Resonance type Buck circuit with low output voltage ripples and direct-current power supply converter

Abstract

The invention discloses a resonance type Buck circuit with low output voltage ripples and a direct-current power supply converter in the technical field of direct-current conversion circuits, the circuit comprises a loop composed of a power supply Vin, a switching tube Q, a main inductor L1 and a load R, the two ends of the load R are connected with an output capacitor C2 in parallel, and the circuit further comprises a fly-wheel diode D. According to the scheme, the resonant branch formed by connecting the resonant capacitor Cs and the resonant inductor Ls in series is connected to the two ends of the fly-wheel diode D in parallel, so that the inductive current is in three states, and therefore, under the condition of the same inductive current average value, compared with a traditional Buck converter, the main power inductive current peak value of the circuit in the scheme is greatly reduced, and output voltage ripples are reduced; in addition, in the face of the same input or load sudden change, the three-state inductive current enables the circuit to have higher transient response speed and better stability.

Description

Technical Field

[0001] This invention relates to the field of DC-DC conversion circuits, and more specifically to a resonant Buck circuit with low output voltage ripple and a DC-DC power converter. Background Technology

[0002] Buck circuits, also known as step-down converters or choppers, are a type of switch-mode DC-DC power converter. Their core function is to convert the input DC voltage into a DC output voltage that is lower than the input voltage. Due to their high efficiency and compact size, they are widely used in electronic devices such as chargers and computer motherboards.

[0003] In existing Buck circuits, the switching of the transistor generates voltage ripple. This voltage ripple is mainly caused by the following factors: the triangular wave ripple formed by the charging and discharging of the output capacitor; and the spike ripple of the equivalent series resistance of the output capacitor. The presence of ripple leads to the following problems in various precision electronic components: The core chips of smart speakers, smart gateways, and high-end routers have low voltage and a large dynamic range of current. If the power supply ripple is large, it will cause the voltage to drop suddenly when the CPU is under high load, causing system lag or crashes and restarts, resulting in a poor user experience. Consumer-grade audio devices using DC-DC power supplies with high ripple may produce noise from the speakers when no audio is playing. For devices such as set-top boxes and network drives that need to be kept on for extended periods, high-efficiency, low-ripple power supplies can reduce heat generation, prevent premature failures caused by capacitor bulging and other issues, and ensure data security. Summary of the Invention

[0004] The purpose of this invention is to provide a resonant Buck circuit and DC power converter with low output voltage ripple, which solves the problem of high output voltage ripple in existing Buck circuits.

[0005] The present invention achieves the above objectives through the following technical solutions: A resonant Buck circuit with low output voltage ripple includes a circuit consisting of a power supply Vin, a switching transistor Q, a main inductor L1, and a load R. An output capacitor C2 is connected in parallel across the load R. The circuit also includes a freewheeling diode D, the anode of which is connected to the negative terminal of the power supply Vin, and the cathode of which is connected to the end of the switching transistor Q away from the power supply Vin. A resonant branch is connected in parallel across the two ends of the switch Q or the two ends of the diode D. The resonant branch includes a resonant inductor Ls and a resonant capacitor Cs connected in series. The switch Q responds to the control signal to perform duty cycle adjustment so that the resonant branch forms a resonant network to suppress voltage ripple.

[0006] As a preferred embodiment of the present invention, the resonant branch forms a resonant network to suppress voltage ripple, including: When the switch Q is turned on, the resonant inductor Ls and resonant capacitor Cs first release energy and then store energy; during the period when the switch Q is turned off, the diode D first freewheels and then turns off, and the resonant branch is connected in series with the main inductor L1 to release energy to the output side and form a resonant network to reduce the peak-to-peak value of the inductor current in order to suppress voltage ripple.

[0007] In a preferred embodiment of the present invention, the switching transistor Q responds to the control signal to perform duty cycle adjustment, and within one switching cycle, the Buck circuit sequentially enters: First operating mode: where the switch Q is turned on, the current of the main inductor L1 increases linearly, and at the same time the current of the resonant branch changes linearly and its direction changes, so that the resonant branch first releases energy and then stores energy. Second operating mode: wherein the switch Q is turned off, the diode D is turned on and the current decreases linearly, the current of the main inductor L1 and the resonant branch decreases linearly, and both release energy to the load R; Third operating mode: wherein the switching transistor Q and diode D are both turned off, and the main inductor L1, the resonant inductor Ls and the resonant capacitor Cs form a resonant network.

[0008] In a preferred embodiment of the present invention, the resonant branch is connected in parallel across the two ends of diode D.

[0009] In a preferred embodiment of the present invention, in the resonant branch, the resonant capacitor Cs is connected to the connection between the source of the switching transistor Q and the cathode of the diode D, and the resonant inductor Ls is connected to the anode of the diode D.

[0010] In a preferred embodiment of the present invention, the process by which the switching transistor Q responds to the control signal to perform duty cycle adjustment, thereby adjusting the output voltage or current of the load R, includes: The required output voltage or current of the load R is obtained and input into the control circuit of the switching transistor Q. The control circuit determines the required duty cycle and executes the switching transistor Q to achieve constant voltage or constant current output.

[0011] In a preferred embodiment of the present invention, the resonant branch is connected in parallel across the two ends of the switching transistor Q.

[0012] In a preferred embodiment of the present invention, in the resonant branch, the resonant inductor Ls is connected to the source of the switch Q and the cathode of the diode D, and the resonant capacitor Cs is connected to the drain of the switch Q and the positive terminal of the power supply Vin.

[0013] In a preferred embodiment of the present invention, the source of the switching transistor Q is connected to the cathode of the freewheeling diode D, and the drain of the switching transistor Q is connected to the positive terminal of the power supply Vin. The negative terminal of the power supply Vin, the output capacitor C2 and the end of the load R away from the main inductor L1, and the anode of the diode D are all grounded.

[0014] To apply the above circuit, the present invention also proposes a DC power converter including any of the above resonant Buck circuits with low output voltage ripple.

[0015] The beneficial effects of this invention are as follows: In this scheme, a resonant branch consisting of a resonant capacitor Cs and a resonant inductor Ls connected in series is connected in parallel across the freewheeling diode D, which makes the inductor current exhibit three states. Therefore, under the same average inductor current, compared with a traditional Buck converter with the same main circuit parameters, the peak value of the main power inductor current of this scheme is greatly reduced, thereby reducing the output voltage ripple. In addition, when facing the same input or load change, the three-state inductor current makes the circuit of this invention have a faster transient response speed and better stability. Attached Figure Description

[0016] Figure 1 This is a circuit diagram of the present invention; Figure 2 This is a schematic diagram of the circuit operation state during the t0 to t1 stage of the present invention; Figure 3 This is a schematic diagram of the circuit operation state during the t1 to t2 stages of the present invention; Figure 4 This is a schematic diagram of the circuit operation state during the t2 to t3 stages of the present invention; Figure 5 This is a schematic diagram of the simulation results of the circuit of the present invention; Figure 6 This is a comparison chart of simulation results of the inductor current of the present invention and the inductor current of a conventional Buck circuit; Figure 7 This is a comparison chart of the simulation results of the circuit output voltage and inductor current of the present invention under sudden load changes with those of the traditional Buck circuit; Figure 8 This is a circuit diagram of the second embodiment of the present invention. Detailed Implementation

[0017] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0018] Example 1 like Figure 1-7 As shown, a resonant Buck circuit with low output voltage ripple includes a circuit consisting of a power supply Vin, a switching transistor Q, a main inductor L1, and a load R. An output capacitor C2 is connected in parallel across the load R. The circuit also includes a freewheeling diode D, with the anode of the freewheeling diode D connected to the negative terminal of the power supply Vin and the cathode connected to the end of the switching transistor Q away from the power supply Vin. A resonant branch is connected in parallel across the two ends of the switching transistor Q. The resonant branch includes a series resonant inductor Ls and a resonant capacitor Cs. The switching transistor Q responds to the control signal to perform duty cycle adjustment so that the resonant branch forms a resonant network to suppress voltage ripple.

[0019] Preferably, in the resonant branch of this embodiment, the resonant capacitor Cs is connected to the connection between the source of the switch Q and the cathode of the diode D, the resonant inductor Ls is connected to the anode of the diode D, the source of the switch Q is connected to the cathode of the freewheeling diode D, the drain of the switch Q is connected to the positive terminal of the power supply Vin, and the negative terminal of the power supply Vin, the output capacitor C2, the end of the load R away from the main inductor L1, and the anode of the diode D are all grounded.

[0020] Compared to the traditional Buck circuit, the resonant Buck circuit in this embodiment incorporates a resonant branch connected in parallel across the freewheeling diode D, consisting of a resonant capacitor Cs and a resonant inductor Ls connected in series. The introduction of this resonant branch causes the inductor current to exhibit a three-state characteristic. Therefore, with the same average inductor current, compared to a traditional Buck converter with the same main circuit parameters, the peak value of the main power inductor current in this circuit is significantly reduced, thus lowering the output voltage ripple. Furthermore, when facing the same input or load surges, the three-state inductor current provides the circuit with faster transient response and better stability.

[0021] The resonant branches form a resonant network to suppress voltage ripple, including: When the switch Q is turned on, the resonant inductor Ls and resonant capacitor Cs first release energy and then store energy; during the period when the switch Q is turned off, the diode D first freewheels and then turns off, and the resonant branch is connected in series with the main inductor L1 to release energy to the output side and form a resonant network to reduce the peak-to-peak value of the inductor current in order to suppress voltage ripple.

[0022] The switching transistor Q responds to the control signal to adjust the duty cycle. Within one switching cycle, the Buck circuit sequentially enters: First operating mode: t0~t1 stage: At time t0, the power switch Q is turned on, the main inductor L1 stores energy, and its current rises linearly; defined as follows. Figure 1The current direction from top to bottom in the resonant branch shown is positive. Before the current in the resonant branch rises to zero, both the resonant inductor Ls and the resonant capacitor Cs release energy to the output side. After the current in the resonant branch crosses zero and becomes positive, both the resonant inductor Ls and the resonant capacitor Cs store energy. If the voltage fluctuation of the resonant capacitor Cs is ignored, the current in the resonant branch also rises linearly. This stage continues until time t1. Second operating mode: t1~t2 stage: At time t1, the power switch Q is turned off. The current flowing through the main inductor L1 and the current flowing through the resonant branch both flow through the freewheeling diode D. Both the main inductor L1 and the resonant inductor Ls release energy, and the resonant capacitor Cs stores energy. When the current in the resonant branch drops to zero and becomes negative, the resonant capacitor Cs releases energy, the resonant inductor Ls stores energy, and the current flowing through the freewheeling diode D gradually decreases. When the current in the resonant branch is equal to the current flowing through the main inductor L1, the freewheeling diode D turns off with zero current, and this mode ends. Similarly, if the voltage fluctuation of the resonant capacitor Cs is ignored, the current in the resonant branch decreases linearly in this stage. Third operating mode: t2~t3 stage: During this stage, the power switch Q is in the off state, the freewheeling diode D is in the cutoff state, and the main inductor L1, resonant inductor Ls and resonant capacitor Cs resonate in series. Since its resonant frequency is usually much lower than the switching frequency, the current flowing through L1, Ls and Cs can be approximately considered to remain constant. Since the inductor current is approximately constant in this mode, the peak-to-peak value of the inductor current can be significantly reduced under the same average inductor current value, thereby obtaining low output voltage ripple.

[0023] The process by which the switching transistor Q responds to the control signal to perform duty cycle adjustment, thereby regulating the output voltage or current of the load R, includes: The required output voltage or current of the load R is obtained and input into the control circuit of the switching transistor Q. The control circuit determines the required duty cycle and executes the switching transistor Q to achieve constant voltage or constant current output.

[0024] Simulation results for the three modes existing in each switching cycle are as follows: Figure 5 As shown in the simulation, the specific parameters of the circuit components involved in the circuit of this invention are as follows: input power supply Vin is 48V, resonant capacitor Cs is 5μF, resonant inductor Ls is 4μH, main inductor L1 is 100μH, output capacitor C2 is 100μF, and load R is 5Ω.

[0025] like Figure 6 As shown, compared with the traditional Buck circuit with the same main circuit parameters, the circuit of this scheme has a smaller peak-to-peak value of inductor current. I(L1) represents the current flowing through the main inductor L1 of this scheme, and I(L2) represents the current flowing through the main inductor L2 of the traditional Buck circuit.

[0026] like Figure 7 The simulation diagram shown illustrates the comparison between the output voltage Vo1 and the current I (L1) flowing through the main inductor of the circuit of the present invention and the output voltage Vo2 and the current I (L2) flowing through the main inductor of the conventional Buck circuit when facing sudden load changes.

[0027] To apply the above circuit, the present invention also proposes a DC power converter including any of the above resonant Buck circuits with low output voltage ripple.

[0028] Example 2 like Figure 8 As shown, compared to Embodiment 1, in this embodiment, the resonant branch is connected in parallel across the two ends of the switching transistor Q. Specifically, in the resonant branch, the resonant inductor Ls is connected to the connection point between the source of the switching transistor Q and the cathode of the diode D, and the resonant capacitor Cs is connected to the connection point between the drain of the switching transistor Q and the positive terminal of the power supply Vin.

[0029] A switching cycle includes the following stages: Phase 1: Switch Q is turned on, diode D is reverse biased, the current in main inductor L1 increases linearly, main inductor L1 stores energy and supplies power to load R, and the resonant branch current decreases approximately linearly (e.g., ...). Figure 8 (It is defined that the current in the resonant branch is positive from left to right). Before the resonant current drops to zero, the resonant inductor Ls releases energy and the resonant capacitor Cs stores energy. After the resonant current drops to zero, the situation is exactly the opposite. Second stage: Switch Q turns off, diode D begins freewheeling and its current value decreases linearly, main inductor L1 releases energy and its current decreases linearly, and the resonant branch current rises approximately linearly. Before the resonant current rises to zero, the resonant inductor Ls and resonant capacitor Cs release energy together. After the resonant current rises to zero, the resonant inductor Ls and resonant capacitor Cs store energy together. When the resonant branch current rises to equal the main inductor L1 current, diode D turns off exactly with zero current, entering the next stage; The third stage: the switching transistor Q is turned off, the diode D is turned off, and the main inductor L1, the resonant inductor Ls, and the resonant capacitor Cs resonate in series. Since its resonant frequency is much lower than the switching frequency, the current flowing through L1, Ls, and Cs can be approximated as constant. Similarly, because the inductor current is approximately constant in this stage, under the same average inductor current, the peak-to-peak value of the inductor current can be significantly reduced compared to the traditional Buck converter, thereby obtaining low output voltage ripple.

[0030] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A resonant Buck circuit with low output voltage ripple, comprising a loop formed by a power supply Vin, a switching transistor Q, a main inductor LI, and a load R, wherein the load R is connected in parallel with an output capacitor C2, characterized in that, A freewheeling diode D is further included, an anode of the freewheeling diode D is connected to a negative pole of the power supply Vin, and a cathode is connected to an end of the switch tube Q away from the power supply Vin; The two ends of the switch tube Q or the two ends of the diode D are connected in parallel with a resonance branch, the resonance branch includes a resonance inductor Ls and a resonance capacitor Cs connected in series, and the switch tube Q performs duty cycle adjustment in response to a control signal, so that the resonance branch forms a resonance network to suppress voltage ripple.

2. The resonant Buck converter with low output voltage ripple according to claim 1, characterized in that, The resonance branch forms a resonance network to suppress voltage ripple, including: When the switch tube Q is turned on, the resonance inductor Ls and the resonance capacitor Cs first release energy and then store energy; during the off period of the switch tube Q, the diode D first freewheels and then turns off, the resonance branch and the main inductor L1 in series release energy to the output side, and form a resonance network to reduce the peak-to-peak value of inductor current, thereby suppressing voltage ripple.

3. The resonant Buck converter with low output voltage ripple of claim 1, wherein, The switch tube Q performs duty cycle adjustment in response to a control signal, and in one switching cycle, the Buck circuit sequentially enters: A first working mode: in which the switch tube Q is turned on, the current of the main inductor L1 linearly rises, and the current of the resonance branch linearly changes and changes direction, so that the resonance branch first releases energy and then stores energy; A second working mode: in which the switch tube Q is turned off, the diode D is turned on and the current linearly decreases, and the currents of the main inductor L1 and the resonance branch linearly decrease and release energy to the load R; A third working mode: in which the switch tube Q and the diode D are both turned off, and the main inductor L1, the resonance inductor Ls and the resonance capacitor Cs form a resonance network.

4. The resonant Buck converter with low output voltage ripple of claim 1, wherein, The resonance branch is connected in parallel across the two ends of the diode D.

5. The resonant Buck converter with low output voltage ripple according to claim 4, characterized in that, In the resonance branch, the resonance capacitor Cs is connected at the connection between the source of the switch tube Q and the cathode of the diode D, and the resonance inductor Ls is connected at the anode of the diode D.

6. The resonant Buck converter with low output voltage ripple according to claim 5, wherein The switch tube Q performs duty cycle adjustment in response to a control signal, and the process of adjusting the output voltage or current of the load R includes: Obtaining the required output voltage or current of the load R and inputting it into the control circuit of the switch tube Q, the control circuit determines the required duty cycle and performs the on-off of the switch tube Q to achieve constant voltage or constant current output.

7. The resonant Buck converter with low output voltage ripple of claim 1, wherein, The resonance branch is connected in parallel across the two ends of the switch tube Q.

8. The resonant Buck converter with low output voltage ripple according to claim 7, wherein, In the resonance branch, the resonance inductor Ls is connected at the connection between the source of the switch tube Q and the cathode of the diode D, and the resonance capacitor Cs is connected at the connection between the drain of the switch tube Q and the positive pole of the power supply Vin.

9. The resonant Buck converter with low output voltage ripple of claim 1, wherein, The source of the switch tube Q is connected to the cathode of the freewheeling diode D, the drain of the switch tube Q is connected to the positive pole of the power supply Vin, and the negative pole of the power supply Vin, the output capacitor C2 and the load R away from one end of the main inductor L1, and the anode of the diode D are grounded.

10. A DC power converter, characterized by, A resonance type Buck circuit with low output voltage ripple is included, as claimed in any one of claims 1-9.

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