GaN on the Half Bridge – Electronic Design | Salisbury Pipes

This article is part of the TechXchange: power adapterly design.

Navitas Semiconductor has introduced its new family of fully integrated half-bridge Gallium Nitride (GaN) ICs to further disrupt the silicon-dominated power electronics market.

The power semiconductor maker said the new chips reduce the component count and area of ​​a complete half-bridge on a circuit board by more than 60%. Navitas went on to say that the result is better overall performance, reliability and power density while keeping system costs and complexity in check.

According to the company, the new series of GaN-based half-bridge power ICs promises to usher in a wide range of new power converter applications and upgrade them from kilohertz to megahertz switching frequencies.

power boost

GaN offers a variety of unique physical properties that make it ideal for power conversion devices such asDS(on)) and inherently fast switching transients.

The lack of reverse recovery and the ability to tolerate elevated temperatures and safely handle high voltages are also part of GaN’s strength. If you zoom out to the system level, you can use GaN to pack more power into everything from fast chargers to solar inverters to power converters in electric cars. It supports smaller form factors that weigh less and generate less heat, improving power density and offering significant efficiency gains.

GaN’s high switching frequencies reduce the size, weight and cost of the transformers, capacitors, EMI filters and other passive components that round out a typical power system, Navitas said.

However, there are tradeoffs. Because of its uniquely fast switching frequencies and other advanced performance capabilities, GaN-based power FETs can be difficult to drive and control. As a result, GaN FETs often need to be paired with a dedicated driver IC to get the best possible performance.

Navitas addressed this issue by monolithically integrating the gate driver into the power stage to switch faster and better drive and protect the power ICs from damage – a feature shared by the new half-bridge switches.

The new chips also include a wide range of built-in defenses: autonomous overcurrent protection (OCP), over-temperature protection (OTP) plus bullet protection, and the ability to tolerate electrostatic discharges (ESD) up to 2kV.

Half bridge in the package

In practice, however, power electronic systems rarely rely on a single switch.

In particular, the half-bridge, one of the most universal configurations in power electronics and widely used in motor drivers and inverters, uses a pair of power switches and a grouping of additional passives and devices.

Modern variable-speed drives for electric motors, found in everything from HVAC systems to industrial robots and electric vehicles, use three half-bridges to create a “three-phase” inverter topology, Navitas said.

The onboard charger (OBC) in a modern electric vehicle also uses multiple half-bridges to handle both the system’s input power factor correction (PFC) stage and the isolation plus DC/DC converter stage.

At higher power levels, data center AC/DC power supplies contain multiple half-bridge devices. In many cases, the half-bridges have to be operated at different frequencies depending on the topology of the power stage.

Navitas’ new series of half-bridge power ICs includes a pair of GaN FETs with drive and autonomous control functions to create this essential power stage building block. Another feature is “lossless” current sensing, which wrings out higher efficiencies and energy savings. Level-shift isolation and high-side bootstrapping are also included.

Integrating more half-bridges into a single package also keeps parasites and other characteristics at bay that can affect the device’s performance, Navitas said. That means faster and cleaner shifting speeds.

looking ahead

The new GaN half-bridge ICs fit into LLC resonant asymmetric half-bridge (AHB), active clamp flyback (ACF), and other AC/DC power converters. They are also ideal for the increasingly popular totem pole PFC topology.

Fast chargers for smartphones and other consumer devices are reaching higher and higher power levels. The new USB PD 3.1 protocol supports delivery of up to 240W of power with USB Type-C cables and connectors. When it comes to these higher power levels, Navitas believes smooth-switching GaN-powered half-bridge power converter topologies bring the fastest switching frequency and best power density to the table.

According to Navitas, the new IC series lends itself well to soft switching, which helps eliminate excess voltage and/or current across the power device before it is switched “on” or “off”, thereby limiting capacitive and switching losses .

Navitas CEO Gene Sheridan said the first generation of its “GaNFast” family had increased frequencies from 50-60kHz to 200-500kHz. He added: “The GaNSense half-bridges take these advantages to the MHz range.”

The first power ICs in the half-bridge GaN family include the NV6247 with a voltage rating of 650V, 160mΩ (dual) and the NV6245C with a voltage rating of 275mΩ (dual). They are housed in standard low-inductance 6 × 8 mm PQFN packages.

According to Navitas, the NV6247 is aimed at consumer electronics, including fast mobile chargers with power levels from 100 to 140 W, and household appliances such as fans with power levels up to 400 W.

The company, which has shipped more than 50 million GaN ICs to date and introduced a 20-year warranty for its GaN-based ICs this year, plans to expand the GanSense half-bridge family in the future.

Navitas announced that a variety of new packages and performance levels will be available in the coming quarters.

This article is part of the TechXchange: power adapterly design.

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