Abstract: A driver for driving a plurality of light emitting diodes (LEDs) is formed of a plurality of LED controllers connected in series between a power supply and a reference voltage. Each controller drives one or more LEDs directly connected to it. Each controller has a voltage input terminal coupled to an output terminal of an adjacent upstream controller, and an output terminal coupled to the voltage input terminal of an adjacent downstream controller. Each controller has a normally-on bypass switch coupled between its voltage input terminal and the voltage input terminal of the adjacent upstream controller. The bypass switch completely bypasses the adjacent upstream controller when the adjacent downstream controller detects that its input voltage is below a threshold insufficient to drive the LED in the adjacent upstream controller. The bypass switch is turned off if the voltage is above the threshold.

Abstract: A driver for driving a plurality of light emitting diodes (LEDs) is formed of a plurality of LED controllers connected in series between a power supply and a reference voltage. Each controller drives one or more LEDs directly connected to it. Each controller has a voltage input terminal coupled to an output terminal of an adjacent upstream controller, and an output terminal coupled to the voltage input terminal of an adjacent downstream controller. Each controller has a normally-on bypass switch coupled between its voltage input terminal and the voltage input terminal of the adjacent upstream controller. The bypass switch completely bypasses the adjacent upstream controller when the adjacent downstream controller detects that its input voltage is below a threshold insufficient to drive the LED in the adjacent upstream controller. The bypass switch is turned off if the voltage is above the threshold.

Abstract: A self-oscillating DCM is disclosed comprising two inductors that charge and discharge 180 degrees out of phase such that the charging inductor is conducting an upward ramping current and the discharging inductor is conducting a downward ramping current. A load receives the upward and downward ramping currents, which combine to create a constant current. The current source that powers the DCM is current limited so as to output a maximum direct current of IIN. A relatively small capacitor is connected across the input terminals of the DCM and allows the inductors to ramp up to a peak current of 2*IIN. Since the current source only supplies the ramping current to one of the inductors at a time up to 2*IIN, and the average current conducted by each inductor is IIN, the current supplied by the current source is a constant IIN. However, since the inductors simultaneously supply two oppositely ramping currents to the load, the load current is a constant current equal to 2*IIN.