How to drive DC motor with smart power ICs

The smart power IC integrates both the power supply devices and the control circuit on one chip. So far, research has focused on a high-voltage integrated circuit and a CMOS-compatible power IC.

These are special high-speed integrated circuits that drive multiphase motors such as brushless DC motors (BLDC) and provide the advanced control functions that are required for modern energy-efficient applications, such as variable speed, current vector control, and even sensor-less control. Older controllers cannot be described as smart because they do not have any microprocessor command interfaces such as SPI (Serial Peripheral Interface), RS232 Serial, or CANBus. This is especially important as more and more industries want to power highly efficient motors.

The figure below shows the internal schematic block of a typical smart power IC. The inputs to the IC are microprocessor-style commands and it can accept torque or speed commands via direct analog voltage or SPI (Serial Peripheral Interface). This IC is not a general-purpose microprocessor, although it has a DSP-like engine at its core. The smart IC provides top-level, ready-to-use instructions for setting motor drive parameters, such as to adjust the output value or adjust the current gain. A single IC can be used to control the speed, torque, or voltage mode of BLDC three-phase motors. It can perform multiple functions including three-phase PWM signal generation, switching, current loop, speed loop, profile generation, hall sensor input, square encoder input and emergency stop processing, along with serial interface Input-output commands, and serial SPI data given at the same time.

Fig: Smart motor controller power IC

When switching on or resetting, the IC checks the presence of the serial EEPROM in the I2C interface. With the serial EEPROM, the configuration commands stored on the chip are read and provide parametric information that can be used during operation. On the other hand, configuration information can be stored in the flash memory. If the initial configuration is not stored in flash or provided by the serial EEPROM, then the default values are used, and then the information would be sent over the serial port from a host device such as a microprocessor or PC. Depending upon the configuration of the control loop, the external analog signals can set speed or torque values. The serial peripheral interface or internal profile generator can also be used for configuration commands.

The current loop control takes place through the direct input of two analog signals that indicate the instantaneous current through the motor windings A and B. These signals are usually received by external series resistors or Hall sensors in the amplifier circuit. This analog current information is then combined with the current required for each phase to generate the symmetric 6 or 3 PWM signals. The IC contains a number of safety functions, including emergency stop signal input, PWM output deactivation, and amplifier output signal deactivation, which can be used to turn the external amplifier circuit on and off.

Expanding on the highly integrated MPC5775E microcontroller, the MCSPTR2A5775E motor control kit enables complex electric motor drive in the most efficient way for application targeting up to ISO 26262 ASIL D.