CN106411130A - Voltage reduction converter and control method thereof - Google Patents

Abstract

The present invention provides a step-down converter and a control method thereof, wherein the step-down converter is located between a power supply and a load, and the step-down converter includes a main converter and an auxiliary converter connected in parallel, wherein: The main converter includes a first power switch, a second power switch, a first driver, a control strategy module, an LC resonant circuit, and an error circuit; the auxiliary converter includes a third power switch, a fourth power switch, a third driver, A fourth driver, a first comparison circuit, a second comparison circuit, and a second inductance connected in parallel with the first inductance in the LC resonant circuit. The buck converter and its control method provided by the present invention can improve the conversion efficiency of the buck converter.

Description

A buck converter and its control method

technical field

The invention relates to the technical field of voltage processing, in particular to a step-down converter and a control method thereof.

Background technique

A common step-down converter, such as a Buck circuit, can be used to convert a high voltage to a low voltage. The Buck circuit mainly includes freewheeling diodes, switching tubes and inductors, among which freewheeling diodes and switching tubes are the main components that cause efficiency loss. The loss of the freewheeling diode includes conduction loss and recovery loss, and the loss of the switch tube includes conduction loss and switching loss.

In the Buck circuit, the output terminal (for example, the drain) of the switching tube is connected to the cathode of the freewheeling diode and connected to the inductor, that is, the switching tube is connected in series with the freewheeling diode, and the freewheeling diode is connected in parallel with the inductor. The switching tube can control the conduction time of the switching tube through the driving circuit to control the step-down of the inductor, so as to realize the conversion from high voltage to low voltage. When the switching tube is turned off, the current on the inductor can be released through the freewheeling diode.

However, since the freewheeling diode is connected in series with the switching tube, and the voltage drop on the freewheeling diode is very small (for example, 1V), the voltage drop on the switching tube is close to the input voltage, so a switching tube with a larger cut-off voltage must be selected. , so that the switching loss and conduction loss are relatively large, thus making the conversion efficiency of the step-down converter low.

Contents of the invention

The purpose of the embodiments of the present invention is to provide a step-down converter and a control method thereof, which can improve the conversion efficiency of the step-down converter.

In order to achieve the above object, an embodiment of the present invention provides a step-down converter on the one hand, the step-down converter is located between the power supply and the load, and the step-down converter includes a main converter and an auxiliary converter connected in parallel, Wherein: the main converter includes a first power switch, a second power switch, a first driver, a control strategy module, an LC resonant circuit, and an error circuit; the error circuit is used to obtain the output voltage and reference of the LC resonant circuit The error voltage between voltages, and input the error voltage into the control strategy module to generate a pulse phase modulation signal; the first driver controls the first power switch and the second power switch according to the pulse phase modulation signal switch on and off; the auxiliary converter includes a third power switch, a fourth power switch, a third driver, a fourth driver, a first comparison circuit, a second comparison circuit and the first inductor in the LC resonant circuit A second inductance connected in parallel; wherein, the first comparison circuit and the second comparison circuit respectively compare the output voltage of the LC resonant circuit with the first preset voltage and the second preset voltage, and compare their respective The voltages are respectively input into the fourth driver and the third driver, so as to respectively control the on-off of the fourth power switch and the third power switch.

Further, the control strategy module includes at least one of a fuzzy control unit, a neural network control unit, and a linear control unit.

Further, the error circuit has two output ports, one output port is directly connected to the control strategy module, and the other output port is connected to the control strategy module through a differentiator.

Further, the inductance value of the first inductor in the main converter is 10 times that of the second inductor in the auxiliary converter.

Further, the first power switch, the second power switch, the third power switch and the fourth power switch are all field effect transistors.

In order to achieve the above object, another aspect of the present application also provides a control method of a step-down converter, the method includes: the error circuit compares the output voltage of the LC resonant circuit with a reference voltage to obtain an error voltage, and the The error voltage is input to the control strategy module to generate a pulse phase modulation signal; the first driver controls the on-off of the first power switch and the second power switch according to the pulse phase modulation signal; the first comparison circuit and the second comparison circuit respectively The output voltage of the LC resonant circuit is compared with the first preset voltage and the second preset voltage, and the obtained comparison voltages are respectively input into the fourth driver and the third driver to control the fourth power switch and the third power switch respectively. On and off of the power switch.

Further, inputting the error voltage into the control strategy module to generate the pulse phase modulation signal specifically includes: splitting the error voltage into two voltages, wherein one voltage is directly input to the control strategy module, and the other voltage is differentiated Input to the control strategy module after processing.

Further, the control strategy module includes at least one of a fuzzy control unit, a neural network control unit, and a linear control unit.

Further, when the second preset voltage is lower than the output voltage of the LC resonant circuit, and the output voltage of the LC resonant circuit is lower than the first preset voltage, the fourth power switch and the first The three power switches are all in the off state; when the second preset voltage is greater than the output voltage of the LC resonant circuit, the first power switch and the third power switch are in the on state, and the first power switch is in the on state. Both the second power switch and the fourth power switch are in an off state.

Further, when the output voltage of the LC resonant circuit is greater than the first preset voltage, both the first power switch and the third power switch are in an off state, and the second power switch and the The fourth power switches are all in a conducting state.

In the implementation manner of the present application, the structure of the step-down converter may be formed by connecting two main and auxiliary converters in parallel. The function of the main converter is to work when the system has no disturbance or slight disturbance, so that the output voltage ripple is small. The role of the auxiliary converter is to help the main converter suppress output voltage fluctuations when a large disturbance occurs in the system, so that the output voltage can quickly restore stability. In addition, by introducing the control strategy module, fuzzy control methods, neural network control methods or linear control methods can be used in the control strategy, so that the system has strong anti-interference ability and can better suppress the power disturbance of the load, thereby improving the voltage reduction. Converter conversion efficiency.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments of the present invention. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention , for those skilled in the art, other drawings can also be obtained according to the content of the embodiment of the present invention and these drawings without any creative effort.

Fig. 1 is the frame diagram of the step-down converter described in the present embodiment;

Fig. 2 is a schematic circuit diagram of the step-down converter described in the present embodiment;

Fig. 3 is the working diagram of power switch in the present embodiment;

Fig. 4 is a flow chart of the control method of the buck converter described in this embodiment.

Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

detailed description

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. The following description includes various specific details to aid in understanding, but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the disclosure. Also, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration only and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents. .

It should be understood that singular forms also include plural references unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

The present application provides a step-down converter, please refer to FIG. 1 , the step-down converter may be located between a power supply and a load, and the step-down converter may include a main converter and an auxiliary converter connected in parallel. In this embodiment, the role of the main converter is to work when there is no disturbance or slight disturbance in the system, so that the output voltage ripple is small; the role of the auxiliary converter is to help the main converter suppress the output voltage when a large disturbance occurs in the system. voltage fluctuations, so that the output voltage can quickly return to stability.

Please refer to Fig. 2. In Fig. 2, the part below the dotted line may represent the main converter, and the part above the dotted line may represent the auxiliary converter. In this embodiment, the main converter may adopt a negative feedback circuit architecture, and the main converter includes a first power switch M1, a second power switch M2, a first driver, a control strategy module, an LC resonant circuit, and an error circuit. Wherein, the LC resonant circuit may include an inductor L1 and a capacitor C, and an output resistor R may be connected in parallel with the capacitor C. The error circuit may be a subtractor for subtracting the voltage V ₀ output by the LC resonant circuit from the reference voltage V _ref to obtain an error voltage.

In this embodiment, after the error circuit obtains the error voltage between the output voltage V ₀ of the LC resonant circuit and the reference voltage V _ref , the error voltage can be input into the control strategy module to generate a pulse phase modulation signal. The first driver can control the on-off of the first power switch M1 and the second power switch M2 according to the pulse phase modulation signal.

In this embodiment, the error circuit has two output ports, one output port is directly connected to the control strategy module, and the other output port is connected to the control strategy module through a differentiator. This can meet the requirements of the fuzzy controller that the input is the error and the rate of change of the error.

In this embodiment, a certain control strategy can be set in the control strategy module, and the control strategy can be, for example, a fuzzy control strategy, a neural network control strategy, a linear control strategy, etc., so that the control strategy module can At least one of a fuzzy control unit, a neural network control unit and a linear control unit is included. Among them, in the fuzzy control, according to the fuzzy input information converted from the precise quantity, fuzzy reasoning can be carried out according to the language control rules obtained by summarizing the manual control strategy, and the fuzzy output judgment can be given, and then converted into precise Quantity, as the feedback to the control effect of the controlled object (or process). This reflects that in the process of controlling the controlled process, people constantly convert the observed process output accurate quantity into fuzzy quantity, and after obtaining fuzzy judgment through logical reasoning, they convert the fuzzy quantity of judgment into precise quantity to realize manual control. the whole process.

In this embodiment, the fuzzy control strategy can be used to output the duty ratio of the first power switch M1, and the control signals of M1 and M2 can be output through the first driver. , and the design method is simple, and the control effect is relatively good.

In this embodiment, the auxiliary converter includes a third power switch M3, a fourth power switch M4, a third driver, a fourth driver, a first comparison circuit, a second comparison circuit, and the LC resonant circuit. The first inductor L1 is connected in parallel with the second inductor L2. Wherein, the first comparison circuit and the second comparison circuit respectively compare the output voltage V ₀ of the LC resonant circuit with the first preset voltage V ₁ and the second preset voltage V ₂ , and compare the respective comparison voltages input into the fourth driver and the third driver respectively, so as to respectively control the on-off of the fourth power switch M4 and the third power switch M3. As the main purpose of the auxiliary converter is to make the system recover quickly under large disturbances, the value of the inductance L2 in the auxiliary converter should be much smaller than the value of the inductance L1 in the main converter. Specifically, the value of the inductance L2 can be 1/10 of the inductance L1.

In this embodiment, the first power switch M1 , the second power switch M2 , the third power switch M3 and the fourth power switch M4 are all field effect transistors.

Please refer to Figure 3, when V ₂ <V ₀ <V ₁ , the system works in the state of no disturbance or slight disturbance, only the main converter participates in the work, the signals received by M3 and M4 are both 0, and they are both in the off state. The current buck converter is equivalent to a buck converter using feedback control, and the duty cycle of M1 and M2 is approximately constant.

When V ₀ <V ₂ , a large disturbance occurs in the system, the auxiliary converter starts to work, the signal of the driver to M1 and M3 is 1, M1 and M3 are in the conduction state; the signal received by M2 and M4 is 0, M2 , M4 is disconnected until the system restores stability.

When V ₀ >V ₁ , a large disturbance occurs in the system, and the auxiliary converter also joins the work. The signal of the driver to M1 and M3 is 0, and the signal to M2 and M4 is 1, which can force M1 and M3 to be in the disconnected state , M2 and M4 are in a conducting state until the system returns to stability.

Please refer to FIG. 4, the present application also provides a control method of a step-down converter, the method comprising:

S1: the error circuit compares the output voltage of the LC resonant circuit with the reference voltage to obtain an error voltage, and inputs the error voltage into the control strategy module to generate a pulse phase modulation signal;

S2: the first driver controls on-off of the first power switch and the second power switch according to the pulse phase modulation signal;

S3: The first comparison circuit and the second comparison circuit respectively compare the output voltage of the LC resonant circuit with the first preset voltage and the second preset voltage, and respectively input the obtained comparison voltages into the fourth driver and the second driver. Among the three drivers, the on-off of the fourth power switch and the third power switch are respectively controlled.

In one embodiment of the present application, inputting the error voltage into the control strategy module to generate a pulse phase modulation signal specifically includes:

The error voltage is split into two voltages, one of which is directly input to the control strategy module, and the other voltage is input to the control strategy module after differential processing.

In one embodiment of the present application, the control strategy module includes at least one of a fuzzy control unit, a neural network control unit, and a linear control unit.

In one embodiment of the present application, when the second preset voltage is lower than the output voltage of the LC resonant circuit, and the output voltage of the LC resonant circuit is lower than the first preset voltage, the fourth power Both the switch and the third power switch are in an off state;

When the second preset voltage is greater than the output voltage of the LC resonant circuit, both the first power switch and the third power switch are in a conduction state, and the second power switch and the fourth power switch The switches are all off.

In one embodiment of the present application, when the output voltage of the LC resonant circuit is greater than the first preset voltage, both the first power switch and the third power switch are in an off state, and the second Both the power switch and the fourth power switch are in a conduction state.

In the implementation manner of the present application, the structure of the step-down converter may be formed by connecting two main and auxiliary converters in parallel. The function of the main converter is to work when the system has no disturbance or slight disturbance, so that the output voltage ripple is small. The role of the auxiliary converter is to help the main converter suppress output voltage fluctuations when a large disturbance occurs in the system, so that the output voltage can quickly restore stability. In addition, by introducing the control strategy module, fuzzy control methods, neural network control methods or linear control methods can be used in the control strategy, so that the system has strong anti-interference ability, can better suppress the load power disturbance, and thus improve the voltage reduction. Converter conversion efficiency.

It should be noted that the various embodiments of the present disclosure as described above generally involve to some extent the processing of input data and the generation of output data. This input data processing and output data generation can be implemented in hardware or software in combination with hardware. For example, specific electronic components may be employed in a mobile device or similar or related circuitry for implementing the functionality associated with various embodiments of the present disclosure as described above. Alternatively, one or more processors operating in accordance with stored instructions may implement the functions associated with various embodiments of the present disclosure as described above. If so, it is within the scope of this disclosure that these instructions may be stored on one or more non-transitory processor readable media. Examples of the processor-readable medium include read-only memory (ROM), random-access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage devices. In addition, functional computer programs, instructions, and instruction segments for realizing the present disclosure can be easily construed by programmers in the field to which the present disclosure pertains.

Each implementation in this specification is described in a progressive manner, the same and similar parts of each implementation can be referred to each other, and each implementation focuses on the differences from other implementations.

While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that changes may be made without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Various changes in form and detail are made to it.

Claims (10)

1. A step-down converter, the step-down converter is located between a power supply and a load, wherein the step-down converter comprises a main converter and an auxiliary converter connected in parallel, wherein: The main converter includes a first power switch, a second power switch, a first driver, a control strategy module, an LC resonant circuit, and an error circuit; the error circuit is used to obtain a difference between an output voltage of the LC resonant circuit and a reference voltage and input the error voltage into the control strategy module to generate a pulse phase modulation signal; the first driver controls the first power switch and the second power switch according to the pulse phase modulation signal On and off; The auxiliary converter includes a third power switch, a fourth power switch, a third driver, a fourth driver, a first comparison circuit, a second comparison circuit, and a second Inductance; wherein, the first comparison circuit and the second comparison circuit respectively compare the output voltage of the LC resonant circuit with the first preset voltage and the second preset voltage, and input the respective comparison voltages into the The fourth driver and the third driver are used to respectively control the on-off of the fourth power switch and the third power switch. 2. The step-down converter according to claim 1, wherein the control strategy module comprises at least one of a fuzzy control unit, a neural network control unit, and a linear control unit. 3. The step-down converter according to claim 1, wherein the error circuit has two output ports, one of which is directly connected to the control strategy module, and the other output port is connected to the control strategy module through a differentiator. The above control strategy modules are connected. 4. The step-down converter according to claim 1, wherein the inductance value of the first inductor in the main converter is 10 times that of the second inductor in the auxiliary converter. 5 . The step-down converter according to claim 1 , wherein the first power switch, the second power switch, the third power switch and the fourth power switch are field effect transistors. 6. A control method applied to the buck converter according to any one of claims 1 to 5, characterized in that the method comprises: The error circuit compares the output voltage of the LC resonant circuit with the reference voltage to obtain an error voltage, and inputs the error voltage into the control strategy module to generate a pulse phase modulation signal; The first driver controls the on-off of the first power switch and the second power switch according to the pulse phase modulation signal; The first comparison circuit and the second comparison circuit respectively compare the output voltage of the LC resonant circuit with the first preset voltage and the second preset voltage, and respectively input the obtained comparison voltages into the fourth driver and the third driver , to respectively control the on-off of the fourth power switch and the third power switch. 7. The control method of the step-down converter according to claim 6, wherein inputting the error voltage into the control strategy module to generate a pulse phase modulation signal specifically comprises: The error voltage is split into two voltages, one of which is directly input to the control strategy module, and the other voltage is input to the control strategy module after differential processing. 8. The control method of the buck converter according to claim 6, wherein the control strategy module includes at least one of a fuzzy control unit, a neural network control unit, and a linear control unit. 9. The control method of a step-down converter according to claim 6, wherein when the second preset voltage is less than the output voltage of the LC resonant circuit, and the output voltage of the LC resonant circuit is less than the set When the first preset voltage is used, both the fourth power switch and the third power switch are in an off state; When the second preset voltage is greater than the output voltage of the LC resonant circuit, both the first power switch and the third power switch are in a conduction state, and the second power switch and the fourth power switch The switches are all off. 10. The control method of the step-down converter according to claim 6, wherein when the output voltage of the LC resonant circuit is greater than the first preset voltage, the first power switch and the second The three power switches are all in the off state, and the second power switch and the fourth power switch are in the on state.