KR20240078332A - High Efficiency Isolation Type Zero Voltage Switching Bidirectional DC-DC Converter - Google Patents

Abstract

In a 2-stage converter prepared by serial connection of two different converters, it is connected in parallel between the two converters and includes an auxiliary circuit that provides bidirectional zero voltage switching (ZVS). A high-efficiency isolated bidirectional DC-DC converter that performs zero-voltage switching is disclosed.
According to an embodiment of the present disclosure, by enabling zero voltage switching in a two-stage DC-DC converter, high efficiency can be maintained even when operated at a high frequency.

Description

High Efficiency Isolation Type Zero Voltage Switching Bidirectional DC-DC Converter}

This disclosure relates to a high-efficiency isolated bidirectional DC-DC converter with zero voltage switching.

Isolation DC-DC converters are largely divided into hard switching-based pulse width modulation converters and soft switching-based resonant converters depending on the difference in switching method. It can be shared.

Hard switching-based pulse width modulation (PWM) converters include flyback converter, forward converter, push-pull converter, half bridge converter, and full bridge converter ( Full Bridge Converter), etc., and soft switching-based resonant converters include series resonant converters (SRC) with an internal resonance circuit, parallel resonant converters (PRC), and LLC resonant converters.

Flyback converters and forward converters have a small transformer utilization rate, but the number of parts is small, so they are often applied to relatively small-capacity converters. Push-pull converters, half-bridge converters, and full-bridge converters are mainly used for large-capacity converters with relatively large output.

If electrical insulation between the input and output terminals is required for safety or other reasons, a circuit with a transformer must be used.

A transformer is a key component of an isolated DC-DC converter, and the efficiency of the transformer has a significant impact on the efficiency and cost of the converter.

In the case of a large-capacity converter, if the capacity of a single converter is insufficient, the output of the converter can be connected in parallel or series. In this case, the ripple of the input/output voltage and current can be reduced by synchronizing the switching frequencies of the connected converters to the same frequency and adjusting the phase appropriately.

Even if it is not a large-capacity converter, if a device or circuit sensitive to switching noise is connected to the input/output terminal, the sensitivity can be lowered by switching in synchronization with a specific frequency sent from the outside.

The external frequency can be changed to a frequency that can lower sensitivity, and if operation is required at a fixed frequency or a switching frequency synchronized to an external signal, pulse width modulation or pulse amplitude modulation method is used. must be controlled.

On the other hand, in the case of an isolated DC-DC converter with a wide fluctuation range of input voltage, making it as a single converter may be inefficient.

In general, non-isolated converters such as buck converters (hereinafter referred to as buck converters) or boost converters (hereinafter referred to as boost converters) have a simpler structure and lower production costs per unit of output than isolated converters.

Therefore, in the case of an isolated bidirectional DC-DC converter with a wide input voltage range, a two-stage converter design that connects a non-isolated converter and an isolated converter to output the desired voltage or current for the input voltage or current is efficient. am.

Figure 1 is a circuit diagram of a two-stage converter in which buck-full bridge converters according to the prior art are connected in series, and Figure 2 is a graph of the operating waveform of the ideal converter of Figure 1.

As shown in Figure 1, the non-isolated converter was selected as a buck converter and the isolated converter was selected as a full bridge converter, and they were connected in series to design an isolated bidirectional DC-DC converter with a wide input voltage range. FIG. 2 shows the operating waveform of an ideal converter without the transformer leakage inductance and capacitive coupling of the converter of FIG. 1 and without the junction capacitor of the switching element.

Figure 3 is a circuit diagram of a two-stage converter in which a full bridge-boost converter according to the prior art is connected in series, and Figure 4 is a graph of the operating waveform of the ideal converter of Figure 3.

As shown in Figure 3, the non-isolated converter was selected as a boost converter and the isolated converter was selected as a full bridge converter, and they were connected in series to design an isolated bidirectional DC-DC converter with a wide input voltage range. FIG. 4 shows the operating waveform of an ideal converter without the transformer leakage inductance and capacitive coupling of the converter of FIG. 3 and without the junction capacitor of the switching element.

On the other hand, when the input/output voltage is low and rectification is performed with a diode or a free wheeling diode is used, the efficiency of the converter may be reduced due to conduction loss due to the forward voltage drop of the diode.

Therefore, efficiency can be improved by using a FET instead of a diode and using synchronous rectification, which reduces conduction loss by turning on the FET at the time the existing diode conducts.

Figure 5 is a circuit diagram of a buck-full bridge converter in which the diode of the two-stage converter of Figures 1 and 3 is replaced with a FET. As shown in Figure 5, a bidirectional two-stage DC-DC converter with synchronous rectification was designed by replacing the diodes in Figures 1 and 3 with FETs for synchronous rectification.

However, since the converter in FIG. 5 operates in a hard switching manner, there is a problem in that efficiency decreases when the frequency is increased.

1. Korean Patent No. 10-2371910 (DC-DC converter) 2. Korean Patent No. 10-2421163 (Bidirectional DC-DC converter)

The present disclosure provides a high-efficiency isolated bi-directional DC-DC that provides a zero-voltage switching function to both the non-isolated converter and the isolated converter when controlling the converter by adding an auxiliary circuit that provides zero voltage switching to a bi-directional two-stage converter that performs synchronous rectification. The purpose is to provide a converter.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

According to one aspect of the present disclosure, in a 2-stage converter provided by serial connection of two different converters, the two converters are connected in parallel and perform bidirectional zero voltage switching (ZVS). ) provides a high-efficiency isolated bidirectional DC-DC converter with zero voltage switching that includes an auxiliary circuit that provides

The two-stage converter is provided with two different converters selected from an isolation type converter or a non-isolation type converter.

The isolated converter is one of a flyback converter, a forward converter, a push-pull converter, a half bridge converter, or a full bridge converter. It is prepared.

The non-isolated converter is provided as either a buck converter, a boost converter, or a buck-boost converter.

The auxiliary circuit includes a first circuit connected to one end of the inductor of the non-isolated converter.

The auxiliary circuit may additionally include a second circuit connected to the other end of the inductor of the non-isolated converter.

The first circuit part includes a first inductor and a first field effect transistor (FET), and the second circuit part includes a second inductor and a second field effect transistor (FET).

The first inductor and the second inductor are arranged opposite each other and are provided as a coupled inductor having two windings on one core.

According to an embodiment of the present disclosure, by enabling zero voltage switching in a two-stage DC-DC converter, high efficiency can be maintained even when operated at a high frequency.

Figure 1 is a circuit diagram of a two-stage converter in which buck-full bridge converters according to the prior art are connected in series.
FIG. 2 is a graph of the operating waveform of the ideal converter of FIG. 1.
Figure 3 is a circuit diagram of a two-stage converter in which a full bridge-boost converter according to the prior art is connected in series.
FIG. 4 is a graph of the operating waveform of the ideal converter of FIG. 3.
Figure 5 is a circuit diagram of a buck-full bridge converter in which the diode of the two-stage converter of Figures 1 and 3 is replaced with a FET.
Figure 6 is a circuit diagram of a high-efficiency isolated bidirectional DC-DC converter performing zero voltage switching according to the present invention.
Figure 7 is a circuit diagram of a converter in which the FET of the high-efficiency isolated bidirectional DC-DC converter (forward direction) according to the present invention is replaced with a diode.
FIG. 8(a) is a graph of the operation waveform of the converter of FIG. 7 from t0 to zero voltage switching, and FIG. 8(b) is a graph of the operation waveform of the converter of FIG. 7 from t1 to zero voltage switching.
Figure 9 is a circuit diagram of a converter in which the FET of the high-efficiency isolated bidirectional DC-DC converter (reverse direction) is replaced with a diode according to the present invention.
FIG. 10(a) is a graph of the operation waveform of the converter of FIG. 9 from t0 to zero voltage switching, and FIG. 10(b) is a graph of the operation waveform of the converter of FIG. 9 from t1 to zero voltage switching.

This disclosure was made on December 15, 2022 in accordance with the parts localization support project hosted by the Defense Acquisition Program Administration. This is a disclosure provided based on a task performed during the period from December 14, 2025. The task number is 'C220028' and the task name is 'Three types of DC/DC converters for Cheongung-II induction electronic devices'.

Hereinafter, some embodiments of the present disclosure will be described in detail using exemplary drawings. When adding reference signs to components in each drawing, it should be noted that the same components are given the same reference numerals as much as possible even if they are shown in different drawings. Additionally, in describing the present disclosure, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present disclosure, the detailed description will be omitted.

In describing the components of the embodiment according to the present disclosure, symbols such as first, second, i), ii), a), and b) may be used. These codes are only used to distinguish the component from other components, and the nature, order, or order of the component is not limited by the code. In the specification, when a part is said to 'include' or 'have' a certain component, this means that it does not exclude other components, but may further include other components, unless explicitly stated to the contrary. .

The detailed description set forth below in conjunction with the accompanying drawings is intended to describe exemplary embodiments of the present disclosure and is not intended to represent the only embodiments in which the present disclosure may be practiced.

Figure 6 is a circuit diagram of a high-efficiency isolated bidirectional DC-DC converter performing zero voltage switching according to the present invention.

Referring to FIG. 6, the high-efficiency isolated bidirectional DC-DC converter with zero voltage switching according to the present invention consists of a 2-stage converter prepared by serial connection of two different converters, and a 2-stage converter is provided between the two converters. It is connected in parallel and includes an auxiliary circuit 100 that provides zero voltage switching (ZVS).

Here, the two-stage converter can be provided as two different converters selected from an isolation type converter or a non-isolation type converter.

The isolated converter is provided as either a flyback converter, forward converter, push-pull converter, half bridge converter, or full bridge converter. It can be.

The non-isolated converter can be provided as either a buck converter, a boost converter, or a buck-boost converter.

The auxiliary circuit 100 includes a first circuit unit 10 connected to one end of the inductor (Lb) of the non-isolated converter. The first circuit unit 10 is configured to be switched in synchronization with the switching operation of the two-stage converter and includes a first inductor 12 and a first FET 14.

In addition, the auxiliary circuit 100 may additionally include a second circuit unit 20 connected to the other end of the inductor (Lb) of the non-isolated converter, and the second circuit unit 20 includes the second inductor 22 and the second FET ( 24).

The first inductor 12 and the second inductor 14 may be arranged opposite each other to form a coupled inductor having two windings on one core.

In other words, the auxiliary circuit 100 of the present invention eliminates noise elements caused by the junction capacitors of the switching element generated during switching of the converter, the switching loss generated by the leakage inductance of the transformer, and the peak voltage generated by their resonance. The ZVS function can be provided to the converter by inducing and dissipating the first inductor 12, the second inductor 22, or the combined inductor.

Hereinafter, with reference to FIGS. 7 to 10, the ZVS process of the high-efficiency isolated bidirectional DC-DC converter with zero voltage switching according to the present invention will be described in detail.

Figure 7 is a circuit diagram of a converter in which the FET of the high-efficiency isolated bidirectional DC-DC converter (forward direction) is replaced with a diode according to the present invention, and Figure 8(a) shows the operation waveform of the converter of Figure 7 from t0 to zero voltage switching. 8(b) is a graph of the operation waveform of the converter of FIG. 7 from t1 to zero voltage switching, and FIG. 9 is a graph of the FET of the high-efficiency isolated bidirectional DC-DC converter (reverse direction) according to the present invention. is a circuit diagram of a converter replacing with a diode, and Figure 10(a) is a graph of the operating waveform from t0 to zero voltage switching for the converter of Figure 9, and Figure 10(b) is a graph of the converter of Figure 9 from zero voltage switching to t1. This is a graph of the operation waveform up to switching.

The waveforms in Figures 2 and 4 assume ideal elements, but in reality, not all elements are ideal, so switching loss occurs due to the leakage inductance of the junction capacitors of the switching element and the transformer, and Vp is caused by the junction capacitors of the switching element and the transformer. Peak voltage occurs due to resonance between leakage inductances.

A feature of the present invention is that an auxiliary circuit 100 is added and a coupled inductor is configured inside the auxiliary circuit 100. In other words, ZVS is implemented in both the isolated converter (hereinafter referred to as 'full bridge converter') and the non-isolated converter (hereinafter referred to as 'buck converter or boost converter') by allowing current to flow once through the coupled inductor during converter switching.

To make it easier to explain the operation, it is divided into forward and reverse operations and is explained on the assumption that synchronous rectification is not performed.

1. Forward

FIG. 7 is a circuit diagram showing the FET in which the current flows in the forward direction of the body diode as a diode when the current flows in the forward direction from the buck converter to the full bridge converter in FIG. 6. Figure 8 shows the operating waveform of the circuit of Figure 7.

In the operation waveform of Figure 2, the point when the buck converter turns on and t0 and t1, which are the switching points of the primary full bridge converter, coincide. Below, the operation of the auxiliary circuit 100 for ZVS and the FETs of the buck converter and full bridge converter become ZVS will be explained in detail through waveforms.

1) When Mzvsp (FET of the auxiliary circuit) is turned on at t0, current begins to flow in the coupled inductor (Lzvs).

2) When ILzvsp and ILb become equal at t1, the junction capacitor of the full bridge converter's FET (Mp1 ~ Mp4) and the coupled inductor (Lzvs) resonate, and ILzvsp continues to increase and Vp begins to decrease.

3) When Vp is about to become less than zero at t2, the body diode of the FET (Mp1 ~ Mp4) of the full bridge converter conducts, so Vp stops decreasing and maintains 0V (forward voltage drop of the FET's body diode).

4) Switching the FET (Mp1 to Mp4) of the full bridge converter at t3, where Vp is maintaining zero voltage, results in zero voltage switching.

5) When Mzvsp is turned off at t4, the energy stored in the coupled inductor (Lzvs) flows through Dzvsb to the other winding. The buck converter's inductor (Lb) current ILb is free wheeling (hereinafter referred to as 'free wheeling') through Db2. When ILzvsb becomes greater than ILb, Db2 is reverse biased and Vb is raised.

6) When Vb becomes greater than Vin at t5, the body diode of Mb1 conducts and Mb1 becomes almost 0V.

7) If Mb1 is turned on at t6, when Mb1 is almost at zero voltage, zero voltage switching occurs.

8) Switching is completed when the current ILzvsb of the coupled inductor (Lzvs) becomes zero at t7.

2. Reverse

FIG. 9 is a circuit diagram showing the FET in which current flows in the forward direction of the body diode as a diode when the current flows in the reverse direction from the full bridge converter direction in FIG. 6 to the boost converter direction. Figure 10 shows the operating waveform of the circuit of Figure 9.

In the operation waveform of Figure 4, the time when the boost converter turns on and t0 and t1, which are the switching times of the secondary full bridge converter, coincide. Below, it will be explained in detail through waveforms that the FETs of the boost converter and the full bridge converter become ZVS by operating the auxiliary circuit 100 for ZVS.

1) When Mzvsb (FET of the auxiliary circuit) is turned on at t0, current begins to flow in the coupled inductor (Lzvs). At the same time, when the FET (Ms1 to Ms4) of the secondary full bridge converter is turned off, Vp begins to decrease.

2) When ILzvsb and ILb become equal at t1, the boost converter's FET (Mb2), the junction capacitor of diode Db1, and the coupled inductor (Lzvs) resonate, and ILzvsb continues to increase and Vb begins to decrease.

3) When Vb is about to become less than zero at t2, the body diode of the FET (Mb2) of the boost converter conducts, so Vb stops decreasing and maintains 0V (forward voltage drop of the FET's body diode).

4) When switching the FETs (Mp1 ~ Mp4) and Mb2 of the full bridge converter that were operating as diodes at t3, where both Vp and Vb are maintaining zero voltage, the FET on the primary side undergoes zero voltage switching. Additionally, switching the FET (Mp1 to Mp4) of the full bridge converter at t3 results in zero voltage switching.

5) When Mzvsb is turned off at t4, the energy stored in the coupled inductor (Lzvs) flows through Dzvsp to the other winding. The boost converter's inductor (Lb) current ILb was freewheeling through the body diodes (Dp1 to Dp4) of the full bridge converter's FETs (Mp1 to Mp4). When ILzvsb becomes greater than ILb, the body diodes (Dp1 to Dp4) are reversed. Bias it and increase Vp.

6) If the energy stored in Lzvs is large enough, t5 occurs where Vs becomes larger than Vo. At t5, when Vs becomes greater than Vo, the body diodes (Ds1 to Ds4) of the FETs (Ms1 to Ms4) of the secondary full bridge converter become conductive, and the voltage of the FETs (Ms1 to Ms4) becomes almost 0V.

7) When the FET (Ms1 ~ Ms4) is turned on at t6, where the voltage of the FET (Ms1 ~ Ms4) is almost zero voltage, zero voltage switching occurs.

8) Switching is completed when the inductor current ILzvsb becomes zero at t7.

According to the embodiment of the present invention, an auxiliary circuit that provides zero voltage switching is added to a bi-directional two-stage converter performing synchronous rectification, thereby providing high-efficiency insulation that provides a zero voltage switching function to both the non-isolated converter and the isolated converter when controlling the converter. type bidirectional DC-DC converter can be provided.

At least some of the components described in the exemplary embodiments of the present disclosure include at least one of a digital signal processor (DSP), a processor, a controller, an application-specific IC (ASIC), a programmable logic device (FPGA, etc.), and other electronic devices. Or, it can be implemented as hardware elements that include a combination of these. Additionally, at least some of the functions or processes described in the exemplary embodiments may be implemented as software, and the software may be stored in a recording medium. At least some of the components, functions, and processes described in the exemplary embodiments of the present disclosure may be implemented through a combination of hardware and software.

Methods according to exemplary embodiments of the present disclosure can be written as a program that can be executed on a computer, and can also be implemented in various recording media such as magnetic storage media, optical read media, and digital storage media.

Implementations of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or combinations thereof. Implementations may include a computer program product, i.e., an information carrier, e.g., machine-readable storage, for processing by or controlling the operation of a data processing device, e.g., a programmable processor, a computer, or a plurality of computers. It may be implemented as a computer program tangibly embodied in a device (computer-readable medium) or a radio signal. Computer programs, such as the computer program(s) described above, may be written in any form of programming language, including compiled or interpreted languages, and may be written as a stand-alone program or as a module, component, subroutine, or part of a computing environment. It can be deployed in any form, including as other units suitable for use. The computer program may be deployed for processing on one computer or multiple computers at one site or distributed across multiple sites and interconnected by a communications network.

Processors suitable for processing computer programs include, by way of example, both general-purpose and special-purpose microprocessors, and any one or more processors of any type of digital computer. Typically, a processor will receive instructions and data from read-only memory or random access memory, or both. Elements of a computer may include at least one processor that executes instructions and one or more memory devices that store instructions and data. Generally, a computer may include one or more mass storage devices that store data, such as magnetic, magneto-optical disks, or optical disks, receive data from, transmit data to, or both. It can also be combined to make . Information carriers suitable for embodying computer program instructions and data include, for example, semiconductor memory devices, magnetic media such as hard disks, floppy disks, and magnetic tapes, and Compact Disk Read Only Memory (CD-ROM). ), optical recording media such as DVD (Digital Video Disk), magneto-optical media such as Floptical Disk, ROM (Read Only Memory), RAM , Random Access Memory), flash memory, EPROM (Erasable Programmable ROM), and EEPROM (Electrically Erasable Programmable ROM). The processor and memory may be supplemented by or included in special purpose logic circuitry.

The processor can execute an operating system and software applications executed on the operating system. Additionally, the processor device may access, store, manipulate, process, and generate data in response to execution of software. For ease of understanding, there are cases where a single processor device is described as being used, but those skilled in the art will understand that the processor device includes multiple processing elements and/or multiple types of processing elements. It can be seen that it may include. For example, a processor device may include multiple processors or one processor and one controller. Additionally, other processing configurations, such as parallel processors, are possible.

Additionally, non-transitory computer-readable media can be any available media that can be accessed by a computer and includes both computer storage media and transmission media.

Although this specification contains details of numerous specific implementations, these should not be construed as limitations on the scope of any invention or what may be claimed, but rather as descriptions of features that may be unique to particular embodiments of particular inventions. It must be understood. Certain features described herein in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable sub-combination. Furthermore, although features may be described as operating in a particular combination and initially claimed as such, one or more features from a claimed combination may in some cases be excluded from that combination, and the claimed combination may be a sub-combination. It can be changed to a variant of a sub-combination.

Likewise, although operations are depicted in the drawings in a particular order, this should not be construed as requiring that those operations be performed in the specific order or sequential order shown or that all of the depicted operations must be performed to obtain desirable results. In certain cases, multitasking and parallel processing may be advantageous. Additionally, the separation of various device components in the above-described embodiments should not be construed as requiring such separation in all embodiments, and the described program components and devices may generally be integrated together into a single software product or packaged into multiple software products. You must understand that it is possible.

Meanwhile, the embodiments of the present invention disclosed in the specification and drawings are merely provided as specific examples to aid understanding, and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that in addition to the embodiments disclosed herein, other modifications based on the technical idea of the present invention can be implemented.

The scope of protection of this embodiment should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of this embodiment.

100: Auxiliary circuit
10: 1st circuit unit
12: 1st inductor 14: 1st FET
20: 2nd circuit unit
22: second inductor 24: second FET

Claims (8)

In a 2-stage converter prepared by serial connection of two different converters,
A high-efficiency isolated bidirectional DC-DC converter that is connected in parallel between the two converters and includes an auxiliary circuit that provides bidirectional zero voltage switching (ZVS).
According to paragraph 1,
The two-stage converter is a high-efficiency isolated bidirectional DC-DC converter that performs zero voltage switching and is composed of two different converters selected from an isolation type converter or a non-isolation type converter.
According to paragraph 2,
The isolated converter is one of a flyback converter, a forward converter, a push-pull converter, a half bridge converter, or a full bridge converter. A high-efficiency isolated bidirectional DC-DC converter with zero voltage switching.
According to paragraph 2,
The non-isolated converter is a high-efficiency isolated bidirectional DC-DC converter that performs zero voltage switching and is provided as either a buck converter, a boost converter, or a buck-boost converter.
According to paragraph 2,
The auxiliary circuit is a high-efficiency isolated bidirectional DC-DC converter for zero voltage switching including a first circuit connected to one end of the inductor of the non-isolated converter.
According to clause 5,
The auxiliary circuit is a high-efficiency isolated bidirectional DC-DC converter for zero voltage switching, wherein the auxiliary circuit additionally includes a second circuit connected to the other end of the inductor of the non-isolated converter.
According to clause 6,
The first circuit part includes a first inductor and a first field effect transistor (FET), and the second circuit part includes a second inductor and a second field effect transistor (FET). DC converter.
In clause 7,
The first inductor and the second inductor are arranged opposite each other and are provided as a coupled inductor having two windings on one core. A high-efficiency isolated bidirectional DC-DC converter for zero voltage switching.