KR101910533B1 - Soft-switching full-bridge converter and control method thereof - Google Patents

Soft-switching full-bridge converter and control method thereof Download PDF

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KR101910533B1
KR101910533B1 KR1020160141561A KR20160141561A KR101910533B1 KR 101910533 B1 KR101910533 B1 KR 101910533B1 KR 1020160141561 A KR1020160141561 A KR 1020160141561A KR 20160141561 A KR20160141561 A KR 20160141561A KR 101910533 B1 KR101910533 B1 KR 101910533B1
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switch
diode
circuit
capacitor
output
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KR20170059390A (en
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최우진
다이 드엉 트란
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숭실대학교산학협력단
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00Conversion of dc power input into dc power output
    • H02M3/22Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33592Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer

Abstract

A full bridge circuit including a transformer for performing voltage conversion including a primary side winding and a secondary side winding, an input capacitor for supplying an input power, and a first switch to a fourth switch, A first rectifier circuit connected to the secondary side winding and having a first diode to a fourth diode, a second rectifier circuit connected to the rectifier circuit, And an additional switch comprising a fifth diode, a sixth diode provided between the clamp capacitor and the fifth diode, an additional switch provided between the clamp capacitor and the sixth diode, and an output inductor The energy received from the primary side circuit through the transformer, A soft switching full bridge converter comprising an output inductor and a secondary circuit delivering it to an output capacitor coupled to the additional circuit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a soft-switching full-bridge converter,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft switching full bridge converter and a driving method thereof, and more particularly, to a soft switching full bridge converter capable of soft switching of switching elements provided on a primary side based on a transformer and a driving method thereof.

Full bridge dc-dc converters are being applied to a variety of devices such as power supplies, renewable energy systems, energy storage systems and traction systems for electric vehicles. This is because full-bridge dc-dc converters have the advantage of achieving simple topology, easy control and high efficiency while allowing high-power control.

Particularly, among full bridge dc-dc converters, a phase shift full-bridge (PSFB) converter adopting a phase shift control method is in the spotlight. Soft switching of power switches is possible and electromagnetic interference EMI: Electromagnetic Interference) and improve power density and efficiency.

Specifically, the full-bridge converter of the phase shift type can achieve the soft switching which is turned on when the voltage applied to the switch element is zero by using the parasitic elements of the switches and the transformer. Therefore, the switching loss in a particularly high power device can be considerably reduced.

However, the disadvantage of this phase-shift full bridge converter is that soft switching conditions are achieved by a complicated PWM switching technique and secondly there is a narrow zero voltage switching (ZVS) Under low conditions. Therefore, in order to ensure the wide zero-voltage switching range of the full-bridge transconductance converter, the leakage inductance of the transformer must be increased, which reduces the effective duty and increases the circulating current period, resulting in increased losses. The cyclic current generated at the primary side of the transformer is another disadvantage of the full bridge converter of the phase shift type because it increases the conduction loss and reduces the efficiency especially when the freewheeling section is continued.

Various methods have been proposed to overcome the shortcomings of the full bridge converter of the phase shift type.

Typically, there is a method of extending the zero voltage switching range by storing an inductive energy sufficient to add an auxiliary current source to the primary side of a phase-shifting full bridge converter to discharge the output capacitance of the switch. Here, the auxiliary current source may be implemented with an external inductor connected in series with the transformer, or a magnetizing inductance added to the transformer. However, this approach is achievable by bulky magnetic elements, which entails the problem of duty cycle loss, volume, manufacturing cost and conduction loss of the converter.

In addition, there is a method of solving a secondary side transient overvoltage and circulation current problem by adopting a snubber in a phase bridge type full bridge converter. This is a method of reducing the circulating current by separating the secondary rectifier circuit from the primary and secondary free wheeling circuits by suppressing the transient voltage by the snubber.

For example, a dissipated RCD snubber is employed in a phase-shifting full bridge converter to mitigate voltage ringing in rectifier diodes. However, such a scheme has the disadvantage that additional loss and snubber resistance There is a problem due to the heat generated by the heat. In addition, there is a method in which an active clamp snubber is applied to a full bridge converter of a phase shift type. Such a method requires an auxiliary driving circuit and an additional inductor, which complicates the implementation and increases the number of elements required to implement the circuit . A coupling-inductor-based capacitor-diode-diode (CDD) topology has also been proposed. This can reduce the circulating current and also achieve the soft switching condition of the switches provided in the primary side lagging legs. However, since the circulating current is not completely removed and the switches of the switches provided on the primary side leg- Current switching (ZCS) can not be turned off.

In order to compensate for the disadvantage of the phase-shift full bridge converter, the proposed methods can completely remove only the circulating current, or the method of expanding the soft switching range by adding additional circuits or complicating the switching method to be.

On the other hand, it is hard to find a way to eliminate the circulating current and expand the soft switching range of the primary side switches. For example, there is a method of including a phase shift active rectifying circuit on the secondary side. This can control the output voltage by replacing one leg of the secondary rectifier diode with an active switch to perform phase shift control between the primary and secondary switches. At this time, the primary switches can be controlled according to a fixed duty cycle (50%) at a constant switching frequency. The full bridge converter adopting this method has a disadvantage in that the implementation of turn-off snubber capacitors for operation in a wide load range is complicated and even if proper turn-off snubber capacitors are implemented, resonating with the parasitic inductor of the circuit, Voltage ringing. In addition, changing the effective capacitance value limits the zero voltage switching range at light load conditions. As another example, a method has been proposed in which a saturable inductor is connected in series to a secondary switch to ensure zero voltage switching of the primary switches by adding inductive energy on the primary side. However, And complicates circuit implementation.

In this way, it can be inferred that, in the case of a phase-shift full bridge converter, it is desirable to add an active switch and a freewheeling diode to the secondary circuit so as to control the rectifier circuit and form an independent freewheeling current loop . This will be described with reference to FIG.

1 is a view showing an example of a full bridge converter to which a switch and a freewheeling diode are added to a secondary side circuit.

1, there is shown a phase shift circuit including a primary side full bridge circuit provided with switch elements around a transformer TR and a secondary side circuit provided with a rectifier circuit, an active switch Q 1 and a freewheeling diode D fwl . Type full bridge converter. A brief description will be given to a driving method for such a phase shift key of the full-bridge converter shown in Figure 1, and a secondary side active switch (Q 1) is delivering power to the load by two-fold operations of the primary-side switching frequency, the output of which Can be controlled by the duty of the secondary side active switch Q 1 . Further, the switch provided in the primary-side full-bridge circuits operative done switch between pairs of opposed on a diagonal line, all of the by operating so as to have a 180-degree phase difference despite the small dead time (t dead) therebetween, and the primary circuit Zero voltage switching of the switches is possible. This is because energy is stored in the magnetizing inductance of the transformer (TR). At this time, when the secondary side active switch Q 1 is turned off earlier than the primary side switch, the primary side current may be reset to satisfy the zero current switching turn off condition of the primary side switches. In addition, no circulating current occurs because there is no phase transition of the primary side switches.

However, in the case of the converter shown in Fig. 1, when the secondary side active switch Q1 is turned off, resonance occurs between the leakage inductance Llk of the transformer and the effective capacitance of the secondary circuit, The ringing voltage appears on the switch Q1 and the rectifier diodes D1 to D4. Therefore, a suitable turn-off snubber circuit is needed to mitigate this ringing voltage.

One aspect of the present invention provides a soft switching full bridge converter having a CDD snubber circuit and a supplementary switch, which function as a non-dissipative snubber in a secondary circuit, and a driving method thereof.

One aspect of the present invention relates to a soft switching full bridge converter including a transformer for performing voltage conversion including a primary side winding and a secondary side winding and an input capacitor for supplying an input power, A first bridge circuit connected to the primary winding and a second bridge connected to the first winding and the second winding, the first bridge including a full bridge circuit provided to the primary winding and the second winding, A fourth diode provided between the clamp capacitor and the fifth diode, a sixth diode provided between the clamp capacitor and the fifth diode, a second diode provided between the clamp capacitor and the sixth diode, An additional circuit comprising a switch and an output inductor connected to the additional circuit, And a secondary circuit for delivering energy transmitted through the transformer from the primary side circuit group to the output capacitor connected to the output inductor and the adding circuit.

Meanwhile, the secondary circuit includes a third leg and a fourth leg connected in parallel, and the first diode and the fourth diode are provided on the third leg and the fourth leg, And an output voltage line connecting the fourth leg may include the rectifying circuit connected to the secondary winding.

The secondary circuit may further include an anode of the sixth diode connected to a node between the one end of the clamp capacitor and the cathode of the fifth diode and the cathode of the sixth diode being provided between the other end of the clamp capacitor and the cathode of the sixth diode And the additional circuit comprising the additional switch.

The secondary circuit is connected to the upper contact of the third leg and the fourth leg and the other end of the clamp capacitor and one end of the additional switch are connected to the lower contact of the third leg and the fourth leg, The anode of the fifth diode and the output capacitor may be connected.

In the secondary circuit, the other end of the additional switch and the cathode of the sixth diode may be connected to one end of the output inductor, and the other end of the output inductor may be connected to the output capacitor.

In addition, the secondary side circuit may charge the clamp capacitor when the additional switch is turned off, and the energy stored in the clamp capacitor may be discharged to the output capacitor when the additional switch is turned on.

In the secondary circuit, a closed loop by the fifth diode and the sixth diode may be formed so that a freewheeling current of the output inductor flows.

The primary side circuit may include a first leg and a second leg connected in parallel, wherein the first switch and the fourth switch are provided on the first leg and the second leg, And a full bridge circuit in which a leakage inductor and a magnetizing inductor are provided on an input voltage line connecting the second leg and the magnetizing inductor is connected in parallel with the primary winding.

In addition, the primary circuit may transmit the input power to the primary winding in accordance with the switching operation of the first switch and the fourth switch operating under soft switching conditions.

In addition, the secondary circuit may include the additional switch that is turned on in the same manner as the first switch and the fourth switch, but turns off prior to the first switch and the fourth switch.

Further, the secondary side circuit may be rectified by the first diode, the fourth diode and the fifth diode operating under soft switching conditions.

According to another aspect of the present invention, there is provided a voltage conversion circuit for converting a voltage between an input capacitor for supplying an input power and an output capacitor connected in parallel to an output load resistor, wherein a primary circuit connected to the input capacitor comprises: Wherein the secondary circuit connected to the output capacitor comprises a rectifying circuit, a clamp capacitor and a fifth diode connected to the rectifying circuit, and a sixth diode provided between the clamp capacitor and the fifth diode, An additional circuit comprising a diode, an additional switch provided between the clamp capacitor and the sixth diode, and an output inductor connected to the additional circuit, wherein the voltage conversion is performed between the primary circuit and the secondary circuit A method of driving a soft switching full bridge converter having a transformer, In the primary circuit, the first switch operating under the soft switching condition transfers the input power to the transformer in accordance with the switching operation of the fourth switch, and in the secondary circuit, the first The rectifier rectifies the input power received from the diode through the fourth diode and the fifth diode through the transformer, and transfers the rectified input power to the output capacitor.

On the other hand, in the primary side circuit, the first switch and the fourth switch provided on the diagonal line of the full bridge circuit, and the second switch and the third switch are paired, and can be turned on or off in the same manner.

In addition, in the secondary circuit, the additional switch may be turned on in the same manner as the first switch and the fourth switch, but may be turned off prior to the first switch or the fourth switch.

In addition, in the secondary circuit, when the additional switch is turned off, the clamp capacitor is charged, and when the additional switch is turned on, energy stored in the clamp capacitor can be discharged to the output capacitor.

In the secondary circuit, a closed loop by the fifth diode and the sixth diode may be formed so that a freewheeling current of the output inductor flows.

According to one aspect of the present invention, the switching elements provided in the primary side full bridge circuit can achieve a soft switching condition in a full load range. Further, there is no duty cycle loss, and the voltage ringing of the rectifying diodes and the additional switches provided in the secondary side circuit can be reduced.

1 is a view showing an example of a full bridge converter to which a switch and a freewheeling diode are added to a secondary side circuit.
2 is a schematic circuit diagram of a soft switching full bridge converter according to an embodiment of the present invention.
3A to 3G are schematic circuit diagrams for explaining a driving method in each operation mode of a soft switching full bridge converter according to an embodiment of the present invention.
FIG. 4 is a diagram showing voltage applied to each element or current flowing in each element in each operation mode of the soft switching full bridge converter according to an embodiment of the present invention.
Figs. 5A to 5C are examples of voltages measured at the primary side switch and the secondary side switch of the converter shown in Figs. 1 and 2.
FIGS. 6A to 10 illustrate advantageous effects of a soft switching full bridge converter according to an embodiment of the present invention.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

2 is a schematic circuit diagram of a soft switching full bridge converter according to an embodiment of the present invention.

Referring to FIG. 2, a soft switching full bridge converter 1000 according to an embodiment of the present invention is a DC-DC converter and includes a first switch 111 to a fourth switch Bridge circuit provided with the first diode 121 to the fourth diode 124. The rectifier circuit and the additional switch 134 and the capacitor-diode-diode (CDD) snubber circuit .

2, the transformer 100 transforms the voltage of the primary side circuit to a voltage of a predetermined 1: n (1: n) voltage of the primary side of the soft switching full bridge converter 1000 according to an embodiment of the present invention. It can be converted according to the turn ratio and transmitted to the secondary circuit. That is, the transformer 100 is composed of a primary side winding and a secondary side winding, and the primary side winding is connected to the primary side circuit and the secondary side winding can be connected to the secondary side circuit.

The primary side circuit of the soft switching full bridge converter 1000 according to an embodiment of the present invention may include a full bridge circuit provided with the first switch 111 to the fourth switch 114. At this time, The circuit is connected to the input capacitor 10 and the leakage inductor 115 and the magnetizing inductor 116 may be provided on the input voltage line 110-3 connecting the pair of legs constituting the full bridge circuit. Here, the magnetizing inductor 116 may be connected in parallel with the primary winding of the transformer 100.

Specifically, the full bridge circuit included in the primary side circuit is composed of a first leg 110-1 and a second leg 110-2 connected in parallel, and the first leg 110-1 and the second leg 110-2 are connected in parallel, The upper contact and the lower contact of the input capacitor 110-2 may be connected to both ends of the input capacitor 10, respectively. A first switch 111 and a second switch 112 are provided on the upper side and the lower side of the first leg 110-1 and on the upper side and the lower side of the second leg 110-2, A third switch 113 and a fourth switch 114 may be provided. At this time, the first to fourth switches 111 to 114 may be, for example, MOSFET switches, and each of the body diode and the parasitic capacitor may be connected in parallel.

The primary side circuit includes an input voltage line 110-3 connecting the first leg 110-1 and the second leg 110-2 of the full bridge circuit, specifically, the first leg 110-1 The first contact a between the first switch 111 and the second switch 112 in the second leg 110-1 and the second contact 112b between the third switch 113 and the fourth switch 114 in the second leg 110-2, And an input voltage line 110-3 connecting the contact point b and a leakage inductor 115 and a magnetization inductor 116 may be provided on the input voltage line 110-3. At this time, the magnetizing inductor 116 may be connected in parallel with the primary winding of the transformer 100.

The secondary circuit of the soft switching full bridge converter 1000 according to an embodiment of the present invention includes a rectifying circuit provided with the first diode 121 to the fourth diode 124, a clamp capacitor 131, a fifth diode 132 A CDD snubber circuit and an additional switch 134 with a sixth diode 133 and a CDD snubber circuit and an additional switch 134 may be connected in series between the output inductor 125 and the output capacitor 20 ). At this time, the output capacitor 20 may be connected in parallel with the output load resistor 30 to deliver the output voltage V o to the output load resistor 30.

More specifically, the rectifier circuit included in the secondary circuit is constituted by the third leg 120-1 and the fourth leg 120-2 connected in parallel, and the upper and lower sides of the third leg 120-1 A first diode 121 and a second diode 122 may be provided respectively and a third diode 123 and a fourth diode 124 may be provided on the upper and lower sides of the fourth leg 120-2, . One end of the clamp capacitor 131 and the additional switch 134 included in the CDD snubber circuit are connected to the upper contacts of the third leg 120-1 and the fourth leg 120-2, A fifth diode 132 included in the CDD snubber circuit may be connected to the lower contacts of the first leg 120-1 and the fourth leg 120-2.

The secondary side circuit includes an output voltage line 120-3 connecting the third leg 120-1 and the fourth leg 120-2 of the rectifying circuit, specifically, the third leg 120-1, A third contact c between the first diode 121 and the second diode 122 and a fourth contact between the third diode 123 and the fourth diode 124 in the fourth leg 120-2, and an output voltage line 120-3 connecting the secondary winding d of the transformer 100 and the secondary winding of the transformer 100 on the output voltage line 120-3.

The CDD snubber circuit included in the secondary side circuit is connected to the rectifying circuit and may include a clamp capacitor 131, a fifth diode 132, and a sixth diode 133. The CDD snubber circuit has a configuration in which a sixth diode 133 is connected between the clamp capacitor 131 and the fifth diode 132. Specifically, one end of the clamp capacitor 131 and the cathode of the fifth diode 132 The anode of the sixth diode 133 may be connected to the fifth contact (e)

Here, the CDD snubber circuit included in the secondary side circuit is connected to the rectifying circuit, and may include the clamp capacitor 131, the fifth diode 132, and the sixth diode 133. The CDD snubber circuit has a configuration in which a sixth diode 133 is connected between the clamp capacitor 131 and the fifth diode 132. Specifically, one end of the clamp capacitor 131 and the cathode of the fifth diode 132 The anode of the sixth diode 133 may be connected to the fifth contact (e) One side of the additional circuit is connected to the rectifying circuit and the other side of the additional circuit is connected to the output inductor 125 and the output capacitor 20 The other end of the clamp capacitor 131 is connected to the upper contact of the third leg 120-1 and the fourth leg 120-2 of the rectifying circuit and the other end of the additional switch 134 And the anode of the fifth diode 132 may be connected to the lower contacts of the third leg 120-1 and the fourth leg 120-2. The cathode of the sixth diode 133 and the other end of the additional switch 134 are connected to the output inductor 125 and the anode of the fifth diode 132 is connected to the output capacitor 20, The output capacitor 125 and the output capacitor 20 may be connected in series and the output inductor 125 may be connected in parallel with the output load resistor 30. [

As described above, the soft switching full bridge converter 1000 according to an embodiment of the present invention performs voltage conversion between the primary circuit and the secondary circuit around the transformer 100, and in particular, The soft switching condition of the rectifying diodes constituting the switches and the rectifying circuit provided in the primary side circuit including the CDD snubber circuit and the additional switch 134 connected to the circuit can be achieved.

Hereinafter, a method of driving the soft switching full bridge converter 1000 according to an embodiment of the present invention will be described with reference to FIGS. 3A to 3G and FIG.

FIGS. 3A to 3G are schematic circuit diagrams for explaining a driving method in each operation mode of a soft switching full bridge converter according to an embodiment of the present invention. FIG. 4 is a circuit diagram illustrating a soft switching full bridge according to an embodiment of the present invention. In which the voltage applied to each element or the current flowing in each element in each operation mode of the bridge converter is shown.

The soft switching full bridge converter 1000 according to an embodiment of the present invention converts an input voltage V s applied to the input capacitor 10 according to seven operation modes of the first to seventh operation modes to output The output voltage V o can be supplied to the output load resistor 30 by transmitting the output voltage V o to the capacitor 20.

4, in the first operation mode to the seventh operation mode, the switches provided on the diagonal line in the primary circuit, that is, the first switch 111 and the fourth switch 114, and the second switch 112 And the third switch 113 may be paired to be turned on or off in the same manner. Further, the additional switch 134 of the secondary side circuit is turned on in the same manner as the switches of the primary side circuit, but can be turned off first.

Referring to Figure 3a, the first operation mode [t 0 ~ t 1] from, the primary side circuit, the first switch 111 and fourth switch 114 is a turn-on state, the second switch 112 and third The switch 113 may be turned off. In the secondary side circuit, the additional switch 134 may be in a turned-on state.

In this first mode of operation, energy can be transferred to the output load resistor 30 through the first switch 111, the fourth switch 114 and the additional switch 134. 4, the current (i pri ) flowing through the primary side circuit is the same as the reflection current of the output inductor 125, and the slope thereof can be calculated by Equation (1) below.

[Equation 1]

Figure 112016105029154-pat00001

In Equation 1, i Lo is the inductance represents the current flowing through the output inductor 125, n is transformer 100 turns ratio, V s is the input voltage, V o is the output voltage, and L o is the output inductor 125 it means.

Next, Referring to Figure 3b, second and mode of operation [t 1 ~ t 2] from, the primary side circuit of the first switch 111 and fourth switch 114 are turned on state, the second switch 112 and And the third switch 113 may be turned off. In addition, in the secondary side circuit, the additional switch 134 may be turned off.

In this second mode of operation, the charging of the parasitic capacitor and the clamp capacitor 131 added to the additional switch 134 can be started at the time t 1 when the additional switch 134 is turned off, The resonance with the leakage inductor 115 and the output inductor 125 of the resonator can be started. At this time, since the inductance of the output inductor 125 is larger than the inductance of the leakage inductor 115 (L o >> L lk ) and the capacitance of the clamp capacitor 131 is larger than the capacitance of the parasitic capacitor added to the additional switch 134 (C clamp >> C oss ), the resonance frequency of the current is approximately

Figure 112016105029154-pat00002
May be computed as, also, the clamp capacitor 131, the voltage across the fifth diode 132 as the charge (v D5) is the voltage across the fifth diode 132 to decrease (v D5) are the following (2) " (2) "

&Quot; (2) "

Figure 112016105029154-pat00003

In the equation (2), v D5 denotes a voltage applied to the fifth diode 132 in the second operation mode, n denotes a transformer turn ratio, V s denotes an input voltage, and i c - clamp (t 1 ) denotes a clamp capacitor 131 at t 1 . L o is the inductance of the output inductor 125, and C clamp is the capacitance of the clamp capacitor 131. At this time, the current i c_clamp (t 1) flowing through the clamp capacitor 131 at t 1 is equal to the maximum value (I Lo_max) of the current flowing through the output inductor (125).

In the second operation mode, the voltage V C_clamp applied to the clamp capacitor 131 becomes equal to the rectified voltage v rect , so that the voltage v D5 applied to the fifth diode 132 reaches zero, a If t 2 d, and the second mode of operation is t can be referred to the operation mode between 1 and t 2, therefore, the time of the second operation mode can be expressed as equation (3) below using the equation (2) .

&Quot; (3) "

Figure 112016105029154-pat00004

In Equation 3 t mode2 the second represents the time of the operation mode, L o is the inductance, C clamp capacitance, n is the transformer turns ratio, V s of the clamp capacitor 131, the output inductor (125) is an input voltage, v C_clamp (t 1 ) represents a voltage applied to the clamp capacitor 131 at t 1 , and I Lo_max represents a maximum current flowing through the output inductor 125.

Also, in the second operation mode, the current flowing in the output inductor 125 can start a freewheel according to the slope of Equation (4) below.

&Quot; (4) "

Figure 112016105029154-pat00005

In Equation 4 i Lo denotes a current flowing through the output inductor (125), n is transformer 100 turns ratio, V s is the input voltage, V c _clamp a voltage, V o applied to the clamp capacitor 131, the output voltage And L o represents the inductance of the output inductor 125.

3C, in the third operation mode [t 2 to t 3 ], the first switch 111 and the fourth switch 114 are turned on in the primary circuit and the second switch 112 and the second switch 112 are turned on, And the third switch 113 may be turned off. In addition, in the secondary side circuit, the additional switch 134 may be turned off.

In this third operation mode, since the voltage (V C_clamp ) applied to the clamp capacitor 131 is the same as the rectified voltage (v rect ), the fifth diode 132 is forward biased, and in the secondary circuit, The commutation of current through the rectifying diodes of the first and second diodes 121 and 124 and the fifth diode 132 occurs. At this time, since the current flowing in the fifth diode 132 gradually increases from the point when the voltage applied to the fifth diode 132 reaches 0, the fifth diode 132 can achieve the zero current switching turn-on.

Also, in the third mode of operation, the clamp capacitor 131 begins resonance with the leakage inductor 115, and the freewheeling current of the transformer 100 flows through the fifth diode 132 and the sixth diode 133 Because. At this time, the current flowing in the clamp capacitor 131 in the third operation mode can be expressed by the following Equation (5), and the voltage applied to the clamp capacitor 131 can be expressed by Equation (6) below.

&Quot; (5) "

Figure 112016105029154-pat00006

&Quot; (6) "

Figure 112016105029154-pat00007

In Equations (5) and (6), i C_clamp represents the current flowing through the clamp capacitor 131, v C_clamp represents the voltage across the clamp capacitor 131, and i C_clamp (t 2 ) represents the voltage flowing through the clamp capacitor 131 at t 2 V c_clamp (t 2 ) is the voltage across clamp capacitor 131 at t 2 , n is the transformer turn ratio, L 1k is the inductance of the leakage inductor 115, C clamp is the capacitance of the clamp capacitor 131, V s And v C_clamp (t 2 ) represents a voltage applied to the clamp capacitor 131 at t 2 .

According to Equation (6), it can be seen that when the inductance of the leakage inductor (115) is large, the voltage applied to the clamp capacitor (131) increases. This is because, unlike the conventional full-bridge full bridge converter, the soft switching full bridge converter 1000 according to an embodiment of the present invention is configured such that the inductance value of the leakage inductor 115 is larger than the inductance value of the zero- The soft switching full bridge converter 1000 according to the embodiment of the present invention can design the ideal transformer 100 even if the inductance value of the leakage inductor 115 is reduced.

In the third operation mode, the rectification of the current through the first diode 121 and the fourth diode 124 is ended and the current i pri flowing in the primary side circuit is equal to the magnetizing current i Lm of the transformer makin, when referred to the time t 3, the third mode of operation is t 2, and t can be referred to the operation mode between the third and therefore, the time of the third operation mode is equation below using equation 57 and As shown in Fig. At this time, the current (i C_clamp (t 3)) flowing through the clamp capacitor 131 at t 3 may be referred to as zero.

&Quot; (7) "

Figure 112016105029154-pat00008

In Equation 7 t mode3 is a time period in the third mode of operation, n is the transformer turns ratio, L lk is the capacitance, i C_clamp (t 2) of the inductance, C clamp the clamp capacitor 131 in the leak inductor 115 the current flowing through the clamp capacitor 131 at t 2 , V s represents the input voltage, and v cclamp (t 2 ) represents the voltage across the clamp capacitor 131 at t 2 .

Here, to c_clamp v (t 2) = nV s d in Equation (7), and this case, the third time t of the operation mode is mode3

Figure 112016105029154-pat00009
Lt; / RTI >

Thus, the clamp capacitor 131 is charged over the second operation mode and the third operation mode, and the charge time can be expressed by the following equation (8).

&Quot; (8) "

Figure 112016105029154-pat00010

In the equation 8 t C _clamp the clamp capacitor 131 is a time period to be filled, t mode2 and t mode3 each second mode of operation and the duration of a time interval in the third operation mode can be obtained from equation (3) and Equation (7) have.

Further, in the third operation mode, the current flowing in the output inductor 125 can be freewheeled continuously according to the slope of Equation (9) below.

&Quot; (9) "

Figure 112016105029154-pat00011

In Equation 9, i Lo represents the current flowing in the output inductor 125, V o represents the output voltage, and L o represents the inductance of the output inductor 125.

Equations (9) and (4) showing the slope of the current flowing through the output inductor 125 may be different from each other. However, in the third operation mode, the voltage applied to the clamp capacitor 131 and the voltage applied to the primary- Since the voltages become equal, Equations (9) and (4) are substantially the same.

3D, in the fourth operation mode [t 3 to t 4 ], the first switch 111 and the fourth switch 114 are turned on in the primary circuit, and the second switch 112 and the second switch 112 are turned on, And the third switch 113 may be turned off. In addition, in the secondary side circuit, the additional switch 134 may be turned off.

In this fourth operation mode, only a very small magnetizing current (i Lm ) flows through the primary side circuit, and the first switch 111 and the fourth switch 114 at t4, the first diode 121 provided at the rectifying circuit, Current switching condition of the fourth diode 124 can be satisfied.

In the fourth operation mode, a closed loop for freewheeling is formed in the secondary side circuit, and the fifth diode 132 and the sixth diode 133 may be included in this closed loop.

Referring to FIG. 3E, in the fifth operation mode [t 4 to t 5 ], the first switch 111 to the fourth switch 114 may all be turned off in the primary circuit. In addition, in the secondary side circuit, the additional switch 134 may be turned off.

In this fifth operation mode, the charging of the parasitic capacitors added to the first switch 111 and the fourth switch 114 by the magnetizing current (i Lm ) in the primary circuit can be started, and the second switch 112 and The discharge of the parasitic capacitors added to the third switch 113 starts and the voltage applied to the second switch 112 and the third switch 113 can be reduced to zero. Further, in the primary side circuit, the primary side current i pri passes through the body diode added to the second switch 112 and the third switch 113 before the second switch 112 and the third switch 113 are turned on The second switch 112 and the third switch 113 can achieve the zero voltage switching turn on condition.

In the fifth operation mode, the rectified voltage v Rect in the secondary side circuit and the voltage v DS_Q1 applied to the additional switch 134 are clamped by the voltage C clamp applied to the clamp capacitor 131 .

3F, in the sixth operation mode [t 5 to t 6 ], the first switch 111 and the fourth switch 114 are turned off and the second switch 112 is turned off in the primary circuit, And the third switch 113 may be turned on. In the secondary side circuit, the additional switch 134 may be in a turned-on state.

In this sixth operation mode, the second switch 112, the third switch 113 and the additional switch 134 can be turned on simultaneously at t 5 . At this time, the second switch 112 and the third switch 113 can achieve zero voltage switching.

In the sixth operation mode, the clamp capacitor 131 can discharge the energy absorbed by the output load resistor 30 in the secondary circuit, and the resonance between the clamp capacitor 131 and the output inductor 125 can occur have. At this time, the voltage applied to the clamp capacitor 131 may gradually decrease as shown in the following Equation (10).

&Quot; (10) "

Figure 112016105029154-pat00012

Where,

Figure 112016105029154-pat00013

V C_clamp (t) denotes the voltage across the clamp capacitor 131, V C_clamp (t 5) and i C_clamp (t 5) is a voltage and the clamp capacitor across the clamp capacitor 131 at t 5, respectively in equation (10) L o is the inductance of the output inductor 125, and C clamp is the capacitance of the clamp capacitor 131.

According to equation (10), a sixth operating mode, because of a value greater than the voltage across the secondary coil of the transformer 100, the voltage across the clamping capacitor (131), (V C_clamp> nV s), the second switch (112 And the third switch 113 are turned on, the energy can not be transmitted from the primary side of the transformer 100 to the secondary side.

Accordingly, the energy stored in the clamp capacitor 131 is transferred to the output load resistor 30. The clamp capacitor 131 has such a characteristic that it can be called a non-dissipative. In addition, since the clamp capacitor 131 serves as a current source in the sixth operation mode and the seventh operation mode described later, energy transfer can be continued as soon as the additional switch 134 is turned on. The soft switching full bridge converter 1000 according to the example has no duty loss.

On the other hand, the sixth mode of operation may be terminated at t 6 , when the voltage across the clamp capacitor 131 is equal to nV s , i.e., the voltage across the secondary winding.

Further, in the sixth operation mode, the current flowing in the output inductor 125 of the secondary side circuit can be increased according to the slope of the following expression (11).

&Quot; (11) "

Figure 112016105029154-pat00014

In the equation (11), Lo represents the current flowing in the output inductor 125, v C_clamp (t 5 ) is the voltage across the clamp capacitor 131 at t 5 , V o is the output voltage, L o is the output inductor 125 < / RTI >

3G, in the seventh operation mode [t 6 to t 7 ], in the primary circuit, the first switch 111 and the fourth switch 114 are turned off and the second switch 112 And the third switch 113 may be turned on. In the secondary side circuit, the additional switch 134 may be in a turned-on state.

In this seventh mode of operation, at t 6 , the primary current i pri flows in a direction opposite to the previous one, and energy transfer from the primary circuit to the secondary circuit can begin. At this time, in the secondary circuit, energy can be transmitted through the second diode 122 and the third diode 123.

Further, in the seventh operation mode, the resonance between the clamp capacitor 131 and the output inductor 125 generated in the previous operation mode continues, and the clamp capacitor 131 can be completely discharged at t 7 .

In the seventh operation mode, the primary side current i pri increases to be equal to the reflection current of the output inductor 125 at t 7 , and energy transfer to the output load resistor 30 can be prepared.

The first to seventh operation modes describe the half period of the switching period T s . Thereafter, during the half period, the direction of the current is different from that of the first to seventh operation modes, Can be repeated.

Hereinafter, advantageous effects in the case where the soft switching full bridge converter 1000 according to the embodiment of the present invention is driven according to the first to seventh operation modes will be described in detail.

First, the soft switching full bridge converter 1000 according to an embodiment of the present invention is capable of switching the zero voltage of all the switches provided in the primary side circuit in the full load range. In this connection, it is assumed that the capacitances of the parasitic capacitors added to the first switch 111 to the fourth switch 114 of the primary side circuit are all the same, and that the magnetizing current is constant during the fourth operation mode (t3 to t4) I will explain.

In the fifth operation mode, the first switch 111 to the fourth switch 114 of the primary side circuit are separated from the secondary side circuit. In the secondary side circuit, the freewheeling current of the output inductor 125 is reduced by the fifth diode 132 And the sixth diode 133. In this case, Accordingly, as the inductive energy is stored on the primary side during the dead time of the switching period of the primary side switch, the zero voltage switching condition of the switching elements provided in the primary side circuit can be achieved.

More specifically, in order to achieve the zero voltage switching conditions of the first switch 111 to the fourth switch 114 provided in the primary circuit, the magnetizing inductor 116 and the leakage inductor 115 of the transformer 100, The energy E ZVS is generated by completely discharging the parasitic capacitors added to the pair of switches operating in the same manner of the first switch 111 to the fourth switch provided in the primary side circuit, Must be fully charged. In order to satisfy such a condition, the transformer 100 should be designed to satisfy the following condition (12), and according to the expression (12), the inductance of the magnetizing inductor 116 becomes larger than the inductance of the leakage inductor 115 The soft switching full bridge converter 1000 according to an exemplary embodiment of the present invention can achieve zero voltage switching of the switching elements provided in the primary circuit regardless of the range of the load It is possible.

&Quot; (12) "

Figure 112016105029154-pat00015

Math inductance, I m represents the magnetizing current of the transformer (100), C oss is the capacitance, V in the parasitic capacitors in addition to the switch provided in the primary circuit of L m is the magnetization inductor 116 in Equation 12 is the input voltage . At this time, the magnetizing current I m of the transformer 100 can be calculated from the following equation (13).

&Quot; (13) "

Figure 112016105029154-pat00016

In Equation 13, V s represents the input voltage, L m represents the inductance of the magnetizing inductor 116, and f s represents the switching frequency of the additional switch 134.

The inductance of the magnetizing inductor 116 can be calculated from Equation (12) and Equation (13) as Equation (14) below.

&Quot; (14) "

Figure 112016105029154-pat00017

In Equation 14, f s represents the switching frequency of the additional switch 134, and C oss represents the capacitance of the parasitic capacitor added to the primary switch.

Therefore, the minimum dead time for achieving the zero voltage switching condition of the switches provided in the primary side circuit, that is, the parasitic capacitors added to the first switch 111 to the fourth switch 114 provided in the primary side circuit, Or the minimum dead time for fully discharging can be calculated as shown in Equation (15) below.

&Quot; (15) "

Figure 112016105029154-pat00018

In Equation 14, f s is the switching frequency of the additional switch 134, C oss is the capacitance of the parasitic capacitor added to the primary switch, and L m is the inductance of the magnetizing inductor 116.

Meanwhile, the soft switching full bridge converter 1000 according to an exemplary embodiment of the present invention is capable of turning off the zero current switching of all the switches provided in the primary side circuit.

Specifically, in general, the switches provided in the primary side circuit are turned off together with the reflected current of the output inductor 125, while the soft switching full bridge converter 1000 according to an embodiment of the present invention, Switch 134. This additional switch 134 is turned off earlier than the switch provided in the primary circuit so that the zero current switching turn-off of all the switches provided in the primary circuit is possible. Referring to FIG. 4, during the zero current switching time (t ZCS ), the magnitude of the primary current i pri may decrease to equal the magnitude of the magnetizing current i Lm . Therefore, the loss in turn-off of the switches provided in the primary side circuit is negligible. The required zero current switching time t ZCS should be longer than the charging time of the clamp capacitor 131 as shown in Equation 16 below.

&Quot; (16) "

Figure 112016105029154-pat00019

The soft switching full bridge converter 1000 according to an embodiment of the present invention includes a first diode 121 to a fourth diode 124 provided in a rectifying circuit included in a secondary circuit, 5 diode 132 turn on and zero current switching turn off is possible and it is possible to solve the reverse recovery problem.

Specifically, the bias conditions of the first diode 121 to the fourth diode 124 provided in the rectifier circuit included in the secondary side circuit and the fifth diode 132 provided in the snubber circuit are applied to the clamp capacitor 131 Since the rectification of the current can be performed after the first diode 121 to the fifth diode 132 are forward biased, the first diode 121 provided in the rectifying circuit included in the secondary circuit, The fourth diode 124 and the fifth diode 132 provided in the snubber circuit are capable of turning on and off the zero current and turning off the zero current switching can also solve the problem of reverse recovery .

On the other hand, in the case of the sixth diode 133 provided in the secondary side circuit, soft switching is not possible. The bias condition of the sixth diode 133 is determined by the switching operation of the additional switch 134 and the clamp capacitor 131 Because. Therefore, the switching loss is inevitable as the voltage applied to the clamp capacitor 131 increases.

Meanwhile, the soft switching full bridge converter 1000 according to the embodiment of the present invention has no duty cycle loss.

Specifically, as shown in FIG. 4, the current flowing in the output inductor 125 increases during the sixth operation mode, the seventh operation mode, and the first operation mode, and decreases in the second operation mode to the fifth operation mode do. Accordingly, the voltage gain can be expressed as Equation (17) below with reference to equations (1), (9) and (11) using the volt-second balance rule.

&Quot; (17) "

Figure 112016105029154-pat00020

V o is the output voltage, L o is the inductance of the output inductor, n is the turn ratio of the transformer 100, and V s is the input voltage. In the equation 17, V C_clamp is the voltage applied to the clamp capacitor 131,

Figure 112016105029154-pat00021
Lt; / RTI >
Figure 112016105029154-pat00022
(= 1 / fs ) .

The output voltage from Equation (17) can be expressed as Equation (18) below.

&Quot; (18) "

Figure 112016105029154-pat00023

In this case, the average value of the voltage applied to the clamp capacitor 131 at t 5 to t 7 is equal to nV s , which is the reflection voltage of the primary side voltage. Therefore, the soft switching full bridge converter 1000 according to the embodiment of the present invention, Can be expressed by the following equation (19). &Quot; (19) "

&Quot; (19) "

Figure 112016105029154-pat00024

In Equation 19, D means the duty of the additional switch 134.

As described above, the soft switching full bridge converter 1000 according to the embodiment of the present invention is configured such that the clamp capacitor 131 is charged during t 1 to t 3 after the addition switch 134 is turned off, is a is turned on after the t 5 ~ t the clamp capacitor 131 for 7 can be discharged. At this time, the clamp capacitor 131 plays a role of a voltage source for t 5 to t 7 , so that no duty loss occurs, and a high DC voltage gain can be obtained.

In addition, the current ripple and the voltage ripple of the output inductor 125 can be calculated as shown in the following equations (20) and (21), respectively. Since the soft switching full bridge converter 1000 according to an embodiment of the present invention has no duty loss, the current and voltage ripple can also be calculated to be smaller than that of the conventional phase shift full bridge converter.

&Quot; (20) "

Figure 112016105029154-pat00025

&Quot; (21) "

Figure 112016105029154-pat00026

In the equations 20 and 21, V o is the output voltage, D is the duty of the additional switch 134, T s is the switching period, C o is the capacitance of the output capacitor 20, L o is the inductance of the output inductor 125 .

Lastly, the soft switching full bridge converter 1000 according to an embodiment of the present invention can reduce the voltage ringing of the rectifying diodes and the additional switches provided in the secondary circuit, and the snubber circuit provided in the secondary circuit can reduce It can serve as a non-dissipative turn-up snubber.

Specifically, voltage ringing of rectifier diodes is generally caused by resonance between the leakage inductance of the transformer and the junction capacitance of the rectifier, and this phenomenon occurs after the rectifying operation of the rectifier diodes, when the primary current reaches the output current of the output inductor . Also, when the voltage across the secondary winding of the transformer is zero and the current of the output inductor reaches the lowest current, the peak value of voltage ringing is twice the input voltage.

On the other hand, when the switch Q 1 is added to the secondary circuit as shown in Fig. 1, but the snubber circuit is not provided, the voltage ringing occurs after the secondary switch Q 1 is turned off, The resonance between the leakage inductance of the rectifier and the junction capacitance of the rectifier and the effective capacitance C eff of the secondary switch Q 1 . At this time, the voltage of the secondary winding of the transformer becomes equal to nVs, and the current of the output inductor can be the maximum value I LO_max . In this case, the inductive energy stored in the leakage inductance of the secondary side circuit can be expressed by Equation (22).

&Quot; (22) "

Figure 112016105029154-pat00027

In Equation 22, W L _ 1k represents the inductive energy of the secondary circuit, n represents the transformer turn ratio, L lk represents the inductance of the leakage inductor, and I LO_max represents the maximum current flowing through the output inductor.

In addition, the relationship between the capacitive energy and the voltage can be expressed by Equation 23 below.

&Quot; (23) "

Figure 112016105029154-pat00028

In Equation 23, C eff represents an effective capacitance of the secondary side switch Q 1 .

In the case of FIG. 1, when the secondary side switch Q 1 is turned off according to the equations (22) and (23), the voltage increase of the effective capacitance can be expressed by the following equation (24).

&Quot; (24) "

Figure 112016105029154-pat00029

Thus, even there is to the secondary side when the circuit switch (Q 1), but in addition to, the snubber circuit is not provided, the voltage ringing the switch (Q 1) in addition to the secondary circuit occurs, such as 1, the present invention The soft switching full bridge converter according to one embodiment of the present invention can prevent this phenomenon by adding a snubber circuit to the secondary circuit. This will be described with reference to Figs. 5A to 5C.

5A to 5C are examples of voltages measured at the primary or secondary switch shown in Figs. 1 and 2. Fig.

Referring to FIG. 5A, the turn-on or turn-off operation of the switch elements provided in the primary circuit and the secondary switch Q 1 can be confirmed.

Referring to FIG. 5B, it can be seen that the voltage of the secondary side switch Q 1 increases sharply during a short period of time because the effective capacitance C eff of the secondary side switch Q 1 is very small .

5C, a soft switching full bridge converter 1000 according to an exemplary embodiment of the present invention includes a non-dissipative CDD snubber circuit in a secondary circuit, It can be confirmed that the switch 134 is clamped, and the peak value can be calculated by the above-mentioned Equation (6).

Hereinafter, a beneficial effect of the soft switching full bridge converter 1000 according to an embodiment of the present invention will be described with reference to FIGS. 6A to 10.

FIGS. 6A to 10 illustrate advantageous effects of a soft switching full bridge converter according to an embodiment of the present invention.

First, to confirm the operation characteristics of the soft switching full bridge converter 1000 according to an embodiment of the present invention and to verify its effect, a converter having the specifications shown in Tables 1 and 2 below was designed, The current and the voltage across each device were measured.

Parameter Designator Value Nominal Input Voltage

Figure 112016105029154-pat00030
200 [V] Nominal Output Voltage
Figure 112016105029154-pat00031
400 [V]
Maximum Output Power
Figure 112016105029154-pat00032
3 [kW]
Primary switching frequency
Figure 112016105029154-pat00033
50 [kHz]
Secondary switching frequency
Figure 112016105029154-pat00034
100 [kHz]
Turn ratio of the SSFB transformer
Figure 112016105029154-pat00035
1: 2.5
Magnetizing inductance
Figure 112016105029154-pat00036
765 [uH]
Leakage inductance
Figure 112016105029154-pat00037
2 [uH]
Clamping capacitor
Figure 112016105029154-pat00038
25 [n
Figure 112016105029154-pat00039
Output inductor
Figure 112016105029154-pat00040
500 [uH]

Component Manufacturer Part # Primary side MOSFET Infineon 220N25NP Secondary side MOSFET Fairchild FCH041N65F Diode Rectifiers Vishay HFA50PA60 Snubber Film Capacitors Avago Z112688575
(22nF)
N113152287
(4.7 nF)

6A and 6B, it can be seen that the first switch 111 provided in the primary circuit and the first diode 121, which is a rectifier diode of the secondary rectifier circuit, achieve zero voltage switching turn-on and zero current switching turn-off Can be confirmed. At this time, it is possible to turn off the zero current switching of the second diode 122 to the fourth diode 124, which functions as a rectifier diode such as the first diode 121, thereby causing a reverse recovery problem .

Referring to FIG. 6C, it can be confirmed that the additional switch 134 provided in the secondary side circuit is completely clamped to 610 V because of the non-consuming CDD snubber circuit provided in the secondary side circuit.

Referring to FIG. 7A, it can be seen that the clamp capacitor 131 included in the snubber circuit of the secondary side circuit is charged to 610 V by resonance. 7B, it can be seen that the fifth diode 132 can achieve zero current switching turn-off and zero current switching turn-on. have. Referring to FIG. 7C, it can be confirmed that the sixth diode 133 is operated by hard switching, but it can be confirmed that the sixth diode 133 is clamped at 610V.

8A shows an example of a current flowing in the primary side switch and a voltage applied to the primary side switch under a light load condition (300 W, 10% load). Referring to FIG. 8A, It can be confirmed that the first to fourth switches 111 to 114 operate under soft switching conditions. This is because the transformer 100 can be designed to sufficiently discharge the output capacitance of the switches provided in the primary circuit during the dead time regardless of the load condition. 8B, it can be confirmed that the rectifier diodes of the rectifier circuit provided on the secondary side also operate under the soft switching condition even under the light load condition (300 W, 10% load). 8C, it can be seen that the additional switch 134 provided in the secondary side circuit operates under hard switching conditions under light load conditions, and the loss caused by the additional switch 134 operates in accordance with the soft switching The largest loss of the full bridge converter 1000 can be said.

9 is a graph showing the relationship between the output voltage of the soft switching full bridge converter 1000 and the output voltage of the conventional phase shift full bridge converter PSFB according to an embodiment of the present invention from an input voltage of 200V to 400V FIG. 5 is a graph showing the efficiency of outputting a voltage. FIG. Referring to FIG. 9, it can be seen that the soft switching full bridge converter 1000 according to an embodiment of the present invention has a maximum efficiency of 96% under an output condition of 500W. In particular, under light load conditions, it can be seen that the soft switching full bridge converter 1000 according to an embodiment of the present invention has a higher efficiency than the conventional phase shift full bridge converter (PSFB). This is because the soft switching full bridge converter 1000 according to the embodiment of the present invention is capable of soft switching of the switches and rectifying diodes provided in the primary side circuit and is free from the circulating current and serves as a non-consuming snubber to be. As the output power increases, the efficiency difference between the soft switching full bridge converter 1000 according to an embodiment of the present invention and the conventional phase shift full bridge converter (PSFB) becomes smaller. The loss increases due to the hard switching of the sixth diode provided in the secondary circuit of the soft switching full bridge converter 1000 according to one embodiment of the present invention.

FIG. 10 is a graph illustrating loss of a soft switching full bridge converter 1000 and a conventional phase shift full bridge converter (PSFB) according to an embodiment of the present invention under different load conditions. Referring to FIG. 10, it can be seen that a large difference occurs between the losses between the two converters due to the switches provided in the primary side circuit and the diodes of the rectifying circuit.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

1000: Soft switching full bridge converter 121: First diode
10: input capacitor 122: second diode
20: Output capacitor 123: Third diode
30: output load resistor 124: fourth diode
100: Transformer 125: Output inductor
111: first switch 130:
112: second switch 131: clamp capacitor
113: third switch 132: fifth diode
114: fourth switch 133: sixth diode
115: Leakage inductor 134: Additional switch
116: magnetizing inductor

Claims (16)

  1. A transformer for performing voltage conversion including a primary winding and a secondary winding;
    And a full bridge circuit connected to an input capacitor for supplying an input power and provided with first to fourth switches so that the input power is transmitted to the primary winding in accordance with a switching operation of the first switch to the fourth switch A primary side circuit; And
    A rectifier circuit connected to the secondary winding and having a first diode to a fourth diode, a clamp capacitor and a fifth diode connected to the rectifier circuit, a sixth diode provided between the clamp capacitor and the fifth diode, An additional circuit comprising an additional switch provided between the clamp capacitor and the sixth diode and an output inductor connected to the additional circuit so that the energy received from the primary circuit through the transformer is supplied to the output inductor and the additional And a secondary side circuit for transferring the output signal to an output capacitor connected to the circuit,
    The secondary side circuit includes:
    Wherein the rectifier is rectified by the first diode, the fourth diode and the fifth diode operating under soft switching conditions.
  2. The method according to claim 1,
    The secondary side circuit includes:
    Wherein the first diode and the fourth diode are provided on the third leg and the fourth leg, and the third leg and the fourth leg are connected in parallel, and the first diode and the fourth diode are provided on the third leg and the fourth leg, And the output voltage line includes the rectification circuit coupled to the secondary side winding.
  3. 3. The method of claim 2,
    The secondary side circuit includes:
    Wherein the anode of the sixth diode is connected to the contact between the one end of the clamp capacitor and the cathode of the fifth diode and the additional switch provided between the other end of the clamp capacitor and the cathode of the sixth diode Soft-switching full-bridge converter with circuitry.
  4. The method of claim 3,
    The secondary side circuit includes:
    The other end of the clamp capacitor and the one end of the additional switch are connected to the upper contact of the third leg and the fourth leg and the anode and the output of the fifth diode are connected to the lower contacts of the third leg and the fourth leg, Soft-switching full-bridge converter with capacitors connected.
  5. 5. The method of claim 4,
    The secondary side circuit includes:
    The other end of the additional switch and the cathode of the sixth diode are connected to one end of the output inductor and the other end of the output inductor is connected to the output capacitor.
  6. The method according to claim 1,
    The secondary side circuit includes:
    Wherein when the additional switch is turned off, the clamp capacitor is charged, and when the additional switch is turned on, the energy stored in the clamp capacitor is discharged to the output capacitor.
  7. The method according to claim 1,
    The secondary side circuit includes:
    And a closed loop by the fifth diode and the sixth diode is formed so that a freewheeling current of the output inductor can flow.
  8. ◈ Claim 8 is abandoned due to the registration fee.
    The method according to claim 1,
    The primary side circuit includes:
    A first switch and a second switch are provided on the first leg and the second leg, and the first switch and the second switch are connected to each other, A full bridge circuit in which a leakage inductor and a magnetizing inductor are provided on an input voltage line and the magnetizing inductor is connected in parallel with the primary winding.
  9. ◈ Claim 9 is abandoned upon payment of registration fee.
    The method according to claim 1,
    The primary side circuit includes:
    And said first switch operating under soft switching conditions transfers said input power to said primary winding in accordance with a switching operation of said fourth switch.
  10. ◈ Claim 10 is abandoned due to the registration fee.
    The method according to claim 1,
    The secondary side circuit includes:
    And the additional switch is turned on in the same manner as the first switch and the fourth switch, but turns off prior to the first switch and the fourth switch.
  11. delete
  12. A primary side circuit connected to the input capacitor performs a voltage conversion between an input capacitor for supplying input power and an output capacitor connected in parallel to the output load resistor, and the primary side circuit includes a full bridge circuit provided with the first to fourth switches And a secondary side circuit connected to the output capacitor includes a rectifying circuit, a clamp capacitor and a fifth diode connected to the rectifying circuit, a sixth diode provided between the clamp capacitor and the fifth diode, the clamp capacitor, A soft switching full bridge converter having an additional circuit comprising an additional switch provided between the primary and secondary circuits and an output inductor connected to the additional circuit and having a transformer for performing voltage conversion between the primary circuit and the secondary circuit, , The method comprising:
    In the primary side circuit,
    The first switch operating under the soft switching condition transmits the input power to the transformer according to the switching operation of the fourth switch,
    In the secondary circuit,
    A first diode to a fourth diode operating under soft switching conditions and a soft switching full bridge converter for rectifying the input power received from the primary side circuit through the transformer by the fifth diode and delivering the rectified input power to the output capacitor Way.
  13. 13. The method of claim 12,
    In the primary side circuit,
    Wherein the first switch and the fourth switch provided on the diagonal line of the full bridge circuit and the second switch and the third switch are paired to turn on or off in the same manner.
  14. 14. The method of claim 13,
    In the secondary circuit,
    Wherein the additional switch is turned on in the same manner as the first switch to the fourth switch, but is turned off earlier than the first switch to the fourth switch.
  15. ◈ Claim 15 is abandoned due to registration fee.
    15. The method of claim 14,
    In the secondary circuit,
    Wherein when the additional switch is turned off, the clamp capacitor is charged, and when the additional switch is turned on, the energy stored in the clamp capacitor is discharged to the output capacitor.
  16. ◈ Claim 16 is abandoned due to registration fee.
    16. The method of claim 15,
    In the secondary circuit,
    Wherein a closed loop is formed by the fifth diode and the sixth diode so that a freewheeling current of the output inductor can flow through the soft switching full bridge converter.
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