To suppress an excessive temperature rise of a DC/DC converter in advance while suppressing a disagreeable feeling to the hearing of an occupant of a vehicle.
A DC/DC converter implements a program including a step (S200) of detecting an auxiliary machinery battery temperature TB; a step (S210) of detecting an auxiliary machinery battery charging/discharging current value IB; a step (S220) of calculating an auxiliary machinery battery SOC; a step (S250) of operating a cooling fan at a required air volume if the auxiliary machinery battery SOC has a value equal to or larger than a allowable value (YES in S230), and if a command value for the allowable air volume is below the required air volume (NO in S240); a step (S260) of operating the cooling fan at the allowable air volume if the auxiliary machinery battery SOC has a value equal to or larger than the allowable value (YES in S230), while the command value of the allowable air volume is below the required air volume (NO in S240); and a step (S270) of operating the cooling fan at a maximum air volume if the auxiliary machinery battery SOC has a value below the allowable value (NO in S230).
Toshio Morita
Takao Matsuyama
Tadashi Muto
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