JP2015070728A - Motor driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor driver that can easily select whether to report only a short circuit current protection signal as an error signal or report an overcurrent protection signal by current detection as well as the short circuit current protection signal as an error signal, to a microcomputer as a host device.SOLUTION: The motor driver includes an abnormality detection circuit 44 for outputting an overcurrent protection signal ERR2 if a current detection value LS exceeds an overcurrent reference value Vocp, and outputting a short circuit current protection signal ERR1 if the current detection value LS exceeds a short circuit current reference voltage Vscp higher than the overcurrent reference value Vocp, and an error signal output circuit 45 for outputting the short circuit current protection signal ERR1 in the form of a low level error signal to a microcomputer 3 from an error terminal TO, and as to the overcurrent protection signal ERR2, outputting a voltage value obtained by dividing a high level by a voltage division circuit (a series circuit of a resistor R2 and a resistor R3) as the low level error signal to the microcomputer 3 from the error terminal TO.

Description

  The present invention relates to a motor driver that drives a motor.

  A motor driver that outputs a drive voltage for driving a motor by converting a drive command from a microcomputer, which is a host device, into a drive signal having an optimum voltage and switching speed and driving a built-in inverter circuit is known. Such a motor driver is provided with, for example, an overcurrent protection circuit that detects an overcurrent such as a motor overload and stops the switching operation, or a short circuit current protection circuit that detects a short circuit current and stops the switching operation. (For example, see Patent Document 1).

JP 2002-369542 A

  However, in the prior art, only the short-circuit current protection signal based on the detection of the short-circuit current is notified to the microcomputer as the host device as an error signal, or the overcurrent protection signal based on the current detection in addition to the short-circuit current protection signal is also an error. It is not decided whether to notify as a signal. Therefore, it is necessary to prepare a motor driver of a type for notifying only a short-circuit current protection signal as an error signal and a type for notifying a short-circuit current protection signal but also an overcurrent protection signal due to current detection as an error signal. There was a problem.

  In view of the above problems, the object of the present invention is to solve the problems of the prior art and notify only the short-circuit current protection signal as an error signal to the microcomputer as the host device or in addition to the short-circuit current protection signal. It is an object of the present invention to provide a motor driver that can easily select whether an overcurrent protection signal based on current detection is also notified as an error signal.

  The motor driver of the present invention has a driver circuit that drives an inverter circuit based on a drive command input from a host device, and the motor driver drives the motor by a drive voltage generated by driving the inverter circuit. When the circuit current of the inverter circuit exceeds an overcurrent reference value, an overcurrent protection signal is output, and when the circuit current of the inverter circuit exceeds a short circuit current reference voltage higher than the overcurrent reference value, a short circuit occurs. An abnormality detection circuit for outputting a current protection signal; and outputting the short-circuit current protection signal as a low level error signal to the host device, and the overcurrent protection signal as a higher level error signal than the low level. And an error signal output circuit for outputting to the apparatus.

  According to the present invention, depending on whether a pull-up resistor is connected to the error terminal, only the short circuit current protection signal is notified as an error signal to the microcomputer as the host device, or in addition to the short circuit current protection signal. It is possible to easily select whether an overcurrent protection signal due to current detection is also notified as an error signal.

It is a circuit block diagram which shows the structure of embodiment of the motor control apparatus using the motor driver which concerns on this invention. FIG. 2 is a circuit configuration diagram illustrating a configuration of an FO circuit illustrated in FIG. 1. It is a figure which shows the signal waveform and operation | movement waveform of each part of the motor driver shown in FIG. It is a circuit block diagram which shows the other example of a connection of the motor driver shown in FIG. 1, and a microcomputer. It is a figure which shows the signal waveform and operation | movement waveform of each part of the motor driver shown in FIG. It is a figure which shows the signal waveform and operation | movement waveform of each part of the motor driver shown in FIG. It is a figure which shows the example of a setting of the overcurrent reference voltage compared with an electric current detection value in the abnormality detection circuit shown in FIG.

  Next, embodiments of the present invention will be specifically described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and a part of the description is omitted.

  The motor control device of the present embodiment is a device that controls the driving of the three-phase brushless motor 1. Referring to FIG. 1, a DC power source 2, a microcomputer 3, a motor driver 4, a current detection resistor RS, And a pull-up resistor R1.

  The direct current power source 2 is constituted by a storage battery or a power source circuit combining an alternating current power source and a converter circuit.

  The microcomputer 3 outputs drive commands Hin1, Hin2, Hin3, Lin1, Lin2, and Lin3 according to position information from the brushless motor 1 and external commands.

  The motor driver 4 includes an inverter circuit 41, a driver circuit 42, and an FO circuit 43.

  The inverter circuit 41 includes a positive DC bus connected to the DC power source 2 and a negative DC corresponding to the U, V, and W phases of the series circuit provided in the high side arm and the low side arm to which the switching element is connected. Connected to the bus. The inverter circuit 41 outputs a driving voltage for driving the brushless motor 1 by performing on / off control of the switching element.

  The driver circuit 42 is an inverter circuit for driving signals Ho1, Ho2, Ho3, Lo1, Lo2, Lo3 obtained by converting the drive commands Hin1, Hin2, Hin3, Lin1, Lin2, Lin3 input to the optimum voltage and switching speed from the microcomputer 3. 41 is output. The drive signals Ho1, Ho2, and Ho3 are drive signals that drive the switching elements of the U, V, and W-phase high-side arms in the inverter circuit 41, and the drive signals Lo1, Lo2, and Lo3 are in the inverter circuit 41. This is a drive signal for driving the switching elements of the U, V, and W phase low side arms. In this embodiment, the high-side drive commands Hin1, Hin2, and Hin3 for driving the switching elements of the high-side arm are chopped by PWM control, and the low-side drive commands Lin1, Lin2, and Lin3 are chopped. ON control (always high level during input).

  As shown in FIG. 1, the current detection resistor RS is provided on a grounded negative DC bus, and a circuit current flowing from the DC power source 2 to the inverter circuit 41 is set as a voltage value (hereinafter referred to as a current detection value LS). It has a function to detect.

  The FO circuit 43 detects an overcurrent based on the current detection value LS and outputs an overcurrent protection signal ERR2, and detects a short circuit current and outputs a short circuit current protection signal ERR1, and a motor driver 4 is provided with an error signal output circuit 45 that outputs an error signal from the error terminal TO provided to 4 to the microcomputer 3.

  The abnormality detection circuit 44 compares the current detection value LS with the overcurrent reference voltage Vocp. When the current detection value LS exceeds the overcurrent reference voltage Vocp, the abnormality detection circuit 44 outputs the overcurrent protection signal ERR2 to the driver circuit 42 and the error signal output circuit 45. Output to. The abnormality detection circuit 44 compares the current detection value LS with the short-circuit current reference voltage Vscp set to a voltage value higher than the overcurrent reference voltage Vocp, and the current detection value LS exceeds the short-circuit current reference voltage Vscp. The short circuit current protection signal ERR1 is output to the driver circuit 42 and the error signal output circuit 45.

  The error signal output circuit 45 includes resistors R2 and R3 and switch elements Q1 and Q2. A series circuit including a resistor R2, a resistor R3, and a switch element Q1 is connected between the internal voltage Reg and the ground terminal, and a switch element Q2 is connected in parallel with the resistor R3 and the switch element Q1. A connection point A between the resistors R2 and R3 is connected to the error terminal TO of the motor driver 4. The switch element Q1 is a switch that is turned on by the output of the overcurrent protection signal ERR2, and the switch element Q2 is a switch that is turned on by the output of the short-circuit current protection signal ERR1. Therefore, when neither the overcurrent protection signal ERR2 nor the short circuit current protection signal ERR1 is output, the internal voltage Reg is output from the error terminal TO as a voltage corresponding to the high level of the error signal FO. When the short circuit current protection signal ERR1 is output, approximately 0 V is output from the error terminal TO as a voltage corresponding to the low level of the error signal FO. Further, when the overcurrent protection signal ERR2 is output, a voltage obtained by dividing the internal voltage Reg by the resistor R2 and the resistor R3 is output from the error terminal TO.

  Next, the overcurrent detection operation in the motor driver 4 of the present embodiment will be described in detail with reference to FIG. FIG. 3 shows signal waveforms and operation waveforms of each part of the motor driver 4 when an overcurrent is detected. 3 (a) is a drive command Hin, (b) is a drive command Lin, (c) is a drive signal Ho, (d) is a drive signal Lo, (e) is a detected current value LS, and (f) is a short circuit current. The protection signals ERR1, (g) show the overcurrent protection signal ERR2, (h) shows the output waveform of the error signal FO, respectively. In FIG. 3, the drive command Hin in (a), the drive command Lin in (b), and the drive signal Ho in (c) and the drive signal Lo in (d) have no in-phase data and are turned on at the same timing. Each phase to be controlled is shown.

  The abnormality detection circuit 44 compares the current detection value LS detected by the current detection resistor RS with the overcurrent reference voltage Vocp. As shown in FIG. 3 (e), the current detection value LS is detected at time ta1. When the overcurrent reference voltage Vocp is exceeded, it is determined whether or not the current detection value LS exceeds the overcurrent reference voltage Vocp continuously for a preset overcurrent filter time Ta to prevent erroneous detection. When the state in which the detected current value LS exceeds the overcurrent reference voltage Vocp continues for the overcurrent filter time Ta, the abnormality detection circuit 44 detects the time Ta2 when the overcurrent filter time Ta has elapsed from the time Ta1 as shown in FIG. ), The overcurrent protection signal ERR2 is output, that is, inverted to a high level.

  The overcurrent protection signal ERR2 is input to the driver circuit 42. As shown in FIGS. 3A and 3B, the driver circuit 42 does not receive the drive commands Hin and Lin from the microcomputer 3 as shown in FIG. As shown in (d), the low-side drive signal Lo is cut off, and the drive of the inverter circuit 41 is stopped. The driver circuit 42 cuts off the drive signal Lo during an overcurrent protection period Tocp (for example, several tens of μs) during which the overcurrent protection signal ERR2 is output (determined to be high level). The overcurrent protection period Tocp is set to one carrier of the PWM frequency, for example.

  Further, the switch element Q1 is turned on by the output of the overcurrent protection signal ERR2, and the voltage at the connection point A between the resistors R2 and R3 is output from the error terminal TO. As shown in FIG. 1, when the pull-up resistor R1 is connected between the external voltage having the same potential as the internal voltage Reg and the error terminal TO, the voltage at the connection point A is the resistance component of the switch element Q1. Is negated as Reg * R3 / {R1 · R2 / (R1 + R2) + R3}. Therefore, by setting the resistance value of the pull-up resistor R1 to be equal to or higher than the resistor R3, the voltage at the connection point A can be set to a middle level that is not recognized as a low level by the microcomputer 3 when the internal voltage Reg is 1/2 or higher. . For example, when the internal voltage Reg is 5 V, the resistance R1: 3 kΩ, the resistance R2: 60 kΩ, and the resistance R3: 6 kΩ, the voltage at the connection point A becomes a middle level of approximately 3.4 V.

  On the other hand, as shown in FIG. 4, when the error terminal TO and the microcomputer 3 are connected without connecting the pull-up resistor R1, the voltage at the connection point A is ignored if the resistance component of the switch element Q1 is ignored. Reg * R3 / (R2 + R3). Therefore, by setting the resistance value of the resistor R2 to a value sufficiently larger than the resistor R3 (for example, 10 times or more), the voltage at the connection point A can be set to a low level that can be recognized by the microcomputer 3. it can. For example, when the internal voltage Reg is 5 V, the resistance R2 is 60 kΩ, and the resistance R3 is 6 kΩ, the voltage at the connection point A is a low level of approximately 0.45 V. As described above, whether or not the overcurrent protection signal ERR2 is output to the microcomputer 3 as the error signal FO can be selected depending on whether or not the pull-up resistor R1 is connected to the error terminal TO.

  Next, at the time Ta3 when the overcurrent protection period Tocp has elapsed from the time Ta2, when the output of the overcurrent protection signal ERR2 ends and is inverted to a low level, the driver circuit 42 has passed the preset error signal filter time Tb. At time ta4, the cutoff of the low-side drive signal Lo is released. When the overcurrent protection signal ERR2 is not output to the microcomputer 3 as the error signal FO, the microcomputer 3 does not recognize the overcurrent protection signal ERR2 as shown in FIGS. 3 (a) and 3 (b). , Lin continues to output. Therefore, the brushless motor 1 rotates with inertia during the overcurrent protection period Tocp, and after the overcurrent protection period Tocp elapses, the drive of the inverter circuit 41 by the drive signals Ho and Lo is resumed from the motor driver 4.

  In the present embodiment, as shown in FIG. 3G, the abnormality detection circuit 44 outputs a pulse signal having an overcurrent protection period Tocp width as the overcurrent protection signal ERR2, and outputs the overcurrent protection signal ERR2. However, the driver circuit 42 may be configured to cancel the blocking of the low-side drive signal Lo after counting the overcurrent protection period Tocp. good.

  Next, the short-circuit current detection operation in the motor driver 4 of the present embodiment will be described in detail with reference to FIGS. 5 and 6 show signal waveforms and operation waveforms of each part of the motor driver 4 when a short-circuit current is detected. 5A and 5B, (a) is a drive command Hin, (b) is a drive command Lin, (c) is a drive signal Ho, (d) is a drive signal Lo, (e) is a current detection value LS, (f). Is a short-circuit current protection signal ERR1, (g) is an overcurrent protection signal ERR2, and (h) is an output waveform of the error signal FO. 5 and 6, the drive command Hin in (a) and the drive command Lin in (b), and the drive signal Ho in (c) and the drive signal Lo in (d) have no in-phase data and are the same. The phases that are on-controlled at timing are shown.

  The abnormality detection circuit 44 compares the current detection value LS detected by the current detection resistor RS with the short-circuit current reference voltage Vscp, and the current detection value LS is detected at time tb1 as shown in FIG. 5 (e). When the short-circuit current reference voltage Vscp is exceeded, it is determined whether or not the current detection value LS exceeds the short-circuit current reference voltage Vscp continuously for a preset short-circuit current filter time Tc to prevent erroneous detection. The short-circuit current filter time Tc is set to a time shorter than the overcurrent filter time Ta. When the state in which the current detection value LS exceeds the short-circuit current reference voltage Vscp continues for the short-circuit current filter time Tc, the abnormality detection circuit 44 detects the time Tb2 when the short-circuit current filter time Tc has elapsed from the time Tb1 at FIG. ), The short-circuit current protection signal ERR1 is output, that is, inverted to a high level.

  The short-circuit current protection signal ERR1 is input to the driver circuit 42. The driver circuit 42 cuts off the high-side and low-side drive signals Ho and Lo as shown in FIGS. 41 drive is stopped.

  Further, the switch element Q2 is turned on by the output of the short circuit current protection signal ERR1, the voltage at the connection point A between the resistor R2 and the resistor R3 becomes approximately 0 V, and the error signal FO is output from the error terminal TO. Thereby, the microcomputer 3 recognizes the short-circuit current, and stops the output of the drive commands Hin and Lin as shown in FIGS.

  The abnormality detection circuit 44 outputs, as the short circuit overcurrent protection signal ERR1, a pulse signal having a short circuit current protection period Tscp width set to a time (for example, several ms) longer than the overcurrent protection period Tocp. When the output of the short-circuit current protection signal ERR1 ends at time Tb3 and is inverted to a low level, the output of the drive commands Hin and Lin from the microcomputer 3 is resumed as shown in FIGS. 5 (a) and 5 (b). As shown in FIGS. 5C and 5D, the output of the drive signals Ho and Lo by the driver circuit 42 is also resumed. The driver circuit 42 has a latch circuit that is not released unless all of the drive commands Hin and Lin input from the microcomputer 3 become low level, and the drive command Hin input from the microcomputer 3 during the short-circuit current protection period Tscp. The output of the drive signals Ho and Lo is resumed on condition that all of Lin become low level. That is, as shown in FIG. 6F, even when the short-circuit overcurrent protection signal ERR1 is output at time tb2, as shown in FIGS. 6A and 6B, the drive command input from the microcomputer 3 If Hin and Lin are continuously input, the microcomputer 3 may be destroyed or runaway. Accordingly, even when the output of the short-circuit current protection signal ERR1 ends at time tb3 and is inverted to the low level, the driver circuit 42 outputs the drive signals Ho and Lo as shown in FIGS. 6 (c) and 6 (d). The secondary destruction is prevented by not restarting.

  In the abnormality detection circuit 44, the overcurrent reference voltage Vocp to be compared with the current detection value LS is decreased at a constant slope at a high temperature (for example, from 100 ° C.) as shown in FIG. By configuring as described above, the switching elements of the inverter circuit 41 may be used to the utmost within a range that does not cause thermal destruction. The generation of such an overcurrent reference voltage Vocp uses a thermal monitor circuit whose output voltage changes according to the temperature as shown in FIG. 7B, and a subtraction circuit as shown in FIG. Generate characteristic X. Then, by subtracting the characteristic X from a preset constant potential, it is possible to generate an overcurrent reference voltage Vocp that decreases at a constant slope at high temperatures. Further, as shown in FIG. 7D, an overcurrent reference voltage Vocp that decreases at a constant slope at a constant temperature (for example, 0 ° C.) may be used by a similar generation method. ), An overcurrent reference voltage Vocp that decreases at a constant gradient at a constant temperature (for example, 0 ° C.) and decreases at a constant gradient at a high temperature (for example, from 100 ° C.) may be used. good.

As described above, the present embodiment has the driver circuit 42 that drives the inverter circuit 41 based on the drive commands Hin and Lin input from the microcomputer 3 that is the host device, and is generated by driving the inverter circuit 41. The motor driver 4 drives the brushless motor 1 with the generated drive voltage. When the current detection value LS, which is the circuit current of the inverter circuit 41, exceeds the overcurrent reference value Vocp, the overcurrent protection signal ERR2 is output and the current When the detected value LS exceeds the short-circuit current reference voltage Vscp higher than the overcurrent reference value Vocp, the abnormality detection circuit 44 that outputs the short-circuit current protection signal ERR1 and the short-circuit current protection signal ERR1 as the low level error signal FO are sent to the microcomputer 3. In addition, the overcurrent protection signal ERR2 is set to low level (short circuit current protection signal ER And an error signal output circuit 45 for outputting to the microcomputer 3 as an error signal FO of the first error signal FO) high than. The overcurrent protection signal ERR2 is output from the error terminal TO to the microcomputer 3 as a voltage value obtained by dividing the high level by a voltage dividing circuit (a series circuit of the resistors R2 and R3).
With this configuration, since the low-level error signal FO is generated by the voltage dividing circuit (series circuit of the resistor R2 and the resistor R3), the microcomputer 3 is connected to the error terminal TO by connecting the pull-up resistor R1 to the low level. A middle level error signal that is not recognized as a level can be easily generated. Therefore, depending on whether or not the pull-up resistor R1 is connected to the error terminal TO, only the short circuit current protection signal ERR is notified as the error signal FO to the microcomputer 3 which is the host device, or the short circuit current protection signal SRR1 is transmitted. In addition, it is possible to easily select whether to notify the overcurrent protection signal ERR2 as an error signal.

Furthermore, according to the present embodiment, when the overcurrent protection signal ERR2 is output from the abnormality detection circuit 44, the driver circuit 42 stops the drive of the inverter circuit 41, and after the overcurrent protection period Tocp has elapsed, 41 drive is resumed. Further, according to the present embodiment, when the short circuit current protection signal ERR1 is output from the abnormality detection circuit 44, the driver circuit 42 stops driving the inverter circuit 41, and the short circuit current longer than the overcurrent protection period Tocp. After the protection period Tscp elapses, the drive of the inverter circuit 41 is resumed on condition that all the drive commands Hin and Lin input from the microcomputer 3 have been temporarily stopped. With this configuration, an error signal is generated due to destruction or runaway of the microcomputer 3. Even in a state where the FO cannot be recognized, secondary destruction can be prevented.

  Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a number, position, shape, and the like that are suitable for implementing the present invention. In each figure, the same numerals are given to the same component.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 DC power supply 3 Microcomputer 4 Motor driver RS Current detection resistance R1 Pull-up resistance 41 Inverter circuit 42 Driver circuit 43 FO circuit 44 Abnormality detection circuit 45 Error signal output circuit R2, R3 Resistance Q1, Q2 Switch element Reg Internal voltage

Claims (3)

A motor driver having a driver circuit for driving an inverter circuit based on a drive command inputted from a host device, and driving a motor by a drive voltage generated by driving the inverter circuit;
When the circuit current of the inverter circuit exceeds an overcurrent reference value, an overcurrent protection signal is output, and when the circuit current of the inverter circuit exceeds a short circuit current reference voltage higher than the overcurrent reference value, a short circuit current protection signal is output. An abnormality detection circuit to output,
An error signal output circuit that outputs the short-circuit current protection signal to the host device as a low level error signal and outputs the overcurrent protection signal to the host device as an error signal that is higher than the low level. A motor driver characterized by   When the overcurrent protection signal is output from the abnormality detection circuit, the driver circuit stops driving the inverter circuit and restarts driving the inverter circuit after an overcurrent protection period has elapsed. The motor driver according to claim 1.   When the short circuit current protection signal is output from the abnormality detection circuit, the driver circuit stops driving the inverter circuit, and is input from a host device after a short circuit current protection period longer than the overcurrent protection period has elapsed. 3. The motor driver according to claim 2, wherein the drive of the inverter circuit is resumed on condition that all drive commands are temporarily stopped.

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