WO2014129707A1

WO2014129707A1 - Multiple-output dc-dc converter using switched capacitor

Info

Publication number: WO2014129707A1
Application number: PCT/KR2013/005942
Authority: WO
Inventors: 백동현; 이정윤; 김영진; 윤선우
Original assignee: 중앙대학교 산학협력단
Priority date: 2013-02-19
Filing date: 2013-07-04
Publication date: 2014-08-28
Also published as: KR101419645B1

Abstract

Disclosed is a multiple-output DC-DC converter using a switched capacitor. The multiple-output DC-DC converter using a switched capacitor comprises: a control signal generation unit for generating a switching control signal to make a plurality of output voltages correspond to respective reference voltage levels; and an output unit for outputting an input voltage to a plurality of output terminals on the basis of the switching control signal, wherein the output unit comprises N (a natural number of 2 or greater) switched-capacitor cells sharing the plurality of output terminals, and wherein each of the N switched-capacitor cells comprises: a common capacitor which charges and discharges the input voltage; and a plurality of switch arrays which switch on and off so that the input voltage is charged to the common capacitor and the charged voltage is outputted to the plurality of output terminals. The present invention has an advantage capable of highly efficient multiple output, and also an advantage capable of efficiently reducing ripples of an output voltage.

Description

Multiple Output DC-DC Converters with Switched Capacitors

Embodiments of the present invention relate to a multiple output DC-DC converter using a switched capacitor, and more particularly, multiple output using a switched capacitor capable of high efficiency power conversion multiple output and efficiently reducing the ripple of the output voltage. It relates to a DC-DC converter.

Recently, many semiconductor parts have been implemented using a System on Chip (SoC) method for miniaturization and cost reduction.

Due to the development of system-on-chip technology, the operating voltage required in a single chip has been diversified. Therefore, a converter having multiple output characteristics is required.

There is an active research on single-inductor multiple-output (SIMO) using only one inductor.

Inductor-based switching converters have the advantage of having a wide range of output voltages to ensure high efficiency, and only one inductor can reduce the size and cost of the converter.

However, in order to achieve high power conversion efficiency, an inductor having a high Q value is required. Therefore, implementing this on-chip requires an expensive additional process.

Switched-capacitor (SC) converters, on the other hand, do not require an inductor for voltage conversion, and thus have received a lot of attention because they can achieve high efficiency without the need for an additional process.

However, until now, only research on single output switched capacitor converters has been mainly conducted, and studies on multiple output switched capacitor converters are insufficient.

In order to solve the problems of the prior art as described above, the present invention proposes a multiple output DC-DC converter using a switched capacitor capable of high efficiency multiple output and efficiently reduce the ripple of the output voltage.

Other objects of the present invention may be derived by those skilled in the art through the following examples.

According to a preferred embodiment of the present invention to achieve the above object, a control signal generation unit for generating a switching control signal so that a plurality of output voltage corresponding to each reference voltage level; And an output unit configured to output an input voltage to a plurality of output terminals based on the switching control signal, wherein the output unit comprises N (two or more natural numbers) switched capacitor cells sharing the plurality of output terminals. Each of the N switched capacitor cells includes: a common capacitor configured to charge and discharge the input voltage; And a plurality of switch strings configured to charge the input voltage to the common capacitor and to switch the charged voltages to be outputted to the plurality of output terminals.

The number of the plurality of switch strings is the same as the number of the plurality of output terminals, and the first switch string of the plurality of switch strings may switch the charged voltage to be output to the first output terminal of the plurality of output terminals. have.

The first switch string may include a 1-1 switch to which the input voltage is applied at one end; A 2-1 switch having one end connected to the other end of the 1-1 switch and one end of the common capacitor; 1-2 switches, one end of which is connected to the other end of the 2-1 switch and the first output terminal; And a 2-2 switch having one end connected to the other end of the 1-2 switch and the other end of the common capacitor, and the other end connected to the ground.

A second switch string of the plurality of switch strings switches the charged voltage to be output to a second output terminal of the plurality of output terminals, and the second switch string is 1-1 to which the input voltage is applied at one end. switch; A 2-1 switch having one end connected to the other end of the 1-1 switch of the first switch string, the other end of the 1-1 switch of the second switch string, and one end of the common capacitor; 1-2 switches, one end of which is connected to the other end of the 2-1 switch of the second switch string and the second output terminal; And a 2-2 switch having one end connected to the other end of the 1-2 switch of the first switch string, the other end of the 1-2 switch of the second switch string, and the other end of the common capacitor, and the other end connected to the ground. can do.

The control signal generation unit may include: a first comparator configured to compare a first output voltage output to the first output terminal with a first reference voltage; And a second comparator for comparing the first output voltage with a second reference voltage, wherein a value corresponding to the first output voltage between the first reference voltage and the second reference voltage based on the comparison result. The first switching control signal to have a can be generated.

The control signal generator generates the first switching control signal using an N-bit binary counter, wherein the N first switch strings constituting the N switched capacitor cells correspond to the N-bit binary counter value. It can work.

The control signal generator adds 1 to the N-bit binary counter when the first output voltage is lower than the first and second reference voltages as a result of the comparison by the comparator, and the first output voltage is the first output voltage. When the reference voltage is higher than the first reference voltage and the second reference voltage, 1 may be subtracted from the N-bit binary counter.

According to the present invention, there is an advantage that high efficiency multiple outputs are possible.

In addition, according to the present invention, there is an advantage that can effectively reduce the ripple of the output voltage.

1 is a view showing an overall schematic diagram of a multiple output DC-DC converter using a switched capacitor according to an embodiment of the present invention.

FIG. 2 is a diagram showing in more detail the schematic diagram of FIG. 1 centering on an output unit. FIG.

3 is a diagram illustrating a detailed configuration of an output unit according to an embodiment of the present invention.

4 is a diagram illustrating an operation of a first switch string controlled using a switching control signal according to an embodiment of the present invention.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

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

1 is a diagram showing an overall schematic diagram of a multiple output DC-DC converter 100 using a switched capacitor according to an embodiment of the present invention.

2 is a diagram illustrating the schematic diagram of FIG. 1 in more detail with reference to the output unit 120. FIG. 3 is a diagram illustrating a detailed configuration of the output unit 120 according to an embodiment of the present invention. .

1 to 3, a multiple output DC-DC converter (hereinafter, referred to as a 'DC-DC converter' for convenience of description) using a switched capacitor includes a control signal generator 110 and an output unit ( 120).

In more detail, the control signal generator 110 generates a switching control signal such that the multiple output voltages correspond to respective reference voltage levels.

Hereinafter, those skilled in the art will understand that the description is based on the example of outputting the input voltage as three output voltages, but is not limited thereto.

To this end, the control signal generator 110 may include a first comparator 111 and a second comparator 112, and three output voltages may be referenced to each reference voltage level by using a comparison result by the two comparators. It is possible to generate a switching control signal to be equivalent to.

The output unit 120 outputs an input voltage to three output terminals based on the switching control signal.

The output unit 120 according to an embodiment of the present invention may be composed of eight switched

capacitor cells

121, 122, 123, ..., 128 sharing three output terminals, each of the eight switched capacitor cells It may include a common capacitor for charging and discharging the input voltage, three switch strings for charging the input voltage to the common capacitor, and switching so that the charged voltage is output to the three output terminals.

That is, among the eight switched capacitor cells, the first switched capacitor cell 121 includes a common capacitor 1212, a first switch string 1214, a second switch string 1216, and a third switch string 1218. The second switched capacitor cell 122 also includes a common capacitor 1222, a first switch string 1224, a second switch string 1226, and a third switch string 1228, in the same manner as the eight switched Capacitor cell 128 also includes a common capacitor 1282, a first switch sequence 1284, a second switch sequence 1286, and a third switch sequence 1288, respectively.

In this case, as shown in FIG. 2, since the eight switched

capacitor cells

121, 122,..., 128 are connected to share three output terminals, the first switch string included in each of the eight switched capacitor cells, That is, the first output voltage is output to the first output terminal V _{OUT_A} by the eight first switch strings 1214, 1224, 1234,..., 1284.

The second output voltage is output to the second output terminal V _{OUT_B} by the eight second switch strings 1216, 1226, 1236,..., And 1286 included in each of the eight switched capacitor cells. The third output voltage is output to the third output terminal V _{OUT_C} by the eight third switch strings 1218, 1228, 1238,..., And 1288 included in each of the switched capacitor cells.

As described above, since the output voltage is output to each output terminal, the number of switch strings is preferably equal to the number of output terminals.

And, since the output unit 120 is composed of eight switched capacitor cells, in the present invention, the control signal generator 110 generates a control signal for the operation of the eight switched capacitor cells using an 8-bit binary counter. It will be explained on the assumption.

That is, the operation of a total of eight first switch strings included in eight switched capacitor cells is controlled by a first 8-bit binary counter, and eight second switch strings are controlled by a second 8-bit binary counter. In turn, the operations of the eighth switch arrays are controlled by the eighth eight-bit binary counter.

On the other hand, the present invention is not limited thereto, and it will be apparent to those skilled in the art that a higher number of switched capacitor cells and corresponding higher bit binary counters may be used as needed.

In addition, it is assumed that there are three switch strings included in each of the eight switched capacitor cells, and one switch string includes four switches. However, depending on the number of multiple outputs required, Can also be changed.

Hereinafter, the first output voltage among the three output voltages is output to the first output terminal V _{OUT_A} among the three output terminals by the DC-DC converter 100 according to the embodiment of the present invention. The first output voltage will be described based on an operation in which the output level is determined by the operation of the first switch string, that is, the eight first switch strings, of the three switch strings included in the eight switched capacitor cells.

For the system-on-chip design, the switch according to an embodiment of the present invention is preferably a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) device.

Before describing the operation of determining the output level, referring to FIG. 3, the connection relationship between the common capacitor 1212 and the first to third switch strings 1214 to 1218 included in the first switched capacitor cell 121 is described. More detailed description is as follows.

First, as described above, the first switch string 1214 may include four switches, and an input voltage VDD is applied to one end of the 1-1 switch 1214a among the four switches.

One end of the 2-1 switch 1214b is connected to the other end of the 1-1 switch 1214a and one end of the common capacitor 1212, and one end of the 1-2 switch 1214c is sequentially connected to the 2-1 switch. It is connected to the other end of the 1214b and the first output terminal (V _{OUT_A} ).

One end of the 2-2 switch 1214d is connected to the other end of the 1-2 switch 1214c and the other end of the common capacitor 1212, and the other end of the 2-2 switch 1214d is connected to ground to form a circuit diagram. do.

Next, the second switch string 1216 may also include four switches, and the input voltage VDD is applied to one end of the 1-1 switch 1216a among the four switches.

One end of the 2-1 switch 1216b is connected to the other end of the 1-1 switch 1216a, one end of the common capacitor 1212, and the other end of the 1-1 switch 1214a of the first switch string, and sequentially One end of the 1-2 switch 1216c is connected to the other end of the 2-1 switch 1216b and the second output terminal V _{OUT_B} .

One end of the 2-2 switch 1216d is connected to the other end of the 1-2 switch 1216c, the other end of the common capacitor 1212, and the other end of the 1-2 switch 1214c of the first switch string. The other end of the second switch 1216d is connected to ground.

In the same manner, the input voltage VDD is applied to one end of the 1-1 switch 1218a among the four switches of the third switch string 1218, and one end of the 2-1 switch 1218b is applied to the 1-1 switch ( The other end of 1218a, one end of the common capacitor 1212, the other end of the 1-1 switch 1214a of the first switch string, and the other end of the 1-1 switch 1216a of the second switch string.

One end of the 1-2 switch 1218c is connected to the other end of the 2-1 switch 1218b and the third output terminal V _{OUT_C} , and one end of the 2-2 switch 1218d is connected to the 1-2 switch 1218c. Is connected to the other end of), the other end of the common capacitor 1212, the other end of the 1-2 switch 1214c of the first switch string, and the other end of the 1-2 switch 1216c of the second switch string, and the 2-2 switch 1218d. The other end of) is connected to ground.

On the other hand, it is connected so as to share the eight switched capacitor cells (121, 122, ..., 128) are three output terminals (V _{OUT_A,} V _{OUT_B,} V _{OUT_C)} as described above, the first output terminal (V _{OUT_A} ) Is not only connected to the other end of the 2-1 switch 1214b of the first switch capacitor cell 121 and one end of the 1-2 switch 1214c, but also to the first switch of the second switched capacitor cell 122. The other end of 2-1 switch 1224b in a row and one end of 1-2 switch 1224c, and in turn, the other end of 2-1 switch 1284b in a first switch row of the eighth switched capacitor cell 128, and It is connected to one end of the 1-2 switch 1284c. The second output terminal V _{OUT_B} and the third output terminal V _{OUT_C} are also the same, and thus a detailed description thereof will be omitted.

Hereinafter, with reference to FIGS. 1 to 4, an embodiment of the present invention will be mainly focused on an operation of determining a level of a first output voltage output to a first output terminal V _{OUT_A} by an operation of eight first switch strings. The voltage output method of the DC-DC converter 100 according to an example will be described in more detail.

As described above, the control signal generator 110 uses the comparison result of the first comparator 111 and the second comparator 112 as a reference to the first output voltage output to the first output terminal V _{OUT_A} . Generate a switching control signal that corresponds to the voltage level.

In this case, the first comparator 111 provides a result of comparing the first output voltage output to the first output terminal V _{OUT_A} with the first reference voltage V _{REF_A_H} to the control signal generator 110. The second comparator 112 may provide a result of the comparison with the second reference voltage V _{REF_A_L} to the control signal generator 110.

In the present invention, it will be described on the assumption that higher than the first reference voltage (V _{REF_A_H)} a second reference voltage (V _{REF_A_L),} and the difference is assumed to be 0.1V.

That is, the control signal generation unit 110 generates a first switching control signal such that the first output voltage has a value corresponding between the first reference voltage and the second reference voltage based on the comparison result by the two comparators. .

More specifically, when it is determined that the output voltage is higher than the first reference voltage and the second reference voltage as a result of the comparison by the first comparator 111 and the second comparator 112, the control signal generator 110 outputs the output. As a control signal for lowering the voltage, for example, a down signal may be generated.

As a result of the comparison by the two comparators, when the output voltage is lower than the first reference voltage and the second reference voltage, the control signal generator 110 is a control signal for increasing the output voltage, for example, an up signal. May occur.

In addition, when it is determined that the output voltage exists between the first reference voltage and the second reference voltage as a result of the comparison by the two comparators, the control signal generator is a control signal for maintaining the output voltage as it is. lock) signal may be generated.

According to an embodiment of the present invention, the generation of the up, down, and lock signals may be performed by the up / down determination unit 113 included in the control signal generator 110.

Subsequently, the control signal generator 110 uses the generated up, down, and lock signals to generate a bit in the form of a synchronized binary counter for controlling the eight first switch strings constituting the eight switched capacitor cells. Output

More specifically, the control signal generator 110 may output a bit having a value added by 1 every clock by using the up signal generated by the up / down determination unit 113, and by using the down signal. The bit of the subtracted value may be output for each clock.

The eight first switch strings are controlled according to the size of the output bit, thereby determining the level of the first output voltage output through the first output terminal.

According to an embodiment of the present invention, the output of the bit may be performed by the digital capacitance modulation (DCpM) control unit 114.

Next, the control signal generator 110 outputs the output bit, i.e., an 8-bit binary counter type bit that can be output by the DCpM controller 114 and an output bit when the output bit is high. The clock may be output, and if it is low, the clock may not be output.

According to an embodiment of the present invention, the output of the clock using the output bit and the input clock may be performed by the decoder 115.

Meanwhile, as the number of phases is used, the ripple of the output voltage is reduced, so that the control signal generator 110 according to the embodiment of the present invention has four 0 °, 45 °, 90 °, and 135 ° four. It may further comprise a four-phase generator 116 for outputting the phase.

That is, the four-phase generator 116 outputs the four phases using the input clock, so that the interleaved phase method can be applied to the present invention.

Switched-capacitor converters are easier to apply multiple interleaved phase schemes compared to inductor-based switching converters, and the reduction of output voltage ripple enables design that greatly reduces or eliminates the load capacitor's capacity, which is advantageous for system-on-chip schemes. Do.

In addition, the control signal generator 110 according to an embodiment of the present invention is a non-overclock generator (non over clock generator) for outputting one input clock as two clocks having different dead time ( 117 may be further included.

When the switch made of PMOS and the switch made of NMOS are turned on at the same time, VDD and GND may be connected to reduce the efficiency of the converter. Therefore, the two switches having different dead times do not turn on at the same time.

FIG. 4 is a diagram illustrating an operation of a first switch string controlled using a switching control signal according to an embodiment of the present invention. As shown in FIG. 4, the first switch string is configured by a decoder and a driver. It can be seen that the operation of the four switches, that is, the voltage applied to the gates of the four MOSFETs is determined.

In addition, the second switch string and the third switch string included in one switched capacitor cell together with the first switch string are operated in the same manner.

As described above, according to the present invention, there is an advantage that high efficiency multiple output is possible and the ripple of the output voltage can be efficiently reduced.

In the present invention has been described by specific details such as specific components and limited embodiments and drawings, but this is only provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments, the present invention Various modifications and variations are possible to those skilled in the art from this disclosure. Therefore, the spirit of the present invention should not be limited to the described embodiments, and all the things that are equivalent to or equivalent to the claims as well as the following claims will belong to the scope of the present invention. .

Claims

A control signal generator configured to generate a switching control signal such that a plurality of output voltages correspond to respective reference voltage levels; And

And an output unit configured to output an input voltage to a plurality of output terminals based on the switching control signal.

The output unit includes: N (two or more natural numbers) switched capacitor cells sharing the plurality of output terminals,

Each of the N switched capacitor cells may include a common capacitor configured to charge and discharge the input voltage; And

And a plurality of switch strings configured to charge the input voltage to the common capacitor and to switch the charged voltages to be outputted to the plurality of output terminals.
The method of claim 1,

The number of the plurality of switch strings is the same as the number of the plurality of output terminals, and the first switch string of the plurality of switch strings switches the charged voltage to be output to the first output terminal of the plurality of output terminals. Multiple output DC-DC converters with switched capacitors.
The method of claim 2,

The first switch string may include a 1-1 switch to which the input voltage is applied at one end;

A 2-1 switch having one end connected to the other end of the 1-1 switch and one end of the common capacitor;

1-2 switches, one end of which is connected to the other end of the 2-1 switch and the first output terminal; And

And a 2-2 switch having one end connected to the other end of the 1-2 switch and the other end of the common capacitor, and the other end connected to the ground. 2.
The method of claim 3,

A second switch string of the plurality of switch strings switches the charged voltage to be output to a second output terminal of the plurality of output terminals,

The second switch string may include a 1-1 switch to which the input voltage is applied at one end;

A 2-1 switch having one end connected to the other end of the 1-1 switch of the first switch string, the other end of the 1-1 switch of the second switch string, and one end of the common capacitor;

1-2 switches, one end of which is connected to the other end of the 2-1 switch of the second switch string and the second output terminal; And

A 2-2 switch having one end connected to the other end of the 1-2 switch of the first switch string, the other end of the 1-2 switch of the second switch string, and the other end of the common capacitor, and the other end connected to the ground; Multiple output DC-DC converter using a switched capacitor, characterized in that.
The method of claim 2,

The control signal generation unit may include: a first comparator configured to compare a first output voltage output to the first output terminal with a first reference voltage; And

And a second comparator comparing the first output voltage with a second reference voltage.

Based on a result of the comparison, the first output voltage generates a first switching control signal having a value corresponding to a value between the first reference voltage and the second reference voltage. -DC converter.
The method of claim 5,

The control signal generator generates the first switching control signal using an N-bit binary counter,

And the N first switch strings constituting the N switched capacitor cells operate in correspondence with the N-bit binary counter value.
The method of claim 6,

The control signal generator adds 1 to the N-bit binary counter when the first output voltage is lower than the first and second reference voltages as a result of the comparison by the comparator, and the first output voltage is the first output voltage. A multi-output DC-DC converter using a switched capacitor, characterized by subtracting 1 from the N-bit binary counter when higher than a first reference voltage and a second reference voltage.