JPH0223063A - Switching power supply device - Google Patents

Abstract

PURPOSE:To improve the reliability of a transformer by branching the primary side current of an insulating converter transformer to two or more sets of windings. CONSTITUTION:In a switching power supply device, its DC input power is controlled ON, OFF by an oscillation driving circuit 24, and supplied to a series resonance circuit having primary windings N1a, N1b of an insulating converter transformer 22, connected in parallel with each other and a capacitor 23 through the primary winding NA of a saturable reactor transformer 21. The winding N1a of the primary windings N1a, N1b of the transformer 22 is wound inside the primary winding unit of a coil bobbin 22B. In this case, the primary side exciting current of the transformer 22 is branched to reduce its heat generation, its secondary side is of bifilar winding to simplify the winding work, and the resonance capacitor of the secondary side is omitted to reduce its cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching power supply device for supplying large amounts of power, and particularly to a switching power supply device using a current resonance magnetic flux control method.

[Summary of the invention]

The present invention provides a switching power supply device in which DC input power is controlled on and off by a switching element of an oscillation drive circuit and supplied to the primary side of an isolated converter transformer, and a constant voltage output is obtained from the secondary side of the isolated converter transformer. By dividing the windings on the primary side or the secondary side of the transformer into two or more sets and winding them, the maximum load power is increased, heat generation is suppressed, and a configuration suitable for supplying large power is realized.

[Conventional technology]

Various types of switching power supply devices are known that perform switching control on a DC input power source and obtain a desired constant voltage output via a power transformer or the like. As an example of such a switching power supply device, the present applicant has previously disclosed Japanese Patent Application Laid-Open No. 62-64266 and Japanese Patent Application Laid-Open No. 62-71382.
In the above publications, a saturable reactor transformer is used, the primary side array resonance impedance is controlled according to the output voltage from the secondary side of the power transformer, and the output voltage is stabilized by controlling the excitation current. We are proposing a switching power supply.

FIG. 7 shows an example of such a switching power supply device. As a DC input power source for the power supply device, for example, a commercial AC input type 'alO1 is rectified by a diode bridge type full-wave rectifier 102 and a smoothing capacitor 103. Obtained by smoothing. This DC input power supply is
Through the primary winding NA of the saturable reactor transformer 111,
It is supplied to a series resonant circuit consisting of a primary winding N of an isolated converter transformer 112 and a capacitor 113.

The current of this DC input power supply is the saturable reactor transformer 1
A switching transistor Q1 whose base is connected to a series resonant circuit of No. 11 secondary winding N□ and a capacitor CI+.
A series resonant circuit consisting of the secondary winding NH and the capacitor C1 is turned on and off by a two-stone automatic oscillation drive circuit 115 using a switching transistor Q2 connected to the base.

As shown in FIG. 8, for example, the saturable reactor transformer 111 has a control winding NC wound in a direction orthogonal to each of the windings N a , N a + and N, 2,
According to the current flowing through the control winding N, the windings N□ and N, ! By controlling the inductance of
The oscillation frequency of the oscillation drive circuit 115 is controlled.

A parallel resonant capacitor C8 and a rectifying and smoothing circuit 116 are connected to the secondary winding N2 of the isolated converter transformer 112, and the DC output voltage from the rectifying and smoothing circuit l16 is converted into a control current by a control circuit 117. It is sent to the control winding Nc of the saturable reactor transformer 111.

Therefore, the inductance of the saturable reactor transformer 111 changes in accordance with the fluctuation of the DC output voltage, and the primary side row resonance impedance of the insulated converter transformer 112 changes to change the excitation current, thereby keeping the DC output voltage constant. can be controlled.

[Problems to be Solved by the Invention] By the way, when applying such a switching power supply device to a large power supply, the insulating converter transformer 11
Problems such as heat generation in the second winding and soaring manufacturing costs arise.

That is, as the wire for the winding of the insulated converter transformer 112, a phosphor wire is used, which has less skin effect at high frequencies and less eddy current loss, but this Litz wire has a diameter of 6.
For example, 130 pieces of 0 μm polyurethane coated thin copper wire, 1
Currently, products made by bundling and twisting 08 or 80 fibers are available, and the greater the number of twists, the higher the manufacturing cost. When the load power increases to about 240W, for example, one of the isolation converter transformers 112
Excitation current flowing through the next winding N! 1 becomes 8A, and even with the above 130 litz wires bundled and twisted, the above primary winding N,
(42 turns) the temperature rise reaches 65°C.

Here, a method of increasing the cross-sectional area of the ferrite core of the insulating converter transformer 112 to reduce the number of turns of the winding wire may be considered, but this is not preferable because the ferrite core becomes large and the transformer becomes large and heavy, and the cost also increases.

Next, the secondary s line N2 of t@ edge converter transformer l12
In this case, not only is an expensive medium-high voltage film capacitor for high frequencies required as the resonance capacitor C5, but also the winding Nz has one winding part centered on the ground point and the other winding part located inside and outside the bobbin. Because it is wound in a j-inclined manner,
The leakage inductances of these inner and outer winding portions appear differently, causing so-called biased magnetization in the hysteresis curve of the ferrite magnetic core, and the currents of the switching transistors and rectifier diodes become asymmetric.
The disadvantage is that heat generation due to losses appears differently. In addition, the number of turns of each of the inner and outer winding parts is 5 each.
Even if the number of turns is 0 to 60, the total number of secondary windings N2 reaches 100 to 120 coils, which has the disadvantage of requiring a long winding time and being poor in mass productivity.

The present invention has been made in view of the conventional situation, and even when the load power increases to, for example, 200 W or more, heat generation in the primary winding of an isolated converter transformer increases and heat generation in the secondary winding increases. The present invention aims to provide a switching power supply device that can effectively prevent a decrease in efficiency and improve maximum load power and power conversion efficiency.

[Means to solve the problem]

In order to solve the above-mentioned problems, the switching 'r4a device according to the present invention has an oscillation drive circuit connected to the primary winding of the insulated converter transformer for controlling the switching of the excitation current on the primary side, and the above-mentioned insulated converter transformer In the switching power supply device, the oscillation state of the oscillation drive circuit is controlled according to the secondary output voltage of the oscillation drive circuit to control the secondary output voltage to a constant voltage. It is characterized by dividing the winding into two or more sets and connecting them in parallel to separate the primary excitation current of the insulating converter transformer, or by dividing the secondary winding of the insulating converter transformer into two sets. It is characterized by being divided, connected at one end, and wound in parallel.

[For production]

By shunting the primary excitation current of the isolated converter transformer, heat generation can be reduced and the reliability of the transformer can be improved. In addition, by using so-called bifilar winding on the secondary side, the winding work is simplified and the
Cost reduction can be achieved by omitting the next-side resonant capacitor.
It is possible to prevent adverse effects caused by biased magnetization of each winding from the ground point.

〔Example〕

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

In FIG. 1, the DC input power to the power supply device is obtained, for example, by rectifying and smoothing the aforementioned commercial AC input power.

The current of this DC input power source is controlled by on/off switching by an oscillation drive circuit 24 to be described later, and the primary windings of isolated converter transformers 22 are connected in series to each other via the primary S line NA of the saturable reactor transformer 21. Line Nla,
l'l+b and a series resonant circuit consisting of a capacitor 23. As shown in FIG. 2, the primary windings N1□, Nlk of the insulated converter transformer 22 are connected to the inside of the L-side winding portion of the coil bobbin 22B. is wound, and windings t, ff N , are wound on the outside thereof with an insulating sheet (interlayer film) 22s interposed therebetween. In this case, the leakage inductance L1. of the inner winding Nl when the secondary winding is short-circuited. and the leakage increment l-+b of the outer winding Nlk are L+->L+b, and these windings NIM, N1 . The current flowing through! 11,
! 3. As shown in FIG. 3, I+a<I+b.

In order to equalize these currents 1111% IIh, as shown in FIG.
It is sufficient to connect L in series with the winding N, .
The figure shows a coil bobbin 22 of an isolated converter transformer 22.
It shows the upper half of the B cross section, and the coil bobbin 22B
The overall cross-section of the structure shown in FIG. 2 is expressed symmetrically to the lower side of the figure.

Next, as explained in FIG. 8, the saturable reactor transformer 21 has a primary winding NA and two secondary windings Nl.
l,! 'Jag and a control winding N, said winding N
The control winding N is wound in a direction perpendicular to the winding direction of s, N□rN@2.

The secondary winding N of such a saturable reactor transformer 21,
, , N, , an oscillation drive circuit 24 for controlling on/off switching of the current of the DC input its.
is provided. This oscillation drive circuit 24 includes a switching transistor Q and a diode D H+ connected between the emitter and base of this transistor Q1.
and another pair of transistors Q! and diode D0
The transistor Q is connected in series with the DC input power supply and the primary winding NA of the saturable reactor transformer 21.
The transistor Q2 is inserted and connected between the primary winding N of the saturable reactor transformer 21 and ground. A series resonant circuit consisting of the secondary winding N,1 of the saturable reactor transformer 21 and a capacitor C□ is connected in parallel with the diode D□ between the emitter and base of the transistor Q1, and A series resonant circuit consisting of the secondary winding N■ of the saturable reactor transformer 21 and the capacitor C1 is connected in parallel with the diode I)ax. Furthermore, starting resistors R1I+R32 are inserted and connected between the DC input power source and the bases of the switching transistors Q, , Q, respectively.

Next, on the secondary side of the isolated converter transformer, a winding N2
, N, , N, are provided, and each of these windings N2
・Respectively rectifying and smoothing circuits 25., Nx and Na are connected to each other.
26.27 are provided.

Here, for example, a 135V 1.5A DC high voltage power supply used for a television image deflection system is taken out from the rectification and smoothing circuit 25, and a 15V 2A DC power supply for a signal processing circuit system is taken out from the rectification and smoothing circuit 26. A 30V2A DC power source for audio and signal systems is taken out from the rectifying and smoothing circuit 27. The DC output voltage from the rectifying and smoothing circuit 25 is converted into a control current by the control circuit 2 and sent to the control winding Nc of the saturable reactor transformer 21, and the control circuit 28 is supplied with the rectifying and smoothing circuit as a circuit power source. DC power is supplied from 26.

In the oscillation drive circuit 24 of the switching power supply device having such a configuration, two of the saturable reactor transformers 21
Next 1. The switching transistor Q1 is driven by a sinusoidal alternating current flowing through the series resonant circuit of vIN□ and the capacitor C1l, and the sine wave alternating current flowing through the series resonant circuit of the secondary windings N, z of the saturable reactor transformer 21 and the capacitor C0 drives the switching transistor Q1. Switching transistor Q! by alternating current! are driven, these transistors Q, ,Q,
The switching operation continues by turning on alternately and repeatedly.

A control winding N of the saturable reactor transformer 21 is supplied with a DC control current from a control circuit 28 obtained by detecting the output voltage of the insulated converter transformer 22, and the insulated converter transformer The control current flowing through the control line N of the saturable reactor transformer 21 is controlled by the control circuit 2 so that the DC output voltage from the transformer 22 is always constant, and the inductance of the secondary winding N,..., Nl1z is As a result, the oscillation frequency of the oscillation drive circuit 24 is controlled.

Here, when the total current (2) on the primary side of the insulated converter transformer 22 is 8App as shown in FIG. 3, each of the aforementioned primary windings N1. , N1. Due to the difference in cage inductance, these windings Nla, N1. The current flowing through r+i, [Ik is, for example, 3.8A□, 4.2A,
, but the winding N1. These currents can be made equal by connecting choke coils 22L in series.

In this way, the primary winding of the insulated converter transformer 22 is connected to each winding portion N1, N1, . The primary side excitation current is divided into ■1
By dividing the current approximately in half, both DC resistance loss and high frequency loss of the winding are significantly reduced, improving reliability. In addition, when there is only one set of conventional primary windings, in order to reduce the temperature rise, the wire material is a Lindt wire of, for example, 60 μm.
Approximately 200 bundles were required, and such wire rods were custom-made and extremely expensive, and the space factor during winding decreased, forcing the size of the coil bobbin to be increased. On the other hand, according to this embodiment, for example, 60 μm
By connecting two sets of 108 bundles of Lindt wire in parallel, it is possible to suppress temperature rise, and the space factor is improved, reducing the number of turns (for example, 42
turn) can be realized. In addition, by dividing the primary winding into three or more sets and using smaller-diameter Lindt wire (for example, 80 bundles of 60 μm) and configuring all the wires, including the secondary, with the same wire, the manufacturing of the transformer, Assembly is easier, which is advantageous in terms of mass production and cost reduction.

By the way, the secondary winding of the isolated converter transformer 22,
In particular, for the winding N2 for high voltage extraction, one winding part and the other winding part are sequentially wound on the inside and outside of the bobbin around the ground point, so the leakage inductance of each of these inside and outside winding parts is appear differently from each other, and a so-called biased magnetization occurs in the hysteresis curve of the ferrite magnetic core.
There is a possibility that the currents in the switching transistors and rectifying diodes will become asymmetrical, and heat generation due to loss will appear differently. Therefore, as in the second embodiment shown in FIG.
The next winding N2 is divided at the ground point to form two sets of winding portions N2.
N. By connecting one end of each of these winding portions Nta and N1 and winding them in parallel around the coil bobbin 22L, as shown in FIG. , Nz>Ni and the cage inductances are made equal to each other. The other configuration of the second embodiment shown in FIG. 4 is the same as that of the embodiment shown in FIG. 1 described above, and therefore the description thereof will be omitted.

With this configuration, the biased magnetization of each winding portion N Preventing negative effects. That is, the collector current of each transistor Q1 and Q2 of the oscillation drive circuit 24 is . , Lx are currents with equal waveforms, as shown in FIG. 6, for example.

In addition, the current Its flowing from each winding portion N□, Nzh of the secondary winding to each diode of the rectifying and smoothing circuit 25,
The combined waveform of Itb has equal peak values on the positive and negative sides, as shown in Figure 6, and flows through the ground point of the secondary winding (the connection point between each winding part Ntm and No). Current! , always have the same peak value as shown in FIG. These waveforms have lower peak values than the conventional case where unbalance occurs due to biased magnetism, which reduces the load on the parts and contributes to improving the reliability of the parts. Become.

Also, capacitance i1 Cz 1, C2t,..., C! between each winding portion N, a, Lb of the secondary winding. occurs, and if each winding part 1'Jza, Nz> is formed by winding 2 m of 43 bundles of Ritz wire with a wire diameter of 60 μm and 55 turns, a combined capacitance of about 1500 to 2000 pF can be obtained. . When the ferrite core of the isolated converter transformer 22 is configured with zero-gamble, a capacitor of about 2200 pF for weak electric field switching noise countermeasures (capacitors C1l and C in FIG. 7 above) is installed on the secondary side for startup.
82) and a parallel resonance capacitor (capacitor CS in Fig. 7 above) were required, but this resonance capacitor can be omitted due to the capacitance between the bifilar windings N2 and NH. This makes it possible to reduce costs by reducing the number of parts. Moreover, since each winding part N 1 B , N z > is bifilar wound, the space factor is improved compared to conventional products, and the number of turns can be increased, which reduces the magnetic flux density of the transformer and reduces the core loss of the transformer. do.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and for example, only the secondary side of the insulating converter transformer may be wound with the bifilar winding.

Furthermore, the switching power supply device to which the present invention is applied is not limited to a magnetic flux control type, and the output voltage is stabilized by detecting the DC output voltage and changing the oscillation frequency of the switching drive circuit and the duty of the switching pulse. It goes without saying that the present invention can be applied to various switching power supply devices.

〔Effect of the invention〕

According to the switching power supply device of the present invention, since the primary side current of the isolated converter transformer is divided into two or more sets of windings, even when used for large load power supply, the winding wire material with a normal diameter can be used. This makes it possible to effectively suppress heat generation and improve the reliability of the transformer. In addition, by using so-called bifilar winding on the secondary side, the winding work is simplified and the resonant capacitor on the secondary side is omitted, reducing costs, and preventing the negative effects of biased magnetization of each winding from the ground point. can.

23... Resonance capacitor 24... Oscillation drive circuit 25.26.27... Rectification smoothing circuit N 1m,
Nlb...Primary winding (each part divided into 2) 22L.
...Choke coil 1'lzm, No.....Secondary winding (each part divided into two)

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a schematic sectional view showing an example of an isolation converter transformer, and FIG.
The figure is a waveform diagram for explaining the operation, FIG. 4 is a circuit diagram showing the main part of the second embodiment of the present invention, and FIG. 5 is a schematic cross section showing an example of the isolation converter transformer of the second embodiment. Figure, 6th
The figure is a waveform diagram to explain the operation, and Figure 7 is the conventional switching? FIG. 8 is a schematic perspective view showing an example of a saturable reactor transformer.

Claims (2)

[Claims] (1) An oscillation drive circuit that switches and controls the excitation current on the primary side is connected to the primary winding of the isolation converter transformer, and the oscillation state of the oscillation drive circuit is determined according to the secondary output voltage of the isolation converter transformer. In a switching power supply device that controls the secondary side output voltage to a constant voltage by controlling A switching power supply device characterized in that a primary side excitation current of a converter transformer is shunted. (2) An oscillation drive circuit that switches and controls the excitation current on the primary side is connected to the primary winding of the isolation converter transformer, and the oscillation state of the oscillation drive circuit is determined according to the secondary output voltage of the isolation converter transformer. The switching power supply device controls the secondary side output voltage to a constant voltage by controlling the secondary winding of the insulated converter transformer, which is characterized in that the secondary winding of the insulated converter transformer is divided into two sets, one end of which is connected and the two sets are wound in parallel. switching power supply.