JPH0278183A - High frequency heating device - Google Patents

Abstract

PURPOSE:To prevent the generation of a high frequency pulse at a magnetron by controlling the 'on' period of a semiconductor switch of an invertor during the starting of a device. CONSTITUTION:A pressure rise transformer 5 is driven by means of the energization of an invertor 12 having a semiconductor switch 9, and a magnetron 15 is actuated by the electric power supplied from the transformer 5. A detection means 16 is provided between a secondary winding 7 of the transformer 5 and the magnetron 15, and the current during the oscillation thereof is detected. The detection signal is connected to a base of the semiconductor switch 9 via a semiconductor switch control unit 17. The 'on' period of the semiconductor switch is shortened by the control unit 17 so as to suppress the generation of a high frequency pulse. Since a high frequency pulse is not generated during the starting, longevity of the device can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-frequency heating device, and particularly to suppression of high-voltage pulses generated in a magnetron during startup.

[Conventional technology]

3rd [F] is a circuit diagram of a conventional high frequency heating device.

(1) is a commercial power supply, (2) is a converter and a sweat device (
3) and a smoothing capacitor (41).The high frequency transformer (5) has primary, secondary, and tertiary windings 61.(7
), (A semiconductor switch (9) is connected in series to the 91st winding (6) of 81 wires, a commutating diode αG and a resonant capacitor +Il+ are connected in parallel to this semiconductor switch (9), and the primary winding One side of the wire +61 is connected to the DC circuit to form an inverter az that serves as a source of high frequency switching power.In addition, a high voltage capacitor α3 and a high voltage diode O4 are connected to the secondary winding of the isolation transformer (7) to generate a half wave multiplier. It constitutes a voltage rectifier circuit.The magnetron supplies high-voltage power to the secondary winding (7) of the isolation transformer through the high-voltage diode α3 of t19.(15a) is the filament of this magnetron, which connects the tertiary winding of the isolation transformer. (8
) is connected to the filament (15a) to supply heater power to (15a), forming a microwave oven heating circuit.

[Problem to be solved by the invention]

In a conventional high-frequency heating device like the one shown above, the heater power and magnetron is used to heat the filament (15a).
Since the high voltage power supplied to the semiconductor switch (9) is supplied from the same transformer, the filament (
The time it takes to heat up the magnetron is approximately -
There was a problem in that a high voltage pulse (bl) of up to 10 KV was generated.

[Failure to solve the problem]

The high-frequency heating device according to the present invention includes a converter for converting commercial power into direct power, and an inverter connected to the converter and having a semiconductor switch.

A high-frequency transformer is energized by this inverter and supplies high-voltage pulses to the magnetron, as well as heater power to the magnetron's filament.

and a semiconductor switch control means for suppressing high voltage pulses by shortening the conduction time of the semiconductor switch until the magnetron oscillates at startup.

[Effect]

In this invention, the semiconductor switch control means is used.

High voltage pulses are suppressed by shortening the conduction time of the dark semiconductor switch until the magnetron oscillates at startup.

〔Example〕

An embodiment of this invention is shown in FIG. The details are explained in Figure 2.

In the figure, 111 to (15a) are the same as conventional high frequency heating devices. (1G is a detector that detects the current during magnetron oscillation, which is installed between the magnetron 719 and the secondary winding (7), and αη is the conduction time of the semiconductor switch (91) that receives the detection signal from this detector. This semiconductor switch control means an
The semiconductor switch 1 is composed of a semiconductor switch conduction time control circuit 01+ and a semiconductor switch control circuit 09.
The conduction time of the dark semiconductor switch (9) until the magnetron a9 oscillates at startup is shortened, and the generation of high voltage pulses is suppressed.

In a high frequency heating device configured like a queen, the second
As shown in the figure, by shortening the ton time of the voltage (el) applied between the base and emitter of the semiconductor switch (91) until the magnetron oscillates, the magnetron high voltage pulse (el) can be suppressed by approximately -6 KV. Capacitor α3. High voltage diode - 10 pieces.

The magnetron αS can be protected from high voltage pulses.

In figure ga2, (di (I'i is the detection voltage of detector αG).

The detector aθ which detects the current during the magnetron oscillation converts the current into a voltage and notifies the semiconductor switch conduction time control circuit ON IIC-q that the magnetron a has started oscillation. In response to this, the semiconductor switch conduction time control circuit +I11 issues a normal TON''' OFF time command to the semiconductor switch control circuit (19).-And after the magnetron is excavated, the voltage of the magnetron t1 is -4KV.
, since the current is also constant, the semiconductor switch control port trace [9
continues to issue the normal TON-TOFF time command between the base and emitter of the semiconductor switch (91).

〔Effect of the invention〕

As explained above, according to the present invention, the semiconductor switch control means suppresses high-voltage pulses by shortening the conduction time of the listener conductor switch until the magnetron oscillates at startup, so that the high-voltage diode, high voltage capacitor,
It can protect the magnetron and extend the life of the high frequency heating device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the high frequency heating device of the present invention, FIG. 2 is a voltage waveform diagram during magnetron oscillation, and FIG.
The figure is a circuit diagram of a conventional high-frequency heating device, and FIG. 4 is a voltage waveform diagram during magnetro oscillation. In the figure, (1) is a commercial electricity J and +2+ is a converter. (5) High frequency transformer (91 is a semiconductor switch, T
l21 is invar-j, α is magnetron, (+
5a) is the filament, side is the detection means, a? ) is a semiconductor switch control means. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A converter that converts commercial power to DC power; an inverter connected to this converter and having a semiconductor switch; a high-frequency transformer energized by the inverter to supply high-voltage pulses to the magnetron and heater power to the magnetron filament; A high-frequency heating device comprising semiconductor switch control means for suppressing high-voltage pulses by shortening the conduction time of the semiconductor switch until the magnetron oscillates.