Functions and advantages of MSK4310 used to drive brushless motors

MSK4310 is a complete closed-loop speed mode controller for driving brushless motors. The device does not require an external speed feedback device to operate. This application note discusses the features and advantages of MSK4310.

MSK4310 is a complete closed-loop speed mode controller for driving brushless motors. The device does not require an external speed feedback device to operate. This application note discusses the features and advantages of MSK4310.

Connect the motor to the correct Hall input and output phases. Then you can start evaluating the circuit. The V+ voltage is set to 28 volts, and the variable DC power supply voltage is input to the SPEED COMMAND input. An input voltage of approximately 0.33V will cause the motor to rotate without load. Increasing the DC voltage to a maximum speed of about 4.1V can increase the speed of the motor. At about 4.1V, the output stage of MSK4310 has reached the maximum voltage to the motor (the maximum duty cycle is 100%), and no longer modulates the output driver. The maximum speed of the motor is about 7600RPM. Checking the output of the error amplifier will confirm that its output has exceeded the maximum PWM input voltage of 4.1V. Higher than 4.

The circuit developed for the demo board includes an averaging circuit for TACH OUT pulses, giving a DC representation of the pulses used to determine the mechanical response of the system-see Figures 1 and 2. The output of ANALOG TACH OUT is scaled to match the average voltage produced by the TACH OUT pulse.

Functions and advantages of MSK4310 used to drive brushless motors
Figure 1 For 1V input to SPEED COMMAND TACH OUT pulse sequence output and ANALOG TACH OUT voltage waveform output

Functions and advantages of MSK4310 used to drive brushless motors
Figure 2 For 3V input to SPEED COMMAND TACH OUT pulse sequence output and ANALOG TACH OUT voltage waveform output

When inputting various stimuli (whether it is a step command voltage or AC sine wave) while viewing ANALOG TACH OUT, the response of the integrator in the error amplifier can be tailored according to the expected response of the motor in the system. Compare the input frequency of SPEED COMMAND with the frequency of ANALOG TACH OUT to perform bandwidth measurement.

In order to check the actual situation, a step change is set in the “speed command”. For the input, a 1V step above the 2V offset is used. The 2V signal will ensure that the controller runs well in closed loop control. A 1V step above 2V will cause a step change in speed in the entire system.

The Links:   SKM75GAL063D LM32019PR

Author: Yoyokuo