JPH10201224A - Back converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back converter that allows frequency to be increased, by reducing loss due to soft switching and noise. SOLUTION: A charge storage capacitor 7 and a charging diode 8 are series- connected with each other, and are connected between the poles of a switching element 3. The primary winding 9a of a transformer 9 for charge regeneration is parallel-connected with the charging diode 8. The secondary winding 9b of the transformer 9 for charge regeneration is series-connected with a diode 10 for charge regeneration and parallel-connected with a reflux diode 4. Thereby spike voltage at the time of turn-off is absorbed without increase in loss which the circuit suffers as a converter, and switching loss is reduced with switching noise reduced as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a DC-DC converter for supplying a stabilized DC voltage, and more particularly to a buck converter.

[0002]

2. Description of the Related Art FIG. 9 is a circuit diagram showing a conventional buck converter disclosed, for example, in "Switching Regulator Design Know-How" (CQ Publishing Co., Ltd., issued in April 1985, written by Akira Hasegawa). In FIG. 9, 1 is a DC input power supply, 3 is a switching element, 4 is a return diode as current return means, 5 is a choke coil, 6 is a smoothing capacitor, and choke coil 5 and smoothing capacitor 6
And constitute an LC filter.

Next, the operation will be described. The switching element 3 receives the controlled pulse drive signal and turns on / off.
The OFF is repeated, and the input of the DC input power supply 1 is intermittently applied to the LC filter. When the switching element 3 is ON, energy is transmitted from the DC input power
At the time of FF, when the return diode 4 is turned on, the current of the choke coil 5 is returned to obtain a stabilized DC output voltage.

The operation waveforms of the buck converter configured as described above will be described with reference to FIGS. 10 (a) to 10 (c) show operation waveforms of each part of the switching element 3, wherein FIG. 10 (a) shows a drive signal of the switching element 3 and FIG. 10 (b) shows switching applied to both ends of the switching element 3. The voltage Vsw, (c) is a current Isw flowing through the switching element 3. When the drive signal is ON, the switching element 3 conducts, Vsw becomes substantially zero, and the current Isw flows. When the drive signal is OFF, the current Isw of the switching element 3 stops flowing. FIG. 11 shows enlarged waveforms of Vsw and Isw and switching loss. As shown in FIG. 11, the switching loss is caused by the overlap of the voltage and the current of the switching element at the time of turn-on and at the time of turn-off. The loss is greater than at turn-on.

[0005]

In the above-mentioned conventional configuration,
In the case of the buck converter shown in FIG. 9, as shown in FIG. 11, switching loss occurs due to the overlap of the voltage and current of the switching element at the time of turn-on and at the time of turn-off, and particularly, the switching loss at the time of turn-off is large.
In addition, the rising and falling of the switching voltage becomes steep, and the switching noise increases, so that it is difficult to increase the frequency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a buck converter capable of reducing a loss due to soft switching, reducing noise, and increasing the frequency. It is in.

[0007]

According to a first aspect of the present invention, there is provided a buck converter comprising an inductive element, a switching element, and a current circulating means connected in series with each other between two poles of a DC input power supply. In a buck converter in which an LC filter consisting of a choke coil and a smoothing capacitor is connected in parallel with the means, a charge storage capacitor and a charging diode connected in series between both poles of the switching element, A secondary winding is connected in parallel with the charging diode, and the secondary winding includes a charge regeneration transformer connected in parallel with the current return means in series with the charge regeneration diode, and the charge storage capacitor when the switching element is turned off. When the switching element is turned on, the charge stored in the Through those where the structure is regenerated to the LC filter side.

According to a second aspect of the present invention, there is provided a buck converter including a diode connected in anti-parallel to a switching element, and a resonance capacitor which resonates with the resonance inductor using the inductive element as a resonance inductor. In the buck converter, a charge storage capacitor and a charging diode connected in series with each other between the poles of the switching element, a primary winding is connected in parallel with the charging diode, and a secondary winding is connected to a charge regeneration diode. A charge regenerating transformer connected in series with the current recirculation means in parallel with the charge regenerating means, wherein the charge stored in the charge storage capacitor is turned off when the switching element is turned off via the charge regenerating transformer when the switching element is turned on. And regenerates to the LC filter side.

The buck converter according to claim 3 is the buck converter according to claim 2, wherein the resonance capacitor is connected in parallel with the current circulating means.

The buck converter according to claim 4 is the buck converter according to claim 2, wherein the resonance capacitor is connected between both ends of a series portion of the resonance inductor and the switching element.

A buck converter according to a fifth aspect of the present invention is the buck converter according to any one of the first to fourth aspects, wherein an impedance element is connected in series with a primary winding of the charge regeneration transformer, and a resonance phenomenon occurs when the switching element is turned on. Is suppressed.

A buck converter according to a sixth aspect of the present invention is the buck converter according to any one of the first to fourth aspects, wherein an impedance element is connected in parallel with a primary winding of the charge regeneration transformer, and a resonance phenomenon when the switching element is turned on. Is suppressed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a buck converter according to Embodiment 1 of the present invention. In the figure,
Reference numerals 1, 3 to 6 are the same as those of the conventional buck converter shown in FIG. Reference numeral 2 denotes a wiring inductance component or an inductive element such as an inductor.
And the switching element 3 is present or connected in series. Reference numeral 7 denotes a charge storage capacitor, and 8 denotes a charging diode, which are connected in series and connected between both poles of the switching element 3. Reference numeral 9 denotes a charge regeneration transformer, the primary winding 9a of which is connected in parallel with the charging diode 8, and the secondary winding 9b which is connected in series with the charge regeneration diode 10 and in parallel with the return diode 4.

Next, the operation will be described. When the switching element 3 is turned off, the current that has been flowing through the inductive element 2 flows into the charge storage capacitor 7 via the charging diode 8. Therefore, switching element 3
2b rises more slowly than 0 V due to the resonance operation of the inductive element 2 and the charge storage capacitor 7 as shown in FIG. 2B, so that the spike voltage at the time of turn-off is absorbed and as shown in FIG. Overlap of the voltage and current of the switching element at the time of turn-off is reduced, so that switching loss is reduced and switching noise is also reduced.

At the time of turn-on, the energy stored in the charge storage capacitor 7 is transferred to the primary winding 9 of the charge regeneration transformer 9.
It flows to the switching element 3 via a. On the other hand, the secondary winding 9b of the charge regeneration transformer 9 is connected in parallel with the freewheel diode 4 via the charge recovery diode 10, but the freewheel diode 4 is conductive during the turn-off period. Therefore, the energy stored in the charge storage capacitor 7 is regenerated to the LC filter via the charge regeneration transformer 9 at the moment of turn-on. That is, the energy stored in the charge storage capacitor 7 flows to the switching element 3 via the primary winding 9a of the charge regeneration transformer 9, and the secondary winding 9b of the charge regeneration transformer 9, the charge regeneration diode 10, the choke coil 5. Flow into the load via the smoothing capacitor 6. The energy stored in the charge storage capacitor 7 added for soft-switching the turn-off by this operation is supplied to the load as a part of the output power at the time of turn-on, so that the soft-switching at the time of turn-off without increasing the loss is performed. Can be achieved.

Embodiment 2 Although the switching element 3 has a trapezoidal current waveform Isw in the first embodiment, a current resonance full-wave configuration having a sinusoidal waveform may be used. It has the effect of reducing noise.

FIG. 4 is a circuit diagram showing a buck converter according to a second embodiment of the present invention. In FIG. 4, 1,
Reference numerals 3 to 10 are the same as those shown in FIG. 1 of the first embodiment. Reference numeral 11 denotes a diode connected in anti-parallel with the switching element 3. In the case of a MOSFET, a parasitic diode can be used instead. 12 is a resonance inductor connected in series with the switching element 3,
Reference numeral 13 denotes a resonance capacitor connected in parallel to the free wheel diode 4.

Next, the operation will be described. As shown in FIG. 5, when the switching element 3 is turned off, the voltage at both ends of the switching element 3 gradually rises from 0 V due to the resonance operation with the charge storage capacitor 7 of the resonance inductor 12, so that the spike voltage at the time of turn-off decreases. While being absorbed, switching noise is also reduced.

While the switching element 3 is on, the current flowing through the switching element 3 resonates by the resonance inductor 12 and the resonance capacitor 13 to form a sine wave. After the resonance current becomes zero during the ON period of the drive signal, as shown in FIG.
1, a resonance current flows. Also in the case of the second embodiment, the energy stored in the charge storage capacitor 7 added for turning off the soft switching is supplied to the load as a part of the output power at the time of turning on. Thus, soft switching at the time of turn-off can be achieved.

Embodiment 3 In the second embodiment, the configuration in which the resonance capacitor 13 is connected in parallel with the free wheel diode 4 is described. However, the resonance capacitor is connected between both ends of the series portion of the switching element 3 and the resonance inductor 12. A configuration may be adopted in which the current waveform Isw of the switching element 3 is sinusoidal, and the switching noise is reduced similarly to the second embodiment.

FIG. 6 is a circuit diagram showing a buck converter according to Embodiment 3 of the present invention. In FIG. 6, 1,
Reference numerals 3 to 12 are the same as those shown in FIG. 4 of the second embodiment. Reference numeral 14 denotes a resonance capacitor connected in parallel to a series portion of the switching element 3 and the resonance inductor 12. The operation is described in the second embodiment.
Since the operation is almost the same as that described above, the description thereof is omitted.

Embodiment 4 FIG. 7 is a circuit diagram showing a buck converter according to Embodiment 4 of the present invention. FIG.
Are the same as those in the first embodiment. Reference numeral 15 denotes an impedance element composed of a diode, a resistor, or the like.
inserted in series with a.

Next, the operation will be described. Since the basic operation is the same as that of the first embodiment, a detailed description is omitted. At the time of turn-off, the voltage across the switching element 3 gradually rises from 0 V due to the resonance between the charge storage capacitor 7 and the inductive element 2, and the voltage across the switching element 3 almost reaches the DC input voltage. Thereafter, resonance may occur between the primary winding 9a of the charge regeneration transformer 9 and the charge storage capacitor 7, and the resonance may increase the voltage across the switching element 3 to increase turn-on noise, The influence of the resonance adversely affects the control system.
Here, by connecting the above-described impedance element 15 in series between the primary winding 9a of the charge regeneration transformer 9 and the charge storage capacitor 7, unnecessary resonance is suppressed, noise is suppressed, and stable operation is achieved. The operation can be performed reliably.

Embodiment 5 FIG. 8 is a circuit diagram showing a buck converter according to a fifth embodiment of the present invention. FIG.
Are the same as those in the first embodiment. Reference numeral 16 denotes an impedance element including a capacitor having a capacity sufficiently smaller than the capacity of the charge storage capacitor 7, and is inserted in parallel with the primary winding 9a of the charge regeneration transformer 9.

Next, the operation will be described. Since the basic operation is the same as that of the first embodiment, a detailed description is omitted. At the time of turn-off, the voltage across the switching element 3 gradually rises from 0 V due to the resonance between the charge storage capacitor 7 and the inductive element 2, and the voltage across the switching element 3 almost reaches the DC input voltage. Thereafter, when resonance occurs between the primary winding 9a of the charge regeneration transformer 9 and the charge storage capacitor 7, the voltage at both ends of the switching element 3 increases due to the resonance, and turn-on noise increases, or resonance occurs. The influence adversely affects the control system. Here, by connecting the above-described impedance element 16 in parallel with the primary winding 9a of the charge regeneration transformer 9, unnecessary resonance can be suppressed, noise can be suppressed, and stable operation can be reliably performed. .

In the fourth and fifth embodiments, the case where the impedance elements 15 and 16 for suppressing the resonance phenomenon are connected to the circuit of the first embodiment (FIG. 1) has been described. A similar resonance phenomenon suppression measure may be adopted for the buck converter.

[0027]

As described above, in the buck converter according to the first aspect, the charge storage capacitor and the charging diode connected in series with each other between the two poles of the switching element, and the primary winding is connected in parallel with the charging diode. Connected, the secondary winding is provided with a charge regeneration transformer connected in parallel with the current return means in series with the charge regeneration diode, and charges the charge stored in the charge storage capacitor when the switching element is turned off. Since the switching element is regenerated to the LC filter side via the charge regeneration transformer when the switching element is turned on, the spike voltage at the time of turn-off is absorbed without increasing the loss as a converter, and the switching loss is reduced. Also, switching noise is reduced.

In the current resonance full-wave buck converter according to the second aspect, the charge storage capacitor and the charging diode connected in series between the two poles of the switching element, and the primary winding is connected in parallel with the charging diode. Connected, the secondary winding is provided with a charge regeneration transformer connected in parallel with the current return means in series with the charge regeneration diode, and charges the charge stored in the charge storage capacitor when the switching element is turned off. Since the switching element is regenerated to the LC filter side via the charge regeneration transformer when the switching element is turned on, the spike voltage at the time of turn-off is absorbed without increasing the loss as a converter, and the switching loss is reduced. Also, switching noise is reduced.

Also, in the current resonance full-wave buck converter according to the third aspect, in which the resonance capacitor is connected in parallel with the current circulating means, the turn-off during turn-off without increasing the converter loss. The spike voltage is absorbed, switching loss is reduced, and switching noise is also reduced.

Also, in the current resonance full-wave buck converter according to claim 4 in which the resonance capacitor is connected between both ends of the series portion of the resonance inductor and the switching element, the loss as the converter is increased. Without this, the spike voltage at the time of turn-off is absorbed, switching loss is reduced, and switching noise is also reduced.

In the buck converter according to the fifth or sixth aspect, an impedance element is connected in series or in parallel with the primary winding of the charge recovery transformer so as to suppress the resonance phenomenon when the switching element is turned on. Accordingly, in addition to the effects of the above-described inventions, unnecessary resonance can be suppressed, increase in turn-on loss can be prevented, noise can be suppressed, and stable operation can be reliably performed.

[Brief description of the drawings]

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

FIG. 2 is an operation waveform diagram of each part of the switching element of FIG.

FIG. 3 is an enlarged view of an operation waveform shown in FIG. 2;

FIG. 4 is a circuit diagram showing a buck converter according to a second embodiment of the present invention.

FIG. 5 is an operation waveform diagram of each part of the switching element of FIG. 4;

FIG. 6 is a circuit diagram showing a buck converter according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram showing a buck converter according to a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram showing a buck converter according to a fifth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a conventional buck converter.

10 is an operation waveform diagram of each part of the switching element of FIG. 9;

11 is an enlarged view of the operation waveform shown in FIG.

[Explanation of symbols]

1 DC input power supply, 2 inductive element, 3 switching element, 4 return diode, 5 choke coil, 6
Smoothing capacitor, 7 charge storage capacitor, 8 charging diode, 9 charge regeneration transformer, 9a primary winding,
9b Secondary winding, 10 Charge regeneration diode, 11
Diode, 12 Resonant inductor, 13, 14 Resonant capacitor, 15, 16 Impedance element.

Claims (6)

[Claims] An inductive element, a switching element, and a current circulating means are connected in series with each other between both poles of a DC input power supply, and an LC comprising a choke coil and a smoothing capacitor is arranged in parallel with the current circulating means. In a buck converter having a filter connected, a charge storage capacitor and a charging diode connected in series between the two poles of the switching element, a primary winding is connected in parallel with the charging diode, and a secondary winding is A charge regenerating transformer connected in parallel with the current recirculation means in series with the charge regenerating diode, and charges the charge stored in the charge storage capacitor when the switching element is turned off when the switching element is turned on. The above LC through a charge regeneration transformer
A buck converter characterized in that it is configured to regenerate to the filter side. 2. An LC comprising a choke coil and a smoothing capacitor in parallel with said current return means, wherein said inductive element, switching element and current return means are connected in series with each other and connected between both poles of a DC input power supply. A buck converter to which a filter is connected, wherein a diode is connected in anti-parallel to the switching element, and a current capacitor including a resonance capacitor that resonates with the resonance inductor using the inductive element as a resonance inductor. In a wave-type buck converter, a charge storage capacitor and a charging diode connected in series to both poles of the switching element, a primary winding is connected in parallel with the charging diode, and a secondary winding is used for charge regeneration. A charge recovery transformer connected in parallel with the current return means in series with the diode; Provided, the electric charges from the charge storage capacitor at turn-off of the switching element through the charge regeneration transformer at turn-on of the switching element LC
A buck converter characterized in that it is configured to regenerate to the filter side. 3. The buck converter according to claim 2, wherein the resonance capacitor is connected in parallel with the current circulating means. 4. The buck converter according to claim 2, wherein the resonance capacitor is connected between both ends of a series portion of the resonance inductor and the switching element. 5. The method according to claim 1, wherein an impedance element is connected in series with a primary winding of the charge regeneration transformer to suppress a resonance phenomenon when the switching element is turned on. Buck converter as described. 6. The method according to claim 1, wherein an impedance element is connected in parallel with a primary winding of the charge regeneration transformer to suppress a resonance phenomenon when the switching element is turned on. Buck converter as described.