Patent ID: 7474069

Claim:
A circuit for optimizing power transferred from an inverter circuit to a motor, the circuit using an open loop method to start-up the motor and have it reach a minimum speed, each phase of the motor receiving voltage from the inverter circuit, the circuit comprising: at least one phase detector circuit for sensing the sign of one or more currents, the sign of the current being used to detect a zero crossing of the current; an interpolator for receiving a voltage reference and outputting a frequency reference and a phase shift reference, the phase shift reference being a difference between an imposed voltage modulation and the one or more currents; and a regulator circuit for using an error between the phase shift reference and the sign of the one or more currents to calculate a phase shift compensation, wherein the sign of the one or more currents is determined to be positive at first sign transition instances when a sinusoidal wave of the current crosses to a positive area and to be negative at second sign transition instances when a sinusoidal wave of the current crosses to a negative area, the first and second sign transition instances being used to detect a phase shift of the current versus the imposed voltage modulation.