Design considerations for high voltage motor control systems

　　In modern robot design, any movement of the head, neck, and limbs requires the support of various motors, such as traditional rotary motors, stepper motors, linear motors, and other special motors. However, the drive and control requirements of these motors are different. How to achieve precise control solutions for various motors? How to control them with the lowest power consumption? It is often a big challenge for designers. This article will discuss in detail what issues should be paid attention to in the specific implementation of each core subsystem of the high-voltage motor control system.

　　High voltage AC (HVAC) motors, industrial inverters or high voltage permanent magnet brushless motors are a few examples of high voltage systems, which are typically classified by their horsepower. Although still the most common, other types of motors have also emerged, such as linear motors and gearhead motors with various actuator implementations embedded. Digital motor control solutions allow precise control of the position, speed and torque of these mechanical drives. The MOSFETs in such large mechanical drives are usually more than 600V in capacity.

　　For example, TI has a gate drive solution, the TPS2829, a non-inverting high-speed MOSFET driver. When combined with the TLV3501 comparator in the feedback loop, the gates in these systems can be digitally controlled. In addition, TI's MOSFET drivers (such as UCC37321 or UCC37323) can directly drive small motors or drive power devices such as MOSFETs or IGBTs.

　　Key Design Considerations for High-Voltage Motor Control Systems

　　The core subsystems of a high-voltage motor control system include: controller, isolation, controller interface, and motion feedback.

　　Controllers: TI also offers a range of control processor solutions, from ultra-low-power MSP430 microcontrollers to TMS470 ARM7-based processors and C2000 digital signal controllers (DSCs). The right controller can optimize motor drive efficiency, improve reliability and reduce overall system cost. The C2000 controller's 32-bit DSP-level performance and on-chip peripherals optimized for motor control allow users to easily implement advanced algorithms such as sensorless vector control of three-phase motors. The C2000 family of controllers (from the low-cost F28016 to the industry's first floating-point DSC TMS320F28335) are all software compatible.

　　Isolation: TI's digital isolators have logic input and output buffers that are isolated with silicon dioxide, providing 4kV isolation. When used in conjunction with isolated power supplies, these devices can block high voltages, isolate grounds, and prevent noise currents from entering the local ground and interfering with or damaging sensitive circuits.

　　Controller interface: RS-232 or RS-422 are sufficient for many systems. RS-485 signaling may be bundled with protocols such as Profibus, Interbus, Modbus, or BACnet, each targeting the specific needs of the end user. Sometimes, Controller Area Network (CAN) or EtherNet/IP (industrial protocol) are preferred for networking requirements. M-LVDS is an alternative that can provide lower power consumption.

　　Motion feedback using external circuits: Isolated Delta-Sigma modulators (AMC1203/AMC1210) are ideal for shunt measurements to flatten glitches and increase current feedback resolution. In addition, the INA19x (x=3 to 8) and INA20x (x=1 to 9) provide wide common-mode voltages for low-side and high-side current shunt monitoring.

　　Hall effect or magnetic sensors are usually more efficient at measuring currents above 10A, and they inherently provide isolation. The ADS1204, ADS1205, and ADS1208 are three recommended devices. To connect ±10V (20Vpp) signals to an ADC with a 3.3V or 5V supply, an INA159 level difference amplifier can be used . ADCs like the ADS7861/ADS7864 or ADS8361/ADS8364 can provide 4-channel or 6-channel simultaneous current sampling.