KR101237843B1 - Dc-to-dc converter for electric vehicle to step a low battery voltage up - Google Patents

Abstract

PURPOSE: A DC-to-DC converter for electric vehicle is provided to minimize the number of an output voltage power semiconductor device by serially connecting a battery and an output condenser. CONSTITUTION: In a first circuit module, a first capacitor(30_1) is serially connected to the positive terminal of an input voltage source(10). The positive terminal of a first inductor(40_1) is connected to the positive terminal of the input voltage source. A first diode(50_1) is connected between the negative terminals of the first inductor and the first capacitor. A first switch(20_1) is connected between the negative terminal of the first inductor and the negative terminal of the input voltage source.

Description

DC-to-DC converter for electric vehicle to step a low battery voltage up}

The present invention relates to a DC-to-DC converter device for an electric vehicle, and more particularly, a boosted DC for securing a DC-link voltage for driving a motor for driving an electric vehicle by efficiently boosting a low battery voltage. It relates to a -to-DC converter device.

Today, with the development of the industry, the consumption of electricity is increasing, and because of the convenience of movement, in order to solve the environmental problems caused by the rapid spread of the internal combustion engine cars, the improvement of the fuel efficiency of the automobiles and the introduction of electric vehicles have recently been introduced. The development of hybrid vehicles using all of them has been achieved to improve fuel efficiency. In the future, the proportion of internal combustion engines will gradually decrease, and eventually, the development of fuel-cell vehicles using pure electric vehicles or fuel cells driven solely with electricity is expected. As the driving ratio of the electric motor increases as described above, the voltage used in the trance motor is used in the high voltage of 300 [V] in consideration of the loss and the advantages of the motor design. However, such a high-voltage power supply system has a problem such as human electric shock, so a system such as a NEV (Neighborhood Electric Vehicle) uses a low battery of up to 70 [V]. Due to these safety and efficiency aspects, the battery uses a low voltage and the motor uses a high voltage, which means that at least four times the boost DC / DC converter development is essential. In addition, due to the issue of electrical safety, isolated converter technology should be developed.

Meanwhile, Toyota's MCU (Motor Control Unit), which adopts a bi-directional DC-to-DC converter to efficiently boost the input voltage of a low battery of an electric vehicle, can select a low input voltage and configure a small number of battery cells. As a result, it is possible to secure structural reliability and, above all, to lower the price of the battery, which occupies the largest price portion of the electric system of the HEV or the electric vehicle. In addition, if the voltage specification of the electric motor is designed to be high, the loss caused by copper loss can be minimized, and it is advantageous to optimize the use of the winding and the heat dissipation structure.

Therefore, it is urgent to develop an electric vehicle converter for increasing the input / output voltage step-up ratio. Among the converters for electric vehicles, there are several types of DC-to-DC converters, such as buck, boost, and buck-boost converters. These are distinguished by whether the output voltage is above or below the input voltage and whether the output voltage spans the entire range of the input voltage. Typically, these converters often use pulse-width-modulation (PWM) as the switching method. If you want to increase the output voltage with a fixed input voltage such as a battery bank, you usually use a boost converter. In this case, there is a problem that the cost of the capacitor is increased.

KR 10-2002-0097369 A, 2002.12.31, p. 2, Fig. 2

 Choi, Mi-Sun, Song-Geun Song, Sung-Jun Park, Dae-Kyung Kim, Yong-Koo Kim, "Development of High-Efficiency Boosted DC / DC Converter for Electric Vehicle", Journal of the Korean Institute of Power Electronics, Vol.15, No.2, pp. 127-133, April 2010.

The present invention is to provide a boost type DC-to-DC converter device for driving a motor for driving an electric vehicle by efficiently boosting the low battery voltage to solve the above problems.

The technical problems to be achieved by the present invention are not limited to the technical problems mentioned above.

In the DC-to-DC converter device of the present invention for achieving the above object, the converter device is composed of a first to second circuit module including a switch, a capacitor, an inductor, a diode, In the first circuit module, the first capacitor is connected in series with the + terminal of the input voltage source, the + terminal of the first inductor is also connected to the + terminal of the input voltage source, and the first terminal is connected between the-terminal of the first capacitor and the first inductor. A diode is connected, a first switch is connected between the-terminal of the first inductor and the-terminal of the input voltage source, a second capacitor is connected in series with the first capacitor of the first circuit module in the second circuit module, The + terminal of the second inductor is also connected to the first capacitor, the second diode is connected between the-terminal of the second capacitor and the second inductor, and the second switch is connected between the-terminal of the second inductor and the-terminal of the input voltage source.The first to second switches are operated through a control signal of a controller connected for control to switch power, and the power is converted and output through an output terminal formed between the second capacitor and an input voltage source. It is done.

Preferably, the DC-to-DC converter device further comprises a third to n-th circuit module for boosting the output voltage, the n- of the n-th module from the n-th circuit module An n-th capacitor is connected in series with the first capacitor, an n-th capacitor is also connected to the + terminal of the n-th inductor, an n-th diode is connected between the n-th capacitor and the-terminal of the n-th inductor, and an n-th inductor The n-th switch is connected between the-terminal of and the-terminal of the input voltage source.

The third to nth switches of the third to nth circuit modules are operated through a control signal of a controller connected for control to switch power, and the power is supplied through an output terminal formed between the nth capacitor and an input voltage source. It is characterized in that the converted and output.

Preferably, energy is stored in the first inductor during the ON period of the first switch, and energy stored in the first inductor during the OFF period of the first switch charges the first capacitor, and during the ON / OFF period of the first switch. The voltage between the terminal of the first capacitor and the input voltage source is the sum of the input voltage and the voltage across the first capacitor.

Furthermore, energy is stored in the second inductor during the ON period of the second switch, and energy stored in the second inductor during the OFF period of the second switch charges the second capacitor, and the second capacitor is turned on during the ON / OFF period of the second switch. The voltage between the negative terminal of the capacitor and the input voltage source is always the sum of the input voltage and the voltage across the first and second capacitors.

As described above, the DC-to-DC converter device for an electric vehicle of the present invention is a structure in which a battery and an output capacitor are coupled in series to form an output voltage, thereby reducing the number of stacking of battery cells, thereby increasing structural reliability. In addition, there is an effect that the electrical reliability can be increased by minimizing the number of output voltage power semiconductor elements.

1 is a view showing the overall configuration of a DC-to-DC converter device according to an embodiment of the present invention.
FIG. 2 shows the main waveforms of the basic first module of the converter in FIG. 1.
FIG. 3 shows the main waveforms of the second module of the converter in FIG. 1.
4 is a diagram showing the voltage of the capacitor of the first module, the voltage of the second capacitor, and the output voltage of the final converter in FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like elements in the figures are denoted by the same reference numerals wherever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

1 is a view showing a DC-to-DC converter 100 device according to an embodiment of the present invention, the converter device is a switch 20, a capacitor 30, an inductor 40, a diode 50, and And an output stage 60.

The DC-to-DC converter 100 is composed of n modules, and each module includes a switch 20, a capacitor 30, an inductor 40, and a diode 50. The first module comprises a switch 20_1, a capacitor 30_1, an inductor 40_1, a diode 50_1, and the nth module includes a position 20_n, a capacitor 30_n, an inductor 40_n, a diode ( 50_n).

Referring to the first module as an example, the first capacitor 30_1 is connected in series with the + terminal of the input voltage source 10, and the + terminal of the first inductor 40_1 is also connected to the + terminal of the input voltage source. The first diode 50_1 is connected between the terminal of the first capacitor 30_1 and the first inductor 40_1. The first switch 20_1 is connected between the negative terminal of the first inductor 40_1 and the negative terminal of the input voltage source 10. The first switch is operated through a control signal of a controller (not shown) connected for control to switch power by switching power.

Referring to the configuration of the second module, the second capacitor 30_2 is connected in series with the first capacitor 30_1 of the first module, and the + terminal of the second inductor 40_2 is also connected to the first capacitor 30_1. The second diode 50_2 is connected between the − terminal of the second capacitor 30_2 and the second inductor 40_2. The second switch 20_2 is connected between the negative terminal of the second inductor 40_2 and the negative terminal of the input voltage source 10. The second switch is operated through a control signal of a controller (not shown) connected for control to switch the power by switching the power.

Referring to the configuration of the n-th module, the n-th capacitor 30_n is connected in series with the n-th capacitor 30_n-1 of the n-th module, and further connected to the n-th capacitor 30_n-1. The + terminal of the n-th inductor 40_n is connected, and the n-th diode 50_n is connected between the n-th capacitor 30_n and the-terminal of the n-th inductor 40_n. The n th switch 20_n is connected between the − terminal of the n th inductor 40_n and the − terminal of the input voltage source 10. The n-th switch is operated through a control signal of a controller (not shown) connected for control to switch power by switching power.

The basic circuit structure of the DC-to-DC converter 100 of the present invention is a switch (20_1, ..., 20_n), a diode (50_1, ..., 50_n), inductor (40_1, ...) as shown in , 40_n), and capacitors 30_1,..., 30_n, have four types of circuit elements, and have an structure _in which an input voltage source V _in 10 and an output capacitor C ₁ 30 are series-coupled. Energy is stored in the inductor 40_1 during the ON period of the switch S ₁ 20_1, and energy stored in the inductor 40_1 during the OFF period of the switch S ₁ 20_1 charges the capacitor C ₁ 30_1. The output voltage 60 is always the sum of the input voltage V _in 10 and the voltage across the capacitor V _C1 30_1 during the ON / OFF period of the switch 20_1. In order to increase the boost ratio in the circuit according to the present invention, the series coupling ( L ₁ + L ₂ +… L _n ) of the inductor (40_1, ..., 40_n) and the series coupling ( C ₁ + C ₂ +. C _n ) (30_1, ..., 30_n) is required. That is, if the voltages applied to the first diode D ₁ 50_1 and the switch S ₁ 20_1 of FIG. 1 are regarded as one input voltage source, the finally expanded circuit includes n diodes 50_1,..., 50_n of FIG. 1. And switches 20_1, ..., 20_n, and capacitors 30_1, ..., 30_n. A non-conductive relationship of the input voltage and the output voltage when the input voltage to the L _n is applied to volt-sec equilibrium condition in the inductor L _n (40_n) hayeoteul as V _n, S _n and the switch is shown in equation (1).

Equation 1

In this case, Vn represents an input voltage in the inductor L _n , Vout represents an output voltage, D represents a duty ratio of the switch 20, and T represents a switching period of the switch 20.

Equation 1 is summarized as follows.

Equation 2

It can be seen from Equation 2 that the relationship between the input-output voltage and the conduction ratio of the DC-to-DC converter is the same as that of the conventional boost converter.

Inductor L _n Applying the volt-sec equilibrium condition at the inductor L _{n -1} (40_n-1) before (40_n) gives:

Equation 3

In this case, Vn represents an input voltage at the inductor L _n , Vn-1 represents an input voltage at the inductor L _{n -1} , and D represents a duty ratio of the switch 20.

Substituting Equation 3 into Equation 2 and summarizing the relationship between the input / output voltage and the conduction ratio is shown in Equation 4, which is established under the assumption that all switches are operated in parallel at the same conduction ratio.

Equation 4

The relationship between the input / output voltage and the conduction ratio when the number of elements (switches, diodes, inductors, and capacitors) constituting the circuit is n from Equations 2, 3, and 4 is defined as in Equation 5.

Equation 5

In this case, Vin denotes an input voltage source, Vout denotes an output voltage, and D denotes a duty ratio of the switch 20.

PSpice-based simulation results are presented for validating the converter. The input voltage was 72 V, the switching frequency was 10 kHz, and 1 kW. By combining the two modules, the two switches are controlled in parallel without phase difference and the conduction ratio of the switches is controlled at 50%.

Figure 2 shows the main waveforms of the basic first module of the converter according to an embodiment of the present invention. From top to bottom, the switch 20_1 voltage across V _S1 , the inductor 40_1 voltage across V _L1 , the diode 50_1 current I _D1 , the output capacitor 30_1 voltage across V _C1 , and FIG. 3 is the main waveform of the expanded second module. Comparing the two waveforms, if the switch 20_1 S ₁ and the switch 20_2 S ₂ are turned on at the same time, the voltages and currents of the inductors 40_1 and 40_2 L ₁ and L ₂ increase, and the capacitors 30_1 and 30_2 C. ₁ and C ₂ start to discharge. When the switch 20_1 S ₁ and the switch 20_2 S ₂ are turned off, the voltages and currents of the inductors 40_1 and 40_2 L ₁ and L ₂ decrease, and the capacitors 30_1 and 30_2 C ₁ and C ₂ are charged.

4 shows the voltage of the capacitor 30_1 C ₁ of the first module, the voltage of the second capacitor 30_2 C ₂ , and the output voltage 60 of the final converter. The voltage 30_1 of C ₁ is similar in magnitude to the input voltage source 10, and the voltage 30_2 of C ₂ is about twice the size of the C ₁ voltage 30_1. Therefore, the final output voltage V _out (60) is expressed as the sum of the magnitudes of the input voltage V _in (10), the voltage of C ₁ (30_1), and the voltage of C ₂ (30_2), and can be confirmed that four times the input voltage (10). have. Theoretically, as the conduction ratio of the switch increases, the output voltage can be boosted according to Equation 5, and when the conduction ratio of the switch is 80%, the boost voltage can be increased to 1800 V corresponding to 25 times the input voltage.

What has been described above is only one embodiment for carrying out the converter device according to the present invention, and the present invention is not limited to the above-described embodiment, and as claimed in the following claims, it departs from the gist of the present invention. Without this, anyone skilled in the art to which the present invention pertains will have the technical spirit of the present invention to the extent that various modifications can be made.

100: DC-to-DC converter 10: input voltage source
20: switch 30: capacitor
40: inductor 50: diode
20_n: nth switch 30_n: nth capacitor
40_n: nth inductor 50_n: nth diode

Claims (5)

In a DC-to-DC converter device,
The converter device is composed of first to second circuit modules including switches, capacitors, inductors, diodes,
In the first circuit module, the first capacitor is connected in series with the + terminal of the input voltage source, and the + terminal of the first inductor is also connected to the + terminal of the input voltage source, and between the first capacitor and the-terminal of the first inductor. 1 diode is connected, the first switch is connected between the terminal of the first inductor and the terminal of the input voltage source,
The second capacitor is connected in series with the first capacitor of the first circuit module in the second circuit module, the + terminal of the second inductor is also connected to the first capacitor, and the negative terminal of the second capacitor and the second inductor. A second diode is connected between the second diode and a second switch is connected between the negative terminal of the second inductor and the negative terminal of the input voltage source.
The first to second switches are operated via a control signal of a control unit connected for control to switch the power,
DC-to-DC converter device characterized in that the power is converted and output through an output terminal formed between the second capacitor and the input voltage source.
The method according to claim 1,
The DC-to-DC converter device further comprises a third to n-th circuit module for boosting the output voltage,
The n th capacitor is connected in series with the n-1 capacitor of the n-1 th module in the n th circuit module, and the + terminal of the n th inductor is also connected to the n-1 capacitor. An n th diode is connected between the-terminal of the n inductor, and an n switch is connected between the-terminal of the n inductor and the-terminal of the input voltage source.
The third to nth switches of the third to nth circuit modules are operated through a control signal of a controller connected for control to switch power.
DC-to-DC converter device characterized in that the power is converted and output through an output terminal formed between the n-th capacitor and the input voltage source.
The method according to claim 1,
Energy is stored in the first inductor during the ON period of the first switch, and energy stored in the first inductor during the OFF period of the first switch charges the first capacitor, and the first capacitor and the first capacitor during the ON / OFF period of the first switch. The voltage between the-terminal of the input voltage source is the sum of the input voltage and the voltage across the first capacitor DC-to-DC converter device.
The method according to claim 3,
Energy is stored in the second inductor during the ON period of the second switch, and energy stored in the second inductor during the OFF period of the second switch charges the second capacitor, and the second capacitor and the second capacitor during the ON / OFF period of the second switch. DC-to-DC converter device, characterized in that the voltage between the terminals of the input voltage source is always the sum of the input voltage and the voltage across the first and second capacitors.
The method according to claim 2,
When the DC-to-DC converter device is composed of n circuit modules,
DC-to-DC converter device, characterized in that the output voltage of the output stage is configured as shown in Equation 1 below.
Equation 1

Where Vin represents an input voltage source, Vout represents an output voltage, and D represents the duty ratio of the switch.

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