CN109391232B - Current detection device applied to photovoltaic power optimizer - Google Patents

Current detection device applied to photovoltaic power optimizer Download PDF

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CN109391232B
CN109391232B CN201710653542.2A CN201710653542A CN109391232B CN 109391232 B CN109391232 B CN 109391232B CN 201710653542 A CN201710653542 A CN 201710653542A CN 109391232 B CN109391232 B CN 109391232B
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voltage
current
operational amplifier
conversion circuit
resistor
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CN109391232A (en
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张永
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Fonrich Shanghai New Energy Technology Co ltd
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Fonrich Shanghai New Energy Technology Co ltd
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02SGENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • H02S50/10Testing of PV devices, e.g. of PV modules or single PV cells
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03KPULSE TECHNIQUE
    • H03K2217/00Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00
    • H03K2217/0027Measuring means of, e.g. currents through or voltages across the switch
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy

Abstract

The invention mainly relates to a current detection device applied to a photovoltaic power optimizer, which is provided with a voltage conversion circuit configured for a photovoltaic module and used for executing maximum power point tracking, wherein the voltage provided by the photovoltaic module after power optimization is carried out is output by the voltage conversion circuit. The voltage difference value of the two ends of the inductor measured by the operational amplifier is divided by the inductance value of the induction inductor to be equal to the change rate of the measured current along with time. The input current and the output current of the voltage conversion circuit which is regarded as the power optimizer are accurately collected on the premise of not causing excessive power loss.

Description

Current detection device applied to photovoltaic power optimizer
Technical Field
The invention mainly relates to the technical field of photovoltaic power generation, in particular to a method for accurately collecting input current and output current of a voltage conversion circuit of a power optimizer on the premise of not causing excessive power loss in the situation of needing monitoring current in the scheme of driving the power optimizer.
Background
When the current detector collects actual current, an analog signal can be output, and because the amplitude of the analog signal is very small, the analog signal is amplified by a one-level or even multi-level amplifying circuit and can be distinguished by the analog-digital signal converter, so that accurate reading can be obtained. There are three main sources of current acquisition errors: error of the current detector; error of amplifying circuit, error of analog-to-digital conversion and error of reference source. For the current detection in a wider range, the amplitude range of the analog signal output by the current detector is wider, different amplification factors are needed to realize signal conditioning, if only one amplification factor is used, the precision of large and small measurement ranges cannot be considered, and the final result is that the precision is higher in a small current section, larger current cannot be measured, or large current can be measured accurately, and the detection precision of small current is reduced. How to ensure the detection precision of the full range, namely to improve the reading precision, is an urgent problem to be solved. Switching regulators, such as voltage regulators used for microprocessor voltage regulation, often need to detect the average inductor current, however, conventional average inductor current detection methods often introduce significant noise components into the detection results and result in low signal-to-noise ratios.
The current transformer is a sensor instrument which converts a large current on a primary side into a small current on a secondary side according to the electromagnetic induction principle to measure current. The current transformer consists of a closed iron core and a winding, the number of turns of the winding on the primary side of the current transformer is small, and the current transformer is connected in a line of current to be measured in series. Therefore, all current of a line always flows through the current transformer, the turn ratio of the secondary side winding is large and the current transformer is connected in series in the measuring instrument and the protection loop, and the secondary side loop of the current transformer is always closed when the current transformer works, so that the impedance of the series coil of the measuring instrument and the protection loop is small, and the working state of the current transformer is close to a short circuit. The current transformer converts a large current on a primary side into a small current on a secondary side for measurement.
In the current detection device of the related art, there are a type of detecting a current from a magnetic field change by a current magnetic field conversion element and a type of detecting a current integrated value to ground at a given time by detecting a voltage across a current detection resistor. The type using the current-magnetic field conversion element has a great advantage and capability of detecting a current at a high speed within a certain sampling period. It is difficult to accurately detect current in a large current range. In particular, errors are likely to occur when detecting a large current. And this type also causes detection errors due to the influence of the residual magnetic component of the element itself. This type of detection means is therefore difficult to detect currents with high precision in the high current range, making its application fields, in particular the photovoltaic field, very unsuitable. The type of integrating the voltage of the current detection resistor has an advantage that the current can be detected with high accuracy, but a non-detection time zone in which the current cannot be detected may occur, that is, the current cannot be detected with high accuracy over the entire time zone, such as a time zone in which the calculated current is communicated. In particular, in the time zone where detection is impossible, if a current abruptly changes, a detection error is significantly increased, and thus there is a disadvantage that the abruptly changed current cannot be accurately detected.
At present, a shunt or a hall sensor is also commonly used for detecting load current and battery current in a power supply system, wherein the shunt is an accurate resistor with a small resistance value and capable of passing large current, when the current flows through the shunt, a voltage of millivolt level appears at two ends of the shunt, and then after the voltage is obtained through measurement, the voltage is converted into the current, and the measurement of the large current is completed. The current divider is connected in series in a circuit, and then a high-precision operational amplifier is adopted to realize the detection of the power supply current by using a differential detection method. However, when current detection is performed using a shunt, in order to ensure detection accuracy, a high-accuracy shunt of a standard specification is generally required to be arranged, and the requirement for the shunt is relatively strict, so that accuracy of current detection is greatly limited, and the high-accuracy shunt also causes problems of large heat generation and high cost, and is not suitable for a shunt in a voltage conversion circuit as a power optimizer.
Disclosure of Invention
In one non-limiting alternative embodiment of the present invention, a current sensing apparatus for a photovoltaic power optimizer is disclosed, which essentially comprises: the voltage conversion circuit is configured for the photovoltaic module and used for executing maximum power point tracking, wherein the voltage provided by the photovoltaic module after power optimization is carried out is output by the voltage conversion circuit; an inductive inductor for sensing an input current of the voltage conversion circuit; and/or an inductive inductance for sensing an output current of the voltage conversion circuit; the two ends of any induction inductor are respectively coupled with the positive phase end and the negative phase end of the operational amplifier, and the operational amplifier compares and amplifies the voltages representing the current flowing through the induction inductor at the two ends of the induction inductor.
The above-mentioned current detection device who is applied to photovoltaic power optimizer, wherein: a first resistor is connected between the inverting end of the operational amplifier and one end of the induction inductor corresponding to the inverting end of the operational amplifier; a third resistor is connected between the positive phase end of the operational amplifier and the other end of the induction inductor corresponding to the positive phase end of the operational amplifier; a second resistor is connected between the inverting end and the output end of the operational amplifier; and a fourth resistor is connected between the positive phase end of the operational amplifier and a preset reference potential.
The above-mentioned current detection device who is applied to photovoltaic power optimizer, wherein: the resistance value of the first resistor is equal to that of the third resistor; the resistance value of the second resistor is equal to the resistance value of the fourth resistor; the ratio of the resistance value of the second resistor to the resistance value of the first resistor is multiplied by the voltage difference between the two ends of the induction inductor to be equal to the output voltage of the operational amplifier.
The above-mentioned current detection device who is applied to photovoltaic power optimizer, wherein: and a capacitor for filtering out high-frequency pulsating voltage components passing through the induction inductor is connected in parallel with two ends of the fourth resistor.
In one non-limiting alternative embodiment of the present invention, a current sensing apparatus for a photovoltaic power optimizer is disclosed, which essentially comprises: the voltage conversion circuit is configured for the photovoltaic module and used for executing maximum power point tracking, wherein the voltage provided by the photovoltaic module after power optimization is carried out is output by the voltage conversion circuit; the voltage conversion circuit includes: first and second switches connected in series between first and second nodes receiving a voltage source provided by the photovoltaic module; the third switch and the fourth switch are connected in series between a third node and a fourth node which provide output voltage after the photovoltaic module is subjected to power optimization; an inductance element is provided between an interconnection node between the first and second switches and an interconnection node between the third and fourth switches; the input current of the voltage conversion circuit is sensed by an induction transistor which forms a mirror circuit with the first switch; the width-to-length ratio of the first switch is proportional to the width-to-length ratio of the sense transistor; and the sensing transistor is connected with a sensing resistor in series, the voltage difference between two ends of the sensing resistor represents the mirror image current of the input current, and the input current and the mirror image current are in proportional relation.
The above-mentioned current detection device who is applied to photovoltaic power optimizer, wherein: the sense transistor is in series with the sense resistor between first and second nodes.
The above-mentioned current detection device who is applied to photovoltaic power optimizer, wherein: the clamping transistor is connected with the sensing transistor and the sensing resistor in series between a first node and a second node; the grid control end of the clamping transistor is coupled to the output end of an operational amplifier; the sensing transistor is connected between the inverting terminal of the operational amplifier and a first node; the first switch is connected between the non-inverting terminal of the operational amplifier and a first node.
The above-mentioned current detection device who is applied to photovoltaic power optimizer, wherein: the voltage conversion circuit also comprises an inductive inductor used for sensing the output current of the voltage conversion circuit; the two ends of the induction inductor are respectively coupled with the positive phase end and the negative phase end of the operational amplifier, and the operational amplifier compares and amplifies the voltage representing the current flowing through the induction inductor at the two ends of the induction inductor.
The above-mentioned current detection device who is applied to photovoltaic power optimizer, wherein: the RC low-pass filter is used for sensing the output current of the voltage conversion circuit; the inductance element is connected with the RC low-pass filter in parallel, and the two ends of a capacitor in the RC low-pass filter are respectively coupled with a positive phase end and an inverted phase end of the operational amplifier; comparing and amplifying the voltages at both ends of the capacitor in the RC low-pass filter by an operational amplifier; the time constant of the RC low-pass filter is equal to the time constant between the inductance of the inductance element and the parasitic resistance of the inductance element; the ratio of the voltage across the capacitor to the resistance of the parasitic resistor in the RC low pass filter represents the output current flowing through the inductive element.
In one non-limiting alternative embodiment of the present invention, a current detection device applied to a photovoltaic power optimizer is disclosed, which mainly comprises: the voltage conversion circuit is configured for the photovoltaic module and used for executing maximum power point tracking, wherein the voltage provided by the photovoltaic module after power optimization is carried out is output by the voltage conversion circuit; the voltage conversion circuit includes: first and second switches connected in series between first and second nodes receiving a voltage source provided by the photovoltaic module; the third switch and the fourth switch are connected in series between a third node and a fourth node which provide output voltage after the photovoltaic module is subjected to power optimization; an inductance element is provided between an interconnection node between the first and second switches and an interconnection node between the third and fourth switches; wherein: further comprising an RC low pass filter for sensing a current of the voltage conversion circuit; the inductance element is connected with the RC low-pass filter in parallel, and the two ends of a capacitor in the RC low-pass filter are respectively coupled with the positive phase end and the negative phase end of the operational amplifier; comparing and amplifying the voltages at both ends of the capacitor in the RC low-pass filter by an operational amplifier; the time constant of the RC low-pass filter is equal to the time constant between the inductance of the inductance element and the parasitic resistance of the inductance element; the ratio of the voltage across the capacitor to the resistance of the parasitic resistor in the RC low pass filter represents the current flowing through the inductive element.
In one non-limiting alternative embodiment of the present invention, a method of detecting a current of a photovoltaic power optimizer is disclosed, wherein a photovoltaic module is configured with a voltage conversion circuit that performs maximum power point tracking, wherein a voltage provided by the photovoltaic module after power optimization is output by the voltage conversion circuit, the voltage conversion circuit comprising: first and second switches connected in series between first and second nodes receiving a voltage source provided by the photovoltaic module; the third switch and the fourth switch are connected in series between a third node and a fourth node which provide output voltage after the photovoltaic module is subjected to power optimization; an inductance element is provided between an interconnection node between the first and second switches and an interconnection node between the third and fourth switches; the method comprises the following steps: the input current of the voltage conversion circuit is detected by using an induction transistor which forms a mirror image circuit with the first switch, and the mirror image current of the input current is represented by the voltage difference between two ends of an induction resistor which is connected with the induction transistor in series; the output current of the voltage conversion circuit is detected by an RC low-pass filter connected with the inductance element in parallel, the time constant of the RC low-pass filter is equal to the time constant between the inductance of the inductance element and the parasitic resistance of the inductance element, and the ratio of the voltage at two ends of the capacitor in the RC low-pass filter to the resistance value of the parasitic resistance represents the output current flowing through the inductance element.
The method described above, wherein: the clamping transistor is connected with the sensing transistor and the sensing resistor in series between a first node and a second node; the grid control end of the clamping transistor is coupled to the output end of an operational amplifier; the sensing transistor is connected between the inverting terminal of the operational amplifier and a first node; a first switch is connected between the non-inverting terminal of the operational amplifier and a first node; the potentials of the positive phase terminal and the negative phase terminal of the operational amplifier are forced to be equal by the operational amplifier.
Drawings
To make the above objects, features and advantages more comprehensible, embodiments accompanied with figures are described in detail below, and features and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the following figures.
FIG. 1 is a schematic diagram of an embodiment of a conventional current sensing device using a shunt or resistor.
Fig. 2 is a schematic diagram of photovoltaic modules connected in series and then in parallel to power an inverter.
Fig. 3 is a schematic diagram of conventional current detection implemented by using an inductive inductor instead of a current divider.
Fig. 4 is a schematic diagram of current sensing using a sense transistor that consumes little power.
Fig. 5 is a schematic diagram of the sense transistor in conjunction with the operational amplifier clamping the positive and negative terminal potentials.
Fig. 6 is a schematic diagram of detecting a current with a low-pass filter that consumes little power.
Detailed Description
The technical solutions of the present invention will be clearly and completely described below with reference to various embodiments, but the described embodiments are only used for describing and illustrating the present invention and not for describing all embodiments, and the solutions obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.
In a switching power supply system, a power supply generally employs a power semiconductor device as a switching element, and a duty ratio of the switching element is controlled to adjust an output voltage by periodically turning on and off the switch. The switch power supply mainly comprises an input circuit, a conversion circuit, an output circuit, a control unit and the like. The power conversion is a core part and mainly comprises a switching circuit, and a transformer is applied to some occasions. In order to meet the requirement of high power density, the converter needs to work in a high-frequency state, the switching transistor needs to adopt a crystal arm with high switching speed and short on and off time, and a typical power switch comprises a power thyristor, a power field effect transistor, an insulated bipolar transistor and the like. The control method is divided into various methods such as pulse width modulation, mixed modulation of pulse width modulation and frequency modulation, pulse frequency modulation, and the like, and the most common method is the pulse width modulation method.
Referring to fig. 1, in order to explain the inventive spirit of the scheme for implementing current detection related to the present application, an illustrative voltage converter for implementing power conversion is taken as an example, and includes: a first front side node NI1 and a second front side node NI2, and further a first back side node NO1 and a second back side node NO 2. In which a switch S1 and a switch S2 employing power transistors are connected in series between a first front-side node NI1 and a second front-side node NI2, and an inductive element L is coupled between an interconnection node NX1 to which both the switch S1 and the switch S2 are connected and a first back-side node NO 1. If the voltage converter is a BUCK circuit, the switch S1 and the switch S2 form a voltage reduction single arm. In the BUCK circuit, the illustrated switches S3-S4 can be directly eliminated from the circuit topology, and the inductive element L of the BUCK circuit can be directly connected between the interconnection node NX1 and the first back-side node NO 1. It is also possible to connect the back side capacitance CO illustrated in the figure between the first back side node NO1 and the second back side node NO2 or to connect the front side capacitance CIN illustrated in the figure between the first front side node NI1 and the second front side node NI 2. The second front side node NI2 and the second back side node NO2 may be directly coupled together to have the same reference potential GRE, such as the ground GND potential. The power conversion BUCK circuit can operate independently.
Referring to fig. 1, in order to explain the inventive spirit of the scheme for implementing current detection related to the present application, an illustrative voltage converter for implementing power conversion is taken as an example, and includes: a first front side node NI1 and a second front side node NI2, and further a first back side node NO1 and a second back side node NO 2. Wherein a switch S3 and a switch S4 employing power transistors are connected in series between the first back side node NO1 and the second back side node NO2, and an inductance L is coupled between an interconnection node NX2 to which both the switch S3 and the switch S4 are connected and the first front side node NI 1. If the voltage converter is a BOOST circuit, the switch S3 and the switch S4 form a BOOST single arm. In the BOOST circuit, the illustrated switches S1-S2 may be directly eliminated from the circuit topology, and the inductor L in the BOOST circuit may be directly connected between the interconnect node NX2 and the first front-side node NI 1. Also the back side capacitance CO illustrated in the figure may be connected between the first back side node NO1 and the second back side node NO2, and the front side capacitance CIN illustrated in the figure may be connected between the first front side node NI1 and the second front side node NI 2. The BOOST circuit of the power conversion can operate independently.
Referring to fig. 1, an alternative voltage converter for power conversion is taken as an example: a first front side node NI1 and a second front side node NI2 are included, and a first back side node NO1 and a second back side node NO2 are included. The switch S1 and the switch S2 using power transistors are connected in series between the first front side node NI1 and the second front side node NI2, the switch S3 and the switch S4 using power transistors are connected in series between the first back side node NO1 and the second back side node NO2, note that the switch S1 and the switch S2 are both connected to the interconnection node NX1, and the switch S3 and the switch S4 are both connected to the interconnection node NX2, and the inductor L is connected between the first interconnection node NX1 and the second interconnection node NX 2. Whereby the single arm S1-S2 as the BUCK of the previous stage and the single arm S3-S4 as the BOOST of the subsequent stage are combined into a BUCK-BOOST circuit which is H-bridged and has both BUCK and BOOST power conversion capability.
Referring to fig. 1, the first front-side node NI1 and the second front-side node NI2 of the power conversion can be coupled to the positive and negative electrodes of various voltage sources, respectively, such as photovoltaic modules, fuel cells, and batteries, and the optimizer can also generate an output voltage, i.e., provide an output voltage between the first rear-side node NO1 and the second rear-side node NO2 after power optimization.
Referring to fig. 1, the first mode: the voltage modulation method for the power conversion circuit to work in the Step-down mode comprises the following steps: the processor outputs a pulse modulated signal to control the switch S1 and the switch S2 to turn on or off. The switches S1-S2 are alternately turned ON during each buck switching cycle, where the time S1-ON for switch S1 to turn ON and the time S1-OFF for switch S1 to turn OFF are set first for each buck switching cycle, and the time S2 is turned ON for switch S2-ON and the time S2 is turned OFF for switch S2-OFF for each buck switching cycle. The dead Time D-Time, in which both switches are off, between the switch S1 being on and the switch S2 being on, prevents both switches S1-S2 from being on at the same Time, which is the operating mechanism of the voltage step-down circuit. If S3-S4 is adopted, the fact that the switch S4 is continuously turned on and the switch S3 is continuously turned off in the Buck mode is defined means that the BOOST function is partially forced to be lost at this stage.
Referring to fig. 1, the second mode: the voltage modulation method for the power conversion circuit to work in the boost mode Step up comprises the following steps: the pulse modulated signal output by the processor controls the switch S3 and the switch S4 to be turned on or off. The switch S3 and the switch S4 are alternately turned ON during each boost switching cycle, where the time S3-ON when the switch S3 is turned ON and the time S3-OFF when the switch S3 is turned OFF during each boost switching cycle are set, and the time S4 is turned ON during each boost switching cycle is S4-ON and the time S4 is turned OFF is S4-OFF. Also, providing a dead Time D-Time during the BOOST switching cycle between the switch S3 being on and the switch S4 being off avoids the switches S3-S4 being turned on directly at the same Time, which is the operating mechanism of the BOOST circuit, which would limit the switch S1 to be continuously on and the switch S2 to be continuously off if S1-S2 were employed, meaning that at this stage the Buck portion is forced to lose its Buck function.
Referring to fig. 1, the third mode: the voltage modulation method under the condition that the power conversion circuit works in a Buck-Boost mode comprises the following steps: the pulse modulated signal output by the processor controls the switch S1 and the switch S2 to be turned on or off. The switches S1-S2 are alternately turned ON during buck switching cycles, with the switch S1 being turned ON for S1-ON and the switch S1 being turned OFF for S1-OFF for each buck switching cycle, and with the switch S2 being turned ON for S2-ON and the second switch S2 being turned OFF for S22-OFF for each buck switching cycle. A dead Time D1-Time is provided between the turning on of the prescribed switch S1 and the turning on of the switch S2, in which both switches are off. The pulse modulation signal output by the processor controls the on or off of the switch S3 and the switch S4 of the subsequent voltage converter in addition to the on or off of the switch S1 and the switch S2 of the preceding voltage converter, and alternately turns on the switch S3 and the switch S4 in each boost switching cycle of the subsequent voltage converter. The Time S3-ON of the switch S3 and the Time S3-OFF of the switch S3 are set in each boost switching period, the Time S4 is set to be S4-ON and the Time S4 is set to be S4-OFF in each boost switching period, and a dead Time D2-Time is set between the turn-ON of the switch S3 and the turn-ON of the switch S4 in the boost switching period. The former-stage voltage converter with the switch S1 and the switch S2 in the third mode is a Buck step-down stage, meanwhile, the latter-stage voltage converter with the switch S3 and the switch S4 in the third mode is a Boost step-up stage, and the whole power conversion circuit is embodied as a Buck-Boost circuit. Note that the second front side node NI2 and the second back side node NO2 may have the same potential, e.g. a common reference ground. When the difference value between the voltage of the NO1-NO2 end of the power conversion circuit and the voltage of the NI1-NI2 end of the power conversion circuit exceeds a preset value, the power conversion circuit works in a voltage reduction or voltage increase working state. Or when the difference value between the voltage of the NO1-NO2 end of the power conversion circuit and the voltage of the NI1-NI2 end of the power conversion circuit is not higher than a preset value, the power conversion circuit works in a buck-boost working state. The power conversion circuit is a bidirectional DC/DC conversion circuit.
Referring to fig. 1, a voltage conversion circuit PO configured by photovoltaic cells PV for performing maximum power tracking is illustrated as an example. The first and second input nodes NI1 and NI2 of the voltage conversion circuit PO are connected to the positive and negative electrodes of the corresponding photovoltaic cells PV, respectively. The actual voltage provided by the photovoltaic cells PV after power-optimized MPPT is output between the first output node NO1 and the second output node NO2 of the voltage conversion circuit PO. The MPPT basic principle of the voltage conversion circuit in the figure is mainly: the first input node and the second input node of the voltage conversion circuit PO extract a dc photovoltaic voltage source from between the anode and the cathode of the photovoltaic cell PV, wherein the pulse width modulation signal PWM generated by the processor 100 operating the MPPT operation drives the voltage conversion circuit PO to perform dc-to-dc voltage conversion, the conversion circuit PO usually has a BUCK circuit, a BOOST circuit or a BUCK-BOOST circuit, the pulse width modulation signal PWM operating the MPPT operation mainly drives the switching tube in the voltage conversion circuit to be turned on and off, and the switching tube rectification control mode of the voltage conversion circuit PO has a synchronous switching mode or switching modes of a main switching tube and a freewheeling diode, etc. It should be noted that, implementing Maximum Power Tracking Maximum Power Point Tracking on a DC/DC to DC voltage conversion circuit in the boundary is a mature technology, and there are a constant voltage method, a conductance increment method, a disturbance observation method, etc. for common Maximum Power Tracking, which is not described in detail herein, and any existing Maximum Power Tracking technology is applicable to the DC/DC voltage conversion circuit PO of the present application.
Referring to fig. 2, in both small-sized power plants and large-sized photovoltaic power plants, a large number of power plants are used in the photovoltaic power plants from the photovoltaic effect of photovoltaic modules to the final generation of ac power for grid connection. Taking arrays of photovoltaic modules as an example, they are the basis for the conversion of light energy into electrical energy in photovoltaic power generation systems. Fig. 2 shows a photovoltaic module array in which parallel cell strings are installed, each cell string is formed by connecting K-stage series photovoltaic modules PV1, PV2 … to PVK in series, where K is a natural number greater than or equal to 1. The photovoltaic modules or cells PV are each provided with a power optimization circuit PO for performing maximum power tracking MPPT, for example, the photovoltaic voltage generated by the first photovoltaic module PV1 is dc-dc voltage converted by the first power optimization circuit PO1 to perform power optimization, the photovoltaic voltage generated by the second photovoltaic module PV2 is voltage converted by the second power optimization circuit PO2, and the photovoltaic voltage generated by the photovoltaic module PVK of the kth class is voltage converted by the power optimization circuit POK of the kth class to perform power optimization. It is only the voltage output by the power optimization circuit PO corresponding to each photovoltaic cell PV that can represent the actual voltage value that the photovoltaic cell PV provides on the photovoltaic cell string. Firstly, assuming that a series of photovoltaic cells of any string is connected in series with a first-stage photovoltaic module PV1, a second-stage photovoltaic module PV2 … and a photovoltaic module PVK of a K-th stage, a first-stage power optimization circuit PO1 is used for performing maximum power tracking on a photovoltaic voltage source of a first-stage photovoltaic cell PV1 to perform voltage conversion and output V1The power optimization circuit POK to the K level performs maximum power tracking on the photovoltaic voltage of the photovoltaic cell PVK of the K level to perform voltage conversion and output VKIt can be learned that the total string level voltage across any string of photovoltaic cell strings eventually equals: voltage V output by first stage power optimization circuit PO11Plus second stage powerVoltage V output by optimization circuit PO22And the output voltage V of the third-stage power optimization circuit PO33… … added to the voltage V output by the power optimization circuit POK of the K stageKThe result of the cascade voltage is equal to V1+ V2+……VK. The power optimizer or voltage conversion circuit in this application is essentially a dc-to-dc converter, such as BUCK, BOOST, and BUCK-BOOST power converters. It should be emphasized that any scheme for tracking the maximum power of the photovoltaic cell in the prior art is also applicable to the voltage conversion circuit of the present application, and the common maximum power tracking methods include a constant voltage method, a conductance increment method, a disturbance observation method, and the like, and the present application does not describe any scheme how the voltage conversion circuit performs maximum power tracking MPPT. The foregoing explains that the voltage output by the power optimization circuit corresponding to each photovoltaic cell is indicative of the actual voltage that the photovoltaic cell provides on the corresponding photovoltaic cell string: the first-stage power optimization circuit PO1, the second-stage power optimization circuit PO2 to the K-th-stage power optimization circuit POK and the like are connected in series through a series connection line, and the series voltage superposed by the optimization circuits PO1-POK on the series connection line is transmitted to electric power equipment similar to a combiner box and/or an inverter INVT through a direct current bus to be combined/inverted.
In the field of photovoltaic power generation, since the output voltage and/or output current of the battery assembly PV itself as a dc voltage source fluctuates with the change of the intensity of the illumination radiation, the input voltage and/or input current of the power optimizer or so-called voltage converter/voltage converter also has synchronous dynamic fluctuations, which makes it difficult to accurately acquire or detect the input current of the power optimizer. Moreover, in order to obtain the commercial power alternating current required by the power grid or the load, a two-stage or even multi-stage architecture is required in the inverter system, that is, the power optimizer in the present application is regarded as a front-stage dc converter to complete the matching and electrical isolation of the input and output voltages of the inverter, the inverter INVT completes the inversion conversion of the direct current and the alternating current, and in practical application, the direct current voltage source provided by the power optimizer is supplied to the rear-stage inverter as a voltage source. Because the output voltage and current of the rear-stage inverter are low-frequency alternating current, the instantaneous power output by the rear-stage inverter contains double-frequency pulsating quantity, and the low-frequency pulsating power enables the input current of the inverter to contain larger double-frequency output voltage frequency alternating current component, namely the output current of the front-stage direct current converter to generate low-frequency pulsation, and the pulsating power is shared by the output filter inductor of the direct current converter and the middle bus capacitor. The input current of the preceding stage boost or buck or boost-buck converter (optimizer), i.e. the output current of the photovoltaic cell, may also pulsate at twice the power frequency, and this pulsation not only reduces the accuracy of maximum power tracking, but also deteriorates electromagnetic interference and causes abnormal heating of the photovoltaic cell, resulting in negative effects on the power generation capacity of the power generation system and the life cycle of the components. The low-frequency ripple component on the inductance of the preceding-stage voltage converter is inevitably transmitted to the input end of the preceding-stage voltage converter PO, which inevitably requires that the similar photovoltaic cell or other equivalent input sources have strong capability of bearing large ripple current, the ripple current has a great threat to the service life of the photovoltaic cell or the storage battery and the fuel cell serving as the input source, especially the service life requirement of the silicon cell is up to more than twenty years, and the current measurement of the voltage converter PO is influenced by the existence of the ripple current.
Referring to fig. 3, the current detection device is mainly used for sensing the input current or the output current of the voltage conversion circuit PO, and utilizes an inductive inductor LSEN. Slightly different from the principle of the current measuring resistor RSEN1-2 in FIG. 1, the current measuring resistor RSEN1 in FIG. 1 is connected between the positive electrode P1 of the module PV and the first front-side node NI1 or between the negative electrode P2 of the module PV and the second front-side node NI2, and the input current is measured by the current measuring resistor RSEN1, which measures the voltage difference across the input current, and then divides the measured voltage difference by the resistance of the current measuring resistor to obtain the input current value. Similarly, it is assumed in fig. 1 that there are a port O1 coupled to the first back-side node NO1 and a port O2 coupled to the second back-side node NO1, wherein the output current of the voltage conversion circuit PO mainly flows from the port O1 to the port O2 and then flows out, the measuring resistor RSEN2 is connected between the port O1 and the first back-side node NO1 or between the port O2 and the second back-side node NO2, the measuring resistor RSEN2 measures the output current by first measuring the voltage difference across the resistor RSEN2, and the measured voltage difference is divided by the resistance of the measuring resistor RSEN2 to substantially equal the output current value. In fig. 3, the measuring resistor RSEN of fig. 1 is replaced by an inductive inductor LSEN. The specific embodiment is as follows: the inductive inductor LSEN1 is connected between the positive pole P1 of the module PV and the first front-side node NI1 or between the negative pole P2 of the module PV and the second front-side node NI2, and the inductive inductor LSEN1 measures the input current by first measuring the voltage difference V across it, the inductive electromotive force V = L (di/dt) of the inductor, and the measured voltage difference divided by the inductive value of the inductive inductor is equal to the rate of change of the input current/the rate of change of the current with time. Similarly, assuming that there are a port O1 coupled to the first back-side node NO1 and a port O2 coupled to the second back-side node NO1, the output current of the voltage conversion circuit mainly flows from the port O1 to the port O2, i.e. flows out, the sense inductor LSEN2 is connected between the port O1 and the first back-side node NO1 or between the port O2 and the second back-side node NO2, the mechanism of the sense inductor LSEN2 for measuring the output current is to first sense the voltage difference across the sense inductor LSEN2, and then the measured voltage difference is divided by the inductance value of the sense inductor to be equal to the rate of change of the current with time. The two ends of the inductor LSEN1-2 are respectively coupled with the positive phase end and the negative phase end of the operational amplifier, the operational amplifier compares and amplifies the voltage at the two ends of the inductor and the voltage substantially represents the current flowing through the inductor, because the measured voltage difference value at the two ends is divided by the inductance value of the inductor to be equal to the measured current, namely the change rate of the output current along with the time.
Referring to fig. 3, taking the example that the inductive inductor LSEN2 measures the output current, two ends of the inductive inductor LSEN2 are respectively coupled to the positive phase terminal and the negative phase terminal of the first operational amplifier a 0: a first resistor R1 is connected between the inverting terminal of the operational amplifier a0 and the first terminal 10 of the corresponding inductive inductor LSEN2, a third resistor R3 is connected between the inverting terminal of the operational amplifier a0 and the second terminal 11 of the corresponding inductive inductor LSEN2, a second resistor R2 is connected between the inverting terminal of the operational amplifier a0 and the output terminal, and a fourth resistor R4 is connected between the inverting terminal of the operational amplifier a0 and a predetermined reference potential, for example, GRE, then the output terminal AO voltage of the operational amplifier a0 can be calculated. In a preferred embodiment, if the resistance of the first resistor R1 is set equal to the resistance of the third resistor R3 and the resistance of the second resistor R2 is set equal to the resistance of the fourth resistor R4, the ratio of the resistance of the second resistor R2 to the resistance of the first resistor R1 is multiplied by the voltage difference across the sense inductor and is equal to the output voltage VOUT of the operational amplifier a 0. In a preferred embodiment, the non-inverting terminal of the operational amplifier a0 may be coupled to the first terminal 10 of the inductor LSEN2 through the third resistor R3, the inverting terminal of the operational amplifier a0 may be coupled to the second terminal 11 of the inductor LSEN2 through the first resistor R1, and the other second and fourth resistors R2-R4 of the operational amplifier a0 may be connected in a constant manner. In other embodiments, a capacitor CB may be connected in parallel across the fourth resistor R4 to filter out the high frequency ripple voltage component passing through the inductor LSEN 2. The voltage difference across the sense inductor LSEN2 is compared and amplified by the operational amplifier a0 and substantially represents the current flowing through the sense inductor LSEN2, since the voltage difference across the LSEN2 divided by the inductance of the sense inductor LSEN2 is equal to the rate of change of the output current over time.
Referring to fig. 3, although the sense inductor LSEN2 is used for measuring the output current, the sense inductor LSEN1 may have an operational amplifier with an inverting terminal and an inverting terminal coupled to its two terminals when measuring the input current. A first resistor is connected between the inverting terminal of the operational amplifier not shown in the figure and one end of the corresponding inductive inductor LSEN1, a third resistor is connected between the inverting terminal of the operational amplifier not shown in the figure and the other end of the inductive inductor LSEN1, a second resistor is connected between the inverting terminal of the operational amplifier not shown in the figure and the output terminal, and a fourth resistor is connected between the inverting terminal of the operational amplifier not shown in the figure and the predetermined reference potential GRE. In other embodiments, a capacitor CB may be connected in parallel across the fourth resistor for filtering out the high frequency ripple voltage component passing through the inductive inductor LSEN 1. The voltage difference across the sense inductor LSEN1 is compared and amplified by an operational amplifier, not shown, and is substantially representative of the current flowing through the sense inductor LSEN1, since the voltage difference across LSEN1 divided by the inductance of the sense inductor LSEN1 is equal to the rate of change of the input current over time. The operational amplifier A0 and the matched resistor can be completely applied to the current measurement scheme of the induction inductor LSEN1, but the operational amplifier A0 and the matched resistor are applied to the induction inductor LSEN2 to measure the output current, and the operational amplifier A1 to measure the input current.
Referring to fig. 4, the input current of the voltage conversion circuit PO is sensed by the sense transistor SS forming a mirror circuit with the first switch S1, the width-to-length ratio W/L of the MOSFET is adjustable in the fabrication process of the transistor, and we set the width-to-length ratio W/L-1 of the first switch S1 to be N times the width-to-length ratio W/L-2 of the sense transistor SS, the former being much larger than the latter in the width-to-length ratio parameter, where N is set to be over 1000. The width-to-length ratio W/L-1 of the first switch S1 is proportional to the width-to-length ratio W/L-2 of the sense transistor, and the ratio is at least greater than 1. The mirror current flowing through the sense transistor SS is approximately one-N of the input current flowing through the first switch S1. The sense transistor SS is connected in series with the sense resistor RS so that the voltage difference across the sense resistor RS can represent the mirror current of the input current, and the input current is proportional to the mirror current, with the ratio of the former to the latter being equal to a multiple of N. In terms of calculation, the voltage difference between the two ends of the sensing resistor RS divided by the resistance of the sensing resistor RS itself is equal to the magnitude of the mirror current flowing through the sensing transistor SS. In the embodiment, the power consumption of the sensing resistor RS is much smaller than that of the original shunt, namely 1/N.
Referring to fig. 4, in a non-limiting alternative embodiment, the sense transistor SS is connected in series with the sense resistor RS between the first front side node NI1 and the second front side node NI 2. The gate of the sense transistor SS is connected to the gate of a first switch S1, also embodied as a power semiconductor field effect transistor. The source of the first switch S1, e.g., a PMOS transistor, and the source of the sense transistor SS are connected together to the first front side node NI1, and the drain of the first switch S1 is connected to the intermediate node NX 1. If the sensing transistor SS is also a PMOS transistor, a sensing resistor RS is connected between the drain of the sensing transistor SS and the second front-side node NI 2. The pwm signal CON1 driving the first switch S1 is also coupled to the gate of the sense transistor SS, which is a standard mirror circuit with the same source potential and the same gate potential as the first switch S1, and can mirror the current. Slight errors in current sensing may occur due to imperfect proportionality between the mirror current flowing through the sense transistor SS and the input current flowing through the first switch S1 due to channel modulation effects of the field effect transistor and process manufacturing variations of the switching transistor.
Referring to fig. 5, the current detection apparatus further includes a clamp transistor SC connected in series with the sense transistor SS and the sense resistor RS between the first front side node NI1 and the second front side node NI 2. The source of the PMOS transistor first switch S1 and the source of the PMOS sense transistor SS are connected to the first front side node NI1, and the drain of the first switch S1 is connected to the intermediate node NX 1. The drain of the sense transistor SS is connected to the source of the PMOS clamp transistor SC, and a sense resistor RS is connected between the drain of the clamp transistor SC and the second front side node NI 2. The gate control terminal of the clamp transistor SC is coupled to the output terminal of the second operational amplifier a1, the sense transistor SS is connected between the inverting terminal of the operational amplifier a1 and the first node NI1, and the first switch S1 is also connected between the positive terminal of the operational amplifier a1 and the first node NI 1. Wherein the inverting terminal of the operational amplifier a1 is connected to the drain of the sense transistor SS and the non-inverting terminal of the operational amplifier a1 is connected to the drain of the first switch S1. The operational amplifier a1 mainly has the function of forcing the drain voltage of the sense transistor SS and the drain voltage of the first switch S1 to be kept consistent in time, and to be substantially equal or the former is time-hopped along with the hopping of the latter, so that the current mirror structure can be improved by reducing the detection error of the current, that is, the problem of excessive deviation of the mirror current which may occur between the first switch S1 and the sense transistor SS can be solved.
Referring to fig. 6, an RC low pass filter for sensing the output current of the voltage converting circuit is further included, wherein it is assumed that the inductance element L itself has an inductance value and also has a parasitic resistance RL, or equivalent resistance, and the original inductance of the inductance element L is connected in series with the parasitic resistance RL. The RC low-pass filter comprises an auxiliary resistor RA and an auxiliary capacitor CA, the auxiliary resistor RA and the auxiliary capacitor CA of the low-pass filter are connected in series, and then both of them are connected in parallel with the inductive element L, for example, the inductive element L is previously set to be connected between the first intermediate node NX1 and the second intermediate node NX2, and then the auxiliary resistor RA and the auxiliary capacitor CA connected in series are also connected between the first intermediate node NX1 and the second intermediate node NX 2. Note that one end of the auxiliary resistor RA is connected to the first intermediate node NX1 in the positional relationship, and then an auxiliary capacitor CA is connected between the opposite other end of the auxiliary resistor RA and the second intermediate node NX 2. The inductance element L is connected in parallel with the RC low pass filter, in which two ends of the auxiliary capacitor CA are respectively coupled to the positive phase terminal and the negative phase terminal of the third operational amplifier a 2: the terminal of the auxiliary capacitor CA connected to the resistor RA is coupled to the non-inverting terminal of the operational amplifier a2 and the opposite terminal of the auxiliary capacitor CA (i.e., the terminal connected to NX 2) is coupled to the inverting terminal of the operational amplifier a 2. Alternatively, an auxiliary resistor RA is provided between the non-inverting terminal of the operational amplifier a2 and the intermediate node NX1, an auxiliary capacitor CA is provided between the non-inverting terminal of the operational amplifier a2 and the intermediate node NX2, and the inverting terminal of the operational amplifier a2 may be directly coupled to the intermediate node NX 2. The voltage difference across the auxiliary capacitor CA in the RC low-pass filter is compared and amplified by a third operational amplifier a 2: as long as the time constant (i.e. the product of CA and RA) of the RC low-pass filter is equal to the time constant between the inductance of the inductance element L and the parasitic resistance RL thereof (i.e. the inductance value of the inductance L is divided by the resistance RL), the ratio of the voltage across the auxiliary capacitor CA and the resistance RL of the parasitic resistance in the RC low-pass filter represents the output current flowing through the inductance element L. The voltage difference across the auxiliary capacitor CA is known from the output value VOUT of the operational amplifier a 2.
From the foregoing, it can be appreciated that the complementary switches S1-S2 are alternately turned on, the complementary switches S3-S4 are alternately turned on, and dead time is provided between turning on of the complementary switches S1-S2 and turning on of the complementary switches S3-S4. As is known to those skilled in the art, the dead time of a complementary switch/push-pull switch means that neither of the two complementary switches is on, during which there is no well-defined current monitoring scheme known in the art. The present application claims that the output current is measured by the embodiment of 6 during the dead time of the two sets of complementary switches S1-S2 and during the dead time of the complementary switches S3-S4. The input current is measured using the embodiment of fig. 4 or 5 during the phase of complementary switches S1-S2 in which switch S1 turns switch S2 off, and using the embodiment of fig. 4 or 5 during the phase of complementary switches S3-S4 in which switch S3 turns switch S4 off. The output current is measured in one embodiment using the embodiment of FIG. 6 during the phase in which switch S1 is off and switch S2 is on in complementary switches S1-S2, and the output current is measured using the embodiment of FIG. 6 during the phase in which switch S3 is off and switch S4 is on in complementary switches S3-S4. This embodiment is a method for implementing current detection in any one complete switching cycle in the switching power supply system, especially in the power-optimized voltage conversion circuit of the present application. Other embodiments may also include the first phase in which switch S1 remains on but switch S2 remains off: the switch S3 is turned on and the switch S4 is turned off, then the switch S3 is turned off and the switch S4 is turned on, and the switch S3 is turned off and the switch S4 is turned on, and the second stage of the switch S1 is turned off and the switch S2 is turned on. In the process of driving the voltage conversion circuit, the first stage is switched by turning on the switch S3 and turning off the switch S4, the state of turning on the switch S3 and turning off the switch S4 is kept for a short period of time, and then the first stage is switched by turning off the switch S3 and turning on the switch S4. A complete switching cycle of the voltage conversion circuit includes a first phase and a second phase. The voltage conversion circuit thus transitions to the first phase for the next cycle after performing the second phase, the voltage conversion circuit cycling between the first phase and the second phase. The power optimizer collects the input current of the optimizer PO, i.e. the output current of the battery, from the embodiment of fig. 4-5 in the first stage, and the output current of the optimizer PO, i.e. the inductor current of the inductor L, from the embodiment of fig. 6 in the second stage. The main purpose of the current detection in stages in the present embodiment is to: in the first stage, the inductor current rises first and then levels, and the current sampling module can be guaranteed to consume the lowest power consumption by collecting the current through the embodiment of the previous figures 4-5; the inductor current is substantially decreased in the second stage, which can ensure the lowest power consumption of the current sampling module by collecting the current according to the embodiment of fig. 6. In this embodiment, it can be observed that the processor 100 in fig. 6 can output four paths of pulse width modulation signals CON1-CON4 for driving four transistors S1-S4, respectively, where CON1 and CON2 are inverted signals and CON3 and CON4 are inverted signals, although the Driver circuit or buffer Driver for driving the switches S1-S4 is omitted in fig. 6. The monitored input current of the voltage conversion circuit is actually the output current of the photovoltaic module which provides a voltage source for the voltage conversion circuit, the monitored output current of the voltage conversion circuit is also actually the inductive current of the inductive element of the voltage conversion circuit, the output voltage of the photovoltaic module and the output voltage of the voltage conversion circuit can be detected in real time, and as the input power of the voltage conversion circuit is approximately equal to the output power, the maximum value obtained by dynamically adjusting the product of the output voltage and the output current of the voltage conversion circuit is actually equivalent to the maximum value obtained by dynamically adjusting the output power of the photovoltaic module. Compared with the high power consumption of the shunt or the detection resistor RSEN of fig. 1, the power consumption of the embodiment of fig. 3 and 6 is much lower because the inductor is used as the detection target, and the current flowing through the resistor RS is 1/N of the original current although fig. 4 and 5 also use the sensing resistor RS as the target, for example, the current may be one multiple of the original current, and the power consumption consumed actually is smaller.
While the present invention has been described with reference to the preferred embodiments and illustrative embodiments, it is to be understood that the invention as described is not limited to the disclosed embodiments. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the invention. Any and all equivalent ranges and contents within the scope of the claims of the present application should be considered to be within the intent and scope of the present invention.

Claims (11)

1. A current detection device applied to a photovoltaic power optimizer is characterized by comprising:
the voltage conversion circuit is configured for the photovoltaic module and used for executing maximum power point tracking, wherein the voltage provided by the photovoltaic module after power optimization is carried out is output by the voltage conversion circuit;
an inductive inductor for sensing an input current of the voltage conversion circuit; and/or
An inductive inductor for sensing an output current of the voltage conversion circuit;
the two ends of any induction inductor are respectively coupled with the positive phase end and the negative phase end of the operational amplifier, and the operational amplifier compares and amplifies the voltages representing the current flowing through the induction inductor at the two ends of the induction inductor;
a first resistor is connected between the inverting end of the operational amplifier and one end of the induction inductor corresponding to the inverting end of the operational amplifier;
a third resistor is connected between the positive phase end of the operational amplifier and the other end of the induction inductor corresponding to the positive phase end of the operational amplifier;
a second resistor is connected between the inverting end and the output end of the operational amplifier;
and a fourth resistor is connected between the positive phase end of the operational amplifier and a preset reference potential.
2. The current detection device applied to the photovoltaic power optimizer of claim 1, wherein:
the resistance value of the first resistor is equal to that of the third resistor;
the resistance value of the second resistor is equal to the resistance value of the fourth resistor;
the ratio of the resistance value of the second resistor to the resistance value of the first resistor is multiplied by the voltage difference between the two ends of the induction inductor to be equal to the output voltage of the operational amplifier.
3. The current detection device applied to the photovoltaic power optimizer of claim 1, wherein:
and a capacitor for filtering out high-frequency pulsating voltage components passing through the induction inductor is connected in parallel with two ends of the fourth resistor.
4. A current detection device applied to a photovoltaic power optimizer is characterized by comprising:
the voltage conversion circuit is configured for the photovoltaic module and used for executing maximum power point tracking, wherein the voltage provided by the photovoltaic module after power optimization is carried out is output by the voltage conversion circuit;
the voltage conversion circuit includes:
first and second switches connected in series between first and second nodes receiving a voltage source provided by the photovoltaic module;
the third switch and the fourth switch are connected in series between a third node and a fourth node which provide output voltage after the photovoltaic module is subjected to power optimization;
an inductance element is provided between an interconnection node between the first and second switches and an interconnection node between the third and fourth switches;
wherein:
the input current of the voltage conversion circuit is sensed by an induction transistor which forms a mirror circuit with the first switch;
the width-to-length ratio of the first switch is proportional to the width-to-length ratio of the sense transistor; and
the sensing transistor is connected in series with a sensing resistor, the mirror current of the input current is represented by the voltage difference between two ends of the sensing resistor, and the input current is in proportional relation with the mirror current.
5. The current detection device applied to the photovoltaic power optimizer of claim 4, wherein:
the sense transistor is in series with the sense resistor between first and second nodes.
6. The current detection device applied to the photovoltaic power optimizer of claim 5, wherein:
the clamping transistor is connected with the sensing transistor and the sensing resistor in series between a first node and a second node;
the grid control end of the clamping transistor is coupled to the output end of an operational amplifier;
the sensing transistor is connected between the inverting terminal of the operational amplifier and a first node;
the first switch is connected between the non-inverting terminal of the operational amplifier and a first node.
7. The current detection device applied to the photovoltaic power optimizer of claim 4, wherein:
the voltage conversion circuit also comprises an inductive inductor used for sensing the output current of the voltage conversion circuit;
the two ends of the induction inductor are respectively coupled with the positive phase end and the negative phase end of the operational amplifier, and the operational amplifier compares and amplifies the voltage representing the current flowing through the induction inductor at the two ends of the induction inductor.
8. The current detection device applied to the photovoltaic power optimizer of claim 4, wherein:
the RC low-pass filter is used for sensing the output current of the voltage conversion circuit;
the inductance element is connected with the RC low-pass filter in parallel, and two ends of a capacitor in the RC low-pass filter are respectively coupled to a positive phase end and an inverting end of the operational amplifier;
comparing and amplifying the voltages at both ends of the capacitor in the RC low-pass filter by an operational amplifier;
the time constant of the RC low-pass filter is equal to the time constant between the inductance of the inductance element and the parasitic resistance of the inductance element;
the ratio of the voltage across the capacitor to the resistance of the parasitic resistor in the RC low pass filter represents the output current flowing through the inductive element.
9. A current detection device applied to a photovoltaic power optimizer is characterized by comprising:
the voltage conversion circuit is configured for the photovoltaic module and used for executing maximum power point tracking, wherein the voltage provided by the photovoltaic module after power optimization is carried out is output by the voltage conversion circuit;
the voltage conversion circuit includes:
first and second switches connected in series between first and second nodes receiving a voltage source provided by the photovoltaic module;
the third switch and the fourth switch are connected in series between a third node and a fourth node which provide output voltage after the photovoltaic module is subjected to power optimization;
an inductance element is provided between an interconnection node between the first and second switches and an interconnection node between the third and fourth switches;
wherein:
further comprising an RC low pass filter for sensing a current of the voltage conversion circuit;
the inductance element is connected with the RC low-pass filter in parallel, and the two ends of a capacitor in the RC low-pass filter are respectively coupled with a positive phase end and an inverted phase end of the operational amplifier;
comparing and amplifying the voltages at both ends of the capacitor in the RC low-pass filter by an operational amplifier;
the time constant of the RC low-pass filter is equal to the time constant between the inductance of the inductance element and the parasitic resistance of the inductance element;
the ratio of the voltage across the capacitor to the resistance of the parasitic resistor in the RC low pass filter represents the current flowing through the inductive element.
10. A method of detecting a current of a photovoltaic power optimizer, wherein a voltage conversion circuit for performing maximum power point tracking is configured for a photovoltaic module, wherein a voltage provided by the photovoltaic module after power optimization is performed is output by the voltage conversion circuit, and the voltage conversion circuit comprises:
first and second switches connected in series between first and second nodes receiving a voltage source provided by the photovoltaic module;
the third switch and the fourth switch are connected in series between a third node and a fourth node which provide output voltage after the photovoltaic module is subjected to power optimization;
an inductance element is provided between an interconnection node between the first and second switches and an interconnection node between the third and fourth switches;
the method comprises the following steps:
the input current of the voltage conversion circuit is detected by using an induction transistor which forms a mirror image circuit with the first switch, and the mirror image current of the input current is represented by the voltage difference between two ends of an induction resistor which is connected with the induction transistor in series;
the output current of the voltage conversion circuit is detected by an RC low-pass filter connected with the inductance element in parallel, the time constant of the RC low-pass filter is equal to the time constant between the inductance of the inductance element and the parasitic resistance of the inductance element, and the ratio of the voltage at two ends of the capacitor in the RC low-pass filter to the resistance value of the parasitic resistance represents the output current flowing through the inductance element.
11. The method of claim 10, wherein:
the clamping transistor is connected with the sensing transistor and the sensing resistor in series between a first node and a second node;
the grid control end of the clamping transistor is coupled to the output end of an operational amplifier;
the sensing transistor is connected between the inverting terminal of the operational amplifier and a first node;
the first switch is connected between the positive phase end and the first node of the operational amplifier;
the potentials of the positive phase terminal and the negative phase terminal of the operational amplifier are forced to be equal by the operational amplifier.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104917458A (en) * 2015-05-22 2015-09-16 江苏固德威电源科技有限公司 Method and circuit for detecting output current in absence of sensor
CN105897161A (en) * 2016-06-06 2016-08-24 河海大学常州校区 Outdoor photovoltaic module detection system based on dynamic capacitance charge and discharge and test method
JP6005109B2 (en) * 2014-08-06 2016-10-12 株式会社MersIntel Solar power optimizer circuit
CN205983286U (en) * 2016-08-23 2017-02-22 无锡隆玛科技股份有限公司 Power optimizer based on SM72445

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6005109B2 (en) * 2014-08-06 2016-10-12 株式会社MersIntel Solar power optimizer circuit
CN104917458A (en) * 2015-05-22 2015-09-16 江苏固德威电源科技有限公司 Method and circuit for detecting output current in absence of sensor
CN105897161A (en) * 2016-06-06 2016-08-24 河海大学常州校区 Outdoor photovoltaic module detection system based on dynamic capacitance charge and discharge and test method
CN205983286U (en) * 2016-08-23 2017-02-22 无锡隆玛科技股份有限公司 Power optimizer based on SM72445

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