System and methods for motor drive using GAN synchronous rectification

A circuit comprising:

• a high-side gallium nitride (GaN) switch having a first gate terminal, a first drain terminal and a first source terminal;
• a low-side GaN switch having a second gate terminal, a second drain terminal and a second source terminal, wherein the first drain terminal is coupled to a power supply, the first source terminal is coupled to the second drain terminal at an output node and the second source terminal is coupled to a ground;
• a drive circuit coupled to the high-side GaN switch and to the low-side GaN switch;
• and
• a sense device coupled to the low-side GaN switch and arranged to sense a magnitude of a current that flows through the low-side GaN switch;
• wherein the drive circuit is arranged to:
• turn on the high-side GaN switch when a control signal that controls a conductivity state of the high-side GaN switch goes high;
• turning off the high-side GaN switch when the control signal goes low;
• turn on the low-side GaN switch when a voltage between the second drain terminal and the second source terminal drops below a predetermined threshold voltage;
• and
• turn off the low-side GaN switch when the magnitude of the current drops below a predetermined threshold current.

A method of operating a motor drive circuit, the method comprising:

• providing a half-bridge circuit including:
• a high-side gallium nitride (GaN) switch having a first gate terminal, a first drain terminal and a first source terminal;
• and
• a low-side GaN switch having a second gate terminal, a second drain terminal and a second source terminal, wherein the first drain terminal is coupled to a power supply, the first source terminal is coupled to the second drain terminal at an output node and the second source terminal is coupled to a ground;
• providing a motor coupled to the output node;
• turning on the high-side GaN switch such that a first current flows through the motor;
• turning off the high-side GaN switch;
• turning on the low-side GaN switch when a voltage between the second drain terminal and the second source terminal drops below a predetermined threshold voltage;
• and
• turning off the low-side GaN switch when the voltage between the second drain terminal and the second source terminal exceeds the predetermined threshold voltage.