JPH0581990U - Magnetron drive control system - Google Patents

Abstract

(57) [Summary] [Structure] The control signal of the switching element 5 for controlling the oscillation of the high frequency output from the magnetron 7 is supplied to the primary winding voltage and the primary winding of the transformer 6 at the initial stage of oscillation of the high frequency output (when the transformer 6 is started). A pulse group (a control signal) that is generated after the oscillation of the high frequency output is stabilized is made into a transformer 6 by forming a pulse group formed by a plurality of pulses with a width equal to or larger than the maximum phase difference of the line current.
The pulse is a single pulse formed by a pulse having a constant width that is synchronized with the primary winding voltage phase. [Effect] It is possible to prevent the generation of a mode in which the switching element is turned on only for a half cycle of the commercial frequency at the initial stage of oscillation of the magnetron, reduce the power consumption in the control circuit using the direct current power supply whose total amount of current is limited, and increase the frequency of the magnetron. The output can be stabilized.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a magnetron drive control system for a cooker that heats and cooks by controlling the high frequency output oscillated from the magnetron.

[0002]

[Prior Art]

 When supplying power for oscillating a high-frequency output to the magnetron, a semiconductor device such as a triac may be used to control the power supplied to the magnetron by a microcomputer. FIG. 3 shows an example of control signals transmitted from the triac. FIG. 3 (A) shows a method of transmitting a control signal composed of a pulse having a constant width synchronized with the primary winding voltage phase of a transformer for driving a magnetron, which controls the supply of electric power in the initial stage of oscillation of the magnetron (hereinafter, referred to as method 1 ) Is a method (hereinafter, method 2) in which the control signal is always in the ON state while the power is being supplied from the initial stage of the magnetron oscillation in FIG. 3 (B), and in FIG. 3 (C) after the magnetron oscillation is stabilized. 3A and 3B respectively show a control signal similar to that shown in FIG. 3A and a control signal for increasing the pulse width (hereinafter referred to as method 3) from the initial oscillation of the magnetron until the oscillation stabilizes.

In the above-described method 1, the delay of the primary winding current of the transformer with respect to the primary winding voltage of the transformer is longer than that after the stabilization of the oscillation of the magnetron in the period from the initial stage of the oscillation of the magnetron until the stable oscillation of the magnetron. Therefore, there is a mode in which the triac is turned on for only a half cycle of the commercial frequency in the initial stage of the magnetron oscillation.

On the other hand, in method 2 or method 3 described above, the unstable operation at the initial stage of magnetron oscillation due to the delay of the primary winding current of the transformer is improved by lengthening the pulse width of the control signal. However, increasing the pulse width increases current consumption and limits the total amount of current.For example, when using a DC power supply that reduces the commercial current power supply with a resistor after rectification, it is not always an effective method. I can not say.

As disclosed in Japanese Unexamined Patent Publication No. Hei 1-163993, it is possible to prevent a mode in which the triac is turned on for only a half cycle of the commercial frequency in the initial stage of the oscillation of the magnetron according to the method 1 described above, and further to the method described above. There is one that attempts to suppress the increase in current consumption by method 2 or method 3. In this example, a microcomputer outputs and outputs the control pulse signal that fires the triac that drives the magnetron power supply and determines the output timing of the control pulse signal.

[0006]

[Problems to be solved by the device]

 However, in this example, the above-mentioned pulse signal is output at a timing delayed by a certain time from the 0 ° phase of the magnetron power supply voltage so that the TRIAC is injected at the 0 ° phase and 180 ° phase of the current, so the 0 ° phase of the current is output. The system requires a voltage phase circuit to estimate how much the power supply voltage lags the 0 ° phase by a microcomputer and a conversion circuit to a DC voltage to detect the voltage value of the commercial power supply. Although the power consumption can be saved, the circuit configuration becomes complicated.

[0007]

[Means for Solving Problems]

 The present invention has been made to solve the above-mentioned problems, and a plurality of pulse signals having a width greater than the maximum phase difference between the primary winding voltage and the primary winding current of the transformer, which is transmitted at the initial stage of the magnetron oscillation, are generated. The pulse signal generated after the stabilization of the magnetron oscillation is a single-shot pulse formed by a pulse of a constant width synchronized with the primary winding voltage phase of the transformer.

[0008]

[Action]

 As described above, the maximum phase difference between the primary winding voltage and the primary winding current of the transformer is generated at the beginning of the magnetron's oscillation by transmitting a pulse consisting of a pulse group formed by multiple pulses as the control signal at the beginning of the magnetron's oscillation. After the oscillation of the magnetron stabilizes, a single pulse with a constant width synchronized with the primary winding voltage phase of the transformer is sent as a control signal to reduce the power consumption related to the high frequency output control of the magnetron. To do.

[0009]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a basic circuit diagram of a cooking device for heating and cooking by high-frequency output oscillated from a magnetron, and FIG. 2 is a time chart of control signals transmitted from the switching element (hereinafter, triac) of the present invention. Show.

In FIG. 1, reference numeral 1 is a commercial power source, and 2 is a rectifying / smoothing circuit for stepping down a voltage obtained by rectifying / smoothing the commercial power source 1 with a resistor to produce a DC power source. Reference numeral 3 is a control circuit for inputting the DC power source produced by the rectification / smoothing circuit 2, and is connected to a microcomputer (hereinafter, microcomputer) 4 whose operation is controlled by the control circuit 3. There is. A triac 5 is driven and controlled by the microcomputer 4, and the primary winding of the magnetron driving transformer 6 is connected to the commercial power source 1 through the triac 5. The secondary winding (for high voltage) of this transformer 6 receives the anode A of the magnetron 7 which is supplied with electric power for generating a high frequency output, and the other secondary winding (for heater) of the transformer 6 Are connected to the cathodes K of the magnetron 7, respectively. Further, the microcomputer 4 generates a pulse composed of a pulse group having a width that covers the phase difference between the primary winding voltage and the primary winding voltage of the transformer 6 which is almost determined by various circuit constants constituting the magnetron drive control system and the magnetron 7. It is output as the control signal of the triac 5 described above at the initial stage of oscillation.

Next, the operation of the magnetron drive control system having the above configuration will be described. First, at the initial stage of oscillation of the high frequency output from the magnetron 7 (at the time of starting the transformer 6), as shown in FIG. 2, a pulse signal of a constant width (90 degrees delayed from the zero point of the primary winding voltage of the transformer 6 via the microcomputer 4 ( Output the control signal) and surely turn on the triac 5. (Period 1) Next, the period until the oscillation of the high frequency output from the magnetron 7 becomes stable, that is, the period until the phase difference between the primary winding voltage of the transformer 6 and the primary winding current of the transformer 6 becomes constant. , The control signal consisting of a plurality of pulses, delayed by a few msec from the zero point of the primary winding voltage of the transformer 6, is intermittently output from the triac 5 until the polarity of the primary winding current of the transformer 6 changes, and the control signal of the triac 5 is output. Prevent malfunction. (Period 2) After the high frequency output oscillated from the magnetron 7 is stabilized, a single pulse signal (control signal) of a certain width is output after delaying a few msec from the zero point of the primary winding voltage of the transformer 6 to turn on the triac 5. .. (Period 3) A similar control signal is used when the high frequency output of the magnetron 7 is turned on and off intermittently.

[0013]

[Effect of the device]

 As described above, according to the present invention, the maximum voltage of the primary winding voltage and the primary winding current of the transformer is generated at the initial stage of oscillation by oscillating the control signal composed of the pulse group with reduced pulse width at the early stage of oscillation of the magnetron. Since it can cover the problems caused by the phase difference, it prevents the generation of the mode in which the triac turns on for only a half cycle of the commercial frequency in the initial stage of the magnetron oscillation, and also synchronizes with the voltage phase of the primary winding of the transformer after the magnetron oscillation stabilizes. It is possible to reduce the power consumption in the control circuit using a DC power supply whose total current amount is limited by transmitting a single pulse signal of a certain width as the control signal, so that it is possible to reduce the power consumption related to the high frequency output control of the magnetron. It is possible to provide a magnetron drive control system that can stabilize the high frequency output of the magnetron.

[Brief description of drawings]

FIG. 1 is a basic circuit diagram of a heating cooker according to a magnetron drive control system according to an embodiment of the present invention.

FIG. 2 is a time chart of a triac control signal that operates when the magnetron outputs a high frequency.

FIG. 3 is a time chart of the same conventional triac control signal.

[Simple explanation of symbols]

 1 Commercial power supply 2 Rectification / smoothing circuit 3 Control circuit 4 Microcomputer 5 Switching element 6 Transformer 7 Magnetron

Claims (1)

[Scope of utility model registration request] 1. A rectifying / smoothing circuit (2) for rectifying / smoothing a commercial power source (1) and stepping it down with a resistor to produce a DC power source, and a control circuit for inputting the DC power source produced by the rectifying / smoothing circuit (2). (3), a microcomputer (4) whose operation is controlled by the control circuit (3), and a switching element (5) whose drive is controlled by the microcomputer (4)
And a transformer (6) for driving a magnetron, which is driven and controlled by a switching element (5), and a transformer (6).
In a magnetron drive control system composed of a magnetron (7) supplied with electric power for generating a high frequency output by the switching element (5), the primary winding voltage and the primary winding voltage of the transformer (6) Control of transmitting a control signal composed of a pulse group having a width equal to or larger than the maximum phase difference of the current at the initial stage of oscillation of the magnetron (7) and a pulse having a constant width synchronized with the primary winding voltage phase of the transformer (6) A magnetron drive control system, which transmits a signal after the oscillation of the magnetron (7) is stabilized.