TA8483CP

2006-3-2

14

Function Description Of TB6520P/PG+TA8483CP

• Three−phase sensorless drive

The TB6520P/PG detects the motor's induced voltage (motor's terminal voltage), compares it with VM (motor's

power supply voltage) divided by 2, and generates a commutation signal based on the comparison result.

Therefore, the TB6520P/PG eliminates the need for the hall elements and hall ICs that have conventionally

been used to detect the motor's rotor position.

• PWM drive

The TB6520P/PG allows output duty cycles to be controlled by using its duty input voltage.

PWM operation is chopped by the upper

−side output on / off operation.

Position detection is accomplished by monitoring the motor's terminal voltage at falling edges of PWN and

comparing the detected voltage with the reference voltage. In this way, avoid effects of the terminal voltage on

PWM are avoided. But this causes a position detection error associated with the PWM signal frequency.

Therefore, care must be taken when using the controller for high

−speed motors.

• Startup method

At startup, no induced voltage develops because the motor is not turning yet. for this reason, the TB6520P/PG

forcibly applies a predetermined commutation pattern to the motor as it starts.

In this case, a problem occurs that the motor cannot be started smoothly depending on its rotor position.

To solve this problem, the TB6520P/PG uses single

−phase excitation (by setting the IP pin high to fix the phase

and allow current to conduct in only one phase) for a predetermined period. This helps to move the rotor

position at startup forcibly to a ready to start position.

However, since the duration of single

−phase excitation and the power applied for it (DUTY input voltage) varies

with each motor, adjustment is required.

• About the duration of single−phase excitation

The duration of single

−phase excitation (DC excitation) can be changed by adjusting the RC constant in the

application circuit shown below.

Setup example: C = 4.7µF, R = 220kΩ

TB6520P/PG

Start − SP

IP

C

R

Start − SP

IP

DUTY

Duration of single − phase

excitation (DC excitation)