Patent ID: 6865095
Filing Date: 2005-03-08
Classification: H02M

Abstract:
1. A power circuit comprising a transformer, wherein a first coil, a second coil and a third coil are provided on a primary side of the transformer, a pulse voltage is applied to the first coil from a power source for outputting a power based on the pulse voltage, each of the second and third coils has one of terminals grounded in common and directions in which the coils are to be wound toward the other terminals are opposite to each other and the numbers of winds of the second and third coils are different from each other, a plurality of coils corresponding to the first, second and third coils on the primary side are provided on a secondary side of the transformer, a primary side of the transformer is provided with a power switching unit connected in series to the first coil and serving to control an input of a power to the transformer, a first integrating circuit for integrating a voltage output through a diode connected to the other terminal of the second coil in a forward direction, a second integrating circuit for integrating a voltage output through a diode connected to the other terminal of the third coil in a forward direction, and abnormality detecting means for detecting an abnormality of a state of a voltage between the second coil and the third coil based on an output of the first integrating circuit, an output of the second integrating circuit and a predetermined set value, a pulse voltage is applied to the first coil so that a power is input to the transformer when the power switching unit is brought into a conduction state, and the power switching unit is brought into a non-conduction state so that the input of the power to the transformer is stopped when the abnormality detecting means detects the abnormality of the state of the voltage between the second coil and the third coil.