Driving circuit and driving method for a plurality of led strings

A constant current driving circuit, comprising:

• a) a plurality of light-emitting diode (LED) strings;
• b) a voltage regulator configured to provide an output voltage signal as a supply for said plurality of LED strings;
• c) a plurality of current regulating circuits corresponding to said plurality of LED strings, and being coupled between said plurality of LED strings and ground, wherein said plurality of current regulating circuits are configured to regulate currents through said plurality of LED strings according to present currents and reference current signals;
• d) a voltage feedback circuit configured to receive input voltage signals of said plurality of current regulating circuits, and to select a minimum one as a voltage feedback signal, wherein said voltage feedback circuit is configured to control said output voltage signal according to said voltage feedback signal and a reference voltage signal;
• and
• e) a plurality of signal generating circuit corresponding to said plurality of current regulating circuits, wherein each signal generating circuit is configured to receive an input voltage signal of a corresponding current regulating circuit, and to generate an error amplifying signal according to said input voltage signal and said reference voltage signal, and to generate said reference current signal and a duty cycle regulating signal according to said error amplifying signal, wherein said duty cycle regulating signal is configured to regulate an average current of said plurality of LED strings.