Patent ID: 6433525
Filing Date: 2002-08-13
Classification: H02M,Y02B

Abstract:
A DC-to-DC converter circuit comprising:a pulse width modulator controller and a hysteretic controller, each controller for converting a first voltage into a second voltage during a series of repeated switching cycles; a mode selection circuit for selecting one of the two controllers in accordance with the current demand of a load coupled to the second voltage; a comparator for comparing the second voltage to a reference voltage and generating a polarity signal representative of the second voltage at the end of each switching cycle; and one or more counters coupled to the comparator and to the mode selection switch for recording the polarity of the second voltage at the end of each switching cycle, for maintaining the mode selection switch in its current mode so long as the polarity of the second voltage at the end of the each cycle is the same as the last n number of cycles and for operating the mode selection switch to select the other controller when the polarity of the second voltage at the end of the cycle changes from the prior cycle and the change in polarity persists for n number of cycles.