JP2005304176A - Motor driver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To protect a motor against an overcurrent by vector controlling the motor or sensorless driving the motor. <P>SOLUTION: A rectifying circuit 2 converts an ac power 1 into a dc power, and drives the motor 4 by an inverter circuit 3. A current detecting means 5 detects the output current of the inverter circuit 3, and detects an overcurrent by an overcurrent detecting means 6. The inverter circuit 3 drives the motor 4 by controlling the inverter circuit 3 by a control means 7, and protects the inverter circuit 3 and the motor 4 against the overcurrent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor drive device, and more particularly to current detection means thereof.

Conventionally, this type of motor driving device detects a current flowing in a plurality of shunt resistors connected to an emitter terminal of a lower arm transistor of an inverter circuit to control the motor (see, for example, Patent Document 1). .
JP 2003-9539 A

  However, since the motor current detection timing of the conventional method was synchronized with the timing of the peak value of the triangular wave modulation, the carrier in the case of an abnormality that requires high-speed interruption such as simultaneous conduction of the upper and lower arms of the inverter circuit and protection of the demagnetizing current of the motor There is a problem that the response of the period becomes slow, and a short circuit failure of the power switching semiconductor of the inverter circuit or demagnetization of the permanent magnet motor occurs due to overcurrent.

  The present invention solves the above-described conventional problems, and separately provides an overcurrent protection means for overcurrent and high-speed interruption of the inverter circuit and the motor current. The power switching semiconductor has an inexpensive configuration with a small number of parts. An object of the present invention is to realize a highly reliable motor drive device that can prevent destruction of an inverter circuit and abnormal heating of a motor due to a short circuit failure.

  In order to solve the above-described conventional problems, the motor driving device of the present invention converts AC power into DC power by a rectifier circuit, drives the motor by an inverter circuit, and detects the output current of the inverter circuit by current detection means. The inverter circuit is PWM-controlled by a signal from the current detection means to drive the motor, and the overcurrent protection operation of the inverter circuit or the motor is performed by the overcurrent protection means.

  The motor drive device of the present invention detects the current flowing through the shunt resistor of the inverter circuit by the current detection means and performs vector control or sensorless sine wave drive, and detects the motor current by the low-cost current detection means. The motor noise can be reduced by sine wave driving, the position sensor can be eliminated and the motor can be downsized, and the inverter circuit or motor current overcurrent can be detected by overcurrent protection means that detects and protects the inverter circuit overcurrent. Since the high-speed shut-off is performed, it is possible to realize a highly reliable motor driving device that can prevent destruction of the inverter circuit due to overcurrent of the power switching semiconductor and demagnetization of the motor with an inexpensive configuration with a small number of parts.

  A first invention is an AC power source, a rectifier circuit that converts AC power of the AC power source into DC power, an inverter circuit that converts DC power of the rectifier circuit into AC power, and a motor driven by the inverter circuit Current detection means for detecting the output current of the inverter circuit, overcurrent protection means connected between the current detection means and the negative voltage terminal of the rectifier circuit, and the inverter circuit by the output signal of the current detection means It comprises control means for controlling and driving the motor, and the overcurrent protection operation of the motor or the inverter circuit is performed by the overcurrent protection means, and the motor current can be detected by an inexpensive current detection means. The motor noise can be reduced by sine wave drive, the position sensor can be eliminated, and the motor can be downsized. Initially prevents capacitor circuit can be realized destruction and the inverter circuit by the power switching semiconductor overcurrent, the motor driving device having high reliability capable of preventing demagnetization of the motor.

  According to a second invention, the inverter circuit in the first invention is constituted by a three-phase full-bridge inverter circuit comprising six transistors and a diode, and the current detection means is a negative arm transistor of the lower arm transistor of the three-phase full-bridge inverter circuit. A plurality of shunt resistors respectively connected to the potential side terminals and a current detection circuit, wherein the inverter circuit is controlled by detecting a current flowing through the shunt resistor, and the overcurrent protection means is in series with the shunt resistor. An overcurrent detection resistor having one terminal connected thereto and an overcurrent detection circuit for detecting a current flowing through the overcurrent detection resistor, and the other terminal of the overcurrent detection resistor is used as a negative voltage terminal of the rectifier circuit Since the motor current can be detected by a shunt resistor, an expensive DC current transformer is not required. Next, at least one of the overcurrent detection resistor and overcurrent detection circuit enables high-speed cut-off of the inverter circuit, inexpensive and reliable motor drive device can be realized.

  According to a third aspect of the present invention, there is provided a current detection circuit for detecting a current of the shunt resistor, a current detection circuit for detecting a current of the overcurrent detection resistor, wherein the connection terminal of the shunt resistor and the overcurrent detection resistor is a ground potential. The ground potential of the current detection circuit is commonly connected to the connection terminal, and the ground potential of the control means comprising a microcomputer or DSP, the ground potential of the current detection circuit, and the overcurrent detection circuit are shared. Therefore, an inexpensive and highly reliable control circuit can be configured with a small number of parts.

  A fourth invention is an AC power source, a rectifier circuit that converts AC power of the AC power source into DC power, an inverter circuit that converts DC power of the rectifier circuit into AC power, and a motor driven by the inverter circuit Current detection means comprising a plurality of shunt resistors and a current detection circuit for detecting an output current of the inverter circuit, overcurrent protection means for detecting an electric current of the shunt resistor and performing an overcurrent protection operation, and the current detection Control means for controlling the inverter circuit according to an output signal of the means to drive the motor, wherein the overcurrent protection means includes a plurality of overcurrent detection circuits for detecting currents of the plurality of shunt resistors and at least one overcurrent. Consists of setting means, and the overcurrent protection means performs the overcurrent protection operation of the motor or the inverter circuit. Yes, motor current and overcurrent can be detected with a shunt resistor, eliminating the need for expensive direct current transformers and overcurrent detection resistors. Overcurrent detection circuit enables high-speed shut-off of the inverter circuit, making it an inexpensive and highly reliable motor. A driving device can be realized.

  According to a fifth invention, in the fourth invention, the current detection circuit is constituted by a single power supply operational amplifier, and a negative power supply voltage is not required, so that the number of parts can be reduced and inexpensive and reliable. A highly efficient motor drive device can be realized.

  According to a sixth invention, in the fourth invention, the motor comprises a plurality of motors driven by an inverter circuit and an output switching means for alternately switching the plurality of motors by a control means, wherein the motor is switched by the output switching means. The setting value of the overcurrent setting means is changed accordingly, and the motor output and the overcurrent setting value can be switched simultaneously by a switching signal from the control means, so the number of parts can be reduced and inexpensive. The reliability is high, and a plurality of motor driving devices using one inverter circuit can be realized.

(Embodiment 1)
FIG. 1 is a block diagram of a motor drive device according to the first embodiment of the present invention. In FIG. 1, AC power is applied to a rectifier circuit 2 from an AC power source 1 to convert it into DC power, and the inverter circuit 3 converts DC power into three-phase AC power to drive a motor 4. In the rectifier circuit 2, capacitors 21a and 21b are connected in series to the DC output terminal of the full-wave rectifier circuit 20, and a connection point of the capacitors 21a and 21b is connected to one terminal of the AC power supply input to constitute a DC voltage doubler circuit. The voltage applied to the inverter circuit 3 is increased to reduce the current, thereby reducing the circuit loss. The current detection means 5 is connected to the negative voltage side of the inverter circuit 3, and the output current of the inverter circuit 3, that is, each phase current of the motor 4 is detected by detecting the current flowing through the lower arms of the three phases of the inverter circuit 3. To do.

  The current detection means 5 is a so-called three-shunt method, and the current flowing in each of the shunt resistors 50a, 50b, 50c connected to the emitter terminal of the lower arm transistor of the inverter circuit 3 and the shunt resistors 50a, 50b, 50c. It comprises a current detection circuit 51 for detecting

  The current detection means 5 detects inverter circuit output current, that is, motor phase current, and performs vector control and position sensorless sine wave drive. At the timing when the lower arm transistor or the lower arm antiparallel diode is turned on. The current corresponding to the motor current is detected. The three-shunt method enables current detection corresponding to the motor phase current by securing the conduction time and dead time of the lower arm transistor, and enables low-cost current detection by omitting the DC current transformer. The so-called one-shunt method is superior to the three-shunt method because a current undetectable region appears when the carrier frequency is high or the modulation degree becomes large.

  The overcurrent protection means 6 connects a non-inductive overcurrent detection resistor 60 between the common connection point G of the non-inductive shunt resistors 50a, 50b, 50c and the negative voltage terminal L2 of the rectifier circuit 2, and the overcurrent detection resistor 60 Is detected by the overcurrent detection circuit 61.

  The control means 7 is composed of a microcomputer or a high-speed processor such as a digital signal processor (abbreviated as DSP), and performs sensorless driving by PWM control of the inverter circuit 3 using a current signal from the current detection means 5. The output transistor of the inverter circuit 3 is instantaneously turned off by the cutoff signal from the protection means 6, and the overcurrent protection operation of the inverter circuit 3 and the motor 4 is performed.

  Since the common connection point G of the shunt resistors 50a, 50b, 50c is set to the ground potential, and the ground potential of each circuit of the current detection circuit 51, the overcurrent detection circuit 61, and the control means 7 can be made common, the DC power supply of the circuit is reduced, The number of parts can be reduced.

  FIG. 2 is a detailed circuit diagram of the inverter circuit 3, which is constituted by a three-phase full-bridge inverter circuit comprising six transistors and diodes. Here, one U-phase arm 30A of the three-phase arm will be described. A parallel connection body of an upper arm transistor 31a1 made of an insulated gate bipolar transistor (hereinafter abbreviated as IGBT) and an antiparallel diode 32a1, and a lower arm made of IGBT. A parallel connection body of the transistor 31a2 and the antiparallel diode 32a2 is connected in series, the collector terminal of the upper arm transistor 31a1 is connected to the positive potential terminal Lp of the DC power supply, and the emitter terminal of the upper arm transistor 31a1 is connected to the output terminal U. The emitter terminal of the lower arm transistor 31a2 is connected to the negative potential side terminal L2 of the DC power source composed of the rectifier circuit 2 via the shunt resistor 50a constituting the current detecting means 5.

  The upper arm transistor 31a1 is driven by the upper arm gate drive circuit 33a1 in accordance with the upper arm drive signal Up, and the lower arm transistor 31a2 is subjected to on / off switching control by the lower arm gate drive circuit 33a2 in accordance with the lower arm drive signal Un. The upper arm gate drive circuit 33a1 incorporates an RS flip-flop circuit that is set and reset by a differential signal, turns on the upper arm transistor 31a1 at the rise of the upper arm drive signal Up, and rises at the fall of the upper arm drive signal Up. The arm transistor 31a1 is turned off. The lower arm gate drive circuit 33a2 does not need an RS flip-flop circuit and does not incorporate it.

  The gate application voltage of the IGBT needs 10 to 15V. When the lower arm transistor 31a2 is turned on, the bootstrap capacitor 36a is charged from the + terminal B1 of the 15V DC power supply via the bootstrap resistor 34a and the bootstrap diode 35a. Therefore, the upper arm transistor 31a1 can be switched on / off by the energy stored in the bootstrap capacitor 36a. Similarly, the bootstrap capacitor 36a is charged when the lower arm antiparallel diode 32a2 is turned on.

  When the overcurrent detection means 6 detects an overcurrent, it outputs an overcurrent signal to the inverter circuit 3 and the control means 7 simultaneously, and when the interruption signal terminal Of of the inverter circuit 3 is set to Lo, the inverter circuit 3 The U-phase, V-phase, and W-phase lower arm transistors are turned off instantaneously.

  The control means 7 adds the signal from the overcurrent detection means 6 to the interrupt input terminal, and cuts off the drive output signal to the inverter circuit 3 at the highest priority speed with respect to the overcurrent signal. Since the shut-off speed is slow, the inverter circuit 3 is provided with a high-speed shut-off signal terminal Of to prevent destruction of the power switching element and demagnetization of the motor 4 due to simultaneous shorting of the upper and lower arms.

  The V-phase arm 30B and the W-phase arm 30C are similarly connected, and the emitter terminals of the lower arm transistors of each arm are connected to the shunt resistors 50b and 50c constituting the current detecting means 5, and the other of the shunt resistors 50b and 50c is connected. The terminal is connected to the DC power source negative potential terminal Ln. If the lower arm transistor is constituted by an IGBT or a power MOSFET, switching can be controlled by controlling the gate voltage. Therefore, the voltage of the shunt resistor connected to the emitter terminal in the case of IGBT and the source terminal in the case of power MOSFET is 1V or less. If the resistance value is selected, the on / off switching control can be performed by the voltage control with little influence on the switching operation, and the inverter circuit output current is detected by detecting the voltages veu, vev, and vew of the shunt resistors 50a, 50b, and 50c. In other words, the motor current can be detected.

  FIG. 3 shows the detection timing of the inverter circuit output current, PWM control is performed by triangular wave modulation, the switching timing of the upper and lower arm IGBTs is removed to reduce the influence of switching noise, and high-speed A / D conversion is performed to Current detection is performed by a motor control processor.

  In FIG. 3, ck is a peak value of the triangular wave modulation signal Vt, that is, a synchronization signal generated at time t3, vu is a U-phase voltage control signal, and the triangular wave modulation signal Vt and the U-phase voltage control signal vu are compared with each other. A drive signal Up for the phase upper arm transistor 31a1 and a drive signal Un for the U phase lower arm transistor 31a2 are generated. The period between t1 and t2 and the period between t5 and t6 is called the dead time Δt in the non-conducting period of the upper and lower arm transistors, and the A / D conversion timing is the time t3 when the upper arm transistor is off and the lower arm transistor is on, It may be performed within a range of time t4 that is shifted from t3 by dead time Δt.

  FIG. 4 shows a detailed embodiment of the current detection circuit according to the present invention. A / D conversion is performed by amplifying current signals detected by the shunt resistors 50a, 50b, and 50c by a non-inverting amplifier and built in a processor such as a microcomputer. The level is converted to a DC voltage level that can be detected by the circuit.

  Since the current detection circuits 51a, 51b, and 51c are the same circuit, the U-phase current detection circuit 51a will be described. The peak value of the voltage veu generated in the shunt resistor 50a corresponds to the U-phase output current of the inverter circuit 3, and the shunt resistor voltage changes between positive and negative with respect to the ground potential of the current detection circuit. Since the A / D conversion circuit built in the microcomputer or the like operates at a predetermined DC voltage, it is necessary to amplify and shift the level so as to change with respect to the center value of the DC voltage. In other words, the motor current signal is set to change within the input dynamic range of the A / D conversion circuit.

  The capacitor 500a is connected in parallel with the shunt resistor 50a, and the resistors 501a and 502a are connected in series with the shunt resistor 50a, and the resistor 502a is pulled up to the DC power source (Vcc) of the current detection circuit 51a. The connection point of the resistor 501a (resistance value R2) and the resistor 502a (resistance value R1) is connected to the + input terminal of the operational amplifier 503a, and the feedback resistor 504a (resistance value R4) is connected between the output terminal and the −input terminal of the operational amplifier 503a. And a resistor 505a (resistance value R3) is connected between the negative input terminal and the ground potential and used as a non-inverting amplifier. When the shunt resistance resistance value is Ro, veu = Ro × I, and when the voltage dividing ratio k between the resistors 501a and 502a is k = R2 / (R1 + R2) and the feedback gain K is K = R4 / R3, the current detection circuit 51a. The output voltage vau is expressed by Equation 1.

  Here, if the product of the voltage division ratio k and the feedback amplification factor K, that is, k × K = 0.5, the voltage signal corresponding to the current I is centered on 1/2 of the DC power supply voltage Vcc. Converted.

  For example, when the voltage division ratio k = 0.1, the feedback amplification factor K = 5, the shunt resistance value Ro = 0.2Ω, and Vcc = 5V, the output voltage of the current detection circuit 51a is vau = 0.9 × I + 2.5. expressed. That is, when the DC voltage of the A / D conversion circuit is 5 V, the center value 2.5 V corresponds to 0 A, and the dynamic range can detect a current up to ± 2.5 A with respect to ± 2.5 V.

  The resistor 506a and the diodes 507a and 508a are connected for overvoltage protection of the A / D conversion circuit.

  FIG. 5 shows another embodiment of the current detection circuit according to the present invention, which amplifies a current signal by an inverting amplifier and converts the voltage level. Only the embodiment of the U-phase current detection circuit 51a1 is shown.

  The circuit connection is a partial change from the embodiment shown in FIG. 4, in which the resistor 502 a is connected to the negative power source Ve by pull-down, and the operational amplifier 503 a is used as an inverting amplifier. The grounding resistor 505a shown in FIG. 4 can be omitted. At this time, the feedback amplification factor K is obtained by dividing the feedback resistor 504a (R4) by the input resistor 501a (R2), and the relational expression between the shunt resistance voltage drop veu and the output voltage vau is expressed by Equation 2.

  Here, when the ratio of the feedback resistor 504a and the resistor 502a is set to R4 / R1 = 0.5, and the DC voltage absolute value of the negative power source Ve is equal to the power source voltage (dynamic range) of the A / D converter, A The shunt resistance voltage is amplified and level-converted so as to change up and down with respect to the center value of the power supply voltage of the / D converter. For example, when Ve = −5V, R4 = 10 kΩ, R1 = 20 kΩ, and R2 = 2 kΩ, it is expressed by vau = 2.5−5 × veu. Assuming that the shunt resistance resistance value is 0.2Ω and the current is I, vau = 2.5−I.

  In the circuit using the non-inverting amplifier described in FIG. 4, the DC power supply voltage (Vcc) to be pulled up is equal to the DC voltage of the A / D converter circuit, the voltage dividing ratio k between the input resistor and the pull-up resistor, and the feedback amplification. If the product of the rate K, that is, k × K is approximately 0.5, the level can be converted to the center value of the DC voltage of the A / D conversion circuit.

  In the circuit using the inverting amplifier described in FIG. 5, the absolute value of the negative power supply voltage is made equal to the DC voltage of the A / D conversion circuit, and the ratio of the feedback resistance and the resistance pull-down connected to the negative power supply (Ve) is approximately 0. 0. It may be set to 5.

  As described above, the current detection circuit of the present invention has a feature that current detection can be easily performed at low cost by using a small number of components and a single power supply operational amplifier.

  The embodiment using the non-inverting amplifier shown in FIG. 4 has a feature that the DC power supply is simplified because it operates with a single power source. The embodiment using the inverting amplifier shown in FIG. The negative voltage that is the same as the range is required, which increases the price. However, since the positive and negative directions of the current signal are equal to the motor current, the calculation is simplified.

  FIG. 6 is a detailed embodiment showing the connection relation between the current detection means 5 and the overcurrent detection means 6 according to the present invention. The overcurrent detection means 6 is an overcurrent detection resistor 60 and a single power supply comparator. The current detection circuit 61 is used. The ground potential of the U-phase current detection circuit 51a is common to the ground potential G, and the details have been described with reference to FIG.

  When an overcurrent flows through the inverter circuit 3 or the motor 4, the overcurrent also flows through the overcurrent detection resistor 60, so that the product of the current I and the overcurrent detection resistance resistance value Ra with respect to the ground potential G A voltage drop (va = I × Ra) occurs. Since the current I is in the negative direction with respect to the ground potential G, the voltage drop is negative. The resistor 600 is connected from the negative voltage terminal (L2) of the overcurrent detection resistor 60, the resistor 601 is connected to the other terminal of the resistor 600, and the DC power supply Vcc terminal is connected. The connection point of the resistor 600 and the resistor 601 is connected to the + input terminal of the comparator 602 commonly connected to the ground potential G. The −input terminal (reference input terminal) of the comparator 602 is connected to the DC voltage Vcc by the resistor 603 and the resistor 604. The divided reference signal vrf is input. When the current flowing through the overcurrent detection resistor 60 is small, the positive input terminal is set to be higher than the negative input terminal (reference input terminal) of the comparator 602, and the output voltage of the comparator 602 becomes Hi level.

  As described above, in the first embodiment according to the present invention, when vector control or sensorless sine wave drive is performed by the inverter circuit 3, the current detection means 5 is configured by the shunt resistors 50a, 50b, 50c and the current detection circuit 51. Since the inverter circuit 3 can be protected at high speed by the overcurrent protection means 6 that is configured and provided separately from the current detection means 5, it prevents demagnetization of the permanent magnet motor and short circuit failure of the upper and lower arms of the power semiconductor due to overcurrent. Therefore, an inexpensive and highly reliable motor driving device can be realized.

  In addition, the current detection means is composed of a plurality of shunt resistors and a single power supply operational amplifier, and the overcurrent detection means can be composed of a single overcurrent detection resistance and a single power supply comparator, eliminating the need for a DC current transformer. An inexpensive current detection means and overcurrent protection means with low resistance can be configured.

  Furthermore, even if the power switching semiconductor of the inverter circuit is short-circuited simultaneously with the upper and lower arms, if the non-flammable overcurrent detection resistor is used, it will be melted and protected inside the small power capacity overcurrent detection resistor. Since the current fuse can be cut off before it blows, and the wiring pattern of the inverter circuit does not burn and the accident that the power switching semiconductor bursts does not occur, a highly reliable protective device can be realized.

  In particular, by using a voltage doubler rectifier circuit to increase the DC voltage and supply it to the inverter circuit to reduce the inverter circuit DC current, a small-capacity overcurrent detection resistor can be used, and it is easy to blow out against overcurrent. Can be increased.

(Embodiment 2)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.

  The overcurrent protection means 6A in the block diagram of FIG. 7 is such that the overcurrent detection resistor 60 is omitted from the block diagram shown in FIG. 1 and the overcurrent is detected by detecting the voltage drop of the shunt resistor. .

  The overcurrent protection circuit 61A includes a plurality of comparators that detect voltage drops in the plurality of shunt resistors 50a, 50b, and 50c. One overcurrent setting unit 62 sets reference potentials for the plurality of comparators.

  FIG. 8 shows a detailed embodiment of the overcurrent protection means 6A. The overcurrent detection circuit 61A is provided with overcurrent detection circuits 61a, 61b, 61c in the U phase, V phase, and W phase, respectively. The overcurrent detection level is set by the overcurrent setting signal vrf of the setting means 62.

  Explaining the overcurrent detection circuit 61a, the terminal voltage signal of the shunt resistor 50a is added to the negative input terminal of the comparator 612a through an integration circuit composed of the resistor 610a and the capacitor 611a. The setting signal vrf is applied to the + input terminal of the comparator 612a. A pull-up resistor is connected to the output terminal of the comparator 612a, and the comparator output signal is connected to the cutoff signal terminal Of of the inverter circuit 3 and the overcurrent stop terminal IRQ of the control means 7 and is connected to the inverter by the inverter circuit 3 and the control means 7. The output transistor of circuit 3 is turned off.

  The comparator output is normally an open collector. When an overcurrent is detected, the comparator output terminal becomes Lo. If the U, V, and W phase comparator output terminals are connected in common, they will remain Lo even if either comparator operates. Thus, the output of the inverter circuit 3 is cut off.

  The overcurrent setting means 62 connects a series connection body of a resistor 621 and a resistor 622 to the DC power source Vcc, and a signal at a connection point of the resistor 621 and the resistor 622, that is, a DC voltage divided signal vrf is detected by the overcurrent detection circuit 61a. , 61b, 61c are applied to the comparator input + terminals.

  Although the embodiment shown in FIG. 8 shows an example of a circuit that detects an overcurrent signal from the shunt resistors 50a, 50b, and 50c, the voltage signal viu at the connection point between the input resistor 501a and the pull-up resistor 502a of the current detection circuit 51a. Is added to the negative input terminal of the comparator 612a, the operation is the same. At this time, the resistor 610a and the capacitor 611a can be omitted, and the number of parts can be reduced.

  As described above, according to the present invention, the current flowing through the shunt resistors 50a, 50b, 50c for sensorless control of the inverter circuit 3 is detected by the overcurrent detection circuit. There is no need to provide a special current detection resistor.

  Further, only one overcurrent setting means is sufficient, and overcurrent protection can be performed with the same current setting value regardless of the current flowing through any of the shunt resistors.

  In addition, by configuring the overcurrent detection circuit with a comparator and connecting the open collector output terminals in common, the inverter circuit can be shut off with a single output signal regardless of the shunt resistance, so the inverter circuit The circuit can be protected by one interrupt input terminal.

(Embodiment 3)
The third embodiment of the present invention will be described below with reference to FIG. FIG. 9 shows an embodiment in which a plurality of motors are alternately switched and driven by one inverter circuit. Since the operation is basically the same as in the second embodiment, only the changes will be described.

  An output switching means 8 constituted by a relay is connected to the output terminal of the inverter circuit 3, and either the motor 4A or the motor 4B is switched by the output switching means 8 and driven. The output switching means 8 is controlled by a switching signal sw from the control means 7A.

  The overcurrent protection means 6B is configured to switch the overcurrent set value according to the motor 4A or the motor 4B by the switching signal sw of the control means 7A. The overcurrent setting means 62a has a plurality of overcurrent set values. The overcurrent detection level can be changed by the overcurrent set value changing means 63.

  As an example of alternately driving a plurality of motors by one inverter circuit, the drive switching of the washing motor drive motor and bath water pump motor, or the switching of the drying fan motor and bath water pump motor of the washing dryer, or A switching drive of the washing pump motor and the drainage pump motor or the drying fan motor of the dishwasher can be considered.

  When driving the motor 4B. A switching signal sw is applied from the control means 7A to the output switching means 8 and the overcurrent set value changing means 63 of the overcurrent protection means 6B, and after a predetermined time has elapsed, the inverter circuit 3 is driven to drive the motor 4B.

  As described above, according to the present invention, since the overcurrent set value of the overcurrent protection means can be changed, the overcurrent detection level can be set to an optimum value according to the motor, and the demagnetization of the permanent magnet motor Even when the motors are driven alternately at different levels, the optimum value can be set according to the motor, and even if the motor is switched, the permanent magnet is protected from demagnetization, so a highly reliable motor drive device Can be realized.

  As described above, the motor driving device of the present invention converts AC power into DC power by the rectifier circuit, drives the motor by the inverter circuit, detects the output current of the inverter circuit by the current detection means, Since the inverter circuit is PWM-controlled by the signal to perform vector control or sensorless sine wave drive, and the overcurrent protection operation of the motor or the inverter circuit is performed by the overcurrent protection means, an inexpensive excessive current Current protection means prevents permanent magnet synchronous motors from demagnetizing and temperature rise due to overcurrent, or destruction of power switching elements, so it can be used in most motor control systems that perform vector control or sensorless control. Can be applied to dishwasher washing pump drive or washing machine motor drive Or the fan motor driving apparatus can be applied to an air conditioner or a refrigerator heat pump motor driving device.

The block diagram of the motor drive device in an embodiment of the invention The figure which shows the inverter circuit of the motor drive device by this invention Current detection timing chart of motor driving device according to the present invention The figure which shows the electric current detection circuit by the non-inverting amplifier of the motor drive device by this invention The figure which shows the electric current detection circuit by the inverting amplifier of the motor drive device by this invention The figure which shows the connection relation of the electric current detection means of the motor drive device by this invention, and an overcurrent protection means. The block diagram of the motor drive device in the 2nd Embodiment of this invention The figure which shows the circuit of the overcurrent protection means of the motor drive device in the 2nd Embodiment of this invention. The block diagram of the motor drive device in the 3rd Embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier circuit 3 Inverter circuit 4 Motor 5 Current detection means 6 Overcurrent protection means 7 Control means

Claims (6)

An AC power source, a rectifier circuit that converts AC power of the AC power source into DC power, an inverter circuit that converts DC power of the rectifier circuit into AC power, a motor driven by the inverter circuit, and the inverter circuit Current detection means for detecting an output current; overcurrent protection means connected between the current detection means and a negative voltage terminal of the rectifier circuit; and the inverter circuit is controlled by an output signal of the current detection means to control the motor. A motor drive device comprising drive control means, wherein the overcurrent protection means performs an overcurrent protection operation of the motor or the inverter circuit. The inverter circuit is composed of a three-phase full-bridge inverter circuit composed of six transistors and a diode, and the current detecting means is a plurality of shunt resistors connected to the negative potential side terminals of the lower arm transistors of the three-phase full-bridge inverter circuit, respectively. And the current detection circuit, the inverter circuit is controlled by detecting the current flowing through the shunt resistor, and the overcurrent protection means has an overcurrent detection in which one terminal is connected in series with the shunt resistor. 2. The motor according to claim 1, wherein the motor comprises a resistor and an overcurrent detection circuit for detecting a current flowing through the overcurrent detection resistor, and the other terminal of the overcurrent detection resistor is connected to a negative voltage terminal of the rectifier circuit. Drive device. The connection terminal of the shunt resistor and the overcurrent detection resistor is set to the ground potential, and the current detection circuit for detecting the current of the shunt resistor and the ground potential of the overcurrent detection circuit for detecting the current of the overcurrent detection resistor are connected to the connection terminal. The motor driving device according to claim 1, wherein the motor driving devices are connected in common. An AC power source, a rectifier circuit that converts AC power of the AC power source into DC power, an inverter circuit that converts DC power of the rectifier circuit into AC power, a motor driven by the inverter circuit, and the inverter circuit Current detection means comprising a plurality of shunt resistors and a current detection circuit for detecting an output current, overcurrent protection means for detecting an electric current of the shunt resistor to perform an overcurrent protection operation, and an output signal of the current detection means It comprises control means for controlling the inverter circuit to drive the motor, and the overcurrent protection means comprises a plurality of overcurrent detection circuits for detecting currents of the plurality of shunt resistors and at least one overcurrent setting means, A motor driving apparatus configured to perform an overcurrent protection operation of the motor or the inverter circuit by the overcurrent protection means. 5. The motor driving apparatus according to claim 4, wherein the current detection circuit is constituted by a single power supply operational amplifier. A plurality of motors driven by an inverter circuit and output switching means for alternately switching the plurality of motors by control means, and the set value of the overcurrent setting means is changed according to the motor switched by the output switching means The motor drive device according to claim 4 which was made.

Images