A switching control method for Boost converter based on output feedback

Abstract

The present invention discloses a switching control method for a Boost converter based on output feedback, belonging to the field of DC-DC Boost converter control technology. The method establishes a state-space switching model of a switching control system, introduces a switching Luenberger observer, observes the system state by sampling the output voltage of the system, designs a switching judgment function based on the observed state, and applies a switching signal to a MOSFET tube through a driving circuit, thereby realizing an output feedback switching control method for a Boost converter. The method of the present application can improve the dynamic characteristics of the system and achieve more flexible control targets. The introduction of output feedback reduces the control cost of the system, and the control target of the system can be achieved only by sampling the output voltage.

Description

Technical Field

[0001] The invention relates to a switching control method of a Boost converter based on output feedback, belonging to the technical field of DC-DC Boost converter control. Background Art

[0002] The boost converter is a typical DC-DC converter used to transform an input voltage and efficiently output a fixed voltage. As a variable DC power supply, it has numerous industrial applications. Traditional DC-DC converter control strategies rely on pulse-width modulation (PWM) based on a small-signal model, achieving steady-state output voltage control through a fixed switching frequency. However, the small-signal model approximates a linear model of the system at its operating point. Therefore, control methods based on this small-signal model can only guarantee the steady-state output of the system at the operating point, but cannot guarantee the dynamic characteristics of the system from the initial point to the operating point. If the dynamic characteristics of the system from the initial point to the operating point cannot be guaranteed, it may lead to a delay in the system reaching steady-state or overshoot, which can damage the device and reduce its service life.

[0003] To improve the system's dynamic characteristics, achieve more flexible control objectives, and reduce overshoot and delay, large-signal model-based control methods, such as variable structure control and state trajectory control, have been applied to DC-DC converter control. However, these large-signal model-based control methods require the acquisition of full system state information, including current and voltage values, which increases system control costs and information redundancy.

[0004] Therefore, the present application proposes a new switching control method for a Boost converter. Summary of the Invention

[0005] In order to improve the dynamic characteristics of the system without increasing the system control cost, the present invention provides a switching control method for a Boost converter based on output feedback. The method is implemented based on a switching control system, which includes: an output voltage acquisition device, a Luenberger observer, a switching judgement device, and a drive circuit;

[0006] The output voltage acquisition device is used to collect the output voltage v of the Boost converter C The Luenberger observer is used to calculate the output voltage v C Observe the state of the Boost converter; the switching judge is used to determine the state of the Boost converter observed by the Luenberger observer and the desired output voltage v refDetermine the state of the switching signal; the driving circuit is used to control the on and off of the MOSFET tube in the Boost converter according to the switching signal to achieve output control of the Boost converter.

[0007] Optionally, the state of the switching signal is determined by a time-varying function σ:

[0008]

[0009] Among them, the positive symmetric matrix P is the switching controller gain; x ref is the desired state of the Boost converter; is the observation state; A i and B i Represents the system parameter matrix of the Boost converter.

[0010] Optionally, the output voltage acquisition device uses an operational amplifier chip LM358 to realize the output voltage v of the Boost converter. C The collection of.

[0011] Optionally, the system uses an STM32F103C8Tx single-chip microcomputer to implement the functions of the Luenberger observer and the switching judge.

[0012] Optionally, data transmission within the system is achieved through a USB-to-serial port chip CH340.

[0013] The present application also provides a switching control method for a Boost converter based on output feedback, the switching control method being implemented based on the above-mentioned switching control system, the method comprising:

[0014] Step S1: Establish a state space switching model of the switching control system:

[0015]

[0016] Among them, the system state x=[i L v C ] · ,i L is the inductor current, v C is the capacitor voltage, i.e. the output voltage; y represents the system output state; A σ 、B σ and C σ , represents the parameter matrix of the system determined according to the state of the switching signal;

[0017] Step S2: According to the expected output voltage v ref Determine the desired state of the Boost converter:

[0018]

[0019] Where R is the load resistance value, E is the power supply input voltage value;

[0020] Step S3, collecting the output voltage v of the Boost converter C , and observe the state of the system according to the output voltage to obtain the observed state of the system:

[0021]

[0022] Where, is the observation state, L σ is the observer gain;

[0023] Step S4: Determine the value of the time-varying function σ based on the observed state output by the observer and the expected state of the closed-loop system, and then determine the state of the switching signal:

[0024]

[0025] Among them, the positive definite symmetric matrix P is the switching controller gain;

[0026] Step S5, controlling the on and off of the MOSFET tube in the Boost converter according to the state of the switching signal, thereby achieving control of the Boost converter.

[0027] Optionally, when the time-varying function σ takes a value of 1, the state of the corresponding switching signal indicates that the MOSFET is turned on; when the time-varying function σ takes a value of 2, the state of the corresponding switching signal indicates that the MOSFET is turned off;

[0028] The corresponding system matrix A σ 、B σ and C σ They are:

[0029] C1=C2=[0 1]

[0030] Where R0 is the inductor series resistance, L is the inductance, and C is the capacitance.

[0031] The beneficial effects of the present invention are:

[0032] By establishing a state-space switching model for a switching control system and introducing a switching Luenberger observer, the system state is observed by sampling the system's output voltage. A switching judgment function is designed using the observed state, and the switching signal is applied to the MOSFET via a drive circuit, thereby implementing an output feedback switching control method for a Boost converter. This method improves the system's dynamic characteristics and achieves more flexible control objectives. The introduction of output feedback reduces the system's control cost, and the system's control objectives can be achieved simply by sampling the output voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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.

[0034] Figure 1 This is a block diagram of the output feedback switching control structure of the Boost converter in one embodiment of the present application.

[0035] Figure 2A 3 is an equivalent circuit diagram of a Boost converter when the switching signal σ=0 in one embodiment of the present application.

[0036] Figure 2B 1 is an equivalent circuit diagram of a Boost converter when the switching signal σ=1 in one embodiment of the present application.

[0037] Figure 3A This is a simulated current state response curve in one embodiment of the present application.

[0038] Figure 3B This is a simulated voltage state response curve in one embodiment of the present application.

[0039] Figure 4A This is a simulated current observation error curve in one embodiment of the present application.

[0040] Figure 4B This is a simulated voltage observation error curve in one embodiment of the present application

[0041] Figure 5A It is the current state response curve of the existing PWM-based PID closed-loop control;

[0042] Figure 5B It is the voltage state response curve of the existing PWM-based PID closed-loop control;

[0043] Figure 6 This is a diagram of the experimental module of a closed-loop control system in one embodiment of the present application.

[0044] Figure 7 This is an experimental output voltage response curve of a closed-loop control system in one embodiment of the present application. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0046] Example 1:

[0047] This embodiment provides a switching control system based on output feedback, see Figure 1 The switching control system is used to realize the control of the Boost converter, and the switching control system includes: an output voltage acquisition device, a Luenberger observer, a desired output voltage setting terminal, a switching controller and a driving circuit; the output voltage acquisition device, the Luenberger observer, the switching judgement device and the driving circuit are connected in sequence; wherein the output voltage acquisition device is used to acquire the output voltage v of the Boost converter C The Luenberger observer is used to observe the state of the Boost converter according to the system output voltage value. The switching controller is used to set the desired output voltage v ref And the Boost converter state observation value Determine the state of the switching signal; the driving circuit is used to control the on or off of the MOSFET tube in the Boost converter according to the state of the switching signal to achieve dynamic control of the Boost converter.

[0048] like Figure 1 As shown in FIG, the Boost converter equivalent circuit includes a power supply E, an inductor L, an inductor series resistor R0, a MOSFET, a freewheeling diode D, and a capacitor C, where R represents the load resistance.

[0049] The output voltage acquisition device can use the operational amplifier chip LM358 to realize the output voltage v of the Boost converter C The system can use the STM32F103C8Tx microcontroller to implement the functions of the Luenberger observer and the switching judge. The data transmission within the system is realized through the USB to serial port chip CH340.

[0050] Example 2:

[0051] This embodiment provides a switching control method for a Boost converter based on output feedback. The method is implemented based on the switching control system described in Embodiment 1 and includes:

[0052] The state space model of the switching control system is established according to the Boost converter equivalent circuit. The turning on and off of the MOSFET tube in the Boost converter equivalent circuit corresponds to the state of the switching signal σ in the switching control system.

[0053] Let the system state x=[i L v C ] · ,i L is the inductor current, v C is the capacitor voltage, such as Figure 1 As shown, the capacitor C is connected in parallel with the load resistor R, so the capacitor voltage v C That is, the output voltage.

[0054] Then the system state space switching model is expressed as:

[0055]

[0056] Where,

[0057] C1=C2=[0 1].

[0058] Where A1, B1, and C1 are the system matrices when the MOSFET is on, A2, B2, and C2 are the system matrices when the MOSFET is off, R0 is the inductor series resistance value, R is the load resistance value, L is the inductance value, C is the capacitance value, and E is the power supply input voltage value.

[0059] The switching control method is based on the input v of the desired output voltage setting terminal ref Determine the desired state of the switching control system:

[0060]

[0061] The Luenberger observer in the switching control method observes the state of the system through the output voltage:

[0062]

[0063] Where, is the observation state, L σ is the observer gain.

[0064] The switching controller in the switching control method determines the state of the system's switching signal by the observed state output by the observer and the expected state of the closed-loop system. Specifically, it is determined according to the time-varying function σ:

[0065]

[0066] Where, the positive definite symmetric matrix P is the switching controller gain.

[0067] The observer gain L in the switching control method i The switching controller gain P can be obtained by solving the following linear matrix inequality conditions:

[0068]

[0069] It can be solved by the LMI toolbox in MATLAB, and the symmetric positive definite matrix can be obtained. and matrix The observer gain is obtained by L i =P -1 R i Please solve.

[0070] Example 3

[0071] This embodiment provides a switching control method for a Boost converter based on output feedback. The method is implemented based on the switching control system described in Embodiment 1 and includes:

[0072] Step 1: Establish a state space switching model of the switching control system, and calculate the system parameter matrix of the state space switching model of the switching control system according to the Boost converter input voltage and component parameters;

[0073] Step 2: Calculate the desired state of the switching control system based on the desired output voltage;

[0074] Step 3: Calculate the observer gain and switching controller gain of the switching control system based on the system parameter matrix determined in step 1 and the desired state calculated in step 2;

[0075] Step 4: Substitute the observer gain into the Luenberger observer to observe the system state. Substitute the switching controller gain into the switching judgment function to determine the system's switching signal, and then act on the MOSFET through the driver to determine whether the MOSFET is on or off.

[0076] In order to verify the effectiveness of the switching control method of the Boost converter based on output feedback, Figure 1 The output feedback switching control structure block diagram of the Boost converter is shown in the figure, and a simulation model is built in MATLAB.

[0077] Figure 3A is the current response curve of the system state response of the Boost converter under the control of the switching control method proposed in this application, Figure 3B This is the output voltage response curve of the system state response of the Boost converter under the control of the switching control method proposed in this application. It can be seen that under the control of the output feedback switching controller, the output voltage can be stabilized to the desired output voltage.

[0078] Figure 4A is the current observation error curve of the Boost converter under the control of the switching control method proposed in this application, Figure 4B This is the output voltage observation error curve of the Boost converter under the control of the switching control method proposed in this application; the observation error refers to the error between the system state and the observed state. It can be seen that the Luenberger observer designed in this application can asymptotically observe the system state.

[0079] Figure 5A It is the current curve of the existing PWM-based PID closed-loop control curve; Figure 5B It is the output voltage curve of the existing PWM-based PID closed-loop control curve. The PID control parameters are adjusted according to the actual output effect through trial and error. For a detailed introduction, please refer to the introduction to PWM technology in "Power Electronics Technology" edited by Wang Zhaoan and Liu Jinjun. It can be seen that the system has a large overshoot, a long stabilization time, and a large steady-state error.

[0080] In order to verify the correctness of the theoretical analysis and simulation results, this application designed Figure 6 The output feedback control platform for the boost converter shown in the figure. The controller uses an STM32F103C8Tx microcontroller to implement the Luenberger observer and switching decision functions. The system clock is 72MHz, and the control timing timer is set to 10kHz. A / D conversion is achieved using the microcontroller's internal A / D converter, voltage sampling is achieved using the LM358 op amp chip, and data transmission is achieved using the CH340 USB-to-serial port chip. The control experimental circuit parameters are the same as the simulation parameters.

[0081] Figure 7 The response curve of the experimental output voltage is given, and it can be seen that the experimental response curve is very close to the simulation response curve.

[0082] In summary, the simulation results are consistent with the experimental results, which verifies the effectiveness of the method of this application.

[0083] Some steps in the embodiments of the present invention may be implemented using software, and the corresponding software program may be stored in a readable storage medium, such as a CD or a hard disk.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit 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 switching control system of a Boost converter based on output feedback, characterized in that: The switching control system includes: an output voltage acquisition device, a Luenberger observer, a switching judge and a driving circuit; The output voltage acquisition device is used to collect the output voltage v of the Boost converter C The Luenberger observer is used to calculate the output voltage v C Observe the state of the Boost converter; the switching judge is used to determine the state of the Boost converter observed by the Luenberger observer and the desired output voltage v ref Determine the state of the switching signal; the driving circuit is used to control the on and off of the MOSFET tube in the Boost converter according to the switching signal to achieve output control of the Boost converter; The state of the switching signal is determined by the time-varying function σ: Among them, the positive symmetric matrix P is the switching controller gain; x ref is the desired state of the Boost converter; is the observation state, i L is the inductor current; A i and B i Represents the system parameter matrix of the Boost converter.

2. The switching control system according to claim 1, wherein: The output voltage acquisition device uses the operational amplifier chip LM358 to realize the output voltage v of the Boost converter C The collection of.

3. The switching control system according to claim 1, characterized in that: The system uses the STM32F103C8Tx single-chip microcomputer to realize the functions of the Luenberger observer and the switching judge.

4. The switching control system according to claim 1, wherein: The data transmission within the system is realized through the USB to serial port chip CH340.

5. A switching control method for a Boost converter based on output feedback, characterized in that: The switching control method is implemented based on the switching control system according to any one of claims 1 to 4, and the method includes: Step S1: Establish a state space switching model of the switching control system: Among them, the system status i L is the inductor current, v C is the capacitor voltage, i.e. the output voltage; y represents the system output state; A σ 、B σ and C σ , represents the parameter matrix of the system determined according to the state of the switching signal; Step S2: According to the expected output voltage v ref Determine the desired state of the Boost converter: Where R is the load resistance value, E is the power supply input voltage value; Step S3, collecting the output voltage v of the Boost converter C , and observe the state of the system according to the output voltage to obtain the observed state of the system: Where, is the observation state, L σ is the observer gain; Step S4: Determine the value of the time-varying function σ based on the observed state output by the observer and the expected state of the closed-loop system, and then determine the state of the switching signal: Among them, the positive definite symmetric matrix P is the switching controller gain; Step S5, controlling the on and off of the MOSFET tube in the Boost converter according to the state of the switching signal, thereby achieving control of the Boost converter.

6. The method according to claim 5, characterized in that When the time-varying function σ takes a value of 1, the state of the corresponding switching signal indicates that the MOSFET is turned on; when the time-varying function σ takes a value of 2, the state of the corresponding switching signal indicates that the MOSFET is turned off; The corresponding system matrix A σ 、B σ and C σ They are: Where R0 is the inductor series resistance, L is the inductance, and C is the capacitance.

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