Polarity independent power supply control methods and systems using the same

A method of controlling a power supply having an output activated in response to a first logic level of a control signal and deactivated in response to a second logic level of the control signal comprising the steps of:

• generating a clock from a second power source;
• initiating a time-out period of a selected number of periods of the clock;
• sensing a state of the output of the power supply during the time-out period;
• in response to said step of sensing, if the state of the output of the power supply is inactive through the time-out period performing the steps of:
• generating the first logic level of the control signal to activate the power supply;
• powering operations of an associated device with the power supply;
• and
• at the completion of said step of powering operations of the associated device, generating the second logic level of the control signal to deactivate the power supply;
• and
• in response to said step of sensing, if the state of the output of the power supply is active during the time-out period performing the steps of:
• maintaining the first logic level of the control signal;
• powering the operations of the associated device with the power supply;
• and
• at the completion of said step of powering operations of the associated device, generating the second logic level of the control signal to deactivate the power supply.

A system comprising:

• functional circuitry;
• an oscillator for generating timing signals for controlling said functional circuitry;
• a first power supply for powering said oscillator;
• a second power supply for powering said functional circuitry and having an output activated and deactivated by respective first and second logic states of a control signal;
• and
• autosense logic for generating said control signal and operable to:
• allow the oscillator to stabilize;
• initiate a time-out period timed by a clock generated from the oscillator output;
• sense a state of an output of the second power supply during the time-out period;
• if the state of the output of the second power supply is in an inactive state after the time-out period, generate the first logic state of the control signal;
• and
• if the state of the output of the second power supply is active during the time-out period, maintaining the first logic state of the control signal.