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Solar powered Laptop Charger Using MPPT

May 3, 2016

Introduction
Now a days the most advance solar charge controller available in the market is Maximum Power Point Tracking (MPPT).The MPPT controller is more sophisticated and more expensive. It has several advantages over the earlier charge controller. It is 30 to 40 % more efficient at low temperature. But making a MPPT charge controller is little bit complex in compare to PWM charge controller. It require some basic knowledge of power electronics.

I put a lot of effort to make it simple, so that any one can understand it easily.If you are aware about the basics of MPPT charge controller then skip the first few steps.

The Maximum Power Point Tracker (MPPT) circuit is based around a synchronous buck converter circuit..It steps the higher solar panel voltage down to the charging voltage of the battery. The Arduino tries to maximize the watts input from the solar panel by controlling the duty cycle to keep the solar panel operating at its Maximum Power Point

These are the required list of material for making a solar laptop charger :
1. MPPT

Electrical specifications :

1.Rated Voltage= 12V
2.Maximum current = 5A
3.Maximum load current =10A
4. In put Voltage = Solar panel with Open circuit voltage from 12 to 25V
5.Solar panel power = 65W
2. 50 Meter Wire
3. Laptop cable (depends on the laptop)
4. Laptop
5. Solder Iron
6. Screw Case

Circuit Connection

Untitled

mppt.jpg
Basic Working Principle:

Solar

System Description
The system under consideration is an Solar Laptop charger. The solar laptop charger consists of Laptop , a solar controller, and a solar panel as shown in Figure.

 
Circuit Description :

The input voltage for the solar controller enters from the solar panel through VIN and GND. The input voltage is filtered by C14. Input under voltage is sensed by R19, R25, and C2, which prevents the controller from operating when the solar panel cannot provide the minimum current. Input over voltage is detected by R27 and R26, which prevents the controller from turning on when the panel voltage is too high or an improper voltage source is connected. The frequency of operation is set by R22 and C1, and can be adjusted up to 1MHz. An external reference is provided that is capable of sourcing a minimum of 2mA when decoupled with C4. The NCP1294 allows the limiting of duty cycle, as well as providing voltage feed forward through R23 and C3. A linear regulator consisting of R20, Z1, and Q5 provide the startup current for the controller. Once the circuit is switching, the current for the controller is provided through R18, D2, C7, and clamped by Z2. The NCP1294 is equipped with power voltage line VC pin and power ground pin PG. The NCP1294 also has a logic voltage line VCC, which is filtered by R15 and C8 with a logic ground LGND to ensure optimal performance. Soft start of the controller can be programmed by adjusting C5. The switching of Q1 is accomplished with the gate pin and rise and fall times can be adjusted with R14. Snubbing of switching noise is provided on the primary side by C16, R11, D4, R17, C18, and R28. The current flowing through Q1 is sensed across R12 and R33 through the filtering of R13 and C6 at the ISENSE pin. Energy is delivered to the secondary side via D1 and D3 which are filtered by C15, C20, and C21. Snubbing is accomplished on the secondary side by C17, R6, R28, and C19. Isolated feedback is provided through U3, but can be modified to provide non-isolated feedback by connecting NIFB and removing ISFB, ISCOMP, ISI, R3, and R33. Phase and gain measurements during the prototyping stage can be accomplished with R9. Type 3 feedback is provided using U2, C11, R7, C12, R3, C10, R4, R5, C9, and R8. A standard ground bypass safety capacitor is provided in C13, but should be shorted if no- isolated operation is required.

Peak Power Tracking:

The NCP1294 allows the user to adjust the current limit via R21 and R24, which are compared to the pulse by pulse current limit measured at Pin 2. The solar panel as discussed earlier has I V characteristics shown in Figure 8 when the current is ramped up. During each on period of a DCM Flyback, the current in Q1 is ramped up from zero current to the maximum allowed internal current limit of the part. If the maximum power of the solar panel is exceeded, the voltage falls to zero. Ideally, the current limit of the part would be set such that it limited at the maximum power point, utilizing the entire capacity of the provided solar panels

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