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APPLICATION OF AC INPUT COMPATIBLE OPTOCOUPLER

INTRODUCTION

With the rapid penetration and diversification of electronic systems, demand for optocouplers is strengthening. Most popular are

products featuring compact design, low cost, and high added value.

To meet the market needs, NEC is expanding the optocoupler. This manual focuses on optocouplers compatible with AC input,

and covers configuration, principles of operation, and application examples.

CONFIGURATION (INTERNAL PIN CONNECTION DIAGRAM)

Figure 1 shows the internal pin connection of the AC input compatible optocoupler PS2505-1, and Figure 2, of the optocoupler

PS2501-1. The most significant difference from the optocoupler (PS2501-1) is that the PS2505-1 incorporates an input circuit

with two LEDs connected in reverse parallel. In the optocoupler (PS2501-1), one LED is connected in the input circuit so that the

LED emits light to provide a signal when a current flows in one direction (1-2 in Figure 2) (one-direction input type).

However, in the configuration shown in Figure 1, when a current flows in direction 1 to 2, LED1 emits light to send a signal, and

when it flows from 2 to 1, LED2 emits light to send a signal (bidirectional input type). Namely, even if the voltage level between 1

and 2 varies, and the positive and negative polarities are changed, either of two LEDs emits light to send a signal. This means

that the one direction input optocoupler permits DC input only, while the bidirectional input type permits AC input as well. There-

fore, the PS2505-1 is described as an AC input compatible optocoupler.

The next section describes the status of output signals when 100 Vac power is directly input to an AC input compatible

optocoupler (PS2505-1) via a current limit resistor.

Figure 1. PS2505-1

Figure 2. PS2501-1

1

2

4

3

(LED2)

(LED1)

1

2

4

3