Abstract: A proportional base drive circuit for a power transistor. A first MOSFET, when enabled by an ON pulse, initially supplies the base drive current from a power supply to the base of the power transistor. The resulting current flow through the transistor to a load causes a proportional current to be induced in a current transformer. The induced current is supplied to the base of the power transistor through the first MOSFET. When an OFF pulse is applied, the first MOSFET is disabled and supplies no current to the base of the transistor. At the same time a second MOSFET causes the base-emitter junction of the power transistor to be negatively biased, thereby quickly switching the power transistor off.

Abstract: A sine wave synthesis controller circuit intended to be utilized in conjunction with a digitally-controlled neutral-point clamped inverter to produce a sinusoidal waveform from a direct current source. The controller circuit is configured so that it provides separate positive and negative control signals to the neutral-point clamped inverter's logic controller. These signals direct the modulation a sinusoidal waveform in response to a reference sine wave, the instantaneous voltage output by the neutral-point clamped inverter, as well as positive and negative reference voltages input to the controller.