Sensorless power angle control for a vehicle alternator

Claim 1

An alternator driven by an engine, the alternator comprising: a. three phase stator windings having three stator winding outputs; b. a rotor having a rotor field winding magnetically coupled to said stator windings and driven by the engine to generate a back EMF in said stator windings and electrical current at said three stator winding outputs; c. a rectifier bridge having a dc output comprising a plurality of transistor switches, said plurality transistor switches comprising at least three pairs of connected upper transistor switches and lower transistor switches and each of said plurality of transistor switches including body diodes bridging said transistor switches, wherein each of said three stator winding outputs are electrically connected to said rectifier bridge between a respective pair of said upper transistor switches and said lower transistor switches; d. a zero crossing detector connected to said three stator winding outputs, said zero crossing detector operable to determine the zero voltage crossings across at least one of said body diodes of said transistor switches and generate a signal indicative of said zero voltage crossings, wherein said zero voltage crossings across at least one of said body diodes are representative of zero crossings of said back EMF in said stator windings; e. a microcontroller connected to said zero crossing detector, said microcontroller for receiving said signal indicative of said zero voltage crossings from said zero crossing detector and controlling the operation of said transistor switches in said rectifier bridge to control the phase angle of phase voltages at said three stator winding outputs and introduce a phase shift between said phase voltages and said back EMF.

Claim 11

A method of operating an alternator having a three phase stator winding with three stator outputs connected to a controlled full wave rectifier bridge having a dc output and including a plurality of transistor switches with body diodes connected across each of said transistor switches, wherein a back EMF is generated in each of the three phase stator windings and phase voltages are generated at the three stator winding outputs, the method comprising the steps of: a. sequentially controlling each of the plurality of transistor switches according to a predefined control sequence; b. monitoring the occurrence of zero voltage crossings across the body diodes in the full wave rectifier bridge, the zero voltage crossings representing the zero crossings of the back EMF generated in the stator winding; and c. further controlling each of the plurality of transistor switches by introducing a time delay in the control sequence, said time delay resulting in phase shifts in the phase voltages and thereby introducing a power angle between the phase of the back EMF and the phases of the phase voltages.

Claim 12

A method of operating an alternator having a three phase stator winding with three stator outputs connected to a controlled full wave rectifier bridge having a dc output and including a plurality of transistor switches with body diodes connected across each of said transistor switches, wherein a back EMF is generated in each of the three phase stator windings and phase voltages are generated at the three stator winding outputs, the method comprising the steps of: a. sequentially controlling each of the plurality of transistor switches according to a predefined control sequence; b. monitoring the occurrence of zero voltage crossings across the body diodes in the full wave rectifier bridge, the zero voltage crossings representing the zero crossings of the back EMF generated in the stator winding; and c. further controlling each of the plurality of transistor switches by introducing a time delay in the control sequence, said time delay resulting in phase shifts in the phase voltages and thereby introducing a power angle between the phase of the back EMF and the phases of the phase voltages.

Claim 15

A method of calculating the position of one phase of a three phase back EMF generated in a three phase stator winding of a vehicle alternator, the three phase stator winding having three stator winding outputs connected to a controlled bridge rectifier driven by a microcontroller, the controlled bridge rectifier comprising three upper transistor switches with body diodes connected across the upper transistor switches and three lower transistor switches with body diodes connected across the lower transistor switches, the upper transistor switches respectively connected to a respective one of said lower transistor switches to form three pairs of upper and lower transistor switches, the method comprising the steps of: a. providing a zero crossing detector to monitor zero voltage crossings across said body diodes of said lower transistor switches; b. delivering a signal indicative of said zero voltage crossings across said body diodes to the microcontroller; c. associating a sinusoidal waveform with a phase of the back EMF and associating the zero voltage crossings across one of said body diodes with the zero crossings of said phase of the back EMF.

Claim 16

A method of calculating the position of one phase of a three phase back EMF generated in a three phase stator winding of a vehicle alternator, the three phase stator winding having three stator winding outputs connected to a controlled bridge rectifier driven by a microcontroller, the controlled bridge rectifier comprising three upper transistor switches with body diodes connected across the upper transistor switches and three lower transistor switches with body diodes connected across the lower transistor switches, the upper transistor switches respectively connected to a respective one of said lower transistor switches to form three pairs of upper and lower transistor switches, the method comprising the steps of: a. providing a zero crossing detector to monitor zero voltage crossings across said body diodes of said lower transistor switches; b. delivering a signal indicative of said zero voltage crossings across said body diodes to the microcontroller; c. associating a sinusoidal waveform with a phase of the back EMF and associating the zero voltage crossings across one of said body diodes with the zero crossings of said phase of the back EMF.