JPS5915269Y2 - Brushless motor drive circuit - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a brushless motor drive circuit.

In conventional brushless motor drive circuits, when switching a plurality of drive transistors connected to a stator coil, they are turned on so that some periods overlap with each other, or the periods in which the outputs of position detection elements are generated are made to coincide with each other. The period was made to overlap so that the ON states of the driving transistors did not overlap electrically.

The present invention is a brushless motor drive circuit with a new configuration different from these conventional ones.

The present invention aims to propose a brushless motor drive circuit that can improve efficiency, improve starting torque, reduce torque ripple during starting, and further reduce electromagnetic noise.

Hereinafter, one embodiment of the present invention will be described. As shown in FIG. Three stator coils 11.12.13 wound around this stator core 2, and these stator coils 11.1
2. Drives a brushless motor consisting of position detection elements such as Hall elements 21, 22, and 23, which are arranged corresponding to the winding positions of 13 and generate detection outputs according to the rotational positions of the opening and closing parts 1. It was designed to do so.

The rotor 1 is rotated by applying a drive current to the stator coils 11, 12.13 based on the detection outputs from the Hall elements 21, 22.23.

FIG. 1 shows the direction of the drive current when only the stator coil 11 is energized.

Furthermore, to explain this example in detail with reference to FIG. 2 and subsequent figures, one end of the stator coil 11.
cc), and the other ends are connected to the collectors of driving transistors 31, 32, and 33, respectively.

The transistors 31, 32, 33 are grounded via a common drive current sensing resistor 3, and the amplifiers 51, 52, 53 each have a negative feedback loop containing a resistor 41, 42, 43 at their base. output is supplied.

The output terminals of Hall elements 21, 22, and 23 are connected to the input terminals of these amplifiers 51, 52, and 53, respectively.

In this case, the gain of the amplifier 51.52.53 is such that the stator coil 11.12.13 is connected to the transistor 3 at the rated rotation.
1, 32, and 33 are set to be sufficiently small so as to obtain enough base current to drive them.

Also, at the time of rated rotation when the gains of the amplifiers 51, 52, and 53 are the smallest, the output voltage Eo of the amplifier 51, 52, and 53 causes the base current I to flow through the transistor 31, 32, and 33.
The period during which the voltage b starts flowing, for example, 0.65 V or more is designed to be 120°.

One ends of the input terminals of these Hall elements 21, 22, 23 are connected in common to the output terminal of the amplifier 4, and the other ends are grounded.

Amplifier 4 has a Hall element 21゜22 at its non-inverting input terminal.
, 23, and is connected to a negative feedback resistor 5, whose inverting input terminal is connected to the emitter of the transistor 31, 32, 33 via a capacitor 6. It is connected to the connection point of the resistor 3 for use.

In this case, the amount of signal obtained at the inverting input terminal of the amplifier 4 via the capacitor 6 increases as the frequency increases and the rotation speed increases, and the control current Id from the amplifier 4 decreases as the speed shifts from startup to rated rotation. Do as it is done.

With the above configuration, the Hall elements 21, 22, 23 generate a detection voltage of Ei2KBId with respect to the external magnetic flux density B and the control current Id.

K is the Hall constant. and amplifier 51.52.53
The output voltage Eo is given by the equivalent resistance R1 of the Hall elements 21, 22, and 23, and the values of the resistors 41, 42, and 43 being R2.

Now, Hall element 21. Amplifier 51 and transistor 31
To explain this using an example, if a substantially sinusoidal magnetic flux density B acts on the Hall element 21 with respect to the rotation angle (meaning an electrical angle, the same applies hereinafter) θ as shown in FIG. 3A, the control current Id
is constant, the Hall element 21 as shown in FIG. 3B
A substantially sinusoidal detection voltage Ei having a predetermined DC level is generated due to the equivalent resistance of .

Also, since the gain of the amplifier 51 is sufficiently small, the amplifier 51
The output voltage Eo is as shown in FIG. 3C.

From the point where this output voltage Eo exceeds, for example, 0.65 V, a base current Ib begins to flow into the next stage transistor 31 as shown in the third diagram.

Further, a collector current Ic flows through the transistor 31 as shown in FIG. 3E.

When the output voltage Eo of the amplifier 51 exceeds, for example, 1.2V, the transistor 31 becomes saturated and its collector current Ic becomes constant.

The waveform in FIG. 3E shows the case where the load of the transistor 31 is a resistor R, and at saturation, the collector current Ic is (Vc
c).

Further, the above explanation is for the case of the rated rotation of the solid line waveform in FIG. 3 BE, and at this time, the substantial energization angle of the stator coil 11 is selected to be 120° for design purposes.

Therefore, in response to the detection voltage of the other Hall elements 22, 23, the output of the amplifier 52, 53 causes the transistor 32 to react in the same manner as described above.
．． 33 is controlled, stator coils 12.
The actual conduction angle of the stator coils 13 is also 120 degrees, and the conduction sections through which the drive current flows through the stator coils 11, 12 and 13 do not overlap with each other.

At such rated rotation, transistors 31, 32, 33
A collector current always flows through one of them, and their collector voltages decrease.

Furthermore, at startup, the rotational speed is lower than at rated rotation, so the frequency of the detection voltage generated across the detection resistor 3 is low, and therefore the detection voltage that is supplied to the inverting input terminal of the amplifier 4 through the capacitor 6 is low. The voltage level is lower than that at rated rotation, the output of the amplifier 4 substantially increases, and the control current Id for the Hall elements 21, 22, 23 also increases.

Therefore, as shown by the dashed line in FIGS. 3B and 3C, for example, the detection voltage Ei of the Hall element 21 and the output voltage Eo of the amplifier 51 have large amplitudes, and as shown by the dashed line in FIGS. The section in which the base current Ib and collector current Ic of 31 flow is wider than at rated rotation, and the actual conduction angle at startup is 180°.
It will be close to.

As the rotational speed increases during startup, the frequency of the detection voltage generated across the resistor 3 also increases, and the amount of signal supplied to the inverting input terminal of the amplifier 4 also increases. The control current Id supplied to 22 and 23 becomes smaller.

Therefore, at rated rotation, the conduction angle becomes narrower as described above.

As is clear from the above, in the present invention, at startup, the detection voltage Ei increases so that a base current sufficient to saturate the driving transistor flows, so the conduction angle increases by 3.
In the case of the phase, the angle increases to nearly 180°, and the effective starting torque improves as shown in FIG. 4B.

Conventionally, the conduction angle is 120° even at startup, so the fourth
A starting torque as shown in Figure A was generated.

However, when the flux linkage from the rotor 1 to the stator coils 11, 12, 13 is sinusoidal, the conduction angle is 120
Torque ripple can be reduced more when the conduction angle is close to 180 degrees than when the conduction angle is close to 180 degrees.

In addition, when the flux linkage changes sinusoidally, the larger the conduction angle, the lower the average flux linkage, and therefore the efficiency (conversion efficiency of converting electrical energy into mechanical energy). However, in the present invention, the energization angle can be reduced to 120° at rated rotation compared to the start-up time, and the energization is conducted in a place where there is a large amount of interlinkage magnetic flux, so the efficiency is good.

Furthermore, the present invention can reduce electromagnetic noise.

That is, when a transistor performs a complete on/off operation as in the conventional case, the drive current corresponding to one unit of the interlinkage magnetic flux shown by the broken line in FIG. 5 has a rapid level change as shown by the solid line. Become something.

Here, since the stator coils 11, 12, and 13 are configured so that the driving current flows in the same direction in a certain section as shown in FIG. 6A, as shown in FIG. A current force is generated by the driving current at
When the drive current level changes rapidly, this current force also changes rapidly, which causes electromagnetic noise.

In contrast, in the present invention, the operation of the driving transistor is such that the current gradually increases through the active region at the beginning of energization, then reaches the saturation region, and then gradually decreases. As shown by the solid line in FIG. 7, the level change of the drive current is relaxed.

Therefore, electromagnetic noise can be reduced, and there is an advantage that there is no need to insert a capacitor between the collector and base or between the collector and emitter of a driving transistor to reduce electromagnetic noise, as in the conventional case.

Note that, unlike the one shown in Fig. 1, the present invention can also be applied to a brushless motor in which the rotor is arranged outside the stator core, and as a position detection element, a magnetoresistive element, a photoelectric element, etc. can be used in addition to a Hall element. You can do it like this.

[Brief explanation of drawings]

Figure 1 shows the constituent countries of brushless motors to which the present invention can be applied, Figure 2 is a connection diagram of one embodiment of the present invention, Figures 3 and 4
The figure is a waveform diagram used to explain the operation, and FIGS. 5 to 7 are diagrams used to explain the reduction of electromagnetic noise. 1 is a rotor, 3 is a detection resistor, 11.12.13 is a stator coil, 21.22.23 is a Hall element, 31
32 and 33 are driving transistors.

Claims (1)

[Scope of utility model registration request] A rotor made of a permanent magnet is provided, a plurality of stator coils are provided in a predetermined positional relationship with respect to the rotor, and a plurality of position detection elements are provided corresponding to the plurality of stator coils to detect the rotational position of the rotor. one end of each of the plurality of stator coils is connected to one terminal of a power supply, the other terminal of the power supply is grounded, and the other end of each of the plurality of stator coils is connected to a plurality of drive transistors, respectively. respectively connected to one end of the load current detector through
The other end of the load current detector is grounded, and the one end of the load current detector is connected via a feedback capacitor to the input terminal of an amplifier that reduces the bias of the plurality of position detection elements. The output terminals are connected to one terminal for bias of each of the plurality of position detection elements, the other terminal for bias of each of the plurality of position detection elements is connected respectively, and the output terminal is connected to one terminal for bias of each of the plurality of position detection elements. The respective detection outputs are respectively supplied to a plurality of amplifiers, the respective output signals of the plurality of amplifiers are respectively supplied to respective control terminals of the plurality of drive transistors, and as the rotational speed of the rotor increases, The plurality of drive transistors are controlled by lowering the gain of each of the plurality of amplifiers, and a drive current having overlapping energization sections is caused to flow through the plurality of stator coils at startup, and the plurality of stator coils are controlled at the rated rotation. A brushless motor drive circuit characterized in that a drive current is caused to flow through the energized sections without overlapping.