Patent ID: 9141019
Filing Date: 2015-09-22
Classification: G03G,H02M

Abstract:
1. A power-supply device that supplies a load with power, comprising: a transformer; a transformer drive circuit configured to drive the transformer; a rectifier circuit configured to output a rectified voltage by rectifying an output from the transformer; a power-supply output terminal configured to supply the load with an output voltage and an output current generated based on the rectified voltage; a comparator circuit including an input terminal to which an indicator voltage is inputted, the comparator circuit configured to compare a comparison voltage corresponding to the output voltage or the output current with the indicator voltage and to control an operation of the transformer drive circuit so as to reduce a difference between the comparison voltage and the indicator voltage; a constant voltage element electrically connected to the power-supply output terminal and configured to limit the output voltage or the output current by operating as a constant voltage source when a value of the output voltage or the output current reaches a threshold; a current mirror circuit connected in series with the constant voltage element; and a current path electrically connecting the current mirror circuit to the input terminal of the comparator circuit, wherein the current mirror circuit is configured to lower the indicator voltage by allowing a current proportional to a current flowing through the constant voltage element to flow through the current path.