JP2014007805A - Device for controlling speed of dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for controlling the speed of a DC motor which can set an arbitrary constant or variable target rotational speed and can perform speed control such that an actual rotational speed well matches the target rotational speed even in a structure in which a supply voltage fluctuates and a load varies.SOLUTION: The device for controlling the speed of a DC motor of the present invention includes: a rotational speed detection circuit for detecting a rotational speed of the DC motor and outputting a detection pulse corresponding to the rotational speed; a target rotational speed setting circuit for outputting a target pulse corresponding to a target rotational speed; a command operation circuit for comparing the detection pulse with the target pulse and outputting a command signal Vref corresponding to a rotational speed difference that is the rotational speed minus the target rotational speed; and a step-up/down power supply section 6 for outputting as a current DC driving voltage VM a DC voltage stepped up/down on the basis of the command signal Vref and a past DC driving voltage (an index voltage Vm).

Description

  The present invention relates to a control device for the rotational speed of a DC motor, and more specifically, a speed for controlling a DC brush motor having a rectifying brush as a main control target so that the rotational speed matches a set target rotational speed. The present invention relates to a control device.

  One type of DC motor is a DC brush motor that has a commutator in the rotating armature and switches the direction of current flow from the brush. For example, it is used for sliding, height adjustment, and reclining angle adjustment of vehicle seat devices. ing. In a DC brush motor, a current ripple is generated due to the rotating armature rotating and the contact between the brush and the commutator switching, and is superimposed on the armature current. Therefore, the rotational phase of the rotating armature can be known by extracting the current ripple for AC included in the DC armature current, shaping the waveform, and detecting singular points such as maximum points, minimum points, and zero-cross points. It can be used in place of a rotational phase sensor or a cumulative rotational amount sensor. That is, it is not necessary to separately provide these sensors, and in the above example, the sliding position, seat height, reclining angle, etc. of the vehicle seat can be detected without sensors.

  A battery is normally used as a power source for driving a DC brush motor mounted on the vehicle, but the battery voltage decreases when it is consumed, and increases and varies greatly during charging. For this reason, in many cases, a power supply unit capable of adjusting the DC drive voltage is provided between the battery and the DC brush motor. In addition, in order to control the rotational speed of the DC brush motor, the rotational speed information is fed back to the power supply unit to adjust the DC drive voltage. That is, the power supply unit has a function of adjusting the rotation speed while eliminating the influence of battery voltage fluctuation. A switching power supply with high conversion efficiency is frequently used in the power supply section.

  An example of this type of DC motor speed control device is disclosed in Japanese Patent Application Laid-Open No. H10-228707. The rotation control device of Patent Document 1 includes a rotation detection brush provided on the stator side separately from a pair of electrode brushes, a differentiation circuit that differentiates a voltage obtained by the rotation detection brush, and an output of the differentiation circuit A pulse generator that generates a pulse in response to a change; a motor drive circuit that supplies a DC drive voltage to a pair of electrode brushes; and a motor control circuit that controls the motor drive circuit by obtaining a rotational speed based on the pulse. It has. Further, the motor control circuit includes a rotation detection means for obtaining the rotation speed, a speed-voltage conversion means for obtaining a DC drive voltage based on the rotation speed, and a drive voltage control means for actually controlling the motor drive circuit. . With such a configuration, it is described that appropriate rotation control based on effective rotation detection of a brush DC motor can be performed using a configuration that is particularly simple and does not occupy space.

Japanese Patent Application Laid-Open No. 2002-10661

  Incidentally, in Patent Document 1, a step-down circuit is used as an output variable power supply circuit that adjusts a DC drive voltage applied to a DC motor (see FIG. 2 of Patent Document 1). For this reason, even if the control for decreasing the rotation speed by lowering the power supply voltage can be performed, the control for increasing the rotation speed cannot be performed. Therefore, when you want to perform constant speed control with a DC power supply with variable power supply voltage, the target rotational speed, that is, the target rotational speed is limited to a value that can be driven even with the lowest power supply voltage (minimum speed). Will be.

  For example, a DC motor that slides a vehicle seat back and forth is driven by an in-vehicle battery, so when you want to perform constant speed control, the minimum speed that can be driven even with a reduced battery voltage at the time of wear is the target rotational speed. To do. For this reason, the slide movement speed of the seat is limited, and it may take time to adjust the slide position and cause the occupant to feel inconvenience. Even if the target rotational speed is set to the lowest speed corresponding to the lowest battery voltage, even if the load is heavy (for example, when the weight of the passenger seated in the vehicle seat is heavy), even the lowest speed cannot be generated. It is also assumed that constant speed control becomes difficult.

  On the other hand, if the target rotation speed is set to the lowest speed corresponding to the lowest battery voltage, a large voltage drop is required in the power supply unit when the battery voltage is actually high. Thereby, the internal loss of the switching power supply used for a power supply part increases, and efficiency falls.

  Further, the rotation detection brush of Patent Document 1 corresponds to a sensor for detecting the rotation phase of the rotor and does not occupy a space, but complicates the apparatus configuration.

  The present invention has been made in view of the above-described problems of the background art, and a constant or variable target rotational speed can be arbitrarily set even when the power supply voltage fluctuates and the load changes. It is an object to be solved to provide a speed control device for a DC motor capable of speed control so that the actual rotational speed is in good agreement with the speed.

  The DC motor speed control device according to claim 1 for solving the above-mentioned problems is a DC motor in which a power supply voltage applied from a DC power supply is controlled so that the rotation speed of the DC motor matches the set target rotation speed. A speed control device for a DC motor that applies a drive voltage to the DC motor, the rotation speed detection circuit detecting the rotation speed of the DC motor and outputting a detection pulse corresponding to the rotation speed, and the target rotation speed A target rotational speed setting circuit that outputs a target pulse corresponding to the above, and the detection pulse and the target pulse are compared, and a command signal corresponding to a rotational speed difference obtained by subtracting the target rotational speed from the rotational speed is output. A command calculation circuit, and a step-up / step-down power supply unit that outputs, as a current DC drive voltage, a DC voltage that is step-up / step-down adjusted based on the command signal and a past DC drive voltage. I was painting.

  The invention according to claim 2 is the ripple detection circuit according to claim 1, wherein the rotational speed detection circuit detects a current ripple included in a motor current flowing through the DC motor and converts it into the detection pulse.

  According to a third aspect of the present invention, in the first or second aspect, the step-up / down power supply unit is a circuit in which a step-up switching power supply unit and a step-down switching power supply unit are connected in series, or a step-up switching power supply unit and a series This is a circuit in which a power supply unit is connected in series.

  According to a fourth aspect of the present invention, in the third aspect, when the current DC drive voltage is equal to or lower than the power supply voltage of the DC power supply, the step-up switching power supply unit is stopped to pass the power supply voltage, The power supply voltage is stepped down to the current DC drive voltage by a step-down switching power supply unit or the series power supply unit.

  According to a fifth aspect of the present invention, in the third aspect, when the current DC drive voltage exceeds the power supply voltage of the DC power supply, the power supply voltage is supplied to the current DC drive by the step-up switching power supply unit. The voltage is stepped up to a voltage slightly higher than the voltage, and stepped down to the current DC drive voltage by the step-down switching power supply unit or the series power supply unit.

  A sixth aspect of the present invention provides the control unit according to any one of the first to fifth aspects, wherein the target rotational speed is set and the cumulative rotational amount of the DC motor is calculated by integrating the target rotational speed over time. Was further provided.

  In the invention of the DC motor speed control device according to claim 1, the command signal corresponding to the rotational speed difference obtained by subtracting the target rotational speed set by the target rotational speed setting circuit from the rotational speed detected by the rotational speed detection circuit is provided. The command calculation circuit outputs, and the DC voltage that is stepped up / down adjusted by the step-up / step-down power supply unit based on the command signal and the past DC drive voltage is output as the current DC drive voltage. Here, since the step-up / step-down power supply unit can perform both step-down operation and step-up operation, unlike the prior art only of the step-down operation exemplified in Patent Document 1, the constant or variable target rotation speed is limited to the minimum speed. Can be set arbitrarily. The minimum speed means a rotation speed that can be driven with a minimum power supply voltage with respect to a standard load.

  Also, the buck-boost power supply section selects either step-down operation or step-up operation according to the level of the power supply voltage and the command signal, and adjusts the amount of step-down or step-up, so that the power supply voltage fluctuates and the load changes Even so, the speed can be controlled so that the actual rotational speed is in good agreement with the target rotational speed. Note that these effects occur not only during constant speed control with a constant target rotational speed, but also during a soft start in which the rotational speed is gradually increased at the time of start-up and a soft stop in which the rotational speed is gradually decreased at the time of stop.

  In the invention according to claim 2, the rotational speed detection circuit is a ripple detection circuit. This eliminates the need for a sensor that detects the rotational phase or rotational speed of the rotor of the DC motor, and simplifies the apparatus configuration.

  In the invention according to claim 3, the step-up / step-down power supply unit is a circuit in which the step-up switching power supply unit and the step-down switching power supply unit are connected in series, or the step-up switching power supply unit and the series power supply unit are connected in series. It is considered as a circuit. Thereby, the step-up / step-down power supply unit capable of both the step-down operation and the step-up operation can be configured easily and economically.

  In the invention according to claim 4, when the current DC drive voltage is equal to or lower than the power supply voltage of the DC power supply, the step-up switching power supply section is stopped to pass through the power supply voltage, and the power supply is supplied from the step-down switching power supply section or the series power supply section. Step down the voltage to the current DC drive voltage. That is, when the step-down operation is required, the step-up switching power supply unit can be stopped, and generation of loss at this portion can be suppressed to ensure high efficiency.

  In the invention according to claim 5, when the current DC drive voltage exceeds the power supply voltage of the DC power supply, the boosting switching power supply unit boosts the power supply voltage to a voltage slightly higher than the current DC drive voltage, The voltage is stepped down to the current DC drive voltage by the step-down switching power supply or series power supply. That is, when a step-up operation is required, a high intermediate transfer voltage is once generated by the step-up switching power supply unit, and the intermediate transfer voltage is slightly stepped down and finely adjusted by the step-down switching power supply unit or the series power supply unit. As a result, high efficiency can be ensured while performing good speed control that can immediately respond to fluctuations in the power supply voltage and changes in the load. If the intermediate transfer voltage is increased excessively in the step-up switching power supply unit, the efficiency of the step-down switching power supply unit or the series power supply unit is greatly reduced, which is not preferable.

  In the invention according to claim 6, the control unit sets the target rotational speed and calculates the cumulative rotational amount of the DC motor by integrating the target rotational speed over time. According to the present invention, since the rotational speed control performance is significantly improved, the actual accumulated rotational amount can be calculated with almost no error if the set target rotational speed is integrated over time. This is true not only at constant speed control but also at the time of soft start and soft stop, so that the cumulative rotation amount sensor can be dispensed with. In the aspect including the ripple detection circuit according to the second aspect, the number of signal lines connected to the control unit from the ripple detection circuit or the number of types of signals to be transmitted can be reduced.

1 is a circuit block diagram showing an overall configuration of a DC motor speed control device according to a first embodiment; It is a figure explaining the setting method of the target rotational speed by control CPU, (1) is the case of constant speed control, (2) has shown the case where it is constant speed control and uses a soft start and a soft stop together. It is a circuit diagram which shows the detail of the output stage of the buck-boost power supply part of 1st Embodiment. It is a circuit diagram which shows the detail of the output stage of the buck-boost power supply part of 2nd Embodiment.

  A DC motor speed control device 1 according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a circuit block diagram showing the overall configuration of a DC motor speed control apparatus 1 according to the first embodiment. The speed control device 1 is a device that controls the rotational speed of a DC motor 9 that is provided to adjust the longitudinal sliding position of a vehicle seat (not shown). The speed control device 1 includes a ripple detection circuit 2, a target rotation speed setting circuit 3, a command calculation circuit 4, a step-up / step-down power supply unit 6, a control CPU 7, a polarity switching unit 8, and the like, and a power supply voltage applied from a battery 5 A DC drive voltage VM in which VB is controlled is applied to the DC motor 9.

  The DC motor 9 to be controlled is a DC brush motor including an armature winding and a rotor having a pair of commutators and a stator having a pair of brushes 91 and 92. The DC motor 9 is switched between forward rotation and reverse rotation by the control from the polarity switching unit 8, and advances the sheet by forward rotation and moves the sheet backward by reverse rotation.

  The battery 5 is a DC power supply mounted on the vehicle, and is used in common for the majority of vehicle mounted electrical components. The negative side terminal 5n of the battery 5 is grounded to the chassis of the vehicle, which is the ground point E, and supplies the power supply voltage VB from the positive side terminal 5p to the buck-boost power supply unit 6. The power supply voltage VB of the battery 5 decreases when it is consumed, and increases during charging. For example, the rated power supply voltage of the battery 5 mounted on the passenger car is generally DC 12V, and when it is consumed, it is reduced to about 8V, and during charging, it is boosted to about 15V and greatly fluctuates.

  The control CPU 7 corresponds to a control unit of the present invention that sets a target rotation speed. The control CPU 7 executes arithmetic processing based on various control programs and maps stored in a ROM (not shown), and temporarily stores the calculation result in a RAM (not shown). The control CPU 7 is connected to the operation switch 71 via an input interface (not shown). The operation switch 71 is a switch operated by an occupant seated on the seat to adjust the slide position of the seat. The operation switch 71 has two output contacts 71a and 71b that separately output a forward command signal Mf for requesting forward movement of the seat and a backward instruction signal Mb for requesting backward movement of the seat. The states of the two output contacts 71a and 71b are determined by the connected control CPU 7.

  Further, the control CPU 7 outputs four polarity switching signals Cp to the polarity switching unit 8 via an output interface (not shown). The polarity switching unit 8 includes an H-shaped bridge unit composed of four switching elements 81 to 84 and a pre-driver 87. The first and second switching elements 81 and 82 are connected in series between the final output terminal 66 of the step-up / step-down power supply unit 6 and one end 22 of the shunt resistor 21, and an intermediate point 85 between the both 81 and 82 is the DC motor 9. The first brush 91 is connected. The third and fourth switching elements 83, 84 are also connected in series between the final output terminal 66 of the step-up / step-down power supply unit 6 and one end 22 of the shunt resistor 21, and an intermediate point 86 between the both 83, 84 is connected to the DC motor 9. The second brush 92 is connected. Therefore, the first and second switching elements 81 and 82 and the third and fourth switching elements 83 and 84 are connected in parallel to each other.

  The pre-driver 87 amplifies the four polarity switching signals Cp received from the control CPU 7 and transmits them to the switching elements 81 to 84 to individually control the conduction state. There are no particular restrictions on the types of the switching elements 81 to 84, and an element of a system that is controlled to be in a conductive state when the polarity switching signal Cp is on and controlled to be in a cutoff state when it is off, for example, an FET transistor is used.

  When the forward command signal Mf is input from the operation switch 71, the control CPU 7 switches the polarity so that the first and fourth switching elements 81 and 84 are turned on and the second and third switching elements 82 and 83 are turned off. The signal Cp is output to the pre-driver 87. As a result, a positive voltage is applied to the first brush 91 of the DC motor 9 to drive it in the forward direction. In addition, when the reverse command signal Mb is input from the operation switch 71, the control CPU 7 sets the first and fourth switching elements 81 and 84 to the cutoff state and sets the second and third switching elements 82 and 83 to the conduction state. The polarity switching signal Cp is output to the pre-driver 87. As a result, a positive voltage is applied to the second brush 92 of the DC motor 9 and is driven in reverse.

  Further, the control CPU 7 sets the target rotational speed in response to the input of the forward command signal Mf and the backward command signal Mb, and specifically outputs the target rotational speed command Cv to the target rotational speed setting circuit 3. There are many methods for setting the target rotational speed command Cv, and two typical embodiments will be described. FIG. 2 is a diagram for explaining a method for setting a target rotational speed by the control CPU 7. FIG. 2 shows a case where (1) is constant speed control, and (2) is a case where constant speed control is used together with soft start and soft stop. ing. In FIG. 2, the horizontal axis represents time t, and the vertical axis represents the voltage level of the target rotational speed command Cv (Cv1, Cv2).

  In the case of the constant speed control (1) in FIG. 2, a simple binary signal can be used as the target rotational speed command Cv1. That is, the target rotational speed command Cv1 is at a low level (Low) before the time t1 when the forward command signal Mf and the reverse command signal Mb are not input, and is at a high level (High) at the time t1 when either one is input. At time t2 when there is no input, and returns to the low level (Low).

  When the constant speed control of (2) in FIG. 2 is used together with soft start and soft stop, a variable control signal is required for the target rotational speed command Cv2, and an analog voltage signal, for example, is used. In this case, the target rotational speed command Cv2 starts to increase from zero at time t3 when one of the forward command signal Mf and the reverse command signal Mb is input, and after reaching the predetermined level CvN at time t4, this level CvN is set. It starts to decrease from time t5 when there is no input, and returns to zero at time t6. The predetermined level CvN is a voltage value corresponding to a desired target rotation speed. Further, the speed change rate, that is, the inclination in the figure may be different when the rotational speed is increasing (time t3 to t4) and when decreasing (time t5 to t6).

  Further, the control CPU 7 always grasps the slide position of the sheet from the accumulated rotation amount of the DC motor 9. In the present embodiment, a detection pulse Vrpl of a ripple detection unit 2 described later is transmitted to the control CPU 7 via the signal line Lsig (see FIG. 1). Therefore, the control CPU 7 can count the number of pulses of the detection pulse Vrpl, add a positive / negative sign to the number of pulses counted by distinguishing between the forward rotation drive and the reverse rotation drive controlled by itself, and calculate the accumulated rotation amount. .

  The method of grasping the seat slide position is not limited to the above, and the control CPU 7 can also calculate the cumulative rotation amount of the DC motor 9 by time-integrating the target rotation speed command Cv output by itself. Even with this method, an operation with almost no error can be performed as compared with the method of counting the number of detection pulses Vrpl. This is a method that is enabled by the remarkable improvement in the control performance of the rotational speed in this embodiment.

  The target rotation speed setting circuit 3 generates a target pulse Vosc corresponding to the target rotation speed command Cv received from the control CPU 7 and outputs the target pulse Vosc to the command calculation circuit 4. The target pulse Vosc is preferably a square wave signal for detecting the timing of the change, and its duty ratio Dosc is not so important.

  In the configuration example in which the target rotation speed command Cv1 is a binary signal for constant speed control, the target rotation speed setting circuit 3 has a fixed frequency oscillation circuit whose oscillation frequency matches the target rotation speed (a constant value). Can be used. In this case, the oscillation circuit operates in a time zone in which the target rotation speed command Cv1 is at a high level and stops in a time zone in which the target rotation speed command Cv1 is at a low level.

  In the configuration example in which the target rotation speed command Cv2 is an analog voltage signal for using both soft start and soft stop, the target rotation speed setting circuit 3 has a voltage whose oscillation frequency is variably controlled by the analog voltage signal. A control-type variable frequency oscillation circuit can be used. In this case, the repetition frequency of the target pulse Wosc output from the oscillation circuit increases or decreases according to the voltage level of the target rotation speed command Cv2.

  The ripple detection circuit 2 corresponds to the rotation speed detection circuit of the present invention, and outputs a detection pulse Vrpl corresponding to the rotation speed of the DC motor 9. One end 22 and the other end 23 of the shunt resistor 21 are connected to the ripple detection circuit 2, and the both-ends voltage Vsh of the shunt resistor 21 is input. As described above, one end 22 of the shunt resistor 21 is connected to the DC motor 9 via the polarity switching unit 8, and the other end 23 is connected to the ground point E to form a return path to the negative terminal 5 n of the battery 5. Yes. Therefore, the motor current Im flows through the shunt resistor 21, and the waveform of the both-end voltage Vsh is similar to the waveform of the motor current Im.

  In the first embodiment, the ripple detection circuit 2 performs a filtering process, a ripple determination process, etc. on the waveform of the voltage Vsh output from the shunt resistor 21 to detect a current ripple, and converts it into a square wave detection pulse Vrpl. And output to the command calculation circuit 4 and the control CPU 7. A digital operation band-pass filter can be used for the filter processing, and a ripple waveform is extracted by removing a direct current component and a high frequency noise component of the motor current Im. In addition, an amplitude detection method is used for the ripple determination processing, and the detection pulse Wrpl is raised at a timing when the ripple waveform is increased by a predetermined rising amplitude threshold, and is lowered at a timing when the ripple waveform is decreased by a predetermined falling amplitude threshold. . The detection pulse Wrpl is preferably a square wave signal in order to detect the timing of the change, and its duty ratio Drpl is not so important. The ripple detection circuit 2 is not limited to the above, and various known circuits can be used.

  The command calculation circuit 4 compares the detection pulse Vrpl and the target pulse Vosc, generates a command signal Vref corresponding to a rotational speed difference obtained by subtracting the target rotational speed from the actual rotational speed, and outputs the command signal Vref to the step-up / down power supply unit 6. . As shown in FIG. 1, the command calculation circuit 4 can be composed of a phase comparison unit 41 and a phase difference voltage conversion unit 42. The phase comparison unit 41 compares the generation intervals of square wave edges of the detection pulse Vrpl and the target pulse Vosc, and detects a phase difference (time difference) corresponding to the rotational speed difference. In the phase difference voltage converter 42, the detected phase difference is converted into a command signal Vref. The command signal Vref increases when the actual rotational speed is slower than the target rotational speed, and decreases when the reverse is the reverse.

  The step-up / step-down power supply unit 6 outputs a DC voltage that has been step-up / step-down adjusted based on the command signal Vref and the past DC drive voltage VM as the current DC drive voltage VM. As shown in FIG. 1, the step-up / down power supply unit 6 includes an error amplifier 61, an output stage 62, and a resistor voltage divider 63. Further, the step-up / step-down power supply unit 6 includes a control input terminal 64 to which a command signal Vref is input from the command calculation circuit 4, a power input terminal 65 to which a power supply voltage VB is input from the battery 5, and a DC drive voltage VM to the DC motor 9. The final output terminal 66 is provided.

The resistor voltage divider 63 is configured by connecting two resistors r1 and r2 in series between the final output terminal 66 and the ground point E. The resistor voltage divider 63 divides the DC drive voltage VM of the final output terminal 66 by a predetermined voltage dividing ratio Rr, and generates an index voltage Vm at an intermediate point 63m between the resistors r1 and r2. As a result, the voltage levels of the index voltage Vm and the command signal Vref are matched so that direct comparison can be performed. Therefore, the voltage division ratio Rr obtained by the following equation is precisely set according to the output specification of the command calculation circuit 4.
Index voltage Vm = (DC drive voltage VM) × (voltage division ratio Rr)
Partial pressure ratio Rr = r2 / (r1 + r2)

  The error amplifier 61 is composed of a known differential amplifier circuit. The positive input terminal 61p is connected to the control input terminal 64, the negative input terminal 61n is connected to the middle point 63m of the resistor voltage divider, and the output terminal. 61o is connected to the output stage 62. Thus, the error amplifier 61 subtracts the index voltage Vm fed back from the command signal Vref, multiplies it by a predetermined amplification factor k, obtains a differential voltage Δ, and outputs it to the output stage 62. The amplification factor k is determined as appropriate so that the output stage 62 operates properly.

  FIG. 3 is a circuit diagram illustrating details of the output stage 62 of the step-up / step-down power supply unit 6 according to the first embodiment. As shown in FIG. 3, the output stage 62 is a circuit in which a step-up switching power supply unit 67 and a step-down switching power supply unit 68 are connected in series at an intermediate transfer point 6X. Further, the differential voltage Δ obtained by the error amplifier 61 is input to the pulse width modulation control unit 69 (PWM 69). The PWM 69 performs pulse width modulation control on the two power supply units 67 and 68 according to the magnitude of the differential voltage Δ.

  The circuit configuration of the step-up switching power supply unit 67 will be described in detail. An inductance L1 and a diode D1 are connected in series between the power supply input terminal 65 and the intermediate transfer point 6X. The diode D1 allows energization from the power input terminal 65 to the intermediate transfer point 6X and prohibits energization in the reverse direction. A step-up transistor Q1 is connected between the intermediate point where the inductance L1 and the diode D1 are connected in series and the ground point E. A capacitor C1 is connected between the intermediate transfer point 6X and the ground point E.

  When the boosting transistor Q1 is switched by the control from the PWM 69, the current flowing from the power input terminal 65 to the ground point E via the inductance L1 is forcibly cut off, and a high voltage is generated at both ends of the inductance L1. Capacitor C1 smoothes the intermittently generated high voltage and stabilizes the voltage at intermediate transfer point 6X. Thereby, the step-up switching power supply unit 67 can variably adjust the intermediate transfer voltage VS higher than the power supply voltage VB of the power input terminal 65 and generate it at the intermediate transfer point 6X. Further, when the boosting transistor Q1 is always kept in the cut-off state, the boosting switching power supply unit 67 does not operate, and the power supply voltage VB of the power supply input terminal 65 is passed through to the intermediate transfer point 6X.

  The circuit configuration of the step-down switching power supply unit 68 will be described in detail. A step-down transistor Q2 and a diode D2 are connected in series between the intermediate transfer point 6X and the ground point E. The diode D2 prohibits energization from the step-down transistor Q2 to the ground point E, and allows energization in the reverse direction. An inductance L2 is connected between the intermediate point where the step-down transistor Q2 and the diode D2 are connected in series and the final output terminal 66. Further, a capacitor C2 is connected between the final output terminal 66 and the ground point E.

  When the step-down transistor Q2 is switched by the control from the PWM 69, the intermediate transfer voltage VS at the intermediate transfer point 6X is converted into an intermittent voltage waveform according to the duty ratio of the switching operation. Inductance L2 and capacitor C2 smooth the intermittent voltage waveform and output DC drive voltage VM. As a result, the step-down switching power supply unit 68 can variably adjust and output the DC drive voltage VM lower than the intermediate delivery voltage VS. If step-down transistor Q2 is always kept in a conductive state, step-down switching power supply unit 68 does not operate and intermediate delivery voltage VS is passed through to final output terminal 66.

  Next, the operation of the DC motor speed control device 1 of the first embodiment configured as described above will be described. Consider the case where the constant speed control of (1) in FIG. 2 is performed when the DC motor 9 is stopped and the operation switch 71 is operated by the occupant and the forward command signal Mf is input to the control CPU 7. First, the control CPU 7 outputs to the pre-driver 87 a polarity switching signal Cp that turns on the first and fourth switching elements 81 and 84 and turns off the second and third switching elements 82 and 83. Thereby, the polarity switching part 8 is set to the state of normal rotation drive.

  Next, the control CPU 7 outputs a target rotational speed command Cv 1 to the target rotational speed setting circuit 3. Thereby, the target rotation speed setting circuit 3 generates the target pulse Vosc and outputs it to the command calculation circuit 4. On the other hand, the ripple detection circuit 2 does not detect the current ripple because the past motor current Im is zero, and the detection pulse Vrpl is not output. That is, the ripple detection circuit 2 outputs a flat signal having no pulse to the command calculation circuit 4 as the detection pulse Vrpl.

  Since the detection pulse Vrpl is a flat signal, the command calculation circuit 4 outputs a large command signal Vref corresponding to one cycle of the target pulse Vosc to the positive input terminal 61p of the error amplifier 61 of the step-up / step-down power supply unit 6. On the other hand, since the past DC drive voltage VM is zero, the index voltage Vm is also zero, and this is input to the negative side input terminal 61 n of the error amplifier 61. Therefore, a large differential voltage ΔV is output from the error amplifier 61 to the PWM 69.

  Here, the PWM 69 gives priority to the case where the battery 5 is not consumed and the DC drive voltage VM can be output only by the step-down switching power supply unit 68, in other words, the case where the DC drive voltage VM is equal to or lower than the power supply voltage VB of the battery 5. Control. That is, the PWM 69 keeps the step-up transistor Q1 in the cut-off state, passes the power supply voltage VB to the intermediate transfer point 6X, and controls the duty ratio of the switching operation of the step-down transistor Q2 according to the differential voltage ΔV. As a result, the DC drive voltage VM is output from the final output terminal 66, and the DC motor 9 is started. Thus, the first control cycle is completed, and thereafter, the control cycle is repeated at regular time intervals.

  In the second and subsequent control cycles, the DC motor 9 is rotated by applying the DC drive voltage VM and the motor current Im flows, so that the ripple detector 2 detects the current ripple, and the index voltage Vm also becomes a certain value. Become. As a result, the command signal Vref and the differential voltage ΔV rapidly decrease, and the actual rotational speed of the DC motor 9 matches the target rotational speed commanded by the rotational speed command Cv.

  However, when the battery 5 is exhausted, there are cases where it is not possible to cope with the step-down switching power supply unit 68 alone. That is, even if the PWM 69 maintains the step-up transistor Q1 in the cut-off state, the duty ratio is set to 1 without switching the step-down transistor Q2, and the output of the battery 5 through the power supply voltage VB is output, the necessary DC drive is required. There is a case where the voltage VM is insufficient. In this case, the PWM 69 controls the boost transistor Q1 to operate the boost switching power supply unit 67. Thereby, since the intermediate delivery voltage VS becomes higher than the power supply voltage VB, the required DC drive voltage VM can be generated, and the actual rotational speed of the DC motor 9 can be matched with the target rotational speed.

  In this case, it is preferable that the intermediate transfer voltage VS is boosted to a voltage slightly higher than the required DC drive voltage VM. For example, when the rated power supply voltage of the battery 5 is 12V, it is sufficient to make the intermediate transfer voltage VS about 1V higher than the DC drive voltage VM. Conversely, if the intermediate transfer voltage VS is excessively boosted by 1 V or more higher than the DC drive voltage VM, the efficiency of the step-down switching power supply unit 68 is greatly reduced, which is not preferable.

  Further, the rotational speed of the DC motor 9 may fluctuate due to the behavior of the occupant while the DC motor 9 rotates at a constant speed and the seat moves at a constant speed. In this case, the detection pulse Vrpl of the ripple detection unit 2 changes, and the command signal Vref changes so as to compensate for the variation of the detection pulse Vrpl. Therefore, in accordance with the command signal Vref, the DC drive voltage VM is changed and controlled, and the rotational speed of the DC motor 9 and the sheet moving speed are kept constant.

  When the slow start and slow stop control of (2) in FIG. 2 is performed, the setting method of the target rotational speed at the time of starting and stopping of the DC motor 9 is different, that is, the target speed command Cv2 is temporal. Changes continuously. As a result, the steepness of rising and falling of the DC drive voltage VM becomes dull, but the control flow is the same as in the case of constant speed control.

  According to the speed control device 1 of the direct current motor 9 of the first embodiment, the step-up / step-down power supply unit 6 can perform both step-down operation and step-up operation. Unlikely, a constant or variable target rotational speed can be arbitrarily set without being limited to the minimum speed. The step-up / step-down power supply unit 6 selects one of the step-down operation and the step-up operation according to the level of the power supply voltage VB of the battery 5 and the command signal Vref, and adjusts the step-down amount or the step-up amount. However, even if the load changes, the speed can be controlled so that the actual rotational speed matches the target rotational speed well. Note that these effects occur not only during constant speed control with a constant target rotational speed, but also during a soft start in which the rotational speed is gradually increased at the time of start-up and a soft stop in which the rotational speed is gradually decreased at the time of stop.

  Further, since the ripple detection circuit 2 is used in the rotation speed detection circuit, a sensor for detecting the rotation phase or rotation speed of the rotor of the DC motor 9 is not required, and the apparatus configuration is simplified. Furthermore, the step-up / step-down power supply unit 6 is configured by connecting a step-up switching power supply unit 67 and a step-down switching power supply unit 68 in series, and is simple and economical. Further, both the step-up and step-down are configured by a switching power supply unit, and the intermediate transfer voltage VS is slightly larger than the DC drive voltage VM at the time of step-up, so that high efficiency can be ensured compared with other types of power supply units. .

  If the control unit CPU 7 adopts a configuration in which the target rotation speed command Cv is integrated over time to calculate the cumulative rotation amount of the DC motor 9 and the position of the sheet is grasped, the detection pulse Vrpl of the ripple detection unit 2 is controlled. The signal line Lsig transmitted to the CPU 7 becomes unnecessary.

  Next, a DC motor speed control apparatus according to a second embodiment having a different configuration of the output stage 62A of the step-up / step-down power supply unit 6A will be described with reference to FIG. FIG. 4 is a circuit diagram showing details of the output stage 62A of the step-up / step-down power supply unit A of the second embodiment. In the second embodiment, the configuration is the same as that of the first embodiment except for the output stage 62A.

  As shown in FIG. 4, the output stage 62A is a circuit in which a step-up switching power supply unit 67 and a series power supply unit 68A are connected in series at an intermediate transfer point 6X. The differential voltage Δ obtained by the error amplifier 61 is input to the pulse width modulation control unit 69A (PWM 69A) and the step-down transistor Q3 of the series power supply unit 68A. The PWM 69A controls the operation of the step-up switching power supply unit 67 according to the magnitude of the differential voltage Δ. The configuration and operation of the step-up switching power supply unit 67 are the same as those in the first embodiment, and a description thereof will be omitted.

  The circuit configuration of the series power supply 68A will be described in detail. A step-down transistor Q3 and a capacitor C3 are connected in series between the intermediate transfer point 6X and the ground point E. The intermediate point where the step-down transistor Q3 and the capacitor C3 are connected in series is connected to the final output terminal 66. The step-down transistor Q3 is an NPN bipolar type and uses an amplification function. That is, the differential voltage Δ obtained by the error amplifier 61 is input as the base voltage to the base B of the step-down transistor Q3, and the inflow current from the collector C to the emitter E changes depending on the magnitude of the base voltage, and the capacitor C3 flows into the capacitor C3. The current is converted into a voltage and smoothed. As a result, the step-down switching power supply unit 68A can variably adjust and output the DC drive voltage VM lower than the intermediate delivery voltage VS.

  The overall operation and effects of the speed control device for the DC motor 9 of the second embodiment are substantially the same as those of the first embodiment, and a description thereof will be omitted.

  Note that the circuit configurations of the step-up switching power supply unit 67 and the step-down switching power supply unit 68 described in the first embodiment and the series power supply unit 68A described in the second embodiment are merely examples, and other known circuit configurations are used. It may be adopted. Moreover, it can replace with the shunt resistance 21 and can also use the electric current detection part using the Hall effect. Various other modifications and applications of the present invention are possible.

1: DC motor speed control device 2: Ripple detection circuit 21: Shunt resistor 3: Target rotation speed setting circuit 4: Command calculation circuit 41: Phase comparison unit 42: Phase difference voltage conversion unit 5: Battery (DC power supply)
6, 6A: Buck-boost power supply unit 61: Error amplifier 62, 62A: Output stage 63: Resistive voltage divider 64: Control input terminal 65: Power input terminal 66: Final output terminal 67: Step-up switching power supply unit 68: Step-down switching Power supply unit 68A: Series power supply unit 6X: Intermediate transfer point 69, 69A: Pulse width modulation control unit (PWM)
7: Control CPU 71: Operation switch 8: Polarity switching unit 81-84: Switching element 87: Pre-driver 9: DC motor 91, 92: First and second brushes Mf: Forward command signal Mb: Backward command signal Cp: Polarity Switching signal Cv, Cv1, Cv2: Target rotational speed command Vrpl: Detection pulse Vosc: Target pulse Vref: Command signal VB: Power supply voltage VS: Intermediate transfer voltage VM: DC drive voltage Vm: Indicator voltage Im: Motor current

Claims (6)

A DC motor speed control device that applies a DC drive voltage, which controls a power supply voltage applied from a DC power supply, to the DC motor so as to match a rotation speed of the DC motor with a set target rotation speed,
A rotational speed detection circuit that detects the rotational speed of the DC motor and outputs a detection pulse corresponding to the rotational speed;
A target rotational speed setting circuit for outputting a target pulse corresponding to the target rotational speed;
A command calculation circuit that compares the detection pulse with the target pulse and outputs a command signal corresponding to a rotational speed difference obtained by subtracting the target rotational speed from the rotational speed;
A DC motor speed control device comprising: a step-up / step-down power supply unit that outputs, as a current DC drive voltage, a DC voltage that is step-up / step-down adjusted based on the command signal and a past DC drive voltage.   2. The DC motor speed control device according to claim 1, wherein the rotational speed detection circuit is a ripple detection circuit that detects a current ripple included in a motor current flowing through the DC motor and converts the current ripple into the detection pulse.   3. The step-up / down power supply unit according to claim 1, wherein the step-up switching power supply unit and the step-down switching power supply unit are connected in series, or the step-up switching power supply unit and the series power supply unit are connected in series. DC motor speed control device that is a circuit.   4. The step-down switching power supply unit or the series according to claim 3, wherein when the current DC drive voltage is equal to or lower than the power supply voltage of the DC power supply, the step-up switching power supply unit is stopped to pass through the power supply voltage. A speed control device for a direct current motor that steps down the power supply voltage to the current direct current drive voltage by a power supply unit.   4. The power supply voltage is increased to a voltage slightly higher than the current DC drive voltage by the step-up switching power supply unit when the current DC drive voltage exceeds the power supply voltage of the DC power supply. A speed control device for a DC motor that boosts and steps down to the current DC drive voltage by the step-down switching power supply unit or the series power supply unit.   The speed of the DC motor according to any one of claims 1 to 5, further comprising a control unit that sets the target rotational speed and calculates the cumulative rotational amount of the DC motor by integrating the target rotational speed over time. Control device.

Images