Ricoh Company, Ltd.

Toshihisa Nagata

Kohji Yoshii

Hideki Agari

Hiizu Okubo

Yusuke Minakuchi

Hideo Fujiwara

Seiji Yamanaka

Takahiro Hino

Akihito Nagahama

A constant voltage circuit includes an output control transistor to control an output current from an output terminal to keep an output voltage constant at a set voltage; and an excess-current protection circuit to control the output control transistor. The excess-current protection circuit includes a current increase restriction element to restrict increase in the output current to decrease the output voltage; a first current limitation circuit to limit a gate voltage of the output control transistor to decrease the output current, when the output voltage is decreased to a first limited voltage; a second current limitation circuit to limit a gate voltage of the output control transistor to decrease the output current, when the output voltage is decreased to a second limited voltage smaller than the first limited voltage; and a selector to select whether the first current limitation circuit is operated or stopped.

Constant voltage circuit and electronic device including same

A semiconductor device is disclosed. The semiconductor device includes a switching signal generating circuit formed of a PMOS transistor, a resistor, and inverters which outputs an internal switching signal for switching an operating mode between a first operating mode and a second operating mode when an operating state satisfies a predetermined condition, a mode selection pad to which an external switching signal capable of selecting the first operating mode is input in priority to the internal switching signal, and a switching circuit formed of an OR circuit which switches the operating mode between the first operating mode and the second operating mode based on the external switching signal or the internal switching signal. An output from the switching signal generating circuit is input to the mode selection pad via a trimming fuse.

Semiconductor device and manufacturing method thereof

A constant voltage circuit is disclosed that includes an output control transistor and an overcurrent protection circuit. The overcurrent protection circuit includes a proportional current generation circuit part, a current division circuit part, a division ratio control circuit part, a current-voltage conversion circuit part, and an output current control circuit part. When the output voltage of the current-voltage conversion circuit part reaches a predetermined voltage, the output current control circuit part prevents an increase in the output current of the output control transistor so as to reduce a voltage output from an output terminal. When the voltage output from the output terminal is reduced to a predetermined limit voltage, the division ratio control circuit part changes the division ratio of the current division circuit part so that a current supplied to the current-voltage conversion circuit part increases so as to reduce the output current of the output control transistor.

Constant voltage circuit

A constant voltage circuit that is capable of realizing high speed response with respect to an abrupt change in an input voltage or a load current is disclosed. The constant voltage circuit includes a first error amplifier with a high direct current gain and a second error amplifier with high speed responsiveness with respect to a change in an output voltage. The constant voltage circuit uses the first and second error amplifiers to conduct operation control of an output voltage control transistor in response to a change in the output voltage.

Constant voltage circuit using plural error amplifiers to improve response speed

A constant-voltage power supply circuit for converting an input voltage applied to an input terminal into a predetermined constant voltage for output from an output terminal includes an output transistor to supply from the input terminal to the output terminal an output current responsive to an applied control signal, an error amplifying circuit unit to receive a predetermined bias current to control an operation of the output transistor, and a bias current adjusting circuit unit to supply the error amplifying circuit unit with the bias current responsive to the output current output from the output transistor, wherein the bias current adjusting circuit unit is configured to suspend the supply of the bias current to the error amplifying circuit unit in response to lowering of the output voltage to a predetermined voltage.

Constant-voltage power supply circuit with fold-back-type overcurrent protection circuit

Voltage regulator with plural error amplifiers

A state control portion causes a sense amplifier portion to be at an active state and for causing the sense amplifier to be at an inactive state. A feedback portion causes the control device to causing the sense amplifier portion to be in the inactive state when a path is formed between a power source and a ground in the sense amplifier. A latch portion holds an output of the sense amplifier output when the path is formed. The state control portion comprises a first transistor acting as a switching device. The feedback portion produces a control signal using an output of the sense amplifier portion and a clock signal obtained from a detection circuit, and supplies the control signal to the first transistor. A second transistor for precharging is connected between the first transistor and the power source.

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Hyogo, Japan

Toshihisa Nagata