JPH0119381Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a DC
-Regarding DC converters.

Saturable reactors have been widely used as a main component of magnetic amplifiers, but recently,
A DC-DC converter using a saturable reactor as a control element for voltage stabilization or overcurrent protection has been proposed. Figure 1 shows an example of this type of DC-DC converter proposed earlier, in which a transistor Q ₁ with its collector connected to the input winding N ₁ of the main transformer T ₁ is connected to the input terminal b. It is forcibly turned on and off by a square wave signal, and the DC input input from DC power supply E ₁ between input terminals a and c is switched, and the switching output is connected to the transformer.
It is taken out to the output winding _N2 side of _T1 , converted to direct current by the output circuit 1, and supplied to the load RL as a direct current output _E0 via output terminals d and e.

Furthermore, an output control circuit 2 is connected between the output circuit 1 and the transistor _Q1 for stabilizing the output voltage or protecting against overcurrent. The output control circuit 2 includes a saturable reactor T ₂ and an output detection circuit 3. Saturable reactor T ₂
has at least two windings N ₃ , N ₄ , winding N ₃
is the resistor that forms the base circuit of transistor _Q1
It is connected between the connection point of R ₁ and the resistor R ₂ and the emitter side of the transistor Q ₁ , and the winding N ₄ is connected to the output side of the detection circuit 3 via the diode D ₁ .

In the above circuit, when a rectangular wave signal with on time = period T is input to the input terminal b, the on time of the transistor _Q1 is determined by the saturation time of the saturable reactor T2, and the on time of the transistor _Q1 is determined by the saturation time of the saturable reactor T2. The output voltage E ₀ appearing at is controlled. Therefore, a bias winding N ₄ is provided in the saturable reactor T ₂ ,
The current If flowing through the winding N ₄ is increased or decreased according to the rise and fall of the output voltage E ₀ by the detection circuit 3, thereby controlling the saturation timing of the saturable reactor T ₂ and stabilizing the output voltage E ₀ at a constant value. It is something that makes you

The saturable reactor T ₂ is constructed by winding wires N ₃ and N ₄ around an annular core 4 as shown in FIG. 2. In this type of DC-DC converter, In order to increase the circuit packaging density and reduce the size, the outer diameter A of the annular core 4 was set to within 15 mm at maximum.

However, conventional DC using saturable reactor
– In a DC converter, the turn of transistor _Q1 . off. The speed was not sufficiently increased, and losses tended to increase.

The present invention eliminates the above-mentioned drawbacks and sharpens the shoulder characteristics of the B-H curve of the saturable reactor, thereby improving the turn of the transistor. on. The purpose is to provide a high-performance DC-DC converter with high speed, good switching characteristics, and low loss.

To achieve the above object, the present invention includes a transformer, a transistor connected to an input winding of the transformer and input through the input winding to switch a DC input, and a transistor connected to the output winding of the transformer to switch a DC input. a circuit that converts a switching output induced in the output winding into direct current and outputs the DC; a saturable reactor having at least two windings and one of the windings connected to the base circuit of the transistor;
A current flowing through the other winding in response to a current flowing through one of the windings of this saturable reactor,
and a circuit that controls according to the DC output signal.
In the DC-DC converter, the saturable reactor has an outer diameter A of 15 mm or less, and 0.6≦, where A is an outer diameter and B is an inner diameter.
It is characterized by having an annular core that satisfies the condition of B/A.

In the DC-DC converter shown in FIG. 1, as described above, the current If flowing through the bias winding _N4 of the saturable reactor _T2 is adjusted according to the rise and fall of the output voltage _E0 by the detection circuit 3. Increase or decrease;
This controls the saturation timing of the saturable reactor T ₂ and stabilizes the output voltage E ₀ at a constant value. Therefore, in order to quickly turn off the transistor _Q1 , the saturable reactor _T2 should have a shoulder characteristic in the B-H curve, that is, a change in the boundary portion from the unsaturated region to the saturated region that is as sharp as possible. It is desirable to use it.

However, in the saturable reactor _T2 used in conventional DC-DC converters, the outer diameter A of the annular core 4 is within 15 mm at most, and the ratio of outer diameter A to outer diameter B (B/A) is 0.5 or less. It was common practice to limit the dimension of the inner diameter B to ensure mechanical strength, so that the wall thickness (A-B)/2 of the annular core 4 becomes thicker and the annular core 4 becomes saturated. It was found that the shoulder characteristics of the B-H curve became duller as the time until the end of the turn became longer, making it difficult to quickly turn off the transistor _Q1 .

Therefore, in the present invention, as shown in FIG. 2, in an annular core 4 whose maximum outer diameter A is 15 mm or less, the inner diameter B is determined so that 0.6≦B/A. With such a structure, the wall thickness (A-B)/2 of the annular core 4 is thinner than before, so when the annular core 4 is used to configure a saturable reactor, the annular core 4 is placed on the inner diameter side. From this point onward, magnetic saturation rapidly occurs toward the outer diameter side. Therefore, the shoulder characteristic in the B-H curve becomes sharp, and the turn. off. It is possible to provide a high-performance DC-DC converter with increased speed, good switching characteristics, and low loss.

Moreover, since the outer diameter of the annular core 4 is 15 mm or less, it is possible to cope with higher circuit packaging density and miniaturization.

Since the annular core 4 is magnetically saturated from the inner diameter side toward the outer diameter side, the thinner the wall thickness (A-B)/2, the faster the magnetic saturation occurs, and the shoulder characteristics of the B-H curve are improved. However, if it is made too thin, mechanical strength cannot be ensured. Therefore, in order to improve shoulder characteristics while ensuring a certain degree of mechanical strength,
From a practical standpoint, it is reasonable to set a lower limit to the wall thickness of the annular core 4, that is, the ratio (B/A) between the outer diameter dimension A and the inner diameter dimension B. From a practical point of view, B/
It is appropriate to set it within the range of A≧0.6.

Further, as shown in FIG. 3, when an annular body 5 made of a non-magnetic material such as plastic is fitted into the inner diameter of the annular core 4, the annular body 5 serves as a reinforcing body, so the annular core 4 can be thinned. Convenient for shaping.
In the case of this embodiment, the leakage magnetic flux increases slightly due to the provision of the annular body 5, but this does not affect the characteristics.

FIG. 4 shows data for demonstrating the effectiveness of the present invention. In the figure, the horizontal axis represents the magnetic field H (Oe), and the vertical axis represents the magnetic flux B (Gauss). curve
_L1 is a BH curve of the saturable reactor according to the present invention with an outer diameter of 6 mm, an inner diameter of 4.2 mm, and B/A=0.7.

As is clear from this figure, the B-H curve L ₁ of the saturable reactor according to the present invention is different from the conventional curve L ₂
The shoulder characteristics (part A in the figure) are sharper compared to .

As described above, the present invention includes a transformer, a transistor connected to the input winding of the transformer and switching the DC input through the input winding, and a transistor connected to the output winding of the transformer. a circuit that converts the switching output induced in the output winding into direct current and outputs it; a saturable reactor having at least two windings and connecting one of the windings to the base circuit of the transistor; A DC-DC converter comprising: a circuit that controls, in response to a current flowing through one of the windings of a saturable reactor, a current flowing through the other of the windings in accordance with a DC output signal, the saturable reactor The reactor is characterized by having an annular core whose outer diameter A is 15 mm or less and satisfies the condition of 0.6≦B/A, where A is the outer diameter and B is the inner diameter. The shoulder characteristics of the B-H curve of the saturation reactor are sharpened, and the turn of the transistor is improved. off. It is possible to provide a high-performance DC-DC converter with increased speed, good switching characteristics, and low loss.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a DC-DC converter using a saturable reactor, Figure 2 is a plan view of the annular core that constitutes the saturable reactor, and Figure 3 is a DC-DC converter used in the present invention. FIG. 4 is a plan view of the annular core of the saturable reactor according to the present invention.
It is a BH curve diagram of a saturable reactor used for a DC-DC converter. 1... Output circuit, 2... Output control circuit, 3...
Detection circuit, 4... Annular core, T ₁ ... Transformer, N ₁
...Input winding, _N2 ...Output winding, T2 _... Saturable reactor, A...Outer diameter dimension, B...Inner diameter dimension.

Claims (1)

[Claims for Utility Model Registration] (1) A transformer, a transistor connected to an input winding of the transformer for switching a DC input input through the input winding, and a transistor connected to the output winding of the transformer for switching a DC input input through the input winding. a circuit that converts a switching output induced in the output winding into direct current and outputs the DC; a saturable reactor having at least two windings and one of the windings connected to the base circuit of the transistor; A DC-DC converter comprising: a circuit that controls a current flowing through one of the windings of the saturable reactor in response to a current flowing through the other of the windings in accordance with a DC output signal; The saturation reactor is a DC characterized by having an annular core whose outer diameter A is 15 mm or less and satisfies the condition of 0.6≦B/A, where A is the outer diameter and B is the inner diameter. -DC converter. (2) The DC-DC according to claim 1, wherein the annular core has an annular body made of a non-magnetic material fitted into its inner diameter.
converter.