Universal DC to DC power converter

A DC to DC voltage converter for producing selectable differential output voltages at a nominally positive output terminal and a nominally negative output terminal comprising:

• means for connecting to a source of DC supply voltage;
• a voltage divider for producing a feedback voltage proportional to the voltage at said nominally positive output terminal,
• a set of voltage dividers for producing a selectable error voltage having a plurality of predetermined values,
• a pulse width modulation controller having means for producing first and second complementary and non-overlapping square wave signals at respective first and second signal outputs each having a substantially constant peak voltage and a pulse width controlled by the difference between said feedback voltage and said selectable error voltage to increase said pulse width as said difference increases and to decrease said pulse width as said difference decreases,
• a first transistor having one grounded terminal operable in response to said first square wave signal and a second transistor having one grounded terminal operable in response to said second square wave signal,
• a transformer having
• a center-tapped primary winding having a first terminal connected to said first power switch, a second terminal connected to said second power switch and a center-tap connected to said source of DC power, and
• a center-tapped secondary winding having a center tap connected to a grounded bus and first and second output terminals each producing an alternating output voltage;
• a diode bridge for rectifying and a capacitor for filtering said alternating output voltage from said first output into a positive DC voltage at a positive bus;
• a diode bridge for rectifying and a capacitor for filtering said alternating output voltage from said second output into a negative DC voltage at a negative bus;
• means for connecting said nominally positive output terminal to said positive bus;
• first switching means having a plurality of positions for selectively connecting said nominally negative output terminal to either said grounded bus or said negative bus;
• and
• second switching means having a plurality of positions for selecting one said sets of voltage dividers to set said error voltage to one of said plurality of predetermined values thereby to change the values of said positive DC voltage at said positive bus and said negative DC voltage at said negative bus to predetermined values;
• said first and second switching means being mechanically ganged to operate together thereby to provide a plurality of predetermined differential voltages between said nominally positive output terminal and said nominally negative output terminal.