Power supply unit and washing machine

Abstract

The goal is to miniaturize the circuit while suppressing harmonic components contained in the power supply current. [Solution] The power supply unit 200 has a rectifier circuit 210 including a rectifier unit 211, a switch unit 212, and a smoothing unit 213. The switch unit 212 includes a transformer 31 including a primary coil 311 and a secondary coil 312, a switching element 32, and a diode 19. The first end of the switching element 32 is connected to a connection point 65 via the primary coil 311 and the diode 17, and the second end is connected to the first power input terminal 61 of the AC power supply 600. The anode of the diode 19 is connected to the first end 68 of the secondary coil 312, and the cathode is connected to the first rectified output terminal 63. The second end 69 of the secondary coil 312 is connected to the second rectified output terminal 64.

Description

Technical Field

[0001] The present disclosure relates to a power supply device for an electrical device.

Background Art

[0002] Techniques for suppressing harmonic components included in an alternating current supplied from an alternating current power supply are known. For example, Patent Document 1 discloses a harmonic current adjustment device including first and second power conversion devices electrically connected to an alternating current power supply via a first electric wire. This harmonic current adjustment device detects a first harmonic current of a predetermined order included in a first current flowing between the first power conversion device and the alternating current power supply, and a second harmonic current of a predetermined order included in a second current flowing between the second power conversion device and the alternating current power supply, obtains an absolute value of a vector sum of the detected first harmonic current and the detected second harmonic current, and controls a phase adjuster so that the absolute value of the vector sum becomes minimum.

[0003] Patent Document 2 discloses a direct current power supply device including a first rectifier circuit that rectifies an alternating current voltage from an alternating current power supply to charge a smoothing capacitor, a second rectifier circuit that rectifies the alternating current voltage, and a boost bias circuit connected between the second rectifier circuit and the smoothing capacitor. This direct current power supply device suppresses harmonic components of a power supply current by flowing a sinusoidal bias current in addition to a pulsed current that charges the smoothing capacitor to an alternating current power supply terminal.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, while the prior art described in Patent Documents 1 and 2 both attempts to suppress harmonic components contained in the power supply current, further improvements are needed from the standpoint of miniaturizing the circuit.

[0006] This disclosure was made to solve these problems and aims to provide a technology that can suppress harmonic components contained in the power supply current while miniaturizing the circuit. [Means for solving the problem]

[0007] A power supply device in one aspect of the present disclosure is a power supply device for an electrical device, comprising a rectifier circuit for rectifying a power supply voltage from an AC power supply, the rectifier circuit comprising a rectifier section connected to the AC power supply, a smoothing section including a first smoothing capacitor and a second smoothing capacitor for smoothing the power supply voltage rectified by the rectifier section, and a switch section connected between the rectifier section and the smoothing section, the switch section comprising a transformer including a primary coil and a secondary coil, a switching element, and a diode, the first end of the switching element being connected to the connection point of the first smoothing capacitor and the second smoothing capacitor via the primary coil, and the second end being connected to the first power supply input terminal of the AC power supply, the anode of the diode being connected to the first end of the secondary coil, and the cathode being connected to the first rectified output terminal of the rectifier circuit, and the second end of the secondary coil being connected to the second rectified output terminal of the rectifier circuit. [Effects of the Invention]

[0008] This configuration allows for miniaturization of the circuit while suppressing harmonic components contained in the power supply current. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view of the washing machine in this embodiment. [Figure 2] This is a circuit diagram of the power supply unit for the washing machine in this embodiment. [Figure 3] This is a waveform diagram of the voltage Vab and the gate signal. [Figure 4] This is a waveform diagram of the power supply current, the current flowing through the switching element, and the current flowing through the first smoothing capacitor. [Figure 5] The top row shows the DC voltage waveform, the middle row shows the power supply voltage waveform, and the bottom row shows the voltage across the first smoothing capacitor and the voltage across the second smoothing capacitor. [Figure 6] These are enlarged views of the waveforms of the voltage Vab and the gate signal G32 when the transformer turns ratio is 1:200. [Figure 7] These are enlarged views of the waveforms of voltage Vab and gate signal G32 when the transformer turns ratio is 1:7. [Figure 8] This is a waveform diagram of voltage Vab and current I32 when the turns ratio is 1:200. [Figure 9] This is a waveform diagram of voltage Vab and current I32 when the turns ratio is 1:7. [Figure 10] This is a waveform diagram of the DC voltage, power supply current, and harmonic components of the power supply current when the duty cycle of the gate signal is 1.0. [Figure 11] This is a waveform diagram of the DC voltage, power supply current, and harmonic components of the power supply current when the duty cycle of the gate signal is 0.6. [Figure 12] This is a waveform diagram of the DC voltage, power supply current, and harmonic components of the power supply current when the duty cycle of the gate signal is 0. [Figure 13] This is a circuit diagram of a power supply device in Modification 1 of the present disclosure. [Figure 14] This is a circuit diagram of a power supply device in modified example 2 of this disclosure. [Modes for carrying out the invention]

[0010] (Knowledge forming the basis of this disclosure) In electrical appliances such as washing machines, a power supply device including a rectifier circuit that converts the power supply voltage from an AC power supply into a DC voltage and a smoothing capacitor, and an inverter circuit that converts the DC voltage from the smoothing capacitor back into an AC voltage and supplies it to an AC load is used. In such a power supply device, there is a problem that the harmonic components of the power supply current flowing between the AC power supply and the rectifier circuit become excessive. When the harmonic components become excessive, the quality of the system power supply deteriorates. Therefore, for such a power supply device, limits for each of a plurality of harmonic components are defined according to standards (the standards of the Electronics and Information Technology Industries Association). Therefore, it is required to design the circuit so that each harmonic component included in the power supply current is below each limit value.

[0011] If a reactor is provided between the rectifier circuit and the AC power supply, the reactor functions like a low-pass filter and can reduce harmonic components. However, since this reactor is large in size, the circuit scale increases. Therefore, the development of a power supply circuit that does not include a reactor is being considered.

[0012] The power conversion device of Patent Document 1 monitors the power supply current, detects a plurality of harmonic components, and has a configuration that varies the phase and voltage of the AC power supply so that the detected harmonic components are adjusted. Thus, although the power conversion device of Patent Document 1 does not have a reactor, a device for adjusting harmonic components is added, so the circuit scale becomes large. Specifically, since the power conversion device of Patent Document 1 requires an arithmetic unit for obtaining a vector sum, the circuit scale becomes large. Furthermore, since the power conversion device of Patent Document 1 adjusts harmonic components by the arithmetic operation of the arithmetic unit, the basic technical idea is different from the present disclosure.

[0013] The DC power supply device of Patent Document 2 does not have a reactor, but since a boost bias circuit for flowing a sine-shaped bias current is added, the circuit scale becomes large.

[0014] Therefore, the inventor of the present invention has obtained the knowledge that if a current is intermittently passed through the smoothing part during charging, the rapid charging of the smoothing part is alleviated and harmonic components can be suppressed without using a reactor, and thus arrived at the present disclosure.

[0015] Hereinafter, embodiments of the washing machine will be described in detail with reference to the drawings. However, a more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters or duplicate descriptions of substantially the same configurations may be omitted. This is to avoid making the following description overly redundant and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0016] (Embodiment) FIG. 1 is a schematic cross-sectional view of a washing machine 100 according to the present embodiment. This washing machine 100 washes and dries processed items such as clothes.

[0017] [Overall Structure of Washing Machine] The washing machine 100 includes a housing 110 and a door portion 111. The housing 110 has an inlet through which processed items are inserted. The housing 110 has a door portion 111 for opening and closing the inlet. The housing 110 houses internal devices for executing a washing mode, a rinsing mode, a dehydration mode, and a drying mode. In the drying mode, there is a timing when the compressor, the fan 152, and the main motor 124 are all driven, and the power tends to be maximized, and the generation of harmonic components becomes an issue.

[0018] The housing 110 includes a water tank 114 and a rotating drum 115. The rotating drum 115 is provided with a large number of small holes 117 formed in the peripheral wall. The rotating drum 115 houses the processed items inserted through the inlet. The water tank 114 stores water in the washing mode and the rinsing mode. The water tank 114 is elastically supported by a suspension mechanism 118 fixed to the bottom wall of the housing 110.

[0019] A water inlet 120 is provided at the top of the peripheral wall of the tank 114. The water inlet 120 supplies water to the tank 114 in washing mode and rinsing mode. A drain outlet 121 is provided at the bottom of the peripheral wall of the tank 114. The drain outlet 121 drains the water used for washing and rinsing.

[0020] An exhaust port 122 is formed on the upper part of the peripheral wall of the water tank 114. In drying mode, the exhaust port 122 exhausts air from the water tank 114 to dry the material being processed. An air inlet 123 is formed on the rear end wall of the water tank 114. In drying mode, the air inlet 123 allows the air exhausted from the exhaust port 122 to flow into the processing chamber 112.

[0021] A main motor 124 for rotating the rotating drum 115 is mounted on the outer surface of the rear end wall of the water tank 114.

[0022] A water supply unit 125 is provided above the water tank 114. The water supply unit 125 supplies water to the processing chamber 112. The upstream end of the water supply unit 125 is exposed on the outer surface of the housing 110 and is connected to a hose (not shown) extending from a water tap.

[0023] A drainage path 129 is provided on the underside of the tank 114. The drainage path 129 drains the water from the tank 114.

[0024] A circulating air passage 131 is provided on the outside of the water tank 114. The circulating air passage 131 is connected between the air intake 123 and the exhaust 122. A fan 152 is positioned inside the circulating air passage 131. The fan 152 draws air from the processing chamber 112 through the exhaust 122 and returns the drawn-out air to the processing chamber 112 through the air intake 123.

[0025] A dehumidifying unit 156 and an adsorbent material 139 are arranged within the circulating air passage 131. The dehumidifying unit 156 and the adsorbent material 139 remove moisture from the air flowing through the circulating air passage 131.

[0026] A heating unit 153 is located downstream of the dehumidifying unit 156. The dehumidifying unit 156 and the heating unit 153 constitute a heat pump device. The dehumidifying unit 156 includes an expansion valve for expanding the refrigerant and fins that are cooled by the expanded refrigerant. The heating unit 153 includes a compressor for compressing the refrigerant and fins that are heated by the compressed refrigerant.

[0027] [Circuit Configuration] Figure 2 is a circuit diagram of the power supply unit 200 of the washing machine 100 in this embodiment. The power supply unit 200 includes a rectifier circuit 210, a smoothing circuit 220, and an inverter circuit 230.

[0028] The rectifier circuit 210 rectifies the power supply voltage V0 from the AC power supply 600. The AC power supply 600 is a grid power supply.

[0029] The smoothing circuit 220 includes a smoothing capacitor 43. The smoothing capacitor 43 further smooths the power supply voltage V0, which has been rectified and smoothed by the rectifier circuit 210, to generate a DC voltage V3.

[0030] The inverter circuit 230 consists of a three-phase inverter and drives the motor 500 under the control of the control circuit 400.

[0031] The rectifier circuit 210 includes a rectifier section 211, a switch section 212, and a smoothing section 213.

[0032] The rectifier section 211 is connected to the AC power supply 600. The rectifier section 211 and the smoothing section 213 consist of a full-wave voltage doubler rectifier circuit in which four diodes 11 to 14 are connected in a full bridge configuration. Specifically, the connection point of diodes 11 and 12 is connected to the AC power supply 600 via a second power input terminal 62, and the connection point of diodes 13 and 14 is connected to the AC power supply 600 via a first power input terminal 61.

[0033] The switch section 212 is connected between the rectifier section 211 and the smoothing section 213. The switch section 212 includes a transformer 31, a switching element 32, a diode 19, and four diodes 15-18. The diodes 15-18 are in a full bridge connection.

[0034] The transformer 31 includes a primary coil 311 and a secondary coil 312. The first end 66 of the primary coil 311 and the first end 68 of the secondary coil 312 have the same polarity.

[0035] The switching element 32 has a collector (an example of a first terminal) connected to connection point 65 via the primary side coil 311, diode 17, and node a. Connection point 65 is the connection point of the first smoothing capacitor 41 and the second smoothing capacitor 42. The switching element 32 has an emitter (an example of a second terminal) connected to the first power supply input terminal 61 via diode 16 and node b.

[0036] Diode 19 has its anode connected to the first terminal 68 of the secondary coil 312, and its cathode connected to the first rectified output terminal 63.

[0037] The secondary coil 312 has its second terminal 69 connected to the second rectifier output terminal 64.

[0038] The smoothing section 213 includes a first smoothing capacitor 41 and a second smoothing capacitor 42, and outputs the voltage from the switch section 212 to the smoothing capacitor 43. The first smoothing capacitor 41 and the second smoothing capacitor 42 are made of, for example, electrolytic capacitors.

[0039] Diodes 15 to 18 constitute a bidirectional switch circuit. Diodes 17 and 16 and the switching element 32 allow current to flow from the AC power supply 600 to the smoothing unit 213 during the period when the power supply voltage V0 has positive polarity. On the other hand, diodes 15 and 18 and the switching element 32 allow current to flow from the AC power supply 600 to the smoothing unit 213 during the period when the power supply voltage V0 has negative polarity.

[0040] When the polarity of the power supply voltage is negative, the switch unit 212 supplies current to node a via node b, diode 15, primary coil 311, switching element 32, and diode 18. On the other hand, when the polarity of the power supply voltage is positive, the switch unit 212 supplies current to node b via node a, diode 17, primary coil 311, switching element 32, and diode 16.

[0041] Diode 15 has its anode connected to the first power input terminal 61 via node b, and its cathode connected to the first terminal 66. Node b is the connection point between diode 15 and diode 16.

[0042] The diode 16 has its anode connected to the emitter of the switching element 32, and its cathode connected to the first power supply input terminal 61 via node b.

[0043] Diode 17 has its anode connected to connection point 65 via node a, and its cathode connected to the first end 66.

[0044] Diode 18 has its anode connected to the emitter of switching element 32 and its cathode connected to node a.

[0045] Diode 19 is a diode that prevents current from flowing back from the first rectifier output terminal 63 to the switch section 212. This protects the switching element 32.

[0046] In the first smoothing capacitor 41, the end opposite to the connection point 65 is connected to the first rectifier output terminal 63. In the second smoothing capacitor 42, the end opposite to the connection point 65 is connected to the second rectifier output terminal 64.

[0047] The smoothing capacitor 43 is connected between the first rectified output terminal 63 and the second rectified output terminal 64. The smoothing capacitor 43 is made of, for example, an electrolytic capacitor. The smoothing capacitor 43 smooths the voltage output from the smoothing unit 213. As a result, a DC voltage V3 is generated across the smoothing capacitor 43.

[0048] The inverter circuit 230 is composed of six switching elements 51 to 56. The connection point of switching element 51 and switching element 52 is connected to the motor 500 via the first AC output terminal 71. The connection point of switching element 53 and switching element 54 is connected to the motor 500 via the second AC output terminal 72. The connection point of switching element 55 and switching element 56 is connected to the motor 500 via the third AC output terminal 73. The collectors of switching elements 51, 53, and 55 are connected to the first rectifier output terminal 63. The emitters of switching elements 52, 54, and 56 are connected to the second rectifier output terminal 64. Switching elements 51 and 52 constitute a U-phase leg, switching elements 53 and 54 constitute a V-phase leg, and switching elements 55 and 56 constitute a W-phase leg.

[0049] Switching elements 32 and 51-56 are composed of, for example, IGBTs (Insulated Gate Bipolar Transistors). However, this is just an example, and switching elements 32 and 51-56 may also be composed of MOSFETs (metal-oxide-semiconductor field-effect transistors). Each of switching elements 32 and 51-56 is connected to a reverse-direction freewheeling diode. Reverse direction means the opposite direction to the forward direction, where the forward direction is defined as the direction in which current flows from the collector to the emitter.

[0050] The control circuit 400 is composed of, for example, a microcontroller. The control circuit 400 controls the switching element 32 by applying a gate signal G32 (an example of a switching signal) to the gate of the switching element 32. The gate signal G32 is, for example, a pulse signal with a duty cycle of 0.6. However, a duty cycle of 0.6 is just an example, and the duty cycle of the gate signal G32 can be adjusted as appropriate within the range of 0 to 1. The gate signal G32 has a higher frequency than the AC power supply 600, for example, 1kHz to 10kHz.

[0051] The control circuit 400 generates gate signals UH, UL, VH, VL, WH, and WL so that the rotational speed of the motor 500 reaches the target value, and inputs the generated gate signals UH, UL, VH, VL, WH, and WL to the gates of the switching elements 51 to 56, respectively. In this way, the control circuit 400 controls the inverter circuit 230 using PWM (Pulse Width Modulation). The gate signals UH, UL, VH, VW, WH, and WL are PWM signals.

[0052] Motor 500 is a three-phase motor. Motor 500 is a fan motor that drives the main motor 124, fan 152, or heat pump motor that drives the compressor of the heating unit 153, etc.

[0053] [Operation] Figure 3 shows the waveforms of the voltage Vab and gate signal G32 between nodes a and b. In Figure 3, the vertical axis represents voltage and the horizontal axis represents time. Voltage Vab is the voltage at node a relative to node b.

[0054] Figure 4 shows the waveforms of the power supply current I0, the current I32 flowing through the switching element 32, and the current I41 flowing through the first smoothing capacitor 41. In Figure 4, the vertical axis represents current and the horizontal axis represents time.

[0055] Figure 5 shows the waveform of the DC voltage V3 in the top row, the waveform of the power supply voltage V0 in the middle row, and the waveforms of the voltage V1 across the first smoothing capacitor 41 and the voltage V2 across the second smoothing capacitor 42 in the bottom row. In Figure 5, the vertical axis represents voltage and the horizontal axis represents time.

[0056] In Figures 3 to 5, timing T1 is the timing when the voltage on the AC power supply 600 side becomes higher than the voltage of the smoothing capacitor 43, and charging of the smoothing capacitor 43 begins due to the current from the AC power supply 600 side. The waveform diagrams in Figures 3 to 5 show various waveforms during the period when the polarity of the power supply voltage V0 is positive.

[0057] As shown in Figure 3, the control circuit 400 constantly applies a gate signal G32 to the gate of the switching element 32. This gate signal G32 turns the switching element 32 on and off. The voltage Vab changes in a pulsed manner according to the on / off state of the switching element 32. The voltage Vab becomes low when the switching element 32 is on and high when the switching element 32 is off. As shown in Figure 8, the envelope of the voltage Vab has a waveform similar in shape and with the same phase as the power supply voltage V0.

[0058] As shown in Figure 4, the power supply currents I0, I32, and I41 do not flow until timing T1. On the other hand, after timing T1, the power supply currents I0, I32, and I41 change in a pulse-like manner in accordance with the on / off operation of the switching element 32. The envelopes of each of the power supply currents I0, I32, and I41 decrease over time from timing T1. This is because the smoothing capacitor 43 gradually approaches full charge.

[0059] As shown in Figure 5, the voltage V2 remains almost constant. This is because the second smoothing capacitor 42 remains fully charged during the period when the polarity of the power supply voltage V0 is positive. In contrast, the voltage V1 gradually increases after timing T1. Since the DC voltage V3 is the sum of voltages V1 and V2, it gradually increases after timing T1 in accordance with the increase in voltage V1. This gradual increase in voltage V1 is due to the switching element 32 switching on and off, which causes the power supply currents I0, I32, and I41 to flow intermittently. When the power supply currents I0, I32, and I41 flow intermittently in this way, the rapid charging of the smoothing unit 213 and the smoothing capacitor 43 is mitigated, and the harmonic components contained in the power supply current I0 are suppressed.

[0060] [Comparison of winding ratios] Figure 6 shows magnified views of the waveforms of voltage Vab and gate signal G32 when the turns ratio of transformer 31 is 1:200. Figure 7 shows magnified views of the waveforms of voltage Vab and gate signal G32 when the turns ratio of transformer 31 is 1:7. In Figures 6 and 7, the gate signal G32 fluctuates with a constant duty cycle (=0.6), but the terminal voltage of voltage Vab differs depending on the turns ratio of transformer 31. The turns ratios of 1:200 and 1:7 represent the turns ratio when the number of turns of the primary coil 311 is set to 1, respectively.

[0061] As shown in Figure 6, when the turns ratio is 1:200, the voltage Vab drops to approximately 0 when the switching element 32 is on. In this case, the maximum amplitude of the voltage Vab is approximately 40V.

[0062] On the other hand, as shown in Figure 7, when the turns ratio is 1:7, the maximum value of the voltage Vab is approximately 40V, which is the same as when the turns ratio is 1:200, but the voltage Vab when the switching element 32 is turned on only drops to approximately 25V. Therefore, the maximum amplitude of the voltage Vab is approximately 15V. This is because when the turns ratio is set to 1:7, which is the ratio of the maximum value of the voltage Vab (=40V) to the maximum value of the DC voltage V3 (=280V), the amplitude of the voltage Vab becomes approximately 15V. Thus, by setting the turns ratio of the transformer 31 to the ratio of the maximum value of the voltage Vab to the maximum value of the DC voltage V3, the voltage difference of the voltage Vab is minimized, and the switching loss generated in the switching element 32 can be reduced.

[0063] Figure 8 shows the waveforms of voltage Vab and current I32 when the turns ratio is 1:200. Figure 9 shows the waveforms of voltage Vab and current I32 when the turns ratio is 1:7. The voltage Vab shown in Figure 8 is a scaled-down version of the voltage Vab shown in Figure 6, and the voltage Vab shown in Figure 9 is a scaled-down version of the voltage Vab shown in Figure 7. In Figures 8 and 9, the period T2 enclosed by the two dotted lines is the charging period of the smoothing unit 213 and the smoothing capacitor 43. Therefore, current I32 flows. The envelope of current I32 rises sharply during period T2, then changes linearly with a downward slope to the right. During period T2, current I32 changes locally in a pulsed manner. The envelope of voltage Vab changes roughly along the power supply voltage V0. Voltage Vab changes locally in a pulsed manner as shown in Figures 6 and 7.

[0064] When the turns ratio is 1:200, as shown in Figure 6, the voltage Vab decreases to 0 when the switching element 32 is turned on. Therefore, as shown in Figure 8, the amplitude of the voltage Vab is large.

[0065] On the other hand, as shown in Figure 9, when the turns ratio is 1:7, the voltage Vab when the switching element 32 is turned on does not drop to 0V. Therefore, the amplitude of the voltage Vab is significantly smaller compared to when the turns ratio is 1:200. This suppresses the switching loss generated in the switching element 32.

[0066] [Comparison of duty cycles] Figure 10 shows the DC voltage V3, power supply current I0, and the waveforms of the harmonic components of the power supply current I0 when the duty cycle of the gate signal G32 is 1.0.

[0067] Figure 11 shows the DC voltage V3, power supply current I0, and the waveforms of the harmonic components of the power supply current I0 when the duty cycle of the gate signal G32 is 0.6.

[0068] Figure 12 shows the DC voltage V3, power supply current I0, and the waveforms of the harmonic components of the power supply current I0 when the duty cycle of the gate signal G32 is 0. The charging period T3 indicates the charging period of the smoothing unit 213 and the smoothing capacitor 43. In the harmonic component waveforms of Figures 10 to 12, the vertical axis represents current, and the horizontal axis represents the order of the harmonic component.

[0069] When the duty cycle of the gate signal G32 is 1.0, the switching element 32 is always on, so the rectifier circuit 210 constitutes a full-wave voltage doubler rectifier circuit. Therefore, the maximum value of the DC voltage V3 becomes approximately twice the maximum value of the power supply voltage V0. Also, because the switching element 32 is always on, the power supply current I0 does not flow intermittently during the charging period T3, as it does when the duty cycle is 0.6. Therefore, harmonic components are not suppressed.

[0070] The DC voltage V3 increases during the charging period T3 due to the charging of the smoothing capacitor 43. On the other hand, once the charging period T3 ends, the DC voltage V3 gradually decreases as the smoothing capacitor 43 begins to discharge. The DC voltage V3 repeats this change every half cycle of the power supply voltage V0.

[0071] When the duty cycle of the gate signal G32 is 0, the switching element 32 is always off, so the rectifier circuit 210 constitutes a full-wave rectifier circuit. Therefore, the maximum value of the DC voltage V3 is reduced to about half compared to when the duty cycle is 1.0. Also, when the duty cycle of the gate signal G32 is 0, the switching element 32 is always off. Therefore, the power supply current I0 does not flow intermittently during the charging period T3, as it does when the duty cycle is 0.6. As a result, harmonic components are not suppressed.

[0072] In contrast, when the duty cycle is 0.6, the power supply current I0 flows intermittently during the charging period T3. Therefore, the rapid charging of the smoothing unit 213 and the smoothing capacitor 43 is mitigated, and harmonic components can be suppressed. In the example in Figure 11, it can be seen that the third harmonic component is significantly reduced compared to the cases where the duty cycle is 1.0 and 0.

[0073] Furthermore, when the duty cycle of the gate signal G32 is 0.6, the maximum value of the DC voltage V3 is an intermediate value between the maximum value of the DC voltage V3 when the duty cycle is 1 and the maximum value of the DC voltage V3 when the duty cycle is 0. This is because the maximum value of the DC voltage V3 increases as the duty cycle of the gate signal G32 increases. As a result, the power supply unit 200 can adjust the maximum value of the DC voltage V3 by adjusting the duty cycle of the gate signal G32.

[0074] [Effects, etc.] In this way, the power supply unit 200 intermittently supplies current to the smoothing unit 213 via the transformer 31 connected to the switching element 32 by switching the switching element 32 on and off. As a result, the rapid charging of the smoothing unit 213 and the smoothing capacitor 43 is mitigated, and the power supply unit 200 can suppress high-frequency components without providing a reactor.

[0075] In the power supply unit 200, the diode 19 has its anode connected to the first terminal 68 of the secondary coil 312 and its cathode connected to the first rectified output terminal 63. Therefore, the power supply unit 200 can prevent current from flowing into the switch unit 212 from the first rectified output terminal 63 side, thereby protecting the switching element 32.

[0076] In the power supply unit 200, the switching element 32 is connected to the transformer 31. Therefore, the power supply unit 200 can adjust the magnitude of the DC voltage V3 output from the smoothing capacitor 43 by adjusting the duty cycle of the switching element 32. Furthermore, by adjusting the turns ratio of the transformer 31, the losses generated in the switching element 32 can be reduced.

[0077] Since the power supply unit 200 has a switch section 212 equipped with a bidirectional switch circuit (diodes 15-18), the switch section 212 can be operated during both the period when the power supply voltage V0 has positive polarity and the period when the power supply voltage V0 has negative polarity to suppress harmonic components.

[0078] Since the power supply unit 200 is composed of diodes 15-18 in a full bridge connection as a bidirectional switch circuit, a bidirectional switch circuit can be constructed without using multiple switching elements, and the switch unit 212 can be constructed at low cost.

[0079] In the power supply unit 200, the turns ratio of the transformer 31 is set to the ratio of the maximum value of voltage Vab to the maximum value of DC voltage V3, so that the voltage difference across the switching element 32 during on / off is minimized, and switching losses can be reduced.

[0080] Since the gate signal G32 of the power supply unit 200 is set to a frequency of 1kHz to 10kHz, the transformer 31 can be made in a small size.

[0081] The following modifications may be adopted for this disclosure.

[0082] (Variation 1) Figure 13 is a circuit diagram of the power supply unit 200A in Modification 1 of the present disclosure. In Modification 1, the same reference numerals are used for components identical to those in the embodiment, and their descriptions are omitted. The power supply unit 200A includes a rectifier unit 211A and a smoothing unit 213, which are configured as a half-wave voltage doubler rectifier circuit in which diodes 11 and 12 are connected in a half-bridge configuration. When the rectifier unit 211A and the smoothing unit 213 are configured as a half-wave voltage doubler rectifier circuit, the rectifier unit 211A outputs a voltage to the first smoothing capacitor 41 during the period when the polarity of the power supply voltage V0 is positive. The rectifier unit 211A also outputs a voltage to the second smoothing capacitor 42 during the period when the polarity of the power supply voltage V0 is negative. In Modification 1, the gate signal G32 of the switch unit 212A is active only when the polarity of the power supply voltage V0 is positive. When the polarity of the power supply voltage V0 is negative, current flows from the AC power supply 600 to the second smoothing capacitor 42 via the freewheeling diode of the switching element 32, thus eliminating the need for a bidirectional switch circuit. Therefore, diodes 15-18 are omitted from the switch unit 212A.

[0083] In detail, the switch section 212A includes a switching element 32, a transformer 31, and a diode 19. The emitter of the switching element 32 is connected to an AC power supply 600 via a first power input terminal 61. The collector of the switching element 32 is connected to a connection point 65 via a primary coil 311. The secondary coil 312 has its first terminal 68 connected to a first rectified output terminal 63 via a diode 19, and its second terminal 69 connected to a second rectified output terminal 64.

[0084] The switching element 32 is constantly switching on and off, as in the embodiment. The switch unit 212A cannot suppress harmonic components when the polarity of the power supply voltage V0 is negative because there are no diodes 15-18. On the other hand, when the polarity of the power supply voltage V0 is positive, the switch unit 212A functions as in the embodiment and suppresses harmonic components.

[0085] (Modification 2) Figure 14 is a circuit diagram of the power supply unit 200B in Modification 2 of the present disclosure. In Modification 2, the same reference numerals are used for components that are the same as those in Embodiment and Modification 1, and their descriptions are omitted.

[0086] Modification 2 includes a rectifier section 211 and a smoothing section 213, which are composed of a full-wave voltage doubling rectifier circuit, and the same switch section 212A as in Modification 1. That is, the switch section 212A does not include diodes 15-18.

[0087] Since the rectifier section 211 and the smoothing section 213 are composed of a full-wave voltage doubling rectifier circuit, they output a rectified voltage even when the polarity of the power supply voltage V0 is negative. The switching element 32 is constantly switching on and off. Since the switch section 212A does not have diodes 15-18, it is not possible to pass current from the inverter circuit 230 to the AC power supply 600 during the negative period, and therefore harmonic components cannot be suppressed.

[0088] However, during the period when the polarity of the power supply voltage V0 is positive, the switch unit 212A can supply current from the AC power supply 600 to the inverter circuit 230. Therefore, during this positive period, the power supply unit 200B can suppress harmonic components.

[0089] (Variation 3) The electrical appliance is not limited to the washing machine 100; it may be any other electrical appliance. Other examples of electrical appliances include dishwashers, air conditioners, and refrigerators.

[0090] (Modification 4) A bidirectional switch circuit may consist of a single switching element capable of passing current in both directions.

[0091] (Technology 1) A power supply device in one aspect of the present disclosure is a power supply device for an electrical device, comprising a rectifier circuit for rectifying a power supply voltage from an AC power supply, the rectifier circuit comprising a rectifier section connected to the AC power supply, a smoothing section including a first smoothing capacitor and a second smoothing capacitor for smoothing the power supply voltage rectified by the rectifier section, and a switch section connected between the rectifier section and the smoothing section, the switch section comprising a transformer including a primary coil and a secondary coil, a switching element, and a diode, the first end of the switching element being connected to the connection point of the first smoothing capacitor and the second smoothing capacitor via the primary coil, and the second end being connected to the first power supply input terminal of the AC power supply, the anode of the diode being connected to the first end of the secondary coil, and the cathode being connected to the first rectified output terminal of the rectifier circuit, and the second end of the secondary coil being connected to the second rectified output terminal of the rectifier circuit.

[0092] In this power supply, the on / off switching of the switching element causes the transformer connected to the switching element to intermittently supply current to the smoothing section. As a result, rapid charging of the smoothing section is mitigated, and this power supply can suppress high-frequency components without the need for a reactor. Furthermore, in this power supply, the diode's anode is connected to the first end of the secondary coil, and its cathode is connected to the first rectified output terminal. Therefore, this power supply can prevent current from flowing into the switch section from the first rectified output terminal, thereby protecting the switching element. Moreover, in this power supply, the switching element is connected to the transformer. Therefore, the power supply can adjust the magnitude of the DC voltage output from the smoothing section by adjusting the duty cycle of the switching element. Furthermore, the power consumption of the switching element can be adjusted by adjusting the turns ratio of the transformer.

[0093] This power supply unit incorporates a switch section instead of a reactor, and this switch section includes switching elements and a transformer. However, since the reactor, which is provided to reduce harmonic components, is significantly larger than the switching elements and transformer that make up the switch section, this power supply unit can be made significantly smaller in circuit size compared to a power supply unit with a reactor.

[0094] Furthermore, the calculator used in Patent Document 1 for adjusting harmonic components has a more complex circuit configuration compared to the switch section, increasing the circuit size and cost. The boost bias circuit shown in Patent Document 2 has a DC bias power supply for supplying a DC voltage lower than the maximum charging voltage of the smoothing capacitor, and an impedance including inductance and resistance connected in series with the DC bias power supply, thus increasing the circuit size compared to the switch section.

[0095] (Technology 2) In the power supply device described in Technical 1, the rectifier section and the smoothing section are composed of a full-wave voltage doubling rectifier circuit, and the switch section further comprises a bidirectional switch circuit, and the bidirectional switch circuit may allow current to flow from the AC power supply side to the smoothing section side during periods when the power supply voltage has positive and negative polarity.

[0096] Since this power supply unit has a bidirectional switch circuit in its switch section, it can suppress harmonic components by operating the switch section during both periods when the power supply voltage has positive polarity and periods when the power supply voltage has negative polarity.

[0097] (Technology 3) In the power supply device described in Technical 2, the bidirectional switch circuit further includes first to fourth diodes connected in a full bridge configuration, wherein the first diode is connected between the primary coil and the first power input terminal, the second diode is connected between the second terminal of the switching element and the first power input terminal, the third diode is connected between the primary coil and the connection point, and the fourth diode is connected between the second terminal of the switching element and the connection point.

[0098] Since this power supply unit consists of first to fourth diodes in a full bridge connection as the bidirectional switch circuit, it is possible to construct a bidirectional switch circuit without using multiple switching elements, and the switch section can be constructed at a low cost.

[0099] (Technology 4) In the power supply device described in any one of Technical 1 to 3, the turns ratio of the primary coil and the secondary coil may be the ratio of the maximum voltage between the connection point and the first power input terminal to the maximum voltage of the smoothing section.

[0100] This power supply minimizes the voltage difference across the switching elements during on / off cycles, thereby reducing switching losses.

[0101] (Technology 5) In the power supply device according to any one of technologies 1 to 4, a control circuit is further provided which inputs a switching signal to the switching element, and the switching signal may have a frequency higher than the power supply voltage.

[0102] Because this power supply operates with switching signals at a frequency higher than the power supply voltage, the transformer can be made in a smaller size.

[0103] (Technology 6) A washing machine in another aspect of this disclosure comprises a power supply device as described in any one of the technologies 1 to 5. [Industrial applicability]

[0104] This disclosure can suppress harmonic components and is therefore applicable to electrical equipment connected to grid power. [Explanation of Symbols]

[0105] 11-19: Diode 31: Trans 32: Switching element 41: First smoothing capacitor 42: Second smoothing capacitor 43: Smoothing Capacitor 51-56: Switching elements 61: First power input terminal 62: Second power input terminal 63: 1st rectified output end 64:Second rectifier output end 65: Connection point 100: Washing machine 200, 200A, 200B: Power supply 210: Rectifier circuit 211, 211A: Rectifier 212, 212A: Switch section 213: Smooth section 220: Smoothing circuit 230: Inverter Circuit 300: Control circuit 311: Primary coil 312: Secondary coil 400: Control circuit 500: Motor 600: AC power supply

Claims

1. A power supply unit for electrical equipment, It is equipped with a rectifier circuit that rectifies the power supply voltage from the AC power supply, The rectifier circuit described above is A rectifier connected to the aforementioned AC power supply, A smoothing unit including a first smoothing capacitor and a second smoothing capacitor, which smooths the power supply voltage rectified by the rectifier unit, The system includes a switch unit connected between the rectifier unit and the smoothing unit, The aforementioned switch section is A transformer including a primary coil and a secondary coil, Switching element and Equipped with a diode, The switching element has a first end connected to the connection point of the first smoothing capacitor and the second smoothing capacitor via the primary coil, and a second end connected to the first power input terminal of the AC power supply. The diode has its anode connected to the first end of the secondary coil and its cathode connected to the first rectified output terminal of the rectifier circuit. The secondary coil has a second end connected to the second rectifier output terminal of the rectifier circuit. power supply.

2. The rectifier section and the smoothing section are composed of a full-wave voltage doubling rectifier circuit. The aforementioned switch section further comprises a bidirectional switch circuit, The bidirectional switch circuit allows current to flow from the AC power supply side to the smoothing section side during periods when the power supply voltage has positive and negative polarity. The power supply device according to claim 1.

3. The bidirectional switch circuit further includes first to fourth diodes connected in a full bridge configuration. The first diode is connected between the primary coil and the first power supply input terminal. The second diode is connected between the second terminal of the switching element and the first power input terminal. The third diode is connected between the primary coil and the connection point. The fourth diode is connected between the second end of the switching element and the connection point. The power supply device according to claim 2.

4. The turns ratio between the primary coil and the secondary coil is the ratio of the maximum voltage between the connection point and the first power input terminal to the maximum voltage of the smoothing section. A power supply device according to any one of claims 1 to 3.

5. The circuit further comprises a control circuit that inputs a switching signal to the switching element, The switching signal has a frequency higher than the power supply voltage. A power supply device according to any one of claims 1 to 3.

6. A washing machine comprising a power supply device according to any one of claims 1 to 3.

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