Panasonic Corporation

Panasonic Intellectual Property Management Co., Ltd.

Matsushita Electric Industrial Co., Ltd.

Nobuo Shirokawa

Haruo Suenaga

Hideaki Moriya

Shinichi Sakai

Manabu Kinoshita

Hisashi Morikawa

Kenji Yasui

Toyotsugu Matsukura

Makoto Mihara

Masato Matsuda

Keiichi Satou

Hauo Suenaga

Toyotsubu Matsukura

Yoshitaka Oda

Sakai Shinichi

Since a protruding portion preventing a rotation during screw fastening of a connection member is disposed to engage with a printed circuit board, and a protruded length of the protruding portion is smaller than a thickness of the printed circuit board, a configuration can be achieved such that the protruding portion does not interfere with an earth member, a bracket, etc., disposed on the back side of the printed circuit board, and the earth member and the bracket can freely be designed.

Grounding structure for circuit board

Since a protruding portion preventing a rotation during screw fastening of a connection member is disposed to engage with an end surface of a printed circuit board, a configuration can be achieved such that the protruding portion does not interfere with an earth member, a bracket, etc. disposed on the back side of the printed circuit board, and the earth member and the bracket can freely be designed.

A resonance type high frequency heating apparatus comprising; a direct current power supply; a series connection circuit consisting of a pair of semiconductor switching elements connected in parallel to the direct current power supply; another series connection circuit having a primary coil of a leakage transformer and a capacitor connected to both ends of one of the pair of semiconductor switching elements; and a drive means for driving each of the pair of semiconductor switching elements; wherein a variable dead time preparation circuit is provided in the drive means, and the variable dead time preparation circuit enables dead time to remain constant at below a predetermined frequency and causes the dead time to increase sharply at a point above a predetermined frequency.

High-frequency heating apparatus

A power supply for a high frequency heating is provided. When processes from a non-oscillation to an oscillation of a magnetron are finely classified, the non-oscillation (a start mode), the oscillation (a start mode), and the oscillation (a steady mode) are obtained. A problem resides in an unstable state immediately after the oscillation. When a PWM setting value at this time is set to a value lower than a PWM setting value in the steady mode, even if the PWM setting value during the steady mode is set to a maximum output value, the input current is not controlled to a large current including the over-shoot immediately after the oscillation. After the magnetron shifts to a stable state, the PWM setting value shifts to a PWM setting value of an actual steady mode, so that the over-shoot of the input current can be suppressed as much as possible.

Power supply for a high frequency heating

Provided is a configuration in which it is possible to mount an applied voltage suppression circuit configured to prevent voltage breakdown of a semiconductor switching element, and a set voltage thereof can be inspected without damaging an IC or the like of a peripheral circuit. In a power converter having a semiconductor switching element, an applied voltage suppression circuit configured to suppress a voltage applied to the semiconductor switching element and at least one component of constituent components of a driving circuit which causes the semiconductor switching element to be turned off if the component is absent are transferred to and disposed on a slave substrate (separate unit) which is divided from and electrically connected to a master substrate including the semiconductor switching element, the driving circuit, a control circuit, and the like mounted thereon.

Power converter having semiconductor switching element

A power control unit for high-frequency dielectric heating is provided. The power control unit controls an inverter circuit for rectifying voltage of an AC power supply, and modulates the on time of a switching transistor during high frequency switching. The power control unit includes an input current detection section for detecting input current from the AC power supply to the inverter circuit and outputting input current waveform information. A conversion section is provided for converting the input current waveform information into a drive signal of the switching transistor of the inverter circuit so that an instantaneous fluctuation of the input current waveform information is suppressed.

Power control apparatus for high-frequency dielectric heating and power control method for the same

An inverter controller controls an inverter. The inverter converts direct current into alternating current of a predetermined frequency. The inverter includes a resonance circuit for fluctuating output of a predetermined object to be controlled. The inverter controller comprises an output fluctuating unit which fluctuates output of the inverter in response to an output value of a temperature detection section which detects a temperature of a switching element of the inverter. The inverter controller further comprises an output increase suppressing unit which suppresses an increase in the output of the inverter for a predetermined time after decrease control in the output of the inverter performed by the output fluctuating unit.

Inverter controller and high-frequency dielectric heating apparatus

A power control unit for high-frequency dielectric heating is provided, and includes an input current detection section for detecting input current from the AC power supply to the inverter circuit and outputting input current waveform information. A conversion section converts the input current waveform information into a drive signal of the switching transistor of the inverter circuit so that instantaneous fluctuation of the input current waveform information is suppressed. A mix circuit mixes the input current waveform information and power control information for controlling so that current or voltage at an arbitrary point of the inverter circuit becomes a predetermined value and generates an on voltage signal. The conversion section converts the on voltage signal into the drive signal so that the on time is shortened in the portion where the input current is large and that the on time is prolonged in the portion where the input current is small.

A power control method for high-frequency dielectric heating is provided. The method includes detecting input current and input voltage from an AC power supply. Input current waveform information and input voltage waveform information are acquired. It is determined whether the magnetron is being oscillated. If so, the input voltage waveform information is added to the input current waveform information until oscillation of the magnetron is detected, and the addition result is converted into the drive signal of a switching transistor of an inverter circuit. If not, the input current waveform, without addition of the input voltage waveform, is converted into the drive signal of the switching transistor of the inverter circuit.

To attain a more reliable prevention of an electric shock by checking whether the earth states for two circuit boards are good. There is detected a voltage generated at an anode current sensing resistorinserted into a path where the anode current of a magnetronflows and a signal is transmitted to a microcomputer. The microcomputeruses a selector switchto determine the earth states for an inverter circuit board and a control panel circuit board before operation of a device. In case either one or both of the circuit boards are in a floating state, operation of a high-frequency heating device is inhibited. Otherwise, operation of the high-frequency heating device is permitted.

High-frequency heating device

A power control unit for high-frequency dielectric heating is provided. The power control includes an input current detection section for detecting input current from an AC power supply to an inverter circuit and outputting input current waveform information. A conversion section converts the input current waveform information into a drive signal of the switching transistor of the inverter circuit so that instantaneous fluctuation of the input current waveform information is suppressed. An input voltage detection section detects input voltage from the AC power supply to the inverter circuit and outputs input voltage waveform information. A selection section selects the input current waveform information or the input voltage waveform information, whichever is larger. The conversion section also converts the selected input current waveform information or input voltage waveform information into the drive signal of the switching transistor of the inverter circuit.

A magnetron driving power source can detect the abnormal condition during no-load running with low cost and space saving. The magnetron driving power source includes a high voltage transformer () for supplying a high voltage to a magnetron (), a switching part () for driving the high voltage transformer at a high frequency, a first control part () for giving a drive signal to the switching part, a second control part () for issuing an output command to the first control part, and a third control part () for correcting the output command in accordance with a decrease in the oscillation threshold value of the magnetron, wherein the first control part () performs a power down control in accordance with a signal from the third control part. Accordingly, the magnetron driving power source of the invention can treat the signal on the control side of the inverter and detect the abnormal condition during no-load running with low cost and space saving.

Magnetron driving power source

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.

An operating state detection technique is provided which makes it possible to accurately detect an abnormality of a high-frequency heating apparatus. An anode current detected by the anode current detection resistorof a magnetron is inputted into the A/D converter terminal of a microcomputeron a control panel circuit board side. The current is subjected to an analog-to-digital conversion to thereby obtain an anode voltage IaDC value. The microcomputerdetermines an operating state based on a plurality of the anode voltage IaDC values thus read. Further, the microcomputerobtains a summed value of the IaDC values corresponding to one period of the revolution of rotary antennasto thereby determines the operating state of the high-frequency heating apparatusbased on the summed value. According to the aforesaid IaDC value reading method, it makes it possible to accurately detect an abnormality without an erroneous operation also in correspondence to the change of the feeding distribution. Further, the microcomputerchanges, in accordance with the set output of the high-frequency heating apparatus, a threshold value used for determining the abnormality and a changing value (increasing amount) from the start of the operation with respect to the change of the output of the apparatus and the operating state of a heated subject etc., whereby it makes it possible to accurately detect an abnormality without an erroneous operation.

State detection device for detecting operation state of high-frequency heating apparatus

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. In a high frequency heating apparatus comprising: a control signal forming circuit for forming a control signal from a difference between an input current of an AC power supply and a reference current; a frequency modulated signal forming circuit for correcting rectified voltage/rectified current which are obtained by rectifying the AC voltage/current of the AC power supply based upon the control signal of the control signal forming circuit; and a dead time forming circuit for receiving the output of the frequency modulated signal forming circuit, a control signal converting circuit having a function capable of further lowering the value of the control signal is provided between the control signal forming circuit and the frequency modulated signal forming circuit.

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Nara, Japan

Nobuo Shirokawa