JP5996188B2 - DC brushless motor drive circuit - Google Patents

Description

  The present invention relates to a DC brushless motor drive circuit, and more particularly, to a circuit for reducing power consumption.

As this type of conventional device, for example, a DC brushless motor driving circuit used for an axial fan motor for cooling equipment is well known, and FIG. 5 shows an example of the circuit configuration. The conventional DC brushless motor driving circuit will be described below with reference to FIG.
The circuit shown in FIG. 5 includes a hall amplifier A that amplifies a sine wave voltage signal output by the hall element H according to the rotor position of the motor, and a winding of the motor M based on the output signal of the hall amplifier A. A driver that supplies a drive current is a main component, and is generally referred to as a linear drive method.

In particular, in the case of linear driving of a single-phase brushless motor often used for a fan motor or the like, the gain of the Hall amplifier A is calculated by the fact that the output waveform of the Hall element H is basically a sine wave. A trapezoidal wave obtained by setting so as to obtain a sufficiently high voltage amplitude of several times is generated as a winding drive signal.
The reason why the winding drive signal is a trapezoidal wave is that the inrush current generated when a rectangular wave is applied to the winding of the motor M does not contribute to the torque generation of the motor M, resulting in vibration, noise and heat generation. This is because it is supposed to cause such as.

Since this circuit can be realized relatively easily, it is often applied to a single-phase brushless motor used at a power supply voltage of about 5V to 12V, and particularly used for a cooling fan motor or the like.
Such circuits are often made into semiconductor integrated circuits (ICs) for miniaturization, including power devices for driving motor windings, which are housed in plastic mold packages of several millimeters to several tens of millimeters square. It has been.

  By the way, the current and voltage for driving the motor winding are limited by the heat generated by the semiconductor chip. The heat generated in the semiconductor chip is mainly due to the loss due to the ON resistance of the power device for winding drive, and the generated loss is determined by the product of (square of operating current) and (ON resistance). The device has a large area, and its size almost determines the current capability of the IC. Since a package of about 5 mm square has an allowable loss of about 400 mw, there are many ICs that have a rated condition of winding current of about 300 mA when the power supply voltage is 5 V and about 150 mA when the power supply voltage is 12 V.

In recent years, motors used in home appliances, industrial facilities, etc. tend to require a motor having the same size as a conventional axial fan motor of 5V or 12V and a higher operating voltage of 24V or 48V. It is in.
Since the cooling capacity, that is, the output of the motor depends on the product of (winding applied voltage) and (winding current), if the winding voltage can be increased, the driving current can be reduced, and the heat generated by the ON resistance is reduced. be able to.

However, conversely, the loss of the power supply circuit for driving the Hall element indispensable for driving the brushless motor, that is, the so-called Hall bias cannot be ignored. In the case of an indium antimony alloy type hall element for driving a motor, the applied voltage is about 1.5 V and the operating current is 1 to 3 mA. However, in consideration of noise margin and temperature characteristics, a current of 5 mA or more may flow. .
For example, as shown in Non-Patent Documents 1 and 2, the Hall bias is often built in the IC. Conventionally, most of the hall bias outputs a dropper type fixed voltage, and the loss is the product of (operating voltage-output voltage) and (hall current). Therefore, when this is applied to an operating circuit of 48V, Even at a current of 3 mA, the loss is about 140 mW. Therefore, in the vicinity of the upper limit of the operating temperature range of the IC, the package of the above-mentioned size may occupy more than half of the allowable loss.

Therefore, it is necessary to reduce the loss due to the Hall bias in order to improve the motor drive capability of the IC.
As a loss reduction method for that purpose, a method of intermittently (chopping) the Hall bias has been proposed and put to practical use, and disclosed in, for example, Patent Document 1 and Non-Patent Document 3. The method disclosed in Non-Patent Document 4 is a method of simultaneously chopping the power supply of the circuit receiving the Hall signal in addition to the Hall element. In this case, the above-described effect can be expected. .

JP 2007-318352 A (page 3-4, FIG. 1 to FIG. 2) New Japan Radio Co., Ltd. Product Catalog NJU7360 Sanyo Electric Co., Ltd. Product Catalog LA6583T Asahi Kasei Microdevices Corporation Product Catalog EM-1712

However, the methods disclosed in the above-mentioned Patent Document 1 and Non-Patent Document 3 mainly focus on providing a switch in the bias circuit and performing chopping driving in order to suppress the power consumption of the Hall element. When the Hall element is used for detecting the rotor position of the motor, another problem arises.
That is, in the case of the linear drive of the single-phase DC brushless motor described above, when the Hall element bias is chopped, the chopping signal is naturally superimposed on the Hall signal and the motor drive signal. Like the inrush current described above, the chopping signal component of such a motor drive signal causes a current that does not contribute to motor torque generation to flow through the windings, generating motor vibration, noise, heat generation, etc., and reducing efficiency. Cause inconvenience.

  The present invention has been made in view of the above circumstances, and is a DC brushless motor drive capable of suppressing power consumption by a Hall bias circuit, removing a harmonic signal, and supplying a drive signal suitable for linear drive. A circuit is provided.

In order to achieve the above object of the present invention, a DC brushless motor driving circuit according to the present invention includes:
A DC brushless motor drive circuit configured to be capable of rotational drive control of a DC brushless motor based on an output signal of a Hall element,
A bias power source configured to be capable of intermittently energizing the Hall element according to a signal input from the outside;
A hall amplifier that amplifies an output signal of the hall element and outputs a phase signal corresponding to a rotor position of the DC brushless motor;
Based on the output signal of the hall amplifier, the signal is synchronized with the rotor rotation, and a signal having a frequency obtained by multiplying the phase signal of the rotor rotation can be output as a signal for interrupting the energization current to the bias power source. A rotational speed signal generator,
The hall amplifier has a cut-off frequency that is approximately one tenth with respect to the maximum frequency of the output signal of the rotational speed signal generator.

According to the present invention, by configuring the Hall amplifier to have a phase compensation function, it is possible to reduce the power loss caused by the chopping of the Hall bias circuit and to improve the output current capability of the small package IC. There is an effect.
In particular, in the configuration in which the output signal of the rotation speed signal generator is used for chopping, a simple configuration can be realized, a configuration in which the oscillator in the IC is omitted can be realized, and a cheaper DC brushless motor drive circuit can be realized. Can be provided.
Further, high frequency noise due to chopping can be removed by phase compensation of the hall amplifier, so that noise and vibration generated in the motor due to chopping can be suppressed.

It is a block diagram which shows the 1st structural example of the DC brushless motor drive circuit in embodiment of this invention. It is a block diagram which shows the 2nd structural example of the DC brushless motor drive circuit in embodiment of this invention. It is a block diagram which shows the 3rd structural example of the DC brushless motor drive circuit in embodiment of this invention. FIG. 4A is a timing diagram showing timings of signals of main parts of the DC brushless motor driving circuit shown in FIG. 1, and FIG. 4A is a timing diagram showing timings of chopping signals for chopping the Hall bias, and FIG. ) Is the timing diagram of the Hall signal when DC is applied, FIG. 4C is the timing diagram of the drive signal when DC is applied as the Hall bias, and FIG. 4D is the Hall when the chopped Hall bias is applied. FIG. 4E is a timing diagram of a drive signal when a chopped hall signal is used. It is a block diagram which shows the example of 1 structure of the conventional DC brushless motor drive circuit.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
First, a first configuration example of the DC brushless motor drive circuit according to the embodiment of the present invention will be described with reference to FIG.
The DC brushless motor drive circuit in the first configuration example includes a bias power source (indicated as “POW” in FIG. 1) 1, an oscillator (indicated as “OSC” in FIG. 1) 2, a hall amplifier 3, and the like. , And a motor driving driver (indicated as “DRV” in FIG. 1) 4.

The bias power source 1 is a power source for supplying a current to the Hall element (indicated as “H” in FIG. 1) 5. In the embodiment of the present invention, in particular, in synchronization with a signal input from the outside. The output current can be interrupted. In FIG. 1, this current intermittent function is represented by a switch element.
The oscillator 2 generates a signal for interrupting the current of the bias power source 1 described above, and its oscillation frequency is sufficiently higher than a general motor rotation speed of several thousand rpm, and from an audible frequency range. It is set to about 20 to 60 kHz in the upper region. The reason why the frequency is sufficiently higher than the motor rotational speed is to avoid this because the motor rotational speed fluctuates when the motor rotational speed is close to the chopping frequency and the motor rotational speed fluctuates.

In order to surely avoid such an influence, it is desirable that the oscillation frequency of the oscillator 2 is 10 times or more the motor rotation speed. The output signal of the oscillator 2 is a square wave signal as shown in FIG.
Therefore, when the bias power supply 1 is turned on by the output signal of the oscillator 2, the specified voltage of the bias power supply 1 is applied to the Hall element 5, while the bias power supply 1 is applied by the output signal of the oscillator 2. When turned off, 0 V is applied to the Hall element 5.

Between the output stage of the bias power source 1 and the ground, a Hall element 5 and a bias adjusting resistor 5a are connected in series in this order from the bias power source 1 side. It is applied to the amplifier 3.
The hall amplifier 3 includes an operational amplifier 11, a feedback resistor 12, an input resistor 13, and a capacitor 14.
That is, the feedback resistor 12 is connected between the output terminal of the operational amplifier 11 and one of the two input terminals, and the input of the Hall element 5 is connected to the one input terminal via the input resistor 13. One output terminal is connected.

The other output terminal of the Hall element 5 is connected to the other input terminal of the operational amplifier 11. Further, a capacitor 14 is connected between the connection point between the Hall element 5 and the input resistor 13 and the other input terminal of the operational amplifier 11.
In the Hall amplifier 3, the capacitor 14, the input resistor 13, and the feedback resistor 12 constitute a phase compensation circuit using an RC primary filter.
In the embodiment of the present invention, 100 to several kΩ is selected for the input resistor 13 from the relationship with the matching with the output resistance of the Hall element 5, and therefore the capacitor 14 has a value of about 0.1 to 1 μF. By setting this, the pole can be configured at several hundred Hz to several kHz.

The motor drive driver 4 is configured to generate and output an energization current to be passed through the windings of the motor 50 based on the output signal of the hall amplifier 3, and its circuit configuration is basically the same as that of the prior art. belongs to.
Each part of the circuit is supplied with a power supply voltage necessary for operation by a power supply 51.
Here, the reason why the phase compensation circuit is required in the Hall amplifier 3 will be described.
First, conventionally, it has been common to apply a constant bias to a Hall element. When a constant voltage bias is applied, the internal resistance value changes according to the magnetic field applied to the Hall element. Therefore, when used for motor position detection, as an output signal (Hall signal) of the Hall element, for example, FIG. As is well known, the Hall element is arranged so that a sine wave voltage is output as shown in FIG. In this case, a so-called trapezoidal wave signal as shown in FIG. 4C is normally applied to the motor as a drive signal.

On the other hand, when the bias of the Hall element 5 is interrupted, a similar voltage change is superimposed on the output of the Hall element 5 as shown in FIG. 4D. As a result, the output of the motor driving driver 4 is As shown in FIG. 4E, the chopping frequency is a signal modulated by the output signal of the Hall element 5.
However, when the amplitude of the superimposed chopping signal component is increased, the power applied to the windings of the motor 50 is reduced, which causes a reduction in the rotational speed of the motor 50 and a higher frequency than the motor rotational speed. The component does not contribute to the torque generation of the motor 50, most of which causes copper loss, leading to deterioration of the operation efficiency of the motor 50 and heat generation.
Therefore, by providing the Hall amplifier 3 with a phase compensation function so as to have a cut-off frequency that is approximately 10 times or more that of a so-called FG (Frequency Generator) signal generated by steady rotation, a high-frequency component of the Hall signal due to chopping is provided. To eliminate the above-mentioned inconveniences.

  For example, the number of rotations of a cooling small axial flow fan is often in the range of 1500 to 6000 rpm, and it is converted to an FG signal frequency generated in a single-phase fan generally at a cycle twice the mechanical rotation number. Since there are many about 200 Hz, a value higher than about 2 kHz is appropriate for the cutoff frequency. For this reason, in order to remove the 20 to 60 kHz component generated at the chopping frequency described above, it is appropriate to have a cutoff frequency of about 2 to 6 kHz, which is approximately one tenth.

Note that the configuration of the phase compensation circuit is not limited to the configuration shown in FIG. 1, and in addition, for example, a method of applying mirror compensation to a differential amplifier that constitutes a Hall amplifier can be employed. In this case, a capacitor of several tens of pF that can be configured on an IC chip has the same effect as the phase compensation in the above-described embodiment of the present invention, so that an IC can be built in and the number of components can be reduced.
In the case of the configuration example shown in FIG. 1, stable motor operation can be ensured even if the drive duty is 40% or less for the Hall element 5.
When applied to a motor drive circuit with a 48V power supply, the power transistor area is reduced by about 15% from the margin of allowable power consumption, or when a power transistor of the same size is used, about 15% of the allowable current. Can be expanded.

Next, a second configuration example will be described with reference to FIG.
The same components as those in the first configuration example shown in FIG. 1 are denoted by the same reference numerals, detailed description thereof is omitted, and different points are mainly described below.
This second configuration example has a configuration in which a rotation speed signal generator 6 is provided instead of the oscillator 2 in the first configuration example shown in FIG.
The rotation speed signal generator 6 has a signal converter 6a and a multiplier 6b.

The signal converter 6a is configured to convert and output the analog output signal (phase signal) of the hall amplifier 3 into a logic signal having the same repetition period, and its output is input to the multiplier 6b. It has become.
The multiplier 6b multiplies the repetitive logic signal input via the signal converter 6a to generate and output a chopping signal having a desired frequency, and its output signal is biased like the oscillator 2 in FIG. The power source 1 is used for intermittent output current.

The drive circuit of the small axial flow fan is mostly an IC, and many ICs are provided with a rotation speed signal generation circuit. Therefore, the configuration as in the second configuration example is used. It is convenient to take.
From the viewpoint of avoiding interference between the motor rotation and the chopping frequency, the previous multiplier 6b needs to multiply at least eight times the input rotation number signal, and considering the switching loss of the bias power supply 1, The multiplier is set so as to be about 20 kHz to 200 kHz.

  The oscillator 2 of the first configuration example shown in FIG. 1 requires, for example, a dozen flip-flop circuits and a capacitor serving as a time constant reference when generating a signal of about 20 kHz. By using the rotation speed signal generator 6 in place of 2, the oscillator 2 having the above-described configuration can be omitted, and the chip size can be further reduced.

Next, a third configuration example will be described with reference to FIG.
In addition, about the same component as the component in each configuration example shown in FIG. 1 or FIG. explain.
In the third configuration example, in particular, a circuit for avoiding instability when the motor is started is added to the first configuration example shown in FIG.
That is, the third configuration example is based on the first configuration example shown in FIG. 1, and further includes a power supply voltage / startup detection circuit (indicated as “P-DET” in FIG. 3) 7 and a rotation. A number signal generator 6, a counter (indicated as “COUNT” in FIG. 3) 8, and an OR circuit 9 are provided.

The counter 8 is configured to output a signal corresponding to the logical value High when a predetermined number of output signals from the rotational speed signal generator 6 are counted. By this output signal, the logical sum circuit 9 is output. The signal of the oscillator 2 is output from the above.
For example, the bias power supply 1 functions so as to be chopped by the output of the oscillator 2 after rotating about 10 rotations after starting.

The power supply voltage / startup detection circuit 7 outputs a startup detection signal to the motor drive driver 4 when the power supply voltage is normally applied by the power supply 51 to enable the motor drive driver 4 to operate. Is configured to output a reset signal to the counter 8 when it falls below a set value.
By providing the power supply voltage / startup detection circuit 7, when the power supply voltage drops below the set value, the counter 8 is reset to ensure stable operation even when restarting due to an instantaneous power supply voltage drop. The Rukoto.

  The present invention can be applied to a brushless motor in which low power consumption of a Hall bias circuit is desired.

DESCRIPTION OF SYMBOLS 1 ... Bias power supply 2 ... Oscillator 3 ... Hall amplifier 4 ... Motor drive driver 5 ... Hall element 6 ... Speed signal generator 7 ... Power supply voltage / startup detection circuit 9 ... OR circuit

Claims (3)

A DC brushless motor drive circuit configured to be capable of rotational drive control of a DC brushless motor based on an output signal of a Hall element,
A bias power source configured to be capable of intermittently energizing the Hall element according to a signal input from the outside;
A hall amplifier that amplifies an output signal of the hall element and outputs a phase signal corresponding to a rotor position of the DC brushless motor;
Based on the output signal of the hall amplifier, the signal is synchronized with the rotor rotation, and a signal having a frequency obtained by multiplying the phase signal of the rotor rotation can be output as a signal for interrupting the energization current to the bias power source. A rotational speed signal generator,
The DC brushless motor driving circuit according to claim 1, wherein the hall amplifier has a cut-off frequency approximately one tenth with respect to a maximum frequency of an output signal of the rotation speed signal generator. An oscillator that outputs a signal of a predetermined frequency;
A counter configured to count the output signal of the rotational speed signal generator and to output a signal when a predetermined count is performed;
A logical sum circuit that outputs a logical sum signal of the output signal of the oscillator and the output signal of the counter as a signal for interrupting the energization current to the bias power supply;
A power supply voltage detector that outputs an active signal when the power supply voltage reaches a certain value;
2. The DC brushless motor drive circuit according to claim 1, wherein the counter is configured to be reset by an active signal output from the power supply voltage detector. A DC brushless motor drive circuit configured to be capable of rotational drive control of a DC brushless motor based on an output signal of a Hall element,
A bias power source configured to be capable of intermittently energizing the Hall element according to a signal input from the outside;
An oscillator that outputs a signal for interrupting the energization current to the bias power supply;
A Hall amplifier that amplifies the output signal of the Hall element, outputs a phase signal corresponding to the rotor position of the DC brushless motor, and has a cut-off frequency of approximately one tenth of the output signal of the oscillator;
A rotational speed signal generator configured to be able to output a signal having a frequency that is synchronized with the rotor rotation based on the output signal of the Hall amplifier and that is obtained by multiplying the phase signal of the rotor rotation;
A counter configured to count the output signal of the rotational speed signal generator and to output a signal when a predetermined count is performed;
A logical sum circuit that outputs a logical sum signal of the output signal of the oscillator and the output signal of the counter as a signal for interrupting the energization current to the bias power supply;
A power supply voltage detector that outputs an active signal when the power supply voltage reaches a certain value;
While configured to be able to energize the DC brushless motor based on the output of the Hall amplifier,
The DC brushless motor driving circuit, wherein the counter is configured to be reset by an active signal output from the power supply voltage detector.

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