Power-supply control apparatus, switched-mode power supply, and vehicle

1 . A power-supply control apparatus, comprising a controller that is configured to perform duty control on a switch device which forms an output stage of a switched-mode power supply which is configured to generate an output voltage from an input voltage, wherein the controller

has an OFF-skip function to skip cyclic OFF transitions of the switch device, and

keeps the switch device turned ON by ignoring a reset signal based on feedback control on the output voltage under a state in which the OFF-skip function is implemented.

2 . The power-supply control apparatus according to claim 1 , further comprising:

a first amplifier that is configured to generate an error signal in accordance with a difference between a feedback voltage in accordance with the output voltage and a predetermined reference voltage;

an oscillator that is configured to generate a set signal at a predetermined switching frequency; and

a comparator that is configured to generate the reset signal by comparing one of the error signal and a control signal in response to the error signal and a ramp signal to each other, wherein the controller

turns ON the switch device in response to the set signal under a state in which the OFF-skip function is stopped, and

turns OFF the switch device in response to the reset signal under the state in which the OFF-skip function is stopped.

3 . The power-supply control apparatus according to claim 2 , further comprising:

a current-detecting circuit that is configured to generate a current-detecting signal in accordance with current which flows through the output stage; and

a second amplifier that is configured to generate the control signal in accordance with a difference between the error signal and the current-detecting signal.

4 . The power-supply control apparatus according to claim 1 , further comprising a boot-strap circuit that is configured to generate a drive voltage for the switch device by charging a capacitor under a state in which the switch device is turned OFF.

5 . The power-supply control apparatus according to claim 4 , wherein the controller keeps the switch device turned OFF at least over a minimum OFF period at a time of turning OFF the switch device.

6 . The power-supply control apparatus according to claim 1 , wherein the controller includes

a first D flip-flop that is configured to

accept input of a set signal via a clock end of the first D flip-flop,

accept input of a fixed voltage via a data end of the first D flip-flop,

accept input of the reset signal via a reset end of the first D flip-flop, and

output a first output signal from an output end of the first D flip-flop,

a second D flip-flop that is configured to

accept input of an inversion set signal via a clock end of the second D flip-flop,

accept input of the first output signal via a data end of the second D flip-flop,

accept input of a power-ON reset signal via a reset end of the second D flip-flop, and

output a second output signal from an output end of the second D flip-flop,

an inverter that is configured to generate the inversion set signal by inverting a logic level of the set signal, and

a logic gate that is configured to generate a duty control signal for the switch device from the first output signal and the second output signal.

7 . A switched-mode power supply, comprising:

the power-supply control apparatus according to claim 1 ; and

the output stage that is driven by the power-supply control apparatus.

8 . The switched-mode power supply according to claim 7 , wherein the switch device is of an N-channel type.

9 . The switched-mode power supply according to claim 7 , wherein the output stage is of one of

a step-down type,

a step-up type,

a step-up/down type, and

an inversion type.

10 . A vehicle, comprising:

the switched-mode power supply according to claim 7 ; and

a battery that is configured to supply the input voltage to the switched-mode power supply.