Overview

Wide bandgap semiconductors find applications in all types of power conversion, including electric vehicles. WBG devices are commonly used in chargers and auxiliary converters, due to the promise of higher efficiency and faster switching speeds leading to potential savings in cost, size and energy, but they are not suitable for mass replacement of IGBTs in traction inverters. Not yet. This article describes how the latest generation SiC FETs are ideal for new inverter designs, with lower losses than IGBTs and proven short-circuit robustness even under high temperature and repeated stress.

38% of US cars in 1900 were electric

In 1900, American cars were 38% electric, 40% steam, and 22% petrol. However, when Henry Ford began mass-producing cheap gasoline cars, the percentage decreased dramatically, and early electric vehicles (EV) almost disappeared. Today, less than 1% of EVs are on the road, but by 2050, 65-75% of light vehicles in the US are projected to be electrified. More broadly, the International Energy Agency (IEA) predicts that by 2025, EVs will make up 25% of the vehicles on the world's roads. In addition, with a view to the transportation sector accounting for approximately one-fourth of greenhouse gas emissions, CEM aims to increase the number of new vehicles sold in CEM participating countries to 30% of the automobile market by 2030 through the EV30@30 campaign. Aiming to be

Since Toyota's Prius was launched in Japan in 1997, modern EVs have advanced dramatically, with advanced battery and motor technology giving a range of over 300 miles. However, the penetration rate of EVs projected to reach 2050 is due to various factors such as low purchase prices, persistently high crude oil prices, tightening of health and environmental regulations, and further technological progress for improving cruising range and quick charging. It relies on certain assumptions.

About efficiency

EV conversion efficiencies appear to have room for improvement, with efficiencies of 59-62% converting battery energy to wheel power. Electric drive engineers point out that the motor itself isn't more than 85-90% efficient, and at least there's a roadmap for improving EV performance with new solid-state switches available in the drivetrain. There is a possibility. The key to improving cruising range is the efficiency of power conversion.

It's not just about motor drive electronics. Considerable energy is used for auxiliary functions such as lighting, air conditioning, and infotainment, so many efforts have been made to reduce power consumption from these areas, such as replacing inefficient conventional lighting with LEDs. has been paid. A variety of power converters that step down the main battery voltage (usually 400V) to 12V or 24V for these functions use modern topologies and exotic semiconductors to make them acceptable even in non-safety-critical applications. You can achieve the highest efficiency while reducing the risks inherent in the technology.

In drivetrains, motor control electronics are considered life-critical, so designers opted for “safe operation” and employed tried and tested techniques. In practice, we use IGBT switches that have proven their robustness for over 30 years. For example, under the high-tech exterior of the Tesla Model S are 66 IGBTs in TO-247 packages that control the traction motors. In EVs, IGBTs switch at around 8-12 kHz. The frequency is kept so low because high-power IGBTs lose rapidly at higher switching rates. A low switching speed is beneficial in maintaining low dV/dt in the motor windings, but the current ripple is high, resulting in high iron losses. However, newer vehicles have just started using wide bandgap (WBG) semiconductors instead of IGBTs, which are expected to increase switching frequency and increase efficiency by 62%.

Wide bandgap semiconductors to compete in EV motor control

In many modern power applications, such as PV inverters, UPS, and EV on-board chargers, IGBTs have already replaced them, manufactured with silicon super-junction MOSFETs and silicon carbide (SiC) and gallium nitride (GaN) materials. New technologies such as WBG semiconductors are adopted. MOSFETs are an established technology, but have made little progress in EV traction applications compared to IGBTs due to the relatively high loss of the high voltage types required and the poor recovery characteristics of the body diodes. However, WBG switches are increasingly being adopted for EV motor drives due to their low inherent losses at high voltages and many other advantages.

In the next article, we will explain the specific advantages of WBG semiconductors in more detail.

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