Connection switching circuit, and high-frequency heating device using the same

Abstract

To provide a high-frequency heating device that is designed for both a commercial AC power supply and battery drive, and when power is supplied only from a battery, achieves both reduction of an additional element and prevention of increase of loss in an inverter circuit.SOLUTION: A connection switching circuit has, as input, a first DC power source having a commercial AC power supply as a power source and a second DC power source having a battery as a power source, and outputs DC voltage to a load. The connection switching circuit has a switching leg in which a first switching element and a second switching element are connected in series, a reactor, a first switch, and a first diode. One end of the switching leg is connected to a positive electrode of the first DC power source. The other end of the switching leg is connected to the first DC power source, the second DC power source, and a negative electrode of the load. One end of the reactor and an anode terminal of the first diode are connected to a middle point of the switching leg. The other end of the reactor is connected to a positive electrode of the second DC power source via the first switch. A cathode terminal of the first diode is connected to a positive electrode of the load.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a connection switching circuit that switches connections between a plurality of power sources and a load, and a high-frequency heating device using the same. [Background technology]

[0002] A conventional high-frequency heating device (microwave oven), as described in Patent Document 1, for example, is composed of a magnetron that generates a high-frequency output, a rectifier circuit that is connected to a commercial AC power source and converts the power source to DC, and an inverter circuit that is connected to the rectifier circuit and drives the magnetron. High-frequency output is generated by applying a high voltage from the AC power source to the magnetron via the inverter circuit.

[0003] Since AC power outlets in ordinary homes have capacity limitations, it is difficult to increase the output beyond a certain level for home appliances that run only on commercial AC power, making it difficult to further improve the high-speed heating feature of high-frequency heating devices. In recent years, battery systems for home use have been proposed to utilize surplus electricity from solar power generation and as backup during power outages, but they require switching breakers and changing the connections of home appliances during power outages, posing an issue in terms of user convenience.

[0004] To address this issue, the technology described in Patent Document 2 proposes a configuration in which a battery is provided inside the high-frequency heating device and power is supplied simultaneously from both a commercial AC power source and the battery, thereby achieving higher output compared to when only an AC power source is used. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5216547 [Patent Document 2] Japanese Patent Application Publication No. 5-226071 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 2, a configuration is provided in which a battery and a charge / discharge circuit for charging and discharging the battery are provided between a rectifier and an inverter circuit, and a voltage lower than the peak voltage of the commercial AC power supply is output from the battery. By supplying power from the battery near the zero crossing of the commercial AC power supply, the utilization rate of the magnetron is improved and a higher output is possible compared to when power is supplied only from the commercial AC power supply.

[0007] However, in the configuration of the second embodiment, when the magnetron is driven only by the power from the battery, it is necessary to control the output voltage from the battery to a value higher than the peak voltage of the commercial AC power supply in order to prevent the power supply from the commercial AC power supply. In this case, it is necessary to expand the operating voltage range of the inverter circuit, but in a general inverter circuit, there is a problem that the power conversion efficiency decreases in order to expand the operating voltage range.

[0008] One possible solution to this problem is to add a switch between the commercial AC power supply and the inverter circuit, and to disconnect the inverter circuit from the commercial AC power supply by turning off the switch when power is supplied only from the battery. In this case, any voltage can be supplied from the battery to the inverter circuit, but the addition of a switch to disconnect the commercial AC power supply within the high-frequency heating device increases the manufacturing costs of the high-frequency heating device, which is an issue. [Means for solving the problem]

[0009] In order to solve the above problems, a connection switching circuit of the present invention is a connection switching circuit that receives as input a first DC power supply using a commercial AC power supply as its power source and a second DC power supply using a battery as its power source, and outputs a DC voltage to a load, the connection switching circuit having a switching leg in which a first switching element and a second switching element are connected in series, a reactor, a first switch, and a first diode, one end of the switching leg is connected to a positive electrode of the first DC power supply and the other end of the switching leg is connected to negative electrodes of the first DC power supply, the second DC power supply, and the load, one end of the reactor and an anode terminal of the first diode are connected to a midpoint of the switching leg, the other end of the reactor is connected to the positive electrode of the second DC power supply via the first switch, and the cathode terminal of the first diode is connected to the positive electrode of the load. Effect of the Invention

[0010] According to the present invention, without using a switch solely for turning on and off the connection between the commercial AC power supply and the load, it is possible to provide the function of turning on and off the connection between the commercial AC power supply and the load by only slightly modifying the configuration of the connection switching circuit for turning on and off the connection between the battery and the load, thereby suppressing increases in manufacturing costs for the device as a whole. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a circuit diagram of a connection switching circuit and a high-frequency heating device according to the first embodiment. [Diagram 2] FIG. 2 is a diagram for explaining an operation mode of the high-frequency heating device of the first embodiment. [Figure 3A] FIG. 4 is a diagram for explaining mode A of the high-frequency heating apparatus according to the first embodiment. [Figure 3B] FIG. 4 is a diagram for explaining mode B1 of the high-frequency heating apparatus according to the first embodiment. [Figure 3C] FIG. 4 is a diagram for explaining mode B2 of the high-frequency heating apparatus according to the first embodiment. [Figure 3D] FIG. 4 is a diagram for explaining mode C1 of the high-frequency heating apparatus according to the first embodiment. [Figure 3E] FIG. 4 is a diagram for explaining mode C2 of the high-frequency heating apparatus according to the first embodiment. [Figure 4A] FIG. 3 is a waveform diagram illustrating voltage and current waveforms when the high-frequency heating device of Example 1 is driven by an AC power source. [Figure 4B] FIG. 4 is a waveform diagram illustrating voltage and current waveforms when the high-frequency heating device of Example 1 is battery-powered. [Diagram 5] FIG. 11 is a circuit configuration diagram of a connection switching circuit according to a second embodiment. [Figure 6] FIG. 11 is a diagram for explaining an operation mode of the high-frequency heating device of the second embodiment. [Figure 7A] FIG. 11 is a diagram for explaining mode D1 of the high-frequency heating device according to the second embodiment. [Figure 7B] FIG. 11 is a diagram for explaining mode D2 of the high-frequency heating apparatus according to the second embodiment. [Figure 7C] FIG. 11 is a diagram for explaining a mode D3 of the high-frequency heating apparatus according to the second embodiment. [Figure 8] FIG. 11 is a waveform diagram illustrating voltage and current waveforms of the high-frequency heating device of the second embodiment. [Figure 9] FIG. 11 is a waveform diagram illustrating the operation of the connection switching circuit of the second embodiment and the high-frequency heating device using the same. [Figure 10] FIG. 11 is a circuit diagram of a connection switching circuit and a high-frequency heating device according to a third embodiment. [Figure 11] FIG. 11 is a diagram for explaining an operation mode of the high-frequency heating device according to the third embodiment. [Figure 12A] FIG. 11 is a diagram for explaining mode A of the high-frequency heating device according to the third embodiment. [Figure 12B] FIG. 11 is a diagram for explaining mode B of the high-frequency heating device according to the third embodiment. [Figure 12C] FIG. 11 is a diagram for explaining mode C of the high-frequency heating device according to the third embodiment. [Figure 12D] FIG. 13 is a diagram for explaining mode D of the high-frequency heating device according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. EXAMPLES

[0013] First, a first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a circuit diagram of a high-frequency heating device 2 using a connection switching circuit 1 of the first embodiment. Fig. 2 and Figs. 3A to 3E are diagrams for explaining operation modes of the high-frequency heating device 2 of the first embodiment. Figs. 4A and 4B are operation waveform diagrams of the high-frequency heating device 2 of the first embodiment.

[0014] 1, the high-frequency heating device 2 of this embodiment is a so-called microwave oven that is connected to a commercial AC power source 3 and includes a battery 20, a rectifier 21, an inverter circuit 22, a magnetron 23, and a connection switching circuit 1. Each component of the high-frequency heating device 2 will be described below in order.

[0015] The battery 20 is a chargeable and dischargeable secondary battery such as a lithium ion battery. In the following, the terminal of the battery 20 on the high potential side is referred to as a positive electrode, and the terminal on the low potential side is referred to as a negative electrode.

[0016] The rectifier 21 converts the voltage V ac The rectified DC voltage V in In the following description, the output terminal of the rectifier 21 on the high potential side is referred to as the positive electrode, and the output terminal on the low potential side is referred to as the negative electrode.

[0017] The inverter circuit 22 is a connection switching circuit that receives a low DC voltage of about 100 V as an input and generates a DC voltage of several kV. Hereinafter, of the input terminals of the inverter circuit 22, the high potential side is referred to as the positive electrode, and the low potential side is referred to as the negative electrode.

[0018] The magnetron 23 is a heating device that supplies a high-frequency voltage into a heating chamber (not shown) to dielectrically heat an object to be heated (food, etc.) in the heating chamber.

[0019] The connection switching circuit 1 includes switching elements S1 and S2, a reactor L, and a switch S b and diode D i It consists of a switch S bBy appropriately operating switching elements S1 and S2, the connection switching circuit 1 switches between a connection in which the magnetron 23 is driven by the commercial AC power supply 3, a connection in which the magnetron 23 is driven by the battery 20, and a connection in which the battery 20 is charged by the commercial AC power supply 3. More specifically, the connection switching circuit 1 has the following configuration.

[0020] That is, in the connection switching circuit 1 of this embodiment, one end of a switching leg in which a switching element S1 and a switching element S2 are connected in series is connected to the positive electrode of a rectifier 21, the other end of the switching leg is connected to the negative electrode of a battery 20, the rectifier 21, and an inverter circuit 22, and one end of a reactor L and a diode D i The anode terminal of the reactor L is connected to the midpoint of the switching leg, and the other end of the reactor L is connected to the switch S b Connect the positive terminal of the battery 20 through the diode D i The cathode terminal of the inverter circuit 22 is connected to the positive electrode of the inverter circuit 22.

[0021] In the high-frequency heating device 2 of the present embodiment, the voltage rectified by the rectifier 21 is input to the inverter circuit 22 in a non-smooth manner, making it possible to make the input current have a waveform close to a sine wave, thereby complying with power supply harmonic regulations.

[0022] <Operation mode of high frequency heating device 2> Next, typical operation modes of the connection switching circuit 1 will be described with reference to Figs. 2 to 4. Fig. 2 shows the operation modes of the switch S b , and show the states of the switching elements S1, S2, and the inverter circuit 22. Fig. 3A to Fig. 3E show the current flow in each operation mode. Fig. 4A shows the operation waveform in the AC drive mode, and Fig. 4B shows the operation waveform in the battery drive mode. The operation waveforms in Fig. 4 correspond to the symbols in Fig. 1.

[0023] <Mode A> Mode A is a mode in which the magnetron 23 is driven only by power from the commercial AC power supply 3. In this mode A, as shown in FIGS. 3 and 4A, the switch S bis in the off state, the battery 20 is disconnected from the connection switching circuit 1. At this time, the switching element S1 is in the on state, the switching element S2 is in the off state, and the DC voltage V rectified by the rectifier 21 is supplied to the inverter circuit 22. in is applied.

[0024] <Mode B> Mode B is a mode in which the magnetron 23 is driven only by power from the battery 20. In this mode B, as shown in FIGS. 3, 4B, and 4C, the switch S b is in the on state, connecting the battery 20 to the connection switching circuit 1. At this time, the switching element S1 is turned off to disconnect the inverter circuit 22 from the commercial AC power source 3. Then, the switching element S2 is subjected to switching operation by PWM control to apply an arbitrary voltage from the connection switching circuit 1 to the inverter circuit 22. Detailed circuit operations in Mode B1 and Mode B2 will be described below.

[0025] In mode B1 shown in FIG. 4B, the switching element S2 is in an ON state, and the switch S b A current flows through the path of the reactor L and the switching element S2, and energy is stored in the reactor L. In mode B1, when the switching element S2 is turned off, a transition is made to mode B2.

[0026] In mode B2 shown in FIG. 4C, the switching element S2 is in an OFF state, and the power supply from the battery 20 to the switch S b , reactor L, diode D i A current flows through the path of the inverter circuit 22, discharging the energy of the reactor L. When the switching element S2 is turned on in the mode B2, the mode transitions to the mode B1.

[0027] In mode B, the power of the battery 20 is basically supplied to the inverter circuit 22 by repeating modes B1 and B2.

[0028] <Mode C> Mode C is a mode in which the battery 20 is charged with power from the commercial AC power supply 3. In this mode C, as shown in FIG. 3, the inverter circuit 22 is stopped. Also, as shown in FIG. 3, FIG. 4D, and FIG. 4E, the switch S b is in the ON state, and the switching element S1 is switched by PWM control to control the charging current of the battery 20. At this time, the switching element S2 is in the OFF state. Detailed circuit operations in Modes C1 and C2 will be described below.

[0029] In mode C1 shown in FIG. b The switching element S1 is in the ON state, the switching element S2 is in the OFF state, and a current flows from the commercial AC power supply 3 through the rectifier 21, the switching element S1, the reactor L, and the battery 20, and energy is stored in the reactor L. At this time, the switching element S1 is turned off to transition to mode C2.

[0030] In mode C2 shown in FIG. b is in the ON state, the switching elements S1 and S2 are in the OFF state, and the stored energy of the reactor L is transferred to the battery 20, the diode D2, the switch S b However, when a MOSFET is used for the switching element S2, synchronous rectification is possible by driving it in a complementary manner with the switching element S1.

[0031] In this manner, in the first embodiment, the switching element S1 and the diode D i By connecting the positive electrodes of the rectifier 21 and the inverter circuit 22 to each other via the rectifier 21, it is possible to cut off the connection between the commercial AC power supply 3 and the inverter circuit 22 by turning off the switching element S1 in the connection switching circuit 1, and to block the power supply from the commercial AC power supply 3, without providing a switch solely for disconnecting the commercial AC power supply 3 in the high-frequency heating device 2. As a result, it is possible to suppress an increase in the manufacturing cost of the high-frequency heating device as a whole. EXAMPLES

[0032] Next, a second embodiment of the present invention will be described with reference to Figs. 5 to 9. However, parts that overlap with the description of the first embodiment will not be described. Fig. 5 is a circuit diagram of a connection switching circuit 1A of the second embodiment. Figs. 6, 7A to 7C, and 8 are diagrams for explaining operation modes of the connection switching circuit 1A of the second embodiment. Fig. 8 shows voltage and current waveforms of each part of the high-frequency heating device 2 of the second embodiment, and Fig. 9 shows waveforms obtained by enlarging the regions of mode D2 and mode D3 in Fig. 8 in time.

[0033] The connection switching circuit 1A of this embodiment includes switching elements S1 and S2, a reactor L, and a diode D i , Switch S b This embodiment is the same as the first embodiment in that it includes a switch S b Switch S b1 and switch S b2 The difference from the first embodiment is that the switch S b In the configuration where the switch S b2 By turning on only this terminal, it becomes possible to simultaneously connect the commercial AC power supply 3 and the battery 20 to the inverter circuit 22. The operation modes will be described below.

[0034] <Mode D1> As shown in Figure 6, switching element S1 and switch S b2 Switch S2 and switch S b1 When the output voltage V of the rectifier 21 is turned off, as shown in FIG. in and the battery voltage V bat The relationship between V in >V bat This region is mode D1.

[0035] At this time, as shown in FIG. 7A, a rectifier 21, a switching element S1, a diode D i Since the current flows through the path of the inverter circuit 22, the current I b becomes zero. Note that the switch S b1The presence of the anti-parallel diodes blocks current flow into the battery 20.

[0036] <Mode D2> In the state of mode D1, the output voltage V of the rectifier 21 in and the battery voltage V bat The relationship is V in =V bat 8 and 9, the mode transitions to mode D2. At this time, as shown in FIG. 7B, the rectifier 21, the switching element S1, the diode D i , the path of the inverter circuit 22, the battery 20, and the switch S b1 , S b2 , reactor L, diode D i Since a current flows through the path of the inverter circuit 22 , power can be supplied to the inverter circuit 22 from both the commercial AC power supply 3 and the battery 20 .

[0037] <Mode D3> In mode D2, the output voltage V of the rectifier 21 in and the battery voltage V bat The relationship is V in <V b In this case, the mode is changed to mode D3 as shown in Fig. 8 and Fig. 9. In mode D3, the switch S b1 , S b2 , reactor L, diode D i At this time, a current flows through the path of the inverter circuit 22. in =V b In this case, the mode changes to D2.

[0038] In this way, by using the connection switching circuit 1A of this embodiment, it becomes possible to supply power from both the commercial AC power supply 3 and the battery 20, which was difficult with the connection switching circuit 1 of the first embodiment. However, in this embodiment, as the period of mode D3 increases, the current distortion on the commercial AC power supply side increases, so the battery voltage V bat It is necessary to set. EXAMPLES

[0039] Next, a third embodiment of the present invention will be described with reference to Figs. 10 to 12. However, parts that overlap with the description of the above-mentioned embodiments will not be described. Fig. 10 is a circuit diagram of a high-frequency heating device 2A of the third embodiment. Figs. 11 and 12 are diagrams for explaining the operation mode of the high-frequency circuit heating device 2A.

[0040] The high-frequency heating device 2A of this embodiment is characterized in that it is provided with two magnetrons 23A, 23B so that the output of the magnetron 23 can be supplied to the object to be heated from two points in the heating chamber. In this embodiment, in order to drive both magnetrons, the high-frequency heating device 2A is configured as follows. That is, a rectifier 21A and an inverter circuit 22A are provided as a configuration for driving the magnetron 23A. Also, a battery 20, a rectifier 21B, an inverter circuit 22B, and a connection switching circuit 1A are provided as a configuration for driving the magnetron 23B. Both the rectifier 21A and the rectifier 21B are connected to a power supply 3. The ... ac are rectified to produce DC voltage V inA , V inB The configuration on the magnetron 23B side is the same as that of the second embodiment.

[0041] Next, the operation mode of the high-frequency heating device 2A will be described with reference to FIGS.

[0042] <Mode A> Mode A is a mode in which power is supplied to the magnetrons 23A and 23B only from the commercial AC power supply 3, and the total output of the magnetrons is restricted by the current capacity of the commercial AC power supply 3. In mode A, as shown in FIG. b By turning on switching element S1 and turning off switching element S2, the voltage of commercial AC power supply 3 is input to each inverter circuit as shown in FIG. 12A.

[0043] <Mode B> In mode B, power is supplied from the commercial AC power source 3 to the magnetron 23A, and power is supplied from the battery 20 to the magnetron 23B. In mode B, the total output of the magnetrons can be increased compared to mode A. In mode B, as shown in FIG. 11, the switch S b By turning on the switching element S1, turning off the switching element S2, and performing a switching operation by PWM control, an arbitrary voltage is output to the inverter circuit 22B as shown in FIG. b is the on-time T of the switching element S2 on and the battery voltage V bat and switching period T sw Therefore, it is determined by the relationship between Equation 1 and Equation 2.

[0044] V b =1 / (1-D)×V bat ... (Formula 1) D=T on / T sw ... (Formula 2) <Mode C> In mode C, as shown in FIG. 12C, power is supplied from the battery 20 only to the magnetron 23B, and the total output of the magnetrons is limited by the power constraint of the battery 20. In this case, as shown in FIG. b The switch S1 is turned on and the switch S2 is turned off, and the switching element S2 is subjected to switching operation by PWM control to output a desired voltage to the inverter circuit.

[0045] <Mode D> In mode D, as shown in FIG. 12D, the battery 20 is charged from the commercial AC power source 3, and power is not supplied to the magnetron. At this time, as shown in FIG. b The charging power to the battery 20 is controlled by turning on the switching element S1, turning off the switching element S2, and performing a switching operation on the switching element S1 by PWM control.

[0046] In this way, by configuring the high-frequency heating device 2A of this embodiment 3 to have multiple magnetrons, it is possible to supply high-frequency output uniformly, for example by supplying the output of two magnetrons to the object to be heated from above and below, which is expected to improve heating efficiency and eliminate uneven heating.

[0047] The present invention is not limited to the above-mentioned embodiment, and various modifications are included. For example, the above-mentioned embodiment has been described in detail to easily explain the present invention, and is not necessarily limited to those including all of the configurations described. Also, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Also, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0048] 1 Connection switching circuit, 2 High frequency heating device, 20 batteries, 21 rectifier, 22 inverter circuit, 23 magnetron, 3 Commercial AC power supply

Claims

1. A connection switching circuit that receives as input a first DC power supply using a commercial AC power supply as a power supply and a second DC power supply using a battery as a power supply, and outputs a DC voltage to a load, a switching leg in which a first switching element and a second switching element are connected in series, a reactor, a first switch, and a first diode; One end of the switching leg is connected to the positive electrode of the first DC power source, the other end of the switching leg is connected to the first DC power source, the second DC power source, and a negative electrode of the load; one end of the reactor and an anode terminal of the first diode are connected to a midpoint of the switching leg; the other end of the reactor is connected to the positive electrode of the second DC power source via the first switch, A connection switching circuit, characterized in that a cathode terminal of the first diode is connected to a positive electrode of the load.

2. 2. The connection switching circuit according to claim 1, a first operation mode in which the first switching element is in an on state and the first switch and the second switching element are in an off state, thereby supplying power from the first DC power source to the load; a second operation mode in which the first switching element is in an off state, the first switch is in an on state, and the second switching element is subjected to a switching operation to supply power from the second DC power source to the load; A connection switching circuit comprising:

3. 2. The connection switching circuit according to claim 1, a second diode connected in anti-parallel to the second switching element; a third operating mode in which the second switching element is turned off and the first switch is turned on, and the first switching element is subjected to switching operation to charge the battery from the commercial AC power source.

4. 2. The connection switching circuit according to claim 1, The first DC power source is a non-smooth power source that varies over time and is obtained by rectifying an AC voltage, The first switch is a first internal switch formed by a combination of a switch and an anti-parallel diode; a second internal switch including a switch and an anti-parallel diode connected in series; A connection switching circuit characterized by having an operating mode in which the sum of power of the first DC power source and the second DC power source is supplied to the load by setting the first switching element to an on state, the second switching element to an off state, the first internal switch to an off state, and the second internal switch to an on state.

5. 2. The connection switching circuit according to claim 1, The connection switching circuit, wherein the second switching element is a MOSFET.

6. A high-frequency heating device comprising the connection switching circuit according to claim 1, the first DC power supply is a first rectifier that rectifies an AC voltage from the commercial AC power supply, The high frequency heating device according to claim 1, wherein the load is a first inverter circuit that boosts an output voltage of the connection switching circuit, and a first magnetron that is driven by the output voltage of the first inverter circuit.

7. The high frequency heating device according to claim 6, the first DC power supply includes a second rectifier that rectifies an AC voltage from the commercial AC power supply; A high-frequency heating device characterized in having, as a load of the second rectifier, a second inverter circuit that boosts the output voltage of the second rectifier, and a second magnetron driven by the output voltage of the second inverter circuit.

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