This invention presents a method that generates a
harmonics free AC
voltage at a specific frequency, such as 60 Hz, from unregulated
DC source by precisely biasing complementary push-pull NOMS and PMOS switches. The precise bias triggering pulse is continuous pulse that is created using a feedback
linear regulator. Since the feedback
linear regulator uses
low power electronics such as op-amps and comparators, the bias triggering pulse is stepped up using low power step-up
transformer for
high voltage applications. The step-up
transformer is used to step-up the bias triggering pulse at the output of the feedback
amplifier to drive the
solid state switches precisely so that the output is
harmonic free
sine wave. In order to minimize the power losses by the switches, two DC-DC
converters are used to control the voltages across the NMOS and PMOS switches. One DC-
DC converter generates a positive
voltage that is connected to the drain of the NMOS switch; where its
voltage follows the output voltage during the positive
half cycle of the load's current. The other DC-
DC converter generates a
negative voltage that is connected to the drain of the PMOS switch and it follows the output voltage during the negative
half cycle of the current. Hence, a
power factor controller is not needed as the NMOS automatically conducts when the load current is positive and the PMOS automatically conducts when the load current is negative. This method is applicable to a
single phase as well as
three phase system, and for a standalone load as well as for grid connected load. Also, this method does not require the need for a high
power filter or bulky inductors to remove the
harmonics as the
harmonics are removed by precisely biasing each switch during its conduction.