Two-level LED security light with motion sensor

  • US 9,743,480 B2
  • Filed: 08/08/2016
  • Issued: 08/22/2017
  • Est. Priority Date: 08/31/2011
  • Status: Active Grant
First Claim
Patent Images

1. A LED security light, comprising:

  • a light-emitting unit, comprising a LED lamp;

    a loading and power control unit;

    a light sensing control unit;

    a motion sensing unit; and

    a power supply unit;

    wherein the light-emitting unit is angle adjustable to provide illumination projection toward desired living spaces for performing security protection;

    wherein the loading and power control unit comprises a microcontroller electrically coupled with a switching circuitry, wherein the switching circuitry is electrically connected with a power source and the LED lamp of the light-emitting unit, wherein the microcontroller outputs a control signal to control a conduction period and a cut-off period of the switching circuitry for delivering different average electric powers from the power source to drive the light-emitting unit for generating different illuminations, wherein the microcontroller controls the switching circuitry respectively to have at least a short conduction period and at least a long conduction period such that the light-emitting unit respectively generates at least a low level illumination and at least a high level illumination according to signal received from the light sensing control unit or the motion sensing unit;

    wherein the power supply unit is an AC/DC power converter to convert AC power into DC power required for operating the LED security light, wherein the power source is a DC power from the power supply unit;

    wherein the switching circuitry comprises at least a unidirectional semiconductor switching device;

    wherein the microcontroller outputs a pulse width modulation (PWM) signal to control the conduction period Ton and the cut-off period Toff of the unidirectional semiconductor switching device for delivering different average electric currents from the power source to drive the light-emitting unit for generating different illuminations; and

    wherein a DC power source in conjunction with the LED lamp is designed with a configuration of in series and in parallel connections such that the electric current passing through each LED of the LED lamp remains at an adequate level such that a voltage V across each LED complies with an operating constraint of Vt<


    Vm featuring electrical characteristics of the LED, wherein Vt is a minimum threshold voltage required to trigger the LED to start emitting light and Vm is a maximum operating voltage across the LED.

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