JPH0357599B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-frequency heating device having a solid-state high-frequency generator as a high-frequency heating heat source.

Conventional configurations and their problems Most conventional high-frequency heating devices used magnetrons as high-frequency generation sources, but with the realization of semiconductor devices that operate at high output in high frequency bands, solid-state heating devices constructed using semiconductor devices have been developed. It has become practically possible to use the high-frequency generator as a high-frequency heating heat source.

This type of high-power solid-state generator has been put into practical use in the communications industry, replacing electron tube oscillators.
When considering installation in a high-frequency heating device, there are differences in the following points.

The first point is that in the communication industry, this type of generator operates continuously at all times, but the generator installed in a high-frequency heating device operates only when heating an object. The operating time for one operation is about two hours at most, and in most cases it is used for less than 10 minutes, and the total operating time for one day is considered to be at most two to three hours. As described above, the solid-state high-frequency generator installed in the high-frequency heating device has a considerably shorter operating time per day than this type of generator in the communications industry.
On the other hand, the solid-state high-frequency generator installed in the high-frequency heating device has the characteristic of being activated many times a day.

The second point is the difference in frequency bands. A high-frequency heating device needs to operate in a much narrower band than this type of solid-state high-frequency generator used in the communications industry, and ideally it should have a solid-state high-frequency generator that exhibits the highest performance at the frequency used. Just configure it. Therefore, the output of the solid-state high-frequency generator can be higher than that of this type of generator used in the communications industry.

The above two points are extremely advantageous for solid-state high-frequency generators used in high-frequency heating heat sources. In other words, it has higher performance and a longer life.

Incidentally, a semiconductor device operating at a high output has a characteristic that the input/output impedance of the device changes nonlinearly depending on the high frequency power level input to the device and the device drive voltage level. Moreover, this input/output impedance value is very small. Therefore, when the device starts operating, that is, when a high-frequency power supply starts operating or when an amplifier circuit drive voltage is applied, there is a risk that the device will self-oscillate due to impedance mismatch with the device, or electric field concentration will occur, resulting in device destruction. Strong sexuality. This danger is especially great in high-frequency heating devices because the generating section is activated many times.

Purpose of the Invention In view of the above points, the present invention prevents self-oscillation of the element or destruction of the element when starting the solid-state high-frequency generator using an effective method, and is installed in a high-frequency heating device. The purpose is to improve the reliability of solid-state high frequency generators.

Structure of the Invention To achieve the above object, the present invention includes a preamplifier circuit, a main amplifier circuit that further amplifies the output high frequency power of the preamplifier circuit, and a current detection means that detects the output current of the preamplifier circuit drive power source. A control circuit is provided that recognizes that the output signal of the current detection means is within a predetermined reference range and operates the drive power source of the main amplifier circuit.

In this way, by operating the drive power supply of the main amplifier circuit after confirming that the preamplifier circuit is operating stably, the input/output impedance of the semiconductor element that operates at high output can be adjusted to the high frequency power level. In contrast to non-linear changes due to the influence of both the input and output impedances and the drive voltage level, it is possible to separate the effects of both over time, reduce the amount of change in input/output impedance over time, and eliminate mismatch between the element and the element drive peripheral circuit. This has the effect of alleviating the oscillation of the element, thereby preventing self-oscillation of the element and destruction of the element.

Description of examples The present invention will be explained below with reference to the drawings.

FIG. 1 is a partially cutaway external view of a high-frequency heating device showing an embodiment of the present invention.

The main components are a solid-state high-frequency generator 1, a preamplifier current detector 2, a drive power supply 3 for driving the solid-state high-frequency generator 1, and a controller 4 for the drive. The output from the solid state high frequency generator 1 is supplied to the heating chamber 6 through the power feeding coaxial line 5.

By inputting the heating time using the time setting key 8 on the operation panel 7 provided on the front of the device and operating the start key 9, a control signal is sent from the control section 4 through the lead wire 10 to the drive power supply section 3. is sent at a predetermined timing to operate the solid-state oscillation circuit power supply, and after a predetermined time delay, turn on the preamplifier circuit power supply. Here, the power is preamplifier circuit power line 1
1, the current is passed through the current detection unit 2 and supplied to the preamplifier circuit. A control signal indicating that a current within a predetermined range has been detected is sent from the current detection section 2 to the control section 4 through the signal line 12, and then a signal is sent from the control section 4 to the drive power supply section 3. and turn on the power to the main amplifier circuit.

When a driving voltage is applied to the main amplifier circuit section, the solid-state high frequency generating section 1 outputs a predetermined high frequency power, and the object to be heated in the heating chamber 6 is heated by this high frequency output. Further, when the heating time ends, when the stop key 13 on the operation panel 7 is operated, and when the door 14 used to store the object to be heated in the heating chamber 5 is opened, the information is controlled. The signal is sent to section 4, and the output of the drive power source is immediately cut off at a predetermined timing.

FIG. 2 is a control system diagram of a high frequency heating heat source showing an embodiment of the present invention. In the figure, the same parts as in FIG. 1 are indicated by the same numbers.

The solid-state high frequency generator 1 includes an oscillation circuit 15 that self-oscillates a high frequency, a preamplifier circuit 16 that amplifies the output of the oscillation circuit, a distributor 17 that equally distributes the output of the preamplifier circuit, and a distributor. It consists of main amplifier circuits 18 and 19 that amplify each of the divided powers, and a combiner 20 that combines the powers of each main amplifier circuit.
The drive power supply section is composed of a drive power supply generator 21 which is a drive applied voltage generation section, and on/off switches 22, 23, and 24 provided at each output of this generator. , is provided in the middle of the preamplifier circuit drive applied voltage supply line. A switch 25 turns on and off the supply of the commercial power supply 26 that drives the drive power generator 21, and is operated by a control signal from the control section 4.
27 and 28 are power terminators.

The operation will be explained below. When starting the operation of the solid state high frequency generator 1, the switch 25 is first closed and the drive power generator 21 starts operating. Next, the switch 22 is closed, the oscillation circuit 15 becomes operational, and then the switch 23 is closed and the preamplifier circuit starts operating. At this time, when the current supplied to the preamplifier circuit is within a predetermined range, the control section 4 receives a control signal from the current detection section 2, responds, and closes the switch 24. As a result, the main amplifier circuits 18 and 19 begin to operate, and high frequency power begins to be output. On the other hand, at the end of the heating time, when the stop key is operated, or when the access door is opened, the switch 24 is first opened and the main amplifier circuit is stopped, and then the preamplifier circuit 16 and the oscillation circuit 15 are opened.
The operation stops in this order, and finally the drive power supply 21 stops.

By adopting the above control method, in a high-frequency heating heat source where the solid-state high-frequency generating section 1 is manipulated to start up, self-excited oscillation of the element at startup and element destruction can be prevented, and the initial characteristics can be exhibited well. I can do it.

Effects of the Invention As described above, the present invention provides improved startup control when starting the solid state generator in a high frequency heating device in which the high frequency heating heat source is configured of a solid state high frequency generator, thereby: (1) solid state heating; Self-sustained oscillation and element destruction of the semiconductor element used in the amplifier circuit of the high frequency generation section can be prevented, and good startup can be maintained.

(2) Initial performance can be easily maintained, especially in response to repeated activation, and a highly reliable device can be provided. It has the following effects.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway external view of a high-frequency heating device showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of a system control circuit for the same high-frequency heating heat source. 1... Solid state high frequency generation section, 2... Current detection section, 3...
Drive power supply section, 4... control section, 15... solid state oscillation circuit,
16...Preamplifier circuit, 18, 19... Main amplifier circuit.

Claims (1)

[Claims] 1. A solid-state oscillation circuit, an oscillation circuit drive power supply that drives the solid-state oscillation circuit that operates in response to a heating operation start operation, a preamplifier circuit that amplifies high-frequency power generated by the solid-state oscillation circuit, and the oscillation circuit. a preamplifier circuit drive power source that drives the preamplifier circuit that operates with a delay from the start of operation of the drive power source;
a main amplifier circuit for further amplifying the output high frequency power of the preamplifier circuit; a current detection means for detecting the output current of the preamplifier circuit driving power source; and a predetermined standard for the output signal of the current detection means. A high-frequency heating device comprising a control means for recognizing that the main amplifier circuit is within the range and operating the drive power source for the main amplifier circuit.