GaN is one of the next generation semiconductor compounds that can achieve space and energy savings when applied to transistors used in various power units. A gate driver is required to drive a transistor; however, general gate drivers for conventional silicon (Si) transistors cannot exploit the potential of GaN transistors since the gate structure of GaN transistors is different from that of Si transistors.
The new high-speed gate driver (AN34092B) helps X-GaN easily and safely achieve high-speed switching performance. It can drive transistors at high frequencies of up to 4 MHz and integrates the active miller clamp function that prevents malfunction during high-speed switching. X-GaN achieves a 600 V breakdown enhancement mode through Panasonic’s unique technology and features high-speed switching and low on-resistance. The combination of X-GaN and dedicated high-speed gate drivers will contribute to significant space and energy savings of various power conversion units for industrial and consumer use.
The active miller clamp is a function that directly fixes the gate voltage to the ground level to reduce voltage spikes on the gate in noisy environments that may cause malfunction of the transistor when it is switched off. An enhancement mode is a characteristic of semiconductor devices that is normally switched off when no voltage is applied to the gate. This is also called normally-off. On-resistance is the resistance between the drain and the source electrode of a transistor when the transistor is switched on. The lower the value is, the smaller the loss of the transistor is.
Current collapse is a phenomenon in which electrons in the drain area are trapped by the energy of the high voltage applied between the drain and the source electrode. Since the trapped electrons prevent current flow from the drain to the source electrode when the transistor is switched on, the on-resistance increases.
X-GaN and dedicated high-speed gate drivers are suitable for various applications such as 100 W to 5 kW power supply units, inverters, data centers, mobile base stations, consumer electronics, audio-visual equipment, industrial and medical devices. X-GaN and dedicated high-speed gate drivers are part of Panasonic’s highlights at electronica 2016 in Munich, Germany.
GaN Properties and Characteristics
The special features of GaN such as high voltage potential, ease of miniaturization and high-speed switching, enable GaN to achieve high breakdown voltage and low conduction resistance. The “high breakdown voltage” is achieved because GaN has a wide band gap property. Band-gap is a region formed on the junction of materials where no electron exists. GaN has a band-gap wider than that of an Si. This enable GaN to achieve higher breakdown voltage than Si. With smaller size than Si devices at the same voltage breakdown, GaN devices allow miniaturization more than Si devices. Also, miniaturization reduces its parasitic capacitance that in turn improves its switching speed.
The ”low conduction resistance” is achieved because the on-resistance of the power device is inversely proportional to the cube of the electrical breakdown. In other words, it is expected that GaN devices will have an on-resistance approximately 3 digits lower than the limit of that of Si devices theoretically. In addition, GaN devices have high electron saturation velocity that makes it suitable for high-speed applications.