KR-102964407-B1 - APPARATUS AND METHOD FOR CONTROLLING LLC RESONANCE CONVERTER

KR102964407B1KR 102964407 B1KR102964407 B1KR 102964407B1KR-102964407-B1

Abstract

The present invention relates to a control method for an LLC resonant converter, comprising the steps of detecting a parameter value associated with the operation of the converter, determining a switching duty of the converter based on the detected parameter value, and controlling the converter with the determined switching duty, thereby improving the nonlinearity of the gain curve of the converter, reducing output current ripple, and enabling low-gain output.

Inventors

장희숭
우동균
김철순
김지헌
박성욱

Assignees

현대자동차주식회사
기아 주식회사

Dates

Publication Date: 20260512
Application Date: 20210803

Claims (14)

As a control method for an LLC resonant converter, A step of detecting the input voltage and output voltage of the converter, which are parameter values associated with the operation of the converter; A step of determining the switching duty of the converter based on the detected parameter value; and The method includes the step of controlling the converter with the switching duty determined above, The step of determining the switching duty of the above converter is, It includes a step of calculating the gain value of the converter using the above input voltage and output voltage, and A control method for an LLC resonant converter, characterized in that the determined switching duty has a first constant value when the gain value is less than or equal to a first reference value, a second constant value when it is greater than or equal to a second reference value, and a value on a straight line or curve passing through the first constant value and the second constant value when it is greater than or equal to the first reference value and less than the second reference value, wherein the first constant value and the second constant value are different from each other.
In Article 1, The step of determining the switching duty of the above converter is, A step of calculating a gain correction value by applying a scale value and an offset value to the above-mentioned calculated gain value; and A control method for an LLC resonant converter characterized by including the step of determining the switching duty from the gain correction value using a predetermined function.
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As a control method for an LLC resonant converter, A step of detecting the switching frequency of the converter, which is a parameter value associated with the operation of the converter; A step of determining the switching duty of the converter based on the detected parameter value; and The method includes the step of controlling the converter with the switching duty determined above, A control method for an LLC resonant converter, characterized in that the above-determined switching duty has a third constant value when the switching frequency is less than or equal to a third reference value, a fourth constant value when it is greater than or equal to a fourth reference value, and a value on a straight line passing through the third constant value and the fourth constant value when the switching frequency is greater than or equal to the third reference value and less than or equal to the fourth reference value, wherein the third constant value and the fourth constant value are different from each other.
In Article 5, The step of determining the switching duty of the above converter is, A step of calculating a switching frequency correction value by applying a scale value and an offset value to the above switching frequency; and A control method for an LLC resonant converter characterized by including the step of determining the switching duty from the switching frequency correction value using a predetermined function.
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In Article 2 or Article 6, A control method for an LLC resonant converter, characterized in that the scale value and the offset value are constant values determined by at least one of the current value and resistance value applied to the converter.
In Article 2 or Article 6, A control method for an LLC resonant converter, characterized in that the above scale value and offset value are determined by finding a switching duty value that eliminates the nonlinearity of the gain curve of the converter and enables linear characteristics, and finding a scale value and offset value that can derive the corresponding switching duty value through iterative simulation.
A converter capable of voltage conversion according to the control of a switch element provided internally; and A duty variable controller that detects the input voltage and output voltage of the converter, which are parameter values associated with the operation of the converter, and determines the switching duty of the switch element based on the detected parameter values, The above-mentioned variable duty controller is, LLC resonant converter control device characterized by calculating a gain value by dividing the output voltage by the input voltage, and determining the switching duty based on a corrected gain correction value obtained by applying a scaling value and an offset value to the calculated gain value.
In Article 10, The above-mentioned variable duty controller is, A parameter detection unit that detects the above parameter value; A parameter correction unit that applies the scaling value and the offset value to the detected parameter value; LLC resonant converter control device characterized by including a duty calculation unit that determines the switching duty from parameter values to which the scaling value and the offset value are applied using a predetermined function.
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In Article 10, A control device for an LLC resonant converter, characterized in that the determined switching duty has a first constant value when the gain value is less than or equal to a first reference value, a second constant value when it is greater than or equal to a second reference value, and a value on a straight line passing through the first constant value and the second constant value when it is greater than or equal to the first reference value and less than the second reference value, wherein the first constant value and the second constant value are different from each other.
A converter capable of voltage conversion according to the control of a switch element provided internally; and a variable duty controller that detects the switching frequency of the converter, which is a parameter value associated with the operation of the converter, and determines the switching duty of the switch element based on the detected parameter value, wherein A control device for an LLC resonant converter, characterized in that the above-determined switching duty has a third constant value when the switching frequency is less than or equal to a third reference value, a fourth constant value when it is greater than or equal to a fourth reference value, and a value on a straight line passing through the third constant value and the fourth constant value when the switching frequency is greater than or equal to the third reference value and less than or equal to the fourth reference value, wherein the third constant value and the fourth constant value are different from each other.

Description

Apparatus and Method for Controlling LLC Resonance Converter The present invention relates to an LLC resonant converter control device and a control method thereof, and more specifically, to an LLC resonant converter with improved nonlinear characteristics of an input/output voltage gain characteristic curve and a control method thereof. Eco-friendly vehicles that charge batteries serving as the energy source for the vehicle's drive motor, such as electric vehicles or plug-in hybrid vehicles, have an on-board charger that converts external alternating current power to output direct current power for charging the battery. Typically, a vehicle-mounted charger includes a power factor correction circuit that compensates for the power factor of external AC power and outputs it as DC, and a DC-DC converter that converts the DC output of the power factor correction circuit into a DC charging voltage for the battery. Here, an LLC resonant converter utilizing LC resonance may be employed as the DC-DC converter. An LLC resonant converter is so named because its characteristics are determined by the resonant frequency set by two inductors and one capacitor acting as resonant tanks surrounding the transformer. Since the LLC resonant converter utilizes the resonant current generated by the two inductors and one capacitor, it has the advantage of significantly reducing switching losses and diode losses. On the other hand, an LLC resonant converter has the disadvantage that the input-output relationship is determined by controlling the switching frequency rather than the duty cycle of the internal switching elements; consequently, the input-output voltage gain characteristic curve exhibits nonlinearity, making control difficult. The matters described above as background technology are intended only to enhance understanding of the background of the present invention and should not be construed as an acknowledgment that they constitute prior art already known to those skilled in the art. FIG. 1 is a diagram illustrating an example of an LLC resonant converter circuit structure to aid in understanding the present invention. Figure 2 is a diagram illustrating the nonlinearity of the gain curve according to the change in switching frequency according to a conventional converter. FIG. 3 is a configuration diagram of a converter control device according to one embodiment of the present invention. FIGS. 4a and 4b are drawings illustrating the configuration of a variable duty controller according to one embodiment of the present invention. FIGS. 5a and 5b are drawings showing the duty and the corresponding gain curve derived by the duty variable controller shown in FIG. 4. FIGS. 6a and 6b are drawings illustrating a variable duty controller according to another embodiment of the present invention. FIGS. 7a and 7b are drawings showing the duty and the corresponding gain curve derived by the duty variable controller shown in FIGS. 6a and 6b. FIGS. 8a and 8b are drawings illustrating result values by a converter control device according to an embodiment of the present invention. FIG. 9 is a flowchart of a converter control method according to one embodiment of the present invention. Embodiments of the present invention will be described in detail below with reference to the attached drawings. The present invention relates to an LLC resonant converter control device and a control method for controlling an LLC resonant converter by varying the switching duty. Hereinafter, these may be briefly referred to as the “converter control device” and the “converter control method,” respectively. Recently, technological development for automotive chargers and converters has focused on increasing efficiency and miniaturization. Among them, the LLC resonant converter is one of the most widely adopted types of resonant converters. This converter performs complementary switching with a fixed duty cycle of 50% and can minimize switching losses through the resonant current caused by L and C resonance by changing the switching frequency. Figure 1 is a diagram illustrating the structure of an LLC resonant converter circuit to aid in understanding the present invention, and the part indicated by the dotted line in the diagram corresponds to the LLC resonant converter. LLC resonant converters are widely applied in industries where the input/output range is limited. This is because if used in environments with a wide input/output range, non-linear characteristics occur on the input/output voltage gain curve, making control very difficult. In this case, proper output voltage/current control becomes impossible, which can significantly affect the durability and burnout of converter components. Figure 2 illustrates the non-linearity of the gain curve according to the change in switching frequency of a conventional converter. Referring to Figure 2, it can be seen that as the switching frequency (f sw ) increases, non-linear characteristics occur in the gain cur