Abstract: The invention relates to a high frequency heating apparatus and provides a tracking method of a frequency modulation in order to prevent an extension of the harmonic current component of an oscillation threshold ebm which varies from moment to moment in accordance with a change in the temperature of a magnetron. A driving signal for driving a first semiconductor switching element (3) and a second semiconductor switching element (4) is transmitted to a driving control IC unit (14), and an input reference signal Ref is used to perform an input current fixed control. In this case, a variation amount of the input current of the input reference signal Ref is understood as an accumulation information POW and a constant is optimally configured in a resistor network in an ebm-tracking bias circuit (20).

Abstract: There is constructed a constitution such that a shunt resistor 30 is interposed in series with a portion capable of measuring an output current of a unidirectional power source portion 1 of a high frequency heating apparatus and a voltage generated at the shunt resistor 30 is outputted by a buffer 31. Further, an operational amplifier 3101 having a high input impedance is used for the buffer 31. Further, a diode bridge 101 and a semiconductor switching element 205 are fixed to a common heat radiating plate 33, the heat radiating plate 33 is formed with a notched portion 33a to thereby ensure insulating distances to the diode bridge 101 and the semiconductor switching element 205, and the shunt resistor 30 is arranged on a straight line the same as that between the diode bridge 101 and the semiconductor switching element 205.

Abstract: The invention relates to a high frequency heating apparatus and provides a tracking method of a frequency modulation in order to prevent an extension of the harmonic current component of an oscillation threshold ebm which varies from moment to moment in accordance with a change in the temperature of a magnetron. A driving signal for driving a first semiconductor switching element (3) and a second semiconductor switching element (4) is transmitted to a driving control IC unit (14), and an input reference signal Ref is used to perform an input current fixed control. In this case, a variation amount of the input current of the input reference signal Ref is understood as an accumulation information POW and a constant is optimally configured in a resistor network in an ebm-tracking bias circuit (20). Sequentially, a portion in which an operating frequency ascends is provided by giving a bias to a frequency modulation waveform, and then a frequency modulation tracking is performed.

Abstract: The invention relates to a high frequency heating apparatus that drives a magnetron such as a microwave, and provides a frequency modulation method of preventing harmonic current occurring due to a high frequency switching operation. When a driving signal is transmitted in order to drive a first semiconductor switching element (3) and a second semiconductor switching element (4), an inverter operating frequency in the every phase of a commercial power supply is provided as a frequency difference (inclination) of the phase range from 0° to 90° using a triangular wave-forming circuit in an oscillation circuit (16). A modulation waveform for a frequency modulation control is formed, configuring an upper limit clamp, a lower limit clamp, a lower limit value corresponding to the lowest frequency in a frequency modulation-forming circuit (15) on the basis of a commercial power rectifying voltage-dividing waveform after rectification.

Abstract: A purpose of the present invention is to provide an inverter circuit capable of firmly turning ON IGBTs under limited condition, while a heat loss and noise can be hardly produced in semiconductor switching elements.

Abstract: An object of the present invention is to provide an inverter circuit in which soft start can be implemented by a simple circuit added thereto. In high-frequency heating apparatus for driving a magnetron, a DC power supply is chopped by two semiconductor switching devices, and this is output as an AC current through a resonance circuit. The high-frequency heating apparatus includes a dead time generation circuit for turning off the semiconductor switching devices concurrently. In the high-frequency heating apparatus, a drive unit for driving the aforementioned semiconductor switching devices has a function of limiting the lowest frequency of a frequency with which the semiconductor switching devices are driven. The aforementioned lowest frequency is set to be high at the beginning of operation of the high-frequency heating apparatus, and the aforementioned lowest frequency is set to be lower gradually thereafter.

Abstract: A purpose of the present invention is to provide an inverter circuit capable of firmly turning ON IGBTs under limited condition, while a heat loss and noise can be hardly produced in semiconductor switching elements.

Abstract: There is constructed a constitution such that a shunt resistor 30 is interposed in series with a portion capable of measuring an output current of a unidirectional power source portion 1 of a high frequency heating apparatus and a voltage generated at the shunt resistor 30 is outputted by a buffer 31. Further, an operational amplifier 3101 having a high input impedance is used for the buffer 31. Further, a diode bridge 101 and a semiconductor switching element 205 are fixed to a common heat radiating plate 33, the heat radiating plate 33 is formed with a notched portion 33a to thereby ensure insulating distances to the diode bridge 101 and the semiconductor switching element 205, and the shunt resistor 30 is arranged on a straight line the same as that between the diode bridge 101 and the semiconductor switching element 205.

Abstract: It is an object to decrease an occupied space in a printed board to carry out space saving and to reduce the size of a unit without sacrificing the performance of a transformer and increasing a cost. A transformer 11 is constituted by a bobbin 13 having at least a primary winding 15 and a secondary winding 17 wound therearound and a core 21, and the side surface of the bobbin 13 is provided with a component holding section for holding high-voltage components such as a capacitor 31 and a diode 33 which constitute a voltage doubler rectifying circuit for rectifying a high voltage having a high frequency from the secondary winding 15.

Abstract: It is an object to decrease an occupied space in a printed board to carry out space saving and to reduce the size of a unit without sacrificing the performance of a transformer and increasing a cost.