JPS6277085A - Drive controlling method for brushless dc motor - Google Patents

Abstract

PURPOSE:To set the output efficiency of a motor to the best state by detecting a counterelectromotive force of each phase coil, thresholding at the prescribed level, and further forming a signal delayed in response to the characteristic of the motor in an energization phase switching signal. CONSTITUTION:Counterelectromotive forces generated in phase coils CL1-CL3 of a brushless DC motor are input to comparators COM1-COM3 to threshold at the prescribed level. The outputs of comparators COM1-COM3 are input to delay circuits DT1-DT3 to be delayed by variable delay time set in response to the characteristic of the motor, and applied to transistors TR1-TR3 as energization switching signal to switch the energizing phase from the delayed signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling the drive of a brushless DC motor used, for example, to drive a fuel supply pump of an automobile.

(Prior Art) Conventionally, in a drive control method in which each phase coil of a brushless DC motor is sequentially driven by the switching operation of a transistor or the like connected to each phase coil, the rotor is rotated by applying direct current. Detect the location and detect the location! The transistors are sequentially switched according to the a-pole position, and a drive current is sequentially applied to each phase coil to rotate the rotor. As a method of detecting the magnetic pole position of the rotor, for example, a method of using an electrical detection sensor such as a Hall element is described in "Mechatro Books 1 Cutting-Edge Control...1 7-Ta" published by Gijutsu Kenkyukai Co., Ltd. , has become a publicly known technology. In addition, there is a method of controlling a brushless DC motor that does not use a magnetic pole position detection sensor or the like. For example, "S to E Technical Pap" issued by General Motors of the United States.
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As described in No. P59, the back electromotive force generated in each phase coil is detected and the back electromotive force is converted into a logic level signal, and the rotor magnetic pole position detection signal is generated at the same timing without delay. This method is used as a control method in which the magnetic pole position detection signal of the rotor is converted into a drive signal for the transistor, the transistor is turned on, and a drive current is sequentially applied to each phase coil to rotate the rotor. There is.

(Problems to be Solved by the Invention) As in the above-mentioned conventional method, a back electromotive force is detected to generate a rotor magnetic pole position signal, and the magnetic pole position signal is outputted at the same timing as the energized phase switching signal, that is, without delay. In the method of using the drive signal as a drive signal to drive a transistor and sequentially passing the drive current to each phase coil, the peak value of the back electromotive force changes in accordance with the rotational speed of the rotor, and the waveform of the back electromotive force changes. Because of the steep fall of the signal, it is not possible to change the threshold level for obtaining the signal, and therefore the timing at which the drive signal is applied to the transistor cannot be changed.

By the way, what is the optimal energizing phase switching timing when sequentially applying drive current to each phase of a brushless DC motor to rotate the rotor, that is, the energizing phase switching timing to efficiently output torque from the brushless DC motor? ,
Since this changes depending on the type of brushless DC motor, if the energized phase is switched using the drive signal obtained by thresholding the back electromotive force detected from each phase coil, the output of the brushless DC upper and lower currents does not necessarily change. There is a problem in that the characteristics cannot be optimized, that is, it is necessary to make the energization phase switching timing variable.

Therefore, in the present invention, J3 detects the back electromotive force generated in each phase coil and thresholds it at a predetermined level.
Furthermore, by using a signal delayed by a variable delay time set according to the characteristics of the brushless DC motor as a drive signal, the energizing phase switching timing can be optimally set according to the output characteristics of the brushless DC motor, and the brushless The technical problem to be solved is to maximize the output efficiency of a DC motor.

(Means for solving the problem) The technical means for solving the above problem is to improve the drive control method of a brushless DC motor by detecting the back electromotive force generated in each phase coil of the brushless DC motor. A signal obtained by thresholding the power is delayed by an adjustable predetermined time to generate a delayed signal, and the delayed signal is used as a driving signal for a switching element for switching the driving current to the next phase coil. That's what I did.

(Example) Next, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows permanent magnets on the circumferential surface of the rotor.

When a 3-phase brushless DC motor magnetized to the N pole is
The waveform of the back electromotive force generated in each phase coil when the rotor rotates in this direction is shown in correspondence to the rotation angle of the rotor.

As shown in the figure, the back electromotive force generated in the first digit coil is
A positive back electromotive force is generated when the rotation angle of the rotor is in the range of 0° to 90', assuming that the rotation start reference position of the rotor is 0°.
In the range of ~180°, there is a negative back electromotive force, and 180°
A positive back electromotive force is generated in the range of 0° to 270°, and a negative back electromotive force is generated in the range of 270° to 360' d3.

On the other hand, the back electromotive force waveform generated in the phase II coil is similar to the back electromotive force waveform of the first digit coil, and is smaller than the positive and negative peaks of the back electromotive force waveform of the phase II coil, respectively. 60
The waveform has positive and negative peaks at rotation angles delayed by °.

Roughly speaking, the back electromotive force waveform generated in the phase II coil is similar to the waveform of the back electromotive force generated in the first digit coil and the phase II coil, and the positive and negative waveforms of the back electromotive force waveform of the phase II coil are similar. The waveform has positive and negative peaks at rotation angles that are 60°d from the peak.

Next, a drive control circuit for the brushless DC motor shown in FIG. 2 will be explained.

For example, a voltage element B from a battery, which serves as a power source for the three-phase brushless DC motor, is connected to each phase coil CL1, C10, C.
10 are connected to one end of each.

Further, the collector of the NPN type transistor TR1 is connected to the other end of the first phase coil CL1, and the collector of the NPN type transistor TR1 is connected to the other end of the first phase coil CL1.
The collector of a 1-transistor TR2 of the same type is connected to the other end of the transistor TR2 of the same type, and the collector of a transistor 1''R3 of the same type is connected to the other end of the phase coil CL3. , TR3 are connected to the ○ volt GND of the battery.

Therefore, when a drive signal corresponding to the logic signal "1" is applied to the base of the transistor TR1 and the transistor TR1 is switched on, a drive current is applied to the phase coil C1, and in the same way, TR2 is switched on. Then, a drive current is applied to the second phase coil CL-2, and similarly, when TR3 is switched on, a drive current is applied to the second phase coil CL3.

The detected voltage of the phase ■ phase coil CL1 is the comparator C0M1
On the other hand, a voltage obtained by dividing the control voltage Vcc by resistors R1 and R2 is applied to the non-inverting input terminal as a threshold voltage VREF. The detected voltage of the second phase coil CL2 is input to the inverting input terminal of the comparator C0M2, while the threshold voltage VREF is applied to the non-inverting input terminal. moreover,
The detection voltage of the phase ■ phase coil CL3 is the comparator C○M3
, and the threshold voltage VREF is applied to the non-inverting input terminal.

Note that each comparator C0M1. C0M2. C
0M3 is each phase coil CL1. A type of comparator is used that outputs a high level signal, for example, a logic signal "1" when the detection voltage of Cl-2°C10 is lower than the threshold voltage VRE.

Each comparator C0M1. C0M2゜C0M3
The output signal of the logic signal "1" from the respective delay circuits [)TI, DT2 . The signal is input to DT3 and is delayed by, for example, a millisecond time unit. Delay circuit DTI
The delay signal outputted from the circuit is applied to the cell 1 terminal of the flip-flop FF1, which is configured with two NOR gates, and is also applied to the reset terminal of the flip-flop FF2, which is configured with a similar gate circuit. Ru. Further, the delay signal output from the delay circuit DT2 is applied to the set terminal of the flip-flop FF2, and is also applied to the reset terminal of the flip-flop FF3. Further, the delay signal output from the delay circuit DT3 is applied to the terminal of the flip-flop FF3 and the reset terminal of the flip-flop FFI.

Flip-flop FF1 with the above configuration. FF2, F"
3, when the logic signal rlJ is applied to each set terminal, the output signal becomes the logic signal rOJ. Therefore,
When the logic signal "1" is applied to the set terminal, the transistor TRI connected to the output terminal of the flip-flop F7 via the resistor R3 is canted off. The transistor TR2 connected to the output terminal via the resistor R4 is turned off, and the transistors R3 connected to the output terminal of the flip-flop FF3 via the resistor R5 are also turned off.

On the other hand, flip-flops FFI, FF2. FF3 outputs a logic signal "1" when a logic signal "1" is applied to each reset terminal, and as a result, the transistors TR1, TR2, and TR3 are respectively turned on, and each phase coil CL1° A drive current is applied to each of C10 and C10.

Next, the operation of the drive control circuit for the brushless DC motor will be explained. Now, with transistor TRI in the on state,
When a drive current is applied to the phase coil CL1 and a back electromotive force as shown in FIG. As shown in FIG. 3, at the moment of the drop, the output of the P1 signal indicated by the solid line is started, and at the same time, the P1 signal is input to the delay circuit DT1 to delay it by a preset predetermined time t. Therefore, the signal output from the delay circuit DTI becomes the P2 signal shown in FIG. 3, which is delayed by the variable setting time t set by the delay circuit 1]T1.

When the output of the delay signal P2 is started from the delay circuit DTI, the flip-flop FFI is set and the flip-flop FF2 is reset, so the transistor TRI goes into the cut-off state, and at the same time, the transistor TR2 goes into the on state. Then, the energized phase is switched from the first set to the second phase.

At this moment, the voltage applied to the inverting input terminal of the comparator COMI becomes higher than the threshold voltage VREF, so the output signal of the comparator COMI becomes "0" and the signal P1 falls as shown in FIG. After a certain period of time, the signal P2 also falls.

Next, the comparator C0M2 selects the second phase coil CL 2
The back electromotive force detected from the threshold voltage VRE
At the moment when the voltage drops below F, output of the P3 signal (shown by the solid line in FIG. 3) is started. The P3 signal is input to the delay circuit DT2, and is delayed by a variable time t set by the delay circuit DT2.

The signal delayed by the delay circuit DT2 becomes a signal indicated by P4 in FIG.

When the output of the delay signal P4 is started from the delay circuit DT2, the flip-flop FF2 is set and the control flop FF3 is turned on, so that the transistor TR2 is cut off and at the same time, the transistor TR3 is turned on. , the energized phase is switched to phase (■).

At this moment, the voltage applied to the inverting input terminal of comparator C0M2 becomes higher than the threshold voltage VREF, so the output signal of comparator C0M2 becomes rOJ, signal @P3 falls, and after some time, signal 24 also falls. .

At the moment when the current-carrying phase is switched from the phase ■ to the phase ■, and the back electromotive force detected by the comparator C0M3 from the phase ■ coil CL3 falls below the threshold voltage VREF,
The comparator C0M3 starts outputting the P5 signal indicated by the solid line in FIG.
will only be delayed. The signal delayed by the delay circuit DT2 becomes a signal indicated by P6 in FIG.

When the output of the delay signal P6 is started from the delay circuit DT3, the flip-flop FF3 is turned off and the flip-flop FF1 is reset, so that the Laran jitter TR is cut off and at the same time the transistor TRI is turned on. Then, the energized phase is switched from the phase (2) to the first set.

At this moment, the voltage applied to the inverting input terminal of the comparator C0M3 becomes higher than the threshold voltage VREF, so the output signal of the comparator C0M3 becomes rOJ, the signal P5 falls, and after some time, the signal P6 also falls.

As described above, the logic signals P1, P3. The delayed signal P2.P5 is delayed by a variable time t. P4. P6 is connected to flip-flops FF1, FF2 . When a drive signal is used to drive transistors 1 to TR1, TR2, and TR3 via FF3, delay circuits DTI, D2, and TR3 are respectively used. D
By adjusting the variable time t set by T3, the timing at which the drive current is applied to each phase coil can be arbitrarily adjusted.

When starting the brushless DC motor, a starting circuit (not shown) is used to avoid starting the brushless DC motor, and from the time when a back electromotive force as shown in Fig. 1 is generated from each phase coil, the brushless DC motor is started by the control circuit of this embodiment. Assume that a DC motor is to be controlled.

(Effects of the Invention) As described above, according to the present invention, the back electromotive force generated in each phase coil is detected and thresholded at a predetermined level. By using a signal delayed by the delay time as the energized phase switching signal for switching the energized phase, the energized phase switching timing can be optimally set according to the output characteristics of the brushless DC motor. This has the effect of optimizing the output efficiency of the DC motor.

[Brief explanation of drawings]

Fig. 1 is a back electromotive force waveform diagram of each phase coil of a three-phase brushless DC motor, Fig. 2 is a brushless DC motor drive control circuit according to an embodiment of the present invention, and Fig. 3 is a DC motor drive control circuit of Fig. 2. FIG. 3 is a signal waveform diagram generated by the circuit. CLI: ■Phase coil Cl3: ■Phase coil C10: ■Phase coil

Claims (1)

[Claims] When the switching element is activated to sequentially apply a drive current to each phase coil of the brushless DC motor to rotate the rotor, the back electromotive force of each phase coil is detected, and the back electromotive force is thresholded. Driving a brushless DC motor characterized in that the delayed signal is generated by delaying the signal by an adjustable predetermined time, and the delayed signal is used as an energization phase switching signal for switching the drive current and energizing the next phase coil. Control method.