JP3298130B2 - Inverter transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter transformer used for an inverter device for driving a fluorescent lamp.

[0002]

2. Description of the Related Art An inverter device for converting a commercial frequency into a high-frequency current has been used as an inverter for driving a fluorescent lamp or the like because of its high efficiency and light weight.

Hereinafter, an inverter device for driving a fluorescent lamp will be described with reference to FIG. In the figure, 1 is a commercial frequency power supply, 2 is a rectifying diode, 3 is a smoothing capacitor, 4
Is an oscillation control circuit, 5 is a resonance capacitor, 6 is a switching transistor, 7 is an inverter transformer, and has a primary coil 8, a secondary coil 9, a heater coil 10
It has. 11 is a fluorescent tube whose heater is connected to the secondary coil 9 and connected to the heater coil 10, 12 is a detection circuit for detecting a voltage generated at both ends of the heater coil 10, and 13 is an output of the detection circuit 12. It is a delay circuit for delaying and is composed of a time constant circuit using a capacitor and a resistor. 14 is a reference voltage source, 15 is a comparison circuit for comparing the output voltage of the delay circuit 13 with the reference voltage of the reference voltage source 14, and 16 is a light receiving unit which receives the light after converting the output voltage of the comparison circuit 15 into light. It is an optical coupling element that converts electricity.

[0004] Next, the operation of the inverter device will be described.
And smoothed by the smoothing capacitor 3. The oscillation control circuit 4 is operated by the DC voltage, and the oscillation control circuit 4 causes a driving current to flow to the base side of the switching transistor 6 at a required high frequency to perform a switching operation for turning on and off the collector side. In this way, a high-frequency alternating current is obtained, and this alternating current is
It is applied to the next coil 8. A high voltage is generated from the secondary coil 9 by applying a voltage to the primary coil 8, the generated high voltage is applied between both terminals of the fluorescent tube 11, and a current is supplied to the heater of the fluorescent tube 11 by the heater coil 10. To turn on the fluorescent tube 11.

The operation control of the heater coil 10 will be described. An AC voltage applied to the heater of the fluorescent tube 11 is detected by a detection circuit 12, and the detected voltage is applied to a delay circuit 1
3, the delay circuit 13 sends the signal delayed by the time constant circuit to the comparison circuit 15, which compares the output voltage of the delay circuit 13 with the reference voltage of the reference voltage source 14, and outputs the output voltage. Is lower than the reference voltage, the heater is maintained in a preheated state, and if higher than the reference voltage, it is sent to the optical coupling element 16. In the optical coupling element 16, the output voltage is optically converted and converted into an electric signal by the light receiving unit, and the converted electric signal is fed back to the oscillation control circuit 4 and controlled by the oscillation control circuit 4.

FIG. 5 shows the configuration of an inverter transformer used in such an inverter device. In the figure, 1
Reference numerals 7 and 18 denote E-shaped cores. The end faces of the magnetic legs at both ends are directly joined to each other, and the end faces of the central magnetic leg are joined to each other via a magnetic gap material 19. 20 is a primary coil,
21 is a secondary coil, 22 is a heater coil. In general, a fluorescent lamp inverter transformer is configured as a leakage transformer so as to have a drooping characteristic in which an output voltage decreases in accordance with an increase in load current in order to ensure stable operation. In order to function as a leakage transformer, it is necessary to provide a large magnetic gap between the end faces of the magnetic legs at the center of the E-shaped cores 17 and 18.

[0007]

However, by providing a wide magnetic gap between the end faces of the magnetic legs at the center of the E-shaped cores 17 and 18, both the inductance of the primary coil 20 and the inductance of the secondary coil 21 are reduced. I do. Therefore, it is necessary to increase the number of turns of the primary coil 20 and the secondary coil 21 by the provision of the magnetic gap member 19. In order to obtain the desired number of turns of the coil in a limited space, the wire must be made thinner. If the copper wire becomes thinner, the heat generation and heat storage by the copper wire increase, and the temperature of the transformer tends to rise.

[0008]

In order to achieve the above object, an inverter transformer according to the present invention is characterized in that an I-shaped core is joined to one end of a U-shaped core magnetic leg through a magnetic gap material, respectively. A magnetic gap is provided between the core and the core, and the I-shaped core and the other U-shaped core magnetic leg end face are directly joined to each other, so that the I-shaped core serves as a magnetic flux leakage bypass.

[0009]

With this configuration, the magnetic path through which the magnetic flux from each coil passes is a closed magnetic path, and the closed magnetic path reduces the magnetic shaft. Accordingly, a high self-inductance can be obtained for both the primary coil and the secondary coil, and the number of turns of the coil can be reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 23 and 24 are Mn-Z.
a U-shaped core made of n-ferrite;
The magnetic gap members 25 and 26 are respectively joined to the end faces of the magnetic legs 3 to form an I-shaped core 2 made of the same material as the U-shaped core 23.
7, 28 are magnetic gap members 2 joined to the U-shaped core 23.
5 and 26, and the end faces of the magnetic legs of the U-shaped core 24 are directly connected to the I-shaped cores 27 and 28, respectively.

The thickness of the magnetic gap members 25 and 26 is small and is provided to absorb variations in the individual magnetic permeability of the core. A magnetic gap 29 is formed between the I-shaped core 27 and the I-shaped core 28. I-shaped core 27, 2
8, and the magnetic gap 29 is for constituting a magnetic flux leakage bypass, and a part of the generated magnetic flux is transferred to the I-shaped core 27-.
The magnetic gap 29-I-shaped core 28 serves to return to the original source.

Reference numeral 30 denotes a bobbin mounted on one of the magnetic legs of the U-shaped core 23, and 31 denotes a bobbin 30 divided and wound.
A secondary coil, 32 is a bobbin mounted on one magnetic leg of the U-shaped core 24, 33 is a secondary coil divided and wound on the bobbin 32, 34 is a coil wound adjacent to the secondary coil 33 of the bobbin 32. This is a lined heater coil.

As shown in FIG. 2, most of the magnetic flux A generated by the primary coil 31 passes through the U-shaped cores 23 and 24, and a part of the magnetic flux B is part of the I-shaped core 27-.
It passes through the path of the magnetic gap 29-I-shaped core 28. Here, if the width of the magnetic gap 29 is changed, the degree of magnetic coupling between the primary coil 31 and the secondary coil 33 can be changed.

When the magnetic flux leakage bypass is provided, as shown in FIG. 3, a non-magnetic gap material 37 having a width equal to the width of the magnetic gap is provided beforehand between the two I-shaped cores 35 and 36. The use of the I-shaped core 38 integrated with the 37 makes it possible to easily and stably perform an assembling operation without adjusting the width of the magnetic gap.

With the above configuration, a high self-inductance can be obtained for both the primary coil and the secondary coil, the number of windings of the coil can be reduced, and the wire diameter of the winding in the same space can be increased. Heat generation and heat storage can be reduced,
An efficient inverter transformer with reduced temperature rise was constructed.

[0016]

As described above, according to the present invention, an I-shaped core serving as a magnetic flux leakage side path is sandwiched between joining surfaces of a pair of U-shaped cores.
By providing a magnetic gap in the middle of the letter-shaped core to leak magnetic flux, it is possible to realize an excellent inverter transformer capable of preventing heat generation of the coil and improving the temperature rise of the transformer.

[Brief description of the drawings]

FIG. 1 is a side view showing an inverter transformer according to an embodiment of the present invention.

FIG. 2 is a sectional view of a core of the transformer.

FIG. 3 is a side view of an I-shaped core according to another embodiment.

FIG. 4 is a circuit diagram showing a configuration of a conventional inverter device such as a fluorescent lamp.

FIG. 5 is a sectional view of a conventional inverter transformer.

[Explanation of symbols]

 23 U-shaped core 24 U-shaped core 25 Gap material 26 Gap material 27 I-shaped core 28 I-shaped core 29 Magnetic gap 30 Bobbin 31 Primary coil 32 Bobbin 33 Secondary coil 34 Heater coil 35 I-shaped core 36 I-shaped core 37 Gap material 38 I-shaped core

Claims (2)

(57) [Claims] 1. A joining one of the U-shaped core magnetic leg end each I-shaped core through a magnetic gap member respectively face, the 2
One of the forms a magnetic gap opposing surface of the I-shaped core, said the respectively other channel-shaped core magnetic leg end faces of the I-shaped core directly bonded, the magnetic flux leaking two I-shaped core forming the magnetic gap An inverter transformer characterized by being configured as a bypass. 2. The inverter transformer according to claim 1, further comprising an I-shaped core formed by bonding and integrating two I-shaped cores through a non-magnetic material magnetic gap material as a magnetic flux leakage side path.