In this paper, we propose an improved boost converter with functions of adjustable output voltages and currents. The DC sources of electronic products using batteries have become indispensable equipment. These charging sources of the diverse batteries must be provided by switching power converters. To obtain functions of adjustable output voltages and currents, a conventional boost converter is usually accepted. However, the power semiconductor devices (power switches and power diodes) of the conventional boost converter are operated at high frequency, which causes high power losses, high temperatures, and low conversion efficiency. To overcome these disadvantages, a passive lossless snubber is incorporated in the conventional boost converter to reduce power losses and increase conversion efficiency. In this paper, we propose an improved boost converter to implement functions of adjustable output voltages and currents. We compare the performance and efficiency between the conventional and improved boost converter with functions of adjustable output voltages and currents. Theoretical analysis and experimental results confirmed that the improved boost converters with functions of adjustable output voltages and currents has lower power losses, lower temperatures and higher conversion efficiency than the conventional boost converter.