Power supply switch circuit with current leakage protection

Abstract

A power supply switch circuit with current leakage protection is used in an electronic device, and is able to prevent the erroneous actions caused by a leakage current in high-temperature environments. The power supply switch circuit comprises a transistor having an emitter, a base and a collector, a field effect transistor having a drain, a source and a gate, and at least two series-connected diodes. The emitter is connected to a voltage source. The collector is connected to a load via a forward biased diode. The drain receives a trigger signal. The source is connected a reference terminal via at least two series-connected diodes. The gate is connected to the collector via a second resistor. One terminal of a third resistor is connected to the gate, and the other terminal is connected to the reference terminal.

1 . A power supply switch circuit with current leakage protection, said power supply switch circuit being used in an electronic device and capable of preventing the erroneous actions caused by a leakage current in high-temperature environments, said power supply switch circuit comprising: 
 a transistor having an emitter, a base and a collector, said emitter being connected to a voltage source, said collector being connected to a load, said base receiving a trigger signal;    a field effect transistor having a drain, a source and a gate, said drain being connected to said base via a first resistor, said gate being connected to said collector via a second resistor and a reference terminal via a third resistor; and    at least two series-connected diodes connected between said source and said reference terminal.    
   
   
       2 . The power supply switch circuit with current leakage protection as claimed in  claim 1 , wherein said second resistor and said third resistor are series connected together to form a voltage divider unit.  
   
   
       3 . The power supply switch circuit with current leakage protection as claimed in  claim 1  further comprising a capacitor, wherein said capacitor is parallel connected between said emitter and said base of said transistor.  
   
   
       4 . The power supply switch circuit with current leakage protection as claimed in  claim 1  further comprising a fourth resistor, wherein said fourth resistor is parallel connected between said emitter and said base of said transistor.  
   
   
       5 . The power supply switch circuit with current leakage protection as claimed in  claim 1 , wherein said transistor is a PNP transistor.  
   
   
       6 . The power supply switch circuit with current leakage protection as claimed in  claim 1 , wherein said field effect transistor is an N-channel field effect transistor.  
   
   
       7 . A power supply switch circuit with current leakage protection, said power supply switch circuit being used in an electronic device and capable of preventing the erroneous actions caused by a leakage current in high-temperature environments, said power supply switch circuit comprising: 
 a transistor whose conduction is controlled by a trigger signal;    a voltage divider unit connected to said transistor and used to output a control bias according to a conduction current of said transistor;    a field effect transistor connected to said transistor and said voltage divider unit, conduction of said field effect transistor being controlled by said control bias and used to keep said transistor on; and    a voltage clamp unit connected to said field effect transistor and providing a reference voltage to increase the level of an on voltage of said field effect transistor;    whereby conduction of said field effect transistor depends on whether said control bias is larger than the sum of said on voltage of said field effect transistor and said reference voltage.    
   
   
       8 . The power supply switch circuit with current leakage protection as claimed in  claim 7 , wherein said transistor is a PNP transistor.  
   
   
       9 . The power supply switch circuit with current leakage protection as claimed in  claim 7 , wherein said field effect transistor is an N-channel field effect transistor.  
   
   
       10 . The power supply switch circuit with current leakage protection as claimed in  claim 7 , wherein said field effect transistor is connected to said transistor via a first resistor.  
   
   
       11 . The power supply switch circuit with current leakage protection as claimed in  claim 7 , wherein said voltage divider unit comprises a second resistor and a third resistor, and those are connected in series.  
   
   
       12 . The power supply switch circuit with current leakage protection as claimed in  claim 7  further comprising a capacitor, wherein said capacitor is parallel connected between an emitter and a base of said transistor.  
   
   
       13 . The power supply switch circuit with current leakage protection as claimed in  claim 7  further comprising a fourth resistor, wherein said fourth resistor is parallel connected between an emitter and a base of said transistor.  
   
   
       14 . The power supply switch circuit with current leakage protection as claimed in  claim 7 , wherein said voltage clamp unit comprises at least two diodes, and said diodes are connected in series.