Patent ID: 11923774
Assignee: MURATA MANUFACTURING CO., LTD.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 12:
13. A switching power supply apparatus comprising:
an inductor that is connected in series to a current path configured through which to supply current to an output portion;
a capacitor that is connected in parallel to the output portion;
a switching element configured to generate switching current flowing through the inductor;
an inductor current detection circuit configured to detect current flowing through the inductor; and
a switching control circuit configured to perform switching control of the switching element at a switching frequency in accordance with a result of detection by the inductor current detection circuit,
wherein
the inductor current detection circuit includes a time constant circuit composed of a detection capacitor and a detection resistor that are connected in series to each other, and the inductor current detection circuit is connected in parallel to the inductor,
the detection capacitor is thermally affected in correlation with variation in temperature of the inductor,
a CR product, which is a product of capacitance of the detection capacitor in the time constant circuit and a resistance value of the detection resistor therein, has certain equality relationship with values of inductance and equivalent series resistance of the inductor at a rated operating temperature,
the time constant circuit has temperature characteristics of a time constant, in which the CR product is decreased with the increasing temperature from the rated operating temperature, and variation of the inductance of the inductor with respect to the temperature and variation of the equivalent series resistance of the inductor with respect to the temperature are compensated by the variation of the CR product with respect to the variation in temperature to keep the certain equality relationship from the rated operating temperature to a high temperature range, and
the inductor current detection circuit outputs a voltage between both ends of the detection capacitor as an electrical signal with which the current flowing through the inductor is detected.