JP2005051870A - Lock protective circuit of motor and integrated circuit, and method for protecting lock of motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the lock protective circuit of a motor which can reduce a circuit area and cost since an external capacitor is not used and to provide an integrated circuit. <P>SOLUTION: The lock protective circuit includes a starting pulse output circuit for outputting a starting pulse in a locked state in which the motor with current supplied to a drive coil is stopped, a starting pulse measuring means for counting the starting pulses, a lock state detecting means for detecting the lock state in response to the counted result, and a drive coil current interruption control means for performing a control for cutting off the current to the drive coil when the lock state is detected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor lock protection circuit, an integrated circuit, and a motor lock protection method.
[0002]
[Prior art]
For example, Japanese Patent Laid-Open No. 2001-57793 (Patent Document 1) discloses a lock protection circuit that cuts off a current of a motor driving coil when a motor used for a cooling fan or the like falls into a locked state (rotation stopped state). ing. In this lock protection circuit, as shown in FIG. 1 of the publication, an external capacitor is used. That is, when the lock state is entered, when the external capacitor is charged and its terminal voltage reaches a predetermined value, it is determined that the lock state is reached, and the lock protection operation is executed.
[0003]
As this lock protection operation, there is a case where not only the motor drive coil current is cut off, but also a restart operation after the current cut-off is performed. In other words, the time from when the current is cut off until restarting (hereinafter simply referred to as “off period”) is also set by the discharge time according to the time constant of the external capacitor.
[0004]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-57793
[Problems to be solved by the invention]
In the conventional technology described above, it is necessary to ensure a long off period, particularly when the motor is used as a cooling fan or the like. For this reason, a capacitor having a relatively large capacity has to be externally attached, and there has been a problem that the substrate area becomes large and the cost cannot be avoided. Further, the off period varies due to variations in the capacitance of the capacitor, the charging current, etc., and there is a disadvantage that the off period cannot be set with high accuracy.
[0006]
[Means for Solving the Problems]
In the main invention according to the present invention, there is provided a lock protection circuit having a start pulse output circuit that outputs a start pulse in a locked state in which a motor to which a current is supplied to a drive coil is stopped, and the start pulse for counting the start pulse Measuring means; lock state detection means for detecting the lock state according to the counting result; and drive coil current cutoff for executing control to cut off the current to the drive coil when the lock state is detected Control means.
[0007]
Therefore, when detecting the locked state of the motor, it is detected by measuring the start pulse without depending on the charge / discharge operation of the external capacitor. Since no external capacitor is used, the circuit area can be reduced and the cost can be reduced.
[0008]
Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
=== Overall Configuration of Motor Drive Circuit ===
The overall configuration of the motor drive circuit according to the present embodiment will be described with reference to the circuit block diagram of FIG. This drive circuit is implemented in the form of an integrated circuit. In the present embodiment, the motor is a sensorless motor that does not have an element (for example, a hall element) for detecting the relative position of the rotor and the stator. As shown in FIG. 1, the U-phase drive coil 2, the V-phase drive coil 4, and the W-phase drive coil 6 are star-connected, have an electrical angle of 120 degrees, and are fixed to a sensorless motor.
[0010]
In order to energize (supply current) the U-phase drive coil 2, the N-channel MOSFET 8 is a source-side transistor, and the N-channel MOSFET 10 is a sink-side transistor. The drain sources of the N-channel MOSFETs 8 and 10 are connected in series between the power source Vp and the ground, and the drain-source connection is connected to one end of the U-phase drive coil 2.
[0011]
Similarly, the N-channel MOSFET 12 is a source-side transistor and the N-channel MOSFET 14 is a sink-side transistor to energize the V-phase drive coil 4. The drain sources of the N-channel MOSFETs 12 and 14 are connected in series between the power source Vp and the ground, and the drain-source connection is connected to one end of the V-phase drive coil 4.
[0012]
Similarly, since the W-phase drive coil 6 is energized, the N-channel MOSFET 16 is a source-side transistor, and the N-channel MOSFET 18 is a sink-side transistor. The drain sources of the N-channel MOSFETs 16 and 18 are connected in series between the power supply Vp and the ground, and the drain-source connection portion is connected to one end of the W-phase drive coil 6.
[0013]
Then, by turning these N-channel MOSFETs 8, 10, 12, 14, 16, and 18 on and off at appropriate timing, a drive current flows through the U-phase drive coil 2, the V-phase drive coil 4, and the W-phase drive coil 6, The rotor of the sensorless motor rotates, for example, in the positive direction. In this rotational operation, driving voltages Vu, Vv, Vw having a phase difference of 120 degrees appear at one end of the U-phase driving coil 2, V-phase driving coil 4, and W-phase driving coil 6, and U-phase driving. A neutral point voltage Vcom appears at a common connection portion of the coil 2, the V-phase drive coil 4, and the W-phase drive coil 6. As the driving transistor, a bipolar transistor can be used instead of the MOSFET.
[0014]
The switching circuit 20 has a U terminal, a V terminal, and a W terminal, and drive voltages Vu, Vv, and Vw are supplied to the U terminal, the V terminal, and the W terminal. The switching circuit 20 switches the U terminal, the V terminal, and the W terminal at a timing of an electrical angle of 60 degrees, and outputs any one of the drive voltages Vu, Vv, and Vw. The switching circuit 20 repeatedly switches in the order of the U terminal, the W terminal, and the V terminal when the sensorless motor rotates normally. On the other hand, when the sensorless motor rotates in the reverse direction, the switching circuit 20 repeats in the order of the U terminal, V terminal, and W terminal. Switch over.
[0015]
The comparator 22 compares any one of the drive voltages Vu, Vv, and Vw (+ terminal) obtained from the switching circuit 20 with the neutral point voltage Vcom (−terminal). As a result, the comparator 22 outputs a rectangular comparison signal CP that changes at a timing of an electrical angle of 60 degrees.
[0016]
The distribution circuit 32 has a U terminal, a V terminal, and a W terminal, and switches the U terminal, the V terminal, and the W terminal at the same timing as the switching circuit 20 and outputs a comparison signal CP. The distribution circuit 32 repeatedly switches in the order of the U terminal, the W terminal, and the V terminal when the sensorless motor rotates in the forward direction. On the other hand, when the sensorless motor rotates in the reverse direction, the order of the U terminal, the V terminal, and the W terminal. To switch repeatedly.
[0017]
From the U terminal of the distribution circuit 32, only a fragmentary signal with an electrical angle of 60 degrees is obtained, and a signal with an electrical angle of 120 degrees for energizing the U-phase drive coil 2 is missing. Similarly, only a fragmentary signal with an electrical angle of 60 degrees can be obtained from the V terminal of the distribution circuit 32, and a signal with an electrical angle of 120 degrees for energizing the V-phase drive coil 4 is missing. . Furthermore, similarly, only a fragmentary signal having an electrical angle of 60 degrees is obtained from the W terminal of the distribution circuit 32, and a signal having an electrical angle of 120 degrees for energizing the W-phase drive coil 6 is lost. Yes.
[0018]
The mask circuit 34 removes noise corresponding to the kickback pulse from the signal having an electrical angle of 60 degrees obtained from the U terminal of the distribution circuit 32. A continuous mask signal Umask for driving the U-phase drive coil 2 is generated and output using the signal having the electrical angle of 60 degrees. Similarly, noise corresponding to the kickback pulse is removed from the signal having an electrical angle of 60 degrees obtained from the V terminal of the distribution circuit 34. A continuous mask signal Vmask for driving the V-phase drive coil 4 is generated and output using the signal having the electrical angle of 60 degrees. Similarly, noise corresponding to the kickback pulse is removed from the signal having an electrical angle of 60 degrees obtained from the W terminal of the distribution circuit 34. A continuous mask signal Wmask for driving the W-phase drive coil 6 is generated and output using the signal having the electrical angle of 60 degrees. Note that the mask signals Umask, Vmask, and Wmask have a phase difference of an electrical angle of 120 degrees.
[0019]
The combining circuit 38 combines the mask signals Umask, Vmask, and Wmask obtained from the mask circuit 34, and outputs a rectangular combined signal FG that changes at a timing of an electrical angle of 60 degrees. That is, the composite signal FG is obtained by removing the superposition pulse based on the kickback pulse from the comparison signal CP.
[0020]
The phase comparator 40, filter 42, buffer 44, voltage controlled oscillator 46, and 1 / N frequency divider 48 constitute a PLL circuit. The phase comparator 40 outputs a voltage signal having a pulse width corresponding to the phase difference between the combined signal FG obtained from the combining circuit 38 and the divided signal DV obtained from the 1 / N frequency divider 48. For example, the phase comparator 40 outputs a positive voltage signal in a state where the phase of the synthesized signal FG is ahead of the phase of the divided signal DV, while the phase of the synthesized signal FG is delayed from the phase of the divided signal DV. In this state, a negative voltage signal is output. This voltage signal is integrated by the filter 42 and then supplied to the voltage controlled oscillator 46 via the buffer 44. The voltage controlled oscillator 46 outputs a frequency signal VCO corresponding to the voltage signal obtained from the buffer 44 and supplies it to the 1 / N frequency divider 48. By repeating this operation, the phase of the synthesized signal FG coincides with the phase of the divided signal DV.
[0021]
The sensorless logic circuit 52 outputs a signal for energizing the U-phase drive coil 2, the V-phase drive coil 4, and the W-phase drive coil 6 at an appropriate timing. The sensorless logic circuit 52 operates from a predetermined initial level of the mask signals Umask, Vmask, and Wmask in consideration that the sensorless motor itself cannot estimate the relative position between the rotor and the stator in the initial state. The sensorless logic circuit 52 outputs a signal for selecting the U terminal of the switching signal 20 and the 32 U terminals of the distribution signal during the period when the energization signal Ulogic1 is at the “M” level. Similarly, the sensorless logic circuit 52 outputs a signal for selecting the V terminal of the switching signal 20 and the 32 V terminals of the distribution signal while the energization signal Vlogic1 is at the “M” level. Similarly, the sensorless logic circuit 52 outputs a signal for selecting the W terminal of the switching signal 20 and the 32 W terminals of the distribution signal while the energization signal Wlogic1 is at the “M” level. Then, the sensorless logic circuit 52 creates and outputs energization signals Ulogic2, Vlogic2, and Wlogic2 that are delayed with respect to the energization signals Ulogic1, Vlogic1, and Wlogic1.
[0022]
The forward / reverse circuit 54 generates and outputs a drive signal for executing a brake of the sensorless motor and a reverse operation in the rotation direction. That is, the forward / reverse circuit 54 outputs a reverse torque brake drive signal based on a brake instruction signal supplied from an external device or the like.
[0023]
The start counter 58 (start pulse output circuit) sets the timing of the electrical angle of 60 degrees of the composite signal in a state where the predetermined speed is not reached, such as when the sensorless motor is locked (rotation of the rotor is stopped). Counting is performed as a reference, and when a predetermined value is counted, a start pulse is generated and output. Then, this start pulse is received by a pulse counter (start pulse measuring means) 60. The pulse counter 60 counts the start pulse and outputs the result to the sensorless logic circuit 52. This sensorless logic circuit (locked state detecting means) 52 detects that it is in a locked state according to the received counting result.
[0024]
=== Lock protection ===
The detection and protection mechanism and operation in a state where the desired rotational speed is not reached, such as when the sensorless motor described in the section of the prior art falls into a locked state (rotation stop state of the rotor) is shown in the flowchart of FIG. A description will be given with reference to the circuit block diagram of FIG.
[0025]
First, as described above, when the rotor is stopped, the start counter 58 generates and outputs a start pulse (S100: YES → S200). The start pulse is counted by the pulse counter 60 (S300). If the number n of activation pulses (n is a natural number) is less than 10, for example, it is assumed that the state is in an unlocked (unlocked) state, and the pulse counter 60 continues counting the activation pulses (S400: YES → S300). Conversely, when the number n of start pulses exceeds 10 (S400: NO), it is determined that the sensorless logic circuit (drive coil current cutoff control means) 52 is in the locked state, and the U-phase drive coil 2, V Control of lock protection such as cutting off current to the phase drive coil 4 and the W-phase drive coil 6 is executed. That is, the sensorless logic circuit 52 stops outputting signals for energizing the drive coils 2, 4, and 6. As will be described later, by setting the configuration of the pulse counter 60, the time (number of activation pulses n = 10) serving as an index for determining the lock state can be changed as appropriate.
[0026]
After executing the lock protection control, after a predetermined time has elapsed, that is, when the number n of activation pulses reaches 100 (S600: YES), the sensorless logic circuit 52 (reactivation means) Control that temporarily estimates that the unlocked state has been reached, and that restarts the supply of current to each of the drive coils 2, 4, 6, assuming that the sensorless motor that may have been heated in the locked state has cooled sufficiently Execute. That is, the sensorless logic circuit 52 resumes outputting signals for energizing the coils 2, 4, and 6, and returns to the process of S 100 described above. Specifically, the sensorless logic circuit 52 changes the level of the mask signals Umask, Vmask, and Wmask to the next electrical angle of 60 degrees. As a result, the sensorless motor is restarted. As will be described later, by setting the configuration of the pulse counter 60, a desired lock protection time for shutting off the current to each of the coils 2, 4 and 6 (off time until restart, number of start pulses n = 100) can be changed as appropriate.
[0027]
=== Configuration Example of Pulse Counter ===
As an example, the configuration of the pulse counter 60 described above will be briefly described with reference to the block diagram of FIG. For convenience, a part of the circuit configuration of the sensorless logic circuit 52 (inverter, AND circuit, constant current circuit, pull-up resistor R, and NPN type bipolar transistor) cooperating with the pulse counter 60 surrounded by a wavy line is also shown in FIG. Are listed. As shown in the figure, the pulse counter 60 is configured by connecting a plurality of D-type flip-flops to which start pulses and reset signals are input. That is, D-type flip-flops in which the D terminal and the inverted Q terminal are short-circuited are cascaded and operate as a frequency divider circuit. In setting the time (number of activation pulses n = 10) as an index for determining the lock state described above with reference to FIG. 2, J D-type flip-flops of FIG. 3 (J is, for example, “8” or the like). Prepared). In setting a desired lock protection time (number of activation pulses n = 100) for cutting off the current to each of the coils 2, 4 and 6, (J + K) D-type flip-flops (K + For example, a natural number such as “64”).
[0028]
As shown in FIG. 3, the signal A input to the inverter, the two signals B and C input to the AND circuit, and the output signal D of the AND circuit are as shown in the chart showing the logical values in FIG. It becomes a value (“H” or “L”) corresponding to the reset state, the lock state, and the start (restart). In accordance with the values of these signals A to D, a signal for controlling current supply to each of the coils 2, 4 and 6 is supplied from the collector of the NPN transistor.
[0029]
As mentioned above, although embodiment of this invention was described concretely based on the embodiment, it is not limited to this, It can change variously in the range which does not deviate from the summary.
[0030]
This embodiment has the following effects.
In detecting the lock state of the motor, it is detected by measuring the start pulse without depending on the charge / discharge operation of the external capacitor. Therefore, no external capacitor is required.
[0031]
Measure the start pulse without using an external capacitor. Therefore, the off time until the restart can be determined with a predetermined value for the measurement result of the start pulse. Therefore, a more accurate off time can be secured as compared with the case where the off time until the restart is determined by the discharge time as an analog value of the external capacitor.
[0032]
The off time until restart can be set with a predetermined value for the measurement result of the start pulse. Therefore, it is easier to change the setting of the off time than when an external capacitor is used.
[0033]
【The invention's effect】
Since no external capacitor is used, the circuit area can be reduced and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram showing a motor drive circuit according to an embodiment of the present invention.
FIG. 2 is a flowchart showing an operation of lock protection according to an embodiment of the present invention.
FIG. 3 is a circuit block diagram showing a configuration example of a pulse counter according to an embodiment of the present invention.
FIG. 4 is a chart showing logic values of a circuit that realizes a lock protection operation according to an embodiment of the present invention.
[Explanation of symbols]
2 U-phase drive coil 4 V-phase drive coil 6 W-phase drive coil 52 Sensorless logic circuit 58 Start-up counter 60 Pulse counter

Claims (5)

A lock protection circuit having a start pulse output circuit that outputs a start pulse in a locked state in which a motor to which current is supplied to a drive coil is stopped,
Start pulse measuring means for counting the start pulse;
Lock state detection means for detecting the lock state according to the result of the counting;
Drive coil current cutoff control means for executing control to cut off the current to the drive coil when the locked state is detected;
A motor lock protection circuit comprising: After executing the control for cutting off the current to the drive coil, when the result of the counting by the start pulse measuring means reaches a predetermined value, the control for restarting the supply of the current to the drive coil is executed. The motor lock protection circuit according to claim 1, further comprising a starting unit. 3. The motor lock protection circuit according to claim 2, wherein the predetermined value is set according to a desired time for cutting off the current to the drive coil. An integrated circuit comprising a lock protection circuit according to any one of claims 1 to 3, wherein the lock protection circuit is integrated to control a current supply to a drive coil of a motor. Count the start pulse output in the locked state where the motor that is supplying current to the drive coil is stopped,
Detecting the locked state according to the result of the counting;
When the locked state is detected, control for cutting off the current to the drive coil is executed.
A method for protecting the lock of a motor.

Images