CN115882722A - Hybrid Buck-Boost DC-DC Converter with Flying Capacitor - Google Patents

Abstract

The present disclosure provides a hybrid buck-boost dc-dc converter with flying capacitor, comprising: an input node connected to an input voltage source for receiving an input voltage; a power inductor, one end of which is connected to the input node and the other end of which is connected to the first switch node; one end of the flying capacitor is connected to the first switch node, and the other end of the flying capacitor is connected to the second switch node; one end of the first switch tube is connected to the second switch node, and the other end of the first switch tube is grounded; one end of the second switch tube is connected to the input node, and the other end of the second switch tube is connected to the second switch node; one end of the third switching tube is connected to the first switching node, the other end of the third switching tube is connected to the output node, and the output node is used for sending out output voltage; one end of the fourth switching tube is connected to the second switching node, and the other end of the fourth switching tube is connected to the output node; and the output end is connected with the output node and comprises an output capacitor and a load resistor which are arranged in parallel, and the output end generates load current under the action of output voltage.

Description

Hybrid Buck-Boost DC-DC Converter with Flying Capacitors

technical field

The present disclosure relates to the technical fields of electronic devices and integrated circuits, and in particular to a hybrid buck-boost DC-DC converter with flying capacitors.

Background technique

In battery-powered mobile devices, the actual supply voltage required by the system circuits may be higher or lower than the battery voltage. The most typical application scenario: powered by a lithium battery, a fixed 3.3V is generated to power the system, and as the lithium battery's usage time increases, the battery voltage drops from 5V to 2.5V. Therefore, the system needs a buck DC-DC converter when the battery voltage is higher than 3.3V, and a step-up DC-DC converter when the battery voltage is lower than 3.3V. In this case, a buck-boost DC-DC converter with both step-up and step-down functions provides a good solution.

The traditional buck-boost converter is to cascade the traditional boost converter and buck converter, so in the power path, there will always be two power transistors connected in series with the inductor, and the pure boost or buck There is only one power tube in series with the inductor in the voltage converter, so the conduction loss of the traditional buck-boost converter will be very large. In order to improve the efficiency, the area of the power tube can only be increased to reduce the on-resistance of the power tube , which will undoubtedly greatly increase the manufacturing cost of the chip.

In addition, the inductor of the traditional buck-boost converter is on the high current side in the boost mode or the buck mode. In other words, the inductor current will be very large. In order to ensure the system efficiency, it is necessary to choose a small DCR The inductance, and for the inductance, the smaller the DCR, the larger the size, which not only increases the size of the chip, but also increases the cost.

Contents of the invention

(1) Technical problems to be solved

Based on the above problems, the present disclosure provides a hybrid buck-boost DC-DC converter with flying capacitors to alleviate technical problems in the prior art such as large volume of buck-boost converters and high cost of improving efficiency .

(2) Technical solution

The present disclosure provides a hybrid buck-boost DC-DC converter with a flying capacitor, including: an input node, a power inductor, a flying capacitor, a first switching tube, a second switching tube, a third switching tube, and a fourth switch tube, output. The input node is connected to the input voltage source for receiving the input voltage; one end of the power inductor is connected to the input node, and the other end is connected to the first switching node; one end of the flying capacitor is connected to the first switching node, and the other end of the flying capacitor is connected to to the second switch node; one end of the first switch tube is connected to the second switch node, and the other end is grounded; one end of the second switch tube is connected to the input node, and the other end is connected to the second switch node; the third switch One end of the tube is connected to the first switch node, and the other end is connected to the output node, and the output node is used to send an output voltage; one end of the fourth switch tube is connected to the second switch node, and the other end is connected to the output node; output The terminal is connected to the output node, the output terminal includes an output capacitor and a load resistor arranged in parallel, and the output terminal generates a load current under the action of the output voltage.

According to an embodiment of the present disclosure, when the input voltage is higher than the output voltage, the converter works in a buck mode, and when the input voltage is lower than the output voltage, the converter works in a boost mode.

According to the embodiment of the present disclosure, in the boost mode, the fourth switch tube is always off, and the boost mode is divided into the first state and the second state according to the linkage state of the first switch tube, the second switch tube and the third switch tube. state.

According to an embodiment of the present disclosure, in the first state, the first switch tube is turned on, the second switch tube and the third switch tube are turned off; the voltage of the first switch node is lower than the input voltage, the voltage difference across the power inductor is greater than 0, and the power The inductor is magnetized, and the current of the power inductor rises and charges the flying capacitor.

According to an embodiment of the present disclosure, in the second state, the first switch tube is turned off, the second switch tube and the third switch tube are turned on, the voltage of the first switch node is the same as the voltage of the output node, and the voltage of the second switch node is equal to The input voltage, the voltage of the first switching node is greater than the input voltage, the voltage difference between the two ends of the power inductor is less than 0, the power inductor is demagnetized, the current of the power inductor drops, and the flying capacitor discharges to transfer charge to the output capacitor.

According to the embodiment of the present disclosure, in the step-down mode, the second switch tube is always off, and the step-down mode is divided into the third state and the fourth state according to the linkage state of the first switch tube, the third switch tube, and the fourth switch tube. state.

According to an embodiment of the present disclosure, in the third state, the first switch tube and the third switch tube are turned on, the fourth switch tube is turned off, the voltage of the first switch node is equal to the output voltage, and the voltage of the second switch node is 0, The voltage of the first switch node is lower than the input voltage, the voltage difference between the two ends of the power inductor is greater than 0, the power inductor is magnetized, the current of the power inductor rises, the flying capacitor is discharged, and the charge flows to the output capacitor.

According to an embodiment of the present disclosure, in the fourth state, the first switch tube and the third switch tube are turned off, the fourth switch tube is turned on, the voltage of the first switch node is twice the output voltage, and the voltage of the second switch node is equal to The output voltage, the voltage of the first switch node is greater than the input voltage, the voltage difference across the power inductor is less than 0, the power inductor is demagnetized, the current of the power inductor drops, and the flying capacitor is charged.

According to an embodiment of the present disclosure, in the boost mode, the power inductor current is equal to the load current; the first switch tube, the second switch tube, and the third switch tube select the switch tube whose maximum withstand voltage is the input voltage, and the fourth switch tube selects The switching tube whose maximum withstand voltage is the output voltage.

According to an embodiment of the present disclosure, in the step-down mode, the power inductor current is smaller than the load current, the first switch tube, the third switch tube, and the fourth switch tube select the switch tube whose maximum withstand voltage is the output voltage, and the second switch tube selects The switch tube whose maximum withstand voltage is the input voltage.

(3) Beneficial effects

It can be seen from the above technical solutions that the disclosed hybrid buck-boost DC-DC converter with flying capacitors has at least one or part of the following beneficial effects:

(1) Both the buck mode and the boost mode can reduce the current on the inductor, thus ensuring high efficiency;

(2) On the premise of ensuring high efficiency, an inductor with a larger DCR can be selected, and the size of the inductor can be reduced;

(3) While reducing the inductor current, the current on each switch tube will also be reduced, and the conduction loss of the switch tube is greatly reduced;

(4) The maximum withstand voltage value of the switch tube in the system is V _IN (5V) or a switch tube with a similar withstand voltage value does not require a high withstand voltage tube. On the premise of ensuring high system efficiency, the size of the switch tube can be reduced. Save chip area and reduce chip manufacturing cost.

Description of drawings

Figure 1a is a schematic diagram of a conventional buck-boost converter.

FIG. 1b is a schematic diagram of the conventional buck-boost converter shown in FIG. 1a in buck mode.

FIG. 1c is a schematic diagram of the conventional buck-boost converter shown in FIG. 1a in boost mode.

Fig. 2a is a schematic diagram of main waveforms of the circuit in the step-down mode of the conventional buck-boost converter shown in Fig. 1a.

Fig. 2b is a schematic diagram of main key waveforms of the circuit in the boost mode of the traditional buck-boost converter shown in Fig. 1a.

Fig. 3a is a schematic diagram of a buck-boost converter with a flying capacitor in the prior art.

Fig. 3b is a schematic diagram of the buck-boost converter with flying capacitor shown in Fig. 3a in the buck mode in the prior art.

FIG. 3c is a schematic diagram of the buck-boost converter with flying capacitor shown in FIG. 3a in boost mode in the prior art.

FIG. 4a is a schematic diagram of main waveforms of the circuit in the buck mode of the buck-boost converter with flying capacitors shown in FIG. 3a in the prior art.

FIG. 4b is a schematic diagram of main waveforms of the circuit in the boost mode of the buck-boost converter with flying capacitors shown in FIG. 3a in the prior art.

FIG. 5 is a schematic diagram of a hybrid buck-boost DC-DC converter with flying capacitors according to an embodiment of the present disclosure.

FIG. 6 a is a schematic diagram of a first state of the hybrid buck-boost DC-DC converter shown in FIG. 5 in boost mode.

FIG. 6b is a schematic diagram of the second state of the hybrid buck-boost DC-DC converter shown in FIG. 5 in boost mode.

FIG. 7 is a schematic diagram of main waveforms of a hybrid buck-boost DC-DC converter with a flying capacitor in boost mode according to an embodiment of the present disclosure.

FIG. 8 a is a schematic diagram of a third state of the hybrid buck-boost DC-DC converter shown in FIG. 5 in buck mode.

FIG. 8 b is a schematic diagram of a fourth state of the hybrid buck-boost DC-DC converter shown in FIG. 5 in buck mode.

FIG. 9 is a schematic diagram of main waveforms of a hybrid buck-boost DC-DC converter with a flying capacitor in buck mode according to an embodiment of the present disclosure.

FIG. 10 is a schematic diagram of a workflow of a hybrid buck-boost DC-DC converter with flying capacitors according to an embodiment of the present disclosure.

Detailed ways

The present disclosure provides a hybrid buck-boost DC-DC converter with flying capacitors, which is a brand-new topology of a hybrid buck-boost DC-DC converter, which can be used in traditional buck-boost conversion On the basis of the converter, a flying capacitor is introduced, which can assist the inductor to charge the output in both the boost mode and the buck mode, thereby reducing the inductor current. Moreover, while reducing the inductor current, the current on each switch tube is also reduced, and the conduction loss of the switch tube is also reduced, and at the same time, no problem of withstand voltage is introduced.

A traditional buck-boost converter is shown in Figure 1a. The converter structure includes four switching tubes S ₁ , S ₂ , S ₃ , and S ₄ and a power inductor L, an output capacitor C _OUT , and load resistor R _OUT . The circuit has two modes of operation:

When the input voltage is greater than the output voltage (V _IN > V _OUT ), as shown in Figure 1b, the circuit works in the step-down mode. The working principle is similar to that of the traditional step-down converter. The two switches S ₁ and S ₂ alternately conduct is on, S ₃ is normally on, and the switch node V _sW1 switches between V _IN and 0. The relationship between the voltage conversion ratio M (M=V _OUT /V _IN ), the average current of the power inductor, and the duty cycle D is:

M=D (1)

I _L = I _OUT (2)

Among them D ∈ (0, 1), M ∈ (0, 1), I _L is the power inductor current, I _OUT is the output current, or the load current of the load resistance R _OUT .

When the input voltage is lower than the output voltage (V _IN < V _OUT ), as shown in Figure 1c, the circuit works in the boost mode, and the working principle is similar to that of the traditional boost converter. The two switches S ₃ and S ₄ alternate is turned on, S ₁ is normally turned on, and the second switch node V _SW2 is switched between V _OUT and 0. The relationship between the voltage conversion ratio M (M=V _OUT /V _IN ), the average inductor current and the duty cycle D is:

M=1/(1-D) (3)

where D ∈ (0, 1), M ∈ (1, ∞).

The key waveforms of the circuit are shown in Figure 2a and Figure 2b. From the above analysis, it can be known that when the traditional buck-boost converter is in the buck or boost mode, each switch is normally on (S ₃ , S ₁ ), which greatly increases the conduction loss of the system. In order to reduce the conduction loss, it is necessary to increase the size of the switch to obtain a lower conduction resistance, which will increase the cost of chip manufacturing. At the same time, when the traditional buck-boost converter is in the buck or boost mode, the inductor current is very large. In order to reduce the loss on the inductor, an inductor with a small DCR must be selected, and the smaller the DCR, the larger the inductor size. This increases the cost and also makes the chip larger.

In order to reduce the conduction loss, ISSCC2017 proposed a new topology structure, as shown in Figure 3a, the structure includes 4 switches, a power inductor L, a flying capacitor C _F , an output capacitor C _OUT , and a load resistor R _OUT .

Similarly, when the input voltage is greater than the output voltage (V _IN > V _OUT ), the circuit works in buck mode, as shown in Figure 3b. In buck mode, just like a traditional buck converter, there are only two switches S ₁ and S ₂ are turned on alternately, the switch node is switched between V _IN and 0, S ₃ and S ₄ are always disconnected, and there is no charging and discharging process on the flying capacitor. Compared with the traditional buck-boost converter, There is one less normally-on switch on the power path, so that the conduction loss of the circuit can be greatly reduced. In buck mode:

M=D (5)

I _L = I _OUT (6)

where D ∈ (0, 1), M ∈ (0, 1). The key waveform diagram of the step-down mode circuit is shown in Figure 4a.

When the input voltage is lower than the output voltage (V _IN < V _OUT ), the circuit works in boost mode, as shown in Figure 3c, in which S ₁ , S ₃ , and S ₄ work, and S ₂ is always disconnected. During the DT-T time period, S ₁ and S ₄ are turned on to charge the flying capacitor, the switch node V _SW1 = V _IN , the voltage value of the second switch node V _SW2 = V _OUT , V _OUT < V _IN , the voltage across the power inductor If the difference V _SW1 -V _SW2 <0, the inductance is demagnetized. At this time _, the _voltage across the flying capacitor is V _CF ＝V _{IN .} The voltage across the capacitor cannot change abruptly, so at this time the voltage value of the first switch node V _SW1 =V _OUT +V _CF =V _IN +V _OUT , the voltage value of the second switch node V _SW2 =V _OUT , V _SW1 -V _SW2 >0 , the voltage difference across the inductor is positive, and the inductor is magnetized. Unfortunately, the voltage stress on S ₁ at this time is V _IN +V _OUT , so S ₁ needs a power transistor with higher withstand voltage, which means an increase in chip area and manufacturing cost. In boost mode:

M=1/(1-D) (7)

Among them D ∈ (0, 1), M ∈ (1, ∞), the average inductor current is greater than the load current. The key waveform diagram of the boost mode circuit is shown in Figure 4b.

It can be seen from the above that the traditional buck-boost converter shown in Figure 1a requires three switching tubes in both boost mode and buck mode, and one switch tube is normally on, and the conduction loss is very large , in order to achieve high efficiency, it is necessary to use a switch tube with a larger area, which increases the chip area and increases the chip manufacturing cost. In addition, the inductor current is very large in boost mode and buck mode. In order to achieve high efficiency, it is necessary to use an inductor with a small DCR. The size of the inductor with a small DCR will be larger, which increases the cost and increases the overall volume of the chip. . In the buck-boost converter with flying capacitors shown in Figure 3a, only two switches work in the buck mode, and three switches work in the boost mode, but there is no one switch like the traditional structure. The switch tube is always on, so in general, compared with the traditional structure, the conduction loss of the switch tube will be reduced, but _S1 needs a high withstand voltage switch tube, which will increase the chip area and manufacturing cost and reduce system efficiency.

In addition, the inductor current of these two structures is very large in the boost mode and the buck mode, so a large-sized inductor is required. At the same time, a large inductor current also means that the conduction loss of the switch tube will also be large.

In response to the above problems, the purpose of the present invention is to propose a novel buck-boost converter topology, which can reduce the inductor current in both the boost mode and the buck mode, and reduce the conduction loss of the switch tube and the loss of the inductor DCR. , and at the same time does not introduce the withstand voltage problem of the switch tube, so as to achieve high efficiency and greatly reduce the cost and volume of the chip.

In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

In an embodiment of the present disclosure, a hybrid buck-boost DC-DC converter with a flying capacitor is provided, as shown in FIG. 5 , the hybrid buck-boost DC-DC converter with a flying capacitor, include:

An input node connected to an input voltage source for receiving an input voltage V _IN ;

A power inductor L, one end is connected to the input node, and the other end is connected to the first switch node V _SW1 ;

a flying capacitor C _F , one end of which is connected to the first switch node V _SW1 , and the other end of the flying capacitor is connected to the second switch node V _SW2 ;

The first switching tube S ₁ , one end is connected to the second switching node V _SW1 , and the other end is grounded;

The second switching tube S ₂ , one end is connected to the input node, and the other end is connected to the second switching node V _SW2 ;

A third switch tube S ₃ , one end is connected to the first switch node V _SW1 , and the other end is connected to an output node, and the output node is used to send out an output voltage V _OUT ;

The fourth switching tube S ₄ , one end is connected to the second switching node V _SW2 , and the other end is connected to the output node;

The output terminal is connected to the output node, the output terminal includes an output capacitor C _OUT and a load resistor R _OUT arranged in parallel, and the output terminal generates a load current under the action of the output voltage.

When the input voltage is higher than the output voltage, the converter works in buck mode, and when the input voltage is lower than the output voltage, the converter works in boost mode. In the boost mode, the fourth switch tube is always turned off, and the boost mode is divided into a first state and a second state according to the linkage state of the first switch tube, the second switch tube, and the third switch tube. In the step-down mode, the second switch tube is always turned off, and the step-down mode is divided into a third state and a fourth state according to the linkage state of the first switch tube, the third switch tube, and the fourth switch tube.

In one embodiment of the present disclosure, when the input voltage is lower than the output voltage (V _IN <V _OUT ), the circuit works in boost mode. In the boost mode, the fourth switch S ₄ is always off, S ₁ , S ₂ and S ₃ are turned on alternately, and the voltage across the flying capacitor V _CF =V _OUT -V _IN .

More specifically, as shown in Fig. 6a, Fig. 7 and Fig. 10, during the time period of the first state (0-DT) of the boost mode, S ₁ is turned on, and S ₂ and S ₃ are turned off. At this time, the first The switch node voltage value V _SW1 = V _OUT -V _IN , the second switch node voltage value V _SW2 = 0, V _SW1 is less than the input voltage V _IN , the voltage difference across the inductor is greater than 0, the inductor is magnetized, the inductor current rises, and goes to Flying capacitor charge + ΔQ = I _L DT, during which time no charge is left from the input to the output capacitor.

More specifically, as shown in Fig. 6b, Fig. 7 and Fig. 10, in the second state (DT-T) time period, S ₁ is off, S ₂ and S ₃ are on, at this time the first switch node voltage value V _SW1 ＝V _OUT , V _SW2 ＝V _IN , V _SW 1 is greater than the input voltage V _IN , the voltage difference across the inductor is less than 0, the inductor is demagnetized, and the inductor current drops. At this time, the flying capacitor discharges and transfers charge to the output capacitor C _OUT . By doing volt-second balance on the inductor, we get:

D(Y _IN -(V _OUT -Y _IN ))＝(1-D)(V _OUT -V _IN ) (9)

Among them, M is the voltage conversion ratio, D is the duty cycle, D∈(0,1), M∈(1,2), V _IN is the voltage value of the input voltage, and V _OUT is the voltage value of the output voltage.

In boost mode, the key signal waveform is shown in Figure 7, the power inductor current I _L =I _OUT is lower than I _L =MI _OUT in the traditional structure (M>1). In the boost mode, the power inductor current is equal to the load current; the first switching tube S ₁ , the second switching tube S ₂ , and the third switching tube S ₃ select the switching tube whose maximum withstand voltage is the input voltage, and the fourth switching tube S ₄ Select a switching tube whose maximum withstand voltage is the output voltage, for example, the range of the input voltage is 2.5V-5V, and the range of the output voltage is 3.3±0.1V.

In one embodiment of the present disclosure, when the input voltage is higher than the output voltage (V _IN >V _OUT ), the circuit works in buck mode, and in the buck mode, S ₂ is always disconnected, S ₁ , S ₃ and S ₄ are turned on alternately, and the voltage at both ends of the flying capacitor is V _CF =V _OUT .

More specifically, as shown in Fig. 8a, Fig. 9 and Fig. 10, during the time period of the third state (0-DT) of buck mode, S ₁ and S ₃ are turned on, and S ₄ is turned off, at this time the switch node V _SW1 = V _OUT , V _SW2 = 0, V _SW1 is less than the input voltage V _IN , the voltage difference across the inductor is greater than 0, the inductor is magnetized, and the inductor current rises. At this time, the flying capacitor is discharging, and the charge flows to the output capacitor Cout.

More specifically, as shown in FIG. 8b , FIG. 9 and FIG. 10 , in the fourth state (DT-T) period, S ₁ and S ₃ are turned off, and S ₄ is turned on. At this time, the switch node V _SW1 =2V _OUT , V _SW2 = V _OUT , V _SW1 is greater than the input voltage V _IN , the voltage difference across the inductor is less than 0, the inductor is demagnetized, the inductor current drops, and the flying capacitor is charging at this time, +ΔQ= _IL DT. By doing volt-second balance on the inductor, we get:

D(V _IN -V _OUT )＝(1-D)(2V _OUT -V _IN ) (11)

Among them, M is the voltage conversion ratio, D is the duty cycle, D∈(0,1), M∈(0.5,1), V _IN is the voltage value of the input voltage, and V _OUT is the voltage value of the output voltage.

In step-down mode, the main signal waveform of the circuit is shown in Figure 9, the inductor current I _L =MI _OUT (M<1), which is lower than I _L =I _OUT in the traditional structure. In step-down mode, the power inductor current is smaller than the load current, the first switching tube S ₁ , the third switching tube S ₃ , and the fourth switching tube S ₄ select the switching tube whose maximum withstand voltage is the output voltage, and the second switching tube S ₂ Select a switching tube with a maximum withstand voltage value of the input voltage, for example, the range of the input voltage value is 2.5V-5V, and the range of the output voltage value is 3.3±0.1V.

So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It should be noted that, in the accompanying drawings or in the text of the specification, implementations that are not shown or described are forms known to those of ordinary skill in the art, and are not described in detail. In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and those skilled in the art can easily modify or replace them.

Based on the above description, those skilled in the art should have a clear understanding of the disclosed hybrid buck-boost DC-DC converter with flying capacitors.

To sum up, the present disclosure provides a hybrid buck-boost DC-DC converter with a flying capacitor. On the basis of the traditional structure of 4 power tubes and 1 power tube, a flying capacitor is introduced, While reducing the inductor current under all working conditions, the conduction loss of the power tube is also greatly reduced. On the premise of ensuring high system efficiency, the chip area and inductor size can be greatly reduced, and the chip cost and volume are reduced.

It should also be noted that the above are different embodiments provided by the present disclosure. These embodiments are used to illustrate the technical content of the present disclosure, rather than to limit the protection scope of the present disclosure. A feature of one embodiment can be applied to other embodiments through appropriate modification, replacement, combination, and separation.

It should be noted that, unless otherwise specified herein, having “a” element is not limited to having a single element, but may include one or more elements.

In addition, in this article, unless otherwise specified, ordinal numbers such as "first" and "second" are only used to distinguish multiple components with the same name, and do not indicate that there is a hierarchy, level, execution sequence, or process sequence. A "first" element and a "second" element may appear together in the same component, or may appear separately in different components. The presence of an element with a higher ordinal number does not necessarily indicate the presence of another element with a lower ordinal number.

In this paper, unless otherwise specified, the so-called feature A "or" (or) or "and/or" (and/or) feature B means that nail exists alone, B exists alone, or A and B exist simultaneously ; The so-called feature A "and" (and) or "and" (and) or "and" (and) feature B means that nail and B exist at the same time; the so-called "includes", "includes", "has", " Contains" means including but not limited to.

In addition, in this article, the so-called "upper", "lower", "left", "right", "front", "rear", or "between" and other terms are only used to describe the distance between a plurality of elements. relative position, and can be generalized in interpretation to include cases of translation, rotation, or mirroring. In addition, herein, unless otherwise specified, "an element is on another element" or similar expressions do not necessarily mean that the element contacts the other element.

In addition, unless specifically described or steps that must occur sequentially, the order of the above steps is not limited to that listed above and may be changed or rearranged according to the desired design. Moreover, the above-mentioned embodiments can be mixed and matched with each other or with other embodiments based on design and reliability considerations, that is, technical features in different embodiments can be freely combined to form more embodiments.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above descriptions are only specific embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Claims (10)

1. A hybrid buck-boost dc-dc converter with flying capacitor, comprising:

an input node connected to an input voltage source for receiving an input voltage;

a power inductor, one end of which is connected to the input node and the other end of which is connected to the first switch node;

one end of the flying capacitor is connected to the first switch node, and the other end of the flying capacitor is connected to the second switch node;

one end of the first switch tube is connected to the second switch node, and the other end of the first switch tube is grounded;

one end of the second switch tube is connected to the input node, and the other end of the second switch tube is connected to the second switch node;

one end of the third switching tube is connected to the first switching node, the other end of the third switching tube is connected to an output node, and the output node is used for sending out output voltage;

one end of the fourth switching tube is connected to the second switching node, and the other end of the fourth switching tube is connected to the output node;

the output end is connected with the output node and comprises an output capacitor and a load resistor which are arranged in parallel, and the output end generates load current under the action of output voltage.

2. The hybrid buck-boost dc-dc converter with flying capacitor of claim 1, the converter operating in buck mode when the input voltage is higher than the output voltage and in boost mode when the input voltage is less than the output voltage.

3. The hybrid buck-boost dc-dc converter with flying capacitor of claim 2, wherein in the boost mode, the fourth switching tube is always turned off, and the boost mode is divided into the first state and the second state according to the linkage state of the first switching tube, the second switching tube and the third switching tube.

4. The hybrid buck-boost dc-dc converter with flying capacitor of claim 3, wherein in the first state, the first switch tube is turned on, and the second switch tube and the third switch tube are turned off; the voltage of the first switch node is smaller than the input voltage, the voltage difference between two ends of the power inductor is larger than 0, the power inductor is magnetized, and the current of the power inductor rises and charges the flying capacitor.

5. The hybrid buck-boost dc-dc converter as claimed in claim 3, wherein in the second state, the first switch is turned off, the second switch and the third switch are turned on, the voltage at the first switch node is the same as the voltage at the output node, the voltage at the second switch node is equal to the input voltage, the voltage at the first switch node is greater than the input voltage, the voltage difference across the power inductor is less than 0, the power inductor is demagnetized, the current at the power inductor is decreased, and the flying capacitor discharges to transfer charge to the output capacitor.

6. The hybrid buck-boost dc-dc converter with flying capacitor of claim 2, wherein in the buck mode, the second switch is always off, and the buck mode is divided into a third state and a fourth state according to the linkage status of the first switch and the third and fourth switches.

7. The hybrid buck-boost dc-dc converter with flying capacitor of claim 6, wherein in the third state, the first switching transistor and the third switching transistor are turned on, the fourth switching transistor is turned off, the voltage at the first switching node is equal to the output voltage, the voltage at the second switching node is 0, the voltage at the first switching node is lower than the input voltage, the voltage difference across the power inductor is greater than 0, the power inductor is magnetized, the power inductor current rises, the flying capacitor discharges, and the charge flows to the output capacitor.

8. The hybrid buck-boost dc-dc converter of claim 6 having a flying capacitor, wherein in a fourth state, the first switching transistor and the third switching transistor are off, the fourth switching transistor is on, the voltage at the first switching node is twice the output voltage, the voltage at the second switching node is equal to the output voltage, the voltage at the first switching node is greater than the input voltage, the voltage difference across the power inductor is less than 0, the power inductor is demagnetized, the power inductor current is decreased, and the flying capacitor is charged.

9. A hybrid buck-boost dc-dc converter having a flying capacitor as claimed in any one of claims 2 to 8, the power inductor current being equal to the load current in boost mode; the first switch tube, the second switch tube, the third switch tube selects the switch tube whose maximum withstand voltage is the input voltage, the fourth switch tube selects the switch tube whose maximum withstand voltage is the output voltage.

10. The hybrid buck-boost dc-dc converter according to any of claims 2 to 8, wherein in buck mode, the power inductor current is less than the load current, the first switch transistor, the third switch transistor, the fourth switch transistor are selected to have the maximum voltage endurance as the output voltage, and the second switch transistor is selected to have the maximum voltage endurance as the input voltage.

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