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Microsemi
Colorado Division
800 Hoyt Street, Broomfield, CO. 80020, 303-469-2161, Fax: 303-466-3775
Page 1
Copyright 2002
AGT.pdf 2002-11-18
WWW.Microsemi .COM
High Current AC Thyristor Applications
COLORADO
DIVISION
MicroNote 603
Anode Gate Thyristors and High Current AC Applications
By Steve McKelvie
The common thyristor solution used in higher current ac switching is two isolated SCR’s. The added
hardware and packaging required to provide the needed isolated heat sinking in this configuration is a cost
drawback. Triacs allow a single heat sink, but are limited by their thermal performance in current, blocking
voltage, and higher frequency applications. The Microsemi AGT (Anode Gate Thyristor) device is a
thyristor providing the reverse electrical switching of the SCR on a common mounting plane. The AGT
effectively mirrors the operation of a matching SCR in the opposite polarity by switching in Quadrant III.
Paired SCR & AGT devices duplicate the function of a Triac without isolation at high currents and blocking
voltages up to 1200V. For example, the Microsemi 050R02GOF AGT complements the popular
05002GOF SCR. Both devices are rated 50A average in a T065 package, and are available up to 1200V. A
common heat sink may be used that eliminates the need for two isolated heat-sink assemblies in the ac
switching circuit.
Applications include phase-controlled, zero-crossover-control, high-current battery chargers, oven
controllers, motor control or simply high ac current electrical power switching. Gate triggering for non-
repetitive switching applications where zero crossing & EMI is not an issue can take advantage of simple ac
rectified trigger switches. Zero-crossing circuits vary with the designer’s needs, sophistication, and
available dc sources. The requirement for the AGT negative voltage trigger can be achieved in a positive
only source or logic level through various schemes including a simple coupling transformer.
Complimentary Microsemi SCR and AGT devices should be used to ensure optimum circuit performance.
Other OEM packages including single modules are feasible and can be addressed by contacting Microsemi.
AGT
