Light emitting device array driver circuit and current splitter circuit and method of splitting current therefor

A current splitter circuit for use in a light emitting device array driver circuit, the light emitting device array including a plurality of light emitting device strings, each light emitting device string including a plurality of light emitting devices and having a first string end and a second string end, the first string ends of the light emitting device strings being connected to a common node, the light emitting device array driver circuit including a power regulator circuit electrically connected with the common node and a ground, for supplying a supply current to the light emitting device array by sensing the supply current and feedback controlling the supply current;

• the current splitter circuit splitting the supply current among the light emitting device strings, the current splitter circuit comprising:
• a minimum selector circuit coupled to the second string ends of the light emitting device strings to sense voltages at the second string ends of the light emitting device strings, and generate a minimum signal which indicates a lowest voltage of the sensed voltages at the second string ends of the light emitting device strings;
• and
• a plurality of current source circuits, each current source circuit including:
• a first current source end, a second current source end, and a current source control end, wherein the first current source ends of the plurality of current source circuits are respectively coupled to the second string ends of the plurality of light emitting device strings;
• the second current source ends of the plurality of current source circuits are coupled to the ground;
• and the current source control ends of the plurality of current source circuits receive a current control signal related to the minimum signal, so as to control currents through the plurality of current source circuits and thereby control currents through the plurality of light emitting device strings.

A light emitting device array driver circuit, the light emitting device array including a plurality of light emitting device strings, each light emitting device string including a plurality of light emitting devices and having a first string end and a second string end, the first string ends of the light emitting device strings being connected to a common node, the light emitting device array driver circuit comprising:

• a power regulator circuit electrically connected with the common node and a ground, for supplying a supply current to the light emitting device array by sensing the supply current and feedback controlling the supply current;
• and
• a current splitter circuit for splitting the supply current among the light emitting device strings, the current splitter circuit comprising:
• a plurality of first current source circuits, each first current source circuit including:
• a first current source end, a second current source end, a voltage control end, and an index end, wherein the first current source ends of the plurality of first current source circuits are respectively coupled to the second string ends of the plurality of light emitting device strings;
• the second current source ends of the plurality of first current source circuits are coupled to the ground;
• the voltage control ends of the plurality of first current source circuits receive a current control signal related to a maximum signal, so as to control currents through the plurality of first current source circuits and thereby control currents through the plurality of light emitting device strings;
• and the index ends of the plurality of first current source circuits output a plurality of indices relating to voltages at the second string ends of the light emitting device strings respectively;
• a maximum selector circuit coupled to the index ends and outputting the maximum signal indicating a highest voltage of the indices;
• and
• a voltage-controlled voltage source circuit coupled to the maximum selector circuit for generating the current control signal according to the maximum signal.

A current splitter circuit for use in a light emitting device array driver circuit, the light emitting device array including a plurality of light emitting device strings, each light emitting device string including a plurality of light emitting devices and having a first string end and a second string end, the first string ends of the light emitting device strings being connected to a common node, the light emitting device array driver circuit including a power regulator circuit electrically connected with the common node and a ground, for supplying a supply current to the .light emitting device array by sensing the supply current and feedback controlling the supply current;

• the current splitter circuit splitting the supply current among the light emitting device strings, the current splitter circuit comprising:
• a plurality of first current source circuits, each first current source circuit including:
• a first current source end, a second current source end, a voltage control end, and an index end, wherein the first current source ends of the plurality of first current source circuits are respectively coupled to the second string ends of the plurality of light emitting device strings;
• the second current source ends of the plurality of first current source circuits are coupled to the ground;
• the voltage control ends of the plurality of first current source circuits receive a current control signal related to a maximum signal, so as to control currents through the plurality of first current source circuits and thereby control currents through the plurality of light emitting device strings;
• and the index ends of the plurality of first current source circuits output a plurality of indices relating to voltages at the second string ends of the light emitting device strings respectively;
• a maximum selector circuit coupled to the index ends and outputting the maximum signal indicating a highest voltage of the indices;
• and
• a voltage-controlled voltage source circuit coupled to the maximum selector circuit for generating the current control signal according to the maximum signal.

A method for splitting current in a light emitting device array, the light emitting device array including a plurality of light emitting device strings, each light emitting device string including a plurality of light emitting devices and having a first string end and a second string end, the first string ends of the light emitting device strings being connected to a common node, the method comprising:

• providing a total supply current to the common node;
• regulating the total supply current according to a sense signal sensing the total supply current;
• sensing voltages at the second string ends of the light emitting device strings and outputting a minimum signal which indicates a lowest voltage of the sensed voltages at the second string ends of the light emitting device strings;
• generating a current control signal relating to the minimum signal;
• and
• controlling currents through the light emitting device strings according to the current control signal, so as to split the total supply current to the light emitting device strings.

A method for splitting current in a light emitting device array, the light emitting device array including a plurality of light emitting device strings, each light emitting device string including a plurality of light emitting devices and having a first string end and a second string end, the first string ends of the light emitting device strings being connected to a common node, the method comprising:

• providing a total supply current to the common node;
• regulating the total supply current according to a sense signal sensing the total supply current;
• generating a plurality of indices relating to voltages at the second string ends of the light emitting device strings respectively;
• generating a maximum signal indicating a highest voltage of the indices, which relates to the lowest voltage at the second string ends of the light emitting device strings;
• generating a current control signal according to the maximum signal;
• and
• controlling currents through the light emitting device strings according to the current control signal.