Method and apparatus for generating PWM waveform of buck circuit

Abstract

A method and apparatus for generating a PWM waveform of a BUCK circuit. The method comprises: measuring a voltage Vin of an input end of an energy storage inductor and a voltage Vout of an output end of the energy storage inductor (S110); using Vin and Vout to determine a voltage VLcon in a freewheeling state of and a voltage VLinj in a magnetizing state of the two ends of the energy storage inductor, and using VLcon and VLinj to calculate a freewheeling time Tcon of the energy storage inductor (S120); and using the value of Tcon to generate a freewheeling switch transistor on-off control waveform PWML whose duty cycle varies with Tcon (S130).

Description

Buck circuit PWM waveform generation method and device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on February 2, 2024, with application number 202410148116.3, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of DC-DC power supplies, and in particular to a method and device for generating a PWM waveform in a BUCK circuit. Background Art

[0003] Direct current to direct current (DC-DC) converters using step-down (buck) converter circuits (such as buck circuits) are widely used in power electronic equipment. To improve converter reliability and prevent switch burnout, it is necessary to control and optimize the dead time between the upper and lower bridge arm switches in the buck circuit. Furthermore, to improve the conversion efficiency of synchronous buck circuits and prevent switch damage, it is necessary to accurately control the on-time of the lower bridge arm, which serves as the freewheeling current for the energy storage inductor.

[0004] A synchronous buck circuit consists of upper and lower bridge-arm switching transistors, an energy storage inductor, and an output filter capacitor. During operation, a pulse-width modulation (PWM) signal controls the alternating conduction of two metal-oxide-semiconductor (MOS) transistors, thereby controlling the charging and discharging of the inductor. Unlike an asynchronous buck circuit architecture, a synchronous buck circuit uses MOS switches for freewheeling, achieving lower freewheeling power consumption than a freewheeling diode.

[0005] In the synchronous BUCK circuit, PWMH is used to represent the driving waveform of the upper bridge arm MOS tube Q1, PWML is used to represent the driving waveform of the lower bridge arm MOS tube Q2, and I L The inductor current waveform is shown in Figure 2. The circuit operates as follows: when PWMH is high and PWML is low, the upper-side MOS transistor Q1 turns on and the lower-side MOS transistor Q2 turns off, causing the inductor current to rise. When PWMH is low and PWML is high, the upper-side MOS transistor Q1 turns off and the lower-side MOS transistor Q2 turns on, allowing the inductor current to continue flowing through Q2. There is a short period of time on the PWMH and PWML waveforms where both PWMH and PWML are low simultaneously. This period is the dead time.

[0006] Dead time exists in synchronous buck circuits because synchronization is relative. It's impossible to perfectly control the upper and lower arm switches, with one on and the other off. Therefore, the controller follows a principle: it's better to have both upper and lower arm switches off simultaneously, preventing current from flowing, than to have both switches on simultaneously, causing current to short-circuit directly from the power input through the upper and lower arm switches to the power ground. Therefore, a certain dead time must exist between the drive signals for the upper and lower arm switches to prevent a short-circuit between the power input and the power ground through the upper and lower arm switches. During this dead time, neither upper nor lower arm switch is conducting. Any controller must avoid simultaneous turning on of both upper and lower arm switches. If this occurs, damage to both switches is very likely. To avoid this, a period of time must elapse after turning off the upper arm switch Q1 before turning on the lower arm switch. During the dead time, the inductor mainly relies on the parasitic diode of the lower arm switch tube or the external diode connected in parallel with the lower arm switch tube for freewheeling.

[0007] In the related technologies, such as Chinese patent applications with application numbers CN201811301863.7 and CN202211149632.5, and the conventional PWM controller chip LM5146, although different methods are provided for optimizing the dead time setting, and a method for determining the freewheeling termination time point by monitoring the change in the voltage across the lower arm switch tube Q2 is also provided, the method is complex and the device cost is high. Summary of the Invention

[0008] The present application provides a BUCK circuit PWM waveform generation method and device to overcome the defects of DC-DC conversion technology in related technologies.

[0009] This application provides a BUCK circuit PWM waveform generation method, including: measuring the energy storage inductor input voltage V in and the output voltage of the energy storage inductor V out ; Use the V in and V out Determine the voltage V across the energy storage inductor in the freewheeling state Lcon And the voltage V in the magnetized state Linj ; Use the V Lcon and V Linj Calculate the freewheeling time T of the energy storage inductor con ; Use the T con The value of the duty cycle generated by T con The changing freewheeling switch on-off control waveform PWML.

[0010] The present application provides a BUCK circuit PWM waveform generation device, comprising: a measurement module, a freewheeling time calculation module and a PWM waveform generation module; wherein,

[0011] The measurement module is set to measure the input voltage V of the energy storage inductor in and the output voltage V of the energy storage inductor out ;

[0012] The freewheeling time calculation module is set to use the V in and V out Determine the voltage V across the energy storage inductor in the freewheeling state Lcon And the voltage V in the magnetized state Linj ; Use the V Lcon and V Linj Calculate the freewheeling time T of the energy storage inductor con ;

[0013] PWM waveform generation module, set to use the T con The value of the duty cycle generated by T con The changing freewheeling switch on-off control waveform PWML. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG1 is a flow chart of a method for generating a PWM waveform of a BUCK circuit according to an embodiment of the present application;

[0015] FIG2 is a schematic diagram of a PWM waveform generating circuit in a BUCK circuit according to an embodiment of the present application;

[0016] FIG3 is a schematic diagram of a freewheeling time determination mechanism of a BUCK circuit according to an embodiment of the present application;

[0017] FIG4 is a schematic diagram of PWM waveform generation of a BUCK circuit according to an embodiment of the present application;

[0018] FIG5 is a schematic diagram of a BUCK circuit PWM waveform generation circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0019] This application provides a BUCK circuit PWM waveform generation method and device to overcome the defects of DC-DC conversion technology in related technologies, such as simplifying the method of determining the freewheeling time length and being able to generate a PWM waveform that can achieve duty cycle adjustment and freewheeling time adjustment.

[0020] The method and device provided in this application are described below with reference to the accompanying drawings.

[0021] The present application provides a BUCK circuit PWM waveform generation method embodiment, comprising the following steps: measuring the energy storage inductor input terminal voltage V in and the output voltage of the energy storage inductor V out ; Use the V in and V out Determine the voltage V across the energy storage inductor in the freewheeling state Lcon And the voltage V in the magnetized state Linj ; Use the V Lcon and V Linj Calculate the freewheeling time T of the energy storage inductor con ; Use the T con The value of the duty cycle generated by T con The changing freewheeling switch on-off control waveform PWML.

[0022] For example, the voltage V at the input terminal of the energy storage inductor is in is the voltage between the input terminal of the energy storage inductor and the power supply ground in the magnetized state; the output terminal voltage V out It is the voltage of the output end of the energy storage inductor to the power ground in the freewheeling state; the input end of the energy storage inductor is the injection end of the magnetizing current or freewheeling current of the energy storage inductor; the output end of the energy storage inductor is the outflow end of the magnetizing current or freewheeling current of the energy storage inductor.

[0023] The BUCK circuit described in this application is a synchronous BUCK circuit that uses a lower-arm switch tube for freewheeling.

[0024] The freewheeling switch tube described in this application is the lower bridge arm opening tube of the BUCK circuit. The conduction time T of the freewheeling switch tube / lower bridge arm opening tube is ON That is the time when the freewheeling switch tube participates in the freewheeling.

[0025] Under normal circumstances, the time T for the freewheeling switch to participate in the freewheeling ON Less than the freewheeling time T of the energy storage inductor con .

[0026] For example, T con =T d1 +T ON +T △ ; Among them, T con is the freewheeling time of the energy storage inductor; T d1 T is the dead time between the falling edge of the energy storage inductor magnetizing switch on / off control waveform PWMH and the rising edge of the energy storage inductor freewheeling switch on / off control waveform PWML; △ For T con The time correction value T △ Used to ensure the continuous flow of the energy storage inductor I conWhen the voltage reaches zero or before it reaches zero, the freewheeling switch is turned off to ensure that no reverse current flows into the energy storage inductor.

[0027] The method provided in this embodiment measures the voltage V at the input terminal of the energy storage inductor. in and the output voltage of the energy storage inductor V out , including: measuring the voltage of the drain or source of the upper arm switch tube of the BUCK circuit relative to the power ground as the input voltage of the energy storage inductor V in ;Measure the voltage across the output capacitor of the BUCK circuit as the output voltage of the energy storage inductor V out .

[0028] For example, referring to FIG. 2 , an input terminal Ti of the inductor L1 is electrically connected to the source of the upper-arm switching tube Q1 and the drain of the lower-arm switching tube Q2. An output terminal To of the inductor L1 is electrically connected to the positive electrode of the output capacitor C1, the negative electrode of the bypass diode D3, and the positive output terminal T1 of the buck circuit. A negative output terminal T2 of the buck circuit is electrically connected to the positive electrode of the bypass diode D3, the negative electrode of the output capacitor C1, and the power ground GND of the buck circuit. A bypass diode D1 is connected in parallel between the source and drain of the upper-arm switching tube Q1, and a bypass diode D2 is connected in parallel between the source and drain of the lower-arm switching tube Q2. The input power source of the buck circuit is a photovoltaic module, which can be a single photovoltaic panel or a series combination of multiple photovoltaic panels. The input power source of the buck circuit can also be a battery or a power source after AC / DC conversion.

[0029] In Figure 2, the measurement module 1 measures the voltage at the output terminal To of the energy storage coil and the input voltage of the BUCK circuit; the measurement module 1 uses the voltage measurement result of the output terminal To of the energy storage coil as the output terminal voltage V out , the measured result of the BUCK circuit input voltage is used as the energy storage inductor input voltage V in In Figure 2, the measurement module 1 measures the voltage V at the input terminal of the energy storage inductor at the drain of the upper arm switch tube Q1 of the BUCK circuit. in The measurement result includes the on-state voltage of the upper arm switch tube Q1; the measurement module 1 measures the voltage V at the input terminal of the energy storage inductor at the source of the upper arm switch tube Q1 of the BUCK circuit. in , the measurement result does not include the on-state voltage of the upper arm switch tube Q1.

[0030] The freewheeling time calculation module 2 obtains the energy storage inductor output terminal voltage V from the measurement module 1 out And the voltage at the input of the energy storage inductor V in The measured value of the upper bridge arm switch Q1 is obtained from the PWM waveform generation module 3, and the on-time value is used as the duration T of the energy storage inductor magnetizing current.inj , use V in 、V out 、T inj And the relationship (V in -V out ) / V out =T con / T inj , solve for the freewheeling time T con and the freewheeling time T con The value is sent to the PWM waveform generation module 3.

[0031] The PWM waveform generation module 3 sends the duration T of the inductor magnetizing current to the freewheeling time calculation module 2. inj The value of the freewheeling time T is received from the freewheeling time calculation module 2 con The value of the freewheeling time T con The value of determines the time parameter of the freewheeling tube Q2 driving waveform PWML. The PWM waveform generation module 3 will use T inj The PWMH waveform is determined by the value of T con The PWML waveform determined by the value is sent to the driving module 4.

[0032] The driving module 4 converts the PWMH sent by the PWM waveform generating module 3 into the signal form required to drive the upper bridge arm switch tube Q1, and converts the PWML sent by the PWM waveform generating module 3 into the signal form required to drive the lower bridge arm switch tube Q2.

[0033] In some embodiments, the chip model of the driving module 4 is NSD1224 or LM5108.

[0034] The method provided in this embodiment uses the V in and V out Determine the voltage V across the energy storage inductor in the freewheeling state Lcon And the voltage V in the magnetized state Linj , for example, including the following steps:

[0035] Use the measured value V in With the measured value V out The difference between the two ends of the energy storage inductor is taken as the voltage at both ends of the energy storage inductor in the magnetized state, and (V in -V out )=V Linj ; Use the measured value V out As the voltage across the energy storage inductor in the freewheeling state, we get V out =V Lcon ;

[0036] The use of V Lcon and VLinj Calculate the freewheeling time T of the energy storage inductor con , for example, including the following steps:

[0037] According to the relationship that the voltage across the inductor is proportional to the rate of change of the current in the inductor, the relationship is obtained: the voltage V across the energy storage inductor in the magnetized state Linj The voltage V across the energy storage inductor in the freewheeling state Lcon The ratio is equal to the magnetizing current I of the energy storage inductor inj The rate of change S1 and the energy storage inductor freewheeling current I con The ratio of the rate of change S2, that is, V Linj / V Lcon =S1 / S2=(V in -V out ) / V out ;

[0038] According to the magnetizing current I inj The rate of change S1 is the slope of the rising slope of the magnetizing current, and the freewheeling current I con The rate of change S2 is the slope of the freewheeling current falling slope. The magnetizing current rising slope and the freewheeling current falling slope are the hypotenuses of two adjacent right triangles, respectively. As well as the definition of the slope, we get the relationship: V Linj / V Lcon =S1 / S2=T con / T inj =(V in -V out ) / V out ;

[0039] The energy storage inductor input voltage V obtained by measurement module 1 in The measured value and the output voltage of the energy storage inductor V out The measured value and the magnetizing current time T determined by the PWM waveform generation module 3 inj The value is taken as a known parameter, and the geometric relationship (V in -V out ) / V out =T con / T inj Solve for the freewheeling time T con The numerical value of .

[0040] For example, (V in -V out ) is the voltage across the energy storage inductor in the magnetized state, V out It is the voltage across the energy storage inductor in the freewheeling state, V out It is also the output voltage of the energy storage inductor, T con is the freewheeling time, T injis the magnetization time.

[0041] For example, referring to FIG3 , in which PWMH is a pulse width modulation waveform generated by the PWM waveform generation module 3 to control the on-off time of the upper arm switch tube Q1, T cyc It represents the cycle of PWMH. The oblique shaded part is the high level time width of PWMH, which is also the conduction time width of the upper bridge arm switch tube Q1 and the magnetizing current duration T of the energy storage inductor L1. inj .

[0042] For example, T cyc The value of is between 5 and 20 microseconds. In this embodiment, T cyc The value is 10 microseconds.

[0043] The L1 voltage waveform is the waveform of the voltage across the energy storage inductor L1 in the magnetizing state and the freewheeling state. inj The voltage across the internal energy storage inductor L1 is (V in -V out ), during the freewheeling current duration T con The voltage across the internal energy storage inductor L1 is (-V out ). The L1 current waveform shows the ratio of the magnetizing current slope S1 to the freewheeling current slope S2 (S1 / S2) and the freewheeling current duration T of the energy storage inductor L1 in the magnetizing state and the freewheeling state. con and the magnetizing current duration T inj Ratio T con / T inj For example, it can be seen from FIG3 that triangle OAE and triangle BAE are two adjacent right triangles, and the common vertex E of these two adjacent right triangles is the maximum magnetizing current I of the energy storage inductor L1. max The slope S1 of the hypotenuse OE of the triangle OAE is the rate of change of the magnetizing current, and the slope S2 of the hypotenuse BE of the triangle BAE is the rate of change of the freewheeling current. According to the definition of slope, the slope S1 of the hypotenuse OE = AE / OA, and the slope S2 of the hypotenuse BE = AE / AB; the length of the base OA of the triangle OAE is the duration T of the magnetizing current. inj , the length of the base AB of the triangle BAE is the duration of the freewheeling current T con From the above, we can get: S1 / S2=(AE / OA) / (AE / AB)=AB / OA=T con / T inj ;

[0044] In the L1 current waveform, from point O to point C on the time axis is a PWM (pulse width modulation) cycle, which is also the cycle in which the energy storage inductor L1 completes one magnetization and freewheeling cycle.

[0045] The method given in this embodiment uses T con The value of the duty cycle generated by T con The variable freewheeling switch on-off control waveform PWML includes:

[0046] Using the relation T ON =T con -T d1 -T △ Determine the conduction time width T of Q2 ON value, where T △ It is T con Time correction value; T d1 It is the first dead time between the lower bridge arm switch tube Q2 and the upper bridge arm switch tube Q1;

[0047] Use the conduction time width T of the lower bridge arm switch tube Q2 ON The value determines the high level time width or duty cycle of the on-off control waveform PWML of the freewheeling switch tube;

[0048] Using the high level time width or duty cycle of the freewheeling switch on / off control waveform PWML, a pulse oscillation circuit with configurable period and duty cycle is configured, for example, including the following steps:

[0049] Using the output waveform PWM3 of the pulse oscillation circuit as the on-off control waveform PWML of the freewheeling switch tube, or using the output waveform PWM3 of the pulse oscillation circuit to construct the on-off control waveform PWML of the freewheeling switch tube; or,

[0050] The output waveform PWM2 of the pulse oscillation circuit is used as the on-off control waveform PWML of the freewheeling switch tube, or the output waveform PWM2 of the pulse oscillation circuit is used to construct the on-off control waveform PWML of the freewheeling switch tube.

[0051] For example, referring to FIG4 , the output waveform PWM3 of the pulse oscillation circuit is used as the on-off control waveform PWML of the freewheeling switch tube, or the output waveform PWM3 of the pulse oscillation circuit is used to construct the on-off control waveform PWML of the freewheeling switch tube, and the pulse oscillation circuit is a pulse oscillation circuit in a single-chip microcomputer chip with simplified functions. For example, the model of a single-chip microcomputer chip with simplified functions may be TLSR8359 produced in China.

[0052] For example, as shown in FIG4 , the pulse oscillator circuit's output waveform PWM2 is used as the freewheeling switch on / off control waveform PWML, or is used to construct the freewheeling switch on / off control waveform PWML. The pulse oscillator circuit is a pulse oscillator circuit within a powerful single-chip microcontroller chip, such as the NRF52811 manufactured by a Norwegian company. When the pulse oscillator circuit within the NRF52811 is used to output the PWM2 waveform, the waveform parameters of PWM2 and its timing relationship with PWM1 are identical to those of the PWM3 waveform shown in FIG4 .

[0053] Exemplarily, the freewheeling tube is the lower arm switch tube Q2 , and the freewheeling switch tube on-off control waveform PWML is a waveform for controlling the on-off time of the lower arm switch tube Q2 .

[0054] For example, the PWML waveform and PWMH waveform given in this embodiment are the on-time waveforms of the lower-arm switch tube Q2 and the upper-arm switch tube Q1, respectively. The PWML waveform and the PWMH waveform need to be converted by the driving circuit 4 to generate the current and voltage parameters required to drive the lower-arm switch tube Q2 and the upper-arm switch tube Q1.

[0055] For example, T △ The value range is: 1 nanosecond ≤ T △ ≤2000 nanoseconds. The freewheeling current duration T is calculated based on different loads and ambient temperatures. con The statistical distribution of the error between the actual value of the freewheeling current duration of the energy storage inductor and T is determined con Time correction T △ To ensure T ON +T d1 =T con -T △ The value of T is less than the actual value of the continuous current duration of the energy storage inductor; or con Time correction T △ During the freewheeling current duration T con The value is between 1% and 20% of the calculated value.

[0056] For example, referring to FIG3 , the waveform PWML is a pulse width modulation waveform generated by the PWM waveform generation module 3 to control the on-off time of the lower arm switch tube Q2. The oblique line shaded portion of the waveform is the high level time width of PWML, which is also the on-time width T of the lower arm switch tube Q2. ON , T ON =T con -T d1 -T △ ; Among them, T ONis the actual time length of the lower bridge arm switch tube Q2 participating in the freewheeling, T con Is to use V in 、V out 、T inj And the relationship (V in -V out ) / V out =T con / T inj The solved freewheeling time, T △ It is T con The time correction amount of T con The value is reduced by a time correction amount T △ After that, it is used as the actual on-time of the lower bridge arm switch tube Q2 to ensure that the actual on-time of the lower bridge arm switch tube Q2 is less than or equal to the freewheeling time actually required by the energy storage inductor L1;

[0057] The T con The value is reduced by a time correction amount T △ The reason why the actual conduction time of the lower bridge arm switch tube Q2 is that the voltage V in and the output voltage of the energy storage inductor V out There are errors in the measured values ​​and the load of the buck circuit will change. These factors will cause the T con There is an error between the value and the actual freewheeling time of the inductor L1. con When the value is greater than the actual freewheeling time of the inductor L1, the lower-arm switch Q2 remains on after the freewheeling of the inductor L1 ends. The inductor L1 will conduct in reverse after the freewheeling ends, causing the electric energy of the output capacitor C1 to flow back through the lower-arm switch Q2 to the power ground. This backflow current reduces the efficiency of the buck circuit and causes current and voltage surges, damaging the lower-arm switch Q2.

[0058] To ensure that the energy in output capacitor C1 does not flow back through lower-arm switch Q2 after the freewheeling of inductor L1 ends, the design strategy is to turn off lower-arm switch Q2 before the freewheeling of inductor L1 ends, leaving a small tail of freewheeling current to complete the freewheeling current through the body diode of lower-arm switch Q2 or the bypass diode D2 connected in parallel with Q2. During this tailing process, although the freewheeling current flows through bypass diode D2, which has a higher conduction voltage, the freewheeling current value at this stage is already very small. Therefore, the increase in freewheeling power consumption caused by turning off lower-arm switch Q2 before the freewheeling of inductor L1 ends is minimal.

[0059] Under a specific PWM duty cycle, as shown in FIG3 and FIG4, after the inductor L1 freewheeling ends, that is, during the freewheeling duration T conAfter that, there will be a T on the PWML waveform off Time, in this T off During this time, both the upper-arm switch Q1 and the lower-arm switch Q2 are in the off state. In addition, the time T from the lower-arm switch Q2 entering the off state to the upper-arm switch Q1 turning on is d2 It is the second dead zone time.

[0060] The method provided in this embodiment uses the output waveform PWM3 of the pulse oscillation circuit to construct the on-off control waveform PWML of the freewheeling switch tube, including:

[0061] Use the first output terminal of the microcontroller as the PWM1 waveform output terminal, and use the second output terminal of the microcontroller as the PWM2 waveform output terminal. The high and low levels of PWM1 and PWM2 are in opposite phases and have the same time period. The waveform PWM1 is used to drive the PWMH of the upper bridge arm switch tube;

[0062] Use the third output terminal of the microcontroller as the PWM3 waveform output terminal. The PWM3 waveform has the same time period T as the PWM2 waveform. cyc The time synchronization between the PWM3 waveform and the PWM2 waveform is achieved through the logical "AND" operation of the PWM3 waveform and the PWM2 waveform. The output waveform of the "AND" operation is the on-off control waveform PWML of the freewheeling switch tube.

[0063] For example, see FIG4 , in which waveform PWM1 / PWMH is the output waveform of the first output terminal of the single-chip microcomputer, waveform PWM2 is the output waveform of the second output terminal of the single-chip microcomputer, and the high and low levels of PWM1 and PWM2 are inversely proportional and the time period T is cyc Similarly, waveform PWM1 is used to drive PWMH of the upper bridge arm switch tube.

[0064] The time synchronization between the PWM3 waveform and the PWM2 waveform is achieved by the logical "AND" operation of the PWM3 waveform and the PWM2 waveform, see the rising edge in the PWM2 and PWM3 waveform diagrams in Figure 4, that is, the rising edge of the PWM3 waveform is synchronized with the rising edge of the PWM2 waveform through the logical "AND" operation of the PWM3 waveform and the PWM2 waveform.

[0065] An exemplary implementation method for generating a PWML waveform is shown in Figure 5. In the figure, the first output end of the single-chip microcomputer circuit included in the PWM waveform generation module 3 is configured to output waveform PWM1, the second output end is configured to output waveform PWM2, and the third output end is configured to output waveform PWM3. Waveform PWM2 and waveform PWM3 are generated into waveform PWML through the "AND" operation circuit included in the PWM waveform generation module 3. Waveform PWML is output to the driving module 4. The driving module 4 controls the conduction time of the freewheeling tube (lower bridge arm switch tube Q2) according to the high level time of waveform PWML.

[0066] Exemplarily, the PWML and PWMH output by the PWM waveform generation module 3 are pulse signals with adjustable duty cycles. There is a certain time correspondence between the pulse signal PWMH with adjustable duty cycles and the pulse signal PWML with adjustable duty cycles. This time correspondence includes:

[0067] There is a dead time between the pulse signal PWMH with adjustable duty cycle and the pulse signal PWML with adjustable duty cycle, both of which are at low level at the same time; and,

[0068] Outside the dead time, the high and low levels of the duty cycle adjustable pulse signal PWMH and the duty cycle adjustable pulse signal PWML are in opposite phases to each other; and

[0069] The cycle time of the pulse signal PWMH with adjustable duty cycle is the same as the cycle time of the pulse signal PWML with adjustable duty cycle.

[0070] The high level of the pulse signal PWML with adjustable duty cycle is used to drive the lower bridge arm switch Q2 for the energy storage inductor to enter the on state. An exemplary implementation method is: using the pulse signal PWML with adjustable duty cycle to send a high level pulse to the control end of the lower bridge arm switch Q2 for the energy storage inductor to enter the on state, and the rising edge of the high level pulse lags behind the falling edge of the pulse signal PWMH in the same period by a first dead time T d1 The falling edge of the high-level pulse precedes the rising edge of the pulse signal PWMH in the next cycle by a second dead time T d2 .

[0071] Typically, the time width T of the high-level pulse sent by the pulse signal PWML with adjustable duty cycle to the control terminal of the lower bridge arm switch Q2 for the freewheeling of the energy storage inductor is ON , the low level duration of the pulse signal PWMH with adjustable duty cycle, the first dead time T d1 and the second dead time T d2 Confirm: T ON =T con -T d1 -T △.

[0072] The method provided in this embodiment measures the voltage V at the input terminal of the energy storage inductor. in and the output voltage of the energy storage inductor V out After that, it also includes:

[0073] The energy storage inductor input terminal voltage V obtained by the measurement module 1 in and the output voltage of the energy storage inductor V out At least one of the following is used to determine the freewheeling current duration T con The estimation is also used to calculate the output power of the photovoltaic power generation component that uses the BUCK circuit for power optimization to achieve maximum power point tracking of the photovoltaic power generation component.

[0074] Exemplarily, the photovoltaic power generation assembly includes a photovoltaic power generation panel composed of a plurality of photovoltaic power generation units.

[0075] The maximum power point tracking of the photovoltaic power generation component is used to maximize the output power of the photovoltaic power generation component under different working conditions. Since the output power of the photovoltaic power generation component is affected by abnormal conditions such as shading, foreign matter coverage and hot spots, when these abnormal conditions occur, the output power of the photovoltaic power generation component will be reduced and will become a load for other photovoltaic power generation components in the photovoltaic component string, thereby affecting the power output capacity and safety of the entire photovoltaic component string. In order to ensure that the photovoltaic power generation component can still output its potential power generation capacity to the best of its ability when these abnormal conditions occur, a photovoltaic power generation component power optimizer can be used to adjust the output power of the photovoltaic panel.

[0076] A photovoltaic power generation module power optimizer uses a BUCK circuit to adjust the output power of the photovoltaic power generation module. The method for optimizing the output power of the photovoltaic power generation module is a maximum power point tracking (MPPT) method, which includes: changing the duty cycle of the BUCK circuit included in the optimizer to change the output power of the photovoltaic power generation module; calculating the output power of the photovoltaic power generation module using the output voltage and output current of the photovoltaic power generation module under different duty cycles, or calculating the output power of the photovoltaic power generation module using the output voltage and output current of the BUCK circuit in the power optimizer; estimating the maximum output power using the output power values ​​of the photovoltaic module under different duty cycles, determining the duty cycle of the BUCK circuit corresponding to the maximum output power, and operating the BUCK circuit under the duty cycle, thereby achieving the photovoltaic power generation module operating at or near its maximum power point.

[0077] The energy storage inductor input voltage V in and the output voltage of the energy storage inductor V outAt least one of the following is used to determine the freewheeling current duration T con The estimation is also used for maximum power point tracking of the photovoltaic power generation component serving as the input power source of the synchronous buck circuit.

[0078] For example, the voltage V at the input terminal of the energy storage inductor is in and the output voltage of the energy storage inductor V out At least one of the following is used for the geometric relationship (V in -V out ) / V out =T con / T inj Solve for the freewheeling time T con and, in the use of the BUCK circuit to implement maximum power point tracking (MPPT) of photovoltaic power generation components, it is used to calculate the output power value of the photovoltaic power generation component.

[0079] The present application provides a BUCK circuit PWM waveform generation device embodiment, comprising: a measurement module 1, a freewheeling time calculation module 2 and a PWM waveform generation module 3; wherein the measurement module 1 is configured to measure the voltage V at the input terminal of the energy storage inductor in and the output voltage of the energy storage inductor V out The measurement module 1 includes a voltage conversion circuit and an analog-to-digital conversion circuit; the freewheeling time calculation module 2 is configured to use the V in and V out Determine the voltage V across the energy storage inductor in the freewheeling state Lcon And the voltage V in the magnetized state Linj ; Use the V Lcon and V Linj Calculate the freewheeling time T of the energy storage inductor con ; Freewheeling time calculation module 2 includes a digital operation circuit and a memory; PWM waveform generation module 3, set to use the T con The value of the duty cycle generated by T con The variable freewheeling switch on-off control waveform PWML, the PWM waveform generation module 3 includes a PWM waveform parameter determination submodule and a PWML / PWMH waveform generation submodule.

[0080] Exemplarily, the PWM waveform parameter determination submodule includes a digital operation circuit and a memory circuit; the PWML / PWMH waveform generation submodule includes a pulse oscillation circuit with configurable period and duty cycle.

[0081] The waveform PWML is the on-off control waveform PWML of the freewheeling switch tube, and the freewheeling switch tube is the lower bridge arm switch tube Q2 of the buck circuit; the waveform PWMH is the on-off control waveform PWMH of the magnetizing switch tube, and the magnetizing switch tube is the upper bridge arm switch tube Q1 of the buck circuit;

[0082] The PWM waveform parameter determination submodule is configured to determine the high level time width T of the on-off control waveform PWML of the freewheeling switch tube. ON Value(T ON The value is the conduction time width T of the freewheeling switch tube ON value, the T ON The value is less than or equal to the freewheeling time T of the energy storage inductor con ), the period T of the waveform PWML cyc and duty cycle, dead time T between waveform PWML and waveform PWMH d1 、T d2 , and is set to determine the period T of the on-off control waveform PWMH of the magnetizing switch tube cyc , duty cycle or high level time width T inj Value(T inj The value is the conduction time width T of the magnetizing switch tube inj value).

[0083] For example, the voltage conversion circuit included in the measurement module 1 is configured to convert the voltage V in and the output voltage of the energy storage inductor V out Converted to a voltage range suitable for the operation of the analog-to-digital conversion circuit. Exemplarily, the voltage conversion circuit includes a voltage divider circuit; the analog-to-digital conversion circuit included in the measurement module 1 is an independent analog / digital (Analog-to-Digital, A / D) conversion chip or an A / D conversion circuit integrated in a single-chip microcomputer.

[0084] The digital operation circuit included in the freewheeling time calculation module 2 calculates the relationship (V in -V out ) / V out =T con / T inj Perform the solution operation and get T con The memory is configured to store the energy storage inductor input voltage V in and the output voltage of the energy storage inductor V out The measured value of the energy storage inductor L1 is T inj Values ​​and operation results.

[0085] The PWM waveform parameter determination submodule includes a digital operation circuit and a storage circuit. The operation circuit performs calculations under the control of the instructions stored in the storage circuit. ON The value is operated and the operation circuit outputs T ON a value is stored in said storage circuit;

[0086] For example, as shown in FIG5 , the digital operation circuit and storage circuit included in the PWM waveform parameter determination submodule are a component of the single-chip microcomputer circuit; the PWML / PWMH waveform generation submodule, as shown in FIG5 , includes a storage circuit / register, a pulse oscillation circuit with configurable period and duty cycle, and an AND operation circuit;

[0087] Exemplarily, the digital operation circuit, storage circuit and PWM waveform output circuit included in the PWML / PWMH waveform generation submodule are a component of the single-chip microcomputer circuit. The PWM waveform output circuit includes the first output end, the second output end and the third output end of the single-chip microcomputer circuit, wherein the first output end is configured to output the waveform PWM1, the second output end is configured to output the waveform PWM2, and the third output end is configured to output the waveform PWM3. The "AND" operation circuit is used for the "AND" operation between the output waveform PWM2 and the output waveform PWM3.

[0088] The device provided in this embodiment, wherein the measuring module 1 performs the measurement of the voltage V at the input terminal of the energy storage inductor. in and the output voltage of the energy storage inductor V out The operation includes the following operations: measuring the voltage of the drain or source of the upper arm switch tube of the BUCK circuit relative to the power ground as the voltage V at the input terminal of the energy storage inductor in ;Measure the voltage across the output capacitor of the BUCK circuit as the output voltage of the energy storage inductor V out .

[0089] As an implementation of a PWM waveform generating device provided in the present application, referring to FIG2 , an input terminal Ti of an inductor L1 is electrically connected to the source of an upper-arm switching tube Q1 and the drain of a lower-arm switching tube Q2. An output terminal To of the inductor L1 is electrically connected to the positive electrode of an output capacitor C1, the negative electrode of a bypass diode D3, and the positive output terminal T1 of a buck circuit. A negative output terminal T2 of the buck circuit is electrically connected to the positive electrode of the bypass diode D3, the negative electrode of the output capacitor C1, and the power ground GND of the buck circuit. A bypass diode D1 is connected in parallel between the source and drain of the upper-arm switching tube Q1, and a bypass diode D2 is connected in parallel between the source and drain of the lower-arm switching tube Q2. The input power source of the buck circuit is a photovoltaic module, which may be a single photovoltaic panel or a series combination of multiple photovoltaic panels. The input power source of the buck circuit may also be a battery or a power source after AC / DC conversion.

[0090] In Figure 2, the measurement module 1 measures the voltage at the output terminal To of the energy storage coil and the input voltage of the BUCK circuit; the measurement module 1 uses the voltage measurement result of the output terminal To of the energy storage coil as the output terminal voltage V out, the measured result of the BUCK circuit input voltage is used as the energy storage inductor input voltage V in In Figure 2, the measurement module 1 measures the voltage V at the input terminal of the energy storage inductor at the drain of the upper arm switch tube Q1 of the BUCK circuit. in The measurement result includes the on-state voltage of the upper arm switch tube Q1; the measurement module 1 measures the voltage V at the input terminal of the energy storage inductor at the source of the upper arm switch tube Q1 of the BUCK circuit. in , the measurement result does not include the on-state voltage of the upper arm switch tube Q1.

[0091] The freewheeling time calculation module 2 obtains the energy storage inductor output terminal voltage V from the measurement module 1 out And the voltage at the input of the energy storage inductor V in The measured value of the upper bridge arm switch Q1 is obtained from the PWM waveform generation module 3, and the on-time value is used as the duration T of the energy storage inductor magnetizing current. inj , use V in 、V out 、T inj And the relationship (V in -V out ) / V out =T con / T inj , solve for the freewheeling time T con and the freewheeling time T con The value is sent to the PWM waveform generation module 3.

[0092] The PWM waveform generation module 3 sends the duration T of the inductor magnetizing current to the freewheeling time calculation module 2. inj The value of the freewheeling time T is received from the freewheeling time calculation module 2 con The value of the freewheeling time T con The value of determines the time parameter of the freewheeling tube Q2 driving waveform PWML. The PWM waveform generation module 3 will use T inj The PWMH waveform is determined by the value of T con The PWML waveform determined by the value is sent to the driving module 4.

[0093] The driving module 4 converts the PWMH sent by the PWM waveform generating module 3 into the signal form required to drive the upper bridge arm switch tube Q1, and converts the PWML sent by the PWM waveform generating module 3 into the signal form required to drive the lower bridge arm switch tube Q2.

[0094] The device provided in this embodiment, wherein the freewheeling time calculation module 2 is executed using the V in and V out Determine the voltage V across the energy storage inductor in the freewheeling stateLcon And the voltage V in the magnetized state Linj The operation, for example, includes the following steps:

[0095] Use the measured value V in With the measured value V out The difference between the two ends of the energy storage inductor is taken as the voltage at both ends of the energy storage inductor in the magnetized state, and (V in -V out )=V Linj ; Use the measured value V out As the voltage across the energy storage inductor in the freewheeling state, we get V out =V Lcon ;

[0096] The freewheeling time calculation module 2, which is executed using V Lcon and V Linj Calculate the freewheeling time T of the energy storage inductor con The operation, for example, includes the following steps:

[0097] According to the physical law that the voltage across the inductor is proportional to the rate of change of the current in the inductor, the relationship is obtained: the voltage V across the energy storage inductor in the magnetized state Linj The voltage V across the energy storage inductor in the freewheeling state Lcon The ratio is equal to the magnetizing current I of the energy storage inductor inj The rate of change S1 and the energy storage inductor freewheeling current I con The ratio of the rate of change S2, that is, V Linj / V Lcon =S1 / S2=(V in -V out ) / V out ;

[0098] According to the magnetizing current I inj The rate of change S1 is the slope of the rising slope of the magnetizing current, and the freewheeling current I con The rate of change S2 is the slope of the freewheeling current falling slope. The magnetizing current rising slope and the freewheeling current falling slope are the hypotenuses of two adjacent right triangles, respectively. As well as the definition of the slope, we get the relationship: V Linj / V Lcon =S1 / S2=T con / T inj =(V in -V out ) / V out ;

[0099] The energy storage inductor input voltage V obtained by measurement module 1 in The measured value and the output voltage of the energy storage inductor V outThe measured value and the magnetizing current time T determined by the PWM waveform generation module 3 inj The value is taken as a known parameter, and the geometric relationship (V in -V out ) / V out =T con / T inj Solve for the freewheeling time T con The numerical value of .

[0100] For example, (V in -V out ) is the voltage across the energy storage inductor in the magnetized state, V out It is the voltage across the energy storage inductor in the freewheeling state, V out It is also the output voltage of the energy storage inductor, T con is the freewheeling time, T inj is the magnetization time.

[0101] For example, referring to FIG3 , in which PWMH is a pulse width modulation waveform generated by the PWM waveform generation module 3 to control the on-off time of the upper arm switch tube Q1, T cyc Indicates the cycle of PWMH. The oblique shaded part is the high-level time width of PWMH, which is also the conduction time width of the upper bridge arm switch tube Q1 and the magnetizing current duration T of the energy storage inductor L1. inj ;

[0102] The L1 voltage waveform is the waveform of the voltage across the energy storage inductor L1 in the magnetizing state and the freewheeling state. inj The voltage across the internal energy storage inductor L1 is (V in -V out ), during the freewheeling current duration T con The voltage across the internal energy storage inductor L1 is (-V out );

[0103] The L1 current waveform shows the ratio of the magnetizing current slope S1 to the freewheeling current slope S2 (S1 / S2) and the freewheeling current duration T of the energy storage inductor L1 in the magnetizing state and the freewheeling state. con and the magnetizing current duration T inj Ratio T con / T inj For example, it can be seen from FIG3 that triangle OAE and triangle BAE are two adjacent right triangles, and the common vertex E of these two adjacent right triangles is the maximum magnetizing current I of the energy storage inductor L1. max; The slope S1 of the hypotenuse OE of the triangle OAE is the rate of change of the magnetizing current, and the slope S2 of the hypotenuse BE of the triangle BAE is the rate of change of the freewheeling current. According to the definition of slope, the slope S1 of the hypotenuse OE = AE / OA, and the slope S2 of the hypotenuse BE = AE / AB; Given that the length of the base OA of the triangle OAE is the duration T of the magnetizing current inj , the length of the base AB of the triangle BAE is the duration of the freewheeling current T con , we can get:

[0104] S1 / S2=(AE / OA) / (AE / AB)=AB / OA=T con / T inj ;

[0105] In the L1 current waveform, from point O to point C on the time axis is a PWM (pulse width modulation) cycle, which is also the cycle in which the energy storage inductor L1 completes one magnetization and freewheeling cycle.

[0106] In the device provided in this embodiment, the PWM waveform generating module 3 is configured to execute the operation using T con The value of the duty cycle generated by T con The operation of changing the on-off control waveform PWML of the freewheeling switch includes, for example, the following steps:

[0107] The PWM waveform parameter determination submodule uses the relationship T ON =T con -T d1 -T △ Determine the conduction time width T of the lower bridge arm switch tube Q2 ON value, where T △ It is T con Time correction value; T d1 is the first dead time between the lower arm switch tube Q2 and the upper arm switch tube Q1; the conduction time width T of the lower arm switch tube Q2 is used. ON The value determines the high level time width or duty cycle of the on-off control waveform PWML of the freewheeling switch tube;

[0108] Using the high-level time width or duty cycle of the freewheeling switch on / off control waveform PWML, the pulse oscillation circuit with configurable period and duty cycle included in the PWML / PWMH waveform generation submodule is configured, for example, including the following steps:

[0109] Using the output waveform PWM3 of the pulse oscillation circuit as the on-off control waveform PWML of the freewheeling switch tube, or using the output waveform PWM3 of the pulse oscillation circuit to construct the on-off control waveform PWML of the freewheeling switch tube; or,

[0110] The output waveform PWM2 of the pulse oscillation circuit is used as the on-off control waveform PWML of the freewheeling switch tube, or the output waveform PWM2 of the pulse oscillation circuit is used to construct the on-off control waveform PWML of the freewheeling switch tube.

[0111] For example, referring to FIG4 , the output waveform PWM3 of the pulse oscillation circuit is used as the on-off control waveform PWML of the freewheeling switch tube, or the output waveform PWM3 of the pulse oscillation circuit is used to construct the on-off control waveform PWML of the freewheeling switch tube, and the pulse oscillation circuit is a pulse oscillation circuit in a single-chip microcomputer chip with simplified functions. For example, the model of a single-chip microcomputer chip with simplified functions may be TLSR8359 produced in China.

[0112] For example, as shown in FIG4 , the pulse oscillator circuit's output waveform PWM2 is used as the freewheeling switch on / off control waveform PWML, or is used to construct the freewheeling switch on / off control waveform PWML. The pulse oscillator circuit is a pulse oscillator circuit within a powerful single-chip microcontroller chip, such as the NRF52811 manufactured by a Norwegian company. When the pulse oscillator circuit within the NRF52811 is used to output the PWM2 waveform, the waveform parameters of PWM2 and its timing relationship with PWM1 are the same as those of the PWM3 waveform shown in FIG4 .

[0113] Exemplarily, the freewheeling switch is the lower arm switch Q2 , and the freewheeling switch on-off control waveform PWML is a waveform used to control the on-time and on-time of the lower arm switch Q2 .

[0114] For example, the PWML waveform and PWMH waveform given in this embodiment are the on-off control waveforms of the lower arm switch tube Q2 and the upper arm switch tube Q1, respectively. The PWML waveform and the PWMH waveform need to be converted by the driving circuit 4 to generate the current and voltage parameters required to drive the lower arm switch tube Q2 and the upper arm switch tube Q1.

[0115] For example, T △ The value range is: 1 nanosecond ≤ T △ ≤2000 nanoseconds.

[0116] T △ The value of is calculated based on the freewheeling current duration T under different loads and ambient temperatures. con The statistical distribution of the error between the actual value of the freewheeling current duration of the energy storage inductor and T is determined con Time correction T △ To ensure T ON +T d1 =T con -T△ The value of T is less than the actual value of the continuous current duration of the energy storage inductor; or con Time correction T △ During the freewheeling current duration T con The value is between 1% and 20% of the calculated value.

[0117] For example, referring to FIG3 , the waveform PWML is a pulse width modulation waveform generated by the PWM waveform generation module 3 to control the on-off time of the lower arm switch tube Q2. The oblique line shaded portion of the waveform is the high level time width of PWML, which is also the on-time width T of the lower arm switch tube Q2. ON , T ON =T con -T d1 -T △ ; Among them, T ON is the actual time length of the lower bridge arm switch tube Q2 participating in the freewheeling, T con Is to use V in 、V out 、T inj And the relationship (V in -V out ) / V out =T con / T inj The solved freewheeling time, T △ It is T con The time correction amount of T con The value is reduced by a time correction amount T △ After that, it is used as the actual on-time of the lower bridge arm switch tube Q2 to ensure that the actual on-time of the lower bridge arm switch tube Q2 is less than or equal to the actual freewheeling time required by the energy storage inductor L1; the T con The value is reduced by a time correction amount T △ The reason why the actual conduction time of the lower bridge arm switch tube Q2 is that the voltage V in and the output voltage of the energy storage inductor V out There are errors in the measured values ​​and the load of the buck circuit will change. These factors will cause the T con There is an error between the value and the actual freewheeling time of the inductor L1. con When the value is greater than the actual freewheeling time of the inductor L1, the lower-arm switch Q2 remains on after the freewheeling of the inductor L1 ends. The inductor L1 reverses conduction after the freewheeling ends, causing the energy of the output capacitor C1 to flow back through the lower-arm switch Q2 to the power ground. This backflow current reduces the efficiency of the buck circuit and causes current and voltage surges, potentially damaging the lower-arm switch Q2.

[0118] To ensure that the energy in output capacitor C1 does not flow back through lower-arm switch Q2 after the freewheeling of inductor L1 ends, the design strategy is to shut down lower-arm switch Q2 before the freewheeling of inductor L1 ends, leaving a small tail of freewheeling current to pass through the body diode of lower-arm switch Q2 or the bypass diode D2 connected in parallel with Q2 to complete the freewheeling current termination process. During this termination process, although the freewheeling current flows through bypass diode D2, which has a higher conduction voltage, the freewheeling current value at this stage is already very small. Therefore, the increase in freewheeling power consumption caused by shutting down lower-arm switch Q2 before the freewheeling of inductor L1 ends is minimal.

[0119] Under a specific PWM duty cycle, as shown in FIG3 and FIG4, after the inductor L1 freewheeling ends, that is, during the freewheeling duration T con After that, there will be a T on the PWML waveform off Time, in this T off During this time, both the upper-arm switch Q1 and the lower-arm switch Q2 are in the off state. In addition, the time T from the lower-arm switch Q2 entering the off state to the upper-arm switch Q1 turning on is d2 It is the second dead zone time.

[0120] In the device provided in this embodiment, the operation of the PWM waveform generating module 3 for constructing the freewheeling switch on / off control waveform PWML using the output waveform PWM3 of the pulse oscillation circuit includes, for example, the following steps:

[0121] Use the first output terminal of the microcontroller as the PWM1 waveform output terminal, and use the second output terminal of the microcontroller as the PWM2 waveform output terminal. The high and low levels of PWM1 and PWM2 are in opposite phases and have the same time period. The waveform PWM1 is used to drive the PWMH of the upper bridge arm switch tube;

[0122] Use the third output terminal of the microcontroller as the PWM3 waveform output terminal. The PWM3 waveform has the same time period T as the PWM2 waveform. cyc The time synchronization between the PWM3 waveform and the PWM2 waveform is achieved through the logical "AND" operation of the PWM3 waveform and the PWM2 waveform. The output waveform of the "AND" operation is the on-off control waveform PWML of the freewheeling switch tube.

[0123] For example, see FIG4 , in which waveform PWM1 / PWMH is the output waveform of the first output terminal of the single-chip microcomputer, waveform PWM2 is the output waveform of the second output terminal of the single-chip microcomputer, and the high and low levels of PWM1 and PWM2 are inversely proportional and the time period T is cycSimilarly, waveform PWM1 is used to drive PWMH of the upper bridge arm switch tube; the time synchronization between the PWM3 waveform and the PWM2 waveform is achieved through the logical "AND" operation of the PWM3 waveform and the PWM2 waveform, referring to the rising edge in the PWM2 and PWM3 waveform diagram in Figure 4, that is, the rising edge of the PWM3 waveform is synchronized with the rising edge of the PWM2 waveform through the logical "AND" operation of the PWM3 waveform and the PWM2 waveform.

[0124] An exemplary implementation method for generating a PWML waveform is shown in Figure 5. In the figure, the first output end of the single-chip microcomputer circuit included in the PWM waveform generation module 3 is configured to output waveform PWM1, the second output end is configured to output waveform PWM2, and the third output end is configured to output waveform PWM3. Waveform PWM2 and waveform PWM3 are generated into waveform PWML through the "AND" operation circuit included in the PWM waveform generation module 3. Waveform PWML is output to the driving module 4. The driving module 4 controls the conduction time of the freewheeling tube (lower bridge arm switch tube Q2) according to the high level time of waveform PWML.

[0125] Exemplarily, the PWML and PWMH output by the PWM waveform generation module 3 are pulse signals with adjustable duty cycles. There is a certain time correspondence between the pulse signal PWMH with adjustable duty cycles and the pulse signal PWML with adjustable duty cycles. This time correspondence includes: there is a dead time between the pulse signal PWMH with adjustable duty cycles and the pulse signal PWML with adjustable duty cycles, in which both are at a low level at the same time; and, outside the dead time, the high and low levels of the pulse signal PWMH with adjustable duty cycles and the pulse signal PWML with adjustable duty cycles are in opposite phases to each other; and, the cycle time of the pulse signal PWMH with adjustable duty cycles is the same as the cycle time of the pulse signal PWML with adjustable duty cycles.

[0126] The high level of the pulse signal PWML with adjustable duty cycle is used to drive the lower bridge arm switch tube Q2 for the energy storage inductor to enter the on state. An exemplary implementation method is: using the pulse signal PWML with adjustable duty cycle to send a high level pulse to the control end of the lower bridge arm switch tube Q2 for the energy storage inductor to continue the current, the rising edge of the high level pulse lags behind the falling edge of the pulse signal PWMH in the same cycle by a first dead zone time, and the falling edge of the high level pulse leads the rising edge of the pulse signal PWMH in the next cycle by a second dead zone time.

[0127] Typically, the time width of the high-level pulse sent by the duty-cycle-adjustable pulse signal PWML to the control end of the lower bridge arm switch tube Q2 for freewheeling the energy storage inductor is determined by the low-level duration of the duty-cycle-adjustable pulse signal PWMH and the first dead time and the second dead time.

[0128] In the device provided in this embodiment, the measuring module 1 is further configured to perform the following operations, for example, including the following steps: the voltage V at the input terminal of the energy storage inductor obtained by the measuring module 1 in and the output voltage of the energy storage inductor V out At least one of the following is used to determine the freewheeling current duration T con The estimation is also used to calculate the output power of the photovoltaic power generation component that uses the BUCK circuit for power optimization to achieve maximum power point tracking of the photovoltaic power generation component.

[0129] Exemplarily, the photovoltaic power generation assembly includes a photovoltaic power generation panel composed of a plurality of photovoltaic power generation units.

[0130] The maximum power point tracking of the photovoltaic power generation component is used to maximize the output power of the photovoltaic power generation component under different working conditions. Since the output power of the photovoltaic power generation component is affected by abnormal conditions such as shading, foreign matter coverage and hot spots, when these abnormal conditions occur, the output power of the photovoltaic power generation component will be reduced and will become a load for other photovoltaic power generation components in the photovoltaic component string, thereby affecting the power output capacity and safety of the entire photovoltaic component string. In order to ensure that the photovoltaic power generation component can still output its potential power generation capacity to the best of its ability when these abnormal conditions occur, a photovoltaic power generation component power optimizer can be used to adjust the output power of the photovoltaic panel.

[0131] The photovoltaic power generation module power optimizer uses a BUCK circuit to adjust the output power of the photovoltaic power generation module. The method for optimizing the output power of the photovoltaic power generation module is the maximum power point tracking (MPPT) method, which includes: changing the duty cycle of the BUCK circuit included in the optimizer to change the output power of the photovoltaic power generation module; under different duty cycles, using the output voltage and output current of the photovoltaic module to calculate the output power of the photovoltaic power generation module, or using the output voltage and output current of the BUCK circuit in the power optimizer to calculate the output power of the photovoltaic power generation module; using the output power values ​​of the photovoltaic module under different duty cycles to estimate the maximum output power, determining the duty cycle of the BUCK circuit corresponding to the maximum output power, and allowing the BUCK circuit to operate at the duty cycle, thereby achieving the photovoltaic power generation module operating at or near its maximum power point.

[0132] The energy storage inductor input terminal voltage V obtained by the measurement module 1 in and the output voltage of the energy storage inductor V out At least one of the following is used to determine the freewheeling current duration T con The estimation is also used for tracking the maximum power point of the photovoltaic power generation component as the input power source of the synchronous BUCK circuit. inand the output voltage of the energy storage inductor V out At least one of the following is used for the geometric relationship (V in -V out ) / V out =T con / T inj Solve for the freewheeling time T con and, in the use of the BUCK circuit to implement maximum power point tracking (MPPT) of photovoltaic power generation components, it is used to calculate the output power value of the photovoltaic power generation component.

[0133] The method provided in the embodiment of the present application can be implemented in whole or in part by at least one of software instructions and hardware circuits; the modules or units included in the device provided in the embodiment of the present application can be implemented using electronic components.

[0134] The methods and devices provided in the embodiments of this application overcome the shortcomings of related DC-DC conversion technologies, such as simplifying the method for determining the freewheeling time length and generating PWM waveforms that adjust both the duty cycle and the freewheeling time. This application can control the freewheeling time during the PWM waveform generation process at a low cost.

Claims

1. A method for generating a PWM waveform in a buck circuit, comprising: Measure the input voltage V of the energy storage inductor in and the output voltage V of the energy storage inductor out ; Use the V in and V out Determine the voltage V across the energy storage inductor in the freewheeling state Lcon And the voltage V in the magnetized state Linj ; Use the V Lcon and V Linj Calculate the freewheeling time T of the energy storage inductor con ; Use the T con The value of the duty cycle generated by T con The changing freewheeling switch on-off control waveform PWML.

2. The method according to claim 1, wherein The input voltage V of the energy storage inductor is measured in and the output voltage V of the energy storage inductor out ,include: Measure the voltage of the drain or source of the upper arm switch tube of the BUCK circuit relative to the power ground, and use the voltage of the drain or source of the upper arm switch tube relative to the power ground as the input terminal voltage V of the energy storage inductor in ; Measure the voltage across the output capacitor of the BUCK circuit and use the voltage across the output capacitor as the output voltage V of the energy storage inductor. out .

3. The method according to claim 1, wherein The use of the V in and V out Determine the voltage V across the energy storage inductor in the freewheeling state Lcon And the voltage V in the magnetized state Linj ,include: Use the V in With V out The difference between the two is taken as the voltage across the energy storage inductor in the magnetized state, and (V in -V out )=V Linj ; Use the V out As the voltage across the energy storage inductor in the freewheeling state, V out =V Lcon ; The use of the V Lcon and V Linj Calculate the freewheeling time T of the energy storage inductor con ,include: According to the relationship that the voltage across the energy storage inductor is proportional to the rate of change of the current in the energy storage inductor, the relationship is obtained: V Linj / V Lcon =S1 / S2=(V in -V out ) / V out , wherein the relationship is expressed as follows: the voltage V at both ends of the energy storage inductor in the magnetized state Linj The voltage V across the energy storage inductor in the freewheeling state Lcon The ratio is equal to the magnetizing current I of the energy storage inductor inj The rate of change S1 is related to the freewheeling current I con The ratio of the rate of change S2; According to the magnetizing current I inj The rate of change S1, the freewheeling current I con The rate of change S2 and the definition of slope give the relationship: V Linj / V Lcon =S1 / S2=T con / T inj =(V in -V out ) / V out , wherein the magnetizing current I inj The rate of change S1 is the slope of the rising slope of the magnetizing current, and the freewheeling current I con The rate of change S2 is the slope of the freewheeling current descending slope, and the magnetizing current ascending slope and the freewheeling current descending slope are the hypotenuses of two adjacent right triangles respectively; The input voltage V in The measured value and the output voltage V of the energy storage inductor out The measured value and the duration T of the energy storage inductor magnetizing current inj The value is taken as a known parameter, and the geometric relationship (V in -V out ) / V out =T con / T inj Solve for the freewheeling time T con The numerical value of .

4. The method according to claim 1, wherein The use of T con The value of the duty cycle generated by T con The variable freewheeling switch on-off control waveform PWML includes: Using the relation T ON =T con -T d1 -T △ Determine the conduction time width value T of the lower bridge arm switch tube of the BUCK circuit ON , where T △ It is T con Time correction, T d1 is the first dead time between the lower bridge arm switch tube and the upper bridge arm switch tube; The conduction time width value T of the lower bridge arm switch tube is used ON Determine the high-level time width required for the on-off control waveform PWML of the freewheeling switch tube or the duty cycle required for the on-off control waveform PWML of the freewheeling switch tube; According to the high-level time width of the freewheeling switch tube on-off control waveform PWML or the duty cycle of the freewheeling switch tube on-off control waveform PWML, the period and duty cycle of the pulse oscillation circuit in the BUCK circuit are configured; the configured pulse waveform of the pulse oscillation circuit is used as the freewheeling switch tube on-off control waveform PWML, or the configured pulse waveform of the pulse oscillation circuit is used to construct the freewheeling switch tube on-off control waveform PWML.

5. The method according to claim 4, wherein: The method of using the configured output waveform PWM3 of the pulse oscillation circuit to construct the on-off control waveform PWML of the freewheeling switch tube includes: Using the first output end of the pulse oscillation circuit as the output end of the pulse waveform PWM1, and using the second output end of the pulse oscillation circuit as the output end of the pulse waveform PWM2, wherein the high and low levels of PWM1 and PWM2 are in opposite phases and have the same time period, and PWM1 is used as the driving waveform PWMH to drive the upper bridge arm switch tube; The third output terminal of the pulse oscillation circuit is used as the output terminal of the pulse waveform PWM3, wherein the PWM3 and the PWM2 have the same time period T cyc ; The time synchronization between the PWM3 and the PWM2 is achieved by performing a logic AND operation on the PWM3 and the PWM2. The waveform output after the logic AND operation is the on-off control waveform PWML of the freewheeling switch tube.

6. The method according to claim 2, wherein the voltage V at the input terminal of the energy storage inductor is measured. in and the output voltage V of the energy storage inductor out Afterwards, the method further comprises: According to the energy storage inductor input voltage V in and the output voltage of the energy storage inductor V out At least one of the following, for the freewheeling time T con Make estimates; According to the input voltage V in and the output voltage V of the energy storage inductor out At least one of the above is used to calculate the output power of the photovoltaic power generation component that uses the BUCK circuit for power optimization to achieve maximum power point tracking of the photovoltaic power generation component.

7. A buck circuit PWM waveform generating device, comprising: A measurement module (1), a freewheeling time calculation module (2) and a PWM waveform generation module (3); wherein, The measuring module (1) is configured to measure the input voltage V of the energy storage inductor. in and the output voltage V of the energy storage inductor out ; The freewheeling time calculation module (2) is configured to use the V in and V out Determine the voltage V across the energy storage inductor in the freewheeling state Lcon And the voltage V in the magnetized state Linj ; Use the V Lcon and V Linj Calculate the freewheeling time T of the energy storage inductor con ; The PWM waveform generating module (3) is configured to use the T con The value of the duty cycle generated by T con The changing freewheeling switch on-off control waveform PWML.

8. The device according to claim 7, wherein The measuring module (1) is configured to measure the input terminal voltage V of the energy storage inductor in the following manner: in and the output voltage V of the energy storage inductor out : Measure the voltage of the drain or source of the upper arm switch tube of the BUCK circuit relative to the power ground, and use the voltage of the drain or source of the upper arm switch tube relative to the power ground as the input terminal voltage V of the energy storage inductor in ; Measure the voltage across the output capacitor of the BUCK circuit and use the voltage across the output capacitor as the output voltage V of the energy storage inductor. out .

9. The device according to claim 7, wherein The freewheeling time calculation module (2) is configured to use the V in and V out Determine the voltage V across the energy storage inductor in the freewheeling state Lcon And the voltage V in the magnetized state Linj : Use the V in With the V out The difference between the two is taken as the voltage across the energy storage inductor in the magnetized state, and (V in -V out )=V Linj ; Use the V out As the voltage across the energy storage inductor in the freewheeling state, V out =V Lcon ; The freewheeling time calculation module (2) is configured to use V Lcon and V Linj Calculate the freewheeling time T of the energy storage inductor con : According to the relationship that the voltage across the energy storage inductor is proportional to the rate of change of the current in the energy storage inductor, the relationship is obtained: V Linj / V Lcon =S1 / S2=(V in -V out ) / V out , wherein the relationship is expressed as follows: the voltage V at both ends of the energy storage inductor in the magnetized state Linj The voltage V across the energy storage inductor in the freewheeling state Lcon The ratio is equal to the magnetizing current I of the energy storage inductor inj The rate of change S1 is related to the freewheeling current I con The ratio of the rate of change S2; According to the magnetizing current I inj The rate of change S1, the freewheeling current I con The rate of change S2 and the definition of slope give the relationship: V Linj / V Lcon =S1 / S2=T con / T inj =(V in -V out ) / V out , wherein the magnetizing current I inj The rate of change S1 is the slope of the rising slope of the magnetizing current, and the freewheeling current I con The rate of change S2 is the slope of the freewheeling current descending slope, and the magnetizing current ascending slope and the freewheeling current descending slope are the hypotenuses of two adjacent right triangles respectively; The input voltage V in The measured value and the output voltage V of the energy storage inductor out The measured value and the duration T of the energy storage inductor magnetizing current inj The value is taken as a known parameter, and the geometric relationship (V in -V out ) / V out =T con / T inj Solve for the freewheeling time T con The numerical value of .

10. The device according to claim 7, wherein The PWM waveform generation module (3) is configured to use T con The value of the duty cycle generated by T con The changing freewheeling switch on-off control waveform PWML: The PWM waveform parameter determination submodule uses the relationship T ON =T con -T d1 -T △ Determine the conduction time width value T of the lower bridge arm switch tube of the BUCK circuit ON , where T △ It is T con Time correction value; T d1 is the first dead time between the lower arm switch tube and the upper arm switch tube; the conduction time width value T of the lower arm switch tube is used ON Determine the high level time width of the freewheeling switch tube on-off control waveform PWML or the duty cycle required by the freewheeling switch tube on-off control waveform PWML; According to the high-level time width required by the freewheeling switch on-off control waveform PWML or the duty cycle required by the freewheeling switch on-off control waveform PWML, the pulse oscillation circuit with configurable period and duty cycle included in the PWML / PWMH waveform generation submodule is configured; The configured pulse waveform of the pulse oscillation circuit is used as the on-off control waveform PWML of the freewheeling switch tube, or the configured pulse waveform of the pulse oscillation circuit is used to construct the on-off control waveform PWML of the freewheeling switch tube.

11. The device according to claim 10, wherein The PWM waveform generating module (3) is configured to construct the freewheeling switch on / off control waveform PWML using the configured pulse waveform PWM3 of the pulse oscillation circuit in the following manner: Using the first output end of the pulse oscillation circuit as the output end of the pulse waveform PWM1, and using the second output end of the pulse oscillation circuit as the output end of the pulse waveform PWM2, wherein the high and low levels of PWM1 and PWM2 are in opposite phases and have the same time period, and PWM1 is used as the control waveform PWMH to drive the upper bridge arm switch tube; The third output terminal of the pulse oscillation circuit is used as the output terminal of the pulse waveform PWM3, wherein the PWM3 and the PWM2 have the same time period T cyc ; The time synchronization between the PWM3 and the PWM2 is achieved by performing a logic AND operation on the PWM3 and the PWM2. The waveform output after the logic AND operation is the on-off control waveform PWML of the freewheeling switch tube.

12. The device according to claim 8, wherein The measuring module (1) is further configured to measure the input terminal voltage V of the energy storage inductor. in and the output voltage V of the energy storage inductor out Afterwards, perform the following actions, including: According to the input voltage V in and the output voltage V of the energy storage inductor out At least one of the following, for the freewheeling time T con Make estimates; According to the input voltage V in and the output voltage V of the energy storage inductor out At least one of the above is used to calculate the output power of the photovoltaic power generation component that uses the BUCK circuit for power optimization to achieve maximum power point tracking of the photovoltaic power generation component.

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