JPS61259511A - Pulse transformer - Google Patents

Abstract

PURPOSE:To inexpensively manufacture a pulse transformer with less irregularity of inductance by securing a magnetic permeable material interposed to regulate the inductance on the opposed surface of the first and second cores to any of two cores or coil bobbins. CONSTITUTION:A core is composed by opposing the first core such as an E- shaped core 2 and the second core such as an I-shaped core 3, and coils 7, 8, 9 wound on a coil bottin 6 are mounted on the core 1. The material of the bottin 6 employs a magnetic permeable material. The bobbin 6 has a coolar 6a at one side, and the collar 6a is interposed as an inductance regulating magnetic permeable material in a gap (t) between the opposing surfaces of the cores 2 and 3. The coils 7-9 are wound on the outer periphery of the cylindrical portion 6b of the bobbin 6, and the core at the center of the core 2 is inserted into the portion 6b. Thus, the mean magnetic path length and the magnetic permeability can be equalized to suppress the irregular inductance of a transformer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pulse transformer used in switching regulators and the like.

(Prior Art) Generally, pulse transformers used in switching regulators and the like have a problem in that the output fluctuates greatly due to the influence of the inductance of the transformer. This concept will be explained below using FIG. □ Figure 8 shows the AC-
The circuit of the DC converter is shown, and the primary winding of the oscillating pulse transformer T (
Ll), an oscillation transistor Q is connected, and further,
A load is connected to the secondary winding (L2) of this oscillating pulse transformer T via an output rectifier diode D.
The other end of the base winding (]-3) of the oscillation pulse transformer T, one end of which is connected to the connection point of the oscillation starting resistor R1 and the oscillation capacitor C2, is connected to the base of the oscillation transistors 1 to Q. has been done. Incidentally, C1 is a noise prevention winding sensor, and the points shown on each winding of oscillation pulse 1 to lance T indicate the winding start polarity of the transformer.

To explain the operation of this circuit, the AC power supply AC is rectified by the rectifier bridge 1, and base current is supplied to the transistors 1 to Q through the oscillation starting resistor R1, and the transistors 1 to Q are turned on. And this 1 ~ Ranjistor Q
is on, the pulse 1 to the primary winding of lance T (L
Energy is stored in L), and when transistors Q1 to Q are turned off, the energy is induced in the secondary winding (L2) and is further discharged through diode D to the load.

The pulse transformer T is
The voltage applied to the primary winding (Ll) of the
If the inductance of l) is 1-1, then the current I flowing through transistor 0 is. is Io−(F+ /L+)t
・−・=−= (1) Current I according to this formula. will continue to increase.

The current amplification factor of transistor Q is. If so, I.

- IB Further increases, the base current becomes insufficient, and transistors 1 to Q are turned off. While the transistor Q is on, current flows through the diode D to the load. Eo is the voltage induced in the secondary winding, and I2 is the peak value of the current flowing in the secondary winding. Note that in equation (1) (21) above, the current at time t is expressed as a function.

When the transistor Q transitions from on to off, the law of ampere turns holds true in the pulse transformer T, so 1 = (N+ /N2) I = (N1
/N2)2p 1p (E1/L+)Too-・----(3) However, N
1 is the number of turns in the primary winding, N2 is the number of turns in the secondary winding,
I4) indicates the time that transistor Q is on. When the current To flowing through the load has finished flowing, the base currents of transistors 1 to Q are supplied again from the oscillation starting resistor R1, and the above operation is repeated.

Io=(1/2)I2p(To,,/T)=(1/2)
(N1 /N2) (E1/L1) Ton”of, (1
/T> ・・・・・・・・・ (4) From the above formula (2), To, [-(shi2/Eo)I2.7 (L2 /
EO)(N1/'N2)(E1/Lt)Ton Substituting this into equation (4), 1o = (1/2)((N1/N2)(El/
L1) Ton) 2 (L2 /EO) (1/T) =・
・-(5) From this equation (5), the output current Io is from pulse 1 to
Since it is affected by the inductance of the lance T, if this inductance 11.12 is not adjusted to a constant value, the output will fluctuate greatly.

Here, a conventional example of the above-mentioned pulse transformer is shown in FIG. In this example, an iron core is constructed by butting an I-type core 3 against an E-type core 2, a coil 4 is wound around the E-type p-ar 2, and a gap 5 between the E-type core 2 and I-type core 3 is Gap paper 5' is inserted. The reason for inserting this gap paper 5' is as follows.

Now, assuming that coil 4 is wound N times around the core,
The inductance L is L-(4π/10)(AN2μ/ρ)×10” [Henry] ・・・・・・・・・(7) However,
ρ is the average magnetic path length, A is the cross-sectional area, and μ is the magnetic permeability.Actually, there is a gap between the butting surfaces of the E-shaped core 2 and the ■-shaped core 3 due to manufacturing errors. Inductance varies greatly depending on the size. In order to suppress this variation in inductance, as described above, eight films of gap paper 5' are inserted into the lug 5 of the gear 11 to keep the distance of the gap 5 constant.

However, the thickness of this gap paper 5' was conventionally 10μ.
Since it is quite thin, with a thickness of about 100 μm to 100 μm,
One aspect of manufacturing was extremely poor workability, which was a major obstacle to reducing costs.

(Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and it is possible to easily adjust the gap between the butting V surfaces of the iron core, that is, adjust the inductance, and therefore, the ease of assembly is improved. The purpose of the present invention is to provide a pulse transformer that is good and can be manufactured at low cost.

(Structure of the Invention) In the present invention, an iron core is constructed by butting a first] and a second], and a coil wound around a coil bobbin is attached to one or both of the above]. In the pulse transformer, a 'fi magnetic bamboo material for inductance adjustment is interposed between the abutting surfaces of the first core and the second core, and this permeable material is interposed between the first core and the second core. Or it is fixed to one of the coil bobbins.

With this configuration, it is possible to easily interpose a magnetically permeable material on the abutting surfaces of the iron core, resulting in good workability during assembly.

(Embodiment) FIGS. 1 to 3 show an embodiment of the present invention, and FIG. 1 is a sectional view thereof, in which a first core, e.g., an E-shaped core 2, and a second core, e.g. An iron core is formed by the butt with the core 3, and a coil 7.8.9 wound around a coil bobbin 6 is wound around one of the E-shaped cores 2 in MW. The material of this bobbin 6 is a magnetically permeable material.

One side of this bobbin 6 has a flange 6a@right side, and this flange 6
A is interposed in the gap 1 between the abutting surfaces of the E-shaped core 2 and the I-shaped core 3 as a magnetically permeable material for adjusting inductance.

Figure 2 is a top view with ■-shaped core 3 removed;
The figure is a perspective view of the coil bobbin 6.
The coils 7, 8°9 are wrapped around the outer periphery of the cylindrical portion 6b,
The center core of the E-shaped core 2 is inserted into the cylindrical portion 6b. As in this embodiment, by keeping the abutting surfaces of the E-shaped core 2 and the I-shaped core 3 constant at the thickness t of the flange 6a of the coil-bobbin 6 made of a magnetically permeable material, the above-mentioned formula (7) can be expressed. The average magnetic path length Ω and magnetic permeability μ shown in can be made constant, and variations in the inductance of the transformer can be suppressed. Since a certain gap is formed by the flange 6a of the coil bobbin 6 in this way, the figure of the transformer is shown in comparison with the conventional structure, and in this embodiment, the flange 6a of the coil bobbin 6 is provided with a frontage 10. By numbering the openings 10, heat radiation and dispersion of heat generated by copper loss, iron loss, etc. of the core are improved, and heat generation of the core is reduced.

Further, in the above embodiment, a combination of the E-shaped core 2 and the ■-shaped core 3 was shown, but the present invention can be similarly applied even if the F-shaped cores are roughly fitted together.

In the above explanation, the coil bobbin itself is used as the magnetically permeable material for inductance adjustment interposed between the abutting surfaces of the cores. Even if the first core or the other second core is integrally molded with a magnetically permeable material, the same effect can be achieved, the inductance can be easily adjusted, and the assembly workability is improved.

Next, pulse 1 to lance of the present invention as described above are connected to the AC-O
An example applied to a C converter will be explained with reference to FIG. '□ The operating principle is the same as described above, and the base current is supplied to the oscillation transistor Q from the AC power supply rectified by the rectifier bridge 1 through the oscillation capacitor C1 and the third volume fit (L3) of the pulse transformer T. The base current flowing at this time becomes a pulse current in a differentiating circuit constituted by the capacitor C1, the inductance L3 of the third winding, and the resistor R1. This base current waveform is
As shown in the figure.

The pulse current is shown in the shaded area in FIG. Due to this pulsed current, transistor Q is overdriven and turns off all at once, and the period of time is very short. After turning on, the inductance of the third winding shortens the time it takes for the transistor Q to turn on, so the voltage V. The waveform when E is turned on is as shown in the shaded area t1 in FIG. Therefore, the loss caused by J- during this time is reduced, and the transistor Q
Thermal stress applied to is reduced. transistor Q
A diode D2 is connected between the emitter and the base of the diode D2 so that the base side is in the forward direction, and = 11- The reverse voltage generated in the inductance 13 causes the transistors 1 to Q, which were on, to be turned on. Ndensa C
2. A current is passed through the resistor R1 and the diode D2, and the forward voltage generated in the diode D2 reverse biases between the emitters and bases of the transistors Q1 to Q. By this - 1 in particular
~The transistor Q is turned off, and therefore the loss occurring during this turn-off is also reduced. That is, the turn-on and turn-off speed of the transistor Q is increased, so that the loss is reduced, and thermal stress is not applied to the transistor Q1. Also, capacitor-Ct.

C2 absorbs the noise generated during switching and also serves as a noise filter. By using the embodiment of the present invention in the above-mentioned pulse transformer, the inductance can be adjusted accurately, so that variations in output current can be almost eliminated.

(Effects of the Invention) As described above, according to the present invention, a magnetically permeable material for inductance adjustment is interposed between the abutting surfaces of the first core and the second core, and this magnetically permeable material is , which is fixed to either the second core or the coil bobbin, and with this configuration, it is possible to create a pulse transformer with extremely small variations in inductance, and it is easy to manufacture. The workability is extremely good, and it has the advantage of being able to provide a pulse transformer at a low cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a pulse transformer according to an embodiment of the present invention, FIG. 2 is a top view of the same pulse transformer, FIG. 4 is a top view corresponding to FIG. 2 according to another embodiment of the present invention, and FIG. A circuit diagram of an AC-DC converter to which the pulse transformer of the present invention is applied, FIG. 6 is a waveform diagram of the base current flowing through transistor Q in the circuit, and FIG. 7 is a waveform diagram of the base current flowing through transistor Q in the same circuit.
Figure 8 shows the waveform diagram of the collector-emitter voltage in a conventional AC-DC converter when the output current is pulse = 1.
3-Circuit diagram for explaining the effect of transformer inductance. FIG. 9 is a perspective view showing an example of the conventional pulse transformer shown in FIG. 8. 2... E-type core (first core), 3... T-type 71 core (second core), 6... Coil bobbin, 6
a...Flame part, 7,8.9...Coil, 1o...Front part, ■...Pulse transformer. Patent applicant Matsushita Electric Works Co., Ltd. = 14 −

Claims (1)

[Scope of Claims] 1. An iron core is formed by butting a first core and a second core, and a coil wound around a coil bobbin is attached to one or both of the cores. In the transformer, a magnetically permeable material for inductance adjustment is interposed between the abutting surfaces of the first core and the second core, and the magnetically permeable material is one of the first core, the second core, or the coil bobbin. A pulse transformer characterized by being fixed to. 2. The pulse transformer according to claim 1, wherein the coil bobbin is made of a magnetically permeable material, and a part of the coil bobbin is interposed between the abutting surfaces of the core. 3. The pulse transformer according to claim 1, wherein the first core is formed into an E-shape, and the second core is formed into an I-shape. 4. The pulse transformer according to claim 1, characterized in that a frontage portion is formed in the magnetically permeable material. 5. The pulse transformer according to claim 1, wherein the magnetically permeable material is integrally formed with the first core or the second core.