Patent ID: 8456321

Claim:
A circuit for checking voltage of a battery, the circuit comprising: a Zener shunt regulator; a pnp type transistor; an npn type transistor; a diode; first, second, third, fourth, and fifth resistors; and a light emitting diode; wherein a cathode of the Zener shunt regulator is connected to a positive pole of the battery, a reference terminal of the Zener shunt regulator is connected to a base of the pnp type transistor through the first resistor, an anode of the Zener shunt regulator is grounded, the reference terminal of the Zener shunt regulator is further connected to the positive pole of the battery, the base of the pnp type transistor is grounded through the second resistor, an emitter of the pnp type transistor is connected to a cathode of the diode, an anode of the diode is connected to the positive pole of the battery, a base of the npn type transistor is connected to a collector of the pnp type transistor through the third resistor, an emitter of the npn transistor is grounded, a collector of the npn transistor is connected to a positive pole of the light emitting diode, a negative pole of the light emitting diode is grounded, the collector of the npn transistor is further connected to the positive pole of the battery through the fourth resistor, the base of the npn type transistor is grounded through the fifth resistor, and a negative pole of the battery is grounded.