CN111934550B - Anti-backflow circuit, control method thereof and photovoltaic charging controller - Google Patents

Anti-backflow circuit, control method thereof and photovoltaic charging controller Download PDF

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Publication number
CN111934550B
CN111934550B CN202010745114.4A CN202010745114A CN111934550B CN 111934550 B CN111934550 B CN 111934550B CN 202010745114 A CN202010745114 A CN 202010745114A CN 111934550 B CN111934550 B CN 111934550B
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driving signal
current
tube
unit
output
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CN111934550A (en
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曹红泽
彭彪
杨桂贤
陈勇
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Shenzhen Shuorixin Energy Technology Co.,Ltd.
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Shenzhen Shuori New Energy Technology Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/35—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention relates to a backflow prevention circuit, which is connected between a solar cell panel and a storage battery, and comprises: the device comprises a BUCK charging unit, a driving unit and a main control unit, wherein the BUCK charging unit is connected between a solar cell panel and a storage battery and comprises a rectifying tube and a follow current tube; the driving unit is connected with the rectifying tube and the follow current tube; the main control unit is connected with the driving unit, and when the BUCK charging unit is in an inductive current discontinuous mode, the main control unit controls the driving unit to respectively output a first driving signal and a second driving signal to the rectifying tube and the follow current tube, wherein the second driving signal is output when the first driving signal is half of the turn-off time; and when the working state of the BUCK charging unit is in an inductive current continuous mode, controlling the driving unit to respectively output a third driving signal and a fourth driving signal to the rectifying tube and the follow current tube, wherein the fourth driving signal is output when the third driving signal is turned off. The main control unit can effectively prevent the energy of the storage battery from flowing backwards and improve the charging efficiency.

Description

Anti-backflow circuit, control method thereof and photovoltaic charging controller
Technical Field
The invention relates to the technical field of charging and discharging, in particular to a backflow prevention circuit, a control method thereof and a photovoltaic charging controller.
Background
A BUCK circuit is mainly adopted in an existing photovoltaic charging controller to reduce voltage and charge a storage battery, and the anti-backflow circuit is mainly designed in two modes.
As shown in fig. 1, the first way is to use a power diode in the freewheeling circuit to freewheel, and this method is suitable for a low-power BUCK circuit, which is stable, because of the unidirectional conduction property of the diode, there is no back flow during charging, the disadvantage is low efficiency, and when it is used for charging a high-power circuit, the freewheeling diode has large loss, and needs a large-volume heat sink, which is not only lower in efficiency, but also high in cost; as shown in fig. 2, the second way is to use fet to freewheel in the freewheel circuit, which has the following disadvantages: in the BUCK circuit of the photovoltaic charging controller, the output end is a storage battery, so that the situation that the storage battery cannot flow backwards to the follow-up tube cannot be guaranteed as in the conventional synchronous rectification BUCK circuit controller method, namely the main power tube and the follow-up tube are always complementary, and the follow-up tube needs to be correspondingly and specially controlled. Therefore, it is desirable to design a backflow prevention circuit, so that the backflow prevention situation does not occur in the photovoltaic charging controller using the circuit.
Disclosure of Invention
The invention aims to solve the technical problems that a backflow preventing circuit, a control method thereof and a photovoltaic charge controller are provided aiming at overcoming the defects in the prior art, and the problems that a storage battery is prone to backflow and the efficiency is not high enough in the conventional photovoltaic charge controller are solved.
The invention is realized by the following technical scheme: in a first aspect, the present invention provides a backflow prevention circuit, connected between a solar panel and a storage battery, including: the BUCK charging unit is connected between the solar cell panel and the storage battery and comprises a rectifying tube and a follow current tube connected with the rectifying tube, the rectifying tube is connected with the solar cell panel to rectify charging current, and the follow current tube is connected with the storage battery to provide a follow current passage for the storage battery; the driving unit is connected with the rectifying tube and the follow current tube of the BUCK charging unit; the main control unit is connected with the driving unit and used for controlling the driving unit to output a first driving signal to the rectifying tube and output a second driving signal to the follow current tube when the BUCK charging unit is in an inductive current discontinuous mode, wherein the second driving signal is output when the first driving signal is half of the turn-off time; and when the working state of the BUCK charging unit is an inductive current continuous mode, the main control unit controls the driving unit to output a third driving signal to the rectifying tube and output a fourth driving signal to the follow current tube, wherein the fourth driving signal is output when the third driving signal is turned off.
Further, the main control unit is further configured to control the driving unit to output a third driving signal to the rectifying tube and a fourth driving signal to the follow current tube in a time-delay manner when the working state of the BUCK charging unit is switched from the discontinuous inductive current mode to the continuous inductive current mode.
Further, the main control unit is further configured to control the driving unit to output a first driving signal to the rectifying tube and a second driving signal to the follow current tube when the working state of the BUCK charging unit is switched from the inductive current continuous mode to the inductive current discontinuous mode.
Further, the BUCK charging unit includes: the solar cell comprises a first field effect tube, a second field effect tube, a third field effect tube, a first capacitor, a second capacitor, a first resistor and an inductor, wherein the source electrode of the third field effect tube is connected with the anode of the solar cell panel, the drain electrode of the third field effect tube is connected with one end of the first capacitor, the other end of the first capacitor is connected with the cathode of the solar cell panel, the drain electrode of the first field effect tube is connected with the drain electrode of the third field effect tube and one end of the first capacitor, the grid electrode of the first field effect tube is connected with the main control unit, the source electrode of the first field effect tube is connected with the drain electrode of the second field effect tube and one end of the inductor, the grid electrode of the second field effect tube is connected with the main control unit, the source electrode of the second field effect tube is connected with the other end of the first capacitor, and the drain electrode of the second field effect tube is connected with one end of the second capacitor, the other end of the second capacitor is connected with the other end of the inductor through the first resistor, one end of the second capacitor is connected with the negative electrode of the storage battery, the other end of the second capacitor is connected with the positive electrode of the storage battery, and the phase point is located at the connecting intersection point of the source electrode of the first field effect transistor and the drain electrode of the second field effect transistor and one end of the inductor.
In a second aspect, the present invention provides a method for controlling a backflow prevention circuit, where the backflow prevention circuit is the backflow prevention circuit according to the first aspect, and the main control unit is configured to execute the method, and the method includes: collecting current charging current, current input voltage and current output voltage; judging the working state of the BUCK charging unit by using a preset rule according to the current charging current, the current input voltage and the current output voltage, wherein the working state comprises an inductive current continuous mode and an inductive current discontinuous mode; when the BUCK charging unit is in an inductive current discontinuous mode, controlling the driving unit to output a first driving signal and a second driving signal to the BUCK charging unit, wherein the second driving signal is output when the first driving signal is turned off for half of the turn-off time; when the working state of the BUCK charging unit is an inductive current continuous mode, the main control unit controls the driving unit to output a third driving signal and a fourth driving signal to the BUCK charging unit, wherein the fourth driving signal is output when the third driving signal is turned off.
Further, the preset rule is as follows: when V isin*D1＜VoutOr, Ic＜K1*IoutWhen the BUCK charging unit works, the working state of the BUCK charging unit is in an inductive current discontinuous mode; when V isin*D2≥VoutAnd Ic≥K2*IoutWhen the BUCK charging unit works, the working state of the BUCK charging unit is an inductive current continuous mode; wherein, the VinIs the current input voltage; the D1 is a first driving signal received by the rectifier tube; the V isoutIs the current output voltage; said IcIs the current charging current; the K1 is a preset first proportional coefficient; said IoutIs a rated charging current; the D2 is the duty ratio of the third driving signal received by the rectifier tube; the K2 is a preset second proportionality coefficient.
Further, the difference between the first proportionality coefficient and the second proportionality coefficient is 1% -3%.
Further, the control method further includes: and when the working state of the BUCK charging unit is converted from the inductive current discontinuous mode to the inductive current continuous mode, the drive unit is controlled to output a third drive signal and a fourth drive signal to the BUCK charging unit in a delayed mode.
Further, the control method further includes: and when the working state of the BUCK charging unit is converted from the inductive current continuous mode to the inductive current discontinuous mode, controlling the driving unit to output a first driving signal and a second driving signal to the BUCK charging unit.
In a third aspect, the present invention provides a photovoltaic charging controller, which includes the backflow prevention circuit as described in the first aspect.
The invention has the beneficial effects that when the solar cell panel charges the storage battery, the main control unit is used for outputting the control signal, the control signal generates the driving signal through the driving unit, the driving signal enables the rectifying tube and the follow current tube of the BUCK charging unit to have different working states, and the BUCK charging unit works in an inductive current discontinuous mode or an inductive current continuous mode, so that the storage battery is charged with high efficiency, and the energy of the storage battery is prevented from flowing backwards.
Drawings
The following detailed description of embodiments of the invention will be made with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic diagram of a reverse flow prevention circuit employing a power diode in a freewheel circuit;
FIG. 2 is a schematic diagram of a reverse-flow prevention circuit using a field effect transistor in a freewheel circuit;
FIG. 3 is a block diagram of the anti-backflow circuit of the present invention;
FIG. 4 is a schematic diagram of a BUCK charging unit according to the present invention;
FIG. 5 is a schematic diagram of the construction of the drive unit and the main control unit of the present invention;
FIG. 6 is a flow chart illustrating a control method of the anti-backflow circuit according to the present invention;
FIG. 7 is a waveform diagram of a first drive signal and a second drive signal of the present invention;
FIG. 8 is a waveform diagram of a third drive signal and a fourth drive signal of the present invention;
FIG. 9 is a diagram of the BUCK charging unit of the present invention converting the driving signal when the current rises;
fig. 10 is a schematic diagram of the BUCK charging unit of the present invention converting the driving signal when the current drops.
Detailed Description
Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention. The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
Referring to fig. 3, the present invention provides a backflow prevention circuit 10 connected between a solar cell panel 140 and a storage battery 150, including: the BUCK charging unit 110 is connected between the solar cell panel 140 and the storage battery 150, the BUCK charging unit 110 comprises a rectifying tube and a follow current tube connected with the rectifying tube, the rectifying tube is connected with the solar cell panel 140 to rectify the charging current, and the follow current tube is connected with the storage battery 150 to provide a follow current path for the storage battery 150; the driving unit 120 is connected to the rectifying tube and the follow current tube of the BUCK charging unit 110; the main control unit 130 is connected to the driving unit 120, and the main control unit 130 is configured to control the driving unit 120 to output a first driving signal to the rectifying tube and output a second driving signal to the freewheeling tube when the BUCK charging unit 110 is in the discontinuous inductive current mode, where the second driving signal is output when half of the turn-off time of the first driving signal; and when the working state of the BUCK charging unit 110 is the inductor current continuous mode, the main control unit 130 controls the driving unit 120 to output a third driving signal to the rectifying tube and a fourth driving signal to the freewheeling tube, wherein the fourth driving signal is output when the third driving signal is turned off.
When the solar cell panel 140 charges the storage battery 150, the main control unit 130 outputs a control signal, the control signal generates a driving signal through the driving unit 120, the driving signal enables the rectifying tube and the follow current tube of the BUCK charging unit 110 to have different working states, and the BUCK charging unit 110 operates in an inductive current discontinuous mode or an inductive current continuous mode, so that the storage battery 150 is charged efficiently, and the energy of the storage battery 150 is prevented from flowing backwards.
In one embodiment, the main control unit 130 is further configured to output the third driving signal and the fourth driving signal to the BUCK charging unit 110 by the delay control driving unit 120 when the operating state of the BUCK charging unit 110 is switched from the discontinuous inductor current mode to the continuous inductor current mode. In the embodiment, the time-delay conversion can make the system more stable, and avoid the erroneous judgment of the working state transition of the BUCK charging unit 110.
In one embodiment, the main control unit 130 is further configured to immediately control the driving unit 120 to output the first driving signal and the second driving signal to the BUCK charging unit 110 when the operating state of the BUCK charging unit 110 is switched from the inductor current continuous mode to the inductor current discontinuous mode. In this embodiment, the immediate switch avoids input glitches: the input voltage is converted from low voltage to high voltage, or the output is suddenly changed: the energy of the battery 150 flows backward due to the reason that the battery end is changed from heavy load to light load.
In one embodiment, referring to fig. 4, the BUCK charging unit 110 includes: a first field effect tube, a second field effect tube, a third field effect tube, a first capacitor, a second capacitor, a first resistor and an inductor, wherein the source electrode of the third field effect tube is connected with the anode of the solar cell panel 140, the drain electrode of the third field effect tube is connected with one end of the first capacitor, the other end of the first capacitor is connected with the cathode of the solar cell panel 140, the drain electrode of the first field effect tube is connected with the drain electrode of the third field effect tube and one end of the first capacitor, the grid electrode of the first field effect tube is connected with the main control unit 130, the source electrode of the first field effect tube is connected with the drain electrode of the second field effect tube and one end of the inductor, the grid electrode of the second field effect tube is connected with the main control unit 130, the source electrode of the second field effect tube is connected with the other end of the first capacitor, the drain electrode of the second field effect tube is connected with one end of the second capacitor, the other end of the second capacitor is connected with the other end of the inductor through the first resistor, one end of the second capacitor is connected to the negative electrode of the battery 150, and the other end of the second capacitor is connected to the positive electrode of the battery 150, wherein the phase point is located at the connection intersection point of the source of the first field effect transistor and the drain of the second field effect transistor and one end of the inductor.
Preferably, in the present embodiment, referring to fig. 5, the driving unit 120 includes: the driving circuit comprises a driving chip, a diode, a second resistor, a third resistor, a fourth resistor, a third capacitor and a fourth capacitor, wherein the VB end of the driving chip is connected with the output end of the diode and the anode of the fourth capacitor, the cathode of the fourth capacitor is connected with the VS end of the driving chip, the VS end of the driving chip is connected with the phase point of the BUCK charging unit 110, the input end of the diode is connected with one end of the fourth resistor, the other end of the fourth resistor is connected with the anode end of the third capacitor and the anode of the driving power supply of the driving chip, the anode end of the driving chip is connected with the anode end of the third capacitor, the cathode end of the third capacitor is grounded, the COM end of the driving chip is grounded, one end of the second resistor is connected with the HIN end of the driving chip, the other end of the second resistor is connected with the main control unit 130, one end of the third resistor is connected with the LIN end of the driving chip, the other end of the third resistor is connected with the main control unit 130, the HO end of the driving chip is connected with the grid electrode of the first field effect tube, and the LO end of the driving chip is connected with the grid electrode of the second field effect tube.
An embodiment of the present invention further provides a control method of the backflow prevention circuit 10, referring to fig. 6, the backflow prevention circuit 10 is the aforementioned backflow prevention circuit 10, the main control unit 130 is configured to execute the control method, and the control method includes:
s01, collecting the current charging current, the current input voltage and the current output voltage;
s02, judging the working state of the BUCK charging unit 110 by using a preset rule according to the current charging current, the current input voltage and the current output voltage, wherein the working state comprises an inductive current continuous mode and an inductive current discontinuous mode;
s03, when the BUCK charging unit 110 is in the inductor current discontinuous mode, controlling the driving unit 120 to output a first driving signal and a second driving signal to the BUCK charging unit 110, wherein the second driving signal is output at a half of the turn-off time of the first driving signal;
s04, when the working state of the BUCK charging unit 110 is the inductor current continuous mode, the main control unit 130 controls the driving unit 120 to output a third driving signal and a fourth driving signal to the BUCK charging unit 110, wherein the fourth driving signal is output when the third driving signal is turned off.
By collecting the current charging current, the current input voltage and the current output voltage, and using the preset rule to judge that the BUCK charging unit 110 is in the inductive current discontinuous mode or the inductive current continuous mode, and generating the control signal through the main control unit 130, the control signal controls the driving unit 120 to output the driving signal, the driving rectifier tube and the follow current tube have different working states, so that the BUCK charging unit 110 works in the judged corresponding working state, thereby achieving the purpose of efficiently charging the storage battery 150, and avoiding the energy of the storage battery 150 from flowing backwards.
In one embodiment, the preset rule is: when V isin*D1＜VoutOr, Ic＜K1*IoutWhen the charging unit is in the charging state, the working state of the BUCK charging unit is in an inductive current discontinuous mode; when V isin*D2≥VoutAnd Ic≥K2*IoutWhen the charging unit is in the inductive current continuous mode, the working state of the BUCK charging unit is in the inductive current continuous mode; wherein, VinIs the current input voltage; d1 is the first driving signal received by the rectifier tube; voutIs the current output voltage; i iscIs the current charging current; k1 is a preset first proportional coefficient; i isoutIs a rated charging current; d2 is the duty ratio of the third driving signal received by the rectifier tube; k2 is a preset second scaling factor. In this embodiment, K is represented by the formula K ═ Ik/Iout100%, wherein the output current is increased from 0A under the condition that the input voltage and the output voltage are rated, the inductive current is measured, and the output current is I when the inductive current is continuousk。
When V is satisfiedin*D1＜VoutOr, Ic＜K1*IoutThe output waveforms of the first drive signal and the second drive signal are as shown in fig. 7. At the moment, the duty ratios of the first driving signal and the third driving signal are according to the required output target voltage and the actually sampled current output voltage VoutFeedback is obtained, wherein the calculation formula of D is as follows: d ═ Vout/Vin100%. In this embodiment, the value of the minimum duty cycle is 3% to 5%, so that when the BUCK charging unit 110 operates in the discontinuous mode of the inductor current, the follow current tube only has a very small duty cycle, i.e., the current flowing through the follow current tube is very small, and other main currents follow the current through the parasitic body diode of the follow current tube, so that the input sudden change can be avoided by using the diode: the input voltage is converted from low voltage to high voltage, or the output is suddenly changed: the energy of the battery 150 flows backward due to the reason that the battery end is changed from heavy load to light load.
When V is satisfiedin*D≥VoutAnd Ic≥K*IoutThe output waveforms of the third drive signal and the fourth drive signal are shown in fig. 8. At the moment, the duty ratio of the third driving signal is according to the required output target voltage and the actually sampled current output voltage VoutThe fourth driving signal is output when the third driving signal is turned off, so that the BUCK charging unit 110 operates in the continuous inductive current mode, and at this time, the rectifier and the follow current tube can operate in the complementary mode, thereby improving the charging efficiency.
In one embodiment, the difference between the first scaling factor and the second scaling factor is between 1% and 3%. In the embodiment, the difference between the first scaling factor K1 and the second scaling factor K2 is 1% -3%, so as to prevent the system from oscillating at the critical point.
In one embodiment, the control method further includes: when the operating state of the BUCK charging unit 110 is switched from the inductor current discontinuous mode to the inductor current continuous mode, the delay control driving unit 120 outputs the third driving signal and the fourth driving signal to the BUCK charging unit 110. Referring to fig. 9, when the BUCK charging unit 110 is in the discontinuous inductor current mode, the charging current rises at time t1, that is, when the operating state of the BUCK charging unit 110 is changed to the continuous inductor current mode, the main control unit 130 may determine and delay after determining for multiple times, and control the driving unit 120 to output the third driving signal and the fourth driving signal to the BUCK charging unit 110 at time t2, which may make the system more stable and avoid the erroneous determination of the operating state change of the BUCK charging unit 110.
In one embodiment, the control method further includes: when the operating state of the BUCK charging unit 110 is switched from the inductor current continuous mode to the inductor current discontinuous mode, the driving unit 120 is immediately controlled to output the first driving signal and the second driving signal to the BUCK charging unit 110. Referring to fig. 10, when the BUCK charging unit 110 is in the inductor current continuous mode, and the charging current drops at time t1, that is, when the operating state of the BUCK charging unit 110 transitions to the inductor current discontinuous mode, the main control unit 130 immediately controls the driving unit 120 to output the first driving signal and the second driving signal to the BUCK charging unit 110 at time t3, which can avoid the input sudden change: the input voltage is converted from low voltage to high voltage, or the output is suddenly changed: the energy of the battery 150 flows backward due to the reason that the battery end is changed from heavy load to light load.
The embodiment of the invention also provides a photovoltaic charging controller, which comprises the backflow prevention circuit 10. By applying the backflow prevention circuit 10 to the photovoltaic charge controller, the energy of the storage battery 150 can be effectively prevented from flowing back to the solar panel.
It should be understood that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same, and those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some technical features; and all such modifications and alterations are intended to fall within the scope of the appended claims.

Claims (6)

1. The utility model provides a prevent flowing backward circuit, its connection is between solar cell panel and battery, a serial communication port, include:
the BUCK charging unit is connected between the solar cell panel and the storage battery and comprises a rectifying tube and a follow current tube connected with the rectifying tube, the rectifying tube is connected with the solar cell panel to rectify charging current, and the follow current tube is connected with the storage battery to provide a follow current path for the storage battery;
the driving unit is connected with the rectifying tube and the follow current tube of the BUCK charging unit;
the main control unit is connected with the driving unit and used for controlling the driving unit to output a first driving signal to the rectifying tube and output a second driving signal to the follow current tube when the BUCK charging unit is in an inductive current discontinuous mode, wherein the second driving signal is output when the first driving signal is half of the turn-off time; and the number of the first and second groups,
when the working state of the BUCK charging unit is an inductive current continuous mode, the main control unit controls the driving unit to output a third driving signal to the rectifying tube and output a fourth driving signal to the follow current tube, wherein the fourth driving signal is output when the third driving signal is turned off;
the main control unit is further used for controlling the driving unit to output a third driving signal to the rectifying tube and a fourth driving signal to the follow current tube in a delayed manner when the working state of the BUCK charging unit is converted from the inductive current discontinuous mode to the inductive current continuous mode;
the main control unit is further used for immediately controlling the driving unit to output a first driving signal to the rectifying tube and a second driving signal to the follow current tube when the working state of the BUCK charging unit is converted from the inductive current continuous mode to the inductive current discontinuous mode.
2. The anti-backflow circuit of claim 1, wherein the BUCK charging unit comprises: the solar cell comprises a first field effect tube, a second field effect tube, a third field effect tube, a first capacitor, a second capacitor, a first resistor and an inductor, wherein the source electrode of the third field effect tube is connected with the anode of the solar cell panel, the drain electrode of the third field effect tube is connected with one end of the first capacitor, the other end of the first capacitor is connected with the cathode of the solar cell panel, the drain electrode of the first field effect tube is connected with the drain electrode of the third field effect tube and one end of the first capacitor, the grid electrode of the first field effect tube is connected with a main control unit, the source electrode of the first field effect tube is connected with the drain electrode of the second field effect tube and one end of the inductor, the grid electrode of the second field effect tube is connected with the main control unit, the source electrode of the second field effect tube is connected with the other end of the first capacitor, and the drain electrode of the second field effect tube is connected with one end of the inductor, the other end of the second capacitor is connected with the other end of the inductor through the first resistor, one end of the second capacitor is connected with the negative electrode of the storage battery, the other end of the second capacitor is connected with the positive electrode of the storage battery, and the phase point is located at the connecting intersection point of the source electrode of the first field effect transistor and the drain electrode of the second field effect transistor and one end of the inductor.
3. A control method of a backflow prevention circuit, wherein the backflow prevention circuit is the backflow prevention circuit of any one of claims 1-2, the main control unit is configured to execute the control method, and the control method includes:
collecting current charging current, current input voltage and current output voltage;
judging the working state of the BUCK charging unit by using a preset rule according to the current charging current, the current input voltage and the current output voltage, wherein the working state comprises an inductive current continuous mode and an inductive current discontinuous mode;
when the BUCK charging unit is in an inductive current discontinuous mode, controlling the driving unit to output a first driving signal and a second driving signal to the BUCK charging unit, wherein the second driving signal is output when the first driving signal is turned off for half of the turn-off time;
when the working state of the BUCK charging unit is an inductive current continuous mode, the main control unit controls the driving unit to output a third driving signal and a fourth driving signal to the BUCK charging unit, wherein the fourth driving signal is output when the third driving signal is turned off;
when the working state of the BUCK charging unit is converted from the inductive current continuous mode to the inductive current discontinuous mode, immediately controlling the driving unit to output a first driving signal and a second driving signal to the BUCK charging unit;
and when the working state of the BUCK charging unit is converted from the inductive current discontinuous mode to the inductive current continuous mode, the drive unit is controlled to output a third drive signal and a fourth drive signal to the BUCK charging unit in a delayed mode.
4. The method of claim 3, wherein the predetermined rule is:
when V isin*D1＜VoutOr, Ic＜K1*IoutWhen the BUCK charging unit works, the working state of the BUCK charging unit is in an inductive current discontinuous mode;
when V isin*D2≥VoutAnd Ic≥K2*IoutWhen the BUCK charging unit works, the working state of the BUCK charging unit is an inductive current continuous mode;
wherein, the VinIs the current input voltage; the D1 is the duty ratio of the first driving signal received by the rectifier tube; the V isoutIs the current output voltage; said IcIs the current charging current; the K1 is a preset first proportional coefficient; said IoutIs a rated charging current; the D2 is the duty ratio of the third driving signal received by the rectifier tube; the K2 is a preset second proportionality coefficient.
5. The method for controlling the backflow prevention circuit according to claim 4, wherein the difference between the first scaling factor and the second scaling factor is 1% -3%.
6. A photovoltaic charge controller comprising the backflow prevention circuit as claimed in any one of claims 1-2.
CN202010745114.4A 2020-07-29 2020-07-29 Anti-backflow circuit, control method thereof and photovoltaic charging controller Active CN111934550B (en)

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