Control method and system for small-duty-ratio BOOST module based on digital control

Abstract

The invention relates to the technical field of switching power supply analog control, in particular to a control method and system for a small-duty-ratio BOOST module based on digital control, and the method comprises the following steps: S1, carrying out the sampling of the equal-proportion reduced output voltage of an operational amplifier through an ADC analog-to-digital converter, processing the sampled voltage value through a filtering algorithm to obtain an output voltage VO; and S2, carrying out calculation processing on the output voltage VO through a PID control algorithm, and obtaining an expected output voltage through a fixed-frequency adjustment duty ratio PWM and a fixed-duty ratio frequency modulation PFM. Efficient and stable voltage boosting is achieved through double-closed-loop digital control, dynamic response and anti-interference capacity are achieved, the core lies in collaborative design of power conversion and a control strategy, input direct-current voltage is boosted to higher stable output voltage, a double-closed-loop (voltage loop + current loop) control strategy is adopted, and the voltage boosting effect is achieved. And closed-loop adjustment is realized by combining PWM driving and ADC sampling.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of analog control of switching power supply, in particular to a control method and system of a small duty ratio BOOST voltage boosting module based on digital control. BACKGROUND

[0002] Traditional switching power supply mostly adopts analog control mode, and the loop composed of analog devices is easy to change with the change of environment, resulting in reduced reliability of the power supply, and once the design is completed, the control strategy cannot be changed, and many complex control modes require more complex analog circuits. Therefore, digital control technology is adopted, which has fewer peripheral devices, is more flexible in loop design, does not need to modify the hardware circuit, has better anti-interference ability, and improves the reliability.

[0003] At present, the analog control implementation mode adopts feedback resistance to sample the output voltage, an error amplifier module obtains an error amount according to the sampled output voltage signal and a reference voltage, a comparator generates a PWM signal according to the error amount and a sawtooth wave, the PWM signal is processed and then sent to the gate of a switching tube, so as to control the turn-on and turn-off of the switching tube and further adjust the output voltage, so as to stabilize the output voltage. The feedback control loop of the analog mode is also a circuit built by components, the circuit design is very complex, the cost is high, the reliability is low, and the components are easy to be affected by environmental factors, and the parameters of the components will also change to a certain extent with the use of the components. Due to the complexity of design and the difficulty of debugging, the development cycle of the analog control power supply is usually long, and experienced engineers need to invest a lot of time and effort. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a control method and system of a small duty ratio BOOST voltage boosting module based on digital control, which is used to solve the problems of intermittent operation and large ripple of the BOOST circuit when the driving signal has a small duty ratio in the design of analog circuit, and the feedback loop of the BOOST voltage boosting circuit built by analog devices depends on the parameters of the components, and some parameters are easy to be affected by external environmental factors to affect the performance of the system.

[0005] The present application is realized by the following technical solutions: A control method of a small duty ratio BOOST voltage boosting module based on digital control, comprising the following steps: S1, an ADC analog-to-digital converter is used to sample the output voltage reduced in proportion by an operational amplifier, and a voltage value is obtained by filtering algorithm processing the sampled voltage value V O ; S2, the output voltage V OThe PID control algorithm is used for calculation and processing, and the desired output voltage is obtained through fixed frequency adjustment duty cycle PWM and fixed duty cycle frequency adjustment PFM.

[0006] Preferably, in S1, the output voltage obtained by the proportional reduction is within the voltage value range of the normal working port of the digital signal processor, i.e. 0-3.3V.

[0007] Preferably, the PID control algorithm is calculated and processed as follows: S21, the main control chip MCU calculates the error amount by subtracting the output voltage collected by the ADC analog-digital converter from the desired output voltage; S22, the main control chip MCU performs PID operation on the error amount, calculates the required duty cycle through the voltage outer loop and current inner loop algorithm, outputs the duty cycle signal to the digital PWM module generator to generate an accurate PWM waveform; S23, when the output voltage is lower than the reference, the fixed duty cycle is started, the frequency is dynamically calculated through the load current or voltage error, the variable frequency signal is generated through the digital oscillator, and the desired output voltage value is obtained.

[0008] Preferably, in S22, the error amount is operated by the double-loop algorithm of voltage outer loop-current inner loop.

[0009] Preferably, the loop control of voltage outer loop-current inner loop is realized by mathematical modeling operation and simulation building.

[0010] Preferably, in the voltage outer loop, the output voltage V O is used as the feedback signal, and the given value V ref is subtracted to output the current given value Iref .

[0011] Preferably, in the current inner loop, the inductor current i dc is used as the feedback signal, and the output of the voltage loop Iref is used as the current given value, which is subtracted from the inductor current i dc to generate the PWM duty cycle signal through the PID algorithm control.

[0012] A control system of a small duty ratio BOOST boost module based on digital control, comprising an auxiliary power supply, an operational amplifier sampling circuit and a main control chip MCU digital signal processor, the auxiliary power supply is used for supplying power to the main control chip MCU, an ADC analog-to-digital converter samples an output voltage signal, the main control chip MCU digital signal processor calculates and processes the sampled signal through a PID control algorithm, and a fixed frequency duty ratio PWM and a fixed duty ratio frequency PFM are used to obtain the expected output voltage.

[0013] Preferably, the power supply comprises a total power supply, an auxiliary power supply and a three-terminal voltage regulator, the auxiliary power supply provides a 5V DC power supply voltage, and the three-terminal voltage regulator is used to stabilize the 5V DC power supply voltage to 3.3V for power supply.

[0014] Compared with the prior art, the present application has the following beneficial effects: The control method of the small duty ratio BOOST boost module based on digital control uses a digital signal processor to control the MCU, through ADC sampling program design and control algorithm design, when the input voltage changes or the load suddenly changes, the two control methods of fixed frequency duty ratio adjustment and fixed duty ratio frequency adjustment are combined to design a loop, so that the output voltage tends to a given value. In the design, PLECS software is used to model and simulate the power stage circuit and each module of the digital control loop, the feasibility and stability of the design system are verified through simulation, the control program of the digital module is written in Visual Studio software, the function simulation of the digital module is completed, and finally the actual module is combined for experimental debugging.

[0015] Further, a PID control algorithm is used to establish a mathematical model to derive a transfer function, set a PID compensator, and realize code programming design.

[0016] Further, in order to avoid intermittent operation caused by too small duty ratio, a double closed-loop control is used, the current inner loop can quickly track the inductor current and suppress input disturbance, and the voltage loop adjusts the output voltage to the target value.

[0017] Further, the control system of the small duty ratio BOOST boost module based on digital control utilizes the digital signal processor to write the control algorithm to control the output voltage, converts the analog quantity into the digital quantity for processing, effectively avoids the interference of the power module, and simultaneously gives the control signal through the digital signal processor to control the control port of the power supply, thereby controlling the turn-on and turn-off of the power supply. The program control is adopted to replace the hardware circuit, the number of devices is greatly reduced, the circuit reliability is improved, and the maintainability is enhanced. The main control MCU calculates and processes the sampled signal through the PID control algorithm to realize the double-loop algorithm control of the voltage outer loop and the current inner loop. In order to avoid the intermittent working condition caused by the small duty ratio, the double-loop control is adopted, the current inner loop can quickly track the inductor current and suppress the input disturbance, and the voltage loop adjusts the output voltage to the target value. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the overall control block diagram of the small duty ratio BOOST boost module based on digital control.

[0019] Figure 2 is the input voltage sampling in the control method of the small duty ratio BOOST boost module based on digital control; Figure 3 is the output voltage sampling in the control method of the small duty ratio BOOST boost module based on digital control; Figure 4 is the PID controller block diagram design in the control method of the small duty ratio BOOST boost module based on digital control; Figure 5 is the gain curve and phase curve diagram of the model after mathematical modeling in the control method of the small duty ratio BOOST boost module based on digital control; Figure 6 is the gain curve and phase curve diagram of the model after compensation design in the control method of the small duty ratio BOOST boost module based on digital control; Figure 7 is the simulation design model implementation in the control method of the small duty ratio BOOST boost module based on digital control; Figure 8 is the auxiliary source schematic diagram in the control method of the small duty ratio BOOST boost module based on digital control. DETAILED DESCRIPTION

[0020] The application will be further described in detail below in combination with specific embodiments, and the description is an explanation but not a limitation of the application.

[0021] The application discloses a control method of a small-duty-ratio BOOST voltage boosting module based on digital control, and refers to Figures 1-8 and comprises the following steps: S1, an operational amplifier sampling circuit is used to sample output voltage and input voltage, as shown in Figure 2 、 Figure 3 , wherein the value range of the output voltage obtained through the operational amplifier is in proportionally reduced, and is the voltage value range (0-3.3V) of the normal working port of a digital signal processor. The voltage value obtained through the filtering algorithm processing of the sampled voltage value is V O .

[0022] S2, the in-proportionally-reduced output voltage V O is processed by a PID control algorithm, and the control block diagram is as shown in Figure 4 、 Figure 1 , the expected output voltage is obtained by fixed-frequency adjustment of the duty ratio and fixed-duty-ratio frequency adjustment, and the specific process is as follows: S21, the output voltage collected by an ADC analog-digital converter is subtracted from the expected output voltage by the main control chip MCU, and the error amount is obtained.

[0023] S22, the error amount is operated by the main control chip MCU by using a voltage outer loop-current inner loop double-loop algorithm, and the fixed and stable duty ratio is obtained. Specifically, the loop of the voltage outer loop-current inner loop can be calculated by mathematical modeling, and the power mathematical model is Gvd(s), the phase curve and the gain curve of the model are as shown in Figure 5 , and the compensated mathematical model is Gc(s):

[0024]

[0025] In the formula, L is inductance, R is equivalent series resistance, and C is output capacitance.

[0026] In the voltage outer loop, the output voltage V O is taken as a feedback signal, and the given value V ref is subtracted to obtain the output current given value Iref calculated by the PID regulator.

[0027] In the current inner loop, the inductance current i dc is taken as a feedback signal, and the current given value Iref is subtracted to generate the PWM duty ratio signal by the PID regulator, wherein 、 、 The calculation is as follows:

[0028]

[0029]

[0030] In the formula, 、 Two zeros are set, and the zero position can be set, is a critical proportional gain, is a proportional term, is an integral term, is a differential term.

[0031] By setting two zeros, a better phase curve and gain curve are obtained, as shown in Figure 6 .

[0032] S23, when the output voltage is lower than the reference, the fixed duty cycle is started, the frequency is dynamically calculated through the load current or voltage error, the variable frequency signal is generated through the digital oscillator, and the expected output voltage value is obtained. Specifically, in S22, it is checked whether the DCM mode appears, if the DCM mode is reached, the PFM regulation mode is switched, that is, the fixed duty cycle reduces the frequency, so as to avoid the small duty cycle pulse jump, so as to obtain the stable output voltage.

[0033] The application also discloses a control system of a small duty cycle BOOST boost module based on digital control, which comprises an auxiliary power supply, an operational amplifier sampling circuit and a main control chip MCU digital signal processor, the auxiliary power supply is used for supplying power to the main control MCU algorithm digital signal processor, and the double closed loop algorithm operation is performed through the main control chip MCU digital signal processor processing to realize the stability of the module output voltage. The digital signal processor is mainly used for using PFM when DCM appears in light load, that is, the duty cycle intermittently works, using the MCU control to generate a fixed duty cycle square wave, and realizing the output voltage stability through frequency conversion. When the load is heavy, PWM control is used, the fixed switching frequency is used, and the output voltage stability is realized through algorithm control and adjustment of the duty cycle.

[0034] The power supply comprises a total power supply, an auxiliary power supply and a three-terminal voltage stabilizer, the auxiliary power supply (as shown in Figure 8 ) provides a 5V direct current power supply voltage, and the three-terminal voltage stabilizer is used for stabilizing the 5V direct current power supply voltage to 3.3V for power supply.

[0035] The application uses digital signal processor control, designs through ADC sampling program, designs control algorithm, when input voltage changes or load mutation, through the combination of fixed frequency duty cycle adjustment and fixed duty cycle frequency adjustment, designs loop, so that the output voltage tends to the given value. In the design, PLECS software is used to model and simulate each module of the power stage circuit and the digital control loop (as shown in Figure 7 The simulation verifies the feasibility and stability of the design system. The control program of the digital module is written in Visual Studio software, and the function simulation of the digital module is completed. Finally, the experiment is debugged in combination with the actual module. The collected input voltage and output voltage protect the circuit, and the power supply is not damaged when the input and output are overvoltage or undervoltage.

[0036] In the application, the output voltage change caused by load switching or input change is processed by the master chip MCU digital signal processor. The heavy load and light load are distinguished by output current sampling. When the load is light, the fixed frequency duty cycle adjustment method is used. When the load is heavy, the fixed frequency duty cycle adjustment method is used. During the control process, when the load changes suddenly, the current change rate is added to the loop operation by using current feedforward, so that the loop response speed is greatly improved, the load fluctuation is reduced, and the output voltage is stable. When the input dynamic changes, the input voltage feedforward control is added, and the feedforward formula is as follows:

[0037] The duty cycle offset is added to the algorithm output of the MCU digital signal processor control, so that the output voltage is stable.

[0038] The application uses a large number of devices, and the hardware circuit is replaced by program control, so that the circuit reliability is improved, and the maintainability is enhanced.

[0039] The application realizes efficient and stable voltage boosting through double closed loop digital control, has dynamic response and anti-interference ability, and the core is the cooperative design of power conversion and control strategy. The input DC voltage is boosted to a higher stable output voltage, a double closed loop (voltage loop + current loop) control strategy is adopted, PWM control and PFM control are combined, and ADC sampling is used to realize double closed loop regulation.

[0040] The above only describes the preferred embodiments of the application, and does not limit the technical solutions of the application in any way. Those skilled in the art should understand that without departing from the spirit and principles of the application, the technical solutions can be modified and replaced in several simple ways, and these modifications and replacements also belong to the protection scope covered by the claims.

Claims

1. A control method of a digital control-based small duty ratio BOOST step-up module, characterized by, Comprise the following steps: S1, the output voltage of the proportional reduction of operational amplifier is sampled by ADC analog-digital converter, and the voltage value after filtering algorithm processing is obtained V O ; S2, using the master chip MCU digital signal processor will output voltage V O PID control algorithm for calculation and processing, through the fixed frequency adjustment duty cycle PWM and fixed duty cycle frequency modulation PFM to obtain the desired output voltage.

2. The control method of a digital control-based small duty ratio BOOST step-up module according to claim 1, characterized in that, In S1, the numerical range of the output voltage collected by the ADC analog-digital converter is reduced in proportion to the voltage numerical range of the normal working port of the digital signal processor, i.e. 0~3.3V.

3. The control method of a digital control-based small duty ratio BOOST step-up module according to claim 1, characterized in that, The calculation process of the PID control algorithm is as follows: In S21, the main control chip MCU digital signal processor calculates the error amount by subtracting the output voltage collected by the ADC analog-digital converter from the expected output voltage; In S22, the main control chip MCU digital signal processor performs PID operation on the error amount, and calculates the required duty ratio through the voltage outer loop and current inner loop algorithm to output the duty ratio signal to the digital PWM module generator to generate an accurate PWM waveform; In S23, when the output voltage is lower than the reference, the fixed duty ratio is started, the frequency is dynamically calculated through the load current or voltage error, and the variable frequency signal is generated through the digital oscillator to obtain the expected output voltage value.

4. The control method of a digital control-based small duty ratio BOOST step-up module according to claim 3, characterized in that, In S22, the error amount is operated by the double-loop algorithm of the voltage outer loop and the current inner loop.

5. The control method of a digital control-based small duty ratio BOOST step-up module according to claim 4, characterized in that, The loop control of the voltage outer loop and the current inner loop is realized by mathematical modeling operation and simulation building to verify.

6. The control method of a digital control-based small duty ratio BOOST step-up module according to claim 4, characterized in that, In the voltage outer loop, the output voltage V O For the feedback signal, the given value V ref The output current given value Iref is compared and PID regulator 7. The control method of a digitally controlled small duty cycle BOOST step-up module according to claim 4, characterized by, In the inner current loop, the inductor current i dc For the feedback signal, the output signal Iref of the voltage loop is used as the given value of the current loop, which is subtracted from the inductor current i dc After the subtraction, the PWM duty cycle signal is generated through the PID algorithm control.

8. A control system for a digitally controlled small duty cycle BOOST step-up module, characterized by, The power supply includes an auxiliary power supply, an operational amplifier sampling circuit and a main control chip MCU digital signal processor, the auxiliary power supply is used to power the main control chip MCU, the ADC analog-digital converter samples the input voltage and output voltage signal, the main control chip MCU digital signal processor calculates and processes the sampled signal through the PID control algorithm, and obtains the expected output voltage through the fixed frequency adjustment duty ratio PWM and the fixed duty ratio frequency adjustment PFM.

9. The control system for a digitally controlled, low duty cycle BOOST step-up module of claim 8, wherein, The power supply includes a total power supply, an auxiliary power supply and a three-terminal voltage regulator, the auxiliary power supply provides a 5V DC power supply voltage, and the three-terminal voltage regulator is used to stabilize the 5V DC power supply voltage to 3.3V for power supply.

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