WO2007043828A1

WO2007043828A1 - Circuit for protecting motor driver using relay

Info

Publication number: WO2007043828A1
Application number: PCT/KR2006/004124
Authority: WO
Inventors: Hyeung-Dae Moon
Original assignee: ROH, Joo-Hong
Priority date: 2005-10-13
Filing date: 2006-10-13
Publication date: 2007-04-19
Also published as: KR100707298B1

Abstract

The present invention relates to a motor driver protection circuit, in particular to a motor driver protection circuit for effectively driving a relay provided between a motor and a motor driver. In the motor driver protection circuit according to the present invention provided between a motor driver for intermittently outputting control signals including a motor rotation signal and a motor stop signal through at least one terminal and a motor driven according to the control signal transmitted by the motor driver to prevent inflow of countercurrent from the motor into the motor driver, the motor driver protection circuit includes a solenoid driving signal generating unit for regarding the control signal as being continuously output in case a time that the intermittently output control signal is not output is within a predetermined time, and generating a solenoid driving signal; and a relay having at least one switch operating as a-contact corresponding to the solenoid.

Description

CIRCUIT FOR PROTECTING MOTOR DRIVER USING RELAY

Technical Field

[1] The present invention relates to a motor driver protection circuit, in particular to a motor driver protection circuit for effectively driving a relay provided between a motor and a motor driver. Background Art

[2] A motor forms a first magnetic field using a permanent magnet provided to a stator, arranges a rotor in a space where the first magnetic field is formed, and winds a coil around the rotor. Current applied from the external is inflowed into the coil and a second magnetic field is generated around the coil. The rotor having the wound coil rotates due to magnet force emitting from the first magnetic field formed by the permanent magnet and the second magnetic field formed around the coil.

[3] However, in the structure of the motor discussed above, if external mechanical force is applied to the motor while the motor is idle thereby to rotate the rotor, counter electromotive force is generated to the coil. Due to the generated counter electromotive force, countercurrent is inflowed into electric wires or control signal transmission lines connected to the coil. The countercurrent is then inflowed into the driver, thereby causing electric damage to the driver. In particular, if the motor rotates a roller transferring a fixing plate in a printer performing a printing operation on an object of print fixed on the fixing plate, when external mechanical force is applied to the fixing plate thereby to rotate the roller, consequently the motor is rotated to cause the above accident.

[4] Accordingly, a solution has been suggested to provide a relay between a driver and a motor to protect the driver from countercurrent generated by rotation of the motor.

[5] Seeing a conventional driver protection circuit having a relay with reference to FIG.

1, the conventional driver protection circuit has a relay 10 provided on a transmission line for transmitting to a motor 200 control singals output from a driver 100.

[6] The relay 10 has a first switch 11 where a second terminal 2 and a fourth terminal 4 are connected to a third terminal 3 by a-contact, a second switch 12 where a fifth terminal 5 and a seventh terminal 7 are connected to a sixth terminal 6 by a-contact, and a solenoid 13 connected to an eighth terminal 8 and a first terminal 1.

[7] In addition, the third terminal 3 of the relay 10 is connected to A terminal of the motor driver 100, and the sixth terminal 6 is connected to B terminal of the motor driver 100. The fourth terminal 4 is connected to A' terminal of the motor 200 and the fifth terminal 5 is connected to B' terminal of the motor 200. Also, the first terminal 1 connected to the solenoid 13 is connected to A terminal of the motor driver 100, and the eighth terminal 8 is connected to B terminal of the motor driver 100. Meanwhile, the second terminal 2 and the seventh terminal 7 are connected to grounds, respectively. Here, A terminal of the motor driver 100 outputs control signals for rotating the motor 200. In addition, B terminal of the motor 200 outputs control singals for counter-rotating the motor 200.

[8] As shown in FIG. 2, if there is the difference in signal between A terminal and B terminal (i.e. in the case that it is intended to rotate or counter-rotate the motor), the solenoid 13 is driven so that the first switch 11 and the second switch 12 hold the closed state (ON) thereby to apply control signals to the motor 200. If the signal of A terminal is the same as the signal of B terminal (i.e. in the case that the motor is idle or in the case of a simultaneous operation of rotation and counter-rotation of the motor, which is typically called as an error driving state), the relay 10 allows the first switch

11 and the second switch 12 to hold the open state (OFF) thereby to prevent inflow of countercurrnt occurring from the motor 200 into the motor driver 100 (see the state of FIG. 1).

[9] The use of the relay 10 prevents inflow of countercurrent from the motor 200 into the motor driver 100. However, in the case of a printer driving a roller to perform a printing operation, the roller moves an object of print divided into a plurality of imaginary lines to a print head thereby to perform a printing operation on each of the imaginary lines by stages. Thus, while the print head is printing a line, the object of print should be fixed, which requires to stop the motor. As a result, a driving signal is intermittently applied in the printer. As such, if A terminal or B terminal intermittently transmits a driving (H; High) signal, the first switch 11 and the second switch 12 of the relay 10 are opened or closed repetitively, thereby resulting in reduced life of the relay 10. In addition, reptitive opening or closing of the first switch 11 and the second switch

12 results in repeated uncomfortable noises during a printing operation.

[10] Generally, if intensity of current flowing through the coil changes, induced electromotive force occurs to the coil. Therefore, if control signals composed of a combination of L signal and H signal are applied to a solenoid having a coil, induced electromotive force occurs to the solenoid according to the change of the control signal, and thus operation of the switch is delayed. In particular, if a motor driver transmits control singals for rotation, counter-rotation or stop of a motor through a single terminal, induced electromotive force continuously occurs to the relay according to the change of the control signal. Thus, the control sigal should be output in consideration of delay time caused by induced electromotive force, which has a difficulty in controlling the motor at high speed. Disclosure of Invention

Technical Problem

[11] The present invention is designed to solve the problems of the prior art, and therefore it is an object of the present invention to provide a circuit capable of reducing unnecessary operation of a relay connected between a motor and a motor driver. Technical Solution

[12] In order to achieve the above-mention object, in a motor driver protection circuit according to the present invention provided between a motor driver for intermittently outputting control signals including a motor rotation signal and a motor stop signal through at least one terminal and a motor driven according to the control signal transmitted by the motor driver to prevent inflow of countercurrent from the motor into the motor driver, the motor driver protection circuit includes a solenoid driving signal generating unit for regarding the control signal as being continuously output if a time that the intermittently output control signal is not output is within a predetermined time and generating a solenoid driving signal; and a relay having a solenoid connected to the solenoid driving signal generating unit and at least one switch operating as a- contact in order to transmit to the motor the control signal transmitted from the motor driver as current inflows into the solenoid. Brief Description of the Drawings

[13] These and other features, aspects, and advantages of preferred embodiments of the present invention will be more fully described in the following detailed description, taken accompanying drawings. In the drawings:

[14] FIG. 1 is a circuit diagram of a conventional motor driver protection circuit.

[15] FIG. 2 is a timing diagram illustrating signal flow at each terminal of the conventional motor driver protection circuit.

[16] FIG. 3 is a circuit diagram of a motor driver protection circuit in accordance with an exemplary embodiment of the present invention.

[17] FIGS. 4 and 5 are circuit diagrams illustrating operation of the motor driver protection circuit according to a control signal in accordance with an exemplary embodiment of the present invention.

[18] FIG. 6 is a timing diagram illustrating signal flow at each terminal of the motor driver protection circuit in accordance with an exemplary embodiment of the present invention. Best Mode for Carrying Out the Invention

[19] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meansings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the invention.

[20] In the exemplary embodiment of the present invention, a motor driver and a motor are provided to drive a flat plate-type printer for printing an object of print fixed on a flat plate. And, the motor driver intermittently outputs control signals including a rotation signal, a counter-rotation signal, or a stop signal of the motor. Thus, the motor is driven according to the control signal to move the flat plate through a roller connected to a rotor of the motor. Although this exemplary embodiment of the present invention shows that the motor driver and the motor are provided to a flat plate-type printer, the present invention is not limited thereto. The present invention may be variously applied to circuits having a driver and a motor for intermittently outputting control signals based on the spirit and scope of the invention.

[21] FIG. 3 is a circuit diagram of a motor driver protection circuit in accordance with an exemplary embodiment of the present invention.

[22] Referring to FIG. 3, the motor driver protection circuit includes a solenoid driving signal generating unit 20 and a relay 30 provided on a transmission line for connecting a motor driver 100 to a motor 200.

[23] The motor driver 100 generates and transmits control signals including a rotation signal or a counter-rotation signal of the motor 200. The control signal may be generated through various methods, and the motor driver 100 may transmit at least one control signal to the motor 200. In the exemplary embodiment of the present invention, the motor driver 100 transmis control signals for controlling the motor 200 through two terminals (A, B) to the motor 200. Here, A terminal outputs a rotation signal of the motor 200 and B terminal outputs a counter-rotation signal of the motor 200. If both of A terminal and B terminal do not output signals, the motor 200 stops.

[24] The solenoid driving signal generating unit 20 has a first timer 21 and a second timer 22 each connected to transmission lines through which the motor driver 100 transmits the control signal to the motor 200, and a OR gate 23 for OR operating the signal output from the first timer 21 and second timer 22.

[25] The first timer 21 is connected to A terminal of the motor driver 100. When the motor driver 100 outputs H(High) signal through A terminal, the first timer 21 maintains the H signal for a predetermined time and transmits the H signal to the OR gate 23. In addition, the second timer 22 is connected to B terminal of the motor driver 100. When the motor driver 100 outptus H(High) signal through B terminal, the second timer 22 maintains the H signal for a predetermined time and transmits the H signal to the OR gate 23. If at least one control signal is H signal, the OR gate 23 outputs H signal. Here, the predetermined time is at least equal to or longer than a time that a flat plate, i.e. the motor 200 should stop for a print head of a flat plate-type printer to perform a printing operation on a single line, and the predetermined time is between several milliseconds and several seconds although it depends on printing speed of the flat plate.

[26] Meanwhile, the OR gate 23 OR operates the control signal input from the first timer

21 and the second timer 22, and outputs the control signal as a single solenoid driving signal. Thus, if at least one control signal input from the first timer 21 or the second timer 22 is H signal, the OR gate 23 outputs H signal.

[27] Although this exemplary embodiment shows the relay 30 is an 8-pin relay having two switches, the present invention is not limited thereto.

[28] The relay 30 includes a first switch 31 where a second terminal 2 and a fourth terminal 4 are connected to a third terminal 3 by a-contact, a second switch 32 where a fifth terminal 5 and a seventh terminal 7 are connected to a sixth terminal 6 by a- contact, and a solenoid 33 connected to an eighth terminal 8 and a first terminal 1.

[29] The third terminal 3 of the relay 30 is connected to A terminal of the motor driver

100, and the sixth terminal 6 is connected to B terminal of the motor driver 100. The fourth terminal 4 is connected to A' terminal of the motor 200, and the fifth terminal 5 is connected to B' terminal of the motor 200. In addition, the eighth terminal 8 connected to the solenoid 33 is connected to C terminal, i.e. an output terminal of the solenoid driving signal genrating unit 20, and the second terminal 2, seventh terminal 7 and first terminal 1 are connected to grounds, respectively.

[30] Now the operation of a motor driver protection circuit according to the exemplary embodiment of the present invention will be described with reference to FIGS. 4 to 6 as follows.

[31] FIGS. 4 and 5 are circuit diagrams illustrating the operation of the motor driver protection circuit according to a control signal in accordance with an exemplary embodiment of the present invention. FIG. 6 is a timing diagram illustrating signal flow at each terminal of the motor driver protection circuit according to an exemplary embodiment of the present invention.

[32] In the case that A terminal of the motor driver 100 outputs H(High) signal and B terminal outputs L(Low) signal (i.e. in the case of rotation of the motor 200, see FIG. 4), the solenoid driving signal generating unit 20 maintains H signal for a predetermined time and outputs the H signal through the OR gate 23. In addition, the solenoid driving signal generating unit 20 then applies the H signal to the eighth terminal 8 of the relay 30. Thus, current flows through the solenoid 33 connected to the eighth terminal 8 of the relay 30, and the first and second switches 31 and 32 come to a closed state (ON). As a result, A terminal of the motor driver 100 is electrically connected to A' terminal of the motor 200. And, B terminal of the motor driver 100 is electrically connected to B' terminal of the motor 200.

[33] Likewise, based on the principle discussed above, in the case that A terminal of the motor driver 100 outputs L signal and B terminal outputs H signal (i.e. in the case of counter-rotation of the motor 200, see FIG. 5), the solenoid driving signal generating unit 20 outputs H signal for a predetermined time. The solenoid driving signal generating unit 20 then applies the H signal to the eighth terminal 8 of the relay 30. Thus, current flows through the solenoid 33 connected to the eighth terminal 8, and the first switch 31 and the second switch 32 come to a closed state (ON). Thereby the control signal generated from the motor driver 100 is transmitted to the motor 200.

[34] The solenoid driving signal generating unit 20 for controlling the operation of the relay 30 delays H signal for a predetermined time and transmits the H signal to C terminal. Thus, in the case that A terminal or B terminal of the motor driver 100 intermittently transmits H signal and L signal, C terminal continuously outputs H signal (see FIG. 6).

[35] Therefore, while the printer performs a printing operation, even though the motor driver 100 intermittently outputs a control signal, the relay 30 holds the closed state (ON), thereby eliminating unnecessary switching operation of the relay 30. Meanwhile, in the case that the motor driver 100 does not output a control signal more than a predetermined time (i.e. in the case that the printer does not perform a printing operation), the relay 30 holds the open state (OFF), thereby preventing inflow of counter electromotive force into the motor driver 100, which is generated from the motor 200 by external mechanical pressure.

[36] Although this exemplary embodiment shows the motor 200 is capable of rotation and counter-rotation, the present invention may be applied to the motor 200 capable of rotation only or counter-rotation only. In this case, the motor driver 100 may be provided with a single output terminal, and the relay 30 may be a 5-pin relay. The solenoid driving signal generating unit 20 may be provided with a single timer, and may be not provided with the OR gate 23.

[37] The present invention has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodimetns of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. Industrial Applicability

[38] As described above, the motor driver protection circuit according to the present invention may prevent inflow of countercurrent into the motor driver caused by counter-rotation of the motor using at least one relay. [39] Also, it may reduce unnecessary operation of a relay contact thereby to maintain the life of the relay and reduce noises resulted from unnecessary operation of the contact. [40] Further, according to the exemplary embodiment of the present invention, it may prevent a response delay of the relay resulted from the change of the motor control signal. [41]

Claims

[1] A motor driver protection circuit provided between a motor driver for intermittently outputting control signals including a motor rotation signal and a motor stop signal through at least one terminal and a motor driven according to the control signal of the motor driver to prevent inflow of countercurrent from the motor into the motor driver, the motor driver protection circuit comprising: a solenoid driving signal generating unit for regarding the control signal as being continuously output in case a time that the intermittently output control signal is not output is within a predetermined time, and generating a solenoid driving signal; and a relay having a solenoid connected to the solenoid driving signal generating unit, and at least one switch operating as a-contact in order to transmit to the motor the control signal transmitted from the motor driver as current inflows into the solenoid.

[2] The motor driver protection circuit of claim 1, wherein the motor rotates a roller for transferring a fixing plate in a printer performing a printing operation on an object of print fixed on the fixing plate.