DC/DC switching regulator having reduced switching loss

A DC to DC converter for generating a voltage at an, output which is lower than a voltage supplied at an input comprising:

• a PMOS transistor coupled between the voltage supply and the series connection of an inductor and a capacitor, voltage across the capacitor being the output voltage;
• a rectifier connected in parallel to the series connected inductor and capacitor;
• a control circuit for the PMOS transistor coupled to a gate thereof and providing a drive signal between substantially the supply voltage and substantially a reference voltage;
• a transmission gate coupled between the gate, a second capacitor and the reference voltage and responsive to a control voltage generated by the control circuit for driving the transmission gate ON after the gate of the PMOS transistor is isolated from the supply voltage and the reference voltage, driving the transmission gate OFF after a predetermined time interval and before the control circuit drives the gate of the PMOS transistor to substantially the supply voltage, the control circuit isolating the gate of the PMOS transistor before driving the transmission gate ON for a predetermined time interval before the drive signal at substantially the reference voltage is applied to the gate of the PMOS transistor.

A method for operating a voltage converter having a semiconductor switch coupled to an inductor, a first capacitor, and a rectifier, the semiconductor switch being driven between ON and OFF states from first and second voltage sources and having parasitic capacitance at a gate thereof, comprising:

• isolating the semiconductor switch from the first and second voltage sources;
• transferring charge from the parasitic capacitance to a second capacitor coupled thereto;
• terminating the charge transfer and isolating the second capacitor from a remainder of the voltage converter;
• changing an ON/OFF state of the semiconductor switch by driving the gate to the other of the first and second voltage sources;
• isolating the semiconductor switch from the first and second voltage sources;
• coupling the second capacitor to the gate to charge the parasitic capacitance prior to isolating the second capacitor from a remainder of the voltage converter and driving the semiconductor switch to the other of the ON/OFF states;
• driving the semiconductor switch to the other of the ON/OFF states.

A cellular telephone comprising:

• a voltage converter for powering a telephone circuit, the voltage converter comprising a semiconductor switch coupled to an inductor, a first capacitor and a rectifier, the semiconductor switch having a gate and being driven between ON and OFF states from first and second voltage sources by a first control circuit;
• a second capacitor;
• a first transmission gate coupled between the second capacitor and the gate of the semiconductor switch, wherein the first control circuit is coupled to the first transmission gate and generates a control signal to turn ON the first transmission gate when the first control circuit isolates the semiconductor switch from the first and second voltage sources, turns OFF the first transmission gate before the control circuit drives the semiconductor switch to a second one of the ON and OFF states, turns on the first transmission gate after the first control circuit isolates the semiconductor switch from the first and second voltage sources and turns OFF the first transmission gate before driving the semiconductor switch from the second of the ON and OFF states to the first of the ON and OFF states, whereby a portion of the charge stored on a parasitic capacitance of the gate of the semiconductor switch is stored in the second capacitor and reused to partially drive the semiconductor switch from the first of the ON and OFF states to the second one of the ON and OFF states.