×

Load control device for a light-emitting diode light source

  • US 8,492,987 B2
  • Filed: 06/11/2010
  • Issued: 07/23/2013
  • Est. Priority Date: 10/07/2009
  • Status: Active Grant
First Claim
Patent Images

1. An LED driver for controlling the intensity of an LED light source, the LED driver comprising:

  • a power converter circuit operable to receive a rectified AC voltage and to generate a DC bus voltage;

    a LED drive circuit operable to receive the bus voltage and to control the magnitude of a load current conducted through the LED light source, so as to control the intensity of the LED light source, the LED drive circuit comprising a controllable-impedance circuit adapted to be coupled in series with the LED light source, the controllable-impedance circuit comprising a linear regulator including a regulation transistor adapted to be coupled in series with the LED light source; and

    a control circuit operatively coupled to the power converter circuit for adjusting the magnitude of the bus voltage, and to the LED drive circuit for controlling the controllable-impedance circuit to thus adjust the magnitude of the load current through the LED light source;

    wherein the control circuit determines the magnitude of a voltage generated across the controllable-impedance circuit and adjusts the magnitude of the bus voltage in response to the magnitude of the voltage generated across the controllable-impedance circuit to reduce the total power dissipation in the power converter circuit and the LED drive circuit, the control circuit operable to control the regulation transistor to operate in the linear region to control the magnitude of the load current conducted through the LED light source, the control circuit operable to control the LED drive circuit to adjust the DC magnitude of a control voltage at a control electrode of the regulation transistor to control the regulation transistor in the linear region; and

    wherein the LED drive circuit further comprises a feedback circuit coupled in series with the regulation transistor and operable to generate a load current feedback signal representative of the magnitude of the load current, the control circuit operable to control the regulation transistor to operate in the linear region in response to the magnitude of the load current.

View all claims
  • 2 Assignments
Timeline View
Assignment View
    ×
    ×