JP2006115585A - Motor driving unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor driving unit which can silence the noise during motor drive by suppressing at least either the rate of increase or the rate of decrease in a coil current. <P>SOLUTION: This motor driving unit is equipped with a driving circuit which supplies the other ends of three-phase motors coil with their one end each connected in common with drive currents to energize the above three-phase motor coils, and a drive current control circuit which varies at least either rate between the rate of the increase of the current flowing to the above motor coil of one phase and the rate of the decrease of the current flowing to the above motor coil of other phase, in a period when the current supplied from the motor coil of one phase between other two phases increases to the motor coil of specified one phase and besides the current supplied from the motor coil of the other phase between the above other two phases decreases. The above driving circuit supplies the above motor coil of one phase and the above motor coil of the other phase with drive currents geared to the output of the above drive current control circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor drive device.

  A motor (for example, a sensorless three-phase brushless DC motor) drive device is connected in series between a power supply voltage VP and a ground VSS as an output stage, for example, and one end of a coil is connected to the connection point of the power supply voltage VP side Source transistors and sink transistors on the ground VSS side for each of the three-phase coils. The other ends of the three-phase coils are connected in common. When the source transistor is turned on, a current flows in the direction of the power supply voltage VP → the source transistor → the coil connected to the source transistor. On the other hand, when the sink transistor is turned on, a current flows in the direction of the coil to which the sink transistor is connected → the sink transistor → the ground VSS. The motor driving device drives the motor by sequentially switching the coil current flowing through the three-phase coil for each predetermined electrical angle. FIG. 9 is a diagram for explaining a waveform of a current flowing in each phase of a conventional motor drive device. As shown in FIG. 9, the U-phase, V-phase, and W-phase motor coils have a high level (upper portion of the staircase waveform), a middle level (center portion of the staircase waveform), and a low level (lower portion of the staircase waveform). ) And the coil currents that are sequentially switched flow with a phase difference of 120 electrical degrees. Here, the current flowing through the coil is at a high level when the source transistor connected to one end of the coil is on, and the current flowing through the coil is at a low level when the source transistor is connected to one end of the coil. This is a period during which the sink transistor connected to is on. In addition, the current flowing through the coil is at the middle level when both the source transistor and the sink transistor connected to one end of the coil are off.

  FIG. 10 is a diagram for explaining changes in the coil current flowing in the three-phase coil in the T period shown in FIG. The current flowing through the U-phase coil 2 changes from the middle level to the high level during the T period, and the current flowing through the W-phase coil 6 changes from the high level to the middle level. The current flowing through the V-phase coil 4 remains at a low level. That is, the current flowing through the W-phase coil 6 or the U-phase coil 2 flows into the V-phase coil 4. Thus, in the case of switching the energization of the coil in the T period of FIG. 9, the path of the current flowing through the three-phase coil is switched from the broken line direction to the solid line direction in FIG. Note that this is not only when current flows from the U-phase coil 2 or W-phase coil 6 to the V-phase coil 4, but also when current flows from the U-phase coil 2 or V-phase coil 4 to the W-phase coil 6. The same can be said for the case where current flows from the phase coil 4 or the W-phase coil 6 to the U-phase coil 2.

  As one of motor driving methods, there is known PWM (Pulse Width Modulatin) control for driving a motor by intermittently supplying a driving current to a coil. In the PWM control, one of the source transistor and the sink transistor that are driven by energization at every electrical angle of 60 degrees is intermittently turned on and off at a predetermined frequency. Then, a driving current corresponding to the duty of the pulse is passed through the coil to drive the motor. Since the motor driving device using such PWM control has low power consumption, heat generation during motor driving can be suppressed.

By the way, as shown in FIG. 9, when the coil current changes stepwise when the coil energization is switched, the driving of the motor becomes unstable and noise is generated when the motor is driven. Therefore, a method has been proposed for smoothing changes in coil current (for example, currents in the U phase and W phase in the T period in FIG. 9) due to switching of energization (see, for example, Patent Document 1). A conventional motor driving device generates a rectangular signal with a gradually increasing duty and a rectangular signal with a gradually decreasing duty by, for example, count outputs of two counters that count two different frequencies, and the coil current switching timing. In addition, by performing PWM control using the rectangular signal, a change in the coil current at the time of switching the energization of the coil is smoothed.
Japanese Patent Laid-Open No. 2002-218783

  The conventional motor drive device performs the PWM control based on the rectangular signal whose duty gradually changes when switching the energization of the coil, and thereby the coil current of the phase where the coil current should be increased and the phase where the coil current should be decreased. The coil current was changed to be smooth.

  For example, during the period T in FIG. 9, the coil current of the W-phase coil 6 is gradually decreased and the coil current of the U-phase coil 2 is gradually increased.

  FIG. 11 is a diagram for explaining changes in the coil current of the U-phase coil 2 and the coil current of the W-phase coil 6 in the T period of FIG. The horizontal axis in FIG. 11 is a duty for turning on / off the source transistor or the sink transistor to which one end of the coil is connected, and the vertical axis is a current value flowing through the coil. The broken line in FIG. 11 shows the change in coil current when the rate of increase in coil current of the U-phase coil is equal to the rate of decrease in coil current of the W-phase coil. Further, the solid line in FIG. 11 shows the change in the coil current flowing in the actual coil. As shown in the figure, the amount of change when the coil current changes is greater at the rate at which the coil current decreases than at the rate at which the coil current increases. And since the rate of decrease and the rate of increase of the coil current are different, the balance of the coil current flowing through the coils of each phase is lost.

  FIG. 12 is a diagram showing a coil current waveform that flows in the coils of each phase when the coil current change during energization switching is smoothed in a conventional motor drive device. As shown in FIG. 12, since the balance of changes in the coil current is poor, the current waveform is depressed where the coil current peaks.

  As described above, in the conventional motor drive device, the rate of decrease in the coil current is different from the rate of increase in the coil current, thereby causing a depression in the peak portion of the current waveform of the coil current, which causes noise when driving the motor. was there. In addition, there is a problem in that the driving torque is reduced due to the depression and the driving efficiency is deteriorated.

  Accordingly, an object of the present invention is to provide a motor drive device that can reduce the noise during motor drive by controlling at least one of the increase rate and decrease rate of the coil current.

  The main invention for solving the above-mentioned problems is a drive in which a driving current for energizing the three-phase motor coil is switched to be supplied at predetermined electrical angles to the other end of the three-phase motor coil commonly connected at one end. The current supplied from the motor coil of one of the other two phases increases with respect to the circuit and the predetermined one-phase motor coil, and the motor of the other phase of the other two phases At least one of the rate of increase in the current flowing in the motor coil of the one phase and the rate of decrease in the current flowing in the motor coil of the other phase during the period when the current supplied from the coil decreases. A drive current control circuit that is variable, and the drive circuit supplies a drive current corresponding to an output of the drive current control circuit to the motor coil of one phase and the motor coil of the other phase. Special To.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  According to the present invention, at least one of the rate of increase of the current flowing in the phase in which the drive current increases and the rate of decrease in the current flowing in the phase in which the drive current decreases are made variable so that the sound of motor driving can be changed. Can be silenced.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

=== Configuration of Motor Drive Device ===
A motor driving apparatus according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a circuit block diagram for explaining a motor drive device according to the present invention. FIG. 2 is a waveform diagram for explaining the motor driving apparatus according to the present invention. In this embodiment, the motor is a sensorless motor of PWM control, for example, a three-phase brushless DC motor.

  The U-phase coil 2, the V-phase coil 4, and the W-phase coil 6 are motor coils, and are wound around the stator with a star connection and a phase difference of 120 electrical degrees.

  The N-channel MOSFET 8 is a source transistor for supplying a coil current from the power source VP to the U-phase coil 2, and the N-channel MOSFET 10 is a sink transistor for supplying a coil current from the U-phase coil 2 to the ground VSS. is there. The drain / source paths of the MOSFETs 8 and 10 are connected in series between the power source VP and the ground VSS, and the drain / source connection portions of the MOSFETs 8 and 10 are connected to one end of the U-phase coil 2. The N-channel MOSFET 12 is a source transistor for supplying a coil current from the power source VP to the V-phase coil 4, and the N-channel MOSFET 14 is a sink transistor for supplying a coil current from the V-phase coil 4 to the ground VSS. is there. The drain / source paths of the MOSFETs 12 and 14 are connected in series between the power supply VP and the ground VSS, and the drain / source connection portions of the MOSFETs 12 and 14 are connected to one end of the V-phase coil 4. The N-channel MOSFET 16 is a source transistor for supplying a coil current from the power source VP to the W-phase coil 6, and the N-channel MOSFET 18 is a sink transistor for supplying a coil current from the W-phase coil 6 to the ground VSS. is there. The drain / source paths of these MOSFETs 16 and 18 are connected in series between the power supply VP and the ground VSS, and the drain / source connection portions of these MOSFETs 16 and 18 are connected to one end of the W-phase coil 6. When the MOSFETs 8, 10, 12, 14, 16, and 18 are turned on / off at appropriate timing, the motor is supplied with coil currents to the U-phase coil 2, the V-phase coil 4, and the W-phase coil 6 to be predetermined. It will rotate to the direction (for example, normal rotation). As a result, coil voltages VU, VV, and VW having a phase difference of 120 electrical degrees are generated at one end of the U-phase coil 2, the V-phase coil 4, and the W-phase coil 6. Note that, as the source transistor and the sink transistor, not only MOSFETs but also bipolar transistors can be used.

  The comparator 22U is applied with the coil voltage VU applied to the + terminal and the neutral point voltage VCOM applied to the − terminal, and changes at the timing of an electrical angle of 180 degrees by comparing the coil voltage VU and the neutral point voltage VCOM. The rectangular comparison signal CPU is output. A pulse based on the kickback pulse KB is superimposed on the comparison signal CPU. In addition, the comparator 22V receives the coil voltage VV applied to the + terminal and the neutral point voltage VCOM applied to the − terminal, and compares the coil voltage VV and the neutral point voltage VCOM so that the timing of the electrical angle is 180 degrees. The rectangular comparison signal CPV that changes in the above is output. A pulse based on the kickback pulse KB is superimposed on the comparison signal CPV. Further, the comparator 22W receives the coil voltage VW at the + terminal and the neutral point voltage VCOM at the − terminal, and compares the coil voltage VW with the neutral point voltage VCOM to thereby obtain a timing of an electrical angle of 180 degrees. A rectangular comparison signal CPW that changes at A pulse based on the kickback pulse KB is superimposed on the comparison signal CPW. The comparison signals CPU, CPV, and CPW each have a phase difference of 120 electrical degrees.

  The mask circuit 26 removes (masks) noise corresponding to the kickback pulse KB from the comparison signal CPU, which is the output of the comparator 22U, based on the rectangular signal RE1, and generates and outputs a mask signal UMASK. The mask circuit 26 removes (masks) noise corresponding to the kickback pulse KB from the comparison signal CPV output from the comparator 22V based on the rectangular signal RE1, and generates and outputs a mask signal VMASK. Further, the mask circuit 26 removes (masks) noise corresponding to the kickback pulse KB from the comparison signal CPW, which is the output of the comparator 22W, based on the rectangular signal RE1, and generates and outputs a mask signal WMASK. Here, the mask signals UMASK, VMASK, and WMASK have a phase difference of an electrical angle of 120 degrees.

  Further, the mask circuit 26 outputs a signal MASK indicating a predetermined period within a half cycle of the rectangular composite signal FG to the timing synthesis circuit 50 and the timing control circuit 36.

  The combining circuit 28 combines the mask signals UMASK, VMASK, and WMASK output from the mask circuit 26, and outputs a rectangular combined signal FG (“first rectangular signal”) that changes at a timing of an electrical angle of 60 degrees.

  The multiplier circuit 30 generates a rectangular signal RE1 (“second rectangular signal”) having a higher frequency than the combined signal FG by multiplying the combined signal FG output from the combining circuit. As a result, the phase of the synthesized signal FG matches the phase of the rectangular signal RE1, and the ½ period of the synthesized signal FG matches the n period (for example, 16 periods) of the rectangular signal RE1. For example, a PLL (Phase Locked Loop) that performs analog signal processing and a DLL (Delay Locked Loop) that performs digital signal processing can be applied to the multiplication circuit 30. In the present embodiment, the multiplier circuit 30 applies the latter DLL.

  The sensorless logic circuit 40 outputs a signal for energizing the U-phase coil 2, the V-phase coil 4, and the W-phase coil 6 at an appropriate timing. That is, the sensorless logic circuit 40 considers that the sensorless motor itself cannot determine the relative position between the rotor and the stator before starting, and when the rotor is stopped, the mask signals UMASK, VMASK, and WMASK are predetermined. It operates from the initial level (for example, UMASK = “L”, VMASK = “L”, WMASK = “H”). In addition, the sensorless logic circuit 40 generates energization signals ULOGIC1 (= UMASK-VMASK), VLOGIC1 (= VMASK-WMASK), and WLOGIC1 (= WMASK-UMASK). When the U-phase coil 2, the V-phase coil 4, and the W-phase coil 6 are energized, the sensorless logic circuit 40 causes the energization signals ULOGIC 2, VLOGIC 2, WLOGIC 2 (“drive signal”) to be delayed from the energization signals ULOGIC 1, VLOGIC 1, WLOGIC 1. ) Is output.

  The frequency switching circuit 32 has a circuit that divides the frequency of the rectangular signal RE1. Then, the frequency switching circuit 32 switches and outputs any one of a plurality of signals having different frequencies obtained based on the rectangular signal RE1 to the RE1 counter 34. FIG. 5 is a diagram illustrating an example of the configuration of the frequency switching circuit 32. The frequency switching circuit 32 shown in FIG. 5 includes a D flip-flop circuit (hereinafter referred to as a D-FF circuit) 70 that divides an input rectangular signal RE1 into, for example, a half frequency, and a rectangular signal RE1 and a D-FF. A selection circuit 72 for selecting and outputting the output signal of the circuit 70 is provided. Then, the selection circuit 72 selects one of the rectangular signal RE1 and the signal obtained by dividing the frequency of the rectangular signal RE1 and outputs the selected signal to the RE1 counter 34. Instead of a single D-FF circuit, a cascade connection of a plurality of D-FF circuits may be prepared so that frequency division signals other than the 1/2 frequency division number can be switched and output. Note that the function of the frequency switching circuit 32 is not limited to switching and outputting the rectangular signal RE1 and the divided signal obtained by dividing the rectangular signal RE1 by a predetermined frequency. For example, two D-FF circuit stages having different numbers of cascade connections (frequency division numbers) may be provided, and one of the frequency division signals may be switched and output.

  The RE1 counter 34 (“first counter”) is, for example, a 4-bit counter, and counts the number of pulses of the signal output from the frequency switching circuit 32. FIG. 6 is a diagram illustrating an example of the configuration of the RE1 counter 34. The RE1 counter 34 illustrated in FIG. 6 includes D-FF circuits 60, 62, 64, and 66. Then, 4-bit signals Q1, Q2, Q3, and Q4 are output from the D-FF circuits 60, 62, 64, and 66 as count outputs. Assuming that the initial values of Q1 to Q4 are all 0, every time the rising edge of the input of the frequency switching circuit 32 is added, the Q output (Q4, Q3, Q2, Q1) becomes (0, 0, 0, 0 ), (0, 0, 0, 1), (0, 0, 1, 0)...

  The D-FF circuits 60, 62, 64, and 66 have a reset R and set S function, and are set and reset with priority by the output of the timing control circuit 36 regardless of the state of the D input and C input. Be able to. For example, since the RE1 counter 34 is 4 bits, it can count 16 but is reset by the output of the timing control circuit 36 when 14 is counted. The output of the timing control circuit 36 can be connected to the reset R or the set S. When the output indicating “L” of the timing control circuit 36 is input to the reset R of the D-FF circuits 60, 62, 64, 66, Q1, Q2, Q3, Q4 are reset to “0”. Become. On the other hand, when the output indicating “L” of the timing control circuit 36 is input to the set S of the D-FF circuits 60, 62, 64, 66, Q1, Q2, Q3, Q4 are set to “1”. Become. In the present embodiment, the output of the timing control circuit 36 is connected to the reset R of the D-FF circuits 60, 62 and 64 and to the set S of the D-FF circuit 66.

  As shown in FIG. 6, when the signal of the timing control circuit 36 is connected to the reset R of the D-FF circuits 60, 62 and 64 and the set S of the D-FF circuit 66, “L” is shown from the timing control circuit 36. When a signal is input, (Q4, Q3, Q2, Q1) = (1, 0, 0, 0). The next time the count is started, the count starts from this initial value. The connection between the reset R and set S of the D-FF circuits 60, 62, 64 and 66 and the output of the timing control circuit 36 may be set in advance, or may be switched using a switch circuit or the like (not shown). You may make it switch suitably.

  In this way, by connecting the output of the timing control circuit 36 to the reset R or set S of the D-FF circuits 60, 62, 64, 66, the initial value at which counting is started can be changed.

The timing control circuit 36 (“delay circuit”) includes, for example, a D-FF circuit (not shown), and delays the signal MASK output from the mask circuit 26 by a predetermined time in accordance with the rectangular signal RE1, thereby causing an RE1 counter. 34.
The PWM counter 42 (“second counter”) is, for example, a 4-bit counter having a D-FF circuit (not shown), and the number of pulses of the system clock MCLK (“third rectangular signal”) is set to, for example, 0 to 15 Repeat until counting up.
The 1 / N frequency dividing circuit 44 outputs a PWM signal obtained by frequency dividing the system clock MCLK to 1/16, for example, to the PWM synthesizing circuit 54.

  The count output of the PWM counter 42 is input to the + (non-inverted input) terminal of the comparator 46, and the count output of the RE 1 counter 34 is input to the − (inverted input) terminal of the comparator 46. The comparator 46 outputs a signal indicating “L” when the count value of the RE1 counter 34 is larger than the count value of the PWM counter 42, and when the count value of the RE1 counter 34 is smaller than the count value of the PWM counter 42, A signal indicating “H” is output.

  The count output of the RE1 counter 34 is input to the + (non-inverting input) terminal of the comparator 48, and the count output of the PWM counter 42 is input to the − (inverting input) terminal of the comparator 48. The comparator 48 outputs a signal indicating “H” when the count value of the RE1 counter 34 is larger than the count value of the PWM counter 42, and when the count value of the RE1 counter 34 is smaller than the count value of the PWM counter 42, A signal indicating “L” is output.

  Based on the signal MASK and the energization signals ULOGIC2, VLOGIC2, and WLOGIC2, the timing synthesis circuit 50 ("switching selection circuit") converts the switching circuits 52U, 52V, and 52W to the signal path on the sensorless logic circuit 40 side, and the comparators 46 and 48. The signal path on the side is selectively switched.

  The switching circuit 52U switches between the energization signal ULOGIC2 and the output signals (“comparison signals”) of the comparators 46 and 48 and outputs them to the PWM synthesis circuit 54. The switching circuit 52V switches between the energization signal VLOGIC2 and the output signals of the comparators 46 and 48 and outputs the switched signal to the PWM synthesis circuit 54. Further, the switching circuit 52W switches between the energization signal WLOGIC2 and the output signals of the comparators 46 and 48 and outputs the switched signal to the PWM synthesis circuit 54. When the coil current increases, one of the comparators 46 and 48 is selected, and when the coil current decreases, the other of the comparators 46 and 48 is selected.

  When the sensorless logic circuit 40 side is selected in the switching circuits 52U, 52V, and 52W, the PWM synthesis circuit 54 is based on the energization signals ULOGIC2, VLOGIC2, and WLOGIC2 output from the sensorless logic circuit 40, and the MOSFET 8 based on the PWM signal. 10, 12, 14, 16, 18 outputs a signal for PWM control. Further, the PWM synthesis circuit 54, when the comparators 46, 48 are selected in the switching circuits 52U, 52V, 52W, the MOSFETs 8, 10, 12, 14, 16, 18 outputs a signal for PWM control.

  Based on the output of the PWM synthesizing circuit 54, a drive current for energizing the U-phase coil 2, the V-phase coil 4, and the W-phase coil 6 is generated, and the motor is driven by this drive current.

  The mask circuit 26, the sensorless logic circuit 40, and the PWM synthesis circuit 54 constitute a drive circuit. Further, the frequency switching circuit 32, the RE1 counter, the timing control circuit 36, the PWM counter 42, the comparators 46 and 48, the switching circuits 52U, 52V, and 52W, and the timing synthesis circuit 50 constitute a drive current control circuit.

=== Comparator 46, 48 ===
FIG. 3 is a diagram for explaining the outputs of the comparators 46 and 48. The comparators 46 and 48 compare the count output of the RE1 counter 34 with the count output of the PWM counter 42. The PWM counter 42 counts the number of pulses of the system clock MCLK, and the RE1 counter 34 counts the number of pulses of the signal output from the frequency switching circuit 32.

  In this embodiment, both the PWM counter 42 and the RE1 counter 34 are 4 bits. The PWM counter 42 is reset after counting 16 pulses of the system clock MCLK, and starts counting again. The RE1 counter is reset after counting the number of pulses of the signal output from the frequency switching circuit 32 to a predetermined value, and starts counting again. Here, the rectangular signal RE1 is a signal whose cycle changes according to the rotation speed of the motor, and the system clock MCLK is a signal having a constant cycle and a cycle shorter than that of the rectangular signal RE1. Therefore, the count outputs of the PWM counter 42 and the RE1 counter 34 have a relationship as shown in FIG. 3, for example. By comparing the count outputs of the two counters, the comparator 48 outputs a rectangular signal whose duty gradually increases, and the comparator 46 outputs a signal whose duty gradually decreases.

  When the energization of the motor coil is switched, if the motor coil is energized by performing the PWM control based on the signal whose duty gradually changes, the change of the coil current can be smoothed.

=== Operation of Motor Drive Device ===
The operation of the motor drive apparatus of the present invention will be described with reference to FIGS.

  FIG. 4 is a time chart for explaining the operation of the motor drive device of the present invention. In addition, U, V, and W of FIG. 4 have shown the coil current which flows into each coil of U phase, V phase, and W phase.

  The synthesizing circuit 28 synthesizes the mask signals UMASK, VMASK, and WMASK to generate a synthesized signal FG, which is output to the multiplier circuit 30. The rising and falling changes of the composite signal FG coincide with the zero crossing of the coil voltages VU, VV, and VW.

  The multiplication circuit 30 multiplies the combined signal FG into a rectangular signal RE1 having a period that is an integral multiple of the combined signal FG, for example, 16 times. That is, a rectangular signal RE1 having 16 periods (16 pulses) is generated in a half period between the rising edge and the falling edge of the composite signal FG. In the multiplier circuit 30, the immediately preceding 1/2 cycle is actually reflected in the operation of the next 1/2 cycle. Specifically, when the half cycle of the combined signal FG in the period TA is “b”, the multiplier circuit 30 operates to generate 16 pulses within the “b” period in the next period TB.

  The rectangular signal RE1 is input to the mask circuit 26, and is used to remove (mask) noise corresponding to the kickback pulse KB from the comparison signals CPU, CPV, CPW. In the mask circuit 26, mask signals UMASK, VMASK, and WMASK are generated by removing the noise corresponding to the kickback pulse KB from the comparison signals CPU, CPV, and CPW. The mask circuit 26 generates a signal MASK based on the rectangular signal RE1. The signal MASK is a signal indicating a period (for example, 14 pulses of the rectangular signal RE1) within a half cycle of the combined signal FG. For example, the signal MASK is a signal indicating “H” in the TA ′ period corresponding to 14 pulses of the rectangular signal RE1 in the TA period of the composite signal FG shown in FIG. 4 and “L” in one pulse before and after the TA ′ period. .

  The timing synthesis circuit 50 switches the phase switching circuits 52U, 52V, 52W in which the coil current changes during the period when the signal MASK is “H” from the sensorless logic circuit 40 side to the comparators 46, 48 side. For example, in the TA ′ period, the coil current flowing in the U phase changes from the middle level to the high level, and the coil current flowing in the W phase changes from the high level to the middle level. Therefore, the timing synthesis circuit 50 compares the switching circuits 52U and 52W with the comparators, respectively. Switch to 48, 46 side. Note that one of the comparator 48 and the comparator 46 is selected depending on whether the coil current increases or decreases. Then, for example, by performing PWM control based on the output signals of the comparators 46 and 48 in the TA ′ period, the U-phase coil current is gradually increased as indicated by a one-dot chain line, and the W-phase coil current is increased by a one-dot chain line. It can be gradually reduced as shown. Similarly, in the TB ′ period in the TB period, the V-phase switching circuit 52V and the W-phase switching circuit 52W are on the comparators 48 and 46 side, respectively, and the U-phase switching circuit 52U is on the sensorless logic circuit 40 side. Note that, during the period in which the signal MASK indicates “L”, the switching circuits 52U, 52V, and 52W are all switched to the sensorless logic circuit 40 side in order to detect a zero cross.

  In practice, the rate at which the coil current flowing through the coil increases is not equal to the rate at which it decreases. Therefore, in the present invention, the rate at which the coil current increases or the rate at which the coil current decreases is adjusted by the frequency switching circuit 32, the RE1 counter 34, and the timing control circuit 36.

  FIG. 7 is a diagram for explaining a coil current waveform using the motor drive device of the present invention. In the present embodiment, a case where adjustment is made for the U phase in which the coil current increases will be described.

As described above, in the switching of energization of the motor coil, the rate of decrease of the phase current in which the coil current should be decreased is larger than the rate of increase in the phase current in which the coil current should be increased. That is, in the period TA ′ in FIG. 4, the U-phase coil current and the W-phase coil current have a relationship as indicated by the broken line in FIG.
Therefore, for example, if the frequency switching circuit 32 selects and outputs signals having different frequencies, the counting speed of the RE1 counter can be changed. That is, since the frequency of the output signals of the comparators 46 and 48 can be changed, the slope of the coil current waveform (the slope of the portion C in FIG. 7) can be adjusted.

Further, by changing the output of the timing control circuit 36 and the connection of the reset R and set S of the RE1 counter 34, it is possible to adjust the initial value of the count of the RE1 counter 34 (part A in FIG. 7). is there.
Further, it is possible to adjust the count start position (part B in FIG. 7) by delaying the timing at which the RE1 counter starts counting by the timing control circuit 36.

  The adjustment of the coil current may be performed in one of the phase in which the coil current should be increased and the phase in which the coil current should be decreased in the switching of the coil current. It may be performed in both phases where the current decreases.

  FIG. 8 shows the waveform of the coil current flowing in each phase of the motor drive device of the present invention. In the motor drive device of the present invention, the depression portion of the coil current waveform generated in the conventional motor drive device is reduced by adjusting at least one of the increase rate of the coil current and the decrease rate of the coil current. A shape close to a sine wave as shown in FIG. And since a coil current waveform can be made into the shape close | similar to a sine wave, the sound of a motor drive can be silenced and efficiency can be improved further.

  As described above, the motor driving device according to the present invention includes the ratio of the current increase in the phase in which the coil current should be increased in switching the energization of the U-phase coil 2, the V-phase coil 4, and the W-phase coil 6, and the coil current. By making at least one of the current reduction ratios of the phases to be reduced variable, the coil current of the motor can be brought close to a sine wave, and the noise during motor driving can be silenced. Furthermore, the drive efficiency of the motor drive device can be improved.

  Further, according to switching of energization of the coil current of each phase during the period when the signal MASK is “H”, the output signal of the sensorless logic circuit 40 and the output signal of the comparators 46 and 48 are appropriately switched to energize the three-phase motor coil. can do.

  Further, by using two comparators 46 and 48 having opposite input polarities, it is possible to simultaneously set the duty when the coil current increases and when the coil current decreases.

  Since the switching circuits 52U, 52V, and 52W are all switched to the sensorless logic circuit 40 side at the change points of the rising and falling of the FG signal in 1/2 cycle, the zero cross can be detected.

  By switching and outputting the rectangular signal RE1 or the signal obtained by dividing the rectangular signal RE1 by the frequency switching circuit 32, the rate of change of the coil current can be changed. In addition, by setting an offset value for resetting the RE1 counter 34 and delaying the count start of the counter after the mask is closed by the timing control circuit 36, the starting point of the coil current change can be changed, The coil current can be adjusted.

  As described above, the present embodiment has been specifically described based on the embodiment. However, the present embodiment is not limited to this, and various modifications can be made without departing from the scope of the present embodiment.

1 is a circuit block diagram of a sensorless motor driving apparatus according to the present invention. It is an operation | movement waveform diagram of the drive device of the sensorless motor concerning this invention. It is a figure for demonstrating the output of the comparators 46 and 48. FIG. It is a time chart for demonstrating operation | movement of the motor drive device of this invention. It is a figure which shows an example of a structure of a frequency switching circuit. It is a figure which shows an example of a structure of RE1 counter. It is a figure for demonstrating the coil current waveform in the motor drive device concerning this invention. It is a coil current waveform which flows into each phase in the motor drive device of the present invention. It is a figure for demonstrating the current waveform which flows into each phase of the conventional motor drive device. It is a figure for demonstrating the change of the electric current which flows into three phases. It is a figure for demonstrating the change of the coil current of U phase and the coil current of W phase. It is a figure which shows the coil current waveform which flows into each phase, when the change of a coil current is made smooth by the conventional motor drive device.

Explanation of symbols

2 U-phase coil 4 V-phase coil 6 W-phase coil 8, 10, 12, 14, 16, 18 MOSFET
22U, 22V, 22W Comparator 26 Mask circuit 28 Synthesis circuit 30 Multiplication circuit 32 Frequency switching circuit 34 RE1 counter 36 Timing control circuit
40 sensorless logic circuit 42 PWM counter 44 1 / N frequency dividing circuit 46, 48 comparator 50 timing synthesis circuit 52U, 52V, 52W switching circuit 54 PWM synthesis circuit

Claims (4)

A drive circuit for switching and supplying a drive current for energizing the three-phase motor coil to the other end of the three-phase motor coil having one end connected in common;
The current supplied from the motor coil of one of the other two phases increases with respect to the predetermined one-phase motor coil, and is supplied from the motor coil of the other of the other two phases. The ratio of the increase in the current flowing in the motor coil of the one phase and the ratio of the decrease in the current flowing in the motor coil of the other phase during the period when the current to be reduced decreases. A drive current control circuit;
With
The drive circuit is
A motor driving device that supplies a driving current according to an output of the driving current control circuit to the motor coil of one phase and the motor coil of the other phase. The drive current control circuit includes:
The number of pulses of the second rectangular signal obtained by multiplying the first rectangular signal whose cycle changes according to the rotation speed of the motor is repeated from an initial value to a predetermined value within a predetermined period within a half cycle of the first rectangular signal. A first counter for counting;
A second counter that repeatedly counts the number of pulses of the third rectangular signal having a shorter cycle than the second rectangular signal from an initial value to a predetermined value;
A comparison circuit for comparing the count output of the first counter and the count output of the second counter;
Each of the motor coils to switch between a signal path for obtaining the drive current based on a drive signal generated by the drive circuit and a signal path for obtaining the drive current based on a comparison signal output from the comparison circuit. A switching circuit provided for the phase;
A switching selection circuit for selectively switching the switching circuit;
With
The switching selection circuit includes:
In a predetermined period within a half cycle of the first rectangular signal,
Switching the switching circuit corresponding to the predetermined one-phase motor coil to the drive circuit side;
Switching the switching circuit corresponding to the one-phase motor coil and the other-phase motor coil to the comparison circuit side;
The motor driving apparatus according to claim 1. The comparison circuit is
One level is output when the count output of the first counter is greater than the count output of the second counter, and the other level when the count output of the first counter is smaller than the count output of the second counter A first comparator that outputs
When the count output of the first counter is larger than the count output of the second counter, the other level is output. When the count output of the first counter is smaller than the count output of the second counter, one level is output. A second comparator that outputs
With
The switching selection circuit includes:
The output of the first comparator is selected as the comparison signal for the motor coil of the one phase, and the output of the second comparator is selected as the comparison signal for the motor coil of the other phase. The motor drive device according to claim 2. The switching selection circuit includes:
4. The motor driving apparatus according to claim 2, wherein all of the switching circuits are switched to the driving circuit side outside the predetermined period of the first rectangular signal. 5.

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