Light emitting diode (LED) driver for backlight improving accuracy of output current and increasing uniformity of brightness between LED channels

A light-emitting diode (LED) driving circuit for driving a backlight unit comprising a plurality of LED channels, the LED driving circuit comprising:

• a current source configured to generate a reference current;
• and
• a plurality of channel driving circuits configured to sequentially sample the reference current received from the current source, and generate output current,
• wherein each of the plurality of channel driving circuits comprises
• a switch-capacitor amplifier circuit configured to sample the reference current and amplify an input voltage corresponding to an input current, the switch-capacitor amplifier circuit including,
• an amplifier including a first input end and a second input end,
• a first capacitor having an end connected to the first input end of the amplifier, the first capacitor configured to store the input voltage, and
• a second capacitor having a first end connected to the second input end of the amplifier,
• an output circuit configured to generate output current according to an output voltage of the switch-capacitor amplifier circuit in response to a dimming control signal, and provide the output current to LED elements, and
• a replica circuit connected to the switch-capacitor amplifier circuit to define a feedback loop when the output circuit is in an off state.

A backlight device comprising:

• a backlight unit (BLU) comprising a plurality of dimming groups;
• a plurality of pixel circuits each configured to drive a corresponding one of the plurality of dimming groups, each of the plurality of pixel circuits comprising a plurality of channel driving circuits configured to provide a plurality of output currents to a plurality of light-emitting diode (LED) channels included in the corresponding one of the plurality of dimming groups;
• and
• a pixel driving circuit configured to provide a reference current to the plurality of pixel circuits,
• wherein each of the plurality of channel driving circuits comprises
• a switch-capacitor amplifier circuit configured to sample the reference current in a first period,
• a replica circuit configured to define a feedback loop with the switch-capacitor amplifier circuit in the first period, the replica circuit including a transistor and a resistor connected to the transistor, the transistor configured to operate based on an output of the switch-capacitor amplifier circuit in the first period, and
• an output circuit including a driving transistor and an output resistor connected to the driving transistor, the driving transistor configured to generate at least one of the plurality of output currents according to an output voltage of the switch-capacitor amplifier circuit in a second period consecutive to the first period, and the output resistor configured to receive the at least one of the plurality of output currents.