JPS5828348Y2 - pulse width control transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulse width control transformer suitable for use in a stabilized power source such as a switching regulator.

The pulse width control transformer was previously proposed by the present inventor, and its basic configuration is shown in FIGS. 1 and 2.

In these figures, the magnetic core 1A that provides the main magnetic path is composed of a UI-type magnetic core, and the magnetic core 1B that provides the pass magnetic path is composed of an EI-type magnetic core, and both magnetic paths are joined at the center of the EI-type magnetic core. ing.

The primary coil 2 to which the input voltage ■1 is supplied is the main coil 2A.
It is divided into two parts: main coil 2A and auxiliary coil 2B.
is commonly wound around one leg of the magnetic core IA and the middle leg of the magnetic core 1B, and the auxiliary coil 2B is wound around the other leg of the magnetic core 1A.

Here, the reason why the primary coil 2 is divided into two is to improve the secondary side output waveform (obtain an output rectangular wave with a good rise compared to the input rectangular wave), but the number of turns of the auxiliary coil 2B is small,
When considering the basic operation, the primary coil 2 can be considered to be the main coil 2A that is substantially provided in common to the main magnetic path and the pass magnetic path.

Furthermore, a secondary coil 3 is wound around the magnetic core 1A of the main magnetic path in close contact with the auxiliary coil 2B to obtain an output voltage 2.

Furthermore, control coils 4A and 4B for controlling the magnetic saturation state of the path magnetic path are provided on both legs of the magnetic core 1B of the path magnetic path.

Here, the control coils 4A and 4B are connected in series so that when the input voltage 1 is applied to the primary coil 2, the voltages induced in the coils 4A and 4B cancel each other out.

This is to prevent fluctuations on the primary side from appearing on the control coil side.

In the above configuration, an appropriate load RL is connected to the secondary coil 3, and a rectangular wave as shown in FIG. 3A is applied as the input voltage to the primary coil 2.
Let us consider the operation when the DC control current Ic applied to the circuit is changed.

First, if the control current Ic is increased to completely bring the path magnetic path into a magnetically saturated state, it is considered that the path magnetic path does not exist equivalently as a magnetic circuit, so the output voltage V2 has the same waveform as the input voltage v1. The amplitude is determined by the primary and secondary winding ratio.

In addition, when the control current 1c is set to a value within a range in which the path magnetic path is not saturated with only the magnetic flux due to the control current Ic, the third
As shown in Figure B, at the time t1 from when the input voltage ■1 is reversed until the path magnetic path transitions from non-saturation to saturation, the input voltage ■
1, most of the magnetic flux generated in the primary coil 2 flows through the path magnetic path, so the output voltage 2 becomes substantially zero.

When the path magnetic path is saturated after time t1, this saturated state is maintained until the input voltage V1 is reversed, so the output voltage
Obtained as 2.

This time t1 can be increased or decreased depending on the value of the control current Ic.

That is, if the control current Ic is relatively large, the degree of magnetization of the path magnetic path becomes strong, and a portion of the path magnetic path becomes saturated in a short time with less magnetic flux.

Therefore, the time t1 shown in FIG. 3B becomes shorter, and the output voltage V
The pulse width of the second waveform becomes longer.

On the other hand, if the control current Ic is set low, the degree of magnetization of the path magnetic path becomes weak and magnetic saturation is difficult to occur, so it takes time for a part of the path magnetic path to become saturated.

As a result, time t1 becomes longer and the pulse width of the waveform of output voltage V2 becomes shorter.

Therefore, according to the pulse width control transformer, the control current Ic
By increasing or decreasing , the pulse width of the waveform of the output voltage (2) can be controlled with high efficiency, and the power transmitted from the input side to the load RL can be electrically controlled.

By the way, in the pulse width control transformer having the basic configuration as described above, when the load RL is in a no-load state or a state where the load RL is high impedance and is close to no-load, the pulse width of the waveform of the output voltage V2 can be well controlled by the control current Ic. This will cause inconvenience.

This conventionally uses a magnetic material such that the magnetic core 1A that forms the main magnetic path and the magnetic core 1B that forms the pulsed magnetic path have a constant magnetic permeability μ with respect to the magnetizing force H before they are saturated.
As a result, in the case of no load or a light load close to it, the magnetic resistance of the main magnetic path becomes small, and the existence of the pass magnetic path does not have much influence on the magnetic flux of the main magnetic path.

In view of the above points, the present invention provides that at least one of the magnetic core forming the main magnetic path and the magnetic core forming the pass magnetic path is made of a magnetic material whose magnetic permeability increases as the magnetizing force increases in the unsaturated region. The present invention aims to provide a pulse width control transformer that is configured to perform output voltage control well under light loads.

Embodiments of the pulse width control transformer according to the present invention will be described below with reference to the drawings.

FIG. 4 is an equivalent circuit when the operation of a pulse width control transformer is qualitatively considered. It can be considered that this is substantially equivalent to a combination of main coil 2B and saturable reactor 11 having main coil 2A inserted in series.

Now, when the inductance L□ of the saturable reactor 11 and the primary inductance of the transformer 10 are L2, the voltage Vll applied to the main coil 2A and the voltage V12 applied to the auxiliary coil 2B are each inductance L1. It is proportional to L2.

In other words, it becomes.

If the DC control current Ic supplied to the control coils 4A and 4B shown in FIG. 1 is large, the inductance L□ of the saturable reactor 11 becomes small.

Therefore, the voltage V,1 is small, the voltage V□2 is a large value, and the output power is large.

If the control current Ic is small, the inductance L1 is large, the voltage ■1□ is large, and the voltage ■1□ is small.

Therefore, the output power is small.

Now, main coil 2A, auxiliary coil 2B, secondary coil 3,
The control coils 4A, 4B have a magnetizing force H as shown in FIG.
The magnetic cores IA and IB are made of a magnetic material whose magnetic permeability .mu. increases as .mu. increases.

Therefore, the inductance L1. L2 also changes depending on the magnetizing force H, the inductance L1 increases as the voltage ■1□ increases, and the inductance L2 increases as the voltage V□2 increases.

As a result, the inductance L2 for the output current I2 of the transformer 10 is as shown in FIG. 6A.

It changes as shown in B.

This means that in a light load region where the output current is small, that is, in a light load region where the output voltage is small, the inductance L1 of the saturable reactor 11 becomes larger than the inductance L2 on the primary side of the transformer 10. This shows that controllability is improved.

Therefore, according to the above embodiment, since the magnetic core 1A forming the main magnetic path and the magnetic core 1B forming the pass magnetic path are made of magnetic materials whose magnetic permeability increases as the magnetizing force increases, the output voltage (2) and The relationship with the output current I2 is as shown by curve A in FIG.
Compared to curve B in the conventional case, voltage fluctuations in the light load region are improved.

In the above embodiment, both the magnetic core 1A, which forms the main magnetic path, and the magnetic core IB, which forms the pass magnetic path, are made of magnetic materials whose magnetic permeability increases as the magnetizing force increases. It may also be used alone.

As described above, according to the present invention, a pulse width control transformer is obtained that enables good output voltage control even in a light load region.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the pulse width control transformer, Fig. 2 is a circuit diagram showing the electrical connection, Fig. 3 is a waveform diagram for explaining the operation of the pulse width control transformer, and Fig. 4 is related to the present invention. An equivalent circuit diagram for explaining an embodiment of a pulse width control transformer, FIG. 5 is a graph showing the characteristics of the magnetic core used in the embodiment, and FIGS. 6A, B, and 7 explain the effects of the embodiment. This is a graph for IA, IB...Magnetic core, 2...Primary coil, 2A...Main coil, 2B...Auxiliary coil, 3...2 Next coil, 4A, 4B...
...Control coil, 10...Transformer, 11.
...Saturable reactor.

Claims (1)

[Scope of utility model registration request] A magnetic core having a main magnetic path and a pass magnetic path, a main primary coil provided in common to the main magnetic path and the pass magnetic path, and a main primary coil provided in the main magnetic path and connected in series to the main primary coil. In a pulse width control transformer comprising an auxiliary primary coil provided in the main magnetic path, a secondary coil provided in the main magnetic path, and a control coil provided in the path magnetic path, the main magnetic path or path magnetic path component part of the magnetic core A pulse width control transformer characterized in that at least one of the transformers is made of a magnetic material whose magnetic permeability increases as the magnetizing force increases in an unsaturated region.