JP5872250B2 - Motor drive device - Google Patents

Description

  The present invention relates to an improvement in a motor drive device that drives a motor connected to a DC power supply by PWM control of a transistor.

   Conventionally, as this type of motor drive device, there is one described in Patent Document 1, for example. The power supply device described in Patent Document 1 has a configuration in which a MOSFET is arranged in parallel to the motor in a load circuit that drives the motor by PWM control of an electronic switch provided between a DC power source and the motor. is there. In this power supply device, the MOSFET is turned on when the electronic switch is turned off, thereby making the MOSFET a reflux path, thereby reducing heat generation and realizing a reduction in energy loss.

JP 2010-154647 A

  By the way, in the power supply device as described above, for example, when the motor is suddenly decelerated, the voltage generated by the rotation of the motor is higher than the average voltage applied to the motor, that is, the regenerative braking state, As a result, the regenerative current flows back to the power source. Such a phenomenon does not pose a problem in a power supply device that can absorb regenerative current, such as a battery, but in a power supply device that does not have a regenerative current absorption function, typically represented by a switching power supply, the power supply voltage is Rises to an overvoltage condition. For this reason, the conventional power supply apparatus has a problem that it cannot be used for a power supply apparatus that does not have a function of absorbing regenerative current, and it has been a problem to solve such a problem.

  The present invention has been made paying attention to the above-described conventional problems, and prevents an overvoltage state caused by a regenerative current in an apparatus for driving the motor by PWM control of a transistor provided between a DC power supply and the motor. An object of the present invention is to provide a motor drive circuit that can be applied to a power supply device that does not have a function of absorbing regenerative current.

  The motor driving device of the present invention includes a first transistor connected between a DC power source and a motor, a second transistor for a reflux path connected in parallel to the motor, and a first transistor and a second transistor. Control means for controlling is provided.

In the motor drive device, the control unit includes a motor current detection unit that detects a motor current, and a comparison unit that compares a detection value of the motor current detection unit with a positive current threshold value including zero. When the detected value is equal to or greater than the threshold value, the on / off control of the first and second transistors is controlled to be opposite to each other, and when the detected value is less than the threshold value, the second transistor is turned off. The above configuration is used as a means for solving the conventional problems.

  The motor driving device of the present invention employs the above-described configuration, so that an overvoltage state caused by a regenerative current can be prevented in a device that drives the motor by PWM control of a transistor provided between a DC power supply and the motor. Therefore, the present invention can be applied to both a power supply device having a function of absorbing a regenerative current and a power supply device having no regenerative current function, and the versatility can be expanded.

It is a circuit diagram explaining one Embodiment of the motor drive device of this invention. FIG. 6 is graphs (A) to (H) for explaining current changes in the motor drive device shown in FIG. 1. It is each graph (A)-(F) explaining the electric current change at the time of a drive and regeneration. It is a circuit diagram explaining other embodiment of the motor drive device of this invention. FIG. 5 is graphs (A) to (L) for explaining current changes in the motor drive device shown in FIG. 4.

1 and 2 are diagrams for explaining an embodiment of a motor drive device of the present invention.
The motor driving device shown in FIG. 1 includes a first transistor TR1 connected between a DC power source E and a motor M, a second transistor TR2 for a reflux path connected in parallel to the motor M, Control means 1 for controlling the PWM (pulse width modulation) of the second transistors TR1 and TR2 is provided. The first and second transistors TR1 and TR2 are field effect transistors (FETs) having parasitic diodes.

  The control means 1 includes a PWM signal generator 2, a peak hold circuit 3, a comparator 4 as comparison means, a gate driver 5, a NOT circuit 6, and an AND circuit 7. The control means 1 generates a PWM signal having a predetermined duty ratio in the generator 2, and controls the first transistor TR <b> 1 on / off via the gate driver 5. The PWM signal controls the second transistor TR2 on / off via the NOT circuit 6 and the gate driver 5. Therefore, the first and second transistors TR1 and TR2 are controlled so that the on / off states are opposite to each other.

Accordingly, in the motor driving device, when the first transistor TR1 is turned on, the second transistor TR2 is turned off, and a driving current (I _ON1 ) flows through the motor M. Further, when the first transistor TR1 is turned off, the second transistor TR2 is turned on, and the second transistor TR2 becomes a path for the return current (I _OFF1 ). Thereby, heat generation and energy loss can be reduced.

  Here, the device for driving the motor M by PWM controlling the first and second transistors TR1 and TR2 as described above is applied to a power supply device having no regenerative current absorption function. May be in a state.

Normally, as shown in FIG. _3A , the drive current (I _ON1 ) of the motor M appears in the same phase as the PWM signal being turned on, and has a rising slope due to motor inductance. As shown in FIG. 3B, the return current (I _OFF1 ) of the motor M appears in the same phase as the PWM signal OFF, and has a falling slope due to motor inductance. As a result, the motor current (I _M1 ) is a continuous current (I _ON1 ) and return current (I _OFF1 ) as shown in FIG.

However, when the motor M is decelerated and the regenerative braking state in which the voltage generated by the rotation of the motor M is higher than the average voltage applied to the motor M, the current flows backward to the power source E when the first transistor TR1 is on. A regenerative current (I _OFF2 ) is generated. This regenerative current (I _OFF2 ) appears as a negative phase opposite to the drive current (I _ON1 ) as shown in FIG.

In the regenerative braking state, when the second transistor TR2 is turned on, a braking current (I _ON2 ) opposite to the return current is generated. As shown in FIG. _{3D, the} braking current (I _ON2 ) appears as a negative phase opposite to the return current (I _OFF1 ). As a result, as shown in FIG. 3F, a motor current (I _M2 ) in the direction opposite to that in the normal state flows through the motor M. At this time, a power supply device without a regenerative current absorption function may be in an overvoltage state.

Therefore, in the motor drive device, the control means 1 detects the motor current detection means 8 for detecting the current of the motor M, and the comparison in which the detection value of the motor current detection means 8 is compared with the positive current threshold value including zero. And a regenerative function for turning on the second transistor TR2 when the detected value is greater than or equal to the threshold and turning off the second transistor TR2 when the detected value is less than the threshold. It has become. In particular, in this embodiment, the motor current detection means 8 uses the drive current (I _ON1 ) of the motor M.

The motor current detection means 8 in the illustrated example is constituted by a resistor R connected between the first transistor TR1 and the power source E and the peak hold circuit 3, and the voltage at the shunt resistor R is used as the drive current of the motor M. obtained as _{(I ON1),} seeking the peak value of the drive current _{(I ON1)} in the peak hold circuit 3, and inputs it to the comparator 4.

Similar to the description of FIG. 3, the drive current (I _ON1 ) of the motor M corresponds to the ON phase of the PWM signal as shown in FIG. 2 (A), and the return current (I _OFF1 ) is _{equal to} FIG. This corresponds to the off phase of the PWM signal as shown in FIG. The current (I _M1 ) of the motor M has a waveform that repeatedly increases and decreases by combining the drive current (I _ON1 ) and the return current (I _OFF1 ) as shown in FIG. The peak hold circuit 3 _obtains the waveform of the current (I _M1 ) of the motor M as the peak hold voltage waveform shown in FIG. 2B from the waveform of the drive current (I _ON1 ), and inputs this to the comparator 4.

  The comparator 4 is preset with a positive current threshold value including zero. More preferably, the threshold value can be set based on the forward voltage of the parasitic diode of the second transistor TR2 and the power consumption due to the return current, thereby more reliably preventing the heat generation of the second transistor TR2. , Energy loss can be further reduced.

  The comparator 4 compares the detection value of the motor current detection means 8 with the current threshold value, inputs the result from the AND circuit 7 to the gate driver 5, and turns on / off the second transistor TR 2 by the gate driver 5. Control.

At this time, if the detection value of the motor current detection means 8 is equal to or greater than the current threshold, the second transistor TR2 is turned on. As a result, since the return current (I _OFF1 ) flows to the resistance region of the second transistor TR2, heat generation is reduced even when the current is large.

As shown in FIG. 2F, when the detection value of the motor current detection means 8 is less than the current threshold, the second transistor TR2 is turned off. That is, when a current less than the threshold value flows in the motor M, the return current (I _OFF1 ) in the PWM control flows through the parasitic diode of the second transistor TR2, and the drive current (I _ON1 ) becomes zero. Even in the regenerative state, the second transistor TR2 remains off, and the both ends of the motor M are not short-circuited by the second transistor TR2. Therefore, as shown in FIGS. current _{(I ON2)} and a regenerative current _{(I OFF2)} is not generated. As shown in FIG. 2H, the reverse motor current (I _M2 ) is not generated.

  Thus, according to the motor drive device of the above embodiment, in the device that drives the motor M by PWM controlling the transistors TR1 and TR2 provided between the DC power source E and the motor M, an overvoltage state caused by a regenerative current is generated. Can be prevented in advance. Therefore, the present invention can be applied to both a power supply device having a regenerative current absorption function such as a battery and a power supply device having no regenerative current absorption function typified by a switching power supply. Is very expensive.

  4 and 5 are diagrams for explaining another embodiment of the motor drive device of the present invention. Note that the same components as those of the previous embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the motor drive device shown in FIG. 4, the control means 1 has a regeneration selection means 10 for turning on / off the regeneration support function. In this case, a second AND circuit 12 is provided between the comparator 4 and the AND circuit 7, and signals from the regeneration selection means 10 and the comparator 4 are input to the second AND circuit 12.

When the regeneration selection means 10 is turned off, the same control as in the previous embodiment is performed, and as shown in FIGS. 5E and _5G , the braking current (I _ON2 ) and No regenerative current (I _OFF2 ) is generated, and no reverse motor current (I _M2 ) is generated as shown in FIG.

On the other hand, when the regeneration selection means 10 is turned on, when the motor M is in the regeneration state, as shown in FIGS. 5 (I) and 5 (L), the drive current (I _ON1 ) and the return current (I _OFF1 ) regeneration negative side of the opposite phase braking current _{(I ON2)} and a regenerative current _{(I OFF2)} is generated, as shown in FIG. 5 (L), current _{(I M2)} in the opposite direction to the motor M flows through A braking state is entered.

  When the motor drive device having the above configuration is applied to a power supply device having a regenerative current absorption function such as a battery, the regenerative selection means 10 is turned on, and the regenerative current absorption is performed like a switching power supply. When the present invention is applied to a power supply device having no function, it is only necessary to turn off the regeneration selection means 10, and the specification can be freely changed to an optimum specification for the function of the power supply device.

In each of the above embodiments, the motor current detection means 8 detects the drive current (I _ON1 ) of the motor M, and the peak hold circuit 3 converts the current (I _M1 ) of the motor M into the waveform of the drive current (I _ON1 ). To obtain the peak hold voltage waveform. In this case, the apparatus can be provided relatively inexpensively, and the comparison determination between the detection value of the motor current detection means 8 and the current threshold value can be performed stably. Furthermore, the motor drive device of the present invention may be configured such that the motor current detection means 8 directly detects the current (I _M1 ) of the motor M. In this case, the structure can be simplified by omitting the peak hold circuit 3 and the resistor R.

  The configuration of the motor drive device of the present invention is not limited to the above-described embodiments, and details of the configuration can be changed as appropriate without departing from the gist of the present invention.

E power supply M motor TR1 first transistor TR2 second transistor 1 control means 4 comparator (comparison means)
8 Motor current detection means 10 Regeneration selection means

Claims (4)

A first transistor connected between the DC power source and the motor;
A second transistor for a reflux path connected in parallel to the motor;
The first and second transistors and a controller for PWM control,
The control means is
A motor current detecting means for detecting the motor current, and a comparing means for comparing the detected value of the motor current detecting means with a positive current threshold value including zero;
When the detected value is greater than or equal to the threshold value, the on / off control of the first and second transistors is controlled to be opposite to each other, and when the detected value is less than the threshold value, the regenerative function for turning off the second transistor is provided. A motor drive device comprising: A first transistor connected between the DC power source and the motor;
A second transistor for a reflux path connected in parallel to the motor;
The first and second transistors and a controller for PWM control,
The control means is
A generator for generating a PWM signal, a NOT circuit and an AND circuit while extending from the generator to the second transistor in series arrangement, a motor current detecting means for detecting a current of the motor, the detected value of the motor current detecting means and a zero the result is compared with the threshold value on the positive side of the current provided with a comparing means for input to aND circuit including,
When the detected value is greater than or equal to the threshold value, the on / off control of the first and second transistors is controlled to be opposite to each other, and when the detected value is less than the threshold value, the regenerative function for turning off the second transistor is provided. A motor drive device comprising: 3. The motor driving apparatus according to claim 1, wherein the threshold value of the current is set based on a forward voltage of a parasitic diode of the second transistor and power consumption by a return current. It said control means, the motor driving apparatus according to claim 1, characterized in that it comprises a regeneration selecting means for turning on / off the regenerative response function.

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