Semiconductor device

Abstract

A coulomb counter is provided. In the coulomb counter, a current generated on charge or discharge of a secondary battery is converted into a voltage by a resistor, and the voltage is amplified by an amplifier circuit. The voltage amplified by the amplifier circuit is converted into a current by a voltage-current converter circuit, and the current is input to a cumulative addition circuit. The cumulative addition circuit charges a capacitor with the current input from the voltage-current converter circuit and generates a signal corresponding to a voltage generated across the capacitor. One terminal of the capacitor is connected to an output of the voltage-current converter circuit through a switch, and the other terminal of the capacitor is supplied with a constant potential. By on/off of the switch, supply of electric charge to the capacitor and storage of the electric charge can be controlled.

1 . (canceled) 
     
     
         2 . A semiconductor device comprising:
 a resistor comprising a pair of terminals;   a first circuit configured to amplify a first voltage generated between the pair of terminals of the resistor when a first current flows through the resistor and output a second voltage corresponding to the first voltage;   a second circuit configured to generate and output a second current corresponding to the second voltage; and   a third circuit configured to generate a first signal in accordance with the second current,   wherein the third circuit comprises a transistor comprising a channel formation region in an oxide semiconductor film.   
     
     
         3 . The semiconductor device according to  claim 2 , further comprising a fourth circuit,
 wherein the third circuit further comprises a capacitor including a first terminal and a second terminal, and
 wherein the fourth circuit is configured to compare a voltage of the first terminal with a reference voltage and output the first signal. 
   
     
     
         4 . The semiconductor device according to  claim 3 ,
 wherein the third circuit is further configured to output a second signal in accordance with the second current,   wherein the third circuit further comprises a fifth circuit,   wherein the fourth circuit is configured to generate the first signal by comparing the voltage of the first terminal with a first reference voltage, and   wherein the fifth circuit is configured to generate the second signal by comparing the voltage of the first terminal with a second reference voltage.   
     
     
         5 . The semiconductor device according to  claim 2 ,
 wherein the resistor is electrically connected to a battery.   
     
     
         6 . A storage device comprising:
 a power storage body;   a power supply control circuit electrically connected to the power storage body;   a microprocessor unit electrically connected to the power supply control circuit; and   a coulomb counter configured to supply a first signal to the microprocessor unit,   wherein the coulomb counter comprises:
 a resistor comprising a pair of terminals; 
 a first circuit configured to amplify a first voltage generated between the pair of terminals of the resistor when a first current flows through the resistor and output a second voltage; 
 a second circuit configured to generate and output a second current corresponding to the second voltage; and 
 a third circuit configured to generate the first signal in accordance with the second current, 
   wherein the third circuit comprises a transistor comprising a channel formation region in an oxide semiconductor film.   
     
     
         7 . The storage device according to  claim 6 , further comprising a fourth circuit,
 wherein the third circuit further comprises a capacitor including a first terminal and a second terminal, and   wherein the fourth circuit is configured to compare a voltage of the first terminal with a reference voltage and output the first signal.   
     
     
         8 . The storage device according to  claim 6 ,
 wherein the microprocessor unit is configured to control the power supply control circuit in accordance with the first signal.   
     
     
         9 . The storage device according to  claim 6 ,
 wherein the microprocessor unit includes a transistor whose channel formation region is in an oxide semiconductor film.   
     
     
         10 . The storage device according to  claim 6 ,
 wherein the power storage body is any one of a lithium-ion secondary battery, a lead storage battery, a lithium-ion polymer secondary battery, a nickel-hydrogen storage battery, a nickel-cadmium storage battery, a nickel-iron storage battery, a nickel-zinc storage battery, a silver oxide-zinc storage battery, a redox flow battery, a zinc-chlorine battery, a zinc-bromine battery, an aluminum-air battery, a zinc-air battery, an iron-air battery, a sodium-sulfur battery, a lithium-iron sulfide battery, and a lithium-ion capacitor.