JP2000078894A - Driving apparatus of stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving apparatus of a stepping motor in which standby holding function of a stepping motor can be realized at a low cost with a small mounting area and low consumption power. SOLUTION: This driving apparatus is equipped with a driving power supply E of a stepping motor M, a switching element Q3 which is arranged between the power supply E and the excitation phase L of the motor M and used commonly to each excitation phase, and an excitation driving means 1, Q4 selecting an excitation phase to be excited. In a standby holding circuit, a charge/ discharge circuit R4, C1 performing charge and discharge by an output of the switching element Q3 when driving of the stepping motor M is halted in the excitation driving means 1, Q4, and a transistor Q2 whose base voltage is controlled by charge and discharge of the capacitor C1 are installed. The switching element Q3 is made to perform switching by on/off control of the transistor Q2 by charging and discharging 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 driving device for a stepping motor, and more particularly, to a technique for applying a standby torque to the stepping motor when the stepping motor is on standby.

[0002]

2. Description of the Related Art Conventionally, in the field of water heaters, for example, as shown in FIG. 3, a bypass pipe d for bypassing and connecting an inlet-side pipe b and an outlet-side pipe c of a heat exchanger a is provided. A provided water heater is provided.

[0003] The bypass pipe d is for adjusting the tap water temperature by adding water from the water inlet side to the hot water heated by the heat exchanger a. A flow regulating valve e is provided therein.

The flow control valve e is configured so that the opening degree of the valve can be adjusted by a stepping motor. However, as a driving device for the stepping motor, FIG. 4A or FIG. A device having a circuit configuration as shown in b) was frequently used.

In other words, the circuit shown in FIG. 4 prevents the motor M's axis from moving (the motor does not rotate) when the stepping motor M is on standby. (Excitation phase) L is provided with a circuit configuration (holding circuit) for flowing a current (standby current) smaller than that at the time of driving.

More specifically, the circuit shown in FIG. 4A is one in which a dummy resistor Rd is provided as a holding circuit in a motor drive circuit generally used in the prior art. In this holding circuit, the transistor f, which was in the on state at the time of driving, shifts to the off state in the motor standby state. At this time, the power supply voltage E is dropped by the dummy resistor Rd and applied to the excitation phase L. , The current flowing in the excitation phase L is made smaller than the current during driving.

The holding circuit shown in FIG. 4 (b) has an ICg for switching the transistor f mounted thereon. By switching the transistor f by the switching ICg, the motor M Is to reduce the average current flowing through the excitation phase L.

[0008]

However, in the conventional holding circuit described above, there are problems such as the heat generated by the dummy resistor and the increase in the manufacturing cost of the circuit, and the improvement has been desired.

That is, in the case of the circuit shown in FIG. 4A, since the current always flows through the dummy resistor Rd during the stand-by state of the motor M, the dummy resistor Rd generates heat due to the current flowing during the stand-by state. was there. Moreover,
In this case, since the current always flows through the dummy resistor Rd during the standby state of the motor, there is a problem that the power consumption during the standby state of the motor increases.

Further, in order to reduce the current flowing in the exciting phase L by utilizing the voltage drop of the dummy resistor Rd, it is necessary to increase the resistance value of the dummy resistor Rd. Because the resistance itself becomes larger,
There is also a problem that the mounting area for the resistor is increased, which hinders mounting of other components and devices.

On the other hand, in the case of the holding circuit shown in FIG. 4B, since the transistor f is switched at the time of motor standby, the above-mentioned problems of heat generation and power consumption are caused by the dummy resistor R.
Although there is an advantage that the number is smaller than in the case where d is provided, since a dedicated IC for switching is used, the manufacturing cost of the holding circuit is increased, and as a result, there is a problem that the motor drive device cannot be provided at low cost.

The present invention has been made in view of such a conventional problem, and provides a driving device for a stepping motor capable of realizing a standby holding function of the stepping motor with a small mounting area and at low cost and low power consumption. The purpose is to do.

[0013]

In order to achieve the above object, a driving apparatus for a stepping motor according to a first aspect of the present invention includes at least a driving power supply for the stepping motor, the driving power supply and the stepping motor. A stepping motor including a switching element common to each excitation phase interposed between the excitation phase and one end of the excitation phase, and excitation drive means connected to the other end of the excitation phase to select an excitation phase to be excited. A driving device, wherein a charging / discharging circuit for performing charging / discharging with an output of the switching element is provided when the driving of the stepping motor is instructed by the excitation driving means, and a base voltage is controlled by the charging / discharging circuit. The collector of the NPN transistor is connected between the drive power supply and the switching element, and the charge / discharge circuit charges / discharges. ON / OFF controlling the NPN type transistor, characterized in that for switching the switching element by the.

As shown in FIG. 1, the driving device for the stepping motor includes a driving power source E for the stepping motor M, and a driving power source E and one end of the excitation phase L of the stepping motor M. A switching element Q3 common to each of the excitation phases mounted thereon and excitation drive means connected to the other end of the excitation phase L to select an excitation phase L to be excited (on / off control by outputs 1 to 4 from the microcomputer 1) When the stepping motor is driven, the following operation is performed.

That is, when the stepping motor M is driven, the voltage of the driving power supply E is applied to the base of the transistor Q1 via the resistor R1 to turn on Q1, and accordingly, the switching element constituted by a PNP transistor Q3 is also turned on, and the power supply voltage E is applied to each of the excitation phases L.

On the other hand, predetermined excitation pattern signals for driving the motor M are output from outputs 1 to 4 of the microcomputer 1 constituting the excitation drive means. Here, an example of this excitation pattern signal is shown, for example, as shown in FIG. 2, from each of the outputs 1 to 4 of the microcomputer 1, "Hi" or "Lo" in the order of steps a, b, c and d.
Is output.

As a result, the transistor Q4 connected to the output port to which the "Hi" signal is output is turned on, and the current from the drive power source E is supplied to the excitation phase L connected to the turned on transistor Q4. Flows. Thereafter, the excitation phase L to be excited is sequentially switched by repeating the above steps a to d, and the motor M is driven.

On the other hand, when the driving of the stepping motor is stopped (at the time of stop standby), the excitation pattern is set to a stationary state in a specific pattern (for example, the state of step a). In the present invention, the switching element Q3 is switched to reduce the current flowing to the excitation phase L (when the stop state is at step a described above, the excitation phase corresponding to the outputs 1 and 2) during standby is stopped. Let me.

More specifically, a charging / discharging circuit (a resistor R4 and a capacitor C4) for charging and discharging with the output of the switching element Q3
1) and a transistor Q2 that is turned on / off by charging / discharging in the charging / discharging circuit. The switching element Q3 is switched by turning on / off the transistor Q2 by charging / discharging in the charging / discharging circuit. , The average current value of the current flowing through the excitation phase L is reduced.

The switching operation is stopped when the motor M is started by limiting the voltage applied to the capacitor C1 by the output 5 of the microcomputer 1 (charging and discharging in the charging and discharging circuit is performed). Means to stop). As a result, the charging / discharging in the charging / discharging circuit is stopped along with the start of the driving of the motor M, and
Reference numeral 3 is fixed to the ON state, and the motor M is driven according to the excitation pattern signal from the excitation drive means.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a stepping motor driving apparatus according to the present invention will be described below in detail with reference to FIG. In FIG. 1, the description of the exciting phase L of the stepping motor M and the transistor Q4 for exciting the stepping motor M, which will be described later, are combined into one. However, as shown in FIG. It is assumed that there are four of each.

The driving device for a stepping motor (hereinafter referred to as a motor driving device) shown in FIG. 1 has a very small current (standby current) in the excitation phase (motor winding) L of the motor even when the stepping motor M is in an operation standby state. And a switching element (transistor for switching the drive power supply E to supply a current to the excitation phase L of the motor M). ) Q3 and exciting phase L to be excited
The microcomputer 1 and the transistor Q4 as means for selecting (excitation drive means), a charging / discharging circuit (resistance R4 and capacitor C1) as means for switching the switching element Q3, and ON / OFF controlled by this charging / discharging circuit. Transistor Q2 as a main part.

More specifically, as shown in FIG.
The switching element Q3 common to each of the excitation phases L is formed of a PNP transistor, and its collector terminal is connected to one end of the excitation phase L, and its emitter terminal is connected to the drive power source E. The driving circuit for the switching element Q3 includes a resistor R
An NPN transistor Q1 to which a base voltage is supplied via a first transistor 1 is used, and the collector terminal of the transistor Q1 is connected to the base of the switching element Q3 via a resistor. A voltage dividing resistor R2 for adjusting the base voltage is arranged on the base side of the transistor Q1.

The collector of the NPN transistor Q2 is connected between the driving power source E and the switching element Q3 via a resistor, and the base thereof is connected to the collector of the switching element Q3 via a resistor R4. It is connected to one end of the excitation phase L. A capacitor C1 is connected in parallel to the base of the transistor Q2.
1 constitutes a charge / discharge circuit. The emitters of the transistor Q1 and the transistor Q2 are both grounded via a resistor R.

On the other hand, the microcomputer 1 as excitation drive means
Outputs a signal as shown in FIG. 2 from its output ports 1 to 4 (outputs 1 to 4 in the figure) when the stepping motor M is driven. That is, when the stepping motor M is driven, output signals “Hi” and “Lo” are output from the output ports 1 to 4 in the order of steps a to d.
While the driving of the motor M is stopped, a signal of the step when the stop is commanded is output (for example, when the motor driving is stopped in step a, “H” is output from the outputs 1 to 4 respectively.
i, "Hi,""Lo," and "Lo" signals are output.)

The output ports 1-4 are connected to the base of the transistor Q4 via a resistor. The transistor Q4 is formed of an NPN transistor, and has a collector connected to the other end of the excitation phase L. The transistor Q4 is turned on when a "Hi" output is received from the microcomputer 1, and the "Hi" output is output. It is configured such that a current flows through the exciting phase L where there is a current.

The output 5 of the microcomputer 1 is a port for stopping charging / discharging of the capacitor C1 described later, and is connected to one end of the capacitor C1 via a diode and a resistor. By setting this port to "Lo" and taking in the voltage applied to the capacitor C1 from the drive voltage E via the resistor R4, the charging and discharging of the capacitor C1 can be stopped.

The "Lo" of the output 5 of the microcomputer 1 is
The switching operation of “Hi” is set to “Lo” so as to stop the charging and discharging of the capacitor C1 while the motor M is being driven, and is set to “Lo” so that the charging and discharging can be performed while the driving of the motor M is stopped. Hi ”.

The operation of the motor driving apparatus according to the present invention having the above-described structure will be described below.

Operation at the time of driving the motor: First, when the driving power supply E is turned on, a voltage is applied to the base of the transistor Q1 via the resistor R1, and the transistor Q1 is turned on. Accordingly, the switching element Q3 is turned on, and the voltage from the drive power supply E is applied to the excitation phase L of the motor M. On the other hand, the selection of the windings to be excited in the excitation phase L of the motor M is determined by the outputs 1 to 4 of the microcomputer 1. In other words, from the outputs 1 to 4 of the microcomputer 1, the excitation patterns shown in FIG.
Are sequentially output, and accordingly, the transistor Q4 connected to the port to which the “Hi” output has been made is turned on, the drive current flows through the excitation phase L to which the “Hi” output has been made, and the motor M is driven. You.

At this time, the output 5 of the microcomputer 1 is set to "Lo" level so that the capacitor C1 does not start charging / discharging via the resistor 4.

Operation when the motor is stopped and held : On the other hand, when the motor is in the stopped and held state, the stepping motor M is output from the output ports 1-4 of the microcomputer 1 as described above.
The signal of the excitation pattern (for example, the pattern of FIG. 2A) when the driving of the motor is stopped is fixedly output, and
The output 5 of the microcomputer 1 is switched to start charging at C1.

Therefore, in this state, step a
Current flows only in the excitation phase L corresponding to the outputs 1 and 2 of the microcomputer 1 in accordance with the signal
Switching from “o” to “Hi” simultaneously starts charging the capacitor C1 via the resistor R4.

[0034] In the state immediately after stopping the motor M, a transistor Q1 and Q3 are turned on, the voltage V _R at the resistor R at this time is determined by Equation 1 below.

[0035]

(Equation 1)

Here, E is the drive voltage value, R1 to R3 are the resistance values of the respective resistors, and VQ1 _(BE) is the base of the transistor Q1.
This shows the voltage between the emitters. Since the base current flowing through the transistors Q1 and Q2 is very small,
Are ignored. Further, in the above equation 1, "R1 // R2" means that the resistors R1 and R2 are connected in parallel (the same applies to the following equation).

[0037] Then, the charged capacitor C1, the voltage V _C1 between the capacitor C1 reaches the state in Equation 2, the transistor Q2 is turned on, and at the same time the transistors Q1, Q3 are off Becomes

[0038]

(Equation 2)

In the above equation ₍ 2 ₎ , V _{Q2 (BE)} indicates a voltage between the base and the emitter of the transistor Q2.

When the transistor Q3 is turned off, the capacitor C1 starts discharging, and when V _C1 becomes the state of the following equation 3, the transistor Q2 is turned off and the transistors Q1 and Q3 are turned off again. It turns on.

[0041]

(Equation 3)

It should be noted that also in this equation 3, the above equation 1
Similarly to the above, the base currents of the transistors Q1 and Q2 are very small and are ignored in the calculation.

Thereafter, charge and discharge are repeated in the capacitor 1 each time the conditions of the above formulas 2 and 3 are satisfied, and the transistor Q3 performs a switching operation.

As described above, in the present embodiment, the switching of the transistor Q3 causes the current flowing in the excitation phase L of the stepping motor M to be repeatedly turned on and off. The current (average current I ₀ ) is expressed as a ratio of the ON time to the entire ON / OFF cycle of the transistor Q3 as in the following Expression 4.

[0045]

(Equation 4)

Here, _RS indicates the internal resistance of the motor.

That is, in the present invention, by switching the transistor Q3 by the charging / discharging circuit, it is possible to stably supply a small current (holding current) to the excitation phase L of the motor M when the motor M is stopped and held. Becomes

At this time, the transistor Q3 is turned on and off.
Since the off cycle can be freely changed by appropriately setting the values of the capacitor C1 and the resistor R4, it is also possible to arbitrarily set the value of the motor holding current expressed by the above equation (4).

The above-described embodiment merely shows a preferred embodiment of the present invention, and the present invention is not limited to this, and various design changes can be made within the scope of the present invention.

For example, in the above-described embodiment, the configuration in which the microcomputer 1 is used as the excitation driving means has been described. However, a commercially available motor driving IC may be used instead of the microcomputer 1. In this case, it is needless to say that the port corresponding to the output 5 needs to be replaced by another means.

[0051]

As described above in detail, according to the stepping motor driving apparatus according to the present invention, the standby current flowing in the excitation phase at the time of standby of the motor can be obtained without depending on the dummy resistor. The problem of resistance heating at the time is eliminated. In addition, since the standby current is obtained by switching of the switching element, power consumption during standby can be reduced.

Further, since the switching operation of the switching element can be realized by the NPN transistor and the charging / discharging circuit (comprising a resistor and a capacitor), the cost can be reduced and the mounting area of the holding circuit can be reduced. Can also be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a schematic configuration of a driving device for a stepping motor according to the present invention.

FIG. 2 is an explanatory diagram showing an example of an excitation pattern output from a microcomputer of the driving device for the stepping motor.

FIG. 3 is an explanatory diagram illustrating a schematic configuration of a water heater to which the driving device for the stepping motor is applied.

FIG. 4 is a circuit diagram illustrating a conventional driving device for a stepping motor. FIG. 4 (a) shows a circuit for providing a standby current using a dummy resistor, and FIG. 4 (b) shows switching using an IC. FIG.

[Explanation of symbols]

 E Drive power supply Q1 to Q4 Transistor R, R1 to R4 Resistance C1 Capacitor 1 Microcomputer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yasuki Takeda 93 Edocho, Chuo-ku, Kobe-shi, Hyogo F-term in Noritz Co., Ltd. 5H580 BB01 EE02 FA14 FD14 FD18

Claims (2)

[Claims] At least a drive power supply for a stepping motor, a switching element interposed between the drive power supply and one end of an excitation phase of the stepping motor, common to each excitation phase, and the other end of the excitation phase A stepping motor driving device connected to the excitation driving means for selecting an excitation phase to be excited, wherein the excitation driving means outputs a signal from the switching element when driving of the stepping motor is instructed to stop. A charging / discharging circuit for performing charging / discharging is provided, and a collector of an NPN transistor whose base voltage is controlled by the charging / discharging circuit is connected between the driving power supply and the switching element, and the charging / discharging circuit charges / discharges. Thereby controlling the on / off control of the NPN transistor to switch the switching element. Driving device for a stepping motor according to symptoms. 2. The stepping motor driving device according to claim 1, wherein said excitation driving means includes means for stopping charging / discharging in said charging / discharging circuit at the start of driving of the motor.