Patent ID: 7778046

Claim:
A non-isolated switching DC-to-DC converter for providing power from a DC voltage source connected between an input terminal and a common terminal to a DC load connected between an output terminal and said common terminal, said converter comprising: an input inductor connected at one end to said input terminal; an input switch with one end connected to said common terminal and another end connected to another end of said input inductor; a capacitor connected at one end to said another end of said input inductor; a first current rectifier with an anode end connected to said common terminal; a second current rectifier with an anode end connected to another end of said capacitor and a cathode end connected to said output terminal; a resonant inductor with one end connected to a cathode end of said first current rectifier and another end connected to said anode end of said second current rectifier; an output capacitor with one end connected to said output terminal and another end connected to said common terminal; switching means for keeping said input switch ON for a duration of an ON-time interval DT S , and keeping it OFF for an OFF-time interval D′T S , where D is a duty ratio and D′ is a complementary duty ratio within one complete and controlled switch operating cycle T S ; wherein said input switch can be implemented with active semiconductor switching devices such as bipolar transistor or MOSFET transistor; wherein said resonant inductor and said capacitor form a resonant circuit during said ON-time interval and define a constant resonant frequency and corresponding constant resonant period; wherein said second rectifier turns ON when said input switch is turned OFF and said second rectifier turns OFF when said input switch is turned ON so that said input switch and said second rectifier operate out-of-phase; wherein turn-ON of said input switch causes a turn-ON of said first rectifier at zero current level and a sinusoidal resonant current flows through said first current rectifier until it reaches a zero current level again and turns OFF said first rectifier making a conduction time interval of said first rectifier equal to half of a resonant period; wherein said input switch is turned OFF at instant when said first rectifier turns OFF, making said ON-time interval DT S constant and equal to half said resonant period; whereby said first rectifier is turned ON and turned OFF at zero current with no switching losses, and whereby an output voltage between said output terminal and said common terminal is regulated by controlling said OFF-time interval D′T S of said input switch; whereby said converter in steady-state has a step-up DC conversion gain characteristics dependent on said duty ratio D; whereby voltage stresses on said input switch, said first current rectifier, and said second current rectifier are equal to said output voltage, and whereby said output voltage has the same polarity as said DC voltage source.