Evaluation of Fairchild's Gate Drive Optocoupler, Type FOD3150, Under Wide Temperature Operation

An optocoupler is a semiconductor device that is used to transfer a signal between different parts of a circuit that need to be electrically isolated from one another - for example, where a high voltage is to be switched with a low voltage control signal. Optocouplers often can be used in place of relays. These optocouplers utilize an infrared LED (light emitting diode) and a photodetector such as a silicon controlled rectifier or photosensitive silicon diode for the transfer of the electronic signal between components of a circuit by means of a short optical transmission channel. For maximum coupling, the wave-length responses of the LED and the detector should be very similar. In switch-mode power supply applications, optocouplers offer advantages over transformers by virtue of simpler circuit design, reduced weight, and DC coupling capability. The effects of extreme temperature exposure and thermal cycling on the performance of a commercial-off-the-shelf (COTS) optocoupler, Fairchild FOD3150, were evaluated in this work. This 1.0 A output current, high noise immunity gate drive optocoupler utilizes an aluminum gallium arsenide (AlGaAs) LED, is capable of driving most 800V/20A IGBT/MOSFETs, and is suited for fast switching in motor control inverter applications and high performance power systems. Some of the specifications of the isolator chip are listed. The device was evaluated in terms of output response, output rise (t(sub r)) and fall times (t(sub f)), and propagation delays (using a 50% level between input and output during low to high (t(sub PLH)) and high to low (t(sub PLH)) transitions). The output supply current was also obtained. These parameters were recorded at various test temperatures between -190 C and +110 C.