Patent ID: 8063581

Claim:
A drive circuit for driving a load, the circuit comprising: (i) an output for connecting the load; (ii) a power supply for supplying an output current at the output (IL); (iii) a current sensor for generating a current sense signal (V 25 ) representing the output current (IL); (iv) a supply controller for controlling the power supply, the supply controller having a current sense input for receiving the current sense signal (V 25 ); wherein the supply controller has a supply control output coupled to the power supply, the supply controller being configured to generate a supply control signal (Ssc) for the power supply; (v) a reference source for generating a reference value (VREF-NOM); wherein the supply controller has a reference input for receiving the reference value (VREF-NOM), the supply controller being configured to compare the received current sense signal (V 25 ) with the reference value (VREF-NOM), and, based on comparison, to generate its supply control signal (Ssc) for adjusting the output current (IL) accordingly; (vi) a controllable switch in series with the output; (vii) a mode controller for controlling the controllable switch, the mode controller having a current sense input for receiving the current sense signal (V 25 ), the mode controller having a switch control output coupled to a control input of the switch, the mode controller being configured to generate a switch control signal (SLC) for the switch based on the received current sense signal (V 25 ); wherein the mode controller is capable of operating in a reduced brightness mode, in which the mode controller generates the switch control signal (SLC) for the switch for alternatively opening and closing the switch to define current pulses and pulse pauses; wherein the supply controller has a disable input for receiving a disable signal having a timing equal to or slightly differing from the timing of the switch control signal (SLC), and wherein the supply controller is configured, responsive to the disable signal, to activate or inactivate the power supply.