Dc/dc converter

Abstract

The invention relates to a DC/DC converter operating on the principle of a charge pump and comprising a first capacitor C,alternatingly charged via four MOSFETs M,-M,to the input voltage and then discharged in series with the input voltage via a second capacitor C,connected to the output of the circuit. To set the starting current for charging the as yet empty capacitors to a precisely defined small value a switchable current mirror M,, M,is used comprising one of the four MOSFETs (M,) and a further small MOSFET (M,) which is connected to a current source,. A comparator,handles selection between the starting phase and the normal charge pump mode by comparing the output voltage V,of the converter to a reference voltage V,, it switching the current mirror and—via two small switches S,and S,connected to the gates of two of the four MOSFETs—also two of the four MOSFETs so that the capacitors may be charged in an energy-saving way. As compared to existing more complicated achievements this novel DC/DC converter is producable integrated on a smaller circuit area, it in addition to this taking into account the short-circuit case of the converter. In one special embodiment a foldback effect is achievable via a further MOSFET connected in parallel to the current source, the gate of this MOSFET being connected to the output of the converter.