Single inductor multiple LED string driver

A system, comprising:

• a plurality of strings of Light Emitting Diodes (LEDs) coupled to an input voltage;
• a common inductor;
• a plurality of switches coupled to the plurality of strings of LEDs;
• a main switch coupled to the common inductor, wherein a plurality of currents flows from the input voltage to the plurality of strings of LEDs and to the plurality of switches, and wherein each of the currents then flows through the common inductor, and then through the main switch to ground;
• and
• a control circuit that alternatively controls each of the plurality of switches such that an average current flowing across each string of LEDs is equal to a target current value.

A system, comprising:

• a plurality of strings of Light Emitting Diodes (LEDs) coupled to an input voltage;
• a common inductor;
• a plurality of switches coupled to the plurality of strings of LEDs;
• a main switch coupled to the common inductor, wherein a plurality of currents flows from the input voltage to the plurality of strings of LEDs and to the plurality of switches, and wherein each of the currents then flows through the common inductor, and then through the main switch to ground;
• and
• a control circuit that alternatively controls each of the plurality of switches such that an average current flowing across each string of LEDs is equal to a target current value, wherein the control circuit is part of an integrated circuit comprising a Pulse-Width Modulation (PWM) controller, wherein during an on time of a PWM signal, the main switch and one of the plurality of the switches are turned on, wherein during an off time of the PWM signal, the main switch is turned off, and wherein the PWM controller comprises a shifter that selectively turns on each of the plurality of switches during the on time of the PWM signal.

A method, comprising:

• (a) generating a plurality of digital control signals that are used to control a plurality of switches coupled to a plurality of strings of Light Emitting Diodes (LEDs), wherein each switch is selectively turned on and off by each corresponding digital control signal;
• (b) determining an integrated charge amount provided by each current that flows from an input voltage through each string of LEDs, through each switch, through a common inductor, and through a main switch to ground;
• and
• (c) in response to the determined integrated charge amount, controlling an on time of each switch such that an average current flowing across each string of LEDs is equal to each other.