Method for improving output efficiency of BUCK / BOOST circuit

Abstract

The invention relates to the technical field of power supply conversion, and discloses a method for improving the output efficiency of a BUCK / BOOST circuit, and the method comprises the steps: S1, detecting an input voltage, an output voltage and a load state, and determining that the circuit is in a BUCK mode, a BOOST mode or a BUCK and BOOST mode transition state; s2, in a BUCK mode; s3, in a BOOST mode; s4, in a transition state between a BUCK mode and a BOOST mode; and S5, the first frequency is used for executing energy conversion control. A first frequency and a second frequency are respectively adopted in a BUCK loop and a BOOST loop to carry out switching control, so that a main energy conversion loop works at the first frequency, a non-dominant loop is kept on or periodically on at the second frequency, and the frequencies of two groups of switching devices are distributed, so that an inductive current path is automatically distinguished along with modes, and the switching efficiency is improved. Therefore, a stable energy transfer relation is formed in a single mode.

Description

Technical Field

[0001] This invention relates to the field of power conversion technology, specifically a method for improving the output efficiency of a BUCK / BOOST circuit. Background Technology

[0002] BUCK and BOOST circuits are two of the most commonly used topologies in power conversion technology. BUCK circuits are used to convert input voltage to a lower output voltage, while BOOST circuits are used to boost to a higher voltage. In applications requiring a wide range of input and output voltage relationships, a BUCK / BOOST circuit structure is often used to achieve buck-boost conversion under different voltage conditions, thus meeting various power supply needs. Existing BUCK / BOOST circuits generally use separate driving of the BUCK and BOOST circuits, switching between the two modes based on the relationship between the input and output voltages, enabling the power system to complete energy conversion in either boost or buck mode.

[0003] However, in current technology, directly switching the main circuit causes a sudden change in the inductor current path at the moment of switching, which can easily lead to discontinuous energy transfer and thus reduce the working efficiency during the mode transition phase. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for improving the output efficiency of BUCK / BOOST circuits, solving the problem of discontinuous energy transfer during the transition phase caused by abrupt changes in the inductor current path during the switching between BUCK and BOOST modes.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for improving the output efficiency of a BUCK / BOOST circuit, applied to a circuit with first switching devices Q1 and Q2 having a BUCK circuit, second switching devices Q3 and Q4 having a BOOST circuit, and an inductor L1 shared by the two circuits, comprising: S1. Detect the input voltage, output voltage, and load status to determine whether the circuit is in BUCK mode, BOOST mode, or a transitional state between BUCK and BOOST modes. S2. In BUCK mode, the first switching devices Q1 and Q2 are controlled to switch at a first frequency, and the second switching devices Q3 and Q4 are controlled to switch at a second frequency, wherein the second frequency is lower than the first frequency. S3. In BOOST mode, the second switching devices Q3 and Q4 are switched at a first frequency, and the first switching devices Q1 and Q2 are switched at a second frequency, wherein the second frequency is lower than the first frequency. S4. In the transition state between BUCK mode and BOOST mode, the circuit can be switched from BUCK mode to BOOST mode by reducing the switching frequency of BUCK circuit and increasing the switching frequency of BOOST circuit, or vice versa. S5. The first frequency is used to perform energy conversion control, and the second frequency is used to maintain the switching device in a low-frequency or periodic on-state.

[0006] Preferably, the second frequency is a switching frequency of 50Hz to 100Hz.

[0007] Preferably, during the transition from BUCK mode to BOOST mode: When the duty cycle of the switching device in the BUCK loop reaches the set upper limit, the controller reduces the switching frequency of the BUCK loop. After the switching frequency of the BUCK circuit decreases to a preset lower limit, the controller increases the switching frequency of the BOOST circuit.

[0008] Preferably, during the transition from BOOST mode to BUCK mode: When the duty cycle of the switching device in the BOOST circuit reaches the set lower limit, the controller reduces the switching frequency of the BOOST circuit. After the switching frequency of the BOOST circuit decreases to a preset lower limit, the controller increases the switching frequency of the BUCK circuit.

[0009] Preferably, at the second frequency, the switching device that is not in the energy conversion state remains on or is periodically on at a low frequency.

[0010] Preferably, the detection step includes detecting the load change trend, and adjusting the switching frequency of the BUCK circuit or BOOST circuit in advance when the load trend reaches a set threshold.

[0011] Preferably, the first frequency is a switching frequency of 100kHz to 1MHz.

[0012] Preferably, the rectification structures in the BUCK circuit and BOOST circuit are synchronous rectification structures, or asynchronous rectification structures that use diodes to replace Q2 and Q4.

[0013] Preferably, the controller selects the following mode based on the comparison result of the input voltage and the output voltage: Select BUCK mode when the input voltage is higher than the output voltage; Select BOOST mode when the input voltage is lower than the output voltage; When the input voltage is close to the output voltage, the BUCK / BOOST mode is selected for transition.

[0014] Preferably, the BUCK / BOOST circuit includes multiple power phases, each of which is equipped with switching devices Q1, Q2, Q3, Q4 and inductors connected thereto. The output terminals of each power phase are connected in parallel, and the switching control signals of each power phase have a fixed phase difference.

[0015] This invention provides a method for improving the output efficiency of a BUCK / BOOST circuit. It has the following beneficial effects: 1. In this invention, the first frequency and the second frequency are used for switching control in the BUCK circuit and the BOOST circuit respectively, so that the main energy conversion circuit works at the first frequency, and the non-dominant circuit remains on or periodically on at the second frequency. By allocating the frequencies of the two sets of switching devices, the inductor current path is automatically distinguished according to the mode, thereby forming a stable energy transfer relationship in a single mode.

[0016] 2. This invention uses a first frequency and a second frequency for switching control in the BUCK circuit and BOOST circuit respectively. The main circuit performs energy conversion at the first frequency, while the non-dominant circuit remains on or periodically on at the second frequency. This adjusts the frequency of the two sets of devices according to the mode switching, so that the inductor current forms a continuous transition between different operating modes, thereby enabling the circuit to maintain a stable energy transfer state under various input and output conditions.

[0017] 3. While performing voltage detection, this invention analyzes the trend of load current change. By setting a trend threshold, the controller can adjust the switching frequency of the BUCK or BOOST circuit in advance before the load enters a new operating range. By judging the trend information, the inductor current can maintain a continuous path before and after the load change, so that the circuit has a more stable operating state under dynamic load conditions. Attached Figure Description

[0018] Figure 1 A flowchart of a method for improving the output efficiency of a BUCK / BOOST circuit according to the present invention; Figure 2 This is a circuit diagram illustrating a method for improving the output efficiency of a BUCK / BOOST circuit according to the present invention. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see the appendix Figure 1 and attached Figure 2 This invention provides a method for improving the output efficiency of a BUCK / BOOST circuit, applied to a circuit with first switching devices Q1 and Q2 in a BUCK loop, second switching devices Q3 and Q4 in a BOOST loop, and an inductor L1 shared by the two loops, comprising: S1. Detect the input voltage, output voltage, and load status to determine whether the circuit is in BUCK mode, BOOST mode, or a transitional state between BUCK and BOOST modes. S2. In BUCK mode, the first switching devices Q1 and Q2 are controlled to switch at a first frequency, and the second switching devices Q3 and Q4 are controlled to switch at a second frequency, wherein the second frequency is lower than the first frequency. S3. In BOOST mode, the second switching devices Q3 and Q4 are switched at a first frequency, and the first switching devices Q1 and Q2 are switched at a second frequency, wherein the second frequency is lower than the first frequency. S4. In the transition state between BUCK mode and BOOST mode, the circuit can be switched from BUCK mode to BOOST mode by reducing the switching frequency of BUCK circuit and increasing the switching frequency of BOOST circuit, or vice versa. S5. The first frequency is used to perform energy conversion control, and the second frequency is used to maintain the switching device in a low-frequency or periodic conduction state.

[0021] Specifically, the controller acquires real-time data of the input voltage Vin, output voltage Vout, and load current Iout through the input voltage sampling module Voltage Measurement1, the output voltage sampling module Voltage Measurement, and the load current sampling module Current Measurement3, respectively. Based on the difference between the input and output voltages and the changes in the load current, the controller determines the current operating region of the circuit. When the input voltage is higher than the output voltage by more than a preset threshold, the current state is determined to be BUCK mode; when the input voltage is lower than the output voltage by more than a preset threshold, the current state is determined to be BOOST mode; when the difference between the input and output voltages is within a preset range, the current state is determined to be a transitional state between BUCK and BOOST modes. Thus, the controller can obtain the real-time operating range of the circuit so as to configure an appropriate switching frequency in subsequent steps. When the circuit is in BUCK mode, the controller outputs a drive signal to the first switching devices Q1 and Q2 at a first frequency, causing them to alternately conduct at high frequency, thereby establishing a path for energy transfer from the input terminal to the inductor L1 via the BUCK loop. Simultaneously, the controller sets the drive frequency of the second switching devices Q3 and Q4 to a second frequency, causing them to be in a low-frequency conduction or periodic conduction state. This ensures that the main energy flow path of the inductor L1 preferentially passes through the BUCK loop, resulting in a stable periodic operation of the main current path within the BUCK loop, while the BOOST loop remains in a non-dominant conduction state. When the circuit is in BOOST mode, the controller outputs a drive signal to the second switching devices Q3 and Q4 at a first frequency, causing them to turn on and off at a high frequency. This controls the charging and discharging path of inductor L1 to form the energy transfer channel of the BOOST circuit. At the same time, the first switching devices Q1 and Q2 are driven at a second frequency to keep them in a low-frequency or periodic on state. Thus, the energy transfer path of inductor L1 is concentrated in the BOOST circuit, while the BUCK circuit is in an auxiliary on state, enabling the system to form a stable boost operation process in BOOST mode. When the controller determines that the circuit is in a transitional state between BUCK and BOOST modes, the controller first reduces the switching frequency of the first switching devices Q1 and Q2, so that the equivalent conduction time of the BUCK circuit gradually changes. Then the controller increases the switching frequency of the second switching devices Q3 and Q4, so that the BOOST circuit gradually undertakes more current transmission tasks of inductor L1, and the energy path of the circuit gradually shifts from the BUCK circuit to the BOOST circuit. If it is a reverse switching, it is executed in the reverse order, that is, first reduce the switching frequency of Q3 and Q4 in the BOOST circuit, and then increase the switching frequency of Q1 and Q2 in the BUCK circuit. Thus, the energy transfer order between the BUCK circuit and the BOOST circuit gradually changes according to the frequency adjustment, so that the current path remains continuous during the mode switching process. The first frequency serves as the high-frequency switching frequency for energy conversion control. By driving the corresponding switching device at this frequency, inductor L1 charges and discharges in the main working circuit according to a set cycle, thus forming a stable power conversion process. The second frequency, as a low-frequency or periodically conducting frequency, triggers the corresponding switching device at this frequency, keeping the circuit in a conducting state or operating at a lower frequency. This concentrates the main energy transfer process on the working circuit corresponding to the first frequency. The frequency difference establishes a relative conduction relationship between the main circuit and the auxiliary circuit, ensuring continuous conduction in different modes of energy transfer.

[0022] The second frequency is a switching frequency of 50Hz to 100Hz.

[0023] Specifically, the second frequency is set to a low-frequency switching frequency of 50Hz to 100Hz. When the controller executes step S2 or step S3, if it is necessary to put the second or first switching device in a low-frequency conduction or periodic conduction state, the corresponding switching device, such as Q3, Q4 or Q1, Q2, is driven and controlled according to the second frequency. When driven in this frequency range, the number of switching actions of the corresponding switching device is significantly lower than the first frequency of the main energy conversion circuit, so that the switching device is kept in a low-frequency conduction relationship. Thus, the main energy transfer path of the circuit is concentrated in the working circuit corresponding to the first frequency. That is, in this frequency setting, the controller outputs a low-frequency drive signal to the corresponding device, so that the circuit in the non-dominant state in the device forms a stable low-frequency conduction mode.

[0024] During the transition from BUCK mode to BOOST mode: When the duty cycle of the switching device in the BUCK loop reaches the set upper limit, the controller reduces the switching frequency of the BUCK loop. After the switching frequency of the BUCK loop drops to a preset lower limit, the controller increases the switching frequency of the BOOST loop.

[0025] Specifically, during the transition from BUCK mode to BOOST mode, the controller monitors the voltage difference between the input and output terminals through the input voltage sampling module and the output voltage sampling module, and calculates the duty cycle of the BUCK circuit switching devices Q1 and Q2 in real time. When the duty cycle reaches the preset upper limit, the controller gradually reduces the driving frequency of Q1 and Q2 from the first frequency, so that the BUCK circuit is in a state of gradually weakening its conduction capability. When the drive frequency of the BUCK circuit drops to the set lower limit, the controller starts to increase the switching drive frequency of Q3 and Q4 in the BOOST circuit, so that the BOOST circuit gradually establishes current control over the inductor L1. Through the frequency adjustment sequence, the current path of the inductor between the BUCK circuit and the BOOST circuit changes gradually according to the set drive strategy, so that the current transmission process of the circuit in this transition phase remains continuous.

[0026] During the transition from BOOST mode to BUCK mode: When the duty cycle of the switching device in the BOOST circuit reaches the set lower limit, the controller reduces the switching frequency of the BOOST circuit. After the switching frequency of the BOOST loop drops to a preset lower limit, the controller increases the switching frequency of the BUCK loop.

[0027] Specifically, during the transition from BOOST mode to BUCK mode, the controller acquires input and output voltage data through the input and output voltage sampling modules. It also monitors the duty cycle of the switching devices Q3 and Q4 in the BOOST circuit in real time. When the duty cycle drops to a preset lower limit, the controller gradually reduces the driving frequency of Q3 and Q4 from the first frequency, thus weakening the inductor current control effect of the BOOST circuit sequentially. When the driving frequency of the BOOST circuit drops to the set lower limit range, the controller begins to increase the switching driving frequency of Q1 and Q2 in the BUCK circuit, allowing the BUCK circuit to gradually assume the current regulation task of inductor L1. Through this configuration sequence of decreasing and then increasing driving frequencies, the inductor current transmission path between the BOOST and BUCK circuits gradually shifts according to the set control method, ensuring continuous current transmission during the switching process between the two modes.

[0028] At the second frequency, switching devices that are not in the energy conversion state remain on or periodically on at low frequency.

[0029] Specifically, when the circuit is in BUCK mode or BOOST mode, the controller, according to the setting of S2 or S3, drives the switching devices that are not involved in energy conversion at the second frequency. For example, when the circuit is in BUCK mode, the switching devices Q3 and Q4 in the BOOST circuit receive the drive signal at the second frequency, keeping them in the conducting state or operating in a low-frequency periodic conducting mode. When the circuit is in BOOST mode, the switching devices Q1 and Q2 in the BUCK loop are driven at the second frequency, so that these two devices are kept in a low-frequency conduction relationship. By driving at the second frequency, the switching devices that are not in the main energy conversion path form a low-frequency conduction path, so that the main current path and the auxiliary conduction path are in a relatively stable distribution state in each working mode.

[0030] The detection process includes detecting load change trends and adjusting the switching frequency of the BUCK or BOOST circuit in advance when the load trend reaches a set threshold.

[0031] Specifically, the controller acquires real-time load current values ​​through a load current sampling module and analyzes the trend of these values ​​over time. For example, the controller can determine whether the load is increasing or decreasing based on the continuously sampled load current increment, rate of change, or direction of change. When the load change trend exceeds a preset threshold range, the controller adjusts the switching frequency of the BUCK or BOOST circuit in advance based on the trend direction: when the load is increasing and is expected to exceed the operating range of the current mode, the controller increases the high-frequency drive in the BOOST or BUCK circuit in advance, enabling the circuit to form the corresponding energy transfer path at the required time; when the load is decreasing, the controller reduces the switching frequency of the corresponding circuit in advance, matching its conduction state with the expected load change. Thus, through trend-predictive drive adjustment, inductor L1 can form a continuous current transmission process before and after load changes.

[0032] The first frequency is a switching frequency of 100kHz to 1MHz; Specifically, the first frequency is set to a high-frequency switching frequency of 100kHz to 1MHz. When executing S2 or S3, the controller sets the switching devices Q1 and Q2 in the BUCK circuit or the switching devices Q3 and Q4 in the BOOST circuit to perform high-frequency conduction and cutoff according to the first frequency, based on the current operating mode. Within this frequency range, the charging and discharging action of the inductor L1 forms a rapid cycle, enabling the main energy transfer circuit to establish a stable periodic current path. The setting of the first frequency ensures that the switching cycle of the main operating circuit matches the energy alternation process of the inductor, allowing the circuit to complete energy transfer according to the predetermined cycle in both BUCK and BOOST modes.

[0033] The rectifier structures in the BUCK and BOOST circuits are either synchronous or asynchronous, using diodes to replace Q2 and Q4.

[0034] Specifically, the BUCK circuit and BOOST circuit can adopt a synchronous rectification structure, that is, the switching devices Q1 and Q2 in the BUCK circuit and the switching devices Q3 and Q4 in the BOOST circuit are turned on and off by controlled drive signals. In another embodiment, Q2 or Q4 can be replaced by diodes to form a asynchronous rectification structure. When using a synchronous rectification scheme, the controller outputs drive signals to each switching device, causing it to conduct according to a specified frequency and timing. When using a asynchronous rectification scheme, the replaced device forms a current path with the corresponding circuit in its inherent unidirectional conduction manner. Through the optional setting of the two rectification structures, the BUCK circuit and BOOST circuit can form current paths corresponding to their structures according to the conduction mode and frequency configured by the controller.

[0035] The controller selects the following modes based on the comparison between the input voltage and the output voltage: Select BUCK mode when the input voltage is higher than the output voltage; Select BOOST mode when the input voltage is lower than the output voltage; When the input voltage is close to the output voltage, the BUCK / BOOST mode is selected for transition.

[0036] Specifically, the controller obtains the real-time values ​​of the input voltage Vin and the output voltage Vout through the input voltage sampling module and the output voltage sampling module, respectively, and determines the circuit's operating mode based on the comparison between the two. When the input voltage is greater than the output voltage and the difference exceeds a preset threshold, the controller sets the circuit to BUCK mode. When the input voltage is less than the output voltage and the difference exceeds another preset threshold, the controller sets the circuit to BOOST mode. When the difference between the input voltage and the output voltage is within a preset transition range, the controller sets the circuit to a BUCK / BOOST mode transition state. This allows the controller to provide corresponding operating range information for subsequent steps when voltage conditions change, so as to configure the corresponding drive frequency relationship in different modes.

[0037] The BUCK / BOOST circuit includes multiple power phases, each equipped with switching devices Q1, Q2, Q3, Q4 and inductors connected thereto. The output terminals of each power phase are connected in parallel, and the switching control signals of each power phase have a fixed phase difference.

[0038] Specifically, the BUCK / BOOST circuit can be composed of multiple power phases. Each power phase is equipped with switching devices Q1 and Q2 for the BUCK circuit, switching devices Q3 and Q4 for the BOOST circuit, and an inductor L1 connected to both circuits. The inductor output terminals of multiple power phases are connected to the same output terminal, so that the outputs of each power phase are converged to the load in parallel. In terms of control strategy, the controller configures a switching drive signal with a fixed phase difference for each power phase, so that each power phase is turned on or off sequentially at different phase angles. This allows multiple power phases to execute the corresponding BUCK or BOOST switching actions according to the set phase sequence. Through this phase-distinguished driving method, each power phase forms a distributed switching cycle in time, so that the same output terminal receives energy transfer from different power phases at different times.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for improving the output efficiency of a BUCK / BOOST circuit, characterized in that, A circuit applied to first switching devices Q1 and Q2 with a BUCK loop, second switching devices Q3 and Q4 with a BOOST loop, and an inductor L1 shared by both loops, includes: S1. Detect the input voltage, output voltage, and load status to determine whether the circuit is in BUCK mode, BOOST mode, or a transitional state between BUCK and BOOST modes. S2. In BUCK mode, the first switching devices Q1 and Q2 are controlled to switch at a first frequency, and the second switching devices Q3 and Q4 are controlled to switch at a second frequency, wherein the second frequency is lower than the first frequency. S3. In BOOST mode, the second switching devices Q3 and Q4 are switched at a first frequency, and the first switching devices Q1 and Q2 are switched at a second frequency, wherein the second frequency is lower than the first frequency. S4. In the transition state between BUCK mode and BOOST mode, the circuit can be switched from BUCK mode to BOOST mode by reducing the switching frequency of BUCK circuit and increasing the switching frequency of BOOST circuit, or vice versa. S5. The first frequency is used to perform energy conversion control, and the second frequency is used to maintain the switching device in a low-frequency or periodic on-state.

2. The method for improving the output efficiency of a BUCK / BOOST circuit according to claim 1, characterized in that, The second frequency is a switching frequency of 50Hz to 100Hz.

3. The method for improving the output efficiency of a BUCK / BOOST circuit according to claim 1, characterized in that, During the transition from BUCK mode to BOOST mode: When the duty cycle of the switching device in the BUCK loop reaches the set upper limit, the controller reduces the switching frequency of the BUCK loop. After the switching frequency of the BUCK circuit decreases to a preset lower limit, the controller increases the switching frequency of the BOOST circuit.

4. The method for improving the output efficiency of a BUCK / BOOST circuit according to claim 1, characterized in that, During the transition from BOOST mode to BUCK mode: When the duty cycle of the switching device in the BOOST circuit reaches the set lower limit, the controller reduces the switching frequency of the BOOST circuit. After the switching frequency of the BOOST circuit decreases to a preset lower limit, the controller increases the switching frequency of the BUCK circuit.

5. The method for improving the output efficiency of a BUCK / BOOST circuit according to claim 1, characterized in that, At the second frequency, switching devices that are not in the energy conversion state remain on or periodically on at low frequency.

6. The method for improving the output efficiency of a BUCK / BOOST circuit according to claim 1, characterized in that, The detection steps include detecting the load change trend, and adjusting the switching frequency of the BUCK or BOOST circuit in advance when the load trend reaches a set threshold.

7. The method for improving the output efficiency of a BUCK / BOOST circuit according to claim 1, characterized in that, The first frequency is a switching frequency of 100kHz to 1MHz.

8. A method for improving the output efficiency of a BUCK / BOOST circuit according to claim 1, characterized in that, The rectifier structures in the BUCK and BOOST circuits are either synchronous rectifier structures or asynchronous rectifier structures that use diodes to replace Q2 and Q4.

9. A method for improving the output efficiency of a BUCK / BOOST circuit according to claim 1, characterized in that, The controller selects the following mode based on the comparison result of the input voltage and the output voltage: Select BUCK mode when the input voltage is higher than the output voltage; Select BOOST mode when the input voltage is lower than the output voltage; When the input voltage is close to the output voltage, the BUCK / BOOST mode is selected for transition.

10. A method for improving the output efficiency of a BUCK / BOOST circuit according to claim 1, characterized in that, The BUCK / BOOST circuit includes multiple power phases, each of which is equipped with switching devices Q1, Q2, Q3, Q4 and inductors connected thereto. The output terminals of each power phase are connected in parallel, and the switching control signals of each power phase have a fixed phase difference.

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