JP2006115598A - Voltage converting circuit and power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-efficiency and low-loss voltage converting circuit achieved by a simple circuit constitution. <P>SOLUTION: In the converting circuit 1 provided with a transformer T1 having a coil L11 disposed on the primary side and coils L21, L22 disposed on the secondary side and connected in series, and turning on/off a voltage supplied to the coil L11 by a FET 1, a cathode terminal of a diode D1 is connected to one end of the coil L21, a cathode terminal of a diode D2 is connected to one end of the coil L22, and an output terminal 13 is connected to a connection between the coils L21 and L22. A switching signal generating circuit 10 detects an output voltage from the output terminal 13, and outputs a pulse voltage having a period in proportion to the output voltage. The FET 1 is controlled and turned on/off based on the output. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a voltage conversion circuit and a power supply device including the voltage conversion circuit.

  A voltage conversion circuit (DC-DC converter) that converts a DC voltage is widely used in a switching power supply circuit and the like (for example, see Non-Patent Document 1).

Cosel, “About Power Supply”, P.36-37, [online], [Search July 15, 2004], Internet <URL: http://www.cosel.co.jp/jp/products/ img / technotes.pdf>

  Here, a typical one of the switching power supply circuits described in Non-Patent Document 1 will be described as an example, and a conventional voltage conversion circuit will be described with reference to each of FIGS.

  A switching power supply circuit 21 shown in FIG. 8 is a typical example of a circuit called “single-ended forward method”, and a DC voltage is supplied from the DC power supply 211 to the primary coil L13 of the transformer T21 by using an FET (Field Effect Transistor). ) 21 to turn on / off.

When the FET 21 is turned on and a DC voltage is supplied to the coil L13, an electromotive force generated in the coil L24 causes a current to flow from the coil L24 through the diode D21 and the choke coil L32, and a DC voltage is output from the output terminals 213 and 214. Is output. Here, a smoothing capacitor C <b> 21 is provided in parallel with the output terminals 213 and 214.
Further, when the FET 21 is turned off, voltage supply to the choke coil L32 is stopped, so that a counter electromotive force is generated in the choke coil L32. Here, due to the back electromotive force of the choke coil L32, a current flows in a current path from the diode D22 via the choke coil L32, and a DC voltage is output from the output terminals 213 and 214.
That is, the switching power supply circuit 21 shown in FIG. 8 outputs a DC voltage by the electromotive force generated in the coil L24 when the FET 21 is on, and when the FET 21 is switched off, the DC voltage is generated by the energy accumulated in the choke coil L32. Is output.

  In the single-ended forward switching power supply circuit that performs the above operation, the voltage applied to the load (corresponding to the voltage of the output terminals 213 and 214 in FIG. 8) is detected, and the gate of the FET connected to the primary coil A PWM (Pulse Width Modulation) control circuit that feedback-controls the ON width of the pulse voltage input to the gate terminal 212 of the FET 21 in FIG.

Japanese Patent Laid-Open No. 11-69804

  The feedback control here controls the pulse width of the pulse voltage output at regular intervals according to the load voltage, thereby suppressing the fluctuation of the voltage supplied to the load according to the load. is doing.

The switching power supply circuit 22 shown in FIG. 9 is a typical example of a circuit called “push-pull system”, and coils L14 and L15 are arranged on the primary side of the transformer T22, and coils L25 and L26 are arranged on the secondary side. Arranged.
The coils L14 and 15 are respectively connected in parallel to the DC power supply 221, the voltage supply to the coil L14 is turned on / off by the FET 22, and the voltage supply to the coil L15 is turned on / off by the FET23.
When the switching power supply circuit 22 operates, the FET 22 and the FET 23 are alternately turned on. When the FET 22 is on, current flows from the diode D24 to the choke coil L33 due to the electromotive force generated in the coil L26. When the FET 23 is on, current flows from the diode D23 to the choke coil L33 due to the electromotive force generated in the coil L25. A DC voltage is output from 224 and 225. Here, a smoothing capacitor C22 is provided in parallel with the output terminals 224 and 225.
When both the FET 22 and the FET 23 are switched off, a current flows through both the diodes D23 and D24, and a DC voltage is output from the output terminals 224 and 225 by the energy accumulated in the choke coil L33.

  The switching power supply circuit 23 shown in FIG. 10 is a typical example of a circuit called a “full bridge system”, and the voltage supply from the DC power supply 231 is supplied to the primary coil L16 of the transformer T23 by the FETs 24, 25, 26, 27. The four FETs are turned on / off. Coils L27 and L28 are provided on the secondary side of the transformer T23. The switching power supply circuit 23 includes a choke coil L34 and a capacitor C23 that rectify and smooth the output voltage.

Of the four FETs 24, 25, 26, and 27, the FET 24 and the FET 27 form a set, the FET 25 and the FET 26 form a set, and the two sets of FETs are alternately turned on / off.
In the state in which the FET 24 and the FET 27 are turned on and the state in which the FET 25 and the FET 26 are turned on, the direction of the current flowing through the coil L16 is opposite. When the FET 24 and the FET 27 are turned on, a current flows from the diode D26 to the choke coil L34 due to the electromotive force generated in the secondary coil L28, and when the FET 25 and the FET 26 are turned on, the secondary coil L27 is turned on. Current flows from the diode D25 to the choke coil L34.
That is, the switching power supply circuit 23 has a configuration in which the two sets of FETs are alternately turned on to drive the transformer T23 and current flows alternately to the secondary side coils L27 and L28.

  The switching power supply circuit 24 shown in FIG. 11 is a typical example of a circuit called “single-end flyback system”, and the secondary power supply is turned on / off by turning on / off the voltage supply to the primary coil L17 of the transformer T24 by the FET 28. This circuit outputs a DC voltage based on the electromotive force generated in the coil L29 on the side. When the FET 28 is on, the anode side terminal of the diode D27 becomes negative due to the electromotive force generated in the coil L29 and no current flows. However, when the FET 28 is switched from on to off, the back electromotive force generated in the primary side coil L17. A DC voltage is output from the coil L29 to the output terminals 243 and 244 by electric power (flyback voltage).

  As illustrated in FIGS. 8 to 11, the conventional voltage conversion circuit has a primary voltage when the electromotive force generated in the primary coil when the current is supplied to the primary coil or when the current in the primary coil is turned off. Only one of the counter electromotive forces generated in the side coil was used. The energy that is not used is lost, but the loss of the voltage conversion circuit is not negligible in various circuits equipped with the voltage conversion circuit, including switching power supply circuits, and higher conversion efficiency is required. It was done.

  Therefore, an object of the present invention is to provide a voltage conversion circuit that can be realized by a simple circuit configuration with high efficiency and low loss.

  In order to achieve the above object, the invention according to claim 1 is a voltage conversion circuit comprising a transformer and switching means for switching on / off of DC voltage supply to the primary side of the transformer, wherein the transformer includes: The first coil is disposed on the primary side, and the second coil and the third coil are disposed on the secondary side, and the voltage supply to the transformer is turned on by the switching means. In this state, after the voltage supply to the transformer is switched from on to off by the switching means, the first current path that outputs a DC voltage based on the electromotive force generated in the second coil, the third current A second current path that outputs a DC voltage based on an electromotive force generated in the coil of the first current path, and output voltages of the first current path and the second current path are detected and compared with the output voltage. Wherein the at a period and a control means for controlling an on / off of the switching means.

  The invention according to claim 2 is the voltage conversion circuit according to claim 1, further comprising a fourth coil disposed on an output line of the first current path and the second current path. A third current path for outputting a DC voltage is formed on the basis of an electromotive force generated in the fourth coil when the DC voltage value output in the second current path is reduced; The output voltage of one current path, the second current path, and the third current path is detected, and on / off of the switching means is controlled in a cycle proportional to the output voltage.

  According to a third aspect of the present invention, in the voltage conversion circuit according to the second aspect, the second coil and the third coil are connected in series, and one end of the fourth coil is connected to the second coil. The third current path is connected to a connection point with the third coil, and the third current path includes a current path including the second coil and the fourth coil, and the third coil and the fourth coil. It is characterized by comprising a current path made of a coil.

  According to a fourth aspect of the present invention, in the voltage conversion circuit according to the second or third aspect, the first rectifier is connected to one end of the second coil, and the other end is connected to the third coil. One end of the third coil is connected to the second coil, the other rectifier is connected to the other end, and one end of the fourth coil is connected to the second coil and the third coil. The other end of the fourth coil is connected to an output terminal of the voltage conversion circuit, and the first current path includes the first rectifier, The second coil and the fourth coil are configured, and the second current path is configured by the second rectifier, the third coil, and the fourth coil, The third current path includes the first rectifier, the second coil, and the fourth coil. Current path consisting of, and characterized by being constituted by a current path consisting of the second rectifying means and said third coil and the fourth coil.

  The invention according to claim 5 is a voltage conversion circuit comprising a transformer and first switching means for switching on / off of DC voltage supply to the primary side of the transformer, the transformer being arranged on the primary side. 1 coil is provided, and the second side and the third coil are provided on the secondary side, and includes a second switching means, and the first switching means is used for the transformer. A first current path for outputting a DC voltage based on an electromotive force generated in the second coil in a state where the voltage supply is turned on, and a third switching means, and the first switching means After the voltage supply to the transformer is switched from on to off, a second current path that outputs a DC voltage based on an electromotive force generated in the third coil, the first current path, A signal generating means for detecting an output voltage of the second current path and outputting an on / off control signal having a period proportional to the output voltage, and an on / off control signal from the signal generating means, The on / off control of the first switching means is controlled, the third switching means is turned off when the second switching means is on, and the third switching means is turned off when the second switching means is off. Control means for controlling on / off of the second switching means and the third switching means so as to turn on the switching means.

  A sixth aspect of the present invention is the voltage conversion circuit according to the fifth aspect, further comprising a fourth coil disposed on an output line of the first current path and the second current path. A third current path for outputting a DC voltage is formed on the basis of an electromotive force generated in the fourth coil when the DC voltage value output in the current path of 2 is reduced; An output voltage of the first current path, the second current path, and the third current path is detected, and an on / off control signal having a period proportional to the output voltage is output.

  According to a seventh aspect of the present invention, in the voltage conversion circuit according to the sixth aspect, the second switching means is connected to one end of the second coil, the other end is connected to the third coil, One end of the third coil is connected to the second coil, the other end is connected to the third switching means, and one end of the fourth coil is connected to the second coil and the third coil. The other end of the fourth coil is connected to the output terminal of the voltage conversion circuit, and the first current path includes the second switching means, The second coil is constituted by the fourth coil, and the second current path is constituted by the third switching means, the third coil, and the fourth coil, The third current path is the second switched And a current path composed of the second coil and the fourth coil, and a current path composed of the third switching means, the third coil, and the fourth coil. Features.

  The invention according to claim 8 is a voltage conversion circuit comprising a transformer and first switching means for switching on / off of DC voltage supply to the primary side of the transformer, the transformer being arranged on the primary side. 1 coil is provided, and the second side and the third coil are provided on the secondary side, and includes a second switching means, and the first switching means is used for the transformer. A first current path for outputting a DC voltage based on an electromotive force generated in the second coil in a state in which the voltage supply is turned on; and a rectifying unit, and a voltage for the transformer by the first switching unit. A second current path for outputting a DC voltage based on an electromotive force generated in the third coil after the supply is switched from on to off; the first current path; and the second current The output voltage is detected and characterized in that it comprises a control means for controlling an on / off of the first switching means and said second switching means at a cycle proportional to the output voltage.

  The invention according to claim 9 is the voltage conversion circuit according to claim 8, further comprising a fourth coil disposed on an output line of the first current path and the second current path. A third current path for outputting a DC voltage is formed on the basis of an electromotive force generated in the fourth coil when the DC voltage value output in the second current path is reduced; The output voltage of one current path, the second current path, and the third current path is detected, and the first switching means and the second switching means are turned on / off in a cycle proportional to the output voltage. It is characterized by controlling.

  According to a tenth aspect of the present invention, in the voltage conversion circuit according to the ninth aspect, the second switching means is connected to one end of the second coil, and the other end is connected to the third coil. One end of the third coil is connected to the second coil, the other rectifier is connected to the other end, and one end of the fourth coil is connected to the second coil and the third coil. The other end of the fourth coil is connected to the connection point, and the other end of the fourth coil is connected to the output terminal of the voltage conversion circuit. The control means is synchronized with the on / off of the first switching means. The second switching means is turned on / off, and the first current path is constituted by the second switching means, the second coil, and the fourth coil, and the second current path Are the rectifying means and the third coil. , The fourth coil, and the third current path includes a current path including the second switching means, the second coil, and the fourth coil, and the rectifying means and the It is characterized by comprising a current path composed of a third coil and the fourth coil.

  An eleventh aspect of the invention is a power supply device including the voltage conversion circuit according to any one of the first to tenth aspects.

  According to one aspect of the present invention, in a voltage conversion circuit including a transformer and switching means for switching on / off of DC voltage supply to the primary side of the transformer, the transformer includes a first coil disposed on the primary side. The second side and the third coil are arranged on the secondary side, and the voltage supply to the transformer is turned on by the switching means via the first current path. The DC voltage is output based on the electromotive force generated in the second coil, and the electromotive force generated in the third coil through the second current path after the voltage supply to the transformer is switched from ON to OFF by the switching means. The DC voltage is output based on the energy of the first coil on the primary side and the energy of the back electromotive force generated when the current of the first coil is turned off. It is possible to use without waste and Energy loss is extremely small, it is possible to perform voltage conversion with very high efficiency. In particular, in the present invention, since the control means is provided, the output voltages of the first current path and the second current path are detected, and the ON / OFF of the switching means is controlled in a cycle proportional to the output voltage, the connection is made. Generates output power according to the load. As a result, it is possible to obtain a stable DC voltage that is hardly affected by the load at the time of heavy load, and it is possible to avoid the generation of useless output power at the time of light load or standby, and the efficiency is high.

  The present invention further includes a fourth coil disposed on the output lines of the first current path and the second current path, when the DC voltage value output in the second current path is reduced. If the third current path for outputting a DC voltage is formed based on the electromotive force generated in the fourth coil, the fourth coil outputs the first current path and the second current path. Since it is disposed on the line, energy is accumulated while a current flows in the first current path and the second current path. The energy accumulated in the fourth coil is output from the third current path. That is, in addition to the energy when a current is passed through the first coil on the primary side and the energy of the back electromotive force generated when the current of the first coil is turned off, the first current path and the second It is possible to use all the energy stored in the fourth coil arranged on the output line of the current path without waste, and to perform voltage conversion with extremely high efficiency with even less loss. it can. The control means detects the output voltages of the first current path, the second current path, and the third current path, and controls on / off of the switching means in a cycle proportional to the output voltage. It is possible to obtain a stable DC voltage that is not easily affected by the load at the time of loading, and it is possible to avoid generation of useless output power at the time of light load or standby, and the efficiency is high.

In the present invention, the second coil and the third coil are connected in series, and one end of the fourth coil is connected to a connection point between the second coil and the third coil. If the current path is constituted by a current path composed of the second coil and the fourth coil and a current path composed of the third coil and the fourth coil, the current path is accumulated in the fourth coil. Due to the energy, a current flows through both the current path composed of the second coil and the fourth coil and the current path composed of the third coil and the fourth coil. Here, since the second coil and the third coil are connected in series, the current flowing through the second coil and the current flowing through the third coil flow in opposite directions. Accordingly, since the magnetic flux generated by the current flowing through the second coil and the magnetic flux generated by the current flowing through the third coil cancel each other, in the transformer, the secondary coil (second coil and third coil) No current is transmitted to the primary side coil (first coil) even if a current flows through.
As a result, the energy stored in the fourth coil can be used without loss, so that voltage conversion can be performed more efficiently.

Furthermore, in the present invention, the first rectifier is connected to one end of the second coil, the other end is connected to the third coil, the one end of the third coil is connected to the second coil, and the like. The second rectifier is connected to the end, one end of the fourth coil is connected to the connection point between the second coil and the third coil, and the other end of the fourth coil is the voltage. The first current path is composed of a first rectifier, a second coil, and a fourth coil, and the second current path is connected to the output terminal of the conversion circuit. The rectifying means, the third coil, and the fourth coil are configured, and the third current path includes a current path including the first rectifying means, the second coil, and the fourth coil, and If the current path is composed of two rectifiers, a third coil, and a fourth coil, When a current flows through the first coil, a DC voltage is output from the first rectifier to the fourth coil via the second coil based on the electromotive force generated in the second coil. In the state where the current of the primary coil on the primary side is switched off, the fourth rectification means passes through the third coil from the second rectification means based on the electromotive force generated in the third coil. A DC voltage is output to the coils, and these DC voltages are smoothed and output by the fourth coil. In the fourth coil, energy is accumulated during the output of the DC voltage, and the energy accumulated in the fourth coil is output via the third current path.
That is, energy when current is passed through the first coil, energy of back electromotive force generated when the current of the first coil is turned off, and energy accumulated in the fourth coil are used without waste. It can be used, and a highly efficient voltage conversion circuit can be realized with very little loss.
The third current path includes a current path including the first rectifier, the second coil, and the fourth coil, and a second rectifier, the third coil, and the fourth coil. Since the current path is configured, the current flowing through the second coil and the current flowing through the third coil flow in opposite directions. For this reason, even if current flows through the second coil and the third coil, magnetic fluxes generated by these currents cancel each other, so that energy is not transmitted to the first coil, and the fourth coil The stored energy can be used without loss.

According to another aspect of the present invention, in a voltage conversion circuit comprising a transformer and first switching means for switching on / off of a DC voltage supply to the primary side of the transformer, the transformer is arranged on the primary side. 1 coil is provided, and the second side and the third coil are provided on the secondary side, and the first current path including the second switching means is provided through the first current path. With the voltage supply to the transformer turned on by the switching means, a DC voltage is output based on the electromotive force generated in the second coil, and the second current path including the third switching means passes through the second current path. After the voltage supply to the transformer is switched from ON to OFF by the switching means 1, a DC voltage is output based on the electromotive force generated in the third coil. Instead of the rectifying means in the power conversion circuit having the first rectifying means and the second rectifying means constituted by the iodine, the second switching means and the third switching means constituted by, for example, FETs are used. Can do. Therefore, the voltage drop due to the rectifying element included in the first current path and the voltage drop due to the rectifying element included in the second current path can both be reduced, and the conversion efficiency is good.
The signal generating means detects the output voltages of the first current path and the second current path and outputs an on / off control signal having a period proportional to the output voltage. The control means outputs the signal from the signal generating means. Based on the on / off control signal, the on / off of the first switching means is controlled, the third switching means is turned off when the second switching means is on, and the second switching means is turned off. Since the on / off of the second switching means and the third switching means is controlled so that the third switching means is turned on at this time, the current flows through the first coil on the primary side. When the DC voltage is output based on the electromotive force generated in the second coil via the first current and the current of the primary coil on the primary side is switched off, the third coil Electromotive force generated in A state in which a DC voltage is output is reliably ensured based.
That is, it is possible to use the energy when the current flows through the first coil on the primary side and the energy of the back electromotive force generated when the current of the first coil is turned off without waste. Loss is extremely small and voltage conversion can be performed with very high efficiency.
In addition, it is possible to obtain a stable DC voltage that is hardly affected by the load at the time of heavy load, and it is possible to avoid generation of useless output power at the time of light load or standby, and the efficiency is high.

  In another aspect of the present invention, the apparatus further includes a fourth coil disposed on the output lines of the first current path and the second current path, and the DC voltage value output in the second current path. If the third current path for outputting the DC voltage is formed based on the electromotive force generated in the fourth coil when the current decreases, the current flowing through the first coil on the primary side In addition to the energy and the energy of the back electromotive force generated when the current of the first coil is turned off, the fourth coil disposed on the output lines of the first current path and the second current path It is possible to use all of the energy stored in the battery without waste, and the voltage conversion can be performed with extremely high efficiency with even less loss.

In another aspect of the present invention, the second switching means is connected to one end of the second coil, the other end is connected to the third coil, and one end of the third coil is connected to the second coil. And the other end of the fourth coil is connected to a connection point between the second coil and the third coil, and the other end of the fourth coil is connected to the other end of the fourth coil. Is connected to the output terminal of the voltage conversion circuit, and the first current path is constituted by the second switching means, the second coil, and the fourth coil, and the second current path is the first current path. 3 switching means, a third coil, and a fourth coil, and the third current path is a current path composed of the second switching means, the second coil, and the fourth coil, and , Third switching means, third coil and fourth coil, If a current flows through the first coil on the primary side, the second switching means to the second coil based on the electromotive force generated in the second coil. In the state where the DC voltage is output to the fourth coil through the first coil and the current of the first coil on the primary side is switched off, the first voltage is switched to the first coil based on the electromotive force generated in the third coil. DC voltage is output from the switching of 3 to the fourth coil via the third coil, and these DC voltages are smoothed and output by the fourth coil. In the fourth coil, energy is accumulated during the output of the DC voltage, and the energy accumulated in the fourth coil is output via the third current path.
That is, energy when current is passed through the first coil, energy of back electromotive force generated when the current of the first coil is turned off, and energy accumulated in the fourth coil are used without waste. It can be used, and a highly efficient voltage conversion circuit can be realized with very little loss.
The third current path is composed of a current path composed of the second switching means, the second coil, and the fourth coil, and a third switching means, the third coil, and the fourth coil. Since the current path is configured, the current flowing through the second coil and the current flowing through the third coil flow in opposite directions. For this reason, even if current flows through the second coil and the third coil, magnetic fluxes generated by these currents cancel each other, so that energy is not transmitted to the first coil, and the fourth coil The stored energy can be used without loss.

According to still another aspect of the present invention, in the voltage conversion circuit including the transformer and the first switching means for switching on / off of the DC voltage supply to the primary side of the transformer, the transformer is arranged on the primary side. 1 coil is provided, and the second side and the third coil are provided on the secondary side, and the first current path including the second switching means is provided through the first current path. In the state where the voltage supply to the transformer is turned on by the switching means, a DC voltage is output based on the electromotive force generated in the second coil, and the voltage supply to the transformer is switched from on to off by the first switching means. After that, since the DC voltage is output based on the electromotive force generated in the third coil through the second current path including the rectifying means, the rectifying element included in the first current path is obtained. , For example, instead of consisting rectifying means a diode can be used, for example the switching means comprised of FET. Therefore, the voltage drop due to the rectifying element included in the first current path can be reduced, and the efficiency is good.
Further, the control means detects the output voltages of the first current path and the second current path, and controls on / off of the first switching means and the second switching means in a cycle proportional to the output voltage. When the current flows through the primary coil on the primary side, a DC voltage is output based on the electromotive force generated in the second coil via the first current, and the primary coil on the primary side is output. In the state where the current is switched off, a state in which a DC voltage is output based on the electromotive force generated in the third coil is reliably ensured.
That is, it is possible to use the energy when the current flows through the first coil on the primary side and the energy of the back electromotive force generated when the current of the first coil is turned off without waste. Loss is extremely small and voltage conversion can be performed with very high efficiency.
In addition, it is possible to obtain a stable DC voltage that is hardly affected by the load at the time of heavy load, and it is possible to avoid generation of useless output power at the time of light load or standby, and the efficiency is high.

  In still another aspect of the present invention, the apparatus further includes a fourth coil disposed on the output lines of the first current path and the second current path, and the DC voltage output in the second current path. If a third current path for outputting a DC voltage is formed based on an electromotive force generated in the fourth coil when the value is reduced, a current is passed through the first coil on the primary side And the energy of the back electromotive force generated when the current of the first coil is turned off, the fourth current disposed on the output lines of the first current path and the second current path. It is possible to use all the energy stored in the coil without waste, and the voltage conversion can be performed with extremely high efficiency with even less loss.

In yet another aspect of the present invention, in the voltage conversion circuit, the second switching means is connected to one end of the second coil, the other end is connected to the third coil, and one end of the third coil. Is connected to the second coil, the other end is connected to the rectifying means, one end of the fourth coil is connected to the connection point between the second coil and the third coil, and the fourth coil The other end of the coil is connected to the output terminal of the voltage conversion circuit, and the control means turns on / off the second switching means in synchronization with the on / off of the first switching means, and the first current The path is constituted by the second switching means, the second coil, and the fourth coil, and the second current path is constituted by the rectifying means, the third coil, and the fourth coil. The third current path comprises the second switching means and the second coil. In the first current path and the second current path, the current path is composed of the fourth coil and the current path composed of the rectifying means, the third coil, and the fourth coil. For example, a special control circuit such as a dead time control circuit required when a switching means such as an FET is used can be omitted. Therefore, a simpler circuit configuration can be realized.
Also, energy when current is passed through the first coil, energy of back electromotive force generated when the current of the first coil is turned off, and energy accumulated in the fourth coil can be used without waste. Since it can be used, a highly efficient voltage conversion circuit with very little loss can be realized.
In addition, the third current path includes a current path composed of the second switching means, the second coil, and the fourth coil, and a current path composed of the rectifying means, the third coil, and the fourth coil. Since it is configured, the current flowing through the second coil and the current flowing through the third coil flow in opposite directions. For this reason, even if current flows through the second coil and the third coil, magnetic fluxes generated by these currents cancel each other, so that energy is not transmitted to the first coil, and the fourth coil The stored energy can be used without loss.

  In addition, since the power supply device of the present invention is equipped with the voltage conversion circuit according to any one of claims 1 to 10, the loss is very small, and extremely high efficiency can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a circuit diagram showing a basic configuration of a conversion circuit 1 according to a first embodiment to which the present invention is applied.

  The conversion circuit 1 shown in FIG. 1 is a circuit that performs voltage conversion based on a DC voltage having a predetermined voltage value and outputs DC voltages having different voltage values, and includes a transformer T1. The conversion circuit 1 includes a positive output terminal 13 and a negative output terminal 14, and a predetermined load L is connected between the output terminal 13 and the output terminal 14.

  The transformer T1 includes a primary side coil L11 and secondary side coils L21 and L22.

The positive electrode of the DC power source 11 is connected to one end of the coil L11, and the drain terminal of the FET 1 is connected to the other end. A pulse voltage 7 having periodic characteristics, which will be described later, is input to the gate terminal G 1 of the FET 1, and the source terminal is connected to the negative electrode of the DC power supply 11.
The FET 1 performs an operation of switching on / off in accordance with the pulse voltage 7 input to the gate terminal G1. When the FET 1 is on, a DC voltage is supplied from the DC power source 11 to the coil L11, and when the FET 1 is off. Both ends of the coil L11 are open.

One end (winding start point) of the coil L22 is connected to one end (winding end point) of the secondary coil L21. The cathode terminal of the diode D1 is connected to the other end (winding start point) of the coil L21, and the cathode terminal of the diode D2 is connected to the other end (winding end point) of the coil L22.
An output line extending to the output terminal 13 is connected to a connection point between the coil L21 and the coil L22. This output line is preferably a midpoint tap on the secondary side.
Therefore, on the secondary side of the transformer T1, the current flows only in the direction from the diode D1 to the output terminal 13 through the coil L21 and in the direction from the diode D2 to the output terminal 13 through the coil L22. It has become.

  A smoothing capacitor C1 is connected between the output line and the output terminal 13, and anode terminals of the diodes D1 and D2 and a capacitor C1 are connected to the output terminal 14. Accordingly, a DC voltage smoothed by the capacitor C1 is output from the output terminal 13.

  A VFO (Variable Frequency Oscillator) 15 is connected between the smoothing capacitor C 1 and the output terminal 13. That is, the output voltage supplied to the load L is detected and input to the VFO 15. The output 5 of the VFO 15 is input to the monostable multivibrator 17, and the output of the monostable multivibrator 17 is input as a pulse voltage 7 to the gate terminal G1 of the FET1 connected in series to the primary side of the transformer T1.

  FIG. 2 is a circuit diagram showing an overall configuration of the switching signal generation circuit 10 including the VFO 15 and the monostable multivibrator 17 shown in FIG.

  The switching signal generation circuit 10 shown in FIG. 2 includes a VFO 15 that takes the circuit form of an astable and multivibrator, a differentiation circuit 16 having a capacitor and a resistor, and a monostable multivibrator 17.

As described above, the output voltage of the conversion circuit 1 is input to the input terminal (IN) of the VFO 15. The output of the VFO 15 is input to the differentiation circuit 16, and the output of the differentiation circuit 16 is input to the monostable multivibrator 17.
The VFO 15 shown in FIG. 2 performs the following operation according to the input voltage (output voltage of the conversion circuit 1). When the input voltage becomes low (ie, under heavy load), the cycle of the output pulse is shortened, and when the input voltage becomes high (ie, during light load or standby), the cycle of the output pulse is lengthened. In FIG. 2, an example of an output waveform of the VFO 15 is indicated by reference numeral 5.
The differentiating circuit 16 detects the rising edge of the output pulse of the VFO 15 and outputs a trigger pulse. In FIG. 2, an example of an output waveform of the differentiating circuit 16 is denoted by reference numeral 6.
The monostable multivibrator 17 outputs a pulse voltage having a constant pulse width using the trigger pulse of the differentiating circuit 16 as a trigger. In FIG. 2, an example of an output waveform of the monostable multivibrator 17 is denoted by reference numeral 7.
As is apparent from the series of waveform changes described above, the switching signal generation circuit 10 configured as described above increases the number of output pulses per unit time as the input voltage decreases, while the input voltage increases. The operation of reducing the number of output pulses per unit time is performed.
That is, the switching signal generation circuit 10 configured as described above detects the output voltage (that is, the load voltage) supplied to the output line of the conversion circuit 1 and outputs a pulse voltage having a period proportional to the output voltage. .

The conversion circuit 1 configured as described above outputs a DC voltage to the load L connected to the output terminals 13 and 14 based on the DC voltage supplied from the DC power supply 11.
Next, the operation of the conversion circuit 1 will be described.

  When the pulse voltage 7 is input to the gate terminal G1 of the FET 1 and the FET 1 is switched on, a DC voltage is supplied to the coil L11.

Thereby, in the coil L21, an electromotive force according to the turns ratio between the coil L11 and the coil L21 is generated, and this electromotive force is positive on the diode D1 side of the coil L21 and negative on the output terminal 13 side. Therefore, since a reverse voltage with the cathode side terminal being positive is applied to the diode D1, no current flows through the diode D1.
On the other hand, in the coil L22, an electromotive force according to the turn ratio between the coil L11 and the coil L22 is generated, and this electromotive force is negative on the diode D2 side of the coil L22 and positive on the output terminal 13 side. Therefore, since a forward voltage with its cathode terminal being negative is applied to the diode D2, a current flows from the diode D2 to the output terminal 13 via the coil L22.
For this reason, a DC voltage based on the electromotive force generated in the coil L22 is output from the output terminal 13 after being smoothed by the capacitor C1.

  Thereafter, when the FET 1 is switched off by the pulse voltage 7, both ends of the coil L11 are opened, and a back electromotive force (flyback voltage) due to the self-inductance of the coil L11 is generated.

In this state, in the coil L21, the energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L21 and becomes an electromotive force of the coil L21. The electromotive force is negative on the diode D1 side of the coil L21 and positive on the output terminal 13 side. Become. Accordingly, since a forward voltage having a negative cathode side terminal is applied to the diode D1, a current flows from the diode D1 to the output terminal 13 via the coil L21.
On the other hand, also in the coil L22, energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L22 and becomes an electromotive force of the coil L22. However, this electromotive force is positive on the diode D2 side of the coil L22 and negative on the output terminal 13 side. Therefore, since a reverse voltage with the cathode side terminal being positive is applied to the diode D2, no current flows through the diode D2.
Accordingly, a DC voltage based on the electromotive force generated in the coil L21 is output from the output terminal 13 after being smoothed by the capacitor C1.

Thus, in the conversion circuit 1 according to the first embodiment, both (1) the voltage supply of the coil L11 is on and (2) the power supply of the coil L11 is switched off. In the state, a DC voltage is output from the output terminal 13.
In the state (1), a DC voltage based on energy supplied from the coil L11 to the coil L22 is output. In a state (2), a DC voltage based on energy supplied from the coil L11 to the coil L21 is output.

  That is, since the conversion circuit 1 outputs a DC voltage using all of the energy transmitted from the coil L11 to the coils L21 and L22, it is possible to perform voltage conversion with very little loss and very high efficiency. is there.

  Here, depending on the state of the load L connected between the output terminal 13 and the output terminal 14, the DC voltage output from the conversion circuit 1 is low (during heavy load) or high (during light load or standby). When trying, the function of the switching signal generation circuit 10 including the VFO 15 and the monostable multivibrator 17 generates a voltage pulse in which the number of pulses per unit time is increased or decreased, respectively. Then, the voltage pulse is applied to the gate terminal G1 of the FET1, thereby controlling on / off of the FET1. As a result, the conversion circuit 1 including the switching signal generation circuit 10 increases the output power of the conversion circuit 1 by increasing the number of times the FET 1 is turned on per unit time when the output voltage is going to be lowered, and conversely outputs the output voltage. When the voltage is to be increased, the output power of the conversion circuit 1 can be reduced by reducing the number of times the FET 1 is turned on per unit time.

  That is, since the conversion circuit 1 generates output power corresponding to the connected load, it can obtain a stable DC voltage that is not easily affected by the load at the time of heavy load, and is useless at the time of light load or standby. Generation of output power can be avoided and efficiency is high.

[Second Embodiment]
FIG. 3 is a circuit diagram showing a basic configuration of a conversion circuit 100 according to the second embodiment to which the present invention is applied. A conversion circuit 100 shown in FIG. 3 is obtained by further adding a coil L31 to the conversion circuit 1 in the first embodiment. Accordingly, circuit elements and the like arranged in the same manner as the conversion circuit 1 in FIG.

In the conversion circuit 100 shown in FIG. 3, in the conversion circuit 1 shown in FIG. 1, a coil L31 is disposed on an output line extending from a connection point between the coil L21 and the coil L22. That is, one end of the coil L31 is connected to a connection point between the coil L21 and the coil L22, and the other end of the coil L31 is connected to the output terminal 13.
Therefore, on the secondary side of the transformer T1, the current flows only in the direction from the diode D1 to the coil L31 via the coil L21 and in the direction from the diode D2 to the coil L31 via the coil L22. Yes.

The coil L31 is a coil that smoothes a direct current output from a connection point between the coil L21 and the coil L22, and is preferably a choke coil.
The other end of the coil L31 is connected to a smoothing capacitor C1, and a DC voltage smoothed by the coil L31 and the capacitor C1 is output from the output terminal 13.

The conversion circuit 100 configured as described above outputs a DC voltage to the load L connected to the output terminals 13 and 14 based on the DC voltage supplied from the DC power supply 11.
Next, the operation of the conversion circuit 100 will be described.

  When the pulse voltage 7 is input to the gate terminal G1 of the FET 1 and the FET 1 is switched on, a DC voltage is supplied to the coil L11.

Thereby, in the coil L21, an electromotive force according to the turn ratio between the coil L11 and the coil L21 is generated, and this electromotive force is positive on the diode D1 side of the coil L21 and negative on the coil L31 side. Therefore, since a reverse voltage with the cathode side terminal being positive is applied to the diode D1, no current flows through the diode D1.
On the other hand, in the coil L22, an electromotive force according to the turn ratio between the coil L11 and the coil L22 is generated, and this electromotive force is negative on the diode D2 side of the coil L22 and positive on the coil L31 side. Therefore, since a forward voltage having a negative cathode side terminal is applied to the diode D2, a current flows from the diode D2 to the coil L31 via the coil L22.
Therefore, a DC voltage based on the electromotive force generated in the coil L22 is output to the coil L31, and the DC voltage is smoothed by the coil L31 and the capacitor C1 and output from the output terminal 13.

  Thereafter, when the FET 1 is switched off by the pulse voltage 7, both ends of the coil L11 are opened, and a back electromotive force (flyback voltage) due to the self-inductance of the coil L11 is generated.

In this state, the energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L21 and becomes an electromotive force of the coil L21. This electromotive force is negative on the diode D1 side of the coil L21 and positive on the coil L31 side. Therefore, since a forward voltage having a negative cathode side terminal is applied to the diode D1, a current flows from the diode D1 to the coil L31 via the coil L21.
On the other hand, also in the coil L22, the energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L22 and becomes an electromotive force of the coil L22. However, this electromotive force is positive on the diode D2 side of the coil L22 and negative on the coil L31 side. Therefore, since a reverse voltage with the cathode side terminal being positive is applied to the diode D2, no current flows through the diode D2.
Therefore, a DC voltage based on the electromotive force generated in the coil L21 is output to the coil L31, and this DC voltage is smoothed by the coil L31 and the capacitor C1 and output from the output terminal 13.

Thereafter, when the flyback voltage of the coil L11 decreases with the passage of time, the potential at the terminals on the coils L21 and L22 side of the coil L31 decreases to approximately 0 volts, and a counter electromotive force is generated in the coil L31 due to self-inductance. The counter electromotive force causes a current to flow in the direction from the coils L21 and L22 toward the coil L31. The direction of the current corresponds to the forward direction of the diodes D1 and D2. Accordingly, current flows in both the path from the diode D1 through the coil L21 to the coil L31 and the path from the diode D2 through the coil L22 to the coil L31.
For this reason, a DC voltage based on the counter electromotive force generated in the coil L31 is output from the output terminal 13.

As described above, in the conversion circuit 100 according to the second embodiment, (1) the voltage supply of the coil L11 is on, (2) the state where both ends of the coil L11 are switched to open, (3) A DC voltage is output from the output terminal 13 in the three states after the flyback voltage of the coil L11 is reduced.
In the state (1), a DC voltage is output from the energy supplied from the coil L11 to the coil L22, and in the state (2), the energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L21 and the coil L21. The DC voltage based on this electromotive force is output, and in the state (3), the DC voltage based on the energy accumulated in the coil L31 is output.

  That is, the conversion circuit 100 outputs a DC voltage using not only the electromotive force induced in the coils L21 and L22 by the coil L11 but also the energy accumulated in the coil L31, so that the loss is extremely small and very high. It is possible to perform voltage conversion with efficiency.

Further, in the state of (3) above, that is, when a DC voltage is output by the energy accumulated in the coil L31, current flows through the secondary side coils L21 and L22, so that energy is transmitted to the coil L11. Can cause loss.
However, in the conversion circuit 100, in the state (3), a current flows through the coil L21 from the diode D1 toward the coil L31, and a current flows through the coil L22 from the diode D2 toward the coil L31. And the current flowing through the coil L22 flow in opposite directions.
For this reason, since the magnetic flux generated by the current flowing through the coil L21 and the magnetic flux generated by the current flowing through the coil L22 cancel each other, no current flows through the coil L11.
Therefore, in the conversion circuit 100, energy transfer from the secondary side to the primary side does not occur, and no loss is caused thereby, so that further improvement in efficiency can be realized.

  Depending on the state of the load L connected between the output terminal 13 and the output terminal 14, the DC voltage output from the conversion circuit 100 may be low (during heavy load) or high (during light load or standby). In this case, the function of the switching signal generation circuit 10 including the VFO 15 and the monostable multivibrator 17 is the same as that of the conversion circuit 1 shown in FIG.

  That is, since the conversion circuit 100 generates output power corresponding to the connected load, it can obtain a stable DC voltage that is not easily affected by the load at the time of heavy load, and is useless at the time of light load or standby. Generation of output power can be avoided and efficiency is high.

[Third Embodiment]
FIG. 4 is a circuit diagram showing a basic configuration of a conversion circuit 110 according to the third embodiment to which the present invention is applied. The conversion circuit 110 shown in FIG. 4 uses FET2 and FET3, respectively, instead of the diode D1 and the diode D2 in the conversion circuit 100 in the second embodiment, and the FET1 and the FET2 and FET3 are turned on / off. A control dead time control circuit 18 is provided. Accordingly, circuit elements and the like arranged in the same manner as the conversion circuit 100 in FIG.

  The conversion circuit 110 shown in FIG. 4 is different from the conversion circuit 100 shown in FIG. 3 in that an FET 2 is provided instead of the diode D1, and an FET 3 is provided instead of the diode D2. That is, one end (winding start point) of the coil L22 is connected to one end (winding end point) of the secondary coil L21, and the drain terminal of the FET 2 is connected to the other end (winding start point) of the coil L21. And the drain terminal of the FET 3 is connected to the other end (winding end point) of the coil L22. The output terminal 14 is connected to the source terminals of FET2 and FET3.

  A dead time control circuit 18 is disposed on the output side of the switching signal generation circuit 10 including the VFO 15 and the monostable multivibrator 17.

  The dead time control circuit 18 is a predetermined pulse voltage applied to the gate terminals G1, G2, and G3 of the FET1, FET2, and FET3 based on the output pulse (ON / OFF control signal) of the switching signal generation circuit 10, respectively. In particular, the dead time control circuit 18 uses the FET2 when the FET3 is on with respect to the pulse voltages applied to the gate terminals G2 and G3 of the FET2 and FET3 disposed on the secondary side of the transformer T1. Is turned off, and a pulse voltage is generated at such a timing as to turn on the FET 2 when the FET 3 is turned off.

Incidentally, it is known that FETs generally used for switching, for example, power MOS-FETs, have a drain-source parasitic diode. For this reason, when the enhancement mode n-channel MOS-FET shown in FIG. 4 is used as the FET2 and FET3, the current flows through the FET as follows depending on the direction of the voltage applied between the drain and the source.
(1) When a positive voltage is applied to the gate in a state where a voltage (forward voltage) in which the drain side of the FET is positive and negative is applied to the source side, a drain current flows from the drain toward the source. When a positive voltage is not applied to the gate, the drain current is cut off and does not flow.
(2) When a positive voltage is applied to the gate in a state where a voltage (reverse voltage) with the drain side of the FET being negative and the source side being positive is applied, a current flows from the source to the drain. When a positive voltage is not applied to the gate, a current flows in a direction from the source to the drain through a parasitic diode between the drain and source.

  Therefore, on the secondary side of the transformer T1, the FET 3 is basically turned on (as will be described later, the FET 3 is turned on with a reverse voltage applied between the drain and source), the FET 3, the coil L22. When the current flows through the current path constituted by the coil L31, the FET 2 is turned off in a state where the forward voltage is applied, so that the current flowing through the FET 2 is interrupted, and the FET 2, the coil L21, and the coil L31 No current flows through the configured current path. On the contrary, the FET 2 is turned on (as will be described later, the FET 2 is also turned on in a state where a reverse voltage is applied between the drain and the source), and the current formed by the FET 2, the coil L21, and the coil L31. When the current flows through the path, the FET 3 is turned off in a state where the forward voltage is applied, so that the current flowing through the FET 3 is interrupted, and the current is configured in the current path constituted by the FET 3, the coil L22, and the coil L31. Not flowing.

  Further, since the dead time control circuit 18 requires a predetermined turn-off time until the FET 2 switches from on to off after the pulse voltage applied to the gate terminal G2 of the FET 2 becomes zero, this turn-off time In order to prevent the FET1 on the primary side of the transformer T1 from being turned on, a pulse voltage is generated by delaying the timing for turning on the FET1, and the pulse voltage is output to the gate terminal G1 of the FET1. When the transformer secondary side FET1 is turned on in a state where the FET2 and FET3 on the secondary side of the transformer are simultaneously turned on due to the turn-off time of the FET2, it is generated in the coils L22 and L21 on the secondary side. Due to the electromotive force, an excessive current flows in the path of the coil L22, the coil L21, the FET2, and the FET3, and the FET2 and the FET3 are destroyed. Therefore, the dead time control circuit 18 effectively prevents this by delaying the timing at which the FET 1 is turned on.

The conversion circuit 110 configured as described above outputs a DC voltage to the load L connected to the output terminals 13 and 14 based on the DC voltage supplied from the DC power supply 11.
Next, the operation of the conversion circuit 110 will be described.

  When a pulse voltage is input from the dead time control circuit 18 to the gate terminal G1 of the FET 1 and the FET 1 is switched on, a DC voltage is supplied to the coil L11.

Thereby, in the coil L21, an electromotive force according to the turn ratio between the coil L11 and the coil L21 is generated, and this electromotive force is positive on the FET2 side of the coil L21 and negative on the coil L31 side. Therefore, a forward voltage with its drain side terminal being positive is applied to FET2. However, at this timing, since no on-pulse is applied from the dead time control circuit 18 to the gate terminal G2 of the FET 2, the FET 2 is in an off state, and the current from the drain to the source of the FET 2 is cut off and no current flows.
On the other hand, in the coil L22, an electromotive force according to the turn ratio between the coil L11 and the coil L22 is generated, and this electromotive force is negative on the FET3 side of the coil L22 and positive on the coil L31 side. Therefore, a reverse voltage having a negative drain side terminal is applied to the FET 3. At this time, an ON pulse is applied from the dead time control circuit 18 to the gate terminal G3 of the FET 3, and the FET 3 is in a conductive state. Therefore, a current flows from the FET 3 to the coil L31 via the coil L22.
Therefore, a DC voltage based on the electromotive force generated in the coil L22 is output to the coil L31, and the DC voltage is smoothed by the coil L31 and the capacitor C1 and output from the output terminal 13.

  Thereafter, when the FET 1 is switched off according to the pulse voltage, both ends of the coil L11 are opened, and a back electromotive force (flyback voltage) due to the self-inductance of the coil L11 is generated.

In this state, the energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L21 and becomes an electromotive force of the coil L21. This electromotive force is negative on the FET2 side of the coil L21 and positive on the coil L31 side. Therefore, a reverse voltage having a negative drain side terminal is applied to the FET 2. At this time, an ON pulse is applied from the dead time control circuit 18 to the gate terminal G2 of the FET 2, and the FET 2 is switched from OFF to ON, and the FET 2 is in a conductive state. Therefore, a current flows in a path from the FET 2 to the coil L31 via the coil L21.
On the other hand, also in the coil L22, energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L22 and becomes an electromotive force of the coil L22. This electromotive force is positive on the FET3 side of the coil L22 and negative on the coil L31 side. However, at this timing, since no on-pulse is applied from the dead time control circuit 18 to the gate terminal G2 of the FET 3, the FET 3 is switched from on to off, and the current from the drain to the source of the FET 3 is cut off, and the current flows. Absent.
Therefore, a DC voltage based on the electromotive force generated in the coil L21 is output to the coil L31, and this DC voltage is smoothed by the coil L31 and the capacitor C1 and output from the output terminal 13.

Thereafter, when the flyback voltage of the coil L11 decreases with the passage of time, the potential at the terminals on the coils L21 and L22 side of the coil L31 decreases to approximately 0 volts, and a counter electromotive force is generated in the coil L31 due to self-inductance. By this counter electromotive force, a current tends to flow in the direction from the coils L21 and L22 toward the coil L31. At this time, a reverse voltage is applied between the drain and source of the FET 2 connected to the coil L21 due to the counter electromotive force generated by the coil L31. Therefore, the FET 2 is in a conducting state in the state where the on-pulse is applied to the gate terminal G2, and a current flows from the source to the drain. A reverse voltage is also applied between the drain and source of the FET 3 connected to the coil L22 due to the counter electromotive force generated by the coil L31. Therefore, even when the FET 3 is in an off state (a state where no on-pulse is applied to the gate terminal G3), a current flows from the source to the drain through the parasitic diode of the FET 3. That is, current flows in both the path from the FET 2 through the coil L21 to the coil L31 and the path from the FET 3 through the coil L22 to the coil L31.
For this reason, a DC voltage based on the counter electromotive force generated in the coil L31 is output from the output terminal 13.

Thus, in the conversion circuit 110 according to the third embodiment, (1) the voltage supply of the coil L11 is on, (2) the state where both ends of the coil L11 are switched to open, (3) A DC voltage is output from the output terminal 13 in the three states after the flyback voltage of the coil L11 is reduced.
In the state (1), a DC voltage is output from the energy supplied from the coil L11 to the coil L22, and in the state (2), the energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L21 and the coil L21. The DC voltage based on this electromotive force is output, and in the state (3), the DC voltage based on the energy accumulated in the coil L31 is output.

  That is, the conversion circuit 110 outputs a DC voltage using not only the electromotive force induced in the coils L21 and L22 by the coil L11 but also the energy accumulated in the coil L31, so that the loss is extremely small and very high. It is possible to perform voltage conversion with efficiency.

[Fourth Embodiment]
FIG. 5 is a circuit diagram showing a basic configuration of a conversion circuit 120 according to the fourth embodiment to which the present invention is applied. The conversion circuit 120 shown in FIG. 5 uses an FET 3 instead of the diode D2 in the conversion circuit 100 in the second embodiment, and receives an on / off control signal from the switching signal generation circuit 10 as a gate terminal of the FET 3. By applying also to G3, the on / off of FET3 is controlled. Accordingly, circuit elements and the like arranged in the same manner as the conversion circuit 100 in FIG.

The conversion circuit 120 shown in FIG. 5 includes the FET 3 instead of the diode D2 in the conversion circuit 100 shown in FIG. That is, one end (winding start point) of the coil L22 is connected to one end (winding end point) of the secondary side coil L21, and the cathode of the diode D1 is connected to the other end (winding start point) of the coil L21. A terminal is connected, and the drain terminal of the FET 3 is connected to the other end (winding end point) of the coil L22. The output terminal 14 is connected to the anode terminal of the diode D1 and the source terminal of the FET 3.
Therefore, on the secondary side of the transformer T1, a current flows in the direction from the diode D1 to the coil L31 via the coil L21, but no current flows in the opposite direction.

The switching signal generation circuit 10 including the VFO 15 and the monostable multivibrator 17 generates a predetermined pulse voltage. The pulse voltage output from the switching signal generation circuit 10 is a pulse voltage having a period proportional to the output voltage of the conversion circuit 120. The pulse voltage is applied to the gate terminals G1 and G3 of the FET1 and FET3, respectively.
Therefore, when the FET 1 connected to the primary side of the transformer T1 is on, the secondary side FET 3 is also on, and when the FET 1 is switched off, the FET 3 is also switched off simultaneously. For this reason, when the FET 1 is on, the FET 3 is turned on with a reverse voltage applied between the drain and the source, so that a current flows through a current path constituted by the FET 3, the coil L22, and the coil L31. On the contrary, when FET1 is off, FET3 is turned off with a forward voltage applied, so that the current flowing through FET3 is cut off, and is composed of FET3, coil L22, and coil L31. No current flows in the current path.

The conversion circuit 120 configured as described above outputs a DC voltage to the load L connected to the output terminals 13 and 14 based on the DC voltage supplied from the DC power supply 11.
Next, the operation of the conversion circuit 120 will be described.

  When the pulse voltage 7 is input to the gate terminal G1 of the FET 1 and the FET 1 is switched on, a DC voltage is supplied to the coil L11.

Thereby, in the coil L21, an electromotive force according to the turn ratio between the coil L11 and the coil L21 is generated, and this electromotive force is positive on the diode D1 side of the coil L21 and negative on the coil L31 side. Therefore, since a reverse voltage with the cathode side terminal being positive is applied to the diode D1, no current flows through the diode D1.
On the other hand, in the coil L22, an electromotive force according to the turn ratio between the coil L11 and the coil L22 is generated, and this electromotive force is negative on the FET3 side of the coil L22 and positive on the coil L31 side. Therefore, a reverse voltage having a negative drain side terminal is applied to the FET 3. At this time, an ON pulse is applied from the switching control circuit 10 to the gate terminal G3 of the FET 3, and the FET 3 is in a conductive state. Therefore, a current flows from the FET 3 to the coil L31 via the coil L22.
Therefore, a DC voltage based on the electromotive force generated in the coil L22 is output to the coil L31, and the DC voltage is smoothed by the coil L31 and the capacitor C1 and output from the output terminal 13.

  Thereafter, when the FET 1 is switched off according to the pulse voltage, both ends of the coil L11 are opened, and a back electromotive force (flyback voltage) due to the self-inductance of the coil L11 is generated.

In this state, the energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L21 and becomes an electromotive force of the coil L21. This electromotive force is negative on the diode D1 side of the coil L21 and positive on the coil L31 side. Therefore, since a forward voltage having a negative cathode side terminal is applied to the diode D1, a current flows from the diode D1 to the coil L31 via the coil L21.
On the other hand, also in the coil L22, energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L22 and becomes an electromotive force of the coil L22. This electromotive force is positive on the FET3 side of the coil L22 and negative on the coil L31 side. However, at this timing, since no ON pulse is applied from the switching control circuit 10 to the gate terminal G3 of the FET 3, the FET 3 is switched from ON to OFF, and the current from the drain to the source of the FET 3 is cut off and no current flows. .
Therefore, a DC voltage based on the electromotive force generated in the coil L21 is output to the coil L31, and this DC voltage is smoothed by the coil L31 and the capacitor C1 and output from the output terminal 13.

Thereafter, when the flyback voltage of the coil L11 decreases with the passage of time, the potential at the terminals on the coils L21 and L22 side of the coil L31 decreases to approximately 0 volts, and a counter electromotive force is generated in the coil L31 due to self-inductance. The counter electromotive force causes a current to flow in the direction toward the coil L21 and the coil L31. The direction of the current corresponds to the forward direction of the diode D1. Therefore, a current flows in a path from the diode D1 through the coil L21 to the coil L31. On the other hand, a reverse voltage is applied between the drain and source of the FET 3 connected to the coil L22 due to the counter electromotive force generated by the coil L31. Therefore, even when the FET 3 is in an off state (a state where no on-pulse is applied to the gate terminal G3), a current flows from the source to the drain through the parasitic diode of the FET 3. That is, current flows in both the path from the diode D1 through the coil L21 to the coil L31 and the path from the FET 3 through the coil L22 to the coil L31.
For this reason, a DC voltage based on the counter electromotive force generated in the coil L31 is output from the output terminal 13.

Thus, also in the conversion circuit 120 in the fourth embodiment, (1) the voltage supply of the coil L11 is on, (2) the state where both ends of the coil L11 are switched to open, (3) A DC voltage is output from the output terminal 13 in the three states after the flyback voltage of the coil L11 is reduced.
In the state (1), a DC voltage is output from the energy supplied from the coil L11 to the coil L22, and in the state (2), the energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L21 and the coil L21. The DC voltage based on this electromotive force is output, and in the state (3), the DC voltage based on the energy accumulated in the coil L31 is output.

  That is, since the conversion circuit 120 outputs a DC voltage using not only the electromotive force induced in the coils L21 and L22 by the coil L11 but also the energy accumulated in the coil L31, the loss is extremely small and very high. It is possible to perform voltage conversion with efficiency.

In the conversion circuit 120 in the fourth embodiment, the dead time control circuit 18 required in the conversion circuit 110 in the third embodiment is unnecessary. In the conversion circuit 120, as described above, when a pulse voltage is input to the gate terminal G1 of the FET 1 connected to the primary side of the transformer T1 and the FET 1 is switched on, the turn ratio between the coil L11 and the coil L22 is changed. However, since a reverse voltage is applied to the diode D1 at this time, no current flows through the diode D1. Accordingly, in the conversion circuit 120, even if the primary FET 1 of the transformer is turned on, a current flows in the path of the coil L22, the coil L21, the diode D1, and the FET 3 due to the electromotive force generated in the secondary coils L22 and L21. This is because there is no need to delay the turn-on timing of the FET 1 in consideration of the turn-off time of the FET 3 as in the conversion circuit 110 of the third embodiment.
That is, according to the conversion circuit 120, an inexpensive and highly efficient conversion circuit can be configured with a small number of parts.

Next, regarding the conversion circuit 120, the operation of the turn-off time until the FET 3 on the secondary side of the transformer T1 is completely turned off will be considered. As described above, the FET 1 is switched off according to the pulse voltage, and at this timing, the FET 3 should be switched from on to off. However, since there are actually variations in FET characteristics, both FET1 and FET3 are not always completely turned off at the same timing. Therefore, until FET3 is completely turned off due to the characteristics of FET3. There may be a delay in turn-off time. During this delayed turn-off time, energy is not supplied on the primary side of the transformer T1, so that the energy stored in the magnetic circuit of the transformer T1 is reduced. However, the diode D1, the secondary coil L21, the coil When a current having a direction corresponding to the forward direction of the diode D1 flows through the path of L22 and the FET 3, the energy accumulated in the magnetic circuit of the transformer T1 is stored without being consumed. Thereafter, when the FET 3 is completely turned off, the energy accumulated in the magnetic circuit of the transformer T1 is transmitted to the coil L21 to become an electromotive force of the coil L21, and a current from the diode D1 to the coil L31 via the coil L21. Begins to flow, and a DC voltage based on the electromotive force generated in the coil L21 is output to the coil L31.
That is, even if there is a delay in switching from on to off of the FET 3 due to the turn-off time of the FET 3, the energy accumulated in the magnetic circuit of the transformer T1 is not consumed during that time. There is an advantage that is good.

  Next, the role of the coil L31 when a current in a direction corresponding to the forward direction of the diode D1 flows through the path of the diode D1, the secondary coil L21, the coil L22, and the FET3 during the delayed turn-off time of the FET3. Consider. When this current flows, the secondary side coil L21 and coil L22 are practically short-circuited, and the voltage at the connection point between the coil L21 and coil L22 is 0 volts. Therefore, there is a possibility that a current flows in a direction from the capacitor C1 to the connection point via the coil L31. However, in the state in which the FET 3 is turned on immediately before the FET 3 is turned off, a current is forcibly flowing in the coil L31 in the direction from the coil L22 to the coil L31. A counter electromotive force is generated at L31. Normally, the action of this counter electromotive force of the coil L31 lasts for a time sufficiently longer than the turn-off time of the FET 3, so that no current flows in the direction from the capacitor C1 to the connection point via the coil L31.

  Note that in the conversion circuit 120, a circuit configuration in which an FET is used in place of the diode D1 and a diode is used in place of the FET3, that is, a circuit configuration in which the diode D1 and the FET3 are just replaced in the conversion circuit 120 cannot be used. The reason for this is that, first, when an event occurs in which the FET and the diode on the secondary side of the transformer are simultaneously turned on due to the turn-off time of the FET, This is because an excessive current flows through the paths of the coil L22, the coil L21, the FET, and the diode due to the electromotive force generated in the side coils L22 and L21, and the FET is destroyed. Second, when an FET is used instead of the diode D1, the FET is completely turned off when the energy stored in the coil L31 is reduced in the operation after the flyback voltage of the coil L11 is reduced. This is because the energy accumulated in the capacitor C1 during this period is lost through the current path passing through the coil L31, the coil L21, the FET, and the capacitor C1. Thirdly, due to the action of the switching control circuit 10, because the output voltage is high (during light load or standby), if the period of the pulse voltage 7 input to the gate terminal G 1 of the FET 1 becomes longer, during the turn-off time period, This is because the energy stored in the capacitor C1 is lost through the same current path as described above.

FIG. 6 is a chart showing the operation of the conversion circuit 100 in the second embodiment.
The waveform in FIG. 6 shows a change in voltage value or current value in each part when the conversion circuit 100 is operated. In FIG. 6, the horizontal axis indicates the passage of time, and the vertical axis indicates the voltage value or current value.

  In FIG. 6, channels CH1 to CH3 each have a waveform indicating a voltage value. The channel CH1 indicates the voltage value at the cathode side terminal of the diode D1, as indicated by “CH1” in FIG. 3, and similarly, the channel CH2 indicates the voltage value at the coil L21 and L22 side terminals of the coil L31. Channel CH3 indicates a voltage value at the cathode side terminal of the diode D2.

  In FIG. 6, channels CH5 to 7 are waveforms indicating current values. The channel CH5 indicates the current value measured at the cathode side terminal of the diode D1, as indicated by “CH5” in FIG. 3, and similarly, the channel CH6 indicates the current value measured at the coil L21 and L22 side terminals of the coil L31. Indicates. Channel CH7 indicates the current value measured at the cathode side terminal of the diode D2.

  In FIG. 6, FET1 (FIG. 3) is switched from OFF to ON at times Z1, Z4, and Z7, and FET1 is switched from ON to OFF at times Z2, Z5, and Z8. Times Z3 and Z6 are times when the flyback voltage in the coil L11 drops to a predetermined level.

When the FET 1 of the conversion circuit 100 (FIG. 3) is switched on at time Z1 in FIG. 6, the DC power supply 11 side of the coil L11 becomes positive and the FET 1 side becomes negative, and a predetermined current flows through the coil L11. At this time, the voltage value at the connection point between the drain terminal of the FET 1 and the coil L11 is 0 volts.
Here, due to the electromotive force generated in the coil L21, the voltage value on the diode D1 side (channel CH1) of the coil L21 rises, the diode D1 is reverse-biased, and no current flows (channel CH5).
On the other hand, in the coil L22, an electromotive force is generated in which the coil L31 side is positive and the diode D2 side is negative, so that the diode D2 is forward biased and a current flows from the diode D2 toward the coil L22 (channel CH7). The voltage on the diode D2 side (channel CH3) is 0.6 volts (residual voltage of the diode), and the voltage on the coil L31 side (channel CH2) is the voltage of the turns ratio between the primary side coil L11 and the secondary side coil L22. Is output.
Since no current flows through the coil L21, all the energy of the primary side coil L11 is supplied to the coil L22.

Next, when the FET 1 is switched off at time Z2 and the current flowing through the coil L11 is interrupted, a counter electromotive force (flyback voltage) is generated in the coil L11. This flyback voltage is positive on the FET1 side of the coil L11.
This flyback voltage generates a mutual induction voltage (channel CH1) with the diode D1 side negative in the coil L21, the diode D1 is forward biased, and a current flows from the diode D1 toward the coil L21 (channel CH5). This current is output from the output terminal 13 via the coil L31 (channel CH6).
On the other hand, in the coil L22, a voltage (channel CH3) with the diode D2 side being positive is generated by the flyback voltage, and a reverse voltage is applied to the diode D2, so that no current flows (channel CH7).

The flyback voltage in the coil L11 decreases with time and almost disappears at time Z3. At this time, the voltage value on the coils L21 and L22 side of the coil L31 decreases (channel CH2), and a back electromotive force is generated in the coil L31.
Then, due to the counter electromotive force of the coil L31, a current flows from the diode D1 to the coil L31 via the coil L21 (channel CH5), and further, a current flows from the FET 3 to the coil L31 via the coil L22 (channel). CH7), the combined current flows through the coil L31 (channel CH6).

  Thus, in the conversion circuit 120, as described above, (1) the state where the voltage supply of the coil L11 is on (time Z1 to time Z2), (2) the state where both ends of the coil L11 are switched to open ( In the three states of time Z2 to time Z3) and (3) after the flyback voltage of the coil L11 has substantially disappeared (time Z3), a current path flowing through the coil L31 is formed, and the output terminal 13 DC voltage is output.

  Then, when the back electromotive force in the coil L31 decreases, that is, at time Z4 in FIG. 6, the above operation is repeated by switching the FET 1 on again, and a DC voltage is continuously output from the output terminal 13. The

  FIG. 7 is a chart showing measurement results of manufacturing a switching power supply device using the conversion circuit 100 and measuring its efficiency. This switching power supply device applies a 100-volt DC voltage obtained by full-wave rectification of a 100-volt AC power supply as the DC power supply 11 of the conversion circuit 100 (FIG. 3), and uses an RCC (Ringing Choke Converter). The transformer T1 is driven.

The horizontal axis in FIG. 7 indicates output power (unit: W) when the output voltage is 5 volts, and the vertical axis indicates conversion efficiency (unit%) and input power (unit W).
7, (1) shows the efficiency of the switching power supply device using the conversion circuit 100, (2) shows the efficiency of the conventional switching power supply device, and (3) is for the switching power supply device using the conversion circuit 100. Input power is shown, (4) shows the input power with respect to the conventional switching power supply device.

As shown in (2) and (4) in FIG. 7, the conventional switching power supply device generally has an efficiency of 70% or less, and the efficiency at the time of low output is particularly low. For example, input power close to 8 W is required to obtain 1 W output power. Also, when the output is zero, the input power does not become zero, which indicates that so-called “standby power” is large.
On the other hand, as indicated by (1) and (3) in FIG. 7, the switching power supply device using the conversion circuit 100 has already achieved an efficiency exceeding 80% when the output power is about 1 W. The conversion efficiency is extremely high, and a stable efficiency is maintained even when the output power changes.
Furthermore, in the switching power supply device using the conversion circuit 100, the input power when the output power is zero is almost equal to zero. For this reason, so-called standby power consumption is almost negligible, and wasteful power consumption can be almost completely eliminated.

As described above, the conversion circuit 100 performs a voltage conversion operation with extremely high efficiency. For example, when the conversion circuit 100 is used in a switching power supply, high efficiency can be realized even at a low output.
In addition, since the efficiency is high and the loss is low, it is easily predicted that there will be almost no problem of heat generation, and a voltage conversion circuit that is extremely useful can be realized.

In the first to fourth embodiments, the specific form of the DC power supply 11 in the conversion circuits 1, 100, 110, and 120 is arbitrary, and a battery or a switching power supply device may be used. Alternatively, a circuit that rectifies an AC power supply and supplies a DC voltage can be used as the DC power supply 11, and the same effect can be obtained in any case.
In particular, when a circuit (such as a diode bridge circuit) that rectifies an AC power supply and supplies a DC voltage is used as the DC power supply 11, the conversion circuits 1, 100, 110, and 120 are used as a constituent circuit of the DC power supply circuit. can do. The DC power supply circuit is mounted on many electrical appliances and electronic devices connected to household AC power supplies, and is extremely useful when the conversion circuit 1 of the present invention is applied to these electrical appliances and electronic devices.

  Further, in the first and second embodiments, it is of course possible to attach the diodes arranged in the conversion circuits 1 and 100 so that the polarities are reversed. In this case, the output DC voltage The same effect as in the first and second embodiments can be obtained only by reversing the polarity.

  Further, the specific configuration of the conversion circuits 1, 100, 110, and 120 is not particularly limited, and it is of course possible to replace some or all of the conversion circuits 1, 100, 110, and 120 with equivalent circuits. For example, the diode included in the conversion circuit 1, 100, 110, 120 is replaced with a circuit having a rectifying function, and / or the FET included in the conversion circuit 1, 100, 110, 120 is turned on / off by an external input signal. It is possible to replace the circuit with a switching function that can be turned off, and it is needless to say that other detailed configurations can be appropriately changed.

  The voltage conversion circuit of the present invention can be applied not only to a device that converts a DC voltage, but also, for example, the input stage of the voltage conversion circuit of the present invention (DC in FIGS. 1, 3, 4, and 5). If a rectifier circuit that rectifies an AC voltage is connected to the power supply 11), it can be used as a power supply circuit (for example, a switching power supply circuit) that outputs a desired DC voltage from the AC voltage. As described above, the voltage conversion circuit of the present invention can be applied to all circuits that require voltage conversion of a DC voltage and devices equipped with the circuits.

It is a circuit diagram which shows the structure of the conversion circuit 1 in 1st Embodiment to which this invention is applied. FIG. 2 is a circuit diagram showing a configuration of a switching signal generation circuit 10 in the conversion circuit 1 shown in FIG. 1. It is a circuit diagram which shows the structure of the conversion circuit 100 in 2nd Embodiment to which this invention is applied. It is a circuit diagram which shows the structure of the conversion circuit 110 in 3rd Embodiment to which this invention is applied. It is a circuit diagram which shows the structure of the conversion circuit 120 in 4th Embodiment to which this invention is applied. 4 is a chart showing an operation state of the conversion circuit 100 shown in FIG. 3. 4 is a chart showing conversion efficiency of the conversion circuit 100 shown in FIG. 3. It is a circuit diagram which shows the example of the conventional voltage conversion circuit. It is a circuit diagram which shows the example of the conventional voltage conversion circuit. It is a circuit diagram which shows the example of the conventional voltage conversion circuit. It is a circuit diagram which shows the example of the conventional voltage conversion circuit.

Explanation of symbols

1,100,110,120 Conversion circuit 10 Switching signal generation circuit 11 DC power supply 13, 14 Output terminal 15 VFO
16 Differentiation circuit 17 Monostable multivibrator 18 Dead time control circuit FET1, FET2, FET3 FET
C1 Capacitor D1, D2 Diode L11, L21, L22, L31 Coil T1 Transformer

Claims (11)

A voltage conversion circuit comprising a transformer and switching means for switching on / off of DC voltage supply to the primary side of the transformer,
The transformer has a configuration in which a first coil is disposed on the primary side, and a second coil and a third coil are disposed on the secondary side,
A first current path for outputting a DC voltage based on an electromotive force generated in the second coil in a state where the voltage supply to the transformer is turned on by the switching means;
A second current path for outputting a DC voltage based on an electromotive force generated in the third coil after the voltage supply to the transformer is switched from on to off by the switching means;
Control means for detecting output voltages of the first current path and the second current path and controlling on / off of the switching means at a period proportional to the output voltage;
A voltage conversion circuit characterized by the above. A fourth coil disposed on output lines of the first current path and the second current path;
A third current path for outputting a DC voltage is formed based on an electromotive force generated in the fourth coil when a DC voltage value output in the second current path is reduced,
The control means detects output voltages of the first current path, the second current path, and the third current path, and controls on / off of the switching means at a period proportional to the output voltage. thing,
The voltage conversion circuit according to claim 1. The second coil and the third coil are connected in series,
One end of the fourth coil is connected to a connection point between the second coil and the third coil,
The third current path is constituted by a current path composed of the second coil and the fourth coil, and a current path composed of the third coil and the fourth coil;
The voltage conversion circuit according to claim 2. A first rectifier is connected to one end of the second coil, and the other end is connected to the third coil.
One end of the third coil is connected to the second coil, and the second rectifier is connected to the other end.
One end of the fourth coil is connected to a connection point between the second coil and the third coil, and the other end of the fourth coil is connected to an output terminal of the voltage conversion circuit. ,
The first current path is constituted by the first rectifying means, the second coil, and the fourth coil.
The second current path is constituted by the second rectifying means, the third coil, and the fourth coil.
The third current path includes a current path composed of the first rectifying means, the second coil, and the fourth coil, and the second rectifying means, the third coil, and the fourth coil. A current path composed of a coil of
4. The voltage conversion circuit according to claim 2 or 3, wherein: A voltage conversion circuit comprising a transformer and first switching means for switching on / off of DC voltage supply to the primary side of the transformer,
The transformer has a configuration in which a first coil is disposed on the primary side, and a second coil and a third coil are disposed on the secondary side,
A first current path that includes a second switching unit and outputs a DC voltage based on an electromotive force generated in the second coil in a state where the voltage supply to the transformer is turned on by the first switching unit; When,
A second switching unit configured to output a DC voltage based on an electromotive force generated in the third coil after the voltage supply to the transformer is switched from on to off by the first switching unit; Current path,
Signal generating means for detecting output voltages of the first current path and the second current path and outputting an on / off control signal having a period proportional to the output voltage;
Based on an on / off control signal from the signal generating means, the on / off of the first switching means is controlled, and the third switching means is turned off when the second switching means is on. And a control means for controlling on / off of the second switching means and the third switching means so that the third switching means is turned on when the second switching means is off. thing,
A voltage conversion circuit characterized by the above. A fourth coil disposed on output lines of the first current path and the second current path;
A third current path for outputting a DC voltage is formed based on an electromotive force generated in the fourth coil when a DC voltage value output in the second current path is reduced,
The signal generation means detects output voltages of the first current path, the second current path, and the third current path, and outputs an on / off control signal having a period proportional to the output voltage. ,
The voltage conversion circuit according to claim 5. The second switching means is connected to one end of the second coil, the other end is connected to the third coil,
One end of the third coil is connected to the second coil, and the third switching means is connected to the other end,
One end of the fourth coil is connected to a connection point between the second coil and the third coil, and the other end of the fourth coil is connected to an output terminal of the voltage conversion circuit. ,
The first current path is constituted by the second switching means, the second coil, and the fourth coil.
The second current path is constituted by the third switching means, the third coil, and the fourth coil.
The third current path includes a current path composed of the second switching means, the second coil, and the fourth coil, and the third switching means, the third coil, and the fourth coil. A current path composed of a coil of
The voltage conversion circuit according to claim 6. A voltage conversion circuit comprising a transformer and first switching means for switching on / off of DC voltage supply to the primary side of the transformer,
The transformer has a configuration in which a first coil is disposed on the primary side, and a second coil and a third coil are disposed on the secondary side,
A first current path that includes a second switching unit and outputs a DC voltage based on an electromotive force generated in the second coil in a state where the voltage supply to the transformer is turned on by the first switching unit; When,
A second current path that includes a rectifying means and outputs a DC voltage based on an electromotive force generated in the third coil after the voltage supply to the transformer is switched from on to off by the first switching means; ,
Control means for detecting output voltages of the first current path and the second current path and controlling on / off of the first switching means and the second switching means at a period proportional to the output voltage. Providing with,
A voltage conversion circuit characterized by the above. A fourth coil disposed on output lines of the first current path and the second current path;
A third current path for outputting a DC voltage is formed based on an electromotive force generated in the fourth coil when a DC voltage value output in the second current path is reduced,
The control means detects output voltages of the first current path, the second current path, and the third current path, and the first switching means and the second current cycle at a period proportional to the output voltage. Controlling on / off of the switching means,
The voltage conversion circuit according to claim 8. The second switching means is connected to one end of the second coil, the other end is connected to the third coil,
One end of the third coil is connected to the second coil, and the other rectifier is connected to the other end.
One end of the fourth coil is connected to a connection point between the second coil and the third coil, and the other end of the fourth coil is connected to an output terminal of the voltage conversion circuit. ,
The control means turns on / off the second switching means in synchronization with on / off of the first switching means,
The first current path is constituted by the second switching means, the second coil, and the fourth coil.
The second current path is constituted by the rectifying means, the third coil, and the fourth coil,
The third current path includes a current path including the second switching unit, the second coil, and the fourth coil, and the rectifying unit, the third coil, and the fourth coil. Comprising a current path consisting of
The voltage conversion circuit according to claim 9. A power supply device comprising the voltage conversion circuit according to claim 1.

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