JP2516413B2 - Power supply for high frequency heater - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in a power supply device for a high-frequency heater such as a microwave oven.

2. Description of the Related Art Conventionally, a power supply device for a microwave oven is composed of a power supply circuit mainly composed of a ferroresonant transformer 32 as shown in FIG.

The magnetron 17 normally has an operating voltage of 3 to 4 KV, and the housing 22 is always grounded to the earth because it is dangerous.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the configuration of the conventional power supply device for the microwave oven, the high voltage winding 23
When the ground wire 33 is grounded when the primary winding 11 and the primary winding 11 are in contact with each other due to some trouble (for example, when the point P and the point Q are in contact with each other), the housing 22 is kept at the ground potential, and the fuse 2 is It is safe because it melts down.

However, if the ground wire 33 is not provided, especially in a power supply situation where one side of the pole transformer is grounded to the ground, the housings 21 and 22 will be about 2 KV when touched at the above-mentioned location.
It is very dangerous for humans to touch this.

Therefore, it is necessary to ground the housings 21 and 22 to the ground in order to guarantee the safety and use the microwave oven in case of emergency.

However, the grounding work is troublesome and very inconvenient when the microwave oven is moved.

Means for Solving the Problems The present invention provides a power supply unit that receives power from a commercial power supply or a battery, a frequency converter that converts the power of the power supply unit into high frequency power, and an output of the frequency converter and a booster. A step-up transformer and a magnetron energized by the output of the step-up transformer are provided, and a shielding member made of a U-shaped metal conductor is arranged between the primary winding and the secondary winding of the step-up transformer. A metal conductor is connected to the step-up transformer or the case.

Effect According to the present invention, since the shielding member having the same potential as the casing is provided between the primary winding and the secondary winding of the step-up transformer according to the above configuration, the high voltage circuit on the secondary side has the same potential space as the casing. Since it has a structure that is closed in, safety can be secured. Also basically U
Since it is a non-magnetic metal body in the shape of a letter, there is no occurrence of loop current,
Moreover, the currents flowing in the two U-shaped opposite sides cancel each other and take a so-called non-induction form, so that the magnetic loss can be reduced.

Embodiment FIG. 1 shows an embodiment of a circuit diagram of a high-frequency heating device according to the present invention.

 The configuration of the present invention will be described.

In the figure, the power supply unit 18 is composed of a commercial power supply 1, a fuse 2, a diode bridge 3, an inductor 4 and a capacitor 5.
And a DC power supply is created.

The power supply is supplied to the control circuit 7 by the resistor 6, and the control circuit 7 controls the transistor 8 to, for example, 20 KHz to 1 MH.
Switching operation is performed at a high frequency of z.

Reference numeral 9 is a diode, and 10 is a resonance capacitor, which constitute a frequency converter 15 which is a resonance type inverter. Therefore, high frequency power having a frequency equal to the switching frequency of the transistor 8 is supplied to the primary winding of the step-up transformer 19, and a high voltage is generated in the secondary winding 23 magnetically coupled through the core 12.

This voltage is doubled and rectified by the capacitor 13 and the diode 14 and supplied to the magnetron 17 whose anode side is grounded to the housing case 22.

The heater winding 16 heats the cathode of the magnetron 17, so that the magnetron 17 oscillates and a radio wave output is generated.

The resonance type inverter 15 is well known to those skilled in the art and will not be described.

A metal conductor 20 is provided between the primary winding 11 and the secondary winding 23 of the step-up transformer 19, and the heater winding 16, and the shield made of the metal conductor is connected to the housing 21.

Therefore, the high voltage circuit on the output side of the high voltage winding 23 is a metal conductor.
Due to the presence of 20, the structure is confined in the shielded space having the same electric potential as the case 21.

Therefore, even if the high-voltage secondary winding 23 is dielectrically broken, the 1-character winding 11 and the secondary winding 23 do not directly contact with each other.

FIG. 2 is a sectional view showing the structure of the step-up transformer 19.
The same reference numerals as those in FIG. 1 are components corresponding to the same parts and portions.

The shielding member made of the metal conductor 20 is attached to the bobbin 24 of the primary winding, and is attached via the distance d ₁ from the bobbin 25 of the secondary winding. The metal conductor 20 is connected to the housing 21 by the lead wire 28.
It is connected to the. The two cores 12 separated by the spacer 26 are fixed by a stopper 27, and the stopper is also connected to the housing 21 by a lead wire 28.

 FIG. 3 shows a configuration example of the shielding member.

 FIG. 4 is a sectional view taken along the line AA of FIG.

A non-magnetic metal body 20 of copper or aluminum is covered with an insulator 30. The metal body 20 is basically U-shaped with two conductors facing each other in substantially parallel, one end being open and the other end being short-circuited,
Two such metal bodies 20 are concentrically arranged,
Each metal body 20 is provided with a grounding connection terminal 31.

The maximum distance d ₂ between the metal conductors is smaller than the distance d ₁ between the bobbins.

The configuration described above is an example, and a U-shaped metal conductor
It is also possible to arrange a large number of 20 in the radial direction rather than in the circumferential direction so that the U-shaped short-circuited ends are continuous in the circumferential direction and a part of which is cut away, as shown in FIG. It is also possible to stack a plurality of shielding members as shown in FIG.

FIG. 6 shows a conventional power supply device, and the same components as those in FIG. 1 are designated by the same reference numerals.

Further, the lead wire 28 connected to the housing case 21 is provided with an abnormal current detecting means in the middle thereof, or the housing case 21 is once formed of a small metal plate, and the housing 22 is connected by a lead wire. The invention includes examples.

As mentioned above, since the metal conductor basically has a U-shape, currents in directions canceling each other flow between two parallel lines,
The current that flows substantially in a loop is small, and the loss due to the heat generation of the metal body due to the magnetic flux between the primary and secondary windings and the operation of the transformer are not adversely affected.

EFFECTS OF THE INVENTION As described above, according to the present invention, the high-voltage part on the output side of the frequency converter can be confined in the shielding space having the same potential as the case by the shielding member made of a metal conductor, which is safe. A high-frequency heater that does not require grounding work can be realized. Further, since the step-up transformer is smaller than the conventional transformer, a highly practical effect that the shielding member can be made small is produced.

[Brief description of drawings]

FIG. 1 is an embodiment of a circuit diagram of a high-frequency heating device of the present invention,
FIG. 2 is a sectional view of a step-up transformer of the same apparatus, FIG. 3, and FIG.
FIG. 5 is a plan view of the shielding member of the present invention and FIG. 3 is a sectional view taken along the line AA, FIG. 5 is a plan view of another embodiment of the shielding member, and FIG. 6 is a circuit diagram of a conventional high-frequency heating device. . 1: Commercial power supply, 2: Fuse, 3: Diode bridge, 4: Inductance, 5: Capacitor, 6: Resistor, 7: Control circuit,
8: Transistor, 9: Diode, 10: Resonant capacitor, 1
1: 1 primary winding, 12: step-up transformer core, 13: capacitor, 14:
Diode, 15: Resonant inverter, 16: Heater winding, 1
7: Magnetron, 18: Power supply section, 19: Step-up transformer, 20: Metal conductor, 21: Case, 23: Secondary winding, 24: Primary winding bobbin, 2
5: Secondary winding bobbin, 26: Spacer, 27: Clasp, 28, 29:
Lead wire, 30: insulator, 31: terminal.

Claims (1)

(57) [Claims] 1. A power supply unit that receives power from a commercial power supply or a battery, a frequency converter that converts the power of the power supply unit into high-frequency power, a booster transformer that boosts the output of the frequency converter, and the booster. A magnetron energized by the output of the transformer is provided, and a shielding member made of a U-shaped metal conductor is arranged between the primary winding and the secondary winding of the step-up transformer, and the metal conductor is connected to the step-up transformer. Or a power supply device for a high-frequency heater configured by being connected to a housing.