Isolated gate drivers offer protection for inverters and motor drives

Louise Davis

Silicon Labs has expanded its ISOdriver portfolio with a family of isolated gate drivers designed to protect sensitive insulated-gate bipolar transistor (IGBT) switches in power inverter and motor drive applications.

The new Si828x ISOdriver family provides industrial-grade isolation (5 kVrms withstand), best-in-class feature integration including an optional dc-dc converter, the industry’s fastest desaturation detection, superior timing characteristics, and exceptional noise and transient immunity.

The Si828x family provides an ideal solution for industrial motor drives, solar inverters, high-voltage power converters, uninterruptable power supplies, and heating, ventilation and air conditioning (HVAC) compressor control. Many of these systems are expected to last more than 25 years while operating in harsh environments. Isolators can be first points of failure and lifetime-limiting devices in these systems. Traditional optocoupler-based isolators have significant limitations in temperature range, noise immunity and product lifetime. Based on Silicon Labs’ proven CMOS isolation technology, Si828x gate drivers can operate over a full industrial temperature range, support product lifetimes of up to 100 years, and meet stringent UL, VDE, CQC and CSA standards.

The Si828x family combines robust isolation, advanced gate driver technology and fast over-current monitoring in a single, cost-effective device designed to protect costly IGBT switches. High-power inverter and power converter systems typically use IGBTs for the switching element, and over-current conditions can destroy IGBTs, compromise system-critical functions, jeopardize product safety and diminish reliability. Efficient switching of IGBTs requires the use of isolated gate drivers like the Si828x devices with specialized monitoring and control features.

The defining Si828x feature is a 4 amp gate driver coupled with desaturation detection to monitor the IGBT for over-current. In that event, the Si828x driver initiates a controlled shutdown of the switch while updating the controller with the fault status, protecting the IGBT and the system. Additional integrated features include split outputs, a Miller clamp to prevent parasitic gate turn-on, and driver power state and fault feedback to the controller.

The Si828x family includes driver versions with an integrated isolated dc-dc converter, which helps developers simplify the layout, reduce component count and board size, and ease the complexity of creating and managing multiple power domains. A single power bus can be routed across the system, eliminating complex spacing concerns. Localising power supplies to each driver reduces inductance, minimises noise and removes transients.