KR20200097237A - Low voltage dc-dc converter and driving method thereof - Google Patents

Abstract

Disclosed are a low-voltage DC converting device and a driving method thereof. According to one aspect of the present invention, a method for setting a turn ratio and a core void of a transformer included in the low-voltage DC converting device, comprises the processes of: determining a power switching element based on a voltage capacity, a current capacity, and a parasitic capacitance; determining a minimum inductance for ensuring a zero-voltage switching operation of the power switching element; adjusting a turn ratio and a core void of a transformer in consideration of an input voltage range of the transformer; calculating leakage inductance of the transformer; comparing the leakage inductance with the minimum inductance; and adaptively performing the adjusting process as a result of the comparing process. According to the present invention, it is possible to reduce the product size, thereby improving power density of the low-voltage DC converting device.

Description

Low voltage DC converter and its driving method {LOW VOLTAGE DC-DC CONVERTER AND DRIVING METHOD THEREOF}

The present invention relates to a low voltage DC converter and a driving method thereof.

A low-voltage DC-DC converter (LDC) is a power supply device that is absolutely required to supply power to electric loads mounted inside an eco-friendly vehicle and to charge the vehicle low voltage auxiliary battery.

There are various types of low-voltage DC converters according to implementation methods, and a full-bridge method that performs an insulated switching operation is used for high power conversion.

However, in the conventional low voltage DC converter, switching power loss occurs during a controlled switching operation of the power switching element.

On the other hand, in order to solve this problem, Korean Patent Application Publication No. 1998-040074 (name of the invention: zero voltage switching DC-DC step-down converter) discloses a zero voltage switching technology of a power switching device.

That is, the prior art uses a zero voltage switching operation to reduce switching power loss.

However, in this prior art, it is necessary to additionally install a zero voltage switching inductor to ensure a zero voltage switching operation.

However, since the zero voltage switching inductor is accompanied by heat generation during a high-speed switching operation of the power switching element, a heat dissipation structure using a heat sink or the like is required, which takes up a lot of space in the system.

An object of the present invention is to provide a low voltage DC converter capable of reducing product material cost and size and improving power density by adding a void to a transformer core region and adjusting a turn ratio of a transformer, and a driving method thereof. .

However, the technical problem to be achieved by the present embodiment is not limited to the technical problem as described above, and other technical problems may exist.

According to an aspect of the present embodiment, in a method of setting a turn ratio and a core void of a transformer included in a low voltage DC converter, power based on voltage capacity, current capacity, and parasitic capacitance (capacitance) Determining a switching element; Determining a minimum inductance for ensuring a zero-voltage switching operation of the power switching device; Adjusting the turn ratio and core void of the transformer in consideration of the input voltage range of the transformer; Calculating leakage inductance of the transformer; Comparing the leakage inductance and the minimum inductance; And adaptively performing the adjusting process according to a result of the comparing process. A method of setting a transformer included in a low voltage DC converter is provided.

According to another aspect of the present embodiment, there is provided a switching element determining unit determining a power switching element based on a voltage capacity, a current capacity, and a parasitic capacitance; An inductance determining unit determining a minimum inductance for ensuring a zero-voltage switching operation of the power switching device; An adjustment unit for adjusting a turn ratio and a core gap of the transformer in consideration of the input voltage range of the transformer; A calculator for calculating a leakage inductance of the transformer; And a comparison unit for comparing the leakage inductance and the minimum inductance, wherein the adjustment unit readjusts the turn ratio and the air gap according to the comparison result of the comparison unit.

According to any one of the above-described problem solving means of the present invention, by adding a void to the transformer core region and adjusting the turn ratio, it is possible to reduce the material cost and size of the product.

In addition, it is possible to improve the power density of the low voltage DC converter by reducing the product size.

1 is a view for explaining a full-bridge type low voltage DC converter according to the prior art.
2 is a block diagram of a low voltage DC converter according to an embodiment of the present invention.
3 is a view for explaining a low voltage DC converter according to an embodiment of the present invention.
4 is a view for explaining a transformer of a low voltage DC converter according to an embodiment of the present invention.
5 is a flowchart of a method of driving a low voltage DC converter according to an embodiment of the present invention.
6 is a flowchart of a method for setting a transformer of a low voltage DC converter according to an embodiment of the present invention.
7 is a view showing the internal structure of a transformer of a low voltage DC converter according to the prior art and an embodiment of the present invention.
8 is a diagram showing an output waveform of a low voltage DC converter according to an embodiment of the prior art and the present invention
9 is a view showing an output value of a low voltage DC converter according to an embodiment of the prior art and the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts not related to the description are omitted in order to clearly describe the present invention.

Meanwhile, terms used in the present specification are for explaining embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless otherwise specified in the phrase. As used herein, "comprise" and/or "comprising" refers to the presence of one or more other constituent elements, step operations and/or elements, or It does not exclude addition.

The present invention relates to a low voltage DC converter 100 and a driving method thereof.

In an eco-friendly vehicle, a low voltage DC converter is an essential device for charging a low voltage auxiliary battery with a high voltage output from a high voltage main battery and supplying power to various electric loads mounted inside the vehicle. In addition, for high power conversion, a full-bridge method that performs an isolated type switching operation is used.

Hereinafter, an operation of a conventional low voltage DC converter will be described with reference to FIG. 1.

1 is a view for explaining a full-bridge type low voltage DC converter according to the prior art.

As shown in Fig. 1, the low voltage DC converter inputs high voltage AC power to the transformer Tr through the switching operation of the power switching elements Q1, Q2, Q3, Q4 using a high voltage battery (HV) as an input power source. Let it.

At this time, since power loss occurs during the switching operation of the power switching elements Q1, Q2, Q3, and Q4, a zero voltage switching operation is used to minimize such switching power loss.

The zero voltage switching operation is a high-speed switching technique for power devices, and is an important design factor contributing to achieving high efficiency in the converter field, but requires a zero voltage switching inductor (Lzvs).

However, since the zero voltage switching inductor (Lzvs) carries heat during the switching operation of the power switching elements (Q1, Q2, Q3, Q4), a heat dissipation structure using a heat sink or a cooling system for this is required. It takes up a lot of space, increasing the product size.

In order to solve the above problems, an embodiment of the present invention is characterized in that a gap is added to the core region of the transformer 120 and the turn ratio of the transformer 120 is adjusted to replace the conventional zero voltage switching inductor. .

Hereinafter, a low voltage DC converter 100 according to an embodiment of the present invention will be described with reference to FIGS. 2 to 4.

2 is a block diagram of a low voltage DC converter 100 according to an embodiment of the present invention, and FIG. 3 is a view for explaining the low voltage DC converter 100 according to an embodiment of the present invention. 4 is a view for explaining the transformer 120 of the low-voltage DC converter 100 according to an embodiment of the present invention.

As shown in FIG. 2, the low voltage DC converter 100 according to an embodiment of the present invention includes a switching unit 110, a transformer 120, and a power supply unit 130.

The switching unit 110 converts the high voltage provided from the high voltage battery of the vehicle into an AC voltage.

Referring to FIG. 3, power switching elements Q1, Q2, Q3, and Q4 are arranged in a full-bridge method in the switching unit 110, so that a zero voltage switching operation can be performed by a leakage inductance Llk1, which will be described later. have.

In addition, the inductor Lzvs installed for the zero voltage switching operation in the prior art is removed from the switching unit 110, and the primary side of the transformer 120 is added by adjusting the turn ratio and adding a gap in the core region of the transformer 120. By replacing the leakage inductance (Llk1), it is possible to reduce the material cost of the product and reduce the product size. Also, by reducing the product size, the power density of the product can be improved.

The transformer 120 steps down the AC voltage output from the switching unit 110 to a low voltage and transmits it to the power supply unit 130.

Referring to FIG. 4, since a void is added to the core region of the transformer 120, the magnetizing inductance Lm is reduced according to Equation 1.

[Equation 1]

Here, Lm is the magnetizing inductance of the transformer 120, N1 is the primary turn ratio of the transformer 120, Rc is the magneto-resistance of the core region, and Rg is the magneto-resistance of the air gap.

The core of the transformer 120 according to the embodiment of the present invention is a magnetic material, and when a current exceeding the saturation characteristic inherent in the magnetic material is applied and the core is saturated, it cannot function normally. In order to reduce the magnetizing current, the transformer The turn ratio of 120 is considered together.

Accordingly, the effect of reducing the magnetizing current im of the transformer 120 according to Equation 2 and an effect of increasing the primary leakage inductance Llk1 of the transformer 120 according to Equation 3 can be obtained through the adjustment of the turn ratio of the transformer 120. .

[Equation 2]

Here, im is the transformer (120) magnetizing current, i1 is the transformer (120) primary input current, N1 is the transformer (120) primary turn ratio, N2 is the transformer (120) secondary turn ratio, i2 is the transformer (120) secondary It means the output current.

[Equation 3]

Here, Llk1 denotes a primary leakage inductance value of the transformer 120, N1 denotes a primary turn ratio of the transformer 120, and R1 denotes the primary circuit resistance of the transformer 120.

The power supply unit 130 rectifies the low voltage output from the transformer 120 and supplies it to the load.

Hereinafter, a method of driving the low voltage DC converter 100 will be described with reference to FIG. 5.

5 is a flowchart of a method of driving the low-voltage DC converter 100 according to an embodiment of the present invention.

In the driving method of the low voltage DC converter 100 with reference to FIG. 5, first, a high voltage provided from a high voltage battery of a vehicle is converted into an AC voltage (S110).

In this case, according to an embodiment of the present invention, in order to convert a high voltage of a vehicle into an AC voltage, the power switching element may be arranged in a full-bridge method.

Next, the AC voltage is stepped down to a low voltage using the transformer 120 in which a void is added to the core region and the turn ratio is adjusted.

At this time, specific details applied by adding a void to the core region of the transformer 120 and adjusting the turn ratio have been described in FIG. 4 and Equations 1 to 3, and thus will be omitted below.

Finally, the low voltage is rectified and supplied to the low voltage auxiliary battery and the electric load of the vehicle (S130).

In the above description, steps S110 to S130 may be further divided into additional steps or may be combined into fewer steps, according to an embodiment of the present invention. In addition, some steps may be omitted as necessary, or the order between steps may be changed. In addition, even if other contents are omitted, the contents already described in FIG. 4 may also be applied to the driving method of the low voltage DC converter 100 of FIG. 5.

Meanwhile, the transformer 120 of the low voltage DC converter 100 according to an embodiment of the present invention may be set in the same manner as in FIG. 6.

6 is a flowchart of a method of setting the transformer 120 of the low voltage DC converter 100 according to an embodiment of the present invention.

Referring to FIG. 6, first, a power switching device is set in consideration of voltage/current capacity and parasitic capacitance (S210).

Next, a minimum inductance (Lmin) value for ensuring a zero voltage switching operation is set (S220).

Here, the minimum inductance value means the minimum value for the conventional zero voltage switching inductor to guarantee the zero voltage switching operation of the power switching element, and the parasitic capacitance of the power switching element is less than the energy stored in the zero voltage switching inductor. Is set.

Next, the turn ratio of the transformer 120 is set and the air gap is adjusted according to an embodiment of the present invention (S230).

In this case, the input voltage range is considered in setting the turn ratio of the transformer 120 and adjusting the air gap in the core region.

Next, the leakage inductance Llk1 value of the transformer 120 is calculated using Equation 3 (S240).

Next, the set minimum inductance (Lmin) value and the calculated leakage inductance (Llk1) value are compared (S250).

As a result of the comparison, when the minimum inductance (Lmin) value is less than the leakage inductance (Llk1) value, the transformer 120 is applied to the product under the condition that the reduced magnetizing current and magnetizing inductance and the increased leakage inductance value are included ( S260).

On the other hand, when the minimum inductance (Lmin) value is greater than the leakage inductance (Llk1) value, the step (S230) of setting a turn ratio and adjusting the air gap is performed again.

Hereinafter, an internal structure of the transformer 120 according to the prior art and an exemplary embodiment of the present invention, and an output value change according to the addition of a void in the core region of the transformer 120 and adjustment of a turn ratio will be described with reference to FIGS. 7 to 9.

7 is a view showing the internal structure of the transformer 120 of the low voltage DC converter 100 according to the prior art and an embodiment of the present invention.

Referring to FIG. 7, an embodiment of the present invention removes the zero voltage switching inductor additionally installed in the transformer 120 in the prior art, adds a void in the core region of the transformer 120, and Zero voltage switching inductors can be replaced by adjusting the turn ratio. This can reduce the number of components compared to a conventional transformer, thereby reducing the material cost of the product and reducing the product size. And by reducing the size of the product, the power density of the product can be improved.

8 is a view showing the output waveform of the low voltage DC converter 100 according to the prior art and an embodiment of the present invention, showing a result of easy comparison among the results of a plurality of trials. 9 is a view showing an output value of the low voltage DC converter 100 according to the prior art and an embodiment of the present invention.

The upper part of FIG. 8 shows the output value of the prior art as a waveform, and the lower part of FIG. 8 shows the output value after adding a void to the core region of the transformer 120 and adjusting the turn ratio according to an embodiment of the present invention. .

According to an embodiment of the present invention, the turn ratio may be adjusted to 11:1:1.

Referring to FIG. 9, the input voltage and the input current are the same. In the case of the prior art, the magnetization inductance was reduced from 800 µH to 210 µH after adding a void to the core region of the transformer 120 and adjusting the turn ratio according to the embodiment of the present invention. And the leakage inductance of the transformer 120 increased from 2.8 μH to 4.3 μH.

As a result of the simulation, it is confirmed that the magnetizing current is reduced as the magnetizing inductance decreases, so that the operating performance of the low-voltage DC converter 100 is equal to or higher than that of the previous one. have. In addition, it was confirmed that it is possible to secure a margin for the duty ratio of the transformer 120.

The above description of the present invention is for illustrative purposes only, and those of ordinary skill in the art to which the present invention pertains will be able to understand that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative and non-limiting in all respects. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as being distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the claims to be described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. do.

100: low voltage DC converter 110: switching unit
120: transformer 130: power supply
Q1, Q2, Q3, Q4: Power switching element Lzvs: Zero voltage switching inductor
C1, C2, C3, C4: parasitic capacitance D1, D2: rectifier diode

Claims (10)

In the method of setting a turn ratio and core void of a transformer included in a low voltage DC converter,
Determining a power switching element based on voltage capacity, current capacity, and parasitic capacitance;
Determining a minimum inductance for ensuring a zero-voltage switching operation of the power switching device;
Adjusting the turn ratio and core void of the transformer in consideration of the input voltage range of the transformer;
Calculating leakage inductance of the transformer;
Comparing the leakage inductance and the minimum inductance; And
A process of adaptively performing the adjustment process according to the result of the comparison process
A method of setting a transformer included in a low voltage DC converter comprising: a. The method of claim 1,
The process of determining the minimum inductance,
The method of setting a transformer included in a low voltage DC converter, characterized in that determining the minimum inductance based on the parasitic capacitance of the power switching element. The method of claim 1,
The adjusting process,
A method of setting a transformer included in a low-voltage DC converter, characterized in that the turn ratio is adjusted based on the primary input current, the secondary input current, and the magnetizing current of the transformer. The method of claim 1,
The adjusting process,
The method of setting a transformer included in a low voltage DC converter, characterized in that the core void is adjusted based on the magnetizing inductance of the transformer, the primary turn ratio, the magnetoresistance of the core region, and the magnetoresistive resistance of the core void. The method of claim 1,
The calculating process,
And calculating the leakage inductance based on the primary-side leakage inductance, the primary-side turn ratio, and the primary-side circuit resistance of the transformer. A switching element determining unit determining a power switching element based on a voltage capacity, a current capacity, and a parasitic capacitance;
An inductance determination unit determining a minimum inductance for ensuring a zero-voltage switching operation of the power switching device;
An adjustment unit for adjusting a turn ratio and a core gap of the transformer in consideration of the input voltage range of the transformer;
A calculator for calculating a leakage inductance of the transformer; And
Comprising a comparison unit for comparing the leakage inductance and the minimum inductance,
The adjustment unit,
Transformer setting device, characterized in that readjusted the turn ratio and the air gap according to the comparison result of the comparison unit. The method of claim 6,
The inductance determination unit,
Transformer setting device, characterized in that determining the minimum inductance based on the parasitic capacitance of the power switching element. The method of claim 6,
The adjustment unit,
Transformer setting device, characterized in that adjusting the turn ratio based on the primary input current, the secondary input current, and the magnetizing current of the transformer. The method of claim 6,
The adjustment unit,
The transformer setting device, wherein the core void is adjusted based on the magnetizing inductance of the transformer, the primary turn ratio, the magnetoresistance of the core region, and the magnetoresistive resistance of the core void. The method of claim 6,
The calculation unit,
And calculating the leakage inductance based on a primary leakage inductance, a primary turn ratio, and a primary circuit resistance of the transformer.

Images