A high-efficiency, dual-mode, dynamic, buck-boost power supply IC for portable applications

Integrated power supplies are critical building blocks in state-of-the-art portable applications, where they efficiently and accurately transform a battery supply into various regulated voltages, as required by their loads. This paper presents a novel low voltage, dual-mode, buck-boost converter IC targeted for dynamic supplies of linear RF power amplifiers (PAs) in wireless handsets. Maintaining high efficiency of the converter over a wide loading range is critical for improving battery life in such systems. The use of a novel, supply-voltage adaptive, on time control for pulse-frequency-modulation (PFM) mode achieves an accurate output ripple voltage, not to mention higher efficiency under light loads. In the high-power mode, the converter is operated in a modified pulse-width-modulation (PWM) control, where its operation is changed adaptively between buck, buck-boost, and boost regions, thereby saving unnecessary switching losses. Appropriate circuit topologies are developed and designed to overcome the challenges of a low supply voltage environment requiring a wide dynamic range converter. The converter is designed and simulated using a 0.5-μm n-well CMOS process for a supply voltage range of 1.4-4.2 V, which is compatible with state-of-the-art Li-ion batteries (2.7-4.2 V), and alternate power sources, e.g. NiCd and NiMH batteries. Simulation results show that the converter generates an output voltage of 0.5-5 V while delivering up to 0.5 A of load current with a maximum ripple of 40 mV. The converter exhibits efficiency of 60-93% in PWM mode and 80% in PFM mode. A 0.9-1 V transient control-step response in PWM mode, which refers to a change in output voltage of 4.5-5 V, from an input supply of 1.4 V, is less than 200 μsec.