Method for deriving precise control over laser power of an optical pickup unit, and associated automatic power calibration circuit

A method for deriving precise control over laser power of an optical pickup unit (OPU), the method comprising:

• providing an analog-to-digital converter (ADC) within an automatic power calibration (APC) circuit to derive a path gain and/or a path offset from the APC circuit;
• and
• selectively performing compensation according to the path gain and/or the path offset, in order to control the laser power by a target command, wherein the step of selectively performing compensation according to the path gain and/or the path offset further comprises:
• compensating the path gain when the path gain is derived;
• and
• canceling the path offset when the path offset is derived;
• wherein the APC circuit comprises an analog gain amplifier for generating a second voltage level according to a first voltage level;
• and the method further comprises:
• multiplexing the first voltage level;
• converting the first voltage level into a first value by utilizing the ADC;
• multiplexing the second voltage level;
• converting the second voltage level into a second value by utilizing the ADC;
• and
• calculating a ratio of the second value to the first value in order to derive the path gain.

An automatic power calibration (APC) circuit for controlling laser power of an optical pickup unit (OPU), the APC circuit comprising:

• an analog-to-digital converter (ADC) for performing analog-to-digital conversion, wherein the ADC is utilized for deriving a path gain and/or a path offset from the APC circuit;
• at least one compensation module, coupled to the ADC, for selectively performing compensation according to the path gain and/or the path offset, in order to maintain precision of a relationship between the laser power and a target command utilized for controlling the laser power;
• and
• a control unit arranged to control the APC circuit, wherein the control unit controls the APC circuit to compensate the path gain when the path gain is derived, and controls the APC circuit to cancel the path offset when the path offset is derived;
• wherein the OPU comprises a front-end PD output (FPDO) for outputting an FPDO value;
• and the control unit applies a compensated target value as the target command, wherein the compensated target value is substantially equal to a product of the FPDO value and the path gain minus the path offset.

An automatic power calibration (APC) circuit for controlling laser power of an optical pickup unit (OPU), the APC circuit comprising:

• an analog-to-digital converter (ADC) for performing analog-to-digital conversion, wherein the ADC is utilized for deriving a path gain and/or a path offset from the APC circuit;
• at least one compensation module, coupled to the ADC, for selectively performing compensation according to the path gain and/of the path offset, in order to maintain precision of a relationship between the laser power and a target command utilized for controlling the laser power;
• a control unit arranged to control the APC circuit, wherein the control unit controls the APC circuit to compensate the path gain when the path gain is derived, and controls the APC circuit to cancel the path offset when the path offset is derived;
• an analog gain amplifier arranged to generate a second voltage level according to a first voltage level;
• and
• a multiplexer arranged to multiplex the first voltage level or multiplex the second voltage level;
• wherein the ADC converts the first voltage level into a first value and further converts the second voltage level into a second value;
• and a ratio of the second value to the first value is calculated in order to derive the path gain.