JP2813798B2 - Stepping motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bifilar winding stepping motor.

[Conventional technology]

Winding the first phase winding and the third phase winding around the same magnetic pole,
A bifilar wound hybrid type stepping motor in which both the second phase winding and the fourth phase winding are wound around the same magnetic pole is known. In this stepping motor, a bipolar transistor for determining an excitation period is connected in series with each winding, and this is turned on / off by an excitation signal. This method has the advantage that the circuit configuration is simple,
There is a disadvantage that the peak value of the current flowing through the winding changes due to a change in the rotation speed, and a large torque cannot be obtained in a high-speed region.

In order to solve this disadvantage, as shown in FIG. 8, first, second, third and fourth windings 2a, 2b, 2c and 2d are connected between one end and the other end of the DC power supply 1. , Diodes 3a, 3b, 3c, 3d
And bipolar transistors 4a, 4b, 4c, 4d and current detection resistors 5a, 5b, respectively, and a transistor 6a for intermittent control (jumpper control) in series with the first to fourth windings 2a to 2d. There is known a method in which the control circuit 7a, 6b is connected and the chopper control transistors 6a, 6b are intermittently controlled by the control circuits 7a, 7b at a period sufficiently shorter than the ON period of the excitation signal. Note that protection diodes D ₁ and D ₂ are connected in parallel with the transistors 6a and 6b. In this method, the control circuit 7a,
Since the transistors 6a and 6b are intermittently controlled (constant-current chopper control) so that the transistor 7b can obtain constant-current characteristics, it is possible to increase the average current and the torque during high-speed rotation.

[Problems to be solved by the invention]

By the way, in the method of FIG.
Connecting 3a-3d not only increased the number of parts, but also increased the power loss.

The backflow preventing diodes 3a to 3d are transistors
It is provided to prevent backflow from the bases 4a to 4d in the direction of the collector. This will be described using the transistor 4a as an example. The drive circuit 9 for the transistor 4a is usually a transistor Q connected in Darlington to the transistor 4a.
A _1, a driving transistor Q ₂ to which connected between the base and the ground of the transistor Q _1, and connected to resistor R between the base and the power supply terminal + V of the transistor Q _1. Note that the off control transistor Q ₂ when the on control transistor 4a, when off control of the transistor 4a is turned on control transistor Q _2. If the circuit configuration in which the backflow preventing diodes 3a to 3d are omitted from FIG. 8, the transistors 4a to 4d may be inadvertently turned on. That is, now, the transistor 4a is in the off state and the transistor 4c is in the on state. In this state, when the chopper transistor 6a is switched from on to off, the upper end of the winding 2a is positive, the lower end is negative, and the upper end of the winding 2c. Becomes negative, the lower end becomes positive potential, ground, transistor Q ₂ during ON period, stray capacitance C between base and collector of transistor Q ₁ , winding 2 a,
Winding 2c, transistor 4c during ON period, current detection resistor 5a
A closed circuit comprising: a ground, a power terminal indicated by + V,
A current flows through a closed circuit including the resistor R, the stray capacitance C, the windings 2a and 2c, the transistor 4c, and the resistor 5a, and the stray capacitance C is charged. When the chopper transistor 6a is turned on in this state, a current flows through a circuit including the winding 2c, the transistor 4c during the ON period, and the current detection resistor 5a, and the voltage directions of the windings 2a and 2c are reversed. And the lower end of the winding 2a becomes positive. As a result, the power supply 1, Chiyotsupa transistor 6a, winding 2a, the stray capacitance C, the transistors Q _2, a stray capacitance C with reverse charge to current flow in the circuit composed of the ground, stray capacitance C, the base of the transistor Q ₁ A current for reversely charging the stray capacitance C also flows between the emitter, between the base and the emitter of the transistor 4a, the circuit including the current detection resistor 5a and the ground. Therefore, the transistor 4a is turned on in spite of the off control period. When the transistors 4a and 4c are turned on at the same time, the magnetic fluxes cancel each other based on the windings 2a and 2c, so that a necessary torque cannot be obtained.

As shown in FIG. 8, when the backflow preventing diodes 3a to 3d are connected, charging of the stray capacitance C is prevented, a large reverse charging current is prevented from flowing, and the transistor 4a is not turned on carelessly. Therefore, the backflow preventing diodes 3a to 3d cannot be omitted from the circuit of FIG.

Therefore, an object of the present invention is to provide a stepping motor that operates well despite its simplified configuration.

Means for Solving the Problems According to the present invention for achieving the above object, a pair of windings is connected between a DC power supply and a ground, and one and the other of the pair of windings have the same magnetic pole. The switching element is connected in series to each of the one and the other windings,
A bifilar winding stepping motor in which a current detection resistor is connected between the switching element and ground, and an excitation control circuit is provided for turning on the one and the other switching elements with a time lag according to a predetermined excitation method. Wherein the switching element comprises a field effect transistor, a source of the field effect transistor is connected to the current detection resistor, a built-in or external diode is connected between a source and a drain of the field effect transistor, No reverse current blocking diode is connected in series with the field effect transistor to allow a reverse current to flow through the line, and a drive circuit is provided between the excitation control circuit and the gate of the field effect transistor. And the driving circuit includes a resistor and a bipolar transistor. The emitter of the bipolar transistor is connected to ground, the collector is connected to the gate of the field effect transistor, the resistor is a power supply terminal for supplying a gate-source voltage to the field effect transistor, and the field effect transistor Between the excitation control circuit and the base of the bipolar transistor, when the field effect transistor is turned on, the bipolar transistor is controlled to be off, and the field effect transistor is turned off. The present invention relates to a stepping motor, wherein a circuit for controlling the bipolar transistor to be turned on at some times is provided.

It is preferable that another bipolar transistor is connected in parallel with the resistor as described in claim 2, and this is turned on when the field effect transistor is turned on. [Operation and Effect of the Invention] According to this configuration, it is possible to prevent an unnecessary current from flowing through the field effect transistor during the off-control period, despite the configuration in which the backflow prevention diode is not connected in series with the field effect transistor.
That is, a field effect transistor is used as a switching element for controlling the current of the winding, and a bipolar transistor is connected between the gate and the source of the field effect transistor to control on / off of the field effect transistor. Since the bipolar transistor is turned on during the off period of the transistor, even if a current based on the floating capacitance between the drain and the gate of the field effect transistor flows into the bipolar transistor during the off control period of the field effect transistor, the bipolar transistor in the on state is turned on. The voltage between the collector and the emitter of the transistor does not exceed the threshold value between the gate and the source of the field effect transistor. As a result, unnecessary ON operation during the OFF control period of the field effect transistor can be prevented without connecting a reverse current blocking diode in series with the field effect transistor to prevent charging and discharging of the stray capacitance of the field effect transistor. Thus, power loss can be reduced.

According to the second aspect of the present invention, another bipolar transistor is connected in parallel to the pull-up resistor between the drive power supply terminal and the gate, and the other bipolar transistor is turned on when the field effect transistor is turned on. Turn on. As a result, the gate-source capacitance of the field-effect transistor is rapidly charged through another bipolar transistor, and the field-effect transistor can be rapidly turned on in the saturation region.

〔Example〕

Next, a stepping motor according to an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, portions having substantially the same functions as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. The first, second, third and fourth windings 2a to 2d have insulated gate field effect transistors, ie, FETs 10a, 10b, 10c, 10
d are connected in series. Each of the FETs 10a to 10d has a p-type region 11, an n-type region 12, an n ^{+ -type} region 13, and an insulating film 14, as shown in principle in FIG. 7, and a drain electrode D is connected to the n-type region 12. , N ^{+ type} region 13 and p type region 11
N-channel FE with substrate connected internally
T. Therefore, a diode (pn junction) is built in between the source and the drain.

The excitation signal generation circuit 15 shown in FIG. 1 is a circuit for generating an excitation signal for determining an excitation period. One output line 15a is directly connected to the first drive circuit 9a, and a NOT circuit is provided. The other output line 15b is directly connected to the second drive circuit 9b via the NOT circuit 16b, and is also connected to the fourth drive circuit 9d via the NOT circuit 16b. It is connected. Each drive circuit 9a, 9b, 9c, 9d
Is connected to the gates of the FETs 10a, 10b, 10c, and 10d.

As is clear from the comparison between FIG. 1 and FIG. 8, the circuit of FIG. 1 is the same as the circuit of FIG.
And those corresponding to the smoothing diodes 8a and 8b are not provided.

Although the internal configuration of the chopper control circuits 7a and 7b is different from that of the conventional circuit shown in FIG. 8, the same reference numerals are used for convenience. The chopper control circuits 7a and 7b include current detection resistors 5a and 5b for controlling the current flowing through the windings 2a to 2d at a constant current.
Are connected via lines 17 and 18.

2 and 3 show the rotor and the stator of the stepping motor. A rotor 22 including a permanent magnet 21 is fixed to a shaft 23. The stator 24 includes the magnetic poles 25a and 25b of the stator core 25.
Are wound around the windings 2a to 2d.
The first and third windings 2a and 2c are wound around the magnetic pole 25a.
5b is wound with second and fourth windings 2b and 2d. Since the structures of the rotor 22 and the stator 24 of the stepping motor are the same as those of a well-known bifilar winding four-phase stepping motor, a detailed description thereof will be omitted.

FIG. 4 shows the chopper control circuit 7a and the driving circuit 9c of FIG.
Is shown in detail. The control circuit 7a includes a comparator 26, an amplifier 27, a trigger pulse generation circuit 28, resistors 30 to 34, 5V
And a power supply terminal 35.

One input terminal of the comparator 26 is connected to one end of the current detecting resistor 5a via the resistor 31, and the other input terminal is connected to a voltage dividing point of the voltage dividing resistors 29 and 30 and the trigger pulse generating circuit 28. A feedback resistor 32 is connected between the output terminal of the comparator 26 and one of the input terminals, a resistor 33 is connected between the output terminal and the 5V power supply terminal 35, and an output terminal and a transistor for controlling the chopper. The amplifier 27 and the resistor 34 are connected to the base of 6a.

The drive circuit 9c includes an npn transistor 38, a pnp transistor 39, an npn transistor 40, resistors 41, 42, and 7
It comprises a V auxiliary power supply terminal 43, a backflow prevention diode 44, and a NOT circuit 45. The emitter of the npn transistor 38 is grounded, the collector is connected to the gate of the FET 10c, and the base is connected to the excitation signal generating circuit 15 via the NOT circuit 16a. Resistor 41 is the collector of transistor 38 and 7V power supply terminal
This is a pull-up resistor consisting of 19 kΩ and connected between it and 43. The emitter of pnp transistor 39 is auxiliary power terminal 4
3, and the collector is connected to the gate of the FET 10c via the backflow preventing diode 44. The emitter of the npn transistor 40 is connected to the ground, the collector is connected to the base of the transistor 39 and connected to the auxiliary power supply terminal 43 via the resistor 42, and the base is connected to two NOT terminals.
It is connected to the excitation signal generating circuit 15 via the circuits 45 and 16a.

The control circuit 7b of FIG. 1 is not shown in detail,
It has the same configuration as the control circuit 7a shown in FIG.
The components a, 9b and 9d have the same configuration as the drive circuit 9c in FIG.

FIG. 5 shows in principle the waveforms of the respective parts when the stepping motor of FIG. 1 is driven by a two-phase excitation method. 5 (A) shows the emitter-collector voltages of the chopper transistors 6a and 6b, and FIGS. 5 (B) and (C) show the excitation signals, and FIGS. 5 (D) (E) (F) ( G) is an applied voltage (excitation voltage) of the windings 2a to 2d. Now, taking the first winding 2a as an example, the gate signal is applied over the entire period of the ON time width T of the excitation signal shown in FIG. 5 (B). However, since the chopper transistor 6a is intermittent as shown in FIG. 5 (A), a voltage is intermittently applied to the winding 2a even during the excitation period as shown in FIG. 5 (D). You.

The first FET 10a is turned on by the excitation signal shown in FIG. 5B, the second FET 10b is turned on by the excitation signal shown in FIG. 5C, and the third FET 10c is turned on by the excitation signal shown in FIG. The ON signal is controlled by the signal obtained by inverting the excitation signal by the NOT circuit 16a, and the fourth FET 10d is controlled by the signal obtained by inverting the excitation signal of FIG. 5C by the NOT circuit 16b.

The drive circuit 9c shown in FIG. 4 turns on the FET 10c when receiving a low-level excitation signal from the NOT circuit 16a.
That is, the period when the output of the NOT circuit 16a is at a high level (OFF period)
, The transistor 38 is turned on, and the gate is grounded, so that the FET 10c is kept off. On the other hand, NOT circuit 16a
When the output is low level (on period), the transistor
Since 38 turns off, the gate voltage is applied to FET 10c,
FET 10c turns on.

By the way, in principle, the FET 10c can be turned on / off only by the pull-up resistor 41 and the transistor 38. However, if the value of the pull-up resistor 41 is reduced in order to shorten the rise time (ON time) from OFF to ON of the FET 10c, the amount of charge of the gate-source capacitance C _gs of the FET 10c increases. The polarity of the charge of the capacitor C _gs at the time of the rise is positive on the gate side. When the chopper control transistor 6a switches from off to on while the FET 10c is on-controlled, the drain current of the FET 10c flows, and the terminal voltage of the current detection resistor 5a is generated. As a result, the source potential of the FET 10c rises, and the gate-source capacitance C _gs tends to be charged in the reverse direction. If the value of resistor 41 is small and transistor 39 and diode 44
If no circuit is provided, the gate-source capacitance C
The discharge (reverse charge) of _gs increases, and the gate-source voltage required by the FET 10c cannot be supplied, resulting in non-saturated operation.

To avoid this unsaturated condition, a pull-up resistor
It is necessary to make the value of 41 3 kΩ or more, but if it is simply increased, the time to charge the capacitance C _gs so that the gate of the FET 10 c reaches the threshold voltage becomes longer, and the FET 10 c
Cannot be turned on quickly.

On the other hand, the pnp transistor 39 is connected in parallel with the pull-up resistor 41 having a large value (19 kΩ) as in the present embodiment.
Connecting a series circuit with the diode 44 not only shortens the rise time of the FET 10c, but also
By limiting the reverse charging of _gs, the unsaturated operation of the FET 10c can be prevented. That is, when the output of the NOT circuit 16a changes from a high level to a low level, the npn transistor 38 turns off and the transistors 39 and 40 turn on. As a result, the gate-source capacitance C _gs is rapidly charged by the current flowing through the transistor 39 and the diode 44, and the FET 10c
Is immediately turned on.

On the other hand, during the ON period (excitation period) of the FET 10c, the chopper control transistor 6a switches from OFF to ON, the drain current of the FET 10c flows, the source potential increases due to the current detection resistor 5a, and the gate-source capacitance C _{Even if} reverse charging (discharging) of _gs is to occur, it is not discharged rapidly because the value of the resistor 41 is large. Also, no discharge current flows through the transistor 39 because of the backflow prevention diode 44. For this reason, a reduction in the gate-source voltage is limited, and the FET 10c can be turned on in a saturated state. Note that the pull-up resistor
Although it operates even if 41 is omitted, it is provided to make the gate-source capacitance C _gs a high charging voltage.

FIG. 6 shows the operation of the chopper control circuit 7a of FIG.
As current in the winding 2a or 2c is shown in FIG. 6 (A) t ₀ ~t ₁
, The detection voltage obtained from the current detection resistor 5a also gradually increases, and the input terminal of the comparator 26
At 32, a combined voltage of the voltage fed back and the detection voltage is obtained. When one input voltage Va of the comparator 26 shown by a solid line in FIG. 6C crosses the other input voltage _Vb of the comparator 26 shown by _a dotted line, the output voltage of the comparator 26 is shown in FIG. 6D. From low level to high level.
As a result, the transistor 6a for chopper is turned off,
Voltage of the sum of the detection voltage and a feedback voltage corresponding to the forward voltage of the diode D ₃ is the input voltage of the comparator 26. When a trigger pulse shown in FIG. 6 (B) at t ₂ time occurs, obtained by adding a trigger pulse to the reference voltage is used as the input of the comparator 26, to the negative terminal input of the comparator 26 is greater than the positive terminal input The output of the comparator 26 is the sixth
As shown in FIG. 7D, the level is changed to low level, and the transistor 6a for the jumper is turned on. Even if a large oscillating current flows due to resonance when the transistor 6a switches from off to on, the output of the comparator 26 is inadvertently inverted because the level of the negative input of the comparator 26 is increased by the trigger pulse. do not do.

During the ON period of the chopper transistor 6a and the FET 10c, the power supply 1, the chopper transistor 6a, the winding 2c,
Winding with a circuit consisting of FET10c, current detection resistor 5a, and ground
When the excitation current of 2c is supplied and the transistor 6a for chopper is turned off during the ON control period of the FET 10c, the winding 2c
The energy stored on the basis of the excitation is released by a closed circuit including the winding 2c, the internal diode of the FET 10c and the FET 10a during the ON period, and the winding 2a. At this time, the current flowing through the windings 2a and 2c contributes to the generation of a magnetic flux in a direction to maintain the torque.

When the FET 10c, which has been in the on-period (excitation period), switches from on to off, the winding 2a, which has been on the non-excitation side,
A diode D _1, a power supply 1, a diode D _3, the energy stored in the exciting period of coil 2c is released in a closed circuit consisting of an internal diode of the FET 10a.

The case where the excitation signal for turning on the third FET 10c is generated from the excitation signal generation circuit 15 has been described above.
The operation during the period when the FET 10a is turned on is essentially the same.

 This embodiment has the following advantages.

(1) As is clear from the comparison between FIG. 1 and FIG. 8, according to the present embodiment, the diodes 3a to 3a in the circuit of FIG.
3d and the diodes 8a and 8b become unnecessary, and cost can be reduced.

(2) As shown in FIG. 4, in the present embodiment, the windings 2a, 2c
8 shows the reverse current blocking diodes 3a and 3c shown in the conventional circuit of FIG.
Is not provided, the field effect transistors 10a and 10c are not unnecessarily turned on based on the stray capacitance between the drain and the gate during the respective off control periods. The field effect transistor 10c shown in FIG.
Field effect transistor 10c to control c on / off
A bipolar transistor 38 is connected between the gate and the source of the field effect transistor 10c, and the bipolar transistor 38 is turned on during the off period of the field effect transistor 10c. Even if a current based on the floating capacitance between the gates flows into the bipolar transistor 38, the voltage between the collector and the emitter of the bipolar transistor 38 in the ON state does not exceed the threshold between the gate and the source of the field effect transistor 10c. As a result, even if it is not necessary to connect a reverse current blocking diode in series with the field effect transistor 10c to prevent charging and discharging of the stray capacitance of the field effect transistor 10c, the field effect transistor 10c
Unnecessary ON operation during the OFF control period can be prevented, and power loss can be reduced.

(3) Since the circuit including the pnp transistor 39 and the diode 44 is provided, it is possible to shorten the rise time when the FETs 10a to 10d are turned on and to prevent the unsaturated operation.

(4) Since a trigger pulse is given to the comparator 26,
The output of the comparator 26 does not reverse due to the input vibration.

[Another embodiment]

FIG. 9 shows another embodiment of the present invention. In FIG. 9, substantially the same portions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the windings 2a to
An energy emitting circuit composed of a series circuit of a Zener diode 51 and a diode 52 is connected in parallel to 2d. Thus, the winding 2c or 2a and the diode 52
The energy can be released in a closed circuit including the power supply and the Zener diode 51.

(Modification)

The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible.

(1) The diodes D ₃ and D ₄ connected in parallel to the current detection resistors 5a and 5b can be omitted.

(2) If the FETs 10a to 10d do not have a built-in diode structure, a diode may be externally connected between the source and the drain.

(3) The present invention is not limited to the two-phase excitation method, and can be applied to a case where another excitation method such as a 1-2-phase excitation method is adopted.

(4) As shown in FIG. 10, the Zener diode 51 of the energy emitting circuit may be shared by the two windings 2a and 2c.

(5) As shown in FIG. 11, an energy emitting circuit including a Zener diode 51 and a diode 52 may be connected in parallel to the transistor 6a and the windings 2a and 2c.
Also in this case, the Zener diode 51 may be shared as shown in FIG.

(6) The energy emission circuits shown in FIGS. 9, 10 and 11 may be constituted only by diodes. Also, capacitors,
9 to 11 may be used together to form an energy release circuit. Further, a switching element may be connected in parallel to the windings 2a to 2d, and the energy may be rapidly released by turning on the switching element. In the circuit shown in FIG. 9, the diodes D ₁ and D ₂ can be omitted.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a stepping motor according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a portion corresponding to line II-II in FIG. 3 showing a stator and a rotor of the stepping motor, 3 is a sectional view of a portion corresponding to the line III-III in FIG. 2, FIG. 4 is a circuit diagram showing the control circuit in FIG. 1 in detail, FIG. 5 is a voltage waveform diagram of each part in FIG. 6 is a waveform diagram of each part of FIG. 4, FIG. 7 is a sectional view showing an FET, FIG. 8 is a circuit diagram showing a conventional stepping motor, and FIG. 9 is a stepping motor of another embodiment of the present invention. FIG. 10 and FIG. 11 are circuit diagrams showing a modified example of the energy release circuit. 1 ...... DC power source, 2 a to 2 d ...... winding, 6a, 6b ...... Chiyotsupa transistor, 10a, 10b, 10c, 10d ...... FET, 51 ...... Zener diodes, 52 ...... diodes, D ₁ to D ₄ ……diode.

Claims (2)

(57) [Claims] A pair of windings are connected between a DC power supply and a ground, and one and the other of the pair of windings are wound around the same magnetic pole, and are serially connected to the one and the other windings, respectively. A switching element is connected to the switching element; a current detection resistor is connected between the switching element and the ground; and an excitation control circuit for turning on the one and the other switching elements at a staggered time according to a predetermined excitation method is provided. In the bifilar winding stepping motor, wherein the switching element comprises a field effect transistor, a source of the field effect transistor is connected to the current detection resistor, and a built-in or an external between the source and the drain of the field effect transistor A diode is connected and the field effect transistor is connected to allow a reverse current to flow through the winding. A reverse current blocking diode is not connected in series with the star; a drive circuit is connected between the excitation control circuit and the gate of the field effect transistor; the drive circuit includes a resistor and a bipolar transistor; The emitter of the transistor is connected to ground, the collector is connected to the gate of the field-effect transistor, and the resistor is connected to a power supply terminal for supplying a gate-source voltage to the field-effect transistor, and the gate of the field-effect transistor. Connected between the excitation control circuit and the base of the bipolar transistor, the bipolar transistor being turned off when the field effect transistor is turned on, and the bipolar transistor being turned off when the field effect transistor is turned off. The circuit that turns on the A stepping motor, characterized by being kicked. 2. The driving circuit according to claim 1, further comprising another bipolar transistor and a reverse current blocking diode of said another bipolar transistor, wherein said another bipolar transistor is connected to said resistor by a reverse current blocking diode of said another bipolar transistor. 2. The stepping motor according to claim 1, further comprising: a circuit connected in parallel via the second transistor to control turning off the another bipolar transistor when the field effect transistor is turned on.