1. Solar Power DC-DC Converter

2. CONTENT Introduction To Solar Cell Knowledge Some Of the Problems
Different IC`s available
Specification & Usage
Block Diagram & Circuit Diagram
Operation
Other IC`s available
Specification
Block Diagram

3. 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.

4. 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.

5. BOOST TOPOLOGY:

6. 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:

7. Circuit For MAX856

8. This circuit enables a seven-cell solar panel to charge a three-cell NiCd battery

10. Operation: High Efficiency C-MOS switching regulator:
The MOSFET used has very low threshold voltage to ensure 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.

11. 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

12. 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:

13. Typical Operating Circuit:

14. This two-stage step-up converter derives 0
This two-stage step-up converter derives 0.5A at 5V from a typical solar-cell array, and guarantees start-up under full load.

16. Usage: 1-Cell Battery-Operated Equipment Backup Supplies Detectors
Pagers
Remote Controls
Solar Powered Applications

17. 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:

18. Solar cell current depends on area and light intensity
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.

20. Operation: Average Current Mode topology:
Fixed frequency PWM with synchronous rectification.
Average inductor current is regulated by a fast current regulator which 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.

21. 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 times that of o/p current at some of operating states and during start-up as impedance is low high current flow can occur.

22. 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

23. IC No:TPS
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:

24. Typical Operating Circuit:

26. OPERATION: Synchronous boost topology
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.

27. Inductor Selection: 4.7μH show good performance over wide range of i/p and o/p.

28. 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

29. 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:

30. Typical Operating Circuit:

31. Working is same as TPS61097-33:

32. 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

33. 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:

36. Operation: Fixed Frequency PWM using Multiple feed forward topology :
I/p , o/p and voltage drop on N MOSFET is monitored and forwarded 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.

37. 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.

38. 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

39. IC No:ZXSC100
Features:
Efficiency maintained over a wide range of input voltages and load currents 82% 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:

42. 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 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.

43. 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

44. 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

45. Circuit For MAX1678

47. 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:

49. Operation: Device is based on average current topology:
Almost same as that of TPS61200 with some minor differences in voltage levels .

50. 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

51. 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:

53. 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

54. 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:

57. Operation: Micro-power Step Up DC-DC Converter:
Power switching regulators optimized for applications where power 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.

58. Usage: Cellular Telephones Pagers Personal Digital Assistants
Electronic Games
Camcorders
Handheld Instruments
Other Similar Products:NCP1450A, NCP1402A

59. 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 V (fixed)
Oscillation frequency: 350 kHz typ. (at Vin = 0.3 V)
Relevant Link:

61. 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

62. THANK YOU!!!