International Rectifier Corporation

Marco Palma

Massimo Grasso

Christian Locatelli

A speed estimation method for determining the speed of a sensorless permanent magnet brushless motor having one or more phases driven by one or more stages of an inverter, each stage including high- and low-switches connected in series across a DC Bus and having a respective common switched node, the respective switched node being coupled to a respective motor phase terminal. The method includes the steps of applying an alternating sequence of Zero Vectors to the inverter, the sequence alternating between a first Zero Vector whereby motor current does not flow in the DC Bus and a second Zero Vector wherein the high and low side switches of the inverter are alternately turned on with active vector components being injected by the inverter for each inverter stage thereby to allow motor current to flow in the DC Bus, whereby the terminals of the motor during the first and second Zero Vectors are shorted to brake the motor without substantially raising the voltage of the DC Bus during the braking time; and the speed of the motor can be determined by measuring the current in a sensor of the DC bus during the time when the second Zero Vector is applied without using a sensor in the motor.

Sensorless speed detection during zero vector

According to one disclosed embodiment, a gate driver circuit for sensorless speed detection and driving a switching stage includes high side and low side switches series connected across a DC bus and having a switching node between the series switches, the gate driver having a bootstrap power supply for powering a high side driver driving the high side switch of the switching stage and a low side driver power supply, and further includes a comparator circuit to periodically compare the voltage between the bootstrap and low side driver power supplies with a threshold and to output a first signal, wherein the first signal indicates current sign and frequency.

Sensorless speed detection of a PM brushless motor with phase terminals shorted

A method of controlling a motor connected to an unbalanced load in accordance with an embodiment of the present application includes operating the motor for a predetermined period of time with a first performance parameter held constant, monitoring a signal related to a second performance parameter, monitoring electrical rotation within the motor and providing an electrical rotation signal indicative of the electrical rotation angle, sampling the signal related to the second performance parameter at a predetermined angle of electrical rotation, arranging samples provided in the sampling step in predetermined order and generating a mechanical rotation signal representing the mechanical rotation angle of a rotor of the motor based on the arrangement of samples. The mechanical rotation signal is used to control at least one of the first and second performance parameters of the motor.

Motor control circuit and method with mechanical angle reconstruction

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 including 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.

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Leini, Italy

Marco Palma