Gate Drivers Engineered for New Era in Power Electronics

Oct. 27, 2023

Check out some of the latest gate-driver IC developments in this installment of the Products of the Week.

Gate Driver Limits Power Loss with 4-A Peak Drive Current

The Si823Hx family of dual-channel, isolated gate-driver ICs from Skyworks are designed to be paired with SiC, GaN, and other power MOSFETs in a wide range of switching power supplies and motor-control systems.

The gate-driver ICs are not unlike other gate drivers in the same class, as they can operate from 3.0- to 5.5-V input voltage from the controller in the system and level-shift them to higher-voltage rails of up to 30 V to act as the gate-drive supply voltage. With a wide temperature range of –40 to 125°C, the chips also have a boost stage that pumps out peak sink and source current—of up to 4 A—at the Miller plateau for faster turn-on times during switching.

Based on its CMOS capacitive isolation technology, the chips feature galvanic isolation ranges up to 5 kV RMS and dead-time programmability. They can also handle high-voltage transients, with up to 125 kV/µs of CMTI.

Undervoltage lockout (UVLO), one of the standard features of any gate driver, is also part of the package. UVLO monitors the gate voltage and prevents it from dropping below a specified threshold. The gate voltage affects the power FET’s output characteristics, and SiC requires a relatively high drive voltage to minimize power losses. If the gate-drive voltage is insufficient, the FET can become saturated faster, causing high conduction losses because it’s not fully turned on. This is detrimental since higher power losses dissipate more heat, which can cause damage to the FET.

Skyworks said the gate drivers add internal overtemperature protection to prevent overheating of the FET, along with the usual overcurrent protection and soft shutdown features. A Miller clamp is integrated, too. Input to the device is digital, while on the output side, the Si828x devices provide separate pull-up and pull-down pins for the FET gate. The gate drivers have −5-V voltage withstand on the output pins.

Maximum propagation delay of 30 ns translates to more accurate power-supply control.

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Change never comes easy in the world of power electronics.

To achieve higher power densities, the latest 3.3 kW switched-mode power supplies (SMPS) are adopting silicon-carbide (SiC) power MOSFETs in the totem-pole PFC stage and gallium-nitride (GaN) power switches in high-voltage DC-DC converter stages. While silicon MOSFETs and IGBTs are always improving, these new semiconductor materials are upping the ante. That’s largely thanks to their ability to manipulate more power at higher voltages and currents than silicon while losing less to heat.

These new switching technologies bring to the table fast switching speeds and other unique properties that lend themselves to use in EV traction inverters and DC-DC converters, uninterruptible power supplies (UPS) in data centers, industrial motor drives, and solar and other types of inverters for renewable-powered grids.

To bring the best out of SiC and GaN power devices, you need to carefully control and drive them. Digital control of both the power-factor-correction (PFC) and DC-DC stages is critical to improving power efficiency and robustness, as is the use of optimal gate-driver ICs.

To that end, semiconductor firms are rolling out more optimized isolated gate-driver ICs that can better manage the pros and cons of SiC and GaN power switches and even the latest silicon or superjunction (SJ) MOSFETs and IGBTs.

Choosing the right gate driver is critical because of the role it plays in power electronics. They act as the (usually isolated) interface between the microcontroller (MCU) or analog controllers—which pump out the pulse-width-modulation (PWM) signals to control a power supply’s duty cycle, frequency, dead time, and phase-shift—and the power MOSFET. It’s standard practice to put the MCU on the low-voltage side of a power supply so that it stays away from the noise and transient voltages that the FETs experience.

The gate driver must supply sufficient current to turn the FET on and off as fast as possible. Doing so shortens the dead time between the on and off phases and reduces power losses that can add up in the interim.

As the demands for gate drivers change rapidly in the era of SiC and GaN, semiconductor firms are rising to the challenge. They’re developing gate-driver ICs with higher sink and source currents, faster propagation delay, and more robust galvanic isolation that can fit into smaller form factors.In this product roundup, we review some of the latest gate driver ICs to hit the market.