and FIG. The characteristics when a resistor is inserted are shown below. FIG. 5 is an electrical circuit diagram similar to FIG. 3 showing a conventional example. 12... Motor (load), 15... Motor drive circuit, 16... Battery, 19... Flip-flop circuit, 20... Switching section, 22... Control section, 25... Transistor switch, 26... Display section, 29... Light emitting diode, 30... Resistor for overcurrent prevention, 31... Resistor for preventing malfunction.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A built-in driving battery 16, a transistor switch 25 that regulates on/off energization of the load 12, a control unit 22 that applies an on-voltage to the base end of the switch 25, and a transistor. A light emitting diode 29 is interposed between the base end of the switch 25 and the control unit 22 and displays light by the inflow of base current, and a malfunction prevention resistor 31 is connected in parallel with the light emitting diode 29. Small, battery-powered electrical equipment. (2) The load 12 to be regulated on and off is a motor, and the utility model registration claim 1 describes that the tape 14 in the magnetic tape cassette 3 is wound onto one reel 6 in conjunction with the rotational drive of the motor. small electrical equipment. (3) The control unit 22 turns on and off the power supply voltage and uses the power supply voltage as an on voltage to control the transistor switch 2.
5. A small electric device according to claim 1 or 2, which is a transistor switch that applies voltage to the base end of a transistor.