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Control unit for occupancy sensor switching of high efficiency lighting

  • US 5,473,202 A
  • Filed: 06/05/1992
  • Issued: 12/05/1995
  • Est. Priority Date: 06/05/1992
  • Status: Expired due to Term
First Claim
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1. A control unit adapted trot switching an AC powered high efficiency lighting load in response to an occupancy sensor comprising:

  • an on/off control circuit for controlling a relay control circuit and a noise-insensitive semiconductor switch control circuit, the on/off control circuit being adapted to receive signals from an occupancy sensor, the control circuit providing an on/off control signal having an on state indicating the load should be turned on when occupancy is sensed and an off state indicating the load should be turned off thereafter;

    the relay control circuit being directly responsive to the on/off control signal and not responsive to the semiconductor switch control circuit and including a delay means for delaying the on state and the off state of the on/off control signal for a delay time;

    a relay having an actuator connected to the relay control circuit which actuates relay switch contacts upon receipt of the delayed on/off control signal, the relay switch contacts being adapted to carry AC load current of the load and being movable from an open to a closed position during a relay closing time and movable from a closed to an open position during a relay opening time;

    the delay time plus the shorter of the relay closing time or the relay opening time being greater than the time between successive zero crossings of the AC power;

    the noise-insensitive semiconductor switch control circuit having an output for controlling a semiconductor switch and a zero voltage crossing detector that switches the output of thee semiconductor switch control circuit only at the zero crossings of the AC power responsive to the on/off control signal;

    a semiconductor switch which switches in response to the noise insensitive semiconductor control circuit immediately, the semiconductor switch being adapted to carry the AC load current and having switch leads connected in parallel across the relay switch contacts; and

    the control unit switching the relay based on the time of the on/off control signal as delayed by the relay control circuit and not based on the time of the zero crossings of the AC power detected by the zero voltage crossing detector in the noise insensitive semiconductor control circuit.

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