JPH0356069A - Resonance convertor - Google Patents

Abstract

PURPOSE:To remove the loss of a switching means by connecting bhe series circuit, consisting of a capacitor and a switch, to a snubber capacitor. CONSTITUTION:One stone type switching power source is composed of an output transformer 11, a capacitor for output smoothing, a diode for output rectification, an inverter transistor, etc. And to this transistor 18, a diode 19 and a capacitor 20 for snubber are connected in parallel, and further a series circuit 21 consisting of a capacitor 22 for another snubber and a switch 23 is connected. As a result, the temporal change rate of invertor voltage at the time of the changeover from on to off of the inverter transistor can be made small, and also the loss can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resonant converter connected to a single-stone switching power supply and using a primary side snubber circuit.

[Prior Art] An example of a resonant converter connected to a conventional single-stone switching power supply and using a next-side snubber circuit is shown in FIG. 1l.

In Figure 11, 1 is the input power supply, 2 is the output transformer 3
4 is the secondary winding of the output transformer 3, 5 is the diode for output rectification, 6 is the capacitor for output smoothing, 7
is an inverter transistor. A snubber diode 8 and a snubber capacitor 9 are connected in parallel to the inverter transistor 7, and these diodes 8 and capacitors 9 constitute a snubber circuit.

Therefore, as shown in FIG. 12, the inverter voltage e
When the peak value Ellaz of 1 is Elmtx<2E (E is the power supply voltage), when the inverter transistor 7 of the output transformer 3 is reset when it is off (see Tl),
With Elm*x as the initial value, the inverter voltage e1 decreases around the power supply voltage E while oscillating sinusoidally with a period of 2πF. In this case, the current iC flowing through the capacitor 9 from the time when the reset of the output transformer 3 is completed when the peak value Elmrx of the inverter voltage e1 starts to decrease.
begins to flow from 0 to the lth winding 2 side, and when Elnux becomes equal to the power supply voltage E (see T2), -Icmaw
And, at T3 where EIIIIX is the minimum value, O
becomes.

[Problems to be Solved by the Invention] However, in such a conventional resonant converter, the inverter voltage e1 is equal to the power supply voltage E - the peak value E
Since it does not drop below the voltage l +ux, when it drops the most, that is, E-Elma! Even if the inverter transistor is switched from off to on at this timing, the inverter transistor has soil C (for E-El)2.
・There was a problem in that a loss represented by 2 f [W] occurred.

Note that this loss is proportional to the switching frequency f, and is one of the reasons why it is difficult to increase the frequency.

The present invention has been made in view of such conventional problems, and the E1! Even if Il■<2E, when the output transformer has finished resetting and the inverter voltage e1 has decreased, e1 can be reduced to e1≦0 and then the inverter transistor can be switched from off to on. The object of the present invention is to provide a resonant converter that reduces loss when switching from off to on.

[Means for Solving the Problems] In order to achieve the above object, the present invention connects one end of the switching means to the primary winding of the output transformer and the other end to the negative side of the input power supply, and connects the switching means to the primary winding of the output transformer. In a resonant converter in which a diode and a snubber capacitor are connected in parallel, a series circuit consisting of another snubber capacitor and a switch is connected in parallel to the capacitor.

[Function] In the present invention, the peak value E1 of the inverter voltage e1
ffl! x is Elnax <2E (E: power supply voltage)
However, when the output transformer has finished resetting and the inverter voltage e1 has decreased, the switch is turned off at a predetermined timing, the capacitance of one of the snubber capacitors is switched to the capacitance of one of the snubber capacitors, and the inverter voltage e1 is
By setting e1≦0 and turning the switching means from off to on during this period, it is possible to eliminate loss when the switching means changes from off to on.

In addition, since the capacitance of the snubber capacitor can be increased, the time rate of change in the inverter voltage when the switching means is turned on can be reduced, and the loss when the switching means is turned off can also be reduced. be able to.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 and FIG. 2 are diagrams showing a first embodiment of the present invention.

First, to explain the configuration, in FIG. 1, 11 is an output transformer, and the output transformer 11 has a primary winding 12, an iron core 13, and a secondary winding 14. Secondary winding 14
An output smoothing capacitor 15 is connected in parallel to the secondary winding l4, and an output rectifying diode 16 is connected in series to the secondary winding l4.

Reference numeral 17 denotes an input power source that outputs the power source voltage E. A primary winding 12 is connected to the positive side of the input power source 17, and a switching means is connected between the primary winding 12 and the negative side of the input power source 17. An inverter transistor 18 is connected thereto.

The inverter transistor 18 has an inverter voltage e1
A diode 19 and a snubber capacitor 20 are connected in parallel to prevent the voltage from becoming negative. 2) is a series circuit in which another snubber capacitor 22 and a switch 23 are connected in series, and this series circuit 21 is connected in parallel to the capacitor 20.

In addition, in the figure, L is the inductance of the primary winding 12 of the output transformer 11, and iC is the snubber capacitor 20.22.
The current flowing through each is shown.

In addition, as the inverter transistor 18, an N-type MOSF
E.T. Or if you use P-type MOSFET, MOSFET
The built-in diode of the ET can be used in place of the diode 19.

Next, the operation will be explained based on FIG.

In FIG. 2, when the transistor inverter 18 is turned from on to off, a flyback voltage, that is, an inverter voltage e1, is generated, and the peak value Elaux of this inverter voltage e1 is Ellll! ! <2E (E is the power supply voltage), when the reset of the output transformer 12 is completed, E
With 1ffi1x as the initial value, T=2π ・C1+
The inverter voltage e1 decreases around the power supply voltage E while vibrating in a sinusoidal manner with a period T of C2 (C1 indicates the capacitor 20 and C2 indicates the capacitor 22, respectively).

Here, the peak value E1lIX of the inverter voltage e1 and the peak value Icm of the current ic flowing through the capacitor 20.22
x! Since the relationship shown in the following formula ■ holds true, C
When 1+C2 becomes smaller, if ICmix is the same, E
As l max becomes equivalently larger, the timing near T1 in FIG. 2, that is, the inverter voltage e1
When becomes equal to the power supply voltage E (when the current Ic flows to the maximum to the primary winding 12 side), the capacitance of C1+C2 can be changed to C1 by turning off the switch 23. In this case, , 2E-Elmax, the inverter voltage e1 can be reduced to e1≦0. In this case, since there is a diode 19 connected in parallel to the inverter transistor 18, the inverter voltage e1 is clamped by the forward voltage e1 of the diode 19 (see FIG. 2).

Therefore, by turning the inverter transistor 18 from off to on during the period of -ef≦e1≦0, it is possible to eliminate the loss when the inverter transistor 18 changes from off to on.

In addition, since there is no need to worry about loss due to discharge of the snubber capacitor 20.22, the snubber capacitor 20.2
Since the capacitance of the inverter transistor 18 can be easily increased, the d▼/di (temporal change rate of el) of the inverter voltage e1 can be reduced, and the loss from turning on to turning off the inverter transistor 18 can also be reduced. I can do it.

In addition, in Fig. 2, T1 is when the reset of the output transformer is completed, T2 is when the inverter voltage e1 becomes the power supply voltage E, and T3 is when the inverter voltage e1 becomes the minimum when the switch 23 is not turned off. (Same as the conventional example,
(indicated by broken lines in the figure) are shown respectively.

Next, FIG. 3 is a diagram showing a second embodiment of the present invention.

In this embodiment, a series circuit 21 in which a capacitor 22 and a switch 23 are connected in series is connected in parallel with the primary winding 12 of the output transformer 11 and in series with the inverter transistor 18.

Next, FIG. 4 is a diagram showing a third embodiment of the present invention.

In this embodiment, a capacitor 20 is connected in parallel to the series circuit 21 of the second embodiment. Capacitor 20 is 1
It is connected in parallel to the next winding 12.

Next, FIG. 5 is a diagram showing a fourth embodiment of the present invention.

In this embodiment, the capacitor 20 of the first embodiment is
It is connected in parallel to the secondary winding 12 and in series with the inverter transistor 18 . The series circuit 21 is connected in parallel to the inverter transistor 18 as in the first embodiment.

Next, FIG. 6 is a diagram showing a fifth embodiment of the present invention. In this embodiment, one end of each of an inverter transistor 18, a diode 19, and a capacitor 20 is connected midway through the primary winding 12. One end of the series circuit 21 is connected to one end of the primary winding 12, and the other end is connected to the negative side of the input power source 17.

FIG. 7 is a diagram showing a sixth embodiment of the present invention.

In this embodiment, one end of the series circuit 21 is connected to the middle of the primary winding 12, and the other end is connected to the negative side of the input power source 17.

FIG. 8 is a diagram showing a seventh embodiment of the present invention.

In this embodiment, the primary winding 1 of the output transformer 11
A primary winding 24 separate from 2 is provided, and a circuit 21 is connected in series to this primary winding 24.

In the second to fourth embodiments, the relative connection between the capacitor 20 and the capacitor 22 is changed, and in the fifth to seventh embodiments, the capacitor 2 is connected via the output transformer 11.
0 and a capacitor 22 are connected.

It goes without saying that in the second to seventh embodiments the same effects as in the first embodiment can be obtained.

In addition, when using the present invention in a single forward system, it is necessary to change the secondary side circuit of the single forward system from FIG. 9 to FIG. 10.

In FIG. 10, SW2 is a switch that keeps the diode D1 off during the period from T1 until the inverter transistor 18 is turned on, and a semiconductor or a saturable choke can be used.

Furthermore, in the first to seventh embodiments, the same effect can be obtained even if the output transformer 11 is connected to the negative side of the input power source 17 and the inverter transistor 18 is connected to the positive side of the input power source 17. it is obvious.

[Effects of the Invention] As explained above, according to the present invention, even if the peak value of the inverter voltage is less than or equal to the power supply voltage x 2, when the output transformer has finished resetting and the inverter voltage has decreased, By reducing the inverter transistor to zero and then turning on the inverter transistor from off, it is possible to reduce the loss when the inverter transistor changes from off to on.

In addition, since there is no need to worry about loss due to snubber capacitor discharge, the capacity of the snubber capacitor can be easily increased, and the rate of change in inverter voltage over time when the inverter transistor is turned on to off can be reduced. Therefore, loss when the inverter transistor is turned on and turned off can also be reduced.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a first embodiment of the present invention, Fig. 2 is a waveform diagram, Fig. 3 is a diagram showing a second embodiment of the invention, and Fig. 4 is a diagram showing a third embodiment of the invention. 5 shows a fourth embodiment of the invention, FIG. 6 shows a fifth embodiment of the invention, FIG. 7 shows a sixth embodiment of the invention, and FIG. is the seventh aspect of the present invention.
Figure 9 is a conventional secondary side circuit diagram, Figure 10 is a single forward system secondary side circuit diagram, Figure 11 is a diagram showing a conventional example, Figure 12 is a conventional waveform diagram. It is. In the figure, 11...Output transformer, 12...Primary winding, 13...Iron core, 14...Secondary winding, 15...Output smoothing capacitor, 16...Output rectification Diode, 17... Input power supply, 18... Inverter transistor (switching means) 19... Diode, 20... Snubber capacitor, 21... Series circuit, 22... Snubber capacitor, 23. ...Switch, 24...Other l-order winding. Figure 2 2] Figure 6 Figure 8 Figure 12

Claims (7)

[Claims] (1) In a resonant converter in which one end of the switching means is connected to the primary winding of an output transformer and the other end is connected to the negative side of the input power supply, and a diode and a snubber capacitor are connected in parallel to the switching means, the capacitor is A resonant converter characterized in that a series circuit consisting of a snubber capacitor and a switch is connected in parallel. (2) The resonant converter according to claim 1, wherein the series circuit is connected in parallel to the primary winding and in series to the switching means. (3) The resonant converter according to claim 2, wherein the snubber capacitor is connected in parallel to the series circuit. (4) The resonant converter according to claim 1, wherein the snubber capacitor is connected in parallel to the primary winding and in series with the switching means. (5) The resonant converter according to claim 1, wherein one end of each of the switching means, the diode, and the snubber capacitor is connected in the middle of the primary winding. (6) The resonant converter according to claim 1, characterized in that one end of the series circuit is connected in the middle of the primary winding. (7) Another method in which the series circuit is provided separately from the primary winding.
The resonant converter according to claim 1, wherein the resonant converter is connected to the next winding.