A New Concept for DC to AC Inverters and Ringing Generators

A new DC to AC inverter concept has a single switching stage followed by a linear amplifier. It provides input to output isolation, circuit simplicity, ruggedness and low manufacturing cost. It is equally suited for operation at low power levels (i.e. ringing generators) and at higher powers since Darlington Transistors or Gemfets can be used in the low frequency linear amplifier stage. This new topology is compared to ferroresonant-transformer inverters, to bridge inverters with two switching stages in tandem, and to forward converter/synchronous rectifier combinations. A 50-VA ringing generator designed for Warren Communications (a unit of General Signal) is described. It operates from 50 VDC, has an adjustable frequency range of 16.67 Hz to 66.67 Hz and has an adjustable voltage range of 80 VAC to above 140 VAC. It is self-protected from overloads and transients. A DC to DC "WRAPAROUND" converter and it\´s Linear Amplifier circuits are described, together with circuits to improve efficiency. Voltage and Current-Mode systems are compared for transient stability and for output paralleling capability. A new circuit to absorb reflected power and improve efficiency for low power-factor inductive loads is described. (See Ref. 11.e and 11.g.)