JP3632305B2 - Motor drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor driving device that drives a brushed DC motor by a PWM (pulse width modulation) system as an example.
[0002]
[Prior art]
FIG. 2 is a block diagram showing a configuration example of a motor drive circuit that is the basis of the present invention, and is used in common in the description of the prior art described below and the description of the embodiment. FIG. 4 is a graph showing the operation state of the circuit element of the prior art, FIG. 5 is a circuit diagram showing a configuration example of the motor drive circuit (hereinafter referred to as drive circuit) 1 of the prior art, and FIG. FIG. 7 is a circuit diagram showing a configuration example on the low side of a power element section described later, and FIG. 7 is a circuit diagram showing a configuration example on the high side of a power element section described later in the drive circuit 1. Hereinafter, the configuration of the conventional motor drive circuit 1 will be described with reference to FIGS. 2 and 5 to 7. In the following prior art and examples, a two-phase motor will be described for the sake of simplification, but this description also applies to the control of motors of other phases such as three phases. .
[0003]
As an example, in a drive circuit 1 that drives a brushed DC motor 3 having a medium withstand voltage (eg, rated voltage = DC24V) by a PWM (pulse width modulation) speed control method with a current limiter.
(1) Perform forward / reverse open-loop speed control of the motor 3 according to the given signal. (2) Suppress the starting current below a certain value.
In order to satisfy this specification, the following configuration is adopted. As shown in FIG. 2, the drive circuit 1 includes a first power supply unit 2a that outputs Vcc = DC24V for driving the motor and a second power supply unit 2b that outputs a DC voltage of DC5V for driving the circuit. And a main control unit 4 for outputting a PWM-modulated speed signal and a switching signal for switching between normal rotation and reverse rotation of the motor 3, and a MOSFET (MOS structure field effect transistor) as an example for outputting a drive current to the motor 3. A power element unit 5 that is an inverter circuit comprising: a C-MOS gate as an example in which the speed signal and the switching signal are input and a drive signal for turning on / off each transistor of the power element unit 5 is output to the power element unit 5 And a slave control unit 6 made of an IC.
[0004]
The power element unit 5 includes a high-side element unit 7 including a P-channel MOSFET that supplies a driving current to the motor 3 and a low-side element unit 8 including an N-channel MOSFET into which a current from the motor 3 flows. . The driving power source Vcc is supplied to the slave control unit 6 and the high-side element unit 7 through a power line 9 and a ground line 10 connected between the power unit 2 and the power element unit 5. When the voltage drop amount of the current sensor 11 is compared with the reference value and the voltage drop amount exceeds the reference value, the ground line 10 outputs an excess signal to the slave control unit 6 to output the power element unit 5. A current sensor 11 including a resistance element that stops the on / off operation is disposed. The ground line 10 is commonly connected to the current sensor 11, the first power supply unit 2 a of the power supply unit 2, the second power supply unit 2 b, the low side element unit 8, and the sub control unit 6.
[0005]
A circuit example of the slave control unit 6 and the power element unit 5 of the conventional driving circuit 1 is shown in FIG. A constant voltage circuit 14 including a Zener diode 12 and a resistor 13 connected to the power supply line 9 in relation to the slave control unit 6 and outputting a constant voltage of 10 V, for example, is provided. The high-side element unit 7 includes P-channel MOSFETs (hereinafter referred to as P-transistors) 7a and 7b, and the low-side element unit 8 includes N-channel MOSFETs (hereinafter referred to as N-transistors) 8a and 8b. The output of the constant voltage circuit 14 is supplied to inverting circuits 15 and 16 (for example, the element TC4011B) that output gate signals to the P transistors 7a and 7b. In the inverting circuits 15 and 16, among the switching signals, a switching signal MF for setting the rotation direction of the motor 3 to the normal rotation direction and a switching signal MR for setting the reverse rotation direction through the transistors 17 and 18, respectively. Entered. Therefore, the gate signals of the P transistors 7a and 7b are level-shifted by the transistors 17 and 18 with the switching signals MF and MR based on the ground potential and passed through the inverter circuits 15 and 16 based on the voltage Vcc, and then the P transistors 7a and 7b. 7b.
[0006]
Further, in the conventional driving circuit 1, as shown in FIG. 5, the speed signal PWM is not input to the high side element unit 7, the switching signals MF and MR are input via the transistors 17 and 18, and the P transistor 7a and 7b are selectively set to a conductive state or a cut-off state. The speed signal PWM is ANDed with the switching signals MF and MR by AND circuits 26 and 27, and the output of the speed signal PWM is ANDed with the output of the overcurrent detection circuit 21 by AND circuits 19 and 20. . The outputs of the AND circuits 19 and 20 (element types are the same as above) are input to the gate terminals of the N transistors 8a and 8b. The overcurrent detection circuit 21 detects a current level from the motor 3 via the low-side element unit 8. When this current is small, the voltage value detected by the current sensor 11 is small and the transistor 22 is cut off. Then, the Zener diode 23 is turned on, and a high potential of a certain level is supplied to one input terminal of each of the AND circuits 19 and 20, and the AND circuits 19 and 20 output the input speed signal PWM. On the other hand, when a large current flows through the motor 3, the voltage value detected by the current sensor 11 increases, the transistor 22 becomes conductive, the potential difference between the terminals of the Zener diode 23 decreases, and the Zener diode 23 enters a cutoff state. . As a result, the ground potential via the transistor 22 is supplied to the AND circuits 19 and 20, and the motor circuit 3 stops rotating.
[0007]
[Problems to be solved by the invention]
An example of the configuration of the AND circuits 19 and 20 and the N transistors 8a and 8b of the slave control unit 6 and an example of the configuration of the inverting circuits 15 and 16 and the P transistors 7a and 7b are shown in FIGS. 5 and 7, respectively. . In either case of the high-side element portion 7 and the low-side element portion 8, voltage output type CMOS gate elements are used for the drive elements 24 and 25. In the following description, it is assumed that the motor 3 is rotating forward and the P transistor 7a is cut off and the P transistor 7b is turned on correspondingly. In this case, the potential difference VDD-G of the P-transistor 7 of the off-side high-side element 7 is 2V which is the threshold voltage Vth of this transistor, and the current capacity of the driving element 25 is about 8 mA, whereas the low-side element 8, the potential difference VDD-G of the N transistor 8 that switches between the on state and the off state is 10 V−Vth = 8 V, the current capacity of the driving element 24 is 16 mA or more, and the off state on the high side element 7 side. Is not determined, and both the high-side element 7 and the low-side element 8 are turned on, short-circuit each other, an excessive abnormal current flows, and a malfunction of the motor 3 occurs.
[0008]
This state is shown in FIG. That is, the current capacity of the low-side drive element 24 that performs switching for rotationally driving the motor 3 is larger than the current capacity of the high-side drive element 25, so that the off-state on the high-side element 7 side is An uncertain situation occurs.
[0009]
The inventions of claims 1 to 3 have been made in order to solve the above technical problem, and an object thereof is to provide a motor driving device capable of preventing malfunction of the motor.
[0010]
[Means for Solving the Problems]
Motor driving apparatus of the first aspect of the present invention, possess a transistor of a first conductivity type for supplying a drive current to the coil of the motor, and a transistor of a second conductivity type into which a driving current flows from the other coils of the motor, inverter circuit and, is PWM speed signal input first driving circuit for driving said first conductivity type transistor on / off of the inverter circuit including a series circuit of the transistors of the transistor and a second conductivity type of the first conductive type When, a second driving circuit for setting to one of the forward-reverse switching signal for switching is inputted or off on the second conductive type transistor state of the motor, the current capacity of the second driving circuit wherein It is characterized by being provided 4 to 6 times the current capacity of the first drive circuit.
[0011]
As a result, the current capacity of the drive circuit that drives the transistor on / off to drive the motor can be made smaller than the current capacity of the drive circuit that sets the transistor to either the on state or the off state. Therefore, it is possible to determine the operation state of the drive circuit that drives the transistors on / off, to prevent the operation state of each of these drive circuits from being determined and to prevent a short circuit between the transistors, Malfunctions can be prevented.
[0012]
In the first aspect of the invention, the first conductivity type may be a P-channel type and the second conductivity type may be an N-channel type. Even in this case, the above-described effects can be achieved. In the first aspect of the invention, the first drive circuit includes a gate integrated circuit element having a current capacity of about 60 mA as a basic configuration, and the second drive circuit includes a gate integrated circuit element having a current capacity of about 20 to 30 mA as a basic configuration. You may make it provide. Also in this case, the function and effect of the first aspect can be realized.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a configuration example of a part of a motor drive circuit according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a schematic configuration example of a motor drive circuit 1 having a configuration as a basis of the present invention. Since it has been described in the prior art, the description thereof is omitted, and the description of the prior art is referred to when necessary. 3 and 4 are graphs showing an operation example of the gate element used in this embodiment.
[0014]
Hereinafter, the configuration of the motor drive circuit 31 of the present embodiment will be described with reference to FIGS.
[0015]
The schematic configuration of the motor drive circuit 31 of this embodiment is shown in FIG. 2, and FIG. 1 is a diagram corresponding to FIG. 5 related to the slave control unit 6 and the power element unit 5 in FIG. is there. That is, the feature of the motor drive circuit 31 of the present embodiment relates to the improvement of the slave control unit 6 and the power element unit 5 shown in FIG. In the present embodiment, the switching operation for rotationally driving the motor 3 is performed by the high side element unit 7, and the low side element unit 8 is in a cut-off state or a conductive state corresponding to the forward or reverse rotation direction of the motor 3. Set to
[0016]
As an example, in a drive circuit 31 that drives a brushed DC motor 3 having a medium withstand voltage (eg, rated voltage = DC24V) by a PWM (pulse width modulation) speed control method with a current limiter.
(1) Perform forward / reverse open-loop speed control of the motor 3 according to the given signal. (2) Suppress the starting current below a certain value.
In order to satisfy the specification, the configuration described with reference to FIG. 2 as described above is employed.
[0017]
FIG. 1 shows a circuit example of a portion related to the slave control unit 6 and the power element unit 5 of the drive circuit 31 of the present embodiment. Although not shown in FIG. 1, a circuit corresponding to the constant voltage circuit 14 described with reference to FIG. The high-side element unit 7 includes P-channel MOSFETs (hereinafter referred to as P-transistors) 7a and 7b, and the low-side element unit 8 includes N-channel MOSFETs (hereinafter referred to as N-transistors) 8a and 8b. The output of the first power supply unit 2a is supplied to the P transistors 7a and 7b.
[0018]
Among the switching signals output by the main control unit 4, the switching signal MF for setting the rotation direction of the motor 3 to the normal rotation direction and the switching signal MR for setting the rotation direction to the reverse direction are a level shift transistor array (hereinafter referred to as an array). ) 32 and 33 and the resistors 34 and 35 whose one ends are grounded to be input to the inverting circuits 36 and 37. Output N transistors 8a inverting circuits 36 and 37, (as an example, TC4049BF, current capacity of about 60mA as an example) the gate circuit is a buffer gate integrated circuit constituting the driving element 6 7 for driving the 8b to 38 Entered. Therefore, the gate signals of the N transistors 8a and 8b are level-shifted by the arrays 32 and 33 and the switching signals MF and MR based on the ground potential are passed through the inverting circuits 36 and 37 based on the voltage Vcc, and then the P transistors 7a, 8b. The output is obtained from the gate circuits 38 and 39 for driving 7b.
[0019]
In the drive circuit 31 of this embodiment, the speed signal PWM is input to the high-side element unit 7 and the P transistors 7a and 7b perform the switching operation as described later, contrary to the case of the drive circuit 1 of the prior art. Do. On the other hand, the switching signals MF and MR are input to the N transistors 8a and 8b via the gate circuits 38 and 39, and the N transistors 8a and 8b are selectively set to a conductive state or a cut-off state. The signal level of the speed signal PWM is shifted through the level shift transistor arrays (hereinafter referred to as arrays) 40 and 41 as described above, and the high side element is connected through the transistors 42 and 43 which are signal transmission transistor circuits. P transistor 7a parts 7, (as an example, TC4093BF) standard gate integrated circuit constituting the driving element 6 6 that drives 7b inputted to each one input terminal of the aND circuit 44, 45 is. The AND circuits 44 and 45 calculate the logical product of the outputs of the transistors 42 and 43 and the output of the OR circuit 46, and supply the outputs to the gate terminals of the P transistors 7a and 7b.
[0020]
The outputs of the transistors 42 and 43 are inverted and inputted to the respective input terminals of the OR circuit 46. When at least one of the outputs of the transistors 42 and 43 is at a low level, the OR circuit 46 outputs a high level signal. The AND circuits 44 and 45 are set in a conductive state. On the other hand, when both the outputs of the transistors 42 and 43 are at a high level, the OR circuit 46 outputs a low level signal, and the AND circuits 44 and 45 are set in a cutoff state in which the signals from the transistors 42 and 43 are cut off. . In this cut-off state, the P transistors 7a and 7b stop operating. In such a case, as an example, there is a transition state or an abnormal state in which the switching signals MF and MR are both at the same level such as a high level. At this time, the transistors 7a and 7b are turned off, and the transistors 8a and 8b are turned on to apply the brake.
[0021]
On the other hand, an overcurrent limiter circuit (hereinafter, limiter circuit) 47 is provided in association with the first power supply unit 2a. The limiter circuit 47 outputs signals from rectifier circuits 49 and 50 in parallel with capacitors 48 arranged in series with the power supply line 9. A Zener diode 65 is connected between the rectifier circuits 49 and 50 so that the rectifier circuit 49 is on the cathode side. The rectifier circuit 49 includes diodes 51 and 52 connected in series with each other, and the cathodes of the diodes 51 and 52 are commonly connected to the gate of the transistor 55 of the limiter circuit 47. The anode of the rectifier circuit 50 is input to the rectifier circuits 56 and 57.
[0022]
The emitter of the transistor 55 is connected to the power supply line 9, and the collector is commonly connected to each input terminal of the AND circuit 58, and connected to the capacitor 48 side of the resistor 49 through a parallel circuit of the resistor 59 and the capacitor 60. Is done. The output of the AND circuit 58 is connected to the cathodes of the diodes 61 and 63 provided in the rectifier circuits 56 and 57, respectively. The anodes of the diodes 61 and 63 are connected to the other input terminals of the AND circuits 44 and 45, respectively. The cathodes of the diodes 62 and 64 that are respectively provided in the rectifier circuits 56 and 57 and are reversely connected to the diodes 61 and 63 are connected to the anodes of the diodes 61 and 63, and the anodes of the diodes 62 and 64 are commonly used. The rectifier circuit 50 is connected to the cathode of the diode 53.
[0023]
Hereinafter, the operation of the drive circuit 31 of this embodiment will be described.
[0024]
The limiter circuit 47 limits the current level from the motor 3 via the high-side element unit 7 to a predetermined level. When this current is small, the voltage value detected by the current sensor 11, which is a resistance element, is small, the transistor 55 is cut off, and a low level signal is input to the AND circuit 58. As a result, the output of the AND circuit 58 is inverted and becomes a high level, and a signal is input to the OR circuit 46. As a result, the output of the OR circuit 46 becomes a high level, the AND circuits 44 and 45 are turned on, and the speed signal PWM through the transistors 42 and 43 is passed through the AND circuits 44 and 45 as described above. 7a and 7b, and the motor 3 is driven.
[0025]
On the other hand, when the current from the motor 3 through the high-side element portion 7 is large, the voltage value detected by the current sensor 11 that is a resistance element also increases, and the transistor 55 is turned on. As a result, a high level signal is input to the AND circuit 58. As a result, the output of the AND circuit 58 is inverted to a low level, and is input to the rectifier circuits 56 and 57. At this time, a low level signal obtained by inverting the high level signal is input to the OR circuit 46 via the rectifier circuits 56 and 57. As a result, the output of the OR circuit 46 becomes low level, the AND circuits 44 and 45 are cut off, and the speed signal PWM via the transistors 42 and 43 is cut off by the AND circuits 44 and 45 as described above, and the P transistors 7a and 7b are not input. Thus, when an overcurrent flows through the motor 3, the rotation of the motor 3 is stopped.
[0026]
A control operation of the motor 3 when a steady current flows through the motor 3 will be described. One of the switching signals MF and MR is selectively set to a low level, and the motor 3 is switched to normal rotation or reverse rotation. At this time, in the drive circuit 31 of the present embodiment, the AND circuits 44 and 45 which are drive elements 66 for driving the high-side element unit 7 are, for example, standard gates having a relatively small current capacity such as a current capacity of 20 to 30 mA. A voltage output type that has a relatively large current capacity, such as TC4049BF (current capacity is about 60 mA as an example), for example, is used as the drive element 67 that is composed of an integrated circuit (for example, TC4093BF) and drives the low-side element unit 8. CMOS gate elements are used. The AND circuits 38 and 39 for driving the low-side element unit 8 have a configuration in which two standard gate integrated circuits (TC4049BF) are connected in parallel, and the current capacity is about 120 mA.
[0027]
Assume that the motor 3 is rotating forward, and the N transistor 8a is cut off and the N transistor 8b is turned on correspondingly. In this case, the gate circuit 38 and 39 can determine the OFF state with the current capacity of about 120 mA when the potential difference VDD-G of the N transistor 8a of the low-side element portion 8 in the OFF state is 2V which is the threshold voltage Vth of this transistor. On the other hand, with respect to the high-side element unit 7 that repeats on / off, the potential difference VDD-G of the P transistor 7 that switches between the on state and the off state is 10V-Vth = 8V, and the current capacity of the AND circuits 44 and 45 Is as small as 20 to 30 mA, and the OFF state on the low-side element 8 side by the AND circuits 44 and 45 on the switching side can be determined.
[0028]
Thereby, the situation where both the high side element 7 and the low side element 8 are turned on is prevented, and it is possible to prevent the malfunction that the motor 3 malfunctions due to a short circuit between each other and an excessive abnormal current flowing.
[0029]
Moreover, the structure demonstrated by the said Example shows one Example of this invention, and does not limit the scope of the present invention. The present invention includes a wide variety of modifications that do not depart from the spirit of the present invention.
[0030]
【The invention's effect】
As described above, according to the first aspect of the present invention, the drive circuit for setting the current capacity of the drive circuit for driving the transistor on / off to drive the motor to either the on state or the off state. Therefore, the operating state of the driving circuit for driving the transistors on / off can be determined, the operating state of each of these driving circuits is not determined, and the transistors are short-circuited. The situation can be prevented, and malfunction of the motor can be prevented.
[0031]
In the first aspect of the invention, the first conductivity type may be a P-channel type and the second conductivity type may be an N-channel type. Even in this case, the above-described effects can be achieved. In the first aspect of the invention, the first drive circuit includes a gate integrated circuit element having a current capacity of about 60 mA as a basic configuration, and the second drive circuit includes a gate integrated circuit element having a current capacity of about 20 to 30 mA as a basic configuration. You may make it provide. Also in this case, the function and effect of the first aspect can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration example of a part of a motor drive circuit 31 according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration example of a motor drive circuit 1 which is a basis of the present invention.
FIG. 3 is a graph showing an operation example of a gate element used in the example.
FIG. 4 is a graph showing an operation state of a circuit element according to a related art and an example.
FIG. 5 is a circuit diagram showing a configuration example of a conventional motor drive circuit 1;
6 is a circuit diagram showing a configuration example on the low side of a power element section described later in the drive circuit 1. FIG.
7 is a circuit diagram showing a configuration example on the high side of a power element section described later in the drive circuit 1. FIG.
[Explanation of symbols]
2 Power supply unit 3 Motor 4 Main control unit 5 Power element unit 6 Sub control unit 7 High side element unit 7a, 7b P High side element unit 8 Low side element unit 8a, 8b Low side element unit 31 Drive circuit 38, 39 Gate circuit 42, 43 Signal Transmission Transistors 44, 45 AND Circuit 46 OR Circuit 47 Overcurrent Limiter Circuit

Claims (3)

A transistor of the first conductivity type for supplying a drive current to the motor coil, have a transistor of a second conductivity type into which a driving current flows from the other coils of the motor, the first conductive type transistor and the second conductivity type An inverter circuit including a series circuit of transistors ;
The first drive circuit and, forward-reverse switching signal for switching is input on state said second conductivity type transistor of a motor PWM speed signal is input to turn on / off driving the first conductivity type transistor of the inverter circuit or a second driving circuit for setting to either the off state,
A motor driving device characterized in that the current capacity of the second driving circuit is 4 to 6 times the current capacity of the first driving circuit. 2. The motor driving device according to claim 1, wherein the first conductivity type is a P-channel type, and the second conductivity type is an N-channel type. 2. The first driving circuit includes a gate integrated circuit element having a current capacity of about 60 mA as a basic configuration, and the second driving circuit includes a gate integrated circuit element having a current capacity of about 20 to 30 mA as a basic configuration. Motor drive device.

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