A BUCK converter and control method thereof

Abstract

The present invention provides a BUCK converter and a control method thereof, wherein the BUCK converter comprises: a first power switch tube, a second power switch tube, a first capacitor, a second capacitor, a first inductor, a second inductor, a resistor, a first diode and a second diode, wherein the drains of the first power switch tube and the second power switch tube are respectively connected to a power supply, the first power switch tube is connected in series with the second inductor, the first capacitor is connected in parallel with the first power switch tube, the second power switch tube is connected in series with the first inductor, the cathode of the first diode is respectively connected to the source of the second power switch tube and the first end of the first inductor, the first diode is connected in series with the resistor, the second end of the resistor is connected to the source of the first power switch tube, the second capacitor is connected in parallel with the resistor, the second inductor is connected in series with the load, and the second end of the load is grounded. The method is used to control the above BUCK converter. The BUCK converter and the control method thereof provided by the embodiment of the present invention improve the reliability of the circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a BUCK converter and a control method thereof. Background Art

[0002] The BUCK converter has many advantages such as simple structure, light weight and high efficiency. It is a widely used circuit. Due to its excellent voltage transformation function, it can be directly used in places where direct voltage reduction is required.

[0003] The BUCK converter can achieve voltage reduction, but the high-frequency switch used in the converter is often in a hard switching working state, that is, a working state in which the voltage and current are not zero. According to P=UI, the switch will produce power loss in the hard switching working state, and in the high-frequency state, the power loss will be greater and will produce harsh noise. There are many problems such as high switching loss and large voltage and current stress. Summary of the invention

[0004] In view of the problems in the prior art, an embodiment of the present invention provides a BUCK converter and a control method thereof, which can at least partially solve the problems in the prior art.

[0005] In one aspect, the present invention provides a BUCK converter, comprising a first power switch tube, a second power switch tube, a first capacitor, a second capacitor, a first inductor, a second inductor, a resistor, a first diode and a second diode, wherein:

[0006] The drains of the first power switch tube and the second power switch tube are respectively connected to the positive electrode of the power supply, the source of the first power switch tube is connected to the first end of the second inductor, the first capacitor is respectively connected to the two ends of the first power switch tube, the source of the second power switch tube is connected to the first end of the first inductor, and the second end of the first inductor is connected to the first end of the second inductor;

[0007] The cathode of the first diode is connected to the source of the second power switch tube and the first end of the first inductor respectively, the anode of the first diode is connected to the first end of the resistor, the second end of the resistor is connected to the source of the first power switch tube and the second end of the first inductor respectively, and the two ends of the second capacitor are connected to the two ends of the resistor respectively;

[0008] The second end of the second inductor is connected to the first end of the load, the second end of the load is grounded, the cathode of the second diode is connected to the first end of the second inductor, and the anode of the second diode is grounded.

[0009] The first inductance is smaller than the second inductance.

[0010] The driving pulse widths of the first power switch tube and the second power switch tube are the same.

[0011] The second power switch tube is closed before the first power switch tube is closed.

[0012] The second power switch tube is disconnected before the first power switch tube is disconnected.

[0013] The BUCK converter further includes a third capacitor, a first end of the third capacitor is respectively connected to the second end of the second inductor and the first end of the load, and a second end of the third capacitor is grounded.

[0014] Wherein, the first power switch tube and the second power switch tube are metal-oxide semiconductor field effect transistors or insulated gate bipolar transistors.

[0015] In another aspect, the present invention provides a control method of the BUCK converter according to any one of the above embodiments, comprising:

[0016] The second power switch tube is closed and the first power switch tube is kept open, so that the current of the power supply passes through the second power switch tube, the first inductor and the second inductor to supply power to the load;

[0017] After a first preset time, the first power switch tube is closed, so that the current of the power supply passes through the first branch and the second branch, and then flows through the second inductor to supply power to the load; wherein the first branch includes the second power switch tube and the first inductor connected in series, and the second branch includes the first power switch;

[0018] The second power switch tube is turned off, and the first power switch tube is turned off after a second preset time, so that the power supply stops supplying power to the load.

[0019] The first preset time and the second preset time are both greater than time t d ,in:

[0020] t d =t+t'

[0021] t=L1I D2 / V in

[0022]

[0023] Where, L1 is the inductance of the first inductor, V in is the voltage of the power supply, I D2 is the current of the second diode when the second power switch tube is turned on, and C1 is the capacitance of the first capacitor.

[0024] The BUCK converter and control method thereof provided by the embodiment of the present invention include a first power switch tube, a second power switch tube, a first capacitor, a third capacitor, a second capacitor, a first inductor, a second inductor, a resistor, a first diode and a second diode, wherein the drains of the first power switch tube and the second power switch tube are respectively connected to the positive electrode of the power supply, the source of the first power switch tube is connected to the first end of the second inductor, the first capacitor is respectively connected to the two ends of the first power switch tube, the source of the second power switch tube is connected to the first end of the first inductor, the second end of the first inductor is connected to the first end of the second inductor, and the cathode of the first diode is respectively connected to the cathode of the second power switch tube. The source of the switch tube is connected to the first end of the first inductor, the anode of the first diode is connected to the first end of the resistor, the second end of the resistor is respectively connected to the source of the first power switch tube and the second end of the first inductor, the two ends of the second capacitor are respectively connected to the two ends of the resistor, the second end of the second inductor is connected to the first end of the load, the second end of the load is grounded, the cathode of the second diode is connected to the first end of the second inductor, and the anode of the second diode is grounded, thereby realizing zero voltage conduction and shutdown of the first power switch tube, and zero current conduction and zero voltage shutdown of the second power switch tube, reducing the switching loss of the power switch tube and improving the reliability of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0026] Figure 1 It is a structural schematic diagram of a BUCK converter provided in one embodiment of the present invention.

[0027] Figure 2 It is a schematic diagram of simulation waveforms of a driving signal, voltage and current of a second power switch tube provided in an embodiment of the present invention.

[0028] Figure 3 It is a schematic diagram of simulation waveforms of a driving signal, voltage and current of a first power switch tube provided in an embodiment of the present invention.

[0029] Figure 4 It is a flowchart of a control method of a BUCK converter provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily.

[0031] In order to facilitate the understanding of the technical solution provided by the present application, the research background of the technical solution of the present application is briefly described below. According to the presence or absence of auxiliary switch tubes, soft switching technology can be divided into active soft switching technology and passive soft switching technology; if divided according to the development history of technology, there are several types such as quasi-resonant circuit, zero switching PWM circuit, zero conversion PWM circuit, etc. Among them, the resonant voltage peak of the traditional quasi-resonant circuit is relatively large, and the requirements for the device are increased, while the latter two circuits often introduce auxiliary switches, which are active soft switching circuits, and can better realize the soft switching of the main circuit. However, only when the auxiliary switch is also in soft switching operation can full soft switching operation be realized, and the control becomes relatively complicated. In comparison, the resonant circuit of the zero conversion PWM circuit is not on the main circuit and is less affected by the main circuit. The BUCK converter provided in the embodiment of the present invention adopts active switching circuits of auxiliary switches and main switches, and both the main and auxiliary switch tubes realize soft switching, and the voltage and current stress are low.

[0032] Figure 1 FIG. 1 is a schematic diagram of the structure of a BUCK converter provided by an embodiment of the present invention. Figure 1 As shown, the BUCK converter provided by the embodiment of the present invention includes a first power switch tube 1, a second power switch tube 2, a first capacitor 3, a second capacitor 5, a first inductor 6, a second inductor 7, a resistor 8, a first diode 9 and a second diode 10, wherein:

[0033] The drains of the first power switch tube 1 and the second power switch tube 2 are respectively connected to the positive electrode of the power supply, the source of the first power switch tube 1 is connected to the first end of the second inductor 7, the first capacitor 3 is respectively connected to the two ends of the first power switch tube 1, the source of the second power switch tube 2 is connected to the first end of the first inductor 6, and the second end of the first inductor 6 is connected to the first end of the second inductor 7;

[0034] The cathode of the first diode 9 is connected to the source of the second power switch tube 2 and the first end of the first inductor 6 respectively, the anode of the first diode 9 is connected to the first end of the resistor 8, the second end of the resistor 8 is connected to the source of the first power switch tube 1 and the second end of the first inductor 6 respectively, and the two ends of the second capacitor 5 are connected to the two ends of the resistor 8 respectively;

[0035] The second end of the second inductor 7 is connected to the first end of the load 11 , the second end of the load 11 is grounded, the cathode of the second diode 10 is connected to the first end of the second inductor 7 , and the anode of the second diode 10 is grounded.

[0036] The working principle of the BUCK converter provided by the embodiment of the present invention is described below.

[0037] When the circuit is working in a stable state, the current in the first inductor 6 is zero. After the power supply Vin is turned on, the second power switch tube 2 is closed, and the first power switch tube 1 is in an open state. At this time, the current in the power supply Vin flows through the second power switch tube 2, the first inductor 6, and the second inductor 7 to supply power to the load 11. After the first preset time, Figure 1 When the voltage at A is close to the voltage of the power supply Vin, the first power switch tube 1 is closed. At this time, the first power switch tube 1 and the second power switch tube 2 are both closed, and the current of the power supply Vin is divided into two branches. The first branch passes through the second power switch tube 2 and the first inductor 6, and the second branch passes through the first power switch tube 1. The two branches are Figure 1 After merging at A, the current flows through the second inductor 7 and then supplies power to the load 11. In the process of closing the above power switch, when the second power switch tube 2 is closed, the current of the first inductor 6 is zero, so the conduction current of the second power switch tube 2 is approximately zero, and the second power switch tube 2 can be regarded as zero current conduction; when the first power switch tube 1 is closed, due to Figure 1 The voltage at A is approximately equal to the voltage of the power supply Vin, so when the first power switch tube 1 is closed, the voltage between its source and drain is approximately zero, and the first power switch tube 1 can be regarded as zero voltage conduction. Among them, the first preset time is set according to actual needs, and the embodiment of the present invention does not limit it.

[0038] When the power supply Vin needs to stop supplying power to the load 11, the second power switch tube 2 is disconnected first, and the current on the second power switch tube 2 is transferred to the first power switch tube 1. The current of the first inductor 6 returns to the first inductor 6 after passing through the parallel circuit of the resistor 8 and the first capacitor 3 and the first diode 9. The energy stored in the first inductor 6 is consumed in the resistor 8. Assuming that the first diode 9 is an ideal device, when the second power switch tube 2 is disconnected, the first diode 9 is immediately turned on, and the drain voltage of the second power switch tube 2 is approximately clamped at the voltage of the power supply Vin. The second power switch tube 2 can be regarded as zero voltage shutdown. After the second preset time, the first power switch tube 1 is disconnected. Due to the existence of the first capacitor 3, the voltage between the drain and the source of the first power switch tube 1 is approximately zero during the disconnection process. The first power switch tube 1 can be regarded as zero voltage disconnection. After the first power switch tube 1 is disconnected, the power supply Vin charges the first capacitor 3, and the current is supplied to the load 11 through the first capacitor 3 and the second inductor 7. When the first capacitor 3 is charged, the second diode 10 is turned on, and the current passes through the second diode 10 and the second inductor 7 to charge the load 11. The second preset time is set according to actual needs and is not limited in the embodiment of the present invention.

[0039] It can be seen from the working principle of the BUCK converter provided by the embodiment of the present invention that the working process of the second inductor 7 during the opening and closing process of the power supply Vin is exactly the same as the working process of the inductor in the existing BUCK converter, outputting the same power and the current not increasing. The first inductor 6 consumes its own stored energy in the resistor 8 only when the second power switch tube 2 is turned off, but because the inductance of the first inductor 6 is small, the increased stress brought to the switch tube second power switch tube 2 by the consumed energy can be ignored. After the first capacitor 3 is charged, its energy is stored in the first inductor 6 during the discharge process, and is supplied to the load 11 through the first inductor 6 to the second inductor 7, so there is no loss of energy on the first capacitor 3. In summary, in the BUCK converter provided by the embodiment of the present invention, the first power switch tube 1 and the second power switch tube 2 realize zero current and zero voltage switching, thereby reducing switching losses. The BUCK converter provided by the embodiment of the present invention does not increase the current and voltage stress of the power switch tube, realizes soft switching, reduces the switching loss of the power switch tube, and improves the reliability of the circuit.

[0040] The BUCK converter provided by the embodiment of the present invention includes a first power switch tube, a second power switch tube, a first capacitor, a third capacitor, a second capacitor, a first inductor, a second inductor, a resistor, a first diode and a second diode, wherein the drains of the first power switch tube and the second power switch tube are respectively connected to the positive electrode of the power supply, the source of the first power switch tube is connected to the first end of the second inductor, the first capacitor is respectively connected to the two ends of the first power switch tube, the source of the second power switch tube is connected to the first end of the first inductor, the second end of the first inductor is connected to the first end of the second inductor, and the cathode of the first diode is respectively connected to the cathode of the second power switch tube. The source of the first power switch is connected to the first end of the first inductor, the anode of the first diode is connected to the first end of the resistor, the second end of the resistor is respectively connected to the source of the first power switch tube and the second end of the first inductor, the two ends of the second capacitor are respectively connected to the two ends of the resistor, the second end of the second inductor is connected to the first end of the load, the second end of the load is grounded, the cathode of the second diode is connected to the first end of the second inductor, and the anode of the second diode is grounded, thereby realizing zero voltage conduction and shutdown of the first power switch tube, and zero current conduction and zero voltage shutdown of the second power switch tube, reducing the switching loss of the power switch tube and improving the reliability of the circuit.

[0041] On the basis of the above embodiments, further, the first inductor 6 is smaller than the second inductor 7, and the first inductor 6 can be set to the uH order of magnitude, such as 10uH, and the second inductor 7 can be set to tens of uH to hundreds of uH, such as 66uH.

[0042] On the basis of the above embodiments, further, the driving pulse widths of the first power switch tube 1 and the second power switch tube 2 are the same.

[0043] On the basis of the above embodiments, further, the second power switch tube 2 is closed before the first power switch tube 1 is closed, that is, the second power switch tube 2 is closed first, and after the first preset time, the first power switch tube 1 is closed, so that the second power switch tube 2 is turned on with zero current and the first power switch tube 1 is turned on with zero voltage.

[0044] On the basis of the above embodiments, further, the second power switch tube 2 is turned off before the first power switch tube 1 is turned off, that is, the second power switch tube 2 is turned off first, and after the second preset time, the first power switch tube 1 is turned off, so that the second power switch tube 2 is turned off with zero voltage, and the first power switch tube 1 is turned off with zero voltage.

[0045] On the basis of the above embodiments, the BUCK converter provided in the embodiment of the present invention further includes a third capacitor 4, a first end of the third capacitor 4 is respectively connected to the second end of the second inductor 7 and the first end of the load 11, and a second end of the third capacitor 4 is grounded.

[0046] On the basis of the above embodiments, further, the first power switch tube 1 is a metal-oxide-semiconductor field-effect transistor (Metal-Oxide-Semiconductor Field-Effect Transistor, referred to as MOSFET) or an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, referred to as IGBT), and the second power switch tube 2 is a MOSFET or an IGBT.

[0047] The BUCK converter provided in the embodiment of the present invention can be divided into 7 modes in one switching cycle. Assume Figure 1 Each electronic device in the BUCK converter is an ideal device, and the working process of the BUCK converter is analyzed as follows.

[0048] Mode 1 (t0-t1): Before time t0, the first power switch tube 1 and the second power switch tube 2 are disconnected, and the current of the first power switch tube 1 and the second power switch tube 2 is 0. The BUCK converter operates in the current continuous mode, the second inductor 7 continues the current through the second diode 10, and the voltage at point A in the circuit is 0. The current of the first inductor 6 drops to 0, and the voltage across the first capacitor 3 is equal to the voltage of the power supply Vin. At time t0, the second power switch tube 2 is closed. Due to the existence of the inductance of the first inductor 6, the conduction current of the second power switch tube 2 cannot change suddenly, and the second power switch tube 2 is turned on with zero current. After the second power switch tube 2 is turned on, the current of the first inductor 6 increases linearly under the action of the power supply Vin, and the current of the second diode 10 decreases linearly. The second diode 10 is turned off with zero current, and the current of the second diode 10 becomes 0 at time t1. Assume that the current of the second diode 10 at time t0 is I D2 , then the time from the second power switch tube 2 being turned on to the current of the second diode 10 being zero is t, t = L1I D2 / V in , where L1 is the inductance of the first inductor 6, V in is the voltage of the power supply.

[0049] Mode 2 (t1-t2): At t1, the current in the second diode 10 becomes zero, and the second diode 10 is turned off with zero current. The first inductor 6 and the first capacitor 3 start to work in resonance, the current in the first inductor 6 increases, the voltage across the first capacitor 3 decreases, and the voltage at point A in the circuit gradually increases. At t2, the voltage across the first capacitor 3 drops to zero, and the voltage at point A in the circuit rises to the voltage of the power supply Vin.

[0050] Mode 3 (t2-t3): At t2, the voltage drop across the first capacitor 3 is 0, and the power supply Vin outputs energy through the second power switch tube 2, the first inductor 6 and the second inductor 7. Thereafter, when the first power switch tube 1 is turned on at any time, it is turned on at zero voltage.

[0051] Mode 4 (t3-t4): At t3, the first power switch tube 1 is closed and is turned on at zero voltage. At this time, both the first power switch tube 1 and the second power switch tube 2 are closed, and the power supply Vin outputs energy backward through the first power switch tube 1 and the second power switch tube 2. The current of the first power switch tube 1 gradually increases, and the current of the second power switch tube 2 gradually decreases.

[0052] Mode 5 (t4-t5): At t4, the second power switch tube 2 is disconnected and the first diode 9 is turned on. Since the resistance of the resistor 8 is very small and there is a bypass capacitor 5, it can be considered that the voltage across the second power switch tube 2 is 0 during the shutdown process of the second power switch tube 2, which is a zero voltage shutdown. The current of the second power switch tube 2 is transferred to the first power switch tube 1. The current of the first inductor 6 returns to the first inductor 6 through the first diode 9, and its energy is consumed in the resistor 8. At t5, the current of the first inductor 6 is zero, and the voltage across the second capacitor 5 is zero. The first inductor 6 releases energy through the resistor 8, and its time constant is τ=L1 / R1, where τ is the time constant, L1 is the inductance of the first inductor 6, and R1 is the resistance of the resistor 8.

[0053] Mode 6 (t5-t6): After time t5, the first power switch tube 1 is disconnected. Since the voltage across the first capacitor 3 cannot change suddenly, the first power switch tube 1 is turned off with zero voltage, and the voltage across the first capacitor 3 gradually increases.

[0054] Mode 7 (t6-t7): At t6, the voltage across the first capacitor 3 is equal to the voltage of the power supply Vin, and the second diode 10 is turned on for freewheeling. At t7, the second power switch tube 2 is closed, and the next switching cycle is entered.

[0055] Figure 2 is a schematic diagram of simulated waveforms of a driving signal, voltage and current of a second power switch tube provided in an embodiment of the present invention, Figure 3 FIG. 1 is a schematic diagram of simulated waveforms of a driving signal, voltage and current of a first power switch tube provided in an embodiment of the present invention. Figure 2 and Figure 3 As shown, the first power switch tube 1 realizes zero voltage switching, and the second power switch tube 2 realizes zero voltage and zero current switching. Figure 2 and Figure 3The simulation waveform in is obtained by simulating the waveform under the conditions that the voltage of the power supply Vin is 96V, the inductance L1 of the first inductor 6 is 1uH, the inductance L2 of the second inductor 7 is 66uH, the resistance R of the resistor 8 is 1 ohm, the capacitance C3 of the second capacitor 5 is 1uF, the capacitance C2 of the third capacitor 4 is 100uF, the resistance of the load 11 is 4 ohms, the switching frequency is 25KHz, the driving phase difference between the first power switch tube 1 and the second power switch tube 2 is 4us, and the duty cycle is 70%.

[0056] The BUCK converter provided by the embodiment of the present invention has a simple circuit structure, is easy to drive, uses a small number of components, and has small voltage stress and current stress of the first power switch tube and the second power switch tube, which is beneficial to cost saving. It can realize soft switching of the power switch tube under a large load range and a large duty cycle, thereby improving the working efficiency of the system.

[0057] Figure 4 FIG. 1 is a flow chart of a control method for a BUCK converter provided by an embodiment of the present invention. Figure 4 As shown, the control method of the BUCK converter according to any of the above embodiments provided in an embodiment of the present invention includes:

[0058] S401, close the second power switch tube and keep the first power switch tube open, so that the current in the power supply passes through the second power switch tube, the first inductor and the second inductor to supply power to the load;

[0059] Specifically, after the power supply is turned on, the second power switch tube is closed and the first power switch tube is kept open. At this time, the current in the power supply flows through the second power switch tube, the first inductor and the second inductor to supply power to the load. When the second power switch tube is closed, since the current in the first inductor is zero, the conduction current during the closing process of the second power switch tube is approximately zero, and the second power switch tube can be regarded as zero current conduction.

[0060] S402: After a first preset time, close the first power switch tube, so that the current of the power supply passes through the first branch and the second branch, and then flows through the second inductor to supply power to the load; wherein the first branch includes the second power switch tube and the first inductor connected in series, and the second branch includes the first power switch;

[0061] Specifically, after the second power switch tube is closed for a first preset time, the voltage at the input end of the second inductor is approximately equal to the voltage of the power supply, and the first power switch tube is closed. At this time, the first power switch tube and the second power switch tube are both closed, and the current of the power supply is divided into two branches, the first branch includes the second power switch tube and the first inductor connected in series, and the second branch includes the first power switch. After the current of the power supply flows through the first branch and the second branch respectively, it converges at the input end of the second inductor, and then supplies power to the load through the second inductor. When the first power switch tube is closed, since the voltage at the input end of the second inductor is approximately equal to the voltage of the power supply, the voltage between the source and the drain of the first power switch tube is approximately zero when the first power switch tube is closed, and the first power switch tube can be regarded as zero voltage conduction. Among them, the first preset time is set according to actual needs, and the embodiment of the present invention is not limited.

[0062] S403: disconnect the second power switch tube, and disconnect the first power switch tube after a second preset time, so that the power supply stops supplying power to the load.

[0063] Specifically, when the power supply stops supplying power to the load, the second power switch tube is first disconnected, and then the first power switch tube is disconnected after the second power switch tube is disconnected for a second preset time, so that the power supply stops supplying power to the load. When the second power switch tube is disconnected, the first diode is immediately turned on, and the drain voltage of the second power switch tube is approximately clamped to the voltage of the power supply, and the second power switch tube can be regarded as zero voltage shutdown. When the first power switch tube is disconnected, due to the presence of the first capacitor, the voltage between the drain and the source of the first power switch tube is approximately zero during the disconnection process, and the first power switch tube can be regarded as zero voltage disconnection.

[0064] The control method of the BUCK converter provided by the embodiment of the present invention can close the second power switch tube and keep the first power switch tube disconnected, so that the current in the power supply passes through the second power switch tube, the first inductor and the second inductor to supply power to the load. After the first preset time, the first power switch tube is closed, so that the current of the power supply passes through the first branch and the second branch and then flows through the second inductor to supply power to the load, and the second power switch tube is disconnected. After the second preset time, the first power switch tube is disconnected, so that the power supply stops supplying power to the load, and the zero voltage conduction and shutdown of the first power switch tube and the zero current conduction and zero voltage shutdown of the second power switch tube are realized, the switching loss of the power switch tube is reduced, and the reliability of the circuit is improved.

[0065] On the basis of the above embodiments, further, the first preset time and the second preset time are both greater than the time t d ,in:

[0066] t d =t+t'

[0067] t=L1I D2 / V in

[0068]

[0069] Where, L1 is the inductance of the first inductor, V in is the voltage of the power supply, I D2 is the current of the second diode when the second power switch tube is turned on, and C1 is the capacitance of the first capacitor.

[0070] Specifically, in order to obtain the best possible soft switching effect of the power switch tube, the first preset time is greater than the time t d , the second preset time is also greater than time t d That is to say, the time that the driving pulse of the first power switch tube lags behind the driving pulse of the second power switch tube is greater than the time t d Among them, t d =t+t'. t is the time from the second power switch tube being turned on to the current of the second diode being zero, t=L1I D2 / V in , where L1 is the inductance of the first inductor, V in is the voltage of the power supply, I D2 is the current of the second diode when the second power switch is turned on. After the current in the second diode becomes zero, the first inductor and the first capacitor start to resonate, the current in the first inductor increases, and the voltage across the first capacitor decreases. Figure 1 The time taken for the voltage at point A to gradually rise to the power supply voltage is t'. Wherein, L1 is the inductance of the first inductor, and C1 is the capacitance of the first capacitor. Wherein, the inductance of the first inductor can be set at the order of 10uH, and the capacitance of the first capacitor can be set at the order of 10nF. d It may occupy one tenth to one fifth of the driving pulse period of the first power switch tube or the second power switch tube.

[0071] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0072] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0073] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0074] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "a specific embodiment", "some embodiments", "for example", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0076] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A BUCK converter, characterized in that: It includes a first power switch tube, a second power switch tube, a first capacitor, a second capacitor, a first inductor, a second inductor, a resistor, a first diode and a second diode, wherein: The drains of the first power switch tube and the second power switch tube are respectively connected to the positive electrode of the power supply, the source of the first power switch tube is connected to the first end of the second inductor, the first capacitor is respectively connected to the two ends of the first power switch tube, the source of the second power switch tube is connected to the first end of the first inductor, and the second end of the first inductor is connected to the first end of the second inductor; the first inductor is smaller than the second inductor; The cathode of the first diode is connected to the source of the second power switch tube and the first end of the first inductor respectively, the anode of the first diode is connected to the first end of the resistor, the second end of the resistor is connected to the source of the first power switch tube and the second end of the first inductor respectively, and the two ends of the second capacitor are connected to the two ends of the resistor respectively; The second end of the second inductor is connected to the first end of the load, the second end of the load is grounded, the cathode of the second diode is connected to the first end of the second inductor, and the anode of the second diode is grounded; Wherein, the second power switch tube is closed before the first power switch tube is closed; the second power switch tube is opened before the first power switch tube is opened; The BUCK converter further includes a third capacitor, a first end of the third capacitor is respectively connected to the second end of the second inductor and the first end of the load, and a second end of the third capacitor is grounded.

2. The BUCK converter according to claim 1, characterized in that: The driving pulse widths of the first power switch tube and the second power switch tube are the same.

3. The BUCK converter according to claim 1 or 2, characterized in that: The first power switch tube and the second power switch tube are metal-oxide semiconductor field effect transistors or insulated gate bipolar transistors.

4. A control method using the BUCK converter according to any one of claims 1 to 3, characterized in that: include: The second power switch tube is closed and the first power switch tube is kept open, so that the current of the power supply passes through the second power switch tube, the first inductor and the second inductor to supply power to the load; After a first preset time, the first power switch tube is closed, so that the current of the power supply passes through the first branch and the second branch, and then flows through the second inductor to supply power to the load; wherein the first branch includes the second power switch tube and the first inductor connected in series, and the second branch includes the first power switch; The second power switch tube is turned off, and the first power switch tube is turned off after a second preset time, so that the power supply stops supplying power to the load.

5. The method according to claim 4, characterized in that The first preset time and the second preset time are both greater than time t d ,in: t d =t+t' t=L1I D2 / V in Where, L1 is the inductance of the first inductor, V in is the voltage of the power supply, I D2 is the current of the second diode when the second power switch tube is turned on, and C1 is the capacitance of the first capacitor.

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