Sensing resistor short determiner, switch control circuit including the same and power supply including the switch control circuit

Abstract

According to the exemplary embodiments, a short-circuit of a sense resistor is detected according to a result of comparison between a sense voltage and a reference voltage at a time based on at least one of a period set based on an input sense voltage and a turn-on time of a power switch. A blanking period is set based on the input sense voltage in a current mode, and a short-circuited resistor detection period is set based on the input sense voltage.

1 - 24 . (canceled) 
     
     
         25 . A short-circuit detection circuit, comprising:
 an input voltage detector circuit configured to detect an input voltage coupled to a power switch and to generate an input sense voltage according to the input voltage;   a sense voltage comparator circuit configured to compare a sense voltage and a reference voltage to generate a comparison signal, the sense voltage being generated by a current that flows from the input voltage through the power switch and a sense resistor when the power switch is turned; and   a blanking period setting circuit configured to assert a blanking signal when the power switch is on, wherein the blanking period setting circuit determines a duration of the blanking signal according to the input sense voltage,   wherein the short-circuit detection circuit is configured to:
 not detect a short-circuit of the sense resistor when the blanking signal is asserted, and 
 detect the short-circuit of the sense resistor according to the comparison signal when the blanking signal is not asserted and the power switch is on. 
   
     
     
         26 . The short-circuit detection circuit of  claim 25 , wherein the assertion of the blanking signal is synchronized to a turn-on time of the power switch. 
     
     
         27 . The short-circuit detection circuit of  claim 26 , wherein the duration of the blanking signal is decreased in response to an increase in the input sense voltage and is increased in response to a decrease in the input sense voltage. 
     
     
         28 . The short-circuit detection circuit of  claim 25 , wherein the short-circuit detection circuit is configured to not detect a short-circuit of the sense resistor when the power switch is off. 
     
     
         29 . The short-circuit detection circuit of  claim 25 , further comprising:
 a signal generator circuit that asserts a short-circuit detection signal in response to a rising edge of a shut-down signal,   wherein the short-circuit detection circuit is configured to assert the shut-down signal in response to detecting the short-circuit of the sense resistor.   
     
     
         30 . The short-circuit detection circuit of  claim 25 ,
 wherein the input voltage is coupled to the power switch through a first coil of a transformer, and   wherein the input sense voltage is generated using a current generated by a second coil of the transformer.   
     
     
         31 . The short-circuit detection circuit of  claim 25 ,
 wherein the input sense voltage is generated using a voltage produced by a voltage divider coupled to the input voltage.   
     
     
         32 . The short-circuit detection circuit of  claim 25 , wherein the short-circuit detection circuit is configured to:
 not detect the short-circuit of the sense resistor during an interval after the power switch is turned on and before a determination to turn off the power switch; and   detect the short-circuit of the sense resistor according to the comparison signal when the blanking signal is not asserted during the interval after the determination to turn off the power switch and before the power switch is turned off.   
     
     
         33 . The short-circuit detection circuit of  claim 32 , further comprising:
 a peak detector signal to determine a peak voltage of the input sense voltage; and   a peak reference generator circuit to determine a peak reference voltage according to the determined peak voltage, the peak reference voltage being less than the peak voltage,   wherein the blanking period setting circuit asserts the blanking signal when the power switch is on and the input sense voltage is greater than the determined peak reference voltage, and de-asserts the blanking signal when the power switch is off or the input sense voltage is less than the determined peak reference voltage.   
     
     
         34 . A short-circuit detection circuit, comprising:
 a blanking period setting circuit configured to receive an input sense voltage and produce a blanking signal having an asserted duration determined using the input sense voltage;   a first comparator circuit configured to compare a sense voltage to a reference voltage and assert a comparison signal when the sense voltage is less than the reference voltage; and   an AND gate configured to receive the blanking signal, the comparison signal, and a gate control signal and to assert a shut-down signal when the blanking signal is asserted, the comparison signal is asserted, and the gate control signal is asserted,   wherein the gate control signal being asserted indicates a power switch is turned on.   
     
     
         35 . The short-circuit detection circuit of  claim 34 , wherein the asserted duration of the blanking signal is synchronized to the assertion of the gate control signal. 
     
     
         36 . The short-circuit detection circuit of  claim 35 , wherein the blanking period setting circuit is configured to increase the asserted duration when the input sense voltage decreases and to decreases the asserted duration when the input sense voltage increases. 
     
     
         37 . The short-circuit detection circuit of  claim 34 , further comprising:
 a signal generator circuit that asserts a short-circuit detection signal in response to a rising edge of a shut-down signal.   
     
     
         38 . The short-circuit detection circuit of  claim 34 , wherein the blanking period setting circuit comprises:
 a peak detector signal to determine a peak voltage of the input sense voltage; and   a peak reference generator circuit to determine a peak reference voltage according to the determined peak voltage, the peak reference voltage being less than the peak voltage,   a second comparator circuit configured to compare the input sense voltage to the peak reference voltage and assert the blanking signal when the input sense voltage is greater than the peak reference voltage.   
     
     
         39 . The short-circuit detection circuit of  claim 34 , further comprising:
 an input voltage detector circuit to produce the input sense voltage according to an input voltage coupled to the power switch.   
     
     
         40 . A method for detecting a short circuit, the method comprising:
 determining, using an input voltage detector circuit, an input sense voltage corresponding to an input voltage coupled to a power switch;   generating, using a blanking period setting circuit, a blanking signal having an asserted duration determined using the input sense voltage;   determining, using a sense voltage comparator circuit, whether a sense voltage is less than a reference voltage;   determining whether the power switch is turned on; and   asserting a shut-down signal in response to the sense voltage being less than the reference voltage when the blanking signal is not asserted and the power switch is turned on,   wherein the sense voltage is generated using a sense resistor coupled in series with the power switch.   
     
     
         41 . The method of  claim 40 , wherein the assertion of the blanking signal is synchronized to the power switch being turned on. 
     
     
         42 . The method of  claim 41 , wherein the asserted duration of the blanking signal is decreased in response to an increase in the input sense voltage and is increased in response to a decrease in the input sense voltage. 
     
     
         43 . The method of  claim 40 , further comprising:
 asserting a short-circuit detection signal in response to a rising edge of a shut-down signal.   
     
     
         44 . The method of  claim 40 , further comprising:
 determining a peak voltage of the input sense voltage;   determining a peak reference voltage using the determined peak voltage, the peak reference voltage being less than the peak voltage;   asserting the blanking signal when the input sense voltage is greater than the determined peak reference voltage; and   de-asserting the blanking signal when the input sense voltage is less than the determined peak reference voltage.