JP7095965B2 - Motor drive - Google Patents

Description

Embodiments of the present invention relate to a motor drive device.

In recent years, brushless DC motors have been widely used from the viewpoint of energy saving and noise reduction. In a brushless DC motor, it is necessary to switch the energization timing according to the position of the rotor. Therefore, the position of the rotor is detected by a magnetic pole position sensor such as a hall sensor, and the energization timing of the motor is switched according to the edge of the sensor signal to drive the motor.

In this case, the motor current can be adjusted by switching the energization timing earlier than the timing at which the edge of the sensor signal arrives to control the advance angle or by changing the energization time. Such control can be realized by using, for example, a timer. For example, it is possible to start the time counting by the timer 1 from the timing of the edge of the sensor signal and start the energization by the interrupt of the timer, and to start the time counting by the timer 2 and end the energization by the interrupt of the timer. Conceivable. Patent Document 1 is presented as an example of energization control of a brushless DC motor performed by using a timer.

Japanese Unexamined Patent Publication No. 2005-117895

However, in the above configuration, when the edge interval of the sensor signal becomes short, for example, the motor accelerates rapidly, the next edge occurs or the next energization timing occurs before the completion of the energization time. By doing so, it is assumed that an abnormal energized state will occur and a large current will flow.

Therefore, when two timers are used for control, a motor drive device that prevents control failure and enables control at a lower advance angle is provided.

The motor drive device of the embodiment includes a power conversion circuit that drives a motor by connecting a plurality of arms including a series circuit of a positive side and a negative side switching element in parallel.
In order to control the motor, a control circuit that generates and outputs an on / off signal for each switching element constituting the power conversion circuit, and a control circuit.
A rotation position portion for detecting the rotation position of the motor is provided.
The control circuit includes first and second timers.
The first timer is started according to the rotation position, and when the first timer clocks a predetermined time, the positive switching element is started to turn on to energize the motor, and the first timer is used. Stop the timekeeping and start the second timer.
When the second timer clocks a predetermined time, the positive switching element is turned off and the clock by the second timer is stopped.
When the rotation position reaches the position where the first timer is activated before the positive switching element is turned off, the positive switching element that is turned on and the positive switching element that is turned on next are turned on. And the second timer is started.

A diagram showing a configuration of a motor drive device according to an embodiment. Assumed Timing chart showing normal operation of the prior art Flowchart showing interrupt processing due to edge generation of rotation position signal Flowchart showing timer 1 interrupt processing Flowchart showing timer 2 interrupt processing Timing chart showing the operation when an abnormality occurs Flow chart showing interrupt processing due to edge generation of rotation position signal in this embodiment Flowchart showing timer 1 interrupt processing Timing chart showing the operation when an abnormality occurs The figure which shows each signal waveform corresponding to the occurrence of an abnormality shown in FIG. The figure which shows each signal waveform when the abnormality correspondence by this embodiment is performed.

Hereinafter, one embodiment will be described with reference to the drawings. In FIG. 1 showing the configuration of the motor drive device, a series circuit of a smoothing capacitor 2, resistance elements 3 and 4, and an inverter circuit 5 are connected in parallel to the DC power supply 1. The inverter circuit 5 corresponding to the power conversion circuit is configured by connecting four N-channel MOSFETs Q1 to Q4 with an H-bridge. Then, a stator winding (not shown) of the single-phase brushless DC motor 6 is connected between the common connection point of the arm which is a series circuit of FET_Q1 and Q2 and the common connection point of the arm which is a series circuit of FET_Q3 and Q4. Has been done. Note that FET_Q1 and Q3 correspond to the positive semiconductor switching element, and FET_Q2 and Q4 correspond to the negative semiconductor switching element.

The FETs_Q1 to Q4 are switched and controlled by the control microcomputer 7. The control microcomputer 7 corresponding to the control circuit outputs a gate drive signal to the gate of each FET_Q1 to Q4 via the gate drive circuits 8 to 11, respectively. The common connection point of the resistance elements 3 and 4 is connected to the input terminal of the control microcomputer 7. The control microcomputer 7 reads the divided voltage of the DC power supply 1 by A / D conversion by the A / D converter 12.

Further, a hall sensor 13 is arranged in the motor 6, and the output terminal of the hall sensor 13 is connected to the input terminal of the control microcomputer 7. The Hall sensor 13 detects the magnetic field of the permanent magnet arranged in the rotor of the motor 6 and outputs the rotation position signal to the control microcomputer 7. The control microcomputer 7 switches the energization direction with respect to the stator winding of the motor 6, that is, the rotation direction of the motor 6 according to the rotation position signal. The Hall sensor 13 corresponds to a rotation position detection unit.

A resistance element 14 which is a current detection unit is inserted in a power supply line connecting the inverter circuit 5 and the ground which is a negative terminal of the DC power supply 1. The terminal on the inverter circuit 5 side of the resistance element 14 is connected to the input terminal of the control microcomputer 7, and the control microcomputer 7 reads the terminal voltage of the resistance element 14 by A / D conversion by the A / D converter 12.

The control microcomputer 7 includes a first PWM circuit 15 and a second PWM circuit 16. The first PWM circuit 15 outputs a gate signal to the FET_Q1 and Q2 sides, and the second PWM circuit 16 outputs a gate signal to the FET_Q3 and Q4 sides. .. The control microcomputer 7 includes a timer 1 control unit 17 and a timer 2 control unit 18 including a timer 1 and a timer 2, respectively. Timers 1 and 2 are programmable and correspond to the first and second timers, respectively. The timer 1 is activated at the edge of the rotation position signal output by the hall sensor 12 and is used for the advance angle control of the motor 6. The timer 2 is started when the timer 1 ends, and is used for controlling the energization time of the FETs_Q1 and Q3.

As is well known, in the H-bridge type inverter circuit 5, the stator windings of the motor 6 are energized in the positive direction by turning on FETs_Q1 and Q4 at the same time, and the same winding is performed by turning on FETs_Q2 and Q3 at the same time. Energize the wire in the opposite direction.

<Explanation of assumed conventional technology>
Here, for convenience of explanation, the prior art assumed as follows will be described with reference to FIGS. 2 to 6. This can be realized by the configuration of the control microcomputer 7 described above, and as shown in FIG. 2, the control sequence is as shown in (1) to (3) below. Further, FIG. 3 is a flowchart of interrupt processing accompanying the occurrence of an edge of a rotation position signal, FIG. 4 is a flowchart of timer 1 interrupt processing, and FIG. 5 is a flowchart of timer 2 interrupt processing.

(1) At the edge of the rotation position signal output by the Hall sensor 13 (FIG. 3; start), the timer 1 is activated (S7). At this time, the timer 1 uses the edge interval time (S1) of the rotation position signal up to the previous time to set the delay time from the signal edge in order to realize the advance angle according to the input advance angle command of the motor 6. Set (S6). The "internal operation command = output on" in step S5 shown in FIG. 3 is a state in which a command for driving the motor 6 is given by the inverter circuit 5.

(2) When the timer 1 clocks the set time, a timer 1 interrupt occurs (FIG. 4; start). In the processing associated with this interrupt, if the signal edge is "rising" (S12; H), FET_Q1 is turned on (S22), and if the signal edge is "falling", (S12; L) FET_Q3 is turned on (S12; L). S16) Start energizing the motor 6. Then, the timer 2 is activated (S18). At this time, the timer 2 is set to the energization time according to the energization command (S17). Further, in order to prevent a malfunction, the timer 1 is stopped (S11) and the timer 1 interrupt flag is cleared (S11a).

At the time when the FET_Q1 is turned on, the time counting by the timer 2 in the control of the following (3) has been completed in the past, and the FET_Q4 has already been turned on accordingly, so that the current is applied in the direction from the FET_Q1 to the Q4. Similarly, when the FET_Q3 is turned on, the FET_Q2 is already turned on, so that the current is applied in the direction of the FET_Q3 → Q2.

(3) When the timer 2 clocks the set time, a timer 2 interrupt occurs (FIG. 5; start). In the processing associated with this interrupt, the positive FET_Q1 or Q3 that is turned on according to the current energization direction is turned off (S40, S36). Before turning off the FET, A / D conversion of the current detected by the resistance element 14 is started (S31). Then, in order to prevent a malfunction as in the timer 1, the timer 2 is stopped (S33).

When the FETs_Q3 and Q4 are turned off in step S36 and the FETs_Q1 and Q2 are turned off in step S40, the dead times are adjusted in steps S37 and S41, and then the FETs_Q4 and Q2 are turned on in steps S38 and S42. As a result, a reflux current flows through the inverter circuit 5, and the energizing current to the motor 6 is in a “freewheel” state (S39). Next, when an edge in the opposite direction of the rotation position signal is generated, the process proceeds to (1).

It is assumed that the following abnormalities occur with respect to this conventional technique. The conventional technique does not cope with the occurrence of an abnormality. In the case shown in FIG. 6, since the arrival of the edge of the rotation position signal is accelerated due to the sudden acceleration of the motor 6, the timers 1 and 2 are stopped, that is, before the advance delay time and the energization time elapse. The following timer 1 start condition has occurred. This makes it impossible to control as desired. Specifically, it becomes impossible to turn off FET_Q3 and turn on FET_Q4 at appropriate timings.

<Abnormal response by this embodiment>
Therefore, in the present embodiment, in order to deal with the occurrence of the above-mentioned abnormality, new steps S51 to S54 are added in the interrupt processing accompanying the edge generation shown in FIG. 7, and steps S31 to S42 in the timer 2 interrupt processing, and Steps S12 to S22 in the timer 1 interrupt process are also executed. If "YES" is determined in step S5, the Hall sensor edge counter that counts the number of edge interrupts is incremented (S51), and it is determined whether or not the value of the counter is greater than "1" (S52).

The Hall sensor edge counter is reset after the execution of step S18 in the timer 1 interrupt process shown in FIG. 8 (S55). Therefore, in the normal operation shown in FIG. 2, since the value of the counter is "1", it is determined as "NO" in step S52, and the process proceeds to step S6.

On the other hand, in the case of an abnormality shown in FIG. 6, since the hall sensor edge is generated before the timer 1 interrupt process shown in FIG. 8 is executed, the value of the counter becomes larger than “1”. Therefore, it is determined as "YES" in step S52, and steps S31 to S42 are executed. However, since the energization direction does not become the "freewheel" in this case, the branch when the "freewheel" is determined in step S35 is deleted. Then, after setting the value of the Hall sensor edge counter to "1" (S53), steps S12 to S22 are executed. After the execution of step S18, the timer 1 is stopped and the timer 1 interrupt flag is cleared, and then the process proceeds to step S6 (S54). Regarding the timer 2 interrupt processing, there is no change in the one shown in FIG.

By performing the abnormality handling process in this way, in FIG. 9, which corresponds to the case shown in FIG. 6, even if the edge of the rotation position signal arrives earlier, the timers 2 and 1 are stopped and restarted at that time. Since it is performed, the FET_Q3 is turned off and the FET_Q4 is turned on accordingly.

FIG. 10 shows each signal waveform corresponding to the case shown in FIG. With the sudden acceleration of the motor 6, the edge generation interval of the rotation position signal is shortened, and the edge interrupt is generated before the advance angle interrupt which is the timer 1 interrupt and the energization interrupt which is the timer 2 interrupt are generated. As a result, FET_Q3 is not turned off and FET_Q4 is not turned on, and a large current flows as shown in the portion surrounded by a circle in the figure. FIG. 11 shows each signal waveform corresponding to the case shown in FIG. Even if the edge generation interval of the rotation position signal is shortened, the FET_Q3 is turned off and the FET_Q4 is turned on, so that a large current does not flow as shown in FIG.

As described above, according to the present embodiment, the control microcomputer 7 includes a timer 1 control unit 17 and a timer 2 control unit 18, activates the timer 1 according to the rotor position of the motor 6, and measures the time by the timer 1. By controlling the on-timing of FET_Q1 and Q3 based on the above, the motor 6 is energized. Further, the control microcomputer 7 activates the timer 2 according to the on-timing, and controls the off-timing of the FETs_Q1 and Q3 based on the time measured by the timer 2. Then, when the rotor rotation position reaches the position where the timer 1 is activated prior to the off timing, the FET_Q1 and Q3 scheduled to be performed at the off timing and the FET_Q1 and Q3 scheduled to be performed at the on timing are turned off. It is turned on and 2 timer 2 is started.

As a result, even if the edge of the next rotation position signal occurs before the time counting by the timers 1 and 2 is completed due to the sudden acceleration of the motor 6, the energization direction to the motor 6 can be appropriately switched. This makes it possible to prevent a large current from flowing through the inverter circuit 5, and stable control can be performed.

Further, the current detection unit 22 detects the current when controlling the off timing of the FET_Q1 and Q3 based on the time measured by the timer 2, and the control microcomputer 7 detects the edge of the next rotation position signal prior to the off timing. Is generated, the current detection unit 22 detects the current, and then the FET_Q1 and Q3 are controlled to be turned off and on. As a result, even when the motor 6 suddenly accelerates, the current can be reliably detected.

(Other embodiments)
It may be applied to a three-phase inverter circuit.
The current detection may be performed only by the timer 2 interrupt processing when dealing with an abnormality.
The switching element is not limited to the MOSFET, but may be an IGBT, a bipolar transistor, or the like.
Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

In the drawing, 1 is a DC power supply, 5 is an inverter circuit, 6 is a brushless DC motor, 7 is a control microcomputer, 13 is a hall sensor, 14 is a resistance element, 17 is a timer 1 control unit, 18 is a timer 2 control unit, and Q1. ~ Q4 indicate N-channel MOSFET.

Claims (1)

A power conversion circuit that drives a motor by connecting multiple arms consisting of a series circuit of positive and negative switching elements in parallel, and
In order to control the motor, a control circuit that generates and outputs an on / off signal for each switching element constituting the power conversion circuit, and a control circuit.
It is provided with a rotation position detection unit that detects the rotation position of the motor.
The control circuit includes first and second timers.
The first timer is started according to the rotation position, and when the first timer clocks a predetermined time, the positive switching element is started to turn on to energize the motor, and the time is measured by the first timer. To start the second timer,
When the second timer clocks a predetermined time, the positive switching element is turned off and the clock by the second timer is stopped.
When the rotation position reaches the position where the first timer is activated before the positive switching element is turned off, the positive switching element that is turned on and the positive switching element that is turned on next are turned on. And a motor drive device that activates the second timer.

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