3kV-isolated SMD transformer supports double-transistor control

July 31, 2015 // By Julien Happich
Embedded AC/DC and DC/DC converters are a growing technology in the automotive marketplace. For EV and HEV cars that become to be produced at huge volumes, both on-board battery chargers and 14V power supplies are required to ensure the transfer of energy from the 50/60Hz mains when charging to the final equipment used during a drive (ECUs, radio-GPS systems, lightning...).

The related power electronics involves not only transformers and filtering chokes built in half- or full-bridge topologies but also semiconductors like IGBTs or MOSFETs that have to be accurately commanded to deliver the expected output voltage while perturbations at the input or load can affect the global performances. The control-loop often requires a good insulation between the primary side connected to the HV DC-bus (typically 350-800V) and the gate of the transistors (10-15V).

A high isolated gate-drive transformer, Premo's GDAU series is less than 8mm high and well suited as a low-profile insulated SMD transformer to control MOS transistors. The 5-gram device guarantees an insulation level of 3kV and a creepage distance greater than 5mm.

The use of special insulated wire and special construction lower the parasitic elements to values (the leakage inductance is 2µH max whereas the prim-sec stray capacitance is less than 12pF) fully optimized for a switching frequency in the 90-125kHz range. The GDAU-001 reference provides a 1:1+1 turn-ratio that can command 2 transistors of the same polarity at once. It can withstand 150Vus without any noticeable saturation (15V control at 100kHz for example).

The GDAU series shows a magnetizing inductance value of no less than 400µH to prevent the output control voltage from any noticeable droop. The low DC resistance values of the windings ensure its capability to drive currents up to 0.5Arms continuous without overheating.

The SMD technology is delivered in Tape&Reel packaging for easy Pick&Place assembling processes. It is fully compliant with most of the RoHS lead-free reflow soldering techniques. This technology is 100% compatible with AOI (Automatic Optical Inspection) system for final assembled PCB control.

Fully compliant with the automotive AEC-Q200 standard, the device has been validated in operation from -40 to +155°C.

Visit Premo at www.grupopremo.com