DC-DC converter, method for determining circuit constants of a DC-DC converter, and method for setting control conditions of a DC-DC converter.

Abstract

To provide a DC-DC converter capable of achieving highly efficient power conversion in high-frequency drive (MHz band), a method for determining the circuit constants of a DC-DC converter, and a method for setting the control conditions of a DC-DC converter. [Solution] The DC-DC converter includes a transformer having a primary winding connected to an input voltage source via a primary line and a secondary winding connected to a capacitor connected to the output terminal via a secondary line; a first inductor connected in series with the primary line; a first switch provided on the primary line for connecting and disconnecting the primary line; a first capacitor connected in parallel with the first switch; a second inductor connected in series with the secondary line; a second switch provided on the secondary line for connecting and disconnecting the secondary line; and a second capacitor connected in parallel with the second switch. The circuit constants of the multiple circuit elements are determined based on the switch voltages of the first and second switches.

Description

[Technical Field]

[0001] The present invention relates to a DC-DC converter, a method for determining circuit constants of a DC-DC converter, and a method for setting control conditions of a DC-DC converter. [Background technology]

[0002] Japan's energy supply is primarily based on fossil fuels, and energy conservation efforts have stagnated in several areas. Energy consumption can be divided into thermal, chemical, and electrical. Electrical energy is widely used in various sectors of society due to its portability and convenience. Furthermore, the application of electrical energy is being promoted in areas such as electric vehicles, highlighting the potential of efficient power conversion circuits.

[0003] Chargers for IT equipment utilize flyback converter circuits, a type of isolated DC-DC converter. Therefore, improving the performance of flyback converter circuits is extremely important. To reduce switching losses and increase power conversion efficiency, development is underway on flyback converter circuits using soft-switching methods. This method achieves the Class E switching conditions of ZVS (Zero Voltage Switching) and ZDS (Zero Derivative Switching), enabling efficient power conversion at high frequencies. Regarding bidirectional flyback converters, there is a known technique for miniaturizing the entire circuit and reducing circuit costs by reducing the number of switching elements compared to conventional bidirectional converters (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-154525 [Overview of the project] [Problems that the invention aims to solve]

[0005] The flyback converters that utilize the aforementioned bidirectional operation have two main challenges. First, there is no quantitative data to demonstrate that highly efficient power conversion can be achieved at high frequencies (MHz band). Second, applications for GaN devices, which are more suitable for high-frequency driving than SiC but have weaker voltage resistance, are not considered. The object of the present invention is to provide a DC-DC converter that can achieve highly efficient power conversion in high-frequency drive (MHz band), a method for determining the circuit constants of a DC-DC converter, and a method for setting the control conditions of a DC-DC converter. [Means for solving the problem]

[0006] (1) One aspect of the present invention is a DC-DC converter comprising: a transformer having a primary winding connected to an input voltage source via a primary line and a secondary winding connected to a capacitor connected to the output terminal via a secondary line; a first inductor connected in series with the primary line; a first switch provided on the primary line for connecting and disconnecting the primary line; a first capacitor connected in parallel with the first switch; a second inductor connected in series with the secondary line; a second switch provided on the secondary line for connecting and disconnecting the secondary line; and a second capacitor connected in parallel with the second switch, wherein the circuit constants of a plurality of circuit elements are determined based on the switch voltages of the first switch and the second switch. (2) One aspect of the present invention is a DC-DC converter as described in (1) above, further comprising a first harmonic resonant filter connected in parallel with the first switch and a second harmonic resonant filter connected in parallel with the second switch. (3) One aspect of the present invention is a DC-DC converter as described in (1) or (2) above, wherein the circuit element is at least one of the first inductor, the first capacitor, the second inductor, and the second capacitor. (4) In one aspect of the present invention, in the DC-DC converter described in (1) above, the inductance of the first inductor, the capacitance of the first capacitor, the inductance of the second inductor, and the capacitance of the second capacitor are determined based on the relationship between the inductance of the first inductor and the switch voltage of the first switch, the relationship between the capacitance of the first capacitor and the switch voltage of the first switch, the relationship between the inductance of the second inductor and the switch voltage of the second switch, and the relationship between the capacitance of the second capacitor and the switch voltage of the second switch. (5) One aspect of the present invention is a DC-DC converter as described in (1) above, further comprising a control unit that controls the first switch and the second switch to realize a boost mode and a buck mode. (6) In one aspect of the present invention, in the DC-DC converter described in (5) above, the circuit constants of each circuit element are determined based on the output voltage, output current and switching frequency, and the relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage and the relationship between the phase difference between the first switch and the second switch and the output voltage are derived based on the determined circuit constants of each circuit element, and the duty cycle of the first switch, the duty cycle of the first switch and the relationship between the duty cycle of the second switch and the output voltage and the relationship between the phase difference between the first switch and the second switch and the output voltage are determined based on the derived relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage and the relationship between the phase difference between the first switch and the second switch and the output voltage. (7) In one aspect of the present invention, in the DC-DC converter described in (5) above, the control unit adjusts the duty cycle of the first switch and the second switch. (8) In one aspect of the present invention, in the DC-DC converter described in (5) or (6) above, the control unit adjusts the timing of turning the first switch and the second switch on or off. (9) In one aspect of the present invention, in the DC-DC converter described in (5) above, the control unit controls the first switch and the second switch based on zero voltage switching (ZVS) and zero differential switching (ZDS) conditions. (10) In one aspect of the present invention, in the DC-DC converter described in (5) above, the control unit switches the first switch and the second switch after achieving both zero voltage switching (ZVS) and zero differential switching (ZDS) conditions. (11) One aspect of the present invention is a method for determining the circuit constants of a DC-DC converter, which is performed by a computer, wherein the DC-DC converter comprises a transformer having a primary winding connected to an input voltage source via a primary line and a secondary winding connected to a capacitor connected to the output terminal via a secondary line; a first inductor connected in series with the primary line; a first switch provided on the primary line for connecting and disconnecting the primary line; a first capacitor connected in parallel with the first switch; a second inductor connected in series with the secondary line; a second switch provided on the secondary line for connecting and disconnecting the secondary line; and a second capacitor connected in parallel with the second switch, wherein the method for determining the circuit constants of the DC-DC converter comprises the step of determining the circuit constants of a plurality of circuit elements based on the switch voltages of the first switch and the second switch. (12) One aspect of the present invention is a method for determining the circuit constants of a DC-DC converter as described in (5) above, wherein the circuit element is at least one of the first inductor, the first capacitor, the second inductor, and the second capacitor. (13) One aspect of the present invention is a method for determining the circuit constants of a DC-DC converter as described in (11) above, comprising the steps of: deriving the relationship between the inductance of the first inductor and the switch voltage of the first switch, the relationship between the capacitance of the first capacitor and the switch voltage of the first switch, the relationship between the inductance of the second inductor and the switch voltage of the second switch, and the relationship between the capacitance of the second capacitor and the switch voltage of the second switch; and determining the inductance of the first inductor, the capacitance of the first capacitor, the inductance of the second inductor and the capacitance of the second capacitor based on the derived relationship between the inductance of the first inductor and the switch voltage of the first switch, the relationship between the capacitance of the first capacitor and the switch voltage of the first switch, the relationship between the inductance of the second inductor and the switch voltage of the second switch, and the capacitance of the second capacitor and the switch voltage of the second switch. (14) One aspect of the present invention is a method for setting control conditions of a DC-DC converter executed by a computer, wherein the DC-DC converter comprises a transformer having a primary winding connected to an input voltage source via a primary line and a secondary winding connected to a capacitor connected to the output terminal via a secondary line, a first inductor connected in series with the primary line, a first switch provided on the primary line for connecting and disconnecting the primary line, a first capacitor connected in parallel with the first switch, a second inductor connected in series with the secondary line, a second switch provided on the secondary line for connecting and disconnecting the secondary line, and a second capacitor connected in parallel with the second switch, wherein the method for setting control conditions of the DC-DC converter comprises an output voltage, an output current, A method for setting control conditions for a DC-DC converter, comprising the steps of: determining the circuit constants of each circuit element based on the switching frequency; deriving the relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage, and the relationship between the phase difference between the first switch and the second switch and the output voltage based on the determined circuit constants of each circuit element; and determining the duty cycle of the first switch, the duty cycle of the first switch, and the phase difference between the first switch and the second switch based on the derived relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage, and the relationship between the phase difference between the first switch and the second switch and the output voltage. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a DC-DC converter that can achieve highly efficient power conversion in high-frequency drive (MHz band), a method for determining the circuit constants of a DC-DC converter, and a method for setting the control conditions of a DC-DC converter. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example of a DC-DC converter according to this embodiment. [Figure 2A]This figure shows an example of design specifications for voltage boosting. [Figure 2B] This figure shows an example of design specifications for step-down voltage conversion. [Figure 3] This diagram illustrates the boost operation of the DC-DC converter in this embodiment. [Figure 4] This figure shows an example of design values ​​for an element. [Figure 5] This shows an example of the primary switch voltage waveform of the first switch of a DC-DC converter during boost operation. [Figure 6A] This shows an example of the relationship between the capacitance and potential difference of a shunt capacitor. [Figure 6B] This shows an example of the relationship between the inductance of an inductor and the potential difference per unit time. [Figure 7] This shows an example of the secondary switch voltage waveform of the second switch of a DC-DC converter during boost operation. [Figure 8A] This figure illustrates an example of a method for setting control conditions for a DC-DC converter according to this embodiment. [Figure 8B] This figure illustrates an example of a method for setting control conditions for a DC-DC converter according to this embodiment. [Figure 8C] This figure illustrates an example of a method for setting control conditions for a DC-DC converter according to this embodiment. [Figure 9] This embodiment shows the design value, measured value, and error rate between the design value and the measured value for each element implemented in the DC-DC converter. [Figure 10] This figure shows an example of the boost operation waveform of the DC-DC converter according to this embodiment. [Figure 11] This figure shows an example of the step-down operation waveform of the DC-DC converter according to this embodiment. [Figure 12] The primary switch voltage waveforms during boost and buck operations are shown. [Figure 13] The secondary switch voltage waveforms during boost and buck operations are shown. [Figure 14]This figure shows an example of a method for determining the circuit constants of a DC-DC converter according to this embodiment. [Figure 15] This figure shows an example of a method for setting control conditions for a DC-DC converter according to this embodiment. [Figure 16] This figure shows an example of a configuration diagram of a DC-DC converter according to a modified example of the embodiment 1. [Figure 17] This figure shows an example of a configuration diagram of a DC-DC converter according to a modified example of the embodiment 2. [Modes for carrying out the invention]

[0009] Next, the DC-DC converter of this embodiment, the method for determining the circuit constants of the DC-DC converter, and the method for setting the control conditions of the DC-DC converter will be described with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the embodiments described below. In all the figures used to illustrate the embodiments, components with the same function are given the same reference numerals, and repeated explanations are omitted. Furthermore, in this application, "based on XX" means "based on at least XX," and includes cases where it is based on another element in addition to XX. Also, "based on XX" is not limited to cases where XX is used directly, but also includes cases where it is based on something that has been calculated or processed from XX. "XX" is any element (for example, any information).

[0010] (Embodiment) Embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows an example of a DC-DC converter 1 according to this embodiment. The DC-DC converter 1 has a transformer TR. Transformer TR primary winding L P The input voltage source E A It is connected to primary lines 11 and 12. The primary side line 11 has an inductor L A These are connected in series, and the input voltage source E A There is a capacitor C smoAare connected in parallel. On the primary side line 12, there is a first switch SW that disconnects this primary side line 12 A and a capacitor C A and an inductor L 2A and a capacitor C 2A are connected in parallel.

[0011] The secondary winding L of the transformer TR S is connected to a capacitor C connected to the output terminal smoB by secondary side lines 21 and 22. In FIG. 1, a state where an output voltage source E B is connected to the output terminal is shown. On the secondary side line 21, an inductor L B is connected in series. On the secondary side line 22, there is a second switch SW that disconnects this secondary side line 22 B and a capacitor C B and an inductor L 2B and a capacitor C 2B are connected in parallel.

[0012] Furthermore, the DC-DC converter 1 includes a control unit 30. The control unit 30 controls the first switch SW A and the second switch SW B to realize a boost mode and a buck mode. When the DC-DC converter 1 converts from DC (direct current) to DC (direct current), in the boost mode, it outputs a voltage higher than the input voltage (boosts). When the DC-DC converter 1 converts from DC (direct current) to DC (direct current), in the buck mode, it outputs a voltage lower than the input voltage (bucks).

[0013] The DC-DC converter 1 incorporates a second harmonic resonance filter on both the primary side and the secondary side. Specifically, on the primary side, an inductor L 2A and a capacitor C 2A are incorporated, and on the secondary side, an inductor L 2B and a capacitor C 2BThis is incorporated. By incorporating a second harmonic resonant filter with the same configuration on both the primary and secondary sides in this way, the peak value of the switch voltage can be significantly suppressed, and bidirectional energy transfer can be facilitated. Such circuits are being applied to automotive power conversion circuits. While lithium-ion batteries, increasingly used in electric vehicles, have a nominal voltage of 3.7V, conventional automotive lead-acid batteries have a nominal voltage of 12V. Therefore, it is possible to power three lithium-ion batteries connected in series with a 12V voltage rating.

[0014] However, lithium-ion batteries, which have a relatively high energy density, may exceed their normal operating range for some reason. To mitigate such risks, DC-DC converter 1 performs both boosting and bucking. For example, it stores and releases energy by switching to an inductor and a capacitor. This configuration prevents short circuits and overcurrents in the lithium-ion battery.

[0015] Next, we will describe an example of the design specifications for DC-DC converter 1 and details of an example of the components used when mounting it on the board. First, as an example, during boost operation, the input voltage V in 3.7V, output voltage V out Let it be 12V. On the other hand, in step-down operation, as an example, the input voltage V in 12V, output voltage V out The voltage is set to 3.7V. These design specifications allow for voltage boosting and bucking between the nominal voltage of lithium-ion batteries (3.7V) and the nominal voltage of automotive lead-acid batteries (12V).

[0016] Switching frequency f SW The selection of this component differentiates it from power conversion circuits with switching frequencies ranging from tens of kHz to hundreds of kHz. Furthermore, parasitic impedance components on the substrate are greatly affected by high-frequency operation, making it difficult to fabricate circuits with resonant structures. In DC-DC converter 1, these factors are taken into consideration, and the switching frequency f SWFor example, it can be set to 1MHz.

[0017] The switching devices (first switch SW) on both the primary and secondary sides of the DC-DC converter 1 A , second switch SW B As an example, a GaN device (GS61004: withstand voltage 100V, rated current 38A, manufactured by GaNSystems) is applicable.

[0018] Transformer and inductor (Inductor L) of a second-harmonic resonant filter 2A , inductor L 2B For the core, as an example, Liqualloy® (GLT110S, manufactured by Alps Alpine) was used. This Fe-based metal powder core material was selected because it has a high saturation magnetic flux density, low iron loss, and does not require an air gap or cutting. It maintains a constant permeability μ [H / m] from 1 MHz to 10 MHz, and the set switching frequency f SW Suitable for use at 1MHz and a resonant frequency of 2MHz. Boost design specifications (Input Voltage: V in Output voltage V out Load Resistance (R), Output Power (W) out Switching frequency f SW Figure 2A shows the design specifications for step-down (Input Voltage V in Output voltage V out Load Resistance (R), Output Power (W) out Switching frequency f SW ) is shown in Figure 2B.

[0019] This section describes the measurement targets for the boost and buck operations of the DC-DC converter 1. Figure 3 is a diagram illustrating the boost operation of the DC-DC converter 1 in this embodiment. As shown in Figure 3, second harmonic resonant filters are incorporated on both the primary side (inverter) and the secondary side (rectifier). Specifically, an inductor L is installed on the primary side. 2A and capacitor C 2A It is incorporated, and on the secondary side there is an inductor L 2B and capacitor C 2B It is incorporated. Furthermore, in order to achieve the Class E switching conditions of ZVS / ZDS, an inductor L is installed on the primary side. A and capacitor C A It is incorporated, and on the secondary side there is an inductor L B and capacitor C B These are incorporated. These elements (primary winding L P Inductance of secondary winding L S Inductance, coupling coefficient k, inductor L A The inductance of the inductor L B Inductance, capacitor C A Capacitance, capacitor C B capacitance, inductor L 2A Inductance, capacitor C 2A capacitance, inductor L 2B Inductance, capacitor C 2B The design values ​​for the capacitance are shown in Figure 4.

[0020] This section describes the parameter adjustment for DC-DC converter 1 that satisfies the ZVS / ZDS conditions. The parameters of the DC-DC converter 1 are adjusted, for example, by an information processing device. The information processing device may be, for example, a stationary computer device, or a portable computer device such as a smartphone or a tablet computer (tablet PC). Figure 5 shows the first switch SW of the DC-DC converter 1 during boost operation. APrimary side switch voltage waveform (V gs1 (Gate-source voltage), V ds1 An example of (drain-source voltage) is shown. In Figure 5, the horizontal axis is time [microseconds (μs)] and the vertical axis is the switch voltage [V]. The parameters of the elements to be adjusted to achieve ZVS are the shunt capacitor C A Therefore, the parameters of the elements to be adjusted to achieve ZDS are the inductor L A This is the shunt capacitor C. A and inductor L A By adjusting the resonance point, Class E switching conditions (ZVS / ZDS) can be achieved. For example, the part shown by the dashed line in Figure 5 is adjusted to become zero.

[0021] The information processing device is a shunt capacitor C A Let the capacitance of the shunt capacitor C be a variable. A We derive the relationship between capacitance and potential difference ΔV. Figure 6A shows the shunt capacitor C A An example of the relationship between capacitance and potential difference ΔV is shown. Here, potential difference ΔV is the difference between the voltage when switching operation is performed and the voltage when it is zero. In Figure 6A, the potential difference ΔV is expressed as an absolute value. According to Figure 6A, the shunt capacitor C A For a capacitance [nF], the potential difference ΔV takes a minimum value. For example, an information processing device can approximate the shunt capacitor C when the potential difference ΔV takes a minimum value by using an n-th order (where n is an integer n>1) polynomial approximation. A The capacitance of the shunt capacitor C is derived. The information processing device uses the derived shunt capacitor C. A The capacitance of the shunt capacitor C A Let the circuit constants be as follows. One example of n is 4.

[0022] The information processing device is an inductor L A Let the inductance of be a variable, A We derive the relationship between the inductance and the potential difference ΔV / Δt per unit time. FIG. 6B shows an example of the relationship between the inductance of inductor L A and the potential difference ΔV / Δt per unit time. The potential difference ΔV is the difference between the voltage when the switching operation is performed and zero voltage. According to FIG. 6B, it can be seen that the potential difference ΔV / Δt per unit time takes a minimum value with respect to the inductance [nH] of inductor L A . For example, the information processing apparatus derives the inductance of inductor L A when the potential difference ΔV / Δt per unit time takes a minimum value by approximating with an n-th order (n is an integer greater than 1) polynomial. The information processing apparatus uses the derived inductance of inductor L A as the circuit constant of inductor L A . An example of n is 3.

[0023] FIG. 7 shows an example of the secondary side switch voltage waveforms (V B (gate-source voltage), V gs2 (drain-source voltage)) of the second switch SW ds2 of the DC-DC converter 1 during the boost operation. In FIG. 7, the horizontal axis is time [microseconds (μs)], and the vertical axis is the switch voltage [V]. The parameter of the element adjusted to achieve ZVS is the shunt capacitor C B . The parameter of the element adjusted to achieve ZDS is the inductor L B . By adjusting the resonance point of the shunt capacitor C B and the inductor L B , the class E switching condition (ZVS / ZDS) is realized. For example, adjustment is made so that the portion indicated by the broken line in FIG. 7 becomes zero. The information processing apparatus derives the capacitance of the shunt capacitor C B and the inductance of the inductor L B . Regarding an example of the derivation method, the method described with reference to FIGS. 6A and 6B can be applied, and thus the description here is omitted. By adjusting the parameters of the inductor and capacitor in the DC-DC converter 1, its influence is significantly manifested in the operating waveform and output performance of the circuit. Therefore, in an example of parameter adjustment, it is carried out in units from several nH to one-tenth of several nH, and from several nF to one-tenth of several nF.

[0024] Actually, the error between the design value and the measured value is 17.2 nH for the inductor L A and 5.8 nF for the shunt capacitor C A ; the inductor L B is 0 nH, and the shunt capacitor C B is 0.4 nF. In order to simplify the manufacture of the DC-DC converter 1, the inductance value of the transformer TR (the inductance of the primary winding L P , the inductance of the secondary winding L S ), the coupling coefficient k, and the inductance values and capacitance values of the second harmonic resonance filters (the inductors L 2A , capacitors C 2A , inductors L 2B , capacitors C 2B ) on both sides of the circuit are measured in advance when performing the circuit design. Returning to FIG. 1, the description will continue.

[0025] The control unit 30 controls the first switch SW A and the second switch SW B based on the ZVS and ZDS conditions. For example, the control unit 30 switches the first switch SW A and the second switch SW B after achieving both the ZVS and ZDS conditions. Specifically, the control unit 30 adjusts the duty ratios of the first switch SW A and the second switch SW B . A method for adjusting the duty ratio of the first switch SW A will be described. The adjustment of the duty ratio of the first switch SW A is performed, for example, by an information processing device. [[ID=五十]]

[0026] Figure 8A is a diagram illustrating an example of a method for setting control conditions for the DC-DC converter according to this embodiment. In Figure 8A, the horizontal axis represents the first switch SW A The duty cycle [%] is shown, and the vertical axis represents the output voltage. Here, the output voltage is normalized.

[0027] According to Figure 8A, the first switch SW A For a given duty cycle [%], the normalized output voltage is convex downwards and takes a maximum value. For example, an information processing device can use an n-th order (where n is an integer n>1) polynomial approximation to determine the first switch SW when the normalized output voltage takes a maximum value. A The duty cycle [%] of the first switch SW is derived. The information processing device uses the derived first switch SW A The duty cycle [%] of the first switch SW is set in the control unit 30. A The DC-DC converter 1 is controlled based on the duty cycle [%] of n. An example of n is 2.

[0028] 2nd switch SW B The duty cycle is adjusted, for example, by an information processing device. Figure 8B is a diagram illustrating an example of a method for setting control conditions for the DC-DC converter 1 according to this embodiment. In Figure 8B, the horizontal axis is the second switch SW B The duty cycle [%] is shown, and the vertical axis represents the output voltage. Here, the output voltage is normalized.

[0029] According to Figure 8B, the second switch SW B For a given duty cycle [%], the normalized output voltage is convex downwards and takes a maximum value. For example, an information processing device can use an n-th order (where n is an integer n>1) polynomial approximation to determine the second switch SW at which the normalized output voltage takes a maximum value. B The duty cycle [%] of the second switch SW is derived. The information processing device uses the derived second switch SW B The duty cycle [%] of the second switch SW is set in the control unit 30. BThe DC-DC converter 1 is controlled based on the duty cycle [%] of n. An example of n is 2.

[0030] The control unit 30 controls the first switch SW A and the second switch SW B Adjust the timing of turning it on or off. Switch 1 A and the second switch SW B This explains how to adjust the timing of turning it on or off. Switch 1 A and the second switch SW B The timing of turning the switch on or off is adjusted, for example, by an information processing device. Figure 8C is a diagram illustrating an example of a method for setting control conditions for the DC-DC converter according to this embodiment. In Figure 8C, the horizontal axis represents the first switch SW A and the first switch SW A The phase difference [ns] is shown, and the vertical axis represents the output voltage. Here, the output voltage is normalized.

[0031] According to Figure 8C, the first switch SW A and the first switch SW A For a phase difference [ns] with respect to the first switch SW, the normalized output voltage is convex downwards and takes a maximum value. For example, the information processing device can use an n-th order (where n is an integer n>1) polynomial approximation to determine when the normalized output voltage takes a maximum value. A and the first switch SW A The phase difference [ns] with respect to is derived. The information processing device then uses the derived first switch SW A and the first switch SW A The control unit 30 sets the phase difference [ns] with respect to the first switch SW. A and the first switch SW A The DC-DC converter 1 is controlled based on the phase difference [ns] between it and the other element. An example of n is 2.

[0032] DC-DC converter 1 was fabricated, and the switching frequency f SWThe operation at 1 MHz was verified. DC-DC converter 1 was fabricated using the design values ​​shown in Figure 4. Based on the experimental results obtained by operating DC-DC converter 1, the switching operation, output power, and power conversion efficiency were specifically analyzed. To achieve bidirectional operation, it is essential to fix the design values ​​of the components of DC-DC converter 1. Therefore, bidirectional operation is achieved by fixing the switching device (first switch SW A , second switch SW B It is presumed that this can be achieved simply by adjusting the duty cycle and phase of the )

[0033] Figure 9 shows the design values, measured values, and error rates between the design values ​​and measured values ​​for each element implemented in the DC-DC converter 1 according to this embodiment. As an example of each element, Figure 9 shows the inductance of the primary winding LP, the inductance of the secondary winding LS, the coupling coefficient k, the inductance of the inductor LA, the inductance of the inductor LB, the capacitance of the capacitor CA, the capacitance of the capacitor CB, the inductance of the inductor L2A, the capacitance of the capacitor C2A, the inductance of the inductor L2B, and the capacitance of the capacitor C2B. First, the element where the error between the design value and the measured value is 0.00% (the primary winding L of the transformer TR) P and secondary winding L S Coupling coefficient k, inductor L B , inductor L 2A , capacitor C 2A , and capacitor C 2B Regarding the DC-DC converter 1, the impedance of each element was measured before manufacturing, and then the circuit was designed using a circuit simulator.

[0034] During the actual manufacture of DC-DC converter 1, in order to achieve the Class E switching conditions (ZVS / ZDS), an inductor (inductor L) was used. A ) and shunt capacitor (capacitor C) A , capacitor C B The impedance value of ) is fine-tuned. The discrepancy between the design values ​​and the measured values ​​is presumed to be due to the failure to consider the parasitic impedance of the DC-DC converter 1's components and board wiring during the design of the DC-DC converter 1. In particular, high-frequency operation (switching frequency f in this embodiment) SW At 1MHz, the parasitic impedance component becomes more pronounced.

[0035] Shunt capacitor (capacitor C) A , capacitor C B The difference between the design value and the measured value of the switching device (first switch SW) is as follows: A , second switch SW B The output capacitance value of ) is the terminal voltage (V ds It depends on the voltage. Therefore, this difference is presumed to be due to the fact that such voltage dependence was not considered during the circuit design.

[0036] Figure 10 shows an example of the boost operation waveform of the DC-DC converter 1 according to this embodiment. Figure 10 shows the voltage and current waveforms during the boost operation of the fabricated DC-DC converter 1. In Figure 10, the horizontal axis is time [microseconds (μs)], and the vertical axis is the input voltage V in [V], Output voltage V out [V], primary side switch voltage V gs1 [V], primary side switch voltage V ds1 [V], secondary switch voltage V gs2 [V], secondary switch voltage V ds2 [V] and input current I in [A] is the answer.

[0037] For operational observation, an electronic load device (LW151-151D, TEXIO) set to constant resistance mode (50Ω) was connected to the output terminal. As a result, the output voltage was calculated to be 11.7V, the output power 2.7W, and the power conversion efficiency 83.2%. Also, the switch voltage waveform (V ds1 , V ds2 It was also confirmed that the system achieves Class E switching conditions (ZVS / ZDS) at 1MHz operation. Furthermore, the drain-source voltage waveform (Vds1 , V ds2 ) showed that certain frequency components were attenuated, and the switch voltage peak was effectively suppressed as intended.

[0038] Figure 11 shows an example of the step-down operation waveform of the DC-DC converter 1 according to this embodiment. In Figure 11, the horizontal axis represents time [microseconds (μs)], and the vertical axis represents the input voltage V in [V], Output voltage V out [V], primary side switch voltage V gs1 [V], primary side switch voltage V ds1 [V], secondary switch voltage V gs2 [V], secondary switch voltage V ds2 [V] and input current I in [A] is the answer.

[0039] To achieve bidirectional operation, the design values ​​of the components of DC-DC converter 1 are fixed, and the switching device (first switch SW) A , second switch SW B This is achieved by adjusting the duty cycle and phase of the voltage. Based on the above, the step-down operation is achieved using the measurements in Figure 8, as in the step-up operation. For operational observation, an electronic load device (LW151-151D, TEXIO) set to constant resistance mode (4.8Ω) was connected to the output terminal. As a result, the output voltage was calculated to be 4.0V, the output power 3.3W, and the power conversion efficiency 81.9%. Also, the switch voltage waveform (V ds1 , V ds2 It was also confirmed that the system achieves Class E switching conditions (ZVS / ZDS) at 1MHz operation. Furthermore, the drain-source voltage waveform (V ds1 , V ds2 ) showed that specific frequency components were attenuated, and the switch voltage peak was effectively suppressed as intended.

[0040] Figure 12 shows the primary side switch voltage waveform (V) during boost operation and buck operation. gs1 , V ds1This shows the relationship between the primary switch voltage V and the primary switch voltage V. In Figure 12, the horizontal axis represents time [microseconds (μs)] and the vertical axis represents the primary switch voltage V. gs1 [V], primary side switch voltage V ds1 [V], where the upper diagram shows the boost operation and the lower diagram shows the buck operation.

[0041] Figure 13 shows the secondary switch voltage waveform (V) during boost and buck operations. gs2 , V ds2 Figure 13 shows the following. In Figure 13, the horizontal axis is time [microseconds (μs)] and the vertical axis is the secondary switch voltage V gs2 [V], secondary switch voltage V ds2 [V], where the upper diagram shows the boost operation and the lower diagram shows the buck operation. The power conversion efficiency was 83.2% in boost operation and 81.9% in buck operation, a difference of 1.3%. This is because both switches (first switch SW) were operating in buck operation. A , second switch SW B The ON time of both switches (first switch SW) during boost operation A , second switch SW B This is presumably because the on-time is longer than that of the device, resulting in conduction losses.

[0042] Furthermore, in contrast to the secondary switch voltage waveform during boost operation (the area enclosed by the dashed line in the upper diagram of Figure 13), the secondary switch voltage waveform during buck operation (the area enclosed by the dashed line in the lower diagram of Figure 13) clearly exhibits ringing due to parasitic inductance and parasitic capacitance components. This energy loss due to ringing is considered to be the cause of the decrease in power conversion efficiency. In order to suppress energy loss due to ringing, the switching device (first switch SW) A , second switch SW B Alternatively, a snubber circuit may be inserted in parallel with the other circuit.

[0043] The method for determining the circuit constants of the DC-DC converter 1 will be described. Figure 14 shows an example of the method for determining the circuit constants of the DC-DC converter 1 according to this embodiment. (Step S1-1) The information processing device derives the relationship between the inductance of the first inductor and the switch voltage of the first switch. (Step S2-1) The information processing device derives the relationship between the capacitance of the first capacitor and the switch voltage of the first switch.

[0044] (Step S3-1) The information processing device derives the relationship between the inductance of the second inductor and the switch voltage of the second switch. (Step S4-1) The information processing device derives the relationship between the capacitance of the second capacitor and the switch voltage of the second switch.

[0045] (Step S5-1) The information processing device determines the inductance of the first inductor, the capacitance of the first capacitor, the inductance of the second inductor, and the capacitance of the second capacitor based on the derived relationship between the inductance of the first inductor and the switch voltage of the first switch, the capacitance of the first capacitor and the switch voltage of the first switch, the relationship between the inductance of the second inductor and the switch voltage of the second switch, and the capacitance of the second capacitor and the switch voltage of the second switch.

[0046] The method for setting the control conditions of the DC-DC converter 1 will be described. Figure 15 shows an example of the method for setting the control conditions of the DC-DC converter according to this embodiment. (Step S1-2) The information processing device determines the circuit constants of each circuit element. (Step S2-2) The information processing device derives the relationship between the duty cycle of the first switch and the output voltage.

[0047] (Step S3-2) The information processing device derives the relationship between the duty cycle of the second switch and the output voltage. (Step S4-2) The information processing device derives the relationship between the phase difference between the first switch and the second switch and the output voltage.

[0048] (Step S5-2) The information processing device determines the duty cycle of the first switch, the duty cycle of the first switch, and the phase difference between the first and second switches based on the derived relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage, and the relationship between the phase difference between the first and second switches and the output voltage.

[0049] In the above-described embodiment, the DC-DC converter 1 has an inductor L on the primary side. 2A and capacitor C 2A It is incorporated, and an inductor L is placed on the secondary side. 2B and capacitor C 2B I've explained the case where it's incorporated, but this isn't the only example. For example, the inductor L incorporated on the primary side 2A and capacitor C 2A The inductor L is omitted and incorporated on the secondary side. 2B and capacitor C 2B The configuration may be configured without omitting it. An inductor L is placed on the primary side. 2A and capacitor C 2A It is incorporated, and an inductor L is placed on the secondary side. 2B and capacitor C 2B By incorporating this feature, the peak value of the switch voltage can be significantly suppressed, and bidirectional energy transfer can be facilitated.

[0050] Also, for example, inductor L 2A and inductor L 2B The transformer may be replaced and combined into a single element. Figure 16 shows an example of a configuration diagram of a DC-DC converter according to modified embodiment 1. According to Figure 16, the inductor L included in the second harmonic resonant filter incorporated on the primary side 2A and the inductor L included in the second harmonic resonant filter incorporated on the secondary side 2BIt can be seen that it has been replaced with a transformer and is configured as a single element.

[0051] Also, for example, a transformer TR and an inductor L 2A and inductor L 2B This may be replaced with a single transformer. Figure 17 shows an example of a configuration diagram of a DC-DC converter according to a modified example 2 of the embodiment. According to Figure 17, the transformer TR and the inductor L included in the second harmonic resonant filter incorporated on the primary side 2A and the inductor L included in the second harmonic resonant filter incorporated on the secondary side 2B It can be seen that the transformers have been replaced and are now configured as a single component.

[0052] According to the DC-DC converter of this embodiment, the DC-DC converter includes a transformer having a primary winding connected to an input voltage source via a primary line and a secondary winding connected to a capacitor connected to the output terminal via a secondary line; a first inductor connected in series with the primary line; a first switch provided on the primary line for connecting and disconnecting the primary line; a first capacitor connected in parallel with the first switch; a second inductor connected in series with the secondary line; a second switch provided on the secondary line for connecting and disconnecting the secondary line; and a second capacitor connected in parallel with the second switch. The circuit constants of the multiple circuit elements are determined based on the switch voltages of the first and second switches. By configuring it in this way, the sign values ​​of the DC-DC converter components are kept constant while the switching device (first switch SW) A , second switch SW B By carefully adjusting the duty cycle and phase, bidirectional functionality can be achieved, enabling highly efficient power conversion in high-frequency drives (e.g., MHz band). Specifically, promising results of 83.2% during boost operation and 81.9% during buck operation can be obtained.

[0053] The DC-DC converter further comprises a first harmonic resonant filter connected in parallel with a first switch, and a second harmonic resonant filter connected in parallel with a second switch. By configuring it in this way, identical second-harmonic resonant filters can be incorporated into both the primary and secondary sides, significantly suppressing the peak value of the switch voltage and facilitating bidirectional energy transfer.

[0054] In a DC-DC converter, the circuit elements are at least one of a first inductor, a first capacitor, a second inductor, and a second capacitor. This configuration allows for adjustment of at least one parameter of the first inductor, first capacitor, second inductor, and second capacitor, thereby achieving Class E switching conditions (ZVS / ZDS). By simultaneously satisfying both the ZVS and ZDS conditions, the slope of the switch voltage termination can be made zero, minimizing the area overlapping with the switch current waveform. This results in lower power consumption and higher efficiency. Furthermore, by suppressing the peak value of the switch voltage, it becomes possible to expand the applications of GaN, which is suitable for high-frequency driving and has low on-resistance.

[0055] In a DC-DC converter, the inductance of the first inductor, the capacitance of the first capacitor, the inductance of the second inductor, and the capacitance of the second capacitor are determined based on the relationship between the inductance of the first inductor and the switch voltage of the first switch, the capacitance of the first capacitor and the switch voltage of the first switch, the relationship between the inductance of the second inductor and the switch voltage of the second switch, and the capacitance of the second capacitor and the switch voltage of the second switch. By configuring it in this way, the inductance of the first inductor, the capacitance of the first capacitor, the inductance of the second inductor, and the capacitance of the second capacitor can be adjusted.

[0056] The DC-DC converter further includes a control unit that controls a first switch and a second switch to realize a boost mode and a buck mode. By configuring it in this way, the DC-DC converter can be controlled between boost mode and buck mode.

[0057] In a DC-DC converter, the circuit constants of each circuit element are determined based on the output voltage, output current, and switching frequency. Based on the determined circuit constants of each circuit element, the relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage, and the relationship between the phase difference between the first and second switches and the output voltage are derived. Based on the derived relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage, and the relationship between the phase difference between the first and second switches and the output voltage, the duty cycle of the first switch, the duty cycle of the first switch, and the phase difference between the first and second switches are determined. By configuring it in this way, the sign values ​​of the DC-DC converter components are kept constant while the switching device (first switch SW) A , second switch SW B Because the duty cycle and phase of the motor can be carefully adjusted, bidirectional functionality can be achieved, enabling highly efficient power conversion in high-frequency drive (MHz band).

[0058] In a DC-DC converter, the control unit adjusts the duty cycles of the first and second switches. By configuring it in this way, the sign values ​​of the DC-DC converter components are kept constant while the switching device (first switch SW) A , second switch SW B Because the duty cycle can be carefully adjusted, bidirectional functionality can be achieved, enabling highly efficient power conversion in high-frequency drive (MHz band).

[0059] In a DC-DC converter, the control unit adjusts the timing of turning the first switch and the second switch on or off. By configuring it in this way, the sign values ​​of the DC-DC converter components are kept constant while the switching device (first switch SW) A , second switch SW B Because the timing of turning the function on or off can be carefully adjusted, bidirectional functionality can be achieved, enabling highly efficient power conversion in high-frequency drive (MHz band).

[0060] In a DC-DC converter, the control unit controls the first switch and the second switch based on zero-voltage switching (ZVS) and zero-derivative switching (ZDS) conditions. By configuring the DC-DC converter in this way, the switching devices (first switch SWA, second switch SWB) can be controlled based on zero-voltage switching (ZVS) and zero-derivative switching (ZDS) conditions while keeping the sign values ​​of the DC-DC converter components constant. This enables bidirectional functionality and highly efficient power conversion in high-frequency drive (MHz band).

[0061] In a DC-DC converter, the control unit switches the first and second switches after achieving both zero-voltage switching (ZVS) and zero-derivative switching (ZDS) conditions. By configuring the DC-DC converter in this way, the sign values ​​of the components can be kept constant, and based on the zero-voltage switching (ZVS) and zero-derivative switching (ZDS) conditions, both the ZVS and ZDS conditions can be achieved before switching the first and second switches. This enables bidirectional functionality and highly efficient power conversion in high-frequency drive (MHz band).

[0062] According to the DC-DC converter 1 of this embodiment, it is possible to simultaneously satisfy "bidirectional operation," "maintaining isolation," "suppression of peak values ​​of switch voltage," "reduction in the number of switching elements," and "power exchange using only phase and duty cycle," which were impossible with conventional circuits. Furthermore, according to the DC-DC converter 1 of this embodiment, it is possible to "use two transformers," "reduce the size of inductors," and "single-to-many topology."

[0063] The nominal electromotive force of a single lithium-ion battery (hereinafter referred to as "LIB cell") newly adopted in electric vehicles is approximately 3.7V, while the conventional lead-acid batteries used in vehicles have a nominal electromotive force of approximately 12V (however, their nominal electromotive force is 2V, and six of these are connected in series). It is not common to use these new and old batteries together. Although it is possible to operate three LIB cells in series to achieve a 12V voltage rating, there is a risk that the high energy density of lithium-ion batteries may exceed their normal operating range for some reason (for example, if a collision occurs while the battery is installed in a vehicle, one of the three cells may short-circuit, resulting in the application of an overvoltage).

[0064] To solve this problem, instead of boosting the voltage by connecting batteries in series, the DC-DC converter 1 achieves the voltage boosting function by storing and releasing energy through switching to a coil and capacitor, thereby preventing the LIB cell from short-circuiting and generating overvoltage.

[0065] One example of an application of the DC-DC converter 1 is its usefulness as a backup power source for automotive batteries. For instance, if a vehicle cannot be started due to aging or other factors, a small LIB cell can be used to start the engine, allowing the vehicle to drive to a repair shop (approximately 4 km). In the case of hybrid vehicles, if the alternator is functioning, it can serve as an even more reliable backup power source.

[0066] Because voltage boosting and bucking can be controlled simply by adjusting the "phase" and "duty cycle" of the control signal, this technology can be used not only in automotive applications but also as a "backup power supply" for a wide range of mobile battery-related products (12V, 9V, 5V, 3.3V, 1.5V, 1.2V, etc.).

[0067] While embodiments and modifications of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the spirit of the present invention. For example, a computer program for realizing the functions of each of the above-mentioned devices (control unit 30, information processing device) may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed. The term "computer system" here may include hardware such as an operating system and peripheral devices.

[0068] Furthermore, "computer-readable recording media" refers to writable non-volatile memory such as flexible disks, magneto-optical disks, ROMs, and flash memory, portable media such as DVDs (Digital Versatile Discs), and storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording media" also includes volatile memory (such as DRAM (Dynamic Random Access Memory)) within computer systems that act as servers or clients when programs are transmitted via networks such as the Internet or communication lines such as telephone lines, which retain programs for a certain period of time.

[0069] Furthermore, the above program may be transmitted from a computer system that stores the program in a memory device or the like to another computer system via a transmission medium or by transmission waves within the transmission medium. Here, the "transmission medium" used to transmit the program refers to a medium that has the function of transmitting information, such as a network (communication network) like the Internet or a communication line (communication line) like a telephone line. Furthermore, the above program may be intended to implement only some of the functions described above. Furthermore, the aforementioned functions can be achieved in combination with programs already recorded in the computer system; these may be so-called differential files (differential programs). [Explanation of Symbols]

[0070] 1...DC-DC converter, TR...Transformer, L P ...Primary winding, L S ...Secondary winding, E A ...Input voltage source, 11, 12...Primary side line, L A , L 2A , L B , L 2B ...inductor, C smoA , C smoB , C A , C 2A , C B , C 2B ...capacitor, SW A ...First switch, SW B ...Second switch, 30...Control unit

Claims

1. A transformer comprising a primary winding connected to an input voltage source via a primary line, and a secondary winding connected to a capacitor connected to the output terminal via a secondary line, A first inductor connected in series to the primary line, A first switch is provided on the primary line and connects and disconnects the primary line, A first capacitor connected in parallel with the first switch, A second inductor connected in series to the aforementioned secondary line, A second switch is provided on the secondary line and connects and disconnects the secondary line, A second capacitor connected in parallel with the second switch, Equipped with, A DC-DC converter in which the circuit constants of a plurality of circuit elements are determined based on the switch voltages of the first switch and the second switch.

2. A first harmonic resonant filter connected in parallel with the first switch, A second harmonic resonant filter connected in parallel with the second switch, The DC-DC converter according to claim 1, further comprising:

3. The DC-DC converter according to claim 1 or claim 2, wherein the circuit element is at least one of the first inductor, the first capacitor, the second inductor, and the second capacitor.

4. The DC-DC converter according to claim 1, wherein the inductance of the first inductor, the capacitance of the first capacitor, the inductance of the second inductor, and the capacitance of the second capacitor are determined based on the relationship between the inductance of the first inductor and the switch voltage of the first switch, the capacitance of the first capacitor and the switch voltage of the first switch, the inductance of the second inductor and the switch voltage of the second capacitor and the switch voltage of the second switch.

5. A control unit that controls the first switch and the second switch to realize a boost mode and a buck mode. The DC-DC converter according to claim 1, further comprising:

6. The circuit constants of each circuit element are determined based on the output voltage, output current, and switching frequency. Based on the circuit constants of each determined circuit element, the relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage, and the relationship between the phase difference between the first switch and the second switch and the output voltage are derived. The DC-DC converter according to claim 5, wherein the duty cycle of the first switch, the duty cycle of the first switch, and the phase difference between the first switch and the second switch are determined based on the derived relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage, and the relationship between the phase difference between the first switch and the second switch and the output voltage.

7. The DC-DC converter according to claim 5, wherein the control unit adjusts the duty cycle of the first switch and the second switch.

8. The DC-DC converter according to claim 5 or claim 6, wherein the control unit adjusts the timing of turning the first switch and the second switch on or off.

9. The DC-DC converter according to claim 5, wherein the control unit controls the first switch and the second switch based on zero voltage switching (ZVS) and zero differential switching (ZDS) conditions.

10. The DC-DC converter according to claim 5, wherein the control unit switches the first switch and the second switch after achieving both zero voltage switching (ZVS) and zero differential switching (ZDS) conditions.

11. A method for determining the circuit constants of a DC-DC converter executed by a computer, The DC-DC converter is A transformer comprising a primary winding connected to an input voltage source via a primary line, and a secondary winding connected to a capacitor connected to the output terminal via a secondary line, A first inductor connected in series to the primary line, A first switch is provided on the primary line and connects and disconnects the primary line, A first capacitor connected in parallel with the first switch, A second inductor connected in series to the aforementioned secondary line, A second switch is provided on the secondary line and connects and disconnects the secondary line, A second capacitor connected in parallel with the second switch, Equipped with, The method for determining the circuit constants of the DC-DC converter is as follows: The step of determining the circuit constants of a plurality of circuit elements based on the switch voltages of the first switch and the second switch. A method for determining the circuit constants of a DC-DC converter, comprising the following:

12. The method for determining the circuit constants of a DC-DC converter according to claim 10 or claim 11, wherein the circuit element is at least one of the first inductor, the first capacitor, the second inductor, and the second capacitor.

13. A step of deriving the relationship between the inductance of the first inductor and the switch voltage of the first switch, the relationship between the capacitance of the first capacitor and the switch voltage of the first switch, the relationship between the inductance of the second inductor and the switch voltage of the second switch, and the relationship between the capacitance of the second capacitor and the switch voltage of the second switch, A step of determining the inductance of the first inductor, the capacitance of the first capacitor, the inductance of the second inductor, and the capacitance of the second capacitor based on the derived relationship between the inductance of the first inductor and the switch voltage of the first switch, the capacitance of the first capacitor and the switch voltage of the first switch, the relationship between the inductance of the second inductor and the switch voltage of the second switch, and the relationship between the capacitance of the second capacitor and the switch voltage of the second switch. A method for determining the circuit constants of a DC-DC converter according to claim 11, comprising the above.

14. A method for setting control conditions for a DC-DC converter executed by a computer, The DC-DC converter is A transformer comprising a primary winding connected to an input voltage source via a primary line, and a secondary winding connected to a capacitor connected to the output terminal via a secondary line, A first inductor connected in series to the primary line, A first switch is provided on the primary line and connects and disconnects the primary line, A first capacitor connected in parallel with the first switch, A second inductor connected in series to the aforementioned secondary line, A second switch is provided on the secondary line and connects and disconnects the secondary line, A second capacitor connected in parallel with the second switch, Equipped with, The method for setting the control conditions of the DC-DC converter is as follows: The steps include determining the circuit constants of each circuit element based on the output voltage, output current, and switching frequency, The steps include deriving the relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage, and the relationship between the phase difference between the first switch and the second switch and the output voltage, based on the circuit constants of each determined circuit element, A step of determining the duty cycle of the first switch, the duty cycle of the first switch, and the phase difference between the first and second switches based on the derived relationship between the duty cycle of the first switch and the output voltage, the relationship between the duty cycle of the second switch and the output voltage, and the relationship between the phase difference between the first and second switches and the output voltage. A method for setting control conditions for a DC-DC converter, comprising the characteristics of a DC-DC converter.

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