JP2000324876A - Brushless motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the leakage current flowing from the winding to the stator to a brushless motor at switching of PWM(pulse width modulation) between upper and lower arms. SOLUTION: A pulse width modulation circuit 39 generates a PWM signal Sm, by comparing a voltage command signal Ss with a triangular wave carrier signal Sc1 generated from a triangular wave generating circuit 38. A switching circuit 41 decides the IGBTs to be subjected to PWM of the IGBTs 14-16 and 17-19 of upper and lower arms based on a discriminate signal Sp, indicating the polarity of the voltage induced in a winding in a non-energized period and outputs PWM signals Smp and Smn for the upper and lower arms to a waveform combining circuit 42. In this case, the switching circuit 41 does not immediately switches the PWM between the upper and lower arms, even when the level of the discriminate signal Sp fluctuates, but rather the circuit switches the PWM, when the triangular wave carrier signal Sc1 becomes a maximum value during the period in which the PWM is turned on thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a switching circuit comprising a positive side switching element group and a negative side switching element group for sequentially energizing windings in accordance with the rotational position of a rotor, based on a pulse width modulation signal. The present invention relates to a brushless motor driving device configured to selectively switch between a positive switching element group and a negative switching element group as a switching element group for performing on / off control.

[0002]

2. Description of the Related Art A driving device for a brushless motor of this type will be described with reference to FIGS. First, in FIG. 7 showing an electrical configuration, a driving device 1 includes a converter circuit 2, an inverter circuit 3, a position detection circuit 4,
It comprises a control circuit 5 and a gate drive circuit 6. Among them, the converter circuit 2 is connected to, for example, a single-phase 100 V AC power supply 7, and includes a well-known combination of a reactor 8 for power factor improvement, a diode bridge circuit 9, and three smoothing capacitors 10, 11, and 12. As a single-phase voltage doubler rectifier circuit.

An inverter circuit 3 is connected between DC power supply lines 13a and 13b, which are output lines of the converter circuit 2. The inverter circuit 3 includes six switching elements, for example, IGBTs 14 to 19, and these IGBs.
This is configured as a well-known voltage-type inverter circuit in which six return diodes 20 to 25 connected in parallel to T14 to T19, respectively, are connected in a three-phase bridge.

The output terminal 2 of each phase of the inverter circuit 3
The terminals of the windings 27u, 27v, 27w of the brushless motor 27 are connected to 6u, 26v, 26w, respectively. The brushless motor 27 includes a stator (not shown) around which the windings 27u, 27v, 27w connected in a three-phase star connection are wound, and a rotor (not shown) provided with permanent magnets. For example, it drives a compressor (not shown) mounted on a refrigerator or an air conditioner.

[0005] The rotor position information required for the control circuit 5 to control the energization of the brushless motor 27 is determined based on the induced voltage appearing at the winding terminals during the non-energization periods of the windings 27u, 27v, 27w. The detection circuit 4 outputs the position signals Pu, Pv, and Pw. This position detection circuit 4 is configured as follows.

That is, resistors 28 and 29 are connected in series between the DC power supply lines 13a and 13b, and a DC voltage output from the converter circuit 2 is connected to a common connection point between the resistors 28 and 29. A reference voltage Vc having a voltage value of 1/2 of Vdc is generated. Comparator 3
0, 31, and 32 denote a U-phase terminal voltage Vu, a V-phase terminal voltage Vv, a W-phase terminal voltage Vw, and the reference voltage V, respectively.
and outputs position signals Pu, Pv, and Pw having a high level or a low level.
In this case, the inverting input terminals of the comparators 30, 31, and 32 are connected to a common connection point between the resistors 28 and 29.

[0007] The control circuit 5 outputs these position signals Pu.
, Pv, Pw, the pulse width modulation (PWM) control by the 120 ° conduction method is performed, and the PWM-controlled drive signals Dup ′ to Dwn ′ are respectively supplied to the gate terminals of the IGBTs 14 to 19 via the gate drive circuit 6. Is to be given. As a result, the brushless motor 2
The three windings 27u, 27v, and 27w of 7 are applied with a rectangular wave-shaped three-phase AC voltage that is turned on and off by PWM.

The control circuit 5 includes a triangular wave generating circuit for generating a triangular carrier signal, and a pulse width modulation circuit for comparing the triangular carrier signal with a voltage command signal. Here, the voltage command signals are position signals Pu, Pv,
Speed detection signal and speed command signal f detected using Pw
s.

Further, the windings 27u to 27d in the non-energized period
A current that causes a brake torque to act on the brushless motor 27 due to the induced voltage of 7 w
In order to prevent a reverse current from flowing through the converter circuit 2 due to the release of the current energy stored in the 27w, the control circuit 5 controls the P.P.R. disclosed in JP-A-7-322681.
WM switching control is performed.

That is, the control circuit 5 determines whether the induced voltage of the windings 27u to 27w in the non-energized period is positive or negative, and based on the positive / negative determination result, the inverter circuit 3
PWM on / off control at the positive side (upper arm)
GBTs 14 to 16 and negative (lower arm) IGBTs 17 to
19 is configured to be switched. By switching the PWM between the upper and lower arms, the motor efficiency is improved, and the loss in the capacitors 10 to 12 is reduced.

With respect to the driving device 1 having the above configuration,
FIG. 8 shows drive signals Dup 'to Dwp' for the upper arm, drive signals Dun 'to Dwn' for the lower arm, terminal voltages Vu, Vv,
The waveforms of Vw and the neutral point voltage VN of the windings 27u to 27w are shown. In FIG. 8, the upper arm is commutated at times t1 and t5, and the lower arm is commutated at time t3. Meanwhile, at time t2, the on / off control by PWM is switched from the upper arm to the lower arm, and at time t4, the on / off control by PWM is switched from the lower arm to the upper arm.

In this case, when the IGBT, which is on / off controlled by the PWM, is in the on state (hereinafter referred to as "when the PWM is on"), the PWM is switched between the upper and lower arms (switching at time t4). The change in neutral point voltage VN at the time of the switching is relatively small. On the other hand, when the IGBT that is on / off controlled by the PWM is in an off state (hereinafter, referred to as “when the PWM is off”).
When the PWM is switched between the upper and lower arms (switching at time t2), the neutral point voltage VN
Sharply changes greatly.

Generally, the winding 27 of the brushless motor 27
There is a stray capacitance coupling between u to 27w and the stator. This coupling can be equivalently expressed as a state in which a capacitor is connected between a neutral point 27N of the brushless motor 27 and a stator having a ground potential, as shown in FIG. Therefore, when the neutral point voltage VN changes sharply, a leakage current (leakage current) almost proportional to the differential value flows from the windings 27u to 27w to the stator. As a result, for example, when the brushless motor 27 drives a compressor mounted on the refrigerator, when a user touches an unpainted metal exposed portion such as a hinge portion or a screw portion of the refrigerator housing, the electric power is generated. You may feel

[0014]

SUMMARY OF THE INVENTION Under such circumstances,
When switching the PWM between the upper and lower arms, the PWM
It is preferable to switch when M is on. As a specific method for this switching, there is a control method disclosed in Japanese Patent Application Laid-Open No. 9-312993. In this control method, an edge of chopping (corresponding to PWM) is detected, and after the edge is detected, control is performed so that chopping of the upper and lower arms is switched when chopping is turned on.

According to this control method, the upper and lower arms are switched immediately after the chopping changes from off to on. However, as shown in FIG. 10, the winding 27u immediately after the chopping changes from off to on.
Ringing is superimposed on the terminal voltages of the windings 27u to 27w (i.e., the neutral point voltage) when the chopping (PWM) between the upper and lower arms is switched when the voltage at which the ringing occurs is not settled. VN) has a problem that the fluctuation of the potential becomes large, which leads to an increase in leakage current and noise.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce a leakage current flowing from a winding of a brushless motor to a stator when switching PWM between upper and lower arms. An object of the present invention is to provide a brushless motor driving device.

[0017]

According to a first aspect of the present invention, there is provided a brushless motor driving apparatus, comprising: a positive side switching element group for sequentially energizing a plurality of phase windings of the brushless motor; A switching circuit comprising a group of negative-side switching elements, position detection means for detecting position information of the rotor of the brushless motor, and an energization signal to the windings of the plurality of phases based on the detected position information of the rotor. Energizing signal generating means for obtaining, a carrier signal generating circuit for generating a triangular carrier signal, a pulse width modulating circuit for comparing a voltage command signal and the triangular carrier signal to obtain a pulse width modulating signal, The positive-side switching element group and the negative-side switching element group as a switching element group that performs on-off control based on And a drive unit for selectively switching the brushless motor, wherein the drive unit includes the positive-side switching element in an ON period of the pulse width modulation signal and at a maximum point or a minimum point of the triangular wave carrier signal. And a switching unit configured to switch between the group and the negative switching element group.

According to this configuration, the pulse width modulation circuit compares the voltage command signal with the triangular carrier signal and generates a pulse width modulation signal for inverting the on / off state of the switching element when the two signals match. in this case,
The maximum point or the minimum point of the triangular wave carrier signal is approximately at the center of the ON period or the OFF period (of pulse width modulation) of the switching element. That is, the driving unit switches the switching element group that performs the pulse width modulation between the positive side and the negative side substantially at the center of the ON period of the pulse width modulation signal. Therefore, the switching of the switching element group between the positive side and the negative side is performed while avoiding a voltage non-settling state such as ringing generated at the winding terminal immediately after the on / off state of the switching element is inverted. By this switching, the efficiency of the brushless motor and the driving device can be improved,
The fluctuation in potential at the neutral point of the winding is reduced, and the leakage current from the winding is suppressed as compared with the conventional case.

According to a second aspect of the present invention, there is provided a brushless motor driving apparatus, wherein a carrier signal generating circuit for generating a sawtooth carrier signal is provided in addition to the switching circuit, the position detecting means, and the energizing signal generating means. A pulse width modulation circuit that obtains a pulse width modulation signal by comparing a command signal and the sawtooth carrier signal; and a positive side switching element group and a negative side as a switching element group that performs on / off control based on the pulse width modulation signal. A drive unit for selectively switching between a switching element group and a brushless motor, wherein the drive unit is an on-period of the pulse width modulation signal, and outputs the voltage command signal and the sawtooth carrier signal. At the center point between the intersection and the maximum or minimum point of the sawtooth carrier signal, the positive-side switching element group and the Characterized in that it is configured to switch between a side switching element group.

According to this configuration, the driving unit switches the switching element group performing the pulse width modulation between the positive side and the negative side at the center point of the ON period of the pulse width modulation signal.
Therefore, similarly to the operation described for the configuration of claim 1, switching between the positive side and the negative side while avoiding ringing or the like occurring at the winding terminal immediately after the on / off state of the switching element is reversed. Switching of the element group is performed,
The effect of suppressing the leakage current from the winding is increased.

When the sawtooth carrier signal is used, the driving means generates a reference signal having a median value between the voltage command signal level and the maximum or minimum value of the sawtooth carrier signal, and generates the reference signal and the sawtooth signal. It is preferable to switch between the positive side switching element group and the negative side switching element group at the intersection with the wave carrier signal. According to this configuration, even if the voltage command signal fluctuates, the reference signal is always held at the median value, and the switching element group is switched between the positive side and the negative side at the center point of the ON period of the switching element. Will be

In the above case, it is preferable that the brushless motor drives a compressor mounted on a refrigerator or an air conditioner. As a result, high-efficiency operation can be performed with the occurrence of leakage current suppressed.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention (corresponding to claims 1 and 4) will be described below with reference to FIGS. In FIG. 1, the same components as those of FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted. Here, different components will be described.

FIG. 1 shows a schematic electrical configuration of a brushless motor driving device. In FIG. 1, an inverter circuit 3 and a position detection circuit 4 correspond to a switching circuit and a position detection means in the present invention, respectively. The driving device 33 and the brushless motor 27
Is mounted on a refrigerator, an air conditioner, or the like, and drives a compressor (not shown).

The driving device 33 is controlled by a control circuit 34 mainly composed of a microcomputer. The control circuit 34 executes an energization control, which will be described later, according to a control program written in a non-volatile memory (not shown) in advance. The function of the control circuit 34 shown in FIG. 1 is shown in the form of a block diagram. That is, the control circuit 34 includes an energization signal generation circuit 35 as an energization signal generation unit, a positive / negative determination circuit 36, a voltage command generation circuit 37, a triangular wave generation circuit 38 as a carrier signal generation circuit, a pulse width modulation circuit 39, and a drive unit. The driving circuit 40 is provided. The drive circuit 40 further includes a switching circuit 41 and a waveform synthesis circuit 42.

The energization signal generation circuit 35 includes the position detection circuit 4
A position signal Pu as position information of the rotor input from the
Performs logical operation on Pv and Pw, and outputs positive (upper arm)
IGBTs 14, 15, 16 corresponding to switching elements
IGBTs 17, 18, and 19 corresponding to the (positive switching element group) and the negative (lower arm) switching element.
Energization signals Dup, D for the (negative side switching element group)
It is configured to generate vp, Dwp, and Dun, Dvn, Dwn.

The position signals Pu, Pv, Pw are also inputted to the positive / negative judgment circuit 36. This positive / negative determination circuit 36 is disclosed in Japanese Patent Application Laid-Open No.
It has the same function as the positive / negative determination means disclosed in Japanese Patent Publication No. That is, the positive / negative determination circuit 36 determines whether the induced voltage of the windings 27u to 27w during the non-conduction period is positive or negative, and outputs the determination result as a determination signal Sp having a high level or a low level. It has become.

The voltage command generation circuit 37 includes a speed detection circuit (not shown) for detecting the speed of the brushless motor 27 based on the position signals Pu, Pv, and Pw, and the control circuit 3
4, a voltage command signal Ss used for pulse width modulation (hereinafter referred to as PWM) is obtained based on the speed command signal fs input from outside.

The pulse width modulation circuit 39 performs pulse width modulation (hereinafter referred to as PWM) by comparing the voltage command signal Ss with the triangular wave carrier signal Sc1 generated by the triangular wave generation circuit 38. Has become. As a result, a pulse width modulation signal Sm (PWM signal Sm), whose level is inverted between a high level and a low level at the coincidence point of the two signals Ss and Sc1, is generated (see FIG. 2). In this case, during a period in which the level of the triangular wave carrier signal Sc1 is equal to or higher than the level of the voltage command signal Ss, the IGBTs 14 to 19, which are on / off controlled by PWM, are in an on state.
That is, "PWM is on".

The switching circuit 41 having the most characteristic feature of the present invention determines which of the IGBTs of the upper arm and the lower arm is to be subjected to the PWM on / off control based on the determination signal Sp. The switching circuit 41 outputs a PWM signal (hereinafter, referred to as a PWM signal) to the upper arm IGBTs 14 to 16.
Upper arm PWM signal Smp) and lower arm IGBT
17 to 19 (hereinafter, lower arm PWM)
(Referred to as a signal Smn) to the waveform synthesizing circuit 42. Here, for example, the IGB of the upper arm
When on / off control is performed on (any of) T14 to T16, the level of the upper arm PWM signal Smp changes to the high level or the low level in synchronization with the turning on or off of the PWM, and the lower arm PWM signal Smn during that time. Is high level constant.

At this time, the switching circuit 41 does not immediately switch the PWM between the upper and lower arms even when the level of the determination signal Sp changes, and thereafter, when the triangular wave carrier signal Sc1 reaches the maximum value (the maximum point), The PWM is switched between the two.

The waveform synthesizing circuit 42 generates the energization signals Dup, Dvp, Dwp, and D from the energization signal generation circuit 35.
un, Dvn, Dwn, the upper arm PWM signal Smp and the lower arm PWM signal Smn, and the drive signals Dup ', Dvp'
, Dwp ', and Dun', Dvn ', Dwn'.

Next, the operation of the present embodiment will be described with reference to FIGS. The control circuit 34 performs energization control based on the 120 ° energization method based on the position signals Pu, Pv, and Pw, and varies the magnitude of the three-phase AC voltage applied to the windings 27u to 27w of the brushless motor 27 by PWM control. Control. In this case, in order to prevent the occurrence of brake torque and the reverse current from flowing to the converter circuit 2 due to the induced voltage of the windings 27u to 27w during the non-energized period having a width of 60 °, the control circuit 34 is provided with the above-mentioned Japanese Unexamined Patent Publication No.
-P between upper and lower arms disclosed in JP-A-322681
WM switching control is performed. Therefore, the switching timing will be described below.

FIG. 2 shows the pulse width modulation circuit 39
Each waveform of the voltage command signal Ss, the triangular wave carrier signal Sc1, and the PWM signal Sm in the WM control is shown. In FIG. 2, the level of the determination signal Sp output from the positive / negative determination circuit 36 is set at time ta, tb, or tc.
In such a case, the switching circuit 41 waits until time td when the triangular wave carrier signal Sc1 reaches the maximum point, and at this time td switches the arm for performing the PWM on / off control between the upper and lower arms.

More specifically, the triangular wave generating circuit 38
For example, a triangular wave carrier signal Sc1 is generated by an up / down counter provided inside the microcomputer. When the up / down counter counts up and reaches an upper limit set value (a value corresponding to the maximum value of the triangular wave carrier signal Sc1), an interrupt signal is generated and, at the same time, a down count is started. After the level of the determination signal Sp is inverted, the switching circuit 41 switches the PWM execution arm when this interrupt signal is generated.

FIG. 3 shows the drive signals Dup 'to
Dwp ', lower arm drive signals Dun' to Dwn ', terminal voltages Vu, Vv, Vw, and neutral point voltage VN of windings 27u to 27w are shown. The times t1 to t5 in this figure correspond to the times t1 to t5 in FIG.
Respectively. In the drive device 1 having the conventional configuration,
Time t2 or time t at which the level of the determination signal Sp is inverted.
Although the PWM was immediately switched between the upper and lower arms in 4, the switching circuit 41 switches at times td1 and td2 when the triangular wave carrier signal Sc1 reaches the maximum point.

As a result, the switching of the PWM between the upper and lower arms is performed at substantially the center of the ON period of the PWM. At this point, the ringing generated at the winding terminal immediately after the PWM changes from off to on is attenuated, and the terminal voltage V
u, Vv, and Vw are set to the level of the DC voltage Vdc or the level of 0V. Therefore, if the PWM is switched between the upper and lower arms at this time, the potential fluctuation of the windings 27u to 27w due to the switching, that is, the fluctuation of the neutral point voltage VN can be suppressed.
Leakage current (leakage current) flowing from 7w to the stator can be reduced.

FIG. 4 shows the upper and lower arm PWM signals S
The waveforms of mp, Smn, the neutral point voltage VN of the windings 27u to 27w, and the leak current are shown. Here, FIG.
4A shows a case where the PWM is switched from the upper arm to the lower arm at the center point of the PWM on period (in the case of the present invention), and FIG.
The case where WM switching is performed is shown. In FIG. 4A, the change in the neutral point voltage VN is small at the time of switching, and the occurrence of a leak current is small. However, in FIG. 4B, the neutral point voltage VN fluctuates greatly at the time of switching, and a large pulse-shaped leak current is generated. are doing.

As described above, according to the present embodiment,
In order to improve the efficiency of the driving device 33 and the brushless motor 27, when the arm for performing the PWM on / off control is switched between the upper and lower arms in accordance with the polarity of the induced voltage of the windings 27u to 27w during the non-energization period, the switching is performed. Is performed at the maximum point of the triangular wave carrier signal Sc1 in the PWM control.

As a result, the PWM is switched between the upper and lower arms substantially at the center of the ON period of the PWM. At this time, the ringing generated at the winding terminal due to the on / off inversion of the PWM is attenuated.
Even if M is switched between the upper and lower arms, a large fluctuation does not occur in the neutral point voltage VN. In addition, P between the upper and lower arms
Since the PWM does not reverse from on to off immediately after the switching of the WM, the ringing generated at the winding terminal does not increase at the time of the on / off reversal after the switching.
Therefore, immediately after the PWM is turned from off to on, the PWM
Leakage current can be reduced more than when switching the target arm, and the user does not feel electricity even when touching exposed metal parts such as refrigerators and air conditioners, and further reduces noise generation I do. Further, since the PWM switching timing can be obtained by an interrupt signal output from an up / down counter inside the microcomputer, it can be easily applied.

(Second Embodiment) Hereinafter, a second embodiment (corresponding to claims 2 to 4) of the present invention will be described with reference to FIGS. In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Different components will be described.

First, in FIG. 5 schematically showing an electric configuration of a driving device of a brushless motor, a control circuit 44 of a driving device 43 has a sawtooth wave generating circuit 38 and a driving circuit 40 in FIG. It comprises a sawtooth wave generating circuit 45 (corresponding to a carrier signal generating circuit according to the present invention) for generating a carrier signal Sc2 and a driving circuit 46 (corresponding to a driving means according to the present invention). Here, the driving circuit 46
Is composed of a switching circuit 47 and a waveform synthesizing circuit 42. The switching circuit 47 receives a voltage command signal Ss from the voltage command generating circuit 37.

The switching circuit 47 generates a reference signal SB having an intermediate level between the level of the voltage command signal Ss and the maximum value of the sawtooth carrier signal Sc2.
And the sawtooth carrier signal Sc2. The switching circuit 47 does not immediately switch the PWM between the upper and lower arms even when the level of the determination signal Sp changes,
When the reference signal SB matches the sawtooth carrier signal Sc2, the PWM is switched between the upper and lower arms. The pulse width modulation circuit 39 turns on the PWM signal Sm during a period in which the level of the sawtooth carrier signal Sc2 is equal to or higher than the level of the voltage command signal Ss.

According to this configuration, as shown in FIG. 6, at the center point (time tg) of the PWM ON period (for example, the period from time tf to time th), the switching circuit 47 switches the PWM between the upper and lower arms. Perform a switch. Therefore, for example, when the level of the determination signal Sp is inverted at times te, tf, etc., the switching circuit 47 waits until time tg, and switches the target arm of the PWM between the upper and lower arms at this time tg. As a result, the same effects as in the first embodiment can be obtained.

Since the level of the voltage command signal Ss changes more slowly than the period of the sawtooth carrier signal Sc2,
The switching circuit 47 does not always need to generate the reference signal SB. For example, at a time tf when the PWM is inverted from off to on, an intermediate level between the level of the voltage command signal Ss at that time and the maximum value of the sawtooth carrier signal Sc2 is obtained, and the intermediate level is supplied to an up counter for generating the sawtooth carrier signal Sc2. The level may be set as the interrupt setting level.

(Other Embodiments) The present invention is not limited to the embodiments described above and shown in the drawings, and the following expansions or modifications are possible. PWM
Although the target arm of the PWM is switched between the upper and lower arms at the center of the ON period, the switching point may be substantially at the center of the ON period.

The pulse width modulation circuit 39 is configured so that PWM is turned on during a period in which the level of the triangular wave carrier signal Sc1 or the sawtooth carrier signal Sc2 is equal to or higher than the level of the voltage command signal Ss. Sc
1. The present invention can also be applied to a case where the PWM is turned on during a period in which the level of Sc2 is equal to or lower than the level of the voltage command signal Ss. In this case, the reference signal SB which is the minimum point of the triangular wave carrier signal Sc1 or the intermediate level between the level of the voltage command signal Ss and the minimum value of the sawtooth carrier signal Sc2 is compared with the sawtooth carrier signal Sc2. At that point, the target arm of the PWM may be switched between the upper and lower arms.

Although the position signals Pu, Pv, Pw are configured to be detected by the position detection circuit 4 in a so-called sensorless manner, they may be detected using a position detection sensor such as a Hall element.

[0049]

As described above, according to the brushless motor driving device of the present invention, the ON period of the pulse width modulation signal and the maximum or minimum point of the triangular wave carrier signal, or the ON period of the pulse width modulation signal And at the center point between the intersection of the voltage command signal and the sawtooth carrier signal and the maximum point or the minimum point of the sawtooth carrier signal, it is configured to switch between the positive side switching element group and the negative side switching element group. The switching element group that performs pulse width modulation at the center point of the ON period of the pulse width modulation signal can be switched between the positive side and the negative side. As a result, the switching is performed while avoiding ringing or the like occurring at the winding terminal immediately after the on / off state of the switching element is inverted, and the potential fluctuation at the neutral point of the winding is further reduced, so that the leakage from the winding is reduced. The current is suppressed more than before.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram of a drive device according to a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining PWM.

FIG. 3 is a waveform diagram of a drive signal, a terminal voltage, and a neutral point voltage of a winding.

FIG. 4 is a waveform diagram of upper and lower arm PWM signals, a neutral point voltage of a winding, and a leak current.

FIG. 5 is a view corresponding to FIG. 1, showing a second embodiment of the present invention;

FIG. 6 is a diagram corresponding to FIG. 2;

FIG. 7 is a diagram corresponding to FIG. 1 showing a conventional configuration.

FIG. 8 is a diagram corresponding to FIG. 3;

FIG. 9 is an explanatory diagram of generation of leakage current.

FIG. 10 is a waveform diagram of ringing appearing in a terminal voltage.

[Explanation of symbols]

In the drawing, 3 is an inverter circuit (switching circuit), 4
Is a position detection circuit (position detection means), and 14 to 16 are IGB
T (positive switching element), 17-19 are IGBT
(Negative side switching element), 27 is a brushless motor,
33 and 43 are drive devices, 35 is an energization signal generation circuit (energization signal generation means), 38 is a triangular wave generation circuit (carrier signal generation circuit), 39 is a pulse width modulation circuit, 40 and 46 are drive circuits (drive means), 45 is a sawtooth wave generation circuit (carrier signal generation circuit).

Claims (4)

[Claims] 1. A switching circuit comprising a positive-side switching element group and a negative-side switching element group for sequentially energizing a plurality of phases of windings of a brushless motor, and a position for detecting position information of a rotor of the brushless motor. Detecting means; energizing signal generating means for obtaining an energizing signal to the windings of the plurality of phases based on the detected position information of the rotor; a carrier signal generating circuit for generating a triangular carrier signal; a voltage command signal; A pulse width modulation circuit that obtains a pulse width modulation signal by comparing with a triangular wave carrier signal; and the positive side switching element group and the negative side switching element group as a switching element group that performs on / off control based on the pulse width modulation signal. A driving device for a brushless motor, comprising: The stage is an ON period of the pulse width modulation signal,
The brushless motor driving device is configured to switch between the positive side switching element group and the negative side switching element group at a maximum point or a minimum point of the triangular wave carrier signal. 2. A switching circuit comprising a positive side switching element group and a negative side switching element group for sequentially energizing a plurality of phase windings of the brushless motor, and a position for detecting position information of a rotor of the brushless motor. Detecting means; energizing signal generating means for obtaining an energizing signal to the windings of the plurality of phases based on the detected position information of the rotor; a carrier signal generating circuit for generating a sawtooth carrier signal; a voltage command signal; A pulse width modulation circuit that compares the sawtooth carrier signal to obtain a pulse width modulation signal; a positive side switching element group and a negative side switching element group as a switching element group that performs on / off control based on the pulse width modulation signal. And a driving means for selectively switching between the driving means and the driving means. , During the ON period of the pulse width modulation signal,
And switching between the positive side switching element group and the negative side switching element group at a center point between an intersection of the voltage command signal and the sawtooth carrier signal and a maximum point or a minimum point of the sawtooth carrier signal. A driving device for a brushless motor, comprising: 3. The driving means generates a reference signal having a median value between a voltage command signal level and a maximum value or a minimum value of a sawtooth carrier signal, and generates a positive signal at an intersection of the reference signal and the sawtooth carrier signal. 3. The brushless motor driving device according to claim 2, wherein the driving device is configured to switch between a side switching element group and a negative switching element group. 4. The brushless motor driving device according to claim 1, wherein the brushless motor drives a compressor mounted on a refrigerator or an air conditioner.