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Optocoupler Structure

Figure 1 shows the internal perspective view of a PS2500 optocoupler and Figure 2 shows the sectional view of the optocoupler.

Figure 2 below shows the optocoupler in a light-tight epoxy resin housing, and a light-sensitive element (phototransistor or photo

Darlington transistor) with light-transmittable epoxy resin medium between them. A light signal emitted by the LED is transferred

to the photosensitive transistor via the internal resin medium.

Both the housing resin and the internal resin have the same expansion coefficient. Namely, the optocoupler elements are molded

twice with epoxy resin. (This structure is referred to as a double molding structure.)

The high isolation voltage is obtained by the long adjacent area of the inner and outer resins (inner boundary) and identical

expansion coefficient of the inner and outer resins (eliminating arc discharges on the inner boundary).

Figure 1. Internal perspective view of optocoupler

Outer resin (Black)

Inner resin (White)

Inner boundary

Figure 2. Sectional view of optocoupler