Patent ID: 9694694
Date: 2017-07-04
CPC Classifications: B60L,H02M,Y02T

Claim:
1. An in-vehicle step-down switching power supply including a first switch element configured to switch conduction and non-conduction to an output side of an input voltage, a switching frequency control circuit configured to output a switching frequency at which the first switch element executes a switching operation, and a rectification unit configured to execute a rectification operation which generates a circulation current by a path of the output side when the first switch element is non-conductive, wherein the switching frequency control circuit includes a switching frequency range setting unit configured to set a switching frequency range to be between fa and fb, fb being a lower frequency than fa, and a switching frequency path setting unit configured to set the switching frequency to a switching frequency within the switching frequency range according to the input voltage, wherein the switching frequency path setting unit is configured to set the switching frequency to fa when the input voltage is equal to or more than a preset threshold, and is configured to set the switching frequency to fc when the input voltage is equal to or less than the threshold, and fc decreases according to a decrease in the input voltage, and is between fa and fb, and the switching frequency path setting unit is configured to set the decreasing frequency fc to skip a frequency band between frequencies fd to fe when decreasing fc according to the decrease in input voltage, fd and fe being within the switching frequency range.