Active rectifier

Abstract

A switching circuit has an active switch, a controller, and at least two terminals. The at least two terminals include two current control terminals for connection at two locations in another circuit. The controller is configured to turn the active switch off to block current between the two locations when the voltage between the two locations is of a first polarity and otherwise to turn the active switch on to conduct current between the two locations, whether or not the two current control terminals are the only ones of the at least two terminals that are connected to the other circuit.

What is claimed is:  
     
         1 . A switching circuit having 
 at least two terminals, the at least two terminals including two current control terminals for connection at two locations in another circuit,    an active switch, and    a controller configured to turn the active switch off to block current between the two locations when the voltage between the two locations is of a first polarity and otherwise to turn the active switch on to conduct current between the two locations, whether or not the two current control terminals are the only ones of the at least two terminals that are connected to the other circuit.    
     
     
         2 . The circuit of  claim 1  in which the at least two terminals comprise exactly two terminals.  
     
     
         3 . The circuit of  claim 1  in which the active switch comprises an active switch in parallel with a diode.  
     
     
         4 . The circuit of  claim 1  in which the active switch comprises a MOSFET.  
     
     
         5 . The circuit of  claim 1  further comprising a bias subcircuit that is configured to use power from the other circuit to provide operating power to the switching circuit.  
     
     
         6 . The circuit of  claim 5  in which the bias subcircuit includes a capacitor, a switch, and a bias voltage controller for the switch.  
     
     
         7 . The circuit of  claim 1  in which the other circuit comprises a power converter.  
     
     
         8 . The circuit of  claim 1  in which the controller is configured to sense a polarity of the voltage between the two locations and to turn the active switch on and off in response to the sensed polarity.  
     
     
         9 . A method comprising 
 turning an active switch off to block current between two locations in a circuit when the voltage between the two locations is of a first polarity and otherwise to turn the active switch on to conduct current between the two locations, without regard to voltages or currents at any other locations in the circuit.    
     
     
         10 . A method comprising 
 attaching an end of each of two conductive sheets to a respective one of at least two current carrying terminations of a semiconductor die, and    attaching another end of each of said two conductive sheets to a respective one of two generally flat connection surfaces of a circuit component so that said switching element is in close proximity to an outer surface of said circuit component.    
     
     
         11 . Apparatus comprising 
 two conductive sheets, an end of each of said conductive sheets being attached to a respective one of at least two current carrying terminations of a semiconductor die and another end of each of said conductive sheets being attached to a respective one of two generally flat connection surfaces of a circuit component, said connections being arranged so that said switching element is in close proximity to an outer surface of said circuit component.    
     
     
         12 . The apparatus of  claim 11  in which the circuit component comprises a capacitor of a power converter and the apparatus comprises a two-terminal synchronous rectifier.  
     
     
         13 . The apparatus of  claim 11  in which the semiconductor die comprises a MOSFET.  
     
     
         14 . The apparatus of  claim 13  in which the semiconductor die further comprises circuitry for controlling the conductivity state of said MOSFET.  
     
     
         15 . The apparatus of  claim 13  in which the semiconductor die further comprises bias circuitry for generating a source of bias voltage.  
     
     
         16 . Apparatus comprising, 
 a substrate,    a semiconductor die comprising a controlled switching element and current carrying terminations,    a conductive sheet having an end connected to a surface of said substrate and to one of said current-carrying terminations,    a conductive strap having an end connected to another of said current-carrying terminations, control circuitry for controlling a conductivity state of said switching element, and bias circuitry that is configured to use power from the other circuit to provide operating power to the switching circuit.    
     
     
         17 . The apparatus of  claim 16  wherein said switching element comprises a MOSFET.  
     
     
         18 . The apparatus of  claim 16  wherein said bias circuitry further comprises a storage capacitor.  
     
     
         19 . The apparatus of  claim 16  wherein said control circuitry and said bias circuitry are mounted to a surface of said substrate.  
     
     
         20 . The apparatus of  claim 18  wherein said storage capacitor is mounted to a surface of said substrate.  
     
     
         21 . The apparatus of  claim 19  in which said control circuitry and said bias circuitry are mounted to a surface of said substrate other than the surface to which said conductive sheet is connected.  
     
     
         22 . The apparatus of  claim 16  wherein said semiconductor die includes said control circuitry.  
     
     
         23 . The apparatus of  claim 16  wherein said semiconductor die includes said bias circuitry.  
     
     
         24 . The apparatus of  claim 16  in which said current-carrying terminations lie on opposite parallel surfaces of said die.  
     
     
         25 . The apparatus of  claim 24  in which said end of said conductive strap is arranged in parallel with said opposite parallel surfaces and with said surface of said substrate.  
     
     
         26 . The circuit of  claim 16  in which said apparatus further comprises multiple switching elements and in which the number of switching elements which are turned on is determined by said control circuitry.  
     
     
         27 . The circuit of  claim 26  in which said control circuitry determines how many controlled switches are turned on based upon an amount of current being conducted.  
     
     
         28 . The circuit of  claim 27  in which the switching devices comprise MOSFETs and in which the control circuitry makes said determination by measuring a voltage across said two locations when said controlled switches are turned on.  
     
     
         29 . The circuit of  claim 1  in which said active switch comprises multiple controlled switching devices and in which the number of switching devices which are turned on is determined by said controller.  
     
     
         30 . The circuit of  claim 29  in which said controller determines how many controlled switching devices are to be turned on based upon an amount of current being conducted.  
     
     
         31 . The circuit of  claim 29  in which the controlled switching devices comprise MOSFETs.  
     
     
         32 . The circuit of  claim 30  in which the controlled switching devices comprise MOSFETs and in which the controller makes said determination by measuring a voltage across the two locations when said controlled switching devices are turned on.