A synthetic rectifier comprises a MOSFET and a control circuit to turn the MOSFET off and on as a synchronous rectifier. The control circuit senses the current through the synthetic rectifier, and in particular is responsive to the rate of decrease of the current so as to anticipate when the current goes to zero and turn off at that instant. The control circuit also senses the voltage across the synthetic rectifier, and in particular is responsive to the rate of decrease of the voltage so as to anticipate when the voltage goes to zero and turn on the synthetic rectifier at that instant. In another embodiment of the invention, the MOSFET comprises groups of cells that can be individually controlled. As the current is decreasing, groups of cells can be turned off progressively as the current decreases so that only a small number of cells which can be turned off very fast is still conducting as the current goes to zero.
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation in part application of a provisional patent applications entitled "Super Rectifiers", Ser. No. 60/432,509, filed on 10 Dec., 2002, and a provisional patent applications entitled "Super Rectifiers", Ser. No. 60/441,953, filed on 23 Jan., 2003.
In a maximum duty control state of a switching regulator control circuit, a period of time during which any one of a step-up switching circuit and a synchronous rectification switching circuit is always off is ensured, thereby preventing the switching efficiency from being remarkably deteriorated. In a maximum duty control state, a voltage difference is provided between a limiter voltage that is inputted to a comparator that controls the switching operation of the step-up switching circuit and a limiter voltage that is inputted to a comparator that controls the switching operation of the synchronous rectification switching circuit, to thereby ensure the period of time during which any one of the step-up switching circuit and the synchronous rectification switching circuit is always off.
A driver circuit includes a first transistor coupled between an input supply node and an output node. The first transistor operates in one of a conductive state to couple the output node with the input supply node and non-conductive state according to cooperative operation of a second transistor and a third transistor. The second transistor is coupled to provide a control input to drive the first transistor to the conductive state thereof in response a first input signal provided at a control input of the second transistor. The third transistor is coupled to provide an output at the output node in response to a second input signal provided at a control input of the third transistor, the first and second input signals being out of phase with each other. Circuitry is coupled between the input supply node and the control input of the first transistor to provide reduced impedance at the control input of the first transistor according to operation of the second transistor.
A switched current power converter including an input power source, an output terminal, and a plurality of current stages. Each current stage includes a converter coupled to the input power source for providing a current, and a switch circuit for selectively coupling the current in such current stage to the output terminal. A control circuit selectively decouples the input power source from less than all of the current stage converters upon detecting a low load condition, thereby reducing circulating current losses and improving operating efficiency under low load conditions.
