KR101031282B1 - Half-Bridge DC / DC Converter - Google Patents

Abstract

The present invention relates to a DC / DC converter, and more specifically, the switching frequency of the half-bridge switching unit is lower than the resonant frequency due to the leakage reactance of the transformer and the capacitance of the output capacitor, so that the soft switching is performed, the separate resonance The present invention relates to a high-efficiency DC / DC converter of a half-bridge type that can be transformed with high efficiency without requiring a reactor, and has an output side configured with a back voltage circuit, which is advantageous for high boost.

Converter, Half-Bridge, Resonant Frequency, Soft Switching

Description

Half-bridge DC / DC converter {DC / DC converter using half-bridge}

The present invention relates to a DC / DC converter, and more specifically, the switching frequency of the half-bridge switching unit is lower than the resonant frequency due to the leakage reactance of the transformer and the capacitance of the output capacitor, so that the soft switching is performed, the separate resonance The present invention relates to a high-efficiency DC / DC converter of a half-bridge type that can be transformed with high efficiency without requiring a reactor, and has an output side configured with a back voltage circuit, which is advantageous for high boost.

With the development of the industry and the expansion of renewable energy, large-capacity DC / DC converters (DC power converters) are being actively researched in terms of small size and light weight, and are widely used in broadcasting communication equipment, OA equipment, industrial electronic application equipment, and precision equipment. It is widely used as a power supply device, a low voltage / large current converter, or a high voltage converter in fields such as a computer and an ozone generator.

In addition, in order to achieve high integration and high efficiency of the DC / DC converter technology, a soft switching method is used to reduce switching loss and switching stress by making the switching point of the switch at zero voltage or zero current of the switch.

Here, in order to implement the soft switching method, a high frequency resonance characteristic is introduced. In this case, since a resonance reactor and a resonance capacitor for resonance must exist, there is a disadvantage in that the cost is increased and high power density is disadvantageous.

The present inventors researched a high efficiency DC / DC converter that can implement soft switching without providing a separate resonance reactor. As a result, the leakage reactance of the transformer unit can be used for resonance, thereby reducing the cost of adding passive elements and realizing high efficiency. The technical configuration of the DC / DC converter has been developed to complete the present invention.

Accordingly, it is an object of the present invention to provide a DC / DC converter having a half-bridge switching section on the input side and a back voltage circuit advantageous for high voltage boosting on the output side.

In addition, another object of the present invention is to provide a DC / DC converter capable of realizing high efficiency by making the switching frequency of the half-bridge switching unit lower than the resonance frequency caused by the leakage reactance of the transformer unit.

In addition, another object of the present invention is to provide a DC / DC converter suitable for high power density by reducing the number of passive elements by reducing the number of passive elements by resonating using the leakage reactance of the transformer without the need for a separate resonance reactor for resonance will be.

The objects of the present invention are not limited to the above-mentioned objects, and other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the present invention allows the input DC power to be supplied to both sides of an input side coil of a transformer unit, the first input capacitor and the second input capacitor connected in parallel to the input DC power in series. And a first switch and a second switch configured to alternately supply power of the first input capacitor or the second input capacitor to both sides of the input side coil, respectively. A first diode connected to a transformer unit having an input side coil and an output side coil, connected to the output side coil, rectifying the boost power, and an anode connected to one end of the output side coil; And a rectifier having a second diode having a cathode connected to one end of the output side coil. The rectified boosted power is charged to form an output DC power supply, one end of which is connected to the cathode of the first diode and the other end of which is connected to the other end of the output coil and one end of which is connected to the other end of the output capacitor. And the other end includes an output unit including a second output capacitor connected to an anode of the second diode, and the switching frequency of the switching unit is a leakage reactance of the transformer unit and a leakage reactance of the first output capacitor or the transformer unit; It provides DC / DC converter which makes soft switching by lower than resonant frequency by capacitance of 2 output capacitor.

In a preferred embodiment, it further comprises an LC filter connected to said output and smoothing said output DC power.

In one embodiment, the LC filter unit has a smoothing inductor, one end of which is connected to one end of the first output capacitor and one end of which is connected to the smoothing inductor, and the other end of which is connected to the other end of the second output capacitor. And a smoothing capacitor.

The present invention has the following excellent effects.

First, according to the DC / DC converter of the present invention, since the switches of the half-bridge switching unit perform a soft switching operation, the switching loss can be reduced, so the conversion efficiency is very excellent.

In addition, according to the DC / DC converter of the present invention, there is no need for a separate resonance reactor in the LC resonance for soft switching operation, and by using the leakage reactance of the transformer to resonate, the number of passive elements is reduced, so that the cost is low and high power density is achieved. Suitable converters can be provided.

In addition, according to the DC / DC converter of the present invention, by using two diodes and an output capacitor as a back-up circuit in the output side coil of the transformer unit, it is possible to provide a converter that is advantageous for high boost.

The terms used in the present invention were selected as general terms as widely used as possible, but in some cases, the terms arbitrarily selected by the applicant are included. In this case, the meanings described or used in the detailed description of the present invention are considered, rather than simply the names of the terms. The meaning should be grasped.

Hereinafter, the technical structure of the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.

However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Like reference numerals designate like elements throughout the specification.

1 is a view showing a DC / DC converter according to an embodiment of the present invention, Figures 2 and 4 are views illustrating the operation of the DC / DC converter according to an embodiment of the present invention, Figure 3 A series resonance equivalent circuit of a DC / DC converter according to an embodiment of the present invention.

Referring to FIG. 1, the DC / DC converter 100 according to an embodiment of the present invention includes a half-bridge switching unit 110, a transformer unit 120, a rectifier 130, and an output unit 140. Is done.

The half-bridge switching unit 110 supplies an input DC power supply (V _in ) to the transformer unit 120 to be described below.

More specifically, the half-bridge switching unit 110 supplies the input DC power (V _in ) so that current alternately flows in both directions of the input side coil 121 of the transformer unit 120.

In addition, the half-bridge switching unit 110 is connected in parallel to the input DC power supply (V _in ) and connected in series with each other, the first input capacitor 111 for dividing and storing the input DC power supply (V _in ). ) And the power stored in the second input capacitor 112 and the first input capacitor 111 or the second input capacitor 112 are alternately supplied to both sides of the input side coil 121, respectively. The first switch 113 and the second switch 114 is included.

When the first switch 113 is 'on', the first switch 113 is connected to the first input capacitor 111 and the input side coil 121 in a closed loop, and the second switch is turned on. In this case, the second input capacitor 112 and the input side coil 121 are connected to each other in a closed loop.

That is, the switches 113 and 114 are alternately 'on' so that current flows in different directions to the input side coil.

A more detailed description will be given with reference to FIGS. 2 and 3.

The transformer unit 120 boosts power stored in each of the input capacitors 111 and 112, and includes an input side coil 121 and an output side coil 122 having a winding ratio a.

In addition, the transformer unit 120 insulates the input DC power (V _in ) and the output DC power (V _out ) to be described below.

In the embodiment of the present invention, the transformer unit 120 is provided with a high frequency transformer.

The rectifier 130 is connected to the output side coil 122 of the transformer unit 120 to rectify the boosted power boosted by the transformer unit 120.

In addition, the rectifier 130 includes a first diode 131 having an anode connected to one end of the output side coil 122 and a second diode 132 having a cathode connected to one end of the output side coil 122.

The output unit 140 charges the boosted power rectified by the rectifier 130 to form an output DC power source, one end of which is connected to the cathode of the first diode 131, and the other end of the output side coil 122. A first output capacitor 141 connected to the other end and a second output capacitor 142 connected to the other end of the first diode 131 and the other end connected to an anode of the second diode 132. Is done.

That is, since the rectifier 130 and the output unit 140 backs up the boosted power output from the transformer unit 120 and outputs the boosted power, the DC / DC converter 100 according to the embodiment of the present invention has a high boost voltage. There is an advantage.

In addition, the output unit 140 may be connected to the LC filter unit 150 for smoothing the output DC power supply, the LC filter unit 150 is one end is connected to one end of the first output capacitor 141. The smoothing inductor 151 and one end thereof may be connected to the smoothing inductor 151, and the other end thereof may include a smoothing capacitor 152 connected to the other end of the second output capacitor.

In addition, since the smoothing capacitor 152 smoothes the output DC power together with the output capacitors 141 and 142, the smoothing capacitor 152 has an advantage of decreasing capacity.

Referring to FIGS. 2 to 4, the operation of the DC / DC converter 100 according to an embodiment of the present invention will be described. First, the first switch 113 is 'on' and the input DC power source V _in ), the first switch 113, the input side coil 121, and the second input capacitor 112 form a closed loop, and the input DC power source is connected to the first input capacitor 111. (V _in ) is divided and charged.

Next, current flows in one direction to the input side coil 121 by the power charged in the first input capacitor 111.

However, it is a matter of course that the second switch 114 is first turned on so that the second input capacitor 112 is charged first.

Next, a current is induced in the output side coil 122, and the output side coil 122, the first diode 131, and the first output capacitor 141 form one closed loop, thereby providing the first output. The capacitor 141 charges the boosted power boosted by the transformer unit 120.

In this case, the DC / DC converter 100 according to the embodiment of the present invention may cause resonance by the leakage reactance L ₁ of the transformer unit 120 and the capacitance C _s of the first output capacitor 141. As shown in FIG. 3, a series resonance equivalent circuit may be illustrated.

In addition, the leakage reactance of the leakage reactance of the output coil (122) to (L _l1) of the input-side coil 121 of the transformer 120 as shown in Equation 1 below, the value of the leakage reactance (L _l) (L _l2 ) Can be reduced to the input side and expressed as a sum.

Here, a is the turn ratio of the transformer unit 120.

In addition, the capacitance C _s of the first output capacitor 141 is also calculated by reducing to the input side of the transformer unit 120 as shown in Equation 2 below.

Here, a is the turn ratio of the transformer unit 120.

In addition, in the series resonance equivalent circuit, the resonance frequency f _o is expressed by Equation 3 below.

In addition, the resonance frequency (f _o) is the first surface is greater than the switching frequency of the switch 113, the inductor current (I _l) is the discrete, said first switch time a group (113) is "on" The inductor current I ₁ starts at 0 [A] and becomes zero current switching (ZCS) operation, and resonance is terminated before the first switch 113 is 'off', so that the first switch ( Since the current flowing through 113 becomes 0 [A], the first switch 113 is soft switched at both 'on' and 'off', and thus there is no switching loss.

In addition, since the soft switching can be implemented without a separate resonance reactor, it is possible to reduce the addition of passive elements.

Next, the first switch 113 is 'off', the second switch 114 is 'on', the input DC power supply (V _in ), the second switch 114, the input side coil 121 ) And the first input capacitor 111 form a closed loop, and the input DC power supply V _in is divided and charged _in the second input capacitor 112, and the second input capacitor is charged. Due to the power charged in the 112, the current flows to the input side coil 121 in the other direction.

Next, a current is induced in the output side coil 121, and the output side coil 121, the second diode 132, and the second output capacitor 142 form one closed loop to form the second output. The capacitor 142 charges the boosted power boosted by the transformer unit 120.

In addition, the zero current switching operation of the second switch 114 is the same as the zero current switching operation of the first switch 113 will be omitted.

Accordingly, the switches 113 and 114 can all be soft switching implemented.

5 is a simulation result of a DC / DC converter according to an embodiment of the present invention.

Referring to FIG. 5, the currents I _sw1 and I _sw2 flowing through the first switch 113 and the second switch 114 are discontinuous and flow in a sinusoidal current instead of a square wave due to resonance. Able to know.

In addition, it can be seen that the zero current switching operation of each of the switches 113 and 114 is caused by the discontinuous flow of current.

In addition, when the input DC voltage (V _in ) is 72 [V], the output DC voltage of 360 [V] is outputted, and it can be seen that there is almost no ripple of the output DC voltage, and the output efficiency is 97.5 [%]. Was very good.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, Various changes and modifications will be possible.

1 is a view showing a DC / DC converter according to an embodiment of the present invention,

2 and 4 are views for explaining the operation of the DC / DC converter according to an embodiment of the present invention,

3 is a series resonance equivalent circuit of a DC / DC converter according to an embodiment of the present invention.

5 is a simulation result of a DC / DC converter according to an embodiment of the present invention.

In the drawings according to the present invention, the same reference numerals are used for components having substantially the same configuration and function.

<Description of the symbols for the main parts of the drawings>

100: DC / DC converter 110: half-bridge switching unit

111: capacitor for first input 112: capacitor for second input

113: first switch 114: second switch

120: transformer section 121: input side coil

122: output side coil 130: rectifier

131: first diode 132: second diode

140: output unit 141: first output capacitor

142: second output capacitor 150: filter

151: smoothing inductor 152: smoothing capacitor

Claims (3)

An input DC power is supplied to both sides of an input side coil of a transformer, and a first input capacitor and a second input capacitor and a first input capacitor or the first input capacitor connected in parallel to the input DC power supply and connected in series with each other. A half-bridge switching unit including a first switch and a second switch to alternately supply power of a second input capacitor to both sides of the input side coil, and not including a resonance reactor as a passive element; A transformer unit for boosting the power of each input capacitor to output a boosted power, the transformer unit having an input side coil and an output side coil; A rectifier connected to the output side coil, rectifying the boosted power source, and having a first diode connected to an end of the output side coil and a second diode connected to a first end of the output coil; A first output capacitor connected to the cathode of the first diode and the other end connected to the other end of the output side coil and one end of the first output capacitor are charged with the boosted power rectified by the rectifier. And an output having a second output capacitor connected to the other end of the second end and connected to an anode of the second diode. The switching frequency of the switching unit is lower than the resonant frequency caused by the leakage reactance of the transformer unit and the leakage reactance of the first output capacitor or the transformer unit and the capacitance of the second output capacitor, so that soft switching is performed. DC / DC converter, characterized in that calculated using the equation. [Equation]

;

;

Here, f ₀ is the resonant frequency, L _l is the leakage reactance of the transformer portion, L _l1 is an input side leakage reactance of the transformer portion, L _l2 is output leakage reactance of the transformer unit, C _s is the first capacitor or It is a capacitance which reduced the said 2nd capacitor to the input side of the said transformer part, and C is the capacitance of the said 1st capacitor or the said 2nd capacitor. The method of claim 1, And an LC filter unit connected to the output unit and smoothing the output DC power supply. The method of claim 2, The LC filter unit may include a smoothing inductor having one end connected to one end of the first output capacitor and a smoothing capacitor having one end connected to the smoothing inductor and the other end connected to the other end of the second output capacitor. DC / DC converter.

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