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: 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: 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: 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: It is provided a magnetron drive power supply wherein a series connection body of first and second semiconductor switch elements that can be brought into reverse conduction and a series connection body of first and second diodes are connected in parallel, first and second capacitors are connected in parallel to the first and second diodes, a series circuit of a commercial power supply and a primary winding of a high-voltage transformer is connected between a connection point of the first and second semiconductor switch elements that can be brought into reverse conduction and a connection point of the first and second diodes, and output of a secondary winding of the high-voltage transformer energizes a magnetron through a high-voltage rectification circuit.

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: It is provided a magnetron drive power supply wherein a series connection body of first and second semiconductor switch elements that can be brought into reverse conduction and a series connection body of first and second diodes are connected in parallel, first and second capacitors are connected in parallel to the first and second diodes, a series circuit of a commercial power supply and a primary winding of a high-voltage transformer is connected between a connection point of the first and second semiconductor switch elements that can be brought into reverse conduction and a connection point of the first and second diodes, and output of a secondary winding of the high-voltage transformer energizes a magnetron through a high-voltage rectification circuit.