CIRCUIT060081

The zero crossing detector circuit changes the comparator’s output state when the AC input crosses the zero reference voltage. This is done by setting the comparator inverting input to the zero reference voltage and applying the attenuated input to the noninverting input. The voltage divider R1 and R2 attenuates the input AC signal. The diode D1 is used to insure the noninverting input never goes below the negative input common mode limit of the comparator. Zero crossing detection is often used in power control circuits.

• Supply:
  • Vcc = 5 V
  • Vee = 0 V
  • Type = single
• Input signal:
  • Vi = 240 V AC RMS
  • f = 50 Hz
• Max AC mains leakage current: I_ac < 500 µA