Control method and device applied to buck converter
Patent Information
- Application Number
- CN202311058125.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-21
- Publication Date
- 2025-02-21
Smart Images
Figure CN119496388A_ABST
Abstract
Description
Technical Field
[0001] The embodiments of this specification relate to the field of adjustable direct current power supplies, and in particular, to a control method and device for a buck converter. Background Art
[0002] Generally speaking, a DC power supply is not only required to have high efficiency, small size, high power, etc., but also to have good dynamic performance and the ability to provide a wide range of adjustable output voltage. Buck converter is a step-down converter, and the circuit structure often has more switches, inductors and capacitors, resulting in a larger circuit size and unable to meet the requirements of lightweight products.
[0003] Therefore, there is an urgent need for a control method for buck converters that can increase the switching frequency of the switch tube, thereby reducing the size of the product and meeting the need for portability. Summary of the invention
[0004] The purpose of the embodiments of this specification is to provide a control method and device for a buck converter to reduce the volume of the product and meet the demand for portability.
[0005] To achieve the above objectives, on the one hand, an embodiment of the present specification provides a control method applied to a buck converter, including:
[0006] According to the switching state of the switch tube in the buck converter, a discrete time model for iteratively calculating the state variable value corresponding to a switching cycle is obtained;
[0007] The input matrix in the discrete time model corresponding to the current switching cycle is obtained by a polynomial fitting method;
[0008] Based on the discrete time model, according to the input matrix corresponding to the current switching cycle and the state variable value corresponding to the current switching cycle, the state variable value of the next switching cycle is calculated;
[0009] Calculating an optimal duty cycle of the next switching cycle according to the state variable value of the next switching cycle;
[0010] When the next switching cycle arrives, the output voltage is controlled to reach the target voltage according to the optimal duty cycle.
[0011] Preferably, the step of obtaining a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle according to the switching state of the switch tube in the buck converter further comprises:
[0012] Different state intervals are obtained according to the switching states of different switching tubes in the buck converter;
[0013] Derived state equations corresponding to different state intervals according to the equivalent circuit diagrams of the different state intervals;
[0014] According to the state equations corresponding to the different state intervals, a discrete time model for iteratively calculating the state variable value corresponding to a switching cycle is obtained.
[0015] Preferably, the step of obtaining a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle according to the state equations corresponding to the different state intervals further comprises:
[0016] The discrete time model for iteratively calculating the state variable value corresponding to a switching cycle is expressed by the following formula:
[0017] x n+1 =Fx n +G(d)U in ;
[0018] in,
[0019] σ3=L(λ1-λ2);
[0020]
[0021] n is the nth switching cycle, n+1 is the n+1th switching cycle, x n+1 is the state variable value of the n+1th switching cycle, F is the constant matrix related to the system parameters of the buck converter, x n is the state variable value of the nth switching cycle, G(d) is the input matrix, d is the duty cycle, U in is the input voltage, L is the inductance of the inductor in the buck converter, T s is the duration of a switching cycle, C is the capacitance of the capacitor in the buck converter, and R is the load resistance in the buck converter.
[0022] Preferably, the step of obtaining the input matrix in the discrete time model corresponding to the current switching cycle by the polynomial fitting method further includes:
[0023] Performing polynomial fitting on elements of an input matrix in a discrete time model to obtain a functional relationship between the elements of the input matrix and the duty cycle;
[0024] According to the functional relationship and the duty cycle of the current switching cycle, an input matrix in the discrete time model corresponding to the current switching cycle is calculated.
[0025] Preferably, the functional relationship between the elements of the input matrix and the duty cycle includes: a linear functional relationship and a quadratic functional relationship between two elements in the input matrix and the duty cycle respectively.
[0026] Preferably, performing polynomial fitting on the elements of the input matrix of the current switching cycle in the discrete time model to obtain the functional relationship between the elements of the input matrix and the duty cycle further comprises:
[0027] The functional relationship between the elements of the input matrix and the duty cycle is obtained by the following formula:
[0028]
[0029] Among them, g 11 (d) is the linear function relationship between the element in the first row and first column of the input matrix and the duty cycle, g 21 (d) is the quadratic function relationship between the elements in the second row and first column of the input matrix and the duty cycle, d is the duty cycle, q1, q2, p1, p2, and p3 are all related to the duty cycle and are fitting coefficients.
[0030] Preferably, the step of calculating the state variable value of the next switching cycle based on the discrete time model according to the input matrix corresponding to the current switching cycle and the state variable value corresponding to the current switching cycle further includes:
[0031] The discrete time model is expanded, and the inductor current and the capacitor voltage of the next switching cycle are calculated according to the input matrix corresponding to the current switching cycle and the inductor current and the capacitor voltage of the current switching cycle.
[0032] Preferably, the step of expanding the discrete time model and calculating the inductor current and capacitor voltage of the next switching cycle according to the input matrix corresponding to the current switching cycle and the inductor current and capacitor voltage of the current switching cycle as the state variable value of the next switching cycle further includes:
[0033] The inductor current and capacitor voltage of the next switching cycle are calculated by the following formula as the state variable values of the next switching cycle:
[0034]
[0035] Where n is the current switching cycle, n+1 is the next switching cycle, and x n+1 is the state variable value of the next switching cycle, F is the constant matrix related to the system parameters of the buck converter, x n is the state variable value of the current switching cycle, G(d n ) is the input matrix corresponding to the current switching cycle, d nis the optimal duty cycle of the current switching cycle, U in is the input voltage, is the expansion symbol, i L(n+1) is the inductor current of the next switching cycle, u c(n+1) is the capacitor voltage of the next switching cycle, i Ln is the inductor current of the current switching cycle, u cn is the capacitor voltage in the current switching cycle, f 11 、f 12 、f 21 、f 22 are all elements of the constant matrix F, g 11 (d n ), g 21 (d n ) is the element value of the input matrix under the duty cycle of the current switching cycle.
[0036] Preferably, the step of calculating the optimal duty cycle of the next switching cycle according to the state variable value of the next switching cycle further comprises:
[0037] Construct a calculation formula for the target voltage based on the inductor current and capacitor voltage of the next switching cycle;
[0038] The calculation formula is transposed and the sign is changed to obtain a transformation formula;
[0039] According to the transformation formula, the optimal duty cycle of the next switching cycle is calculated.
[0040] Preferably, the step of performing transposition and sign change on the calculation formula to obtain a transformation formula further comprises:
[0041]
[0042] Among them, d opt is the optimal duty cycle of the next switching cycle, g 21 (do pt ) is the element value of the input matrix in the discrete time model under the optimal duty cycle of the next switching cycle, U ref is the target voltage, f 21 、f 22 are all elements of the constant matrix related to the system parameters of the buck converter, i L(n+1) is the inductor current of the next switching cycle, u c(n+1) is the capacitor voltage in the next switching cycle, U in is the input voltage.
[0043] On the other hand, an embodiment of the present specification provides a control device applied to a buck converter, the control device comprising:
[0044] A sampling module is used to obtain a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle according to the switching state of the switch tube in the buck converter;
[0045] A fitting module, used for obtaining an input matrix in a discrete time model corresponding to a current switching cycle by a polynomial fitting method;
[0046] A state variable value calculation module, configured to calculate the state variable value of the next switching cycle based on the discrete time model, according to the input matrix corresponding to the current switching cycle, and the state variable value corresponding to the current switching cycle;
[0047] An optimal duty cycle calculation module, used to calculate the optimal duty cycle of the next switching cycle according to the state variable value of the next switching cycle;
[0048] The control module is used to control the output voltage to reach the target voltage according to the optimal duty cycle when the next switching cycle arrives.
[0049] On the other hand, the embodiments of the present specification further provide a control system applied to a buck converter, the control system comprising: a buck converter, and a control device for controlling the buck converter as described above.
[0050] On the other hand, a power supply device is provided with: the control system as described above.
[0051] On the other hand, the embodiments of the present specification further provide an electrical appliance, wherein the electrical appliance is provided with: the power supply device as described above.
[0052] Through the method of the embodiment of this specification, according to the switching state of the switch tube in the buck converter, the discrete time model is obtained, and the input matrix in the discrete time model is obtained by using the polynomial fitting method. Based on the discrete time model and the input matrix, as well as the state variable value of the current switching cycle, the state variable value of the next switching cycle is calculated to further calculate the optimal duty cycle of the next switching cycle. Since the buck converter has a one-beat delay, when the next switching cycle arrives, the corresponding optimal duty cycle can be used to control the output voltage to reach the target voltage. The method of the embodiment of this specification can shorten the calculation time of the optimal duty cycle of the next switching cycle, and the switching cycle can also be reduced, that is, it can be said that a higher switching frequency is achieved, so that the selection of inductance and capacitance is reduced accordingly, thereby reducing the size of the charger, and the charger becomes light and compact, and convenient to use.
[0053] In order to make the above and other purposes, features and advantages of the present specification more obvious and easy to understand, the following specifically cites preferred embodiments and describes them in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0054] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0055] Figure 1 A flow chart of a control method applied to a buck converter provided in an embodiment of this specification is shown;
[0056] Figure 2 A circuit diagram of a buck converter provided in an embodiment of this specification is shown;
[0057] Figure 3 A schematic diagram of a process for obtaining a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle provided in an embodiment of this specification is shown;
[0058] Figure 4A An equivalent circuit diagram of a first state interval provided in an embodiment of this specification is shown;
[0059] Figure 4B An equivalent circuit diagram of the second state interval provided in the embodiment of this specification is shown;
[0060] Figure 5 A schematic diagram of a process of obtaining an input matrix in a discrete time model corresponding to a current switching cycle by a polynomial fitting method in an embodiment of this specification is shown;
[0061] Fig. 6A A schematic diagram showing a linear function relationship between the elements in the first row and the first column of the input matrix and the duty cycle provided in an embodiment of this specification is shown;
[0062] Figure 6B A schematic diagram showing the quadratic function relationship between the elements in the second row and the first column of the input matrix and the duty cycle provided in an embodiment of this specification is shown;
[0063] Figure 7 A schematic diagram of a process for calculating an optimal duty cycle for the next switching cycle according to a state variable value for the next switching cycle in an embodiment of this specification is shown;
[0064] Figure 8 A schematic diagram of the module structure of a control device applied to a buck converter provided in an embodiment of this specification is shown.
[0065] Description of the accompanying symbols:
[0066] 100. Sampling module;
[0067] 200, fitting module;
[0068] 300. State variable value calculation module;
[0069] 400. Optimal duty cycle calculation module;
[0070] 500. Control module. DETAILED DESCRIPTION
[0071] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the embodiments of this specification.
[0072] Generally speaking, a DC power supply is not only required to have high efficiency, small size, high power, etc., but also to have good dynamic performance and the ability to provide a wide range of adjustable output voltage. Buck converter is a step-down converter, and the circuit structure often has more switches, inductors and capacitors, resulting in a larger circuit size and unable to meet the requirements of lightweight products.
[0073] In order to solve the above problems, an embodiment of the present specification provides a control method applied to a buck converter. Figure 1 This is a flow chart of a control method applied to a buck converter provided in an embodiment of this specification. This specification provides method operation steps as described in the embodiment or flow chart, but more or fewer operation steps may be included based on conventional or non-creative labor. The order of steps listed in the embodiment is only one way of executing the order of many steps and does not represent the only execution order. When the system or device product is executed in practice, it can be executed in the order of the method shown in the embodiment or the drawings or in parallel.
[0074] It should be noted that the terms "first", "second", etc. in the description and claims of the embodiments of this specification and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of this specification described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, device, product or equipment that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.
[0075] Reference Figure 1 , the embodiment of this specification provides a control method applied to a buck converter, including:
[0076] S101: according to the switching state of the switch tube in the buck converter, a discrete time model for iteratively calculating the state variable value corresponding to a switching cycle is obtained;
[0077] S102: obtaining an input matrix in a discrete time model corresponding to the current switching cycle by a polynomial fitting method;
[0078] S103: Based on the discrete time model, according to the input matrix corresponding to the current switching cycle and the state variable value corresponding to the current switching cycle, calculate the state variable value of the next switching cycle;
[0079] S104: Calculating an optimal duty cycle of the next switching cycle according to the state variable value of the next switching cycle;
[0080] S105: When the next switching cycle arrives, the output voltage is controlled to reach the target voltage according to the optimal duty cycle.
[0081] Reference Figure 2 The buck converter includes two switches S1 and S2, an inductor L, a capacitor C, and a load resistor R. The input voltage is U in , the output voltage is U o , wherein the drain of the switch tube S1 is connected to the positive electrode of the input voltage, the source of the switch tube S2 is connected to the drain of the switch tube S2, the source of the switch tube S2 is connected to the negative electrode of the input voltage, one end of the inductor is connected to the drain of the switch tube S2, and the other end is connected to the capacitor, the other end of the capacitor is connected to the source of the switch tube S2, and the load resistor is connected in parallel with the capacitor.
[0082] The driving signals of the switch tubes S1 and S2 are opposite, and their switch states are also opposite. If S1 is turned on, S2 is turned off, and if S1 is turned off, S2 is turned on. Taking S1 as an example, the time it takes for S1 to complete the opening and closing is a switching cycle. The timing starts from the moment S1 is turned on. After it has completed the opening and closing, S1 is turned on again and the next switching cycle begins.
[0083] The switching states of S1 and S2 are complementary. Taking S1 as an example, if the opening time of S1 is t on , its off time is t off , then the switching period of S1 is T s =t on +t off , the duty cycle is t on / T s When the switching cycle is determined, once the duty cycle is obtained, the conduction time of the switch tube S1 is determined. The DSP controller provides switching signals to S1 and S2. When the duty cycle is determined, the drive signals of S1 and S2 are automatically generated by the DSP controller. The duty cycle determines the output voltage. The purpose of adjusting the duty cycle is to adjust the output voltage.
[0084] The target voltage is a known voltage. After being controlled by the control method, the output voltage of the buck converter should be the target voltage. For example, when a mobile phone needs to be charged, the voltage required by the mobile phone is 5V, and the target voltage is 5V. The output voltage of the buck converter needs to be controlled to 5V to charge the mobile phone.
[0085] Specifically, when controlling, the DSP controller can be used for control. The function of the DSP is to provide a driving signal to the switch tube of the buck circuit and to realize some calculation functions. In the embodiment of this specification, steps S101-S105 are all realized by the DSP controller. Since the buck converter has a one-beat delay that will delay an entire switching cycle, the optimal duty cycle of the next switching cycle must be calculated in advance and then loaded into the controller, waiting for the next switching cycle.
[0086] Through the method of the embodiment of this specification, according to the switching state of the switch tube in the buck converter, the discrete time model is obtained, and the input matrix in the discrete time model is obtained by using the polynomial fitting method. Based on the discrete time model and the input matrix, as well as the state variable value of the current switching cycle, the state variable value of the next switching cycle is calculated to further calculate the optimal duty cycle of the next switching cycle. Since the buck converter has a one-beat delay, when the next switching cycle arrives, the corresponding optimal duty cycle can be used to control the output voltage to reach the target voltage. The method of the embodiment of this specification can shorten the calculation time of the optimal duty cycle of the next switching cycle, and the switching cycle can also be reduced, that is, it can be said that a higher switching frequency is achieved, so that the selection of inductance and capacitance is reduced accordingly, thereby reducing the size of the charger, and the charger becomes light and compact, and convenient to use.
[0087] The parameter values of the buck converter can be shown in Table 1.
[0088] Table 1
[0089]
[0090] In the embodiments of this specification, refer to Figure 3 , the step of obtaining a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle according to the switching state of the switch tube in the buck converter further includes:
[0091] S201: obtaining different state intervals according to the switching states of different switching tubes in the buck converter;
[0092] S202: According to the equivalent circuit diagrams of the different state intervals, write circuit KCL and KVL equations to derive state equations corresponding to the different state intervals;
[0093] S203: According to the state equations corresponding to the different state intervals, a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle is obtained.
[0094] According to the switching state of the switch tubes S1 and S2, it can be divided into two state intervals. When the switch tube S1 is turned on and S2 is turned off, it corresponds to the first state interval. The equivalent circuit diagram of the first state interval is as follows: Figure 4A As shown, when the switch tube S1 is turned off and S2 is turned on, it corresponds to the second state interval. The equivalent circuit diagram of the second state interval is as follows Figure 4B shown.
[0095] Specifically, the step of obtaining a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle according to the state equations corresponding to the different state intervals further includes:
[0096] The discrete time model for iteratively calculating the state variable value corresponding to a switching cycle is expressed by the following formula:
[0097] x n+1 =Fx n +G(d)U in (1)
[0098] in,
[0099]
[0100] σ3=L(λ1-λ2);
[0101]
[0102] n is the nth switching cycle, n+1 is the n+1th switching cycle, x n+1 is the state variable value of the n+1th switching cycle, F is the constant matrix related to the system parameters of the buck converter, x n is the state variable value of the nth switching cycle, G(d) is the input matrix, d is the duty cycle, U in is the input voltage, L is the inductance of the inductor in the buck converter, T s is the duration of a switching cycle, C is the capacitance of the capacitor in the buck converter, and R is the load resistance in the buck converter.
[0103] It can be seen from the above formula (1) that the constant matrix F has nothing to do with the duty cycle, and the input matrix G(d) is related to the duty cycle. As the duty cycle changes, the elements in the input matrix will also change accordingly.
[0104] In the embodiments of this specification, refer to Figure 5 , the step of obtaining the input matrix in the discrete time model corresponding to the current switching cycle by the polynomial fitting method further includes:
[0105] S301: performing polynomial fitting on elements of an input matrix in a discrete time model to obtain a functional relationship between the elements of the input matrix and the duty cycle;
[0106] S302: According to the functional relationship and the duty cycle of the current switching cycle, an input matrix in a discrete time model corresponding to the current switching cycle is calculated.
[0107] The functional relationship between the elements of the input matrix and the duty cycle includes: a linear functional relationship and a quadratic functional relationship between two elements in the input matrix and the duty cycle respectively.
[0108] Specifically, performing polynomial fitting on the elements of the input matrix of the current switching cycle in the discrete time model to obtain the functional relationship between the elements of the input matrix and the duty cycle further includes:
[0109] The functional relationship between the elements of the input matrix and the duty cycle is obtained by the following formula:
[0110]
[0111] Among them, g 11 (d) is the linear function relationship between the element in the first row and first column of the input matrix and the duty cycle, g 21 (d) is the quadratic function relationship between the elements in the second row and first column of the input matrix and the duty cycle, d is the duty cycle, q1, q2, p1, p2, and p3 are all related to the duty cycle and are fitting coefficients.
[0112] Reference Fig. 6A and Figure 6B It can be seen that the fitting results can be obtained through the fitting function toolbox of the software MTATLAB. 11 (d) and g 21 (d) is an element in the input matrix, so the analytical result can be calculated by the input matrix G(d).
[0113] Among them, q1 = 0.2268, q2 = -0.00014444, p1 = -0.006426, p2 = 0.01287, p3 = -1.355 × 10 -6 .
[0114] In an embodiment of the present specification, the step of calculating the state variable value of the next switching cycle based on the discrete time model according to the input matrix corresponding to the current switching cycle and the state variable value corresponding to the current switching cycle further includes:
[0115] The discrete time model is expanded, and the inductor current and the capacitor voltage of the next switching cycle are calculated according to the input matrix corresponding to the current switching cycle and the inductor current and the capacitor voltage of the current switching cycle.
[0116] Specifically, the discrete time model is expanded, and according to the input matrix corresponding to the current switching cycle, and the inductor current and capacitor voltage of the current switching cycle, the inductor current and capacitor voltage of the next switching cycle are calculated as the state variable value of the next switching cycle, further including:
[0117] The inductor current and capacitor voltage of the next switching cycle are calculated by the following formula as the state variable values of the next switching cycle:
[0118]
[0119] Where n is the current switching cycle, n+1 is the next switching cycle, and x n+1 is the state variable value of the next switching cycle, F is the constant matrix related to the system parameters of the buck converter, x n is the state variable value of the current switching cycle, G(d n ) is the input matrix corresponding to the current switching cycle, d n is the optimal duty cycle of the current switching cycle, U in is the input voltage, is the expansion symbol, i L(n+1) is the inductor current of the next switching cycle, u c(n+1) is the capacitor voltage of the next switching cycle, i Ln is the inductor current of the current switching cycle, u cn is the capacitor voltage in the current switching cycle, f 11 、f 12 、f 21 、f 22 are all elements of the constant matrix F, g 11 (d n ), g 21 (d n ) is the element value of the input matrix under the duty cycle of the current switching cycle.
[0120] Calculating the state variable value of the next switching cycle is to calculate the inductor current and capacitor voltage of the next switching cycle.
[0121] It should be noted that due to the one-shot delay, the optimal duty cycle of the current switching cycle is calculated in the previous switching cycle. After the optimal duty cycle of the current switching cycle is calculated in the previous switching cycle, it can be stored in the register for use when the current switching cycle arrives. 11 、f 12 、f 21 、f 22 are all elements of a constant matrix, namely the element of the first row and first column, the element of the first row and second column, the element of the second row and first column, and the element of the second row and second column of the constant matrix. The specific values are related to the switching frequency of the buck converter.
[0122] In the embodiments of this specification, refer to Figure 7 , the step of calculating the optimal duty cycle of the next switching cycle according to the state variable value of the next switching cycle further comprises:
[0123] S401: constructing a calculation formula for a target voltage according to the inductor current and capacitor voltage of the next switching cycle;
[0124] S402: Shifting the terms and changing the signs of the calculation formula to obtain a transformation formula;
[0125] S403: Calculate the optimal duty cycle of the next switching cycle according to the transformation formula.
[0126] Among them, the calculation formula for the target voltage is constructed as follows:
[0127] U ref =f 21 i L(n+1) +f 22 u c(n+1) +g 21 (d opt ) in (4)
[0128] Among them, d opt is the optimal duty cycle of the next switching cycle, g 21 (do pt ) is the element value of the input matrix in the discrete time model under the optimal duty cycle of the next switching cycle, U ref is the target voltage, f 21 、f 22 are all elements of the constant matrix related to the system parameters of the buck converter, i L(n+1) is the inductor current of the next switching cycle, u c(n+1) is the capacitor voltage in the next switching cycle, U in is the input voltage.
[0129] After transposing and changing the sign, the transformation formula is:
[0130]
[0131] Among them, d opt is the optimal duty cycle of the next switching cycle, g 21 (do pt ) is the element value of the input matrix in the discrete time model under the optimal duty cycle of the next switching cycle, U ref is the target voltage, f 21 、f 22 are all elements of the constant matrix related to the system parameters of the buck converter, i L(n+1) is the inductor current of the next switching cycle, u c(n+1) is the capacitor voltage in the next switching cycle, U in is the input voltage.
[0132] The optimal duty cycle d for the next switching cycle can be calculated by the above formula (5): opt .
[0133] Based on the above-mentioned control method applied to a buck converter, an embodiment of this specification also provides a control device applied to a buck converter. The device may include a system (including a distributed system), software (application), module, component, server, client, etc. using the method described in the embodiment of this specification and a device combined with necessary implementation hardware. Based on the same innovative concept, the device in one or more embodiments provided in the embodiment of this specification is as described in the following embodiments. Since the implementation scheme and method of the device to solve the problem are similar, the implementation of the specific device in the embodiment of this specification can refer to the implementation of the aforementioned method, and the repetitions will not be repeated. As used below, the term "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.
[0134] Specifically, Figure 8 This is a schematic diagram of a module structure of an embodiment of a control device for a buck converter provided in an embodiment of this specification, referring to Figure 8 As shown, a control device applied to a buck converter provided in an embodiment of the present specification includes: an acquisition module 100, a fitting module 200, a state variable value calculation module 300, an optimal duty cycle calculation module 400, and a control module 500.
[0135] The sampling module 100 is used to obtain a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle according to the switching state of the switch tube in the buck converter;
[0136] The fitting module 200 is used to obtain the input matrix in the discrete time model corresponding to the current switching cycle by a polynomial fitting method;
[0137] The state variable value calculation module 300 is used to calculate the state variable value of the next switching cycle based on the discrete time model, according to the input matrix corresponding to the current switching cycle, and the state variable value corresponding to the current switching cycle;
[0138] An optimal duty cycle calculation module 400, configured to calculate an optimal duty cycle of a next switching cycle according to a state variable value of the next switching cycle;
[0139] The control module 500 is used to control the output voltage to reach the target voltage according to the optimal duty cycle when the next switching cycle arrives.
[0140] Based on the above control device applied to a buck converter, an embodiment of the present specification further provides a control system applied to a buck converter, the control system comprising: a buck converter, and the above control device for controlling the buck converter.
[0141] Based on the above control device applied to a buck converter, an embodiment of the present specification further provides a power supply device, wherein the power supply device is provided with: the above control system.
[0142] Based on the above control device applied to a buck converter, an embodiment of the present specification further provides an electrical appliance, wherein the electrical appliance is provided with: the above power supply device.
Claims
1. A control method for a buck converter, characterized in that: include: According to the switching state of the switch tube in the buck converter, a discrete time model for iteratively calculating the state variable value corresponding to a switching cycle is obtained; The input matrix in the discrete time model corresponding to the current switching cycle is obtained by a polynomial fitting method; Based on the discrete time model, according to the input matrix corresponding to the current switching cycle and the state variable value corresponding to the current switching cycle, the state variable value of the next switching cycle is calculated; Calculating an optimal duty cycle of the next switching cycle according to the state variable value of the next switching cycle; When the next switching cycle arrives, the output voltage is controlled to reach the target voltage according to the optimal duty cycle.
2. The control method for buck converter according to claim 1, characterized in that: The step of obtaining a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle according to the switching state of the switch tube in the buck converter further includes: Different state intervals are obtained according to the switching states of different switching tubes in the buck converter; Derived state equations corresponding to different state intervals according to the equivalent circuit diagrams of the different state intervals; According to the state equations corresponding to the different state intervals, a discrete time model for iteratively calculating the state variable value corresponding to a switching cycle is obtained.
3. The control method for buck converter according to claim 2, characterized in that: The step of obtaining a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle according to the state equations corresponding to the different state intervals further includes: The discrete time model for iteratively calculating the state variable value corresponding to a switching cycle is expressed by the following formula: x n+1 =Fx n +G(d)U in ; in, σ3=L(λ1-λ2); n is the nth switching cycle, n+1 is the n+1th switching cycle, x n+1 is the state variable value of the n+1th switching cycle, F is the constant matrix related to the system parameters of the buck converter, x n is the state variable value of the nth switching cycle, G(d) is the input matrix, d is the duty cycle, U in is the input voltage, L is the inductance of the inductor in the buck converter, T s is the duration of a switching cycle, C is the capacitance of the capacitor in the buck converter, and R is the load resistance in the buck converter.
4. The control method for buck converter according to claim 1, characterized in that: The step of obtaining the input matrix in the discrete time model corresponding to the current switching cycle by the polynomial fitting method further includes: Performing polynomial fitting on elements of an input matrix in a discrete time model to obtain a functional relationship between the elements of the input matrix and the duty cycle; According to the functional relationship and the duty cycle of the current switching cycle, an input matrix in the discrete time model corresponding to the current switching cycle is calculated.
5. The control method for buck converter according to claim 4, characterized in that: The functional relationship between the elements of the input matrix and the duty cycle includes: a linear functional relationship and a quadratic functional relationship between two elements in the input matrix and the duty cycle respectively.
6. The control method for buck converter according to claim 5, characterized in that: The performing polynomial fitting on the elements of the input matrix of the current switching cycle in the discrete time model to obtain the functional relationship between the elements of the input matrix and the duty cycle further includes: The functional relationship between the elements of the input matrix and the duty cycle is obtained by the following formula: Among them, g 11 (d) is the linear function relationship between the element in the first row and first column of the input matrix and the duty cycle, g 21 (d) is the quadratic function relationship between the elements in the second row and first column of the input matrix and the duty cycle, d is the duty cycle, q1, q2, p1, p2, and p3 are all related to the duty cycle and are fitting coefficients.
7. The control method for buck converter according to claim 1, characterized in that: The step of calculating the state variable value of the next switching cycle based on the discrete time model and the input matrix corresponding to the current switching cycle and the state variable value corresponding to the current switching cycle further includes: The discrete time model is expanded, and the inductor current and the capacitor voltage of the next switching cycle are calculated according to the input matrix corresponding to the current switching cycle and the inductor current and the capacitor voltage of the current switching cycle.
8. The control method for buck converter according to claim 7, characterized in that: Expanding the discrete time model, calculating the inductor current and capacitor voltage of the next switching cycle according to the input matrix corresponding to the current switching cycle and the inductor current and capacitor voltage of the current switching cycle as the state variable value of the next switching cycle further includes: The inductor current and capacitor voltage of the next switching cycle are calculated by the following formula as the state variable values of the next switching cycle: Where n is the current switching cycle, n+1 is the next switching cycle, and x n+1 is the state variable value of the next switching cycle, F is the constant matrix related to the system parameters of the buck converter, x n is the state variable value of the current switching cycle, G(d n ) is the input matrix corresponding to the current switching cycle, d n is the optimal duty cycle of the current switching cycle, U in is the input voltage, is the expansion symbol, i L(n+1) is the inductor current of the next switching cycle, u c(n+1) is the capacitor voltage of the next switching cycle, i Ln is the inductor current of the current switching cycle, u cn is the capacitor voltage in the current switching cycle, f 11 、f 12 、f 21 、f 22 are all elements of the constant matrix F, g 11 (d n ), g 21 (d n ) is the element value of the input matrix under the duty cycle of the current switching cycle.
9. The control method for buck converter according to claim 1, characterized in that: The step of calculating the optimal duty cycle of the next switching cycle according to the state variable value of the next switching cycle further comprises: Construct a calculation formula for the target voltage based on the inductor current and capacitor voltage of the next switching cycle; The calculation formula is transposed and the sign is changed to obtain a transformation formula; According to the transformation formula, the optimal duty cycle of the next switching cycle is calculated.
10. The control method for buck converter according to claim 9, characterized in that: The step of performing term shifting and sign changing of the calculation formula to obtain a transformation formula further includes: Among them, d opt is the optimal duty cycle of the next switching cycle, g 21 (d opt ) is the element value of the input matrix in the discrete time model under the optimal duty cycle of the next switching cycle, U ref is the target voltage, f 21 、f 22 are all elements of the constant matrix related to the system parameters of the buck converter, i L(n+1) is the inductor current of the next switching cycle, u c(n+1) is the capacitor voltage in the next switching cycle, U in is the input voltage.
11. A control device for a buck converter, characterized in that: The control device comprises: A sampling module is used to obtain a discrete time model for iteratively calculating a state variable value corresponding to a switching cycle according to the switching state of the switch tube in the buck converter; A fitting module, used for obtaining an input matrix in a discrete time model corresponding to a current switching cycle by a polynomial fitting method; A state variable value calculation module, configured to calculate the state variable value of the next switching cycle based on the discrete time model, according to the input matrix corresponding to the current switching cycle, and the state variable value corresponding to the current switching cycle; An optimal duty cycle calculation module, used to calculate the optimal duty cycle of the next switching cycle according to the state variable value of the next switching cycle; The control module is used to control the output voltage to reach the target voltage according to the optimal duty cycle when the next switching cycle arrives.
12. A control system applied to a buck converter, characterized in that: The control system comprises: a buck converter, and a control device for controlling the buck converter as claimed in claim 11.
13. A power supply device, characterized in that: The power supply device is provided with: a control system as described in claim 12.
14. An electrical appliance, characterized in that: The electrical appliance is provided with: a power supply device as described in claim 13.