Friday, March 26, 2010

Simple High efficiency Inverter Circuits

Simple High efficiency Inverter Circuits


1. Field of the InventionThis invention relates generally to the field of electrical energy conversion systems and more particularly to push-pull inverter circuits utilizing a solid state active element oscillator of the multivibrator type to convert an input DC voltageto a high frequency AC output voltage.2. Description of the Prior ArtPush-pull inverter circuits are generally recognized as the most efficient type for converting DC voltage into an AC output voltage. Such circuits typically include a source of DC potential, an output transformer, and a pair of switchingtransistors connected to control the flow of current through the output transformer for thereby producing an AC voltage output across the transformer. Efficient conversion of the DC voltage into the AC output voltage requires that the conduction of theswitching transistors be precisely controlled. Such precise control can serve to minimize undesirable energy losses within the circuit itself. Some of the causes of such energy losses have been recognized and are generally regarded as inherent in suchcircuits, or in the components making up such circuits. Some of these losses are:1. Common-mode conduction which occurs when both of the switching transistors conduct simultaneously. This loss is usually related to the inherent and generally unavoidable delay associated with the turn-off action of the conducting transistor,coupled with the fact that there generally is no corresponding delay associated with the turning on of the other transistor.2. Turn-off transition loss which is due to the power dissipation that occurs within each transistor during its turn-off transition. To minimize this loss, it is necessary to operate each transistor near its maximum switching speed capability. This in turn requires that the charge carriers stored at the transistor base-emitter junction be evacuated as rapidly as possible.It is also more important to prevent the collector voltage from rising significantly be

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