Driving apparatus for a light emitting device and method for the same

An apparatus, comprising:

• a drive transistor having a first conduction terminal, a second conduction terminal and a control terminal;
• an operational amplifier having a first input, a second input and an output;
• a first switch coupled between the second input and the second conduction terminal;
• a second switch coupled between the output and a reference node;
• wherein the first and second switches are actuated in response to a pulse width modulation (PWM) control signal;
• a first resistive circuit coupled between the second conduction terminal and the reference node, wherein the first resistive circuit has a variable resistance value;
• a second resistive circuit coupled between the first input and the reference node;
• and
• a control circuit configured to change the variable resistance value in response to a change in logic state of the PWM control signal.

An apparatus, comprising:

• a drive transistor having a first conduction terminal, a second conduction terminal and a control terminal;
• an operational amplifier having a first input, a second input and an output;
• a first switch coupled between the second input and the second conduction terminal;
• a second switch coupled between the output and a reference node;
• wherein the first and second switches are actuated in response to a pulse width modulation (PWM) control signal;
• a first resistive circuit coupled between the second conduction terminal and the reference node;
• a second resistive circuit coupled between the first input and the reference node, wherein the second resistive circuit has a variable resistance value;
• and
• a control circuit configured to change the variable resistance value in response to a change in logic state of the PWM control signal.

An apparatus, comprising:

• a driving current source module including an operational amplifier coupled to a drive transistor that is configured to supply current to a light emitting device via a node;
• wherein the operational amplifier comprises a differential transconductance stage and a Miller compensation capacitor;
• and
• a circuit included in the driving current source module that is configured to improve dimming accuracy by reducing delay caused by the operational amplifier upon dimming in a pulse width modulation (PWM) mode;
• wherein the circuit reduces delay by increasing current flowing through the differential transconductance stage and supplying power to the Miller compensation capacitor in response to a logic state change of a PWM signal.

An apparatus, comprising:

• a driving current source module including an operational amplifier coupled to a drive transistor that is configured to supply current to a light emitting device via a node;
• wherein the operational amplifier comprises a differential transconductance stage including:
• a pair of differential input transistors, wherein first ends of the differential input transistors are coupled to a current mirror circuit and second ends of the differential input transistors are coupled to a current stage,
• a first additional current source circuit connected in parallel to the current mirror circuit,
• a second additional current source circuit, and
• a third additional current source circuit,
• wherein the second and third additional current source circuits are coupled to the second ends of the pair of the differential input transistors;
• and
• a circuit included in the driving current source module that is configured to improve dimming accuracy by reducing delay caused by the operational amplifier upon dimming in a pulse width modulation (PWM) mode;
• wherein the circuit reduces delay by increasing current flowing through the differential transconductance stage with the first additional current source circuit, the second additional current source circuit, and the third additional current source circuit being selectively actuated to supply additional current in response to said logic state change of a PWM signal.