Current Driver Circuit

Abstract

A current driver circuit includes a converter part having a switching element and converting an input voltage into an output voltage; a current detector which generates a detection signal indicative of the current of the switching element; an input voltage compensating circuit which generates a compensation signal corresponding to the input voltage; a comparator which compares the detection signal and the compensation signal against each other; and a switch driver circuit which generates a drive signal. The drive signal turns the switching element off in accordance with an output of the comparator, and turns the switching element on again after a lapse of a prescribed time from the switching element being turned off.

What is claimed is: 
     
         1 . A current driver circuit, comprising:
 an input terminal inputting a direct current voltage;   
       a converter part, which has a switching element, converting direct current voltage into an output voltage and supplying a current to a load;
 a current detector which generates a detection signal indicating a current of the switching element; 
 an input voltage compensating circuit which inputs the direct current voltage and generates a compensation signal corresponding to the input voltage; 
 a comparator which compares the detection signal with the compensation signal; and 
 a switch driver circuit which generates a drive signal, the drive signal turning the switching element off in accordance with an output of the comparator, and turning the switching element on after a lapse of a prescribed time from the switching element being turned off, 
 
       wherein:
 the converter part is a boost converter, and 
 the input voltage compensating circuit is configured to generate the compensation signal that becomes lower as the input voltage becomes higher. 
 
     
     
         2 . The current driver circuit according to  claim 1 , wherein:
 the converter part is a boost converter, and   the input voltage compensating circuit is configured to generate the compensation signal that is inversely proportional to the input voltage.   
     
     
         3 . The current driver circuit according to  claim 1 , wherein:
 the switch driver circuit includes a latch circuit and a clock circuit, and   the latch circuit is set by a clock signal from the clock circuit and reset by an output of the comparator, the latch circuit having a function of generating the drive signal.   
     
     
         4 . The current driver circuit according to  claim 1 , wherein:
 the switch driver circuit includes a latch circuit and an off-time period timer, and   the off-time period timer has a function of starting counting time since when the switching element is turned off, and ending counting time after a lapse of a prescribed time to output a turn-on signal, and   the latch circuit is set by the turn-on signal from the off-time period timer and reset by an output of the comparator, the latch circuit having a function of generating the drive signal.   
     
     
         5 . A current driver circuit, comprising:
 a buck-boost converter, which has a switching element, converting an input voltage into an output voltage and supplying a current to a load;   a current detector which generates a detection signal indicating a current of the switching element;   an input voltage compensating circuit which generates a compensation signal corresponding to the input voltage, and said compensation signal becomes lower as the input voltage becomes higher;   a comparator which compares the detection signal with the compensation signal; and   a switch driver circuit which generates a drive signal, the drive signal turning the switching element off in accordance with an output of the comparator, and turning the switching element on after a lapse of a prescribed time from the switching element being turned off.   
     
     
         6 . The current driver circuit according to  claim 5 , wherein the input voltage compensating circuit is configured to generate the compensation signal that is proportional to a sum of the output voltage of the converter part and the input voltage, and that is inversely proportional to the input voltage.