Switching regulator
View Patent ↗In order to provide a switching regulator having high efficiency even under light load, the switching regulator is configured so that ON/OFF of a switching element is controlled by an output signal of an oscillation circuit having an oscillation frequency controlled by an output signal from an error amplifier. Thereby, the oscillation frequency can be suppressed under light load, thus reducing a switching loss.
1. A switching regulator comprising:
an error amplifier that amplifies a difference between a divided voltage and a reference voltage, the divided voltage being obtained by dividing an output voltage, the divided voltage connected to an inverting input of the error amplifier, the error amplifier outputting an output signal comprising the amplified difference,
wherein a magnitude of the output signal directly corresponds with changes in an output load current of the switching regulator;
an oscillation circuit that outputs a rectangular wave in accordance with an output signal from the error amplifier, the oscillation circuit including
a constant current source that feeds constant current,
a capacity that is charged with the constant current of the constant current source,
a comparator that compares a voltage of the capacity with a bi-level reference voltage and outputs a rectangular wave, and
a transistor circuit that controls charge/discharge current of the capacity in accordance with an output signal from the comparator and the output signal from the error amplifier, such that the charge/discharge current is proportional to a current of the transistor circuit; and
a switching element, an ON/OFF state of the switching element being controlled by an output signal from the oscillation circuit,
wherein an oscillation frequency of the oscillation circuit increases and decreases in direct correspondence with the output signal from the error amplifier and the output load current.
2. The switching regulator according to claim 1 , wherein the oscillation circuit further includes a circuit that switches the bi-level reference voltage in accordance with the output signal from the comparator.