JP2004112991A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transformer, generating only a small loss and being high in magnetic coupling between primary/ secondary windings, and a switching power supply, using this transformer high in efficiency of conversion. <P>SOLUTION: This switching power supply has the transformer, having a constitution provided with at least a first primary coil, a first secondary coil, a second secondary coil, and a second primary coil, to be stacked sequentially in the order of the first primary coil, the first secondary coil, the second secondary coil, and the second primary coil, for connecting one end of the first secondary coil and one end of the second secondary coil taken out as a center tap; a switching means applying voltage alternately in positive/negative reverse directions to the transformer, the center tap of the transformer; a rectifying means rectifying voltage, induced between the other end of the first secondary coil and the other end of the second secondary coil; a smooth out means smoothing the voltage of the rectifying means; and a control means on/off controlling the switching means so as to make the output voltage fixed. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a switching power supply that supplies a stabilized DC voltage to industrial and consumer electronic devices.

In recent years, as electronic devices have become smaller, there has been a strong demand for smaller and thinner magnetic components such as transformers used in switching power supply devices. In order to respond to such demands, as the transformer winding of the switching power supply device, a coil in which a conductive wire is spirally wound and a spiral coil in which a thin conductor is punched out are used, and each coil is of the same type or combined. A laminated laminated transformer is used.

Hereinafter, a conventional switching power supply device will be described with reference to FIG.
6A and 6B show a conventional switching power supply device. FIG. 6A is a circuit configuration diagram of a full-bridge converter, FIG. 6B is a cross-sectional view of a winding portion of the transformer, and FIG. FIG. 4 is an external view of a spiral coil that is one of the windings of the section.
6A includes an input DC power supply 1, input terminals 2a-2b, a transformer 3, a first switching element 4, a second switching element 5, a third switching element 6, and a fourth switching element. It has an element 7, a first rectifier diode 8a, a second rectifier diode 8b, an inductance element 9, a smoothing capacitor 10, output terminals 11a-11b, a load 12, and a control circuit 20. G1, G2, G3 and G4 indicate turn-on signals generated by the control circuit 20.
The input DC power supply 1 is connected to the input terminals 2a-2b and supplies a power supply voltage Vin.
The first switching element 4 and the second switching element 5 are connected in series and connected to the input terminals 2a-2b. The third switching element 6 and the fourth switching element 7 are connected in series and connected to the input terminals 2a-2b.

One end of the primary winding 3a is connected to a connection point between the first switching means 4 and the second switching means 5, and the other end is connected to a connection point between the third switching means 6 and the fourth switching means 7. Connected. The first secondary winding 3b and the second secondary winding 3c are connected in series. The turns ratio of the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is N: 1: 1 (N is an arbitrary positive number).
The anode of the first rectifier diode 8a is connected to one end of the first secondary winding 3b of the transformer 3, and the anode of the second rectifier diode 8b is connected to one end of the second secondary winding 3c. ing. The cathodes of both rectifier diodes are connected to each other. The other end of the first secondary winding 3b and the other end of the second secondary winding 3c are connected to each other, and are connected to the output terminal 11b.

The inductance element 9 and the smoothing capacitor 10 are connected in series to form a smoothing circuit. One end of the inductance element 9 is connected to a connection point between the cathode of the first rectifier diode 8a and the cathode of the second rectifier diode 8b, and the other end is connected to the output terminal 11a. One end of the smoothing capacitor 10 is connected to the output terminal 11a, and the other end is connected to a connection point (output terminal 11b) between the first secondary winding 3b and the second secondary winding 3c.
The smoothing capacitor 10 has a sufficiently large capacitance and rectifies and smoothes a voltage generated in the secondary winding of the transformer 3. The voltage Vout (the voltage between 11a and 11b) across the smoothing capacitor 10 is the output voltage.
A load 12 is connected to the output terminals 11a-11b and consumes power.
Reference numeral 20 denotes a control circuit which outputs the first switching element 4, the second switching element 5, the third switching element 6, and the fourth switching element by outputting turn-on signals G1 to G4 to stabilize the output DC voltage Vout. The switching element 7 is driven at a predetermined on / off ratio.

The transformer 3 will be described in detail with reference to FIGS. 6B and 6C. FIG. 6B is a cross-sectional view of a transformer winding portion, and FIG. 6C is an external view of a spiral coil.
As shown in FIG. 6B, the transformer 3 includes a first primary coil 3a1, a second primary coil 3a2, a third primary coil 3a3, a fourth primary coil 3a4, and a first secondary coil 3a1. It has a secondary coil 3b1, a second secondary coil 3c1, a third secondary coil 3b2, and a fourth secondary coil 3c2.
The first primary coil 3a1, the second primary coil 3a2, the third primary coil 3a3, and the fourth primary coil 3a4 are connected in series, and constitute the primary winding 3a of FIG. . The first secondary coil 3b1 and the third secondary coil 3b2 are connected in series to form the first secondary winding 3b of FIG. 6A, and the second secondary coil 3c1 and the fourth secondary coil 3c1 are connected to each other. The secondary coil 3c2 is connected in series and forms a second secondary winding 3c in FIG.
Regarding the stacking order of the coils, from the top, the first primary coil 3a1, the first secondary coil 3b1, the second primary coil 3a2, the third secondary coil 3b2, the third primary coil 3a3, The second secondary coil 3c1, the fourth primary coil 3a4, and the fourth secondary coil 3c2 are stacked in this order.
By laminating in this manner, it is possible to increase the magnetic coupling between the primary coil and the secondary coil. FIG. 6C is an external view of one of the windings of the winding part of the transformer 3.

The operation of the switching power supply configured as described above will be described.
FIG. 7 shows an operation waveform diagram of each part of the conventional switching power supply device. 7A shows a voltage waveform of a signal G1 for controlling on / off of the first switching element 4, and FIG. 7B shows a voltage waveform of a signal G2 for controlling on / off of the second switching element 5. (C) is a voltage waveform of a signal G3 for controlling on / off of the third switching element 6, and (d) is a voltage waveform of a signal G4 for controlling on / off of the fourth switching element 7. (E) is a waveform of the voltage Vp applied to the primary winding 3a of the transformer 3. (F) is a waveform of the current Id1 flowing through the first rectifier diode 8a, and (g) is a waveform of the current Id2 flowing through the second rectifier diode 8b.

As shown in FIG. 7, in the conventional power supply device, the switching element 4 and the switching element 7 form a set and are turned on at the same time, and the switching element 5 and the switching element 6 are formed as a set and are turned on at the same time. These are alternately turned on and off, so that the voltage of Vin and -Vin are alternately applied to the primary winding 3a of the transformer 3.
First, when the second switching element 5 and the third switching element 6 are simultaneously turned on by the turn-on signals G2 and G3 from the control circuit 20, a voltage of -Vin is applied to the primary winding 3a of the transformer 3. . At this time, a voltage -Vin / N is generated in the first secondary winding 3b of the transformer 3, the first rectifier diode 8a is turned off in a reverse bias, and the second rectifier diode 8b is turned in a forward bias. And turn it on.

Next, after both G2 and G3 are turned off by the turn-on signal from the control circuit 20, the first switching element 4 and the fourth switching element 7 are simultaneously turned on by the turn-on signals G1 and G4 from the control circuit 20. Then, the input voltage Vin is applied to the primary winding 3a of the transformer 3. At this time, a voltage Vin / N is generated in the first secondary winding 3b of the transformer 3, the first rectifier diode 8a is turned on with a forward bias, and the second rectifier diode 8b is turned on with a reverse bias. Turn off. A current based on the voltage induced in the first secondary winding 3b of the transformer 3 flows through the inductance element 9.
The current flowing through the inductance element 9 increases linearly. At this time, a current flowing through the inductance element 9 flows through the first secondary winding 3b of the transformer 3, and a current having a turn ratio multiple (1 / N times) of the transformer 3 flows through the primary winding 3a of the transformer 3. Flows.
When both the second switching element 5 and the third switching element 6 are turned off, the primary winding 3a of the transformer 3 is opened, and the first secondary winding 3b and the second secondary winding 3c of the transformer 3 are opened. Is zero. In order to maintain the continuity of the magnetic flux of the transformer 3, a current is split and flows to the first secondary winding 3b and the second secondary winding 3c of the transformer 3. Hereinafter, a period during which the current is divided and flows through the transformer secondary winding will be referred to as a shunt period.

JP-A-6-302443

During the shunt period, the current flowing through the first secondary winding 3b and the second secondary winding 3c strongly influences the space between the first secondary winding 3b and the second secondary winding 3c. A magnetic field is generated. During the shunt period, the primary winding 3a is in an open state, so that the current is zero between the terminals of the primary winding 3a. For this reason, the surface of the third primary coil 3a3 located between the first secondary winding 3b and the second secondary winding 3c has a surface so that the current sum of the conductor as a whole becomes zero. The strong magnetic field generated by the first secondary winding 3b and the second secondary winding 3c induces a loop current, and the induced current causes a problem of loss.
For example, in a transformer having a structure in which an ordinary wire is wound around an EI cut core and a primary winding and a secondary winding are completely separated from each other, the average distance between the primary winding and the secondary winding is long. Another problem is that sufficient magnetic coupling cannot be obtained between the primary winding and the secondary winding. Therefore, the switching power supply device using the transformer having the above configuration has a problem that high conversion efficiency cannot be obtained.
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a switching power supply having high conversion efficiency using a transformer having high magnetic coupling between a primary winding and a secondary winding and low loss. And

た め In order to solve the above problems, the present invention has the following configurations. The invention according to claim 1 includes at least a first primary coil, a first secondary coil, a second secondary coil, and a second primary coil, wherein the first primary coil, A first secondary coil, the second secondary coil, and the second primary coil are stacked in this order, and one end of the first secondary coil and one end of the second secondary coil are connected to each other. A transformer having a configuration connected and taken out as a center tap, switching means for alternately applying a voltage to the transformer in the positive and negative directions, the center tap of the transformer, and the other end of the first secondary coil or Rectifying means for rectifying the voltage induced between the other end of the second secondary coil, smoothing means for smoothing the voltage of the rectifying means, and turning on / off of the switching means so that the output voltage is constant. Having control means for performing control. It is a switching power supply device according to symptoms.

The invention according to claim 2 includes at least a first primary coil, a first secondary coil, a second secondary coil, and a second primary coil, wherein the first primary coil, A unit laminated body laminated in the order of a first secondary coil, the second secondary coil, the second primary coil, and at least the first primary coil, the first secondary coil, A second secondary coil, the second primary coil, wherein the first primary coil, the second secondary coil, the first secondary coil, and the second primary coil One end of the first secondary coil, in which one of the unit laminates sequentially stacked is stacked in a plurality of stages, or a combination of both is stacked in a plurality of stages, and the plurality of unit stacks are respectively connected. And a transformer connected to one end of the second secondary coil and taken out as a center tap. Switching means for alternately applying a voltage to the transformer in the positive and negative directions, the center tap of the transformer, and the other end of the first secondary coil to which a plurality of unit laminates are respectively connected or the second A rectifier for rectifying a voltage induced between the other end of the secondary coil, a smoother for smoothing a voltage of the rectifier, and a control for performing on / off control of the switching unit so that an output voltage is constant. And a switching power supply device.
A unit stack in which the unit stack is turned upside down (for example, a unit stack in the order of a second primary coil, a second secondary coil, a first secondary coil, a first primary coil, or a second 1 The primary coil, the first secondary coil, the second secondary coil, and the first primary coil may be laminated in this order.

According to a third aspect of the present invention, in the switching power supply device, all the primary coils are connected in series in the transformer.

5. The switching power supply according to claim 4, wherein in the transformer, a primary coil used for a unit laminate is connected in parallel to form a parallel connection, and the parallel connection is connected in series. Device.

According to a fifth aspect of the present invention, in the transformer, the primary coil and the secondary coil are composed of printed circuit board coils having a conductor pattern on an insulating substrate, and are stacked in multiple stages, and the primary coil and the secondary coil are provided. Is a switching power supply device characterized by being connected via a connection portion at an inner end or an outer end of a coil pattern to form a winding.

According to a sixth aspect of the present invention, in the switching power supply device, the number of turns of the primary coil and / or the secondary coil in each layer or the whole of the transformer is one turn. A printed circuit board (layer) having a one-turn coil pattern is laminated, and the whole is connected in series or in parallel to form a primary winding and / or a secondary winding.
For example, when the voltage applied to the primary winding is a predetermined high voltage or more, it is necessary to ensure a certain creepage distance between the primary winding, the secondary winding, and the core according to safety standards. If the coil pattern exceeds one turn, it is necessary to provide a through hole at the inner end of the coil pattern. However, when a through-hole is provided to ensure a certain or more creepage distance between the through-hole and another pattern or core, there is a problem that the transformer becomes large. In the present invention, it is not necessary to provide a through hole at the inner end of the coil pattern for a winding in which the coil pattern on the substrate has one turn. According to the present invention, a small and thin transformer can be realized.

According to a seventh aspect of the present invention, in the transformer, the number of turns of the primary coil is N turns (N is any positive number) in each layer or the whole, and the number of turns of the first secondary coil and the second secondary coil is N. The switching power supply device is characterized in that the number of turns is one turn.
In the transformer of the switching power supply of the present invention, the turns ratio of the primary coil, the first secondary coil, and the second secondary coil is N: 1: 1.
Printed boards having an N-turn coil pattern are stacked, and the whole is connected in series or in parallel to form a primary winding. A printed circuit board having a one-turn coil pattern is stacked, and the whole is connected in series or in parallel to form a secondary winding. The secondary winding is connected via a connection at the outer end of the coil pattern. According to the present invention, a small and thin transformer can be realized.
The present invention has an effect that a switching power supply device having high conversion efficiency using a transformer having high magnetic coupling between a primary winding and a secondary winding and low loss can be realized.

According to the present invention, there is obtained an advantageous effect that a switching power supply device having high conversion efficiency using a transformer having high magnetic coupling between the primary winding and the secondary winding and low loss can be realized.
In the switching power supply of the present invention, the current flowing between the first secondary winding and the second secondary winding during the shunt period causes the current between the first secondary winding and the second secondary winding to change. Even if a strong magnetic field is generated in the space, there is no conductor between the first secondary winding 3b and the second secondary winding 3c, so that no current is induced and no loss occurs. Effects can be obtained. Further, currents in opposite directions flow through the adjacent first secondary winding 3b and second secondary winding 3c during the shunt period, and the magnetic fields induced by the two currents cancel each other. Therefore, there is an advantageous effect that no current is induced in the primary winding sandwiched between the first secondary winding 3b and the second secondary winding 3c, and no loss occurs.
Further, since the average distance between the first secondary winding and the second secondary winding is short, the magnetic coupling between the first secondary winding and the second secondary winding is high. Therefore, an advantageous effect that a switching power supply device with high conversion efficiency can be provided is obtained.

Hereinafter, an embodiment that specifically shows the best mode for carrying out the present invention will be described with reference to the drawings.

First Embodiment A switching power supply according to a first embodiment of the present invention will be described with reference to FIG.
The overall circuit configuration of the switching power supply of this embodiment is the same as the circuit configuration of the conventional example shown in FIG. The switching power supply device of the present embodiment is characterized by the winding part of the transformer 3 and the circuit configuration and circuit operation are the same as those of the conventional switching power supply device, and therefore the description thereof is omitted.
Hereinafter, the configuration of the winding part of the transformer 3 of the switching power supply of the present embodiment will be described with reference to FIG. FIG. 1 is a sectional view of a transformer 3 according to the present embodiment.
As shown in FIG. 1, the transformer 3 includes a first primary coil 3a1, a second primary coil 3a2, a third primary coil 3a3, a fourth primary coil 3a4, and a first secondary coil 3b1. , A second secondary coil 3c1, a third secondary coil 3b2, and a fourth secondary coil 3c2.

The first primary coil 3a1, the second primary coil 3a2, the third primary coil 3a3, and the fourth primary coil 3a4 are connected in series, and constitute the primary winding 3a of FIG. . The first secondary coil 3b1 and the third secondary coil 3b2 are connected in series to form the first secondary winding 3b of FIG. 6A, and the second secondary coil 3c1 and the fourth secondary coil 3c1 are connected to each other. The secondary coil 3c2 is connected in series, and forms the second secondary winding 3c in FIG. The first secondary winding 3b and the second secondary winding 3c are connected in series. Up to this point, it is the same as the conventional example.
As for the order of stacking the coils, from the top, the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, the second primary coil 3a2, the third primary coil 3a3, The third secondary coil 3b2, the fourth secondary coil 3c2, and the fourth primary coil 3a4 are stacked in this order. The turn ratio between the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is N: 1: 1 (N is any positive number).

Also in this embodiment, as in the conventional example, the current flowing through the first secondary winding 3b and the second secondary winding 3c during the shunt period causes the first secondary winding 3b and the second secondary winding 3b to rotate. A strong magnetic field is generated in the space between the windings 3c. However, in the winding configuration of the present embodiment, since there is no conductor between the first secondary winding 3b1 and the second secondary winding 3c1, no current is induced between them and loss occurs. do not do. Currents in opposite directions flow through the adjacent first secondary winding 3b2 and second secondary winding 3c2 during the shunt period, and the magnetic fields induced by the two currents cancel each other. Similarly, currents in opposite directions flow through the adjacent first secondary winding 3b1 and second secondary winding 3c1 during the shunt period, and the magnetic fields induced by the two currents cancel each other. Therefore, no current is induced in the two primary windings (3a2 and 3a3) sandwiched between the first secondary winding 3b2 and the second secondary winding 3c1, and no loss occurs. .
The degree of magnetic coupling between the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is as high as in the conventional example (FIG. 6). For example, compared to a transformer in which the primary winding and the secondary winding are completely separated and wound on the EI cut core, the magnetic coupling between the primary winding and the secondary winding of the transformer of the present invention is different. The degree is high.

In the switching power supply of this embodiment, the windings of the transformer are the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 from above. Although the description has been made using a unit laminate in which two unit laminates are laminated in this order, the same effect can be obtained by applying at least a laminate of the unit laminate in one or more stages. Here, FIG. 2 shows a cross-sectional view of the transformer winding portion in the one-stage model of the unit laminate. In the one-stage model of the unit laminate, since no conductor exists between the first secondary winding and the second secondary winding, no current is induced between the first secondary winding and the second secondary winding, and no loss occurs.
For example, in a transformer in which unit laminates including 3a1 to 3a4, 3b1, 3b2, 3c1 and 3c2 shown in FIG. 1 are stacked in two stages, the adjacent first secondary winding 3b2 and second secondary winding Currents in opposite directions flow through 3c2 during the shunt period, and the magnetic fields induced by the two currents cancel each other. Similarly, currents in opposite directions flow through the adjacent first secondary winding 3b1 and second secondary winding 3c1 during the shunt period, and the magnetic fields induced by the two currents cancel each other. Therefore, no current is induced in the two primary windings (3a2 and 3a3) sandwiched between the first secondary winding 3b2 and the second secondary winding 3c1, and no loss occurs. .

A unit laminated body in which the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 are laminated in this order, the first primary coil 3a1, the first Alternatively, a transformer may be formed by combining and stacking unit secondary bodies 3c1, the first secondary coil 3b1, and the second primary coil 3a2 in this order. Further, the transformer may be formed by stacking these unit stacks which are turned upside down. With such a configuration, the same effect as that of the embodiment can be obtained.

(4) By connecting the primary coils in series, it is possible to prevent extremely uneven current distribution of the current flowing through each primary coil. Although the case has been described where the respective coils constituting the first secondary winding 3b and the second secondary winding 3c are connected in series, the respective coils are connected in parallel to form the first secondary winding 3b and It goes without saying that a similar effect can be obtained even if the second secondary winding 3c is configured. In the simulation and the experiment, the AC resistance viewed from the primary coil side when the secondary winding is short-circuited can be reduced by 20% to 30% compared with the configuration of the conventional transformer winding (FIG. 6B). It was confirmed. In addition, although the description has been given of a switching circuit having a full-bridge converter system, the same applies to a half-bridge converter, a push-pull converter, and a switching power supply using various circuit systems based on the circuit. Needless to say, the effect is obtained.

Second Embodiment A switching power supply according to a second embodiment of the present invention will be described with reference to FIGS.
The overall circuit configuration of the switching power supply of this embodiment is the same as the circuit configuration of the conventional example shown in FIG. The switching power supply device of the present embodiment is characterized by the winding part of the transformer 3 and the circuit configuration and circuit operation are the same as those of the conventional switching power supply device, and therefore the description thereof is omitted.
Hereinafter, the configuration of the winding part of the transformer 3 of the switching power supply of the present embodiment will be described with reference to FIG. FIG. 3 is a sectional view of the transformer 3 of the present embodiment.
As shown in FIG. 3, the transformer 3 includes a first primary coil 3a1, a second primary coil 3a2, a third primary coil 3a3, a fourth primary coil 3a4, and a first secondary coil 3b1. , A second secondary coil 3c1, a third secondary coil 3b2, and a fourth secondary coil 3c2.

The first primary coil 3a1 and the second primary coil 3a2 are connected in parallel to form a first parallel connection body 3d1, and the third primary coil 3a3 and the fourth primary coil 3a4 are connected in parallel. , And a second parallel connection body 3d2. The first parallel connection body 3d1 and the second parallel connection body 3d2 are connected in series to form the primary winding 3a in FIG. The first secondary coil 3b1 and the third secondary coil 3b2 are connected in series to form the first secondary winding 3b of FIG. 6A, and the second secondary coil 3c1 and the fourth secondary coil 3c1 are connected to each other. The secondary coil 3c2 is connected in series and forms a second secondary winding 3c in FIG. The first secondary winding 3b and the second secondary winding 3c are connected in series.
As for the order of stacking the coils, from the top, the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, the second primary coil 3a2, the third primary coil 3a3, The third secondary coil 3b2, the fourth secondary coil 3c2, and the fourth primary coil 3a4 are stacked in this order. The turns ratio of the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is N: 1: 1.

By configuring the transformer winding as in the present embodiment, the first parallel connection body 3d1 and the second parallel connection body 3d2 are connected in series even in a case where the turns ratio of the primary winding 3a is small. This allows a large current to flow through the primary winding 3a.
Also, as in the first embodiment, since there is no conductor between the first secondary winding 3b1 and the second secondary winding 3c1, a current is generated by a strong magnetic field generated in the space therebetween during the shunt period. No induction occurs and no loss occurs. Currents in opposite directions flow through the adjacent first secondary winding 3b2 and second secondary winding 3c2 during the shunt period, and the magnetic fields induced by the two currents cancel each other. Similarly, currents in opposite directions flow through the adjacent first secondary winding 3b1 and second secondary winding 3c1 during the shunt period, and the magnetic fields induced by the two currents cancel each other. Therefore, no current is induced in the two primary windings (3a2 and 3a3) sandwiched between the first secondary winding 3b2 and the second secondary winding 3c1, and no loss occurs. .
The degree of magnetic coupling between the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is as high as in the conventional example (FIG. 6). For example, the degree of magnetic coupling between the primary winding and the secondary winding of the transformer of the present invention is smaller than that of a transformer in which the primary winding and the secondary winding are completely separated and wound on an EI cut core. high.

In the switching power supply device of the present embodiment, the windings of the transformer include the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 from above. Although the description has been given using the case where the unit laminates which are sequentially laminated are laminated in two stages, a similar effect can be obtained by applying at least one unit laminated body. Here, FIG. 4 shows a cross-sectional view of the transformer winding portion in the one-stage model of the unit laminate. In the one-stage model of the unit laminate, since no conductor exists between the first secondary winding and the second secondary winding, no current is induced between the first secondary winding and the second secondary winding, and no loss occurs. Also, the case where the parallel connection of the primary coils in the unit laminate is connected in series has been described, but the same effect can be obtained when the parallel connection is connected in parallel.
A unit laminated body in which the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 are laminated in this order, the first primary coil 3a1, the first Alternatively, a transformer may be formed by combining and stacking unit secondary bodies 3c1, the first secondary coil 3b1, and the second primary coil 3a2 in this order. Further, the transformer may be formed by stacking these unit stacks which are turned upside down. With such a configuration, the same effect as that of the embodiment can be obtained.

Although the case where the respective coils constituting the first secondary winding 3b and the second secondary winding 3c are connected in series has been described, the first secondary winding 3b is connected by connecting the respective coils in parallel. Needless to say, the same effect can be obtained even if the second secondary winding 3c is configured. In the simulation and the experiment, the AC resistance viewed from the primary coil side when the secondary winding is short-circuited can be reduced by 20% to 30% compared with the configuration of the conventional transformer winding (FIG. 6B). It was confirmed. In addition, although the description has been given of a switching circuit having a full-bridge converter system, the same applies to a half-bridge converter, a push-pull converter, and a switching power supply using various circuit systems based on the circuit. Needless to say, the effect is obtained.

Third Embodiment A switching power supply according to a third embodiment of the present invention will be described with reference to FIG.
The overall circuit configuration of the switching power supply of this embodiment is the same as the circuit configuration of the conventional example shown in FIG. The switching power supply device of the present embodiment is characterized by the winding part of the transformer 3 and the circuit configuration and circuit operation are the same as those of the conventional switching power supply device, and therefore the description thereof is omitted.

FIG. 5A is a perspective view showing the outer shape of a transformer having a structure in which the printed circuit board coils of the present embodiment are stacked, FIG. 5B is a front view thereof, and FIG. FIG. 5D is a schematic view showing the appearance of one printed circuit board coil. In FIG. 5, reference numeral 30 denotes a laminated body in which a plurality of printed board coils are stacked, 34 denotes terminals, 35 denotes a core, and 37 denotes one printed board coil. Each printed board coil 37 has a coil pattern 31, an inner end through hole 32, and an outer end through hole 33, and a through hole 36 is provided at the center. As shown in FIG. 5C, the core 35 has its middle foot portion penetrated through the through hole 36 to form a magnetically closed circuit.

In the transformer of this embodiment, a laminated body 30 in which printed circuit board coils 37 each having a conductor pattern provided on an insulating substrate are laminated in multiple layers is used as the winding of the transformer. The printed board coil 37 is a printed board having four or more layers, and one printed board may have a plurality of layers of coils. The multilayer printed board coil 37 is laminated with an insulating layer of a required thickness interposed between the coil patterns, and the terminals (the inner end 32 and the outer end 33) of each coil pattern are connected to the other upper and lower printed board coils 37. To form a coil. For example, the inner end 32 is connected to one of the through holes 38 to 44 provided around the printed circuit board coil 37 by a conductor pattern provided on the back surface of the printed circuit board coil 37 which is a double-sided printed circuit board. The terminal 34 is connected to the through hole and the outer end 33 to connect the upper and lower printed circuit board coils 37 to each other. For example, a first primary coil 3a1, a first secondary coil 3b1, a second secondary coil 3c1, a second primary coil 3a2, a third primary coil 3a3, a third secondary coil 3b2, A different conductor pattern is provided for each of the fourth secondary coil 3c2 and the fourth primary coil 3a4, and different through holes are used as connection terminals, thereby forming each winding of the transformer.

Hereinafter, the configuration of the winding part of the transformer 3 of the switching power supply of the present embodiment will be described with reference to FIG. Connection and lamination of each coil of the transformer 3 of this embodiment are the same as those of the first embodiment shown in FIG. FIG. 1 is a sectional view of a transformer 3 according to the present embodiment.
In FIG. 1, the first primary coil 3a1, the second primary coil 3a2, the third primary coil 3a3, and the fourth primary coil 3a4 are formed through a through hole 32 at the inner end of the coil pattern 31 and outside the coil pattern 31 The primary winding 3a of FIG. 6 is connected in series via the through hole 33 at the end.

The first secondary coil 3b1 and the third secondary coil 3b2 are connected in series via a through hole 32 at the inner end and a through hole 33 at the outer end of the coil pattern 31, and the first secondary winding shown in FIG. 6b, the second secondary coil 3c1 and the fourth secondary coil 3c2 are connected in series via a through hole 32 at the inner end of the coil pattern 31 and a through hole 33 at the outer end of the coil pattern 31. Of the secondary winding 3c. The first secondary winding 3b and the second secondary winding 3c are connected in series.
As for the order of stacking the coils, from the top, the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, the second primary coil 3a2, the third primary coil 3a3, The third secondary coil 3b2, the fourth secondary coil 3c2, and the fourth primary coil 3a4 are stacked in this order. The turns ratio of the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is N: 1: 1.

With such a configuration, it is possible to manufacture a transformer in which the interlayer distance between the coils is constant with high accuracy.
Also, as in the first embodiment, since there is no conductor between the first secondary winding 3b1 and the second secondary winding 3c1, a current is generated by a strong magnetic field generated in the space therebetween during the shunt period. No induction occurs and no loss occurs. Currents in opposite directions flow through the adjacent first secondary winding 3b2 and second secondary winding 3c2 during the shunt period, and the magnetic fields induced by the two currents cancel each other. Similarly, currents in opposite directions flow through the adjacent first secondary winding 3b1 and second secondary winding 3c1 during the shunt period, and the magnetic fields induced by the two currents cancel each other. Therefore, no current is induced in the two primary windings (3a2 and 3a3) sandwiched between the first secondary winding 3b2 and the second secondary winding 3c1, and no loss occurs. . The degree of magnetic coupling between the primary winding 3a, the first secondary winding 3b, and the second secondary winding 3c is as high as in the conventional example (FIG. 6). For example, the degree of magnetic coupling between the primary winding and the secondary winding of the transformer of the present invention is smaller than that of a transformer in which the primary winding and the secondary winding are completely separated and wound on an EI cut core. high.

In the switching power supply of this embodiment, the windings of the transformer are the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 from above. Although the description has been made using the multilayer printed circuit board coil in which the unit laminated bodies laminated in this order are laminated in two stages, the same effect can be obtained by applying at least one layer laminated. In the one-stage model of the unit laminate, since no conductor exists between the first secondary winding and the second secondary winding, no current is induced between the first secondary winding and the second secondary winding, and no loss occurs.
Also, the case has been described where the respective coils constituting the first secondary winding and the second secondary winding are connected in series. However, by connecting the respective coils in parallel, the first secondary winding and the second secondary winding are connected. It goes without saying that the same effect can be obtained even if the second secondary winding is formed.

A unit laminated body in which the first primary coil 3a1, the first secondary coil 3b1, the second secondary coil 3c1, and the second primary coil 3a2 are laminated in this order, the first primary coil 3a1, the first Alternatively, a transformer may be formed by combining and stacking unit secondary bodies 3c1, the first secondary coil 3b1, and the second primary coil 3a2 in this order. The transformer may be formed by laminating these unit laminated bodies upside down. With such a configuration, the same effect as that of the embodiment can be obtained. In the simulation and the experiment, the AC resistance viewed from the primary coil side when the secondary winding is short-circuited can be reduced by 20% to 30% compared with the configuration of the conventional transformer winding (FIG. 6B). It was confirmed.

In the transformer 3, the number of turns of the primary coil may be one turn in each layer constituting the printed board coil 37 or as a whole. In the transformer 3, the number of turns of the secondary coil may be one turn in each layer constituting the printed board coil 37 or in the whole. In each layer or the whole of the printed circuit board coil 37 in the transformer 3, the number of turns of the primary coil may be N turns, and the number of turns of the first secondary coil and the second secondary coil may be one turn. By making the coil pattern of each layer constituting the printed board coil 37 one turn and connecting the coil patterns of all the layers in parallel, the number of turns of the coil can be one turn as a whole.
Preferably, the number of turns of the coil pattern of the primary coil of each layer constituting the printed circuit board coil 37 is one turn, and all are connected in series or in parallel. Further, the number of turns of the coil pattern of the secondary coil of each layer constituting the printed board coil 37 is one turn, and all are connected in series or in parallel.

If the number of turns of the coil is greater than one turn in each layer, the coil pattern 31 becomes spiral. Therefore, it is necessary to provide a through hole 32 at the inner end of the coil pattern and connect the coil patterns of each layer by the through hole 32. When the input voltage on the primary side is higher than a predetermined value, the creepage distance between the primary coil, the secondary coil, and the core 35 must be equal to or greater than a distance (for example, 10 mm) according to safety standards. However, providing the through hole 32 at the inner end of the coil pattern while securing a predetermined creepage distance causes an increase in the size of the transformer 3 and an increase in power loss. Furthermore, the connection portion of the inner end of the coil pattern formed by the through hole 32 has a small current capacity, so that a large current cannot flow through the coil.
With the one-layer one-turn configuration, connection through the through hole 32 at the inner end of the coil pattern is completely unnecessary. A circuit board having no through hole and formed of a predetermined material itself serves as an insulating sheet. In this case, the spatial distance between the primary coil, the secondary coil and the core 35 can be reduced, and an effective creepage distance conforming to safety standards can be secured. This makes it possible to reduce the size and thickness of the transformer and increase the input / output current capacity, and reduce power loss.

Although the description has been given of the one having the switching circuit of the full-bridge converter system, the same effect can be obtained even when applied to a half-bridge converter, a push-pull converter, and a switching power supply device using various circuit systems based on the circuit. It goes without saying that you can get it.
As in the third embodiment, it goes without saying that the transformer of the second embodiment and the switching power supply device using the same can be realized by the configuration in which the printed circuit board coils are stacked.

The switching power supply according to the present invention is useful as a switching power supply for supplying a stabilized DC voltage to industrial and consumer electronic devices.

Sectional view of the transformer winding part of the switching power supply device of Embodiment 1. FIG. 4 is a cross-sectional view of a transformer winding unit having a unit laminate structure of the switching power supply device according to the first embodiment. Sectional view of the transformer winding part of the switching power supply device of Embodiment 2. Sectional view of a transformer winding unit having a unit laminate structure of the switching power supply device of Embodiment 2. 5A is a perspective view of a transformer of the switching power supply device according to the third embodiment, FIG. 5B is a front view thereof, FIG. 5C is a cross-sectional view taken along a line II, FIG. d) is a diagram showing a schematic appearance of one printed circuit board coil 6A is a circuit diagram of a conventional switching power supply, FIG. 6B is a cross-sectional view of a transformer winding of the switching power supply, and FIG. 6C is a transformer winding of the switching power supply. Outline drawing of one of the windings Operation waveform diagram of each part of conventional switching power supply device

Explanation of reference numerals

Reference Signs List 1 input DC power supply 2a-2b input terminal 3 transformer 3a primary winding 3a1 first primary coil 3a2 second primary coil 3a3 third primary coil 3a4 fourth primary coil 3b first secondary Winding 3b1 First secondary coil 3b2 Third secondary coil 3c Second secondary winding 3c1 Second secondary coil 3c2 Fourth secondary coil 4 First switching element 5 Second switching element Reference Signs List 6 third switching element 7 fourth switching element 8a first rectifier diode 8b second rectifier diode 9 inductance element 10 smoothing capacitor 11a-11b output terminal
DESCRIPTION OF SYMBOLS 12 Load 20 Control circuit 30 Laminated body 31 Coil pattern 32 Inner end through hole 33 Outer end through hole 34 Terminal 35 Core 36 Through hole 37 Printed circuit board coil 38 to 44 Through hole

Claims (7)

At least a first primary coil, a first secondary coil, a second secondary coil, a second primary coil, the first primary coil, the first secondary coil, the first 2 secondary coil and the second primary coil are stacked in this order, and one end of the first secondary coil and one end of the second secondary coil are connected and taken out as a center tap. And a transformer having
Switching means for alternately applying a voltage to the transformer in the opposite direction,
Rectifying means for rectifying a voltage induced between the center tap of the transformer and the other end of the first secondary coil or the other end of the second secondary coil;
Smoothing means for smoothing the voltage of the rectifier means,
And a control means for performing on / off control of the switching means so that the output voltage becomes constant. At least a first primary coil, a first secondary coil, a second secondary coil, a second primary coil, the first primary coil, the first secondary coil, the first 2 secondary coils, the unit laminated body laminated in the order of the second primary coil, and at least the first primary coil, the first secondary coil, the second secondary coil, A unit laminated body having two primary coils, the first primary coil, the second secondary coil, the first secondary coil, and the second primary coil being laminated in this order; Is stacked in a plurality of stages, or a combination of both is stacked in a plurality of stages, and one end of the first secondary coil and a second end of the second secondary coil respectively connected to a plurality of unit laminates. A transformer having a configuration connected to one end and taken out as a center tap;
Switching means for alternately applying a voltage to the transformer in the opposite direction,
Rectification for rectifying a voltage induced between the center tap of the transformer and the other end of the first secondary coil or the other end of the second secondary coil respectively connected to a plurality of unit laminates. Means,
Smoothing means for smoothing the voltage of the rectifier means,
And a control means for performing on / off control of the switching means so that the output voltage becomes constant. The switching power supply device according to claim 1, wherein all the primary coils are connected in series in the transformer. 3. The switching power supply device according to claim 2, wherein in the transformer, a primary coil used for a unit laminate is connected in parallel to form a parallel connection, and the parallel connection is connected in series with each other. 4. In the transformer, the primary coil and the secondary coil are composed of printed circuit board coils provided with a conductor pattern on an insulating substrate and are stacked in multiple stages, and the primary coil and the secondary coil are provided at the inner end or outer end of the coil pattern. The switching power supply device according to any one of claims 1 to 4, wherein the switching power supply device is connected via a connection portion to form a winding. The switching power supply device according to claim 5, wherein in the transformer, the number of turns of the primary coil and / or the secondary coil is one turn in each layer or in the whole. In the above transformer, the number of turns of the primary coil is N turns (N is an arbitrary positive number), and the number of turns of the first secondary coil and the second secondary coil is one turn in each layer or the whole. The switching power supply according to claim 2, 5, or 6.

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