JP2012070540A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PAM (Pulse-Amplitude-Modulation) control type motor capable of being driven stably even in a low voltage although it has a simple circuit structure.SOLUTION: A PAM (Pulse-Amplitude-Modulation) control type motor 1 where a driving voltage Vm changes has a driving device 4 for supplying driving current to a coil 6 through a plurality of current in/out wiring lines 7. The driving device 4 comprises: an upstream side power element 21 and a downstream side power element 22 for switching the current in/out wiring lines 7; a control circuit 31 for applying a control voltage VG to the upstream side power element 21 and the downstream side power element 22; and a control voltage formation circuit 41, which is provided between the control circuit 31 and the upstream side power element 21, for forming the control voltage Vg by dividing the driving voltage Vm. A P-channel MOSFET is used for the upstream side power element 21, and the control voltage formation circuit 41 is provided with a low voltage auxiliary circuit 50 for increasing the control voltage Vg when the control voltage Vg decreases to a predetermined value or lower.

Description

  The present invention relates to a PAM (Pulse Amplitude Modulation) control system motor.

  In this type of motor, in order to variably control the rotation speed, the applied drive voltage changes in magnitude. Accordingly, there is a demand for performance capable of stably rotating in a wide range from a high voltage region where the drive voltage is high to a low voltage region where the drive voltage is low.

  When a motor is driven to rotate, it is necessary to supply a predetermined pattern of current to the coil. In general, the control is performed by turning on / off a power element (MOSFET: Metal Oxide Semiconductor Field Effect Transistor). There are many.

  MOSFETs include N-channel MOSFETs and P-channel MOSFETs. In the case of an N channel MOSFET, by applying a positive potential to the gate electrode, a current flows between the source electrode and the drain electrode (ON state). In the case of a P channel MOSFET, the negative electrode side is applied to the gate electrode. Is turned on by applying the potential. Near the threshold voltage, the amount of current flowing between the source electrode and the drain electrode is affected by the magnitude of the potential applied to the gate electrode.

  A motor drive circuit using an N-channel MOSFET as a power element is disclosed (Patent Document 1).

  The motor drive circuit is provided with a charge pump circuit that boosts the drive voltage, and the boosted voltage boosted by the charge pump circuit is converted to a regulated voltage that is made constant by the regulator circuit. The converted regulated voltage is output to the gate of the power element.

JP 2008-259340 A

  Conventionally, a drive voltage is reduced at a constant voltage dividing ratio, and a control voltage is output to a power element using the reduced voltage. However, in this case, if the drive voltage is lowered, the control voltage output to the power element is also lowered in accordance with the drop in the drive voltage. Therefore, if the drive voltage is greatly lowered, the on / off operation of the power element is disabled. There is a problem that the motor performance becomes stable and the original motor performance cannot be obtained, such as a decrease in rotational speed and torque.

  FIG. 1 schematically shows a drive circuit for the power element 100. The figure shows a case where a P-channel MOSFET is used for the power element 100. In the case of this power element 100, two P-type regions (a source electrode 102 and a drain electrode 103) are formed apart on the N-type semiconductor 101, and an oxide film 104 is interposed in the channel region between these 102 and 103. A gate electrode 105 is stacked.

  The power element 100 is connected in the middle of a current supply line 106 that supplies current to the coil, the power supply side (high potential side) is connected to the source electrode 102, and the coil side (low potential side) is connected to the drain electrode 103. It is connected. A drive voltage Vm is applied to the current supply line 106.

  A voltage dividing circuit 110 that applies a control voltage to the power element 100 includes a first resistor 111 and a second resistor 112 connected in series, and the driving voltage Vm is also applied to the voltage dividing circuit 110. The gate electrode 105 is electrically connected so that the potential between the first resistor 111 and the second resistor 112 is the same.

  Since the potential is not output to the gate electrode 105 when the voltage dividing circuit 110 is not energized, the channel region is not conducted (OFF state), but when the voltage dividing circuit 110 is energized as shown in FIG. The potential on the negative electrode side is output, and the control voltage generated by the voltage drop is applied to the gate electrode 105 (gate voltage Vg). Then, the channel region becomes conductive and current flows from the source electrode 102 to the drain electrode 103 (ON state).

  However, when the drive voltage Vm is lowered, as shown in FIG. 2, the gate voltage Vg is also lowered accordingly. The power element 100 has a lower limit value VgL of the gate voltage Vg that functions stably. Below that value, the on / off operation becomes unstable, for example, the power element 100 is not turned on even when the gate voltage Vg is applied. In addition, even if the channel is turned on, the channel section has a large electric resistance, so that an appropriate amount of current cannot be obtained, and the original motor performance such as a decrease in the rotational speed and torque cannot be obtained.

  In this regard, in the motor drive circuit disclosed in Patent Document 1, since the drive voltage is boosted by the charge pump circuit, an excessive decrease in the gate voltage can be prevented even if the drive voltage is lowered. However, since the circuit structure is complicated, there are disadvantages in terms of member cost and reliability.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a PAM control system motor that can be driven stably even at a low voltage while having a simple circuit structure.

  The motor of the present invention includes a motor body having a rotor supported rotatably, a plurality of coils, and three or more current input / output paths connected to the coils, and at least any two of the current input / output paths. And a drive device that supplies a drive current to the coil and rotationally drives the rotor, and a PAM control type motor in which the drive voltage changes.

  The drive device includes a plurality of switching paths arranged in parallel, a current supply path for supplying the driving current to the motor body, an upstream power element connected to a high potential side of the switching path, and the In order to control each of the plurality of power elements that switch the current input / output path, and each of the upstream power element and the downstream power element, including downstream power elements disposed on the low potential side of the switching path, A control device that outputs a control signal at a predetermined timing; and a control voltage forming device that is provided between the control device and the upstream power element and forms a control voltage of the upstream power element from the drive voltage. Have.

  The control voltage forming device includes a voltage dividing path having a first resistor and a second resistor connected in series in order from a high potential side to which the driving voltage is applied, and between the first resistor and the second resistor. And a first potential output path for outputting the potential to the upstream power element.

  A P-channel MOSFET is used for the upstream power element, and the control voltage generator is provided with a low voltage auxiliary circuit for changing the control voltage to a high level when the control voltage drops below a predetermined value. Yes.

  According to the motor having such a configuration, since the P-channel MOSFET is used for the upstream power element, the upstream power element can be turned on by outputting the negative potential to the gate electrode. . When the drive voltage is lowered, the control voltage is also lowered. However, by outputting a lower potential to the gate electrode, the control voltage can be changed higher.

  The control voltage forming device is provided with a low voltage auxiliary circuit that changes the control voltage to a high level when the control voltage drops below a predetermined value. Therefore, the control voltage is increased even under the lowered drive voltage. be able to. Therefore, the upstream power element can be driven stably at a low voltage without providing a complicated circuit structure, and the motor performance can be exhibited stably.

  For example, the low voltage auxiliary circuit includes a variable voltage dividing ratio circuit that can be switched between a first voltage dividing ratio and a second voltage dividing ratio for low voltage at which the control voltage is higher than the first voltage dividing ratio. Can be configured.

  Then, the low voltage auxiliary circuit can be formed by adding a few circuits to the existing circuit.

  Specifically, the variable voltage dividing ratio circuit includes, in addition to the voltage dividing circuit, a third resistor connected in series to a portion on the higher potential side of the first resistor in the voltage dividing path, and the voltage dividing path. A sub-voltage dividing path having a fourth resistor and a switch element connected in series in order from the high potential side, connected in parallel with the portion where the third resistor and the first resistor are provided An N-channel MOSFET is used for the switch element, and a second potential for outputting a potential between the third resistor and the first resistor to the switch element between the voltage dividing path and the sub-voltage dividing path. An output path may be provided.

  Further, the low voltage auxiliary circuit is based on an instruction from the comparison circuit that compares whether or not the control voltage has decreased below a predetermined value, and an instruction from the comparison circuit when the control voltage has decreased below a predetermined value. And a minimum potential output circuit that outputs a minimum potential to the upstream power element.

  Also in this case, when the control voltage drops below a predetermined value, a lower minimum potential can be output to the gate electrode, so that the control voltage can be further increased.

  For example, the comparison circuit includes a comparator that outputs a predetermined potential from a potential output terminal according to the comparison result, and the minimum potential output circuit has one end that is lower in potential than the second resistance in the voltage dividing path. And a switching element provided in the middle of the minimum potential output path, and an N-channel MOSFET is used for the switching element. In addition, a third potential output path for outputting the potential of the potential output terminal to the switch element may be provided between the comparison circuit and the minimum potential output path.

  Furthermore, the above-described variable voltage division ratio circuit, comparison circuit, and minimum potential output circuit can be combined.

  Then, the control voltage can be controlled more finely, so that the upstream power element can be driven more stably even in the low voltage region, and the motor performance can be exhibited stably.

  As described above, according to the present invention, a PAM control type motor that can be driven stably even in a low voltage region can be realized with a simple circuit structure.

It is the schematic which shows an example of the drive circuit of a power element. It is a graph which shows the relationship between the drive voltage Vm and the control voltage Vg. It is the schematic which shows the motor of 1st Embodiment. It is the schematic showing the circuit structure of the drive device. It is the schematic showing the control voltage formation circuit. (A), (b) is a figure for demonstrating operation | movement of a control voltage formation circuit. It is the schematic showing the relationship between a drive voltage and a control voltage. It is the schematic showing the circuit structure of the drive device in the motor of 2nd Embodiment. It is the schematic showing the circuit structure of the minimum electric potential output circuit. It is the schematic showing the circuit structure of the comparison circuit. It is the schematic showing the circuit structure of the drive device in the motor of a modification. It is the schematic showing the principal part of the low voltage auxiliary circuit in the motor of a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the following description is merely illustrative in nature and does not limit the present invention, its application, or its use.

<First Embodiment>
FIG. 3 shows an outline of the motor 1 according to this embodiment to which the present invention is applied. The motor 1 is a PAM control type three-phase brushless DC motor used for a fan of a blower, for example. The motor 1 includes a rotor 2, a motor main body 3, a driving device 4, and the like.

  The rotor 2 is rotatably supported by a motor case 5 via a shaft, and a motor body 3 that rotationally drives the rotor 2 is accommodated in the motor case 5. The structure of the motor body 3 is the same as that of a conventional motor. For example, in the case of an inner rotor type, the rotor 2 is formed in a columnar shape having a plurality of magnets on the outer periphery. An annular stator having a plurality of coils 6 (see FIG. 4) is arranged outside the rotor 2 with a slight gap therebetween.

  The coil 6 is composed of, for example, three-phase coils 6u, 6v, and 6w of U, V, and W, and these coils 6u, 6v, and 6w are connected by Y connection or delta connection according to the specifications of the motor. Incidentally, in this embodiment, Y-connection is made. The motor body 3 is provided with a current input / output wiring 7 (current input / output path), through which a drive current is supplied from the drive device 4 to the coils 6u, 6v, 6w in a predetermined order.

  By doing so, torque is generated by the action of each of the coils 6u, 6v, 6w, which are sequentially excited, and the permanent magnet, and the rotor 2 rotates. In order to change the rotation speed, the drive voltage Vm is changed to a large or small value by the PAM control method.

  The drive device 4 is, for example, a circuit board configured with an IC or the like, and is incorporated in the motor case 5. The drive device 4 is connected to an external device 8 in order to receive power supply or the like. In the vicinity of the motor body 3, a position sensor 9 such as a Hall element for detecting the position (rotation angle) of the rotor 2 is arranged. The position data of the rotor 2 detected by the position sensor 9 is output to the driving device 4.

  FIG. 4 is a schematic diagram illustrating a circuit configuration of the driving device 4. As shown in the figure, the drive device 4 includes a current supply wiring 11 (current supply path), power elements 21 and 22, a control circuit 31 (control device), and a control voltage formation circuit 41 (control voltage formation device). It has been. The control voltage generating circuit 41 includes a voltage dividing circuit 47 and a low voltage auxiliary circuit 50, and the low voltage auxiliary circuit 50 is provided with a variable voltage dividing ratio circuit 51.

  The current supply wiring 11 has a high-potential-side wiring 12 having one end connected to the drive power supply side and three switching wirings 13a, 13b, 13c (switching) arranged in parallel by branching from the other end of the high-potential-side wiring 12. Path) and a low potential side wiring 14 having one end connected to the low potential side of the switching wirings 13a, 13b, 13c. The other end of the low potential side wiring 14 is grounded via the lower resistor 15, and is configured such that the driving voltage Vm is applied to the current supply wiring 11 when the motor 1 is driven.

  The power elements 21 and 22 are switch elements that can be turned on / off, and two power elements are connected in series to each of the three switching wirings 13a, 13b, and 13c. These power elements 21 and 22 include a power element 21 (upstream power elements 21a, 21b, 21c) disposed on the high potential side and a power element 22 (downstream power elements 22a, 22b) disposed on the low potential side. 22c), a P-channel MOSFET is used for the upstream power element 21, and an N-channel MOSFET is used for the downstream power element 22.

  The current input / output wiring 7 is composed of three current input / output wirings 7a, 7b, 7c, and these currents are provided in a portion between the upstream power element 21 and the downstream power element 22 in each switching wiring 13a, 13b, 13c. Input / output wirings 7a, 7b and 7c are connected to each other. Then, any one of the upstream power elements 21a, 21b, and 21c is on-controlled, and any one of the downstream power elements 22a, 22b, and 22c is on-controlled so that the drive voltage Vm is applied 1 Two closed circuits are formed.

  That is, a drive current having a predetermined flow is supplied to a predetermined coil 6 in a predetermined order through two current input / output lines 7 and 7 out of the three current input / output lines 7a, 7b and 7c. For example, when the upstream power element 21a is turned on and the downstream power element 22c is turned on, the drive current is supplied in the order of the switching wiring 13a, current input / output wiring 7a, coil 6w, coil 6v, current input / output wiring 7c, and switching wiring 13c. Flowing.

  The control circuit 31 outputs an energization signal (control signal) at a predetermined timing in order to perform on / off control of the power elements 21 and 22. The control circuit 31 includes a position detection input unit 32, a timing control unit 33, an energization signal forming unit 34, an upper arm drive circuit unit 35, a lower arm drive circuit unit 36, and the like. For driving the control circuit 31, a circuit voltage Vcc lower than the drive voltage Vm is used.

  The position detection input unit 32 receives position data output from the position sensor 9, converts the position data into a position signal, and outputs the position signal to the timing control unit 33. The timing control unit 33 generates an on / off signal for turning on / off each of the power elements 21 and 22 based on the position signal and a previously stored timing chart, and outputs the on / off signal to the energization signal forming unit 34. The energization signal forming unit 34 generates an energization signal (specifically, a potential based on the circuit voltage Vcc) for turning on / off the power elements 21 and 22 at a predetermined timing based on the on / off signal, and drives the upper arm. In cooperation with each of the circuit unit 35 and the lower arm drive circuit unit 36, the energization signal is output to the current supply wiring 11 side.

  An energization signal is output from the lower arm drive circuit unit 36 to the gate electrode of a predetermined downstream power element 22. On the other hand, an energization signal is output from the upper arm drive circuit unit 35 to a control voltage forming circuit 41 provided between the control circuit 31 and the upstream power element 21.

  FIG. 5 shows a circuit configuration of the control voltage forming circuit 41. The control voltage forming circuit 41 is provided for forming a control voltage (also referred to as a first control voltage Vg) for controlling the upstream power element 21. The control voltage forming circuit 41 is provided for each of the upstream power elements 21a, 21b, and 21c, and FIG. A drive power supply is connected to the upstream side of the control voltage forming circuit 41, and the drive voltage Vm is applied to the control voltage forming circuit 41. In the control voltage forming circuit 41, the first control voltage Vg is formed by dividing the drive voltage Vm at a predetermined voltage dividing ratio.

  In particular, the control voltage forming circuit 41 is provided with a low voltage auxiliary circuit 50 that changes the first control voltage Vg to a high level when the first control voltage Vg drops below a predetermined value as the drive voltage Vm drops. It has been. In the present embodiment, as the low voltage auxiliary circuit 50, the voltage dividing ratio can be switched between the first voltage dividing ratio for normal voltage and the second voltage dividing ratio for low voltage where the first control voltage Vg is higher than this. A circuit 51 is provided.

  First, the control voltage forming circuit 41 includes a voltage dividing wiring 45 (voltage dividing path) having a first resistor 43 and a second resistor 44 connected in series in order from the high potential side, and the upstream power element 21 includes In order to apply one control voltage Vg, a potential output wiring 46 (first potential output path) for outputting the potential between the first resistor 43 and the second resistor 44 to the upstream power element 21 is provided. A pressure circuit 47 is provided.

  A portion on the lower potential side than the second resistor 44 is grounded via a switch element (also referred to as a first switch element 48). The first switch element 48 is an N-channel MOSFET, and its gate electrode is connected to the upper arm drive circuit unit 35 via the control wiring 49, and the first switch element 48 is turned on / off by an energization signal output therefrom. Be controlled.

  In addition to the voltage dividing circuit 47, the variable voltage dividing ratio circuit 51 includes a third resistor 52, a fourth resistor 53, a switch element (also referred to as a second switch element 54), and the like. The third resistor 52 is connected in series to a portion of the voltage dividing wiring 45 on the higher potential side than the first resistor 43. A sub-divided wiring 55 (sub-voltage dividing path) is connected in parallel with a portion (also referred to as a voltage dividing resistor portion) provided with the third resistor 52 and the first resistor 43, and there is a high potential side. The fourth resistor 53 and the second switch element 54 are connected in series in order.

  The second switch element 54 of this embodiment is also an N-channel MOSFET. In order to apply a control voltage (also referred to as a second control voltage) to the second switch element 54, a portion of the voltage dividing wiring 45 between the third resistor 52 and the first resistor 43 and a gate electrode of the second switch element 54 Are connected by a potential output wiring 56 (second potential output path), and the potential between the third resistor 52 and the first resistor 43 is output to the gate electrode of the second switch element 54. Then, when the second control voltage is applied to the second switch element 54, the second switch element 54 is turned on and the sub-divided wiring 55 is energized.

  The resistance values of the third resistor 52 and the first resistor 43 are appropriately set according to the performance of the second switch element 54 and the gate electrode of the upstream power element 21.

  In addition, a Zener diode 57 (overvoltage prevention device) is provided in parallel with the voltage dividing resistor portion and the sub voltage dividing wiring 55. As a result, a voltage higher than a predetermined value is not applied to the second switch element 54 and the gate electrode of the upstream power element 21.

  The operation of the control voltage generation circuit 41 having such a configuration will be described with reference to FIG. When the motor 1 is driven under the normal drive voltage Vm by the PAM control, the resistance value of the third resistor 52 and the like is set so that the second switch element 54 is stably turned on. Therefore, the sub-divided wiring 55 is energized, resulting in a circuit configuration shown in FIG. 5A that generates the first voltage division ratio for normal voltage.

  When the second switch element 54 is turned off as the drive voltage Vm decreases, the sub-divided wiring 55 is cut off, and the circuit configuration shown in FIG. Become.

  In this case, since the total resistance of the voltage dividing resistor portion and the sub-divided wiring 55 is larger than the first voltage dividing ratio, the amount of voltage drop increases, and the voltage between the first resistor 43 and the second resistor 44 is increased. The potential further decreases. Therefore, in the second voltage division ratio, the first control voltage Vg applied to the gate electrode of the upstream power element 21 is higher than in the case of the first voltage division ratio.

  When the normal drive voltage Vm is restored again, the second switch element 54 is turned on, and the circuit configuration is switched to produce the first voltage division ratio.

  FIG. 7 shows the relationship between the drive voltage Vm and the first control voltage Vg. In the figure, the broken line represents the first voltage division ratio for normal voltage, and the solid line represents the second voltage division ratio for low voltage. In the low voltage region, since the second voltage division ratio is applied, the value of the first control voltage Vg with respect to the drive voltage Vm is relatively high. Therefore, even if the drive voltage Vm is greatly reduced, the first control voltage Vg can be kept high, so that the on / off operation of the upstream power element 21 can be stabilized and the motor performance can also be exhibited stably.

Second Embodiment
In the present embodiment, as the low voltage auxiliary circuit 50, the comparison circuit 61 or the like is used instead of the voltage dividing ratio variable circuit 51, and the first control voltage Vg is switched to the minimum potential when the low voltage region is reached. Since the basic configuration of the present embodiment is the same as that of the first embodiment, the same reference numerals are used for the same configurations and the description thereof is omitted, and different points will be described in detail.

  In FIG. 8, the schematic showing the circuit structure of the drive device 4 in the motor 1 of this embodiment is shown. As shown in the figure, the control voltage forming circuit 41 of the driving device 4 is provided with a comparison circuit 61 and a minimum potential output circuit 71. Not only the drive voltage Vm but also the circuit voltage Vcc is applied to the control voltage forming circuit 41.

  FIG. 9 shows a circuit configuration of the minimum potential output circuit 71. The minimum potential output circuit 71 is set to 0 V (set by the motor 1) when the first control voltage Vg drops below a predetermined value (also referred to as a threshold) that may cause the ON state of the upstream power element 21 to become unstable. Is provided to output to the upstream power element 21.

  Specifically, the minimum potential output circuit 71 includes a minimum potential output wiring 72 (minimum potential output path) and a switch element (also referred to as a third switch element 73).

  One end of the minimum potential output wiring 72 is connected to a portion having the same potential as the ground on the lower potential side than the second resistance 44 in the voltage dividing wiring 45, and the other end is connected to the first resistance 43 and the second resistance in the voltage dividing wiring 45. The portion connected to the resistor 44 is connected. Incidentally, this portion is connected to the gate electrode of the upstream power element 21. The third switch element 73 is provided in the middle of the minimum potential output wiring 72 and is in parallel with the second resistor 44. An N-channel MOSFET is used for the third switch element 73, and one end of a potential output wiring 74 (third potential output path) is used to apply a control voltage (also referred to as a third control voltage) to the gate electrode. Is connected.

  FIG. 10 shows a circuit configuration of the comparison circuit 61. The comparison circuit 61 is provided to compare whether or not the first control voltage Vg has dropped below a predetermined value. The comparison circuit 61 includes a first voltage dividing wiring 62, a second voltage dividing wiring 63, and a comparator 64 (comparator).

  A fifth resistor 65 and a sixth resistor 66 are connected in series to the first voltage dividing wiring 62 in order from the high potential side. A seventh resistor 67 and an eighth resistor 68 are connected in series to the second voltage dividing wiring 63 in order from the high potential side. A circuit voltage Vcc is applied to the first voltage dividing wiring 62. A drive voltage Vm is applied to the second voltage dividing wiring 63. The resistance values of the fifth resistor 65 and the like are set as appropriate according to the performance of the gate electrode of the upstream power element 21 and the comparator 64.

  The portion of the first voltage dividing wiring 62 between the fifth resistor 65 and the sixth resistor 66 is connected to the high potential side terminal 64a of the comparator 64, and the seventh resistor 67 and the The portion between the eight resistors 68 is connected to the terminal 64 b on the low potential side of the comparator 64. The other end of the potential output wiring 74 is connected to the output terminal 64 c (potential output terminal) of the comparator 64.

  The comparator 64 compares the potential of the high potential side terminal 64a with the potential of the low potential side terminal 64b to compare whether or not the first control voltage Vg has fallen below the threshold value. When the first control voltage Vg falls below the threshold value, the comparator 64 outputs an H level potential for applying the third control voltage to the gate electrode of the third switch element 73 through the potential output wiring 74. The third switch element 73 is turned on.

  Then, since the minimum potential output wiring 72 is energized, a potential of 0 V is output to the gate electrode of the upstream power element 21, and the first control voltage Vg is further increased. Therefore, even in this motor 1, when the drive voltage Vm is greatly reduced, the on / off operation of the upstream power element 21 can be stabilized, and the motor performance can also be exhibited stably.

  On the other hand, when the first control voltage Vg exceeds the threshold value, the comparator 64 outputs an L-level potential (for example, 0 V) to the gate electrode of the third switch element 73 through the potential output wiring 74, and the third The switch element 73 is turned off. Therefore, in this case, since the minimum potential output wiring 72 is cut off, the first control voltage Vg generated under the normal voltage dividing circuit 47 is applied to the upstream power element 21.

(Modification)
In the motor 1 of this modification, the low voltage auxiliary circuit is obtained by combining the voltage dividing ratio variable circuit 51 of the motor 1 of the first embodiment with the comparison circuit 61 and the minimum potential output circuit 71 of the motor 1 of the second embodiment. 50 is configured.

  In FIG. 11, the circuit structure of the drive device 4 in the motor 1 of this modification is shown. Since the components such as the voltage division ratio variable circuit 51 in the motor 1 are the same as those in the above-described embodiments, the same reference numerals are used and description thereof is omitted.

  FIG. 12 shows a portion of the low voltage auxiliary circuit 50 of the present modification excluding the comparison circuit 61 (the comparison circuit 61 is the same as that of the second embodiment). In the case of this motor 1, the first control voltage Vg in the low voltage region can be switched in two stages.

  For example, a first reference voltage and a second reference voltage lower than the first reference voltage are set, the voltage division ratio variable circuit 51 is controlled based on the first reference voltage, and the comparison circuit 61 is controlled based on the second reference voltage. Control etc. By doing so, the ON / OFF operation of the upstream power element 21 in the low voltage region can be controlled more finely, so that the ON / OFF operation of the upstream power element 21 can be further stabilized, and the performance of the motor 1 is further improved. It will be able to be demonstrated stably.

  In addition, the motor of this invention is not limited to embodiment mentioned above, The other various structure is included. For example, the motor 1 may be an outer rotor type. The switch element (second switch 54) is not limited to a MOSFET but may be another transistor.

1 Motor 2 Rotor 3 Motor body 4 Drive device 6 Coil 7 Current input / output wiring (current input / output path)
11 Power supply wiring (Power supply path)
13a, 13b, 13c Switching wiring (switching path)
21, 22 Power elements 21a, 21b, 21c Upstream power elements 22a, 22b, 22c Downstream power elements 31 Control circuit (control device)
41 Control voltage forming circuit (control voltage forming device)
43 1st resistor 44 2nd resistor 45 Voltage dividing wiring (voltage dividing path)
46 Potential output wiring (first potential output path)
47 Voltage Divider 48 Switch Element 50 Low Voltage Auxiliary Circuit 51 Voltage Divider Variable Circuit 52 Third Resistor 53 Fourth Resistor 54 Switch Element 55 Sub Voltage Dividing Line (Sub Voltage Dividing Path)
56 Potential output wiring (second potential output path)
61 Comparison Circuit 62 First Voltage Dividing Line 63 Second Voltage Dividing Line 64 Comparator (Comparator)
64c Output terminal (potential output terminal)
71 Minimum potential output circuit 72 Minimum potential output wiring (minimum potential output path)
73 Switch element 74 Potential output wiring (third potential output path)
Vm Drive voltage Vg First control voltage

Claims (6)

A rotor supported rotatably;
A motor body having a plurality of coils and three or more current input / output paths connected to the coils;
A drive device for supplying a drive current to the coil through at least any two of the current input / output paths and rotating the rotor;
With
A PAM control type motor in which the drive voltage changes,
The driving device includes:
A plurality of switching paths arranged in parallel, a current supply path for supplying the drive current to the motor body;
A plurality of power elements that switch the current input / output path, including upstream power elements respectively connected to the high potential side of the switching path and downstream power elements respectively disposed on the low potential side of the switching path;
A control device that outputs a control signal at a predetermined timing in order to perform on / off control of each of the upstream power element and the downstream power element;
A control voltage forming device provided between the control device and the upstream power element, and forming a control voltage of the upstream power element from the drive voltage;
Have
The control voltage generator is
A voltage dividing path having a first resistor and a second resistor, to which the driving voltage is applied and connected in series from the high potential side;
A first potential output path for outputting a potential between the first resistor and the second resistor to the upstream power element;
A voltage divider circuit having
A P-channel MOSFET is used for the upstream power element,
A motor provided with a low-voltage auxiliary circuit for changing the control voltage to a high level when the control voltage drops below a predetermined value in the control voltage generator. The motor according to claim 1,
The low voltage auxiliary circuit is
A motor having a variable voltage dividing ratio circuit that can be switched between a first voltage dividing ratio and a second voltage dividing ratio for low voltage at which the control voltage is higher than the first voltage dividing ratio. The motor according to claim 2,
The variable voltage dividing ratio circuit is in addition to the voltage dividing circuit,
A third resistor connected in series to a portion on the potential side higher than the first resistor in the voltage dividing path;
A sub-voltage-dividing path having a fourth resistor and a switch element connected in series with the third resistor and the first resistor in the voltage-dividing path, connected in series from the high potential side;
Have
An N-channel MOSFET is used for the switch element,
A motor in which a second potential output path for outputting a potential between the third resistor and the first resistor to the switch element is provided between the voltage dividing path and the sub voltage dividing path. The motor according to claim 1,
The low voltage auxiliary circuit is:
A comparison circuit for comparing whether or not the control voltage falls below a predetermined value;
A minimum potential output circuit that outputs a minimum potential to the upstream power element based on an instruction from the comparison circuit when the control voltage drops below a predetermined value;
Having a motor. The motor according to claim 4,
The comparison circuit has a comparator that outputs a predetermined potential from a potential output terminal according to a comparison result;
The minimum potential output circuit includes:
A minimum potential output path having one end connected to a lower potential side than the second resistance in the voltage dividing path and the other end connected to the upstream power element;
A switch element provided in the middle of the minimum potential output path;
Have
An N-channel MOSFET is used for the switch element,
A motor in which a third potential output path for outputting the potential of the potential output terminal to the switch element is provided between the comparison circuit and the minimum potential output path. The motor according to claim 2,
Furthermore, the motor which has the said comparison circuit of Claim 4, and the said minimum electric potential output circuit.

Images