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US 8,786,317 B2Granted
Low voltage detection circuit
AssigneeMitsumi Electric Co., Ltd.
InventorsAkihiro Terada, Shinichiro Maki
Life of this patent
Estimating the term…
Abstract
Disclosed is a low voltage detection circuit. The low voltage detection circuit includes, a voltage comparison circuit, an output stage, an electric current circuit, and a judgment circuit. When the voltage comparison circuit detects that the voltage of the detection target is a predetermined voltage value or less, an output state of the output stage is promptly changed. When the voltage comparison circuit detects that the voltage of the detection target is a predetermined voltage value or more, the output state of the output stage is changed after a delay time obtained by the electric current circuit.
Claims4
A low voltage detection circuit comprising:
- a voltage comparison circuit which compares a voltage in proportion to a detection target voltage with a predetermined reference voltage;
- an output stage which outputs a detection result;
- an electric current circuit which includes a constant current source and which obtains a predetermined delay time by charging a condenser with a constant current;
- and
- a judgment circuit which judges that a charging electric potential of the condenser reaches a predetermined electric potential;
- wherein:
- when the voltage comparison circuit detects that the detection target voltage becomes the predetermined reference voltage or less, an output state of the output stage is promptly changed;
- when the voltage comparison circuit detects that the detection target voltage becomes the predetermined reference voltage or more, the output state of the output stage is changed after the delay time obtained by the electric current circuit;
- when the voltage comparison circuit detects that the detection target voltage becomes the predetermined reference voltage or less, the electric current circuit is set to a state in which the electric current of the constant current source is cut;
- and
- when the voltage comparison circuit detects that the detection target voltage becomes the predetermined reference voltage or more, the electric current circuit is set to a state in which the electric current of the constant current source is flown, the charging of the condenser is started, and a control signal from the judgment circuit cuts the electric current flown in the constant current source after the delay time;
- wherein the electric current circuit includes:
- a first switch section which is controlled based on an output of the voltage comparison circuit to be able to conduct or cut the electric current flown in the constant current source;
- a first transistor which is connected in series with the constant current source;
- a second transistor which is connected to compose a current mirror circuit with the first transistor to flow an electric current in proportion with the electric current flown in the constant current source;
- a third transistor connected in series with the second transistor;
- and
- a fourth transistor connected in parallel with the second transistor;
- and
- wherein:
- when the voltage comparison circuit detects that the detection target voltage becomes the predetermined reference voltage or less, the first switch section is set to a state in which the electric current is cut, the third transistor is set to an on state and the fourth transistor is set to an off state;
- and
- when the voltage comparison circuit detects that the detection target voltage becomes the predetermined reference voltage or more, the first switch section is set to a state in which the electric current is conducted, the third transistor is set to an off state, the electric current circuit starts the charging of the condenser and after the delay time, the judgment circuit outputs a control signal to cut the electric current flown in the constant current source, and in addition, the fourth transistor is set to an on state.
20 more elements
Dependencies are inferred from the claim text.