Apparatus and method for adaptively controlling power supplied to a hot-pluggable subsystem

A method for controlling a power supply current from a power supply output coupled to a hot-pluggable sub-system, wherein said power supply current is conducted through a pass device having a gate, said method comprising:

• supplying a current to said gate;
• detecting a gate voltage of said pass device;
• and
• subsequently controlling said pass device in conformity with said detected gate voltage.

A power supply control circuit having exactly three electrical connections, comprising:

• a first electrical connection terminal for connecting to a source of direct current;
• a second electrical connection terminal for connecting to a ground reference associated with said source of direct current;
• a third electrical connection terminal for connecting to a gate of an pass device external to said power supply control circuit, wherein said pass device has a channel coupled between said source of direct current and a hot-pluggable subsystem power connection;
• and
• a control circuit coupled to said third electrical connection terminal, wherein said control circuit controls charging of said pass device in conformity with a voltage of said third electrical connection terminal.

A power supply circuit having exactly three electrical connections, comprising:

• a first electrical connection terminal for connecting to a source of direct current;
• a second electrical connection terminal for connecting to a ground reference associated with said source of direct current;
• a third electrical connection terminal for connecting to a hot-pluggable subsystem power input;
• a pass device having a channel coupled between said first electrical connection terminal and said third electrical connection terminal;
• and
• a control circuit coupled to a gate of said pass device, wherein said control circuit detects a gate voltage of said pass device and controls charging of said pass device in conformity with said gate voltage.

A power supply circuit for detachably coupling a hot-pluggable subsystem, wherein said power supply circuit comprises:

• a power supply output for supplying power to a load;
• a pass device coupled to said power supply output for controlling said supplied power;
• and
• a control circuit coupled to a gate of said pass device, wherein said control circuit comprises a normally-on shunt device coupled to said gate of said pass device, and wherein said shunt device clamps the voltage of said gate of said pass device until said control circuit reaches a predetermined operating voltage.

A power supply circuit for detachably coupling a hot-pluggable subsystem, wherein said power supply circuit comprises:

• a power supply input for connection to a source of direct current;
• a power supply output for supplying power to a load;
• a pass device coupled to said power supply output and further coupled to said power supply input for controlling said supplied power;
• and
• a control circuit coupled to a gate of said pass device, wherein said control circuit comprises an under-voltage lockout protection circuit for detecting that a voltage supplied to said pass device is insufficient for proper operation of said power supply circuit, and wherein said control circuit prevents charging of said gate unless said voltage supplied to said pass device is sufficient for proper operation, and whereby said under-voltage lockout protection level may be varied by coupling said power supply input to said source of direct current through a voltage-dropping component.