Control circuit for a light-emitting diode string

A control circuit for a light-emitting diode (LED) string, comprising:

• a controller;
• and
• an LED string including n LED units, where n is a number of the LED units, an input terminal of the respective LED units being connected to the controller through a first line, and a bidirectional terminal and an output terminal of the respective LED units being connected in series with each other and to the controller through a second line;
• wherein each of the LED units comprises an LED chip, a driver circuit, a storage element, a temporary storage element and a counter, and the driver circuit is connected to the LED chip, the storage element, the temporary storage element and the counter;
• wherein the control circuit is configured to perform the following steps:
• step 1-1:
• the controller, via the first line, sends to each of the LED units a setting signal including mi bits;
• step 1-2:
• the counter of each LED unit counts a number of bits mi of the setting signal;
• step 1-3:
• steps 1-1 to 1-2 are repeated x times, where x is an integer from 1 to not greater than n−1, and i is from 1 to x, wherein a bit count obtained in step 1-2 is cumulatively added, resulting in a first accumulated count, and the (x)th LED unit is configured, after receiving the (x−1)th setting signal, to write the first accumulated count into the temporary storage element;
• and
• step 1-4:
• the controller, via the first line, sends a programming signal to each of the LED units, and each LED unit, upon receiving the programming signal, writes the first accumulated count stored in the temporary storage element into the storage element;
• wherein the first accumulated count written into the storage elements of the respective LED units is different for the respective LED units.