JPH06165573A - Motor driving method - Google Patents

Abstract

PURPOSE:To attain stabilized rotation of a motor by a constitution wherein a transistor to be fed with a current having maximum absolute value is constantly turned ON through out one cycle of PWM modulation whereas other transistors are turned ON/OFF depending on the phase current thereof. CONSTITUTION:When currents iu, iv, iw flowing through the driving coils 1, 2, 3 for respective phases U, V, W of a motor satisfy a following relationship iu>iv>0> iw, transistors OH, VH, WH are turned ON according to the direction of current while other transistors UL, VL, WL are turned OFF. When ¦iw¦iu>iv, a transistor WL to be fed with a current having maximum absolute value is constantly turned ON through out one cycle of PWM modulation whereas other transistors UH, VH are turned ON/OFF depending on the currents iu, iv. This constitution establishes current circulation in specific section thus attaining stabilized rotation of motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor driving method, and more particularly, to prevent motor deceleration due to back electromotive current when driving a sine wave drive type brushless motor with a pulse signal of a pulse width modulation (PWM) method. For new improvements for.

[0002]

2. Description of the Related Art Generally, in a sine wave drive type brushless motor, as shown in FIG. 3, it is necessary to control the currents flowing in three-phase drive coils 1, 2, 3 of U, V, W in a sine wave shape. Therefore, a total of six transistors UH, UL, VH, VL, W provided in pairs for each drive coil 1, 2, 3
An appropriate voltage must be applied to each of the U, V, and W phase drive coils by controlling ON / OFF of H and WL. Therefore, conventionally, the pulse width modulation method shown in FIG.
The driving method using a pulse signal according to the M method) was adopted.

That is, in the above-mentioned method, the transistors U on the high arm side of each phase, that is, each drive coil 1, 2, 3 are used.
H, VH, WH and low-arm side transistors UL, V
ON and OFF are opposite to L and WL, and PW
In one cycle of the M method, in the section a, in each phase, the high-arm side transistors UH, VH, and WH are on, so the voltage difference between the U, V, and W phases becomes zero, and no current flows. .

Next, at the section opening of FIG. 4, since the high-arm side transistors UH and VH are on for the U and V phases and the low-arm side transistor WL is on for the W phase, they are referred to as the U and V phases. A voltage difference of V _CC occurs between the W phase and a current flows from the U and V phases to the W phase. Next, in the section C, since the high-arm side transistor UH is on for the U phase and the low-arm side transistors VL and WL are on for the V and W phases,
A voltage difference of V _CC occurs between the U phase and the V and W phases, and V and W from the U phase
Current flows into the phases.

Next, in section D, since the U-, V-, and W-phase transistors UL, VL, and WL of the low-arm phase are on, there is no voltage difference in the U, V, and W phases, and no current flows.

Further, in the PWM method, since the cycle T of one cycle is short, the U, V, and W phases are averaged by Vu, Vv, and Vw (0 <Vw <Vv <Vu) due to the movements in the sections I to D.
Is equivalent to the voltage applied to the U phase, V phase, W phase
The respective currents iu, iv, iw of the phases flow corresponding to the voltage difference. In this case, iu> 0, iv = 0,
iw <0, and the voltages iu, iv, and iw are the drive coils 1, 2, and 3 even in the section where the voltage difference between the phases U, V, and W is zero (0) as in the sections A and D described above. The current tends to continue to flow due to the action of the inductance of. That is, in the section a, UH → U → W is generated by the flywheel diode DWH provided in parallel with the transistors UH and WH.
→ It flows by the circulation loop of DWH. In section d, the flywheel diode DUL of the transistor UL continues to flow in a circular loop of DUL → U → W → WL.

If the circulation loop as described above cannot be performed, the current that has been flowing instantly becomes zero (0), and due to the action of the inductance, a reverse surge voltage is generated. Therefore, it is not desirable to turn off all the six transistors UH to WL even in the zero voltage application section.

[0008]

Since the conventional motor driving method is configured as described above, the following problems exist. That is, when the motor rotates, an induced voltage proportional to the rotation speed is generated in the drive coil of each phase,
Therefore, for example, in the above-mentioned intervals a and d, only this induced voltage is applied, and this induced voltage generally tries to flow the current in the direction to stop the rotation. The flowing current gradually decreases, and when this induced voltage is large, a reverse current (back electromotive current) flows. In this case, in section a, W
It becomes a circulation loop of H → W → U → DUH, and S in section 2
It becomes a circulation loop of WL → W → U → UL. Therefore, when the counter electromotive current flows in this way, the motor tries to decelerate, so that the control is particularly inefficient in the case of high speed rotation. That is, all the transistors on the high arm side or the low arm side are turned on in the zero voltage application section of the PWM method, so that the above-described loop for flowing the counter electromotive current is generated.

The present invention has been made to solve the above problems, and in particular, a counter electromotive current when a sine wave drive type brushless motor is driven by a pulse signal of a pulse width modulation (PWM) system. It is an object of the present invention to provide a motor driving method that prevents motor deceleration due to.

[0010]

In the motor driving method according to the present invention, a total of six pairs of three-phase driving coils are provided.
In the motor driving method in which the transistors are controlled via individual transistors, among the transistors, the high-arm side or low-arm side transistor of the phase in which the absolute value of the current to be passed is the maximum is during one cycle of pulse width modulation. This is a method in which the transistor is always turned on, and the other transistors are turned on / off according to the current flowing in the phase.

[0011]

In the motor driving method according to the present invention, among the transistors, the transistor having the maximum absolute value of the current to be flowed is always on during one cycle of pulse width modulation, and the other transistors are the currents to flow in the relevant phase. For example, as shown in FIGS. 1 and 2, a current circulation is formed in a specific section, and even if a counter electromotive current in the opposite direction flows due to an induced voltage, Since there is no loop for passing current in the opposite direction, back electromotive force does not flow,
It is possible to obtain stable rotation of the motor.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a motor driving method according to the present invention will be described in detail below with reference to the drawings. Note that FIG.
Each of the transistors UH to WL shown in FIG.
3, each phase U, V, W, each flywheel diode DUH
Since the same configuration is used for DWL to DWL, the description thereof is omitted here and the configuration of FIG. 3 is used as it is.

First, in FIG. 3, the currents iu, iv, iw flowing through the drive coils 1, 2, 3 of the respective phases U, V, W are in the case of iu>iv>0> iw in FIG. In this case, the transistors to be turned on are the transistors UH, VH, and WL according to the direction of the current, and the other transistors UH
L, VL, and WH are turned off. Also, │iw│>iu>
Since it is iv, the transistor WL having the maximum absolute value of the current to be flowed is always turned on during one PWM cycle as shown in FIG. 1, and the other transistors UH and VH are connected to the current iu,
Turns on and off according to iv.

Therefore, the current o in the sections a and b in FIG.
u and iv flow, and in section C, the current due to the circulation loop in the following Table 1 tries to continue flowing.

[0015]

[Table 1] That is, in the circulation loop shown in Table 1 above, the first phase of the U phase from the flywheel diode DUL of the transistor UL is increased.
The drive coil 1 and the W-phase third drive coil 3 circulate through the transistor WL, and the flywheel diode DVL of the transistor VL connects the V-phase second drive coil 2 and the W-phase third drive coil 3 to the transistor WL. In this section c, a loop in which a reverse electromotive current flows in the opposite direction is not formed, and stable driving can be obtained.

Next, FIG. 2 shows that the currents iu, iv, iw flowing through the drive coils 1, 2, 3 are iu> 0 in FIG.
>Iv> iw, and in this case, the transistors that turn on are transistors UH, VL,
WL, and the other transistors UL, VH, WH are turned off. Moreover, since | iu |>iv> | iw, the transistor UH having the maximum absolute value of the current to flow is shown in FIG.
As described above, the PWM is always turned on during one cycle, and the other transistors VL and WL are turned on / off according to the currents iv and iw.

Therefore, the current i in the sections a and b in FIG.
v and iw flow, and in section C, the current due to the circulation loop in Table 2 below tries to continue flowing.

[0018]

[Table 2] That is, in the circulation loop of Table 2 described above, the U-phase first drive coil 1 and the V-phase second drive coil 2 circulate through the flywheel diode DVH of the transistor VH and the first drive Coil 1
Can be circulated through the W-phase third drive coil 3 and the flywheel diode DWH of the transistor WH, and in this section C, a loop in which a reverse electromotive current flows in the opposite direction is not formed, and stable drive can be obtained. You can

Therefore, in FIG. 1 and FIG. 2 described above, each phase U,
Transistors UH, VH, WH on the high-ohm side of V, W
Alternatively, the transistors UL, VL, WL on the low arm side are selected, and the other transistors are always turned off during one PWM cycle. Also, of the selected transistors,
Transistor with the maximum absolute value of current (Fig. 1)
, WL (UH in FIG. 2) is always turned on during one PWM cycle, and the other transistors are turned on / off by an amount corresponding to the current to be passed through the relevant phase. Therefore, even if a counter electromotive current in the opposite direction tries to flow due to the generation of the induced voltage of the motor, there is no circulation loop that allows it, so that the flow of the reverse current can be prevented. It should be noted that the above-mentioned control such as selection of each transistor and detection of the magnitude of each current detected by a current detector (not shown) is performed through a control unit (not shown).

[0020]

According to the motor driving method of the present invention, the transistor having the maximum absolute value of the current to be flowed is always turned on during one cycle of pulse width modulation, and the other transistors are turned on / off. A loop in which a counter electromotive current flows due to an induced voltage is not formed, and stable motor driving without deceleration can be performed.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing a motor driving method according to the present invention.

FIG. 2 is a waveform diagram showing another motor driving method according to the present invention.

FIG. 3 is a circuit diagram showing a motor drive circuit of the present invention and a conventional motor drive circuit.

FIG. 4 is a waveform diagram showing a conventional motor driving method.

[Explanation of symbols]

 1, 2, 3 U, V, W drive coils UH-WL transistors

Claims (1)

[Claims] 1. A motor drive method in which each pair of three-phase drive coils (1, 2, 3) is controlled through a total of six transistors (UH to WL), wherein each transistor (U
H-WL), the transistor on the high-arm side or the low-arm side of the phase with the maximum absolute value of the current to be flowed is always on during one cycle of pulse width modulation, and the transistors on the other phases are A method of driving a motor, characterized in that the motor is turned on / off according to the current flowing in any one of (3).