34

DIRECT INPUT OF 100 Vac

Figure 3 shows the circuit diagram when 100 Vac power is directly input to an AC input compatible optocoupler via a current limit

resistor. The relationship between input and output signals is as shown in Figure 4.

+

0

_

+

0

LED 1

LED 2

LED 1

LED 2

LED 1

LED 2

Deviation due to

the differences in

light emission and

coupling efficiencies

of LEDs

Input signal

AC 100 V

LED light

emission

output

Output signal

Graph 1 Upper: 100 Vac Input Signal 100 V/DIV

Lower: Output Signal 1 V/DIV

As described above, when an AC input compatible optocoupler is used, an AC input signal can be extracted as a full-wave

rectified output signal. The output signal is smoothed by inserting a capacitor in the last stage of the circuit of a phototransistor if

necessary.

In the one-direction input optocoupler (PS2501 series), when an AC signal is to be input, it must be full-or half-wave rectified by a

diode bridge or CR circuit. On the other hand, the AC input compatible optocoupler permits direct input of an AC signal. This

enables simpler configuration, space saving, and reduced design cost.

The next section demonstrates three examples of applications.

Figure 4. Input/Output Signal

(LED2) (LED1)

PS2505-1

11 k

Ω

AC 100 V

100

Ω

Output signal

Figure 3. 100 Vac Direct Input Circuit