JPS6131512Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a power supply device for a magnetron used in a microwave oven, etc., and proposes a power supply device that can effectively prevent leakage of microwaves with a particularly small number of parts.

Figure 2 is a general configuration diagram of the power supply circuit of a magnetron used in a microwave oven.
is converted into direct current by the rectifier stack 22, smoothed by the capacitor 23, and then passed to the frequency converter 24.
The primary winding 2 of the step-up transformer 25 is converted into a high frequency of 18KHz or more by
5a. Secondary winding 2 of step-up transformer 25
One end of 5b is connected to the anode of diode 26 and the cathode of diode 27, and the other end is connected to capacitors 28 and 2 of 0.001 to 0.01 μF.
9 to the cathode of the diode 26 and the anode of the diode 27, respectively, for voltage double rectification. The positive terminal of this voltage doubler rectifier circuit,
That is, the cathode of the diode 26 is connected to the magnetron 3.
0 anode. Step-up transformer 25
The tertiary winding 25c is about several turns,
It is used as a power source for the heater of the magnetron 30, and its both ends are connected to both ends of the cathode of the magnetron 30 via feedthrough capacitors 33 and 34 and choke coils 31 and 32, respectively, provided to prevent leakage of microwaves. The negative electrode of the voltage doubler rectifier circuit, ie, the anode of the diode 27, is connected to one end of the tertiary winding 25c.

Now, in the above circuit, feedthrough capacitors 33 and 34 that function as noise filters to prevent leakage of microwaves must be made of high withstand voltage, which requires high quality control standards and is expensive. There is a problem.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a magnetron power supply device that achieves the same microwave leakage prevention effect as the conventional one without using such a feedthrough capacitor.

The present invention will be described in detail below with reference to drawings showing embodiments thereof. FIG. 1 is a circuit diagram showing a magnetron power supply device according to the present invention (hereinafter referred to as the device of the present invention), in which a step-up transformer 5 using a ferrite core is shown.
The primary side circuit is similar to that of the conventional power supply device shown in FIG. The signal is converted to a high frequency of 18 KHz or higher and supplied to the primary winding 5a of the step-up transformer 5. The inverter circuit on the primary side has a push-pull inverter configuration similar to that in FIG. 2, but is not limited to this.

The secondary winding 5b of the step-up transformer 5 has a diode 6,
7 and 0.001 to 0.01 μF capacitors 8 and 9, which are connected to a voltage doubler rectifier circuit. That is, one end of the secondary winding 5b is connected to the anode of the diode 6 and the cathode of the diode 7, and the other end is connected to the cathode of the diode 6 and the anode of the diode 7 via capacitors 8 and 9, respectively. . The tertiary winding 5c of the step-up transformer 5 has several turns and serves as a power source for the heater of the magnetron 10. Both ends of the tertiary winding 5c are connected to both ends of the cathode of the magnetron 10 via the choke coils 11 and 12, respectively. Also, both ends of the tertiary winding 5c are connected to one end of a capacitor 13 for a noise filter. As this capacitor 13, one having sufficiently low impedance with respect to the oscillation frequency of the magnetron 10 is used.

The positive terminal of the voltage doubler rectifier circuit, that is, the diode 6
The cathode of is connected to the anode of the magnetron 10 and also grounded. Further, the negative electrode of the voltage doubler rectifier circuit, that is, the anode of the diode 7 is connected to one of the terminals of the tertiary winding 5c of the step-up transformer 5.

In the present device configured as described above, the magnetron 10 is of course excited by the output of the voltage doubler rectifier circuit, but the heater voltage of the magnetron 10 is approximately
3.2V, and the impedance of the tertiary winding 5c is as low as 1Ω or less, so as the capacitor 13,
Oscillation frequency of magnetron 10 for microwave oven
A capacitor having a sufficiently low impedance for 2.45 GHz can be used, so that the heater current does not bypass the capacitor, and the magnetron 10 can be excited without any problem.

On the other hand, when looking at preventing microwave leakage,
It is biased in a direct current manner through the capacitor 13 to double the voltage, and is grounded in an alternating current manner through the capacitors 8 and 9, thereby preventing its leakage. That is, in the present device, capacitors 8 and 9 for voltage doubler generation, together with capacitor 13, also function as a noise filter. Note that it is also possible to use a transformer other than the step-up transformer 5 as the power source for the heater of the magnetron.

In the case of the proposed device as described above, one low withstand voltage capacitor 13 is used instead of two feedthrough capacitors.
By simply using this product, it is possible to prevent microwave leakage, reduce the number of parts, make it lighter and smaller, and reduce the number of assembly steps. The present invention has excellent effects, such as making it possible to significantly reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of the present device, and FIG. 2 is a circuit diagram showing a conventional power supply device. 1... Commercial power supply, 2... Rectifier stack, 4...
Frequency converter, 5... Step-up transformer, 6, 7... Diode, 8, 9, 13... Capacitor, 10...
...Magnetron, 11, 12...Chiyoke coil.

Claims (1)

[Scope of utility model registration request] In a magnetron power supply device equipped with a step-up transformer that boosts high-frequency voltage, a voltage doubler rectifier circuit for the voltage induced in this step-up transformer, and a heater power supply connected to its cathode, the oscillation frequency is sufficiently low compared to the magnetron's oscillation frequency. has an impedance,
1. A power supply device for a magnetron, characterized in that a noise filter is constituted by a capacitor interposed between both ends of a heater power supply and a capacitor constituting the voltage doubler rectifier circuit.