| 摘要 |
PURPOSE: A voltage supply device is provided to protects an internal circuit from a transient voltage in case of the reapplication of an voltage by alternatively selecting a first NTC(Negative Temperature Coefficient) thermistor and a second NTC thermistor when the falling time of a fist DC voltage from a first rectification circuit is longer than the rising time of the first DC voltage. CONSTITUTION: A first rectification circuit(1) rectifies an AC input voltage and generates a first DC voltage. A DC/DC converter(5) converts the first DC voltage from the first rectification circuit into a DC output voltage and includes a first NTC thermistor(3), a second NTC thermistor(4), a switching circuit(2), and a switching controller(8). The switching circuit applies the first DC voltage to any one of the first and second NTC thermistors. The switching controller controls the switching circuit to alternatively select the first and second NTC thermistors.
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