Application of portable power supply

Portable power applications are broad and varied. Products range from wireless sensor nodes with average power consumption of only a few microwatts to in-vehicle medical or data acquisition systems with battery packs of several hundred watt hours. However, despite the variety, they show relatively consistent development trends - designers continue to require higher power in their products to support more functions and expect to charge the battery from any available power source. The first trend requires increased battery capacity. Unfortunately, users are often impatient, and the increased battery capacity must be charged in a reasonable time, which must lead to an increase in charging current. The second trend requires great flexibility in battery charging solutions. We will explore each of these issues in more detail.

Modern handheld devices, whether consumer or industrial, are likely to include a cellular modem, a WiFi module, a Bluetooth module, a large backlit display, and more. The power architecture of many handheld devices is mirrored by the cell phone. Typically, a 3.7V Li-ion battery is used as the primary power source due to its high gravimetric (Wh/kg) and volumetric (Wh/m3) energy density. In the past, many high power density devices used a 7.4V Li-ion battery to reduce current requirements, but the availability of cheap 5V power management ICs has led to a shift to lower voltage architectures for more and more handheld devices. Tablets are a good example of this - the standard tablet has a rich feature set and a very large (for a portable device) screen. When powered by a 3.7V battery, the battery capacity must be several thousand mA. In order to charge such a battery in a few hours, several thousand mA of charging current is required.