Patent ID: 7567223
Filing Date: 2009-07-28
Classification: H05B,Y02B

Abstract:
1. An apparatus for controlling a current in one or more light-emitting diodes (LEDs), comprising: a series-connection of elements, including: a sense signal amplifier with an input connection and an output connection, wherein the sense signal amplifier input connection is coupled to the current-sensing element, and wherein the sense signal amplifier outputs an amplified sense signal; a window comparator switching controller with an input connection and an output connection, wherein the switching controller input connection is coupled to the sense signal amplifier output connection to receive the amplified sense signal, and wherein the window comparator switching controller outputs a control signal that controls on and off switching of an externally supplied voltage source of the series-connection of elements based on the signal in order to perform hysteretic control on the current in the one or more LEDs; a switching element with an input connection, an output connection and a control connection, wherein the switching element input connection is coupled to the LED output connection, wherein the switching element output connection is coupled to a ground, wherein the switching element control connection is communicatively coupled to the window comparator switching controller output connection, and wherein on and off states of the switching element respectively turn on and off the externally supplied voltage for the series-connection of elements, the switching element being switched on or off based upon the control signal output by the window comparator switching controller; and a storage element configured to store excess energy when the window comparator switching controller controls on switching of the externally supplied voltage source, and configured to dissipate the stored energy to the one or more LEDs when the window comparator switching controller controls off switching of the externally supplied voltage source, such that the current in the one or more LEDs approximates a ramping function that linearly increases when the externally supplied voltage source is switched on and linearly decreases when the externally supplied voltage source is switched off.