CN110690821B - Control system and control method for phase shift calculation of buck-boost resonant converter - Google Patents
Control system and control method for phase shift calculation of buck-boost resonant converter Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
- H02M3/1582—Buck-boost converters
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- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/157—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators with digital control
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0009—Devices or circuits for detecting current in a converter
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0012—Control circuits using digital or numerical techniques
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
- H02M1/0054—Transistor switching losses
- H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
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- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention provides a control system and a control method for phase shift calculation of a buck-boost resonant converter, and belongs to the technical field of control of resonant converters. The control system includes: the device comprises a control circuit taking a microcontroller as a core, a GaN driving circuit, a sampling isolation amplifying circuit and a sampling circuit. The control circuit with the microcontroller as the core comprises: the device comprises an AD module, a duty ratio D calculation module, a Phase shift Phase calculation module and an HRPWM module. By calculating the duty ratio and phase shift compensation, the control system can realize zero-voltage switching of the first switching tube and the second switching tube by the compensated phase shift, realize accurate control, eliminate steady-state errors and improve the response speed of the system. The output voltage and the negative current of the buck-boost resonant converter are ensured to stably work in a set range. The control process of the phase shift takes the influence of various factors into consideration, the fluctuation is small, and the negative current control is accurate.
Description
Technical Field
The invention relates to the technical field of control of a buck-boost resonant converter, in particular to a control system and a control method for phase shift calculation of the buck-boost resonant converter.
Background
The Buck-Boost converter has a wide input voltage range, and can be combined with an LLC converter to form the Buck-Boost LLC converter, namely a Buck-Boost resonant converter, in order to improve the working efficiency of the Buck-Boost converter. The buck-boost resonant converter is not only suitable for a wide voltage range, but also has the capability of realizing zero-voltage switching of the switching tube, so that the efficiency of the buck-boost resonant converter is higher than that of the traditional converter.
In the prior art, a control method of a buck-boost resonant converter is mainly a PWM + Phase-Shift regulation mode, that is, a PWM wave for controlling the duty ratio of a switching tube is regulated to stabilize an output voltage at a set value, and Phase Shift is regulated at the same time, so that the switching tube can realize zero-voltage switching under different input voltages and different loads.
The phase shift is determined mainly as follows: constant phase shift methods, table look-up methods, phase shift fitting equations, etc. Although the constant phase shift method is simple to control and convenient to implement, the buck-boost resonant converter has the problems of loss increase and the like due to the fact that zero-voltage switching cannot be guaranteed under a severe working condition; the table look-up method is used for inquiring a preset relation table of phase shift, duty ratio and power, but the situation that corresponding data cannot be found in actual work may occur, and a larger relation table is needed for improving the precision, so that the table look-up time is increased, and the real-time control of the buck-boost resonant converter is not facilitated; the phase shift fitting formula method is a relation of fitting phase shift with respect to input voltage and output current, but the fitting result is not only complex, but also the fitting formula is closely related to the actual working condition, and the problem of inaccurate fitting may occur. Therefore, the research on phase shift calculation of the Buck-Boost LLC converter is significant for improving the real-time control of the Buck-Boost resonant converter.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a control system and a control method for calculating the phase shift of a buck-boost resonant converter.
In order to solve the technical problems, the invention provides the following technical scheme:
the invention provides a control system for calculating the phase shift of a buck-boost resonant converter, which comprises: the device comprises a control circuit taking a microcontroller as a core, a GaN driving circuit, a sampling amplification isolation circuit and a sampling circuit. The three output ends of the sampling circuit are respectively connected with the three input ends of the sampling amplification isolation circuit, the input end of the control circuit taking the microcontroller as a core is connected with the output end of the sampling amplification isolation circuit, the output end of the control circuit taking the microcontroller as a core is connected with the input end of the GaN driving circuit, and the signal output end of the GaN driving circuit is connected with the driving control end of the buck-boost resonant converter;
wherein, use microcontroller as the control circuit of core including: the device comprises an AD module, a duty ratio D calculation module, a Phase shift Phase calculation module and an HRPWM module.
The sampling circuit inputs an input voltage signal, an output current signal and an inductive current signal of the buck-boost resonant converter into the AD module; the AD module converts the analog signals into digital signals and then transmits the digital signals to the duty ratio D calculation module and the Phase shift Phase calculation module through a DMA mode, the duty ratio D calculated by the duty ratio D calculation module and the Phase shift Phase calculated by the Phase shift Phase calculation module are both transmitted to the HRPWM module, and then the HRPWM module generates a driving signal for controlling the GaN driving circuit, so that the buck-boost resonant converter works under the optimal condition.
Further, the microcontroller means MCU or DSP.
The sampling circuit includes: the circuit comprises an input voltage sampling circuit, an inductive current sampling circuit and an output current and voltage sampling circuit.
The input end of the input voltage sampling circuit is connected with the input end of the buck-boost resonant converter, the input end of the output current and voltage sampling circuit is connected with the output end of the buck-boost resonant converter, and the input end of the inductive current sampling circuit is connected with the inductive current output end of the buck-boost resonant converter; the output end of the input voltage sampling circuit is connected with the first input end of the sampling amplification isolating circuit, the output end of the output current and voltage sampling circuit is connected with the second input end of the sampling amplification isolating circuit, and the output end of the inductive current sampling circuit is connected with the third input end of the sampling amplification isolating circuit.
The sampling amplification isolation circuit comprises: the device comprises a first sampling chip, a second sampling chip, a third sampling chip and a fourth sampling chip; each sampling chip has a signal input terminal, a signal ground input terminal and a signal output terminal; the signal ground input ends of the first sampling chip, the second sampling chip, the third sampling chip and the fourth sampling chip are all directly grounded; the signal input end of the first sampling chip is connected with the first input end of the sampling amplification isolation circuit and receives an input voltage sampling signal, and the signal output end of the first sampling chip transmits the input voltage signal subjected to amplification and isolation processing to the AD module; the signal input end of the second sampling chip is connected with the second input end of the sampling amplification isolation circuit and receives the output voltage sampling signal, and the signal output end of the second sampling chip transmits the output voltage signal subjected to amplification and isolation processing to the AD module; the signal input end of the third sampling chip is connected with the second input end of the sampling amplification isolation circuit and receives the output current sampling signal, and the signal output end of the third sampling chip transmits the output current signal subjected to amplification isolation processing to the AD module; the signal input end of the fourth sampling chip is connected with the third input end of the sampling amplification isolation circuit and receives the inductive current sampling signal, and the signal output end of the fourth sampling chip transmits the inductive current signal subjected to amplification isolation processing to the AD module.
The input voltage sampling circuit is a voltage dividing circuit formed by connecting a first resistor and a second resistor in series. One end of the first resistor is connected with the input voltage of the buck-boost resonant converter, the other end of the first resistor is connected with one end of the second resistor at a point A and is connected with a signal input end of a first sampling chip in the sampling amplification isolation circuit, and the other end of the second resistor is connected with an input ground end. The input voltage sampling circuit is connected with the input end of the buck-boost resonant converter circuit. The input voltage sampling circuit transmits the sampled input voltage to the AD module after isolating and amplifying the input voltage.
On the primary winding side of a transformer in the buck-boost resonant converter, the drain electrode of the first switching tube and the grid electrode of the second switching tube are connected to a point E, and the drain electrode of the third switching tube and the grid electrode of the fourth switching tube are connected to a point F. And an inductive current sampling circuit is connected between the point E and the point F. The inductive current sampling circuit consists of a sampling inductor primary winding, a sampling inductor auxiliary winding and a first sampling resistor, wherein the sampling inductor auxiliary winding is connected with the first sampling resistor in parallel, one end of the first sampling resistor is connected with the signal input end of the fourth sampling chip, and the other end of the first sampling resistor is connected with the input ground end. The inductive current sampling circuit isolates and amplifies the sampled inductive current and then transmits the inductive current to the AD module.
The output voltage and current sampling circuit comprises three parallel loops, wherein the first parallel loop is an isolation capacitor, the second parallel loop is formed by connecting a load resistor and a second sampling resistor in series, and the third parallel loop is formed by connecting a third resistor and a fourth resistor in series. One end of the first parallel loop, one end of the second parallel loop and one end of the third parallel loop are connected to the point B, and the other end of the first parallel loop, the other end of the second parallel loop and the other end of the third parallel loop are connected with the input ground end. In the second parallel loop, one end of a load resistor is connected to a point B, and the other end of the load resistor is connected with one end of a second sampling resistor and is also connected with a signal input end of a third sampling chip in the sampling amplification isolating circuit. In the third parallel loop, one end of a third resistor is connected to the point B, and the other end of the third resistor is connected with one end of a fourth resistor and also connected with a signal input end of a second sampling chip in the sampling amplification isolation circuit. The output current and voltage sampling circuit is used for transmitting the sampled output current and output voltage to the AD module after isolating and amplifying the output current and the output voltage.
The control method for calculating the phase shift of the buck-boost resonant converter has the following working principle: the sampling inductor of the buck-boost resonant converter works in a discontinuous state. The current flowing through the sampling inductor in one working period is divided into four stages: the first phase is from the starting time to the first time, the second phase is from the first time to the second time, the third phase is from the second time to the third time, and the fourth phase is from the third time to the fourth time.
Two switch tubes are correspondingly turned on in each stage, and the turn-on sequence is as follows: the first stage starts the second switch tube and the fourth switch tube, the second stage starts the first switch tube and the fourth switch tube, the third stage starts the first switch tube and the third switch tube, and the fourth stage starts the second switch tube and the third switch tube.
The duty cycle is a ratio of a duration from the first time to the third time to a duration of one period, and the phase shift is a ratio of a duration from the start time to the first time to a duration of one period. According to a control strategy, the opening time of the third switch tube and the opening time of the fourth switch tube respectively account for half of the time of one period.
The state of the current flowing through the sampling inductor at each stage is as follows:
in the first stage, the voltage at two ends of the sampling inductor is close to zero, the current of the sampling inductor is basically kept unchanged and is maintained at a negative current level, and the negative current is beneficial to zero-voltage switching of the first switching tube and the second switching tube; in the second stage, the voltage at two ends of the sampling inductor is the input voltage of the buck-boost resonant converter, and the current of the sampling inductor rises to the first current; in the third stage, the voltage at two ends of the sampling inductor is the difference value between the input voltage and the output voltage of the buck-boost resonant converter, the sampling inductor current is increased or decreased, and the sampling inductor current reaches the second current depending on whether the difference value between the input voltage and the output voltage of the buck-boost resonant converter is positive or negative; and in the fourth stage, the voltage at the two ends of the inductor is the output voltage of the negative buck-boost resonant converter, and the current of the sampling inductor is reduced to negative current.
In order to realize zero-voltage switching of the first switching tube, the negative current of the first stage is required to satisfy the following condition:
in the above formula, CdsIs the gate-source parasitic capacitance of the first switch tube, VdsThe voltage across the gate and the source of the first switch tube is equal to the input voltage t of the buck-boost resonant converterdtThe dead time before the first switch tube is conducted is shown.
Therefore, for different input voltages, the magnitude of the negative current needs to be adjusted to satisfy the zero-voltage switching of the first switching tube. For the zero-voltage switch of the second switch tube, it can be satisfied under normal conditions, but under light load, the current of the sampling inductor in the second stage and the third stage rises more slowly, and even the second current reached by the inductive current at the third moment may be smaller than zero.
Therefore, the current of the sampling inductor in one working period satisfies the following relation:
in the above formula, I0Is a negative current, VinFor input voltage, VoutL is the value of the sampling inductance for the output voltage.
The input power satisfies the following relation:
in the above formula, T is the duration of one working cycle, PinIs the input power.
Further, the expression of the input power is as follows:
in the above formula, D is the duty cycle and P is the phase shift.
The expression of negative current is obtained by continuously solving the above expression:
as can be seen from the above equation, the variables affecting the negative current are mainly: input voltage, duty cycle, output voltage, and input power. The duty ratio is obtained by calculating the duty ratio D module, the input voltage is obtained by the input voltage sampling circuit, and the output voltage is obtained by the output voltage and current sampling circuit.
The input power is mainly energy transmitted by a power supply through the sampling inductor when the first switching tube is conducted, the conduction time period of the first switching tube is a second stage and a third stage due to the fact that the input voltage is approximately unchanged, and the current of the sampling inductor changes linearly. Therefore, the current value of the inductor is sampled at the first time, the second time and the third time to calculate the average input current. Input power PinThe following relation is satisfied:
in the above formula, I0The sampling value is negative current and is an inductive current sampling value at a first moment; i is1Is a first current and is an inductive current sampling value at a second moment; i is2Is the second current and is the inductor current sample value at the third moment.
The expression for the phase shift can be derived from the previous formula for the negative current:
furthermore, in order to improve the control precision, the first switch tube and the second switch tube are both switched on and off at zero voltage, so that the phase shift is compensated twice. The first compensation provides a first compensation amount to the phase shift, the second compensation provides a second compensation amount to the phase shift, and the compensated phase shift satisfies the following relation:
Psupplement device=P+ΔP1+ΔP2
In the above formula,. DELTA.P1For the first compensation amount, Δ P2Is the second compensation amount.
The first compensation is performed according to the magnitude of the second current, the second current should be at least greater than zero in order to realize zero-current switching of the second switching tube, if the second current does not satisfy the condition of being greater than zero, the phase shift is reduced, and at this time, the first compensation amount is a negative value; if the second current satisfies the condition of being greater than zero, the phase shift remains unchanged.
The second compensation is based on the PI compensation algorithm. And calculating an integral value of a deviation value between the negative current sampled at the first moment and the set negative current required for realizing zero-voltage switching under the specific input voltage, and multiplying the integral value by a proportional coefficient and an integral coefficient respectively to obtain a second compensation quantity.
The compensated phase shift can not only meet the requirement that the first switching tube and the second switching tube realize zero-voltage switching, but also realize accurate control, eliminate steady-state errors and improve the response speed of the system.
Compared with the prior art, the control system and the control method for calculating the phase shift of the buck-boost resonant converter have the following benefits:
1. the duty ratio and the phase shift can be calculated under different working conditions, and the output voltage and the negative current of the buck-boost resonant converter can be ensured to stably work in a set range.
2. The control process of the phase shift takes the influence of various factors into consideration, the fluctuation is small, and the negative current control is accurate.
3. The accurate control of the phase shift ensures zero-voltage switching of the switch, reduces the loss of the circuit, eliminates steady-state errors and improves the response speed of the system.
Drawings
Fig. 1 is a block diagram of the overall structure of a control system for calculating the phase shift of a buck-boost resonant converter according to the present invention.
Fig. 2 is a schematic circuit diagram of a buck-boost resonant converter and a control system for calculating a phase shift of the buck-boost resonant converter according to the present invention.
Fig. 3 is a step diagram of a control method for phase shift calculation of a buck-boost resonant converter according to the present invention.
Fig. 4 is a waveform diagram of the inductor current at each stage of the buck-boost resonant converter.
Fig. 5 is a graph of voltage waveforms across the inductor at each stage of the buck-boost resonant converter.
Detailed Description
The following detailed description of embodiments of the invention is provided in connection with the accompanying drawings and the detailed description.
Example 1. The overall structure diagram of the control system for calculating the phase shift of the buck-boost resonant converter is shown in fig. 1. The control system includes: the control circuit, the gaN drive circuit, the sampling amplification isolation circuit, the sampling circuit with microcontroller as the core, sampling amplification isolation circuit's three input is connected respectively to sampling circuit's three output, sampling amplification isolation circuit's output is connected to microcontroller as the control circuit's of core input, the input of gaN drive circuit is connected to microcontroller as the control circuit's of core output, the drive control end of step-up and step-down resonant converter is connected to gaN drive circuit's signal output part.
Wherein, use microcontroller as the control circuit of core including: the device comprises an AD module, a duty ratio D calculation module, a Phase shift Phase calculation module and an HRPWM module.
The sampling circuit inputs an input voltage signal, an output current signal and an inductive current signal of the buck-boost resonant converter into the AD module; the AD module converts the analog signals into digital signals and then transmits the digital signals to the duty ratio D calculation module and the Phase shift Phase calculation module through a DMA mode, the duty ratio D calculated by the duty ratio D calculation module and the Phase shift Phase calculated by the Phase shift Phase calculation module are both transmitted to the HRPWM module, and then the HRPWM module generates a driving signal for controlling the GaN driving circuit, so that the buck-boost resonant converter works under the optimal condition.
The duty ratio D calculation module calculates a theoretical duty ratio by detecting an input voltage and a set output voltage target value, and then calculates an actual duty ratio by a PI compensation algorithm. The PI compensation algorithm is to calculate the duty ratio after PI compensation by integrating the deviation between the set value and the actual value of the output voltage and multiplying the integral by a proportional coefficient and an integral coefficient, respectively.
Further, the microcontroller means MCU or DSP.
The sampling circuit includes: the circuit comprises an input voltage sampling circuit, an inductive current sampling circuit and an output current and voltage sampling circuit.
The input end of the input voltage sampling circuit is connected with the input end of the buck-boost resonant converter, the input end of the output current and voltage sampling circuit is connected with the output end of the buck-boost resonant converter, and the input end of the inductive current sampling circuit is connected with the inductive current output end of the buck-boost resonant converter; the output end of the input voltage sampling circuit is connected with the first input end of the sampling amplification isolating circuit, the output end of the output current and voltage sampling circuit is connected with the second input end of the sampling amplification isolating circuit, and the output end of the inductive current sampling circuit is connected with the third input end of the sampling amplification isolating circuit.
In the control system for calculating the phase shift of the buck-boost resonant converter, which is provided by the invention, the circuit schematic diagram of the sampling circuit is shown in fig. 2.
The sampling amplification isolation circuit comprises: the device comprises a first sampling chip, a second sampling chip, a third sampling chip and a fourth sampling chip; each sampling chip has a signal input terminal, a signal ground input terminal and a signal output terminal; the signal ground input ends of the first sampling chip, the second sampling chip, the third sampling chip and the fourth sampling chip are all directly grounded; the signal input end of the first sampling chip is connected with the first input end of the sampling amplification isolation circuit and receives an input voltage sampling signal, and the signal output end of the first sampling chip transmits the input voltage signal subjected to amplification and isolation processing to the AD module; the signal input end of the second sampling chip is connected with the second input end of the sampling amplification isolation circuit and receives the output voltage sampling signal, and the signal output end of the second sampling chip transmits the output voltage signal subjected to amplification and isolation processing to the AD module; the signal input end of the third sampling chip is connected with the second input end of the sampling amplification isolation circuit and receives the output current sampling signal, and the signal output end of the third sampling chip transmits the output current signal subjected to amplification isolation processing to the AD module; the signal input end of the fourth sampling chip is connected with the third input end of the sampling amplification isolation circuit and receives the inductive current sampling signal, and the signal output end of the fourth sampling chip transmits the inductive current signal subjected to amplification isolation processing to the AD module.
The input voltage sampling circuit is a first resistor R1And a second resistor R2A voltage divider circuit formed by connecting in series. A first resistor R1One end of the voltage-boosting and voltage-reducing resonant converter is connected with an input voltage V of the voltage-boosting and voltage-reducing resonant converterinFirst resistance R1And the other end of the first resistor and a second resistor R2One end of the second resistor is connected with the point A and is connected with the signal input end of the first sampling chip in the sampling amplification isolating circuit, and the second resistor R2The other end of the input terminal is connected with the input ground terminal. The input voltage sampling circuit is connected with the input end of the buck-boost resonant converter circuit. The input voltage sampling circuit transmits the sampled input voltage to the AD module after isolating and amplifying the input voltage。
The primary winding side of a transformer in a buck-boost resonant converter, a first switching tube S1And the second switch tube S2Is connected to point E, and a third switching tube S3Drain electrode of and fourth switching tube S4Is connected to point F. And an inductive current sampling circuit is connected between the point E and the point F. The inductor current sampling circuit is composed of a sampling inductor primary winding LbAnd an auxiliary winding L 'of a sampling inductor'bAnd a first sampling resistor Rs1Composition, wherein an inductance auxiliary winding L 'is sampled'bAnd a first sampling resistor Rs1Connected in parallel, a first sampling resistor Rs1One end of the first sampling resistor R is connected with the signal input end of the fourth sampling chips1The other end of the input terminal is connected with the input ground terminal. The inductive current sampling circuit isolates and amplifies the sampled inductive current and then transmits the inductive current to the AD module.
The output voltage and current sampling circuit comprises three parallel loops, wherein the first parallel loop is an isolation capacitor, and the second parallel loop is composed of a load resistor RLAnd a second sampling resistor Rs2Connected in series, the third parallel circuit being formed by a third resistor R3And a fourth resistor R4Are connected in series. One end of the first parallel loop, one end of the second parallel loop and one end of the third parallel loop are connected to the point B, and the other end of the first parallel loop, the other end of the second parallel loop and the other end of the third parallel loop are connected with the input ground end. In the second parallel loop, the load resistance RLOne end of which is connected to point B, a load resistor RLAnd the other end of the first resistor and a second sampling resistor Rs2Is connected with the signal input end of the third sampling chip in the sampling amplification isolation circuit. In a third parallel loop, a third resistor R3One end of which is connected to point B, a third resistor R3And the other end of the first resistor and a fourth resistor R4Is connected with the signal input end of the second sampling chip in the sampling amplification isolation circuit. The output current and voltage sampling circuit is used for transmitting the sampled output current and output voltage to the AD module after isolating and amplifying the output current and the output voltage.
The GaN driving circuit outputs six driving signals, specifically: for buck-boost resonanceThe primary winding side of the transformer in the converter, the first driving signal is input into the first switch tube S1A second driving signal is inputted to the second switching tube S2The third driving signal is input to the third switch tube S3A fourth driving signal is inputted to the fourth switching tube S4A source electrode of (a); for the secondary winding side of the transformer in the buck-boost resonant converter, a fifth driving signal is input to the first transistor Q1The sixth driving signal is inputted to the second transistor Q2Of the substrate.
Example 2. The flow of the control method for calculating the phase shift of the buck-boost resonant converter is shown in fig. 3. The method comprises the following specific steps:
step S1: initialization of each module, clock initialization and initialization of related parameters.
The initialization of each module comprises the following steps: GPIO pins are initialized, and the multi-channel ADC is initialized.
The clock initialization means: the clock of the microcontroller is initialized.
The related parameter initialization comprises the following steps: and configuring a DMA mode for transmitting output AD sampling data, initializing a high-precision timer for generating HRPWM, initializing main parameters of a duty ratio D calculation module and initializing main parameters of a Phase shift Phase calculation module.
Step S2: and (3) soft starting of the buck-boost resonant converter circuit.
And entering a soft start link of the buck-boost resonant converter circuit after initialization, wherein the phase shift is a fixed value, and the duty ratio D is slowly and linearly increased along with time so as to ensure that the output voltage can be stably increased to a preset range.
Step S3: steady state regulation of the buck-boost resonant converter circuit.
And when the output voltage reaches a preset range, the buck-boost resonant converter enters a steady-state regulation link from a soft start link.
Step S4: sampling output voltage VoutOutput current IoutInput voltage VinAnd the inductor current iL。
In consideration of the microcontroller and the sampling circuitUnder the condition that the error of the circuit exists, the data are corrected, and the average value is obtained by sampling for multiple times for filtering. Wherein the inductive current iLIs required to be sampled at a first time t1A second time t2And a third time t3These three points in time are sampled, the sampling signals of which are controlled by a microcontroller.
Step S5: the method comprises two parts of calculation: duty ratio D calculation, phase shift P calculation.
And calculating the duty ratio D, specifically comprising the following steps: by first detecting the input voltage VinAnd a set output voltage VoutThe theoretical duty cycle is calculated by the target value, and then the actual duty cycle is calculated by a PI compensation algorithm. The PI compensation algorithm is to output the voltage VoutIntegral of deviation of set value and actual valueerrAnd the integral is respectively related to the proportionality coefficient KpAnd integral coefficient KiAnd multiplying, namely calculating the duty ratio D after PI compensation.
Phase shift P calculation, comprising: and calculating the negative current required by the zero-voltage switch according to the input voltage, and calculating the input power by three-point sampling of the inductive current. And calculating the phase shift by a formula and performing first compensation and second compensation.
(1) The specific steps of calculating the negative current required for zero voltage switching from the input voltage are as follows:
sampling inductance primary winding L of buck-boost resonant converterbSampling inductor current i working in discontinuous, each stageLAs shown in fig. 4. Current i flowing through the sampling inductor in one working cycleLThe method comprises four stages: the first phase is from the starting instant t0To a first time t1The second stage is from the first time t1To a second time t2The third stage is from the second time t2To a third time t3The fourth stage is from the third time t3To a fourth time t4。
Two switch tubes are correspondingly turned on in each stage, and the turn-on sequence is as follows: the first stage turns on the second switch tube S2And a fourth switching tube S4And the second stage opens the first switch tube S1And fourthSwitch tube S4The third stage is to turn on the first switch tube S1And a third switching tube S3The fourth stage turns on the second switch tube S2And a third switching tube S3。
As can be seen from fig. 4, from a first time t1To a third time t3Has a time length of T2+T3One period T has a duration of T1+T2+T3+T4The ratio of the duty ratio D; from a starting instant t0To a first time t1Has a time length of T1The ratio of which to the duration of one period T is the phase shift P. And a third switching tube S according to a control strategy3Duration of turn-on T3+T4And a fourth switching tube S4Duration of turn-on T1+T2Each taking half the duration of one period T.
In combination with the voltage waveform across the sampling inductor shown in FIG. 5, the current i flowing through the sampling inductorLThe state analysis at each stage is as follows:
in the first phase of fig. 5, the voltage across the sampling inductor is close to zero, and the sampling inductor current remains substantially constant and is maintained at the negative current I as shown in fig. 40Negative current is favorable for the first switching tube S1And a second switching tube S2The zero voltage switch of (2); in the second stage of fig. 5, the voltage across the sampling inductor is the input voltage V of the buck-boost resonant converterinSampling the inductor current up to a first current I1(ii) a In the third stage of fig. 5, the voltage across the sampling inductor is the input voltage V of the buck-boost resonant converterinAnd an output voltage VoutThe sampled inductor current is rising or falling, depending on the input voltage V of the buck-boost resonant converterinAnd an output voltage VoutPlus or minus the difference, sampling the inductor current to a second current I2(ii) a In the fourth stage of fig. 5, the voltage across the inductor is negative-V of the output voltage of the buck-boost resonant converteroutThe sampling inductor current drops to a negative current I0。
According to the realization of zero-voltage switching of the first switching tube, a first phase of negative current I is required0The following conditions are satisfied:
calculating the negative current I under the current input voltage according to the conditions0The set value of (2).
(2) The specific steps of calculating the input power by three-point sampling of the inductive current are as follows:
at a first time t1A second time t2And a third time t3These three time points are relative to the inductor current iLSampling according to a formulaCalculating the input power P of the current period by combining the sampling value of the inductive currentin。
(3) The specific steps of calculating the phase shift by the formula and performing the first compensation and the second compensation are as follows:
according to the formulaCarry-in output voltage VoInput voltage VinOf the sampling value, the calculated value of the duty ratio D and the input power PinTo obtain the theoretical value of the phase shift P.
According to a third time t3The inductance current sampling value I2Whether the zero voltage switch of the second switch tube can be realized is judged according to the size of the first switch tube. If a third moment t occurs3The inductance current sampling value I2If the phase shift P is too small, the phase shift P is required to have a first compensation amount Δ P1(ii) a If the third time t3The inductance current sampling value I2If the requirement is satisfied, the first compensation amount is delta P1Is zero.
Then, the phase shift P is compensated for the second time, which is PI compensation, i.e. for the first time t1Sampled value of inductor current-I0And a negative current I0Is subtracted to obtain the integral value ^ I of the deviation value of the negative currenterrThen multiplied by a scaling factor KpAnd integral coefficient KiThen, a second compensation amount Δ P of the phase shift can be obtained2。
Finally, according to the relation PSupplement device=P+ΔP1+ΔP2To obtain a compensated dependence PSupplement device。
Step S6: and the duty ratio D and the phase shift P are used as control signals and are transmitted to the HRPWM module, and the GaN driving circuit is controlled to realize the control of each switching tube in the buck-boost resonant converter.
Step S7: detecting output current IoIf the change has occurred, the process returns to step S4, otherwise the current status is maintained.
The above embodiments and examples are specific supports for the technical ideas of the control system and the control method for phase shift calculation of the buck-boost resonant converter provided by the present invention, and the protection scope of the present invention cannot be limited thereby.
Claims (4)
1. The control method for calculating the phase shift of the buck-boost resonant converter is characterized by comprising the following steps of: realized by a control system, the control system comprises: the device comprises a control circuit taking a microcontroller as a core, a GaN drive circuit, a sampling amplification isolation circuit and a sampling circuit, wherein three output ends of the sampling circuit are respectively connected with three input ends of the sampling amplification isolation circuit;
the control circuit with the microcontroller as a core comprises: the sampling circuit inputs an input voltage signal, an output current signal and an inductive current signal of the buck-boost resonant converter into the AD module; the AD module converts the analog signals into digital signals and then transmits the digital signals to the duty ratio D calculation module and the Phase shift Phase calculation module through a DMA mode, the duty ratio D calculated by the duty ratio D calculation module and the Phase shift Phase calculated by the Phase shift Phase calculation module are both transmitted to the HRPWM module, and then the HRPWM module generates a driving signal for controlling the GaN driving circuit, so that the buck-boost resonant converter works under the optimal condition;
the control method comprises the following specific steps:
step S1: initializing each module, initializing a clock and initializing related parameters;
the initialization of each module comprises the following steps: initializing GPIO pins and a multi-channel ADC;
the clock initialization means: initializing a clock of the microcontroller;
the related parameter initialization comprises the following steps: configuring a DMA mode for transmitting output AD sampling data, initializing a high-precision timer for generating HRPWM, initializing parameters of a duty ratio D calculation module and initializing parameters of a Phase shift Phase calculation module;
step S2: soft starting of the buck-boost resonant converter circuit;
after initialization, entering a soft start link of a buck-boost resonant converter circuit, wherein the phase shift is a fixed value, and the duty ratio is linearly increased along with time so as to ensure that the output voltage can be increased to a preset range;
step S3: steady state regulation of the buck-boost resonant converter circuit;
when the output voltage reaches a preset range, the buck-boost resonant converter enters a steady-state regulation link from a soft start link;
step S4: sampling output voltage, output current, input voltage and inductive current;
under the condition that the microcontroller and the sampling circuit have errors, the sampling values of the output voltage, the output current, the input voltage and the inductive current are corrected, and the average value is obtained by sampling for multiple times for filtering; the sampling of the inductive current needs to be carried out at three time points of a first time, a second time and a third time, and sampling signals of the sampling are controlled by a microcontroller;
step S5: the method comprises two parts of calculation: duty ratio calculation and phase shift calculation;
duty ratio calculation, the specific steps are as follows: firstly, calculating a theoretical duty ratio by detecting an input voltage and a set output voltage target value, and then calculating an actual duty ratio by a PI compensation algorithm; the PI compensation algorithm is that the deviation of the set value and the actual value of the output voltage is integrated, and the integral is multiplied by a proportional coefficient and an integral coefficient respectively, so that the duty ratio after PI compensation is calculated;
phase shift calculation, comprising the steps of:
the negative current required for zero voltage switching is calculated from the input voltage: the zero-voltage switch of the first switch tube requires that the inductor current sampling value at the first moment meets the following conditions:in the above formula, CdsIs the gate-source parasitic capacitance of the first switch tube, VdsThe voltage across the gate and the source of the first switch tube is equal to the input voltage t of the buck-boost resonant converterdtThe dead time before the first switching tube is conducted is taken as the dead time; calculating a set value of the negative current under the current input voltage according to the conditions;
the input power is calculated from the samples of the inductor current at three times: the inductive current is sampled at the end time of three stages of the inductive current to obtain inductive current sampling values of three time points of a first time, a second time and a third time, and then the inductive current sampling values are obtained according to a formulaCalculating the input power P of the current period by combining the sampling valuesin(ii) a In the formula I0For the first moment in time of the inductor current sample value, I1For the value of the inductor current sample at the second moment, I2Is a third moment of the inductor current sample value, VinFor the input voltage, T is the duration of one duty cycle, T1、t2And t3Respectively a first time, a second time and a third time;
and then calculating the phase shift by a formula and performing first compensation and second compensation: according to the formulaSubstituting the output voltage, the sampling value of the input voltage, the calculated value of the duty ratio and the calculated value of the input power to obtain the theoretical value of the phase shift; wherein P is phase shift, L is sampling inductance value, and VoutIs the output voltage, D is the duty cycle; judging whether the zero voltage switch of the second switching tube can be realized according to the magnitude of the inductive current sampling value at the third moment; if the inductive current sampling value at the third moment is less than zero so that the situation that whether the second switching tube can realize zero-voltage switching cannot be judged, the phase shift needs to have a first compensation amount; if the inductive current sampling value at the third moment meets the requirement, the first compensation quantity is zero; then, performing second compensation on the phase shift, wherein the second compensation is PI compensation, namely, the sampling value of the inductive current at the first moment is deviated from the set value of the negative current, the integral value of the deviation is obtained, and then a proportionality coefficient and an integral coefficient are multiplied respectively to obtain a second compensation quantity of the phase shift; finally, according to the relation PSupplement device=P+ΔP1+ΔP2Obtaining a compensated phase shift, wherein: delta P1For the first compensation amount, Δ P2For the second compensation, PSupplement deviceTo compensate for the post phase shift;
step S6: the duty ratio and the phase shift are used as control signals and are transmitted to the HRPWM module, and the GaN driving circuit is controlled to realize the control of each switching tube in the buck-boost resonant converter;
step S7: and detecting whether the output current changes or not, if so, returning to the step S4, and if not, maintaining the current state.
2. The control method for phase shift calculation of a buck-boost resonant converter according to claim 1, characterized by comprising the following steps: the microcontroller refers to an MCU or a DSP.
3. The control method for phase shift calculation of a buck-boost resonant converter according to claim 1, characterized by comprising the following steps: the sampling circuit includes: the device comprises an input voltage sampling circuit, an inductive current sampling circuit and an output current and voltage sampling circuit;
the input end of the input voltage sampling circuit is connected with the input end of the buck-boost resonant converter, the input end of the output current and voltage sampling circuit is connected with the output end of the buck-boost resonant converter, and the input end of the inductive current sampling circuit is connected with the inductive current output end of the buck-boost resonant converter; the output end of the input voltage sampling circuit is connected with the first input end of the sampling amplification isolating circuit, the output end of the output current and voltage sampling circuit is connected with the second input end of the sampling amplification isolating circuit, and the output end of the inductive current sampling circuit is connected with the third input end of the sampling amplification isolating circuit.
4. The control method for phase shift calculation of a buck-boost resonant converter according to claim 1, characterized by comprising the following steps: the sampling amplification isolation circuit comprises: the device comprises a first sampling chip, a second sampling chip, a third sampling chip and a fourth sampling chip; each sampling chip has a signal input terminal, a signal ground input terminal and a signal output terminal; the signal ground input ends of the first sampling chip, the second sampling chip, the third sampling chip and the fourth sampling chip are all directly grounded; the signal input end of the first sampling chip is connected with the first input end of the sampling amplification isolation circuit and receives an input voltage sampling signal, and the signal output end of the first sampling chip transmits the input voltage signal subjected to amplification and isolation processing to the AD module; the signal input end of the second sampling chip is connected with the second input end of the sampling amplification isolation circuit and receives the output voltage sampling signal, and the signal output end of the second sampling chip transmits the output voltage signal subjected to amplification and isolation processing to the AD module; the signal input end of the third sampling chip is connected with the second input end of the sampling amplification isolation circuit and receives the output current sampling signal, and the signal output end of the third sampling chip transmits the output current signal subjected to amplification isolation processing to the AD module; the signal input end of the fourth sampling chip is connected with the third input end of the sampling amplification isolation circuit and receives the inductive current sampling signal, and the signal output end of the fourth sampling chip transmits the inductive current signal subjected to amplification isolation processing to the AD module;
on the primary winding side of a transformer in the buck-boost resonant converter, the drain electrode of the first switching tube and the source electrode of the second switching tube are connected to a point E, and the drain electrode of the third switching tube and the source electrode of the fourth switching tube are connected to a point F; the inductance current sampling circuit is composed of a sampling inductance primary winding, a sampling inductance auxiliary winding and a first sampling resistor, wherein the sampling inductance primary winding is connected between a point E and a point F, the sampling inductance auxiliary winding is connected with the first sampling resistor in parallel, one end of the first sampling resistor is connected with the signal input end of the fourth sampling chip, and the other end of the first sampling resistor is connected with the input ground end.
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