JP2004023925A - Motor driving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain cost reduction in the whole device without providing a dedicated watchdog circuit nor driving a motor even if a microcomputer runs away. <P>SOLUTION: This circuit includes conversion circuits R23, C1, C2, D1, D2 which input a pulse type AC signal corresponding to a watchdog pulse signal and convert the AC signal into DC voltage, MOSFETs 21, 22 to which driving voltage (DC voltage) is supplied from the conversion circuits and which controls ON/OFF of a driving power of the motor 24, and a relay circuit 23 which supplies the driving power to the motor 24 corresponding to the operation of the MOSFETs. When the pulse type AC voltage is supplied to the conversion circuits, the DC voltage of constant voltage is applied to the MOSFETs 21, 22, and when the DC voltage is supplied to the conversion circuits, a DC voltage level to be supplied to the MOSFETs 21, 22 is dropped to turn off the MOSFETs 21, 22. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motor drive circuit that drives a motor according to an instruction from a microcomputer.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a motor driving device that drives a motor in accordance with an instruction from a microcomputer, for example, a motor driving device that controls opening and closing of a latch of a back door of an automobile is known.
[0003]
In this motor drive device, the microcomputer recognizes that the switch has been operated by the user, releases the latch of the back door, brings the back door into a so-called half-door state, or changes the back door from the open state to the half-door state. In this case, the direction of power supply to the motor is controlled so that the latch is closed.
[0004]
[Problems to be solved by the invention]
By the way, the microcomputer of the conventional motor drive circuit is provided with a watchdog circuit in order to prevent the motor from being driven due to runaway of the microcomputer. This watchdog circuit monitors that a pulse is generated at a constant cycle, and for example, when the pulse signal becomes a substantially DC signal, detects that a microcomputer runaway or the like has occurred, Stop the operation of the drive circuit.
[0005]
However, in the conventional motor drive circuit, it was necessary to provide a dedicated watchdog circuit, so that the cost of the entire apparatus was increased.
[0006]
Therefore, the present invention has been proposed in view of the above-described circumstances, and without providing a dedicated watchdog circuit, without driving a motor even when a microcomputer runs away, the cost of the entire apparatus can be reduced. It is an object of the present invention to provide a motor drive circuit that can reduce power consumption.
[0007]
[Means for Solving the Problems]
In the motor drive circuit according to the present invention, a pulse-like AC signal corresponding to a watchdog pulse signal is input from the motor drive circuit, and a conversion path for converting the AC signal into a DC voltage; Voltage) is supplied, and a switch circuit that controls on / off of the drive power of the motor, and a motor drive unit that supplies drive power to the motor in accordance with the operation of the switch circuit.
[0008]
In this motor drive circuit, a constant DC voltage is applied to the switch circuit when a pulsed AC voltage is supplied to the conversion circuit, and the switch is applied when the DC voltage is supplied to the conversion circuit. The above problem is solved by reducing the DC voltage level supplied to the circuit and turning off the switch circuit.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0010]
The present invention is applied to, for example, a door drive system including a switch signal input circuit configured as illustrated in FIG. 1 and a motor drive circuit configured as illustrated in FIG. Note that the above embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and other than the present embodiment, various modifications may be made according to the design and the like within a range not departing from the technical idea according to the present invention. Can be changed.
[0011]
[Configuration of switch signal input circuit]
This switch signal input circuit connects a positive terminal of a battery 1 that generates a battery voltage and an emitter terminal of a PNP transistor 2, and connects a base terminal of the PNP transistor 2 and an O / S handle switch via resistors R1 and R2. 3 is connected to one terminal. The other terminal of the O / S handle switch 3 is connected to the negative terminal of the battery 1 and the GND terminal 4.
[0012]
In the present example, the O / S handle switch 3 is a switch for releasing the latch of the back door of the automobile to bring the back door into a half-door state, and is opened and closed by the user.
[0013]
The base terminal of the NPN transistor 5 is connected to the collector terminal of the PNP transistor 2 via the resistors R3 and R4. A drive power supply terminal 6 applied to a switch signal input terminal 11a of the microcomputer 11 is connected to a collector terminal of the NPN transistor 5 via a resistor R5. When the NPN transistor 5 is turned on and off, the drive power supply Vcc is switched as a switch signal. Apply to the signal input terminal 11a.
[0014]
The switch signal input circuit detects that the back door has been changed from the open state to the half-door state, and the switch 7 for driving the latch of the back door in the closing direction and the actuator for driving the latch are in the terminal position. A switch 8 is provided for detecting the arrival.
[0015]
The switch 7 has one terminal connected to the base terminal of the PNP transistor 9 and the other terminal connected to the negative terminal and the GND terminal 4 of the battery 1, similarly to the O / S handle switch 3. Like the PNP transistor 2, the PNP transistor 9 has an emitter terminal connected to the positive terminal of the battery 1, and a collector terminal connected to the base terminal of the NPN transistor 10. The NPN transistor 10 has a collector terminal connected to the drive power supply terminal 11 and the switch signal input terminal 11b, and an emitter terminal grounded.
[0016]
The switch 8 has one terminal connected to the base terminal of the PNP transistor 12 and the other terminal connected to the negative terminal and the GND terminal 4 of the battery 1, similarly to the O / S handle switch 3. Like the PNP transistor 2, the PNP transistor 12 has an emitter terminal connected to the positive terminal of the battery 1, and a collector terminal connected to the base terminal of the NPN transistor 13. The NPN transistor 13 has a collector terminal connected to the drive power supply terminal 14 and the switch signal input terminal 11c, and an emitter terminal grounded.
[0017]
In such a switch signal input circuit, when the O / S handle switch 3 is not operated and is in an open state, the battery voltage is applied to the base terminal of the PNP transistor 2 via the resistor R1. And the PNP transistor 2 is off. Therefore, no base current is supplied from the PNP transistor 2 to the NPN transistor 5, so that the NPN transistor 5 is also turned off. In this state, the switch signal applied from the drive power supply terminal 6 to the switch signal input terminal 11a is at a high (H) level, and the microcomputer 11 recognizes that the O / S handle switch 3 is not operated. . Similarly, even when the switches 7 and 8 are not operated, a high (H) level switch signal is applied to the switch signal input terminals 11b and 11c.
[0018]
On the other hand, when the O / S handle switch 3 is operated to be in a closed state, a low (L) level voltage is applied to the base terminal of the PNP transistor 2 and a current is generated between the emitter terminal and the base terminal. As a result, the PNP transistor 2 is turned on, and a base current is supplied to the base terminal of the NPN transistor 5 to turn the NPN transistor 5 on. Then, a low (L) level switch signal is applied to the switch signal input terminal 11a. Thus, the microcomputer 11 recognizes that the O / S handle switch 3 has been operated. Further, even when the switches 7 and 8 are turned on, the L-level switch signal is similarly applied to the switch signal input terminals 11b and 11c.
[0019]
[Operation of switch signal input circuit]
Next, the operation of the above-described switch signal input circuit when the battery voltage temporarily drops due to the cranking of the battery 1 or the like will be described with reference to the timing chart of FIG.
[0020]
In this switch signal input circuit, when the battery 1 is generating a voltage of, for example, 12 V (FIG. 2A), the O / S handle switch 3 is turned on (operated) from off (non-operation) at times t1 to t2. ) (FIG. 2B), the NPN transistor 5 is turned on as described above, and the switch signal applied to the switch signal input terminal 11a changes from H level to L level (FIG. 2D). ).
[0021]
On the other hand, even if the voltage of the battery 1 drops from 12 V at time t3 due to some cause, the NPN transistor 5 is not turned on in the switch signal input circuit of FIG. The voltage level supplied to the input terminal 11a never goes low. Therefore, even if the battery voltage suddenly drops for some reason, the microcomputer 11 does not erroneously recognize that the O / S handle switch 3 has been operated.
[0022]
In addition, it goes without saying that the open switch 7 and the close switch 8 perform the same operation.
[0023]
[Effect of switch signal input circuit]
According to this switch signal input circuit, the PNP transistor 2 can be held in an off state unless the O / S handle switch 3 is operated, even when an instantaneous power interruption such as cranking occurs. Erroneous recognition of the microcomputer 11 due to the variation of the Therefore, according to the switch signal input circuit, it is possible to reliably prevent the microcomputer 11 from erroneously recognizing and driving the back door to the half-door state even when the O / S handle switch 3 is not operated. .
[0024]
[Configuration of motor drive circuit]
Next, the configuration of the motor drive circuit in the door drive system will be described. In this example, a motor drive circuit that is connected to the above-described switch signal input circuit via the microcomputer 11 and drives a latch (not shown) of the back door under the control of the microcomputer 11 will be described.
[0025]
As shown in FIG. 3, the motor drive circuit outputs a control signal from a motor drive terminal 11 d and a motor drive terminal 11 e of the microcomputer 11, so that a metal-oxide-semiconductor field effect MOSFET (MOSFET) is provided. By controlling on / off of the MOSFET 21 and the MOSFET 22, a current is supplied from the motor drive power supply VB to the motor 24 via the relay circuit 23.
[0026]
The relay circuit 23 is connected to a motor drive battery (not shown), and is supplied with a motor drive power supply VB. The relay circuit 23 includes a relay 31 connected to the MOSFET 21, a relay 32 connected to the MOSFET 22, a switch circuit 33, and a switch circuit 34.
[0027]
In this relay circuit 23, the terminal b and the terminal a or the terminal c of the switch circuit 33 are connected so that the motor drive power supply VB in any direction is applied to the motor 24 in accordance with an instruction from the microcomputer 11, and The terminal b of the switch circuit 34 is connected to the terminal a or the terminal c. In the relay circuit 23, when releasing the latch of the back door, the terminals b and c of the switch circuit 33 are connected, and the terminals b and a of the switch circuit 34 are connected. VB is set in the direction of the electric current indicated by the arrow in the figure. Conversely, when locking the latch of the back door, the terminal b of the switch circuit 33 is connected to the terminal a, and the terminal b of the switch circuit 34 is connected to the terminal c.
[0028]
When the switch 8 is turned on, the signal of the motor drive terminal 11e or 11d becomes L level, and naturally the MOSFET 22 or 21 is turned off.
[0029]
In this motor drive circuit, when controlling the motor 24 to release the latch, a pulse-like motor drive signal corresponding to a watchdog pulse is generated at the motor drive terminal 11e. As shown in FIG. 4A, the motor drive signal is output from the microcomputer 11 at a period of, for example, 400 μsec. When the motor drive signal is input to the resistor R23, a voltage waveform as shown in FIG. And applied to the capacitor C1. Then, the motor drive signal is applied to the diode D2 and the capacitor C2 in a voltage waveform as shown in FIG. 4C by the capacitor C1 and the diode D1, and is applied by the diode D2 and the capacitor C2 as shown in FIG. A substantially DC waveform is obtained. In this way, a conversion circuit for converting a pulse signal into a DC signal is formed at the output terminal of the motor drive terminal 11e, and a substantially DC waveform is supplied to the gate terminal of the MOSFET 22 via the resistors R24 and R25 to turn on the MOSFET 22.
[0030]
Here, when an abnormality occurs in the microcomputer 11 and no pulse-like motor drive signal is generated as in the time after time t11 in FIG. 4A, the voltage is clamped at the H level from the motor drive terminal 11e. May be output.
[0031]
At this time, in the motor drive circuit, since the capacitor C1 is connected in series to the terminal 11e as described above, no motor drive signal is input as a pulse signal, and therefore, as shown in FIG. The level of the motor drive signal supplied to the gate terminal gradually decreases, and the MOSFET 22 is turned off. As a result, no current for releasing the latch flows through the motor 24.
[0032]
[Effects of motor drive circuit]
As described above in detail, according to the motor drive circuit, even when the H level motor drive signal is output due to the abnormality of the microcomputer, the motor 24 is not driven and therefore the latch is released. Can be prevented.
[0033]
Further, according to this motor drive circuit, since a watchdog pulse can be used as a motor drive signal, there is no need to provide a watchdog circuit or the like, and the cost of the entire apparatus can be reduced.
[0034]
When the motor drive circuit closes the latch, an H level motor drive signal is supplied from the motor drive terminal 11d to the gate terminal of the MOSFET 21 via the resistors R21 and R22, and the MOSFET 21 is turned on. As a result, the terminal b of the switch circuit 33 is connected to the terminal a by the relay coil 31 of the relay 23, and a current is supplied from the motor drive power supply VB to the motor 24 in a direction opposite to the direction shown by the arrow.
[0035]
【The invention's effect】
According to the motor drive circuit of the present invention, a pulse-like AC signal corresponding to a watchdog pulse signal generated by the microcomputer is converted into a DC voltage, and this DC voltage is applied to the switch circuit to drive the motor. In the case where an abnormality occurs in the microcomputer, a pulse-like AC signal is not generated, and a DC voltage is generated, the voltage level supplied to the switch circuit is reduced, and the switch circuit is not turned on. . That is, even when an abnormality occurs in the microcomputer and a substantially DC motor drive signal is supplied from the microcomputer, the motor is not driven. Further, according to this motor drive circuit, it is not necessary to provide a watchdog pulse signal monitoring circuit or the like, and the cost of the entire apparatus can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of a switch signal input circuit.
FIG. 2 is a timing chart for explaining the operation of the switch signal input circuit.
FIG. 3 is a circuit diagram showing a configuration of a motor drive circuit to which the present invention is applied.
FIG. 4 is a timing chart for explaining the operation of the motor drive circuit to which the present invention is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Battery 2 PNP transistor 3 O / S handle switch 4 GND terminal 5 NPN transistor 6 Drive power supply terminal 7 Switch 8 Switch 9 PNP transistor 10 NPN transistor 11 Microcomputer 12 PNP transistor 13 NPN transistor 14 Drive power supply terminal 21 MOSFET
22 MOSFET
23 Relay circuit 24 Motor 31, 32 Relay 33, 34 Switch circuit

Claims (2)

Motor and
A microcomputer for generating a pulsed AC signal,
A conversion circuit for converting the AC signal generated by the microcomputer into a DC voltage signal,
A switch circuit that controls on / off of drive power supplied to the motor according to the DC voltage signal output from the conversion circuit;
Motor drive means for supplying drive power to the motor in accordance with the operation of the switch circuit,
When a pulsed AC voltage is supplied, the conversion circuit applies a constant DC voltage to the switch circuit, and supplies a DC voltage instead of a pulsed AC signal due to an abnormality in the microcomputer. A motor driving circuit configured to reduce a DC voltage level to be supplied to the switch circuit when the switching is performed. 2. The motor drive circuit according to claim 1, wherein the conversion circuit includes a capacitor connected in series to the microcomputer and the switch circuit.

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