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US 8,476,891 B2Granted
Constant current circuit start-up circuitry for preventing power input oscillation
AssigneeSeiko Instruments Inc.
InventorsTomoki Hikichi, Minoru Ariyama, Daisuke Muraoka, Manabu Fujimura
Life of this patent
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Abstract
Provided is a constant current circuit capable of low current consumption operation, which is prevented from repeating a start-up state and a zero steady state and entering an oscillating state when power is activated. When power is activated, until a node (A) reaches a start-up state, an excitation current is continued to be supplied to a node (B), to thereby reliably start up the constant current circuit in a short period of time without repeating the start-up state and the zero steady state.
Claims10
A constant current circuit, comprising:
- a constant current circuit section comprising:
- a first transistor including a source connected to a first power source;
- a second transistor including a drain and a gate which are connected to a drain of the first transistor, and a source connected to a second power source;
- a third transistor including a source connected to the first power source, and a drain and a gate which are connected to a gate of the first transistor;
- and
- a fourth transistor including a source connected to a first resistor, a gate connected to the gate and the drain of the second transistor, and a drain connected to the gate and the drain of the third transistor,
- the first resistor including one end connected to the source of the fourth transistor and another end connected to the second power source;
- and
- a start-up circuit comprising:
- a fifth transistor including a source connected to the first power source, and a gate connected to the gate of the second transistor;
- a sixth transistor including a source connected to the second power source, and a gate connected to the gate of the second transistor;
- and
- a seventh transistor including a gate connected to a drain of the fifth transistor and a drain of the sixth transistor, a drain connected to the gate of the third transistor, and a source connected to the second power source.
10 more elements
A constant current circuit, comprising:
- a constant current circuit section comprising:
- a first resistor including one end connected to a first power source;
- a first transistor including a source connected to another end of the first resistor;
- a second transistor including a drain and a gate which are connected to a drain of the first transistor, and a source connected to a second power source;
- a third transistor including a source connected to the second power source, and a gate connected to the gate of the second transistor;
- and
- a fourth transistor including a source connected to the first power source, and a gate and a drain which are connected to the gate of the first transistor and a drain of the third transistor;
- and
- a start-up circuit comprising:
- a fifth transistor including a source connected to the second power source, and a gate connected to the gate of the fourth transistor;
- a sixth transistor including a source connected to the first power source, and a gate connected to the gate of the fourth transistor;
- and
- a seventh transistor including a gate connected to a drain of the fifth transistor and a drain of the sixth transistor, a drain connected to the gate of the third transistor, and a source connected to the first power source.
10 more elements
Dependencies are inferred from the claim text.