Switching power supply
AssigneeRenesas Technology Corp.
InventorsTakuya Ishigaki, Takashi Sase, Akihiko Kanouda, Koji Tateno, Ryotaro Kudo
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Abstract
In a switching power supply apparatus for performing a switching control of a power MOS transistor that flows current to a coil and converting input voltage into output voltage, even if there occurs offset voltage in a current sensing operational amplifier, source potential of a current sensing MOS transistor is precisely kept at source potential of a low side power MOS transistor. For example, an offset cancel capacitor is arranged at an inverting input terminal of the current sensing operational amplifier, and voltage in the direction to offset the offset voltage occurring in the operational amplifier is charged to this capacitor.
Claims10
A switching power supply apparatus for performing a switching control of a power semiconductor element that flows current to an inductor and converting input voltage into specified output voltage, comprising
- a current sensing circuit wherein a feedback loop is structured by use of a single power supply operational amplifier that operates with positive voltage so that voltage of the same potential as that of source voltage or emitter voltage of the power semiconductor element should be applied to a node that connects a current sensing semiconductor element to which the power semiconductor element is connected with drain terminals thereof or collector terminals thereof, and a current sensing resister that is connected to source terminal or emitter terminal of the current sensing semiconductor element, wherein
- a first capacitor is arranged at the input terminal at one side of the single power supply operational amplifier, and current sensing signals are output on the basis of signals occurring in the current sensing resister.
Dependencies are inferred from the claim text.