Automatic power control system for optical disc drive and method thereof
An automatic power control system, a down sampling circuit and a down sampling method. The automatic power control system is incorporated in an optical disc drive comprising a laser diode for receiving a control signal to generate a laser beam; and a photodetector for detecting the laser beam to generate an analog input signal. The automatic power control system comprises an analog-to-digital converter, a down sampling circuit, a comparator, and a digital-to-analog converter. The analog-to-digital converter converts the analog input signal to digital data. The down sampling circuit, coupled to the analog-to-digital converter, comprises a down sampler, a counter, and a controller. The down sampler receives a predetermined amount of digital data to generate representation data. The counter, coupled to the down sampler, calculates the amount of digital data, and resets the down sampler when the amount equals or exceeds the predetermined count. The controller, coupled to the counter, disables the counter when the digital data is invalid. The comparator, coupled to the down sampling circuit, compares the representation data with predetermined target data to generate error data. The digital-to-analog converter, coupled to the comparator, converts the error data to analog to generate the control signal.
1. An automatic power control system for an optical disc drive to control the power of laser beam, the optical disc drive comprising a laser diode for receiving a control signal to generate a laser beam; and a photodetector for detecting the laser beam to generate an analog input signal; the automatic power control system, comprising:
an analog-to-digital converter, converting the analog input signal into digital data;
a down sampling circuit, coupled to the analog-to-digital converter, comprising:
a down sampler, receiving a predetermined amount of digital data to generate representation data;
a counter, coupled to the down sampler, calculating an amount of the digital data, and resetting the down sampler when the amount equals or exceeds the predetermined count; and
a controller, coupled to the counter, disabling the counter when the digital data is invalid;
a comparator, coupled to the down sampling circuit, comparing the representation data with predetermined target data to generate error data; and
a digital-to-analog converter, coupled to the comparator, converting the error data to analog to generate the control signal.
2. The automatic power control system of claim 1 , wherein the down sampler is an accumulator accumulating the digital data to generate the representation data.
3. The automatic power control system of claim 1 , wherein the down sampler discards the representation data when any of the digital data is invalid.
4. The automatic power control system of claim 1 , wherein the down sampler generates the representation data using the valid digital data immediately before the invalid data when the digital data is invalid.
5. The automatic power control system of claim 1 , wherein the controller disables the counter by resetting the counter, and the counter further resets the down sampler.
6. The automatic power control system of claim 1 , wherein the controller disables the counter by holding the counter, and the counter further holds the down sampler.
7. The automatic power control system of claim 1 , wherein the down sampler is a finite impulse filter (FIR).