JP7209893B2 - Converter circuit and motor drive circuit - Google Patents

Description

The present disclosure relates to a converter circuit that converts AC voltage to DC voltage and a motor drive circuit that includes this converter circuit.

Conventional air conditioner motor drive circuits rectify AC power supply voltage in a converter circuit equipped with a diode bridge, which is a rectifier circuit, and convert it to DC voltage. are supplying to

Patent Literature 1 discloses a motor drive circuit that supplies a DC voltage rectified by a diode bridge to an inverter circuit and also to an outdoor control unit that controls an outdoor unit.

JP 2012-117704 A

The motor drive circuit disclosed in Patent Document 1 has a problem that noise generated in the outdoor control unit to which the DC voltage is supplied other than the inverter circuit is transmitted to the power supply side, increasing the noise terminal voltage.

The present disclosure has been made in view of the above, and supplies a DC voltage obtained by rectifying an AC voltage in a rectifier circuit to an inverter circuit and a supply target other than the inverter circuit, and generates in the supply target other than the inverter circuit. It is an object of the present invention to obtain a converter circuit that suppresses the transmission of noise to the power supply side.

In order to solve the above-described problems and achieve the object, a converter circuit according to the present disclosure includes a rectifier circuit that rectifies an AC voltage supplied from an AC power supply and outputs a DC voltage, and a DC voltage that is output from the rectifier circuit. and a voltage doubler circuit for stepping up the voltage. Further, the converter circuit according to the present disclosure includes a DC reactor connected between the rectifier circuit and the voltage doubler circuit, and a noise reduction circuit including a first relay for passing current by bypassing the DC reactor. , an inrush prevention circuit including an inrush prevention resistor connected between the rectifier circuit and the voltage doubler circuit, and a second relay for bypassing the inrush prevention resistor and allowing current to flow. Further, the converter circuit according to the present disclosure includes a power supply circuit that is connected between a noise reduction circuit and a voltage doubler circuit and outputs a DC voltage output from a rectifier circuit, a noise reduction circuit, an inrush prevention circuit, and a voltage doubler circuit. and a control unit that controls switching of current paths in the voltage circuit. The voltage doubler circuit includes a positive diode whose anode is connected to the positive output line, a negative diode whose cathode is connected to the negative output line, and series connections between the cathode of the positive diode and the anode of the negative diode. A positive side capacitor and a negative side capacitor are connected, and a positive side switching element and a negative side switching element are connected in series between the anode side of the positive side diode and the cathode side of the negative side diode. A portion between the positive electrode side capacitor and the negative electrode side capacitor and a portion between the positive electrode side switching element and the negative electrode side switching element are connected. During the boosting operation of the voltage doubler circuit, the positive side switching element and the negative side switching element are alternately turned on with a dead time during which both the positive side switching element and the negative side switching element are turned off. During the dead time, the first relay is turned on and the second relay is turned off.

A converter circuit according to the present disclosure supplies a DC voltage obtained by rectifying an AC voltage in a rectifier circuit to an inverter circuit and a supply target other than the inverter circuit, and noise generated in the supply target other than the inverter circuit is transmitted to the power supply side. There is an effect that it can be suppressed.

1 shows a configuration of a motor drive circuit according to Embodiment 1; FIG. FIG. 4 shows a modification of the motor drive circuit according to the first embodiment; Timing chart of the output voltage of the voltage doubler circuit of the motor drive circuit according to Embodiment 1, the gate signals of the positive side switching element and the negative side switching element, and the drive signal of the first relay and the second relay Timing chart of switching element, first relay, and second relay of voltage doubler circuit of motor drive circuit according to Embodiment 1 FIG. 4 shows the state of the voltage doubler circuit in the second state of the motor drive circuit according to the first embodiment; FIG. 5 is a diagram showing current paths during charging of the positive electrode side capacitor in the third state of the motor drive circuit according to the first embodiment; FIG. 5 is a diagram showing current paths during charging of the negative electrode side capacitor in the third state of the motor drive circuit according to the first embodiment; FIG. 5 is a diagram showing current paths during dead time in the third state of the motor drive circuit according to the first embodiment; FIG. 10 is a diagram showing the state of the voltage doubler circuit in the fourth state of the motor drive circuit according to the first embodiment; FIG. 4 is a diagram showing a configuration in which functions of a controller of the motor drive circuit according to Embodiment 1 are realized by hardware; FIG. 4 is a diagram showing a configuration in which functions of a controller of the motor drive circuit according to Embodiment 1 are realized by software;

A converter circuit and a motor drive circuit according to embodiments will be described in detail below with reference to the drawings.

Embodiment 1.
FIG. 1 is a diagram showing a configuration of a motor drive circuit according to Embodiment 1. FIG. The motor drive circuit 100 has a converter circuit 10 and an inverter circuit 8 . The converter circuit 10 includes a diode bridge 1 , an inrush prevention circuit 2 , a noise reduction circuit 3 , a power supply circuit 4 and a voltage doubler circuit 5 . A controller 6 that controls each part is connected to the converter circuit 10 . The illustration of lines connecting each part of the converter circuit 10 and the controller 6 is omitted.

A diode bridge 1, which is a rectifier circuit, has four diodes arranged in a bridge shape. The diode bridge 1 performs full-wave rectification of the single-phase AC voltage supplied from the AC power supply 90 by utilizing the property of diodes that are energized only when a forward voltage is applied, and outputs a DC voltage. FIG. 2 is a diagram showing a modification of the motor drive circuit according to Embodiment 1. FIG. The AC power supply 90 may supply a three-phase AC voltage. A diode bridge 1 for rectifying three-phase alternating current has a circuit configuration in which six diodes are arranged in a bridge shape. A rectifier circuit that half-wave rectifies the AC voltage supplied from the AC power supply 90 may be used.

The inverter circuit 8 converts the DC voltage into a three-phase AC voltage. Since the power supply voltage is generally an AC voltage of 50 Hz or 60 Hz, the motor drive circuit 100 converts the power supply voltage into a DC voltage with the diode bridge 1 and converts the DC voltage into an AC voltage with the inverter circuit 8. , an AC voltage of any frequency can be output to the motor 9 to control the rotation speed of the motor 9 .

The rush prevention circuit 2 and the noise reduction circuit 3 are connected between the diode bridge 1 and the voltage doubler circuit 5 . The noise reduction circuit 3 has a DC reactor 31 installed on the positive output line 11 of the diode bridge 1 and a first relay 32 connected in parallel with the DC reactor 31 . When the first relay 32 is turned on, current flows through the first relay 32 bypassing the DC reactor 31 . When the first relay 32 is turned off, current flows through the DC reactor 31 . The rush prevention circuit 2 has a rush prevention resistor 21 installed on the positive output line 11 of the diode bridge 1 and a second relay 22 connected in parallel to the rush prevention resistor 21 . When the second relay 22 is turned on, current flows through the second relay 22 bypassing the inrush prevention resistor 21 . When the second relay 22 is turned off, current flows through the inrush prevention resistor 21 .

The power supply circuit 4 is connected between the noise reduction circuit 3 and the voltage doubler circuit 5 . The power supply circuit 4 is connected between a power supply diode 41 whose anode is connected to the positive output line 11 of the diode bridge 1 and between the cathode side of the power supply diode 41 and the negative output line 12 of the diode bridge 1 . and a power supply capacitor 42 . Both ends of the power supply capacitor 42 are connected to another system 7 not included in the motor drive circuit 100 . Therefore, the DC voltage Vc for the separate system 7 is the voltage across the power supply capacitor 42 . A power supply circuit 4 steps down the DC voltage output from the diode bridge 1 and outputs it.

When the motor drive circuit 100 is used to drive the motor 9 of the compressor of the air conditioner, another system 7 can be exemplified as an air conditioner indoor board that checks the driving state of the motor 9 through mutual communication with the controller 6 and controls the motor 9 . However, it is not limited to this.

The voltage doubler circuit 5 includes a positive diode 51 whose anode is connected to the positive output line 11 of the diode bridge 1, a negative diode 52 whose cathode is connected to the negative output line 12 of the diode bridge 1, and a positive diode 51. A positive capacitor 53 and a negative capacitor 54 connected in series between the cathode side of the positive diode 51 and the anode side of the negative diode 52, and a positive capacitor 53 and a negative capacitor 54 connected in series between the anode side of the positive diode 51 and the cathode side of the negative diode 52. A positive electrode side switching element 55 and a negative electrode side switching element 56 are provided. A portion between the positive electrode side capacitor 53 and the negative electrode side capacitor 54 and a portion between the positive electrode side switching element 55 and the negative electrode side switching element 56 are connected. The voltage doubler circuit 5 switches the current path of the DC voltage rectified by the diode bridge 1 between a path passing through one of the positive electrode side capacitor 53 and the negative electrode side capacitor 54 and a path passing through both of them. and the negative electrode side capacitor 54 are each charged with a DC voltage having the same magnitude as the power supply voltage Vs.

The switching of the positive electrode side switching element 55 and the negative electrode side switching element 56 and the ON/OFF of the first relay 32 and the second relay 22 are the current paths in the noise reduction circuit 3 , the rush prevention circuit 2 and the voltage doubler circuit 5 . It is controlled by a controller 6, which is a control unit that controls switching. Controller 6 also controls pulse width modulation in inverter circuit 8 . The illustration of the positive electrode side switching element 55, the negative electrode side switching element 56, the first relay 32, the second relay 22, and the connection lines between the inverter circuit 8 and the controller 6 is omitted.

FIG. 3 is a timing chart of the output voltage of the voltage doubler circuit of the motor drive circuit according to Embodiment 1, the gate signals of the positive side switching element and the negative side switching element, and the drive signals of the first relay and the second relay. is. The motor drive circuit 100 has four states, and switches ON/OFF of each element for each state.

The first state is the state after the motor drive circuit 100 is started until the bus voltage Vdc reaches the power supply voltage Vs. When the motor drive circuit 100 is started, a large current flows through the circuit to charge the positive electrode capacitor 53 and the negative electrode capacitor 54, and each element may be destroyed. Therefore, in the first state, the second relay 22 of the rush prevention circuit 2 is turned off, and current flows through the rush prevention resistor 21 . By passing current through the inrush prevention resistor 21, the inrush current at startup can be suppressed. Also, the first relay 32 of the noise reduction circuit 3 is turned off, and current is passed through the DC reactor 31 . Common mode noise can be reduced by passing current through the DC reactor 31 .

In the second state, the positive side capacitor 53 and the negative side capacitor 54 are charged until the bus voltage Vdc reaches the power supply voltage Vs, and the voltage doubler circuit 5 does not operate. The power supply voltage Vs is full-wave rectified by the diode bridge 1, and the bus voltage Vdc is a DC voltage having the same magnitude as the maximum value of the power supply voltage Vs. When the bus voltage Vdc reaches a steady state, the inrush current does not flow. Therefore, the second relay 22 of the inrush prevention circuit 2, which was turned off in the first state, is turned on to bypass the inrush prevention resistor 21 and cause the current to flow. , the power consumption of the motor drive circuit 100 is reduced.

The third state is the state from the start to completion of boosting the bus voltage Vdc. During boosting, switching of the positive side switching element 55 and the negative side switching element 56 of the voltage doubler circuit 5 and switching of the first relay 32 and the second relay 22 are performed. Switching of the positive electrode side switching element 55, the negative electrode side switching element 56, the first relay 32, and the second relay 22 during boosting will be described later.

4 is a timing chart of the switching element, first relay, and second relay of the voltage doubler circuit of the motor drive circuit according to Embodiment 1. FIG. When controlling the positive switching element 55 and the negative switching element 56 of the voltage doubler circuit 5, if the positive switching element 55 and the negative switching element 56 are turned on at the same time, the power supply and the ground are short-circuited, resulting in a large current. may flow and damage the element. Therefore, when switching on/off the positive electrode side switching element 55 and the negative electrode side switching element 56, it is necessary to provide a period during which both elements are turned off in consideration of the response speed of the elements. A period during which both the positive side switching element 55 and the negative side switching element 56 are turned off is called a dead time.

FIG. 5 is a diagram showing the state of the voltage doubler circuit in the second state of the motor drive circuit according to the first embodiment. Before the start of boosting, a voltage of 0.5 Vs is applied to the positive capacitor 53 and the negative capacitor 54, respectively, and the output of the bus voltage Vdc is a DC voltage of the same magnitude as Vs. In order to boost the output of the bus voltage Vdc to double the power supply voltage Vs, it is necessary to store an additional charge of 0.5 Vs in each of the positive electrode side capacitor 53 and the negative electrode side capacitor 54 .

Switching of the positive electrode side switching element 55, the negative electrode side switching element 56, the first relay 32, and the second relay 22 at the time of boosting will be described. FIG. 6 is a diagram showing current paths during charging of the positive electrode side capacitor in the third state of the motor drive circuit according to the first embodiment. FIG. 7 is a diagram showing current paths during charging of the negative electrode side capacitor in the third state of the motor drive circuit according to the first embodiment. FIG. 8 is a diagram showing current paths during dead time in the third state of the motor drive circuit according to the first embodiment. When charging the positive electrode side capacitor 53, the negative electrode side switching element 56 is turned on. On the other hand, when charging the negative electrode side capacitor 54, the positive electrode side switching element 55 is turned on. The charging currents of the positive capacitor 53 and the negative capacitor 54 during the boosting operation are larger than those in the steady state. , part of the current for charging the positive capacitor 53 and the negative capacitor 54 is held by the DC reactor 31 and flows into the power supply circuit 4 when the switching period shifts to the dead time. When part of the current for charging the positive capacitor 53 and the negative capacitor 54 flows into the power supply circuit 4, the DC voltage Vc instantaneously increases.

Therefore, in the third state, the DC reactor 31 is prevented from stepping up the DC voltage Vc by turning on the first relay 32 during the dead time to bypass the DC reactor 31 and flow the current. Furthermore, since a rush current flows when the first relay 32 is turned on, the second relay 22 is turned off to pass current through the rush prevention resistor 21 to suppress the rush current.

FIG. 9 is a diagram showing the state of the voltage doubler circuit in the fourth state of the motor drive circuit according to the first embodiment. The fourth state is a steady state after the completion of boosting. The bus voltage Vdc is a DC voltage twice as large as the power supply voltage Vs. In the fourth state, switching of the positive electrode side switching element 55 and the negative electrode side switching element 56 is performed in order to maintain the doubled voltage output. is small, the magnitude of the DC voltage Vc does not fluctuate regardless of whether current flows through the DC reactor 31 or not. Therefore, the first relay 32 is turned off and the second relay 22 is turned on.

As described above, the motor drive circuit 100 according to the first embodiment treats the DC voltage obtained by rectifying the AC voltage by the diode bridge 1 and the DC voltage obtained by boosting the rectified DC voltage by the voltage doubler circuit 5 as different targets. The noise reduction circuit 3 can suppress the transmission of noise generated in the separate system 7 to which the rectified DC voltage is supplied to the AC power supply 90 side. Also, by turning on the first relay 32 to short-circuit the DC reactor 31 during the dead time when the voltage doubler circuit 5 boosts, the instantaneous boosting of the DC voltage Vc supplied to the separate system 7 is suppressed. can be done.

The functions of the controller 6 of the motor drive circuit 100 according to the first embodiment are implemented by a processing circuit. The processing circuit may be dedicated hardware or a processing device that executes a program stored in a storage device.

If the processing circuit is dedicated hardware, it may be a single circuit, multiple circuits, a programmed processor, a parallel programmed processor, an application specific integrated circuit, a field programmable gate array, or a combination thereof. is applicable. FIG. 10 is a diagram showing a configuration in which the functions of the controller of the motor drive circuit according to the first embodiment are realized by hardware. The processing circuit 29 incorporates a logic circuit 29 a that implements the functions of the controller 6 .

When the processing circuit 29 is a processing device, the functions of the controller 6 are implemented by software, firmware, or a combination of software and firmware.

FIG. 11 is a diagram showing a configuration in which functions of the controller of the motor drive circuit according to the first embodiment are implemented by software. The processing circuit 29 has a processor 291 that executes the program 29b, a random access memory 292 that the processor 291 uses as a work area, and a storage device 293 that stores the program 29b. The functions of the controller 6 are realized by the processor 291 developing the program 29b stored in the storage device 293 on the random access memory 292 and executing it. Software or firmware is written in a programming language and stored in the storage device 293 . Processor 291 can be exemplified by, but not limited to, a central processing unit. The storage device 293 is a semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), or EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory). can. The semiconductor memory may be either non-volatile memory or volatile memory. In addition to the semiconductor memory, the storage device 293 may be a magnetic disk, flexible disk, optical disk, compact disk, mini disk, or DVD (Digital Versatile Disk). Note that the processor 291 may output data such as calculation results to the storage device 293 for storage, or may store the data in an auxiliary storage device (not shown) via the random access memory 292 .

The processing circuit 29 implements the functions of the controller 6 by reading and executing the program 29b stored in the storage device 293 . It can also be said that the program 29b causes a computer to execute procedures and methods for realizing the functions of the controller 6. FIG.

The processing circuit 29 may implement part of the functions of the controller 6 with dedicated hardware and part of the functions of the controller 6 with software or firmware.

Thus, the processing circuit 29 can implement each function described above by means of hardware, software, firmware, or a combination thereof.

The configuration shown in the above embodiment shows an example of the contents, and it is possible to combine it with another known technique, and part of the configuration is omitted or changed without departing from the scope. is also possible.

1 diode bridge, 2 inrush prevention circuit, 3 noise reduction circuit, 4 power supply circuit, 5 voltage doubler circuit, 6 controller, 7 separate system, 8 inverter circuit, 9 motor, 10 converter circuit, 11 positive output line, 12 negative Output line, 21 inrush prevention resistor, 22 second relay, 29 processing circuit, 29a logic circuit, 29b program, 31 DC reactor, 32 first relay, 41 power supply diode, 42 power supply capacitor, 51 positive diode , 52 negative diode, 53 positive capacitor, 54 negative capacitor, 55 positive switching element, 56 negative switching element, 90 AC power supply, 100 motor drive circuit, 291 processor, 292 random access memory, 293 storage device.

Claims (5)

a rectifier circuit that rectifies an AC voltage supplied from an AC power supply and outputs a DC voltage;
a voltage doubler circuit that boosts the DC voltage output from the rectifier circuit;
A noise reduction circuit including a DC reactor connected between the rectifier circuit and the voltage doubler circuit, and a first relay for passing current by bypassing the DC reactor;
an inrush prevention circuit including an inrush prevention resistor connected between the rectifier circuit and the voltage doubler circuit, and a second relay for bypassing the inrush prevention resistor to flow current;
a power supply circuit connected between the noise reduction circuit and the voltage doubler circuit for outputting a DC voltage output from the rectifier circuit;
A control unit that controls switching of current paths in the noise reduction circuit, the rush prevention circuit, and the voltage doubler circuit,
The voltage doubler circuit
a positive diode whose anode is connected to the positive output line of the rectifier circuit ;
a negative diode whose cathode is connected to the negative output line of the rectifier circuit ;
a positive side capacitor and a negative side capacitor connected in series between the cathode side of the positive side diode and the anode side of the negative side diode;
A positive side switching element and a negative side switching element connected in series between the anode side of the positive side diode and the cathode side of the negative side diode,
a portion between the positive electrode side capacitor and the negative electrode side capacitor and a portion between the positive electrode side switching element and the negative electrode side switching element are connected,
During the boosting operation of the voltage doubler circuit, the positive side switching element and the negative side switching element are alternately turned on with a dead time during which both the positive side switching element and the negative side switching element are turned off,
A converter circuit that turns on the first relay and turns off the second relay during the dead time. 2. The converter circuit according to claim 1, wherein the rectifier circuit performs full-wave rectification of the AC voltage supplied from the AC power supply. The power supply circuit is
a power supply diode having an anode connected to the positive output line of the rectifier circuit;
A power supply capacitor connected between the cathode side of the power supply diode and the negative output line of the rectifier circuit,
3. The converter circuit according to claim 1, wherein the DC voltage is output from both ends of the power supply capacitor. 4. The converter circuit according to claim 1, wherein said DC reactor is connected between said rectifier circuit and said power supply circuit. A converter circuit according to any one of claims 1 to 4, and an inverter circuit that converts the DC voltage output by the voltage doubler circuit into an AC voltage,
A motor drive circuit for driving a motor by the AC voltage output by the inverter circuit.

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