Level-Up Your Industrial Design with Isolation

Motor Control

Motor control and drive applications consist of three main segments: control, power and communications. 

The control portion consists of the MCU or FPGA and components like voltage/current sense circuits. 

The power stage consists of the high-voltage AC mains, conversion to a DC link voltage, and power switches like MOSFETs/IGBT’s or increasingly, SiC. These power switches modulate the DC voltage per the signals provided by the MCU to invert it back to an AC signal which powers the motor to maximize efficiency while providing the optimal torque and/or speed as required by the system.

The communications stage typically consists of an RS-485 (or CAN) transceiver that helps link this motor control unit to a master controller that may govern many such units in a factory type setting. All these stages require to be isolated for safety and noise immunity reasons. Silicon Labs provides robust and differentiated products for each of these segments as tabulated below.

Programmable Logic Controller

Programmable Logic Controllers (PLCs) are used in industrial automation for controlling machines, such as CNC lathes and drills, as well as for process control in manufacturing plants. 

PLC manufacturers face multiple challenges. Making the systems compact, while also supporting up to 128 channels per board, is a prime concern. System parameters are dependent on geography, making the manufacturing more challenging. Increasingly, servo motor control is being done through PLCs, which creates the need for high-speed capability. 

The Si838x is a highly targeted solution for PLC inputs that provides an integrated isolated multi-channel, bi-polar and high- speed device in a compact package. Isolation is also required for communication with other nodes in the factory automation network. Multi-channel isolators, such as the Si86xx and the Si88xx, are good solutions.

Communications

The entire industrial system can be monitored and controlled via a communication bus. The bus is isolated with digital isolators and digital isolators with integrated DC/DC power converters like the Si86xx and Si88xx.

Power Supplies

Isolated power supply systems are prevalent in server systems, industrial applications, and telecommunication and networking equipment. The most critical parameter for power supply design is improved power density, or watts per centimeter cubed. The other issue driving decisions for power supply customers is safety. Improving product lifetimes is important to ensure safety for the end user.

Designers today have one overriding objective—to maximize power per volume(W/mm³).  One way to achieve this is to use higher switch rates - new products like GaN FETs are now available that enable high-speed switching capability.

However, fast switching does not come for free—it produces high-noise transients that could cause problems. To avoid this, the noise immunity of gate drivers has to be very high. Silicon Labs provides isolated gate drivers that fit these requirements.  Multi-channel digital isolators are also needed for transferring feedback and/or control signals across the isolation boundary.

In the quest to increase power density, one of the best tools available is to increase the switching frequency of the modulation scheme. This has the advantage of reducing the size of the magnetic components, such as inductors and transformers, while increasing efficiency and improving transient response. However, there is a risk associated with higher frequency. That is, the faster switching causes higher slew rates and thus high-noise transients. With a high-performance noise immunity of 200 kV/µs, the Si827x eliminates the risk posed by faster switching speeds. The high noise-transients generated by the faster switching will not affect signal integrity through the driver, thereby eliminating the risk of loss of modulation.

Explore the rest of the Silicon Labs' isolation portfolio here.

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