JPH0487291A - Magnetron device - Google Patents

Abstract

PURPOSE:To extend the life of a magnetron by connecting a reactance element changing the heater input to the magnetron to a heater winding in the opposite direction to the control direction of the input power of the magnetron via the variable high frequency. CONSTITUTION:A reactance element 21 changing the heater input to a magnetron 20 is connected to a heater winding 13 in the opposite direction to the control direction of the input power of the magnetron 20 via the variable high frequency. The high frequency is changed low by a switching element 5 to increase the input power of the magnetron 20, for example. The reactance of the reactance element 21 is increased, the synthetic impedance of a heater circuit is increased, and the heater current is decreased. The increasing tendency of the heater temperature due to an increase of the anode current is suppressed. The input power of the magnetron 20 can be changed stably and widely, and the life of the magnetron 20 can be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Application Field) The present invention relates to a magnetron device that drives a magnetron using an inverter power source, and is used in microwave ovens and the like.

(Conventional technology) One of the factors that determines the lifespan of magnetrons used in microwave ovens and the like is the heater temperature Tf, and in order to keep the heater temperature Tf constant, the heater voltage Ef or heater current If is usually adjusted. It is being controlled to a constant value.

However, even if the heater voltage Ef or the heater current If is controlled to a constant value, the magnetron heater temperature Tf is
When the anode current 1b is varied for input power control, it changes depending on the value of the anode current 1b, and as the value of the anode current rb becomes large, as shown by the characteristic lines S and C in FIG. The heater temperature Tf becomes higher. Therefore, at the maximum input power point where the anode current 1b becomes high, the heater temperature T
If the heater current If is adjusted so that f becomes the optimum temperature, the heater current If becomes insufficient at the minimum input power point. From this, the heater current If is set such that each heater temperature Tf at the maximum input power point and the minimum input power point satisfies the maximum heater temperature TfMAX determined from the life of the magnetron and the minimum heater temperature TfMIN determined from the emission characteristics. The value of is determined to be constant.

(Problem to be solved by the invention) However, when considering the wide operating power range for magnetrons due to the demand for smaller outputs aimed at increasing the 8-power microwave oven and improving defrosting performance, etc., the value of heater current 1f Even if Tf is constant, the heater temperature Tf remains constant over the entire operating power range.
, the maximum heater temperature TfMAX and the minimum heater temperature TfM
It is difficult to suppress during IN. For this reason, it is difficult to widen the variable range of the input power to the magnetron, and even if the heater temperature Tf can satisfy the range between the maximum heater temperature Tfk4AX and the minimum heater temperature TfMIN,
Considering that the range of change in heater temperature Tf is the maximum range of change, this cannot be said to be the optimal operating range, and there is a problem that the life of the magnetron is likely to be shortened.

In addition, there is a magnetron drive power supply that uses the stability of the magnetron's anode voltage Eb to make the heater heating power constant. This causes a phenomenon in which the anode voltage Eb decreases, and the value of the heater current If also changes. Therefore, even when such a magnetron drive power source is used, there is a problem in that it is difficult to stably vary the power over a wide range.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetron device that can stably and widely vary the input power to the magnetron, and can also extend the life of the magnetron.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention supplies a high frequency wave obtained by periodically switching the input DC voltage using a switching element to the primary winding of a high frequency transformer, A voltage obtained by rectifying the secondary side high frequency generated from the secondary winding in the high frequency transformer is applied to the magnetron as an anode voltage, and a heater voltage generated from the heater winding is applied to the heater of the magnetron and converted by the switching element. A magnetron device comprising an inverter that controls the input power to the magnetron by varying the frequency of the high frequency, the magnetron being supplied to the magnetron in a direction opposite to the direction in which the input power of the magnetron is controlled by varying the frequency of the high frequency. The gist is that a reactance element for varying the heater input is connected to the heater winding.

(Function) If the frequency of the high frequency converted by the switching element is varied low, for example, and the input power to the magnetron is controlled to be large, the reactance of the reactance element increases, the combined impedance of the heater circuit increases, and the heater circuit The current becomes smaller.

This suppresses the tendency for the heater temperature to increase due to an increase in the anode current. In this way, the magnetron heater temperature becomes less dependent on changes in human power, and the width of change in heater temperature due to changes in anode current becomes smaller, making it possible to stably widen the variable range of input power. Furthermore, since the range of change in heater temperature is reduced, the life of the magnetron can be extended.

(Example) Embodiments of the present invention will be described below based on the drawings.

1 to 5 are diagrams showing one embodiment of the present invention.

This embodiment is applied to a magnetron device using a single-stone quasi-E class inverter.

First, to explain the configuration of the magnetron drive power source, the first
In the figure, 1 is a commercial AC power supply, and after the AC voltage from this commercial AC power supply 1 is rectified by a rectifier bridge 2, it is smoothed by a choke coil 3 and a smoothing capacitor 4 to obtain an input DC voltage. ing. 5 is IG
BT (1n5ulated Gate B jp
polar transformer), and the collector of the switching element 5
A freewheeling diode 6 and a resonant capacitor 7 are connected in parallel between the emitters to form a resonant switching circuit.

10 is a high frequency transformer, and is provided with a primary winding 11, a secondary winding 12, and a heater winding 13. The human-powered DC voltage is supplied to the collector of the switching element 5 via the primary winding 11 of the high-frequency transformer 10. 14 is a control circuit, and the switching element 5 is turned on and off by a drive signal from the control circuit 14, and the input DC voltage is periodically switched and converted to a high frequency. At this time, a sinusoidal resonant voltage appears between the collector and emitter of the switching element 5 constituting the resonant switching circuit, and this sinusoidal high frequency is the high frequency transformer]
It is supplied to the next winding 11. Further, a voltage doubler rectifier circuit including a voltage doubler capacitor 15 and high voltage rectifier diodes 16 and 17 is connected to the secondary winding 12. This voltage doubler rectifier circuit doubles and rectifies the high frequency voltage generated in the secondary winding 12 of the high frequency transformer 10 to obtain a DC high voltage.
The anode voltage Eb is applied between the anode 18 of zero and the cathode 19 (hereinafter, the same reference numeral as the cathode will be used even when referred to as a heater). Note that the magnetron 20 is grounded on the anode 18 side.

Further, the heater voltage generated in the heater winding 13 of the high frequency transformer 10 is supplied to the heater 19 of the magnetron 20, and a capacitance element 21 as a capacitive reactance element is connected in series to the heater winding 13.

As described above, a magnetron device including the magnetron 20 and an inverter power source for driving the magnetron is configured.

The magnetron device configured as described above changes the input power to the magnetron 20 by varying the frequency of the drive signal from the control circuit 14 to change the switching period of the switching element 5, and by varying the frequency of the high frequency wave to be converted. is now under control. FIG. 2 shows the relationship between the required range of change in the input power to the magnetron 20 and the operating frequency range. magnetron 2
The value of human power to 0 changes inversely proportional to the direction of frequency variation. That is, for example, when the frequency is lowered, the input power value changes to become larger.

This embodiment attempts to suppress the range of change in heater temperature Tf by connecting the capacitance element 21 in series to the heater winding 13 even if the input power is greatly changed within the required range by varying the frequency described above. be. Figure 3 shows
It shows a change in the combined impedance of the resistance of the heater 19 and the capacitance of the capacitance element 21 with respect to a change in frequency.

For example, if the frequency is varied low to increase the value of human power, the combined impedance becomes large, the heater current If becomes small, and the tendency of the heater temperature Tf to increase is suppressed. FIG. 4 shows the relationship between this input power and heater current If.

In this way, the heater 1
By changing the composite impedance of 9, the heater temperature Tf becomes less dependent on the change in input power (in Figure 5, the a characteristic ), heater temperature Tf
The range of change in the input power becomes smaller, making it possible to stably widen the variable range of input power.

Next, FIGS. 6 and 7 show another embodiment of the present invention.

In this embodiment, the switching circuit in the inverter power supply includes two switching elements 22 each consisting of a transistor.
．． 23 and freewheeling diodes 24, 25, etc., it is a half-bridge system. 26 and 27 are drivers for driving each switching element 22 and 23.

FIG. 7 shows the relationship between the operating frequency and the input power to the magnetron 2o. In this embodiment, there is a capacitive range in which the input power monotonically increases with increasing frequency in the operating frequency range, and an inductive range in which the input power monotonically decreases with increasing frequency in the other operating frequency range. be. Therefore, in this embodiment, in order to reduce the range of change in the heater temperature Tf with respect to changes in input power, as in the case of the previous embodiment, the actance element 28 connected in series with the heater winding 13 has a capacitive range. When the operating range is set as the operating range, an inductance element that is an inductive reactance element is used, and when the operating range is set as the inductive range, a capacitance element that is a capacitive reactance element is used.

[Effects of the Invention] As explained above, according to the present invention, a reactance element that varies the heat input to the magnetron in the opposite direction to the direction in which the input power to the magnetron is controlled by varying the high frequency is connected to the heater winding. Since the input power is connected to the magnetron, the range of change in heater temperature is reduced in response to changes in the anode current due to changes in input power, making it possible to stably vary the input power over a wide range. It is possible to achieve a longer service life.

[Brief explanation of the drawing]

1 to 5 show an embodiment of a magnetron device according to the present invention, in which FIG. 1 is a circuit diagram, and FIG. 2 is a characteristic diagram showing the relationship between operating frequency and input power to the magnetron. Figure 3 is a characteristic diagram showing changes in the combined impedance of the heater circuit with respect to changes in frequency, Figure 4 is a characteristic diagram showing changes in heater current with respect to changes in human power, and Figure 5 is a characteristic diagram showing changes in heater current with respect to changes in anode current. Fig. 6 is a circuit diagram showing another embodiment of the present invention, and Fig. 7 shows the relationship between the operating frequency and the input power to the McNetron in the embodiment of the above function. It is a characteristic diagram. 5.22.23 Niswitching completed, ]0 High frequency transformer, 11: Primary winding, 12:
Secondary winding, 13. Heater winding, 18 near nodes,
19. Heater, 20・Magnetron, 2] Capacitance element (capacitive reactance element)
, 28: Reactance element.

Claims (1)

[Claims] A voltage obtained by supplying a high frequency wave obtained by periodically switching an input DC voltage using a switching element to the primary winding of a high frequency transformer, and rectifying the secondary side high frequency wave generated from the secondary winding of the high frequency transformer. is applied to the magnetron as an anode voltage, a heater voltage generated from a heater winding is applied to the heater of the magnetron, and the inverter controls the input power to the magnetron by varying the frequency of the high frequency wave converted by the switching element. A magnetron device comprising: a reactance element connected to the heater winding to vary a heater input to the magnetron in a direction opposite to a direction in which input power to the magnetron is controlled by varying the frequency of the high frequency. A magnetron device featuring: