JP7185538B2 - Inverter device for washing machine - Google Patents

Description

An embodiment of the present invention relates to an inverter device driven by a motor that generates a driving force for performing a washing operation.

2. Description of the Related Art Conventionally, in order to increase the rotational torque of a washing machine motor that is driven via an inverter circuit, it has been practiced to increase the voltage of the drive power supplied to the inverter circuit. For example, AC power input through an inductor is rectified by a bridge circuit, and the output terminals of the bridge circuit are short-circuited by a switching element to boost the voltage.

JP 2017-86596 A

By the way, a low-voltage power supply for driving the switching elements needs to be generated using a separate power supply circuit. When the voltage doubler circuit includes the rectifier circuit described above, the maximum value of the voltage output by the voltage doubler circuit is about 280V when the AC power supply voltage is 100V. In this case, since the ground level on the switching element side and the ground level on the inverter circuit side are different, it is necessary to separate the two grounds. Then, as shown in FIG. 5, the output voltage of the rectifying bridge circuit is rectified and smoothed through, for example, an oscillating circuit having an oscillation frequency of about several tens of kHz and an insulating transformer to generate a low-voltage driving power supply. However, since the oscillation circuit and the isolation transformer are expensive parts, the above configuration has been a factor in increasing the cost of the washing machine.

Therefore, an inverter device for a washing machine is provided that can generate a drive power source for a switching element with a low-cost configuration without causing a short circuit between grounds.

An inverter device for a washing machine according to an embodiment includes an inverter circuit driven by a motor that generates a driving force for performing a washing operation;
an inductor inserted on the AC power supply side;
a rectifying bridge circuit for rectifying AC power input via the inductor;
a switching element connected between the output terminals of the rectifying bridge circuit;
a driving power supply circuit that is connected between the output terminals and generates a power supply for driving the switching element by dividing the voltage between the output terminals ;
The control circuit ground, which is the ground for the inverter circuit, and the driver ground, which is the ground for the drive power supply circuit, are different grounds .

1 is a diagram showing a configuration of an inverter device according to a first embodiment, which is mounted in a washing machine and includes a booster circuit; FIG. Diagram showing configuration of drive power supply circuit Voltage, current, and signal waveform diagrams showing the boost operation of the boost circuit FIG. 4 shows the configuration of the drive power supply circuit according to the second embodiment; Diagram showing a configuration example of a conventional drive power supply circuit

(First embodiment)
A first embodiment will be described below with reference to FIGS. 1 and 2. FIG. FIG. 1 shows the configuration of an inverter device 1 mounted in a washing machine and having a booster circuit. A rectifying bridge circuit 3 formed by bridge-connecting four diodes is connected to one end of a 100 V commercial AC power supply via an inductor 2 . A series circuit of smoothing capacitors 4 a and 4 b and an inverter circuit 5 are connected between output terminals of the rectifying bridge circuit 3 . A common connection point of the smoothing capacitors 4a and 4b is connected to the other end of the commercial AC power supply. These components constitute a voltage doubler rectifier circuit, which generates a smoothed DC voltage containing a ripple of about 280V at maximum.

The inverter circuit 5 is configured by connecting, for example, six IGBTs 6, which are switching elements, in a three-phase bridge. A freewheeling diode 7 is connected between the collector and emitter of the IGBT 6 . Each phase output terminal of the inverter circuit 5 is connected to one end of each phase stator winding 9U, 9V, 9W of the motor 8 which is star-connected. The motor 8 is, for example, a DC brushless motor, and rotates a drum of a washing machine, for example, in order to perform washing operation and spin-drying operation.

A resistance element 10 is connected between the negative side of the inverter circuit 5 and the control circuit ground. Both ends of the resistive element 10 are connected to input terminals of a control circuit 11 composed of a microcomputer. The resistive element 10 detects a phase current supplied to the motor 6 via the inverter circuit 5, and in this embodiment, a one-shunt current detection method is employed. The control circuit 11 detects each phase current of U, V, and W by A/D converting and reading the terminal voltage of the resistance element 10 at a predetermined timing. Then, the control circuit 11 generates a PWM signal based on the detected current, and outputs it to each IGBT 6 forming the inverter circuit 5 as a gate signal. The operating power supply voltage of the control circuit 11 is, for example, 5V.

Another rectifying bridge circuit 12 is connected in parallel to the rectifying bridge circuit 3 . An IGBT 13 that is a voltage-driven semiconductor element is connected between the output terminals of the rectifying bridge circuit 12 . A freewheel diode 14 is connected between the collector and emitter of the IGBT 13 . The emitter of IGBT 13 is connected to the driver ground. A booster circuit 16 is composed of the inductor 2 , the rectifying bridge circuit 12 and the IGBTs 13 . The control circuit 11 outputs a gate signal to the IGBT 13 via the photocoupler 15 which is a driver. A power supply with a voltage of, for example, 15 V is supplied to the photocoupler 15 as a power supply for driving the IGBT 13 .

FIG. 2 shows the configuration of a driving power supply circuit 21 that generates the driving power described above. The drive power supply circuit 21 is connected between output terminals of the rectifying bridge circuit 12 . The maximum value of the pulsating current voltage between the output terminals is about 140V. The drive power supply circuit 21 includes a series circuit of a resistance element 22 and a Zener diode 23 and an electrolytic capacitor 24 connected in parallel with the Zener diode 23 . The resistance element 22 has, for example, a resistance value of 20 kΩ and a wattage of 3 W, and the Zener voltage of the Zener diode 23 is 15V. As a result, a 15V driving power supply is generated with the driver ground as a reference.

FIG. 3 shows voltage, current, and signal waveforms when the control circuit 11 performs switching control of the IGBT 13 to perform the boosting operation by the booster circuit 16, which corresponds to FIG. The IGBT 13 is turned on and off a plurality of times within the cycle of the commercial AC power supply to generate a short-circuit current, and the boost operation is performed by the current flowing through the inductor 2, which is a reactor in the figure. In the drive power supply circuit 21 of the present embodiment, since the rectifying bridge circuit 12, the IGBT 13, and the photocoupler use the common driver ground as a potential reference, ground-to-ground short-circuiting does not pose a problem.

As described above, according to this embodiment, the inverter circuit 5 driven by the motor 8 that generates the driving force for the washing operation, the inductor 2 inserted on the power supply side, and the input through the inductor 2 A rectifying bridge circuit 12 for rectifying AC power, an IGBT 13 connected between the output terminals of the rectifying bridge circuit 12, a power source connected between the output terminals and for driving the IGBT 13 via a photocoupler 14 is connected to the output terminal. A driving power supply circuit 21 is provided to divide and generate the voltage between the two. With this configuration, the power source for driving the IGBT 13 can be generated with an inexpensive configuration.

Specifically, since the driving power supply circuit 21 is composed of the series circuit of the resistance element 22 and the Zener diode 23, and the electrolytic capacitor 24 connected in parallel to the Zener diode 23, the driving power supply for the IGBT 13 can be accurately supplied. can be produced stably. Further, by using the voltage-driven IGBT 13 for the booster circuit 16, the drive current is reduced, so the capacitance of the capacitor 24 can be reduced.

(Second embodiment)
Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted, and different parts will be described. As shown in FIG. 4, the driving power supply circuit 31 of the second embodiment has a diode 32 connected in the forward direction between the resistive element 22 and the Zener diode 23 in the configuration of the first embodiment. The diode 32 is for preventing discharge of the capacitor 24 . This makes it possible to further stabilize the voltage of the driving power supply.

(Other embodiments)
The driving power supply circuit may be configured to divide the voltage between the output terminals of the rectifying bridge circuit.
The switching elements are not limited to IGBTs, and may be MOSFETs, bipolar transistors, or the like.
Current detection is not limited to the one-shunt method, and a three-shunt method or a current sensor may be used.
Specific numerical values such as the power supply voltage and the resistance value may be appropriately changed according to individual designs.
The washing machine may be of a vertical type, and the motor may be one that drives a pulsator.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

In the drawings, 1 is an inverter device, 2 is an inductor, 3 is a rectifying bridge circuit, 5 is an inverter circuit, 8 is a motor, 13 is an IGBT, 15 is a photocoupler, 16 is a booster circuit, 21 is a drive power supply circuit, and 22 is a resistor. Element 23 is a Zener diode, 24 is an electrolytic capacitor, 31 is a drive power supply circuit, and 32 is a diode.

Claims (4)

an inverter circuit driven by a motor that generates a driving force for performing the washing operation;
an inductor inserted on the AC power supply side;
a rectifying bridge circuit for rectifying AC power input via the inductor;
a switching element connected between the output terminals of the rectifying bridge circuit;
a driving power supply circuit that is connected between the output terminals and generates a power supply for driving the switching element by dividing the voltage between the output terminals ;
In the washing machine inverter device, a control circuit ground, which is the ground of the inverter circuit, and a driver ground, which is the ground of the driving power supply circuit, are different grounds . The drive power supply circuit includes a series circuit of a resistive element and a Zener diode;
2. The washing machine inverter device according to claim 1, further comprising a capacitor connected in parallel with said Zener diode. 3. The washing machine inverter device according to claim 2, wherein said drive power supply circuit includes a discharge prevention diode connected between said resistance element and said Zener diode. The washing machine inverter device according to any one of claims 1 to 3, wherein the switching element is a voltage-driven semiconductor element.

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