SWITCHED-MODE POWER SUPPLY DEVICE

摘要

An error amplifier outputs an error voltage to the primary side as a feedback signal indicating a state of the load. An oscillator controls a switching frequency of the switching operation such that the switching frequency is reduced from a highest normal frequency to a lowest normal frequency based on the feedback signal in a load range from a heavily-loaded state to a lightly-loaded state in a normal oscillating operation that continuously performs the switching operation. An intermittent oscillation control circuit intermittently performs the switching operation by stopping the switching operation based on the feedback signal when the load is lighter than a previously set reference. The oscillator increases the switching frequency from an intermittent-operation frequency lower than the lowest normal frequency in an intermittent oscillation duration in which the switching operation is performed in the intermittent oscillating operation.

主权项

1. A switched-mode power supply device, comprising:
a transformer comprising a primary winding in a primary side to which a DC voltage is applied and a secondary winding; a switching circuit connected to the primary winding; a rectifying-smoothening circuit that rectifies and smoothens a pulse voltage generated at the secondary winding, by switching the switching element; an output unit that outputs an output voltage obtained by the rectifying-smoothening circuit to a load; an error amplifier that outputs an error voltage to the primary side as a feedback signal indicating a state of the load, the error voltage being obtained by comparing the output voltage to a reference voltage; an oscillator that controls a switching frequency of the switching operation such that the switching frequency is reduced from a highest normal frequency to a lowest normal frequency based on the feedback signal in a load range from a heavily-loaded state to a lightly-loaded state in a normal oscillating operation that continuously performs the switching operation; and an intermittent oscillation control circuit that intermittently performs the switching operation by stopping the switching operation based on the feedback signal when the load is lighter than a previously set reference, wherein the oscillator increases the switching frequency from an intermittent-operation frequency lower than the lowest normal frequency in an intermittent oscillation duration in which the switching operation is performed in the intermittent oscillating operation.