Download Solar Power DC

CONTENT
Introduction
To Solar Cell
Different
IC`s available
Other IC`s
available
• Knowledge
• Some Of the Problems
• Specification & Usage
• Block Diagram & Circuit Diagram
• Operation
• Specification
• Block Diagram
Abstract:
Solar Cell Knowledge;
Characteristic Equation:
I = IL − ID − ISH
Vj = V + IRS
Shockely Diode Equation:
•Variation in internal R cause o/p voltage variation.
•Intensity is inversely proportional to current, which limits at constant
voltage.
I-V characteristic Of Solar cell:
•Direct connection to battery is not possible due to variation in battery voltage.
•Varying sunlight affects current, hence electronics to optimize power is
needed.
BOOST TOPOLOGY:
IC No:MAX856-MAX859
Features:
 0.8V to 6.0V Input Supply Voltage
 85% Efficiency at 100mA
 Pin-selectable output voltage of 3.3V or 5V
 Circuit extracts the maximum power from a solar array
to charge a battery stack
 Up to 500kHz Switching Frequency
Relevant Link:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1207
http://www.maxim-ic.com/appnotes.cfm/an_pk/484
Circuit For MAX856
This circuit enables a seven-cell solar panel to charge a three-cell NiCd battery
Operation:
High Efficiency C-MOS switching regulator:
 The MOSFET used has very low threshold voltage to ensure
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start-up at low voltages.
Unique minimum turn-off time PFM control scheme is
unique feature of the device.
No oscillator; switching is accomplished by a pair of one shots
that set a maximum LX on-time (4.5μs type) and a minimum LX
off-time(1μs). LX on-time will be terminated early if the inductor
current reaches 0.5A before 4.5μs elapses.
Device has a low battery detection facility.
Bootstrapped device , hence can turn on at very low voltage.
Usage:
 2-Cell and 3-Cell Battery-Operated Equipment
 3.3V to 5V Step-Up Conversion
 Glucose Meters
 Medical Instrumentation
 Palmtop Computers
 Personal Data Communicators/Computers
 Portable Data-Collection Equipment
 Solar Powered Applications
IC No:MAX866-MAX867
(Using MAX1771 boost controller)
Features:
 0.8V to 6.0V Input Supply Voltage
 80% Efficiency Over Wide Load Range
 0.9V Guaranteed Start-Up Supply Voltage
 Provide 5V rail under full load and as low as 0.8V input
voltage
 Up to 250khz Switching Frequency
 A two-step approach (Figure ) enables the system to start
up and produce the 5V rail under full load.
Relevant Link:
http://www.maxim-ic.com/appnotes.cfm/an_pk/1029
Typical Operating Circuit:
This two-stage step-up converter derives 0.5A at 5V from a typical solar-cell array,
and guarantees start-up under full load.
Usage:
 1-Cell Battery-Operated Equipment
 Backup Supplies
 Detectors
 Pagers
 Remote Controls
 Solar Powered Applications
IC No:TPS61200 TPS61201
TPS61202
Features:
 Operating Input Voltage Range from 0.3 to 5.5
 More than 90% Efficiency at
 300 mA Output Current at 3.3 V (VIN ≥ 2.4 V)
 600 mA Output Current at 5 V (VIN ≥ 3 V)
 Start-up into Full Load at 0.5 V Input Voltage
 Fixed and Adjustable Output Voltage Options from 1.8 V to
5.5 V
Relevant Link:
http://focus.ti.com/docs/prod/folders/print/tps61200.html
•Solar cell current depends on
area and light intensity. As an
effect its important to control
current in an application.
•This can be done either by
limiting current to a certain
value or controlling power
circuit to operate in most
efficient manner.
•This is accomplished by
keeping I/p voltage to a
Certain value where power
delivered to supply is
maximum , called as
maximum power point
regulation(MPP).
•This circuit also helps in
start-up by avoiding access
current to flow.
Operation:
Average Current Mode topology:
 Fixed frequency PWM with synchronous rectification.
 Average inductor current is regulated by a fast current regulator which
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is controlled by a voltage control loop.
Changes in i/p and o/p voltages is monitored through feed-forward ,
and can immediately change the o/p to achieve fast response to these
errors.
Controller also sense the maximum peak current for stable and safe
operation.
3 N-MOSFETs to maintain synchronous power conversion.
Down regulation circuit is turned on when i/p exceeds o/p voltage, in
this mode controller changes the behavior of 2 MOSFET switches to
ensure proper and stable regulation of o/p voltage.
 Power saving mode facility is available to improve efficiency at light
loading conditions and low frequency.
 Under-voltage lock out, over temperature protection, over voltage
protection, soft start , short circuit protection is provided.
 Due to efficiency constraints i/p current can sometimes be more than
10-20 times that of o/p current at some of operating states and during
start-up as impedance is low high current flow can occur.
Usage:
 All Single-Cell, Two-Cell and Three-Cell Alkaline,
 NiCd or NiMH or Single-Cell Li Battery Powered
Products
 Fuel Cell And Solar Cell Powered Products
 Portable Audio Players
 PDAs
IC No:TPS61097-33
Features:
 Operating Input Voltage Range From 0.9 V to 5.5 V
 Up to 95% Efficiency at Typical Operating
Conditions
 Fixed Output Voltage Options From 1.8 V to 5.0 V
 Power-Save Mode for Improved Efficiency at
Low Output Power
 Over temperature Protection
Relevant Link:
http://focus.ti.com/docs/prod/folders/print/tps61097-33.html
Typical Operating Circuit:
OPERATION:
Synchronous boost topology. For power switching two actively controlled low R
MOSFETs are used.
 Controller Circuit
• Hysteretic Current Mode controller.
• VOUT is monitored through FB n o/p is reflected in current offset which
regulates the o/p voltage.
• Bypass switch turns off when EN is high to make IC as standard Boost
Converter , when EN is low it turns on n bypasses I/p to O/p.
• For low i/p start up circuit turns on to build up sufficient voltage. And
as soon as voltage reaches 1.8V it turns of and i/p voltage controls the
circuit.
• Circuit provides under voltage lockout, overvoltage protection, over
temperature protection.
 Inductor Selection: 4.7μH show good performance over wide range of
i/p and o/p.
Usage:
 All Single-Cell, Two-Cell, and Three-Cell
Alkaline, NiCd, NiMH, or Single-Cell Li-Battery
Powered Products
 Personal Medical Products
 Fuel Cell and Solar Cell Powered Products PDAs
 Mobile Applications
 White LEDs
IC No:TPS61220,TPS61221,
TPS61222
Features:
 Operating Input Voltage Range From 0.7 V to 5.5 V
 Up to 95% Efficiency at Typical Operating
Conditions
 Fixed Output Voltage Options From 1.8 V to 5.0 V(also
available in fixed voltage)
 Power-Save Mode for Improved Efficiency at
Low Output Power
 Over temperature Protection
Relevant Link:
http://focus.ti.com/docs/prod/folders/print/tps61220.html
Typical Operating Circuit:
Working is same as TPS61097-33:
Usage:
 All Single-Cell, Two-Cell, and Three-Cell
Alkaline, NiCd, NiMH, or Single-Cell Li-Battery
Powered Products
 Fuel Cell and Solar Cell Powered Products
 PDAs
 Mobile Applications
 White LEDs
IC No:TPS61020,TPS61024,
TPS61025,TPS61026,TPS61027,
TPS61028, TPS61029
Features:
 Input Voltage Range: 0.9 V to 6.5 V
 96% Efficient Synchronous Boost Converter
 Fixed and Adjustable Output Voltage Options Up to 5.5 V
 Output Voltage Remains Regulated When Input Voltage
Exceeds Nominal Output Voltage
 Low EMI-Converter (Integrated Anti ringing Switch)
Relevant Link:
http://focus.ti.com/docs/prod/folders/print/tps61020.html
Operation:
Fixed Frequency PWM using Multiple feed forward topology :
 I/p , o/p and voltage drop on N MOSFET is monitored and forwarded
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to regulator.(It avoids a slow way through control circuit and error
amplifier, and hence increased o/p response).
So control circuit has to handle only small error signal through FB to
create more stable o/p.
Peak current on N-MOSFET is sensed to limit current to 1.5A.
Device integrates 2 N and P MOSFETS, due to use of low R P channel
MOSFET instead of Schottky rectifier increases efficiency.
Special circuit is deployed using back-gate diode of P-MOSFET to
disconnect the o/p load from battery when EN is low. IT hence avoids
depletion of battery during shutdown.
 Two grounds(GND & PGND) to avoid ground shift.
 Down regulation mode is turned on when i/p voltage exceeds o/p
voltage, in this mode behavior of P-MOSFET changes accordingly to
regulate the voltage.
 Circuit enters into a PRECHARGE phase during startup to avoid large
current. In this phase it charges the different capacitor till o/p reaches
to a certain value.
 Circuit provides short circuit protection, under voltage lockout,
thermal protection, overvoltage protection.
 Device integrates a circuit to avoid ringing when device enters into
discontinuous mode.
Usage:
 All One-Cell, Two-Cell and Three-Cell Alkaline, NiCd
or NiMH or Single-Cell Li Battery, Solar Powered
Products
 Portable Audio Players
 PDAs
 Cellular Phones
 Personal Medical Products
 Camera White LED Flash Light
IC No:ZXSC100
Features:
 Efficiency maintained over a wide range of input voltages
and load currents
82% efficiency @ Vin=1V
 Start up under full load
 Minimum operating input voltage Vin=0.926V
 Adjustable output voltage down to Vin to 20 v
 Quiescent current typically 150μA referred to input voltage
Relevant Link:
http://diodes.com/products/catalog/detail.php?itemid=1624&popup=datasheet
Operation:
Non-Synchronous PFM DC-DC controller IC:
 Shutdown circuits turns on/off when VCC=1v.
 At start up COMP1 turns on, hence driver circuit and switching
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transistor. This circuit will remain active until voltage at FB exceeds
730mV.
An external resistive network at FB sets the o/p voltage level .
COMP 2 forces switching transistor to turn off when Isense (voltage at
emitter of switching transistor) voltage exceeds 25mV.
A mono-stable following the COMP2 extends turn off time of drive to
minimum of 2 µS ensuring sufficient time for discharge of inductor.
AND gate ensures switching transistor is always on until Isense
threshold is reached and minimum discharge period is always asserted.
Usage:
 Cordless telephones
• MP3 players
• PDA
• Pagers
• Battery backup supplies
• Electronic toothbrush
• GPS receivers
• Digital camera
• Palmtop computers
• Hand held instruments
• Portable medical equipment
• Solar powered equipment
Other Important IC`s
MAX1678(Efficient 1-Cell Step-Up Converter)
0.87V Guaranteed Start-Up
Up to 90% Efficiency
Efficient 1-Cell Step-Up Converter
Output voltage is preset to 3.3V or can be adjusted
from +2V to +5.5V
Vin=.7v to 5.5 v
45mA Output Current at 3.3V for 1-Cell Input
90mA Output Current at 3.3V for 2-Cell Input
Circuit For MAX1678
IC No:TPS63000,TPS63001,
TPS63002
Features:
 Input Voltage Range: 1.8V to 5.5V
 Up to 96% Efficiency
 Fixed and Adjustable Output Voltage Options from 1.2V to
5.5V
 Automatic Transition between Step Down and Boost Mode
 Up to 800-mA Output Current at 3.3V in Boost Mode (VIN
> 2.4V)
Relevant Link:
http://focus.ti.com/docs/prod/folders/print/tps63000.html
Operation:
Device is based on average current topology:
 Almost same as that of TPS61200 with some minor
differences in voltage levels .
Usage:
 All Two-Cell and Three-Cell Alkaline, NiCd or NiMH
or Single-Cell Li Battery Powered Products
 Portable Audio Players
 PDAs
 Cellular Phones
 Personal Medical Products
 White LEDs
IC No:AP6714
Features:
 Input Voltage Range: .9V to 5.5V
 94% Efficient Step-Up DC to DC Converter
 Fixed and Adjustable Output Voltage Options from 1.8V to
5V
 Current Mode Operation for faster transient response and
better loop stability
 1.8MHz Operating Frequency
Relevant Link:
http://diodes.com/products/catalog/detail.php?item-id=4769
Usage:
 All One-cell, Two-cell, Three cell, Alkaline, NiCd or
NiMh or Single-cell Li+ Battery Powered Devices.
 Cell Phones
 Digital Cameras
 MP3 Players
 PDAs
IC No: NCP1400A: 100 mA,
Fixed Frequency PWM Step-Up
Micro-power Switching Regulator
Features:
 Extremely Low Start-Up Voltage of 0.8 V
 Operation Down to Less than 0.2 V
 Only Four External Components for Simple Highly
Efficient Converters
 Up to 100 mA Output Current Capability
 Fixed Frequency Pulse Width Modulation Operation
 Output voltage can be vary from 1.8 to 5.5v(in fixed mode)
Relevant Link:
http://www.onsemi.com/PowerSolutions/product.do?id=NCP1400ASN25T
1G
Operation:
Micro-power Step Up DC-DC Converter:
 Power switching regulators optimized for applications where power
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drain must be minimized.
Designed to operate in discontinuous mode as fixed frequency voltage
mode boost converter.
Soft-start circuit initially pumps up the voltage up to 1.5 v at a fixed D,
the level at which it can operate normally.
Device is designed to operate in discontinuous mode . An internal
circuit is employed to insure stability at all i/p and o/p voltage levels.
Over voltage protection, excessive current limit, thermal shutdown is
provided.
Usage:
 Cellular Telephones
 Pagers
 Personal Digital Assistants
 Electronic Games
 Camcorders
 Handheld Instruments
Other Similar Products:NCP1450A, NCP1402A
IC No:S-882Z(A charge Pump
IC for low power DC-DC
conversion)
Features:
 Operating input voltage: 0.3 to 3.0 V
 Current consumption: During operation 0.5 mA max. (at
VIN = 0.3 V), During shutdown 0.6 µA max. (at VIN = 0.3 V)
 Discharge start voltage: 1.8 to 2.4 V (selectable in 0.2 V
steps)
 Shutdown voltage: Discharge start voltage + 0.1 V (fixed)
 Oscillation frequency: 350 kHz typ. (at VIN = 0.3 V)
Relevant Link:
http://www.sii-ic.com/en/product1.jsp?subcatID=3&productID=1788
Usage:
 Stepping up from low-voltage power supply such as
solar cell and fuel cell
 Stepping up internal power supply voltage of RF tag
 Intermittent power supply to intermittently operating
system