Patent ID: 8085005

Claim:
A DC to DC, buck-boost voltage converter comprising: a buck switching circuit comprising at least one buck switching transistor coupled between an input voltage and a first end of an inductor, the buck switching circuit being coupled to charge and discharge the inductor during a buck mode of the converter; a boost switching circuit comprising at least one boost switching transistor connected between a second end of the inductor and ground, the boost switching circuit being coupled to charge and discharge the inductor during a boost mode of the converter; an output capacitor coupled to smooth a current through the inductor; an output voltage terminal coupled to the output capacitor for providing a regulated voltage to a load; an error amplifier connected to receive a voltage proportional to the regulated voltage and output an error signal; a differential transconductance amplifier having a first input connected to the error signal and a second input connected to receive a signal corresponding to an instantaneous inductor current; a low pass filter filtering an output of the differential transconductance amplifier, an output of the low pass filter providing a rippling voltage having an average level set by the error signal; a sample and hold circuit connected to an output of the low pass filter, the sample and hold circuit comprising a clock and a storage device that samples an output of the low pass filter at particular time during each switching cycle and outputs a held sampled voltage until a next sampling time; and a modulator that compares the held sampled voltage to a buck sawtooth waveform and to a boost sawtooth waveform, wherein crossing times of the held sampled voltage by the buck sawtooth waveform or boost sawtooth waveform control a switching duty cycle of the at least one buck switching transistor or the at least one boost switching transistor, depending on a magnitude of the held sampled voltage, to generate the regulated voltage.