JPH0426367A - One stone forward converter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a one-stone forward converter suitable for switching power supplies and the like.

[Prior Art] Conventionally, a single-stone forward converter shown in FIG. 13 has been used in switching power supplies and the like.

In the configuration of this conventional one-stone forward converter, 1 is a DC input power supply, 2 is a switching element, 3 is a transformer, 4 is an output rectifying element, 5 is an output flywheel element,
6 is a smoothing choke fill, 7 is a smoothing capacitor, 8
is the load.

Trance 3 is! It has a primary winding 11 and a secondary winding 12. The primary winding 1! DC input power supply l is connected to the winding start terminal of
The positive side of the primary winding 11 is connected, and the winding end terminal of the primary winding 11 is connected to the negative side of the DC input power source l through the switch element 2. In addition, in the connection on the secondary winding 12 side of the transformer 3, the winding start of the secondary winding 12 - the output rectifying element 4 - the smoothing titak coil 6 - the smoothing capacitor 7 - 2
A series circuit is formed at the end of the next winding 12, and the load 8 is connected in parallel to the smoothing capacitor 7.

The output flywheel element 5 is connected between the connection point between the output rectifying element 4 and the choke coil 6 and the winding end terminal of the secondary winding 12.

The operation of the conventional circuit configured as described above will be explained with reference to FIG. 14.

FIG. 14 is an equivalent circuit diagram of a conventional one-stone forward converter for explaining the reset operation of the transformer 3 shown in FIG. 13. In the figure, 21 is the output capacitance of the switching element 2, and 31 is the excitation inductance of the transformer 3.

First, when the switch element 2 is turned on, a closed circuit is formed from the positive side of the DC input power source I, through the primary winding 11 of the transformer 3, to the switch element 2, and then to the negative side of the DC input power source l, and the current flows. The voltage of the DC input power source 1 is applied to the primary winding 11 of the transformer 3, and a voltage proportional to the voltage of the DC input power source 1 is generated in the secondary winding 12 of the transformer 3. As a result, the output rectifying element 4 is turned on, and power is supplied to the load 8 via the choke coil 6.

Moreover, the electrostatic energy accumulated in the output capacitor 21 is consumed inside the switch element 2 and becomes a loss when the switch element 2 is turned on.

Excitation energy proportional to the time during which the switch element 2 is on and the voltage of the DC input power source 1 is stored in the excitation inductance 3I.

Subsequently, when the switch element 2 is turned off, the excitation inductance 31 turns off the switch element 2 in order to keep the excitation current flowing.
Generates voltage in the opposite direction to when it is on. The output capacitor 21 is charged with the sum of the voltage generated in the excitation inductance 31 and the voltage of the DC input power source 1, and the excitation energy stored in the excitation inductance 31 is transferred to the output capacitor 2.
Let's move on to the electrostatic energy of I. When all of the excitation energy of the excitation inductance 3I is transferred to the electrostatic energy of the output capacitor 21, the charging current of the output capacitor 21 becomes zero. The final energy transferred to the output capacitor 21 is released in the same loop in the current direction opposite to that during charging, returns as excitation energy of the excitation inductance 31, and the transformer 3 is reset. The operation that transformer 3 resets is 1 of transformer 3.
This is resonance caused by the excitation inductance of the next winding 11 and the output capacitance of the switch element 2, and the reset time of the transformer 3 is influenced by the values of the excitation inductance of the transformer 3, the output capacitance of the switch element 2, etc.

Next, changes in the potential of each part of the conventional single-stone forward converter during the reset operation will be explained.

FIG. 15 is an explanatory diagram in which the one-stone forward converter whose circuit configuration is shown in FIG. 13 has been redrawn so that the structure of the transformer 3 in particular is clarified to the necessary extent.

In the figure, 9 is the core of the transformer 3, 10 is the bohin of the transformer 3, 11 is the primary winding of the transformer 3, 12 is the secondary winding of the transformer 2, I3 is the winding start terminal of the winding 11, 1
4 is the winding end terminal of the winding 11, 15 is the winding start terminal of the winding 12, and 16 is the winding end terminal of the winding 12.

FIG. 16 is an explanatory diagram showing the relationship between the potentials of the terminals 13 to 16 in the state of the switch element 2 in FIG. 15. However, the turns ratio of the winding lI and the winding 12 is l・l, the voltage of the DC input power supply 1 is vl, and the voltage induced in the primary winding 11 of the transformer 3 during the period when the switch element 2 is off. Let the maximum value be VP. Further, it is assumed that the negative side of the DC input power source 1 and the negative side of the load 8 are grounded and at zero potential.

First, in FIG. 15, the terminals 13, 14, 1 of each winding when the switch element 2 is changed from on to off to on.
The change in potential of 5.16 will be explained with reference to FIG.

During this state change of the switch element 2, the potential of the winding start terminal 13 of the primary winding 11 is always Vl, and the potential of the winding start terminal 13 of the primary winding 11 is always Vl.
The potential of the winding end terminal 16 is always 0■. The potential of the winding end terminal 14 of the primary winding 11 is oV when the switching element 2 is off and Vl when it is off, but during the reset period, the induced voltage of the maximum VP (half wave of a sine wave) is applied to Vl. ) is added. On the other hand, the potential at the winding start terminal 15 of the secondary winding I2 is Vl when the switching element 2 is on and oV when it is off, or a reverse voltage of maximum VP is induced during the reset period.

As a result of the above, in the conventional example, the potential difference between the primary winding 11 and the secondary winding 12 of the transformer 3 (the potential difference between the terminals 13 and 15 and the potential difference between the terminals 4 and 16) It fluctuated from 0 to vl when the element 2 was off, from Vl to V1+VP during the reset period, and from vl to 0 when the switch element 2 was on.

[Problems to be Solved by the Invention] However, in the conventional one-wheel forward converter described above, as shown in FIG.
In the case of a structure in which the secondary winding 12 and the
The above-described fluctuation in the potential difference between the primary winding It and the secondary winding 12 causes the distributed capacitance to be charged and discharged, and the charging and discharging phenomenon due to this potential difference fluctuation increases the reset time of the transformer 3 and the switching element 2. The problem was that switching caused an increase in loss and output noise.

The present invention was devised in order to solve the above problems.
Either prevent the charging/discharging phenomenon of the distributed capacitance between the secondary windings and eliminate the increase in reset time due to this charging/discharging, or It is an object of the present invention to provide a one-stone forward converter that prevents the charging and discharging phenomenon of distributed capacitance and eliminates loss and noise increase due to this charging and discharging.

[Means for Solving the Problems] The configuration of the one-wheel forward converter of the present invention for achieving the above-mentioned objects includes: a transformer having at least a primary winding and a secondary winding, a switching element, and an output rectifier. In the one-stone forward converter, the transformer includes a primary winding element, an output flywheel element, a smoothing choke coil, and a smoothing capacitor. Using a transformer having a structure in which the winding starts of the wires are overlapped and further wound in an overlapping manner so that magnetic flux is formed in the same direction when current is passed from the winding start of the primary winding and the secondary winding, the switch element and the Output rectifying elements are connected to the winding start terminal of the primary winding and the winding start terminal of the secondary winding, respectively, or the output rectifying elements are connected to the winding end terminal of the primary winding and the winding end terminal of the secondary winding. Connect to the last terminal.

In addition, one aspect of the present invention to achieve the above-mentioned another object.
Another configuration of the stone forward converter is when forming a series circuit of the secondary winding of the transformer, the output rectifying element, the smoothing capacitor, and the smoothing choke coil in the above-mentioned configuration. It is specially recommended that the smoothing choke coil be connected between the output rectifying element and the smoothing capacitor.
[Operations] The present invention has the advantage that, depending on how the primary and secondary windings of the transformer are stacked and how the transformer is connected to the switching element and the output rectifying element, Prevents fluctuations in the potential difference that occur during the reset period, prevents charging and discharging of the distributed capacitance between the primary and secondary windings during this reset period, and eliminates the increase in reset time due to this charging and discharging. . In addition to the way the primary winding and the secondary winding are stacked and the way the transformer is connected to the switch element and the output rectifying element, the way the smoothing choke coil is connected can also be This prevents fluctuations in the potential difference that occurs between the secondary windings when the switch element is turned on and off, and prevents the charging and discharging phenomenon of the distributed capacitance between the primary and secondary windings that occurs during on and off times. This eliminates the loss and increase in noise caused by charging and discharging.

``Example'' Hereinafter, examples of the present invention will be explained in detail based on the drawings.
/Nika BF'4 t It is an explanatory diagram that has been redrawn to make it clear to the necessary extent. In the configuration of this embodiment, l is a DC input power supply, 2 is a switch element, and 3
is a transformer, 4 is an output rectifying element, 5 is an output flywheel element, 6 is a smoothing choke coil, 7 is a smoothing capacitor, 8 is a load, 9 is the core of transformer 3, 10
is the bobbin of transformer 3, 11 is the primary winding of transformer 3,
I2 is the secondary winding of transformer 3, 13 is the start terminal of winding 11, I4 is the end terminal of winding II, and 15 is the winding 1 terminal.
2 is a winding start terminal, and 16 is a winding end terminal of the winding 12. In this embodiment, as the transformer 3, the primary winding 1
A transformer is used in which the beginning of winding 1 and the beginning of winding of secondary winding are overlapped, and the windings 11 and 12 are wound in such a way that magnetic flux is formed in the same direction when current is passed from the beginning of winding. .

In the connection of this embodiment, the switching element 2 and the terminal 14 of the transformer 3 and the output rectifying element 4 and the terminal 16 of the transformer 3 are connected. This is different from the conventional example in that this is the end of the winding.

That is, the positive side of the DC input power supply l is connected to the winding start terminal 13 of the primary winding II, and the winding end terminal 14 of the primary winding 11 is connected to the switch element 2, through which the DC input power supply 1 is connected. Connected to the negative side. In addition, in the connection on the secondary winding I2 side of the transformer 3, the secondary winding 1
A series circuit is formed in which the winding start terminal 15 of No. 2 → the smoothing capacitor 7 → the smoothing capacitor 7 − the output rectifying element 4 − the winding end terminal 16 of the secondary winding J112 is formed, and the load 8 is connected in parallel to the smoothing capacitor 7. be done. The output flywheel element 5 is connected between the connection point between the output rectifying element 4 and the smoothing capacitor 7 and the winding start terminal 15 of the secondary winding 12 .

The operation and effects of the first embodiment configured as above will be described.

FIG. 3 is an explanatory diagram showing the relationship between the state of the switch element 2 and the potentials of the terminals 13, 14, 15, 16 of the transformer 3 in the first embodiment. However, winding 11 and winding 1
The winding ratio of the transformer 2 is 1.1, the voltage of the DC input power source l is vl, and the maximum value of the voltage induced in the primary winding 11 of the transformer 3 during the period when the switch element 2 is off is VP. Also,
It is assumed that the negative side of the DC input power source 1 and the negative side of the load 8 are grounded and at zero potential.

First, in FIG. 2, switch element 2 is turned on and off.
Terminals 13, 14, 15 of each winding when turned on
．． 16 will be explained with reference to FIG. During this state change of the switch element 2, the potential at the winding start terminal 13 of the primary winding 11 is always Vl, and the potential at the winding end terminal 14 is OV when the switch element 2 is on, and Vl when the switch element 2 is off. However, during the reset period, the potential V
l is the excitation inductance of transformer 3 and switch element 2.
A voltage of maximum vP is induced and applied due to a resonance phenomenon caused by the output capacitance, etc. On the other hand, the potential at the winding start terminal 15 of the secondary winding 12 becomes Vl when the switch element 2 is on, and becomes OV due to the output flywheel element 5 when the switch element 2 is off. Further, the potential at the winding end terminal 16 of the secondary winding is OV except during the reset period, or during the reset period, the output rectifying element 4 is turned off and the potential is induced to the maximum vp described above.

As a result of the above, in this embodiment, the potential difference between the winding 1 and the winding 12 (the potential difference between the terminal 13 and the terminal 15, and the potential difference between the terminal I4
The potential difference between the switch element 2 and the terminal 16 changes between 0 and Vl when the switch element 2 is turned on and off, or remains constant at Vl during the reset period and does not change. This means that the distributed capacitance existing between winding II and winding 12 of transformer 3 is not charged or discharged during the reset period, and therefore the reset time due to charging and discharging is increased. It disappears.

Next, a second embodiment of the present invention will be described.

FIG. 4 is a circuit diagram of a one-stone forward converter showing the second embodiment, and FIG. It is an explanatory diagram redrawn and shown. This embodiment is composed of the same members, including the transformer 3, as those having the same reference numerals as those constituting the first embodiment, but the way they are connected is different.

In the connection of this embodiment, the switching element 2 and the terminal 13 of the transformer 3 and the output rectifying element 4 and the terminal 15 of the transformer 3 are connected, and both the terminal 13 and the terminal I5 are connected to the winding 11 and the winding 12. This differs from the conventional example in that the winding starts and the connection position of the choke coil 6 is different from the conventional example. That is, its primary winding! The winding start terminal 13 of (2) is connected to the switch element 2, through which it is connected to the positive side of the DC input power source l, and the winding end terminal 14 of the primary winding 11 is connected to the negative side of the DC input power source l.

In addition, in connection of the 12 examples of the secondary winding of the transformer 3,
Winding start terminal 15 of secondary winding 12 - Output rectifying element 4 -
A series circuit of smoothing capacitor 7 - smoothing choke coil 6 - winding end terminal 16 of secondary winding 12 is formed,
Load 8 is connected in parallel to smoothing capacitor 7. The output flywheel element 5 connects the connection point between the output rectifying element 4 and the smoothing capacitor 7 and the winding end terminal 1 of the secondary winding 12.
Connected between 6 and 6.

The operation and effect of the second embodiment configured as above will be described.

FIG. 6 shows the state of the switch element 2 and the terminal 13 of the transformer 3 in the second embodiment. FIG. 4 is an explanatory diagram showing the relationship between the potentials of +4.15 and +6. However, winding 11 and winding 1
The winding ratio of the transformer 2 is l:l, the voltage of the DC input power supply 1 is v■, the output voltage applied to the load 8 is vP, and the voltage induced in the primary winding 11 of the transformer 3 during the period when the switch element 2 is off is Let vP be the maximum value of the voltage. Further, it is assumed that the negative side of the DC input power source 1 and the negative side of the load 8 are grounded and at zero potential.

First, in Fig. 5, switch element 2 is turned on and off →
Terminal I3 of each winding when turned on, +4.15
．． 16 will be explained with reference to FIG. During this state change of the switch element 2, the potential of the winding start terminal I3 of the next winding 11 becomes Vl when the switch element 2 is on and becomes OV when it is off, but during the reset period, the above-mentioned resonance phenomenon occurs. A reverse voltage of maximum VP is induced at Also,
The winding end terminal 14 of the primary winding 11 is at OV while the switch element 2 is on and off. On the other hand, the potential at the winding start terminal 15 of the secondary winding 12 is vP except during the reset period, but during the reset period, the output rectifying element is turned off and a reverse voltage of maximum VP is induced and added to V2. Further, the potential of the winding end terminal 16 of the secondary winding 12 is V2-Vl when the switch element 2 is off, and is V2-Vl when the switch element 2 is off.
It becomes P.

As a result of the above, in this embodiment, the potential difference between the winding 11 and the winding 12 (the potential difference between the terminal I3 and the terminal 15, and the potential difference between the terminal I3 and the terminal 14)
The potential difference between the terminal 16 and the terminal 16 fluctuates between -V2 and Vl-V2 when the switch element 2 is turned on and off, but during the reset period, it is always constant at -V2 and does not fluctuate. This means that the distributed capacitance existing between the windings 11 and 12 of the transformer 3 is not charged or discharged, and therefore, similarly to the first embodiment, the distributed capacitance that exists between the windings 11 and 12 of the transformer 3 is not charged or discharged. The accompanying reset time increases or disappears.

Next, a third embodiment of the present invention will be described.

FIG. 7 is a circuit diagram of a one-stone forward converter showing the third embodiment, and FIG. 8 shows the structure of the third embodiment, especially to clarify the structure of the transformer 3 within the necessary range. This is an explanatory diagram redrawn and shown. This embodiment is composed of the same members, including the transformer 3, as those having the same reference numerals as those constituting the first embodiment, but the way they are connected is different.

In the connection of this embodiment, the switching element 2 and the terminal 14 of the transformer 3 and the output rectifying element 4 and the terminal 16 of the transformer 3 are connected, and both the terminal 14 and the terminal I6 are connected to the winding 11 and the winding 12. This is different from the conventional example in that the winding end is the end of the winding, and the connection position of the choke fill 6 is different from the conventional example. That is, the positive side of the DC input power supply l is connected to the winding start terminal 13 of the primary winding 11, and the switch element 2 is connected to the winding end terminal 14 of the primary winding 11, through which the DC input power supply 1 is connected. Connected to the negative side. In addition, in the connection on the secondary winding 12 side of the transformer 3, the winding start terminal 15 of the secondary winding I2 - the smoothing capacitor 7 - the smoothing choke coil 6 - the output rectifying element 4 - the winding of the secondary winding 12. A series circuit called an end terminal 16 is formed, and the load 8 is connected in parallel to the smoothing capacitor 7. The output flywheel element 5 is connected between the connection point between the output rectifying element 4 and the choke coil 6 and the winding start terminal 15 of the secondary winding 12 .

The operation and effect of the third embodiment configured as above will be described.

FIG. 9 is an explanatory diagram showing the relationship between the state of the switch element 2 and the potentials of the terminals 13, 14, 15, and 16 of the transformer 3 in the third embodiment. However, winding 11 and winding 1
The turns ratio of 2 is l : l, and the voltage of DC input power supply l is Vl.
, the output voltage applied to the load 8 is v2, and the maximum value of the voltage induced in the primary winding 11 of the transformer 3 during the period when the switching element 2 is off is VP. Further, it is assumed that the negative side of the DC input power source 1 and the negative side of the load 8 are grounded and at zero potential.

First, in FIG. 8, the switch element 2 is turned on and off.
Terminal 13.14.15 of each winding when turned on
．． 16 will be explained with reference to FIG. During this state change of the switch element 2, the potential at the winding start terminal 13 of the primary winding 11 is always Vl, and the potential at the winding end terminal 14 is OV when the switch element 2 is on, and Vl when the switch element 2 is off. However, during the reset period, the potential v
l is the excitation inductance of transformer 3 and switch element 2.
A maximum voltage of VP is induced and applied due to a resonance phenomenon caused by the output capacitance of the . On the other hand, the potential at the winding start terminal 15 of the secondary winding I2 is always v2 during the state change of the switch element 2, and the potential at the winding end terminal 16 is V2-vl when the switch element 2 is on, and when it is off. When it becomes V2,
During the reset period, an induced voltage of maximum VP is applied to v2.

As a result of the above, in this embodiment, the potential difference between the winding 11 and the winding 12 (terminal 13 and terminal 1
The potential difference between terminals 14 and 16) is always constant at Vl-V2 and does not vary. This means that the distributed capacitance existing between the windings 11 and 12 of the transformer 3 is not charged or discharged, and therefore the reset time, loss, and
No increase in output noise.

Next, a fourth embodiment of the present invention will be described.

FIG. 1O is a circuit diagram of a one-stone forward converter showing the fourth embodiment, and FIG. 11 shows the configuration of this fourth embodiment, especially to clarify the structure of the transformer 3 within the necessary range. It is an explanatory diagram redrawn and shown. In this example,
Although it is composed of the same members including the transformer 3 as those having the same reference numerals constituting the first embodiment, the way they are connected is different.

In the connection of this embodiment, the switching element 2 and the terminal 13 of the transformer 3 and the output rectifying element 4 and the terminal 15 of the transformer 3 are connected, and both the terminal I3 and the terminal I5 are connected to the winding II and the winding 12. This is different from the conventional example in that the winding begins at the beginning of the winding.

That is, the winding start terminal I3 of the primary winding II is connected to the switch element 2, through which it is connected to the positive side of the DC input power supply l, and the winding end terminal 14 of the primary winding 11 is connected to the positive side of the DC input power supply l. Connected to the negative side. In addition, in connection of the 12 secondary windings of the transformer 3, the secondary winding 12
A series circuit is formed including the winding start terminal 15 - output rectifying element 4 - smoothing choke coil 6 -> smoothing capacitor 7 -> winding end terminal 16 of the secondary winding 12, and the load 8 is connected in parallel to the smoothing capacitor 7. Connected. The output flywheel element 5 is connected between the connection point between the output rectifying element 4 and the choke coil 6 and the winding end terminal 16 of the secondary winding I2.

The operation and effect of the fourth embodiment configured as above will be described.

FIG. 12 shows the switch element 2 of the fourth embodiment.
FIG. 3 is an explanatory diagram showing the relationship between the state of the transformer 3' and the potentials of the terminals 13.14.about.15.16 of the transformer 3'. However, the turns ratio of winding it and winding 12 is l:1, and the voltage of DC input power supply I is Vl.
, 1 of the transformer 3 during the period when the switch element 2 is off.
Let the maximum value of the voltage induced in the next winding 11 be VP. Further, it is assumed that the negative side of the DC input power source 1 and the negative side of the load 8 are grounded and at zero potential.

First, in FIG. 11, the terminals 13, 14, 1 of each winding when the switch element 2 is changed from on to off to on.
The change in potential of 5.16 will be explained with reference to FIG.

During this state change of the switch element 2, the potential of the winding start terminal 13 of the primary winding 11 is V when the switch element 2 is on.
1 and becomes OV when off, but a reverse voltage of the maximum VP is induced and applied during the reset period due to the resonance phenomenon. Further, the potential of the winding end terminal 14 of the primary winding If is always O.
It is V. On the other hand, the potential at the winding start terminal 15 of the secondary winding 12 is Vl when the switching element 2 is on and OV when it is off, but during the reset period, a reverse voltage of the maximum VP is induced and added due to the resonance phenomenon. . Further, the potential of the winding end terminal 16 of the secondary winding is always OV.

As a result of the above, in this embodiment, the terminals 13 and 1 of the transformer 3 are
5 and the potentials of terminals 14 and 16 are always the same potential, and regardless of the state of switch element 2, winding 11
The potential difference between and winding 12 (the potential difference between terminal 13 and terminal 15 and the potential difference between terminal 14 and terminal I6) is always 0.
It is constant and does not change. This means that the distributed capacitance existing between the windings 11 and 12 of the transformer 3 is not charged or discharged, and therefore, similarly to the third embodiment, the distributed capacitance that exists between the windings 11 and 12 of the transformer 3 is not charged or discharged. The associated reset time, loss, and increase in output noise are eliminated.

In each of the above embodiments, n is used as a switch element.
The explanation was given using MOSFET as an example, but py! 1. M
The same applies to other switching elements such as OSFETs and bipolar transistors. Also, the turns ratio of transformer 3 is 1:
It is also clear that a corresponding effect can be obtained even if it is not 1. As described above, the present invention can be applied in various ways and can take various embodiments in accordance with its gist.

[Effects of the Invention] As is clear from the above description, the invention of the one-wheel forward converter of claim 1 has the advantage of overlapping the winding start of the primary winding and the winding start of the secondary winding in the transformer, and , using a structure in which the secondary winding is wound in layers so that magnetic flux is formed in the same direction when current is passed from the beginning of the winding, and the switching element and the output rectifying element are connected to the windings of the primary and secondary windings. By connecting to the same terminal at the beginning or end of the winding, the distributed capacitance between the primary and secondary windings of the transformer is not charged or discharged during the off period of the switch element, so the reset time associated with this distributed capacitance is This can eliminate the increase in This makes it possible to raise the upper limit of the conversion frequency, which has been limited by an increase in the reset time, and has the advantage that the one-stone T-word converter can be made smaller by increasing the conversion frequency.

Furthermore, the invention of the single-stone forward converter according to claim 2 is as follows:
In the series circuit of the transformer secondary winding, the output rectifying element, the smoothing capacitor, and the smoothing choke coil according to claim 1, the smoothing choke coil is connected between the output rectifying element and the smoothing capacitor. Regardless of the state of the element, the distributed capacitance between the primary and secondary windings of the transformer is not charged or discharged, so due to this distributed capacitance,
This has the advantage of eliminating reset time, loss, and noise increase.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a first embodiment of the present invention, Fig. 2 is an explanatory diagram depicting the main configuration of the first embodiment, and Fig. 3 shows the operation of the first embodiment. FIG. 4 is a circuit diagram showing the second embodiment of the present invention. FIG. 5 is an explanatory diagram depicting the main structure of the second embodiment. FIG. FIG. 7 is a circuit diagram showing the third embodiment of the present invention, and FIG. 8 is a diagram showing the main structure of the third embodiment. 9 is an explanatory diagram of the potential change of the transformer terminal in the operation of the third embodiment, FIG. 1O is a circuit diagram showing the fourth embodiment of the present invention, and FIG. FIG. 12 is an explanatory diagram depicting the configuration of the main parts of the fourth embodiment, FIG. 12 is an explanatory diagram of potential changes at the transformer terminals in the operation of the fourth embodiment, FIG. 13 is a circuit diagram showing a conventional example, and FIG. 14 is an equivalent circuit diagram of the conventional example, FIG. 15 is an explanatory diagram depicting the main structure of the conventional example, and FIG. 16 is an explanatory diagram of potential changes at the transformer terminals during operation of the conventional example. ■...DC input power supply, 2...Switch element, 21.
・Output capacity of switch element 2, 3...Transformer, 3■
...Excitation inductance of transformer 3, 4.Output rectification element, 5.Output flywheel element, 6..
Smoothing choke coil, 7... Smoothing capacitor, 8
...Load, 9 -Core, 10...Bobbin, II...1
Next winding, 12... Secondary winding, 13.14.15.16
...Winding terminal. Switch element cedar]Cony'P Fig. 3 Fig. 4 Fig. 5 Sui note element 1θ diagram Figure 11 Suishina Tokikosugi] Kofu Oi Figure 18 Figure 14 Switch element transformer terminal σl2' [ Figure 16

Claims (2)

[Claims] (1) Comprising a transformer having at least a primary winding and a secondary winding, a switching element, an output rectifying element, an output flywheel element, a smoothing choke coil, and a smoothing capacitor. In the one-stone forward converter, the transformer has a structure in which the winding start of the primary winding and the winding start of the secondary winding are overlapped, and when current flows from the winding start of the primary winding and the secondary winding, the current flows in the same direction. The switch element and the output rectifying element are each connected to the above 1 by using a transformer having a structure in which they are wound in layers to form a magnetic flux of 1.
The winding start terminal of the next winding is connected to the winding start terminal of the secondary winding, or the winding end terminal of the primary winding is connected to the winding end terminal of the secondary winding. Features a one-stone forward converter. (2) In the one-stone forward converter according to claim 1, when forming a series circuit of the secondary winding of the transformer, the output rectifying element, the smoothing capacitor, and the smoothing choke coil,
A one-stone forward converter, characterized in that the smoothing choke coil is connected between the output rectifying element and the smoothing capacitor.