Double DC-DC converter having power holding portion

Abstract

Power supply circuitry is disclosed which suppresses changes in a converted voltage regardless of changes in a load state without substantially increasing the volume and weight of the power supply circuitry and raising the manufacturing cost. The circuitry has a direct current power source. A first DC-to-DC converter converts a voltage of the direct current power source. A smoothing filter smoothes the converted voltage of the first DC-to-DC converter and outputs it. The power supply circuitry further includes a power supply section. The power supply section has a voltage detecting portion for detecting a decrease in the converted voltage and outputs a voltage-decrease detection signal. A power holding portion charges capacitor devices with the converted voltage or a voltage of the direct current power source, and discharges the capacitor devices when a voltage-decrease detection signal is output. A second DC-to-DC converter converts an output of the power holding portion and synthesizes the converted output with the converted voltage of the first DC-to-DC converter. A predetermined voltage at which the voltage-decrease detection signal starts to be generated is set lower than the internal control voltage of the first DC-to-DC converter.

Dependencies are inferred from the claim text.