US 6,958,595 B2Granted

Step-up/step-down DC-DC converter and portable device employing it

AssigneeRohm Co., Ltd.

InventorsKenichi Niiyama, Michiaki Yama

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Abstract

In a step-up/step-down DC-DC converter, an error signal commensurate with a difference between a voltage commensurate with the output voltage and a predetermined reference voltage and a triangular wave signal are compared by a first comparator, whose output is used to turn on and off a step-up switching circuit. An inverted signal obtained by inverting the error signal and the triangular wave signal are compared by a second comparator, whose output is used to turn on and off a step-down switching circuit. The median level between the outputs of the first and second comparators is set to be lower than the maximum level of the triangular wave signal and higher than the minimum level thereof. Thus, when step-up and step-down modes are switched from one to the other, an overlap period is produced during which the step-up and step-down modes overlap. This makes possible smooth switching between the step-up and step-down modes.

Claims8

Dependent claims

A step-up/step-down DC-DC converter that yields an output voltage by stepping up or down an input voltage, comprising:

an error signal generation circuit that generates an error signal commensurate with a difference between a voltage commensurate with the output voltage and a predetermined reference voltage;
an inverting circuit that generates an inverted signal by inverting the error signal with respect to a predetermined inversion reference voltage;
a triangular wave generation circuit that generates a triangular wave signal whose maximum level is higher than the predetermined inversion reference voltage and whose minimum level is lower than the predetermined inversion reference voltage;
a first comparator that compares the error signal with the triangular wave signal;
a second comparator that compares the inverted signal with the triangular wave signal;
a step-up switching circuit that is turned on and off according to an output of the first comparator;
a step-down switching circuit that is turned on and off according to an output of the second comparator;
an inductor to and from which energy is accumulated and released as the step-up switching circuit and/or the step-down switching circuit is turned on and off;
and
a smoothing circuit that smoothes the output voltage by receiving the energy released from the inductor.

7 more elements

A portable device comprising:

a step-up/step-down DC-DC converter that yields an output voltage by stepping up or down an input voltage,
wherein the step-up/step-down DC-DC converter comprises:
an error signal generation circuit that generates an error signal commensurate with a difference between a voltage commensurate with the output voltage and a predetermined reference voltage;
an inverting circuit that generates an inverted signal by inverting the error signal with respect to a predetermined inversion reference voltage;
a triangular wave generation circuit that generates a triangular wave signal whose maximum level is higher than the predetermined inversion reference voltage and whose minimum level is lower than the predetermined inversion reference voltage;
a first comparator that compares the error signal with the triangular wave signal;
a second comparator that compares the inverted signal with the triangular wave signal;
a step-up switching circuit that is turned on and off according to an output of the first comparator;
a step-down switching circuit that is turned on and off according to an output of the second comparator;
an inductor to and from which energy is accumulated and released as the step-up switching circuit and/or the step-down switching circuit is turned on and off;
and
a smoothing circuit that smoothes the output voltage by receiving the energy released from the inductor.

9 more elements

Dependencies are inferred from the claim text.