Buck circuit structure and buck converter

Abstract

The utility model is applicable to the field of electronic circuit technology, and provides a step-down circuit structure and a step-down converter, wherein the step-down circuit structure includes a step-down main circuit, a first capacitor, a second capacitor and a first switch tube, wherein the first capacitor and the second capacitor form a series body, the first end of the series body is connected to the line between the first end of the step-down main circuit and the positive electrode of the power supply, the second end of the series body is connected to the line between the negative electrode of the power supply and the first end of the first switch tube, the second end of the first switch tube is connected to the second end of the step-down main circuit, and the control end of the first switch tube is connected to the controller. By connecting the first capacitor and the second capacitor in series, each capacitor and the step-down main circuit are mutually restrained to achieve automatic current and voltage balance, which can achieve low input current ripple and low output ripple current, simplify the circuit control scheme, and at the same time reduce the terminal voltage of the switch tube in the step-down main circuit at startup, reduce the stress of the switch tube, and improve the conversion efficiency.

Description

Technical Field

[0001] The utility model belongs to the technical field of electronic circuits, and in particular relates to a step-down circuit structure and a step-down converter. Background Art

[0002] For the traditional BUCK converter, the schematic diagram is as follows Figure 1 As shown. The BUCK converter is a DC-DC converter based on the principle of inductive energy storage. In the BUCK converter, the DC voltage provided by the input power supply is converted into an adjustable low-voltage output by controlling the on and off state of the switch tube by controlling the PWM wave with a variable input duty cycle, thereby meeting the power supply requirements of different circuits. The output and input voltage conversion ratio of the traditional BUCK converter is D. When the input voltage is much greater than the output voltage, it will lead to large switch tube losses and larger output current ripples. In addition, the too low duty cycle also brings inconvenience to the control of loop stability.

[0003] To improve the voltage conversion ratio, a series capacitor step-down converter can be used, whose output voltage is like Figure 2 As shown, since the voltage across the capacitor in the circuit is 0 at startup, the stress of the switch tube at startup will be equal to the input voltage Vin, the switch stress is large, the conversion ratio is low, and the output ripple current is large and the efficiency is low. Utility Model Content

[0004] The embodiment of the utility model provides a step-down circuit structure, aiming to solve the problems of large switch stress, low conversion ratio, large output ripple current and low efficiency in the existing step-down circuit structure.

[0005] The embodiment of the utility model is implemented as follows: a step-down circuit structure includes a step-down main circuit, a first capacitor, a second capacitor and a first switch tube;

[0006] The first capacitor and the second capacitor form a series body, the first end of the series body is connected to the line between the first end of the step-down main circuit and the positive electrode of the power supply, the second end of the series body is connected to the line between the negative electrode of the power supply and the first end of the first switch tube, the second end of the first switch tube is connected to the second end of the step-down main circuit, and the control end of the first switch tube is connected to the controller.

[0007] Furthermore, the step-down main circuit includes a voltage sampling circuit, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a first main circuit capacitor, a second main circuit capacitor, a first inductor, a second inductor and a first resistor;

[0008] The second end of the second switch tube is connected to the positive electrode of the power supply, and the first end of the second switch tube is connected to one end of the first main loop capacitor and the second end of the third switch tube;

[0009] The first end of the third switch tube is connected to the second end of the fourth switch tube and one end of the second inductor, and the first end of the third switch tube is also connected to the connection line between the first capacitor and the second capacitor;

[0010] The first end of the fourth switch tube is connected to the second end of the first switch tube and the first end of the fifth switch tube;

[0011] The other end of the first main loop capacitor is connected to one end of the first inductor and the second end of the fifth switch tube, the other end of the first inductor and the other end of the second inductor are both connected to the first input end of the voltage sampling circuit, and the first input end of the voltage sampling circuit is also connected to one end of the second main loop capacitor and one end of the first resistor;

[0012] The second input end of the voltage sampling circuit, the second end of the first switch tube, the other end of the second main loop capacitor and the other end of the first resistor are grounded;

[0013] The control ends of the second switch tube, the third switch tube, the fourth switch tube and the fifth switch tube are all connected to the controller.

[0014] Furthermore, the first switch tube, the second switch tube, the third switch tube, the fourth switch tube and the fifth switch tube include any one of a MOS tube, a triode, an IGBT and a relay.

[0015] In a second aspect, the present application also provides a buck converter, comprising the buck circuit structure as described above.

[0016] The beneficial effect of the present application is that the buck circuit structure of the present application includes a buck main circuit, a first capacitor, a second capacitor and a first switch tube, wherein the first capacitor and the second capacitor form a series body, the first end of the series body is connected to the line between the first end of the buck main circuit and the positive electrode of the power supply, the second end of the series body is connected to the line between the negative electrode of the power supply and the first end of the first switch tube, the second end of the first switch tube is connected to the second end of the buck main circuit, and the control end of the first switch tube is connected to the controller. By controlling the on and off of the first switch tube, the connection between the first capacitor and the second capacitor and the buck main circuit is realized, so that each capacitor and the buck main circuit are mutually restrained to achieve the automatic balance of current and voltage, and low input current ripple and low output ripple current can be achieved, which simplifies the circuit control scheme, and at the same time reduces the terminal voltage of the switch tube in the buck main circuit at startup, reduces the stress of the switch tube, and improves the conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the topology of a traditional BUCK converter;

[0018] Figure 2It is a schematic diagram of the topological structure of a conventional series capacitor step-down converter;

[0019] Figure 3 It is a topological structure diagram of an embodiment of the buck circuit structure provided by the present application;

[0020] Figure 4 This is a schematic diagram of the driving waveform of the switch tube of an embodiment of the buck circuit structure provided by the present application;

[0021] Figure 5 This is a schematic diagram of capacitor terminal voltage in one embodiment of a step-down circuit structure provided by the present application;

[0022] Figure 6 This is a schematic diagram of the drain-source voltage of a switch tube in one embodiment of a step-down circuit structure provided by the present application;

[0023] Figure 7 It is a schematic diagram of the current waveform of the inductor of an embodiment of the buck circuit structure provided by the present application. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of embodiments are shown in the accompanying drawings, in which the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the utility model, and cannot be understood as limiting the utility model. In addition, it should be understood that the specific embodiments described herein are only used to explain the utility model and are not used to limit the utility model.

[0025] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "left", "right", "horizontal", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0026] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0027] In the description of the present utility model, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0028] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0029] The disclosure below provides many different embodiments or examples for realizing different structures of the utility model. In order to simplify the disclosure of the utility model, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the utility model. In addition, the utility model can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, and does not indicate the relationship between the various embodiments and / or settings discussed in itself. In addition, the utility model provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0030] The buck circuit structure of the present application includes a buck main circuit, a first capacitor, a second capacitor and a first switch tube, wherein the first capacitor and the second capacitor form a series body, the first end of the series body is connected to the line between the first end of the buck main circuit and the positive electrode of the power supply, the second end of the series body is connected to the line between the negative electrode of the power supply and the first end of the first switch tube, the second end of the first switch tube is connected to the second end of the buck main circuit, and the control end of the first switch tube is connected to the controller. By controlling the on and off of the first switch tube, the connection between the first capacitor and the second capacitor and the buck main circuit is realized, so that each capacitor and the buck main circuit are mutually restrained to achieve the automatic balance of current and voltage, which can achieve low input current ripple and low output ripple current, simplify the circuit control scheme, and at the same time reduce the terminal voltage of the switch tube in the buck main circuit at startup, reduce the stress of the switch tube, and improve the conversion efficiency.

[0031] Embodiment 1

[0032] like Figures 1 to 7 As shown, an embodiment of the present application provides a buck circuit structure, including a buck main loop, a first capacitor C1, a second capacitor C2 and a first switch tube Q1;

[0033] The first capacitor C1 and the second capacitor C2 form a series body, the first end of the series body is connected to the line between the first end of the step-down main circuit and the positive electrode of the power supply V1, the second end of the series body is connected to the line between the negative electrode of the power supply V1 and the first end of the first switch tube Q1, the second end of the first switch tube Q1 is connected to the second end of the step-down main circuit, and the control end of the first switch tube Q1 is connected to a controller (not shown).

[0034] During implementation, the step-down main circuit, namely the BUCK circuit, is used to convert the DC voltage provided by the power supply V1 into an adjustable low voltage output, thereby meeting the power supply requirements of different circuits.

[0035] The first capacitor C1 and the second capacitor C2 are connected in series and then in parallel with the power supply V1. That is, one end of the first capacitor C1 is connected to the positive electrode of the power supply V1, the other end of the first capacitor C1 is connected to one end of the second capacitor C2, and the other end of the second capacitor C2 is connected to the negative electrode of the power supply V1.

[0036] One end of the first capacitor C1 is also connected to the first end of the step-down main circuit, the other end of the second capacitor C2 is also connected to the first end of the first switch tube Q1, and the second end of the first switch tube Q1 is connected to the second end of the step-down main circuit.

[0037] Optionally, the first switch tube Q1 may be a triode, a MOS tube, an IGBT or a relay, etc., without limitation.

[0038] The first switch tube Q1 includes a first end, a second end and a control end, wherein the control end of the first switch tube Q1 is connected to a controller, and the controller may be an MCU or other components with a control function. The controller may control the on and off of the first switch tube Q1, thereby controlling the connection state between the first capacitor C1 and the second capacitor C2 and the buck main circuit.

[0039] It should be noted that the step-down main circuit has a switch tube, a capacitor and an inductor. The first capacitor C1, the second capacitor C2 and the capacitor and inductor in the step-down main circuit are mutually restrained to achieve a balance, which can effectively simplify the control scheme of the overall circuit. At the same time, since the first capacitor C1 and the second capacitor C2 are connected in parallel with the power supply V1, they can be charged and divided to make the voltage of the capacitor in the step-down main circuit non-zero at startup. In other words, at startup, the capacitor of the step-down main circuit has a voltage, so that the stress of the switch tube of the step-down main circuit at startup is lower than the power supply V1 voltage, so that a switch tube with a lower on-resistance can be used, thereby further improving the conversion efficiency of the circuit.

[0040] The buck circuit structure of the present application includes a buck main circuit, a first capacitor C1, a second capacitor C2 and a first switch tube Q1, wherein the first capacitor C1 and the second capacitor C2 form a series body, the first end of the series body is connected to the line between the first end of the buck main circuit and the positive electrode of the power supply V1, the second end of the series body is connected to the line between the negative electrode of the power supply V1 and the first end of the first switch tube Q1, the second end of the first switch tube Q1 is connected to the second end of the buck main circuit, and the control end of the first switch tube Q1 is connected to the controller. By controlling the on and off of the first switch tube Q1, the connection between the first capacitor C1 and the second capacitor C2 and the buck main circuit is realized, so that each capacitor and the buck main circuit are mutually restrained to achieve the automatic balance of current and voltage, and low input current ripple and low output ripple current can be achieved, which simplifies the circuit control scheme, and at the same time reduces the terminal voltage of the switch tube in the buck main circuit at startup, reduces the stress of the switch tube, and improves the conversion efficiency.

[0041] In some optional embodiments, the step-down main circuit includes a voltage sampling circuit U6, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a fifth switch tube Q5, a first main circuit capacitor C3, a second main circuit capacitor C4, a first inductor L1, a second inductor L2 and a first resistor R1;

[0042] The second end of the second switch tube Q2 is connected to the positive electrode of the power supply V1, and the first end of the second switch tube Q2 is connected to one end of the first main circuit capacitor C3 and the second end of the third switch tube Q3;

[0043] A first end of the third switch tube Q3 is connected to a second end of the fourth switch tube Q4 and one end of the second inductor L2, and the first end of the third switch tube Q3 is also connected to a connection line between the first capacitor C1 and the second capacitor C2;

[0044] A first end of the fourth switch tube Q4 is connected to the second end of the first switch tube Q1 and a first end of the fifth switch tube Q5;

[0045] The other end of the first main loop capacitor C3 is connected to one end of the first inductor L1 and the second end of the fifth switch tube Q5, the other end of the first inductor L1 and the other end of the second inductor L2 are both connected to the first input end of the voltage sampling circuit U6, the first input end of the voltage sampling circuit U6 is also connected to one end of the second main loop capacitor C4, and the first input end of the voltage sampling circuit U6 is also connected to one end of the first resistor R1;

[0046] The second input end of the voltage sampling circuit U6, the second end of the first switch tube Q1, the other end of the second main loop capacitor C4 and the other end of the first resistor R1 are all grounded;

[0047] Control ends of the second switch tube Q2 , the third switch tube Q3 , the fourth switch tube Q4 and the fifth switch tube Q5 are all connected to the controller.

[0048] In implementation, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4 and the fifth switch tube Q5 include any one of a MOS tube, a triode, an IGBT and a relay. The first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4 and the fifth switch tube Q5 all include a first end, a second end and a control end. Exemplarily, taking the MOS tube as an example, the first end of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4 and the fifth switch tube Q5 is the source of the MOS tube, the second end of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4 and the fifth switch tube Q5 is the drain of the MOS tube, and the control end of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4 and the fifth switch tube Q5 is the gate of the MOS tube.

[0049] In some other embodiments, taking the triode as an example, the first ends of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4 and the fifth switch tube Q5 are emitters of the triode, the second ends of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4 and the fifth switch tube Q5 are collectors of the triode, and the control ends of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4 and the fifth switch tube Q5 are bases of the triode.

[0050] In implementation, the output end out of the voltage sampling circuit U6 is the output end of the buck circuit. The working stages of the buck circuit structure provided by the present application include:

[0051] (1) The second switch tube and the fourth switch tube are turned on, and the others (the first switch tube, the third switch tube, and the fifth switch tube) are turned off;

[0052] In this stage, the current of the first inductor increases, while the second inductor is in the freewheeling state, the first capacitor is discharged, and the second capacitor and the first main circuit capacitor are charged. At this time, the terminal voltage of the first inductor is V L1 =V C1 -V C3 -V out , the terminal voltage of the second inductor is V L2 =-V out , where V C1 is the voltage of the first capacitor, V C3 is the voltage of the first main circuit capacitor, V out is the voltage at the output terminal out of the voltage sampling circuit.

[0053] (2) The fourth switch tube and the fifth switch tube are turned on, and the first switch tube, the second switch tube and the third switch tube are turned off;

[0054] At this time, the first inductor and the second inductor are both in the freewheeling state, and the terminal voltage of the first inductor and the second inductor is V L1 =V L2 =-V out .

[0055] (3) The third switch tube, the fifth switch tube and the first switch tube are turned on, and the second switch tube and the fourth switch tube are turned off;

[0056] At this time, the current of the second inductor increases linearly, the second inductor is in the freewheeling state, and the terminal voltage of the second inductor is V L2 =V C3 -V out , the terminal voltage of the first inductor is V L1 =-V out .

[0057] (4) The fourth switch tube and the fifth switch tube are turned on, and the first switch tube, the second switch tube and the third switch tube are turned off. The state is the same as (2).

[0058] According to the second-volt balance theorem of inductance, combined with the terminal voltage of the inductor at different stages, the following formula can be listed:

[0059] (V C1 -V C3 -V out )×D×T=V out ×(1-D)×T

[0060] (V C3 -V out )×D×T=V out ×(1-)×T

[0061] Obviously, V C1 +V C2 =in , V in is the power supply voltage, and V C2 =V C3 , can be obtained

[0062]

[0063] Therefore, under the condition of the same input voltage and duty cycle, the present application can achieve lower output voltage conversion.

[0064] The driving signal of the second switch tube Q2 is PWM1, the driving signals of the first switch tube Q1 and the third switch tube Q3 are both PWM2, the driving signal of the fifth switch tube Q5 is PWM3, and the driving signal of the fourth switch tube Q4 is PWM4. The driving waveforms of PWM1, PWM2, PWM3 and PWM4 are as follows: Figure 4 The terminal voltages of the first capacitor C1, the second capacitor C2 and the first main circuit capacitor C3 are shown in Figure 5 As shown, the drain-source (DS) voltages of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4 and the fifth switch tube Q5 are as follows: Figure 6 As shown, the current waveforms of the first inductor L1 and the second inductor L2 are as follows: Figure 7 shown.

[0065] In addition, due to the existence of the first capacitor C1, the second capacitor C2 and the first main loop capacitor C3, their terminal voltages can be mutually restrained with the currents of the second inductor L2 and the first inductor L1 to achieve balance, thereby simplifying the control scheme of the overall circuit. For example, when the inductor current of the second inductor L2 increases, the voltage of the first capacitor C1 increases, the voltage of the second capacitor C2 and the first main loop capacitor C3 decreases, the voltage of the left end of the first capacitor C1 to the ground increases, and the voltage of the left end of the second inductor L2 to the ground decreases, so the inductor current of the first inductor L1 increases, and the inductor current of the second inductor L2 decreases until a balanced state. Conversely, the voltage changes of the first capacitor C1, the second capacitor C2 and the first main loop capacitor C3 refer to the above description.

[0066] The present application achieves a high voltage conversion ratio without generating an excessively low duty cycle, thereby avoiding excessive conduction and switching losses. In addition, compared with the traditional solution, the present application has two series input capacitors (the first capacitor C1 and the second capacitor C2), so the startup and steady-state stresses are at most only 2 / 3 of the input voltage (power supply V1 voltage). Therefore, a switch tube with a smaller Rdson (equivalent resistance when the MOS tube is turned on) can be selected, thereby improving the overall efficiency of the circuit.

[0067] In addition, the present application can make the current and voltage automatically tend to balance by restraining each other through the voltage of three capacitors and the current of two inductors, thereby simplifying the overall control scheme of the circuit. In addition, due to the presence of two series capacitors, the input ripple current is only about 1 / 6 of the output current, and the requirement for input capacitance is smaller under the same input ripple circuit.

[0068] Embodiment 2

[0069] In some optional embodiments, the present application also provides a buck converter, including the buck circuit structure as described above.

[0070] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, the structure and implementation principle of the buck converter described above can refer to the corresponding structure and implementation principle in the aforementioned embodiment 1, and will not be repeated here.

[0071] The buck circuit structure of the present application includes a buck main circuit, a first capacitor C1, a second capacitor C2 and a first switch tube Q1, wherein the first capacitor C1 and the second capacitor C2 form a series body, the first end of the series body is connected to the line between the first end of the buck main circuit and the positive electrode of the power supply V1, the second end of the series body is connected to the line between the negative electrode of the power supply V1 and the first end of the first switch tube Q1, the second end of the first switch tube Q1 is connected to the second end of the buck main circuit, and the control end of the first switch tube Q1 is connected to the controller. By controlling the on and off of the first switch tube Q1, the connection between the first capacitor C1 and the second capacitor C2 and the buck main circuit is realized, so that each capacitor and the buck main circuit are mutually restrained to achieve the automatic balance of current and voltage, and low input current ripple and low output ripple current can be achieved, which simplifies the circuit control scheme, and at the same time reduces the terminal voltage of the switch tube in the buck main circuit at startup, reduces the stress of the switch tube, and improves the conversion efficiency.

[0072] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A step-down circuit structure, characterized in that: It includes a step-down main circuit, a first capacitor, a second capacitor and a first switch tube; The first capacitor and the second capacitor form a series body, the first end of the series body is connected to the line between the first end of the step-down main circuit and the positive electrode of the power supply, the second end of the series body is connected to the line between the negative electrode of the power supply and the first end of the first switch tube, the second end of the first switch tube is connected to the second end of the step-down main circuit, and the control end of the first switch tube is connected to the controller.

2. The step-down circuit structure according to claim 1, characterized in that: The step-down main circuit includes a voltage sampling circuit, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a first main circuit capacitor, a second main circuit capacitor, a first inductor, a second inductor and a first resistor; The second end of the second switch tube is connected to the positive electrode of the power supply, and the first end of the second switch tube is connected to one end of the first main loop capacitor and the second end of the third switch tube; The first end of the third switch tube is connected to the second end of the fourth switch tube and one end of the second inductor, and the first end of the third switch tube is also connected to the connection line between the first capacitor and the second capacitor; The first end of the fourth switch tube is connected to the second end of the first switch tube and the first end of the fifth switch tube; The other end of the first main loop capacitor is connected to one end of the first inductor and the second end of the fifth switch tube, the other end of the first inductor and the other end of the second inductor are both connected to the first input end of the voltage sampling circuit, and the first input end of the voltage sampling circuit is also connected to one end of the second main loop capacitor and one end of the first resistor; The second input end of the voltage sampling circuit, the second end of the first switch tube, the other end of the second main loop capacitor and the other end of the first resistor are grounded; Control ends of the second switch tube, the third switch tube, the fourth switch tube and the fifth switch tube are all connected to the controller.

3. The step-down circuit structure according to claim 2, characterized in that: The first switch tube, the second switch tube, the third switch tube, the fourth switch tube and the fifth switch tube include any one of a MOS tube, a triode, an IGBT and a relay.

4. A buck converter, characterized in that: The invention comprises a step-down circuit structure as claimed in any one of claims 1 to 3.

Images