KR20100135988A - Single inductor voltage converter - Google Patents

Abstract

PURPOSE: A DC voltage converter is provided to generate DC voltages which have different levels from a single input voltage by using a single inductor. CONSTITUTION: A one end of an inductor(L) is connected to a first node. The other end of the inductor is connected to a second node. A first output voltage is outputted from one end of a first capacitor. A second output voltage is outputted from one end of a second capacitor. A first switch(S1) is located between the first node and an input. A second switch(S2) is located between the second node and a first output. A third switch(S3) is located between the second node and the ground. A fourth switch(S4) is located between the first node and the second output. The first capacitor(C1) is located between the first output and the ground. The second capacitor(C2) is located between the second output and the ground.

Description

Single Inductor DC Voltage Converters {SINGLE INDUCTOR VOLTAGE CONVERTER}

The present invention relates to a direct current voltage converter, and more particularly, to a direct current voltage converter using a single inductor to generate voltages having different polarities.

In general, in order to convert a DC voltage to a DC voltage of a different size, a switching DC converter using high speed switching is widely used. The switching type DC converter may be classified into a buck converter that lowers the voltage and a boost converter that increases the voltage.

1A and 1B are circuit diagrams illustrating a buck switching converter and a boost switching converter, respectively. Referring to FIG. 1A, the output Vout1a is a voltage across the capacitor C1a when the switch S1a is on, and the output Vout1 is when the switch S1a is off. The voltage is at a level separated by the voltage occupied by the inductor L1a at the input Vin. When the switch S1a is switched at a high speed, the output Vout1a always has a lower level than the input Vin1a, and is smoothed by the inductor L1a and the capacitor C1a and output as a direct current voltage.

Referring to FIG. 1B, the inductor L1b is magnetized and the capacitor C1b is also charged while the switch S1b is on. When the switch S1b is turned off, the magnetized inductor L1b supplies power to the load as an energy source. When the on / off of the switch S1b is repeated and reaches a steady state, the output Vout1b is always at a higher level than the input by adding the voltage across the inductor L1b to the input voltage Vin1, and the inductor L1b and The capacitor C1b is smoothed and output as a direct current voltage.

Conventionally, two or more of these DC voltage converters must be used to simultaneously obtain voltages having different levels, especially two or more voltages having different polarities. Since a conventional DC voltage converter has one inductor, in order to configure several converters, an inductor must be formed by the number of converters. Implementing an inductor on a chip takes up a lot of area, so it is not advisable to make more than one. If a small inductor is used, it can occupy a smaller chip area, but this requires higher switching frequency and effective noise rejection, which usually requires complex control circuitry.

The problem to be solved by the present invention is to generate a plurality of voltages having different levels or polarities without taking up a small chip area and increasing the complexity of the control circuit.

In order to solve this problem, the DC voltage conversion circuit according to an embodiment of the present invention includes an inductor, first and second capacitors, and a plurality of switches,

A voltage appearing at one end of the first capacitor is output as a first output voltage, a voltage appearing at one end of the second capacitor is output as a second output voltage,

The plurality of switches may receive and store energy in the inductor from an input power source during a first time period, transfer some of the energy stored in the inductor to the first capacitor during a second time period, and transmit the inductor for a third time period. It is wired to transfer some of the energy stored in the second capacitor, and can also be switched at high speed so that the first and second output voltages appear to be substantially DC voltages.

Advantageously, said plurality of switches

The inductor may be switched to be connected to the input power during the second time period, and the first output voltage may be output as the voltage of the input power substantially added to the voltage of the input power.

Advantageously, said plurality of switches

The inductor may be switched to be separated from the input power during the third time period.

Preferably, each other end of the first and second capacitors may be connected to a ground voltage.

DC voltage conversion circuit according to another embodiment of the present invention includes an inductor and a plurality of capacitors and a plurality of switches,

Each voltage appearing at one end of each of the plurality of capacitors is output as output voltages,

The plurality of switches may be supplied from an input power supply in a first time period among a plurality of time periods that are not overlapped with each other, and the plurality of switches may use some of the energy stored in the inductor every time period except the first time period among the plurality of time periods. It is wired to transfer to one of the capacitors of and can also be switched at high speed so that the output voltages appear as a direct current voltage.

Preferably, the plurality of switches,

An output voltage output from one end of at least one capacitor to receive energy for the at least one time period, wherein the inductor is switched to be connected to the input power source for at least one of the remaining time periods except the first time period May be substantially output as the voltage of the input power plus the voltage of the inductor.

Preferably, each other end of the plurality of capacitors may be connected to a ground voltage.

DC voltage conversion circuit according to another embodiment of the present invention

A first switch connecting between the input power supply and one end of the inductor during the first and second time periods;

A second switch connecting between the other end of the inductor and one end of the first capacitor during the second time period;

A third switch connecting between the other end of the inductor and a ground voltage during the first time period and the third time period; And

A fourth switch connecting between one end of the inductor and one end of the second capacitor during the third time period,

A first output voltage is output at one end of the first capacitor, a second output voltage is output at one end of the second capacitor, and the other ends of the first and second capacitors are connected to a ground voltage,

The first to fourth switches may switch at high speed such that the first and second output voltages appear to be substantially DC voltages.

According to embodiments of the present invention, with a DC voltage conversion circuit having one inductor, it is possible to generate DC voltages having different levels from one input voltage, in particular to generate DC voltages having different polarities. have.

With respect to the embodiments of the present invention disclosed in the text, specific structural to functional descriptions are merely illustrated for the purpose of describing embodiments of the present invention, embodiments of the present invention may be implemented in various forms and It should not be construed as limited to the embodiments described in.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. The same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

2 is a circuit diagram illustrating a single inductor voltage converter according to an embodiment of the present invention.

Referring to FIG. 2, a single inductor voltage converter includes one inductor L and two capacitors C1 and C2, and includes four switches, namely, first to fourth switches S1, S2, S3, and S4. Include.

In essence, the present invention receives and stores magnetic energy from an input power source in the inductor L in a first time period, while transferring energy from the inductor L to the first capacitor C1 in a second time period. The voltage shown across the first capacitor C1 is output as the first output voltage Vout1, and in the third time period, the second capacitor C2 transfers energy from the inductor L to the second capacitor C2. A circuit and a method for simultaneously generating an output having two levels by outputting a voltage shown at both ends of the second output voltage Vout2 and repeating the first to third time periods.

In this case, during the second time period, when energy is continuously supplied and stored from the input power source to the inductor L following the first time period, the first output voltage may be at a higher level than the input, whereas When the energy supply to the inductor L is cut off from the input power supply for two time periods, the first output voltage may be at a lower level than the input.

Furthermore, when the output voltage is output at each one end of the first and second capacitors C1 and C2 and the other end is connected to ground GND, the first output voltage has a positive polarity and the second The output voltage can be made to have a negative polarity.

Furthermore, three or more DC output voltages may be obtained if additional capacitors and switches are used and the voltage across the added capacitor is output as an additional output voltage while transferring energy from the inductor (L) to the additional capacitor for an additional period of time. have.

Specifically, in the embodiment of FIG. 2, one end of the inductor L is connected to the first node N1 and the other end of the inductor is connected to the second node N2. There is a first switch S1 between the first node N1 and the input Vin. There is a second switch S2 between the second node N1 and the first output Vout1. There is a third switch S3 between the second node N2 and the ground GND. There is a fourth switch S4 between the first node N1 and the second output Vout2. There is a first capacitor C1 between the first output Vout1 and ground GND, and a second capacitor C2 between the second output Vout2 and ground GND.

Each of the switches is applied with control signals ph1, ph2, ph3, ph4 that control the on / off of the switch. These control signals ph1 to ph4 are provided from the outside and repeat the control steps consisting of three time periods. These control steps are described in detail later.

The single inductor voltage converter according to the present invention is applied with an input voltage Vin, a voltage higher than the level of the input voltage Vin, preferably a positive first voltage Vout1 and an input voltage. As a voltage lower than the level of Vin, a second voltage Vout2, which is preferably negative, may be generated.

Briefly describing the circuit of FIG. 2, in a steady state, the first output Vout1 is a voltage higher than the input voltage Vin by adding the input voltage Vin to the voltage across the inductor L, i.e., positive It is output as a voltage. In the normal state, the second output Vout2 is output as a voltage lower than the voltage applied to the second capacitor C2 than the ground voltage, that is, as a negative voltage. In this way it is possible to simultaneously output two voltages of different polarity with one converter circuit.

Each output may be appropriately smoothed and output according to the filtering effect provided by the inductor L and the capacitors C1 and C2. In some embodiments, the addition of a low pass filter between the respective outputs Vout1 and Vout2 and the load can reduce or eliminate the ripple caused by switching of the switches.

3 is a table illustrating control signals applied to the switch of FIG. 2 according to an embodiment of the present invention.

Referring to Figures 3 and 2, the control of the switches is made of three time periods. In the first time period (phase 1), the first switch S1 is turned on, the second switch S2 is turned off, the third switch S3 is turned on, and the fourth switch S4 is turned off. In this state, the current path Path1 is formed as a path from the input Vin through the inductor L to the ground GND, and the inductor L is magnetized by the current. The voltage charged in the first capacitor C1 is output to the first output Vout1, and the voltage charged in the second capacitor C2 is output to the second output Vout2.

In the second time period (phase 2), the first switch S1 is turned on, the second switch S2 is turned on, the third switch S3 is turned off, and the fourth switch S4 is turned off. In this state, the current path Path2 is formed as a path from the input Vin through the inductor L and the first capacitor C1 to the ground GND, and the current which magnetized the inductor L is now zero. One capacitor C1 is charged to charge the first capacitor C1. In the initial stage of operation, the first output Vout1 may appear low because the first capacitor C1 is not sufficiently charged yet. The voltage at (Vin) is added to the voltage across the inductor (L) and is larger than the voltage at the input (Vin). In the meantime, the second output Vout2 is a voltage charged in the second capacitor C2.

In the third time period (phase 3), the first switch S1 is turned off and the second switch S2 is turned off, while the third switch S3 is turned on and the fourth switch S4 is turned on. . In this state, the current path Path3 is disconnected from the input Vin and passes through the third switch S3, the second capacitor C2 and the fourth switch S4 from the magnetized inductor L (i.e., Clockwise) as a closed circuit. The magnetic field energy accumulated in the inductor L is the electric field energy of the second capacitor C2 by the current flowing from the inductor L to the third switch S3, the second capacitor C2, and the fourth switch S4. Is converted, and the second capacitor C2 is charged. At this time, since the current is supplied to the second capacitor C2 from the third switch S3, the voltage at the terminal side connected to the fourth switch S4 of both terminals of the second capacitor C2, that is, the second output. Since Vout2 is lower than the other voltage and the terminal connected to the third switch S3 is the ground GND voltage, the second output Vout2 has a negative polarity. On the other hand, in this time period, the first output Vout1 is the voltage of the first capacitor C1.

The first to third time periods are repeated at high speed, and when the steady state is reached, the first output Vout1 is output at a voltage higher than the input Vin, and the second output Vout2 is greater than the input Vin. The low polarity is output with a negative voltage.

The duration of the first time period to the third time period may be appropriately determined depending on which size of output is desired. For example, in order to obtain a high level of the first output Vout1 or the second output Vout2, the duration of the first time period may be increased, and the duration of the second or third time period may be reduced.

4 is a circuit diagram illustrating a single inductor voltage converter implemented using a MOSFET according to an embodiment of the present invention.

Referring to FIG. 4, the circuit of FIG. 4 has essentially the same configuration as the circuit of FIG. 3, except that the switches S1 to S4 of FIG. 3 are converted into PMOS M1 and M2 and NMOS M3 and M4, respectively. It can be seen that it is implemented. Depending on the embodiment, the switch can also be implemented in other suitable forms.

FIG. 5 is a waveform diagram illustrating control signals applied to the MOSFET of FIG. 3 in accordance with an embodiment of the present invention.

4 and 5, the control of the first to fourth transistors M1 to M4 is performed in three steps by the first to fourth control signals ph1 to ph4. In the first time period (phase 1), the first to fourth control signals ph1, ph2, ph3, and ph4 have low, high, high, and low levels, respectively. The four transistors M1, M2, M3, M4 are turned on, off, on and off, respectively. In this state, the current path is formed as a path from the input Vin through the inductor L to the ground GND, and the inductor L is magnetized by the current. The voltage charged in the first capacitor C1 is output to the first output Vout1, and the voltage charged in the second capacitor C2 is output to the second output Vout2.

In the second time period (phase 2), the first to fourth control signals ph1, ph2, ph3, and ph4 have low, low, low, and low levels, respectively, and the first to fourth transistors M1, M2, M3, and M4 are turned on, on, off and off respectively. In this state, the current path is formed as a path from the input Vin through the inductor L and the first capacitor C1 to the ground GND, and the current which magnetized the inductor L is now the first capacitor ( The first capacitor C1 is charged while flowing C1). When the circuit reaches a steady state, both ends of the first capacitor C1 are larger than the voltage of the input Vin as the voltage of the inductor L is added to the voltage of the input Vin. In the meantime, the second output Vout2 is a voltage charged in the second capacitor C2.

In the third time period (phase 3), the first to fourth control signals ph1, ph2, ph3, and ph4 have high, high, high, and high levels, respectively, and the first to fourth transistors M1, M2, M3, M4) are turned off, off, on and on, respectively. In this state, the current path is disconnected from the input Vin and is configured as a closed circuit passing from the magnetized inductor L through the third switch S3, the second capacitor C2 and the fourth switch S4. . The magnetic field energy accumulated in the inductor L is the electric field energy of the second capacitor C2 by the current flowing from the inductor L to the third switch S3, the second capacitor C2, and the fourth switch S4. Is converted to and the second capacitor C2 is charged. Since the second output Vout2 is lower than the ground GND, the second output Vout2 has a negative polarity. In this time period, the first output Vout1 is the voltage of the first capacitor C1.

The first to third time periods are repeated at high speed, and when the steady state is reached, the first output Vout1 is output at a voltage higher than the input Vin, and the second output Vout2 is greater than the input Vin. The low polarity is output with a negative voltage.

The pulse period of the first to fourth control signals is a repetition period of the first to third time periods, and the duty of each control signal may be appropriately determined depending on which size of output is desired. For example, in order to obtain high levels of the first output Vout1 and the second output, the duty of the second and third control signals may be increased, and the duty of the first and fourth control signals may be reduced.

When implemented with real transistors, since switching operations of the transistors do not occur instantaneously, unwanted short-circuit conditions may occur at the time of switching between each time period. For example, at the time of switching from the first time period to the second time period, both the second transistor M2 and the third transistor may be in an energized state for a short time according to the timing of the control signal. In this case, the electric charge charged in the first transistor C1 is instantaneously discharged to destroy the circuit element, or at least the desired voltage will not be generated.

Therefore, in order to prevent this, according to an embodiment, the transistors may be controlled to have a predetermined dead time at the switching transition time.

For example, at the time of switching from the first time period to the second time period, the second control signal is switched low (i.e. slightly later off to on) later by the predetermined dead time than the switching time point, or It is possible to cause the three control signals to be switched low (on earlier on to off) by a predetermined dead time before their switching time. Further, at the time of switching from the second time period to the third time period, the first control signal and the second control signal are switched high (ie, earlier off) earlier by a predetermined dead time than the switching time point, or The third control signal and the fourth control signal can be switched high (i.e., later on) later by a predetermined dead time than the switching time. Further, at the time when the third time period is switched back to the first time period, the first control signal is switched low (ie, slightly later on) later by a predetermined dead time than the switching time point, or the fourth control. The signal can be switched low (off earlier) by a predetermined dead time earlier than its switching point, and the third control signal is low for a predetermined dead time before and after the switching point and then high again (i.e., Can be off for a while).

By giving the dead time to the switches at this point in time, the transistors can be controlled to avoid unwanted current paths.

FIG. 6 illustrates an output waveform obtained as a result of simulating a single inductor voltage converter according to an embodiment of the present invention illustrated by the circuit of FIG. 4 and the control signal waveform of FIG. 5.

In the simulation, the inductors were 2.2 uH, the capacitors were 20 uF, respectively, the input Vin was 5 V, and the switching time periods were 1 usec. The first time period lasts for about 0.5 usec, and the second and third time periods each last about 0.25 usec. The dead time is given to the third control signal at the end of the first time period, the first and second control signals at the end of the second time period, and further to the third and fourth control signals at the end of the third time period.

Under these conditions, when the circuit of FIG. 4 is simulated, the first output Vout1 gradually increases from 0, converges to about + 6V within 0.5 msec, and the second output Vout2 starts at 0 Gradually lowered, you can see the convergence to about -6V within 0.5 msec.

Thus, embodiments of the present invention can output two DC voltages having different polarities as one circuit having a single inductor.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited to the above-described embodiments, which can be modified by those skilled in the art to which the present invention pertains. Modifications are possible. Accordingly, the spirit of the invention should be understood only by the claims set forth below, and all equivalent or equivalent modifications will fall within the scope of the invention.

1A and 1B are circuit diagrams illustrating a buck switching converter and a boost switching converter, respectively.

2 is a circuit diagram illustrating a single inductor voltage converter according to an embodiment of the present invention.

3 is a table illustrating control signals applied to the switch of FIG. 2 according to an embodiment of the present invention.

4 is a circuit diagram illustrating a single inductor voltage converter implemented using a MOSFET according to an embodiment of the present invention.

FIG. 5 is a waveform diagram illustrating control signals applied to the MOSFET of FIG. 3 in accordance with an embodiment of the present invention.

FIG. 6 illustrates an output waveform obtained as a result of simulating a single inductor voltage converter according to an embodiment of the present invention illustrated by the circuit of FIG. 4 and the control signal waveform of FIG. 5.

Claims (8)

A DC voltage converting circuit comprising an inductor, first and second capacitors and a plurality of switches, A voltage appearing at one end of the first capacitor is output as a first output voltage, a voltage appearing at one end of the second capacitor is output as a second output voltage, The plurality of switches may receive and store energy in the inductor from an input power source during a first time period, transfer some of the energy stored in the inductor to the first capacitor during a second time period, and transmit the inductor for a third time period. Wired to transfer a portion of the energy stored in the second capacitor, and switching at a high speed such that the first and second output voltages appear substantially as a direct current voltage. The method of claim 1, wherein the plurality of switches The inductor is switched to be connected to the input power source during the second time period, and the first output voltage is substantially output as the voltage of the input power source plus the voltage of the inductor. . The method of claim 1, wherein the plurality of switches And the inductor is switched to be separated from the input power during the third time period. The DC voltage converting circuit of claim 1, wherein each other end of the first and second capacitors is connected to a ground voltage. In a DC voltage conversion circuit comprising an inductor and a plurality of capacitors and a plurality of switches, Each voltage appearing at one end of each of the plurality of capacitors is output as output voltages, The plurality of switches may be supplied from an input power supply in a first time period among a plurality of time periods that are not overlapped with each other, and the plurality of switches may use some of the energy stored in the inductor every time period except the first time period among the plurality of time periods. And transfer at high speed so that the output voltages appear as direct current voltages. The method of claim 5, wherein the plurality of switches, The inductor is switched to be connected to the input power for at least one of the remaining time periods except the first time period, and an output voltage output from one end of at least one capacitor receiving energy during the at least one time period is substantially And the voltage of the input power is added to the voltage of the inductor. The DC voltage converting circuit of claim 5, wherein each other end of the plurality of capacitors is connected to a ground voltage. A first switch connecting between the input power supply and one end of the inductor during the first and second time periods; A second switch connecting between the other end of the inductor and one end of the first capacitor during the second time period; A third switch connecting between the other end of the inductor and a ground voltage during the first time period and the third time period; And A fourth switch connecting between one end of the inductor and one end of the second capacitor during the third time period, A first output voltage is output at one end of the first capacitor, a second output voltage is output at one end of the second capacitor, and the other ends of the first and second capacitors are connected to a ground voltage, And said first to fourth switches switch at high speed such that said first and second output voltages appear substantially as direct current voltages.

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