Patent ID: RE42142

Claim:
A controllably alternating buck mode DC-DC converter comprising: an upper switching stage and a lower switching stage having controlled current flow paths therethrough coupled between an input voltage terminal adapted to receive an input voltage, and a reference voltage terminal adapted to receive a reference voltage, a common node between said upper switching stage and said lower switching stage being coupled through an output inductor to an output port for charging a battery, said upper switching stage having an upper control terminal to which a first pulse width modulation (PWM) waveform is applied for controlling the conduction and non-conduction of said upper switching stage, and wherein said lower switching stage has a lower control terminal to which a second PWM waveform, referenced to said first PWM waveform, is selectively applied for controlling the conduction and non-conduction of said lower switching stage; and a lower switching stage controller, which is operative, in response to a positive inductor current flow from said common node to said output port at the end of one or more cycles including a respective ith cycle of said first PWM waveform, to allow said second PWM waveform to be applied to said lower control terminal of said lower switching stage during the (i+1)th cycle of said first PWM waveform, and thereby cause said buck mode DC-DC converter to operate in synchronous buck mode for the (i+1)th cycle of said first PWM waveform, and in response to inductor current dropping to zero during said one or more cycles including said respective ith cycle of said first PWM waveform, to cause diode emulation of said lower switching stage during the (i+1)th cycle of said first PWM waveform, and thereby cause said buck mode DC-DC converter to operate in standard buck mode for the (i+1)th cycle of said first PWM waveform.