JP2014168575A - Motor driving device for dewaterer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a circuit element from an overvoltage generating accompanying regenerative electric power during a reset period of a microcomputer, while suppressing complication of a circuit configuration and increase in a production cost.SOLUTION: A motor driving device drives a motor for rotating a dewatering tub of a dewaterer, and it includes: an inverter circuit; a microcomputer and a potential fixing circuit. The inverter circuit includes a plurality of switching elements connected in a bridge shape. The microcomputer includes a control signal output terminal for outputting a control signal for controlling the drive of the switching element and an input/output terminal, and controls an operation of the inverter circuit. The potential fixing circuit executes a potential fixing operation for fixing the potential of the control signal to a level in which one of an upper arm side switching element and a lower arm side switching element is blocked and the other is conducted when the input/output terminal becomes a high impedance state, and stops the potential fixing operation when the input/output terminal becomes an output state of outputting a signal of a predetermined logical level.

Description

  Embodiments described herein relate generally to a motor drive device for a dehydrator.

  A rotating tub (washing tub, dehydrating tub) such as a washing machine or a dehydrator is rotated by a motor. In addition, the motor is driven by a motor driving device including an inverter circuit and a microcomputer (hereinafter also referred to as a microcomputer) that controls the inverter circuit. In such a configuration, in a state where the rotating tub is being rotated by the motor, if the motor driving is stopped due to some abnormality in the motor driving device, electric power corresponding to the rotational energy of the motor (regenerative power) May be regenerated to the inverter circuit side, and the main circuit voltage may abnormally rise to damage the circuit element.

  Furthermore, in recent years, for the purpose of energy saving (water saving and power saving), there is a tendency to increase the rotation speed of the rotating tank particularly during rinsing and dehydration before drying. For this reason, the regenerative power of the motor described above is increased, and the overvoltage applied to the inverter circuit is further increased. Accordingly, there is an increasing need to prevent damage to circuit elements from such an abnormal voltage (overvoltage), and various measures have been considered.

  For example, a comparator for monitoring the DC power supply voltage (main circuit voltage) supplied to the inverter circuit is provided outside the microcomputer, and the microcomputer has exceeded the normal range based on the output signal of the comparator. A configuration is considered in which, when it is detected that the value has been reached, an abnormal process is performed to deal with the occurrence of an abnormal voltage. However, in this configuration, since it is necessary to provide a comparator outside the microcomputer, there is a problem that the circuit configuration becomes complicated and the manufacturing cost increases.

  Further, a configuration in which the above-described voltage monitoring comparator is built in a microcomputer and the same processing is performed is also considered. However, the program and internal circuits of the microcomputer do not operate during the reset period. Therefore, in the configuration in which the comparator is built in the microcomputer, there is a problem that the abnormal process for protecting the circuit element from the abnormal voltage is not executed during the reset period of the microcomputer.

JP 2009-17474 A

  Therefore, a motor drive device for a dehydrator that can protect circuit elements from overvoltage caused by the regenerative power of the motor, even during the reset period of the microcomputer, while suppressing the complexity of the circuit configuration and high manufacturing cost. provide.

  The motor drive device of the dehydrator according to the present embodiment drives a motor that rotates the dewatering tank of the dehydrator, and includes an inverter circuit, a microcomputer, and a potential fixing circuit. The inverter circuit converts direct current into alternating current and supplies it to the motor, and includes a plurality of switching elements connected in a bridge shape. The microcomputer includes a control signal output terminal for outputting a control signal for controlling driving of the switching element and an input / output terminal, and controls the operation of the inverter circuit. The potential fixing circuit is a potential that fixes the potential of the control signal to a level that shuts off one of the switching elements on the upper arm side and the switching element on the lower arm side and makes the other conductive when the input / output terminal is in a high impedance state. Perform fixed actions. The potential fixing circuit stops the potential fixing operation when the input / output terminal is in an output state in which a signal of a predetermined logic level is output.

Shows the present embodiment, a schematic longitudinal side view of the washing and drying machine Electrical configuration of motor drive unit Flow chart showing contents of main processing Flow chart showing the contents of reset exception handling A flowchart showing the contents of interrupt processing when an overcurrent condition is detected Operation timing chart when reset occurs during dehydration operation FIG. 6 equivalent diagram showing the prior art

Hereinafter, an embodiment of a motor drive device will be described with reference to the drawings.
As shown in FIG. 1, an input port 2 for taking in and out laundry is formed on the front surface of an outer box 1 a that forms the outer shell of a drum-type washing and drying machine 1 (corresponding to a dehydrator). A door 3 is disposed to allow the insertion port 2 to be opened and closed. Further, support legs 4 for floor installation are provided at the corners of the bottom plate of the outer box 1a.

  A substantially non-porous cylindrical water tank 5 is provided inside the outer box 1a, and the water tank 5 has a large number of through holes 6a in the peripheral wall and is rotatable around the horizontal axis. A rotating tank 6 (drum) is disposed concentrically. Each of the water tank 5 and the rotating tank 6 has a bottomed cylindrical shape whose front surface (left side in FIG. 1) is open. The water tank 5 is elastically supported in the outer box 1a by a plurality of suspensions 7 (only one is shown). As a result, the water tank 5 and the rotating tank 6 are supported in a slightly upwardly inclined state so that their substantial openings face the charging port 2. In addition, an elastically expandable / contractible bellows 11 is connected between the inlet 2 and the opening of the water tank 5 in a watertight manner and is in close contact with the back surface of the door 3 from the water tank 5 side to the inside / outside of the outer box 1a. Prevents water leakage.

  A plurality of baffles 6b (only one is shown) for scooping up laundry are provided on the inner surface of the body of the rotating tub 6. The rotary tub 6 is used for dehydration and drying as well as being easy to wash by storing laundry and being driven to rotate. That is, the rotating tub 6 functions as a washing tub when it is easy to wash, functions as a dehydrating tub during dehydration, and functions as a drying chamber during drying. Further, the through-hole 6a provided in the rotating tub 6 functions as a hole for water passage during washing, rinsing and dehydration, and also functions as a hole for ventilation during drying. In addition, for example, a liquid-sealed rotary balancer 8 is provided around the opening of the rotary tank 6.

  A motor 9 is disposed at the center of the back surface of the water tank 5. The motor 9 is, for example, an outer rotor type DC brushless (DCBL) motor. A rotating shaft 10 connected to a rotor (not shown) of the motor 9 is inserted into the water tank 5, and the rotating tank 6 is directly connected to a tip portion thereof. Accordingly, when the motor 9 is energized, the rotating tub 6 is directly rotated in conjunction with the rotor of the motor 9. Although details will be described later, the motor 9 is driven by an inverter.

  A drainage port (not shown) is formed at the lowermost rear portion of the water tank 5, and one end side of a drainage hose 13 through the drainage valve 12 is connected to the drainage port in the middle. The other end of the drainage hose 13 is connected to and communicated with an outside lead-out hole (not shown) formed in the lower side of the outer box 1a, so that water in the water tank 5 can be discharged outside the machine. It is said.

  The circulation duct 14 is arranged so as to bypass the lower part of the water tank 5. The circulation duct 14 includes an exhaust duct 16, an air supply duct 18, and a heat exchange duct 19. The exhaust duct 16 is connected to a hot air outlet 15 formed at the upper part of the front surface of the water tank 5. The air supply duct 18 is connected to the hot air supply port 17 on the back side of the water tank 5. The heat exchange duct 19 is connected to the lower ends of the exhaust duct 16 and the air supply duct 18 so as to be extendable and contractible. In this way, a circulation duct 14 that is substantially a closed space is formed via the water tank 5.

  The air blower 20 is provided so as to be interposed in the connection part of the heat exchange duct 19 and the air supply duct 18 in order to circulate the air in the water tank 5, the rotary tank 6 and the circulation duct 14. The blower 20 includes a blower fan 20a, a fan motor 20b, and the like, and generates an air flow in the direction of solid arrows in the figure. The blower 20 and the heat exchange duct 19 are installed on the bottom side of the outer box 1a.

  The lint capturing device 21 is provided so as to be located on the air flow inflow side (exhaust duct 16 side) of the heat exchange duct 19. The lint capturing device 21 has a lint filter 21 a disposed so as to intersect the passage of the heat exchange duct 19. The lint filter 21a is provided so that it can be taken in and out from the outside of the front surface of the outer box 1a. The lint capturing device 21 captures lint such as lint generated from the laundry during the drying operation so that the lint does not enter the downstream side of the heat exchange duct 19.

  The heat exchange duct 19 has a configuration in which fin tubes (not shown) of the evaporator 23 and the condenser 24 constituting the heat pump mechanism 22 arranged at the bottom in the outer box 1a are interposed, and air and heat flowing between them. Exchange can be done. The heat pump mechanism 22 includes a compressor 25 that compresses and discharges the refrigerant, a condenser 24 that dissipates and condenses the high-temperature and high-pressure refrigerant, an expansion valve (not shown) that decompresses the high-pressure refrigerant, and evaporates the decompressed refrigerant. It has a configuration in which an evaporator 23 or the like that absorbs heat is connected in a ring shape. In the heat pump mechanism 22, an evaporator 23 is disposed on the upstream side, and a condenser 24 is disposed on the downstream side. A blower device 20 is disposed on the downstream side of the condenser 24. Therefore, the air circulates in the direction of the solid arrow in the circulation duct 14 including the heat exchange duct 19 by driving the blower 20.

  During the drying operation for drying the laundry, the heat pump mechanism 22 is operated and the blower 20 is rotated. As a result, the air flowing through the heat exchange duct 19 is heated by the condenser 24 and is supplied into the water tank 5 from the air supply duct 18 through the hot air supply port 17 on the back side of the water tank 5 as hot air for drying. In the rotating tub 6 that rotates, it comes into contact with the laundry and performs the drying action. The hot air that has performed the drying action is discharged to the exhaust duct 16 from the hot air outlet 15 formed in the upper part through the rotary tank 6 and the water tank 5. The warm air (exhaust air) reaches the heat exchange duct 19 again through the lint capturing device 21, and moisture is dehumidified by the evaporator 23 from the exhaust gas, and is heated again by the condenser 24. Thus, the heat pump mechanism 22 mainly functions as a heating device that heats the circulating air, and constitutes a hot air unit that generates hot air by the heating device and the blower device 20.

  A water supply means 30 having a water supply valve 28 and a water supply path 29 is provided in the upper part of the outer box 1a. The water supply path 29 is for supplying water from an external water source such as tap water into the water tank 5. The water supply valve 28 is disposed upstream of the water supply path 29 and is connected to an external water source. The downstream end of the water supply path 29 is connected to the upper part in the water tank 5. In the middle of the water supply path 29, a cleaning agent input device 31 is arranged, and liquid detergent or the like can be input together with water supply into the water tank 5.

  An operation panel portion 26 is provided at the upper front of the outer box 1a. The operation panel unit 26 is provided with a display and various operation switches (not shown). A control circuit 27 is provided on the back surface of the operation panel unit 26. The control circuit 27 controls the overall operation of the washing / drying machine, and is mainly composed of a microcomputer. The control circuit 27 controls the water supply valve 28, the motor 9, the drain valve 12, and the like according to the operation of the operation switch of the operation panel unit 26, and drives the motor 9, the compressor 25 and the washing operation of washing, rinsing and dehydration. The drying operation is executed by controlling the compressor motor and the like.

  Then, the structure of the motor drive device which drives the motor 9 for rotating the rotation tank 6 is demonstrated. As shown in FIG. 2, the motor drive device 41 includes an inverter circuit 42, a control circuit 27 (hereinafter also referred to as a microcomputer 27), a potential fixing circuit 43, and the like. The inverter circuit 42 converts a DC voltage supplied from the DC power supply circuit 44 based on a PWM (Pulse Width Modulation) signal supplied from the microcomputer 27 into a three-phase AC voltage (line voltage is controlled by voltage and frequency). Sine wave). The inverter circuit 42 has a configuration in which six switching elements 45 to 50 are connected in a three-phase bridge shape. The switching elements 45-50 are comprised, for example by IGBT. Hereinafter, the switching elements 45 to 50 are referred to as IGBTs 45 to 50. Between the collectors and emitters of the IGBTs 45 to 50, free-wheeling diodes 45a to 50a are connected. Each phase output terminal of the inverter circuit 42 is connected to each phase terminal (each phase winding) of the motor 9.

  The emitters of the IGBTs 48 to 50 on the lower arm side are connected to the ground via shunt resistors R1 to R3. The interconnection points between the emitters of the IGBTs 48 to 50 and the shunt resistors R1 to R3 are connected to the A / D input terminal of the microcomputer 27 via the level shift circuit 51 and also to the overcurrent determination circuit 52. Note that the resistance values of the shunt resistors R <b> 1 to R <b> 3 are determined based on the maximum current flowing through the winding of the motor 9.

  The level shift circuit 51 amplifies the terminal voltage of the shunt resistors R1 to R3 and applies a bias so that the output range of the amplified signal falls within a predetermined range that can be input to the microcomputer 27. The overcurrent determination circuit 52 is provided to detect an overcurrent that occurs, for example, when the upper and lower arms of the inverter circuit 42 are short-circuited. The overcurrent determination circuit 52 has a configuration including, for example, a comparator. When the overcurrent determination circuit 52 detects an overcurrent state based on the terminal voltages of the shunt resistors R <b> 1 to R <b> 3, the overcurrent determination circuit 52 outputs an overcurrent detection signal to the microcomputer 27. The microcomputer 27 has an overcurrent protection function that forcibly turns off (cuts off) all the IGBTs 45 to 50 when an overcurrent detection signal is given.

  A DC power supply circuit 44 is connected to the input side of the inverter circuit 42. The DC power supply circuit 44 includes a rectifier circuit formed by connecting diodes in a bridge shape, two smoothing capacitors connected in series (both not shown), and the like. The DC power supply circuit 44 supplies a DC voltage (main circuit voltage) of about 280 V to the inverter circuit 42 by performing double voltage full-wave rectification on the AC (AC 100 V) supplied from the commercial power supply 53.

  The microcomputer 27 operates by receiving a power supply voltage (for example, 5 V) supplied from a control power supply circuit (not shown) through a control power supply terminal 54. The microcomputer 27 detects the current flowing through each phase of the inverter circuit 42, that is, the current flowing through each phase winding of the motor 9, via the level shift circuit 51. The microcomputer 27 is configured to perform vector control of the motor 9 based on the detected current value, a speed command given from the outside, and the like, and pulse width modulation for turning on and off the IGBTs 45 to 50 according to the control. The generated six PWM signals Sup, Svp, Swp, Sun, Svn, and Swn (corresponding to control signals) are generated. The generated PWM signals Sup to Swn are given from the control signal output terminals P1 to P6 of the microcomputer 27 to the drive circuit 55 through the output lines Lup, Lvp, Lwp, Lun, Lvn, and Lwn.

  The drive circuit 55 operates by receiving a power supply voltage (for example, 15 V) supplied from a drive power supply circuit (not shown) through a drive power supply terminal 56. The drive circuit 55 outputs an on drive signal for turning on the IGBTs 45 to 50 or an off drive signal for turning off the IGBTs 45 to 50 to the gates of the IGBTs 45 to 50 in accordance with the PWM signals Sup to Swn. Specifically, the drive circuit 55 outputs an off drive signal when the PWM signals Sup to Swn are at the L level (ground potential = 0 V), and at the H level (the output voltage of the control power supply circuit = 5 V). An ON drive signal is output at a certain time. The drive circuit 55 includes a circuit (a charge pump circuit, a bootstrap circuit, or the like) that boosts the ON drive signal (voltage) of the IGBTs 45 to 47 on the upper arm side.

  The six input terminals of the drive circuit 55, that is, the output lines Lup to Lwn of the PWM signals Sup to Swn are pulled down via resistors R4 to R9, respectively (connected to the ground). These pull-down resistors R4 to R9 are provided for the following reason. That is, when the signal is not given to the input terminal of the drive circuit 55, such as when the output lines Lup to Lwn are disconnected or the PWM signal Sup to Swn is not output from the microcomputer 27, the IGBTs 45 to 50 are driven. The state becomes indeterminate, and there is a possibility of malfunction (false ON) due to, for example, noise. Therefore, by pulling down the input terminal of the drive circuit 55 as described above, the IGBTs 45 to 50 are maintained in the OFF state even when no signal is applied, and the occurrence of the erroneous ON is prevented.

  In the present embodiment, the IGBTs 45 to 50 and the diodes 45a to 50a, the drive circuit 55, and the resistors R4 to R9 constituting the inverter circuit 42 are configured as an integrated intelligent power module. ing. In FIG. 2, the intelligent power module is shown as IPM 57.

  The rotor of the motor 9 is provided with a rotational position sensor 58 made up of, for example, a Hall IC for use at startup. The rotor position signal output from the rotational position sensor 58 is given to the microcomputer 27. The microcomputer 27 performs vector control using the rotational position sensor 58 until the rotational speed at which the rotor position can be estimated when the motor 9 is started, and after reaching the rotational speed, the rotational position sensor 58. Switch to sensorless vector control without using.

  Resistors R10 and R11 are connected in series between the output terminal of the DC power supply circuit 44 and the ground. The voltage (divided voltage) at the interconnection point of the resistors R10 and R11 is applied to the A / D input terminal of the microcomputer 27. The microcomputer 27 detects the main circuit voltage based on the divided voltage and uses it as a reference for determining the duty of the PWM signal. Further, the microcomputer 27 controls the operation of the inverter circuit 42 so as to cancel (cancel) the output fluctuation accompanying the fluctuation (ripple) of the main circuit voltage based on the detected value of the main circuit voltage.

  Further, when the microcomputer 27 determines that the main circuit voltage has abnormally increased (for example, main circuit voltage = 480 V or more) based on the detected value of the main circuit voltage, the microcomputer 27 executes emergency braking (short circuit braking). The short circuit brake is to stop the short circuit between the terminals (between the windings) of the motor 9. In this case, the microcomputer 27 sets the level of the PWM signals Sup to Swn so that the IGBTs 45 to 47 on the upper arm side are turned off (cut off) and the IGBTs 48 to 50 on the lower arm side are turned on (conducted). By doing so, short-circuit braking is performed.

  The reset circuit 59 is provided for resetting the microcomputer 27 when the power supply voltage (5 V) applied through the control power supply terminal 54 is less than a predetermined value (about 4.2 V). The reset circuit 59 outputs to the reset input terminal of the microcomputer 27 a reset signal whose logic level changes depending on whether or not the power supply voltage is less than a predetermined value. The reset signal becomes active level (L level) when the power supply voltage is lower than a predetermined value, and becomes inactive level (H level) when the power supply voltage is higher than the predetermined value.

The microcomputer 27 is in the reset state when the reset signal applied to the reset input terminal is at the L level, and is in the state in which the reset is released (normal state) when the reset signal is at the H level. According to the above configuration, the microcomputer 27 is reset in the following case.
(1) When power is supplied to the motor drive device 41 (power-on reset)
(2) When the power supply voltage falls below a predetermined value due to the influence of noise, etc. (3) When the microcomputer 27 is forcibly set to L level due to noise superimposed on the reset signal. During the reset period, all the output terminals and input / output terminals are configured to be in a high impedance state (hereinafter also referred to as Hi-z). Further, after the microcomputer 27 enters the reset state, when the state is released (during the transition period from the reset state to the normal state), an initialization process (initial process) for initializing the inside is executed, and thereafter Normal operation is started. The microcomputer 27 can set (control) the state of each output terminal during the transition period.

  The potential fixing circuit 43 includes a first potential fixing unit 61 and a second potential fixing unit 62. The first potential fixing unit 61 includes transistors T1 to T3 and resistors R11 to R17, which are NPN bipolar transistors. The collectors of the transistors T1 to T3 are connected to output lines Lup, Lvp, and Lwp, respectively. The bases and emitters of the transistors T1 to T3 are connected via resistors R11 to R13, respectively. Each emitter of the transistors T1 to T3 is connected to the ground. Each base of the transistors T1 to T3 is connected to a first input / output terminal P11 of the microcomputer 27 via resistors R14 to R16, respectively. The first input / output terminal P11 is connected to the control power supply terminal 54 via the resistor R17.

  The second potential fixing unit 62 includes transistors T4 to T6, which are PNP bipolar transistors, and resistors R18 to R24. The collectors of the transistors T4 to T6 are connected to output lines Lun, Lvn, and Lwn, respectively. The bases and emitters of the transistors T4 to T6 are connected via resistors R18 to R20, respectively. Each emitter of the transistors T4 to T6 is connected to the control power supply terminal 54. Each base of the transistors T4 to T6 is connected to the second input / output terminal P12 of the microcomputer 27 via resistors R21 to R23, respectively. The second input / output terminal P12 is connected to the ground via a resistor R24. The resistance value of the resistor R24 (for example, 10 kΩ) is higher than the resistance value of the resistor R17 (for example, 1 kΩ). The resistors R11 to R13 and R18 to R20 have the same resistance value. The resistors R14 to R16 and R21 to R23 have the same resistance value.

  The input / output terminals P11 and P12 of the microcomputer 27 are both general-purpose I / O ports. In the normal state, the microcomputer 27 sets the first input / output terminal P11 to an output state for outputting an L level (0V) signal and outputs the second input / output terminal P12 to an H level (5V) signal. Set the output status to As described above, the input / output terminals P11 and P12 become Hi-z during the reset period in which the microcomputer 27 is reset, as described above.

  Next, the potential fixing operation by the potential fixing circuit 43 configured as described above will be described. In the potential fixing operation, the output lines Lup, Lvp, Lwp (PWM signals Sup, Svp, Swp) are fixed at the L level, and the output lines Lun, Lvn, Lwn (PWM signals Sun, Svn, Swn) are fixed at the H level. To do. When such a potential fixing operation is executed, all the IGBTs 45 to 47 on the upper arm side are turned off (shut off), and all the IGBTs 48 to 50 on the lower arm side are turned on (conducted). The brake will work.

  First, when the microcomputer 27 is in a normal state, the first input / output terminal P11 is at the L level and the second input / output terminal P12 is at the H level. Therefore, all of the transistors T1 to T6 of the first potential fixing unit 61 and the second potential fixing unit 62 are turned off. Accordingly, the potentials of the output lines Lup to Lwn are not fixed (the potential fixing operation is stopped). In this case, the PWM signal Sup to Swn output from the microcomputer 27 is directly supplied to the drive circuit 55 (the PWM signals Sup to Swn are validated).

  On the other hand, in the reset period when the microcomputer 27 is reset, the input / output terminals P11 and P12 become Hi-z. Therefore, all of the transistors T1 to T6 of the first potential fixing unit 61 and the second potential fixing unit 62 are turned on. Accordingly, the output lines Lup, Lvp, and Lwp are connected to the ground through the transistors T1 to T3, and the output lines Lun, Lvn, and Lwn are connected to the control power supply terminal 54 through the transistors T4 to T6. That is, the PWM signals Sup, Svp, Swp are fixed at the L level, and the PWM signals Sun, Svn, Swn are fixed at the H level (potential fixing operation is executed).

  Among the potential fixing operations described above, the potential fixing operation by the first potential fixing unit 61 is performed in the following flow. That is, when the first input / output terminal P11 becomes Hi-z, a current (base current) flows in a path from the control power supply terminal 54 to the ground through the resistor R17 and the bases and emitters of the transistors T1 to T3, etc. ~ T3 turns on. Then, current flows from the output lines Lup, Lvp, and Lwp to the ground through the transistors T1 to T3. The current discharges a parasitic capacitance (not shown) formed between the output lines Lup, Lvp, Lwp and the ground, and finally the potentials of the output lines Lup, Lvp, Lwp are 0 V (L level). )

  On the other hand, the potential fixing operation by the second potential fixing unit 62 is performed in the following flow. That is, when the second input / output terminal P12 becomes Hi-z, a current (base current) flows in a path from the control power supply terminal 54 to the ground between the emitters and bases of the transistors T4 to T6 and the resistor R24. ~ T6 turns on. Then, current flows from the control power supply terminal 54 to the output lines Lun, Lvn, and Lwn through the transistors T4 to T6. The electric current charges a parasitic capacitance (not shown) formed between the output lines Lun, Lvn, Lwn and the ground. Finally, the potentials of the output lines Lun, Lvn, Lwn are 5 V (H level). )become.

  In such an operation, the timing at which the potentials of the output lines Lup, Lvp, and Lwp become L level, that is, the timing at which the potential fixing operation by the first potential fixing unit 61 is performed is the parasitic capacitance of the output lines Lup, Lvp, and Lwp. It depends on the resistance value (1 kΩ) of the resistor R17. The timing at which the potentials of the output lines Lun, Lvn, Lwn become H level, and the timing at which the potential fixing operation by the second potential fixing unit is executed are the parasitic capacitance of the output lines Lun, Lvn, Lwn and the resistance value of the resistor R24. Depends on (10 kΩ). Since the parasitic capacitance is considered to have substantially the same value, the difference between the resistance values of the resistors R17 and R24 has the greatest influence on the timing at which the potential fixing operation is performed. Accordingly, in this case, the timing at which the output lines Lup, Lvp, and Lwp are at the L level is earlier than the timing at which the output lines Lun, Lvn, and Lwn are at the H level. That is, in the present embodiment, the potential fixing operation by the first potential fixing unit 61 is performed prior to the potential fixing operation by the second potential fixing unit 62.

Next, the operation of the motor drive device 41 configured as described above will be described. Note that the operations described below are performed mainly by the microcomputer 27 unless otherwise specified.
When power supply to the motor drive device 41 is started, the microcomputer 27 starts operation. When the microcomputer 27 starts its operation, it executes main processing having the contents shown in the flowchart of FIG. In the main process, it is first determined whether or not to start the motor 9 (step S1). If it is necessary to start the motor 9 such as when a washing operation or a drying operation is performed (YES), the process proceeds to step S2. If it is not necessary to start the motor 9 (NO), the processing is ended as it is (END).

  In step S2, the first input / output terminal P11 is set to the L level output state, and the second input / output terminal P12 is set to the H level output state. As a result, the potential fixing operation by the potential fixing circuit 43 is stopped. After step S2, the process proceeds to step S3, and duty control of the output PWM signals Sup to Swn is performed to rotate the motor 9 under a desired condition. Thereafter, when driving of the motor 9 is terminated (“YES” in step S4), it is determined whether or not the motor 9 is stopped (step S5). If it is determined that the motor 9 is stopped (YES), all the PWM signals Sup to Swn are set to the L level (step S6). Further, the first input / output terminal P11 is set to the H level output state, and the second input / output terminal P12 is set to the L level output state (step S7). By doing so, the output lines Lup to Lwn are fixed to the L level by the operation of the potential fixing circuit 43, so that the IGBTs 45 to 50 are more reliably maintained off. Note that step S7 may be omitted.

  When the motor 9 is driven in the main process described above, if the microcomputer 27 is reset, for example, by superimposing noise on the reset signal, a reset exception process as shown in the flowchart of FIG. 4 is executed. The In the reset exception process, all input terminals and input / output terminals (control signal output terminals P1 to P6 and input / output terminals P11, P12, etc.) are set to Hi-z (step X1). Then, a potential fixing operation by the potential fixing circuit 43 is executed, whereby a short-circuit brake is applied to the motor 9. Thereafter, it is determined whether or not the motor 9 is rotating by using the rotor position signal output from the rotational position sensor 58 (step X2).

  If it is determined that the motor 9 is rotating (YES), the input / output terminals P11 and P12 are kept at Hi-z, and the potential fixing operation by the potential fixing circuit 43 and the short-circuit braking are continued (step X3). . On the other hand, if it is determined that the motor 9 is not rotating, that is, has stopped (NO), the potential fixing operation by the potential fixing circuit 43 and the short-circuit brake are released (step X4), and the process ends (END).

  Further, when the motor 9 is driven in the main process described above, if an overcurrent state is detected, an interrupt process as shown in the flowchart of FIG. 5 is executed. In this interrupt process, first, the first input / output terminal P11 is maintained in the L level output state and the second input / output terminal P12 is maintained in the H level output state, and the PWM signals Sup to Swn are all set to the L level ( Step Y1). Thereby, all the IGBTs 45 to 50 are turned off. In step Y1, the control signal output terminals P1 to P6 may be set to Hi-z. Also in this case, all the IGBTs 45 to 50 are turned off by the action of the pull-down resistors R4 to R9.

  If the overcurrent occurs as described above and all the IGBTs 45 to 50 are turned off while the motor 9 is rotating, the main circuit voltage of the inverter circuit 42 is increased by the regenerative power of the motor 9. However, in this embodiment, since the microcomputer 27 performs a short-circuit brake when it is determined that the main circuit voltage has abnormally increased, the main circuit voltage of the inverter circuit 42 is prevented from increasing excessively even in such a case. Is done.

  After step Y1, the process proceeds to step Y2, where it is determined whether or not the interrupt process has been executed continuously a predetermined number of times (for example, three times). If it has not been executed continuously for a predetermined number of times (NO), the process proceeds to step Y3, normal motor control is executed again (restart), and the process ends (END). On the other hand, when this interrupt process is executed continuously a predetermined number of times (“YES” in step Y2), the process proceeds to step Y4. In step Y4, it is determined that an abnormality (failure) has occurred, and an error display indicating that fact is executed, and then the process ends (END).

As described above, according to the present embodiment, the following effects can be obtained.
If the microcomputer 27 of the motor drive device 41 determines that the main circuit voltage has risen abnormally based on the detected value of the main circuit voltage, it executes a short-circuit brake. Therefore, according to the present embodiment, when the microcomputer 27 is in a normal state, the circuit element such as the inverter circuit 42 can be protected from the overvoltage generated by the regenerative power of the motor 9 by the above operation. Further, when the microcomputer 27 enters a state in which an excessive current flows due to a short circuit between the upper and lower arms of the inverter circuit 42, the microcomputer 27 detects the overcurrent state and turns off the IGBTs 45-50. Thereby, even if it will be in an overcurrent state, the state will be eliminated rapidly. At this time, since all the IGBTs 45 to 50 are turned off, the main circuit voltage of the inverter circuit 42 is increased by the regenerative power of the motor 9, but the short circuit brake is executed by the control during the normal operation by the microcomputer 27 described above. Even in such a case, the main circuit voltage is prevented from increasing unnecessarily.

  In this embodiment, even when the microcomputer 27 is reset while the motor 9 is rotating, an increase in the main circuit voltage due to the regenerative power of the motor 9 can be suppressed. Hereinafter, the operation and effect of the present embodiment will be described with reference to FIGS. 6 and 7. FIG. 6 shows the operation timing of the motor drive device 41 when a reset due to noise or the like occurs during the dehydration operation. In this case, it is assumed that the dehydration operation is performed at 1300 rpm, for example. FIG. 7 is a comparative example and is a view corresponding to FIG. 6 in the configuration of the prior art.

  6 and 7, (a) shows the main circuit voltage of the inverter circuit, (b) shows the U-phase upper arm PWM signal Sup, and (c) shows the U-phase lower arm PWM signal Sun. 6 and 7, illustration of PWM signals Svp, Svn, Swp, and Swn for the V-phase upper and lower arms and the W-phase upper and lower arms is omitted.

  When the microcomputer 27 is reset due to noise or the like during driving of the motor 9, all of the control signal output terminals P1 to P6 are Hi-z. At this time, for example, in the case of the configuration not including the potential fixing circuit 43, that is, the configuration of the prior art, the PWM signals Sup to Swn are all at the L level by the pull-down resistors R4 to R9 ((b) in FIG. 7). (See (c)). Then, since all the IGBTs 45 to 50 are turned off, regenerative electric power corresponding to the rotational energy of the motor 9 (rotating tank 6) is generated, thereby causing the main circuit voltage of the inverter circuit 42 to rapidly increase ((( a)).

  In this case, the main circuit voltage rises to a voltage value (for example, 540 V) exceeding the voltage value Vmax (for example, 500 V) at which the circuit element of the inverter circuit 42 is damaged after about 300 milliseconds from the occurrence of the reset. As described in the section of the prior art, in recent years, the number of rotations during dehydration tends to increase. For example, the moisture of clothes may be efficiently squeezed at 1700 rpm. The higher the number of revolutions during dehydration, the faster and higher the main circuit voltage that accompanies the regenerative power, and thus the possibility of damage caused by it increases.

  On the other hand, according to the configuration of the present embodiment, when the microcomputer 27 is reset, the control signal output terminals P1 to P6 become Hi-z, and the input / output terminals P11 and P12 also become Hi-z. Then, the potential fixing operation by the potential fixing circuit 43 is executed, the PWM signals Sup, Svp, Swp are fixed to the L level, and the PWM signals Sun, Svn, Swn are fixed to the H level ((b) of FIG. 6). (See (c)). Thereby, a short-circuit brake works and the rotational energy is self-consumed in the winding of the motor 9. Therefore, as shown in FIG. 6A, according to the configuration of the present embodiment, the main circuit voltage hardly rises even when the microcomputer 27 is reset.

  The potential fixing circuit 43 uses relatively inexpensive elements such as resistors R11 to R24 and transistors T1 to T6, and the circuit configuration is simple. That is, according to the present embodiment, the regenerative power of the motor 9 is reduced even during the reset period of the microcomputer 27 that could not be protected by the prior art while suppressing the complexity of the circuit configuration and the increase in manufacturing cost. An excellent effect is obtained that the circuit element can be protected from the accompanying overvoltage.

  The potential fixing operation by the potential fixing circuit 43 is executed when the input / output terminals P11 and P12 are Hi-z. Therefore, when the microcomputer 27 returns from the reset state to the normal state, the potential fixing operation is canceled when the state of the input / output terminals P11 and P12 is changed to a state different from Hi-z by an initialization process or the like. There is a risk of being. However, in this embodiment, the microcomputer 27 positively sets the input / output terminals P11 and P12 to Hi-z when the motor 9 is rotating when shifting from the reset state to the normal state. . Therefore, even when shifting from the reset state to the normal state, it is possible to reliably prevent the occurrence of overvoltage associated with the regenerative power of the motor 9.

  When the potential fixing operation is executed by the potential fixing circuit 43, the timing at which the output lines Lup, Lvp, Lwp become L level is earlier than the timing when the output lines Lun, Lvn, Lwn become H level. did. According to such a configuration, it is possible to reliably prevent the upper and lower arms from being short-circuited in the inverter circuit 42 when the potential fixing operation is performed.

(Other embodiments)
The washing / drying machine 1 may have a so-called vertical axis shape in which the water tank 5 and the rotary tank 6 are arranged in a vertical axis shape.
The motor drive device 41 can be applied not only to the washing / drying machine 1 having a washing and drying function, but also to a washing machine, a dehydrator and the like.
The microcomputer 27 may have a configuration incorporating a reset circuit 59. Even in such a configuration (built-in type), an external terminal for forcibly executing reset from the outside is provided. Therefore, it is conceivable that noise is superimposed on the reset signal through the external terminal and the reset is erroneously performed. That is, even if the microcomputer has a configuration with a built-in reset circuit, it is sufficiently considered that the reset is erroneously performed while the motor 9 is rotating. Therefore, the operation and effect of the above embodiment are beneficial.
The switching element included in the inverter circuit 42 is not limited to the IGBT, and various semiconductor switching elements such as a power MOSFET and a bipolar transistor can be employed.

  In order to prevent fluctuation of the PWM signals Sup to Swn due to noise, a capacitor (for example, about 100 pF) may be provided between the output lines Lup to Lwn and the ground. As the capacitors, those having a larger capacitance (for example, 100 pF) than the parasitic capacitance described above are used. In such a case, the capacitance Ch of the capacitor provided for the output lines Lup to Lwp on the upper arm side and the capacitance Cl of the capacitor provided for the output lines Lun to Lwn on the lower arm side are expressed as “Ch. It is better to set the relationship <Cl>. This is because although the values of the parasitic capacitances of the output lines Lup to Lwn are substantially the same, there are some variations. As described above, if the capacitances of the capacitors to be removed for noise are differentiated, the potential fixing operation by the first potential fixing unit 61 and the second potential fixing unit 62 even if the value of the parasitic capacitance varies somewhat. The execution timing can be varied to ensure that it is desired. Therefore, it is possible to more reliably prevent the upper and lower arms from being short-circuited when the potential fixing operation is performed.

If the problem of a short circuit between the upper and lower arms when the potential fixing operation is performed does not occur or is acceptable, the potential fixing circuit 43 is operated by the first potential fixing unit 61 and the second potential fixing unit 62. The potential fixing operation may be performed at the same time.
The potential fixing circuit 43 is not limited to the configuration shown in FIG. 2. When the input / output terminals P11 and P12 are Hi-z, one of the switching elements on the upper arm side and the lower arm side is cut off and the other is made conductive. The potential fixing operation for fixing the potential of the PWM signal to such a level is executed, and the potential fixing operation is stopped when the input / output terminals P11 and P12 are in an output state for outputting a signal of a predetermined logic level. If so, it can be appropriately changed.

In the main process shown in FIG. 3, step S2 may be provided before step S1. That is, as soon as the microcomputer 27 starts to operate, settings may be performed so that the output of the normal PWM signals Sup to Swn becomes effective.
Step X3 of the reset exception process shown in FIG. 4 may be changed as follows. That is, in step X3, the microcomputer 27 sets the first input / output terminal P11 to the L level output state and the second input / output terminal P12 to the H level output state, and then turns off the IGBTs 45 to 47 on the upper arm side. The levels of the PWM signals Sup to Swn may be set so as to turn on the IGBTs 48 to 50 on the lower arm side. Even in such a change, since the short-circuit brake is continuously executed in step X3, it is possible to prevent the occurrence of overvoltage when shifting from the reset state to the normal state.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  In the drawings, 1 is a washing / drying machine (dehydrator), 6 is a rotating tank (dehydrating tank), 9 is a motor, 27 is a control circuit (microcomputer), 41 is a motor drive device, 42 is an inverter circuit, and 43 is a potential fixed. Circuits 45 to 50 are switching elements, 52 is an overcurrent determination circuit, 61 is a first potential fixing unit, 62 is a second potential fixing unit, P1 to P6 are control signal output terminals, and P11 and P12 are input / output terminals. .

Claims (4)

A motor drive device for a dehydrator that drives a motor that rotates a dewatering tank of the dehydrator,
Converting direct current into alternating current and supplying the motor, an inverter circuit including a plurality of switching elements connected in a bridge shape;
A microcomputer having a control signal output terminal and an input / output terminal for outputting a control signal for controlling the driving of the switching element, and controlling the operation of the inverter circuit;
When the input / output terminal is in a high impedance state, the potential of the control signal is fixed so that one of the switching element on the upper arm side and the switching element on the lower arm side is cut off and the other is made conductive. A potential fixing circuit that executes the operation and stops the potential fixing operation when the input / output terminal is in an output state of outputting a signal of a predetermined logic level;
A motor drive device for a dehydrator characterized by comprising: In the motor drive device of the dehydrator according to claim 1,
The microcomputer sets the input / output terminal to a high impedance state or sets the input / output terminal to the output state while the motor is rotating at the time of transition from the reset state to the normal state. Then, the level of the control signal is set to a level such that one of the switching element on the upper arm side and the switching element on the lower arm side is cut off and the other is turned on. Motor drive device. In the motor drive device of the dehydrator according to claim 1 or 2,
An overcurrent determination circuit that outputs an overcurrent detection signal when detecting an overcurrent state of the current flowing through the inverter circuit;
When the overcurrent detection signal is output, the microcomputer sets the input / output terminal to the output state, and then one or both of the switching element on the upper arm side and the switching element on the lower arm side A motor driving apparatus for a dehydrator, wherein the level of the control signal is set to a level that interrupts the operation. In the motor drive device of the dehydrator according to any one of claims 1 to 3,
The potential fixing circuit is:
A first potential fixing unit that fixes the potential of the control signal to a level that blocks one of the switching element on the upper arm side and the switching element on the lower arm side;
A second potential fixing portion that fixes the potential of the control signal to a level at which the other of the switching element on the upper arm side and the switching element on the lower arm side is conductive;
With
When the potential fixing operation is executed, the potential fixing operation by the first potential fixing unit is performed prior to the potential fixing operation by the second potential fixing unit.

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