JPH06225557A - Drive circuit of small-sized motor - Google Patents

Abstract

PURPOSE:To secure the start of a motor, and also, enable the use of a motor being not accompanied with increase of current consumption and besides low- cost, by applying high-voltage power instantaneously in its early stage of the start of the motor and then, changing it over to low-voltage power, being equipped with high-voltage power and low-voltage power. CONSTITUTION:When a third transistor Tr3 is turned on, a second transistor Tr2 is turned on, while a first transistor Tr1 keeps off while high-voltage potential is applied to the base through a diode D1. And, a motor 3 is started, being supplied instantaneously with the power charged in the capacitor C1 from a high-voltage power source 2 through a resistor R1, and then the voltage of the route drops sharply by a current limiting resistor R1. By this voltage drop, the first transistor Tr1 is turned on, and the motor 3 is supplied with the power from the low-voltage power source 1 in place of the high-voltage power source 2, and it continues the rotation. What is more, during the suspension of the motor 3, it provides for the next start of motor, charging the capacitor C1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit for an electronic device having a small motor, and more particularly to a means for ensuring rotation start.

[0002]

2. Description of the Related Art For example, a small pager (pager)
In some cases, a pager has a vibrator incorporated therein as a call alerting means at a place where the alarm sound is transmitted during a meeting or in a hospital. If the mode is switched to the vibration mode in advance, the vibrator is driven instead of outputting the alarm sound when the call is received, and the vibration can detect the call. A small motor is generally used for such a vibrator, and an eccentric flywheel is attached to the rotary shaft of the motor to rotate the motor by a battery to generate vibration.

As such a motor, an ultra-compact motor capable of rotating at a low voltage has been developed so far. Generally, the battery of the pager is an AA type or AAA type dry battery or a rechargeable battery. Is used and its voltage is at most 1.2V-1.5
It is about V. Therefore, it is difficult to start the motor,
There was a case that it did not rotate even when the power was turned on.

As a motor for this purpose, a motor having as small an inertia as possible is made so as to easily start rotation even at a low voltage. However, when the battery voltage decreases due to battery consumption, rotation starts. It was difficult to do. For this reason, various measures have been taken such as supplying a larger current than necessary to increase the rotating torque and making it a coreless motor. However, such a method has a problem that the current consumption increases and that an expensive motor must be used.

[0005]

SUMMARY OF THE INVENTION The present invention is a conventional small-sized motor as described above.
The present invention has been made in order to solve the problems in use of a motor, and an object thereof is to provide a motor drive circuit that enables the use of a low-cost motor without increasing the current consumption. And

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a high voltage power source and a low voltage power source, and instantaneously applies the high voltage power source to the motor at the beginning of the motor startup, and thereafter switches to the low voltage power source. This configuration ensures that the motor is started.

[0007]

Embodiments of the present invention will now be described based on the illustrated embodiments.
The drive circuit will be described in detail.

FIG. 1 is a motor drive circuit showing an embodiment of the present invention, in which 1 is a 1.5V low voltage power source and 2 is 2.7V.
Is a high voltage power supply.

The present invention comprises two power sources, a high voltage and a low voltage. Generally, in recent years, a battery voltage of 1.5 V is boosted by using a D / A converter or the like to 2.7 V or more. 3V
Is generated and supplied to a logic circuit requiring a relatively high voltage, a logic power supply can be used in a pager of this type.
Of course, it is also possible to prepare an individual high voltage power supply.

The above circuit further includes PNP transistors TR ₁ and TR ₂ for supplying two power supply voltages to the motor 3 and an NP for controlling ON / OFF of these two transistors.
The N-transistor TR ₃ is connected as shown. That is, the low-voltage power supply 1 is connected to the motor 3 via the emitter and collector of the first transistor TR ₁ , and the high-voltage power supply 2 is connected to the resistor R ₁ and the emitter of the second transistor TR ₂ ,
It is also supplied to the motor 3 via the collector. This second
Of the transistor TR ₂ has a relatively large capacitance C ₁ between the emitter and the ground, and the collector of the second transistor, that is, the + terminal of the motor 3 and the base of the first transistor TR ₁ . A diode D ₁ is inserted between the spaces. Further, the third transistor TR ₃ of base - the M o d - control signal which becomes a high potential is inputted when the driven motor, for current limiting in the collector of the transistor resistance R _2, R ₃
Are connected to the bases of the _first and second transistors TR ₁ and TR ₂ , respectively. The capacitor and the coil connected in parallel to the motor 3 are circuits for absorbing noise generated from the motor and are not directly related to the operation of the present invention.

[0011] In operation In the above configuration, first, the third transistor TR ₃ of base - the high potential is applied to the scan of the transistor TR ₃ Collector -, emitter is turned on, first , Second transistors TR ₁ , TR
_A current flows between the _two emitter bases and both transistors are turned on, but a high voltage potential is applied to the base of the first transistor TR ₁ through the diode D ₁ , Meanwhile, the transistor is kept in the OFF state.

On the other hand, the mode from the second transistor TR _{2 is changed.}
The voltage supplied to the motor 3 drives the motor 3 to rotate, but the collector of the transistor TR ₂ is current limited by the resistor R _{1 having} a relatively large value. Therefore, the capacitor C ₁ is charged. When the generated electric power is momentarily supplied to the motor 3, the voltage of this route sharply drops thereafter.
Therefore, due to this voltage drop, the first transistor TR
The base potential of ₁ is lowered, this transistor is turned on, and the electric power from the low voltage power source 1.5V is supplied to the motor 3 in place of the high voltage power source, and the motor is rotated. Is continued. Mode - eccentric in motor flywheel - the required because Le is added Baibure - a Deployment occurs, the motor - motor of rotation of the control transistor TR ₃ base - the voltage supplied to the scan is a low potential The transistor TR ₁
And TR ₂ are turned off, the motor rotation is stopped. The capacitor C ₁ is charged during the motor stop period to prepare for the motor start.

With the configuration and operation described above, the high voltage power source is instantaneously supplied only when the motor is started, and thereafter the motor is rotated by the low voltage power source.
The rotation start is established and is smoothly executed. At this time, since only the electric power charged in the capacitor C flows from the high voltage power source to the motor, a large amount of current does not flow and it is not necessary to increase the capacity of the high voltage power source.

FIG. 2 is a circuit configuration diagram showing a modified embodiment of the present invention. While the above-described example operates in an analog manner, in this example, low / high voltage switching is performed digitally. It is a thing. In this example, the same reference numerals and numbers as those in FIG. 1 are the same parts and the operation is the same, so a duplicated description will be omitted. However, in this embodiment, instead of the control transistor TR ₃ , a transistor TR _{1 is used.}
And two NAND gates G connected to the base of TR _2
1 , G ₂ and an inverter G ₃ connected to one input terminal of the second NAND gate G ₂ , a counter 10 for counting a clock signal, and a logic output value inverted to a high potential by the counter output. It is characterized in that it includes a flip-flop circuit 11.

FIG. 3 is a diagram showing the signal waveform of each part of the circuit of FIG. 2, and (a) to (g) are signal waveform diagrams of the same reference numerals in FIG.

The operation of this embodiment will be described with reference to the above two drawings. First, when the motor drive signal becomes high potential as shown in FIG. 3A, the rising signal triggers the counter 10 to start counting the input clock pulses. This count value regulates the time to apply the high voltage power supply to the motor at the time of starting the motor, and it is appropriately determined according to the motor used and the high voltage power supply value, but a relatively short time is not necessary. Easy to understand. Counter 1
When 0 counts a preset value (Fig. (B)), a trigger pulse is generated from its output, which changes the state of the flip-flop 11 at the next stage to generate a high potential (Fig. C).
The output of the flip-flop has a high potential for the gate G (Fig. C), and an inverted low potential for the gate G ₂ (Fig. E).
However, prior to this, a high potential is applied to the two inputs of the second gate G ₂ by the application of the motor drive signal (a), so that the output becomes a low potential. Therefore, during that time, the second transistor TR ₂ becomes conductive, and the output of the gate G ₂ is inverted to the high potential as the counter 10 counts up (FIG. F). Also, the other gates by simultaneously Kauntoapppu - Output DOO G ₁ is a low voltage power source in place of the high-voltage power supply since a low potential mode - is applied to the motor 3 (Fig. E). Therefore, since a high voltage is momentarily applied at the beginning of the motor start and a low voltage is applied thereafter, the motor rotation start is surely performed as in the first embodiment. In this embodiment, the second transistor T
Since the ON-OFF of R ₂ itself is controlled, the resistance R ₁₂ inserted between the emitter and the high voltage power source has a small resistance value, and the capacitor C ₁ may be removed, and further the resistor R ₁₂ may be removed. It is also possible to do so. If the resistor R ₁₂ is removed, the voltage drop applied at the time of starting the motor will be small, so that the starting will be more reliable and convenient.

Although two embodiments have been described above, the present invention is not limited to these embodiments and various modifications can be made. For example, FET instead of transistor
Alternatively, it is effective to use other switching elements, use a simple CR time constant circuit instead of the counter circuit, or simply use the RS flip-flop circuit to simplify the circuit. Ah

[0018]

As described above, according to the present invention, when the motor is driven, the high voltage is instantaneously applied at the initial stage of starting the motor, so that the motor can be surely started. Further, since a relatively small current is required to continue the rotation of the motor that has been started up, the current to be supplied from the low voltage power supply may be a small value, and as a result, driving at a lower voltage and low current consumption. It is also possible to drive the battery, which is effective for extending the life of the battery.

[0019]

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a motor drive circuit according to the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the present invention.

FIG. 3 is a signal waveform diagram for explaining the operation of the circuit shown in FIG.

[Explanation of symbols]

1 ... Low-voltage power supply 2 ... High-voltage power supply 3 ... Motor 10 ... Counter 11 ... Flip-flop circuit TR ₁ , TR ₂ , TR ₃ ... Transistor R ₁ , R ₂ , R ₃ , R ₁₂ ... Resistor C ₁ ... Capacitor D ₁ ... Diode G ₁ , G ₂ ... NAND gate G ₃ ...

Claims (2)

[Claims] 1. An apparatus for driving a small motor by a low voltage power source, comprising a high voltage power source and a low voltage power source, wherein the high voltage power source supplies power to the motor at the time of starting the motor. A drive circuit for a small motor, comprising a switching circuit for supplying electric power from the low-voltage power supply after the motor is started. 2. A means for supplying power to the motor from a high voltage power source via the first switch means, and a means for supplying power to the motor from a low voltage power source via the second switch means. A driving circuit for a small motor, characterized in that it comprises a switching means for electrically connecting the first switch means at the initial stage of starting the motor and then electrically connecting the second switch.