CN105207471A - Low-voltage-stress high-voltage-drop DC/DC converter - Google Patents

Abstract

The invention provides a low-voltage-stress high-voltage-drop DC/DC converter. The low-voltage-stress high-voltage-drop DC/DC converter comprises two power inductors, two diodes and n voltage drop units. Each voltage drop unit is composed of two power switches and two capacitors, wherein the two capacitors are connected vertically in series, the node of the capacitor on the upper portion and the drain electrode of the corresponding power switch serves as a first port, the source electrode of the power switch on the upper portion serves as a second port, the drain electrode of the power switch on the lower portion serves as a third port, and the node of the capacitor on the lower portion and the source electrode of the power switch on the lower portion serves as a fourth port. Compared with an existing voltage drop converter, the low-voltage-stress high-voltage-drop DC/DC converter is simple in design and implementation scheme, no transformer or coupling inductor is included, the EMI characteristic is good, the input-output voltage drop ratio is adjustable, the voltage stress of a switching device is greatly reduced, and the overall working efficiency of the converter is improved.

Description

A Low Voltage Stress High Step-Down DC/DC Converter

technical field

The invention relates to a DC-DC converter, in particular to a DC/DC converter with low voltage stress and high step-down.

Background technique

In the existing technology, the basic two-phase step-down DC/DC converter has problems such as excessive voltage stress of switching devices, large loss, and low efficiency, and cannot meet the requirements in some occasions with a large input-output step-down ratio. . Therefore, a large number of experts and scholars have done a lot of research on these problems and put forward corresponding solutions. Generally speaking, there are two solutions with the help of transformers and coupled inductors. With the help of transformers, a high-frequency transformer is added in the middle of the original DC-DC converter to achieve a large step-down by changing the transformer ratio, but The energy conversion process of this scheme is complicated, and the energy conversion efficiency of the whole system is low. The topology constructed by using coupled inductors, due to the existence of leakage inductance, the voltage stress of the switching device is relatively large, and the loss of the converter is large.

Contents of the invention

In order to solve the technical problems of low working efficiency of existing converters and high voltage stress of switching devices, the present invention proposes a low voltage stress high step-down DC/DC converter, which has the characteristics of low voltage stress and high step-down capability, and simultaneously reduces Pressure capacity is adjustable.

The technical scheme adopted in the present invention is:

A low-voltage-stress high-step-down DC/DC converter, comprising a first inductor L1, a second inductor L2, a diode D1, a diode D2, and n step-down units, and the output ends of the first inductor L1 and the second inductor L2 are simultaneously Connect the positive pole of the output filter capacitor Co and the load, and the input ends of the first inductor L1 and the second inductor L2 are respectively connected to the cathodes of the diode D1 and the diode D2;

The input terminal of the first inductor L1 is connected to the second interface of the nth step-down unit, and the input terminal of the first inductor L1 is connected to a node between the upper and lower capacitors of the odd-numbered step-down unit;

The input terminal of the second inductor L2 is connected to a node between the upper and lower capacitors of the even-numbered step-down unit;

The third port of the nth unit is connected to the anodes of the diode D1 and the diode D2 at the same time, and its node is connected to the output filter capacitor Co and the negative pole of the load at the same time;

The first port of the first step-down unit is used as the positive pole of the DC source, and the fourth port of the first step-down unit is used as the negative pole of the DC source;

The second port of the first step-down unit is connected to the first port of the second step-down unit, the third port of the first step-down unit is connected to the fourth port of the second step-down unit, and the second step-down unit The second port of the second step-down unit is connected to the first port of the third step-down unit, the third port of the second step-down unit is connected to the fourth port of the third step-down unit, and so on until the nth step-down unit;

Among them, the step-down unit is composed of two power switches and two capacitors, the two capacitors are connected in series up and down, the junction of the upper capacitor and the drain of the upper power switch is used as the first port of the step-down unit, and the source of the upper power switch is used as the first port of the step-down unit. The second port of the step-down unit, the drain of the lower power switch is used as the third port of the step-down unit, and the node between the lower capacitor and the source of the lower power switch is used as the fourth port of the step-down unit;

n is a natural number, the value range is n≥1;

The gates of each power switch are respectively connected to their respective controllers.

A low-voltage stress high-step-down DC/DC converter, the control method of which is that the power switches of each phase adopt an interleaved control strategy, that is, the difference between the drive phases of odd-numbered switches and even-numbered switches is 180°.

Compared with the prior art, the present invention provides a low-voltage-stress high-step-down DC/DC converter, which has the following beneficial effects:

1) The present invention utilizes a step-down unit to form a step-down network, and realizes an input-output step-down ratio that is 1/2n times that of a basic Buck step-down converter.

2) The voltage stress of the switching devices in the circuit is effectively reduced.

3) Compared with the existing step-down converter, it does not contain transformers and coupled inductors, has good EMI characteristics, simple circuit topology, and low difficulty in design and implementation of the control system.

4) The converter can be designed with different numbers of step-down units according to the specific application occasions, which expands the application occasions of the converter.

Description of drawings

FIG. 1 is a general circuit schematic diagram when n voltage-reducing units are included in an embodiment of the present invention.

FIG. 2 is a schematic circuit diagram of an embodiment of the present invention including only four sets of step-down units.

Fig. 3 is a circuit diagram of a single step-down unit used in the present invention.

In Fig. 3: ①-the first port, ②-the second port, ③-the third port, ④-the fourth port.

Detailed ways

A low-voltage-stress high-step-down DC/DC converter, comprising a first inductor L1, a second inductor L2, a diode D1, a diode D2, and n step-down units, and the output ends of the first inductor L1 and the second inductor L2 are simultaneously Connect the positive pole of the output filter capacitor Co and the load, and the input ends of the first inductor L1 and the second inductor L2 are respectively connected to the cathodes of the diode D1 and the diode D2;

The input terminal of the first inductor L1 is connected to the second interface of the nth step-down unit, and the input terminal of the first inductor L1 is connected to a node between the upper and lower capacitors of the odd-numbered step-down unit;

The input terminal of the second inductor L2 is connected to a node between the upper and lower capacitors of the even-numbered step-down unit;

The third port of the nth unit is connected to the anodes of the diode D1 and the diode D2 at the same time, and its node is connected to the output filter capacitor Co and the negative pole of the load at the same time;

The first port of the first step-down unit is used as the positive pole of the DC source, and the fourth port of the first step-down unit is used as the negative pole of the DC source;

The second port of the first step-down unit is connected to the first port of the second step-down unit, the third port of the first step-down unit is connected to the fourth port of the second step-down unit, and the second step-down unit The second port of the second step-down unit is connected to the first port of the third step-down unit, the third port of the second step-down unit is connected to the fourth port of the third step-down unit, and so on until the nth step-down unit;

Among them, the step-down unit is composed of two power switches and two capacitors, the two capacitors are connected in series up and down, the junction of the upper capacitor and the drain of the upper power switch is used as the first port of the step-down unit, and the source of the upper power switch is used as the first port of the step-down unit. The second port of the step-down unit, the drain of the lower power switch is used as the third port of the step-down unit, the node of the lower capacitor and the source of the lower power switch is used as the fourth port of the step-down unit; n is a natural number, the value The range is n≥1.

The grids of the power switches are respectively connected to their respective controllers.

A low-voltage stress high-step-down DC/DC converter, the control method of which is that the power switches of each phase adopt an interleaved control strategy, that is, the difference between the drive phases of odd-numbered switches and even-numbered switches is 180°.

Example:

As shown in Fig. 2, a DC/DC converter with low voltage stress and high step-down is composed of a first inductor L1, a second inductor L2, two diodes D1, D2 and four step-down units. The four step-down units are composed of eight power switches S1, S2, S3, S4, S5, S6, S7, S8 and eight capacitors C1, C2, C3, C4, C5, C6, C7, C8. Its circuit connection relationship is:

The output ends of the first inductance L1 and the second inductance L2 are simultaneously connected to the positive pole of the output filter capacitor Co and the load, and the input ends of the first inductance L1 and the second inductance L2 are respectively connected to the cathodes of the diode D1 and the diode D2; the gates of all power switches The poles are respectively connected to their respective controllers.

The power switches S1, S3, S5, and S7 are connected in series, and the power switches S2, S4, S6, and S8 are connected in series, wherein the source of the power switch S1 is connected to the drain of the power switch S3, and the source of S3 is connected to the drain of the power switch S5 , the source of S5 is connected to the drain of power switch S7, the source of S8 is connected to the drain of power switch S6, the source of S6 is connected to the drain of power switch S4, the source of S4 is connected to the drain of power switch S2 The poles are connected; capacitors C1 and C2 are connected in series, C3 and C4 are connected in series, C5 and C6 are connected in series, C7 and C8 are connected in series, among which capacitors C1, C3, C5 and C7 are located at the top, and capacitors C2, C4, C6 and C8 are located at the bottom; capacitors C1 and The node of S1 is used as the positive pole of the input source, and the node of capacitors C2 and S2 is used as the negative pole of the input source; the upper end of the capacitor C3 is connected to the node connected in series with the power switches S1 and S3, and the lower end of the capacitor C4 is connected in series with the power switches S2 and S4 The upper end of capacitor C5 is connected to the node connected in series with power switches S3 and S5, the lower end of capacitor C6 is connected to the node connected in series with power switches S4 and S6; the upper end of capacitor C7 is connected to the node connected in series with power switches S5 and S7 The lower end of the capacitor C8 is connected to the node connected in series with the power switches S6 and S8; the upper end of the capacitor C7 is connected to the drain of the power switch S8, and the lower end of the capacitor C8 is connected to the source of the power switch S8.

At the same time, the input terminal of the first inductor L1 is connected to the source of the power switch S7, the cathode of the diode D1 is connected in series with the nodes of the capacitors C1 and C2, and the node of the series connected capacitors C5 and C6; the input terminal of the second inductor L2 is connected to the diode D2 The cathode, the node connected in series with the capacitors C3 and C4 and the node connected in series with the capacitors C7 and C8; the drain of the power switch S8 and the nodes of the anodes of the two diodes D1 and D2 are simultaneously connected to the output filter capacitor Co and the negative pole of the load.

According to the different states of the power switch, the circuit can be divided into three working states:

Mode 1: The controller controls the power switches S1, S4, S5, and S8 to be turned on, S2, S3, S6, and S7 to be turned off, D1 to be turned on, and D2 to be turned off. The current of L1 discharges to the output capacitor and load through D1; part of the current of L2 passes through D1 through the output capacitor and load, S8, C8, part of it passes through D1, C5, S5, and C7, part of it flows through C2 and the DC source, and the other part flows through C1, S1, C3, and some of them pass through C4, S4, and C6. During this process, L1, C1, C4, C5, and C8 are discharged, and L2, C2, C3, C6, and C7 are charged. The DC source supplies capacitors C1, C2 charges.

Mode 2: The controller controls the power switches S1, S3, S5, S7, S2, S4, S6, S8 to be turned off, and D1, D2 to be turned on. In this mode, the inductors L1 and L2 discharge the output capacitor and the load.

Mode 3: The controller controls the power switches S1, S4, S5, and S8 to be turned off, S2, S3, S6, and S7 to be turned on, D1 to be turned off, and D2 to be turned on. The current of L2 discharges to the output capacitor and load through D2; part of the current of L1 passes through the output capacitor and load, S7, C7 through D1, part of it passes through D2, C8, S6, C6, part of it flows through C4, S2, DC source, and the other part It flows through C3, S3, C5, and part of it passes through C4, S2, and C2. During this process, L1, C1, C4, C5, and C8 are charged, and L2, C2, C3, C6, and C7 are discharged. The DC source feeds the capacitor C1 and C2 charge.

To sum up, the voltage stress of the switching device of the topology circuit proposed by the present invention is low, and the step-down ratio is adjustable, so it can be flexibly applied to occasions requiring high step-down capability. The implementation example only adopts a DC/DC converter with a high step-down ratio of 4 sets of step-down units for the sake of simple explanation of the working principle. In actual applications, the number of voltage doubler units can be reasonably selected according to the actual application situation. In order to achieve the purpose of optimizing efficiency and cost.

Claims (2)

1. a low voltage stress height step-down DC/DC converter, comprise the first inductance L 1, second inductance L 2, diode D1, diode D2, n pressure unit, it is characterized in that, the output of the first inductance L 1 and the second inductance L 2 connects the positive pole of output filter capacitor Co and load simultaneously, and the input of the first inductance L 1 and the second inductance L 2 connects the negative electrode of diode D1 and diode D2 respectively;

Second interface of input termination n-th pressure unit of the first inductance L 1, the node up and down between two electric capacity of an input termination odd-times pressure unit of the first inductance L 1;

The node up and down between two electric capacity of an input termination even-times pressure unit of the second inductance L 2;

3rd port of Unit n-th is connected with the anode of diode D1, diode D2 simultaneously, and its node connects the negative pole of output filter capacitor Co and load simultaneously;

First port of first pressure unit is as the positive pole of DC source, and the 4th port of first pressure unit is as the negative pole of DC source;

Second port of first pressure unit connects the first port of second pressure unit, 3rd port of first pressure unit connects the 4th port of second pressure unit, second port of second pressure unit connects the first port of the 3rd pressure unit, 3rd port of second pressure unit connects the 4th port of the 3rd pressure unit, analogize in proper order, until the n-th pressure unit;

Wherein, pressure unit is made up of two power switchs and two electric capacity, two electric capacity are connected up and down, the node of the drain electrode of top electric capacity and top power switch is as the first port of pressure unit, the source electrode of top power switch is as the second port of pressure unit, the drain electrode of below power switch is as the 3rd port of pressure unit, and the node of the source electrode of below electric capacity and below power switch is as the 4th port of pressure unit;

N is natural number, and span is n >=1;

The grid of each power switch connects respective controller respectively.

2. a kind of low voltage stress height step-down DC/DC converter according to claim 1, is characterized in that, differs 180 ° between odd-times switch and even-times switch drive phase place.