KR20180004655A - Hybrid full-bridge llc converter and control method thereof - Google Patents

Abstract

Disclosed are a hybrid full bridge LLC converter, and a driving method thereof. The hybrid full bridge LLC converter of the present invention which performs voltage conversion between an input capacitor for supplying an input voltage and a battery, and is operated in accordance with a constant current (CC) mode or a constant voltage (CV) for charging the battery, comprises: a switching unit connected to an input capacitor, and including a full-bridge circuit provided with first to fourth switches; a first full-bridge LLC converter including a first transformer connected to the switching unit to convert the input voltage transmitted through the switching unit, a first rectifier circuit for receiving the input voltage converted by the first transformer to rectify the same, and a first output capacitor connected to the first rectifier circuit; and a second full-bridge LLC converter including a second transformer connected to the switching unit to convert the input voltage transmitted through the switching unit, a second rectifier circuit for receiving the input voltage converted by the second transformer to rectify the same, and a second output capacitor connected to the second rectifier circuit. Therefore, zero voltage switching in a CC mode, and a main switching operation under a zero voltage switching condition can be performed, and the main switching operation can be performed under the zero voltage switching in the CC mode.

Description

HYBRID FULL-BRIDGE LLC CONVERTER AND CONTROL METHOD THEREOF FIELD OF THE INVENTION [0001]

The present invention relates to a hybrid full bridge LLC converter and a driving method thereof, and more particularly, to a hybrid full bridge LLC converter and a driving method thereof for a battery charging apparatus.

Electric vehicles (EVs) or plug-in hybrid EVs (PHEVs) can be used to increase energy security, reduce fuel costs, and reduce emissions. One of the important technical factors is an on-board charger (OBC) having high power density and efficiency in such EVs or plug-in hybrid electric vehicles (PHEVs).

The onboard charger (OBC) is generally composed of an AC-DC converter followed by a DC-DC converter, which can be charged and transferred to the vehicle's battery by a DC-DC converter. In order to further improve the manufacturing cost, stability and efficiency of the DC-DC converter for charging the battery, various studies have been conducted and commercialized. In particular, a full bridge LLC converter is most widely used. In this regard, the description will be made with reference to Fig.

1 is a circuit diagram of a conventional full bridge LLC converter.

Referring to FIG. 1, it can be seen that four switches S1, S2, S3, and S4 are provided on the primary side of the converter. All of the switches on the primary side of the full bridge LLC converter, Zero voltage switching (ZVS) can be achieved. In addition, the full-bridge LLC converter can turn off all the switches on the primary side at a low current when the output voltage range is narrow, and the zero-current switching (ZCS) of the rectifying diodes D1, D2, D3 and D4 .

However, the battery charger requires a constant current (CC) and a constant voltage (CV) mode. In the CC mode, the output voltage varies in a wide range according to the battery's state of charge (SOC) And the resonance efficiency is reduced. That is, in a wide range of switching frequencies, a high circulating current is generated at a lowest switching frequency, a high current turn-off occurs at a maximum switching frequency, and it is difficult to achieve an optimized design.

Therefore, a control method combining a phase shift and a frequency shift for minimizing a circulating current generated in a full bridge LLC converter has been proposed. This is a control method for reducing the circulating current under light load condition. The control is carried out under heavy load condition. In the case of under light load condition, Based on the duty cycle, the phase angle between the leading-leg and the lagging-leg of the primary side full bridge circuit can be controlled. According to this method, as the circulating current is reduced, the turn-off current is also removed to realize a better switching operation under the light load condition. However, as described above, the circulating current under the light load condition can be reduced, A better effect under the conditions is unexpected.

In addition, optimization design methods have been proposed to overcome the shortcomings of full bridge LLC converters. For example, there is a method of increasing the adjustment range and conversion efficiency of an output voltage under light load conditions using resonance inductance, a method of removing low frequency and high frequency current ripple in a battery, A resonant tank design method, and a time-averaged weight index based on a charge profile feature for optimizing parameters have been proposed. However, all of these approaches are difficult to completely solve the problem of a full bridge LLC converter because the switching loss of semiconductor devices depends on the circuit topology.

Meanwhile, a dual-bridge LLC converter has been proposed as a DC-DC converter for charging a battery. This is because the fixed frequency PWM control scheme is applied to freely adjust the voltage gain range from the quality factor and reduce the influence of the magnetizing inductance on the DC gain so that a large inductor can be applied, The current can be reduced. However, this dual-bridge LLC converter requires two additional active switches to change from half-bridge to full-bridge, with the problem that a total of six switch elements have a specific turn-off current.

Referring again to FIG. 1, a typical full bridge LLC converter has two resonant frequencies, one of which is to maintain a constant output current at a resonant frequency generated by the sum of resonant capacitors and resonant inductors and magnetizing inductors, And the other is a resonance frequency generated by the resonance capacitor and the resonance inductor so that the output voltage remains constant regardless of the change of the load. At this time, if the Full Bridge LLC converter is designed to operate at a constant-current frequency for the CC mode and to operate at a constant-voltage frequency for the CV mode applied to the battery charger, A circulating current does not occur, but in the CC mode, it operates in a capacitive region, causing ZVS turn-on damage of the switches provided in the full bridge circuit.

One aspect of the invention is a hybrid full bridge LLC converter comprising a first full bridge LLC converter operating under fixed resonant network conditions and a second full bridge LLC converter operating under resonant network conditions varying between CC mode and CV mode, Thereby providing a driving method.

A hybrid full bridge LLC converter according to one aspect of the present invention performs voltage conversion between an input capacitor for supplying an input voltage and a battery, and operates in accordance with a constant current (CC) mode or a constant voltage (CV) A full bridge bridge LLC converter including a full bridge circuit connected to the input capacitor and having first to fourth switches, and a switching unit connected to the switching unit to convert the input voltage transmitted through the switching unit A first full bridge LLC converter including a first transformer, a first rectifier circuit for receiving and rectifying the input voltage converted through the first transformer, and a first output capacitor connected to the first rectifier circuit, A second transformer connected to convert the input voltage transmitted through the switching unit, And a second full bridge LLC converter including a second rectifier circuit for receiving and rectifying the input voltage converted by the amplifier, and a second output capacitor connected to the second rectifier circuit.

Meanwhile, the first full-bridge LLC converter may include a first leakage inductor, a first magnetizing inductor, and a first resonating capacitor on the primary side of the first transformer so as to form a resonant network.

The second full bridge LLC converter includes a second leakage inductor, a second magnetizing inductor, and a CC mode capacitor on the primary side of the second transformer so as to form a resonant network, and the CC mode capacitor is connected in series CV mode capacitors and mode switches.

The second full bridge LLC converter maintains the turn-off state of the mode switch when operating in the CC mode, maintains the turn-on state of the mode switch when operating in the CV mode, The resonant network conditions can be changed between the modes.

The first output capacitor and the second output capacitor are connected in series, and the first output capacitor and the second output capacitor connected in series may be connected in parallel with the battery.

The switching unit may include first and second legs connected in parallel, wherein the first switch and the second switch are provided on the first leg, and the third switch and the fourth switch are provided on the second leg, A switch may be provided.

The first switch to the fourth switch may be connected in parallel with a parasitic capacitor and a body diode, respectively.

Further, the first rectifying circuit includes a third leg and a fourth leg connected in parallel,

A first diode and a third diode may be provided on the third leg, and a second diode and a fourth diode may be provided on the fourth leg.

Further, the second rectifying circuit includes a fifth leg and a sixth leg connected in parallel,

A fifth diode and a seventh diode may be provided on the fifth leg, and a sixth diode and an eighth diode may be provided on the sixth leg.

According to another aspect of the present invention, there is provided a method of driving a hybrid full bridge LLC converter, comprising: operating according to a constant current (CC) mode or a constant voltage (CV) mode for charging the battery between an input capacitor for supplying an input voltage and the battery, And a first full bridge LLC converter and a second full bridge LLC having a separate secondary circuit and sharing a switching unit connected to the input capacitor and composed of a full bridge circuit of the first to fourth switches as a primary circuit, Wherein the first full bridge LLC converter performs voltage conversion under the same resonant network conditions when operating in the CC mode and the CV mode, , And the second full bridge LLC converter is configured to switch between the CC mode and the CV mode And performing a voltage conversion under different resonant network condition passes the input voltage to the battery.

On the other hand, the first full-bridge LLC converter includes a first transformer for performing voltage conversion between the primary circuit and the secondary circuit, and a first leakage inductor A first magnetizing inductor and a first resonance capacitor are provided to perform voltage conversion under the same resonance network conditions when operating in the CC mode and the CV mode.

The second full bridge LLC converter further includes a second transformer for performing a voltage conversion between the primary circuit and the secondary circuit, and a second leakage inductor Mode capacitor is connected in parallel to a CV mode capacitor and a mode switch connected in series so that the CC mode capacitor and the CV mode capacitor are connected in parallel to each other in the CC mode and the CV mode according to the switching operation of the mode switch. It is possible to perform voltage conversion under resonant network conditions.

The second full bridge LLC converter maintains the turn-off state of the mode switch when operating in the CC mode, maintains the turn-on state of the mode switch when operating in the CV mode, The resonant network conditions can be changed between the modes.

In operation in the CC mode, a current flowing in the switching unit according to a turn-on or a turn-off operation of the first switch to the fourth switch is supplied to the primary side of the first full bridge LLC converter and the second full bridge LLC converter To the primary side.

According to the present invention described above, the main switching operation is possible under the zero voltage switching and almost zero current switching conditions in the CC mode, and the main switching operation is possible under the zero voltage switching condition in the CV mode. In addition, only one additional switch is added to convert the resonant tank so that switching losses associated with this are not generated. Further, since both the CC mode and the CV mode operate on a fixed resonance frequency, low circulating energy is generated. In addition, resonant operation over the CC mode and CV mode allows full soft-switching to the rectifier diodes, which may not result in reverse recovery current problems. In addition, two converters and two rectifying bridges can be connected in series to provide a high voltage gain and a low voltage rate of the rectifier diode.

1 is a circuit diagram of a conventional full bridge LLC converter.
2 is a schematic circuit diagram of a hybrid full-bridge LLC converter according to an embodiment of the present invention.
3 is an AC equivalent circuit diagram of a single full bridge LLC converter.
4 is an AC equivalent circuit of a hybrid full bridge LLC converter when operating in CC mode.
5 is a graph showing the voltage gain characteristics of the first full bridge LLC converter and the output current characteristics of the second full bridge LLC converter according to different load states.
6 is an AC equivalent circuit of a hybrid full bridge LLC converter in operation in the CV mode.
7 is a diagram showing voltage gain characteristics of the first full bridge LLC converter and the second full bridge LLC converter under different load conditions.
8 is a diagram showing voltage applied to each device or current flowing in each device according to time when the hybrid full-bridge LLC converter according to an embodiment of the present invention operates in the CC mode.
9 is a flowchart showing a specific method of designing a resonance tank of a hybrid full-bridge LLC converter.
10 is a diagram showing the relationship between the magnitude of the RMS value of the primary side current and the second magnetizing inductance under a certain condition.
FIG. 11 is a graph showing input impedance characteristics of a hybrid full bridge LLC converter designed according to the resonant tank designing method of FIG. 9 according to changes in battery impedance.
12 is a circuit diagram of a hybrid full-bridge LLC converter according to another embodiment of the present invention.
FIGS. 13 to 18 are examples of waveforms in the respective devices when the hybrid full-bridge LLC converter operates in the CC mode according to an embodiment of the present invention.
FIGS. 19 to 24 are examples of waveforms in the respective devices when the hybrid full-bridge LLC converter according to the embodiment of the present invention operates in the CV mode.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the present invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is noted that the terms " comprises "and / or" comprising ", as used herein, do not exclude the presence or addition of one or more other elements, steps and operations.

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 hybrid full-bridge LLC converter according to an embodiment of the present invention.

Referring to FIG. 2, the hybrid full bridge LLC converter 1000 according to the present embodiment is a DC-DC converter included in the battery charging device, performs voltage conversion between the input capacitor 10 and the battery 20, The first full bridge LLC converter 100 and the second full bridge LLC converter 200 share a switching unit 300 composed of switch elements on the primary side.

Such a hybrid full bridge LLC converter 1000 operates as a voltage source or current source on a constant resonance frequency, such as an LLC resonant converter. That is, the hybrid full bridge LLC converter 1000 may operate in a constant current (CC) mode or a constant voltage (CV) mode for battery charging. Specifically, the CC mode is implemented by operating the first full bridge LLC converter 100 and the second full bridge LLC converter 200 respectively as voltage and current sources, and the CV mode is implemented by the first full bridge LLC converter 100 And the second full-bridge LLC converter 200 all operate as a voltage source.

Hereinafter, each component of the hybrid full bridge LLC converter 1000 according to an embodiment of the present invention shown in FIG. 2 will be described in detail.

The first full bridge LLC converter 100 is a DC-DC resonance type converter in which a primary side circuit and a secondary side circuit are electrically insulated from each other around a first transformer 110, and a primary side circuit includes a first switch 310, Bridge circuit including the fourth switch 340 and the secondary circuit may include a rectifying circuit provided with the first diode 131 to the fourth diode 134. [

The primary side circuit of the first full bridge LLC converter 100 is connected to the input capacitor 10 and the secondary side circuit is connected to the battery 20 and is connected to the input capacitor 10 To the battery 20, as shown in FIG.

Specifically, the first full bridge LLC converter 100 may include a first transformer 110 that converts the voltage of the primary circuit at a ratio of 1: n1 and transfers the converted voltage to the secondary circuit. In other words, the first transformer 110 is composed of a primary winding and a secondary winding, the primary winding is connected to the primary circuit of the first full bridge LLC converter 100 and the secondary winding is connected to the first full bridge LLC converter And may be connected to the secondary circuit of the microcomputer 100.

The primary side circuit of the first full bridge LLC converter 100 includes a switching unit 300, a first leakage inductor 121 connected to the switching unit 300, a first magnetizing inductor 122 and a first resonance capacitor 123). At this time, the first leakage inductor 121 may serve as a resonance inductor of the first transformer 110.

Meanwhile, the switching unit 300 connected to the primary circuit of the first full bridge LLC converter 100 is shared with the primary circuit of the second full bridge LLC converter 200. The switching unit 300 includes a first leg 300-1 and a second leg 300-2 connected in parallel. The upper contact and the lower contact of the first leg 300-1 and the second leg 300-2 may be respectively connected to both ends of the input capacitor 10. The upper and lower contacts of the first leg 300-1 and the second leg 300-2 may be connected to both ends of the input capacitor 10, The first switch 310 and the second switch 320 may be provided and the third switch 330 and the fourth switch 340 may be provided on the upper and lower sides of the second leg 300-2, . In this case, the first to third switches 310 to 340 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 of the first full bridge LLC converter 100 is connected to the first input voltage line 300-2 connecting the first leg 300-1 and the second leg 300-2 of the switching unit 300, 3). Specifically, the first input voltage line 300-3 is connected to the first contact a between the first switch 310 and the second switch 320 in the first leg 300-1 and the second contact 120- 2, the second contact b between the third switch 123 and the fourth switch 124 is connected. A first leakage inductor 121, a first magnetizing inductor 122 and a first resonating capacitor 123 are provided on the first input voltage line 300-3 to form a resonant network of the first full bridge LLC converter 100 can do. At this time, the first magnetizing inductor 122 may be connected in parallel with the primary winding of the first transformer 110. [

The secondary circuit of the first full bridge LLC converter 100 includes a first rectifying circuit composed of a first diode 131 to a fourth diode 134 and a first rectifying circuit composed of a first output capacitor 135 ).

Here, the first rectifying circuit includes a third leg 130-1 and a fourth leg 130-2 connected in parallel in the form of a full bridge circuit. The upper contact and the lower contact of the third leg 130-1 and the fourth leg 130-2 may be respectively connected to both ends of the first output capacitor 135 and the upper and lower contacts of the third leg 130-1 and 130-2 may be connected to both ends of the first output capacitor 135, A first diode 131 and a third diode 133 are provided on the lower side and a second diode 132 and a fourth diode 134 are provided on the upper side and the lower side of the fourth leg 130-2, .

The secondary circuit of the first full bridge LLC converter 100 is connected to the first output voltage line 130-3 (130-3) connecting the third leg 130-1 and the fourth leg 130-2 of the first rectifier circuit. ). More specifically, the first output voltage line 130-3 is connected between the first diode 131 and the third diode 133 in the third leg 130-1 and the second diode 133 in the fourth leg 130-2. A secondary winding of the first transformer 110 may be provided on the first output voltage line 130-3 as a line connecting the contact between the diode 132 and the fourth diode 134. [

The second full bridge LLC converter 200 is a DC-DC resonance type converter in which a primary side circuit and a secondary side circuit are electrically insulated from each other around a second transformer 210, and the primary side circuit includes a first switch 310, Bridge circuit including the fourth switch 340 and the secondary circuit may be connected to the second rectification circuit provided with the fifth diode 231 to the eighth diode 234. [ In particular, the second full bridge LLC converter 200 may include two resonant capacitors in the primary circuit, unlike the first full bridge LLC converter 100, to change the equivalent capacitors of the resonant network in CC mode and CV mode have. A detailed description thereof will be given later.

The primary side circuit of the second full bridge LLC converter 200 is connected to the input capacitor 10 through the switching unit 300 and the secondary side circuit is connected to the battery 20 so that the second transformer 210 To convert the voltage of the input capacitor 10 to the battery 20.

Specifically, the second full bridge LLC converter 200 may include a second transformer 210 that converts the voltage of the primary circuit at a turn ratio of 1: n2 and transfers the converted voltage to the secondary circuit. That is, the second transformer 210 is composed of a primary winding and a secondary winding, the primary winding is connected to the primary circuit of the second full bridge LLC converter 200, and the secondary winding is connected to the second full bridge LLC And may be connected to the secondary circuit of the converter 200.

The primary side circuit of the second full bridge LLC converter 200 is connected to the switching unit 300 which is shared with the primary side circuit of the first full bridge LLC converter 100 as described above and the second leakage inductor 221, A second magnetization inductor 222 and a CC mode capacitor 223 and a CV mode capacitor 224 connected in parallel. At this time, the second leakage inductor 221 may serve as a resonant inductor of the second transformer 210.

The primary side circuit of the second full bridge LLC converter 200 is connected to the second input voltage line 300-2 connecting the first leg 300-1 and the second leg 300-2 of the switching unit 300, 4). Specifically, the second input voltage line 300-4 has a first contact a between the first switch 310 and the second switch 320 and a second contact 300b between the second leg 300- (B) between the third switch (330) and the fourth switch (340) in the second switch (2). A second leakage inductor 221, a second magnetizing inductor 222 and a CC mode capacitor 223 are provided on the second input voltage line 300-4 and the CC mode capacitor 223 is connected in series Can be connected in parallel with the CV mode capacitor 224 and the mode switch 225 to form the resonant network of the second full bridge LLC converter 200. In this case, the second magnetizing inductor 222 may be connected in parallel with the primary winding of the second transformer 210. [ Accordingly, the equivalent capacitor in the resonant network of the second full-bridge LLC converter 200 can be changed in accordance with the switching operation of the mode switch 225. This mode switch 225 is turned off when operating in the CC mode, Mode can be turned on.

The secondary circuit of the second full bridge LLC converter 200 includes a second rectifying circuit composed of the fifth diode 231 to the eighth diode 234 and a second output capacitor 235 connected to the second rectifying circuit ). The second output capacitor 235 may be connected in series with the first output capacitor 135 included in the secondary circuit of the first full bridge LLC converter 100 and may include a first output capacitor 135 and a second output capacitor 135 connected in series. A second output capacitor 235 may be connected across the battery 20.

In addition, the second rectifier circuit includes a fifth leg 230-1 and a sixth leg 230-2 connected in parallel in the form of a full bridge circuit, and the fifth leg 230-1 and the sixth leg 230-2 may be connected to both ends of the second output capacitor 235, respectively. A fifth diode 231 and a seventh diode 233 are provided on the upper side and the lower side of the fifth leg 230-1 and a sixth diode 233 is provided on the upper side and the lower side of the sixth leg 230-2, 232 and an eighth diode 234 may be provided.

The secondary circuit of the second full bridge LLC converter 200 is connected to the second output voltage line 230-3 (230-3) connecting the fifth leg 230-1 and the sixth leg 230-2 of the second rectifying circuit. ) Can be connected. Specifically, the second output voltage line 230-3 is connected between the fifth diode 231 and the seventh diode 233 in the fifth leg 230-1, and the sixth and seventh legs 230-2, A secondary winding of the second transformer 210 may be provided on the second output voltage line 230-3 as a line connecting the contact between the diode 232 and the eighth diode 234. [

As described above, the hybrid full bridge LLC converter 1000 according to an embodiment of the present invention is configured in such a manner that the first full bridge LLC converter 100 and the second full bridge LLC converter 200 are combined. The first full bridge LLC converter 100 and the second full bridge LLC converter 200 are connected to the input capacitor 10 and are connected to the switching unit 100 of the full bridge circuit provided with switch elements for transmitting the input voltage Vdc to the transformer. (300). In particular, the second full bridge LLC converter 200 may further include a separate external circuit provided with a resonant capacitor to change the resonant network conditions according to the CC charging mode or the CV charging mode of the battery 20 connected to the output terminal have.

Hereinafter, the operation characteristics and the driving principle of the single full bridge LLC converter shown in FIG. 1 will be described.

3 is an AC equivalent circuit diagram of the single full bridge LLC converter shown in FIG. The AC equivalent circuit diagram of the single full bridge LLC converter shown in FIG. 3 is a circuit derived by First Harmonic Approximation (FHA) and has two resonant frequencies f _r1 and f _r2 .

Specifically, the first resonance frequency f _r1 is a high frequency of the two resonance frequencies, and is determined by the resonance inductor L _r and the capacitance C _r of the resonance capacitor, and can be expressed by Equation 1 below .

[Equation 1]

Also, the output voltage of this single full bridge LLC converter can be expressed by Equation (2).

&Quot; (2) "

Therefore, when the single full bridge LLC converter operates at the first resonant frequency f _r1 , since the coefficient of the AC load resistance R _ac in Equation (2) becomes '0', the voltage gain becomes a value independent of the load change . Thus, the full bridge LLC converter can operate as a constant voltage source on the first resonant frequency (f _r1 ), and the switches on the primary side can achieve Zero Voltage Switching (ZVS) turn on.

The second resonance frequency f _r2 is a lower one of the two resonance frequencies and is expressed by the following equation 3 by the resonance inductor L _r , the capacitance C _r of the resonance capacitor, and the inductance L _m of the magnetizing inductor .

&Quot; (3) "

In addition, the output current of this single full bridge LLC converter can be expressed by Equation (4).

&Quot; (4) "

Therefore, when the single full bridge LLC converter operates at the second resonant frequency f _r2 , the coefficient of the AC load resistance R _ac in Equation (4) becomes '0', so that the output current is a value independent of the load change . Thus, the full bridge LLC converter can operate as a constant current source on the second resonant frequency (f _r2 ). However, a single full-bridge LLC converter with such a second resonant frequency can achieve Zero Current Switching (ZCS) turn-off, but can not achieve ZVS turn-on, which is an undesirable aspect in terms of switch power .

Hereinafter, the operation characteristics and driving principle of the hybrid full bridge LLC converter 1000 shown in FIG. 2 will be described in comparison with the single full bridge LLC converter described above.

The hybrid full bridge LLC converter 1000 according to the present embodiment includes two full bridge LLC converters that share a switching unit on the primary side.

The first full bridge LLC converter of such a hybrid full bridge LLC converter is always designed to operate as a voltage source on the first resonant frequency. The second full bridge LLC converter, on the other hand, is further designed to operate as a current source in the CC mode and as a voltage source in the CV mode, by further including a mode switch for converting the resonance frequency and resonance frequency. That is, the first full bridge LLC converter performs voltage conversion under the same resonant network conditions in both the CC mode and the CV mode to transfer the input voltage to the battery. In addition, the second full bridge LLC converter performs voltage conversion between the CC mode CV modes under different resonant network conditions to transmit the input voltage to the battery.

Table 1 shows the use relationships of the resonance tank and the resonance frequency in the resonance tank, the resonance frequency, the CC mode, and the CV mode in the hybrid full bridge LLC converter according to the present embodiment.

)가 사용됨을 살 수 있다. As shown in Table 1, the first full bridge LLC converter (FBLLC1 converter) includes a resonance tank including inductances Llk1 and Lm1 of the first leakage inductor and the first magnetizing inductor and a capacitance Cr1 of the first resonance capacitor Both in the CC mode and the CV mode, the first resonance frequency (

) Can be used.

,

) 및 CC 모드 커패시터의 커패시턴스(

)를 포함하는 제 1 공진 탱크와, 제 2 누설 인덕터 및 제 2 자화 인덕터의 인덕턴스(

,

) 및 CC 모드 및 CV 모드 커패시터의 커패시턴스의 합과 같은 커패시턴스

를 포함하는 제 2 공진탱크를 포함한다. On the other hand, the second full bridge LLC converter (FBLLC2 converter) converts the inductance of the second leakage inductor and the second magnetizing inductor

,

) And the capacitance of the CC mode capacitor (

, And a second resonance tank including an inductance of the second leakage inductor and the second magnetization inductor

,

) And a capacitance equal to the sum of the capacitance of the CC mode and the CV mode capacitor

And a second resonant tank.

In the CC mode, the second resonant frequency of the second full bridge LLC converter (FBLLC2 converter) and a second resonant frequency and operating as a current source in (f _{r2 _ LLC2),} wherein the second full-bridge LLC converter (FBLLC2 converter) (f _{r2 _ LLC2} ) may be designed to be the same as the first resonant frequency (f _{r1_LLC1} ) of the first full bridge LLC converter (FBLLC1 converter).

On the other hand, in CV mode, the mode switch is turned on to operate at a first resonant frequency (f _{r1 _ LLC3)} a voltage source a second full bridge LLC converter (FBLLC2 converter) in. In addition, it is possible to operate on a first full bridge LLC converter (FBLLC1 converter) and a second full bridge LLC converter (FBLLC2 converter) are each of a first resonant frequency (f _{r1 _ LLC1,} f _{r1 _ LLC3).} On the other hand, when the mode switch is turned on, the resonance tank of the second full bridge LLC converter (FBLLC2 converter) can be converted so as to resonate on the first resonance frequency ( _{fl1_LLC3} ).

4 is an AC equivalent circuit of a hybrid full bridge LLC converter when operating in CC mode.

First, in CC mode, a first full bridge LLC converter operates as a voltage source, and a second full bridge LLC converter operates as a current source.

In addition, the output voltage (V _o1 ) of the first full bridge LLC converter must be designed to be lower than the output voltage of the minimum battery voltage (e.g., 250V) since the entire converter must be operated as a current source. In the second full bridge LLC converter side, since the mode switch is off in the CC mode, the resonance tanks of the second full bridge LLC converter may be composed of Llk2, Lm2, and Cr2. At this time, the second resonant frequency of the full bridge LLC first resonant frequency (f _{r1_LLC1)} and the second full bridge LLC converter of the converters (f _{r2 _ LLC2)} can be expressed by equation (5) and Equation (6) below, respectively .

&Quot; (5) "

&Quot; (6) "

On the other hand, as shown in Fig. 4, since the two converters share the primary side switch, the resonance tanks of the two converters must be designed to have the same resonance frequency. That is, the first full-bridge LLC first resonant frequency (f _{r1 _ LLC1)} and the second resonant frequency (f _{r2 _ LLC2)} of the second full bridge LLC converter of the converter may be the same design on the CC mode, and as a result As shown in Fig. 5 is a graph showing the voltage gain characteristics (FIG. 5A) of the first full bridge LLC converter and the output current characteristics (FIG. 5B) of the second full bridge LLC converter according to different load states to be. 5, it can be seen that both the first full bridge LLC converter and the second full bridge LLC converter resonate at the switching frequency fs, whereby the first full bridge LLC converter is a constant voltage source and the second full bridge LLC converter Respectively, as a constant current source.

으로 나타낼 수 있고, 제 2 풀브릿지 LLC 컨버터는 상수 전류 소스

로 나타낼 수 있으며, 각각의 상수 전압 소스

및 상수 전류 소스

는 아래 수학식 7 및 수학식 8 과 같은 관계식을 갖는다.4, the first full bridge LLC converter includes a constant voltage source

And the second full bridge LLC converter can be represented by a constant current source

Respectively, and each constant voltage source

And constant current sources

(7) and (8): " (7) "

&Quot; (7) "

Where n ₁ is the turn ratio of the first transformer of the first full bridge LLC converter.

&Quot; (8) "

)는 CC 모드 상에서의 배터리의 충전 전류(

)와 같아야 한다. 따라서, 제 1 풀브릿지 LLC 컨버터 및 제 2 풀브릿지 LLC 컨버터의 출력 파워는 아래 수학식 9 와 같이 정의될 수 있다. On the other hand, in the CC mode, the outputs of the two converters which are the voltage source and the current source are connected in series, and the output current of the second full bridge LLC converter

) Is the charge current of the battery in CC mode (

). Therefore, the output powers of the first full bridge LLC converter and the second full bridge LLC converter can be defined by Equation (9) below.

&Quot; (9) "

,

,

Here, the output voltage of the first full bridge LLC converter may be designed to be one half of the maximum battery voltage (e.g., 210V) that is less than the minimum battery voltage (e.g., 250V) so that the charge current of the battery is only limited to the second full bridge LLC Can be determined by the output current of the converter.

6 is an AC equivalent circuit of a hybrid full bridge LLC converter in operation in the CV mode.

,

, 및 병렬로 연결된 공진 커패시턴스(

,

)의 합성 커패시턴스 값

이다. 따라서, CV 모드 상에서의 제 2 풀브릿지 LLC 컨버터의 공진 주파수는 아래 수학식 10 과 같다. First, the mode switch must be turned on to operate the Hybrid Full Bridge LLC converter in CV mode. As a result, the resonance tank on the side of the second full bridge LLC converter is changed, and as shown in Fig. 6, the changed resonance tank

,

, And the resonant capacitance connected in parallel (

,

) ≪ / RTI >

to be. Thus, the resonant frequency of the second full bridge LLC converter in the CV mode is given by Equation 10 below.

&Quot; (10) "

In addition, the two, so the converter is to be resonant at the same switching frequency on the CV mode, the first full-bridge first resonant frequency of the LLC converter first resonant frequency (f _{r1 _ LLC1)} and the second full bridge LLC converter (f _{r1 _ LLC3} shall be designed the same. 7 is a diagram showing the voltage gain characteristics of the first full bridge LLC converter (FIG. 7A) and the second full bridge LLC converter (FIG. 7B) under different load conditions. Referring to FIG. 7, it can be seen that both the first full bridge LLC converter and the second full bridge LLC converter resonate at the switching frequency fs, so that both converters can operate as constant voltage sources.

는 아래 수학식 11 과 같고, 여기서 n₂는 제 2 풀브릿지 LLC 컨버터의 제 2 변압기의 턴비이다. 6, the output of the second full bridge LLC converter, which is a constant voltage source

It is equal to Equation 11 below, where n ₂ is the turns ratio of the second transformer of the second full bridge LLC converter.

&Quot; (11) "

,

)가 직렬 연결된 상태이므로, CV 모드 상에서의 컨버터 출력(V_o)은 아래 수학식 12 와 같이 표현될 수 있다. Further, the output side has two voltage sources (

,

) Is connected in series, the converter output (V _o ) in the CV mode can be expressed by Equation (12) below.

&Quot; (12) "

8 is a diagram showing voltage applied to each device or current flowing in each device according to time when the hybrid full-bridge LLC converter according to an embodiment of the present invention operates in the CC mode.

Referring to FIG. 8, the hybrid full bridge LLC converter according to the present embodiment is configured such that, when operating in the CC mode, the first to fourth switches of the switching unit provided on the primary side of the first transformer and the second transformer are turned on or off It can operate in four operation modes. At this time, the mode switch included in the second full bridge LLC converter is always turned off.

]를 살펴보면, 먼저 제 2 스위치 및 제 3 스위치는 t=

에서 거의 영전류(ZCS) 스위칭 조건하에 턴 오프될 수 있다. 제 2 및 제 3 스위치가 턴 오프되면, 하이브리드 풀브릿지 LLC 컨버터의 1차측 전류(

) 는 제 1 스위치 및 제 4 스위치의 출력 커패시터를 방전시키고, 이로 인해 제 1 및 제 4 스위치가 모두 방전되어 제 1 및 제 4 스위치에 걸리는 전압이 '0' 이 되면, 제 1 및 제 4 스위치의 바디 다이오드로 전류가 흐름으로써 영전압 스위칭(ZVS) 조건이 달성될 수 있다. 이때, 제 1 자화전류

의 기울기값은 아래 수학식 13 을 따른다.Specifically, in the first operation mode [

], The second switch and the third switch are connected at t =

Lt; RTI ID = 0.0 > (ZCS) < / RTI > When the second and third switches are turned off, the primary side current of the hybrid full bridge LLC converter (

) Discharges the output capacitors of the first and fourth switches. When the first and fourth switches are discharged and the voltage applied to the first and fourth switches is '0', the first and fourth switches ZVS conditions can be achieved by allowing current to flow through the body diode of the switch. At this time, the first magnetizing current

The following equation (13) is satisfied.

&Quot; (13) "

]에서는, 먼저 제 1 및 제 4 스위치가 t=

에서 영전압 스위칭 조건 하에 턴온된다. 또한, 제 1 누설 인덕턴스(

) 및 제 1 컨덕턴스(C_r1)로 구성된 제 1 풀브릿지 LLC 컨버터의 공진 탱크가 공진하기 시작하고 이로 인해 제 1 풀브릿지 LLC 컨버터의 일차측 전류(

)는 아래 수학식 14 와 같이 나타낼 수 있다.Thereafter, the second operation mode [

], First, the first and fourth switches are turned on at t =

Lt; / RTI > under zero voltage switching conditions. Also, the first leakage inductance (

) And the first conductance ( _Cl1 ) of the first full bridge LLC converter begin to resonate and thereby cause the primary side current of the first full bridge LLC converter

) Can be expressed by the following equation (14).

&Quot; (14) "

는 각스위칭 주파수(

)에서의 제 1 풀브릿지 LLC 컨버터의 입력 임피던스이고,

는 전압

의 기본 주파수 성분에 대한 1차측 전류의 위상각이다. here,

() ≪ / RTI >

) Is the input impedance of the first full bridge LLC converter,

The voltage

Is the phase angle of the primary side current to the fundamental frequency component of the primary side.

), 제 2 누설 인덕턴스(L_lk2), 제 2 커패시턴스(

)로 구성된 공진 탱크도 동시에 공진하기 시작하며, 이때 제 2 풀브릿지 LLC 컨버터의 일차측 전류(

)는 아래 수학식 15 와 같이 나타낼 수 있다. Also, the second magnetizing inductance of the second full bridge LLC converter (

), A second leakage inductance (L _lk2 ), a second capacitance

Resonant tank begins to resonate at the same time, where the primary side current of the second full bridge LLC converter

) Can be expressed by the following equation (15).

&Quot; (15) "

는 각스위칭 주파수(

)에서의 제 2 풀브릿지 LLC 컨버터의 입력 임피던스이고,

는 전압

의 N번째 성분에 대한 N번째 1차측 전류의 위상각이다. here,

() ≪ / RTI >

) Is the input impedance of the second full bridge LLC converter,

The voltage

Of the Nth primary current of the Nth component of the Nth primary current.

,

)의 합은 도 8 에 도시된 바와 같이, 일차측 스위칭부의 전류값(

)과 같다. 즉, 제 1 스위치 내지 제 4 스위치의 턴온 또는 턴오프 동작에 따라 스위칭부에 흐르는 전류는 제 1 및 제 2 풀브릿지 LLC 컨버터의 1차측으로 흐르는 것이다. On the other hand, the primary side current (< RTI ID = 0.0 >

,

) Is calculated by multiplying the current value of the primary side switching unit (

). That is, the currents flowing in the switching unit according to the turn-on or turn-off operations of the first to fourth switches flow to the primary side of the first and second full bridge LLC converters.

]에서는,

에서 제 2 풀브릿지 LLC 컨버터의 일차측 전류의 크기값이 제 2 변압기의 자화 전류의 크기값과 같아진다. 이로 인해 제 2 변압기에 의한 파워 변환이 종료되고, 제 5 다이오드가 영전류 스위칭(ZCS) 조건하에 턴 오프될 수 있다. 또한, 제 3 동작 모드 상에서는, 제 1 및 제 2 풀브릿지 LLC 컨버터의 일차측 전류가 상술한 수학식 14 및 수학식 15 에 따르므로, 제 2 자화 전류(

) 값은 아래 수학식 16 과 같이 표현될 수 있다. Third operating mode [

],

The magnitude value of the primary side current of the second full bridge LLC converter becomes equal to the magnitude value of the magnetizing current of the second transformer. This causes the power conversion by the second transformer to be terminated, and the fifth diode can be turned off under the zero current switching (ZCS) condition. Further, in the third operation mode, since the primary side currents of the first and second full bridge LLC converters are according to the above-described expressions (14) and (15), the second magnetization current

) Can be expressed by Equation (16) below.

&Quot; (16) "

]에서는,

에서 제 1 및 제 4 스위치가 거의 영전류 스위칭(ZCS) 조건하에 턴오프될 수 있고, 제 1 다이오드가 영전류 스위칭(ZCS) 조건 하에 턴 오프될 수 있다. Fourth operation mode [

],

The first and fourth switches can be turned off under substantially zero current switching (ZCS) conditions and the first diode can be turned off under zero current switching (ZCS) conditions.

Meanwhile, FIG. 8 illustrates a half-period operation method of the switching cycle of the hybrid full-bridge LLC converter according to the present embodiment. Since the operation method of the half period of the switching cycle is the same, description thereof will be omitted.

Hereinafter, a method of implementing a hybrid full-bridge LLC converter according to an embodiment of the present invention will be described with reference to FIGS. 4, 6, and 9. FIG.

9 is a flowchart showing a specific method of designing a resonance tank of a hybrid full-bridge LLC converter.

) 값을 결정(410)한다. CC 모드상에서, 제 2 풀브릿지 LLC 컨버터는 제 2 공진 주파수(

) 상에서 동작하고 제 2 풀브릿지 LLC 컨버터의 임피던스는 스위칭 주파수

에서 '0' 이 되므로, 아래 수학식 17 이 도출될 수 있다.Referring to FIG. 9, first, the second magnetization inductance (

(410). In CC mode, the second full bridge LLC converter has a second resonant frequency (< RTI ID = 0.0 >

) And the impedance of the second full bridge LLC converter is on the switching frequency

0 ", so that the following equation (17) can be derived.

&Quot; (17) "

=

, 수학식 11)을 통해 최종적으로 제 2 자화 인덕턴스(

) 값이 아래 수학식 18 과 같이 도출될 수 있다.Equations (17) and (18) derived from the equation (17) and the AC equivalent circuit on the CC mode and the CV mode,

=

(11), the second magnetizing inductance (

) Can be derived as shown in Equation (18) below.

&Quot; (18) "

) 값이 결정되면(410), 제 2 누설 인덕턴스 값(

)을 결정한다(420). 이때, 제 2 풀브릿지 LLC 컨버터의 1차측 전류(

)의 RMS 값이 제 2 누설 인덕턴스 값 (

)에 의존하는 특성을 이용하여 제 2 누설 인덕턴스 값(

)이 결정될 수 있다. Second Magnetization Inductance (

(410), a second leakage inductance value (< RTI ID = 0.0 >

(420). At this time, the primary current of the second full bridge LLC converter (

) Is the second leakage inductance value (

), A second leakage inductance value (< RTI ID = 0.0 >

) Can be determined.

)은 아래 수학식 19 와 같다.Specifically, the RMS value of the primary side current of the second full bridge LLC converter (

) ≪ / RTI >

&Quot; (19) "

)의 크기는 제 2 풀브릿지 입력 임피던스의 크기에 의존하며, 이때 각스위칭 주파수(

) 에서의 제 2 풀브릿지 LLC 컨버터의 입력 임피던스(

)는 아래 수학식 20으로 나타낼 수 있다.On the other hand, according to equation (19), the RMS value of the primary side current

) Is dependent on the magnitude of the second full bridge input impedance, where each switching frequency (< RTI ID = 0.0 >

) Input impedance of the second full bridge LLC converter at (

) Can be expressed by the following equation (20).

&Quot; (20) "

이다.here,

to be.

)이 제 2 공진 주파수(

) 상에서

로 나타낼 수 있으므로, 제 2 풀브릿지 LLC 컨버터의 입력 임피던스(

) 는 아래 수학식 21 에 따른다. On the other hand, the second resonance capacitance value

) Is the second resonant frequency (

)

The input impedance of the second full bridge LLC converter (

) ≪ / RTI >

&Quot; (21) "

) 는 부하 임피던스가 설정되면 제 2 누설 인덕턴스(

)와 제 2 자화 인덕턴스(

)에 의존함을 알 수 있다. 또한, 제 2 자화 인덕턴스(

)는 수학식 18 에 따르므로, 1차측 전류의 RMS 값(

)의 크기는 제 2 누설 인덕턴스(

)에 의존하게 된다. 이러한 1차측 전류의 RMS 값의 크기와 제 2 자화 인덕턴스의 관계는 도 10 과 같다. 도 10 은 일정 조건(

,

and

) 하에서의 1차측 전류의 RMS 값의 크기와 제 2 누설 인덕턴스(

)의 관계를 도시한 도면으로서, 도 10 에 따르면, 1차측 전류의 RMS 값의 크기와 제 2 누설 인덕턴스(

)는 서로 반비례한 관계를 갖음을 알 수 있다. 따라서, 본 실시예에서는, 제 2 누설 인덕턴스(

) 값을 최대한 크게 설계하여 1차측 전류의 RMS 값의 크기를 최소로 설계하며, 이로 인해 1차측에 접속된 스위칭부의 컨덕션 로스를 줄일 수 있다. 예컨대, 제 2 누설 인덕턴스 값이 120

로 설계되면, 1차측 전류의 RMS 값의 크기가 5.5 A 이하로 줄일 수 있다. According to equation (21), the input impedance of the second full bridge LLC converter (

Is set to a second leakage inductance (< RTI ID = 0.0 >

) And the second magnetizing inductance (

). ≪ / RTI > Also, the second magnetizing inductance (

) Is given by Equation (18), the RMS value of the primary side current

) Is the second leakage inductance (

). The relationship between the magnitude of the RMS value of the primary side current and the second magnetization inductance is shown in FIG. Fig.

,

and

The magnitude of the RMS value of the primary side current and the second leakage inductance (

10, the magnitude of the RMS value of the primary current and the magnitude of the second leakage inductance (

) Are inversely proportional to each other. Therefore, in this embodiment, the second leakage inductance (

) Value is designed to be as large as possible to minimize the RMS value of the primary side current, thereby reducing the conduction loss of the switching part connected to the primary side. For example, if the second leakage inductance value is 120

, The RMS value of the primary current can be reduced to 5.5 A or less.

) 값이 결정된다(430). 이러한 제 2 공진 커패시턴스(

) 값은 상술한 수학식 6 으로부터 아래 수학식 22 와 같이 도출될 수 있다.After the second leakage inductance value is thus determined 420, the second resonant capacitance (

) Value is determined (430). This second resonant capacitance (

) Can be derived from Equation (6) as shown in Equation (22) below.

&Quot; (22) "

) 값이 결정되면(430), 제 3 공진 커패시턴스(

) 값이 결정된다(440). 구체적으로, 제 3 공진 커패시턴스(

) 값은 상술한 수학식 10 으로부터 아래 수학식 23 과 같이 도출될 수 있다.The second resonant capacitance (

(430), a third resonant capacitance (< RTI ID = 0.0 >

) Is determined (440). Specifically, the third resonant capacitance (

) Can be derived from Equation (10) as shown in Equation (23) below.

&Quot; (23) "

) 값이 결정되면(440), 제 2 풀브릿지 LLC 컨버터의 공진 탱크 설계가 완료되고, 이후에서는 제 1 풀브릿지 LLC 컨버터의 공진 탱크가 설계된다. 구체적으로, 제 1 누설 인덕턴스 값(

)을 결정한다(450). 제 1 풀브릿지 LLC 컨버터는 항상 제 1 공진 주파수(f_{r1 _ LLC1}) 상에서 동작하고 자화 전류가 1차측 스위칭부의 출력 커패시터를 방전시키므로 제 1 누설 인덕턴스 값은 특별한 조건을 필요로 하지는 않는다. 그러나, 제 1 공진 커패시터(

) 상에 인가되는 전압 스트레스를 줄이기 위해 바람직하게는, 제 1 누설 인덕턴스(

) 값이 최소화되도록 설계될 수 있다. The third resonant capacitance (

Is determined (440), the resonant tank design of the second full-bridge LLC converter is completed, and thereafter, the resonant tank of the first full-bridge LLC converter is designed. Specifically, the first leakage inductance value (

(450). A first full bridge LLC converter is always the first resonant frequency because the operation, and the magnetizing current is discharged to the primary side switching part on the output capacitor (f _{r1 _ LLC1)} first leakage inductance does not require any special conditions. However, the first resonant capacitor (

, A first leakage inductance (< RTI ID = 0.0 >

) Values can be minimized.

)이 결정(460)될 수 있다. 이러한 제 1 공진 커패시턴스 값(

)은 이전 단계의 제 1 누설 인덕턴스 값(

)이 결정되면, 아래 수학식 24 와 같이 도출될 수 있다.Thereafter, the first resonance capacitance value (

(460). ≪ / RTI > This first resonant capacitance value (

) Is the first leakage inductance value of the previous step (

) Is determined, it can be derived as the following Equation (24).

&Quot; (24) "

)이 결정되면(460), 마지막으로 제 1 자화 인덕턴스 값(

)이 결정(470)될 수 있다. 한편, CC 모드 상에서 제 1 및 제 2 풀브릿지 LLC 컨버터는 영전압 스위칭(ZVS) 및 영전류 스위칭(ZCS) 영역상에서 각각 동작하여야 한다. 특히, 전체 부하 영역에서 스위치 턴 온 및 턴오프 시 소프트한 스위칭이 보장되려면 제 1 및 제 2 풀브릿지 LLC 컨버터가 모두 영전압 스위칭이 되어야 한다. 이하에서는, 이러한 1차측 스위칭부의 영전압 스위칭 및 거의 영전류 스위칭을 보장하기 위한, 제 1 자화 인덕턴스(

) 값의 도출과정을 설명한다. The first resonant capacitance value (

Is determined (460), finally, the first magnetizing inductance value (

(470). ≪ / RTI > Meanwhile, in the CC mode, the first and second full bridge LLC converters must operate in the zero voltage switching (ZVS) and the zero current switching (ZCS) regions, respectively. In particular, to ensure soft switching during switch turn-on and turn-off in the full load range, both the first and second full bridge LLC converters must be at zero voltage switching. Hereinafter, a first magnetizing inductance (hereinafter referred to as " first magnetizing inductance "

) Value is described.

)가 스위칭부의 출력 커패시터에 저장된 용량성 에너지(

)보다 클 때에 달성될 수 있으므로, 영전압 스위칭(ZVS)을 위해 아래 수학식 25 와 같은 관계식이 도출될 수 있다.First, the zero voltage switching of the switching unit is performed by the inductive energy stored in the switching unit

) Is the capacitive energy stored in the output capacitor of the switching unit

(ZVS), a relation as shown in the following Equation 25 can be derived.

&Quot; (25) "

)는 아래 수학식 26 과 같다.On the other hand, the total inductive energy stored in the primary-side switching unit

) ≪ / RTI >

&Quot; (26) "

,

,

,

,

는 전압

에 대한 일차측 전압(

)의 위상각이다. here,

,

,

,

,

The voltage

The primary side voltage (

).

) 는 아래 수학식 27 과 같이 도출된다. Also, the capacitive energy stored in a pair of output capacitors of the primary-

) Is derived as shown in Equation (27) below.

&Quot; (27) "

Equations (25) through (27) can be used to derive the following equation (28).

&Quot; (28) "

) 값은 거의 영전류 스위칭(ZCS)을 달성하도록 가능한 한 크게 설계될 수 있다. 구체적으로, 제 1 자화 인덕턴스(

) 값은 수학식 28 및 아래 수학식 29 의 조건을 만족하도록 설계될 수 있다.On the other hand, in order to minimize the turn-off current of the primary side switching unit, the first magnetizing inductance (

) Values can be designed as large as possible to achieve near zero current switching (ZCS). Specifically, the first magnetizing inductance (

) Value can be designed to satisfy the condition of the expression (28) and the expression (29) below.

&Quot; (29) "

Further, the input impedance value may be set to satisfy Equation 30 below so that a full-soft switching condition is ensured in the CC mode.

&Quot; (30) "

는 제 1 풀브릿지 LLC 컨버터의 입력 임피던스이고,

는 제 2 풀브릿지 LLC 컨버터의 입력 임피던스이며, 각 입력 임피던스는 아래 수학식 31 에 따른다.here,

Is the input impedance of the first full bridge LLC converter,

Is the input impedance of the second full bridge LLC converter, and each input impedance is given by Equation (31) below.

&Quot; (31) "

및

는 제 1 및 제 2 풀브릿지 LLC 컨버터의 반사된 부하 레지스턴스값이고, 각각은 아래 수학식 32 에 따른다.here,

And

Is the reflected load resistance value of the first and second full bridge LLC converters, respectively, according to Equation (32) below.

(32)

Fig. 11 is a graph showing the input impedance characteristics (the phase of the input / output impedance is shown in Fig. 11 (a) and the magnitude of the input impedance is (See Fig. 11 (b)). 11, since the change of the phase of the input impedance at the switching frequency value is only about 3 to 8 degrees in spite of a large change in the battery impedance R _o , Switching and nearly zero current switching can be achieved.

The hybrid full bridge LLC converter according to the present invention can ensure a fixed switching frequency and a full-soft switching condition on the CC mode and the CV mode, provided that a proper design of the resonance tank is made. However, the characteristics of such a hybrid full bridge LLC converter can only be guaranteed when the input voltage is always constant. Therefore, perfect resonance conditions can not be guaranteed when the actual input voltage fluctuates within a range of ± 5% will be. Therefore, the hybrid full bridge LLC converter shown in FIG. 12 further includes a separate controller to ensure resonance condition even if the input voltage fluctuates.

12 is a circuit diagram of a hybrid full-bridge LLC converter according to another embodiment of the present invention.

Referring to FIG. 12, the hybrid full bridge LLC converter 2000 according to the present embodiment further includes a closed loop controller 400, unlike the hybrid full bridge LLC converter 1000 shown in FIG. The closed loop controller 400 includes a PI controller 410, a mode selection switch 420 for selecting a CC mode or a CV mode, a limiter (not shown) And an anti-windup 430 that attenuates the overshoot and transition time caused by the limiter. This closed loop controller 400 controls the current controller to charge the battery with a constant current when the battery voltage is less than the maximum charging voltage (for example, 420 V), and when the battery voltage reaches the maximum charging voltage, The voltage controller can be activated by switching. Other configurations are the same as those of the hybrid full bridge LLC converter 1000 shown in FIG. 2, and a description thereof will be omitted.

Hereinafter, advantageous effects of the hybrid full-bridge LLC converter according to an embodiment of the present invention will be described in detail with reference to FIGS. 13 to 24. FIG.

First, to verify the operation characteristics of the hybrid full bridge LLC converter according to an embodiment of the present invention, a converter having the specifications as shown in Tables 2 and 3 was designed and applied to a battery charger of 3.3 Kw Respectively.

Parameter Designator Value Input voltage

380-420

Output voltage (Battery Voltage)

250-420

Power rating

3.3

CC charge current

7.8

CVcharge voltage

420

Switching frequency

Parameter Value

Primary switches

IPW65R041CFD Turns ratio of

1: 0.55 Leakage inductance of

(

Magnetizing inductance of

345

Resonant capacitor of FBLLC1

Core size of

PQ50 / 50 Turn ratio of

1: 0.55 Leakage inductance of

(

128

Magnetizing inductance of

272

Resonant capacitor of FBLLC2

Resonant capacitor

Core size of

PQ50 / 50 Rectifier diodes

) HFA50PA60C

Hereinafter, the operation characteristics and effects of the hybrid full bridge LLC converter operating in the CC mode according to an embodiment of the present invention having such specifications will be described.

FIGS. 13 to 18 are examples of waveforms in the respective devices when the hybrid full-bridge LLC converter operates in the CC mode according to an embodiment of the present invention.

) 는 400V, 출력 전압(

)는 250V, 출력 전력(

)은 1.95kW, 출력 전류(

)는 7.8A, 스위칭 주파수(

)는 50kHz 이다. Here, the input voltage (

) Is 400V, the output voltage (

) Is 250V, output power (

) Is 1.95kW, the output current (

) Is 7.8 A, the switching frequency (

) Is 50 kHz.

Referring to FIG. 13, current and voltage flowing in the first switch S1 of the primary side switching unit can be checked. At this time, the current and voltage in the same manner as in Fig. 13 can be measured in the first switch to the fourth switch of the primary side switching unit. 13, when the hybrid full bridge LLC converter operates in the CC mode according to an embodiment of the present invention, the first to fourth switches of the primary side switching unit can be turned on under the zero voltage switching (ZVS) condition , And can be turned off under almost zero current switching (ZCS) conditions.

)이 5A 이고 제 2 변압기(TR₂)의 누설 인덕턴스(

)가 128

인 점(표 3 참조)을 고려할 때, 1차측 전류의 RMS 값(

)이 효과적으로 억제되었음을 알 수 있다. Figs. 14 and 15 show current and voltage characteristics of the primary and secondary sides of the first transformer and the second transformer. Fig. 14 and 15, the RMS value of the primary side current (

) Is 5A and the leakage inductance of the second transformer TR ₂ (

) Is 128

(See Table 3), the RMS value of the primary current (

) Was effectively suppressed.

FIG. 16 shows the current-voltage characteristics of the first to fifth diodes. According to FIG. 16, it can be seen that the zero current turn-off of the rectifier diodes connected to the secondary side is achieved and there is no reverse recovery.

FIG. 17 is a graph showing characteristics of output current and voltage of a hybrid full-bridge LLC converter according to an embodiment of the present invention, and FIG. 18 is a graph showing characteristics of efficiency of a hybrid full bridge LLC converter according to an embodiment of the present invention, Fig. 17 and 18, the soft hybrid full bridge LLC converter according to the present embodiment has higher efficiency than the conventional converter due to its soft switching characteristic and can achieve 98% as the maximum efficiency value .

Hereinafter, the operation characteristics and effects of the hybrid full bridge LLC converter operating in the CV mode will be described with reference to FIGS. 19 to 24. FIG.

Figs. 19 and 20 are diagrams showing current and voltage waveforms at the light-load and heavy-load conditions of the first switch S1 of the primary-side switching unit. Fig. According to Figs. 19 and 20, it can be seen that although the first switch can be turned on under the zero voltage switching (ZVS) condition, the turn-off current is somewhat large.

Fig. 21 is a diagram showing the primary side voltage and current characteristics of the first transformer and the second transformer in the CV mode. According to Fig. 21, the first and second full bridge LLC converters including the first transformer and the second transformer It can be seen that it operates in a perfect resonance state.

22 shows the voltage and current characteristics of the first to fifth diodes. According to Fig. 22, the diodes on the rectifier side are turned off under the ZCS (Zero Current Switching) condition, and as a result, Is not generated.

FIG. 23 is a graph showing characteristics of output current and output voltage of a hybrid full-bridge LLC converter according to an embodiment of the present invention, and FIG. 24 is a diagram illustrating efficiency of a hybrid full-bridge LLC converter in a CV mode. 23 and 24, it can be seen that the hybrid full bridge LLC converter according to the present invention in the CV mode has a higher efficiency than the conventional LLC converter and has a maximum efficiency of 97%.

According to the present invention described above, the main switching operation is possible under the zero voltage switching and almost zero current switching conditions in the CC mode, and the main switching operation is possible under the zero voltage switching condition in the CV mode. In addition, only one additional switch is added to convert the resonant tank so that switching losses associated with this are not generated. Further, since both the CC mode and the CV mode operate on a fixed resonance frequency, low circulating energy is generated. In addition, resonant operation over the CC mode and CV mode allows full soft-switching to the rectifier diodes, which may not result in reverse compensation problems. In addition, two converters and two rectifying bridges can be connected in series to provide a high voltage gain and a low voltage rate of the rectifier diode.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1000: Hybrid Full Bridge LLC Converter
100: First Full Bridge LLC Converter
200: 2nd Full Bridge LLC Converter
300:

Claims (14)

A hybrid full bridge LLC converter for performing voltage conversion between an input capacitor for supplying an input voltage and a battery and operating in a constant current mode or a constant voltage mode for charging the battery,
A switching unit connected to the input capacitor and including a full bridge circuit having first to fourth switches;
A first transformer connected to the switching unit to convert the input voltage transmitted through the switching unit, a first rectifier circuit receiving and converting the input voltage converted through the first transformer, and a second rectifier circuit connected to the first rectifier circuit A first full bridge LLC converter including a first output capacitor; And
A second transformer connected to the switching unit to convert the input voltage transmitted through the switching unit, a second rectifier circuit receiving and converting the input voltage converted through the second transformer, and a second rectifier circuit connected to the second rectifier circuit A second full bridge LLC converter including a second output capacitor. The method according to claim 1,
The first full bridge LLC converter includes:
A first leakage inductor, a first magnetizing inductor and a first resonating capacitor are provided on a primary side of the first transformer so as to form a resonant network. 3. The method of claim 2,
Wherein the second full bridge LLC converter comprises:
A second leakage inductor, a second magnetizing inductor and a CC mode capacitor are provided on a primary side of the second transformer so as to form a resonant network, and the CC mode capacitor is connected in parallel with a CV mode capacitor and a mode switch connected in series Hybrid Full Bridge LLC Converter. The method of claim 3,
Wherein the second full bridge LLC converter comprises:
A hybrid pool which maintains a turn-off state of the mode switch when operating in the CC mode and maintains a turn-on state of the mode switch when operating in the CV mode to change a resonant network condition between the CC mode and the CV mode; Bridge LLC Converter. The method according to claim 1,
Wherein the first output capacitor and the second output capacitor are connected in series and the first output capacitor and the second output capacitor connected in series are connected in parallel with the battery. The method according to claim 1,
The switching unit includes:
A first leg and a second leg connected in parallel,
Wherein the first switch and the second switch are provided on the first leg and the third switch and the fourth switch are provided on the second leg. The method according to claim 1,
Wherein the first switch to the fourth switch are respectively connected in parallel with parasitic capacitors and body diodes. The method according to claim 1,
Wherein the first rectifying circuit includes:
A third leg and a fourth leg connected in parallel,
A first diode and a third diode are provided on the third leg, and a second diode and a fourth diode are provided on the fourth leg. The method according to claim 1,
Wherein the second rectifying circuit comprises:
A fifth leg and a sixth leg connected in parallel,
A fifth diode and a seventh diode are provided on the fifth leg, and a sixth diode and an eighth diode are provided on the sixth leg. The battery pack is operated in accordance with a constant current (CC) mode or a constant voltage (CV) mode for charging the battery between an input capacitor for supplying an input voltage and a battery, A method of driving a hybrid full-bridge LLC converter including a first full-bridge LLC converter and a second full-bridge LLC converter sharing a switching unit constituted by a full bridge circuit of a switch as a primary circuit,
The first full bridge LLC converter includes:
The voltage conversion is performed under the same resonance network conditions in the CC mode and the CV mode to transmit the input voltage to the battery,
Wherein the second full bridge LLC converter comprises:
And transferring the input voltage to the battery by performing voltage conversion between the CC mode and the CV mode under different resonant network conditions. 11. The method of claim 10,
The first full bridge LLC converter includes:
And a first transformer for performing a voltage conversion between the primary side circuit and the secondary side circuit, wherein a first leakage inductor, a first magnetizing inductor, and a first resonance capacitor are provided on a primary side of the first transformer so as to form a resonance network, And performing voltage conversion under the same resonant network conditions when operating in the CC mode and the CV mode. 11. The method of claim 10,
Wherein the second full bridge LLC converter comprises:
A second leakage inductor, a second magnetizing inductor and a CC mode capacitor are connected to the primary side of the second transformer so as to form a resonant network, and a second transformer for performing a voltage conversion between the primary side circuit and the secondary side circuit Wherein the CC mode capacitor is connected in parallel with a CV mode capacitor and a mode switch connected in series to perform a voltage conversion between the CC mode and the CV mode under different resonant network conditions in accordance with a switching operation of the mode switch, A method of driving a full bridge LLC converter. 13. The method of claim 12,
Wherein the second full bridge LLC converter comprises:
A hybrid pool which maintains a turn-off state of the mode switch when operating in the CC mode and maintains a turn-on state of the mode switch when operating in the CV mode to change a resonant network condition between the CC mode and the CV mode; A method of driving a bridge LLC converter. 11. The method of claim 10,
In operation in the CC mode, a current flowing in the switching unit according to a turn-on or a turn-off operation of the first switch to the fourth switch is supplied to the primary side of the first full bridge LLC converter and the second full bridge LLC converter A method of driving a Hybrid Full Bridge LLC converter flowing to the primary side.

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