JP2013013163A - Inverter device and induction heating apparatus using the same - Google Patents

Abstract

An object of the present invention is to provide an inverter device and an induction heating device using the same that extend the service life of a switching element and improve an increase in loss of the switching element due to a decrease in driving voltage.
A converter circuit 30 that converts an AC voltage into a DC voltage, an inverter circuit 31 that includes a switching element 24, converts the DC voltage into power of an arbitrary voltage and frequency, and supplies a high-frequency current to a load, and an inverter A drive circuit 25 for supplying a switching signal to the switching element 24 of the circuit 31 and a power detection means 26 for detecting the output power of the inverter circuit 31 are provided. The inverter circuit 31 has a power detection means 26 according to the power detected by the power detection means 26. By including the drive voltage varying means 27 that varies the drive voltage of the switching signal supplied to the switching element 24, the drive voltage of the switching element 24 can be varied according to the output power of the inverter. Become.
[Selection] Figure 1

Description

  The present invention relates to an inverter control device that controls an inverter that converts direct current into alternating current, and an induction heating device that includes a plurality of heating means for heating an object to be heated on a top plate using the inverter control device.

  Conventionally, as this type of inverter device and an induction heating device using the inverter device, an inverter control device having a variable resistance as a gate resistance connected between a drive circuit for driving the switching element and a gate terminal of the switching element is known. (For example, refer to Patent Document 1).

  FIG. 4 is a diagram of the inverter control device described in Patent Document 1. In FIG. FIG. 4 shows an inverter control device in which noise generated during switching is reduced by arbitrarily determining dv / dt in switching by using the variable resistor 8a as the resistor 8.

JP-A-7-236266

  However, in the conventional configuration, the gate resistance can be varied to adjust the switching speed and reduce the noise. However, the loss during switching increases or the driving voltage for driving the switching element is Since it is constant, there has been a problem that a breakdown phenomenon with time of the gate oxide film or the like of the switching element occurs, and the durability of the switching element is shortened.

  In addition, it is possible to extend the service life of the switching element by lowering the driving voltage for driving the switching element. However, by lowering the driving voltage, the switching speed of the switching element is reduced and the switching element is turned on. There has been a problem that loss increases due to an increase in resistance.

  The present invention solves the above-described conventional problems, and provides an inverter device and an induction heating device using the same that extend the life of the switching device and also improve the increase in loss of the switching device by lowering the drive voltage. For the purpose.

  In order to solve the above-described conventional problems, an inverter device of the present invention and an induction heating device using the inverter device include a converter that converts an AC voltage into a DC voltage, and a switching element, and the DC voltage is converted to an arbitrary voltage and frequency. An inverter unit that converts power into high-frequency current to a load; a drive circuit that supplies a switching signal to a switching element of the inverter unit; and a power detection unit that detects output power of the inverter unit. Drive voltage varying means for varying the drive voltage of the switching signal supplied to the switching element of the inverter unit according to the detected power.

  As a result, by changing the drive voltage of the switching element according to the output power of the inverter, it is possible to extend the life of the switching element and improve the loss of the switching element due to the reduction of the drive voltage. .

  Since the inverter device of the present invention and the induction heating device using the inverter device can extend the life of the switching element and can also improve the increase in loss of the switching element due to the reduction of the driving voltage, the switching element is used. The product life of the inverter device itself can be extended and the loss increase is also improved, so that an efficient inverter device and an induction heating device using the inverter device can be provided.

The circuit block diagram of the induction heating apparatus in this Embodiment 1. Switching element characteristic diagram according to the first embodiment The circuit block diagram of the vacuum cleaner in this Embodiment 2. Configuration diagram of another conventional inverter control device

  According to a first aspect of the present invention, there is provided a converter configured to convert an AC voltage into a DC voltage, a switching element, converts the DC voltage into electric power having an arbitrary voltage and frequency, and supplies a high-frequency current to a load. A drive circuit for supplying a switching signal to the switching element and a power detection means for detecting the output power of the inverter unit, and driving the switching signal supplied to the switching element of the inverter unit according to the power detected by the power detection unit Drive voltage varying means for varying the voltage. Thereby, the control according to the output electric power of an inverter part becomes possible easily.

  According to a second aspect of the present invention, when the power detected by the power detection means is equal to or higher than the predetermined power, the switching signal supplied to the switching element of the inverter unit is controlled with the rated drive voltage, and the power detected by the power detection means Is less than the predetermined power, the switching signal supplied to the switching element of the inverter unit is controlled below the rated drive voltage.

  As a result, the life of the switching element can be extended, and the increase in loss of the switching element due to the reduction of the driving voltage can be improved.

  The third invention is characterized in that the switching element of the inverter section is a wide gap semiconductor such as diamond, GaN, SiC or the like. Thereby, the switching loss at the time of a switching element switching, and the conduction loss at the time of a switching element being conductive can be reduced, and the energy saving of an inverter apparatus and an induction heating apparatus using the same can be aimed at.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a main circuit configuration of Embodiment 1 of the present invention, taking an induction heating device as an example, and shows a power conversion circuit and an inverter circuit.

The induction heating apparatus shown in FIG. 1 is turned on / off at a predetermined timing from a 200 V commercial power supply 21 via a filter circuit unit 22 including a rectifier circuit and a power factor correction circuit, and a converter circuit 30 of a smoothing circuit 23. An inverter circuit 31 that generates high-frequency power of a predetermined frequency by the switching element 24; a drive circuit 25 that supplies a drive signal for driving the switching element 24; and a power detection means 26 that detects the output power of the inverter circuit 30; A control circuit 32 including a drive voltage varying means 27 for varying the voltage of a drive signal for driving the switching element 24 according to the power of the power detection means 26, and a heating means 28 for generating a high frequency magnetic flux by the high frequency power. And a resonance capacitor 29 connected in series with the heating means 28.

  Although not shown, a hard glass top plate disposed above the heating means 28 and an object to be heated such as a pan on the glass top plate on the heating means 28 are installed. By performing the heating operation, induction heating of the object to be heated is performed.

  The operation and action of the induction heating apparatus configured as described above will be described below. When the user installs an object to be heated and starts the heating operation, the inverter circuit 31 rectifies the commercial power supply 21 with the rectifier circuit 22 by turning on and off the switching element 24 based on the drive signal of the drive circuit 25. The direct current smoothed by the smoothing circuit 23 is converted into high frequency alternating current, and a high frequency current is passed through the heating means 28 to generate an eddy current in the heated object magnetically coupled to the heating means 28, and the heated object is heated by the Joule heat. The induction heating.

  Next, the power detection means 26 detects the output power of the inverter circuit 30 when the object to be heated is inductively heated, and the drive voltage variable means 27 drives the switching element 24 according to the detected output power. Vary the voltage of the signal. In the first embodiment, the value of power for changing the voltage of the drive signal is 1500 W, and the rated drive voltage for driving the switching element 24 is 20V.

  Thereby, for example, when the power detected by the power detection means 26 is 2000 W, the driving voltage of the switching element 24 is driven at 20 V, and when the detected power is 1000 W, the driving voltage of the switching element 24 is rated. It can be driven at 15V, which is 20V or less of the drive voltage. Moreover, SiC, GaN, SiGe, MOSFET, IGBT, or a transistor is used for the switching element.

  FIGS. 2A, 2B, and 2C show examples of characteristic diagrams of the driving voltage of the switching element, the on-resistance of the switching element, the switching speed, and the durable life, respectively. The higher the drive voltage of the switching element, the lower the on-resistance of the switching element and the faster the switching speed, so that the loss of the switching element can be reduced.

  However, if the drive voltage of the switching element is increased, a breakdown phenomenon over time such as the gate oxide film of the switching element may occur in less than a predetermined number of years, and the product that uses the switching element is less than the warranty years As a result, the switching element is destroyed. Moreover, it is possible to extend the service life of the switching element by lowering the drive voltage, but the loss increases and the heating efficiency of the product deteriorates.

  Therefore, by changing the drive voltage in accordance with the output power of the inverter as in the present embodiment, the service life of the switching element can be extended and the loss of the switching element can be improved.

  In this embodiment, the inverter circuit uses a full-bridge inverter, but it goes without saying that other inverters can be applied.

  Moreover, although the output power of the inverter is detected by the power detection means 26, the input current may be detected before the rectifier circuit 22, and the drive voltage of the switching element may be varied according to the input current.

In the present embodiment, only one threshold for changing the drive voltage is provided, but the drive voltage may be divided into two or more.

  In this way, it is possible to realize efficient heating without increasing the service life of the switching element and without extremely increasing the loss of the switching element.

(Embodiment 2)
FIG. 3 shows a main circuit configuration of the second embodiment of the present invention using a vacuum cleaner as an example.

  The vacuum cleaner shown in FIG. 3 is switched on / off at a predetermined timing via a filter circuit unit 42 including a rectifier circuit, a power factor correction circuit and the like, and a converter circuit 50 of a smoothing circuit 43 from an AC power supply 41. An inverter circuit 44 that generates high-frequency power of a predetermined frequency by the element, a drive circuit 48 that supplies a drive signal for driving the switching element, a current detection means 47 that detects a current flowing through the motor 45, and a current detection means And a control circuit 51 including drive voltage varying means 49 for varying the voltage of a drive signal for driving the switching element in accordance with the current value of 47. 45 is a motor and 46 is a fan.

  The operation and action of the vacuum cleaner configured as described above will be described below. The power input from the AC power source 41 is rectified by the filter circuit unit 42 and then converted into a desired AC by the inverter circuit 44 as DC power smoothed through the smoothing capacitor 43, and the fan 46 is used as a load. The motor 45 is driven to rotate.

  Next, the current flowing through the motor is detected by the current detection means 47. If the detected current is equal to or greater than a predetermined current value, the drive voltage for driving the switching element is set as the rated drive voltage, and if the current is less than the predetermined current value. The switching element is driven with a voltage lower than the rated drive voltage.

  Further, in the present embodiment, the drive voltage is varied by detecting the current flowing through the motor 45, but the drive voltage depends on the power value of the power detection means 50 installed at the input unit from the AC power supply 41. May be variable.

  In this way, by varying the drive voltage of the switching element according to the current flowing through the motor, the motor can be driven efficiently without increasing the service life of the switching element and extremely increasing the loss of the switching element. It can be realized.

  As described above, the present invention can be applied to all fields using an inverter circuit. In particular, when used in an inverter device provided in an induction heating device, a high-efficiency and long-life induction heating device is realized. Can do.

24 switching element 25 drive circuit 26 power detection means 27 drive voltage variable means 28 heating means 29 resonance capacitor 30 converter circuit 31 inverter circuit 32 control circuit

Claims (4)

An inverter unit configured by switching elements to convert a DC voltage into electric power of an arbitrary voltage and frequency and supplying a high frequency current to a load; a drive circuit for supplying a switching signal to the switching element of the inverter unit; An inverter comprising: a power detection means for detecting output power; and a drive voltage varying means for varying a drive voltage of a switching signal supplied to the switching element of the inverter unit according to the power detected by the power detection means. apparatus. If the power detected by the power detection means is equal to or higher than a predetermined power, the switching signal supplied to the switching element of the inverter unit is controlled with the rated drive voltage, and the power detected by the power detection means is the predetermined power. The inverter device according to claim 1, wherein a switching signal supplied to the switching element of the inverter unit is controlled to be equal to or lower than a rated driving voltage if the power is less than the rated driving voltage. The inverter device according to claim 1, wherein the switching element of the inverter unit is a wide gap semiconductor such as diamond, GaN, SiC or the like. The induction heating apparatus using the inverter apparatus of any one of Claims 1-3.

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