GaN Systems and ON Semi Develop Half-Bridge Evaluation Board to Drive GaN Power Switches

November 11, 2019 by Gary Elinoff

The new evaluation board simplifies the process of evaluating gallium nitride-based, half-bridge or full-bridge power supplies.

GaN Systems and ON Semiconductor have teamed up to create the NCP51820 HB GaN Driver Evaluation Board (EVB), an EVB intended to replace the driver and power MOSFETs used in existing half-bridge or full-bridge power supplies.


Half-Bridge Evaluation Board from GaN Systems and ON Semiconductor.

Half-bridge evaluation board from GaN Systems and ON Semiconductor. Image (modified) used courtesy of GaN Systems 


The device demonstrates how to properly drive two gallium nitride power switches used in a high-voltage, totem-pole configuration, and how to do it using a minimal number of components.


The First of Many EVBs

The EVB is to be the first of many that the two companies will produce. It can be used not only for evaluation but also as a highly-efficient subset of independent power systems. The benefits of such an EVB include reductions in overall weight, size, and BOM costs. 


Photo of the EVB

The EVB functions using a minimal number of components. Image from On Semiconductor

As described by Ryan Zahn, Director of Marketing at ON Semiconductor, "The expansion of the GaN components ecosystem including driver ICs, such as our NCP51820, remove design barriers and take advantage of the numerous benefits that GaN E-HEMTs provide.” The NCP51820 is ON Semiconductor's high-speed gate driver (650V) that aims to meet the requirements of driving-enhancement mode.


NCP51820 Specifications

The NCP51820 is purposed to meet the tough conditions required to work with gallium nitride (GaN) power switches in off-line, half-bridge power topologies. It provides short and matched propagation delays and provides −3.5V to +650V (typical) common-mode voltage range for the high-side drive. The device also offers −3.5V to +3.5V common-mode voltage range for the low-side drive. 


 NCP51820, Functional Block Diagram

 Block diagram of NCP51820. Image from On Semiconductor


Additionally, the NCP51820 can operate reliably even in high dV/dt environments of up to 200 V/ns. To further protect the gates of the GaN power switches against excessive voltage, both drive stages employ voltage regulators as well as active clamping to maintain the gate-source drive signal amplitude.


Connecting the Evaluation Board to an Existing Power Board

The NCP51820 evaluation board is described as a “daughterboard” and as a “kit” with only 23 components. The NCP51820 HB EVB datasheet provides extensive instructions on how to modify this kit and connect it to existing power boards—a stated purpose to this device beyond evaluation.

As shown below, the NCP51820 EVB can be used to replace the MOSFETs and driver circuitry in a FAN7688 250W, 400V-to-12.5V LLC converter. That device’s MOSFETs and gate drive resistors were removed and the EVB is shown being wired in to replace them.


The FAN7688 LLC the NCP51820 EVB installed

The FAN7688 LLC the NCP51820 EVB installed. Image from On Semiconductor


The FAN7688 is a Fairchild product, and Fairchild is now part of ON Semiconductor.


GaN Systems Experience

GaN Systems has previously built evaluation boards designed to work with its own GS66508B—an enhancement-mode, GaN-on-silicon power transistor—with other industry partners, such as Analog Devices.

As described by Charles Bailley, Senior Director of worldwide business development at GaN Systems, “The new evaluation board developed in collaboration with ON Semiconductor makes it easier and more cost-effective to design with GaN – opening the door for smaller, lighter, and more efficient power converters.”

He goes on to state that “This collaboration signals the innovation not only happening with end products designed with GaN but in components, design tools, and reference designs that optimize the use of GaN.”



What obstacles do you face when designing with GaN? Share your experiences in the comments below.