Motor control apparatus

A motor control apparatus supplying braking power to brake a motor comprises a braking power providing unit to receive input power having an input power voltage lower than a braking power voltage and to boost the input power voltage up to the braking power voltage to brake the motor; a switching unit closing to allow the braking power providing unit to store the input power and opening to allow the braking power providing unit to output the braking power by boosting the input power voltage and a stored power voltage up to the braking power voltage; and a controller to control the switching unit to close and to open. With this configuration, a motor control apparatus is provided, in which an additional braking power supply supplying braking power to brake a motor is not needed, thereby decreasing a production cost and a size of a product.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2003-7873, filed Feb. 7, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a motor control apparatus, and more particularly, to a motor control apparatus in which a power supply to drive other components is employed in braking a motor without an additional power supply.

2. Description of the Related Art

A three-phase motor has three windings and is driven by three-phase power. To control the three-phase motor, a motor control apparatus, as shown inFIG. 1, comprises a controller power supply160to supply power to an inverter controller122and a braking controller124, an inverter110to supply the three-phase power to a motor100, an inverter controller122to control the inverter110to generate the three-phase power, a braking circuit part130to brake the three-phase motor100, and a braking controller124to output a braking signal to brake the three-phase motor100to the braking circuit part130.

The inverter110converts DC (direct current) power into three-phase AC (alternating current) power and supplies the three-phase AC power to the three-phase motor100, wherein the DC power is supplied through a rectifying part (not shown) and a capacitor (not shown) which rectify and smooth commercial AC power of an AC power supply (not shown). Here, the inverter110comprises a plurality of transistors120and a plurality of diodes140.

The inverter controller122operates at a voltage of 5V and selectively turns on/off the transistors120of the inverter110, thereby controlling the inverter110to convert the DC power into the three-phase AC power.

The braking circuit part130includes a relay part132closing and opening so as to control a supply of braking power from a braking power supply170to the three-phase motor100, and a braking condenser134to store the braking power supplied from the braking power supply170. Further, the braking power supplied from the braking power supply170via the braking condenser134generally has a voltage of 24V. The relay part132is closed/opened by a relay driving circuit132aaccording to control by the braking controller124.

Further, the braking circuit part130comprises a braking diode136to prevent a voltage spike generated a moment when the relay part132is opened from being supplied to the braking power supply170, and a freewheeling diode137to bypass a current remaining in the three-phase motor100when the three-phase motor100is disconnected from the braking circuit part130by, for example, a disconnection of a connector138.

However, in the conventional motor control apparatus, the power supplied to the inverter controller122and the braking controller124is different from that supplied to the braking circuit part130in a voltage thereof, so that the braking power supply170is further provided to generate the braking power to brake the three-phase motor100. Therefore, a production cost and a size of a product are increased for the conventional motor control apparatus.

SUMMARY OF THE INVENTION

Accordingly, it is an aspect of the present invention to provide a motor control apparatus to generate braking power without an additional power supply.

Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious form the description, or may be learned by practice of the invention.

The above and/or other aspects are achieved by providing a motor control apparatus supplying braking power to brake a motor, comprising a braking power providing unit to receive input power having an input power voltage lower than a braking power voltage and to boost the input power voltage up to the braking power voltage to brake the motor; a switching unit being closed to allow the braking power providing unit to store the input power and being opened to allow the braking power providing unit to output the braking power by boosting the input power voltage and a stored power voltage up to the braking power voltage; and a controller to control the switching unit to selectively close and open.

The motor control apparatus may further comprise a controller power supply to supply driving power to the controller, wherein the driving power from the controller power supply is used as the input power to be supplied to the braking power providing unit.

The braking power providing unit may comprise an inductor to store the input power supplied from the controller power supply; and a condenser to output the input power and a stored power of the inductor as the braking power, when the switching unit is opened.

The switching unit may be connected to opposite ends of the condenser.

The switching unit may be an FET having a gate terminal connected to the controller, and drain and source terminals respectively connected to the opposite ends of the condenser.

The motor control apparatus may further comprise a diode having an anode connected to the inductor and a cathode connected to the condenser, and preventing a voltage spike generated a moment when the condenser is disconnected from the motor from being supplied to the inductor.

The controller may output a boost signal having a predetermined duty cycle and a braking signal to brake the motor; and the motor control apparatus may further comprise an AND circuit part performing an AND operation between the boost signal and the braking signal which are outputted from the controller, and outputting a logical value to the gate terminal of the FET.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 2is a circuit diagram of a motor control apparatus according to an embodiment of the present invention.

Referring toFIG. 2, a motor control apparatus comprises a braking power providing unit30to receive input power having an input power voltage lower than a braking power voltage and to boost the input power voltage up to the braking power voltage to brake a motor1; a switching unit40closing to allow the braking power providing unit30to store the input power and opening to allow the braking power providing unit30to output braking power by boosting the input power voltage and a stored power voltage up to the braking power voltage; and a controller20to control the switching unit40to close and to open. Further, the motor control apparatus comprises an inverter10to generate multi-phase AC power to drive the motor1.

To the inverter10is supplied DC power through a rectifying part (not shown) and a capacitor (not shown) which rectify and smooth commercial AC power of an AC power supply (not shown). The inverter10receives the DC power through the rectifying part and the capacitor and converts the DC power into the multi-phase AC power having various frequencies, thereby supplying the three-phase AC power to the motor1. The motor1is driven to rotate by the multi-phase AC power supplied from the inverter10. Further, the inverter10comprises a plurality of transistors12and a plurality of diodes14, and the controller20selectively turns on/off the transistors12of the inverter10so as to control the inverter10to convert the DC power into the three-phase AC power having the various frequencies.

Further, the motor control apparatus comprises a controller power supply60to supply driving power to the controller20. Further, a driving power voltage to drive the controller20is lower than the braking power voltage to brake the motor1, and the driving power from the controller power supply60is used as the input power to supply the braking power providing unit30.

The braking power providing unit30comprises an inductor32to store the input power supplied from the controller power supply60, and a condenser34to smooth the input power and the stored power of the inductor32when the switching unit40is open and outputting the braking power.

The switching unit40is connected to opposite ends of the condenser34. An FET (field effect transistor) is, as shown inFIG. 2, such that the gate terminal of the FET40is connected to the controller20, and a drain terminal of the FET40and a source terminal of the FET40are, respectively, connected to the opposite ends of the condenser34. The drain and source of the FET40are connected to each other or are disconnected from each other according to a control signal, which is outputted from the controller20to the gate terminal of the FET40.

Further, the motor control apparatus comprises an AND circuit part70provided between the controller20and the gate terminal of the FET40and performing an AND operation between a boost signal and a braking signal (“Br on/off”) which are outputted from the controller20, thereby outputting a logical value to the gate terminal of the FET40. Further, an AND gate may be used as the AND circuit part70, which outputs a logical signal having a first level of “1” only when both the boost signal and the braking signal have logical values of “1”, and, otherwise, outputs the logical signal having a second level of “0”. The FET40may turn off when the AND circuit part70outputs the logical signal having the first level of “1”, and may turn on when the AND circuit part70outputs the logical signal having the second level of “0”.

With this configuration of the motor control apparatus, a process of outputting the braking power to brake the motor1will be described with reference toFIGS. 2 through 5D.

The controller20controls the transistors12of the inverter10to selectively turn on/off to supply the three-phase AC power to the motor1. Further, the controller20operates by a voltage of 5V supplied from the controller power supply60.

Further, the controller20continuously outputs the boost signal having a predetermined duty cycle to the AND circuit part70. Simultaneously, the controller20outputs the braking signal having a logical value of “0” to the AND circuit part70. The AND circuit part70performs the AND operation between the boost signal and the braking signal, which has the logical value of “0” and outputs the logical signal having the second level of “0” to the gate terminal of the FET40to connect the drain terminal of the FET40and the source terminal of the FET40, i.e., turning on the FET40.

FIG. 3illustrates power flow on the braking power providing unit30when the FET40is turned on. In this case, the input power having the voltage of 5V is stored in the inductor32while the FET40is turned on. Further, voltage “VL” applied between opposite ends of the inductor32can be written as follows, where inductance of the inductor32is “L”.

However, when the controller20senses a predetermined signal to brake the motor1(refer to “t1” inFIG. 5D), the controller20outputs the braking signal having the logical value of “1” and the braking signal having the logical value of “1” is transmitted to the AND circuit part70, and the AND circuit part70performs the AND operation between the boost signal and the braking signal having the logical value of “1”, to output the logical signal. Further, the logical signal outputted from the AND circuit part70has a waveform corresponding to a waveform of the boost signal, and turns on/off the FET40in response to a duty cycle of the braking signal.

FIG. 4illustrates a power flow on the braking power providing unit30when the FET40is turned off. In this case, the input power from the controller power supply60and the power stored in the inductor32are stored in the condenser34. The power stored in the condenser34is outputted and used as the braking power to brake the motor1. Further, a voltage “VB” outputted to the condenser34can be written as follows.
VB=5V−VL

Where VL(refer to equation 1) is a voltage applied between the opposite ends of the inductor32, whose positive and negative ends are reversed when the FET40is turned off, the VLhaving a negative value. Therefore, the voltage “VB” outputted to the condenser34is higher than the input power of 5V applied to the inductor32. That is, the braking power voltage outputted through the condenser34is higher than the input power voltage inputted to the inductor32.FIG. 5Dillustrates that the braking power “VB” outputted through the condenser34is 24V.

Further, when the controller20does not sense a predetermined signal to brake the motor1or senses a predetermined signal to interrupt braking of the motor1(refer to “t2” inFIG. 5D), the controller20outputs the braking signal having the logical value of “0”. Then, the braking signal having the logical value of “0” is transmitted to the AND circuit part70, and the AND circuit part70outputs the logical signal having the second level of “0”, thereby turning on the FET40and allowing the inductor32to store the input power supplied from the controller power supply60.

Further, the motor control apparatus comprises a spike diode50having an anode connected to the inductor32and a cathode connected to the condenser34, and preventing a voltage spike generated a moment the condenser34is disconnected from the motor1from being supplied to the inductor32. Thus, when the condenser34disconnects from the motor1according to a disconnection of a connector80or to a broken wire connecting the condenser34with the motor1, the inductor32or the controller power supply60is prevented from being damaged by a reverse-current of the voltage spike.

The motor control apparatus may use the power supplied from the controller power supply60to the controller20in generating the braking power. However, power having a voltage lower than that of the braking power voltage used to drive other components may be used in generating the braking power.

The FET40may be used as the switching unit40. However, a different kind of transistor, a relay, etc. may be used as the switching unit40, which is connectable to the opposite ends of the condenser40and turns on/off according to the control signal of the controller20.

The controller20may control both the inverter10and the switching unit40. However, the inverter10and the switching unit40may be controlled by an inverter controller and a braking controller, respectively.

The motor control apparatus may be applied to the motor1having the three-phase configuration. However, the motor control apparatus may be applied to a single-phase motor.

As described above, the motor control apparatus comprises the braking power providing unit30to receive the input power having an input power voltage lower than the braking power voltage and to boost the input power voltage up to the braking power voltage to brake the motor1; the switching unit40closing to allow the braking power providing unit30to store the input power and opening to allow the braking power providing unit30to output the braking power by boosting both the input power voltage and the stored power voltage up to the braking power voltage; and the controller20to control the switching unit40to close and to open. The conventional braking power supply is not required to supply braking power, thus, a production cost and a size of a product is decreasable.

As described above, a motor control apparatus is provided, in which an additional braking power supply supplying braking power to brake a motor is not needed, thereby decreasing the production cost and the size of the product.