Constant voltage circuit with phase compensation
AssigneeRicoh Company, Ltd.
InventorKohzoh Itoh
Life of this patent
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Abstract
A constant-voltage circuit uses a capacitor having a low ESR (equivalent serial resistance), such as a ceramic capacitor, for phase compensation, wherein a voltage drop of an output voltage due to a resistance provided for optimizing the phase compensation is compensated for by providing output current to an output a current proportional to an voltage detecting resistance through a current mirror circuit thereby the voltage drop of the output voltage is compensated for.
Claims15
A constant-voltage circuit for converting an input voltage provided to an input terminal of said constant-voltage circuit into a predetermined constant voltage, and for providing said constant voltage to a load, comprising:
- a reference voltage generating circuit unit for generating and outputting a predetermined reference voltage;
- an output voltage detecting unit for detecting said constant voltage, and generating and outputting a voltage that is proportional to said detected voltage;
- an output transistor for outputting a current provided from said input terminal to said load according to a control signal;
- an error amplifying circuit unit for providing said control signal for controlling operations of said output transistor so that said proportional voltage becomes equal to said reference voltage;
- an output current detecting unit for detecting said current output from said output transistor, and generating and outputting a proportional current that is proportional to the detected current;
- a first resistance connected to said output voltage detecting unit;
- a proportional current supply circuit unit for supplying said proportional current, which is proportional to the output current, from said output current detecting unit to said first resistance;
- a second resistance connected between said output transistor and said load;
- and
- a capacitor connected to a junction where said second resistance and said load are connected;
- wherein said second resistance and said capacitor constitute a phase compensating circuit unit for carrying out phase compensation for said error amplifying circuit unit.
Dependencies are inferred from the claim text.