Report on PCB
Designing
EE302.3Power Electronics & Applications
(Elective)
K.J.P. FERANDO
20845 (20.2)
Table of Contents
Introduction ......................................................................................................2
Schematic Diagram ..........................................................................................3
List of Components ..........................................................................................4
Functionality .....................................................................................................7
Calibrations of the Circuit ...............................................................................9
Safety Features ................................................................................................11
PCB Design using EasyEDA .........................................................................13
Appendix .........................................................................................................19
PAGE 1
Introduction
The aim of this report is to present the design and development of a printed circuit
board (PCB) for a maximum power point tracking (MPPT) solar charge controller.
The objective of this project is to create a device that can efficiently charge a 2S
lithium-ion battery using a small poly-Si technology solar panel with Pmax 10w,
Vmp 18V, and Imp 560mA. The device is intended to be used to power the house's
emergency LED lights. The previous charging method for the battery involved a
buck converter, which relied on grid current. So that MPPT solar charger was
developed to efficiently charge the battery, even in poor sunlight conditions.
This report will provide an
overview of the design process,
including component selection,
schematics, PCB layout. The
efficiency of the MPPT charge
controller
is
dependent
on
various factors such as the solar
driver
temperature,
battery
temperature, solar panel quality,
Figure 1 -3D View
and conversion efficiency.
In addition to that this project
development also supports alternative charging input as DC input jack as an extra
option to use this charger while solar is not productive or found to be defective. And
these two LEDs indicate the functionality of the charger whether it is charging the
battery or not charging the battery. And the potentiometer provides the capability to
adjust the input with the different specifications for different solar panels.
PAGE 2
Schematic Diagram
I was able to create a straightforward and reasonably cost schematic layout for an
automatic cut-off 12V lead acid battery charger after doing some research and
gathering information. I created the design with the aid of the internet and the
EasyEDA platform. The image below shows the schematic diagram I came up with.
To guarantee accessibility, I took care to choose components that were easily
accessible on the market. The design is particularly cost-effective since it
concentrates on utilizing just the components that are necessary for the circuit to
work. I am convinced that using this schematic, I have produced a dependable and
useful power efficiency MPPT charge controller which will help to charge the
batteries in my application without being harmed.
Figure 2 – Schematic Diagram
PAGE 3
List of Components
Figure 3 – Bill of Materials (BOM)
The term "bill of materials," or "BOM," refers to a list of all the parts needed to
construct a certain electrical circuit. Above table describes the components that
required to build the MPPT charge Controller. The BOM tool in EasyEDA creates a
list of all the parts used in a circuit's schematic diagram automatically. Each
component's name, amount, manufacturer, part number, and other pertinent details
are included. Users may more easily keep track of the components they need to buy,
their prices, and their availability thanks to this functionality. Likewise, in here, I am
selecting LCSC as the supplier for all the components of the project and I have
selected accordingly selecting the components by referring their specification that
describes in their own website. The BOM may also be altered by users of EasyEDA
to suit their requirements by adding or deleting components, altering quantities, or
changing part numbers.
PAGE 4
Let’s go through some of the major components that I used in this PCB designing
project one by one.
• LT3652
LT3652 is a high-efficiency, monolithic
synchronous buck regulator and battery
charger IC designed for use with singlecell
or
multiple-cell
Lithium-ion
batteries. The LT3652 is available in an
MSOP-12 package and has a small size
of L4.0-W3.0-P0.65-LS4.9-BL-EP. It
operates at a wide input voltage range of
4V to 32V and can charge batteries with
up to 2A charging current. The device
Figure 4 – LT3652 IC
also includes a maximum power point
tracking (MPPT) feature that maximizes
the energy extracted from solar panels or other current-limited power sources.
• 1N5819
The 1N5819 is a Schottky diode, which is a
type of semiconductor device that allows
current to flow through it more efficiently
than a regular diode. It has a low forward
voltage drop and a high current carrying
capability, making it useful in power
applications. The 1N5819 can handle a
maximum current of 1A and a reverse
voltage of 40V. It is commonly used as a
rectifier in DC power supplies, voltage
clamping in surge protection circuits, and in
Figure 5 – 1N5819 Schottky Diode
battery charging circuits.
PAGE 5
• 10k Potentiometer
3386P-1-103LF is a through-hole
resistor manufactured by Bourns. It
has a resistance of 10 kΩ with a power
rating of 0.5 W. The resistor has a
linear taper and is enclosed in a
compact 6 mm package. It is
commonly used in electronic circuits
for
voltage
dividers,
signal
conditioning, and other applications
that require precise resistance values.
Figure 6 – 10k Potentiometer
• 68uH Inductor
SHOU HAN CYH127-68UH is an inductor with an inductance value of 68
microhenries (68uH). It is compact size and is designed for surface mount
technology (SMT) applications.
The inductor is constructed with a
ferrite core and features high
saturation
current,
resistance,
temperature
and
stability.
low
DC
excellent
It
is
commonly used in power supplies,
DC-DC
converters, and other
applications where energy storage
Figure 7 – 68uH Inductor
and
filtering
are
necessary.
PAGE 6
Functionality
The LT3652 is a monolithic step-down battery charger used in the circuit. It operates
over a wide input voltage range of 4.95V to 32V, making it suitable for both solar
and adapter power sources. The device provides constant current / constant voltage
charging characteristics and can be programmed through current sense resistors for
a maximum charge current of 2A.
The output section of the charger employs a 3.3V float voltage feedback reference,
which allows any desired battery float voltage up to 14.4V to be programmed with
a resistor divider. The LT3652 also features a programmable safety timer using a
simple capacitor, which is used for charge termination after the desired time is
reached. This feature is useful for detecting battery faults.
The LT3652 requires an MPPT setup, where a potentiometer is used to set the MPPT
point. When powered using a solar panel, the input regulation loop is used to
maintain the panel at peak output power. The regulation point is determined by the
MPPT setup potentiometer.
The various components of the circuit, including VR1, R2, R3, and R4, are used to
set the 2S battery charging voltage at 8.4V. The formula used to set the battery
voltage is given by:
RFB1 = (VBAT(FLT) • 2.5 • 105) / 3.3
and
RFB2 = (RFB1 • (2.5 • 105))/(RFB1 - (2.5 • 105))
PAGE 7
The capacitor C2 is used to set up the charge timer, and the timer can be set using
the formula:
tEOC = CTIMER • 4.4 • 106 (in hours)
The D3 and C3 components are the boost diode and boost capacitor, respectively.
They drive the internal switch and facilitate the saturation of the switch transistor.
The boost pin operates from 0V to 8.5V.
The current sense resistor in the schematic is selected as 0.5 Ohms and 0.22 Ohms,
which are connected in parallel to create 0.15 Ohms.
Using the formula:
RSENSE = 0.1/ ICHG(MAX)
it will produce almost 0.66A of charge current. The C4, C5, and C6 components are
the output filter capacitors.
Overall, the LT3652 and its associated components and formulas work together to
provide a reliable and efficient battery charging solution for the circuit.
PAGE 8
Calibrations of the Circuit
Calibration is an important process in electronics manufacturing that ensures that the
final product meets the specifications and functions as intended. In the case of the
PCB using LT3652, there are a few components that require calibration to ensure
that the charger operates efficiently and effectively.
Firstly, the MPPT setup potentiometer (VR1) needs to be calibrated to set the MPPT
point. This is done by adjusting the potentiometer until the input regulation loop
maintains the solar panel at peak output power. The optimal MPPT point is the point
where the solar panel produces maximum power, and the MPPT algorithm should
keep the panel at this point to ensure efficient charging.
Next, the resistor divider (R2, R3, and R4) needs to be calibrated to set the battery
charging voltage. The formula provided in the circuit schematic can be used to
determine the resistance values required for a desired battery float voltage. Once
these values have been determined, the resistors can be selected and installed on the
PCB.
The charge timer can also be calibrated using the capacitor C2. The formula provided
in the schematic can be used to determine the required capacitance for a desired
charge time. Once the capacitance value has been determined, the capacitor can be
selected and installed on the PCB.
Finally, the current sense resistor (R5 and R6) needs to be calibrated to ensure that
the charge current is within the desired range. The formula provided in the schematic
can be used to determine the resistance value required for a desired charge current.
Once the resistance values have been determined, the resistors can be selected and
installed on the PCB.
PAGE 9
During the calibration process, it is important to ensure that all components are
installed correctly and that the circuit is operating as intended. Testing and
verification should be carried out at various stages of the calibration process to
ensure that the final product meets the desired specifications.
PAGE 10
Safety Features
The PCB design of the charger using the LT3652 includes several safety features to
prevent any damage to the battery, charger, or other connected components. One of
the primary safety features of the LT3652 itself is the constant current/constant
voltage charge characteristics. This ensures that the battery is not overcharged,
which could damage the battery and cause safety hazards.
Another safety feature of the charger is the programmable safety timer, which is used
for charge termination after the desired time is reached. This feature is useful to
detect battery faults and prevent overcharging.
The MPPT setup of the LT3652 is another safety feature that helps to prevent any
damage to the charger or battery. When the charger is powered using a solar panel,
the input regulation loop is used to maintain the panel at peak output power. This
ensures that the panel is not overpowered and prevents any damage to the charger or
battery.
The use of current sense resistors also adds to the safety features of the charger. The
charge current can be calculated using the formula provided, and the selected current
sense resistors in the schematic ensure that the charge current does not exceed the
maximum charge current limit of 2A. This prevents any damage to the battery or
charger due to overcharging.
The boost diode and boost capacitor are used to drive the internal switch and
facilitate the saturation of the switch transistor. This feature ensures that the switch
transistor does not exceed its maximum rating, which could cause damage to the
charger or other connected components.
PAGE 11
The output filter capacitors also add to the safety features of the charger by
smoothing the output voltage and filtering any noise or ripple. This ensures that the
battery receives a stable and safe voltage, preventing any damage or safety hazards.
Finally, the DC barrel jack is connected in such a way that the solar panel will get
disconnected if an adapter jack is inserted into the adapter socket. This prevents any
reverse current flow from damaging the solar panel or the adapter during no charging
condition. Additionally, the D1 diode provides reverse polarity protection to the
charger and battery, preventing any damage due to reverse current flow.
In summary, the safety features of the charger include constant current/constant
voltage charge characteristics, programmable safety timer, MPPT setup, current
sense resistors, boost diode and capacitor, output filter capacitors, and reverse
polarity protection. These features ensure that the battery and charger remain safe
and prevent any damage due to overcharging, overvoltage, or reverse current flow.
PAGE 12
PCB Design using EasyEDA
• Design Considerations
When designing an MPPT charge controller circuit with the given specifications,
several considerations need to be considered.
Firstly, the circuit must be designed to regulate the input voltage from both the solar
panel and the adapter to ensure efficient charging of the battery. The MPPT setup
must be carefully calibrated to ensure that the maximum power point of the solar
panel is tracked, and the battery is charged with the maximum power. The circuit
must also be designed to limit the charging current to a maximum of 600mA, which
can be achieved by carefully selecting the appropriate current sense resistor.
Additionally, the circuit must be designed to provide an option for additional
charging using an adapter, which requires the inclusion of a DC barrel jack and
appropriate reverse current protection diode.
Finally, the circuit must be designed to include a programmable safety timer to
ensure safe and efficient charging of the battery. Overall, careful consideration of
these factors will result in a well-designed MPPT charge controller circuit that is
both efficient and reliable.
PAGE 13
• PCB Design
PCB design using EasyEDA
involves
Firstly,
several
the
steps,
schematic
diagram of the circuit is
drawn
using
EasyEDA's
intuitive schematic capture
tool. Once the schematic is
complete, the PCB layout
can
be
generated
automatically by EasyEDA's
Figure 8 – 3D View
powerful layout engine.
The PCB can then be customized by adding
additional components or modifying the
layout as per the design requirements.
Dimensions of the PCB are 58 mm x 57
mm in size.
Figure 9 – PCB Information
PAGE 14
Top Copper Layer
Figure 10 – Top Copper Layer
Bottom Copper Layer
Figure 11 – Bottom Copper Layer
PAGE 15
Top Silk Layer
Figure 12 – Top Silk Layer
Bottom Silk Layer
Figure 13 – Bottom Silk Layer
PAGE 16
Top Solder Mask Layer
Figure 14 – Top Solder Mask Layer
Bottom Solder Mask Layer
Figure 15 -Bottom Solder Mask Layer
PAGE 17
2D View
Figure 16 – 2D View of PCB
3D View
Figure 17 - 3D View of PCB
PAGE 18
Appendix
Figure 1 -3D View ........................................................................................................................ 2
Figure 2 – Schematic Diagram ................................................................................................... 3
Figure 3 – Bill of Materials (BOM) ............................................................................................. 4
Figure 4 – LT3652 IC .................................................................................................................... 5
Figure 5 – 1N5819 Schottky Diode ............................................................................................ 5
Figure 6 – 10k Potentiometer ...................................................................................................... 6
Figure 7 – 68uH Inductor ............................................................................................................ 6
Figure 8 – 3D View..................................................................................................................... 14
Figure 9 – PCB Information ...................................................................................................... 14
Figure 10 – Top Copper Layer ................................................................................................. 15
Figure 11 – Bottom Copper Layer............................................................................................ 15
Figure 12 – Top Silk Layer ........................................................................................................ 16
Figure 13 – Bottom Silk Layer .................................................................................................. 16
Figure 14 – Top Solder Mask Layer ......................................................................................... 17
Figure 15 -Bottom Solder Mask Layer .................................................................................... 17
Figure 16 – 2D View of PCB ..................................................................................................... 18
Figure 17 - 3D View of PCB ...................................................................................................... 18
Gerber File Download Link
https://drive.google.com/file/d/1-gK1ll1IQ4ovq0V6Pt9VojL9jfwl7eCr/view?usp=share_link
PAGE 19