Power supply apparatus
View Patent ↗A power supply apparatus capable of setting a ripple current to be not more than an acceptable value regardless of an input voltage is obtained. The apparatus calculates switching frequency by a current detected by a current detector so that the switching frequency is set to be low if the current is large and the switching frequency is set to be high if the current is small. The switching frequency is set to be high if the input voltage is high and switching frequency is set to be low if the input voltage is low depending on a voltage inputted to an input terminal; and a switching element is controlled by restricting the switching frequency so that the switching frequency to be set by the current detected by the current detector is not lower than the switching frequency to be set by the input voltage.
1. A power supply apparatus comprising:
a switching element which is connected to an input terminal and performs switching driving;
a rectifying element;
a reactor which smoothes an input voltage transformed by said switching element and said rectifying element;
a smoothing capacitor which smoothes the output of said reactor;
a current detector which detects an output current; and
a switching control unit which calculates a duty ratio of said switching element by an output voltage and a target voltage, calculates switching frequency from a load state to be determined by the current detected by said current detector, and controls said switching element,
the calculation of the switching frequency being performed by the current detected by said current detector so that the switching frequency is set to be low if the current is large and the switching frequency is set to be high if the current is small,
wherein the switching frequency is set to be high if the input voltage is high and the switching frequency is set to be low if the input voltage is low depending on the input voltage inputted to said input terminal, and
said switching element is controlled by restricting the switching frequency so that the switching frequency to be set by the current detected by said current detector is not lower than the switching frequency to be set by the input voltage.
2. The power supply apparatus according to claim 1 ,
wherein said switching element is controlled such that the switching frequency to be set by the current detected by said current detector is compared with the switching frequency to be set by the input voltage and higher switching frequency is selected.
3. The power supply apparatus according to claim 1 ,
wherein said switching element has an initial duty ratio which is calculated by the input voltage inputted from said input terminal and the target voltage.
4. The power supply apparatus according to claim 2 ,
wherein said switching element has an initial duty ratio which is calculated by the input voltage inputted from said input terminal and the target voltage.