Page 46 - PEN eBook July 2023

Design

added, either N-type or P-type. A diode is formed by adding a heavily doped layer of N material
on one surface of a P-type resistor, allowing current to flow in one direction only. The MOSFET
combines the resistor and diode functions and has a switch to select between modes. An IGBT is

similar to a MOSFET, but with an additional doping layer to change its behavior.

Lastly, B-TRAN is a bidirectional bipolar junction transistor equipped with a control on both sides
for enhanced performance and inherent bidirectionality. “By incorporating all the features into one
die using both sides of the wafer, a bidirectional switch can be made without using pairs of IGBTs
and diodes like traditional bidirectional circuits,” Brdar said.

B-TRAN PERFORMANCE

Figure 2: (a) B-TRAN symbol; (b) real B-TRAN; and (c) B-TRAN specifications

Figure 2 displays the circuit symbol and device along with its bidirectional operating characteristics.
The device, with its two control inputs, can block voltage in both polarities and conduct current in
both directions. This makes it suitable for bidirectional applications like voltage source inverters or
battery chargers, as well as unidirectional applications.

“Coming up with a version of technology that is really a bidirectional switch targeted for applications
that require faster switching speeds, for example, using silicon carbide can be an option,” Brdar

said.

However, to create a bidirectional switch, two MOSFETs or two IGBTs plus two diodes must be
connected in a common-emitter configuration, which significantly increases the part count for
bidirectional power converters.

46 JULY 2023 | www.powerelectronicsnews.com