Silicon carbide isolation gate device analysis

What is a silicon carbide isolated gate device? What does it do? Maxim Integrated has introduced a silicon carbide (SiC) isolated gate driver for high-efficiency power supplies in the industrial market. The company claims that the new device consumes 30% less power and has a 30% lower carbon footprint compared to competing solutions.

System manufacturers are increasingly interested in improving the power efficiency of their designs. The combination of energy efficiency and cost reduction is becoming a key market leadership position. From a semiconductor materials perspective, the field has made considerable progress, and there are now products that can switch at high speeds, reducing size while increasing system-level efficiency.

As devices become smaller, power supplies need to keep pace. Therefore, designers today have one priority goal: maximizing power per volume (W/mm3). One way to achieve this is to use high-performance power switches. The path forward for new power electronics is already paved with gallium nitride (GaN) and silicon carbide (SiC), although further R&D projects are needed to improve performance and safety despite the use of these wide bandgaps (WBG) in the design phase Materials require additional work to design.

Properties such as energy band gap (eV), breakdown field, thermal conductivity, electron mobility and electron drift velocity are the main benefits engineers gain from using WBG semiconductors such as GaN and SiC. The advantages of WBG semiconductor power switching modules include high current density, faster switching speed and lower drain-to-source resistance (RDS (on)).

SiC will determine power rates in several industrial applications. It has a band gap of 3.2 electron volts (eV) and the energy required to move electrons in the conduction band provides higher voltage performance in the same package size. The high operating temperature range and thermal conductivity enable efficient thermal management.

Many switching power supply applications employ SiC solutions to improve energy efficiency and system reliability.

High switching frequencies in power supplies result in operational difficulties that generate noisy transients, making the overall system inefficient. The new technology's chemical structure gives the new device low-charge properties compared to silicon and the opportunity for rapid switching.

Isolated gate drivers are widely used to drive MOSFETs and IGBTs and provide galvanic isolation. Switching frequencies above 10 kHz are common in MOSFETs and IGBTs. However, SiC and GaN-based systems can operate at higher switching frequencies without significant power loss during the transition. Significant advantages are reduced size and reduced distortion (Figure 1).

Rapid switching generates transient noise that can cause loss of modulation or even permanent damage to the system due to latch-up. To solve this problem, it is necessary to improve the noise immunity of the components used in the drive system. Power dissipation or conduction losses during switching generate heat that must be dissipated through the heat sink. The size of the heat sink increases the size of the solution.

The intensity of these transients may be caused by spurious pulses in the drive circuit of the gate, resulting in a short circuit condition. The drive circuitry controlling the power converter must be designed to withstand these noise sources and thus possible secondary short circuits. The driver circuit's ability to withstand these common-mode noise transients is defined by common-mode transient immunity (CMTI), expressed in kV/µs, which is a key parameter for all gate drivers that handle differential voltages between two independent grounds. Reference (Isolated Gate Driver). Understanding and measuring sensitivity to these transients is an important step in designing new power supplies. The capacitance across the barrier provides a path for these fast transients to cross the isolation barrier and corrupt the output waveform.

The new MAX22701E driver features high CMTI immunity of 300 kV/µs, increasing system uptime. The driver is designed for switching power sources in high-power industrial systems such as solar inverters, motor drives and energy storage systems. The MAX22701E is compatible with driving SiC or GaN FETs. Technical specifications significantly reduce downtime and energy losses. The MAX22701E is available in an 8-pin (3.90 x 4.90mm) narrow-body SOIC package with an extended temperature range of -40 to +125°C (Figure 2).

A higher CMTI determines the correct operation of both sides of the driver, minimizing errors and thus making the gate driver used more reliable. CMTI is one of three key functions related to isolators. Other key features are propagation delay matching and operating voltage. The MAX22701E provides the industry's lowest 5ns (max) part-to-part propagation delay matching between the high-side and low-side gate drivers. This helps minimize transistor dead time and maximize power efficiency. The device provides strong galvanic isolation of 3kVRMS for 60s. The above is an efficient solution for silicon carbide isolation gate devices. I hope it can help you during design.