Title: A constant voltage circuit, a power system unit including plurality of the constant voltage circuit and control method
Application Number: 200610092590 Application Date: 2006.06.16
Publication Number: 1896898 Publication Date: 2007.01.17
Approval Pub. Date: Granted Pub. Date:
International Classifi-cation: G05F1/56;H02H9/02;H02H7/20
Applicant(s) Name: Ricoh KK Address:
Inventor(s) Name: Itoh Kohzoh
Attorney & Agent: yang wu wang jinggang
Abstract:
    The invention relates to a constant voltage circuit with an overcurrent protection circuit, a power system unit including plurality of the constant voltage circuit and control method. When output current io1 reaches an overcurrent protective current value, drain current of an NMOS transistor M6 increases, and voltage drop of a resistor R3 exceeds each threshold voltage of PMOS transistors M3 and M4. Therefore, both the PMOS transistors M3 and M4 are ON. When the PMOS transistor M3 is ON, gate voltage of an output transistor M1 is controlled to restrict the output current io1. When the PMOS transistor M4 is ON, input voltage of a buffer BUF1 becomes high level. Therefore, the buffer BUF 1 outputs a signal of S1 of high level from a terminal Po1. The constant voltage circuit with a control device for controlling a load to which power is supplied from the constant voltage circuit can detect the state of the load, a power supply system device having a plurality of constant voltage circuits, and a control method of the device.
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