FIELD OF INVENTION
The present invention relates to a solar charge controller, particularly to a solar charge controller with maximum power point tracking.
RELATED ART
The solar charge controller is an electronic device used to regulate the charging of a battery bank from solar panels. The charge controller regulates the current to the battery through pulse width modulation technique.
In a conventional charge controller when the batteries are low, they are connected to the PV panels through a semiconductor switch. In such a case the PV panels operating voltage is approximately equal to the battery voltage which in most of the cases is not the maximum power point of the panels according to their I-V characteristic. So the net power available from the PV panels is less than what the panels can produce if they are operated at the maximum power point of the panels.
MPPT based solar charge controller generally uses dc-dc converter between panel and battery banks. In a standard buck converter, the freewheeling diode turns ON, on its own, shortly after the switch turns off, as a result of the rising voltage across the diode. This voltage drop across the diode results in a power loss which is equal to
P = VD*(1-D)*I0 where:
VD is the voltage drop across the diode at the load current I0, D is the duty cycle, and I0 is the load current.
As the losses in the freewheeling diode in the buck converter are directly proportional to the (1-D) where D is the operating duty cycle thus lower the duty cycle higher the losses.
By replacing diode D with a switch, which is selected for low losses, the converter's efficiency can be improved. For example, a MOSFET with low RDSON is selected for a switch providing power loss in switch which is
P = I02(l-D)*RDsoN
By comparing these equations one can see that in both the cases, power loss is strongly dependent on the duty cycle, D. It stands to reason that the power loss on the freewheeling diode

or lower switch will be proportional to its on-time. Therefore, systems designed for a low duty cycle operation will suffer from higher losses in the freewheeling diode or lower switch.
The other problem with the existing charge controllers is that the MPPT efficiency is low as some of existing charge controller use open circuit voltage of the panels as VMPP reference. According to the solar panel characteristic and design parameter from datasheet, the maximum power point voltage (VMPP) of a panel comes out to be a fractional value of the panel open circuit voltage (Voc) -
VMPP = K*Voc
where the value of K is < 1 and varies between 73% and 85%. But, there is strong temperature dependence and results show that this leads to a significant variation in the absolute value of K. Thus, MPPT efficiency will be fairly low if open circuit voltage alone is used as a reference for
VMPP.
US patent no 6,111,391 and 6,204,645 use a pure analog control for maximum power point tracking. They use the open circuit voltage of the solar panels Voc for the calculation of maximum, power point of the panels. This theory is based on the fact that by the characteristic design parameters of solar panels the maximum power point of a PV panel is a fractional value of its open circuit voltage i.e. VMPP= K* Voc where K<1 as mentioned above this method has some limitations.
The open circuit voltage calculation is done by periodically reducing the duty cycle of buck converter to zero and measuring the open circuit voltage of the panels. Then VMPP is calculated
by
VMpp=(V0c-AV-A)
Where AV is a user programmable voltage and coefficient A is used for compensating voltage drop in cables from the panels to the charge controller.
AV is defined as the difference between the datasheet value of Voc and VMPP.
The drawback of this scheme is that it is too much dependent on the panel characteristic and the type of panels used in the array. With so many panel manufactures, there is a substantial variation in the difference between Voc and VMPP voltages defined in the datasheets. These differences can vary from 70% to 85%. With such a large variation it would be extremely difficult to set the user programmable settings accurately. Moreover, the user is required to alter these settings each time panels are changed or panels are used from different manufacturers in the array. Even for a same panel, it would be extremely difficult for a layman to perform these settings correctly because of the dynamic nature of the weather, Further, it is a difficult and time consuming task to judge at which setting maximum power is achieved.
Moreover, the calculation of VMpp by using fractional open circuit voltage alone is not a true MPPT method. This method also requires periodic tuning of the user programmable settings for better results.
The prior art uses a buck converter between the solar panels array and a battery which maintains the panel voltage at the VMpp by regulating the duty cycle of the buck converter. This topology uses a semiconductor switch of the high side and a freewheeling diode in the lower side of the buck converter.
hi case of the conditions when the VMPP is at a higher level due to low temperature or due to the panel characteristics, the buck converter would operate at a lower duty cycle. This means that the freewheeling diode turn ON time would be large and thus there would be more losses in the diode. Because of this, there would be a loss in the efficiency of the converter.
This problem increases further when a higher panel voltage array is used to charge a lower voltage battery bank. In this case user operates the buck converter at lower duty cycle. The losses are directly proportional to (1-D), so lower the duty cycle, the higher will be the losses in the system.
Additionally patent no. 6,111,391 and 6,204,645 use an analog control and thus there is a lack in the flexibility of control. Both these patents use an external sample and hold a circuit for the analog measurement. An oscillator is being used with fixed intervals for calculating the open circuit voltage of the PV array and relays to disconnect the PV array from the battery when the PV voltage is low (during night) to prevent reverse current flow at night. There is no provision of connectivity through communication for remote monitoring and control of the charge controller for its performance analysis. It provides limited settings on the display. It cannot perform automatic equalization of the batteries periodically. The user has to perform this operation manually.
US patent no. 6,984,970 presents a mathematical model for the calculation of the maximum power point. It calculates four points on the current verses voltage graph of panels and with the help of numerical analysis calculates maximum power point voltage from characteristic equations, which is then fed to the controller as an MPPT reference. The controller then operates the system at the MPPT point. The patent describes a system where the VMPP reference generator is independent of the controlling system.
The patent relates to solar generator and an associated conditioning method for applications such as high power satellites. The method used in this patent requires calculation of complex equations in real time to calculate the maximum power point voltage of the power supply.
Further, a very high end processor or dedicated ASIC is required to solve such equations, thereby making the overall system design very complicated.
US patent application 200610132102 uses one of said hardware topology and control algorithm to track the maximum power point. This application specifically targets the maximum power point tracking of non-ideal power source for charging double layer capacitor. This patent has a

very limited scope and it can be used only when the charge storage device is a double layer capacitor. This is the biggest drawback as it only targets one type of energy storage device.
With all the above discussed restrictions or limitations it is required to have improved maximum power point tracking solar charge controller for extracting the maximum available power from the panels with higher efficiency and low heat dissipation.
OBJECTS OF THE INVENTION-
The primary object of the present invention is to propose a solar charge controller, particularly to a solar charge controller with maximum power point tracking for extracting the maximum available power from the panels, which is independent of the characteristics of the solar panel and environmental condition.
Another object of the present invention is to design an improved hardware based on synchronous buck converter.
Another object of the present invention is to sense the PV panel current, PV panel voltage, battery current and battery voltage and temperature for implementing software algorithm based on fuzzy logic to calculate the maximum power point voltage of the panels connected and controlling the panel voltage at that maximum power point voltage.
Another object of the present invention is to reduce the power loss due to the periodic calculation of VQC- The object is achieved by reducing the frequency for the Voc calculation when the change in the power is small. By reducing the frequency of calculation the power loss is reduced.
Yet another object of the present invention is to charge a lower voltage battery bank from higher voltage PV panels by using synchronous buck converter topology.
Still another object of the present invention is to implement the fuzzy logic controlled battery charging with auto/manual temperature compensation and equalization.
Still another object of the present invention is to provide the default factory sellable and user adjustable boost/float charging voltages and other settings.
Still another object of the present invention is to provide isolated communication channel for monitoring and control of the solar charge controller. The solar charge can also be configured with the help of monitoring software.
Still another object of the present invention is to propose a solar charge controller with improved user interface for display of message in case of fault events or error conditions such as PV voltage high, wrong configuration of the battery voltage, battery high current protection, high heat sink temperature etc.

STATEMENT OF INVENTION
According to this invention there is provided a MPPT based solar charge controller comprising of DC-DC synchronous buck converter section, power supply section, signal conditioning circuits along with isolated communication section and control section in connection with each other
SUMMARY OF THE INVENTION
In order to overcome the above mentioned problems and to achieve said objects, the present invention provides a solar charge controller that uses the fuzzy logic based maximum power point tracking technique for charging the battery from PV panels. The charge controller uses synchronous buck for the DC-DC converter to transfer the current from PV panels to the battery for high efficiency. The control section is made up of a digital signal controller. The controller senses the PV panel current, PV panel voltage, battery current and voltage and temperature for controlling the operation. The digital signal controller calculates the maximum power point voltage of the connected panels by first measuring the open circuit voltage of the panels to get the approximate range of the VMPP and then uses fuzzy logic based perturb and observe method for calculating the exact VMPP and then maintains the panel's working voltage at that point. The panel voltage is regulated by varying the duty cycle of the DC-DC synchronous buck converter attached between the solar PV panel and the batteries.
The digital signal controller on the charge controller regulates the duty cycle of the switching devices based on the feedback sense of PV voltages, PV current, battery voltage and battery current using fuzzy logic. The controller implements the maximum power point tracking algorithm to operate the PV module on the maximum power point voltage so that at any given time maximum possible power can be extracted from the modules.
The controller also regulates the charging of the battery bank connected at the output of DC-DC synchronous buck converter and implements the multiple stages charging strategy with temperature compensation and automatic or manual equalization. The controller also monitors the heat sink temperature to prevent any fault condition. The solar charge controller also provides serial communication for monitoring and data logging of various parameters on the computer.
In an embodiment of the present invention, the power storage device can be other than battery such as double layer capacitor etc.
In another embodiment of the present invention, the display of;the solar charge controller can be changed from LCD to touch panel or some other advance smart panel.
In another embodiment of the present invention, the MOSFET switches can be replaced with some other semiconductor device such as transistor, IGBT etc.

In another embodiment of the present invention, the isolated communication channel can be modified to provide advance communication interfaces such as RS485, Ethernet, wireless, CAN, USB etc.
In yet another embodiment of the present invention, the MPPT tracking algorithm can use fuzzy logic based incremental conductance method.
In still another embodiment of the present invention, the current sensor can be replaced by some other type of sensor such as hall sensor.
The foregoing as well as additional objects, features and advantages of the invention will be more readily apparent from the drawings and their detailed descriptions.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
Fig. 1 shows the block diagram for the arrangement of solar charge controller according to the present invention;
Fig. 2 shows the DC/DC synchronous buck converter section;
Fig. 3 a shows the main power supply section/controller supply section;
Fig. 3b shows two isolated flyback supplies;
Fig. 4a shows the circuit diagram for sensing the solar panel voltage;
Fig 4b shows protection circuits;
Fig 4c shows battery voltage and configuration sensing circuit;
Fig 4d shows PV current sensing circuit;
Fig 4e shows battery current sensing circuit;
Fig 4f shows ambient temperature sensing circuit;
Fig 4g shows heat sink temperature sensing circuit;
Fig 4h shows equalization switch sensing circuit;
Fig 4i shows boost voltage reference sensing circuit;

Fig 4j shows MPPT offset reference sensing circuit;
Fig 5 shows isolated communication interface;
Fig.6 shows a flowchart for the firmware control algorithm;
Fig.7 shows a flowchart of communication interface/graphical user interface.
Fig.8 shows comparison of MPPT based charge controller in normal mode (mppt disabled) and mppt mode (mppt enabled).
Fig.9 shows a communication graphical user interface.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference may be made to Fig.l, which shows the block diagram for arrangement of solar charge controller 1. The solar charge controller 1 is divided into different sections such as DC-DC synchronous buck converter section 2, power supply section 3, signal conditioning circuits 4 along with isolated communication section 5 and control section 6. The main power supply is derived from battery 7 and with the help of main supply two isolated supply are provided in the supply section 3. The solar charge controller 1 uses synchronous buck topology for the DC-DC converter 2 for high efficiency. The control section 6 contains digital signal controller, which is responsible for the complete operation of the charge controller 1. The controller 6 senses the voltage and current of the connected PV panels 8, battery current and voltage of the batteries 7 connected and temperature through the sense signal conditioning circuits 4 for controlling the operation. The digital signal controller 6 calculates the maximum power point voltage of the connected panels 8 and then maintains the panel's working voltage at that point. The system configuration settings section 9 is used for the system configuration such as battery voltage, bulk voltages and reference MPPT offset voltage. These settings can also be performed through communication by monitoring and controlling software. The isolated communication section 5 is used for the computer interfacing, which can also be used for some other external control interface. Switch 10 is provided for the activation or deactivation of manual or automatic mode of equalization process for the batteries connected.
The solar charge controller 1 provides LCD interface 11 for the display of system parameters to the user. The display shows panel voltage, panel current, battery voltage, battery current, temperature, system charging mode, and system status. The charge controller 1 also displays the messages in case of fault events or error conditions such as PV voltage high, wrong configuration of the battery voltage, battery high current protection, high heat sink temperature etc. Shunts 12 & 13 are provided for current sensing. In case of over current/overload, fuse protection 14 is available that opens the circuit and protects the battery bank 7 from excessive current. The gate drivers 15 are used for driving the high side 16 and low side 17 switches from the PWM signals of the digital signal controller 6.

Fig. 2 shows the DC-DC synchronous buck converter section 2 which comprises of a synchronous buck converter. The solar panel voltage 201 from the PV array 8 is connected at the input of the synchronous buck converter 2. The output of the converter 2 is connected to the battery bank 7. With the DC-DC synchronous buck converter between the solar panels and battery banks, a lower voltage battery bank can be charged from a higher solar panel voltage. A synchronous buck converter 2 is a modified version of the basic buck converter circuit in which the freewheeling diode is replaced by semiconductor switchs'LS. By using the semiconductor (MOSFET) switch LS in place of freewheeling diode in synchronous buck converter 2, the losses are reduced and system efficiency is increased. The gate driver 15 drives the high side and low side switches 16,17 from the PWM signals of the digital signal controller 6.
Fig. 3a & 3b constitute the power supply section 3. Fig. 3a indicates the main power supply section/controller supply section 31. The controller section power supply is derived from the battery side 7. An adjustable linear voltage regulator 301 is used to make a power supply for the control section and signal conditioning circuits.
Fig. 3b shows two isolated fly-back supplies 32 that are designed in a way that they are controlled by the digital signal controller 6 through pulse width modulation. An SMPS transformer 302 with two secondary windings is used to make these supplies. One of the isolated supplies is used for the high side semiconductor switch 16 and the other is used for the isolated supply for communication section 5.
Fig. 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, 4i and 4j constitute the sense signal conditioning circuit4. Fig. 4a shows the sensing circuit diagram 41 for sensing the solar panel voltage 201 through the voltage divider resistance network 401. The sensed voltage is then provided to digital signal controller 6.
Fig. 4b shows the protection circuit diagram 42 of solar charge controller 1 for protection from surge voltages on battery 7 and solar panels 8 by providing MOV's 402a, 402b, 402c, 402d.
Fig. 4c shows the battery voltage and configuration sensing circuit 43. The main controller 6 senses the battery voltage configuration 403 through comparators 404 & 405. The battery voltage 403 is sensed with the resistance divider network 406. The system has user selectable battery voltage settings through the jumper selection 407. It can be configured in 12V, 24V and 48V battery voltage.
Fig. 4d and Fig. 4e show the PV current sensing circuit diagram 44 and the battery current sensing circuit diagram 45. These are measured using the shunt resistances 12 & 13 on the high side. The output of the shunts 12 & 13 is given to the operational amplifier 408 in fig. 4d and 409 in fig. 4e. The current sense signal for the solar charge controller is made by converting the voltage drop across the shunts 12, 13 to a proportional current by driving a transistor 410 in fig. 4d and 411 in fig. 4e connected at the output of the rail to rail operational amplifier. This current is then converted to sense voltage by dropping it across a fixed resistance 412 in fig. 4d and 413 in fig. 4e. This signal is then forwarded through the operational amplifier buffers 414 in fig. 4d

and 415 in fig. 4e to the ADC channels 416 in fig. 4d and 417 in fig. 4e. The battery high current signal 418 is generated through the comparator 419 attached at the output of the battery current sense.
Fig. 4f and 4g show the circuit diagram 46 & 47 for ambient temperature and heat sink temperature sense respectively through temperature sensor 420 and 421 interfaced to digital signal controllers ADC channels.
Fig 4h shows equalization switch sensing circuit 48 where the switch 10 is provided in case user desires to activate or deactivate the manual or automatic equalization process of the battery.
Fig 4i shows boost voltage reference sensing circuit 49. The user can set the boost voltage for the battery bank 7 connected to the solar charge controller 1 through these settings.
Fig 4j shows MPPT reference sensing circuit 50, reference of which is set to the approximate value of the MPPT offset voltage specific to the panels 8 connected.
Fig. 5 shows isolated communication interface 5 and high-speed opto-couplers 501 are used to isolate the communication signals from the controller 6 to the output port 502.
Fig. 6 shows a flowchart for the firmware control algorithm. At step 601, the control algorithm uses fuzzy logic controls to track the maximum power point voltage with perturb and observe method. The improved control algorithm uses open circuit voltage of the solar panel to get the reference range of the approximate maximum power point voltage and then tracks the actual maximum power point based on the fuzzy logic controlled perturb and observe method.
At step 602, the open circuit voltage calculation time interval varies with the present state of the power received from the panels. In case the change in power is below a threshold, the new open circuit voltage calculation is delayed for a specified time. In case there is large change in the power, the time period for the calculation of the VQC is reduced to track the VMPP-
By reducing the frequency of calculation when the change in power is small, the power lost due to periodic calculation of VQC can be reduced.
Battery charging control
The battery charging control is a fuzzy logic based multiple stages charging control with temperature compensation and auto and manual equalization to keep the battery charged. When the battery voltage is below the boost voltage setting, the charge controller operates in the bulk-charging mode. In this mode the charge controller supplies the maximum available charging current to the battery. The PV panels are operated at the maximum power point voltage by controlling the duty cycle of the synchronous buck converter. Once the boost voltage is achieved, the charge controller operates in the absorption mode, In this mode the charge controller

maintains the battery voltage at the boost voltage level for a fixed interval of time and the current to the batteries is reduced in order to maintain the battery voltage.
After the fixed interval is completed, the charge controller comes into float charging mode. In this case, the battery voltage is dropped to the float voltage level of the battery and then regulated at that voltage. When the battery voltage drops below float voltage for specified time, the charge controller again comes into bulk charging mode and the cycle repeats again. The bulk voltage of the battery can be set through the programmable user setting.
Temperature compensation
At step 606, the solar charge controller provides temperature compensation in charging mode. The boost voltage of the battery is temperature compensated so that at higher temperature levels the boost voltage is set to a lower value. The temperature compensation of the batteries is important because if batteries are charged to a higher boost voltage at high temperature, it may result in emission of gases, loss of electrolyte and excessive heating in the batteries, which may result in premature damage.
Equalization settings
The batteries can be equalized both manually and automatically. In the manual mode, pressing the equalization switch activates the battery equalization. In automatic mode, the equalization is carried out after a fixed interval of time without user intervention.
Protection
The solar charge controller provides protection against a number of conditions that can occur during the operation. When the PV panel voltage is low (during the night), the charge controller sets the duty cycle of the charge controller to zero so that no reverse current flows from the batteries to the panels at night.
At step 603, the system gives warning against improper voltage of the battery in case the user connects a battery with voltage different than the voltage configuration settings done in the hardware through the jumper settings. It also gives a warning if the panel voltage exceeds a high threshold limit in case a user connects the panels with a voltage higher than the maximum allowed settings.
At step 604, high current protection is provided in the system. In case the battery current crosses a threshold limit, the current is automatically reduced below the maximum limit to protect the system or the system is put in idle state for a fixed interval. When the time elapses, the controller again checks the current.
At step 605, the heat sink temperature is monitored to prevent any excessive heating that may lead to failure of semiconductor devices.

Hardware protection is also provided for any fault condition and fuse protection is provided on the battery side in case a large current flows into the battery.
Fig. 7 shows a flowchart of communication interface/graphical user interface for monitoring and controlling the charge controller. To communicate with the charge controller port connections are provided.
At step 701, the software reads the data from the charge controller, and then at the step 702 logs the data in database with time stamp after that at the step 703 the GUI is updated with the new values. At the step 704 data analysis is performed to show the system performance over the selected time zone. Step 705 shows the numerical data in tabular format. The graph print along with the report is generated at step 706.
The charge controller also provides the facility of event logging and daily history. The digital signal controller logs all the related data in the internal eeprom with time stamp. The events include all the fault events such as PV high, wrong battery connection, high battery high current etc along with this the charge controller also keeps record of the energy produced daily and also cumulative over the period of operation.
All this information can later be accessed with the help of the monitoring and controlling software.
Fig. 8 shows the comparison of the operation of charge controller in normal charging mode and in mppt charging mode. From the graph it can be easily concluded that, when operating in the mppt mode the charge controller extracts more power from the PV panel in almost the same operating condition and also the battery charging current is boosted. It was observed that the increase in power is greater than 10% to 15% depending on the operating conditions. As soon as the charge controller comes into normal mode from mppt mode a dip in the input power is observed.
Fig.9 shows the graphical user interface of monitoring and controlling software. Graphical user interface software is used for monitoring and controlling the solar charge controller. The communication channel is isolated from rest of the hardware through opto-couplers.
The main window displays online graph for PV voltage, battery voltage and charging current. The current system status is shown through symbols on the graphical user interface. The system parameters such as system capacity, PV voltage, battery voltage, charging current, AH input, temperature etc are also shown numerically. The data is logged in the local database on the computer connected to the charge controller. The data in database can later be accessed through the software.
User can select the sampling time for logging the data from a list of time intervals. The data is logged on the computer with user selectable sampling time. The data is date and time stamped

and stored in a table in the database. With the help of this data, the system performance can be analyzed over a period of time.
The database stores the data on the PC for analysis of the system performance over hours, days and month and provides a graphical representation of the system parameters over the selected time span in the past.
The system settings can also be configured with the help of monitoring software. The equalization interval in auto mode can also be configured through the software. The monitoring and controlling facility can be further extended to remote monitoring and control of charge controller by altering some system and software settings.
Communication with the charge controller and data analvsis-
The charge controller communicates with the PC through serial communication using standard serial port on the pc. Port connections are made to communicate with a charge controller by selecting the proper COM port that is connected to the hardware from the main menu bar. On successful connection, the system is ready for communication.
The user can connect with the charge controller by pressing the "Connect" button on the window. On successful communication, the communication status changes to "Connected". The user can select "Online Graph" from File menu to open the graph window. The new window displays online graph and system parameters as well as system status. Selecting the sampling time and pressing "Start Graph" button starts online graph.
The previously stored data can be viewed by pressing "Data" from the main menu. The data in respect of the graphs can also be viewed from the graph query table on the data window.
Previous day's graphs are viewed by clicking on the "Analysis" in the main menu. The new window opens that displays the data from the database in the form of line graph with the user selectable time zone. The graph shows PV voltage, battery voltage, charging current and other parameters, which the user can scroll through the graph data with time to analyze the performance of system. The data can be viewed for a selected date or selected hour of a date.
The information of event logging can also be accessed through the software. All the events information is read from the internal memory of the charge controller and stored on the computer. The events are shown in a tabular format showing the event with the date and time of occurrences.
The daily history data of the operation of the charge controller is also shown in the table. The communication interface has the facility of upgrading for remote monitoring and control of the charge controller through various means.
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims: -

WE CLAIM;
1. A MPPT based solar charge controller comprising of DC-DC synchronous buck
converter section, power supply section, signal conditioning circuits along with
isolated communication section and control section in connection with each other.
2. A MPPT based solar charge controller as claimed in claim 1 wherein the solar charge
controller is provided with means which implements the fuzzy logic based maximum
power point tracking algorithm based on the feedback sense of PV panel current, PV
panel voltage, battery current, battery voltage and temperature for extracting the
maximum available power from the panels at any instant.
3. A MPPT based solar charge controller as claimed in claim 1 or 2 wherein gate drivers
are provided for driving the high side and low side switches from the PWM signals of
the digital signal controller.
4. A MPPT based solar charge controller as claimed in any of the preceding claims
wherein the controller senses the voltage and current of the connected PV panels,
battery current and voltage of the batteries connected and temperature through the
sense signal conditioning circuits for controlling the operation.
5. A MPPT based solar charge controller as claimed in any of the preceding claims
wherein the isolated communication section is used for the computer interfacing,
which can also be used for some other external control interface.
6. A MPPT based solar charge controller as claimed in any of the preceding claims
wherein switch is provided with multiplexed functions for the activation or
deactivation of manual or automatic mode of equalization process for the connected
batteries.
7. A MPPT based solar charge controller as claimed in claim 1 wherein protection for
reverse current flow from battery to PV panel is provided with the help of
semiconductor switches.
8. A MPPT based solar charge controller as claimed in any of the preceding claims
wherein the synchronous buck converter is a modified version of the basic buck
converter circuit in which the freewheeling diode is replaced by semiconductor
switch LS.
9. A MPPT based solar charge controller as claimed in any of the preceding claims
wherein the power storage device can be other than battery such as double layer
capacitor etc.
10. A MPPT based solar charge controller substantially as herein described with
reference to the accompanying drawings.