Abstract: A purpose of the present invention is to provide an inverter circuit capable of suppressing an overshooting phenomenon of an input current at an instantaneous time when an initiating operation of the inverter circuit is switched to the normal operation thereof, and thus, capable of preventing damages of IGBTs and a magnetron.

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 high-frequency dielectric heating device includes: a microwave output unit including an inverter unit using a semiconductor switching element, heat-radiating fins for radiating the heat generated by an IGBT, and a printed board having a thermistor for detecting the temperature of the semiconductor switching element, The thermistor is soldered to a leg portion of the semiconductor switching element or near to the leg portion thereof on the side of the soldering surface of the printed board. The device also includes: a booster transformer, a high-voltage rectifier unit, and a magnetron; and a heat-cooking chamber fed with microwaves radiated from the magnetron. When the thermistor has assumed a predetermined resistance, a power-down control operation is effected by greatly decreasing the power fed to the semiconductor switching element. Then, permitting the power fed to the semiconductor switching element to vary depending upon the resistance of the thermistor.

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: A booster transformer 100 for driving a magnetron includes a bobbin 11 on which at least a first winding 13 and a secondary winding 15 are wound and a core 19 inserted through the center of the bobbin 11, wherein a winding area of the secondary winding 15 is divided into two areas while interposing a partition wall 23, and an outer diameter d of a wire material of the secondary winding 15 and a width t1 of each of the divided winding areas are so set as to satisfy the relation t1<11d.

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 present invention provides a high-frequency dielectric heating device comprises: a microwave output unit including an inverter unit using a semiconductor switching element, heat-radiating fins for radiating the heat generated by an IGBT, a printed board having a thermistor for detecting the temperature of the semiconductor switching element, wherein the thermistor being soldered to a leg portion of the semiconductor switching element or near to the leg portion thereof on the side of the soldering surface of the printed board, a booster transformer, a high-voltage rectifier unit, and a magnetron; and a heat-cooking chamber fed with microwaves radiated from the magnetron. When the thermistor has assumed a predetermined resistance, a power-down control operation is effected by greatly decreasing the power fed to the semiconductor switching element. Then, permitting the power fed to the semiconductor switching element to vary depending upon the resistance of the thermistor.

Abstract: Timing of zero voltage in zero-voltage detector for detecting zero voltage of a commercial power supply 1 is predicted and input from the zero-voltage detector 6 is received only for a given time before and after the predicted timing, whereby overvoltage and overcurrent caused by a zero point shift can be prevented. Thus, it is provided a magnetron drive power supply which is excellent in stability for change in the power supply environment such as noise or instantaneous power interruption.

Abstract: In a step-up transformer for magnetron driving in which two ferrite cores are opposed to each other with a gap G interposed therebetween, thereby forming a magnetic circuit including a middle core section, an outer core section and a coupling core section for coupling the middle core section and the outer core section, and a primary winding and a secondary winding are arranged to surround the middle core respectively, a sectional area of the middle core is increased, a number of winds in a radial direction of each of the primary winding and the secondary winding is increased and a number of winds in an axial direction is decreased, and the primary winding and the secondary winding are provided close to each other and a ratio of the sectional area of the middle core to that of the outer core is decreased to be 2:1 or less.

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: Timing of zero voltage in zero-voltage detector for detecting zero voltage of a commercial power supply 1 is predicted and input from the zero-voltage detector 6 is received only for a given time before and after the predicted timing, whereby overvoltage and overcurrent caused by a zero point shift can be prevented. Thus, it is provided a magnetron drive power supply which is excellent in stability for change in the power supply environment such as noise or instantaneous power interruption.

Abstract: A high-frequency dielectric heating power control method comprises: detecting the input current of an inverter circuit for rectifying the voltage of an AC power source to convert the rectified voltage into an AC voltage of a predetermined frequency; rectifying the detected current to determine an input current waveform; shaping the waveform to determine a reference waveform; determining the difference between the input current waveform and the reference waveform; and mixing the differential information and the current control output by a mix circuit to convert the mixed one into the drive output of a switching transistor of the inverter circuit.

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.

Abstract: In a step-up transformer for magnetron driving in which two ferrite cores are opposed to each other with a gap G interposed therebetween, thereby forming a magnetic circuit including a middle core section, an outer core section and a coupling core section for coupling the middle core section and the outer core section, and a primary winding and a secondary winding are arranged to surround the middle core respectively, a sectional area of the middle core is increased, a number of winds in a radial direction of each of the primary winding and the secondary winding is increased and a number of winds in an axial direction is decreased, and the primary winding and the secondary winding are provided close to each other and a ratio of the sectional area of the middle core to that of the outer core is decreased to be 2:1 or less.

Abstract: A high-frequency induction heating power control method comprises: detecting the input current of an inverter circuit for rectifying the voltage of an AC power source to convert the rectified voltage into an AC voltage of a predetermined frequency; rectifying the detected current to determine an input current waveform; shaping the waveform to determine a reference waveform; determining the difference between the input current waveform and the reference waveform; and mixing the differential information and the current control output by a mix circuit to convert the mixed one into the drive output of a switching transistor of the inverter circuit.