Double Modulation Converter

Abstract

The Double Modulation Converter (Dmc) Is A Dc-Ac Converter For Driving An Ac-Dc Converter. It Has Two Input Terminals For Connection To A Dc Voltage Source, Two Output Terminals For Connection To An Ac-Dc Converter, And A Plurality Of Circuit Control Terminals For Receiving A Plurality Of Control Waveforms Which Cause A Bipolar Stream Of Width- And Amplitude-Modulated Pulses To Appear At The Output Terminals When A Load Is Connected Across The Output Terminals. The Basic Elements Of The Dmc Are Two Switches Connected In Series Across The Input Terminals. One Output Line Connects An Output Terminal To The Junction Of The Two Switches. The Other Output Line Connects The Other Output Terminal To One Of The Input Terminals. During Operation, The Two Switches Periodically And Alternately Open And Close, The Closure Of One Switch Causing A Pulse Of One Polarity To Appear Across The Output Terminals, And The Closure Of The Other Switch Causing A Pulse Of Opposite Polarity To Appear Across The Output Terminals. A Switch Is Closed Only When A Near-Zero Voltage Exists Across The Switch. In Order To Bring About This Result, A Diode And Capacitor Are Connected In Parallel With Each Switch And An Inductor Is Placed In Output Line. When One Switch Opens, The Other Switch Closes Only When There Is Less Than 0.7 Volts Across The Switch. The Time Period During Which The Voltage Across The Switch To Be Closed Is Less Than 0.7 Volts Is A Function Of The Resonant Frequency Of The Capacitance Associated With The Switch To Be Closed And The Inductance Associated With The Output Lines And The Load To Which The Output Lines Are Connected. One Or More Capacitors Are Placed In One Of The Output Lines To Block Dc. The Resonant Frequency Of The Output-Line Capacitors And Inductor Is At Least A Factor Of Two Less Than The Switching Frequency.