Patent ID: 6226193
Filing Date: 2001-05-01
Classification: H02M

Abstract:
A DC/DC converter operating on the charge pump principle and regulated to a predetermined output voltage, includinga first circuit array comprising a first charge pump capacitor, the one electrode of which is connectable via a first switch to the input of the converter and via a second switch to ground and the other electrode of which is connectable via a third switch to the input of the converter and via a fourth switch to the output of the converter;a second circuit array configured the same as said first circuit array, in which the one electrode of its capacitor is connectable to the other electrode of the capacitor of said first circuit array via a further switch, all switches being controllable switches;a control circuit capable of controlling the switches so that the charge pump is changed over between a charging phase and a discharge phase, and which is capable of operating the charge pump in two modes, whereby in the charging phase in the first mode the third switch of said second circuit array, the second switch of said first circuit array and the further switch and in the second mode each of the second and third switches of the two circuit arrays are ON, and in the discharge phase of the two modes the first and fourth switch each of the two circuit arrays is ON, whilst each other switch not mentioned is OFF;a regulator circuit capable of setting when the charge pump is active in the charging phase in the first mode the ON resistance of a switch present in the charge path of the charge pump capacitors or in the second mode the ON resistance of two switches present each in one of the charging paths of the first or second charge pump capacitor so that the charging voltage presented to the charge pump capacitors in the charging phase assumes the minimum value possible for a specific input voltage of the converter;a measuring circuit capable of determining the voltage occurring at one of the charge pump capacitors at a defined point in time of the charging phase; anda comparator capable of comparing the measured voltage to a predetermined voltage and then when the former attains the latter, changing over the charge pump into the corresponding other mode;wherein said predetermined voltage is selected so that the efficiency of the converter is optimized and the charging condition of said charge pump capacitors is not altered on changeover.