JPH0216673B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive circuit for a DC motor, and more particularly to a drive circuit suitable for voltage protection of a power transistor used in the drive circuit.

Now, it is equipped with at least two current-carrying coils, a magnetic plate having an N-pole region and a S-pole region, and a current-carrying switching means for alternately switching the two current-carrying coils to supply DC current, and the current flowing through the current-carrying coils. The magnetic plate rotates as a rotor relative to the current-carrying coil due to the interaction between the magnetic flux and the magnetic flux generated in the magnetic plate, and the current flow is switched by the current-carrying switching means according to the relative rotational position of the magnetic plate with respect to the current-carrying coil. 2. Description of the Related Art A DC motor whose operation is controlled so that a magnet plate continues to rotate as a rotor is known as, for example, a cylinder drive motor in a magnetic recording/reproducing device (VTR).

FIG. 1A is a side view showing the basic structure of such a conventional DC motor, and FIG. 1B is a top view of the same.

In these figures, 1 is a disk-shaped yoke, 2
1A is a disc-shaped magnet, 3A, 3B, 4A and 4B are current-carrying coils as shown in a perspective view in FIG. 1A, and 5 is a shaft. FIG. 1B is a top view of the magnet plate 2. If the magnet plate 2 is a transparent body, as shown by the dotted line,
It should be seen that the energizing coils 3A, 3B and 4A, 4B are placed on the yoke 1. Each energizing coil, as shown in FIG. 1A, consists of a coil wound in a triangular shape around a small plastic core K, for example, having a triangular shape.

The magnetized region in the disc-shaped magnet plate 2 is the 1st B
As shown in the figure, there are N, S, zero, N, S, and zero areas around the center point at angles of 60 degrees. Note that the zero region is a non-magnetized region, but it actually consists of a weak (S) region and a weak (N) region divided as shown by dotted lines.

Coils 3A and 3B form one set, coils 4A and 4B form another set, and DC current is switched and energized for each set. A closed magnetic path is constructed from the magnet plate 2 through the yoke 1, so this magnetic flux and
Interaction with the direct current flowing through the current-carrying coils (for example 3A and 3B) generates a torque, and in this case, since the current-carrying coils on the yoke 1 are fixed, the magnet plate 2 rotates together with the shaft 5. Depending on the rotational position of the magnet plate 2, for example, the energized coil 3A
The direct current that was flowing through the set of coils 4A and 3B is
By switching to the set 4B and 4B, the rotation operation of the magnet plate 2 as a rotor is continued, and this rotation operation will be explained later.

In FIG. 1B, when the magnet plate 2 is rotated in the direction of the arrow, the change in magnetic flux density observed at a fixed point P on the periphery of the magnet plate 2 is shown in FIG. 2A. That is, a positive magnetic flux density is observed in the N region, a negative magnetic flux density is observed in the S region, and weak positive and negative magnetic flux densities are observed in the zero region.
The waveform shown in FIG. 2A is schematically shown in FIG. 2B. If we place a Hall element that converts the strength of the magnetic field (magnetic flux density) into an electrical quantity at point P and observe its output waveform (a or b in Figure 2), we can conversely determine the rotation of the rotor (magnetic plate 2). Since the position can be known, such a Hall element can be used as a rotational position detector of the rotor.

Now, in the conventional DC motor as outlined above, the rectangular wave output (strictly speaking, it is a distorted waveform as shown in Figure 2 B) from the rotational position detector (for example, a Hall element) of the rotor, When amplified, it becomes a rectangular wave, so the rectangular wave output was used to switch the current between the two sets of current-carrying coils. This will be specifically explained with reference to FIG.

FIG. 3 is a circuit diagram showing a conventional DC motor drive circuit. In the figure, 6 is a rotor rotational position detector such as a Hall element, 7 is an energization switching means, and 8 is a rotor rotational position detector such as a Hall element.
a and 8b are drive transistors, 9a and 9
b is a capacitor, 3 and 4 are energizing coils, and 10 is a motor voltage. The control current generation circuit 11 is a circuit that controls the current flowing through the coil 3 or 4 by the switching action of the energization switching means 7 so that the rotational speed of the motor is constant.

In FIG. 3, the rectangular wave output from the position detector 6 activates the energizing means 7 that sequentially switches the coils 3 and 4, and the drive transistors 8a and 8b amplify the current from the control current generation circuit 11. ,4
energized sequentially as a rectangular wave current. Reference numeral 12 shown in FIG. 4A indicates the base voltage waveform of the driving transistors 8a and 8b, and reference numeral 13 shown in FIG. As can be seen from the collector voltage waveform 13, the energization to the coils 3 and 4 is abruptly cut off.
That is, when the drive transistors 8a, 8b are abruptly turned off, the current supplied to the transistors 8a, 8b due to the voltage of the sum of the back electromotive force generated in the coils 3, 4 and the motor voltage 10 causes the Due to the voltage drop occurring in the off-resistances of the transistors 8a and 8b, the collector potential rises rapidly as shown at 13 in FIG.

With this potential increase, the drive transistors 8a, 8
The potential rises beyond the collector-emitter withstand voltage limit of the drive transistors 8a, 8.
b may destroy it. In order to prevent this, in the circuit example shown in Fig. 3, the collector
Large capacity capacitors 9a and 9b are attached between the emitters. In another example, in addition to the collector-emitter capacitor, a relatively small capacitor is provided between the collector and the base. Therefore, when considering the use of ICs for DC motor drive circuits, large capacitance capacitors have the disadvantage of being unsuitable for use with ICs.

In order to improve these shortcomings, the coils are sequentially switched and energized by gradually starting and slowly cutting off the current, thereby reducing the back electromotive force generated at the end of the coil. The inventors of the present invention have separately proposed a DC motor drive circuit that can eliminate the capacitance or reduce the capacitance value, and have filed a patent for it, so an outline of this will be explained below.

In the drive circuit separately proposed by the present inventors,
Instead of directly inputting the rectangular wave output with steep rises and falls from the rotor position detector to the coil sequential energization switching means, means is provided to generate a trapezoidal wave from the rectangular wave output. , the above-mentioned drawbacks are improved by operating the coil sequential energization switching means using the trapezoidal wave, and sequentially energizing the coils with the control current in the trapezoidal waveform.

First, FIG. 5 is an explanatory diagram for accurately explaining once again the principle of rotation of the DC motor which has been briefly explained above. In the figure, in order to make it easier to understand the relative positional relationship between the magnet plate 2 and the two sets of energizing coils 3A, 3B and 4A, 4B, the magnet plate 2 is placed in the center and the energizing coils are placed around the periphery. Indicated.

In FIG. 5, reference numeral 6 denotes a rotational position detector (for example, a Hall element) of the rotor, and the magnetization state of the magnet plate 2 is as previously described in detail with reference to FIG. 1B. , 4A, 4B are wound at an angle of 60 degrees, and the interval between adjacent coils is 30 degrees, and the magnet plate 2 serves as a rotor.

First, as shown in Figure 5a, when a current flows through the coil 4A as shown by the arrow, the outward current and the central current flow in the coil parts, respectively, according to Fleming's left-hand rule. rotational torque is generated. However, coil 3 (A, B),
4 (A, B) are fixed, so the magnet plate 2 will rotate counterclockwise. Magnet plate 2 at position angle
When it moves by 30 degrees, the positional relationship will be as shown in Figure 5b. Here, if the coil 3B is energized as shown by the arrow, torque will be generated in the portion of the coil through which the outward current flows, and the rotational motion will be maintained. Furthermore, in FIG. 5c, where the position angle is rotated by 90 degrees, by energizing the coil 3B, torque is generated in the coil portion where the current flows toward the center, and the rotational motion is maintained. This is electrical angle 360
degree, that is, the position angle of 180 degrees, it can be seen that the magnet plate 2 always rotates counterclockwise. Here, the reason why there are two coils 3 and 4, A and B, respectively, is to increase rotational efficiency.

Reference numeral 33 shown in FIG. 6A is a waveform diagram showing the output waveform of the position detector 6 in FIG. 5, which was previously explained with reference to FIG. 2. As previously explained, the zero region of the magnet plate 2 is weakly magnetized by S and N so that the magnetic flux density changes smoothly from the "N" region to the "S" region rather than steeply. As can be seen from the output waveform 33, by providing the magnet plate 2 with a magnetic flux distortion means (existence of a zero region), there is no point where the resultant rotational torque becomes zero in 360 electrical degrees; however, from this output waveform 33, Since it is technically difficult to directly create a trapezoidal wave with the same slope at the rising and falling edges, it is first converted into a rectangular wave as shown at 34 in Figure 6(b), and then the waveform is shown in Figure 6(c). It is better to create a trapezoidal wave 35 like this.

FIG. 7 is a block diagram showing a DC motor drive circuit separately proposed by the present inventors. In the figure, the same components as in FIG. 3 are given the same reference numerals, except that 14 is a trapezoidal wave generating circuit, and 15a and 15b are current amplifiers, respectively.

In FIG. 7, a trapezoidal wave generating circuit 14 receives the rectangular wave output from the rotor rotational position detector 6.
creates and outputs a trapezoidal wave, and activates the energization switching means 7, thereby controlling the current amplifier 1.
5a and 15b alternately amplify the current from the control current generation circuit 11 and supply it to the coils 3 and 4 as trapezoidal wave currents, respectively.

FIG. 8 is a specific circuit diagram of a DC motor drive circuit separately proposed by the inventors. In the figure, a Hall element 6A is used as a rotational position detector of the rotor. In addition, 16 is a differential amplifier, 17 is a constant current source (current value I ₀ of constant current), 18,
19 and 20 are transistors, 21 is an emitter follower circuit, 23 and 24 are transistors, and 25 is a power supply.

In FIG. 8, the output of the Hall element 6A is amplified by a differential amplifier 16, converted into a rectangular wave, and sent to a trapezoidal wave generation circuit 14. The trapezoidal wave from the control current generating circuit 14 causes the current switching means 7 (in this example, a differential switching circuit consisting of transistors 23 and 24 whose base input is the trapezoidal wave output) to control the current from the control current generating circuit 11. is alternately switched and supplied to current amplifiers 15a and 15b (here, the base current of a Darlington-connected transistor). In this way, the current obtained by amplifying the trapezoidal input current is applied to the coils 3 and 4.

Next, details of the trapezoidal wave generating circuit 14 will be explained. Two outputs from the differential amplifier 16 are input to the bases of transistors 18 and 19 forming a high gain differential amplifier. 17 is a constant current source (current value I ₀ ), D ₁ is a diode, R ₁ and R ₂ are each a resistor, and 20 is a transistor. The output of the high-gain differential amplifier is taken out from a point Q where the collectors of transistors 20 and 19 meet. Therefore, it has a high output impedance. As the transistor 19 turns on and off, the IC terminal 2 is connected to the capacitor C.
Charging and discharging are performed via 2. IC terminal 22
This is a terminal necessary for externally connecting capacitor C, and is not directly related to this proposal.

The charging and discharging path to the capacitor C is explained in an easy-to-understand manner as follows. First, when the transistor 18 is on, current flows through the diode _D1 and the resistor _R1 , so the transistor 20 is also turned on, and current also flows through the transistor 20 and the resistor _R2 . The current at this time is the current obtained by discharging the capacitor C. Conversely, when transistor 19 is on, transistor 18 is off. Then,
Since no current flows through the diode D ₁ and the resistor R ₁ , the transistor 20 is also turned off. Therefore, the current flowing from the constant current source 17 through the transistor 19 flows into the capacitor C to charge it. At this time, since the output impedance of the differential amplifier is large, it can be considered that charging and discharging occurs equivalently through a current source. When charging and discharging the capacitor C through a current source, the time and the amount of charge charged and discharged are proportional. That is, let the capacitance of capacitor C be C ₀ ,
When the amount of charge stored in the capacitor is Q and the voltage across the capacitor is V, the following equation holds true.

Q=C ₀ V (1) Therefore, by transforming this, we obtain the following equation.

V=Q/C ₀ =∫idt/C ₀ ………(2) However, i is the current flowing into the capacitor, but in this case, it is a constant current I ₀ , so rewriting the above equation (2) It will look like this:

V=I ₀・t/C ₀ (3) where t is time.

From the above equation (3), the voltage V across capacitor C is:
It can be seen that when the capacitor is charged, it rises with a slope of I ₀ /C ₀ , and when it is discharged, it falls with a slope of -I ₀ /C ₀ . On the other hand, the emitter follower 24 is operated with the voltage divided by the bias resistors R ₄ and R ₃ to create a reference voltage source. And the limiter diode D ₂ ,
At D ₃ , the voltage at the other end of capacitor C rises or falls to the reference voltage ±V _F (however, V _F is connected to diode D ₂ ,
Apply a limiter at the point where the voltage drops due to D ₃ ). This creates a trapezoidal wave.

Reference numeral 36 shown in FIG. 9A is a waveform diagram showing the generated trapezoidal wave. Its amplitude 37 is 2V _F , and its center potential is the output potential of the emitter follower 21. 9th
38 and 39 shown in Figures B and C are currents flowing through the coils 3 and 4, respectively, and 40 and 39 shown in Figures 9D and E respectively
41 is the potential generated at the other ends of the coils 3 and 4 when speed control is applied (in this example, the collector potential of the Darlington-connected transistor)
It shows. It can be seen that no sudden potential rise occurs. Furthermore, if the current value I ₀ from the constant current source 17 is made small, the capacitance value of the capacitor C connected from the terminal 22 outside the IC circuit can also be made small, which is convenient.

In the drive circuit separately proposed by the inventors as described above, the rectangular wave output from the rotor position detector is converted into a trapezoidal wave and inputted to the energization switching means, but the slope of the trapezoidal wave is was always constant, so when the motor current became large, it equivalently meant that the energization was abruptly switched. This will be explained below in an easy-to-understand manner with reference to FIG.

FIG. 10A is a waveform diagram of the trapezoidal wave output input to the energization switching means. That is, in the energization switching means, energization switching is completed during the time Δt.
The slope θ of the waveform was always constant. Assuming that the motor current reaches a steady value _I1 , the current value _I1 is changed over time Δt by the energization switching means, as shown in FIG. 10B.
Since it must change from zero to I ₁ (or vice versa) during that time, the tilt angle becomes θ ₁ . Next, when a large starting current _I2 is flowing when starting the motor, as shown in Figure 10C, the starting current _I2 changes from zero to I during the time Δt due to the function of the energization switching means. ₂ (or vice versa), so the tilt angle becomes θ ₂ and θ ₂ >
θ ₁ . A large inclination angle θ ₂ is equivalent to steep current switching, which leads to destruction of the drive transistor.

In other words, in the drive circuit separately proposed by the present inventors, the slope θ of the trapezoidal wave is always constant, so even though it is effective during steady rotation of the DC motor, the rotation speed may change during startup, etc. is slow,
This method has the disadvantage that it is not necessarily effective when a large starting current flows.

The present invention has been made to eliminate the drawbacks of the separately proposed DC motor drive circuit as described above, and therefore, an object of the present invention is to switch energization when the motor current is large, such as during startup. The time Δt required for switching is increased by decreasing the slope θ of the trapezoidal wave output input to the means, and when the motor current is steady and relatively small, the slope θ of the trapezoidal wave output is
To provide a DC motor drive circuit which can shorten the time Δt required for switching by increasing Δt, and can keep the rise in the collector potential of a drive transistor caused by the back electromotive force of a coil within a certain limit regardless of the magnitude of the motor current. There is a particular thing.

The present invention achieves the above object by varying the slope of the trapezoidal wave input that activates the energization switching means that sequentially energizes each coil in accordance with the output of the motor speed control circuit.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 11 is a block diagram showing one embodiment of the present invention. In the figure, 14A is a trapezoidal wave generating circuit according to the present invention. In addition, 42 is a circuit power supply, 43 is a constant current source with a variable current amount for charging the capacitor 47, and 45 is a constant current source with a variable current amount for discharging the capacitor 47 (however, both current sources are used at the same current value). ), 44 is a charging/discharging switching means for the capacitor 47, and 46 is an IC terminal for externally connecting the capacitor 47. A control input terminal 48 receives a speed control voltage from a motor speed detection means (not shown). In other words, when the motor speed is low and a large motor current (starting current) is required, such as when starting the motor, the control voltage input to the terminal 48 becomes high.
When the motor speed reaches steady speed and the motor current can be small, the control voltage will be low. 49 is a reference voltage, and 50 is a control amplifier.

Next, the operation will be explained. Receiving the rectangular wave output from the rotor rotational position detector 6, the trapezoidal wave generating circuit 14
Create a trapezoidal wave with A. Even with this trapezoidal wave, the sequential switching energization means 7 of the coils 3 and 4 is operated to amplify the output from the control current generation circuit 11 with the current amplifiers 15a and 15b, and the sequential switching energization of the coils 3 and 4 is performed in the trapezoidal wave. It is done with electric current. Here, in the trapezoidal wave generation circuit 14A, the switching means 44 performs a switching operation according to the rectangular wave output from the rotational position detector 6, and when the terminals a and b are connected, the constant current source 43 The capacitor 47 is charged with a constant current, and when the terminals a and c are connected, the constant current source 45 is used to discharge the capacitor 47 with a constant current. As already explained with reference to FIG. 8, the trapezoidal wave is created by the charging and discharging action of the capacitor.

By the way, when the control voltage input to the control input terminal 48 increases, indicating that the motor current is large, the trapezoidal wave generating circuit 14A accordingly changes the constant current values of the variable current constant current sources 43 and 45. Make it smaller with variable control. Then, according to equation (3), the slope of the trapezoidal wave can be made small, so that the energization switching means 7 can avoid abrupt changes, interruptions, and switching even though the motor current is large. An error voltage between the control voltage input to the control input terminal 48 and the reference voltage 49 is output from the control amplifier 50 and reaches the control current generation circuit 11 to control the motor current.

When the motor is started, the voltage input to the control input terminal 48 drops and the motor current decreases, but the constant current values in the constant current sources 43 and 45 are increased accordingly to change the slope of the trapezoidal wave. Return to original.

FIG. 12 shows current and voltage waveforms at various parts in the circuit of FIG. 11. 53 and 54 are output waveforms of the trapezoidal wave generating circuit 14A, 54 is a waveform when a large current is passed through the coil, and the slope changes linearly from waveform 53 to 54. 55 and 56 are 5 each
This is the waveform of the current flowing through the coil 3 or 4 when the energization switching means 7 is activated by the trapezoidal waves No. 3 and 54. That is, the slopes of the trapezoidal waves 55 and 56 are always constant. As a result, the current amplifier 1 shown in 57
The output voltage waveform of 5a or 15b does not generate a large back electromotive voltage even when the motor current is large.

FIG. 13 is a specific circuit diagram showing one embodiment of the present invention. In the same figure, 14A is a trapezoidal wave generation circuit, 50 is a control amplifier, 7 is energization switching means, and 11
6A is a Hall element as a rotor position detector, and 16 is a differential amplifier.

Now, in FIG. 13, the output of the Hall element 6A serving as a rotor position detector is amplified by a differential amplifier 16, converted into a rectangular wave, and sent to a trapezoidal wave generation circuit 14A.
The trapezoidal wave from the generation circuit 14A causes the energization switching means 7 (in this embodiment, differential switching circuits 73 and 74 with the trapezoidal wave output as the base input) to change the output current of the control current generation circuit 11 into a current. The signal is sequentially switched and supplied to amplifiers 15a and 15b. The currents amplified by the amplifiers 15a and 15b are applied to the coils 3 and 4.

Details of the trapezoidal wave generation circuit 14A will be explained. Two outputs from the differential amplifier 16 are input to the bases of transistors 65 and 66 forming the differential amplifier.
60 is a constant current source (current value I ₀ ). The output of the differential amplifier is taken out from a connection point Q formed by connecting the collectors of transistors 66 and 68. Therefore, it has a high output impedance.
As the transistor 66 turns on and off, the capacitor C (capacitance value C ₀ ) is charged and discharged. In this charging/discharging path, as described above in the explanation of FIG. 8, when the transistor 65 is on, the transistor 68 is also on, and the capacitor C is discharged through the transistor 68. Further, when the transistor 66 is on, the transistors 65 and 68 are off, so that the capacitor C is charged from the constant current source 60 through the transistor 66. Hereinafter, the operation procedure for generating the trapezoidal wave is the same as that described with reference to FIG. 8, so the description will not be repeated.

Now, in the control amplifier 50, the transistor 7
9 and 80 are connected as shown, the base of transistor 80 is at constant potential _E2 . Therefore, the base potential of the transistor 79 has a constant potential E ₂
If it becomes higher, extra current will flow towards transistor 79. A connection point between the collector of transistor 83 and the collector of transistor 80 is connected to control current generation circuit 11 . Now, the base potential of the transistor 79 becomes high and the transistor 79
Assume that a large amount of current flows through the transistor 80 and no current flows through the transistor 80. Then diode D ₄
A current flows through the transistor 83, and the same amount of current flows through the transistor 83 as well. This current flows in the direction of arrow Y and is supplied to the control current generation circuit 11. Conversely, when the base potential of the transistor 79 decreases to approximately equal to or lower than the reference potential _E2 , the transistor 79 is turned off and no current flows through the diode _D4 either. Then, no current flows through the transistor 83 either. Then, the current flowing through the transistor 80 flows from the control current generating circuit 11 in the opposite direction as indicated by the arrow S. Since the base potential of the transistor 79 is determined by the magnitude of the control voltage input to the control input terminal 48 (turning the transistor 75 on or off), the current supplied from the control current generation circuit 11 can be adjusted depending on the magnitude of the motor speed. It means you are in control.

Next, the function of changing the slope of the trapezoidal wave output from the trapezoidal wave generating circuit 14A will be explained. It is now assumed that the control voltage input to the control input terminal 48 has become high, and a large current is required in the motor. Then, the transistor 75 turns on, so that the current flowing from the power supply 25 through the resistor R ₂ increases, and the voltage drop across the resistor R ₂ increases. Then, in the transistor 62, the emitter potential becomes lower than the base potential, and the transistor 62 is turned off. Then, capacitor C
Since the constant current source 60 is the only current source that contributes to charging and discharging, the value of the charging and discharging current becomes small, and the slope of the trapezoidal wave becomes small according to the above equation (3).

On the other hand, when the control voltage input to the control input terminal 48 decreases and a large current is not required in the motor, the transistor 75 is turned off. Then, the current flowing to the transistor 75 through the resistor R ₂ also disappears, so the emitter potential of the transistor 62 rises and the transistor 62 is turned on. Then, the current flowing through the resistors R ₂ and R ₁ is determined by the reference potential E ₁ applied to the base of the transistor 62 and the power supply 25. That is, in addition to the current from the constant current source 60, the current flowing through the transistor 62 is added to the charging/discharging current of the capacitor C, so the current value increases, and as a result, the slope of the trapezoidal wave output from the circuit 14A increases. .

Although the present invention has been described above with respect to a motor having two coils, the present invention can also be applied to other motors having two or more coils, in which the energization of each coil is sequentially switched according to the rotation of the motor. it is obvious.

According to the present invention, even when the amount of current flowing through the motor coil changes, the slope of the trapezoidal wave current flowing through the coil is kept constant, and the rise in the collector potential of the drive transistor caused by the back electromotive force of the coil is kept within a certain limit. Since the voltage can be suppressed, a transistor with a relatively low breakdown voltage can be used as a drive transistor. Therefore, a circuit configuration suitable for IC implementation can be obtained.

[Brief explanation of drawings]

FIG. 1A is a side view showing the basic structure of a conventional DC motor, FIG. 1B is a top view, FIG. 1A is a perspective view of the energizing coil, and FIG. Figure 2A is a waveform diagram showing the change in magnetic flux density observed at surrounding fixed points P when the magnet plate 2 is rotated in the direction of the arrow in Figure 1B, and Figure 2B is a schematic diagram showing the change in magnetic flux density. The waveform diagram shown in
FIG. 3 is a circuit diagram showing a conventional DC motor drive circuit, FIG. 7 is a block diagram showing a DC motor drive circuit separately proposed by the present inventors, and FIG. 8 is a DC motor drive circuit separately proposed by the present inventors. A specific circuit diagram of the circuit, FIG. 9 is a waveform diagram of various signals in the circuit of FIG. 8, and FIG. 10 is a waveform diagram for explaining the drawbacks of the DC motor drive circuit separately proposed by the present inventors. FIG. 11 is a block diagram showing one embodiment of the present invention, FIG. 12 is a waveform diagram of various signals in FIG. 11, and FIG. 13 is a specific circuit diagram showing one embodiment of the present invention. Description of symbols, 1...Yoke, 2...Magnetic plate, 3,
4... Coil, 5... Axis, 6... Rotation position detector, 7... Energization switching means, 10... Motor voltage, 11... Control current generation circuit, 14... Trapezoidal wave generation circuit, 15... ... Current amplifier, 16 ... Differential amplifier, 17 ... Constant current source, 21 ... Emitter follower, 25 ... Power supply, 42 ... Circuit power supply, 43, 4
5... Constant current source with variable current, 44... Charge/discharge switching means, 48... Control input terminal, 49... Reference voltage, 50... Control amplifier.

Claims (1)

[Scope of Claims] 1. At least two current-carrying coils, a magnetic plate having an N-pole region and a S-pole region, and energization switching that alternately switches and energizes the two current-carrying coils with direct current from a control current generation circuit. and trapezoidal wave generating means for instructing the switching timing to the energization switching means by generating a trapezoidal wave, and also instructing the switching speed by the slope of the trapezoidal wave, Due to the interaction between the flowing current and the magnetic flux generated in the magnetic plate, the magnetic plate rotates as a rotor relative to the current-carrying coil, and position detection is obtained from a detector of the relative rotational position of the magnetic plate with respect to the current-carrying coil. By inputting a signal to the trapezoidal wave generating means and controlling the energization switching operation by the energization switching means in accordance with the trapezoidal wave obtained from the trapezoidal wave generating means in synchronization with the signal, the rotating operation of the magnet plate as a rotor is achieved. In the DC motor, the magnitude of the DC current generated from the control current generation circuit is controlled according to the rotation speed of the DC motor, and the trapezoidal wave generation means is controlled according to the rotation speed of the motor. 1. A DC motor drive circuit comprising a slope adjusting means for controlling and adjusting the slope of a trapezoidal wave generated therefrom. 2. In the DC motor drive circuit according to claim 1, the trapezoidal wave generating means comprises a capacitor and a constant current charging/discharging circuit for the capacitor,
A DC motor drive circuit characterized in that the slope adjusting means comprises means for varying the constant current value for charging and discharging the constant current according to the motor rotation speed.