Optical drive for controlling output power of a pick-up head using apc loop

Abstract

An optical drive includes a comparator for comparing a first input signal with a second input signal to generate a first output signal at a first node; a signal source coupled to a second node, the signal source outputting a second output signal; and a switch for outputting a third output signal at a third node, the third output signal controlling a laser power of the optical drive, wherein when the switch is switched to the first node, the first output signal is transmitted to the third node and serves as the third output signal, and when the switch is switched to the second node, the second output signal is transmitted to the third node and serves as the third output signal.

1 . An optical drive, comprising: 
 a comparator for comparing a first input signal with a second input signal to generate a first output signal at a first node;    a signal source coupled to a second node, the signal source outputting a second output signal; and    a switch for outputting a third output signal at a third node, the third output signal controlling a laser power of the optical drive, wherein when the switch is switched to the first node, the first output signal is transmitted to the third node and serves as the third output signal, and when the switch is switched to the second node, the second output signal is transmitted to the third node and serves as the third output signal.    
   
   
       2 . The optical drive of  claim 1 , further comprising: 
 a switch controller for controlling the switching operation of the switch in response to the first output signal and the second output signal.    
   
   
       3 . A circuit, comprising: 
 a comparator for comparing a first input signal with a second input signal to generate a first output signal at a first node;    a first signal source coupled to a second node, for outputting a second output signal;    a first switch coupled to a third node, wherein when the first switch is switched to the first node, the first output signal is transmitted to the third node, and when the first switch is switched to the second node, the second output signal is transmitted to the third node; and    a switch controller for controlling the switching operation of the first switch in response to the first output signal and the second output signal.    
   
   
       4 . The circuit of  claim 3 , further comprising: 
 a power supply for outputting a first reference signal at a fourth node and a second reference signal at a fifth node;    a second signal source for outputting the second input signal to the comparator, wherein a value of the first reference signal is greater than that of the second input signal, and a value of the second reference signal is less than that of the second input signal; and    a second switch coupled to a sixth node, the first input signal being communicated to the comparator thorough the sixth node, wherein when the second switch is switched to the fourth node, the fourth node is connected to the sixth node, and when the second switch is switched to the fifth node, the fifth node is connected to the sixth node.    
   
   
       5 . A circuit, comprising: 
 a comparator comprising a first input and a second input;    a power supply for outputting a first reference signal at a first node and a second reference signal at a second node;    a first signal source for outputting a first output signal to the second input of the comparator, wherein a value of the first reference signal is greater than that of the first output signal, and a value of the second reference signal is less than that of the first output signal; and    a first switch coupled to a third node, the third node being coupled to the first input of the comparator, wherein when the first switch is switched to the first node, the first node is connected to the third node, and when the first switch is switched to the second node, the second node is connected to the third node.    
   
   
       6 . The circuit of  claim 5 , wherein the first reference signal is a voltage signal and the second reference signal is a voltage signal.  
   
   
       7 . The circuit of  claim 5 , wherein the first reference signal is a current signal and the second reference signal is a current signal.  
   
   
       8 . The circuit of  claim 5 , wherein the comparator compares a first input signal from the first input with a second input signal from the second input to generate a second output signal at a fourth node, the circuit further comprising: 
 a second signal source for outputting a third output signal at a fifth node; and    a second switch for outputting a fourth output signal at a sixth node, wherein when the second switch is switched to the forth node, the second output signal is transmitted to the sixth node and serves as the fourth output signal, and when the second switch is switched to the fifth node, the third output signal is transmitted to the sixth node and serves as the fourth output signal.