JP2003259646A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power supply in which a surge voltage applied to a switching element is reduced. <P>SOLUTION: The switching power supply comprises an input capacitor 10, a transformer 30, a full-bridge type switching circuit 20 having first and second arms and interposed between the input capacitor 10 and the transformer 30, output circuits 50 and 60 connected with secondary windings 32 and 33 of the transformer 30, and a circuit 70 for controlling the switching circuit 20 wherein the first arm has a pair of switch elements composed of first and second switch elements 21 and 22 arranged such that a terminal connected with the input capacitor 10 is closer to the input capacitor 10 than a common connection terminal. With such an arrangement, a parasitic inductance component causing a surge voltage in the first arm can be reduced. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device, and more particularly to a switching power supply device using a full bridge circuit.

[0002]

2. Description of the Related Art So-called DC / DC converters have been known as switching power supply devices. In a typical DC / DC converter, a DC input is once converted into an AC using a switching circuit, then this is transformed (boosted or stepped down) with a transformer, and then this is converted into DC using an output circuit. This is a device for producing a direct current output having a voltage different from the input voltage. Here, a so-called full-bridge circuit is generally used as a switching circuit of a switching power supply device that requires a large capacity, but as a drive system capable of reducing the switching loss generated in this type of switching circuit. A so-called phase shift control method is known.

[0003]

However, in the switching power supply device based on the phase shift control system,
There has been a problem that a surge voltage is applied to the switch element forming the full bridge circuit with the switching operation.

When such a surge voltage is generated, the switch element forming the full bridge circuit may be destroyed. Therefore, it is necessary to use a switch element having a high withstand voltage, which increases the cost and enlarges the entire apparatus. Was the cause. Further, it has also been a cause of deterioration of conversion efficiency.

Therefore, an object of the present invention is to provide a switching power supply device in which the surge voltage applied to the switch element is reduced.

[0006]

The object of the present invention is to:
An input capacitor, a transformer, a full-bridge type switching circuit provided between the input capacitor and the primary winding of the transformer and having first and second arms, and a secondary winding of the transformer. Connected output circuit,
A switching power supply device comprising: a control circuit for controlling the switching circuit, wherein the first arm is a first
And a pair of switching elements composed of a second switching element, wherein the first and second switching elements are connected to the input capacitor at a terminal connected to the input capacitor rather than at a common connection terminal. This is achieved by a switching power supply device characterized by being arranged close to each other.

According to the present invention, both the first and second switching elements are arranged such that the terminal connected to the input capacitor is closer to the input capacitor than the common connection terminal. , It is possible to reduce the parasitic inductance component that causes a surge voltage in the first arm. As a result, each switch element that constitutes the switching circuit is prevented from being destroyed, so that it is not necessary to use a particularly high withstand voltage element, which not only makes it possible to reduce the cost but also downsizes the entire device. Is possible. It also becomes possible to improve the conversion efficiency.

In a preferred aspect of the present invention, the second arm has a pair of switch elements each including a third switch element and a fourth switch element, and each of the third and fourth switch elements includes: The terminal connected to the input capacitor is arranged closer to the input capacitor than the common connection terminal.

According to a preferred embodiment of the present invention, the second
It is possible to reduce the parasitic inductance component that causes a surge voltage in the arm.

In a further preferred aspect of the present invention, the terminals of the first to fourth switch elements are arranged in the same manner.

According to a further preferred embodiment of the present invention, since the switching elements of the same type are used, the cost can be reduced.

In a further preferred aspect of the present invention, the control terminals of the first to fourth switch elements are arranged between a terminal connected to the input capacitor and the common connection terminal.

According to a further preferred aspect of the present invention, it is possible to further reduce the parasitic inductance component that causes a surge voltage in the first and second arms.

In a further preferred aspect of the present invention, the arrangement of terminals of the first and second switch elements is different from each other, and the arrangement of terminals of the third and fourth switch elements is different from each other, and the first The terminals of the third and third switch elements are arranged in the same manner, and the terminals of the second and fourth switch elements are arranged in the same manner.

According to a further preferred aspect of the present invention, it is possible to further reduce the parasitic inductance component that causes a surge voltage in the first and second arms.

In another preferred embodiment of the present invention, the second arm has a pair of switching elements composed of third and fourth switching elements, and the input capacitor has the first and second switching elements. It is arranged between a switch element and the third and fourth switch elements.

According to another preferred embodiment of the invention,
It is possible to reduce the parasitic inductance component that causes a surge voltage in the first and second arms as a whole.

In another more preferable aspect of the present invention, the terminals of the first to fourth switch elements are arranged in the same manner.

According to another more preferred embodiment of the present invention, since the same type of switching element is used,
It is possible to reduce costs.

In another more preferred aspect of the present invention, in each of the third and fourth switch elements, a terminal connected to the input capacitor is closer to the input capacitor than a common connection terminal. It is arranged to be.

According to another more preferred embodiment of the present invention, it is possible to reduce the parasitic inductance component that causes a surge voltage in the first and second arms as a whole.

In another more preferable embodiment of the present invention, the terminals of the first to fourth switch elements are arranged differently from each other.

According to another more preferred embodiment of the present invention, it is possible to further reduce the parasitic inductance component that causes the surge voltage in the first and second arms as a whole.

The object of the present invention is also to provide a full bridge type switching having an input capacitor, a transformer and first and second arms provided between the input capacitor and the primary winding of the transformer. A switching power supply device comprising a circuit, an output circuit connected to a secondary winding of the transformer, and a control circuit for controlling the switching circuit, wherein the first arm is connected to one terminal of the input capacitor. A third switch element having a first switch element connected thereto and a second switch element connected to the other terminal of the input capacitor, wherein the second arm is connected to the one terminal of the input capacitor. A fourth element connected to the switch element and the other terminal of the input capacitor
A switching power supply device characterized in that the arrangement of terminals of the first and second switch elements is different from each other, and the arrangement of terminals of the third and fourth switch elements is different from each other. To be done.

According to the present invention, it is possible to reduce the parasitic inductance component that causes a surge voltage in the first and second arms. This prevents damage to the switching elements that make up the switching circuit.
In particular, it is not necessary to use an element having a high breakdown voltage, so that not only the cost can be reduced, but also the entire device can be downsized. It also becomes possible to improve the conversion efficiency.

In a preferred aspect of the present invention, the terminals of the first and third switch elements are arranged in the same manner and the terminals of the second and fourth switch elements are arranged in the same manner.

In another preferred embodiment of the present invention, the terminals of the first to fourth switch elements are arranged differently from each other.

The object of the present invention is also to provide a full-bridge type switching having an input capacitor, a transformer and first and second arms provided between the input capacitor and the primary winding of the transformer. A switching power supply device comprising a circuit, an output circuit connected to a secondary winding of the transformer, and a control circuit for controlling the switching circuit, wherein the first arm is connected to one terminal of the input capacitor. A third switch element having a first switch element connected thereto and a second switch element connected to the other terminal of the input capacitor, wherein the second arm is connected to the one terminal of the input capacitor. A fourth element connected to the switch element and the other terminal of the input capacitor
And a switching element, wherein the input capacitor is arranged between the first and second switching elements and the third and fourth switching elements. It

According to the present invention, it is possible to reduce the parasitic inductance component that causes a surge voltage in the first and second arms as a whole. This prevents destruction of each switching element that constitutes the switching circuit, eliminating the need to use a particularly high breakdown voltage element.
Not only can the cost be reduced, but the entire device can be downsized. It also becomes possible to improve the conversion efficiency.

In a preferred embodiment of the present invention, the distance from the one terminal of the input capacitor to the first switch element and the distance from the one terminal of the input capacitor to the third switch element Are substantially equal, and the distance from the other terminal of the input capacitor to the second switch element is substantially equal to the distance from the other terminal of the input capacitor to the fourth switch element.

According to a preferred embodiment of the present invention, the first
There is no need to distinguish the second arm from the second arm.

The object of the present invention is also to provide a full bridge type switching having an input capacitor, a transformer and first and second arms provided between the input capacitor and the primary winding of the transformer. A switching power supply device comprising a circuit, an output circuit connected to a secondary winding of the transformer, and a control circuit for controlling the switching circuit, wherein the first arm is connected to one terminal of the input capacitor. A third switch element having a first switch element connected thereto and a second switch element connected to the other terminal of the input capacitor, wherein the second arm is connected to the one terminal of the input capacitor. A fourth element connected to the switch element and the other terminal of the input capacitor
And a distance from the one terminal of the input capacitor to the first switch element and a distance from the one terminal of the input capacitor to the third switch element are substantially equal to each other. A switching distance from the other terminal of the input capacitor to the second switch element and a distance from the other terminal of the input capacitor to the fourth switch element are substantially equal. Achieved by the power supply.

According to the present invention, the parasitic inductance component that causes a surge voltage in the first and second arms can be reduced as a whole, and it is necessary to distinguish the first arm and the second arm. Lost. This allows
Since the destruction of each switch element that constitutes the switching circuit is prevented, it is not necessary to use an element with a particularly high withstand voltage, which not only makes it possible to reduce the cost but also makes it possible to downsize the entire device. Become. It also becomes possible to improve the conversion efficiency.

[0034]

DETAILED DESCRIPTION OF THE INVENTION Referring to the accompanying drawings,
A preferred embodiment of the present invention will be described in detail.

FIG. 1 is a circuit diagram of a switching power supply device according to a preferred embodiment of the present invention.

As shown in FIG. 1, the switching power supply device according to this embodiment lowers the input voltage Vin supplied from the DC input power supply 1 to the pair of input power supply terminals 2 and 3 to generate the output voltage Vo. , A pair of output power supply terminals 4,
5, an input capacitor 10 connected to the input power supply terminals 2 and 3, a full-bridge type switching circuit 20 connected to the input capacitor 10, a primary winding 31 and a secondary winding 32. , 30 having 33
And the primary winding 3 of the switching circuit 20 and the transformer 30.
1 and the inductor 40 inserted between the transformer 30 and
Of the rectifier circuit 50 connected to the secondary windings 32 and 33, the smoothing circuit 60 connected between the rectifier circuit 50 and the pair of output power supply terminals 4 and 5, and control for controlling the operation of the switching circuit 20. The circuit 70 and the insulating circuits 71 to 74 are provided. A load 6 is connected between the pair of output power supply terminals 4 and 5. The rectifying circuit 50 and the smoothing circuit 60 form an output circuit.

The switching circuit 20 includes a first switch element 21 connected in series between both ends of the input capacitor 10.
And the second switch element 22, the third switch element 23 and the fourth switch element 24 connected in series across the input capacitor 10, and the first to fourth switch elements 21 to 24, respectively. 21c connected in parallel
24c, and the first and second switch elements 21, 2
The series body composed of 2 constitutes the first arm of the full bridge circuit, and the series body composed of the third and fourth switch elements 23 and 24 constitutes the second arm of the full bridge circuit. As the first to fourth switch elements 21 to 24, various known switch elements can be used, but FET (field effect transistor) is preferably used.

Further, the switching circuit 20 includes inductors 25 to 28, and the inductor 25 is
The inductor 26 is a parasitic inductance component existing in the wiring between the high-side terminal H1 of the first arm and the high-side electrode of the input capacitor 10. The inductor 26 is a low-side terminal L1 of the first arm and the low-level terminal of the input capacitor 10. It is a parasitic inductance component existing in the wiring between the side electrode. The inductor 27 is connected to the high-side terminal H1 of the first arm and the second terminal H1 of the second arm.
Is a parasitic inductance component existing in the wiring between the high-side terminal H2 of the first arm and the low-side terminal L1 of the first arm and the low-side terminal L of the second arm.
It is a parasitic inductance component existing in the wiring between the two. Further, the middle point M1 of the first arm is connected to one end of the primary winding 31 of the transformer 30, and the middle point M2 of the second arm is connected to the 1st point of the transformer 30 via the inductor 40.
It is connected to the other end of the next winding 31.

As described above, the transformer 30 is provided with the primary winding 31 and the secondary windings 32 and 33, and the turn ratio (= primary winding 31: secondary winding 32,33) is n. : 1.

The rectifier circuit 50 is a first rectifier circuit connected between one end of the secondary winding 32 of the transformer 30 and the rectified output point 50a.
And the second diode 52 connected between one end of the secondary winding 33 of the transformer 30 and the rectified output point 50a.

The smoothing circuit 60 comprises an output choke 61 connected between the rectified output point 50a and the output power supply terminal 4, and an output capacitor 62 connected between the pair of output power supply terminals 4 and 5. . The output power supply terminal 5 is directly connected to the secondary side center tap 30a of the transformer 30.

The control circuit 70 is a circuit that monitors the output voltage Vo appearing across the output capacitor 62 and controls the operation of the switching circuit 20 so that the output voltage Vo becomes a predetermined value based on the output voltage Vo. The output signals OUT-A to OUT-D are generated by the phase shift control method. Further, the insulating circuits 71 to 74 secure the insulation state between the primary side circuit and the secondary side circuit of the switching power supply device, and at the same time, output signals OUT-A to be output from the control circuit 70.
OUT-D is respectively connected to the first to fourth switch elements 21 to 21.
It is a circuit for supplying each to 24 gates.

FIG. 2 is a waveform diagram of the output signals OUT-A to OUT-D generated by the control circuit 70.

As shown in FIG. 2, the control circuit 70 outputs the output signals OUT-A and OUT with a predetermined dead time.
-B is alternately set to the high level, and similarly, the output signals OUT-C and OUT-D are alternately set to the high level with a predetermined dead time in between. Output signals OUT-A and OUT-D
Transformer 3 during the period when both are high level
The voltage Vmt of the primary winding 31 of 0 is in the negative direction, and
Since the voltage Vmt of the primary winding 31 of the transformer 30 is in the positive direction during the period when both the output signals OUT-B and OUT-C are at the high level, during these periods, 1
Power is transferred from the secondary circuit to the secondary circuit.

Further, output signals OUT-A and OUT-B
And a pair of output signals OUT-C and OUT-D
The phase difference with respect to the signal set consisting of is determined based on the output voltage Vo. More specifically, as the current output voltage Vo is lower than a predetermined value, the output signals OUT-A and OUT-D are increased by increasing the phase difference.
Is high level, and the output signal O
The period in which both UT-B and OUT-C are at the high level is lengthened to increase the amount of power transmission. On the contrary, the higher the current output voltage Vo is than the predetermined value, the smaller the phase difference becomes, so that the output signal OUT-
The period in which both A and OUT-D are at a high level and the period in which both output signals OUT-B and OUT-C are at a high level are shortened to reduce the amount of power transmission.
In this way, the output voltage Vo can be stabilized at a predetermined value by adjusting the phase difference.

Here, as shown in FIG.
It can be seen that the start timing of the period in which the voltage Vmt of the primary winding 31 is in the negative direction is defined by the rising edge of the output signal OUT-A, and the end timing is defined by the falling edge of the output signal OUT-D. Similarly,
The start timing of the period in which the voltage Vmt of the primary winding 31 of the transformer 30 is in the positive direction is defined by the rising edge of the output signal OUT-B, and the end timing thereof is the output signal OU.
It is defined by the fall of TC. Therefore, in the present specification, the output signals OUT-A and OU are
The set of signals including T-B may be referred to as a "power transmission start signal", and the set of signals including output signals OUT-C and OUT-D may be referred to as a "power transmission end signal".

In this embodiment, the output signal OUT-
A power transmission start signal consisting of A and OUT-B controls the operation of the first arm, and output signals OUT-C and OUT-
It is important that the power transmission end signal consisting of D controls the operation of the second arm. The significance will be described below in detail.

FIG. 3 is an equivalent circuit diagram showing the state of the primary side circuit in the period a shown in FIG. As shown in FIG. 2, the period a is a period from the fall of the output signal OUT-B to the rise of the output signal OUT-A. In other words, it is a period from turning off the second switch element 22 to turning on the first switch element 21.

As shown in FIG. 3, during the period a, only the output signal OUT-D is at the high level and the other output signals are at the low level. As a result, the fourth switch element 24 is on and the other switch elements are off. During this period, free resonance operation is performed between the capacitor 21c and the inductor 40 and between the capacitor 22c and the inductor 40.

FIG. 4 is an equivalent circuit diagram showing the state of the primary side circuit in the period b shown in FIG. As shown in FIG. 2, the period b is a period from the rise of the output signal OUT-A to the fall of the output signal OUT-D. In other words, it is a period from turning on of the first switch element 21 to turning off of the fourth switch element 24.

As shown in FIG. 4, in the period a, the output signals OUT-A and OUT-D are both at the high level,
That is, since both the first switch element 21 and the fourth switch element 24 are turned on, electric power is transmitted from the primary side circuit to the secondary side circuit. Here, FIG.
Is an inductance component equivalently representing the influence of the output choke 61 on the primary side circuit, and
h ′ = n ² · Lch.

FIG. 5 is an equivalent circuit diagram showing the state of the primary side circuit in the period c1 shown in FIG. As shown in FIG. 2, the period c1 is the first half of the period from the fall of the output signal OUT-D to the rise of the output signal OUT-C. In other words, it is the first half of the period from when the fourth switch element 24 is turned off to when the third switch element 23 is turned on.

As shown in FIG. 5, in the period c1,
Only the output signal OUT-A is at high level, and the other output signals are at low level. As a result, the first switch element 21 is in the on state and the other switch elements are in the off state. In this period, the resonance operation is performed between the capacitor 23c and the inductor 40, the inductance component Lch 'and the primary winding 31, and the capacitor 24c and the inductor 40, the inductance component Lch' and the primary winding are performed. Resonant operation is performed with the composite inductor made of 31. As a result, the capacitor 23c is discharged and the capacitor 24c is charged,
The voltage of the capacitor 23c becomes 0V, and the capacitor 24
When the voltage of c becomes Vin, the period ends.

FIG. 6 is an equivalent circuit diagram showing the state of the primary side circuit in the period c2 shown in FIG. As shown in FIG. 2, the period c2 is the latter half of the period from the fall of the output signal OUT-D to the rise of the output signal OUT-C. In other words, it is the latter half of the period from when the fourth switch element 24 is turned off until when the third switch element 23 is turned on.

As shown in FIG. 6, the period c2 is a period in which the energy of the inductor 40 is regenerated through the body diode of the third switch element 23. In this period, the regenerative operation of the output choke 61 is started in the secondary side circuit.

FIG. 7 is an equivalent circuit diagram showing the state of the primary side circuit during the period d shown in FIG. As shown in FIG. 2, in the period d, after the output signal OUT-C rises,
This is a period until the output signal OUT-A falls. In other words, it is a period from turning on of the third switch element 23 to turning off of the first switch element 21.

As shown in FIG. 7, in the period d, the output signals OUT-A and OUT-C are both at the high level,
That is, both the first switch element 21 and the third switch element 23 are in the ON state. This period is a period in which the energy of the inductor 40 is continuously regenerated via the first switch element 21 and the third switch element 23.

FIG. 8 is an equivalent circuit diagram showing the state of the primary side circuit in the period e shown in FIG. As shown in FIG. 2, the period e is a period from the fall of the output signal OUT-A to the rise of the output signal OUT-B. In other words, it is a period from when the first switch element 21 is turned off to when the second switch element 22 is turned on.

As shown in FIG. 8, in the period e, only the output signal OUT-C is at the high level and the other output signals are at the low level. As a result, the third switch element 23 is on and the other switch elements are off. In this period, free resonance operation is performed between the capacitor 21c and the inductor 40 and between the capacitor 22c and the inductor 40, as in the period a described above.

The above is the operation of the switching power supply device according to the present embodiment, but at the time of transition from the period a to the period b, a surge voltage is unavoidably generated due to the influence of the parasitic inductance component of the switching circuit 20. Resulting in.

FIG. 9 is an equivalent circuit diagram showing the state of the primary side circuit when a surge voltage is generated.

As shown in FIG. 9, when the period a shifts to the period b, that is, when the first switch element 21 is turned on, the discharge current Ia is discharged from the capacitor 21c connected in parallel to the first switch element 21. At the same time, the charging current Ib flows through the capacitor 22c connected in parallel to the second switch element 22. Such charging current I
b is an inductor 25, which is a parasitic inductance component,
As a result, the surge voltage is generated.

However, in this embodiment, the output signal O is supplied to the first arm which is closer to the input capacitor 10.
Since the power transmission start signal composed of UT-A and OUT-B is supplied, the parasitic inductance components causing the surge voltage are only the inductors 25 and 26,
Therefore, the surge voltage is suppressed. That is, if the power transmission start signal is supplied to the second arm far from the input capacitor 10, the parasitic inductance component that causes the surge voltage is the inductor 25.
.About.28, which causes a larger surge voltage.

As a comparative example, FIG. 10 is an equivalent circuit diagram showing the state of the primary side circuit when a surge voltage is generated when a power transmission start signal is supplied to the second arm.

As shown in FIG. 10, when the power transmission start signal is supplied to the second arm, the third switch element 23
Is turned on, the discharge current I is discharged from the capacitor 23c.
At the same time, the charging current Id flows through the capacitor 24c. Since the charging current Id flows through the inductors 25 to 28 that are parasitic inductance components, this causes a large surge voltage as compared with the present embodiment.

FIG. 11 is a waveform diagram showing changes in the source-drain voltage when the second switch element 22 is turned off in the present embodiment, and FIG. 12 shows the fourth switch element 24 in the comparative example. It is a wave form diagram which shows the change of the source-drain voltage at the time of turning off.

In the measurement of the waveform diagram shown in FIG. 11, the capacitors 21c and 22c each have a capacitance of 3300 pF, the capacitors 23c and 24c each have a capacitance of 1000 pF, and the inductor 40
Inductance of 10μH, input voltage Vin of 420
Set to V, output voltage Vo is 14.5V, output current Io
Was controlled to be 20 A. In the measurement of the waveform diagram shown in FIG. 12, the capacitors 21c and 22c each have a capacitance of 1000 pF, and the capacitors 23c and 24c each have a capacitance of 330 pF.
0 pF, the inductance of the inductor 40 is 10 μH,
Input voltage Vin is set to 420V, output voltage Vo is 1
The control was performed so that the output current Io was 4.5 V and the output current Io was 20 A. Since the set of output signals supplied to the first arm and the set of output signals supplied to the second arm are opposite in the present embodiment and the comparative example, FIGS. 11 and 12 are the same. It can be said that it is a waveform diagram in which a switch element having a function is measured under the same conditions.

As shown in FIG. 11, in this embodiment, the peak voltage applied to the second switch element 22 is 4
While it is 42V, the peak voltage applied to the fourth switch element 24 is 458V in the comparative example, as shown in FIG. That is, it can be seen that the peak voltage applied to the switch element is 16V lower in this embodiment.

From the above, it is understood that the surge voltage is reduced in the switching power supply device according to this embodiment. As a result, each switch element constituting the switching circuit 20 is prevented from being destroyed, so that it is not necessary to use an element having a particularly high breakdown voltage, which not only makes it possible to reduce the cost but also downsizes the entire apparatus. It becomes possible. It also becomes possible to improve the conversion efficiency.

As described above, according to this embodiment,
It is possible to reduce the surge voltage applied to each switch element that constitutes the switching circuit 20.

Next, a switching power supply device according to another preferred embodiment of the present invention will be described.

This embodiment can be applied together with the above embodiment or in place of the above embodiment, and the first to fourth embodiments can be applied.
The above-mentioned surge voltage is reduced by devising the actual arrangement of the switch elements 21 to 24.

FIG. 13 shows the first to fourth switch elements 2
It is a schematic perspective view which shows the external shape of FET80 which can be used as 1-24, (a) is the figure seen from the upper surface direction,
(B) is the figure seen from the bottom (mounting surface) direction.

As shown in FIG. 13, the FET 80 has an outer shape of a substantially rectangular parallelepiped, and has a source terminal S, a drain terminal D, and a gate terminal provided in this order from the bottom surface (mounting surface) 81 to the side surface 82. It has G. The FET 80 having such a configuration is placed so that the bottom surface (mounting surface) 81 is in contact with the printed board, and the source terminal S, the drain terminal D, and the gate terminal G are formed on the printed board by using solder or the like. It can be used by connecting to the corresponding wiring pattern.

FIG. 14 is a top view schematically showing a state in which the switching circuit 20 is formed on the printed circuit board by using the four FETs 80. In order to make the figure easier to see,
In FIG. 14, the components forming the capacitors 21c to 24c are omitted.

As shown in FIG. 14, in the present embodiment, the FET 80 forming the first arm controlled by the power transmission start signal forms the second arm controlled by the power transmission end signal. It is mounted closer to the input capacitor 10 than the FET 80 that operates. Thereby, the wiring between the high-side terminal H1 of the first arm and the high-side electrode of the input capacitor 10, and the wiring between the low-side terminal L1 of the first arm and the low-side electrode of the input capacitor 10 Can be shortened, and inductors 25 and 2
The inductance of 6 is reduced.

Further, in this embodiment, the common connection terminal of the two FETs 80 forming each arm, that is, the first switch element 21 (third switch element 2).
3), the FET 80 constituting the source terminal S, the FET 80 constituting the second switch element 22 (fourth switch element 24), the drain terminal D than the terminal connected to the input capacitor 10, that is, For the FET 80 that constitutes the first switch element 21 (third switch element 23), the FE that constitutes the drain terminal D and the second switch element 22 (fourth switch element 24)
For T80, the source terminal S is the input capacitor 1
It is arranged so as to be close to zero. As a result, the wiring that causes the inductors 25 and 27 can be shortened, and the inductance of the inductors 25 and 27 can be reduced.

As a comparative example, FIG. 15 is a top view schematically showing a state in which the positional relationship between the common connection terminals of the two FETs 80 forming each arm and the terminals connected to the input capacitor 10 is reversed. .

As shown in FIG. 15, if the positional relationship of these terminals is reversed, the wirings that cause the inductors 25 and 27 become longer by EX, as compared with the embodiment shown in FIG.
It can be seen that the inductance of the inductors 25 and 27 increases.

FIG. 16 shows the first and third switch elements 2
It is a schematic perspective view which shows the external shape of FET90 which is suitable to be used instead of 1 and 23, (a) is the figure seen from the upper surface direction, (b) is the figure seen from the bottom surface (mounting surface) direction.

As shown in FIG. 16, the FET 90 is a FET
It has substantially the same outer shape as 80, and its bottom surface (mounting surface) 9
The gate terminal G, the source terminal S, and the drain terminal D are provided in this order from 1 to the side surface 92.
Like the FET 80, the FET 90 having such a configuration is mounted such that the bottom surface (mounting surface) 91 is in contact with the printed board, and the source terminal S, the drain terminal D, and the gate terminal G are connected to the printed board by using solder or the like. It can be used by connecting to the corresponding wiring pattern formed above.

FIG. 17 shows two FETs 80 and two FEs.
Switching circuit 20 on the printed circuit board using T90
It is a top view which shows typically the state which comprised. Note that the capacitor 21c is also shown in FIG.
The components constituting 24c are omitted.

As shown in FIG. 17, when the two FETs 80 and 90 are used, the wirings that cause the inductors 25 and 27 can be further shortened as compared with the example shown in FIG. , 27 can be further reduced.

FIG. 18 shows the first to fourth switch elements 2
It is a schematic perspective view which shows the external shape of FET85 which is preferably used instead of 1-24, (a) is the figure seen from the upper surface direction, (b) is the figure seen from the bottom surface (mounting surface) direction.

As shown in FIG. 18, the FET 85 is a FET
It has substantially the same outer shape as 80, and its bottom surface (mounting surface) 8
A source terminal S, a gate terminal G, and a drain terminal D are provided in this order from 6 to the side surface 87.
That is, the gate terminal G is provided between the source terminal S and the drain terminal D. FE having such a configuration
Similar to the FET 80, the T85 is placed so that the bottom surface (mounting surface) 86 is in contact with the printed board, and the source terminal S, the drain terminal D, and the gate terminal G are formed on the printed board by using solder or the like. It can be used by connecting to a wiring pattern.

FIG. 19 is a top view schematically showing a state in which the switching circuit 20 is formed on the printed circuit board by using the four FETs 85. In order to make the figure easier to see,
Also in FIG. 19, the components forming the capacitors 21c to 24c are omitted.

As shown in FIG. 19, the FE in which the gate terminal G is provided between the source terminal S and the drain terminal D
When T85 is used, the wiring that causes the inductors 25 and 27 can be further shortened as compared with the example shown in FIG. 14, so that the inductance of the inductors 25 and 27 can be further reduced. In addition, FIG.
Since it is not necessary to use a plurality of types of FETs as in the example shown in (1), it is possible to reduce the component cost.

FIG. 20 is a top view schematically showing another state in which the switching circuit 20 is formed on the printed circuit board by using the four FETs 80. Also in FIG. 20, the components forming the capacitors 21c to 24c are omitted for the sake of clarity.

As shown in FIG. 20, in the present example, unlike the arrangement shown in FIG. 14, the input capacitor 10 has two FETs 80 forming the first arm and two FETs 80 forming the second arm. It is located between. This makes it possible to reduce the inductor that causes the surge voltage as a whole. In this case, the FET that constitutes one end of the input capacitor 10 and the first switch element 21
The distance between the drain terminal D of 80 and the drain terminal D of the FET 80 that constitutes the third switch element 23 is substantially equal, and the other end of the input capacitor 10 and the source of the FET 80 that constitutes the second switch element 22. If the distance between the terminal S and the source terminal S of the FET 80 forming the fourth switch element 24 is substantially equal, it is not necessary to distinguish between the first arm and the second arm. Therefore,
In this case, the power transmission start signal may be supplied to any arm.

FIG. 21 shows FETs 80, 90, 100, 1
FIG. 3 is a top view schematically showing a state in which a switching circuit 20 is formed on a printed circuit board using 10. In order to make the diagram easier to see, the capacitors 21c to 21c ...
The components that make up 24c are omitted. FET 10
Regarding the structure of 0 and 110, basically FET80 and F
Same as ET90, but the arrangement of each terminal is different. That is, in the FET 100, the drain terminal D, the source terminal S, and the gate terminal G are arranged in this order, and in the FET 110, the gate terminal, the drain terminal D, and the source terminal S are arranged in this order.

As shown in FIG. 21, such an FET 8
When 0, 90, 100 and 110 are used, it is possible to further reduce the inductor that causes the surge voltage as a whole, as compared with the example shown in FIG. Also in this case, one end of the input capacitor 10 and the first switch element 2
1 and the drain terminal D of the FET 100 constituting the third switch element 23 and the drain terminal D of the FET 90 constituting the third switch element 23 are substantially equal in distance, and the input capacitor 1
FET1 that configures the other end of 0 and the second switch element 22
If the distance between the source terminal S of 10 and the source terminal S of the FET 80 forming the fourth switch element 24 is substantially equal, it is not necessary to distinguish between the first arm and the second arm, and power transmission is started. The signal may be supplied to either arm.

As described above, in this embodiment, since the surge voltage is reduced by devising the actual arrangement of the first to fourth switch elements 21 to 24, the switching circuit 20 is configured. It is not necessary to use an element having a particularly high breakdown voltage as each of the switching elements, and it is possible not only to reduce the cost but also to downsize the entire device. It also becomes possible to improve the conversion efficiency.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. It goes without saying that it is a thing.

For example, in the switching power supply device shown in FIG. 1, a diode is used as the rectifying element that constitutes the rectifying circuit 50, but a synchronous rectifying circuit may be configured by using a transistor or the like as the rectifying element. Absent.

Further, in the switching power supply device shown in FIG. 1, the control circuit 70 belongs to the secondary side circuit,
The control circuit 70 and the switching circuit 20 are insulated from each other by the insulating circuits 71 to 74. However, by insulating the control circuit 70 and the output circuit from each other, the control circuit 70 belongs to the primary side circuit. It may be configured.

Further, in the switching power supply device shown in FIG. 1, a full bridge type switching circuit 20 is provided.
Is phase-shift controlled by the control circuit 70,
The control method for the full-bridge type switching circuit 20 is not limited to the phase shift control method, and the full-bridge type switching circuit may be controlled by any method. For example, the inductor 40 directly connected to the primary winding 31 of the transformer 30 may be omitted, and the switching circuit 20 may be controlled by the most general control method as shown in FIG.

[0097]

As described above, according to the present invention,
It is possible to provide a switching power supply device in which the surge voltage applied to the switch element is reduced. Therefore, it is not necessary to use a switch element having a particularly high breakdown voltage, which not only makes it possible to reduce the cost but also makes it possible to reduce the size of the entire device. It also becomes possible to improve the conversion efficiency.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a switching power supply device according to a preferred embodiment of the present invention.

FIG. 2 is an output signal OU generated by a control circuit 70.
It is a waveform diagram of T-A to OUT-D.

FIG. 3 is an equivalent circuit diagram showing a state of a primary side circuit in a period a.

FIG. 4 is an equivalent circuit diagram showing a state of a primary side circuit in a period b.

FIG. 5 is an equivalent circuit diagram showing a state of a primary side circuit in a period c1.

FIG. 6 is an equivalent circuit diagram showing a state of a primary side circuit in a period c2.

FIG. 7 is an equivalent circuit diagram showing a state of a primary side circuit in a period d.

FIG. 8 is an equivalent circuit diagram showing a state of a primary side circuit in a period e.

FIG. 9 is an equivalent circuit diagram of an embodiment showing a state of a primary side circuit when a surge voltage is generated.

FIG. 10 is an equivalent circuit diagram of a comparative example showing the state of the primary side circuit when a surge voltage is generated.

FIG. 11 illustrates a second switch element 22 according to an embodiment.
FIG. 6 is a waveform diagram showing a change in the source-drain voltage when is turned off.

FIG. 12 is a waveform diagram showing changes in the source-drain voltage when the fourth switch element 24 is turned off in the comparative example.

FIG. 13 is a schematic perspective view showing the outer shape of an FET 80,
(A) is a view seen from the top direction, (b) is a bottom surface (mounting surface)
It is the figure seen from the direction.

FIG. 14 is a top view schematically showing a state in which a switching circuit 20 is configured on a printed board using four FETs 80.

FIG. 15 shows, as a comparative example, two F's forming each arm.
It is a top view which shows the state which reversed the positional relationship of the common connection terminal of ET80, and the terminal connected to the input capacitor 10 typically.

16 is a schematic perspective view showing the outer shape of an FET 90, FIG.
(A) is a view seen from the top direction, (b) is a bottom surface (mounting surface)
It is the figure seen from the direction.

FIG. 17 is a top view schematically showing a state in which the switching circuit 20 is configured on the printed circuit board by using the two FETs 80 and 90.

FIG. 18 is a schematic perspective view showing the outer shape of the FET 85,
(A) is a view seen from the top direction, (b) is a bottom surface (mounting surface)
It is the figure seen from the direction.

FIG. 19 is a top view schematically showing a state in which the switching circuit 20 is configured on a printed circuit board by using four FETs 85.

FIG. 20 is a top view schematically showing another state in which the switching circuit 20 is configured on the printed circuit board by using the four FETs 80.

FIG. 21 is a top view schematically showing a state in which a switching circuit 20 is formed on a printed circuit board using FETs 80, 90, 100 and 110.

FIG. 22 is a switching circuit 2 based on a general control method.
It is an operation waveform diagram of 0.

[Explanation of symbols]

1 DC input power supply 2,3 Input power supply terminal 4,5 Output power supply terminal 6 load 10 input capacitors 20 switching circuits 21 First switch element 22 Second switch element 23 Third switch element 24 Fourth switch element 21c to 24c capacitors 25-28 inductor 30 transformers 30a Secondary side center tap 31 Primary winding 32, 33 secondary winding 40 inductor 50 rectifier circuit 51 First Diode 52 Second diode 50a Rectification output point 60 smoothing circuit 61 Output choke 62 Output capacitor 70 Control circuit 71-74 Insulation circuit 80,85,90,100,110 FET 81, 86, 91 Bottom surface (mounting surface) 82,87,92 Sides H1 High side terminal of the first arm H2 High-side terminal of second arm L1 Low-side terminal of first arm L2 second arm low side terminal Midpoint of M1 first arm M2 Midpoint of second arm G gate terminal S source terminal D drain terminal

Continued front page    F-term (reference) 5H730 AA15 BB27 DD04 EE02 EE03                       EE08 EE59 FD01 FG02 ZZ11                       ZZ15

Claims (15)

[Claims] 1. A full bridge type switching circuit having a first arm and a second arm, which is provided between the input capacitor, a transformer, a primary winding of the transformer, and a transformer. A switching power supply device comprising: an output circuit connected to a secondary winding; and a control circuit for controlling the switching circuit, the switching power supply device comprising:
Arm has a pair of switch elements composed of first and second switch elements, and the first and second switch elements are both terminals connected to the input capacitor rather than a common connection terminal. Is arranged so as to be close to the input capacitor. 2. The second arm has a pair of switch elements including a third and a fourth switch element, and the third arm
And the fourth switch element is arranged such that a terminal connected to the input capacitor is closer to the input capacitor than a common connection terminal. Switching power supply. 3. The switching power supply device according to claim 1, wherein terminals of the first to fourth switch elements are arranged in the same manner. 4. The control terminal of each of the first to fourth switch elements is arranged between a terminal connected to the input capacitor and the common connection terminal. Switching power supply. 5. The terminals of the first and second switch elements are different from each other, the terminals of the third and fourth switch elements are different from each other, and the terminals of the first and third switch elements are different from each other. 3. The switching power supply device according to claim 1, wherein the arrangements are equal to each other, and the arrangements of the terminals of the second and fourth switch elements are equal to each other. 6. The second arm has a pair of switch elements including third and fourth switch elements, and the input capacitor has the first and second switch elements and the third and fourth switch elements. The switching power supply device according to claim 1, wherein the switching power supply device is disposed between the switching power supply device and the switching device. 7. The switching power supply device according to claim 6, wherein the terminals of the first to fourth switch elements are arranged in the same manner. 8. The third and fourth switch elements are arranged such that a terminal connected to the input capacitor is closer to the input capacitor than a common connection terminal. The switching power supply device according to claim 6. 9. The switching power supply device according to claim 8, wherein terminals of the first to fourth switch elements are arranged differently from each other. 10. A full bridge type switching circuit having a first arm and a second arm, which is provided between the input capacitor, a transformer, a primary winding of the transformer, and a transformer. A switching power supply device comprising: an output circuit connected to a secondary winding; and a control circuit for controlling the switching circuit, wherein the first arm is connected to one terminal of the input capacitor. A third switch element having the switch element and a second switch element connected to the other terminal of the input capacitor, and the second arm connected to the one terminal of the input capacitor, and the input capacitor A fourth switch element connected to the other terminal of the third switch element, the terminals of the first and second switch elements having different arrangements from each other, And a terminal arrangement of the fourth switch element is different from each other. 11. The switching according to claim 10, wherein terminals of the first and third switch elements are arranged in the same manner and terminals of the second and fourth switch elements are arranged in the same manner. Power supply. 12. The switching power supply device according to claim 10, wherein the terminals of the first to fourth switch elements are arranged differently from each other. 13. An input capacitor, a transformer, a full-bridge type switching circuit provided between the input capacitor and the primary winding of the transformer and having first and second arms, and the transformer. A switching power supply device comprising: an output circuit connected to a secondary winding; and a control circuit for controlling the switching circuit, wherein the first arm is connected to one terminal of the input capacitor. A third switch element having a switch element and a second switch element connected to the other terminal of the input capacitor, the second arm being connected to the one terminal of the input capacitor, and the input capacitor A fourth switch element connected to the other terminal of the input capacitor, wherein the input capacitor includes the first and second switch elements and the third and third switch elements. A switching power supply device, wherein the switching power supply device is arranged between the fourth switching element and the fourth switch element. 14. The distance from the one terminal of the input capacitor to the first switch element and the distance from the one terminal of the input capacitor to the third switch element are substantially equal to each other, 14. The distance from the other terminal of the input capacitor to the second switch element and the distance from the other terminal of the input capacitor to the fourth switch element are substantially equal. The switching power supply device according to. 15. A full-bridge type switching circuit having a first arm and a second arm, which is provided between the input capacitor, a transformer, a primary winding of the transformer, and a transformer. A switching power supply device comprising: an output circuit connected to a secondary winding; and a control circuit for controlling the switching circuit, wherein the first arm is connected to one terminal of the input capacitor. A third switch element having a switch element and a second switch element connected to the other terminal of the input capacitor, the second arm being connected to the one terminal of the input capacitor, and the input capacitor A fourth switch element connected to the other terminal of the input capacitor from the one terminal of the input capacitor to the first
Of the input capacitor and the distance from the one terminal of the input capacitor to the third switch element are substantially equal, and the distance from the other terminal of the input capacitor to the second switch element. And a distance from the other terminal of the input capacitor to the fourth switch element are substantially equal to each other.