Power supply and oscillator for a computer system providing automatic selection of supply voltage and frequency

A power system for providing a supply voltage to a computer system and automatically establishing the magnitude of said supply voltage responsive to the magnitude of the current being supplied to the computer system, said power system comprising:

• supply voltage circuit means for generating said supply voltage at an output terminal, said supply voltage circuit means including a control terminal for receiving a control signal;
• and
• voltage selection circuit means including comparator means having first and second input terminals and an output terminal, first circuit means for generating a reference voltage and coupling said reference voltage to said first input terminal of said comparator means, second circuit means for generating a second voltage having a magnitude proportional to said supply voltage and coupling said second voltage to said second input of said comparator means, means coupling the output of said comparator means to said control terminal of said supply voltage circuit means, and current sensing circuit means having an input coupled to said supply voltage circuit means and an output coupled to said second circuit means, said current sensing circuit means operating to generate at its output a voltage having a magnitude proportional to the supply current, whereby for a supply current equal to or less than a predetermined value, the output from said comparator means controls said supply voltage circuit to cause said supply voltage to be a first value, and for supply currents greater than said predetermined value, the output from said comparator means causes said supply voltage to be a second value.