Recent improvements in semiconductor technologies have made the design of efficient low-voltage portable electronic devices possible. Buck converter is mostly used in low-voltage power supplies because of its simplicity and low cost. However, employing the traditional buck converter in a low-voltage power supply would result in low efficiency because of the freewheeling diode in the output path of the converter. Synchronous rectifiers in which MOSFETs are applied to mimic the operation of diodes can resolve this problem. Portability is another important parameter in designing portable devices. Device portability requires a converter with low weight and small size. Integrating the converter is attractive approach which is used recently in portable devices to reduce the size and decrease the weight. Portable devices are also supplied with batteries and the internal resistance of the batteries increases by aging. In other words, the output voltage of the batteries is variable during their life time. Therefore, employing a switching power supply for portable applications is a vital requirement for creating constant output voltage. However, in switching power supplies, applying a passive filter is necessary to regulate the output voltage of the converter. This passive filter usually consists of a large inductor and a bulky capacitor. Consequently, the output filter of a switching power supply requires large area for implementation. This is a fundamental drawback of the switching power supplies in portable applications. The size of the filter components decreases by increasing the switching frequency. Therefore, integrated switching power supplies in which very high switching frequencies can be attained is used for portable applications. In integrated switching power supplies, the switching frequency of the converter is increased up to several MHz. By increasing the frequency, the efficiency of the converter decreases significantly. To resolve this problem and improve the converter efficiency, several techniques such as energy-recovery, energy-recycling and energy-reuse are employed. In this thesis, the stored energy in the converter output capacitor is used for supplying the converter drive circuits. In addition, a energy recycling technique is applied to improve the converter efficiency. This technique has achieved about 10% efficiency improvement. Another application for low voltage buck converter is in the microprocessor power supplies. A fixed area on the motherboard is assigned to the processor power supply. Therefore, switching frequency of the converter must be increased to reduce the converter size. Recent processors require low-voltage and very high current power supply to operate properly. Creating these conditions is very challenging. In addition, these requirements would result in a very narrow pulse width for driving the switch. This narrow pulse create several drawbacks in converter operation. Therefore, this narrow duty-cycle must be extended. In previous works, to extend the duty-cycle, transformers are applied to the converter. In addition, to improve the efficiency of the converter, current source drivers are used. In this thesis, coupled inductors are used in the buck converter to extend the narrow converter duty-cycle. The energy stored in the leakage inductance of the coupled inductors is also recovered to supply the drivers of the switches. Utilizing these techniques has resulted in 5% efficiency improvement. Therefore, the efficiency of the converter is increased up to 83%. Keywords: Low-Voltage Switching Power Supply, Low-Voltage High-Current Buck Converter, Integrated switching power supplies, Synchronous Rectifier, Energy-Recovery Techniques