Marktech Introduces Toshiba’s Newest PWM Sensorless

Latham, New York: Marktech introduces the Toshiba TB6575FNG PWM sensorless controller for 3-phase full wave Brushless DC motors. A brushless DC (BLDC) motor is a synchronous motor, which means the rotor position has to be known to generate the appropriate field. BLDC motors are popular because of their durability, linear control characteristics, efficiency and torque-to-volume ratio. Normally sensors (usually Hall-effect devices) are used to determine the rotor position. These sensors are a disadvantage because they add to the system cost, are a source of failure, require extra wires, and are sensitive to EMI. The TB6575FNG provides sensorless commutation and PWM current control for 3-phase full-wave BLDC motors. Rotation speed is controlled through a variable PWM duty cycle controlled by an analog input voltage. On receiving an analog voltage command input, the rotor is aligned to a known position in DC excitation mode. The rotation is started in forced commutation mode by applying a PWM signal to the motor. As the rotor moves, back-EMF is measured and applied to the position signal input pin. Subsequently the device switches from forced commutation to natural commutation (based on the back-EMF sensing) to drive the BLDC motor in sensorless mode.

• Over-current protection
• Forward/reverse rotation
• Overlap commutation
• 20mA current sink capability on PWM output pins
• Lead angle control (7.5° and 15°)
• Rotation speed sensing signal
• DC excitation mode to improve startup characteristic
• DC excitation time and forced commutation time for start-up operation can be changed
• Forced commutation frequency can be selected (fXT/(6 × 216), fXT/(6 × 217), fXT/(6 × 218))
• Output polarity switching (P-channel + N-channel, N-channel + N-channel)
• Supply voltage: 4.5-5.5 V
• Package: SSOP-24