JPH0378498A - Driving circuit for stepping motor - Google Patents

Abstract

PURPOSE:To reduce the copper loss of a phase winding by half by setting the absorption voltage of a counter-electromotive force absorbing circuit to be low voltage till counter-electromotive current flowing at the time of switching the phase winding is reduced into almost zero. CONSTITUTION:When start signal is applied, then from an over-drive signal generator 3 and a pulse train generator 1, output is generated and working is started. By the output of a distributing circuit 2, transistors TR1, TR2 are turned ON/OFF, and current is fed to phase windings L1, L2. When the transistor TR1 is turned OFF, then electromagnetic energy stored in the phase winding L1 is regenerated to a power source E1 via a diode D2, the phase windings L2, L1, a diode D3, and the transistor TR5 of a counter-electromotive force absorbing circuit 10. In this case, the transistor TR6 of an absorption voltage switching circuit 11 is turned ON, and the transistor TR5 is also ON, and so a loss is less at the transistor TR5. Besides, counter-electromotive current is to be of 1/2 of the conventional one, and so a copper loss is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stepping motor drive circuit.

"Prior Art" Fig. 2 shows part of a conventional four-phase stepping motor drive circuit.The illustrated part drives the stepping motor in conjunction with another set of the same components (not shown). FIG. 3 shows a time chart when the four-phase stepping motor shown in FIG. 2 is driven by a two-phase excitation force type.

In FIG. 2, this stepping motor drive circuit is
A start signal is applied from the outside to drive the stepping motor, and a stop signal is applied from the outside to end the driving of the stepping motor. A start signal and a stop signal are given to a pulse train generator 1 and an overdrive signal generator 3.

The pulse train generator 1 generates a narrow pulse signal at predetermined intervals from when a start signal is applied until when a stop signal is applied. The distribution circuit 2 generates two pulse signals whose levels are inverted every time the output signal of the pulse train generator 1 is applied, and which have opposite phases to each other. It is applied to the base of The overdrive signal generator 3 takes an H level only from the arrival time of the start signal to the arrival time of the stop signal, that is, outputs a pulse signal that defines the drive period. One-shot multivibrator circuit 4
The pulse train generator 1 outputs a pulse signal that takes an L level for a certain period of time every time a pulse is output. The AND gate 5 takes the AND of the output signals of the overdrive signal generator 3 and the multivibrator circuit 4, and this output signal is used as an on/off control signal for the transistor TR4.

A pair of NPN transistors TRI and TR2 whose emitters are commonly grounded are phase selection transistors. A pair of phase windings L1 and L2 of the stepping motor are bifilar-wound and have one terminal connected to each other. The other terminals of the phase windings L1 and L2 are connected to the collectors of the corresponding phase selection transistors TRI or TR2.

NPN where the output signal of AND gate 5 is applied to the gate
type transistor TR4 and a PNP type transistor TR3 whose gate is connected to the collector of this transistor TR4 via a resistor R2 and whose emitter is connected to the power supply +E1, the phase windings L1 and L2 are connected to the power supply +E1.
This is for applying 1.

Diodes D1 and D2 connected in parallel to each of the phase selection transistors TRI and TR2, and a diode D5 connected in parallel to the power supply voltage application transistor TR3 are connected to the phase winding L1 and the inductive load. L2
This is to regenerate the back electromotive current of 1 to the power supply 1E1.

Diodes D3 and D4 whose cathodes are connected to each other and whose anodes are connected to the collectors of the corresponding phase selection transistors TRI and TR2, and diodes D3 and D4 whose anodes are connected to the power supply +E1 and whose cathodes are connected to the collectors of the corresponding phase selection transistors TRI and TR2.
Zener diode ZD1 connected to the cathode of
This is to protect the phase selection transistors TRI and TR2 from an excessive back electromotive voltage that occurs when the phase windings L1 and L2 are insufficiently coupled.

Next, the operation of the conventional circuit having the above configuration will be explained.

This stepping motor drive circuit receives a start signal and starts overdrive signal generator 3 as shown in FIG. 3(a).
The pulse train generator 1 operates by outputting the overdrive signal Sa shown in FIG. 3, and the pulse train generator 1 outputting the pulse train signal sb shown in FIG. 3(b).

Every time the pulse train signal sb arrives, the distribution circuit 2 inverts the logic levels of the on/off signals Se and Sf, which have an opposite phase relationship, as shown in FIGS. 3(e) and 3(f). As a result, the phase selection transistors TRI and TR2 turn on and off in a predetermined sequence.

Also, from the multi-by-break circuit 4, as shown in FIG. 3(C)
A pulse signal Sc that takes the L level for a certain period of time from the time when the pulse train signal sb as shown in FIG.
As a result, as shown in FIG. 3(d), the AND gate 5 outputs a pulse signal Sd that takes the L level for a certain period of time within one operation cycle of the phase selection transistors TRI and TR2.
is output. When this pulse signal Sd is at H level, transistors TR4 and TR3 are turned on. That is, after a certain period of time from the switching point of the selected phase winding L1 or L2, the phase windings L1 and L2 are switched through the transistor TR3.
Power supply voltage +E1 is applied to.

Therefore, at a time point ta when a certain period of time has elapsed after the start signal is given, the pulse signal of the AND gate 5 becomes H level and the transistor TR3 turns on. When an ON command and an OFF command are given as shown in FIG. 3(e) and (f), respectively, the phase current 11 flows into the phase winding L1 from time ta as shown in FIG. 3(a). flows.

Thereafter, at time tb, when the on/off signal Se for the phase selection transistor TR1 is switched to an OFF command and the on/off signal Sf for the phase selection transistor TR2 is switched to an ON command, the phase selection transistor TRI is turned off.

Here, Zener voltage VZ of Zener diode ZD1
1 and the power supply voltage +E1 so as to satisfy the following formula % (1), the electromagnetic energy stored in the phase winding L1 is transferred between the bifilar-wound phase windings L1 and L2. Due to the mutual induction of the diode D2, the phase winding L2, the diode D5 and the power supply +
It is converted into a back electromotive current that is regenerated to the power supply +E1 via the path of E1.

Note that at time tb, the on/off signal Sf shown in FIG. 3(t') reaches the on command level, but the selection transistor T
R2 does not turn on immediately, and as shown in FIG. 3(h), at the time tc when the back electromotive current flowing through the diode D2 becomes 0, this transistor TR2 turns on, and the phase current flows forward in the phase winding L2. 12 flows.

As described above, the phase selection transistor TR,1 or TR
2 is turned on alternately, the current in the phase winding L1 or L2 is switched to the composite current 1 of the phase currents 11 and 12.
l-i2 becomes as shown in FIG. 3(i), and the stepping motor is driven by this combined current 1l-i2.

[Problems to be Solved by the Invention] However, in the above-mentioned energy regeneration type stepping motor drive circuit, when driving at high speed, the proportion of time during which the back electromotive current flows in the switching period of the phase current increases, and therefore , the reached current value of the phase current becomes smaller, and the torque generated by the motor decreases.

As a countermeasure for this inconvenience, firstly, the power supply voltage +E1
Second, it is possible to increase the current value reached by the phase current by decreasing the resistance value of the phase winding, but either method increases the amount of heat generated by the motor.

The present invention has been made in consideration of the above points, and is capable of reducing the amount of heat generated by a stepping motor.
Therefore, it is an object of the present invention to provide a power-saving, energy-regenerating stepping motor drive circuit that can increase torque.

[Means for Solving the Problems] In order to solve the problems, the present invention drives a stepping motor by sequentially switching the n-phase windings and passing a current in the positive direction of the windings. A stepping motor drive circuit that regenerates back electromotive current during switching into a power source was configured as follows.

In other words, the back electromotive current path was set so that the back electromotive current flows through one of the two-phase bifilar windings in the opposite direction and the other in the forward direction, and the back electromotive current flows in series toward the power supply. . Further, a back electromotive voltage absorption circuit that absorbs a back electromotive voltage and is inserted in the back electromotive current path, and an absorption voltage switching circuit that switches the absorption voltage of this back electromotive voltage absorption circuit are provided. Then, the absorption voltage of the back electromotive voltage absorption circuit is set to a low voltage by the absorption voltage switching circuit only during a predetermined time when the back electromotive current flowing during phase switching is decreasing, and the absorption voltage of the back electromotive voltage absorption circuit is set to a low voltage during a predetermined time period when the back electromotive current flowing during phase switching is decreasing. The absorption voltage is now set to a high voltage.

[Function] In order to reduce the back electromotive current that flows during phase switching and suppress copper loss in the phase winding, the back electromotive current flows in one direction of the bifilar two-phase phase winding and in the other direction in the positive direction. At the same time, a regeneration path for the back electromotive current was set so that the back electromotive current flows in series toward the power source. That is, the back electromotive current flowing through each phase winding is reduced by causing the back electromotive current to flow through both of the phase windings forming a pair at the time of phase switching.

Even if an attempt is made to suppress heat generation by setting such a new regeneration path, if the absorption voltage is high, heat generation in the part absorbing the back electromotive force will become a problem. Therefore, a back electromotive force absorption circuit is provided on this regeneration path to absorb the back electromotive voltage, and the absorption voltage by the back electromotive force absorption circuit is set to a low level by the absorption voltage switching circuit while the electromotive current is flowing during phase switching. I tried to keep the heat generated here small.

During periods other than this, the absorption voltage was set high to prevent the back electromotive current from flowing, so that the power was appropriately applied to the phase windings.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Fig. 1 is a circuit diagram showing a part of a four-phase stepping motor drive circuit as an example, and Fig. 4 shows a case where the four-phase stepping motor to be driven is driven by a two-phase excitation force type. This is a time chart of each part. The configuration shown in FIG. 1 is used to drive a four-phase stepping motor by using two sets. Further, in FIG. 1, the same components as those of the conventional circuit shown in FIG. 2 are denoted by the same reference numerals, and a description thereof will be omitted.

The stepping motor drive circuit of this embodiment differs from the conventional drive circuit shown in FIG. 2 in the following points.

That is, the back electromotive force regeneration diode D5 is deleted, the protective Zener diode ZDI of the phase selection transistors TRI and TR2 is replaced with a back electromotive force absorption circuit 10 that also functions as a regeneration path, and this back electromotive force The difference is that an absorption voltage switching circuit 11 that switches the absorption voltage of the absorption diagram 810 between high voltage and low voltage according to the output of the one-shot multivibrator circuit 4 is provided. This example is
The absorption voltage of the back electromotive force absorption circuit 10 is set to a low voltage during a certain period of time when the back electromotive current that flows when switching between the phase winding L1 or L2, which is an inductive load, is regenerated to the power supply +E1. This point causes a difference in configuration from the conventional circuit.

In FIG. 1, the back electromotive force absorption circuit 10 is composed of a PNP transistor TR5, a Zener diode ZD2, and a resistor R3. The emitter of the transistor TR5 is connected to the phase selection transistors TRI and TR2 from the back electromotive voltage.
It is commonly connected to the cathodes of diodes D3 and D4 for protecting the diodes D3 and D4, and its collector is connected to the power supply element E1 and the anode of the Zener diode ZD2. The cathode of the Zener diode ZD2 is connected to the base of the transistor TR5 and the absorption voltage switching circuit 11. Note that a resistor R3 is connected between the emitter and base of the transistor TR5.

The absorption voltage switching circuit 11 includes an inverter circuit 12, an NPN
It consists of a type transistor TR6 and resistors R4 and R5. The inverter circuit 12 inverts the output signal of the multivibrator circuit 4, and applies the inverted logic level to the base of the transistor TR6. The transistor TR6 is provided as a switching transistor, and is turned on and off depending on the inverted logic level. The collector of this transistor TR6 is connected to the base of the transistor TR5 of the back electromotive force absorption circuit 10 via a resistor R4.

That is, it is connected so that the internal state of the back electromotive force absorption circuit 10 can be switched.

Next, the operation of the stepping motor drive circuit according to the embodiment having the above configuration will be explained using FIG. 4.

Also in the stepping motor drive circuit of this embodiment, the start signal is given, and the overdrive signal generator 3
The driving operation is performed by outputting the overdrive signal Sa shown in FIG. 4(a), and the pulse train generator 1 outputting the pulse train signal sb shown in FIG. 4(b).

The distribution circuit 2 inverts the logic levels of the on/off signals Se and Sf, which have an opposite phase relationship, as shown in FIGS. 4(e) and 4(f), every time the pulse train signal sb arrives. As a result, the phase selection transistors TRI and TR2 are turned on or off in a predetermined sequence.

Further, the multivibrator circuit 4 outputs a pulse signal Sc that takes the L level for a certain period of time as shown in FIG. 4(C) from the time when the pulse train signal sb is applied.
As a result, as shown in FIG. 4(d), the AND gate 5 outputs a pulse signal Sd which takes the L level for a certain period of time within one operation cycle of the phase selection transistors TRI and TR2.
is output. When this pulse signal Sd is at H level, transistors TR4 and TR3 are both turned on.

That is, the power supply voltage +E1 is applied to the phase windings L1 and L2 via the transistor TR3 after a certain period of time from the switching point of the selected phase winding L1 or L2.

Therefore, at a time point ta when a certain period of time has elapsed after the start signal is given, the pulse signal of the AND gate 5 becomes H level and the transistor TR3 turns on. When on-off signals Se and Sf instructing ON command and OFF command are given as shown in FIG. 4(e) and (f), respectively, phase winding starts from time ta as shown in FIG. 4(g). Phase current 110 flows through line L1.

Thereafter, the on/off signal Se shown in FIG.
When switched to the b″″cL level, the phase selection transistor TRI is turned off. Furthermore, when the output signal Sc of the one-shot multivibrator circuit 4 reaches the L level at this point tb'''C' as shown in FIG. 4(C), the output signal Sd of the AND gate 5 becomes the L level. The power supply transistors TR4 and TR3 are both turned off, and at the same time, the output signal of the inverter circuit 12 becomes H level, the transistor TR6 of the absorption voltage switching circuit 11 is turned on, and the transistor of the back electromotive force absorption circuit 10 is turned on. TR5 also enters a state where it can be turned on.

When the phase selection transistor TR1 turns off at the above-mentioned time point tb, the electromagnetic energy stored in the phase winding L1 becomes phase currents 110 and 120 due to mutual induction between the bifilar-wound pair of phase windings L1 and L2. As shown with diagonal lines in FIGS. 4(g) and (h), from this time point tb, the diode D2, the phase windings L2 and LL, the diode D3, and the transistor TR5 of the back electromotive force absorption circuit 10
It is converted into an electromotive current that is regenerated to the power supply +E1 via the path of the power supply +E1.

In this way, the point where the back electromotive current flows through both of the two phase windings L1 and L2 is that the back electromotive current flows only through one phase winding L1 or L2 due to the functions of the Zener diode ZD1 and the diode D5. This is different from conventional circuits.

At this time, the transistor TR6 of the absorption voltage switching circuit 11
is in the on state, a part of the back electromotive current flows to the transistor TR6 via the emitter and base of the transistor TR5 of the back electromotive force absorption circuit 10 and the resistor R4.

Since the transistor TR5 is also in the on state, the absorption voltage of the back electromotive force absorption circuit 10, that is, the emitter-collector voltage of the transistor TR5 is a low voltage (approximately 0).
(2) Even if the transistor TR5 is used, the energy loss in the transistor TR5 is as small as that through the regeneration path of the conventional circuit.

Since the sum of the magnetic fluxes of the phase windings L1 and L2 is equal before and after the phase selection transistor TRI turns off at time tb, the following formula % Formula % (2) (φ is the sum of magnetic flux, L is the phase windings L1 and L2 The inductance of It becomes 1/2 and each phase winding!! flows through L1 and L2.

Here, the effective value of this back electromotive current is 1. /317
Approximating with a triangular wave of 2, the copper loss of phase winding LIL2 (
The sum of (corresponding to the shaded area) can be expressed by the following formula 2 (%) (3) (R is the resistance component of each phase winding). On the other hand, the copper loss of the conventional circuit shown in FIG. 2 can be expressed by the following formula (%). As is clear from these formulas,
Phase winding L1 during the regeneration period of the back electromotive current in this embodiment
The copper loss occurring in L2 and L2 is 1/2 that of the conventional circuit.

Note that in this embodiment, the L of the multivibrator circuit 4
The level output time is set to a time until the back electromotive currents of the phase windings L1 and L2 reach approximately O, and when the level reaches approximately O, the processing for the next cycle is started.

When the output signal Sc of the multivibrator circuit 4 returns to H level at the time tci when the back electromotive current becomes almost 0, the output signal of the inverter circuit 12 becomes L level and the transistor TR6 of the absorption voltage switching circuit 11 is turned off. become. When the output signal Sc of the multivibrator circuit 4 returns to the H level, the transistors TR4 and TR3 are turned on to apply the power supply voltage element E1 to the phase windings L1 and L2, as at the time ta already described.

At this time, a back electromotive force of E1/2 remains at both ends of the phase winding L1, so the cathode voltage of the diode D3 becomes 3·E1/2, and the emitter of the transistor TR5 of the back electromotive force absorption circuit 10 - Voltage E1/2 is applied between the collectors. However, since the transistor TR6 is in the off state, the transistor TR5 does not turn on. If the Zener voltage VZ2 of the Zener diode ZD2 is set to VZ2>El as in the conventional circuit, the back electromotive voltage applied between the emitter and collector of the transistor TR5 is lower than the Zener voltage VZ2 of the Zener diode ZD2, so the transistor TR5 is not activated and the back electromotive current flows through phase winding LL, diode D3 . The current cannot flow around the loop of the back electromotive force absorption circuit 10 and the transistor TR3, and as a result, the transistor TR3 is almost O.
The power supply voltage +E1 is applied to the phase windings L1 and L2.

Incidentally, if the transistor TR6 of the absorption voltage switching circuit 11 is in the on state when the output signal SC of the multi-bye break circuit 4 returns to H level, the back electromotive force absorption circuit 10
The transistor TR5 remains in the on state, and at that time, a back electromotive force E1/2 remains across the phase winding L1, and even if an attempt is made to turn on the transistor TR3, it does not reach the saturated state and is conductive in the active state. Phase winding L1, diode D
3. A back electromotive current flows through the loop of the back electromotive force absorption circuit 10 and the transistor TR3, and only when the back electromotive voltage of the phase winding L1 drops to OV does the transistor TR3 become saturated (
conducts to (OV). Therefore, during this period, a voltage lower than the power supply voltage +E1 is applied to the phase winding L2, and the phase currents cannot be switched smoothly as in the conventional circuit.

Therefore, in order to perform the above-mentioned smooth switching between the phase currents 110 and 120, the multivibrator circuit 4
The output signal Sc is inverted via the inverter circuit 12 and applied to the base of the transistor TR6.

When the power supply voltage +E1 is applied to the phase winding L2 at the above-mentioned time point tc1, the base of the transistor TR2 is at H level at that time, so the transistor TR2 is turned on, and thus the phase winding L2 has a positive direction. phase current 120
flows.

As described above, phase selection transistors TRI and TR2
By alternately turning on the currents i10 and 120 of the phase windings L1 and L2, the phase currents i10. The composite current 110-120 of i20 flows as in the conventional circuit, thus driving the stepping motor.

Therefore, according to the embodiment described above, the absorption voltage of the back electromotive force absorption circuit 10 is set to a low voltage by the absorption voltage switching circuit 11 during the time until the back electromotive current flowing at the time of phase winding switching becomes almost zero. Compared to a conventional circuit in which a back electromotive current flows only through one phase winding, the copper loss in the phase windings L1 and L2 due to the back electromotive current can be halved, and the heat generation of the stepping motor can be reduced. .

As a result, compared to the conventional circuit, the power supply voltage +E1 can be increased, and/or the resistance value of the phase winding can be decreased to increase the reaching current value of the phase current, and the generated torque can be increased. Therefore, the applications of motors using such a drive circuit can be expanded.

In the above-described embodiment, a drive circuit for a four-phase stepping motor is shown, but the present invention is not limited to four phases, and the present invention can be applied to a drive circuit for a multi-phase stepping motor. However, it is required that the bifilar-wound two-phase phase windings form a pair.

[Effects of the Invention] As described above, according to the stepping motor drive circuit of the present invention, the regeneration path of the back electromotive current is connected in series with one phase winding of the two-phase bifilar winding in the reverse direction and the other in the positive direction. A back electromotive force absorption circuit is installed in series with the back electromotive current path, and an absorption voltage switching circuit is installed for the time until the back electromotive current flowing when switching the phase winding becomes almost 0. Since the absorption voltage of the back electromotive force absorption circuit is set to a low voltage, the back electromotive current flows to both bifilar-wound phase windings and the copper loss in the phase windings can be halved. Heat generation of the motor can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a stepping motor drive circuit according to the present invention, FIG. 2 is a circuit diagram showing a conventional circuit,
3 is a time chart of each part of FIG. 2, and FIG. 4 is a time chart of each part of the embodiment shown in FIG. 1. 1... Pulse train generator, 2... Distribution circuit, 3...
Overdrive signal generator, 4... One-shot multi-by-break circuit, 5... AND gate, 10...
・Back electromotive force absorption circuit, 11...absorption voltage switching circuit, L
L, L2... Phase winding, TRI, TR2... Phase selection transistor, Dl, D2... Diode for back electromotive current regeneration, D3, D4... Protection diode for phase selection transistor. Fig. 2 Timing chart for each part Fig. 3 Timing chart for each part in Fig. 1 Fig. 4

Claims (1)

[Claims] A stepping motor is driven by sequentially switching the n-phase windings and passing a current in the positive direction of the windings.
In a stepping motor drive circuit that regenerates back electromotive current during phase switching into a power supply, the back electromotive current flows through one of the bifilar two-phase windings in the opposite direction and the other in the forward direction, and the back electromotive current A back electromotive current path is set so that it flows in series toward the power supply, and a back electromotive voltage absorption circuit is inserted in the back electromotive current path to absorb the back electromotive voltage, and the absorption voltage of this back electromotive voltage absorption circuit is and an absorption voltage switching circuit for switching, and the absorption voltage by the back electromotive voltage absorption circuit is set to a low voltage by the absorption voltage switching circuit only during a predetermined time when the back electromotive current flowing at the time of phase switching is decreasing. . A stepping motor drive circuit characterized in that the voltage absorbed by the back electromotive voltage absorption circuit is set to a high voltage at times other than the predetermined time.