36

Example 3: Sequencer circuit input section

AC 100 V

PS2505-2

Common

Common

PS2501-2

AC 100V

(a) AC input compatible optocoupler

(bidirectional input)

(b) Conventional optocoupler

(one-direction input)

(Full-wave rectified by diode bridge)

PRECAUTIONS FOR DESIGN

The AC input compatible optocoupler is identical to the conventional optocoupler except for the presence of two LEDs connected

in reverse parallel in the input circuit. Therefore, the circuit configuration can be designed as conventionally. The difference is

that there are two types of current transfer ratios (CRT) because two LEDs are connected in the input circuit. The two CTRs are

not necessarily the same, owing to the differences in light emission and coupling efficiencies of LEDs. Consequently, this causes

characteristics.

A

A

A

LED 2

LED 1

Figure 5. CTR Measuring Circuit