Linear programming circuit for adjustable output voltage power converters

An adjustable output voltage power converter for converting a DC voltage source to a regulated output voltage having a nominal value across a first and a second output port, said adjustable power converter having an input port for accepting a programming resistor for adjusting the regulated output voltage about the nominal value as a substantially linear function of said programming resistor, said adjustable power converter comprising:

• a controller having a first input terminal and a second input terminal, said controller controlling the amount of power transferred from the DC voltage source to said first and said second output ports as a function of the difference between the signals at said first and said second input terminals;
• a reference voltage source having a fixed reference voltage coupled to said first input terminal;
• a first resistor having a first end coupled to said first output port and a second end;
• a first transistor having a base, an emitter coupled to said second end of said first resistor, and a collector coupled to said second input terminal;
• a second transistor having a base coupled to said programming resistor, an emitter coupled to said base of said first transistor, and a collector coupled to said first output port;
• a second resistor having a first end coupled to said first voltage source and a second end;
• a third transistor having an emitter coupled to said second end of said second resistor, a collector coupled to said programming resistor, and a base;
• a third resistor having a first end coupled to said first voltage source and a second end coupled to said base of said third transistor;
• a fourth resistor having a first end coupled to said first output port and a second end coupled to said base of said third transistor;
• a fifth resistor having a first end coupled to said first voltage source and a second end;
• a fourth transistor having a base, an emitter coupled to said second end of said fifth resistor, and a collector coupled to said second input terminal of said controller;
• a sixth resistor having a first end coupled to said first voltage source and a second end coupled to said base of said fourth transistor;
• and
• a seventh resistor having a first end coupled to said first output port and a second end coupled to said base of said fourth transistor.

In a power converter for converting a DC voltage source to a regulated output DC voltage including a first and a second output port, a controller having a first and a second input terminal, said controller generating across said first and said second output ports said regulated output DC voltage from said DC voltage source as a function of the difference between the signals at said first and said second input terminals of said controller, a first reference voltage source having a fixed reference voltage coupled to said first input terminal of said controller, comparison signal generation means having an input terminal and an output terminal, said comparison signal generation means generating a comparison signal at its output terminal as a linear function of a signal at its input terminal, means for coupling a signal representative of the regulated output DC voltage to said input terminal of said comparison signal generation means, means for coupling said comparison signal to said second input terminal of said controller, and means for adjusting said regulated output DC voltage as a linear function of an input programming signal, said adjustment means comprising:

• current generation means for generating a first current as a substantially linear function of said programming signal;
• and
• means for coupling said first current to said input terminal of said comparison signal generation means such that said comparison signal is a linear function of the regulated output voltage across said first and said second output ports and a linear function of said first current.