JPS602755B2 - magnetron drive device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetron drive device for use in microwave ovens and the like.

Microwave ovens efficiently heat food and drinks using microwaves generated by a magnetron, and have become increasingly popular in recent years.

FIG. 1 shows a subordinate magnetron drive device used in the above-mentioned microwave oven.

In this figure, a commercial power supply input from a commercial power supply 1 is boosted by a high voltage transformer 2 having constant current characteristics such as a leakage transformer, and is boosted by a voltage doubler rectifier circuit consisting of a capacitor 4 and a diode 5 connected to a high voltage winding 3. The rectified signal is applied between the anode and cathode (filament) of the magnetron 6. In addition, the heater winding 7 includes a feedthrough capacitor 8,
It is connected to the filament of the magnetron 6 via a noise filter consisting of a coil 9. In this case, the capacitance of the feedthrough capacitor 8 is set to 50% so as not to become a load on the high voltage winding 3 side and to obtain a sufficient noise prevention effect.
It is normal to set it to about 1000 PF from Misaki F. By the way, if the configuration is such that the commercial power input is directly increased as described above, the high voltage transformer becomes large and the device itself becomes large and heavy, making it inconvenient to handle. Therefore, it is necessary to convert the commercial power input into a flat high frequency A high-frequency drive type magnetron drive device has been proposed that supplies high voltage V to the magnetron by boosting the voltage from It becomes a heavy load and causes inconvenience. Therefore, in the high frequency drive type, a different measure is taken instead of inserting a noise prevention capacitor on the filament side of the magnetron. Now, for the purpose of miniaturization, weight reduction, and continuous variable output, a magnetron drive device using a pulse width control transformer as shown in FIG. 2 was proposed prior to the present invention.

In this figure, a commercial power input from a commercial power source 1 is rectified by a rectifier 10, and then converted to a high frequency of approximately several tens of KHz by a converter 11, which is applied to an input winding 21 of a pulse width control transformer 20. Here, as shown in FIG. 3, the pulse width control transformer 20 has a UI type magnetic core 22 forming a main magnetic path and an EI type magnetic core 23 forming a path magnetic path, and the input winding 21 is connected to the magnetic core. The output winding 24 is commonly wound around one leg of the magnetic core 22 and the middle leg of the magnetic core 23 , and the output winding 24 is wound around the other leg of the magnetic core 22 . Further, control windings 25A and 25B are wound around both legs of the magnetic core 23, respectively, and when an input voltage is applied to the input winding 21, the voltage induced in each control winding 25A and 25B is canceled out. are connected in series to match each other. Such a pulse width control transformer 20 has a control winding 25A.
, 25B, the magnetization state of the magnetic core 23 forming the path magnetic path can be changed, and the pulse width of the voltage appearing in the output winding 24 can be controlled. There is. Now, a voltage doubler rectifier circuit consisting of a capacitor 4 and a diode 5 is connected to the output winding 24 of the pulse width control transformer 20, whereby the high voltage induced in the output winding 24 is rectified and applied to the magnetron 6. It will be done.

Note that a desired electric power is supplied to the filament of the magnetron 6 from the heater winding 31 of the heater transformer 30, and a DC control current lc of a predetermined magnitude is supplied to the control windings 25A and 25B from the control circuit 32. . According to the configuration shown in FIG. 2 above, not only can the device be made smaller and lighter, but also the microwave output of the magnetron 6 can be made continuously variable.

By the way, in the magnetron drive device shown in Fig. 2 above, the anode current flows through the magnetron 6 and oscillation starts after the filament has been sufficiently heated. During this period, the anode current does not flow much, and as a result, the output winding 24 side of the pulse width control transformer 20 is in a no-load state.

When there is no load on the output side of the pulse width control transformer, the magnetic resistance of the main magnetic path becomes small, and the presence of the path magnetic path does not affect the magnetic flux of the main magnetic path so much that the control function is lost and the input/output Since the output voltage is generated depending on the winding ratio of The object of the present invention is to provide a magnetron drive device that makes it possible to prevent abnormally high pressure without causing a problem in the oscillation operation of the magnetron.

Embodiments of the magnetron drive device according to the present invention will be described below with reference to the drawings.

In FIG. 4, a capacitor 34 having a capacitance of 4.times.1 cape F to 8 cape F is connected between the filament of the magnetron 6 and the anode.

The other configurations are the same as in the case of FIG. 2. According to the embodiment described above, during the child heating period when no anode current is flowing through the magnetron 6 immediately after the power is turned on, a small amount of current flows to the capacitor 34 side, and this capacitor 34 acts as a pseudo load.

When the small capacity capacitor 34 is lOPF, the glue actance XC is Xc=1/(C)=5.3×1(
Q) {However,: Angular frequency (2 mf, f: 3 plates), C: Capacity of the capacitor} The high voltage applied to the magnetron 6 is Eht (4 x 1 pitch) "The capacitor 3
When the dummy current flowing through 4 is lo, 10=Eht
/Xc, lo = 4 x 1 bi/(5.3 x 1 pi) (A) Ni7,5 (skin A) Also, when the small capacitance capacitor 34 is 80PF, lo is 60 skin A. Become.

On the other hand, the conduction current of the magnetron is 250 mA, and l
By setting o to 7.5 to 60 A, it is possible to sufficiently suppress the occurrence of abnormally high pressure.

Furthermore, using a capacitor as a pseudo load is also effective in preventing noise.

As a result, it is possible to prevent abnormally high voltage from occurring due to no load on the output side of the pulse width control transformer 20. Furthermore, after the magnetron 6 starts oscillating, the capacitance of the capacitor 34 is sufficiently small, so power loss can be ignored, and the magnetron 6 starts to oscillate. This does not cause any trouble to the operation of the engine 6. Now, since one end of the capacitor 34 is grounded, it is possible to change the layer to a feedthrough capacitor.

FIG. 5 shows another embodiment of the present invention using a feedthrough capacitor. In FIG. 6, the pulse width control transformer 201
The heater winding 31 of the heater transformer 30 connected in parallel
and the connection line 33A with the filament of the magnetron 6,
Through-hole capacitors 34A and 34B are inserted into 33B, respectively. Here, the sum of the capacitances of the feedthrough capacitors 34A and 348 is set to about 10 to 8 F. Note that the other configurations are the same as in the case of FIG. 2. According to the above embodiment, it is essentially the same as if a capacitor with a capacity of several 1 F is connected in parallel between the anode and cathode of the magnetron 6. During the period when no anode current flows through the magnetron 6, the feedthrough capacitor 34A. 34B acts as a pseudo load. As a result, generation of abnormally high pressure can be prevented. In addition, after the magnetron 6 starts oscillating, the feedthrough capacitors 34A and 34B
Since the capacity of the magnetron 6 is small, power loss can be ignored, and the operation of the magnetron 6 is not hindered in any way. In addition"
In each of the above embodiments, the heater transformer is provided separately from the pulse width control transformer, but the heater winding is attached to the pulse width control transformer so as to be magnetically coupled to the input winding of the pulse width control transformer. It is also applicable to the same aircraft when it is added.

As described above, according to the present invention, it is possible to obtain a magnetron drive device that can prevent abnormally high voltage from being generated on the output side of a pulse width control transformer immediately after power is turned on without causing any hindrance to the normal oscillation operation of the magnetron. . Brief explanation of the drawings Figure 1 is a circuit diagram showing a conventional magnetron drive device, Figure 2 is a circuit diagram showing a conventional magnetron drive device.
The figure is a circuit diagram showing a conventional magnetron drive device using a pulse width control transformer, FIG. 3 is a perspective view showing an example of a pulse width control transformer, and FIG. 4 is a circuit diagram showing an example of a magnetron drive device according to the present invention. FIG. 5 is a circuit diagram showing another embodiment of the present invention.

1... Commercial power supply, 2... Magnetron, 1
0... Rectifier, 11... Converter, 20...
... Pulse width control transformer, 30... Heater transformer,
31... Heater winding, 32... Control circuit, 33
A, 33B... Connection line, 34... Capacitor, 34A, 34B... Feedthrough capacitor.

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 The first magnetic core part forming the main magnetic path, the second magnetic core part forming the path magnetic path.
a magnetic core portion, an input winding commonly wound around the first and second magnetic core portions, an output winding wound around the first magnetic core portion, and an output winding wound around the second magnetic core portion. A pulse width control transformer is provided with a control winding, and is capable of controlling the pulse width of the output voltage of the output winding by changing the magnetization state of the path magnetic path by flowing a control current through the control winding. A magnetron drive device that applies a high frequency to the input winding of the magnetron and rectifies the output voltage of the output winding and applies it to the magnetron, and is connected to the output winding of the pulse width control transformer via a rectifier circuit. A magnetron drive device, characterized in that a capacitor of a small capacity of about 10PF to 80PF is provided between the filament of the magnetron and the anode, and is operated as a pseudo load for the pulse width control transformer during the magnetron preheating period.