KR100901501B1 - Multi-level DC/DC Converter for Reducing Ripple of Output Voltage - Google Patents

Abstract

The present invention relates to a DC-DC converter, and more particularly, to a multilevel DC-DC converter for reducing output voltage ripple.

Multilevel Converter, Buck Converter, Ripple

Description

Multi-level DC / DC Converter for Reducing Ripple of Output Voltage

1 is a view illustrating a configuration of a buck-converter, which is a commonly used DC-DC converter,

2 is a circuit diagram showing the configuration of a multilevel DC / DC converter of the present invention;

3 is a graph showing an effect of reducing output voltage ripple as the number of levels in Equation 6 increases;

4 is a diagram illustrating a configuration of a multilevel DC / DC converter according to an embodiment of the present invention;

FIG. 5 is a diagram illustrating an operation mode according to an output voltage level and a switch on / off in a four-level DC / DC converter as shown in FIG. 4;

6 is a diagram illustrating a switching signal and a filter stage applied voltage according to levels in the proposed multilevel DC / DC converter.

The present invention relates to a DC-DC converter, and more particularly, to a multilevel DC-DC converter for reducing output voltage ripple.

DC-DC converter is a type of Switched-Mode Power Supply (SMPS), which uses a semiconductor device such as a power transistor as a switch to convert a DC input voltage into a square wave voltage and then is controlled through a filter. This circuit obtains a DC output voltage.

In general, high switching frequency is required in the DC / DC converter to reduce the size of magnetic elements such as inductors and transformers and smoothing capacitors. However, a problem arises in that the switching loss due to the increase in the switching frequency is increased and the efficiency is reduced. Recently, researches to solve this problem can be divided into two fields. The first is a variety of soft switching schemes to minimize switching losses during high switching frequency operation, and the second is to improve converter structure such as multilevel converters with low switching frequency operation.

The soft switching method has an advantage of reducing switching loss, but has a disadvantage in that the current or voltage peak value is increased to increase the rating of the switching element and an additional auxiliary circuit for soft switching is required.

The multilevel converter method has an advantage of reducing output voltage ripple even at low switching frequency operation, but has a disadvantage in that the number of switching elements increases proportionally as the number of levels increases. In addition, in the general multilevel structure, the loss of the switching element is increased due to the increase in the number of switching elements that are conducted regardless of the magnitude of the output voltage.

FIG. 1 is a diagram illustrating a configuration of a buck-converter, which is a commonly used DC-DC converter.

In the converter shown in FIG. 1, the output voltage is controlled by the duty ratio of the switching element, and the filter stage input voltage is represented by Equation 1 below.

As can be seen in Equation 1, the filter stage input voltage is composed of a harmonic component that is a multiple of a DC component and a switching frequency. Therefore, if the harmonic component is removed by the filter, only the DC component appears in the output voltage, and the input-output relation is expressed by Equation 2 below.

 In the DC / DC converter as shown in FIG. 1, the inductor current ripple is expressed by Equation 3 below.

The current ripple of the inductor is represented by the voltage ripple of the smoothing capacitor, and the output voltage ripple is shown in Equation 4 below.

The maximum ripple of the output voltage according to the rate is obtained by differentiating Equation 4, and the value is when the rate is 0.5. Therefore, the maximum ripple of the output voltage according to the ratio can be obtained as shown in Equation 5 below.

As can be seen from Equation 5, the ripple of the output voltage of the DC / DC converter is determined by the switching frequency, the capacitance, the ratio of the inductor and the capacitor, and the input voltage, and in order to reduce the ripple of the output voltage, increase the switching frequency or filter. The capacity of the inductor and capacitor should be increased or the input voltage should be decreased.

Increasing the switching frequency comes with limitations such as reduced efficiency due to increased switching losses. In addition, increasing the capacity of the inductor or the smoothing capacitor has the disadvantage of economic problems due to the increase in size and the number of embroidery.

The present invention was devised to solve the above problems, and an object of the present invention is to provide a multi-level DC / DC converter that can reduce the number of devices that increase with the increase in the number of levels.

The configuration of the present invention for achieving the above object is a first input portion is connected to the ground end; A first switch having one end connected to the other end of the first input unit; A first diode having an anode connected to the first node which is the other end of the first switch; A reflux diode having a cathode connected to a common node which is a cathode of the first diode, and an anode connected to a ground which is one end of the first input unit; A low pass filter connected in parallel with the reflux diode between the common node and the ground; an input unit connected in parallel to both ends N ₁ and CN of the first diode D ₁ and connected in series; A plurality including (V _i2 (t), ..., V _{i (N-1)} (t), V _iN (t)) and a switch (Q ₂ , ..., Q _N-1 , Q _N ) a level circuit _{(LC 1, ..., LC N} -1, LC N);, and including said level circuit _{(LC 1, ..., LC N} -1, LC N) is the respective level circuit Inputs (V _i2 (t), ..., V _{i (N-1)} (t), V _iN (t)) and switches Q of (LC ₁ , ..., LC _N-1 , LC _N ) ₂ , ..., Q _N-1 , Q _N ) are connected in series with each other so as to be alternated, and the level circuit at one end of the level circuits LC ₁ , ..., LC _N-1 , LC _N An input portion (V _i2 (t)) of (LC ₁ ) is connected to the first node (N ₁ ), and the switch (Q _N ) of the level circuit (LC _N ) at the other end is connected to the common node (CN). and, the level of each circuit node between _{(LC 1, ..., LC N} -1, LC N) (N 2, ..., N N-1) and the common node (CN) But connected to, each anode is connected to each node _{(N 2, ..., N N} -1) between the level circuits (LC _1, ..., _N-1 LC, LC _N), the cathode Is provided with a plurality of diodes (D ₂ ,..., D _N-1 ) connected to the common node (CN).

In a preferred embodiment, a multilevel converter according to the present invention comprises: a first input having one end connected to ground; A first switch having one end connected to the other end of the first input unit; A first diode having an anode connected to the first node which is the other end of the first switch; A reflux diode having a cathode connected to a common node which is a cathode of the first diode, and an anode connected to a ground which is one end of the first input unit; A low pass filter connected in parallel with the feedback diode between the common node and ground; A second input unit, a second switch, and a second diode connected in parallel with the first diode and connected in series with each other; A third input unit, a third switch, and a third diode connected in parallel with the second diode and connected in series with each other; And a fourth input unit and a fourth switch connected in parallel with the third diode and connected in series with each other.

In a preferred embodiment, the low pass filter is an LC filter.

The present invention provides a multilevel DC / DC converter capable of reducing the input voltage to reduce the output voltage ripple. The structure of the multilevel DC / DC converter of the present invention is characterized in that a diode is connected in series to the output of a conventional buck converter to prevent a short circuit between the outputs of each converter, and the upper part between the diode and the switching element. However, it is connected to the sub-power of the buck converter to form multiple levels.

In the conventional multilevel inverter, the number of switching elements, diodes, and capacitors increases rapidly with the increase in the number of levels, but the number of switching elements and diodes in the N-level DC / DC converter of the present invention is relatively reduced to N, respectively. In addition, since the stage operating according to the voltage level to be generated is minimized, the power consumption of the upper stage which is not operated can be reduced.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The multilevel DC / DC converter according to the embodiment of the present invention is a type in which a general buck converter is connected in series, and a diode is connected in series to the output of the buck converter to prevent a short circuit between the outputs of each converter. Multiple levels are formed by connecting the diode and the switching element to the secondary supply of the upper buck converter.

[First Embodiment]

2 is a circuit diagram showing the configuration of a multilevel DC / DC converter of the present invention.

), 제 1스위치(Q1), 제 1다이오드(D1), 환류다이오드(Do) 및 저역통과필터로 구성되는 단일레벨 DC-DC 벅 컨버터(DC-DC Buck Converter)에, 직렬로 연결된 제 2입력부(

), 제 2스위치(Q2) 및 제 2다이오드(D2)가 상기 제 1다이오드(D1)와 병렬로 연결되어 제 2레벨을 형성하고, 동일한 방식으로 제 3레벨, 제 4레벨, ... 제 N-1레벨을 형성하고, 상기 제 (N-1)다이오드와 병렬로 제 N입력부(

) 및 제 N스위치(QN)를 연결하여 제 N레벨을 형성하는 다중레벨 컨버터이다.
또한, 상기 제 2레벨 내지 제 N레벨들에 구비되는 입력부와 스위치를 각각 레벨회로(LC₁,...,LC_N-1,LC_N)로 정의하기로 한다.Referring to FIG. 2, the multilevel DC / DC converter of the present invention includes a first input unit (

A second input connected in series to a single-level DC-DC buck converter composed of a first switch (Q1), a first diode (D1), a reflux diode (Do), and a low pass filter. (

), The second switch Q2 and the second diode D2 are connected in parallel with the first diode D1 to form a second level, and the third level, the fourth level, ... An N-1 level, and an Nth input unit in parallel with the (N-1) th diode;

) And the Nth switch QN to form an Nth level.
In addition, an input unit and a switch provided in the second to Nth levels are defined as level circuits LC ₁ ,..., LC _N-1 , LC _N , respectively.

Referring to the configuration of the converter of the present invention in more detail as follows.

)의 일단은 접지에 연결되고 타단이 상기 제 1스위치(Q1)의 일단에 연결된다.The first input unit (

Is connected to ground and the other end is connected to one end of the first switch Q1.

)에 연결되고 타단이 제 1노드에 연결되며, 트랜지스터를 이용하여 구현된다.One end of the first switch Q1 has the first input unit (

) And the other end to the first node, and are implemented using a transistor.

The first diode D1 has an anode connected to the first node and a cathode connected to a common node.

)의 일단인 접지에 연결된다.The reflux diode Do has a cathode connected to the common node and an anode of the first input unit (

Is connected to ground.

The low pass filter is an LC filter which is connected in parallel with the reflux diode between the common node and ground, and is composed of an inductor (L) and a capacitor (C).
The level circuits LC ₁ , LC _N-1 , LC _N are connected in parallel to both ends N ₁ and CN of the first diode D ₁ , respectively, and are connected in series. V _i2 (t), ..., V _{i (N-1)} (t), V _iN (t) and switches Q ₂ , ..., Q _N-1 , Q _N.
In addition, each of the level circuit (LC _1, ..., _N-1 LC, LC _N) is input (V _i2 (of the respective level circuit (LC _1, ..., _N-1 LC, LC _N) t), ..., V _{i (N-1)} (t), V _iN (t)) and switches (Q ₂ , ..., Q _N-1 , Q _N ) are connected in series to each other The input part V _i2 (t) of the level circuit LC ₁ at one end of the level circuits LC ₁ ,..., LC _N-1 , LC _N is the first node N ₁ . The switch Q _N of the level circuit LC _N at the other end is connected to the common node CN.

In addition, the node N ₂ ,..., N _N-1 between the level circuits LC ₁ ,..., LC _N-1 , LC _N is connected to the common node CN. , Each anode is connected to each node (N ₂ , ..., N _N-1 ) between the level circuits LC ₁ ,..., LC _N-1 , LC _N , and a cathode is the common A plurality of diodes D ₂ ,..., D _N-1 connected to the node CN are provided.

라 둘 수 있다. 이때 도 2와 같은 N레벨 컨버터에서 출력전압 리플은 아래의 수학식 1과 같다.It is common to use the same input voltage with the same voltage.

Can be In this case, the output voltage ripple in the N-level converter as shown in FIG. 2 is represented by Equation 1 below.

As can be seen from the above equation, the output voltage ripple is 1 / N times.

3 is a graph illustrating an effect of reducing output voltage ripple as the number of levels in Equation 6 increases.

As can be seen in Figure 3 compared to the conventional buck converter 50% in the second level, about 16.7% when the first level increased from 2 levels to 3 levels, 8.3%, 4 levels when increased by 1 level from 3 levels to 4 levels Increasing the level from 5 to 5 levels will result in a 5% ripple reduction effect. The output voltage ripple reduction effect gradually decreases as the number of levels increases, and when the level is increased from 9 to 10 levels, the ripple reduction effect is about 1%, which is relatively small.

Therefore, in the first embodiment of the present invention, the four-level DC / DC converter as shown in FIG. 4 is designed in consideration of the increase in the number of switching elements and the ripple effect of increasing the number of levels.

4 is a diagram illustrating a configuration of a multilevel DC / DC converter according to a first embodiment of the present invention.

), 제 1스위치(Q1), 제 1다이오드(D1), 환류다이오드(Do) 및 저역통과필터로 구성되는 단일레벨 DC-DC 벅 컨버터(DC-DC Buck Converter)에, 직렬로 연결된 제 2입력부(

), 제 2스위치(Q2) 및 제 2다이오드(D2)가 상기 제 1다이오드(D1)와 병렬로 연결되어 제 2레벨을 형성하고, 직렬로 연결된 제 3입력부(

), 제 3스위치(Q3) 및 제 3다이오드(D3)가 상기 제 2다이오드(D2)와 병렬로 연결되어 제 3레벨을 형성하고, 상기 제 3다이오드(D3)와 병렬로 제 4입력부(

) 및 제 4스위치(Q4)를 연결하여 제 4레벨을 형성하는 다중레벨 컨버터이다.Referring to FIG. 4, the multilevel DC / DC converter according to the first embodiment of the present invention includes a first input unit (

A second input connected in series to a single-level DC-DC buck converter composed of a first switch (Q1), a first diode (D1), a reflux diode (Do), and a low pass filter. (

), The second switch Q2 and the second diode D2 are connected in parallel with the first diode D1 to form a second level, and the third input unit connected in series (

), A third switch Q3 and a third diode D3 are connected in parallel with the second diode D2 to form a third level, and in parallel with the third diode D3, a fourth input unit (

) And a fourth switch Q4 to form a fourth level.

)의 일단은 접지에 연결되고 타단이 상기 제 1스위치(Q1)의 일단에 연결된다.The first input unit (

Is connected to ground and the other end is connected to one end of the first switch Q1.

)에 연결되고 타단이 제 1노드에 연결되며, 트랜지스터를 이용하여 구현된다.One end of the first switch Q1 has the first input unit (

) And the other end to the first node, and are implemented using a transistor.

The first diode D1 has an anode connected to the first node and a cathode connected to a common node.

)의 일단인 접지에 연결된다.The reflux diode Do has a cathode connected to the common node and an anode of the first input unit (

Is connected to ground.

The low pass filter is an L-C filter which is connected in parallel with the reflux diode between the common node and ground, and is composed of an inductor (L) and a capacitor (C).

)가 순차적으로 직렬로 연결되며, 상기 제 2입력부(

)는 상기 제 1노드에 연결된다.The cathode of the second diode D2 is connected to the common node, and the second switch Q2 and the second input unit are connected to the anode of the second diode D2.

) Are sequentially connected in series, and the second input unit (

) Is connected to the first node.

)가 순차적으로 직렬로 연결되며, 상기 제 3입력부(

)는 상기 제 2다이오드의 애노드인 제 2노드에 연결된다.The cathode of the third diode D3 is connected to the common node, and the third switch Q3 and the third input unit are connected to the anode of the third diode D3.

) Are sequentially connected in series, and the third input unit (

) Is connected to a second node which is an anode of the second diode.

)와 제 4스위치(Q4)는 상기 공통노드와 상기 제 3다이오드(D3)의 애노드인 제 3노드와 병렬로 연결된다.Fourth input unit connected in series

) And the fourth switch Q4 are connected in parallel with the common node and the third node which is an anode of the third diode D3.

인 경우를 보여준다.FIG. 5 illustrates an operation mode according to an output voltage level and a switch on / off in a four-level DC / DC converter as shown in FIG. 4.

Shows the case.

Fig. 5A shows the current loop at the one level and operates in the same manner as the conventional buck type converter in this mode.

Fig. 5B shows the current loop at two levels. At this time, the first switch Q ₁ , which is a switch of the first level buck converter, is always in an on state, and the second switch Q ₂ , which is a switch of the second level buck converter, performs a PWM operation. When the second switch Q ₂ is in the on state, a current loop through Q ₁ -Q ₂ -D ₂ -LC is formed to apply a voltage twice the input voltage to the filter input terminal, and the second switch Q _{When 2} ) is OFF, the input voltage is applied to the filter input terminal by forming a current loop through Q ₁ -D ₁ -LC.

FIG. 5C shows a current loop at three levels, and Q ₃ operates in PWM with the first and second switches Q ₁ and Q ₂ on. At this time, three times and two times the input voltage are applied to the filter input terminal according to the third switch Q ₃ being turned on and off.

Fig. 5 (d) shows a current loop at four levels, and in this case as well, at the filter input stage, the fourth switch Q ₄ is four times and three times the input voltage depending on On / Off. A double voltage is applied. Therefore, according to the switch on / off of the upper stage at each level, a voltage as shown in Equation 7 below is applied to the filter stage.

As can be seen from Equation 7, the voltage applied to the filter stage is n times or (n-1) times the input voltage according to the switch on / off of the upper stage.

6 shows the switching signal and filter stage applied voltage according to the level in the proposed multilevel DC / DC converter.

As can be seen in FIG. 6, the output voltage according to the ratio of the upper stage switch in the proposed multilevel DC / DC converter is expressed by Equation 8 below.

Second Embodiment

7 is a diagram illustrating a configuration of a multilevel DC / DC converter according to a second embodiment of the present invention.

), 제 1다이오드(D1), 환류다이오드(Do) 및 저역통과필터로 구성되는 단일레벨 DC-DC 벅 컨버터(DC-DC Buck Converter)에, 직렬로 연결된 제 2입력부(

), 제 2스위치(Q2) 및 제 2다이오드(D2)가 상기 제 1다이오드(D1)와 병렬로 연결되어 제 2레벨을 형성하고, 직렬로 연결된 제 3입력부(

), 제 3스위 치(Q3) 및 제 3다이오드(D3)가 상기 제 2다이오드(D2)와 병렬로 연결되어 제 3레벨을 형성하고, 상기 제 3다이오드(D3)와 병렬로 제 4입력부(

) 및 제 4스위치(Q4)를 연결하여 제 4레벨을 형성하는 다중레벨 컨버터이다.Referring to FIG. 7, a multilevel DC / DC converter according to a second embodiment of the present invention may include a first input unit (

), A second input unit connected in series to a single-level DC-DC buck converter composed of a first diode D1, a reflux diode Do, and a low pass filter.

), The second switch Q2 and the second diode D2 are connected in parallel with the first diode D1 to form a second level, and the third input unit connected in series (

), The third switch Q3 and the third diode D3 are connected in parallel with the second diode D2 to form a third level, and in parallel with the third diode D3, a fourth input unit (

) And a fourth switch Q4 to form a fourth level.

That is, the multilevel DC / DC converter according to the second embodiment of the present invention has a structure without the first switch Q1 in the first embodiment, and all other components are multilevel DC shown in the first embodiment. Same as / DC converter.

) 이상의 출력전압을 요구하는 경우 기전전압을 담당할 스위치의 기능은 불필요하게 된다. 따라서 본 발명의 제 2실시예에서 보인 다중레벨 DC/DC컨버터와 같이 기저전압 이하의 출력전압을 담당하는 스위치를 제거하는 것이 바람직하다. 기전전압 이상을 담당하는 다중레벨 전압은 출력전압의 최대치를 (

)라하면 그 값은 아래의 수학식 9와 같다. Like the battery charger, the output voltage is the base voltage (

In the case of requesting an output voltage above), the function of the switch that is responsible for the electromotive voltage becomes unnecessary. Therefore, it is preferable to remove a switch that is responsible for an output voltage below the base voltage, such as the multilevel DC / DC converter shown in the second embodiment of the present invention. The multilevel voltage responsible for the abnormal voltage is higher than the output voltage.

), The value is shown in Equation 9 below.

According to the multilevel DC / DC converter shown in the second embodiment of the present invention, when the base voltage is large, the degree of the output voltage can be further increased.

In the above, the configuration and operation of the present invention has been shown in accordance with the above description and drawings, but this is merely described, for example, and various changes and modifications are possible without departing from the spirit and scope of the present invention. .

As described above, according to the present invention, the number of switching elements, diodes, and capacitors increases rapidly with the increase in the number of levels in the conventional multilevel converter, whereas the number of switching elements and diodes in the N-level DC / DC converter of the present invention. Has the advantage that N is relatively reduced as N each.

In addition, since the stage operating according to the voltage level to be generated is minimized, there is an advantage that the power consumption of the upper stage that is not operated can be reduced.

Claims (6)

A first input unit _Vi1 (t) having one end connected to ground; A first switch Q ₁ having one end connected to the other end of the input part; A first diode D ₁ having an anode connected to the first node N ₁ which is the other end of the first switch Q ₁ ; And a cathode coupled to the cathode of a common node (CN) of the first diode (D _1), which anode is connected to one end of the ground (GN) of the first input (V _i1 (t)) a reflux diode (D ₀ ); A low pass filter (LPF) connected in parallel with the reflux diode (D ₀ ) between the common node (CN) and ground (GN); And Input parts V _i2 (t),..., V _{i (N-1)} (t), V connected in parallel to both ends N ₁ and CN of the first diode D ₁ , respectively, and connected in series. _iN (t)) and a plurality of level circuits LC ₁ ,..., LC _N-1 , LC _N including switches Q ₂ ,..., Q _N-1 , Q _N. , Said level circuit _{(LC 1, ..., LC N} -1, LC N) is input (V _i2 (t) of the respective level circuit _{(LC 1, ..., LC N} -1, LC N) , ..., V _{i (N-1)} (t), V _iN (t) and switches (Q ₂ , ..., Q _N-1 , Q _N ) are connected in series to each other, the level circuits (LC _1, ..., _N-1, LC, LC _N) input (V _i2 (t)) of the level circuit (LC ₁₎ of the one end is connected to said first node (N ₁₎ The switch Q _N of the level circuit LC _N at the other end is connected to the common node CN. Each node N ₂ ,..., N _N-1 between the level circuits LC ₁ ,..., LC _N-1 , LC _N is connected to the common node CN, respectively. An anode of is connected to each node (N ₂ , ..., N _N-1 ) between the level circuits LC ₁ ,..., LC _N-1 , LC _N , and a cathode of the common node ( A multilevel DC / DC converter having a plurality of diodes (D ₂ , ..., D _N-1 ) connected to CN). A first input part whose one end is connected to ground; A first switch having one end connected to the other end of the first input unit; A first diode having an anode connected to the first node which is the other end of the first switch; A reflux diode having a cathode connected to a common node which is a cathode of the first diode, and an anode connected to a ground which is one end of the first input unit; A low pass filter connected in parallel with the feedback diode between the common node and ground; A second input unit, a second switch, and a second diode connected in parallel with the first diode and connected in series with each other; A third input unit, a third switch, and a third diode connected in parallel with the second diode and connected in series with each other; And And a fourth input unit and a fourth switch connected in parallel with the third diode and connected in series with each other. The method according to claim 1 or 2, The low pass filter is a multi-level DC / DC converter, characterized in that the LC filter. A first input unit _Vi1 (t) having one end connected to ground; A first diode D ₁ having an anode connected to the first node N ₁ which is the other end of the first switch Q ₁ ; And a cathode coupled to the cathode of a common node (CN) of the first diode (D _1), which anode is connected to one end of the ground (GN) of the first input (V _i1 (t)) a reflux diode (D ₀ ); A low pass filter (LPF) connected in parallel with the reflux diode (D ₀ ) between the common node (CN) and ground (GN); And Input parts V _i2 (t),..., V _{i (N-1)} (t), V connected in parallel to both ends N ₁ and CN of the first diode D ₁ , respectively, and connected in series. _iN (t)) and a plurality of level circuits LC ₁ ,..., LC _N-1 , LC _N including switches Q ₂ ,..., Q _N-1 , Q _N. , Said level circuit _{(LC 1, ..., LC N} -1, LC N) is input (V _i2 (t) of the respective level circuit _{(LC 1, ..., LC N} -1, LC N) , ..., V _{i (N-1)} (t), V _iN (t) and switches (Q ₂ , ..., Q _N-1 , Q _N ) are connected in series to each other, the level circuits (LC _1, ..., _N-1, LC, LC _N) input (V _i2 (t)) of the level circuit (LC ₁₎ of the one end is connected to said first node (N ₁₎ The switch Q _N of the level circuit LC _N at the other end is connected to the common node CN. Each node N ₂ ,..., N _N-1 between the level circuits LC ₁ ,..., LC _N-1 , LC _N is connected to the common node CN, respectively. An anode of is connected to each node (N ₂ , ..., N _N-1 ) between the level circuits LC ₁ ,..., LC _N-1 , LC _N , and a cathode of the common node ( A multilevel DC / DC converter having a plurality of diodes (D ₂ , ..., D _N-1 ) connected to CN). A first input part whose one end is connected to ground; A first diode having an anode connected to the first node which is the other end of the first input unit; A reflux diode having a cathode connected to a common node which is a cathode of the first diode, and an anode connected to a ground which is one end of the first input unit; A low pass filter connected in parallel with the feedback diode between the common node and ground; A second input unit, a second switch, and a second diode connected in parallel with the first diode and connected in series with each other; A third input unit, a third switch, and a third diode connected in parallel with the second diode and connected in series with each other; And And a fourth input unit and a fourth switch connected in parallel with the third diode and connected in series with each other. The method according to claim 4 or 5, The low pass filter is a multi-level DC / DC converter, characterized in that the LC filter.

Images