JP2005237050A - Method of controlling single-phase motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling a single-phase motor, where it is easy to measure a current value in a phase in the vicinity of a phase where a voltage waveform crosses zero. <P>SOLUTION: In usual control, PWM control is executed, using only the voltage pulse of either a positive voltage pulse or a negative voltage pulse. On the other hand, specified control is performed in the vicinity of the phase where a voltage waveform crosses zero. In this specified control, the PWM control is executed, using the two voltage pulses of a positive voltage pulse and a negative voltage pulse. In this specified control, the width of the voltage pulse of either the positive voltage pulse or the negative voltage pulse is larger than the minimum width that an ammeter can measure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for controlling a single-phase motor.

  Conventionally, PWM (Pulse Width Modulation) control has been used as a control method for a single-phase motor. An inverter circuit is used for this PWM control. The inverter circuit forms a plurality of voltage pulses constituting the U phase and a plurality of voltage pulses constituting the V phase having a waveform that is 180 ° out of phase with the U phase waveform. The AC voltage waveform is formed by superimposing the U-phase voltage pulse and the V-phase voltage pulse. At this time, since a positive DC voltage and a negative DC voltage are applied within the PWM cycle (carrier cycle), the current ripple is large. Therefore, high frequency loss occurs.

  A plurality of current pulses flowing in each of the U phase and the V phase are formed by repeating ON / OFF operations of the switching elements. Therefore, a switching loss occurs in the inverter circuit.

As a technique for reducing the above-described switching loss and high-frequency loss, a technique for preventing the ON / OFF operation of a pair of switching elements in any one of the U phase and the V phase is conceivable. That is, the method uses an AC voltage using only a voltage pulse formed by an ON / OFF operation of a pair of switching elements in the other phase while the pair of switching elements in one phase is always turned on or off. This is a method of forming a half wavelength of a waveform. At this time, the width of the voltage pulse formed by the ON / OFF operation of only the pair of switching elements in the other phase is the theoretical voltage pulse obtained by superimposing the U-phase voltage pulse and the V-phase voltage pulse. It is set to be the same as the width of.
JP-A-6-153526 Proceedings of the 1984 National Congress of the Institute of Electrical Engineers of Japan [6], April 1983, No. 498

  When the above-described method is used, the duty ratio of the voltage pulse formed by the ON / OFF operation of the pair of switching elements in the other phase becomes extremely small in the phase near the phase where the voltage waveform crosses zero. This makes it difficult to measure the current value.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for controlling a single-phase motor that can easily measure a current value of a phase in the vicinity of a phase in which a voltage waveform zero-crosses. .

  The system used in the method for controlling a single-phase motor of the present invention includes a single-phase motor, a drive circuit that applies an AC voltage to the single-phase motor, and a control device that controls the drive circuit. The drive circuit includes first and second switching elements connected in series with each other and third and fourth switching elements connected in series with each other. The third and fourth switching elements are connected in parallel to the first and second switching elements in this order. One terminal of the single-phase motor is connected to a node between the first switching element and the second switching element. The other terminal of the single-phase motor is connected to a node between the third switching element and the fourth switching element.

  The control device can execute a first control and a third control described below.

  In the first control, the first switching element is turned on, the second switching element is turned off, the third switching element is turned off, and the fourth switching element is turned on.

  In the second control, the first switching element is turned off, the second switching element is turned on, the third switching element is turned on, and the fourth switching element is turned off.

  In the single-phase motor control method of the present invention, basically, PWM control is executed by adjusting the voltage pulse width in the first control and the voltage pulse width in the second control as control in the normal section. Thereby, an alternating voltage is applied to the single-phase motor.

  In the normal section, the width of one voltage pulse constituting the waveform of the AC voltage applied to the single-phase motor is larger than the reference width. Further, for each normal section, the first normal control in which only the first control is repeated a plurality of times and the second normal control in which only the second control is repeated a plurality of times are alternately performed.

  Further, in a specific section other than the normal section, PWM control is executed using both the voltage pulse generated by the execution of the first control and the voltage pulse generated by the execution of the second control.

  The width of the voltage pulse formed by the execution of the first control in the specific section before and after the first normal control and the width of the voltage pulse formed by the second control in the specific section before and after the second normal control, respectively. However, it is larger than the minimum pulse width at which the control device can detect the current value corresponding to the voltage pulse.

  According to the above control method, each of the phase sections before and after the phase in which the voltage waveform applied to the linear motor zero-crosses is compared with the case where PWM control is executed only by the first normal control and the second normal control. That is, in a specific section, the width of the voltage pulse can be made larger than the minimum width at which the current value can be detected. Therefore, it becomes easy to measure the current value of the phase near the phase where the voltage waveform is zero-crossed. That is, it is easy to distinguish whether the voltage is positive or negative in the vicinity of the phase where the voltage waveform crosses zero. As a result, it is possible to accurately recognize the timing at which the voltage waveform crosses zero.

  The control device described above can execute the third control between the first control and the second control. In the third control, the first switching element is turned on and the second switching element is turned off, the third switching element is turned on, and the fourth switching element is turned off.

  In a specific section before and after the first normal control, the time obtained by subtracting the total time of the third control and the second control from the total time of the first control and the third control is PWM control by the first normal control. It is desirable that the time is the same as the time when the first control is executed. In a specific section before and after the second normal control, the time obtained by subtracting the total time of the third control and the first control from the total time of the third control and the second control is PWM control by the second normal control. When it is assumed that the second control is executed, it is desirable that the time is the same as the time when the second control is executed.

  In the above control method, the width of the voltage pulse in the specific section is substantially the same as the width of the voltage pulse in the section corresponding to the specific section of the control method in which only the first normal control and the second normal control are performed. Therefore, according to the above method, the voltage waveform applied to the linear motor is substantially the same as the control method in which only the first normal control and the second normal control are performed. Can be formed.

  In addition, it is desirable that the specific section is performed only in a section in which the control device cannot detect the current value corresponding to the voltage pulse, assuming that only the first normal control and the second normal control are executed.

  The PWM control is executed using a carrier wave that draws a sine curve and a signal wave that draws a symmetrical triangular wave. In this case, the amount of deviation between the central axis of the voltage pulse formed by the first control and the central axis of the symmetric triangular wave, and the central axis of the voltage pulse formed by the second control and the central axis of the symmetric triangular wave It is desirable that the sum with the amount of deviation between them be the minimum value.

  According to the above control method, the deviation amount between the central axis of the combined component of the positive voltage pulse and the negative voltage pulse and the central axis of the symmetric triangular wave can be minimized. Therefore, the voltage waveform applied to the linear motor can be approximated to a sine wave as much as possible.

  Two types of reference widths are provided, and the first reference width when shifting from the specific section to the normal section is larger than the second reference width when shifting from the normal section to the specific section.

  In general, when shifting from a specific section to a normal section, the probability that chattering of a voltage waveform occurs is higher than when shifting from a normal section to a specific section. Therefore, the occurrence of chattering is efficiently prevented by making the first reference width when shifting from the specific period to the normal section larger than the second reference width when shifting from the normal section to the specific section. .

Hereinafter, a method for controlling a single-phase motor according to an embodiment of the present invention will be described with reference to the drawings.
First, a general single phase motor system will be described.

  In PWM (Pulse Width Modulation) control of a linear motor M as an example of a single phase motor, a motor driving circuit 100 as shown in FIG. 1 is used. The motor drive circuit 100 has four switching elements and is connected to the linear motor M in a manner as shown in FIG. The four switching elements are transistors Gu, Gv, Gx, and Gy, each of which has a flywheel diode connected between the source electrode and the drain electrode.

  As can be seen from FIG. 1, the transistor Gu and the transistor Gx are connected in series, and the transistor Gv and the transistor Gy are connected in series. The transistors Gu and Gx and the transistors Gv and Gy are connected in parallel with each other in this order.

  The linear motor M has one terminal connected to a node U between the transistor Gu and the transistor Gx, and the other terminal connected to a node V between the transistor Gv and the transistor Gy.

  The microcomputer 1000 transmits a control signal to the respective gate electrodes of the transistors Gu, Gv, Gx, and Gy, and the AC voltage applied to the linear motor M by the opening / closing operation of the transistors corresponding to the gate electrodes. To control. Thereby, the electric current which flows into the coil of a single phase motor is controlled. As a result, the amplitude and cycle of the reciprocating motion of the piston of the linear motor M are controlled.

  A smoothing capacitor C is provided in parallel with the motor drive circuit 100. A rectifier D is provided in parallel to the smoothing capacitor C. Further, an AC power supply G is provided in parallel with the rectifier D. Further, one of the two terminals of the voltmeter V is connected to each of the two terminals of the linear motor M, and the voltage value obtained by the voltmeter V is transmitted from the voltmeter V to the microcomputer 1000. The An ammeter A is provided between the smoothing capacitor C and the linear motor M, and the current value obtained by the ammeter A is transmitted from the ammeter A to the microcomputer 1000.

  More specifically, the method for acquiring the voltage value and the current value is as follows. In obtaining the actual voltage value, first, the voltage applied to the linear motor M is divided, and the divided voltage value is input to the microcomputer 1000. The microcomputer 1000 performs A / D (analog / digital) conversion on the divided voltage value, thereby calculating an actual voltage value. Regarding the actual current value acquisition, first, the potential difference between both ends of the shunt resistor is amplified, and the amplified potential difference value is input to the microcomputer 1000. The microcomputer 1000 A / D converts the amplified potential difference value, thereby calculating the actual current value.

  FIG. 2 is a block diagram for explaining the configuration of a microcomputer 1000 for controlling a single-phase linear motor in which one PWM inverter control timer (one channel) is incorporated.

  The microcomputer 1000 can control the output modes of the control signals of two phases (U phase and V phase) with one built-in timer (one channel). That is, the microcomputer 1000 is designed so that it can control each of the four transistors Gu, Gx, Gv, and Gy as the switching elements shown in FIG.

  The microcomputer 1000 outputs a control signal for controlling the four switching elements. The microcomputer 1000 includes a clock circuit as an oscillator, a CPU as a calculation means, a RAM as a rewritable storage means, and a read-only ROM. The ROM stores a program for controlling the four switching elements. A RAM (Random Access Memory) is a storage means for temporarily storing the results of CPU arithmetic processing performed in accordance with a program stored in the ROM, and includes a temporary storage means such as a register. Also good. Further, the clock is used to form a clock pulse that is a basis for operating a timer described later, using a signal transmitted from the oscillator.

  The microcomputer 1000 includes an up / down timer 1. A circuit is provided for outputting a signal for controlling each of the U phase and the V phase according to the count value of the up / down timer 1. Further, the microcomputer 1000 is provided with two registers corresponding to the two phases of the up / down timer 1, respectively.

  The control signal output from the circuit that controls the U phase of the up / down timer 1 is transmitted to each of the transistors Gu and Gx. The control signal output from the circuit for controlling the V phase of the up / down timer 1 is transmitted to each of the transistors Gv and Gy.

  Next, a method for determining a set value to be updated in the register will be described. Hereinafter, the set value means the set value of the register.

In the present embodiment, it is assumed that PWM basic frequency fb = 10 kHz and motor driving frequency fm = 50 Hz. At this time, the half cycle (half of the carrier cycle) of the up / down timer 1 is 1/10 ⁴ Hz / 2 = 100 μsec / 2 = 50 μsec.

  When a relatively large value is set as the U-phase set value or the V-phase set value of the up / down timer 1 of the microcomputer 1000, the pulse width becomes relatively small. For example, as can be seen from FIG. 3, when a voltage pulse having the largest width is output to the linear motor M, the set value of the up / down timer 1 may be set to zero. When a voltage pulse having the smallest width is output to the linear motor M, the set value of the up / down timer 1 may be set to 1000. When the set value of the up / down timer 1 is set to 650, a voltage pulse as shown in FIG. 3 is generated in each of the transistors Gu and Gx. For example, when the set value of the U phase of the up / down timer 1 is set to 500, a voltage pulse is output for 50 usec in the U phase.

  As shown in FIG. 4, in the set value determination process, it is first determined in ST11 whether or not a required drive power value has been input. That is, it is determined whether or not a value for specifying at what driving power the single-phase motor is driven is input to the microcomputer 1000 from the outside.

If YES in ST11, the process proceeds to ST12. In ST12, the peak value (or effective value of the AC voltage) of the AC voltage applied to the linear motor M and the frequency (wavelength) of the AC voltage are determined. This determination is performed by the CPU using a program built in the ROM. Next, in ST13, the voltage pulses i _1, i ₂ in one cycle of the determined AC voltage in ST12, ..., the width of each of the _{i n w 1, w 2,} ..., to determine the respective w _n.

At this time, the widths w ₁ , w ₂ ,..., W _n of the voltage pulse gradually increase from the minimum value, gradually decrease when reaching the maximum value, and gradually increase again when reaching the minimum value. That is, the voltage pulses _{i 1, i 2, ...,} i n is a whole, forms an AC voltage (current) waveform.

Next, in ST14, the voltage pulses i ₁ determined in _{ST13, i 2, ..., i} n
Width w _1, w ₂ respectively of, ..., with each value of w _n, up / set value SU ₁ down timer 1 of U-phase, SU _2, ..., SU _n and V-phase of the set value SV ₁₁ , SV ₂₂ ,..., SV _nn are determined. This setting _{SU 11, SU 12, ...,} SU nn and setpoint SV _11, SV _22, ..., by determination of SV _nn, transistors Gu, Gx, the respective operation timing of Gv and Gy are determined. When the process of ST14 is completed, the process of ST11 is repeatedly executed, that is, the microcomputer 1000 waits until the required drive power value is changed.

  In the present embodiment, in the setting value determination process, the microcomputer 1000 executes each calculation of steps ST12 to ST14 based on a program built in the ROM.

According to this method, according to the drive power input to the microcomputer 1000, a plurality of types of set values SU ₁₁ , SU ₁₂ ,..., SU _nn and set value SV ₁₁ , SV _{22 ,.} 1 is selected, and the motor drive circuit 100 is controlled using the data string of the selected set value.

  Next, the board-like concept of the control method of the single phase motor of this Embodiment is demonstrated using FIGS.

  First, the timing of each opening / closing operation of the transistors Gu, Gx, Gv, and Gy in the control method of the comparative example of the control method of the single-phase motor of the present embodiment will be described with reference to FIGS.

  FIG. 5 is a timing chart showing opening / closing operations of the transistors Gu, Gx, Gv, and Gy when the phase is 0 ° to 180 °, and FIG. 6 is a transistor when the phase is 180 ° to 360 °. It is a timing chart which shows the opening / closing operation | movement of Gu, Gx, Gv, and Gy.

As shown in FIG. 5, when the up / down timer 1 reaches the set values SU ₁₁ , SU ₂₂ ,..., SU _nn during the count-up, the transistor Gx is turned off, and the transistor Gu is turned on after the predetermined time has elapsed. A control signal is automatically output from the microcomputer 1000 so as to be turned on. Next, after a predetermined time has elapsed, the transistor Gu is automatically turned OFF a predetermined time before the ON timing of the transistor Gx described below. When the up / down timer 1 reaches the set values SU ₁₁ , SU ₂₂ ,..., SU _nn during the countdown, a control signal is automatically output from the microcomputer 1000 to the transistor Gx. The transistor Gx is turned on. At this time, in the V phase, the transistor Gv is always OFF and the transistor Gy is always ON.

As shown in FIG. 6, when the up / down timer 1 reaches the set values SV ₁₁ , SV ₂₂ ,..., SV _nn during counting up, the transistor Gy is turned off, and after the predetermined time has elapsed, the transistor Gv is turned off. A control signal is automatically output from the microcomputer 1000 so as to be turned on. Next, the transistor Gv is automatically turned off after a predetermined time elapses and a predetermined time before the ON timing of the transistor Gy described below. When the up / down timer 1 reaches the set values SV ₁₁ , SV ₂₂ ,..., SV _nn during the countdown, a control signal is automatically output from the microcomputer 1000 to the transistor Gy. The transistor Gy is turned on. At this time, in the U phase, the transistor Gu is always OFF and the transistor Gx is always ON.

In the control method of the single phase motor of the comparative example, the set values of the U phase and V phase registers of the up / down timer 1 are sequentially changed. That is, the set values SU ₂₂ and SV ₂₂ of the up / down timer 1 in FIGS. 5 and 6 are smaller than the set values SU ₁₁ and SU ₁₁ , respectively. Thus, each of SU _mm and SV _mm gradually decreases as m increases from 1 to n. Therefore, the width of the current pulse increases gradually as n increases, as in t ₁ , t ₁ + 2 × t ₂ .

  As can be seen by comparing FIG. 5 and FIG. 6, the operations of the transistors Gu and Gx and the operations of the transistors Gv and Gy are interchanged. Thereby, in FIG. 5 and FIG. 6, the current pulses flowing through the linear motor M are reversed between positive and negative. Except for these, the U-phase control and the V-phase control are the same.

  According to the single-phase motor control method of the comparative example as described above, unlike the conventional single-phase motor control method, a positive DC voltage and a negative DC voltage are generated within the PWM cycle (carrier cycle). High-frequency loss and switching loss due to are reduced.

  Further, in the control of the linear motor of the comparative example, a generally used symmetrical triangular wave comparison method is adopted as described with reference to FIGS. In other words, each of the plurality of voltage pulse waveforms is symmetric in the front-rear direction around the half time point of the carrier period.

  FIG. 7 is a diagram showing the duty ratio of the time when each of the transistor Gu and the transistor Gv is ON when the modulation factor is 100%. Also, if the DC voltage applied to the inverter circuit is 300 v, the U-phase terminal voltage is the potential difference between the U-phase transistor Gu and the transistor Gy, and the potential difference between the V-phase transistor Gv and the transistor Gx. The V-phase terminal voltage and the output voltage (U-V interphase voltage) applied to the linear motor M are as shown in FIG.

  When the U-V phase voltage, that is, the output voltage applied to the linear motor M is positive, the transistors Gv and Gx are turned off and only the transistors Gu and Gy are turned on as shown in FIG. On the other hand, when the U-V phase voltage, that is, the output voltage applied to the linear motor M is negative, as shown in FIG. 6, the transistors Gu and Gy are turned off and only the transistors Gx and Gv are turned on. As a result, a voltage pulse is formed in each of the U phase and the V phase, and the voltage corresponding to the difference between the U phase voltage pulse and the V phase voltage pulse width is applied to the linear motor M. Thus, the total number of switching times of the transistor Gu and Gx pair and the transistor Gv and Gy pair can be halved without lowering the output voltage. Therefore, the switching loss is reduced to ½.

  Next, a current detection method will be described with reference to FIGS. 9 to 12 showing current paths in four ON / OFF patterns of each transistor.

  In the period of ΔT1 in FIG. 5, that is, in the section in which each of the transistors Gu and Gv is OFF and each of the transistors Gx and Gy is ON, the current path is a path as indicated by an arrow in FIG. No current is detected by ammeter A.

  In the period of ΔT2 in FIG. 5, that is, in a section in which each of the transistors Gv and Gx is OFF and each of the transistors Gu and Gy is ON, the current path is a path as indicated by an arrow in FIG. The direct current value Idc detected by the ammeter A is + Iuv.

  In the period of ΔT1 in FIG. 6, that is, in a section in which each of the transistors Gx and Gy is ON and each of the transistors Gu and Gv is OFF, the current path is a path as indicated by an arrow in FIG. No current is detected by ammeter A.

  In the period of ΔT4 in FIG. 6, that is, in the section in which each of the transistors Gu and Gy is OFF and each of the transistors Gv and Gx is ON, the current path is a path as indicated by an arrow in FIG. The direct current value Idc detected by the ammeter A is -Iuv.

  From the above, the section in which the ammeter A can detect the current is only the section ΔT2 in which the phase is between 0 ° and 180 ° or ΔT4 in the section in which the phase is 180 ° to 360 °. Since each of these ΔT2 and ΔT4 is an extremely short interval in the vicinity of the timing at which the voltage waveform zero-crosses, the time during which the ammeter A can detect the current is shortened, and an appropriate current value is obtained. Detection becomes difficult.

  FIG. 13 shows the transistors Gu and Gx in the phase sections of 0 ° to 180 ° and 180 ° to 360 ° in the first normal control and the second normal control, which will be described later, of the control method of the linear motor M of the present embodiment. , Gv, and Gy, ON / OFF timing charts are shown, and the relationship of the operation of these transistors is the same as that of the linear motor control method described with reference to FIGS. That is, in the present embodiment, basically, the control as shown in FIGS. 5 and 6 is performed.

  FIG. 14 shows ON / OFF timings of the transistors Gu, Gx, Gv, and Gy in a phase section other than the normal control of the linear motor of the present embodiment to be described later, that is, a phase in the vicinity of the phase where the voltage waveform zero-crosses. This shows the relationship between the U-phase and V-phase voltages.

  First, in the linear motor control method according to the first embodiment, the transistor Gu shown in FIG. 13 is turned on as shown in FIG. Compared to the timing time (ΔT2 of FIG. 13 indicated by a dotted line), the ON timing time of the transistor Gu is lengthened by ΔT5, and the transistor Gv is turned ON for ΔT5 time. Note that, in a section where the current value is easily detected in the section where the phase is 0 ° to 180 °, the control of the linear motor shown in FIG. 13 is executed.

  Also, in the section where the current value is difficult to detect in the section where the phase is 180 ° to 360 °, as shown in FIG. 14, the ON timing time of the transistor Gv shown in FIG. 13), the ON timing time of the transistor Gv is lengthened by ΔT6 and the transistor Gu is turned ON for ΔT6 time. In the section where the current value is easy to be detected in the section where the phase is 180 to 360 °, the control of the linear motor shown in FIG. 13 is executed.

  Note that the values of ΔT5 and Δ6 may change for each carrier period. The timing of the ON time of the transistor Gu and the timing of the ON time of the transistor Gv may be different.

  As described above, as shown in FIG. 14, only the difference between the ON time of the U-phase transistor Gu and the ON time of the V-phase transistor Gv is turned ON. One of the U-phase transistor Gu and the V-phase transistor Gv while maintaining the same ON time in the control, that is, while setting the output voltage (voltage between U phase and V phase) applied to the linear motor M to substantially the same value. The width of the section in which only one is turned on, that is, the section in which the current can be detected by the ammeter A (each of ΔT2 and T4) can be widened. As a result, current detection by the ammeter A is facilitated.

  FIG. 15 shows another example of the relationship between the ON / OFF timings of the transistors Gu, Gx, Gv, and Gv and the voltage between the U phase and the V phase in a phase section other than the normal control of the linear motor according to the present embodiment described later. Is shown.

  Also in the linear motor control method of the second embodiment shown in FIG. 15, the same effect as that obtained by the linear motor control method of the first embodiment is obtained by the same method as the linear motor control method of the first embodiment shown in FIG. The effect of can be obtained.

  In the linear motor control method shown in FIG. 15, adjustment is made so that a section in which one of the transistors Gu and Gv capable of detecting current is turned on (the section ΔT2 or ΔT4 in FIGS. 5 and 6) is minimized. Has been. For example, in the section of 180 ° to 360 °, the third control (ΔT3) described later is not performed. In other words, immediately after the second control in which the transistor Gu is OFF, Gx is ON, Gv is ON, and Gy is OFF, the first control in which the transistor Gu is ON, Gx is OFF, Gv is OFF, and Gy is ON is performed. It is. In this case, if the period of ΔT4 is the minimum value of the negative voltage pulse whose current can be detected by the ammeter A, the center axis C2 of the carrier cycle and the central axis P2 of the negative voltage pulse formed by the second control And the width between the center axis C2 of the carrier period and the center axis P4 of the positive voltage pulse formed by the first control is the minimum necessary for executing the specific section It becomes the width of. In short, the center axis C2 of the carrier cycle exists at any position from the center axis P2 of the negative voltage pulse formed by the second control to the center axis P4 of the positive voltage pulse formed by the first control, If there is no section in which the third control (ΔT3) in which the transistor Gu is ON, Gx is OFF, Gv is ON, and Gy is OFF, the width between the central axis C2 and the central axis P4, the central axis C2, The sum with the width between the central axis P4 and the center axis P4 is the minimum width necessary for executing the specific section. In the control in the specific section of 180 ° to 360 ° in FIG. 15, the center axis C2 of the carrier cycle and the center axis P2 of the ON timing of the transistor Gv coincide.

  The characteristics and effects of the control method of the single-phase motor according to the present embodiment are summarized as follows.

  The microcomputer 1000 as the control device can execute first control, second control, third control, and fourth control described below.

  In the first control, the transistor Gu as the first switching element is turned on and the transistor Gx as the second switching element is turned off, as shown in the respective ΔT2 sections of FIGS. 13, 14, and 15. At the same time, the transistor Gv as the third switching element is turned off, and the transistor Gy as the fourth switching element is turned on.

  In the second control, as shown in each section of ΔT4 in FIGS. 13, 14, and 15, the transistor Gu is turned off, the transistor Gx is turned on, the transistor Gv is turned on, and the transistor Gy turns off.

  In the third control, as shown in the respective ΔT3 sections of FIGS. 14 and 15, the transistor Gu is turned on, the transistor Gx is turned off, the transistor Gv is turned on, and the transistor Gy is turned off. To do.

  In the fourth control, as shown in the respective ΔT1 sections of FIGS. 14 and 15, the transistor Gu is turned off, the transistor Gx is turned on, the transistor Gv is turned off, and the transistor Gy is turned on. To do.

  In the control method for the single-phase motor according to the present embodiment, basically, as shown in FIG. 13, the voltage pulse width in the first control and the voltage pulse width in the second control are adjusted. Thus, the PWM control is executed, and thereby, the control in the normal section in which the AC voltage is applied to the linear motor M is executed.

  However, as shown in FIG. 16, in the normal section where the width of one voltage pulse constituting the waveform of the AC voltage applied to the single-phase motor is larger than the reference width α (β), for example, the normal section Every time, as in the phase interval of 0 ° to 180 ° in FIG. 13, the first normal control in which only the first control (ΔT2) is repeated a plurality of times, and in the phase interval of 180 ° to 360 ° in FIG. The second normal control in which only the second control (ΔT4) is repeated a plurality of times is alternately performed every time the phase of the voltage waveform changes by 180 °.

  Furthermore, in a specific section other than the normal section shown in FIG. 16, that is, in the phase near the phase where the voltage waveform zero-crosses, for example, as shown in FIG. 14, the positive voltage formed by the first control (ΔT2) PWM control is executed using both the pulse and the negative voltage pulse formed by the second control (ΔT4).

  Further, as shown in FIG. 16, the width of the voltage pulse formed by the first control (ΔT2) in the specific section before and after the first normal control performed in the phase section of 0 ° to 180 °, and 180 ° to Each of the widths of the voltage pulses formed by the second control (ΔT4) in the specific section before and after the second normal control performed in the phase section of 360 ° is a current value corresponding to the voltage pulse by the microcomputer 1000. That is, the current value corresponding to the voltage pulse is larger than the minimum voltage pulse width (α or β) that can be detected by the ammeter A.

  According to the above control method, compared to the case where the PWM control is executed only by the first normal control and the second normal control, the phase interval before and after the phase where the voltage waveform applied to the linear motor M crosses zero. In each case, that is, in the specific section of FIG. 16, the width of all voltage pulses can be made larger than the minimum width (α or β of FIG. 16) in which the current value can be detected by the ammeter A. Therefore, it becomes easy to measure the current value of the phase near the phase where the voltage waveform is zero-crossed.

  Further, in the specific section before and after the first normal control shown in FIG. 16 in the phase range of 0 ° to 180 °, as shown in FIG. 14, the sum of the first control (ΔT2) and the third control (ΔT3). When the time (ΔT5) obtained by subtracting the total time of the third control (ΔT3) and the second control (ΔT4) from the time is assumed that the PWM control is executed by the first normal control shown in FIG. It is desirable to be the same as the time for which one control (ΔT2 in FIG. 13) is executed. Further, as shown in FIG. 14, in a specific section before and after the second normal control shown in FIG. 16, the third control (ΔT3) is calculated from the total time of the third control (ΔT3) and the second control (ΔT4). The time obtained by subtracting the total time with the first control (ΔT2) is the same as the time when the second control (ΔT4 in FIG. 13) is executed when it is assumed that the PWM control is executed by the second normal control. It is desirable to be.

  In the above control method, only the first normal control and the second normal control shown in FIGS. 13 and 16 are performed with the width of the voltage pulse of the composite component of the positive voltage pulse and the negative voltage pulse in the specific section. The voltage pulse width (ΔT2 or ΔT4 in FIG. 13) in the section corresponding to the specific section of the control method is substantially the same. Therefore, according to the above method, the voltage waveform applied to the linear motor M is substantially the same as the control method in which only the first normal control and the second normal control shown in FIGS. 13 and 16 are performed. A voltage pulse having a shape close to a wave can be formed.

The specific section corresponds to a section in which the microcomputer 1000 cannot detect a current value corresponding to the voltage pulse, that is, assuming that only the first normal control and the second normal control are executed. It is desirable that the current value to be detected is only performed in a section where the ammeter A cannot detect the current value (a section where the voltage pulse width is smaller than α or β shown in FIG. 16). For this purpose, a value of the minimum width Wmin of the voltage pulse that can be appropriately measured by the ammeter A is calculated in advance. Further, a process of comparing each of the current pulse widths W ₁ , W ₂ ,..., W _n calculated in the process of ST13 shown in FIG. 4 with the value of the voltage pulse having the minimum width Wmin is performed. Based on this comparison process, in the phase section where the current pulse width W _m calculated in the process of ST13 is smaller than the minimum width Wmin, the above-described specific section is controlled, and conversely, calculated in the process of ST13. In the phase interval in which the current pulse width W _m is larger than the minimum width Wmin, it is determined to perform the control in the normal interval. In FIG. 16, the reference width α and the reference width β are different. However, when the specific section is controlled only in the minimum necessary phase section, the reference width α and the reference width β have the same value. Become.

  According to this control method, it is possible to minimize the phase interval in which the voltage pulse having a mode different from the voltage pulse of the normal control (first normal control and second normal control) is formed. Therefore, high frequency loss due to current ripple can be minimized.

  Further, the PWM control of the present embodiment is executed in the microcomputer 1000 using a carrier wave that draws a sine curve and a signal wave that draws a symmetrical triangular wave as shown in FIGS. In this case, as shown in FIG. 15, when the phase is between 0 ° and 180 °, it is between the central axis P1 of the positive voltage pulse formed by the first control (ΔT2) and the central axis C1 of the symmetrical triangular wave. The sum of the amount of deviation (period) and the amount of deviation (period) between the central axis P3 of the negative voltage pulse formed by the second control (ΔT4) and the central axis C1 of the symmetrical triangular wave becomes the minimum value. It is desirable. Further, the shift amount (period) between the central axis P2 of the voltage pulse formed by the second control (ΔT4) and the central axis C2 of the symmetrical triangular wave, and the center of the voltage pulse formed by the first control (ΔT2) The sum of the shift amount (period) between the axis P4 and the central axis C2 of the symmetric triangular wave is desirably a minimum value.

  According to the above control method, the shift amount between the central axis of the composite component of the positive voltage pulse and the negative voltage pulse and the central axis of the symmetric triangular wave is minimized in each of the carrier periods. be able to. Therefore, the voltage waveform applied to the linear motor M can be approximated to a sine wave as much as possible.

  In addition, as shown in FIG. 6, the control method for the single-phase motor according to the present embodiment has two types of reference widths (α and β), and from the specific section shown in FIG. 14 or FIG. The reference width α when moving to the normal section shown is larger than the reference width β when moving from the normal section shown in FIG. 13 to the specific section shown in FIG.

  In general, as shown in FIG. 16, when moving from the specific section shown in FIG. 14 or 15 to the normal section shown in FIG. 13, when moving from the normal section shown in FIG. 13 to the specific section shown in FIG. Compared to the above, there is a high probability that voltage waveform ripple (chattering) occurs. Therefore, as shown in FIG. 16, the reference width α when shifting from the specific period shown in FIG. 14 or FIG. 15 to the normal section shown in FIG. 13 is changed from the normal section shown in FIG. The occurrence of chattering is efficiently prevented by making the width larger than the reference width β when shifting to the section.

  More specifically, it is as follows.

  When the reference width β is the minimum width Wmin of the voltage pulse whose current value can be properly detected by the ammeter A, the reference width α is a larger value. Therefore, when the reference width α is used as a reference value, even if the width of the voltage pulse fluctuates up and down near the minimum width Wmin of the voltage pulse, if the reference width α is not exceeded, the control from the specific section to the normal section Since the change to the control is not made, it is possible to suppress the inconvenience that the control change between the control in the specific section and the control in the normal section is repeated a plurality of times in a short section.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram of the system used in the control method of the single phase motor of embodiment. It is a block diagram of the microcomputer of an embodiment. 6 is a timing chart showing the relationship between the ON / OFF operation of the transistor and the set value of the up / down timer according to the embodiment. It is a flowchart for demonstrating a setting value determination process. It is a timing chart for demonstrating the relationship between ON / OFF operation | movement of the transistor used in the control method of embodiment in U phase, and the setting value of an up / down timer. It is a timing chart for demonstrating the relationship between ON / OFF operation | movement of the transistor used in the control method of embodiment in V phase, and the setting value of an up / down timer. It is a graph which shows the relationship between the gate duty ratio and voltage phase of each transistor of U phase and V phase. It is a graph which shows the relationship of a U-phase terminal voltage, a V-phase terminal voltage, and a U-V phase voltage. It is a 1st example of the electric current path of an inverter circuit. It is a 2nd example of the electric current path | route of an inverter circuit. It is a 3rd example of the electric current path of an inverter circuit. It is a 4th example of the electric current path of an inverter circuit. It is a figure for demonstrating the control method of the inverter circuit of the normal area of embodiment. FIG. 3 is a diagram for explaining a control method for a specific section of the inverter circuit according to the first embodiment. FIG. 10 is a diagram for explaining a control method for a specific section of the inverter circuit according to the second embodiment. It is a figure for demonstrating the aspect of the several voltage pulse applied to a linear motor in the case of having two types of reference widths.

Explanation of symbols

  100 motor drive circuit, 1000 microcomputer.

Claims (5)

A single-phase motor,
A drive circuit for applying an AC voltage to the single-phase motor;
A control device for controlling the drive circuit,
The drive circuit is
First and second switching elements connected in series with each other;
A third and a fourth switching element connected in series with each other;
The third and fourth switching elements are connected in parallel to the first and second switching elements in this order,
One terminal of the single-phase motor is connected to a node between the first switching element and the second switching element; and
A method for controlling a single phase motor, wherein the other terminal of the single phase motor is connected to a node between the third switching element and the fourth switching element,
The control device includes:
A first control for turning on the first switching element and turning off the second switching element, turning off the third switching element, and turning on the fourth switching element;
It is possible to execute a second control that turns off the first switching element and turns on the second switching element, turns on the third switching element, and turns off the fourth switching element.
Basically, PWM control is executed by adjusting the voltage pulse width in the first control and the voltage pulse width in the second control, whereby the AC voltage is applied to the single-phase motor. Normal section control is executed,
In the normal section, the width of one voltage pulse constituting the waveform of the AC voltage applied to the single-phase motor is larger than a reference width,
For each normal section, a first normal control that repeats only the first control a plurality of times and a second normal control that repeats only the second control a plurality of times are alternately performed,
In a specific section other than the normal section, PWM control is executed using both the voltage pulse generated by the execution of the first control and the voltage pulse generated by the execution of the second control,
The width of the voltage pulse formed by the first control in the specific section before and after the first normal control and the width of the voltage pulse formed by the second control in the specific section before and after the second normal control. A control method for a single-phase motor, each of which is larger than a minimum pulse width at which the control device can detect a current value corresponding to a voltage pulse. The control device turns on the first switching element and turns off the second switching element and turns on the third switching element between the first control and the second control, and The third control for turning off the fourth switching element can be executed,
In the specific section before and after the first normal control, a time obtained by subtracting the total time of the third control and the second control from the total time of the first control and the third control is the first time. When it is assumed that the PWM control is executed by the normal control, the time is the same as the time when the first control is executed.
In the specific section before and after the second normal control, a time obtained by subtracting the total time of the third control and the first control from the total time of the third control and the second control is the second time. 2. The method for controlling a single-phase motor according to claim 1, wherein the second control is executed for the same time as when the second control is executed when it is assumed that the PWM control is executed by the normal control.   The specific section is performed only in a section in which the control device cannot detect a current value corresponding to a voltage pulse when it is assumed that only the first normal control and the second normal control are executed. Item 2. A method for controlling a single-phase motor according to Item 1. The PWM control is executed using a carrier wave that draws a sine curve and a signal wave that draws a symmetrical triangular wave,
In the specific section, the amount of deviation between the central axis of the voltage pulse formed by the first control and the central axis of the symmetric triangular wave, and the central axis of the voltage pulse formed by the second control and the symmetry. 2. The method for controlling a single-phase motor according to claim 1, wherein a sum of a deviation amount from a central axis of the triangular wave is a minimum value within a range in which the control of the specific section can be executed. There are two types of reference widths,
2. The method for controlling a single-phase motor according to claim 1, wherein a first reference width when shifting from the specific section to the normal section is larger than a second reference width when shifting from the normal section to the specific section. .

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