TPS61200

• Designing DC-DC converters using TI TPS61200 controller By Oleg Mazurov
• TPS61200 board modifications. Part 1 – changing undervoltage lockout By Oleg Mazurov
• TPS61200 Power Step-Up Converter Booster V0Made By BBTech

• This module provide a power supply solution for products powered by either a single-cell, two-cell, or thress-cell alkaline, NiCd or NiMH, or one-cell Li-Ion or Li-polymer battery.
• Power save mode: set by jump. (default: disable)
• Undervoltage lockout mode: set by resistors. (default: disable)
• 78xx series pin compatible.
• Module size: 0.67 * 0.38 in.
• Base on TI TPS61200 boost converter.
• Wide input voltage range: 0.3 to 5.5 VDC.
• Minimum input voltage at startup: 0.5 VDC.
• Wide output voltage range: 1.8 to 5.5 VDC. (Adjustable)
• More than 90% efficiency.
• Average input current is limited to a maximum value of 1500 mA.
• Automatic transition between boost mode and down conversion mode.
• Output short circuit protection and thermal shutdown.

TI documentation

• Application SLVA345 August2009 Revised September 2011 Supplying TPS61200 With a Single Solar Cell

This application report explains how to use the TPS61200 in combination with a single solar cell to charge
a battery or storage device. A characteristic of solar cells is the internal resistance that can vary from less
than 10 Ω up to more than 100 Ω. Therefore, it is important to control the load placed on the solar cell to
ensure a reliable start-up of the application. This report describes an application that avoids the solar cell
output voltage breaking down and manages the load as the solar cell power changes. The solution
provides a reliable start-up of the TPS61200 using solar cells that can deliver at least 3 mA at 0.5 V

For indoor solar cells, the reference is mostly 100 and 1000 lux, which covers
most indoor light conditions from a single bulb lamp to indirect sunlight through a window. For comparison,
1250 lux is approximately 1 mW/cm 2 .

0.5V input, 3.3V output...The calculation also impressively shows that the input current I L is more than 13 times higher than the output current

Two features of the TPS61200 ideally fit the needs of applications running from a single solar cell. The
first and most important feature is the very low start-up voltage. The TPS61200 is able to start from a load
of 0.5 V and will run down to voltages below 0.3 V. This feature differentiates this boost converter from
other converters and makes it ideal for being supplied by solar cells.

The second feature offers a great advantage for additional circuitry that do not consume much power but
needs to be started or running while the main circuit is still not running. The additional circuitry can run
from the V AUX output. This output already offers a voltage at very low input voltages (>150 mV typ.) and
can drive currents of about 1 mA.

The deliverable current is proportional to the area of the
solar cell and greatly depends on the light source which is available. As an effect of this behavior, it is
important to limit the current flow into the application. This can be done either by just limiting the current to
a certain value, or by controlling the power supply circuit in such a way that it operates the solar cell in the
most efficient manner. This is accomplished by keeping the input voltage at a certain value where the
power that is delivered to the supply is at its maximum, called the maximum power point regulation (MPP).
The following schematic shows an example of a circuit that monitors the supply voltage of the TPS61200
with an additional operational amplifier and compares this voltage with a reference voltage.