KR20200086009A - Low Voltage Isolation DC/DC Converter for Electric Vehicles - Google Patents

Abstract

Disclosed is a low voltage isolated direct current (DC)/DC converter for an electric vehicle. The disclosed DC/DC converter comprises: a first inverter outputting a first positive voltage and a first negative voltage based on an input voltage charged in a battery for an electric vehicle; a second inverter outputting a second positive voltage and a second negative voltage based on the input voltage; a first transformer changing a voltage based on the first positive voltage and the first negative voltage; a second transformer changing a voltage based on the second positive voltage and the second negative voltage; a power balancer connected between a primary side of the first transformer and a primary side of the second transformer; and an output unit connected to a secondary side of the first transformer and a secondary side of the second transformer and rectifying voltages outputted from the secondary side of the first transformer and the secondary side of the second transformer to output the output voltage.

Description

Low Voltage Isolation DC/DC Converter for Electric Vehicles

Embodiments of the present invention relates to a low voltage insulated DC/DC converter for an electric vehicle, and more specifically, a high frequency switching is possible by a phase shift method at a high input voltage, and has a distributed design structure to cope with a high capacity, distributed design It relates to a DC / DC converter that can solve the power balance problem that occurs in the city.

Electric vehicles use low-voltage DC/DC converters to supply the power of internal components. A low-voltage DC/DC converter having an output voltage of 12V and a power capacity of 1 to 2kW is used for an ordinary passenger car, and a low-voltage DC/DC converter having an output voltage of 24V and a power capacity of 2 to 5kW is used for a commercial vehicle. .

The low voltage DC/DC converter uses the battery voltage as an input power source. In the case of a typical battery, it has a nominal voltage of about 400V and a wide voltage range of 200V to 450V depending on the battery condition. To cope with this wide input voltage range, low input voltage of 12 V or 24 V and large output current, a full bridge converter using a center tap rectifier as shown in FIG. 1 is widely used.

Power converters for electric vehicles generally require high power density, and in order to satisfy this, in the prior art, a low-voltage DC/phase-shift-driven method capable of reducing switching loss, soft switching operation, and using a simple pulse transformer can be used. DC converters are being used.

In order to increase the cruising distance of automobiles, research and development for increasing the battery voltage has been recently conducted. In order to increase the power density of these high input voltage and low voltage DC/DC converters, it is necessary to use a low-breakdown voltage switch capable of high-frequency switching, and it is also required to develop a technology capable of optimizing power density through a distributed design.

In order to solve the problems of the prior art as described above, in the present invention, high-frequency switching is possible from a high input voltage to a phase shift method, has a distributed design structure to cope with high capacity, and solves the power balance problem that occurs during distributed design. I would like to propose a low voltage DC/DC converter that can be solved.

Other objects of the present invention may be derived by those skilled in the art through the following examples.

According to a preferred embodiment of the present invention to achieve the above object, in the low-voltage isolated DC / DC converter, based on the input voltage charged in the battery for the electric vehicle to output the first positive voltage and the first negative voltage A first inverter; A second inverter outputting a second positive voltage and a second negative voltage based on the input voltage; A first transformer that changes a voltage based on the first positive voltage and the first negative voltage; A second transformer that changes a voltage based on the second positive voltage and the second negative voltage; A power balancer connected between the primary side of the first transformer and the primary side of the second transformer; And an output unit connected to the secondary side of the first transformer and the secondary side of the second transformer, and rectifying the voltage output from the secondary side of the first transformer and the secondary side of the second transformer to output an output voltage. A DC/DC converter is provided, which is characterized by including.

The power balancer may include a common mode coupled inductor having a transformer structure.

The winding ratio between the primary side and the secondary side of the common mode coupled inductor may be 1:1.

The common mode coupled inductor can prevent the current deviation between the first transformer and the second transformer from occurring due to the deviation of the leakage inductance of the first transformer and the second transformer.

The primary side of the common mode coupled inductor may be connected in series with the primary side of the first transformer, and the secondary side of the common mode coupled inductor may be connected in series with the primary side of the second transformer.

The first positive voltage is applied to one end of the winding on the primary side of the first transformer, the first negative voltage is applied to one end of the winding on the primary side of the common mode coupled inductor, and 1 of the first transformer. The other end of the winding on the secondary side and the other end of the winding on the primary side of the common mode coupled inductor are connected to each other, and the second positive voltage is applied to one end of the winding on the secondary side of the common mode coupled inductor, and the second The negative voltage may be applied to the other end of the winding on the primary side of the second transformer, and the other end of the winding on the secondary side of the common mode coupled inductor and one end of the winding on the primary side of the second transformer may be connected to each other.

The DC/DC converter further includes a voltage divider that divides the input voltage into a first voltage and a second voltage, and the first inverter portion includes a switching element 1A, a switching element 2A, a switching element 3A, and switching connected in series. Element 4A may be included, and the second inverter unit may include a switching element 1B, a switching element 2B, a switching element 3B, and a switching element 4B connected in series.

The voltage distribution unit includes a first input capacitor and a second input capacitor connected in series, one end of the first input capacitor, one end of the switching element 1A, and one end of the switching element 4B are electrically connected, and the first input The other end of the capacitor, the other end of the switching element 2A, the other end of the switching element 3B, one end of the second input capacitor, one end of the switching element 3A, and one end of the switching element 2B are electrically connected, and the second input capacitor The other end of the, the other end of the switching element 4A and the other end of the switching element 1B may be electrically connected.

The first positive voltage is output from a node to which the other end of the switching element 1A and one end of the switching element 2A are connected, and the first negative voltage is output from a node to which the other end of the switching element 3A and one end of the switching element 4A are connected. The second positive voltage is output from a node to which the other end of the switching element 4B and one end of the switching element 3B are connected, and the second negative voltage is a node to which the other end of the switching element 2B and one end of the switching element 1B are connected. Can be output from

In the DC/DC converter, the first mode, the second mode, the third mode, the fourth mode, the fifth mode, and the sixth mode are sequentially and repeatedly operated. In the first mode and the second mode, the The switching element 1A, the switching element 1B, the switching element 4A and the switching element 4B are turned on, the switching element 2A, the switching element 2B, the switching element 3A and the switching element 3B are turned off, and in the third mode. , The switching element 1A, the switching element 1B, the switching element 3A and the switching element 3B are turned on, the switching element 2A, the switching element 2B, the switching element 4A and the switching element 4B are turned off, and the fourth In the mode and the fifth mode, the switching element 2A, the switching element 2B, the switching element 3A and the switching element 3B are turned on, the switching element 1A, the switching element 1B, the switching element 4A and the switching element 4B Is off, in the sixth mode, the switching element 2A, the switching element 2B, the switching element 4A and the switching element 4B are turned on, and the switching element 1A, the switching element 1B, the switching element 3A and the switching Device 3B may be turned off.

The winding on the secondary side of the first transformer includes a first winding and a second winding connected in series, and the winding on the secondary side of the second transformer includes a third winding and a fourth winding connected in series, and the output part comprises A rectifier including one diode and a second diode, an output inductor and an output capacitor, wherein the input terminal of the first diode is connected to one end of the first winding and one end of the third winding, and of the second diode The input terminal is connected to the other end of the second winding and the other end of the fourth winding, one end of the output inductor is connected to the output terminal of the first diode and the output terminal of the second diode, and one end of the output capacitor is the output Connected to the other end of the inductor, the other end of the output capacitor may be connected to the other end of the first winding, the other end of the third winding, one end of the second winding, and one end of the fourth winding.

In addition, according to another embodiment of the present invention, in a low voltage insulated DC/DC converter, the first positive voltage and the first negative voltage are output to the first output terminal based on the input voltage charged in the battery for the electric vehicle, A high frequency inverter unit for outputting a second positive voltage and a second negative voltage to the second output terminal; A first transformer connected to the first output terminal of the high frequency inverter unit; A second transformer connected to the second output terminal of the high frequency inverter unit; A common mode coupled inductor connected between the primary side of the first transformer and the primary side of the second transformer and having a transformer structure; And a first output unit rectifying the voltage output from the secondary side of the first transformer to output a first output voltage. And a second output unit rectifying the voltage output from the secondary side of the second transformer to output a second output voltage.

In addition, according to another embodiment of the present invention, in a low voltage insulated DC/DC converter, based on an input voltage charged in an electric vehicle battery, the first positive voltage and the first negative voltage are output to the first output terminal, , A high-frequency inverter unit for outputting a second positive voltage and a second negative voltage to the second output terminal; A transformer connected to the first output terminal and the second output terminal of the high-frequency inverter unit, and composed of two windings, each of the primary and secondary sides-the primary side of the transformer is composed of a first winding and a second winding, and 2 of the transformer The secondary side consists of a third winding and a fourth winding -; A common mode coupled inductor connected between the first winding and the second winding and having a transformer structure; And an output unit rectifying the voltage output from the secondary side of the transformer to output the output voltage.

The low voltage DC/DC converter according to the present invention has the advantage of being capable of high-frequency switching by a phase shift method at a high input voltage and solving the power balance problem that occurs in distributed design.

In addition, it should be understood that the effects of the present invention are not limited to the above-described effects, and include all effects that can be deduced from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a view showing an example of a full-bridge converter using a center tap rectifier used in a conventional low-voltage DC/DC converter.
2 is a view showing a schematic configuration of a low-voltage DC-DC converter according to a first embodiment of the present invention
3 to 9 are diagrams for explaining the operation of the low-voltage DC / DC converter according to the first embodiment of the present invention.
10 to 16 are diagrams for explaining the results of the simulation of the low voltage isolated DC/DC converter according to the first embodiment of the present invention.
17 is a view showing a schematic configuration of a low-voltage DC-DC converter according to a second embodiment of the present invention.
18 is a view showing a schematic configuration of a low-voltage DC-DC converter according to a third embodiment of the present invention.

As used herein, a singular expression includes a plural expression unless the context clearly indicates otherwise. In this specification, the terms "consisting of" or "comprising" should not be construed as including all of the various components, or various steps described in the specification, among which some components or some steps It may not be included, or it should be construed to further include additional components or steps. In addition, terms such as “... unit” and “module” described in the specification mean a unit that processes at least one function or operation, which may be implemented in hardware or software, or a combination of hardware and software. .

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

2 is a view showing a schematic configuration of a low-voltage DC-DC converter according to a first embodiment of the present invention.

2, the low-voltage DC-DC converter according to the first embodiment of the present invention, the voltage distribution unit 210, the inverter unit 220, the switching control unit 230, the first transformer 240, the second It includes a transformer 250, a power balancer 260 and an output unit 270.

The voltage distribution unit 210 distributes the input voltage V _DC charged in the battery for the electric vehicle to the first voltage V _in1 and the second voltage V _in2 , and for this purpose, the first input capacitor C connected in series _in1 ) and a second input capacitor C _in2 . At this time, if the parameters of the transformers 250 and 260 described below are the same, the first voltage V _in1 applied to the first input capacitor C _in1 and the second input capacitor C _in2 are applied. The second voltage V _in2 is always maintained at half of the input voltage (V _DC /2) regardless of the load.

High-frequency inverter unit 220 includes a first inverter 221 and second, and an inverter 221, a first output terminal for outputting the signal output from the first inverter 221 (V _pp1, V _pn1) and, the 2 includes a second output terminal (V _pp2 , V _pn2 ) for outputting the signal output from the inverter 222. At this time, the first inverter 221 and the second inverter 221 may have a half bridge structure. The output signals of the respective inverters 221 and 222 are applied to the first transformer 240 and the second transformer 250, and then rectified at the output unit 270 to form the output voltage Vo.

At this time, the first inverter 221 is received is the input voltage (V _DC), first chulryeokdanreul through the first outputs a positive voltage (V _pp1) and a first negative voltage (V _pn1), series-connected switches which for this purpose It includes element 1A 2211, switching element 2A 2212, switching element 3A 2213, and switching element 4A 2214. Here, the first positive voltage (V _pp1) is output from the one end is connected to the node of the switching device 1A (2211) the other end and switching elements 2A (2212), the first negative voltage (V _pn1) are switching devices 3A (2213) The other end of and the one end of the switching element 4A 2214 is output from the connected node.

In addition, the second inverter 222 receives the input voltage (V _DC ) and outputs the second positive voltage (V _pp2 ) and the second negative voltage (V _pn2 ) through the second output terminal. It includes element 1B 2221, switching element 2B 2222, switching element 3B 2223, and switching element 4B 2224. Here, the second positive voltage V _pp2 is output from a node to which the other end of the switching element 4B 2224 and one end of the switching element 3B 233 are connected, and the second negative voltage V _pn2 is the switching element 2B 2222. The other end of and the one end of the switching element 1B 2221 is output from the connected node.

Looking at the connection relationship between the components of the voltage distribution unit 210 and the components of the first inverter 221 and the second inverter 222 are as follows.

First, one end of the first input capacitor C _in1 , one end of the switching element 1A 2211 and one end of the switching element 4B 2224 are electrically connected, and the other end of the switching element 1A 2211 and the switching element 2A (222 One end of) 221 is electrically connected, and the other end of switching element 4B 2224 and one end of switching element 3B 2223 are electrically connected. And, the other end of the first input capacitor (C _in1 ), the other end of the switching element 2A (2212), the other end of the switching element 3B (2223), one end of the second input capacitor (C _in2 ), one end of the switching element 3A (2213) , One end of the switching element 2B (2222) is electrically connected. In addition, the other end of the second input capacitor C _in2 , the other end of the switching element 4A 2214 and the other end of the switching element 1B 2221 are electrically connected, and the other end of the switching element 3A 2213 and the switching element 4A 2214 One end of) is electrically connected, and the other end of switching element 2B 2222 and one end of switching element 1B 2221 are electrically connected.

Meanwhile, each of the switching elements 2221, 2212, 2213, 2214, 2221, 2222, 2223, 2224 included in the first inverter 221 and the second inverter 222 may have a structure in which transistors, diodes, and capacitors are connected in parallel. In addition, on/off is controlled through a control signal output from the switching control unit 230 operating in a PWM (Pulse Width Modulation) method.

A first transformer 240 changes the voltage on the basis of being connected to the first output terminal of the high-frequency inverter 220, a first positive voltage (V _pp1) and a first negative voltage (V _pn1). At this time, the secondary side of the first transformer 240 is composed of two taps. That is, the winding on the secondary side of the first transformer 240 includes a first winding 241 and a second winding 242 connected in series. In addition, the winding ratio of the primary side winding and the secondary side winding of the first transformer 240 may be set to N:1.

Then, the second transformer 250 is connected to the second output terminal of the high frequency inverter unit 220, and changes the voltage based on the second positive voltage V _pp2 and the second negative voltage V _pn2 . At this time, the secondary side of the second transformer 250 is composed of two taps. That is, the winding on the secondary side of the second transformer 250 includes a third winding 251 and a fifth winding 252 connected in series. In addition, the winding ratio of the primary side winding and the secondary side winding of the second transformer 250 may be set to N:1.

The power balancer 260 is connected between the primary side of the first transformer 240 and the primary side of the second transformer 250, and the deviation of the leakage inductance of the first transformer 240 and the second transformer 250 is determined. Accordingly, current deviation between the first transformer 240 and the second transformer 250 is prevented from occurring.

According to the present invention, the power balancer 260 may be a common mode coupled inductor (CMCI) having a transformer structure. In this case, the primary side 261 of the common mode coupled inductor is connected in series with the primary side of the first transformer 240, and the secondary side 262 of the common mode coupled inductor is 1 of the second transformer 250. It can be connected in series with the secondary side, and the winding ratios of the primary side 261 and secondary side 262 of the common mode coupled inductor can be set to 1:1 to accommodate the same power load.

The connection relationship between the first transformer 240, the second transformer 250, and the power balancer 260 will be further described as follows.

The first positive voltage (V _pp1) has a first blocking capacitor in series (C _B1) and the first through the leakage inductor (L _lk1) is applied to one end of the winding of the primary winding of the first transformer 240, a first negative The voltage V _pn1 is applied to one end of the winding of the primary side 261 of the common mode coupled inductor, and the other end of the winding of the primary side of the first transformer 240 and the primary side 261 of the common mode coupled inductor. The other ends of the windings are connected to each other.

Then, the second positive voltage (V _pp2 ) is applied to one end of the winding of the secondary side 262 of the common mode coupled inductor through the second blocking capacitor (C _B2 ), and the second negative voltage (V _pn2 ) is 2 is applied to the other end of the winding on the primary side of the transformer 250, the other end of the winding on the secondary side 262 of the common mode coupled inductor and one end of the winding on the primary side of the second transformer 250 is a second leakage inductor It is connected to each other through (L _lk2 ).

In addition, the voltage across both ends of the first blocking capacitor C _B1 (V _CB1 ) and the voltage across both ends of the second blocking capacitor C _B2 (V _CB2 ) are equal to half the voltage of the input voltage V _DC (V _DC /2) ).

In short, the first inductor 221 and the second inductor 222 operate with the same signal, but power may not be uniformly distributed to the transformers 240 and 250 due to variations in parameters such as transformer leakage. To achieve this, common mode coupled inductors having a 1:1 turns ratio are disposed on the primary side of the first transformer 240 and the second transformer 250.

The output unit 270 is connected to the secondary side of the first transformer 240 and the secondary side of the second transformer 250, and is output from the secondary side of the first transformer 240 and the secondary side of the second transformer 250. The rectified voltage is rectified to output the output voltage. To this end, the output unit 270 includes a first diode D ₁ , a second diode D ₂ , an output inductor L _O and an output capacitor C _O.

In more detail, the input terminal of the first diode D _{1 is} connected to one end of the first winding 241 and one end of the third winding 252, and the input terminal of the second diode D ₂ is the second winding 242 ) And the other end of the fourth winding 252, one end of the output inductor L _O is connected to the output terminal of the first diode D ₁ and the output terminal of the second diode D ₂ , and the output capacitor One end of (C _O ) is connected to the other end of the output inductor (L _O ), the other end of the output capacitor (C _O ) is the other end of the first winding 241, the other end of the third winding 251, the second winding ( 242) and one end of the fourth winding 252.

Meanwhile, in the DC/DC converter according to the present invention, the first mode, the second mode, the third mode, the fourth mode, the fifth mode, and the sixth mode are sequentially and repeatedly operated. 3 is a diagram showing an operating waveform of the low voltage DC/DC converter according to the present invention. Hereinafter, the operation for each mode will be described in detail with reference to FIGS. 3 and 4 to 9 described below.

1.Mode 1

4 is a diagram illustrating a low voltage DC/DC converter operating in mode 1 according to an embodiment of the present invention.

3 and 4, in mode 1, switching element 1A 2211, switching element 1B 2221, switching element 4A 2214, and switching element 4B 2224 are turned on, and switching element 2A 2212, Switching element 2B 2222, switching element 3A 2213 and switching element 3B 2223 are turned off.

At this time, the primary current (i _p1 ) of the first transformer 240 and the primary current (i _p2 ) of the second transformer 250 before the switching element 1A 2211 and the switching element 1B 2221 are conducted. Since it flows in the negative direction, switching element 2A 2212 and switching element 2B 2222 are blocked. Then, when the switching element 1A (2211) and the switching element 1B (2221) is conducting, the primary side current (i _p1 ) of the first transformer 240 and the primary side current (i) of the second transformer 250 due to the leakage of the transformer The direction of _p2 ) is switched with a slope.

Accordingly, as the current flows through the body diodes of the switching element 1A 2211, the switching element 1B 2221, the switching element 4A 2214, and the switching element 4B 2224, if the current has a positive value, the switching element A current flows through each channel of 1A 2211, switching element 1B 2221, switching element 4A 2214, and switching element 4B 2224. In addition, during the mode 1, both the first diode D ₁ and the second diode D ₂ are conducted. The primary current (i _p1 ) of the first transformer 240 and the primary current (i _p2 ) of the second transformer 250 set the output current (i _Lo ) of the first transformer 240 and the second transformer 250 When the reduction current viewed from the primary side of) becomes the same, mode 1 ends.

2. Mode 2

5 is a view showing a low voltage DC/DC converter operating in mode 2 according to an embodiment of the present invention.

3 and 5, mode 2 is a mode in which power is supplied through switching element 1A 2221, switching element 1B 2221, switching element 4A 2214, and switching element 4B 2224, mode 1 In the same manner as switching element 1A 2211, switching element 1B 2221, switching element 4A 2214 and switching element 4B 2224 are turned on, switching element 2A 2212, switching element 2B 2222, switching element 3A 2213 and switching element 3B 2223 are turned off. Accordingly, current flows through the channels of the switching element 1A 2211, the switching element 1B 2221, the switching element 4A 2214, and the switching element 4B 2224, and the first diode D ₁ is conducted.

And this time, the first output voltage (V _pp1 -V _pn1) and output voltage (V _{pn2 pp2} -V) are respectively the input voltage (V _DC) of the second inverter 2212 in 2211, the first blocking capacitor (C _B1) and the second blocking capacitor (C _B2) is because it is biased to V _DC / 2, the first transformer 240 and a second transformer 250, respectively, the primary side of the is applied to a voltage of V _DC / 2 . Therefore, the current of the output inductor L _O rises with a slope of (V _DC /2n-V _o )/L _o .

3. Mode 3

6 is a diagram illustrating a low voltage DC/DC converter operating in mode 3 according to an embodiment of the present invention.

3 and 6, in mode 3, switching element 1A 2211, switching element 1B 2221, switching element 3A 2213, and switching element 3B 2223 are turned on, and switching element 2A 2212, Switching element 2B 2222, switching element 4A 2214 and switching element 4B 2224 are turned off. That is, in the state where the switching element 1A 2211 and the switching element 1B 2221 are conducting, the switching element 4A 2214 and the switching element 4B 2224 are blocked, and the switching element 3A 2213 and the switching element 3B 2223 ) Is conducted.

Then, the first inverter (2211) outputs a voltage (V _pp1 -V _pn1) and output voltage (V _{pn2 pp2} -V) of the second inverter 2212 is of a V _DC / 2, respectively, a first blocking capacitor (C _{Since B1} ) and the second blocking capacitor C _B2 are biased to V _DC /2, a voltage of 0 is applied to the primary side of each of the first transformer 240 and the second transformer 250.

Therefore, the current flowing in the transformer leakage is circulated through the channels of the switching elements 1A 2211 and 1B 2221 and the body diodes of the switching elements 3A 2213 and 3B 2223, and the first transformer ( 240) and the second transformer 250, since the primary voltage of each of the primary voltage is almost zero, the current of the output inductor L _O decreases with a slope of -V _o /L _o .

4. Mode 4

7 is a view showing a low voltage DC/DC converter operating in mode 4 according to an embodiment of the present invention.

3 and 7, in mode 7, the switching element 2A 2212, the switching element 2B 2222, the switching element 3A 2213 and the switching element 3B 2223 are turned on, and the switching element 1A 2211, Switching element 1B 2221, switching element 4A 2214 and switching element 4B 2224 are turned off. Therefore, the operation in mode 4 is performed similarly to the operation in mode 1 described above.

5. Mode 5

8 is a diagram illustrating a low voltage DC/DC converter operating in mode 5 according to an embodiment of the present invention.

Referring to FIGS. 3 and 8, mode 5 is a mode in which power is supplied through switching element 2A 2212, switching element 2B 2222, switching element 3A 2213, and switching element 3B 2223, mode 4 In the same manner as switching element 2A 2212, switching element 2B 2222, switching element 3A 2213 and switching element 3B 2223 are turned on, switching element 1A 2211, switching element 1B 2221, switching element 4A 2214 and switching element 4B 2224 are turned off. Therefore, the operation in mode 5 is performed similarly to the operation in mode 2 described above.

6. Mode 6

9 is a diagram illustrating a low voltage DC/DC converter operating in mode 6 according to an embodiment of the present invention.

3 and 9, in mode 6, switching element 2A 2212, switching element 2B 2222, switching element 4A 2214, and switching element 4B 2224 are turned on, and switching element 1A 2211, Switching element 1B 2221, switching element 3A 2213 and switching element 3B 2223 are turned off. Therefore, the operation in mode 6 is performed similarly to the operation in mode 3 described above.

Meanwhile, the voltage balance and current balance of the low voltage DC/DC converter of the present invention through the operation of modes 1 to 6 are summarized as follows.

end. Voltage balance

A first input capacitor (C _in1) both-end voltage (V _in1) and the second input capacitor a voltage equal to the both-end voltage (V _in2) of (C _in2) of V _DC / 2 to remain, regardless of the duty ratio change of the converter the first is to be the same current (iC _in2) flowing in the current (iC _in1) and a second input capacitor (C _in2) flowing through the input capacitor (C _in1). At this time, the first electric current (iC _in2) flowing in the current (iC _in1) and a second input capacitor (C _in2) flowing through the input capacitor (C _in1) can be expressed as shown in Equation 1 below.

At this time, referring to FIG. 3, the current (i _M1A 221) of the switching element 1A 221 and the current (i _{M1B 232)} of the switching element 1B 2221 and the current of the switching element 4A 2214 (i _{M4A (224)} ) and the current (i _{M4B (234)} ) of the switching element 4B (2224) is the same current, the current flowing through the first input capacitor (C _in1 ) (iC _in1 ) and the second input capacitor (C) _The current flowing in _in2 ) (iC _in2 ) becomes the same current regardless of the operation of the converter, and the voltage across both ends of the first input capacitor C _in1 (V _in1 ) and the voltage across both ends of the second input capacitor C _{in2 in2} ) always maintains V _DC /2.

I. Power balance

A first inverter output voltage (V _pp1 -V _pn1) and the primary current (i _p1) of the first transformer 240 according to the output voltage (V _{pn2 pp2} -V) of the second inverter 230 of the 220 and When the primary current i _p2 of the second transformer 250 is the same, power balance can be achieved. By the way, the common mode coupling connection structure of the inductor is a turns ratio of 1: 1 transformer and the same, common mode coupled-a magnetizing inductance of the inductor sufficiently large, the first primary-side current of the transformer (240) (i _p1) of the first transformer The primary current i _p2 of 250 is always the same current, so the power delivered by the first transformer 240 and the second transformer 250 is always the same.

In short, the low voltage DC/DC converter according to the first embodiment of the present invention uses a low voltage switch to facilitate the design of a large capacity LDC having a high input voltage. In order to stably use the low voltage switch, voltage balancing is important, and the present invention proposes a method for solving this in a circuit structure. The most important part of module design is the balance of power for each module, and in the present invention, it can be implemented using a simple common mode coupled inductor without going through control. In addition, a phase shift method is employed to simplify the configuration of the driving circuit.

Hereinafter, a simulation of the low-voltage isolated DC/DC converter of the present invention will be described with reference to FIGS. 10 to 16.

To confirm the operation of the proposed converter, the input voltage (V _DC ) is 800 V, the turns ratio (N) of the first transformer 240 and the second transformer 250 is 6, and the switching frequency (f _s ) is 100 kHz. Experiment with.

10 is a simulation circuit diagram for verifying a low voltage isolated DC/DC converter according to the present invention.

And, Figures 11 and 12 is a simulation experiment to show the balance of the voltage of the input capacitors (C _in1 , C _in2 ) according to the load in the low-voltage isolated DC/DC converter according to the present invention. 11 and 12, voltage (V _in2) of the first input capacitor voltage (V _in1) and second input capacitor (C _in2) of (C _in1) according to the load is good with 1/2 of the input voltage It can be confirmed that it is maintained.

In addition, FIGS. 13 and 14 are simulations for checking whether power balance flowing to the primary side of the transformers 240 and 250 is balanced according to the leakage deviation. Here, the leakage deviation was assumed to be 50%, and a simulation was conducted according to the presence or absence of a common mode coupled inductor for power balance in the leakage deviation.

13 and 14, when a common mode coupled inductor is present, the primary currents of the transformers 240 and 250 remain the same, and the variation of the input voltage is limited to 6%. In this case, the apparent power of the first transformer 240 is 4.49 kVA, the apparent power of the second transformer 250 is 4.48 kVA, and it can be confirmed that power balance is well achieved.

However, in the absence of a common mode coupled inductor, power deflection occurs with a low-leakage transformer, and the input voltage deviation also rises to 8.5%. In this case, the apparent power of the first transformer 240 is 5.60 kVA, the apparent power of the second transformer 250 is 3.75 kVA, and the variation in the apparent power of the transformer is not large due to the variation in the input current, although the variation in the input voltage is not large. Big.

Also, referring to FIG. 16, in the absence of a common mode coupled inductor, the switching of the leading-leg switch voltage is not completely reduced to 0 due to the distortion of the primary currents of the transformers 240 and 250. , Lead-leg switch does not operate with Zero-Voltage-Switching (ZVS), resulting in switching loss and switching noise. However, when the common mode coupled inductor is present as shown in FIG. 15, ZVS is possible because there is no distortion of the primary current of the transformers 240 and 250.

17 is a view showing a schematic configuration of a low-voltage DC-DC converter according to a second embodiment of the present invention.

17, the low voltage DC-DC converter according to the second embodiment of the present invention, except that the structure of the output unit 1700 is different, the low voltage according to the first embodiment of the present invention shown in FIG. It is the same as DC-DC converter. Therefore, only the structure of the output unit 1700 will be described.

The output unit 1700 includes a first output unit 1710 and a second output unit 1720. At this time, the first output unit 1710 rectifies the voltage output from the secondary side of the first transformer (T1) to the first output voltage (V _o1P , V _o1N ), and the second output unit 1720 rectifies the voltage output from the secondary side of the second transformer T2 to generate a second output voltage V _o2P , V _o2N ).

More specifically, the winding on the secondary side of the first transformer T1 includes the first winding 1173 and the second winding 1732 connected in series, and the winding on the secondary side of the second transformer T2 is connected in series. It includes a third winding (1741) and a fourth winding (1742). In addition, the first output unit 1710 includes a first diode D ₁ , a second diode D ₂ , a first output inductor L _O1 and a first output capacitor C _O1 , and a second output The unit 1720 includes a third diode D ₃ , a fourth diode D ₄ , a second output inductor L _O2 and a second output capacitor C _O2 .

Here, the input terminal of the first diode (D ₁ ) is connected to one end of the first winding (1731), the input terminal of the second diode (D ₂ ) is connected to the other end of the second winding (1732), the first output inductor One end of (L _O1 ) is connected to the output terminal of the first diode (D ₁ ) and the output terminal of the second diode (D ₂ ), and one end of the first output capacitor (C _O1 ) is of the first output inductor (L _O1 ). It is connected to the other end, and the other end of the first output capacitor C _{O1 is} connected to the other end of the first winding 1173 and the other end of the second winding 1732.

And, the input terminal of the third diode (D ₃ ) is connected to one end of the third winding (1741), the input terminal of the fourth diode (D ₄ ) is connected to the other end of the fourth winding (1742), the second output inductor One end of (L _O2 ) is connected to the output terminal of the third diode (D ₃ ) and the output terminal of the fourth diode (D ₄ ), and one end of the second output capacitor (C _O2 ) is of the second output inductor (L _O2 ). It is connected to the other end, and the other end of the second output capacitor C _{O2 is} connected to the other end of the third winding 1742 and the other end of the fourth winding 1742.

In short, the low voltage DC-DC converter according to the second embodiment of the present invention uses two outputs 1710 and 1720, that is, two rectifiers. In this case, since the two voltages V _O1 and V _O2 are formed, and the above-mentioned voltages are the same voltage, in the case of a low voltage such as 12V, the circuit can be configured in parallel, and in the case of 24V, the circuit can be configured in series. Therefore, the same circuit can be designed to correspond to two output voltages.

18 is a view showing a schematic configuration of a low-voltage DC-DC converter according to a third embodiment of the present invention.

Referring to FIG. 18, in the low voltage DC-DC converter according to the third embodiment of the present invention, except that the structures of the transformer 1810 and the output unit 1820 are different, the first of the present invention shown in FIG. 2 is It is the same as the low-voltage DC-DC converter according to the embodiment. Therefore, only the structures of the transformer 1810 and the output unit 1820 will be described.

The low voltage DC-DC converter according to the third embodiment of the present invention uses only one transformer 1810. At this time, the primary and secondary sides of the transformer 1810 are composed of two taps. That is, the primary side of the transformer 1810 is composed of the first winding 1811 and the second winding 1812, and the secondary side of the transformer 1810 is composed of the third winding 1813 and the fourth winding 1814. do.

At this time, the first positive voltage (V _pp1) through the series-connected first blocking capacitor (C _B1) and a first leakage inductor (L _lk1) is applied to one end of the first coil 1811, the first negative voltage ( V _pn1 ) is applied to one end of the winding of the primary side 1831 of the common mode coupled inductor, and the other end of the first winding 1811 and the other end of the winding of the primary side 1831 of the common mode coupled inductor are connected to each other. do.

Further, the second positive voltage V _pp2 is applied to one end of the winding of the secondary side 1832 of the common mode coupled inductor through the second blocking capacitor C _B2 , and the second negative voltage V _pn2 is 2 is applied to the other end of the winding 1812, and the other end of the winding of the secondary side 1832 of the common mode coupled inductor and one end of the second winding 1812 are connected to each other through the second leakage inductor L _lk2 .

In addition, the output unit 1820 includes a first diode D ₁ , a second diode D ₂ , an output inductor L _O and an output capacitor C _O. At this time, the input terminal of the first diode D _{1 is} connected to one end of the third winding 1813, the input terminal of the second diode D ₂ is connected to the other end of the fourth winding 1814, and the output inductor ( One end of L _O ) is connected to the output terminal of the first diode D ₁ and the output terminal of the second diode D ₂ , and one end of the output capacitor C _O is connected to the other end of the output inductor L _O , the other end of the output capacitor (C _O) is connected to one end of the other end and a fourth winding (1814) of the third coil 1813.

In short, the low voltage DC-DC converter according to the third embodiment of the present invention uses one transformer 1820, and thus can be applied to a high voltage low capacity design.

As described above, in the present invention, it has been described by specific matters such as specific components, etc. and limited embodiments and drawings, which are provided to help the overall understanding of the present invention, but the present invention is not limited to the above embodiments, Those skilled in the art to which the present invention pertains can make various modifications and variations from these descriptions. Therefore, the spirit of the present invention should not be limited to the described embodiments, and should not be determined, and all claims that are equivalent or equivalent to the scope of the claims as well as the claims described below will be included in the scope of the spirit of the invention. .

Claims (16)

In the low-voltage isolated DC/DC converter,
A first inverter outputting a first positive voltage and a first negative voltage based on the input voltage charged in the battery for the electric vehicle;
A second inverter outputting a second positive voltage and a second negative voltage based on the input voltage;
A first transformer that changes a voltage based on the first positive voltage and the first negative voltage;
A second transformer that changes a voltage based on the second positive voltage and the second negative voltage;
A power balancer connected between the primary side of the first transformer and the primary side of the second transformer; And
And an output unit connected to the secondary side of the first transformer and the secondary side of the second transformer, and rectifying the voltage output from the secondary side of the first transformer and the secondary side of the second transformer to output an output voltage. DC/DC converter, characterized in that. According to claim 1,
The power balancer DC / DC converter, characterized in that it comprises a common mode coupled inductor having a transformer structure. According to claim 2,
DC/DC converter, characterized in that the winding ratio between the primary and secondary sides of the common mode coupled inductor is 1:1. According to claim 2,
The common mode coupled inductor DC/DC converter, characterized in that to prevent the current deviation of the first transformer and the second transformer according to the deviation of the leakage inductance of the first transformer and the second transformer. According to claim 2,
DC characterized in that the primary side of the common mode coupled inductor is connected in series with the primary side of the first transformer, and the secondary side of the common mode coupled inductor is connected in series with the primary side of the second transformer. /DC converter. The method of claim 5,
The first positive voltage is applied to one end of the winding on the primary side of the first transformer, the first negative voltage is applied to one end of the winding on the primary side of the common mode coupled inductor, and 1 of the first transformer. The other end of the winding on the secondary side and the other end of the winding on the primary side of the common mode coupled inductor are connected to each other,
The second positive voltage is applied to one end of the winding on the secondary side of the common mode coupled inductor, the second negative voltage is applied to the other end of the winding on the primary side of the second transformer, and the common mode coupled inductor DC / DC converter, characterized in that the other end of the secondary winding of the winding and one end of the primary winding of the second transformer are connected to each other. According to claim 1,
The DC/DC converter further includes a voltage divider that divides the input voltage into a first voltage and a second voltage,
The first inverter portion includes a switching element 1A, a switching element 2A, a switching element 3A and a switching element 4A connected in series, and the second inverter portion is a switching element 1B, a switching element 2B, a switching element 3B and a switching element 4B connected in series. DC / DC converter comprising a. The method of claim 7,
The voltage distribution unit includes a first input capacitor and a second input capacitor connected in series,
One end of the first input capacitor, one end of the switching element 1A and one end of the switching element 4B are electrically connected, the other end of the first input capacitor, the other end of the switching element 2A, the other end of the switching element 3B, the One end of the second input capacitor, one end of the switching element 3A, one end of the switching element 2B is electrically connected, the other end of the second input capacitor, the other end of the switching element 4A and the other end of the switching element 1B are electrically DC/DC converter characterized in that it is connected. The method of claim 8,
The first positive voltage is output from a node to which the other end of the switching element 1A and one end of the switching element 2A are connected, and the first negative voltage is output from a node to which the other end of the switching element 3A and one end of the switching element 4A are connected. The second positive voltage is output from a node to which the other end of the switching element 4B and one end of the switching element 3B are connected, and the second negative voltage is a node to which the other end of the switching element 2B and one end of the switching element 1B are connected. DC / DC converter characterized in that the output. The method of claim 9,
In the DC/DC converter, the first mode, the second mode, the third mode, the fourth mode, the fifth mode, and the sixth mode are sequentially and repeatedly operated.
In the first mode and the second mode, the switching element 1A, the switching element 1B, the switching element 4A and the switching element 4B are turned on, and the switching element 2A, the switching element 2B, the switching element 3A and the Switching element 3B is off,
In the third mode, the switching element 1A, the switching element 1B, the switching element 3A and the switching element 3B are turned on, and the switching element 2A, the switching element 2B, the switching element 4A and the switching element 4B are off. And
In the fourth mode and the fifth mode, the switching element 2A, the switching element 2B, the switching element 3A and the switching element 3B are turned on, and the switching element 1A, the switching element 1B, the switching element 4A and the Switching element 4B is off,
In the sixth mode, the switching element 2A, the switching element 2B, the switching element 4A and the switching element 4B are turned on, and the switching element 1A, the switching element 1B, the switching element 3A and the switching element 3B are off. DC / DC converter, characterized in that. According to claim 1,
The winding on the secondary side of the first transformer includes a first winding and a second winding connected in series, and the winding on the secondary side of the second transformer includes a third winding and a fourth winding connected in series,
The output unit includes a rectifier including a first diode and a second diode, an output inductor and an output capacitor,
The input terminal of the first diode is connected to one end of the first winding and one end of the third winding, and the input terminal of the second diode is connected to the other end of the second winding and the other end of the fourth winding, and the output One end of the inductor is connected to the output terminal of the first diode and the output terminal of the second diode, one end of the output capacitor is connected to the other end of the output inductor, the other end of the output capacitor is the other end of the first winding, the DC / DC converter, characterized in that connected to the other end of the third winding, one end of the second winding and one end of the fourth winding. In the low-voltage isolated DC/DC converter,
A high frequency inverter unit for outputting a first positive voltage and a first negative voltage to the first output terminal and outputting a second positive voltage and a second negative voltage to the second output terminal based on the input voltage charged in the battery for the electric vehicle;
A first transformer connected to the first output terminal of the high frequency inverter unit;
A second transformer connected to the second output terminal of the high frequency inverter unit;
A common mode coupled inductor connected between the primary side of the first transformer and the primary side of the second transformer and having a transformer structure; And
A first output unit rectifying the voltage output from the secondary side of the first transformer to output a first output voltage; And
And a second output unit rectifying the voltage output from the secondary side of the second transformer to output a second output voltage. The method of claim 12,
The first output part includes a first diode, a second diode, a first output inductor and a first output capacitor, and the second output part includes a third diode, a fourth diode, a second output inductor and a second output capacitor Ha,
The winding on the secondary side of the first transformer includes a first winding and a second winding connected in series, and the winding on the secondary side of the second transformer includes a third winding and a fourth winding connected in series,
The input terminal of the first diode is connected to one end of the first winding, the input terminal of the second diode is connected to the other end of the second winding, and one end of the first output inductor is the output terminal of the first diode and the Is connected to the output terminal of the second diode, one end of the first output capacitor is connected to the other end of the first output inductor, the other end of the first output capacitor is the other end of the first winding and the other end of the second winding Connected,
The input terminal of the third diode is connected to one end of the third winding, the input terminal of the fourth diode is connected to the other end of the fourth winding, and one end of the second output inductor is the output terminal of the third diode and the It is connected to the output terminal of the fourth diode, one end of the second output capacitor is connected to the other end of the second output inductor, the other end of the second output capacitor is the other end of the third winding and the other end of the fourth winding DC/DC converter characterized in that it is connected. In the low-voltage isolated DC/DC converter,
A high frequency inverter unit for outputting a first positive voltage and a first negative voltage to the first output terminal and outputting a second positive voltage and a second negative voltage to the second output terminal based on the input voltage charged in the battery for the electric vehicle;
A transformer connected to the first output terminal and the second output terminal of the high-frequency inverter unit, each of which is composed of two windings on the primary side and the secondary side-the primary side of the transformer is composed of a first winding and a second winding, and 2 of the transformer The secondary side consists of a third winding and a fourth winding -;
A common mode coupled inductor connected between the first winding and the second winding and having a transformer structure; And
DC / DC converter comprising a; output unit for rectifying the voltage output from the secondary side of the transformer to output the output voltage. The method of claim 14,
The first positive voltage is applied to one end of the first winding, the first negative voltage is applied to one end of the winding on the primary side of the common mode coupled inductor, and the other end of the first winding and the common mode couple The other end of the winding on the primary side of the de-inductor
The second positive voltage is applied to one end of the winding on the secondary side of the common mode coupled inductor, the second negative voltage is applied to the other end of the second winding, and the winding on the secondary side of the common mode coupled inductor. DC / DC converter, characterized in that the other end of the second winding is connected to each other. The method of claim 14,
The output unit includes a first diode, a second diode, an output inductor and an output capacitor,
The input terminal of the first diode is connected to one end of the third winding, the input terminal of the second diode is connected to the other end of the fourth winding, and one end of the output inductor is the output terminal of the first diode and the second DC/DC, which is connected to the output terminal of the diode, one end of the output capacitor is connected to the other end of the output inductor, and the other end of the output capacitor is connected to the other end of the third winding and one end of the fourth winding. Converter.

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