JPH0729760Y2 - Stepping motor drive circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step motor drive circuit, and more particularly, to a step motor drive circuit that generates a drive pulse to rotationally drive a step motor.

2. Description of the Related Art FIG. 3 shows a circuit diagram of an example of a conventional step motor drive circuit. In the figure, the voltage applied between the power supply terminals 1a and 1b is stabilized by a constant voltage circuit composed of a transistor TR, a resistor R ₁ and a phenor diode Z _D , and the power supply terminals 2a and 2b of the motor drive integrated circuit 2 are stabilized. Applied to.

The motor driving integrated circuit 2 includes a crystal oscillator 3 and a capacitor.
A drive pulse signal of a rectangular wave as shown in FIG. 4 (A) is generated by dividing the signal of the oscillation frequency determined by C ₁ and C ₂ , and the drive pulse signal is supplied from the terminals 2c and 2d to the step motor 4 Supply to. The capacitor C ₀ is for keeping the voltage of the drive pulse constant. As a result, the step motor 4 rotates by a predetermined angle every one second, and the hands of the timepiece attached to the rotating shaft rotate.

The pulse width of the positive or negative polarity drive pulse is set to be larger than the time during which the step motor 4 rotates by a predetermined angle, and the current flowing through the coil of the step motor 4 by the drive pulse is shown in FIG. 4 (B). As shown, the waveform includes ringing.

The ringing of the current waveform of the step motor is caused by the inertial force of the rotor of the step motor 4 and gears driven by the rotor, which causes the rotor to vibrate around its stop position, thereby vibrating the rotor. This is because the counter electromotive force is generated by.

The vibration of the rotor is damped by the friction of the gears and the like, and a rectangular wave drive pulse is supplied to the coil of the step motor 4 until it is sufficiently damped and the pointer stops at a predetermined angle position.

Problems to be solved by the invention However, even after the rotor rotates by a predetermined angle and starts to vibrate,
Since the rectangular-wave drive pulse is supplied to the coil of the step motor 4, the current flowing through the coil becomes vibration energy, and the time until the vibration of the rotor is attenuated and stopped becomes long. Therefore, there is a problem in that the hands, especially the second hand, vibrate for a long time and are hard to see, and the noise generated by the friction of the gears is large.

Therefore, an object of the present invention is to provide a step motor drive circuit that solves the above problems by providing a resistor.

Means for Solving the Problems In the present invention, the resistance of the coil of the step motor and the internal resistance of the integrated circuit are provided between a constant voltage circuit and one power supply terminal of the integrated circuit and a connection point with the capacitor. The current supplied to the step motor coil as a drive pulse is provided with a current limiting resistor having a resistance value that is about 1/2 or more of the sum of They are the current from the voltage circuit, the current that the capacitor discharges due to the time constant of the capacitance of the capacitor and the resistance value of the coil of the step motor and the integrated circuit.

Function In the present invention, the current supplied to the coil of the step motor is the sum of the current from the resistor and the discharge current of the capacitor, and the value of the resistance is the resistance of the coil of the step motor and the internal resistance of the integrated circuit. About half or more of the sum of
In addition, by setting it to less than twice, the current that becomes the vibration energy of the rotor after the rotor has rotated by a predetermined angle is significantly smaller than in the conventional case, and the vibration of the rotor is quickly attenuated.

Embodiment FIG. 1 shows a circuit diagram of an embodiment of the circuit of the present invention. In the figure, those parts which are the same as those corresponding parts in FIG. 3 are designated by the same reference numerals, and a description thereof will be omitted.

In FIG. 1, for example, the power supply voltage 1 is provided between the power supply terminals 1a and 1b.
2V is applied. The base bias resistor R ₁ is 2.
The Zener voltage of the Zener diode Z _D is set to 2 kΩ and 7.5 V, for example. To the emitter of the transistor TR, one end of a current limiting resistor R ₀ of, for example, 330Ω is connected,
The other end is connected to the power supply terminal 2a of the motor driving integrated circuit 2. In addition, the power supply terminal of the motor driving integrated circuit 2
The capacitance of the capacitor C ₀ connected between 2a and 2b is, for example, 2
It is 20 μF.

The motor driving integrated circuit 2 is a timepiece integrated circuit having a C-MOS (complementary MOS) structure, and its internal resistance is several tens Ω when a positive or negative driving pulse is output and several tens kΩ when the driving pulse is not output. is there. Further, the step motor 4 connected to the terminals 2c and 2d of the motor driving integrated circuit 2
The DC resistance of the coil is, for example, 330Ω.

Next, the circuit operation will be described. When the drive pulse is not output, that is, when no current flows in the coil of the step motor 4, the internal resistance of the motor driving integrated circuit 2 is sufficiently larger than the resistance R ₀ , so that the capacitor C ₀ is charged.

When a positive or negative drive pulse is generated and a current starts to flow in the coil of the step motor 4, the potential of the terminal higher than the terminal 2c or 2d of the motor drive integrated circuit 2 suddenly drops, The current flowing through the resistor R ₀ from the transistor TR flows into the terminal 2a, and the discharge current of the capacitor C ₀ flows into the terminal 2a. The discharge time constant of the capacitor C ₀ depends on its capacitance and the internal resistance of the motor driving integrated circuit 2 (10
Ω) and the DC resistance of the coil of the step motor 4 (330
Ω) and the sum.

When the potential of the higher one of the terminals 2c and 2d and the potential of the terminal 2a match, the discharge of the capacitor C ₀ is stopped, and thereafter, the resistor R ₀ is applied to the terminal 2a only during the period when the drive pulse is generated. Only the current that has passed through flows in. In this way, the voltage of the drive pulse signal output from the terminals 2c and 2d gradually decreases after the positive drive pulse rises up to about 6.8V as shown in FIG. 2 (A). For example, after reaching about 6V, it rapidly drops to OV, and the negative drive pulse has its inverted waveform.

Accordingly, the current flowing through the coil of the step motor 4 due to the drive pulse has a waveform as shown in FIG. 2 (B). In FIG. 2 (B), the shaded area on the lower left below the value i ₁ [A] is the current supplied through the resistor R ₀ , and the value i
_The shaded area on the lower right that exceeds ₁ [A] is the discharge current of the capacitor C ₀ .

Thus, the current flowing through the coil of the step motor 4 is
Since the rotor gradually decreases after rotating by a predetermined angle, the vibration energy of the rotor becomes significantly smaller than in the conventional case, and the vibration of the rotor is damped faster and stopped. For this reason, the second hand is easier to see, and the noise generated by friction of gears etc. is also reduced by about 1.6 dB compared to the conventional one.

By the way, the constant of the resistance R ₀ is approximately 1/2 of the sum of the internal resistance of the motor drive circuit 2 and the DC resistance of the coil of the step motor 4.
If it is less than (≈100Ω), the value i ₁ shown in FIG. 2 (B) becomes high and the vibration energy becomes large, and if the constant of the resistance R ₀ is twice the above sum (≈800Ω) or more. Since the motor drive circuit 2 does not operate normally, the resistance R ₀ is selected within the range of these values.

Effect of the Invention As described above, in the circuit of the present invention, after the rotor rotates by a predetermined angle, the electric current that becomes the vibration energy of the rotor is significantly smaller than the conventional one, the vibration of the rotor is quickly damped and stopped, and the second hand etc. The pointers are easy to see, and the noise generated by friction of gears is reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the circuit of the present invention, and FIG.
FIG. 3 is a waveform diagram for explaining the operation of the illustrated circuit, FIG. 3 is a circuit diagram of an example of a conventional circuit, and FIG. 4 is a waveform diagram for explaining the operation of the circuit shown in FIG. 2 ... Motor driving integrated circuit, 2 a to 2 c ... terminal, 4 ... stepping motor, C ₀ ... capacitor, Z _D ... Zener diode,
R ₁ , R ₀ ... Resistors, TR ... Transistors.

Claims (1)

[Scope of utility model registration request] 1. A drive for rotating a step motor by supplying an output voltage of the constant voltage circuit between a constant voltage circuit for stabilizing and outputting a power supply voltage and a pair of power supply terminals connected in parallel with a capacitor. A step motor drive circuit including an integrated circuit for generating a pulse, wherein a resistance of a coil of the step motor and the integrated circuit are provided between the constant voltage circuit and a connection point between one power supply terminal of the integrated circuit and the capacitor. A resistor for limiting current, which has a resistance value that is approximately ½ or more of the sum of the internal resistance of the step motor and less than twice, and supplies the current to be supplied to the coil of the step motor as the drive pulse. The current is supplied from a constant voltage circuit limited by a resistance, the electrostatic capacity of the capacitor and the discharge current of the capacitor due to the time constant of the resistance value of the coil and the integrated circuit are configured to be supplied. Step motor drive circuit.