Got a Smartphone, tablet or any other portable electronic device? If you have the history of getting frustrated due to battery draining too fast then you need a portable power bank. We want small, lightweight, thin and stylish gadgets that are easy to carry and rich in features. However, your all wishes cannot come true. More features mean more use. When you are using your Smartphone without break, the battery is likely to be drained out. A power bank is a portable secondary source of power when there is no source power available.
Power Bank Operation Board
If you look at the operation board of the power bank, you will find:
On/off switch
Battery gauging indicators
Mini USB to charge the power bank
One or more than one USB for charging tablet, Smartphone, PSP and other gadgets
A power bank can have different battery cells. It depends on the budget and form factor of the device. The capacity of the battery of the power bank is measured in mAh (milliamp hours). Some power banks make use of lithium polymer batteries cells for achieving thin form factor. Power banks with battery capacity in tens of thousands of mAh use 18650 batteries (cylindrical cells 65 mm height and 18 mm diameter) for high capacity while keeping cost that can be easily affordable.
Form Factor determines the capacity and size of the power bank. There are several other basic application requirements and technical aspects that must be considered during the development of the power bank.
Application requirements | Technical challenges |
Flexibility and mobility | High integration with host control option |
Automatic detection of USB D+/D- pins | Advanced digital-circuit design technology |
Low Electromagnetic Interference | Optimized IC/PCB layout and switching cycle performance |
Voltage based battery gauge function | Voltage-based battery capacity gauging with integrated ADC. |
Long battery life and backup times | High boost power efficiency and battery charging voltage accuracy. |
Following are the two stages of a straightforward two-stage power bank:
- Single cell battery charger
- Boost converter
Single-Cell Battery Charger
The single-cell battery charger can be switching charger or a linear charger. Small size, low cost and low EMI are the advantages of the linear charger. However, for high capacity power bank battery having several thousand mAh, switching chargers are ideal as charging time and rise in temperature are low.
Boost Converter
It steps up battery voltage to 5V. It depends on the cable resistance and output current.
A two stage power bank requires two sets of inductors and switches for boosting OTG (on-the-go) and buck charging. This increases the total cost. On the other hand, fully integrated single chip power bank ICs have a single set of inductor and switch for performing both boost and charging functions.
The input current capability is determined by the USB D+D- detection. The charger makes sure that input current does not exceed the detected value. There is a special circuitry that prevents the device from damage due to over current and overheating.
A power bank is a portable power solution that can be your perfect travel companion. However, you should buy the right power bank for your device.