Methods and apparatus to reduce inrush current in universal serial bus circuits and systems

Abstract

Methods, apparatus, systems and articles of manufacture are disclosed including a capacitor, located in a universal serial bus schematic. The methods, apparatus, systems and articles of manufacture include a controller, include a controller including a state machine and a control signal generator, wherein the controller is configured to be coupled to a connector and to a power supply, the state machine is configured to determine a state of the connector, and the control signal generator is configured to, in response to an indication of a device not connected to the connector, generate a signal to indicate to the power supply to charge a capacitor to a threshold voltage, and wherein the control signal generator is further configured to generate the signal until a second state.

What is claimed is: 
     
         1 . An apparatus comprising:
 a power supply having a power control input and having a power output;   a single field effect transistor (FET) having a source, a drain and a gate, wherein the source is connected to a voltage bus, and the drain is directly connected to the power output; and   a controller including a state machine and a control signal generator, wherein the controller is coupled to a connector and to a power supply;   wherein the state machine is configurable to provide an indication of a first state of the connector, and the control signal generator is configurable to provide a control signal to initiate the power supply charging a capacitor to a threshold voltage in response to the indication of the first state, and the control signal generator is configurable to provide the control signal until a second state.   
     
     
         2 . The apparatus of  claim 1 , wherein the controller has a gate output, a connector input and a control output, in which the gate output is directly connected to the gate, the connector input is coupled to a controller terminal on the connector, and the control output is coupled to the power control input. 
     
     
         3 . The apparatus of  claim 1 , wherein the single FET has a parasitic body diode with an anode directly connected to a protection terminal on a connector, and a cathode directly connected to the power output. 
     
     
         4 . The apparatus of  claim 3 , further comprising a system capacitor directly connected between the cathode and a ground terminal. 
     
     
         5 . The apparatus of  claim 1 , wherein the connector is a universal serial bus type-c connector. 
     
     
         6 . The apparatus of  claim 5 , wherein the connector is a first universal serial bus connector, the controller is configured to be coupled to a second connector, and the second connector is a second universal serial bus connector. 
     
     
         7 . The apparatus of  claim 6 , wherein the control signal is a first control signal, the state machine is further configured to determine a third state of the second connector, and the control signal generator is further configured to, in response to an indication of the third state of the second connector, provide a second control signal to initiate the power supply charging the capacitor to the threshold voltage. 
     
     
         8 . The apparatus of  claim 6 , wherein the second connector is compatible with universal serial bus type-c power delivery applications. 
     
     
         9 . The apparatus of  claim 1 , wherein the control signal generator is configured to, in response to the second state, provide a second control signal to initiate the power supply to supply power to a device. 
     
     
         10 . The apparatus of  claim 9 , wherein the controller further includes a negotiator configured to negotiate a contract with the device to initiate the power supply to supply power to the device. 
     
     
         11 . A system comprising:
 a power supply having a power control input and having a power output;   a single transistor having a source, a drain and a gate, wherein the source is connected to a voltage bus, and the drain is directly connected to the power output and a capacitor;   a controller coupled to a connector, the power supply, and the single transistor, wherein the controller includes:
 a state machine configurable to determine a state of a connection at the connector; and 
 a control signal generator configurable to provide a signal to modify an operation of the power supply in response to an indication from the state machine. 
   
     
     
         12 . The system of  claim 11 , wherein the control signal generator generates the signal to modify the power supply to charge the capacitor in response to the indication being indicative of no devices being connected to the connector. 
     
     
         13 . The system of  claim 12 , wherein the control signal generator provides the signal until a device is connected to the connector and a contract is negotiated. 
     
     
         14 . The system of  claim 13 , wherein the controller further includes a negotiator, and the control signal generator provides a second signal to modify the power supply to supply power to the device connected to the connector in response to the negotiator contracting with a device connected to the connector. 
     
     
         15 . The system of  claim 11 , further including a universal serial bus type-a host connected to a universal serial bus type-a to universal serial bus type-c adapter, wherein the universal serial bus type-a to universal serial bus type-c adapter is connected to the connector. 
     
     
         16 . The system of  claim 11 , further including a second transistor having third and fourth current terminals, wherein the third current terminal is coupled to a second connector, and the fourth current terminal is coupled to the capacitor and the power supply. 
     
     
         17 . The system of  claim 16 , wherein the state machine determines a second state of the second connector. 
     
     
         18 . The system of  claim 11 , wherein the connector is a universal serial bus type-c connector, and the connector is compatible with universal serial bus type-c power delivery applications.