When a pan made of a nonmagnetic material, such as aluminum, is used for cooking while the is being controlled, notification is made to the user to the effect that the temperature control function has been stopped and that the temperature should be manually adjusted. When the material detection section detects that the pan is made of a non-magnetic material or a pan-floating phenomenon has occurred, in order to prevent abnormal increase in the temperature of the pan due to incorrect, temperature detection caused by the pan-floating phenomenon, a set temperature is lowered.

Induction Heating Apparatus

An RF power supply that is capable of tracking rapid changes in the resonant frequency of a load and capable of quickly responding to varying load conditions so as to deliver the desired amount of power. The present invention also provides an RF power supply capable of delivering a wide range of power over a broad frequency range to a load that is remotely located from the power supply. According to one embodiment, the RF power supply includes a direct current (DC) voltage source that provides a DC voltage within a predetermined voltage range; an amplifier, coupled to the DC voltage source, that provides an alternating voltage to a tank circuit connected to an output of the RF power supply; a frequency controller, coupled to the amplifier, to set the frequency of the alternating voltage produced by the amplifier; and a sensor, coupled to the load, to provide a signal to the frequency controller, where the frequency controller sets the frequency of the alternating voltage based on the signal received from the sensor.

Resonant frequency tracking system and method for use in a radio frequency (RF) power supply

The inverter includes a DC to AC converter circuit including a plurality of transistors which are switched on and off to convert a DC signal into an AC signal. The converter circuit also includes diodes which are alternately forward and reverse biased during the operation of the converter circuit, the diode having a reverse recovery period whenever the diode is switched from a forward to a reverse biased condition during which the reverse resistance of the diode is substantially zero. An inductor is connected to the diode for limiting the current through the diode during the reverse recovery period such that shoot through currents which pass through both the diode and the inductor are limited to desired levels.

Converter with lossless snubbing components

A high frequency heating generator which includes an electron tube amplifier, the output of which is connected to a resonant circuit that is electromagnetically coupled to a part to be heated, and a controlled frequency oscillator. The oscillator outputs a high frequency signal to the input of the amplifier. It also includes circuitry to measure the phase shift between the current output to the resonant circuit and the voltage at its terminals, and to modify the frequency of the oscillator as a function of this phase shift. The invention can be applied notably to devices for heating by electromagnetic induction, dielectric losses or plasma.

High frequency heating generator having an improved matching network between a tetrode amplifier and a resonant circuit

A control system for a transistor inverter comprising a circuit for detecting the load current or the output voltage from the inverter to produce a detection output; a circuit for outputting a control instruction for adjusting the load current; a leading angle forming circuit for combining the detection output with the control instruction to form a control signal corresponding to a leading angle at which the inverter output voltage is controlled with a leading phase relative to the load current; and a circuit receiving the control signal from the leading angle forming circuit and for forming a switching control signal, which is supplied to the switching devices in the inverter. The load current is not controlled directly by controlling the frequency of the inverter, but by changing the phase difference γ between the load current and the inverter output voltage.

Control system for an inverter apparatus

A solid state radio frequency high power generator for induction heating applications uses MOSFET devices controlled at radio frequency by a current loop which is automatically corrected against the possible occurrence of a leading phase shift by a voltage-current phase shift detection loop which responds to digital signals corrected against inherent time delays.

Solid state radio frequency power generator

Transducer ultrasonic power supply

A high frequency current-fed inverter of the series/parallel compensated type is started directly with the main thyristors of the inverter by charging the series capacitor through the input inductor of the DC supply during a first time interval with one pole, by discharging the same during a second time interval with the other pole, then passing to free-running operation at an initial frequency from which load operation can begin. The first and second time intervals are established while a constant DC voltage is being applied so that commutation of the outgoing thyristor is insured. DC voltage regulation is eliminated as soon as the free-running operation has been initiated.

Chuck F. Der

Papers

Solid state radio frequency power generator

Transducer ultrasonic power supply

Method and apparatus for starting a parallel-tuned current fed inverter