JPS58186392A - Drive circuit for motor - Google Patents

Abstract

PURPOSE:To equalize power consumption of two sets of transistor groups by controlling one transistor group to control the speed of a motor, simultaneously detecting the central voltage of the coil group of the motor and controlling the other transistor group. CONSTITUTION:The current of a motor coil 4 is flowed by controlling the bases of output transistors 9-11 with a differential amplifier which has transistors 21, 22 and a constant-current source 23 according to the signal 27 from a position detector, the central voltage of a coil 4 is detected through resistors 28-30 of respective phases connected to the coil 4 applied to a differential amplifier having transistors 16, 17 and a constant-current source 24, and fed back to control the currents of output transistors 6-8. Accordingly, transistors 6-8 are controlled so that the central voltage of the coil 4 always becomes 1/2 of the motor drive voltage, thereby optimally controlling the base currents of two sets of transistor groups.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive circuit for a brushless motor, and particularly to a drive circuit suitable for controlling an output transistor that conducts current to a drive coil in both directions.

An example of a three-phase motor as a conventional motor drive circuit is shown in FIG. In the figure, 1 is a position detector that detects the rotational position of the rotor magnet, 2 is a signal generator that generates a switching signal for the motor drive coil from the output of this position detector,
5 is a drive amplifier that supplies current to the motor drive coil; 4
5 indicates a drive coil of the motor, and 5 indicates a rotating body of the motor.

Here, the drive amplifier 3 that supplies current to the motor drive coil 4 is composed of transistors 6 to 11, and supplies current to each coil by sequentially turning on these transistors. This switching signal is determined by the position detector 1 and the signal generator 2. An example is shown in FIG. The means for obtaining these signals are generally known and will be omitted here. In FIG. 2, for example, at 11 o'clock, transistor 6 and transistor 10 become conductive, and current is supplied to drive coil 4 via reference power supply 12.

Here, when speed control is applied, the amount of current supplied to each drive coil is varied by controlling the amount of base current of each transistor. In this case, PNP transistors 6 to 8 and N
Due to the difference in FW of PN transistors 9 to 11, it was difficult to apply optimal base current control to both.For this reason, one (PNP transistor side or NPN)
Base current control was applied only to the transistor side), and sufficient base current was supplied to the other side even at maximum load. In this case, the loss due to the pace current mentioned above at light loads becomes a problem, and the power consumption on the PNP transistor side and the NPN transistor side becomes unbalanced, and only the transistor controlling the pace current generates heat. There were drawbacks.

The object of the present invention is to provide a circuit that always optimally controls the base current of two transistors for supplying current to a motor drive coil in both directions, reduces power loss, and at the same time equalizes the power consumption of the two transistors. Our goal is to provide the following.

In the present invention, speed control is performed by controlling the base current of one transistor group, and at the same time, the center voltage of the motor drive coil group is detected so that this voltage is always 1/2 of the motor drive power supply voltage. The above object is achieved by performing feedback control to control the base current of the other transistor group.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 6, the same symbols as in FIG. 1 indicate the same functions. Also,
13-17 are NPN transistors, 18-22 are PN transistors.
23 and 24 are constant current sources, 25 and 26 are constant voltage sources, 27 is a control input terminal, and 28 to 30 are resistors, respectively.

Here, transistors 15 to 15 are respectively driver drivers that drive output transistor row 8, and transistors 18 to 20 are output transistors 9 to 1, respectively.
This is a pre-driver that drives 1. On the other hand, these base input signals i-T represent inverted signals of a-f shown in FIGS. 1 and 2, respectively.

Here, the amount of current flowing through the drive coil 4 is determined by the amount of current flowing through the transistor 2.
1.22 and a constant current source 2!1. That is, as the control input terminal 27 decreases with respect to the constant voltage @25, the collector current flowing to the transistor 21 increases, and the collector current flows through the output transistor 9 through the transistors 18 to 20, which operate as a 3-differential switch circuit. It is controlled as the base current of one of the output transistors.

On the other hand, the current flowing through the upper output transistor ~8 is
It is controlled by a differential amplifier consisting of transistors 14 and 17 and a constant current source 24. That is, the voltage at the midpoint of the drive coil group 4 (point X in the connection of the drive coil group shown in FIG. 5) is detected by adding the resistances from the coil terminals of each phase of the drive coil group 4 using the resistors 28 to 30. Feed pack control is performed so that this midpoint voltage is approximately equal to that of the constant voltage source 26. For example, when this midpoint voltage increases, the collector current of the transistor 16 constituting the differential amplifier decreases, and one of the upper output transistor groups 6 to 8 is connected via the transistors 13 to 15 constituting the 6 differential switch circuit. The current supplied as the pace current decreases, working in the direction of lowering the midpoint voltage.

Here, by setting the constant voltage source 26 to about 1/2 of the voltage #i12, each output transistor when the current flowing through the drive coil group 4 is controlled from the control input terminal 27.
The power consumed by each of the 11 is approximately equal.

According to the present invention, since the base current of each output transistor can always be optimally controlled, there is no need to keep an excessive pace current flowing at all times, and furthermore, the midpoint voltage of the drive coil group can be reduced to 1/2 of the power supply voltage. Since it can be controlled, there is an effect that the loss of each output transistor is equalized.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a conventional three-phase motor drive circuit, Fig. 2 is a waveform diagram showing the waveforms of the main parts of Fig. 1, and Fig. 5 is a five-phase motor drive according to the present invention. FIG. 2 is a circuit diagram showing a part of the circuit. １・・・・・・・・・Position detector, ２・・・・・・・・・
・Signal generator. 6.......Drive amplifier, 4........
・Drive coil. 5...Rotating body, 6-11...
...Output transistor. 13-22...Transistor, 25.
24... Constant current source. 25.26... Constant voltage source, 27...
...Control input terminal. 28-30・・・・・・Resistance. Oh 1lli:i Second mouth. ko←-shiichi-L: f: 3rd mouth■-

Claims (1)

[Claims] between a fixed magnetized rotor, a fixed prewinding m# that generates a magnetic field to give rotational force to the rotor, and a first reference power source for sequentially switching the current flowing through the stator winding group. A first transistor group whose emitters and collectors are connected, a second transistor group whose emitters and collectors are connected between a second reference power supply, and a 111f) switch group connected to the base of the first transistor group. a first current source connected in common; a second current source commonly connected to the pace of the second transistor group via a second switch group; a position signal generator that generates a signal; and an output of the position signal generator to generate the first signal. In a motor drive circuit in which a second switch group is sequentially switched to supply a current between a first reference power source and a second reference power source via a stator winding, the first current source is varied. A brushless motor characterized by controlling the current flowing through the stator winding group and at the same time providing a second current source with negative feedback so as to fix the midpoint voltage of the stator winding group at a predetermined value. drive circuit.