A reconfigurable battery pack for improving power conversion efficiency in portable devices

Extending battery life for portable computing systems not only requires new power management techniques and high efficiency power delivery systems but also must address low power consumption modes. Mobile systems spend most of their operating time in very low power modes, in which the voltage regulators (VRs) that feed the different components typically exhibit low efficiencies. Variable frequency control is one of the most commonly used methods to minimize both driving and switching losses by scaling the switching frequency at light loads. However, further benefit can be achieved if the input voltage scales as well. This paper proposes a novel reconfigurable battery pack (RBP) concept to improve power conversion efficiency of VRs under light load conditions. It describes a methodology to change the input voltage of VRs based on load conditions by changing the internal connection of battery cells to provide a variable input bus voltage to the system and extend battery life as a result of power loss reduction. Experimental results show ~15 min battery life improvement for a typical Thin & Light Laptop.