Isolated gate drivers offer protection for inverters and motor drives

12th September 2016
Daisy Stapley-Bunten

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 (5kVrms withstand), best-in-class feature integration including the following:

  • an optional DC/DC converter
  • the industry’s fastest desaturation detection
  • superior timing characteristics
  • 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 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, jeopardise product safety and diminish reliability. Efficient switching of IGBTs requires the use of isolated gate drivers like the Si828x devices with specialised monitoring and control features.

The defining Si828x feature is a 4A 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.

“Today’s power inverters and converters for industrial and green energy designs require state-of-the-art signal isolation technology with superior timing characteristics, lower emissions and higher reliability,” said Ross Sabolcik, Vice President of power products at Silicon Labs. “Silicon Labs’ new Si828x ISOdriver family provides the ultimate gate driver solution for these applications by helping developers achieve higher system efficiency and noise immunity, minimize design complexity, and enhance system safety and product lifetimes.”

Si828x ISOdriver family highlights

  • industrial-grade isolation: high transient immunity, high reliability, 5kVrms withstand
  • most comprehensive feature integration in the isolated gate driver market
  • optional integrated DC/DC converter simplifying board layout and driver supply design
  • industry’s fastest desaturation detection: up to 10x faster than competitive alternatives
  • fastest, most accurate timing specs with low propagation delay (< 55ns): up to 10x better than optocoupler solutions and up to twice as good as competing CMOS solutions
  • long lifetimes under high-voltage conditions (100 years at 1,000V)

Silicon Labs offers three evaluation kits to help developers evaluate Si828x ISOdriver performance and key features:

  • Si8285_86-KIT demonstrates the basic Si828x driver functionality
  • Si8281-KIT demonstrates the driver with an integrated DC/DC converter
  • Si8284-KIT demonstrates the driver with full-featured DC/DC converter capable of using higher supply voltages

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