JPS596584B2 - Single stone converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a single-stone converter, and particularly to an improvement in a magnetic flux reset circuit of an output conversion transformer.

Figure 1 shows an example of the circuit of a conventional single-stone converter.
is a semiconductor switch (hereinafter referred to as a transistor); 3 is a drive circuit for the transistor 2; 4 is a diode for output rectification; 5 is a two-terminal circuit network including a load; this two-terminal network 5 is a smoothing choke coil 51; , a capacitor 52, a load 53, a freewheel diode 54, and the like.

6 is a magnetic flux reset circuit for transformer 1, which includes a diode 61;
It is composed of a resistor 62, a condenser 63, and the like.

The operation of this circuit is such that when the transistor 2 is turned on (conducted) by the operation of the drive circuit 3, a current flows from the DC power supply E1 to the input winding 1a of the transformer 1. Along with this, the voltage generated in the output winding Ib is rectified via the rectifying diode 4 to supply direct current to the two-terminal circuit network 5. On the other hand, when the transistor 2 is OFF (non-conducting), the transformer 1
A back electromotive force is generated on the input (primary) winding side of the transformer 1, which is rectified by the diode 61 of the reset circuit 6 and charged and discharged by the resistor 62 and capacitor 63, thereby resetting the magnetic flux of the transformer 1.

However, such conventional circuits do not perform well when resetting the magnetic flux (
Since the energy stored in the capacitor 63 is discharged and consumed through the resistor 62 when the transistor is off (when the transistor is OFF), a loss occurs and the efficiency decreases, and the temperature of the entire device increases due to the loss. This not only adversely affects other parts, but also hinders miniaturization of the device. Furthermore, the magnetic flux density of the transformer (iron core) can only be used on one side (+ side) of the coercive force H on the B-H characteristic curve, and in the case of an iron core with a high residual magnetic flux density B, a gap is provided to reduce the residual magnetic flux density. It has disadvantages such as a decrease in efficiency because it is used at a reduced rate. In view of the above points, the present invention resets the magnetic flux of the transformer using a reactive current, and the magnetic flux energy of the transformer is released to the two-terminal circuit network (load side) when the transistor is turned on in the next cycle. The aim is to solve the shortcomings of the converter all at once, and to provide a compact single-stone converter that improves efficiency, reduces the number of parts, and reduces temperature rise.
The present invention will be explained in detail below using the drawings.

FIG. 2 is a circuit diagram showing an embodiment of the present invention, and the same reference numerals as in the conventional example indicate equivalent parts. That is, the present invention eliminates the conventional circuit resetting circuit 6, and instead provides a capacitor 71 at both ends of the rectifying diode 4, and also increases the capacitance of the capacitor 71 when the magnetic flux of the transformer 1 is reset (transistor The present invention is characterized by the provision of a magnetic flux set circuit 7 selected so that the discharge is completed at the final stage (0FF time of 2). This will be explained with reference to the figures.

Fig. 3 is an explanatory diagram of the operating mode and timing of the circuit of the present invention, Fig. 4 is an operation waveform diagram of each part, and Fig. 5 is a B-H diagram of the transformer.
FIG. However, now mode O (transistor 0N) timing T.

However, when the transistor 2 turns ON, a voltage is generated between both ends 66 of the output winding 16 of the transformer 1 as shown in FIG.
This is rectified by a rectifier diode 4 and fed to a two-terminal circuit network 5. Mode 1 (reset part 1) timing t1
When the transistor 2 turns 0FF, the current due to the magnetic energy (back electromotive force) of the transformer 1 first flows through the path of the transformer output winding terminal 5 → the two-terminal circuit network 5 → point [with] → the capacitor 71 → the terminal G, and the current flows to the capacitor 71. to charge.

(However, this current is determined by the inductance L of the input winding 1a of the transformer 1 and the capacitance C<7 of the capacitor 71)L
Flows due to free vibration due to C. ) Mode 2 (Reset Part 2) At timing T2, the capacitor 71 is discharged, and as in mode 1, a discharge current flows in the opposite path to mode 1 due to free vibration.

(See figure 4, opening and c). Mode 3 (transformer potential inversion)
In mode 2, the discharge of the capacitor 71 is completed, and at timing T3, the potential of the capacitor 71 is reversed (the left side of the capacitor 71 becomes potential (4)), and the voltage is applied to the thread of the rectifier diode 4. When the shold level is reached, the rectifier diode 4 becomes conductive and continues to flow the magnetic energy of the transformer 1 to the two-terminal network 5.

(Note that in mode 3, the magnetic flux is set for the transformer (iron core), but the voltage-time product is small and the change in magnetic flux is small.) Mode 4 (transistor 0N) If transistor 2 is 0N at timing T4, it is the same as mode O. The power from the power source E is then fed to the two-terminal network 5.

At this time, the voltage of the output winding 1b of the transformer 1 becomes a voltage corresponding to the input/output turns ratio of the power source E1, and the magnetic energy stored in the transformer 1 is released to the load side in mode 3 described above. This energy release continues until the coercive force H of the transformer 1 becomes zero T5. FIG. 5B shows the B-H characteristics of the transformer 1 in modes O to 4, and T in the figure.

-T4 indicates the timing of each mode, and T5 indicates the time when the holding force H becomes zero. That is, according to the present invention, the voltage-time product when the magnetic flux of the transformer 1 is set (mode O or 4 and mode 3) and the voltage-time product when the magnetic flux is set (modes 1 and 2) operate equally, so that the magnetic flux of the transformer is During this time, the coercive force H
Can be used on the (4) side and ←1st territory. Figure 5A is a B-H characteristic diagram of transformer 1 in the conventional circuit, and as is clear from the drawing, in the conventional circuit shown in Figure 1, the coercive force H of transformer 1 is on the (4) side. Only available.

As described above, according to the present invention, a magnetic flux setting circuit consisting of a capacitor whose capacitance is selected such that discharge is completed when the semiconductor switch is OFF is connected to both ends of the rectifier diode, and a two-terminal circuit is established when the semiconductor switch is OFF. The present invention is constructed so that the magnetic flux setting current of the transformer is applied through the network, and (1) a resistor is not used in the magnetic flux setting circuit, so a highly efficient converter with nearly zero loss can be provided.

(2) Since the number of parts is reduced and loss is reduced, temperature rise is reduced, and the device (unit) can be made smaller and more economical.

(3) Since the magnetic flux density region of the transformer (iron core) is used in both the (G) side and (D) side, there is a large margin up to 1 saturation magnetic flux density, and the magnetic flux density can be designed to be high. The transformer can be made smaller.

@Compared to the conventional circuit, the coercive force H is shifted to (g) and (c), so the current when the transistor is switched 0N and 0FF decreases correspondingly to the shift, improving efficiency.

◎ In conventional circuits, when an iron core with high residual magnetic flux density is used, a core gap is provided to increase the core excitation current, which increases the loss of the magnetic flux setting circuit, but according to the present invention, the loss in the magnetic flux setting circuit increases. This is not necessary and there is no loss.

O If the same magnetic flux density is used as in the conventional circuit, the hysteresis loss of the transformer (iron core) will be reduced. (4) When a rectifying diode requires a surge suppressing capacitor and a resistor, the capacitor 71 can serve these functions. By the way, in a converter with input (DC) 48V, DC output 25V, 3A (75W), size EI4O, material HC7cl (TDK
) As a result of an experiment using a transformer with a magnetic flux density of 2300 Gauss and a driving frequency of 44.8 KH, the efficiency of the conventional circuit (.
? The efficiency and loss were 85.42% and the loss was 12.8W, but in the circuit of the present invention, the efficiency and loss were 87.41%, respectively.
% and 10.8 W, it was confirmed that the efficiency increased by about 2% and the loss decreased by 2 W (15.6%).

In contrast to the conventional circuit, the resistance value of the resistor 62 of the set circuit 6 was set to 3.83.8KΩ, and the loss due to this resistance was measured to be about 1.2W.

Therefore, 0.8 W of the above-mentioned reduced loss (2 W) can be considered to be the reduced loss region of the transformer during switching of the transistor. As is clear from the above description, the present invention can provide a highly efficient, compact, and economical converter, which has extremely large practical effects.

[Brief explanation of the drawing]

Figure 1 is a conventional circuit, Figure 2 is a circuit showing an embodiment of the present invention, Figures 3 and 4 are diagrams explaining the operation (mode, timing) of the circuit of the present invention and operation waveform diagrams of each part, Figure 5. A and B
are B- of the transformer in the conventional circuit and the circuit of the present invention, respectively.
It is an H characteristic diagram. DESCRIPTION OF SYMBOLS 1... Output conversion transformer, 1a, 1b... Input winding and output winding, 2... Semiconductor switch (transistor included) 3... Drive circuit, 4... Rectifier diode, 5
...2-terminal circuit network, 53...Load, 7...Magnetic flux set circuit, 71...Capacitor, B...Magnetic flux density, H...Coercive force.

Claims (1)

[Claims] 1 ON of the semiconductor switch connected to the input winding side of the transformer. In a single-stone converter configured to supply DC output to a two-terminal circuit network including a load via a rectifying diode connected to the output winding side of the transformer by OFF operation, when the rectifying diode Equipped with a capacitor connected to both ends, when the semiconductor switch is turned off, the 2
A single-stone converter, characterized in that a magnetic flux reset current of the transformer is circulated through a terminal circuit network, and the capacitance of the capacitor is selected so that discharging is completed when the semiconductor switch is turned off.