JP5030157B2 - Switching power supply - Google Patents

Description

The present invention relates to a switching power supply device using an output transformer having an insulating structure.

  Conventionally, as a circuit configuration for canceling the common mode current in this type of switching power supply device, for example, there is the one shown in FIG.

  The switching power supply device of FIG. 10 includes a power supply terminal 110a and a ground terminal 110b that perform AC input, a line filter circuit 112, a diode bridge 1154 that performs full-wave rectification, an input capacitor C1, a drive circuit 116, and a pair of MOS-FETs 18 and 120. Inverter circuit 114 provided, output transformer 122 provided with primary winding 124 and secondary winding 126 having an insulating structure, rectifying / smoothing circuit 128, power supply output terminal 130a for supplying a stabilized DC voltage to a load, and a ground terminal 130b.

  In addition to this, as a circuit for canceling the common mode current, a ground capacitor C2 is provided between the ground line of the primary side inverter circuit 114 and the ground line to the ground terminal 132 known as the FG terminal connected to the ground. In addition, a grounding capacitor C3 is connected between the ground line and the ground line of the secondary side rectifying and smoothing circuit.

  In such a switching power supply circuit, in order to cancel the common mode current ic flowing through the grounding capacitors C2 and C3, when the MOS-FET 118 of the inverter circuit 114 is turned on, the equivalent capacitance Ca of the output transformer 122 is obtained. The common mode current ia flowing from the primary side to the secondary side via the first and the common mode current ib flowing from the secondary side to the primary side via the equivalent capacitance Cb when the MOS-FET 120 is turned on Need to be equal.

  For this purpose, it is necessary to adjust so that the relationship Ca≈Cb is established between the equivalent capacitances Ca and Cb formed from the primary winding 124 to the secondary winding 126 of the output transformer 122.

In order to realize this relationship, it is necessary to devise such as providing a canceling winding for equalizing the equivalent capacity in the internal structure of the transformer or arranging an electrostatic shield.
Japanese Patent Laid-Open No. 10-52036 JP 2001-25242 A JP 2000-341951 A

  However, in such a conventional method of canceling the common mode current, the relationship of Ca≈Cb in relation to the equivalent capacitances Ca and Cb formed from the primary winding 124 to the secondary winding 126 of the output transformer 122. In order to realize the above, the transformer structure becomes complicated by requiring a winding for returning the current flowing from the primary side to the secondary side from the secondary side to the primary side in the output transformer. There is a problem.

  In addition, there is a problem that the design work takes time to realize the relationship of Ca≈Cb, and the design man-hour is increased.

  Another problem is that the winding or electrostatic shield wound to return from the secondary side to the primary side causes an eddy current to flow in linkage with the magnetic flux inside the output transformer, increasing the loss.

  Furthermore, prioritizing the relationship Ca≈Cb sacrifices other characteristics. Specifically, it is not possible to prioritize a structure that prioritizes low loss, a structure that prioritizes miniaturization, or a structure that increases the coupling between windings, resulting in increased loss, increased size, or poorly coupled output. There is a problem of becoming a transformer.

It is an object of the present invention to provide a switching power supply device that can cancel a common mode current without changing the structure of an output transformer.

The present invention provides a switching power supply,
It has an even number of output transformers having the same structure including primary windings and secondary windings that are insulated, and the primary windings of the even number of output transformers are wound around the position of the AC stable potential. An output transformer circuit section in which positions are arranged symmetrically and connected in series;
An inverter circuit for alternately controlling on and off by inserting and connecting a switching element between one end of the primary winding connected in series and the power supply line and the other end of the primary winding connected in series and the ground line;
A rectifying / smoothing circuit for supplying DC power to a load after individually smoothing and rectifying AC output from secondary windings of an even number of output transformers;
It is provided with.

The present invention further includes a first grounding capacitor that is connected between the ground line and the grounding line of the inverter circuit and allows a common mode current to flow.
A second grounding capacitor that is connected between the output-side ground line and the grounding line of the rectifying and smoothing circuit unit and allows a common mode current to flow;
It is provided with.

  Here, the inverter circuit and the smoothing rectifier circuit unit are a single forward inverter circuit, a full bridge inverter circuit, or a flyback inverter circuit in which an even number of output transformers can be arranged symmetrically from the AC stable potential of the output transformer circuit unit. Including a circuit configuration.

  The smoothing rectifier circuit unit connects a rectifying / smoothing circuit to each of the secondary sides of the even number of output transformers, and the rectifying diode provided in each rectifying / smoothing circuit is placed at the position of the AC stable potential of the output transformer circuit unit. Place them symmetrically.

The smoothing rectification circuit unit supplies DC power to the load by connecting the outputs of the even number of rectification smoothing circuits in parallel. Further, the smoothing rectifier circuit unit may supply DC power to the load by connecting the outputs of the even number of rectifying and smoothing circuits in series.

  According to the present invention, an even number of output transformers having the same structure are arranged so that the winding position is symmetrical with respect to the position where the primary winding is connected in series with the AC stable potential, The common mode current flowing from the primary side to the secondary side via the equivalent capacitance of the output transformer arranged at one of the symmetrical positions is converted into the secondary via the equivalent capacitance of the output transformer arranged at the other of the symmetrical positions. Can be recovered as a common mode current flowing from the primary side to the primary side, and the common mode current flows between an even number of output transformers without going through the grounding capacitor, completely canceling the common mode current flowing through the grounding capacitor. Can do.

  In this way, by simply arranging an even number of output transformers with the same configuration, the noise terminal voltage is reduced by canceling the common mode current flowing through the grounding capacitor, and the line filter circuit provided to reduce the noise terminal voltage is compact. The loss of the line filter circuit can be reduced and the installation area can be reduced.

  Further, since the capacitance of the grounding capacitor can be reduced, the leakage current can be reduced.

  In addition, as a measure for reducing the equivalent capacity from the primary side to the secondary side of the output transformer, it is not necessary to provide a canceling winding or an electrostatic shield. It is possible to design an output transformer that prioritizes downsizing or increasing the coupling between windings, and the characteristics of the switching power supply device can be improved as a whole.

  Further, in the case of an output transformer in which a winding is formed on a substrate, in order to mount an even number of output transformers, the output transformer circuit unit of the present invention can be simply configured by simply attaching a core to the substrate.

In addition, by using an even number of output transformers with the same structure, there are no worries about insertion errors with respect to the board, the benefits of ordering and inventory management of output transformers are great, and variations between output transformers are reduced, making stable cancellation possible. Operation is obtained.

  FIG. 1 is a circuit block diagram showing an embodiment of a switching power supply device according to the present invention. In FIG. 1, the switching power supply device of this embodiment includes a line filter circuit 12 following a power input terminal 10a and a ground input terminal 10b to which AC power is input.

  For example, the line filter circuit 12 is a common circuit that attenuates low-frequency common mode noise formed by winding a copper wire around a toroidal coil core between a power supply line from the power supply input terminal 10a and a ground line from the ground input terminal 10b. Mode choke coil, X capacitor connected across the input and output lines of common mode choke coil (Across the line capacitor), and output side for attenuating high-frequency common mode noise and normal mode noise Y capacitor (line bypass capacitor) connected between the power line and the ground line.

  Following the line filter circuit 12, a diode bridge 15 for full-wave rectification of the AC power supply is provided. Following the diode bridge 15, an input capacitor C1 is provided.

  Subsequently, an inverter circuit 14 is provided. The inverter circuit 14 is composed of MOSFETs 18 and 20 which are switching elements disposed on the power supply side and the ground side of the drive circuit 16 and the output transformer circuit unit 22, respectively.

  As the inverter circuit 14 of the present embodiment, as will be clarified in the following description, a flyback inverter, a forward inverter, or the like that can arrange switching elements on the power supply side and the ground side with respect to the output transformer circuit unit 22. Use a full bridge inverter.

  The drive circuit 16 controls on and off of the MOSFETs 18 and 20 so as to stabilize the output voltage for the load at a predetermined voltage. In this case, the output voltage for the load is detected and input via an isolation circuit such as a photocoupler. However, illustration of this point is omitted.

  Following the inverter circuit 14, an output transformer circuit unit 22 is provided. The output transformer circuit unit 22 of the present embodiment has an even number of the same structure, that is, four output transformers 22-1 to 22-4 in the present embodiment, and the output transformers 22-1 to 22-4. Each of which has primary windings 24-1 to 24-4 and secondary windings 26-1 to 26-4 that are insulated, and the primary windings 24-1 to 24-4 are connected to an AC stable potential 34. The winding positions are arranged symmetrically with respect to the positions, and are connected in series.

  That is, the output transformers 22-1 to 22-4 have polarities indicated by dots in the primary windings 24-1 to 24-4 and the secondary windings 26-1 to 26-4, respectively. The positions of the dots indicating the polarities of the primary windings 24-1 to 24-4 are arranged so as to be symmetric with respect to the position of the stable potential 34.

  Following the output transformers 22-1 to 22-4, rectifying and smoothing circuits 28-1 to 28-4 are provided. The rectifying / smoothing circuits 28-1 to 28-4 include a rectifying diode and a smoothing capacitor, and the specific circuit configuration is based on a flyback method, a forward method, or a full bridge method in the inverter circuit 14. Take different circuit configurations.

  The outputs of the rectifying / smoothing circuits 28-1 to 28-4 are connected in parallel, and are connected to a power output terminal 30a and a common output terminal 30b for supplying DC power to a load.

  Further, a ground capacitor (first ground) for causing a common mode current to flow between the ground line of the inverter circuit 14 which is the primary side of the output transformer circuit section 22 and the ground line from the ground terminal 32 connected to the ground. (Capacitor) C2 and a grounding capacitor (second grounding capacitor) that also causes a common mode current to flow between the ground line and the ground line connected to the common output terminal 30b on the secondary side of the output transformer circuit unit 22. ) C3 is connected.

  FIG. 2 is a circuit block diagram showing the operation of canceling the common mode current by taking out the output transformer circuit unit 22 of FIG. 1 together with the inverter-side MOSFET and the rectifying / smoothing circuit.

  The four output transformers 22-1 to 22-4 provided in the output transformer circuit unit 22 of the present embodiment are output transformers having the same structure. The output transformers 22-1 to 22-4 have equivalent capacitances Ca1 and Cb1 due to the transformer structure between the primary windings 24-1 to 24-4 and the secondary windings 26-1 to 26-4. , Ca2 and Cb2, Ca3 and Cb3, and Ca4 and Cb4, respectively. Since each transformer has the same structure, their equivalent capacities are almost the same between the transformers.

That is, by using the same output transformers 22-1 to 22-4, the equivalent capacitance relationship is expressed as Ca 1 = Ca 2 = Ca 3 = Ca 4.
Cb1 = Cb2 = Cb3 = Cb4
The relationship is automatically realized.

  Since the output transformers 22-1 to 22-4 are arranged symmetrically with respect to the AC stable potential 34 and connected, the voltage applied in accordance with the alternate on / off operation of the MOSFETs 18 and 20 of the inverter circuit 14 is also Applied symmetrically with respect to the AC stable potential 34.

For this reason, when the same AC voltage is applied to the capacitors Ca1, Ca2, Ca3, Ca4 and Cb1, Cb2, Cb3, Cb4 having the same capacity,
I = ωCV
It turns out that the alternating current which flows by becomes the same value.

That is, ia1 = ia4 between the currents flowing through the equivalent capacitance of the output transformer 22-1.
ia2 = ia3
ib1 = ib4
ib2 = ib3
The relationship is established.

  Here, at the timing when the MOSFET 18 is turned on and at the same time the MOSFET 20 is turned off, the equivalent capacitances Ca1, Cb2, Ca2, and Cb2 of the output transformers 22-1 to 22-2 are respectively passed through as shown in the figure. Currents ia1, ib1, ia2, ib2 flow from the secondary side to the secondary side.

  On the other hand, for the output transformers 22-3 and 22-4 that are symmetrical with respect to the AC stable potential 34, the currents ia3, ib3 from the secondary side to the primary side via the equivalent capacitors Ca3, Cb3, Ca4, Cb4. ia4 and ib4 flow.

  That is, in the output transformers 22-1 and 22-2, the common mode current flowing from the primary side to the secondary side does not pass through the grounding capacitors C <b> 2 and C <b> 3, and the output transformer 22 is symmetric with respect to the AC stable potential 34. Since the secondary side of −3, 22-4 can be recovered from the primary side, their combined current is theoretically zero.

  The combined current of the common mode current that has flowed through the output transformer circuit section 22 flows through the ground capacitor C3 on the secondary side to become a common mode current ic, and is measured as a noise terminal voltage when measured at the ground terminal 32.

  In the present embodiment, since the common mode current ic becomes zero, the noise terminal voltage is zero even when measured at the ground terminal 32 and is not measured, and the common mode current is almost completely cancelled. Can be produced.

  Of course, in an actual circuit, there is some variation between the output transformers 22-1 to 22-4 even if they have the same structure, and their equivalent capacitances are not necessarily the same, but this level is slightly small. The combined current generated by the variation is very small, and as a result, the common mode current ic can be suppressed to a very small current.

  FIG. 3 is a circuit block diagram showing a circuit configuration of a rectifying / smoothing circuit when a flyback inverter circuit is used as the inverter circuit of this embodiment.

  In FIG. 3, the flyback inverter circuit 14-1 can create the AC stable potential 34 by disposing the MOSFETs 18 and 20 on the power supply side and the ground side with respect to the output transformer circuit unit 22.

  The rectifying / smoothing circuits 28-1 to 28-4 provided on the secondary side of the output transformers 22-1 to 22-4 arranged symmetrically with respect to the AC stable potential 34 with respect to the flyback inverter circuit 14-1. D11 and C11, D12 and C12, D13 and C13, and D14 and C14, each comprising a diode and a capacitor, are provided.

  The arrangement of the rectifying diodes and the smoothing capacitors of the rectifying / smoothing circuits 28-1 to 28-4 is also symmetric with respect to the AC stable potential 34, similarly to the output transformers 22-1 to 22-4. It is arranged.

  Specifically, the rectifying diodes D11, D12, D13, and D14 are arranged on the lines with the dots indicating the polarities of the output transformers 22-1 to 22-4, so that a symmetric circuit configuration is obtained.

  As shown in the rectifying / smoothing circuits 28-1 to 28-4 of FIG. 3, the circuit composed of the rectifying diode and the smoothing capacitor is arranged so as to be symmetrical with respect to the AC stable potential 34. 2 can realize the symmetrization of the AC voltage applied to the equivalent capacitances Ca1 to Ca4 and Cb1 to Cb4 of the output transformers 22-1 to 22-4 shown in FIG. The circuit accuracy for reducing the combined current of the current flowing through the capacitor to zero can be improved.

  In the flyback inverter circuit 14-1, for example, when the output transformer 22-1 is taken as an example, energy is stored in the output transformer 22-1 when the MOSFET 18 is on, and a diode D11 when the MOSFET 18 is off. To supply energy to the load. Since energy is supplied to the load by discharging the capacitor C11, a capacitor having a relatively large capacity is required.

  FIG. 4 is a circuit block diagram showing another rectifying / smoothing circuit corresponding to the flyback inverter circuit 14-1. In the rectifying / smoothing circuits 28-1 to 28-4 of FIG. 4, the polarity shown for the secondary windings 26-1 to 26-4 of the output transformers 22-1 to 22-4, contrary to FIG. 3. By connecting rectifying diodes D11, D12, D13, D14 to the line on the opposite side to the dot indicating, a rectifying / smoothing circuit is arranged vertically symmetrically with respect to the AC stable potential 34.

  With respect to the symmetrical arrangement of the diodes of the rectifying and smoothing circuit, the AC voltages applied to the equivalent capacitors Ca1 to Ca4 and Cb1 to Cb4 of the output transformers 22-1 to 22-4 in FIG. Therefore, the AC voltage applied to each can be made the same, and the AC current flowing through the equivalent capacitance can be made the same.

  FIG. 5 is a circuit block diagram showing a circuit configuration of a rectifying / smoothing circuit when the forward inverter circuit 14-2 is used as the inverter circuit of this embodiment.

  Even when the forward inverter circuit 14-2 is used as the inverter circuit, the MOSFETs 18 and 20 are symmetrically arranged on the power supply side and the ground side of the output transformer circuit unit 22 to perform switching control.

  In the forward inverter circuit 14-2, the rectifying / smoothing circuits 28-1 to 28-4 provided on the secondary side of the output transformers 22-1 to 22-4 are diodes D11 to D14, D21 to D24, and choke coils L11 to L14. And capacitors C11 to C14.

  In this embodiment, the rectifying / smoothing circuits 28-1 to 28-4 of the forward inverter circuit 14-2 are compared to the rectifying / smoothing circuits 28-1.28-2. , 28-4 are arranged so as to be vertically symmetrical with respect to the AC-side stable potential 34 on the primary side.

  That is, the diodes D11 to D14 and the choke coils L11 to L14 are connected to the AC stable potential on the line side to which the dots indicating the polarities of the secondary windings 26-1 to 26-4 of the output transformers 22-1 to 22-4 are attached. The diodes D21 to D24 are connected so as to be symmetrical with respect to the AC stable potential 34.

  As described above, the rectifying / smoothing circuits 28-1 to 28-4 are also arranged symmetrically with respect to the AC stable potential 34, so that the alternating current applied to the equivalent capacitors of the output transformers 22-1 to 22-4. By making the voltage the same, it is possible to increase the accuracy with which the alternating currents flowing through the equivalent capacitors are made the same.

  Here, in the forward inverter circuit 14-2, for example, when the output transformer 22-1 side is taken as an example, when the MOSFET 18 is turned on, the diode D11 conducts and current flows through the load, and when the MOSFET is turned off. Supplies the energy stored in the choke coil L11 to the load through the diode D12. Therefore, the capacitance of the capacitor C11 can be reduced as compared with the flyback inverter circuit 14-1 shown in FIGS.

  FIG. 6 is a circuit block diagram showing another embodiment of the rectifying / smoothing circuit corresponding to the forward inverter circuit 14-2. In the rectifying / smoothing circuits 28-1 to 28-4 of the embodiment of FIG. 6, the dots indicating the polarities shown for the secondary windings 26-1 to 26-4 of the output transformers 22-1 to 22-4 are provided. Diodes D11 to D14 and choke coils L11 to L14 are connected to a line opposite to the attached line, and diodes D21 to D24 are connected correspondingly.

  Also in this case, the rectifying / smoothing circuits 28-1, 28-2 and the rectifying / smoothing circuits 28-3, 28-4 have a symmetrical circuit arrangement with respect to the primary AC stable potential 34, and the forward inverter The AC voltage applied to each of the output transformers 22-1 to 22-4 in accordance with the switching operation of the circuit 14-2 is made the same so that the currents flowing in the equivalent capacitors are made the same, thereby making the combined current zero and the secondary side grounding The common mode current ic flowing through the capacitor C3 can be made zero.

  FIG. 7 is a circuit block diagram showing another embodiment in which the outputs of the rectifying and smoothing circuit are connected in series. 7, the inverter circuit 14 and the output transformer circuit unit 22 are the same as those in the embodiment of FIG. 1, but the output side of the rectifying / smoothing circuits 28-1 to 28-4 is connected to the power output terminal 30a for the load and the common output. The terminal 30b is connected in series. As a result, a voltage obtained by adding the DC voltages generated by the four rectifying and smoothing circuits 28-1 to 28-4 can be supplied to the load.

  Also in this case, the MOSFETs 18 and 20, the output transformers 22-1 to 22-4, and the rectifying / smoothing circuits 28-1 to 28-4 are symmetrically arranged in the illustrated state with respect to the AC stable potential 34. The AC voltage applied to the output transformers 22-1 to 22-4 in accordance with the switching operation of the inverter circuit 14 is the same, the currents flowing through the equivalent capacitors on the primary side and the secondary side are made the same, and the synthesis By setting the current to zero, the common mode current ic flowing through the secondary side grounding capacitor C3 can be canceled as zero.

  7 is connected in series in the case of the flyback inverter circuit 14-1 in FIGS. 3 and 4, the forward inverter circuit 14 in FIGS. The same applies to the case of -2.

  FIG. 8 is a circuit diagram showing another embodiment using a full bridge inverter circuit. In the full bridge inverter circuit 14-3 of FIG. 8, a full bridge circuit is configured by arranging MOSFETs 18-1, 18-2 and MOSFETs 20-1, 20-2 with respect to the output transformer circuit unit 22. Yes.

  That is, when the MOSFETs 18-1 and 18-2 are simultaneously turned on, a current is passed from the left to the right through the primary windings 24-1 to 24-2 connected in series with the output transformers 22-1 to 22-4. The MOSFETs 20-1 and 20-2 are simultaneously turned on, and a current is passed through the primary windings 24-1 to 24-2 connected in series from the right to the left, and this is repeated.

  The output transformers 22-1 to 22-4 are arranged so as to be symmetrical with respect to the AC stable potential 34 of the primary windings 24-1 to 24-4 connected in series in the illustrated circuit diagram.

  As a result, the AC voltage applied to the output transformers 22-1 to 22-4 accompanying the switching operation of the full bridge inverter circuit 14-3 is made the same, the currents flowing through the respective equivalent capacitors are made the same, and the combined current is made zero. The common mode current ic flowing in the secondary side grounding capacitor C3 can be canceled to zero.

  FIG. 9 is a circuit block diagram showing a specific circuit configuration of the rectifying / smoothing circuits 28-1 to 28-4 in the full-bridge inverter circuit 14-3 of FIG.

  In FIG. 9, rectifying / smoothing circuits 28-1 to 28-4 corresponding to the full bridge inverter circuit 14-3 include diodes D11 to D14, diodes D21 to D24, choke coils L11 to L14, and capacitors C11 to C14. For the secondary windings 26-1 to 26-2, diodes D 11 to D 14 and diodes D 21 to D 24, and choke coils L 11 to L 14 are connected to the dot side indicating polarity, and the AC stable potential 34 is In this case, the rectifying / smoothing circuits 28-1, 28-2 and the rectifying / smoothing circuits 28-3, 28-4 are arranged so as to be symmetrical.

  In the above embodiment, the MOSFET is taken as an example of the switching element of the inverter, but other switching elements may be used.

  In the above embodiment, the case where the number of output transformers provided in the output transformer circuit unit is four is taken as an example, but the number of output transformers may be an even number other than this, for example, two. Or it is good also as six pieces.

  In this case, if the number of output transformers increases, each output transformer can be miniaturized if the capacity is the same. However, if the number is too large, there is a problem in circuit implementation, so the maximum number of output transformers is limited to a certain value. Is done.

  Moreover, as an output transformer used in this embodiment, the coil is formed with a conductor pattern on a circuit board as well as a normal transformer structure in which a primary winding and a secondary winding are arranged in an insulating structure on a core. There may be a plane mounting type output transformer structure in which the core is mounted, and an appropriate transformer structure can be applied as it is as long as the structure is the same.

  In the present invention, the primary winding of the output transformer connected in parallel to the AC stable potential point may be connected in series.

  Further, although the above-described embodiment includes the ground capacitors C2 and C3, it may be a switching power supply device in which the ground capacitors C2 and C3 are eliminated, and in this case, a noise reduction effect can be effectively obtained.

Further, the present invention includes appropriate modifications that do not impair the object and advantages thereof, and is not limited by the numerical values shown in the above embodiments.

The circuit block diagram which showed embodiment of the switching power supply device by this invention A circuit block diagram showing the operation of canceling the common mode current by taking out the output transformer circuit section of FIG. The circuit block diagram which showed the output transformer circuit part of this embodiment provided with the smoothing rectifier circuit corresponding to a flyback inverter circuit The circuit block diagram which showed the output transformer circuit part of this embodiment provided with another smoothing rectifier circuit corresponding to a flyback inverter circuit The circuit block diagram which showed the output transformer circuit part of this embodiment provided with the smoothing rectifier circuit corresponding to a forward inverter circuit A circuit block diagram showing an output transformer circuit unit of this embodiment provided with another smoothing rectifier circuit corresponding to the forward inverter circuit The circuit block diagram which showed other embodiment which connected the output of the rectification smoothing circuit in series Circuit block diagram showing another embodiment using a full bridge inverter circuit The circuit block diagram which showed embodiment of the rectification smoothing circuit part in the full bridge inverter circuit of FIG. Circuit block diagram showing common mode current canceling operation in a conventional switching power supply

Explanation of symbols

10a: power input terminal 10b: ground input terminal 12: line filter circuit 14: inverter circuit 14-1: flyback inverter circuit 14-2: forward inverter circuit 14-3: full bridge inverter circuit 15: diode bridge 16 : Drive circuit 18, 20: MOSFET
22: Output transformer circuit section 22-1 to 22-4: Output transformer 24-1 to 24-4: Primary winding 26-1 to 26-4: Secondary winding 28-1 to 28-4: Rectification smoothing Circuit 30a: power supply output terminal 30b: common output terminal 32: ground terminal 34: AC stable potential point

Claims (6)

An even number of output transformers having the same structure including primary windings and secondary windings arranged in an insulated manner, and the primary windings of the even number of output transformers with respect to the position of the AC stable potential An output transformer circuit section in which winding positions are arranged symmetrically and connected in series;
An inverter circuit for alternately turning on and off by inserting and connecting a switching element between one end of the primary winding connected in series and the power supply line and the other end of the primary winding connected in series and the ground line When,
A rectifying / smoothing circuit for supplying direct current power to a load after individually smoothing and rectifying AC output from secondary windings of the even number of output transformers;
A switching power supply device comprising:
The switching power supply device according to claim 1, further comprising:
A first grounding capacitor connected between the ground line of the inverter circuit and the grounding ground line to flow a common mode current;
A second grounding capacitor that is connected between the output-side ground line and the grounding ground line of the rectifying and smoothing circuit unit and allows a common mode current to flow;
A switching power supply device comprising:
2. The switching power supply device according to claim 1, wherein the inverter circuit and the smoothing rectifier circuit unit are capable of arranging an even number of output transformers symmetrically from the AC stable potential of the output transformer circuit unit, A switching power supply comprising a circuit configuration including a full bridge inverter circuit or a flyback inverter circuit.
2. The switching power supply device according to claim 1, wherein the smoothing rectifier circuit unit includes a rectifying / smoothing circuit connected to each of the secondary sides of the even number of output transformers, and a rectifying diode provided in each rectifying / smoothing circuit. Is arranged symmetrically with respect to the position of the AC stable potential of the output transformer circuit section.
2. The switching power supply device according to claim 1, wherein the smoothing rectifier circuit unit supplies the DC power to a load by connecting outputs of the even number of rectifying and smoothing circuits in parallel.
  2. The switching power supply unit according to claim 1, wherein the smoothing rectifier circuit unit supplies the DC power to the load by connecting the outputs of the even number of rectifying and smoothing circuits in series.

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