Current-level Decision Device for a Power Supply Device and Related Power Supply Device

Abstract

An current-level decision device for a power supply device includes a reception end for receiving a current sense signal, a reference voltage generator for generating a first reference voltage, a reference voltage correction unit coupled to the reference voltage generator and the reception end for adjusting the reference voltage according to variation of the current sense signal, so as to generate a second reference voltage, a comparator coupled to the reception end and the reference voltage correction unit for comparing the current sense signal and the second reference voltage to generate a comparison result, and a control unit coupled to the comparator for controlling a switch transistor of the power supply according to the comparison result.

1 . A current-level decision device for a power supply comprising:
 a reception end for receiving a current sense signal;   a reference voltage generator for generating a reference voltage;   a reference voltage correction unit, coupled to the reference voltage generator and the reception end, for adjusting the first reference voltage according to variation of the current sense signal, so as to generate a second reference voltage;   a first comparator, coupled to the reception end and the reference voltage correction unit, for comparing the current sense signal and the second reference voltage, to generate a first comparison result; and   a control unit, coupled to the first comparator, for controlling a power switch of the power supply according to the first comparison result.   
   
   
       2 . The current-level decision device of  claim 1 , wherein the reference voltage correction unit comprises:
 a switch unit, comprising a first end, a second end and a third end, for conducting a signal connection between the first end and the third end according to signals received by the second end;   a first current source, coupled to the first end of the switch unit, for generating a first current;   a second comparator, coupled to the reference voltage generator, the reception end and the second end of the switch unit, for comparing the first reference voltage and the current sense signal, to generate a second comparison result to the second end of the switch unit;   a filtering unit, coupled to the third end of the switch unit, for performing filtering on signals of the third end of the switch unit;   a division unit, coupled to the filtering unit, for generating a current signal according to a filtering result of the filtering unit; and   a current to voltage conversion unit, coupled to the division unit and the first comparator, for generating the second reference voltage to the first comparator according to the current signal generated by the separation unit.   
   
   
       3 . The current-level decision device of  claim 2 , wherein the switch unit is a p-type metal oxide semiconductor field effect transistor, the first end is a source, the second end is a gate, and the third end is a drain. 
   
   
       4 . The current-level decision device of  claim 2 , wherein the filtering unit comprises:
 a first capacitor, having one end coupled to the third end of the switch unit, and the other end coupled to a ground;   a resistor, coupled to the third end of the switch unit; and   a second capacitor, having one end coupled to the resistor, and the other end coupled to a ground.   
   
   
       5 . The current-level decision device of  claim 2 , wherein the division unit comprises:
 a current output end, coupled to the current to voltage conversion unit, for outputting the current signal;   a second current source, coupled to the current output end, for generating a second current to the current output end; and   a third current source, coupled to the current output end, the filtering unit and a ground, for generating a third current from the current output end to the ground, and adjusting the third current according to the filtering result of the filtering unit.   
   
   
       6 . The current-level decision device of  claim 2 , wherein the current to voltage conversion unit is a resistor. 
   
   
       7 . The current-level decision device of  claim 2  further comprising a reset unit, having a first end coupled to the third end of the switch unit, a second end coupled to a reset signal generator, and a third end coupled to a ground, for conducting a signal connection between the first end and the third end according to signals received by the second end. 
   
   
       8 . The current-level decision device of  claim 7 , wherein the reset unit is an n-type metal oxide semiconductor field effect transistor, the first end is a drain, the second end is a gate, and the third end is a source. 
   
   
       9 . A power supply capable of preventing an over-current damage comprising:
 a transformer, comprising a primary winding circuit and a secondary winding circuit;   a switch transistor, coupled to the primary winding circuit;   a current sensing unit, coupled to the switch transistor, for generating a current sense signal according to current flowing through the switch transistor in the primary winding circuit; and   a current-level decision device, coupled to the current sensing unit and the switch transistor, comprising:
 a reception end for receiving a current sense signal; 
 a reference voltage generator for generating a first reference voltage; 
 a reference voltage correction unit, coupled to the reference voltage generator and the reception end, for adjusting the first reference voltage according to variation of the current sense signal, so as to generate a second reference voltage; 
 a first comparator, coupled to the reception end and the reference voltage correction unit, for comparing the current sense signal and the second reference voltage, to generate a first comparison result; and 
 a control unit, coupled to the first comparator, for controlling a power switch of the power supply according to the first comparison result. 
   
   
   
       10 . The power supply of  claim 9 , wherein the reference voltage correction unit comprises:
 a switch unit, comprising a first end, a second end and a third end, for conducting a signal connection between the first end and the third according to signals received by the second end;   a first current source, coupled to the first end of the switch unit, for generating a first current;   a second comparator, coupled to the reference voltage generator, the reception end and the second end of the switch unit, for comparing the first reference voltage and the current sense signal, to generate a second comparison result to the second end of the switch unit;   a filtering unit, coupled to the third end of the switch unit, for performing filtering on signals of the third end of the switch unit;   a division unit, coupled to the filtering unit, for generating a current signal according to a filtering result of the filtering unit; and   a current to voltage conversion unit, coupled to the division unit and the first comparator, for generating the second reference voltage to the first comparator according to the current signal generated by the separation unit.   
   
   
       11 . The power supply of  claim 10 , wherein the switch unit is a p-type metal oxide semiconductor field effect transistor, the first end is a source, the second end is a gate, and the third end is a drain. 
   
   
       12 . The power supply of  claim 10 , wherein the filtering unit comprises:
 a first capacitor, having one end coupled to the third end of the switch unit, and the other end coupled to a ground;   a resistor, coupled to the third end of the switch unit; and   a second capacitor, having one end coupled to the resistor, and the other end coupled to a ground.   
   
   
       13 . The power supply of  claim 10 , wherein the division unit comprises:
 a current output end, coupled to the current to voltage conversion unit, for outputting the current signal;   a second current source, coupled to the current output end, for generating a second current to the current output end; and   a third current source, coupled to the current output end, the filtering unit and a ground, for generating a third current from the current output end to the ground, and adjusting the third current according to the filtering result of the filtering unit.   
   
   
       14 . The power supply of  claim 10 , wherein the current to voltage conversion unit is a resistor. 
   
   
       15 . The power supply of  claim 10  further comprising a reset unit, having a first end coupled to the third end of the switch unit, a second end coupled to a reset signal generator, and a third end coupled to a ground, for conducting a signal connection between the first end and the third end according to signals received by the second end. 
   
   
       16 . The power supply of  claim 15 , wherein the reset unit is an n-type metal oxide semiconductor field effect transistor, the first end is a drain, the second end is a gate, and the third end is a source.