Low power photocontrol for luminaire

• US 9,538,612 B1
• Filed: 09/03/2015
• Issued: 01/03/2017
• Est. Priority Date: 09/03/2015
• Status: Active Grant

• Current Assignee: Express Imaging Systems, LLC
• Original Assignee: Express Imaging Systems, LLC
• Inventors: Reed, William G.
• Primary Examiner(s): Le, Tung X
• Application Number:
  US14/844,944
• Time in Patent Office: 488 Days
• Field of Search: 315/152, 315/209.R, 315/291, 315/307, 315/308
• US Class Current: 1/1
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: H05B 47/165 following a pre-assigned programmed sequence; Logic control [LC]
• CPC Class Codes: H05B 47/185 via power line carrier transmission
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

Photocontrol apparatus that controls a luminaire or other load such that the luminaire is switched on during nighttime hours and off during the daytime. The photocontrol consumes only microwatts of power in either the ON or the OFF state, unlike traditional relay- or triac-based photocontrols. The photocontrol does not require a voltage generating photo sensor to generate power for the photocontrol. A solar cell, semiconductor photo diode or photo diode string, cadmium sulfide cell, semiconductor ambient light sensor, etc., may be used as the sensor element. The photocontrol switches power to the load at the zero-crossing of an AC input voltage, which reduces inrush current and the switching currents caused by traditional photocontrols which may switch at any point on the AC input voltage waveform.

Claims

1. A photocontrol apparatus to selectively provide alternating current (AC) power from an AC power source to a luminaire, the photocontrol apparatus comprising:

an ambient light sensor having an output terminal which provides a signal responsive to an amount of light sensed by the ambient light sensor;

an ambient light detection circuit including an input terminal and an output terminal, the input terminal electrically coupled to the output terminal of the ambient light sensor, the output terminal of the ambient light detection circuit provides an ambient light control signal which has a luminaire-on state and a luminaire-off state, the luminaire-on state indicates an ambient light level detected by the ambient light sensor is at a level such that AC power is to be provided to the luminaire, the luminaire-off state indicates the ambient light level detected by the ambient light sensor is at a level such that AC power is not to be provided to the luminaire;

an AC sense circuit having an input terminal and an output terminal, the input terminal of the AC sense circuit electrically coupleable to the AC power source, the output terminal provides an AC sense signal indicative of at least one characteristic of the AC power source;

a switch including an input terminal, an output terminal and a control terminal, the input terminal electrically coupleable to a line terminal of the AC power source, the output terminal electrically coupleable to a load terminal of the luminaire, the switch having a closed state in which the switch electrically couples the luminaire to the AC power source and an opened state in which the switch electrically decouples the luminaire from the AC power source; and

a switch control circuit having a first input terminal, a second input terminal and an output terminal, the first input terminal electrically coupled to the output terminal of the AC sense circuit to receive the AC sense signal therefrom, the second input terminal electrically coupled to the output terminal of the ambient light detection circuit to receive the ambient light control signal therefrom, and the output terminal of the switch control circuit electrically coupled to the control terminal of the switch to provide a switch control signal thereto, the switch control circuit;

detects a change of state of the ambient light control signal from the luminaire-off state to the luminaire-on state;

detects a zero-crossing of the AC power source based at least in part on the received AC sense signal; and

responsive to the detection of the zero-crossing of the AC power source, causes the switch to transition from the opened state to the closed state which causes AC power to be provided to the luminaire from the AC power source.

2. The photocontrol apparatus of claim 1 wherein the switch control circuit:

causes the switch to transition from the opened state to the closed state responsive to detection of a zero-crossing of the AC power source from a positive voltage to a negative voltage.

3. The photocontrol apparatus of claim 1, further comprising:

a direct current (DC) power supply circuit that includes a line input node electrically coupleable to the line node of the AC power source, a neutral input node electrically coupleable to a neutral node of the AC power source, and an output node which supplies DC power to at least one of the ambient light detection circuit, the ambient light sensor, or the switch control circuit.

4. The photocontrol apparatus of claim 3 wherein the DC power supply circuit comprises:

a bridge rectifier comprising a plurality of diodes, the bridge rectifier including a positive terminal and a negative terminal;

a reservoir capacitor electrically coupled between the positive terminal of the bridge rectifier and the negative terminal of the bridge rectifier; and

a zener diode having a cathode electrically couple to the positive terminal of the bridge rectifier and an anode electrically coupled to the negative terminal of the bridge rectifier.

5. The photocontrol apparatus of claim 1 wherein the switch control circuit comprises a delay flip-flop circuit having a data input terminal, an enable terminal, and an output terminal, the data input terminal of the delay flip-flop circuit comprising the second input terminal of the switch control circuit, the enable terminal of the delay flip-flop circuit comprising the first input terminal of the switch control circuit, and the output terminal of the delay flip-flop circuit comprising the output terminal of the switch control circuit.

6. The photocontrol apparatus of claim 1 wherein the AC sense circuit comprises a voltage divider circuit which includes at least two resistors.

7. The photocontrol apparatus of claim 1 wherein the switch comprises a bidirectional switch which conducts current in opposite directions.

8. The photocontrol apparatus of claim 1 wherein the switch comprises two source-connected metal oxide semiconductor field-effect transistors (MOSFETs).

9. The photocontrol apparatus of claim 1 wherein the switch comprises an enhancement mode Metal Oxide Semiconductor Field Effect Transistor (MOSFET).

10. The photocontrol apparatus of claim 1 wherein the ambient light sensor comprises at least one of a solar cell, a semiconductor photo diode, a cadmium sulfide (CDS) cell, or a semiconductor ambient light sensor.

11. The photocontrol apparatus of claim 1 wherein the switch, the switch control circuit, the AC sense circuit, and the ambient light detect circuit comprise surface mount devices.

12. The photocontrol apparatus of claim 1 wherein the ambient light detection circuit comprises at least one of a comparator integrated circuit, an operational amplifier integrated circuit, or a comparator circuit composed of discrete components.

13. The photocontrol apparatus of claim 1, further comprising:

a housing at least partially enclosing the switch and the ambient light sensor, the housing including a translucent portion formed from at least one of polycarbonate or silicone.

14. The photocontrol apparatus of claim 1 wherein at least a portion of the ambient light detection circuit or at least a portion of the switch control circuit comprise a microcontroller.

15. The photocontrol apparatus of claim 14 wherein the output terminal of the switch control circuit is directly electrically coupled to the control terminal of the switch.

16. The photocontrol apparatus of claim 14 wherein the ambient light detection circuit controls the ambient light control signal to change between the luminaire-on state and the luminaire-off state with hysteresis.

17. The photocontrol apparatus of claim 16 wherein the hysteresis varies over time.

18. A photocontrol apparatus to selectively provide alternating current (AC) power from an AC power source to a luminaire, the photocontrol apparatus comprising:

an ambient light detection circuit which includes an output terminal which provides an ambient light control signal indicative of an luminaire-on state and a luminaire-off state, the luminaire-on state indicates an ambient light level detected by the ambient light detection circuit is at a level such that AC power is to be provided to the luminaire, the luminaire-off state indicates the ambient light level detected by the ambient light detection circuit is at a level such that AC power is not to be provided to the luminaire;

an AC sense circuit electrically coupleable to the AC power source and which includes an output terminal which provides an AC sense signal indicative of at least one characteristic of the AC power source;

a switch including an input terminal, an output terminal and a control terminal, the input terminal electrically coupleable to a line terminal of the AC power source, the output terminal electrically coupleable to a load terminal of the luminaire, the switch having a closed state in which the switch electrically couples the luminaire to the AC power source and an opened state in which the switch electrically decouples the luminaire from the AC power source; and

a switch control circuit electrically coupled to the respective output terminals of the ambient light detection circuit and the AC sense circuit, and electrically coupled to the control terminal of the switch, the switch control circuit;

detects a change of state of from the luminaire-off state to the luminaire-on state;

detects a zero-crossing of the AC power source; and

responsive to the detection of the zero-crossing of the AC power source, causes the switch to transition from the opened state to the closed state which causes AC power to be provided to the luminaire from the AC power source.

19. The photocontrol apparatus of claim 18 wherein the switch control circuit:

causes the switch to transition from the opened state to the closed state responsive to detecting a zero-crossing of the AC power source from a positive voltage to a negative voltage.

20. The photocontrol apparatus of claim 18, further comprising:

a direct current (DC) power supply circuit that which receives AC power from the AC power source and which supplies DC power to at least one of the ambient light detection circuit or the switch control circuit.

21. The photocontrol apparatus of claim 20 wherein the DC power supply circuit comprises:

a bridge rectifier comprising a plurality of diodes, the bridge rectifier including a positive terminal and a negative terminal;

a reservoir capacitor electrically coupled between the positive terminal of the bridge rectifier and the negative terminal of the bridge rectifier; and

a zener diode having a cathode electrically couple to the positive terminal of the bridge rectifier and an anode electrically coupled to the negative terminal of the bridge rectifier.

22. The photocontrol apparatus of claim 18 wherein the switch control circuit comprises a delay flip-flop circuit having a data input terminal, an enable terminal, and an output terminal.

23. The photocontrol apparatus of claim 18 wherein the AC sense circuit comprises a voltage divider circuit which includes at least two resistors.

24. The photocontrol apparatus of claim 18 wherein the switch comprises a bidirectional switch which conducts current in opposite directions.

25. The photocontrol apparatus of claim 18 wherein the switch comprises two source-connected metal oxide semiconductor field-effect transistors (MOSFETs).

26. The photocontrol apparatus of claim 18 wherein the switch comprises an enhancement mode Metal Oxide Semiconductor Field Effect Transistor (MOSFET).

27. The photocontrol apparatus of claim 18 wherein the ambient light detection circuit comprises at least one of a solar cell, a semiconductor photo diode, a cadmium sulfide (CDS) cell, or a semiconductor ambient light sensor.

28. The photocontrol apparatus of claim 18 wherein the switch, the switch control circuit, the AC sense circuit, and the ambient light detection circuit comprise surface mount devices.

29. The photocontrol apparatus of claim 18 wherein the ambient light detection circuit comprises at least one of a comparator integrated circuit, an operational amplifier integrated circuit, or a comparator circuit composed of discrete components.

30. The photocontrol apparatus of claim 18, further comprising:

a housing at least partially enclosing the switch and the ambient light detection circuit, the housing including a translucent portion formed from at least one of polycarbonate or silicone.