Method and device for determining follow current time of BUCK circuit

Abstract

The invention provides a method for determining follow current time of a BUCK circuit. The method comprises the following steps: measuring an input end voltage Vin of an energy storage inductor and an output end voltage Vout of the energy storage inductor; determining an equal-ratio relational expression (Vin-Vout) / Vout = Tcon / Tinj by using the physical rule that the voltage at the two ends of the inductor is in direct proportion to the change rate of the current in the inductor, and solving the numerical value of the follow current time Tcon by using the equal-ratio relational expression; wherein (Vin-Vout) is the voltage of the two ends of the energy storage inductor in the magnetizing state, Vout is the voltage of the two ends of the energy storage inductor in the follow current state, Vout is the voltage of the output end of the energy storage inductor, Tcon is the follow current time, and Tinj is the magnetizing time; determining the turn-on time width TON value of a lower bridge arm switch tube Q2 by using the value of the Tcon; and determining the time parameter of the driving waveform PWML of the follow current tube by using the turn-on time width TON value of the lower bridge arm switch tube Q2. And the follow current time can be controlled in a PWM waveform generation link, and the cost is low.

Description

Technical Field

[0001] The present invention relates to the field of DC-DC power supplies, and particularly to a method and device for determining the freewheeling time of a BUCK circuit. Background Art

[0002] DC-DC converters using BUCK circuits are widely used in power electronic devices. In order to improve the reliability of the converter and avoid burning out the switching tubes, it is necessary to control and optimize the dead time between the upper and lower arm switching tubes of the BUCK circuit. In addition, in order to improve the conversion efficiency of the synchronous BUCK circuit and avoid damage to the switching tubes, it is necessary to accurately control the conduction time of the lower arm for energy storage inductor freewheeling.

[0003] A synchronous BUCK circuit consists of upper and lower arm switching tubes, an energy storage inductor, and an output filter capacitor. When the circuit works, two MOS tubes are controlled to conduct alternately by PWM signals, so as to control the inductor charging and discharging. The difference from the asynchronous BUCK circuit architecture is that the synchronous BUCK circuit uses MOS switches to participate in freewheeling to obtain lower freewheeling power consumption than freewheeling diodes.

[0004] In a synchronous BUCK circuit, PWMH is used to represent the driving waveform of the upper arm MOS Q1, and PWML is used to represent the driving waveform of the lower arm MOSQ2; I L is used to represent the inductor current waveform. Then, there is a short period of time on the PWMH and PWML waveforms during which PWMH and PWML are both low, and this time interval is the dead time. When PWMH is high and PWML is low, the upper arm tube MOS Q1 is turned on and the lower arm tube Q2 is turned off, and the inductor current rises; when PWMH is low and PWML is high, the upper arm tube MOSQ1 is turned off and the lower arm tube Q2 is turned on, and the inductor realizes freewheeling through Q2.

[0005] The existence of dead time in a BUCK circuit is because the so-called synchronization is relative. It is impossible to control the upper and lower arm switching transistors to be exactly one open and one closed in a perfect fit. Therefore, the controller follows a principle: it is better for the upper and lower arm switching transistors to be closed simultaneously to prevent current from passing through, rather than allowing the upper and lower arm switching transistors to have the chance to be open simultaneously, which would cause the current to directly short-circuit from the power input terminal through the upper and lower arm switching transistors to the power ground. Therefore, there must be a certain dead time between the drive signals of the upper and lower arm switching transistors to prevent the power input terminal from short-circuiting to the power ground through the upper and lower arm switching transistors. That is, within the dead time, neither the upper nor the lower arm switching transistor conducts. Any controller needs to avoid the upper and lower arm switching transistors being open simultaneously. If this state occurs, it is very easy to cause damage to the upper and lower arm switching transistors. To avoid this state, after the upper arm switching transistor Q1 is turned off, we have to wait for a period of time before operating to turn on the lower arm switching transistor. And the state where both the upper and lower arm switching transistors are off is what we call dead time. During the dead time, the freewheeling mainly depends on the parasitic diode of the lower arm switching transistor or an external diode connected in parallel with the lower arm switching transistor.

[0006] The patent with the application number CN201811301863.7 and the invention title "A Dead Time Setting Method and Its Application Device" gives a method of controlling the switching transistor for power output in an inverter to be turned on with a delay of a first duration and turned off with a delay of a second duration, so as to increase the on-time of the switching transistor as much as possible, improve the quality of the circuit output current, and effectively reduce harmonic distortion. At the same time, by controlling the other switching transistor driven in a complementary manner to be turned off normally and turned on with a delay of a third duration, and the third duration is greater than the second duration, to ensure that there is a dead time in the complementary control signals for these two switching transistors and avoid shoot-through. And when the power factor of the circuit where these two switching transistors are located changes, this method will obtain different judgment results according to the different power factors, and further set the respective durations of the delay on and off of the two switching transistors under the current power factor, avoiding the problem in the prior art that the dead time compensation effect is weakened due to different power factors. This patent sets a dead time Td between the control signals of the two switching devices on the upper and lower arms of the same phase; changes the original control signals D1 / D11 to D1’ / D11’, so that after the conducting power device is reliably turned off, after a certain time, the turned-off power device is triggered again. During this time, the power devices on both the upper and lower arms are in the off state.

[0007] The driving circuit given in the patent with the application number CN202211149632.5 and the invention title "A Driving Circuit for a High-Efficiency Buck Converter" includes: a through-conduction protection circuit, a high-side circuit, and a low-side circuit; the through-conduction protection circuit is respectively connected to the high-side circuit and the low-side circuit; the through-conduction protection circuit is used to prevent circuit damage; the high-side circuit is used to receive the PWM signal transmitted by the through-conduction protection circuit and generate a dynamic dead time from the high side to the low side; the low-side circuit is used to receive the PWM signal transmitted by the through-conduction protection circuit and generate a dead time from the low side to the high side. This application combines the application scenario of a wide input voltage range, uses the inductor current to change the charge and discharge time of the SW node capacitor, and then realizes the dynamic adjustment of the dead time under different load current conditions, ensuring the reliability of DC-DC while reducing power loss and improving efficiency; at the same time, the narrow pulse generation circuit part is omitted to further reduce the static power consumption and improve the system efficiency.

[0008] In existing PWM control chips, such as the PWM controller chip LM5146 of Texas Instruments, the end time of the freewheeling in the energy storage inductor is determined by detecting the change in the voltage between the source and drain of the lower-bridge switching transistor Q2. Specifically, a voltage comparator is used to monitor the voltage between the drain and source of Q2. When the voltage between the drain and source of Q2 changes from negative to positive, the zero-crossing point of the voltage between the drain and source of Q2 is used as the end time point of the freewheeling current of the energy storage inductor. After the voltage comparator detects this zero-crossing point, it outputs a level change signal, and this level change signal is used to turn off the lower-bridge switching transistor Q2.

[0009] In the prior art, although different methods are given for the optimization of the dead time setting, and a method for determining the freewheeling termination time point by monitoring the change in the voltage across the lower-bridge switching transistor Q2 is also given, however, the existing methods do not give a simple method for determining the freewheeling time length, nor do they give a PWM waveform generation method that comprehensively realizes duty cycle adjustment and freewheeling time adjustment in the generation of the control waveforms PWMH / PWML of the upper and lower-bridge switching transistors. Summary of the Invention

[0010] The present invention provides a method and device for determining the freewheeling time of a BUCK circuit, which are used to overcome the shortcomings of the existing DC-DC conversion technology, namely, the lack of a simple method for determining the freewheeling time length and the lack of a PWM waveform generation method that comprehensively realizes duty cycle adjustment and freewheeling time adjustment in the generation of the control waveforms PWMH / PWML of the upper and lower-bridge switching transistors.

[0011] The present invention provides a method for determining the freewheeling time of a BUCK circuit, including the following steps: Measure the input voltage V of the energy storage inductor in and the output voltage V of the energy storage inductor out ; Using the physical law that the voltage across an inductor is proportional to the rate of change of the current in the inductor, an equal ratio relationship (V in -V out ) / V out =T con / T inj is determined, and this equal ratio relationship is used to solve the value of the freewheeling time T con ; where, (V in -V out ) is the voltage across the energy storage inductor in the magnetizing state, V out is both the voltage across the energy storage inductor in the freewheeling state and the output voltage of the energy storage inductor, V out is also the output voltage of the energy storage inductor, T con is the freewheeling time, and T inj is the magnetizing time; Using the value of T con to determine the on-time width T ON value of the lower bridge arm switch tube Q2; using the on-time width T ON value of the lower bridge arm switch tube Q2 to determine the time parameter of the freewheeling tube drive waveform PWML.

[0012] The present invention provides a device for determining the freewheeling time of a BUCK circuit, comprising: a measurement module (1), a freewheeling time determination module (2) and a PWM waveform generation module (3); where, the measurement module (1) is used to measure the input voltage V in of the energy storage inductor and the output voltage V out of the energy storage inductor, and comprises a voltage conversion circuit and an analog-to-digital conversion circuit; the freewheeling time determination module (2) is used to use the physical law that the voltage across an inductor is proportional to the rate of change of the current in the inductor to determine an equal ratio relationship (V in -V out ) / V out =T con / T inj , and use this equal ratio relationship to solve the value of the freewheeling time T con ; where, (V in -V out ) is the voltage across the energy storage inductor in the magnetizing state, V out is both the voltage across the energy storage inductor in the freewheeling state and the output voltage of the energy storage inductor, V out is also the output voltage of the energy storage inductor, T con is the freewheeling time, and T inj is the magnetizing time, and comprises a digital arithmetic circuit and a memory; the PWM waveform generation module (3) is used to use T conThe value determines the conduction time width T of the lower-bridge switching tube Q2 ON value, and is used to use the conduction time width T of the lower-bridge switching tube Q2 ON value to determine the time parameter of the freewheeling diode drive waveform PWML; specifically, it includes the conduction time width T of the lower-bridge switching tube Q2 ON value to determine the sub-module and the PWML / PWMH waveform generation sub-module.

[0013] The method and device provided by the embodiments of the present invention can overcome the shortcomings of the existing DC-DC conversion technology, which lacks a simple method for determining the freewheeling time length and lacks a PWM waveform generation method that comprehensively realizes duty cycle adjustment and freewheeling time adjustment in the control waveform PWMH / PWML generation link of the upper and lower bridge switching tubes. It can control the freewheeling time in the PWM waveform generation link with low cost.

[0014] Other features and advantages of the present invention will be described in the subsequent specification. Brief Description of the Drawings

[0015] Figure 1 is a flowchart of a method for determining the freewheeling time of a BUCK circuit provided by an embodiment of the present invention; Figure 2 is a schematic diagram of the composition of a PWM waveform generation circuit for a BUCK circuit supporting automatic adjustment of freewheeling time provided by an embodiment of the present invention; Figure 3 is a schematic diagram of the mechanism for determining the freewheeling time of a BUCK circuit provided by an embodiment of the present invention; Figure 4 is a schematic diagram of PWM waveform generation for adaptively adjusting the freewheeling time provided by an embodiment of the present invention; Figure 5 is a schematic diagram of a PWM waveform generation circuit for adaptively adjusting the freewheeling time provided by an embodiment of the present invention.

[0016] In the figure, 1, measurement module; 2, freewheeling time determination module; 3, PWM waveform generation module; 4, drive module.

[0017] Embodiment The present invention provides a method and device for determining the freewheeling time of a BUCK circuit, which are used to overcome the shortcomings of the existing DC-DC conversion technology, which lacks a simple method for determining the freewheeling time length and lacks a PWM waveform generation method that comprehensively realizes duty cycle adjustment and freewheeling time adjustment in the control waveform PWMH / PWML generation link of the upper and lower bridge switching tubes.

[0018] To make the objectives, technical solutions, and advantages of the present invention more clear and understandable, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined arbitrarily with each other.

[0019] The following will give examples of the method and device provided by the present invention with reference to the accompanying drawings.

[0020] Example 1, an example of a method for determining the freewheeling time of a BUCK circuit An embodiment of the method for determining the freewheeling time of a BUCK circuit provided by the present invention includes the following steps: Measure the voltage V at the input end of the energy storage inductor in and the voltage V at the output end of the energy storage inductor out ; Using the physical law that the voltage across the inductor is proportional to the rate of change of the current in the inductor, determine the equal ratio relationship (V in -V out ) / V out =T con / T inj , and use this equal ratio relationship to solve the value of the freewheeling time T con ; where, (V in -V out ) is the voltage across the energy storage inductor in the magnetizing state, V out is both the voltage across the energy storage inductor in the freewheeling state and the voltage at the output end of the energy storage inductor, V out is also the voltage at the output end of the energy storage inductor, T con is the freewheeling time, and T inj is the magnetizing time; Use the value of T con to determine the on-time width T ON value of the lower-bridge switching transistor Q2; use the on-time width T ON value of the lower-bridge switching transistor Q2 to determine the time parameters of the freewheeling transistor drive waveform PWML.

[0021] Specifically, the voltage V at the input end of the energy storage inductor in is the voltage of the input end of the energy storage inductor with respect to the power supply ground in the magnetizing state; The voltage V at the output end of the energy storage inductor out is the voltage of the output end of the energy storage inductor with respect to the power supply 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.

[0022] The BUCK circuit described in the present invention is a synchronous BUCK circuit that uses the lower - arm switch transistor for freewheeling.

[0023] The method given in this embodiment, wherein, measuring the voltage V at the input end of the energy - storage inductor in and the voltage V at the output end of the energy - storage inductor out , includes: Measuring the voltage of the drain or source of the upper - arm switch transistor of the BUCK circuit relative to the power ground as the voltage V at the input end of the energy - storage inductor in ; Measuring the voltage across the output capacitor of the BUCK circuit as the voltage V at the output end of the energy - storage inductor out .

[0024] Specifically, as shown in Figure 2 , in the figure, the input end Ti of the inductor L1 is electrically connected to the source of the upper - arm switch transistor Q1 and the drain of the lower - arm switch transistor Q2. The output end 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. The 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 - supply ground wire GND of the BUCK circuit. A bypass diode D1 is connected in parallel between the source and drain of the upper - arm switch transistor Q1, and a bypass diode D2 is connected in parallel between the source and drain of the lower - arm switch transistor Q2. The input power supply 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 supply of the BUCK circuit can also be a battery or a power supply after AC - DC conversion.

[0025] Figure 2 In [], the measurement module 1 measures the voltage at the output end To of the energy - storage coil and the input voltage of the BUCK circuit; the measurement result of the voltage at the output end To of the energy - storage coil by the measurement module 1 is used as the voltage V at the output end of the energy - storage inductor out , and the measurement result of the input voltage of the BUCK circuit is used as the voltage V at the input end of the energy - storage inductor in ; Figure 2 In [], the measurement module 1 measures the voltage V at the input end of the energy - storage inductor at the drain of the upper - arm switch transistor Q1 of the BUCK circuit in , and its measurement result includes the on - voltage of the upper - arm switch transistor Q1; the measurement module 1 measures the voltage V at the input end of the energy - storage inductor at the source of the upper - arm switch transistor Q1 of the BUCK circuit in , then the measurement result does not include the on - voltage of the upper - arm switch transistor Q1.

[0026] The freewheeling - time determination module 2 obtains the voltage V at the output end of the energy - storage inductor out and the voltage V at the input end of the energy - storage inductor from the measurement module 1in The measured value, obtain the conduction time value of the upper-bridge arm switching transistor Q1 from the PWM waveform generation module 3, and this conduction time serves as the duration T of the magnetizing current of the energy storage inductor inj , use V in , V out , T inj as well as the relational expression (V in -V out ) / V out = T con / T inj , solve for the freewheeling time T con , and send the value of this freewheeling time T con to the PWM waveform generation module 3

[0027] The PWM waveform generation module 3 sends the value of the duration T of the magnetizing current of the inductor to the freewheeling time determination module 2, receives the value of the freewheeling time T inj from the freewheeling time determination module 2, and uses the value of this freewheeling time T con to determine the time parameters of the drive waveform PWML of the freewheeling diode Q2. The PWM waveform generation module 3 sends the PWMH waveform determined using the value of T con and the PWML waveform determined using the value of T inj to the drive module 4 con

[0028] The drive module 4 converts the PWMH sent by the PWM waveform generation module 3 into the signal form required to drive the upper-bridge arm switching transistor Q1, and converts the PWML sent by the PWM waveform generation module 3 into the signal form required to drive the lower-bridge arm switching transistor Q2

[0029] For the method given in this embodiment, where using the physical law that the voltage across an inductor is proportional to the rate of change of the current in the inductor, determine the equal ratio relational expression (V in -V out ) / V out = T con / T inj , including determine the equal relationship between the ratio of the voltage across the energy storage inductor in the magnetizing state (V in -V out ) to the voltage V out across the energy storage inductor in the freewheeling state and the ratio of the rate of change S1 of the magnetizing current I inj of the energy storage inductor to the rate of change S2 of the freewheeling current I con of the energy storage inductor: (V in -V out ) / V out ​= S1 / S2; According to the magnetizing current I inj The change rate S1 of is the slope of the rising diagonal line of the magnetizing current, and the change rate S2 of the freewheeling current I con is the slope of the falling diagonal line of the freewheeling current. The rising diagonal line of the magnetizing current and the falling diagonal line of the freewheeling current are the hypotenuses of two adjacent right triangles, and according to the definition of the slope, the relational expression is obtained: (V in -V out ) / V out = S1 / S2=T con / T inj ; The use of the geometric ratio relational expression (V in -V out ) / V out =T con / T inj to solve the freewheeling time T con value, including: Taking the measured value of the voltage V at the input end of the energy storage inductor obtained by using the measurement module (1) and the measured value of the voltage V at the output end of the energy storage inductor, and the magnetizing current time T in determined by the PWM waveform generation module (3) out value as known parameters, using the geometric ratio relational expression (V inj -V in ) / V out ) =T out / T con to solve the freewheeling time T inj value. con

[0030] Specifically, as shown in Figure 3 , in the figure, PWMH is the pulse width modulation waveform generated by the PWM waveform generation module 3 to control the on-off time of the upper bridge arm switch tube Q1, T cyc represents the period of PWMH, the slanted shaded part is the high-level time width of PWMH, which is also the on-time width of the upper bridge arm switch tube Q1 and the magnetizing current duration T inj of the energy storage inductor L1; Specifically, the value of T cyc is between 5 and 20 microseconds. In this embodiment, the value of T cyc is 10 microseconds.

[0031] The L1 voltage waveform is the waveform of the voltage across the energy storage inductor L1 in the magnetizing state and the freewheeling state. The voltage across the energy storage inductor L1 within the magnetizing current duration T inj is (V in -V out ), and within the freewheeling current duration T​​con The voltage across the internal energy storage inductor L1 is (-V out ); The current waveform of L1 shows the ratio S1 / S2 of the slope S1 of the magnetizing current to the slope S2 of the freewheeling current of the energy storage inductor L1 in the magnetizing state and the freewheeling state, and the freewheeling current duration T con and the magnetizing current duration T inj ratio T con / T inj The equal relationship between them; specifically, it can be seen from the figure 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 value I of the magnetizing current of the energy storage inductor L1 max ; The slope S1 of the hypotenuse OE of triangle OAE is the change rate of the magnetizing current, and the slope S2 of the hypotenuse BE of triangle BAE is the change rate 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 triangle OAE is the magnetizing current duration T inj , and the length of the base AB of triangle BAE is the freewheeling current duration T con , we get: S1 / S2 = (AE / OA) / (AE / AB) = AB / OA = T con / T inj In the current waveform diagram of L1, from point O to point C on the time axis is a PWM (pulse width modulation) period, which is also the period for the energy storage inductor L1 to complete one magnetizing and freewheeling cycle.

[0032] The method given in this embodiment, where The value of using T con to determine the on-time width T ON of the lower-arm switch Q2 includes: Using the relationship T ON = T con - T d1 - T △ to determine the on-time width T ON of Q2, where T △ is the time correction amount for T con ; T d1 is the first dead time between the lower-arm switch Q2 and the upper-arm switch Q1.

[0033] The on-time width T ONThe time parameters of the freewheeling diode drive waveform PWML are determined by values, including: The conduction time width T of the lower-arm switch Q2 is used. ON The value determines the high-level time width or duty cycle of the freewheeling diode drive waveform PWML.

[0034] Specifically, the freewheeling diode is the lower-arm switch Q2, and the freewheeling diode drive waveform PWML is the drive waveform of the lower-arm switch Q2.

[0035] Specifically, the PWML waveform and PWMH waveform given in this embodiment are the on-time waveforms of the lower-arm switch Q2 and the upper-arm switch Q1 respectively. The PWML waveform and PWMH waveform need to be converted by the drive circuit 4 to generate the current and voltage parameters required to drive the lower-arm switch Q2 and the upper-arm switch Q1.

[0036] Specifically, T △ The value range of is: 1 nanosecond ≤ T △ ≤ 2000 nanoseconds.

[0037] Furthermore, the value of T △ is determined according to the statistical distribution of the error between the calculated freewheeling current duration T con and the true value of the energy storage inductor freewheeling current duration for different loads and different ambient temperatures to determine the time correction amount T con of T △ so as to ensure that T ON + T d1 = T con - T △ is less than the true value of the energy storage inductor freewheeling current duration; or The time correction amount T con of T △ is within the range of 1% to 20% of the calculated value of the freewheeling current duration T con .

[0038] Specifically, as shown in Figure 3 , where the waveform PWML is the pulse width modulation waveform generated by the PWM waveform generation module 3 to control the on and off time of the lower-arm switch Q2. The shaded part of the waveform is the high-level time width of PWML and also the conduction time width T ON of the lower-arm switch Q2, T ON = T con - T d1 - T △ ; where T ON is the actual time length for which the lower-arm switch Q2 participates in freewheeling, and T con is the time using V in 、Vout , T inj and the relational expression (V in - V out ) / V out = T con / T inj The freewheeling time T obtained by solving, △ is the time correction amount for T con ; reducing the obtained value of T con by a time correction amount T △ and using it as the actual conduction time of the lower-arm switching transistor Q2 is to ensure that the actual conduction time of the lower-arm switching transistor Q2 is less than or equal to the actual freewheeling time required by the energy storage inductor L1; Reducing the obtained value of T con by a time correction amount T △ and using it as the actual conduction time of the lower-arm switching transistor Q2 is because, due to the error in the measured values of the input voltage V in and the output voltage V out of the energy storage inductor and the change in the load of the BUCK circuit, these factors will cause an error between the obtained value of T con and the actual freewheeling time of the inductor L1. When the obtained value of T con is greater than the actual freewheeling time of the inductor L1, after the freewheeling of the inductor L1 ends, the lower-arm switching transistor Q2 is still in the conduction state. After the freewheeling of the inductor L1 ends, it will conduct in the reverse direction, causing the electric energy of the output capacitor C1 to flow back to the power ground wire through the lower-arm switching transistor Q2. This reverse current reduces the efficiency of the BUCK circuit and will cause current and voltage surges, damaging the lower-arm switching transistor Q2.

[0039] To ensure that the electric energy in the output capacitor C1 does not flow back through the lower-arm switching transistor Q2 after the freewheeling of the inductor L1 ends, the design principle to be adopted is: turn off the lower-arm switching transistor Q2 before the freewheeling of the inductor L1 ends, leaving a little tail of the freewheeling current to complete the ending process of the freewheeling current through the body diode of the lower-arm switching transistor Q2 or the bypass diode D2 connected in parallel with Q2. During this ending process, although the freewheeling current flows through the bypass diode D2 with a higher conduction voltage, the value of the freewheeling current at this stage is already very small. Therefore, the increase in freewheeling power consumption caused by turning off the lower-arm switching transistor Q2 before the freewheeling of the inductor L1 ends is negligible.

[0040] At a specific PWM duty cycle, as shown in Figure 3 and Figure 4 , after the freewheeling of the inductor L1 ends, that is, after the freewheeling duration T con , there will be a time T off on the PWML waveform. During this Toff Within a certain period of time, both the upper-bridge switching transistor Q1 and the lower-bridge switching transistor Q2 are in the off state; in addition, the time T between when the lower-bridge switching transistor Q2 enters the off state and when the upper-bridge switching transistor Q1 starts to conduct d2 is the second dead time.

[0041] For the method provided in this embodiment, using the conduction time width T of the lower-bridge switching transistor Q2 ON to determine the high-level time width or duty cycle of the freewheeling diode drive waveform PWML, including: Using the first output terminal of the single-chip microcomputer as the PWM1 waveform output terminal, and using the second output terminal of the single-chip microcomputer as the PWM2 waveform output terminal. The high and low levels of PWM1 and PWM2 are inverted and have the same time period. The waveform PWM1 is used as PWMH for driving the upper-bridge switching transistor; Using the third output terminal of the single-chip microcomputer as the PWM3 waveform output terminal. The PWM3 waveform and the PWM2 waveform have the same time period T cyc , and 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 freewheeling diode drive waveform PWML; According to the conduction time width T of the lower-bridge switching transistor Q2 ON value, determine the high-level time width or duty cycle of PWM3, so as to determine the high-level time width of the freewheeling diode drive waveform PWML.

[0042] Specifically, as shown in Figure 4 , in the figure, the waveform PWM1 / PWMH is the output waveform of the first output terminal of the single-chip microcomputer, the waveform PWM2 is the output waveform of the second output terminal of the single-chip microcomputer. The high and low levels of PWM1 and PWM2 are inverted and have the same time period T cyc same, and the waveform PWM1 is used as PWMH for driving the upper-bridge switching transistor; 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. Refer to Figure 4 the rising edges in the PWM2 and PWM3 waveform diagrams in, that is, the rising edge of the PWM3 waveform is synchronized by the rising edge of the PWM2 waveform through the logical "AND" operation of the PWM3 waveform and the PWM2 waveform; A specific implementation method for generating the PWML waveform, refer to Figure 5As shown in the figure, in the PWM waveform generation module 3, the first output terminal of the single-chip microcomputer circuit is configured to output waveform PWM1, the second output terminal is configured to output waveform PWM2, and the third output terminal is configured to output waveform PWM3. Waveform PWM2 and waveform PWM3 generate waveform PWML through the "AND" operation circuit included in the PWM waveform generation module 3, and waveform PWML is output to the drive module 3. The drive module 3 controls the conduction time of the freewheeling diode (lower bridge arm switch Q2) according to the high-level time of waveform PWML.

[0043] Specifically, PWML and PWMH output by the PWM waveform generation module 3 are pulse signals with adjustable duty cycles. There is a definite time correspondence relationship between the pulse signal PWMH with adjustable duty cycle and the pulse signal PWML with adjustable duty cycle. This time correspondence relationship includes: There is a dead time when both the pulse signal PWMH with adjustable duty cycle and the pulse signal PWML with adjustable duty cycle are at low level; and, Outside the dead time, the high and low levels between the pulse signal PWMH with adjustable duty cycle and the pulse signal PWML with adjustable duty cycle are inverted with each other; and, 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.

[0044] Using the high level of the pulse signal PWML with adjustable duty cycle to drive the lower bridge arm switch Q2 that freewheels the energy storage inductor to make it enter the conduction state, a specific implementation method is: using the pulse signal PWML with adjustable duty cycle to send a high-level pulse to the control terminal of the lower bridge arm switch Q2 that freewheels the energy storage inductor. The rising edge of this high-level pulse lags behind the falling edge of the pulse signal PWMH in the same period by a first dead time T d1 , and the falling edge of this high-level pulse leads the rising edge of the pulse signal PWMH in the next period by a second dead time T d2 .

[0045] Generally, 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 that freewheels the energy storage inductor ON is determined by 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 : T ON = T con - T d1 - T △ .

[0046] The method given in this embodiment, where, The voltage V at the input terminal of the energy storage inductor in and the voltage V at the output terminal of the energy storage inductor out At least one of them is used for estimating the duration T con of the freewheeling current, and is also used for the maximum power point tracking of the photovoltaic power generation module serving as the input power source of the synchronous BUCK circuit.

[0047] Specifically, the photovoltaic power generation module includes a photovoltaic panel composed of multiple photovoltaic power generation units.

[0048] The maximum power point tracking of the photovoltaic power generation module is used to maximize the output power of the photovoltaic power generation module under different working conditions; since the output power of the photovoltaic power generation module is affected by abnormal conditions such as shading, foreign object coverage, and hot spots, the output power of the photovoltaic power generation module will decrease and will become the load of other photovoltaic power generation modules in the photovoltaic module string when these abnormal conditions occur, thus affecting the power output capacity and safety of the entire photovoltaic module string; in order to ensure that the photovoltaic power generation module can still output its potential power generation capacity to the best of its ability when these abnormal conditions occur, a photovoltaic power generation module power optimizer can be used to adjust the output power of the photovoltaic panel.

[0049] 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 realizing the optimization of the output power of the photovoltaic power generation module by the maximum power point tracking (MPPT: Maximum Power Point Tracing) method includes: changing the duty cycle of the BUCK circuit included in the optimizer to change the output power of the photovoltaic power generation module; at different duty cycles, calculating the output power of the photovoltaic power generation module using the output voltage and output current of the photovoltaic module, 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 value of the output power using the output power values of the photovoltaic module at different duty cycles, determining the duty cycle of the BUCK circuit corresponding to the maximum value of the output power, and making the BUCK circuit work at this duty cycle so as to make the photovoltaic power generation module work at or near its maximum power point.

[0050] The voltage V at the input terminal of the energy storage inductor in and the voltage V at the output terminal of the energy storage inductor out At least one of them is used for estimating the duration T con of the freewheeling current, and is also used for the maximum power point tracking of the photovoltaic power generation module serving as the input power source of the synchronous BUCK circuit. Specifically, The voltage V at the input terminal of the energy storage inductor in and the voltage V at the output terminal of the energy storage inductor out At least one of them is used for the equal ratio relationship (Vin -V out ) / V out =T con / T inj Solve for the freewheeling time T con value; and, In using the BUCK circuit to implement the maximum power point tracking (MPPT) of the photovoltaic power generation module, it is used to calculate the output power value of the photovoltaic power generation module.

[0051] Example 2, an example of a device for determining the freewheeling time of a BUCK circuit An embodiment of a device for determining the freewheeling time of a BUCK circuit provided by the present invention includes: A measurement module (1), a freewheeling time determination module (2) and a PWM waveform generation module (3); where The measurement module (1) is used to measure the voltage V at the input end of the energy storage inductor in and the voltage V at the output end of the energy storage inductor out , and includes a voltage conversion circuit and an analog-to-digital conversion circuit; The freewheeling time determination module (2) is used to use the physical law that the voltage across the inductor is proportional to the rate of change of the current in the inductor to determine the equal ratio relationship (V in -V out ) / V out =T con / T inj , and use this equal ratio relationship to solve for the freewheeling time T con value; where, (V in -V out ) is the voltage across the energy storage inductor in the magnetizing state, V out is both the voltage across the energy storage inductor in the freewheeling state, V out is also the voltage at the output end of the energy storage inductor, T con is the freewheeling time, T inj is the magnetizing time, and includes a digital arithmetic circuit and a memory; The PWM waveform generation module (3) is used to use the value of T con to determine the conduction time width T ON value of the lower bridge arm switch Q2, and is used to use the conduction time width T ON value of the lower bridge arm switch Q2 to determine the time parameters of the freewheeling diode drive waveform PWML; specifically includes a sub-module for determining the conduction time width T ON value of the lower bridge arm switch Q2 and a PWML / PWMH waveform generation sub-module.

[0052] Specifically, the voltage conversion circuit is used to convert the voltage V at the input end of the energy storage inductor in and the voltage V at the output end of the energy storage inductorout Convert to a voltage range suitable for the operation of the analog-to-digital conversion circuit. Typically, the voltage conversion circuit includes a voltage dividing circuit; The analog-to-digital conversion circuit is an independent A / D conversion chip or an A / D conversion circuit integrated in a microcontroller.

[0053] Specifically, the digital arithmetic circuit performs a solution operation on the relational expression (V in - V out ) / V out = T con / T inj under the control of an operation instruction; the memory is used to store the measured values of the input voltage V in and the output voltage V out of the energy storage inductor, the T inj value of the energy storage inductor L1, and the operation result.

[0054] The conduction time width T ON value determination sub-module of the lower bridge arm switching transistor Q2 includes a digital arithmetic circuit and a storage circuit. The arithmetic circuit performs an operation to calculate the T ON value under the control of the instruction stored in the storage circuit, and stores the T ON value output by the arithmetic circuit in the storage circuit; Preferably, as shown in Figure 5 , the digital arithmetic circuit and the storage circuit included in the conduction time width T ON value determination sub-module of the lower bridge arm switching transistor Q2 are a component of the microcontroller circuit; The PWML / PWMH waveform generation sub-module, as shown in Figure 5 , includes a digital arithmetic circuit, a storage circuit, a PWM waveform output circuit, and an "AND" arithmetic circuit; Specifically, the digital arithmetic circuit, the storage circuit, and the PWM waveform output circuit included in the PWML / PWMH waveform generation sub-module are a component of the microcontroller circuit. The PWM waveform output circuit includes the first, second, and third output terminals of the microcontroller circuit. Among them, the first output terminal is configured to output waveform PWM1, the second output terminal is configured to output waveform PWM2, the third output terminal is configured to output waveform PWM3, and the "AND" arithmetic circuit is used to output the "AND" operation between waveform PWM2 and output waveform PWM3.

[0055] For the device given in this embodiment, where the measurement module (1) that performs the operation of measuring the input voltage V in and the output voltage V out of the energy storage inductor further includes the following operations: Measure the voltage of the drain or source of the upper-bridge-arm switch tube of the BUCK circuit relative to the power supply ground as the input voltage V of the energy storage inductor in ; Measure the voltage across the output capacitor of the BUCK circuit as the output voltage V of the energy storage inductor out .

[0056] Specifically, as shown in Figure 2 , in the figure, the input terminal Ti of the inductor L1 is electrically connected to the source of the upper-bridge-arm switch tube Q1 and the drain of the lower-bridge-arm switch tube Q2. The 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. The 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 supply ground wire GND of the BUCK circuit. A bypass diode D1 is connected in parallel between the source and drain of the upper-bridge-arm switch tube Q1, and a bypass diode D2 is connected in parallel between the source and drain of the lower-bridge-arm switch tube Q2. The input power supply 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 supply of the BUCK circuit can also be a battery or a power supply after AC-DC conversion

[0057] Figure 2 , in which 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 result of the voltage at the output terminal To of the energy storage coil by the measurement module 1 is used as the output voltage V of the energy storage inductor out , and the measurement result of the input voltage of the BUCK circuit is used as the input voltage V of the energy storage inductor in ; Figure 2 , in which the measurement module 1 measures the input voltage V of the energy storage inductor at the drain of the upper-bridge-arm switch tube Q1 of the BUCK circuit in , and the measurement result includes the conduction voltage of the upper-bridge-arm switch tube Q1; the measurement module 1 measures the input voltage V of the energy storage inductor at the source of the upper-bridge-arm switch tube Q1 of the BUCK circuit in , then the measurement result does not include the conduction voltage of the upper-bridge-arm switch tube Q1

[0058] The freewheeling time determination module 2 obtains the measured values of the output voltage V of the energy storage inductor and the input voltage V of the energy storage inductor from the measurement module 1, and obtains the conduction time value of the upper-bridge-arm switch tube Q1 from the PWM waveform generation module 3. This conduction time is used as the duration T of the magnetizing current of the energy storage inductor out and the input voltage V of the energy storage inductor in , and uses V inj , V in , T out and the relationship formula (V inj -V in -Vout ) / V out =T con / T inj , solve for the freewheeling time T con , and send the value of this freewheeling time T con to the PWM waveform generation module 3.

[0059] The PWM waveform generation module 3 sends the duration T inj of the inductor magnetizing current to the freewheeling time determination module 2, and receives the freewheeling time T con from the freewheeling time determination module 2, and uses the value of this freewheeling time T con to determine the time parameters of the freewheeling diode Q2 drive waveform PWML. The PWM waveform generation module 3 will use T inj to determine the PWMH waveform and use T con to determine the PWML waveform and send them to the drive module 4.

[0060] The drive module 4 converts the PWMH sent by the PWM waveform generation 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 generation module 3 into the signal form required to drive the lower bridge arm switch tube Q2.

[0061] For the device given in this embodiment, where the freewheeling time determination module (2), which performs the operation of using the physical law that the voltage across the inductor is proportional to the rate of change of the current in the inductor to determine the equal ratio relationship (V in -V out ) / V out =T con / T inj , and uses this equal ratio relationship to solve for the value of the freewheeling time T con further includes the following operations: Determine the ratio between the voltage (V in -V out ) across the energy storage inductor in the magnetizing state and the voltage V out across the energy storage inductor in the freewheeling state is equal to the ratio between the rate of change S1 of the magnetizing current I inj of the energy storage inductor and the rate of change S2 of the freewheeling current I con of the energy storage inductor: (V in -V out ) / V out = S1 / S2; According to the rate of change S1 of the magnetizing current I inj , that is, the slope of the rising diagonal line of the magnetizing current, the freewheeling current I conThe rate of change S2 is the slope of the freewheeling current decline slope. The magnetization current rise slope and the freewheeling current decline slope are the hypotenuses of two adjacent right triangles, and from the definition of the slope, the relational expression is obtained: (V in -V out ) / V out = S1 / S2 = T con / T inj ; Taking the measured value of the voltage V in at the input end of the energy storage inductor obtained by using the measurement module (1) and the measured value of the voltage V out at the output end of the energy storage inductor, as well as the value of the magnetization current time T inj determined by the PWM waveform generation module (3) as known parameters, and using the equal ratio relational expression (V in -V out ) / V out = T con / T inj to solve for the numerical value of the freewheeling time T con .

[0062] Specifically, as shown in Figure 3 , in the figure, PWMH is the pulse width modulation waveform generated by the PWM waveform generation module 3 to control the on - off time of the upper - bridge - arm switch Q1. Tcyc represents the period of PWMH. The slanted shaded part is the high - level time width of PWMH, which is also the on - time width of the upper - bridge - arm switch Q1 and also the magnetization current duration T inj of the energy storage inductor L1; The L1 voltage waveform is the waveform of the voltage across the energy storage inductor L1 in the magnetization state and the freewheeling state. The voltage across the energy storage inductor L1 within the magnetization current duration T inj is (V in -V out ), and the voltage across the energy storage inductor L1 within the freewheeling current duration T con is (-V out ); The L1 current waveform shows the ratio S1 / S2 of the slope S1 of the magnetization current to the slope S2 of the freewheeling current of the energy storage inductor L1 in the magnetization state and the freewheeling state, and the ratio T con of the freewheeling current duration T inj to the magnetization current duration T con / T inj between them; specifically, it can be seen from the figure 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 value I max of the magnetization current of the energy storage inductor L1; 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 ,get: S1 / S2=(AE / OA) / (AE / AB)=AB / 0A=T con / T inj 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.

[0063] The device provided in this embodiment, wherein: The PWM waveform generation module (3) includes the conduction time width T of the lower bridge arm switch tube Q2 ON The value determines the use of T performed by the submodule con The value of determines the conduction time width T of the lower bridge arm switch tube Q2 ON Value operations further include the following operations: 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 arm switch tube Q2 and the upper arm switch tube Q1.

[0064] The PWML / PWMH waveform generation submodule included in the PWM waveform generation module (3) uses the conduction time width T of the lower bridge arm switch tube Q2. ON The operation of determining the time parameter of the freewheeling tube driving waveform PWML further includes the following operations: 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 freewheeling tube drive waveform PWML.

[0065] Specifically, the freewheeling tube is the lower arm switch tube Q2 , and the freewheeling tube driving waveform PWML is the driving waveform of the lower arm switch tube Q2 .

[0066] Specifically, the PWML waveform and PWMH waveform given in this embodiment are the on-time waveforms of the lower-bridge switch Q2 and the upper-bridge switch Q1 respectively. The PWML waveform and PWMH waveform need to be converted by the drive circuit 4 to generate the current and voltage parameters required to drive the lower-bridge switch Q2 and the upper-bridge switch Q1.

[0067] Specifically, the value range of T △ is: 1 nanosecond ≤ T △ ≤ 2000 nanoseconds.

[0068] Furthermore, the value of T △ is determined according to the statistical distribution of the error between the calculated freewheeling current duration T con and the true value of the freewheeling current duration of the energy storage inductor to determine the time correction amount T con for T △ so as to ensure that T ON + T d1 = T con - T △ is less than the true value of the freewheeling current duration of the energy storage inductor; or the time correction amount T con for T △ is within the range of 1% to 20% of the calculated value of the freewheeling current duration T con .

[0069] Specifically, as shown in Figure 3 , the waveform PWML is the pulse width modulation waveform generated by the PWM waveform generation module 3 to control the on and off time of the lower-bridge switch Q2. The shaded area with a diagonal line in the waveform is the high-level time width of PWML and also the on-time width T ON of the lower-bridge switch Q2. T ON = T con - T d1 - T △ ; where T ON is the actual time length for the lower-bridge switch Q2 to participate in freewheeling, T con is the freewheeling time solved using V in , V out , T inj and the relationship (V in - V out ) / V out = T con / T inj , T △ is the time correction amount for T con ; the obtained value of T con is reduced by a time correction amount T△ It is used as the actual conduction time of the lower-bridge arm switching transistor Q2 later, in order to ensure that the actual conduction time of the lower-bridge arm switching transistor Q2 is less than or equal to the actual freewheeling time required by the energy storage inductor L1; The obtained T con value is reduced by a time correction amount T △ The reason for using it as the actual conduction time of the lower-bridge arm switching transistor Q2 later is that due to the voltage V at the input end of the energy storage inductor in and the voltage V at the output end of the energy storage inductor out measurement values have errors, and the load of the BUCK circuit will change. These factors will cause an error between the obtained T con value and the actual freewheeling time of the inductor L1. When the obtained T con value is greater than the actual freewheeling time of the inductor L1, after the freewheeling of the inductor L1 ends, the lower-bridge arm switching transistor Q2 is still in the conduction state. After the freewheeling of the inductor L1 ends, it will conduct reversely, causing the electric energy of the output capacitor C1 to flow back to the power ground wire through the lower-bridge arm switching transistor Q2. This reverse current reduces the efficiency of the BUCK circuit and will cause current and voltage shocks, damaging the lower-bridge arm switching transistor Q2.

[0070] In order to ensure that the electric energy in the output capacitor C1 does not flow back through the lower-bridge arm switching transistor Q2 after the freewheeling of the inductor L1 ends, the design principle to be adopted is: turn off the lower-bridge arm switching transistor Q2 before the freewheeling of the inductor L1 ends, leaving a little tail of the freewheeling current to complete the ending process of the freewheeling current through the body diode of the lower-bridge arm switching transistor Q2 or the bypass diode D2 connected in parallel with Q2. During this ending process, although the freewheeling current flows through the bypass diode D2 with a higher conduction voltage, the value of the freewheeling current at this stage is already very small. Therefore, the increase in freewheeling power consumption caused by turning off the lower-bridge arm switching transistor Q2 before the freewheeling of the inductor L1 ends is negligible.

[0071] Under a specific PWM duty cycle, as shown in Figure 3 and Figure 4 shown, after the freewheeling of the inductor L1 ends, that is, after the freewheeling duration T con later, there will be a T off time on the PWML waveform. During this T off time, both the upper-bridge arm switching transistor Q1 and the lower-bridge arm switching transistor Q2 are in the off state; in addition, the time T d2 from when the lower-bridge arm switching transistor Q2 enters the off state to when the upper-bridge arm switching transistor Q1 starts to conduct is the second dead time.

[0072] The device given in this embodiment, where The operation of determining the high-level time width or duty cycle of the freewheeling diode drive waveform PWML by using the conduction time width T of the lower-bridge switching transistor Q2, which is performed by the PWML / PWMH waveform generation sub-module included in the PWM waveform generation module (3), further includes the following operations: ON Using the first output terminal of the single-chip microcomputer as the PWM1 waveform output terminal, using the second output terminal of the single-chip microcomputer as the PWM2 waveform output terminal, the high and low levels of PWM1 and PWM2 are inverted and have the same time period, and the waveform PWM1 is used as the PWMH for driving the upper-bridge switching transistor; Using the third output terminal of the single-chip microcomputer as the PWM3 waveform output terminal, the PWM3 waveform has the same time period T as the PWM2 waveform cyc By performing a logical "AND" operation on the PWM3 waveform and the PWM2 waveform to achieve time synchronization between the PWM3 waveform and the PWM2 waveform, and the output waveform of the "AND" operation is the freewheeling diode drive waveform PWML; According to the conduction time width T ON value of the lower-bridge switching transistor Q2, determine the high-level time width or duty cycle of PWM3, so as to determine the high-level time width of the freewheeling diode drive waveform PWML.

[0073] Specifically, as shown in Figure 4 In the figure, the waveform PWM1 / PWMH is the output waveform of the first output terminal of the single-chip microcomputer circuit, the waveform PWM2 is the output waveform of the second output terminal of the single-chip microcomputer, the high and low levels of PWM1 and PWM2 are inverted and have the same time period T cyc the same, and the waveform PWM1 is used as the PWMH for driving the upper-bridge switching transistor; The time synchronization between the PWM3 waveform and the PWM2 waveform is achieved by performing a logical "AND" operation on the PWM3 waveform and the PWM2 waveform. Refer to Figure 4 the rising edges in the PWM2 and PWM3 waveform diagrams in, that is, the rising edge of the PWM3 waveform is synchronized by the rising edge of the PWM2 waveform through the logical "AND" operation on the PWM3 waveform and the PWM2 waveform; A specific implementation method for generating the PWML waveform is shown in Figure 5 In the figure, the first output terminal of the single-chip microcomputer circuit included in the PWM waveform generation module 3 is configured to output the waveform PWM1, the second output terminal is configured to output the waveform PWM2, the third output terminal is configured to output the waveform PWM3, the waveform PWM2 and the waveform PWM3 generate the waveform PWML through the "AND" operation circuit included in the PWM waveform generation module 3, and the waveform PWML is output to the drive module 3. The drive module 3 controls the conduction time of the freewheeling diode (lower-bridge switching transistor Q2) according to the high-level time of the waveform PWML.

[0074] ​Specifically, 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 cycle and the pulse signal PWML with adjustable duty cycle, both of which are at low level at the same time; and, 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 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.

[0075] 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. A specific 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.

[0076] 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.

[0077] The device provided in this embodiment, wherein: 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 maximum power point tracking of the photovoltaic power generation component serving as the input power source of the synchronous buck circuit.

[0078] Specifically, the photovoltaic power generation assembly includes a photovoltaic power generation panel composed of a plurality of photovoltaic power generation units.

[0079] The maximum power point tracking of the photovoltaic power generation module is used to maximize the output power of the photovoltaic power generation module under different working conditions. Since the output power of the photovoltaic power generation module is affected by abnormal conditions such as occlusion shadows, foreign object coverage, and hot spots, when these abnormal conditions occur, the output power of the photovoltaic power generation module will decrease and will become the load of other photovoltaic power generation modules in the photovoltaic module string, thereby affecting the power output capacity and safety of the entire photovoltaic module string. In order to ensure that the photovoltaic power generation module can still output its potential power generation capacity to the best of its ability when these abnormal conditions occur, a photovoltaic power generation module optimizer can be used to adjust the output power of the photovoltaic panel.

[0080] The photovoltaic power generation module optimizer uses a BUCK circuit to adjust the output power of the photovoltaic power generation module. The method for realizing the optimization of the output power of the photovoltaic power generation module is the maximum power point tracking (MPPT: Maximum Power Point Tracing) 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; at different duty cycles, calculating the output power of the photovoltaic power generation module using the output voltage and output current of the photovoltaic module, 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 value of the output power using the output power values of the photovoltaic module at different duty cycles, determining the duty cycle of the BUCK circuit corresponding to the maximum value of the output power, and making the BUCK circuit work at this duty cycle to enable the photovoltaic power generation module to work at or near its maximum power point.

[0081] At least one of the input terminal voltage V of the energy storage inductor obtained by the measurement module (1) in and the output terminal voltage V of the energy storage inductor out is used not only for estimating the duration T of the freewheeling current con , but also for the maximum power point tracking of the photovoltaic power generation module that is the input power supply of the synchronous BUCK circuit. Specifically, At least one of the input terminal voltage V of the energy storage inductor in and the output terminal voltage V of the energy storage inductor out is used for the equal ratio relationship formula (V in -V out ) / V out =T con / T inj to solve for the value of the freewheeling time T con ; and, In using the BUCK circuit to achieve the maximum power point tracking (MPPT) of the photovoltaic power generation module, it is used to calculate the output power value of the photovoltaic power generation module.

[0082] The method provided by the embodiments of the present invention can be implemented wholly or partly by software instructions and / or hardware circuits; the modules or units included in the device provided by the embodiments of the present invention can be implemented by electronic components.

[0083] As described above, it is only a preferred implementation of the present invention and is not used to limit the protection scope of the present invention. Any person skilled in the art within the field of the present invention can make any modifications and changes in the form of implementation and details without departing from the spirit and scope disclosed by the present invention. However, the protection scope of the present invention shall be subject to the defined scope of the appended claims.

[0084] The method and device provided by the embodiments of the present invention overcome the disadvantages of the existing DC-DC conversion technology, which lacks a method for simply determining the length of the freewheeling time and lacks a PWM waveform generation method for comprehensively implementing duty cycle adjustment and freewheeling time adjustment in the control waveform PWMH / PWML generation link of the upper and lower bridge arm switching tubes. The freewheeling time can be controlled in the PWM waveform generation link, and the cost is low.

Claims

1. A method for determining the freewheeling time of a buck circuit, comprising the following steps: Measure the voltage V at the input of the energy storage inductor in and the output voltage of the energy storage inductor V out ; Using the physical law that the voltage across the inductor is proportional to the rate of change of the current in the inductor, we can determine the geometric relationship (V in -V out ) / V out =T con / T inj , use this geometric relationship to solve the continuous flow time T con The value of ; where (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; Use T con The value of determines the conduction time width T of the lower bridge arm switch tube Q2 ON value; use the conduction time width T of the lower bridge arm switch tube Q2 ON The value determines the time parameter of the freewheeling tube drive waveform PWML.

2. The method according to claim 1, wherein The measured energy storage inductor input voltage V in and the output voltage of the energy storage inductor V 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 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 .

3. The method according to claim 1, wherein The physical law that the voltage across the inductor is proportional to the rate of change of the current in the inductor is used to determine the geometric relationship (V in -V out ) / V out =T con / T inj ,include: Determine the voltage across the energy storage inductor in the magnetized state (V in -V out ) and the voltage V across the energy storage inductor in the freewheeling state out The ratio of the energy storage inductor magnetizing current I inj The rate of change S1 and the energy storage inductor freewheeling current I con The relationship between the rate of change of S2 is equal to: (V in -V out ) / V out = S1 / S2; 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, and the definition of the slope gives the relationship: (V in -V out ) / V out = S1 / S2= T con / T inj ; The geometric relationship (V in -V out ) / V out =T con / T inj Solve for the freewheeling time T con The values include: The energy storage inductor input voltage V is obtained using the 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 .

4. The method according to claim 1, wherein The use of T con The value of determines the conduction time width T of the lower bridge arm switch tube Q2 ON Values, including: 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 arm switch tube Q2 and the upper arm switch tube Q1.

5. The conduction time width T of the lower bridge arm switch tube Q2 is used ON The time parameters of the freewheeling tube drive waveform PWML are determined by the value, including: 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 freewheeling tube drive waveform PWML.

6. The method of claim 4, wherein: The conduction time width T of the lower bridge arm switch tube Q2 is used. ON The value determines the high-level time width or duty cycle of the freewheeling tube drive waveform PWML, including: 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; 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 freewheeling tube drive waveform PWML; According to 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 PWM3, thereby determining the high-level time width of the freewheeling tube drive waveform PWML.

7. The method of claim 2, wherein: 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 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.

8. A device for determining a freewheeling time of a buck circuit, comprising: A measuring module (1), a continuous flow time determination module (2) and a PWM waveform generation module (3); wherein, Measuring module (1), used 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 , including a voltage conversion circuit and an analog-to-digital conversion circuit; The freewheeling time determination module (2) is used to determine the geometric relationship (V in -V out ) / V out =T con / T inj , use this geometric relationship to solve the continuous flow time T con The value of 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 It is the magnetization time, including digital operation circuit and memory; PWM waveform generation module (3) is used to use T con The value of determines the conduction time width T of the lower bridge arm switch tube Q2 ON value, and the conduction time width T used for the lower bridge arm switch tube Q2 ON The value determines the time parameter of the freewheeling tube drive waveform PWML; specifically includes the conduction time width T of the lower bridge arm switch tube Q2 ON value determination submodule and PWML / PWMH waveform generation submodule.

9. The device according to claim 7, wherein The measuring module (1) 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 Operations further include the following operations: Measure 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 .

10. The device according to claim 7, wherein The freewheeling time determination module (2) uses the physical law that the voltage across the inductor is proportional to the rate of change of the current in the inductor to determine the geometric relationship (V in -V out ) / V out =T con / T inj , use this geometric relationship to solve the continuous flow time T con The numerical operation further includes the following operations: Determine the voltage across the energy storage inductor in the magnetized state (V in -V out ) and the voltage V across the energy storage inductor in the freewheeling state out The ratio of the energy storage inductor magnetizing current I inj The rate of change S1 and the energy storage inductor freewheeling current I con The relationship between the rate of change of S2 is equal to: (V in -V out ) / V out = S1 / S2; 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, and the definition of the slope gives the relationship: (V in -V out ) / V out = S1 / S2= T con / T inj ; The energy storage inductor input voltage V is obtained using the 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 .

11. The device according to claim 7, wherein The PWM waveform generation module (3) includes the conduction time width T of the lower bridge arm switch tube Q2 ON The value determines the use of T performed by the submodule con The value of determines the conduction time width T of the lower bridge arm switch tube Q2 ON Value operations further include the following operations: 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 arm switch tube Q2 and the upper arm switch tube Q1.

12. The PWML / PWMH waveform generation submodule included in the PWM waveform generation module (3) uses the conduction time width T of the lower bridge arm switch tube Q2 ON The operation of determining the time parameter of the freewheeling tube driving waveform PWML further includes the following operations: 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 freewheeling tube drive waveform PWML.

13. The device according to claim 10, wherein The PWML / PWMH waveform generation submodule included in the PWM waveform generation module (3) uses the conduction time width T of the lower bridge arm switch tube Q2 to generate the PWM waveform. ON The operation of determining the high level time width or duty cycle of the freewheeling tube drive waveform PWML further includes the following operations: 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; 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 freewheeling tube drive waveform PWML; According to 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 PWM3, thereby determining the high-level time width of the freewheeling tube drive waveform PWML.

14. The device according to claim 8, wherein 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 maximum power point tracking of the photovoltaic power generation component serving as the input power source of the synchronous buck circuit.

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