JP2019121543A - Induction cooker - Google Patents

Abstract

To provide an induction cooker in which short circuit occurring when driving an inverter after bootstrap operation can be suppressed.SOLUTION: The induction cooker comprises an inverter driving part having a current resonance type circuit in which upper and lower arms supplying a power for driving a heating coil are separated, wherein the inverter driving part is provided with: an IGBT; a snubber capacitor between a corrector and an emitter of the IGBT; and a charging and discharging resistance connected in parallel to the snubber capacitor. The induction cooker further comprises: an IGBT drive circuit for driving the IGBT; an IGBT power supply 82 supplying the power to the IGBT drive circuit; a capacitor 75 for the drive circuit and a diode 76 supplying the power to the capacitor for the drive circuit from the IGBT power supply, wherein the capacitor 75 and the diode 76 are provided in a power supply of a drive circuit 73a of the upper arm IGBT. The power is accumulated in the capacitor for the drive circuit through the diode when the lower arm IGBT is turned ON, the lower arm IGBT is then turned OFF, and after that, driving of the inverter driving part is started.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a heating cooker of a type provided with heating means for heating an object to be heated by induction heating, and the heating means being driven by an inverter circuit.

  Conventionally, the inverter apparatus used for the induction heating cooker has a high voltage side arm of the power supply terminal (hereinafter referred to as an upper arm), a first switching element, and a low voltage side arm (hereinafter referred to as a lower arm). An alternating current is generated in the heating coil by arranging the two switching elements and operating the switching elements of the upper and lower arms alternately.

  Under the present circumstances, in order to ensure the power supply voltage of the drive circuit of an upper arm, the power supply circuit called a bootstrap circuit is used (patent document 1).

  In addition, a capacitor (hereinafter referred to as a snubber capacitor) is mounted in parallel with the switching elements of the upper and lower arms in order to suppress short circuit current in the inverter circuit and to protect the elements and reduce noise. ).

JP, 2011-35983, A Unexamined-Japanese-Patent No. 2017-22144

  In the conventional inverter circuit, after the operation of the bootstrap circuit, the applied voltage of the snubber capacitor of the upper arm is equal to the amplitude of the commercial power supply voltage. Therefore, an inrush current occurs at the moment when the switching element of the upper arm is turned on for the first time after the operation of the bootstrap circuit.

  The inrush current may cause problems such as destruction of the element and reduction of the life of the switching element and the snubber capacitor. In addition, since it is necessary to select a component that can withstand the inrush current, there is a problem that options for selecting components can be narrowed.

  The induction heating cooker according to the present invention has been made to solve the above-mentioned problems, and includes a heating coil 13 for heating an object to be heated by induction heating, and supplies power for driving the heating coil 13. The inverter drive unit has a current resonance type circuit configuration separated into an upper arm and a lower arm, and the inverter drive unit includes an upper arm IGBT 69a for supplying power to the heating coil 13 to the upper arm and the lower arm respectively. Upper arm snubber capacitor 70a and lower arm snubber capacitor 70b absorbing the surge voltage between the lower arm IGBT 69b and collector-emitter of upper arm IGBT 69a and lower arm IGBT 69b, and in parallel with upper arm snubber capacitor 70a and lower arm snubber capacitor 70b Connected upper arm charge / discharge resistance 74a and lower And an upper arm IGBT drive circuit 73a and a lower arm IGBT drive circuit 73b for driving the upper arm IGBT 69a and the lower arm IGBT 69b, and the upper arm IGBT drive circuit 73a and the lower arm IGBT drive circuit 73b. An IGBT power supply 82 for supplying power is provided, a drive circuit capacitor 75 is provided to the power supply of the upper arm IGBT drive circuit 73a, and a diode 76 for supplying power from the IGBT power supply 82 to the drive circuit capacitor 75 is provided. Electric power is stored in the drive circuit capacitor 75 via the diode 76 when the IGBT 69b is turned on, and then the driving of the inverter drive unit is started after the lower arm IGBT 69b is turned off.

  According to the present invention, the short circuit current after the bootstrap operation can be suppressed, and it is possible to prevent the destruction of the element and the reduction of the life and to expand the choice of component selection.

It is a perspective view of the state which accommodated the induction heating cooker of this invention in the system kitchen. It is explanatory drawing which shows the state which removed the plate of the induction heating cooker. It is the principal cross section figure seen from the side of the induction heating cooker. It is explanatory drawing of the upper surface operation part of the induction heating cooker. It is a schematic diagram of the bootstrap circuit of the induction heating cooker.

  Hereinafter, embodiments of the present invention will be described with reference to the above drawings.

  In addition, even if it is a stationary-type heating cooker mounted in a kitchen other than the built-in type inserted in a kitchen, a present Example does not interfere.

  The main body 2 of the heating cooker is incorporated by being dropped from the upper surface of the system kitchen 1 and installed.

  A pot (not shown) of the object to be heated which is to be cooked is made possible by being placed on the placement portion 6 of the plate 3 which is made of heat resistant glass or the like disposed on the upper surface of the main body 2 and transmits light. .

  In the placement unit 6, the placement unit right 6a and the placement unit left 6b are disposed in front of the upper surface of the plate 3 on the upper surface of the main body 2, and the placement unit 6 is placed at the back (center rear) between the two placement units 6a and 6b. Part center 6c is arranged. And the heating coil unit 25 later mentioned for heating a pan under the each mounting part 6 on both sides of the plate 3 is installed, respectively. The arrangement is such that the heating coil unit right 25a is below the mounting portion right 6, the heating coil unit left 25b is below the mounting portion left 6b, and the heating coil unit center 25c is below the mounting portion center 6c. It is provided.

  A frame 14 is provided on the peripheral end face of the plate 3 to protect the plate 3. The frame 14 has a frame front 14a attached to the front upper edge of the plate 3, a frame rear 14b attached to the rear upper edge of the plate 3, a frame 14c attached to the right upper edge, and a frame attached to the left upper edge It consists of the left 14d.

  Inside the main body 2, there are provided a heating coil unit 25 which will be described later, which is a heat generating member, and electronic parts constituting a control circuit. In the rear of the heating coil unit 25 and the control circuit, they are cooled. A blower fan 20, an intake port 7 for sucking in air from the outside of the main body 2, and an exhaust port 8 for discharging the cooled exhaust gas are provided.

  The air taken in through the air intake port 7 is discharged from the air exhaust port 8 to the outside of the main body 2 after cooling a heating coil unit 25 described later which generates heat inside the main body 2 and electronic components.

  Further, on the left side of the main body 2, a roaster 4 for baking fish, pizza and the like is provided.

  Next, the heating coil which is a heating means which heats the pan of a to-be-heated material is demonstrated.

  The heating coil unit 25 for heating a pan (not shown) is composed of a heating coil 13, a coil base 24, and a ferrite (not shown). Then, a fixed gap is provided between the plate 3 and the heating coil unit 25, and a part of the cooling air from the blower fan 20 flows in the gap to cool the back surface of the plate 3 and the heating coil unit 25. doing.

  The winding of the heating coil 13 employs a litz wire in order to suppress the skin effect. A voltage of several tens of kHz and several hundreds of volts is applied to the heating coil 13 from an inverter board (left and right inverter board 18 and central inverter board 17) described later in order to heat the cooking pot (not shown).

  The coil base 24 fixes the heating coil 13 from below, and ferrite (not shown) is embedded substantially radially.

  Further, a temperature detection element 21 for detecting the temperature of the pan at the time of automatic cooking or the like is attached to a space substantially at the center of the heating coil 13.

  Next, cooling of the heating coil 13 and the inverter substrate will be described.

  The inverter board is composed of a left and right inverter board 18 mounted with an inverter circuit for driving the left and right heating coils 13a and 13b, and a central inverter board 17 for driving the heating coil center 13c.

  The left and right inverter boards 18 and the center inverter board 17 are disposed in the board case 26, and the heat dissipating fins 22, 23 are provided so that the heat generated by the electronic components is efficiently exchanged with the cooling air from the blower fan 20 to lower the temperature. It is provided.

  Cooling air drawn from the air inlet 7 by the blower fan 20 flows through the inside of the substrate case 26 and removes heat from the left and right inverter substrates 18, the central inverter substrate 17, and the electronic components of the control substrate 19 on which the control circuit is mounted. After that, the substrate case 26 is blown out to cool the heating coil 13 and other components in the main body 2 and the back surface of the plate 3 and then discharged from the exhaust port 8 to the outside.

  The substrate case 26 is installed below the heating coil unit right 25a opposite to the heating coil unit left 25b where the roaster 4 is installed. In this embodiment, the heating coil unit is disposed under the right 25a, and by arranging the left and right inverter boards 18 and the central inverter board 17, the radiation heat from the heating coil 13 and the roaster 4 is shielded at the time of cooking. An air path is formed through which the cooling air passes so that the cooling air can be efficiently distributed.

  Next, the operation unit and the display unit will be described.

  The main power switch 9d is formed of a push button, and switches between the power on state and the stop state each time it is pressed.

  The upper surface operation unit 9 is configured of a touch key that detects a change in capacitance.

  The key parts are the off / start keys 48, 56, 61, the low fire keys 49a, 57a, the low fire keys 49b, 57b, the middle fire keys 49c, 57c, the high fire keys 49d, 57d, and the menu key provided on the upper surface operation unit 9. 52, 60, 64, etc. are shown.

  The upper surface operation portion 9 is provided on the front side of the plate 3 and corresponds to the placement portion right 6a, the placement portion center 6c, and the placement portion left 6b from the right, the upper surface manipulation portion right 9a, the upper surface manipulation portion center 9c, The upper surface operation unit left 9b is disposed. Then, on the upper side of each upper surface operation unit 9, an upper surface display unit 10 including an upper surface display unit right 10a, an upper surface display unit center 10c, and an upper surface display unit left 10b is provided.

  The upper surface display unit 10 is pressed against the plate 3 by the display holder 32, and a display substrate 33 including a drive circuit for displaying characters and the like on the display unit is fixed at the central portion.

  Next, each key part of the upper surface operation unit 9 (typically, the upper surface operation unit right 9a) for setting the heating condition to the pan will be described.

  Reference numeral 48 is a turning off / starting key for starting or stopping the cooking, and during cooking, "off / starting" displayed on the key portion of the turning off / starting key 48 lights up. Details of lighting of the key section will be described later.

  The cooking power is selected by the fire key 49. The thermal power key 49 is divided into four stages of keys: “Toroku”, “low heat”, “medium heat”, and “high heat”, and the necessary thermal power can be set by one operation. Among the four firepower keys 49, the borofire key 49a is "1", the low fire key 49b is "4", the middle fire key 49c is "7", and the high fire key 49d is a "10" firepower. The indicator of the department lights up.

  51 is a timer key which is mainly selected when performing timer cooking such as simmering and heat retention. 52 is a "menu" key for selecting automatically cooked rice, fried foods, boiling water, etc. When the menu key 52 is pressed (contacted with a finger), a menu is displayed on the upper surface display unit 10, and the menu key 52 Each time you press, the displayed menu changes, and this selects the menu to use.

  In addition, adjustment of thermal power, setting of time at the time of timer cooking, setting of quantity of rice at the time of rice cooking, setting of finish adjustment of automatic cooking, setting of oil temperature at the time of fried food can be performed by the setting key 50 . The setting key 50 is composed of an UP key 50a for increasing the quantity at the time of setting and the like and a DOWN key 50b for reducing it.

  In addition, since the upper surface operation unit left 9b has the same operation and arrangement as the upper surface operation unit right 9a, the description is omitted.

  Next, the upper surface operation unit center 9c will be described. The main cooking of the placement center 6c is heat retention and simmering. Therefore, the heating power of the heating coil center 13c is also designed smaller than the heating power of the other heating coils. For this reason, the thermal power notation is sufficient in three stages of low heat, low heat and medium heat, and even if the setting key 62 is cyclic type, it returns to the original if pressed up to 3 times, so the heat power is similar to the front two heating coils 25a, 25b. There is no corresponding thermal power setting key.

  An electrode for detecting a change in capacitance serving as each input key of the upper surface operation unit 9 described above is provided on the operation substrate 12 disposed on the lower surface of the plate 3.

  The operation board 12 is divided into an operation board 12a and an operation board 12b. The operation board 12a corresponds to the upper surface operation unit right 9a and the upper surface operation unit center 9c, and the operation substrate 12b corresponds to the upper surface operation portion left 9b.

  34 is a cable for connecting the substrates.

  The control circuit incorporated in the control board 19 is based on the content set by the upper surface operation unit 9 and a program such as automatic cooking incorporated in advance, the start and stop of cooking, and the left and right inverters with control information of thermal power as control signals. It is sent to the substrate 18 and the central inverter substrate 17 to control the heating coil 13 and the like.

  Next, components that constitute an inverter circuit that supplies necessary power to the heating coil 13 will be described.

  Reference numeral 81 denotes a power supply obtained by rectifying an AC power supplied from a power supply by a diode bridge or the like.

  82 is a power supply for IGBT which supplies electric power to the IGBT drive circuit 73 and IGBT69 which were each incorporated in the upper and lower arms mentioned later.

  The inverter drive unit has a circuit configuration of current resonance type in which upper and lower arms are separated to supply electric power to the heating coil 13, and an IGBT 69, a snubber capacitor 70, a resonant capacitor 71, charge and discharge resistance 74 and The heating coil 13 is configured to turn on the upper and lower IGBTs 69 alternately to send power to the heating coil 13, to generate an alternating magnetic field from the heating coil 13 to supply energy to the object to be heated.

  A snubber capacitor 70 provided between the collector and the emitter of the IGBT 69 absorbs a surge voltage as a protection circuit of the IGBT 69. Furthermore, the charge and discharge resistor 74 is connected in parallel to the snubber capacitor 70.

  In addition, power supply to the IGBT drive circuit 73 for driving the IGBT 69 incorporated in the upper and lower arms ON / OFF and power supply to the upper arm IGBT drive circuit 73a of the upper arm is the power supply portion of the upper arm IGBT drive circuit 73a. A drive circuit capacitor 75 is provided, power is stored in the drive circuit capacitor 75 from the IGBT power supply 82 via the diode 76, and power is supplied from the drive circuit capacitor 75 to the upper arm IGBT drive circuit 73a.

  Next, the operation will be described.

  First, a bootstrap circuit for supplying a drive voltage of the upper arm IGBT drive circuit 73a will be described.

  At the start of operation of the inverter circuit, only the lower arm IGBT 69b is first turned ON (or ON and OFF are alternately repeated), and the point A of the circuit section is connected to GND to start the diode 76 from the IGBT power supply 82. Thus, the drive circuit capacitor 75 for charging the power of the upper arm IGBT drive circuit 73a is charged. Then, the drive voltage of the upper arm IGBT drive circuit 73a can be secured (end of the bootstrap operation).

  Thereafter, the lower arm IGBT 69b is turned OFF, whereby the preparation for starting the operation of the inverter drive unit is completed.

  As described above, when the lower arm IGBT 69b is turned ON (or alternately turned ON and OFF alternately), the point A of the circuit section is connected to GND, so that the upper arm snubber capacitor 70a has a power of 81 volts. Is charged. However, when the lower arm IGBT 69b is turned off, the voltage at point A becomes a voltage according to the voltage division ratio of the upper arm charge / discharge resistance 70a, the lower arm charge / discharge resistance 70b and the resistance value, and this voltage becomes the upper arm snubber capacitor. The reference numeral 70a discharges through the upper arm charge / discharge resistance 70a to reduce the collector-emitter voltage when the upper arm IGBT 69a is turned on.

  The time constant of the snubber capacitor 70 and the charge / discharge resistor 74 is sufficiently shorter than the time constant of the drive circuit capacitor 75 serving as the power supply of the IGBT drive circuit 73 and sufficiently longer than the operation cycle of the inverter circuit. The resistance value of the charge and discharge resistance 74 is set.

  In addition, when the upper and lower IGBTs 69 are simultaneously turned off after the bootstrap operation is completed, the simultaneous OFF time is longer than in the inverter operation, and the collector voltage of the upper arm IGBT 69a is determined according to the voltage division ratio of the upper and lower charge / discharge resistors 74 The voltage between the emitters is smaller than the voltage (amplitude) of the power supply 81. Thereafter, by turning on the upper arm IGBT 69a, it is possible to suppress the short circuit current at the moment of turning on as compared with the case where the charge and discharge resistance 74 is not provided.

  13 Heating coil 69a Upper arm IGBT 69b Lower arm IGBT 70a Upper arm snubber capacitor 70b Lower arm snubber capacitor 73a Upper arm IGBT drive circuit Lower arm IGBT drive circuit 74a Upper arm charge / discharge resistance 74b Lower arm charge / discharge resistance 75 Capacitor for drive circuit 76 Diode 82 Power supply for IGBT

Claims (1)

A heating coil for heating the object to be heated by induction heating;
It includes an inverter drive unit having a current resonance type circuit configuration separated into an upper arm and a lower arm which supply power for driving the heating coil,
The inverter drive unit
An upper arm IGBT and a lower arm IGBT for supplying power to the heating coil to the upper arm and the lower arm, respectively;
An upper arm snubber capacitor and a lower arm snubber capacitor for absorbing a surge voltage between the collector and the emitter of the upper arm IGBT and the lower arm IGBT;
Providing an upper arm charge / discharge resistance and a lower arm charge / discharge resistance connected in parallel to the upper arm snubber capacitor and the lower arm snubber capacitor;
An upper arm IGBT drive circuit and a lower arm IGBT drive circuit for driving the upper arm IGBT and the lower arm IGBT;
An IGBT power supply for supplying power to the upper arm IGBT drive circuit and the lower arm IGBT drive circuit;
A drive circuit capacitor as a power supply of the upper arm IGBT drive circuit;
A diode for supplying power from the power supply for IGBT to the capacitor for drive circuit;
Electric power is stored in the capacitor for the drive circuit through the diode when the lower arm IGBT is turned on, and then driving of the inverter drive unit is started after the lower arm IGBT is turned off Cooking device.

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