JP2000341947A - Dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC-DC converter, including a snubber circuit having the transformer reset function that can reduce a loss by LC snubber without using a resistor, will not reduce efficiency and dispenses with the reset coil of the transformer by preventing generation of heat. SOLUTION: A second switching element 16 is turned on during the on-period of a first switching element 3. Thereby, the charges filling a capacitor 14 during the off-period of the first switching element 3 with the excitation energy of the transformer 2 and the energy accumulated in the leakage inductance and wiring inductance are recovered for the DC input power supply 1 by utilizing the resonance phenomenon between the capacitor 14 and a reactor 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a DC / DC converter, and more particularly to an improvement and a function expansion of a snubber circuit.

[0002]

2. Description of the Related Art FIG. 15 shows, for example, "Basics of Switching Converter" (issued on Feb. 25, 1992, Corona, Inc.).
Conventional RCD shown on page 104
It is a circuit diagram showing a forward type DC / DC converter with a snubber circuit. In FIG. 15, 1 is a DC input power supply, 2 is a transformer, 2a is a first winding, 2b is a second winding, 2c is a reset winding, 3 is a switching element, and 4 is a current rectifier. Rectifier diode, 5
Is a circulating diode as current circulating means, 6 is a choke coil, 7 is a smoothing capacitor, and the choke coil 6 and the smoothing capacitor 7 constitute an output LC filter. Reference numeral 8 denotes a transformer reset diode, 9 denotes a snubber diode, 10 denotes a snubber capacitor, and 11 denotes a snubber discharge resistor. An RCD snubber circuit 12 is composed of the snubber diode 9, the snubber capacitor 10, and the snubber discharge resistor 11.

Next, the operation will be described. FIG. 16 shows DC
FIG. 7 is an operation waveform diagram of the / DC converter. In the figure, (a) is a drive waveform of the switching element 3, (b) is a current / voltage waveform of the switching element, (c) is a current waveform of the diode 8, and (d) is a capacitor of the snubber capacitor 10. FIG. 7E shows a voltage waveform of the first winding 2 a of the transformer 2.

When the switching element 3 is turned on, the rectifying diode 4 is turned on, and power is supplied to the load via the choke coil 6 and the smoothing capacitor 7. Also, an exciting current flows through the transformer 2, and the exciting energy is stored. When the switching element 3 is turned off, a back electromotive force is generated in the first winding 2a, the rectifying diode 4 is turned off, and the circulating diode 5 is turned on, so that a current continuously flows through the choke coil 6 and the load is reduced. The power supply to is continued. The output voltage to the load can be controlled by adjusting the ON / OFF time distribution of the switching element 3.

As shown in FIG. 1B, when the switching element 3 is turned off, the voltage rises sharply, and a spike voltage is generated by the energy stored in the leakage inductance and the parasitic inductance of the transformer 2. In order to suppress this spike voltage, the RCD snubber circuit 12
Is connected.

In the RCD snubber circuit 12, when the switching element 3 is turned off, the snubber diode 9 becomes conductive, and the energy stored in the leakage inductance of the transformer and the parasitic inductance of the wiring is charged in the snubber capacitor 10 (FIG. 16). (D)) The spike voltage generated in the switching element 3 is suppressed. When the voltage of the switching element 3 becomes lower than the voltage of the snubber capacitor 10, the energy charged in the snubber capacitor 10, that is, the snubber energy becomes the snubber discharge resistance 11.
Is discharged.

The reset of the magnetic flux of the transformer 2 is performed by the reset winding 2c and the reset diode 8 while the switching element 3 is off (FIG. 16C).
(E)) is performed by regenerating the excitation energy stored in the transformer 2 to the DC input power supply 1 during the ON period of the switching element 3. Note that the RCD snubber circuit 1
2, the magnetic flux of the transformer 2 can be reset. In this case, the reset winding 2c and the reset diode 8 of the transformer 2 become unnecessary. However, transformer 2
Is consumed by the snubber discharge resistor 11.

[0008]

In the above-mentioned conventional configuration,
The energy stored in the leakage inductance of the transformer and the parasitic inductance of the wiring is transferred to the snubber capacitor 10.
After being charged, the battery is consumed by the snubber discharge resistor 11, so that there is a problem that the loss increases, the efficiency decreases, and the heat generation increases.

In order to reduce the switching loss and generated noise by suppressing the rate of voltage rise when the switching element 3 is turned off, it is necessary to increase the capacitance of the snubber capacitor 10. The larger the value of is, the more the loss in the RCD snubber circuit 12 increases, and there is a problem that efficiency is reduced and heat generation is increased.

When the reset winding 2c and the reset diode 8 for resetting the magnetic flux of the transformer 2 are further eliminated, all the excitation energy accumulated in the transformer 2 during the ON period of the switching element 3 is lost.
There is a problem that the efficiency is further reduced and the heat generation increases, and the omission of the reset winding is limited to the application to the converter having a very small capacity.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an L-type device that does not use a resistor.
Provided is a DC / DC converter provided with a snubber circuit having a transformer reset function, which can reduce a loss due to a C snubber, does not reduce efficiency, prevents heat generation, and eliminates the need for a transformer reset winding. It is in.

[0012]

A DC / D according to the present invention
The C converter connects the first switching means and the first winding of the transformer in series to a DC input power supply, and is induced in the second winding of the transformer by the on / off operation of the first switching means. Rectifying means for rectifying the output voltage, smoothing means for smoothing the output from the rectifying means and supplying the load to the load, and energy stored in the smoothing means during a time period when there is no output from the rectifying means to the load. In a DC / DC converter provided with a reflux means for supplying, a series connection of a first diode and a capacitor, connected between the poles of the first switching means, and a first diode and a capacitor And an inductive element connected between the connection point of
When the second switching means is turned on within the ON period of the first switching means, the excitation energy of the transformer is further accumulated in the leakage inductance and the wiring inductance. The energy stored in the capacitor during the off period of the first switching means is regenerated to the DC input power supply by utilizing the resonance phenomenon between the capacitor and the inductive element, and the reset winding of the transformer is used. Is unnecessary.

In the DC / DC converter according to the present invention, the first switching means and the first winding of the transformer are connected in series and connected to a DC input power supply, and the first switching means is turned on and off by the on / off operation. The first of the above transformers
Rectifying means for rectifying a combined voltage induced in the first winding and the second winding connected in series with the first winding, and smoothing an output from the rectifying means to supply the output to a load. And a recirculation means for supplying energy stored in the smoothing means to the load during a time period when there is no output from the rectification means, in the boost type DC / DC converter. A series connection of a first diode and a capacitor, connected between the poles of the means;
And a series connection of an inductive element and a second switching means connected between a connection point between the first diode and the capacitor and the DC input power supply;
By turning on the second switching means during the on-period of the switching means, the excitation energy of the transformer, the leakage inductance thereof, and the energy stored in the inductance of the wiring are stored during the off-period of the first switching means. The electric charge charged in the capacitor is regenerated to the DC input power supply by utilizing the resonance phenomenon between the capacitor and the inductive element, thereby eliminating the need for the reset winding of the transformer.

Further, the DC / DC converter according to the present invention includes a DC input power supply, first switching means having a low potential side terminal connected to the low potential side terminal of the DC input power supply, and a first winding. And a transformer connected between the high potential side terminal of the DC input power supply and the high potential side terminal of the first switching means, and a transformer connected between the terminals of the second winding of the transformer. DC / DC comprising: a series connection of a rectifier diode and a return diode whose polarities are opposite to each other; and an LC filter connected in parallel with the return diode and configured by a series connection of a smoothing reactor and a smoothing capacitor. In the converter, a first diode having an anode terminal connected to the high potential side terminal of the first switching element, and one terminal connected to a cathode terminal of the first diode And the other terminal is connected between the connection point of the first diode and the capacitor and the high potential side terminal of the DC power supply, and the other terminal is connected to the low potential side terminal of the first switching means. And a series connection of an inductive element and a second switching means.

Further, a DC / DC converter according to the present invention comprises a DC input power supply, a first switching means having a low potential side terminal connected to the low potential side terminal of the DC input power supply, and a first winding. Is connected between the high-potential terminal of the DC input power supply and the high-potential terminal of the first switching means, and the anode terminal is connected to the first terminal of the transformer.
A rectifying diode connected to one terminal of a second winding connected in series with the winding; an anode terminal connected to the high potential side terminal of the DC input power supply; and a cathode terminal connected to the rectifying diode. A return diode connected to the cathode terminal, and an LC filter comprising a series connection of a smoothing reactor and a smoothing capacitor connected between the cathode terminal of the return diode and the low potential side terminal of the DC input power supply. A boost type DC / DC converter comprising: a first diode having an anode terminal connected to the high potential side terminal of the first switching element;
A capacitor having one terminal connected to the cathode terminal of the first diode and the other terminal connected to the low potential side terminal of the first switching means; a connection point between the first diode and the capacitor; It has a series connection of an inductive element and a second switching means, which is connected between the high potential side terminal of the input power supply.

In the DC / DC converter according to the present invention, the anode terminal is connected to the low potential side terminal of the first switching means, and the cathode terminal is connected to the high potential side terminal of the first switching means. It has two diodes.

The DC / DC converter according to the present invention includes a second diode having an anode terminal connected to the low potential side terminal of the first switching means and a cathode terminal connected to one terminal of a capacitor. It is a thing.

Further, the DC / DC converter according to the present invention includes a DC input power supply, first switching means having a low potential side terminal connected to the low potential side terminal of the DC input power supply, and a first winding. And a transformer connected between the high potential side terminal of the DC input power supply and the high potential side terminal of the first switching means, and a transformer connected between the terminals of the second winding of the transformer. DC / DC comprising: a series connection of a rectifier diode and a return diode whose polarities are opposite to each other; and an LC filter connected in parallel with the return diode and configured by a series connection of a smoothing reactor and a smoothing capacitor. In the converter, a first diode having an anode terminal connected to the high potential side terminal of the first switching element, and one terminal connected to a cathode terminal of the first diode A capacitor connected to the other terminal connected to the low potential side terminal of the first switching means, a second switching means having one terminal connected to the connection point of the first diode and a capacitor,
An inductive element connected between the other terminal of the second switching means and the high-potential terminal of the DC input power supply; and an anode terminal connected to the low-potential terminal of the first switching means and connected to the cathode. A terminal is provided with a second diode connected to a connection point between the second switching means and the inductive element.

Further, the DC / DC converter according to the present invention includes a DC input power supply, first switching means having a low potential side terminal connected to the low potential side terminal of the DC input power supply, and a first winding. Is connected between the high-potential terminal of the DC input power supply and the high-potential terminal of the first switching means, and the anode terminal is connected to the first terminal of the transformer.
A rectifying diode connected to one terminal of a second winding connected in series with the winding; an anode terminal connected to the high potential side terminal of the DC input power supply; and a cathode terminal connected to the rectifying diode. A return diode connected to the cathode terminal, and an LC filter comprising a series connection of a smoothing reactor and a smoothing capacitor connected between the cathode terminal of the return diode and the low potential side terminal of the DC input power supply. A boost type DC / DC converter comprising: a first diode having an anode terminal connected to the high potential side terminal of the first switching element;
A capacitor having one terminal connected to the cathode terminal of the first diode and the other terminal connected to the low-potential side terminal of the first switching means, and one terminal connecting the first diode and the capacitor; A second switching means connected to a point; an inductive element connected between the other terminal of the second switching means and a high potential side terminal of the DC input power supply; and an anode terminal connected to the first terminal. And a second diode connected to the low potential side terminal of the switching means and having a cathode terminal connected to the connection point of the second switching means and the inductive element.

Further, the DC / DC converter according to the present invention includes a DC input power supply, first switching means having a high potential side terminal connected to the high potential side terminal of the DC input power supply, and a first winding. And a transformer connected between a low potential side terminal of the DC input power supply and a low potential side terminal of the first switching means, and a transformer connected between terminals of a second winding of the transformer. DC / DC comprising: a series connection of a rectifier diode and a return diode whose polarities are opposite to each other; and an LC filter connected in parallel with the return diode and configured by a series connection of a smoothing reactor and a smoothing capacitor. In the converter, a first diode having a cathode terminal connected to the low potential side terminal of the first switching element, and one terminal connected to an anode terminal of the first diode And a capacitor whose other terminal is connected to the high-potential terminal of the first switching means, and which is connected between a connection point of the first diode and the capacitor and the low-potential terminal of the DC input power supply. And a series connection body of the inductive element and the second switching means.

Further, the DC / DC converter according to the present invention includes a DC input power supply, first switching means having a high potential side terminal connected to the high potential side terminal of the DC input power supply, and a first winding. A transformer connected between the low potential side terminal of the DC input power supply and the low potential side terminal of the first switching means, and an anode terminal connected to the first potential of the transformer.
A rectifying diode connected to one terminal of a second winding connected in series with the winding; an anode terminal connected to the high potential side terminal of the DC input power supply; and a cathode terminal connected to the rectifying diode. A return diode connected to the cathode terminal, and an LC filter comprising a series connection of a smoothing reactor and a smoothing capacitor connected between the cathode terminal of the return diode and the low potential side terminal of the DC input power supply. A first diode having a cathode terminal connected to the low potential side terminal of the first switching element, and a boost type DC / DC converter comprising:
A capacitor having one terminal connected to the anode terminal of the first diode and the other terminal connected to the high-potential terminal of the first switching means; a connection point between the first diode and the capacitor; It has a series connection of an inductive element and a second switching means connected between the low potential side terminal of the input power supply.

Also, in the DC / DC converter according to the present invention, the anode terminal is connected to the low potential side terminal of the first switching means, and the cathode terminal is connected to the high potential side terminal of the first switching means. It has two diodes.

The DC / DC converter according to the present invention includes a second diode having a cathode terminal connected to the high potential side terminal of the first switching means and an anode terminal connected to one terminal of the capacitor. It is a thing.

Further, the DC / DC converter according to the present invention comprises a DC input power supply, first switching means having a high potential side terminal connected to the high potential side terminal of the DC input power supply, and a first winding. And a transformer connected between a low potential side terminal of the DC input power supply and a low potential side terminal of the first switching means, and a transformer connected between terminals of a second winding of the transformer. DC / DC comprising: a series connection of a rectifier diode and a return diode whose polarities are opposite to each other; and an LC filter connected in parallel with the return diode and configured by a series connection of a smoothing reactor and a smoothing capacitor. In the converter, a first diode having a cathode terminal connected to the low potential side terminal of the first switching element, and one terminal connected to an anode terminal of the first diode A capacitor connected to the other terminal connected to the high potential side terminal of the first switching means, a second switching means having one terminal connected to the connection point of the first diode and a capacitor,
An inductive element connected between the other terminal of the second switching means and the low potential side terminal of the DC input power supply; and an anode having a cathode terminal connected to the high potential side terminal of the first switching means. A terminal is provided with a second diode connected to a connection point between the second switching means and the inductive element.

Further, the DC / DC converter according to the present invention includes a DC input power supply, first switching means having a high potential side terminal connected to the high potential side terminal of the DC input power supply, and a first winding. A transformer connected between the low potential side terminal of the DC input power supply and the low potential side terminal of the first switching means, and an anode terminal connected to the first potential of the transformer.
A rectifying diode connected to one terminal of a second winding connected in series with the winding; an anode terminal connected to the high potential side terminal of the DC input power supply; and a cathode terminal connected to the rectifying diode. A return diode connected to the cathode terminal, and an LC filter comprising a series connection of a smoothing reactor and a smoothing capacitor connected between the cathode terminal of the return diode and the low potential side terminal of the DC input power supply. A first diode having a cathode terminal connected to the low potential side terminal of the first switching element, and a boost type DC / DC converter comprising:
One terminal is connected to the anode terminal of the first diode, the other terminal is connected to the high potential side terminal of the first switching means, and one terminal is the connection between the first diode and the capacitor. A second switching means connected to a point, an inductive element connected between the other terminal of the second switching means and the low potential side terminal of the DC input power supply, and a cathode terminal connected to the first terminal. And a second diode having an anode terminal connected to the high potential side terminal of the switching means and an anode terminal connected to a connection point between the second switching means and the inductive element.

In the DC / DC converter according to the present invention, the field effect transistor is used as the first switching means, so that the parasitic diode functions as the second diode.

Further, in the DC / DC converter according to the present invention, the second switching means is turned on during the on-period of the first switching means, and the second switching means is turned on.
The on time of the switching means is set to be at least half the resonance period determined by the capacitor and the inductive element.

Also, the DC / DC converter according to the present invention detects the current of the second switching means, and turns off the second switching means after the current becomes zero from the on state. It was done.

In the DC / DC converter according to the present invention, the second switching means has a polarity, and is automatically turned off when the current becomes zero from the on state.

In the DC / DC converter according to the present invention, the on / off operation of the first switching means and the on / off operation of the second switching means are synchronized.

Further, in the DC / DC converter according to the present invention, the minimum on-time of the first switching means is less than 1/2 of the resonance period determined by the capacitor and the inductive element.
Further, the second switching means is turned on during the on-period of the first switching means.

In the DC / DC converter according to the present invention, the on / off operation of the first switching means and the on / off operation of the second switching means are synchronized.

Also, in the DC / DC converter according to the present invention, the second switching means is a series connection of a field effect transistor and a diode for preventing backflow.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a forward type D having a snubber circuit according to a first embodiment of the present invention.
It is a circuit diagram of a C / DC converter. In the figure, 1 is a DC input power supply, 2 is a transformer, a first winding 2a, a second
Reset winding 2 which is conventionally required.
c (FIG. 15) is omitted. 3 is a first switching element such as a transistor or IGBT, 4 is a rectifying diode as rectifying means for rectifying a voltage induced in the second winding 2b of the transformer 2, and 6 and 7 are rectifying diodes. A choke coil and a smoothing capacitor as smoothing means for smoothing the output from the diode 4 and supplying the smoothed output to a load (not shown). And a reflux diode to be supplied to the load.
Although not shown, the rectifying diode 4 is not limited to being inserted at the position shown in FIG.
May be inserted between the anode terminal of the second winding 2b and the other terminal of the second winding 2b, or may be inserted at both the position shown in FIG.

A first diode 13 and a capacitor 14 are connected in series, and are connected in parallel with the first switching element 3. The anode terminal of the first diode 13 is connected to a connection point between the first winding 2a of the transformer 2 and the first switching element 3, and the cathode terminal of the first diode 13 serves as an inductive element connected in series. The reactor 15 and one end of a second switching element 16 serving as an auxiliary switching element are connected to each other, and the other end is connected to a high potential side terminal of the DC input power supply 1. Further, a second diode 17 is connected in antiparallel with the first switching element 3 to form a snubber circuit 18.

Next, the operation will be described. FIG. 2 is an operation waveform diagram showing one embodiment of the operation of the forward DC / DC converter and the snubber circuit of the present invention. FIG. 3A shows a driving waveform of the first switching element 3,
(B) is a drive waveform of the second switching element 16, (c) is a waveform of the current is and the voltage Vs of the first switching element 3, (d) is a waveform of a current (ic) of the capacitor 14, and (FIG. e) is a waveform of the voltage Vc of the capacitor 14, FIG. 7F is a waveform of the current iL flowing through the reactor 15 or the second switching element 16, and FIG. 7G is a waveform of the current iD flowing through the second diode 17. .

Since the basic operation of the converter is the same as that of the conventional converter, a detailed description will be omitted. However, when the first switching element 3 is turned off as shown in FIG.
The energy stored in the leakage inductance of the transformer 2 and the parasitic inductance of the wiring passes through the first diode 13 as shown in FIG.
2C, the voltage applied to the first switching element 3 gradually rises as shown in FIG. 2C, and absorbs the spike voltage at the time of turn-off. Further, the overlap of the voltage and current of the first switching element 3 at the time of turning off is reduced, so that the switching loss is reduced and the switching noise is also reduced. Further, the excitation energy stored in the transformer 2 during the ON period of the first switching element 3 also turns off the first switching element 3, and the first diode 1
3, the capacitor 14 is charged. These energies charged in the capacitor 14 are retained during the off period of the first switching element 3.

When the second switching means 16 is turned on at the same time as the first switching means 3 is turned on as shown in FIGS.
As shown in FIG. 2 (e), the energy stored and held in the battery starts discharging. This discharge is performed by resonance between the capacitor 14 and the reactor 15, and the waveform of the current flowing through the reactor 15 and the second switching means 16 is as shown in FIG.
It has a sine wave shape as shown in FIG. The snubber energy and the excitation energy stored in the capacitor 14 are converted from the capacitor 14 → reactor 15 → second switching means 1
6 → DC input power 1 → regeneration to DC input power 1 via capacitor 14

As shown in FIG. 2E, when the voltage Vc of the capacitor 14 becomes zero, the second diode 17 is turned on, and the remaining energy of the reactor 15 is transferred to the reactor 15 → the second switching means 16 → The DC input power supply 1 → the second diode 17 → the first diode 13 → reactor 15 continuously regenerates to the DC input power supply 1 via the reactor 15. As shown in FIG. 2F, the reactor 15 or the second
After the current iL flowing through the switching means 16 becomes zero, the second switching means 16 is turned off.

As described above, the energy stored in the leakage inductance of the transformer of the forward type DC / DC converter, the parasitic inductance of the wiring, and the excitation energy of the transformer are charged in the capacitor 14, and these energies are supplied to the DC input power supply 1. Since it is regenerated, it does not cause a loss, prevents a decrease in efficiency, and prevents heat generation. Further, since the snubber circuit of the present invention has the reset function of the transformer 2, the reset circuit of the transformer of the conventional forward type DC / DC converter, that is, the reset winding and the reset diode are not required. Furthermore, the capacitor 14
As a result, the voltage applied to the first switching means 3 changes gradually, the spike voltage at the time of turn-off is absorbed, the overlap of the voltage and current of the first switching means 3 at the time of turn-off is reduced, and the switching loss is reduced. Switching noise is also reduced.

The connection relationship between the reactor 15 and the second switching means 16 may be reversed. Also, the second
The same operation and effect can be obtained as long as the turning on of the switching means 16 is not simultaneous with the turning on of the first switching means 3 but after the first switching means 3 is turned on.

Further, in the above description, the regeneration of the energy remaining in the reactor 15 after the voltage Vc of the capacitor 14 becomes zero is performed via the second diode 17. If the condition holds, the second
Even if the diode 17 is omitted, the residual energy of the reactor 15 can be regenerated. That is, if the absolute value of the current flowing during the ON period of the first switching element 3 is larger than the absolute value of the current flowing when the residual energy of the reactor 15 is regenerated, even if the second diode 17 is not provided, This is because a path of the reactor 15 → the second switching element 16 → the DC input power supply 1 → the first switching element 3 → the first diode 13 → the reactor 15 is established, and the regenerative operation becomes possible.

Embodiment 2 In the first embodiment, it is detected that the current iL flowing in the reactor 15 or the second switching element 16 has become zero, and thereafter, the second
Of the first switching element 3 is turned off without using the current detecting means.
, The on-time of the second switching element 16 may be set in advance to a time that is approximately half or more of the resonance cycle of the capacitor 14 and the reactor 15, as in the first embodiment. It has an effect,
There is an effect that the current detecting means is not required and the cost can be reduced.

FIG. 3 is an operation waveform diagram showing an operation of the snubber circuit according to the second embodiment of the present invention. FIG. 3A shows a driving waveform of the first switching element 3, and FIG.
(C) shows the waveform of the voltage Vc of the capacitor 14, and FIG.
Alternatively, the waveform of the current iL flowing through the second switching element 16, and FIG.
It is a waveform of D. The operation will be described with reference to FIG.

The operation of the first switching element 3 shown in FIG. 1 during the off period is exactly the same as that of the first embodiment, and the description is omitted. After the first switching element 3 is turned on and after a preset time Td, FIG.
Then, the second switching element 16 is turned on. The capacitance value C of the capacitor 14 and the inductance value L of the reactor 15 are set in advance so that the time that is approximately half the resonance cycle of the capacitor 14 and the reactor 15 is within the minimum on-time Ton1 of the first switching element 3.
Is set, and the ON time Ton2 of the second switching element 16 is set to be at least half the time of the resonance cycle of the capacitor 14 and the reactor 15. When the second switching element 16 is turned on, the capacitor 14
The energy stored and held in the battery starts discharging as shown in FIG. This discharge is performed by resonance between the capacitor 14 and the reactor 15, and the waveform of the current flowing through the reactor 15 and the second switching element 16 is as shown in FIG.
It has a sine wave shape as shown in FIG. The snubber energy and the excitation energy stored in the capacitor 14 are converted from the capacitor 14 → the reactor 15 → the second switching element 1
6 → DC input power 1 → regeneration to DC input power 1 via capacitor 14

As shown in FIG. 3C, when the voltage Vc of the capacitor 14 becomes zero, the second diode 17 is turned on, and the remaining energy of the reactor 15 is transferred to the reactor 15 → the second switching element 16 → The DC input power supply 1 → the second diode 17 → the first diode 13 → reactor 15 continuously regenerates to the DC input power supply 1 via the reactor 15. When a time equal to or more than half of the resonance cycle of the capacitor 14 and the reactor 15 elapses, the current iL flowing through the reactor 15 or the second switching element 16 becomes zero as shown in FIG. The second switching element 16 is turned off at the set ON time Ton2 of the second switching element 16. With this operation, the same effect as in the first embodiment can be obtained.

The first switching element 3 and the second switching element 16 are generally different in hardware, and the capacity of the former is usually larger than that of the latter. Therefore, when a control system (not shown) sends a turn-on signal to both switching elements 3 and 16 at the same time, the second switching element 16 is connected to the first switching element 3 by a difference in turn-on operation characteristics based on a difference in hardware between the two. The possibility of turning on earlier cannot be ruled out. In this case, the second switching element 16
May affect the operation of the main circuit of the DC / DC converter. However, as shown in FIG. 3B, the turn-on timing of the second switching element 16 is set to be delayed by the time Td from that of the first switching element 3, and the value of Td is set to the characteristic of both. If an appropriate selection is made in consideration of the above, the turn-on timing of the second switching element 16 will always be later than that of the first switching element 3, and the above-mentioned problem of the problem will be solved.

In the second embodiment, the second switching element 16 is turned on after a preset time Td after the first switching element 3 is turned on. Similarly, the same effect can be obtained by turning on the second switching element 16 at the same time when the first switching element 3 is turned on.

Embodiment 3 In the second embodiment, the case where the on-time Ton2 of the second switching element 16 is set in advance at least half of the resonance cycle of the capacitor 14 and the reactor 15 has been described. The second switching element 16 may be turned off in synchronization with the turn-off of the first switching element 3 as long as the time is equal to or longer than half the time, and the same effect as in the second embodiment is exerted.

FIG. 4 is an operation waveform diagram showing an operation of the snubber circuit according to the third embodiment of the present invention. Figures (a) to ()
(E) is a waveform of the same part as that of FIG. The operation will be described with reference to FIG.

The operation of the first switching element 3 during the off period is exactly the same as in the first and second embodiments, and the description is omitted. After the first switching element 3 of FIG. 1 is turned on, the second switching element 16 is turned on as shown in FIG. 4B after a preset time Td. The capacitance value C of the capacitor 14 and the inductance value L of the reactor 15 are set in advance so that the time that is approximately half the resonance period between the capacitor 14 and the reactor 15 is within the minimum on-time Ton1 of the first switching element 3. Keep it. The time Ton2, which is the difference between the minimum on-time Ton1 of the first switching element 3 and the delay time Td from when the first switching element 3 is turned on to when the second switching element 16 is turned on, is determined by the capacitor 1
The time is set in advance so as to be at least half the time of the resonance cycle of the reactor 4 and the reactor 15. Since the energy regenerating operation is the same operation as in the second embodiment, the detailed description is omitted. However, after the second switching element 16 is turned on, the time period of about half or more of the resonance period of the capacitor 14 and the reactor 15 is longer than the time. After elapse, the reactor 15 or the second switching element 16 as shown in FIG.
And the second switching element 16 is turned off in synchronization with the first switching element 3 being turned off, the same effect as that of the first or second embodiment can be obtained. it can.

Embodiment 4 FIG. It should be noted that the first to the first embodiments
3, the on-time of the first switching element 3 and the on-time of the second switching element 16 are different. However, the on-time only needs to be at least a half of the resonance cycle of the capacitor 14 and the reactor 15. The on / off operation of the first switching element 3 and the on / off operation of the second switching element 16 may be synchronized, and the same effects as those of the first to third embodiments can be obtained. The control circuit and the drive circuit of the first switching element 3 and the second switching element 16 can be simplified, and the capacitance value C of the capacitor 14 and the inductance value L of the reactor 15 can be selected in a wider range.

FIG. 5 is an operation waveform diagram showing another embodiment of the operation of the forward DC / DC converter and the snubber circuit of the present invention. 2A to 2G show waveforms of the same parts as those in FIG. The operation will be described with reference to FIG.

The operation of the first switching element 3 during the off period is exactly the same as in the first to third embodiments, and the description is omitted. In synchronization with the turning on of the first switching element 3 in FIG. 1, the second switching element 16 is turned on as shown in FIG. 5B. The capacitance value C of the capacitor 14 and the inductance value L of the reactor 15 are set in advance so that the time that is approximately half the resonance period between the capacitor 14 and the reactor 15 is within the minimum on-time Ton1 of the first switching element 3. Keep it. Since the energy regenerating operation is the same as that in the first to third embodiments, detailed description is omitted, but the second switching element 1
After the turn-on of No. 6 and the time of about half or more of the resonance cycle of the capacitor 14 and the reactor 15 elapses, FIG.
As shown in FIG. 5E, the voltage Vc of the capacitor 14 is zero, and as shown in FIG.
Alternatively, since the current iL flowing through the second switching means 16 is zero, the second switching element 16 can be turned off in synchronization with the turn-off of the first switching element 3. Thereby, the same effect as in the first to third embodiments can be easily obtained, and the second
Since the ON time Ton2 of the switching element 16 is set to the maximum allowable time, the capacitance value C of the capacitor 14 and the inductance value L of the reactor 15 can be selected in a wider range, and no current detecting means is required, and the delay time Td Is unnecessary, and the control circuit and the drive circuit can be simplified.

The turn-off timing of the second switching element 16 is such that the second switching element 16 itself has a polarity, and is not related to the turn-off timing of the first switching element 3. Of course, the switching element 16 may be turned off at the timing when the current of the switching element 16 becomes zero.

Embodiment 5 It should be noted that the first to the first embodiments
4 shows a case where the second diode 17 conducts after the voltage of the capacitor 14 becomes zero, but a field-effect transistor is used for the first switching element 3;
The parasitic diode may be used in place of the second diode 17. The same effect as in the first to fourth embodiments can be obtained, and the effect that the second diode 17 becomes unnecessary and the cost can be reduced can be obtained. is there.

FIG. 6 is a circuit diagram of a forward DC / DC converter according to a fifth embodiment having a snubber circuit of the present invention. In the figure, reference numerals 1 to 7 and 13 to 16 are equivalent to the components of the first embodiment shown in FIG. Reference numeral 3 denotes a first switching element, which uses a field effect transistor. Reference numeral 19 denotes a parasitic diode of the field-effect transistor, which functions similarly to the second diode 17 in FIG. Reference numeral 16a similarly uses a field-effect transistor as the second switching element, and reference numeral 16b denotes a diode for preventing backflow, which constitutes a snubber circuit 20.

The forward type DC / DC shown in FIG.
The operation of the converter is the same as that of the above-described first to fourth embodiments except that the parasitic diode 19 of the field-effect transistor 3 works instead of the second diode 17, and a description thereof will be omitted.

Embodiment 6 FIG. In the first to fifth embodiments, the case where the second diode 17 is connected in antiparallel with the first switching element 3 or the case where the parasitic diode 19 of the field effect transistor 3 is used has been described. A diode may be connected in parallel with the capacitor 14 to achieve the same effect as in the first to fourth embodiments, and the current path after the voltage of the capacitor 14 becomes zero includes the first diode 13. The energy of the conduction loss of the first diode 13 is effectively
There is an effect that can be regenerated.

FIG. 7 shows another embodiment of the present invention. In the figure, 1 to 7 and 13 to 16 are the same as the components of the first embodiment shown in FIG. The difference is that instead of the second diode 17 connected in anti-parallel with the first switching element 3, a second diode 21 is connected in parallel with the capacitor 14 to form a snubber circuit 22. .

Next, the operation will be described. The basic operation is almost the same as that of the above-described first to fifth embodiments, and a detailed description thereof will be omitted. The difference is the current path after the voltage Vc of the capacitor 14 has become zero, and the reactor 15 → the second switching element 16 → the DC input power supply 1 →
In the path from the second diode 21 to the reactor 15, the power is regenerated to the DC input power supply 1 without passing through the first diode 13, and the energy corresponding to the conduction loss of the first diode 13 is effectively regenerated to the DC input power supply 1. it can.

Embodiment 7 In the first to sixth embodiments, the case where the low potential side terminal of the first switching element 3 is connected to the low potential side terminal of the DC input power supply 1 has been described, but the high potential side terminal of the first switching element 3 is described. May be connected to the high-potential side terminal of the DC input power supply 1, and have the same effects as those of the first to sixth embodiments.

FIGS. 8 to 10 show another embodiment of the present invention. In the figure, 1 to 7 and 13 to 1
7, 19, and 21 are equivalent to the components of the first to sixth embodiments shown in FIG. 1, FIG. 6, or FIG. 8, reference numeral 14 denotes a capacitor, and 13 denotes a first diode, which are connected in series and connected in parallel with the first switching element 3. Reference numeral 15 denotes a reactor, 16 denotes a second switching element serving as auxiliary switching means, which are connected in series, and one end of which is connected to a connection point between the capacitor 14 and the first diode 13. The other end is connected to the low potential side terminal of the DC input power supply 1. The high potential side terminal of the DC input power supply 1 is connected to the high potential side terminal of the first switching element 3, and the cathode side of the first diode 13 is connected to the low potential side terminal of the first switching element 3. Have been. Further, a second diode 17 is connected in anti-parallel with the first switching element 3 to form a snubber circuit 23. Note that the connection relationship between the reactor 15 and the second switching element 16 may be reversed.

In FIG. 9, as in FIG.
As the switching element 3, a field effect transistor is used. Reference numeral 19 denotes a parasitic diode of the field-effect transistor, which has the same function as the second diode 17 in FIG. 16a similarly uses a field-effect transistor as the second switching element, and 16b
Is a diode for preventing backflow, and constitutes a snubber circuit 24.

In FIG. 10, instead of the second diode 17 connected in antiparallel with the first switching element 3 as in FIG.
Are connected to form a snubber circuit 25.

Next, the operation will be described. The basic operation is substantially the same as that of the first to sixth embodiments, and thus the detailed description is omitted. The different point is the discharge path of the energy accumulated and held in the capacitor 14 when the second switching element 16 or 16a is turned on, and the capacitor 14 → DC input power supply 1 → second switching means 16, or The snubber energy and the excitation energy are being regenerated to the DC input power supply 1 in the path of 16a and 16b → reactor 15 → capacitor 14.

8 and 9, the current path after the voltage Vc of the capacitor 14 has become zero is the reactor 15 →
First diode 13 → second diode 17 or parasitic diode 19 → DC input power supply 1 → second switching element 16 (or 16b, 16a) → reactor 1
5, the regenerative power is continuously supplied to the DC input power supply 1 through a path opposite to that of the first to sixth embodiments. In FIG. 10, the reactor 15 →
The difference is that the power is regenerated to the DC input power supply 1 without passing through the first diode 13 on the path of the second diode 21 → DC input power supply 1 → second switching element 16 → reactor 15.

In the circuit shown in FIG. 8, the second diode 17 may be omitted depending on the condition of the energized state during the ON period of the first switching element 3, as described in the first embodiment. .

Embodiment 8 FIG. By the way, there is a case where the minimum ON time of the first switching element 3 becomes a very short time, for example, when there is no load or a light load. Since it is necessary to increase the capacitance value of the capacitor 14 to some extent in order to suppress, reduce the switching noise, and reduce the switching loss, the half of the resonance period of the capacitor 14 and the reactor 15 is the minimum ON time of the first switching element 3. It may happen that the time is longer than the time. In this case, the second switching element 16 is turned off in a state where a current is flowing through the reactor 15, that is, in a state where energy remains, and an excessive spike voltage is applied to the second switching element 16 when the second switching element 16 is turned off. This causes a problem that noise is increased, efficiency is reduced, or heat is generated.
There is also a problem that may lead to destruction.

The eighth embodiment has been studied in order to solve this problem. After the voltage Vc of the capacitor 14 becomes zero, the energy of the reactor 15 does not pass through the second switching element 16 without passing through the second switching element 16. The DC input power 1
It is possible to regenerate to a new location.

FIG. 11 is a diagram showing another embodiment of the present invention. In the figure, 1 to 16 are the same as the components shown in FIG. First switching element 3
In parallel, a first diode 13 and a capacitor 14 connected in series are connected, and a second switching element 16 and a reactor 15 are connected in series to a connection point between the first diode 13 and the capacitor 14 in series. Is a circuit in which the other end of the DC input power supply 1 is connected to the high potential side terminal of the DC input power supply 1, and the low potential side terminal of the DC input power supply 1 is connected to the low potential side terminal of the first switching element 3. Connection point between switching element 16 and reactor 15 and DC input power supply 1
A second diode 26 is connected between the second diode 26 and the low potential side terminal to form a snubber circuit 27.

The basic operation is almost the same as that of the sixth embodiment, and therefore, the detailed description is omitted. The difference is that the current path after the voltage Vc of the capacitor 14 becomes zero becomes a path of the reactor 15 → DC input power supply 1 → second diode 26 → reactor 15 without passing through the second switching element 16, Second switching element 16
The energy corresponding to the conduction loss of the DC input power source 1 can be effectively regenerated.

The current path after turning off the second switching element 16 is the reactor 15 → DC input power supply 1 → second
In this case, there is an effect that the energy remaining in the reactor 15 can be regenerated to the DC input power supply 1 through the above-described path, and the spike voltage at the time of turn-off is applied to the second switching element 16. This has the effect of preventing the occurrence of noise, preventing the generation of noise, preventing the efficiency from being lowered, preventing heat generation, and preventing the destruction of the second switching element 16. In this case, the second switching element 16
Are set within the on-time of the first switching element 3.

If the minimum ON time of the first switching element 3 is shorter than half the resonance period of the capacitor 14 and the reactor 15, the current path after the second switching element 16 is turned off , The path from the reactor 15 to the DC input power supply 1 → the second diode 26 → the reactor 15, and the energy remaining in the reactor 15 can be regenerated to the DC input power supply 1.

When the minimum on-time of the first switching element 3 is shorter than half the resonance cycle of the capacitor 14 and the reactor 15, the first switching element 3 is turned on and off by the second on-off operation. By synchronizing the ON and OFF of the second switching element 16, the ON time of the second switching element 16 can be the same as the maximum allowable ON time of the ON time of the first switching element 3. The stored energy can be regenerated to the maximum of the DC input power supply 1 and the residual charge of the capacitor 14 can be minimized.

Embodiment 9 In the eighth embodiment, the first
The low potential side terminal of the switching element 3 is a DC input power supply 1
Although the connection to the low potential side terminal of the first switching element 3 is shown, the high potential side terminal of the first switching element 3 may be connected to the high potential side terminal of the DC input power supply 1. A similar effect is achieved.

FIG. 12 is a diagram showing another embodiment of the present invention. In the figure, 1 to 16 are the same as the components shown in FIG. A capacitor 14 and a first diode 13 connected in series are connected in parallel with the first switching element 3, and a second switching element 16 and a reactor 15 are sequentially connected in series at a connection point between the capacitor 14 and the first diode 13. , The other end of the reactor 15 is connected to the low potential side terminal of the DC input power supply 1, and the high potential side terminal of the DC input power supply 1 is connected to the first switching element 3.
The second diode 26 is connected between the connection point of the second switching element 16 and the reactor 15 and the high potential side terminal of the DC input power supply 1 to form a snubber circuit 28. Is configured.

The basic operation is the same as that of FIG.
Since the operation is almost the same as that of 0, detailed description is omitted.
The difference is that the current path after the voltage Vc of the capacitor 14 becomes zero is changed from the reactor 15 to the second diode 26.
It becomes a path from the DC input power supply 1 to the reactor 15, and the energy corresponding to the conduction loss of the second switching element 16 can be effectively regenerated to the DC input power supply 1 without passing through the second switching element 16.

When the minimum on-time of the first switching element 3 is shorter than half the resonance cycle of the capacitor 14 and the reactor 15, the current path after the second switching element 16 is turned off is , The path of the reactor 15 → the second diode 26 → the DC input power supply 1 → the reactor 15, and the energy remaining in the reactor 15 can be regenerated to the DC input power supply 1.

As in the eighth embodiment, the minimum ON time of the first switching element 3 is
In the case where the time is shorter than half the resonance period between the first switching element 3 and the reactor 15, the second switching element 16 is synchronized with the on / off operation of the first switching element 3 to perform the second switching. Since the ON time of the element 16 can be set to the maximum allowable ON time, the energy stored in the capacitor 14 can be regenerated to the maximum in the DC input power supply 1 and the residual charge of the capacitor 14 can be minimized.

Embodiment 10 FIG. In the first to ninth embodiments, the snubber circuit of the forward type DC / DC converter is shown. However, a configuration in which the snubber circuit of the present invention is connected to the boost type forward converter may be adopted.
The same effects as in the first to ninth embodiments can be obtained.

FIGS. 13 and 14 show Embodiment 1 of the present invention.
FIG. 3 is a configuration diagram showing a boost type forward converter of zero. In the figure, 1 to 3 and 13 to 18 and 23 are the same as the components of the first or seventh embodiment shown in FIG. 1 or FIG. 29 is a rectifying diode,
30 is a reflux diode, 31 is a choke coil, 32
Is a smoothing capacitor.

Next, the operation will be described. The basic operation is substantially the same as in the first and seventh embodiments, but in this boost converter, the second winding 2b of the transformer 2 is connected in series with the first winding 2a. Thus, a voltage corresponding to a combined voltage of the first and second windings 2a and 2b can be output. However, the operation of the snubber circuit is exactly the same as that of the previous embodiment, and the snubber energy and the excitation energy of the transformer are regenerated to the DC input power supply.

The snubber circuit 18 shown in FIG.
May be replaced by the snubber circuit 20 of FIG. 7, the snubber circuit 22 of FIG. 7, or the snubber circuit 27 of FIG. FIG.
The snubber circuit 23 may be replaced by the snubber circuit 24 of FIG. 9 or the snubber circuit 25 of FIG. 10 or the snubber circuit 28 of FIG. 12, and the same effects are obtained.

[0085]

As described above, according to the present invention, the first switching means and the first winding of the transformer are connected in series to a DC input power supply, and the first switching means is turned on and off by the on / off operation. A rectifier for rectifying a voltage induced in the second winding of the transformer, a smoother for smoothing an output from the rectifier and supplying the output to a load, and a rectifier for a time period when there is no output from the rectifier. In a DC / DC converter provided with a return means for supplying energy stored in a smoothing means to the load, a series connection of a first diode and a capacitor connected between the poles of the first switching means. A connection body, and a series connection body of an inductive element and second switching means connected between the connection point between the first diode and the capacitor and the DC input power supply. When the second switching means is turned on during the on-period of the first switching means, the excitation energy of the transformer and the leakage inductance and the energy accumulated in the wiring inductance cause the first switching means to turn on. The charge charged in the capacitor during the off period is regenerated to the DC input power supply by utilizing a resonance phenomenon between the capacitor and the inductive element, so that a reset winding of a transformer is unnecessary, and A spike voltage at the time of turn-off of the first switching means can be absorbed without loss and heat generation, and the overlap of the voltage and current at the time of turn-off is reduced to reduce switching loss and switching noise.
A C / DC converter can be provided.

Further, in the present invention, the first switching means and the first winding of the transformer are connected in series and connected to a DC input power supply, and the first switching means is turned on and off to thereby enable the first switching means to operate. Rectifying means for rectifying a combined voltage induced in the first winding and the second winding connected in series with the first winding, and smoothing an output from the rectifying means to supply the output to a load. Means and a recirculation means for supplying energy stored in the smoothing means to the load during a time period when there is no output from the rectification means.
A series connection of a first diode and a capacitor, connected between the poles of the switching means, and an inductive circuit connected between the connection point of the first diode and the capacitor and the DC input power supply. A series connection of an element and a second switching means, wherein the second switching means is turned on within an on-period of the first switching means, whereby the excitation energy of the transformer, the leakage inductance thereof, and the wiring The electric charge charged in the capacitor during the off period of the first switching means by the energy accumulated in the inductance is regenerated to the DC input power supply by utilizing the resonance phenomenon between the capacitor and the inductive element. Therefore, the transformer reset winding is not required, and the first
It is possible to provide a boost type DC / DC converter capable of absorbing a spike voltage at the time of turn-off of the switching means, reducing overlap of voltage and current at the time of turn-off, and reducing switching loss and switching noise.

In the present invention, an anode terminal is connected to a high potential side terminal of the first switching element, and one terminal is connected to a cathode terminal of the first diode and the other terminal is connected to the other terminal. Is the first terminal
A capacitor connected to the low potential side terminal of the switching means, and a connection point between the connection point of the first diode and the capacitor and the high potential side terminal of the DC power supply;
Since a series connection of an inductive element and a second switching means is provided, a simple configuration eliminates the need for a reset winding of a transformer, and furthermore, without loss and heat generation, the first switching means can be used. It is possible to provide a DC / DC converter that can absorb a spike voltage at the time of turn-off, reduce overlap of voltage and current at the time of turn-off, and reduce switching loss and switching noise.

In the present invention, an anode terminal is connected to the high potential side terminal of the first switching element, and one terminal is connected to a cathode terminal of the first diode and the other terminal is connected to the other terminal. Is the first terminal
And a capacitor connected to the low potential side terminal of the switching means, an inductive element connected between the connection point of the first diode and the capacitor, and the high potential side terminal of the DC input power supply. Since it has a series connection with the switching means, a simple configuration eliminates the need for a reset winding of the transformer, and also absorbs a spike voltage when the first switching means is turned off without loss and heat generation. Thus, it is possible to provide a boost type DC / DC converter in which overlapping of voltage and current at the time of turn-off is reduced and switching loss and switching noise are reduced.

Further, according to the present invention, there is provided a second diode having an anode terminal connected to the low potential side terminal of the first switching means and a cathode terminal connected to the high potential side terminal of the first switching means. Therefore, irrespective of the current during the ON period of the first switching means, the regenerative operation to the DC input power supply after the voltage of the capacitor becomes zero is realized.

Further, according to the present invention, since the second diode having the anode terminal connected to the low potential side terminal of the first switching means and the cathode terminal connected to one terminal of the capacitor is provided, The regenerative operation to the DC input power supply becomes possible without passing through the diode, and the regenerative efficiency is improved accordingly.

In the present invention, the anode terminal is connected to the high potential side terminal of the first switching element, and the first diode is connected to the cathode terminal of the first diode and the other terminal is connected to the other terminal. Is the first terminal
A capacitor connected to the low potential side terminal of the switching means, a second switching means having one terminal connected to a connection point of the first diode and the capacitor, and another terminal of the second switching means. An inductive element connected between the first switching means and the high potential side terminal of the DC input power supply; an anode terminal connected to the low potential side terminal of the first switching means; The second connected to the connection point of the conductive element
After the voltage of the capacitor becomes zero, it becomes possible to regenerate energy to the DC input power supply without passing through the second switching means. It is possible to provide a DC / DC converter capable of preventing the destruction of the second switching means even when the minimum ON time of the switching means is short.

In the present invention, the anode terminal is connected to the high potential side terminal of the first switching element, and the other terminal is connected to the cathode terminal of the first diode. Is the first terminal
A capacitor connected to the low potential side terminal of the switching means, a second switching means having one terminal connected to a connection point of the first diode and the capacitor, and another terminal of the second switching means. An inductive element connected between the first switching means and the high potential side terminal of the DC input power supply; an anode terminal connected to the low potential side terminal of the first switching means; The second connected to the connection point of the conductive element
After the voltage of the capacitor becomes zero, it becomes possible to regenerate energy to the DC input power supply without passing through the second switching means. A boost type DC / DC converter that can prevent the destruction of the second switching means even when the minimum on-time of the switching means is short can be provided.

Also, in the present invention, a first diode whose cathode terminal is connected to the low potential side terminal of the first switching element and one terminal which is connected to the anode terminal of the first diode are connected to the other terminal. Is the first terminal
A capacitor connected to the high-potential side terminal of the switching means, an inductive element connected between the connection point of the first diode and the capacitor, and the low-potential side terminal of the DC input power supply. Since it has a series connection with the switching means, a simple configuration eliminates the need for a reset winding of the transformer, and also absorbs a spike voltage when the first switching means is turned off without loss and heat generation. Thus, it is possible to provide a DC / DC converter in which the overlap of voltage and current at the time of turn-off is reduced and switching loss and switching noise are reduced.

In the present invention, the cathode terminal is connected to the low potential side terminal of the first switching element, and the first terminal is connected to the anode terminal of the first diode and the other terminal is connected to the other terminal. Is the first terminal
A capacitor connected to the high-potential side terminal of the switching means, an inductive element connected between the connection point of the first diode and the capacitor, and the low-potential side terminal of the DC input power supply. Since it has a series connection with the switching means, a simple configuration eliminates the need for a reset winding of the transformer, and also absorbs a spike voltage when the first switching means is turned off without loss and heat generation. Thus, it is possible to provide a boost type DC / DC converter in which overlapping of voltage and current at the time of turn-off is reduced and switching loss and switching noise are reduced.

Further, according to the present invention, there is provided a second diode having an anode terminal connected to the low potential side terminal of the first switching means and a cathode terminal connected to the high potential side terminal of the first switching means. Therefore, irrespective of the current during the ON period of the first switching means, the regenerative operation to the DC input power supply after the voltage of the capacitor becomes zero is realized.

Also, in the present invention, since the cathode terminal is connected to the high potential side terminal of the first switching means and the anode terminal is connected to one terminal of the capacitor, the second diode is provided. The regenerative operation to the DC input power supply becomes possible without passing through the diode, and the regenerative efficiency is improved accordingly.

In the present invention, the cathode terminal is connected to the low potential side terminal of the first switching element, and the one terminal is connected to the anode terminal of the first diode and the other terminal is connected to the other terminal. Is the first terminal
A capacitor connected to the high potential side terminal of the switching means, a second switching means having one terminal connected to a connection point of the first diode and the capacitor, and another terminal of the second switching means. An inductive element connected between the first switching means and the low potential side terminal of the DC input power supply; a cathode terminal connected to the high potential side terminal of the first switching means; The second connected to the connection point of the conductive element
After the voltage of the capacitor becomes zero, it becomes possible to regenerate energy to the DC input power supply without passing through the second switching means. It is possible to provide a DC / DC converter capable of preventing the destruction of the second switching means even when the minimum ON time of the switching means is short.

Also, in the present invention, a first diode having a cathode terminal connected to the low potential side terminal of the first switching element and one terminal connected to an anode terminal of the first diode are connected to the other terminal. Is the first terminal
A capacitor connected to the high potential side terminal of the switching means, a second switching means having one terminal connected to a connection point of the first diode and the capacitor, and another terminal of the second switching means. An inductive element connected between the first switching means and the low potential side terminal of the DC input power supply; a cathode terminal connected to the high potential side terminal of the first switching means; The second connected to the connection point of the conductive element
After the voltage of the capacitor becomes zero, it becomes possible to regenerate energy to the DC input power supply without passing through the second switching means. A boost type DC / DC converter that can prevent the destruction of the second switching means even when the minimum on-time of the switching means is short can be provided.

Further, in the present invention, the parasitic diode is made to function as the second diode by using a field effect transistor for the first switching means. The second diode connected in parallel becomes unnecessary,
The cost is reduced accordingly.

Also, in the present invention, the second switching means is turned on within the on-period of the first switching means, and the on time of the second switching means is determined by the capacitor and the inductive element. Since the resonance period is set to １ ／ or more, the energy stored in the capacitor can always be surely regenerated to the DC input power supply.

In the present invention, the current of the second switching means is detected, and after the current becomes zero from the on state, the second switching means is turned off. An appropriate off operation of the switching means is ensured.

Further, in the present invention, the second switching means has a polarity, and is automatically turned off when the current becomes zero from the on state, so that the current detecting means is not required. The OFF operation of the second switching means is reliably performed.

Further, according to the present invention, the on / off operation of the first switching means and the on / off operation of the second switching means are synchronized with each other, so that the configuration for driving both switching means is simplified. The capacitance value of the capacitor and the inductance value of the inductive element can be selected in a wider range.

Further, according to the present invention, the minimum ON time of the first switching means is less than １ ／ of the resonance period determined by the capacitor and the inductive element, and the minimum ON time is within the ON period of the first switching means. Since the second switching means is turned on, the DC / DC converter according to the present invention can be applied even when the minimum on-time of the first switching means is extremely short.

Further, according to the present invention, the on / off operation of the first switching means and the on / off operation of the second switching means are synchronized with each other, so that the configuration for driving both switching means is simplified. The capacitance value of the capacitor and the inductance value of the inductive element can be selected in a wider range.

Further, in the present invention, since the second switching means is a series connection of a field effect transistor and a diode for preventing backflow, an appropriate off operation of the second switching means is ensured. You.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a forward DC / DC converter according to a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram of each part of the forward-type DC / DC converter of FIG. 1 and its snubber circuit.

FIG. 3 is an operation waveform diagram of each part of the snubber circuit according to the second embodiment of the present invention.

FIG. 4 is an operation waveform diagram of each part of the snubber circuit according to Embodiment 3 of the present invention.

FIG. 5 is an operation waveform diagram of each part of a forward DC / DC converter and a snubber circuit according to a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram showing a forward DC / DC converter according to a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a forward DC / DC converter according to Embodiment 6 of the present invention.

FIG. 8 is a circuit diagram showing a forward DC / DC converter according to a seventh embodiment of the present invention.

FIG. 9 is a circuit diagram showing another forward type DC / DC converter according to a seventh embodiment of the present invention.

FIG. 10 is a circuit diagram showing another forward type DC / DC converter according to a seventh embodiment of the present invention.

FIG. 11 is a circuit diagram showing a forward DC / DC converter according to an eighth embodiment of the present invention.

FIG. 12 is a circuit diagram showing a forward DC / DC converter according to a ninth embodiment of the present invention.

FIG. 13 is a circuit diagram showing a boost forward converter according to a tenth embodiment of the present invention.

FIG. 14 is a circuit diagram showing another boost type forward converter according to the tenth embodiment of the present invention.

FIG. 15 is a circuit diagram showing a conventional forward DC / DC converter with an RCD snubber circuit.

16 is an operation waveform diagram of each part of the forward-type DC / DC converter of FIG. 15 and its snubber circuit.

[Explanation of symbols]

1 DC input power supply, 2 transformers, 1a first winding of transformer 2b, 2b 2nd winding of transformer 2, 3rd
Switching element, 4,29 rectifier diode,
5,30 freewheel diode, 6,31 choke coil, 7,32 smoothing capacitor, 13 first diode, 14 capacitor, 15 reactor, 16 second
Switching element, 17, 21, 26, second diode, 18, 20, 22, 23, 24, 25, 27, 2
8 Snubber circuit, 19 Parasitic diode of field effect transistor.

Claims (22)

[Claims] 1. A first switching means and a first winding of a transformer are connected in series to a DC input power supply, and the first switching means is induced in a second winding of the transformer by an on / off operation of the first switching means. Rectifying means for rectifying the voltage to be applied, smoothing means for smoothing the output from the rectifying means and supplying the load to the load, and energy stored in the smoothing means during a time period when there is no output from the rectifying means. A DC / DC converter provided with a recirculation means for supplying the first switching means to the first switching means.
A series connection of a diode and a capacitor, and a series connection of an inductive element and a second switching means connected between the connection point between the first diode and the capacitor and the DC input power supply. When the second switching means is turned on during the on-period of the first switching means, the first switching means is turned on by the excitation energy of the transformer, the leakage inductance thereof, and the energy accumulated in the wiring inductance. The charge charged in the capacitor during the off period is regenerated to the DC input power supply by utilizing the resonance phenomenon between the capacitor and the inductive element, thereby eliminating the need for the reset winding of the transformer. DC / DC converter. 2. A first switching means and a first winding of a transformer are connected in series to a DC input power supply, and the first winding of the transformer and the first winding of the transformer are connected by an on / off operation of the first switching means. A rectifier for rectifying a combined voltage induced in the first winding and the second winding connected in series, a smoother for smoothing an output from the rectifier and supplying the output to a load; Boost type DC / DC having a recirculation means for supplying the energy stored in the smoothing means to the load during a time period when there is no output from the means.
In the converter, a first switching means connected between the poles of the first switching means.
A series connection of a diode and a capacitor, and a series connection of an inductive element and a second switching means connected between the connection point between the first diode and the capacitor and the DC input power supply. When the second switching means is turned on during the on-period of the first switching means, the first switching means is turned on by the excitation energy of the transformer, the leakage inductance thereof, and the energy accumulated in the wiring inductance. The charge charged in the capacitor during the off period is regenerated to the DC input power supply by utilizing the resonance phenomenon between the capacitor and the inductive element, thereby eliminating the need for the reset winding of the transformer. DC / DC converter. 3. A DC input power supply, first switching means having a low potential side terminal connected to the low potential side terminal of the DC input power supply, and a first winding comprising a high potential side terminal of the DC input power supply. A rectifier diode connected between the first switching means and the high-potential side terminal of the first switching means, a rectifying diode connected between the terminals of the second winding of the transformer and having the same polarity and opposite to each other; A series connection with a diode,
In a DC / DC converter provided with an LC filter composed of a series connection of a smoothing reactor and a smoothing capacitor connected in parallel with the reflux diode, an anode terminal is connected to a high potential side terminal of the first switching element. A connected first diode, a capacitor having one terminal connected to a cathode terminal of the first diode and the other terminal connected to a low potential side terminal of the first switching means, DC / DC comprising a series connection of an inductive element and a second switching means connected between a connection point of a diode and a capacitor and a high potential side terminal of the DC input power supply.
converter. 4. A DC input power supply, first switching means having a low potential side terminal connected to the low potential side terminal of the DC input power supply, and a first winding comprising a high potential side terminal of the DC input power supply. A transformer connected between the first switching means and the high potential side terminal of the first switching means, and an anode terminal connected to one terminal of a second winding connected in series with the first winding of the transformer. A rectifying diode, an anode terminal connected to the high-potential side terminal of the DC input power supply, and a cathode terminal connected to the cathode terminal of the rectifying diode; a cathode terminal of the rectifying diode; Boost type DC / D provided with an LC filter composed of a series connection of a smoothing reactor and a smoothing capacitor, connected between the low potential side terminal of the DC input power supply.
In the C converter, an anode terminal is connected to a high-potential side terminal of the first switching element, a first diode is connected to a cathode terminal of the first diode, and the other terminal is connected to the first diode. And a capacitor connected to the low potential side terminal of the switching means, an inductive element connected between the connection point of the first diode and the capacitor, and the high potential side terminal of the DC input power supply. DC / DC characterized by comprising a series connection with switching means
converter. 5. A semiconductor device comprising a second diode having an anode terminal connected to a low potential side terminal of the first switching means and a cathode terminal connected to a high potential side terminal of the first switching means. The DC / DC converter according to claim 3 or 4, wherein: 6. A capacitor according to claim 3, further comprising a second diode having an anode terminal connected to the low potential side terminal of said first switching means and a cathode terminal connected to one terminal of a capacitor. DC / DC according to 4.
converter. 7. A DC input power supply, first switching means having a low potential side terminal connected to the low potential side terminal of the DC input power supply, and a first winding comprising a high potential side terminal of the DC input power supply. A rectifier diode connected between the first switching means and the high-potential side terminal of the first switching means, a rectifying diode connected between the terminals of the second winding of the transformer and having the same polarity and opposite to each other; A series connection with a diode,
In a DC / DC converter provided with an LC filter composed of a series connection of a smoothing reactor and a smoothing capacitor connected in parallel with the reflux diode, an anode terminal is connected to a high potential side terminal of the first switching element. A first diode connected, a capacitor having one terminal connected to the cathode terminal of the first diode and the other terminal connected to the low potential side terminal of the first switching means, and one terminal connected to A second switching means connected to a connection point of the first diode and the capacitor; and an inductive terminal connected between the other terminal of the second switching means and a high potential side terminal of the DC input power supply. An element and an anode terminal are connected to the low potential side terminal of the first switching means, and a cathode terminal is connected to the second switching means and the second switching means. And a second diode connected to a connection point of the inductive element.
C / DC converter. 8. A DC input power supply, first switching means having a low potential side terminal connected to the low potential side terminal of the DC input power supply, and a first winding having a high potential side terminal of the DC input power supply. A transformer connected between the first switching means and the high potential side terminal of the first switching means, and an anode terminal connected to one terminal of a second winding connected in series with the first winding of the transformer. A rectifying diode, an anode terminal connected to the high-potential side terminal of the DC input power supply, and a cathode terminal connected to the cathode terminal of the rectifying diode; a cathode terminal of the rectifying diode; Boost type DC / D provided with an LC filter composed of a series connection of a smoothing reactor and a smoothing capacitor, connected between the low potential side terminal of the DC input power supply.
In the C converter, an anode terminal is connected to a high-potential side terminal of the first switching element, a first diode is connected to a cathode terminal of the first diode, and the other terminal is connected to the first diode. A capacitor connected to the low potential side terminal of the switching means, a second switching means having one terminal connected to a connection point of the first diode and the capacitor, and another terminal of the second switching means. An inductive element connected between the first switching means and the high potential side terminal of the DC input power supply; an anode terminal connected to the low potential side terminal of the first switching means; And a second diode connected to a connection point of the conductive element.
C / DC converter. 9. A DC input power supply, first switching means having a high potential side terminal connected to the high potential side terminal of the DC input power supply, and a first winding comprising a low potential side terminal of the DC input power supply. A rectifying diode connected between a terminal of the second winding of the transformer and a rectifying diode having the same polarity facing each other and a rectifying diode connected between the transformer and the low potential side terminal of the first switching means. A series connection with a diode,
In a DC / DC converter provided with an LC filter composed of a series connection of a smoothing reactor and a smoothing capacitor connected in parallel with the reflux diode, a cathode terminal is connected to a low potential side terminal of the first switching element. A first diode connected thereto, a capacitor having one terminal connected to an anode terminal of the first diode and the other terminal connected to a high potential side terminal of the first switching means, DC / DC comprising a series connection of an inductive element and a second switching means connected between a connection point of a diode and a capacitor and a low potential side terminal of the DC input power supply.
converter. 10. A DC input power supply, first switching means having a high potential side terminal connected to the high potential side terminal of the DC input power supply, and a first winding comprising a low potential side terminal of the DC input power supply. A transformer connected between the first switching means and the low potential side terminal of the first switching means; and an anode terminal connected to one terminal of a second winding connected in series with the first winding of the transformer. A rectifying diode, an anode terminal connected to the high-potential side terminal of the DC input power supply, and a cathode terminal connected to the cathode terminal of the rectifying diode; a cathode terminal of the rectifying diode; A boost type DC / DC having an LC filter connected between a low potential side terminal of a DC input power supply and a series connection of a smoothing reactor and a smoothing capacitor.
In the DC converter, a cathode terminal is connected to a first diode connected to a low potential side terminal of the first switching element, one terminal is connected to an anode terminal of the first diode, and the other terminal is connected to the first terminal. A capacitor connected to the high-potential side terminal of the switching means, an inductive element connected between the connection point of the first diode and the capacitor, and the low-potential side terminal of the DC input power supply. DC / DC characterized by comprising a series connection with switching means
converter. 11. A semiconductor device comprising a second diode having an anode terminal connected to the low potential side terminal of the first switching means and a cathode terminal connected to the high potential side terminal of the first switching means. Claim 9 or 10
4. The DC / DC converter according to 1. 12. A capacitor according to claim 9, further comprising a second diode having a cathode terminal connected to the high-potential terminal of said first switching means and an anode terminal connected to one terminal of a capacitor. 10. DC /
DC converter. 13. A DC input power supply, first switching means having a high potential side terminal connected to the high potential side terminal of the DC input power supply, and a first winding comprising a low potential side terminal of the DC input power supply. A rectifying diode connected between a terminal of the second winding of the transformer and a rectifying diode having the same polarity facing each other and a rectifying diode connected between the transformer and the low potential side terminal of the first switching means. LC comprising a series connection of a diode and a series connection of a smoothing reactor and a smoothing capacitor connected in parallel with the reflux diode.
In a DC / DC converter including a filter, a cathode terminal is connected to a low potential side terminal of the first switching element, and one terminal is connected to an anode terminal of the first diode. A capacitor having the other terminal connected to the high-potential side terminal of the first switching means; a second switching means having one terminal connected to a connection point of the first diode and the capacitor; An inductive element connected between the other terminal of the switching means and the low potential side terminal of the DC input power supply; a cathode terminal connected to the high potential side terminal of the first switching means; A second diode connected to a connection point between the second switching means and the inductive element.
C / DC converter. 14. A DC input power supply, first switching means having a high potential side terminal connected to the high potential side terminal of the DC input power supply, and a first winding comprising a low potential side terminal of the DC input power supply. A transformer connected between the first switching means and the low potential side terminal of the first switching means; and an anode terminal connected to one terminal of a second winding connected in series with the first winding of the transformer. A rectifying diode, an anode terminal connected to the high-potential side terminal of the DC input power supply, and a cathode terminal connected to the cathode terminal of the rectifying diode; a cathode terminal of the rectifying diode; A boost type DC / DC having an LC filter connected between a low potential side terminal of a DC input power supply and a series connection of a smoothing reactor and a smoothing capacitor.
In the DC converter, a cathode terminal is connected to a first diode connected to a low potential side terminal of the first switching element, one terminal is connected to an anode terminal of the first diode, and the other terminal is connected to the first terminal. A capacitor connected to the high potential side terminal of the switching means, a second switching means having one terminal connected to a connection point of the first diode and the capacitor, and another terminal of the second switching means. An inductive element connected between the first switching means and the low potential side terminal of the DC input power supply; a cathode terminal connected to the high potential side terminal of the first switching means; And a second diode connected to a connection point of the conductive element.
C / DC converter. 15. The DC / DC converter according to claim 5, wherein a parasitic diode is functioned as a second diode by using a field-effect transistor for the first switching means. . 16. The second switching means is turned on during an on-period of the first switching means, and the on-time of the second switching means is set to 1 / resonance of a resonance period determined by a capacitor and an inductive element. 16. The DC / DC converter according to claim 3, wherein the number is two or more. 17. The method according to claim 3, wherein a current of said second switching means is detected, and said second switching means is turned off after said current becomes zero from an on state. DC / D according to any one of 16.
C converter. 18. The apparatus according to claim 3, wherein the second switching means has a polarity, and is automatically turned off when the current becomes zero from the on state.
The DC / DC converter according to any one of the above. 19. The D according to claim 16, wherein the on / off operation of the first switching means is synchronized with the on / off operation of the second switching means.
C / DC converter. 20. The minimum on-time of the first switching means is 1/1 / resonance period determined by the capacitor and the inductive element.
The DC / DC according to any one of claims 7, 8, 13, and 14, wherein the second switching means is turned on when the value is less than 2 and within the on-period of the first switching means. converter. 21. The D according to claim 20, wherein the on / off operation of the first switching means is synchronized with the on / off operation of the second switching means.
C / DC converter. 22. The DC / DC converter according to claim 1, wherein the second switching means is a series connection of a field-effect transistor and a diode for preventing backflow.