JPS5856239B2 - High frequency heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvement of a high-frequency heating device, and its first purpose is to convert commercial frequency power into high-frequency (for example, 20 KH2) power using a frequency converter and then boost the power. By doing so, the step-up transformer can be made smaller and lighter, and the entire high-frequency heater can be used to save resources, thereby providing a low-cost, compact, and easy-to-use high-frequency heating device.

The second purpose is to use the magnetron itself as a rectifying means to further reduce costs and improve reliability.

Figure 1 shows a conventional example, in which 1 and 1' are commercial power supply terminals, 2
3 is a leakage transformer, 3 is a capacitor, and 4 is a rectifier, to which high-voltage power and heater heating power are supplied to the magnetron 5.

Capacitors 14a, 14b, inductors 13a, 13b
constitutes a filter A for reducing the level of unnecessary radiation of the magnetron, and these are attached to the cathode part of the magnetron 5 and built into the magnetron. includes filter A.

Since the leakage transformer 2 is a so-called iron-resonant type constant voltage transformer, it has a large leakage inductance and is therefore extremely large and heavy, making it difficult to handle in the overall design of the high-frequency heater.・It was also inconvenient to transport the high-frequency heater.

The present invention has been made in view of these points, and FIG. 2 shows a circuit of one embodiment thereof.

In FIG. 2, the same reference numerals as in FIG. 1 are equivalent.

Capacitors 6a, 6b, 5c, 6d. 6e, choke coils 7a and 7b constitute a filter section C,
The purpose of this L-ru is to prevent the generation of terminal noise from the magnetron's power supply to the commercial power supply, and to prevent unnecessary radiation through the wiring.

Note that the capacitors 5d and 6e are conventional capacitors.

8 is a rectifier, 9 is a capacitor, and a unidirectional power source is formed.

10 is a step-up transformer, and 11 is a transistor. When the transistor 11 is turned on by the control circuit 12 and a current force of 1 flows through the primary winding W1 of the step-up transformer, the high-voltage secondary winding W2 is forward-biased to the magnetron. A high pressure car is generated.

Further, a voltage is generated in the low voltage secondary winding W3 so as to reverse bias the diode 15.

When the transistor 11 is turned off, the energy stored in the winding is supplied to the heater for heating the cathode of the magnetron, and the heater is heated.

Therefore, when the cathode is sufficiently heated, the magnetron 5 oscillates when the transistor 11 is on.

In other words, when the transistor of the magnetron 5 is off,
Since it works as a rectifier, it is possible to supply power to the heater.

That is, the output of the low voltage secondary winding W3 is the output of the diode 15.
Since L is supplied to the cathode heater of the magnetron 5 through L, it operates as a so-called flyback transformer, and when the cathode heats up,
Since the energy stored in W2 is also supplied to the heater, heating up can be accelerated.
Surge voltage at the time of cold cathode can be suppressed.

Then, when the magnetron 5 starts oscillating, it operates only with the energy stored in the low-voltage secondary winding W3, and appropriate heater power is supplied.

By the way, this magnetron houses a filter with a conventional capacitor, like the conventional L.
L.

That is, as shown in the figure, the magnetron has a built-in filter B consisting of choke coils 13a and 13b.

In order to use the magnetron 5 as a rectifier, it is necessary to have an impedance in parallel with the magnetron 5 (・
This is because L゛ or h''== is necessary.

That is, the high voltage secondary winding W2 of the step-up transformer 10 and the magnetron 5 form a single loop.
This is a necessary condition for using the magnetron as a rectifier.

In addition, since the magnetron 5 is intermediate between a so-called pulse oscillation magnetron and a continuous oscillation magnetron, its operating voltage (ebm) is lower than that of the conventional one (3
~4KV), it has a high L value.

Therefore, although the efficiency of the magnetron itself is improved, the instantaneous maximum oscillation output is much lower than that of the conventional magnetron.

This means that with the same filter as the conventional one, there is a possibility that the level of unnecessary radiation will increase.

FIG. 3 is a structural diagram of a high frequency heating device showing an embodiment of the present invention.

Note that the same symbols as in FIG. 2 are equivalent.

24 is a housing of the high frequency heating device, 23 is an oven, 5 is a magnetron body, 20 is a magnet, 21 is a radiation fin, 16
is a magnetron case, and 13a and 13b are choke coils.

10 is a step-up transformer, D is a power supply circuit section, and C is a filter, which are housed in a closed shield case 17.

The shield case 17 is sealed to the extent that it can substantially shield microwave spurious waves.
・Ru.

Also, magnetron case 16 and shield case 1
7 is electrically connected to the same potential by a shield tube 18, and is connected to the high voltage supply terminal of the magnetron (L, which is shared with the heater power supply terminal) and the step-up transformer 10.
．． This is for housing the power supply circuit section, the power supply section of the magnetron including the filter C, etc. in a substantially closed shielded space.

Of course, the purpose of the shield tube 18 is to prevent unnecessary radiation from the lead wire 25 that connects the magnetron 5 and the power supply section of the magnetron, so the coaxial cable, a certain L, may be made of tubular metal steel, etc., and is substantially shielded. All you have to do is create a space.

In this way, by providing the filter capacitors 6d, 6e, etc. on the low-voltage side of the power supply circuit of the high-frequency heating device to connect the low-voltage circuit and the case 16 of the magnetron, it is possible to eliminate the L-type capacitors that were conventionally provided between the anode and cathode of the magnetron. By removing 14a and 14b, it becomes possible to realize the function of the magnetron 5 as a current collector and to prevent unnecessary radiation.

22 is a cooling fan, and 19 is a power supply lead wire.

As described above, according to the present invention, since a frequency converter is used to convert the high-frequency power into high-frequency power and boost the voltage, the step-up transformer can be made smaller, lighter, and lower in cost, and its output level can also be lowered.
It can be controlled extremely easily by controlling the on/off time ratio of the transistor, making it extremely easy to use and convenient.

Further, by supplying the low voltage secondary winding of the step-up transformer to the cathode heater via the rectifier, the magnetron cathode heat-up can be accelerated and the generation of surge voltage in the high voltage transformer can be suppressed.

In particular, by providing a filter capacitor between the low voltage circuit and the magnetron case, the filter capacitor provided between the anode and cathode of the magnetron can be removed and the magnetron can have a rectifier function. , and if unnecessary radiation can be suppressed, an L-effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, FIG. 2 is a circuit diagram of a high frequency heating device showing an embodiment of the present invention, and FIG. 3 is a sectional view of the same high frequency heating device. 5...Macnetron, 6a-6e...
Capacitor, 8... Rectifier, 9... Capacitor, 10... Step-up transformer 12...
...Control circuit.

Claims (1)

[Claims] 1. A magnetron power supply device is configured by connecting a rectifying means for converting a commercial power source to a unidirectional power source, and a series circuit of a primary winding of a step-up transformer and a switching element to the unidirectional power source, and the high voltage of the step-up transformer is The output of the secondary winding is supplied between the anode and cathode of the magnetron, and the low voltage 2
The output of the secondary winding is supplied to the cathode heater of the magnetron via a rectifying means connected to conduct when the high voltage secondary winding has a polarity that reversely biases the magnetron. A high-frequency heating device in which a high-voltage terminal and a low-voltage circuit including the step-up transformer and switching elements are housed in a case having substantially the same potential, and a filter capacitor is provided only between the case and the low-voltage circuit.