Gate driver designs for heavy EVs

Power Integrations (PI) has developed two versions of its gate driver board that is suitable for powertrain designs in heavy equipment such as trucks, buses, and agricultural and construction equipment (writes Nick Flaherty).

The Scale EV gate driver boards are designed to fit on top of Infineon’s EconoDual half-bridge modules in the same footprint. The modules use pure silicon IGBT devices, but there is also a variant for silicon carbide (SiC) modules in the same footprint.

PI also plans to support other modules such as those from Hitachi for construction equipment.

The gate driver board incorporates two reinforced channels for driving the gates of the IGBT power transistors, as well as the associated power supplies and monitoring telemetry. The board is certified to ASIL B with redundancy in key areas of the power chain, allowing it to be used in ASIL C traction inverter designs.

That saves design and certification time in powertrain development, and adds other safety features such as the ability to discharge through the gate driver in order to protect the IGBT module. The module uses two separate inputs for active discharge and short-circuit protection.

This higher level of integration is possible by using PI’s FluxLink isolation technology. This allows the entire driver board, including power to the gate of the transistors, to fit onto the outline of the power module, while still providing the spacing necessary for reinforced isolation according to the IEC 60664 standard. The gate driver package provides 11.4 mm of creepage and clearance, and is specifically designed to meet the requirements for 800 V systems.

FluxLink uses galvanic isolation in the gate driver package to separate out the HV and LV parts of the design. This allows the active discharge pins to be separated from the short-circuit pins, for example, and reduces the number of components for a gate driver by more than 25%.

The boards have been developed as original, clone and SiC variants. The original has the same interface as the Scale drivers developed for high-power renewable energy applications, while the clone version mimics the interface of the Infineon gate driver. 

The SiC variants will support the varying voltage input requirements of different SiC modules, says Smith, adding that many SiC modules have different threshold voltages, so there is no standard gate driver.

The first board supports the Infineon EconoDual 900 A, 1200 V IGBT half-bridge module. The board has a 5500 m altitude rating for construction equipment that might have to operate in different regions of the world, particularly in China. There is an optional conformal coating to protect the board in hostile environments, particularly for agricultural and construction equipment.

The design includes active short-circuit protection as well as active discharge of a connected DC-link capacitor. Overvoltage limitation is provided via active gate control, diagnostic functions such as gate monitoring, signal transmission monitoring and on-chip temperature monitoring. The board also supports short-circuit and over-current response of less than 1 µs for the SiC MOSFET variant, and less than 3 µs for the IGBT board.

PI offers design services to tune switching performance for specific IGBT or SiC die, and to customise the layout for other module form-factors. Samples of the first variant, the 2SP02152FQ for IGBT modules are available now, with full production release due later this year.