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US 7,072,162 B2Granted
Bi-directionally driven forward converter for neutral point clamping in a modified sine wave inverter
OwnerJames D'Amatoinventor
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OwnerJames D'Amatoinventor
Estimating the term…
A bi-directionally driven forward converter for neutral point clamping in a modified sine wave inverter maintains wave shape integrity when the half bridge output is subjected to loads of varying impedances. This bi-directionally driven forward converter is supported by a dual primary coupled to a common secondary transformer of which both primaries are wound in opposition to each other. A high frequency snubbing pulse generator outputs a series of pulses coincidental with the turn off of the half bridge power transistors and pending the polarity of the modified sine wave output would permit current flow through either of the two primary windings. Given that the transformer secondary voltage is ultimately rectified, filtered, and tied to the input of the inverter itself, reflects back an impedance to the primary winding that is non-dissipative. The series of pulses emanating from the snubbing pulse generator ultimately suppresses any reverse voltage transients developed as a result of the load during the dead time of the modified sine wave output thereby maintaining the output wave shape under the most adverse applied conditions.
A method by which on the output of a dc to ac inverter when used in producing a modified sine wave is clamped to a midpoint level between the voltages used within thereby providing an output waveform that remains consistent and independent of any given load comprising:
A transformer able to operate at a high switching frequency and at a medium to high power level with two low impedance primary windings magnetically coupled to one low impedance secondary winding wherein each primary winding has current passing within it when its associated three terminal semiconductor device closes the circuit.
The transformer as claimed in 2 further comprising the characteristics wherein both of the said low impedance primary windings have an identical quantity of turns, are wound in an opposing manner to one another and the said one low impedance secondary winding is wound with the same sense of only one primary winding.
The transformer as claimed in 2 further comprising the characteristics wherein each low impedance primary winding is magnetically coupled to the common said one low impedance secondary winding and for each positive voltage alternately induced across each said low impedance primary winding will produce a positive voltage across the common said one low impedance secondary winding that is synchronously resistively loaded thereby declaring that the said transformer is operating in the forward converter mode.
The transformer as claimed in 2 further comprising the characteristics wherein the said one low impedance secondary winding having its output rectified, filtered, and connected to the source input of the said dc to ac inverter thereby creating a non-dissipative load with efficient utilization of transformed energy and simultaneously reflecting back to the said low impedance primary winding a lower impedance for actively snubbing transients incurred by an output inductive load only for the duration of the output said modified sine wave deadtime.
Dependencies are inferred from the claim text.