Single phase motor drive

An inverter bridge for driving a motor, said motor having a rotatable assembly and a stationary assembly in magnetic coupling relation thereto, said stationary assembly including a winding, said motor also having a power supply link that includes an upper rail and a lower rail supplied by a power supply and having a control circuit for generating a motor control signal to control commutation of the winding, said bridge comprising:

• a set of upper power switches connected between the winding and the upper rail;
• a set of lower power switches connected between the winding and the lower rail, said lower switches receiving and responsive to the motor control signal, each of said lower switches corresponding to one of said upper switches, said switches each having a conducting state and a nonconducting state;
• and
• a drive circuit responsive to the state of the lower switches for driving the upper switches to selectively connect the rails of the power supply link to the winding whereby the winding is energized to produce an electromagnetic field for rotating the rotatable assembly relative to the stationary assembly, said drive circuit controlling the upper switches to provide a delay interval between the conducting states of the corresponding upper and lower switches thereby reducing shoot-through currents.

A motor system comprising:

• a rotatable assembly;
• a stationary assembly in magnetic coupling relation to the rotatable assembly, said stationary assembly including a winding;
• a power supply link having an upper rail and a lower rail supplied by a power supply;
• a bridge circuit including a set of upper power switches connected between the winding and the upper rail and a set of lower power switches connected between the winding and the lower rail, said switches each having a conducting state and a nonconducting state, each lower switch corresponding to the upper switch on the same side of the winding as the lower switch, wherein the corresponding upper and lower switches define an arm of the bridge circuit and wherein the state of each upper switch is determined by the state of its corresponding lower switch on the same arm of the bridge circuit;
• a control circuit for generating a motor control signal to control the switches, said lower switches receiving and responsive to the motor control signal, said motor control signal defining commutation intervals during which one of the lower switches and one of the upper switches from different arms of the bridge circuit are conducting to connect the winding to the upper and lower rails of the power supply link;
• and
• a drive circuit responsive to the state of the lower switches for driving the upper switches to selectively connect the rails of the power supply link to the winding whereby the winding is energized to produce an electromagnetic field for rotating the rotatable assembly relative to the stationary assembly, said drive circuit having a lower turn-on resistor connected to each lower switch, said lower switches receiving and responsive to the motor control signal via the lower turn-on resistors, said lower turn-on resistors causing the lower switches to each turn on at a slower speed than the upper switch on the same arm of the bridge circuit turns off so that the upper switch becomes nonconducting before its corresponding lower switch on the same arm becomes conducting to provide a delay interval between the conducting states of the corresponding upper and lower switches thereby reducing shoot-through currents.

An inverter bridge for driving a motor, said motor having a rotatable assembly and a stationary assembly in magnetic coupling relation thereto, said stationary assembly including a winding, said motor also having a power supply link that includes an upper rail and a lower rail supplied by a power supply and having a control circuit for generating a motor control signal defining commutation intervals to control commutation of the winding, said bridge comprising:

• a set of upper power switches connected between the winding and the upper rail;
• a set of lower power switches connected between the winding and the lower rail, said switches each having a conducting state and a nonconducting state, said lower switches receiving and responsive to the motor control signal, each of said lower switches corresponding to the upper switch on the same side of the winding as the lower switch, wherein the corresponding upper and lower switches define an arm of the bridge and wherein the state of each upper switch is determined by the state of its corresponding lower switch on the same arm of the bridge, wherein one of the lower switches and one of the upper switches from different arms of the bridge are conducting at the commutation intervals defined by the motor control signal to connect the winding to the upper and lower rails of the power supply link;
• and
• a drive circuit responsive to the state of the lower switches for driving the upper switches to selectively connect the rails of the power supply link to the winding whereby the winding is energized to produce an electromagnetic field for rotating the rotatable assembly relative to the stationary assembly, said drive circuit including a lower turn-on resistor connected to each lower switch, said lower switches receiving and responsive to the motor control signal via the lower turn-on resistors, said lower turn-on resistors causing the lower switches to each turn on at a slower speed than the upper switch on the same arm of the bridge circuit turns off so that the upper switch becomes nonconducting before its corresponding lower switch on the same arm becomes conducting to provide a delay interval between the conducting states of the corresponding upper and lower switches thereby reducing shoot-through currents.