JP3696068B2 - Brushless motor drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brushless motor driving device that performs a commutation operation based on an induced voltage of a brushless motor for a fan having a stator having an N-phase winding and a rotor made of a permanent magnet.
[0002]
[Prior art]
A fan motor used in a refrigerator or the like is generally one in which a load rotates in a refrigerator under a substantially constant condition and is operated at a substantially constant speed, and a brushless motor driven by an inverter circuit is used. The driving device for driving the brushless motor needs to detect the rotational position of the rotor.
[0003]
In the sensorless type, the three-phase brushless motor drive device compares the induced voltage of each phase of the three-phase winding with the reference voltage using a comparator circuit such as a comparator in order to detect the rotational position of the rotor. The timing at which both coincide with each other is detected, and the next energization switching timing is determined based on the time interval of the zero cross points sequentially input from each phase every 60 ° electrical angle of this signal, and the commutation operation is performed. .
[0004]
FIG. 3 shows a timing chart in which overlap energization with an electrical angle of 30 ° is performed when the conventional three-phase brushless motor drive device has a lead angle of 0 °.
In this example, the inside of the drive unit composed of a microcomputer or the like is configured so that 3ch (channel) interrupt can be processed independently for one fan motor, and the position detection signal accompanying the position detection interrupt is input. As a result, the time for various interrupts is determined.
[0005]
That is, upon detecting the time interval (electric angle time shown in FIG. 3, (1)) when the brushless motor rotor has reached the electrical angle of rotation of 60 ° in the past, the drive device detects the position of the rotor with respect to the brushless motor stator. By checking and substituting the calculation of (time interval when the electrical angle reaches 60 °) / 2 for the 30 ° energization switching timing (time of electrical angle 30 °) when commutation interruption is performed 1ch timer is set (electric angle time shown in FIG. 3, (2)). At the same time, the time for permitting the input of the position detection signal to the driving device is calculated as (time of electrical angle 30 °) ÷ 2 + (time of electrical angle 30 °) and set to the timer of 2ch (FIG. 3, ▲ 3) Electrical angle time indicated by ▼). At the same time, overlap energization is started. Thereafter, when the time calculated by the 1ch timer elapses, the driving device switches the phase to be energized by the timer interruption. Thereafter, when the time calculated by the 2ch timer elapses, the driving device permits the position detection interrupt by the timer interrupt. After that, by inputting a position detection signal at an electrical angle of 120 ° (electric angle time shown in FIG. 3, (4)), the drive device again detects the position of the rotor with respect to the stator of the brushless motor, and the position detection interrupt Is prohibited, and the brushless motor is driven by sequentially repeating the process between the next electrical angles of 60 °.
[0006]
[Problems to be solved by the invention]
However, such a conventional configuration has the following problems.
That is, in the above configuration, the driving device used to control the rotation of one fan motor has 1 ch for the timer used for commutation interrupt, 1 ch for the timer used for position detection start interrupt, and the next position detection interrupt. Since one channel is occupied for each process, the driving device needs to perform a process corresponding to a total of three channel interrupts for one fan motor. In particular, when controlling the fan motor installed in the refrigerator, the drive device needs to be controlled at a high speed of about 2000 rpm, and the fan motor for the freezing room, the fan motor for the refrigerating room, and the compressor cooling In order to control a total of three fan motors, it is necessary to be able to process (3 × 3ch) = 9 interrupts, thereby increasing the cost of the drive unit.
[0007]
In addition, especially when used as a device for driving a fan motor in a refrigerator, a 4-pole motor currently used as a standard product has a large noise due to cogging or the like. Use a brushless motor with more poles. In that case, as the number of poles increases, the ratio of the mechanical angle to the electrical angle decreases, and when the motor is rotated at the same number of revolutions, the greater the number of poles, the faster it is necessary to perform the processing performed inside the drive device. That is, it is necessary to configure a drive device that can be processed even in such a situation, and there arises a problem that the cost increases as described above.
[0008]
The present invention has been made in view of the above circumstances, and an object thereof is to eliminate the need to use a large number of interrupted channels (channels) that operate independently even if the number of installed fan motors and the number of poles thereof are increased. Another object of the present invention is to provide an inexpensive brushless motor drive device that can suppress the noise of the fan motor and can be operated stably.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a brushless motor driving apparatus according to claim 1 is a brushless motor for a fan having a stator having an N-phase winding (N is an integer of 2 or more) and a rotor made of a permanent magnet. In the drive device of the brushless motor that controls a plurality of driving,
For each of the plurality of brushless motors
An inverter circuit for energizing the N-phase winding;
A power supply circuit for applying a DC voltage to the inverter circuit;
A reference voltage generating means for generating a reference voltage from a DC voltage of the power supply circuit;
Comparing means for outputting a result of comparing the reference voltage of the reference voltage generating means and the induced voltage of the N-phase winding, and
1ch timer for each of the plurality of brushless motors, each of the plurality of brushless motors, Based on the comparison output of the comparison means, a position detection interrupt is performed so as to detect a plurality of zero cross points of the induced voltage, and the N-phase windings until the next position detection interrupt is started. Energization switching timing Is set by the timer Control means for performing commutation by sequentially interrupting; The control means detects the elapse of a preset time from the energization switching timing by the timer and permits the signal input of the position detection interrupt after the detection time. And has characteristics.
[0010]
According to such a structure, it acts as follows. When two-phase energization is performed on the windings of each phase of the fan brushless motor according to a predetermined energization pattern by the inverter circuit, an induced voltage is generated at the terminal of the winding that is not energized. The comparison means compares the induced voltage with the reference voltage generated by the reference voltage generation means via the power supply circuit. The control means detects the zero crossing point of the induced voltage in the comparison output for each of the plurality so as to reduce the burden of the interrupt processing, determines the energization switching timing until the next position detection interrupt is started, and performs the switching. Flow operation. For example, the zero cross point of the induced voltage of the three-phase winding is detected every 60 ° electrical angle, but the control means detects every plural times (for example, 120 ° electrical angle if 2 times). That is, according to the present driving device, it is possible to reduce the probability that many interrupt processes processed by the control means compete, and to reduce the burden required for the interrupt processing of the control means when driving the inverter circuit. Therefore, when driving a brushless motor for a fan that has a small load fluctuation and maintains a constant rotational frequency, a plurality of brushless motors and a brushless motor having a large number of poles can be driven simultaneously.
[0014]
further, Since the control means does not need to perform processing for calculating the start timing of the position detection interrupt, the load required for the interrupt processing processed by the control means can be reduced, and the brushless motors for a plurality of fans are controlled simultaneously. At this time, it is possible to prevent the start timing of the position detection interrupt of the brushless motor for the fan having a particularly low interrupt priority from being delayed with respect to the position detection timing, and it is possible to control at a higher speed.
[0015]
Further, it is desirable that the control means is configured to set the start timing of the position detection interrupt and the energization switching timing based on a value obtained by averaging a plurality of detection time intervals of the zero cross point of the induced voltage. 2 ).
[0016]
According to such a configuration, when a rotor error is detected, if a sudden error due to noise or the like from the time at which the zero cross point of the induced voltage should be detected is detected, the error is detected so as to be absorbed. The time interval can be calculated, and the start timing of the position detection interrupt and the energization switching timing can be set with high accuracy.
[0017]
Furthermore, the control means can be configured to control the drive of the brushless motor by applying an overlap current. 3 ).
[0018]
According to such a configuration, since energization is gradually switched for each phase, noise caused by the brushless motor for the fan in the refrigerator can be reduced.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 shows the electrical configuration of the present embodiment. In this embodiment, a brushless motor 1a that is a fan motor for a freezer compartment, a brushless motor 1b that is a fan motor for a refrigerator compartment, and a drive device that rotates a brushless motor 1c that is a fan motor for cooling a compressor are shown. The brushless motors 1a, 1b, and 1c have a U-phase, V-phase, and W-phase sensorless brushless motor structure, respectively. 1 includes a power supply circuit (not shown), a control circuit 2 as control means, drive circuits 3a, 3b, 3c, inverter circuits 4a, 4b, 4c, and a voltage dividing circuit as reference voltage generating means. 5a, 5b, 5c and comparison circuits 6a, 6b, 6c as comparison means are mainly configured.
[0020]
Since the configuration other than the control circuit 2 constituting the drive unit for the brushless motors 1a, 1b, and 1c is substantially the same, the configuration of the drive unit for one brushless motor 1a is shown, and the drive unit for the brushless motors 1b and 1c is configured. The same parts of the circuit are denoted by the same reference numerals using different subscripts in the same drawing, and the description of the configuration and operation is omitted. Different parts will be described each time.
[0021]
In the portion for driving the brushless motor 1a of FIG. 1, the power supply circuit is configured by a rectifier circuit (not shown) and the like, generates a DC voltage Vdc of about 15 [V], and generates a drive circuit 3a, an inverter circuit 4a, and a voltage divider. A DC voltage is supplied to the circuit 5a. The power supply circuit also generates a DC voltage Vcc of about 5 [V] and supplies the DC voltage Vcc to the control circuit 2, the drive circuit 3a and the comparison circuit 6a. The capacitors 7a and 7b are connected between the power supply line 8 to which the DC voltage Vdc is applied and GND.
[0022]
The control circuit 2 includes a microcomputer, a ROM, a RAM, and the like, and includes 3 ch timers (not shown) that operate independently and a PWM frequency generation circuit. One PWM frequency generation circuit is provided for each of the brushless motors 1a, 1b, and 1c, and the rotation speed of the brushless motors 1a, 1b, and 1c can be controlled by changing the PWM duty as described later. It is configured. In addition, six output terminals and one input terminal are provided as control terminals for the brushless motor 1a. Similarly, the control terminals for the brushless motors 1b and 1c have six output terminals and one input terminal, respectively.
[0023]
The three output terminals of the control circuit 2 for driving the brushless motor 1a are connected to the respective gate terminals of the MOSFETs 10u, 10v, 10w of the inverter circuit 4a through resistors 9u, 9v, 9w, respectively. The gate terminals of the MOSFETs 10u, 10v, and 10w are all connected to one end of the resistor 12 through the resistors 11u, 11v, and 11w. The other end of the resistor 12 is connected to GND. The other three output terminals of the control circuit 2 for driving the brushless motor 1a are emitter terminals of NPN transistors 14u, 14v, 14w constituting the drive circuit 3a via resistors 13u, 13v, 13w, respectively. Connected to each. The collector terminals of the NPN transistors 14u, 14v, and 14w are connected to one ends of the resistors 15u, 15v, and 15w, and are connected to the gate terminals of the P-channel MOSFETs 16u, 16v, and 16w, respectively. The other ends of the resistors 15u, 15v, 15w are all connected to the power supply line 8 to which the DC voltage Vdc is applied. The base terminals of the NPN transistors 14u, 14v, 14w are connected to the DC voltage Vcc.
[0024]
The inverter circuit 4a includes P-channel MOSFETs 16u, 16v, 16w on the upstream side and N-channel MOSFETs 10u, 10v, 10w on the downstream side between the power supply line 8 and the resistor 12, respectively. A free-wheeling diode 17-22 is connected in parallel, and a three-phase bridge connection is made. The voltage dividing circuit 5 a is configured by connecting resistors 23 and 24 in series between the power supply line 8 and the resistor 12, and a voltage value of Vdc / 2 together with the resistor 12 at a common connection point between the resistor 23 and the resistor 24. A reference voltage Vm is generated.
[0025]
The resistor 12 limits the current flowing through the drive circuit 3a, the voltage dividing circuit 5a, the inverter circuit 4a, and the brushless motor 1a, and functions as an adjustment resistor for the drive circuit 3a and the voltage dividing circuit 5a. It is configured.
[0026]
The three-phase brushless motor 1a that is rotationally driven includes a stator (not shown) around which windings 25u, 25v, and 25w that are three-phase star-connected are wound, and a rotor (not shown) that is provided with permanent magnets. It consists of and. The terminals of the windings 25u, 25v, 25w are connected to the output terminals 26u, 26v, 26w of the respective phases of the inverter circuit 4a.
[0027]
Output terminals 26u, 26v, 26w of the drive circuit output from the inverter circuit 4a are connected to one ends of resistors 27u, 27v, 27w having the same resistance value. The other ends of the resistors 27u, 27v, and 27w are connected in series to one end of the resistor 28, and the other end is connected to the GND via the capacitor 29 and also connected to the non-inverting input terminal of the comparator 30. Yes. As a result, the induced voltage generated in each phase is added and then stepped down as appropriate. Further, the steep induced voltage change generated in the windings 25u, 25v, and 25w is smoothed. The inverting input terminal of the comparator 30 is connected to a common connection point between the resistor 23 and the resistor 24 in the voltage dividing circuit 5 a and is connected to GND via the capacitor 31. The capacitor 31 is provided in order to protect the capacitor 31 from destruction due to a sudden change in the voltage input to the comparator 30. The comparison circuit 6a includes resistors 27u, 27v, and 27w, a resistor 28, a capacitor 29, a comparator 30, and a capacitor 31.
[0028]
The output terminal of the comparator 30 is connected to the input terminal of the control circuit 2 via a pull-up resistor 32 connected in parallel to the DC voltage Vcc. The power supply input terminal of the comparator 30 is connected to the DC voltage Vcc, and the GND terminal is connected to GND. When the power supply circuit is activated, the comparator 30 is also activated.
[0029]
The drive circuits 3b and 3c, voltage dividing circuits 5b and 5c, inverter circuits 4b and 4c, brushless motors 1b and 1c, and comparison circuits 6b and 6c for driving the brushless motors 1b and 1c, respectively, drive the brushless motor 1a. Therefore, the description thereof is omitted, and the connections to the DC voltages Vcc, Vdc, and GND for the respective constituent circuits are omitted from the drawings.
[0030]
Next, the operation of this embodiment will be described with reference to FIG.
FIG. 2 shows a timing chart of the present embodiment. In this timing chart, a method in which the advance angle control is not performed is used, that is, an example in which the advance angle is 0 ° in this case and 30 ° section overlap energization is performed. It is assumed that the position of the rotor is detected at the timing of A in FIG. 2 when the driving device is driving the brushless motor.
[0031]
For simplification of description, first, the case where each MOSFET 16u, 16v, 16w, 10u, 10v, 10w constituting the inverter circuit 4a is turned on and the case where it is turned off will be described, and then the position detection of the brushless motor 1a will be performed. A description will be given along the timing chart.
[0032]
The operation of the P-channel type MOSFETs 16u, 16v, 16w of the inverter circuit 4a will be described. When the control circuit 2 outputs the voltage of the DC voltage Vcc from the output terminal via the resistors 13u, 13v, and 13w, the NPN transistors 14u, 14v, and 14w are turned off because the base current does not flow, and the resistors 15u and 15v are turned off. , 15w, and the gate voltages of the P-channel type MOSFETs 16u, 16v, 16w are substantially Vdc. That is, in this case, each MOSFET 16u, 16v, 16w is turned off.
[0033]
When the control circuit 2 outputs the GND voltage from its output terminal via the resistors 13u, 13v, and 13w, the NPN transistors 14u, 14v, and 14w are turned on when a base current flows, and the MOSFETs 16u, 16v, and 16w are turned on. The gate voltage is substantially equal to the GND voltage. That is, in this case, the MOSFETs 16u, 16v, and 16w are turned on.
[0034]
The operation of the N-channel MOSFETs 10u, 10v, 10w of the inverter circuit 4a will be described. When the control circuit 2 outputs the voltage of the DC voltage Vcc from the output terminal via the resistors 9u, 9v, and 9w, the gate voltage of each of the N-channel MOSFETs 10u, 10v, and 10w uses the DC voltage Vcc as the resistors 9u, The voltage is divided by 9v, 9w, resistors 11u, 11v, 11w, and resistor 12. By this divided voltage, each of the N-channel MOSFETs 10u, 10v, 10w is turned on.
[0035]
When the control circuit 2 outputs the GND voltage from the output terminal via the resistors 9u, 9v, and 9w, the gate voltages of the N-channel MOSFETs 10u, 10v, and 10w substantially coincide with the GND voltage. That is, the MOSFETs 10u, 10v, 10w are turned off. That is, the upstream side MOSFETs 16u, 16v, and 16w are driven by Lo active, and the downstream side MOSFETs 10u, 10v, and 10w are driven by Hi active.
[0036]
That is, the control circuit 2 outputs PWM signals to the six output terminals, whereby the MOSFETs 16u, 16v, 16w, 10u, 10v, and 10w are repeatedly turned on and turned off, and are subjected to PWM control. As described above, the PWM frequency generation circuit (not shown) formed in the control circuit 2 changes the PWM duty and energizes the windings 25u, 25v, and 25w of the brushless motor 1a through the drive circuit 3a and the inverter circuit 4a. The current is changed to control the rotational speed of the rotor of the brushless motor 1a.
[0037]
At this time, the windings 25u, 25v, and 25w generate an induced voltage, and the comparison circuit 6a adds the induced voltage generated in each phase and then steps down appropriately to compare with the reference voltage Vm. Output to the input terminal. This is a position signal to be described later.
[0038]
Next, the actual operation of the driving apparatus will be described using the timing chart shown in FIG. The timing chart of FIG. 2 shows a schematic waveform diagram when driving the brushless motor 1a, and omits the actually driven PWM waveform.
2A to 2C show changes with time of the respective terminal voltages Vu, Vv, Vw of the windings 25u, 25v, 25w of the brushless motor 1a. 2D to 2I show the states of the MOSFETs 16u, 10u, 16v, 10v, 16w, and 10w based on the output signals from the control circuit, respectively, and are PWM-driven when “ON”. (This state is hereinafter referred to as “on state”. Conversely, when it is “off”, PWM drive is not performed. In this case, it is referred to as “off state”). In the ON state, the PWM frequency generation circuit in the control circuit 2 generates PWM signals for driving the MOSFETs 16u, 10u, 16v, 10v, 16w, and 10w so as to be synchronized. FIG. 2 (j) shows a position signal input to the input terminal of the control circuit 2. The 30 ° section overlap energization in the present embodiment refers to an energization method in which the on-state sections of the MOSFET 16u and the MOSFET 16v shown in FIGS. 2D and 2F overlap each other by 30 °, for example. In this 30 ° section, the windings 25u, 25v are energized to the winding 25w (the same applies to the U phase, V phase, and W phase).
[0039]
First, when starting the brushless motor 1a, the windings 25u, 25v, and 25w do not generate an induced voltage when stopped, and therefore the position signal waveform of FIG. 2 (j) does not appear. The control circuit 2 cannot grasp the position of the electrical angle of the rotor of the brushless motor 1a. The control circuit 2 forcibly performs a commutation operation at a certain time period using a certain arbitrary energization pattern recorded in advance in the ROM in the control circuit 2. As a result, an output such as the position signal of FIG. 2 can be obtained.
[0040]
After that, when the induced voltage is detected by gradually rotating the rotor of the brushless motor 1a, the control circuit 2 obtains a detection time interval from that point and uses it to determine the timing of the next commutation operation and position detection. At this time, the PWM frequency generation circuit in the control circuit 2 increases the PWM duty at a predetermined rate per unit time, and increases the rotational speed of the rotor of the brushless motor 1a. Thereafter, it is assumed that interrupt input of a signal to the input terminal of the control circuit 2 for position detection is permitted in the control circuit 2 at a time point immediately before A in FIG. Further, it is assumed that an energization pattern indicating the order in which commutation is performed on the drive circuit 3a and the inverter circuit 4a is stored in advance in a ROM (not shown) in the control circuit 2.
[0041]
When the rotor of the brushless motor 1a is rotating, the induced voltage of the terminal voltage Vu gradually increases and exceeds the DC voltage Vdc / 2, whereby the control circuit 2 outputs a position signal output from the comparison circuit 6a. When the PWM waveform is detected (FIG. 2 (j), A), the terminal voltage reaching the reference voltage Vm from the state in which each MOSFET 16u, 10u, 16v, 10v, 16w, 10w is energized is a U-phase voltage. Detect that there is. Inside the control circuit 2, interrupt input of a signal to the input terminal for position detection is prohibited. Thereafter, a PWM signal is generated from a PWM frequency generation circuit (not shown) that is configured inside, and the state of the output terminal corresponding to the MOSFET 16u of the control circuit 2 is changed (FIG. 2 (d), A). That is, in this case, the MOSFET 16u is turned on, and a PWM waveform with an amplitude up to the maximum voltage Vdc appears as the terminal voltage Vu. At this time, the detection time interval Tw0 of the previous electrical angle of 120 ° is calculated. On the other hand, the control circuit 2 sets a time Ta for setting the next energization switching timing,
Ta ← Tw0 ÷ 4 (1)
Is set to the timer in the control circuit 2 from the substitution formula. After that, when the rotor of the brushless motor 1a rotates about 30 ° in electrical angle from the point A in FIG. 2, the control circuit 2 detects that the time Ta has elapsed by the timer. Thereafter, the MOSFET 16w is changed from the on state to the off state (FIG. 2 (h), B). Thereafter, the control circuit 2 resets the timer and sets a time Tb for setting the next energization switching timing,
Tb ← Ta (2)
Is set to the timer in the control circuit 2 from the substitution formula. Similarly, when the rotor of the brushless motor 1a rotates about 30 ° in electrical angle from the point B in FIG. 2, the control circuit 2 detects that the time Tb has elapsed by the timer. Thereafter, the MOSFET 10w is changed from the off state to the on state (FIG. 2 (i), C). Similarly, a time Tc for resetting the timer and setting the next energization switching timing,
Tc ← Tb (3)
The timer in the control circuit 2 is set from the equation Similarly, when the rotor of the brushless motor 1a rotates about 30 degrees in electrical angle from the time point C in FIG. 2, the control circuit 2 detects that the time Tc has elapsed by the timer. The control circuit 2 switches the MOSFET 10v from the on state to the off state (FIG. 2 (g), D). Thereafter, the timer T is reset, and the time Td until the start of the position detection interrupt input to the input terminal of the control circuit 2 is started.
Td ← Tc ÷ 2 (4)
The timer in the control circuit 2 is set from the following equation. When the rotor of the brushless motor 1a rotates about 15 ° in electrical angle from the time point D in FIG. 2, the control circuit 2 detects that the time Td has elapsed by the timer. Thereafter, the control circuit 2 permits an interrupt input of a signal to the input terminal for position detection, and starts time measurement (FIG. 2, E). After that, when the control circuit 2 detects that the position signal is input from the comparison circuit 5 to the input terminal of the control circuit 2 (FIG. 2 (j), F), the time measurement described above is stopped, and the time Te in between is stopped. Remember. At this time, the control circuit 2 detects that the terminal voltage reaching the reference voltage Vm is a V-phase voltage from the state in which the MOSFETs 16u, 10u, 16v, 10v, 16w, and 10w are energized. The control circuit 2 prohibits permission of interrupt input for position detection, and then sets the detection time interval Tw to
Tw ← Ta + Tb + Tc + Td + Te (5)
It calculates from the formula of and substitutes newly. In the next detection time interval Tw (FIG. 2, F → G) of the electrical angle of 120 °, the control circuit 2 uses the detection time interval Tw to set the time Ta2, Tb2, Tc2 and The time Td2 until the position detection interrupt permission is started is calculated, and in the same manner as described above, the MOSFET 16u (on state to off state after time Ta2 elapses), MOSFET 10u (off state to off state after time Tb2 elapses), MOSFET 10w The position of the rotor of the brushless motor is detected at the time indicated by G in FIG. 2 by repeating commutation with respect to (from the on state to the off state after the elapse of time Tc2). Similarly, the commutation operation can be performed for the brushless motors 1b and 1c by timers provided in separate control circuits 2 (not shown).
[0042]
As described above, according to the above-described embodiment, the times Ta, Tb, Tc for setting the energization switching timing from the previous detection time interval Tw0 and the time Td until the start of the position detection interrupt permission are determined. In order to control the driving of the three brushless motors 1a, 1b, and 1c, it is only necessary to use a 1ch interrupt as a timer in the control circuit 2 that drives the brushless motor 1a. Can be realized by using a 3ch timer. Therefore, it is not necessary to use a large number of channels (channels) of interrupts that operate independently even if the number of installed fan motors and the number of poles are increased. Further, since energization is gradually switched for each phase, noise caused by cogging of a brushless motor for a fan can be reduced, and stable operation can be achieved.
[0043]
The present invention is not limited to the embodiment described above and shown in the drawings, and can be expanded or changed as follows.
In the above-described embodiment, the position detection is performed at the time points A, F, and G in FIG. 2, but when the brushless motor 1 a is started, for example, up to a relatively low rotational speed of 600 rpm or less, Position detection may also be performed at time C in FIG. That is, the control circuit 2 sets the start timing of the position detection interrupt between B and C in FIG. 2 at the time point B in FIG. 2, and the PWM signal is input from the comparison circuit 5 to the input terminal of the control circuit 2. The time point (FIG. 2 (j), C) when no input is detected from the existing state is detected. This indicates that when the brushless motor 1a is started, the position of the brushless motor 1a is detected at an electrical angle of 60 ° from the time point A in FIG. 2 because the rotational speed of the rotor of the brushless motor 1a is low. Since the rotational speed of the rotor is low, the detection time interval Tw is increased accordingly. Since the zero crossing point of the induced voltage is detected every electrical angle of 60 °, the burden on the control circuit 2 due to interruption is not increased. Thereby, the position detection accuracy at the time of starting can be improved without impairing the effects of the above-described embodiment.
[0044]
In the above-described embodiment, the time Td until the start of the permission for the position detection interrupt is obtained from the equation (4). This time Td is a time set in advance in the ROM or RAM in the control circuit 2, For example, it can be set after a certain time of 200 μs. This is to reduce the burden of the interrupt processing at the time point D in FIG. The predetermined time is determined in advance by taking into account the time delayed by the interruption of all fan brushless motors driven by the control circuit 2 (for example, one interruption is 30 μs) and the time for performing the commutation operation. It is desirable. Further, in the period of position detection from A to F in FIG. 2, after the commutation operation at the point of time D in FIG. 2 at the maximum use rotational speed of the brushless motor 1a, position detection is performed in an electrical angle range of, for example, 20 °. It is desirable to set the start timing to start as a constant timing. As a result, it is possible to reduce the burden required for the interrupt processing performed by the control circuit 2, and when performing simultaneous rotation control of the brushless motors for a plurality of fans, the position detection of the brushless motor for the fans having a particularly low interrupt priority. It is possible to reduce the delay of the interrupt start timing with respect to the position detection timing as much as possible, and it is possible to control at higher speed.
[0045]
Furthermore, in the description of the above-described embodiment, the detection time interval Tw2 is determined at time G in FIG.
Tw2 ← Ta2 + Tb2 + Tc2 + Td2 + Te2 (6)
And stored in a RAM (not shown) in the control circuit 2, and the detection time interval Twz is
Twz ← (Tw + Tw2) ÷ 2 (7)
It is also possible to calculate the energization switching timing between G and H in FIG. 2 and the start timing of the position detection interrupt using the detection time interval Twz using the averaged values as shown in FIG. That is, when an error from the time at which the detection time interval Tw2 should be detected occurs due to sudden noise or the like, the error of Tw2 can be absorbed by calculating the detection time interval Twz. As a result, the start timing of the position detection interrupt and the energization switching timing can be set with high accuracy.
[0046]
The brushless motors 1a, 1b, and 1c for fans are not limited to fan motors for refrigerators, and can be applied to commonly used fan motors. Further, the number of brushless motors driven by the driving device is not limited to three, but may be two or four or more.
[0047]
【The invention's effect】
As described above, according to the brushless motor driving apparatus of the present invention, the following effects can be obtained.
That is, according to the first aspect of the present invention, it is possible to reduce the probability that a large number of interrupt processes processed by the control means compete, and to reduce the burden required for the interrupt processing of the control means when driving the inverter circuit. . Therefore, especially when driving a brushless motor for a fan that has a low load fluctuation and maintains a constant rotation speed, the number of interrupts that operate independently even if the number of installed fan motors or the number of poles is increased ( Therefore, it is possible to provide an inexpensive brushless motor driving apparatus that can be operated stably without using a channel.
[0049]
More In addition, Since the control means does not need to perform processing for calculating the start timing of the position detection interrupt, the burden required for the interrupt processing processed by the control means can be reduced, and the brushless motors for a plurality of fans can be controlled simultaneously. In particular, the start timing of the position detection interrupt of a brushless motor for a fan with a particularly low interrupt priority can be prevented from being delayed from the position detection timing, and can be controlled at a higher speed. .
[0050]
Claim 2 According to the described invention, when a sudden error due to noise or the like from the time at which the zero-cross point of the induced voltage should be detected at the time of detecting the rotor position, the detection time is absorbed so as to absorb the error. The interval can be calculated, and the start timing of the position detection interrupt and the energization switching timing can be set with high accuracy.
Claim 3 According to the described invention, since the energization is gradually switched for each phase, noise to the brushless motor for the fan in the refrigerator can be reduced.
[Brief description of the drawings]
FIG. 1 is an electrical configuration diagram showing an embodiment of the present invention.
FIG. 2 is a timing chart showing changes in each signal accompanying driving of a brushless motor.
FIG. 3 is a diagram corresponding to FIG.
[Explanation of symbols]
2 is a control circuit (control means), 4a, 4b and 4c are inverter circuits, 5a, 5b and 5c are voltage dividing circuits (reference voltage generation means), 6a, 6b and 6c are comparison circuits (comparison means), 25u and 25v. , 25w are windings.

Claims (3)

In a brushless motor driving apparatus for controlling driving of a plurality of brushless motors for a fan having a stator having N-phase (N is an integer of 2 or more) windings and a rotor made of permanent magnets,
For each of the plurality of brushless motors
An inverter circuit for energizing the N-phase winding;
A power supply circuit for applying a DC voltage to the inverter circuit;
A reference voltage generating means for generating a reference voltage from a DC voltage of the power supply circuit;
Comparing means for outputting a result of comparing the reference voltage of the reference voltage generating means and the induced voltage of the N-phase winding, and
A timer that operates independently for each of the plurality of brushless motors is provided for each channel, and for each of the plurality of brushless motors, the zero-cross point of the induced voltage is detected every plurality of times based on the comparison output of the comparison unit. performs position detection interrupt, control for performing commutation operation by performing the setting to sequentially interrupt the energization switching timing the timer to N phase windings between until the start of the next position detection interrupt Means ,
Said control means drives the brushless motor, wherein a permission child a lapse of a preset time the signal input of the position detection interruption detected after the detection time by the timer from the energization switching timing. The control means sets the start timing of the position detection interrupt and the energization switching timing based on a value obtained by averaging a plurality of detection time intervals of the zero cross point of the induced voltage. brushless motor drive device of. The brushless motor drive device according to claim 1, wherein the control unit performs drive control on the brushless motor by applying an overlap current .

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